JPH0754792B2 - Method for manufacturing mask for X-ray exposure - Google Patents

Description

The present invention relates to a method for manufacturing an X-ray exposure mask for an X-ray exposure apparatus, which transfers a fine pattern with high accuracy.

[Conventional technology]

In order to overcome the limit of miniaturization by diffraction, there is X-ray exposure as an exposure method that applies electromagnetic waves of shorter wavelength.

For X-ray exposure, an exposure mask having a sufficiently high contrast of X-ray transmittance is required, a material having excellent X-ray transmittance is selected and used for the substrate, and a thin film of X-ray absorbing material is formed on the substrate. An X-ray absorptive pattern is provided and typically has a wavelength of 4
~ Soft X-rays of several tens of liters are used.

This X-ray exposure method is roughly classified into a batch transfer method and a step-and-repeat method. In the former case, a large area is transferred at once, so the transfer accuracy is lowered in the pattern transfer of 1 μm or less. Therefore, the step-and-repeat method is mainly used for pattern transfer of 1 μm or less.

When the pattern transfer of 1 μm or less is performed by the step-and-repeat method, it is required to transfer the pattern to the adjacent positions one after another with a transfer interval as small as possible. At that time, in order to prevent fogging of the resist on the transferred substrate due to double exposure, the X-ray exposure mask is surrounded by the X-ray absorptive pattern, and the X-ray exposure area is provided around the mask. An X-ray absorptive pattern that defines an X-ray shielding frame pattern having the same X-ray contrast is provided.

However, even in the conventional X-ray exposure mask provided with the X-ray light shielding frame pattern in this way, the light shielding frame fog cannot be completely eliminated, and as shown in FIG.
It was unavoidable that the light-shielding frame fog region 13 was generated between one exposure region 11 and the window outer periphery 12 located outside thereof. Therefore, in the example of the exposure arrangement shown in FIG. 3 (b), depending on the location, it may be duplicated in a part of the adjacent printing pattern area.
This fog region is exposed three times, and as a result, the X-ray exposure amount contrast on the printing pattern is significantly reduced. In the maximum overhang portion 14 in this example, the light-shielding frame fog occurs three times, and the X-ray exposure dose contrast is the lowest.

Here, the general relationship between the exposure dose contrast, the mask contrast of the X-ray absorptive pattern, and the mask contrast of the X-ray shielding frame pattern will be discussed in more detail below.

X-ray absorption pattern and X-ray at X-ray of specific wavelength
The X-ray transmittance of the line shading frame pattern is T ₁ and T ₂ , respectively,
Triple maximum overlap X-ray exposure dose contrast C '
Is defined as the exposure dose ratio of the X-ray absorbing pattern-baked portion and the non-pattern-baked portion on the baked substrate, Can be expressed as In addition, decibel display is possible due to the relationship of γ '[dB] =-10logC' .... Using these formulas,
Further, assuming that the mask contrasts of the X-ray absorbing pattern and the X-ray shielding frame pattern are γ ₁ [dB] and γ ₂ [dB], respectively, the relationship shown in FIG. 5 is obtained.

Next, in order to specifically show the relationship between the mask contrast and the film thickness of the X-ray absorbing pattern, here, a Si (7.1 Å) ray source is used, and Au, W, Ta, Mo is used as the X-ray absorbing material. FIG. 4 shows an example of the relationship between the film thickness d [μm] and the mask contrast γ [dB] in the case of the occurrence.

