JP2002278040A - Half-tone type phase shift mask and hole pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dimensional accuracy of a hole pattern by reducing optical proximity effect in pattern exposure even when the hole pitch becomes small and to improve the focal depth in the pattern exposure regardless of whether the hole pitch is large or small. SOLUTION: A resist film 21 after being formed by coating a substrate 20 with negative resist is irradiated with exposure light 22 through a half-tone type phase shift mask 10 having an isolated shading part 11 of 50% in light transmissivity and a massed shading part 12 of 25% in light transmissivity. Then the resist film 21 is developed to form a resist pattern 21A having an isolated hole pattern 23 corresponding to the isolated shading part 11 and a massed hole pattern 24 corresponding to the massed shading part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a halftone type phase shift mask used for manufacturing a semiconductor device or a liquid crystal device, and a method for forming a fine pattern using the same.

[0002]

2. Description of the Related Art In recent years, as miniaturization of large-scale integrated circuit devices (hereinafter referred to as LSIs) using semiconductors has progressed,
In a lithography process, which is one of the LSI manufacturing processes, a pattern dimension to be formed has been miniaturized to a resolution limit defined by a light source wavelength λ and a numerical aperture NA of an exposure apparatus. In particular, when a hole pattern is formed, the hole pattern is greatly related to the degree of integration of the LSI, so that it is required to realize a pattern size equal to or smaller than the light source wavelength λ.

In general, a super-resolution technique such as a phase shift mask or an oblique incidence illumination is used to form a pattern having a size on the order of the resolution limit.

In a known method of forming a fine hole pattern using a positive resist (hereinafter referred to as a first conventional example), an opening (hole pattern) formed in a light-shielding film on a mask is formed. Since the area of the light-transmitting portion is small, the exposure light hardly passes through the opening, so that the resolution limit is reached sooner than when a hole pattern of the same size is formed using a negative resist. I will.

On the other hand, a fine hole pattern forming method using a phase shift mask and oblique incidence illumination together with a negative resist (hereinafter referred to as a second conventional example) has been reported (Japanese Patent Laid-Open No. 6-151280). reference).

Hereinafter, a method of forming a hole pattern according to a second conventional example will be described with reference to the drawings.

FIG. 8 is a plan view of a phase shift mask used in the hole pattern forming method according to the second conventional example, specifically, a halftone type phase shift mask.

[0008] As shown in FIG.
Is a dot-shaped light-shielding portion (hereinafter, referred to as an isolated light-shielding portion) 81 for forming a hole pattern having holes arranged in isolation, and a hole having a plurality of holes arranged at a predetermined pitch in an array. A plurality of dot-shaped light-shielding portions for forming a pattern (hereinafter, referred to as dense light-shielding portions) 8
2 is provided. Isolated light shield 81 and dense light shield 82
Consists of a translucent film formed on a translucent mask substrate. Further, the light transmittance of each of the isolated light shielding portion 81 and the dense light shielding portion 82 is the same value (for example, 6%). Further, the phase of the light transmitted through each of the isolated light-shielding portion 81 and the dense light-shielding portion 82 is determined by the light-transmitting portion of the phase shift mask 80 (the region where the isolated light-shielding portion 81 and the dense light-shielding portion 82 are not formed, that is, the light-transmitting portion). The phase is shifted by 180 degrees with respect to the phase of the light transmitted through the opening formed in the translucent film on the mask substrate.

In this specification, when a hole is arranged at a distance of about 2 μm or more from another adjacent hole, the hole is regarded as being isolated.

FIGS. 9A to 9C show a hole pattern forming method according to a second conventional example, specifically, a hole pattern using a halftone type phase shift mask (phase shift mask 80) shown in FIG. It is sectional drawing which shows each process of a formation method.

First, as shown in FIG.
A chemically amplified negative type resist is applied on the resist film 9
Form one.

Next, as shown in FIG. 9B, an exposure light 92 is applied to the resist film 91 through a phase shift mask 80 using annular illumination, for example, 2/3 annular illumination. At this time, an exposure apparatus having a numerical aperture NA of 0.65 and using a KrF excimer laser as a light source is used. Ring illumination is one method of oblique incidence illumination, and a ring-shaped opening is provided in an illumination system stop. In the 2/3 annular illumination, a coherence factor σ (hereinafter, referred to as “outside”) of the ring-shaped opening is used.
The ratio of the coherence factor σ (hereinafter referred to as σ _in ) inside the ring-shaped opening to σ _out ) is 2 /
3 is set.

