Polishing End Point Detection Using Dual-Wavelength Extrema
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical polishing end point detection methods are affected by initial film thickness and polishing rate, leading to errors in detecting the polishing end point, which complicates management and reduces productivity in semiconductor fabrication processes.
Innovation Solution
A method that applies light to a substrate during polishing, monitors first and second characteristic values calculated from reflection intensities at different wavelengths, detects a point when extremal points of these values appear within a predetermined time difference, and determines the polishing end point based on this detection, ensuring accurate detection regardless of initial film thickness and polishing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the monitoring start point is delayed to avoid unstable waveforms, then the stability of characteristic value monitoring is improved, but the accuracy of polishing end point detection deteriorates due to shift of local maximum points
Solution Approach 1:
The patent applies preliminary action by measuring the initial film thickness before polishing and using this measurement to calculate and set the monitoring start point. This preliminary measurement allows the system to anticipate the correct starting position for monitoring, compensating for the delay needed to achieve waveform stability while ensuring accurate end point detection.
Solution Approach 2:
The patent changes the parameter of monitoring start point based on the measured initial film thickness. By adjusting the start point position according to the specific initial thickness value, the system adapts to different film conditions, ensuring both waveform stability and accurate end point detection for each specific case.
2Quantity of substance
If the initial film thickness is large, then the film formation capacity is improved, but the accuracy of polishing end point detection deteriorates due to shift of local maximum points
Solution Approach 1:
The system performs preliminary measurement of the initial film thickness before polishing begins. This advance knowledge allows the monitoring start point to be specifically set for each film thickness condition, preventing the shift of local maximum points that would otherwise occur with large initial thicknesses.
Solution Approach 2:
The monitoring start point parameter is changed based on the measured initial film thickness. For different initial thickness values, the system adjusts the start point position accordingly, ensuring accurate end point detection regardless of whether the initial film thickness is large or small.
3Productivity
If the polishing rate varies, then the polishing efficiency is improved, but the accuracy of polishing end point detection deteriorates due to shift of local maximum points
Solution Approach 1:
The system adjusts the monitoring start point parameter based on the measured initial film thickness, which indirectly compensates for variations in polishing rate. By setting the start point according to the specific film thickness condition, the system maintains accurate end point detection even when polishing rates vary.
4Ease of operation
If the monitoring start point is fixed, then the operation simplicity is improved, but the accuracy of polishing end point detection deteriorates due to inability to adapt to different initial film thicknesses
Solution Approach 1:
The system performs self-service by automatically measuring the initial film thickness and calculating the appropriate monitoring start point without requiring manual intervention. This automatic adaptation maintains operational simplicity while achieving accurate end point detection for different film thickness conditions.
Solution Approach 2:
The monitoring start point parameter is automatically changed based on the measured initial film thickness. This dynamic adjustment occurs without additional manual operations, preserving ease of use while adapting to different film conditions.
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 allows for accurate detection of the polishing end point without being influenced by initial film thickness and polishing rate, maintaining consistency and improving productivity by simplifying management procedures.
Implementation Method 1
light is applied to a surface of a film during polishing of the film, and a characteristic value is calculated using an intensity of the reflected light
Implementation Method 2
This characteristic value changes periodically according to a change in the film thickness. This is because of interference between a light ray reflected off the surface of the film and a light ray reflected off a surface of an underlying layer underneath the film
Data Source
AI summary
A method for detecting an end point of a polishing operation (e.g., a polishing stop point or a changing point of polishing conditions) of a film of a substrate is described. The method includes applying light to a surface of a substrate during polishing of the substrate; receiving reflected light from the surface of the substrate, monitoring a first characteristic value and a second characteristic value calculated from reflection intensities at different wavelengths; detecting a point when an extremal point of the first characteristic value and an extremal point of the second characteristic value appear within a predetermined time difference; after detecting the point, detecting a predetermined extremal point of the first characteristic value or the second characteristic value; and determining a polishing end point based on a point when the predetermined extremal point is detected.