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Why Hasn't This Been Done with Silicon Carbide

Started by John Savard December 12, 2014
Today's microprocessors are all made using the CMOS logic family.

It has the advantage of using a minimum amount of electricity, since - exce=
pt for leakage currents, which are becoming more important as transistors a=
nd wires shrink - electrical power is only used during changes of state.

However, the performance of CMOS circuits is limited by the slower P-type F=
ET branch of them - this can be helped by going to Germanium, which has hig=
h hole mobility, or by using stretched silicon, or by using domino logic...=
 the IBM CELL processor used an alternative approach instead of domino logi=
c which also worked.

And the fastest logic family used to be ECL, because the transistors didn't=
 saturate. But it was an energy hog.

Silicon carbide can tolerate high temperatures, and it's a semiconductor. T=
he trouble is that silicon carbide crystals are riddled with defects, so it=
's a challenge to even make decent single transistors out of it, let alone =
microprocessors with millions of transistors!

However, the thought occurred to me that surely there must be some material=
 that forms nice single crystals, free of defects, with the same interatomi=
c lattice spacing as silicon carbide. One could use wafers of _that_ - pres=
uming it's also an insulator - and using chemical vapor deposition, produce=
 good silicon carbide transistors in large numbers per die...

No doubt there are good reasons why that is harder than it seems.

John Savard
On Friday, December 12, 2014 10:35:48 AM UTC, John Savard wrote:
> Today's microprocessors are all made using the CMOS logic family. >=20 > It has the advantage of using a minimum amount of electricity, since - ex=
cept for leakage currents, which are becoming more important as transistors= and wires shrink - electrical power is only used during changes of state.
>=20 > However, the performance of CMOS circuits is limited by the slower P-type=
FET branch of them - this can be helped by going to Germanium, which has h= igh hole mobility, or by using stretched silicon, or by using domino logic.= .. the IBM CELL processor used an alternative approach instead of domino lo= gic which also worked.
>=20 > And the fastest logic family used to be ECL, because the transistors didn=
't saturate. But it was an energy hog.
>=20 > Silicon carbide can tolerate high temperatures, and it's a semiconductor.=
The trouble is that silicon carbide crystals are riddled with defects, so = it's a challenge to even make decent single transistors out of it, let alon= e microprocessors with millions of transistors!
>=20 > However, the thought occurred to me that surely there must be some materi=
al that forms nice single crystals, free of defects, with the same interato= mic lattice spacing as silicon carbide. One could use wafers of _that_ - pr= esuming it's also an insulator - and using chemical vapor deposition, produ= ce good silicon carbide transistors in large numbers per die...
>=20 > No doubt there are good reasons why that is harder than it seems. >=20 > John Savard
What exactly is the result of a transistor built on a defective piece of cr= ystal? NT
On Fri, 12 Dec 2014 08:25:56 -0800, meow2222 wrote:

> On Friday, December 12, 2014 10:35:48 AM UTC, John Savard wrote: >> Today's microprocessors are all made using the CMOS logic family. >> >> It has the advantage of using a minimum amount of electricity, since - >> except for leakage currents, which are becoming more important as >> transistors and wires shrink - electrical power is only used during >> changes of state. >> >> However, the performance of CMOS circuits is limited by the slower >> P-type FET branch of them - this can be helped by going to Germanium, >> which has high hole mobility, or by using stretched silicon, or by >> using domino logic... the IBM CELL processor used an alternative >> approach instead of domino logic which also worked. >> >> And the fastest logic family used to be ECL, because the transistors >> didn't saturate. But it was an energy hog. >> >> Silicon carbide can tolerate high temperatures, and it's a >> semiconductor. The trouble is that silicon carbide crystals are riddled >> with defects, so it's a challenge to even make decent single >> transistors out of it, let alone microprocessors with millions of >> transistors! >> >> However, the thought occurred to me that surely there must be some >> material that forms nice single crystals, free of defects, with the >> same interatomic lattice spacing as silicon carbide. One could use >> wafers of _that_ - presuming it's also an insulator - and using >> chemical vapor deposition, produce good silicon carbide transistors in >> large numbers per die... >> >> No doubt there are good reasons why that is harder than it seems. >> >> John Savard > > What exactly is the result of a transistor built on a defective piece of > crystal?
Generally, a useless piece of crystal with an interesting doping profile. I'm not sure down to the atomic level what's going on, but any crystal defect that conducts electricity and that slashes across what should be an insulating layer will kill the thing, as would any crystal defect that carries the wrong dopant into the wrong part of the device during manufacture. I try not to dwell too much on "if only", if only because you end up wasting a lot of time on useless wishing. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
On Fri, 12 Dec 2014 02:35:43 -0800 (PST), John Savard
<jsavard@ecn.ab.ca> wrote:

>Today's microprocessors are all made using the CMOS logic family. > >It has the advantage of using a minimum amount of electricity, since - except for leakage currents, which are becoming more important as transistors and wires shrink - electrical power is only used during changes of state. > >However, the performance of CMOS circuits is limited by the slower P-type FET branch of them - this can be helped by going to Germanium, which has high hole mobility, or by using stretched silicon, or by using domino logic... the IBM CELL processor used an alternative approach instead of domino logic which also worked. > >And the fastest logic family used to be ECL, because the transistors didn't saturate. But it was an energy hog. > >Silicon carbide can tolerate high temperatures, and it's a semiconductor. The trouble is that silicon carbide crystals are riddled with defects, so it's a challenge to even make decent single transistors out of it, let alone microprocessors with millions of transistors! > >However, the thought occurred to me that surely there must be some material that forms nice single crystals, free of defects, with the same interatomic lattice spacing as silicon carbide. One could use wafers of _that_ - presuming it's also an insulator - and using chemical vapor deposition, produce good silicon carbide transistors in large numbers per die... > >No doubt there are good reasons why that is harder than it seems. > >John Savard
Compound semiconductors, in addition to defects, tend to make only N-type devices. So, no equivalent of CMOS. Silicon is unique in that SiO2 makes a great implantation mask, so the photolithography process works really well. I don't think anyone has sold even an opamp from SiC. There are microwave ICs made from InP and GaAs and such, but tend to be relatively simple, with distributed amps being the high end of commercial products. http://www.semiconductor-today.com/news_items/2014/AUG/KTH_010814.shtml http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6019027&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6019027 That is NOT very impressive so far. Gigabit Logic once made GaAs logic chips, long gone now. SiC fets on the market now are slow, due to high gate contact resistances. They need a lot of gate voltage swing, too. GaN seems to be better. -- John Larkin Highland Technology, Inc picosecond timing laser drivers and controllers jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
"John Larkin" <jlarkin@highlandtechnology.com> wrote in message 
news:i9am8ah27bp9bf5ifch26p4gso3ip8a744@4ax.com...
> Compound semiconductors, in addition to defects, tend to make only > N-type devices. So, no equivalent of CMOS.
Specifically, the hole mobility is balls. So for example, the Cray-1 or whatever it was that was constructed entirely from GaAs and ran at a blazing 60MHz -- was made in old fashioned NMOS. No CMOS, no low voltage, no ECL. Almost as hot as ECL though. At least, that's what I remember reading.
> Silicon is unique in that SiO2 makes a great implantation mask, so the > photolithography process works really well.
Well, SiC too I suppose. Unless they need enough implantation energy that it goes on through regardless. Not sure about Ge, but no one uses that stuff pure because temp performance is nonexistent.
> SiC fets on the market now are slow, due to high gate contact > resistances. They need a lot of gate voltage swing, too. GaN seems to > be better.
Too bad no one's making GaN these days. Not much anyway, not for power. There's the lower voltage EPC dies, and this thing is brand new, http://www.mouser.com/ProductDetail/GaN-Systems/GS66508P-E03-TY/?qs=sGAEpiMZZMshyDBzk1%2fWi6IaY8dKw19I0Ueh0isV9Zg5enZmT3gDjg%3d%3d and with suspiciously familiar ratings if I do say so myself... Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
On Fri, 12 Dec 2014 13:56:40 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"John Larkin" <jlarkin@highlandtechnology.com> wrote in message >news:i9am8ah27bp9bf5ifch26p4gso3ip8a744@4ax.com... >> Compound semiconductors, in addition to defects, tend to make only >> N-type devices. So, no equivalent of CMOS. > >Specifically, the hole mobility is balls. > >So for example, the Cray-1 or whatever it was that was constructed >entirely from GaAs and ran at a blazing 60MHz -- was made in old fashioned >NMOS. No CMOS, no low voltage, no ECL. Almost as hot as ECL though. > >At least, that's what I remember reading.
The Gigabit Logic parts were all n-fets, with depletion fets for loads, pretty much RTL type logic; absurd power hogs.
> >> Silicon is unique in that SiO2 makes a great implantation mask, so the >> photolithography process works really well. > >Well, SiC too I suppose. Unless they need enough implantation energy that >it goes on through regardless. > >Not sure about Ge, but no one uses that stuff pure because temp >performance is nonexistent.
GeO isn't good like SiO. There are very few germanium parts made any more. One germanium device made with actual lithography is a back diode, a fairly obscure microwave detector diode. There are germanium photodiodes.
> >> SiC fets on the market now are slow, due to high gate contact >> resistances. They need a lot of gate voltage swing, too. GaN seems to >> be better. > >Too bad no one's making GaN these days. Not much anyway, not for power. >There's the lower voltage EPC dies, and this thing is brand new, >http://www.mouser.com/ProductDetail/GaN-Systems/GS66508P-E03-TY/?qs=sGAEpiMZZMshyDBzk1%2fWi6IaY8dKw19I0Ueh0isV9Zg5enZmT3gDjg%3d%3d >and with suspiciously familiar ratings if I do say so myself...
GaN is big in RF, especially military stuff. Lots of people are investing big time, and shipping parts. Macom, Cree, Triquint, Nitronics, Amcom, IR, probably more. I haven't seen a SiC or GaN fet with avalanche ratings. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Tim Williams wrote:


> So for example, the Cray-1 or whatever it was that was constructed > entirely from GaAs and ran at a blazing 60MHz -- was made in old fashioned > NMOS. No CMOS, no low voltage, no ECL. Almost as hot as ECL though.
The Cray-1 and Cray-1S were made with traditional ECL, although a custom fast version somewhere between ECL100K and EclinPs types, with about 750 ps propagation delay. That's why the static DC power dissipation was about 100KW. The clock was 80 MHz. See <http://american.cs.ucdavis.edu/academic/readings/papers/CRAY- technology.pdf> for at least one reference supporting that it WAS ECL. Jon
On Fri, 12 Dec 2014 12:27:13 -0800, John Larkin wrote:

<clip>

> I haven't seen a SiC or GaN fet with avalanche ratings.
http://www.cree.com/Power/Products/MOSFETs/TO247/C2M0040120D data sheet claims it is avalanche rugged and includes an avalanche SOA graph. Do any silicon MOSFETs beat the 1200 V, "19 A" ~10ns rise/fall performance of this part (smallest of the series)?
On 12/12/2014 3:27 PM, John Larkin wrote:
> On Fri, 12 Dec 2014 13:56:40 -0600, "Tim Williams" > <tiwill@seventransistorlabs.com> wrote: > >> "John Larkin" <jlarkin@highlandtechnology.com> wrote in message >> news:i9am8ah27bp9bf5ifch26p4gso3ip8a744@4ax.com... >>> Compound semiconductors, in addition to defects, tend to make >>> only N-type devices. So, no equivalent of CMOS. >> >> Specifically, the hole mobility is balls. >> >> So for example, the Cray-1 or whatever it was that was constructed >> entirely from GaAs and ran at a blazing 60MHz -- was made in old >> fashioned NMOS. No CMOS, no low voltage, no ECL. Almost as hot >> as ECL though. >> >> At least, that's what I remember reading. > > > The Gigabit Logic parts were all n-fets, with depletion fets for > loads, pretty much RTL type logic; absurd power hogs. > >> >>> Silicon is unique in that SiO2 makes a great implantation mask, >>> so the photolithography process works really well. >> >> Well, SiC too I suppose. Unless they need enough implantation >> energy that it goes on through regardless. >> >> Not sure about Ge, but no one uses that stuff pure because temp >> performance is nonexistent. > > GeO isn't good like SiO.
GeO2 is water soluble, in fact, but it still isn't as bad a mask as CO2. ;)
> > There are very few germanium parts made any more. One germanium > device made with actual lithography is a back diode, a fairly obscure > microwave detector diode. > > There are germanium photodiodes.
I was talking to a photodiode manufacturer the other day, who said that it was becoming hard to get high-resistivity Ge wafers, so they couldn't make me Ge PIN diodes any more. :( Germanium is unique in that it responds well from 350 to 1800 nm, which is really important in instruments applications.
