Channel Stop Research Articles

Influence of the STI on Single-Event Transients in Bulk FinFETs

The single-event transient (SET) produced by laser irradiation in a bulk FinFET is found to have a large plateau current in the tail. 3D technology computer-aided design (TCAD) simulation results show that the cause of the plateau current is the shallow trench isolation (STI) on both sides of the channel stop of a bulk FinFET. When the bulk FinFET is irradiated by heavy ions or laser, the electron-hole pairs are generated by ionization in the active region and the STI of the device. The electron mobility in the STI is much greater than that of the hole, so the electrons generated in the STI are collected quickly, and the holes are left in the STI. The holes left in the STI generate an electric field and form an electron inversion layer in the channel stop. Under the bias voltage of the drain terminal, the electrons in the source flow to the drain through the electron inversion layer in the channel stop to form a drain current. Since holes can exist in the the STI for more than 100 ns, the drain current caused by the electron inversion layer forms a plateau current at the tail of the pulse. And the plateau current increases as the gate length of the bulk FinFET becomes shorter, and decreases as the fin width of the bulk FinFET becomes larger.

Reach-through effect in deep depletion TESS CCDs

TESS CCDs are backside illuminated deep depletion devices fabricated on high resistivity p-type silicon substrate and thinned down to a thickness of 100 microns. In order to fully deplete the substrate and increase the near-IR efficiency, we apply a bias voltage to the back side of the device. A bias of -20V is sufficient to fully deplete this device, but overdepletion is desirable to minimize lateral diffusion which can blur images and in turn affect the photometric precision by increasing an area (and, hence, readout and background noise) associated with a given object of interest. For this reason much larger negative bias voltages have been applied. We can achieve sharper images with larger negative substrate voltage, but we also discovered an unexpected dramatic increase of the full well capacity beyond a certain threshold voltage. A large full well above 200,000e- is accompanied by poor charge conservation once the device is in the bloomed well condition. Both phenomena can be explained by backside voltage reaching through the substrate volume in the channel stop region, eliminating the barrier for holes, and dragging the floating channel stops to a more negative potential.

Quantum efficiency calibration for low energy detector in hard X-ray modulation telescope satellite

Low energy X-ray telescope, working over 0.7-15 keV energy band, is one of the main payloads in the hard X-ray modulation telescope satellite. The primary scientific objectives are to survey large sky area to investigate galactic X-ray transient sources as well as the cosmic X-ray background, and to observe X-ray binaries or black holes for studying the dynamics and emission mechanism in strong gravitational or magnetic field. The detector of low energy X-ray telescope is CCD236, a new generation of swept charge device, which has good time and energy resolution. Quantum efficiency (QE) of the detector has a crucial influence on X-ray spectrum fitting and absolute luminosity calculation. To provide valuable scientific data, QE should be calibrated in detail. In this paper, QE calibration is accomplished with respect to a silicon drift detector (SDD), using an Fe-55 radioactive source, at energy points Mn-Kα (5.899 keV) and Mn-Kβ (6.497 keV). The energies of Mn-Kα and Mn-Kβ are near that of iron-K, which is an important line in X-ray observation. Additionally, Mn-Kα and Mn-Kβ X-ray will partially pass through the depletion region of CCD236, and these energy points can be used to measure the depletion thickness. This experiment is set up in a vacuum cooling chamber. The X-ray source perpendicularly illuminates SDD and CCD236 through a small hole, whose area is far less than those of two detectors; therefore, QE measurements are irrelevant to neither the distance nor the azimuth angle between the X-ray source and the detector. For CCD236, split events should be corrected. Energy spectra of SDD and CCD236 are fitted with two Gaussian distributions, respectively, to obtain peak positions and standard variations of Mn-Kα and Mn-Kβ. With known structure of SDD, the QE of CCD236 can be calculated. QE values at Mn-Kα and Mn-Kβ are 71% and 62%, respectively. QE and temperature are uncorrelated with each other in a temperature range from -95 ℃ to -30 ℃. According to the specific structure of CCD236 and the measured QE, without considering the effect of channel stop, the best-fit thickness of depletion region is obtained to be 38 μm. When CCD236 is applied with different driving or substrate voltages, no obvious variation of QE is observed. It indicates that the thickness values of depletion region with high and low level voltages are equal. Furthermore, it shows that working CCD236 is deep depleted, and the thickness of depletion region will not change because it reaches its maximum, the edge of epitaxial layer and substrate layer.

