CMP Pad Cooling Nozzle for Polishing Temperature Uniformity
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in temperature control, leading to variations in removal rate, polishing uniformity, erosion, dishing, and residue due to temperature fluctuations on the polishing pad, affecting within-wafer and wafer-to-wafer uniformity.
Innovation Solution
A convergent-divergent nozzle system is used to deliver coolant gas and liquid onto the polishing pad, controlling temperature by forming ice droplets that efficiently cool the pad through latent heat of fusion, reducing direct contact with solid bodies and minimizing contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional temperature control methods are used, then temperature control is achieved, but direct contact with solid bodies causes contamination and reduced polishing uniformity
Solution Approach 1:
The patent uses a gas jet system (pneumatic method) to cool the polishing pad instead of direct solid body contact. Gas is delivered through a nozzle positioned close to the polishing pad surface, creating a boundary layer that conducts heat away from the pad without mechanical contact, thereby eliminating contamination while maintaining temperature control
Solution Approach 2:
The patent introduces gas as an intermediary medium between the cooling system and the polishing pad. The gas forms a thermal boundary layer that acts as a mediator to transfer heat from the pad surface without requiring direct contact between solid cooling elements and the pad, thus preventing contamination
2Manufacturing precision
If temperature control is not optimized, then simpler systems are used, but temperature variations cause removal rate inconsistencies and dishing
Solution Approach 1:
The patent employs a dynamic gas flow control system where the gas flow rate can be adjusted based on polishing conditions. The system dynamically responds to temperature variations by modulating the gas delivery, allowing optimal cooling at different stages of the polishing process to maintain uniform temperature and prevent dishing
Solution Approach 2:
The patent changes the physical parameters of the cooling system by using gas flow rate, pressure, and temperature as controllable variables. By adjusting these parameters, the system can precisely control the cooling effect on the polishing pad to maintain optimal temperature conditions for uniform polishing
3Temperature
If gas flow rate is increased for better cooling, then temperature control improves, but energy consumption increases
Solution Approach 1:
The patent applies cooling locally at the polishing pad surface through a positioned nozzle rather than cooling the entire system. The gas is delivered precisely where heat generation occurs at the pad-substrate interface, providing effective temperature control with minimal gas flow and energy consumption
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
Quick and efficient temperature control of the polishing pad reduces temperature variation, improving polishing uniformity, extending pad life, and enhancing wafer-to-wafer and within-wafer uniformity by minimizing dishing and corrosion.
Implementation Method 1
cooling the gas by flowing the gas through the convergent-divergent nozzle
Implementation Method 2
forming ice droplets that efficiently cool the pad through latent heat of fusion
Implementation Method 3
forming ice droplets that efficiently cool the pad through latent heat of fusion
Data Source
AI summary
A chemical mechanical polishing system includes a platen to support a polishing pad having a polishing surface, a conduit having an inlet to be coupled to a gas source, and a dispenser coupled to the conduit and having a convergent-divergent nozzle suspended over the platen to direct gas from the gas source onto the polishing surface of the polishing pad.