In the case of an X-ray exposure mask provided with an X-ray shielding frame pattern having the same X-ray contrast as the conventional X-ray absorbing pattern,
The mask contrasts of the X-ray absorptive pattern and the X-ray shielding frame pattern are equal, and the exposure amount contrast γ ′ of the maximum overhang portion shown in FIG. 5 has a relationship of a broken line of γ ₁ = γ ₂ . Here, as the absorber, the most popular Au
Consider a case in which Au is used as a single layer and having a mask contrast characteristic as shown in FIG. 4 for a Si (7.1 Å) radiation source. When the mask contrast γ ₁ of the X-ray absorptive pattern and the X-ray shielding frame contrast γ ₂ are both set to 10 dB, as shown in Table 1 (A) from FIG. 4 and FIG.
It can be seen that when the film thickness is 0.69 μm, the exposure amount contrast γ ′ of the maximum overlap portion is lowered to 5.1 dB. In order to set the exposure contrast γ ′ of the maximum overlap portion to 10 dB, which is the same as the mask contrast γ ₁ of the X-ray absorbing pattern in Table 1 (a), as shown in (a) of the table, γ ₁ = γ ₂ = 15.7 dB, required A
u The film thickness must be 1.08 μm.

That is, in order to make the exposure contrast of the maximum overlapping portion the same as the mask contrast of the X-ray absorbing pattern, the Au film thickness must be increased. Generally, in fine processing of an absorptive pattern including a submicron width pattern, the processing accuracy tends to deteriorate as the film thickness increases, and as a result, the X-ray absorptive pattern is formed in order to obtain a high-contrast exposed image. The thickening results in extremely losing the processing accuracy of the fine pattern.

[Problems to be Solved by the Invention]

Therefore, a problem to be solved by the present invention is to provide a method of manufacturing an X-ray exposure mask that prevents the contrast of the X-ray exposure amount from being lowered by the local multiple exposure due to the light-blocking frame fog.

[Means for solving problems]

As a result of research to solve the above-mentioned problems, the present inventor found that the film thickness of the X-ray absorptive pattern in the X-ray exposure mask having the X-ray absorptive pattern in the inner region surrounded by the X-ray shielding frame pattern. The X-ray shielding frame pattern mask contrast is made larger than the X-ray absorbing pattern mask contrast while maintaining the processing accuracy required for processing a fine pattern without making it extremely thick, and the light-shielding frame fog region is subjected to multiple exposure. In order to obtain an X-ray shielding frame pattern having a mask contrast larger than that of the X-ray absorptive pattern, it is possible to obtain an exposure image having an exposure dose contrast higher than desired by improving the exposure dose contrast of a portion to be exposed. First, an X-ray shielding frame supplementary layer is formed on the X-ray transparent thin film, and then X-ray absorption is performed in the same step as the formation of the X-ray absorbing pattern. It found that may be formed a light frame-based layer in the X-ray shielding frame supplementary layer, and completed the present invention based on this finding.

In the above X-ray exposure mask, a step of laminating an X-ray transparent thin film on one surface side of the Si wafer substrate, and providing a protective film on the Si wafer substrate surface area corresponding to the lower surface of the supporting frame on the other surface side of the Si wafer substrate Step and covering the surface area of the X-ray transparent thin film except the surface area where the X-ray shielding frame pattern is provided with a resist pattern, and X
Forming a X-ray absorbing material layer, and then removing the resist pattern to form an X-ray shielding frame supplementing layer; and forming an X-ray absorbing pattern using the X-ray absorbing material and X-ray absorbing pattern. Forming a layer of the main body of the light-shielding frame on the supplementary layer of the X-ray light-shielding frame, and removing a part of the Si wafer substrate by etching only once from the surface side provided with the protective film to form a window. Can be manufactured. In the above-mentioned manufacturing method of the present invention, as the X-ray transparent thin film, for example, Si ₃ N ₄ , SiN, SiO ₂ , SiC, BN formed on one surface of the Si wafer substrate by the CVD method or the sputtering method, etc. A thin film having a thickness of 0.2 to 4 μm of the above inorganic material can be applied.

Next, as a protective film, Si ₃ N ₄ , SiN, Si on the other surface of the Si wafer substrate.
It is possible to apply a thin film of inorganic material such as O ² , SiC, and BN having a thickness of 0.2 to 4 μm formed by a CVD method or a sputtering method, and then removing unnecessary portions by etching.

Next, as the X-ray shielding frame supplementary layer, an X-ray absorbing material layer made of heavy metal such as Au, W, Ta, Mo, etc. is formed to a thickness of 0.1 to 1.2 μm by vapor deposition or sputtering, and then on the resist pattern. It is possible to form the X-ray absorbing material layer portion formed in (1) by removing the resist pattern together with the resist-only removing solution and removing it together with the resist pattern.

