JP3540503B2 - Pattern formation method - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pattern forming method.
[0002]
[Prior art]
Conventionally, during the manufacture of a semiconductor device or the like, for example, in the step of forming an electrode, if wet etching is used, the electrode size and shape may change due to undesired over-etching of the electrode metal. The lift-off technique is used in the forming step and the like.
[0003]
FIG. 3 is a diagram illustrating an example of a pattern forming method used in a conventional lift-off technique.
[0004]
First, as shown in FIG. 3A, after a polymer material film 52 such as a photoresist or polyimide is formed on the upper surface of a semiconductor crystal body 51, a metal film 53 such as Al or Au is formed using a vacuum deposition technique. An opening 53a is formed in the metal film 53 using a photolithography technique and an etching technique.
[0005]
Next, as shown in FIG. 3B, using the metal film 53 having the opening 53a as a mask, the polymer material film 52 is etched away by side etching using an oxygen plasma etching technique or the like, and the overhang portion 54a is formed. Is formed.
[0006]
Thereafter, although not shown, a metal film as a material for an electrode such as Au is formed on the semiconductor crystal body 51 through the pattern 54 by using a vacuum deposition technique, and then the pattern 54 is removed to obtain a predetermined shape. And the like.
[0007]
Next, FIG. 4 is a diagram showing another example of a pattern forming method used in a conventional lift-off technique.
[0008]
First, as shown in FIG. 4A, after a quinonediazide-based positive photoresist film 62 is formed on the upper surface of a semiconductor crystal 61, ultraviolet light is exposed through a photomask 63.
[0009]
Next, as shown in FIG. 4B, heat treatment or monochlorobenzene treatment is performed to transform the vicinity of the surface of the unexposed portion into a resistance-improved portion 64 having improved resistance to a developing solution.
[0010]
Thereafter, as shown in FIG. 4C, the photoresist film 62 is developed to form a pattern 65 having an overhang portion 65a.
[0011]
Thereafter, similarly to the conventional example shown in FIG. 3, an electrode or the like having a predetermined shape is manufactured using the pattern 64.
[0012]
FIG. 5 shows another example of a pattern forming method used in the conventional lift-off technique.
[0013]
First, as shown in FIG. 5A, a first positive photoresist film 72 having sensitivity to ultraviolet rays and a second positive photoresist film 73 having sensitivity to far ultraviolet rays are formed on the upper surface of a semiconductor crystal 71. Are formed in this order.
[0014]
Next, as shown in FIG. 5B, an opening 73a is formed in the second positive photoresist film 73 by a photolithography technique and an etching technique using far ultraviolet light having a wavelength of 250 nm, for example.
[0015]
Thereafter, as shown in FIG. 5C, the first positive photoresist film 72 is exposed to ultraviolet light having a wavelength of, for example, 480 nm using the second positive photoresist film 73 having the opening 73a as a mask. The first positive photoresist film 72 is developed and removed so as to be side-etched to form a pattern 74 having an overhang portion 74a.
[0016]
Thereafter, similarly to the conventional example shown in FIG. 3, an electrode or the like having a predetermined shape is manufactured using the pattern 74.
[0017]
[Problems to be solved by the invention]
However, in the case of the conventional example shown in FIG. 3, it is difficult to accurately form the thickness of the metal film 53 constituting the overhang portion 54a and the opening 53a of the metal film 53. In addition to the problem that it is difficult to form the film into a predetermined shape, there is a problem that the manufacturing process is complicated.
[0018]
In addition, in the case of the conventional example shown in FIG. 4, the reproducibility of the production of the resistance-improved portion by heat treatment or monochlorobenzene treatment is low, and the overhang portion 65a formed of the resistance-improved portion is thin and has a very small heat capacity. There is a problem in that it is easily deformed by heat and it is therefore difficult to form a metal film such as an electrode into a predetermined shape.
[0019]
In the case of the conventional example shown in FIG. 5, since two types of exposure light, ultraviolet light and far ultraviolet light, are necessary, there is a problem that the manufacturing process is complicated, and a second light sensitive to far ultraviolet light. Since the resist film 73 has a low effect of blocking ultraviolet rays, the first resist film 72 is exposed to ultraviolet rays using the second resist film 73 as a mask, and the overhang portion 74a formed by development is controlled to a predetermined shape. There was a problem that it was difficult.
