JPH05197125A - Phase shift mask - Google Patents

Abstract

PURPOSE:To prevent a pattern transfer at the edge sections of phase shifter layers. CONSTITUTION:The first and second phase shifter layers 13a, 13b are provided alternately at multiple light transmission sections between multiple shading patterns 12, both the first and second phase shifter layers 13a, 13b have the relative phase difference alpha of pi/2 or below against a mask substrate 11, and the first and second phase shifter layers 13a, 13b have the phase difference 2alpha of pi or below between them. Since the relative phase difference against the mask substrate 11 is made pi/2 or below, the light intensity on a wafer at the edge sections of the phase shifter layers 13a, 13b is increased, and a pattern transfer at the edge sections is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask used in a photolithography process in manufacturing a semiconductor device, and more particularly to a phase shift mask for enhancing the contrast of a fine pattern by using a phase difference.

[0002]

2. Description of the Related Art Conventionally, as a phase shift mask, for example, "IEEE TRANSACTIONS ON ELECTRON DEVICE (IEEE TRANSACTIONS ON ELECTRON DEVICE) is used.
S) ", ED-29 [12] (1982-12) (US) P.1828-1836. The configuration will be described below.

FIG. 11 shows the structure and characteristics of the conventional phase shift mask described in the above-mentioned document. (A) is a sectional view of the phase shift mask, and (b) is the amplitude of light on the mask. , (C) shows the amplitude of light on the wafer, and (d) shows the light intensity on the wafer.

In FIG. 11 (a), this phase shift mask has a light-transmissive substrate 1 made of glass. On the substrate 1, light-shielding materials such as chromium (Cr) and chromium oxide (CrO ₂ ) are shielded. The pattern 2 is selectively formed. On the substrate 1 exposed between the light shielding patterns 2, the phase shifter layer 3 is formed on one of the opposite light transmitting portions.

The phase shifter layer 3 is a light transmissive film having a single layer structure of photoresist, SiO ₂ , SOG or MgF ₂ after exposure. The film thickness d of the phase shifter layer 3 is d = λ / 2 (n−1) where n is the refractive index and λ is the exposure wavelength.
The relationship is set to hold.

When a wafer 4 (not shown) is irradiated with light 4 having a wavelength λ through the phase shift mask having the above-described structure, the phase shift mask passing through the phase shifter layer 3 has a structure shown in FIG.
The amplitude of light as shown in (b) is obtained. That is, a phase difference of 180 ° is given to the amplitude of light. As a result, the amplitude of light on the wafer becomes as shown in FIG. 11 (c), and the light intensity on the wafer increases as shown in FIG. 11 (d).

As described above, in the repetitive pattern as shown in FIG. 11 (a), by providing the phase shifter layer 3 on one of the opposite light transmitting portions on the phase shift mask, the light intensity on the wafer is increased. Therefore, the contrast of the projected image can be fundamentally improved.

[0008]

However, in the phase inversion method using the phase shift mask having the above-described structure, the edge portion of the phase shifter layer 3 arranged in the light transmitting portion of the phase shift pattern has the shifter layer 3 and the shifter layer 3 at the edge portion. Phase difference with the part without layer (shifter layer: 180 °, transmission part 0
°) reduces the light intensity and increases the contrast at those boundaries.

As a result, the edge portion of the phase shifter layer 3 is transferred and an unnecessary pattern is formed,
Therefore, there is a problem that such a phase shifter layer can be applied only to a pattern in which the light transmission part is closed.

These will be described below with reference to actual examples. FIG. 12 shows a repeating pattern in which the line portion is a light shielding portion and the space portion is a light transmitting portion.
A shifter layer 3 for inverting the phase (180 °) is arranged in the space portion (phase 0 °).

In FIG. 13 (A), a curve a and a curve b
Is the central portion (Y2-
Y2 ') and the light intensity distribution on the wafer at the edge portion (Y1-Y1') are shown. Further, in FIG. 13B, a curve c shows the distribution of the maximum value of the light intensity on the wafer in the phase shifter section (X1-X1 ') in the above phase shift pattern.

