Light Pipe Pyrometer for Process Chamber Temperature Measurement
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Solution Overview
Problem
Semiconductor manufacturing processes face challenges in measuring temperatures within process chambers due to lamp radiation, which causes thermal shock and inaccuracies in temperature readings, leading to issues like wafer warping and 'Wafer Out Of Pocket' conditions.
Innovation Solution
A light pipe pyrometer assembly is used, comprising a lamp radiation filtering window, a sapphire light pipe with a bevel, an optical assembly with aspherical condenser lenses and a bandpass filter, and a temperature circuit, to measure internal assembly temperatures in semiconductor processing chambers, filtering out specific wavelengths of lamp radiation and reducing contamination and background thermal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If lamp radiation is used to heat the wafer, then the wafer reaches process temperature, but the lamp radiation also heats chamber components causing temperature mismatch and thermal shock
Solution Approach 1:
A light pipe pyrometer assembly acts as an intermediary measurement device that can detect temperatures through the chamber window without being affected by lamp radiation. The light pipe transmits infrared radiation from chamber components to the pyrometer detector, enabling indirect temperature measurement that prevents thermal shock while maintaining heating efficiency.
Solution Approach 2:
The system uses pyrometer-based temperature measurement with feedback control to monitor chamber component temperatures and adjust heating accordingly. This feedback mechanism prevents excessive temperature mismatches between the wafer and chamber components, eliminating thermal shock while maintaining efficient wafer heating.
2Measurement precision
If traditional temperature measurement methods are used in the presence of lamp radiation, then temperature readings can be obtained, but the readings are inaccurate due to radiation interference
Solution Approach 1:
The light pipe serves as an intermediary that physically separates the measurement device from the lamp radiation environment. It transmits only the infrared radiation from chamber components to the pyrometer, blocking harmful lamp radiation while allowing accurate temperature measurement of chamber components.
Solution Approach 2:
The system uses wavelength-selective filtering to measure only specific infrared wavelengths that correspond to chamber component radiation, while ignoring lamp radiation wavelengths. This local quality approach in the spectral domain enables accurate temperature measurement despite the presence of intense lamp radiation.
3Measurement precision
If a light pipe pyrometer assembly is installed in the process chamber, then accurate temperature measurement is achieved, but the light pipe becomes contaminated affecting measurement accuracy
Solution Approach 1:
A purge gas flow acts as an intermediary protective barrier between the light pipe and the chamber environment. The purge gas prevents contaminants from depositing on the light pipe surface while allowing infrared radiation to pass through, maintaining measurement accuracy over extended operation periods.
Solution Approach 2:
The light pipe is extracted from direct exposure to the chamber environment by positioning it through a chamber window. This extraction removes the light pipe from the contaminated chamber atmosphere while maintaining its ability to measure temperatures of chamber components through the window.
4Measurement precision
If existing chambers are modified to accommodate temperature measurement, then measurement capability is added, but extensive modifications increase cost and complexity
Solution Approach 1:
The light pipe pyrometer assembly is designed as a universal measurement device that can be installed through existing chamber windows without requiring chamber-specific modifications. The same basic assembly can measure temperatures of different chamber components (edge rings, susceptors, etc.) by simply repositioning the light pipe, providing multi-functional measurement capability.
Solution Approach 2:
The system uses optical copying principles where the light pipe creates an optical path from the chamber component to the pyrometer detector outside the chamber. This optical copy allows temperature measurement without physical contact or complex internal instrumentation, simplifying the measurement system.
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 minimizes temperature mismatches between wafers and chamber components, preventing warping and 'Wafer Out Of Pocket' issues, while being cost-effective and easily retrofittable to existing chambers without requiring extensive modifications.
Implementation Method 1
the lamp radiation filtering window is made of a wet quartz material that absorbs radiation with a wavelength of approximately 2.7 microns to approximately 2.8 microns
Implementation Method 2
the light pipe has a first end with a bevel configured to redirect infrared radiation emitted from the assembly through the light pipe
Implementation Method 3
an optical assembly configured to collimate, filter, and focus the infrared radiation from the second end of the light pipe
Implementation Method 4
an optical assembly configured to collimate, filter, and focus the infrared radiation from the second end of the light pipe
Implementation Method 5
the optical assembly includes a first aspherical condenser lens, an optical bandpass filter, and a second aspherical condenser lens
Implementation Method 6
an optical detector configured to receive an output from the optical assembly and to generate at least one signal representative of the infrared radiation
Implementation Method 7
a housing with liquid cooling channels that surrounds at least part of the light pipe and the optical assembly and configured to flow coolant to reduce background thermal emission
Data Source
AI summary
An apparatus for measuring a temperature of an assembly that is internal to a process chamber. The apparatus may include a light pipe positioned between a lamp radiation filtering window and the assembly, the light pipe has a first end with a bevel configured to redirect infrared radiation emitted from the assembly through the light pipe and has a second end distal to the first end, an optical assembly configured to collimate, filter, and focus infrared radiation from the second end of the light pipe, an optical detector configured to receive an output from the optical assembly and generate at least one signal representative of the infrared radiation, a temperature circuit that transforms the at least one signal into a temperature value, and a controller that is configured to receive the temperature value and to make adjustments to other process parameters of process chamber based on the temperature value.