JPH0511434A - Photomask - Google Patents

Abstract

PURPOSE:To provide the photomask which can prevent the formation of unnecessary patterns in a resist by the shifter edge lines for a phase shift method. CONSTITUTION:A 1st polarizing plate 62 and a 2nd polarizing plate 63 are provided on a substrate 61. Spacer layers 64 are provided on these polarizing plates and shifters 64 are provided on these spacer layers. The 1st and 2nd polarizing plates 62, 63 are so provided on the substrate 61 that the light transmission axes of both polarizing plates intersect orthogonally with each other and the edges of these polarizing plates come into contact with each other and that the joint lines of the edges with each other overlap substantially on the prescribed parts of the edge lines of the shifters 65.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used in a projection exposure method and having a phase shift method shifter.

[0002]

2. Description of the Related Art The phase shift method is drawing attention in the field of photolithography technology. This is because it is possible to form a fine resist pattern that can be used for high integration of a semiconductor device using almost the existing device.

As one example of the use of such a phase shift method, for example, there is a photomask for the phase shift method disclosed in Japanese Patent Publication No. 62-59296. 8A is a plan view showing this photomask as seen from the side where the light-shielding film or the like is formed, and FIG. 8B shows this photomask in I of FIG. 8A.
It is sectional drawing cut | disconnected and shown along the -I line. Incidentally, in the plan view, the corresponding portion is hatched in order to clarify the region of the light shielding portion.

In this photomask 10, light shielding portions 13 are provided on a glass substrate 11 at regular intervals, and the phase of exposure light is placed on every other light transmitting portion 15 between the light shielding portions 13. Each of them was provided with a transparent thin film (this thin film is referred to as a "shifter") 17 for shifting.

In this photomask 10, the light intensity at the portion of the resist (not shown) exposed through the photomask 10 facing the light-shielding portion 13 and the light intensity at the portion facing the light transmitting portion 15 are set. The difference is improved as compared with the case where the shifter 17 is not provided. For this reason, finer line-and-scan than when exposed through a photomask without the shifter 17 is provided.
The space pattern was obtained.

Further, as another application example of the phase shift method,
There was a pattern forming method (disclosed in Reference: Applied Physics Society (1990.9.27), Lecture No. 27p-ZG-3) in Japanese Patent Application No. 2-190162 related to the applicant of this application.

This pattern forming method uses a photomask in which a part of the contour line (edge line) of the shifter for the phase shift method is located in the light transmitting region, and an extremely fine portion is formed in a portion corresponding to the edge line of the resist. It was a method of forming an unexposed portion of a line. This method utilizes a phenomenon in which the intensity distribution of the exposure light sharply changes on the edge line of the shifter when the edge line is in the light transmission region.

In this pattern forming method, when a resist pattern for a gate pattern having a gate electrode and a pad portion is formed, two types of photomasks (first and second photomasks) are used and the exposure is performed twice. Had formed a pattern. This will be briefly described with reference to FIGS. 9A and 9B, 10 and 11.
Here, FIG. 9A is a plan view showing the first photomask as viewed from above, and FIG. 10 is a plan view showing the second photomask as viewed from above. Further, FIG. 9B is a plan view for explaining the latent image formed on the resist when the first photomask is used, and FIG. 11 shows two exposures using the first and second photomasks. FIG. 7 is a plan view for explaining a latent image formed on a resist later. However, in all the figures, an example in which two gate patterns are formed is shown. In addition, in order to clarify the regions of the light-shielding portion and the unexposed portion in the plan view, the corresponding portions are hatched.

