X-ray Diffraction Endpoint Detection for CMP
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Solution Overview
Problem
Existing endpointing techniques for abrasive removal processes in microfeature workpieces, such as CMP, fail to accurately determine the actual endpoint, leading to over-polishing and reduced throughput due to variability in substrates and process conditions, especially in complex applications like polysilicon contact formation and stop-on-nitride planarization.
Innovation Solution
Irradiating a periodic structure on the workpiece with a wide spectrum of radiation and obtaining an intensity distribution to determine critical dimensions, which allows for real-time monitoring and outputting a control signal to accurately terminate the abrasive removal process at the desired endpoint, using a controller with a computer-operable medium to process the intensity data and generate endpoint signals based on predetermined models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional endpointing methods (reflectance measurement, friction measurement) are used, then the endpoint detection is simplified and can be performed in-situ, but the measurement precision is insufficient leading to over-polishing or under-polishing
Solution Approach 1:
The patent replaces conventional optical reflectance measurement and friction-based endpoint detection with X-ray diffraction measurement. This substitution enables precise determination of the actual endpoint by measuring the position of material interfaces through diffraction patterns, eliminating the inaccuracies of previous methods while maintaining in-situ capability during abrasive removal processes.
Solution Approach 2:
The patent changes the measurement parameter from optical reflectance or friction force to X-ray diffraction intensity and position. By using X-ray diffraction, the system can directly measure the physical position of material interfaces and determine critical dimensions, providing accurate endpoint detection that accounts for variations in polishing rate and material composition.
2Manufacturing precision
If the abrasive removal process is stopped at the detected endpoint, then over-polishing is reduced, but under-polishing may occur due to inaccuracies in endpoint detection
Solution Approach 1:
The patent implements real-time feedback by continuously monitoring X-ray diffraction patterns during the abrasive removal process. The system measures the position of material interfaces and critical dimensions in-situ, providing continuous feedback on the actual removal progress. This enables precise control of the endpoint, stopping the process exactly when the desired surface planarity is achieved, thereby eliminating both over-polishing and under-polishing while optimizing throughput.
3Productivity
If in-situ endpoint detection is implemented, then throughput is maintained, but the measurement accuracy is insufficient compared to ex-situ measurements
Solution Approach 1:
The patent replaces ex-situ measurement methods (which require removing the workpiece from the polishing apparatus) with in-situ X-ray diffraction measurement. The X-ray diffraction system is integrated into the polishing apparatus, enabling accurate measurement of material interface positions and critical dimensions without interrupting the polishing process, thus maintaining both high throughput and measurement accuracy.
Solution Approach 2:
The patent uses X-ray diffraction as an intermediary measurement technique that can penetrate through the polishing pad and workpiece structure to measure internal material interfaces in-situ. This intermediary method provides accurate measurement of critical dimensions and interface positions without requiring physical access to the measurement location, enabling precise endpoint detection during the polishing process.
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 method enables precise and accurate termination of abrasive removal processes, reducing over-polishing and improving throughput by directly monitoring changes in critical dimensions of periodic structures, thus enhancing the efficiency and efficacy of abrasive removal processes.
Implementation Method 1
irradiating a periodic structure on the workpiece with a wide spectrum of radiation and analyzing the intensity distribution of the returning radiation to determine critical dimensions or physical parameters
Implementation Method 2
irradiating a periodic structure on the workpiece with a wide spectrum of radiation and analyzing the intensity distribution of the returning radiation
Data Source
AI summary
Methods and apparatus for controlling the removal of material from microfeature workpieces in abrasive removal processes. An embodiment of such a method comprises irradiating a periodic structure of the workpiece and obtaining an intensity distribution of radiation returning from the periodic structure. The workpiece can be irradiated with a wide spectrum of wavelengths (e.g., white light), or the workpiece can be irradiated with a laser or lamp at specific wavelengths. The intensity distribution can be an image or other signal from which a dimension or other physical parameter of the periodic structure can be determined. For example, the intensity distribution can be an intensity signal of radiation returning from the workpiece in a selected bandwidth (e.g., 200 nm-900 nm) or an image of a diffraction pattern of radiation that has been scattered by the periodic structure. The method further includes outputting a control signal based on the obtained intensity distribution. For example, the control signal can be an endpoint signal indicating the actual endpoint of the abrasive removal process.