Etch depth control in bulk GaAs using patterning and real time spectroscopic ellipsometry (original) (raw)
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Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1999
Real time spectroscopic ellipsometry ͑RTSE͒ was used to monitor etching of GaAs/ Al 0.3 Ga 0.7 As/GaAs heterostructures in citric acid:hydrogen peroxide:de-ionized water ͑25:1:75͒. Etch rates of GaAs and AlGaAs of 15.3 and 17.6 nm/min, respectively, were determined by numerically fitting the RTSE data. A variable delay in the onset of etching was observed, and was related to variations in surface cleanliness and the initial oxide thickness. Real time monitoring was also used to control stopping of the nonselective etch after removal of the GaAs cap layer. In addition, etch depth control in the AlGaAs layer was demonstrated. Etching was stopped with 100 nm of AlGaAs remaining. Finally, RTSE was used to monitor wet etching of a patterned sample ͑75% of the surface area was covered by photoresist͒.
In Situ Control of Wet Etching Using Spectroscopic Ellipsometry
MRS Proceedings, 1998
Etching of a GaAs/Al0.3Ga0.7As/GaAs heterostructure in a nonselective etch solution of 25:1:75 (citric acid: H2O2:H2O) was studied in-situ using real time spectroscopic ellipsometry (RTSE). Etch rates for GaAs and AIGaAs of 15.3 nm/min and 17.6 nm/min, respectively, were determined by numerically fitting RTSE data. RTSE was successfully used to stop the etch after removal of the thin GaAs cap, while removing very little of the underlying AlGaAs layer. In addition, etch depth into the AIGaAs layer was accurately controlled, using RTSE to stop the etch with 100 nm remaining. Finally, RTSE data for wet etching of a patterned sample (75% coverage with photoresist) showed similar behavior to that for the unpattemed sample.
A new ellipsometric model of wet and dry etched GaAs surfaces
Thin Solid Films, 1995
In this paper we describe the application of ellipsometry to study (lOO)GaAs surfaces. Investigations concern the surfaces after polishing, cleaning, wet and dry etching of GaAs substrates and the surfaces of liquid phase epitaxy-and molecular beam epitaxy-grown GaAs epilayers. A new model is proposed to interpret the ellipsometric data. It assumes the presence of a transitional layer characterized by spherical disturbances situated between the bulk GaAs and the native oxide layer. The ellipsometric parameters are analysed as a function of the size and density of the spherical disturbances and the transitional and native oxide layers. Different angles (70:75") of the incident light beam are used at a wavelength of 546.1 nm. A refractive index of 1.81 for the oxide film and (4.05 -iO.304) for the GaAs substrate are assumed.
Sample size effect in photoelectrochemical etching of n-GaAs
Applied Physics Letters, 2000
A sample size effect on the etching rate in the photoelectrochemical etching of n-GaAs is demonstrated using synchrotron radiation x rays as the light source. It is shown that the etching rate increases significantly with the ratio of sample size to x-ray illuminated area. The rate-limiting effect on the charge transfer across the semiconductor-electrolyte junction is found to account for the phenomenon. It is also found that the etching rate relates to the nonilluminated area with a rather simple function.
CH3I vapor etching of masked and patterned GaAs
Journal of Crystal Growth, 1995
CH3I vapor etching of masked and patterned GaAs substrates has been experimentally investigated. For GaAs samples masked with silicon nitride stripes that are wider than 30 tzm, the etch depth increased compared to unmasked samples, the magnitude of which increased with increasing mask width. Etching of bulk substrates of (lll)Ga and (lll)As GaAs revealed a dependence of etch rate on crystal orientation, with (lll)Ga > (100)GaAs > (lll)As. Increasing etch temperature reduced the orientation dependence of etch rates. Orientation dependence of etch rates was also observed on non-planar GaAs substrates patterned to expose different orientations on wet-etched groove structures. In this case, etch rate differences between the different orientations were amplified when compared to the bulk substrate results. Finally, it was found that the extent of mask undercutting depended on the direction of mask stripes in a fashion consistent with the orientation reactivity results. Mask stripes on (100)GaAs oriented in the [011] direction were severely undercut whereas stripes oriented in the [011] direction were undercut less.
