Electron-cyclotron resonance etching of mirrors for ridge-guided lasers

Swanson, Paul N.; Shire, D. B.; Tang, C. L.; Parker, M. A.; Kimmet, James S.; Michalak, Richard J.

doi:10.1109/68.388738

Cited by 15 publications

(6 citation statements)

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“…Wet etching has potential advantages over dry etching, [1][2][3] including lower cost, smoother surfaces, and larger etch rates. Integrated devices require a variety of etched-sidewall profiles and angles ranging from shallow etched-slopes for electrical contacts to vertical flat smooth surfaces for integrated laser mirrors.…”

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Fabricating Vertical Sidewalls in GaAs∕AlGaAs Heterostructure Using Light-Induced Wet Etching

Parker

2006

J. Electrochem. Soc.

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We investigate the effects of light-induced wet etching ͑LIWE͒ on sidewall profile and etch rate for n-and p-type GaAs bulk, epitaxial AlGaAs layers and two different types of laser heterostructure using three different etch masks and three light-emitting diodes as light sources. The experiments show that the LIWE parameters ͑light-source wavelength, mask conductivity, sample layer structure͒ control the sidewall angle and etch rate. The technique successfully produced vertical sidewalls and "on-demand" etch-stop layers in laser heterostructure using sulfuric acid ͑H 2 SO 4 ͒: hydrogen peroxide ͑H 2 O 2 ͒: DI water ͑H 2 O͒ etch system. Wet etching has potential advantages over dry etching, 1-3 including lower cost, smoother surfaces, and larger etch rates. Integrated devices require a variety of etched-sidewall profiles and angles ranging from shallow etched-slopes for electrical contacts to vertical flat smooth surfaces for integrated laser mirrors. Vertical etches must maintain good control of lateral etching to inhibit smoothing of patterned features, prevent undercutting of metal contacts, and to increase the degree of integration for some types of devices including micro-optical-electrical-machines ͑MOEMs͒ with close-fitting moveable parts. 4 The sidewall profiles obtained from wet chemical etching normally depend on the etching solution and the material crystal direction. 5-8 Light-induced wet etching ͑LIWE͒ 9 potentially expands the fabrication options offered by anisotropic dry etching by using light to break the normal crystal-plane etching and thereby provides control over the sidewall profiles with angles ranging from several degrees to 90 degrees while retaining many favorable wetetching properties.The present research investigates the effects of LIWE on sidewall profiles and etch rate for n-and p-type GaAs bulk, epitaxial AlGaAs layers, and two different types of laser heterostructure with three different etch masks. The sidewall angle and etch rate are controlled by the etch condition including wavelength of the light source, electrical property of the mask, and layer structure of the material. The results show that a judicious choice of wavelength during the LIWE of heterostructure can transform a normally etching layer into an etch-stop layer or alter the etched-sidewall angle. The LIWE experiments reported here have successfully etched a vertical sidewall in laser heterostructure material.Photochemical etching has many possible applications such as maskless etching, selective etching, and control of the etched side wall profile. Podlesnik et al. 10 show that laser light increases the etch rate in illuminated regions of the sample. Deep trenches in n-type GaAs and AlGaAs have been fabricated by applying a focused laser beam 10-12 directly to a bulk sample positioned within the etching solution. Van de Ven et al. 13 fabricate square contours on GaAs samples by scanning a laser beam in a square pattern. The technique gives rise to the possibility of maskless etching whereby accurate control of the ...

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Fabricating Vertical Sidewalls in GaAs∕AlGaAs Heterostructure Using Light-Induced Wet Etching

Parker

2006

J. Electrochem. Soc.

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“…The UV-LED LIWE potentially replaces dry etchers such as the electron cyclotron resonant etcher. 1 Both dissolution mechanisms require the GaAs to capture holes from the surrounding environment. For chemical dissolution, the GaAs captures holes from the oxidizing agent 4,5 in the etchant while for photo-dissolution, the GaAs captures holes from light-generated electron-hole pairs in the semiconductor.…”

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“…Integrated optical components, such as mirrors, often use etches several micrometers deep having sidewall angles to within several degrees of vertical and surface roughness variations on the order of tens of nanometers. 1 Dry etching represents one of the most popular methods for vertical anisotropic etching. However, a dry etcher does not generally produce all of the various profiles and has drawbacks of high equipment and operational costs, large size, and low etching rates with little information available on deep anisotropic etching.…”

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Control of Sidewall Angles Using UV LEDs during Wet Etching of GaAs

Thakurdesai

Parker

2004

Electrochem. Solid-State Lett.

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The ultraviolet ͑UV͒ light induced wet etching for micro-optical electromechanical systems applications produces a range of sidewall angles depending on the relative contributions of photo and chemical dissolution. The technique uses recently developed multi-element UV light emitting diodes ͑LEDs͒ that feature broad area coverage and relatively low cost compared with laser-based systems. The UV LED illumination creates sidewall profiles with angles ranging from 55°to 90°by changing the oxidizer content and the light intensity.Etching has become a critical fabrication process for microoptical electromechanical systems ͑MOEMS͒ where etching depth, sidewall angle, and post-etched surface roughness determine the device performance. As the range of MOEMS applications expand to three dimensions, various sidewall angles and deep vertical etching on the order of 100 m can be required for the device structure. Integrated optical components, such as mirrors, often use etches several micrometers deep having sidewall angles to within several degrees of vertical and surface roughness variations on the order of tens of nanometers. 1 Dry etching represents one of the most popular methods for vertical anisotropic etching. However, a dry etcher does not generally produce all of the various profiles and has drawbacks of high equipment and operational costs, large size, and low etching rates with little information available on deep anisotropic etching.We demonstrate a technique for light induced wet etching ͑LIWE͒ that creates sidewall angles in the range 55°to 90°over relatively broad area (ϳ1 cm 2 ). The apparatus incorporates the recently developed multi-element ultraviolet ͑UV͒ light emitting diodes ͑LEDs͒ as the optical source rather than frequency-doubled UV lasers. 2,3 The LIWE technique typically uses lasers to produce vertical via holes. The lasers do not easily provide uniform etching over broad areas. The UV-LED LIWE technique varies the light intensity and oxidizer content to control the relative contributions of two different dissolution mechanisms. We show this combination of mechanisms controls the sidewalls for the case of n-type GaAs etched in a solution of sulfuric acid, hydrogen peroxide and deionized ͑DI͒ water. The UV-LED LIWE potentially replaces dry etchers such as the electron cyclotron resonant etcher. 1 Both dissolution mechanisms require the GaAs to capture holes from the surrounding environment. For chemical dissolution, the GaAs captures holes from the oxidizing agent 4,5 in the etchant while for photo-dissolution, the GaAs captures holes from light-generated electron-hole pairs in the semiconductor. 6,7 Both dissolution mechanisms change surface GaAs to the form ͓HOGaAsOH͔. Then through intermediate steps, the sulfuric acid dissolves the oxidized complex. 4,6,7 This research starts from two different hole-capturing mechanisms. For a profile of (1 10) cleaved plane, the chemical dissolution produces a sidewall angle of 55°with respect to the ͑001͒ plane since the Ga rich ͑111͒ plane is more difficult t...

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“…For the fabrication of many photonic devices [1][2][3][4][5], dry etching is often essential to obtain the precise dimensions and highly anisotropic structural profile [6,7]. Different chemistries, such as CH 4 / H 2 [8][9][10][11][12][13], Cl 2 (with different additives) [14][15][16][17][18], SiCl 4 [19], BCl 3 [20] and N 2 /H 2 [21] have been demonstrated for etching InP.…”

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confidence: 99%