JP2001057331A - Superposing transfer mask for electron-beam exposure and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely form patterns on a membrane without being affected by a loading effect by dividing patterns of different line widths to be transferred to a photosensitized substrate in a small area of a membrane into patterns of the same line width and allocating them to a plurality of transfer masks. SOLUTION: A set of transfer masks consists of two sheets of overlap transfer masks for electron-beam exposure, and each transfer mask is provided with a membrane on which patterns to be transferred to a photosensitized substrate are formed. Each of a plurality of open patterns (2, 3, 4, 5, 6, 7, 8) having different line widths and enabling to be formed in a small area 1 on a transfer mask is divided into patterns of the same line width to allocate them to respective small areas (9, 10) of two sheets of transfer masks. As a result, influences by a micro-loading effect or a loading effect can be reduced, and open patterns of the transfer mask can be formed highly precisely on the membranes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer mask for electron beam exposure used in an electron beam reduction transfer apparatus and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor integrated circuit elements, charged particle beams (hereinafter, referred to as X-rays, electron beams, ion beams, etc.) have been developed in order to improve the resolution of an optical system limited by the diffraction limit of light. An exposure method (lithography technique) using a charged particle beam (hereinafter simply referred to as a charged particle beam) has been developed. Among them, electron beam exposure, in which a pattern is formed using an electron beam, is characterized in that a fine pattern of 1 μm or less can be formed because the electron beam itself can be reduced to several Å (angstrom). is there.

However, since the conventional electron beam exposure method is a one-stroke writing method, the finer the pattern, the more the electron beam must be drawn with a narrower electron beam, the longer the drawing time, and the cost of device production. It was not used for exposure of mass-produced wafers. Therefore, there has been proposed a charged particle beam reduction transfer apparatus which irradiates a transfer mask having a predetermined pattern with an electron beam and reduces and transfers a pattern in the irradiation range to a wafer by a projection lens.

In order to project a circuit pattern, a transfer mask on which the circuit pattern is drawn is required. As a transfer mask, as shown in FIG. 4 (a), there is no through-hole, and a scattered transmission transfer mask 21 having a scatterer pattern 24 formed on a membrane 22, and as shown in FIG. 4 (b), A membrane 3 having a thickness enough to scatter electron beams
2. A scattering stencil transfer mask 31 having a through-hole pattern 34 formed thereon is known.

[0005] In these, a large number of small regions 22a and 32a each having a pattern to be transferred to the sensitive substrate on the membranes 22 and 32 are divided by a boundary region where no pattern exists, and a support 23 is provided at a portion corresponding to the boundary region. , 33
Is provided. In the scattering stencil transfer mask, the membrane is made of a silicon membrane having a thickness of about 2 μm, and the membrane is provided with an opening (corresponding to a pattern to be transferred to a sensitive substrate) through which an electron beam passes.

That is, since the area exposed by one electron beam is about 1 mm square, the pattern to be transferred to the area of one chip (one chip semiconductor) of the sensitive substrate is placed in this small area of 1 mm square. Are formed, and a large number of these small areas are spread. Therefore, the pattern transfer method using charged particle beam,
As shown in FIG. 4C, each of the small regions 22a and 32a is scanned stepwise by a charged particle beam, and a pattern corresponding to the opening of each small region or the arrangement of the scatterer is formed by an optical system (not shown). Since it is a method in which the transfer mask is reduced and transferred to the sensitive substrate 27, the pattern for each small area 22a of the transfer mask is connected on the sensitive substrate 27.

As a method of manufacturing a scattering stencil transfer mask, a blank for a transfer mask having a membrane is prepared, a resist is applied on the membrane, and a predetermined fine pattern is transferred using an electron beam drawing apparatus or the like. Method of completing a scattering stencil transfer mask by etching a membrane using a resist to which a predetermined pattern has been transferred as an etching mask (back-etch preceding process)
After the opening pattern to be transferred to the photosensitive substrate is formed in the silicon active layer of the SOI substrate, the opening pattern to transfer the silicon active layer to the photosensitive substrate by etching the supporting silicon substrate and the silicon oxide layer into a predetermined pattern is formed. There is a method of completing a transfer mask by forming a formed membrane (back-etch process).

When a ring-shaped pattern 42 is to be formed in the small area 41 as shown in FIG. 5A, there is no means for supporting the membrane inside the ring.
Since it is impossible in practice, the pattern is divided and divided into two transfer masks as shown in FIGS. 5B and 5C, and the divided pattern (43, 44) is divided into one small area (43, 44). 42a, 42b) are formed.

