SPAD Sensor Chip With Light Collector for Reduced Crosstalk
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Solution Overview
Problem
Existing sensor chips with single photon avalanche diodes (SPADs) face challenges in improving Photon Detection Efficiency (PDE), particularly due to light loss and crosstalk issues when light escapes from the pixel area.
Innovation Solution
The sensor chip incorporates a diffractive lens between the SPAD and a light reflection film to collect and reflect light back towards the SPAD, enhancing light utilization and reducing crosstalk by diffusing incoming light and increasing optical path length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sensor chip structure without light collector is used, then the device complexity is low, but the photon detection efficiency is insufficient due to light loss
Solution Approach 1:
A light collector is introduced as an intermediary component between the SPAD and the light reflector. This light collector captures light that has passed through the SPAD and redirects it toward the light reflector, preventing light loss and improving photon detection efficiency without significantly complicating the overall device structure
Solution Approach 2:
The light collector utilizes the vertical dimension (depth) within the pixel structure to redirect light paths. By positioning the light collector at a specific depth between the SPAD and light reflector, it captures light in the vertical dimension and redirects it, effectively utilizing space that would otherwise be wasted
2Object-affected harmful factors
If light is allowed to pass through the photoelectric converter without collection, then the device complexity is low, but light escapes to adjacent pixels causing crosstalk
Solution Approach 1:
The light collector acts as an intermediary that intercepts light before it can escape to adjacent pixels. By capturing and redirecting light toward the light reflector, it prevents lateral light propagation that would cause crosstalk between neighboring pixels
Solution Approach 2:
The light collector extracts light from the general propagation path and redirects it specifically toward the light reflector. This extraction prevents light from following unintended paths that would lead to adjacent pixels, thereby eliminating the harmful effect of crosstalk
3Reliability
If the optical path length is increased to improve light utilization, then the photon detection efficiency improves, but the device complexity increases
Solution Approach 1:
Instead of increasing the horizontal optical path length, the light collector utilizes the vertical dimension to extend the light path. By redirecting light downward toward the light reflector and back up through the SPAD, it effectively increases the optical path length within the available vertical space of the pixel structure
Solution Approach 2:
The light collector ensures continuous useful action by capturing light that would otherwise be lost and redirecting it back through the SPAD. This creates a continuous light path that maximizes the utilization of photons, improving detection efficiency without requiring additional complex components
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
The design improves Photon Detection Efficiency (PDE) by increasing the amount of light reflected back to the SPAD, thereby enhancing detection capabilities and reducing light escape to adjacent pixels, thus suppressing crosstalk.
Implementation Method 1
The light collector is provided between the photoelectric converter and the light reflector... collects the light passing through the photoelectric converter toward the light reflector
Implementation Method 2
carriers (electrons) generated by a photoelectric effect are accelerated by an electric field and cause impact ionization
Implementation Method 3
avalanche multiplication (avalanche breakdown) which involves a repetitive process in which carriers (electrons) generated by a photoelectric effect are accelerated by an electric field and cause impact ionization
Data Source
AI summary
A sensor chip according to an embodiment of the present disclosure includes a pixel. The pixel includes a photoelectric converter, a light reflector, and a light collector. The photoelectric converter includes a light entering surface which light enters and a multiplication region in which avalanche multiplication of carriers is caused by a high electric-field region. The light reflector is provided to oppose a surface, of the photoelectric converter, on an opposite side to the light entering surface. The light collector is provided between the photoelectric converter and the light reflector.