SiC CMP Cooling Control With Chilled Slurry and Aluminum Platen
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Solution Overview
Problem
The high heat generation during aggressive chemical mechanical polishing (CMP) of silicon carbide (SiC) wafers leads to issues such as deformation of polymeric polishing pads and instability of permanganate-based slurries, necessitating effective temperature control to maintain polishing effectiveness.
Innovation Solution
A combination of features including a larger platen diameter, aluminum platen, platen cooling, and a flow-through heat exchanger to chill slurry, enhancing cooling performance and maintaining pad surface temperature below critical levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aggressive polishing conditions are used to increase productivity, then polishing removal rate is improved, but pad surface temperature rises causing pad deformation and slurry instability
Solution Approach 1:
The polishing pad is pre-cooled by circulating coolant through channels in the platen before polishing begins. This preliminary cooling action ensures the pad starts at a controlled temperature, allowing aggressive polishing conditions to be applied without immediately exceeding temperature thresholds that cause pad deformation or slurry instability.
Solution Approach 2:
A coolant fluid acts as an intermediary between the heat generated at the pad-wafer interface and the platen structure. The coolant absorbs excess thermal energy through convection in the platen channels, transferring heat away from the pad surface and maintaining temperature control while enabling sustained high removal rates.
2Temperature
If longer polishing times are used to improve temperature control, then pad surface temperature is maintained, but productivity decreases
Solution Approach 1:
The coolant circulation system operates continuously throughout the polishing process, providing uninterrupted thermal management. This continuous cooling action maintains stable pad temperature without requiring interruptions or extended polishing times, enabling consistent high removal rates while preventing temperature excursions that would degrade pad or slurry performance.
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
Enables more aggressive polishing conditions with higher productivity and improved polishing removal rates by effectively dissipating heat and stabilizing slurry performance.
Implementation Method 1
The surface temperature generally rises within the wafer track as polishing proceeds until an approximate balance is achieved between the average amount of energy per unit area being generated at the surface and the energy per unit area being dissipated through various cooling mechanisms of the machine
Implementation Method 2
Platen cooling (achieves heat dissipation from undersurface of pad)
Implementation Method 3
A flow-through heat exchanger to chill slurry dispensed onto polishing pad
Implementation Method 4
An aluminum platen (improved heat transfer compared to stainless steel or ceramic)
Data Source
AI summary
A wafer polishing apparatus for abrasively polishing silicon carbide semiconductor materials is adapted to maintains an advantageous temperature at a wafer/polishing surface interface and includes a rotating circular platen having a polishing pad with a circular aluminum backing plate with an increased diameter compared to standard platens. It also includes one or more overhead oscillating carriers for moving the wafer over the rotating platen such that the increased diameter results in an enlarged wafer track. The apparatus also includes a slurry delivery circuit to distribute chilled slurry to the wafer/polishing surface interface via delivery tubes suspended over the platen.