JPS61267762A - Production of photomask - Google Patents

Abstract

PURPOSE:To decrease extremely black color defects and to improve quality of a mask by constituting a mask blank material of the 1st light shieldable film to be dry etched on a substrate and the 2nd light shieldable film which is resistant to dry etching and is to be wet etched. CONSTITUTION:The photomask blank 4 is constituted of the 1st light shieldable film 2 which is to be dry etched and consists of a Ta film, etc. on the light transmittable substrate 1 consisting of quartz glass, etc. and the 2nd light shieldable film 3 which is resistant to the dry etching, is to be wet etched and consists of a Cr film, etc. A photoresist 5 is coated on such film and is exposed and developed to form a resist pattern 8 and thereafter the dry etching is executed to form the 2nd light shieldable film pattern 9. The film 2 is dry etched with the pattern 9 as a mask. The thorough cleaning and drying are executed prior to the etching of the film 2 and therefore the foreign matter is removed and the black color defects are eliminated. The quality of the mask is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a photomask used in manufacturing semiconductors, IC1LSIs, and the like. More specifically, the present invention relates to a method of manufacturing a photomask used when transferring a predetermined pattern to a resist coated on a substrate to be microfabricated, such as a silicon wafer or a photomask blank.

(Prior Art) As the density of LSI increases, photomasks are becoming increasingly finer, and the recent photomask manufacturing method is shifting from the conventional wet etching method to a dry etching method.

This dry etching method for producing a photomask involves first polishing the main surface of a transparent substrate made of glass, quartz, etc., and then depositing a light-shielding film containing Cr as a main component on the main surface by sputtering. Then, a photomask blank is produced. Next, after coating a photoresist on the light-shielding film, a photomask blank with a resist pattern obtained through a selective exposure process, a development process, a rinsing process, and a drying process is placed in a plasma reaction chamber using carbon tetrachloride, etc. The light-shielding film is selectively patterned by dry etching using gas plasma. Then, the resist pattern on this light-shielding film pattern is removed by oxygen plasma treatment to obtain a photomask.

Compared to those obtained by wet etching, photomasks obtained by dry etching have the advantage that the amount of dry etching is small, pattern width changes due to excessive etching are small, and etching time tolerance is large. There is.

[Problem that the invention seeks to solve]

However, even if the light-shielding film is etched using the dry etching method, the photo-I/resist development process is performed wet, so as mentioned above, a drying process is required before the etching process. . In this drying process, in the photomask blank with a resist pattern, particles often adhere to the exposed surface of the light-shielding film that is not covered with the resist pattern. For example, tens to hundreds of foreign particles are attached to each 6-inch square substrate. Such foreign matter acts as a mask in the next dry etching step, and the portion of the light-shielding film under the foreign matter is not etched, resulting in so-called black defects.

Cleaning with an organic solvent, acid, alkali, etc. can be considered as a means for removing such foreign substances, but in the case of a photomask blank with a resist pattern after the drying process described above, the resist pattern may be maintained as it is. hand,
It is impossible to remove only the adhered foreign matter using the current manufacturing method. Therefore, at present,
Strict controls have been put in place to remove foreign substances from the developing solution, the rinsing solution, and the environment during each development, rinsing, and drying process, but no fundamental improvements have been made.

[Means for solving problems]

The method for manufacturing a photomask according to the present invention has been made to solve the problems listed in L. A second light-shielding film that is etched by wet etching and is resistant to the dry etching is formed on each of the crotches, and (2) the resist coated on the second light-shielding film is exposed and developed to form a resist pattern. and (2) selectively etching the second light-shielding film by wet etching to form a second light-shielding film on the first light-shielding film.
forming a light-shielding film pattern; (1) removing the resist pattern, cleaning and drying; and then selectively etching the first light-shielding film by dry etching using the second light-shielding film pattern as a mask; It is characterized by

[For production]

