JP3414107B2 - Method for manufacturing semiconductor device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method suitable for forming a fine pattern by lithography and a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art As a peripheral technique of lithography required to satisfy the dimensional accuracy and resolution required for ULSI manufacturing, reflection of exposure light from a substrate is reduced by utilizing light absorption in a thin film or optical interference. There is technology. When the exposure light is reflected from the substrate, thin film interference occurs in a photosensitive thin film, for example, a resist film, and exposure unevenness in the resist film thickness direction called a standing wave and pattern dimension fluctuation caused by resist film thickness fluctuation called multiple interference occur. . The former lowers the resolution and the latter lowers the dimensional accuracy. Further, due to halation in which the exposure light is reflected in an oblique direction or a random direction due to the unevenness of the substrate, there arises a problem that a region which should be originally shielded is exposed and a desired pattern cannot be formed. These problems depend on the intensity of the reflected light from the substrate, and the more the reflected light is reduced, the less these problems are reduced. Therefore, many attempts have been made to reduce the reflected light from the substrate.

The antireflection method can be roughly classified into two types according to its principle. One is a method of using a so-called light-absorbing film, which has a strong property of absorbing exposure light, as an antireflection film, and the other is a method of preventing reflection by utilizing optical interference. As a representative of the former, an AR in which a light-absorbing organic film is applied on a substrate before applying a resist
There is a C (Anti-Reflective Coating) method. Light that passes through the resist film and travels toward the substrate is absorbed by the light-absorbing organic film before being reflected by the surface of the substrate, so that the reflected light returning from the substrate to the resist film is reduced. Examples of the latter antireflection film include Si and TiN. Si on a metal such as W or Al,
SiO _x N _y : An antireflection film such as H or TiN, in which the reflected light from the interface between the resist film and the antireflection film and the reflected light from the interface between the antireflection film and the substrate have mutually opposite phases. Deposit thick to reduce reflected light. Conventionally, antireflection is performed by these methods.

Regarding the ARC method, the 1991 Proceeding of SP
s of SPIE) 1463, pp. 16-29 and JP-A-59-93448. Regarding the antireflection film utilizing optical interference, Japanese Patent Laid-Open No. 59-654.
No. 0 and JP-A-57-130481 and 1994.
Proceedings of the Year (Proc
eedings of SPIE) Vol. 2197, pages 722-732 or 1982 Technical Digests of International Electron Device Meeting (Technical Digests of International Elect)
ron Device Meeting) pp. 399 to 402.

[0005]

The problems of the conventional antireflection technique will be described below by dividing them into an antireflection technique utilizing optical interference and an ARC technique utilizing light absorption.

In the antireflection method utilizing optical interference, it is necessary to make the reflectance of the resist film / antireflection film interface equal to the reflectance of the antireflection film / substrate interface to cancel the reflected light from each interface. Since it is necessary to reverse the phase of the light reflected from the resist film / antireflection film interface and the light reflected from the antireflection film / substrate interface, the thickness of the antireflection film is set to a certain constant value at any place. There is a need. It is almost impossible to achieve this on a stepped substrate. this is,
This is because, as shown in FIG. 2, the film thickness 21 at the step portion of the antireflection film 20 is thicker than the film thickness 22 at the flat portion even if the antireflection film can be uniformly deposited. Furthermore, when the substrate surface layer is a transparent film such as a silicon oxide film, the phase of the light reflected from the reflective interface below the silicon oxide film and the light reflected from the resist film / antireflection film interface must be reversed. I won't. For this purpose, a precise film thickness control including the Si oxide film is required. However, when the Si oxide film is used as the interlayer film on the step substrate, this film thickness control is impossible. . This is because the film thickness of the Si oxide film varies greatly depending on the location. Therefore, in such a case, it is impossible to sufficiently prevent reflection by using the antireflection film having optical coherence. There is also a problem that the complex refractive index of the antireflection film material needs to be optimized depending on the substrate material (more precisely, the complex refractive index of the substrate material) in order to obtain the same reflectance. That is, in the antireflection method utilizing optical interference, it is necessary to change the antireflection film material for each substrate material, and there is also a problem of lacking versatility.

Since the ARC method uses a coating film, it has advantages in that it is simple in process and is versatile, that is, it is effective regardless of the substrate material. On the other hand, there is a problem that the antireflection film becomes thick and is not suitable for forming a fine pattern. If the substrate has a step, the film thickness 31 of the antireflection film 30 on the step is 31 as shown in FIG.
Is smaller than the film thickness 32 below the step and the film thickness 33 at the flat portion, it is necessary to set the film thickness thicker in consideration of the above step. Further, it is necessary to form a thick film even when performing lithography on a flat substrate. To increase the light absorption in the antireflection film and reduce its thickness, it is sufficient to increase the absorbance of the antireflection film, but when the absorbance is increased, the light reflectance at the interface between the antireflection film and the resist film is increased. As a result, a sufficient antireflection effect cannot be obtained. In particular, when the extinction coefficient indicating the absorbance exceeds 0.5, the interface reflection rapidly increases. Therefore, in order to obtain a sufficient antireflection effect, it is necessary to increase the thickness of the antireflection film. However, when a thick antireflection film is used, the ratio of the film thickness to the pattern width, that is, the aspect becomes very large in a fine pattern, and the processing of the antireflection film becomes very difficult and formed. The pattern falls and becomes defective. For example, in order to form a 0.2 μm pattern with an accuracy of ± 5%, it is necessary to suppress the reflectance from the substrate to 0.23% or less (energy-reflectance). Therefore, in order to obtain this reflectance, the thickness of the antireflection film is set to 0.
It should be 15 μm or more. The aspect ratio with respect to the pattern is 0.75. For finer patterns, higher dimensional accuracy is required, and the reflectance must be further reduced accordingly. Therefore, the film thickness of the antireflection film is further increased, and the aspect ratio is further increased.

The present invention has been made in view of the above problems of the prior art. That is, the object of the present invention is to obtain a sufficient antireflection effect even when the substrate step is large, without being affected by substrate reflection even in a substrate having a high reflectance, it can be used universally regardless of the substrate material, Further, a resist pattern forming method and a resist pattern forming method capable of forming a fine pattern with high dimensional accuracy by obtaining a sufficient antireflection effect even when the thickness of the antireflection film cannot be increased due to the limitation of aspect ratio and the like. It is intended to provide an antireflection film.

[0009] Here, the light energy directed from the resist film to the substrate - a I _0, the light energy emerging from the substrate side in the resist film - I when was the I _{r r} / I ₀ (reflected A film having a ratio of 10% or less is called an antireflection film.

[0010]

[Means for Solving the Problems]
It can be achieved in any of two ways.

The first method is to form an antireflection film on the substrate to be processed, which has a higher absorptance of exposure light on the substrate surface side than on the resist film surface side.

There are the following methods for changing the light absorptance of exposure light in the antireflection film.

(1) After forming a film having a high light absorption property on a substrate, exposing the surface of the film to a liquid or gaseous chemical solution and diffusing the chemical solution into the film to decompose the light-absorbing component which has reacted with the chemical solution. And give the absorbance a distribution.

(2) After a film having a high light absorption property is formed on a substrate, a mixing layer of the light absorption film and the resist film is generated when the resist film is formed by coating, and the light absorption property is generated in the mixing layer. Have a change.

(3) The antireflection film is formed by CVD (Chemical Vap).
A film formed by our deposition, and the light absorption is changed by changing the film formation conditions (gas composition etc.) during the film formation.

(4) The antireflection film is a film formed by the sputtering method, and the light absorption is changed by changing the composition of the atmosphere gas during the film formation of this film.

(5) After forming a film containing a light absorbent having a property of volatilizing by heat on a substrate, heat treatment is applied.

(6) Light having a certain wavelength (absorption adjusting light) having the property of absorbing pattern exposure light on the substrate to be processed.
To form a film having the property of absorbing the pattern exposure light as well as absorbing the pattern exposure light in response to the absorption adjusting light.
Then, the entire surface is irradiated with absorption adjusting light to form an antireflection film having a smaller pattern exposure light absorptance in the surface layer portion of the film than in the deep portion.

(7) Light of a certain wavelength (absorption adjusting light) having the property of absorbing the pattern exposure light on the substrate to be processed.
It also absorbs the light, and in addition to the absorption-adjusting light, the heat
A film having the property of absorbing the exposure light is gradually lost, and the entire surface is irradiated with the absorption adjusting light. Thereafter, heat treatment is performed to form an antireflection film having a pattern exposure light absorptance in the surface layer portion of the film smaller than that in the deep portion.

The second method is to form a two-layer reflective film consisting of an upper layer and a lower layer on a substrate. The upper layer film is an interference film against the exposure light, and the lower layer film is a light shielding film having a higher exposure light absorption rate than the upper layer film. Here, a film having an energy ratio of 10% or less with respect to exposure light is called a light-shielding film.

The third method is to form a two-layer film consisting of an upper layer and a lower layer on a substrate, the upper layer film being an interference film against exposure light, and the lower layer film being a film reflecting exposure light. The upper layer film may be a single layer film or a multilayer film. Here, the exposure light is 50% or more (energy
What is reflected is called a reflective film.

The reason why the reflectance does not decrease even if the absorbance of the antireflection film is increased by the conventional method is that the reflectance of the interface between the antireflection film and the resist film increases as the absorbance of the antireflection film increases. If the complex refractive indices of the antireflection film and the resist film are n ₁ -ik ₁ and n ₂ -ik ₂ , respectively, the light passing through the antireflection film is attenuated by exp (-4πk ₁ d / λ), while ^{_{((n 1 -n 2) 2}} + (k 1 -k 2) 2) / ((n 1
+ N ₂ ) ² + (k ₁ + k ₂ ) ² ) reflection occurs at the interface between the resist film and the substrate. When k ₁ indicating the absorbance becomes large, the reflection at the interface between the antireflection film and the resist film becomes large. Note that d is the film thickness of the resist, and λ is the wavelength of exposure. k
₁ and k ₂ are also called the extinction coefficient of each material.

According to the first method of the present invention, by gradually changing the absorptivity of the antireflection film from the surface thereof, the reflection at the interface of the resist film / antireflection film is prevented while a high absorbance is obtained, so that a high antireflection property is obtained. It is an effect. That is, by gradually changing the extinction coefficient k from the resist film to the antireflection film, the reflection caused by the change of k is reduced. Although a slight amount of reflection occurs each time k is changed, the reflecting surface is slightly shifted, and the phase of the reflected light is gradually changed to cancel each other. Therefore, the total reflection is small. Even if the extinction coefficient of the antireflection film is large, the reflection at the interface is reduced for this reason, and thus a high antireflection effect can be obtained.
Since the extinction coefficient of the antireflection film can be increased without restriction of interfacial reflection, use of this antireflection film can sufficiently prevent reflection even on a substrate having a high reflectance or a substrate whose upper layer film is a transparent film.

Further, a kind of interference phenomenon is used for preventing the interface reflection. However, as the interference phenomenon, since only a portion having a certain thickness on the upper surface side of the antireflection film is used, the film thickness of the antireflection film is Even if the thickness is changed, a sufficient antireflection effect can be obtained if the thickness is not less than a certain value. Therefore, it is not affected by the substrate step. Moreover, since the phase of the reflected light gradually changes, the averaging effect works, and the change in the reflectance with respect to the change in the extinction coefficient distribution becomes small. By this,
Antireflection can be stably performed.

