Multi-layer Polishing Pad Low-Pressure Uniformity
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Solution Overview
Problem
Conventional polishing pads exhibit unacceptable polishing uniformity at low pressures, particularly below 0.5 psi, due to the rigidity of the backing layer which fails to 'flatten out' the covering layer, resulting in non-uniform pressure transmission and polishing rates across the substrate.
Innovation Solution
A polishing pad design featuring a thinner, harder polishing layer with a thickness non-uniformity and a thicker, more compressible backing layer, allowing the polishing surface to deflect sufficiently under low pressures to compensate for thickness variations, ensuring uniform contact and pressure distribution across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional polishing pad with a rigid backing layer is used, then the pad maintains structural stability, but the polishing uniformity deteriorates at low pressures due to inability to flatten the covering layer
Solution Approach 1:
The polishing pad is divided into two distinct layers: a harder, more stable covering layer for polishing and a softer, more compressible backing layer for pressure distribution. This segmentation allows each layer to perform its specific function optimally - the covering layer provides polishing stability while the backing layer ensures uniform pressure transmission at low pressures, resolving the contradiction between structural stability and polishing uniformity.
Solution Approach 2:
Different regions of the polishing pad have different properties: the covering layer has higher hardness and lower compressibility for stable polishing, while the backing layer has lower hardness and higher compressibility for pressure equalization. This local differentiation of material properties enables the pad to simultaneously maintain structural integrity and achieve uniform pressure distribution across the substrate surface.
2Manufacturing precision
If pressure is increased to improve polishing uniformity, then contact uniformity improves, but the risk of delamination increases for sensitive materials
Solution Approach 1:
The invention changes the compressibility parameter of the backing layer to be significantly higher than conventional pads, allowing it to deform and flatten the covering layer at very low pressures (0.1-0.5 psi). This parameter change enables achievement of uniform contact without increasing pressure, thereby preventing delamination of sensitive materials while maintaining polishing uniformity.
3Manufacturing precision
If a thicker backing layer is used to improve compressibility, then pressure distribution improves, but the overall pad thickness increases
Solution Approach 1:
The invention applies local quality by concentrating the compressibility function in the backing layer while keeping the covering layer thin and hard. The backing layer thickness is optimized to provide sufficient compressibility for pressure distribution, while the covering layer is minimized to only what is needed for polishing stability. This localized functional assignment achieves good pressure distribution without excessive overall thickness.
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 design improves polishing uniformity at low pressures, enabling effective polishing of materials like low-k dielectric materials without delamination, by ensuring the polishing surface remains in uniform contact with the substrate, even at pressures as low as 0.1 psi.
Implementation Method 1
The backing layer has a second compressibility greater than the first compressibility. The first thickness, first compressibility, second thickness and second compressibility are such that the polishing surface deflects more than the thickness non-uniformity of the polishing layer at an applied pressure of 1 psi or less.
Implementation Method 2
The polishing surface deflects more than the thickness non-uniformity of the polishing layer at an applied pressure of 1 psi or less
Implementation Method 3
The polishing layer has a first thickness, a first compressibility, a hardness between about 40 to 80 Shore D
Data Source
AI summary
A polishing pad has a polishing layer and a backing layer secured to the polishing layer. The polishing layer has a polishing surface, a first thickness, a first compressibility, and a hardness between about 40 to 80 Shore D. The backing layer has a second thickness greater than the first thickness and a second compressibility greater than the first compressibility. The first thickness, first compressibility, second thickness and second compressibility are such that the polishing surface deflects at least 2 mil under an applied pressure of 1 psi or less.