Method of manufacturing a CMOS image sensor
View Patent ↗A method of manufacturing a CMOS image sensor. The present invention enables forming micro-lenses having a uniform shape throughout a semiconductor substrate. The method of manufacturing a CMOS image sensor includes: coating a color filter layer and a semiconductor substrate with a first photoresist; selectively exposing the first photoresist to light to define a planarization layer; coating the first photoresist with a second photoresist; selectively exposing the second photoresist to define a plurality of micro-lens bodies; and baking the plurality of micro-lens bodies to form a plurality of micro-lenses.
1. A method of manufacturing microlenses in a CMOS image sensor, comprising:
(a) coating a color filter layer over a semiconductor substrate with a first photoresist;
(b) selectively exposing the first photoresist to light;
(c) coating the first photoresist with a second photoresist;
(d) selectively exposing the second photoresist to light to define a plurality of micro-lens bodies;
(e) removing areas of the first photoresist to form a planarization layer under the plurality of micro-lens bodies; and
(f) heating the plurality of micro-lens bodies to form a plurality of micro-lenses.
2. The method according to claim 1 , further comprising removing exposed parts of the second photoresist after selectively exposing the second photoresist.
3. The method according to claim 2 , comprising removing unexposed parts of the first photoresist after removing exposed parts of the second photoresist.
4. The method according to claim 1 , wherein the first photoresist has a thickness of from about 1.3 μm to about 3 μm.
5. The method according to claim 1 , wherein the second photoresist has a thickness of from about 1.1 μm to about 1.3 μm.
6. The method according to claim 1 , wherein the first photoresist comprises a negative-type photoresist.
7. The method according to claim 6 , wherein the second photoresist comprises a positive-type photoresist.
8. The method according to claim 1 , wherein the second photoresist comprises a negative-type photoresist.
9. The method according to claim 8 , wherein the first photoresist comprises a positive-type photoresist.
10. The method according to claim 1 , wherein an amount of energy in the step of selectively exposing the second photoresist is from about 300 mJ to about 500 mJ.
11. The method according to claim 1 , wherein an energy used in selectively exposing the second photoresist to light does not expose the first photoresist beneath the second photoresist to light.
12. The method according to claim 1 , wherein the first photoresist has a relatively low sensitivity to a wavelength of the light in the step of selectively exposing the second photoresist.
13. The method according to claim 12 , wherein the first photoresist has a sensitivity of less than 10% to the wavelength of the light in the step of selectively exposing the second photoresist.
14. The method according to claim 12 , wherein the second photoresist has a relatively high sensitivity to a wavelength of The light in the step of selectively exposing the second photoresist.
15. The method according to claim 12 , wherein the second photoresist has a sensitivity of more than 25% to the wavelength of the light in the step of selectively exposing the second photoresist.
16. The method according to claim 1 , wherein coating the first photoresist with the second photoresist includes coating the area(s) of the first photoresist that are selectively exposed to light with the second photoresist.
17. The method according to claim 1 , wherein heating the plurality of micro-lens bodies is performed at a temperature of about 150° C.
18. The method according to claim 7 , wherein the first photoresist does not melt or reflow to an appreciable extent during the heating step.