JP2543546B2 - Method of manufacturing mask for X-ray exposure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an X-ray exposure mask used in an X-ray exposure apparatus for transferring a fine pattern with high accuracy.

[Conventional technology]

The X-ray exposure method is known as a technique capable of transferring an extremely fine pattern by using soft X-rays having a wavelength of 4 to 50 Å. As a conventional method for manufacturing an X-ray exposure mask, there is, for example, "X-ray exposure mask and its manufacturing method" in Japanese Patent Laid-Open No. 60-5519. This manufacturing method will be described with reference to FIG.

First, in FIG. 5a, a mask substrate 2 is formed on a Si wafer 1.

Next, in FIG. 5b, the X-ray absorber layer 3 made of tantalum Ta is formed on the mask substrate 2.

Next, in FIG. 5c, an etching mask layer 4 made of a SiO ₂ layer, which will be used as an electron absorber layer later, is formed on the X-ray absorber layer 3 to a thickness of 2000 angstroms.

Next, in FIG. 5d, a resist layer 5 is formed on the etching mask layer 4.

Next, as shown in FIG. 5e, a resist pattern 6 is formed by an exposure process having a desired pattern on the resist layer 5 and a subsequent phenomenon process.

Next, in FIG. 5f, the resist pattern 6 is used as a mask and a gas such as C ₂ F ₆ is used to perform a reactive sputter etching process on the etching mask layer 4. As a result, the etching mask pattern 7 made of a finely patterned SiO ₂ film is formed.

In FIG. 5g, after removing the resist pattern 6 from above the etching mask pattern 7, CBrF ₃ gas is used with the etching mask pattern 7 as a mask to remove the X-ray absorber layer 3
Then, the X-ray absorber pattern 8 made of tantalum Ta is formed by performing the reactive sputter etching process on the.

Finally, in FIG. 5h, the Si frame 9 is formed by etching the Si wafer 1.

The internal stress of the X-ray absorber pattern 8 of the X-ray exposure mask 1 manufactured by the above process is about ± 1 × 10 ⁹ dyn.
The range is / cm ² .

[Problems to be solved by the invention]

However, it is widely known that the mask stress is generated by the internal stress of the X-ray absorber pattern, and the X-ray absorber pattern made of a refractory metal has ± 1 × 10 ⁹ d.
Internal stress in the range of yn / cm ² is not sufficient. This results in the formation of an X-ray exposure mask in which the positional accuracy of the X-ray absorber pattern is poor, and further improvement in internal stress is desired.

An object of the present invention is to provide a method of manufacturing an X-ray exposure mask in which the positional accuracy is improved by improving the internal stress of the X-ray absorbing pattern made of a refractory metal.

[Means for solving problems]

In order to achieve the above object, the present invention provides a method of forming an X-ray absorbing material region of a refractory metal on a X-ray transmitting thin film formed on a substrate using a sputtering apparatus, and A method for manufacturing an X-ray exposure mask including a step of heating a material region for a predetermined time.

[Action]

In the method of manufacturing the X-ray exposure mask as described above, after the step of forming the X-ray absorbing material region, the X-ray absorbing material region is formed.
By heating at a temperature of 100 to 300 ° C. for a predetermined time, the internal stress of the X-ray absorbing material region can be reduced. By reducing the internal stress, the position of the exposure pattern on the X-ray exposure mask becomes accurate.

[Examples] A method for manufacturing an X-ray exposure mask of the present invention will be described below with reference to the drawings. The schematic cross-sectional views of FIGS. 1a to 1f are examples showing the manufacturing steps of a method for manufacturing an X-ray exposure mask.

First, in Fig. 1a, mirror-polished Si with a thickness of 0.3-4.0 mm is used.
Thickness 0.2 with tensile stress of 2 × 10 ⁸ to 2 × 10 ⁹ dyn / cm ² on both sides of the wafer substrate 1 by CVD method or sputtering method.
A SiN film 10 as an X-ray transparent thin film having a thickness of ˜4 μm is formed. A protective film 11 is formed by etching away unnecessary portions of the SiN film 10 using the photoresist pattern as a mask on the other surface of the SiN film 10 on both surfaces.

