X-ray Dark-Field Inspection for Semiconductor Voids
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Solution Overview
Problem
Current x-ray inspection techniques for semiconductor packaging, particularly for smaller voids and defects, face challenges in sensitivity and throughput, with conventional methods like Talbot-Lau interferometry being too slow and increasing radiation dose, while 3D inspection schemes are not practical for 100% inspection.
Innovation Solution
A dark-field-only x-ray imaging system that satisfies the Lau condition, utilizing a configuration with two absorption gratings and an x-ray source with sub-sources, where the second grating blocks direct x-rays while allowing scattered x-rays to reach the detector, enhancing sensitivity to micron-scale features without absorption or phase contrast.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Talbot-Lau interferometry is used for x-ray inspection, then measurement precision is improved, but productivity deteriorates because the inspection process becomes too slow for 100% inspection
Solution Approach 1:
The patent extracts and isolates only the dark-field scattering contrast mechanism from the complete Talbot-Lau interferometry system. By using a simple absorption grating instead of the full interferometric setup with multiple gratings and phase-stepping mechanisms, the system removes unnecessary complexity while retaining sensitivity to micron-scale defects through dark-field imaging alone.
Solution Approach 2:
The patent changes the operational parameters by eliminating the need for phase-stepping movements and multiple grating configurations. The system uses a fixed grating configuration with electron bombardment of the target material to generate x-rays, achieving rapid acquisition of dark-field contrast images without the time-consuming phase-stepping procedure required by conventional Talbot-Lau interferometry.
2Measurement precision
If conventional Talbot-Lau interferometry is used for x-ray inspection, then measurement precision is improved, but use of energy worsens due to increased radiation dose to the sample
Solution Approach 1:
The patent extracts only the essential dark-field scattering detection function from the complex Talbot-Lau interferometry system. By using a single absorption grating and eliminating the need for phase-stepping and multiple gratings, the system reduces the total x-ray exposure required while maintaining sensitivity to small defects through dark-field contrast alone.
Solution Approach 2:
The patent employs a simpler, more disposable-like grating configuration that does not require the精密 alignment and multiple moving components of conventional Talbot-Lau interferometry. This simplified setup reduces the cumulative radiation dose to the sample while achieving the necessary defect detection capability through dark-field imaging.
3Measurement precision
If 3D inspection schemes are used for semiconductor packaging, then measurement precision is improved for complex defects, but device complexity increases making it impractical for 100% inspection
Solution Approach 1:
The patent extracts the essential dark-field scattering contrast mechanism from complex 3D inspection schemes. By using a simple absorption grating configuration and focusing solely on dark-field imaging without requiring multiple viewing angles or complex 3D reconstruction algorithms, the system maintains sensitivity to micron-scale defects while dramatically reducing system complexity for high-volume inspection.
4Device complexity
If conventional x-ray inspection methods are used, then device complexity is kept simple, but measurement precision deteriorates for smaller voids and defects
Solution Approach 1:
The patent introduces an absorption grating as an intermediary element that enhances dark-field scattering contrast from small defects. The grating periodic structures modulate the x-ray beam to amplify the scattering signal from micron-scale voids and defects, improving measurement precision while adding only a single static component to the otherwise simple inspection system.
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 configuration improves sensitivity to smaller voids and defects, reduces radiation exposure, and increases throughput by focusing on dark-field contrast, enabling efficient 100% inspection of semiconductor samples without the need for absorption or phase contrast imaging.
Implementation Method 1
an x-ray source comprising a plurality of sub-sources in thermal communication with a substrate and that are configured to emit x-rays when bombarded by electrons
Implementation Method 2
The first grating comprises periodic structures configured to absorb at least some of the x-rays received from the x-ray source
Implementation Method 3
The sample is configured to scatter and emit a first portion of the x-rays and to emit without scattering a second portion of the x-rays
Implementation Method 4
The second grating comprises periodic structures configured to substantially block transmission of the second portion of the x-rays from reaching the at least one x-ray detector while substantially allowing transmission of the first portion of the x-rays to the at least one x-ray detector
Data Source
AI summary
An x-ray imaging/inspection system includes an x-ray source having a plurality of sub-sources in thermal communication with a substrate. The system further includes a first grating positioned to receive at least some of the x-rays from the x-ray source, a stage configured to hold a sample positioned to receive at least some of the x-rays from the x-ray source, at least one x-ray detector, and a second grating having periodic structures. The x-ray source, the first grating, and the second grating are configured such that a ratio of a pitch p0 of the plurality of sub-sources to a pitch p2 of the periodic structures of the second grating is substantially equal to a ratio of a distance dS-G1 between the plurality of sub-sources and the first grating and a distance dG1-G2 between the first grating and the second grating: (p0/p2)=(dS-G1/dG1-G2).