Overview of ionizing radiation effects in image sensors fabricated in a deep-submicrometer CMOS imaging technology

An overview of ionizing radiation effects in imagers manufactured in a 0.18-μm CMOS image sensor technology is presented. Fourteen types of image sensors are characterized and irradiated by a 60Co source up to 5 kGy. The differences between these 14 designs allow us to separately estimate the effect of ionizing radiation on microlenses, on low- and zero-threshold-voltage MOSFETs and on several pixel layouts using P+ guard-rings and edgeless transistors. After irradiation, wavelength dependent responsivity drops are observed. All the sensors exhibit a large dark current increase attributed to the shallow trench isolation that surrounds the photodiodes. Saturation voltage rises and readout chain gain variations are also reported. Finally, the radiation hardening perspectives resulting from this paper are discussed

Analysis of total dose-induced dark current in CMOS image sensors from interface state and trapped charge density measurements

The origin of total ionizing dose induced dark current in CMOS image sensors is investigated by comparing dark current measurements to interface state density and trapped charge density measurements. Two types of photodiode and several thick-oxide-FETs were manufactured using a 0.18-µm CMOS image sensor process and exposed to 10-keV X-ray from 3 krad to 1 Mrad. It is shown that the radiation induced trapped charge extends the space charge region at the oxide interface, leading to an enhancement of interface state SRH generation current. Isochronal annealing tests show that STI interface states anneal out at temperature lower than 100°C whereas about a third of the trapped charge remains after 30 min at 300°C

Generic radiation hardened photodiode layouts for deep submicron CMOS image sensor processes

Selected radiation hardened photodiode layouts, manufactured in a deep submicron CMOS Image Sensor technology, are irradiated by 60Co gamma-rays up to 2.2 Mrad(SiO2) and studied in order to identify the most efficient structures and the guidelines (recess distance, bias voltage) to follow to make them work efficiently in such technology. To do so, both photodiode arrays and active pixel sensors are used. After 2.2 Mrad(SiO2), the studied sensors are fully functional and most of the radiation hardened photodiodes exhibit radiation induced dark current values more than one order of magnitude lower than the standard photodiode

Optoelectrical performance evolution of CMOS image sensors exposed to gamma radiation

In this paper we present a study of ionizing radiation effects, up to 5 kGy, in several CMOS image sensors manufactured using a commercial 0.18 μm technology dedicated to imaging

High performances monolithic CMOS detectors for space applications

During the last 10 years, research about CMOS image sensors (also called APS -Active Pixel Sensors) has been intensively carried out, in order to offer an alternative to CCDs as image sensors. This is particularly the case for space applications as CMOS image sensors feature characteristics which are obviously of interest for flight hardware: parallel or semi-parallel architecture, on chip control and processing electronics, low power dissipation, high level ofradiation tolerance... Many image sensor companies, institutes and laboratories have demonstrated the compatibility of CMOS image sensors with consumer applications: micro-cameras, video-conferencing, digital-still cameras. And recent designs have shown that APS is getting closer to the CCD in terms ofperformance level. However, the large majority ofthe existing products do not offer the specific features which are required for many space applications. ASTRI1JM and SUPAERO/CIMI have decided to work together in view of developing CMOS image sensors dedicated to space business. After a brief presentation of the team organisation for space image sensor design and production, the latest results of a high performances 512x512 pixels CMOS device characterisation are presented with emphasis on the achieved electro-optical performance. Finally, the on going and short-term coming activities of the team are discussed

Smart-Pixel Cellular Neural Networks in Analog Current-Mode CMOS Technology

This paper presents a systematic approach to design CMOS chips with concurrent picture acquisition and processing capabilities. These chips consist of regular arrangements of elementary units, called smart pixels. Light detection is made with vertical CMOS-BJT’s connected in a Darlington structure. Pixel smartness is achieved by exploiting the Cellular Neural Network paradigm [1], [2], incorporating at each pixel location an analog computing cell which interacts with those of nearby pixels. We propose a current-mode implementation technique and give measurements from two 16 x 16 prototypes in a single-poly double-metal CMOS n-well 1.6-µm technology. In addition to the sensory and processing circuitry, both chips incorporate light-adaptation circuitry for automatic contrast adjustment. They obtain smart-pixel densities up to 89 units/mm2, with a power consumption down to 105 µW/unit and image processing times below 2 µs

Radiation damages in CMOS image sensors: testing and hardening challenges brought by deep sub-micrometer CIS processes

This paper presents a summary of the main results we observed after several years of study on irradiated custom imagers manufactured using 0,18 µm CMOS processes dedicated to imaging. These results are compared to irradiated commercial sensor test results provided by the Jet Propulsion Laboratory to enlighten the differences between standard and pinned photodiode behaviors. Several types of energetic particles have been used (gamma rays, X-rays, protons and neutrons) to irradiate the studied devices. Both total ionizing dose (TID) and displacement damage effects are reported. The most sensitive parameter is still the dark current but some quantum eficiency and MOSFET characteristics changes were also observed at higher dose than those of interest for space applications. In all these degradations, the trench isolations play an important role. The consequences on radiation testing for space applications and radiation-hardening-by-design techniques are also discussed

Space optical instruments optimisation thanks to CMOS image sensor technology

Today, both CCD and CMOS sensors can be envisaged for nearly all visible sensors and instruments designed for space needs. Indeed, detectors built with both technologies allow excellent electro-optics performances to be reached, the selection of the most adequate device being driven by their functional and technological features and limits. The first part of the paper presents electro-optics characterisation results of CMOS Image Sensors (CIS) built with an optimised CMOS process, demonstrating the large improvements of CIS electro-optics performances. The second part reviews the advantages of CMOS technology for space applications, illustrated by examples of CIS developments performed by EADS Astrium and Supaéro/CIMI for current and short term coming space programs