精确预计Si BJT微波功率器件峰值结温的方法

三维全热程热电一体地模拟了Si BJT微波功率器件.热场计算包括从芯片的有源区经芯片-粘接层-基片-粘接层-底座直到固定于70℃的安装台面的整个散热过程.在处理热电正反馈时把有源区的60个基本单元(子胞)当成60个并联子胞晶体管进行建模，子胞模型包括子胞晶体管本身、基区横向扩展电阻、发射区横向扩展电阻.热电一体分析除了涉及Vbe随温度变化外，还有子胞发射极有效面积随子胞发射极电流上升而下降的效应（以下称面积效应）.与对有源区各点直接进行分析相比，子胞建模不仅大大简化了计算，而且摸拟结果与器件结构、版图结构、工艺参数关系清楚.模拟预计的热斑温度（204℃）与投片后三个样品的平均测量结果（197℃）在实验误差（10℃）内一致.模拟结果说明面积效应对抑制热电正反馈有重要作用.

Precise Prediction on the Operating Peak Junction Temperature for Power Microwave Si BJT

A 3D electro-thermal simulation has been done for a power microwave Si BJT,involving the heat dissipation process from the active region through the chip,the joint under the chip,the substrate,the joint under the substrate and at last to the heat sink,whose bottom keeping 70℃.The 60 units (cells) in the active region are considered as 60 sub-cell transistors and each of which was modeled as a circuit,consisting of sub-transistor itself,base lateral resistor Rbb,emitter lateral resistor Ree.In addition to the fact that Vbe decreases as the temperature increases,the area effect,i.e.the effective emitter area of a cell decreases when the cell current increases,has also been discussed.The area effect plays an important role to the depression of the positive electro-thermal feedback.The predicted peak junction temperature(204℃) agrees with the average of the measured value of 197℃,as is within the range of experimental error(10℃).