CMP Polishing Control with Eddy Current Layer Exposure Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges in achieving uniformity when polishing stacks of adjacent conductive layers on a substrate, particularly in detecting the exposure of underlying conductive layers, which affects the precision and efficiency of the polishing process.
Innovation Solution
An in-situ real-time profile control system using an eddy current monitoring system to measure thickness and conductivity changes, allowing for adjustments in polishing parameters to ensure uniformity by detecting changes in polishing rate and applying different control algorithms based on predetermined criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single control algorithm is used for polishing conductive layers, then the control logic is simple, but the polishing uniformity deteriorates when transitioning between layers with different conductivities
Solution Approach 1:
The system dynamically switches between different control algorithms based on the detected conductivity characteristics of the current layer. When the eddy current monitoring system detects a change in conductivity indicating layer transition, the controller automatically switches from a first control algorithm optimized for high-conductivity layers to a second control algorithm optimized for low-conductivity layers, maintaining optimal polishing uniformity throughout the process
Solution Approach 2:
The system changes control parameters including switching between different control algorithms and Preston matrices based on the conductivity parameters of the conductive layers being polished. This parameter adaptation allows the system to optimize polishing pressure and speed parameters for each specific layer type, resolving the contradiction between algorithm simplicity and polishing precision
2Manufacturing precision
If real-time monitoring and parameter adjustment is implemented, then polishing precision is improved, but the system complexity increases
Solution Approach 1:
The system implements real-time feedback through an eddy current monitoring system that continuously measures the conductivity characteristics of the conductive layers during polishing. The controller processes this feedback signal to detect layer transitions and automatically adjusts polishing parameters, achieving high endpoint detection accuracy while managing system complexity through automated closed-loop control
Solution Approach 2:
The system replaces complex mechanical measurement and adjustment mechanisms with an eddy current-based electrical monitoring system and automated electronic control. This substitution achieves precise real-time detection and parameter adjustment using electrical fields and software control, reducing mechanical complexity while maintaining or improving measurement precision
3Manufacturing precision
If polishing parameters are adjusted frequently to maintain uniformity, then polishing uniformity is improved, but the response time increases
Solution Approach 1:
The system performs preliminary characterization of different conductive layers using Preston matrices that pre-calculate the relationship between polishing parameters and material removal rates for each layer type. When a layer transition is detected, the controller immediately applies the pre-characterized parameters for the new layer, achieving rapid adaptation without requiring extensive real-time adjustments, thus maintaining uniformity while minimizing process time
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 system effectively detects exposure of underlying conductive layers, enabling precise adjustments to achieve improved within-wafer polishing uniformity and ensuring that both target and control zones reach desired thicknesses simultaneously.
Implementation Method 1
an in-situ eddy current monitoring system may be used to induce eddy currents in a conductive region on the substrate to determine parameters such as the local thickness of the conductive region
Data Source
AI summary
A method of controlling polishing includes polishing a stack of adjacent conductive layers on a substrate, measuring with an in-situ eddy current monitoring system a sequence of characterizing values for the substrate during polishing, calculating a polishing rate from the sequence of characterizing values repeatedly during polishing, calculating one or more adjustments for one or more polishing parameters based on a current polishing rate using a first control algorithm for an initial time period, detecting a change in the polishing rate that indicates exposure of the underlying conductive layer, and calculating one or more adjustments for one or more polishing parameters based on the polishing rate using a different second control algorithm for a subsequent time period after detecting the change in the polishing rate.