Contains reports on six research projects.Joint Services Electronics Program (Contract DAAG29-78-C-0020)Joint Services Electronics Program (Contract DAAG29-80-C-0104)M.I.T. Sloan Fund for Basic ResearchU.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)Lawrence Livermore Laboratory (Subcontract 206-92-09)U.S. Department of Energy (Contract DE-ACO2-80-E10179)Harkness Foundatio

Bezdjian, Krikor A.

Dana, Stephane S.

Hawryluk, Andrew M.

Horwitz, Christopher M.

Kastner, Marc A.

Kwasnick, Robert F.

Melngailis, John

Rotter, Shlomo

Smith, Henry I.

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XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCHAcademic and Research StaffProf. H.I. Smith Dr. J. MelngailisDr. C.M. Horwitz* Dr. N. Tsumita+Graduate StudentsK.A. Bezdjian C. Fuleihan A.M. HawryluktS.S. Dana E.M. Garber R.F. Kwasnick1. OPERATION OF SUBMICRON STRUCTURES LABORATORYJoint Services Electronics Program (Contracts DAAG29-78-C-0020 andDAAG29-80-C-0104)M.I.T. Sloan Fund for Basic ResearchJohn Melngailis, Henry I. SmithThe goals of the Submicron Structures Laboratory are to develop methods offabricating surface structures of nanometer to micrometer linewidths and to usethese structures in a variety of research projects.Since May 1979, when the Submicron Structures Laboratory was inauguratedwithin the Research Laboratory of Electronics, all of the equipment needed forfabrication has been operating and in heavy use. Support personnel has been ex-panded from one technician to three. A scanning electron microscope has beenbought and put into operation. The main projects of the laboratory are outlinedbelow. In addition, the laboratory has served as a resource for numerous researchprojects of neighboring laboratories and has participated in smaller collaborativeprojects. Some examples:a. P.F. Liao of Bell Laboratories visited our laboratory for two weeks andfabricated a grid of silver dots with 0.3 pm period in two orthogonaldirections. This permitted the first observation and study of theVisiting Harkness Fellow from the University of Sydney, Sydney, Australia.+Visiting Scientist from Hitachi Central Research Laboratory, Tokyo, Japan.tResearch Assistant, M.I.T. Lincoln Laboratory.PR No. 123 107(XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCH)surface-enhanced Raman effect on artificially produced particles of1controlled size.b. R.M. Fastow fabricated thermal desorption arrays for the molecular micro-scope as a B.S. physics thesis with Prof. J.G. King.c. D.H. Liang has fabricated micron-sized contacts for measuring the elec-trical currents in a single nerve cell. The design and production ofthis structure was carried out in the Submicron Structures Laboratory.This nerve cell project is being done in collaboration with Prof. R.G.Mark of the E.E.C.S. Department, Dr. William Barry of the Peter BentBrigham Hospital and S. Frankel, formerly of Harvard.d. Square-wave profile gratings of 0.3 im to 1 pm period have been fabricatedby H. von Kanel for research on liquid crystal alignment. This work is incollaboration with Prof. J.D. Litster.e. Surface-acoustic-wave structures, which consist of gratings on a YZLiNbO 3 parallel-faced slab, have been fabricated. The aim is to exploitthe recently discovered, very efficient, surface-wave-to-bulk-plate-modecoupling in gratings to make low-loss narrow-band filters. 2'3 This workis done in collaboration with Prof. H.A. Haus, A. Lattes, and E.M. Garber.Publications and References1. P.F. Liao, J.G. Bergman, D.S. Chemla, A. Wokaun, J. Melngailis, A.M. Hawryluk,and N.P. Economou, "Surface Enhanced Raman Scattering from MicrolithographicSilver Particle Surfaces," submitted to Phys. Rev. Letters.2. J. Melngailis, H.A. Haus, and A. Lattes, "Efficient Conversion of SurfaceAcoustic Waves in Shallow Gratings to Bulk Plate Modes," Appl. Phys. Lett. 35,324 (1979).3. H.A. Haus, A. Lattes, and J. Melngailis, "Grating Coupling between SurfaceAcoustic Waves and Plate Modes," IEEE Trans. on Sonics and Ultrasonics, SU-27,258-266 (1980).4. H.I. Smith, "The Impact of Submicrometer Structures on Future Integrated Elec-tronics," EASCON '79 Record, pp. 296-297.PR No. 123 108(XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCH)2. DEVELOPMENT OF MICROFABRICATION TECHNIQUESJoint Services Electronics Program (Contracts DAAG29-78-C-0020 andDAAG29-80-C-0104)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)Andrew M. Hawryluk, John Melngailis, Henry I. SmithTechniques are being developed for the fabrication of artificial microstruc-tures having minimum feature sizes in the range of 100 A to 1 pm. Methods thatare applicable to periodic and quasi-periodic structures are emphasized, including:holographic lithography, spatial-periodic division, and x-ray replication of"shadowed" relief gratings. These techniques were initiated at M.I.T. LincolnLaboratory. Starting with holographically exposed patterns we have producedgrating masks and have x-ray-replicated linewidths as fine as 500 A. Structuresof 500 A linewidth were etched into Si0 2 substrates by reactive ion etching. Insome cases, sawtooth and square-wave profile relief gratings in polymide wereobliquely shadowed with heavy elements to yield high-contrast x-ray masks, whichwere then x-ray replicated. We hope to achieve 100 A linewidths with this orsimilar techniques. To expose gratings with spatial periods below 1000 A we willuse the near-field diffraction pattern of a grating of narrow slits, so-called"spatial-period division." Techniques for fabricating a 2000 A period grating of500 A wide slits in thick gold, to serve as the parent grating, are being devel-oped.PR No. 123 109(XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCH)3. X-RAY LENSES AND GRATINGSLawrence Livermore Laboratory (Subcontract 206-92-09)Joint Services Electronics Program (Contracts DAAG29-78-C-0020 andDAAG29-80-C-0104)U.