Non-contact monitoring of Ge and B diffusion in B-doped epitaxial Si1-xGex bi-layers on silicon substrates during rapid thermal annealing by multiwavelength Raman spectroscopy

Min-Hao Hong,Yen Chuang,Chun-Wei Chang,Yu-Ta Fan,Kuan-Ching Lee,Shiu-Ko Jang Jian,Wei-Fan Lee,Woo Sik Yoo,Dung-Ching Perng

doi:10.1063/1.4748294

Abstract

B-doped, thin Si1-xGex bi-layers with different Ge content and B concentrations were epitaxially grown on Si(100) device wafers. Diffusion behavior of Ge and B atoms during rapid thermal annealing were monitored by multiwavelength micro-Raman spectroscopy. Raman spectra indicating possible Ge and B redistribution by thermal diffusion was observed from B-doped, thin Si1-xGex bi-layers on Si(100) wafers after rapid thermal annealing at 950°C or higher. Significant Ge and B diffusion in Si1-xGex bi-layers and Si substrates was verified by secondary ion mass spectroscopy. Pile up of B atoms at the surface and at the boundary between Si1-xGex bi-layers was observed in the early stages of thermal diffusion.

Highlights

For performance enhancement of Si-based complementary metal-oxide-semiconductor (CMOS) devices, device scaling has been the most important principle for more than last three decades
Since the performance of CMOS devices is limited by hole mobility of pchannel devices, significant emphasis has been placed on stressor material (Si1-xGex) engineering for p-channel devices
In an effort to develop a non-contact, in-line monitoring technique for process-induced Ge and B concentration variations in Si1-xGex, multiwavelength micro-Raman characterization was done on B-doped Si1-xGex bi-layers on Si(100) device wafers

Summary

INTRODUCTION

For performance enhancement of Si-based complementary metal-oxide-semiconductor (CMOS) devices, device scaling has been the most important principle for more than last three decades. Undoped and B-doped Si1-xGex layers are epitaxially grown on Si (100) substrates in the early stage of device fabrication. They are typically exposed to subsequent thermal processing steps with significantly higher temperature than their epitaxial growth conditions. Understanding of thermal behavior of Ge and B in B-doped Si1-xGex layers is very important in designing appropriate device structures.[6,8,9,10,11] Nondestructive monitoring of Ge content and B concentration, before and after subsequent high temperature process steps, would be very beneficial for device structure optimization. The Raman characterization results were compared with Ge and B depth profiles from secondary ion mass spectroscopy (SIMS) for verification of effectiveness of multi-wavelength mirco-Raman spectroscopy as a viable, non-contact, in-line Ge and B monitoring technique

EXPERIMENT

RESULTS AND DISCUSSIONS

SUMMARY