Optical Microcavity Probe for Wafer Topography Metrology
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Solution Overview
Problem
Current optical metrology systems for wafer feature scanning are inadequate in terms of speed, cost, and accuracy, particularly as feature sizes in integrated circuits (ICs) decrease, leading to challenges in providing precise wafer topography inputs.
Innovation Solution
The use of optical microcavity sensors, coupled with fibers, to detect features on wafers through near-field interactions, enabling high sensitivity and accuracy by measuring shifts in interference signals and controlling the position and height of the sensors relative to the wafer, thereby enhancing optical metrology measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current scanning technologies are used for wafer feature scanning, then the system can operate with existing technology, but the measurement speed is too slow and accuracy is insufficient
Solution Approach 1:
The patent replaces traditional mechanical scanning systems with optical microcavity sensors that utilize optical near-field interactions. This substitution enables non-contact scanning with higher speed and precision, resolving the contradiction between measurement accuracy and measurement speed by using optical field interactions instead of mechanical probe scanning.
Solution Approach 2:
The patent changes the operating parameters by using optical microcavity resonance frequencies to detect wafer topography. By monitoring shifts in resonance frequency or quality factor (Q-factor) of the optical microcavity, the system achieves high-precision measurements at high speeds, simultaneously improving both accuracy and productivity.
2Manufacturing precision
If feature sizes in integrated circuits are reduced to increase device density, then more devices can be integrated, but the requirements for scanning accuracy and sensitivity increase
Solution Approach 1:
The patent introduces optical microcavity sensors as an intermediary between the measurement system and the wafer features. These sensors convert nanoscale topography variations into measurable optical resonance shifts, enabling high-precision measurement of sub-wavelength features that would be difficult to measure directly with conventional optical methods.
Solution Approach 2:
The patent transitions from direct spatial measurement to frequency domain measurement by detecting resonance frequency shifts. This dimensional transformation from spatial to spectral measurement enables higher precision characterization of small features, as frequency measurements can achieve higher resolution than direct spatial probing.
3Measurement precision
If traditional e-beam imaging or electron microscopy methods are used, then high resolution can be achieved, but the measurement process is slow and complex
Solution Approach 1:
The patent replaces electron beam-based mechanical scanning with optical microcavity-based non-contact sensing. This substitution eliminates the time-consuming processes of electron beam raster scanning and image processing, achieving high-resolution measurements much faster through parallel optical detection of resonance frequency shifts.
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 significantly improves measurement speed and accuracy, reducing errors associated with previous methods like e-beam imaging and electron microscopy, and allows for precise overlay measurements with robustness against process variations, enabling fast non-contact scanning with high resolution.
Implementation Method 1
optical microcavity sensors, coupled with fibers, to detect features on wafers through near-field interactions
Implementation Method 2
detect features on a wafer by shifts in an interference signal between reference radiation and near-field interactions of radiation in the microcavities and wafer features
Data Source
AI summary
Systems and methods are provided which utilize optical microcavity probes to map wafer topography by near-field interactions therebetween in a manner which complies with high volume metrology requirements. The optical microcavity probes detect features on a wafer by shifts in an interference signal between reference radiation and near-field interactions of radiation in the microcavities and wafer features, such as device features and metrology target features. Various illumination and detection configurations provide quick and sensitive signals which are used to enhance optical metrology measurements with respect to their accuracy and sensitivity. The optical microcavity probes may be scanned at a controlled height and position with respect to the wafer and provide information concerning the spatial relations between device and target features.