JPH0667406A - Phase shift photomask blank and phase shift photomask - Google Patents

Abstract

PURPOSE:To make the application of ordinary acid washing possible with the phase shift photomask blank by using an etching stop layer consisting of an alumina film which has high transmittability in a UV region, sufficient dry etching resistance and has sufficient acid resistance for the above-mentioned photomask. CONSTITUTION:The alumina film subjected to a heat treatment at >=600 deg.C has the improved acid transmittance and >=85% transmittance in a 200 to 850nm wavelength range. The application of the ordinary acid washing method at the time of production is possible and the phase shift photomask having decreased defects is produced if such alumina film is used as the etching stop layer of the phase shift photomask having at least the etching stop layer and phase shift layer on a transparent substrate and its blank. In addition, the application thereof to not only an exposure device using i rays of an ultra-high- pressure mercury lamp but an exposure device using a krypton fluoride excimer laser is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift photomask used in the manufacture of high density integrated circuits such as LSI and VLSI, and in the manufacture of high speed devices using compound semiconductors, and a phase shift photomask blank therefor. In particular, the present invention relates to a phase shift photomask blank and a phase shift photomask having an etching stop layer for protecting a transparent substrate when etching the phase shift layer.

[0002]

2. Description of the Related Art The function required as an etching stop layer of a phase shift photomask is arranged under the phase shift layer when the phase shift layer is partially dry-etched to form a phase shift pattern. The etching stop layer is difficult to be etched, and the transmittance is high for the exposure wavelength (i-line wavelength of ultra-high pressure mercury lamp: 365 nm, krypton fluoride / excimer laser wavelength: 248 nm, etc.) when using a phase shift photomask. That is, at least the transmittance is 85% or more, and the acid cleaning method (for example, dipping in concentrated sulfuric acid) which is widely used as one of the cleaning methods in the normal photomask manufacturing process is used in the phase shift photomask manufacturing process. It has sufficient acid resistance so that it can be used.

At present, a film mainly made of tin oxide is often used as an etching stop layer of a phase shift photomask for i-line, but its dry etching resistance is not sufficient and a krypton fluoride excimer laser wavelength 24
It is widely known that, in the wavelength region of 350 nm or less including 8 nm, the transmittance is poor and it is not suitable for a phase shift photomask for a krypton fluoride excimer laser.

A phase formed by a vacuum deposition method having an etching stop layer made of an alumina film having a high transparency even in a wavelength range of 350 nm or less including a krypton fluoride excimer laser wavelength of 248 nm and having sufficient dry etching resistance. A shift photomask has been reported (Proceedings of the 52nd Annual Meeting of the Japan Society of Applied Physics,
p. 539), it was simultaneously reported that the alumina film was weak against acid.

[0005]

As described above, as described above,
The alumina film has a poor acid resistance, and there is a problem that ordinary acid cleaning cannot be applied to a phase shift photomask having the alumina film as an etching stop layer.

The present invention has been made in view of the above circumstances, and an object thereof is to form an alumina film having high transparency in the ultraviolet region, sufficient dry etching resistance, and sufficient acid resistance. To provide a phase shift photomask blank and a phase shift photomask using an etching stop layer.

[0007]

In view of the above problems, the present invention has developed and researched an etching stop layer having acid resistance and capable of supporting a krypton fluoride laser, and as a result, a transparent substrate By forming a film of alumina (Al ₂ O ₃ ) on it and baking it at 600 ° C or higher in the atmosphere,
It was found that a film having excellent acid resistance and having a transmittance of 85% or more at a wavelength of 200 nm or more can be obtained, and the present invention has been completed based on such findings.

In FIG. 5, an alumina film having a thickness of 1 is formed on a quartz substrate.
The change in the etching rate of hot-sulfuric acid for a film heat-treated in the atmosphere for 1 hour after sputtering by 10 nm depending on the firing temperature is shown. From this figure, it can be seen that the acid resistance of the alumina film is increased by the heat treatment in the oxidizing atmosphere. In particular, it is desirable to fire at 600 ° C. or higher.

