Electromigration tests at temperatures between 340 and 400 °C and current densities between 1.0 and 3.0 MA/cm2 have been performed to determine the temperature dependence of the critical length effect in 0.5-μm-wide Cu/oxide dual-damascene interconnects with 0.1 μm silicon nitride (SiNx) passivation. A focused-ion-beam-induced contrast imaging technique is used to locate failure sites of critical length test structures. Statistical analysis [E. T. Ogawa et al., Appl. Phys. Lett. 78, 18 (2001)] yields a threshold-length product (jL)c, of 3700 A/cm, and a temperature dependence is not observed within the temperature range 340–400 °C.
We have developed a broad-band technique for measuring the relative permittivity of low-thin films using microstrip transmission-line measurements. From measurements of the complex microstrip propagation constant and the characteristic impedance, we determined the relative permittivity of thin films incorporated in microstrip lines. We present measurement results to 40 GHz for both an oxide and a bisbenzocyclobutene lowthin film and show a variability of permittivity of approximately 5% over the entire frequency range.
Electromigration results have provided clear evidence of a short or “Blech” length effect in dual- damascene, Cu/oxide, multilinked interconnects. The test structure incorporates a repeated chain of Blech-type line elements and is amenable to failure analysis tools such as focused ion beam imaging. This large interconnect ensemble provides a statistical representation of electromigrationinduced damage in the regime where steady-state interconnect stress is manifest. Statistical analysis yields a critical length of 90 μm for interconnects with line width 0.5 μm at j=1.0×106 A/cm2 and T=325 °C.
Abstract-Efficient use of radio spectrum is a necessity for 3000 MHz were intended to clarify, among other aspects, future wireless systems. This can, for example, be accomplished the questions of channel occupation, how those channels are by cognitive radios. An important point for designing future sys-occupied (i.e., modulation scheme, data rate, etc.), and how tems is to gain knowledge about the occupation of the frequency .'. ' ' bands which may be used by the cognitive radio. This includes many tnsitr arept in a and andtwhre teyiae the general characterization of the traffic density at the frequency located. In [6] a concept of spectral agile software defined bands as well as a detailed analysis of the temporal frequency radios has been discussed where a method for estimating occupation. Thus, this paper describes measurements taken in underutilized spectrum bands has been presented. the GSM network at three different scenarios. Furthermore, INTRODUCTION system. Therefore, the major incentive of this paper is to T HE demand for mobile services steadily increases. Often present measurements of a typical primary system, thereupon radio resources are proclaimed to be scarce resources, but describing the statistical characteristics and discussing potenthis scarcity only arises due to an inefficient usage. By em-tial consequences for the design of cognitive radios. ploying adaptive allocation and dynamic pricing mechanismsThe remainder of the paper is organized as follows: In these resources can be exploited more efficiently. One possible section II the measurement system is described by specifying technique to realize dynamic spectrum access may be based the equipment used and the parameters chosen. The scenarios on spectrum pooling [1], [2].in which the measurements have been performed are charIn a spectrum pooling system the same spectrum is locally acterized in section III. Measurements provide information used by secondary users following proper rules to transmit about the time-frequency occupation of the frequency range wirelessly without disturbing the incumbent user. For example, under consideration. This time-frequency occupation serves spectrum pooling systems may be realized by primary systems as starting point for the statistical analysis conducted in allowing a secondary system to send in the time-frequency section IV. Possible impacts of the results on the design of gaps whenever the primary users do not transmit. Thus, the cognitive radios are discussed in section V. Finally, the paper secondary system needs to detect the primary system and it is summarized. must be able to decide about transmitting and adapting its radio access technology to the current spectrum configura uoon.rTion. eAuREment sYstAssuming that the secondary system gets no signaling inforThe measurement equipment mainly consists of an antenna, mation from the primary system, the secondary system needs a spectrum analyzer and a computer (see figure 1). The to learn about the past and act accordingly. This requirement intention ...
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