Conformal and Ultra Shallow Junction Formation Achieved Using a Pulsed-Laser Annealing Process Integrated With a Modified Plasma Assisted Doping Method

Abstract

Recently, a shallow and conformal doping profile is required for promising 3D structured devices. In this study, we deposited the dopant phosphorus (P) using modified plasma assisted doping (PaD) followed by an annealing process to electrically activate the dopants. A rapid thermal annealing process (RTP) was the first approach tested for activation but it resulted in a deep junction (>35 nm). To reduce the junction depth, we tried the flash lamp annealing process (FLP) to shorten the annealing time. We also predicted the annealing temperature by numerical thermal analysis, which reached 1,020 °C. However, the FLP resulted in a deep junction (~ 30 nm), which was not shallow enough to suppress short channel effects. Since an even shorter annealing process was required to form a ultra-shallow junction, we tried the laser annealing process (LAP) as a promising alternative. The LAP, which had a power density of 0.3 J/cm2, increased the surface temperature up to 1,100 °C with a shallow isothermal layer. Using the LAP, we achieved a USJ with an activated surface dopant concentration of 3.86×10 19 cm-3 and a junction depth of 10 nm, which will allow further scaling-down of devices.

Keywords

• Ultra-shallow junction
• phosphorus
• plasma assisted doping
• laser annealing process