In this pattern forming method, as shown in FIG. 9A, the first photomask 20 including the light transmitting portion 21, the rectangular light shielding portion 23, and the phase shift method shifter 25, which is the shifter 25, is used. The resist is exposed through the first photomask 20 in which a part of the edge is located in the light transmitting portion 21. In the resist that has been exposed using the first photomask 20, as shown in FIG. 9B, a region facing the light shielding part 23 becomes an unexposed part 23 a, and a region facing the edge line of the shifter 25 becomes. Due to the effect of the phase shift effect, the unexposed portion 25a is formed, and the other portions are exposed portions 27a. As is apparent from FIG. 9B, only the exposure using the first photomask 20 causes all the resist portions facing the edge lines of the shifter 25 to be unexposed portions, and unnecessary unexposed portions are generated. Therefore, a desired gate pattern cannot be obtained. Therefore, in this pattern forming method, a second photomask 30 having a light shielding portion 31 corresponding to the rectangular light shielding portion of the first photomask as shown in FIG. A portion corresponding to a predetermined portion of the edge portion located in the light transmitting portion of the shifter of the photomask is the light shielding portion 33.
Exposure is performed through the second photomask 30 which is supposed to be. An unexposed state is maintained in a region facing the light shielding portion 31 and a region facing the light shielding portion 33 of the resist exposed through the second photomask 30. Therefore, after the exposure process using both photomasks 20 and 30 is completed, as shown in FIG.
An unexposed portion 41 formed by the light shielding portion 23 of the first photomask (may be considered as the light shielding portion 31 of the second photomask), the edge portion of the shifter of the first photomask, and the light shielding of the second photomask. A latent image having an unexposed portion 43 formed by the overlapping portion of the portion 33 is formed.

Then, when the exposed resist is developed as shown in FIG. 11, if the resist is a negative type, a resist pattern in which the unexposed portions 41 and 43 of the resist are removed is obtained. This can be used as a resist pattern for forming the gate electrode and the pad portion by the lift-off method. If the resist is a positive type, a resist pattern in which only the unexposed portions 41 and 43 of the resist remain can be obtained. In either case, the portion that was the unexposed portion 43 is the portion for forming the gate electrode of the resist pattern, and the portion that was the unexposed portion 41 is the portion for forming the pad portion of the resist pattern.

According to this pattern forming method, it was possible to form a gate pattern having a fine gate electrode having a line width (dimension corresponding to the channel length) of 0.2 μm or less.

[0012]

However, when the resist is exposed through the photomask disclosed in Japanese Patent Publication No. 62-59296, the light transmitting portion of the edge line of the shifter 17 shown in FIG. Since the phase shift effect occurs in the portion 17a located inside 15, the portion of the resist facing the edge portion 17a is in an unexposed state. Therefore, as shown in FIG. 12, in the resist 50 exposed through this photomask, unnecessary unexposed portions 53 are generated in addition to the unexposed portions 51 formed by the original light shielding portions. When the resist is a negative type, the unexposed portion is removed by the development, and thus such unnecessary unexposed portion 5 is removed.
3 does not pose a problem, but when the resist is a positive type, this unnecessary unexposed portion 53 causes an unnecessary pattern, which causes a problem.

Further, in the pattern forming method described with reference to FIGS. 9 to 11, it is necessary to use two types of photomasks and to perform exposure twice, so that there is a problem that the pattern forming process becomes long. .

The present invention has been made in view of the above points, and therefore an object of the present invention is to provide a photomask having a shifter for the phase shift method, and to prevent unnecessary unexposed portions from occurring once. Another object of the present invention is to provide a photomask capable of forming a desired pattern by exposure of.

[0015]

In order to achieve this object, according to the present invention, in a photomask having a shifter for a phase shift method on a substrate, a first polarizing plate and a second polarizing plate are provided on the substrate. The polarizing plate and the polarizing plate are planarly arranged so that the light transmission axes of these polarizing plates are not parallel to each other and the edges of the polarizing plates are in contact with each other, and the joining line between the edges is a predetermined edge line of the shifter. It is provided so that it substantially overlaps the part,
It is characterized in that the shifter is provided on these polarizing plates.