[0020]
The present invention has been made in view of the above problems, and has as its object to provide a method for forming a photoresist pattern that is simple and highly accurate.
[0021]
[Means for Solving the Problems]
The pattern forming method of the present invention comprises the steps of forming a positive photoresist film and a negative photoresist film made of a synthetic rubber-based material in this order on a material body, and forming the negative photoresist film on a predetermined portion of the negative photoresist film. Irradiating an ultraviolet light as a photosensitive photoresist film exposure light, selectively developing and removing the negative photoresist film to pattern it into a predetermined shape, and removing the patterned negative photoresist film. a mask, the a positive photoresist film with a said positive photoresist film photosensitive optical, the same wavelength as the negative photoresist film photosensitive optical, and said negative photoresist film is an effect of shielding A step of irradiating with ultraviolet light, and a resist pattern having an overhang portion by selectively developing and removing the positive photoresist film. And having a step of forming a. Note that the material body is not limited to a semiconductor substrate or a semiconductor substrate on which semiconductor layers are stacked, and can be applied to various materials such as a glass plate.
[0022]
According to the present invention, since a pattern having an overhang portion is formed by a resist, the resist can be easily manufactured by a general photolithography technique or the like, and the resist can be selectively etched compared to a metal, so that undesired side etching is performed. Can be suppressed.
[0023]
Moreover, since the negative type photoresist film on the positive type photoresist film, which is of the opposite type to the positive type, has an effect of blocking the light for exposure of the positive type photoresist film, the negative type photoresist film can be accurately applied to a predetermined portion of the positive type photoresist film. Exposure can be performed, so that the exposed portion can be developed and removed with high accuracy.
[0024]
In addition, the negative photoresist film can be made thicker in the overhang portion as compared with the conventional example in which a resistance-improved portion is produced by changing the quality, so that when forming a metal film such as an electrode through a resist pattern, Deformation of the overhang portion due to undesired heat applied to the overhang portion of the resist pattern can be suppressed.
[0025]
Therefore, the present invention can provide a simple and accurate method for forming a photoresist pattern.
[0026]
In addition, in the present invention, it is possible to use light having the same wavelength as the light for exposure of the positive type and negative type photoresist film, and it is possible to further simplify the manufacturing process.
[0027]
In particular, the patterned negative photoresist film blocks the light for exposure of the positive photoresist film by 30% or more.
[0028]
In this case, when exposing the positive-type photoresist film, the patterned negative-type photoresist film that shields by 30% or more functions as a good mask, and thus is preferable.
[0029]
Further, the light for negative photoresist film exposure and the light for positive photoresist film exposure are light of the same wavelength range from the same light source.
[0030]
In this case, since light of the same wavelength range from the same light source can be used for the negative and positive photoresist films, a pattern can be formed with a simple apparatus and a simple manufacturing process.
[0031]
Particularly, the negative photoresist film is made of a synthetic rubber material.
[0032]
The negative photoresist film made of the synthetic rubber material is thermally stable and can cut, for example, ultraviolet light as photosensitive light by 50% or more. Therefore, since the deformation of the overhang portion due to undesired heat can be satisfactorily suppressed, and it functions well as a mask for the positive type photoresist film photosensitive light, the negative type photoresist film made of this synthetic rubber material is preferable. .
[0033]
In particular, the blocking rate of a negative photoresist film made of a synthetic rubber material against ultraviolet light increases substantially in proportion to the film thickness, and sufficient thickness can be easily cut by setting the film thickness. The light is preferably ultraviolet light.
[0034]
Further, the positive photoresist film is made of a quinonediazide-based material.
[0035]
The positive-type photoresist film made of this quinonediazide-based material can be easily removed by an alcohol such as methyl alcohol or an organic solvent such as acetone without using a special removing solution, so that a lift-off process can be easily performed, which is preferable.
