CMP Slurry Switching for Faster Polishing With Fewer Scratches
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes in semiconductor manufacturing face challenges in real-time monitoring and adjusting polishing conditions, leading to suboptimal polish performance and increased risk of wafer scratching due to inconsistent slurry distribution and pressure variations during the polishing process.
Innovation Solution
The implementation of a CMP tool with a wafer carrier and polishing pad system that uses two distinct slurries with different abrasive particle sizes, temperatures, and dispensing durations, along with pressure, concentration, and temperature sensors to monitor and control the polishing process in real-time, ensuring optimal slurry distribution and pressure conditions for both coarse and fine polishing stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single slurry is used for the entire polishing process, then the process is simple and fast, but the polish performance is suboptimal and surface roughness is increased
Solution Approach 1:
The polishing process is divided into multiple stages (coarse polishing and fine polishing), with each stage using a different slurry formulation. The first slurry contains larger abrasive particles for rapid material removal, while the second slurry contains smaller abrasive particles for surface smoothing, thereby resolving the contradiction between polish performance and process simplicity
Solution Approach 2:
The slurry dispensing system is made dynamic by enabling real-time switching between different slurry formulations based on the polishing stage. The system transitions from dispensing the first slurry during coarse polishing to dispensing the second slurry during fine polishing, allowing optimal polish performance without excessive complexity
2Manufacturing precision
If slurry dispensing continues throughout the polishing process, then continuous lubrication is maintained, but slurry waste increases and polish performance decreases due to pressure variations
Solution Approach 1:
Slurry dispensing is implemented as a periodic action rather than continuous dispensing. The system dispenses the first slurry during coarse polishing, then switches to dispensing the second slurry during fine polishing. This periodic switching optimizes lubrication at each stage while reducing overall slurry waste and maintaining consistent polish performance
Solution Approach 2:
The system prepares and dispenses the appropriate slurry formulation in advance for each polishing stage. The first slurry is dispensed before and during coarse polishing to prepare the surface, and the second slurry is dispensed before and during fine polishing to achieve final surface quality, thereby optimizing polish performance while controlling slurry usage
3Productivity
If pressure is increased to improve polishing speed, then productivity increases, but the risk of wafer scratching increases
Solution Approach 1:
The system changes the physical and chemical parameters of the slurry between polishing stages. The first slurry has higher viscosity and larger abrasive particles optimized for rapid material removal at higher pressures, while the second slurry has lower viscosity and smaller abrasive particles optimized for surface smoothing at lower pressures, thereby achieving both high productivity and scratch prevention
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
This approach enhances polishing performance by ensuring consistent and controlled CMP processes, reducing surface roughness and wafer scratching risks, while also minimizing slurry waste and accommodating customized CMP requirements.
Implementation Method 1
The slurry is a liquid having the ability to lubricate the moving interface between the semiconductor wafer and the polishing pad
Implementation Method 2
mildly abrading and polishing the semiconductor wafer surface with a polishing agent
Data Source
AI summary
A chemical mechanical polishing method includes holding a wafer in a carrier over a polishing pad, dispensing a first slurry comprising a plurality of first abrasive particles into the carrier, rotating at least one of the carrier and the polishing pad, halting the dispensing of the first slurry, and dispensing a second slurry into the carrier after halting the dispensing of the first slurry, wherein the second slurry comprises a plurality of second abrasive particles smaller than the first abrasive particles.