JP2003031479A - Exposure method and mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To connect the boundary section of a pattern formed by a complementary with high precision. SOLUTION: By third and fourth stencil masks 13 and 14 manufactured by opening a position corresponding to a pattern boundary section generated in a pattern being formed by first and second stencil masks 11 and 12, the pattern boundary section is exposed. Thus the pattern boundary section is reliably exposed by exposure using the third and fourth stencil masks 13 and 14, even if the pattern boundary section is not connected precisely by the first and second stencil masks 11 and 12. As a result, the connection failure of the pattern boundary section is prevented, thus improving pattern connection accuracy. Additionally a defect transfer property onto the exposure substrate of defect seed generated at a pattern connection section or the like can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method, and more particularly to an exposure method for forming a pattern by exposure using a plurality of complementary masks.

[0002]

2. Description of the Related Art In electron beam lithography, for example, a stencil mask having an opening corresponding to a pattern to be formed is formed on a silicon substrate, and a resist on the substrate is exposed by an electron beam passing through the opening of the stencil mask. Then, a pattern is formed.

However, when a pattern is formed using a stencil mask having such an opening, when a donut type pattern is to be formed with a single stencil mask, the portion inside the donut type is masked. However, there is a so-called stencil problem that the structure cannot be retained.

In recent years, various exposure methods have been proposed to solve this type of problem. FIG. 5 is a diagram for explaining an example of a conventional donut-shaped pattern forming method,
(A) is a formed donut pattern, (b) is a plan view of a first stencil mask, and (c) is a plan view of a second stencil mask.

A donut-shaped pattern 30 shown in FIG.
5 (b) and 5 (c) to form
A first stencil mask 31 and a second stencil mask 32 having a pattern that can be structurally retained as shown in FIG. Next, exposure is performed using the first stencil mask 31 shown in FIG. 5B, and further exposure is performed using the second stencil mask 32 shown in FIG. 5C. In this way, the doughnut-shaped pattern 30 shown in FIG. 5A is formed by performing exposure twice using the first and second stencil masks complementarily.

A method of forming a desired pattern by using the complementary stencil mask having the complementary relationship is as follows.
Not only the formation of the donut-shaped pattern 30 described above, application to pattern formation of various shapes is considered.

For example, when a long line pattern is formed on the stencil mask, there is a problem that the central portion of the pattern is bent due to the weight of the stencil mask. As a result, when the stencil mask in such a state is used, the line width of the pattern changes, and the pattern cannot be formed accurately. Therefore, when forming a long line pattern, a method of using a complementary stencil mask in which the line pattern is divided into short line patterns has been proposed.

6A and 6B are views for explaining an example of a conventional line pattern forming method. FIG. 6A is a formed line pattern, FIG. 6B is a plan view of a first stencil mask, and FIG.
[Fig. 6] is a plan view of a second stencil mask.

In order to form the line pattern 40 shown in FIG. 6A, first, a short line pattern having a size which does not bend due to its own weight as shown in FIGS. 6B and 6C is formed. A first stencil mask 41 and a second stencil mask 42 to be provided are prepared. Then, FIG.
The first stencil mask 41 shown in (b) is used for exposure, and the second stencil mask 42 shown in FIG. 6 (c) is used for exposure. In this way, the first and second two
The line pattern 40 shown in FIG. 6A is formed by performing the exposure twice using the stencil masks in a complementary manner.
Form the shape of.

[0010]

However, in forming the line pattern 40 as shown in FIG. 6A by the complementary stencil mask, the first stencil mask 41 shown in FIG. 6B is used. When the second exposure and the second exposure using the second stencil mask 42 of FIG. 6C are performed, the pattern boundary portions between the exposed patterns may not be accurately connected. Similarly to this,
Even in the formation of the doughnut-shaped pattern 30 as shown in FIG. 5A using the complementary stencil mask, the pattern boundary portion between the patterns exposed using the two stencil masks may not be accurately connected. There was a problem.

Regarding the problem of such pattern connection accuracy, for example, in Japanese Patent Laid-Open No. 11-204423, there is a pattern boundary part that extends over both patterns connecting these patterns and is below the resolution of the pattern transfer device. A method has been proposed in which exposure is performed using a stencil mask in which a connecting pattern is formed in a complementary manner to improve the connecting accuracy. However, in the case of this method, for example, in the production of a low-magnification stencil mask in the case of performing pattern formation by exposing the electron beam as it is without being reduced-projection, fine processing for forming a pattern with a resolution or less. There was a problem that it was difficult.

As another example of the pattern connecting accuracy improving method, Japanese Patent Laid-Open No. 7-209855 discloses a reticle which is not a stencil mask but has a so-called checkered flag-like pattern formed complementarily at the pattern connecting portion. A method of performing exposure using a pattern has been proposed. However, in the case of this method, when applied to the stencil mask, the checkered flag-shaped pattern of the pattern connecting portion has a shape in which the donut pattern is continuously formed. There was a problem that it could not be realized.

