US 11,810,936 B2
Pixel array including air gap reflection structures
ChunHao Lin, Tainan (TW); Feng-Chien Hsieh, Pingtung (TW); Yun-Wei Cheng, Taipei (TW); and Kuo-Cheng Lee, Tainan (TW)
Assigned to Taiwan Semiconductor Manufacturing Company, Ltd., Hsinchu (TW)
Filed by Taiwan Semiconductor Manufacturing Company, Ltd., Hsinchu (TW)
Filed on Nov. 20, 2020, as Appl. No. 16/949,927.
Prior Publication US 2022/0165776 A1, May 26, 2022
Int. Cl. H01L 27/146 (2006.01)
CPC H01L 27/14629 (2013.01) [H01L 27/14685 (2013.01); H01L 27/1463 (2013.01); H01L 27/1464 (2013.01); H01L 27/14623 (2013.01)] 20 Claims
OG exemplary drawing
 
15. A method, comprising:
forming, for a pixel sensor of a pixel array included in an image sensor, a plurality of openings through an un-doped silicate glass (USG) layer of the image sensor and in an interlayer dielectric (ILD) layer of the image sensor;
forming an inter-metal dielectric (IMD) layer on the USG layer,
wherein the IMD layer closes the plurality of openings to form a plurality of air gap reflection structures of the pixel sensor, and
wherein the plurality of air gap reflection structures are formed to have an aspect ratio, between a depth of an air gap reflection structure of the plurality of air gap reflection structures and a width of the air gap reflection structure, greater than approximately 2; and
forming a photodiode in a silicon layer above the ILD layer,
wherein the photodiode is formed over the plurality of air gap reflection structures.