Single Crystal Growth and Characterization of Silicon Germanium Alloys
Abstract
Silicon and germanium exhibit complete solid solubility for all binary concentrations. However, the growth of single crystalline SiGe alloys by bulk growth processes is hindered by the relatively wide separation of the solidus and liquidus lines. Previous research has yielded single crystals grown by the Czochralski method which are limited to only a few atomic percent of solute (Si or Ge), and even these crystals must be grown slowly (on the order of a millimeter per hour). On both a macroscopic and a microscopic scale, these crystals exhibit large axial variation in the solute distribution. This research investigates Si(x)Ge(1-x) alloys with 0<x<-0.05. Several growth parameters that affect axial and radial segregation as well as growth interface stability and micro segregation are investigated. Specifically, this research investigates methods to influence the Si axial composition fluctuations, minimize dislocation density in the crystal, and allow for a relatively fast growth rate while maintaining single crystalline growth. In the reported growth experiments, single crystalline growth was limited to boule concentrations of less than 1 at% Si. For this concentration range of Si, the growth rate could be varied; this work resulted in single crystalline growth for growth rates between 2 and 11 mm/hr. For the thermal configuration used, concentrations of Si higher than 1 at% resulted in all instances in polycrystalline growth regardless of the growth rate. Axial macro segregation of solute in the boule was found to lie in the middle of values reported in the literature. The effective distribution coefficient (k(eff)) of Si in the concentration range investigated was found to be 2.75. Seed rotation rate variations between 15 and 45 rpm were not found to affect the macrosegregation of solute, indicating segregation was dominated by convective currents and not a solute boundary layer (diffusion).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 25, 1999
- Accession Number
- ADA360049
Entities
People
- Tilghman L. Rittenhouse
Organizations
- Massachusetts Institute of Technology