Double-Side Polishing Method for Wafer Flatness Control
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Solution Overview
Problem
Conventional double-side polishing methods for semiconductor wafers struggle to achieve stable overall and circumferential flatness due to variations in carrier thickness over time, leading to issues like outer circumference rise and sag, and require separate measurement and adjustment processes that reduce productivity.
Innovation Solution
A double-side polishing method that involves first and second polishing stages with measured flatness-based adjustments, including changes in polishing load, rotational speeds, and polishing time, to improve wafer flatness without relying on carrier thickness, enabling in-line measurement and more precise determination of polishing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If separate measurement and adjustment processes are implemented to improve flatness precision, then manufacturing precision is improved, but productivity deteriorates due to apparatus stoppage and operator involvement
Solution Approach 1:
The patent implements self-service by enabling the double-side polishing apparatus to automatically measure flatness and adjust polishing conditions without external operator intervention. The integrated control system performs measurement, analysis, and parameter adjustment autonomously, eliminating the need for manual measurement processes and keeping the apparatus continuously operational.
Solution Approach 2:
The patent merges the measurement function and control function into the polishing apparatus itself. By integrating the flatness measuring device and control system within the polishing apparatus, the system combines polishing and measurement capabilities into a single unified system, eliminating separate measurement steps and maintaining continuous production flow.
2Manufacturing precision
If carrier thickness is used as reference for adjusting finishing thickness, then overall flatness can be controlled, but reliability deteriorates due to carrier thickness variations over time
Solution Approach 1:
The patent applies feedback by using actual flatness measurement results to dynamically adjust polishing conditions. Instead of relying on predetermined carrier thickness values, the system continuously measures flatness and uses this feedback to compensate for carrier wear and thickness variations, ensuring stable and reliable flatness control throughout the carrier's service life.
Solution Approach 2:
The patent performs preliminary measurement of flatness before determining the next polishing batch conditions. By measuring the actual flatness state and using this information to pre-calculate optimal polishing parameters, the system proactively compensates for carrier thickness variations before they affect the polishing outcome, ensuring consistent reliability.
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 method stabilizes wafer flatness by adjusting polishing conditions based on measured flatness, effectively improving both overall and circumferential flatness without being affected by carrier thickness variations, while reducing productivity losses associated with separate measurement processes.
Implementation Method 1
a polishing pad 4 for polishing a surface of the wafer W
Implementation Method 2
flatness of the polished wafer is measured
Data Source
AI summary
The present invention is directed to a double-side polishing method including interposing a wafer held by a carrier between upper and lower turn tables to which respective polishing pads are attached, and rotating and revolving the carrier while supplying a polishing agent to polish both surfaces of the wafer at the same time, the method including the steps of: first polishing at a high polishing rate; second polishing at a low polishing rate; measuring flatness of the polished wafer; and determining polishing conditions of the second polishing in a next polishing batch on a basis of the measured flatness. The method can stably improve the flatness of a wafer without being affected by variations in carrier thickness over time.