4 September 1998 Shallow p-type source/drain extension formation using B2H6 plasma doping for deep submicron CMOS
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Abstract
In this paper, we studied the feasibility of using a commercial etch chamber to perform plasma doping to form shallow p+-n junction. The plasma doping has the advantage of high wafer throughput compared to conventional low energy implanters. Ultra-shallow boron implantation was done in a plasma reactor with a Helicon plasma source and a gas mixture of He+B2H6. 0.18 micrometer class PMOS devices were fabricated using the plasma doping and compared with devices with a conventional BF2 S/D extension implant (10 keV BF2 implant, Xj approximately equals 650 Angstrom). The key results are as follows. (1) Shallow boron implant with good process uniformity on a wafer was achieved using the plasma doping process. Boron dose of approximately 5E14 cm-2 and junction depth (Xj) of approximately 250 Angstrom was achieved after S/D annealing. (2) The pMOS devices fabricated using the plasma doping have much better short channel effect (SCE) characteristics than the devices fabricated with 10 keV BF2 implant. The improvement of Xj in the vertical direction of a transistor (from approximately 650 angstrom to approximately 220 angstrom) using the plasma doping resulted in an improvement of approximately 450 angstrom in the lateral direction shown in Lgmin. (3) Degradation in gate-depletion was observed for the plasma doping devices; however, the degradation can be recovered by using an extra gate implant step. (4) Compared to devices with the conventional implant, higher Rsd was found in devices with the plasma doping process. This higher Rsd for the B2H6 cases was most likely due to the less gate-to-drain overlap and carbon/oxygen contaminants introduced during the plasma doping process. (5) Higher gate- edge diode leakage was also observed in the plasma doping devices. The high diode leakage was believed also due to the contaminants.
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Jerry C. Hu, Robert Kraft, Mark Rodder, Ih-Chin Chen, "Shallow p-type source/drain extension formation using B2H6 plasma doping for deep submicron CMOS", Proc. SPIE 3506, Microelectronic Device Technology II, (4 September 1998); doi: 10.1117/12.323993; https://doi.org/10.1117/12.323993
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