Multipactor discharges can cause severe problems in high voltage rf systems like rf antennae or transmission lines of ion cyclotron resonance heating (ICRH) in nuclear fusion devices, where they may initiate gas breakdown. To study this eventual transition from a starting multipactor into an ordinary rf discharge detailed investigations were performed using a parallel plate geometry, 50 MHz operating frequency and up to one kilovolt rf amplitude. Measurements of electric data (rf amplitude, absorbed and reflected power, discharge current), electronic parameters (electron current density and energy distribution) and light emission were used for characterization. As a main result a new type of well defined discharge regime was identified, which seems important for the transition from multipactor into gas breakdown in rf devices.
This paper addresses the various aspects of e-beam lithography as they relate to device fabrication at and below 0.25 μm. These dimensions will eventually be necessary for the fabrication of 256 MB DRAM chips. It is important to evaluate how key components in lithography have to be integrated to provide this necessary early learning. E-beam lithography tools today may consist of Gaussian round and variable shape beam systems. The understanding of the performance of the tool goes hand in hand with directly related issues such as electron-resist interaction, proximity effect correction, etc. Since each of these parameters can be optimized independently, but not simultaneously as a complete set, tradeoffs will have to be made. The discussion will therefore focus on compromises between critical issues such as beam profile, throughput, image quality, process latitude, degree of accuracy in proximity effect correction, and overall process engineering for very high resolution lithography. All of these aspects are strategically important components in support of device technology research. The implementation of an ‘‘integrated e-beam lithography’’ operation as it relates to fully scaled and partially scaled device programs will be discussed. Current work on device fabrication below 0.25 μm demonstrates the capability of integration of all sectors of e-beam lithography to provide early research work for ULSI device technology.
Electron beams as a viable technique for contactless testing of electrical functions and electrical integrity of different active devices in VLSI -chips has been demonstrated over the past years. This method of testing electronic networks, most widely used in the laboratory environment, is based on an electron probe which is deflected from point to point in the network. A current of secondary electrons emitted in response to the impingement of the electron probe is converted to a signal indicating the presence of a voltage or varying potential at the different points. Voltage contrast, electron beam induced current, dual potential approach, stroboscopic techniques and other methods have been developed and are used to detect different functional failures in devices.Besides the VLSI application, the contactless testing of three dimensional conductor networks of a 10cm x 10cm x .8cm multilayer ceramic module poses a different and new application for the electron beam test technique. A dual potential electron beam test system allows to generate electron beam induced voltage contrast. The same system at a different potential is used to detect this voltage contrast over the large area without moving the substrate and thus test for the electrical integrity of the networks.1-5Less attention in most of the applications has been paid to the electron optical environment, mostly SEM's were upgraded or converted to do the job of a "voltage contrast" machine. This by no means will satisfy all requirements and more thoughts have to be given to aspects such as: low voltage electron guns: thermal emitter, Schottky emitter, field emitter, low voltage electron optics, two lens systems, different means of detection, signal processing -storage and others. This paper will review available E -beam test techniques, specific applications and some critical components.
High-voltage (≥50 kV) electron beam lithography (EBL) is the preferred technique for fabrication of additive-process x-ray masks, because the high-voltage minimizes scattering in the resist and membrane, resulting in better resolution, straighter sidewalls, and reduced proximity effect. We have designed and built a new 100 kV column for a vector scan EBL machine for the purpose of writing high-resolution, high-precision x-ray masks in order to explore the technological and fundamental limits of x-ray lithography. The column features a 100 kV thermal field emission gun with an electrostatic condenser lens, conjugate blanking, and a liquid-cooled magnetic final lens with high-precision double magnetic deflection. The two-lens optics provides a beam diameter of 30 nm at a current of 5 nA, sufficient to expose moderately sensitive resists at pixel rates approaching the maximum deflection speed of 10 MHz. Results obtained include proximity corrected, complex patterns in thin resist with feature sizes down to 50 nm. Comparisons of proximity effects, exposure parameters, and actual resist profiles, show that 100 kV is clearly superior to 50 kV and even 75 kV for feature sizes below 0.25 μm in thick (0.75 μm) resist. Excellent linewidth control has been obtained on plated gold x-ray masks with feature sizes as small as 75 nm. Problems of patterning nanometer features with aspect ratios as high as 10:1, which include forward scattering, development effects, and plating effects, are discussed.
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