电子倍增层表层掺杂分布对EBCMOS电荷收集效率的影响

Influence of Doping Distribution in Electron Multiplier Surface Layer on Charge Collection Efficiency of EBCMOS

摘要:

设计了电子倍增层的多种表层结构,并模拟分析了表层掺杂分布对电子轰击型CMOS(EBCMOS)成像器件的电荷收集效率的影响。结合离子注入工艺优化设计电子倍增层表层结构,并利用离子注入模拟软件TRIM模拟分析了不同掩蔽层种类、厚度、离子注入剂量、注入角度和注入能量次数对掺杂分布的影响。再依据载流子传输理论并结合蒙特卡洛模拟方法,模拟分析了相应结构下EBCMOS中电子倍增层的电荷收集效率。模拟研究结果表明:通过选择SiO₂作为掩蔽层、减小掩蔽层厚度、增加注入能量次数等方法可以提高电荷收集效率。在注入剂量选择方面,对电子倍增层表层进行重掺杂,使掺杂浓度下降幅度足够大、下降速度足够缓慢,也可以有效提高电荷收集效率。仿真优化后表层结构所对应器件的电荷收集效率最高可以达到93.61%。

Abstract:

In this paper, various surface structures of electron multiplier layer are designed, and the influence of doping distribution on the charge collection efficiency of electron bombardment CMOS (EBCMOS) imaging device is simulated and analyzed. Combined with ion implantation process, the surface structure of electron multiplier layer was optimized, and the influence of different kinds and thickness of masking layer, ion implantation dose, implantation angle and implantation times on doping distribution was analyzed by using ion implantation simulation software TRIM. According to the carrier transport theory and Monte Carlo simulation method, the charge collection efficiency of electron multiplier layer in EBCMOS is simulated and analyzed. The simulation results show that the charge collection efficiency can be improved by selecting SiO₂ as the masking layer, reducing the thickness of the masking layer and increasing the number of energy injection. In the aspect of injection dose selection, heavily doping the surface layer of the electron multiplication layer can make the doping concentration decrease large enough and slow enough, which can also effectively improve the charge collection efficiency. After optimization, the charge collection efficiency of the device corresponding to the surface structure can reach 93.61%.