In this way, two transfer masks are set as a set, and each transfer mask is exposed as described above, that is, it is overlaid and exposed on the photosensitive substrate. As a result, the divided patterns are joined to form a ring pattern. It is formed.

[0010]

However, as described above, using a resist to which a predetermined pattern has been transferred as a mask for etching, using an etching apparatus having a predetermined function or more, the membrane (the membrane is divided by a support, When a predetermined pattern is formed by etching a small area, a plurality of small areas are extracted and a pattern formed in the small area is compared. An opening pattern cannot be accurately formed on the membrane due to a loading effect in which an etching rate varies due to a difference in the area of the small region).

Further, even if the pattern density between the small areas is substantially the same, as shown in FIG.
In the case where patterns having different line widths are formed in 5, the microloading effect (the etching rate of the opening 46 becomes faster than that of the opening 47), in which the etching rate is different due to the difference in the line width, is accurate. An opening pattern cannot be formed on the membrane.

Since the circuit pattern rule is 0.1 μm or less on the semiconductor chip, it is necessary to control the pattern size with high precision even in the pattern on the transfer mask.
Therefore, the present invention has been made in view of such a conventional problem, and is not affected by a microloading effect and a loading effect, and is capable of accurately forming a pattern on a membrane of a transfer mask blank. And a method for producing the same.

[0013]

According to the present invention, there is provided a transfer mask for superimposing electronic exposure provided with a membrane on which an opening pattern is formed, wherein a line to be transferred to a photosensitive substrate is provided. Patterns with different widths are divided so that the line widths are approximately the same in a small area made of membrane,
The present invention provides a pair of superposed electron exposure transfer masks (Claim 1), which are divided into two transfer masks and have an opening pattern formed on the membrane.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect, further comprising: distributing the two transfer masks so that the pattern density is substantially uniform between the small areas in the same transfer mask. And a transfer mask for combined electron exposure (Claim 2). In addition, the present invention provides a third step of preparing a pair of transfer mask blanks each having a membrane, a step of applying a resist on the membrane of each of the transfer mask blanks, and a step of transferring a resist to a photosensitive substrate. Fine patterns obtained by dividing patterns having different line widths so that the line widths become substantially the same are respectively allocated to the two transfer mask blanks, and the allocated patterns are transferred to a resist. A method of manufacturing a pair of superposed transfer masks for electron exposure, comprising: a step of etching a membrane as an etching mask.

[0015] Further, the fourth aspect of the present invention is that the method further includes a step of distributing the pattern to two transfer masks so that the pattern density is substantially uniform between the small areas in the same transfer mask. The present invention also provides a method for producing a transfer mask for overlay electron exposure (Claim 4). Further, the present invention fifthly provides a "step of preparing two SOI substrates each composed of a supporting silicon substrate, a silicon oxide layer, and a silicon active layer, and a step of applying a resist on the silicon active layer of each of the SOI substrates. A fine pattern obtained by dividing a pattern having a different line width to be transferred to the photosensitive substrate so that each line width becomes substantially the same is allocated to each of the two SOI substrates, and the allocated pattern is transferred to a resist. Etching the silicon active layer using the resist to which the pattern has been transferred as an etching mask; and etching the support silicon substrate and the silicon oxide layer to make the silicon active layer a membrane on which the opening pattern is formed. And a method of manufacturing a pair of superimposed transfer masks for electron exposure (claim 5).

In a sixth aspect of the present invention, the method further comprises the step of: distributing the pattern to two transfer masks such that the pattern density is substantially uniform between the small areas in the same transfer mask. The present invention also provides a method for producing a transfer mask for overlay electron exposure according to the present invention (claim 6).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A transfer mask and a method of manufacturing a transfer mask according to embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a pattern (a) having different line widths in one small area to be transferred to a photosensitive substrate, divided into two transfer masks, and a pair of superposed electronic exposure transfer of the embodiment. It is the schematic of the opening pattern (b) (c) formed in one small area | region of each transfer mask of a mask.

The transfer mask of the embodiment is a set of two superposed electron exposure transfer masks.
A membrane for forming a pattern to be transferred to the photosensitive substrate, an outer peripheral frame for fixing and supporting the outer periphery of the membrane, and supporting columns for supporting the membrane and dividing the membrane into a plurality of small regions; In one small area (not shown), the pattern is divided as described in the related art,
A divided pattern of a pattern (for example, a ring-shaped pattern) that must be distributed to two transfer masks is formed, and a plurality of lines having different line widths that can be formed on one transfer mask are formed in other small areas. The opening patterns (2, 3, 4, 5, 6, 7, 8) are divided so that the line widths are substantially the same, and each pattern is divided into small areas (9, 10) of two transfer masks. Each pattern is distributed and formed.

