Silicon Near-Infrared Sensor Using Trench Photodiode Array

Yutaka Arima

doi:10.1109/access.2021.3065251

Yutaka Arima

Open Access

https://doi.org/10.1109/access.2021.3065251

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Abstract

In this paper, we report a method of increasing the sensitivity of a silicon near-infrared sensor. The sensor is realized by forming multiple trench-type photodiodes in a silicon chip. The trench photodiodes can be formed using conventional semiconductor fabrication equipment. The device structure allows the depletion layer to be spread over the entire sensor chip even at a bias voltage of 10 V or less. The sensor chip can thereby extend the collection area of photoelectrons to the maximum. At a chip thickness of 540 μm, the conversion efficiency for near-infrared wavelengths between 940 and 1020 nm is more than 80% at room temperature. In addition, the electrical characteristics and response performance of the fabricated 2.4 mm ×2.4 mm test chips are reported. Since the proposed method can achieve a high conversion efficiency at low voltage without cooling in silicon semiconductors, it is expected to provide a low-cost and compact solution for various near-infrared receiver devices such as these for Internet of Things (IoT) applications.

Highlights

There are various objects and information scattered throughout in our living environment
We propose a near-infrared sensor optimized for 1 μm wavelength using a silicon semiconductor with excellent temperature characteristics and low manufacturing cost to solve the problem
When electrodes are placed on the front and back of a sensor chip made from the wafer, a high voltage of more than 1.000 V is required to form a 400 μm depletion layer

Summary

INTRODUCTION

There are various objects and information scattered throughout in our living environment. The response performance of the sensor must be able to communicate with traffic lights, road signs, and other vehicles at a distance of several hundred meters and at a data rate of about 10 Mbps, which is capable of communicating 100 kbit data in 10 ms (moving 28 cm at 100 km/h) Given these limitations, we propose a near-infrared sensor optimized for 1 μm wavelength using a silicon semiconductor with excellent temperature characteristics and low manufacturing cost to solve the problem. A method of increasing the light absorption rate by doubling the optical path length in silicon through reflection, scattering, or diffraction mechanisms on the silicon surface has been reported [17][18][19] Even with these structures, a depletion layer thickness of about 250 μm is necessary to absorb 95% of 1 μm near-infrared light. This work reveals that by optimizing its trench photodiode array structure for near-infrared wavelengths of 1 μm, a depletion layer as thick as the chip (about 500 μm) with a low bias voltage of less than 10 V is formed and a high optical absorption rate even for 1 μm near-infrared light is achieved

OPTICAL SENSOR WITH TRENCH PHOTODIODE ARRAY STRUCTURE

ELECTRICAL CHARACTERISTICS

RESPONSE PERFORMANCE

Findings

DISCUSSION

CONCLUSION