JPH05267129A - Mask for x-ray exposure and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the positional displacement of an X-ray absorber by forming an X-ray absorber pattern, an X-ray transmission film supporting the pattern, an X-ray mask supporter fixing the outer circumference of the transmission film, a reinforcing frame reinforcing the supporter and a solid-phase bonding layer containing Cr formed between the reinforcing frame and the supporter. CONSTITUTION:A Cr film 4 is deposited on the rear of an Si substrate 1 by a vacuum deposition device using electron beams, and a resist pattern is formed at the central section of the Cr film 4 through a normal photolithographic technique. A W film 6 is deposited on an aluminum oxide film 3 by employing a magnetron DC sputtering device. An Al2O3 film 7 is deposited on the W film 6, and a C film 8 as a protective film is deposited thereon. A reinforcing frame 9 composed of silicon and the Si substrate 1 as a mask supporter are joined through diffusion joining through the Cr film 4. The upper section of the C film 8 is coated with a chemical amplification type resist as an electron beam resist 10, and a desired pattern is acquired through drawing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray mask,
In particular, the present invention relates to an X-ray exposure mask with improved bonding of a reinforcing frame and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, X-ray lithography that uses X-rays having a shorter wavelength than light has attracted attention as a means of overcoming the limit of pattern miniaturization by light exposure. This X
Unlike the exposure method using light in line lithography, an X-ray mask that selectively transmits X-rays is not provided between the X-ray source and the object to be exposed, instead of reducing and transferring a predetermined pattern. By arranging and irradiating X-ray through this X-ray mask, a transfer pattern is formed on the surface of the exposure object,
A 1: 1 transfer method is used.

In this equal-magnification transfer system, the dimensional accuracy and the positional accuracy of the X-ray mask pattern directly become the device accuracy. Therefore, the X-ray mask pattern has a dimensional accuracy of about 1/10 of the minimum line width of the device. , Position accuracy is required.
Therefore, in order to realize X-ray lithography, X
The development of the line mask structure and manufacturing method is the most important key.

The X-ray mask generally has the following structure. That is, a thin film made of an X-ray transmissive material having a particularly low X-ray absorptivity is provided on a mask support adhered to a ring-shaped reinforcing frame, and the X-ray absorptivity is provided on the X-ray transmissive thin film. Has a structure in which a mask pattern (X-ray absorber pattern) made of a large material is formed. Since the X-ray transparent thin film is extremely thin and mechanically weak, the mask support is provided to support it, and the reinforcing frame prevents the mask support from being deformed by the tensile stress of the X-ray transparent thin film. It is provided to do. Conventionally, such an X-ray mask has been manufactured by a method as shown in FIGS.

First, as shown in FIG. 3A, a film thickness of 1 μm is formed on a Si substrate (mask support) 1 by the LPCVD method.
X-ray transparent thin film 2 such as SiC is formed. Next, a SiC film 2'is similarly formed on the back surface of the Si substrate 1. The X-ray transparent thin film is required to be a self-supporting film that transmits X-rays, has excellent transparency to alignment light (visible light), and has tensile stress. At present, BN, Si, SiN, diamond and the like have been reported as the material in addition to SiC.

Next, as shown in FIG. 3B, after the central portion of the SiC film 2'on the back surface side is selectively removed, a W film 6 as an X-ray absorber is formed on the SiC film 2 on the front surface side. Form.
The X-ray absorber is required to have a large X-ray absorption coefficient at an exposure wavelength (about 1 nm), low internal stress, and easy microfabrication. As such X-ray absorber materials, Au, Ta, WNx are currently available in addition to W.
Etc. have been reported. The internal stress of the X-ray absorber is 1 × 10 ⁷ N / m ² It is indispensable that the stress is as low as possible, and the stress is finely adjusted by Ar ion implantation after depositing while controlling the internal stress by a sputtering method capable of controlling stress. The stress is obtained from the warp of the Si substrate 1.

Next, as shown in FIG. 3C, after a resist 10 for electron beam drawing is applied on the W film 6, pattern drawing is performed by an electron beam drawing device to form the resist 10
To form a desired pattern. Then, as shown in FIG. 3D, the W film 6 is selectively etched by dry etching using the resist 10 as a mask. Then, as shown in FIG. 3E, the SiC film 2'on the back surface is formed by a liquid phase etching method using a potassium hydroxide (KOH) solution or the like.
Using the as a mask, the Si substrate 1 is etched (back etching). Finally, as shown in FIG. 3 (f), the reinforcing frame 9 made of ring-shaped Pyrex glass is attached to the adhesive 11
To adhere to the SiC film 2 '. An X-ray mask has been manufactured through the above steps. In such an X-ray mask manufacturing process, it has been a serious problem that the X-ray absorber pattern is displaced when the last reinforcing frame is bonded.

On the other hand, it is possible to bond the reinforcing frame before the back etching. However, since the adhesive, which is an elastic body, is deformed by the stress of the X-ray permeable film, the back frame may be damaged during the back etching. The X-ray mask support is deformed, and the X-ray absorber pattern is displaced.

