Contains reports on seven research projects.National Science Foundation (Grant ENG78-10436)M.I.T. Sloan Fund for Basic ResearchJoint Services Electronics Program (Contract DAAG29-78-C-0020)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)M.I.T. Cabot FundLawrence Livermore Laboratory (Subcontract 206-92-09)National Science Foundation (Grant DMR78-23555

Bezdjian, Krikor A.

Dana, Stephane S.

Flanders, Dale C.

Griswold, Marsden P.

Hawryluk, Andrew M.

Kappes, Manfred M.

Kastner, Marc A.

Kwasnick, Robert F.

Litster, James David

Melngailis, John

Smith, Henry I.

Staley, Ralph H.

Von Känel, Hans

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XIX. MICROSTRUCTURE FABRICATIONAcademic and Research StaffProf. H,I. SmithDr. J. MelngailisDr. H. Von KgnelGraduate StudentsK.A. Bezdjian A.M. Hawryluk M.M. KappesS.S. Dana R.F. Kwasnick1. CREATION OF THE SUBMICROMETER STRUCTURES LABORATORYNational Science Foundation (Grant ENG78-10436)M.I.T. Sloan Fund for Basic ResearchHenry I. Smith, John MelngailisThe goals of the Submicrometer Structures Laboratory are to develop methods offabricating surface-relief and doping structures with linewidths ranging from 100 Ato a few micrometers and to use these structures in a variety of research projects.The administrative structures and funding for the Laboratory were establishedearly in 1978. Laboratory renovations were started in August of 1978 and the mainpieces of equipment were installed in December of 1978. The Laboratory was inaugu-rated on May 8, 1979.The Submicrometer Structures Laboratory has the following capabilities:substrate cleaning and contamination-free handlingphotolithographyholographic lithographyx-ray lithographyion beam etchingplasma etchingreactive ion etchingadvanced optical microscopyelectron-beam evaporationsurface profilometry.PR No. 122(XIX. MICROSTRUCTURE FABRICATION)The Laboratory is closely coupled to a similar but larger facility at LincolnLaboratory which is also directed by H.I. Smith. The Lincoln Laboratory facilityhas all of the above capabilities as well as electron-beam lithography,In addition to the research programs described under separate headings below, theSubmicrometer Structures Laboratory collaborates in a number of other research proj-ects. The grating in the PblxSn xTe distributed feedback laser in the thesis work ofH.H. Hsieh was ion beam-etched in the laboratory. S. Frankel of Harvard and the PeterBent Brigham Hospital is designing and will build miniature thin-film electrodes tobe used to probe electrical signals in individual living cells. S. Asoury has usedthe ion beam-etching apparatus in a charge-flow transistor project. These are a fewexamples where the unique capabilities and equipment of the Submicrometer StructuresLaboratory have made possible or facilitated other research projects at M.I.T.2. DEVELOPMENT OF MICROSTRUCTURE FABRICATION TECHNIQUESJoint Services Electronics Program (Contract DAAG29-78-C-0020)Stephane S. Dana, Andrew M. Hawryluk, Robert F. Kwasnick,John Melngailis, Henry I. SmithThe objective of this program is to establish reliable techniques for fabri-cating artificial microstructures, such as surface-relief structures and doping pro-files, having dimensions ranging from 100 A to a few micrometers. In some cases theeffort consists of acquiring technologies developed at M.I.T. Lincoln Laboratory orelsewhere. In other cases the technologies are refined or extended in specializedmanners. The following technologies are being established and developed:conformable photomask lithographyholographic lithographyx-ray lithographyspatial-period divisionshadowingreactive ion etchingplasma etchingion beam etching.PR No. 122(XIX. MICROSTRUCTURE FABRICATION)3. GRAPHOEPITAXYU.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)M.I.T. Cabot FundKrikor A. Bezdjian, Stephane S. Dana, John Melngailis, Henry I. SmithRecently, D.C. Flanders and H.I. Smith at M.I.T. Lincoln Laboratory demon-strated that oriented crystalline overlayers could be obtained on amorphous sub-strates by first producing an artificial surface-relief structure in the substrate.The technique is called graphoepitaxy. In collaboration with M.W. Geis, grapho-epitaxy was demonstrated for Si over SiO 2 in 1979. In the Submicrometer StructuresLaboratory graphoepitaxy research is pursued along two avenues: basic studies ofnucleation and growth over surface-relief structures; and development of grapho-epitaxial approaches to solar cells. Our studies of nucleation and growth havefocused on silicon and GaAs deposited by chemical vapor deposition (CVD). Recently,ion beam sputtering of Si has been added. Gratings are fabricated in Si3N4 mem-branes about 2000 A thick. Thin films are grown over these gratings and the phenom-ena of nucleation and island formation are studied by transmission electron micros-copy. As expected, the artificial surface-relief structures have a profound effecton film growth.The research on graphoepitaxy for solar cells is concentrating on crystallizingamorphous Si films over artificial surface gratings in carbon or other conductingsubstrates.4. ATTACHMENT AND PROPERTIES OF MOLECULES ON SUBMICROMETER STRUCTURESU.