Epitaxial Silicon Wafer Cooling Temperature Control
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Solution Overview
Problem
Existing methods for manufacturing epitaxial silicon wafers face challenges in preventing dislocation defects, particularly due to temperature differences between the silicon wafer and susceptor during the cooling process, which are difficult to monitor and control, especially in the outer circumferential portion.
Innovation Solution
The method involves monitoring and controlling the temperature difference between the outer circumferential portion of the silicon wafer and the susceptor by using a predictive calculation based on the center portion's temperature, adjusting the output of external heaters like halogen lamps to maintain a predetermined temperature difference, and using a susceptor with reduced heat capacity to minimize stress and dislocation generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the silicon wafer is cooled rapidly after epitaxial growth, then the productivity is improved, but the temperature difference between the wafer and susceptor increases causing dislocation defects
Solution Approach 1:
The patent applies local quality by differentiating temperature control between the center and outer circumferential portions of the silicon wafer. The outer circumferential portion, which contacts the susceptor, receives targeted heating to maintain temperature difference within 30°C, while the center portion follows the overall cooling process. This localized differential heating resolves the contradiction by enabling rapid cooling without causing dislocation at the critical contact region.
Solution Approach 2:
The patent changes the temperature parameter dynamically during the cooling process. After epitaxial growth at high temperature (800-1200°C), the system transitions to a controlled cooling phase where the outer circumferential portion's temperature is actively regulated to maintain a maximum 30°C difference from the susceptor. This parameter change enables both rapid cooling for productivity and precise temperature control for defect prevention.
2Manufacturing precision
If the temperature of the outer circumferential portion is monitored and controlled, then the dislocation defects are prevented, but the device complexity increases due to additional sensors and control systems
Solution Approach 1:
The patent introduces an intermediary approach by using the susceptor as a thermal mediator. Instead of directly monitoring and controlling the wafer's outer circumferential temperature with complex sensors, the system controls the susceptor's temperature, which indirectly regulates the wafer contact region. This intermediary control method reduces device complexity while maintaining effective temperature difference control to prevent dislocation.
Solution Approach 2:
The patent applies self-service by utilizing the inherent thermal conduction properties of the susceptor-wafer contact interface. The susceptor naturally conducts heat from the outer circumferential portion of the wafer, creating a self-regulating thermal pathway. By controlling the susceptor temperature, the system leverages this natural heat transfer mechanism to maintain appropriate temperature gradients without requiring additional active cooling or heating elements at the wafer edge.
3Stability of the object's composition
If the heat capacity of the susceptor is increased to maintain temperature, then the temperature stability is improved, but the energy consumption increases
Solution Approach 1:
The patent implements periodic action by applying intermittent or pulsed heating to the susceptor during the cooling process. Rather than maintaining continuous high-power heating to sustain temperature stability, the system applies heat in periodic cycles or pulses to the susceptor, which then distributes this thermal energy to the wafer's outer circumferential region. This periodic heating achieves temperature stability while significantly reducing average energy consumption compared to continuous heating.
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 dislocation defects by maintaining a controlled temperature difference, ensuring high-quality epitaxial wafers with reduced defects during the cooling process.
Implementation Method 1
the temperature of the main surface of the silicon wafer is measured with a radiation thermometer
Implementation Method 2
the output of external heaters (for example, a halogen lamp) is controlled
Implementation Method 3
the output of high-frequency inductive heater to heat the susceptor is controlled
Implementation Method 4
high-frequency inductive heater
Implementation Method 5
the heat transfer from the susceptor to the silicon wafer may be regulated
Data Source
AI summary
A method of manufacturing an epitaxial wafer in which an epitaxial layer is grown over a main surface of a silicon wafer placed substantially horizontally on a susceptor is provided. The method comprises: a growing step of the epitaxial layer; and a cooling step of cooling the epitaxial wafer having the epitaxial layer. The cooling step comprises: a wafer measurement step of measuring a temperature of the epitaxial wafer; a susceptor measurement step of measuring a temperature of the susceptor; and a control step of controlling a heater capable of heating at least the susceptor or the epitaxial wafer such that difference between a temperature of the epitaxial wafer and a temperature of the susceptor is within a predetermined range.