The X-ray transmissive thin film may be composed of a single layer or a composite layer of Si ₃ N ₄ , SiC, BN or the like, or may be composed of a composite layer of polyimide or the like by a coating baking method.

Next, in FIG. 1b, tantalum (Ta) as an X-ray absorbing material region having an internal stress of about ± 1 × 10 ⁹ dyn / cm ² and a thickness of 0.3 to 2.0 μm is formed on the SiN film 10. ) Membrane 12 is Argon A
It is formed by a magnetron sputtering method using a rare gas such as r, xenon Xe, or krypton Kr.

The above-mentioned internal stress has a positive value indicating tensile stress, and a negative value indicates compressive stress.

After this step, the tantalum film 12 is heat-treated for 2 hours in a nitrogen gas atmosphere at 150 ° C. and in an atmosphere of atmospheric pressure or reduced pressure. The internal stress is about 1 × 10 ⁸ d due to this heat treatment.
It becomes as low as yn / cm ² . The internal stress of the tantalum film 12 after the heat treatment will be described in detail later.

Next, in FIG. 1c, an etching mask layer 13 made of SiO ₂ or SiN is formed on the tantalum film 12 by a sputtering method or a CVD method. After forming the etching mask layer 13,
A resist pattern 14 is formed on the etching mask layer 13 by an electron beam exposure method or the like.

In FIG. 1d, using the resist pattern 14 as a mask, C ₂ F ₆ ,
The etching mask layer 13 is subjected to reactive etching treatment with a gas such as C ₄ F ₈ . Then, the resist pattern 14 is removed to form an etching mask pattern 15.

When the resist pattern 14 is an organic resist, reactive sputter etching treatment is performed with oxygen O ₂ gas or the like.

Next, in FIG. 1e, using the etching mask pattern 15 as a mask, the tantalum film 12 is subjected to reactive sputter etching treatment with a gas such as CBrF ₃ or SF ₆ . As a result, the X-ray absorptive pattern 16 is formed.

Finally, in FIG. 1f, the support frame 17 is formed by etching away the portion of the Si wafer substrate 1 not protected by the protective film 11 from the back surface.

At the time of this etching, a jig made of Teflon, an O-ring, etc. is used to protect the X-ray absorbing pattern 16.
As an etching solution, a 20-30% KOH aqueous solution or HF: HN
O ₃ : CH ₃ COOH = 1: 3: 1
A part of the Si wafer substrate 1 can be removed by etching.

Through the steps described above, the X-ray exposure mask of the present invention is obtained.

Next, FIGS. 2 to 4 show how the internal stress of the tantalum film 12 changes and becomes small as a result of the heat treatment of the tantalum film 12 in the temperature range of 100 to 300 ° C. for a predetermined time. It will be explained based on experimental data.

FIG. 2 shows the amount by which the internal stress of the tantalum film 12 changes depending on the temperature when the tantalum film 12 is heat-treated in a nitrogen atmosphere in the temperature range of 100 to 300 ° C. for 1 hour. As is clear from this graph, it is possible to control the internal stress to be sufficiently smaller than the conventional value in the range of ± 1 × 10 ⁹ dyn / cm ² by the predetermined heat treatment.

FIG. 3 shows the amount of change in the internal stress of the tantalum film 12 at temperatures of 100 ° C., 150 ° C., and 200 ° C. depending on the heat treatment time. As shown in this graph, the heat treatment temperature is preferably 100 ° C. or higher.

