JP3443377B2 - Phase shift mask having three different phase shift regions and manufacturing method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask, and more particularly to three problems to solve the so-called corner round problem in which corners are rounded in an unexposed edge region due to light diffraction or scattering. The present invention relates to a phase shift mask having different phase shift regions.

[0002]

2. Description of the Related Art With the increasing demand for higher integration of integrated circuits, development is underway toward further miniaturization of devices and circuits. Photolithography technology is the technology that plays the most important role in such miniaturization.
For example, metals such as thin film patterns and dopant regions
The dimensions of structures associated with oxide semiconductors (MOS) are basically determined by this technology. As described above, whether or not the integration in the semiconductor industry is developed to the line width of 0.15 μm or less is dependent on the development of the photolithography technology. Based on such a large demand, optical proximity correction (OPC)
mity correction) and phase shift mask (PSM: phase s)
A method for increasing the resolution of a photo mask such as a hift mask) has been proposed.

The method of optical proximity correction is based on the proximity effect (proximi
critical dimension caused by the ty effect
This is for eliminating the deviation of (dimension). When the light beam is incident on the wafer through the pattern of the photomask, the light beam is scattered and the area on the wafer illuminated by the light is increased. On the other hand, the light beam is reflected from the semiconductor substrate of the wafer and causes interference with the incident light beam. As a result, double exposure occurs and the exposure degree of the wafer (exp
osure degree) changes. The proximity effect becomes more pronounced when the critical dimension is close to the wavelength of the incident light.

1 and 2 show a conventional optical proximity correction method. In FIG. 1A, the photomask 100 has a pattern 105 composed of three rectangular mask regions,
The remaining area of the photomask 100 is a transparent area 110. As a substrate material for the photomask, glass or quartz is mainly used to form a transparent region. The mask area is mainly made of a chrome (Cr) layer. Figure 1
In (b), when the light beam is incident on the photomask 100, three dark regions 125 are formed in the bright region 130 on the wafer substrate 120 placed directly below the photomask 100.

As shown in FIG. 1B, the mask region 105
Is a rectangle with sharp corners, but the pattern transferred onto the wafer substrate 120 is a dark area 125 with rounded corners and reduced dimensions. Although not shown, deformation and distortion that cannot be ignored in other mask regions often pose a problem. For example, when the mask areas of the patterns are close to each other, the patterns transferred onto the wafer substrate by exposure may be merged with each other, or distortion from the original shape of the patterns may occur.

In practice, in order to prevent the above-mentioned distortion that occurs at the corners and edges of the mask area 105, serif
Auxiliary tools such as (serif) and hammerhead are added to the original pattern. For example, FIG. 2 (a)
As shown in, the serifs 150 and 155 are arranged along the corners and the edges. The serifs 150 arranged at the corners solve the problem that the corners are rounded, and the serifs 155 arranged along the edges prevent the reduction of the pattern size. As shown in FIG. 2B, by introducing this method, the photomask 100 is removed from the wafer substrate 120.
The fidelity of the pattern transferred to is greatly improved. The roundness of the corner portion of the dark region 125a becomes small, and the size of the dark region 125a approaches the size of the mask region 105 in the photomask 100.

[0007]

However, the distance between the patterns is further reduced, and the critical dimension is 0.1 μm.
When scaled down to m or less, the above method faces its limitations. That is, when adopting a method of correcting or compensating a pattern, the space or area in which an assisting tool such as a serif can be placed is limited.

[0008]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a phase shift mask having three different phase shift regions which can alleviate the above problems. An opaque pattern is formed so as to cover the first portion of the transparent substrate and ensure the translucency of the second portion of the transparent substrate. The three phase shift regions provided by etching on the second portion of the transparent substrate are 120
They differ from each other by a phase shift of °. The adjacent regions around the corners of the opaque pattern are evenly divided by the three different phase shift regions, and these three phase shift regions are formed with different etching depths . Also, the second portion of the transparent substrate away from the proximity region includes a phase edge formed between two of the three phase shift regions instead of the three phase shift regions.

