JP3257130B2 - Method for manufacturing edge-enhancement type phase shift mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an edge-enhanced phase shift mask, and more particularly, to a phase shift method capable of patterning both a phase shift layer and a light-shielding film while a photomask blank is housed in a dry etching apparatus. The present invention relates to a method for manufacturing a mask.

[0002]

2. Description of the Related Art FIG.
Or it has a cross-sectional shape as shown in FIG. That is, this edge-enhancement type phase shift mask is provided with a light-shielding pattern formed of a metal light-shielding film b partially provided on a transparent substrate a and a phase shift pattern formed of a high-refractive-index transparent film c. The phase shift pattern formed by the transparent refractive index member c has a shape slightly projecting around the light-shielding pattern.

The edge-enhancement type phase shift mask is used, for example, to partially expose a photoresist applied to a semiconductor substrate. That is, the edge-enhanced photomask and the semiconductor substrate having a photoresist are mounted on a reduction projection exposure apparatus (for example, a stepper), and the exposure light beam is irradiated through the edge-enhancement type phase shift mask. The photoresist is exposed to the pattern shape of the light transmitting portion excluding the light shielding pattern shape. At this time, the phase of the light beam transmitted through the phase shift pattern portion is delayed by about 波長 wavelength compared to the phase of the light beam transmitted through the outside phase shift pattern non-existent portion.
Therefore, the diffracted light generated from the periphery of the light-shielding pattern and transmitted through the phase shift pattern and the light transmitted through the phase-shift-pattern-free portion interfere with each other to generate a steep intensity distribution of the transmitted light. Can transfer a light-shielding pattern onto the photoresist with extremely high precision.

In the edge-enhancement type phase shift mask shown in FIG. 4, a phase shift pattern c having a larger area is arranged on a light shielding pattern composed of a metal light shielding film b having a relatively small area. Manufacturing method. That is, first, as shown in FIG. 6, a metal light-shielding film b and a high-refractive-index transparent body c are sequentially formed on the entire surface of the transparent substrate a, and an electron beam resist d is applied on the high-refractive-index transparent body c. . Then, as shown in FIG. 7, the electron beam resist is subjected to electron beam exposure and development in the form of a phase shift pattern, and the exposed high refractive index transparent body c is patterned by dry etching and removed. Next, by immersing in an etchant, the exposed metal light-shielding film b is removed by etching, and the edge of the metal light-shielding film c is removed by etching using side etching accompanying the penetration of the etchant. The metal light-shielding film b is processed into a light-shielding pattern having an area smaller than that of the phase shift pattern c to manufacture the phase shift mask.

The phase shift mask shown in FIG. 5 has a relatively large area of the metal light shielding film b on a relatively large area of the phase shift pattern c. Therefore, the phase shift mask is manufactured by the following method. I was That is, first, as shown in FIG. 8, a high-refractive-index transparent body c and a metal light-shielding film b are sequentially formed on the entire surface of a transparent substrate a, an electron beam resist d is applied, and a light-shielding pattern having a small area is exposed. After the development, the metal light-shielding film b is exposed and etched to remove the metal light-shielding film b at the exposed portion, thereby patterning the metal light-shielding film b. Next, as shown in FIG. 9, the electron beam resist d is applied again, exposed and developed into a phase shift pattern, and the high refractive index transparent body at the exposed portion is dry-etched and patterned to form the edge-enhanced phase shift. Manufactures masks.

[0006]

Incidentally, in any of the above-mentioned manufacturing methods, dry etching is required for patterning of the high refractive index transparent body. Therefore, the dry etching is carried out in a vacuum state dry etching apparatus. Although it is necessary to perform processing, it is impossible to etch the metal light-shielding film while housed in the dry etching apparatus.

In other words, in manufacturing the edge-enhancement type phase shift mask shown in FIG. 4, dry etching is indispensable for patterning a high refractive index transparent body.
On the other hand, this dry etching is so-called anisotropic etching and does not cause side etching. Therefore, an isotropic etching process using an etchant is required for processing the end portion of the metal light shielding film by the side etching.