Here, the substrate can be composed of a glass substrate or the like which is usually used in photomask fabrication. Further, the light transmission axis of the polarizing plate means, for example, the transmission axis described in the literature (“Latest Liquid Crystal Technology” published by Industrial Research Society (1984), p.149). In addition, the provision of these polarizing plates on the substrate so that the light transmission axes of the first and second polarizing plates are non-parallel means that the light transmission axes of the first and second polarizing plates are preferably orthogonal or close to each other. Both polarizing plates are provided. This is because the vibrating surface of the linearly polarized light that has passed through the first polarizing plate and the vibrating surface of the linearly polarized light that has passed through the second polarizing plate can be made orthogonal or substantially orthogonal to each other. The first polarizing plate and the second polarizing plate referred to in the present invention are, of course, not only independent polarizing plates, but apparently integrated polarizing plates and transmitting light at a certain position. It also includes the case of a polarizing plate whose axis is changed.

Also, "substantially overlapping the joining line of the first polarizing plate and the second polarizing plate on the edge line of the shifter" means that when the joining line and the edge line are superposed on each other, they are substantially aligned. Both are included when overlapping. However, it is preferable that the joining line and the edge line are aligned and overlapped.

Further, in carrying out the present invention, it is difficult to complete the bonding of the first and second polarizing plates without loss of light. The exposure light may be attenuated. In such a case, if the first and second polarizing plates are in direct contact with the shifter, the bonding line of the first and second polarizing plates may be included in the depth of focus for pattern formation. There is a risk that an unexposed portion may be formed due to the joining line. Therefore, in a preferred embodiment of the present invention, a spacer layer made of a material substantially transparent to exposure light is provided over the first polarizing plate and the second polarizing plate, and the above-mentioned shifter is provided on this spacer layer. .

[0019]

According to the structure of the present invention, the periphery of the portion of the photomask where the edge line of the shifter and the joining line of the first and second polarizing plates overlap each other has a substrate on one side with the edge line portion as a boundary, It has a laminated structure composed of a polarizing plate and a shifter, and has a laminated structure composed of a substrate and a polarizing plate on the other side. Therefore, if the polarizing plate in contact with the shifter is considered as, for example, the first polarizing plate, the light passing through the first polarizing plate and the shifter and the second polarizing plate are provided in the resist portion facing the edge line portion. The light passing through is illuminated.
At this time, the phase of the light that has passed through the first polarizing plate (hereinafter, referred to as “first linearly polarized light”) is the light that has passed through the second polarizing plate due to the influence of the shifter (hereinafter, “second linearly polarized light”). ".)
However, since the light transmission axes of the first polarizing plate and the second polarizing plate are not parallel to each other, the vibrating planes of the first and second linearly polarized light are not parallel to each other, so both linearly polarized light Interference is smaller than that in the case where the polarizing plate is not provided (normal phase shift mask). Particularly, when the first and second polarizing plates are provided so that their optical axes are orthogonal to each other, the interference between the two linearly polarized lights can be substantially eliminated.

In the case of a structure in which a spacer layer made of a material substantially transparent to exposure light is provided on the first polarizing plate and the second polarizing plate, the shifter is provided on the spacer layer. The bonding line of the first and second polarizing plates and the shifter are separated by the thickness of the spacer layer. Therefore, it is difficult to focus the joining line of the first and second polarizing plates during patterning.

[0021]

Embodiments of the photomask of the present invention will be described below with reference to the drawings. It should be noted that the drawings used in the following description schematically show the dimensions, shapes, and arrangement relationships of the respective constituent components to the extent that the present invention can be understood. In the plan views of the following drawings, corresponding regions are hatched in some cases in order to clarify the regions of the first polarizing plate and the second polarizing plate.

1. First Embodiment The photomask of the first embodiment is a photomask which can form two fine line patterns parallel to each other by utilizing the edges of a shifter. FIGS. 1A to 1C are views for explaining the photomask 60 of the first embodiment. In particular,
FIG. 1A is a plan view showing the photomask 60 as seen from the side where the shifter or the like is formed (the side facing the resist).
1B is a cross-sectional view showing the photomask cut along the line P-P of FIG. 1A, and FIG. 1C is a cross-sectional view of the photomask cut along the line Q-Q of FIG. FIG.

