Laser Probe for Satellite Disk Speed Measurement
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Solution Overview
Problem
The existing MOCVD equipment lacks an accurate method to measure the rotational speed of satellite disks, which affects temperature consistency and wafer production yield.
Innovation Solution
A method and apparatus using a laser detection probe to emit a beam of laser light onto a planetary susceptor, converting reflected light into an electrical signal, and calculating the rotational speed of satellite disks based on the angle variation between the edge of the wafer entering and leaving a viewport, utilizing a multi-channel synchronous data acquisition card for precise measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the rotational speed of the satellite disk is adjusted by airflow, then the temperature consistency of the wafer is improved, but the measurement precision of the rotational speed deteriorates
Solution Approach 1:
A laser detection probe is introduced as an intermediary device to measure the rotational speed of the satellite disk. The laser beam reflects off the satellite disk and wafer, and the reflected light is converted into electrical signals by a detector. This intermediary measurement system enables precise rotational speed measurement without interfering with the airflow-driven temperature control mechanism.
Solution Approach 2:
The patent replaces direct mechanical measurement methods with an optical measurement system. Instead of using mechanical sensors that would interfere with the airflow, the system uses laser light reflection and photoelectric conversion to non-contactively measure rotational speed, thereby maintaining temperature consistency while achieving precise measurement.
2Measurement precision
If a laser detection probe is installed on the chamber observation window, then the measurement precision of rotational speed is improved, but the device complexity increases
Solution Approach 1:
The laser detection probe installed on the chamber observation window serves multiple functions: it provides signals for planetary susceptor revolution, generates trigger pulse signals for synchronization, and enables satellite disk rotational speed measurement. This multi-functionality reduces the need for separate measurement systems, thereby limiting the increase in device complexity.
Solution Approach 2:
The system uses the existing chamber observation window as a mounting location for the laser detection probe, utilizing the existing structural opening rather than requiring additional penetrations or complex mounting mechanisms. The probe leverages the existing optical path and chamber structure to perform measurements without adding significant complexity to the overall 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
Enables accurate measurement of satellite disk rotational speed, improving temperature consistency and wafer production yield by providing precise control over the rotational speed.
Implementation Method 1
converting reflected laser light into an electrical signal
Data Source
AI summary
A method for measuring a rotational speed of a satellite disk on a MOCVD planetary susceptor includes emitting a beam of laser light on the MOCVD equipment, the laser light irradiating on the planetary susceptor of the MOCVD equipment. As the planetary susceptor is revolving, the laser light is irradiating on a satellite disk and wafers on the satellite disk, splitting and converting the reflected laser light into an electrical signal and sampling the electrical signal at a fixed frequency within a time period of two trigger pulse signals to obtain an angle revolved by the planetary susceptor for each sampling. The rotational speed of the satellite disk is obtained by calculating variation between Φ0 to Φ1, wherein the rotation angle of Φ0 is obtained when the edge of the wafer enters a viewport, and Φ1 is calculated when the edge of the same wafer leaves the viewport.