Next, after the resist film 91 is baked, the resist film 91 is developed,
As shown in FIG. 9C, a resist pattern 91 having an isolated hole pattern 93 corresponding to the isolated light shielding portion 81 and a dense hole pattern 94 corresponding to the dense light shielding portion 82.
Form A. FIG. 10 is a plan view of the resist pattern 91A shown in FIG. 9C, in other words, a plan view of a resist pattern having a hole pattern formed by the hole pattern forming method according to the second conventional example. I have.

[0014]

However, a circuit pattern of a logic circuit or the like in which a plurality of patterns arranged at various pitches are mixed in one chip, for example, a combination pattern of an isolated hole pattern 93 and a dense hole pattern 94 is used. The hole patterns having various hole pitches (distances between the centers of a pair of adjacent holes) are formed in the second
If the hole patterns are simultaneously formed by the conventional method, the following two problems occur.

<First Problem> In the formation of a hole pattern, the optimum illumination condition differs depending on the hole pitch. Therefore, when simultaneously forming hole patterns having various hole pitches, it is difficult to set the illumination condition. And the depth of focus cannot be improved. Also,
In general, the aforementioned super-resolution techniques, such as oblique incidence illumination,
Since it is often effective only for forming a hole pattern using only a specific hole pitch, it is difficult to apply the super-resolution technique to forming an actual pattern such as a hole pattern having various hole pitches.

<Second Problem> FIG. 11 shows a simulation of the dependence of the hole size (specifically, the diameter) on the hole pitch in the hole pattern formed by the hole pattern forming method according to the second conventional example. FIG. 9 is a diagram showing a result obtained (white square in the figure). FIG.
In FIG. 1, for reference, the results (black squares in the figure) of the dependence of the hole dimensions on the hole pitch in the hole pattern formed by the hole pattern forming method according to the first conventional example are also shown. I have.

In each of the first conventional example and the second conventional example, an exposure apparatus having a numerical aperture NA of 0.65 and using a KrF excimer laser as a light source was used. Further, in the first conventional example, an exposure condition in which the coherence factor σ is 0.60 is used in consideration of the balance of the depth of focus in the simultaneous formation of the isolated hole pattern and the dense hole pattern. On the other hand, in the second conventional example, σ _in and σ
_out is set to 0.53 and 0.80 respectively 2 /
Three-zone lighting was used. Furthermore, in each of the first conventional example and the second conventional example, a hole turn was formed with a target of a hole size of 160 nm using a halftone type phase shift mask provided with a light shielding portion having a light transmittance of 6%. .
At this time, in each of the first conventional example and the second conventional example, in consideration of the offset due to the use of the halftone type phase shift mask, the mask size of the light shielding portion corresponding to the hole size of 160 nm (specifically, Is 20)
It was set to 0 nm. However, in this specification, the dimension on the mask is represented by a value obtained by dividing the actual dimension on the mask by the magnification of the reduction projection optical system. Further, the fact that the shape of the light shielding portion of the halftone phase shift mask is rectangular (specifically, square) while the shape of the hole in the hole pattern is circular is because the mask pattern can be easily formed. This is because the resist pattern is not formed up to the corners of the fine rectangular light-shielding portion.

As shown in FIG. 11, either of the first conventional example (using a positive resist) and the second conventional example (using a negative resist) to form a hole pattern with a hole size target of 160 nm. Even in the case where the hole pitch is used, if the hole pitch is smaller than about 0.40 μm, the hole size in the actually formed hole pattern greatly deviates from the target size of 160 nm due to the optical proximity effect. Further, as shown in FIG. 11, the amount of deviation of the hole size from the target size is about three times larger in the case of using the second conventional example than in the case of using the first conventional example. As a result, as shown in FIGS. 9C and 10, the problem that the hole size Y ′ in the dense hole pattern 94 becomes extremely larger than the hole size X ′ in the isolated hole pattern 93, in other words, In addition, there is a problem (second problem) that the hole size is enlarged with the miniaturization of the hole pitch. At this time, if the light transmittance of the light-shielding portion in the halftone type phase shift mask is increased in order to further improve the depth of focus, the optical proximity effect increases and the second problem is further exacerbated.

As a method of solving the second problem in the second conventional example, that is, a method of applying a mask bias, that is, a method of suppressing the enlargement of the hole size due to the miniaturization of the hole pitch, that is, a mask of the light shielding portion There is a method to reduce the upper dimension. However, as a light-shielding portion for forming a hole pattern is miniaturized, drawing a dot-shaped pattern of the light-shielded portion on a mask is, for example, more resolvable than drawing a line-shaped pattern on a mask. It becomes severe. As a result, it becomes difficult to form a fine light shielding portion for forming a hole pattern while maintaining dimensional linearity.

