CMP Polishing Pad UV Endpoint Detection Window
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Solution Overview
Problem
Conventional CMP polishing pads with endpoint detection windows suffer from degradation when exposed to light with wavelengths below 400 nm and have low transmittance at these wavelengths, leading to increased polishing defects and incompatibility with softer polishing materials.
Innovation Solution
A CMP polishing pad with endpoint detection windows made from a reaction mixture of cycloaliphatic diisocyanates and a polyol mixture of polymeric diol and triol, with a UV cut-off at 325 nm or lower, providing improved durability and transmittance at wavelengths below 400 nm, and using a tin-containing or amine catalyst for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polymer containing endpoint detection windows are used, then the polishing pad can perform CMP polishing, but the windows exhibit degradation upon exposure to light with wavelength of 330 to 425 nm
Solution Approach 1:
The patent changes the chemical composition parameters of the polyurethane resin by specifying aromatic ring density of 2 wt. % or less and using specific polyol combinations (polyester polycarbonate polyols with molecular weight 500-1000 and polyether polyols with molecular weight 1000-2000) to achieve UV resistance while maintaining optical properties
Solution Approach 2:
The patent creates a composite polyurethane resin system combining polyester polycarbonate polyols and polyether polyols in specific ratios, along with cycloaliphatic diisocyanates, to achieve both UV stability and high transmittance at wavelengths below 400 nm
2Illumination intensity
If conventional endpoint detection window materials are used, then the polishing pad can detect polishing endpoints, but the materials have low transmittance at wavelengths below 400 nm
Solution Approach 1:
The patent optimizes the molecular weight parameters of the polyols (polyester polycarbonate polyols: 500-1000, polyether polyols: 1000-2000) and aromatic ring density (≤2 wt. %) to achieve high transmittance at wavelengths below 400 nm while maintaining durability
Solution Approach 2:
The patent applies different polyol types with specific molecular weights to different functional requirements: polyester polycarbonate polyols for UV resistance and structural stability, and polyether polyols for flexibility and transmittance enhancement
3Reliability
If softer polishing layer material is used to reduce polishing defects, then defectivity performance improves, but conventional endpoint detection window materials do not pair well leading to increased polishing defectivity
Solution Approach 1:
The patent develops a composite polyurethane resin formulation that is specifically compatible with softer polishing materials (Shore D hardness 40-90), allowing the endpoint detection window to function properly with defect-reducing soft pad formulations
Solution Approach 2:
The patent adjusts the hardness parameters of the polyurethane resin through controlled selection of polyol molecular weights and ratios, enabling the window material to match the mechanical properties of softer polishing layers
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 durable endpoint detection windows with high transmittance at wavelengths below 400 nm, reducing polishing defects and improving compatibility with softer polishing materials, while maintaining durability and preventing bulging or buckling during processing.
Implementation Method 1
a reaction mixture of (A) from 30 to 56 wt. % of one or more cycloaliphatic diisocyanates or polyisocyanates with (B) from 43 to 69.9999 wt. % of a polyol mixture
Implementation Method 2
which at a thickness of 2 mm would have a UV cut-off at a wavelength of 325 nm or lower and which are the product of a reaction mixture
Data Source
AI summary
The present invention provides a chemical mechanical (CMP) polishing pad for polishing, for example, a semiconductor substrate, having one or more endpoint detection windows (windows) which at a thickness of 2 mm would have a UV cut-off at a wavelength of 325 nm or lower which are the product of a reaction mixture of (A) from 30 to 56 wt. % of one or more cycloaliphatic diisocyanates or polyisocyanates with (B) from 43 to 69.9999 a polyol mixture of (i) a polymeric diol having an average molecular weight of from 500 to 1,500, such as a polycarbonate diol for hard windows and a polyether polyol for soft windows and (ii) a triol having an average molecular weight of from 120 to 320 in a weight ratio of (B)(i) polymeric diol to (B)(ii) triol ranging from 1.6:1 to 5.2:1, and a catalyst, preferably a secondary or tertiary amine, all weight percent's based on the total solids weight of the reaction mixture.