The phase shift mask having three different phase shift regions of the present invention has a problem that a corner of the transferred pattern is rounded, that is, a so-called corner round effect.
Deformation such as (corner rounding effect) can be eliminated. This is because the incident light is split into three light beams when passing through the three phase shift regions at the corners of the pattern on the photomask. These three
The two phase shift regions differ from each other by a phase shift of 120 °, so that the sum of the three split light beams is zero. As a result, light diffraction, scattering and interference at the corners of the wafer can be eliminated. In this way, the fidelity of the transfer pattern is improved. further,
In other parts of the photomask, a phase edge is formed between the two phase shift regions. These two phase shift regions differ from each other by a 120 ° phase shift. Therefore, the lights do not completely cancel out at the phase edge. As a result, there is no concern of forming undesired dark areas on the wafer.

A further object of the present invention is to provide a method of manufacturing a phase shift mask having the above three different phase shift regions. The phase shift mask of the present invention can be formed by two etching steps. That is, three different phase shift regions can be formed by performing the etching process twice on the second portion of the transparent substrate other than the first portion covered by the opaque pattern.

The above description of the present invention and the detailed description of the present invention given below are both illustrative, and the present invention is not limited thereto.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

In FIG. 3A, a photomask 200
Includes a mask pattern 210 having corners 215. The mask pattern 210 is made of a material such as chrome that blocks incident light. That is, the mask pattern 21
Reference numeral 0 is an opaque mask region, and the remaining region of the photomask 200 is transparent to incident light and is made of, for example, glass or quartz. The adjacent region around the corner 215 has three phase shift regions 220, 230, 24.
It is evenly divided by 0. If the angle of the corner 215 is a °, the phase shift regions 220, 230 and 2
40 is respectively around the intersection point corresponding to the angle 215.
It will have an angle of (360-a °) / 3.

By etching the transparent area of the photomask 200, the phase of the incident light can be changed according to the depth of the etching area. In this embodiment,
First, by performing a first etching process on the regions corresponding to the phase shift regions 220 and 240, 120 °,
That is, a phase region having a phase of 2 / 3π is formed.
Next, a region corresponding to the phase shift regions 230 and 240 is subjected to a second etching process to form a phase shift region having a phase of 240 °, that is, 4 / 3π. As a result, the region 240 that has been subjected to both the first and second etching treatments is 0 ° (= 360 °), that is, 2π.
The phase shift region has a phase of. The three phase shift regions 220, 230, 240 obtained in this way
Have a phase difference of 2 / 3π from each other.

FIG. 3 (b) shows the vectors of the three light beams obtained by the incident light passing through these regions. Further, FIG. 3C shows the time change of the amplitude of the light beam. As is clear from these figures, the three light beams cancel each other out. Therefore, at the corner 215, the incident light beam will be split and offset. This is the corner 215 during exposure.
Means substantially not illuminated by light. In the present invention, the effect obtained by adding an auxiliary tool around the corner in order to improve the fidelity of the transfer pattern can be achieved in the present invention without adding such an auxiliary tool. it can.

In the above, it has been shown that the deformation of the corner can be eliminated by providing three phase shift areas in the adjacent area around the corner 215. However, the entire pattern of the photomask has not been considered yet. FIG. 4A shows a mask region 310 of the photomask 300 of the present invention.
At each corner of the mask pattern of the photomask 300, in order to eliminate the deformation caused by the corner round effect, three different phase shift areas are provided in the adjacent area around each corner. In FIG. 4A, the area 320 hatched by the diagonal line descending to the right is 12
A region 330 having a phase shift of 0 ° and hatched with a downward-sloping diagonal line has a phase shift of 240 °, and a region 340 further hatched with a halftone dot has a phase shift of
It has a phase shift of 360 °. The mask area 310
Is a mask pattern made of an opaque material such as chrome.

