JPH05210231A - Phase shift mask and its production - Google Patents

Abstract

(57) [Summary] [Purpose] To simplify the phase shifter creation process,
To improve the phase shift effect. A phase shifter is provided with a step difference between a gelatin layer containing no silver component provided in an unexposed area on a transparent substrate and the gelatin layer in an exposed area adjacent to the unexposed area. The silver salt-containing gelatin layer was prepared. [Effect] It is possible to simplify the complicated manufacturing process of the phase shift mask and prevent the surface contamination of the phase shifter. Further, due to the excellent transmittance of gelatin, it is possible to deal with light having a short wavelength of i-line or less, and the phase difference can be freely adjusted, and the range of the phase shift effect can be expanded. Further, there is an advantage that the concentration of the silver salt which is blackened by reducing the silver salt-containing gelatin layer in the exposed area of the pattern area can be adjusted freely.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask having a phase shifter comprising a silver salt-containing gelatin layer and a silver layer containing no silver component, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, a phase shift method for increasing contrast by utilizing a phase difference of light has been attracting attention as a lithography technology for 16M (mega) to 64M DRAM. An electron beam resist film such as PMMA, which is an EB resist, an SOG film, a Cr film, or the like has been conventionally used as a shifter material that is a material of a phase shifter that inverts the phase difference of light.

[0003]

However, in the phase shift mask, the transmittance of the g-line and i-line and the exposure light of the excimer laser and the difference in the refractive index from the glass substrate are important factors. The EB resist such as PMMA or the conventional shifter material such as SOG or Cr cannot obtain a sufficient effect as a phase shifter.

Further, as for the processed surface of the phase shifter in the phase shift mask, a vertical processed surface is required to invert the phase of the exposure light with good control. Therefore, a dry etching technique such as RIE is required. However, this dry etching technique not only complicates the phase shifter manufacturing process but also may cause surface contamination of the phase shifter.

[0005]

The present invention comprises a transparent substrate which is transparent to exposure light and a phase shifter which inverts the phase of light formed thereon. The phase shifter is a transparent substrate. A gelatin layer containing no silver component provided in the upper unexposed area and a gelatin layer containing a silver salt provided with a step in the exposed area adjacent to the unexposed area. It is a phase shift mask.

Further, from another viewpoint, the present invention applies a silver salt-containing gelatin emulsion onto a transparent substrate transparent to exposure light and exposes it with a mask to form an unexposed area. An exposed area is formed, and then a silver salt is removed from the unexposed area by treating with a developing solution to form a gelatin layer having a step with respect to the exposed area and containing no silver component. A method of manufacturing a phase shift mask is provided.

That is, the present invention uses a silver salt-containing gelatin emulsion containing silver in gelatin as the material of the phase shifter. Specifically, this invention is
A lithographic method using a silver salt-containing gelatin emulsion layer used in photographic films is used to apply a silver salt-containing gelatin emulsion onto a transparent substrate film that is transparent to exposure light. After the exposure of the silver salt-containing gelatin emulsion layer, the subsequent development / fixing process removes the silver particles from the unexposed portion of the silver salt-containing gelatin emulsion layer, whereby the silver salt-containing gelatin is released. Exposure of emulsion layer
Between the exposed film, which is a reduced and blackened silver salt formed by both development processes, and the unexposed film in which the silver salt is desorbed from the silver salt-containing gelatin emulsion layer It was developed based on the phenomenon that steps occur. By utilizing this phenomenon, a phase shift mask and a light absorption type phase shift mask consisting of only EB resists or shifter materials such as SOG and Cr, which have been conventionally proposed, can be easily formed with a good cross-sectional shape of the shifter material.

Further, due to the excellent transmittance of the gelatin emulsion, it is possible to deal with light having a short wavelength of i-line or less, and the phase difference can be adjusted freely, and the range of the phase shift effect can be expanded. That is,
Generally, from the transmittance curve of gelatin emulsion, i-line (36
This is because the transmittance is as high as 99.5% even in the vicinity of 5 nm), while the transmittance is about 90% for EB resists such as PMMA and SOG.

Further, in the exposed area of the pattern area,
There is an advantage that the concentration of the silver salt that is blackened by reducing the silver salt-containing gelatin emulsion layer can be adjusted freely.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a halftone phase shift mask having a phase shifter formed using a silver salt-containing gelatin emulsion. In FIG. 1, the phase shift mask is composed of a glass substrate 3 transparent to exposure light and a phase shifter, and the phase shifter has a film thickness A of 3 μm provided in an unexposed region M on the glass substrate. The thickness B of the gelatin layer 1 containing no silver component and the exposed area N adjacent to the unexposed area M on the glass substrate was 3.5 μm, and the transmittance was controlled to about 16%. , The gelatin layer 4 is reduced and blackened to form the silver salt 2.

Further, the height d between the gelatin layer 1 containing no silver component and the silver salt 2 is 0.5 μ with respect to the gelatin layer 1.
There is a step D of m. In this embodiment, since the refractive index n of the gelatin layer is n = 1.3 to 1.4, d = λ / [2 when the height d of the step D is λ is the wavelength of the exposure light.
A phase difference can be produced by controlling the (n-1)]. The manufacturing method will be described below.

4 to 6 show a method for producing a halftone type phase shift mask having a phase shifter using a gelatin emulsion containing silver salt. As shown in FIG. 4, a silver salt-containing gelatin emulsion is applied onto a transparent substrate 3 which is transparent to exposure light, and exposed using a mask (not shown) to form an unexposed area M. An exposed area N is formed.

