JPH06260397A - Mask for x-ray exposure and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a mask for X-ray exposure and a manufacture thereof in which the resistance to X-ray irradiation can be increased, and the transmitting support film is not easily damaged during the manufacturing. CONSTITUTION:The main portions of the mask for X-ray exposure comprise a frame 2 of silicon having an X-ray transmitting window 1 in the center thereof, a transmitting support film 3 made of an Si3N4 film transmitting an X-ray, the edge of which is supported by the frame 2 and the internal stress of which is released, an X-ray absorbing substance 4 of Ta provided in the form of a pattern on the principal surface of the transmitting support film 3, and a protection film 5 provided on the side and rear of the frame 2 and comprised of the same material as the transmitting support film 3. In addition, since the transmitting support film 3 is comprised of the stoichiometric Si3N4 film, its chemical bonding stabilizes to increase the resistance to X-ray irradiation, and since it is comprised of the Si3N4 film the internal stress is released, the damage of the transmitting support film due to the internal stress can be avoided during the manufacturing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray exposure mask used in X-ray lithography and a method for manufacturing the same, and more particularly, to an improvement in X-ray irradiation resistance and damage of a transparent support film during manufacturing. The present invention relates to an X-ray exposure mask which is less likely to occur and an improvement in its manufacturing method.

[0002]

2. Description of the Related Art As an X-ray exposure mask of this kind, for example, as shown in FIG. 9, a frame body b having an X-ray transmission window a in the center, and a peripheral portion of the frame body b held by the frame body b are aligned. A transparent support film c that transmits both light and X-rays, an X-ray absorber d provided in a pattern on the main surface of the transparent support film c opposite to the frame b, and the frame. It is known that a main part is constituted by a protective film e provided on the side surface and the back surface of the body b and made of the same material as the permeable support film. The protective film e acts as an etching mask for back-etching the base material forming the frame to form the X-ray transmission window a.

This X-ray exposure mask is usually
It is manufactured through the steps shown in FIGS.

First, a transparent support film c is formed on the main surface of a flat base material b'constituting the frame body b, and a protective film e is formed on the side surface and the back surface of the base material b '. Membrane (Figure 10A)
reference). At that time, the transparent support film c and the protective film e are generally formed of the same material and at the same time. Next, as shown in FIG. 10 (B), an X-ray absorber film d ′ composed of Au, W, etc. is uniformly formed on the transparent support film c, and this X-ray absorber is formed. A resist pattern is formed on the film d ', and the X-ray absorber film d'exposed from the resist is removed by etching to be patterned, as shown in FIG.
An X-ray absorber d as shown in is formed. The protective film e is also patterned by the same photolithography process to remove the central part (see FIG. 10D), and the base material b ′ is back-etched using the patterned protective film e as a mask. By forming the X-ray transmission window a, an X-ray exposure mask as shown in FIG. 10 (E) is manufactured.

By the way, although this X-ray exposure mask is used by being mounted on an X-ray exposure apparatus, it is necessary to align it with a semiconductor substrate or the like which is an object to be exposed at the time of exposure. In this alignment operation, the X-ray exposure mask is irradiated with visible light (alignment light) having a specific wavelength in the range of 400 to 700 nm, and the alignment light transmitted through the X-ray exposure mask is exposed. Is performed by detecting the positional deviation between the two, and the X-ray exposure mask is moved by an appropriate amount in the x and y directions based on this detection signal. Therefore, the transparent support film c of the X-ray exposure mask is required to have a high visible light transmittance.

Further, since the X-ray exposure mask is irradiated with high-intensity X-rays during exposure, the transparent supporting film c is exposed to X-rays.
A film having excellent radiation resistance is required.

As a material satisfying these required characteristics, SiN, particularly stoichiometric (stoichiometric ratio) Si ₃ N ₄ is known.

