JPH04284618A - Manufacture of optical mask - Google Patents

Abstract

PURPOSE:To make the uniformity inside a face of the title mask high, to make the reproducibility of the title mask high and to make the resolution of the title mask high regarding the manufacturing method of a phase-shift mask used at the manufacturing process of a semiconductor device. CONSTITUTION:A polysilicon film 12 is applied to the whole surface of a quartz substrate 11. After a resist 13 has been coated on the whole surface, it is patterned. The polysilicon film 12 is etched by making use of the resist 13 as a mask, and opening parts 14a, 14b are formed. The polysilicon film 12 revealed on sidewalls at the opening parts 14a, 14b is oxidized; it is changed to SiO2 films 15a, 15b, 15c, 15d. The resist 13 is stripped. As a result, a light- shielding part composed of the polysilicon film 12, light-transmitting parts composed of the opening parts 14a, 14b and phase shift parts composed of the SiO2 films 15a, 15b, 15c, 15d are formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical mask, and more particularly to a method of manufacturing a phase shift mask used in the manufacturing process of semiconductor devices. "Mask" is used as a general term for master mask (full size mask) and reticle (enlarged mask).

In recent years, as semiconductor integrated circuit devices have become more highly integrated, miniaturization of the lithography process has been required. For this reason, in exposure apparatuses, reduction projection exposure apparatuses (steppers) have been made to have higher NA and light sources have shorter wavelengths, and resists have also been made to have higher resolution. Furthermore, in the field of optical masks, development of optical masks using the phase shift method is progressing.

0003

2. Description of the Related Art FIGS. 5 and 6 are diagrams showing a conventional example, showing each step of a conventional method for manufacturing a phase shift mask. The steps will be explained below in order. [Step 1, FIG. 5(a)] Chromium (Cr
) Deposit membrane 52.

[Step 2, FIG. 5(b)] Resist 5 on the entire surface
After applying 3, patterning is performed. [Step 3, FIG. 5(c)] Using the resist 53 as a mask, the chromium (Cr) film 52 and the quartz substrate 51 are etched to form openings 54a and 54b.

[Step 4, FIGS. 5(c) and 6(d)] Chromium (Cr) film 5 exposed on the side walls of the openings 54a and 54b
2 is side-etched to remove a predetermined width. [Step 5, FIGS. 6(d) and (e)] The resist 53 is peeled off.

A phase shift mask is completed through the above steps.

[0007]

[Problem to be solved by the invention] The phase shift mask is
The exposure radiation is transmitted through openings 54a and 54b shown in FIG. 6(e).
When transmitting the light, the phase difference between the light that has passed through part A and the light that has passed through part B is 180 degrees, thereby increasing the resolution. In order to satisfy this condition, the opening 5
It is necessary to set the etching depth t of portion A of 4a and 54b to a value expressed by the following equation.

t=λ/2(n-1) where λ is the exposure wavelength and n is the refractive index of quartz. Therefore,
The etching depth of portion A of the openings 54a and 54b is required to be uniform within the mask plane. Furthermore, the width of portion B of the openings 54a and 54b is also important in terms of resolution, and is required to be uniform within the mask plane.

Conventionally, reactive ion etching (RIE) has been used to etch portion A of the openings 54a and 54b, that is, to etch the quartz substrate 51. In addition, wet etching was used for side etching of the chromium (Cr) film 52 to form portions B of the openings 54a and 54b. The amount of etching was determined by controlling the environment or atmosphere during RIE and wet etching, and the time required for etching.

However, it is difficult to control the environment or atmosphere during etching and the etching time as determined in advance. Therefore, if the environment or atmosphere during etching differs from a predetermined one, or if the etching time is poorly controlled, the etching amount will deviate from the predetermined value. As a result, the openings 54a, 54
The etching depth of portion A and the width of portion B of b become non-uniform within the mask plane. Furthermore, each time a mask is manufactured, a different mask is produced, resulting in poor reproducibility.

As described above, the conventional method for manufacturing a phase shift mask has the problem that the transparent portion cannot be formed uniformly within the mask surface and that reproducibility is poor. The present invention solves this problem, improves in-plane uniformity, and
It is an object of the present invention to provide a method for manufacturing an optical mask that can improve reproducibility and increase resolution, particularly a method for manufacturing a phase shift mask used in the manufacturing process of semiconductor devices.

