JPH09204034A - Exposure mask and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Problem] An optimum engraving amount can be set for each pattern, and dimensional controllability can be improved. In an exposure mask having a light-shielding pattern and a transparent phase shift pattern on a light-transmissive substrate, the transparent phase shift pattern is such that the engraving amounts of openings between the light-shielding patterns are different from each other. 2. The opening pattern dimension is set to 3. With the wavelength of the exposure light being .lamda.
It was set to have a phase difference of 176 to 194 degrees in a pattern larger than 2λ, and to have a phase difference of 166 to 173 degrees in a pattern having a mask aperture size smaller than 3.2λ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure technique used in a lithography process in manufacturing a semiconductor device, and more particularly to a projection exposure mask used for projection exposure and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the progress of semiconductor technology, semiconductor devices, and eventually semiconductor elements, are being accelerated and highly integrated. Along with this, finer pattern dimensions and higher precision are required. To meet this demand,
Light having a short wavelength such as far-ultraviolet light has been used as an exposure light source. On the other hand, in recent years, attempts have been made to miniaturize the exposure light source without changing it. There is a phase shift method as one of the methods. In this method, a phase inversion layer is partially provided in the light transmitting portion to eliminate the adverse effect of light diffraction generated between adjacent patterns and improve the pattern accuracy.

Among the phase shift methods, there is a Shibuya Levenson type phase shift method described in Japanese Patent Laid-Open No. 62-50811 as a method for improving the resolution performance. In this method, the phase shifters are alternately provided for the adjacent light transmitting portions in the mask in which the light shielding pattern is arranged. The phase of the light transmitted through the phase shifter is inverted by 180 ° with respect to the light transmitted through the portion where the phase shifter is not arranged.

In this way, by reversing the phase of the light of the adjacent transmitting portions, negative interference of light is generated between the patterns, and the resolution performance is improved. For this Levenson-type phase shift mask, a method is known in which a substrate is formed by engraving as shown in JP-A-62-189468.

By the way, in the mask disclosed in Japanese Unexamined Patent Publication No. 62-189468, even if the size of the opening is the same, there is a difference in the light intensity between the phase shift portion where the substrate is dug and the non-phase shift portion where the substrate is not dug. There was a problem that. This issue is described by RLKostelak et al. (J.Vac.Sci.Technol
B10 (6) (1992) p3055) (Exposure characteris
tics of alternate aperture phase-shifting masks fa
As discussed in (blicated using a subtractive process), the aperture size is optically narrowed by the interference of the pattern edge part parallel to the optical axis in the phase shift part.

For this problem Christophe Pierrat
Et al. (SPIE. Vol. 1927 (1993) p28) (Phase-Shif
ting Mask Technology Effect on Lithographic Image
Quality), we propose a method to correct the light intensity by anisotropically etching a vertical phase difference of 180 degrees and then using isotropic etching to etch the sidewalls of the concave part. ing. However, this method has a problem that it is difficult to inspect a space formed by isotropic etching and it is difficult to correct a defect in the space under the light-shielding film.

As another method of correcting the light intensity, Japanese Patent Application No.
No. 43618 (→ Japanese Patent Application Laid-Open No. 7-), an exposure in which both openings are dug and the difference in depth between the deep dug portion and the shallow dug portion is transmitted through a translucent substrate having the same thickness. The phase difference is adjusted so that it has a phase difference of approximately λ / 2 with respect to the light, and the depth of the shallow engraved portion is approximately λ / 2 with respect to the exposure light transmitted through the transparent substrate having the same thickness. A method has been proposed in which a uniform light intensity is achieved in both openings by adjusting so that

Although this method improves the dimensional controllability,
According to experiments and earnest research conducted by the present inventors, it has been found that the amount of engraving depends on the pattern size, and that there is an optimal amount of engraving for each pattern. Therefore, it is considered that further improvement in dimensional controllability can be achieved by setting the optimum engraving amount for each pattern having different opening dimensions.

[0009]

As described above, both of the openings are dug, and the depth difference between the two dug portions is set so as to have a phase difference of approximately λ / 2 with respect to the exposure light. In the exposure mask that adjusts, the engraving amount depends on the pattern dimension, and it is expected that further improvement of the dimension controllability can be realized by setting the optimal engraving amount for each pattern. .

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to make an optimum engraving for each pattern in a Levenson type phase shift mask in which both openings are engraved. It is an object of the present invention to provide an exposure mask which can set the amount and can further improve the dimensional controllability, and a method for manufacturing the same.

