Stacked Image Sensor Substrate Segmentation for Chip Size Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional image sensors with counting units for each pixel result in increased chip size due to the need for peripheral circuits, leading to higher costs and reduced efficiency in photon detection.
Innovation Solution
The image sensor design involves stacking two circuit boards, with one board containing a pixel region and the other containing counter and peripheral circuits, where the pixel region includes both light-shielded and unshielded pixels, and the counter region includes counters for each type of pixel, with the peripheral circuits overlapping with the pixel region to minimize chip size and optimize photon counting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a counting unit is provided for each pixel, then photon detection capability is improved, but chip size increases due to peripheral circuits
Solution Approach 1:
The image sensor is divided into two separate substrates: a first substrate containing only the light receiving elements (pixels), and a second substrate containing the counting units and peripheral circuits. This segmentation allows each substrate to be optimized independently, enabling photon counting functionality while reducing the overall chip size by eliminating the need for peripheral circuits on the same substrate as the pixels.
Solution Approach 2:
The patent transitions from a planar single-substrate layout to a three-dimensional stacked configuration. By stacking the first substrate (pixels) and second substrate (counting units and peripheral circuits) vertically, the design utilizes the third dimension (depth) to accommodate all necessary components, thereby reducing the horizontal footprint and overall chip size while maintaining full functionality.
2Device complexity
If peripheral circuits are integrated on the same substrate as pixels, then device complexity is reduced, but chip size increases
Solution Approach 1:
The device is segmented into two functional substrates: the first substrate dedicated to light receiving elements and the second substrate dedicated to counting units and peripheral circuits. This segmentation maintains functional integration (all components work together as a unified system) while physically separating the circuits from the pixels, thereby reducing chip size without compromising device functionality.
Solution Approach 2:
The patent introduces an intermediary connection structure (such as through-substrate conductors or bonding interfaces) that links the first substrate and second substrate. This intermediary enables seamless communication and signal transmission between the pixels on the first substrate and the counting units/peripheral circuits on the second substrate, maintaining system integration despite the physical separation.
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 design effectively suppresses the increase in chip size, allowing for efficient photon detection and correction of dark current influences, thereby enhancing the image sensor's performance and reducing costs.
Implementation Method 1
each pixel having a photoelectric conversion unit and a circuit that outputs a pulse signal indicative of incidence of photon in response to incidence of light on the photoelectric conversion unit
Implementation Method 2
When a single photon is incident on an APD to which a reverse bias voltage higher than the breakdown voltage is applied, carriers are generated, avalanche multiplication occurs, and a large current is generated
Data Source
AI summary
An image sensor comprises a first circuit board and a second circuit board stacked so as to overlap each other. The first circuit board comprises a pixel region in which first pixels shielded from light and second pixels not shielded from light are arranged in a matrix. Each pixel has a photoelectric conversion unit and a circuit that outputs a pulse signal indicative of incidence of photon. The second circuit board comprises a counter region in which first counters that counts pulse signals from the first pixels and second counters that count pulse signals from the second pixels are arranged in a matrix, and a peripheral circuit region including a circuit that controls driving of the pixels and counters. At least part of the peripheral circuit region is arranged in a region that overlaps with the first pixels.