19 research outputs found
Near-field scanning microwave microscope for interline capacitance characterization of nanoelectronics interconnect
We have developed a noncontact method for measurement of the interline
capacitance in Cu/low-k interconnect. It is based on a miniature test vehicle
with net capacitance of a few femto-Farads formed by two 20-\mu m-long parallel
wires (lines) with widths and spacings the same as those of the interconnect
wires of interest. Each line is connected to a small test pad. The vehicle
impedance is measured at 4 GHz by a near-field microwave probe with 10 \mu m
probe size via capacitive coupling of the probe to the vehicle's test pads.
Full 3D finite element modeling at 4 GHz confirms that the microwave radiation
is concentrated between the two wires forming the vehicle. An analytical lumped
element model and a short/open calibration approach have been proposed to
extract the interline capacitance value from the measured data. We have
validated the technique on several test vehicles made with copper and low-k
dielectric on a 300 mm wafer. The vehicles interline spacing ranges from 0.09
to 1 \mu m and a copper line width is 0.15 \mu m. This is the first time a
near-field scanning microwave microscope has been applied to measure the lumped
element impedance of a test vehicle
Microwave Electrodynamics of the Antiferromagnetic Superconductor GdBa_2Cu_3O_{7-\delta}
The temperature dependence of the microwave surface impedance and
conductivity are used to study the pairing symmetry and properties of cuprate
superconductors. However, the superconducting properties can be hidden by the
effects of paramagnetism and antiferromagnetic long-range order in the
cuprates. To address this issue we have investigated the microwave
electrodynamics of GdBa_2Cu_3O_{7-\delta}, a rare-earth cuprate superconductor
which shows long-range ordered antiferromagnetism below T_N=2.2 K, the Neel
temperature of the Gd ion subsystem. We measured the temperature dependence of
the surface resistance and surface reactance of c-axis oriented epitaxial thin
films at 10.4, 14.7 and 17.9 GHz with the parallel plate resonator technique
down to 1.4 K. Both the resistance and the reactance data show an unusual
upturn at low temperature and the resistance presents a strong peak around T_N
mainly due to change in magnetic permeability.Comment: M2S-HTCS-VI Conference Paper, 2 pages, 2 eps figures, using Elsevier
style espcrc2.st
Noncontact electrical metrology of Cu/low-k interconnect for semiconductor production wafers
We have demonstrated a technique capable of in-line measurement of dielectric
constant of low-k interconnect films on patterned wafers utilizing a test key
of ~50x50 \mu m in size. The test key consists of a low-k film backed by a Cu
grid with >50% metal pattern density and <250 nm pitch, which is fully
compatible with the existing dual-damascene interconnect manufacturing
processes. The technique is based on a near-field scanned microwave probe and
is noncontact, noninvasive, and requires no electrical contact to or grounding
of the wafer under test. It yields <0.3% precision and 2% accuracy for the film
dielectric constant
A near-field scanned microwave probe for spatially localized electrical metrology
We have developed a near-field scanned microwave probe with a sampling volume
of approximately 10 micron in diameter, which is the smallest one achieved in
near-field microwave microscopy. This volume is defined to confine close to 100
percent of the probe net sampling reactive energy, thus making the response
virtually independent on the sample properties outside of this region. The
probe is formed by a 4 GHz balanced stripline resonator with a few-micron tip
size. It provides non-contact, non-invasive measurement and is uniquely suited
for spatially localized electrical metrology applications, e.g. on
semiconductor production wafers.Comment: 6 pages, 3 figures, submitted to Appl. Phys. Let
Synchronous Chip-to-Chip Communication with a Multi-Chip Resonator Clock Distribution Network
Superconducting digital circuits are a promising approach to build
packaged-level integrated systems with high energy-efficiency and computational
density. In such systems, performance of the data link between chips mounted on
a multi-chip module (MCM) is a critical driver of performance. In this work we
report a synchronous data link using Reciprocal Quantum Logic (RQL) enabled by
resonant clock distribution on the chip and on the MCM carrier. The simple
physical link has only four Josephson junctions and 3 fJ/bit dissipation,
including a 300 W/W cooling overhead. The driver produces a signal with 35\,GHz
analog bandwidth and connects to a single-ended receiver via 20 Nb
Passive Transmission Line (PTL). To validate this link, we have designed,
fabricated and tested two 3232 mm MCMs with eight 55 mm
chips connected serially and powered with a meander clock, and with four
1010 mm chips powered with a 2 GHz resonant clock. The meander
clock MCM validates performance of the data link components, and achieved 5.4
dB AC bias margin with no degradation relative to individual chip test. The
resonator MCM validates synchronization between chips, with a measured AC bias
margin up to 4.8 dB between two chips. The resonator MCM is capable of powering
circuits of 4 million Josephson junctions across the four chips with a
projected 10 Gbps serial data rate.Comment: 8 pages, 8 figure
Microwave Electrodynamics of Electron-Doped Cuprate Superconductors
We report microwave cavity perturbation measurements of the temperature
dependence of the penetration depth, lambda(T), and conductivity, sigma(T) of
Pr_{2-x}Ce_{x}CuO_{4-delta} (PCCO) crystals, as well as parallel-plate
resonator measurements of lambda(T) in PCCO thin films. Penetration depth
measurements are also presented for a Nd_{2-x}Ce_{x}CuO_{4-delta} (NCCO)
crystal. We find that delta-lambda(T) has a power-law behavior for T<T_c/3, and
conclude that the electron-doped cuprate superconductors have nodes in the
superconducting gap. Furthermore, using the surface impedance, we have derived
the real part of the conductivity, sigma_1(T), below T_c and found a behavior
similar to that observed in hole-doped cuprates.Comment: 4 pages, 4 figures, 1 table. Submitted to Physical Review Letters
revised version: new figures, sample characteristics added to table, general
clarification give
Propagation of Picosecond Pulses on Superconducting Transmission Line Interconnects
Interconnects are a major discriminator for superconducting digital
technology, enabling energy efficient data transfer and high-bandwidth
heterogeneous integration. We report a method to simulate propagation of
picosecond pulses in superconducting passive transmission lines (PTLs). A
frequency-domain propagator model obtained from the Ansys High Frequency
Structure Simulator (HFSS) field solver is incorporated in a Cadence Spectre
circuit model, so that the particular PTL geometry can be simulated in the
time-domain. The Mattis-Bardeen complex conductivity of the superconductor is
encoded in the HFSS field solver as a complex-conductivity insulator.
Experimental and simulation results show that Nb 20 Ohm microstrip PTLs with
1um width can support propagation of a single-flux-quantum pulse up to 7mm and
a double-flux-quantum pulse up to 28mm