Optical mask using phase shift and method of producing the same

Claim 1

A phase shift optical mask used for exposing a pattern using an exposure light, said phase shift optical mask comprising a substrate (1, 6) which is transparent with respect to the exposure light; and a light blocking layer (2, 3; 7, 8) which is non-transparent with respect to the exposure light and is provided on said substrate, characterized in that said light blocking layer (2, 3; 7, 8) has an opening (5, 10) which has a predetermined shape and size and is defined by a side wall of said light blocking layer; that there is provided a phase shift layer (4, 9) which is transparent with respect to the exposure light and is provided on said light blocking layer and said substrate (1, 6) which is exposed within the opening, that said phase shift layer has a uniform thickness, and that said light blocking layer (2, 3; 7, 8) has a predetermined thickness (PS) so that a phase of the exposure light transmitted through said phase shift layer (4, 9) provided on the side wall of said light blocking layer is shifted by approximately 180° relative to a phase of the exposure light transmitted through said phase shift layer provided on said substrate (1, 6).

Claim 11

A method of producing a phase shift optical mask which is used for exposing a pattern using an exposure light, characterized in that said method comprises the steps of: (a) forming an opening (5, 10) in a light blocking layer (2, 3; 7, 8) which is provided on a substrate (1, 6), said light blocking layer being non-transparent with respect to the exposure light, said substrate being transparent with respect to the exposure light, said opening having a predetermined shape and size defined by a side wall of said light blocking layer; and (b) forming a phase shift layer (4, 9) which is transparent with respect to the exposure light on said light blocking layer and said substrate which is exposed within the opening, said phase shift layer being formed to a uniform thickness, said light blocking layer having a predetermined thickness (PS) so that a phase of the exposure light transmitted through said phase shift layer provided on the side wall of said light blocking layer is shifted by approximately 180° relative to a phase of the exposure light transmitted through said phase shift layer provided on said substrate.

Claim 15

The method as claimed in any of claims 11 to 14, characterized in that said step (b) forms said phase shift layer (4, 9) so that the thickness of said phase shift layer on said substrate (1, 6), the thickness of said phase shift layer on said light blocking layer (2, 3; 7, 8) and the thickness of said phase shift layer on the side wall of said light blocking layer are identical.

Claim 16

A method of producing a phase shift optical mask used for exposing a pattern on a wafer via an exposure lens using an exposure light, characterized in that said method comprises the steps of: (a) forming an opening which has a width 1.5m λ/NA in a first light blocking layer (46) which is provided on a substrate (41), said first light blocking layer being non-transparent with respect to the exposure light, said substrate being transparent with respect to the exposure light, where m denotes a reducing projection magnification, L denotes a width of an opening actually developed on the wafer, λ denotes a wavelength of the exposure light and NA denotes a numerical aperture of an exposing lens; (b) forming a first phase shift layer (45) on the first light blocking layer and the substrate which is exposed within the opening, said first phase shift layer being transparent with respect to the exposure light and having a stepped part in correspondence with the opening, said first phase shift layer having a thickness 0.1m λ/NA on a side wall of the first light blocking layer defining the opening; (c) forming a second light blocking layer (44) on the first phase shift layer, said second light blocking layer being non-transparent with respect to the exposure light and having a thickness 0.1m λ/NA on a side wall of at the stepped part of the first phase shift layer; and (d) forming a second phase shift layer (43) on a side wall of the second light blocking layer on the first phase shift layer, said second phase shift layer being transparent with respect to the exposure light and having a width (m λ/2NA)[1.1 - (NA/λ)(L + 0.2 λ/NA)].

Claim 19

The method as claimed in any of claims 16 to 18, characterized in that said step (b) includes the substeps of forming the first phase shift layer (45) on the first light blocking layer (46) and the substrate (41) which is exposed within the opening, and etching back the first phase shift layer so that the first phase shift layer has the thickness 0.1mλ/NA on the side wall of the first light blocking layer defining the opening.

Claim 20

The method as claimed in any of claims 16 to 19, characterized in that said step (c) includes the substeps of forming the second light blocking layer (44) on the first phase shift layer (45), and etching back the second light blocking layer so that the second light blocking layer has the thickness 0.1m λ/NA on the side wall of at the stepped part of the first phase shift layer.

Claim 21

The method as claimed in any of claims 16 to 20, characterized in that said step (d) includes the substeps of forming the second phase shift layer (43) on the side wall of the second light blocking layer (44) on the first phase shift layer (45), and etching back the second phase shift layer so that the second phase shift layer has the width (mλ/2NA)[1.1 - (NA/λ)(L + 0.2λ/NA)].

Claim 22

The method as claimed in any of claims 16 to 21, characterized in that said step (d) includes forming an opening in the second and first phase shift layers (43, 45) to expose the substrate (41) so that the second phase shift layer formed on the side wall of the second light blocking layer has the width (mλ/2NA)[1.1 - (NA/λ)(L + 0.2λ/NA)].