Multifunctional Endpoint Detection Window for Slurry Sealing
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Solution Overview
Problem
Existing polishing pads with integrated windows for endpoint detection suffer from issues such as deformation, scratching, and reduced pad lifetime due to differences in modulus, stiffness, and thermal expansion between the window material and the surrounding pad, leading to restricted compatibility with multiple endpoint detection systems.
Innovation Solution
A polishing pad design featuring a window region with a top and bottom window material, where the bottom window material is elastomeric and can deform under pressure, forming seals to prevent slurry leakage and facilitate transmission of light and vibrational signals, allowing compatibility with both optical and vibrational endpoint detection systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a rigid window material is used for endpoint detection, then optical detection accuracy is improved, but pad deformation and scratching increase due to modulus and stiffness differences
Solution Approach 1:
The patent changes the material parameter (modulus of elasticity) of the window material to match or closely approximate the surrounding pad material. This parameter matching prevents differential compression and deformation during polishing, eliminating the scratching problem while maintaining optical detection capability through the window region.
Solution Approach 2:
The patent creates a window region with specific local properties (optical transparency, matched modulus) that differs from the bulk pad material. This localized modification allows optical detection in the window region while the overall pad maintains its polishing function without deformation.
2Measurement precision
If a rigid window material is used for endpoint detection, then optical signal transmission is improved, but pad lifetime is reduced due to differential compression and deformation
Solution Approach 1:
The patent changes the mechanical parameter (modulus of elasticity) of the window material to match the pad material, preventing differential compression during polishing. This eliminates the protrusion and deformation that lead to premature pad failure, thereby extending pad lifetime while maintaining optical transmission.
3Ease of manufacture
If a single-material window is used, then manufacturing is simplified, but compatibility with multiple endpoint detection systems (optical and vibrational) is restricted
Solution Approach 1:
The patent divides the window into multiple material layers (first window material and second window material) with different properties. The first material provides optical transparency while the second material provides vibrational signal transmission, allowing the single window structure to support multiple detection systems simultaneously.
Solution Approach 2:
The patent uses composite window construction with different materials having complementary properties. The composite structure combines optical transparency with vibrational signal transmission capability, enabling compatibility with both optical and vibrational endpoint detection systems in a single integrated window.
4Temperature
If the window material has different thermal expansion coefficient than the pad, then thermal management is simplified, but scratch defects increase due to transient stress during friction heating
Solution Approach 1:
The patent changes the thermal parameter (coefficient of thermal expansion) of the window material to match or closely approximate the pad material. This prevents differential thermal expansion during friction heating, eliminating transient stress and the resulting scratch defects while allowing efficient heat dissipation through the window region.
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 design enhances endpoint detection accuracy by preventing slurry interference and reducing scratch defects, while extending pad lifetime and ensuring compatibility with various endpoint detection methods.
Implementation Method 1
the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing
Implementation Method 2
the pad includes a path in the window region for transmitting columnated or non-columnated light through the thickness of the pad
Implementation Method 3
vibrational signals can be transmitted through the top window material and the bottom window material enabling acoustic end-point detection
Data Source
AI summary
A polishing pad having a window extending through the polishing pad from the polishing surface to a backside surface of the pad. The window includes a top window material separated from a polishing material, a bottom window wherein the bottom window material is elastomeric and can deform into a void space adjacent to the bottom window material when the pad is under pressure during polishing. A seal between the subpad material and the top window material and/or bottom window material or a seal between the polishing layer and the bottom window material prevents particles or liquid used in the chemical mechanical polishing from passing from above the polishing layer to below the subpad layer. The pad can be used for polishing with either optical or vibrational end-point detection.