The pattern 2 is divided into eight, and the divided patterns (2a, 2a,
c, 2e, 2g) are formed, and divided patterns (2b, 2d, 2f, 2h) are formed in the other small region 10. The pattern 3 is divided into two parts, and one of the small areas 9
The divided pattern 3a is formed on the other small area 10, the divided pattern 3b is formed on the other small area 10, the pattern 4 is divided into two, the divided pattern 4a is formed on one small area 9, and the divided pattern 4 is formed on the other small area 10. 4b is formed, the pattern 5 is divided into two, and the divided pattern 5
a is formed, the divided pattern 5b is formed in the other small region 10, the pattern 6 is divided into three, the divided patterns 6a and 6c are formed in one small region 9, and the other small region 10 is formed.
The pattern 7 is divided into eight, and the divided patterns (7a, 7c, 7
e, 7g) are formed, and divided patterns (7b, 7d, 7f, 7h) are formed in the other small area 10, and a pattern 8 is formed.
Is divided into eight, and the division pattern (8a,
8c, 8e, and 8g), and divided patterns (8b, 8d, 8f, and 8h) are formed in the other small region 10.

Further, it is preferable that the pattern density between the small areas in each transfer mask of the pair of superposed electron exposure transfer masks is substantially the same. In that case, first, patterns having different line widths are divided, and a plurality of patterns are arranged in each small area so that the pattern density between the small areas before being distributed to two transfer masks is substantially the same. Therefore, it is preferable to divide each pattern so that the line widths are substantially the same and distribute the divided patterns to two transfer masks.

The transfer mask for overlay electron exposure of this embodiment can be manufactured by the following method, but is not limited to this manufacturing method. FIG. 2 is a diagram illustrating a process of manufacturing a transfer mask blank used for a transfer mask for overlay electron exposure. First, the supporting silicon substrate 11 and the silicon oxide layer 1 manufactured by a general manufacturing method
2. SOI (Silicon on I) composed of silicon active layer 13
nsulater) Prepare a substrate (Figure 2a).

A silicon oxide layer 14 is formed on the back surface of the substrate (FIG. 2b), and a part of the silicon oxide layer (the position corresponding to the position where the pillar is formed) is etched into a window (opening) pattern shape 15 to perform dry etching Forming mask 16 (FIG. 2c). Next, the supporting silicon substrate 11 is etched in accordance with the opening pattern 15 formed in the dry etching mask 16 (FIG. 2D).

Due to the difference in the etching selectivity between silicon and silicon oxide, the etching of the supporting silicon substrate 11 is performed up to the silicon oxide layer 12 and the silicon oxide layer 12 is etched.
And a silicon active layer 13 supported by a silicon outer frame 11b and a silicon support 11a.
Then, a structure having an opening between the columns 11a and between the columns 11a is formed.

Next, when the silicon oxide layer 12 exposed at the opening is removed with hydrofluoric acid, the silicon active layer 13 becomes the silicon membrane 13a, and the blank for the transfer mask is completed (FIG. 2E). FIG. 3 is a diagram illustrating a manufacturing process of a pair of superimposed electron exposure transfer masks of the present embodiment.

The transfer mask blanks thus manufactured are prepared as a set of two blanks. A resist is applied on the membrane 13a of each transfer mask blank, and a predetermined fine pattern is transferred using an electron beam drawing apparatus or the like (FIG. 3A), and the resist on which the predetermined pattern is transferred is used as a mask 17 as a membrane 13a. Is etched (FIG. 3b) to complete the stencil transfer mask (FIG. 3)
c).

In this embodiment, the transfer mask blanks manufactured by using the dry etching method from the SOI substrate are described as an example. However, the transfer mask blanks are manufactured by using the wet etching method from the silicon substrate having the boron doped layer in which boron is diffused. The present invention can be applied to transfer mask blanks. After the membrane is formed, the opening pattern to be transferred to the photosensitive substrate is formed on the membrane, that is, the so-called “back-etch preceding process” has been described. However, the pattern to be transferred to the photosensitive substrate is formed on the silicon active layer of the SOI substrate After that, the supporting silicon substrate and the silicon oxide layer are etched into a predetermined pattern, and the silicon active layer is formed into a membrane having an opening pattern to be transferred to the photosensitive substrate. Is obtained.

