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ABSTRACT: We present a method for noncontact, noninvasive measurements of dielectric
constant, k, of 100-nm- to 1.5-\mu m-thick blanket low-k interconnect films on
up to 300 mm in diameter wafers. The method has about 10 micron sampling spot
size, and provides <0.3% precision and <2% accuracy for k-value. It is based on
a microfabricated near-field scanned microwave probe formed by a 4 GHz parallel
strip transmission line resonator tapered down to a few-micron tip size.
08/2011;
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ABSTRACT: 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.
08/2011;
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ABSTRACT: Near-field scanning microwave microscopy is employed for quantitative imaging at 4 GHz of the local impedance for monolayer and few-layer graphene. The microwave response of graphene is found to be thickness dependent and determined by the local sheet resistance of the graphene flake. Calibration of the measurement system and knowledge of the probe geometry allows evaluation of the AC impedance for monolayer and few-layer graphene, which is found to be predominantly active. The use of localized evanescent electromagnetic field in our experiment provides a promising tool for investigations of plasma waves in graphene with wave numbers determined by the spatial spectrum of the near-field. By using near-field microwave microscopy one can perform simultaneous imaging of location, geometry, thickness, and distribution of electrical properties of graphene without a need for device fabrication.
ACS Nano 07/2010; 4(7):3831-8. · 10.77 Impact Factor
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ABSTRACT: We have experimentally verified a recently proposed theoretical model for near-field microwave microscopy of multilayer media. The model addresses a near-field microwave probe as an electrically small antenna with a Gaussian-like current distribution that has a single characteristic length scale on the order of the probe size. Electrodynamic response of an antenna is calculated using Green functions in the form of integral transforms for electric and magnetic fields (both quasistatic and propagating), which are generated by a pointlike dipole. Experimental data were obtained at 4 GHz using a near-field scanning microwave microscope with aperture size of approximately 5 microm for a set of six SiO(2) films with thickness ranging from 0.1 to 1.5 microm. For each sample the probe resonant frequency was both measured and simulated as a function of the tip-sample distance, and good agreement between the theory and experimental data was observed. It was found that the model is capable of determining thin film dielectric constant with accuracy of approximately 5%-7%.
The Review of scientific instruments 12/2008; 79(11):113708. · 1.52 Impact Factor
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ABSTRACT: 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 ∼50×50 μ m <sup>2</sup> in size. The test key consists of a low- k film backed by a Cu grid with ≫50% metal pattern density and ≪0.25 μ m 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.
Applied Physics Letters 07/2006; · 3.84 Impact Factor
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01/2006: pages 207-245;
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ABSTRACT: 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. Lett
11/2005;
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ABSTRACT: We have developed a novel microwave near-field scanning probe technique for non-contact measurement of the dielectric constant of low-k films. The technique is non-destructive, noninvasive and can be used on both porous and non-porous dielectrics without any sample preparation. The probe has a few-micron spot size, which makes the technique well suited for real time low-k metrology on production wafers. For dielectrics with k<4 the precision and accuracy are better than 2% and 5%, respectively. Results for both SOD and CVD low-k films are presented and show excellent correlation with Hg-probe measurements. Results for k-value mapping on blanket 200mm wafers are presented as well.
MRS Proceedings. 12/2003; 812.
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ABSTRACT: We have developed a novel scanning near-field microwave probe capable of precise quantitative measurements of dielectric constant of thin dielectric films. The technique is noncontact and has a few-micron sampling spot-size. For dielectric films with k<7 and thickness down to 200 nm the probe provides precision and accuracy better than 1% and 5%, respectively. The probe is based on a balanced parallel-plate microwave transmission line operating at 4 GHz. Unlike the apertureless STM- or AFM-based schemes that have been previously employed, our “apertured” approach allows for truly quantitative measurements on a few-micron length scale with result that is insensitive to the material property outside this probing volume.We will present quantitative measurements on a variety of so-called low-k dielectric films, which are of great interest to the semiconductor industry as replacements for SiO2 in interconnect wiring. When the probe is placed in close proximity to the film under test its fringe capacitance is governed by the sample permittivity, the tip geometry, and the tip-sample separation. We measure this capacitance with a resolution down to 30 zF using a microwave resonator. Extraction of the film dielectric constant is based on an original approach providing for removal of the substrate contribution. Bulk Si and a set of variable thickness thermal oxide films are employed to calibrate the probe. There is no need to know the absolute value of the tip-sample separation for either measurement or calibration procedures; this separation must only be kept nominally the same for both measurements, which is achieved by a virtually material independent shear-force distance control.
MRS Proceedings. 12/2003; 838.
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ABSTRACT: The near-field scanning microwave microscope has become a popular instrument to quantitatively image high-frequency properties of metals and dielectrics on length scales far shorter than the wavelength of the radiation. We have developed several new ways to operate this microscope to dramatically improve its spatial resolution and material property sensitivity. These include a novel distance-following method that takes advantage of the stability of a synthesized microwave source to improve the signal-to-noise ratio of our earlier frequency-following imaging technique. We also discuss novel height-modulated imaging techniques, culminating in a new tapping-mode method, which makes a 14 dB improvement in sensitivity, a 17.5 dB improvement in signal-to-noise ratio, and a factor of 2.3 improvement in spatial resolution compared to distance-following imaging. © 2003 American Institute of Physics.
Review of Scientific Instruments 05/2003; 74(6):3167-3170. · 1.37 Impact Factor