Beilstein journal of nanotechnology, 2016
Reflectance anisotropy spectroscopy (RAS) equipment is applied to monitor dry-etch processes (here specifically reactive ion etching (RIE)) of monocrystalline multilayered III-V semiconductors in situ. The related accuracy of etch depth control is better than 16 nm. Comparison with results of secondary ion mass spectrometry (SIMS) reveals a deviation of only about 4 nm in optimal cases. To illustrate the applicability of the reported method in every day settings for the first time the highly etch depth sensitive lithographic process to form a film lens on the waveguide ridge of a broad area laser (BAL) is presented. This example elucidates the benefits of the method in semiconductor device fabrication and also suggests how to fulfill design requirements for the sample in order to make RAS control possible.
Automated System for Selective Etching of the AlxGa1¡xAs/GaAs System and Some Applications
2005
A simple and fast method to remove semiconductor substrates from epitaxialy grown thin films can be very useful for studies of their optical properties. After substrate removal it is possible to make optical transmission studies, investigate ultra-fast time-resolved spectroscopy in semiconductors, and also measure the propagation time of photons in microcavities. In this work, we developed a simple and fast method to remove GaAs substrates in AlxGa1ixAs/GaAs systems using an electro-optical controlled etching jet. The prepared surface with this method present good optical quality and it is well suited for optical studies. Some examples of works that can be done after sample preparation are presented to reinforce the etching precision of this technique. The same system can be used for etching other substrates with its corresponding etching solution and electro-optical relation.
The use of optical metrology, including ellipsometry and reflectometry, has been successful for process monitoring. However, their applications to actual production are limited due to the problems inherent in the analysis of reflected light from patterned structures. In this paper, we examine techniques for the quantitative analysis of data from both highly regular grating structures and from patterns with low local order. We find good quantitative agreement of vector diffraction theory to specular reflection data. It is demonstrated that the shape evolution of spectroscopic ellipsometry data during etching process is useful for in situ analysis of wafer state. We conclude that there is significant promise for the use of specular techniques for in situ monitoring of topography provided that computational speed issues can be improved.
Size-selective laser-induced etching of semi-insulating GaAs: Photoluminescence studies
2009
The size-selective laser-induced etching of semi-insulating GaAs /10 0S is carried out to create a porous structure by varying the laser beam exposure time. The etch-time dependent photoluminescence (PL) spectroscopy results show that a direct tuning of the size of the nanocrystallites has a limit and it can be effectively carried out till the oxides layers developed on the top surface make a damping in the redox reaction process. The etch rate $0.3-0.5 nm/s is observed in the initial state and it continued with much slower rate for longer etching duration. The formation of GaAs nanostructures as well as chemical reaction byproducts on the top surface is observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). An estimate of the etch-time dependent nanocrystallite size and its size distribution on the etched layer is obtained by using the quantum confinement model.
In situ reflectance monitoring of the growth and etching of AlAs/GaAs structures in MOVPE
Journal of Crystal Growth, 2004
We report the in situ optical monitoring of AlAs/GaAs structure elaborated and etched by CCl 4 in metalorganic vapour phase epitaxy reactor. We describe the modelling of experimental reflectivity response to determine the properties of AlAs/GaAs structure such as the refractive index and growth/etch rate. Etching rates of AlAs and GaAs increase with the increase of the flow of CCl 4 or the substrate temperature. In most of the cases, the etching rate of GaAs is higher than that of AlAs. This fact might be related to the difference between the chloride species responsible to the mechanism of the etching. The thermodynamic analysis of the two mixtures (solid GaAs+H 2 +CCl 4 and solid AlAs+H 2 +CCl 4 ) suggests that GaCl and AlCl x (x ¼ 1 À 2) are the species responsible for the etching of GaAs and AlAs by CCl 4 , respectively. The surface flatness of GaAs and AlAs etched by CCl 4 is also qualitatively monitored in situ by laser reflectometry. Specifically, we have studied the evolution surface morphology with etching rate. The smoothest surface is reached by optimizing the etching parameters. r