CMP Profile Control Using Multi-Phase Algorithms and Eddy Current Sensing
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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 and adjust polishing parameters based on changes in polishing rates, allowing for precise detection of underlying conductive layer exposure and adjustment of polishing parameters to ensure uniformity across the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single control algorithm is used for polishing the stack of conductive layers, then the device complexity is reduced, but the manufacturing precision deteriorates because it cannot accurately detect exposure of underlying layers
Solution Approach 1:
The polishing process is segmented into distinct phases: polishing the outer conductive layer and polishing the underlying conductive layer. A first control algorithm is used during the first phase, and a second control algorithm is used during the second phase after exposure of the underlying layer is detected. This segmentation allows each algorithm to be optimized for its specific phase, improving overall polishing precision without requiring a single overly complex algorithm to handle all phases.
Solution Approach 2:
The control algorithm dynamically switches from a first control algorithm to a second control algorithm based on real-time detection of underlying layer exposure. This dynamic adaptation allows the system to respond to changing conditions during polishing, maintaining high manufacturing precision throughout the process while keeping individual algorithms relatively simple.
2Measurement precision
If in-situ eddy current monitoring is used to detect layer exposure, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The in-situ eddy current monitoring system provides real-time feedback on the thickness and exposure status of conductive layers during polishing. This feedback is used by the control algorithms to dynamically adjust polishing parameters and switch between control phases, enabling precise detection of layer exposure and maintaining high measurement precision throughout the process.
Solution Approach 2:
The patent replaces mechanical measurement methods with an in-situ eddy current monitoring system that uses electromagnetic induction to measure layer thickness and detect exposure. This substitution provides non-contact, real-time measurements with high precision while reducing mechanical complexity compared to physical sampling or contact-based measurement methods.
3Productivity
If polishing parameters are adjusted in real-time based on multiple control algorithms, then the productivity is improved through better process control, but the device complexity increases
Solution Approach 1:
The control system is configured with multiple control algorithms prepared in advance, each optimized for specific phases of the polishing process. The system switches between these pre-configured algorithms based on detection of layer exposure, enabling smooth transitions and continuous optimization without requiring complex real-time algorithm generation or switching logic.
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 improves within-wafer polishing uniformity by detecting exposure of underlying conductive layers and modifying polishing parameters in real-time, ensuring that both the outer and underlying layers are polished to the same thickness simultaneously, thereby enhancing the precision and efficiency of the CMP process.
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
During polishing of a stack of adjacent layers, a plurality of instances of a profile control algorithm are executed on a controller with different instances having different values for a control parameter. A first instance receives a sequence of characterizing values from an in-situ monitoring system during an initial time period to control a polishing parameter, and a second instance receives the sequence of characterizing values during the initial time period and a subsequent time period to control the polishing parameter. Exposure of the underlying layer is detected based on the sequence of characterizing values from the in-situ monitoring system.