[0008]

By the way, when silicon-rich SiN is applied as the permeable support film,
This SiN has a problem that its chemical bond state is largely deviated from the stoichiometric ratio and its X-ray irradiation resistance becomes insufficient, and thus X-ray irradiation easily causes X-ray irradiation damage such as discoloration of the film. Was.

On the other hand, when stoichiometric (stoichiometric ratio) Si ₃ N ₄ is applied to form the above-mentioned permeable support film, this Si ₃ N ₄ has a stable chemical bond state and is therefore excellent in X-rays. It has irradiation resistance, but on the other hand, this Si ₃ N ₄
The film has a very large tensile stress,
_When a part of the base material provided adjacent to the permeable support film made of ₃ N ₄ film is removed by the back etching process, the permeability is increased due to the large tensile stress of the permeable support film. There was a problem that the supporting film was easily damaged.

The present invention has been made by paying attention to such a problem, and its object is to improve the X-ray irradiation resistance and prevent the breakage of the permeable support film during manufacturing. An object is to provide an exposure mask and a manufacturing method thereof.

[0011]

That is, in the invention according to claim 1, a frame body having an X-ray transmission window in the center and a peripheral portion of the frame body is held by the frame body, and both alignment light and X-rays are transmitted therethrough. A transparent support film, an X-ray absorber provided in a pattern on the main surface of the transparent support film opposite to the frame body, and a transparent support provided on the side surface and the back surface of the frame body. Assuming an X-ray exposure mask provided with a protective film made of the same material as the film, the transparent support film is made of SiNx.
(However, 1.0 <x ≤ 1.5) and the internal stress is relieved to form a silicon nitride film.

According to the X-ray exposure mask of the first aspect of the present invention, SiNx (where 1.0 <x ≤
Since the permeable support film is composed of a silicon nitride film having a small deviation from the stoichiometric ratio shown in 1.5), the chemical bond state is stable and the X-ray irradiation resistance is improved. Since the silicon nitride film having a small deviation from the stoichiometric ratio has a smaller refractive index than Si-rich SiN, the transmittance of visible light (alignment light) is improved, and the above-mentioned transparent support film has an internal stress Since it is composed of the released silicon nitride film, it is possible to avoid damage to the permeable support film due to this internal stress during manufacturing.

In particular, the effect is great when the permeable support film is composed of a stoichiometric Si ₃ N ₄ film. The invention according to claim 2 is made for such a technical reason.

That is, the invention according to claim 2 is claim 1
Based on the X-ray exposure mask according to the invention described above, the silicon nitride is Si ₃ N ₄ .

Next, the invention according to claim 3 relates to a method for producing an X-ray exposure mask, which is capable of improving the X-ray irradiation resistance in this way and which is less likely to damage the transparent support film during the production. Is.

That is, in the invention according to claim 3, a frame body having an X-ray transmission window in the center, and a transparent support film whose peripheral portion is held by the frame body and which transmits both alignment light and X-rays, An X-ray absorber provided in a pattern on the main surface of the transparent support film opposite to the frame body, and the same material as the transparent support film provided on the side surface and the back surface of the frame body. Based on the method of manufacturing an X-ray exposure mask having a protective film that is formed, S is formed on both surfaces of a flat base material that forms a frame.
A shape in which a silicon nitride film represented by iNx (1.0 <x ≤ 1.5) is formed, and only the silicon nitride film on the main surface side is removed to make the main surface convex on the main surface side. And the step of transforming into both sides of the transformed base material again.
A silicon nitride film represented by iNx (1.0 <x ≤ 1.5) is formed, and the second silicon nitride film formed on the back surface side is removed to restore the substrate to a flat shape. Accordingly, the step of releasing the internal stress of the silicon nitride film formed on the main surface of the base material is provided.