In view of the above, it is an object of the present invention to improve the dimensional accuracy of a hole pattern by reducing the optical proximity effect at the time of pattern exposure even when the hole pitch is reduced, and to perform pattern exposure regardless of the size of the hole pitch. It is an object to improve the depth of focus at the time.

[0021]

In order to achieve the above-mentioned object, the present inventor has proposed that the light transmittance of the light-shielding portion is 16% or 9%.
And 4%, the dependence of the hole size on the hole pitch in the hole pattern formed by using each of the three types of halftone phase shift masks (hereinafter sometimes simply referred to as masks) together with the negative resist. I tried it by simulation. FIG. 1 shows the simulation results. In FIG. 1, a simulation result corresponding to a mask having a light transmittance of 16% of the light shielding portion is indicated by a black square, and a simulation result corresponding to a mask having a light transmittance of 9% of the light shielding portion is indicated by a white square. The simulation result corresponding to a mask having a light transmittance of 4% is indicated by black triangles.

In each of the masks, the mask size of the light-shielding portion corresponding to each hole in the hole pattern is set to 200 nm. Further, the exposure amount at which the hole size of the isolated hole pattern formed by the mask having the light transmittance of the light-shielding portion of 16% is about 160 nm is set to the exposure using any of the masks (simulation).
Also used in.

As shown in FIG. 1, when the hole pitch is smaller than about 0.50 μm regardless of the light transmittance of the light shielding portion, the hole size becomes larger. On the other hand, as the light transmittance of the light-shielding portion decreases, the hole size decreases as a whole. That is, in the halftone type phase shift mask, by reducing the light transmittance of the light shielding portion, the same effect as applying a mask bias, that is, the same effect as reducing the mask size of the light shielding portion is obtained. Turned out to be.

FIG. 2 shows a hole pattern formed by using a halftone type phase shift mask in which the light transmittance of the light shielding portion is changed according to the hole pitch based on the simulation result shown in FIG. 1 together with a negative type resist. The simulation result of a hole dimension is shown. Specifically, the results shown in FIG. 2 indicate that the light transmittance when the hole pitch is 0.44 μm or more is set to 16%,
When the hole pitch is 0.36 μm or more and less than 0.44 μm, the light transmittance is set to 9%, and the hole pitch is 0.32 μm.
It is obtained by setting the light transmittance in the case of not less than μm and less than 0.36 μm to 4%.

As shown in FIG. 2, when the hole pitch is reduced and the hole size is deviated to some extent from the target size (about 160 nm), the light transmittance of the light-shielding portion is reduced so that the mask bias is not applied to some extent. The optical proximity effect can be reduced. At this time, the dimensional deviation of the hole pattern that could not be completely corrected by changing the light transmittance of the light shielding portion is further corrected by fine adjustment of the mask bias, that is, the light transmittance adjustment and the mask bias adjustment are used. By performing the two-stage optical proximity effect correction, the dimensional accuracy of the hole pattern is further improved.

Further, the present inventor has proposed a half-tone type for forming a dense hole pattern having a plurality of holes arranged in an array at a pitch of 0.32 μm and for forming an isolated hole pattern. The depth of focus during pattern exposure was evaluated by simulation while varying the light transmittance of the light-shielding portion in the phase shift mask in various ways. FIG. 3A shows an evaluation result of the depth of focus when a dense hole pattern is formed.
FIG. 3B shows the evaluation result of the depth of focus when an isolated hole pattern is formed.

In both the case of forming a dense hole pattern and the case of forming an isolated hole pattern, the size of the light shielding portion on the mask is set to 210 nm regardless of the light transmittance and the numerical aperture NA is set to 0.1. 2/3 annular illumination is performed by using 65 exposure apparatuses. The evaluation of the depth of focus is based on the hole size at the time of the best focus (specifically, 16 holes).
0 nm) is subtracted from the hole size when defocused by 0.3 μm with respect to the best focus. In other words, the smaller the value, the less the effect of defocus and the wider the depth of focus, that is, the larger the focus margin.

