斜角造型高压硅器件表面特性的光感生电流法检测

Surface Characteristics of Bevel-Shaped High Voltage Silicon Devices Detected by Optical Beam Induced Current Method

采用激光探针表面电荷测量系统,实现了有机/无机介质膜保护下的高压硅器件表面耗尽区展宽的测量,分析了光感生电流(OBIC)曲线与硅表面少子扩散长度、表面复合速率以及波长相关吸收系数的关系.实验和计算结果表明,He Ne激光束由于具有较大的吸收系数(>3200cm-1)和适当的透射深度(≈3 1μm),对曲线上下沿变化影响很小,测量结果可以直接反映硅表面本身的响应.小正斜角造型大功率硅整流管在反向偏置下,表面耗尽区在稳态光电导下的扩展几乎都是在低掺杂的n区进行,p区的扩展被"钉扎".表面保护不良时,OBIC曲线可直接反映出局部的电场倍增状态.对不同腐蚀时间处理的磨角造型硅表面,OBIC测量结果表明,当腐蚀时间短时,表面少子寿命较低;反之,则寿命会有所提高.

By utilizing laser beam surface charge measurement system, the width and extension of the power device surface depletion region which is passivated by organic or inorganic materials can be quickly measured, and the relationships of optical beam induced current (OBIC) curve with minority carrier diffusion length, surface recombination velocity and light absorption coefficient were theoretically analyzed. He-Ne laser beam has greater absorption coefficient (>3200 cm-1) and proper penetration depth (3.1 μm), which facilitates obviously lowering the influence on the edges of OBIC curve, so the results can reflect the actual property of silicon device surface. For small positive angle bevelled power diode under reverse biased voltage, the surface depletion region extension is almost in the low doped n region, the extension in p region seems to be pinched. Field multiplication can also be observed if the surface is improperly protected. And OBIC can directly exhibit the influence of different erosion time on the surface minority carrier lifetime-the shorter erosion time, the lower surface minority carrier lifetime.