On the other hand, since the conventional antireflection film utilizing the interference phenomenon interferes with the reflected light from the resist film / antireflection film interface and the reflected light from the antireflection film / substrate interface, the total thickness of the antireflection film is However, if the value of (1) changes, a sufficient effect of reducing reflected light cannot be obtained, and the influence of the substrate step is greatly affected.
The film thickness of the portion where the absorptance changes in this antireflection film is the average refractive index (real part) of the antireflection film within that film thickness.
Is n _A and the exposure wavelength is λ, it is desirable to secure λ / 4n _A or more. Particularly, it is desirable that it is an odd multiple of λ / 4n _A. Also, as a method of gradually changing k along the depth direction, there are a method of continuously changing and a method of gradually changing in a stepwise manner. However, when a diffusion phenomenon or a mixing phenomenon is used, it is a stepwise process to change continuously. Easy to.

The methods (6) and (7) described in the means for solving the problems have the property of absorbing the pattern exposure light and certain light (to be referred to as absorption adjusting light). In addition, after forming an antireflection film on the substrate which loses the property of absorbing the pattern exposure light in response to the absorption adjusting light, the entire surface is irradiated with the absorption adjusting light. The absorption adjusting light is attenuated in the antireflection film, and has an attenuation distribution according to the Lambert-Beer's law with respect to the traveling direction of the absorption adjusting light from the surface thereof as a starting point. At the same time, an absorption distribution for the pattern exposure light is also generated starting from the surface of the antireflection film. That is, as shown by the absorption characteristic curve 51 in FIG. 5, assuming that the position of the surface is 0 and the film thickness of the antireflection film is d, the absorption of the pattern exposure light is weak at the surface side, that is, the position 0, and the depth is small. A distribution of absorption is created in the antireflection film, with absorption increasing in the direction. Since this distribution starts from the surface side, it does not change even if there is a step on the substrate and the film thickness of the antireflection film varies depending on the location as shown in FIG. That is, as shown in FIG. 6, the pattern exposure light absorption distributions are almost the same for the places where the film thickness is thin above the step (34 in FIG. 3) and the places where the film thickness is thick below (35 in FIG. 3). The light absorption distribution does not change up to the depth d ₀ where the absorption adjusting light is transmitted, and the light absorption is constant at a deeper place. Here, d ₁ and d ₂ in FIG. 6 are the positions of the substrate surface at the positions 34 and 35 when the surface of the antireflection film is 0, and the film thicknesses 31 and 32 are
Is the same value as. To be exact, the absorption distribution does not change in the film thickness direction, but does not change in the light traveling direction. For example, when the surface of the antireflection film has a slop due to the influence of the step of the substrate, the absorption adjusting light 41 is refracted on the surface of the antireflection film as shown in FIG. The distribution is obtained. 42 in FIG. 4 here
Is a substrate having a step, 43 is a portion of the antireflection layer having a changed absorbance (extinction coefficient) (having an absorption gradient), and 44 is a portion of the antireflection layer having a constant absorbance. Since the pattern exposure light is also refracted at the interface of the antireflection film, a uniform absorption distribution can be obtained for the pattern exposure light, and the reflection can be reduced without depending on the step.

By this process, the extinction coefficient k can be gradually changed from the resist film to the antireflection film,
The reflection caused by the sudden change of k is reduced.
Although a slight amount of reflection occurs each time k is changed, the reflecting surface is slightly displaced, and the phase of the reflected light is gradually changed to cancel each other. Therefore, the total reflection is small. Even if the extinction coefficient of the antireflection film is large, the reflection at the interface is reduced for this reason, and thus a high antireflection effect can be obtained. Since the extinction coefficient of the antireflection film can be increased without the restriction of interface reflection, this antireflection film can provide sufficient antireflection even on a substrate with high reflectance and a substrate whose upper layer film is a transparent film. It Although a kind of interference phenomenon is used for this interface reflection prevention, the thickness of the antireflection film changes because the interference phenomenon uses only a certain thickness on the upper surface side of the antireflection film. However, if it has a certain thickness or more, a sufficient antireflection effect can be obtained. Moreover, since the thickness used as the interference effect is sufficiently controlled in the traveling direction of light as described above, the antireflection rate is high. Therefore, it is not affected by the substrate step. On the other hand, the conventional antireflection film utilizing the interference phenomenon causes the reflected light from the resist film / antireflection film interface and the reflected light from the interface of the antireflection film / substrate interface to interfere with each other, so that the thickness of the entire antireflection film changes. Then, a sufficient reflected light reducing effect cannot be obtained, which is greatly affected by the substrate step. The thickness of the antireflection film at the portion where the absorptance changes (43 in FIG. 4 and FIG.
In the range of position 0 to d ₀ ), the average refractive index (real part) of the antireflection film within the film thickness is n _A , and the wavelength of the exposure light is λ.
Then, it is desirable to secure λ / 4n _A or more. Particularly, it is desirable that it is an odd multiple of λ / 4n _A.

The antireflection film, which has the property of absorbing the pattern exposure light and loses the property of absorbing the pattern exposure light in response to the absorption adjusting light, becomes transparent as the light strikes. It can be obtained by dispersing a light absorber having a so-called breaching property in the organic film. Alternatively, it is obtained by using a film in which a substance that absorbs the absorption adjusting light and loses the property of absorbing the pattern exposure light by heat treatment or chemical treatment after the absorption of this light is added to the organic film. You can

In the second method, since the lower layer film has a high absorptance of the exposure light, it blocks the light reflected from the substrate. Therefore, a sufficient antireflection effect can be obtained even on a substrate having a high reflectance and a substrate on which a transparent film is interposed. The blocking of the reflected light from the substrate does not depend on the substrate material because it utilizes not the interference but the light absorption effect. However, in general, when an absorption film that is a thin film and sufficiently blocks the reflected light from the substrate is used, the imaginary part (extinction coefficient) of the refractive index of the antireflection film is increased, and the reflectance of the resist film / antireflection film interface is increased. Is increasing
A sufficient antireflection effect cannot be obtained. In this method, this problem is solved by the upper interference film. That is, the reflected light from the resist film / upper layer antireflection film interface and the reflected light from the upper layer antireflective film / lower layer antireflective film interface should cancel each other (the upper layer film thickness should be such that their phases are reversed). Interference). The above problem can be solved by reducing the interface reflection by the upper antireflection film and by reducing the reflected light from the substrate by the lower antireflection film.

In the third method, the antireflection film is composed of an upper layer film and a lower layer film, but the phase and intensity of the reflected light can be controlled by reflecting the exposure light on the surface of the lower layer film. That is, since the reflection surface is not the substrate surface but the lower layer film surface, the reflected light has a constant phase and intensity regardless of the optical constant of the substrate and the presence or absence of the transparent film. Then, this reflected light is cut by the upper interference film. That is, the reflected light from the resist film / upper layer antireflection film interface and the reflected light from the upper layer antireflective film / lower layer antireflective film interface are canceled by each other (the upper layer film having a film thickness such that their phases are reversed). Interfere (set the thickness).
The reason why the reflected light can be cut by the upper interference film is that the phase and intensity of the reflected light can be made constant, and this is achieved by introducing the reflective film. The present invention is characterized in that a reflection film is introduced to prevent reflection.

FIG. 28 shows an example of line width accuracy with respect to reflectance (amplitude ratio). The square of the amplitude reflectance is the energy
It is the reflectance. Higher precision processing is possible by lowering the reflectance. In particular, when the reflectance (amplitude ratio) is 0.2 (4% in energy ratio), a line width accuracy of about 25 nm is obtained, which is applicable to a 0.25 μm processing process.

[0032]

DETAILED DESCRIPTION OF THE INVENTION

(Embodiment 1) An embodiment of the present invention will be described below with reference to FIG.
Will be explained. First, as shown in FIG. 1A, the substrate 1
An organic material containing nitrone was applied on top to form an organic film 2. The coating film thickness was 0.2 μm. Here, although a step is not formed on the substrate in this figure, a step may be provided. Next, as shown in FIG. 1B, the substrate 1 on which the organic film 2 was formed was exposed to the HCl-containing gas 3. The time of exposure to HCl was 2 minutes. By this treatment, hydrogen chloride (HCl) gas penetrated into the organic film 2 to a depth of about 0.15 μm. Here, the reference depth λ / 4n _A for changing the absorptance for preventing the interfacial reflection is about 0.05 μm in the case of the i-line (wavelength 365 nm), and the depth in this embodiment is about 3 times (odd times) the depth. Is. In addition, n _{A of the} organic film 2
Is about 1.65. A cyclization reaction occurred in the nitrone at the place where HCl penetrated, depending on the HCl concentration, and the absorbance for i-line decreased. Since the concentration of HCl is high on the surface of the organic film 2, an i-line antireflection film having a small absorptivity on the surface of the organic film 2 and having a continuous absorptance along the depth direction should be formed on the substrate. I was able to.

Although the case where HCl gas is used is shown here, an aqueous HCl solution can also be used. One of the differences between the two is the penetration depth into the organic film, which is deep in the case of gas and shallow in the case of aqueous solution. It can be used properly by setting the depth. For example, when ArF excimer laser light (wavelength 193 nm) is used as the exposure light, it is necessary to form an extremely fine pattern, and therefore the antireflection film also needs to be particularly thin. In such a case, an aqueous solution is advantageous.

Thereafter, as shown in FIG. 1C, a resist film 4 was applied and baked, and exposure light 6 was applied to the resist film 4 through a mask 5 by a usual method. Here, i-line was used as the exposure light. Note that, although the drawing shows the case where the masks are brought close to each other for exposure, the exposure may be performed through a lens or a mirror. Next, as shown in FIG. 1D, the resist pattern 4a was formed by developing according to a usual method.
After that, as shown in FIG. 1E, the resist pattern 4a is formed.
The antireflection film 2 ′ was etched using the above as a mask to form a resist pattern 7 including the processing of the antireflection film 2 ′ on the substrate.

The resist pattern formed by using this antireflection method had a dimensional accuracy of about 10% higher than that obtained by using a conventional antireflection method such as the ARC method.

One of the features of this method is that it is a method using a coated organic film that is simple and easy to remove from the device, and that the absorption coefficient change region is changed by changing the diffusion length of gas or solution into the organic film. That is, it can be easily applied to various exposure methods.

(Embodiment 2) A second embodiment of the present invention is shown in FIG.
Will be explained. First, as shown in FIG. 7A, the organic film 72 was applied on the substrate and heat-treated. The heat treatment temperature was 100 ° C., and the coating film thickness was 0.08 μm on the flat surface.
m was 0.15 μm in a thick place. As the substrate, a Si wafer 70 having a step formed with an Al film 71 (containing 2% of Si) having a thickness of 0.2 μm was used, and a novolac resin was used as the organic film. Note that here, a case where a step is formed on the substrate is shown, but the step may not be provided.

Next, as shown in FIG. 7B, the organic film 7 is formed.
A resist film 73 was applied onto the top surface of No. 2. The resist is PMMA
(Polymethylmethacrylate), 200 ℃ after coating
The heat treatment of was added. At this time, a mixing layer 74 of PMMA and novolac resin was formed at the interface between the resist film 73 and the organic film 72. The thickness of the mixing layer is about 0.035 μm
That is, it was the same as the reference depth λ / 4n _A for changing the absorptance for preventing interface reflection with respect to ArF excimer laser light. Although there was a step on the substrate and the film thickness of the organic film 72 varied depending on the location, the thickness of this mixing layer was constant.

