Modeling of Phosphorus Clustering Associated with Point Defects

Nonplanar field effect transistors (FETs) such as fin field effect transistors (FinFETs) have been used in integrated circuits as the major devices for high-performance computing. FinFETs use a small cross-sectional fin structure to suppress short channel effects. However, the narrow fin structure causes a high series resistance, degrading the operation speed of integrated circuits. High dopant activation is needed to reduce the contact resistance. Supersaturation of active phosphorus can be obtained using solid-phase epitaxial regrowth (SPER) after high-dose phosphorus implantation on preamorphized silicon surface. Therefore, the active phosphorus concentration is able to exceed the solid solubility of phosphorus in silicon. However, phosphorus clusters may be formed at low temperatures, reducing the stability of active phosphorus. Unfortunately, the reaction mechanisms between point defects and phosphorus clusters are not clear. This project will study the reactions between point defects and phosphorus clustering and their impact on phosphorus deactivation. We will perform silicon implantation to create an amorphous layer followed by phosphorus or carbon implantation. The excess interstitials released from residual defects after SPER may react with active phosphorus atoms in the recrystallized layer. These excess interstitials could be blocked by the implanted carbon. After analysis of phosphorus deactivation, the reaction between interstitials and phosphorus clusters can be identified according to the difference in the deactivation behaviors between samples with and without carbon. A model for phosphorus clustering with point defects will be developed based on the experimental results. Atomistic simulation using kinetic Monte-Carlo (KMC) method will be performed to identify the microscopic clustering mechanism. A continuum equation model for clustering will be established as well. After the reactions between phosphorus clustering and point defects are well understood, the stability of active phosphorus can be improved. Thus the series resistance in transistors can be minimized for better circuit performance.

Project ID:PB10708-2137
External Project ID:MOST107-2221-E182-043