JPH024247A - Photomask blank and photomask - Google Patents

Abstract

PURPOSE:To obtain a photomask blank having thin and uniform film thickness and satisfactory step coverage by providing a glass layer contg. a photosensitive metal on a light shielding film on a light transmissive substrate. CONSTITUTION:In the title photomask blank, a pattern forming glass layer contg. a photosensitive metal behaving similarly as a resist film is formed on a light shielding film. Accordingly, a selective exposure treatment can be executed without requiring a resist film additionally. Since the glass layer contg. a photosensitive metal is formed by a film-forming means such as sputtering, CVD, vapor deposition, etc., the control of the film thickness is easy unlike a resist film. Moreover, satisfactopy step coverage is attained even if there are protrusions or stages on the light shielding film. Since the glass layer contg. a photosensitive metal can be formed to a thinner thickness than resist film (for example, to <=1,000Angstrom film thickness), a photomask having increased resolution of a light shielding film pattern is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photomask blank and a photomask used in the manufacturing process of semiconductor integrated circuits, high-density integrated circuits, and the like.

[Prior Art] Conventionally, photomask blanks have been prepared by depositing a film made of, for example, chromium on the main surface of a light-transmitting substrate such as glass with a thickness of 800 to 1,000 yen.
It was manufactured by forming a light-shielding film of 1,000 yen using a film-forming method such as a sputtering method.

Further, a photomask was manufactured in the following manner using the photomask blank described above.

That is, a resist solution is applied onto the light-shielding film of the photomask blank using a spin coating method at a rotation speed of 1,000 to 3.00 rpm, and then prebaked to form a film with a thickness of 3,000 to 10,000 Å. A resist film is formed.

Next, the photomask blank with a resist film obtained above is selectively exposed, then wet-developed using an alkaline aqueous solution or an organic solvent, and then post-baked to obtain a photomask blank with a resist pattern.

Next, the resist patterned photomask blank obtained above is subjected to a wet or dry etching process using the resist pattern as a mask to remove the portion of the light-shielding film that is not covered with the resist pattern. After forming a pattern of a light-shielding film corresponding to the above, the resist pattern is peeled off to obtain a photomask in which a pattern of a light-shielding film is formed on a light-transmitting substrate.

[Problems to be Solved by the Invention] However, the conventional photomask manufacturing method using the above photomask blank has the following drawbacks.

(a) When a resist solution is applied onto a photomask blank by a spin coating method, it is difficult to control the film thickness because the resist solution is a diluted solution of an organic resin in a solvent.

For example, when applying a resist film for 3,000 people, it is estimated that a variation in film thickness of about ±200 people occurs when the resist is applied.

(b) Photomask blank with a height of 10,000 Å
Below, it is inevitable that protrusions will occur due to foreign substances such as abrasives of about 2,000 OOX, but when the above resist solution is spin-coated, the resist film at the top of the protrusions and in the vicinity The resist film becomes significantly thinner than the resist film on the flat portion where no protrusion exists, while the resist film at the base of the protrusion portion and its vicinity becomes significantly thicker than the resist film on the flat portion where no protrusion exists. When this resist film is a positive resist film, when the protrusion is exposed, the thin resist film at the top and its vicinity will be overexposed (over-kojimai), while the thick resist film at the base and its vicinity will be overexposed. This results in insufficient exposure (underexposure), and a doughnut-shaped resist film remains in a portion where the resist film should originally be removed by exposure.

Furthermore, if the protruding portion is an unexposed portion, a resist pattern will be formed in this portion, but cracks are likely to occur in the thin resist film at the top of the protruding portion and in the vicinity.
The etching solution for the light-shielding film penetrates into these cracks, creating undesirable pinholes (white defects).

(C> It has been theoretically recognized that by reducing the thickness of the resist film, it is possible to miniaturize the resist pattern and, by extension, to miniaturize the light-shielding film. It has been confirmed that when the resist film is thinned, the number of pinholes increases significantly.Therefore, the resist film cannot be made thinner than the thickness currently used (3,000 to 10,000).