[0009]

As described above, when the X-ray mask support is bonded to the reinforcing frame, or when the back etching is performed after the reinforcing frame is bonded, the X-ray mask support is deformed, and There is a problem that displacement of the line absorber pattern occurs.

The present invention has been made in view of the above circumstances. An object of the present invention is to eliminate the positional shift of the X-ray absorber pattern in the manufacturing process of the X-ray mask.
Moreover, it is an object of the present invention to provide an X-ray mask and a method for manufacturing the same, which manufacturing process is simple.

[0011]

In order to solve the above-mentioned problems, in the first invention, an X-ray absorber pattern, an X-ray transparent film supporting the X-ray absorber pattern, and an X-ray mask for fixing the outer periphery of the film. An X-ray exposure mask provided with a support, a reinforcing frame for reinforcing the support, and a solid phase bonding layer containing Cr provided between the reinforcing frame and the support. And

In the second invention, X is formed on the main surface of the substrate.
A step of forming a radiation transparent film, a step of forming an x-ray absorber layer on the x-ray transparent film, a step of forming a metal film containing Cr on the back surface of the substrate, and a step of forming the metal film on the outer peripheral portion. A step of removing and leaving the metal film, a step of superposing and pressing the substrate and the reinforcing frame on which the metal film is provided on the back surface, and performing solid-phase bonding between the metal film and the substrate and the reinforcing frame; A method for manufacturing an X-ray exposure mask, comprising: a step of patterning a layer; and a step of etching the substrate from the back surface of the substrate using the metal film as a mask.

[0013]

In the present invention, the X-ray absorption which has been conventionally caused by joining the reinforcing frame to the substrate by using the solid phase joining layer which does not have an elastic body having a small Young's modulus unlike the conventional adhesive. It is possible to prevent displacement of the body. Further, since the Cr layer having excellent etching resistance is used as the solid phase bonding layer, the Cr layer can be used also as a mask for bonding and back etching, and the manufacturing method can be simplified.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a manufacturing process of an X-ray mask according to an embodiment of the present invention.

First, using a high-frequency heating type LPCVD apparatus, a 3-inch Si substrate 1 having a surface orientation of (100) double-side polished was placed on a susceptor having a graphite surface coated with SiC. By performing vapor phase etching of the substrate, Si
The natural oxide film and heavy metal contaminants existing on the substrate 1 were removed. This completes the Si substrate surface cleaning process.

Next, as shown in FIG. 1A, silane (SiH ₄ ) is used as a Si raw material, acetylene (C ₂ H ₂ ) is used as a C raw material, hydrogen chloride (HCl) is added gas, and hydrogen (H) is used as a carrier gas. ₂ ) Each gas is supplied and the SiC film 2 is 1 μm on the Si substrate 1 at the substrate temperature of 1100 ° C.
m deposited. Then, as shown in FIG. 1B, an aluminum oxide film 3 having a thickness of 90 nm was formed as an antireflection film by a reactive sputtering method. Aluminum oxide was used as the sputtering target, and a mixed gas of Ar and O ₂ was used as the sputtering gas.

Next, as shown in FIG. 1 (c), a Cr film 4 is deposited to a thickness of 0.1 μm on the back surface of the Si substrate 1 by a vacuum vapor deposition apparatus using an electron beam, and then a normal photo film is used. A resist pattern 5 having a 30 mm square opening was formed in the center of the Cr film 4 by the lithography technique. Then, as shown in FIG. 1D, liquid phase etching of the Cr film 4 was performed using a ceric ammonium nitrate solution and using the resist 5 as a mask.

Next, as shown in FIG. 1 (e), a W film 6 was deposited to a thickness of 0.5 μm on the aluminum oxide film 3 using a magnetron DC sputtering device. The sputtering power was set to 1 kW, the gas pressure was set to a low pressure side so that a W film having high density could be formed, and 3 mTorr so that the stress was close to zero. The stress of the formed W film 6 is 3 × 10 ⁷ as a result of measurement from the warp of the Si substrate 1.
N / m ² Met. Therefore, the energy of 180 keV,
Injection rate 3 × 10 ¹⁵ icns / cm ² Under the conditions of
Was carried out to reduce the stress of the W film 6 to zero.

Next, an Al ₂ O ₃ film 7 as an etching mask is formed on the W film 6 by a sputtering method in an amount of 0.05 μm.
After being deposited to a thickness of m, a C film 8 as a protective film was similarly deposited to a thickness of 0.03 μm by the sputtering method (FIG. 1 (e)).

Next, as shown in FIG. 1 (f), the reinforcing frame 9 made of silicon and the Si substrate 1 which is the mask support are placed in a C
It joined by diffusion joining via the r film 4. At this time, the reinforcing frame 9 is held on a stage laid with a 1 mm-thick rubber, which is an elastic body, and is joined to the bonding surface of the Si substrate 1 via the Cr film 4, and the temperature is 200 ° C. and 1.0 kg / cm ² Was applied for 1 minute.