The present invention has been made in view of the above circumstances, and provides an exposure method for preventing a connection failure by accurately connecting patterns at their pattern boundaries in pattern formation using a complementary mask. The purpose is to

[0014]

According to the present invention, in a method of exposing a pattern to be formed by using a complementary mask having openings of complementary divided shapes, a complementary mask is used. There is provided an exposure method, which comprises forming a pattern and exposing the pattern boundary portion using a boundary portion mask which is a mask having openings at positions corresponding to the pattern boundary portion generated in the pattern.

According to the above-mentioned structure, the boundary portion mask is formed by opening the position corresponding to the pattern boundary portion between the patterns formed in the pattern formed by using the complementary mask. With such a boundary mask,
Since the pattern boundary part generated in the pattern is exposed,
Even if the pattern boundary portions are not accurately connected by the exposure using the complementary mask, the pattern boundary portions are reliably exposed by the exposure using the boundary portion mask.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1A and 1B are explanatory diagrams of an electron beam exposure method according to an embodiment of the present invention. FIG. 1A is a formation pattern, FIG. 1B is a first stencil mask, FIG. 1C is a second stencil mask, and FIG. ) Is the third stencil mask,
(E) is a plan view of a fourth stencil mask.

In order to form the pattern shown in FIG. 1A, first, this pattern is divided into short patterns.
The first to fourth stencil masks shown in FIGS. 1B to 1E are manufactured.

The first stencil mask 11 and the second stencil mask 12 have the pattern 1 shown in FIG.
It is a complementary mask manufactured so that 0 has a complementary divided shape.

Here, the third stencil mask 13 is
A boundary which is a mask which has an opening 13a at a position corresponding to a pattern boundary portion formed when the first stencil mask 11 and the second stencil mask 12 are used for exposure, and which exposes the pattern boundary portion. Functions as a partial mask. Similarly, the fourth stencil mask 14 includes the first stencil mask 11 and the second stencil mask 1.
2 has an opening 14a at a position corresponding to the pattern boundary portion formed when the pattern boundary portion 2 is exposed, and functions as a boundary portion mask which is a mask for exposing the pattern boundary portion. Further, the third stencil mask 13 and the fourth stencil mask 14 are manufactured so that the pattern 10 shown in FIG. 1A has a complementary divided shape.

When exposure is performed using a stencil mask having such a complementary relationship, first, a pattern formed using the first stencil mask 11 and the second stencil mask 12, and a third stencil are formed. Mask 1
3 is used for exposure. As a result, part of the pattern boundary portion formed by the first stencil mask 11 and the second stencil mask 12 is exposed, and this pattern boundary portion can be connected. Further, by exposing using the fourth stencil mask 14, the remaining pattern boundary portions that are not connected when exposed using the third stencil mask 13 are exposed and connected. At this time, the third stencil mask 1
The pattern boundary portion formed by using the third and fourth stencil masks 14 is located on the pattern formed by using the first stencil mask 11 and the second stencil mask 12 and is not the pattern boundary portion. Because
The connection at the pattern boundary is secured.

Next, the method of forming the line pattern will be specifically described. When forming the pattern 10 shown in FIG. 1A, first, by using the first stencil mask 11, the exposure amount required for forming the pattern 10 is half the total exposure amount. The substrate is exposed.

Next, the second stencil mask 12 is used to expose the substrate with an exposure amount of ½ of the total exposure amount. Further, the third stencil mask 13 is used to expose the substrate with an exposure amount of ½ of the total exposure amount. The third stencil mask 13 exposes the pattern boundary portion formed by the first stencil mask 11 and the second stencil mask 12.

Finally, the fourth stencil mask 14 is used to expose the substrate with an exposure amount of ½ of the total exposure amount. The fourth stencil mask 14 exposes the remaining pattern boundary portion which is not connected when the third stencil mask 13 is used for exposure.

The pattern 1 is formed by the above electron beam exposure method.
The exposure is performed so that the total exposure amount becomes a predetermined total exposure amount over 0. Further, since the pattern boundary portion formed by using the first to fourth stencil masks is manufactured so as to be exposed, there is no connection failure at the pattern boundary portion. Furthermore, on a stencil mask,
In particular, even if a defect species is present at the end portion, the defect transferability onto the substrate can be reduced because the defective portion is exposed by another stencil mask by multiple exposure. In addition, the size of the opening of the stencil mask can be manufactured without restriction such that the size is smaller than the resolution of the pattern transfer device used.

In the above description, the case where the pattern 10 is formed by dividing the total exposure amount into two equal parts and performing the exposure four times has been described. As long as the total exposure amount reaches a predetermined value, the exposure amount can be changed for each exposure.