As is apparent from FIGS. 13 (A) and 13 (B),
At the point A (light intensity I ₂ ) on the boundary (shifter edge portion) between the phase shifter and the light transmitting portion, the light intensity is significantly reduced with respect to the center B (light intensity I ₁ ) of the phase shifter. The contrast of the graph markedly increases as shown by a curve h in FIG. As a result, in pattern formation using a positive resist, for example, as shown in FIG. 14, an edge transfer 4 of the shift pattern occurs at the shift pattern edge portion, resulting in a pattern defect in which regular patterns are connected to each other. Occur.

The present invention has been made in view of the above points, and an object thereof is to provide a phase shift mask capable of preventing pattern transfer at the edge of the phase shifter layer.

[0014]

According to the present invention, in a phase shift mask, first and second phase shifter layers are alternately provided in a plurality of light transmitting portions between a plurality of light shielding patterns on a mask substrate. The relative phase difference between the first and second phase shifter layers with respect to the mask substrate is α of π / 2 or less, and the phase difference between the first and second phase shifter layers is 2 or less.
It is set to be α.

[0015]

In the phase shift mask as described above, the contrast of the fine pattern is enhanced by using the relative phase difference between the first and second phase shifter layers, and the maximum resolving power is obtained when the relative phase difference is π. can get.

Further, by setting the relative phase difference between the first and second phase shifter layers and the mask substrate to be π / 2 or less, the light intensity at the edge of the phase shifter layer is increased and the contrast at the edge is increased. Of the phase shifter layer prevents pattern transfer at the edge of the phase shifter layer.

Further, by making the relative phase difference between the first phase shifter layers and the second phase shifter layers, which are alternately provided, relative to the mask substrate both be equal to α (however, π / 2 or less), the image plane is formed. The light intensity profile is symmetrical.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view showing a phase shift mask according to a first embodiment of the present invention, and FIG. 2 is a plan view showing a pattern portion of the mask. In this figure, 11 is a light-transmitting mask substrate, on which a plurality of light-shielding patterns 12 are formed by an MgF ₂ film or the like. The first phase shifter layers 13a and the second phase shifter layers 13b are alternately provided in the plurality of transmissive portions between the light shielding patterns 12.

The first and second phase shifter layers 13a,
13b has a relative phase difference of π / 2 with respect to the mask substrate 11.
The following α and the first and second phase shifter layers 13
The phase difference between a and 11b is 2α which is π or less. Specifically, in this embodiment, the phase of the first phase shifter layer 13a is 90 ° and the phase of the second phase shifter layer 13b is 270 with respect to the phase 0 ° or 360 ° of the mask substrate 11.
°. Such first and second phase shifter layers 13
a and 13b are formed as follows. Now, when the exposure light is an i-line having a wavelength of 365 nm and the phase shifter layer is formed of MgF ₂ having a refractive index of 1.38, the first phase shifter layer 13a at 90 ° has a MgF ₂ thickness of about 2400Å, 270
The second phase shifter layer 13b having a temperature of 60 ° may be formed of MgF ₂ with a thickness of about 7200Å. In addition, SiC with a refractive index of 2.83
When forming a phase shifter layer with MgF ₂ and
Of the first phase shifter layer 13a of MgF ₂ is about 2400Å, and the second phase shifter layer 13b of 270 ° is SiC 1
It may be formed to a thickness of about 500Å.

FIG. 3A shows the central portion of the pattern (Y in FIG. 2) when the phase shift mask having such a structure is irradiated with light.
4-Y4 ') and the edge portion (Y3-Y3' in FIG. 2)
3 shows the light intensity distribution on the wafer in FIG. As is clear from this figure, according to the above phase shift mask, the first and second phase shifter layers 1
The contrast of the fine pattern is enhanced by the relative phase difference between 3a and 13b, and high resolution can be obtained. The resolving power is maximum when the relative phase difference between the first and second phase shifter layers 13a and 13b is π as in this embodiment.

