JPH02212843A - Photomask blank, photomask and production thereof - Google Patents

Abstract

PURPOSE:To lower reflectivity by adding further gaseous carbon sources, such as CH4 and CF4, in addition to nitrogen and oxygen into argon at the time of lamination of a reflection preventing film. CONSTITUTION:The surface low-reflection photomask blank is produced by successively laminating a light shieldable film and the reflection preventing film consisting of a chromium carbide-contg. chromium oxynitride on a light transparent substrate. The reflection preventing film is formed by adding further the gaseous carbon sources in addition to the nitrogen and oxygen into the argon at the time of sputtering of the reflection preventing film in this case. Although the etching rate is lowered in this way, the reflectivity is lowered and the lower reflectivity is easily attained with good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photomask blank with a low surface reflection for semiconductor manufacturing, a photomask produced from the blank, and a method for producing the same.

[Prior Art and its Problems] A photomask blank is a base material for producing a photomask used for pattern exposure of IC1LSI. It is produced by laminating films on glass using a thin film forming device such as a sputtering device.

The lower the surface reflectance is, the more preferable it is in order to prevent halation during exposure.

When sputtering chromium metal, nitrogen and oxygen are added to argon to form a chromium oxynitride film. A photomask blank with low surface reflection is formed by forming a chromium oxynitride film on a chromium film in this manner.

When sputtering chromium metal with a gas mixture of nitrogen and oxygen in argon, the reflectance easily decreases to 12-13%, but in order to decrease it below this level, it is necessary to reconsider the concentration range over a fairly wide range. is necessary.

In this way, it may be possible to reduce the reflectance to 10% or less, but with conventional methods, in order to achieve low reflectance with good reproducibility, it is necessary to check the reflectance during sputtering and to check the reflectance when the reflectance is high. This required complicated operations such as film formation while adjusting gas conditions and other equipment parameters.

Therefore, it has been expected that there will be a means to lower the reflectance much more easily and with better reproducibility than conventional methods, and a photomask blank with low surface reflection produced using this method.

Means for Solving Problem C] As a result of intensive studies to solve the problem, the inventors of the present invention found that in addition to adding nitrogen and oxygen to argon when laminating the antireflection film, CH4, CF, Adding a gaseous carbon source such as
It was discovered that the reflectance at 8ni can be easily reduced to a film thickness of 2GO to 300mm, and the present invention was completed.

[Effects] Although the details of the cause are still unknown, it is assumed that the cause is that chromium oxynitride containing chromium carbide is formed and the refractive index decreases.

Low surface reflection blanks are commercially available from Hoya Wholesale, Dainippon Bohishin Co., Ltd., and ULVAC Co., Ltd. (I). All products basically have the same configuration.
/1. It consists of a light film/transparent substrate. In the chromium film, carbon, nitrogen, oxygen, whelk, etc. are added to chromium. Excessive use of additives lowers the light absorption coefficient and inhibits the luminosity.

In anti-reflection films, more nitrogen and oxygen are usually added to chromium than in reflective films. In addition to nitrogen and oxygen,
Furthermore, there is a disclosure of fluorine-added products (Unexamined Japanese Patent Application Publication No. Sho EI
3-32553). The purpose of adding fluorine is to reduce the etching rate and to reduce the adverse effects caused by etching rate mismatching with the photoluminescent film. As the amount of nitrogen and oxygen added to chromium increases, the etching rate also increases (.

The present inventors have already recognized the fact that the etching rate in the depth direction of the antireflection film is 100 to 200 λ/sea, while the etching rate of the optical layer is an order of magnitude smaller at 10 to 20 people/sec. . On the side edges of the anti-reflective coating,
At this rate, there is no progress, rather it is slow. Therefore, the present inventors focused on the reflectance reduction effect and completed the present invention.The anti-reflection film of the photomask blank is an "uneven film" whose refractive index changes in the depth direction, and the surface The reflectance is determined by the mismatching of the refractive index at the upper and lower interfaces. Therefore, the problem is matching with the underlying chromium and matching with the air above, but in this project, the latter is the problem, and in order to improve the matching, the refractive index at the film surface should be made as close to I as possible. becomes important.

Adding a gaseous carbon source to argon according to the method of the present invention reduces the etching rate, but also reduces the reflectance;
Low reflectance can be achieved easily and with good reproducibility.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Fused quartz substrate for photomask (5″ square, 0.08°t)
After processing by a normal cleaning method, the substrate was set in a DC magnetron sputtering device. Residual gas pressure! ,
After evacuation to 5X10-' Torr, argon gas was introduced and reverse sputtering was performed at a pressure of ~2X10-' Torr (high frequency of 13.56 Mz, with the substrate side as the cathode). After cleaning for about 5 minutes, the tube was cleaned again. Exhaust, 1
．． It was evacuated to 5XIO-' Torr. Next, a chromium metal target was press-battered for 5 minutes (Ar gas pressure 2 Xl0-
'Torr), then introduce gases at a flow rate of argon 45SC (11, nitrogen Scc) and 2~3XlO-'
Torr), a chromium layer of about 700 people was formed.

Thereafter, 35 acs of oxygen and 25 ccm of methane were further introduced, and after forming the first layer, pre-sputtering was performed under the same sputtering conditions without breaking the vacuum, and then main sputtering was performed to form about 300 chromium oxynitride layers. The surface reflectance of the photomask blank thus obtained was measured (
When I tested it using a new model 34G spectrophotometer manufactured by Hitachi, I found that it was 436.
8% at 01, 259A at 700nm,
A reflectance 4 to 5% (at 436 nm) lower than that of the conventional method was obtained. It was found that by adding methane, the same reflectance was obtained every time, and that this significantly improved reproducibility compared to the case without the addition of methane.

[Effects of the Invention] According to the implementation of the present invention, it is much easier to achieve a low reflectance than in the past, and the reproducibility thereof is also good. With conventional techniques, achieving a low reflectance has poor reproducibility and requires complicated operations such as checking the reflectance and, if the reflectance is high, depositing a film while adjusting gas conditions and other equipment parameters.

According to the present invention, low reflectance can be achieved stably and with good reproducibility, so there is an advantage that these complicated operations can be omitted.

Further, according to the present invention, a relatively good low reflectance value can be obtained compared to the conventional method.

Patent applicant: Toppan Printing Co., Ltd.

Claims (4)

[Claims] (1) A photomask blank with low surface reflection, which is made by sequentially laminating a glossy film and an antireflection film made of chromium carbide-containing chromium oxynitride on a transparent substrate. (2) A photomask with low surface reflection, which is formed by forming a pattern on a translucent substrate, with a glossy film and an antireflection film made of chromium carbide-containing chromium oxynitride. (3) A method for manufacturing a photomask blank with low surface reflection, which comprises sequentially laminating a glossy film and an antireflection film made of chromium carbide-containing chromium oxynitride on a transparent substrate, the method comprising: A manufacturing method characterized by adding a gaseous carbon source to argon in addition to nitrogen and oxygen during sputtering to form a film. (4) A method for manufacturing a photomask with low surface reflection, which comprises sequentially laminating a glossy film and an antireflection film made of chromium carbide-containing chromium oxynitride on a transparent substrate,
A manufacturing method characterized by adding a gaseous carbon source to argon in addition to nitrogen and oxygen when sputtering an antireflection film.