BSI Image Sensor Stacking With Backside Auxiliary Chip Integration
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Solution Overview
Problem
Conventional image sensors face challenges in achieving optimal image quality due to light being obstructed by circuitry and structural elements on the substrate, and integrating auxiliary chips with different sizes and high-speed processing requirements is inefficient and costly.
Innovation Solution
Positioning an auxiliary circuit chip on the backside illuminated (BSI) surface of the image sensor chip, adjacent to the color filter array and microlens array, and connecting it through the image sensor chip to the primary circuit chip, allowing for efficient customization and low-latency communication while minimizing wasted surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If light is incident on the frontside of the sensor through circuitry and dielectric layers, then the substrate structure is simple, but image quality is deteriorated due to light obstruction
Solution Approach 1:
The patent inverts the conventional illumination direction by implementing backside illumination (BSI) architecture. Light is incident on the backside of the substrate rather than the frontside, allowing light to reach the pixel array without traversing through circuitry, dielectric layers, and metal interconnects that would otherwise obstruct and degrade the light signal.
2Manufacturing precision
If the backside substrate is made thin to enable backside illumination, then image quality is improved, but substrate strength is reduced
Solution Approach 1:
The patent employs a composite substrate structure combining a thin BSI image sensor chip with a separate support substrate. The thin image sensor chip (first substrate) provides optimal light transmission for high-quality imaging, while the support substrate (second substrate) mechanically reinforces the assembly, compensating for the reduced strength of the thinned first substrate.
3Reliability
If auxiliary chips are integrated on the frontside with primary circuit chip, then connectivity is achieved, but surface area is wasted and customization is inefficient
Solution Approach 1:
The patent transitions from traditional frontside integration to backside integration by positioning auxiliary circuit chips on the backside of the support substrate, opposite to the frontside where the primary circuit chip resides. This spatial reconfiguration enables auxiliary chips to connect through the substrate without competing for frontside surface area, improving both area utilization and customization flexibility.
4Reliability
If multiple chips are stacked with frontside illumination, then connectivity is achieved, but light transmission is obstructed by interconnect structures
Solution Approach 1:
The patent inverts the illumination path by implementing backside illumination architecture. Light enters through the backside of the thin first substrate, traveling directly to the pixel array without intersecting metal interconnects, dielectric layers, or circuitry that would be present in frontside illumination designs, thereby maximizing light transmission intensity.
Data Source
AI summary
A semiconductor device may include a primary circuit chip and an image sensor chip stacked thereon. The image sensor chip may have a backside illuminated (BSI) surface and a frontside surface opposed to the BSI surface, with the image sensor chip being disposed on the primary circuit chip with the frontside surface facing the primary circuit chip. An auxiliary chip may be disposed on the BSI surface of the image sensor chip and connected to the primary circuit chip through the image sensor chip.