WO1997033295A2 - Electronic tube system and method of manufacturing same - Google Patents

Abstract

In known electronic tube systems the upper limit frequency and noise characteristics are limited by the known methods of producing miniaturised multiple electrode tubes, i.e. diodes, triode tubes and multi-electrode tubes. The tube systems disclosed here comprise one or more field-emission or field-ionisation cathodes connected in parallel for electrons or ions, a grid electrode with one or more annular apertures, and one or more anodes. All electrodes are formed consecutively or simultaneously, using corpuscular radiation lithography with indexed deposition, on a planar conducting strip structure which delivers the voltages. The electrode spacing is made sufficiently small to ensure that on average only a mean free path length of the molecules at normal pressure can pass between the emitters and the anode. The range of possible uses of the invention is very wide but relates in particular to high-frequency technology.

Description

Pipe systems and manufacturing processes therefor

Description:

The invention relates to pipe systems of the kind defined in the preamble of claim 1 and to a production method for such pipe systems. Such micro-tube systems are known in vacuum micro-electrical engineering [Brodle, J. J. Muray "The physics of micro and nano-fabrication" Plenum Press, NY (1992)]

Such tube systems are equipped with "Spmdt" cathodes called lithographically made cathodes. These cathodes are produced with complicated lithographic processes in multilayer structuring with optical or corpuscular beam lithography with partly self-adjusting processes. The field emission cathode can be etched from silicon, covered with heavy metals or built up from metal by vapor deposition. However, the reproducibility of the production process is so low that many cathodes arranged in an array must always be used in order to ensure the emittance of the cathode and to achieve the required low internal resistance "transconductance" of the tubes.

Due to the large number of cathodes arranged in flat areas, the parasitic stray capacitance of the arrangement grows and limits the systems to operation at a few GHz, such as the aforementioned reference [Brodle, JJ Muray "The physics of micro and nano-fabrication" Plenum Press, NY (1992 )] is removable. The object of the invention is to provide pipe systems which are suitable for substantially higher frequencies and to specify a practical manufacturing process for this purpose.

The invention achieves the first part of this object with a system described in the characterizing part of patent claim 1.

An advantageous development for this is described in the characterizing part of patent claim 2.

The second part of this task is solved by the manufacturing method according to the characterizing part of patent claim 3.

An advantageous development of this method is described in the characterizing part of patent claim 4.

In the following exemplary embodiments, the invention is explained in more detail with its various possible variations and effect variants. In the accompanying drawings, the

Fig. 1: Principle structure for diode, triode and deflection

Tetrode with THz switching properties, Fig. 2: Top: triode made of cathode, emitter and anode.

Below: triode consisting of several cathodes, grid and anode to increase the emission current,

3: micro-triode with potential profile, cathode 0 V,

Grid 50 V, anode 60 volt, Fig. 4: Micro pentode from field emitter cathode K, grids Gl to G3 and anode A with potentials, Fig. 5: Micro tubes constructed using the

Electron beam-induced deposition and computer control in a scanning electron microscope, top view, bottom side view of 2 tubes, Fig. 6: Oblique view of 2 microtube assemblies made of platinum-containing nanocrystalline material. The tube systems described consist of one or more field emission or field ionization cathodes connected in parallel for electrons or ions, a grid electrode with one or more ring-shaped openings and one or more anodes. All electrodes are built up one after the other using corpuscular beam lithography with induced deposition or simultaneously on a planar conductor track structure which supplies the voltages. The electrode spacing is chosen so small that on average only a medium free path of the molecules at normal pressure fits between the emitter and anode electrode. At air and normal pressure, this distance is approximately 0.5 μm.

In order to avoid electrical flashover due to the growth of molecular chains that start above 10 ^ V / cm, the electrodes supplying voltage are thick and the conductor tracks are made far apart. Diameters of 0.1 μm and distances of> 0.5 μm are sufficient to keep the field strengths in the pipes at the operating voltage of <50 V below the limit required for permanent operation.

Such tubes require no or only a mild vacuum (1 Torr) for permanent operation and are therefore not called vacuum microelectronic tubes, but miniaturized multi-electrode tubes. The tubes can be operated with different polarities, since electrons are ionized at 2 ^· IO ⁷ V / cm and water at IO ⁷ V / cm. These field strengths are achieved when etched single crystals are not used as field emitters or field ionizers, but when the nanocrystalline composite materials that are generated during electron beam or ion beam-reduced deposition are used.

These materials are nanocrystalline and can be used as super tips on blunt, prefabricated tips or electrodes be put on. Due to their nanocrystalline structure, these super peaks emit or ionize absorbed water or other gases at the specified field strengths, which are already achieved at low voltages below 50 V, if the cathode-anode distance is smaller than the mean free path length of the gases at normal pressure. Such tubes have very small capacities and a flight time of the electrons of less than 1 ps or <40 psec of the ions. This means that these tubes can be successfully used as an electronic component in ultra-high frequency technology. Due to the small space requirement of a few μm ^ several of these tubes can be interconnected in close proximity to arithmetic circuits. With the corpuscular beam-induced deposition, resistors with very small capacitances, small capacitances and inductivities with μm dimensions can be manufactured and built into the circuits, so that the integrated tube electronics for GHz applications is possible.