Analysis of TID Process, Geometry, and Bias Condition Dependence in 14-nm FinFETs and Implications for RF and SRAM Performance

Total ionizing dose results are provided, showing the effects of different threshold adjust implant processes and irradiation bias conditions of 14-nm FinFETs. Minimal radiation-induced threshold voltage shift across a variety of transistor types is observed. Off-state leakage current of nMOSFET transistors exhibits a strong gate bias dependence, indicating electrostatic gate control of the sub-fin region and the corresponding parasitic conduction path are the largest concern for radiation hardness in FinFET technology. The high- $V_{\textit {th}}$ transistors exhibit the best irradiation performance across all bias conditions, showing a reasonably small change in off-state leakage current and $V_{\textit {th}}$ , while the low- $V_{\textit {th}}$ transistors exhibit a larger change in off-state leakage current. The “ worst-case” bias condition during irradiation for both pull-down and pass-gate nMOSFETs in static random access memory is determined to be the on-state ( $V_{\textit {gs}}=V_{\textit {dd}}$ ). We find the nMOSFET pull-down and pass-gate transistors of the SRAM bit-cell show less radiation-induced degradation due to transistor geometry and channel doping differences than the low- $V_{\textit {th}}$ transistor. Near-threshold operation is presented as a methodology for reducing radiation-induced increases in off-state device leakage current. In a 14-nm FinFET technology, the modeling indicates devices with high channel stop doping show the most robust response to TID allowing stable operation of ring oscillators and the SRAM bit-cell with minimal shift in critical operating characteristics.

Ge FET Fabrication by Plasma Etch at 45nm Pitch

The effect of germanium channel introduction was shown [1] to be sizable up to the high performance expectations when technological nodes pass 10-nm line. At that moment, the Si-based fin FET (FFT) technology should approach its limits, which would not be feasible to overcome by applying any boosting techniques anymore.In the work, a self-aligned double patterning (SADP) was selected to print the Ge fins with 45-nm pitch (from initial 90-nm), but in the future the EUV litho is considered to become an ultimate way to pattern active layer structures for such small nodes. The dry plasma etch development was performed in the Lam Research 2300® Kiyo®E Series 300 mm conductor etch reactor. The SiCl4-based advanced chamber condition control strategy was applied prior to etching of every individual wafer, which helps provide superior etch reproducibility [2].The 30-nm Ge channel was epitaxially grown on top of a thick SiGe strain-relaxed buffer (SRB) layer. The targeted depth of fin etch was set to be in the range of 120-140 nm, which means the etching should be done through the Ge channel stopping in the SiGe SRB. The final clean of the structure was performed ex situ to strip polymers formed during the Ge and SiGe etching, which was done with N2O/forming gas plasmas followed by a short 0.6%HF clean [3].Fig.1. shows the patterning stack used for SADP of Ge/SiGe fins. The critical dimensions (CDs) obtained during the first transfer layer etching (called CORE etch) determine the space between fins in the final 45-nm pitch structure, while the thickness of SiN spacer deposited on top of the CORE determines the final fin’s CD. More details on SADP sequence can be found in [4].After both the CORE and the SiN spacer patterning were completed, the focus of the study was to develop a Ge/SiGe fin etch process using the second transfer layer as a mask. A slightly tapered single-sloped fin profile is the desired outcome of such patterning, which structure has to be compatible with the following step of void-free oxide filling.Fig.2 depicts two types of the Ge/SiGe FFT etching. The result of the fin etching with the main etch chemistry consisting of HBr/Cl2/O2 and CH2F2 can be seen in Fig.2a. The process conditions were taken from the study of 200-nm relaxed pitch Ge FFT patterning [5], where the CH2F2–based passivation used during fin etch was shown to allow for an advanced controlling of the fin shape. However, the mechanism does not work so well for 45-nm dense pitch structures where the diffusion of active species into the narrow trenches is limited. It leads to several issues. First, there is a pronounced depth loading, which means the depth difference between isolated and dense structures. Thus, for the 95-nm tall fins shown in Fig.2a, the isolated structures were etched almost twice as deep.Re-entered profile in the top part of a fin is another problem of the structure shown in Fig. 2a, though the latter could probably be fixed by means of process optimization similarly to what was done in the etch of Fig. 2b.As it was shown for Si, depth loading can be naturally addressed by switching to a Cl2-based chemistry without any fluorocarbon or hydrocarbon additives [6]. Thus, an alternating process consisting of a Cl2-based etching step and O2-based passivation has been successfully tested to pattern the Ge/SiGe fins, shown in Fig. 2b. In the etching step of such cyclic process, the RF bias pulsing was applied at 100Hz in order to facilitate the etch process selectivity. More information on RF pulsing advantages can be found in [7].