[0011]

[Means for Solving the Problems]

(Structure) In order to solve the above problem, the present invention employs the following structure. That is, the present invention is an exposure mask comprising a light-shielding pattern and a transparent phase shift pattern on a transparent substrate, wherein the transparent phase shift pattern is
The opening pattern size is constituted by a pattern in which the engraving amount of the openings between the light-shielding patterns is set to be different from each other, and the engraving amount of a portion with a small engraving amount is defined as the wavelength of the exposure light λ. Is variably set according to whether the value is larger or smaller than 3.2λ.

Here, the following are preferred embodiments of the present invention. (1) In the pattern in which the opening pattern size is larger than 3.2λ, the depth of the shallow part of the opening is different with respect to the refractive index n and the exposure wavelength λ of the transparent substrate. It was set to be approximately λ / (2 × (n-1)) and approximately 0.95λ / (2 × (n-1)) for a pattern having an opening pattern size smaller than 3.2λ. thing. The exposure wavelength is 436 nm, 36
It is preferable to use any one of 5 nm, 248 nm and 193 nm. Further, the transparent substrate is made of SiO ₂ , C.
It is preferable to use aF ₂ , MgF ₂ , Al ₂ O ₃ , Si ₃ N ₄ or the like. (2) With respect to the light transmitted through the non-processed area on the pattern surface of the light-transmissive substrate, the depth of the shallow portion of the opening is different from that of the opening pattern dimension is larger than 3.2λ. The pattern is set to have a phase difference of 177 to 194 degrees, and the aperture pattern size is set to have a phase difference of approximately 166 to 173 degrees in a pattern smaller than 3.2λ. (3) When the exposure light source has a wavelength of 248 nm and quartz is used as the light-transmissive substrate, the depth of the shallow part of the opening is different when the size of the opening pattern is larger than 0.8 μm. 22 (including 0.8 μm)
235 in a pattern in the range of 0 nm to 250 nm and having an opening pattern size smaller than 0.8 μm
It is set to be in the range of nm to 265 nm. (4) When the wavelength of 248 nm is used as the exposure light source and quartz is used as the translucent substrate, the difference in the engraving amount between the deep portion and the shallow portion of the opening where the engraving amount is different is 235 nm to 245 n.
m. (5) When the wavelength of 365 nm is used as the exposure light source and quartz is used as the light-transmissive substrate, the amount of engraving in the shallow part of the opening portion where the engraving amount is alternately different is a pattern in which the opening pattern dimension is larger than 1.2 μm. In the range of 350 nm to 380 nm, and in the case of a pattern having an opening pattern size smaller than 1.2 μm, the range is set to 370 nm to 400 nm. (6) When a wavelength of 365 nm is used as an exposure light source and quartz is used as a light-transmissive substrate, the difference in the engraving amount between the deep portion and the shallow portion of the opening is different from 365 nm to 380 n.
m. (7) When the wavelength of 193 nm is used as the exposure light source and quartz is used as the translucent substrate, the depth of the shallow part of the opening is different from the pattern of the opening pattern size larger than 0.6 μm. In the range of 170 nm to 190 nm, and in the case of a pattern having an opening pattern size smaller than 0.6 μm, the range is set to 180 nm to 200 nm. (8) When the wavelength of 193 nm is used as the exposure light source and quartz is used as the translucent substrate, the difference in the engraving amount between the deep portion and the shallow portion of the opening where the engraving amount is different is 180 nm to 190 n.
m.

According to the present invention, in the method of manufacturing an exposure mask having the above structure, a step of forming a light-shielding pattern on a translucent substrate and an opening having an opening pattern size larger than 3.2λ with respect to the exposure wavelength λ. Simultaneously etching the pattern and the opening pattern whose opening pattern dimension is smaller than 3.2λ and deeper than the adjacent opening, and the opening pattern dimension is larger than 3.2λ and deeper than the adjacent opening for the exposure wavelength λ. The method is characterized by including the step of simultaneously etching an opening pattern to be dug and an opening pattern having an opening pattern size smaller than 3.2λ.

More preferably, the opening pattern size is 3.
The etching rate of the opening pattern larger than 2λ is 1.7 to 6.7% faster than the etching rate of the opening pattern whose opening pattern dimension is smaller than 3.2λ. (Operation) FIG. 2 shows the relationship between the optimum relative engraving amount and the engraving amount of a shallow portion when a wavelength of 248 nm is used as an exposure light source, showing a wafer size of 0.15 μm line & space and 0.18 μm line & space. These are obtained for each of the patterns. 2A shows a line and space of 0.15 μm, and FIG. 2B shows a line and space of 0.18 μm. The mask is made of a quintuple (the size of the wafer pattern is set to five times the wafer pattern). Further, NA = 0.5, σ = 0.
3, dimensional margin ± 10%, exposure margin 10%.

