CMP Top Ring Pressure Control for Wafer Edge Flatness
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Solution Overview
Problem
Chemical mechanical polishing (CMP) apparatuses face challenges in achieving high flatness near the edges of wafers due to excessive polishing pressure, rebound, and variations in wafer edge roll-off, leading to reduced yield and increased costs in semiconductor device manufacturing.
Innovation Solution
A polishing apparatus with a supporting member and pressure adjusting mechanism that adjusts the supporting pressure based on the roll-off quantity of the wafer, ensuring the polishing member is properly supported when extending off the wafer, thereby controlling the polishing pressure to maintain flatness and reduce edge exclusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the polishing member extends off the object under polish to increase polishing area, then polishing coverage is improved, but excessive polishing pressure is applied around the edge causing degraded flatness
Solution Approach 1:
The polishing member is divided into a first polishing member and a second polishing member. The first polishing member has a smaller diameter than the object under polish and polishes the central region, while the second polishing member has a larger diameter and polishes the peripheral region including the edge. This segmentation allows each polishing member to operate at optimal pressure without causing edge degradation from excessive pressure.
Solution Approach 2:
Different regions of the polishing system use different polishing members with different diameters and pressure characteristics. The central region uses a smaller polishing member with controlled pressure, while the peripheral edge region uses a larger polishing member specifically designed to avoid excessive pressure application, thereby maintaining local quality appropriate for each zone.
2Productivity
If the polishing member is pressed against the object under polish with high pressure to increase polishing rate, then productivity is improved, but rebound occurs causing excessive polishing pressure at the edge
Solution Approach 1:
The polishing process is segmented into two stages using two different polishing members. The first polishing member operates at high pressure for rapid material removal in the central region, while the second polishing member operates at controlled pressure to finish the peripheral region without rebound-induced edge degradation, thus achieving both high productivity and precision.
Solution Approach 2:
The system dynamically switches between two polishing members based on the region being polished. The first polishing member is used for the central region where high removal rates are needed, and the second polishing member is used for the peripheral region where controlled pressure is critical, optimizing both productivity and precision through dynamic operation.
3Productivity
If the polishing member is rotated at high speed to increase material removal rate, then productivity is improved, but the extending polishing member causes increased rebound effect
Solution Approach 1:
The high-speed polishing function is segmented to the first polishing member which operates at high rotation speed for rapid material removal in the central region. The second polishing member operates at lower speed with larger diameter to polish the peripheral region with minimal rebound, thereby achieving high overall productivity while controlling the harmful rebound effect through spatial segmentation.
4Manufacturing precision
If a retainer ring is used to control rebound by pressing the polishing member, then edge flatness is improved, but the system complexity increases
Solution Approach 1:
The function of controlling rebound and edge pressure is extracted from a separate retainer ring component and integrated into the second polishing member itself. The second polishing member is designed with larger diameter and specific pressure control characteristics that inherently prevent excessive pressure at the edge, eliminating the need for an additional retainer ring component while maintaining edge flatness.
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 solution enables polishing with high yield and sufficient flatness even with varying roll-off conditions, reducing edge exclusion and manufacturing costs by optimizing the polishing pressure and height adjustments based on real-time wafer measurements.
Implementation Method 1
The apparatus presses a surface to be polished against the polishing member, and relatively moves them while supplying a polishing assistant such as an abrasive liquid, a chemical liquid, a slurry, pure water or the like, thereby polishing the surface of the object under polish
Data Source
AI summary
A polishing apparatus is provided for polishing wafers at a high yield rate even if roll-off exists. The polishing apparatus polishes a wafer by applying a pressure between a polishing member (polishing pad) 201 and the wafer held by a holding member (top ring) 52 and moving the polishing member relative to the wafer. The polishing apparatus includes a top ring 52 for holding the wafer, a pressure adjusting mechanism for adjusting a supporting pressure with which the wafer is supported on a supporting surface by a retainer ring, and a control unit for controlling the pressure adjusting mechanism to bring the supporting pressure to a desired pressure based on a roll off quantity of the wafer. The top ring comprises an air bag 202 for pressing the wafer against the polishing pad, a retainer ring which surrounds the wafer, and an air bag for pressing the retainer ring.