Wafer Polishing Head Control Using Pad Thermal Feedback
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Solution Overview
Problem
Existing polishing systems for semiconductor and solar wafers struggle with maintaining wafer flatness due to pad wear, leading to issues like 'dishing' or 'doming', and rely on delayed and inaccurate vacuum adjustments based on post-polishing shape measurements.
Innovation Solution
A polishing apparatus with a temperature sensor and controller that uses thermal data to dynamically adjust the polishing head assembly, varying the removal profile of the wafer in real-time to maintain flatness by controlling the pressure within the polishing chamber.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If vacuum adjustment is used to correct wafer shape after polishing, then wafer flatness can be improved, but the feedback is delayed and inaccurate because shape measurement occurs after polishing
Solution Approach 1:
The patent applies preliminary action by measuring wafer shape before polishing using a profilometer or interferometer. This pre-measurement data is used to predict the wafer shape after polishing, allowing vacuum adjustments to be made in advance rather than waiting for post-polishing measurements. The system calculates expected shape changes based on pad wear patterns and adjusts vacuum accordingly before the polishing operation completes.
Solution Approach 2:
The patent implements feedback by using pre-polishing shape measurements to inform vacuum adjustments during polishing. The system continuously monitors wafer shape parameters before polishing and uses this information to adjust vacuum levels dynamically. This creates a closed-loop control system where shape data feeds back into the polishing process parameters, enabling real-time correction rather than delayed post-process adjustment.
2Manufacturing precision
If vacuum is increased to correct convex wafer shape, then wafer flatness improves, but the approach assumes known current wafer shape which is not available in real-time
Solution Approach 1:
The system performs preliminary shape measurement before polishing to establish the current wafer shape state. This pre-acquired shape information is used to determine appropriate vacuum adjustment levels before the polishing operation begins, eliminating the need for real-time shape data during polishing.
Solution Approach 2:
The patent applies beforehand cushioning by using pre-measured shape data to predict and compensate for expected shape changes during polishing. The system calculates anticipated shape deviations based on pad wear characteristics and pre-determines vacuum adjustment strategies to counteract these changes, cushioning against future shape problems before they occur.
3Productivity
If pad wear is allowed to occur during polishing operations, then polishing can continue for extended periods, but wafer flatness degrades due to dishing or doming
Solution Approach 1:
The system performs preliminary measurements of wafer shape before polishing to establish baseline data. This pre-measurement information is used to predict how pad wear will affect wafer flatness over time, allowing the system to plan pad replacement or reconditioning schedules that maintain flatness while maximizing productivity.
Solution Approach 2:
The patent implements feedback by continuously monitoring wafer shape parameters before polishing and using this data to track pad wear effects. The system analyzes shape measurement trends to detect when pad wear begins to significantly impact flatness, providing feedback that triggers pad replacement or reconditioning actions to maintain manufacturing precision.
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 ensures precise and efficient polishing, reducing the time to identify and correct convex or concave profiles, improving wafer yield and process capability while automating adjustments for uneven surfaces.
Implementation Method 1
receiving, at the controller, thermal data of a portion of the polishing pad from the temperature sensor
Implementation Method 2
operating, by the controller, the polishing head assembly to position the silicon wafer in contact with the polishing pad and to selectively vary the removal profile of the silicon wafer based at least in part on the thermal data
Data Source
AI summary
A polishing assembly for polishing of silicon wafers includes a polishing pad, a polishing head assembly, a temperature sensor, and a controller. The polishing head assembly holds a silicon wafer to position the silicon wafer in contact with the polishing pad. The polishing head assembly selectively varies a removal profile of the silicon wafer. The temperature sensor collects thermal data from a portion of the polishing pad. The controller is communicatively coupled to the polishing head assembly and the temperature sensor. The controller receives the thermal data from the temperature sensor and operates the polishing head assembly to selectively vary the removal profile of the silicon wafer based at least in part on the thermal data.