The resist film surface side of this mixing layer is PM
It was MA-like, and the organic film surface side was novolak-like. The extinction coefficient of PMMA for ArF excimer laser light is 0.018, and that of heat-treated novolak resin is about 1. The extinction coefficient of the mixing layer was about 0.02 on the upper surface (resist film surface) side and about 1 on the lower surface (organic film) side, and the extinction coefficient changed continuously during that time. After that, as shown in FIG. 7C, the resist film 73 was irradiated with the exposure light 76 through the mask 75 by a usual method. Here, ArF excimer laser light was used as the exposure light. At this time,
The two layers of the organic film 72 and the mixing layer 74 function as an antireflection film. Note that, although the drawing shows the case where the masks are brought close to each other for exposure, the exposure may be performed through a lens or a mirror.

Next, as shown in FIG. 7 (d), the resist pattern 73a was formed by development in accordance with a usual method. After that, as shown in FIG.
The mixing layer 74, which is an antireflection film, and the organic film 72 were etched using 3a as a mask to form a resist pattern 77 including the antireflection film processing on the substrate.

When a 0.15 μm pattern was formed using this antireflection method, a dimensional accuracy of 10% was obtained. On the other hand, when the ARC type antireflection method (conventional antireflection method) having a film thickness of 0.08 μm was used, the dimensional accuracy was 20% even if the absorption coefficient was optimized. When the thickness of the ARC film is increased, a dimensional shift occurs during etching and the resist pattern collapses, which is a defect.

Another advantage of using the mixing layer 74 is that the mixing layer 74 functions as an adhesive layer,
It is difficult to cause pattern collapse (peeling).

The point of this method is to form the mixing layer 74. Other resists can be used in place of the PMMA resist, as described below. After forming the mixing layer 74 according to the above method, the PMMA resist was removed by DUV irradiation and development. Then, a resist film was formed on the mixing layer according to a usual method and baked. After that, exposure and development were performed. Then, the mixing layer and the organic film were etched to form a resist pattern including an antireflection film processing.

(Embodiment 3) A third embodiment of the present invention is shown in FIG.
Will be explained. First, as shown in FIG. 8 (a), an A wafer having a thickness of 0.3 μm is formed on a Si wafer 80 having steps.
1 film 81 (containing 2% of Si) is deposited, and P is further formed thereon.
A substrate having an SG (phosphorus added glass) film 82 adhered thereon was prepared.
Here, the thickness of the PSG film was 0.3 μm in the thin place and 0.6 μm in the thick place due to the influence of the substrate step. In addition,
The PSG film is KrF excimer laser light (wavelength 248 nm).
Transparent to.

Next, as shown in FIG.
The SiOxNyHz film 83 was formed by the plasma CVD method. SiOxNy
A mixed gas of silane and nitrous oxide was used for forming the Hz film, and the mixed gas ratio was changed during the film formation. SiOxNyHz film thickness is 0.0
8 μm, and as shown in FIG. 11, the deposition was performed at a mixed gas ratio such that the extinction coefficient was 1.5 with respect to the KrF excimer laser light, and then the mixed gas ratio was gradually changed to the resist surface side. The extinction coefficient was 0.02. Since it is a CVD film, it was possible to deposit the film with a uniform film thickness, even though there was a step on the substrate. This is C
This is an advantage when using the VD method. By changing the extinction coefficient linearly, the reduction of the reflected light from the substrate due to the absorption of light and the light reflection caused by the difference of the extinction coefficient were balanced, and the reflection could be sufficiently reduced despite the thin film thickness.
Further, as described later, in this example, the extinction coefficient of the antireflection film on the resist film side interface was made the same as the extinction coefficient of the resist. As a result, reflection at the resist film interface could be sufficiently suppressed. If the difference in extinction coefficient at this interface is large, the reflection at this interface becomes large.

Next, as shown in FIG. 8C, the SiOxNyHz film 8 is formed.
A resist film 84 was applied on the antireflection film of No. 3. XP89131 (Shipley brand name) was used as the resist. The extinction coefficient of this resist against KrF excimer laser light was 0.02, which was equal to the extinction coefficient of the SiOxNyHz film surface. After that, as shown in FIG. 8D, the resist film 84 was irradiated with the exposure 86 through the mask 85 by a usual method. Here, KrF excimer laser light was used for the exposure. Although not shown in the figure, a reduction projection exposure method with a lens numerical aperture of 0.45 was used for this exposure. However, this is an experimental condition, and for example, proximity exposure may be used in which the mask and the substrate are brought close to each other by several microns.

Next, as shown in FIG. 8 (e), development was performed by a normal method to form a resist pattern 84a. After that, as shown in FIG.
The SiOxNyHz antireflection film 83 was etched using 4a as a mask to form a resist pattern 87 including the antireflection film processing on the substrate.

When a pattern of 0.25 μm was formed by using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional CVD type antireflection film and the conventional ARC type antireflection film having a thickness of 0.08 μm are used, the dimensional accuracy can be improved from 10% no matter how the absorption coefficient is optimized. There wasn't.

In this example, an antireflection film was applied so that the extinction coefficient was 1.5 at the lowermost portion on the interface side of the substrate. However, this extinction coefficient is not limited to 1.5, and as shown in FIG. 23, when the extinction coefficient is 0.6 or more, the antireflection effect becomes strong,
In particular, the effect becomes noticeable when it is 1 or more and 2 or less. When it is 1 or more, it has a feature that it is less dependent on the antireflection film, the substrate structure and the material. When the extinction coefficient is 1, the film thickness is 50 nm
If it is above, the reflectance becomes 0.1 or less in terms of amplitude ratio and 1% or less in terms of energy ratio.

Further, the dimensional accuracy is further improved by combining the underlaying antireflection film of this embodiment with so-called upper surface reflection for forming an interference film on the upper surface of the resist film to improve dimensional accuracy.

(Embodiment 4) A fourth embodiment of the present invention is shown in FIG.
Will be explained. First, as shown in FIG. 9A, a W having a thickness of 0.2 μm is formed on a Si wafer 90 having steps.
A film 91 is deposited, and SOG (Spin on Glas
s) A substrate having a film 92 deposited thereon was prepared. Here, the SOG film thickness was 0.2 μm in a thin place and 0.5 μm in a thick place due to the influence of the substrate step. The SOG film is made of KrF.
It is transparent to excimer laser light (wavelength 248 nm).

Next, as shown in FIG. 9B, a SiNx film 93 was formed on the SOG film by a DC sputtering method using Si as a target and an atmosphere gas of a mixed gas of Ar and N ₂ . The thickness of the SiNx film is 0.07 μm, and the first 0.042
.mu.m (93a in FIG. 9) was deposited on the KrF excimer laser light with a mixed gas ratio such that the extinction coefficient was 2.8.
After that, gradually change the mixed gas ratio to obtain the remaining 0.028μ.
m (93b in FIG. 9) was deposited. This remaining 0.028μ
For the m coating, the extinction coefficient starts from 2.8 and finally has an extinction coefficient distribution so that it becomes 0.02. Since this film is formed by the sputtering method, it is a film with few defects such as dust in the apparatus and low defects. This is an advantage when using the sputtering method.

Average refractive index of this SiNx film (real part)
Was 2.2 for KrF excimer laser light. Therefore, the reference depth λ / 4n _A for changing the absorptance for preventing the interface reflection with respect to this light is about 0.028 μm, and
It is almost equal to the film thickness of the portion where the extinction coefficient of the Nx film is changing.

Next, as shown in FIG. 9C, the SiNx
A resist film 94 was applied on the antireflection film composed of the films 93 (93a and 93b). XP89131 (Shipley brand name) was used as the resist. The extinction coefficient of this resist for KrF excimer laser light is 0.02, and SiNx
It was equal to the extinction coefficient of the film surface.

Thereafter, as shown in FIG. 9D, the exposure light 96 is exposed to the resist film 94 through the mask 95 by a usual method.
Was irradiated. Here, the exposure light is KrF excimer ray.
The light was used. Although not shown in the figure, a reduction projection exposure method with a numerical aperture of a lens of 0.5 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure may be used. Next, as shown in FIG. 9 (e), the resist pattern 94a was formed by developing by a normal method. After that, as shown in FIG. 9F, the SiNx antireflection film 93 is etched using the resist pattern 94a as a mask to form the resist pattern 9 including the antireflection film processing.
7 was formed on the substrate.

When a 0.25 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional CVD type antireflection film and the conventional ARC type antireflection film having a thickness of 0.07 μm are used, the dimensional accuracy cannot be improved from 10% even if the absorption coefficient is optimized. It was

As can be seen from Example 3 and Example 4, S
By changing x and y in iOxNyHz and x in SiNx, KrF excimer laser light and i can be obtained.
Both the refractive index (real part) and the extinction coefficient can be changed for linear light. The change in x and y is shown in FIG. 27 for the SiOxNyHz film formed by the CVD method and the SiNx film formed by the sputtering. Generally, silicon-rich films have a high extinction coefficient. When z is less than 0.02, the refractive index has little influence on the change of z.

(Embodiment 5) An embodiment of the present invention will be described with reference to FIG. 10 which is a process chart. First, as shown in FIG. 10A, an organic film 102 serving as an antireflection film was applied onto a substrate 101. The coating film thickness was 0.1 μm. This organic film is made by adding anthracene to a novolac resin as a light absorbent. Here, although a step is not formed on the substrate in this figure, a step may be provided. After applying the organic film 102 1
A heat treatment of 00 ° C was applied. By this heat treatment, anthracene existing near the surface of the organic film was volatilized and a distribution of the light absorber was generated. That is, there was a large amount of the light absorbing agent on the substrate surface side and a small amount of the light absorbing agent on the surface side.

Next, as shown in FIG. 10B, a water-soluble resist film 103 was applied on the substrate 101 on which the organic film 102 'having the distribution of the light absorber was formed. After that, FIG.
As shown in (c), the resist film 103 was irradiated with the exposure light 105 through the mask 104 by a usual method. Here, KrF excimer laser light was used as the exposure light. In addition,
Although the drawing shows the case where the masks are brought close to each other, the exposure may be performed via a lens or a mirror. Next, FIG.
As shown in (d), the development is performed according to the usual method,
A resist pattern 103a was formed. After that, FIG.
As shown in (e), the antireflection film 102 'was etched using the resist pattern 103a as a mask to form a resist pattern 106 including the antireflection film processing on the substrate.

The resist pattern formed by using this antireflection method had a dimensional accuracy of about 10% higher than that obtained by using a conventional antireflection method such as the ARC method.

An anthracene derivative may be used in place of the anthracene used as the light absorber here. That is, the bonding group may be replaced with hydrogen, and may be replaced with a methyl group, a methoxy group, an ethyl group, chlorine or the like. In this case, the volatility varies depending on the bonding group,
By changing the bonding group, it becomes possible to give the organic film or the resist film a wide range of heat treatment conditions.

One of the features of this method is that an optimum antireflection film can be obtained with a coating machine and a baking oven which are simple in terms of equipment.