According to the method of manufacturing an X-ray exposure mask according to the invention of claim 3, SiNx (1.0 <x ≤ 1.5) is provided on both surfaces of the flat base material forming the frame. After depositing a silicon nitride film with a small deviation from the stoichiometric ratio, the tensile stress of the silicon nitride film deposited on the back surface side is By acting, the base material is deformed into a convex shape on the main surface side, and at the same time, internal stress due to this deformation is generated in the base material.

Then, SiN is again applied to both sides of the deformed substrate.
x (1.0 <x ≤ 1.5), a silicon nitride film with a small deviation from the stoichiometric ratio is formed, and at the same time, nitriding of the front surface side (that is, the main surface side) and the back surface side is performed. Since the stress of the silicon film is balanced, the shape of the base material having a convex main surface side is maintained as it is.

If at least the second silicon nitride film formed on the back surface side is removed in this state, the tensile stress of the silicon nitride film on the back surface side is correspondingly reduced, so that the base material is formed on the main surface side. The internal stress of the film-formed silicon nitride film is deformed in a direction in which the internal stress is relaxed to return to the original flat shape, and the internal stress generated in the base material is also released.

Therefore, SiNx (however, 1.0 <
It becomes possible to form the above-mentioned permeable support film by the silicon nitride film represented by x ≤ 1.5) and the internal stress of which is released.

Even if a part of the base material is removed by a back etching process to form an X-ray transmission window, the transparent support film is composed of a silicon nitride film whose internal stress is released. Therefore, the risk of damage is eliminated, and therefore, it is possible to manufacture the X-ray exposure mask having the above-mentioned X-ray irradiation resistance and the alignment light transmittance improved.

Particularly, the effect is great when the permeable support film is composed of a stoichiometric Si ₃ N ₄ film. The invention according to claim 4 is made for such a technical reason.

That is, the invention according to claim 4 is claim 3
Based on the method for manufacturing an X-ray exposure mask according to the invention described above, the silicon nitride is Si ₃ N ₄ .

In such technical means, SiNx
As a method of forming the silicon nitride film, which is represented by (1.0 <x ≦ 1.5) and constitutes the above-mentioned permeable support film and protective film, for example, a material gas such as SiH ₂ Cl ₂ and NH ₃ is used. A known low pressure chemical vapor deposition method (LPCVD method) can be applied, and the film thickness thereof is set to about 0.5 to 2.0 μm. As a means for removing this silicon nitride film, a reactive ion etching method using an etching gas such as C ₂ F ₆ can be applied.

Next, a known silicon substrate or the like can be applied as the base material constituting the frame body, and a heavy metal having a large atomic number such as Au, W or Ta can be used as the X-ray absorber formed in a pattern. Can be applied, and the film thickness is usually 0.2 to
It is set to 1.0 μm.

[0026]

According to the inventions according to claims 1 and 2, SiNx
(However, since the permeable support film is composed of a silicon nitride film having a small deviation from the stoichiometric ratio shown by 1.0 <x ≤ 1.5), its chemical bond state is stable and X-ray is stable. The irradiation resistance is improved, and the visible light transmittance is improved because the silicon nitride film having a small deviation from the stoichiometric ratio has a smaller refractive index than silicon-rich SiN.
Moreover, since the permeable support film is composed of the silicon nitride film in which the internal stress is released, it is possible to avoid damage to the permeable support film due to the internal stress during manufacturing.

On the other hand, according to the inventions of claims 3 to 4,
The SiNx (1.0
<X ≦ 1.5) After forming a silicon nitride film with a small deviation from the stoichiometric ratio, if only the silicon nitride film on the main surface side is removed, the silicon nitride film formed on the back surface side The tensile stress of the film acts on the base material to deform the base material into a shape in which the main surface side is convex, and at the same time, internal stress due to this deformation is generated in the base material.

Then, SiN is again applied to both sides of the deformed substrate.
x (1.0 <x ≤ 1.5), a silicon nitride film with a small deviation from the stoichiometric ratio is formed, and at the same time, nitriding of the front surface side (that is, the main surface side) and the back surface side is performed. Since the above stress of the silicon film is balanced, the shape of the base material having the convex main surface side is maintained as it is.

