ABSTRACT
We have observed that the electro-chemical etching of the recess region occurs near the gate electrode during the deionized water rinse in the fabrication process of 0,1 μm gate pseudomorphic InGaAs/AlGaAs HEMT, and it strongly affects the RF performance of the device. Such an electro-chemical etching is related to the dissolved oxygen in the deionized water, which causes OH- ion by the electro-chemical reaction with H2O. To solve this problem, we have applied the deionized water with the dissolved oxygen of 2ppb for the rinse process in the N2 ambiance to prevent incorporation of oxygen from the air. High fT and MSG of 104GHz and 10.8dB at 60GHz, respectively, were achieved by the suppression of the electro-chemical etching. Using two dimensional device simulation, we have verified the correlation between the depth of electro-chemical etching and the gate capacitance, which agrees with the experimental result.
