Wafer Alignment Detection in Plasma Processing Trays
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Solution Overview
Problem
Conventional plasma processing apparatuses fail to ensure proper alignment of wafers in housing holes, leading to inadequate cooling and potential resist burning due to misalignment, as the cold gas does not sufficiently spread on the wafer's lower face when it is misaligned with the housing hole.
Innovation Solution
A plasma processing apparatus equipped with a housing state detection unit that includes a height detection system to determine if wafers are misaligned by comparing the height of the wafer's surface with the tray's surface, preventing plasma processing on misaligned wafers to avoid exposure to high-temperature plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafers are collectively supported in a tray with housing holes, then processing efficiency is improved by batch processing, but misalignment of wafers in housing holes occurs leading to insufficient cooling and potential resist burning
Solution Approach 1:
The patent applies preliminary action by detecting wafer alignment status in the alignment unit before the wafer is transferred to the processing chamber. The height detection unit measures the wafer surface height at predetermined positions, and the determination unit compares these measurements against reference values to identify misalignment. This pre-detection prevents misaligned wafers from entering plasma processing, thereby maintaining reliability while preserving batch processing efficiency.
2Productivity
If wafer alignment is not detected, then the plasma processing apparatus operates continuously without interruption, but misaligned wafers are exposed to high-temperature plasma causing resist burning
Solution Approach 1:
The patent implements feedback by using the height detection unit to continuously monitor wafer alignment status and providing this information to the determination unit. When misalignment is detected, the system generates appropriate responses (such as preventing plasma processing or triggering alerts). This feedback mechanism ensures that misaligned wafers are identified and protected from harmful plasma exposure while minimizing interruption to overall system operation.
3Reliability
If a height detection unit is added to detect wafer alignment, then misaligned wafers can be identified and prevented from processing, but the device complexity increases
Solution Approach 1:
The patent replaces complex mechanical alignment detection mechanisms with a height detection unit that measures wafer surface height at predetermined positions. This unit includes a detector (such as a laser displacement sensor or capacitive sensor) that non-contactively measures height, and a determination unit that processes the measurements to identify misalignment. This substitution reduces mechanical complexity while improving detection reliability.
4Productivity
If misaligned wafers are processed anyway, then processing throughput is maintained, but the quality of processed wafers deteriorates due to insufficient cooling and resist burning
Solution Approach 1:
The patent performs preliminary alignment detection in the alignment unit before wafers are transferred to the processing chamber. The height detection unit measures wafer surface height at multiple predetermined positions, and the determination unit compares these measurements against reference values to identify misalignment. By detecting and preventing misaligned wafers from entering plasma processing, the system ensures high processing quality while maintaining throughput by quickly identifying and excluding only the defective wafers.
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
Prevents resist burning by ensuring wafers are properly aligned before plasma processing, maintaining the integrity of the wafers and enhancing processing efficiency by detecting misalignment and returning misaligned trays to the stock unit.
Implementation Method 1
a height detection unit for detecting a height at a wafer side target point of a surface of the wafer housed in each of the plurality of housing holes
Implementation Method 2
a determination unit for determining whether or not the wafer is misaligned with respect to the corresponding housing hole, based on the height of the surface of the wafer at the wafer side target point detected by the height detection unit
Implementation Method 3
each wafer is cooled down by a cold gas (such as helium gas) supplied from a cold gas supply pipe line provided in the support stand through the tray
Implementation Method 4
Each wafer in the tray is electrostatically absorbed by an electrostatic absorption apparatus provided in the support stand through the tray
Data Source
AI summary
A plasma processing apparatus includes a stock unit, a processing unit, and an alignment chamber. The stock unit supplies and collects a conveyable tray formed with a plurality of housing holes in each of which a wafer is housed. In the processing chamber, plasma processing is executed on the wafers housed in the tray supplied from the stock unit. The alignment chamber is provided with a rotating table on which the tray before being subjected to the plasma processing is set to perform positioning of the wafers on the rotating table. A housing state determination unit of a control device determines whether or not the wafer is misaligned with respect the housing hole of the tray based on a height detected by height detecting sensors.