Silica Glass Crucible Layering for Void Defect Prevention
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Solution Overview
Problem
The production of silicon single crystals for semiconductor devices is hindered by void defects caused by gas bubbles in the silica glass crucible, which are difficult to detect and result in significant yield loss due to pinholes in the wafers.
Innovation Solution
A silica glass crucible with a two-layer structure, featuring a natural silica outer layer and a synthetic silica inner layer with a first synthetic silica layer at the crucible bottom having a thickness of 0.5 mm to 1.5 mm and a high OH group concentration, and a second layer with a thicker synthetic silica layer, is used to prevent gas bubble formation and void defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick synthetic silica layer is used in the crucible inner layer, then purity is improved and impurity incorporation is prevented, but gas bubbles are generated due to reduced heat resistance strength
Solution Approach 1:
The crucible structure is segmented into multiple layers with different materials and functions: an outer layer for heat resistance, an intermediate layer for transition, and an inner layer for purity. This segmentation allows each layer to optimize its specific function without compromising the others, preventing gas bubble generation while maintaining high purity.
Solution Approach 2:
The crucible employs composite material construction combining natural silica (for heat resistance) and synthetic silica (for purity) in a layered structure. The intermediate layer uses a gradient composition to smoothly transition between the outer and inner layers, eliminating abrupt material property changes that cause gas bubbles while maintaining both heat resistance and purity.
2Strength
If natural silica is used to increase heat resistance strength, then strength is improved, but impurity elution occurs and purity decreases
Solution Approach 1:
The crucible is divided into functional segments where the outer layer uses natural silica for heat resistance and the inner layer uses synthetic silica for purity. This spatial segmentation allows each material to perform its optimal function without the drawbacks of using it throughout the entire crucible structure.
Solution Approach 2:
A composite structure combining natural silica and synthetic silica layers is employed, with each layer optimized for its specific purpose. The intermediate transition layer gradually changes composition to prevent thermal shock and gas bubble formation, enabling the system to simultaneously achieve both high strength and high purity.
3Productivity
If the crucible size is increased to accommodate larger silicon ingots, then productivity is improved, but gas bubble removal becomes more difficult and void defects increase
Solution Approach 1:
The crucible structure is designed in advance with an optimized layered composition and thickness distribution that prevents gas bubble formation during the melting process. The intermediate layer's gradient structure is pre-configured to facilitate smooth heat transfer and minimize thermal gradients that would cause gas bubbles, addressing the problem before it occurs during crystal growth.
Solution Approach 2:
The physical and chemical parameters of the crucible materials are optimized, including the composition gradient in the intermediate layer, thickness ratios of different layers, and material purity levels. These parameter changes enable the crucible to maintain appropriate thermal properties and gas permeability even at larger sizes, preventing void defects while supporting high productivity.
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 configuration reduces the likelihood of gas bubbles and void defects in the silicon single crystal, enhancing the quality and yield of the crystal growth by controlling the viscosity and impurity levels, thereby minimizing pinhole generation and maintaining high crystal quality.
Implementation Method 1
a concentration of an OH group included within the first synthetic silica glass layer is 100 ppm or more
Implementation Method 2
forming an outer layer of the crucible with natural silica and increasing the strength of the crucible under a high temperature and forming an inner layer of the crucible which contacts with the silicon melt with synthetic silica and which prevents incorporating impurities
Implementation Method 3
the thickness of the first synthetic silica glass layer is 0.5 mm or more and 1.5 mm or less
Data Source
AI summary
A silica glass crucible for pulling up a silicon single crystal including an outer layer formed from a natural silica glass layer, and an inner layer formed from a synthetic silica glass layer, wherein the synthetic silica glass layer includes a first synthetic silica glass layer formed in a region within a certain range from the center of a crucible bottom section, and a second synthetic silica glass layer formed in a region which excludes the formation region of the first synthetic silica glass layer, and wherein the first synthetic silica glass layer has a thickness of 0.5 mm or more and 1.5 mm or less and a concentration of an OH group included in the first synthetic silica glass layer being 100 ppm or less.