Lina Gatilova

Surface loss rates of H and Cl radicals in an inductively coupled plasma etcher derived from time-resolved electron density and optical emission measurements

A study is undertaken of the loss kinetics of H and Cl atoms in an inductively coupled plasma (ICP) reactor used for the etching of III-V semiconductor materials. A time-resolved optical emission spectroscopy technique, also referred to as pulsed induced fluorescence (PIF), has been combined with time-resolved microwave hairpin probe measurements of the electron density in a pulsed Cl2/H2-based discharge for this purpose. The surface loss rate of H, kwH, was measured in H2 plasma and was found to lie in the 125–500 s−1 range (γH surface recombination coefficient of ∼0.006–0.023), depending on the reactor walls conditioning. The PIF technique was then evaluated for the derivation of kwCl, and γCl in Cl2-based plasmas. In contrast to H2 plasma, significant variations in the electron density may occur over the millisecond time scale corresponding to Cl2 dissociation at the rising edge of the plasma pulse. By comparing the temporal evolution of the electron density and the Ar-line intensity curves with 10% of...

Investigation of InP etching mechanisms in a Cl2/H2 inductively coupled plasma by optical emission spectroscopy

Optical emission spectroscopy (OES) has been used in order to investigate the InP etching mechanisms in a Cl2–H2 inductively coupled plasma. The authors have previously shown that anisotropic etching of InP could be achieved for a H2 percentage in the 35%–45% range where the InP etch rate also presents a local maximum [J. Vac. Sci. Technol. B 24, 2381 (2006)], and that anisotropic etching was due to an enhanced passivation of the etched sidewalls by a silicon oxide layer [J. Vac. Sci. Technol. B 26, 666 (2008)]. In this work, it is shown that this etching behavior is related to a maximum in the H atom concentration in the plasma. The possible enhancement of the sidewall passivation process in the presence of H is investigated by comparing OES measurements and etching results obtained for Cl2–H2 and Cl2–Ar gas mixtures.

High-aspect-ratio inductively coupled plasma etching of InP using SiH4/Cl2: Avoiding the effect of electrode coverplate material

A new SiH4/Cl2 chemistry is proposed for the high-aspect-ratio etching of InP-based heterostructures. Anisotropic etching is obtained through the deposition of a SiOx passivation layer on the etched sidewalls. SiH4 has been chosen as a single precursor for both Si and H species that are necessary to promote the passivation process. Previously developed Cl2/H2- or HBr-based chemistries for anisotropic etching of laser waveguides or vertical microcavities require a silicon wafer below the InP samples in order to assist the passivation mechanism. In contrast, the authors show that a SiOx passivation can be achieved and maintained almost independent of the nature of the wafer surface when SiH4 is added. This is of practical importance for the processing of III-V wafers having the same size as the electrode or for III-V heterogeneous integration when III-V dies bonded onto a 200/300 mm diameter wafer have to be etched. Smooth, notch-free, anisotropic etching of InGa(Al)As/InP heterostructures is demonstrated. ...

Addition of Si-Containing Gases for Anisotropic Etching of III?V Materials in Chlorine-Based Inductively Coupled Plasma

We discuss the possibility of obtaining high-aspect-ratio etching of InP materials in Cl2- and HBr-based inductively coupled plasmas (ICP) with the addition of Si-containing gases (SiH4 or SiCl4). A vertical and smooth etching profile is demonstrated in SiCl4/H2 plasma. The effect of adding of a small amount of SiH4 to a previously optimised Cl2/H2 chemistry is presented, and new SiH4/Cl2 and SiH4/HBr chemistries are proposed. Ex-situ energy-dispersive X-ray spectroscopy coupled to transmission electron microscopy (EDX–TEM) is used to analyze the composition of the thin passivation layer deposited on the etched sidewalls. We show that it consists of a Si-rich silicon oxide (Si/O~1) in Cl2/H2/SiH4 chemistry, and is changed to nano-crystalline (nc-) Si in SiH4/Cl2 chemistry depending on the SiH4 percentage. Moreover, we show that deep anisotropic etching of InP independent of the electrode coverplate material can be obtained via a SiOx passivation mechanism with the addition of Si-containing gases.

Monte Carlo Study of 2-D Capacitance Fringing Effects in GaAs Planar Schottky Diodes

Nanometer scale planar Schottky barrier diodes (SBDs) with realistic geometries have been studied by means of a 2-D ensemble Monte Carlo simulator. The topology of the devices studied in this paper is based in real planar GaAs SBDs used in terahertz applications, such as passive frequency mixing and multiplication, in which accurate models for the diode capacitance are required. The intrinsic capacitance of such small devices, which due to edge effects strongly deviates from the ideal value, has been calculated. In good agreement with the classical models, we have found that the edge capacitance is independent of the properties of the semiconductor beneath the contact and, as novel result, that the presence of surface charges at the semiconductor dielectric interface can reduce it almost 15%. We have finally provided a compact model for the total capacitance of diodes with arbitrary shape that could be easily implemented in design automation software such as Advance Design System (ADS).

Solid state sub millimeter-wave frequency doubler using intergrated schottky membrane technology

Four doublers working at 330 GHz, 380 GHz, 448 GHz and 575 GHz are successful designed by using 5um membrane sub-millimeter wave integrated circuit fabrication technology. Details of the design methodology for the doublers by using the membrane substrate are discussed. Its validity is qualified in the measurement with the simulation result.

Solid state 448GHz frequency doubler using intergrated schottky membrane technology

The design is to accomplish a frequency doubler by using thin membrane sub-millimeter wave integrated circuit fabrication technology. The Goubau line theory is firstly incorporated here to predefine the dimension of the channel, which is the key to the doublers performance. The detailed linear and nonlinear co-simulation method is presented as followed, usually several iterations are needed during the optimization flow. Finally, the expected pass-band of doubler is from 430GHz to 470GHz over 22% efficiency. And the mesa size is 10μm×8.2μm and the membrane thickness is 5μm. It shows that we can realize high efficiency frequency multipliers even up to several THz in the future by using this thin membrane fabrication technology.