Shared-Microlens APD Pixel Layout for Low-Jitter Phase Detection
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Solution Overview
Problem
Existing photoelectric conversion devices with avalanche photodiodes (APDs) face challenges in phase difference detection, particularly when pixel shapes are not square, as they struggle to appropriately arrange APDs to guide electric charges to the avalanche multiplication region efficiently, leading to sensitivity degradation and timing jitter.
Innovation Solution
The device incorporates a microlens shared by multiple APDs with varying semiconductor region lengths, where the first semiconductor region extends in the long side direction and cathode electrodes are arranged more in the long side direction, allowing for improved electric field formation and charge guidance to the avalanche multiplication region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a microlens is shared by multiple APDs in a non-square pixel arrangement, then the device complexity is reduced, but the sensitivity degrades due to inefficient charge guidance
Solution Approach 1:
The patent applies asymmetry by configuring the first semiconductor region with different lengths in the first and second directions (L1 ≠ L2), and arranging cathode electrodes asymmetrically with different numbers in each direction. This asymmetric design enables efficient charge guidance to the avalanche multiplication region while maintaining the shared microlens structure, resolving the contradiction between device simplicity and detection sensitivity.
2Manufacturing precision
If the first semiconductor region has equal lengths in both directions, then the manufacturing precision is simplified, but the timing jitter increases due to poor charge guidance
Solution Approach 1:
The patent introduces asymmetry in the first semiconductor region dimensions (different lengths L1 and L2 in orthogonal directions) and asymmetric cathode electrode arrangement. This asymmetric configuration optimizes the electric field distribution to guide charges efficiently to the avalanche multiplication region, reducing timing jitter while maintaining manufacturability through clear dimensional specifications.
3Stability of the object's composition
If cathode electrodes are arranged equally in all directions, then the structural homogeneity is maintained, but the detection precision decreases at edge portions of rectangular APDs
Solution Approach 1:
The patent implements asymmetric cathode electrode arrangement with different numbers of electrodes in the first and second directions, specifically optimized for rectangular APD geometries. This asymmetric configuration creates appropriate electric field distribution that effectively guides charges from all regions including edge portions to the avalanche multiplication region, improving detection precision while maintaining structural stability.
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 detection sensitivity and reduces timing jitter by effectively guiding electric charges to the avalanche multiplication region, even at the edge portions of rectangular APDs, thereby improving the overall performance of the photoelectric conversion device.
Implementation Method 1
a photoelectric conversion device that includes an avalanche photodiode
Implementation Method 2
avalanche photodiode (hereinafter, 'APD')
Data Source
AI summary
A device includes a plurality of photodiodes each including a first region of a first conductivity type and a second region of a second conductivity type, a microlens provided to be shared by at least a first photodiode and a second photodiode of the plurality of photodiodes, and a first contact configured to supply a first voltage to the first region, wherein a length in a first direction of the first region of the first photodiode is different from a length in a second direction of the first region of the first photodiode orthogonal to the first direction.