Method of reducing edge height at the overlap of a layer deposited on a stepped substrate

1 . A method for preparing a stepped substrate, comprising:

depositing photoresist on a stepped substrate;

removing at least a first portion of the photoresist;

reflowing the remaining portion of the photoresist; and

etching at least a portion of the reflowed remaining photoresist and at least a portion of the stepped substrate.

2 . The method of claim 1 , wherein the stepped substrate comprises amorphous silicon.

3 . The method of claim 1 , wherein the stepped substrate is multi-layered and a first upper layer of the multi-layers is amorphous silicon and a second lower layer is indium phosphide.

4 . The method of claim 1 , wherein the photoresist is about 3 micrometers thick.

5 . The method of claim 1 , wherein said removing at least a first portion of the photoresist comprises photolithographically etching the first portion of the photoresist.

6 . The method of claim 1 , wherein said etching at least a portion of the remaining photoresist comprises plasma etching.

7 . The method of claim 1 , wherein said etching at least a portion of the remaining photoresist and at least a portion of the stepped substrate comprises: descumming;

carbon tetraflouride plasma etching the at least the portion of the remaining photoresist and the at least the portion of the stepped substrate; and

oxygen plasma etching the at least the portion of the remaining photoresist.

8 . The method of claim 1 , wherein said reflowing reduces the remaining portion of the photoresist from about 3 micrometers thick to about 2.5 micrometers thick.

9 . The method of claim 1 , wherein said reflowing comprises heating the stepped substrate at 125° C. for five minutes.

10 . An apparatus, comprising:

a deposited photoresist layer on a stepped substrate, wherein at least a portion of the photoresist is removed;

at least a reflowed portion of the remaining photoresist;

at least an etched portion of the reflowed photoresist; and

at least an etched portion of the stepped substrate.

11 . The apparatus of claim 10 , wherein said stepped substrate comprises amorphous silicon.

12 . The apparatus of claim 10 , wherein said stepped substrate is multi-layered and a first upper layer of the multi-layers is amorphous silicon and a second lower layer is indium phosphide.

13 . The apparatus of claim 10 , wherein said deposited photoresist layer is about 3 micrometers thick.

14 . The apparatus of claim 10 , wherein at least a portion of said at least a reflowed portion of the remaining photoresist is about 3 micrometers to about 2.5 micrometers thick.

15 . An system for preparing a stepped substrate, comprising:

a first processing tool for depositing at least a portion of photoresist on the stepped substrate;

a second processing tool for removing at least a first portion of the photoresist;

a third processing tool for reflowing at least a portion of the remaining portion of the photoresist; and

a fourth processing tool for etching at least a portion of the reflowed photoresist and at least a portion of the stepped substrate.

16 . The system of claim 15 , wherein said first processing tool deposits the photoresist on an amorphous silicon stepped substrate.

17 . The system of claim 15 , wherein said first processing tool deposits photoresist on a stepped substrate having a first upper layer of amorphous silicon and a second lower layer of indium phosphide.

18 . The system of claim 15 , wherein said first processing tool deposits a layer of about 3 micrometers thickness of photoresist on the stepped substrate.

19 . The system of claim 15 , wherein said second processing tool further comprises a photolithographical processing tool capable of photolithographically etching said portion of photoresist.

20 . The system of claim 15 , wherein said third processing tool further comprises a plasma etching processing tool capable of plasma etching said portion of the remaining photoresist.

21 . The system of claim 15 , wherein said fourth processing tool further comprises:

a descumming processing tool;

a carbon tetraflouride plasma etching processing tool capable of plasma etching said remaining photoresist portion and at least the portion of the stepped substrate; and

an oxygen plasma etching processing tool capable of oxygen plasma etching said remaining photoresist portion.

22 . The system of claim 15 , wherein said plasma etching processing tool is capable of reducing said portion of the remaining photoresist from about 3 micrometers thick to about 2.5 micrometers thick.

23 . The system of claim 15 , wherein said third processing tool further comprises a heating processing tool capable of heating the stepped substrate at 125° C. for five minutes.