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Title: | Optimization of a plasma immersion ion implantation process for shallow junctions in silicon |
Authors: | Rao, V. Ramgopal |
Keywords: | EEE Plasma immersion ion implantation (PIII) Mass spectroscopy |
Issue Date: | Oct-2014 |
Publisher: | AIP |
Abstract: | A plasma immersion ion implantation (PIII) process has been developed for realizing shallow doping profiles of phosphorus and boron in silicon using an in-house built dual chamber cluster tool. High Si etch rates observed in a 5% PH3 in H2 plasma have been ascribed to high concentration of H(α) radicals. Therefore, subsequent work was carried out with 5% PH3 in He, leading to much smaller etch rates. By optical emission spectroscopy, the radical species H(α), PH*2, and PH* have been identified. The concentration of all three species increased with pressure. Also, ion concentrations increased with pressure as evidenced by Langmuir data, with a maximum occurring at 0.12 mbar. The duty cycle of pulsed DC bias has a significant bearing on both the implantation and the etching process as it controls the leakage of positive charge collected at the surface of the silicon wafer during pulse on-time generated primarily due to secondary electron emission. The P implant process was optimized for a duty cycle of 10% or less at a pressure of 0.12 mbar with implant times as low as 30 s. Secondary ion mass spectroscopy showed a P dopant depth of 145 nm after rapid thermal annealing (RTA) at 950 °C for 5 s, resulting in a sheet resistance of 77 Ω/◻. Si n+/p diodes fabricated with phosphorus implantation using optimized PIII and RTA conditions exhibit Jon/Joff > 106 with an ideality factor of nearly 1.2. Using similar conditions, shallow doping profiles of B in silicon have also been realized. |
URI: | https://pubs.aip.org/avs/jva/article/32/6/061302/244833/Optimization-of-a-plasma-immersion-ion http://dspace.bits-pilani.ac.in:8080/xmlui/handle/123456789/12621 |
Appears in Collections: | Department of Electrical and Electronics Engineering |
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