Wafer Centering Stage Alignment for Stable Polishing Width
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wafer centering mechanisms in polishing apparatuses suffer from accuracy limitations, leading to unstable polishing widths and potential wafer warping, due to mechanical dimensional errors and wear of centering hands.
Innovation Solution
A substrate processing apparatus and method that includes a centering stage, a processing stage, an eccentricity detector, and an aligner to accurately align the wafer center with the processing stage's central axis, using a moving and rotating mechanism to adjust the centering stage's position and orientation based on measured eccentricity, allowing precise centering without requiring perfect alignment of the centering stage's axis with the processing stage's axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional centering mechanism with centering hands is used to hold and center the wafer, then the wafer can be positioned on the substrate stage, but the centering accuracy is limited due to mechanical dimensional errors and wear, resulting in unstable polishing width
Solution Approach 1:
The patent replaces the mechanical centering hands system with an optical detection system. The detection unit uses light to non-contactively detect the wafer's position and orientation, eliminating mechanical contact and its associated dimensional errors and wear. This substitution directly addresses the centering accuracy limitation by using optical precision instead of mechanical precision.
Solution Approach 2:
The patent creates a digital copy or model of the wafer's position and orientation through optical detection. The detection unit captures light reflections from the wafer to determine its precise location and alignment, which is then processed by the control unit to calculate the necessary adjustments. This copying approach allows for high-precision measurement without physical contact.
2Productivity
If the polishing head presses the polishing tool against the peripheral portion of the wafer, then polishing can be performed, but the entirety of the wafer may warp causing defects in the peripheral portion
Solution Approach 1:
The patent performs preliminary centering and positioning actions before the polishing process begins. The control unit calculates the optimal position and orientation of the wafer on the substrate stage based on detected wafer characteristics, and adjusts the wafer position in advance. This preliminary positioning ensures that the wafer is correctly aligned before polishing pressure is applied, preventing warping while enabling effective polishing.
3Reliability
If a support stage is added to support the peripheral area of the wafer to prevent warping, then wafer stability improves, but the device complexity increases and alignment between stages becomes critical
Solution Approach 1:
The patent extracts and eliminates the separate support stage from the system. Instead of adding a support stage to prevent warping, the invention uses the optical detection and control system to precisely position and align the wafer on the existing substrate stage. This extraction approach maintains wafer stability through precise positioning rather than additional mechanical support, thereby reducing device complexity.
4Ease of manufacture
If the central axis of the centering stage does not coincide with the central axis of the processing stage, then manufacturing and assembly become easier, but the centering accuracy between stages deteriorates
Solution Approach 1:
The patent implements a feedback control system where the detection unit continuously monitors the wafer's position and orientation relative to the processing stage. The control unit receives this feedback information and calculates real-time adjustments to the wafer position and orientation. This feedback mechanism compensates for any misalignment between the centering stage and processing stage axes, maintaining high centering accuracy despite manufacturing tolerances.
Solution Approach 2:
The patent introduces dynamic adjustment capabilities to the centering stage, allowing it to move and rotate during the centering process. The centering stage is not fixed but can be actively adjusted based on detected wafer characteristics and calculated optimal positions. This dynamic approach enables the system to compensate for axis misalignment between stages through real-time positional adjustments.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
There is disclosed a substrate processing apparatus which can align a center of a substrate, such as a wafer, with a central axis of a substrate stage with high accuracy. The substrate processing apparatus includes: an eccentricity detector configured to obtain an amount of eccentricity and an eccentricity direction of a center of the substrate, when held on a centering stage, from a central axis of the centering stage; and an aligner configured to perform a centering operation of moving and rotating the centering stage until the center of the substrate on the centering stage is located on a central axis of a processing stage. The aligner is configured to calculate a distance by which the centering stage is to be moved and an angle through which the centering stage is to be rotated, based on an initial relative position of the central axis of the centering stage with respect to the central axis of the processing stage, the amount of eccentricity, and the eccentricity direction.