[0036]
The lift-off technique using the pattern forming method according to the present invention is not limited to a step of forming an electrode of a semiconductor element such as formation of source and drain electrodes of a field effect transistor and the like, and a step of selecting an insulating film such as a silicon oxide film and a silicon nitride film. It can be used in various processes such as a forming process and a process of forming wiring on a semiconductor substrate.
[0037]
BEST MODE FOR CARRYING OUT THE INVENTION
A lift-off process using a pattern forming method according to an embodiment of the present invention will be described in detail with reference to FIG.
[0038]
First, as shown in FIG. 1A, on a main surface of a semiconductor crystal (material) 1 such as a GaAs semiconductor substrate, a quinonediazide-based photoresist as a positive photoresist, in this embodiment, a product name OFPR8600 (Tokyo) Is applied by spin coating, and baked at 110 ° C. for 40 minutes to form a first photoresist film 2 having a thickness of 1.5 μm.
[0039]
Next, as shown in FIG. 1B, on the first photoresist film 2, a synthetic rubber-based photoresist as a negative photoresist, in this embodiment, Waycoat [way coat] (COG Microelectronic Materials Inc.) is baked at 80 ° C. for 20 minutes to form a second photoresist film 3 having a thickness of 0.8 μm.
[0040]
Subsequently, as shown in FIG. 1 (c), an ultraviolet light having a wavelength of 480 nm as a second photoresist film exposure light is irradiated with a second photo resist under the conditions of a light amount of 10 mW and a time of 15 seconds through a photo mask (not shown). After irradiating the resist film 3 (after the photolithography step), the second photoresist film 3 is formed into a rectangular shape on the upper surface by developing with a dedicated developer for the second resist film and removing the non-irradiated portion. Pattern.
[0041]
Thereafter, as shown in FIG. 1 (d), using the patterned second photoresist film 3 as a mask, the first photoresist film 2 is exposed to the same wavelength as the first photoresist film photosensitive light using the second photoresist film 3 as a mask. After irradiating 480 nm ultraviolet light to the first resist film 2 under the second resist film 3 for a predetermined amount by diffraction action with a light amount of 10 mW and a time of 100 seconds, the liquid temperature is changed with a dedicated developer for the first resist film. By developing at 25 ° C. for 60 seconds to remove the irradiated portion, the surface of the material body 1 is exposed, and the area of the first photoresist film 2 is smaller than that of the second photoresist film 3. Form. As a result, the resist pattern 4 including the first and second photoresist films 2 and 3 has a protrusion of the second photoresist film 3 from the first photoresist film 2 to be an overhang portion 4a. Become.
[0042]
Subsequently, as shown in FIG. 1E, an electrode metal film 5 is formed on the substrate 1 in a state substantially perpendicular to the substrate with the resist pattern 4 interposed therebetween. In this embodiment, as the electrode metal film 5, an AuGe alloy film having a thickness of 0.1 μm, a Ni film having a thickness of 0.01 μm, and an Au film having a thickness of 1 μm are formed in this order by a vacuum evaporation method.
[0043]
Thereafter, as shown in FIG. 1F, the first resist film 2 is removed with a first resist film removing liquid, for example, acetone in this embodiment, to form an electrode 6 having a predetermined shape.
[0044]
In this method, a highly accurate electrode 6 having a predetermined shape can be formed.
[0045]
Next, a lift-off technique using a pattern forming method according to another embodiment of the present invention will be described in detail with reference to FIG.
[0046]
First, as shown in FIG. 2A, a quinonediazide-based photoresist as a positive photoresist, which is a trade name AZ1350J (SHIPLEY), is formed on a main surface of a semiconductor crystal (material) 11 such as a GaAs semiconductor substrate. Co., Ltd.) is applied by spin coating, and baked at 110 ° C. for 40 minutes to form a first photoresist film 12 having a thickness of 1.5 μm.
[0047]
Next, as shown in FIG. 2B, a synthetic rubber-based photoresist as a negative photoresist, in this embodiment, OMR85 (manufactured by Tokyo Ohka Co., Ltd.) is spin-coated on the first photoresist film 12. After coating by a method, baking is performed at 95 ° C. for 30 minutes to form a second photoresist film 13 having a thickness of 0.8 μm.