(Embodiment 6) An embodiment of the present invention will be described below with reference to FIG. 12 which is a process chart. First, as shown in FIG. 12A, an organic film 112 was applied on a substrate and heat treatment was applied. The heat treatment temperature was 100 ° C. The coating film thickness was 0.1 μm on the flat surface, but the film thickness was 0.06 μm in a thin place and 0.18 μm in a thick place due to the influence of the substrate step. Absorption rate change reference depth λ / 4n to prevent interface reflection
_A is about 0.05 μm, which is thinner than the film thickness of the organic film, because i-line (wavelength 365 nm) was used as the pattern exposure light. As the organic film 112, nitrone, which is a light absorbing agent for bleaching, was used. As a substrate, an Al film 11 having a thickness of 0.2 μm is formed on a Si wafer 110 having steps.
1 (containing 2% Si) was used.

Next, as shown in FIG. 12B, the entire surface of the wafer was irradiated with i-line 113. The surface 11 is transparent to the organic film 112 by this whole-surface exposure light (absorption adjusting light) 113, and the layer 11 has an absorbance distribution in which the absorbance increases in the thickness direction.
4 was formed. The i-line is used as the absorption adjusting light because of the characteristics of the light absorbing material used here, and it goes without saying that the wavelength of the whole surface exposure light is changed according to the change of the material. The light wavelengths of the overall exposure light 113 and the pattern exposure light 117 described later coincided with each other because this light absorbent was used. If the light absorbent changes, the wavelength of the overall exposure light also changes. It goes without saying that the wavelength of the exposure light also changes.

Next, as shown in FIG. 12 (c), a resist film 115 is applied and formed on the organic film 112 having a layer 114 having a light absorption distribution on the surface side, and then, a mask 116 is interposed by a usual method. Exposure light 117 was applied to the resist film 115. As described above, the i-line is used as the exposure light here. Although the drawing shows the case where the masks are brought close to each other, the exposure may be performed through a lens or a mirror. The apparatus configuration in that case is shown in FIG.

Light emitted from the light source 501 shown in FIG. 13 is a fly-eye lens 502 and condenser lenses 503 and 505.
And illuminate the mask 506 via the mirror. Mask 5
A pellicle 507 is provided on 06 to prevent pattern transfer failure due to adhesion of foreign matter. The mask pattern drawn on the mask 506 is projected onto a wafer 509 which is a sample substrate via a projection lens 508. The mask 506 is placed on the mask stage 518 controlled by the mask position control means 517, and the center thereof and the optical axis of the projection lens 508 are accurately aligned.
The wafer 509 is vacuum-adsorbed on the sample table 510. The sample table 510 is mounted on a Z stage 511 that is movable in the optical axis direction of the projection lens 508, that is, the Z direction, and is further mounted on an XY stage 512. Z
The stage 511 and the XY stage 512 are the main control system 5
Each drive means 51 according to the control command from 19
Since it is driven by 3, 514, it can be moved to a desired exposure position. The position is accurately monitored by the laser length measuring machine 515 as the position of the mirror 516 fixed to the Z stage 511.

Further, the surface position of the wafer 509 is measured by the focus position detecting means composed of the detection light generating section 520, the detection light 523 and the light receiving section 521. Next, FIG. 12 (d)
As shown in FIG. 5, the resist pattern 115a was formed by developing according to a usual method.

After that, as shown in FIG. 12E, the organic film 11 including the layer 114 with the resist pattern 115a as a mask.
The antireflection film of No. 2 was etched to form a resist pattern 118 including the antireflection film processing on the substrate. When a 0.35 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, the dimensional accuracy was 10% when a commercially available ARC type antireflection method (conventional antireflection method) having a film thickness of 0.1 μm was used. When the thickness of the conventional ARC film is increased, a dimension shift occurs during etching, and the resist pattern collapses.

(Embodiment 7) A seventh embodiment of the present invention will be described below. First, in the same manner as in Example 6, an organic film was applied on the substrate and heat treatment was applied. The heat treatment temperature was 100 ° C.
The coating film thickness was 0.1 μm on the flat surface, but due to the step difference of the substrate, the film thickness was 0.06 μm in a thin place and 0.1 μm in a thick place.
It was 18 μm. The absorptance change reference depth λ / 4n _A for preventing interfacial reflection is about 0.06 μm, which is thinner than the film thickness of the organic film, because the h-line (wavelength 405 nm) was used as the pattern exposure light. As the organic film, nitrone, which is a light absorber for bleaching, was used. As a substrate, an oxide film with a thickness of 5 nm is formed on a Si wafer having steps.
A polysilicon film having a thickness of 0.15 μm and an oxide film having a thickness of 0.2 μm were sequentially laminated and used. The thickness of the oxide film is affected by the step as described with reference to FIG. 2 and varies depending on the location.

Next, the entire surface of the wafer was irradiated with i-line. This whole-surface exposure light (absorption adjusting light) formed a layer on the surface side of the organic film, which had a transparent surface and an absorbance distribution in which the absorbance increased in the thickness direction. The wafer was then exposed to an acid atmosphere. Here, an antireflection film made of an organic film whose surface was modified by exposure to a hydrogen chloride gas atmosphere was formed. By carrying out this treatment, the nitrone is illuminated by light irradiation.
Change to a substance that does not ching. That is, after the organic film is bleached with the absorption adjusting light to form the absorbance distribution of the film, the absorbance distribution is fixed by the acid atmosphere treatment, and the absorbance distribution does not change with respect to the pattern exposure light performed thereafter. Made into a membrane.

Then, after forming a resist film on the organic film by coating, the resist film was irradiated with a pattern exposure light through a mask by a usual method. As described above, the h-line is used as the pattern exposure light here.

Then, the antireflection film was etched using the resist pattern as a mask to form a resist pattern including the antireflection film processing on the substrate. When a 0.4 μm pattern was formed by using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, a commercially available AR with a film thickness of 0.1 μm
The dimensional accuracy was 10% when the C-type antireflection method (conventional antireflection method) was used. When the thickness of the conventional ARC film is increased, a dimension shift occurs during etching, and the resist pattern collapses.

Although nitrone was used as the organic film in this example, it is also possible to use an organic film in which diazonaphthoquinone is used as a light absorber instead of nitrone, and a base polymer is added thereto. It is also possible to use a mixture of a diazonium salt and phenol for the organic film and use an alkali vapor such as ammonia gas as a fixing gas having breaching characteristics.

(Embodiment 8) An eighth embodiment of the present invention will be described below. First, an organic film was formed by coating on the substrate and heat treatment was applied. The heat treatment temperature was 100 ° C. The coating film thickness was 0.08 μm on the flat surface, but the film thickness was 0.05 μm in the thin portion and 0.15 μm in the thick portion due to the influence of the substrate step. Absorption rate change reference depth λ / to prevent interfacial reflection
4n _A was about 0.035 μm because KrF excimer laser light (wavelength 248 nm) was used as the pattern exposure light.
And is thinner than the film thickness of the organic film. As the organic film, a novolak resin to which indene bis azide was added was used. However, not only indene bis azide but also other aromatic azide can be used. As a substrate, an oxide film with a film thickness of 10 nm, 0.1 μm, is formed on a Si wafer on which steps are formed.
A m-thickness tungsten polycide film was further used, on which a 0.15 μm-thickness oxide film was deposited.

Next, the entire surface of the wafer was irradiated with light having a wavelength of 308 nm. After that, heat treatment at 250 ° C. was performed. Indenbis azide absorbs light of 308 nm, and distribution of indenbis azide reacted with this light is generated from the surface side. The indenbis azide that did not react shows a strong absorption property for the light of 248 nm by the subsequent heat treatment. Therefore, after heat treatment, light of 248 nm is strong on the bottom side,
A film that absorbs as much as a resist film could be formed on the surface side.

Next, after forming a resist film on the above organic film by coating, the resist film was irradiated with a pattern exposure light through a mask by a usual method. As described above, KrF excimer laser light is used as the exposure light here. Next, the resist pattern was formed by developing according to a usual method. After that, the antireflection film made of the above organic film modified by using the resist pattern as a mask was etched to form a resist pattern including an antireflection film processing on the substrate. When a 0.25 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained.

On the other hand, the dimensional accuracy was 8% when the commercially available ARC type antireflection method (conventional antireflection method) having a film thickness of 0.1 μm was used. When the thickness of the conventional ARC film is increased, a dimension shift occurs during etching, and the resist pattern collapses. When a gate of a logic LSI was formed using this technique, a dimensional accuracy of 5% was obtained, and a high-speed operation logic LSI could be manufactured.

(Embodiment 9) Next, as a ninth embodiment, a semiconductor memory device was manufactured by using the resist pattern forming method of the present invention. FIG. 14 is a cross-sectional view showing the main steps of manufacturing the element. As shown in FIG. 14A, P-type Si
The semiconductor 171 is used as a substrate, and an element isolation region 172 is formed on the surface of the substrate by a known element isolation technique.

Next, for example, polycrystalline Si having a thickness of 150 nm is used.
A structure in which a film and a SiO ₂ film having a thickness of 200 nm are stacked is formed (this polycrystalline Si film functions as the word line 173). Furthermore, using a chemical vapor deposition method, for example, 150 nm
SiO ₂ is deposited and anisotropically processed to form side spacers 174 of SiO _{2 on} the sidewalls of the word lines.

Next, the n diffusion layer 175 is formed by a usual method. Next, as shown in FIG. 14B, a data line 176 made of polycrystalline Si or refractory metal silicide, or a laminated film of these is formed through a normal process.

Next, as shown in FIG. 14C, a storage electrode 178 made of polycrystalline Si is formed through a normal process. After that, Ta ₂ O ₅ , Si ₃ N ₄ , SiO ₂ , a ferroelectric substance, or a composite film thereof is deposited to form a capacitor insulating film 179. Continued polycrystalline Si, refractory metal, refractory metal silicide, or Al, Cu
A plate electrode 180 is formed by depositing a low resistance conductor such as.

Next, as shown in FIG. 14D, the wiring 181 is formed through a normal process. Next, a memory element was manufactured through a normal wiring layer forming process and a passivation process. However, here, only the typical manufacturing process was described, but other than this, the normal device manufacturing process was used. The present invention can be applied even if the order of each step is changed.

Although the antireflection method shown in the sixth embodiment is applied to most of the steps in the lithographic process in the above-mentioned device manufacturing process, the present invention is not necessarily applied to the process in which the deterioration of the dimensional accuracy due to the reflected light does not matter. There is no need to do it. Conducting hole forming process in passivation process,
The present invention was not applied to the pattern forming step for forming an ion implantation mask having a large pattern.

When the word line 173 is formed by using the antireflection method of Embodiment 13 described later, the antireflection film is automatically removed, which is also positively advantageous. Although the sixth and thirteenth embodiments have been described here, other methods may be used.

Next, a pattern formed by lithography will be described. FIG. 15 shows a pattern layout of a memory portion of a typical pattern that constitutes a manufactured memory device. Figure 15
(A) shows an example of the pattern of the produced 1st element. 1
Reference numeral 82 is a word line, 183 is a data line, 184 is an active region, 185 is a storage electrode, and 186 is a pattern of electrode extraction holes. The present invention is used in a process requiring resolution of a fine pattern from the lithography process. In the pattern shown in FIG. 15 (a), the present invention was used to form all patterns. Further, FIG. 15B shows an example of the pattern of the manufactured second element. 187 is a word line, 188 is a data line,
189 is an active region, 190 is a storage electrode, and 191 is a pattern of electrode extraction holes. Also in this example, the present invention was used to form all of the patterns shown here. The present invention was used in the process using the minimum design rule other than the pattern formation shown here.

