Wafer Polishing System with Segmented Pad Sweeping
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Solution Overview
Problem
Existing semiconductor wafer polishing systems face challenges in achieving uniform thickness and smooth surfaces due to non-planar layers, leading to uneven polishing results and reduced yield and throughput, especially when applicators fail to compensate for tangential velocity variations across the wafer.
Innovation Solution
A polishing system using a smaller polishing pad that sweeps over the semiconductor wafer in a programmable pattern, with multiple pads for increased flexibility and throughput, and an auxiliary polishing system for rework without removing the wafer from the table, allowing for adaptive metrology-driven polishing profiles and in-line cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large polishing pad is used to cover the entire wafer surface, then the polishing area is increased, but the uniformity of polishing across the wafer deteriorates due to tangential velocity variations
Solution Approach 1:
The polishing process is segmented into multiple passes, each covering only a portion of the wafer surface. The polishing head moves to different positions and orientations, polishing specific regions sequentially rather than attempting to polish the entire wafer in a single pass with a large pad.
Solution Approach 2:
The polishing system dynamically adjusts the polishing head position, orientation, and the polishing pad rotation direction between passes. The pad rotates in opposite directions in different passes, and the head moves to different locations on the wafer, creating a dynamic polishing process that compensates for velocity variations.
2Manufacturing precision
If multiple polishing passes are performed to improve uniformity, then the polishing precision is improved, but the processing time increases
Solution Approach 1:
The polishing process is designed as a continuous operation where the wafer remains on the polishing table throughout multiple passes. The polishing head moves between different positions and orientations without removing the wafer, and the polishing pad continuously rotates and contacts different regions of the wafer surface in each pass.
Solution Approach 2:
The system dynamically repositions the polishing head and reverses the pad rotation direction between passes, allowing multiple polishing actions to be performed efficiently on the same wafer without interruption or removal, thereby reducing total processing time while maintaining uniformity.
3Ease of manufacture
If the wafer is removed from the table for cleaning or rework, then the cleaning effectiveness is improved, but the productivity decreases due to transfer time
Solution Approach 1:
The cleaning function is merged with the polishing process by integrating a cleaning mechanism directly on the polishing table. The cleaning head can access the wafer surface while it remains in position on the table, combining polishing and cleaning operations in a single station without requiring wafer removal or transfer between stations.
Solution Approach 2:
The polishing table serves multiple functions: it holds the wafer during polishing, supports the wafer during cleaning operations, and enables rework polishing. The same table and wafer positioning system are used for both polishing and cleaning, eliminating the need for separate transfer mechanisms and offline cleaning stations.
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
The system achieves high uniformity and flexibility in polishing, reduces wafer transfer time, and increases yield and throughput by enabling adaptive polishing and in-line cleaning without offline stations.
Implementation Method 1
the polishing head simultaneously applies a force to press the semiconductor wafer against the rotating polishing pad
Implementation Method 2
mechanical planarization (MP) and chemical mechanical planarization/polishing (CMP)
Implementation Method 3
a chemical slurry is introduced to facilitate wafer polishing
Data Source
AI summary
A method of using a polishing system includes securing a wafer to a support, wherein the wafer has a first diameter. The method further includes polishing the wafer using a first polishing pad rotating about a first axis, wherein the first polishing pad has a second diameter greater than the first diameter. The method further includes rotating the support about a second axis perpendicular to the first axis after polishing the wafer using the first polishing pad. The method further includes polishing the wafer using a second polishing pad after rotating the support, wherein the second polishing pad has a third diameter less than the first diameter. The method further includes releasing the wafer from the support following polishing the wafer using the second polishing pad.