SiC Wafer Retardation Control via Insulating Material Density
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Solution Overview
Problem
The challenge in manufacturing silicon carbide wafers is achieving consistent properties and low defect density due to variations in crucible properties and process conditions, leading to difficulties in securing regular silicon carbide ingots and wafers with controlled retardation and crystal quality.
Innovation Solution
A method involving the use of an insulating material with a specific density range (0.14 g/cc to 0.28 g/cc) and thermal expansion coefficient (2.65 × 10^-6 /°C to 2.75 × 10^-6 /°C) surrounding the reactor, which controls temperature distribution and residual stress, allowing for the growth of silicon carbide ingots with improved retardation distribution and reduced defects, followed by precise cutting and polishing steps to achieve wafers with low retardation values and excellent crystal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If physical vapor transport (PVT) method is used to manufacture silicon carbide ingot, then high growth rate is achieved, but current density changes and temperature distribution changes depending on crucible properties and process condition, making it difficult to secure regular properties of silicon carbide ingot and wafer
Solution Approach 1:
The patent applies parameter changes by controlling the density of the insulating material wrapping to be within 0.14-0.28 g/cc. This specific parameter range optimizes the thermal insulation properties, stabilizing temperature distribution during the PVT process while maintaining high growth rate, thereby resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The insulating material wrapping acts as an intermediary between the induction heating system and the crucible. By selecting materials with appropriate density (0.14-0.28 g/cc), it mediates heat distribution to achieve uniform temperature fields, enabling both high growth rate and regular ingot properties simultaneously
2Ease of manufacture
If insulating material with inappropriate density is used, then manufacturing process is simplified, but retardation distribution and crystal quality deteriorate
Solution Approach 1:
The patent establishes specific parameter ranges for insulating material density (0.14-0.28 g/cc) and thermal expansion coefficient (2.65×10^-6 to 2.75×10^-6 /°C). These parameter specifications ensure optimal temperature control during crystal growth, achieving both ease of manufacture through standardized material selection and high manufacturing precision in retardation distribution and crystal quality
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
The method results in silicon carbide wafers with average and maximum retardation values of 38 nm or less, low dislocation density, and improved crystal quality, minimizing distortion and defects, and enhancing the properties of semiconductor elements.
Implementation Method 1
the reactor comprises an insulating material surrounding the external surface
Implementation Method 2
heating the crucible to sublimate by an induction heating method
Implementation Method 3
adjusting the temperature, the pressure, and the atmosphere of the inner space to sublimate the material
Data Source
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AI summary
Example embodiments provide a wafer having retardation distribution measured with light of a wavelength of 520 nm, and in which the average value, the maximum value, the deviation of the retardation is a certain value or less, and a method of manufacturing the same. A wafer according to example embodiments has a low retardation value measured with light of a wavelength of 520 nm, and shows good crystal quality without distortion or twist of the crystal.