JPS6033556A - Material of photomask for dry etching - Google Patents

Abstract

PURPOSE:To prevent inferior etching by using a specified low alkali glass as a base in the titled photomask using a thin film composed essentially of W. CONSTITUTION:Glass to be used as a base is low alkali glass, such as borosilicate glass or quartz glass, having an alkali metal oxide content of 0-5wt%, substantially transparent in the exposure wavelength region of 400-450nm, having a transparency of >=75%. A thin film made of W, optionally contg. about <=50atomic % Ti, Cr, Ta, etc. is formed on the base made of said galss. The obtained photomask material is prevented almost from production of an alkali-metal-W complex and etching failures occur very little.

Description

Detailed Description of the Invention (1) Background Technical Field of the Invention The present invention relates to a photomask material for dry etching having a thin film on a substrate.

Prior Art and its Problems As LSIs become more highly integrated, photomasks used in LSI manufacturing are also required to have higher precision and fewer defects.

With conventional wet chemical etching, the image quality of the etched pattern is poor and it is difficult to form fine patterns. Therefore, dry etching has been proposed as an etching method that eliminates these drawbacks. "Dry etching" means, for example, CF4°C2F6. C.C.
Sentence 2F2. CCC60CHF3゜C2HF5, SFa
A sample is placed in an atmosphere containing an organic halide gas such as oxygen, nitrogen, etc., and high-frequency power is applied to generate a glow discharge.

However, when a chromium-based mask, which has conventionally been widely used in wet etching, is used in a dry etching process, the etching speed is slow, resulting in a decrease in hard mask productivity.

In view of these circumstances, the present inventors have previously proposed a tungsten film as a material with a high etching rate.

However, it has been found that this tungsten mask reacts with alkaline components in the substrate glass, and the altered portions cause etching defects.

TI OBJECTS OF THE INVENTION The main object of the present invention is to provide a dry etching mask material in which etching defects are improved by using a thin film mainly composed of tungsten which has a high dry etching rate.

JP-A-Sho GO-33556 (2) Such objects are achieved by the invention described below.

That is, the present invention is a photomask material for dry etching characterized by having a thin film mainly composed of tungsten on a low-alkali glass substrate having an alkali metal oxide content of 5% by weight or less.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The substrate of the photomask material of the present invention has an alkali metal oxide content of 5% by weight or less, particularly 3% or less, or is made of low alkali glass containing no alkali metal oxide.

In this case, alkali metal oxide (Nap.

If the content of KO, LiO, etc. exceeds 5% by weight, the progress of dry etching is inhibited and the number of dry etching defects increases significantly.

This is because tungsten in the thin film, which will be described later, reacts with water and alkali metal oxides, resulting in Na (w 12046H10) 23 H20 and K (W + 20 a e H1o) -23H2
It is thought that this is because the oxidants form a complex such as 0, etc., and inhibit the progress of the dry etching reaction with organic halides, oxygen, and the like.

On the other hand, if a low alkali glass that does not contain alkali metal oxides or has an alkali metal oxide content of 5% by weight or less is used, the progression of the complex formation reaction described above is prevented, and dry etching defects are prevented. It has good retention properties.

The low alkali glass to be used is in the exposure range (400 to 4
Substantially transparent (transmittance 75% or more) at 50 nm)
;), and there are no other restrictions as long as the alkali metal oxide content is 0 to 5% by weight.

That is, any of borosilicate glass, aluminoborosilicate glass, aluminosilicate glass, quartz glass, etc. may be used.

The light-shielding thin film provided on such a low-alkali glass substrate has tungsten as its main component.

In this case, the thin film may be made of tungsten alone, with Ti in an amount of 50 at% or less.

A tungsten alloy containing one or more of Cr, Ta, etc. may be used.

Furthermore, one or more of nitrogen, oxygen, carbon, etc. may be included. In these cases, the nitrogen content is 50 at% or less, the oxygen content is 30 at% or less, and the carbon content is 30 at% or less.

Note that one or more of nitrogen, oxygen, carbon, etc. may be contained with a uniform concentration distribution in the film thickness direction, or may have a concentration gradient.

That is, in addition to uniform concentrations of nitrogen, oxygen, and carbon over the film thickness direction, a region with a high concentration of nitrogen, oxygen, and carbon, particularly oxygen, may be provided on the surface side opposite to the support.
In such a case, the effect of surface anti-reflection 11 and the effect of improving reprintability occur.

Alternatively, a region with high concentrations of nitrogen, oxygen, and carbon can also be provided on the support side. At this time, the adhesion of the film to the support is improved, and an effect is produced on the back anti-reflection film 1.

These high concentration regions of nitrogen and oxygen on the front side and/or the back side are generally formed under conditions where the average concentration over the entire thin film falls within the above range, with nitrogen at 30 to 50 at% and oxygen at 20 to 7 at%.
It is assumed to be about 0 at%. In addition, its thickness is 10 to 5
It is said that there were about 00 people.

Note that these high concentration regions may be provided as a layer separate from the main body of the thin film.

In addition, between the above thin film and the substrate, or on the thin film, if necessary, other base layers or protective layers of about 10 to 500 layers are separately added for antireflection, stiffness, and film adhesion. may be formed.

Such a thin film is formed by vapor deposition, ion blasting, sputtering, or the like.

There are no particular restrictions on the conditions, method, etc. for these vapor phase depositions.

