BSI Image Sensor Bond Pad Vertical Connection Structure
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Solution Overview
Problem
Conventional bond pads in CMOS image sensor packaging are prone to peeling due to insufficient strength, which affects the reliability of electrical contacts during the bonding process.
Innovation Solution
A method and apparatus for forming a bond pad in a backside illuminated (BSI) image sensor device, where a buffer layer is formed above the substrate with openings reaching the first metal layer, and a pad metal layer is deposited to connect the bond pad vertically to the first metal layer, enhancing support and bondability without requiring additional processes or masks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If bond pads are formed through the backside on the inter-layer dielectric layer and metal layers, then the packaging process can be simplified, but the bond pad strength becomes insufficient causing peeling during or after bonding
Solution Approach 1:
The patent transitions from forming bond pads only on the backside surface to creating a three-dimensional structure that extends vertically through openings in the inter-layer dielectric layer to reach the metal layers. This vertical dimension provides additional support area and structural reinforcement, preventing peeling while maintaining process simplicity.
Solution Approach 2:
The bond pad structure combines multiple materials including the inter-layer dielectric layer, metal layers, and bond pad material formed in openings. This composite structure leverages the mechanical support of the dielectric and the electrical conductivity of the metal layers to create a bond pad assembly with both strength and functionality.
2Device complexity
If conventional bond pads are formed on the backside, then the structure remains simple, but the bondability and support are insufficient for reliable electrical contacts
Solution Approach 1:
The patent performs preliminary actions by forming openings in the inter-layer dielectric layer and depositing metal layers before final bond pad formation. This preparatory structuring ensures that when bond pads are formed, they have immediate structural support and electrical connection pathways, enhancing reliability without significantly increasing overall complexity.
Solution Approach 2:
The bond pad structure embeds the bond pad material within openings of the inter-layer dielectric layer, with metal layers nested at the bottom of these openings. This nested configuration provides both mechanical support and electrical connectivity, improving reliability while maintaining a compact design.
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
The solution provides improved bond pad support and bondability, reducing the likelihood of peeling and ensuring stable electrical connections, thus enhancing the reliability of the packaging process.
Implementation Method 1
a pad metal layer is deposited to connect the bond pad vertically to the first metal layer
Data Source
AI summary
Methods and apparatus for forming a bond pad of a semiconductor device such as a backside illuminated (BSI) image sensor device are disclosed. The substrate of a device may have an opening at the backside, through the substrate reaching the first metal layer at the front side of the device. A buffer layer may be formed above the backside of the substrate and covering sidewalls of the substrate opening. A pad metal layer may be formed above the buffer layer and in contact with the first metal layer at the bottom of the substrate opening. A bond pad may be formed in contact with the pad metal layer. The bond pad is connected to the pad metal layer vertically above the substrate, and further connected to the first metal layer of the device at the opening of the substrate.