Microprobe THz Wafer Inspection Using Polarized Femtosecond Beams
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Solution Overview
Problem
Existing near-field THz spectroscopy methods for wafer inspection are complex and time-consuming due to the need for multiple measurements before and after each process, as they measure terahertz waves affected by both top and lower layers, complicating the inspection process.
Innovation Solution
A terahertz signal-based inspection device using a femtosecond laser beam split into vertically and horizontally polarized sub-lights, detected by intersecting first and second microprobes, allowing simultaneous measurement of terahertz waves through a wafer in a non-destructive manner.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are performed before and after each process to overcome signal interference from lower layers, then measurement accuracy is improved, but inspection time and process complexity increase
Solution Approach 1:
The patent segments the terahertz wave measurement into two independent components: vertically polarized light measures the top layer while horizontally polarized light measures the lower layer. By separating the measurement functions of different layers into distinct polarization channels, the system achieves accurate measurement of each layer independently without requiring multiple sequential measurements, thus improving measurement precision while reducing inspection time.
2Measurement precision
If multiple measurements are performed before and after each process to overcome signal interference from lower layers, then measurement accuracy is improved, but process complexity increases
Solution Approach 1:
The patent segments the terahertz wave measurement into two independent components: vertically polarized light measures the top layer while horizontally polarized light measures the lower layer. By separating the measurement functions of different layers into distinct polarization channels, the system achieves accurate measurement of each layer independently without requiring multiple sequential measurements, thus improving measurement precision while reducing inspection time.
Solution Approach 2:
The patent introduces polarization direction as an additional dimension to separate layer measurements. Instead of using sequential time-based measurements, the system uses orthogonal polarization states (vertical and horizontal) to simultaneously distinguish between top and lower layer signals, thereby simplifying the measurement process while maintaining high accuracy.
3Device complexity
If conventional single-probe terahertz measurement is used, then device simplicity is maintained, but measurement accuracy decreases due to signal interference from multiple layers
Solution Approach 1:
The patent merges two microprobes with orthogonal polarization detection capabilities into a single integrated measurement system. The first microprobe detects vertically polarized light while the second microprobe detects horizontally polarized light, and both measurements are combined to provide comprehensive layer information. This merging approach maintains relative device simplicity while achieving high measurement accuracy through polarized light separation.
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 device simplifies the inspection process and reduces time by enabling simultaneous measurement of terahertz waves through multiple layers, providing accurate insights into wafer structures and properties without destructive testing.
Implementation Method 1
a first optical array configured to separate the first light into a first sub-light and a second sub-light and to provide the first and the second sub-lights to an inspection target, wherein the first sub-light and the second sub-light are polarized in different directions
Implementation Method 2
a microprobe configured to detect a photoelectric signal caused by incidence of the first and the second sub-lights on the inspection target
Data Source
AI summary
Provided is an inspection device including: a light source generating and outputting a femtosecond laser beam; a beam splitter configured to split the femtosecond laser beam into a first light and a second light; a first optical array configured to separate the first light into a first sub-light and a second sub-light and to provide the first and the second sub-lights to an inspection target, wherein the first sub-light and the second sub-light are polarized in different directions; a microprobe configured to detect a photoelectric signal caused by incidence of the first and the second sub-lights on the inspection target, the microprobe including a first microprobe configured to detect the first sub-light and a second microprobe configured to detect the second sub-light; and a second optical array configured to provide the second light to the microprobe.