The characteristics of the element manufactured by using the present invention were good as compared with the characteristics of the element manufactured by the conventional method. Specifically, since the variation in the width of the word lines is small, the data reading speed is fast and the characteristics are stable. Since the variation of the area of the storage electrode is small, the data retention characteristic is stable. It was possible to improve the characteristics such as. Further, the yield of yielding good products of elements was 40% or less in the conventional method, but could be improved to 70% or more. A clear improvement effect was obtained.

Although the memory LSI is shown in this embodiment, the operation speed of the logic LSI is stable and improved, and the yield of non-defective products is also improved. The biggest reason is the improvement of the gate size controllability.

(Embodiment 10) Before irradiating the organic film with absorption adjusting light in Example 8, as shown in FIG. 16, the organic film 192 had substantially the same refractive index as the resist film, and the absorption adjusting light was absorbed. And a transparent film 193 was coated. Here, polyvinylpyrrolidone was used as the coating film. Absorption adjusting light 194 passes through this coating film.
Was irradiated to the organic film. After this light irradiation, the coating film was removed, and after resist coating, the same treatment as in Example 8 was performed to form a resist pattern. The polyvinylpyrrolidone was removed by washing with water. When a water-insoluble film is used as the organic film, this washing with water does not give damage to the organic film such as alteration or film slippage. By this process,
The refraction angle θ of the absorption adjusting light at the interface between the coating film 193 and the organic film 192 matches the refraction angle of the pattern exposure light at the interface between the resist film and the organic film. That is, even when the substrate step is large, the light absorption distribution in the antireflection layer can be made the same along the traveling direction of the pattern exposure by this step, and the control of the light interference in the antireflection layer can be performed. Can be performed more precisely and the reflection is smaller. In this embodiment, the substrate step is increased by 0.1 μm as compared with the eighth embodiment, but the 0.35 μm pattern is increased by 4.
It could be formed with an accuracy of 5%.

In this embodiment, the refraction angle θ was adjusted using the coating film, but it is also possible to use a liquid instead of using the coating film. That is, it is possible to adjust the refraction angle θ by immersing the wafer in a liquid and irradiating it with absorption adjusting light. When the refractive index of the liquid for the absorption adjusting light is close to the refractive index of the resist film for the pattern exposure light, the refraction angle of the pattern exposure light at the interface between the resist film and the organic film and the liquid and the organic film The refraction angles of the absorption adjusting light at the interface become almost equal, and the light interference in the antireflection film can be controlled more precisely. Water or oil can be used as the liquid. The feature of using a liquid is that the process of coating and removing the cover film is not required, and the process is simple.

(Embodiment 11) The process of the present invention will be described below with reference to FIG. First, as shown in FIG. 17A, 0.2 μm is formed on the Si wafer 201 on which a step is formed.
A W film 202 having a thickness is deposited, and SOG (Sp
A substrate on which (in on glass) 203 was adhered was prepared. Here, due to the influence of the substrate step, the SOG film thickness is 0.2 at a thin place.
μm, and 0.5 μm in a thick place. In addition, SO
The G film is transparent to KrF excimer laser light (wavelength 248 nm).

Next, as shown in FIG. 17B, a Si film 204 (light-shielding antireflection film) was formed on the SOG film by a DC sputtering method using Si as a target and an atmosphere gas of Ar. The thickness of this Si film was 0.025 μm.

The refractive index (real part) of this film with respect to KrF excimer laser light was 2.3, and the extinction coefficient was 2.8. The transmittance of KrF excimer laser light of this film is 3% or less (energy ratio), and the reflected light from the substrate reciprocates through this film and returns to the resist film, so that it becomes a sufficient light-shielding film.

Thereafter, a film thickness of 0.025 μm is formed on the Si film.
The SiN _x film 205 (interference reflection preventing film) of m was formed by the DC sputtering method using Si as a target and N ₂ and Ar gas as atmosphere gas. Here, the refractive index (real part) of the SiN _x film with respect to the KrF excimer laser light is the SiN x film 20.
The gas mixture ratio was adjusted so that the extinction coefficient was 2.3 uniformly in the five films.

The film thickness and the refractive index are antireflection conditions for the interference film. This SiN _x / Si two-layer film is an antireflection film, and the reflectance of KrF excimer laser light, which is exposure light, does not depend on the location due to this two-layer film (irrespective of the influence of the SOG film thickness and steps). Almost no reflection was possible at 0.01% or less (energy ratio). Since this two-layer film is formed by the sputtering method, it does not contain a component such as ammonia that deteriorates the characteristics of the chemically amplified resist. Therefore, the selection range of resists to be combined is widened. This is an advantage when using the sputtering method.

Further, here, the Si film forming chamber and Si
The N _x film forming chamber used another sputtering apparatus. By using another chamber, a desired gas mixing ratio was stably obtained. However, it is also possible to form these two types of films in one chamber. Needless to say, sharing the chamber can reduce the cost of the device.

Next, as shown in FIG. 17C, the SiN
_A resist film 206 was applied on the _x film 205. The refractive index (real part) of this resist film with respect to KrF excimer laser light is 1.8, and the extinction coefficient is 0.02. Then Figure 1
As shown in FIG. 7 (d), the resist film 206 was irradiated with the exposure light 208 through the mask 207 by a usual method. Here, KrF excimer laser light was used as the exposure light. Although not shown in the figure, a reduction projection exposure method with a lens numerical aperture of 0.45 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure may be used.

Next, as shown in FIG. 17E, development was performed by a usual method to form a resist pattern 206a. After that, as shown in FIG. 17F, the SiNx antireflection film 205 and the Si film 204 were etched using the resist pattern 206a as a mask to form a resist pattern 209 including the antireflection film processing on the substrate.

When a pattern of 0.25 μm was formed by using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 10% even if the absorption coefficient was optimized. When pattern detection for alignment was performed through this antireflection film, a sufficient pattern detection signal was obtained. This is because this antireflection film has a sufficient light shielding property for KrF excimer laser light, but a transmittance of 95% or more is obtained for light having a wavelength longer than 540 nm which is pattern detection light. This is one of the features when the SiN _x / Si two-layer antireflection film is used.

Although the case where the thickness of the Si film is 0.025 μm is shown here, the Si film is not limited to this thickness and may be thicker than this. Further, as is clear from FIG. 18 showing the change of the reflectance with respect to the film thickness of the SiN _x film, by controlling the film thickness of the SiN _x film in the range of 0.017 to 0.039 μm, the conventional An antireflection effect is obtained.

(Embodiment 12) A twelfth embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 19A, 0.3 μm is formed on the Si wafer 221 having a step.
A substrate was prepared in which an Al film 222 (containing 2% of Si) having a thickness of m 2 was deposited, and PSG (phosphorus-doped glass) 223 was further deposited thereon. Here, the PSG film thickness was 0.3 μm in a thin place and 0.6 μm in a thick place due to the influence of the substrate step. The PSG film is transparent to the KrF excimer laser light.

Next, as shown in FIG. 19B, a SiO _x N _y H _z film 224 was formed on the PSG film by a plasma CVD method. A mixed gas of silane and nitrous oxide was used for the formation of the SiO _x N _y H _z film, and a mixed gas ratio with which the extinction coefficient for KrF excimer laser light was 1.8 was used. The refractive index (real part) at this time was 2.2. The film thickness is 0.025μ
m. The transmittance of KrF excimer laser light of this film is 10% or less (energy ratio), and the reflected light from the substrate goes back and forth through this film and returns to the resist film, so that it becomes a sufficient light-shielding film.

Thereafter, a film thickness of 0.0 is formed on the light shielding film 224.
A 27 μm SiO _x N _y H _z film 225 was formed by plasma CVD. A mixed gas of silane and nitrous oxide was used for the formation of the SiO _x N _y H _z film as in the case of the film 224. In this case, the extinction coefficient for KrF excimer laser light is uniformly 0. A mixed gas ratio of 7 was used. The refractive index (real part) at this time was 2.1. Since it is a CVD film, the film can be deposited with a uniform film thickness even if there is a step on the substrate, and the film thickness controllability is high. This is an advantage when using the CVD method.

By the two-layer antireflection film composed of the films 224 and 225, the reflectance of KrF excimer laser light was 0.02% or less (energy ratio) irrespective of the location, which was almost non-reflection.

Next, as shown in FIG.
A resist film 226 was applied on the O _x N _y H _z film 225.
The resist film used here has a refractive index of 1.8 and an extinction coefficient of 0.02 for KrF excimer laser light. Thereafter, as shown in FIG. 19D, the mask 22 is formed by a normal method.
The resist film 226 was irradiated with the exposure light 228 through the No. 7 film. Here, KrF excimer laser light was used as the exposure light. Although not shown in the figure, a reduction projection exposure method with a lens numerical aperture of 0.45 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure may be used.

Next, as shown in FIG. 19E, development was performed by a usual method to form a resist pattern 226a. Thereafter, as shown in FIG. 19F, the SiO _x N _y H _z antireflection film 22 is formed using the resist pattern 226a as a mask.
4, 225 were etched to form a resist pattern 229 including antireflection film processing on the substrate.

When a 0.25 μm pattern was formed by using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional CVD type antireflection film having a thickness of 0.052 μm was used, the dimensional accuracy could not be improved from 10% no matter how the absorption coefficient was optimized.

(Embodiment 13) An embodiment of the present invention will be described below with reference to FIG. 20, which is a process chart. First, FIG. 20 (a)
As shown in FIG. 3, an oxide film 232 (gate oxide film) having a thickness of 4.5 nm was formed on the Si wafer 231, and a polysilicon film 233 having a thickness of 0.3 μm was further formed thereon. Then, phosphorus was diffused into polysilicon to form polysilicon as a conductive film. On top of that, an HLD (H
igh temperature Low pressure Decomposition) film 23
4 was formed.

After that, as shown in FIG. 20B, a Si film 235 (light-shielding film) having a thickness of 0.025 μm is formed on the HLD film 234 by a DC sputtering method using Si as a target and an atmosphere gas of Ar. . The refractive index of this film for KrF excimer laser light was 2.3, and the extinction coefficient was 2.8. As in Example 1, the transmittance of KrF excimer laser light of this film is 3% or less (energy ratio), and the reflected light from the substrate travels back and forth through this film to return to the resist film, so that it becomes a sufficient light-shielding film. . This Si film serving as the light-shielding film may be thicker than this.

Thereafter, a film thickness of 0.025 μm is formed on the Si film.
The SiN _x film 236 (interference reflection preventing film) of m ₂ was formed by the DC sputtering method using Si as a target and using N ₂ and Ar gas as atmosphere gas. Here, as in Example 11, the gas mixture ratio was adjusted such that the SiN _x film had a refractive index (real part) of 2.3 with respect to KrF excimer laser light and an extinction coefficient of 0.6. The two-layer film including the Si film 235 and the SiNx film 236 serves as an antireflection film. After that, the SiN _x film 236 is formed.
A resist film 237 was applied and formed thereon. The refractive index (real part) of the resist film with respect to KrF excimer laser light is 1.8, and the extinction coefficient is 0.02.

