Orbital Microfabrication

Fabricating microchips or semiconductor crystals in orbit by benefitting from ultra-high vacuum among others. Microgravity-grown crystals have increased single crystal size and suppressed impurities and defects.4

Last updated: 2018-12-19

Status

Terrestrial microfabrication techniques are difficult to transfer into microgravity and other methods have been developed and tested on a small scale in space. Microgravity Research Associates was founded in 1979 to produce gallium arsenide chips, but has been dormant for decades.

Applications

  • Gallium Nitride (GaN)
  • Gallium Nitride on diamond (GaN-on-diamond)
  • Gallium Arsenide (GaAs)
  • Silicon Carbide (SiC)
  • Space-based microsensors

Why & Solution

Semiconductor microchips are high value per mass products whose fabrication requires many of the resources available in low-Earth orbit. It is hypothesized that orbital fabrication of silicon microchip devices may be more economically attractive than traditional Earth-based fabrication based upon the inherent advantages of the space environment: vacuum, cleanliness, and microgravity.3

Gallium nitride, used to make LEDs, is difficult to solidify in large amounts at a time because its two constituent molecules don't always bind perfectly in order, leading to defects. Reducing the movement of the melted fluid as hotter and less-dense fluid rises, which occurs because of gravity, can decrease those defects — as can preventing the highly reactive substance from touching the sides of its container, according to Randy Giles, chief scientist at the Center for the Advancement of Science in Space. Someday, substances like that could benefit from in-space creation.2

Using orbital vacuum for enhanced semiconductor fabrication was pioneered in the Wake Shield project which produced ultra-high vacuums for epitaxial growth of high quality GaAs like materials. A proposed alternative uses the native Low Earth Orbit vacuum levels to achieve the silicon microfabrication processes needed for manufacturing silicon microchips. However standard terrestrial fabrication techniques are difficult to transfer into the microgravity and vacuum environment of space.  They are optimized for using in-situ resources: water, power, air pressure and gravity that are plentiful on Earth.  An alternative microfabrication process has been developed using the native vacuum environment which could replace wet terrestrial based microfabrication, with significant savings in equipment size, mass and consumables, while reducing cycle time.3

It is found that by developing new, dry processes that are vacuum compatible, fabricating semiconductor devices in orbit is both technically and economically feasible.  The outcome is a synergistic, orbital-based methodology for micro-fabrication capable of building and delivering commercially marketable microfabricated structures.  The base case modeled, production of 5,000 ASIC wafers per month, indicates that orbital fabrication is 103% more expensive than existing commercial facilities.  However, optimization of process parameters and consumable requirements is shown to decrease the cost of orbital fabrication dramatically.  Modeling indicates that the cost of orbital fabrication can be decreased to 58% that of an advanced, future Earth-based facility when trends of increasing process equipment costs and decreasing orbital transport costs are considered.3

Taking advantages of microgravity environment, amorphous semiconductors made a remarkable improvement both in quality and quantity. Space is considered to be a favorable environment for many things including the followings that were investigated: semiconductor joining by atomic adhesion, fabrication of thin films of diamond and amorphous silicon alloys, CVD processes, production of super-minute grains, light element analysis by SIMS (Secondary Ion Mass Spectrometry), and anti-proton generation by laser accelerators. This report reviews the potentials of material processing in space. Processing technologies of spacecraft construction materials, thin solid films, and fine alloys are reviewed. Light element analyzing method and antiproton storing technology for liquid metal MHD (Magnetohydrodynamic) power generator are also reviewed. 5

References