Viscoelastic Polishing Pad Structure for Wafer Flatness
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Solution Overview
Problem
Existing polishing pads fail to provide sufficient flatness to polished surfaces due to inadequate consideration of the interaction between the polishing layer and cushion layer, leading to issues like dishing and erosion during semiconductor wafer processing.
Innovation Solution
A polishing pad comprising a polishing layer and cushion layer with specific ratios of storage elastic moduli and loss factors in dynamic viscoelasticity measurements, ensuring balanced responsiveness to polishing pressure and edge contact forces, thereby maintaining uniform polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only the configuration of the polishing layer is specified, then the polishing pad structure is simplified, but sufficient flatness cannot be obtained on the polished surface
Solution Approach 1:
The invention applies composite material principles by combining the polishing layer and cushion layer with specific viscoelastic property ratios. The polishing layer and cushion layer are made of different materials with coordinated mechanical properties, where the polishing layer has higher storage elastic modulus and the cushion layer has lower storage elastic modulus, creating a composite structure that achieves both structural simplicity and high flatness through material property optimization rather than structural complexity
Solution Approach 2:
The invention changes the critical parameters of storage elastic modulus and loss factor to specific ranges and ratios. By controlling the ratio of storage elastic moduli (E′B40/E′C40 between 3.0-15.0) and loss factors (tan δ between 0.10-0.30), the invention optimizes the viscoelastic properties of the polishing pad to simultaneously achieve simplified structure and superior flatness, resolving the contradiction through precise parameter control
2Force
If the storage elastic modulus ratio E′B40/E′C40 is increased to improve responsiveness to polishing pressure, then polishing pressure responsiveness improves, but the polishing pad becomes too rigid for edge contact
Solution Approach 1:
The invention optimizes the storage elastic modulus ratio E′B40/E′C40 to a specific range of 3.0-15.0, which balances the responsiveness to polishing pressure with the adaptability to edge contact. This parameter optimization ensures that the polishing pad has sufficient rigidity to respond to polishing pressure while maintaining enough flexibility for edge contact, resolving the contradiction through precise parameter control
Solution Approach 2:
The invention utilizes the dynamic viscoelastic properties of the polishing pad materials, measuring storage elastic modulus and loss factor under dynamic conditions (bending and compression modes at 10 rad/s). This dynamic approach allows the polishing pad to exhibit appropriate stiffness during polishing pressure application while maintaining flexibility for edge contact, achieving adaptability across different operational states
3Productivity
If the loss factor tan δ is decreased to reduce energy loss, then polishing efficiency improves, but the polishing pad becomes less compliant under varying temperatures
Solution Approach 1:
The invention optimizes the loss factor tan δ to a specific range of 0.10-0.30 under bending mode conditions, which balances polishing efficiency with temperature adaptability. This parameter optimization ensures that the polishing pad maintains sufficient compliance under varying temperatures while preserving adequate polishing efficiency, resolving the contradiction through precise parameter control
Solution Approach 2:
The invention measures and controls the loss factor under dynamic bending conditions at 10 rad/s, capturing the viscoelastic behavior of the polishing pad materials. This dynamic measurement approach ensures that the polishing pad maintains appropriate compliance across varying temperatures and frequencies, achieving adaptability while preserving polishing efficiency through optimized energy dissipation characteristics
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 proposed polishing pad achieves improved flatness on polished surfaces by stabilizing physical properties under varying temperatures and pressures, reducing dishing and erosion, and enhancing overall polishing quality.
Implementation Method 1
dynamic viscoelasticity measurement performed under a bending mode condition, a ratio of a storage elastic modulus at 40° C. in dynamic viscoelasticity measurement performed under a bending mode condition to a storage elastic modulus at 40° C. in dynamic viscoelasticity measurement performed under a compression mode condition
Data Source
AI summary
The present invention relates to a polishing pad including a polishing layer and a cushion layer, wherein a ratio E′B40/E′C40 of a storage elastic modulus at 40° C. in dynamic viscoelasticity measurement performed under a bending mode condition with a dry state, a frequency of 10 rad/s, and 20 to 100° C., E′B40, to a storage elastic modulus at 40° C. in dynamic viscoelasticity measurement performed under a compression mode condition with a dry state, a frequency of 10 rad/s, and 20 to 100° C., E′C40, is 3.0 or more and 15.0 or less, and a loss factor tan δ in the dynamic viscoelasticity measurement performed under the bending mode condition is 0.10 or more and 0.30 or less in a range of 40° C. or more and 70° C. or less.