JPH09230577A - Transmission type phase shift photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form light exposure alignment by a stepper, etc., and the high- accuracy resistance patterns on a wafer simply by using only a transparent film for phase shifters on a transparent substrate. SOLUTION: This photomask is provided with the phase shift patterns 3p in exposure regions and the exposure alignment patterns 3p' in the peripheries of the exposure regions only with a transparent film 3 having a phase shift effect on the transparent substrate 1. At the time of reticle alignment of the stepper, etc., the sufficient contrast at the transparent parts and the edges is obtainable by the irregular reflection of the edges of the exposure alignment patterns 3p' and, therefore, the high-accuracy projection transfer on the wafer, etc., is made possible. Since there is no need for executing the stage for forming the conventional light shielding film patterns, the much reduction of the time for manufacturing the transmission type phase shift photomask is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type phase shift photomask, and more particularly to an LSI, a super LSI, an ultra super L
The present invention relates to a transmission type phase shift photomask which is a photomask used for manufacturing a high density integrated circuit such as SI and which projects and forms a fine pattern on a wafer at a high density.

[0002]

2. Description of the Related Art Conventionally, semiconductor integrated circuits such as IC, LSI and VLSI are coated with a resist layer on a substrate to be processed such as Si wafer, exposed to a desired pattern by a stepper, and then developed and etched. It is manufactured by repeating what is called a lithography process.

A photomask called a reticle used in such a lithography process tends to be required to have a higher density as the semiconductor integrated circuit becomes more complicated and highly integrated.

For example, taking a DRAM which is a typical LSI as an example, the dimensional deviation of a 5 × reticle for a 4M bit DRAM, that is, a reticle having a size 5 × the pattern to be exposed is an average value ± 3σ. Even when (σ is the standard deviation), the dimensional accuracy of 0.1 to 0.15 μm is required, and similarly, the quintuple reticle for 16 Mbit DRAM requires the dimensional accuracy of 0.05 to 0.1 μm. Has been done.

Furthermore, the line width of the device pattern formed by using these reticles is 4 Mbit DRAM.
0.8 μm, 16 Mbit DRAM 0.6 μm
And more and more miniaturization is required. Also, 64 Mbit D
In the case of a RAM device pattern, resolution of 0.35 μm line width is required, and in the conventional optical exposure method using a stepper, the resolution limit of the resist pattern can be reached sooner. For example, phase shift photomasks such as those disclosed in JP-A-58-173744 and JP-B-62-59296 have been proposed.

Although the basic idea and principle of the phase shift photomask have already been described, the merit of continuing the optical exposure system using the current stepper as it is has been reviewed, and various types of phase shift photomasks have been developed. Is being actively considered. Phase shift lithography using a phase shift photomask
This is a technique for improving the contrast and resolution of a projected image by manipulating the phase of light passing through a phase shift photomask.

Phase shift lithography will be briefly described with reference to the drawings. FIG. 2 is a diagram for explaining the principle of the phase shift photomask, and FIG. 3 is a diagram for explaining the principle of the conventional photomask.

2A and 3A are cross-sectional views of the photomask, FIGS. 2B and 3B are amplitudes of light on the photomask, and FIGS. 2C and 3C. 2C shows the amplitude of light on the wafer, FIG. 2D and FIG. 3D show the light intensity on the wafer, respectively, 1 is a transparent substrate made of quartz or the like (hereinafter referred to as substrate), and 2 is. A light-shielding film made of chromium or the like (hereinafter referred to as a light-shielding film), 2p is a light-shielding pattern, 3 is a transparent film for phase shifter, 3p is a phase shifter pattern, and 4 is incident light.

In the conventional method, as shown in FIG. 3A, the light-transmitting portion of the pattern is simply formed on the substrate 1 by the light-shielding pattern 2p. However, in the phase shift lithography, the pattern shown in FIG. As shown in the figure, a phase shifter pattern 3p made of a transmissive film for inverting the phase by 180 ° is provided on one of the adjacent light transmissive portions on the reticle. Therefore, in the conventional method, the light amplitude on the reticle has the same phase as shown in FIG. 3B, and the light amplitude on the wafer also has the same phase as shown in FIG. 3C. Since they are in the same phase, the patterns on the wafer cannot be separated as shown in FIG.

On the other hand, in the phase shift method in which the phase shifter pattern 3p is provided on one side of the transmission part, the amplitude of the light on the reticle is opposite to each other between the adjacent patterns as shown in FIG. 2 (b). Since the phase is changed, the amplitude of the light on the wafer also has the opposite phase, as shown in FIG. Therefore, the light intensity becomes zero at the boundary between the patterns, and the adjacent patterns can be clearly separated as shown in FIG. Thus, in phase shift lithography, patterns that could not be separated by conventional methods can be separated, which is useful as a means for improving resolution.

