| 摘要: | 本論文首先介紹異質接面雙極性電晶體(射極面積1×240?m2)之VBIC模型之基本架構與參數意義，以及各種參數之萃取方法，參數取得之後，VBIC模型則建立完成，接下來必須驗證大訊號功率特性及線性度，以確定VBIC模型的準確性。 在單一電晶體VBIC模型建立完成之後，我們用此模型套用於大面積的功率元件上，利用ADS模擬軟體，在電晶體並聯後計算出模擬與量測值之誤差率，並說明如何利用電晶體外部修正，補足因並聯而產生的寄生效應，使得誤差率降低。 接著論文中會分析，從單一電晶體(射極面積1×240?m2)到八顆電晶體並聯(射極面積8×240?m2)，其在常溫到高溫所量測到的直流、交流、功率與線性度等特性，並且說明電晶體並聯與溫度效應的影響。 最後為功率元件的熱效應分析，我們用兩種量測方法作比較，第一種為I-V特性曲線(CW mode)，當電晶體在高功率操作時，熱效應造成的集極電流下降會相當顯著，由不同溫度下之集極電流量測值可計算出熱電阻值。第二種為藉由熱影像圖(IR thermograph)方式，經由金屬溫度校正(calibration)後得到元件表面的最高溫度，再經由公式計算出電阻值。 This thesis focuses on the establishment of VBIC model and the characteristics analysis, including the thermal influence, of power HBTs. It contains three parts: (1) the simplification and the optimization for the elementary cell HBT model, which is applied to large-size power HBTs, (2) investigating the characteristics with thermal effect, (3) obtaining thermal resistance and junction temperature by means of two measured methods. After the simplification and the optimization procedure of the VBIC model, the characteristics of HBT for elementary cell could be derived efficiently and exactly. However, when the model was applied to the HBTs which operate in parallel, the model would not perform correctly. Therefore, the developed model is necessary to be used to improve the accuracy. Adding the lumped equivalent circuit into the elementary cell, the proposed approach could reduce error ratio when applying to the large-size device. Furthermore the power HBT’s characteristics, including the thermal effect, is also investigated. Since such HBTs are operated at high power levels, the device temperature will significantly rise, which results in the self-heating effect and degrade the device performance and reliability. Thermal resistance is the key parameter of thermal effect. Two different methods would be applied to measure the thermal resistance. Firstly, a CW mode method to accurately obtain the thermal resistance of HBT’s is presented. The key advantage of the method is its simplicity, because it requires only the measurement of the device DC output characteristics at two different temperatures. In addition, the other method is the measurement of IR thermograph, which could derive the highest temperature of device surface, following to obtain the thermal resistance. The thermal resistance obtained with two methods would be in comparison finally. |