Next, FIG. 6 shows the spectral transmittance of the alumina film after the heat treatment at 600 ° C. in the wavelength range of 200 to 850 nm.

From the above, the acid resistance of the alumina film heat-treated at 600 ° C. or higher is improved to 200 nm to 850 nm.
It was found that the transmittance was 85% or more in the wavelength range of.

By the way, as the phase shift layer arranged on the alumina film after such heat treatment, a silicon dioxide film formed by a sputtering method, a CVD method or the like or an SOG (Spin-On) formed by a coating / firing method is used. -Glas
s: coatable glass) film or the like is preferable.

As the light-shielding thin film layer, chromium, tantalum, molybdenum silicide or the like formed by sputtering or the like, or a single layer or a composite layer mainly containing an oxide, nitride or oxynitride thereof is preferable. Is.

That is, the phase shift photomask blank of the present invention is a phase shift photomask blank having at least an etching stop layer and a phase shift layer on a transparent substrate, wherein the etching stop layer is formed by a sputtering method. It is characterized in that it is composed of an alumina film which is subsequently heat-treated in an oxidizing atmosphere.

In this case, it is preferable that the alumina film is formed by heat treatment at 600 ° C. or higher.

The phase shift photomask of the present invention is one in which a phase shift pattern is formed by selectively removing a part of the phase shift layer of such a phase shift photomask blank.

[0016]

In the present invention, the etching stop layer is
Since the alumina film is formed by the sputtering method and then heat-treated in an oxidizing atmosphere, the etching stop layer has excellent acid resistance and excellent transparency in the ultraviolet to visible range. Therefore, when manufacturing a phase shift photomask, a normal acid cleaning method can be applied,
A phase shift photomask with few defects can be manufactured. Moreover, the phase shift photomask applicable not only to the exposure apparatus using the i-line of the ultra-high pressure mercury lamp but also to the exposure apparatus using the krypton fluoride excimer laser can be constructed.

[0017]

Embodiments of the phase shift photomask blank and the phase shift photomask of the present invention will be described below with reference to the drawings. 1 and 2 are cross-sectional views showing a photomask blank and a photomask manufactured by the present invention, respectively. FIG. 1A is a lower shifter type blank in which the phase shift layer is below the light shielding layer. In order to manufacture this blank, a film of alumina having a thickness of about 100 nm is formed on the quartz substrate 1 by the RF magnetron sputtering method, heated in an oxidizing atmosphere at 600 ° C. or higher to form the alumina film 2, and The SOG (spin-on-glass: coatable glass) material that will become the phase shift layer 3 is spin-coated on the alumina film 2 and then baked in an oven or the like to produce 380
The SOG film 3 having a thickness of up to 430 nm is formed, and the chromium film which is the light shielding layer 4 is formed by the sputtering method to complete the lower shifter type blank shown in FIG. In addition, FIG.
(C) and (d) are other examples of the blank according to the present invention, which are an upper shifter type, a halftone type and a transmission type blank each having a phase shift layer on a light shielding layer. In the case of FIG. 2B, the alumina film 2 is provided on the quartz substrate 1 in the same manner as in FIG. 1A, and the light shielding layer 4 or the semi-transmissive layer 5 is directly provided thereon. In the case of FIG.
The alumina film 2 is provided on the quartz substrate 1 in the same manner as in FIG. 1A, and the phase shift layer 3 and the semi-transmissive layer 5 are formed in this order on the alumina film 2. Furthermore, in the case of FIG.
An alumina film 2 is provided on a quartz substrate 1 in the same manner as in FIG. 1A, and a phase shift layer 3 is provided thereon.

Further, FIGS. 2 (a), 2 (b), 2 (c),
1 (a), (b), (c), and FIG.
The completed sectional view of the phase shift photomask manufactured using the blank of (d) is shown. These detailed operations are well known and will not be described.

