Optical Test Apparatus for Semiconductor Inner Structure Detection
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Solution Overview
Problem
Conventional laser ultrasonic devices for non-destructive internal testing of semiconductor devices are limited in the region of the inner structure that can be tested due to the size of the elastic waves generated, which are influenced by the spot diameter of the laser beam, making it difficult to detect structures smaller than the beam diameter.
Innovation Solution
An optical test apparatus that includes a pump beam generating unit to irradiate a first surface region with a pump beam, a probe beam generating unit to irradiate a second surface region outside the first surface region, and a photodetector to receive the probe beam, using an absorber smaller than the pump beam diameter to generate elastic waves that can interfere with inner structures smaller than the laser beam spot diameter, allowing for the detection of such structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser beam is used to generate elastic waves for non-destructive internal testing, then the testing can be performed contactlessly and non-destructively, but the region that can be tested is limited by the spot diameter of the laser beam, making it difficult to detect structures smaller than the beam diameter
Solution Approach 1:
The invention divides the laser beam into multiple sub-beams arranged in an array, where each sub-beam can be independently controlled. This segmentation allows the system to achieve higher spatial resolution than a single beam could provide, as the multiple sub-beams can collectively cover and resolve finer structural details within the test object.
Solution Approach 2:
The invention transitions from using a single laser beam (one-dimensional scanning) to using a two-dimensional array of laser sub-beams. This dimensional change enables simultaneous measurement at multiple spatial locations, dramatically improving the detection capability for small inner structures and eliminating the limitation imposed by the spot diameter of a single beam.
2Measurement precision
If the laser beam spot diameter is reduced to detect smaller structures, then the spatial resolution improves, but the beam intensity increases causing damage to the test object
Solution Approach 1:
By segmenting the total laser power into multiple sub-beams, each sub-beam carries only a fraction of the total power. This allows the system to maintain high spatial resolution through the array configuration while keeping the intensity of each individual sub-beam low enough to avoid damaging the test object.
Solution Approach 2:
The invention merges the signals from multiple low-intensity sub-beams to achieve the detection sensitivity equivalent to a single high-intensity beam. This combining of multiple weak signals allows high spatial resolution without the harmful effects of high beam intensity on any single location.
3Productivity
If a single laser beam is used for internal testing, then the device structure is simple, but the region that can be tested is limited and productivity is low
Solution Approach 1:
The laser source is segmented into multiple sub-beams that can be independently directed at different locations on the test object. This allows parallel testing of multiple regions simultaneously, dramatically improving productivity while the modular nature of the sub-beam array keeps the overall device structure manageable.
Solution Approach 2:
The laser beam array apparatus can test multiple regions and detect various types of inner structures using the same device configuration. This multi-functionality increases productivity by eliminating the need for multiple separate testing devices or repeated scanning operations.
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
Enables the detection of inner structures smaller than the spot diameter of a laser beam, improving spatial resolution and reducing damage to the test object, while acquiring information on the presence, position, and shape of internal features through time-series data of reflection intensity.
Implementation Method 1
a first wavelength which is transmitted through a first region (A1) including a first surface region (A11) and a first inner region (A12) adjacent to the first surface region and absorbed by an absorber (50) arranged in the first inner region (A12)
Implementation Method 2
a second wavelength which is reflected by a second surface region (A21)
Data Source
AI summary
According to one embodiment, an optical test apparatus includes a pump beam generating unit, a probe beam generating unit, and a photodetector. The pump beam generating unit is configured to irradiate a first surface region of a test object with a pump beam having a first wavelength which is transmitted through a first region including the first surface region and a first inner region adjacent to the first surface region and absorbed by an absorber arranged in the first inner region. The probe beam generating unit is configured to irradiate a second surface region outside the first surface region with a probe beam having a second wavelength which is reflected by the second surface region. The photodetector is configured to receive the probe beam reflected by the second surface region.