FIG. 3B is a diagram showing a curve f showing the transition of the maximum light intensity value on the wafer in the first and second phase shifter layers 13a and 13b (X2-X2 'in FIG. 2). Is. As is clear from this figure, according to the phase shift mask, the first and second phase shifter layers 13a and 13b are provided.
Since the relative phase difference between the mask substrate 11 and the mask substrate 11 is π / 2,
Center point D of the first and second phase shifter layers 13a and 13b
The decrease in light intensity at the edge portions (point C, light intensity I ₄ ) of the first and second phase shifter layers with respect to (light intensity I ₃ ) is 4
It will be about 0%. Therefore, if the distance between the light shielding patterns 12 is set so that the maximum light intensity is 1.5 or more, as shown by the curve g in FIG. Even at the edge portion, a light intensity of 0.9 or more can be obtained on the wafer, and the contrast can be reduced, so that the pattern transfer at the edge portion of the phase shifter layer can be prevented. The resist pattern obtained by the phase shift mask of this example is shown in FIG. There is no pattern transfer at the edge of the phase shifter layer, and each pattern is distinguished.

According to the above phase shift mask, the first
And the mask substrate 1 of the second phase shifter layers 13a and 13b
Since the relative phase difference with respect to 1 is made equal to π / 2,
A symmetrical light intensity profile can be obtained on the image plane (wafer). This point will be described below.

In FIG. 5A, three light-shielding patterns 12 are formed on the mask substrate 11, one light-transmitting portion between the light-shielding patterns 12 is provided with the first phase shifter layer 13a, and the other light-transmitting pattern is provided. 3 shows a phase shift mask in which a second phase shifter layer 13b is provided in a part. In this phase shift mask,
When the relative phase difference between the first and second phase shifter layers 13a and 13b with respect to the mask substrate 11 is π / 2,
Transmitted light L ₁ of the mask substrate portion outside the first phase shifter layer 13a, the transmitted light L ₂ of the first phase shifter layer 13a portion, light transmitted through the second phase shifter layer 13b moiety L
₃ , when the transmitted light of the mask substrate portion outside the second phase shifter layer 13b is L ₄ , the transmitted light L ₁ , L ₂ and L ₃ interfere with each other and the transmitted light L ₂ , L ₃ By equalizing the light interference between L ₄ , a symmetrical light intensity profile is obtained at the image plane as shown in FIG. 5 (b). The symmetry of this light intensity profile is due to the mask substrate 11 of the first and second phase shifter layers 13a and 13b.
The relative phase difference can be always obtained as long as they are equal to each other, and the relative phase difference is not limited to π / 2.

In the above phase shift mask, the relative phase difference between the first and second phase shifter layers with respect to the mask substrate is set to π / 2 or less to increase the light intensity at the edge portion of the phase shifter layer, Although the pattern transfer at the edge part was prevented, by additionally devising the edge part,
It is possible to increase the light intensity at the edge of the phase shifter layer and prevent the pattern transfer at the edge. FIG. 6 shows one of them, which is a second embodiment of the present invention. As shown in FIG.
The edges of 3 (first and second phase shifter layers) are shifted inward.

FIG. 6 (b) shows the light intensity pattern when the phase shifter layer is not provided in the light transmitting portion between the light shielding patterns 12 at the light shielding pattern intervals with the maximum light intensity of about 1 to 1.5.
In FIG. 6C, the edges of the light-shielding pattern 12 and the edges of the phase shifter layer 13 are aligned and the phase shifter layer 13 is aligned.
7 shows a light intensity pattern when is provided in the light transmitting portion between the light shielding patterns. As is clear from the two light intensity patterns, the light-shielding pattern 12 is formed in the light-shielding pattern interval.
If the edges of the phase shifter layer 13 are aligned with the edges of, the light intensity at the edges drops significantly. Therefore, in the second embodiment, the edge of the phase shifter layer 13 is shifted inward from the edge of the light-shielding pattern 12 to disperse the decrease in the light intensity due to the edge, so that the phase shifter layer 13 (the first and second To secure a large light intensity at the edge of the phase shifter layer.

FIG. 7 shows a third embodiment of the present invention. In the third embodiment, as shown in FIG.
The edge of the phase shifter layer 13 (first and second phase shifter layers) is extended to the mask substrate surface (11 is the mask substrate) outside the pattern group where the light intensity is higher than that of the pattern group, and the light of the edge portion is extended. The strength is higher. further,
In the third embodiment, the protrusion 15 is provided on the wafer 14 at the edge of the phase shifter layer 13, and the protrusion 15 is formed.
The photoresist 16 is applied thinly on the edge of the phase shifter layer 13. If the photoresist 16 becomes thin, even the weak exposure light is sufficiently exposed, so that the edge transfer of the phase shifter layer is further eliminated.

