An anti-crosstalk inverted U-type buried layer photodiode and its production method

Abstract

The invention discloses an anti-crosstalk reverse-U-shaped buried layer photodiode and a generation method. The anti-crosstalk reverse-U-shaped buried layer photodiode comprises a surface P+ clamping layer on the upper portion of a P-type epitaxial layer, an initial N-type light induction area arranged on the lower portion of the P-type epitaxial layer, two ring-shaped P-type light dope buried layers arranged below the initial N-type light induction area, and secondary N-shaped light induction buried layers arranged in the ring-shaped P-type light dope buried layers. According to the anti-crosstalk reverse-U-shaped buried layer photodiode and the generation method, a built-in electric field where the P-type light dope buried layer to the P-type epitaxial layer is established, so that carriers stimulated by long-band incident light produced in the epitaxial layer and a substrate are drifted to a top layer light induction N buried layer under the action of forces of the built-in electric field and collected, transverse diffusion of charges is prevented, and a charge crosstalk phenomenon is inhibited; reduction of a charge crosstalk rate, produced by a diffusion mechanism, of the carriers stimulated by long-band light between adjacent pixel units can be guaranteed under the condition that filling factors in the light induction area are not lost, and key indexes of full trap capacity, quantum efficiency and the like are improved.

Description

technical field [0001] The invention belongs to the field of CMOS image sensors, in particular to an anti-crosstalk inverted U-shaped buried layer photodiode and a production method. Background technique [0002] CMOS image sensors have gradually replaced CCDs to occupy the mainstream market of image sensors due to their advantages of low power consumption, low cost, and compatibility with CMOS semiconductor integrated circuit manufacturing processes. The pixel structure using the clamp photodiode (PPD) as the photosensitive unit further reduces the reset noise, dark current, fixed mode noise and other indicators of the sensor, and can compensate the imaging quality through correlated double sampling technology. These advantages make the PPD pixel widely used In modern high-performance CMOS image sensors. [0003] The conventional PPD pixel circuit is composed of a clamped photodiode, a floating diffusion node, a transmission tube, a reset tube, a source follower and a row ...

AI Technical Summary

Problems solved by technology

Therefore, considering the influence of the crosstalk effect, the above-mentioned conventional PPD pixel structure will be interfered by adjacent pixels, reducing image resolution, and there are certain limitations in application.

[0005] At present, the research on crosstalk effect at home and abroad has some publicly published results, especially for charge crosstalk, some solutions have been proposed, which can be summarized into three types: the first is to increase the active area between adjacent pixels and inject P+ The guard ring provides a low-resistance discharge path for the photogenerated charge generated on the substrate, so that it cannot diffuse to other pixels. This method will greatly increase the sensor chip area and is not conducive to the design of the fill factor of the photosensitive area; the second is to increase The doping concentration of the epitaxial layer reduces the lifetime of minority carriers and the diffusion length, so that the charges are recombined before they diffuse to the photosensitive absorption region of the adjacent pixel. The disadvantage is that the increase in the concentration of the P-type epitaxial layer is not conducive to Extending, it affects the absorption of long-wavelength light, reduces the quantum efficiency, and limits the spectral response range of the sensor; the third is to use deep trench isolation technology (DTI) to electrically isolate the pixel unit, which is limited by the technology level. It also increases the dark current generation rate, making it difficult to be widely used

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