Precise in situ etch depth control of multilayered III-V semiconductor samples with reflectance anisotropy spectroscopy (RAS) equipment (original) (raw)
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Monitoring of (reactive) ion etching (RIE) with reflectance anisotropy spectroscopy (RAS) equipment
Applied Surface Science, 2015
A measurement technique, i.e. reflectance anisotropy/difference spectroscopy (RAS/RDS), which had originally been developed for in-situ epitaxial growth control, is employed here for in-situ real-time etch-depth control during reactive ion etching (RIE) of cubic crystalline III/V semiconductor samples. Temporal optical Fabry-Perot oscillations of the genuine RAS signal (or of the average reflectivity) during etching due to the ever shrinking layer thicknesses are used to monitor the current etch depth. This way the achievable in-situ etch-depth resolution has been around 15 nm. To improve etch-depth control even further, i.e. down to below 5 nm, we now use the optical equivalent of a mechanical vernier scale-by employing Fabry-Perot oscillations at two different wavelengths or photon energies of the RAS measurement light-5% apart, which gives a vernier scale resolution of 5%. For the AlGaAs(Sb) material system a 5 nm resolution is an improvement by a factor of 3 and amounts to a precision in in-situ etch-depth control of around 8 lattice constants.
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.
Photoelectrochemical etching of compound semiconductors: Wavelength dependence
Applied Physics A Solids and Surfaces, 1985
Argon-ion-laser photoetching was performed at various wavelengths, around the absorption edge of ZnSe and CdS. The surface etch pit density is observed to decrease with increasing penetration depth of the light. This observation is explained in terms of the recent theory of non-uniform charge flow within semiconductor junctions.
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Controlled Etching of III-V Materials with Optical Emission Interferometry (OEI)
ECS transactions, 2011
For plasma etching processes, Optical Emission Interferometry (OEI) combines the advantages of Optical Emission Spectroscopy (OES) and laser interferometry. Radiation emitted by the plasma is reflected from the substrate surface and monitored using a multiwavelength spectrometer. Analysis of the OEI signal can provide endpoint data, as well as etch rate and etch depth information for both single and multi-component materials. Examples of these applications are described.
Advanced Engineering Materials, 2017
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New dry-etch chemistries for III–V semiconductors
Materials Science and Engineering: B, 1994
For some dry etching applications in IlI-V semiconductors, such as via hole formation in InP substrates, the currently used plasma chemistries have etch rates that are up to a factor of 30 too slow. We report on the development of 3 new classes of discharge chemistries, namely C1 2 /CH 4 /H 2 /Ar at 150 0 C (yielding InP etch rates of >1 gm • min-I at 1 mTorr and-80V dc), HBr/H 2 for selective etching of InGaAs over AlInAs, and iodine-based plasmas (HI/H 2 , CH 3 I/H 2) that offer rapid anisotropic etching of all III-V materials at room temperature. In all cases, Electron Cyclotron Resonance sources (either multipolar or magnetic mirror) with additional rf biasing of the sample position are utilized to obtain low damage pattern transfer processes that generally use metal contacts on device structures as self-aligned etch masks. The temperature dependence of etch rates with these new chemistries display non-Arrhenius behavior in the range 50-250°C and a detailed study of the phenomenon are reported. Electrical, optical and chemical analysis of the etched surfaces show that it is possible to achieve essentially damage-free pattern transfer.
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We present epi-diffraction phase microscopy (epi-DPM) as a non-destructive optical method for monitoring semiconductor fabrication processes in real time and with nanometer level sensitivity. The method uses a compact Mach-Zehnder interferometer to recover quantitative amplitude and phase maps of the field reflected by the sample. The low temporal noise of 0.6 nm per pixel at 8.93 frames per second enabled us to collect a three-dimensional movie showing the dynamics of wet etching and thereby accurately quantify non-uniformities in the etch rate both across the sample and over time. By displaying a gray-scale digital image on the sample with a computer projector, we performed photochemical etching to define arrays of microlenses while simultaneously monitoring their etch profiles with epi-DPM.