For example, when forming the pattern 10 shown in FIG. 1A as in the above case, first, the first stencil mask 11 is used and the substrate is exposed at an exposure amount of ⅔ of the total exposure amount. Do the top exposure. Then, the second stencil mask 12 is used to expose the substrate with an exposure amount of ⅔ of the total exposure amount. Further, the third stencil mask 13 is used to expose the substrate at an exposure amount of 1/3 of the total exposure amount, and finally, the fourth stencil mask 14 is used to perform exposure to 1/3 of the total exposure amount. The substrate is exposed with an exposure amount of.

Also in this case, the exposure is performed so that the total exposure amount becomes a predetermined total exposure amount over the entire pattern 10. Also, the third stencil mask 13
Exposes and connects the pattern boundary portion formed by the first stencil mask 11 and the second stencil mask 12, and the fourth stencil mask 14 is exposed by using the third stencil mask 13. Since the remaining pattern boundary part not connected to is exposed and connected,
There is no poor connection at the pattern boundary. In addition, the multiple exposure also reduces the defect transferability onto the substrate.

Next, the case where the present invention is applied to the formation of a donut pattern will be described. An example of a pattern having a donut pattern is SRAM (Static Random).
m Access Memory) element isolation layer.

FIG. 2 is a plan view of the SRAM element isolation layer pattern, and FIG. 3 is a plan view of the complementary stencil mask.
FIG. 4A is a plan view of a first stencil mask, FIG. 4B is a plan view of a second stencil mask, and FIG. 4 is a plan view of a complementary stencil mask. It is a top view of the stencil mask of FIG.

The donut-shaped pattern portion 20a shown in FIG.
First, as shown in FIG.
As shown in FIGS. 3A and 3B, a first stencil mask which is a complementary mask having openings 21a and 22a in which the donut pattern portion 20a of the pattern 20 is complementarily divided. 21 and a second stencil mask 22 are produced. That is, this first
Stencil mask 21 and second stencil mask 22
Means that the pattern 20 shown in FIG. 2 has a complementary divided shape.

The third stencil mask 23 shown in FIG. 4 (a) is a pattern boundary portion of the pattern 20a formed when exposure is performed using the first stencil mask 21 and the second stencil mask 22. Has an opening 23a at a position corresponding to, and functions as a boundary portion mask which is a mask for exposing the pattern boundary portion. Figure 4 (b)
The fourth stencil mask 24 shown in FIG. 2 has an opening 24a, and the third stencil mask 23 and the fourth stencil mask 24 are formed so that the pattern 20 has a complementary divided shape. There is.

Therefore, the first stencil mask 21
And the pattern 20 by the second stencil mask 22.
Can be formed, and the shape of the pattern 20 can be formed by the third stencil mask 23 and the fourth stencil mask 24.
Stencil mask 21 and second stencil mask 22
A pattern boundary portion of a pattern formed by and
The position is different from the pattern boundary portion of the pattern formed by the third stencil mask 23 and the fourth stencil mask 24.

When exposure is performed using the stencil mask having such a complementary relationship, first, a pattern formed by using the first stencil mask 21 and the second stencil mask 22 is further formed, and further, a third stencil is formed. Mask 2
3 is used for exposure. As a result, the pattern boundary portion formed by the first stencil mask 21 and the second stencil mask 22 is exposed, so that the pattern boundary portion can be connected. Further, by exposing using the fourth stencil mask 24, the entire area of the pattern 20 is equally exposed with a predetermined total exposure amount. At this time, the pattern boundary portion formed by using the third stencil mask 23 and the fourth stencil mask 24 is the pattern 20 formed by using the first stencil mask 21 and the second stencil mask 22.
Since it is located on a and not on the pattern boundary part,
The connection of the pattern boundary portion of the pattern 20a is secured.

Next, a method for forming the donut pattern will be specifically described. When forming the pattern 20 shown in FIG. 2, first, the first stencil mask 21 is used to expose the substrate with an exposure amount that is one half of the total exposure amount that is the exposure amount required to form the pattern 20. Expose.

Then, the second stencil mask 22 is used to expose the substrate with an exposure amount of ½ of the total exposure amount. Further, the third stencil mask 23 is used to expose the substrate with an exposure amount of ½ of the total exposure amount. The third stencil mask 23 exposes the pattern boundary portion formed by the first stencil mask 21 and the second stencil mask 22.

Finally, the fourth stencil mask 24 is used to expose the substrate with an exposure amount of ½ of the total exposure amount, and the entire area of the pattern 20 is equally exposed with a predetermined total exposure amount. .

By the above-mentioned electron beam exposure method, the pattern boundary portion is surely exposed, so that connection failure at the pattern boundary portion can be prevented. Further, even if there is a defect species on one stencil mask, especially at the edge thereof, the defective portion is exposed by another stencil mask by multiple exposure, so that the defect transferability onto the substrate can be reduced. it can.

