JP2003248294A - Method of manufacturing photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a photomask which can easily manufacture the photomask without introducing a fresh destaticizing facility and special manufacturing processes and can surely prevent dielectric breakdown. <P>SOLUTION: Independent patterns 2 which are electrically independent of light shielding patterns 2 formed on a photomask substrate 1 and peripheral light shielding parts 4 are electrically connected by dummy patterns 3. The dummy patterns 3 are formed at a width of the extent not producing the transfer patterns corresponding thereto during transfer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a photomask used in a photolithography process when manufacturing a semiconductor device.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a mask pattern on a photomask is transferred in a photolithography process to form a desired element pattern.
Photomasks usually used for these have a light-shielding pattern formed on a glass substrate such as quartz by a metal thin film such as chromium or chromium oxide.

The photomask may be charged on the light-shielding pattern due to the influence of static electricity depending on the use environment and the mask pattern. Then, when a potential difference occurs between the independent individual patterns, discharge occurs between the corners of the pattern where electric field is likely to be concentrated, and a defect occurs in the light shielding pattern. If this defect pattern is transferred as an element pattern of a semiconductor product, it may cause a product defect,
It was a problem.

As a countermeasure against these electrostatic breakdowns, there is a method of using a device for neutralizing the generated static electricity with ions of opposite polarity and eliminating the static electricity. Further, Japanese Patent Laid-Open No. 2000-321777
The official gazette discloses an exposure apparatus provided with a static eliminator using soft X-ray irradiation. Further, a method of forming a transparent conductive film on the photomask to make the photomask conductive and discharging the charged static electricity is also disclosed.

[0005]

However, in the case of using the static eliminator, there is a problem that the equipment is newly purchased and the equipment cost is increased. In addition, when the photomask is made conductive, not only the cost of the photomask substrate becomes high, but also a special process is required for manufacturing the photomask, which causes a problem of increasing the price of the photomask.

The object of the present invention is to solve these problems, and a photomask which can be easily manufactured and can surely prevent electrostatic breakdown without introducing new static elimination equipment or a special manufacturing process. It is to provide a manufacturing method of.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing a photomask used in a photolithography process for manufacturing a semiconductor device, wherein a plurality of island-shaped independent patterns are formed on a photomask substrate. , A dummy pattern that electrically connects the independent patterns is formed, and when the minimum width of the dummy pattern that becomes the resolution limit in the photolithography process is Wc, the width W1 of the dummy pattern to be formed is A method of manufacturing a photomask, wherein the dummy pattern is formed so as to satisfy the formula W1 <Wc.

A method of manufacturing a photomask according to a second aspect is the method of manufacturing a photomask according to the first aspect, characterized in that the width W1 of the dummy pattern is formed to about 0.8 μm.

According to a third aspect of the present invention, there is provided a method for producing a photomask used in a photolithography process for producing a semiconductor device, wherein the photomask substrate is provided with:
A plurality of island-shaped independent patterns and a dummy pattern for electrically connecting the independent patterns are formed, and the width of the transfer pattern corresponding to the dummy pattern transferred in the photolithography step is set to W3, and the transfer is performed. The minimum width that the pattern can remain in the subsequent etching process is W
The dummy pattern is formed so that the width W3 of the transfer pattern satisfies the formula W3 <Wd when d.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a first embodiment for explaining a photomask manufacturing method according to the present invention.
2A is a configuration diagram showing a main part of a light-shielding pattern of the photomask 6, FIG. 7A is an enlarged view of a main part other than the peripheral part of the photomask 6, and FIG. FIG.

In FIG. 1, a light-shielding pattern 2 on a photomask substrate 1 made of a glass material such as quartz is formed of a metal thin film and is electrically isolated from each other as island-shaped independent patterns 2a, 2b, .... , A dummy pattern 3 having a width W1 for electrically connecting the independent patterns, and a peripheral light shielding portion 4 for masking the peripheral portion of the photomask substrate 1. The independent patterns 2a, 2b, ... Are patterns that are originally desired to be transferred.

The dummy patterns 3 electrically connect the individual patterns 2a, 2b, ... On the photomask substrate 1, and also electrically connect the peripheral light shielding portion 4 as shown in FIG. By electrically connecting them, the entire light shielding pattern 2 is electrically connected.

It is to be noted that the discharge is likely to occur at the corners of the individual patterns 2a, 2b ... Therefore, in order to prevent this more effectively, the individual patterns are electrically connected to each other near the corners. As described above, it is preferable to dispose the dummy pattern 3.

In the photomask fabrication, the width of the light-shielding pattern that can be resolved and manufactured is Wb, and the width of the light-shielding pattern at the resolution limit in the photolithography process to be performed is W.
When c is set, the dummy pattern 3 is formed such that the width W1 of the actually formed dummy pattern 3 satisfies the following expression (1) Wb ≦ W1 <Wc (1).

