Ti(20 nm)/Al(30 nm)/P型4H-SiC LDMOSFET欧姆接触的改善

The Improvement of Ohmic Contacts Property in P-Type 4H-SiC LDMOSFET Using Ti(20 nm)/Al(30 nm) Electrodes

摘要: 碳化硅横向双扩散金属-氧化物-半导体晶体管(Silicon Carbide laterally diffused Metal-Oxide-Semi- conductor Field Effect Transistor, SiC LDMOSFET)在高压集成电路中有着越来越广泛的应用前景。目前为止，依旧存在着限制SiC LDMOSFET器件进一步发展的瓶颈，欧姆接触便是其中之一。对于p型碳化硅，金属铝被认为是有利于形成欧姆接触的材料，但厚度较厚。研究表明，钛的加入能减小接触电阻，提高热稳定性。主要研究了一种新组分的钛/铝薄层金属用于p型4H-SiC的欧姆接触。通过溅射台将Ti(20 nm)/Al(30 nm)金属电极先后溅射到掺杂浓度为1 × 1020 cm−3的p型4H-SiC上，然后在氩气氛围中快速热退火(退火温度为1000℃，时间为2.5 min)形成欧姆接触。用传输线方法测量比接触电阻。最终得到比接触电阻值的优值为5.71 × 10−4 Ω•cm2，比预期结果的比接触电阻值降低了一个量级。此结果对Ti/Al基p型SiC LDMOSFET的进一步研究有着积极的意义。

Abstract: Silicon Carbide laterally diffused Metal-Oxide-Semiconductor Field Effect Transistor (SiC LDMOSFET) is widely used in high voltage integrated circuits. Until now, one of the obstacles which restrict its further development is its ohmic contact with p-type SiC. Previously, Aluminum is used to form the ohmic contact for p-type SiC. To form the ohmic contact with p-type SiC, Al metal was deposited and then annealed at high temperature subsequently. However, at high temperature, its thermal stability is supposed to be degraded, and will make the device performance getting worse. The re-search showed that the addition of titanium can decrease the contact resistance and improve the thermal stability. In this paper, a Ti(20 nm)/Al(30 nm) contact was formed by sputtering on p-type 4H-SiC Epitaxial film respectively with doping concentration of 1 × 1020 cm−3. Then, rapid thermal annealing was performed in argon atmosphere at 1000˚C for 2 min to form the ohmic contact. Transmission-line-model (TLM) method was examined to extract the contact resistivity. In case of Ti(20 nm)/Al(30 nm)/p-type SiC, a specific contact resistance of 5.71 × 10−4 Ω•cm2 was obtained, nearly one order of magnitude lower than the respected value. This research has a positive effect on the device performance of SiC LDMOSFETs.