Solid-State Imaging Device Chip Stacking with Protective Film
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Solution Overview
Problem
Current solid-state imaging devices face challenges in improving quality and reliability due to issues with wafer-on-wafer technology, such as increased cost and complexity in connecting chips of different sizes, leading to reduced yield and increased power consumption, as well as contamination during thinning processes.
Innovation Solution
A solid-state imaging device is developed with a sensor substrate and signal processing chips stacked and electrically connected, where a protective film, such as silicon nitride, is formed on the side surfaces of the chips to prevent contamination and facilitate thinning, improving the connection efficiency and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wafer-on-wafer technology is used to connect chips of different sizes, then integration is achieved, but manufacturing complexity and cost increase
Solution Approach 1:
The sensor substrate is divided into an effective pixel region and a non-effective region. The non-effective region is further segmented to accommodate chips of different sizes through selective stacking, allowing each region to serve its specific function without requiring the entire wafer to be uniformly structured.
Solution Approach 2:
Different regions of the sensor substrate are assigned different functions: the effective pixel region contains imaging elements, while the non-effective region contains signal processing circuits. This local differentiation allows chips of varying sizes to be stacked in appropriate regions, optimizing both integration and manufacturing simplicity.
2Productivity
If chips are connected in wafer state, then connection efficiency improves, but power consumption increases
Solution Approach 1:
The device is segmented into distinct functional modules: imaging elements on the sensor substrate and signal processing circuits on separate chips. This modular segmentation allows for optimized signal transmission paths, reducing unnecessary power consumption while maintaining efficient connections through the stacked architecture.
3Ease of manufacture
If thinning process is performed without protective film, then processing is simpler, but contamination occurs
Solution Approach 1:
A protective film is formed on the chip surfaces before the thinning process. This preliminary protective action prevents contamination during thinning while allowing the process to proceed. The protective film is later removed from specific regions to enable proper electrical connections, thus resolving the contradiction between protection and processing simplicity.
4Reliability
If protective film is formed on chip side surfaces, then contamination is prevented, but manufacturing steps increase
Solution Approach 1:
The protective film is selectively formed on specific side surfaces of the chips rather than uniformly across all surfaces. This localized approach provides contamination prevention where needed while minimizing the number of manufacturing steps and avoiding unnecessary complexity in regions where protection is not required.
Data Source
AI summary
A solid-state imaging device that can further improve the quality and reliability of the solid-state imaging device is provided. There is provided a solid-state imaging device including: a sensor substrate having an imaging element that generates a pixel signal in a pixel unit; and at least one chip having a signal processing circuit necessary for signal processing of the pixel signal, wherein the sensor substrate and the at least one chip are electrically connected to and stacked on each other, and wherein a protective film is formed on at least a part of a side surface of the at least one chip, the side surface being connected to a surface of the at least one chip on a side on which the at least one chip is stacked on the sensor substrate.