Step-over lithography to produce parabolic photoresist profiles for microlens formation
View Patent ↗A method of microlens fabrication for use in a photosensor includes preparing a photodetector element array which is sensitive to light in a specific color domain and depositing microlens material on the photodetector element array. The structure is coated with photoresist, and the photoresist is masked and exposed in a separate exposure for each color in the color domain. The photoresist is developed and the microlens material etched to form a microlens array.
1. A method of microlens fabrication for use in a photosensor, comprising:
preparing a photodetector element array which is sensitive to light in a specific color domain;
depositing microlens material on the photodetector element array;
coating the microlens material with photoresist;
masking and exposing the photoresist in a separate exposure for each color in the color domain;
developing the photoresist;
etching the microlens material to form a microlens array; and
completing the photosensor.
2. The method of claim 1 wherein said exposing includes exposing the photoresist above a photodetector element while preventing exposure above a photodetector element from a neighboring pattern.
3. The method of claim 2 wherein the exposed and developed photoresist has a pattern which does not leave a thickness of photoresist over an associated photodetector element.
4. The method of claim 1 wherein said masking and exposing includes providing a separate mask and exposure for each color of the color domain.
5. The method of claim 1 wherein said masking and exposing includes providing a separate mask and exposure for each color of the color domain, wherein each mask is constructed and arranged as a function of a refractive index of the microlens material for each wavelength of the color in the color domain.
6. A method of microlens fabrication for use in a photosensor, comprising:
preparing a photodetector element array which is sensitive to light in a specific color domain;
depositing microlens material on the photodetector element array;
coating the microlens material with photoresist;
masking and exposing the photoresist in a separate exposure for each color in the color domain, including providing a separate mask and exposure for each color of the color domain;
developing the photoresist;
etching the microlens material to form a microlens array; and
completing the photosensor.
7. The method of claim 6 wherein said exposing includes exposing the photoresist above a photodetector element while preventing exposure above a photodetector element from a neighboring pattern.
8. The method of claim 7 wherein the exposed and developed photoresist has a pattern which does not leave a thickness of photoresist over an associated photodetector element.
9. The method of claim 6 wherein said masking and exposing includes providing a separate mask and exposure for each color of the color domain, wherein each mask is constructed and arranged as a function of a refractive index of the microlens material for each wavelength of the color in the color domain.
10. A method of microlens fabrication for use in a photosensor, comprising:
preparing a photodetector element array which is sensitive to light in a specific color domain;
depositing microlens material on the photodetector element array;
coating the microlens material with photoresist;
masking and exposing the photoresist in a separate exposure for each color in the color domain, wherein said masking and exposing includes providing a separate mask and exposure for each color of the color domain, wherein each mask is constructed and arranged as a function of a refractive index of the microlens material for each wavelength of the color in the color domain;
developing the photoresist;
etching the microlens material to form a microlens array; and
completing the photosensor.
11. The method of claim 10 wherein said exposing includes exposing the photoresist above a photodetector element while preventing exposure above a photodetector element from a neighboring pattern.
12. The method of claim 11 wherein the exposed and developed photoresist has a pattern which does not leave a thickness of photoresist over an associated photodetector element.