CPL mask and a method and program product for generating the same

1. A method of forming a mask for printing a pattern comprising a plurality of features, said method comprising the steps of:

depositing a layer of transmissive material having a predefined percentage transmission on an upper surface of a mask substrate;

depositing a layer of opaque material on said transmissive material;

etching a portion of said mask substrate to achieve a partial etching depth less than a target depth, said partial etching depth being based on an etching selectivity between said transmissive layer and said mask substrate;

exposing a portion of said patterned transmissive layer by etching said opaque material; and

etching said exposed portion of said transmissive layer so as to expose a portion of said upper surface of said mask substrate from underneath the patterned transmissive layer, said etched portion of said mask substrate being further etched along with said transmissive layer, thereby achieving the target depth;

wherein said exposed portion of said upper surface of said mask substrate and said etched portion of said mask substrate further etched along with said transmissive layer exhibit a predefined phase shift relative to one another with respect to an illumination signal impinging on the mask.

2. The method of forming a mask according to claim 1 , wherein said partial etching depth of said mask substrate is equal to the target depth minus a predefined delta, said predefined delta corresponding to a thickness of said transmissive layer times the etching selectivity between said transmissive layer and said mask substrate.

3. The method of forming a mask according to claim 1 , wherein said layer of opaque material comprises chrome.

4. The method of forming a mask according to claim 1 , wherein said transmissive layer comprises MoSiON.

5. The method of forming a mask according to claim 1 , wherein said transmissive layer has a percentage transmission in the range of 5 to 12 percent.

6. The method of forming a mask according to claim 1 , wherein said opaque material operates as a hard mask during the etching of said mask substrate.

7. The method of forming a mask according to claim 1 , wherein said etched portion of said mask substrate forms a background portion of said mask, said background portion being a clear field.

8. A device manufacturing method comprising the steps of:

(a) providing a chip substrate that is at least partially covered by a layer of radiation-sensitive material;

(b) providing a projection beam of radiation using an imaging system;

(c) forming a mask utilized to endow the projection beam with a pattern in its cross-section;

(d) projecting the patterned beam of radiation onto a target portion of the layer of radiation-sensitive material,

wherein, in step (c), said mask is formed by a method comprising the steps of:

depositing a layer of transmissive material having a predefined percentage transmission on an upper surface of a mask substrate;

depositing a layer of opaque material on said transmissive material;

etching a portion of said mask substrate to achieve a partial etching depth less than a target depth, said partial etching depth being based on an etching selectivity between said transmissive layer and said mask substrate;

exposing a portion of said patterned transmissive layer by etching said opaque material; and

etching said exposed portion of said transmissive layer so as to expose a portion of said upper surface of said mask substrate from underneath the patterned transmissive layer, said etched portion of said mask substrate being further etched along with said transmissive layer, thereby achieving the target depth;

wherein said exposed portion of said upper surface of said mask substrate and said etched portion of said mask substrate further etched along with said transmissive layer exhibit a predefined phase shift relative to one another with respect to the beam of radiation impinging on the mask.

9. The method of forming a mask according to claim 8 , wherein said partial etching depth of said mask substrate is equal to the target depth minus a predefined delta, said predefined delta corresponding to a thickness of said transmissive layer times the etching selectivity between said transmissive layer and said mask substrate.

10. The method of forming a mask according to claim 8 , wherein said layer of opaque material comprises chrome.

11. The method of forming a mask according to claim 8 , wherein said transmissive layer comprises MoSiON.

12. The method of forming a mask according to claim 8 , wherein said transmissive layer has a percentage transmission in the range of 5 to 12 percent.

13. The method of forming a mask according to claim 8 , wherein said opaque material operates as a hard mask during the etching of said mask substrate.

14. The method of forming a mask according to claim 8 , wherein said etched portion of said mask substrate forms a background portion of said mask, said background portion being a clear field.

15. The method of claim 8 , wherein the method further comprises: in step (c), prior to the step of etching a portion of the mask substrate, patterning the layer of transmissive material and the layer of opaque material to expose the portion of the mask substrate to be etched.

16. The method of claim 1 , wherein the method further comprises: prior to the step of etching a portion of the mask substrate, patterning the layer of transmissive material and the layer of opaque material to expose the portion of the mask substrate to be etched.