Figure 4 shows the tantalum film 12 heat treated at a temperature of 200 ° C. 3
The state where the internal stress of each sample changes with the heat treatment time is shown. The internal stress before heat treatment is 5.1 for sample b.
× 10 ⁸ dyn / cm ² , 2.6 × 10 ⁸ dyn / cm ^{2 for} sample B, and
Sample C shows 0.5 × 10 ⁸ dyn / cm ² . Heat treatment 1
The internal stress after the time is 2.6 × 10 ⁸ dyn / cm ² for Sample A, 1.5 × 10 ⁸ dyn / cm ^{2 for} Sample B, and -0.5 × for Sample C.
It shows 10 ⁸ dyn / cm ² . The internal stresses after 2 hours of heat treatment are 1.7 × 10 ⁸ dyn / cm ² , 0.9 × 10 ⁸ dyn / cm ² , and −0.9 × 10 ⁸ dyn / cm ² in Sample B.

As described above, the internal stress of the X-ray absorbing pattern 16 formed on the SiN film 10 is ± 1 within a range of ± 1 × 10 ⁹ dyn / cm ^2.
It can be controlled with an accuracy of × 10 ⁷ dyn / cm ² .

Although the above heat treatment was performed in a nitrogen gas atmosphere, there was no great difference in the experimental results of the heat treatment regardless of whether the nitrogen gas atmosphere was at atmospheric pressure or under reduced pressure.

Although the above heat treatment is performed in the manufacturing process of FIG. 1b, it is also possible to perform the heat treatment after forming the X-ray absorbing pattern 16 in the process of FIG. 1f.

In the above-mentioned embodiment, as shown in the experimental data of FIGS. 2 to 4, the internal stress of the X-ray absorbing pattern 16 can be formed in a relatively wide range depending on the heat treatment, so that the internal stress can be freely selected. .

〔The invention's effect〕

From the above description, the X-ray exposure mask formed by the method for manufacturing an X-ray exposure mask of the present invention has the X-ray absorptivity of the conventional X-ray exposure mask obtained by heat-treating the X-ray absorptive material region. Since an X-ray absorptive pattern having an internal stress lower than the internal stress of the pattern could be formed, conventionally, mask strain is easily generated in the X-ray absorptive pattern due to the high internal stress, but this problem is solved. The adhesion of the X-ray absorptive pattern to the X-ray absorptive thin film is good, and even if the X-ray absorptive thin film is displaced, it is not affected and the position of the X-ray absorptive pattern is maintained accurately. it can. As a result, X-ray exposure with good positional accuracy can be realized by using the X-ray exposure mask according to the present invention.

[Brief description of drawings]

1a to 1f are cross-sectional views showing each step of the method for manufacturing an X-ray exposure mask of the present invention, FIG. 2 is a graph showing a state in which internal stress changes according to a heat treatment temperature, and FIG. FIG. 4 is a graph showing a state in which internal stress changes according to heat treatment time, FIG. 4 is a graph showing a state in which internal stress changes according to a sample to be heat treated, and FIG. 5 is a cross-sectional view showing a conventional manufacturing process. . 1 ... Substrate (Si wafer substrate), 10 ... X-ray transparent film (Si
N film), 12 ... X-ray absorbing material layer (tantalum film), 13,1
4,15 …… Etching mask (etching mask layer, resist pattern, etching mask pattern), 16 …… X
Line absorption pattern.

Claims (3)

(57) [Claims] 1. After the step of forming an X-ray absorbing material region of a refractory metal on a X-ray transmitting thin film formed on a substrate by using a sputtering apparatus, the X-ray absorbing material region is formed into a predetermined area. A method for manufacturing an X-ray exposure mask, comprising a step of heating for a time. 2. The X-ray absorptive material region is an X-ray absorptive material layer formed on the X-ray transmissive thin film by using a sputtering apparatus. X
Method for manufacturing line exposure mask. 3. The X-ray absorptive material region is formed by forming an etching mask on an X-ray absorptive material layer formed on the X-ray absorptive thin film by using a sputtering apparatus and then performing an etching process. The method for producing an X-ray exposure mask according to claim 1, which is an absorptive pattern.