Stacked Imaging Unit Bonding Structure for Warpage Control
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Solution Overview
Problem
Existing imaging units face challenges in achieving high dimensional precision and efficient manufacturing due to warpage and distortion, which affect their imaging performance.
Innovation Solution
The proposed solution involves a two-layer structure imaging unit with a sensor board and a circuit board bonded through an inorganic insulating material, where the circuit board is covered by an organic insulating layer, and the sensor board is covered by an inorganic insulating layer, allowing for precise bonding and improved flatness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a WoW stacking technique is used to reduce the size of the imaging unit, then the size is reduced, but warpage and distortion occur affecting dimensional precision
Solution Approach 1:
The imaging unit is divided into separate wafer components (imaging device wafer, memory circuit wafer, signal processing circuit wafer) that are manufactured independently and then stacked through bonding. This segmentation allows each wafer to be optimized separately while maintaining overall dimensional precision through controlled bonding interfaces.
Solution Approach 2:
Multiple different wafer materials are combined in a stacked configuration, with each wafer layer serving specific functions. The composite structure integrates imaging devices, memory circuits, and signal processing circuits across different material platforms, achieving size reduction while maintaining precision through careful material selection and bonding control.
2Adaptability or versatility
If wafer stacking is performed to improve integration, then functionality is enhanced, but warpage and distortion increase
Solution Approach 1:
Different regions of the stacked wafer structure are designed with different properties - bonding interfaces are optimized for strong adhesion, while active regions maintain their specific functional characteristics. The bonding films are strategically placed at specific locations to provide structural support where needed while preserving functionality in active regions.
Solution Approach 2:
Bonding films are introduced as intermediary layers between different wafer components to facilitate stable bonding. These bonding films act as mediators that accommodate thermal expansion differences and mechanical property mismatches between adjacent wafers, thereby maintaining structural stability while enabling high-level integration.
3Ease of manufacture
If conventional bonding methods are used, then manufacturing is simpler, but dimensional precision and flatness are compromised
Solution Approach 1:
Bonding films are formed on wafer surfaces before the actual stacking and bonding process. This preliminary action prepares the surfaces with controlled properties (thickness, material composition, surface roughness) that facilitate precise alignment and bonding, thereby achieving high dimensional precision while maintaining manufacturing efficiency through standardized pre-treatment processes.
Data Source
AI summary
Provided is an imaging unit more efficiently manufacturable with high dimensional precision. The imaging unit includes: a sensor board including an imaging device, in which the imaging device has a plurality of pixels and allows generation of a pixel signal by receiving outside light in each of the plurality of pixels; a bonding layer including an inorganic insulating material; and a circuit board including a circuit chip and an organic insulating layer, in which a circuit chip has a signal processing circuit that performs signal processing for the pixel signal and is bonded to the sensor board through the bonding layer, and the organic insulating layer covers a vicinity of the circuit chip.