In the above description, when the third stencil mask 23 is used for exposure, the pattern boundary portion formed by the first stencil mask 21 and the second stencil mask 22 is exposed. Of course, the present invention is not limited to this. That is, the pattern boundary portion formed by the first stencil mask 21 and the second stencil mask 22, the third stencil mask 23, and the fourth stencil mask 2
The position of the pattern boundary portion formed by 4 and 4 may be different.

In the above description, the method of forming the line pattern 10 and the donut pattern 20 has been described as an example, but the present invention can be applied to pattern formation by exposure of other shapes such as an L-shape.

In the above description, an exposure method using a stencil mask having an opening and utilizing transmission of an electron beam has been described. However, the present invention also utilizes an unscattered electron beam passing through the mask. The same effect can be obtained when applied to an exposure method in which a mask pattern is formed on the membrane mask and exposed.

Further, the present invention can be applied not only to the exposure with the electron beam but also to the exposure method using X-rays or light. Also in this case, a stencil mask or a membrane mask can be used.

[0042]

As described above, according to the present invention, the boundary portion mask formed by opening the position corresponding to the pattern boundary portion between the patterns formed in the pattern formed by using the complementary mask is used. The pattern boundary portion formed in the pattern is exposed. As a result, even if the pattern boundary portions are not accurately connected by the exposure using the complementary mask, the pattern boundary portions are surely exposed by performing the exposure using the boundary portion mask. . Therefore, it is possible to prevent the connection failure at the pattern boundary portion and improve the pattern connection accuracy.

Furthermore, it becomes possible to reduce the defect transferability of the defect species generated in the pattern connecting portion or the like onto the substrate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an electron beam exposure method according to an embodiment of the present invention, in which (a) is a formation pattern, (b) is a first stencil mask, and (c) is a second stencil mask.
(D) is a plan view of a third stencil mask and (e) is a plan view of a fourth stencil mask.

FIG. 2 is a plan view of an SRAM element isolation layer pattern.

FIG. 3 is a plan view of a complementary stencil mask,
It is a top view of the (a) 1st stencil mask and the (b) 2nd stencil mask.

FIG. 4 is a plan view of a complementary stencil mask,
It is a top view of (a) 3rd stencil mask and (b) 4th stencil mask.

FIG. 5 is a diagram illustrating an example of a conventional method for forming a donut pattern, in which (a) is a formed donut pattern;
(B) is a plan view of a first stencil mask, and (c) is a plan view of a second stencil mask.

6A and 6B are diagrams illustrating an example of a conventional line pattern forming method, FIG. 6A is a formed line pattern, FIG. 6B is a plan view of a first stencil mask, and FIG. 6C is a second stencil mask. FIG.

[Explanation of symbols]

10 ... pattern, 11 ... first stencil mask,
12 ... second stencil mask, 13 ... third stencil mask, 13a ... opening, 14 ... fourth stencil mask, 14a ... opening, 20 ... pattern,
20a ... pattern, 21 ... first stencil mask, 21a ... opening, 22 ... second stencil mask, 22a ... opening, 23 ... third stencil mask, 23a ... opening, 24 ... 4th stencil mask, 24a ... Opening part, 30 ... Pattern, 31 ... 1st stencil mask, 32 ... 2nd stencil mask, 40 ... Pattern, 41 ... 1st stencil Mask, 42 ... second stencil mask

Continued front page    F-term (reference) 2H095 BA08 BB02                 2H097 CA16 GB00                 5F046 GD10 GD20                 5F056 AA22 FA05

Claims (8)

[Claims] 1. An exposure method in which a pattern to be formed is exposed using a complementary mask having openings of complementary divided shapes, wherein the pattern is formed by exposure using the complementary mask, An exposure method characterized in that the pattern boundary portion is exposed by using a boundary portion mask which is a mask having an opening at a position corresponding to the pattern boundary portion generated in the pattern. 2. The exposure method according to claim 1, wherein, in the boundary portion mask, the pattern is divided in a complementary manner, and an opening is formed at a position corresponding to the pattern boundary portion. 3. The exposure method according to claim 1, wherein the complementary mask and the boundary mask are stencil masks. 4. The exposure method according to claim 1, wherein the complementary mask and the boundary mask are membrane masks. 5. The exposure method according to claim 1, wherein the exposure is performed by using one of an electron beam, an X-ray, and light. 6. Exposure is performed using a complementary mask having an opening having a shape in which a pattern to be formed is complementarily divided,
A mask, wherein a position corresponding to a pattern boundary portion generated in the formed pattern is opened. 7. The mask according to claim 6, which is a stencil mask. 8. The mask according to claim 6, which is a membrane mask.