In the manufacture of the edge-enhancement type phase shift mask shown in FIG. 5, an electron beam resist must be applied twice, but cannot be applied inside a dry etching apparatus.

Therefore, in any of the manufacturing methods,
There is a problem that separate steps are required for the etching of the high-refractive-index transparent body and the etching of the metal light-shielding film, and the manufacturing process must be complicated.

The present invention has been made on the basis of such technical problems. That is, an object of the present invention is to provide a patterning and a high refraction of the metal light-shielding film while being housed in a dry etching apparatus. It is an object of the present invention to provide a method of manufacturing an edge-enhancement type phase shift mask which enables both patterning of a transparent material and simplifies a manufacturing process.

[0011]

By the way, when an electron beam resist is drawn in a pattern and then developed, the film at the end of the patterned electron beam resist remaining after development due to the variation in electron beam drawing accuracy. The thickness is smaller than the film thickness at the center of the pattern. Then, when the high refractive index transparent body is dry-etched, the electron beam resist is also etched and its film thickness is uniformly reduced. Therefore, the film thickness of the electron beam resist and the dry etching conditions are appropriately controlled. This makes it possible to etch away the electron beam resist at the pattern end of the patterned electron beam resist. If the exposed surface of the electron beam resist is formed of a metal light-shielding film, the metal light-shielding film exposed at the end is removed by dry etching while being housed in the dry etching apparatus. By exposing the high-refractive-index transparent body, it becomes possible to manufacture an edge-enhanced phase-shift mask including a phase-shift layer made of the high-refractive-index transparent body on the periphery of the metal light-shielding film.

The present invention has been completed based on such a technical principle. That is, the present invention comprises sequentially laminating a high refractive index transparent film, a light shielding film and an electron beam resist on a transparent substrate. Exposure of the electron beam resist in a pattern
By developing, the electron beam resist is left in the pattern shape of the phase shifter layer, and the film thickness of the pattern peripheral portion is made thinner than the central portion of the pattern of the electron beam resist, and the exposed portion of the light shielding film is dried. The high-refractive-index transparent body film thus exposed is dry-etched to form a phase shift layer, and the dry-etching uniformly reduces the thickness of the remaining electron beam resist to remove electrons in the peripheral portion of the pattern. The line resist is removed to expose the remaining pattern peripheral portion of the light shielding film, and then the exposed pattern peripheral portion of the light shielding film is removed by dry etching.

In such technical means, a known quartz glass substrate or the like can be used as the transparent substrate.

As the high refractive index transparent body, a silicon oxide thin film having a refractive index of about 1.47 can be used. The silicon oxide thin film is formed by using a sputtering gas of a mixed gas of argon and oxygen and a target of SiO _2. The film can be formed by RF sputtering.

The high refractive index transparent body thin film constitutes a phase shift layer of the edge-enhancing type phase shift mask, and is used when a light-shielding pattern of the photomask is projected and exposed on a photoresist on a semiconductor substrate. The phase of the exposure light beam is displaced by about 波長 wavelength with respect to the exposure light beam at the portion where the phase shift layer does not exist. For this reason,
When the thickness of the high refractive index transparent thin film is d, the refractive index is n ₁ , the refractive index of air is n ₀ = 1.00, and the wavelength of the exposure light is λ, the thickness d is (n ₁ − 1.00) × d = 1 /
It is desirable to satisfy 2 × λ. When the high-refractive-index transparent thin film is made of a silicon oxide thin film having a refractive index of 1.47 and the exposure light beam is made of an i-ray having a wavelength of 365 nm,
The thickness d of the high-refractive-index transparent thin film satisfying the above equation is about 388.
nm.

As the metal light-shielding film, a thin film of metal chromium or metal nickel can be used. For example, a film can be formed by RF sputtering using a mixed gas of nitrogen and argon as a sputtering gas and a target of metal chromium. The metal light-shielding film only needs to be capable of substantially preventing light transmission of the exposure light, and may have a thickness of, for example, 20 nm or more.

