CMP Endpoint Detection via Slurry Spectroscopy
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Solution Overview
Problem
Chemical-mechanical polishing (CMP) processes face challenges in determining the endpoint, especially when dealing with soft materials, as excessive pressure can deform them, leading to issues like dishing, and friction changes are difficult to detect with light downforces.
Innovation Solution
Incorporating spectroscopic analysis of used slurry to determine the endpoint by monitoring reflectance and transmittance, allowing for precise termination of the CMP process without deforming soft materials, even with low downforces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If light downforce is applied during CMP of soft materials, then material deformation and dishing are reduced, but endpoint detection becomes difficult due to insufficient friction changes
Solution Approach 1:
The patent introduces an intermediary measurement system (optical sensor, capacitive sensor, or friction sensor) that mediates between the polishing process and endpoint detection. This intermediary provides a reliable signal for endpoint detection without requiring high downforce, thus resolving the contradiction between gentle polishing and accurate detection
Solution Approach 2:
The patent replaces the traditional mechanical friction-based endpoint detection with optical, capacitive, or other non-mechanical sensing methods. This substitution allows for accurate endpoint detection under light downforce conditions, eliminating the need to apply heavy pressure to generate sufficient friction signals
2Difficulty of detecting and measuring
If heavy downforce is applied during CMP, then endpoint detection through friction changes becomes easier, but soft materials are deformed causing dishing and surface defects
Solution Approach 1:
The patent introduces an intermediary measurement system (optical sensor, capacitive sensor, or friction sensor) that mediates between the polishing process and endpoint detection. This intermediary provides a reliable signal for endpoint detection without requiring high downforce, thus resolving the contradiction between gentle polishing and accurate detection
Solution Approach 2:
The patent replaces the traditional mechanical friction-based endpoint detection with optical, capacitive, or other non-mechanical sensing methods. This substitution allows for accurate endpoint detection under light downforce conditions, eliminating the need to apply heavy pressure to generate sufficient friction signals
3Manufacturing precision
If CMP process continues after upper structure removal to ensure complete polishing, then polishing thoroughness is improved, but soft base material is deformed causing dishing
Solution Approach 1:
The patent implements real-time feedback through optical sensors, capacitive sensors, or friction sensors that continuously monitor the polishing process. When the endpoint is detected (indicating complete removal of upper structure), the system immediately provides feedback to stop the process, preventing over-polishing and deformation of soft base materials
Solution Approach 2:
The patent employs preliminary endpoint detection methods that predict when the upper structure will be completely removed. By detecting endpoint signals in advance (such as changes in optical properties, capacitance, or friction), the system can prepare to stop the polishing process at the optimal moment, ensuring complete polishing without deforming the soft base material
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
Enables accurate and prompt endpoint detection in CMP processes, preventing material deformation and ensuring a smooth, effective polishing of semiconductor substrates with soft materials, reducing the risk of dishing and other defects.
Implementation Method 1
monitoring reflectance and transmittance
Implementation Method 2
monitoring reflectance and transmittance
Data Source
AI summary
Some embodiments include an apparatus having a polishing mechanism configured to polish a surface of a wafer. The polishing mechanism converts fresh slurry to used slurry during a polishing process. At least one emitter is configured to direct electromagnetic radiation onto or through the used slurry. At least one detector is configured to detect transmittance of the electromagnetic radiation through the used slurry or reflection of the electromagnetic radiation from the used slurry. An identification system is coupled with the at least one detector and is configured to identify a property of the used slurry indicating that an endpoint of the polishing process has been reached. Control circuitry is coupled with the identification system and is configured to stop the polishing process based on receiving a trigger from the identification system. Some embodiments include polishing methods.