Modulated exposure mask and method of using a modulated exposure mask

• US 6,613,498 B1
• Filed: 09/16/1999
• Issued: 09/02/2003
• Est. Priority Date: 09/17/1998
• Status: Expired due to Term

• Current Assignee: Mems Optical, Inc. (Jenoptik AG)
• Original Assignee: Mems Optical, Inc. (Jenoptik AG)
• Inventors: Brown, David R., Tuck, Gerald, Scott, Miles, McCoy, Barry S., Peters, Bruce
• Primary Examiner(s): Ashton, Rosemary
• Assistant Examiner(s): Walke, Amanda C.
• Application Number:
  US09/397,133
• Time in Patent Office: 1,447 Days
• Field of Search: 430/314, 430/322, 430/323, 430/321
• US Class Current: 430/322
• CPC Class Codes: G03F 1/50 Mask blanks not covered by G03F1/20 - G03F1/34; Preparation thereof
• CPC Class Codes: G03F 7/0005 Production of optical devices or components in so far as characterised by the lithographic processes or materials used therefor
• CPC Class Codes: G03F 7/70216 Mask projection systems

Abstract

A photolithographic process includes providing a layer of photoresistive material on a target substrate. Radiation is transmitted to the photoresistive material through a layer of absorbing material that absorbs the radiation with a transmittance proportional to the thickness of the absorbing material. A surface relief structure is formed in the absorbing material, so that the photoresistive material is only partially exposed in a pattern corresponding to the surface relief structure. Thus, when the photoresistive material is developed, it has a surface relief structure corresponding to the surface relief structure in the absorbing material. Etching the developed photoresistive material and target substrate then forms a surface relief structure in the target substrate that corresponds to the surface relief structure in the developed photoresistive material.

Claims

1. A photolithographic process, comprising:

providing a layer of photoresistive material on a target substrate;

partially exposing the photoresistive material by transmitting radiation to the photoresistive material through a layer of absorbing material that

(1) absorbs the radiation with a transmittance proportional to the thickness of the absorbing material, and

(2) has a surface relief structure formed therein;

developing the photoresistive material to form a surface relief structure in the developed photoresistive material that corresponds to the surface relief structure in the absorbing material; and

etching the developed photoresistive material and target substrate to form a surface relief structure in the target substrate that corresponds to the surface relief structure in the developed photoresistive material.

2. The process according to claim 1, wherein the surface relief structure on the target substrate has an analog topography.

3. The process according to claim 1, wherein the etching step is performed with a dry etching process.

4. The process according to claim 1, wherein the etching step is performed with a wet etching process.

5. The process according to claim 1, wherein the etching step is performed with a chemically assisted etching process.

6. The process according to claim 1, wherein the photoresistive material has a linear contrast curve in the applied energy range of the transmitting radiation.

7. A photolithographic process, comprising:

providing a layer of photoresistive material on a target substrate;

partially exposing the photoresistive material by transmitting radiation to the photoresistive material through a layer of absorbing material that

(1) absorbs the radiation with a transmittance proportional to the thickness of the absorbing material, and

(2) has a surface relief structure formed therein;

developing the photoresistive material to form a surface relief structure in the developed photoresistive material that corresponds to the surface relief structure in the absorbing material.

8. The process according to claim 7, wherein the surface relief structure in the developed photoresistive material has an analog topography.

9. The process according to claim 7, wherein the photoresistive material has a linear contrast curve in the applied energy range of the transmitting radiation.

10. A photolithographic process, comprising:

providing a layer of photoresistive material on a target substrate;

partially exposing the photoresistive material by transmitting radiation to the photoresistive material through a layer of absorbing material that

(1) absorbs the radiation with a transmittance proportional to the thickness of the absorbing material, and

(2) has a surface relief structure formed therein; and

etching the photoresistive material and target substrate to form a surface relief structure in the target substrate that corresponds to the surface relief structure in the photoresistive material.

11. The process according to claim 10, wherein the surface relief structure on the target substrate has an analog topography.

12. The process according to claim 10, wherein the etching step is performed with a dry etching process.

13. The process according to claim 10, wherein the etching step is performed with a wet etching process.

14. The process according to claim 10, wherein the etching step is performed with a chemically assisted etching process.

15. The process according to claim 10, wherein the photoresistive material has a linear contrast curve in the applied energy range of the transmitting radiation.