Light Receiving Element Reflection Film for Pixel Light Confinement
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Solution Overview
Problem
In distance measurement systems using an indirect time of flight (ToF) scheme, near-infrared light with a wavelength of approximately 940 nm experiences low absorption and quantum efficiency in silicon semiconductor layers, leading to leakage of incident light to adjacent pixels.
Innovation Solution
A light receiving element with a semiconductor layer between an on-chip lens and a wiring layer, incorporating a photodiode and a transfer transistor, where the wiring layer includes a reflection film that overlaps the photodiode and is made of a material different from metal wiring connected to the transfer transistor's gate, along with an inter-pixel light shielding unit to prevent light leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical path length is extended to increase quantum efficiency, then light absorption is improved, but light leakage to adjacent pixels increases
Solution Approach 1:
The patent introduces inter-pixel light shielding units that divide and isolate the optical paths of adjacent pixels. These shielding structures segment the light reception zones, preventing light from one pixel from leaking into neighboring pixels while maintaining the extended optical path length needed for high quantum efficiency in the near-infrared range.
Solution Approach 2:
The patent implements localized light shielding structures positioned between adjacent pixels. These shielding units are strategically placed only where needed to block light leakage, while leaving the optical path within each pixel intact. This local quality approach allows each pixel to maintain its extended optical path for high quantum efficiency while preventing cross-pixel interference.
2Reliability
If a reflection film is added to extend optical path, then quantum efficiency is improved, but device complexity increases
Solution Approach 1:
The patent combines the reflection film function with the inter-pixel light shielding units into a single integrated structure. The reflection film is formed on the same layer as or integrated with the light shielding units, allowing both functions (extending optical path and preventing light leakage) to be achieved with minimal additional structural complexity.
Solution Approach 2:
The inter-pixel light shielding units serve multiple functions simultaneously: they block light leakage to adjacent pixels, provide structural support, and work in conjunction with the reflection film to extend the optical path. This multi-functionality reduces the need for separate components and minimizes overall device complexity.
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
Enhances quantum efficiency and sensitivity by reflecting and confining light within its own pixel, reducing erroneous detection in adjacent pixels and improving the accuracy of distance measurements.
Implementation Method 1
the wiring layer includes a reflection film which is disposed such that at least a portion thereof overlaps the photodiode when seen in a plan view
Implementation Method 2
a semiconductor layer which is disposed between the on-chip lens and the wiring layer and includes a photodiode
Data Source
AI summary
The present technology relates to a light receiving element, a distance measurement module, and electronic equipment which are capable of reducing leakage of incident light to adjacent pixels. The light receiving element includes an on-chip lens, a wiring layer, and a semiconductor layer which is disposed between the on-chip lens and the wiring layer and includes a photodiode. The wiring layer includes a reflection film which is disposed such that at least a portion thereof overlaps the photodiode when seen in a plan view, and a transfer transistor which reads charge generated by the photodiode, and the reflection film is formed of a material different from that of a metal wiring electrically connected to a gate of the transfer transistor. The present technology can be applied to, for example, a distance measurement module that measures a distance to a subject, and the like.