Scott E. Rickert

ELECTRON BEAM RESISTS PRODUCED FROM MONOMER–POLYMER LANGMUIR–BLODGETT FILMS

Abstract Recent technological advances in very-large-scale integration are beginning to outstrip the technology used to produce these circuits. UV and optical lithography techniques are producing resist patterns with resolutions approaching the expected minimum. Application needs demand that this minimum be improved to achieve more features per unit area of circuit. We have achieved improved resolution of resist patterns. Through the use of monomer-polymer multilayers, fine line resolution, produced by way of a novel computer-controlled electron beam technique, is now possible. The relative ease and high reliability of multilayer formation ensures uniform films of a thickness an order of magnitude less than that of spin-cast films. The high electron sensitivities of these films enables excellent degradation (or polymerization) upon exposure to an electron beam. Final pattern resolution, for both positive and negative resists, is an order of magnitude higher than conventional resist resolution, offering possible improvement in circuit capability. Morphological studies of these multilayer films provide unique information on domain size and structure. The ultimate morphology of these films is shown to be dependent on deposition conditions as well as the substrate used.

The study of metal-insulator-semiconductor structures with Langmuir-Blodgett insulators

Abstract Metal-insulator-semiconductor structures were fabricated using a polymerizable diacetylene film on silicon substrates using the Langmuir-Blodgett technique. A mercury probe was used to measure the high frequency capacitance-voltage (C-V) characteristics of the structure. The C-V curves indicate accumulation, depletion and deep depletion of the silicon surface. The dielectric constant of the 10,12-nonacosadiynoic acid (16-8 polydiacetylene) film was calculated to be 2.13. The effective fixed charge density at the insulator-silicon interface ranged from 1010 to 1011 cm−2. Hysteresis was observed in the C-V curves and appears to be consistent with charge trapping at the silicon-insulator interface. Using the C-V technique as a criterion, the polydiacetylene was thermally stable up to 120 °C.

Epitaxial crystallization of polyoxymethylene

Epitaxial growth of synthetic polymers on alkali‐halide surfaces usually proceeds along the preferred 〈110〉 directions parallel to the {100} plane of the substrate. Polyoxymethylene was epitaxially crystallized as thin films on alkali halides and analyzed using the electron microscope. The metastable orthorhombic crystal form was obtained on substrates which exhibited a lattice match with the [100] distance of the orthorhombic form. Matching was not necessary for the growth of the normal hexagonal crystal form, although it did affect both the nucleation process and the growth rate of the epitaxial crystallization. The technique seems to be quite generally applicale in affecting the general morphology of the crystallization and the formation of metastable polymeric forms.

The Formation of Single Crystal Films of Polydiacetylenes

Abstract The two-step process of epitaxial polymerization has been applied to symmetrically substituted diacetylenes. First, the monomers have been crystallized epitaxially on alkali halides substrates from solution and the vapor phase. The oriented monomer crystals are then polymerized under the substrates influence by gamma-irradiation. The diacetylenes in this study are 2,4-hexadiyn-1,6-diol (HD) and the bisphenylurethane of 5,7-dodecadiyn-1,12-diol (TCDU). The polydiacetylene crystal structures and morphologies have been examined with the electron microscope. Reactivity and polymorphism are found to be controlled by the substrate.

Epitaxial polymerization of (SN)x: Lattice effects on structures and topochemistry

Disulfur dinitride was epitaxially crystallized from the vapor phase on freshly cleaved (100) faces of monovalent alkali halide single crystals. Subsequently, the dimer was polymerized in the solid state, while still on the substrates. This epitaxial polymerization leads to highly oriented crystalline polythiazyl [(SN)x] which shows no evidence of the usual fibrullar morphology. Fibrils of (SN)x have been produced by epitaxial polymerization of a second layer of dimer on a previously polymerized layer. Three new structures of polythiazyl have been observed from crystals grown on NaCl, KBr, and KI. The structures differ significantly from the usual α phase of (SN)x. Because of such large differences in the polymer chain spacing in these forms when compared to the normal form, a new polymerization mode and direction may be involved. The diagnosis of the true effect of water on (SN)x using Fourier‐transform infrared spectroscopy (FT‐ir) aided in discovering why structural studies from samples exposed to wate...

