Silicon nitride (SiN) is a promising candidate material for becoming a standard high-performance solution for integrated
biophotonics applications in the visible spectrum. As a key feature, its compatibility with the complementary-oxidemetal-
semiconductor (CMOS) technology permits cost reduction at large manufacturing volumes that is particularly
advantageous for manufacturing consumables. In this work, we show that the back-end deposition of a thin SiN film
enables the large light-cladding interaction desirable for biosensing applications while the refractive index contrast of the
technology (Δn ≈ 0.5) also enables a considerable level of integration with reduced waveguide bend radii. Design and experimental validation also show that several advantages are derived from the moderate SiN/SiO2 refractive index contrast, such as lower scattering losses in interconnection waveguides and relaxed tolerances to fabrication
imperfections as compared to higher refractive index contrast material systems. As a drawback, a moderate refractive
index contrast also makes the implementation of compact grating couplers more challenging, due to the fact that only a
relatively weak scattering strength can be achieved. Thereby, the beam diffracted by the grating tends to be rather large
and consequently exhibit stringent angular alignment tolerances. Here, we experimentally demonstrate how a proper
design of the bottom and top cladding oxide thicknesses allows reduction of the full-width at half maximum (FWHM)
and alleviates this problem. Additionally, the inclusion of a CMOS-compatible AlCu/TiN bottom reflector further
decreases the FWHM and increases the coupling efficiency. Finally, we show that focusing grating designs greatly
reduce the device footprint without penalizing the device metrics.
We analyze a new method for single-photon frequency upconversion. This technique uses a byproduct of the avalanche
process - electroluminescence resulting from hot-carrier recombination - as a means of upconversion. Because the
spectrum of the emitted photons peaks near the bandgap of the multiplying material and has a significant tail at higher
energies, it is possible to generate secondary photons at significantly higher energies than the primary absorbed photon.
The secondary photons can then be detected by a coupled CMOS silicon single-photon avalanche diode (SPAD), where
the information can also be processes. This upconversion scheme does not require any electrical connections between the
detecting device and the silicon SPAD, so glass-to-glass bonding can be used, resulting in inexpensive, high-density
arrays of detectors. We calculate the internal and system upconversion efficiencies, and show that the proposed scheme
is feasible and highly efficient for application such as quantum key distribution and near infrared low-light-level
imaging.
We demonstrate a new single-photon avalanche diode (SPAD) device, which utilizes the silicon-dioxide shallow-trench isolation (STI) structure common to all deep-submicron CMOS technologies, both for junction planarization and as an area-efficient guard-ring. This makes it possible to achieve an order-of-magnitude improvement in fill factor and a significant reduction in pixel area compared with existing CMOS SPADs, and results in improved SPAD performance. We present numerical simulations as well preliminary experimental results from a test chip, which was manufactured in an IBM 0.18 μm CMOS technology, and which incorporates the devices. With these new and efficient structures, 12 μm-pitch pixels with sub-10ns dead times are achievable without requiring active recharge, creating the opportunity to integrate large arrays of these ultra-fast SPADs for use in biological imaging systems.
Electron detector arrays are employed in numerous imaging applications, from low-light-light-level imaging to astronomy, electron microscopy, and nuclear instrumentation. The majority of these detectors are fabricated with dedicated processes, use the semiconductor as a stopping and detecting layer, and utilize CCD-type charge transfer and detection. We present a new detector, wherein electrons are stopped by an exposed metal layer, and are subsequently detected either through charge collection in a CCD-type well, or by a measurement of a potential drop across a capacitor which is discharged by these electrons. Spatial localization is achieved by use of two metal planes, one for protecting the underlying gate structures, and another, with metal pixel structures, for 2D detection. The new device does not suffer from semiconductor non-uniformities, and blooming effects are minimized. It is effective for electrons with energies of 2-6 keV. The unique structure makes it possible to achieve a high fill factor, and to incorporate on-chip processing. An imaging chip implementing several test structures incorporating the new detector has been fabricated using a 2 micron double-poly double-metal process, and tested inside a JEOL 640 electron microscope.
Electron detector arrays are employed in numerous imaging applications, from low-light-level imaging to astronomy, electron microscopy, and nuclear instrumentation. The majority of these detectors are fabricated with dedicated processes, use the semiconductor as a stopping and detecting layer, and utilize CCD-type charge transfer and detection. We present a new detector, wherein electrons are stopped by an exposed metal layer, and are subsequently detected either through charge collection in a CCD-type well, or by a measurement of a potential drop across a capacitor which is discharged by these electrons. Spatial localization is achieved by use of two metal planes, one for protecting the underlying gate structures, and another, with metal pixel structures, for 2D detection. The new deice doe not suffer from semiconductor non-uniformities, and blooming effects are minimized. It is effective for electrons with energies of 2-6 keV. The unique structure makes it possible to achieve a high fill factor, and to incorporate on-chip processing. An imaging chip implementing several test structures incorporating the new detector has been fabricated using a 2 micron double-poly double-metal process, and has been tested inside a JEOL 6400 electron microscope.
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