Pulsed Inductively-Coupled Plasma Doping of Phosphorus for N+-P Junction Fabrication

Abstract

Plasma doping is an attractive technology that may be capable of producing ultra-shallow junctions with high productivity. We used a pulsed inductively-coupled plasma (ICP) to increase the plasma density and to reduce particulates and deposits. We doped phosphorus ions at a low substrate bias voltage (0.2 to 2 kV) by using PH3 as the process gas. An n+-p junction with low sheet resistance was then formed by spike rapid thermal annealing (RTA). We investigated the density of the pulsed plasma as a function of time to determine the optimal delay time for the substrate pulse bias after the RF power of the ICP antenna had been switched on. The pulse width of the substrate bias was optimized to 50 s to maximize the throughput. We compared the plasma doping with a traditional beam-line ion implantation and found that it resulted in a lower junction depth and a higher sheet resistance at the same voltage. A junction depth of 34 nm and a sheet resistance of 590 / were obtained by plasma doping at 0.5 kV with spike RTA at 950 C.