Integrated metal-Langmuir-semiconductor field effect transistors

Abstract An array of integrated, n-channel, enhancement mode, field effect transitors using Langmuir-Blodgett films as gate insulators have been fabricated and studied. Effective insulator charge densities for the metal-Langmuir-semiconductor field effect transistors (MLSFETs) were found to be on the order of 1011q cm-2. The surface mobility of the MLSFETs was found to be between 550 and 600 cm2 V-1 s-1 at effective fields of 5 × 107 V m-1. The mobility was also found to be independent of the effective insulator charge density. These mobility figures compare quite favorably with the published figures for Si-SiO2 devices with similar effective charge densities and fields. Stability of the MLSFETs was studied and found to be good; unencapsulated storage for several days to a week at room temperature and humidity levels produced no discernable difference in the I-V characteristics. The characteristics of the devices are shown to be accurately modeled using the traditional MOSFET model and equations. Saturated transconductance vs. the gate width-to-length ratio and gate bias plots were linear, indicating that the device would be useful as a replacement for a similar MOSFET.

Constructing a processing window for a Langmuir-Blodgett film☆

Abstract The effect of Langmuir-Blodgett process parameters on the stability of monolayers at the gas-water interface and on the preparation of multilayers was investigated for a fatty acid (brassidic acid). Creep tests, used to determine stability, were found to correlate well with stability information obtained from standard pressure-area isotherms. The isotherm was utilized as a monolayer stability (strength) test in evaluating the effects of various process parameters. A “process window” was eventually developed that allowed reproducible production of homogeneous films by outlining the allowable ranges of the various parameters.

50 nm resolution, defect-free, electron-beam resists produced with monomer/polymer multilayer films

Recent technological advances in very large scale integration (VLSI) are beginning to outstrip the technology used to produce these circuits. Ultraviolet and optical lithography techniques are producing resist patterns with resolutions approaching the expected minimum. Application needs demand that this minimum be improved to achieve more features per unit area of circuit. We have achieved a potentially major breakthrough towards improving the resolution of resist patterns. Through the use of monomer/polymer multilayers, line resolutions produced by way of a novel computer-controlled electron beam technique is now possible. The relative ease and high reliability of multilayer formation ensures uniform films of a thickness an order of magnitude less than spin cast film thicknesses. The high electron sensitivities of these films enables excellent degradation (or polymerization) upon exposures to an electron beam. Final pattern resolution, for both positive and negative resists, is an order of magnitude higher than conventional resist resolutions, offering possible improvement in circuit capability. Morphological studies of these multilayer films provide unique information on domain size and structure. The ultimate morphology of these films is shown to be dependent on deposition conditions as well as the substrate used.

Epitaxial polymerization of (SN)x: Chemical defects

Epitaxially polymerized (SN)x on various substrates has been studied by Fourier‐transform infrared spectroscopy (FT‐ir). Those substrates include Pt‐shadowed KI, AgCl, NaCl, KCl, KI, KBr, RbI, and NaI. All samples of the polymer contained significant amounts of chemical defects, mostly as NH and S=O groups. The spectral variation observed with (SN)x polymerized on various substrates appeared to be due to differences in its degradation by water. There are at least two distinct degradation mechanisms. One is the degradation by water incorporated into the S2N2 crystals prior to the polymerization, and the other is the attack of moisture on the polymer. The nature of the chemical defects were studied by deuterium exchange and degradation by H2 18O as well as H2 16O. The band at 1400 cm−1 was assigned to the NH group while two bands at 1220 and 1090 cm−1 were assigned to S=O groups with different chemical environments. The band at 1220 cm−1 is related to a structure produced during the early stages of degradat...

Low surface energy polymers and surface-active block polymers IV: Monolayers at the air-water interface

Abstract The spreading of five block copolymers of 2-(p-(t-butyl)phenyl) oxazoline (hydrophobic block) and 2-ethyl oxazoline (hydrophilic block) at the air-water interface was studied using Langmuir-Blodgett film balance techniques. Three regions of compression were found. At low force, the hydrophilic block was being compressed. This continued until the hydrophobic tails contacted each other. The second region was the compression of the hydrophobic tails lying almost flat on the water surface. As the pressure increased to 40 mN m−1, the hydrophobic tail rotated so that the side chains were perpendicular to the surface. The area of the hydrophobic block in the most compressed state was about equal to its thickness multiplied by its chain length. As chain length increased, packing efficiency decreased slightly. All compressed phases remained liquid like. The films remained as monolayers up to the pressure (about 70mNm −1) permitted by the trough.