According to the present invention, in the process before etching the first light-shielding film, the resist pattern on the second light-shielding film pattern can be removed, and the process of cleaning and drying can be included. The exposed surface of the first light-shielding film that is not covered with the pattern can be sufficiently cleaned to remove foreign matter.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

First, cut the quartz glass to the specified dimensions (this example: 6x6xO11
2 inches), polished the amphibious surface of this quartz glass, washed it with pure water and isopropyl alcohol, etc.
After drying, a transparent substrate 1 made of quartz glass before film formation is obtained. A first light-shielding film 2 (Jll thickness: 800 layers) made of a Ta film is deposited on the −1 surface of the light-transmitting substrate 1 by sputtering using D as a target. Next, on this first light-shielding film 2, a second light-shielding film 3 (thickness:
200 people) to obtain a photomask blank 4 on which a first light-shielding film 2 and a second light-shielding film 3 are formed (Fig. 1 (
a)). Note that the optical density of this photomask blank 4 was 3.0.

Next, a positive photoresist 5 (this example: HP-1350 manufactured by Hoechst Co., Ltd., film thickness: soo.

After coating the positive photoresist 5 with deep ultraviolet light or ultraviolet light 7 (wavelength = 200-400n11) from above the positive photoresist 5 through the exposure mask 6 to obtain the desired pattern line width.
) is exposed to light ((b) in the same figure).

Next, development is performed for a predetermined time (near 0 seconds in this example) using a developer (this example: HP-1350 exclusive developer) to remove the exposed portion of the positive photoresist 5 and form a resist pattern 8 on the unexposed portion. Formed on the second light-shielding film 3 (
Same figure (C)).

Next, wet etching is performed for a predetermined time (this example: 15 seconds) using an etching solution suitable for the second light-shielding film 3 (this example: a mixture of cerium ammonium nitrate and perchloric acid). A second light-shielding film pattern 9 is formed on the first light-shielding WIA 2 (FIG. 4(d)). In this wet etching,
The lower first light-shielding film 2 is not easily etched in this example, but the film thickness is somewhat thinner (e.g. aOOm→600mm).
(a person) may also be etched.

Next, the resist pattern 8 is removed using a stripping solution (this example: hot concentrated sulfuric acid).
1190° C.), immersed in sulfuric acid at room temperature to lower the temperature, subjected to ultrasonic cleaning in water and isopropyl alcohol, and dried in Freon steam (FIG. 3(e)).

Next, the blank with the second light-shielding film pattern 9 is placed in a parallel plate type plasma etching apparatus and dry etched using CF4 gas as a reaction gas.

At this time, the 2″m photogonadal pattern 9 is not affected by the CF4 gas plasma and acts as a mask.
Only the exposed surface of the first light-shielding film 2 that is not coated with the second light-shielding film pattern 9 is dry-etched, resulting in the first light-shielding film pattern 10 and the second light-shielding film pattern 9.
A photomask 11 having a light-shielding film pattern with a two-layer structure consisting of the following is obtained (FIG. 2(f)).

According to this example, after the completion of dry etching, the number of areas where the light-shielding film should not remain (black defects with dimensions of 1 μm or more) is on average about 8 to 9 per 6-inch square sheet (sample number = 10 sheets), which made it possible to reduce the number of sheets to a very small number. Further, the dimensional change between the resist pattern and the actual light-shielding film pattern due to side etching is 0.0000.
Since the size was as small as about 1 μm, the advantage of dry etching, which is suitable for fine patterns, could be fully utilized.