The present invention will be described again with reference to FIG. 4. When light is applied to the photomask 300, the light applied to each corner portion of the mask region 310 is converted into these three regions 320, 330 ,. The light beam is split into three light beams having different phases by 340. These three light beams have a phase shift of 120 ° 240 ° and 360 ° respectively. FIG. 4B shows the vectors of these three light beams. The combination of these three light beams is equal to zero, and the incident light on the near region around the corner is canceled. Therefore, phenomena such as diffraction, scattering and interference can be avoided. in this way,
It is possible to solve the deformation problem such as the corner round effect.

In addition to these corners, the three phase shift regions 320, 330 and 340 also extend to other transparent regions on the photomask 300. That is, as shown in FIG. 4A, the phase edge is formed in the translucent region of the photomask 300 other than the adjacent region around the corner. For example, the phase edge of the portion indicated by the number 360 is the region 330 and the region 340.
It is formed between and. Of course, a phase edge may be formed between the regions 320 and 330 or between the regions 320 and 340. Further, as shown in FIG. 4A, each side of the mask pattern 310 is adjacent to one of the phase shift regions 320, 330 and 340. For example, in the area indicated by the number 350,
The region 340 is adjacent to the mask pattern 310.

FIG. 4 (c) shows the sum of the light beams passing through the phase edge between regions 320 and 340. In addition, in FIG. 4D, a region 320 and a region 3
The total number of light beams passing through the phase edge between 30 and 30 is shown. Further, in FIG.
The total number of light beams passing through the phase edge between the region 340 and the region 340 is shown. As is clear from these figures, unlike the phase edges between complementary phase shift regions, for example, between 0 ° and 180 ° phase shift regions, in the present invention, the positions at the phase edges are different. Since the phase difference is 120 °, the light beams do not have to be canceled at the phase edge. 4 (c)-
As shown in (e), the sum of these two light beams has substantially the same amplitude as these two light beams,
Its phase is in the middle of the phases of the two light beams. Therefore, by using the phase shift mask of the present invention, it is possible not only to solve the problem of shape deformation at the corners, but also to form an undesired dark region on the wafer after exposure (phase edge effect (phase edge
effect) can be avoided.

The above-mentioned phase shift region can be formed by etching the translucent region of the photomask substrate at different depths . The translucent regions having different depths change the optical path through which incident light passes. Thus, the three phase shift regions of the present invention have different thicknesses.

FIG. 5 shows an example of a photomask 400 for forming an array of rectangular patterns 405. In addition, a method of forming three phase shift regions at each corner of the rectangular pattern 405 of this photomask is shown in FIG.
It is shown in (a)-(c). First, the photomask 410
Are etched to form an opaque pattern of vertical stripes corresponding to the mask area 415, as shown in FIG. This is the first etching step. As previously mentioned, this opaque region 415 is primarily made of chrome.
By this first etching process, a 120 ° etching region 420 having a light transmitting property and a phase of 120 ° is formed. Then, the photomask 410 is formed as shown in FIG.
Etched to form an opaque pattern of horizontal stripes corresponding to the mask area 415, as shown in FIG. This is the second etching step. By this second etching process, the light-transmissive and phase of 240 ° 24
A 0 ° etching region 425 is formed. FIG. 6C shows a region etched by both the first etching process and the second etching process, that is, 360 ° (1
A region 450 having a phase of 20 ° + 240 ° is depicted. In this way, the adjacent regions at the respective corners of the rectangular mask region 415 of FIG. 6C are evenly divided by the first to third phase shift regions 430, 440 and 450.

7 to 10 show a case where three phase shift regions of the present invention are formed in a photomask having a mask pattern different from the above. Figure 5
FIG. 4 is a diagram showing a mask pattern to be formed on a photomask, which is made of an opaque material such as chrome,
It consists of alternating rectangular blocks. The first to third phase shift regions can be formed through two etching steps, as in the above. When forming the three phase shift regions in the photomask having the mask pattern shown in FIG. 7, the etching process can be performed using various patterns as described below.

