Silicon Substrate Defect Measurement via Thermal Consolidation and Enlargement
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Solution Overview
Problem
Current methods cannot effectively detect or measure defects in silicon substrates smaller than 20 nm, which are critical for producing high-quality silicon on insulator (SOI) substrates, as these defects can lead to through-defects in ultrathin active layers, making it difficult to select suitable substrates for the SMARTCUT method.
Innovation Solution
A method involving two heat treatments - a consolidation phase at 750° C to 850° C and an enlargement phase at 900° C to 1000° C - to enlarge defects to a size greater than 20 nm, followed by measurement using light scattering tomography to calculate the initial defect size, allowing for the selection of suitable substrates for SOI production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional measurement methods are used, then measurement simplicity is maintained, but measurement precision is insufficient for defects smaller than 20 nm
Solution Approach 1:
The patent applies preliminary heat treatments (consolidation at 750-850°C for 30-60 minutes, then enlargement at 900-1000°C for 1-10 hours) to the silicon substrate before measurement. These treatments enlarge defects smaller than 20 nm to detectable sizes, enabling conventional measurement methods to accurately measure what would otherwise be undetectable, thus improving measurement precision without requiring advanced measurement equipment
Solution Approach 2:
The patent changes the physical state and size parameters of defects through controlled heat treatment. By heating the substrate to specific temperatures for specific durations, the defects undergo consolidation and enlargement, transforming from undetectable sizes (<20 nm) to detectable sizes (≥20 nm), thereby enabling accurate measurement of initial defect characteristics
2Measurement precision
If heat treatment is applied to enlarge defects, then measurement precision is improved, but manufacturing precision may be affected
Solution Approach 1:
The heat treatment is applied as a preliminary action to a test substrate (not the actual donor substrate) to measure defect characteristics. This allows characterization of the silicon ingot's defect structure without permanently altering the quality of substrates intended for SOI production, thus maintaining manufacturing precision while achieving measurement precision
Solution Approach 2:
The patent uses a test substrate as a copy or representative sample of the donor substrate. By performing heat treatment and measurement on this copy, the initial defect characteristics of the actual donor substrate can be determined without subjecting it to potentially damaging heat treatment, thereby preserving manufacturing precision
3Productivity
If substrates with defects are used for SOI production, then productivity is maintained, but reliability of the SOI substrate decreases
Solution Approach 1:
The patent establishes a feedback loop where defect measurements from heat-treated test substrates provide information about the silicon ingot's quality. This feedback enables selection of donor substrates with acceptable defect characteristics before SOI production, ensuring that only suitable substrates are used and thereby maintaining both productivity and reliability
Solution Approach 2:
By performing defect measurement through preliminary heat treatment on test substrates before SOI production, the patent enables advance identification of suitable donor substrates. This preliminary quality assessment ensures that only substrates meeting quality criteria are used for SOI production, maintaining reliability while avoiding rework and ensuring continuous productivity
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
Enables the detection and measurement of defects smaller than 20 nm, ensuring the selection of high-quality substrates for producing SOI substrates with ultrathin active layers, reducing the risk of through-defects and improving the quality of SOI substrates.
Implementation Method 1
applying a heat treatment which consolidates and enlarges the defects
Implementation Method 2
the enlarged defects containing oxygen precipitates
Implementation Method 3
measuring size and density of the enlarged defects in a surface layer of the substrate
Data Source
AI summary
A method for measuring defects in a silicon substrate obtained by silicon ingot pulling, wherein the defects have a size of less than 20 nm. The method includes applying a first defect consolidation heat treatment to the substrate at a temperature of between 750° C. and 850° C. for a time period of between 30 minutes and 1 hour to consolidate the defects; applying a second defect enlargement heat treatment to the substrate at a temperature of between 900° C. and 1000° C. for a time period of between 1 hour and 10 hour hours to enlarge the defects to a size of greater than or equal to 20 nm, with the enlarged defects containing oxygen precipitates; measuring size and density of the enlarged defects in a surface layer of the substrate; and calculating the initial size of the defects on the basis of the measurements of the enlarged defects.