At this time, a silver salt-containing gelatin emulsion is applied to form a silver salt-containing gelatin layer 4 having a film thickness C adjusted to 4 μm, and then a g-ray filter is used as a light source to expose light. 5 is irradiated with 150 Lx as an exposure amount for 2 seconds to expose the silver salt-containing gelatin layer 4. Next, after processing with a developing solution, fixing is performed (see FIGS. 5 and 6).

At this time, first, a stock solution (using Konica's CDH100 containing hydroquinone as a main component): pure water =
1: 4 HRP (high resolution plate)
After performing dip development at 20 ° C. for 210 seconds using a developing solution, stopping is performed at 20 ° C. for 180 seconds in a state of using pure water, and subsequently, using HRP fixing solution at 20 ° C. for 180 seconds.
It was fixed for a second, and then washed with pure water at 20 ° C. for 180 seconds. Further, as a result of setting the exposure light 5 as described above, the transmittance of the silver salt 2 blackened by reducing the silver salt-containing gelatin layer 4 can be adjusted to 16%.
The degree to which the silver salt-containing gelatin layer 4 in the exposed area N is reduced and blackened is proportional to the exposure amount of the exposure light 5 in FIG.

In this way, as shown in FIG. 6, the height between the gelatin layer 1 containing no silver component and the silver salt 2 reduced and blackened by the gelatin layer 4 is higher than that of the silver salt 2. A step D of d is formed. By setting this height d to d = λ / [2 (n-1)], a phase difference of π can be generated. Thus, in order to form the step D formed between the exposed portion and the unexposed portion of the silver salt-containing gelatin layer 4, the silver in the unexposed portion is removed and retreats during both the developing and fixing processes. The property is used.

In this way, a halftone type phase shift mask having a phase shifter using a silver salt-containing gelatin emulsion is formed. In this halftone phase shift mask, from the shape of the amplitude distribution of light on the mask in FIG. 2 and the shape of the light intensity distribution on the wafer in FIG. It can be seen that it can be applied to light with a short wavelength and the range of the phase shift effect can be expanded.

That is, from FIG. 2, the silver salt in which the gelatin layer 4 in the unexposed area M has a smaller amplitude of light in the exposed area N and the gelatin layer 4 is reduced and blackened. It can be seen that it is higher than the amplitude of light in 2. Also, from FIG. 3, the light intensity in the gelatin layer 1 containing no silver component in the unexposed area M is higher than that in the silver salt 2 in which the gelatin layer 4 is reduced and blackened in the exposed area N. You can see that it is more prominent.

In the above embodiment, the halftone type phase shift mask uses a silver salt-containing gelatin emulsion as the phase shifter. However, the silver salt-containing gelatin emulsion was formed on the conventional Cr pattern by the method of the present invention. It is also possible to prepare a Levenson-type phase shift mask in which the phase shifter is formed by applying the gelatin emulsion of the above. Further, the transmittance of the blackened silver salt obtained by reducing the silver salt-containing gelatin layer formed in the exposed portion of the halftone type phase shift mask of the above example is changed from 16% to 100% by using the decolorizing agent. By doing so, it is also possible to create a transmission type phase shift mask.

[0019]

As described above, according to the present invention, the use of the silver salt-containing gelatin emulsion as the material of the phase shifter simplifies the complicated process of preparing the phase shift mask and also makes Surface contamination can be prevented. Further, due to the excellent transmittance of gelatin, it is possible to deal with light having a short wavelength of i-line or less, and the phase difference can be freely adjusted, and the range of the phase shift effect can be expanded. Further, there is an advantage that the concentration of the silver salt which is blackened by reducing the silver salt-containing gelatin layer in the exposed area of the pattern area can be adjusted freely.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an amplitude distribution of light on a mask in a halftone type phase shift mask using gelatin as a material for a phase shifter in the above example.

FIG. 3 is a characteristic diagram showing a light intensity distribution on a wafer in a halftone type phase shift mask using gelatin as a phase shifter material in the above example.

FIG. 4 is a structural explanatory view showing a first step of the forming method of the above embodiment.

FIG. 5 is a structural explanatory view showing a second step of the forming method of the above embodiment.

FIG. 6 is a structural explanatory view showing a third step of the forming method of the above embodiment.

[Explanation of symbols]

 1 a gelatin layer containing no silver component 2 a silver salt in which a silver salt-containing gelatin layer is reduced and blackened 3 a glass substrate transparent to exposure light 4 a silver salt-containing gelatin layer 5 exposure light M unexposed area region N Exposure area D Step

Claims (3)

[Claims] 1. A transparent substrate transparent to exposure light, and a phase shifter for inverting the phase of light formed thereon, the phase shifter being provided in an unexposed area of the transparent substrate. A phase shift mask comprising a gelatin layer containing no silver component and a silver salt-containing gelatin layer provided with a step between the gelatin layer in the exposed area adjacent to the unexposed area. 2. The phase shift mask according to claim 1, wherein the phase shifter comprises a Cr film and a gelatin layer formed on the Cr film and containing no silver component. 3. An unexposed area and an exposed area are formed by applying a silver salt-containing gelatin emulsion on a transparent substrate which is transparent to exposure light, and exposing using a mask.
Then, by processing with a developing solution to remove the silver salt from the unexposed area, a gelatin layer having a step with respect to the exposed area and containing no silver component is formed. Production method.