Backside Illuminated Sensor Carrier Substrate Redistribution Layer
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Solution Overview
Problem
Conventional front side illuminated semiconductor imaging sensors face challenges in efficiently routing electrical connections and providing structural support, leading to complexities in manufacturing and packaging, especially when transitioning from chip scale to board scale connections.
Innovation Solution
A backside illuminated imaging sensor design incorporating a carrier substrate with a re-distribution layer that routes electrical signals between the imaging array and the bonding surface, providing structural support and maximizing chip surface area by distributing connections effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If electrical contacts are routed out through the side of the wafer in front side illuminated devices, then electrical connections can be established, but the manufacturing process becomes complex and requires additional processing steps including ground down, cut through, and forming metal connections on sidewall
Solution Approach 1:
The patent inverts the conventional approach by making the carrier substrate transparent to light and forming the imaging array on the opposite surface. This allows light to enter through the carrier substrate while electrical contacts are formed on the same surface, eliminating the need for complex sidewall routing operations such as ground down, cut through, and metal connection formation on sidewalls.
Solution Approach 2:
The carrier substrate serves multiple functions: it provides structural support during manufacturing, acts as a light-transparent window for light entry, and serves as the surface for forming electrical contacts and bonding pads. This multi-functionality eliminates the need for separate structures for each function, simplifying the overall manufacturing process.
2Illumination intensity
If the carrier substrate is made transparent to light, then light can be received at the imaging array from the carrier substrate side, but additional processing steps are required to form the transparent carrier substrate
Solution Approach 1:
The patent extracts the light-blocking properties from the carrier substrate by selecting materials or applying treatments that make the substrate transparent to the wavelengths of light used in imaging. This allows the carrier substrate to function as both a structural support and a light-transmissive window, eliminating the need for separate light-transmissive components.
3Ease of operation
If connections are distributed along the back side of the sensor, then electrical contacts can be accessed, but the chip surface area is reduced and packaging efficiency decreases
Solution Approach 1:
The patent moves electrical contacts from the back side (one dimension) to the front surface (another dimension) where the imaging array is formed. This allows electrical contacts to be distributed across the surface without occupying back side area, maximizing chip surface area while maintaining electrical contact accessibility.
Data Source
Figure 1A~1C
Figure 1D~1E
Figure 2A
AI summary
A backside illuminated imaging sensor includes a semiconductor substrate having a front surface and a back surface. The semiconductor substrate has at least one imaging array formed on the front surface. The imaging sensor also includes a carrier substrate to provide structural support to the semiconductor substrate, where the carrier substrate has a first surface coupled to the front surface of the semiconductor substrate. A re-distribution layer is formed between the front surface of the semiconductor substrate and the second surface of the carrier substrate to route electrical signals between the imaging array and a second surface of the carrier substrate.