Epitaxial Silicon Wafer BMD Density Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing epitaxial silicon wafers face challenges in maintaining gettering capability while preventing slip dislocations due to excessive BMD density in the outer peripheral region, which reduces wafer strength and increases the risk of defects.
Innovation Solution
The epitaxial silicon wafer is designed with a nitrogen concentration range of 1×10^2 to 1×10^13 atoms/cm^3, ensuring a BMD density of 1×10^8 to 3×10^9/cm^3 over the radial direction, with a controlled distribution to maintain higher oxygen concentration in the outer peripheral region, reducing the variation in BMD density and preventing slip dislocations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the BMD density is increased to enhance gettering capability, then the gettering capability is improved, but the residual oxygen concentration in the outer peripheral region is reduced, resulting in easy occurrence of slip dislocation
Solution Approach 1:
The patent applies local quality by creating different BMD density zones within the wafer. The center region has high BMD density (1×10^8 to 3×10^9/cm³) for strong gettering capability, while the outer peripheral region has lower BMD density to maintain residual oxygen concentration and prevent slip dislocation. This spatial differentiation of BMD density allows simultaneous optimization of gettering performance and mechanical strength in different regions.
2Reliability
If heat treatment is applied before epitaxial growth to increase BMD density, then the gettering capability is enhanced, but the oxygen concentration in the outer peripheral portion is excessively reduced, causing slip dislocation
Solution Approach 1:
The patent implements local quality by controlling BMD density distribution to be non-uniform across the wafer. The center region undergoes sufficient BMD formation during heat treatment to achieve high gettering capability, while the outer peripheral region maintains lower BMD density to preserve oxygen concentration and prevent slip dislocation. This localized control of BMD density resolves the contradiction between gettering enhancement and slip dislocation prevention.
3Reliability
If the nitrogen concentration is increased to enhance gettering capability, then the BMD density is increased, but the width of the R-OSF region is increased, enlarging the region where epitaxial defects occur
Solution Approach 1:
The patent applies parameter changes by precisely controlling the nitrogen concentration within a specific range (1×10^12 to 1×10^13 atoms/cm³). This optimized nitrogen level achieves sufficient BMD density for enhanced gettering capability while limiting the width of the R-OSF region to minimize epitaxial defect formation. The parameter optimization balances gettering performance with defect reduction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the wafer's strength and gettering capability by maintaining a desired BMD density in the center region while reducing the risk of slip dislocations in the outer peripheral region, ensuring high-quality and reliable epitaxial silicon wafers.
Implementation Method 1
a thermally stable BMD hard to be eliminated even undergoing high-temperature heat treatment in an epitaxial process is formed in a crystal growth stage of a single crystal ingot
Implementation Method 2
heavy metal impurities are trapped in the BMD
Implementation Method 3
a silicon wafer is heated at a high temperature of 1000° C. to 1200° C. At this time, minute oxygen-precipitation nuclei in the wafer are reduced or eliminated by high-temperature heat treatment
Data Source
AI summary
An epitaxial silicon wafer includes a silicon wafer consisting of a COP region in which a nitrogen concentration is 1×108−3×109 atoms/cm3, and an epitaxial silicon film formed on the silicon wafer. When heat treatment for evaluation is applied, a density of BMD formed inside the silicon wafer is 1×108−3×109 atoms/cm3 over the entire radial direction of the silicon wafer. An average density of the BMD formed in an outer peripheral region of the silicon wafer which is a 1-10 mm range separated inward from an outermost periphery thereof is lower than the average density of the BMD formed in a center region. A variation in the BMD density in the outer peripheral region is 3 or less, and a residual oxygen concentration in the outer peripheral region is 8×1017 atoms/cm3 or more.