JP4801268B2 - Electron beam exposure mask, electron beam exposure method, and semiconductor device manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electron beam exposure mask and an exposure method using the mask, and more particularly to an electron beam exposure stencil having a pattern that is structurally easily damaged, such as a long dimension L & S pattern, a large area pattern, and a donut-shaped pattern. The present invention relates to a mask and an exposure method using the mask.
[0002]
[Prior art]
In recent years, with the increase in the density of integrated circuit devices, there has been a demand for ultra-fine processing technology for forming semiconductor elements and wirings for forming integrated circuits, and the development of techniques for realizing them has become an urgent issue. ing. For example, in order to form a fine pattern having a line width of 0.1 μm or less, there is a technique of performing fine patterning using an electron beam when exposing a resist film.
[0003]
The electron beam has an essentially high resolution because the wavelength as a material wave is very short compared to other exposure techniques and the diffraction aberration is negligibly small. However, with the conventional electron beam exposure technology (variable shaping electron beam exposure method), exposure is performed while directly painting a pattern with an electron beam shaped into a rectangle with a size of about several μm. It is a drawback. This variable shaped electron beam exposure system is described in detail in, for example, Japanese Patent Application Laid-Open No. 7-21626.
[0004]
In order to eliminate the low throughput in the variable shaped electron beam exposure method, a technique called partial batch electron beam exposure (also called cell projection exposure or block exposure) method has been put into practical use. This partial collective electron beam exposure technique is described in detail, for example, in JP-A-7-161605.
[0005]
This partial collective electron beam exposure technology is a stencil type electron beam mask (stencil mask, aperture, partial collective mask, cell projection mask, or block) in which a pattern repeatedly present in a device pattern is formed in Si having a film thickness of about 20 μm. The area pattern of several μm square is transferred at once using a mask. As a result, the number of electron beam shots is greatly reduced from the conventional variable shaped electron beam exposure method, and throughput can be improved.
[0006]
However, even with this partial batch electron beam exposure method, a non-repeatable pattern in a device pattern is drawn while directly painting the pattern with an electron beam formed into a rectangle of about several μm (variable shaped electron beam exposure). In consideration of mass production of devices, further improvement in throughput is required.
[0007]
Therefore, in recent years, as an electron beam exposure method aiming at dramatically higher throughput than the partial batch electron beam exposure method, a mask having a circuit pattern of one whole semiconductor chip is prepared, and an electron beam is applied to a certain area of the mask. There has been proposed an electron beam large area batch exposure apparatus that irradiates and reduces and transfers an image of a pattern in the irradiation range by a projection lens. This technique is generally called an electron beam projection exposure system (EPL for short).
[0008]
This EPL method is described in detail in, for example, Japanese Patent Application Laid-Open No. 2000-58446. In the variable shaped electron beam exposure method and the partial batch electron beam exposure method that have been used in the past, the area to be transferred at one time is as small as about 5 μm square, but in the above EPL technology, the batch transfer area is about 250 μm square. It is expected to greatly increase the throughput.
[0009]
As described above, the electron beam exposure technique is changing from the conventional variable shaped electron beam exposure method that does not use a mask to a partial batch electron beam exposure method that uses a mask or an EPL method in order to improve throughput.
[0010]
Here, the masks used in the electron beam exposure technique are roughly classified into two types: a membrane mask and a stencil mask. The stencil mask is described in, for example, Japanese Patent Application Laid-Open No. 5-216216. The stencil mask is a mask having an open region (no substance is present in the space), and the open region corresponds to an electron transmission region, and the non-open region corresponds to an electron scattering region. Usually, a silicon wafer is processed by opening a pattern by a dry etching method using a chemical gas.
[0011]
The greatest advantage of the stencil mask is its high contrast. Since there is no substance in the open area of the stencil mask, basically the electrons pass through without being scattered, and basically the silicon exists with a certain thickness in the open area. The electrons are scattered and not transmitted. However, the biggest disadvantage of stencil masks is that due to their structure, the pattern is formed by opening, so the mask strength, such as long dimension line and space (L & S) patterns and patterns that support large areas in small areas, etc. There will be a weak pattern. If such a weak pattern is to be processed on the mask, the mask is likely to be damaged. In addition, a generally floating pattern called a donut pattern cannot be formed with a stencil mask.