The present invention is not limited to the film forming materials, wet etching solutions, and dry gas plasmas mentioned in the above examples. Regarding the first light-shielding film, instead of Ta, No.
Any light-shielding film that can be dry-etched may be used, such as Ni, W, Wb, V, Zr, and silicides of Hicolera. Regarding the second light-shielding film, instead of gold LCR, Cr
It may also be a light-shielding film whose main component is Cr containing O, N, and C. 1st. Regarding the mutual thickness relationship of the second light-shielding film, in order to effectively utilize the advantages of dry etching, the thickness of the first light-shielding film is thicker than that of the second light-shielding film. preferable. The wet etching solution is selected appropriately depending on the material to be etched.
(Fe(CN) a ) etc. may also be used. The etching gas for dry etching is also selected appropriately depending on the material to be etched.
+ (02) etc. Other film forming methods have been changed to vacuum evaporation and ion blating, translucent substrates have been changed to multi-component glasses such as aluminosilicate glass, and resists have been changed to negative photoresists, positive or screw-type EB resists, etc. Of course you can do that.

(Effects of the Invention) As described above, according to the present invention, the first image is placed on the transparent substrate. After forming a second light-shielding film and wet-etching the upper second light-shielding film, the resist is removed, washed and dried,
Next, by dry etching the lower first light-shielding film, black defects, which were difficult to remove by conventional dry etching, can be greatly reduced and the quality of the photomask can be improved.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an embodiment of the method for manufacturing a photomask according to the present invention. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... First light-shielding film, 3...
Second light-shielding film, 4... Photomask blank, 5...
・Positive photoresist, 6... Exposure mask, 7...
・Deep ultraviolet light or ultraviolet light, 8...resist pattern,
9... 2nd "a" photosensitive film pattern, 10... 1st light-shielding film pattern, 11... Photomask procedure amendment (voluntary) 1. Indication of incident Patent Application No. 109782 of 1985 No. 2, Title of the Invention: Mask Blank and Photomask Manufacturing Method 3, Relationship with the Amendment Person Case Address of Patent Applicant: 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo 161
T E L 03 (952) 1151 Name H
- YA Co., Ltd. 4, Number of inventions increased by amendment...25, Subject of amendment (1) "Name of invention column" and [Number of inventions stated in claims column] of the application ] (2) "Title of the invention column", "Claims column", "Detailed description of the invention IIIJ" and "Brief description of drawings column" 6. Contents of amendment (1) Amend the application as shown in the attached sheet. (2) Amend the entire specification as shown in the attached sheet. 1. Description (corrected full text) 1. Name of the invention Photomask blank and photomask manufacturing method 2. First photosensitive film of a photomask blank obtained by sequentially acidifying the claims from the transparent substrate side Option 3: Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a photomask blank used in the manufacture of semiconductors, ICs, LSIs, etc., and a method of manufacturing a photomask. More specifically, the present invention relates to a method for manufacturing a photomask used to transfer a predetermined pattern to a resist coated on a base to be microfabricated such as a silicon wafer or a photomask blank, and a photomask blank as a material thereof. [Prior Art] As the density of LSI increases, photomasks are becoming increasingly finer, and the recent method of manufacturing photomasks is shifting from the conventional wet etching method to a dry etching method. This dry etching method for producing a photomask involves first polishing the main surface of a transparent substrate made of glass, quartz, etc., and then depositing a light-shielding film containing Cr as a main component on the main surface by sputtering. Then, a photomask blank is produced. Next, after coating a photoresist on the light-shielding film, a photomask blank with a resist pattern obtained through a selective exposure process, a development process, a rinsing process, and a drying process is placed in a plasma reaction chamber using carbon tetrachloride, etc. The light-shielding film is selectively patterned by dry etching using gas plasma. Then, the resist pattern on this light-shielding film pattern is removed by oxygen plasma treatment to obtain a photomask. A photomask obtained by such a dry etching method has the advantage that the amount of side etching is small, the change in pattern width due to excessive etching is small, and the allowable range of etching time is large, as compared to a photomask obtained by a wet etching method. [Problems to be Solved by the Invention] However, even if the light-shielding film is etched using a dry etching method, the photoresist development process is carried out in a wet manner, so as mentioned above, the etching process A drying process is required beforehand. In this drying process, the resist patterned photomask blank is
