Wafer Inspection Calibration via Virtual VCSEL Emulation
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Solution Overview
Problem
Traditional wafer inspection apparatus calibration methods are unreliable due to factors like optical distortion, temperature-induced drift, and misalignment, especially when testing VCSEL arrays with varying laser characteristics, leading to inconsistent and inaccurate measurement results.
Innovation Solution
A calibration system comprising a fixture with an optical fiber and a wafer emulator substrate with portholes to accommodate the fixture, emulating the beam profile of a VCSEL array, ensuring consistent and accurate calibration of the wafer inspection apparatus by simulating the laser characteristics and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional calibration methods using a preselected VCSELA as reference are used, then the calibration process is simple, but the measurement precision deteriorates over time due to aging, handling, and environmental changes
Solution Approach 1:
The patent creates a virtual copy of the VCSELA characteristics through software simulation rather than using a physical reference VCSELA. The virtual reference maintains stable laser characteristics (wavelength, power, beam divergence) that do not degrade over time, eliminating the precision deterioration problem while keeping the calibration process simple.
Solution Approach 2:
The patent replaces the physical mechanical reference VCSELA with a software-based virtual reference model. This substitution eliminates the physical degradation issues (aging, handling damage, environmental sensitivity) associated with physical references while maintaining the calibration functionality.
2Device complexity
If traditional calibration methods are used, then the device complexity is low, but the reliability of measurement results deteriorates due to optical distortion, temperature drift, and misalignment
Solution Approach 1:
By using a virtual reference that replicates VCSELA characteristics through software, the system eliminates reliability issues caused by physical reference degradation, optical distortion, temperature drift, and misalignment while adding minimal complexity to the calibration system.
Solution Approach 2:
The patent changes the reference from a physical object with fixed parameters to a software model where parameters (wavelength, power, beam divergence) can be precisely controlled and maintained stable, thereby improving measurement reliability without significantly increasing system complexity.
3Ease of manufacture
If conventional wafer inspection is performed on VCSEL arrays, then the manufacturing cost is reduced, but the measurement precision deteriorates due to variations in VCSEL characteristics and inspection apparatus shortcomings
Solution Approach 1:
The virtual reference creates accurate baseline characteristics for VCSEL arrays, enabling precise measurement of optical power and beam divergence despite variations in individual VCSEL characteristics and inspection apparatus shortcomings, thereby maintaining cost-effectiveness while improving measurement precision.
Solution Approach 2:
The virtual reference acts as an intermediary that mediates between the inspection apparatus and the actual VCSEL measurements, compensating for apparatus shortcomings and providing a stable reference that improves measurement precision without increasing testing costs.
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
The proposed calibration system provides consistent, repeatable, and accurate measurement results by stabilizing the calibration process and accounting for variations in VCSEL arrays, improving the reliability of wafer inspection.
Implementation Method 1
The first optical fiber is inserted through the first hole in the first fixture whereby a proximal end of the first optical fiber is exposed at the top surface of the first fixture, the proximal end having a light emitting profile that emulates a beam profile of a semiconductor laser.
Implementation Method 2
A distal end of the first optical fiber is coupled to a laser beam for propagating a laser beam through the first optical fiber.
Data Source
AI summary
Illustrative systems and methods disclosed herein pertain to calibrating a wafer inspection apparatus. In one exemplary embodiment, a calibration system includes a wafer emulator in the form of a substrate having a first porthole extending from a bottom major surface of the substrate to a top major surface of the substrate. The first porthole accommodates a fixture that holds an optical fiber such that a proximal end of the optical fiber is coplanar to the top major surface of the substrate. The optical fiber has a light emitting profile that emulates a beam profile of a semiconductor laser element. A laser transmitter is coupled to a distal end of the optical fiber and propagates a laser beam through the optical fiber and out of the proximal end of the optical fiber. The wafer inspection apparatus is arranged to receive the laser beam and use the laser beam for calibration purposes.