0012

[Means for Solving the Problems] In order to achieve the above object, the present invention is constructed as follows. (1) A method for manufacturing a phase shift mask used in the manufacturing process of semiconductor devices, which includes the steps of attaching a light-shielding film to the entire surface of a transparent glass substrate, applying a resist to the entire surface, and then exposing and developing the resist. a process of selectively forming openings using resist as a mask; a process of etching the light-shielding film using a resist as a mask to form the opening; and a process of oxidizing the light-shielding film exposed on the side walls of the opening to transform it into a transparent film. and a step of peeling off the resist.

(2) A method for manufacturing a phase shift mask used in the manufacturing process of semiconductor devices, which includes a step of attaching a light-shielding film to the entire surface of a transparent glass substrate, and a step of depositing an oxide of a substance constituting the light-shielding film on the entire surface. a step of applying a resist to the entire surface and then exposing and developing the resist to selectively form openings; and a step of etching the transmitting film and the light-shielding film using the resist as a mask. The method is configured to include the steps of: forming an opening using a wafer, oxidizing the light-shielding film exposed on the sidewall of the opening to change it into a transmitting film, and peeling off the resist.

[0014]

[Operation] In the present invention, a phase shift portion is formed by depositing a light-shielding film on the entire surface of a transparent glass substrate and then selectively oxidizing the light-shielding film to change it into a transparent film. This makes it possible to manufacture a phase shift mask that is uniform within the surface and has good reproducibility, without performing etching that is difficult to control as in the past. Therefore, the key point of the present invention is to use a material that can be easily oxidized and whose transmittance is improved by oxidation as the light shielding film.

Materials that satisfy the above conditions include polysilicon, aluminum (Al), titanium (Ti), and magnesium (Mg). These substances can be easily oxidized, and when oxidized, they form SiO2 and A, respectively.
It consists of l2O3, TiO2, and MgO.

[0016]

Embodiment (First Embodiment) FIGS. 1 and 2 are diagrams showing each process of a first embodiment of the present invention. The steps will be explained below in order.

[Step 1, FIG. 1(a)] Polysilicon 12 was deposited on the entire surface of quartz substrate 11 by sputtering. [Step 2, FIG. 1(b)] After coating the entire surface with resist 13, patterning was performed using an EB (electron beam) exposure method.

[Step 3, FIG. 1(c)] Using the resist 13 as a mask, the polysilicon film 12 was etched using the RIE method to form openings 14a and 14b. [Step 4, FIG. 1(c), FIG. 2(d)] Opening 14a, 1
The polysilicon film 12 exposed on the side wall of the polysilicon film 4b was anodized and changed into SiO2 15a, 15b, 15c, and 15d.

[Step 5, FIGS. 2(d) and 2(e)] The resist 13 was peeled off. The phase shift mask completed through the above steps includes a light shielding part made of the polysilicon film 12, openings 14a and 14b.
a transmission part consisting of, and SiO2 films 15a, 15b,
It is composed of a phase shift section consisting of 15c and 15d.

In this example, the phase shift section (SiO
2 The thickness t of the films 15a, 15b, 15c, 15d) is
t=λ/2(n-1) Here, when λ is the exposure wavelength and n is the refractive index of SiO2, the phase difference between the light transmitted through the transmission part and the light transmitted through the phase shift part is 180 degrees. Therefore, the light intensity at the pattern portion is the strongest.

Since the thickness t of the phase shift portion is the same as the thickness of the polysilicon film 12, in order to satisfy the above conditions, it is necessary to The thickness of the polysilicon film 12 may be set to t. For example, in the case of exposure by g-line (wavelength λ=436 nm), since the refractive index n of SiO2 is approximately 1.45, the thickness t of the polysilicon film 12 is approximately 4800 Å.

(Second Embodiment) FIGS. 3 and 4 are diagrams showing each process of a second embodiment of the present invention. The steps will be explained below in order. [Step 1, FIG. 3(a)] A polysilicon film 22 was deposited on the entire surface of the quartz substrate 21 using a sputtering method.

