N.A. Masnari

A novel submicron fabrication technique

A novel technique for producing submicron linewidths and devices has been developed. The technique does not require electron beam or other exotic lithographic techniques, but instead uses conventional photolithography and a selective edge planing step. In this step, a metal is plated to the edge of a conventionally patterned metal layer. This plated edge is then used as a mask for subsequent plasma etching of underlying conductors or dielectrics. This technique has produced linewidths as small as 0.04 µm and can be applied to the fabrication of a variety of microwave devices. In particular, it has been used to produce GaAs MESFETs with gold-plated chromium gates as short as 0.1 µm. The performance of GaAs MESFETs produced in this manner is comparable to that of devices fabricated using more complex and expensive gate patterning techniques. For example, MESFETs on ion-implanted GaAs with 5 µm source-drain spacings, 0.3 µm gate lengths, and 250 µm gate widths, have exhibited maximum available gains of over 10 dB at a frequency of 12 GHz.

Fabrication of hemispherical structures using semiconductor technology for use in thermonuclear fusion research

Initial investigations and laboratory experiments in the area of target fabrication using solid state circuit processing techniques to create special target components have indicated the feasibility of a unique advanced manufacturing concept. A question of the applicability of silicon integrated circuit technology and how it might be applied to the fabrication of inertial confinement fusion targets was posed. The combined efforts of the University of Michigan Electron Physics Laboratory, and the Division of Material Sciences of KMS Fusion, Inc. have provided some relatively quick and very encouraging answers and results. The initial efforts to demonstrate electron beam patterning and etching of micron‐high letters through the walls of glass microballoons, the fabrication of free‐standing thin‐walled flanged hemispheres joined to form spherical structures, and a pellet support membrane have been the proof‐of‐principle milestones and goals.

Analog Representation of Poisson's Equation in Two Dimensions

A new analog device, called a Poisson cell, has been developed which aids in obtaining solutions to either Laplaces equation or Poissons equation. The cell may be used to simulate such potentials as electric potential, magnetic potential, gravitational potential, and the velocity potential of irrotational flow; it has applications in the fields of hydrodynamics, heat conduction, and aerodynamics. The cell is a solid volume-conducting medium made from a homogeneous mixture of hydrostone and graphite. Electrode configurations may be painted on the surface with conducting paint or imbedded directly in the structure. In the case of Poissons equation, where ?2?(x, y) = f(x, y), the function f(x, y) is simulated by injecting currents into the underside of the cell. The application of the Poisson cell to numerous problems and in particular to problems in electron flow is discussed m detail, along with the incorporation of the cell into either an analog computer system or a combined analog-digital computer system.

A method for the mass production of ICF targets

Abstract The application of semiconductor process technology to the manufacture of inertial-confinement fusion targets is described. The use of optical and electron-beam lithography together with silicon etching technology allows the reproducible fabrication of a variety of target configurations for research and may provide a means for the high-volume production of low-cost targets for commercial reactor systems.

A simplified model of a TRAPATT diode

A simplified computer model of a TRAPATT (trapped plasma avalanche triggered transit) diode was developed and is used to investigate realistic voltage-current waveforms (i.e., waveforms that produce negative conductances at all signal frequencies). Oscillator efficiency variations due to fundamental and second-harmonic current tuning were studied. The computed waveforms show good agreement with the TRAPATT waveforms obtained experimentally.

The Operation of S-Band TRAPATT Oscillators with Tuning at Multiple Harmonic Frequencies (Short Papers)

A simplified TRAPATT oscillator model that allows the investigation of arbitrary terminal waveforms was utilized to investigate realistic TRAPATT waveforms and the tuning conditions necessary for high-efficiency operation. The effects of the higher harmonics on oscillator frequency and efficiency were studied. Cicuit impedance measurements of S-band TRAPATT oscillators support the theoretical predictions.

Optimization of S-Band TRAPATT Oscillators

The optimization of S-band TRAPATT oscillators has been investigated experimentally from both the device and circuit points of view. Methods for selecting a device for optimum operation with a given circuit are discussed. A relatively straightforward circuit optimization technique has resulted in an increase in oscillator efficiency of between 5 and 8 percentage points, representing an RF power increase of approximately 20 percent.

Intermodulation Characteristics of X-Band IMPATT Amplifiers

Abstract The intermodulation products produced when two equal amplitude signals are applied to the input of an X-band IMPATT diode amplifier have been measured. A Si p+nn+ IMPATT diode was operated in a double-slug-tuned reflection amplifier circuit that was tuned to provide 20 dB of small-signal gain at 9.340 GHz. The intermodulation tests consist of measurements of the magnitudes and frequencies of the amplifier output signals as a function of the input signal drive levels and frequency separations. The gain and single-frequency characteristics of the amplifier were also measured and are used along with the theoretical device and circuit admittance characteristics as a basis for explanation of the intermodulation results. A low-frequency dominance mechanism is found to exist in which the low-frequency signals are amplified more than the high-frequency signals. This mechanism becomes more significant as the amplifier drive level is increased.

MP-A7 fabrication of devices with submicrometer dimensions using a selective edge plating technique and conventional photolithography

device has been shown to have high charge e f f i~ i ency .~ This device differs from a conventional buried-channel CCD in yet another significant aspect. Instead of the p-substrate, n-active layer arrangement typically used in buried-channel CCD technology, this device employs a semi-insulating substrate and ntype active layer. The semi-insulating substrate has important implications for high-speed applications since stray capacitance is reduced substantially with the consequence that power dissipation jn the clock drivers (Pd = cv2f) is reduced accordingly. Also, the semi-insulating substrate eliminated the need for a separate channel stop. The first device described by Deyhimi e t aL2y4 was a 30-gate device and served to prove the concept of the Schottkybarrier gate, buriedchannel CCD, and to characterize it with respect t o transfer efficiency, linearity, and floating gate capability. A new device has been fabricated and very recently operated and transfer efficency has been verified to be >0.999 per transfer. ~ This device employs 4.5 pm X 100 pm transfer gates (separated by I-vm gaps), as well as an on-chip reset amplifier. A 131-gate and a 259-gate version of this device have been successfully operated. The CCD transfer gates are connected in a 4-phase configuration. The active layer of the device is n-type with ND = 1 X 10 l6 /cm3. The device channel is isolated with a mesa etch and the electrode interconnection patterns are printed directly on the semi-insulating substrate. The device employs two-level metallization isolated by a plasma-deposited silicon-nitride. The 13 1-gate version of this device has been operated at up to 500 MHz. The results of transfer efficiency measurements will be reported.

Experimental investigation of TRAPATT diode trigger conditions

Experimental studies have been carried out to determine the mechanisms by which the TRAPATT mode can be triggered into operation in the S-band frequency range. These investigations indicate that the TRAPATT mode can be triggered either by VHF oscillations or by IMPATT oscillations. The various frequencies interact to control the turn-on time and the current required to trigger the diode into oscillation. The interactions between the frequencies is controlled by the microwave and bias circuits. Changing the bias circuit alters the interaction thus causing the turn-on time and trigger current to be different. From this information the necessary bias conditions can be given to reduce the turn-on time and trigger current. With appropriate circuit elements the VHF have been observed to trigger the TRAPATT mode into operation in 5 ns. The IMPATT mode of triggering, however, results in a 20 to 25 ns delay before the TRAPATT signal appears.