Image sensor

Abstract

The invention discloses an image sensor. A photosensitive structure and a pixel reading circuit are respectively formed on a semiconductor substrate with an insulated buried layer. The image sensor has the advantages of high speed, low power consumption, interlock resistance and radiation resistance. The photosensitive structure comprises four doping regions which are transversely arrayed and arein an encircled structure; and the four doping regions comprise a light absorbing layer and an avalanche multiplication region. The transverse encircled structure can be used for eliminating the limitation to the thickness of the light absorbing layer caused by a thinner top-layer semiconductor layer and increasing the width and the area of the light absorbing layer, and thereby, the light absorbing efficiency of the photosensitive structure can be improved. According to the avalanche multiplication region, the photoelectric conversion efficiency of the photosensitive structure can be greatlyimproved, and further, the light absorbing efficiency of the photosensitive structure is improved.

Description

technical field [0001] The invention relates to an image sensor, in particular to a CMOS image sensor with an insulating buried layer, belonging to the technical field of semiconductors. Background technique [0002] In the 1970s, CCD image sensors and CMOS image sensors started at the same time. CCD image sensor has gradually become the mainstream of image sensor due to its high sensitivity and low noise. However, due to technological reasons, sensitive components and signal processing circuits cannot be integrated on the same chip, resulting in a camera assembled from a CCD image sensor with large volume and high power consumption. CMOS image sensor has been more and more widely used due to its advantages of high integration, low power and low cost. [0003] Existing CMOS image sensors include CMOS digital-analog circuits and pixel unit circuit arrays. According to the number of transistors included in one pixel unit circuit, existing CMOS image sensors are divided into ...

AI Technical Summary

Problems solved by technology

In Chinese invention patent 200910083526.X, the photodiode is still formed on the silicon substrate. The reason is that the structure of the photodiode is a vertical structure. Since the thickness of the top layer of silicon is relatively thin, the photodiode with the vertical structure is formed on a thinner substrate. In the top layer of silicon, the width of the depletion region formed when the photodiode is reverse-biased, that is, when the reverse bias voltage is added, is small, which reduces the light absorption efficiency of the photodiode.

However, although the above-mentioned patent can make other circuits outside the CMOS image sensor photodiode have the advantages of high speed, low power consumption, anti-lockup and low soft error probability, since the photodiode is still formed in the silicon substrate, the photodiode also has the advantages of Parasitic Effects and Issues with Radiation Resistance

Images