As shown in FIG. 3A, when a dense hole pattern is formed, the depth of focus increases as the light transmittance of the light-shielding portion decreases. In contrast, FIG.
As shown in (b), when an isolated hole pattern is formed, the depth of focus increases as the light transmittance of the light-shielding portion increases. That is, in the halftone phase shift mask, the light transmittance of the light-shielding portion for forming a hole pattern with a large hole pitch is increased, and the light transmittance of the light-shielding portion for forming a hole pattern with a small hole pitch is increased. By lowering, in other words,
It has been found that the depth of focus can be improved irrespective of the size of the hole pitch by reducing the light transmittance of the light shielding portion as the hole pitch becomes smaller.

The present invention has been made based on the above findings. Specifically, the first halftone phase shift mask according to the present invention has at least a light-shielding portion for forming a hole pattern. It has two types of light transmittance.

According to the first halftone type phase shift mask, since the light-shielding portion for forming the hole pattern has two or more types of light transmittance, the light transmittance of the light-shielding portion is changed according to the hole pitch. Can be. For this reason, the light transmittance of the light-shielding portion can be reduced as the hole pitch becomes smaller, so that exposure can be performed under the condition that the depth of focus is almost optimal in all the hole pattern formation regions of the resist film. That is, it is possible to improve the depth of focus at the time of pattern exposure regardless of the size of the hole pitch, thereby improving the dimensional accuracy even when forming a hole pattern having a hole size smaller than the normal resolution limit. Can be. Further, since the light transmittance can be reduced as the hole pitch becomes smaller, the optical proximity effect at the time of pattern exposure can be reduced and the dimensional accuracy of the hole pattern can be improved even when the hole pitch is small. Therefore, since the amount of mask bias for reducing the optical proximity effect can be suppressed, the mask can be easily formed in terms of the mask pattern dimensions.

In the first halftone type phase shift mask, it is preferable that the light shielding portion has a light transmittance that changes according to the hole pitch of the hole pattern.

With this configuration, the light transmittance of the light shielding portion can be reliably reduced as the hole pitch becomes smaller.

In this case, it is preferable that the light shielding portion has a light transmittance that decreases as the hole pitch of the hole pattern decreases.

In this way, the depth of focus during pattern exposure can be reliably improved irrespective of the size of the hole pitch, and the optical proximity effect during pattern exposure can be reliably reduced even when the hole pitch is small. Thus, the dimensional accuracy of the hole pattern can be reliably improved.

The second halftone phase shift mask according to the present invention comprises a first light-shielding portion for forming a first hole pattern having a relatively large hole pitch, and a first light-shielding portion for forming a first hole pattern having a relatively small hole pitch. A second light-shielding portion for forming a second hole pattern, the second light-shielding portion having a lower light transmittance than the first light-shielding portion.

According to the second halftone type phase shift mask, the light shielding portion for forming a hole pattern with a small hole pitch has a lower light transmittance than the light shielding portion for forming a hole pattern with a large hole pitch. Have. That is, since the light transmittance of the light shielding portion is reduced as the hole pitch becomes smaller, the depth of focus during pattern exposure can be improved regardless of the size of the hole pitch. And the dimensional accuracy of the hole pattern can be improved.

In the third halftone phase shift mask according to the present invention, the first halftone phase shift mask having the hole pitch within the first range is used.
A first light-shielding portion for forming a second hole pattern having a hole pitch within a second range; and a third light-shielding portion for forming a second hole pattern having a hole pitch within a second range.
And a third light-shielding portion for forming a third hole pattern in the range of 1. The first light-shielding portion has a first light transmittance, and the second light-shielding portion has a second light-shielding portion. And the third light-shielding portion has a third light transmittance.

According to the third halftone type phase shift mask, the first light-shielding portion for forming the hole pattern having the hole pitch within the first range has the first light transmittance, A second light-shielding portion for forming a hole pattern having a hole pitch within a second range has a second light transmittance, and forms a hole pattern having a hole pitch within a third range. Third light-blocking portion has a third light transmittance. That is, since the light transmittance of the light shielding portion is changed according to the hole pitch, the light transmittance of the light shielding portion can be reduced as the hole pitch becomes smaller. Therefore,
Depth of focus during pattern exposure can be improved regardless of the size of the hole pitch, and even when the hole pitch is small, the optical proximity effect during pattern exposure can be reduced and the dimensional accuracy of the hole pattern can be improved.

The method for forming a hole pattern according to the present invention comprises:
A step of applying a negative resist on a substrate to form a resist film, and a step of irradiating the resist film with exposure light through a halftone type phase shift mask having a light-shielding portion having at least two types of light transmittance. And forming a hole pattern corresponding to the light-shielding portion in the resist film by developing the resist film.