As shown in FIG. 2, the relative engraving amount (deep engraving portion-shallow engraving portion) hardly depends on the pattern size. However, the amount of engraving in the shallow portion largely depends on the pattern size. The same tendency as the 0.18 μm pattern was observed for the line & space pattern of 0.16 to 0.30 μm or more. 0.16 μm to 0.15 μ
In the pattern of m, the optimum value of the shallow engraving amount changed depending on the pattern size.

FIG. 3 is a diagram showing the phase bias dependence of a portion of the double-drilling type Levenson mask in which the amount of engraving is shallow. FIG. 3A shows a line and space of 0.15 μm,
(B) is a line & space of 0.18 μm. The DOF on the vertical axis is standardized with respect to the phase bias (degree) on the horizontal axis. Also, the wavelengths of the exposure light source λ, NA, σ
The conditions such as are the same as those in the case of FIG.

From this figure, in the case of a line and space of 0.15 μm, the DOF is 0..0 with a phase difference of 166 to 173 degrees.
It can be seen that the DOF is 0.9 or more with a phase difference of 176 to 194 degrees when the line and space is 0.18 μm or more. Further, a pattern smaller than 0.15 μm shows almost the same characteristics as 0.15 μm, and a pattern of 0.16 μm
The larger pattern showed almost the same characteristics as 0.18 μm.

Since the mask is a pentaploid,
0.16 μm × 5 = 0.8 μm is about 3.2λ (λ = 24
8 nm). Therefore, with respect to the light transmitted through the non-processed area on the pattern surface of the translucent substrate, the depth of the shallow portion of the opening portion having different depths of the pattern is larger than 3.2λ. At 17
Approximately 166 to 1 in a pattern having a phase difference of 6 to 194 degrees and an opening pattern size smaller than 3.2λ.
By setting so as to have a phase difference of 73 degrees, it is possible to always form a pattern with good dimensional controllability.

On the other hand, when etching a fine pattern, the etching rate changes according to the pattern size.
An example is shown in FIG. In FIG. 4, for example, a speed difference of about 2% occurs between the mask size of 0.6 μm and 0.8 μm. Here, when the precision of the tetraploid phase shift part when compared with the conventional manufacturing process and the case where it is created according to the present method are compared, the following (Table 1) is obtained.

[0020]

[Table 1]

In the conventional method, when each etching condition is adjusted to a wafer of 0.15 μm (mask of 0.6 μm),
It can be seen that a pattern of a wafer 0.20 μm (mask 0.8 μm) largely deviates from the optimum value. When the deterioration of the depth of focus is calculated in comparison with FIG. 2, the depth of focus of the 0.20 μm pattern is reduced to about 80% compared with the case where the etching amount is optimized. On the other hand, according to the present invention, it is possible to prevent deterioration of the depth of focus in each pattern size.

Here, the optimum etching conditions for achieving this method will be described in detail. In the present invention, it is necessary to carry out etching under the following two conditions. (A) A dimension smaller than 3.2λ is set to 174 degrees and 3.2.
The dimension larger than λ is 177 to 194 degrees. (B) The dimension smaller than 3.2λ is 166 to 173 degrees, and the dimension larger than 3.2λ is 174 degrees. Relative etching rate to satisfy (a) is 1.01
It becomes 7-1.115. On the other hand, the relative etching rate for satisfying (b) is 1.005 to 1.048.
For each of the etchings (a) and (b), the etching rate may be adjusted with a pattern larger than 3.2λ and a pattern smaller than 3.2λ, but it can be considered that the etching rate ratio is generally determined when etching is performed under the same conditions. In that case,
Since an effective rate ratio common to both etchings is required, it can be said that it is desirable to set the etching rate of a pattern of 3.2λ or more to 1.7 to 4.8% as compared with the pattern etching rate of 3.2λ or less.

The above (Table 1) can be expressed as shown in the following (Table 2) by using the refractive index of quartz at 248 nm of 1.5 and the relative phase difference with respect to the non-processed surface of the quartz plate.

[0024]

[Table 2]

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Details of the present invention will be described below with reference to embodiments. (Embodiment 1) This embodiment relates to a Levenson-type phase shift mask created to realize a cell circuit of 0.15 μm rule and a peripheral circuit of 0.20 μm rule, and a mask pattern data creating method.