The photomask 60 of the first embodiment has a first polarizing plate 6 on a quartz glass substrate 61 as a substrate.
2 and the second polarizing plate 63 are provided in a plane, and a spacer layer 64 substantially transparent to exposure light is provided over the polarizing plates 62 and 63, and a shifter 65 having a rectangular plane shape is provided on the spacer layer 64. Made up of.

Here, the second polarizing plate 63 is the first portion 6
3a and the second part 63b. The first polarizing plate 62 has the same width as one width W ₁ of the rectangular shifter 65 and is provided on the substrate 61 so as to overlap with the shifter 65. Further, the first portion 63 a and the second portion 63 b of the second polarizing plate 63 are arranged on the substrate 61 such that the first portion 63 a of the second polarizing plate 63 is in the width direction of the first polarizing plate 62. The second portion 63 of the second polarizing plate 63 is in contact with one end (side).
b is provided so as to contact the other end (side) of the first polarizing plate 62 in the width direction, and the light transmission axis of the second polarizing plate 63 is orthogonal to that of the first polarizing plate 62. It is provided to do so. In FIG. 1A, L ₁ indicates the vibration direction of linearly polarized light by the first polarizing plate 62, and L ₂ indicates the second polarizing plate 63 (63
a, 63b) shows the vibration direction of linearly polarized light.

Further, the thickness of the spacer layer 64 is set so that the bonding line of the first and second polarizing plates 62, 63 is formed from the focal position of the shifter 65 or the like in order to prevent the bonding line from forming an image on the resist. The thickness should be adjustable. This thickness is not limited to this, but may be several μm. The spacer layer 64 can be made of, for example, SiO ₂ or a suitable organic thin film.

With such a configuration, in the photomask 60 of the first embodiment, the first polarized light is provided below the pair of opposing edge lines 65a and 65b among the edge lines of the rectangular shifter 65. The joining line of the plate 62 and the second polarizing plate 63 is located.

When the resist is exposed through the photomask 60 of the first embodiment, the phase shift effect is caused by the shifter 6
Among the 5 edge lines, it occurs in the edge line located on the first polarizing plate 62, and does not occur in the edge lines indicated by 65a and 65b in FIG. The resist portion corresponding to the edge line portions shown by 65a and 65b in FIG. This is because the exposure is performed with the polarized light and the linearly polarized light that has passed through the second polarizing plate 63, so that the phase shift effect does not occur. As a result, of the edge lines of the shifter 65, only the resist portion corresponding to the edge line located on the first polarizing plate 62 becomes the unexposed portion. FIG. 2 is a plan view showing the situation. 67 is a resist, 68 is an unexposed area, and 69 is an exposed area.

2. Second Embodiment The photomask of the second embodiment is a photomask which can form the gate pattern shown in FIG. 11 by one exposure. Figure 3
(A)-(C) are the top views and sectional views with which the photomask 70 of this 2nd Example is demonstrated. These figures are shown in the same notation as in FIGS. 1 (A) to 1 (C). Further, in FIG. 3, the same components as those in FIG.
It is shown with the same numbers as those used in
The description is omitted.

The photomask 70 of the second embodiment has a first
The photomask 60 of the embodiment is newly provided with a light-shielding portion 71 (a portion which is clearly shown in FIG. 2A by hatching) corresponding to the light-shielding portion 23 shown in FIG. 9A. Configured. The light shielding portion 71 may be formed of a light shielding film made of, for example, a chrome film. Further, the light shielding portion 71 is provided between the spacer layer 64 and the shifter 65 so as to overlap a predetermined portion of the shifter. In some cases, it may be on the shifter 65.

When the resist is exposed through the photomask 70 of the second embodiment, the resist portion corresponding to the portions indicated by 65c and 65d in FIG. 3 among the edge lines of the shifter becomes an unexposed portion of an ultrafine line, and is shielded from light. The resist portion corresponding to the portion 71 becomes a rectangular unexposed portion, and the other resist portions become exposed portions. The unexposed portion of the ultrafine wire can be used as a gate electrode forming pattern, and the rectangular unexposed portion can be used as a pad forming pattern. As a result, the resist latent image for the gate pattern shown in FIG. 11 can be formed by one exposure.

