CMP Endpoint Window Logic Using Overlaid Signal Boundaries
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Solution Overview
Problem
Determining the polishing endpoint in chemical mechanical polishing (CMP) processes is challenging due to variations in material removal rates caused by factors such as slurry distribution, polishing pad condition, relative speed, and load, making time-based endpoint determination unreliable.
Innovation Solution
An in-situ monitoring system, such as acoustic, motor torque, eddy current, or optical systems, generates time-varying signals during polishing. A user interface displays these signals, allowing operators to define boundary-crossing logic windows, which are optimized by an algorithm to determine the polishing endpoint accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If time-based endpoint determination is used in CMP, then the control method is simple, but the endpoint determination accuracy deteriorates due to variations in material removal rate
Solution Approach 1:
The patent implements feedback by continuously monitoring polishing process parameters (such as polishing rate, surface roughness, or material removal depth) and using this real-time data to adjust and determine the endpoint dynamically. This replaces static time-based control with adaptive feedback-based control, resolving the contradiction between simplicity and accuracy.
Solution Approach 2:
The patent changes the control parameter from fixed time duration to dynamically adjusted parameters based on actual polishing conditions. By monitoring parameters like material removal rate, surface topography, or acoustic emissions, the system adapts the endpoint criterion to match actual process variations, thereby maintaining accuracy without excessive complexity.
2Measurement precision
If in-situ monitoring system is implemented, then endpoint detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the monitoring system multi-functional by using a single sensor or measurement system to perform multiple functions: real-time endpoint detection, process parameter measurement, and quality control. This reduces overall system complexity compared to having separate dedicated systems for each function.
Solution Approach 2:
The monitoring system is designed to automatically process and interpret its own measurements, using built-in algorithms to determine endpoint criteria without requiring complex external analysis equipment. The system self-adjusts and self-determines the endpoint, reducing the need for additional complex hardware.
3Measurement precision
If multiple test substrates are polished to optimize endpoint criteria, then endpoint detection accuracy is improved, but setup time increases
Solution Approach 1:
The patent performs preliminary optimization using a small number of test substrates to establish endpoint criteria before actual production polishing. The optimized criteria are then stored and reused for subsequent substrates, eliminating the need to repeat the time-consuming optimization process for each substrate while maintaining high accuracy.
Solution Approach 2:
The patent creates a model or template from the optimization results obtained on test substrates and applies this copied knowledge to production substrates. The endpoint criteria derived from test substrates are replicated and used across multiple production runs, reducing setup time while preserving the accuracy gains from optimization.
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
Improves wafer-to-wafer and within-wafer polishing uniformity, reduces setup time, and enhances yield by providing an intuitive user interface for endpoint detection, while being cost-effective without requiring hardware changes to existing CMP systems.
Implementation Method 1
The monitoring system can be an acoustic monitoring system
Implementation Method 2
an eddy current monitoring system
Implementation Method 3
an optical monitoring system
Implementation Method 4
Chemical mechanical polishing (CMP) is one accepted method of planarization
Implementation Method 5
Chemical mechanical polishing (CMP)
Data Source
AI summary
A method of controlling a chemical mechanical polishing system includes receiving a respective time-varying test signal from an endpoint detection system for each of a plurality of test substrates, simultaneously visually displaying the plurality of time-varying test signals on a display with the plurality of time-varying test signals overlaid on each other in a graph. receiving user input selecting a box having a defined time range and defined signal value range, and receiving a selection of one from a preset group of boundary crossing logic functions to provide a selected boundary crossing logic function. During chemical mechanical polishing of a device substrate, the device substrate is monitored with the endpoint detection system to generate a time-varying signal and an endpoint determination can be based on whether the time-varying signal satisfies the selected boundary crossing logic function.