ITC irst

Trento, Italy
Trento, Italy
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Calvo M.,University of Rome La Sapienza | Calvo M.,National Institute of Nuclear Physics, Italy | Giordano C.,University of Rome La Sapienza | Giordano C.,National Institute of Nuclear Physics, Italy | And 8 more authors.
EAS Publications Series | Year: 2010

Large millimetric and submillimetric telescopes can play a crucial role in our understanding of the Universe, allowing the direct measurement of early galaxies or the investigation of the earliest stages of star formation. The B modes of CMB polarization are a direct probe of the Inflationary epoch and their measurement promises to provide information on the scale of energies at which the process took place. For these investigations (and many others), large detectors arrays with thousands of pixels are needed, to achieve high mapping speeds. This is especially true in the case of mm and sub/mm observations from extremely cold and dry locations like Dome-C, where ultra-low temperature detectors, reaching photon noise limited performance, are needed to fully exploit the excellent quality of the site. In this paper we present the working principle of the Microwave Kinetic Inductance Detectors and their status of development in Italy, focusing on the key aspects that make them ideal for large arrays of sensors. © 2010 EAS, EDP Sciences.

Kuo M.-S.,University of Maryland University College | Hua X.,University of Maryland University College | Oehrlein G.S.,University of Maryland University College | Ali A.,Texas Instruments | And 3 more authors.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010

The authors evaluated photoresist (PR) stripping processes that are compatible with ultralow dielectric constant (ULK) materials using H2 -based remote plasmas generated in an inductively coupled plasma reactor. The materials used were 193 nm PR and nanoporous SiCOH-based ULK (JSR LKD 5109). PR ashing rates and ULK damage (carbon depletion) were measured for H2, H2 / N2, and H2 /Ar discharges as a function of substrate temperature over the range of 200-275 °C. They employed ellipsometry, x-ray photoelectron spectroscopy (XPS), optical emission spectroscopy, and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) for analysis. For their H2 remote plasmas and a substrate temperature in the range of 200-275 °C, the PR ashing rate varied from 270 to 880 nm/min, whereas 3-5 nm of ULK damage was measured for 20 s remote plasma exposure. As a useful process metric, they defined ashing efficiency as the thickness of PR removed over the thickness of ULK simultaneously damaged. PR stripping processes can be optimized to an ashing efficiency of ∼60 for substrate temperatures above 250 °C, if pure H2 discharges are employed. The addition of N2 or Ar to H2 did not improve the ashing rate and, especially for N2, such additions dramatically increased ULK damage. This resulted in reduced ashing efficiency for these cases. To clarify the impact of etching/ashing process interactions on ULK modification, they exposed blanket ULK film to C4 F8 /Ar -based etching plasmas employing a dual frequency (40.68/4 MHz) capacitively coupled plasma (CCP) reactor. Plasma exposures of the ULK were performed utilizing a silicon roof, which shielded the ULK film located underneath from direct ion bombardment. Since the aspect ratio of the small gap structure was selected to be equal to that of an actual trench structure, trench sidewall-like surface modifications induced by etching processes along with their impact on ashing damage that were introduced during a subsequent PR stripping process can be simulated and studied on blanket films with appropriate size. XPS revealed fluorocarbon (FC) deposition together with ∼3 nm of ULK damage on the ULK film surface after the FC plasma etching process. Most of the deposited FC material was removed during a subsequent H2 -based remote plasma treatment at 275 °C. The influence of surface modifications introduced by the prior C4 F8 /Ar -based etching exposure on hydrogen permeation of the ULK material during a subsequent H2 remote plasma ashing process was studied by substituting deuterium (D2) for H2 in the remote plasma process and performing ToF-SIMS analysis. ToF-SIMS depth profiling of ULK films exposed to D2 plasma showed reduced D permeation in the ULK films with C4 F8 /Ar etching plasma exposure relative to that without such FC plasma exposure. Photoresist patterned ULK structures were also processed, employing the same ashing conditions after prior FC plasma etching in the CCP reactor. The ULK damage results measured with trench structures were consistent with the above findings obtained with blanket ULK films. © 2010 American Vacuum Society.

