Wafer IR Temperature Sensing During Plasma Heating
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Solution Overview
Problem
Conventional plasma processing methods face challenges in accurately determining wafer temperature using IR light, leading to reduced processing yield and throughput due to combined IR light from the heating source and external IR light sources, which affects the geometry and temperature control during etching processes.
Innovation Solution
A method involving a semiconductor wafer placed on a sample stage within a processing chamber, where IR light emitted from a lamp above the stage is used for desorption, and IR light exiting from the wafer's rear surface is detected using a detector below, analyzing characteristic changes in IR light intensity across multiple wavelengths to determine the wafer's temperature and adjust it accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IR light from a lamp is used to heat the wafer for desorption, then the desorption efficiency is improved, but the temperature measurement accuracy deteriorates due to combined IR light from the heating source and external IR light sources
Solution Approach 1:
The patent implements periodic switching between heating mode and measurement mode. The IR lamp is turned on during desorption phases and turned off during temperature measurement phases, allowing the detector to measure only external IR light without interference from the heating source. This periodic action separates the heating function from the measurement function in time, resolving the contradiction between desorption efficiency and measurement accuracy.
Solution Approach 2:
The patent introduces a chopper as an intermediary device that modulates the IR light from the heating lamp. By chopping the light at a specific frequency, the system can distinguish between light from the heating source and external light sources through frequency analysis, enabling accurate temperature measurement even when the lamp is active.
2Productivity
If the wafer temperature is not accurately controlled, then the processing speed can be maintained, but the processing yield and geometry accuracy deteriorate
Solution Approach 1:
The patent implements a feedback control system where the detector continuously monitors the wafer temperature by measuring external IR light, and the controller adjusts the IR lamp power or gas flow based on the measured temperature to maintain the desired temperature range. This feedback mechanism ensures both high processing speed and accurate geometry control by dynamically adjusting process parameters.
Solution Approach 2:
The system performs preliminary temperature measurements and adjustments before the main etching process begins, and conducts measurements at critical transition points during processing. This preliminary action ensures the wafer is at the correct temperature before sensitive operations, preventing geometry errors while maintaining overall processing efficiency.
3Device complexity
If conventional temperature monitoring methods are used, then the device complexity is low, but the temperature control reliability deteriorates due to interference from combined IR light sources
Solution Approach 1:
The patent introduces a chopper as an intermediary device that modulates the IR light from the heating lamp. By chopping the light at a specific frequency, the system can distinguish between light from the heating source and external light sources through frequency analysis, enabling accurate temperature measurement even when the lamp is active.
Solution Approach 2:
The patent implements periodic switching between heating mode and measurement mode. The IR lamp is turned on during desorption phases and turned off during temperature measurement phases, allowing the detector to measure only external IR light without interference from the heating source. This periodic action separates the heating function from the measurement function in time, resolving the contradiction between desorption efficiency and measurement accuracy.
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 approach enhances the accuracy and efficiency of temperature monitoring and control, improving the repeatability and yield of the plasma processing by accurately determining and regulating the wafer temperature during heating and cooling cycles.
Implementation Method 1
desorbing the product layer formed on the wafer surface by heating the wafer with infrared (IR) light emitted from a lamp disposed above the wafer
Implementation Method 2
detecting IR light emitted from the wafer by a detector disposed below the wafer and analyzing characteristic changes in light intensities at a plurality of wavelengths
Data Source
AI summary
A plasma processing apparatus includes a stage disposed in a processing chamber for mounting a wafer, a plasma generation chamber disposed above the processing chamber for plasma generation using process gas, a plate member having multiple introduction holes, made of a dielectric material, disposed above the stage and between the processing chamber and the plasma generation chamber, and a lamp disposed around the plate member for heating the wafer. The plasma processing apparatus further includes an external IR light source, an emission fiber arranged in the stage, that outputs IR light from the external IR light source toward a wafer bottom, and a light collection fiber for collecting IR light from the wafer. Data obtained using only IR light from the lamp is subtracted from data obtained also using IR light from the external IR light source during heating of the wafer. Thus, a wafer temperature is determined.