[0023] SiO2 was applied to the entire surface using a sputtering method.
A membrane 23 was deposited. [Step 2, FIG. 3(b)] After coating the entire surface with resist 24, patterning was performed using the EB exposure method.

[Step 3, FIG. 3(c)] Using the resist 24 as a mask, the SiO2 film 23 and polysilicon film 22 are etched using the RIE method to form openings 25a and 25b.
was formed. [Step 4, FIG. 3(c), FIG. 4(d)] Openings 25a, 2
The polysilicon film 22 exposed on the side wall of the polysilicon film 5b was anodized and changed into SiO2 26a, 26b, 26c, and 26d.

[Step 5, FIGS. 4(d) and 4(e)] The resist 24 was peeled off. The phase shift mask completed through the above steps includes a light-shielding part made of the polysilicon film 22, a transmitting part made of the openings 25a and 25b, and an opening 25a.
, 25b formed on the side walls of the SiO2 films 26a, 26
26c, 26d, and a phase shift section consisting of an SiO2 film 23 thereon. Polysilicon film 2
The SiO2 film 23 on 2 functions as a protective film.

In this example, the phase shift section (SiO
2 The thickness t of the films 26a, 26b, 26c, 26d and the SiO2 film 23) thereon is t=λ/2(n-1), where λ is the exposure wavelength and n satisfies the refractive index of SiO2. At this time, the phase difference between the light that has passed through the transmission part and the light that has passed through the phase shift part is 180 degrees, so the light intensity in the pattern part is the strongest.

The thickness t of the phase shift portion is the thickness of the SiO2 film 2.
The thickness of 6a, 26b, 26c, 26d is t1, SiO
2 When the thickness of the film 23 is t2, it is expressed as t=t1 +t2. SiO2 film 26a, 26b, 26c, 2
Since the thickness of 6d is the same as the thickness of the polysilicon film 22, in order to satisfy this condition, step 1 [FIG. 3(a)
], the thickness of the polysilicon film 22 deposited on the quartz substrate 21 may be set to t1, and the thickness of the SiO2 film 23 may be set to t2. As an example, g-line (wavelength λ = 43
6 nm), the refractive index of SiO2 is n≒1
．． 45, the thickness t1 of the polysilicon film 22,
If the thickness of the SiO2 film 23 is t2, then t=t1 +
Polysilicon film 22 is formed so that t2≒4800 Å.
And the thickness of the SiO2 film 23 may be controlled.

[0028]

According to the present invention, it is possible to manufacture a phase shift mask with high in-plane uniformity, good reproducibility, and high resolution.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first embodiment (Part 1).

FIG. 2 is a diagram showing the first embodiment (Part 2).

FIG. 3 is a diagram showing a second embodiment (part 1).

FIG. 4 is a diagram showing a second embodiment (Part 2).

FIG. 5 is a diagram showing a conventional example (Part 1).

FIG. 6 is a diagram showing a conventional example (Part 2).

[Explanation of symbols]

11 Quartz substrate 12 Polysilicon film 13 Resist 14 Opening 15 SiO2 film 21 Quartz substrate 22 Polysilicon film 23 SiO2 film 24 Resist 25 Opening 26 SiO2 film

Claims (2)

[Claims] 1. A method for manufacturing a phase shift mask used in the manufacturing process of semiconductor devices, which comprises the steps of attaching a light-shielding film to the entire surface of a transparent glass substrate, applying a resist to the entire surface, and then exposing the resist to light.・The process of developing and selectively forming openings, the process of using the resist as a mask and etching the light-shielding film to form the openings, and the process of oxidizing the light-shielding film exposed on the side walls of the opening and turning it into a transparent film. 1. A method for manufacturing an optical mask, comprising the steps of: removing the resist; and removing the resist. 2. A method for manufacturing a phase shift mask used in the manufacturing process of semiconductor devices, comprising the steps of: attaching a light-shielding film to the entire surface of a transparent glass substrate; a step of applying a resist to the entire surface and then exposing and developing the resist to selectively form openings; and a step of etching the transmitting film and the light-shielding film using the resist as a mask. A method for manufacturing an optical mask, comprising the steps of forming an opening, oxidizing a light-shielding film exposed on the sidewall of the opening to change it into a transmitting film, and peeling off a resist.