<d> For the development treatment after selective exposure of the resist film, it is necessary to adopt a wet method that involves post-cleaning and drying steps and requires treatment of waste liquid. Even if it is carried out, the wet development process described above is required, and the entire process cannot be made into a dry process, making the operation complicated. Further, it is inevitable that the organic resin constituting the resist swells due to the above-mentioned wet treatment, which becomes a barrier to pattern refinement.

Therefore, an object of the present invention is to provide a photomask blank, a photomask, and a method for manufacturing the photomask, which can overcome the drawbacks of the prior art described above.

[Means for Solving the Problems] The present invention has been made to achieve the above objects, and includes the following four aspects.

(1) A photomask blank comprising a light-shielding film on a light-transmitting substrate, and further comprising a photosensitive metal-containing glass layer on the light-shielding film.

(2) A photomask having a pattern of a light-shielding film on a light-transmitting substrate, and further comprising a pattern of a photosensitive metal-containing glass layer on the pattern of the light-shielding film.

(3) Aspect (1) above, which has a light-shielding film on a light-transmitting substrate, and further has a photosensitive metal-containing glass layer on the light-shielding film.
) After selectively exposing the photosensitive metal-containing glass layer of the photomask blank, a development treatment is performed to form a pattern of the photosensitive metal-containing glass layer, and then the pattern of the photosensitive metal-containing glass layer is used as a mask. The pattern of the light-shielding film is formed by etching the light-shielding film, the pattern of the light-shielding film is formed on a light-transmitting substrate, and the pattern of the light-shielding film contains a photosensitive metal. The method for manufacturing a photomask according to the above aspect (2), which has a pattern of a glass layer.

(4) A photomask having a pattern of a light-shielding film on a light-transmitting substrate, characterized in that the pattern of the photosensitive metal-containing glass layer of the photomask obtained by the method of aspect (3) above is peeled off. manufacturing method.

[Function] The photomask blank of the present invention has a patternable photosensitive metal-containing glass layer formed on the light-shielding film, which functions in the same way as a conventional resist film, so it is not necessary to provide a separate resist film. selective exposure processing can be performed without This photosensitive metal-containing glass layer is formed by a film forming method such as a sputtering method, an ion blasting method, a CVD method, or an evaporation method, as will be described later, and therefore, unlike a conventional resist film, the film thickness can be easily controlled. In addition, step coverage is good even if the light-shielding film has protrusions or stepped parts, so the problem mentioned above when applying a resist film (residual donut-shaped resist film in exposed areas in the case of positive resist, and unexposed areas) occurrence of pinholes, etc.)
is resolved.

In addition, the photosensitive metal-containing glass layer is thinner than the resist film (
For example, the film thickness can be reduced to less than 1,000 mm), so a photomask with improved resolution of the light-shielding film pattern can be obtained.

Furthermore, since the photosensitive metal-containing glass layer can be developed by a dry method, a completely dry photomask manufacturing process can be achieved. Further, problems such as swelling of the resin due to wet development of a resist film made of an organic resin naturally do not occur.

[Example] Embodiments of the present invention will be described below with reference to FIG.

Example 1 (Example of manufacturing a photomask blank of the present invention) A light-shielding film 2 with a thickness of 80 mm was placed on the main surface of a 2.3 mm thick transparent substrate 1 made of quartz glass or low expansion glass.
A chromium film of 0 to 1,000 layers was formed by sputtering (see FIG. 1(a)).

Next, a photosensitive metal-containing glass layer 3 having a thickness of 1,000 wafers was formed on the light-shielding film 2 made of a chromium film by high-frequency sputtering (see FIG. 1 (1)). The details are as follows.

First, as a photosensitive metal-containing glass, the composition is 5% by weight.
i02 81.5%, Li2O12゜0%, , 2
0 3.5%, Al2O33゜0%, CeO2
Prepare a glass consisting of 0.03% Ag and 0.02% Ag, and cut this glass to a predetermined size (150 mmφ).
It was processed into a target. Next, the obtained target was attached to an electrode section in a high frequency sputtering device.

Further, the light-transmitting group &1 having the light-shielding film 2 was placed at a position approximately 50 meters away from the target attached to the electrode section.

