JP3125104B2 - Optical mask and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an optical mask and an improvement in a manufacturing method thereof. In particular, the present invention relates to an improvement for improving the resolution of an optical mask having a phase shifter and a manufacturing method thereof.

[0002]

2. Description of the Related Art Phase shift masks have been developed to improve the resolution in lithography using a mask. In this phase shift mask, a region that transmits the exposure light as it is and a region that inverts the phase of the exposure light are formed adjacent to or close to each other, and these regions (the width of this region is determined by the wavelength of the exposure light and The effect of light interference with each other at the lens aperture (NA) is effectively used.

As one of optical masks having a phase shift mask, a mask having a configuration shown in FIG. 7A is known. In the figure, 21 is a glass substrate, 22 is a light shielding film made of a chromium film, and 23 is a phase shift film made of a silicon dioxide film. FIG. 7B shows the light amplitude of the light transmitted through the light transmitting region 24 of the phase shift mask.
In the figure, a positive direction indicates a positive phase, and a negative direction indicates a reverse phase. FIG. 7C shows the light amplitude of the light transmitted through the phase shift film 23. In the figure, the positive direction indicates the positive phase and the negative direction indicates the opposite phase, as in the above description. As a result, the exposure intensity of this phase shift mask becomes as shown in FIG.
And an extremely thin single line can be drawn.

As another optical mask having a phase shift mask, a mask having a configuration shown in FIG. 8A is also known. In the figure, 21 is a glass substrate, 25 is a light shielding film made of a chromium film, and 26 is a phase shift film made of a silicon dioxide film. FIG. 8B shows the light amplitude of the light transmitted through the light transmitting region 27 of the phase shift mask. FIG. 8C shows the amplitude of light transmitted through the region 26. As a result, the exposure intensity of this phase shift mask becomes as shown in FIG. 8D, and one very thin line can be drawn.

[0005]

The inventor of the present invention has proposed a phase shift mask having a configuration in which these two phase shift masks are superposed (the phase shift mask whose configuration is shown in FIG. , The first phase shift film, the first light-shielding film, the second phase shift film, and the second light-shielding film are formed.) The idea is that extremely thin lines can be drawn. I got

It is an object of the present invention to embody this idea ,
Ri near possible to further improve the resolution of the conventional phase shift mask having phase shifters, two objects (the optical mask
Improvement and improvement of the manufacturing method).

[0007]

Means for Solving the Problems Among the above objects, the first one is
(The purpose of providing an optical mask) is to have a light-transmitting region (12) having a width of about m ( L + 0.2λ / NA) on a light-transmitting substrate (11). On both sides of (12), (mλ / 2NA) [1.1- (NA / λ) (L +
0.2λ / NA)].
And a first light-shielding film (14) having a width of about 0.1 mλ / NA on both sides of the first phase-shift film (13).
0.1 m on both sides of the first light shielding film (14).
This is achieved by an optical mask having a second phase shift film (15) having a width of about λ / NA, and having a second light shielding film (16) on both sides of the second phase shift film (15). . Here, m is the reduction projection magnification, L is the finished aperture size, λ is the wavelength of the exposure light, and NA is the numerical aperture of the exposure lens.

A third phase is formed on the light transmitting region (12), the first phase shift film (13), the first light shielding film (14), and the second phase shift film (15). It may be covered with the shift film (17).

Among the above objects, a second object (object of providing a method of manufacturing an optical mask) is a light-transmitting substrate (1).
1) The width is about 1.5 mλ / NA and the thickness is λ /
A second light-shielding film (16) having a thickness of about (2n-2) is formed, and the width of the step side wall is about 0.1 mλ / NA when etched back on the second light-shielding film (16). A second film (15a) of the phase shift material is formed to a thickness, and the width of the step side wall is reduced to about 0.1 mλ / NA when etched back on the second film (15a) of the phase shift material. A first film (14a) of a light-shielding material is formed to a predetermined thickness, and the first film (14a) of the light-shielding material is etched back to form a step sidewall of the first film (14a) of the light-shielding material. Leaving only the first
The first light-shielding film (14) is formed.
Film (15a) of the phase shift material having the step on the step side wall
When etch back is performed, the width of the step side wall is (mλ /
2NA) [1.1- (NA / λ ) (L + 0.2λ / NA)] degree
After forming the first film (13a) of the phase shift material to a thickness that is as small as possible, or after forming the first light-shielding film (14), the first light-shielding film (14) is formed on the step side wall. The width of the step side wall of the second film (15a) of the phase shift material is (mλ / 2NA) on the second film (15a) of the phase shift material having
An optical mask for manufacturing an optical mask including a step of forming a first film (13a) of a phase shift material to a thickness of about [1.1- (NA / λ) ( L + 0.2λ / NA)]. Is achieved.

