Materials and processes at CCST Sandia II

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by Jo Ann McDonald, US Correspondent Uncle Sam looked into his crystal ball and dug deeper into almost empty pockets, and came up with a few more millions of the taxpayers hard earned dollars for compound semiconductor material development. $31.5 million for GaAs wafers out of old Title III Defense Production Act funds, at least $10 million from ARPA for high temperature SiC and Nitride development, and $816,000 from the Air Force's Wright Labs to form a SiC consortium. dd to that ongoing ripples of support through SB|Rs and any other mechanism the services can unearth, and you continue to have a decent foundation for compounds and thin films, thanks to government support. After all, it's still the military that needs these esoteric niche technologies, and they know all too well that, to get what they need, somebody has to pay for the N R E s entailed. In this issue of T F R ' s Inside Edge, we'll take a detailed look at what's going on within those funding circles from the government point of view, and look to the recipients" end of the spectrum next time. One other noteworthy government program is what some may feel is a controversial new pursuit of good cubic phase SiC material, being led by the U.S. Army.

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Unfinished business Remember the piece I wrote on SiGe last issue'? It seems I misinterpreted Charles Fadcl's c o m m e n t s in one rather important place in the article, I implied that the lattice strain was the reason Analog Devices "no bid" on the contract with IBM. This was

indeed N O T the case. The decision not to bid was based purely on the specifications of the converters, not to potential problems with SiGe. My apologies. Analog Devices further pointed that "although there is a lattice mismatch between Si and Ge, this is not a problem, so long as the GexSi]_x layer thickness and Ge concentration are well-contTolled, the layer is then s t r a i n e d ( p s e u d o morphic) but defect free. Dr Myers o n ' s development of u l t r a - h i g h vacuum continuous vapour deposition ( U H V / C V D ) provides us with the process to consistently manufacture SiGe devices. The fact that we've demonstrated that working DAC, with 3000 devices, at good yields, proves that this is more thaq feasible," Also, Charles Fadel has moved his offices at Analog Devices. His new c o n t a c t is: A n a l o g Devices, 181 Ballardsvale St., Wilmington, MA 01887-3482, Tel/Fax: 617/937-1113, 1051. The company's talk at M T T went over quite well, but before we let the I B M / A D SiGe team off the hook, however, it's interesting to note that everything you may read on the subject may not be quite as it should be.

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For example, when discussing the prospects of SiGe during my interview with Lou Tomasetta, CEO of Vitesse Semiconductor (See America's Best, pg. 26 this issue), Lou (who has never been too keen on epi) pointed out that one of the misperceptions from the trade press regarding SiGe is in regard to "this claim that, because it uses Si substrates, it's by definition not expensive. My view of this is probably the reverse, it's really a bipolar technology with a very sophisticated Ge epitaxial layer. If you're doing bipolar, it's by definition very complicated, and therefore a lot more expensive than if you were doing FETs. Therefore, the costeffective touting should be taken with a grain of salt. For real small parts, and small die sizes, I think the cost of the wafer is probably not a big portion of the total price. From an economic standpoint, that limits the kinds of applications that you can do with technology. The technology is sort of interesting, but I'm not sure, if within a company that had a good G a A s M M I C process that could build parts, they'd stop what they were doing to switch to a SiGe process. It'll be interesting to see what devel-

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ops, and I'm sure they'll find a few customers." Letting Analog Devices' Rupert Baines get in the last word, Rupert countered with: "although commercial prices have not yet been established, it appears that SiGe should n o t be as expensive as stated. The UHV/ CVD deposition is a single, and comparatively simple processing step, carried out using commercial equipment on standard, cost-effective Si wafers. When you remember that manufacture will be on 8" (200 ram) wafers with FOUR TIMES the area of 4" wafers (typical in GaAs), the economics of scale become clear." And now that we've brought up the subject of epi, my inside sources say that those highly touted multi-wafer processing machines of Riber, which Bandgap bragged on and on about, have found their way now to Raytheon, which picked up the two machines for a song when Bandgap went under. The problem now is, what does Raytheon do with them? Calls are going out from Raytheon for credible numbers on future need for epi GaAs wafers. Raytheon's upper managment, no doubt, would like to see something done with their new toys. My answer regarding credible numbers for future epi needs is that that's a contradiction in terms, and therefore why I personally ~don't do numbers." Over the last 15 years in this business, I've never seen a set of numbers that panned out, except for the sellers of the studies, and trade press editors seem to feed on them, usually for lack of a decent opinion of their own on any given subject. Nevertheless, whether pro-thin film or anti (GaAs or SiGe), pro-cubic SiC or necesarily living with the existing hex on your house, needless to say, it appears to remain a hot season for compounds, at least in the USA.

