Reflective Filter Window for Pyrometer Interference in Thermal Processing
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Solution Overview
Problem
In rapid thermal processing of semiconductor substrates, accurate temperature measurement is hindered by radiation interference from the heat source, especially at lower temperatures, due to the substrate being transparent to source radiation, which affects the interpretation of pyrometer signals.
Innovation Solution
A system with a window having reflective coatings that prevent radiation from the heat source within specific wavelengths from reaching the pyrometer, using materials that are transparent to the heat source radiation but reflective to the interfering wavelengths, thereby isolating the pyrometer readings to only substrate-emitted radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the substrate is transparent to heat source radiation at lower temperatures, then the heat source can effectively heat the substrate, but the pyrometer cannot accurately measure the substrate temperature due to interference from source radiation
Solution Approach 1:
A filter is introduced as an intermediary component between the heat source and the pyrometer. This filter selectively transmits heat source radiation wavelengths while blocking pyrometer measurement wavelengths, allowing the pyrometer to measure only substrate-emitted radiation without interference from the heat source
Solution Approach 2:
The filter is positioned specifically in the optical path between the heat source and the pyrometer, affecting only the radiation reaching the pyrometer while leaving the heating function intact. This localized intervention resolves the measurement interference without compromising the heating process
2Measurement precision
If a filter is added to block heat source radiation from reaching the pyrometer, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The filter serves multiple functions simultaneously: it blocks pyrometer wavelengths from the heat source, transmits heat source wavelengths for heating, and allows substrate radiation to reach the pyrometer. This multi-functionality reduces the need for additional separate components
Solution Approach 2:
The filter's optical properties are specifically designed to differentiate between wavelength ranges - transmitting in the heat source wavelength range while blocking in the pyrometer wavelength range. This parameter-based differentiation allows a single component to resolve the measurement interference
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 solution enhances the accuracy of temperature measurements by preventing source radiation interference, allowing for precise temperature control and uniformity during substrate processing, even at lower temperatures.
Implementation Method 1
having a first reflective coating and a second reflective coating on a surface between the heat source and the substrate holder, the reflective coatings being substantially reflective to radiation in the second range of wavelengths
Implementation Method 2
the window being made from a material which is substantially transparent to radiation in the first range of wavelengths
Implementation Method 3
a pyrometer to measure the temperature of the substrate when the substrate disposed on a substrate holder within a process area of the chamber by detecting radiation in a second range of wavelengths within the first range of wavelengths
Data Source
AI summary
Methods and apparatus for processing substrates and measuring the temperature using radiation pyrometry are disclosed. A reflective layer is provided on a window of a processing chamber. A radiation source providing radiation in a first range of wavelengths heats the substrate, the substrate being transparent to radiation in a second range of wavelengths within the first range of wavelengths for a predetermined temperature range. Radiation within the second range of wavelength is reflected by the reflective layer.