>> >>> SiC fets on the market now are slow, due to high gate contact >>> resistances. They need a lot of gate voltage swing, too. GaN >>> seems to be better. >> >> Too bad no one's making GaN these days. Not much anyway, not for >> power. There's the lower voltage EPC dies, and this thing is brand >> new, >> http://www.mouser.com/ProductDetail/GaN-Systems/GS66508P-E03-TY/?qs=sGAEpiMZZMshyDBzk1%2fWi6IaY8dKw19I0Ueh0isV9Zg5enZmT3gDjg%3d%3d >> >> >>and with suspiciously familiar ratings if I do say so myself... > > > GaN is big in RF, especially military stuff. Lots of people are > investing big time, and shipping parts. Macom, Cree, Triquint, > Nitronics, Amcom, IR, probably more. > > I haven't seen a SiC or GaN fet with avalanche ratings.
Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On Fri, 12 Dec 2014 12:27:13 -0800, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Fri, 12 Dec 2014 13:56:40 -0600, "Tim Williams" ><tiwill@seventransistorlabs.com> wrote: > >>"John Larkin" <jlarkin@highlandtechnology.com> wrote in message >>news:i9am8ah27bp9bf5ifch26p4gso3ip8a744@4ax.com... >>> Compound semiconductors, in addition to defects, tend to make only >>> N-type devices. So, no equivalent of CMOS. >> >>Specifically, the hole mobility is balls. >> >>So for example, the Cray-1 or whatever it was that was constructed >>entirely from GaAs and ran at a blazing 60MHz -- was made in old fashioned >>NMOS. No CMOS, no low voltage, no ECL. Almost as hot as ECL though. >> >>At least, that's what I remember reading. > > >The Gigabit Logic parts were all n-fets, with depletion fets for >loads, pretty much RTL type logic; absurd power hogs. > >> >>> Silicon is unique in that SiO2 makes a great implantation mask, so the >>> photolithography process works really well. >> >>Well, SiC too I suppose. Unless they need enough implantation energy that >>it goes on through regardless. >> >>Not sure about Ge, but no one uses that stuff pure because temp >>performance is nonexistent. > >GeO isn't good like SiO. > >There are very few germanium parts made any more. One germanium device >made with actual lithography is a back diode, a fairly obscure >microwave detector diode. > >There are germanium photodiodes. > >> >>> SiC fets on the market now are slow, due to high gate contact >>> resistances. They need a lot of gate voltage swing, too. GaN seems to >>> be better. >> >>Too bad no one's making GaN these days. Not much anyway, not for power. >>There's the lower voltage EPC dies, and this thing is brand new, >>http://www.mouser.com/ProductDetail/GaN-Systems/GS66508P-E03-TY/?qs=sGAEpiMZZMshyDBzk1%2fWi6IaY8dKw19I0Ueh0isV9Zg5enZmT3gDjg%3d%3d >>and with suspiciously familiar ratings if I do say so myself... > > >GaN is big in RF, especially military stuff. Lots of people are >investing big time, and shipping parts. Macom, Cree, Triquint, >Nitronics, Amcom, IR, probably more. > >I haven't seen a SiC or GaN fet with avalanche ratings.
SiGe makes for screamingly fast bipolar devices... <http://en.wikipedia.org/wiki/Silicon-germanium> ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.