In Situ Control of Wet Etching Using Spectroscopic Ellipsometry (original) (raw)
Related papers
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.
Etch depth control in bulk GaAs using patterning and real time spectroscopic ellipsometry
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2002
Real time spectroscopic ellipsometry ͑RTSE͒ was used to monitor and control the depth of etching into a bulk GaAs wafer. Lateral interference due to patterning is the mechanism by which this optical technique, normally used for thin film measurement, can determine etch depth into bulk material. Scalar analysis permits fast data fitting and real time control. GaAs wafers were patterned with photoresist in line or square patterns with periods of 10, 20, or 40 m, and etched in a solution of citric acid-hydrogen peroxide-de-ionized water. RTSE data were collected and simultaneously analyzed for etch depth. When the depth reached a preselected target value of up to 1.6 m the etch was stopped. Final etch depth as measured by scanning electron microscopy was always within 5% of the target depth. Ex situ spectroscopic ellipsometry analysis of the etched GaAs, with the photoresist removed, also agreed well with the RTSE results.
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.
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.
Excimer laser assisted etching of AlGaAs and GaAs
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1995
Laser assisted etching of AlGaAs and GaAs by chlorine using ArF and KrF excimer lasers was investigated. The etching rate of AlGaAs was shown to be larger than that of GaAs. Quadrupole mass spectroscopy analysis of the etching products for KrF assisted etching showed intense Ga ϩ and As ϩ signals from AlGaAs. It is suggested that a laser-induced neutral atom desorption process is enhanced in the AlGaAs etching. Hall measurements of a shallow channel heterostructure sample and GaAs Schottky diode characterization demonstrated the low damage of the etching process. The etching profile was examined by scanning electron microscopy and feasibility for field effect transistor gate recess etching was shown.
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.
Microelectronic Engineering
We investigate the parameter optimization for micron-scale etching by Inductive Coupled Plasma-Deep Reactive Ion Etching (ICP-DRIE) of GaAs/AlGaAs semiconductor heterostructures. Although dry etching approaches have been reported in the literature using a broad variety of plasma etch tools, there is still need to meet the majority of microsystems dry etching requirements. The etch process family studied here, is dominated by the relative pressures of BCl 3 (Boron trichloride) and Cl 2 (Chlorine) gases. The influence of using a BCl 3 /Cl 2 / Ar/N 2 mixture at different pressures has been investigated: A small addition of N 2 (Nitrogen) is very effective inducing sidewall protection when using photoresist masks. The etch profile quality has been characterized as a function of the plasma process and of the etched feature sizes. The desired etch characteristics for GaAs/AlGaAs heterostructures can be achieved by controlling the various process parameters with good reliability, high selectivity, andsimultaneouslyhigh etch rates and sidewall verticality. Etch rates from 1 to over 5.5 μm/min have been obtained. The selectivity with optical photoresist varies from 2.3 to 16. The presented results can be valuable for a wide range of applications involving fabrication of micro-electro-mechanical-systems or Micro Optoelectronic Mechanical Systems.
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.
Electrochimica Acta, 2000
We have applied photoelectron spectroscopy to investigate the surface composition after different surface treatments involving Br 2 -H 2 O mixtures in order to study wet chemical etching. Emersion experiments from Br 2 -H 2 O solution are compared with model experiments, in which Br 2 -H 2 O adsorbate and coadsorbate mixtures react with clean GaAs surfaces. Our results indicate that Ga-and As-bromides formed initially are hydrolyzed to form the respective oxides. Without addition of Br 2 , only slight oxidation of the surface takes place. There is an enrichment of Ga due to loss of As both in adsorption as well as in emersion experiments. Since in emersion experiments only a final situation is analyzed, the relative influence of surface reactivity and subsequent solvation effects cannot be distinguished easily, while model experiments give clear information on reaction products formed intermediately. However, model experiments differ in environment and temperature from the real solid-liquid interface. The presented results demonstrate that a combination of emersion and model experiments provide valuable insight into the mechanism of wet chemical etching on a microscopic level.
Chemical etching of (100) GaAs in a sulphuric acid-hydrogen peroxide-water system
Journal of Materials Science, 1987
A detailed investigation of the etching of (1 00) GaAs in H2SO4-H202-H20 systems has been made. The influence of the concentration of particular etchant components on etching rate and on the shape of the crystal surface was examined. From these resuRs the Gibbs" triangle of etching bath compositions was divided into parts corresponding to the various states of the crystal surfaces and various etching mechanisms. The shape of the crystal surface after etching was closely related to the profiles of the grooves etched in the [1 1 0] direction in the same solution.