In this case, in order to contain oxygen and nitrogen in the thin film, sputtering or the like may normally be performed in an atmosphere containing N2,02. In addition, N2.
It is also possible to implant 02 or the like in the form of ions or neutral particles1, or to perform various oxidation or nitridation treatments as post-treatments. Further, in order to contain carbon, a corresponding carbide target may be used.

(2) Specific Effects of the Invention The mask material of the present invention is made into a mask according to the usual dry etching method.

That is, to give one example, first, a photoresist for dry etching is applied to the surface of a thin film of a mask material and prebaked. The next step is to print the image with actinic radiation appropriate for the photoresist, develop it, and expose the surface of the material in an imagewise manner.

Thereafter, the material is washed with water and dry etched using a cylindrical plasma etching device, a parallel plate type reactive ion etching device, or the like to selectively remove a thin film of the material for use in images.

In this case, the dry etching atmosphere is used, for example, CF4, C2F, 00F2F2.

CCC60, C) (Uses a mixture of organic halide gas such as F3, C2HF5, SFa, etc. and 02.N2, etc.). Then, high frequency power is applied to generate glow discharge, and these ions and neutral radicals cause Perform dry etching.The operating pressure is 1O-100
The input power is about 0.05 to 0.5 W/am'.

Next, the photoresist is removed by dry etching in an atmosphere of 02 or the like to produce a mask.

The mask produced in this way has 400 to 45 On
The +* exposure area is useful as a photomask.

(2) Specific Effects of the Invention According to the present invention, the progress of the complex formation reaction between the alkali metal and tungsten is prevented, so that dry etching defects are extremely reduced. That is, even when stored under high temperature and high humidity conditions, there are very few dry etching defects and the storage stability is extremely high.

(2) Specific Examples of the Invention Examples of the present invention will be shown below to explain the present invention in further detail.

Example Pyrex 7740 was used as the substrate.

The content of alkali metal oxide in this glass substrate is 4.
It was 6wt%.

This glass substrate is installed in a sputtering device and
, OX I After exhausting to 0-5 torr, a mixed gas of Ar gas and 02 gas was heated to a pressure of 5 torr,
OXl (introduced until the pressure reached j-3 torr).
The partial pressure of 02 gas in the mixed gas was 5%.

450 between the 7 maid and the cathode of the sputtering equipment
A voltage of V is applied to generate plasma, and a tungsten thin film containing oxygen (oxygen content 10a
t%) was formed.

Subsequently, the partial pressure ratio of oxygen gas was set to 20% and a voltage of 550 V was applied to form a high concentration oxygen-containing tungsten layer (oxygen content 40 at%) on the oxygen-containing tungsten thin film.
300 people were formed.

As described above, 50% of photoresist AZ1350 (manufactured by Silapray) was applied to a blank substrate in which two layers of oxygen-containing tungsten were laminated on a low-alkali substrate.
The resist layer was coated to a thickness of 0.00 mm and heated in air to about 90° C. for about 30 minutes to solidify the resist layer.

The photoresist layer was then exposed and developed to form the desired resist pattern.

Next, using this resist pattern as a mask, the portions of the oxygen-containing tungsten stack not covered by this mask were dry etched to form a pattern as follows.

That is, using a parallel plate plasma etching apparatus, a mixed gas of CF4 gas and 02 gas (gas composition: C
When the laminate was etched using F4:02=19:1), it took 1 minute and 40 seconds.

Note that the gas pressure was 40 pa and the high frequency output was 150 W.

After forming a pattern on the thin film in this manner, the resist was removed as described below to produce a mask.

That is, when the resist on the pattern was removed using 02 gas using a parallel plate plasma etching apparatus, it took 3 minutes.

Note that the gas pressure was 120 pa, and the high frequency output was 300 W.

1 Comparative Example As a comparative example, a mask was formed in the same manner as in the example except that a soda glass substrate (alkali content 30%) was used as the substrate.

In the above Examples and Comparative Examples, after the photomask material was prepared, it was stored at 50°C and 50% relative humidity for one week, and after storage, a photoresist layer was applied, and the photoresist layer was exposed to fog light over the entire surface. A mask was formed.

In the comparative example, as shown in FIG. 1, it can be seen that the portions that should have been etched were not etched at the peripheral edge.

On the other hand, according to the above example, etching was performed uniformly over the entire mask area, and there were no etching defects at all.

2

[Brief explanation of the drawing]

FIG. 1 is a photograph showing the structure of a comparative photomask material after dry etching. Applicant Konishi Roku Photo Industry Co., Ltd. Agent Patent Attorney Yo Ishii - taX Figure 7. Contents of Supplementary IF Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 143529, filed in 1982,2, Name of the invention, photomask material for dry etching3, Person making the amendment, Relationship to the case, Appointment of patent applicant. Address: 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name:
(127) Konishiroku Photo Industry Co., Ltd. Representative Nobuhiko Yomoto 4, Agent 171 Address 1st floor, Yabe Building, 5-17-11 Nishiikebukuro, Toshima-ku, Tokyo Telephone 988-1680 November 29, 1988
Date (Shipping) 6. The column ``3. Detailed explanation of the invention j'' of the specification subject to amendment is amended as follows. After "Material", insert 1n (50X50 Upeng)j. 2) On page 13, line 1O to line 12, the phrase "In the comparative example, it can be seen that..." was replaced with "In the comparative example, 2 to 5 An unetched area of the intestinal gyrus has occurred. Correct it as j. Delete. ■ Delete the drawing "Figure 1".

Claims (1)

[Claims] (2) A photomask material for dry etching, characterized by having a thin film containing tungsten as a main component on a low-alkali glass substrate with an alkali metal oxide content of 5% by weight or less.