High-Tc bolometers with silicon-nitride spiderwebsuspension for far-infrared detection

High-Tc GdBa2Cu3O7-δ (GBCO) superconducting transition edge bolometers with operating temperatures near 90 K have been made with both closed silicon-nitride membranes and patterned silicon-nitride (SiN) spiderweb-like suspension structures. As a substrate silicon-on-nitride (SON) wafers are used which are made by fusion bonding of a silicon wafer to a silicon wafer with a silicon-nitride top layer. The resulting monocrystalline silicon top layer on the silicon-nitride membranes enables the epitaxial growth of GBCO. By patterning the silicon-nitride the thermal conductance G is reduced from about 20 to 3 μW/K. The noise of both types of bolometers is dominated by the intrinsic noise from phonon fluctuations in the thermal conductance G. The optical efficiency in the far infrared is about 75% due to a goldblack absorption layer. The noise equivalent power NEP for FIR detection is 1.8 pW/√Hz, and the detectivity D* is 5.4×1010 cm √Hz/W. Time constants are 0.1 and 0.6 s, for the closed membrane and the spiderweb like bolometers respectively. The effective time constant can be reduced with about a factor 3 by using voltage bias. Further reduction necessarily results in an increase of the NEP due to the 1/f noise of the superconductor

Low noise far-infrared detection at 90 K using high-T(c) superconducting bolometers with silicon-nitride beam suspension

High-T(c) GdBa2Cu3O7-d (GBCO) superconducting transition edge bolometers with operating temperatures near 90 K and receiving area of 1 mm2 have been made with both closed silicon-nitride membranes and patterned silicon-nitride (Si(x)N(y)) spiderweb-like suspension structures. To enable epitaxial growth of the GBCO layer, a thin monocrystalline Si layer is prepared on the silicon-nitride base, using fusion bonding techniques. By pattering the silicon-nitride supporting membrane the thermal conductance G is reduced from 20 to 3.5 μW/K. The noise of both types of bolometers is fully dominated by the intrinsic noise from phonon fluctuations in the thermal conductance G. The optical efficiency in the far infrared is about 75% due to a gold black absorption layer. The optical noise equivalent power (NEP) is 1.8 pW/√Hz, and the detectivity D* is 5.4x1010 cm√Hz/W. Time constants are 0.1 and 0.6 s, for the closed membrane and the spiderweb like bolometers respectively. We have observed an empirical limit for the NEP for this type of bolometers. The effective timeconstant can be reduced with a factor of 3 by using an electronic feedback system or by using voltage bias. A further reduction necessarily results in an increase of the NEP due to the 1/f noise of the superconductor

HTSL-Kantenbolometer fuer IR-Spektrometer. Teilvorhaben: Devicetechnologie Abschlussbericht

Available from TIB Hannover: F00B753 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman

Technologie thermischer Strahlungsdetektoren auf HTSL-Basis fuer radiometrischer Anwendungen. Device- und Aufbautechnologie Schlussbericht

Die technologischen Grundlagen empfindlicher und spektral breitbandiger Strahlungsempfaenger (Bolometer) auf HTSL-Basis wurden im Rahmen eines Verbundprojektes entwickelt. Funktionsmuster der Bolometerstrukturen weisen eine Detektivitaet von D*=3,8x10"9 cm Hz"1"/"2 W"-"1 bei einer Zeitkonstanten von T=0,4 ms auf. Das Verbundprojekt gliederte sich in drei getrennte Arbeitsbereiche: (a) Device- und Aufbautechnologie, (b) HTSL-Schichtherstellung und (c) Systemtechnik. Die entwickelte Technologiekette besteht bei der Device-und Aufbautechnologie (Teil a) aus folgenden Schritten: 1. Membranherstellung: Eine 1x1 mm"2 grosse und 1 #mu#m dicke Membranen wurden mit einem KOH-Aetzprozess mikromechanisch in das Si-Substrat geaetzt. Dazu wurde ein Bor-dotierter Aetzstopp und Si_3N_4 auf SiO_2 als Aetzmaske verwendet. 2. Pufferschichtepitaxie: Nach dem Entfernen des SiO_2, der chemischer Oxidation und der Rekonstruktion der Si-Oberflaeche durch Desorption im UHV bei 650 C wurden epitaktische Pufferschichten (YSZ, YSZ/Y_2O_3 oder YSZ/CeO_2) mittels Elektronenstrahlverdampfer aus dem Si-Substrat abgeschieden. 3. Strukturierung der HTSL-Schichten: Durch die Strukturierung der Pufferschicht (Argon-Sputteraetzprozess) vor der HTSL-Abscheidung ('Inhibit-Technik') kann die Technologiekette in drei aufeinanderfolgende Blocks unterteilt werden (Siliziumtechnologie, HTSL-Technologie und Montagetechnik). (orig./MM)The technology of highly sensitive broadband thermal radiation detectors (bolometers) on HTSC-basis has been developed within a joined research projekt. Prototypes of bolometer structures reveal a detectivity of D*=3,8x10"9 cm Hz"1"/"2 W"-"1 and a timeconstant of T=0,4 ms. The joined research projekt has three separate divisions: (a) Device- and assembly-technology (IHT, University of Hannover, Germany), (b) HTSC-deposition (IPHT, Jena, Germany), and (c) system engineering (TZN, Unterluess, Germany). Processing of bolometers in device and assembly-technology (part a) contains mainly the following steps: 1. Membrane fabrication: Membranes of 1x1 mm"2 area and 1 #mu#m thickness were micromachined in KOH, using borondoping as an etch-stop and Si_3N_4 on SiO_2 as an etch mask. 2. Buffer layer epitaxy: After etching of SiO_2, chemical oxidation, and reconstruction of the silicon surface by desorption in UHV at 650 C, epitaxial buffer layers (YSZ, YSZ/Y_2O_3 and YSZ/CeO_2) were deposited by electron beam evaporation. Thin film quality on bulk and membrane substrates was investigated by LEED, XRD, RBS, and HRTEM. 3. HTSC-structuring: By structuring of the buffer layer (Ar-sputter-etch) before HTSC-deposition ('inhibit-technology') processing is devided into three subsequent blocks (silicon technology, HTSC technology, and packaging and interconnection). Thus processing steps of the different technologies can be performed at different locations. (orig./MM)Available from TIB Hannover: F96B123+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman

