Polishing Pad Recess Design for CMP Uniformity
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Solution Overview
Problem
Chemical mechanical polishing pads experience uneven wear, leading to reduced polishing uniformity as the service life progresses, with the peripheral portion having a lower polishing rate due to insufficient retention of polishing liquid.
Innovation Solution
A polishing pad design featuring a central portion with concentric annulus recesses and a peripheral portion with annulus-contoured peripheral recesses, where the lower part of the peripheral recesses has a larger diameter area and capacity than the upper part, ensuring consistent polishing liquid distribution across the pad.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the polishing pad is used for a long time, then the central portion maintains high polishing rate, but the peripheral portion develops insufficient polishing liquid retention leading to reduced polishing uniformity
Solution Approach 1:
The patent applies local quality by designing different recess structures for different regions of the polishing pad. The peripheral portion has recesses with larger lower parts to increase polishing liquid retention, while the central portion has different recess characteristics. This regional differentiation addresses the specific wear pattern where the periphery loses polishing liquid retention capability faster than the center during extended use.
Solution Approach 2:
The patent introduces a vertical dimension to the recess design by making the lower part of peripheral recesses larger than the upper part. This three-dimensional structure creates additional volume for polishing liquid storage in the peripheral region, compensating for the reduced retention capacity that develops during prolonged polishing operations.
2Reliability
If the polishing pad conditioner continuously conditions the polishing pad, then the polishing pad surface is maintained, but the central portion wears out faster creating a concave structure
Solution Approach 1:
The patent applies preliminary action by pre-forming recesses in the polishing pad before use, particularly in the peripheral portion. These pre-designed recesses with enlarged lower parts are prepared in advance to compensate for the anticipated wear pattern caused by continuous conditioning, ensuring polishing liquid retention is maintained throughout the pad's service life.
3Ease of manufacture
If the peripheral recesses have uniform cross-section, then manufacturing is simpler, but polishing liquid retention is insufficient in the peripheral portion
Solution Approach 1:
The patent transitions from a two-dimensional uniform cross-section recess design to a three-dimensional structure where the lower part of peripheral recesses is enlarged. This vertical expansion increases the volume available for polishing liquid storage without significantly complicating the manufacturing process, as the gradual enlargement can be achieved through standard molding or machining techniques.
Data Source
AI summary
A polishing pad and a chemical mechanical polishing apparatus are provided. The polishing pad includes: a central portion, designed with a central recess; and a peripheral portion surrounding the central portion, and designed with at least one peripheral recess. The at least one peripheral recess is disposed along an annulus contour. A lower part of the peripheral recess is greater than an upper part of the peripheral recess in terms of diameter area, and is different from the upper part in shape.