[0027]

As described above, according to the method of manufacturing a transfer mask for superimposed electron exposure according to the present invention, the effects of the microloading effect and the loading effect can be reduced, so that the transfer mask opening can be precisely formed. A pattern can be formed. The transfer mask for overlay electron exposure according to the present invention, since the opening pattern is formed with high accuracy, when used in an electron beam reduction transfer device,
A desired circuit pattern can be accurately transferred onto the photosensitive substrate.

[Brief description of the drawings]

FIG. 1 shows a pattern (a) having a different line width in one small area to be transferred to a photosensitive substrate, divided into two transfer masks, and a pair of superposed electrons according to an embodiment of the present invention. It is the schematic of the opening pattern (b) and (c) formed in one small area | region of each transfer mask of the exposure transfer mask.

FIG. 2 is a diagram illustrating a manufacturing process of a pair of transfer mask blanks for superimposed electron exposure according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a manufacturing process of a pair of superposed electron exposure transfer masks according to an embodiment of the present invention.

4A and 4B are schematic diagrams of a scattering transmission mask, a scattering stencil mask, and a pattern transfer method using an electron beam, respectively. It is a schematic perspective view shown.

FIG. 5 is a schematic view showing a general pair of superposed electron exposure transfer masks.

FIG. 6 is a schematic view showing a pattern formed in a small area of a conventional transfer mask.

[Explanation of symbols]

1, 9, 10, 41, 43, 44, 45 ... small area 2, 3, 4, 5, 6, 7, 8, 46, 47 ... patterns with different line widths 11 ... supporting silicon substrate 12, 14 ... silicon oxide layer 12a ... silicon oxide part 13 ... silicon active layer 13a ... silicon membrane 13b ... silicon membrane on which an opening pattern is formed 15 ... window (opening) pattern 16 ... Dry etching mask 17 ... Resist mask 21 ... Scattering / transmission mask 22, 32 ... Membrane 23, 33 ... Column 24 ... Scattering body pattern 27 ... Photosensitive substrate 31 ..Scattering stencil mask 34 ... through-hole pattern 42 ... ring-shaped pattern

Claims (6)

[Claims] 1. A transfer mask for superimposed electron exposure comprising a pair of membranes each having an opening pattern formed thereon, wherein a pattern having a different line width to be transferred to a photosensitive substrate is formed in a small region made of the membrane. , A pair of superposed electron exposure transfer masks, each of which is divided so that the line width is substantially the same, divided into two transfer masks, and an opening pattern is formed on the membrane. 2. The transfer mask for superimposed electron exposure according to claim 1, wherein the transfer mask is divided into two transfer masks so that the pattern density becomes substantially uniform between the small areas in the same transfer mask. 3. A step of preparing a pair of transfer mask blanks having a membrane, a step of applying a resist on a membrane of each of said transfer mask blanks, and a line width to be transferred to a photosensitive substrate. A fine pattern obtained by dividing the pattern so that each line width becomes substantially the same is allocated to each of the two transfer mask blanks, the allocated pattern is transferred to a resist, and the resist to which a predetermined pattern is transferred is used as an etching mask. A method of manufacturing a pair of superimposed electron exposure transfer masks, comprising: a step of etching a membrane. 4. The method according to claim 3, further comprising the step of distributing the pattern to two transfer masks so that the pattern density is substantially uniform between the small areas in the same transfer mask. A method for manufacturing a transfer mask. 5. A step of preparing two SOI substrates each comprising a supporting silicon substrate, a silicon oxide layer, and a silicon active layer, a step of applying a resist on the silicon active layer of each of the SOI substrates, and a photosensitive substrate. A fine pattern obtained by dividing a pattern having a different line width to be transferred onto the two SOI substrates so that each line width is substantially the same is allocated to each of the two SOI substrates, the allocated pattern is transferred to a resist, and a predetermined pattern is transferred. Etching the silicon active layer using the resulting resist as an etching mask; and etching the support silicon substrate and the silicon oxide layer to form the silicon active layer into a membrane on which the opening pattern is formed. And a method for manufacturing a pair of superposed transfer masks for electronic exposure. 6. The method according to claim 5, further comprising the step of allocating the two transfer masks so that the pattern density becomes substantially uniform between the small areas in the same transfer mask. A method for manufacturing a transfer mask.