Czochralski Silicon Crystal Growth Devitrification Control
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Solution Overview
Problem
The existing silicon single crystal growth methods, such as the Czochralski method, face challenges in preventing dislocations and variances in oxide film thicknesses due to inadequate devitrification and non-uniform Li concentration, leading to reduced yield and productivity.
Innovation Solution
Applying a DC voltage between the quartz crucible's outer wall and the pulling wire, with a constant electric current flowing through the silicon single crystal, to induce devitrification and control Li concentration, using a crucible with natural quartz for the outer wall and synthetic quartz for the inner wall to manage alkali metal ion content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC voltage is applied between the quartz crucible outer wall and pulling wire to induce devitrification, then dislocations are prevented and crystal quality is improved, but Li concentration becomes non-uniform and oxide film thickness varies
Solution Approach 1:
The patent applies a DC voltage between the quartz crucible outer wall and pulling wire to induce controlled devitrification of the quartz crucible. This parameter change (applying voltage) transforms the quartz structure to prevent brownish ring formation and dislocations, improving crystal quality while managing Li concentration distribution
Solution Approach 2:
The patent uses natural quartz for the outer wall and synthetic quartz for the inner wall of the crucible. This local differentiation of material quality allows the outer wall to undergo devitrification for dislocation prevention while the inner wall maintains purity for uniform Li concentration and oxide film formation
2Productivity
If the quartz crucible is used to hold silicon melt at high temperature for extended periods to improve productivity, then more single crystals can be produced, but brownish rings form and cause dislocations
Solution Approach 1:
The patent applies DC voltage to induce devitrification before brownish rings can form during prolonged melt holding. This preliminary action prevents the harmful transformation of quartz at high temperature, allowing extended production cycles without quality degradation
Solution Approach 2:
The patent converts the potentially harmful effect of high-temperature prolonged exposure (which causes brownish rings) into a beneficial devitrification process by applying DC voltage. The controlled devitrification prevents brownish ring formation and dislocations, turning a quality risk into a quality improvement mechanism
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 effectively prevents dislocations, enhances crystal yield and productivity, and ensures uniform oxide film thicknesses by maintaining a controlled Li concentration, thereby improving the quality of silicon single crystals for semiconductor applications.
Implementation Method 1
applying a DC voltage between an outer wall of the quartz crucible acts as a positive electrode and a pulling wire or pulling shaft for pulling up the silicon single crystal acts as a negative electrode; to induce devitrification
Implementation Method 2
fixing an electric current flowing through the silicon single crystal over a period of time for pulling up the single crystal
Data Source
AI summary
The present invention resides in a silicon single crystal growth method of pulling up and growing a single crystal from a melt of a silicon raw material in a quartz crucible based on a Czochralski method, wherein the method comprises the steps of: applying a DC voltage between an outer wall of the quartz crucible acts as a positive electrode and a pulling wire or pulling shaft for pulling up the silicon single crystal acts as a negative electrode; and fixing an electric current flowing through the silicon single crystal over a period of time for pulling up the single crystal, to grow the single crystal; as well as a pulling apparatus therefor.