Method of manufacturing photomask

1. A method of manufacturing a photomask, the method comprising:

forming a mask pattern on a transparent substrate, the mask pattern includes a first film including a first material and a second film including a second material different from the first material, the first film being on the substrate and the second film being on the first film;

conformally forming a protective layer on a top of the transparent substrate, a side wall of the mask pattern, and a top of the mask pattern; and

forming a protective layer pattern on the side wall of the mask pattern by patterning the protective layer, wherein the patterning of the protective layer includes exposing the top of the mask pattern and the top of the transparent substrate.

2. The method as claimed in claim 1 , wherein the patterning of the protective layer includes patterning the protective layer by an anisotropic etching process.

3. The method as claimed in claim 1 , wherein an etching rate of the protective layer pattern to H 2 SO 4 and/or NH 4 OH is lower than that of the mask pattern.

4. The method as claimed in claim 1 , wherein the forming of the protective layer includes forming the protective layer through an atomic layer deposition (ALD) process.

5. The method as claimed in claim 1 , wherein:

a width of the second film is larger than a width of first film, the width of the first film and the width of the second film being measured in a direction parallel to the transparent substrate and perpendicular to the side wall of the mask pattern.

6. The method as claimed in claim 1 , wherein:

the protective layer pattern includes a first area and a second area,

the first area is closer to the transparent substrate than the second area, and

a width of the first area is larger than a width of second area, the width of the first area and the width of the second area being measured in a direction parallel to the transparent substrate and perpendicular to the side wall of the mask pattern.