Three - University of Arkansas Physics Department

Fabrication techniques and electrical properties of YBazCuO7-x multilayers with
rf sputtered amorphous SiOr interlayers
4. Afonso, aK. Y. Chen, aQ. Xiong, aF. T: Chan, aG. J. Salamo, bJ: W. Cooksey, bS. Scott, bS. Ang,
bW. D. Brown, andbL. W. Schaper.
aDepartment of Physics and bDepartment of Electrical EnginneeringIHigh Density Electronics
Center, University of Arkansas, Fayetteville, AR 72701, USA
We have successfully fabricated YBazCus07.1NSZISi02/YSZrYB~C~s07.x multilayer
structures on single crystal LaAlOs (loo), substrates. The YBazCus01.~(Yl3CO) layers were
deposited using pulsed laser ablation (PLD), the biaxiaUy aligned YSZ ( 250 nm thick) layers
were deposited using ion beam assisted PLD (IBAD-PLD), and an amorphous SiOz (1-2w) layer
fabricated via rf sputtering was sandwiched between the YSZ layers. Fabrication techniques and
characterization results are reported for patterned layers in this work.
1. INTRODUCTION
For high temperature superconductor
multichip module(HTS-MCM) applications
the basic building block is the HTSAnsulator
(thickness >lpm)/HTS structure. A HTS-
MCM can be defined as a miniaturized
version of a multilayered printed wiring
board with superconducting interconnects.
Previously such a HTS-MCM protot~e
using a YBCOISrTiOs(500nm)/YBCO has
been successfully fabricated by Bums et a1
[I]. Recently the use of ion beam assisted
deposition to deposit biaxially aligned YSZ
buffer layers on polycrystalline or
amorphous substrates allowed for good
quality YBCO films on these substrates [2-51.
Reade et a1 [6] were able to demonstrate
using the ion beam assisted pulsed
deposition @BAD-PLD) technique that it was
possible to fabricate the YBCOIYSZlamorphousYSZ(5pm)NSZM3CO
multilayers
on oriented YSZ substrates with the top
YBCO Tc - 87 K. They also fabricated the
same structure using amorphous SiOz, but
cracks in the top YBCO layer did not permit
electrical measurements of the top layer.
The main advantage of Si03 ~EJ ih low
dielectric constant (- 3.89), which makes it
an ideal insulator material for MCMe.
In this paper we briefly describe the
method to fabricate and the results obtained
from the characterization of the YBCOfYSZ-
/Si02/YSZM3CO multilayers.
2. EXPERIMENTS
The first YBCO layer (300nm thick) was
fabricated by pulsed laser deposition using
standard conditions. &r patterning, part
of the pads were masked to allow for
transport measurements later. Next a 250
nm thick YSZ layer was deposited via IBAD
PLD using conditions described in 151. After
this a 1-2 pn thick SiOz layer was deposited
by reactively sputtering a Si target in
oxygen ambient (the details of this process
are described in 141). Following the SiOn
deposition another 250 nm thick biaxially
aligned YSZ bufferlcapping layer was
deposited via IBAD PLD. Finally the masks
were taken off and the top YBCO was
deposited using the same conditions as the
first YBCO except that the deposition
temperature was kept - 20-30" lower. For
the first set of multilayers the top YBCO
layer was patterned intm bridges over the
underlying bridge patterns but shifted a
little to the side so that the top bridge goes
over step edges. The patterning was carried
out by using photolithography and ion
milling. For the second set of multilayers
the top YBCO layer was patterned into
092 14534/97/$17.00 0 Elsevier Science 8.V A11 rights reserved
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