[0012]
One membrane mask is described in detail, for example, in Japanese Patent Application No. 5-62888. The membrane mask is formed by forming an electron scattering film on the electron transmission film and patterning only the electron scattering film. That is, since electrons are scattered in the region where the electron scattering film remains on the electron transmission film, the electrons are basically not transmitted. In addition, in the region where the electron scattering film does not exist on the electron permeable film (that is, the region where only the electron permeable film exists), since electrons are less likely to be scattered, the electrons are basically transmitted at a certain rate. It will be.
[0013]
However, even in an electron transmission film, electrons are scattered at a certain ratio, so that the contrast cannot be increased as much as a stencil mask that forms a pattern with an opening. However, since the electron scatterer is positioned on the electron permeable film, it is advantageous in terms of mask strength, and even a pattern that is difficult or impossible to form with a stencil mask can be formed with almost no problem.
[0014]
[Problems to be solved by the invention]
In the electron beam exposure technique, the partial batch electron beam exposure method has a track record and there is a tendency to use many stencil masks that are advantageous in terms of resolution. However, as described above, the stencil mask has a pattern that is difficult or impossible to form due to its structure.
[0015]
For example, FIG. 6A shows a long line & space pattern (long dimension L & S pattern) in the longitudinal direction. In such a long dimension L & S pattern, there is a problem that the pattern is distorted as shown in FIG. FIG. 2A shows a structure in which a long line is supported by only one side. Such a pattern has a problem of being easily broken at the base of the line. FIG. 3A shows a structure in which a long L-shaped pattern is supported by a small area. Similar to the case of FIG. 2, this also has a problem that a crack is generated in the region serving as a fulcrum and is easily broken. 4A has a structure in which a large area pattern is supported by a small region. In such a pattern, there is a problem that a crack is generated in a region serving as a fulcrum and is likely to be broken.
[0016]
FIG. 5A shows a pattern generally called a donut pattern. Such a pattern floating in the hollow cannot be processed with a stencil mask that forms a pattern by opening. Thus, in the stencil mask, there are patterns that are difficult or impossible to process due to the structure.
[0017]
In order to solve this problem, for example, a donut pattern as shown in FIG. 7A is divided into two masks as shown in FIGS. 7B and 7C, and two exposures are combined. There is a method of forming a desired pattern (FIG. 7A). This method is disclosed in, for example, JP-A-1-199384.
[0018]
This technique has a temporary effect in that a pattern that cannot be processed in a stencil mask can be formed. However, in this technique, since a plurality of masks must be manufactured and combined with a plurality of exposures, the merit of improving the throughput using the masks is lost to some extent. Also, the mask cost is increased.
[0019]
Further, for example, a method of creating an aperture by supporting a donut pattern as shown in FIG. 8A by supporting a donut pattern with a thin beam non-transmission pattern below the resolution limit as shown in FIG. 8B. is there. This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 61-183926.
[0020]
This technique has a temporary effect in that a pattern that cannot be processed in a stencil mask can be formed by erasing the pattern if the pattern width is less than a certain level. However, with this technique, it is difficult to accurately process a thin beam non-transmission pattern 83 below the resolution limit on the mask, and a large area pattern is supported by the thin beam non-transmission pattern 83 below the resolution limit. Is insufficient in strength and still has a problem that the mask is easily damaged.
[0021]
The present invention has been made in view of the above-mentioned problems, and its main purpose is to reliably retain these patterns even when they have long-sized L & S patterns, large-area patterns, and donut-shaped patterns. Another object of the present invention is to provide an electron beam exposure mask and an exposure method using the mask.
[0022]
[Means for solving problems]
In order to achieve the above object, an electron beam exposure mask according to the present invention has an electron beam exposure mask formed by opening an electron beam transmission region by dry etching. a beam for reinforcement having a predetermined strength that can maintain the shape of the formed beams for reinforcement have a thickness which a pattern is formed by exposure by an electron beam, and the opening serving as the electron beam transmission region Is provided .
