Drift region doping effects on characteristics and reliability of high-voltage n-type metal–oxide–semiconductor transistors

Abstract

In this study, off-state breakdown voltage (V BD) and hot-carrier-induced degradation in high-voltage n-type metal–oxide–semiconductor transistors with various BF2 implantation doses in the n− drift region are investigated. Results show that a higher BF2 implantation dose results in a higher V BD but leads to a greater hot-carrier-induced device degradation. Experimental data and technology computer-aided design simulations suggest that the higher V BD is due to the suppression of gate-induced drain current. On the other hand, the greater hot-carrier-induced device degradation can be explained by a lower net donor concentration and a different current-flow path, which is closer to the Si–SiO2 interface.

Investigation of characteristics and hot-carrier reliability of high-voltage MOS transistors with various doping concentrations in the drift region

“…The gate oxide thickness is about 40 nm. The n − drift region is implanted with phosphorus with three doping levels to fabricate three devices denoted by devices A, B, and C. The doping concentrations in the drift region near Si-SiO 2 interface are roughly 6.5×10 16 , 5×10 16 , and 3.5×10 16 cm −3 for devices A, B, and C, respectively. To measure the device characteristics, the drain current (I D ) versus gate voltage (V G ) characteristics are measured under linear-region (with the drain voltage, V D , biased at 0.1 V) and saturation-region (V D =3.3 V) with the source and substrate terminals grounded.…”

“…Because the devices are operated under high voltages, the off-state breakdown voltage is a key device parameter. Furthermore, hot-carrier induced device degradation, caused by the damage near the Si-SiO 2 interface and/or charge trapping in the gate oxide due to a high electric field near the drain end of the channel, is prone to developing into a serious reliability concern [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. For the design of n-type highvoltage MOS transistors, a lightly doped n − drift region next to the drain is usually employed to achieve the required breakdown voltage.…”

“…For the design of n-type highvoltage MOS transistors, a lightly doped n − drift region next to the drain is usually employed to achieve the required breakdown voltage. The design of the n − drift region, such as by varying the doping concentration, has been shown to impact the hot-carrier reliability of n-type high-voltage MOS transistors [5,6,8,16]. Specifically, one report shows that increasing the doping concentration in the n − drift region results in a higher substrate current (I sub ) but its effect on hotcarrier induced device degradation is small [5].…”

“…Specifically, one report shows that increasing the doping concentration in the n − drift region results in a higher substrate current (I sub ) but its effect on hotcarrier induced device degradation is small [5]. Other reports show that increasing the donor concentration in the n − drift region also results in a higher I sub , however, hot-carrier induced device degradation is reduced [6,8,16]. Since the electric field near the drain end of the channel is a complex function of device design and bias conditions, the inconsistent results mentioned above may arise from different device design and bias conditions used in previous literatures.…”