ECR Plasma Etching Research Articles

Hydrogen Effects in ECR-Etching of 3C-SiC(100) Mesa Structures

An anisotropic etching process for mesa structures using fluorinated plasma with hydrogen addition was developed in an electon cyclotron resonance setup. The evolution of the mesa morphology was studied in dependence on the gas composition, the applied bias and the pressure. The achieved side wall slope approached 90° with a negligible trenching. The aspect ratios of the fabricated structure in the developed residue free ECR plasma etching process were between 5 and 20.

Chalcogenide Glass Optical Waveguides for Optical Communication

The present research work is focused on fabricating the chalcogenide glass optical waveguides keeping in mind their application in optical communication. The propagation loss of the waveguides is also studied at three different wavelengths. The waveguides were fabricated by dry etching using ECR Plasma etching and the propagation loss is studied using Fabry-Perot technique. The waveguides having loss as low as 0.35 dB/cm at 1.3m is achieved. The technique used to fabricate waveguide is simple and cost effective.

Thermally assisted ECR etching of CdTe in CCl 2F 2/Ar discharge under different gas flow ratio

II–VI compounds have attracted increasing attention, primarily because of the large range of energy band gaps available. ECR plasma etching of CdTe in a CCl 2F 2/Ar discharge with rf biasing were investigated at different temperature and different flow rate ratio. The etch rate increases with the increase in flow rate of reactive gas and temperature. The use of ECR conditions with additional rf biasing provides the good etching of the surface and fast etch rates. The etch depths were measured by Dektek profilometry and the surface morphology with scanning electron microscopy. This paper reports the thermal effect on the etch process of CdTe and the effect of various gas flow rates and ratio between CCl 2F 2 and Ar.

Silicon Pillar Fabricated for SGT with Varying the Content of O2 in Cl2/O2 Gases by Using ECR Plasma Etching

not Available.

ECR plasma etching of GaAs in CCl2F2/Ar/O2 discharge and IR studies of the etched surface

The etching of GaAs materials under electron cyclotron resonance conditions has been performed in an ECR etching system with rf biasing using the CCl2F2/Ar/O2 plasma chemistry. Etching experiments were carried out at a pressure between 0.015 and 0.020 mbar, rf power 0.39 W/cm2, and dc bias voltage 200 V. The surface morphology and etch depth were taken by scanning electron microscopy and Dektek Profilometry respectively. The use of ECR conditions with additional rf biasing provides the good etching of the surface and fast etch rates. Moreover, the surface of the GaAs material display smooth and stoichiometric surfaces at higher ECR powers. The surface damages on the GaAs samples after the plasma exposure have been studied using IR spectroscopy.

Effects of nitrogen addition on methane-based ECR plasma etching of gallium nitride

The effects of nitrogen addition on methane-based ECR plasma etching of GaN were studied. The etch rate 30 nm/min and r.m.s. roughness 2.6 nm were obtained when the GaN sample was etched by a methane-based gas mixture without N 2. The addition of N 2 gas resulted in a decrease of etch rate and a smoother etched surface. The r.m.s. roughness became less than 0.4 nm even only 1.5 sccm N 2 gas was added to the mixture. In situ XPS measurements showed that, without N 2, heavy N-depletion took place on the etched surface, resulting in appearance of Ga metal on the surface. In contrast, the loss of N was compensated when the N 2 gas was added, and the etched surface approached the stoichiometric one with the increase of N 2 gas flow. This suppression of preferential loss of N was considered to be the main reason that improved the etched surface morphology.

Antireflective structures in CdTe and CdZnTe surfaces by ECR plasma etching

A rigorous coupled-wave analysis procedure has been used to design structures which can be embedded in Cd(Zn)Te surfaces to make them antireflective in the 8–14 m spectral region. Gray scale lithography was used to produce these patterns in photoresist layers. High fidelity transfer of patterns into Cd(Zn)Te surfaces was accomplished by utilizing an electron cyclotron resonance plasma with etch selectivity values in the range of 6.7–13.3. Transmission values at patterned surfaces were measured to be as high as 99.3%.

Dry-etch fabrication of reduced area InGaAs/InP DHBT devices for high speed circuit applications

We have fabricated reduced area InGaAs/InP DHBTs for high speed circuit applications. To produce the small dimensions required, a process involving both wet chemical and ECR plasma etching was developed. Optical emission spectroscopy was used for end-point detection during plasma etching. With this improved process, an ft of 170 and fmax of 200 GHz were achieved for 1.2 × 3 µm2 emitter size devices with a 500 A base.