For example, when the step shown in FIG. 8 is adopted, the first etching step is performed based on the pattern shown in FIG. 8A to form the first phase shift region having a phase of 120 °. . Then, a second etching process is performed based on the pattern shown in FIG.
Forming a second phase shift region having a phase of. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way, a phase shift mask (FIG. 8C) in which the first to third phase shift regions are formed around each corner of the rectangular pattern is obtained.

Further, instead of FIG. 8, the process shown in FIG. 9 may be adopted. That is, FIG. 9 different from FIG.
A first etching process is performed based on the pattern of (a) to form a first phase shift region having a phase of 120 °. Then, a second etching process is performed based on the same pattern of FIG. 9B as that of FIG. 8B to form a second phase shift region having a phase of 240 °. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way, the first
A phase shift mask (FIG. 9C) in which the third phase shift region is formed around each corner of the rectangular pattern is obtained. Although the arrangement of the first to third phase shift areas in FIG. 9C is different from that in FIG. 8C, the arrangement of the mask areas formed of rectangular blocks is the same as that in FIG. 8C.

Further, instead of FIG. 8, the process shown in FIG. 10 may be adopted. That is, the first etching process is performed based on the pattern of FIG. 10A different from FIG. 8A to form the first phase shift region having a phase of 120 °. Then, a second etching process is performed based on the same pattern of FIG. 10B as that of FIG. 8B to form a second phase shift region having a phase of 240 °. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way
A phase shift mask (FIG. 10C) in which the first to third phase shift regions are formed around each corner of the rectangular pattern is obtained. Although the arrangement of the first to third phase shift areas in FIG. 10C is different from that in FIG. 8C, the arrangement of the mask areas formed of rectangular blocks is the same as that in FIG. 8C.

In each of FIGS. 8 (c), 9 (c) and 10 (c), the adjacent regions around the corners of the mask region are evenly divided by the first to third phase shift regions, As a result, the areas near the corners are not exposed,
The problem of deformation of the transferred corner shape can be eliminated.

11 to 13 show a case where three phase shift regions of the present invention are formed in a photomask having another mask pattern. Figure 11
FIG. 8 is a diagram showing a mask pattern to be formed on a photomask, which is composed of rectangular blocks arranged alternately according to a rule different from FIG. 7.

When the step shown in FIG. 12 is adopted, the first etching step is carried out based on the pattern shown in FIG. 12A to form the first phase shift region having a phase of 120 °. Then, a second etching process is performed based on the pattern shown in FIG. 12B to form a second phase shift region having a phase of 240 °. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way, the phase shift mask in which the first to third phase shift regions are formed around each corner of the rectangular pattern (FIG. 12C).
Is obtained.

Further, instead of FIG. 12, the process shown in FIG. 13 may be adopted. That is, the first etching process is performed based on the pattern of FIG. 13A different from FIG. 12A to form the first phase shift region having a phase of 120 °. Then, a second etching process is performed based on the same pattern of FIG. 13B as that of FIG.
Forming a second phase shift region having a phase of. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way, the first to third phase shift regions are formed around each corner of the rectangular pattern (FIG. 13C).
Is obtained. The arrangement of the first to third phase shift areas in FIG. 13C is different from that in FIG. 12C, but the arrangement of the mask areas formed of rectangular blocks is the same as that in FIG. 12C.

14 and 15 show a case where three phase shift regions of the present invention are formed in a photomask having a convex block mask pattern.
A first etching process is performed based on the pattern shown in FIG. 15A to form a first phase shift region having a phase of 120 °. Then, a second etching step is performed based on the pattern shown in FIG.
Forming a second phase shift region having a phase of. The overlapping region of the two etching processes becomes the third phase shift region having the phase of 360 °. In this way, the first to third phase shift regions are formed around the corners of the convex mask pattern (see FIG. 15).
(c)) is obtained. As shown in FIG. 15C, the adjacent regions around the corners of the mask pattern are 12
It is evenly divided by three phase shift regions which differ by a phase difference of 0 °.