Diodes, triodes, tetrodes, pentodes, miniaturized accelerators and filters and other corpuscular beam optical arrangements can be built using this technique. Tips as field emission cathodes for electron emitters and for ion emitters can be used in other prefabricated circuits and tubes and the operating voltage required can thus be greatly reduced. With the help of electron beam-induced deposition, nanocrystalline composite material can be built with nanometer precision into nanoelectronic assemblies and circuits in a given wiring level.

With this new technology, which uses new material and computer control and automation, new, unprecedented services can be achieved. Some preferred embodiments of tube systems which are built up on an insulating medium on conductor path structures prefabricated in planar technology with lithography using field current emission cathodes with a passive current stabilizing resistor and which are assigned at least one anode made of one or more wires are:

A diode with field electron emitter switched and operated with electrons,

A diode connected as an ion emitter and operated with H ₃ O + ions (since all surfaces are covered with water in air and therefore field ionization is used for field strengths above IO ⁷ volts / cm and the inner tube resistance is determined),

• a triode of conventional design, which can also be operated again with ions or electrons, in which in addition to the cathode and anode em grid in the form of one or more openings or even only in the form of 2 rods without upper and lower limits of the field between the two Electrodes is connected, • a tetrode or pentode, in which one or more grids are connected downstream of the first grid,

• a tetrode or pentode, in which a plurality of gratings and partial gratings are connected downstream of the first grid and which can be switched separately by two potential feeds, and thereby additionally also enable fast switching between two anodes which are insulated from one another.

All of these tubes can be operated in a moderate vacuum of 1 Torr, so that the mean free path of the electrons or ions in the gas is set at this pressure such that the tubes become functional due to the tube dimensions.

The tubes can be hermetically encapsulated in an evacuated vessel and the electrical feeds through the capsule be run as thin lines or the electrical leads are made through the walls of the encapsulation as lead-through wires in insulated filled bores.

Several tubes, 3a whole circuits can be built and sealed hermetically in a larger vacuum space filled with suitable pressure and gas or water from the sufficient partial pressure, and the cavity can be kept constant with a vacuum by means of a getter material, as shown in FIG the pipe technology is common.

To achieve a lower internal tube resistance and to increase the emission current, several electron or ion emitters can be connected in parallel.

The resistors for passive current control of the emitters connected upstream of the electron or ion emitters can, depending on the position m of the tubes, be designed in such a way that the field strength variation m of the tubes is compensated for and uniform current emission is achieved from the individual cathodes .

With the corpuscular beam-mediated deposition, conductive and insulating wires can be built up in the plane and in space. The wire diameter is approx. 0.1 μm, the length up to 10 μm. The wires can withstand 2 mA / cm 2 current densities. The value is 8 times higher than for example with aluminum (250000 A / cm2). Field emission is possible from the wire tips with approximately 15 times less internal resistance per emitter than with conventional field emitters in vacuum microelectronics. With this technology, field emitter electron sources can be built with a built-in current stabilizing resistor. Each tip works independently and in a controlled manner and passively stabilizes its emission current. So that the request for Redundancy at the tips in the tubes or m the parallel emitters reduced.

The wires end in a very fine tip with radii> 5 nm, but with nanometer-sized crystals that protrude from the tip and thus cause a field strengthening. This manifests itself in a greatly reduced extraction voltage for the field electron current. The resistance of the deposited materials can be set in the range of 5 orders of magnitude via the deposition conditions. The computer-controlled deposition produces 3-dimensional structures which serve as electrodes for micro tubes and tube systems, which generate individual beams, or which can often be produced side by side. A technology has thus been found with which multiple electron beams can be produced on lithographic circuits and carrier boards, which in turn can then be used as production means for deposition structures. With this, the production technology has been found with which microtubes, Dynatron oscillators and fast amplifying switches or fast digital memories that can be erased with 100 GHz can be produced in parallel production technology.

Due to the delicacy of the definition of material production in deposition with corpuscular beam-induced deposition with computer control, novel tubes, components, differential amplifiers and circuits can be written directly without the use of semiconductor materials. Because of the small size and the nanometer precision, these circuits can be operated at higher frequencies than can be achieved with conventional tubes. The manufacturing technology for electronic circuits is greatly simplified and the packing density is greatly increased.

As a first application example, FIG. 1 shows the basic structure for a diode, triode and deflection tetrode with THz Switching characteristics. With the deflection electrode, the amplification factor and a superimposed circuit can be carried out on 2 anodes, which enables particularly stable operation.

