Optical Via Inspection via Transparent Capping Layer
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Solution Overview
Problem
The challenge in fabricating through-silicon vias (TSVs) for nanofluidic networks is ensuring complete formation, as incomplete or malformed TSVs can cause device malfunction, and existing methods like DRIE make optical inspection impossible due to silicon transparency and constraints on accessing the etched side.
Innovation Solution
A microfluidic channel with a pattern of material on a silicon substrate that is optically distinguishable, allowing for non-destructive optical inspection of via formation by comparing images of the substrate surface to reference images, indicating whether the via is fully or partially formed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DRIE is used to etch TSVs from the backside of the silicon wafer, then the nanofluidic network can be sealed under a glass cover, but optical inspection of via formation becomes impossible due to silicon transparency
Solution Approach 1:
A transparent capping layer is introduced as an intermediary element between the silicon substrate and the external environment. This layer allows optical signals to pass through while maintaining the sealing integrity of the nanofluidic network, enabling both reliable sealing and optical inspection of via formation.
Solution Approach 2:
The patent utilizes optical contrast changes during the etching process. As the etch progresses and removes material, the optical properties of the substrate change, allowing detection of via formation status through optical microscopy despite silicon's inherent transparency.
2Adaptability or versatility
If the nanofluidic network is sealed under a glass cover, then device integration is improved, but access to the front-end of TSVs for inspection becomes impossible
Solution Approach 1:
The transparent capping layer serves as a mediator that allows optical access through the sealed structure. It maintains the integrated sealed configuration while enabling non-destructive optical inspection of via formation without requiring physical access to the front-end of the TSVs.
Solution Approach 2:
The patent replaces mechanical access methods (such as probe card contact or physical opening of the seal) with optical inspection methods. This substitution allows inspection through the sealed structure without compromising the mechanical integrity or sealing of the integrated device.
3Measurement precision
If scanning probes or invasive methods are used to probe TSV formation, then via formation can be detected, but the cost increases and the sealing may be compromised
Solution Approach 1:
The patent replaces complex mechanical scanning probe systems with simple optical microscopy. This substitution reduces device complexity and cost while maintaining the ability to detect via formation, and avoids the need to compromise the sealing structure for access.
Solution Approach 2:
The transparent capping layer enables the sealed structure to serve its own inspection function. The sealing structure itself becomes transparent to optical inspection, eliminating the need for separate invasive probing systems and allowing self-verification of via formation through the existing sealed configuration.
Data Source
AI summary
Techniques regarding one or more structures for checking the via formation are provided. For example, one or more embodiments described herein can comprise an apparatus, which can comprise a microfluidic channel positioned on a silicon substrate. The apparatus can also comprise a pattern of material comprised within the microfluidic channel and positioned on a surface of the silicon substrate. Further, the pattern of material can define a future location of a through-silicon via. An advantage of such an apparatus can be that the pattern of material can facilitate checking whether the through-silicon via is fully or partially formed.