Nanowell Sensor Structure With Buried Bond Pads for Larger Flow Channels
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Solution Overview
Problem
In sensor systems, such as biosensor systems, the need to increase data throughput requires reducing nanowell sizes and increasing their numbers, while maintaining compatibility with electronic components like bond pads, which are often damaged or corroded by fluid flow and surface functionalization processes.
Innovation Solution
The bond pads are positioned under a passivation stack, allowing the flow channel to be enlarged over them, and protected from fluid exposure, enabling a larger number of nanowells within a fixed footprint by using a through-silicon via (TSV) and redistribution layer (RDL) for electrical connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bond pads are exposed on the surface for electrical connectivity, then electrical connection is achieved, but bond pads are damaged or corroded by fluid flow and surface functionalization processes
Solution Approach 1:
The bond pads are nested within the passivation stack structure, specifically positioned in the device stack beneath the passivation layers. This nesting approach protects the bond pads from fluid flow and surface functionalization processes while maintaining electrical connectivity through the stacked configuration of passivation layers and bonding interfaces.
Solution Approach 2:
The passivation stack acts as an intermediary barrier between the bond pads and the external environment (fluid flow and surface functionalization processes). This intermediary structure protects the bond pads while allowing electrical connection to be established through controlled interfaces within the stack.
2Productivity
If flow channel area is restricted by bond pad placement, then bond pad accessibility is maintained, but the number of nanowells that can be accommodated is reduced
Solution Approach 1:
The solution transitions from a planar arrangement where bond pads occupy surface area to a three-dimensional stacked configuration. By positioning bond pads within the device stack beneath passivation layers, the flow channel area in the horizontal plane is expanded while electrical connectivity is maintained through vertical interfaces, enabling more nanowells to be accommodated.
Solution Approach 2:
The device is segmented into distinct functional stacks: the device stack containing bond pads, the passivation stack providing protection, and the flow channel structure. This segmentation allows the bond pads to be isolated in a protected region while the flow channel occupies the maximum available area above them, increasing nanowell capacity.
3Productivity
If nanowell size is reduced to increase data throughput, then more nanowells can be accommodated, but compatibility with electronic components and surface chemistry becomes increasingly critical
Solution Approach 1:
The bond pads are extracted from the surface plane and relocated to the device stack beneath the passivation layers. This extraction removes the bond pads from the critical surface chemistry environment, allowing surface functionalization processes and fluid flow to proceed without damaging electronic components, while enabling higher nanowell density.
Data Source
AI summary
A system includes an image sensor structure and a flow cell. The image sensor structure includes an image layer disposed over a base substrate. A device stack is disposed over the image layer. A bond pad is disposed in the device stack. A passivation stack is disposed over the device stack and the bond pad. An array of nanowells is disposed in a top layer of the passivation stack. A through-silicon via (TSV) is in electrical contact with the bond pad. The TSV extends through the base substrate. A redistribution layer (RDL) is disposed on a bottom surface of the base substrate. The RDL is in electrical contact with the TSV. The flow cell is disposed upon the top layer of the passivation stack to form a flow channel therebetween. The flow channel is disposed over the array of nanowells and the bond pad.