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)Dale C. Flanders, Manfred M. Kappes, Ralph H. StaleyTechniques are being developed to provide area-selective covalent attachment ofchemicals to artificial microstructures. Research has centered on linking specificclasses of compounds to silica surfaces by means of silane reagents. Techniques havebeen explored which provide uniform thin-film coverages of the order of a monolayer.Complementary work has been pursued in three related areas: (1) chemically blockingPR No. 122(XIX. MICROSTRUCTURE FABRICATION)the attachment-active sites on silica, (2) attachment to an anodized gold surface,and (3) transition metal complexation to surface-attached ligands. Initial appli-cations of these attachment procedures have focused on surface-conductivity measure-ments across 2 micrometers of chemically modified silica surfaces. By choosing thecorrect mode of surface derivatization it is possible to prepare sensors in whichsurface conductivity is modulated as a result of changes in the chemical environmentof the attached species.5. ELECTRONIC TRANSPORT IN QUASI-ONE-DIMENSIONAL SUBMICROMETERSTRUCTURES IN SILICON INVERSION LAYERSJoint Services Electronics Program (Contract DAAG29-78-C-0020)Marc A. Kastner, Robert F. Kwasnick, John MelngailisThere is a great deal of recent interest in the behavior of electrons confinedto one dimension. In particular, reduced dimensionality is expected to reveal thestrong effects of localization, electron-electron, and electron-phonon interactions.For example, Thouless has argued that all wires are insulators at sufficiently lowtemperature. The effects of electron-electron and electron-phonon interactionshould be dramatic if electrons can be confined to two-dimensional quantum levelsbut kept free in the third dimension. Inversion layers on the surface of siliconhave been used to quantize the energy levels in one dimension, creating a two-dimensional electron gas. We are extending this technique to create a one-dimen-sional electron gas. Using the facilities of the Submicrometer Structures Laboratory,we are attempting to fabricate a quasi-one-dimensional inversion layer in Si in afield-effect transistor-type structure,6. X-RAY LENSES AND DIFFRACTION GRATINGSLawrence Livermore Laboratory (Subcontract 206-92-09)Marsden P. Griswold, John Melngailis, Henry I. SmithUnder this program, techniques for fabricating x-ray zone plates are developedat M.I.T. Lincoln Laboratory, and techniques for making x-ray diffraction gratingsPR No. 122(XIX. MICROSTRUCTURE FABRICATION)are developed in the Submicrometer Structures Laboratory. Testing is done atLawrence Livermore Laboratory. Zone plates were fabricated with minimum zone widthsof 3000 A, and imaging with 1-micrometer resolution was demonstrated. The next gener-ation of zone plates will involve 1000 A zone widths.7. SUBMICROMETER STRUCTURES AND LIQUID-CRYSTAL RESEARCHU.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)National Science Foundation (Grant DMR78-23555)J. David Litster, John Melngailis, Henry I. Smith, Hans Von KgnelWell-aligned phases of liquid crystals are necessary for studies of theirproperties by means of scattering spectroscopy. The objective of this program isto use artificial-surface microstructures, such as gratings, to induce uniformalignment of liquid-crystal phases. Various liquid crystals have been aligned onsurface-relief gratings of 1-micrometer period etched into fused-silica substrates.Alignment of butoxybenzylidene-p-oktylanilene established in the nematic phasecould be retained down to almost one degree below the nematic-to-smectic transi-tion. Farther below this the formation of focal conics could not be prevented butthe defects could be removed entirely by heating the sample into the nematic phase.By reducing the spatial period of the gratings, we hope to reduce the number offocal conics in the smectic A phase which should enable us to investigate thesmectic A-to-smectic B phase transition.PublicationsMelngailis, J., H.A. Haus, and A. Lattes, "Efficient Conversion of Surface AcousticWaves in Shallow Gratings to Bulk Plate Modes," Appl. Phys. Lett. 35, 324(1979).PR No. 122

Microstructure Fabrication

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Microstructure Fabrication

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