JPH06252029A - Manufacture of x-ray exposure mask - Google Patents

Abstract

PURPOSE:To provide the manufacture of an X-ray exposure mask, which can manufacture a highly accurate X-ray exposure mask where a flat reflection preventive film equal in quality and close and small in irregularity can be formed in the arbitrary position of the mask membrane. CONSTITUTION:This manufacture of an X-ray mask structure, which has an X-ray absorber, a support film supporting the X-ray absorber, and a support frame supporting the support film, contains a process of forming a silicon oxide film 2'' on the surface S1 of a silicon substrate, a process of forming an X-ray transmitting film 3 on the oxide film, and a process of forming a desired X-ray absorber pattern 4 on the X-ray transmitting film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask, and more particularly to a method of manufacturing an X-ray exposure mask used in the manufacturing process of semiconductor devices.

[0002]

2. Description of the Related Art As a characteristic of a support film that supports a transfer pattern (absorber pattern) of an X-ray exposure mask structure used in X-ray exposure, it is necessary to transmit X-rays as exposure light well. To be done. At the same time, it is possible to improve the alignment accuracy between the mask and the wafer by transmitting well the alignment light used for aligning the X-ray mask and the wafer which is the substrate to be exposed, which is essential in the exposure process. Therefore, it is an important characteristic required for the X-ray exposure mask. However, it is rare that a support film for supporting a transfer pattern forming an exposure mask (hereinafter, this film is referred to as a mask membrane) has a desirable transmittance for exposure light and alignment light at the same time. ,
In order to improve the transmittance of alignment light, it is common to add an antireflection film or a reflection increasing film to the mask membrane. Also, due to multiple reflections of alignment light within the mask membrane, which is a thin film, there is also a problem that the transmitted light intensity may fluctuate greatly in the range from the maximum value to the minimum value, depending on the film thickness of the mask membrane. In order to prevent this problem, an antireflection film or the like is used in the exposure mask.

A first aspect of the manufacturing process of the X-ray exposure mask in the conventional example will be described with reference to the schematic view of FIG. First, a flat Si wafer with little unevenness is prepared as the Si mask substrate 1 (FIG. 3A). Next, for example, by using a film forming technique such as Rf sputtering in which a material such as Al ₂ O ₃ suitable as an antireflection film is used as a sputtering target 5, an appropriate film thickness is formed on the Si mask substrate 1. And the antireflection film 2 is formed (FIG. 3B).
(Shown). Next, as the mask membrane 3, for example, S
A film made of iN, SiC or the like is formed by CVD (Chemical
Al Vapor Deposition) method is used to form a film on the antireflection film 2 described above, and then Au, T
An X-ray absorbing film 4 made of a heavy metal such as a and W is deposited (shown in FIG. 3C). Then, a desired pattern is patterned on the X-ray absorbing film 4 by a photolithography technique using an EB resist (shown in FIG. 3D). Next, the Si mask substrate 1 is back-etched from the side opposite to the X-ray absorption film 4 using an etching solution such as an aqueous solution of potassium hydroxide to remove Si from the mask membrane 3 including the antireflection film 2. , Mask substrate 1 ′ (shown in FIG. 3 (e)). Through the above general steps,
An X-ray exposure mask including an antireflection film is generally prepared.

FIG. 5 is a schematic view showing a manufacturing process of an X-ray exposure mask of a second aspect of the conventional example. In general, the antireflection film 2 provided for transmitting the alignment light favorably reduces the X-ray transmittance of the exposure light with respect to the exposure light. In some cases, the antireflection film is formed only on the portion having the alignment mark, and the X-ray exposure mask is formed so that the antireflection film is not formed on the portion where the exposure light passes. The second conventional example is a manufacturing process of the X-ray exposure mask in such a case. First, after forming the mask membrane 3 and the X-ray absorbing film 4 on the Si mask substrate 1,
The X-ray absorption film 4 is patterned (FIGS. 5A to 5C).
(Shown). Here, the X-ray absorbing film 41 is an alignment pattern, and the X-ray absorbing film 42 is a so-called IC pattern of a semiconductor integrated circuit or the like to be exposed on the wafer. Next, the antireflection film 2'of Conventional Example 2 is attached from the opposite side to the X-ray absorption films 41 and 42 of the mask membrane 3 by the Rf sputtering method or the like, and then the antireflection film 2'is formed. A photoresist 6 for patterning is attached (shown in FIG. 5D). Next, the photoresist 6 is patterned (shown in FIG. 5E), and the patterned photoresist 6 is used to form the antireflection film 2 ′ only on the portion of the X-ray absorption film 41 used as a pattern for alignment. Is left (shown in FIG. 5 (f)).

