1. Reactive ion etching

2. Material selectivity

3. Ion Beam milling @INESC Nordiko 3000 IBD system Etch rates [Å/min] @ 70ºpan 65 W130 W * junctions, spin valves ~ 60 Al ~ 160 Al 2 O 3 ~ 57 SiO 2 ~ 170 CoZrNb~ 130 Photoresist~ 55 * PR baked @110ºC, 5 min. 65 W RF grids: +500V, -200V 8 sccm Ar 40% rotation 70º or 40º pan

4. Challenges in Dry etching Damage by surface charging Feature size control within a wafer Etch rate of a material depends on the surface area of the etchable material but a large unmasked area exposed to the beam consumes more etch species than a single trench – local modulation of the plasma chemistry. Etch rate of a material depends on the ratio feature size : feature depth Aspect ratio dependent etch rate

5. Etching end-point Visual inspection Direct measurements: sample electrical resistivity Mass spectroscopy – monitor the chamber atmosphere composition during the etching

6. Patterning thick and hard materials Disk head slider machining – reactive ion etching SF 6  etching TiC CF 2  etching Al 2 O 3 Temperature: 40-100ºC Etch ratio: Resist:AlTiC ~ 5:1 rate: 370-490 Å/min Surface smoothing: < 250Å Etch depth 0.5 to 5  m Al 2 O 3 -TiC sliders

7. Patterning thin films to sub-micron Courtesy of Ed Murdoch, Seagate shield sv Ins. lead pm

8. Bibliography - VLSI Technology, S.M.Sze, McGraw-Hill International Editions - Nanoelectronics and information technology – Advanced Electronic Materials and Novel Devices, Rainer Waser (Ed.), Wiley-VCH (2003) - Fundamentals of Microfabrication – The science of miniaturization, Marc J.Madou, CRC press (2002) - “Lift-off techniques for fine line metal patterning”, J.M.Frary and P.Seese, SEMICONDUCTOR INTERNATIONAL, pp.72-88 (December 1981) - “Ion etching for pattern delineation”, C.M.Melliar-Smith, J.Vac.Sci.Technol., Vol.13 (5), pp.1008-1022 (September 1976) - “Ion Beam Etching”, R.R.Puckett, S.L.Michel and W.E.Hughes, Thin Film Processes II, Chapt.V-2, Academic Press. Inc. (1991) - “Etch rates for Micromachining processing”, K.R.Williams and R.S.Muller, J.Microelectromechanical Systems, Vol.5 (4), pp.256-269 (December 1996) - “Reactive Ion etching of alumina/TiC substrates”, US Pattent nº 6,001,268 (IBM Corporation), 1997