JPS5962854A - Production of photomask - Google Patents

Abstract

PURPOSE:To improve the manufacturing efficiency and quality of a photomask by introducing a treatment using a surfactant in place of post baking and subjecting the original mask plate treated by the surfactant to an etching treatment. CONSTITUTION:A positive type photoresist is coated and formed on the mask layer of a mask substrate. The resist is then subjected to prebaking for about 20min at 90 deg.C. Said layer is then exposed by using an exposing device and is subjected to developing and rinsing treatments in succession. The mask treated in such a way is treated by a surfactant. The treatment may be made by either spraying of a surfactant soln. or dipping the mask substrate in said soln. and the treatment time may be about 20sec. Since the hydrophilic property of the mask substrate is improved by the treatment with the surfactant, the etching treatment is smoothly progressed and the satisfactory result of etching is obtd. The shortest possible time since the completion of the developing treatment until the etching of the mask layer is started is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention makes it possible to efficiently manufacture photomasks used in the manufacture of semiconductor devices, etc., and further improves the quality of the photomasks. This invention relates to a method for manufacturing a mask.

Conventional structure and its problems Photomasks are frequently used in the photolithography process that is essential in the production of semiconductor devices, and the quality of this photomask has a bearing on the quality of the characteristics of the semiconductor device manufactured as is. do. For this reason, high quality photomasks are strongly required. As the degree of integration of semiconductor integrated circuits increases as in recent years, the finer measurements of patterns have become more advanced, and the patterns of photomasks used to manufacture the circuits have also become finer. When mask patterns are miniaturized in this way, even slight defects cannot be ignored.

In fact, the cost of producing a photomask is quite high due to the high cost of the equipment used to produce it. Therefore, by increasing the production efficiency, the total cost of producing a photomask can be reduced, and ultimately the cost of producing a photomask can be reduced. It is also important to reduce the cost of semiconductor devices and the like.

A conventional method for manufacturing a chrome mask will be described below with reference to FIG. First, as shown in FIG. 1(a), a mask substrate is prepared in which a chromium layer 2 of a predetermined thickness is formed on the main surface of a glass plate 1 that will serve as a mask substrate, and a resist layer 3i is applied and formed on this. After this, a heat treatment (prebaking) is performed to remove the solvent remaining in the resist layer 3.

Next, the resist layer 3 is exposed using an exposure device and further developed to form a resist pattern 4, and then the adhesion between the chromium layer 2 and the resist pattern 4 thereon is strengthened and the exposed chromium layer portion is removed. A post-bake process is performed to remove impurities on the surface. FIG. 1(b) is a diagram showing the state after the above process.

In this way, the chrome layer 2 of the mask substrate with the resist pattern 4 of a predetermined shape formed on the chrome layer 2 is subjected to an etching process using the entire resist pattern 4 as a mask, and finally, the resist pattern 4 is removed. By doing so, a chrome pattern 5 shown in FIG. 1(C) is formed.

In the conventional method, a photomask has been manufactured through the basic manufacturing process described above. According to this method, the photomask shown in FIG. 1(C) can basically be manufactured.

However, in the conventional method, if dust or the like adheres to the exposed chromium layer 2 after exposure and development, this will be baked in during post-baking, and the etching process of the chromium layer 2 carried out after this will remove the dust from the mask. This results in the inconvenience of chromium remaining on the surface.

FIG. 2 is a diagram for explaining the occurrence of this inconvenience, and FIG. 2(a) shows the state after the resist layer 3 is coated and formed similarly to FIG. 1(a).

Thereafter, a resist pattern is formed through bleed, exposure, and development processes. By the way, as shown in FIG. 2 (1)), the exposed chromium layer 2 is removed before the boss peeling process.
If a substance 6 such as dust adheres thereto, it may be burned in the post-baking process and remain on the 1-inch chromium layer 2.

The material 6 baked in this way acts equivalently to the resist pattern 4 in the etching process of the chromium layer 2 carried out after post-baking, and therefore acts as a resist pattern 4 in FIG.
), a chromium layer residue 7 is formed in a portion where a chromium layer should not originally exist. Therefore, in the conventional method, it is necessary to perform sufficient post-bake pretreatment and to ensure environmental conditions that can completely eliminate the adhesion of dust and the like.

was extremely important. Further, post-baking requires a considerable amount of time, and workability is significantly impaired by the above-mentioned pretreatment and this post-baking.

Purpose of the Invention The present invention aims to eliminate the problems of the conventional methods described above, that is, the inconveniences associated with post-baking, and to improve the manufacturing efficiency and quality of photomasks. A method for manufacturing a mask is provided.

