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We studied dry etching of AlGaAs and InGaP in a planar inductively coupled BCl3 plasma. The process parameters were planar ICP source power (0–500 W), reactive ion etching (RIE) chuck power (0–150 W), and chamber pressure (5–15 mTorr). The process results were characterized in terms of etch rate, surface morphology, and surface roughness. The planar inductively coupled BCl3 plasmas were also monitored with in situ optical emission spectroscopy (OES). BCl3 planar inductively coupled process (ICP) etching of AlGaAs showed very vertical sidewall, clean and smooth surface, while that of InGaP showed somewhat rough surface after etching. Etch rates of AlGaAs were generally higher than those of InGaP in the planar BCl3 ICP etching. It indicated that InClX byproducts had relatively low volatility during InGaP etching in the planar inductively BCl3 plasmas. Increase of ICP source power and RIE chuck power strongly raised etch rates of both AlGaAs and InGaP. That of pressure decreased etch rate of both materials. OES data showed that emission intensity of the planar BCl3 ICP was a strong function of ICP source power and chamber pressure, while it was almost independent of RIE chuck power.

A parametric study of the etch characteristics of Ga-based (GaAs, GaSb, and AlGaAs) and In-based (InGaP, InP, InAs, and InGaAsP) compound semiconductors in BCl 3 /Ar planar inductively coupled plasmas (ICPs) was performed. The Ga-based materials etched at significantly higher rates, as expected from the higher volatilities of the As, Ga, and Al trichloride, etch products relative to InCl 3 . The ratio of BCl 3 to Ar proved critical in determining the anisotropy of the etching for GaAs and AlGaAs, through its effect on sidewall passivation. The etched features in In-based materials tended to have sloped sidewalls and much rougher surfaces than for GaAs and AlGaAs. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square (RMS) roughness and similar stoichiometry to their unetched control samples, while the surfaces of In-based materials are degraded by the etching. The practical effect of the Ar addition is found to be the ability to operate the ICP source over a broader range of pressures and to still maintain acceptable etch rates.

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Both Ga-based ͑GaAs, AlGaAs͒ and In-based ͑InGaP, InP, InAs, and InGaAsP͒ compound semiconductors were etched in a planar inductively coupled plasma ͑ICP͒ reactor in pure BCl 3 . The Ga-based materials etched at significantly higher rates, as expected from the higher volatilities of their trichloride etch products relative to InCl 3 . In contrast to the more common cylindrical geometry ICP sources, the dc self-bias which controls ion energy is not strongly dependent on source power up to ϳ400 W while etch rates increase rapidly over this power range. The source tunes easily even at very low powers ͑Ͻ100 W͒ but operates inefficiently above ϳ10 mTorr, with a marked decrease in both emission intensity from the discharge and in resulting etch rates of the compound semiconductors. The etched surfaces of both AlGaAs and GaAs have comparable root-mean-square roughness and similar stoichiometry to the unetched control samples, while the surfaces of In-based materials are degraded by the BCl 3 etching.The GaAs/AlGaAs and InP/InGaAsP heterostructures are the basis of most modern compound semiconductor electronic and photonic devices. [1][2][3][4][5] In particular, devices such as high electron mobility transistors ͑HEMTs͒ and heterojunction bipolar transistors ͑HBTs͒ rely on the ability to selectively etch one component of the heterostructure over the other in applications such as microwave power amplifiers and low noise amplifiers. 6-28 Further requirements for this etching are vertical sidewalls and minimal surface disruption. The latter involves both the lattice damage created by ion bombardment and any changes in stoichiometry. High density plasmas have proven attractive for these applications, with the ability to control both ion density and ion energy. [8][9][10][11][12][13] A key point that emerged from past studies with both electron cyclotron resonance ͑ECR͒ and cylindrical geometry inductively coupled plasma ͑ICP͒ etching of these heterostructures is that significant damage can be created even at moderate source powers ͑300-500 W͒, 12,16,18 so it is essential to develop high density sources that can operate efficiently over a broad range of powers and be usable over a continuous range of conditions. Our initial experience with planar ICP sources is that they are continuously tunable at low powers ͑0-200 W͒ and therefore offer a versatile range of operating conditions for applications from through-wafer vias to low damage mesa formation.In this paper we describe the results of etching GaAs, AlGaAs, InP, InGaP, InAs, and InGaAsP in a planar ICP tool with a single BCl 3 chemistry. The system appears well suited to patterning of GaAs/AlGaAs at room temperature, producing clean, vertical profiles. ExperimentalGaAs, InP, and InAs wafers were cut from Czochralski-grown boules and were nominally undoped with ͑100͒ orientation in all cases. The In 0.5 Ga 0.5 P and Al 0.2 Ga 0.8 As were grown lattice-matched to GaAs substrates by either metalorganic molecular beam epitaxy ͑MOMBE͒ or metalorganic chemical vapor deposition ͑...