Silicon Wafer LPD Reduction via Boron Oxygen Heat Treatment
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Solution Overview
Problem
Silicon wafers often exhibit unevenly distributed light point defects (LPDs) related to boron and oxygen concentrations, which can potentially affect semiconductor device performance, especially with advancements in microfabrication.
Innovation Solution
A method involving heat treatment at 300°C or more for silicon wafers with specific boron and oxygen donor concentration ranges, and cutting wafers within 50 days after ingot growth to prevent or reduce these defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If heat treatment is performed on silicon wafers with specific boron and oxygen concentrations, then unevenly distributed LPDs are reduced, but additional processing steps and time are required
Solution Approach 1:
The patent applies parameter changes by performing heat treatment at specific temperatures (500-600°C) for controlled durations (4-6 hours) to modify the physical state of the silicon wafer, thereby reducing unevenly distributed LPDs through thermal diffusion and defect annealing processes
2Manufacturing precision
If wafers are cut within 50 days after ingot growth, then unevenly distributed LPDs are prevented, but production scheduling flexibility is reduced
Solution Approach 1:
The patent applies preliminary action by establishing a time constraint (cutting within 50 days after ingot growth) to prevent the formation of unevenly distributed LPDs before they can develop, thereby proactively ensuring wafer quality through controlled timing of the cutting process
3Reliability
If heat treatment is performed for 4-6 hours at 500-600°C, then LPDs are reduced to the utmost limit, but energy consumption and processing complexity increase
Solution Approach 1:
The patent optimizes the heat treatment parameters by specifying a temperature range (500-600°C) and duration (4-6 hours) that achieves maximum LPD reduction while balancing energy consumption, representing an optimized parameter combination for industrial production
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
Significantly reduces or eliminates unevenly distributed LPDs, enhancing the quality of silicon wafers for semiconductor devices by determining the necessity of heat treatment based on boron and oxygen concentrations and timing of wafer cutting.
Implementation Method 1
a heat treatment process in which a silicon wafer that is sliced from a defect-free silicon single crystal and subjected to mirror polishing is heat-treated for a time period of four hours or more and six hours or less at a temperature of 500° C. or more and 600° C. or less
Data Source
AI summary
A manufacturing method of this invention includes: a step of slicing a silicon single crystal containing boron as an acceptor and obtaining a non-heat-treated silicon wafer, a step of determining a boron concentration with respect to the non-heat-treated silicon wafer, and a step of determining an oxygen donor concentration with respect to the non-heat-treated silicon wafer, in which a determination as to whether or not to perform a heat treatment at a temperature of 300° C. or more on the non-heat-treated silicon wafer is made based on a boron concentration determined in the step of determining a boron concentration, and an oxygen donor concentration determined in the step of determining an oxygen donor concentration. By this means, a wafer in which unevenly distributed LPDs that are present on the wafer are reduced is obtained.