Fabrication, characterization and simulation of channel stop for n in p-substrate silicon pixel detectors

Silicon detectors made on p-substrates are expected to have a better radiation hardness as compared to detectors made on n-substrates. However, the fixed positive oxide charges induce an inversion layer of electrons in the substrate, which connects the pixels. The common means of solving this problem is by using a p-spray, individual p-stops or a combination of the two. Here, we investigate the use of field plates to suppress the fixed positive charges and to prevent the formation of an inversion layer. The fabricated detector shows a high breakdown voltage and low interpixel leakage current for a structure using biased field plates with a width of 20 μm. By using a spice model for simulation of the preamplifier, a cross talk of about 1.6% is achieved with this detector structure. The cross talk is caused by capacitive and resistive coupling between the pixels.

Further improved technique for channeled stopping power measurements

A few years ago, an ingenious method was proposed to quickly and accurately measure the difference between random and aligned stopping powers without the need for free-standing mono-crystalline thin films; the main idea was to increase the energy of the incident ion beam so that the channel numbers for a characteristic feature in the backscattering spectrum in random and aligned direction coincide, thus compensating for the difference in stopping power endured by the outgoing ions (Greco et al. 2007) [7]. A small drawback of this method is that the total length of the path that the ion travels through the thin film is slightly different in random and aligned geometries. We have improved this method by changing the measurement geometry such that the aligned and random ions travel the exact same distance through the thin film. Representative results for 0.5–3MeV He ions channeled in <011> Si are presented and show that earlier measurements appear to overestimate slightly the reduction in stopping power for channeled ions.

High Density Low Leakage SRAM Standby Current Reduction with a Channel Stop Implant in p-Type Well in 40nm CMOS Development

In this paper, 32M 0.242 um2 SRAM cell array leakage was reduced significantly by ~ one order of magnitude without affecting the N+/PW junction capacitance after introducing a channel stop implant (CSI) in P-type well. The space for N+ in PW to NW is generally much smaller for SRAM than for logic device, therefore SRAM is normally the weakest point for N+ in PW to NW well isolation. After checking the N+ in PW to NW leakage, we found that its leakage is the dominant factor for the high SRAM standby current. Furthermore, NMOS performance was also improved with this channel stop implant. The N+/PW diode, N+/PW/DNW and P+/NW/PW bipolar were confirmed to be comparable with the baseline without the channel stop implant. P-type well proximity effect (WPE) and NMOS body effect performance were also analyzed.

Experimental studies of the surface plasmon polaritons waveguide filter in microwave band

Based on theoretical analysis, in this paper studied are the low pass and band stop filter effects of the μ-negative materials/double positive materials/μ-negative materials (MNG-DPS-MNG) surface plasmon polaritons waveguide with branch defect. The research results show that the defect is equivalent to a sub wavelength resonator. The central frequency of the band stop filter is determined by the resonator length and it is independent of the position where the resonator is located in the MNG region. The transmission dips of the waveguide are closely related to the coupling distance. So the filter characteristics of the surface plasmon polariton waveguide can be adjusted by changing the resonator length and number and the coupling distance. The experimental results are in good agreement with simulation results. These properties will have potential application value in the tunable single channel or multi-channel band stop filters.

Stopping Power and Energy Straggling of Channeled He-Ions in GaN

GaN epitaxial layers are usually grown on sapphire substrates. To avoid disastrous effect of the large lattice mismatch a thin polycrystalline nucleation layer is grown at 500 ◦C followed by the deposition of thick GaN template at much higher temperature. Remnants of the nucleation layer were visualized by transmission electron microscopy as defect agglomeration at the GaN/sapphire interface and provide a very useful depth marker for the measurement of channeled ions stopping power. Random and aligned spectra of He ions incident at energies ranging from 1.7 to 3.7 MeV have been measured and evaluated using the Monte Carlo simulation code McChasy. Impact parameter dependent stopping power has been calculated for channeling direction and its parameters have been adjusted according to experimental data. For virgin, i.e. as grown, samples, the ratio of channeled to random stopping power is constant and amounts to 0.7 in the energy range studied. Defects produced by ion implantation largely influence the stopping power. For channeled ions the variety of possible trajectories leads to different energy loss at a given depth, thus resulting in much larger energy straggling than that for the random path. Beam energy distributions at different depths have been calculated using the McChasy code. They are significantly broader than those predicted by the Bohr formula for random direction.