Next, the X-ray absorptive pattern is formed and the X-ray shielding frame main layer is formed by vapor deposition or sputtering of Au, W, Ta, Mo, etc. and then patterning by dry etching, or an X-ray transparent thin film. For example, 50 to 200 Å Cr and 200 to 600 Å Au are continuously vapor-deposited or sputtered on the surface and on the X-ray shielding frame supplement layer to form a plating underlayer, and then the plating underlayer surface is formed into an X-ray absorbing pattern. This can be carried out by a method in which a corresponding portion is covered with a resist pattern having openings and is then plated with Au, and then the resist pattern is removed. After formation of the X-ray absorbing pattern, unnecessary portions of the plating underlayer can be easily removed by a sputter etching method using Ar gas, for example.

[Action]

The X-ray light shielding frame pattern formed in a thick film having a higher X-ray contrast than that of the X-ray absorptive pattern prevents a decrease in the exposure dose contrast in the maximum overlapping portion of the light shielding frame fog region.

〔Example〕

 The present invention will be described in detail by explaining examples below.

Embodiment 1 FIGS. 1 (a) to 1 (e) are schematic sectional views showing a manufacturing process of an embodiment according to the present invention. Note that FIG. 1 (e)
FIG. 3 is a cross-sectional view of an X-ray exposure mask manufactured according to this example.

First, as shown in FIG. 1 (a), S ₃ N ₄ , SiN, SiO ₂ , is deposited on one surface of a Si wafer substrate 4'which is mirror-polished with a thickness of 0.3 to 3 mm.
An X-ray transparent thin film 2 made of an inorganic material such as SiC or BN and having a weak tensile stress and having a thickness of 0.2 to 4 μm is formed by, for example, CVD (Chem.
Laminated and fixed by a chemical vapor deposition) method or a sputtering method. Then, on the other side, Si ₃ N ₄ , SiN, SiO ₂ , S
After forming a film of iC, BN or the like having a thickness of 0.2 to 4 μm by the CVD method or the sputtering method, the protective film 5 is formed by removing unnecessary portions by etching using the photoresist pattern as a mask.

Next, as shown in FIG. 1 (b), a resist pattern 9 is formed on the X-ray transmissive thin film 2 by a conventional ultraviolet exposure method in a portion other than the portion where the X-ray shielding frame pattern is formed. From the Au,
X-ray absorbing materials containing heavy metals such as W, Ta, Mo etc.
Adhere to ~ 1.2 μm. After that, the resist pattern 9 and the X-ray absorptive material layer 10 adhered thereon are removed by using a resist-removing liquid, and as shown in FIG. Obtain a substrate with 6 '.

FIG. 1 (d) further shows a desired X-ray absorbing pattern 3 and an X-ray shielding frame having a thickness of 0.2 to 1.2 μm and made of an X-ray absorbing material, which is mainly composed of heavy metals such as Au, W, Ta and Mo. A state in which the main body layer 6'is formed by the simultaneous process is shown.

The X-ray absorptive pattern 3 and the X-ray shielding frame main layer 6'are formed by vapor-depositing or sputtering Au, W, Ta, Mo or the like and then patterning by dry etching, or on the X-ray transparent thin film surface and the X-ray thin film surface. 50-200 on the supplementary layer of the line shading frame
ÅCr and 200-600ÅAu are continuously vapor-deposited or sputtered to form a plating underlayer, and then the plating underlayer surface is covered with a resist pattern having openings corresponding to the X-ray absorbing pattern, and then Au It can be performed by a method of plating and then removing the resist pattern. After formation of the X-ray absorbing pattern, unnecessary portions of the plating underlayer can be easily removed by a sputter etching method using Ar gas, for example.

By forming the X-ray absorbing pattern 3 and the X-ray shielding frame main layer 6'as described above, the X-ray absorbing pattern 3 is formed.
At the same time, the X-ray shielding frame pattern 6 having a mask contrast higher than that of the absorptive pattern 3 is formed.

