Source follower tube and forming method of CMOS sensor

Abstract

The invention provides forming methods of a source electrode following tube and a CMOS sensor. The method for forming the source electrode following tube comprises the steps: providing a substrate, and forming an active region and a shallow trench isolation structure adjacent to the active region on the substrate; forming a buried channel in the active region, wherein two sides of the buried channel are in contact with the shallow trench isolation structure; forming gate silicon oxide on the active region; partially etching the middle position of the gate silicon oxide to form patterned gate silicon oxide with a thin middle part and two thick sides; and forming a gate structure on the gate silicon oxide and the shallow trench isolation structure. According to the invention, patterned gatesilicon oxide with two thick sides and a thin middle part is formed through etching, so that a large part of carriers in the buried channel are transmitted from the middle part of the patterned gate silicon oxide so as to be far away from the interface of the shallow trench isolation structure, improve the disturbance of the interface of the shallow trench isolation structure to the carriers, improve the anti-noise capability of the CMOS sensor and improve the quality of an image obtained by the CMOS sensor.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a method for forming a source follower transistor and a CMOS sensor. Background technique [0002] Usually, an active pixel unit of a CMOS image sensor includes a P+ / N+ / P- photodiode 200 (PD, Photo Diode) located in the P-type epitaxial layer 100 and several transistors. Taking a 4T structure CMOS image sensor as an example, four The transistors specifically include a transfer transistor 300 (TX, Transfer), a source follower transistor 400 (SF, Source Follow), a reset transistor 500 (RST, Reset) and a row selection transistor 600 (RS, Row Select). figure 1 A schematic diagram of a 4T structured CMOS image sensor is shown. [0003] Such as figure 1 The basic working principle of the CMOS image sensor shown is as follows: before lighting, the reset transistor 500 and the transfer transistor 300 are turned on to release the original electrons in the area of ​​the photodiode...

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