This value W1 can be easily determined according to the type and performance of the exposure machine used, the exposure wavelength, the sensitivity of the photosensitive material (photosensitive resist), the resolution, the exposure conditions, and the development conditions. For example, FIG. 9 is a graph plotting the dimensions of a formed pattern with respect to exposure energy in a certain positive resist material.

In this example, a photolithography process is assumed in which a resist film is formed under a prebaking condition of 100 ° C. (90 seconds) with a thickness of 1 μm, exposed by a contact exposure machine, and then developed with an alkali developing solution for 60 seconds. There is. At this time, when a pattern is formed with a photomask having a pattern width of 15 μm, a change in the exposure energy condition causes
It is possible to change the finished pattern width from 13 μm to 25 μm, and it is shown that the pattern width becomes smaller as the exposure amount is increased.

Taking this resist material as an example, 120 m
When exposed with an exposure energy of J / cm ² , the finished pattern width becomes 13 μm and the mask pattern width is 15 μm.
A thinner pattern of 2 μm (1 μm on each side) can be obtained as a resist pattern. Therefore, the mask width is 2μ
A pattern of less than m cannot be formed as a resist pattern. Then, as the developing time becomes longer, the width of the formed pattern becomes smaller.

As described above, in this case, the light-shielding pattern width Wc at the resolution limit in the photolithography process is 2 μm.
m, and the dummy pattern width W1 satisfying the above equation (1) can be set to 0.8 μm, for example.

Therefore, by setting the width W1 of the dummy pattern 3 in a range satisfying the above expression (1), when the light shielding pattern 2 is transferred to a semiconductor product by a photolithography process, as will be described later, this dummy is used. The pattern 3 is not transferred as it is.

FIG. 2 is a diagram for explaining an exposure process and a development process when a pattern is transferred by using the photomask 6 shown in FIG. 1 in a photolithography process for manufacturing a semiconductor device. FIG. 2 is a cross-sectional view of a cross section passing through a portion corresponding to the instruction line 101 in FIG.

As shown in FIG. 1A, the semiconductor device 8 is coated with a photosensitive resist layer 9, and the light-shielding pattern 2 formed on the photomask substrate 1 is brought into close contact with the photosensitive resist layer 9 or a predetermined pattern. It is installed to have a distance. Exposure is performed in this state, and the independent pattern 2 of the light-shielding pattern 2 is
., a, 2b, ... Are transferred to the photosensitive resist layer 9. still,
In this embodiment, a positive resist is used as the resist.

After that, when development is performed, the resist in the light-exposed portion is eluted and the resist in the light-shielded portion remains, and the resist is transferred to the resist layer 9 by the light-shielding pattern 2 of the photomask as shown in FIG. The pattern 2'is transferred.

On the other hand, FIG. 3 is a cross-sectional view of the exposure process and the development process of the photolithography process, which is taken from the direction of arrow A, showing a cross section passing through a portion corresponding to the instruction line 102 of FIG.

As shown in FIG. 3A, at this position, that is, the portion of the dummy pattern 3, the width W1 is expressed by the above equation (1).
The dummy pattern 3 is not transferred to the photosensitive resist layer 9 after the development, as shown in FIG.

FIG. 4 is a plan view of the semiconductor device 8 after the photolithography process is completed. As shown in FIG. 4, at this stage, the light shielding pattern 2 is formed into the respective independent patterns 2a, 2b, ... The corresponding transfer pattern 2a ',
Only 2b '... Are formed in the semiconductor device 8.

As described above, according to the structure of the light shielding pattern 2 of the photomask of the first embodiment, the dummy pattern 3 is used.
Since all the portions of the light shielding pattern 2 are electrically connected by this, it is possible to prevent electrostatic breakdown due to discharge of static electricity. Therefore, the life of the photomask is extended and the manufacturing cost can be reduced. Moreover,
Since a general mask material can be used as the mask material for the photomask, the cost is not increased for this reason, and it is not necessary to newly install a large-scale equipment such as a static eliminator.

Embodiment 2. FIG. 5 is a configuration diagram showing a main part of a light-shielding pattern of the photomask 16 of the second embodiment for explaining the photomask manufacturing method of the present invention. FIG. 2B is an enlarged view of the main part of FIG.

In the figure, a light shielding pattern 12 formed on a photomask substrate 11 made of a glass material such as quartz is formed of a metal thin film, and is arranged in an orderly manner and is an island-shaped independent pattern 12a, which is electrically independent from each other. 12b ...,
It comprises a dummy pattern 13 having a width W2 for electrically connecting the independent patterns, and a peripheral light shielding portion 14 for masking the peripheral portion on the photomask substrate 11.