Kuo M.-S.,University of Maryland University College | Pal A.R.,University of Maryland University College | Oehrlein G.S.,University of Maryland University College | Lazzeri P.,ITC irst | Anderle M.,ITC irst
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics | Year: 2010

In situ photoresist (PR) ashing processes are attractive because of the ease of process integration with plasma etching processes. The authors have examined the performance of carbon dioxide (CO2) as a source gas for in situ PR ashing processes compatible with ultralow k (ULK) materials and compared it with the results obtained using O2. They performed measurements of 193 nm PR ashing rates in a dual frequency capacitively coupled plasma reactor. The damage to porous ULK feature sidewalls was simulated by exposing blanket ULK films in a non-line-of-sight fashion in a small gap structure to the plasma-generated reactants. The pressure for the in situ ashing processes was varied from 10 to 100 mTorr, and the self-bias voltages ranged from floating potential to ∼-400 V. To increase line-of-sight etching of PR by inert ion bombardment, Ar/CO2 mixtures with up to 75% Ar were investigated. The ULK material modifications were analyzed by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Plasma-damage of the ULK material primarily is detected as the removal of carbon from the SiCOH ULK films. To compare the performance of different ashing processes for PR stripping from ULK material, the authors introduced an ashing efficiency (AE) parameter which is defined as the thickness of PR removed over the thickness of ULK simultaneously damaged, and can be considered a process figure of merit. AE with CO2 was about three times greater than AE with O2 for the same process conditions. When a 75% Ar/CO2 gas mixture was used and a-100 V substrate bias was applied during PR ashing, a PR ashing rate of 200 nm/min could be achieved for a 10 mTorr Ar/CO2 plasma. For this process, the measured AE was 230, more than 10× greater than AE achieved with O2 discharges using the same conditions. The authors found that ULK damage showed a direct dependence on the atomic oxygen densities of both CO2 and O 2 discharges which was characterized by optical emission of discharges. The question whether in-diffusion of carbon species from CO 2 discharges into ULK material was significant was also examined. For this the authors substituted 13CO2 for 12CO2 and performed ToF-SIMS analysis of the exposed ULK films. No significant amount of 13C from 13CO2 plasmas was detected either on the surface or in the bulk of the 13CO2 plasma-exposed ULK. © 2010 American Vacuum Society.

De Luca G.,University of Pisa | Bisogni M.G.,University of Pisa | Collazuol G.,University of Padua | Argentieri A.,Polytechnic of Bari | And 4 more authors.
IEEE Nuclear Science Symposium Conference Record | Year: 2012

Time Of Flight PET is a promising technique that can improve the image quality of a PET scanner. A TOF PET detector must be designed by optimizing its energy and time resolution. Present study aims to assess the overall performances of a detector composed by LSO:Ce,Ca crystal coupled with SiPM, connected to a transimpedence amplifier. Simulation and measurements have been performed focusing on the influence of the Ca codoping concentration in the detector energy and time resolution. © 2011 IEEE.

Type: Journal Article | Journal: Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2011

This work reports on (i) the gas barrier properties of a-C:H films rf-sputtered in Ar-H(2) plasmas from a graphite target on polyethylene terephthalate (PET) and (ii) the influence of the film chemical structure and defect properties on the gas permeability. The intrinsic permeabilities of the films to He, CO(2), O(2), N(2) gases and H(2)O vapour were determined and found to be orders of magnitude lower than that of the bare PET. Indirect evidence was given to a solubility-diffusion process as the more probable permeation mechanism, over a gas flow through microdefects or gas transport through nanodefects by a Knudsen diffusion mechanism. The barrier capability of the films was found to scale as the gas molecular diameter within the He, CO(2), O(2) and N(2) series, and inversely with the gas critical temperature for the CO(2), O(2), N(2) and H(2)O series. A correlation between the film Urbach energy, E(u), and the gas permeability was established, except for H(2)O. Such findings further favour a bulk diffusion contributing mechanism to permeation over the gas state transport. Conversely, this E(u)-permeability relation shed more light on the origin of the valence band tailing of the amorphous carbon electron structure.

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