In this review/tutorial paper, we cover the history, physics, and current status of vacuum microelectronic devices. First we overview the performance requirements of vacuum microelectronic devices necessary for them to replace, or fill voids left by, solid state devices. Next we discuss the physical characteristics of micro-field-emission sources important to device applications. These characteristics include fundamental features, such as current-voltage data and noise, in addition to engineering considerations, such as life expectancy and procedures for tube assembly. We conclude with a review of a wide variety of demonstrated and proposed devices based on vacuum microelectronic principles, including electron guns, microwave tubes, and flat-panel displays. >

Vacuum microelectronic devices

High-temperature electronics applications are found in combustion systems, well logging, industrial processes, air stagnation points in supersonic aircraft, vehicle brakes, nuclear reactors, and dense electronic packages. We summarize physical effects and materials issues important for reliable operation of semiconductor device technologies at high temperatures (> 125° C). We review the high-temperature potential of Si, GaAs, other III-V compounds, and SiC. For completeness, we also comment on nitrides, diamond, and vacuum microelectronics. We conclude that Si on insulator (SOI) technology can be developed readily for small signal operation up to about 300° C. There is some ongoing work in this area. GaAs offers little advantage over Si because of poor device isolation and the lack of reliable contacts above 250° C

An overview of high-temperature electronic device technologies and potential applications

The present invention relates generally to a new integrated Vacuum Microelectronic Device (VMD) and a method for making the same. Vacuum Microelectronic Devices require several unique three dimensional structures: a sharp field emission tip, accurate alignment of the tip inside a control grid structure in a vacuum environment, and an anode to collect electrons emitted by the tip. Also disclosed is a new structure and a process for forming diodes, triodes, tetrodes, pentodes and other similar structures. The final structure made can also be connected to other similar VMD devices or to other electronic devices.

Process and structure of an integrated vacuum microelectronic device

Vacuum microelectronics is a new interdisciplinary field utilizing the mechanism of electron emission into a vacuum for devices requiring bulk and surface micromachining. By fabricating arrays of conductive or semiconductive structures that are either gated or ungated, a multitude of devices can be formed that utilize cold emission and ballistic transport of electrons from emitting cathodes to appropriate collector electrodes. Potential applications include flat panel vacuum fluorescent displays, ultrahigh-frequency power sources and amplifiers, high-speed logic and signal processing circuits, and sensors. The technology of vacuum microelectronics may be capable of operation within extremely harsh environments in terms of temperature and radiation, assuming the availability of compatible packaging materials. The author summarizes the state of the art for vacuum microelectronics, with special emphasis on operation, device fabrication, testing, experimental results, and potential applications.

https://iopscience.iop.org/article/10.1088/0960-1317/2/2/001/pdf

Vacuum microelectronics-1992

High-temperature electronics applications are found in combustion systems, well logging, and industrial processes, air stagnation points in supersonic aircraft, vehicle brakes, nuclear reactors, and dense electronic packages. We summarize physical effects and materials issues important for reliable operation of semiconductor device technologies at high temperatures (>125/spl deg/C). We review the high-temperature potential of Si, GaAs, other III-V compounds, and SiC. For completeness, we also comment on nitrides, diamond, and vacuum microelectronics. We conclude that Si on insulator (SOI) technology can be developed readily for small signal operation up to about 300/spl deg/C. There is some ongoing work in this area. GaAs offers little advantage over Si because of poor device isolation and the lack of reliable contacts above 250/spl deg/C. Other III-V compounds could be developed for operation to /spl sim/600/spl deg/C, using processes similar to those used for optoelectronics. There may be a market niche for III-V power devices above 200/spl deg/C. There is considerable activity in semiconducting SiC, and device functionality has been demonstrated above 600/spl deg/C. SiC is promising for operation above 300/spl deg/C, and for power devices at frequencies from dc to /spl sim/10 GHz, but it faces numerous challenges to achieve manufacturable status. We attempt to match technologies with application areas. >

The authors discuss the modeling and fabricating miniature, vacuum, field-emission diodes and triodes for use in electronics in hazardous environments. They are micrometer-sized devices that are fabricated on a semiconductor wafer using integrated-circuit fabrication techniques and that use field emission rather than thermionic emission to generate charge carriers. Compared to existing semiconductor devices, they should be faster and much more tolerant of high temperatures and radiation. The device design uses the sacrificial layer technique to produce the device on a silicon wafer. All of the processing is completely compatible with existing integrated-circuit technology, making possible eventual integration of these devices and existing integrated-circuit components. To model these devices, the authors have used a static field modeling code to analyze the effect of device design variations on the field at the field-emission tip. Using these field results, they have calculated the tube's plate resistance, transconductance, gain, and current versus voltage characteristics. They have completed construction of a diode and are currently testing and interpreting the results. In addition, they have nearly completed a triode design. >

Modeling and fabricating micro-cavity integrated vacuum tubes

The design and building of micron-sized vacuum diodes and triodes using the sacrificial layer process is discussed. The devices use silicon field emitters etched into the surface of a silicon wafer. The field emitters are then buried in layers of glass and conductive polysilicon to produce the grid and anode. The last step is to remove the glass layers, leaving the free-standing anode and grid with 1-2- mu m separations. Vacuum microelectronics are expected to be hard to more than 10/sup 17/ neutrons/cm/sup 2/ and 10/sup 8/ rad(Si) of gammas without sustaining permanent damage. This is three to four orders of magnitude greater than the radiation levels that comparable silicon devices can withstand. Upset is expected to be on the order of 10/sup 11/ rad(Si)/s, compared to 10/sup 8/ rad(Si)/s for silicon devices. Vacuum microelectronics should also be able to withstand in excess of 775 K, compared to a maximum of 650 K for the best silicon devices. Current work involves enhancing the sharpness of the field emitters, so that they can operate at lower voltages. Recent application of an oxidation sharpening method has created tips with a radius of curvature on the tip of less than 10 AA. >

C.F. McConaghy

Papers

Modeling and fabricating micro-cavity integrated vacuum tubes

A progress report on the Livermore Miniature Vacuum Tube Project