3. Third Embodiment The photomask of the third embodiment is an example in which the present invention is applied to the line-and-space forming photomask 10 described with reference to FIG. 8 having a shifter. FIG. 4A is a plan view for explaining the photomask 80 of the third embodiment, and is a plan view similar to FIG. 8A. Note that FIG.
In FIG. 8A, the same components as those shown in FIG. 8A are designated by the same numbers as those used in FIG. The same components as those shown in FIG. 1 are designated by the same numbers as those used in FIG.

In the photomask 80 of the third embodiment, the first polarizing plate 62 is provided on the substrate (not shown) on the shifter 17 and the region where the light shielding portion 13 is to be formed. Further, the first portion 63a of the second polarizing plate is in contact with the upper end portion of the first polarizing plate 62 in the figure, and the second portion 63b of the second polarizing plate is at the lower end portion. The first portion 63a and the second portion 63b are provided on the substrate so as to be in contact with each other. In addition, these first and second polarizing plates 62, 63
A spacer layer (not shown) is provided on the upper surface as in the first embodiment. Then, the light shielding portion 13 and the shifter 17 are provided on this spacer layer in the same manner as in FIG.

In the photomask 80 of the third embodiment, since the joining line of the first and second polarizing plates is located below the portion 17a of the edge line of the shifter 17 located in the light transmitting portion, this edge portion is located. No optical interference occurs at 17a (no phase shift effect occurs). Therefore, as shown in FIG. 4B, the resist 81 exposed through the photomask 80 has an unexposed portion 82 corresponding to the light shielding portion 13 and an exposed portion 83 other than the exposed portion. As a result, a desired line and space pattern can be obtained even when the resist is a positive type.

4. Other Embodiments FIGS. 5A and 5B, 6A and 6B, and FIG.
(A) And (B) is a figure offered for description of each other Example. In all of the drawings, (A) is a plan view showing the photomask of each example, and (B) is a plan view showing the latent image formed on the resist exposed through the corresponding photomask. .. 5 (A), 6 (A) and 7 (A), the shifter 65 and the first polarizing plate 6 are all shown.
2 is schematically shown to the extent that the two-dimensional positional relationship between the second polarizing plate 63 and the second polarizing plate 63 can be understood.

The photomask 91 shown in FIG. 5A is constructed so that the joining line at the edges of the first polarizing plate 62 and the second polarizing plate 63 overlaps with the edge line corresponding to one side of the rectangular shifter 65. It is a photo mask. When the resist is exposed through this photomask 91, as shown in FIG. 5B, in the resist 67, a portion facing the remaining three sides of the rectangular shifter 65 becomes an unexposed portion 91a of an extra fine line. Thus, a latent image is formed in which the other portion is the exposed portion 69.

In the photomask 92 shown in FIG. 6A, the joining lines at the edges of the first polarizing plate 62 and the second polarizing plate 63 are overlapped with the edge lines corresponding to the three sides of the rectangular shifter 65. It is a configured photomask. When the resist is exposed through this photomask 92, as shown in FIG. 6B, the resist 67 has an unexposed portion 92a of a fine line in a portion facing the remaining one side of the rectangular shifter 65. A latent image in which the other portion is the exposed portion 69 is formed.

In the photomask 93 shown in FIG. 7A, the joining lines at the edges of the first polarizing plate 62 and the second polarizing plate 63 overlap with the edge lines corresponding to the two orthogonal sides of the rectangular shifter 65. It is a photomask configured as described above. When the resist is exposed through this photomask 93, as shown in FIG. 7B, in the resist 67, a portion facing the remaining two sides of the rectangular shifter 65 becomes an unexposed portion 93a of an extra fine line. Thus, a latent image is formed in which the other portion is the exposed portion 69.

