具有高电流增益-击穿电压优值的新型应变Si/SiGe HBT

为了改善器件的高压大电流处理能力,利用SILVACOTCAD建立了应变Si/SiGe HBT模型,分析了虚拟衬底设计对电流增益的影响.虚拟衬底可在保持基区-集电区界面应力不变的情况下实现基区Ge组分的高掺杂,进而增大电流增益.但器件的击穿电压仍然较低,不利于输出功率的提高和系统信噪比的改善.考虑到集电区设计对电流增益影响不大但与器件击穿电压密切相关,在采用虚拟衬底结构的同时,对器件的集电区进行选择性注入设计.该设计可在集电区引入横向电场,进而提高击穿电压.结果表明:与传统的SiGe HBT相比,新器件的电流增益和击穿电压均得到显著改善,其优值β·V_(CEO)。改善高达14.2倍,有效拓展了微波功率SiGe HBT的高压大电流工作范围.

Novel Strained Si/SiGe HBT for High Product of Current Gain and Breakdown Voltage

To improve the high voltage and high current handling capability, a model of strained Si/SiGe HBT is established with SILVACO TCAD to study the influence of the virtual substrate on current gain of the device. Higher Ge composition of the base can be achieved with the virtual substrate while keeping the strain between the base and the collector constant, and hence the current gain is enhanced. However, the breakdown voltage is too low to increase the output power and signal-to-noise ratio of the system. A new design of selectively implanted collector in device with virtual substrate is proposed considering that collector design is associated with the breakdown voltage while irrelevant of the current gain. A lateral electric field is built up with the design, and thereby the breakdown voltage is enhanced. Results show that for the novel device, both the current gain and the breakdown voltage are markedly improved and the figure of merit β·VCEO is 14.2 times as much as that of the traditional SiGe HBT, which effectively develops the high voltage and high current application of microwave power SiGe HBT.