JP2000124117A - Membrane mask and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a membrane from breakdown by a method, wherein stresses are restrained from concentrating on a part of the membrane in contact with a support which supports the membrane. SOLUTION: This mask is irradiated with a charged particle beam for transferring a pattern. The mask formed by etching a silicon wafer is equipped with a membrane 13, where a pattern is formed and wall-like supports 3 which support the membrane 13, for which a contact angle which the support 3 makes with the membrane 13 is 10 deg. or larger to 45 deg. or smaller. The part of the support 3 brought into contact with the membrane is rounded or curved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a membrane mask and a method for manufacturing the same. In particular, the present invention relates to a membrane mask in which the destruction of the membrane is prevented by alleviating stress concentration on a contact portion between the membrane and a supporting portion that supports the membrane, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional stencil mask for a partial batch transfer charged beam is formed from a Si wafer. The membrane for forming the pattern portion is made by wet etching the wafer. The supporting portion supporting the membrane (the etched side surface when the wafer was wet-etched) was inclined at about 55 ° with respect to the vertical direction of the membrane surface.

On the other hand, a mask of a batch transfer EB exposure machine (a mask comprising an electron beam scatterer portion and a supporting portion for supporting the same).
Has a mask pattern region (small membrane) 2 having a thickness of 2 μm and a square shape of about 1 mm square as shown in FIG. A silicon membrane 1 in a non-pattern area is continuously provided on the outer periphery of the pattern area 2, and a pattern area 2 is provided on the lower surface of the silicon membrane 1.
Is formed in the shape of a vertical wall (pillar) -shaped support portion 3 for supporting the support. This support 3 is for increasing the strength of the mask. FIG. 4 is a sectional view showing a conventional membrane mask.

[0004]

By the way, in the above-mentioned conventional membrane mask, since the silicon membrane 1 and the wall-shaped support portion 3 are in contact at right angles, stress concentrates on this contact portion, and the membrane 1 There is a problem that is easily broken.

[0005] The distortion of the pattern position in the membrane 1 is based on the SIA (SEMICONDUCTOR INDUSTRY ASSOCIATION).
According to the roadmap1997 version, a 16G DRAM requires 20 nm or less. In this case, the internal stress of the 1 mm square membrane needs to be 7 MPa or less. On the other hand, the stress of the membrane is caused by atoms in the membrane (eg, Ge, B
It is well-known that the adjustment can be performed by the following methods. However, even when this is used, the stress can be set to 7 Mpa at the central portion of the membrane in the conventional membrane mask, but the stress is affected by the support portion 3 at the peripheral portion of the membrane because the contact portion is at a right angle. It becomes 30 MPa, and the pattern position distortion becomes 30 nm or more.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a membrane from being broken by alleviating a stress concentration on a contact portion between the membrane and a supporting portion for supporting the membrane. To provide a membrane mask and a method for manufacturing the same.

[0007]

In order to solve the above-mentioned problems, a membrane mask according to the present invention is a membrane mask which transfers a pattern by irradiating a charged beam;
A membrane formed by etching the substrate, a membrane on which the pattern is formed, and a support for supporting the membrane, wherein a contact angle between the membrane and the support is 10 ° or more and 45 ° or less. There is a feature. It is well known that considering the stress, the smaller the contact angle, the better. However, when the contact angle of the support portion is reduced, the tail of the support portion shown in FIG. 2 becomes long, and the pattern area becomes narrow. Further, since the variation in the etching amount in the depth direction of the dry etching is several μm, for example, when the variation in the remaining Si film (described later) is
°, the tail will vary by ~ 30 μm. This means variation in the shape of the non-pattern area. Actually, the non-pattern area is 1
Although it is about 00 μm, if the contact angle is 10 ° or less, it exceeds this and becomes an unnecessary size as a mask. On the other hand, at a contact angle of 45 ° or more, there was no merit of stress reduction. Note that this membrane mask is preferably used for a charged beam transfer exposure apparatus.
Further, the contact angle is preferably about 10 °. Further, it is preferable that a contact portion between the membrane and the supporting portion has a curvature. Preferably, the membrane is stenciled. However, the stencil type is not necessarily required, and a scattering type may be used.

[0008] In the above-mentioned membrane mask, by setting the contact angle between the membrane and the supporting portion to 10 ° or more and 45 ° or less, stress concentration at the contact portion between the membrane and the supporting portion can be relaxed. Destruction can be prevented.

Further, a method of manufacturing a membrane mask according to the present invention is a method of manufacturing a membrane mask for transferring a pattern by irradiating a charged beam; and performing dry etching including isotropic etching conditions on a substrate. Thus, a membrane for forming the pattern and a support portion for supporting the membrane are formed, and a contact angle between the membrane and the support portion is set to 10 ° or more and 45 ° or less. Also, after performing the above dry etching,
It is preferable to perform wet etching on the dry etching surface of the substrate.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the background art of the present invention will be described below. When fabricating a membrane mask from a silicon wafer, the silicon wafer is back-etched to form a membrane. There are two general etching methods, wet etching and dry etching.

