N-type Silicon Crystal Resistivity Control via Preliminary Doping
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Solution Overview
Problem
The production of low resistivity n-type silicon single crystals using volatile dopants like red phosphorus and arsenic is hindered by dislocation issues during the Czochralski process, leading to increased manufacturing costs and inability to achieve desired resistivity ranges.
Innovation Solution
Controlling the resistivity at the start position of the silicon single crystal to specific ranges (0.8-1.05 mΩcm for red phosphorus and 1.9-2.3 mΩcm for arsenic) and sequentially lowering it to achieve resistivity of 0.5-0.7 mΩcm or 1.2-1.4 mΩcm, respectively, to prevent dislocation and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the resistivity is controlled to a target value to achieve constant electrical resistivity throughout the silicon single crystal, then the electrical resistivity uniformity is improved, but dislocation easily occurs during the pulling up process
Solution Approach 1:
The patent applies preliminary action by controlling the resistivity at the start position of the straight body portion to a specific range (0.8-1.05 mΩcm) before the main pulling process. This preliminary resistivity control prevents dislocation at the critical start position where dislocation is most likely to occur, while still achieving the target constant resistivity in the subsequent body portion of the crystal.
2Manufacturing precision
If volatile dopants like red phosphorus and arsenic are used to achieve low resistivity, then the electrical resistivity is improved, but dislocation occurs in the straight body start portion and manufacturing cost increases
Solution Approach 1:
The patent applies parameter changes by specifically controlling the resistivity parameter at the start position of the straight body portion to be within 0.8-1.05 mΩcm, which is higher than the final target resistivity. This parameter change at the critical start position prevents dislocation caused by volatile dopant evaporation, while still achieving the desired low resistivity (0.5-0.7 mΩcm) in the main body of the crystal through sequential lowering.
3Reliability
If the pulling up process is repeated to prevent dislocation, then the dislocation occurrence is reduced, but the manufacturing cost increases
Solution Approach 1:
The patent applies preliminary action by establishing the correct resistivity range (0.8-1.05 mΩcm) at the start position before the main pulling process begins. This preliminary control ensures that dislocation does not occur during the normal pulling process, eliminating the need for repeated pulling operations and thereby reducing manufacturing costs while maintaining high reliability.
4Manufacturing precision
If the resistivity is lowered sequentially during pulling up, then the low resistivity range is achieved, but dislocation may occur at the start position
Solution Approach 1:
The patent applies preliminary action by first establishing the resistivity at the start position within the safe range of 0.8-1.05 mΩcm before sequential lowering begins. This preliminary high resistivity control acts as a protective measure that prevents dislocation at the vulnerable start position, while allowing the resistivity to be subsequently lowered to the target low range (0.5-0.7 mΩcm) in the body portion.
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 prevents dislocation and produces low resistivity n-type silicon single crystals without increasing manufacturing costs, enabling the production of ingots, wafers, and epitaxial wafers with desired resistivity ranges, which can be provided at lower prices.
Implementation Method 1
pulling up a silicon single crystal from a silicon melt containing volatile dopant red phosphorus as a principal dopant and growing the silicon single crystal by the Czochralski process
Implementation Method 2
n-type dopants such as red phosphorus and arsenic, which are volatile dopants, are evaporated during the pulling up
Data Source
AI summary
An n-type silicon single crystal production method of pulling up a silicon single crystal from a silicon melt containing red phosphorus as a principal dopant and growing the silicon single crystal by the Czochralski process, the method including: controlling electrical resistivity at a start position of a straight body portion of the silicon single crystal to 0.80 mΩcm or more and 1.05 mΩcm or less; and sequentially lowering the electrical resistivity of the silicon single crystal as the silicon single crystal is up and grown, thereby adjusting electrical resistivity of a part of the silicon single crystal to 0.5 mΩm or more and less than 0.6 mΩcm.