Next, FIG. 3 and FIG.
7A and 7B are cross-sectional views for explaining a manufacturing process of the phase shift photomask shown in FIGS.

As shown in FIG. 3 (a), a normal ionizing radiation resist is applied on the blank of FIG. 1 (a), a predetermined pattern is drawn and exposed by ionizing radiation from an electron beam exposure device or the like, and developed. After rinsing, a resist pattern 16 is formed. Next, the chromium film 4 exposed from the opening of the resist pattern 16 is dry or wet etched,
After forming the chrome pattern 14, the resist pattern 16 is peeled off (FIG. 3B). Then chrome pattern 14
An ionizing radiation resist or the like is applied on top, and alignment with the chrome pattern 14 is performed by a conventional method, followed by exposure and phenomenon to form a resist pattern 17 (FIG. 3).
(C)). Next, the phase shift layer 3 is subjected to dry or wet etching and the resist pattern 17 is peeled off to complete the phase shift photomask having the phase shift pattern 13 as shown in FIG.

Further, as shown in FIG.
After forming the resist pattern 16 on the blank of (b), the chrome film 4 is selectively etched to remove the resist pattern 16 (FIG. 4B), and the phase shift is performed as shown in FIG. 4C. After the layer 3 is formed and the resist pattern 17 is further formed thereon (FIG. 4D), the phase shift layer 3 is dry or wet-etched, and the resist pattern 17 is peeled off. The upper shifter type phase shift photomask having the phase shift pattern 13 as shown in FIG.

The phase shift photomasks shown in FIGS. 2C and 2D can be manufactured in substantially the same manner.

The phase shift photomask blank and the phase shift photomask of the present invention have been described above based on some embodiments, but the present invention is not limited to these embodiments and various modifications can be made.

[0024]

As is apparent from the above description, according to the present invention, the etching stop layer of the phase shift photomask is made of an alumina film which is heat-treated in an oxidizing atmosphere after being formed by the sputtering method. Therefore, the etching stop layer has excellent acid resistance and excellent transparency in the ultraviolet region to the visible region. Therefore, when manufacturing a phase shift photomask, a normal acid cleaning method can be applied, and a phase shift photomask with few defects can be manufactured. Moreover, since the phase shift photomask applicable not only to the exposure apparatus using the i-line of the ultra-high pressure mercury lamp but also to the exposure apparatus using the krypton fluoride excimer laser can be constructed, it can be used in high-performance LSIs, ultra-LSIs, etc. In manufacturing a high density integrated circuit or a high-speed element, a finer pattern can be formed with a high yield, so that a higher performance integrated circuit or a high-speed element can be manufactured with a high yield.

[Brief description of drawings]

FIG. 1 is a sectional view of a phase photomask blank according to the present invention.

FIG. 2 is a sectional view of a phase photomask according to the present invention.

FIG. 3 is a cross-sectional view showing a manufacturing process of the phase shift photomask of FIG.

FIG. 4 is a cross-sectional view showing a manufacturing process of the phase shift photomask of FIG. 2 (b).

FIG. 5 is a diagram showing changes in the etching rate of an alumina film according to the present invention depending on the firing temperature.

FIG. 6 is a diagram showing a spectral transmittance of an alumina film according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Alumina film 3 ... Phase shift layer 4 ... Light-shielding layer 5 ... Semi-transmissive layer 13 ... Phase shift pattern 14 ... Chrome pattern 15 ... Patterned semi-transmissive layer 16, 17 ... Resist pattern

Claims (3)

[Claims] 1. A phase shift photomask blank comprising at least an etching stop layer and a phase shift layer on a transparent substrate, wherein the etching stop layer is formed by a sputtering method and then heat-treated in an oxidizing atmosphere. Phase shift photomask blank, which is formed of a formed alumina film. 2. The phase shift photomask blank according to claim 1, wherein the alumina film is formed by heat treatment at 600 ° C. or higher. 3. A phase shift photomask according to claim 1, wherein a part of the phase shift layer of the phase shift photomask blank is selectively removed to form a phase shift pattern.