# Silicon Carbide

Healing Silicon Carbide (SiC) wafers to make them almost defect free and much higher quality.

Last updated: 2020-09-05

#### Status

ACME Advanced Materials healed Silicon Carbide (SiC) wafers on parabolic flights of aircraft starting from 2014, but seems to be dormant and worthwhile advantages for healing wafers in orbit are lacking.

#### Applications

• Microchips that can operate at much higher temperature.
• Microchips that can withstand radiation much better.
• Automotive (used in Teslas).

#### Why & Solution

Silicon Carbide Wafers (SiC), a compound of silicon and carbon, can be used to produce wafers for the manufacture of computer chips that can operate at temperatures up to 1,000°C, can withstand 10 times the electric fields that standard semiconductors made of silicon can withstand, and offer high radiation resistance, high thermal conductivity, high maximum current density, and several other interesting properties that make them superior to standard semiconductors manufactured using silicon wafers (Department of Energy (DOE) 2015).1

SiC wafers can be produced in microgravity at much higher quality than those produced on Earth. On Earth, gravity prevents atoms from settling into their lowest energy states on a wafer, producing defects that interfere with the flow of electricity across the wafer. In microgravity, by cycling the pressure and temperature, these defects can be removed, resulting in “S-grade” (“space” grade) wafers with 99 percent of the original defects removed and little to no edge effects (Glover 2016; ACME 2016). With some redesign, SiC wafers can replace wafers made from silicon (DOE 2015). Because chips and other products manufactured from SiC wafers operate at very high temperatures, substituting SiC-based power electronics for traditional power electronics reduces required heat sinks (Hull 2013). Other uses for SiC include photovoltaic inverters, electric and hybrid vehicles, solar arrays, power grids, and wind turbines (Anagenesis 2015, expert interview).1

#### Revenue Estimation

We assume the space station would be able to capture the profits generated by manufacturing wafers on orbit in the form of charges for leasing; it would also generate revenues for astronaut time.
For our low estimate, multiplying 75,000 wafers per year by $1,125 yields$84.4 million. Subtracting total costs of $73.7 million ($63.7 million in variable costs ($850 per wafer times 75,000) plus$9.9 million in astronaut time) yields $10.7 million available for lease payments. Adding in the$9.9 million in charges for astronaut time generates $20.6 million in revenues for the station. For our high estimate, we assume 115,320 wafers are healed each year, yielding gross revenues of$129.7 million. Subtracting production costs of $113.3 million ($98.0 million of which is variable costs of $850 per wafer times 115,320) yields$16.4 million available for lease payments. The higher number of astronaut hours yields an additional $15.3 million in space station revenues, for potential total revenues of$31.7 million.1

##### Expenses Estimation

A future private station could generate revenues by leasing space for the production of high-grade SiC wafers. To determine how much revenue a private station could generate through such leases, we first estimate the costs of “healing” wafers in orbit. ACME Advanced Materials, based in Albuquerque, New Mexico, has been reprocessing or healing low-grade SiC wafers in microgravity to create high purity wafers with valuable material properties.
According to ACME, poorer quality wafers manufactured on Earth that can be healed in microgravity sell for $250 (Glover 2016). We assume that a manufacturer in space purchases low-grade SiC wafers for$250 per wafer and then transports these wafers to the space station for processing. To calculate launch costs, we use the fact that SiC has a density of 3.21 grams per cubic centimeter (Patnaik 2009); hence, a 4-inch diameter wafer with a thickness of 1 millimeter weighs about 0.03 kg. At a cost of $20,000 per kg to transport wafers to the space station, each wafer would cost$600 to transport to the space station. Thus, the total variable costs for healing a low-quality wafer is $850, the sum of the purchase price of the wafer ($250) and transport costs ($600).1 Additionally, we assume some astronaut time would be needed for healing the wafers. For our low estimate, we assume that the manufacturing operation needs 5 hours per week of astronaut time for supervision and maintenance. At a cost of$38,000 per hour times 260 hours per year (52 weeks times 5 hours), the annual cost of astronaut time would be $9.9 million per year. We assume that the space station provides electric power and other services as part of the rental payment paid by the manufacturer to the station. For our high estimate, to produce a greater number of wafers, we assume a proportional increase in astronaut time to 7.7 hours per week to handle the increased production volume—in other words, 400 hours per year, which would cost$15.3 million.1

#### Earthly Solution Risk

Very high, see below for reasons.

#### Risks

• Parabolic flights are much cheaper, because SiC wafer healing is additive over multiple parabolas and a total of 6 minutes is enough. 1
• ACME Advanced Materials seems to be dormant based on social platforms and LinkedIn.

#### References

1. Keith W. Crane et al. Market Analysis of a Privately Owned and Operated Space Station. IDA Science & Technology Policy Institute. Published in March 2017. Source

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