After that, after reducing the entire system to 2X10-6 torr or less,
Introducing Ar gas, 5 to 50 x 10-3t, or
A high-frequency power of about 100 W was applied while maintaining the temperature at about r to form a photosensitive metal-containing glass layer 3 on the light-shielding film 2, thereby obtaining a photomask blank of the present invention. The film thickness of the photosensitive metal-containing glass layer 3 can be easily controlled by changing the sputtering time.
Sputtering ended when it became a person. In addition, when applying a conventional resist film, the film thickness is 3,000 to 1
In this example, the film thickness could be reduced to 1,000 people (it is also possible to make it less than 1.000 people). Further, the variation in film thickness was ±30 people, which was extremely small compared to the case of applying a conventional resist film.

Practical Example 2 (Manufacturing Example of Photomask of the Present Invention) (1) Photomask blank obtained in Example 1 and having a light-shielding film 2 and a photosensitive metal-containing glass layer 3 in this order on a light-transmitting substrate 1 An electron beam lithography system (PerkinElmer MEBESI [I
) was used to selectively expose the photosensitive metal-containing glass layer 3 to electron beam exposure. Details of the electron beam exposure process using the above apparatus are as follows.

First, a photomask blank having the photosensitive metal-containing glass layer 3 to be imaged was loaded into a predetermined cassette.

Next, this cassette was placed in a jig called a magazine that could accommodate up to 10 cassettes, and then placed in a vacuum chamber.

After a predetermined degree of vacuum was obtained in this vacuum chamber, the above-mentioned cassette was extracted from the magazine and automatically set in the drawing chamber.

Next, the desired pattern is converted into data, and the desired pattern is drawn on the photosensitive metal-containing glass layer 3 using an electron beam 4 having a preset current density under computer control using this data. (See FIG. 1(C)) to form a latent image 3b in the exposed area. In addition, in this drawing operation, the accelerating voltage was 10 KV, the spot size was 0°5 μm, and the dose amount was 50 μC without indicating the exposure intensity.
/d.

After the electron beam exposure treatment, plasma etching treatment using CF4 gas (pressure crab 35 Pa, power: 0.24
W/fl, gas: CF4 84sccm+02 50s
ecm, time: 2 to 10 minutes) to remove the latent image 3b portion of the photosensitive metal-containing glass layer to form a pattern 3a of the photosensitive metal-containing glass layer (FIG. 1(d)). reference).

(2) Next, using the pattern 3a of the photosensitive metal-containing glass layer as a mask, plasma etching treatment is performed using CCl4 gas (pressure crab 35 Pa, power: 0.29 W/-1 force: CC
l4 133sccm+02O2100sc, time=3
~10 minutes), the part (exposed part) of the light-shielding film 2 made of a chromium film that is not covered with the pattern 3a of the photosensitive metal-containing glass layer is removed, and the pattern of the photosensitive metal-containing glass layer is removed. Light-shielding film pattern 2 corresponding to 3a
A was formed (see FIG. 1(e)).

A pattern 2a of a light-shielding film and a pattern 3 of a photosensitive metal-containing glass layer are formed on the transparent substrate 1 thus obtained.
The photomask of this example has a photosensitive metal-containing glass layer having a film thickness of 1,000 people and less variation in film thickness, instead of the conventional resist film. Since it was obtained using a blank, the above-mentioned problems that are unavoidable when applying a resist film on a conventional photomask were not observed, and the pattern of the light-shielding film, which was fine and faithful to the latent image 3b, was transparent. It was formed on a photosensitive substrate.

Furthermore, since the pattern of the photosensitive metal-containing glass layer on the pattern of the light-shielding film is a pattern having anti-reflection ability containing 5i02 as a main component, it is preferably used as a photomask having an anti-reflection film.

(Manufacturing Example of Other Photomask of the Present Invention) Pattern 2 of the light-shielding film on the light-transmitting substrate 1 obtained in Example 2
A photomask having a pattern 3a of a photosensitive metal-containing glass layer was etched using CF 4 gas (power: 300W).