Foreign matter often adheres to the exposed surface of the light-shielding film that is not covered with the resist pattern. For example, tens to hundreds of foreign particles are attached to each 6-inch square substrate. Such foreign matter becomes a mask during the next dry etching time, and the portion of the light-shielding film under the foreign matter is not etched, resulting in so-called black defects. Cleaning with an organic solvent, acid, alkali, etc. can be considered as a means for removing such foreign substances, but in the case of a photomask blank with a resist pattern after the drying process described above, the resist pattern may be maintained as it is. hand,
It is impossible to remove only the attached foreign matter using the current manufacturing method. Therefore, at present, strict controls are being implemented to remove foreign substances from the developing solution, rinsing solution, and the environment during each development, rinsing, and drying process, but fundamental improvements have not yet been made. . [Means for Solving Problem C] The photomask blank and photomask manufacturing method according to the present invention have been made to solve the above-mentioned problems. A first light-shielding film and a second light-shielding film are sequentially laminated on the film, and the first light-shielding film is the film-forming material to be dry-etched, and the
The photosensitive film is resistant to the dry etching and is a film forming material that can be wet etched,
The method for manufacturing a photomask includes using the photomask blank as a material and selectively wet-etching a second light-shielding film to form a second light-shielding film pattern on the first light-shielding film;
The method is characterized in that the first light-shielding film is selectively dry-etched using the second light-shielding film pattern as a mask. [Function] According to the present invention, the process of removing the resist pattern on the second light-shielding film pattern, washing and drying can be included in the pre-process of etching the first light-shielding film. The exposed surface of the first light-shielding film that is not covered with the second light-shielding film pattern can be sufficiently cleaned to remove foreign matter. [Example] Hereinafter, an example of the present invention will be described in detail with reference to FIG. First, measure the quartz glass to the specified dimensions (in this example: 6x6x0.1
2 inches), polished the amphibious surface of this quartz glass, washed it with pure water and isobu-O-vinyl alcohol, etc.
After drying, a transparent substrate 1 made of quartz glass before film formation is obtained. A first light-shielding film 2 (film thickness: 800 layers) made of a Ta film is deposited on the −1 surface of the light-transmitting substrate 1 by sputtering using Ta as a target. Next, this first
A second light-shielding film 3 made of a Cr film (thickness: 200 mm
layer), the first light-shielding film 2 and the second light-shielding film 1!12
Obtain a photomask blank 4 on which 3 is deposited (see Fig. 1 (
a)). Note that the optical density of this photomask blank 4 was 3.0. Next, a positive photoresist 5 (this example:
Hoechst MP-1350. Film thickness: soo. After coating the positive photoresist 5 with deep ultraviolet light or ultraviolet light 7 (wavelength = 200 to 400 nm) from above the positive photoresist 5 through an exposure mask 6 to obtain the desired pattern line width.
) is exposed to light ((b) in the same figure). Next, development is performed for a predetermined time (near 0 seconds in this example) using a developer (this example: HP-1350 exclusive developer) to remove the exposed portion of the positive photoresist 5 and form a resist pattern 8 on the unexposed portion. Formed on the second light-shielding film 3 (
Same figure (C)). Next, wet etching is performed for a predetermined time (in this example: 15 seconds) using an etching solution (this example: a mixture of cerium ammonium nitrate and perchloric acid) that is compatible with the second "a" photosensitive film 3. , a second light-shielding film pattern 9 is formed on the first light-shielding film 2 (FIG. 2(d)). In this wet etching, the lower first light-shielding film 2 is not easily etched in this example; The film thickness will be slightly thinner (e.g. 800 people → 600 people)
