Y. B. Hahn

Relative merits of Cl2 and CO/NH3 plasma chemistries for dry etching of magnetic random access memory device elements

A typical magnetic random access memory stack consists of NiFe/Cu/NiFeCo multilayers, sandwiched by contact and antioxidation layers. For patterning of submicron features without redeposition on the sidewalls, it is desirable to develop plasma etch processes with a significant chlorinated etch component in addition to simple physical sputtering. Under conventional reactive ion etch conditions with Cl2-based plasmas, the magnetic layers do not etch because of the relatively involatile nature of the chlorinated reaction products. However, in high ion density plasmas, such as inductively coupled plasma, etch rates for NiFe and NiFeCo up to ∼700 A min−1 are achievable. The main disadvantage of the process is residual chlorine on the feature sidewalls, which can lead to corrosion. We have explored several options for avoiding this problem, including use of in situ and ex situ cleaning processes after the Cl2-etching, or by use of a noncorrosive plasma chemistry, namely CO/NH3. In the former case, removal of th...

Reactive ion beam etching of GaAs and related compounds in an inductively coupled plasma of Cl2–Ar mixture

Reactive ion beam etching (RD3E) of GaAs, GaP, AIGaAs and GaSb was performed in a Cl2-Ar mixture using an Inductively Coupled Plasma (ICP) source. `The etch rates and yields were strongly affected by ion energy and substrate temperature. The RJBE was dominated by ion-assisted etching at <600 eV and by physical sputtering beyond 600 eV. The temperature dependence of the etch rates revealed three different regimes, depending on the substrate temperature: 1) sputtering-etch limited, 2) products-resorption limited, and 3) mass-transfer limited regions. GaSb showed the overall highest etch rates, while GaAs and AIGaAs were etched at the same rates. The etched features showed extremely smooth morphologies with anisotropic sidewalls.

Cl2-based inductively coupled plasma etching of CoFeB, CoSm, CoZr and FeMn

Abstract Thin films of CoFeB, CoSm, CoZr and FeMn have been etched in inductively coupled plasma Cl 2 discharges with He, Ar or Xe as the inert gas additive as an additional physical component to the etch process. The etch rates decrease with pressure and go through maxima with rf chuck power and discharge composition. There is a transition from net deposition to etching with increasing source power and rf chuck power, consistent with the need to provide sufficient ion energy and ion/neutral flux ratio to achieve efficient etching of magnetic materials.

Comparison of ICl- and IBr-Based Plasma Chemistries for Inductively Coupled Plasma Etching of GaN, InN and AlN

A parametric study of the etch characteristics of GaN, AIN and InN has been earned out with IC1/Ar and IBr/Ar chemistries in an Inductively Coupled Plasma discharge. The etch rates of InN and AIN were relatively independent of plasma composition, while GaN showed increased etch rates with interhalogen concentration. Etch rates for all materials increased with increasing rf chuck power, indicating that higher ion bombardment energies are more efficient in enhancing sputter resorption of etch products. The etch rates increased for source powers up to 500 W and remained relatively thereafter for all materials, while GaN and InN showed maximum etch rates with increasing pressure. The etched GaN showed extremely smooth surfaces, which were somewhat better with IBr/Ar than with IC1/Ar. Maximum selectivities of- 14 for InN over GaN and >25 for InN over AIN were obtained with both chemistries.

Inductively coupled plasma etching of CoFeB, CoZr, CoSm and FeMn thin films in interhalogen mixtures

Abstract Two new plasma chemistries (ICl and IBr) have been employed for patterning of CoFeB, CoZr, CoSm and FeMn thin films for application in magnetic memories. The interhalogen mixtures produced faster etch rates for FeMn, CoSm, and CoZr in both chemistries compared to Cl 2 plasmas under the same conditions. The etch rates are a strong function of discharge composition, pressure, ion flux and ion energy. The data are consistent with an ion-assisted desorption mechanism for the metal chloride etch products. No effect on magnetic properties of etched CoSm was detectable under our conditions.

Interhalogen plasma chemistries for dry etch patterning of Ni, Fe, NiFe and NiFeCo thin films

Abstract ICl/Ar and IBr/Ar plasmas operated in an inductively coupled plasma (ICP) source have been examined for dry etching of Ni, Fe, NiFe and NiFeCo. The removal of the Fe etch products limits the etch rates under most conditions, but rates of ∼500 A min−1 are obtained for both NiFe and NiFeCo in both chemistries. The etched surfaces are smooth (atomic force microscopy root-mean-square roughness

Selective dry etching using inductively coupled plasmas: Part I. GaAs/AlGaAs and GaAs/InGaP

Abstract Selective etching of GaAs over AlGaAs and InGaP was examined in different plasma chemistries (BCl3/SF6, BCl3/NF3, IBr, ICl, BI3, and BBr3) in a high density plasma reactor. The normal etch stop reactions involving formation of involatile AlF3, InF3, or InCl3 are found to be less effective under high density conditions because of the higher ion-assisted etch product desorption efficiency. Addition of SF6 to BCl3 produces higher selectivities than NF3 as an additive, while IBr, ICl and BBr3 are essentially non-selective for both heterostructure systems. Selective etching of InGaP over GaAs is achieved using the BI3 chemistry.

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries. Part I: GaAs, GaSb, and AlGaAs

High-density plasma etching of GaAs, GaSb, and AlGaAs was performed inICl/Ar and IBr/Ar chemistries using an Inductively Coupled Plasma (ICP)source. GaSb and AlGaAs showed maxima in their etch rates for both plamachemistries as a function of interhalogen percentage, while GaAs showedincreased etch rates with plasma composition in both chemistries. Etchrates of all materials increased substantially with increasing rf chuckpower, but rapidly decreased with chamber pressure. Selectivities >10 forGaAs and GaSb over AlGaAs were obtained in both chemistries. The etchedsurfaces of GaAs showed smooth morphology, which were somewhat better withICl/Ar than with IBr/Ar discharge. Auger Electron Spectroscopy analysisrevealed equirate of removal of group III and V components or thecorresponding etch products, maintaining the stoichiometry of the etchedsurface.

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries. Part II: InP, InSb, InGaP, and InGaAs

A parametric study of Inductively Coupled Plasma (ICP) etching of InP, InSb, InGaP, and InGaAs has been carried out in ICl/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 for InP, 3.6 for InSb, 2.3 for InGaP, and 2.2 μm/min for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: The etch rates increased substantially with increasing ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than ICl/Ar, but the etched surface morphologies were fairly poor for both chemistries.

Dry Etching to form Submicron Features in CMR Oxides: (Pr,Ba,Ca)MnO 3 and (La,Sr)MnO 3

Effective pattern transfer into (Pr,Ba,Ca)MnO 3 and (La,Sr)MnO 3 has been achieved using Cl 2 /Ar discharges operated under Inductively Coupled Plasma conditions. Etch rates up to 900 A-min −1 for (La,Sr)MnO 3 and 300 A-min −1 for (Pr,Ba,Ca)MnO 3 were obtained, with these rates being a strong function of ion flux, ion energy and ion-to-neutral ratio. The etching is still physically-dominated under all conditions, leading to significant surface smoothing on initially rough samples. Sub-micron (0.35 μm) features have been produced in both materials using SiN x as the mask.