The data preparation procedure was performed as follows. (1) All the light-shielding patterns were selected, and this was used as a first pattern group to create first mask data. (2) A second pattern group in which a phase shift pattern is arranged in the opening and selected as a 0.15 μm rule, and a 0.20 μm rule (0.20 μm in the opening)
The second mask data composed of the third pattern group including all of the above (including the above) was created. (3) A fourth pattern group in which the phase shift pattern is arranged in the opening and all the patterns of the rule of 0.15 μm are selected, and the phase shift pattern is arranged in the opening and 0.20 μm Third mask data composed of the fifth pattern group selected as a rule was created. (Embodiment 2) This embodiment relates to a quadruple 248 nm exposure Levenson phase shift mask created to realize a 0.15 μm rule cell circuit and a 0.20 μm rule peripheral circuit. The present invention relates to a method for creating a Levenson phase shift mask using created mask data.

First, as shown in FIG. 1A, a light shielding film 1 in which Cr and CrOx are sequentially laminated on a transparent substrate 101.
A light-shielding pattern was formed by applying a photosensitive resin material to the surface having No. 02, drawing with an electron beam using the first mask data, and developing. Here, the area a is 0.
The 15 μm pattern region and the region b are 0.20 μm pattern regions.

Then, as shown in FIG. 1B, a resist pattern 103 is formed by applying a photosensitive resin material on this surface, drawing with laser light using the second mask data, and developing. did.

Then, as shown in FIG. 1C, the translucent substrate 101 was etched by using a fluorocarbon gas (for example, CF ₄ gas) with the resist pattern 103 and the light shielding film 102 as a mask. The etching amount at this time is 2 in the region a with respect to the non-processed region of the transparent substrate 101.
The depth was adjusted to 39.3 nm. At this time,
The etching rate was also adjusted so that the depth in the region b was about 247 nm with respect to the transparent substrate surface. Here, the area a is a mask opening of 0.6 μm (0.
15 μm) pattern area, and area b shows a pattern area of a mask opening 0.8 μm (0.20 μm on the wafer).

Then, after removing the resist pattern 103 as shown in FIG. 1D, a photosensitive resin material is further applied to this substrate as shown in FIG.
A resist pattern 104 was formed by drawing and developing with laser light using the third mask data.

Next, as shown in FIG. 1F, the translucent substrate 101 is etched using the resist pattern 104 and the light-shielding film 102 as a mask by using a fluorocarbon gas (for example, CF ₄ gas). . The etching amount at this time was adjusted so that the depth in the region b was 239.3 nm with respect to the non-processed region of the transparent substrate 101. At this time, the etching rate was also adjusted so that the region a had a depth of about 235 nm with respect to the transparent substrate surface.

Then, as shown in FIG. 1G, the resist pattern 104 was removed to obtain a desired exposure mask.
Although the laminated film of Cr and CrOx is used as the light-shielding film in the present embodiment, the present invention is not limited to this.
The same effect can be obtained by using a light-shielding film using a single layer or a laminated layer of oxides, nitrides, oxynitrides, fluorides, etc. of a system type, a Si type or the like.

Further, although quartz is used as the light-shielding substrate in this embodiment, CaF ₂ , MgF ₂ , Al ₂ O ₃ and Si _{3 are used.}
N ₄ or the like may be used. The engraving amount in this case may be calculated from the refractive index at the exposure wavelength.

Although 248 nm is used as the exposure light source in this embodiment, the mask manufacturing method shown in this embodiment is 36
It can be applied to a mask used for any exposure wavelength such as 5 nm and 193 nm. In that case, in the region a having a mask opening size smaller than 3.2λ with respect to the exposure wavelength λ, the difference in the engraving amount of the shallow engraved portion with respect to the transparent substrate surface is relative to the refractive index n of the transparent substrate. Almost 0.95λ / (2
X (n-1)) and the pattern is larger than 3.2λ, the difference is approximately λ / (2 × (n-1)).
It should be adjusted so that At the same time, the difference between the deep digging amount and the shallow digging amount in both the regions a and b may be set to be approximately 0.975λ / (2 × (n−1)).

In this embodiment, the processing of the phase shift portion is the second step.
The mask data and the third mask data are sequentially used, but the order is not limited to this, and the third mask data and the second mask data are used in this order to form a corresponding resist pattern and perform a corresponding etching. It can also be created by giving a quantity. (Embodiment 3) This embodiment relates to a method of creating a pattern in which a cell circuit of a 0.15 μm rule and a peripheral circuit of a 0.20 μm rule are present, using the 248 nm exposure Levenson phase shift mask created according to the second embodiment. This shows the effectiveness of the mask for main exposure for device fabrication.

