Single-photon avalanche diodes (SPADs) are nowadays the most consolidate solid-state alternative to photomultiplier
tubes and time-correlated single-photon counting. Optical benches are used for the characterization of the noise figures
of these detectors, including dark count, afterpulsing effects and cross-talk. With accurate optical setups it is possible to
obtain resolutions down to 5 microns, but with today's technologies, this spot size can cover more than one single pixel.
Moreover, on other common and envisaged applications like particle detection in Nuclear and High Energy Physics or as
silicon photomultipliers for Cerenkov telescopes, this does not allow to observe what happens when a charge is
generated between consecutive pixels.
This work presents the innovative characterization of single-photon detectors with the aid of the electron beam generated
in a dual beam FIB/SEM apparatus. A simple setup allows a very good control of the dose and the spot down to 5 nm at
30 keV, The characterization has been proven in photodetectors fabricated in a standard CMOS technology. The results
have been validated by comparison with those obtained by optical setups, with simulation with PENELOPE (Penetration
and Energy Loss of Positrons and Electrons) and by technology simulations with ISE-tCAD.
In the last years the fabrication of SPAD cameras has become one of the main fields of interest in 3-D imaging and bioapplications.
In this paper we present the comparison between two standard CMOS technologies to fabricate SPADs
cameras. The two technologies used in the comparison are a high voltage 0.35μm technology from AMS and a high
integration 130nm technology from STM. The advantage of using a standard CMOS technology among a dedicated is
the possibility of integrating the control/reading electronics into the same die. Neither of the processes is optimized for
optical applications, and no post-processing has been applied to improve the features.
The technologies have been selected due to the different integration density, and different intrinsic process parameters
with similar cost. Comparison has been done by fabricating several structures in both technologies which allow
analyzing sensibility, noise, and time response.
Experimental results show that the high voltage technology has a lower level of dark counts than the 130nm. Instead, the
high integration technology has a shorter quenching time, 1.5ns, which reduces the afterpulsing events to a negligible
level. In optical applications it is important to have a high integration of the camera reducing the pitch of the pixel, while
noise effects can be corrected in post-processing. For low frequency events, such as high energetic particle tracking, the
noise frequency has to be lower, but it is also required a high fill factor. Depending on the specific application this
analysis allows to opt for the most suitable technology.
This paper presents a System On Chip (SoC) designed specifically to control a mm<sup>3</sup>- sized microrobot called I-SWARM. The robot is intended to be part of a colony of 1000 I-SWARM robots for studying swarm behavior in real time and in a real swarm. The SoC offers a well-suited hardware platform to run multi-agent systems software. It is composed of an 8051 microcontroller with 2 kB of data memory and 8 kB of program memory. The processor is provided with specific hardware modules for controlling the locomotion unit, the communications and the vibrating contact sensor of the robot. These modules perform basic tasks as movements or communications so the 8051 can focus on processing data and taking decisions. With these capabilities, the robot is able to avoiding collisions with other members of the swarm, performing cooperative tasks, sharing information and executing specialized tasks. The SoC has been fabricated with a 0.13 &mgr;m ultra low power CMOS process of STMicroelectronics and consumes less than 1 mW.
Nowadays Atomic Force Microscopy is one of the most extended techniques performed in biological measurements. Due to the higher flexibility in respect to conventional equipments, a novel approach in this field is the use of a microrobot equipped with an AFM tool. In this paper it is presented an integrated controller for an AFM tool assembled in a 1 cm<sup>3</sup> wireless microrobot. The AFM tool is mounted on the tip of a rotational piezoelectric actuator arm. It consists on a XYZ positioning scanner, based in 4 piezoelectric stacked actuators, and an AFM piezoresistance probe. Two types of AFM working modes are implemented in the controller, i.e., nanoidentation and AFM scanning. Correction of the mismatch of the piezoactuators composing the arm is possible. A programmable PID control is included in the controller in order to get more flexibility in terms of scanning speed and resolution. An IrDA protocol is used to program the parameters of the AFM tool controller and the positioning of the robot in the working area. Then the values of the nanoindentation or of the scanning can be read through the IrDA interface without any other external action.
Due to the strong power and area restrictions, the controller has been implemented in specific logic in a 0.35um technology. The design has been done using functional specifications with high level tools and RTL synthesis. The AFM scanner can be positioned with a resolution of 10 nm and scan areas up to 1 μm<sup>2</sup> with an expected vertical resolution of 1nm.