Channelized melt flow in downwelling mantle: Implications for 226Ra‐210Pb disequilibria in arc magmas

We present the results of an analytical model of porous flow of viscous melt into a steadily dilating “channel” (defined as a cluster of smaller veins) in downwelling subarc mantle. The model predicts the pressure drop in the mantle wedge matrix surrounding the channel needed to drive melt flow as a function of position and time. Melt is sucked toward the dilatant region at a near‐constant velocity (10−5 s−1) until veins comprising the channel stop opening (t = τ). Fluid elements that complete their journey within the time span t &lt; τ arrive at a channel. Our results make it possible to calculate the region of influence sampled by melt that surrounds the channel. This region is large compared to the model size of the channelized region driving flow. For a baseline dilation time of 1 year and channel half width of 2 m, melt can be sampled over an 80‐m radius and has the opportunity to sample matrix material with potentially contrasting chemistry on geologically short timescales. Our mechanical results are consistent with a downgoing arc mantle wedge source region where melting and melt extraction by porous flow to a channel network are sufficiently rapid to preserve source‐derived 238U‐230Th‐226Ra, and potentially also 226 Ra‐210Pb, disequilibria, prior to magma ascent to the surface. Since this is the rate‐determining step in the overall process, it allows the possibility that such short‐lived disequilibria measured in arc rocks at the surface are derived from deep in the mantle wedge. Stresses due to partial melting do not appear capable of producing the desired sucking effect, while the order of magnitude rate of shear required to drive dilation of ∼10−7 s−1 is much larger than values resulting from steady state subduction. We conclude that local deformation rates in excess of background plate tectonic rates are needed to “switch on” the dilatant channel network and to initiate the sucking effect.

Magnetically controlled valve for flow manipulation in polymer microfluidic devices

A simple, external in-line valve for use in microfluidic devices constructed of elastomer such as polydimethylsiloxane (PDMS) is described. The actuation of the valve is based on the principle that flexible polymer walls of a liquid channel can be pressed together by the aid of a permanent magnet and a small metal bar. In the presence of a small NdFeB magnet lying below the channel of interest, the metal bar is pulled downward simultaneously pushing the thin layer of PDMS down thereby closing the channel stopping any flow of fluid. The operation of the valve is dependent on the thickness of the PDMS layer, the height of the channel, the gap between the chip and the magnet and the strength of the magnet. The microfluidic channels are completely closed to fluid flows commonly used in microfluidic applications. The valve allows for fabrication of a “thin chip” that allows for detection of chromophoric species within the microchannel via an external fiber optics detection system. C18-Modified reverse phase silica particles are packed into the microchannel using a temporary taper created by the magnetic valve and separations using both pressure and electrochromatographic driven methods is detailed.

A technique to measure stopping power difference between channeled and non-channeled ions in crystalline solids

For high accuracy in energy-depth conversion in channeling Rutherford backscattering spectrometry (RBS) analysis, the precise knowledge of the channeling stopping powers of helium ions in crystalline solids is demanded. Here, we propose a novel approach to measure the stopping power difference between channeled and random He ions in silicon. In this technique, energies of incident He ions are adjusted such that the detector measured energies of ions which are backscattered from a buried maker in silicon are the same for the channeled and random incident ions. Therefore, the amount of energy adjustments for the incident beams represents the difference in energy loss between channeled and random ions in their inward paths. The technique avoids the use of a self-standing thin film which is normally required in stopping power measurements.

Novel Mach-Zehnder interferometer structure for tunable optical interleaver

A novel optical interleaver scheme based on nested optical glass pairs is proposed. The assembly of pairs behaves as a cascaded Mach-Zehnder interferometer. The interleaver, with simple structure, low cost, and compact size, can be easily implemented with inexpensive material and mature preparation technology. Small channel spacing (50 GHz), high isolation (<–30 dB), a wide, flat passband and stop band (>2/11 period), and center-frequency tunability can be obtained simultaneously. An optimum design of a 50-GHz tunable interleaver based on this structure is given as an example. Its environmental temperature sensitivity and fabrication tolerance are also analyzed.

An automated and efficient substrate noise analysis tool

This paper presents a methodology for the efficient modeling of substrate noise coupling. A closed-form Green's function for nonuniformly doped substrates is employed with the correct singular characteristics. A novel global surface impedance matrix scheme is introduced to efficiently model nonuniformly doped wells, channel stop implants, and buried layers. Layout, device, and netlist extractors are developed so as to integrate our boundary element method (BEM) solver with commercial layout and circuit simulation tools.