Next, as shown in FIG. 20C, the resist film 2 is exposed to the exposure light 239 through the mask 238 by a usual method.
Irradiate 37. Here, KrF excimer laser light was used as the exposure light. Although not shown in the figure, a reduction projection exposure method with a lens numerical aperture of 0.45 was used for this exposure.
However, this is one experimental condition, and for example, proximity exposure may be used.

Next, as shown in FIG. 20D, development was performed by a usual method to form a resist pattern 237a. Thereafter, as shown in FIG. 20E, the SiN _x antireflection film 236, S is formed using the resist pattern 237a as a mask.
The i film 235 and the HLD film 234 are etched to form Si.
N _x pattern 236a, Si pattern 235a and HL
D pattern 234a was formed. After that, as shown in FIG. 20F, the resist pattern 237a was removed by a usual method.

[0112] Then SiN as shown in Figure 20 (g) _x
The polysilicon film 233 was etched using the pattern 236a, the Si pattern 235a and the HLD pattern 234a as a mask to form a gate wiring pattern 233a. At this time, the Si film 235a and the SiN _x film 236a, which have a small film thickness and a small etching rate difference from polysilicon, were simultaneously removed during this etching. Thus, it is one of the features when this material is used that the antireflection film can be removed without a special removal process. This feature can be obtained not only in the case of the polysilicon gate wiring film, but also in the case of using a tungsten silicide film, a tungsten polycide film, or a laminated film thereof including polysilicon.

When a gate wiring pattern having a width of 0.25 μm was formed by this method, a dimensional accuracy of 5% was obtained.
On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 10% even if the absorption coefficient was optimized.

(Embodiment 14) As in Embodiment 11, a 0.2 μm-thick W film is deposited on a Si wafer having steps, and SOG (Spin on Glass) is further deposited thereon. The prepared substrate was prepared. Here, due to the influence of the substrate step, SOG
The film thickness is 0.2μm in thin places and 0.5μ in thick places
was m. The SOG film is i-line (wavelength 365n
It is transparent to m).

Next, a Si film (light-shielding antireflection film) is formed on the SOG film.
With Si as the target and Ar as the atmospheric gas
It was formed by the sputtering method. The thickness of this Si film is 0.025
μm. The refractive index (real part) of the film with respect to i-line was 4.6, and the extinction coefficient was 2.7. The i-line transmittance of this film is 10% or less (energy ratio), and the reflected light from the substrate travels back and forth through this film to return to the resist film, so that it becomes a sufficient light-shielding film.

Then, a film thickness of 0.029 μm is formed on the Si film.
A SiN _x film (interference reflection preventing film) of m was formed by a DC sputtering method using Si as a target and N ₂ and Ar gas as atmosphere gases. Here, the gas mixture ratio was adjusted so that the refractive index (real part) for the i-line of this SiN _x film was 2.8 and the extinction coefficient was 0.4. This film thickness and refractive index are the antireflection conditions for the interference film. With this anti-reflection film composed of the SiN _x / Si bilayer film, the reflectance of the i-line, which is the exposure light, does not depend on the location (irrespective of the film thickness of the SOG or the step difference).
Almost no reflection was possible at 0.2% or less (energy ratio).

Next, a resist film was formed by coating on the SiN _x film. The refractive index (real part) of the resist film with respect to i-line is 1.7, and the extinction coefficient is 0.00. Then, the resist film was irradiated with the exposure light through a mask by a usual method.
Here, i-line was used as the exposure light. Next, development was performed by a usual method to form a resist pattern.

After that, using the resist pattern as a mask, SiN
_The antireflection film and the Si film were etched to form a resist pattern including the antireflection film processing on the substrate.

When a 0.35 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 15% even if the absorption coefficient was optimized. The case where the SiN _x film has a thickness of 0.029 μm is shown here, but when the film thickness can be increased to 0.1 μm, the refractive index thereof is 2.6.
By setting the extinction coefficient to 0.2, the reflectance is 0.1%
And I was able to make it even smaller.

(Embodiment 15) Si in which a step is formed
A W film having a thickness of 0.2 μm was deposited on the wafer, and HLD was further deposited thereon to a thickness of 1 μm to prepare a substrate. And C
The surface was flattened by MP (Chemical Mechanical Polishing). Although the surface became flat, the film thickness of the HLD was 0.5 μm in a thin place and 0.75 μm in a thick place due to the influence of the substrate step. Note that the HLD film has an i-line (wavelength 365
nm) is transparent.

Next, a Si film (light-shielding antireflection film) is formed on the HLD film.
With Si as the target and Ar as the atmospheric gas
It was formed by the sputtering method. The thickness of this Si film is 0.025
μm. The refractive index (real part) of the film with respect to i-line was 4.6, and the extinction coefficient was 2.7. The i-line transmittance of this film is 10% or less (energy ratio), and the reflected light from the substrate travels back and forth through this film to return to the resist film, so that it becomes a sufficient light-shielding film.

After that, BA that is ARC is formed on the Si film.
RL-i (Hoechst trade name) was applied, and ordinary heat treatment was performed. The film thickness was 0.06 μm. This BARL-
The extinction coefficient of i with respect to the i line was 0.41. The extinction coefficient of the upper antireflection film is smaller than that of the lower antireflection film. With the antireflection film formed of the BARL-i / Si bilayer film, the reflectance of the i-line as the exposure light is 1
% Or less (energy ratio), almost no reflection was achieved.

Next, a resist film was formed by coating on the BARL-i film. I line of this resist film (wavelength 365n
The refractive index (real part) for m) is 1.7, and the extinction coefficient is 0.0
It is 0. Then, the resist film was irradiated with the exposure light through a mask by a usual method. Here, i-line was used as the exposure light. Next, development was performed by a usual method to form a resist pattern. After that, the BARL-i film and the Si film were etched using the resist pattern as a mask to form a resist pattern including an antireflection film processing on the substrate.

When a 0.4 μm pattern was formed by using this antireflection method, a dimensional accuracy of 5% was obtained. on the other hand,
The reflectance was 16% only with BARL-i having a thickness of 0.06 μm, and the reflectance could be only 40% with only the Si film having a thickness of 0.025 μm. That is, the conventional one-layer antireflection film could not obtain the antireflection effect as in this example. In addition, in this two-layer antireflection film, BAR
Even if the film thickness of L-i is as thin as 0.04 μm, the reflectance is 10
Fell below%.

(Embodiment 16) An embodiment of the present invention will be described below with reference to FIG. 21, which is a process chart. First, FIG. 21 (a)
As shown in (1), a substrate was prepared by depositing a W film 312 having a thickness of 0.2 μm on a Si wafer 311 having a step formed thereon, and further depositing an SOG (Spin on Glass) 313 thereon. Here, due to the influence of the substrate step, the SOG film thickness was 0.2 μm in a thin place and 0.5 μm in a thick place.
The SOG film is a KrF excimer laser light (wavelength: 248n).
It is transparent to m).

Next, as shown in FIG. 21B, a Si film 314 (reflection film) was formed on the SOG film by a DC sputtering method using Si as a target and an atmosphere gas of Ar. Si
The film thickness was 0.025 μm. Here, Ar
Although a mixed gas of N ₂ and N ₂ was used, it is not limited to Ar,
Other inert gas such as Xe or Kr may be used. Membrane K
The refractive index (real part) for rF excimer laser light is 2.
3, the extinction coefficient was 2.8. This film is a reflective film that reflects 97% or more (energy ratio) of KrF excimer laser light. After that, a film thickness of 0.025 μm is formed on the Si film.
The SiN _x film 315 (interference antireflection film) was formed by the DC sputtering method using Si as a target and N ₂ and Ar gas as atmosphere gas.

The gas mixture ratio was adjusted so that the SiN _x film had a refractive index (real part) of 2.3 and an extinction coefficient of 0.6 with respect to KrF excimer laser light. This film thickness and refractive index are the antireflection conditions for the interference film.

With this antireflection film composed of the SiN _x / Si bilayer film, the reflectance of the KrF excimer laser light, which is the exposure light, with respect to the resist film does not depend on the location (irrespective of the influence of the SOG film thickness or the step difference). ) 0.01% or less (energy ratio)
And I could make it almost non-reflective. In addition, here, the Si film forming chamber and the SiN _x film forming chamber used different sputtering devices. By using another chamber, a desired gas mixing ratio was stably obtained. However, it is also possible to form these two types of films in one chamber. In this way, sharing the chamber can reduce the cost of the apparatus.

Further, in this embodiment, since the sputtered film is formed in the N ₂ or Ar gas atmosphere, the film does not contain any substance that interacts with the chemically amplified resist utilizing the acid catalytic reaction such as ammonia. 1994 Proceedings
Proceedings of SPIE No. 2
195, pp. 422-446,
It had the feature that defects such as abnormal resist pattern shapes that occurred at the substrate interface were unlikely to occur.

Next, as shown in FIG. 21C, a resist film 316 was applied on the SiN _x film 315. The refractive index (real part) of the resist film with respect to KrF excimer laser light is 1.8, and the extinction coefficient is 0.02. After that, FIG.
As shown in (d), the resist film 316 was irradiated with the exposure light 318 through the mask 317 by a usual method. Here, KrF excimer laser light was used as the exposure light. Although not shown in the figure, the numerical aperture of the lens is 0.4 for this exposure.
5 reduction projection exposure method was used. However, this is one experimental condition, and for example, proximity exposure may be used.

Next, as shown in FIG. 21E, development was performed by a usual method to form a resist pattern 316a. After that, as shown in FIG. 21F, the antireflection film composed of the two-layer film of the SiN _x antireflection film 315 and the Si film 314 is etched using the resist pattern 316a as a mask, and the resist pattern including the antireflection film processing is etched. 319
Was formed on the substrate. Since the etching film thickness was as thin as 0.05 μm even when the SiN _x antireflection film 315 and the Si film 314 were combined, no dimensional shift was observed during etching.

Using the antireflection method of this embodiment, 0.25 μ
When the m 2 pattern was formed, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional antireflection film with a thickness of 0.05 μm is used, the dimensional accuracy is 1 even if the absorption coefficient is optimized.
It could not be improved from 0%. Further, when pattern detection for alignment was performed through the antireflection film composed of this two-layer film, a sufficient pattern detection signal was obtained. This antireflection film has a sufficient light shielding property for KrF excimer laser light, but has a transmittance of 95% for light having a wavelength longer than 540 nm which is pattern detection light.
This is because the above can be obtained. This is one of the features when using the SiN _x / Si two-layer antireflection film.

Although the case where the thickness of the Si film is 0.025 μm is shown here, the Si film is not limited to this thickness and may be thicker than this. Further, as is clear from FIG. 22 showing the change in reflectance with respect to the film thickness of the SiN _x film, by controlling the film thickness of the SiN _x film in the range of 0.017 to 0.039 μm, the conventional antireflection film can be obtained. The above antireflection effect is obtained.

(Embodiment 17) An embodiment of the present invention will be described below with reference to the process chart of FIG. First, FIG. 26 (a)
The organic film 352 was applied on the substrate as shown in FIG. The heat treatment temperature was 150 ° C. The coating film thickness was 0.15 μm on the flat surface, but the film thickness was 0.08 μm in the thin place and 0.23 μm in the thick place due to the influence of the substrate step. As the organic film 352, a methacrylic acid-methacrylic acid 9-anthrylmethyl copolymer, which is a film for bleaching, was used. Si with a step formed on the substrate
A wafer 350 on which a W film 351 having a thickness of 0.2 μm was deposited was used.

