Optical Sensor Pixel Array Background Correction
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Solution Overview
Problem
Current optical monitoring systems for semiconductor processes face challenges in accurately detecting small changes due to mixed signals from optical emission spectroscopy (OES) and interferometric endpoint (IEP) methods, which are continuous and discrete in time, respectively, leading to difficulties in process control and increased complexity and cost.
Innovation Solution
The system employs an optical measurement system with a pixel area and reduced illumination regions to characterize and adjust digital representations of electrical charges, using dark level estimates and broadband calibration to isolate and correct non-optical signal variations, thereby improving signal-to-noise ratios and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical emission spectroscopy (OES) and interferometric endpoint (IEP) methods are used continuously for monitoring semiconductor processes, then process monitoring capability is improved, but signal accuracy deteriorates due to mixed signals from both methods
Solution Approach 1:
The patent segments the pixel array into multiple regions including active pixels for OES/IEP measurement and reduced illumination pixels for background signal characterization. This spatial segmentation allows simultaneous collection of process signals and background references without interference, resolving the contradiction between continuous monitoring and signal accuracy.
Solution Approach 2:
The reduced illumination pixels act as an intermediary element that captures background signal variations (thermal drift, dark current) separately from the active measurement pixels. This intermediary region enables the system to characterize and subtract background effects, thereby maintaining high measurement precision while continuously monitoring semiconductor processes.
2Object-affected harmful factors
If background correction is performed using traditional methods, then some signal interference is reduced, but non-optical signal variations (thermal drift, dark current) are not adequately corrected
Solution Approach 1:
The system performs preliminary characterization of background signal variations using reduced illumination pixels before actual measurement. By continuously monitoring thermal drift and dark current in the reduced illumination region, the system pre-characterizes background effects that will affect active pixels, enabling accurate real-time correction and improving measurement precision.
Solution Approach 2:
The patent changes the illumination parameter for specific pixels (reduced illumination pixels receive less or no light) to isolate and characterize non-optical signal variations. This parameter change enables separate measurement of thermal drift and dark current components, allowing the system to correct these effects in active pixels and achieve higher correction accuracy.
3Reliability
If separate processing systems are used for OES and IEP methods, then each method can be optimized, but system complexity and cost increase
Solution Approach 1:
The patent implements a universal pixel array that serves multiple functions: active pixels perform both OES and IEP measurements, while reduced illumination pixels provide background correction for both methods. This multi-functional design allows simultaneous optimization of OES and IEP within a single integrated system, reducing overall complexity and cost while maintaining reliability.
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 enhances the ability to monitor semiconductor processes by minimizing non-optical signal interference, improving signal accuracy, and reducing costs by integrating signal processing within the spectrometer, allowing for more precise control of semiconductor processes.
Implementation Method 1
a pixel area of an optical sensor having multiple pixels that store an electrical charge corresponding to a received optical signal
Data Source
AI summary
The disclosure provides features for improved processing of optical data by identifying and characterizing stationary and transient signals in the electrical data representing the data collected from an optical sensor of an optical measurement system. In one example, an optical measurement system is disclosed that includes: (1) a pixel area of an optical sensor having multiple pixels that store an electrical charge corresponding to a received optical signal, (2) one or more reduced illumination regions that provide signal levels intrinsic to the optical sensor, and (3) one or more processors configured to adjust, during active operation of the system, digital representations of the electrical charges from the pixels of the pixel area using characterizations of the signal levels from the one or more reduced illumination regions.