Analysis of Basal Plane Dislocation Motion Induced By P+ Ion Implantation Using Synchrotron X-Ray Topography
Authors: Chen Zeyu , Liu Yafei , Cheng Qianyu , Hu Shanshan , Raghothamachar Balaji , Dudley Michael 
Published: February 2024

Silicon Carbide (SiC) is a promising wide bandgap semiconductor for future power devices since it has a wide bandgap, high breakdown voltage and good thermal stability [1]. The most mature method to perform selective area doping in 4H-SiC epiwafers during fabrication is ion implantation [2]. However, such implantation processes employing high energy ions can damage the lattice in the epilayers that can subsequently lead to formation and migration of basal plane dislocations (BPDs) which are known to be detrimental to the performance of the devices [3-4]. Implantation processes are typically conducted under room temperature (RT) conditions, but high temperature (HT) implantation is favorable when the dose level is high [5]. Oxide layer for blocking purpose is inevitable since photoresist can barely remain intact under such high temperature, which will increase the time, cost, and complexity [6-7].

Here, we will primarily emphasize the motion of the BPDs under stress from RT implantation. 1.2 kV-rated 4H-SiC PiN diodes with junction termination extension (JTE) annealed with same conditions have been successfully fabricated by implantation with different dose levels and concentration profiles under room temperature and at 600 ˚C. Concentration profiles simulated by Stopping and Range of Ions in Matter (SRIM) are shown in Fig.1(a) [8]. The JTEs were implanted with lower concentrations. Synchrotron monochromatic beam X-ray topography (SMBXT) has been performed to characterize the defects induced by implantation and annealing process. Topographs of PIN diodes are shown in Fig.1 (b)-(h). For the diodes implanted with 1x under RT and HT, there is no evidence of dislocations generated due to implantation and annealing. However, formation of BPD half loops, as highlighted in the red and yellow boxes, can be observed from the edge of the device when the dose level is elevated to 5x and 9x. In addition to that, the basal plane density (BPD) density of 5x RT Box due to implantation and annealing is much more significant than that of 5x RT and 9x RT, indicating that concentration profile can affect the defect generation. Fig.1 (e) shows topograph of PiN diode implanted with 5x under high temperature. The absence of BPDs compared to the RT implanted device to the same concentration profile suggests the generation of BPD is suppressed by the high temperature condition. In 5x RT Box device, opposite sign BPDs are nucleated from opposite edges of device, as indicated in Fig.1 (f)&(g). Here, we will analyze the motion of dislocations generated by ion implantation and annealing.

Reference:

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Figure 1