Isolated Bond Pad Via Interconnect for Backside Illuminated Imagers
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Solution Overview
Problem
Backside illuminated imager devices face challenges in forming electrical connections to bond pads without creating uneven topography and additional processing features on the color filter array side, which complicates subsequent processing steps and increases costs.
Innovation Solution
The method involves forming isolated bond pads by creating a via through the substrate to a buried bond pad, using dielectric material to isolate and connect the bond pad to the surface, and depositing conductive material to form an interconnect, thereby minimizing surface features and processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If portions of the substrate are removed to provide connections to electrical pads below the substrate, then electrical connections can be established, but additional features on the color filter array side and uneven topography are created
Solution Approach 1:
Instead of removing substrate material to create connections, the patent inverts the approach by depositing conductive material and dielectric layers to build connections upward from the bond pad. This creates a planar surface while establishing electrical connections through the substrate thickness direction, eliminating the need for substrate removal and associated topography issues.
Solution Approach 2:
The patent transitions from a lateral connection approach (removing substrate to expose pads) to a vertical connection approach (depositing layers through substrate thickness). By utilizing the thickness dimension for electrical connections, the surface remains planar and suitable for subsequent color filter array processing.
2Reliability
If conventional methods are used to form electrical connections to bond pads, then connections are established, but the number and size of surface features increase
Solution Approach 1:
The patent merges the electrical connection function with the bond pad structure by forming conductive interconnects that extend vertically from the bond pad through the substrate. This integration eliminates the need for separate connection features on the surface, reducing the overall footprint and number of surface features.
3Reliability
If substrate portions are removed for wire bonds, then electrical connections are provided, but processing steps and costs increase
Solution Approach 1:
The bond pad structure serves multiple functions: it provides electrical connection, mechanical support, and defines the connection location. The conductive interconnects formed through substrate deposition automatically create the necessary pathways without requiring additional processing steps for separate connection features.
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 approach reduces the number and size of surface features, minimizes processing steps, and results in a more cost-effective product with improved wire bond reliability and light block capabilities.
Implementation Method 1
depositing conductive material to form an interconnect
Data Source
AI summary
An integrated circuit for use, for example, in a backside illuminated imager device includes circuitry provided on a first side of a substrate, a first conductive pad connected to the circuitry and spaced from the first side of the substrate, a second conductive pad spaced from a second side of the substrate, an electrically conductive interconnect formed through the substrate to interconnect the first and second conductive pads, and a dielectric surrounding the second conductive pad and at least a portion of the interconnect. Methods of forming the integrated circuit are also described.