Silicon Substrate Defect Density Control via Nitrogen Adjustment
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Solution Overview
Problem
Existing methods for controlling defect density in silicon single crystal substrates through particle beam irradiation and heat treatment face variability in device characteristics due to factors like carbon and oxygen impurities, despite efforts to control carbon and oxygen concentrations, leading to inconsistent defect densities.
Innovation Solution
A method involving the preparation of silicon single crystal substrates with varying nitrogen concentrations, followed by particle beam irradiation and heat treatment, where the nitrogen concentration is adjusted based on correlations established from test substrates to achieve precise control over defect densities, particularly for composites containing carbon or oxygen, using techniques like cathode luminescence or photoluminescence for measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If particle beam irradiation and heat treatment are performed to control defect density, then recombination lifetime can be adjusted, but device characteristics vary due to impurity concentration differences
Solution Approach 1:
The patent changes the parameter being controlled from defect density directly to nitrogen concentration in the silicon substrate. By establishing a correlation between nitrogen concentration and defect density through preliminary experiments, the invention controls defect density indirectly by precisely controlling nitrogen concentration, which is more stable and controllable during crystal growth.
Solution Approach 2:
The patent performs preliminary particle beam irradiation and heat treatment on test substrates with different nitrogen concentrations before actual production. This preliminary action establishes the correlation between nitrogen concentration and defect density, allowing optimization of nitrogen concentration to achieve target defect density before manufacturing actual devices.
2Manufacturing precision
If carbon and oxygen concentrations are controlled to reduce light element composite formation, then defect density should be reduced, but variation in defect density persists
Solution Approach 1:
The patent shifts the control parameter from carbon and oxygen concentrations to nitrogen concentration. Experimental results show that nitrogen concentration has a more direct and controllable relationship with defect density than carbon or oxygen concentrations. By controlling nitrogen concentration within a specific range (e.g., 1×10^14 to 1×10^15 atoms/cm³), the invention achieves better uniformity in defect density.
3Reliability
If multiple types of defects are introduced by particle beam irradiation, then recombination centers are created, but thermally unstable defects remain causing variability
Solution Approach 1:
The patent performs preliminary heat treatment at specific temperatures (e.g., 350°C±10°C) on test substrates after particle beam irradiation to annihilate thermally unstable defects. By conducting this preliminary heat treatment and measuring the resulting defect density, the invention determines the optimal nitrogen concentration that compensates for defect annihilation, ensuring consistent defect density in 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
This approach allows for highly precise control of defect densities, reducing variations and enhancing the consistency of device characteristics by adjusting nitrogen concentrations within a 10% range, particularly suitable for power devices using nitrogen-added FZ silicon single crystal substrates.
Implementation Method 1
When a silicon single crystal substrate is irradiated with a particle beam having high energy, a silicon atom at a lattice position is flicked out, and interstitial silicon (I) and vacancy (V) which is an empty shell thereof are produced.
Implementation Method 2
a heat treatment step of performing a heat treatment on the silicon single crystal substrate after the particle beam irradiation step
Implementation Method 3
using techniques like cathode luminescence or photoluminescence for measurement
Implementation Method 4
using techniques like cathode luminescence or photoluminescence for measurement
Data Source
Figure 1~3(b)
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AI summary
The present invention is a method for controlling a defect density in a silicon single crystal substrate by performing: a preparation step of preparing a silicon single crystal substrate; a particle beam irradiation step; and a heat treatment step after the particle beam irradiation step. The method includes: a measurement step including irradiating test silicon single crystal substrates with a particle beam in advance before performing the preparation step, then carrying out a heat treatment, and measuring densities of defects thus produced; and a correlation acquisition step of acquiring a correlation between the measured defect densities and nitrogen concentrations. Based on the acquired correlation, a nitrogen concentration of the prepared silicon single crystal substrate is adjusted in such a manner that the defect density in the silicon single crystal substrate reaches a target value after the heat treatment step. This provides a method for controlling a defect density in a silicon single crystal substrate in such a manner to enable highly precise control of the defect density and reduction of a variation in defect density resulting from silicon single crystal substrates in a device manufacturing process which controls defect density by particle beam irradiation and heat treatment.