Next, as shown in FIG. 2G, a chemically amplified resist (SAL601) as an electron beam resist 10 is applied on the C film 8 to a thickness of 0.05 μm, and a dose is applied by an electron beam drawing apparatus. Amount 13 μc / cm ² Draw and develop to obtain the desired pattern (minimum line width 0.1
5 μm) was formed. At this time, development was performed using a 0.36N alkaline developer, but no change was observed in the Al ₂ O ₃ film 7.

Next, as shown in FIG. 2 (h), the C film 8 is etched with O ₂ gas using the resist 10 as a mask by using a magnetron etching apparatus, and then the C film 8 is used as a mask for Al ₂ The O ₃ film 7 was etched. Then, as shown in FIG. 2I, the etching gas is SF ₆ +.
The W film 6 was anisotropically etched using CHF ₃ with the Al ₂ O ₃ pattern 7 as a mask. The pressure at this time was 30 mTorr, and the applied power was 50 W.

Next, as shown in FIG. 2 (j), a 30% potassium hydroxide solution heated to 95 ° C. was used to remove Cr.
Liquid phase etching of the Si substrate 1 was performed using the film 4 as a mask. As a result, a 30 mm square opening was formed in the Si substrate.

The X-ray mask formed by the above steps,
The displacement of the X-ray absorber pattern from the design value was measured by a laser interferometer, and found to be 0.03 μm (3
A significantly smaller value of σ) or less was achieved. this is,
Positional distortion of the X-ray absorber pattern due to deformation of the adhesive with low mechanical strength due to stress of the X-ray transparent film,
By using Cr, the positional distortion of the X-ray absorber pattern due to the volume change of the adhesive when the adhesive is hardened and the flatness of the X-ray mask due to the uneven thickness of the adhesive are eliminated by using Cr. The X-ray mask was produced.

The present invention is not limited to the above embodiment. For example, in the above-mentioned embodiment, the X-ray mask support and the reinforcing frame are joined together, and then the X-ray absorber pattern is formed and the back etching is performed. Even when solid-phase bonding is performed between the X-ray mask support on which the pattern is formed and back-etched and the reinforcing frame, the positional distortion of the X-ray absorber pattern is eliminated as compared with the conventional method. Further, the X-ray absorber is not limited to W, and Ta, Mo, and their nitrides and carbides can be used, and a Cr film containing Au as well as a Cr film or the like can be used as the solid-state bonding layer. it can. Also,
Also in the X-ray transparent thin film, not only SiC but also diamond, SiN, BC, or boron-doped Si can be used. Further, the reinforcing frame is not limited to silicon, but may be a compound of silicon (SiO ₂ ) or glass such as Pyrex glass. Further, the antireflection film is not limited to aluminum oxide, but may be aluminum nitride, silicon oxide, or the like. Other than the above, the present invention can be carried out with various modifications without departing from the scope of the present invention.

[0026]

As described above, by forming a metal layer containing Cr on the lower surface of the X-ray mask support and solid-phase bonding it to the reinforcing frame, it is usually caused by the volume change of the adhesive. It is possible to eliminate the deformation of the X-ray mask support and the displacement of the X-ray absorber pattern. Further, since this metal layer containing Cr is also used as an etching mask for the silicon substrate, it is not necessary to form a layer of SiC or the like, and the process is simplified.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of the present invention.

FIG. 2 is a process drawing showing an embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of a conventional X-ray mask.

[Explanation of symbols]

1 ... Si substrate (mask support) 2 ... SiC film (X
Line transparent thin film) 2 '... SiC film (back etching mask) 3 ...
… Aluminum oxide film (antireflection film) 4 …… Cr film
5 ... Resist 6 ... W film (X-ray absorber thin film) 7 ...
… Al ₂ O ₃ film 8 …… C film 9 …… Reinforcement frame 10 ……
Electron beam resist 11 ... Adhesive

Claims (2)

[Claims] 1. An X-ray absorber pattern, an X-ray transmissive film that supports the X-ray absorber pattern, an X-ray mask support that fixes the outer periphery of the film, a reinforcement frame that reinforces the support, and a reinforcement frame. An X-ray exposure mask, comprising: a solid phase bonding layer containing Cr provided between the support and the support. 2. A step of forming an X-ray transparent film on the main surface of the substrate, a step of forming an X-ray absorber layer on the X-ray transparent film, and a metal film containing Cr on the back surface of the substrate. The step of forming, the step of removing the metal film leaving the outer peripheral portion, and the substrate and the reinforcing frame provided with the metal film on the back surface are overlapped and pressed, and the metal film and the substrate and the reinforcing frame are separated from each other. Solid-state bonding, patterning the X-ray absorber layer,
And a step of etching the substrate from the back surface of the substrate using the metal film as a mask, the method for producing an X-ray exposure mask.