Polyurethane Foam Polishing Pad with Layered Structure
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Solution Overview
Problem
Conventional polishing pads for semiconductor wafers face challenges in achieving high planarity and planarization efficiency while minimizing scratching, due to nonuniform foam structures and inadequate hardness, which also leads to short pad life and difficulty in cleaning.
Innovation Solution
A polymer material with specific properties, such as a tensile modulus of 130-800 MPa, loss tangent of ≤0.2, and contact angle ≤80°, derived from a polyurethane foam with a controlled nitrogen content and molecular weight, is used to create a polishing pad with a layered structure combining a hard polishing layer and a soft elastic layer for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a soft nonwoven fabric polishing pad is used, then good contact properties and excellent polishing slurry retention are achieved, but the capacity to planarize the surface is inadequate and the pad life is short due to clogging of void regions
Solution Approach 1:
The invention uses a composite structure combining a nonwoven fabric layer with a foam layer. The nonwoven fabric layer provides good contact properties and slurry retention, while the foam layer provides planarization capacity and prevents clogging. This composite structure resolves the contradiction by allowing each layer to perform its specialized function.
Solution Approach 2:
The polishing pad is divided into multiple functional layers: a nonwoven fabric layer for contact and slurry retention, and a foam layer for planarization and debris management. This segmentation allows each layer to optimize its specific function without compromising the others, resolving the contradiction between softness for contact and hardness for planarization.
2Manufacturing precision
If a polymer foam polishing pad is used, then planarization capacity and ease of cleaning are improved, but the contact properties and slurry retention are reduced
Solution Approach 1:
The invention combines a foam layer (for planarization) with a nonwoven fabric layer (for contact properties and slurry retention). This composite structure allows the foam to provide planarization capacity while the nonwoven fabric maintains good contact and slurry retention, resolving the contradiction between these opposing requirements.
3Manufacturing precision
If the hardness of the polishing pad is increased to raise planarization efficiency, then planarization capacity is improved, but the risk of generating scratches on the wafer surface increases
Solution Approach 1:
The invention creates different hardness levels in different layers: the foam layer has higher hardness for planarization, while the nonwoven fabric layer has softer properties that prevent scratching. This local differentiation of material properties allows the system to achieve planarization efficiency without increasing scratch risk at the wafer-contact surface.
4Manufacturing precision
If a high-hardness polyurethane foam is used, then planarization efficiency is improved, but the polishing characteristics fluctuate due to nonuniformity in the foam structure
Solution Approach 1:
The invention carefully controls the density of the foam layer within a specific range (0.3-1.0 g/cm³) and the thickness ratio between layers to achieve optimal planarization efficiency while maintaining stable polishing characteristics. This parameter optimization resolves the contradiction between hardness for planarization and uniformity for stability.
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 provides a polishing pad that achieves stable polishing rates with reduced scratching and enhanced planarity, maintaining performance even in the presence of water, and extends the pad's lifespan by preventing slurry infiltration and debris accumulation.
Implementation Method 1
a tensile modulus at 50° C. after saturation swelling with 50° C. water of 130 to 800 MPa
Implementation Method 2
due to their independent cell structure, polishing pads that use a polymer foam are not subject to the in-depth infiltration into void regions by polishing slurry and polishing debris
Data Source
AI summary
The subject is to provide a polymer material which enables to improve planarity and planarization efficiency of a polished surface and is useful as a polishing pad which generates only a few scratches. The said subject is solved by a polymer material having a tensile modulus at 50° C. after saturation swelling with 50° C. water of 130 to 800 MPa, a loss tangent at 50° C. of not more than 0.2, and a contact angle with water of not more than 80°.