Novel fabrication of C-doped base InGaAs/InP DHBT structures for high speed circuit applications

We have fabricated InGaAs/InP based DHBTs for high speed circuit applications. A process involving both wet chemical and ECR plasma etching was developed. Carbon was employed as the p-type dopant of the base layer for excellent device stability. Both the emitter–base and base–collector regions were graded using quaternary InGaAsP alloys. The extrinsic emitter–base junction is buried for junction passivation to improve device reliability. The use of an InP collector structure with the graded region results in high breakdown voltages of 8-10 V, with no current blocking. The entire structure is encapsulated with spin-on-glass. These devices show no degradation in d.c. characteristics after operation at an emitter current density of 90 kA cm −2 and a collector bias, V CE, of 2 V at room temperature for over 500 h. Typical common emitter current gain was 50. An f t of 80 and f max of 155 GHz were achieved for 2×4 μm 2 emitter size devices.

Micro-technology of densely spaced non-conventional patterns for space applications

Regular arrays of sub-0.5 μm tips are of increasing interest, for example, as field emitters, calibration structures, or, in our particular case, as collector surfaces for sub-μm dust particles in a space experiment. This contribution describes the preparation of 1 × 1 cm 2 arrays of micro-columns with a high aspect ratio (10:1) and a diameter in the sub-micrometer range (150 – 300 nm). The process is based upon a chemically amplified novolak resist (CAR), electron beam lithography, and ECR plasma etching.

Precise Evaluation of Pattern Distortion with Variation of the Impurity Concentration and Conductivity of Silicon Films

Many types of silicon film are used as materials for the gate electrodes of ultra large scale integration (ULSI) devices. The influence of varying the type of silicon film on local side etch depth and etch rate is investigated using an ECR plasma etching system. Resistivity of silicon films is varied using various impurity concentrations and annealing temperatures. The etch rate of silicon film is confirmed to increase as resistivity decreases in the case of phosphorus doped film. However, the etch rate is constant or decreases to a small extent in the case of boron doped silicon film. In contrast, it is found that the dependence of local side etch depth on resistivity is different to the dependence of etch rate on resistivity. The local side etch depth decreases in the case of phosphorus doped silicon and is almost constant in the case of boron doped silicon as the resistivity decreases. Thus it is found that local side etch depth does not always increase as resistivity of silicon film decreases. The depth of local side etch is influenced by the vertical etch rate, because the ratio of the just etching time to the overetching time is fixed. It is found that the local side etch rate is almost constant in this experiment. Therefore, it is concluded that the difference in local side etch depth is mostly caused by the difference in vertical etch rate.

Novel Fabrication of C-Doped Base InGaAs/InP DHBT Structures For High Speed Circuit Applications

AbstractWe have fabricated InGaAs/InP based DHBTs for high speed circuit applications. A process involving both wet chemical and ECR plasma etching was developed. Carbon was employed as the p-type dopant of the base layer for excellent device stability. Both the emitter-base and base-collector regions were graded using quaternary InGaAsP alloys. The extrinsic emitter-base junction is buried for junction passivation to improve device reliability. The use of an InP collector structure with the graded region results in high breakdown voltages of 8V to IOV, with no current blocking. The entire structure is encapsulated with spin-on-glass. These devices show no degradation in DC characteristics after operation at an emitter current density of 90kA/cm2 and a collector bias, VCE, of 2V at room temperature for over 500 hours. Typical common emitter current gain was 50. An ft of 80 and fmax of 155 GHz were achieved for 2 × 4 μm2 emitter size devices.

High-performance 0.1 μm-self-aligned-gate GaAs MESFET technology

We report on 0.1-/spl mu/m gate-length self-aligned Au/WSiN-gate GaAs MESFET technology. The FET we produced using this technology has a planar structure with a selective ion-implanted channel layer and self-aligned n/sup +/- layers. One of the key structural parameters affecting device performance is the offset separating the gate electrode from lightly-doped source and drain n' layers. A 0.1-/spl mu/m gate length is attained by i-line photolithography using an anti-reflection top coat film and SF/sub 6/ gas ECR plasma etching. We demonstrate FET uniformity in a 3-in wafer and excellent high-frequency performance. The standard deviation of the threshold voltages is 0.058 V with an average of about 0 V at a gate length of 0.126 /spl mu/m and the current gain cutoff frequency (f/sub T/) is 168 GHz at a gate length of 0.06 /spl mu/m.

Hydrogen incorporation in GaN, AlN, and InN duringCl 2 /CH 4 /H 2 /Ar ECR plasma etching

Hydrogen concentrations up to ~1020 cm-3 in GaN and AlN and ~1019 cm-3 in InN are found to be incorporated during ECR plasma etching in Cl2/CH4/H2Ar at 170°C. Even very short duration (40 s) etch treatments produce hydrogen incorporation depths ≥0.2 µm ahead of the etch front, and may lead to electrical passivation effects within this region. Post-etch annealing at 450 – 500°C restores the initial conductivity.