Next, as shown in FIG. 26B, a resist film 353 was applied on the organic film 352 by a usual process, and a pre-exposure bake was performed.

Next, as shown in FIG. 26C, the exposure light 356 is exposed to the resist film 35 through the mask 355 in the usual manner.
Irradiate 3. Here, KrF excimer laser light was used as the exposure light. Although the drawing shows the case where the masks are brought close to each other, the exposure may be performed through a lens or a mirror. At this time, the exposure light reaches the organic film 352, the surface side of the exposed portion of the organic film is bleached, and a region 354 where the surface is transparent to the exposure light and the light absorption increases toward the bottom is formed in the organic film 352. Formed in. This automatically forms an absorption distribution in the organic film in which the absorption on the surface side is low and the absorption on the substrate side is high, so that this organic film can be used as an antireflection film.

Next, as shown in FIG. 26 (d), development was carried out according to a usual method to form a resist pattern 353a.

After that, as shown in FIG. 26E, the antireflection film made of the above organic film was etched using the resist pattern 353a as a mask to form a resist pattern 357 including the antireflection film processing on the substrate. . When a 0.25 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained.

On the other hand, a commercially available ARC having a film thickness of 0.15 μm
The dimensional accuracy was 8% when the mold antireflection method (conventional antireflection method) was used. When the thickness of the ARC film is increased, a dimensional shift occurs during etching and the resist pattern collapses.

The feature of this method is that it is possible to automatically provide a light absorption distribution in the antireflection film without performing any special treatment. Therefore, this method is very effective in shortening the process and reducing the cost.

(Embodiment 18) Hereinafter, an embodiment of the present invention will be described with reference to the process chart of FIG. First, FIG. 24 (a)
As shown in FIG. 3, an oxide film 342 (gate oxide film) having a thickness of 4.5 nm was formed on a Si wafer 341, and a W film 343 having a thickness of 0.2 μm was further formed thereon. Furthermore, HLD (High temperature Low pressur
An eDecomposition) film 344 was formed. After that, FIG.
As shown in (b), a thickness of 0.02 is formed on the HLD film 344.
A μm W film 345 (reflection film) was deposited. Kr of this film
The refractive index with respect to F excimer laser light was 3.40, and the extinction coefficient was 2.85. This film has KrF in the air.
It is a reflective film that reflects excimer laser light by 50% or more (energy ratio). This W film, which is a reflection film, may be thicker than this.

Thereafter, a film thickness of 0.028 μ is formed on the W film.
The SiN _x film 346 (interference antireflection film) of m is formed by an RF sputtering method using Si as a target and an atmosphere gas of N ₂ and Ar gas to form an antireflection film composed of a two-layer film of a W film and a SiN x film. did. KrF excimer of this SiN _x film
The light has a refractive index (real part) of 2.3 and an extinction coefficient of 0.6.
The gas mixture ratio was adjusted so that Then SiN _x
A resist film 347 was applied on the film 346. Refractive index of this resist film for KrF excimer laser light (real part)
Is 1.8 and the extinction coefficient is 0.02.

Next, as shown in FIG. 24C, the resist film 347 was irradiated with the exposure light 349 through the mask 348 by a usual method. Here, KrF excimer laser light was used as the exposure light. Although not shown in the figure, a reduction projection exposure method with a lens numerical aperture of 0.45 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure or the like may be used.

Next, as shown in FIG. 24D, development was performed by a usual method to form a resist pattern 347a. Then, as shown in FIG. 24E, the SiN _x antireflection film 346, W is formed using the resist pattern 347a as a mask.
By etching the reflection film 345 and the HLD film 344, S
Pattern 3410 composed of iN _x , W reflective film and HLD
Was formed. The etching rate ratio at this time was 3 for the SiN _x film, 1.3 for the W reflective film and 3 for the HLD film with respect to the resist film 1.

After that, the resist pattern 347a was removed by a usual method as shown in FIG. afterwards,
As shown in FIG. 24 (g), SiN _x , W reflection film and HL
The W film 343 is masked with the pattern 3410 made of D as a mask.
Gate wiring pattern 3 by etching using F ₆ gas
43a was formed. The etching rate ratio at this time is W
With respect to the film 1, the SiN _x was 1.2 and the HLD film was 1. Therefore, the thin W reflective film and the SiN _x interference antireflection film were simultaneously removed during this etching. Here, a microwave etching device was used as the etching device. However, this is one experimental condition, and etching may be performed by using another method. SF ₆ is used as the etching gas here. However, this is an experimental condition, and for example, etching may be performed using a gas such as CF ₄ or NF ₃ .

One of the features of using this material is that the antireflection film can be removed without any special removing process. This feature can be obtained not only in the case of the W gate wiring film, but also in the case of using a tungsten silicide film, a tungsten polycide film, or a laminated film thereof including polysilicon. When a gate wiring pattern having a width of 0.25 μm was formed by this method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 10% even if the absorption coefficient was optimized.

(Example 19) A SOG film (interlayer insulation and planarization film) having a thickness of 0.3 μm was formed on a stepped wafer having a gate formed thereon, and an Al film having a thickness of 0.4 μm was further formed thereon. (Si2% content) was formed. On top of that, HLD (High temperature Low pressure) with a film thickness of 0.2 μm is formed.
Decomposition) film was formed. Then, a 0.04 μm thick Al film (reflection film) was deposited on the HLD film. This film had a refractive index of 0.19 and an extinction coefficient of 2.94 for KrF excimer laser light. This film is K in air
It is a reflective film that reflects 90% or more (energy ratio) of rF excimer laser light. This Al film, which becomes the reflection film, may be thicker than this.

Thereafter, a film thickness of 0.019 is formed on the Al film.
A μm SiO _x N _y H _z film was formed by the plasma CVD method. S
A mixed gas of silane and nitrous oxide was used for forming the iO _x N _y H _z film. In this case, a mixed gas ratio was used such that the extinction coefficient for KrF excimer laser light was 0.9. The refractive index (real part) at this time was 2.48. CV
Since it is a D film, the film can be deposited with a uniform film thickness even if there is a step on the substrate, and the film thickness controllability is high. This is an advantage when using the CVD method.

After that, a resist film was formed by coating on the SiO _x N _y H _z film. The refractive index (real part) of this resist to KrF excimer laser light is 1.8, and the extinction coefficient is 0.02.
Is. Next, the resist was irradiated with exposure light through a mask by a usual method. Here, KrF excimer laser light was used as the exposure light. For this exposure, the numerical aperture of the lens is 0.
45 reduced projection exposure method was used. However, this is one experimental condition, and for example, proximity exposure or the like may be used. Next, development was performed by a usual method to form a resist pattern.

Then, using the resist pattern as a mask, Si
The antireflection film and the HLD film, which are a two-layer film of an O _x N _y H _z film and an Al reflective film, are etched to form a SiO _x N _y H _z film, A
A pattern composed of an I film and an HLD film was formed. Then, the resist pattern was removed by a usual method. After that, the Al wiring pattern was formed by etching the Al film having a thickness of 0.4 μm using the pattern composed of the SiO _x N _y H _z film, the Al film and the HLD film as a mask. At this time, the thin Al film
The antireflection film consisting of the reflection film and the two-layer film of the SiO _x N _y H _z interference film was simultaneously removed during this etching. One of the features of using this material is that the antireflection film can be removed without any special removal process.

These antireflection effects can be obtained not only in the case of the Al wiring film but also in the case of using the Ti film, the Ta film or the Pt film. However, since the Al film has a particularly high reflectance of the material itself. , Is more effective than other materials. When a wiring pattern having a width of 0.25 μm was formed by the method of this embodiment, a dimensional accuracy of 5% was obtained.

On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 10% even if the absorption coefficient was optimized.

(Embodiment 20) As in Embodiment 16, an Al film having a thickness of 0.2 μm is deposited on a Si wafer having steps formed thereon, and an SOG (Spin on Glass) film is further deposited thereon. The attached substrate was prepared. Here, the thickness of the SOG film was 0.2 μm in a thin place and 0.5 μm in a thick place due to the influence of the substrate step. The SOG film is transparent to KrF excimer laser light (wavelength 248 nm). Then S
An Al film (reflection film) was deposited on the OG film. The thickness of this Al film was 0.041 μm. The refractive index (real part) of the film with respect to KrF excimer laser light was 0.19, and the extinction coefficient was 2.94. This film is a reflective film having a reflectance of KrF excimer laser light in the air of 90% or more (energy ratio). After that, a film thickness of 0.01 is formed on the Al film.
A 9 μm SiN _x film (interference antireflection film) was formed by a DC sputtering method using Si as a target and N ₂ and Ar gas as atmosphere gases, to form an antireflection film composed of a two-layer film of an Al film and a SiN x film. Here, the gas mixture ratio was adjusted so that the SiN _x film had a refractive index (real part) to KrF excimer laser light of 2.48 and an extinction coefficient of 0.9. This film thickness and refractive index are the antireflection conditions for the interference film.

By the antireflection film formed of the SiN _x / Al bilayer film, the reflectance of the KrF excimer laser light, which is the exposure light, with respect to the resist film does not depend on the location (irrespective of the influence of the SOG film thickness and steps). Almost no reflection was possible at 0.01% or less (energy ratio). Next, a resist film was formed by coating on the SiN _x film. The refractive index (real part) of the resist film with respect to KrF excimer laser light is 1.8, and the extinction coefficient is 0.02. Then, the resist film was irradiated with the exposure light through a mask by a usual method. Here, KrF excimer laser light was used as the exposure light. A reduction projection exposure method with a numerical aperture of 0.45 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure or the like may be used.

Next, development was carried out by a usual method to form a resist pattern. After that, the SiN _x antireflection film and the Al film were etched using the resist pattern as a mask to form a resist pattern including the antireflection film processing on the substrate. When a 0.25 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, FIG. 25 showing changes in reflectance with respect to the film thickness of the Al film.
As is clear from the above, when the thickness of the Al film is 0.04 μm or more, a sufficient antireflection effect can be obtained.

When a conventional antireflection film having a thickness of 0.06 μm is used, the dimensional accuracy is 1 even if the absorption coefficient is optimized.
It could not be improved from 0%. A Pt film could be used instead of the Al reflective film.

(Example 21) As in Example 16, a 0.3 μm thick W film (containing 2% of Si) was deposited on a Si wafer having steps, and PSG (phosphorus added) was further deposited on the W film. A substrate coated with (glass) was prepared. Here, the PSG film thickness was 0.3 μm in a thin place and 0.6 μm in a thick place due to the influence of the substrate step. The PSG film is made of Kr
It is transparent to F excimer laser light. Next, a W film was deposited on the PSG film. The W film had a refractive index (real part) of 3.4 with respect to KrF excimer laser light and an extinction coefficient of 2.85. The film thickness was 0.02 μm. The reflectance of KrF excimer laser light in the air of this film was 50% or more (energy ratio).

Then, a film thickness of 0.034 is formed on the reflective film.
A μm SiO _x N _y H _z film was formed by a plasma CVD method to form an antireflection film consisting of a two-layer film of a W film and a SiOxNyHz film. The SiO _x N _y H _z film was formed using a mixed gas of silane and nitrous oxide. In this case, a mixed gas ratio was used such that the extinction coefficient for KrF excimer laser light was 0.6. The refractive index (real part) at this time was 2.08. Since it is a CVD film, the film can be deposited with a uniform film thickness even if there is a step on the substrate, and the film thickness controllability is high. This is an advantage when using the CVD method. The antireflection film composed of the SiO _x N _y H _z / W bilayer film makes the reflectivity of KrF excimer laser light to the resist film 0.01% or less (energy ratio) regardless of the location, which makes the film almost non-reflective. did it.