According to the hole pattern forming method of the present invention, since the first halftone phase shift mask according to the present invention is used, the same effect as the mask can be obtained.

In the hole pattern forming method of the present invention, the light-shielding portion preferably has a light transmittance that changes according to the hole pitch of the hole pattern, and the light-shielding portion has a light transmittance that decreases as the hole pitch of the hole pattern decreases. More preferably, it has a ratio.

[0042]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a halftone type phase shift mask according to a first embodiment of the present invention and a method of forming a hole pattern using the same will be described with reference to the drawings.

FIG. 4 is a plan view of the halftone type phase shift mask according to the first embodiment, specifically, a halftone type phase shift mask for forming a hole pattern in a resist film made of a negative type resist. is there.

As shown in FIG. 4, the phase shift mask 10
Is a dot-shaped light-shielding portion (hereinafter, referred to as an isolated light-shielding portion) 11 for forming a hole pattern having holes arranged in isolation, and a hole having a plurality of holes arranged at a predetermined pitch in an array. A plurality of dot-shaped light-shielding portions (hereinafter, referred to as dense light-shielding portions) 1 for forming a pattern
2 is provided. Isolated light shield 11 and dense light shield 12
Consists of a translucent film formed on a translucent mask substrate. The light transmittance of the isolated light-shielding portion 11 is, for example, 5
On the other hand, the light transmittance of the densely shaded portion 12 is, for example, 2%.
5%. In addition, the isolated light-shielding portion 11 and the dense light-shielding portion 12
Are transmitted through the phase shift mask 1
0 relative to the phase of light passing through a light-transmitting part (a region where the isolated light-shielding part 11 and the dense light-shielding part 12 are not formed, that is, an opening provided in the translucent film on the light-transmitting mask substrate)
It is shifted by 80 degrees. The on-mask dimensions (specifically, widths) of the isolated light-shielding portion 11 and the dense light-shielding portion 12 are, for example, 210 nm and 180 nm, respectively. It is set to be larger than the target (for example, 160 nm).

FIGS. 5A to 5C show a hole pattern forming method according to the first embodiment, specifically, a halftone type phase shift mask (phase shift mask 10) shown in FIG.
FIG. 6 is a cross-sectional view showing each step of a hole pattern forming method using the method.

First, as shown in FIG.
A chemically amplified negative type resist is coated on the resist film 2
Form one.

Next, as shown in FIG. 5B, the exposure light 22 is applied to the resist film 21 through the phase shift mask 10 for two times.
Irradiate using / 3 annular illumination. At this time, the numerical aperture NA
Is 0.65, and an exposure apparatus using a KrF excimer laser as a light source is used.

Next, a baking process is performed on the resist film 21, and then the resist film 21 is developed.
As shown in FIG. 5C, a resist pattern 21 having an isolated hole pattern 23 corresponding to the isolated light shielding portion 11 and a dense hole pattern 24 corresponding to the dense light shielding portion 12 is formed.
Form A. At this time, the holes in the dense hole pattern 24 were arranged in an array at a pitch of 0.32 μm. Further, both the opening size (diameter) X of the holes in the isolated hole pattern 23 and the opening size Y of each hole in the dense hole pattern 24 are the same as the target size.
It was 60 nm. Furthermore, both the isolated hole pattern 23 and the dense hole pattern 24 could be formed while ensuring a sufficient depth of focus during pattern exposure.
FIG. 6 shows the resist pattern 21A shown in FIG.
In other words, a plan view of a resist pattern having a hole pattern formed by the hole pattern forming method of the first embodiment is shown.

As described above, according to the first embodiment, in the phase shift mask 10 used for forming a hole pattern in the resist film 21 made of a negative resist, the dense hole pattern 24 is formed. Has a lower light transmittance than the isolated light-shielding portion 11 for forming the isolated hole pattern 23. That is, since the light transmittance of the light shielding portion in the phase shift mask 10 decreases as the hole pitch decreases, the exposure can be performed under the condition that the depth of focus is almost optimal in all the hole pattern formation regions of the resist film 21. . For this reason, the depth of focus during pattern exposure can be reliably improved regardless of the size of the hole pitch, so that dimensional accuracy is ensured even when forming a hole pattern having a hole size smaller than the normal resolution limit. Can be improved. Further, since the light transmittance is reduced as the hole pitch becomes smaller, even when the hole pitch is small, the optical proximity effect at the time of pattern exposure can be reliably reduced, and the dimensional accuracy of the hole pattern can be reliably improved. Therefore, the amount of mask bias for reducing the optical proximity effect, that is, the amount of reduction of the on-mask dimension of the light-shielding portion can be suppressed, so that the mask can be easily formed in terms of the mask pattern dimension.

