高功率電晶體之製作

Abstract

在本研究過程中，我們已成功地設計並發展出高功率元件的製 程。整個過程從製作FET的最基本三個步驟:元件隔離、歐姆接點、 閘極製作著手，另外也增添新的製程技術，如:電鍍、空橋架設， 整合這些製程，順利地完成高功率元件的製作。在電鍍上，電鍍金 的厚度至少可達2μm以上，最高達12μm，且電鍍區與非電鍍區的 界線十分明顯。在空橋的架設方面，最長距離可達30μm，與晶片表 面距離2μm。在量測方面，元件在300K下的直流特性，最大飽和 電流Idss=150mA/mm' gm=115ms/mm;高頻特性上，fT為8．2GHz、 fmax，可達16GHz ，操作頻率2．4GHz下，在輸入功率(Pin)7.8dBm ，輸出功率(Pout)1OdBm時達到P1dB點。

In this study, we have developed the processing techniques for GaAs Power HEMT. The process starts with the three basic fabrication steps used in general FET processing. These include meas etch, obmic contact formation and gate formation. We have also successfully developed two specific process steps: electropalting and airbridge setting. In the process of electroplating, the thickness of Au can be controlled in the ranges from 2 μm and 12 μm maximum, and the boundary between the electroplated and unelectroplated areas is very sharp. From the airbridge process, the maximum length of airbridge can be 30 μm, and the distance between airbridge and wafer is 2μm. Finally, a 1.8 μm gate length GaAs power HEMT was successfully fabricated, which exhibited a output power of 1OdBm at 2.4 GHz. The maximum transconductance and saturated current of the device were 115mS/mm and 150mA/mm, respective. The HEMT demonstrated a current gain cut-off frequency, fT, of 8.2 GHz, and power gain cut-off frequency, fmax,of 16 GHz.