Next, a resist film was formed by coating on the SiO _x N _y H _z film. The resist film used here has a refractive index of 1.8 with respect to KrF excimer laser light and an extinction coefficient of 0.02. Then, the resist film was irradiated with the exposure light through a mask by a usual method. Here, KrF excimer laser light was used as the exposure light. A reduction projection exposure method with a numerical aperture of 0.45 was used for this exposure. However, this is one experimental condition, and for example, proximity exposure or the like may be used.

Next, development was carried out by a usual method to form a resist pattern. Then, the antireflection film composed of the SiO _x N _y H _z film and the W film was etched using the resist pattern as a mask to form a resist pattern including the antireflection film processing on the substrate. When a 0.25 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, the conventional C with a film thickness of 0.054 μm
When the VD type antireflection film was used, the dimensional accuracy could not be improved from 10% no matter how the absorption coefficient was optimized.

(Embodiment 22) As in Embodiment 16, a 0.2 μm-thick W film is deposited on a Si wafer having steps, and SOG (Spin on Glass) is further deposited thereon. The prepared substrate was prepared. Here, due to the influence of the substrate step, SO
The thickness of G is 0.2 μm in a thin place and 0.5 in a thick place.
was μm. The SOG film is i-line (wavelength 365n
It is transparent to m). Next, a Si film (reflection film) was formed on the SOG film by a DC sputtering method using Si as a target and an atmosphere gas of Ar. The thickness of this Si film is 0.0
It was set to 25 μm. Refractive index of this film for i-line (real part)
Was 4.6 and the extinction coefficient was 2.7. The reflectance of i-line in the air of this film is 50% or more (energy ratio).

Thereafter, a film thickness of 0.029 is formed on the Si film.
A SiN _x film (interference film) of μm was formed by a DC sputtering method using Si as a target and an atmosphere gas of N ₂ and Ar gas to form an antireflection film composed of a two-layer film of a Si film and a SiN x film. Here, the refractive index of the SiN _x film for i-line (real part)
Was adjusted to 2.8 and the extinction coefficient was 0.4. This film thickness and refractive index are the antireflection conditions for the interference film. The reflectance of the i-ray light, which is the exposure light, with respect to the resist film is 0.2% or less irrespective of the location (irrespective of the SOG film thickness or the step difference) by the antireflection film including the SiN _x / Si bilayer film. (Energy ratio) and almost no reflection was possible.

Next, a resist film was formed by coating on the SiN _x film. The refractive index (real part) of the resist film with respect to i-line is 1.7, and the extinction coefficient is 0.00. Then, the resist film was irradiated with the exposure light through a mask by a usual method. Here, i-line was used as the exposure light. Next, development was performed by a usual method to form a resist pattern.

Then, using the resist pattern as a mask, Si
The antireflection film composed of the N _x film and the Si film was etched to form a resist pattern including the antireflection film processing on the substrate. When a 0.35 μm pattern was formed using this antireflection method, a dimensional accuracy of 5% was obtained. On the other hand, when the conventional antireflection film having a thickness of 0.05 μm was used, the dimensional accuracy could not be improved from 15% even if the absorption coefficient was optimized. Although the thickness of the SiN _x film is 0.029 μm here, the refractive index should be 2.6 and the extinction coefficient should be 0.2 if the thickness can be increased to 0.1 μm. As a result, the reflectance could be further reduced to 0.1%.

[0165]

EFFECTS OF THE INVENTION An extremely high antireflection effect can be obtained on various substrates such as a substrate having a transparent film interposed therebetween and a substrate having a high reflectance such as a metal film without any problem of the aspect ratio during processing of the antireflection film. By this method, a fine and highly accurate resist pattern can be formed. Therefore, the yield and reliability of the element to be manufactured are improved. Furthermore, when applied to logic LSIs, gates can be made with high dimensional accuracy and their operating speed is increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing a process of a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing a problem of a conventional method (coherent antireflection method).

FIG. 3 is a conceptual diagram showing problems of the conventional method (ARC method).

FIG. 4 is a conceptual diagram showing characteristics of the antireflection film of the present invention.

FIG. 5 is a characteristic diagram showing light absorption characteristics in the antireflection film of the present invention.

FIG. 6 is a characteristic diagram showing light absorption characteristics in the antireflection film of the present invention.

FIG. 7 is a sectional view showing a process of the second embodiment of the present invention.

FIG. 8 is a sectional view showing a process of the third embodiment of the present invention.

FIG. 9 is a sectional view showing a process of the fourth embodiment of the present invention.

FIG. 10 is a sectional view showing a process of the fifth embodiment of the present invention.

11 is a characteristic diagram of light absorption of the antireflection film in Example 3. FIG.

FIG. 12 is a process drawing showing a sixth embodiment of the present invention.

FIG. 13 is a configuration diagram showing a configuration of a projection exposure apparatus which realizes the present invention.

FIG. 14 is a cross-sectional view showing the method of manufacturing a semiconductor device of the present invention.

FIG. 15 is a plan view of main patterns forming a semiconductor device of the present invention.

FIG. 16 is a conceptual diagram showing the features of the tenth embodiment.

FIG. 17 is a process drawing showing the eleventh embodiment of the present invention.

FIG. 18 is a characteristic diagram showing an antireflection effect in Example 11.

FIG. 19 is a process drawing showing a twelfth embodiment of the present invention.

FIG. 20 is a process drawing showing a thirteenth embodiment of the present invention.

FIG. 21 is a process drawing showing the 16th embodiment of the present invention.

22 is a characteristic diagram showing the antireflection effect in Example 16. FIG.

FIG. 23 is a diagram showing a relationship between extinction coefficient and reflectance.

FIG. 24 is a process drawing showing the eighteenth embodiment of the present invention.

FIG. 25 is a characteristic diagram showing an antireflection effect in Example 20.

FIG. 26 is a process drawing showing the 17th embodiment of the present invention.

FIG. 27 is a diagram showing changes in refractive index and extinction coefficient with changes in x and y of a SiOxNyHz film and x of SiNx.

FIG. 28 is a diagram showing an example of dimensional accuracy with respect to reflectance.

[Explanation of symbols]

1 ... Substrate, 2 ... Organic film, 3 ... HCl gas, 4 ... Resist, 4a ... Resist pattern, 5 ... Mask, 6 ... Exposure,
7 ... A resist pattern including antireflection film processing. 20 ...
Antireflection film, 21 ... Film thickness of antireflection film at step, 22
... the thickness of the antireflection film in the flat portion, 30 ... the antireflection film (A
RC film), 31 ... ARC film thickness, 32 ... ARC film thickness, 33 ... ARC film thickness at flat portion, 34 ... step upper portion, 35 ... step lower portion. 41 ... Absorption adjusting light, 42 ... Substrate,
43 ... Antireflection part having absorption gradient, 44 ... Antireflection part having constant light absorption, 51 ... Absorption characteristic of antireflection film, 61
... Absorption characteristics of the antireflection film formed on the step, 62 ...
Absorption characteristics of the antireflection film formed under the step. 110 ...
Si wafer, 111 ... Al film, 112 ... Organic film, 113
... entire exposure light (absorption adjusting light), 114 ... transparent layer,
115 ... resist, 115a ... resist pattern, 11
6 ... Mask, 117 ... Exposure light, 118 ... Resist pattern including antireflection film processing, 172 ... Element isolation region, 1
73, 182, 187 ... Word line, 176, 183, 1
88 ... Data line, 180 ... Plate electrode, 178, 18
5, 190 ... Storage electrode. 508 ... Projection lens, 512 ...
XY stage, 501 ... Light source, 506 ... Mask, 509
... Wafer, 201 ... Si wafer, 202 ... W, 203
... SOG, 204 ... Si film (lower antireflection film), 205
... SiN _x film (upper antireflection film), 206, 226, 2
37 ... Resist, 206a, 226a, 237a ... Resist pattern, 207, 227, 238 ... Mask, 20
8, 228, 239 ... Exposure light, 209, 229 ... Resist pattern including anti-reflection film processing, 221, 231
... Si wafer, 222 ... Al, 223 ... PSG, 22
4, 225 ... SiO _x N _y H _z film, 232 ... Oxide film, 2
33 ... Polysilicon, 233a ... Gate wiring pattern
(Polysilicon pattern), 234 ... HLD film, 234a
... HLD pattern, 235 ... Si film, 235a ... Si pattern, 236 ... SiN _x film, 236a ... SiN _x pattern, 311 ... Si wafer, 312 ... W, 313 ... SO
G, 314 ... Si film (reflection film), 315 ... SiN _x film (antireflection film), 316 ... Resist, 316a ... Resist pattern, 317 ... Mask, 318 ... Exposure light, 319
... resist pattern.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01L 21/314 H01L 21/314 M 21/30 574 (56) Reference JP-A-7-326608 (JP, A) JP-A 6-138664 (JP, A) JP-A-5-43540 (JP, A) JP-A-62-136027 (JP, A) JP-A-4-234109 (JP, A) JP-A-6-242596 (JP, A) A) Tokuyo HEI 8-501190 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/027 G03F 7/11 503 H01L 21/312 H01L 21/314

Claims (6)

(57) [Claims] 1. A step of forming an antireflection film on a substrate on which a thin film transparent to exposure light is formed, a step of forming a photosensitive thin film on the antireflection film, and the photosensitive thin film. And a step of developing the exposed photosensitive thin film, wherein the antireflection film has a light absorption coefficient gradient in the film thickness direction with respect to the exposure light. A method for manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein a light absorptance of the antireflection film with respect to the exposure light is larger on the substrate surface side than on the photosensitive thin film surface side. . 3. The method of manufacturing a semiconductor device according to claim 1, wherein the antireflection film contains a light absorbing agent that volatilizes from the film surface by heat treatment. 4. The method according to claim 1, wherein the step of forming the antireflection film has a property of absorbing the exposure light and the absorption adjusting light, and the exposure is performed by applying a heat treatment after the irradiation of the absorption adjusting light. The step of depositing a thin film also having a property that the absorption capacity for light is reduced on the substrate, irradiating the thin film with the absorption adjusting light, and the absorption rate of the exposure light on the surface side of the thin film from the deep part of the thin film. And a step of reducing the size of the semiconductor device. 5. A substrate on which a thin film is formed is transparent to exposure light, a step of forming a thin film containing nitrone, irradiating the absorption adjustment light on the thin film, the thin film hydrogen chloride Placing in a gas atmosphere, then forming a photosensitive thin film on the thin film, exposing the photosensitive thin film to a desired pattern with exposure light, and developing the exposed photosensitive thin film A method of manufacturing a semiconductor device, comprising: 6. A thin film formed on a substrate which is transparent to exposure light, a step of forming a thin film containing a diazonium salt and phenol, comprising the steps of irradiating the absorption adjust light on the thin film, the thin film In an alkali vapor atmosphere, then forming a photosensitive thin film on the thin film, exposing the photosensitive thin film with a desired pattern by exposure light, and exposing the exposed photosensitive thin film. And a step of developing the semiconductor device.