In the case of wet etching, a membrane is manufactured by utilizing the fact that the dissolution rate of a chemical in a crystal plane is different. For example, K. According to Pertersen, KO
The etching rates of crystal planes (100) and (111) by H are as follows (K. Petersen: “Siliconasa
Mechanical Material, ”Proceeding of the IEE, Vo
l.70 p.420-457,1982. ). (100) plane / (111) plane ratio = 400: 1 (85 ° C, KO
H: 44gr / water 100ml

In the case of wet etching, it is difficult to adjust the contact angle because the etched surface is a crystal surface.

On the other hand, in dry etching, by adjusting the plasma conditions, the inclination of the wall-shaped support portion,
The flatness of the etching surface of the membrane can be adjusted. In the present embodiment, the condition of dry etching is adjusted, and the contact angle between the membrane and the wall-shaped support is adjusted. Further, a decrease in the flatness of the membrane due to dry etching can be improved by using wet etching.

An embodiment of the present invention will be described below with reference to the drawings. 1A to 1H are cross-sectional views illustrating a method for manufacturing a membrane mask according to an embodiment of the present invention. FIG. 2 shows the membrane surface 4 shown in FIG.
It is sectional drawing which expanded. FIG. 3 is an enlarged cross-sectional view of a contact portion between the membrane 13 and the wall-shaped support portion 3 shown in FIG.

First, as shown in FIG. 1A, a silicon wafer 11 is doped with boron. Thus, a boron-doped layer 13 is formed on the surface of the wafer 11. The depth of the boron-doped layer 13 is set to the finally required thickness of the membrane.

Thereafter, as shown in FIG. 1B, both surfaces of the wafer 11 are thermally oxidized to form a surface-side SiO ₂ film 15a having a thickness of 2 μm on the surface of the wafer 11, and 2 μm thick backside SiO 2 on the backside of No. 11
_Two films 15b are formed.

Next, as shown in FIG.
A resist film 17 is applied on the iO ₂ film 15b, and a pattern of a support portion for patterning a wall (column) support portion for supporting a membrane, which will be described later, is exposed on the resist film 17 by an aligner. Thereafter, development is performed. Next, by dry-etching the back side SiO ₂ film 15b and the resist film 17 as a mask to transfer the pattern of the resist film on the SiO ₂ film 15b.

Thereafter, as shown in FIG. 1D, the silicon wafer 11 is dry-etched using the back side SiO ₂ film 15b as a mask. At this time, a silicon wafer of about several μm is left from the lower surface of the boron doped layer 13 (remaining film).
As a result, a wall-shaped support portion 3 for supporting the membrane is formed.

Next, as shown in FIG.
By performing wet etching in the etching direction 6 using the iO ₂ film 15b as a mask, the required thickness (usually 3
A silicon membrane (boron-doped layer) 13 etched to about μm) is formed.

Thereafter, as shown in FIG. 1F, the surface-side SiO ₂ film 15a is peeled off from the membrane 13 and a resist film 19 is applied on the surface of the membrane 13.

Next, as shown in FIG. 1G, a resist pattern is obtained by exposing a pattern for patterning the membrane 13 to the resist film 19 and then performing development.

Thereafter, as shown in FIG. 1H, the silicon membrane 13 is dry-etched using the resist film 19 as a mask, thereby forming the silicon membrane 13.
A through-hole is made in the hole, and the pattern is transferred. Next, the resist film 19 is removed.

In the above-described process of fabricating the membrane mask, the contact angle between the membrane 13 and the wall-shaped support 3 is determined by the steps shown in FIGS. 1 (d) and 1 (e). That is, in the dry etching (anisotropic etching) step shown in FIG. 1D, the dry etching conditions are determined so that the contact angle between the wall-shaped support portion 3 and the dry etching surface 4 becomes a right angle. Then, in the wet etching step shown in FIG. 1E, anisotropic etching is performed on the wafer 11 because the remaining film is small, but the contact angle is maintained at a right angle. As a result, the contact angle becomes a right angle. A certain wall-shaped support portion 3 is formed. In this case, the membrane 13 is easily broken from a contact portion between the membrane surface and the support portion 3.

Therefore, in the present embodiment, in the dry etching step shown in FIG. 1D, the dry etching is performed so that the contact angle between the wall-shaped support portion 3 and the dry etching surface 4 becomes 10 ° or more and 45 ° or less. By setting the etching conditions,
A dry etching surface 4 as shown in FIG. 2 is formed. In the subsequent wet etching step shown in FIG.
Although the anisotropic etching is performed on the wafer 11, the final contact angle does not change significantly, and as a result, the wall-shaped support portion 3 whose contact angle 7 is 10 ° or more and 45 ° or less as shown in FIG. It is formed.

