銅金屬化製程及閘極介電層於低成本、低功率損耗AlGaAs/InGaAs假晶高電子遷移率電晶體單刀雙擲開關之應用

Abstract

這篇論文為研究低製作成本，低功率損耗之鋁砷化鎵/銦砷化鎵 (AlGaAs/InGaAs) 假晶高電子遷移率電晶體(pseudomorphic high-electron-mobility transistor, PHEMT) 單刀雙擲 (single-pole-double-throw, SPDT) 開關之技術。內容包含了使用銅金屬化製程應用在AlGaAs/InGaAs PHEMT單刀雙擲開關的金屬內導線上，和評估不同溫度下銅金屬化製程單刀雙擲砷化鎵開關的電性特徵；及使用高介電係數之氧化鋁技術於AlGaAs/InGaAs金屬氧化物半導體假晶高電子遷移率電晶體單刀雙擲開關，以降低開關控制電流，減少損耗功率。 在銅內連接導線方面，本篇研究使用鉑做為擴散阻障層材料做為銅金屬化擴散阻障層以應用在AlGaAs/InGaAs PHEMT單刀雙擲開關上。比較使用金內連接導線之砷化鎵開關，銅製程單刀雙擲開關展現出相似的電特性，在2.5 GHz頻率下介入損耗小於0.5 dB，隔離度大於35 dB和input P1dB為 27 dBm特性。從熱穩定測試，這些銅製程開關在250 ℃溫度退火20個小時後，直流特徵沒有降低。此外經過高溫150 ℃儲存壽命 (HTSL) 環境測試，這些銅製程開關仍舊保持優秀之功率處理特性。在操作可靠度測試方面，將銅製程開關在室溫施以24小時，控制電壓交換 +3/0 V之on/off加速測試，元件經過on/off加速測試後依舊保持優秀之微波特性。 之後我們更進一步研究鉑做為擴散阻障層製作出銅製程AlGaAs/InGaAs PHEMT單刀雙擲開關，在不同溫度下的電性特徵，首先比較金內連接導線之砷化鎵開關，銅製程單刀雙擲開關展現出在2.5 GHz頻率下可比較的介入損耗小於0.5 dB，反射損耗大於20 dB，隔離度大於35 dB和input P1dB為 28.3 dBm特性。為了研究高溫應用上，溫度效應對於銅製程單刀雙擲開關的直流和微波特性的影響，在不同溫度下測試單刀雙擲開關，元件在300 °K到500 °K的溫度區間展現出低的熱啟始電壓係數 (δVth/δT)，其值為 -0.25 mV/°K，在2.5 GHz頻率及380 °K溫度操作下，其介入損耗小於0.5 dB，隔離度大於40 dB和input P1dB為 28.45 dBm等好的微波特性。 另外我們使用原子層沈積技術氧化鋁為閘極氧化層製作AlGaAs/InGaAs金屬氧化物半導體假晶高電子遷移率電晶體單刀雙擲開關。相較於傳統的PHEMT，MOS-PHEMT有相若的直流表現和較低的閘極漏電流，微波測試顯示MOS-PHEMT開關在2.5 GHz頻率下其介入損耗小於0.5 dB，反射損耗大於15 dB，隔離度大於30 dB和input P1dB為 31.4 dBm等微波特性。由以上的結果顯示，我們成功的製作出銅製程AlGaAs/InGaAs假晶高電子遷移率電晶體單刀雙擲開關和完成原子層沈積技術氧化鋁為閘極氧化層製作AlGaAs/InGaAs金屬氧化物半導體假晶高電子遷移率電晶體單刀雙擲開關。這是文獻上第一次發表AlGaAs/InGaAs假晶高電子遷移率電晶體單刀雙擲開關之銅金屬化製程及使用金屬氧化物半導體，這些成果，有助於製造低成本、低功率損耗之SPDT switch以供無線通訊應用。

In this dissertation, the performances of the copper (Cu)-metallized AlGaAs/InGaAs pseudomorphic high-electron-mobility transistor (PHEMT) single-pole-double-throw (SPDT) switches and the AlGaAs/InGaAs metal-oxide-semiconductor PHEMT (MOS-PHEMT) SPDT switches with Al2O3 were studied. Cu-metallized AlGaAs/InGaAs PHEMT SPDT switches utilizing platinum (Pt, 70 nm) as the diffusion barrier is reported. In comparison with the gold (Au)-metallized switches, the Cu-metallized SPDT switches exhibited comparable performance with insertion loss of less than 0.5 dB, isolation larger than 35 dB and the input power for one dB compression (input P1dB) of 27 dBm at 2.5 GHz. To test the thermal stability of the Pt diffusion barrier, these switches were annealed at 250 ℃ for 20 h. After the annealing, the switches showed no degradation of the DC characteristics. In addition, after 144 h of high temperature storage life (HTSL) environment test at 150 ℃, these Cu-metallized switches still remained excellent and reliable radio frequency (RF) characteristics and power handling capability. To test the operation reliability of the Cu-metallized switches, the Cu-metallized switches were subjected to on/off (control voltage = +3/0 V exchange) stress test for 24 h at room temperature. The devices maintained excellent RF characteristics after the stress test. The electrical characteristics of these Cu-metallized AlGaAs/InGaAs PHEMT SPDT switches were also evaluated at elevated temperatures. Compared to the Au-metallized switches, the Cu-metallized SPDT switches exhibited comparable performance with insertion loss less than 0.5 dB, return loss larger than 20 dB, isolation larger than 35 dB, and the input P1dB of 28.3 dBm at 2.5 GHz. In order to evaluate the temperature impact on DC and RF characteristics of the Cu-metallized switches for high-temperature applications, the switches were tested at different temperatures. The device exhibits low thermal threshold coefficients (δVth/δT) of −0.25 mV/°K from 300 °K to 500 °K, good microwave performance at 380 °K with insertion loss less than 0.5 dB, isolation higher than 40 dB, and the input P1dB of 28.45 dBm at 2.5 GHz. An AlGaAs/InGaAs MOS-PHEMT SPDT switch using Al2O3 high-κ gate dielectric by atomic layer deposition (ALD) is fabricated for RF switch application. The MOS-PHEMT exhibited the comparable DC performance and much lower gate current as compared to the conventional PHEMT. RF test shows the MOS-PHEMT switch has an insertion loss of less than 0.5 dB, an isolation larger than 30 dB, a return loss larger than 15 dB, and an input P1dB of 31.4 dBm at 2.5 GHz. Overall, we have successful developed the Cu metallization process for the AlGaAs/InGaAs SPDT switch and the Al2O3 high-κ gate dielectric process for the MOS-PHEMT SPDT switch, and have reported the fabrication process and electrical performances of the Cu-metallized switches and the MOS-PHEMT switches with Al2O3 dielectric for low cost and low power consumption SPDT switches for wireless communication applications.