Inductively-coupled Plasma Chemical Vapor Research Articles

Performance Improvement in AlGaN/GaN High‐Electron‐Mobility Transistors by Low‐Temperature Inductively Coupled Plasma–Chemical Vapor Deposited SiNx as Gate Dielectric and Surface Passivation

This work demonstrates performance improvements in AlGaN/GaN metal–insulator–semiconductor high‐electron‐mobility transistors (MIS‐HEMTs) using low‐temperature inductively coupled plasma chemical vapor deposited (ICP–CVD) silicon nitride (SiN x ). The low‐temperature SiN x is used for both device passivation and gate dielectric. The bandgap of SiN x (4.9 eV) and AlGaN/SiN x type‐II staggered band alignment (ΔE c = 1.4 eV) are determined using ultraviolet‐visible spectroscopy and ultraviolet photoelectron spectroscopy, respectively. The SiN x layer effectively increases the in‐plane tensile strain in the AlGaN barrier layer. The tensile strain increases by 0.08% for a 150 nm SiN x layer. The corresponding increase in the piezoelectric polarization and 2D electron gas (2DEG) density is 1.5 × 1012 and 1.44 × 1012 cm−2, respectively. The transistor's on‐resistance decreases to 9.33 Ω mm compared with 14 Ω mm measured for the control devices with gate length 1 μm and source and drain separation of 11 μm. The gate leakage current reduces by more than three orders of magnitude. The I ON/I OFF ratio increases by two orders of magnitude. The improvements in the physical and electrical properties of the low‐temperature‐deposited ICP–CVD SiN x MIS‐HEMTs make it a viable candidate for low‐thermal‐budget fabrication. This nitride can be used with non‐alloyed Ohmic contacts on GaN for extremely low‐thermal‐budget transistors.

The Characteristics of Transparent Non-Volatile Memory Devices Employing Si-Rich SiOX as a Charge Trapping Layer and Indium-Tin-Zinc-Oxide

We fabricated the transparent non-volatile memory (NVM) of a bottom gate thin film transistor (TFT) for the integrated logic devices of display applications. The NVM TFT utilized indium–tin–zinc–oxide (ITZO) as an active channel layer and multi-oxide structure of SiO2 (blocking layer)/Si-rich SiOX (charge trapping layer)/SiOXNY (tunneling layer) as a gate insulator. The insulators were deposited using inductive coupled plasma chemical vapor deposition, and during the deposition, the trap states of the Si-rich SiOx charge trapping layer could be controlled to widen the memory window with the gas ratio (GR) of SiH4:N2O, which was confirmed by fourier transform infrared spectroscopy (FT-IR). We fabricated the metal–insulator–silicon (MIS) capacitors of the insulator structures on n-type Si substrate and demonstrated that the hysteresis capacitive curves of the MIS capacitors were a function of sweep voltage and trap density (or GR). At the GR6 (SiH4:N2O = 30:5), the MIS capacitor exhibited the widest memory window; the flat band voltage (ΔVFB) shifts of 4.45 V was obtained at the sweep voltage of ±11 V for 10 s, and it was expected to maintain ~71% of the initial value after 10 years. Using the Si-rich SiOX charge trapping layer deposited at the GR6 condition, we fabricated a bottom gate ITZO NVM TFT showing excellent drain current to gate voltage transfer characteristics. The field-effect mobility of 27.2 cm2/Vs, threshold voltage of 0.15 V, subthreshold swing of 0.17 V/dec, and on/off current ratio of 7.57 × 107 were obtained at the initial sweep of the devices. As an NVM, ΔVFB was shifted by 2.08 V in the programing mode with a positive gate voltage pulse of 11 V and 1 μs. The ΔVFB was returned to the pristine condition with a negative voltage pulse of −1 V and 1 μs under a 400–700 nm light illumination of ~10 mWcm−2 in erasing mode, when the light excites the electrons to escape from the charge trapping layer. Using this operation condition, ~90% (1.87 V) of initial ΔVFB (2.08 V) was expected to be retained over 10 years. The developed transparent NVM using Si-rich SiOx and ITZO can be a promising candidate for future display devices integrating logic devices on panels.

