Reactive ion etching. Material selectivity Ion Beam milling @INESC Nordiko 3000 IBD system Etch rates [Å/min] @ 70ºpan 65 W130 W * junctions, spin valves.

Reactive ion etching

Reactive ion etching

Material selectivity

Ion Beam milling @INESCNordiko 3000 IBD system

Etch rates [Å/min] @ 70ºpan

65 W 130 W *

junctions, spin valves ~ 60Al ~ 160Al2O3 ~ 57 SiO2 ~ 170CoZrNb ~ 130Photoresist ~ 55

*PR baked @110ºC, 5 min.

65 W RF grids: +500V, -200V 8 sccm Ar 40% rotation 70º or 40º pan

Ar

Assistgun

Plasma

~20V

Rotating table

sample

Assistgun

Plasma

~20V

Assistgun

Rotating table

sample

Ar ions

+500V-200V

Ar

Assistgun

Plasma

~20V

Rotating table

sample

Assistgun

Plasma

~20V

Assistgun

Rotating table

sample

Rotating table

sample

Ar ions

+500V-200V

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

Etching end-point

• Visual inspection

• Direct measurements: sample electrical resistivity

• Mass spectroscopy – monitor the chamber atmosphere composition during the etching

Starting structure

Easy Axis

1st.Lithography Step

1.5 μm thick photoresist

After Ion Milling and resist strip

750μmx 50μm

Patterning thick and hard materialsDisk head slider machining – reactive ion etching

SF6 etching TiC

CF2 etching Al2O3

Temperature: 40-100ºC

Etch ratio: Resist:AlTiC ~ 5:1 rate: 370-490 Å/min

Surface smoothing: < 250Å

Etch depth 0.5 to 5 m

Al2O3-TiC sliders

Patterning thin films to sub-micron

Courtesy of Ed Murdoch, Seagate

shield

shield

sv

Ins.

Ins.

lead

lead

pm

pm

Hard Magnet

Lead

NM Layer

Hard Magnet

Lead

NM Layer

Free FM Layer

Spacer

Pinned FM Layer

AF Pinning Layer

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