Structure of the Invention In the photomask manufacturing method of the present invention, the post-bake performed in the conventional method is eliminated from the first mask manufacturing process, and the post-bake is replaced by a treatment with a surfactant. At the same time, the mask original plate treated with the surfactant is subjected to an etching process. According to the method of the present invention, although the post-baking treatment that strengthens the adhesion of the resist layer is removed, the treatment with a surfactant improves the compatibility with the mask layer to be etched. Etching proceeds smoothly and a predetermined mask pattern can be formed without causing any inconvenience such as peeling off of the resist layer.

DESCRIPTION OF EMBODIMENTS An example of manufacturing a chrome mask using the manufacturing method of the present invention will be described below.

A chromium layer and an oxidized chromium layer are successively deposited on a glass plate with a thickness of about 2.3 degrees. A mask substrate having a mask layer having a total thickness of approximately 900 layers is prepared.

On the mask layer of this mask substrate, a positive resist commercially available as AZ 1350 from 5hipley Co., Ltd. is coated to a thickness of about 5,000 mm. The thickness of this resist layer is the standard thickness (approximately 400 mm) selected using the conventional manufacturing method using wet etching.
It's a shame that Yoshi has been selected to be more than 20% thick. That is, in the method of the present invention, since the post-baking process is omitted, the film quality of the resist layer is not densified by the post-baking process. Therefore, by selecting a thick film as described above, the occurrence of defects such as pinholes is suppressed. By selecting the thickness as described above, the number of defects generated in the resist layer was extremely small, similar to when post-baking was performed.

Next, the resist layer is prebaked at a temperature of 90"C for about 20 minutes. Thereafter, it is exposed to light using an exposure device, and then exposed, imaged, and washed with water.

A surfactant (e.g. ethylene glycol), which is a feature of the method of the present invention, is applied to the mask original plate that has undergone the above two treatments.
Processing is performed. This treatment d: may be performed by either spraying a surfactant liquid or immersing the mask substrate in the same liquid, and the treatment time may be about 20 seconds. After this, an etching process 'ff: is performed, but since the hydrophilicity of the mask substrate is enhanced by the treatment with a surfactant, the etching process proceeds smoothly and good etching results can be obtained.

Note that ceric ammonium nitrate was used as the etching solution, and etching of the mask layer was completed in about 30 to 40 seconds. By the way, it is best to wait as much time as possible to start etching the mask layer after the development process is completed. Good results were obtained by starting. If this time becomes longer, problems such as peeling of the resist layer may occur.

Next, the resist layer that served as an etching mask is removed, thereby completing the production of the photomask according to the manufacturing method of the present invention.

However, in the conventional method of Boss i/Bake kFm, fuming nitric acid or the like was used to remove the resist.
In the method of the present invention, which eliminates post-bake, caustic potash (KO
Removal was possible with a solution of H).

Effects of the Invention In the photomask manufacturing method of the present invention described above with reference to the embodiments, post-baking of the resist layer, which is conventionally required, is omitted. Finally, the inconvenience of dust and the like being baked in during the post-baking process and resulting in mask layer residue should be completely eliminated. In fact, the heating device required for post-baking is no longer required, and the time-consuming post-baking process is omitted, which improves work efficiency and reduces manufacturing costs.

Furthermore, since the resist layer can be removed using caustic potash solution instead of fuming nitric acid, work safety is also greatly improved.

In addition, although the above description has exemplified a case where the mask layer has a two-layer structure consisting of all chromium and chromium oxide, the mask layer may be similarly applied to a case where the mask layer is formed only of a chromium oxide layer. The present invention can be applied not only to a full-wavelength shielding type photomask such as a chrome mask that completely blocks the projection light for exposure, but also to a method for manufacturing a partial wavelength shielding type photomask.

[Brief explanation of the drawing]

Figures 1 (a) to (C) are diagrams for explaining the photomask manufacturing process, and Figures 2 (a) to (C) explain chromium residue, which is a cause of post-baking on the resist layer. This is a diagram for 1...Glass substrate, 2...Chromium layer (
mask layer), 3...resist layer, 4...
・Resist pattern, 6...Chrome pattern,
6...Dust, A...Chromium remains. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 17J1 3 2 7! Ic) 6. , s σ Fig. 2

Claims (2)

[Claims] (1) After pre-baking a single layer of resist covering the mask layer formed on the mask substrate, the resist layer is exposed and developed to form a predetermined resist pattern, and then the resist pattern and... 1. A method for manufacturing a photomask, which comprises treating a portion of a mask layer that is exposed without being covered with a surfactant, and then etching and removing the entire portion of the mask layer to form a mask pattern. (2) The method for manufacturing a photomask according to claim 1, wherein etching of the mask layer is started within one minute after the development of the resist layer.