Vacuum degree: 0.2 torr, Gas: 98% CF4,22
%02), pattern 3a of photosensitive metal-containing glass layer
(See FIG. 1(f)) to expose the light-shielding film pattern 2a made of a chromium film to obtain a light-transmitting substrate 1 having only the light-shielding film pattern 2a). The light-transmitting substrate 1 with the light-shielding film pattern 2a is also preferably used as a photomask.

Although the present invention has been described above based on examples, the present invention includes the following modifications and applications.

(1) As the material for forming the photosensitive metal-containing glass layer and its pattern, photosensitive glass (A ) and (B) can also be used.

(A) (B) Si20 72.5 79 Li20 12.5 9 Na20 2 20 5 2.5 AI203
10 7.5Ce02 o, 0
2 0. O2Ag 0.002
0.002 (unit: % by weight) It is also possible to use the photosensitive glass described in Japanese Patent Publication No. 32-5080.

(2) In the examples, a photosensitive metal-containing glass layer was formed on a transparent substrate using a high frequency sputtering method, but other sputtering methods such as reactive sputtering and plasma sputtering may be used. . Further, instead of the sputtering method, a vacuum evaporation method, a CVD method, or an ion blating method may be used.

(3) In the examples, selective exposure of the photosensitive metal-containing glass layer was carried out using an electron beam lithography device, but a mask having a predetermined pattern was placed on the photosensitive metal-containing glass layer,
It may also be carried out by irradiating with ultraviolet rays.

(4) For the development of the photosensitive metal-containing glass layer after selective exposure, it is preferable to carry out dry development as in Example 2 from the viewpoint of completely drying the process, but an acid or the like may be used as necessary. Wet development processing can also be employed.

(5) For the etching treatment of the light-shielding film using the pattern of the photosensitive metal-containing glass layer as a mask, it is preferable to perform dry etching treatment as in Example 2, but wet treatment can also be adopted as necessary. . (6) An antireflection film made of chromium oxide or the like may be provided on the pattern of the light-shielding film on the transparent substrate obtained in Example 3.

[Effects of the Invention] As described above, according to the present invention, since a photosensitive metal-containing glass layer is provided, a photomask blank used for manufacturing a photomask as it is without providing a separate resist film can be used. provided.

This photomask blank has the features of a thin and uniform photosensitive metal-containing layer and good step coverage, so by using this photomask blank, you can create a fine and precise light-shielding film pattern. A photomask having the following is provided.

Furthermore, since dry-developable photosensitive metal-containing glass is used, a photomask manufacturing method has been provided that allows the entire process to be completely dry, if necessary.

[Brief explanation of the drawing]

FIG. 1 is a process diagram for manufacturing a photomask blank and a photomask according to the present invention. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... Light blocking film, 2a... Pattern of light blocking film, 3... Photosensitive metal-containing glass layer,
3a... pattern of photosensitive metal-containing glass layer, 3b...
...Latent image, 4...Electron beam.

Claims (1)

[Scope of Claims] 1. A photomask blank comprising a light-shielding film on a light-transmitting substrate, and further comprising a photosensitive metal-containing glass layer on the light-shielding film. 2. A photomask having a pattern of a light-shielding film on a light-transmitting substrate, and further comprising a pattern of a photosensitive metal-containing glass layer on the pattern of the light-shielding film. 3. Selecting the photosensitive metal-containing glass layer of the photomask blank according to claim 1, which has a light-shielding film on a light-transmitting substrate, and further has a photosensitive metal-containing glass layer on the light-shielding film. After being exposed to light, a pattern of the photosensitive metal-containing glass layer is formed by developing, and then the light-shielding film is etched using the pattern of the photosensitive metal-containing glass layer as a mask to form a pattern of the light-shielding film. The photomask according to claim 2, having a pattern of a light-shielding film on a light-transmitting substrate, and further having a pattern of a photosensitive metal-containing glass layer on the pattern of the light-shielding film. manufacturing method. 4. Production of a photomask having a pattern of a light-shielding film on a light-transmitting substrate, characterized by peeling off the pattern of the photosensitive metal-containing glass layer of the photomask obtained by the method according to claim 3. Method.