A transfer transistor structure

Abstract

A transmission transistor structure capable of enhancing signals output by a CMOS image sensor comprises a photodiode, a P-type silicon substrate, a drain terminal, an insulating layer, a polycrystalline silicon grid, a conductive channel and a heavily-doped region. The photodiode of a transmission transistor serves as a single photo-electric conversion diode and is responsible for converting optical signals to electric signals, and meanwhile, the photodiode of the transmission transistor also serves as the source end of the transmission transition responsible for electron transmission in the structure of the CMOS image sensor and is directly connected with the transmission transistor. The heavily-doped region with the junction depth being 0.12-0.18 micrometer is formed at the position, close to the polycrystalline silicon grid of the transmission transistor, of the photo diode through ion implantation, and the injected doping ion concentration is higher than the originally-injected doping ion concentration of the photodiode. According to the transmission transistor structure, when the CMOS image sensor outputs signals, the phenomenon that the conductive channel is pinched off too early can be avoided, photoelectrons are transmitted out as many as possible, and therefore the output strength of electric signals of the CMOS image sensor is enhanced.

Description

Technical field [0001] The present invention relates to the technical field of integrated circuit manufacturing, in particular to a transmission transistor structure in a CMOS (Complementary Metal Oxide Semiconductor) image sensor chip manufacturing process. Background technique [0002] In the basic structure of CMOS image sensor chips, transfer transistors are generally used, such as figure 1 , figure 2 with image 3 As shown, 1 is a photodiode, 2 is a transfer transistor, 3 is a capacitor, 4 is a reset tube, 5 is an amplifier, 6 is a gate, 7 is polysilicon, 8 is a P-type silicon base, and 9 is a drain terminal. 10 is an insulating layer, 11 is a polysilicon gate, and 12 is a conductive channel; each CMOS image sensor generates a pixel, and each pixel contains a photodiode and a transmission transistor. The function of the transmission transistor is to increase the sensitivity of the circuit. The photodiode 1 is converted into photoelectrons, which enter the circuit through th...

AI Technical Summary

Problems solved by technology

[0008] 1) The turn-on voltage of the transfer transistor is increased, which increases the difficulty of turning it on, resulting in a delay in signal transmission of the CMOS image sensor;

[0009] 2) The increase in the length of the conductive channel increases the volume of the CMOS image sensor chip, which consumes a lot of power during use, and does not conform to the development trend of miniaturization and intensive integration of semiconductor devices;

[0011] 4) Although the current method is beneficial to increase the inversion region, there is still the problem of a rapid decrease in the electron input rate of the photodiode, which in turn leads to the problem that the output signal at the signal output terminal is significantly weakened

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