The conditions of the dry etching shown in FIG. 1D will be described. A dry etching apparatus having strong anisotropy is an apparatus capable of realizing low-temperature and high-density plasma, and an apparatus using inductively-coupled or helicon-type plasma is mainly used. In such an apparatus, the isotropy in dry etching can be improved by slightly increasing the plasma density or the plasma temperature from the above-described plasma condition in which the contact angle becomes a right angle. By using such etching conditions, the contact portion between the wall-shaped support portion 3 and the dry etching surface 4 has a curvature as shown in FIG.

Since the dry etching conditions strongly depend on the type of the etching apparatus, it is difficult to describe them in detail. Accordingly, a typical example of the dry etching condition will be described below, but this condition may be appropriately changed depending on the type of the etching apparatus.

It is known that the transition from anisotropic etching to isotropic etching in dry etching is possible by introducing SF ₆ gas into an etching chamber (plasma). Here, the introduction amount of SF ₆ gas is adjusted so that the etching condition is obtained.

The contact angle 7 shown in FIG.
The following two methods are also available for reducing the angle to 5 ° or less.

One method is to adjust the remaining film thickness of the silicon wafer 11 up to the lower surface of the boron doped layer 13 shown in FIG. That is, if the remaining thickness is increased, the amount of anisotropic etching in the wet etching step shown in FIG. 1E is increased, and the contact angle becomes about 55 ° with a crystal plane appearing. Although the contact angle cannot be shifted from 90 °, it is not so much improved from the viewpoint of stress.

A second method is to adjust the etching selectivity of wet etching shown in FIG. 1E (change the concentration of the etching solution). That is, when the selection ratio is reduced, the curvature of the contact portion between the support portion 3 and the membrane 13 can be relatively increased. As a result, the contact angle 7 shown in FIG. 3 can be reduced.

According to the above embodiment, the membrane 13
The internal stress can be reduced to 10 Mpa or less even at the contact portion between the membrane 13 and the support portion 3 by setting the contact angle between the support 13 and the wall-shaped support portion 10 to 45 ° or less, and the pattern position distortion is maximized. However, it can be suppressed to 15 nm or less.

In the above embodiment, the silicon wafer 11
Is used, and the etching condition is gradually changed when the silicon wafer 11 is dry-etched (that is, the isotropic property in the dry etching is changed). By changing the etching conditions in the direction of increasing the thickness, the contact angle between the membrane and the supporting portion can be increased by 10 ° to 45 ° even in the dry etching only process.
° is also possible.

The present invention can be applied not only to a mask for an exposure apparatus using a charged beam, but also to an X-ray mask using a similar membrane mask.

The present invention can be applied not only to the production of a membrane mask but also to other fine processing, for example, to the production of a micromachine or the like.

[0035]

As described above, according to the present invention, the contact angle between the membrane and the supporting portion is set to 10 ° or more and 45 ° or less. Therefore, it is possible to provide a membrane mask in which the destruction of the membrane is prevented by alleviating the concentration of stress on the contact portion between the membrane and the supporting portion that supports the membrane, and a method for manufacturing the same.

[Brief description of the drawings]

FIGS. 1A to 1H are cross-sectional views illustrating a method of manufacturing a membrane mask according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing an etched surface when a wafer is dry-etched in the step shown in FIG.

FIG. 3 is a conceptual diagram in which the contact angle between the membrane and the wall-shaped support shown in FIG. 1 (e) is changed, and is an enlarged cross-sectional view of the contact between the membrane and the support shown in FIG. 1 (e). It is.

FIG. 4 is a cross-sectional view showing a conventional membrane mask.

[Explanation of symbols]

1 ... Silicon membrane 2 ... mask pattern region 3 ... wall-shaped support portions 4 ... dry etched surface 6 ... wet etching direction 7 ... contact angle 11 ... silicon wafer 13 ... boron-doped layer (membrane) 15a ... surface side SiO ₂ film 15b ... Back side SiO ₂ film 17: resist film 19: resist film

Claims (5)

[Claims] 1. A membrane mask for transferring a pattern by irradiating a charged beam, comprising: a membrane formed by etching a substrate, on which the pattern is formed; and a supporting portion for supporting the membrane. A contact angle between the membrane and the supporting portion is 10 ° or more and 45 ° or more.
A membrane mask characterized by the following. 2. The membrane mask according to claim 1, wherein a contact portion between said membrane and said support portion has a curvature. 3. The membrane mask according to claim 1, wherein the membrane is stenciled. 4. A method for producing a membrane mask for transferring a pattern by irradiating a charged beam, comprising: performing a dry etching including isotropic etching conditions on a substrate to form a membrane for forming the pattern; A method for producing a membrane mask, comprising: forming a support portion for supporting the membrane; and making a contact angle between the membrane and the support portion not less than 10 ° and not more than 45 °. 5. The method according to claim 4, wherein the wet etching is performed on the dry etching surface of the substrate after performing the dry etching.