As described above, the present invention has been explained based on the preferred embodiments, but the present invention is not limited to these embodiments. As will be easily understood by those skilled in the art, appropriate changes and modifications may be made within the scope of the technical idea of the present invention as necessary. Therefore, the scope of the claims of the present invention should be made based on the broad interpretation including such changes and modifications.

[0032]

As described in detail based on the above embodiment, the present invention comprises three different phase shift regions having the ability to cancel the light transmitted through the adjacent regions around the corners of the pattern of the photomask. And a phase shift mask. By using this phase shift mask, the distortion generated in the transferred pattern, particularly the corner round effect in which the corner is rounded, can be eliminated without using a correction aid. Therefore, even when the distance between the patterns is small, high fidelity of pattern transfer onto the wafer can be achieved. As described above, the phase shift mask of the present invention is particularly effective for a pattern having a small critical dimension in which the space available for arranging the auxiliary tool is limited, and its utility value is high.

[Brief description of drawings]

FIG. 1A is a diagram showing a conventional photomask,
(b) is a figure which shows the transfer pattern obtained using it.

FIG. 2A is a diagram showing a photomask subjected to a conventional optical proximity correction method, and FIG. 2B is a diagram showing a transfer pattern obtained by using the photomask.

FIG. 3 (a) is a top view showing an example of a phase shift mask according to an embodiment of the present invention, and FIG. 3 (b) is a view showing division when transmitting a proximity region around a corner of a mask pattern of the phase shift mask. It is a figure which shows the vector of the three light beams made into, and (c) is a wave form diagram which shows that three light beams cancel as a result.

FIG. 4 (a) is a plan view showing first, second and third phase shift regions of the phase shift mask of the present invention, and FIG.
FIG. 3 is a diagram showing the vectors of three light beams that are divided when passing through a neighboring region around the corner of the mask pattern of the phase shift mask, and (c) to (e) are two of the three phase shift regions. It is a figure which shows the vector of two light beams which are divided when transmitting the phase edge formed between areas, and the vector obtained by combining them.

FIG. 5 is a diagram showing a pattern to be formed on a photomask.

FIG. 6A is a diagram showing a pattern for forming a 120 ° etching region, FIG. 6B is a diagram showing a pattern for forming a 240 ° etching region, and FIG.
FIG. 3 is a diagram showing a phase shift mask having three different phase shift regions of the present invention obtained by overlapping the patterns of (a) and (b).

FIG. 7 is a diagram showing a pattern to be formed on a photomask.

FIG. 8A is a diagram showing a pattern for forming a 120 ° etching region, FIG. 8B is a diagram showing a pattern for forming a 240 ° etching region, and FIG.
FIG. 3 is a diagram showing a phase shift mask having three different phase shift regions of the present invention obtained by overlapping the patterns of (a) and (b).

9A is a diagram showing another pattern for forming a 120 ° etching region, FIG. 9B is a diagram showing a pattern for forming a 240 ° etching region, FIG.
(c) is a figure which shows the phase shift mask which has three different phase shift areas of this invention obtained by overlapping the pattern of (a) and (b).

FIG. 10A is a view showing still another pattern for forming a 120 ° etching region, and FIG.
It is a figure which shows the pattern for forming a 0 degree etching area | region, (c) is a phase shift mask which has three different phase shift area | regions of this invention obtained by superposing the pattern of (a) and (b). FIG.

FIG. 11 is a diagram showing a pattern to be formed on a photomask.

FIG. 12A is a diagram showing a pattern for forming a 120 ° etching region, and FIG. 12B is a diagram showing a pattern for forming a 240 ° etching region;
(c) is a figure which shows the phase shift mask which has three different phase shift areas of this invention obtained by overlapping the pattern of (a) and (b).

