Cross-Wafer Capacitor Alignment in Stacked Image Sensors
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Solution Overview
Problem
In vertically stacked image sensors, existing technologies face challenges in integrating additional electrical components and ensuring proper alignment and reducing cross-capacitance between capacitors, which can affect image quality and sensor performance.
Innovation Solution
The implementation of cross-wafer capacitors formed by conductive segments on adjacent bonding surfaces of stacked wafers, which can include multiple capacitors configured to isolate each other and reduce cross-capacitance, and a method to test wafer alignment by measuring capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional electrical components are integrated into vertically stacked image sensors, then the functionality and performance of the image sensor are enhanced, but the device complexity and difficulty of ensuring proper alignment increase
Solution Approach 1:
The patent employs self-aligned capacitor structures where conductive segments on opposite wafer surfaces automatically align during the bonding process. The capacitor formation occurs inherently through the bonding process itself, eliminating the need for separate alignment steps. This self-service approach allows additional electrical components to be integrated without proportionally increasing alignment difficulty.
Solution Approach 2:
The patent prepares conductive segments on wafer surfaces in advance before bonding, with their positions pre-determined to ensure proper alignment. By preparing the capacitor-forming structures preliminarily on each wafer separately, the alignment complexity is reduced during the final assembly process, as the components are designed to self-align rather than requiring complex alignment procedures.
2Adaptability or versatility
If multiple capacitors are configured in vertically stacked image sensors, then the electrical functionality is improved, but cross-capacitance between capacitors increases affecting image quality
Solution Approach 1:
The patent extracts or removes the harmful cross-capacitance effect by designing capacitor structures that are electrically isolated from each other. By separating the capacitor structures into distinct, non-interacting units on opposite wafer surfaces, the harmful cross-capacitance between adjacent capacitors is eliminated while maintaining the desired electrical functionality of multiple capacitors in the stacked configuration.
Solution Approach 2:
The patent applies local quality by giving each capacitor structure distinct electrical characteristics and isolation properties. Each capacitor is designed with specific local features that prevent electrical interaction with neighboring capacitors, such as localized conductive segments and insulating layers. This local differentiation allows multiple capacitors to coexist without cross-capacitance interference.
3Ease of manufacture
If conductive segments are positioned at bonding surfaces for capacitor formation, then the integration of electrical components is simplified, but the precision of capacitor formation depends heavily on wafer alignment accuracy
Solution Approach 1:
The patent employs self-aligned capacitor structures where conductive segments on opposite wafer surfaces automatically align during the bonding process. The capacitor formation occurs inherently through the bonding process itself, eliminating the need for separate alignment steps. This self-service approach allows additional electrical components to be integrated without proportionally increasing alignment difficulty.
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
This configuration enhances the integration of additional electrical components in image sensors, improves image quality by reducing cross-capacitance, and provides a reliable method for ensuring proper wafer alignment, thereby enhancing the performance of vertically stacked image sensors.
Implementation Method 1
Together the first and second conductive segments form at least one cross-wafer capacitor
Implementation Method 2
The second and fifth conductive segments can both be connected to ground. In this manner, the intermediate cross-wafer capacitor may isolate the adjacent cross-wafer capacitors and reduce or prevent cross-capacitance from developing between the adjacent cross-wafer capacitors
Data Source
AI summary
One or more cross-wafer capacitors are formed in an electronic component, circuit, or device that includes stacked wafers. One example of such a device is a stacked image sensor. The image sensor can include two or more wafers, with two wafers that are bonded to each other each including a conductive segment adjacent to, proximate, or abutting a bonding surface of the respective wafer. The conductive segments are positioned relative to each other such that each conductive element forms a plate of a capacitor. A cross-wafer capacitor is formed when the two wafers are attached to each other.