Silicon Single Crystal Pulling Apparatus Thermal Insulation
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Solution Overview
Problem
The challenge is to grow a silicon single crystal with desired resistivity and high concentration of N++ type electrical characteristics without breaking the crystal during the growth process, as high-concentration dopants can cause crystal breakage and dislocation issues, and maintaining dopant sublimation until the first half of the straight body portion is formed is difficult.
Innovation Solution
A silicon single crystal pulling apparatus with an insulation mechanism that thermally isolates the sample chamber from the pulling furnace, preventing dopant vaporization until deactivation, allowing assured addition of sublimable dopants at a desired time, and using a supply means to input the dopant after insulation is deactivated, thereby stabilizing crystal growth and reducing breakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high concentration dopant is added to obtain N++ type silicon single crystal with low resistivity, then electrical characteristics are improved, but crystal breakage occurs during growth
Solution Approach 1:
The patent applies preliminary action by forming a neck portion with reduced diameter before the main crystal growth phase. This neck portion serves as a preparatory structure that eliminates dislocations and creates a stable foundation for subsequent high-concentration doping. The neck formation occurs first, followed by dopant addition, ensuring crystal integrity is established before introducing stress-inducing dopants.
Solution Approach 2:
The crystal growth process is segmented into distinct phases: neck portion formation, shoulder formation, and straight body portion growth. Each phase has specific dopant concentration requirements. The patent segments the doping process by controlling dopant addition timing and concentration for each segment, allowing high concentration doping only after the neck and shoulder portions are formed, thus preventing crystal breakage.
2Reliability
If dopant sublimation is maintained during growth to ensure doping, then electrical characteristics are achieved, but dislocation elimination becomes difficult
Solution Approach 1:
The patent applies periodic action by controlling dopant sublimation in periodic phases rather than continuously. During neck portion formation, dopant sublimation is suppressed to enable dislocation elimination. During shoulder and straight body portion growth, dopant sublimation is activated to achieve desired electrical characteristics. This periodic control of sublimation resolves the contradiction between dislocation control and electrical property achievement.
3Manufacturing precision
If neck portion diameter is reduced to eliminate dislocation, then dislocation control is improved, but growth time increases
Solution Approach 1:
The patent applies partial action by forming a neck portion with reduced diameter only for the specific purpose of dislocation elimination, rather than maintaining reduced diameter throughout the entire crystal. The neck portion is formed with sufficient length to eliminate dislocations, then the crystal diameter is increased for the straight body portion to maximize productivity. This partial application of reduced diameter achieves dislocation control without excessive growth time.
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 the growth of silicon single crystals with desired resistivity and N++ type electrical characteristics without extending the time required for forming the first half of the straight body portion, reducing dislocation issues, and enabling high-concentration dopant input during stable crystal growth, resulting in a larger and more stable neck portion.
Implementation Method 1
an insulation mechanism that thermally insulates the sample chamber from the pulling furnace
Implementation Method 2
heating and subliming a sublimable dopant by radiation heat from the melt
Implementation Method 3
heating and subliming a sublimable dopant by radiation heat from the melt
Data Source
AI summary
Disclosed is a silicon single crystal pull-up apparatus that can grow a silicon single crystal having a desired electrical resistivity, to which a sublimable dopant has been reliably added, regardless of the length of the time necessary for the formation of a first half part of a straight body part in a silicon single crystal. Also disclosed is a process for producing a silicon single crystal. The silicon single crystal pull-up apparatus pulls up a silicon single crystal from a melt by a Czochralski method. The silicon single crystal pull-up apparatus comprises a pull-up furnace, a sample chamber that is externally mounted on the pull-up furnace and houses a sublimable dopant, a shielding mechanism that thermally shields the pull-up furnace and the sample chamber, and supply means that, after the release of shielding of the shielding mechanism, supplies the sublimable dopant into the melt.