In the first embodiment, the isolated light shielding portion 11 for forming the isolated hole pattern 23 and the dense light shielding portion 12 for forming the dense hole pattern 24 having the hole pitch of 0.32 μm are used. However, three or more types of light transmittance may be given to the light-shielding portion for forming the hole pattern. For example, in addition to the isolated hole pattern 23 and the dense hole pattern 24, the hole pitch is 0.3
When simultaneously forming a hole pattern larger than 2 μm, the light transmittance of the light shielding portion for forming the hole pattern is set to a value between the light transmittance of the isolated light shielding portion 11 and the light transmittance of the dense light shielding portion 12. Set to.

In the first embodiment, each of the isolated light-shielding portions 11 and the dense light-shielding portions 12 has a light transmittance of 50%.
And 25%, but the light transmittance of each light-shielding portion is preferably set to an appropriate value according to the hole pitch of the corresponding hole pattern. At this time, for example, by adjusting the thickness of the translucent film constituting each light shielding portion, the light transmittance of each light shielding portion can be adjusted.

In the first embodiment, a square is used as the shape of each light shielding portion (the isolated light shielding portion 11 and the dense light shielding portion 12) in the phase shift mask 10, but the shape of each light shielding portion is particularly limited. Not something.

Further, in the first embodiment, the distance between each light-shielding portion and the light-transmitting portion of the phase shift mask 10 is 180 °.
The phase difference is provided, but the phase difference is not particularly limited as long as the function of the phase shift mask 10 as a halftone type phase shift mask is realized.

In the first embodiment, the mask size of each light shielding portion in the phase shift mask 10 is set to be larger than the target of the hole size in consideration of the offset caused by using the halftone type phase shift mask. However, in this case, it is preferable to set the exposure amount close to overexposure. By doing so, the exposure margin can be widened, so that the pattern can be formed stably.

In the first embodiment, the light proximity effect correction is performed by changing the light transmittance of each light-shielding portion in the phase shift mask 10 according to the hole pitch. Correcting the dimensional deviation of the hole pattern that could not be corrected by changing the light transmittance by further fine-tuning the mask bias, that is, a two-stage optical proximity effect using light transmittance adjustment and mask bias adjustment Preferably, a correction is made. By doing so, the dimensional accuracy of the hole pattern is further improved.

(Second Embodiment) Hereinafter, a halftone phase shift mask according to a second embodiment of the present invention and a hole pattern forming method using the same will be described with reference to the drawings.

FIG. 7 is a plan view of a halftone type phase shift mask according to the second embodiment, specifically, a halftone type phase shift mask for forming a plurality of hole patterns in a resist film made of a negative type resist. FIG.

As shown in FIG. 7, the phase shift mask 10
0 denotes a first light-shielding portion 101 for forming a hole pattern having a hole pitch of 0.44 μm or more, and a second light-shielding portion for forming a hole pattern having a hole pitch of 0.36 μm or more and less than 0.44 μm. 102 and a third light-shielding portion 103 for forming a hole pattern having a hole pitch of 0.32 μm or more and less than 0.36 μm. The first light shielding unit 101, the second light shielding unit 102, and the third
Each of the light shielding portions 103 is formed of a translucent film formed on a translucent mask substrate. The light transmittance of the first light shielding unit 101 is, for example, 16%, the light transmittance of the second light shielding unit 102 is, for example, 9%, and the light transmittance of the third light shielding unit 103 is, for example, 4%. It is. In addition, the first light shielding unit 10
The phase of the light passing through each of the first, second light-shielding part 102 and the third light-shielding part 103 is determined by the light-transmitting part of the phase shift mask 100 (the first light-shielding part 101, the second light-shielding part 102, and the third light-shielding part). (The opening where the light-shielding portion 103 is not formed, that is, the opening provided in the translucent film on the translucent mask substrate) is shifted by 180 degrees with respect to the phase of the light passing therethrough. further,
Each mask dimension (specifically, width) of the first light-shielding portion 101, the second light-shielding portion 102, and the third light-shielding portion 103
Is, for example, 200 nm, and is set to be larger than the target of the hole size (for example, 160 nm) in consideration of the offset due to the use of the halftone phase shift mask.

That is, in the halftone phase shift mask according to the first embodiment, the light-shielding portions having two kinds of light transmittances are provided, but the halftone phase shift mask according to the second embodiment is provided. The mask is provided with light shielding portions having three types of light transmittance.