In this state, if at least the second silicon nitride film formed on the back surface side is removed, the tensile stress of the silicon nitride film on the back surface side is reduced by that amount, so that the above-mentioned base material is formed on the main surface side. Since the silicon nitride film is deformed in a direction to relax the internal stress and returns to the original flat shape, the internal stress generated in the base material is also released.
The permeable support film can be made of a silicon nitride film represented by SiNx (1.0 <x ≦ 1.5) and the internal stress of which has been released.

[0030]

Embodiments of the present invention will now be described in detail with reference to the drawings.

First, in the X-ray exposure mask according to this embodiment, as shown in FIG. 1, a frame 2 made of silicon having an X-ray transmission window 1 in the center and a peripheral portion of the frame 2 are held by the frame 2. 2 μm thick Si that transmits both the alignment light and X-rays
_A transparent support film 3 made of ₃ N _4, and an X-ray absorber 4 made of Ta and having a thickness of 1 μm, which is provided in a pattern on the main surface of the transparent support film 3 opposite to the frame 2. A main part of the protective film 5 is provided on the side surface and the back surface of the frame body 2 and has a thickness of 2 μm and is made of the same material as the permeable support film 3.

The X-ray exposure mask is manufactured through the following steps.

First, with respect to a silicon substrate 20 having a diameter of 3 inches and a thickness of 1 mm, a thin film 31 made of Si ₃ N ₄ and having a thickness of 2 μm is formed on both surfaces thereof by the LPCVD method using SiH ₂ Cl ₂ and NH ₃ as source gases. 51 was deposited (see FIG. 2).

Next, the thin film 31 formed on the main surface (that is, the surface) side of the silicon substrate 20 is subjected to a reactive ion etching process using C ₂ F ₆ as an etching gas to remove the thin film 31. . By this treatment, tensile stress of the thin film 51 formed on the back surface side acts on the silicon substrate 20, so that the silicon substrate 20 is deformed into a shape in which the main surface side is convex as shown in FIG. Internal stress due to this deformation is generated in the silicon substrate 20.

Then, on both surfaces of the deformed silicon substrate 20, thin films 32 and 52 made of Si ₃ N ₄ and having a thickness of 2 μm were formed again by the LPCVD method. Since the tensile stresses of the thin films 32 and 52 formed at the same time are balanced, the convex shape of the main surface side of the silicon substrate 20 is maintained (see FIG. 4).

Next, in this state, the second thin film 52 formed on the back surface side of the silicon substrate 20 is subjected to reactive ion etching (RIE) using C ₂ F ₆ as an etching gas to remove it. Since the tensile stress on the back surface side of the substrate 20 is reduced, the silicon substrate 2
In 0, the thin film 32 formed on the main surface side is deformed in a direction to relax the internal stress and returns to the original flat shape, and the internal stress generated in the silicon substrate 20 is also released (see FIG. 5). . By this treatment, the internal stress of the thin film 32 of Si ₃ N _{4 formed} on the main surface side of the silicon substrate 20 is released.

Next, after opening the central portion in the window shape, as shown in FIG. 6 is subjected to reactive ion etching to thin film 51 provided on the back surface side of the silicon substrate 20, the Si ₃ N 1 μm thick T on the thin film 32 of ₄
The X-ray absorber layer 40 made of a was uniformly formed by the RF sputtering method (see FIG. 7). Then, a resist pattern (not shown) is formed on the X-ray absorber layer 40, patterning is performed by reactive ion etching using the resist pattern as a mask, and the patterned X-ray absorption as shown in FIG. 8 is performed. Body 4 formed.

Finally, using the thin film 51 (that is, the protective film 5) remaining on the back surface side of the silicon substrate 20 as a mask, the silicon substrate 20 is subjected to etching treatment with a hot alkali, and the frame body 2 having the X-ray transmission window 1 is formed. Then, an X-ray exposure mask as shown in FIG. 1 was manufactured.