[0023]
The electron beam exposure method using the electron beam exposure mask of the present invention is a pattern that is weak and easily damaged in the electron beam exposure method using a mask formed by opening an electron beam transmission region by dry etching. The pattern is transferred using a mask provided with a reinforcing beam having a predetermined strength capable of maintaining the shape of the pattern, and the mask is removed, and a point electron beam is applied to the beam region. And an exposure step or a variable shaped electron beam exposure step.
[0024]
In the present invention, it is preferable that the pattern includes an L & S pattern, a pattern supported only at one end, or an island-shaped pattern.
[0025]
As described above, according to the present invention, a long-sized L & S pattern, a large area pattern, or a donut-shaped pattern can be reliably held by the above-described configuration, and after performing pattern exposure using a mask, Since only the portion is separately exposed by the point electron beam exposure method or the variable shaped electron beam exposure method, the beam portion does not remain and a desired pattern can be formed.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
An exposure method using an electron beam exposure mask according to the present invention, in a preferred embodiment thereof, is a pattern that is weak and easily damaged (for example, a long dimension L & S pattern, a large area pattern in which only one end is supported, , A reinforcing beam having a predetermined strength capable of maintaining the shape of the pattern is applied to a predetermined region (for example, for a long dimension L & S pattern, a line at the longitudinal center of the line). A stencil mask provided on the other end side for a large area pattern in which only one end is supported in a substantially orthogonal direction, and several surrounding areas for a donut-like pattern) is formed, and this pattern reinforcement is applied. A first step of exposing the pattern using the mask, and removing the mask and applying a point electron beam exposure method or variable shaping electron to the beam region Combining the second step of exposing using chromatography beam exposure method, and forms a final desired pattern.
[0027]
【Example】
In order to describe the above-described embodiment of the present invention in more detail, an electron beam exposure mask and an exposure method using the mask according to an embodiment of the present invention will be described with reference to FIGS. . 1 to 5 are plan views schematically showing the structure of a stencil mask for electron beam projection lithography (abbreviated as EPL) according to an embodiment of the present invention.
[0028]
The stencil mask of this embodiment is formed, for example, by performing an opening process on a 8-inch silicon wafer by a dry etching method using a chemical gas. Here, the hatching area indicates the non-opening area 11 (silicon), and the white area indicates the opening area 12 (area where nothing exists in the space).
[0029]
First, when a desired pattern is formed on a mask, if the pattern is a long dimension line and space (L & S) pattern as shown in FIG. Due to the occurrence of stress (thermal stress, vibration, etc.) at the time, there arises a problem that the patterns come into close contact with each other. Therefore, such a pattern is difficult to form with a stencil mask, or even if it can be formed, it is likely to be damaged.
[0030]
Therefore, as shown in FIG. 1B, the mask 13 can be prevented from being damaged by inserting a beam 13 indicated by a hatched area and shortening the length in the longitudinal direction of the L & S pattern. Here, the beam 13 has a dimension that can sufficiently prevent damage to the mask.
[0031]
Then, collective electron beam exposure is performed using a stencil mask as shown in FIG. 1 (b), and then variable shaping electron beam exposure method using the same electron beam light source (electron gun) in the same apparatus. Thus, the region of the beam 13 can be exposed to form a desired pattern as shown in FIG.
[0032]
Further, the pattern having a structure in which a long line as shown in FIG. 2A is supported by only one side has a problem that it is easily broken at the root of the line. On the other hand, if the beam 23 is inserted so as to reinforce the pattern strength as shown in FIG. 2B, a desired pattern can be formed in the same manner as in FIG.
[0033]
In addition, the pattern having a structure in which a long L-shaped pattern as shown in FIG. 3A is supported in a small region has a problem that a crack is easily generated in the region serving as a fulcrum. In contrast, if a beam 33 is inserted so as to reinforce the pattern strength as shown in FIG. 3B, a desired pattern can be formed in the same manner as in FIG.
[0034]
In addition, there is a problem that a pattern having a structure in which a large area pattern as shown in FIG. 4A is supported by a small region and a crack is easily generated in a region serving as a fulcrum. In contrast, if a beam 43 is inserted so as to reinforce the pattern strength as shown in FIG. 4B, a desired pattern can be formed in the same manner as in FIG.
[0035]
FIG. 5A shows a pattern generally called a donut pattern, and such a floating pattern cannot be processed with a stencil mask that forms a pattern by an opening. On the other hand, if the beam 53 is inserted so as to reinforce the pattern strength as shown in FIG. 5B, a desired pattern can be formed in the same manner as in FIG.