13A is a diagram showing another pattern for forming a 120 ° etching region, FIG. 13B is a diagram showing a pattern for forming a 240 ° etching region, and FIG. FIG. 3 is a diagram showing a phase shift mask having three different phase shift regions of the present invention obtained by overlapping the patterns of (a) and (b).

FIG. 14 is a diagram showing a pattern to be formed on a photomask.

FIG. 15A is a diagram showing a pattern for forming a 120 ° etching region, and FIG. 15B is a diagram showing a pattern for forming a 240 ° etching region;
(c) is a figure which shows the phase shift mask which has three different phase shift areas of this invention obtained by overlapping the pattern of (a) and (b).

[Explanation of symbols]

410 Photo mask 415 mask area 420 120 ° etching area 425 240 ° etching area 430 First phase shift region 440 Second phase shift region 450 Third Phase Shift Area

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-7-72611 (JP, A) JP-A-9-101616 (JP, A) JP-B-1-51825 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) G03F 1/00-1/16

Claims (11)

(57) [Claims] 1. A transparent substrate, an opaque pattern covering the first portion of the transparent substrate while maintaining the translucency of the second portion of the transparent substrate, and an opaque pattern provided on the second portion of the transparent substrate by etching. Different with 120 ° phase shift 3
And three phase shift regions, the adjacent region around the corner of the opaque pattern is evenly divided by the three phase shift regions, and the three phase shift regions are formed with different etching depths. A phase shift mask having three different phase shift regions. 2. The corners have an angle of a °, and the adjacent regions are evenly divided into the three phase shift regions, each having an angle of (360 ° -a °) / 3. The phase shift mask according to claim 1. 3. The three phase shift masks are 120
First phase shift region having a phase shift of °, 240 °
A second phase shift region having a phase shift of
The phase shift mask according to claim 1, comprising a third phase shift region having a phase shift of 0 °. 4. A phase edge is formed between two of the three phase shift regions in a light-transmissive portion of the transparent substrate away from a neighboring region around the corner. 1. The phase shift mask described in 1. 5. A step of providing a transparent substrate, the transparent substrate being etched according to a first pattern, and a first phase shift region having a phase shift of 120 ° in a portion etched according to the first pattern. The transparent substrate is etched based on the second pattern with a different etching depth from the first etching process to form the first etching process, and a 240 ° phase shift is applied to the etched portion based on the second pattern. A second etching step of forming a second phase shift region having, wherein a portion of the transparent substrate etched by both the first and second etching steps has a phase shift of 360 °. A method of manufacturing a phase shift mask having three different phase shift regions, which are regions. 6. The first pattern and the second pattern are designed so that a neighboring region around a corner is equally divided into the first to third phase shift regions. A method for manufacturing the described phase shift mask. 7. The first pattern and the second pattern are first, second, and third phase shift regions in which adjacent regions around a corner are arranged adjacent to each other, and other regions of the transparent substrate are 6. The method for manufacturing a phase shift mask according to claim 5, wherein one of the first to third phase shift areas or two areas adjacent to each other. 8. A transparent substrate, an opaque pattern that exposes a second portion of the transparent substrate and has at least one corner that covers the first portion of the transparent substrate, and the second portion is provided by etching. A first, a second, and a third phase shift region having a phase difference of 120 ° from each other, wherein the first to third phase shift regions equally divide the proximity region of the second portion around the corner. , The first to third phase shift regions are differently etched
A phase shift mask having three different phase shift regions characterized by being formed in depth . 9. The corner has an angle of a °, and each of the first to third phase shift regions has (360 ° −a °).
The phase shift mask according to claim 8, wherein the phase shift mask has an angle of / 3. 10. The first phase shift region has a phase shift of 120 °, and the second phase shift region is 240 °.
And the third phase shift region is 360
9. The phase shift mask according to claim 8, having a phase shift of °. 11. The phase edge is formed between two regions of the first to third phase shift regions in a second portion of the transparent substrate which is distant from the adjacent region. The phase shift mask described in 1.