Taiwan Semiconductor Manufacturing Comp. Ltd.

An Min Chiang

Wei-Kun Yeh

Chi-Hsiang Lee

Shau-Tsung Yu

Hua Yu Yang

Peng Yung-Sung

Min-Yi Lin

A process for reducing the dark current generation of an image sensor cell, fabricated on a semiconductor substrate, has been developed. The process features the use of polysilicon pad structure, formed simultaneously with a polysilicon gate structure of a reset transistor, with the polysilicon pad structure located overlying, and contacting, a portion of the top surface of the photodiode element, of the image sensor cell. A small diameter opening, in a composite polysilicon-silicon oxide layer, exposes the portion of photodiode element to be contacted by the polysilicon pad structure. The small diameter opening is created using a procedure which allows the surface of the photodiode element, exposed in the small diameter opening to experience only a minimum of RIE processing at end point, thus minimizing damage to the surface of the photodiode element, and thus reducing dark current generation. A metal contact structure, used to communicate with the photodiode element, is then formed on the polysilicon pad structure.

Method of reducing dark current for an image sensor device via use of a polysilicon pad

A method for forming an aperture with a uniform void-free sidewall etch profile through a multi-layer insulator layer. There is formed upon a semiconductor substrate a multi-layer insulator layer which has a minimum of a first insulator layer and a second insulator layer. The second insulator layer is formed upon the first insulator layer. There is then etched through a first etch method a first aperture completely through the second insulator layer. The first etch method has: (1) a first perpendicular etch selectivity ratio for the second insulator layer with respect to the first insulator layer of at least about 4:1; and (2) a lateral:perpendicular etch selectivity ratio for the second insulator layer of from about 0.5:1 to about 1:1. The first aperture is then etched through a second etch method to form a second aperture completely through the second insulator layer and the first insulator layer. The second etch method has: (1) a second perpendicular etch selectivity ratio for the second insulator layer with respect to the first insulator layer of no greater than about 2:1; and (2) a lateral etch selectivity ratio of the second insulator layer with respect to the first insulator layer of from about 0.5:1 to about 1:1. The second aperture has a uniform void-free sidewall etch profile.

Method for controlling the etch profile of an aperture formed through a

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Hsin-Chu, Taiwan

An Min Chiang