[0010]

In order to achieve the above object, as described in the object section, the structure shown in FIG. 5 (with the first phase shift film, the first light shielding film, and the second light Phase shift film and second
Are formed. ) Can be realized. However, for this purpose, as shown in FIG. 5, for example, the exposure wavelength is 436 nm and the numerical aperture (NA) is 0.45.
Then, in order to realize a line width of 0.4 μm, m ×
A phase inversion region having a width of m × 0.2 μm, a light-shielding region having a width of m × 0.1 μm, and a phase inversion region having a width of m × 0.1 μm are formed on both sides of the light transmission region having a width of 0.6 μm. Must. Here, m is a reduction projection magnification, and a value of 5 or less is usually used.

However, it has conventionally been difficult to form the phase inversion region having a fine line width and the light-shielding region with accurate alignment accuracy, and it is difficult to manufacture an optical mask having the structure shown in FIG. Was.

Therefore, according to the present invention, after forming a phase inversion film or a light shielding film on a surface having a step, the film is etched back to form a phase inversion region having extremely small accuracy and a light shielding film on the step side wall. By successfully forming the region, the optical mask having the configuration shown in FIG. 5 can be manufactured, and the above configuration is realized, thereby completing the present invention.

FIG. 1 or FIG. 5 showing the basic structure of an optical mask according to the present invention.
(A) and (b) are obtained. In FIG. 6A, G is the transmitted light amplitude of the light transmitting region 12, H is the transmitted light amplitude of the first phase shift film 13, and I is the transmitted light amplitude of the second phase shift film 15. It is. Since the transmitted light intensity of the entire optical mask is a combination of G, H, and I, FIG.
As shown in (b), the effective exposure width can be set to 0.4 μm.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of an optical mask according to a first embodiment of the present invention;

First Embodiment See FIG. 2 On a quartz glass substrate 11, a film of a light shielding material such as chromium
に (λ / (2n−2)) thick. λ is the wavelength of the exposure light, and n is the refractive index of the phase inversion material used for this optical mask.

[0016] using a lithography method, the above-mentioned black
An opening with a width of 7.5 μm is formed in the light-shielding material film
The film of the light shielding material such as chrome is converted to the second light shielding film 16 . A silicon dioxide film 15a as a phase shift material having a thickness of 5000 ° is formed thereon.

On top of this, a film 14a of a light shielding material such as chrome having a thickness of 5000 ° is formed. In this way, the light shielding material film
Both the step 14a and the film 15a of the phase shift material have a step sidewall width of 0.5 μm.

Referring to FIG. 3, when the film 14a of the light-shielding material is etched back using a reactive etching method using a mixed gas of carbon tetrafluoride and oxygen, the side wall of the step 15a of the film 15a of the phase shift material is etched. The first light shielding film 14 remains.

Referring to FIG. 4, a silicon dioxide film 13a as a phase shift material is formed to a thickness of 1 μm. The width of the step side wall of the silicon dioxide film 13a is 1 μm.

Referring to FIG. 1, when the silicon dioxide film 13a is etched back using a reactive etching method using carbon tetrafluoride as a reactive gas, a first phase shift film is formed on the step side wall of the first light shielding film 14.
13 remains. The silicon dioxide film on the step side wall portion of the light shielding film 16 is the first phase shift film 13.

Second Embodiment The same function can be obtained even if the step of etching back the silicon dioxide film 13a in the first embodiment is omitted and the state shown in FIG. 4 is left. In this case, as shown in parentheses in FIG. 4, a part of the silicon dioxide film 13a becomes the light-transmitting region 17, and the first phase shift film 13 is composed of the original first phase shift film 13 and silicon dioxide. It becomes a double layer with the membrane 13a,
The second phase shift film 15 is a double layer of the original second phase shift film 15 and the silicon dioxide film 13a.

FIG. 6 shows the intensity of transmitted light of each part and the synthesis thereof.
And as described in the section of operation.

