Heater Power Control for Thermal History Stability
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Solution Overview
Problem
Variations in heater resistance and input voltage during semiconductor wafer heat treatment lead to inconsistent thermal histories and critical dimension variations in resist patterns, resulting in increased fabrication costs due to the need for larger, more expensive power supply devices to handle high currents.
Innovation Solution
A heat treatment apparatus with a temperature detecting part, power control unit, AC power supply, voltage detecting part, and correction part that adjusts the power control signal based on detected temperature and voltage differences, using correction values to manage the conduction rate of AC voltage and heater resistance, thereby stabilizing thermal histories and reducing device size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heater's rated wattage is increased to handle maximum voltage and power variations, then the reliability of heat treatment is improved, but the device size and fabrication cost increase
Solution Approach 1:
The patent applies dynamic control by adjusting the conduction rate of AC voltage based on actual heater resistance and input voltage conditions. Instead of using a fixed high-power heater and oversized electric devices, the system dynamically modulates the power delivery through conduction rate control, allowing the use of smaller, more cost-effective components while maintaining heat treatment reliability through real-time adaptation to varying conditions
Solution Approach 2:
The system changes the conduction rate parameter of AC voltage based on detected heater resistance and input voltage variations. By monitoring actual conditions and adjusting the conduction rate accordingly, the system maintains consistent thermal history without requiring oversized electric devices designed for maximum worst-case scenarios, thus resolving the contradiction between reliability and device size
2Stability of the object's composition
If the conduction rate of AC voltage is increased to compensate for heater resistance decrease, then the temperature stability is improved, but the current increase leads to larger electric device requirements
Solution Approach 1:
The patent implements feedback control by detecting the heater's actual resistance and input voltage, then adjusting the conduction rate accordingly. This closed-loop system maintains temperature stability by compensating for resistance variations without requiring excessive current increases, as the feedback mechanism optimizes power delivery efficiency and prevents oversized electric device requirements
Solution Approach 2:
The system dynamically adjusts the conduction rate based on real-time measurements of heater resistance and voltage conditions. This dynamic control allows the system to maintain temperature stability while managing current load efficiently, avoiding the need for oversized electric devices that would be required if static high-power components were used
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 solution effectively stabilizes thermal histories across multiple heat treatment modules, preventing critical dimension variations in resist patterns and reducing the size and cost of power supply devices by managing current flow efficiently.
Implementation Method 1
a heater such as a heating resistor for heating the seating plate
Implementation Method 2
a temperature detecting part to detect temperature of an object to-be-processed
Data Source
AI summary
Disclosed is a heat treatment apparatus for performing a heat treatment on an object to-be-processed by a heater, which can inhibit variation in thermal histories among the objects to-be-processed. The heat treatment apparatus includes, among others, a correction part to correct a power control signal output from an adjusting unit so that a conduction rate of an AC voltage applied to a heater is decreased. Specifically, the correction is performed based on a value obtained by multiplying a first correction value with a second correction value, where the first correction value is generated according to a ratio of the voltage detection value of AC power source to a predetermined reference voltage, and the second correction value is generated according to a ratio of the resistance value of the heater to a predetermined reference resistance value.