Optimized energy window of He beams for accurate determination of depth in channeling Rutherford backscattering spectrometry

We propose a method to improve accurate determination of damage/impurity depth profiles by channeling Rutherford backscattering by using He+4 beams in an energy window of 400–800 keV. This is based on the study of the stopping power of He+4 ions as a function of incident energy along the Si ⟨100⟩ axis, which shows that the channeling stopping power within the above energy window is close to the random stopping power. Experiments on 100 nm deep Sb-doped Si superlattices show that the approach significantly reduces the error in determining the depth location of Sb, for example, from 8% by using 2-MeV He+4 to 1% by using 600-keV He+4 ions.

The Channeled Stopping Powers of Boron Ions and Range Calculations in Si

An analytical fitting expression is obtained for the channeled stopping power of B ions in crystalline silicon. Ions incident in the Si 〈100〉 direction at energies from 50 keV/amu to 900 keV/amu are considered. The mean projected ranges of ions have been determined within the framework of the transport theory formalism where the fitting relation obtained for the stopping power was used. For this purpose, a first order ordinary differential equation including second order stopping coefficients is solved numerically by usingFehlberg fourth-fifth order Runge-Kutta method. By using the results for the channeled ion ranges, a transformation relation is proposed for the conversion of channeled/random ion ranges for the ion target system under consideration. The obtained results are compared with widely used standard programs such as Crystal-TRIM, SRIM and PRAL and our program applied to crystalline targets is in good agreement with Crystal-TRIM.

Energy loss measurements of H 2 and H 3 molecular beams along random and [formula omitted] directions of Si

The energy loss of H 2 and H 3 molecules along the 〈1 1 0〉 and non-aligned directions of Si was measured through the Rutherford backscattering technique in combination with a SIMOX target. The experiments were performed at 300, 500 and 700 keV/atom. The results show the following features: First, the random and channeling molecular stopping powers are larger than the corresponding atomic one. Second, at a given energy per atom, the H 3 energy loss is larger than the one of H 2. Third, within the experimental errors, the channeling and random molecular stopping powers are equal. Finally, there are strong indications that the contribution of the screened Coulomb explosion to the energy straggling of molecular beam increases with the molecular velocity.

Hot-Carrier Lifetime Dependence on Channel Width and Silicon Recess Depth in N-Channel Metal-Oxide-Semiconductor Field-Effect-Transistors with the Recessed Local Oxidation of Silicon Isolation Structure

Narrow width n-channel metal-oxide-semiconductor field-effect-transistors (nMOSFETs) fabricated with recessed local oxidation of silicon (R-LOCOS) isolation structures and deeper field oxide recess exhibit less hot-carrier degradation as compared to wide channel devices when stressed under the maximum substrate current condition. Through the investigation of many possible causes, such as channel stop doping effect, lateral channel electric field, mechanical stress effect, and recess depth effect, the cause of the smaller degradation in narrow channel nMOSFETs was found. This was due to a hole-attractive vertical electric field across the width of the narrow channel nMOSFET, which results in less interaction of the channel hot electrons with the silicon-silicon dioxide interface, and thus contributing to less interface-state generation. It was also found that a deeper field oxide recess in narrow channel nMOSFETs leads to lesser hot-carrier degradation, which is possibly related to the reduced impact ionization rate in the channel.

Direct measurement of sub-pixel structure of the EPIC MOS CCD on-board the XMM/NEWTON satellite

We have used a mesh experiment in order to measure the sub-pixel structure of the EPIC MOS CCDs on-board the XMM/NEWTON satellite. The EPIC MOS CCDs have 40 μm -square pixels which have an open electrode structure in order to improve the detection efficiency for low-energy X-rays. We obtained restored pixel images for various X-ray event grades (e.g. split-pixel events, single pixel events, etc.) at various X-ray energies. We confirmed that the open electrode structure results in a distorted horizontal pixel boundary. The open electrode region generates both single pixel events and vertically split events, but no horizontally split events. Because the single pixel events usually show the best energy resolution, we discuss a method of increasing the fraction of single pixel events from the open electrode region. Furthermore, we have directly measured the thickness of the electrodes and dead-layers by comparing spectra from the open electrode region with those from the other regions: electrodes, electrode finger and channel stop. We can say that EPIC MOS CCDs are more radiation hard than front-illumination chips of ACIS on-board Chandra X-ray Observatory because of their extra absorption thickness above the charge transfer channel. We calculated the mean pixel response and found that our estimation has a good agreement with that of the ground calibration of EPIC MOS CCD.