Low-Temperature Processing Technology of SiC Devices

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(1) Results in 1996(a) Aluminum atoms have been doped in n type 6H-SiC (n= 1.4x10^<18>cm^<-3>) and 4H-SiC substrates set in doping chamber containing mixed gases of tri-methyl aluminum and hydrogen with a pressure of 100 Torr. Al atoms are distributed in the range of 50 nm, and the doped region showed p type conduction in as-doped conditions. Hole concentration and the mobility are estimated to be 2-4x10^<18>cm^<-3>,1-2x10^2cm^2/Vsec, and 2-4x10^<18>cm^<-3>,70-100cm^2/Vsec, respectively.(b) Ni-ohmic electrodes have been fabricated on n-type 6H-SiC substrates (n= 1.5x10^<18>cm^<-3>) by KrF excimer laser irradiation during Ni deposition. A shallow Ni-doped layr 120nm deep was formed by room temperature processes (laser energy density 1.0J/cm^2 and 1,000 pulses). Contact resistivity was estimated to be 6x10^<-3>OMEGAcm^2.Results in 1997(c) Boron-doping has been examined in n-type 6H-SiC substrates set in the gas mixture of tri-methyl boron and hydrogen by using KrF excimer laser irradiation processes. Inconditions of the laser energy density 0.8J/cm^2 and number of laser shots 1000-5000, SIMS analysis shows B atoms are doped in the range of 10-20 nm. P-type conduction with Hall measurements has not been assured due to shallow depth of the doped region(d) Tungsten ohmic contacts stable at 1000ﾟC (2 hours) have been fabricated on n-type 6H-SiC (n= 1.8x10^<18>cm^<-3>) substrates using both laser ablation of W pellets (purity 99.9%), and laser doping of deposited W with a KrF excimer laser inthe same process chamber. Shallow and abrupt contacts formed 10-20 nm deep in the substrates showed good ohmic characteristics without post-heat treatments (contact resistivity 2.2x10^<-4>OMEGAcm^2). The surface was found to be very smooth even after laser irradiation of the energy density 2.0J/cm^2.