[0038]

As is apparent from the above description, according to the photomask of the present invention, the first and second polarizing plates are provided below the predetermined portion of the edge line of the shifter, and the light transmission axes of these polarizing plates are The polarizing plates are provided so as to be non-parallel to each other so that the edges of the polarizing plates are in contact with each other, and the joining line between the edges is substantially overlapped with a predetermined portion of the edge line of the shifter. . Therefore, since the lights passing through both regions with the edge line around the predetermined part of the photomask as a boundary have different polarization directions, a polarizing plate is provided for the interference of the lights even if they are out of phase by the shifter. It can be reduced compared to the case without it. Therefore, the exposure state can be obtained in the resist portion corresponding to the predetermined portion of the edge line of the shifter, so that an unnecessary pattern does not occur.

Therefore, when the present invention is applied to, for example, the formation of an ultrafine line gate pattern using the edge line of a shifter, a desired gate pattern can be obtained by a single exposure using one photomask. . Further, when the present invention is applied to a line-and-space pattern photomask with a shifter, unnecessary patterns that have been conventionally generated when a positive resist is used are not generated.

[Brief description of drawings]

1A to 1C are a plan view, a sectional view taken along the line PP and a sectional view taken along the line QQ for explaining a photomask according to a first embodiment.

FIG. 2 is a diagram for explaining a latent image formed on a resist exposed through a photomask of the first embodiment.

3A to 3C are a plan view, a sectional view taken along the line PP and a sectional view taken along the line QQ of the photomask of the second embodiment.

FIG. 4A is a plan view for explaining a photomask of a third embodiment, and FIG. 4B is a view showing a latent image formed on a resist exposed through the photomask of the third embodiment.

5 (A) and 5 (B) are diagrams for explaining another embodiment.

6 (A) and 6 (B) are diagrams for explaining yet another embodiment.

FIGS. 7A and 7B are diagrams for explaining yet another embodiment. FIG.

8A and 8B are explanatory views of a conventional line-and-space photomask with a shifter.

9A and 9B are diagrams for explaining a conventional pattern forming method, FIG. 9A is an explanatory diagram of a first photomask, and FIG. 9B is an exposure through the first photomask. FIG. 6 is a diagram showing a latent image formed on a resist.

FIG. 10 is a diagram for explaining a conventional pattern forming method.
It is an explanatory view following the above, and is an explanatory view of a second photomask.

FIG. 11 is a diagram for explaining a conventional pattern forming method.
It is explanatory drawing following 0, and is a figure which showed the latent image formed in the resist exposed through the 1st and 2nd photomask.

FIG. 12 is a diagram for explaining a problem in a conventional photomask for line and space.

[Explanation of symbols]

60: Photomask of the first embodiment 61: substrate 62: First polarizing plate 63: Second polarizing plate 63a: the first part of the second polarizing plate 63b: the second part of the second polarizing plate 64: Spacer layer 65: Shifter 65a, 65b: predetermined portions of edge line of shifter 67: Resist 68: Unexposed area 69: Exposure unit 70: Photomask of the second embodiment 71: Light-shielding part 80: Photomask of the third embodiment 13: Shading section 17: Shifter 17a: a predetermined portion of the edge line of the shifter 81: Resist 82: Unexposed part 83: Exposure unit 91, 92, 93: Photomasks of other embodiments 91a, 91b, 91c: unexposed parts

Claims (3)

[Claims] 1. A photomask having a shifter for a phase shift method on a substrate, wherein a first polarizing plate and a second polarizing plate are arranged on the substrate so that the light transmission axes of these polarizing plates are not parallel to each other. And so that the edges of these polarizing plates are in contact with each other in a plane and the joining line between the edges substantially overlaps a predetermined portion of the edge line of the shifter. A photomask comprising the shifter. 2. The photomask according to claim 1, wherein a spacer layer made of a material substantially transparent to exposure light is provided on the first polarizing plate and the second polarizing plate, and the spacer layer is provided on the spacer layer. A photomask provided with the shifter. 3. The photomask according to claim 1, further comprising a light-shielding film which is overlapped with a predetermined portion of the shifter as required.