In this work, we demonstrate a transferrable single crystalline 4H-SiC nanomembrane (SiC NM) released from a SiC-on-insulator (SiCOI) wafer. High resolution X-ray diffraction (XRD) and atomic force microscopy (AFM) were performed on the SiC NM and confirmed similarly good crystallinity and surface morphology. In addition, the refractive index and extinction coefficient of the SiC NM were investigated using ellipsometry analyses. Despite its thinness (i.e., 200 nm), the SiC NM achieved an absorption greater than 40% in the wavelength range of 200–260 nm with a maximum absorption of 73.8% at 256 nm. Our transferrable SiC NM provides not only good mechanical flexibility, but also exhibits excellent ultraviolet (UV) light absorption which could be readily utilized for high sensitivity flexible UV detectors.

Transferrable single crystalline 4H-SiC nanomembranes

In manufacturing a semiconductor device, static electricity is generated while contact holes are formed in an interlayer insulating film by dry etching. Damage to a pixel region or a driving circuit region due to travel of the static electricity generated is prevented. Gate signal lines are spaced apart from each other above a crystalline semiconductor film. Therefore a first protective circuit is not electrically connected when contact holes are opened in an interlayer insulating film. The static electricity generated during dry etching for opening the contact holes moves from the gate signal line, damages a gate insulating film, passes the crystalline semiconductor film, and again damages the gate insulating film before it reaches the gate signal line. As the static electricity generated during the dry etching damages the first protective circuit, the energy of the static electricity is reduced until it loses the capacity of damaging a driving circuit TFT. The driving circuit TFT is thus prevented from suffering electrostatic discharge damage.

Semiconductor Device and Method of Manufacturing the Same

Self-terminated etching of GaN with a high selectivity over AlGaN under inductively coupled Cl 2 /N 2 /O 2 plasma with a low-energy ion bombardment

Formation of single-layered Au nanoparticles in Au ion implanted TiO2 and SrTiO3

This paper reports an experimental study of the effects of different metal claddings on the performance of terahertz quantum cascade lasers. The experimental results show that by using a metal cladding made of Ta/Cu/Au to replace that of Pd/Ge/Ti/Pt/Au, the maximum lasing temperature of the devices is increased from 132 to 172 K, and the threshold current density of the devices at 10 K can be reduced from 0.74 to 0.68 kA cm−2. The improvement of the device performance is attributed to lower optical losses associated with the metal cladding layers. The different effects of the metal contacts on device optical properties and electrical properties are also discussed.

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On metal contacts of terahertz quantum cascade lasers with a metal-metal waveguide

In this work, ohmic contacts were formed by varying the Ti/Al thickness ratio in the metal stack of Ti/Al/Ni/Au on Al .28 Ga .72 N/GaN HEMT epistructure followed by annealing in the temperature range 740–860 °C by rapid thermal processor (RTP). The contacts were electrically characterized for contact resistance ( R c ) and the sheet resistance ( R s ) of AlGaN/GaN epistructure. The ohmic contacts formed by Ti/Al metal thickness ratio of 1/5 exhibited lowest R c values and better surface morphology compared to the contacts formed by other Ti/Al metal thickness ratios. The difference observed in the electrical characterization of these contacts was correlated with their X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS) analyses. The surface morphology of the ohmic metal post annealing showed two distinct regions in scanning electron microscope (SEM) images. The energy dispersive X-ray analysis (EDAX) identified these regions as Ni–Al and Au–Al rich. Ni–Al rich region is believed to be responsible for rough morphology. Further, the contact formed with Ti/Al metal thickness ratio 1/5 showed less number of elemental Al and Ti atoms and therefore was correlated with lower oxidation probability of the contact compared to ohmic contact formed by other metal thickness ratios.

Micro-structural evaluation of Ti/Al/Ni/Au ohmic contacts with different Ti/Al thicknesses in AlGaN/GaN HEMTs

A study of Cl2/BCl3-based inductively coupled plasma (ICP) was conducted using thick photoresist mask for anisotropic etching of 50 μm diameter holes in a GaAs wafer at a relatively high average etching rate for etching depths of more than 150 μm. Plasma etch characteristics with ICP process pressure and the percentage of BCl3 were studied in greater detail at a constant ICP coil/bias power. The measured peak-to-peak voltage as a function of pressure was used to estimate the minimum energy of the ions bombarding the substrate. The process pressure was found to have a substantial influence on the energy of heavy ions. Various ion species in plasma showed minimum energy variation from 1.85 eV to 7.5 eV in the pressure range of 20 mTorr to 50 mTorr. The effect of pressure and the percentage of BCl3 on the etching rate and surface smoothness of the bottom surface of the etched hole were studied for a fixed total flow rate. The etching rate was found to decrease with the percentage of BCl3, whereas the addition of BCl3 resulted in anisotropic holes with a smooth veil free bottom surface at a pressure of 30 mTorr and 42% BCl3. In addition, variation of the etching yield with pressure and etching depth were also investigated.

Experimental Study of the Influence of Process Pressure and Gas Composition on GaAs Etching Characteristics in Cl2/BCl3-Based Inductively Coupled Plasma

Effect of BCl3 concentration and process pressure on the GaN mesa sidewalls in BCl3/Cl2 based inductively coupled plasma etching

Thermal reliability of n-GaAs/Ti/Pt/Au Schottky contacts with thin Ti films for reduced gate resistance

In this study we have investigated the reactive ion etching of 60 μm diam, 200 μm deep holes in 3 in. diam semi-insulating GaAs wafer using a combination of CCl 2 F 2 and CCl 4 gases for fabrication of through substrate via holes for grounding in monolithic microwave integrated circuits (MMICs). The effect of process parameters viz. pressure, CCl 4 /CCl 2 F 2 ratio, and power on GaAs etch rate and resultant etch profile was investigated. Two kind of masks, photoresist and Ni, were used to etch GaAs and their performance was compared by investigating effect on etch rate, etch depth, etch profile, and surface morphology. The etch profile, etch depth, and surface morphology of as-etched samples were characterized by scanning electron microscopy. The desired 200 μm deep strawberry profile, with a top diam = 60 ′ 10 μm and bottom diam = 180 ′ 10 μm, was obtained at 40 mTorr process pressure with an average etch rate ∼1.3 μm/min using Ni mask. The vias were then metallized by depositing a thin seed layer of Ti/Au (1000 A) using radio frequency sputtering and Au (5 μm) electroplated to connect the front side pad and back side ground plane. The parasitic inductance offered by these vias was ∼76 pH. The developed process was then integrated into the MMIC process line and a 16-18 GHz amplifier was fabricated using grounding vias with yield >90%.

B. K. Sehgal

Papers

Micro-structural evaluation of Ti/Al/Ni/Au ohmic contacts with different Ti/Al thicknesses in AlGaN/GaN HEMTs

Experimental Study of the Influence of Process Pressure and Gas Composition on GaAs Etching Characteristics in Cl2/BCl3-Based Inductively Coupled Plasma

Effect of BCl3 concentration and process pressure on the GaN mesa sidewalls in BCl3/Cl2 based inductively coupled plasma etching

Thermal reliability of n-GaAs/Ti/Pt/Au Schottky contacts with thin Ti films for reduced gate resistance

Anisotropic Etching of GaAs Using CCl2 F 2 / CCl4 Gases to Fabricate 200 μm Deep Via Holes for Grounding MMICs