As the phase shift method, another method as shown in FIG. 4 has been proposed. As shown in FIG. 4A, the transmission type phase shift photomask in FIG. 4 has only the phase shifter pattern 3p in the exposure region on the substrate 1. As shown in FIG. 4 (b), the amplitude of the light on the reticle is such that the phase is inverted at the phase shifter pattern 3p, so the amplitude of the light on the wafer is as shown in FIG.
As shown in FIG. 4C, the amplitude of the opposite phase occurs near the center of the phase shifter pattern 3p, so that finally, as shown in FIG.
As shown in (d), the patterns are separated at both edges of the phase shifter pattern 3p.

Next, a conventional manufacturing process of a phase shift photomask will be described with reference to a sectional view of the manufacturing process of FIG. 5 while taking a transmission type phase shift photomask as an example. FIG.
As shown in FIG. 5A, a chrome reticle (photomask) completed by providing a light shielding pattern 2p on a substrate 1 is prepared, and then, as shown in FIG.
A transparent film 3 for a phase shifter made of SiO ₂ or the like is formed on p. Next, as shown in FIG. 5C, an ionizing radiation resist layer 5 such as chloromethylated polystyrene is formed on the transparent film 3 for phase shifter, and the resist layer 5 is formed as shown in FIG. 5D. According to a conventional method, alignment is performed as necessary, a predetermined pattern is drawn by ionizing radiation 6 such as an electron beam exposure device, and development and rinsing are performed.
As shown in (e), a resist pattern 5p is formed.

Next, after performing a heat treatment and a descum treatment as needed, as shown in FIG. 5F, the transparent film 3 for the phase shifter exposed from the opening of the resist pattern 5p is etched with an etching gas plasma. Dry etching is carried out by 7 to form the phase shifter pattern 3p. In addition,
The phase shifter pattern 3p may be formed by wet etching instead of dry etching using the etching gas plasma 7.

Next, the remaining resist is ashed and removed by oxygen plasma 8 as shown in FIG. 5 (g). Through the above steps, as shown in FIG. 5H, the transmission type phase shift photomask having the phase shifter pattern 3p is completed.

[0015]

In the above transmission type phase shift photomask, only the transparent film for the phase shifter having the phase shift effect is provided in the exposure area.
There is an advantage that a high-definition resist pattern can be formed on the wafer. However, in the production of such a transmission type phase shift photomask, in order to improve the accuracy of reticle alignment of a stepper or the like, an exposure alignment pattern composed of a light shielding pattern for exposure alignment and a transmission part was previously formed around the exposure region. After that, in order to form a phase shifter pattern made of a transparent film in the exposed area, it is necessary to perform the drawing and plate making process twice, and there is a problem that it takes a lot of time to manufacture the photomask.

The present invention has been made in order to solve the above-mentioned problems in a transmission type phase shift photomask, and an object thereof is to use only a transparent film for a phase shifter on a transparent substrate and to obtain a stepper. It is an object of the present invention to provide a transmissive phase shift photomask capable of performing photo-exposure alignment by means of the above, and forming a highly accurate resist pattern on a wafer.

[0017]

SUMMARY OF THE INVENTION The present invention is a transmission type phase shift photomask for transferring a pattern onto a wafer or the like by projection exposure, and a phase shift for the exposure light when the pattern is transferred onto the wafer or the like. Providing only the transparent film pattern that has the effect in the exposure area on the transparent substrate,
Further, it is a transmission type phase shift photomask in which an exposure alignment pattern by the transparent film and the transmission portion is simultaneously formed in the periphery of the exposure region in one drawing step.
Further, during the exposure alignment, the exposure alignment is performed by using the contrast change such as irregular reflection at the edge portion of the exposure alignment pattern.

That is, in the transmission type phase shift photomask of the present invention, a pattern of a transparent film having a phase shift effect on an exposure light when a pattern is transferred onto a substrate such as a wafer by projection exposure is formed on the transparent substrate. Is provided and
In the transmission type phase shift photomask in which the light shielding film is not arranged in the exposure region, the exposure alignment pattern composed of the light shielding film pattern is not arranged in the periphery of the exposure region.

In this case, it is desirable that only a pattern made of a transparent film having a phase shift effect is provided on the transparent substrate.

Further, it is preferable that an exposure alignment pattern composed of a transparent film pattern similar to the transparent film having a phase shift effect is formed around the exposed region on the transparent substrate. In this case, the edge of the exposure alignment pattern is formed. It is desirable that the exposure alignment be performed by using the contrast change due to irregular reflection in the portion.

As described above, in the transmission type phase shift photomask of the present invention, only the pattern of the transparent film having the phase shift effect is provided in the exposure area on the transparent substrate, and the phase shift is provided around the exposure area. Since the exposure alignment pattern composed of the same transparent film pattern as the effective transparent film is provided, it can be formed in one drawing and plate making step, and the manufacturing time can be shortened.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The transmission type phase shift photomask of the present invention will be described below based on the manufacturing process of one embodiment thereof. FIG. 1 shows one embodiment of a manufacturing process of a transmission type phase shift photomask of the present invention. FIG.
As shown in (a), a transparent film 3 for phase shifter made of SiO ₂ or the like is formed on a substrate 1. Next, as shown in FIG. 1B, an ionizing radiation resist layer 5 such as chloromethylated polystyrene is formed on the transparent film 3 for phase shifter,
As shown in FIG. 1C, alignment is performed on the resist layer 5 according to a conventional method as needed, a predetermined pattern is drawn by ionizing radiation 6 such as an electron beam exposure device, and development,
After rinsing, a resist pattern 5p is formed as shown in FIG.