[0023]

As described above, in the optical mask according to the present invention, the first phase shift film, the first light shielding film, the second phase shift film, and the second light shielding film sandwich the light transmitting region. Are provided so that the width of each film satisfies a predetermined requirement, so that the configuration is a combination of the phase shift mask shown in FIG. 7 and the phase shift mask shown in FIG. Lines of about 4 μm or less can be patterned. Note that the optical mask having the above configuration is realized by forming a film on a surface having a step and etching back the film.

[Brief description of the drawings]

FIG. 1 is a configuration diagram (cross-sectional view) of an optical mask according to an embodiment of the present invention.

FIG. 2 is a manufacturing process diagram of an optical mask according to one embodiment of the present invention.

FIG. 3 is a manufacturing process diagram of an optical mask according to one embodiment of the present invention.

FIG. 4 is a manufacturing process diagram of an optical mask according to one embodiment of the present invention (a configuration diagram (cross-sectional view) of an optical mask according to another embodiment of the present invention).

FIG. 5 is a diagram showing a basic configuration of an optical mask according to the present invention.

FIGS. 6A and 6B are geometric distribution diagrams of each transmitted light of the optical mask according to the present invention and its combined light.

FIGS. 7 (a), (b), (c) and (d) are diagrams showing a configuration of an example of an optical mask according to a conventional technique and a distribution of transmitted light.

8 (a), (b), (c), and (d) are diagrams showing another example of the configuration of an optical mask according to the related art and a distribution of transmitted light.

[Explanation of symbols]

 11 translucent substrate (glass plate) 12 translucent region 13 first phase shift film (silicon dioxide film) 14 first light-shielding film (chromium film) 15 second phase shift film (silicon dioxide film) 16 second 17a Third phase shift film (silicon dioxide film) 13a First film of phase shift material (silicon dioxide) 14a First film of light shield material (chromium) 15a Phase shift material (silicon dioxide) ) Second film 21 glass substrate 22 light shielding film 23 phase shift film 24 light transmitting region 25 light shielding film 26 phase shift film 27 light transmitting region

Claims (4)

(57) [Claims] 1. The method according to claim 1, wherein m ( L + 0.2λ / N
A) a light-transmitting region having a width of about A), and (mλ / 2NA) [1.1- (NA /
λ) (L + 0.2λ / NA)], and a first light-shielding film having a width of about 0.1 mλ / NA on both sides of the first phase shift film. A second phase shift film having a width of about 0.1 mλ / NA on both sides of the first light shielding film, and a second light shielding film on both sides of the second phase shift film. An optical mask comprising: Here, m is the reduction projection magnification, L is the finished aperture size, λ is the wavelength of the exposure light, and NA is the numerical aperture of the exposure lens. 2. The light-transmitting region, the first phase-shift film, the first light-shielding film, and the second phase-shift film have a third shape.
2. The optical mask according to claim 1, wherein the optical mask is covered with the phase shift film. 3. A light-transmitting substrate having a width of 1.5 mλ / NA
And a second light-shielding film having a thickness of about λ / (2n−2) is formed on the second light-shielding film. A second film of the phase shift material having a thickness of about 0.1 mλ / NA on the second film of the phase shift material when the width of the step side wall is about 0.1 mλ / NA when etched back. To
Forming a first film of a light-shielding material, etching back the first film of the light-shielding material, forming a first light-shielding film while leaving only a step side wall of the first film of the light-shielding material; When etched back on the second film of the phase shift material having the first light shielding film on the step side wall, the width of the step side wall is (mλ / 2NA) [1.1− (NA / λ) (L + 0.2λ / N
2. The method of manufacturing an optical mask according to claim 1, wherein the first film of the phase shift material is formed to a thickness of about A)]. 4. A light-transmitting substrate having a width of 1.5 mλ / NA
And a second light-shielding film having a thickness of about λ / (2n−2) is formed on the second light-shielding film. A second film of the phase shift material having a thickness of about 0.1 mλ / NA on the second film of the phase shift material when the width of the step side wall is about 0.1 mλ / NA when etched back. To
Forming a first film of a light-shielding material, etching back the first film of the light-shielding material, forming a first light-shielding film while leaving only a step side wall of the first film of the light-shielding material; On the second film of the phase shift material having the first light-shielding film on the step side wall, the width of the step side wall of the second film of the phase shift material is (mλ / 2NA) [1.1- ( NA / λ) (L + 0.
3. The method of manufacturing an optical mask according to claim 2, wherein the first film of the phase shift material is formed to a thickness of about 2λ / NA)].