JPH0690502B2 - Photomask blank manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a photomask blank, which is a material for a photomask.

<Prior Art> A photomask blank is one in which a light-shielding film is formed on the surface of a transparent substrate, and the light-shielding film is formed into a predetermined pattern to form a photomask.

The pattern formation is usually performed by a photolithography method. That is, the resist film formed on the surface of the light-shielding film is formed into a predetermined pattern and then subjected to etching to pattern the light-shielding film corresponding to the pattern.

In general, a glass substrate is used as the transparent substrate, and chromium formed by a vacuum deposition method or a sputtering method is used as the light shielding film, which is manufactured by the steps shown in FIGS.

That is, the light-shielding film 2 of a metal chromium film is formed on the glass substrate 1 by vacuum deposition or sputtering.

<Problems to be Solved by the Invention> The light-shielding film of chromium that is generally used is not sufficient in terms of chemical and mechanical durability, and the mask pattern is used during the photomask manufacturing process or photomask cleaning. There is a defect that defects such as a lack of are generated. Further, metallic chromium has a high surface light reflectance of the light shielding film, which is inconvenient in the wafer process.

An object of the present invention is to provide a manufacturing method capable of forming a light-shielding film composed of a chromium layer having excellent chemical and mechanical durability and low surface light reflectance.

<Means for Solving the Problems> The present invention provides a method of manufacturing a photomask blank, which comprises a step of forming a light-shielding film made of a chromium layer on the surface of a glass substrate by vacuum deposition, sputtering or the like. After-before forming the resist film, the method further comprises the step of subjecting the surface of the light-shielding film to plasma treatment to form a chromium compound layer made of an oxide film or a nitride film on the surface of the light-shielding film.

<Operation> By performing the plasma treatment, it is possible to improve the mechanical durability of the light-shielding film made of a metal chromium film, and it is possible to reduce the reflectance of the light-shielding film.

Further, by performing the plasma treatment, the residual organic substances on the surface of the light-shielding film are removed, and the adhesion with the resist film formed in a later step is improved.

<Example> Hereinafter, an example of a method for manufacturing a photomask blank of the present invention will be described with reference to the drawings.

1A to 1C are explanatory views showing an example of a method of manufacturing a photomask blank according to the present invention in the order of steps, and FIG. 3 is an explanatory view of a parallel plate type plasma surface treatment apparatus.

On the glass substrate 10 shown in FIG. 1a, a chromium metal film layer of about 1000 Å is formed by vacuum deposition or sputtering as in the conventional method.
11 is formed as shown in FIG. 1b.

Next, the substrate 12 having the metal chromium layer is placed in the plasma surface treatment apparatus 20 as shown in FIG. 3, and plasma is generated by high frequency discharge of about 13.56 MHz in the oxygen gas atmosphere, and the metal chromium layer 11 is formed. The reaction of the surface of the. As a result, a substrate 14 having a plasma treated film layer 13 obtained by oxidizing the surface of the metallic chromium layer 11 as shown in FIG. 1C is obtained.

In FIG. 3, a table 22 is provided in the vacuum processing chamber 21.
Is installed, the upper electrode 24 is installed above the table, and the lower electrode 23 is installed below the table. When performing the plasma processing, the target material is deposited on the table, the processing chamber 21 is first evacuated to a vacuum, and oxygen gas is introduced from the gas introduction port 26, while being exhausted from the exhaust port 27 to exhaust the inside of the processing chamber. Keep pressure constant. Therefore, plasma processing is performed by performing high-frequency discharge from the high-frequency power supply 25.

Further, it is possible to form a nitride film or a compound film by using nitrogen gas or a gas containing oxygen or nitrogen instead of oxygen gas.

The plasma-treated film (chromium compound layer) formed by the above method is an oxide film or nitride film that is thicker than the conventional passive film formed by natural oxidation, and has improved mechanical strength.

For example, a metallic chromium film that has been plasma treated under the conditions of oxygen gas flow rate 100 [SCCM] and pressure 0.1 [Torr] is 2500
In the high pressure water cleaning (75 times repeated) of [PSI], the number of pinhole defects generated in the metallic chromium film without plasma treatment was 1.7 [pieces / cm ² ], whereas it was 0.9 [pieces / cm ² ].
And significantly decreased.

Furthermore, oxygen gas flow rate 50-150 [SCCM], pressure 0.1-1.0
The reflectance of the metallic chromium film subjected to the plasma treatment under the condition of [Torr] was reduced to less than 5% as compared with the metallic chromium film of high reflectance not subjected to the plasma treatment.

In addition, the shape of the metallic chromium pattern after etching the metallic chromium film having such a plasma treated film by the conventional wet etching method was not different from that of the case where the plasma treatment was not performed.

<Effects of the Invention> The present invention is excellent in both chemical and mechanical durability,
There is provided a manufacturing method capable of forming a light shielding film made of a chromium layer having a low surface light reflectance.

Further, it is clear from the fact that the shape of the metallic chromium pattern after etching the metallic chromium film having the plasma-treated film by the conventional wet etching method in the subsequent step was not changed from that in the case where the plasma treatment was not performed. As described above, the etching suitability in the case where the light shielding film is subjected to the plasma treatment is the same as that in the conventional case where the plasma treatment is not performed. Therefore, the photomask blank according to the present invention can be applied to the production of a photomask using conventional equipment in the subsequent process.

[Brief description of drawings]

The drawings show an embodiment of the invention, which is illustrated in FIGS.
c is an explanatory view showing an embodiment of a method for manufacturing a photomask blank in the order of steps, and FIGS. 2A and 2B are views for explaining a conventional technique. It is explanatory drawing which shows an example in order of process. FIG. 3 is an explanatory view showing an example of the plasma surface treatment apparatus used in the present invention. 10 …… Glass substrate 11 …… Light-shielding film layer 12 …… Photomask blank before forming conventional resist coating 13 …… Plasma treatment film layer 14 …… Photomask blank after plasma treatment film formation

Claims (1)

[Claims] 1. A method of manufacturing a photomask blank comprising a step of forming a light-shielding film made of a chromium layer on the surface of a glass substrate by vacuum deposition or sputtering, after the formation of the light-shielding film-before forming the resist film, A method of manufacturing a photomask blank, comprising a step of subjecting the surface of the light-shielding film to plasma treatment to form a chromium compound layer made of an oxide film or a nitride film on the surface of the light-shielding film.