As the electron beam resist, a polychloromethylstyrene-based negative electron beam resist or a polybutene-1-sulfone-based positive electron beam resist can be used. This electron beam resist can be spin-coated on the metal light-shielding film, and the film thickness is appropriate according to the etching conditions of the dry etching of the metal light-shielding film and the dry etching of the high-refractive-index transparent thin film. It is desirable to set to. That is, the electron beam resist is drawn by electron beam exposure, exposed, developed, and the end of the patterned electron beam resist remaining is etched simultaneously with the dry etching of the metal light shielding film and the dry etching of the high refractive index transparent thin film. It is necessary that the film thickness be such that the metal light-shielding film below the lever resist is exposed on the surface.

Then, the metal light-shielding film is formed in a parallel plate type reactive etching apparatus by using CCl ₄ or CHC.
a mixed gas of a chloride carbonaceous gas or Cl ₂ O ₂ of l ₃ such as an etching gas can be dry-etched. On the other hand, when the high refractive index transparent body is made of silicon oxide, this silicon oxide thin film is formed by using a fluorocarbon gas such as CF ₄ or CHF _{3 in the} parallel plate type reactive etching apparatus. During the dry etching of the silicon oxide thin film, the thickness of the electron beam resist is reduced at the same time, and the metal light shielding film at the end is exposed. The light-shielding film pattern can be formed by dry-etching the exposed metal light-shielding film again. The dry etching of the metal light-shielding film can be performed again using the above-mentioned carbon chloride-based gas or a mixed gas of Cl ₂ and O ₂ as an etching gas. The dry etching of the metal light-shielding film twice and the dry etching of the silicon oxide thin film can be performed inside the same apparatus only by exchanging the etching gas. By performing dry etching a number of times, both the patterning of the metal light shielding film and the patterning of the phase shift layer can be performed.

The high refractive index transparent body is made of silicon oxide.
If formed, dry etch of this silicon oxide thin film
Is there a risk that the transparent substrate will also be etched during
Then, the exposure light is transmitted through the transparent substrate and the
Etching that is not dry-etched by carbon
The silicon oxide thin film is formed via a chuck stopper layer.
Is desirable. Such an etching stopper layer
Can be silicone nitride, polysilicon, or oxidized
Aluminum (Al_TwoO_Three) Is available. The film thickness is 10
~ 200 nm, and the sputtering gas is argon, target
Set to Al_TwoO _ThreeBy RF sputtering
can do.

[0020]

According to the present invention, the electron beam resist laminated on the light-shielding film is exposed and developed in the form of a pattern so that the electron beam resist remains in the pattern shape of the phase shifter layer, and the pattern of the electron beam resist is changed. The thickness of the peripheral portion of the pattern is processed to be thinner than that of the central portion, and the exposed portion of the light shielding film is removed by dry etching, and the exposed high refractive index transparent film is dry etched to form a phase shift layer. At the same time, the film thickness of the remaining electron beam resist is uniformly reduced by the dry etching to remove the electron beam resist at the peripheral portion of the pattern to expose the peripheral portion of the pattern of the remaining light-shielding film. In order to remove the peripheral portion of the pattern of the light-shielding film by dry etching, the pattern of the metal light-shielding film and the pattern of the high refractive index transparent body Despite the different, it is possible to pattern the both inside the dry etching apparatus.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. That is, as shown in FIG. 1A, an etching stopper layer 2 made of Al ₂ O ₃ having a thickness of 10 to 20 nm and a high refractive index transparent body made of silicon oxide having a refractive index of 1.47 are sequentially formed on a quartz glass substrate 1. Thin film 3 (thickness about 388n
m), a metal chrome light shielding film 4 having a thickness of 100 nm was laminated. These films are all formed by RF sputtering using an appropriate target and a sputtering gas.

Next, a negative-type electron beam resist 5 was applied on the metal chrome light-shielding film 4, and an electron beam was drawn in a desired phase shift pattern and developed (FIG. 1B). FIG. 2 shows the cross-sectional shape at the end of the electron beam resist 5 pattern remaining after development.
Shown in As apparent from FIG. 2, the thickness of the electron beam resist 5 remaining after the development is substantially the same as the film thickness at the central portion of the pattern before development, whereas the thickness of the electron beam resist 5 becomes smaller as approaching the edge of the pattern. It can be seen that is gradually decreasing.