[0036]
In this embodiment, the example in which the structure of the present invention is applied to the mask for the electron beam projection exposure system is described. However, the present invention is not limited to the above embodiment, and this is applied to partial collective electron beam exposure. The same effect can be obtained even when applied to a membrane mask for electron beam and membrane type mask for electron beam exposure.
[0037]
Further, the case where the beam region is exposed by the variable shaped electron beam method has been described, but the same effect can be obtained even when the beam region is exposed by the point electron beam method.
[0038]
In addition, the case where the same electron beam light source (electron gun) for irradiating the mask and the electron beam light source (electron gun) for variable shaping electron beam exposure used for exposing the beam has been described. The same effect can be obtained by applying the electron beam light source (electron gun) for the mask and the variable shaping.
[0039]
Further, the electron beam exposure using the mask and the variable shaped electron beam exposure have been described as being performed in the same chamber apparatus, but the same effect can be obtained even when the exposure is individually performed by different apparatuses. Is obtained.
[0040]
【The invention's effect】
As described above, according to the electron beam exposure mask of the present invention and the exposure method using the mask, even in a stencil mask having a long dimension L & S pattern, a large area pattern, or a donut-shaped pattern, By providing a beam having strength, these patterns can be securely held, and after exposure by an electron beam projection exposure method or the like using the stencil mask, only the beam part is formed by a variable shaped electron beam method or By exposing by the point electron beam method, a desired pattern can be reliably formed.
[Brief description of the drawings]
FIG. 1 is a plan view schematically showing the structure of an electron beam projection exposure stencil mask according to an embodiment of the present invention.
FIG. 2 is a plan view schematically showing the structure of an electron beam projection exposure stencil mask according to an embodiment of the present invention.
FIG. 3 is a plan view schematically showing the structure of an electron beam projection exposure stencil mask according to an embodiment of the present invention.
FIG. 4 is a plan view schematically showing the structure of an electron beam projection exposure stencil mask according to an embodiment of the present invention.
FIG. 5 is a plan view schematically showing the structure of an electron beam projection exposure stencil mask according to an embodiment of the present invention.
FIG. 6 is a diagram showing a problem of a conventional stencil mask.
FIG. 7 is a diagram illustrating a conventional method for forming a donut pattern.
FIG. 8 is a diagram showing the structure of a conventional donut pattern.
[Explanation of symbols]
11, 21, 31, 41, 51, 61, 71, 81 Non-opening region 12, 22, 32, 42, 52, 62, 72, 82 Opening region 13, 23, 33, 43, 53 Beam 83 Area 83 Beam non-transmission pattern

Claims (5)

In an electron beam exposure mask formed by opening an electron beam transmission region by dry etching,
For a pattern that is weak and easily damaged, a reinforcing beam having a predetermined strength capable of maintaining the shape of the pattern is provided,
The beam for reinforcement, the electron beam exposure mask, characterized in that provided in an opening have a thickness which a pattern is formed by exposure by an electron beam, and the said electron beam transmission region.   2. The electron beam exposure mask according to claim 1, wherein the pattern includes an L & S pattern, a pattern supported only at one end, or an island-shaped pattern. In an electron beam exposure method using a mask formed by opening an electron beam transmission region by dry etching,
Transferring the pattern using a mask provided with a reinforcing beam having a predetermined strength capable of maintaining the shape of the pattern for a pattern that is weak and easily damaged; and
Removing the mask and exposing the beam region by a point electron beam exposure method or a variable shaped electron beam exposure method;
An electron beam exposure method comprising:   4. The electron beam exposure method according to claim 3, wherein the pattern includes an L & S pattern, a pattern supported only at one end, or an island-shaped pattern. In a manufacturing method of a semiconductor device using a mask formed by opening an electron beam transmission region by dry etching,
Transferring the pattern using a mask provided with a reinforcing beam having a predetermined strength capable of maintaining the shape of the pattern for a pattern that is weak and easily damaged; and
Removing the mask and exposing the beam region by a point electron beam exposure method or a variable shaped electron beam exposure method;
A method for manufacturing a semiconductor device, comprising:

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