Attenuated phase shift mask and process for fabricating such a mask

Claim 2

The attenuated phase shift mask of Claim 1 wherein said first layer comprises a material selected from the group consisting of metals and metal oxides.

Claim 3

The attenuated phase shift mask of Claim 2 wherein said first layer comprises a material selected from the group consisting of chromium, molybdenum, polysilicon, silicon nitride, titanium oxide, and selenium oxide.

Claim 4

The attenuated phase shift mask of Claim 3 wherein said first layer consists essentially of chromium and has a thickness within the range of about 25 to 75 nm for an incident wavelength of 365 nm.

Claim 5

The attenuated phase shift mask of Claim 1 wherein said desired phase shift is 180°.

Claim 6

The attenuated phase shift mask of Claim 5 wherein said second layer comprises a material selected from the group consisting of oxides and polymers.

Claim 7

The attenuated phase shift mask of Claim 6 wherein said second layer consists essentially of silicon dioxide and has a thickness within the range of about 400 to 450 nm for an incident wavelength of 365 nm.

Claim 8

An attenuated phase shift mask providing a phase shift of 180°, comprising (a) a first layer formed on a transparent substrate, said first layer consisting essentially of chromium, having a transmission within the range of about 3 to 10%, and having a thickness within the range of about 25 to 75 nm for an incident wavelength of 365 nm, and (b) and a second layer formed on said first layer, said second layer consisting essentially of silicon dioxide and having a thickness within the range of 400 to 450 nm for an incident wavelength of 365 nm.

Claim 9

A process for fabricating an attenuated phase shift mask comprising a first layer having a transmission in the range of about 3 to 10% formed on a transparent substrate and a second layer comprising a transparent material having a thickness to provide a desired phase shift and formed on said first layer, said process comprising: (a) providing said transparent substrate; (b) forming said first layer on a surface of said transparent substrate; (c) forming said second layer on said first layer; (d) forming a masking layer on said second layer; (e) patterning and etching said masking layer to expose portions of said second layer; (f) etching through said exposed portions of said second layer to form first openings and to expose portions of said first layer; (g) removing said masking layer; and (h) etching through said exposed portions of said first layer to form second openings.

Claim 10

The process of Claim 9 wherein said first layer comprises a material selected from the group consisting of metals and metal oxides.

Claim 11

The process of Claim 10 wherein said first layer comprises a material selected from the group consisting of chromium, molybdenum, polysilicon, silicon nitride, titanium oxide, and selenium oxide.

Claim 12

The process of Claim 11 wherein said first layer consists essentially of chromium and is deposited to a thickness within the range of about 25 to 75 nm for an incident wavelength of 365 nm.

Claim 13

The process of Claim 9 wherein said desired phase shift mask is 180°.

Claim 14

The process of Claim 13 wherein said second layer comprises a material selected from the group consisting of oxides and polymers.

Claim 15

The process of Claim 14 wherein said second layer consists essentially of silicon dioxide and has a thickness within the range of about 400 to 450 nm for an incident wavelength of 365 nm.

Claim 16

The process of Claim 15 wherein said oxide layer is etched by a dry etching process to provide substantially vertical walls defining said first openings.

Claim 17

The process of Claim 15 wherein said oxide layer is etched by an isotropic wet etching process to provide substantially parabolically-profiled walls defining said first openings.

Claim 18

A process for fabricating an attenuated phase shift mask providing a phase shift of 180°, said attenuated phase shift mask comprising (a) a first layer formed on a transparent substrate, said first layer consisting essentially of chromium, having a transmission in the range of about 3 to 10%, and having a thickness within the range of about 25 to 75 nm for incident light of 365 nm, and (b) a second layer formed on said chromium layer, said second layer consisting essentially of silicon dioxide and having a thickness within the range of about 400 to 450 nm for incident light of 365 nm, said process comprising: (a) providing said transparent substrate; (b) forming said chromium layer on a surface of said transparent substrate; (c) forming said silicon dioxide layer on said chromium layer; (d) forming a photoresist masking layer on said silicon dioxide layer; (e) patterning and etching said photoresist masking layer to expose portions of said silicon dioxide layer; (f) etching through said exposed portions of said silicon dioxide layer to form first openings and to expose portions of said chromium layer; (g) removing said photoresist masking layer; and (h) etching through said exposed portions of said chromium layer to form second openings.

Claim 19

The process of Claim 18 wherein said silicon dioxide layer is etched by a dry etching process to provide substantially vertical walls defining said first openings.

Claim 20

The process of Claim 18 wherein said silicon dioxide layer is etched by an isotropic wet etching process to provide substantially parabolically-profiled walls defining said first openings.