Silicon Carbide Wafer Growth for Low Retardation and Defect Control
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Solution Overview
Problem
The challenge in manufacturing silicon carbide wafers is achieving consistent properties due to varying density and temperature distribution within the crucible during the physical vapor transport process, making it difficult to secure constant silicon carbide ingot and wafer quality.
Innovation Solution
The method involves using an insulating material with a specific density and coefficient of thermal expansion to control temperature and pressure conditions within the reactor, ensuring a silicon carbide ingot is grown with reduced defects and improved crystal quality, and subsequently manufacturing a wafer with controlled retardation distribution and surface roughness.
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 and temperature distribution inside the crucible vary making constant properties difficult to secure
Solution Approach 1:
The patent applies parameter changes by precisely controlling temperature gradients, pressure conditions, and gas flow rates during the PVT process. Specific parameters including temperature distribution (2000-2600°C), pressure (1-200 torr), and inert gas flow rate (70-300 sccm) are optimized to achieve both high growth rate and constant ingot properties. The reactor design with heated regions and cooling regions creates controlled thermal parameters that resolve the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent implements feedback control through monitoring and adjusting process parameters during growth. The system maintains constant properties by detecting variations in temperature distribution and current density, then adjusting heating power, gas flow, and pressure to compensate for deviations. This feedback mechanism ensures consistent ingot quality while maintaining high growth rates throughout the manufacturing process.
2Productivity
If higher temperature is used to increase growth rate, then productivity improves, but temperature distribution variation increases making constant properties difficult to secure
Solution Approach 1:
The patent segments the reactor into distinct heated regions and cooling regions to control temperature distribution. The crucible is positioned in a heated region at 2000-2600°C while cooling regions are strategically placed to create appropriate temperature gradients. This segmentation allows high temperature for rapid growth in the crucible zone while maintaining overall temperature uniformity through controlled cooling zones, resolving the contradiction between growth rate and temperature uniformity.
Solution Approach 2:
The patent applies local quality by creating different temperature conditions in different spatial zones. The crucible region maintains high temperature (2000-2600°C) for rapid silicon carbide growth, while peripheral and upper regions have controlled cooling to establish stable temperature gradients. This localized temperature control enables high productivity in the growth zone while maintaining overall thermal stability and uniformity throughout the reactor.
3Productivity
If current density is increased to improve growth rate, then productivity increases, but current density distribution variation increases making constant properties difficult to secure
Solution Approach 1:
The patent uses gas flow (pneumatics) to control current density distribution. Inert gas flows at 70-300 sccm are introduced to modify the electrical conductivity distribution within the crucible, thereby controlling current density uniformity. The gas flow patterns create plasma conditions that distribute current more evenly across the silicon carbide material, enabling high growth rates without excessive current density variations that would compromise ingot 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
This approach results in silicon carbide wafers with low retardation values, minimized distortion, and excellent crystal quality, as evidenced by reduced defect density and improved rocking curve full width at half maximum values, enhancing the performance and properties of semiconductor devices.
Implementation Method 1
The reactor includes an insulating material surrounding an external surface of the reactor and a heater for adjusting a temperature of the reactor or the temperature of the inner space
Implementation Method 2
a heater for adjusting a temperature of the reactor or the temperature of the inner space
Implementation Method 3
adjusting a temperature, a pressure, and an atmosphere of the inner space to sublimate the raw material
Implementation Method 4
physical vapor transport (PVT) is a method of charging a silicon carbide material inside a crucible, disposing a seed crystal consisting of silicon in upper side of the crucible, heating the crucible to sublimate the silicon carbide material
Data Source
AI summary
The wafer having a retardation distribution measured with a light having a wavelength of 520 nm, wherein an average value of the retardation is 38 nm or less, wherein the wafer comprises a micropipe, and wherein a density of the micropipe is 1.5/cm2 or less, is disclosed.