JPS61292643A - Photomask - Google Patents

Abstract

PURPOSE:To form both of a phase shift layer removed at openings and that remaining there with one time of exposure by exposing a resist film applied onto a light shading film with exposure energy partly different, and forming a resist pattern different in thickness between the phase shift layer at the openings to be removed and at those to be left as it is. CONSTITUTION:An SiO2 film 2 is vapor deposited on a glass base 1, the light shading film 3 of Cr is vapor deposited on the film 2, and it is coated with the resist 6. It is exposed to light having the pattern of the openings, with a different exposure energy at each part of the pattern, resulting in perfectly removing the pattern parts 4-2, 4-4 of the resist pattern after development processing, and reducing the film thickness to about their halves at the pattern parts 4-1, 4-3, 4-5. The openings 4-2, 4-4 are formed by etching the Cr layer 3 and further etching the SiO2 layer 2 with diluted HF, and the remaining resist is vertically dry etched to reduce the film thickness to remove the resist of the pattern parts 4-1, 4-3, 4-5, and the Cr layer 3 is again etched and finally, all the resist remaining on the surface is removed.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a photomask (original image) for a reduction projection exposure apparatus.
The present invention relates to photomasks suitable for transferring fine patterns, particularly to photomasks suitable for transferring fine patterns.

[Background of the invention]

A reduction projection exposure apparatus that illuminates a mask with an original pattern (hereinafter referred to as a reticle) with an illumination system and transfers the pattern on the reticle onto a wafer is required to miniaturize the pattern that can be transferred. The resolution, which indicates how fine a pattern a reduction projection exposure system can transfer, is evaluated by whether two adjacent bright areas on a wafer can be separated using a reticle pattern that periodically changes in brightness and darkness. Ru. It is known that one method for improving this resolution is to change the phase of illumination light at two adjacent transparent parts on the reticle. Conventionally, regarding reticle patterns that change the phase of illumination light, IE Transactions on Electron Devices, ED-29, No. 12 (1982)
Page 1828 (IEEE Trans on t<1e
ctron Devices, vol ED-29
Marc D, Levenson (1982) p 1g2g)
1' Improving Resolution Improving Photolithography with Shift Marks (Improving Resolution I
n Photolithography with a
The reticle proposed in this document has a light-shielding part that serves as the original image of the pattern on the reticle substrate, and further changes the phase of the illumination light on top of that. (hereinafter referred to as phase shift layer). Therefore, when manufacturing a reticle, it is first necessary to expose to light to form a light-shielding pattern. After forming the light-shielding pattern by etching, etc., the next step is to form a phase shift layer. It is necessary to expose the pattern while correctly aligning it with the light-shielding pattern.For this reason, two exposure steps are required to manufacture the reticle, which makes the process complicated, and also causes alignment errors when exposing the pattern of the phase shift layer. If this occurs, there are drawbacks such as the ability to change the phase of illumination light deteriorates.

[Purpose of the invention]

An object of the present invention is to provide a photomask (reticle) that solves the above v2 drawbacks and can simultaneously form both a light-shielding pattern and a pattern of a layer that changes the phase of illumination light in a single exposure process. It is in.

[Summary of the invention]

In order to achieve the above object, in the present invention, a phase shift layer is first provided on a reticle substrate, and a light shielding pattern is provided on the phase shift layer. When manufacturing a reticle, after a resist is applied on the light-shielding film, exposure is performed with different exposure energies in parts to create different thicknesses between the part where the phase shift layer in the aperture is removed and the part where it is left as is. A resist pattern was formed. By etching the light shielding film and phase shift layer, dry etching the resist, and etching the light shielding film in this order, a desired reticle can be provided.

[Embodiments of the invention]

The present invention will be explained below using examples. FIG. 1 is a cross-sectional view of a reticle to which the present invention is applied. Here, the light shielding film 3 made of Cr has five openings 4-1.
An example in which five line patterns of 4-2.4-3.4-4°4-5 are formed is taken up, and a cross section perpendicular to the longitudinal direction of the line patterns is shown. The illustrated reticle is characterized in that a phase shift layer 2 made of vapor-deposited SiO2 is sandwiched between a glass substrate 1 and a light shielding film 3. The thickness t of the phase shift layer 2 is:

When the refractive index is n and the wavelength of the illumination light is λ, it is given by λ, and in this example, it is 0.38 μm (n
=1.47. λ=0.365 μm), as shown in Figure 1, every other opening 4- out of the five openings
2 and 4-4, the phase shift layer 2 is removed. Therefore, when this reticle is illuminated from the top surface with illumination light with a high degree of coherence, the amplitude distribution of the light transmitted through the reticle is
As shown in the figure, the signs are reversed at adjacent apertures, resulting in an effect exactly equivalent to that of a conventional reticle that changes the phase of illumination light.

Next, the manufacturing procedure of the reticle of the present invention will be explained using FIG. First, as shown in (A), S
3800 people vapor deposited iO22, and 800 people vapor deposited Cr, which is the light shielding film 3, thereon. Further, a resist 6 is applied thereon. Next, the pattern of openings is exposed. At this time, since the exposure intensity is changed for each pattern, the resist pattern after development processing is as shown in (B), although the pattern parts 4-2 and 4-4 are completely removed, the pattern parts In the case of 4-1.4-3.4-5, the resist film thickness is only reduced to about one.

A method of changing the exposure moment for each pattern is possible by changing the scanning time in the case of EB writing. By etching Cr 1 and then etching the Sin layer 2 with diluted hydrofluoric acid, openings 4-2 and 4-4 are formed as shown in (C). Next, as shown in (D), the remaining resist is dry-etched in the vertical direction to reduce the film thickness, and the pattern area 4-1.4 is etched.
-3.Remove the resist of 4-5 6 When Cr is etched again, five openings are formed in the light shielding film 3 as shown in (E). Finally, by removing all the resist remaining on the surface, the reticle of the present invention shown in FIG. 1 is completed.

In this embodiment, a deposited film of SiO□ was used as one phase shift layer, but this material may be any material as long as it satisfies the conditions of formula (1) and is resistant to reticle cleaning.

[Effects of the Invention] According to the present invention, in manufacturing a reticle having a layer that changes the phase of illumination light, a pattern to be formed on a light shielding film and a pattern to be formed in a phase shift layer can be formed in one exposure process. They can be formed simultaneously on the resist. That is,
Unlike conventional methods, there is no process of newly exposing a phase shift layer to match the light shielding pattern, and there is no deterioration of the pattern due to alignment errors.This simplifies the reticle manufacturing process and improves the reliability of the pattern. effective.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a cross section of the reticle of the invention, FIG. 2 is a diagram showing the amplitude distribution of illumination light after passing through the reticle of the invention, and FIG. 3 is a diagram showing the manufacturing process of the reticle of the invention. . DESCRIPTION OF SYMBOLS 1... Reticle substrate, 2... Layer for changing the phase of illumination light, 3... Light-shielding film, 4-1 to 4-5... Openings formed in light-shielding film portion, 5...・Amplitude distribution after passing through the reticle, 6...Resist.

Claims (1)

[Claims] A phase shift layer that changes the phase of illumination light is provided between the glass substrate and the light shielding film, and the phase shift layer is removed from a specific part of the opening where the light shielding film is partially removed, and the phase shift layer is removed from the other part. A photomask characterized in that the phase shift layer is left in the opening.