Image sensor having inner lens
View Patent ↗An image sensor includes an inner lens to enable incident light to reach a condensing lens, so that the incident light may further reach photodiodes. Light loss can be reduced and photosensitivity can be improved. The image sensor includes at least one microlens that focuses incident light onto at least one photosensor that receives a light signal transmitted from the at least one microlens. The image sensor also includes at least one inner lens, disposed between the at least one microlens and the at least one photosensor, having an upper surface of a predetermined curvature to compensate photosensitivity of light received from the at least one microlens.
1. A method for fabricating an image sensor, comprising:
forming a photoresist layer on a planarization layer;
performing an alignment exposure with respect to the photoresist layer;
performing a dry etching process with respect to the exposed photoresist layer; and
forming an oxide layer on the etched photoresist layer by silation using a silane gas.
2. The method of claim 1 , further comprising:
performing a heat-treatment process to impart a predetermined curvature to an upper surface of the etched photoresist layer, thereby forming an inner lens.
3. The method of claim 2 , wherein the inner lens is heat-treated by a silation process performed in-situ at a temperature of approximately 90 to 150° C.
4. The method of claim 2 , further comprising:
forming a color filter portion that enables a color separation in a transmitted light signal on the inner lens.
5. The method of claim 4 , wherein the inner lens is disposed below the color filter portion that enables a color separation in a transmitted light signal.
6. The method of claim 4 , wherein the color filter portion is formed after forming the oxide layer.
7. The method of claim 1 , wherein the photoresist layer is formed with a predetermined thickness for determining inner lens formation.
8. The method of claim 7 , wherein the predetermined thickness of the photoresist layer is approximately 0.5 to 1.5 μm.
9. The method of claim 1 , wherein the planarization layer is a passivation layer.
10. The method of claim 1 , wherein the dry etching process is performed using O 2 plasma gas.
11. The method of claim 1 , wherein the dry etching process removes approximately 50 to 90% of the thickness of the photoresist layer.
12. The method of claim 1 , wherein the dry etching process is performed under an N 2 atmosphere at a process temperature of 120° C. or less, an RF power of approximately 10 to 100 W, and an O 2 flow rate of approximately 10 to 50 sccm.