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)Andrew M. Hawryluk, John Melngailis, Henry I. SmithStarting with a mask generated by scanning electron-beam lithography, Fresnelzone plates are being fabricated to be used as x-ray lenses. This work is cur-rently being done partly at Lincoln Laboratory and partly at the Submicron Struc-tures Laboratory. So far, a number of zone plate patterns with 0.3 pm minimumlinewidth and 0.7 to 1.0 pm gold thickness have been fabricated on a glass sub-strate. X-ray replication and microplating techniques needed to achieve thesestructures have been developed. Techniques for removing the glass to leave afree-standing structure are being refined.A 0.3 pm period grating of 0.7 pm thick gold lines has been fabricated on a20.7 pm thick polymide film over an area of 1 cm . This will serve as a trans-mission grating for x-rays and is being tested at Lawrence Livermore Laboratory.Very thick (lO0 pm) zone plates with 5 pm minimum zone width for so-called"coded imaging" are being fabricated in collaboration with the Lawrence LivermoreLaboratory. For this fabrication a procedure for directional reactive ion etchingof organic films with oxygen was employed.PublicationsH.I. Smith, "Equivalent Data Rate of X-Ray Lithography Systems," Proc. 9th Inter-national Conference, Electron and Ion Beam Science and Technology, St. Louis,Missouri, May 1980 (in press).PR No. 123 110(XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCH)4. GRAPHOEPITAXYU.S. Navy - Office of Naval Research (Contract N00014-79-C-0908)U.S. Department of Energy (Contract DE-ACO2-80-E10179)Stephane S. Dana, Krikor A. Bezdjian, Shlomo Rotter, Henry I. SmithThe graphoepitaxy work has two main goals: to understand the fundamentalmechanisms of orientation by artificial steps on substrates and to produce uni-formly oriented semiconductor films on conducting substrates appropriate forsolar cells. Silicon crystallites have been nucleated on 3000 A period gratingstructures using chemical vapor deposition. The nuclei appear to be orientedand to grow primarily in the bottoms of the grooves where they are confined bythe vertical sidewalls. To further study the orientation mechanisms on reliefgratings, NaCl crystals have been grown from an aqueous solution. Orientation dueto the grating is observed, and experiments are being carried out to determine theconditions needed for this.Fine gratings on conducting molybdenum substrates have been successfullyprepared by electron-beam evaporation and lift-off. Attempts will be made togrow InP and GaAs on these substrates by liquid-phase epitaxy. In addition,liquid-phase epitaxy has been carried out on patterned lead tin telluride sub-strates. The pattern consists of square islands produced by crossing two 3.8 Imperiod gratings. The morphology of the lead tin telluride layers grown on thepatterned substrates improved substantially. The electrical characteristics ofthese "homographoepitaxial" layers will be studied.PR No. 123 111(XIX. SUBMICRON STRUCTURE FABRICATION AND RESEARCH)5. ONE-DIMENSIONAL CONDUCTION IN SILICONJoint Services Electronics Program (Contracts DAAG29-78-C-0020 andDAAG29-80-C-0104)Robert F. Kwasnick, Marc A. Kastner, John MelngailisA field-effect transistor-type structure has been fabricated in which theconduction path under the gate electrode is divided into sharp ridges. The tipsof the ridges on a preliminary grating have 30-nm radius. With this structure,effects due to electron localization in the one-dimensional conductors are ex-pected to be observed. One structure has been tested as a function of tempera-ture. Preliminary results resemble the behavior of an MOS transistor.6. REACTIVE ION ETCHINGHarkness FoundationJoint Services Electronics Program (Contracts DAAG29-78-C-0020 andDAAG29-80-C-0104)Christopher M. HorwitzThe reactive ion-etching rates of Al, Cr, Si, Si0 2, and MgF 2 have been studiedfor various gas compositions, pressures, and bias voltages. The aim of this workis to fabricate highly conducting metal grids of about 0.75 pm period and narrowlinewidth to serve as optical filters or as contacts on solar cells, and to de-velop random arrays of pointed conical structures, with an average spacing of lessthan 0.1 pm, to serve as optically nonreflecting structures. For both of theseapplications very directional etching is needed, which can only be adhieved with alow mask-to-substrate etch-rate ratio. Several important results have been achieved,o far: the Si0 2/Si etch-rate ratio has been controlled between 8.6 and 0.02. TheA1/MgF 2 etch-rate ratio in C12 mixtures can be as high as 130 provided care istaken with vacuum techniques. For other gas mixtures Al can be an excellent mask.For example, an etch-rate ratio for Si/Al of greater than 3000 has been observed.PR No. 123

Submicron Structure Fabrication and Research

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Submicron Structure Fabrication and Research

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