College of Science & Engineering

Novel CMOS Sensors for Near Infra-Red Imaging and Spectroscopy

Supervisor: Dr Dima Maneuski

School: Physics and Astronomy

Industry Partner: Image Sensor Design & Innovation Ltd

Description:

Near Infrared (NIR) imaging and spectroscopy can be used in many biomedical applications thanks to the ability of infrared radiation to penetrate skin and tissues. For example, Raman Spectroscopy (RS) as one of the key spectroscopic techniques employs NIR in addition to visible light. RS has many uses across biomedical fields including applications in the in vivo measurement of blood glucose level. This is due to sensitivity of molecules of glucose in blood to NIR radiation. New research is also studying the use of RS for the in vivo imaging of tissues and solid tumours for clinical diagnosis. However, due to the low absorption rate of NIR radiation in silicon, conventional CMOS image sensor technology must be adapted to have sufficient Quantum Efficiency (QE) for NIR radiation.

ISDI is an established UK-based leader in developing CMOS image sensor technology for applications in X-ray radiography. The company recently developed a prototype Selene-based image sensor for visible and NIR spectroscopy applications. This small area sensor (128 rows x 1024 columns) employs a large pixel pitch design (14 μm x 14 μm) and an increased epitaxial layer thickness of 40 μm, allowing the Selene image sensor to detect radiation in the NIR range with high QE (62% or 73% when measured with the addition of micro-lenses) while maintaining low leakage current.

In this project we aim for the first time to characterise this prototype sensor by combining applicant’s extensive expertise in sensor characterisation with ISDI’s in-depth knowledge of the CMOS sensor fabrication technology. The researcher has 15 years of experience in characterisation of various types of sensors for a wide range of applications. Particle Physics Experimental group laboratories has unique suite of characterisation instruments and data analysis techniques perfectly aligned with the effective means of characterisation of this prototype sensor. In addition to this, ISDI will also purchase and loan the group a high-performance monochromator which extends beyond the wavelength range currently available in PPE laboratories for a comprehensive QE characterisation of the sensor.

The intern will perform measurements using a monochromator to explore the spectral responses of different variants of ISDI’s newly developed NIR image sensor. This includes variants having different resistivity and epitaxial layer thickness, and with micro-lenses. These measurements will cover the relative quantum efficiency and MTF at different wavelengths, enabling ISDI to determine to optimum combination of chip parameters for operation in the 840 nm – 960 nm spectrum.