JESSI project: advanced technolgoy for 0.25 #mu#m CMOS and below. Subproject: process modules evaluation and integration. Theme 5 Multilevel metallization. Final report

Titanium- and cobaltdisilicide were investigated as material for shallow, low-resistive contacts in a CMOS-metallization system. ITM and DDS were used as self-aligned manufacturing processes. The TiSi_2- and CoSi_2-contact-systems were compared concerning manufacturing process and electrical and physical properties. The CoSi_2-contact-system shows the best properties. CVD-W was used to fill up vias and interconnects. To this a selective tungsten CVD process on CoSi_2 and a blanket deposition process were developed. Due to the excellent selectivity concerning the contact filling, a planarization effect was achieved. Accelerated tests show a high current-carrying capacity for the interconnects. Electromigration was identified as degradation mechanism. PECVD- and TEOS-PECVD-processes were investigated for the deposition of intermetal-dielectrics. An electrical and physical characterization of the layers have been performed. Processes with good step coverage and processes with a planarization effect were specified. Etch-back procedures using photo-resist and spin-on-techniques with various polyimides and a spin-on-glass were investigated in view of a planarization of the chip surface. The best results were achieved using the spin-on-technique with polyimide. (orig.)SIGLEAvailable from TIB Hannover: F94B1507+a+b / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman

Low noise high-Tc superconducting bolometers on silicon nitride membranes for far-infrared detection

High-Tc GdBa2Cu3O7 – delta superconductor bolometers with operation temperatures near 89 K, large receiving areas of 0.95 mm2 and very high detectivity have been made. The bolometers are supported by 0.62 µm thick silicon nitride membranes. A specially developed silicon-on-nitride layer was used to enable the epitaxial growth of the high-Tc superconductor. Using a gold black absorption layer an absorption efficiency for wavelengths between 70 and 200 µm of about 83% has been established. The noise of the best devices is fully dominated by the intrinsic phonon noise of the thermal conductance G, and not by the 1/f noise of the superconducting film. The temperature dependence of the noise and the resulting optimum bias temperature have been investigated. In the analysis the often neglected effect of electrothermal feedback has been taken into account. The minimum electrical noise equivalent power (NEP) of a bolometer with a time constant tau of 95 ms is 2.9 pW/Hz1/2 which corresponds with an electrical detectivity D* of 3.4 × 1010 cm Hz1/2/W. Similar bolometers with tau = 27 ms and NEP = 3.8 pW/Hz1/2 were also made. No degradation of the bolometers could be observed after vibration tests, thermal cycling and half a year storage. Measurements of the noise of a Pr doped YBa2Cu3O7 – delta film with Tc = 40 K show that with such films the performance of air bridge type high-Tc bolometers could be improved

Fortschrittliche Kupfer-Metallisierungssysteme (FOKUM). Teilvorhaben: Prozesstechnologie und Zuverlaessigkeit von Kupfermetallisierungen Schlussbericht

Available from TIB Hannover: F01B152+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany)DEGerman