FIG. 6 shows a third aspect of the conventional example, which is Si.
FIG. 6 is a schematic view of a manufacturing process of an X-ray exposure mask when the antireflection film 2 is provided on the same side as the X-ray absorption films 41 and 42 with respect to the surface of the mask substrate 1. In FIG. 6, first, the antireflection film 2 is attached on the Si mask substrate 1 by the Rf sputtering method or the like (shown in FIG. 6B). Next, a photoresist 6 is attached and desired patterning is performed (FIG. 6C). Next, photoresist 6
Using, the antireflection film 2 is removed, leaving only the portion where the alignment mark is patterned (see FIG. 6).
(D) Illustration). Next, a SiN film, a SiC film, or the like to be the mask membrane 3 is formed thereon by using the CVD method or the like (shown in FIG. 6E). Next, the X-ray absorption films 41 and 42 are patterned on the mask membrane 3 (see FIG. 6).
(F) shown), the Si mask substrate 1 is back-etched to form a substrate 1 '(shown in FIG. 6 (g)).

[0006]

However, in the conventional example of the above-mentioned first aspect, as shown in FIG. 3B, the antireflection film 2 is formed so that the surface of the film is prone to have irregularities. Since the thickness is formed by a film forming method such as Rf sputtering, which is difficult to control, the antireflection film 2 is formed as shown in FIG.
There are problems that irregularities are generated on the surface of the mask membrane 3 formed by CVD or the like on the upper layer, and it is difficult to maintain the uniformity of the film thickness. Further, in the conventional example of the second aspect, as shown in FIGS. 5C to 5F, when the selective processing such that the antireflection film 2 is formed only on the alignment mark 41 is performed. For this reason, it is necessary to carry out a plurality of processes with the mask substrate 1 ′ left after the mask substrate 1 is back-etched.
Combined with the fact that it is as thin as ~ 3 µm, it was not a preferable processing method in the formation of a highly accurate X-ray exposure mask.

Further, in the conventional example of the third aspect, when selective film formation is performed, for example, the antireflection film 2 is formed only under the alignment mark before back etching the mask substrate 1. As shown in FIG. 6 (e), the mask membrane 3 rises at the portion where the antireflection film 2 is attached,
Interface 7 between Si mask substrate 1 and mask membrane 3
When is used as a reference plane when measuring the film thickness of the mask membrane 3, the difference between the film thickness h ′ in the vicinity of the antireflection film 2 and the film thickness h in the portion without the antireflection film. There was a drawback that Further, the thickness of the mask membrane 3 near the antireflection film 2 becomes thin, or the shape becomes complicated by the antireflection film 2 so that the strength of the mask membrane 3 locally weakens. There was a problem. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to form a flat antireflection film having uniform and dense film quality and less unevenness at any position of a mask membrane. An object of the present invention is to provide a method of manufacturing an X-ray exposure mask capable of manufacturing a highly accurate X-ray exposure mask.

[0008]

The above object can be achieved by the present invention described below. That is, the present invention provides a method for manufacturing an X-ray mask structure having an X-ray absorber, a support film that supports the X-ray absorber, and a support frame that supports the support film, on a silicon substrate surface. It includes a step of forming a silicon oxide film by an oxidation reaction, a step of forming an X-ray transparent film on the oxide film, and a step of forming a desired X-ray absorber pattern on the X-ray transparent film. An X-ray mask manufacturing method characterized by the above.

[0009]

According to the present invention, in an X-ray exposure mask manufacturing method used in a semiconductor device manufacturing process, a part of a mask substrate used for the X-ray exposure mask is chemically reacted to change optical characteristics. By adding the step of forming an antireflection film by the method described above, an antireflection film having few uneven portions and a uniform film thickness is formed. Further, according to the method of manufacturing an X-ray exposure mask of the present invention, it becomes easy to selectively process the antireflection film, so that the antireflection film having few uneven portions and a uniform film thickness can be formed at any position. Is formed.

