Single Crystal Silicon Plate Oxygen Control
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Solution Overview
Problem
Single crystal silicon substrates produced from the upper portion of ingots exhibit high oxygen concentrations, leading to uneven oxygen distribution and increased oxygen precipitate formation, which reduces minority carrier lifetime and device performance in semiconductor and solar cell applications.
Innovation Solution
A single crystal silicon plate-shaped body with an interstitial oxygen concentration of 25 ppma to 45 ppma and a substitutional carbon concentration of 0.5 ppma or less, where oxygen precipitates form a polyhedral structure after heating, is quarried from the upper portion of a CZ method ingot, minimizing dislocation and improving substrate quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the upper portion of the single crystal silicon ingot is used as a substrate, then the oxygen concentration is high (25-45 ppma), but oxygen precipitates form excessively, reducing minority carrier lifetime and device performance
Solution Approach 1:
The patent changes the physical-chemical parameters of oxygen precipitates by controlling their shape through specific heating treatments. By maintaining the ingot at 1000-1200°C for 1-48 hours after crystal growth, the patent transforms oxygen precipitates into a controlled distribution and morphology, preventing excessive precipitate formation while preserving the beneficial high oxygen concentration for internal gettering.
Solution Approach 2:
The patent applies preliminary heating treatment to the single crystal silicon ingot immediately after crystal growth while it is still in the crucible. This preliminary action of heating at 1000-1200°C for 1-48 hours prepares the oxygen distribution and precipitate morphology in advance, ensuring that when the substrate is later processed, the oxygen precipitates are already in a controlled state that prevents excessive formation and maintains high minority carrier lifetime.
2Object-generated harmful factors
If rapid cooling is applied to reduce oxygen precipitates, then precipitate formation decreases, but the oxygen concentration distribution becomes uneven, with higher concentration in the upper portion
Solution Approach 1:
The patent changes the thermal processing parameters by applying controlled heating at 1000-1200°C for 1-48 hours after crystal growth. This parameter change transforms the oxygen distribution and precipitate morphology, creating a stable composition where oxygen is evenly distributed and precipitates are controlled, eliminating the uneven distribution caused by rapid cooling.
Solution Approach 2:
The patent applies preliminary heating treatment to counteract the harmful effect of uneven oxygen distribution that would result from rapid cooling. By heating the ingot at 1000-1200°C for 1-48 hours while it is still in the crucible, the patent prevents the formation of uneven oxygen concentration zones, ensuring uniform distribution before the substrate is sliced and processed.
3Object-generated harmful factors
If substitutional carbon concentration is increased to 0.5 ppma or less, then oxygen precipitate nuclei formation is reduced, but manufacturing precision and substrate quality improve
Solution Approach 1:
The patent changes the substitutional carbon concentration parameter to 0.5 ppma or less, which directly reduces the formation of oxygen precipitate nuclei. This parameter change, combined with the controlled heating treatment, achieves both reduction of harmful precipitate formation and improvement of substrate quality, as the low carbon concentration prevents nucleus formation while the heating treatment ensures uniform oxygen distribution.
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 significantly reduces oxygen precipitate formation, enhancing minority carrier lifetime and device performance by controlling the shape and density of oxygen precipitates, resulting in improved solar cell characteristics and yield.
Implementation Method 1
the silicon melt is coagulated below the seed crystal by a so-called pulling up method of pulling up the seed crystal slowly, and is grown into a crystal
Implementation Method 2
the inner wall surface of the quartz crucible reacts with the silicon melt and dissolves, and oxygen melts into the silicon melt
Implementation Method 3
The oxygen in the single crystal silicon is supersaturated in a heating treatment process performed in a production process of semiconductor devices or solar cells, precipitates in the crystal as oxygen precipitates
Implementation Method 4
precipitates in the crystal as oxygen precipitates
Implementation Method 5
is pulled upward in a CZ apparatus and cooled
Data Source
AI summary
A single crystal silicon plate-shaped body as cut out from an upper portion of a straight body portion of a CZ method single crystal silicon ingot has an interstitial oxygen concentration in a crystal is 25 ppma to 45 ppma and a substitutional carbon concentration is 0.5 ppma or less in a radial center. In the radial center, oxygen precipitates are not observed in a bulk in an image of 200,000 times by a transmission electron microscope, and after heating the single crystal silicon plate-shaped body at 950° C. for 60 minutes, oxygen precipitates are observed in an image of the 200,000 times, and a shape of the oxygen precipitates is observed in a polyhedral structure in an image of 2,000,000 times.