Heater Resistor Temperature Control with RMS Noise Suppression
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Solution Overview
Problem
In substrate processing apparatuses, the noise from AD converters degrades the control accuracy for heater temperature and calculation accuracy of the resistance value, necessitating a technique to improve these accuracy levels.
Innovation Solution
A substrate processing apparatus is designed with an AD converter that outputs digital values of voltage and current applied to a heater resistor, and a controller calculates resistance values using a combination of digital signals and noise signals, specifically reducing noise impact through methods like RMS calculation and noise signal manipulation to enhance accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If digital values from AD converter are used directly for temperature control, then the control system is simple, but noise degrades the calculation accuracy of resistance value and control accuracy of heater temperature
Solution Approach 1:
The patent applies preliminary action by performing RMS calculation on the digital values before using them for resistance calculation. The controller calculates the RMS value of the digital voltage and current values from the AD converter, which preliminarily processes the noisy signals to reduce their impact on subsequent resistance and temperature calculations, thereby improving measurement precision without adding complex noise filtering hardware
Solution Approach 2:
The patent changes the parameter representation by transforming raw digital values into RMS-based parameters. Instead of using direct digital voltage and current values, the system calculates RMS values which statistically represent the effective values, thereby changing the parameter form to reduce noise impact while maintaining the essential information needed for accurate temperature control
2Measurement precision
If noise processing is applied to digital signals, then calculation accuracy improves, but processing time increases
Solution Approach 1:
The RMS calculation is performed as a preliminary step that can be computationally efficient compared to more complex filtering methods. By calculating RMS values of the digital signals before resistance computation, the system achieves noise reduction with relatively simple mathematical operations, minimizing additional processing time while improving temperature control accuracy
Data Source
AI summary
A substrate processing apparatus includes an AD converter configured to output digital values of a voltage applied to a heater resistor and a current flowing in the heater resistor; and a controller configured to control a temperature of the heater resistor by using a calculation voltage and a calculation current configured to calculate a resistance value of the heater resistor, which are obtained from an output result of the AD converter. The controller calculates at least one of the calculation voltage or the calculation current, based on a combination result of a digital signal obtained from the output result of the AD converter and a noise signal including a normal distribution noise.