Boron Diffusion and Silicon Self-Interstitial Recycling between SiGeC layers
- PDF / 10,826,243 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 32 Downloads / 259 Views
C3.5.1
Boron Diffusion and Silicon Self-Interstitial Recycling between SiGeC layers M. S. Carroll1 J. C. Sturm, Dept. of Electrical Engineering, Princeton University, Princeton NJ 08544 1
Current address: Sandia National Laboratories, Albuquerque, NM 87185-1077
ABSTRACT Substitutional carbon is known to locally reduce silicon self-interstitial concentrations and act as a barrier to self-interstitial migration through the carbon rich regions. A silicon spacer between two carbon rich SiGe layers is fabricated in this work to examine self-interstitial generation in a region that is isolated from self-interstitial formation at the surface or in the silicon bulk. Boron marker layers above, below and in between two SiGeC layers are used to monitor the self-interstitial concentration between the substitutional carbon. No evidence of selfinterstitial depletion in the silicon spacer is observed, despite annealing in conditions believed sufficient to allow the self-interstitials to reach and react with surrounding substitutional carbon. Simulations of the self-interstitial and carbon indicate that the silicon self interstitial concentration in the spacer layer can be sustained in part due to a silicon self-interstitial recycling process through a reverse “kick-out” reaction. INTRODUCTION Accurate modeling of silicon front-end processes has become increasingly important because of the increasing expense of trial and error experiments for advanced complementary metal oxide semiconductor (CMOS). A necessity for simulation of dopants like boron is the ability to predict relative silicon self-interstitial concentrations, which promote boron diffusion [1]. However, critical parameters like self-interstitial diffusivities and generation rates are still under investigation [2-4]. Previously it has been shown that a SiGeC layer efficiently getters interstitials that migrate to the carbon layer. This effect can be used to effectively insulate the silicon below the SiGeC layer from interstitials introduced from the surface. Therefore, a region of silicon between two SiGeC layers is effectively insulated from interstitials injected from the surface and the bulk. Furthermore, self-interstitials in a silicon region between two SiGeC layers will diffuse to the surrounding carbon layers, where they would be expected to react with the carbon removing them from the silicon spacer. Because it is believed that the SiGeC layers insulate the silicon spacer from the bulk and the surface, the interstitial concentration in the spacer will depend entirely on a detailed balance between the self-interstitial generation rate in the spacer and the rate of interstitials that diffuse to the surrounding carbon layers where they are consumed. This novel structure offers a method to probe the generation rate of silicon self-interstitials.
EXPERIMENT Single crystal, 25 nm thick boron marker layers located at 150, 440, 600, and 900 nm below the surface were grown by rapid thermal chemical vapor deposition at temperatures of 550750°C on Czchokralski silicon s
Data Loading...
