Optical Heating Device Temperature Control via Periodic Light Cycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing temperature control methods for semiconductor substrates during heat treatments, such as those using photoirradiation, face challenges in accurately measuring and controlling the temperature due to interference from light emitted by the light source, leading to errors in temperature measurement and slow convergence to target temperatures.
Innovation Solution
A temperature control method involving a light source that repeatedly switches between a light-on and light-off state, allowing for accurate temperature measurement by a radiation thermometer during the light-off state, and adjusting electricity supply based on proportional, integral, and derivative controls to achieve precise temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the light source continuously emits light to heat the substrate, then heating efficiency is improved, but temperature measurement accuracy deteriorates due to light interference
Solution Approach 1:
The light source is controlled to operate in periodic cycles, alternating between light emission (heating phase) and light-off (measurement phase). This periodic operation allows the system to achieve both continuous heating over time and accurate temperature measurement during the off periods, resolving the contradiction between heating efficiency and measurement accuracy
2Measurement precision
If the light source is turned off to measure temperature accurately, then temperature measurement accuracy is improved, but heating efficiency deteriorates
Solution Approach 1:
By implementing periodic cycling between light-on and light-off states, the system ensures that measurement periods are sufficient for accurate temperature detection while heating periods are sufficient to maintain heating efficiency. The duty cycle can be optimized to balance these two requirements
3Speed
If the light source emits strong light to achieve fast heating, then heating speed is improved, but temperature measurement accuracy deteriorates due to increased light interference
Solution Approach 1:
The system allows for strong light emission during heating phases to achieve fast heating, followed by complete light-off during measurement phases to eliminate interference entirely. This temporal separation enables both high heating power and high measurement accuracy without compromise
4Measurement precision
If temperature measurement is performed continuously, then temperature control accuracy is improved, but light interference from the light source increases causing measurement errors
Solution Approach 1:
Continuous temperature control is achieved through high-frequency periodic measurement cycles. The light source is pulsed off at regular intervals to allow measurement, creating a continuous feedback loop that maintains temperature control accuracy while eliminating light interference during each measurement instant
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 method reduces errors in temperature measurement and control, enabling the substrate to quickly and accurately reach and maintain the target temperature, improving heating efficiency and precision.
Implementation Method 1
measuring the temperature of the semiconductor wafer with a temperature measurement instrument of a noncontact-type such as a thermograph
Implementation Method 2
a heat treatment method using photoirradiation is often employed to enable noncontact treatment
Data Source
AI summary
A method includes a step (A) of causing the light source part to repeatedly switch between a light-on state and a substantially light-off state, a step (B) of measuring the temperature of the substrate to be treated by observing infrared light radiated from the substrate to be treated while the light source part is kept in the substantially light-off state in the step (A), and a step (C) of determining either of a level of electricity supplied to the light source part in a next round of the light-on state and a time for which the light source part is kept in the next round of the light-on state based on the temperature of the substrate to be treated measured in the step (B) and a predetermined target temperature.