[0010]

The present invention will be described in more detail with reference to the preferred examples. Example 1 FIG. 1 is a diagram showing a first example of the present invention. First,
As the mask substrate 1, a Si wafer having a surface S1 that is so-called a mirror surface, the surface of which is polished and the surface unevenness is small, which is used in the manufacturing process of a semiconductor device, is used (FIG. 1A). Next, the Si mask substrate 1
The surface of the Si substrate is thermally oxidized in a high temperature process of about 600 to 1100 ° C. to chemically react the Si substrate with oxygen O ₂ to form an oxide film 2 ″ having a constant thickness on the surface of the Si mask substrate 1. (FIG. 1 (b)).

The SiO ₂ film 2 ″ obtained by thermal oxidation at such a high temperature, combined with the fact that the surface of the Si mask substrate 1 is in a mirror surface state, is formed by a general SiO ₂ film forming method. SiO produced by Rf sputtering at a certain low temperature
Compared with the _two films, the film quality is uniform and dense, and the surface irregularities are smaller. Further, it is possible to easily control the film thickness uniformly. Therefore, on this oxide film, SiC or SiN
When the mask membrane 3 is formed by, for example, the film thickness of the mask membrane 3 is uniform and unevenness is small, the SiO ₂ film 2 ″ obtained by thermal oxidation is In manufacturing, it has a preferable shape.

Further, as described above, when the Si mask substrate, Si, is oxidized to form the SiO ₂ film 2 ″, the optical characteristics change. For example, the refractive index becomes about 1.5, and
It is transparent to visible light that is generally used as alignment light. As described above, since the oxide film is easy to control the film quality and the film thickness uniformly, it is excellent in the uniformity of the optical characteristics as the antireflection film 2 ″. Here, the oxide film 2 ″
Is used as the antireflection film of the mask membrane 3, its thickness t, the wavelength of the alignment light is λ, the oxide film 2 ″ and the refractive index for the alignment light in the atmosphere near the mask are n ₁ , respectively. When n ₂ is set, t = λ / 4 (n
_1- n ₂ ) is preferable from the viewpoint of preventing reflection of alignment light. In this embodiment, after the antireflection film 2 ″ is formed by the oxidation reaction, the mask membrane 3 is formed by the CVD method or the like, and the X-ray absorption film 4 is formed on the X-ray absorption film 4 by X-ray absorption.
A film is formed by using a substance such as Au and Ti that absorbs rays well (FIG. 1C).

The case of the antireflection film on the Si mask substrate has been described above with reference to FIG. 1. Here, the thickness of the antireflection film 2 ″ obtained by oxidation is t = λ / 4 (n ₁ -N
By changing from ₂ ) to t = λ / 2 (n ₁ −n ₂ ), it is possible to form a reflection-increasing film having excellent optical characteristics, like the antireflection film 2 ″ shown in this embodiment. is there.
In FIG. 1, 1 is a Si mask substrate using a Si wafer, and Sl is a surface of 1 of the Si mask substrate, which is a wafer mirror surface polished so that surface irregularities are reduced to several tens of liters or less. . Further, 2 ″ is an antireflection film obtained by oxidizing the mirror surface Sl of the Si mask substrate 1,
Reference numeral 3 is a mask membrane which is a thin film for holding an alignment pattern, an IC pattern and the like. Further, 4 is an X for forming an alignment pattern or an IC pattern.
It is a line absorption film.

