Transcript Etch rates [Å/min]

Reactive ion etching
Reactive ion etching
Material selectivity
Ion Beam milling @INESC
Rotating
table
Ar
Assist
Assist
gun
gun
Plasma
Ar ions
~20V
+500V
sample
-200V
Nordiko 3000 IBD system
65 W RF
grids: +500V, -200V
8 sccm Ar
40% rotation
Etch rates [Å/min]
junctions, spin valves
Al
Al2O3
SiO2
CoZrNb
Photoresist
*PR baked @110ºC, 5 min.
@ 70ºpan
65 W
~ 60
130 W *
~ 160
~ 57
~ 170
~ 130
~ 55
70º or 40º pan
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
Easy Axis
1.5 μm thick photoresist
750μm x 50μm
• Visual inspection
Starting structure
1st. Lithography Step
After Ion Milling and
resist strip
•
Direct measurements: sample electrical resistivity
•
Mass spectroscopy – monitor the chamber atmosphere
composition during the etching
Patterning thick and hard materials
Disk head slider machining – reactive ion etching
Al2O3-TiC sliders
SF6

etching TiC
CF2  etching Al2O3
Temperature: 40-100ºC
Etch ratio: Resist:AlTiC ~ 5:1
Surface smoothing: < 250Å
Etch depth 0.5 to 5 mm
rate: 370-490 Å/min
Patterning thin films to sub-micron
lead
pm
shield
Ins.
sv
lead
Lead
Hard Magnet
Free FM Layer
Lead
Spacer
Hard Magnet
Pinned FM Layer
NM Layer
AF Pinning Layer
NM Layer
Ins.
shield
pm
Courtesy of Ed Murdoch, Seagate
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