FIG. 2 shows a triode made of cathode, emitter and anode at the top and a triode made of several cathodes, grating and anode at the bottom for increasing the emission current and reducing the internal resistance.

3 shows a micro-triode with a potential profile. The cathode is at 0 V, the grid at 50 V and the anode at 60 V. Multiple electrodes that are installed between the cathode and anode can be used to thaw multi-electrode tubes, accelerators and decelerators and other tubes.

4 shows a micro pentode consisting of field emitter cathode K, grids G1 to G3 and anode A with potentials.

Structures already implemented to form triodes are shown in FIG. 5. The structure of two micro tubes is shown here. The tubes are constructed in a non-optimized form with the help of electron beam-induced deposition and computer control in the scanning electron microscope. Above the two pipes are shown m top view and below m side view.

6 shows 2 micro-tube structures made of platinum-containing nanocrystalline material in the oblique view. The picture shows the technical feasibility for structuring with additive lithography.

5 and 6 show the first time the arrangement of the existing macros "FEBOGEN" and "STACIR"

VIDAS beam control on the JSM 840 F. Wires have grown to 1 mm. By varying the parameters, the height adjustment of the top position to the grid square can still be optimized. By varying the parameters in the "STACIR" macro, an approximately round grid can be created.

By means of suitable deposition conditions, the hairpin carrying the tip can be designed as a low-resistance heating element and the shaft carrying the tip as a high-resistance passive stabilizing resistor. By heating the

Peak adsorbed gases can be desorbed and the emissions stabilized during operation. This is also due to continued heating or occasional "flashing", i.e. H. the tip is heated briefly, the tip being cleaned in a conventional manner by these methods.

The characteristic data that can be achieved with the triodes can be determined from the following data. The field emitter tube operates at 150 uA emission current, with an acceleration voltage U _{eχ r} <10 V. Then the internal resistance ("transconductance") R _χ > 15 μS. Conventional field emitters achieve 1 - 2 μS! , The field emission tubes can be switched in different ways:

1. Apply switching voltage to the extraction voltage at the top of _{-U eχ} p. The extractor and the anode are at 0 V or positive.

2. Apply the switching voltage to the extractor at + U _ex t _r . The peak is at 0 V.

3. Deflection of the beam with deflection plates Up <10 V by dividing the extraction grid into two and applying different voltages to the two halves. Then the beam is directed onto the two separate anodes (switching tubes with continuous jet). The storage capacity to be loaded is C = eo * e _r * F / d = 8.86-10 ^-12 *! * (0.2 * 10 ^_6 ) ² / 10- ⁶ As / V = 3.5 * 10 ^{~ 18} F.

With a rod diameter of 0.2 μm and a length of 1 μm at a distance of 1 μm and with the dielectric of vacuum or air e _r = 1, the capacity is 3.5 attoFarad. In order to charge this capacitance to a 5 volt deflection voltage, a charge of Q = C * U = 1.6 • 10 ^{~ 17} As = 100E = 100 electrons! required. This charge can be applied in 1 psec (1 THz) with a current of 16 uA. The statistical error is then 10% or SN = 10 (corresponds to the signal-to-noise ratio).

Switching with 0.1 ps can take place at 160 μA discharge current (voltage pulse at the extractor tube). This means that these tubes, which are constructed without semiconductor materials, considerably exceed the switching speed of circuits made of III / V or II / VI semiconductors.

Claims

Claims: 1. Pipe systems consisting of multi-electrode arrangements with any combination of electrodes, connections and functions, which are hermetically sealed in an evacuated vessel, characterized in that the electrodes and their spacings are chosen so small that on average only a medium one The free path of the molecules at normal pressure fits between the emitter and anode electrode, that the voltage supplying electrodes are thick and the interconnects are wide apart, the cathodes / emitters in needle form are nano-crystalline or prefabricated as super tips on blunt ones Tigt tips or electrodes are formed and that the evacuated vessels contain residual gases of particularly defined types and pressure ranges. 2. Pipe systems according to claim 1, characterized in that pipe systems of different operating modes are connected to one another by different additions with grids, anodes and other components capable of integration, and by separation into sub-vessels connected by leadthroughs. 3. Manufacturing process for pipe systems, characterized in that on emem m planar technology with lithography prefabricated insulating medium by means of computer-controlled corpuscular beam-induced deposition in partly simultaneous and partly successive steps with nanometer precision nanocrystalline composite material to nanoelectrical Tromschen assemblies and circuits are built into a given wiring level, which are finally included in a vessel system, while at the same time the operating mode of the tubes is determined by means of the type and pressure of the residual gases. 4. Manufacturing process for pipe systems according to claim 3, characterized in that tubes are used as ion emitters and are operated with H30 + ions by specifically drying undried or from a supply Residual gases are used until field ionization sets in at field strengths above IO ⁷ volts / cm and the tube internal resistance is determined.