Each dummy pattern 13 is formed on the photomask substrate 11 as an independent pattern 12a, 12b ...
The light-shielding patterns 12 are electrically connected to each other by electrically connecting the light-shielding patterns and the peripheral light-shielding portion 14 as shown in FIG.

It is to be noted that the discharge is likely to occur at the corners of the individual patterns 12a, 12b ... Therefore, in order to prevent this more effectively, the individual patterns are electrically connected to each other near the corners. As described above, it is preferable to dispose the dummy pattern 13.

In the photomask manufacture, the width of the light-shielding pattern that can be resolved and manufactured is Wb, the width of the transfer pattern when the dummy pattern of width W2 is transferred is W3, and the width between W2 and W3 is set. , And the minimum width of the transfer pattern that can remain in the etching step described later is Wd, the width W2 of the dummy pattern 13
Is set to satisfy the following equations (2) to (4) Wb ≦ W2 (2) W3 = α × W2 (3) W3 <Wd (4).

For example, when 1 μm of side etching is included in etching, the above-mentioned transfer pattern width W3
The pattern is not formed unless it is transferred with a width of 2 μm or more. Therefore, the above-mentioned width Wd is 2 μm or more, so that the transfer pattern width W3 is W3 = 2 μm.
m, and the transfer pattern width W3 in the resist
When the light-shielding pattern width W2 is 1: 1, that is, α = 1, the dummy pattern width W2 can be W2 = 2 μm.

FIG. 6 shows an example of a process of processing an aluminum (hereinafter referred to as Al) film into an electrode or the like by etching through a photolithography process using the photomask 16 shown in FIG. FIG. 5 is a diagram for explaining the second embodiment of FIG.
It is the sectional view which looked at the section which passes along the portion corresponding to the indicator line 201 of (a) from the arrow A direction.

As shown in FIG. 3A, the semiconductor device 18
Is formed with an Al film 19 to be processed. This A
A photosensitive resist layer 20 is coated on the I film 19, and the light shielding pattern 12 formed on the photomask substrate 11 is placed so as to be in close contact with the photosensitive resist layer 20 or to have a predetermined distance. Exposure is performed in this state, and the independent patterns 12a, 12b, ... Of the light shielding pattern 12 are transferred to the photosensitive resist layer 20. In this embodiment, a positive resist is used as the resist.

In FIG. 3B, the steps of exposure and subsequent development are completed, the resist in the light-shielding portion remains, and the transfer pattern 12 'by the light-shielding pattern 12 of the photomask is transferred to the photosensitive resist layer 20. It shows the situation.

FIG. 6C shows a state in which the Al film 19 is further etched by, for example, wet etching from the state shown in FIG. As shown in the figure, by this etching process, an electrode pattern 12 ″ corresponding to the transfer pattern 12 ′ is formed on the Al film 19.

When performing this wet etching process, first, generally, baking is performed to cure the resist. This is arbitrarily determined by the resist material and the subsequent etching step, and is performed at 120 ° C., for example.

In wet etching of Al, for example, phosphoric acid warmed to 50 ° C. is used. In wet etching, the etchant liquid permeates under the resist, and side etching enters. The amount is, for example, one on one side
It is about μm. Therefore, in this case, if the width of the transfer pattern 12 ′ which is the resist pattern is 2 μm or less,
The pattern disappears and the Al pattern is not formed.

On the other hand, FIG. 7 is a sectional view of the series of exposure step, developing step, and etching step, which is taken from the direction of arrow A through a portion corresponding to the instruction line 202 in FIG. 5A.

As shown in FIG. 6A, at this position, that is, the portion of the dummy pattern 13, the width W2 is set in the range satisfying the above equations (2) to (4). As shown in b), the transfer pattern 12 'having the same width W2 (because α = 1) as the dummy pattern 13 is formed in the resist layer 20 at the stage when the developing process is completed, but the subsequent etching process described above is performed. At the stage of performing the wet etching treatment in
No pattern corresponding to the transfer pattern 12 'remains on the film 19.

FIG. 8 is a plan view of the semiconductor device 18 after the above-described series of exposure, development and etching steps are completed. As shown in FIG. 8, the light-shielding pattern 12 is originally transferred at this stage. Each independent pattern 12a, 12b ...
The electrode patterns 12a ″, 12b ″, ... Corresponding to ...
... are formed in the semiconductor device 18.

As described above, according to the structure of the light-shielding pattern 12 of the photomask of the second embodiment, since all the portions of the light-shielding pattern 12 are electrically connected by the dummy pattern 13, the above-described embodiment is performed. It is possible to obtain the same effects as the effects described in the form 1.

