Non-Porous CMP Subpad Structure for Uniform Wafer Polishing
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Solution Overview
Problem
Existing polishing pads used in chemical mechanical polishing (CMP) are thermally insulating and compressible, leading to variations in polishing performance across the pad diameter and inconsistent removal rates, with issues like slurry wicking and excessive deformation affecting semiconductor wafer yields.
Innovation Solution
A polishing pad comprising a non-porous subpad with specific elastic modulus and thermal conductivity properties, combined with a polishing layer featuring recesses, to enhance uniformity and thermal management, thereby stabilizing the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a porous polymeric polishing pad is used, then the pad provides cushioning and compliance during polishing, but the pad becomes thermally insulating and compressible leading to variation in polishing performance across the diameter
Solution Approach 1:
The invention uses a composite structure combining a porous polymer polishing layer with a non-porous subpad layer. The non-porous subpad layer has superior thermal conductivity and controlled compressibility compared to traditional fully porous pads, while the porous polishing layer maintains cushioning and compliance. This composite approach resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The invention applies different structural qualities to different regions of the pad. The polishing layer remains porous for cushioning, while the subpad layer is non-porous for thermal management and dimensional stability. This local differentiation allows each layer to optimize its function without compromising the other.
2Adaptability or versatility
If a compressible polishing pad is used, then the pad conforms to the substrate surface, but the compressibility leads to variation in polishing performance across the diameter of the pad
Solution Approach 1:
The composite structure separates the conformance function (polishing layer with controlled compression) from the uniformity function (non-porous subpad with stable elastic modulus). The non-porous subpad maintains consistent mechanical properties under compression, preventing the performance variation that occurs in fully porous pads.
3Manufacturing precision
If a non-porous subpad is used, then thermal management is improved and polishing uniformity is enhanced, but the device complexity increases
Solution Approach 1:
The invention integrates a non-porous subpad layer into the existing polishing pad structure. This addition, while increasing structural complexity, provides significant benefits in thermal management and polishing uniformity that justify the enhanced design.
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 improved global polishing uniformity, reduced edge effects, and consistent removal rates, enhancing semiconductor wafer yields by maintaining stable temperature profiles during polishing.
Implementation Method 1
The subpad layer has an average elastic modulus under compression at pressures of from 24 to less than 48 kPa of 1 to 5 MPa and an average elastic modulus under compression at pressures of 48 to 76 kPa of 5 to 20 MPa and a true strain of less than or equal to 10% over compression pressures of up to 1.2 MPa
Data Source
AI summary
A polishing pad for chemical mechanical polishing comprises a polishing layer and a subpad. The polishing layer has a polishing surface and a polishing layer interface surface opposite the polishing surface and comprises a polishing material. The subpad layer has a subpad interface surface adjacent to the polishing layer interface surface and a bottom surface opposite the subpad interface surface, and comprises a subpad material. The subpad layer has an average elastic modulus under compression at pressures of from 24 to less than 48 kPa of 1 to 5 MPa and an average elastic modulus under compression at pressures of 48 to 76 kPa of 5 to 20 MPa and a true strain of less than or equal to 10% over compression pressures of up to 1.2 MPa.