The hole pattern forming method according to the second embodiment uses a phase shift mask shown in FIG. 7 instead of the phase shift mask 10 shown in FIG. 4 (halftone type phase shift mask according to the first embodiment). Except that the mask 100 is used, the method is the same as the hole pattern forming method according to the first embodiment shown in FIGS. 5A to 5C. However, FIG.
As the resist pattern 21A shown in FIG. 6C and FIG. 6, a pattern corresponding to the light shielding portion pattern of the phase shift mask 100 is formed. FIG. 2 shows a simulation result of a hole size in a hole pattern formed by using the phase shift mask 100 shown in FIG. 7 together with a negative resist.

As described above, according to the second embodiment, in the phase shift mask 100 for forming a hole pattern in a resist film made of a negative resist, a hole pattern having a hole pitch of 0.44 μm or more is used. The light transmittance of the first light shielding portion 101 to be formed is 16
%, And the hole pitch is 0.36 μm or more and 0.44 μm.
The light transmittance of the second light-shielding portion 102 for forming a hole pattern of less than m is 9% and the hole pitch is 0.3.
The light transmittance of the third light shielding portion 103 for forming a hole pattern of 2 μm or more and less than 0.36 μm is 4%.
That is, as the hole pitch becomes smaller, the light transmittance of the light-shielding portion in the phase shift mask 100 becomes lower, so that the exposure can be performed under the condition that the depth of focus becomes almost optimum in all the hole pattern forming regions of the resist film. For this reason, the depth of focus during pattern exposure can be reliably improved regardless of the size of the hole pitch, so that dimensional accuracy is ensured even when forming a hole pattern having a hole size smaller than the normal resolution limit. Can be improved. Further, since the light transmittance is reduced as the hole pitch becomes smaller, even when the hole pitch is small, the optical proximity effect at the time of pattern exposure can be reliably reduced and the dimensional accuracy of the hole pattern can be reliably improved. Therefore, since the amount of mask bias for reducing the optical proximity effect can be suppressed, the mask can be easily formed in terms of the mask pattern dimensions.

In the second embodiment, the first light shielding unit 101, the second light shielding unit 102, and the third light shielding unit 103
, Three different light transmittances are given to the light-shielding portion 101. Alternatively, the same light transmittance is given to any two of the light-shielding portions 101 to 103, whereby the light-shielding portion 101 is provided. Two different light transmittances may be given to に 対 し て 103. For example, the light transmittance of the first light shield 101 and the second light shield 102 is set to 16%,
May be set to 4%.

In the second embodiment, the first light-shielding portion 101, the second light-shielding portion 102, and the third light-shielding portion 10
The light transmittance of No. 3 was 16%, 9% and 4%, respectively, but it is preferable that the light transmittance of each light-shielding portion is set to an appropriate value according to the hole pitch of the corresponding hole pattern. At this time, for example, by adjusting the thickness of the translucent film constituting each light shielding portion, the light transmittance of each light shielding portion can be adjusted.

In the second embodiment, each light shielding portion (light shielding portions 101 to 10) in the phase shift mask 100 is used.
Although a square was used as the shape of 3), the shape of each light shielding portion is not particularly limited.

In the second embodiment, the distance between each light-shielding portion and the light-transmitting portion in the phase shift mask 100 is 18.
Although a phase difference of 0 degree is provided, the phase difference is not particularly limited as long as the function of the phase shift mask 100 as a halftone type phase shift mask is realized.

Further, in the second embodiment, the mask size of each light shielding portion in the phase shift mask 100 is set to be larger than the target of the hole size in consideration of the offset caused by using the halftone type phase shift mask. However, in this case, it is preferable to set the exposure amount close to overexposure. By doing so, the exposure margin can be widened, so that the pattern can be formed stably.

In the second embodiment, the light proximity effect correction is performed by changing the light transmittance of each light-shielding portion in the phase shift mask 100 in accordance with the hole pitch. It is preferable that the dimensional deviation of the hole pattern that could not be corrected by changing the light transmittance is further corrected by fine adjustment of the mask bias. By doing so, the dimensional accuracy of the hole pattern is further improved.

