Wafer Polishing Apparatus Pocket Depth Feedback Control
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Solution Overview
Problem
The existing waxless mount polishing technologies face challenges in maintaining the flatness of wafers due to fluctuations in the pocket depth of the template, caused by abrasion and deformation of the annular member and backing pad, leading to variations in wafer flatness over time.
Innovation Solution
A method and apparatus that measure the pocket depth of the template before and after polishing, calculate the difference in depth, and adjust polishing conditions such as relative speed and pressure to maintain consistent pocket depth, thereby stabilizing wafer flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the template is used for polishing wafers over time, then polishing productivity is maintained, but the pocket depth changes due to abrasion and deformation causing wafer flatness to deteriorate
Solution Approach 1:
The patent implements a feedback mechanism where the pocket depth is measured before and after polishing operations, and the difference value is calculated and used to adjust subsequent polishing conditions. This closed-loop control system continuously monitors template degradation and compensates for it, maintaining wafer flatness while allowing continuous use of the template for high productivity.
Solution Approach 2:
The patent changes polishing parameters (such as polishing pressure, relative speed between polishing head and turntable, or polishing pad selection) based on the measured pocket depth difference. By dynamically adjusting these parameters in response to template wear, the system maintains consistent wafer flatness throughout the template's service life without requiring frequent template replacement.
2Manufacturing precision
If the template is replaced frequently to maintain wafer flatness, then manufacturing precision is improved, but productivity is reduced due to replacement time and adjustment delays
Solution Approach 1:
Instead of replacing the template based on predetermined time intervals or conservative estimates, the system implements real-time feedback by measuring actual pocket depth changes. This allows the template to be used until its actual degradation affects flatness, maximizing template utilization while maintaining quality standards and avoiding unnecessary replacements that would reduce productivity.
Solution Approach 2:
The system performs self-diagnosis by automatically measuring pocket depth before and after polishing operations and calculating the difference value. This self-monitoring capability eliminates the need for manual inspection and enables automatic adjustment of polishing conditions, reducing downtime and maintaining high productivity while ensuring flatness requirements are met.
3Manufacturing precision
If polishing conditions are adjusted frequently to compensate for template aging, then wafer flatness is maintained, but operational complexity and time consumption increase
Solution Approach 1:
The system automatically performs the complex task of measuring pocket depth, calculating the difference value, and determining appropriate polishing condition adjustments. This automation eliminates manual measurement and calculation work, reducing operational complexity and time consumption while maintaining precise control over wafer flatness throughout the polishing process.
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 effectively reduces variations in wafer flatness by monitoring and adjusting the pocket depth, minimizing the impact of abrasion and deformation, and ensuring consistent polishing results without reducing productivity.
Implementation Method 1
pressing a wafer W held by the polishing head (2) against a polishing pad (4) attached to an upper side of a turntable (3) for polishing
Data Source
AI summary
The present invention provides a method for polishing a wafer including, after unloading and before loading to hold a next wafer to be polished: measurement to measure a depth PDt of a concave portion of a template after taking out a polished wafer; calculation to calculate a difference ΔPD between the measured depth PDt of the concave portion and a depth PD0 of the concave portion of the template before being used for polishing; and adjustment to adjust polishing conditions for a next wafer to be polished in accordance with the calculated difference ΔPD. Consequently, there are provided the method for polishing a wafer and a polishing apparatus which enable adjusting a fluctuation in flatness of each wafer caused due to a fluctuation in numerical value of a pocket depth of a template.