Silicon nitride deposition using Inductive Coupled Plasma Chemical Vapor Deposition technique to study optoelectronics behavior for solar cell application

Silicon nitride (Si3N4) is one of the promising dielectric materials for electronic devices, since it has extensive variety of applications in the semiconductor industries such as high speed semiconductor devices, solar cells, etc. This paper is mainly focus on comprehensive study of silicon nitride deposition using ICPCVD (Inductive Coupled Plasma Chemical Vapor Deposition) for potential application in the field of c-Si solar cell and on III–V semiconductor based solar cell. It helps to increases the minority carrier lifetime and reduces the reflectance in c-Si solar cell. Deposition parameters like temperature, power and deposition time have been optimized for getting the nitride layer which will be free from trap states.

Impact of SiNx passivation on the surface properties of InGaAs photo-detectors

We investigate surface passivation effects of SiNx films deposited by inductive coupled plasma chemical vapor deposition (ICPCVD) and plasma enhanced chemical vapor deposition (PECVD) technologies for InAlAs/InGaAs/InP photo-detectors. It is found that ICPCVD deposited SiNx film effectively reduces the densities of the interface states and slow traps near SiNx/InAlAs interface, which realize the small surface recombination velocity and low surface current for InAlAs/InGaAs/InP photo-detectors. By comparing C-V and XPS results, it is suggested that the trap density reduction by ICPCVD technology could be attributed to the disorder suppression on InAlAs surface due to the high density of SiNx film and less processing energy to the InAlAs surface.

Improvement of surface leakage current of 2.6 µm InGaAs photodetectors by using inductive coupled plasma chemical vapor deposition technology

Low surface leakage current is one of the prerequistites to reach the low leakage and high efficiencies of mesa type photodiodes. In this paper, we have studied the surface leakage of 2.6 µm mesa InGaAs p–i–n photodetectors by using two different passivation technologies: inductive coupled plasma chemical vapor deposition (ICPCVD) and plasma enhanced chemical vapor deposition (PECVD). It is found that the total leakage current of the detector with ICPCVD technology is significantly reduced compared to that with PECVD technology due to the decrease of the device’s surface leakage current. A TCAD-based dark current model further reveals that the reduction of the surface leakage current at the low reverse voltage is about two orders of magnitude. As a result, ICPCVD is the promising deposition technology for SiNx passivation layer on mesa InGaAs photodetectors.

Electrical and Mechanical Characteristics of Room Temperature Deposited Silicon Nitride Using Two Inner Parallel Cylindrical Coils Inductively Coupled Plasma Chemical Vapor Deposition

For investigating silicon nitride (SiN) thin film deposition process at room temperature without additional substrate heating, we studied inductively coupled plasma chemical vapor deposition with two inner parallel cylindrical coils which can activate the more radicals and charged species in the plasma. We investigated the influence of plasma RF power on the characteristics of room temperature deposited SiN films. Deposition rates, dielectric constant, refractive index, and stress of the films ranged from 4.5 nm/min to 8.3 nm/min, 8.4 to 10, 1.8 to 2.1, and 0.54 to 0.15, respectively. According to the FTIR measurements, the concentration of the Si--H and N--H bonds was decreased as the RF power increased, and the Si--H bonds tended to disappear at RF power over 500 W. This reduction in the hydrogen content was accompanied by the increases in the deposition rate and refractive index. It was confirmed that the breakdown field could be also maximized to 10 MV/cm.

Optical properties of SiOC film by PL spectrometer and reflectance

SiOC films made by the inductive coupled plasma chemical vapor deposition were analyzed by the photo luminance spectra and reflectance. Chemical shift obtained by PL spectra was observed and the reflectance was decreased at sample with low refractive index. The refractive index was in inverse proportion to the thickness of SiOC film. Lowering the reflectance caused to decrease the energy band gap and polarization, so increased an absorbance of the light. Low polarization of SiOC film was induced from the recombination and dissociation of alkyl sites by neighboring high electro negative oxygen. The electron affinity related to the energy band gap at surfaces increased at sample with low polarization, and finally, the reflectance decreased according to the reduction of polarity.

Interface structure of microcrystalline silicon deposited by inductive coupled plasma using internal low inductance antenna

Hydrogenated microcrystalline silicon (µc-Si:H) films were prepared by inductive coupled plasma chemical vapor deposition (ICP-CVD) system using internal low inductance antenna (LIA) units on various under layer composed of Si, O, and N. The resultant changes in the crystallinity of the µc-Si:H films were investigated using Raman scattering spectroscopy and the details of the interface structure were observed by high resolution transmission electron microscope. We had found that µc-Si:H film on the SiNx layer treated by O2 plasma has good interface quality. The highly crystallized µc-Si:H films with no amorphous incubation layer at interface of Si/SiNx could be directly deposited on the SiNx layer.