Finally, the portion of the wafer substrate 4'which is not protected by the protective film 5 processed into the desired window opening pattern is removed by etching from the back surface to form the desired window 7 as shown in FIG. 1 (e). At the time of this etching, in order to protect the X-ray transparent thin film 2; the X-ray absorbing pattern 3 and the X-ray shielding frame pattern 6, a jig made of Teflon, an O-ring or the like is used, and the etching solution is, for example, 20 ~ 30% aqueous KOH or HF:
A part of the Si wafer can be satisfactorily removed by etching by using the HF-based mixed solution of HNO ₃ : CH ₃ COOH = 1: 3: 1.

As described above, the X-ray absorptive pattern 3 is formed on one surface of the X-ray transmissive thin film 2 and the X-ray exposure area is limited to the outside thereof, and the X-ray shielding frame has a higher mask contrast than the X-ray absorptive pattern. An X-ray exposure mask 1 having a pattern 6 was obtained as shown in FIG.

〔The invention's effect〕

As described above in detail, the X-ray exposure mask according to the present invention is
Since the exposure amount contrast at the maximum amount of the light shielding frame fog region is prevented from lowering, the exposure amount contrast can be kept high over the entire printing region, and the X-ray absorbing pattern region and the light shielding frame pattern can be formed in contact with each other. Therefore, according to the X-ray exposure mask of the present invention, a high-quality resist pattern can be obtained on the printed substrate, and transfer can be performed efficiently with a high effective area ratio.

Further, according to the manufacturing method of the present invention, the processing accuracy of the X-ray absorptive pattern of the X-ray exposure mask having the above advantages is the same as that of the conventional X-ray absorptive pattern. It can be manufactured while maintaining a certain level.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process of an embodiment of the present invention, and FIG. 3 is an X-ray exposure mask having an X-ray light shielding frame pattern including the present invention used for step-and-repeat X-ray exposure. FIG. 5 is a plan view for explaining the exposure condition on the hot-baked substrate, FIG. 4 is a view showing a relationship between a typical absorber film thickness and a mask contrast when using a Si (7.1Å) ray source, FIG.
The figure generally shows the exposure contrast of the maximum overlap portion of the fogging area of the light-shielding frame and the mask contrast of the light-shielding frame pattern when the X-ray exposure mask having the X-ray light-shielding frame pattern is used for the step-and-repeat X-ray exposure. It is a figure which shows a relationship. 1 ... X-ray exposure mask 2 ... X-ray transmissive thin film 3 ... X-ray absorbing pattern 4 ... Support frame 4 '... Si wafer substrate 5 ... Protective film 6 ... X-ray light shielding frame pattern 6 '... X-ray shielding frame supplementary layer 6 "... X-ray shielding frame main layer 7 ... Window 9 ... Resist pattern 10 ... X-ray absorbing material layer 11 ... Exposure area 12 ... Window area 13 ... … Shading frame fog area 14 …… Maximum overlap area

Continuation of the front page (56) References JP-A-59-62855 (JP, A)

Claims (1)

[Claims] 1. A step of laminating an X-ray transparent thin film on one surface side of a Si wafer substrate, and a step of providing a protective film in a Si wafer substrate surface area corresponding to the lower surface of a support frame on the other surface side of the Si wafer substrate,
A surface region of the X-ray transmissive thin film except a surface region where the X-ray shielding frame pattern is provided is covered with a resist pattern, and an X-ray absorbing material layer is formed on the X-ray transmissive thin film provided with the resist pattern, Then, the step of forming the X-ray shielding frame supplementary layer by removing the resist pattern, and the step of forming the X-ray absorbing pattern using the X-ray absorbing material and X
The step of stacking the main layer of the X-ray shielding frame on the supplementary layer of the X-ray shielding frame, and removing a part of the Si wafer substrate by etching only once from the surface side provided with the protective film to form the window. A method for manufacturing an X-ray exposure mask, comprising the steps of: forming.