Title ill D P A funds resurrected As JoAnne Dalton at M/A-COM noted regarding the unleashing of funds through the Defense Production Act (DPA), at long last, "it's a little like finding a wallet on the street." We all knew the money was there, but where and when it would finally turn up, and who would be able to lay claim to it were the unanswered questions. The handful

of US SI GaAs wafer suppliers, M/ACOM, Airtron, and AXT who won the prize, and in their collective opinion it was worth the wait. M/ACOM Inc. Semiconductor Division (Lowell, Massachusetts) received $12.5 million, Airtron Division, Litton Systems Inc. Electronic Materials Group (Morris Plains, New Jersey) received $10.1 million, and American Xtal Technology (AXT), also known as Bestal Corp. (Dublin, California) received $8.9 million. The three companies are just a few months into the four-year, two-phase program, and we'll delve into details of what each is doing in our next issue of TFR. In this issue, we'll procure the government's perspective. Considering that there is a grave possibility of once again going to war with North Korea, it is especially interesting that the Title III Defense Production Act was originally enacted in 1950 to assist the mobilization for the original Korean conflict. As usual, following a war, the US disarmed (American's hate the thought of war, especially when one is over), and the DPA lay virtually inactive as interest in the defense industrial base waned. Concerned about U.S. industrial, with international competitiveness on the rise, the Act was updated by Congress in 1984 at the height of the Cold War advanced technology build-up, and again in 1992 to provide impetus for development of domestic production capacity for high tech materials deemed essential for both military and commercial systems. It has literally taken the proverbial 'tAct of Congress" to update the Act and unleash the funds. Thanks to a renewal of interest in "dual use technologies" and the well-supported defense conversion programs such as the popular Technology Reinvestment Project (TRP), if it sounds like something that will put the U.S. on a better competitive footing, while putting the right components on standby for the military, a given technology stands a decent chance of Congressional support. Evidently, GaAs wafers made the cut. The mission of this unique program is to maintain U.S. technological leadership in defense production, according to John Blevins, Title III GaAs Program Manager of the Manufacturing Technology Directo-

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rate, WL/MTD at Wright Labs, Wright-Patterson AFB, OH 454336533, Section 303, Title III of the DPA of 1950 as amended (50 U.S.C. app. 2093), which authorizes the use of Government purchases and purchase commitments to encourage private efforts to establish or expand industrial capacity, develop technical processes, and produce essential materials needed for national security...etc., etc., etc. You can see why it has taken patience and perseverance to procure the funds. The official objective of the GaAs Wafer Project is to strengthen the overall viability of U.S. domestic GaAs wafer manufacturers in order to secure long-term, world-class manufacturing capabilities to produce semi-insulating GaAs wafers in support of DoD and commercial requirements. Unofficially, it gives these three companies extra funds to hasten the pace of doing do what they are already doing, which shoring up their plants to go toe-to-toe with Asian and European suppliers, and be ready with 6 inch materials by the time the users in the U.S. reach plant capacity in 4 inch and need to move on up to 6. As Lou Tomasetta of Vitesse Semiconductor, an obvious user of the wafers, "its 10 years too late, but better late than never." Companies such as Spectrum Technologies, (which did much of the original painful wafer development in the U.S.) are now dead and gone. They might have survived had those funds been unlocked two years ago when they were first discovered. M/ A-COM with it's high pressure LEC material, and Airtron with its low pressure approach, persevered, and both companies only recently turned the corner towards profitability. AXT, a relative newcomer on the scene, is focusing on an interesting Vertical Gradient Freeze (VGF) methodology. All parties involved want consistency and high quality, boule after progressively bigger boule. Phase I of the program, which lasts 24 months, calls for process improvement and material qualification. Phase II, which also lasts 24 months, entails formal market planning and a Government purchase commitment which serves an "Incentive Sales Continued on page 44