Fabrication of Silicon and Germanium Nanostructures by Combination of Hydrogen Plasma Dry Etching and VLS Mechanism

Silicon and germanium nanostructures were fabricated by the combination of dry etching and vapor-liquid-solid (VLS) mechanism. Gold nanoparticles, about 20 nm in diameter, captured by self-assemble monolayer were adopted as the hard mask for dry etching and catalyst of germanium growth. Reactive ion etching in an inductive coupled plasma chemical vapor deposition (ICPCVD) system was used to fabricate various silicon nanostructures. Instead of CF4, SF6, and SiCl4 gases, hydrogen plasma was used alone as the etching species to construct high-aspect-ratio silicon nanowires. Germanium nanostructures were then fabricated on the surface of silicon nanowires by dry etching and VLS mechanism.

Synthesis of Aligned Carbon Nanotubes by Inductively Coupled Plasma Chemical Vapor Deposition

Inductively coupled plasma chemical vapor deposition combined with substrate biasing using a gas mixture of methane and hydrogen was applied to low-temperature synthesis of aligned carbon nanotubes and nanofibers. We found that the resultant carbon nanotubes, which were grown at 500°C, were aligned perpendicular to the substrate, and the aligned carbon nanofibers were synthesized even at a growth temperature as low as 200°C. The growth mechanism of the aligned carbon nanotubes and carbon nanofibers is discussed in terms of the moderate etching of carbon deposit by hydrogen species in inductively coupled plasma.

UV crystallization of poly-si using a CeO2 seed layer on plastic substrate for microelectronics applications

We are reporting the crystallization of amorphous silicon (a-Si) film using XeCl excimer laser annealing. Polycarbonate (PC) plastic substrate was used to deposit poly-Si film at low temperatures. We deposited the a-Si films at a room temperature using an inductive coupled plasma chemical vapor deposition (ICPCVD). Then it was crystallized as a function of laser energy density using a XeCl excimer laser. As the laser energy density increases, crystallinity value decreases from 72.78 to 81.72%. The relationship between the film transmittance and crystallinity was analyzed as a function of process pressure. In another process, CeO2 seed layer was grown by sputtering method. a-Si film was deposited over this layer using ICPCVD and then it was crystallized using the XeCl excimer laser. It was observed that the crystallization could be accomplished at lower energy density with a seed layer than that without such layer. In this paper, we present the crystallization properties of a-Si on the plastic substrate.

Hydrogen dilution effect on the properties of coplanar amorphous silicon thin-film transistors fabricated by inductively-coupled plasma CVD

The electrical and optical properties of the hydrogenated amorphous silicon (a-Si:H) films deposited by inductively-coupled plasma (ICP) chemical vapor deposition (CVD) with a variation of H/sub 2/ flow rate have been studied. The photosensitivity of a-Si:H is /spl sim/10/sup 7/ when the H/sub 2//SiH/sub 4/ ratio is between 3 and 8. With increasing H/sub 2//SiH/sub 4/, the SiH/sub 2/ mode infrared absorption has a minimum at a H/sub 2//SiH/sub 4/ ratio of 8. Coplanar a-Si:H thin-film transistors (TFT's) were fabricated using a triple layer of thin a-Si:H, silicon-nitride, and a-Si:H deposited by ICP-CVD using ion doping and low resistivity Ni silicide. After patterning the thin a-Si:H/silicon-nitride layers on the channel region, the gate and source/drain regions were ion-doped and then heated at 230/spl deg/C to form Ni silicide layers. The low resistive Ni silicide formed on the a-Si:H reduces the offset length between gate and source/drain, leads to a coplanar a-Si:H TFT. The TFT exhibited a field effect mobility of 0.6 cm/sup 2//Vs and a threshold voltage of 2.3 V at the H/sub 2//SiH/sub 4/ ratio of 8. The effect of H/sub 2/ dilution in SiH/sub 4/ on the coplanar a-Si:H TFT performance has been investigated. We found that the performance of the TFT is the best when the SiH/sub 2/ mode density in a-Si:H is the minimum. The coplanar TFT is very suitable for large-area, high density TFT displays because of its low parasitic capacitance between gate and source/drain contacts.