Atomic layer sensitive in-situ plasma etch depth control with reflectance anisotropy spectroscopy (RAS)

Doering, Christoph; Kleinschmidt, Ann-Kathrin; Barzen, Lars; Strassner, Johannes; Fouckhardt, Henning

doi:10.1117/12.2269708

Cited by 2 publications

(2 citation statements)

References 35 publications

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“…This way the RIE-RAS signals and signal transients have been meaningful and we have achieved an accuracy in in situ etch-depth control of 16 nm. (In cases with low etch rates (below ≈75 nm/min) we have even resolved monolayer etch ablation [39].) The details of the RIE-RAS principle and of its experimental results during film-waveguide etching are given elsewhere [28,38].…”

Section: Technological Workmentioning

confidence: 99%

“…In order to have an in situ (real-time) etch-depth control with this demanding accuracy we have successfully employed an adequate measurement techniques, by transferring the concept of reflectance anisotropy spectroscopy (RAS), which is well-known from epitaxy for growth control by now [29][30][31][32][33][34][35], to reactive ion etching (RIE) of monocrystalline semiconductor layer sequences [36][37][38][39]. We have used argon as the plasma gas and 2 volume-% of chlorine as the reactive gas.…”

Section: Technological Workmentioning

confidence: 99%

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Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

Fouckhardt

Kleinschmidt

Strassner

et al. 2017

Advances in OptoElectronics

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Previously we focused on fundamental transverse mode selection (TMS#0) of broad area semiconductor lasers (BALs) with two-arm folded integrated resonators for Fourier-optical spatial frequency filtering. The resonator had a round-trip length of 4f, where f is the focal length of the Fourier-transform element (FTE), that is, a cylindrical mirror in-between the orthogonal resonator branches. This 4f set-up can be called "retracted once" due to the reflective filter after 2f ; that is, the 2f path was used forwards and backwards. Now the branches are retracted once more resulting in a compact 1f long linear resonator (called "retracted twice") with a roundtrip length of 2f. One facet accommodates the filter, while the other houses the FTE, now incorporating a film-waveguide lens. The BAL facet with the filter represents both the Fourier-transform plane (after 2f, i.e., one round-trip) as well as the image plane (after 4f, two round-trips). Thus filtering is performed even after 4f, not just after 2f. Experimental results reveal good fundamental TMS for pump currents up to 20% above threshold and a one-dimensional beam quality parameter 2 1D = 1.47. The BALs are made from AlGaInAsSb, but the concept can equally well be employed for BALs of any material system.

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Section: Technological Workmentioning

confidence: 99%

Section: Technological Workmentioning

confidence: 99%

Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

Fouckhardt

Kleinschmidt

Strassner

et al. 2017

Advances in OptoElectronics

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In-situ etch-depth control better than 5 nm with reflectance anisotropy spectroscopy (RAS) equipment during reactive ion etching (RIE): A technical RAS application

Doering¹,

Strassner²,

Fouckhardt³

2019

AIP Advances

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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.

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Atomic layer sensitive in-situ plasma etch depth control with reflectance anisotropy spectroscopy (RAS)

Cited by 2 publications

References 35 publications

Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

Fundamental Transverse Mode Selection (TMS#0) of Broad Area Semiconductor Lasers with Integrated Twice-Retracted 4f Set-Up and Film-Waveguide Lens

In-situ etch-depth control better than 5 nm with reflectance anisotropy spectroscopy (RAS) equipment during reactive ion etching (RIE): A technical RAS application

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