Multispot Optical Monitoring for Wafer Etch Spatial Precision
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Solution Overview
Problem
Existing optical monitoring systems for semiconductor processes face challenges in accurately monitoring fast etch rates and small feature sizes due to limited spatial information and signal integration, particularly in multipoint monitoring of optical signals during semiconductor processes.
Innovation Solution
A multi-spot optical system that utilizes a light source to create multiple interrogation spots on a wafer, combined with optical elements and a spectrometer to collect and process reflected light from these spots, allowing for precise spatial information and improved signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-spot optical monitoring system is used, then the device complexity is low, but the measurement precision and spatial information are insufficient for monitoring fast etch rates and small features
Solution Approach 1:
The optical system is segmented into multiple independent optical paths, each targeting a specific spot on the wafer. Multiple beams are generated from a single source and directed to different locations through optical elements such as beam splitters and mirrors, enabling simultaneous multi-point measurement without requiring a single complex scanning system
Solution Approach 2:
The system transitions from single-point temporal monitoring to multi-point spatial monitoring by adding the spatial dimension. Multiple beams are distributed across different locations on the wafer surface, creating a two-dimensional array of measurement points that provides comprehensive spatial information about the etching process
2Measurement precision
If signal integration is used to improve signal-to-noise ratio, then the signal quality improves, but the spatial resolution and ability to detect local variations is lost
Solution Approach 1:
The detection system is segmented into multiple independent detectors, each receiving light from a specific spot on the wafer. This segmentation allows the system to maintain spatial resolution by keeping measurement channels separate while still achieving improved signal-to-noise ratio through the collective data from multiple spots
Solution Approach 2:
The system merges multiple measurement channels by combining the optical paths and detector signals. The collected light from multiple spots is processed together to enhance the signal-to-noise ratio while preserving the spatial information through correlated analysis of the multi-point data
3Productivity
If multiple interrogation spots are monitored simultaneously, then the productivity and process control capability improve, but the device complexity and optical system requirements increase
Solution Approach 1:
A single optical system is designed to perform multiple functions: generating multiple beams, directing them to different spots, collecting reflected light from each spot, and routing it to appropriate detectors. This multi-functional design eliminates the need for separate monitoring systems for each spot, reducing overall complexity while maintaining high productivity
Solution Approach 2:
Optical intermediaries such as beam splitters, mirrors, and optical fibers are used to distribute and collect light between the source and multiple measurement points. These intermediary elements enable simultaneous multi-point monitoring without requiring direct line-of-sight from the source to each spot, simplifying the optical architecture
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
Enhances the ability to monitor and control semiconductor processes by providing detailed spatial information and improved signal-to-noise ratio, enabling accurate detection of small changes in film thickness and feature sizes.
Implementation Method 1
a light source configured to provide source light to a source plane to form a plurality of first subbeams
Implementation Method 2
the optical elements are further configured to modify each of the plurality of first subbeams upon reflection from the wafer to form a plurality of second subbeams upon an image plane
Implementation Method 3
a spectrometer configured to receive collected light from the plurality of second subbeams
Data Source
AI summary
The disclosure provides an optical system, a semiconductor processing system, and a method for processing a semiconductor wafer. In one example, the optical system includes: (1) a light source configured to provide source light to a source plane to form a plurality of first subbeams, (2) optical elements configured to modify each of the plurality of first subbeams to form a plurality of interrogation spots on a wafer according to a predetermined pattern, wherein the optical elements are further configured to modify each of the plurality of first subbeams upon reflection from the wafer to form a plurality of second subbeams upon an image plane, and (3) a spectrometer configured to receive collected light from the plurality of second subbeams.