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A voltage detector and its connected focusing system for voltage measurements on integrated circuits by laser induced photoemission are presented. The capabilities of the system are analyzed theoretically and verified experimentally. Application to metal lines of submicrometer width and spacing is possible, combined with picosecond time resolution and a voltage sensitivity far exceeding that of electron beam probing. An excellent insensitivity to static crosstalk perturbations is demonstrated. Voltage contrast measurements and measurements of photoemission spectra have also been performed with this system.

A setup for photoemission testing, which compares favorably with results from electron-beam testing, particularly in terms of measurement time, is presented. The photoemission sampling system described has a unique detector design and a viewer for the added convenience of the equipment operator. performance results when this technique is used to measure delay and rise times on integrated gallium arsenide MESFET circuits are reported. The switching time of these circuits is around 200 ps. The system measures electrical pulses with an 8-ps rise time, so these GaAs circuits can be tested by the system. An interesting feature for special testing is the system's ability to activate devices within a chip by a pulsed visible light beam. >

High-quality etched mirrors for AlGaAs/GaAs power lasers for applications in optical storage have been fabricated by chemically assisted ion-beam etching (CAIBE). In order to ensure flat mirror facets of the ridge-waveguide lasers, a flared-waveguide end section is used. This results in a very slight mirror roughness of approximately 20 nm across the beam cross section, and yields excellent beam properties allowing diffraction-limited focusing up to 50-mW output power. >

The rapid evolution of advanced VLSI and VHSIC technologies, with advanced devices switching on time scales of less than 10psec creates new demands on high-speed diagnostic and testing instruments. The most important demands are the capability of contactless and noninvasive measurement of switching times and voltage states on internal nodes of VLSI ICs with a high time resolution (1–5 psec), a high voltage resolution (1–10 mV) in conjunction with a short measurement time, and a spatial resolution in the submicron range. It should be emphasized that these requirements have to be achieved simultaneously. In addition, it is desirable to have a diagnostic technique that is applicable to all semiconductor technologies rather than being limited to exclusively silicon- (Si) or gallium-arsenide- (GaAs) based circuitry.

Recent achievements in solving the problem of the microscopic nature of the ferromagnetic-to paramagnetic-phase transition of ferromagnetic metals by employing the method of spin- and angle-resolved photoemission spectroscopy with synchrotron radiation (from the storage ring BESSY in Berlin) are briefly summarized. Emphasize is also given to the theoretical interpretation of the data, from which a short-range order in Fe near the Curie pointTc of at least 4 A has been derived. This excludes the validity of the disordered local moment picture for Fe at high temperatures.

A novel approach to contactless measurement of voltages on internal nodes of integrated circuits is presented. The method is based on time-resolved photoemission exploiting the single-photon process with short laser pulses in the ultra-violet. The method allows spatial resolution in the submicron range given by the diffraction limit for UV photons, a time resolution of a few picoseconds given by the width of the laser pulses and the electron transit-time effect, and a voltage resolution of a few microvolts within a signal integration time of one second.

Using spin-polarized photoemission with high energy- and angle resolution (ΔE=100 meV, ΔΘ=±3°) we have investigated the temperature dependence of the exchange splitting of Ni in the temperature range 0.5≦T/T c≦0.94. At room temperature we findΔ ex=0.18 eV for the exchange splitting of theS 4 band at theX point of the Brillouin zone. With increasing temperature the total (spin-averaged) energy distribution shows a narrowing and merges into one peak. The spin-resolved energy distribution curves approach each other and are strongly broadened. A discussion of the data within current theories of itinerant electron magnetism is given. The spectra indicate that neither the pure Stoner model nor the prediction of local band theory, assuming a temperature independent exchange splitting are justified for Ni. We conclude that the exchange splitting decreases with increasing temperature and that transverse as well as longitudinal spin fluctuations are responsible for the broadening of the spin-resoived energy distribution curves.

Calculations of spin-polarized threshold-photoemission spectra for Ni(001), Ni(111), and Ni(110) surfaces are presented, obtained with a one-step model of the photoemission process. As in the previous work of Moore and Pendry, good agreement with the angle-integrated experimental results for emission from the (001) and (111) surfaces is obtained within a normal-emission approximation. In contrast, for emission from the (110) surface it is found that the angle-integrated spectra are dominated by non-normal-emission contributions. In addition, the influences of relativistic dipole selection rules and surface-state emission on the spin polarization from the (110) surface are discussed briefly.

