HERE - American Association for Crystal Growth

More documents

Recommendations

Info

Interview with David WitterContributed by David BlissDuring his career as a crystal grower and inventor, DavidWitter contributed to many research and development projectsin semiconductor, optical, and magnetic materials. Overthe years, he became an expert at designing control systemsfor crystal growing equipment. He met with David Blissrecently to talk about his experiences.DB: How did you get started in crystal growth?DW: When I started my freshman year at NC State UniversityI got a job as a technician in the Engineering ResearchDepartment growing crystals of sapphire and magnesiumaluminate spinel using a plasma torchfollowing the work of Tom Reed of MIT.After seven years in Ceramic Engineeringat NC State, I took my first job atthe new Union Carbide Crystal Products(UCC) plant in San Diego, CA in 1968working for G. A. Keig and Fedia Charvat.My education has always benefitedfrom a kind of informal apprenticeshipsystem.DB: Who did you work with in the earlydays?Morton Jones and Roland Johnson on GGG for lasers andmagnetic bubble memories. I was sharing an office withFrank Bruni for six months before he left TI for the newAllied Chemical plant in Charlotte.DB: How did you get to know Gordon Teal and Jack Kilby?DW: Gordon Teal came to TI from Bell Labs to be thefirst VP of Research in 1952. He had invented the Teal-Little crystal growth process that later became known asCzochralski growth. Mort Jones had been one of his firstcrystal growers at TI.In 1990, several of the crystal growthprofessionals at TI started the TexasSection of the AACG. I was installedas president. The first meeting washeld at Taffy’s Restaurant. I was ableto get Jack Kilby to come and speak tous when I told him that Gordon Tealwas coming to the meeting. It wasa great evening and Gordon broughtreprints of his first germanium andsilicon crystal growth publications.DW: In San Diego at UCC I met RalphHutcheson; he grew the first ruby lasercrystal for Ted Maiman’s laser. Ralphstarted Scientific Materials later in Bozeman,MT. Ted worked for the UCC sistercompany “KORAD” in Santa Monica,CA. We had several meeting withthem concerning our YAG and ruby laser components overlunch at the Ball restaurant in Santa Monica.After four years at UCC, I left San Diego and went to workat the Allied Chemical Corporation in Morristown, NJwhere Jack Gillman (dislocations in LiF) was the director. Iworked for Bob Linares and M. Alton Gilleo, both formerlyof Bell Labs. Then, four years later, Allied moved the groupto Charlotte, NC so I interviewed and found better opportunitieswere available at Lawrence Livermore National Laboratory,Texas Instruments (TI), Motorola and Airtron.I moved to TI Central Research in Dallas in 1976 to work for12David WitterJack arrived at the meeting after gettingoff of a plane from Japan just intime to say how significant Gordon’swork was to the invention of the integratedcircuit. Gordon passed awayin 2001 and Jack in 2003.As an Industry Professor at Texas A&M University, I wasasked to represent TI at a faculty senate meeting to recommendJack Kilby for an Honorary Doctorate. I rememberstepping outside the building with Jack during the deliberationso that he could smoke several cigarettes. He addedthe TAMU Doctorate to the many honorary doctorates thathe already had from other Universities.Later I worked for Jules Levine on the Kilby invention ofa solar array based on single crystal silicon spheres. Mypatented process for crystal growth of the spheres went intoproduction many years later at ATS Spheral Solar, but thereAACG Newsletter Summer 2013
were continuing bonding problems between silicon and aluminumand the company withdrew its IPO.DB: How did you manage the transition from GGG to silicon?DW: TI had a policy of promoting transfers with a JobOpportunities Bulletin that came out every Monday. It wasnot necessary to leave TI in order to gain experience withother projects. After the market for bubble memory burst in1980 (due to the success of CMOS and the Winchester harddisk technology), I worked on VLSI silicon and grew thefirst 125 mm silicon crystals at TI in the research building. Ifound the IDEA program at TI very useful for starting newprojects and in 1983 I became a Senior Member of TechnicalStaff because of my successful IDEA project. Thatproject resulted in the deployment of my automatic crystalgrowth control system using video from the recently