Vertical PNP bipolar transistor test structures were fabricated and measured, attempting to electrically obtain information on carrier lifetime in the voltage-supporting base region of Insulated Gate Bipolar Transistors (IGBTs). Owing to the structural similarity, the test structures and functional IGBTs can be integrated on the same wafers, making it possible to directly correlate lifetime data and IGBT characteristics. To solve a problem of leaky backside PN junction, common base current gain of the test devices was measured without applying a reverse bias between the collector and base terminals, which suppressed the leakage to an acceptable level. A simple analytical formula to convert the current gain to hole lifetime in the N-type base region was proposed and used, that takes into account the existence of a commonly used N-buffer layer adjacent to the backside P-collector layer. The validity of the formula was confirmed using TCAD simulations. This method was applied to IGBT wafers with two different wafer thicknesses (i.e., base lengths): $120~{{\mu }}\text{m}$ and $360~{{\mu }}\text{m}$ . Consistent lifetime values extracted in spite of the largely different thicknesses supports the validity of the proposed lifetime estimation method.

中文翻译：

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用于提取 IGBT 中少数载流子寿命的双极晶体管测试结构

制造和测量垂直 PNP 双极晶体管测试结构，试图从电学上获得有关绝缘栅双极晶体管 (IGBT) 的电压支持基区中载流子寿命的信息。由于结构相似，测试结构和功能 IGBT 可以集成在同一晶片上，从而可以直接关联寿命数据和 IGBT 特性。为了解决背面PN结漏电的问题，在集电极和基极端子之间没有施加反向偏置的情况下测量了测试器件的公共基极电流增益，从而将泄漏抑制到了可接受的水平。提出并使用了一个简单的解析公式，用于将电流增益转换为 N 型基区中的空穴寿命，这考虑了与背面 P 集电极层相邻的常用 N 缓冲层的存在。使用 TCAD 模拟证实了该公式的有效性。该方法应用于具有两种不同晶圆厚度（即基极长度）的 IGBT 晶圆： $120~{{\mu}}\text{m}$ 和 $360~{{\mu}}\text{m}$ . 尽管厚度大不相同，但提取的一致寿命值支持所提出的寿命估计方法的有效性。