Atmospheric Plasma Heating for SiC Substrate Annealing
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Solution Overview
Problem
Current heat treatment technologies for semiconductor fabrication, particularly for silicon carbide (SiC) substrates, face issues with thermal efficiency, furnace material wear, and surface roughing due to high temperatures, leading to increased costs and reduced throughput.
Innovation Solution
A heat treatment apparatus using atmospheric-pressure glow discharge between parallel-plate electrodes filled with a rare gas, where a high-frequency voltage is applied to induce plasma heating, allowing for efficient and uniform heating up to 2000°C while minimizing radiation loss and surface damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a resistance heating furnace is used to heat at 1200°C or more, then the heating capability is achieved, but thermal efficiency is markedly degraded due to radiation heat dissipation
Solution Approach 1:
The patent replaces the resistance heating system with an induction heating system. The induction heating apparatus uses an induction coil to generate a magnetic field that induces eddy currents in the heating region, converting electromagnetic energy directly into heat in the workpiece. This substitution eliminates the need for high-temperature resistance heating and reduces radiation heat loss to the furnace body, thereby improving thermal efficiency while maintaining the required heating temperature of 1200°C or more.
2Object-affected harmful factors
If a double pipe structure is adopted to avoid heater contamination, then contamination is prevented, but the heating region is widened and thermal efficiency is reduced
Solution Approach 1:
The induction heating system replaces the resistance heating system with double pipe structure. The induction coil generates a magnetic field that directly induces heat in the workpiece without physical contact, eliminating the need for double pipe structures. This direct heating method prevents heater contamination while concentrating heat in the immediate heating region, thereby improving thermal efficiency.
Solution Approach 2:
The induction coil acts as an intermediary that transfers energy wirelessly through magnetic field coupling. The coil generates a time-varying magnetic field that penetrates the workpiece and induces eddy currents, transferring electromagnetic energy to thermal energy without physical contact. This intermediary mechanism eliminates the need for direct thermal contact structures like double pipes, preventing contamination while maintaining heating efficiency.
3Temperature
If the heater is brought to higher temperature to compensate for heat loss in double pipe structure, then heating capability is maintained, but energy efficiency is further degraded
Solution Approach 1:
The induction heating system replaces the resistance heating system. Instead of heating a resistance element to high temperature and transferring heat through double pipes, the induction system directly induces eddy currents in the workpiece, converting electromagnetic energy to thermal energy within the workpiece itself. This eliminates the need to overheat the heating element and significantly improves energy efficiency.
4Temperature
If graphite or SiC materials are used for furnace body at 1800°C, then high temperature resistance is achieved, but material wear and replacement costs increase
Solution Approach 1:
The induction heating system operates at lower temperatures compared to flame or resistance heating methods required for SiC processing. By reducing the operating temperature, the thermal stress on the furnace body materials is reduced, thereby extending the service life of graphite or SiC furnace components and reducing replacement frequency and costs.
5Temperature
If high temperature heating is applied to SiC substrate, then activation annealing is achieved, but surface roughing occurs due to Si evaporation
Solution Approach 1:
The induction heating system provides rapid and uniform heating through eddy current induction. The time-varying magnetic field penetrates the SiC substrate and induces currents throughout the workpiece, achieving uniform temperature distribution. This rapid heating reduces the time the substrate spends at high temperature, minimizing Si evaporation and surface roughing while still achieving the required activation annealing效果.
Solution Approach 2:
The induction heating system uses time-varying alternating magnetic fields to heat the workpiece. The periodic magnetic field induces eddy currents that generate heat throughout the substrate volume. This periodic action enables rapid heating and cooling cycles, reducing the total time at high temperature and thereby minimizing surface roughing from Si evaporation while achieving the required annealing temperature.
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 enhances thermal efficiency, reduces material wear and costs, and prevents surface roughing, enabling faster processing times and improved device properties with reduced thermal stress.
Implementation Method 1
atmospheric-pressure glow discharge between parallel-plate electrodes filled with a rare gas
Implementation Method 2
a high-frequency voltage is applied to induce plasma heating
Implementation Method 3
a high-frequency voltage is applied to induce plasma heating
Data Source
AI summary
The present invention relates to a heat treatment apparatus that performs activation annealing or defect repair annealing and surface oxidization which succeed impurity doping intended to control the conductive property of a semiconductor substrate. In the present invention, a sample to be heated is placed on a lower electrode in a plasma treatment chamber. A gap between an upper electrode and the lower electrode is filled with a gap whose main raw material is a rare gas (helium, argon, krypton, xenon, or the like) having a pressure close to the atmospheric pressure. A power fed from a high-frequency power supply is applied to the upper electrode in order to induce an atmospheric-pressure glow discharge. Gas heating in the gap between the electrodes, which depends on the glow discharge, is used to heat-treat the sample to be heated.