inventedcharge-coupled device (CCD) cameras that were muchmore linear and sensitive than vidicon tubes.DB: Did you also work on compound semiconductors?DW: In 1988 two people, a Senior Member of TechnicalStaff and a TI Fellow, left a big hole in the TI crystal growtheffort of mercury cadmium telluride (MCT) by resigning inthe same month. I was requisitioned to manage the DefenseAdvanced Research Project Agency (DARPA) project forthe Traveling Heater Method (THM) growth of MCT forcooled focal plane arrays (Javelin Missile). Later it was decidedthat the 90 day long THM process was too expensiveand too difficult for development of a reproducible product,and all 25 stations were shut down. A decision was madeto use Liquid Phase Epitaxy (LPE) (a four hour process).After that, I worked on the horizontal Bridgman growth ofcadmium zinc telluride for substrates for LPE of MCT.DB: Did you work on other projects at TI?DW: In 1991, I transferred to the Uncooled Focal PlaneArray group to make four inch diameter fine-grained bariumstrontium titanate (BST) wafers. BST was a photocapacitorfor 8-12 micron infrared imaging. We set the phase transitiontemperature to 25 °C and put the device on a thermoelectriccooler to hold it at 25 degrees regardless of the ambient.The dielectric constant of each ceramic pixel changedfrom 500 to 25000 with a two degree change in temperature.A scene viewed through long wavelength infrared optics wasmechanically chopped to produce a video signal. The camerahad fantastic imaging capability due to the uniformityand fine-grained structure in the ceramic wafers. However,laser reticulation of the pixels was slow and not easily replacedby ion milling, so the development effort shifted toPLZT (lanthanum stabilized lead zirconium titanate) whichnever made it into production of focal plane arrays.DB: Did you work on developing crystal growth equipmentor processing equipment?DW: In 1976 when I first joined TI Jerry Alford, formerlyof UCC and Allied, called me to see if I could help himfind an application for his Ford Aerospace laser inspectiontechnology developed for textiles. I put him in touch withJoe Ayres in Sherman, TX and the whole wafer inspectiontechnology was born.My last years at TI before retiring in 1998 were in the siliconmaterials department which merged with MEMC in1994, leading to the construction of a $450M 200mm siliconcrystal growth factory. I was the materials manager forthe critical supplies used in silicon crystal growth. Polysilicon,quartz crucibles, graphite heaters, graphite fiber insulationand boron quality were my responsibility. Everypolished wafer was scanned for defects on the commerciallaser inspection stations that had resulted from my earlierresponse to Jerry Alford. Correlation of the scanned defectswith critical material lots and parts used in the growthfurnaces identified problems and kept the yields high.DB: After retirement, did you continue working?DW: Yes, I became Director of Engineering at NorthropGrumman SYNOPTICS in 2000 after I retired from TI andI also started consulting as ANAXTAL. At SYNOPTICS,I emphasized process automation. Weight control systemsfor Czochralski growth were substantially improved usinga rotary contactor with a transduced digital signal instead ofthe low voltage analog signal of the load cell. Since SYN-OPTICS is the merged Litton Airtron and Allied Chemicalfacility that I did not move to in 1976, I felt as though I wasreturning from a 24 year sabbatical at TI.DB: How do you think the US crystal growth communitycan sustain itself, given the migration of crystal growthtechnology to lower-cost countries?DW: The US has outsourced and off-shored much of ourmaterials manufacturing in the last 20 years. Therefore,our crystal growth technology has suffered tremendously.Only a few companies survive as “National Treasures” andeven some of them have gone offshore for their crystallineproduct manufacturing. We need to think smarter and useAACG Newsletter Summer 2013 13
Page 3 and 4: AACG newsletterEDITORCandace LynchI
Page 5 and 6: AACG Newsletter Summer 2013 5
Page 7 and 8: ObituaryIchiro SunagawaIchiro Sunag
Page 9 and 10: Upcoming EventsJuly 7-12, 2013Gordo
Page 11: At lunch on the harbor at Poulithra
Page 15 and 16: Announcing theACCGE-19Photo Contest
Page 17 and 18: Recent Government Contracts Awarded
Page 19: Crystal IS- Albany, New YorkCrystal

HERE - American Association for Crystal Growth

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?