Electron beam nanolithography with image reversal by ECR plasma oxidation

A new image-reversal process has been developed for electron beam nanolithography. This process is based on Si oxidation with ECR oxygen plasma through openings in resist patterns. Si on SiO 2 is selectively etched by either Cl 2-based ECR plasma etching or KOH anisotropic etching. This image-reversal process achieves 10-nm-scale Si line and dot patterns.

Fabrication of Novel III-N and III-V Modulator Structures by ECR Plasma Etching

AbstractQuantum well microdisk laser structures have been fabricated in the GaN/InGaN, GaAs/AlGaAs and GaAs/InGaP systems using a combination of ECR dry etching (Cl2/CH4/H2/Ar, BC13/Ar or CH4/H2/Ar plasma chemistries respectively) and subsequent wet chemical etching of a buffer layer underlying the quantum wells. While wet etchants such as HF/H2O and HCI/HNO3/H2O are employed for AlGaAs and InGaP, respectively, a new KOH-based solution has been developed for AlN which is completely selective over both GaN and InGaN. Typical mask materials include PR or SiNx, while the high surface recombination velocity of exposed AlGaAs (∼105cm·sec-1) requires encapsulation with ECR-CVD SiNx to stabilize the optical properties of the modulators.

ECR plasma etching of GaN, AlN and InN using iodineor bromine chemistries

The dry etching characteristics of GaN, AlN and InN in HI-H/sub 2/-Ar and HBr-H/sub 2/-Ar were examined using electron cyclotron resonance discharges operating at high microwave power (1000 W) and low pressure (1 mtorr). For an RF-induced DC bias of -150 V, the HI chemistry provides approximately 20% faster etch rates for GaN and AlN than more conventional chlorine-based plasmas. For InN the rates were up to a factor of 5 faster. The HBr chemistry produced slower etch rates for all three nitrides compared to chlorine chemistries. Highly anisotropic etched features were obtained in the three materials with both iodine and bromine chemistries.

Cl2‐ECR plasma etching of III/V semiconductors and its application to photonic devices

AbstractA 1.3‐μm InGaAsP/InP laser diode (LD), a 1‐μm InGaAs/GaAs LD, and a 0.65‐μm GaInP/AlGaInP LD were fabricated using Cl2 reactive ion beam etching. Four desirable features of dry etching, i.e., smoothness, controllability, uniformity, and capability of fine pattern formation, were investigated through the fabrication of these devices. the morphology of dry‐etched InP generally is not as good as that of GaAs; but, nevertheless, we achieved very smooth InP etching with a roughness of only 1.4 nm. the InGaAsP/InP LD made using this etching had a threshold current of 20 mA, which is as low as that of a wet‐etched LD. Precise control of etching depth is necessary for AlGaInP‐LD fabrication, and ion‐current monitoring made this possible with an accuracy of 22 nm. the deviation of AlGaInP etching depth is only 15 nm across a 2‐inch wafer. This good uniformity resulted in a small deviation of threshold current fabricated in 2‐inch form. an InGaAs/GaAs vertical‐cavity surface‐emitting laser array having uniform threshold current was fabricated making use of the capability of fine pattern formation, and the record low‐threshold current of 190 μA was achieved in an air‐post VCSEL etched by reactive ion beam etching (RIBE).

X-ray lithography for sub-half-micrometer devices.

Steeply profiled high-aspect-ratio Ta patterns for X-ray masks have been fabricated using low-temperature ECR plasma etching with SF6 gas. Side etching of the Ta patterns was restrained without using any additional gas to form a sidewall protection polymeric film. This X-ray mask technology has been applied to sub-half-micrometer pattern fabrication using an X-ray lithography system based on a compact synchrotron. N-channel MOS transistors with 0.3-μm gates have been fabricated using the X-ray lithography for all four mask levels.

ECR/magnetic mirror coupled plasma etching of GaAs using CH4:H2:Ar

A study of CH4:H2:Ar microwave ECR-plasma etching of GaAs is presented. GaAs etch rates are measured as a function of the constituent gas flow rates, applied RF and microwave powers, substrate temperature and magnetic-table separation. The results indicate that for CH4:H2:Ar ECR etching of GaAs, etch rates of 25 nm min-1 can be achieved. The electrical 'damage' in a GaAs/AlGaAs HEMT Hall bar structure was investigated by etching off the GaAs capping layer. Results indicate that ECR-plasma etching with an additional RF-table bias in the range of -40 to 0 V does not significantly increase the source-drain resistances, measured at 300 K, to that of a wet etched sample. Some degradation in n and mu was found at 1.2 K.