Next, after performing heat treatment and descum treatment as needed, as shown in FIG. 1E, the portion of the transparent film 3 for the phase shifter exposed from the opening of the resist pattern 5p is etched with an etching gas plasma. Dry etching is carried out by 7 to form the phase shifter pattern 3p. In addition,
The phase shifter pattern 3p may be formed by wet etching instead of dry etching using the etching gas plasma 7.

Next, the remaining resist is ashed and removed by oxygen plasma 8 as shown in FIG. 1 (f). Through the above steps, a transmission type phase shift photomask having a phase shifter pattern 3p is obtained as shown in FIG. The pattern around the exposure area in the phase shifter pattern 3p is the exposure alignment pattern 3p '.
Used as

In the first embodiment of the present invention, when the reticle alignment is performed by the i-line stepper using this transmission type phase shift photomask, the exposure formed by the transparent film for the phase shifter provided in the periphery of the exposure area in advance. When the alignment pattern 3p ′ is irradiated with the i-line light (wavelength λ = 365 nm) that is the alignment light of the i-line stepper, it is diffusely reflected at the edge part of the exposure alignment pattern 3p ′, and the i-line light transmitting part and the edge part are exposed. The reticle alignment functioned properly because the contrast at was sufficiently high. After that, the phase shifter pattern 3p provided in the exposure area of the transmission type phase shift photomask is projected and exposed on a wafer coated with an i-line resist, and after development processing is performed, the resist pattern is observed with an electron microscope. As a result, a normal resist pattern was formed.

In the second embodiment of the present invention, i of another model is used.
When reticle alignment is performed with a line stepper, the above-mentioned exposure alignment pattern 3p ′ is irradiated with halogen lamp light as alignment light, and similarly, diffuse reflection is caused at the edge portion, and the contrast between the transmission portion and the edge portion is sufficient. The reticle alignment worked normally because the image was recognized. When the resist pattern was observed after projection exposure on the wafer in the same manner as described above, a normal resist pattern was formed.

In Example 3 of the present invention, the production time of the transmission type phase shift photomask of the present invention was compared with that of the conventional transmission type phase shift photomask. As a result, the patterning step for one layer was omitted. It was possible to significantly improve the production time (it was reduced to one third or less).

The transmission type phase shift photomask of the present invention has been described above based on its manufacturing process and method of use, but the present invention is not limited to these embodiments and various modifications can be made.

[0029]

As is apparent from the above description, according to the transmission type phase shift photomask of the present invention, the phase shifter pattern and the exposure in the exposure region are formed only by the transparent film having the phase shift effect on the transparent substrate. An exposure alignment pattern around the area is provided, and during reticle alignment of a stepper or the like, high-precision projection transfer onto a wafer or the like can be achieved because the contrast between the transmissive part and the edge part is sufficient due to irregular reflection of the edge of the exposure alignment pattern. It will be possible. Further, since it is not necessary to perform the step of forming the conventional light-shielding film pattern, it is possible to significantly reduce the manufacturing time of the transmission type phase shift photomask.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of a manufacturing process of a transmission type phase shift photomask of the present invention.

FIG. 2 is a diagram for explaining the principle of a phase shift photomask.

FIG. 3 is a diagram for explaining the configuration and action of a photomask according to a conventional method.

FIG. 4 is a diagram for explaining the configuration and action of a transmission type phase shift photomask.

FIG. 5 is a diagram for explaining a manufacturing process of a conventional transmission type phase shift photomask.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 3 ... Transparent film for phase shifter 3p ... Phase shifter pattern 3p '... Exposure alignment pattern 5 ... Resist layer 5p ... Resist pattern 6 ... Ionizing radiation 7 ... Etching gas plasma 8 ... Oxygen plasma

Claims (4)

[Claims] 1. A pattern of a transparent film having a phase shift effect with respect to exposure light when a pattern is transferred onto a substrate such as a wafer by projection exposure, and a light-shielding film is provided in an exposure region. A transmission type phase shift photomask in which the exposure alignment pattern made of a light shielding film pattern is not disposed around the exposure region in the transmission type phase shift photomask in which the above is not arranged. 2. The transmission type phase shift photomask according to claim 1, wherein only a pattern made of a transparent film having a phase shift effect is provided on the transparent substrate. 3. An exposure alignment pattern comprising a transparent film pattern similar to the transparent film having the phase shift effect is formed around the exposed area on the transparent substrate. 2. The transmission type phase shift photomask described in 2. 4. The transmission type phase shift photomask according to claim 3, wherein the exposure alignment is performed by using a contrast change due to irregular reflection at an edge portion of the exposure alignment pattern.