电子轰击引起CMOS图像传感器增益衰减研究

Gain attenuation of CMOS image sensor caused by electron bombardment

摘要:

为探究氧化铝钝化层结构的CMOS图像传感器在较高电流密度的电子轰击后电子倍增系数减小问题，本文模拟氧化铝钝化层CMOS图像传感器制备工艺方法。在晶向为(100)，掺杂浓度为5×10¹⁸ cm^-3的P型硅表面制备氧化铝钝化层，模拟电子束轰击CMOS图像传感器的条件，对制备P型硅样品表面进行轰击，并利用高频C-U测试装置对该样品轰击前、后的高频C-U曲线进行测试。根据测试数据及SRH理论和少数载流子输运方程分析，得出电子轰击引起该型图像传感器钝化层内部正电荷沉积，以及硅界面缺陷态密度增加，是引起其电子倍增系数减小的内在原因。

Abstract:

To investigate the issue of reduced electron multiplication factor in Complementary Metal Oxide Semiconductor(CMOS) image sensors with an aluminum oxide passivation layer structure after being bombarded with high current density electrons, this paper simulates the fabrication process of CMOS image sensors with an aluminum oxide passivation layer. An aluminum oxide passivation layer is prepared on the surface of P-type silicon with a crystal orientation of (100) and a doping concentration of 5×10¹⁸ cm^-3. The conditions for electron beam bombardment of CMOS image sensors are simulated, and the prepared P-type silicon samples are bombarded. A high-frequency C-U testing device is employed to test the high-frequency C-U curves of the samples before and after bombardment. Based on the test data and analysis using the Shockley-Read-Hall(SRH) theory and minority carrier transport equations, it is concluded that the internal positive charge deposition in the passivation layer and the increase in defect state density at the silicon interface caused by electron bombardment are the intrinsic reasons for the reduction in the electron multiplication factor of this type of image sensor.