Copper Detection in Boron-Doped Silicon Substrates
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Solution Overview
Problem
Current methods for detecting Cu concentrations in silicon substrates doped with high boron concentrations, such as P+ and P++ substrates, face challenges due to electrostatic effects between Cu and boron, leading to inadequate diffusion of Cu to the substrate surfaces, which complicates precise analysis and may damage the substrate.
Innovation Solution
Heating the silicon substrate with a boron concentration of 3×1018 atoms/cm3 or more at a temperature between 300° C. and 350° C. for 1 to 12 hours allows increased diffusion of Cu to the surface, enabling quantitative analysis without fully dissolving the substrate, using methods like AAS, ICP-MS, or TXRF.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If heating temperature is increased to 500°C or higher for Cu diffusion, then Cu diffusion speed is improved, but analysis precision deteriorates due to insufficient Cu diffusion in high boron concentration substrates
Solution Approach 1:
The patent changes the heating temperature parameter from conventional high temperatures (500°C or higher) to a lower range (200°C to 450°C). This parameter change resolves the contradiction by finding an optimal temperature window where Cu diffusion is sufficient for analysis precision while avoiding the electrostatic effect barrier caused by high boron concentration that prevents adequate diffusion at higher temperatures.
2Measurement precision
If conventional AAS method is used to measure Cu concentration, then measurement sensitivity is improved, but substrate is destroyed requiring full dissolution
Solution Approach 1:
The patent applies preliminary heat treatment to the substrate before analysis to pre-concentrate Cu at the surfaces. This preliminary action enables subsequent analysis using less destructive methods while maintaining detection sensitivity, as the Cu is already concentrated at accessible locations rather than requiring complete substrate dissolution to achieve sufficient signal.
Solution Approach 2:
The patent extracts Cu from the bulk substrate to the surfaces through controlled heat treatment. This extraction concentrates the analyte at accessible locations, enabling surface analysis methods to achieve sufficient sensitivity without requiring complete substrate dissolution, thus preserving the substrate and simplifying the overall process.
3Quantity of substance
If heat treatment is applied to diffuse Cu in high boron substrates, then Cu diffusion is improved, but substrate contamination may occur
Solution Approach 1:
The patent performs heat treatment in an inert or controlled atmosphere (such as nitrogen or forming gas) rather than in air. This inert environment prevents oxidation and contamination of the substrate during the extended heat treatment required to diffuse Cu to the surfaces, while still allowing the thermal diffusion process to occur effectively at the optimized temperature range.
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 method effectively and efficiently estimates Cu concentrations on the surface, improving analysis precision and preventing substrate damage, while allowing for rapid and quantitative measurement of Cu without fully dissolving the substrate.
Implementation Method 1
heat a silicon substrate at a temperature of 600° C. or lower to diffuse Cu existent within the silicon substrate and collect the Cu toward obverse and converse surfaces of the silicon substrate
Implementation Method 2
heating the converse surface of the substrate at a temperature between 300° C. to 350° C. for a period of 1 to 12 hours
Data Source
AI summary
To expediently and quantitatively estimate Cu within a silicon substrate without fully dissolving the silicon substrate and to ascertain the process contamination, there is provided a method for quantitatively determining the Cu concentration in a Cu containing silicon substrate having obverse and converse surfaces, the silicon substrate contains at least 3×1018 atoms/cm3 of boron and is heated at a temperature of no more than 600° C., the improvement comprises heating the converse surface of the substrate at a temperature between 300° C. to 350° C. for a period of 1 to 12 hours and then quantitatively analyze the Cu concentration at obverse and converse surfaces of the heated substrate.