FIG. 8 shows a fourth embodiment of the present invention. In the fourth embodiment, a region (a region where the light intensity is high) 17 in which the space between the light shielding patterns 12 is widened by forming a recess in the side wall of the light shielding pattern 12 and bending is formed, and the first and second phases are formed in this region 17. By arranging the edges of the shifter layers 13a and 13b, the light intensity of the edges is increased and the pattern transfer of the edge portions is prevented.

FIG. 9 shows a fifth embodiment of the present invention. In the fifth embodiment, the edges of the light-shielding pattern 12 are projected every other line to form a region 18 in which the space between the light-shielding patterns 12 is widened, and in the region 18, the first and second phase shifter layers 13a, By arranging the edge 13b, the light intensity of the edge is increased to prevent the pattern transfer of the edge portion.

FIG. 10 shows a sixth embodiment of the present invention.
In the sixth embodiment, a region 19 in which the light-shielding patterns 12 are widened by bending the light-shielding pattern 12 in the lateral direction is formed, and the edges of the first and second phase shifter layers 13a and 13b are arranged in this region 19. By doing so, the light intensity at the edge is increased and the pattern transfer of the edge is prevented.

[0030]

As described in detail above, according to the phase shift mask of the present invention, the phase difference between the first and second phase shifter layers, which are alternately provided in the plurality of light transmitting portions between the light shielding patterns, makes it possible to reduce the fineness. The contrast of the pattern can be enhanced to obtain a high resolution, and the relative phase difference between the first and second phase shifter layers with respect to the mask substrate is π / 2.
With the following, the light intensity on the wafer at the edge of the phase shifter layer can be increased, and the pattern transfer at the edge of the phase shifter layer can be prevented. Further, by making both the relative phase differences of the first and second phase shifter layers with respect to the mask substrate equal, it is possible to obtain a symmetrical light intensity profile on the wafer.

By further devising the edge portion as in the second to sixth embodiments, the light intensity on the wafer at the edge portion of the phase shifter layer can be further increased, and the phase can be more reliably achieved. It is possible to prevent the pattern transfer at the edge portion of the shifter layer.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a phase shift mask of the present invention.

FIG. 2 is a plan view showing a pattern portion of the phase shift mask of the first embodiment.

FIG. 3 is a characteristic diagram showing a light intensity characteristic according to the first embodiment.

FIG. 4 is an evaluation diagram showing an example of resist pattern evaluation according to the first embodiment.

FIG. 5 is a diagram for explaining the symmetry of the light intensity profile according to the first example.

FIG. 6 is a configuration diagram and characteristic diagram illustrating a second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a third embodiment of the present invention.

FIG. 8 is a plan view showing a fourth embodiment of the present invention.

FIG. 9 is a plan view showing a fifth embodiment of the present invention.

FIG. 10 is a plan view showing a sixth embodiment of the present invention.

FIG. 11 is a configuration and characteristic diagram of a conventional phase shift mask.

FIG. 12 is a plan view of a pattern portion of a conventional phase shift mask.

FIG. 13 is a light characteristic diagram of a conventional example.

FIG. 14 is a pattern evaluation diagram of a conventional example.

[Explanation of symbols]

 11 Mask Substrate 12 Light-shielding Pattern 13a First Phase Shifter Layer 13b Second Phase Shifter Layer 13 Phase Shifter Layer

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[Procedure amendment]

[Submission date] January 11, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 4]

[Figure 3]

[Figure 5]

[Figure 7]

[Figure 8]

FIG. 14

[Figure 6]

[Fig. 12]

[Fig. 13]

[Figure 9]

[Figure 10]

FIG. 11

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Taguchi No. 1 Taira, off Ohira Village, Kurokawa-gun, Miyagi Miyaki Oki Electric Co., Ltd.

Claims (1)

[Claims] 1. A plurality of light-shielding patterns are formed on a light-transmitting mask substrate, and a plurality of light-transmitting portions between the light-shielding patterns are alternately provided with first and second phase shifter layers. The second phase shifter layer and the second phase shifter layer both have a relative phase difference with respect to the mask substrate of α of π / 2 or less, and the phase difference between the first and second phase shifter layers is 2α of π or less. And phase shift mask.