Second Embodiment FIG. 2 is a diagram showing a second embodiment of the present invention. In the figure, reference numeral 1'denotes a Si mask substrate after the Si mask substrate 1 is back-etched. Reference numeral 2 denotes an antireflection film formed by partially oxidizing a Si mask substrate. Reference numeral 41 is an alignment pattern formed by the X-ray absorber 4 and the like, while reference numeral 42 is an IC pattern. Reference numeral 6 is a photoresist used in a semiconductor process. First, like the first embodiment, the mirror surface S
The Si mask substrate 1 having 1 is used as a mask substrate (FIG. 2A). Next, after applying a photoresist 6 on the Si mask substrate, patterning is performed through an exposure process (FIG. 2B). Next, the Si mask substrate 1 is oxidized only in the openings without the photoresist by a method such as thermal oxidation, and S
An antireflection film 2 is formed on the i-mask substrate 1 by partial oxidation. At this time, the oxide film formed is
As described in Example 1, the film quality and film thickness are uniform. Further, the film thickness t of the antireflection film 2 is t = λ / 4
By selecting either (n ₁ −n ₂ ) or t = λ / 2 (n ₁ −n ₂ ), a good antireflection film or reflection increasing film can be obtained (FIG. 2C). Next, after removing the photoresist 6, the mask membrane 3 and the X-ray absorbing film 4 are attached (FIG. 2D). Next, the X-ray absorption film 4
Is patterned to form an alignment pattern 41 and an IC pattern 42 (FIG. 2E). In this embodiment, since the antireflection film 2 is formed for the purpose of preventing reflection or increasing reflection of alignment light, the antireflection film 2 is formed only at the position of the alignment pattern 41. Next, by back-etching the Si mask substrate 1 from the reflection side of the alignment pattern 41, the mask membrane 3 is held by the back-etched Si mask substrate 1 '.

In this embodiment, before the Si wafer substrate 1 is back-etched, the Si wafer substrate 1 is left back-etched to form the antireflection film 2.
Thin and weak mask membrane 2 to 3 μm thick 3
Compared to the case of the conventional example in which the antireflection film is directly attached to
It is possible to selectively form the antireflection film 2 without deforming the mask membrane 3. Further, the surface of the antireflection film 2 can be formed flat so as to correspond to the flatness of the wafer mirror surface Sl.

Further, as shown in FIG. 2C, in this embodiment, the antireflection film 2 can be formed as if it was embedded in the Si substrate 1 without changing the shape of the substrate surface. Therefore, as shown in FIG. 2D, the mask membrane 3
The entire surface to which the is attached is flat. Therefore, FIG. 2 (f)
As shown in FIG. 6, in the X-ray exposure mask of the present invention, unlike the conventional example, the film thickness h of the mask membrane 3 is uniform and uniform with the film thickness h ′ of the mask membrane 3 in the vicinity of the antireflection film 2. It is possible to keep the alignment pattern 41 and I
The film thickness and film quality are constant over the entire area of the mask membrane 3 in which the C pattern 42 is formed, and when the X-ray exposure mask of the present invention is opposed to the exposure wafer, the mask and the wafer It is also possible to keep the gap amount between them uniform.

[0017]

As described above, the method for manufacturing an X-ray exposure mask of the present invention has a step of forming a silicon oxide film on the surface of a silicon substrate, which is a mask substrate, by an oxidation reaction. By changing the characteristics and forming the antireflection film on the silicon substrate, it is possible to form a flat antireflection film with uniform and dense film quality and less unevenness at any position of the mask membrane. , A highly accurate X-ray exposure mask is formed.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a second embodiment.

FIG. 3 is a diagram showing a first conventional example.

FIG. 4 is a diagram showing an outline of a sputtering method.

FIG. 5 is a diagram showing a second conventional example.

FIG. 6 is a diagram showing a third conventional example.

[Explanation of symbols]

 Sl: Wafer mirror surface 1: Si mask substrate 1 ': Back-etched Si mask substrate 2: Attached antireflection film 2': Antireflection film attached by sputtering method 2 ": Antireflection film formed by oxidation 2 ¨: Antireflection film formed by partial oxidation 3: Mask membrane 4: X-ray absorption film 41: Alignment pattern 42: IC pattern 5: Sputtering target 6: Photoresist 7: Si mask substrate and mask membrane Interface h: Film thickness of mask membrane h ': Film thickness of mask membrane near the antireflection film

Claims (2)

[Claims] 1. A method for manufacturing an X-ray mask structure having an X-ray absorber, a support film for supporting the X-ray absorber, and a support frame for supporting the support film, wherein oxidation is performed on a surface of a silicon substrate. A step of forming a silicon oxide film by a reaction, a step of forming an X-ray transparent film on the oxide film, and a step of forming a desired X-ray absorber pattern on the X-ray transparent film. A method for manufacturing an X-ray mask, comprising: 2. In the step of forming a silicon oxide film, the alignment light of an alignment optical system used for aligning the film thickness of the silicon oxide film with the substrate to be exposed in the X-ray exposure apparatus in the X-ray exposure apparatus. The X according to claim 1, which is formed by adjusting so as to have a desired reflectance with respect to a wavelength.
Method for manufacturing line mask structure.