Then, the exposed metal chromium 4 and silicon oxide thin film 3 were dry-etched in a parallel plate type reactive etching apparatus using the remaining electron beam resist 5 as a resist pattern (FIG. 1C). This process was continuously performed by exchanging the etching gas while taking out the etching device without taking it out of the etching device. That is, first, the metal chromium light-shielding film 4 at the above-mentioned exposed portion was etched and removed using CCl ₄ as an etching gas, and then the etching gas was replaced with CF ₄ to expose the metal chrome light-shielding film 4 with the etching. The exposed portion of the silicon oxide thin film 3 was removed by etching. FIG. 3 shows an end cross-sectional shape of the electron beam resist 5 pattern at this time. In the figure, the broken line shows the cross-sectional shape of the electron beam resist 5 before etching. From this figure, the film thickness of the electron beam resist 5 decreases uniformly with the dry etching, and the decrease in the residual metal It can be seen that the end 4a of the chrome light-shielding film 4 is exposed on the surface.

Next, while being accommodated in the parallel plate type reactive etching apparatus, the etching gas is again supplied with CCl _4.
And the end 4a of the metal chrome light-shielding film 4 exposed on the surface as described above was dry-etched (FIG. 1D). The edge-enhancement type phase shift mask thus obtained is shown in FIG.
As is clear from the cross-sectional view, the end faces of the phase shift layer 3 and the metal chromium light-shielding film 4 are substantially perpendicular to the surface of the glass substrate 1, and it is understood that the pattern precision is excellent.

[0025]

According to the present invention, although the pattern of the metal light-shielding film and the pattern of the high-refractive-index transparent body are different,
Since both of these can be patterned inside the dry etching apparatus, the manufacturing process of the edge-enhancement type phase shift mask is significantly simplified, and the mask can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a manufacturing process of an edge-enhancement type phase shift mask according to an embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view showing a cross-sectional shape of an end portion of a pattern after exposure and development of an electron beam resist according to the embodiment of the present invention.

FIG. 3 is a cross-sectional explanatory view showing a cross-sectional shape of a pattern end portion after dry etching of a metal chrome light-shielding film and a silicon oxide thin film according to the embodiment of the present invention.

FIG. 4 is an explanatory sectional view of a conventional edge-enhancement type phase shift mask.

FIG. 5 is an explanatory sectional view of a conventional edge-enhanced phase shift mask.

FIG. 6 is an explanatory sectional view showing a manufacturing process of the edge-enhancement type phase shift mask of FIG. 4 according to a conventional example.

FIG. 7 is an explanatory sectional view showing a manufacturing process of the edge-enhancement type phase shift mask of FIG. 4 according to a conventional example.

FIG. 8 is an explanatory sectional view showing a manufacturing process of the edge-enhancement type phase shift mask of FIG. 5 according to a conventional example.

FIG. 9 is an explanatory sectional view showing a manufacturing process of the edge-enhancement type phase shift mask of FIG. 5 according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 quartz glass substrate 2 etching stopper layer 3 silicon oxide thin film 4 metallic chromium thin film 5 electron beam resist

Claims (1)

(57) [Claims] 1. A transparent film having a high refractive index is sequentially formed on a transparent substrate.
A light-shielding film and an electron beam resist are laminated, and the electron beam resist is exposed and developed in a pattern to leave the electron beam resist in the pattern shape of the phase shifter layer. Then, the exposed portion of the light-shielding film is dry-etched and removed, and the exposed high refractive index transparent body film is dry-etched to form a phase shift layer and dry etching. The thickness of the remaining electron beam resist is reduced uniformly to remove the electron beam resist in the peripheral portion of the pattern to expose the peripheral portion of the pattern of the remaining light-shielding film. A method for manufacturing an edge-enhancement type phase shift mask, characterized by removing portions by dry etching.