After a short review of the basic principles of time-resolved photoemission and its capabilities as a method for contactless electrical testing of integrated circuits, this paper reports on the progress made toward meeting the requirements for integrated-circuit (IC) testing and diagnostic equipment. The goals of IC testing are to provide high time and voltage resolutions with short testing time, and simultaneously high spatial resolution independent of the circuit technology (Si, GaAs). Here, the emphasis is on the time and voltage resolutions and short testing time. In the photoemission process, these parameters are independent of the spatial resolution in the regime of interest. The investigation is carried out with a pulsed-laser system generating picosecond pulses in the UV range. The measurements presented were performed on photoconductive switches. This allows testing the time resolution of the method by ultra-fast signals, and generating the electric transients to be sampled by the same laser source as the sampling pulse, guaranteeing almost jitter-free operation. The results clearly demonstrate that photoemission sampling is capable of contactless diagnostics and testing of very high-speed circuits with a high-voltage resolution and short testing time.

The newly developed method of photoemission sampling, based on the single‐photon process, has been applied to measure the dispersion of a picosecond voltage pulse traveling on a transmission line. The dispersion of the propagating pulse is clearly revealed in the spectra which show signal rise times of about 17 ps at 2 mm away from the pulse generating switch, and change into rise times of about 30 ps at 1.5 mm further away. The time resolution of the measurements is better than 7 ps. Therefore, photoemission sampling with picosecond laser pulses permits the measurement of changes in signal waveforms at arbitrary points of a transmission line and for arbitrary substrate materials with sufficient time resolution.

The idea of utilizing time -resolved photoemission for contactless electrical testing on internal nodes of IC's israther young. Initial studies quickly showed the advantages the technique offers over other methods. After a shortreview of the basic principle and its attractive features, this paper reports on the progress made toward meeting therequirements for IC testing and diagnostic equipment. The goals of IC testing are to provide high time and voltageresolutions with short testing time, and simultaneously high spatial resolution independent of the circuit technology(Si, GaAs). Here, the emphasis is on the time and voltage resolutions and short testing time. In the photoemissionprocess, these parameters are independent of the spatial resolution in the regime of interest. The investigation iscarried out with a pulsed -laser system generating picosecond pulses in the UV range. The measurements presentedwere performed on a photoconductive switch. This allows testing the time resolution of the method by ultra -fastsignals and generating the electric transients to be sampled by the same laser source as the sampling pulse. Thelatter point guarantees almost jitter -free operation. The results clearly demonstrate that photoemission sampling iscapable of contactless diagnostics and testing of very high -speed circuits with a high voltage resolution and shorttesting time.IntroductionThe major challenge for contactless IC testing is the combination of the three measuring parameters: 1) Timeresolution in the low picosecond range; 2) spatial resolution in the submicrometer range, and 3) voltage resolutionbelow 10 mV accomplished with short testing time as well as a wide range of applicability.Only a few years ago, was there just one feasible method to probe internal nodes of integrated circuits bycontactless means: electron beam probing.1-3 The ever -increasing switching speed and decreasing voltage swingsof modern high -speed electronic circuits have exceeded the performance limits of existing e-beam testing

The basic principles, fundamental limits, and recent results of the novel photoemission probing method are reviewed. The possible range of applications as a contactless diagnostic method for integrated circuits in the real-time and sampling modes of photoemission probing is discussed on the basis of theoretical and experimental studies. In photoemission sampling, electron emission is induced in a sample by an incident light beam (in most cases a laser beam), and the photoemitted electrons are then accelerated towards a reference or retarding field electrode. If the reference electrode is at the same potential as the point of electron emission on the VLSI circuit, all photoemitted electrons can pass the reference electrode and are guided towards an electron detector. >

After giving brief background information on photoemission testing with emphasis on measurement time, the authors describe progress made in detector design and viewing capability. The usefulness of equipment, using the photoemission sampling technique has been demonstrated through measurements delay and rise times of integrated GaAs MESFET circuits. The switching time of these circuits is around 200 ps, therefore presenting no challenge to the time resolution of the system, which had been substantiated by earlier measurements of electrical pulses with 8-ps rise time. The ability to activate devices within a chip by a pulsed visible light beam is also demonstrated. >

We report on the first voltage measurements of signals with rise times below 20 ps by photoemission stampling based on the single-photon process. The high time and voltage resolution together with the potential of a submicrometre spatial resolution enables tesing of very high-speed VLSI circuits by this newly developed method.