Further, as compared with the case of the above-described first embodiment, the width of the dummy pattern can be set wider, so that there is an advantage that a large design margin can be secured. Furthermore, since the design rules of the pattern to be actually transferred and the dummy pattern are close, in order to obtain the accuracy of the dummy pattern, for example,
Without using a highly accurate mask manufacturing method,
Mask manufacturing is easy.

[0044]

According to the method of manufacturing a photomask of the present invention, since a potential difference does not occur between the patterns of the photomask due to the dummy pattern, it is possible to prevent electrostatic breakdown due to electrostatic discharge. Therefore, the life of the photomask is extended and the manufacturing cost can be reduced. Moreover, since a general mask material can be used as the mask material of the photomask, the cost does not increase, and it is not necessary to newly install a large-scale facility such as a static eliminator.

Further, according to another method of manufacturing a photomask of the present invention, the width of the dummy pattern can be set wider, which has an advantage that a large design margin can be secured.

Further, according to the photomask manufacturing method of the present invention, the design rule of the pattern to be actually transferred is close to that of the dummy pattern. Therefore, for example, a highly accurate mask manufacturing method is used to obtain the accuracy of the dummy pattern. Without that, the mask manufacturing becomes easy.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of a light-shielding pattern of a photomask 6 according to a first embodiment for explaining a method of manufacturing a photomask of the present invention. FIG. FIG. 3B is an enlarged view of the main part of FIG.

FIG. 2 is a cross-sectional view for explaining an exposure process and a development process when transferring an independent pattern portion of the photomask 6.

FIG. 3 is a cross-sectional view for explaining an exposure process and a development process when transferring a dummy pattern portion of the photomask 6.

FIG. 4 is a plan view of the semiconductor device 8 after the photolithography process is completed.

FIG. 5 is a configuration diagram showing a main part of a light-shielding pattern of a photomask 16 according to a second embodiment for explaining a method of manufacturing a photomask according to the present invention. FIG.
4B is an enlarged view of a main part other than the peripheral part of FIG. 4B, and FIG.

FIG. 6 is a cross-sectional view for explaining an exposure process and a development process when transferring and etching an independent pattern portion of the photomask 16.

FIG. 7 is a cross-sectional view for explaining an exposure process and a development process when transferring and etching a dummy pattern portion of the photomask 16.

FIG. 8 is a plan view of the semiconductor device 18 after completion of a series of exposure, development, and etching steps.

FIG. 9 is a graph plotting the dimensions of a formed pattern with respect to exposure energy in a certain positive resist material.

[Explanation of symbols]

1 photomask substrate, 2 light shielding pattern, 2 '
Transfer pattern, 2a to 2h independent pattern, 3 dummy pattern, 4 peripheral light shielding part, 6 photomask, 8 semiconductor device, 9 photosensitive resist layer, 11
Photomask substrate, 12 light shielding pattern, 12 '
Transfer pattern, 13 dummy pattern, 14 peripheral light shielding portion, 16 photomask, 18 semiconductor device, 19 Al film, 20 photosensitive resist layer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masumi Yanaka             One share at 550 Higashi-Asakawacho, Hachioji City, Tokyo             Oki Digital Imaging (72) Inventor Susumu Ozawa             One share at 550 Higashi-Asakawacho, Hachioji City, Tokyo             Oki Digital Imaging (72) Inventor Hiroyuki Fujiwara             One share at 550 Higashi-Asakawacho, Hachioji City, Tokyo             Oki Digital Imaging F term (reference) 2H095 BA01 BB01 BB31

Claims (3)

[Claims] 1. A method of manufacturing a photomask used in a photolithography process for manufacturing a semiconductor device, wherein a plurality of island-shaped independent patterns and a dummy pattern for electrically connecting the independent patterns are provided on a photomask substrate. The dummy pattern is formed such that the width W1 of the dummy pattern to be formed satisfies the formula W1 <Wc, where Wc is the minimum width of the dummy pattern that is the resolution limit in the photolithography process. A method of manufacturing a photomask, comprising: 2. The width W1 of the dummy pattern is 0.8 μm.
The photomask manufacturing method according to claim 1, wherein the photomask is formed to a thickness of about m. 3. A method for manufacturing a photomask used in a photolithography process for manufacturing a semiconductor device, wherein a plurality of island-shaped independent patterns and a dummy pattern for electrically connecting the independent patterns are provided on a photomask substrate. And the width of the transfer pattern corresponding to the dummy pattern transferred in the photolithography process is W3,
When the minimum width of the transfer pattern that can remain in the subsequent etching step is Wd, the width W3 of the transfer pattern is
Is a method of manufacturing a photomask, wherein the dummy pattern is formed so as to satisfy the formula W3 <Wd.