During this process, since the internal stress of the thin film 32 made of Si ₃ N ₄ is released, the thin film 32 is removed.
(That is, the permeable support membrane 3) did not break.

[0040]

According to the inventions of claims 1 and 2, Si
Since the permeable support film is made of a silicon nitride film having a small deviation from the stoichiometric ratio represented by Nx (1.0 <x ≤ 1.5), its chemical bonding state is stable. The silicon nitride film, which has improved radiation resistance and a small deviation from the stoichiometric ratio, is a silicon-rich Si.
Since the refractive index is smaller than that of N, the visible light transmittance is improved, and since the transparent support film is composed of the silicon nitride film in which the internal stress is released, it is caused by the internal stress during manufacturing. It has the effect of avoiding damage to the permeable support membrane.

According to the inventions of claims 3 to 4,
This has the effect that the X-ray exposure mask can be reliably and easily manufactured with improved resistance to X-ray irradiation and in which damage to the transparent support film is less likely to occur during manufacture.

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view of an X-ray exposure mask according to an example.

FIG. 2 is an explanatory view showing a manufacturing process of the X-ray exposure mask according to the embodiment.

FIG. 3 is an explanatory view showing a manufacturing process of the X-ray exposure mask according to the embodiment.

FIG. 4 is an explanatory view showing a manufacturing process of the X-ray exposure mask according to the embodiment.

FIG. 5 is an explanatory view showing a manufacturing process of the X-ray exposure mask according to the embodiment.

FIG. 6 is an explanatory view showing a manufacturing process of the X-ray exposure mask according to the embodiment.

FIG. 7 is an explanatory view showing the manufacturing process of the X-ray exposure mask according to the example.

FIG. 8 is an explanatory view showing the manufacturing process of the X-ray exposure mask according to the example.

FIG. 9 is a cross-sectional explanatory view of a conventional X-ray exposure mask.

10A to 10E are explanatory views showing a manufacturing process of an X-ray exposure mask according to a conventional example.

[Explanation of symbols]

 1 X-ray transmission window 2 Frame 3 Transparent support film 4 X-ray absorber 5 Protective film

Claims (4)

[Claims] 1. A frame body having an X-ray transmission window in the center, a transparent support film whose peripheral portion is held by the frame body and transmits both alignment light and X-rays, and the frame of the transparent support film. An X-ray absorber provided in a pattern on the main surface opposite to the body, and a protective film provided on the side surface and the back surface of the frame body and made of the same material as the transparent support film. In the mask for X-ray exposure, the transparent support film is made of SiNx (provided that 1.0 <x
An X-ray exposure mask, which is formed of a silicon nitride film whose internal stress is released by ≦ 1.5). 2. The X-ray exposure mask according to claim 1, wherein the silicon nitride is Si ₃ N ₄ . 3. A frame body having an X-ray transmission window in the center, a transparent support film whose peripheral portion is held by the frame body and transmits both alignment light and X-rays, and the frame of the transparent support film. An X-ray absorber provided in a pattern on the main surface opposite to the body, and a protective film provided on the side surface and the back surface of the frame body and made of the same material as the transparent support film. In the method for manufacturing an X-ray exposure mask, SiNx (1.0
<X ≤ 1.5), forming a silicon nitride film, and removing only the silicon nitride film on the main surface side to deform the substrate into a shape in which the main surface side is convex. , SiNx (1.0 <1.0
x ≤ 1.5) is formed, and the second silicon nitride film formed on the back surface side is removed to return the above-mentioned base material to a flat shape, thereby forming a main surface of the base material. And a step of releasing the internal stress of the silicon nitride film formed on the surface, the method for manufacturing an X-ray exposure mask. 4. The method of manufacturing an X-ray exposure mask according to claim _{3, wherein the} silicon nitride is Si ₃ N ₄ .