It may be etched up to Next, the resist pattern 8 is removed with a stripping solution (this example: hot concentrated sulfuric acid 9
0°C), immersed in sulfuric acid at room temperature to lower the temperature, and ultrasonically cleaned in water and isopropyl alcohol.
Dry in Freon steam ((e) in the same figure). Next, the blank with the second light-shielding film pattern 9 is placed in a parallel plate type plasma etching apparatus and dry etched using CF4 gas as a reaction gas. At this time, the second light-shielding film pattern 9 is not disturbed by the CFa gas plasma and acts as a mask, so that only the exposed surface of the first light-shielding film 2 that is not covered by the second light-shielding film pattern 9 is exposed. After being dry etched,
Since the first light-shielding film pattern 10 and the second light-shielding film pattern 9 are used, a photomask 11 having a two-layer structure light-shielding film pattern can be obtained (see the figure ()). After etching, the number of black defects with dimensions of 1 μm or more (in areas where the light-shielding film should not remain) is on average about 8 to 9 per 6 inch square sheet (number of samples = 10 sheets). In addition, the dimensional change between the resist pattern and the actual light-shielding film pattern due to side etching can be reduced to 0.0.0 because the second light-shielding film is thin and the wet etching time is short.
Since it was minute, about 1 μm, it was possible to fully utilize the advantage of dry etching, which is suitable for fine patterns. The present invention is not limited to the film forming materials, wet etching solutions, and dry gas plasmas mentioned in the above examples. Regarding the first light-shielding film, instead of Ta, )to
, Ni1W, Nb, V1Zr, and silicides thereof, which can be dry-etched, may be used. Regarding the second light-shielding film, instead of metal Cr, C
It may be a light-shielding film whose main component is Cr containing O, N, and C in r. Regarding the mutual film thickness relationship between the first and second light-shielding films, in consideration of effectively utilizing the advantages of dry etching, the thickness of the first light-shielding film is equal to that of the second light-shielding film. It is preferable that the wet etching solution is thicker than the above.The wet etching solution is appropriately selected depending on the material to be etched.
It may also be Fe(CM)s) or the like. The etching gas for dry etching is also selected appropriately in relation to the material to be etched.
02) etc. Other film forming methods have been changed to vacuum evaporation and ion blating, translucent substrates have been changed to multi-component glasses such as aluminosilicate glass, and resists have been changed to negative photoresists, positive or screw-type EB resists, etc. Of course you can do that. [Effects of the Invention] As described above, according to the photomask blank of the present invention,
A first light-shielding film that is dry-etched and a second light-shielding film that is resistant to the dry etching and wet-etched are sequentially laminated on a light-transmitting substrate, so that this photomask can be used. When manufacturing a photomask using a blank as a material, the resist can be removed, washed, and dried after wet-etching the 21st light-shielding film on the upper layer, and then dry-etching the 1st light-shielding film on the lower layer. The black defects that tend to occur with conventional dry etching can be greatly reduced, and the quality of the photomask can be improved. 4. Brief Description of the Drawings FIG. 1 is a process diagram showing an embodiment of the method for manufacturing a photomask blank and a photomask according to the present invention. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 2... First light-shielding film, 3...
Second light-shielding film, 4... Photomask blank, 5...
・Positive photoresist, 6... Exposure mask, 7...
・Deep ultraviolet light or ultraviolet light, 8...resist pattern,
9... 2nd''m light film pattern, 10... 1st light shielding film pattern, 11... Photomask

Claims (1)

[Claims] (1) A first light-shielding film etched by dry etching on a light-transmitting substrate, and a second light-shielding film etched by wet etching on the first light-shielding film and having resistance to the dry etching. Form each film,
A resist coated on the second light-shielding film is exposed and developed to form a resist pattern, and the second light-shielding film is selectively etched by wet etching to form a resist pattern on the first light-shielding film.
After forming a second light-shielding film pattern on the light-shielding film, removing the resist pattern, cleaning and drying, dry etching the first light-shielding film using the second light-shielding film pattern as a mask. A method for manufacturing a photomask characterized by selective etching.