基于π型多晶硅电阻网络的片上衰减器
On-chip attenuator based on π-type polysilicon resistive network

为了满足衰减器低成本、小尺寸和可重用的发展需求,提出一种基于π型多晶硅电阻网络的宽频带(0~20 GHz)片上衰减器。对精确控制多晶硅方块电阻(40~400Ω/sq)进行研究,通过控制硼B离子的掺杂浓度(5×1018~1.4×1020 cm-3)和热退火条件(950~1050℃, 10~30 min),得出薄膜方块电阻随工艺条件的变化规律,方阻误差小于4%。结合片上衰减器的尺寸需求选择方阻,设计了10和20 dB片上衰减器,采用HFSS三维建模软件对器件进行仿真优化。仿真结果表明:在0~20 GHz内, 10 dB衰减器的衰减精度为0.26 dB,电压驻波比(VSWR)小于1.13; 20 dB衰减器的衰减精度为0.04 dB, VSWR小于1.29。电阻网络的面积均为265μm×270μm,衰减器尺寸小于1000μm×800μm。所设计的片上衰减器精度高,适用于微波测试仪器前端。
Abstract：An on-chip 0~20 GHz attenuator was developed based on a π-type polysilicon resistive network as low cost attenuators with adjustable size that are compatible with other circuits. The sheet resistance(100~400Ω/sq) of the polysilicon resistor can be controlled by varying the boron-doping concentrations(5×1018~1.4×1020 cm-3) and post-annealing conditions(950~1050℃, 10~30 min). The resistance error was controlled less than 4%. The on-chip attenuator size can be set by selecting the sheet resistance for the on-chip 10 dB and 20 dB attenuating resistive networks. The devices were modelled in 3-D with HFSS with the simulation results showing excellent performance. The attenuation accuracies of the 10 dB and 20 dB attenuators were 0.26 dB and 0.04 dB over the entire frequency band(0~20 GHz), while the voltage standing wave ratios(VSWR) were less than 1.13 and 1.29, respectively. Both resistive networks were 265μm×270μm in size while both attenuators were less than 1000μm×800μm in size. These high accuracy attenuators can be used in microwave test instruments.