[0048]
Subsequently, as shown in FIG. 2C, an ultraviolet light having a wavelength of 480 nm as a second photoresist film exposure light is irradiated with a second photo-resist under a condition of a light amount of 10 mW and a time of 5 seconds through a photomask (not shown). After irradiating the resist film 13 (after the photolithography step), the second photoresist film 13 is patterned into a pattern having an opening 13a by developing and removing the non-irradiated portion.
[0049]
Thereafter, as shown in FIG. 2D, the first photoresist film 12 is used as a first photoresist film exposure light at the same wavelength as the first photoresist film 12 using the patterned second photoresist film 13 as a mask. After irradiating ultraviolet light of 480 nm to the first resist film 12 under the second resist film 13 for a predetermined amount by diffraction to emit a predetermined amount of light of 10 mW for a time of 50 seconds, the first resist film is subjected to a liquid temperature by a dedicated developer for the first resist film. By developing at 25 ° C. for 40 seconds to remove the irradiated portion, the upper surface of the material body 11 is exposed, and the second photoresist film 13 is formed so as to protrude from the first photoresist film 12. As a result, the resist pattern 14 including the first and second photoresist films 12 and 13 has a protrusion of the second photoresist film 13 from the first photoresist film 12 to be the overhang portion 14a. Become.
[0050]
Subsequently, as shown in FIG. 2E, an electrode metal film 15 is formed on the substrate 11 in a state substantially perpendicular to the substrate with the resist pattern 14 interposed therebetween. In this embodiment, as the electrode metal film 15, an AuZn alloy film having a thickness of 0.1 μm and an Au film having a thickness of 1 μm are formed in this order by a vacuum evaporation method.
[0051]
Thereafter, as shown in FIG. 2F, the first resist film 12 is removed using a first resist film removing liquid, for example, acetone in this embodiment, to form the electrode 16 having a predetermined shape.
[0052]
In this method, a highly accurate electrode 16 having a predetermined shape can be formed.
[0053]
In addition, not limited to the above embodiments, the OFPR8600 and the MR85 may be combined, or the AZ1350J and the Waycaot may be combined. Further, as the developing solution of the OFPR8600 and the AZ1350J, a dedicated developing solution is used. However, for example, isopropyl alcohol may be used. Of course, the present invention is not limited to the above-described photoresist and removing liquid, and various other appropriate ones can be applied.
[0054]
【The invention's effect】
According to the present invention, it is possible to provide a simple and accurate method for forming a photoresist pattern.
[Brief description of the drawings]
FIG. 1 is a lift-off process diagram using a pattern forming method according to an embodiment of the present invention.
FIG. 2 is a lift-off process diagram using a pattern forming method according to another embodiment of the present invention.
FIG. 3 is a diagram showing a conventional pattern forming process.
FIG. 4 is a view showing another conventional pattern forming process.
FIG. 5 is a view showing another conventional pattern forming process.
[Explanation of symbols]
1, 11 Material body 2, 12 First resist film (positive photoresist film)
3, 13 Second resist film (negative photoresist film)
4a, 14a Overhang part 4, 14 pattern

Claims (4)

Forming a positive-type photoresist film and a negative-type photoresist film made of a synthetic rubber-based material in this order on the material body; Irradiating ultraviolet light, selectively developing and removing the negative photoresist film and patterning it into a predetermined shape, and using the patterned negative photoresist film as a mask , the positive photoresist and with the positive photoresist film sensitive optical membrane is the same wavelength as the negative photoresist film photosensitive optical, irradiating ultraviolet light and an effect of the negative photoresist film shields, Forming a resist pattern having an overhang by selectively developing and removing the positive photoresist film. Pattern forming method comprising and. 2. The pattern forming method according to claim 1, wherein the patterned negative type photoresist film shields the positive type photoresist film exposure light by 30% or more. 3. The pattern forming method according to claim 1, wherein the light for exposing the negative photoresist film and the light for exposing the positive photoresist film are light from the same light source. 4. The pattern forming method according to claim 1, wherein the positive photoresist film is made of a quinonediazide-based material.

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