Low Damage SiNX Surface Passivation using Remote ICP-CVD for AlGaN/GaN HEMTs

1. Introduction The surface trap of AlGaN/GaN high electron mobility transistors (HEMTs) can cause current collapse phenomenon which is the most serious limiting factor of the device's output power at high frequency operation. The surface passivation is a key step to reduce surface state effects and the quality of surface passivation film is very important [1]. Silicon nitride (SiNX) is widely used for Al-GaN/GaN HEMTs passivation layer and is generally deposited by plasma enhanced chemical vapor deposition (PECVD) method. The RF power of in-ductively coupled plasma (ICP) source can easily crack N2 whose bonding energy is relatively strong. In ICP-CVD system, N2 gas can be used as a reactor instead of NH3 gas which is used generally at PECVD. Since nitrogen ion is supplied without hydrogen to deposit SiNX, the hydrogen concentration of SiNX film can be decreased [2]. The semiconductor surface and 2-dimensional electron gas (DEG) of AlGaN/GaN heterostructure can be damaged by plasma during deposition. Because such plasma damage can degrade the surface pas-sivation effects [3], 'remote-mode PECVD', in which the film deposition region is away from plasma generating region, is an attractive method [4] for AlGaN/GaN HEMT's passivation [5]. In this paper, the low plasma damage high quality SiNX surface passivation method was developed using remote ICP-CVD and it was applied to AlGaN/GaN HEMTs. And DC, RF, pulsed I-V and output power characteristics are measured to confirm surface passivation effects by the remote ICP-CVD.