After forming a film for the purpose of preventing exposure light reflection on the base substrate by a coating method, a photosensitive resin material is formed to a film thickness of 5
It was formed with a thickness of 00 nm. The height difference of the base substrate is 0.5.
It was about μm.

The underlying substrate was subjected to alignment exposure, and the portion of the photosensitive resin material that was soluble in the developing solution was developed and removed to form a circuit pattern. Here, the exposure is NA =
The condition was 0.6 and σ = 0.3. As a result, 0.1
A good Levenson effect can be obtained even in each pattern area of 5 μm and 0.20 μm. All pattern areas could be created within ± 5% of line width control.

On the other hand, in the case of using the mask prepared by the conventional method (for the depth of engraving, refer to the numerical values of the conventional method in (Table 1)), the line width control can be suppressed within ± 5% in the 0.15 μm region. On the other hand, the line width is ± 10% in the 0.20 μm region.
, And the superiority of the mask used in this study was confirmed.

[0039]

As described above, according to the present invention, the Levenson-type phase shift mask method, which is created by alternately changing the engraving depth of the mask opening, has an optimum depth according to the opening pattern size. The dimensional controllability of the wiring and the like formed by using the exposure mask using the same can be remarkably improved, and the reliability as a device can be greatly improved.

Further, according to the present invention, the Levenson type phase shift mask method, which is created by alternately changing the engraving depth of the mask opening, is highly accurate so that the optimum depth can be given according to the opening pattern size. Made it possible to process.

[Brief description of drawings]

FIG. 1 is a sectional view showing a manufacturing process of an exposure mask according to a first embodiment of the present invention.

FIG. 2 is a diagram showing mask pattern dimension dependence of (deep engraved portion-shallow engraved portion) and (shallow engraved portion-transparent substrate surface).

FIG. 3 is a diagram showing the phase bias dependency of a shallowly dug-out Levenson mask in a dug-down type mask.

FIG. 4 is a diagram showing a difference in etching rate with respect to a pattern dimension.

[Explanation of symbols]

 101 ... Transparent positive substrate 102 ... Shading film 103, 104 ... Resist pattern a ... Mask opening smaller than 3.2λ b ... Mask opening larger than 3.2λ

Claims (5)

[Claims] 1. An exposure mask comprising a light-shielding pattern and a transparent phase shift pattern on a light-transmissive substrate, wherein the transparent phase shift pattern has different amounts of openings dug between the light-shielding patterns. The digging amount of a portion having a shallow digging amount is variably set according to whether the opening pattern size is larger or smaller than 3.2λ, where λ is the wavelength of the exposure light. An exposure mask that is characterized by 2. The refractive index n and the exposure wavelength λ of the transparent substrate.
On the other hand, in the pattern in which the opening pattern size is larger than 3.2 λ, the digging amount of the shallow portion of the opening portion having the different digging amount is approximately λ / (2 × (n−1)).
And a pattern having an opening pattern size smaller than 3.2λ is approximately 0.95λ / (2 × (n−
The exposure mask according to claim 1, which is 1)). 3. With respect to light transmitted through a non-processed area on the pattern surface of the translucent substrate, the shallow engraving amount of the opening portions having different engraving amounts and the opening pattern dimension is 3 177 for patterns larger than 2λ
It has a phase difference of 194 degrees and the opening pattern size is 3.
The exposure mask according to claim 1, wherein the exposure mask is set to have a phase difference of 166 to 173 degrees in a pattern smaller than 2λ. 4. A method of manufacturing an exposure mask comprising a light-shielding pattern and a transparent phase shift pattern on a light-transmitting substrate, the step of forming the light-shielding pattern on the light-transmitting substrate, and the exposure wavelength λ. Simultaneously etching an opening pattern having an opening size larger than 3.2λ and an opening pattern having an opening size smaller than 3.2λ and being dug deeper than an adjacent opening, and an opening size of 3.2λ for the exposure wavelength λ. A method of manufacturing an exposure mask, comprising the step of simultaneously etching an opening pattern which is deeper than a larger adjacent opening and an opening pattern having an opening size smaller than 3.2λ. 5. The etching rate of an opening pattern having an opening size larger than 3.2λ is 1.7 to 10 times higher than the etching rate of an opening pattern having an opening size smaller than 3.2λ.
The method for manufacturing an exposure mask according to claim 4, wherein the method is 6.7% faster.