[0068]

According to the present invention, in a halftone type phase shift mask, the light transmittance of a light shielding portion for forming a hole pattern is reduced as the hole pitch becomes smaller. For this reason, the depth of focus during pattern exposure can be improved regardless of the size of the hole pitch, so that the dimensional accuracy can be improved even when a hole pattern having a hole size equal to or less than the normal resolution limit is formed. Can be. Further, even when the hole pitch is small, the optical proximity effect at the time of pattern exposure can be reduced and the dimensional accuracy of the hole pattern can be improved, so that the mask bias amount for reducing the optical proximity effect can be suppressed, and as a result, the mask pattern size can be reduced. In this respect, the mask can be easily formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hole having a hole size in a hole pattern formed by using three types of halftone type phase shift masks having a light transmittance of 16%, 9% and 4% together with a negative resist. FIG. 9 is a diagram illustrating a simulation result of determining dependency on pitch.

FIG. 2 is a view showing a hole dimension of a hole pattern formed by using a halftone type phase shift mask in which the light transmittance of a light shielding portion is changed according to a hole pitch based on a simulation result shown in FIG. 1 together with a negative resist; It is a figure showing a simulation result.

FIG. 3 (a) shows the evaluation of the depth of focus during pattern exposure while changing the light transmittance of the light-shielding portion in the halftone phase shift mask when forming a dense hole pattern having a hole pitch of 0.32 μm. It is a figure which shows a simulation result and (b) shows the simulation result which evaluated the focal depth at the time of pattern exposure, changing the light transmittance of the light-shielding part in a halftone type phase shift mask variously when forming an isolated hole pattern. FIG.

FIG. 4 is a plan view of a halftone type phase shift mask according to the first embodiment of the present invention.

FIGS. 5A to 5C are cross-sectional views showing each step of the hole pattern forming method according to the first embodiment of the present invention.

FIG. 6 is a plan view of a resist pattern having a hole pattern formed by the hole pattern forming method according to the first embodiment of the present invention.

FIG. 7 is a plan view of a halftone type phase shift mask according to a second embodiment of the present invention.

FIG. 8 is a plan view of a halftone phase shift mask used in a conventional hole pattern forming method.

FIGS. 9A to 9C are cross-sectional views showing steps of a conventional hole pattern forming method.

FIG. 10 is a plan view of a resist pattern having a hole pattern formed by a conventional hole pattern forming method.

FIG. 11 is a diagram showing a simulation result in which the dependence of a hole size on a hole pitch in a hole pattern formed by a conventional hole pattern forming method is obtained.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Phase shift mask 11 Isolated light shielding part 12 Dense light shielding part 20 Substrate 21 Resist film 21A Resist pattern 22 Exposure light 23 Isolated hole pattern 24 Dense hole pattern 100 Phase shift mask 101 First light shielding part 102 Second light shielding part 103 Third X Dimensions of holes in isolated hole pattern 23 Y Dimensions of holes in dense hole pattern 24

Claims (8)

[Claims] 1. A halftone phase shift mask, wherein a light-shielding portion for forming a hole pattern has at least two types of light transmittance. 2. The halftone phase shift mask according to claim 1, wherein the light shielding portion has a light transmittance that changes according to a hole pitch of the hole pattern. 3. The halftone phase shift mask according to claim 2, wherein the light shielding portion has a light transmittance that decreases as a hole pitch of the hole pattern decreases. 4. A first light-shielding portion for forming a first hole pattern having a relatively large hole pitch, and a second light-shielding portion for forming a second hole pattern having a relatively small hole pitch. A halftone phase shift mask, wherein the second light-shielding portion has a lower light transmittance than the first light-shielding portion. 5. A method according to claim 1, wherein the hole pitch is within a first range.
A first light-shielding portion for forming a second hole pattern, a second light-shielding portion for forming a second hole pattern having a hole pitch within a second range, and a third light-shielding portion for forming a second hole pattern having a hole pitch within a third range. A third light-shielding portion for forming a third hole pattern, wherein the first light-shielding portion has a first light transmittance, and the second light-shielding portion has a second light-shielding portion. A halftone phase shift mask having a light transmittance, wherein the third light-shielding portion has a third light transmittance. 6. A step of applying a negative resist on a substrate to form a resist film; and forming a resist film on the resist film via a halftone type phase shift mask having a light-shielding portion having at least two types of light transmittance. A hole pattern forming method, comprising: a step of irradiating exposure light; and a step of forming a hole pattern corresponding to the light shielding portion in the resist film by developing the resist film. 7. The method according to claim 6, wherein the light blocking portion has a light transmittance that changes according to a hole pitch of the hole pattern. 8. The method according to claim 7, wherein the light-shielding portion has a light transmittance that decreases as a hole pitch of the hole pattern decreases.