Diamond may be grown at low pressures where it is the metastable form of carbon. Recent advances in a wide variety of plasma and electrical discharge methods have led to dramatic increases in growth rates. All of these methods have certain aspects in common, namely, the presence of atomic hydrogen and the production of energetic carbon-containing fragments under conditions that support high mobilities on the diamond surface. Some understanding of the processes taking place during nucleation and growth of diamond has been achieved, but detailed molecular mechanisms are not yet known. Related research has led to the discovery of a new class of materials, the "diamondlike" phases. Vapor-grown diamond and diamondlike materials may have eventual applications in abrasives, tool coatings, bearing surfaces, electronics, optics, tribological surfaces, and corrosion protection.

https://science.sciencemag.org/content/sci/241/4868/913.full.pdf

Low-Pressure, Metastable Growth of Diamond and "Diamondlike" Phases

A Three Dimensional Structure (3DS) Memory (100) allows for physical separation of the memory circuits (103) and the control logic circuit (101) onto different layers (103) such that each layer may be separately optimized. One control logic circuit (101) suffices for several memory circuits (103), reducing cost. Fabrication of 3DS memory (100) involves thinning of the memory circuit (103) to less than 50 microns in thickness and bonding the circuit to a circuit stack while still in wafer substrate form. Fine-grain high density inter-layer vertical bus connections (105) are used. The 3DS memory (100) manufacturing method enables several performance and physical size efficiencies, and is implemented with established semiconductor processing techniques.

Three dimensional structure memory

Graphene films grown on Cu foils have been fluorinated with xenon difluoride (XeF2) gas on one or both sides. When exposed on one side the F coverage saturates at 25% (C4F), which is optically transparent, over 6 orders of magnitude more resistive than graphene, and readily patterned. Density functional calculations for varying coverages indicate that a C4F configuration is lowest in energy and that the calculated band gap increases with increasing coverage, becoming 2.93 eV for one C4F configuration. During defluorination, we find hydrazine treatment effectively removes fluorine while retaining graphene’s carbon skeleton. The same films may be fluorinated on both sides by transferring graphene to a silicon-on-insulator substrate enabling XeF2 gas to etch the Si underlayer and fluorinate the backside of the graphene film to form perfluorographane (CF) for which calculated the band gap is 3.07 eV. Our results indicate single-side fluorination provides the necessary electronic and optical changes to be prac...

Properties of Fluorinated Graphene Films

The etch rates for 317 combinations of 16 materials (single-crystal silicon, doped, and undoped polysilicon, several types of silicon dioxide, stoichiometric and silicon-rich silicon nitride, aluminum, tungsten, titanium, Ti/W alloy, and two brands of positive photoresist) used in the fabrication of microelectromechanical systems and integrated circuits in 28 wet, plasma, and plasmaless-gas-phase etches (several HF solutions, H/sub 3/PO/sub 4/, HNO/sub 3/+H/sub 2/O+NH/sub 4/F, KOH, Type A aluminum etchant, H/sub 2/O+H/sub 2/O/sub 2/+HF, H/sub 2/O/sub 2/, piranha, acetone, HF vapor, XeF/sub 2/, and various combinations of SF/sub 6/, CF/sub 4/, CHF/sub 3/, Cl/sub 2/, O/sub 2/, N/sub 2/, and He in plasmas) were measured and are tabulated. Etch preparation, use, and chemical reactions (from the technical literature) are given. Sample preparation and MEMS applications are described for the materials.

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Etch rates for micromachining processing

An Interferometric Modulator (IMod) is a microelectromechanical device for modulating light using interference. The colors of these devices may be determined in a spatial fashion, and their inherent color shift may be compensated for using several optical compensation mechanisms. Brightness, addressing, and driving of IMods may be accomplished in a variety of ways with appropriate packaging, and peripheral electronics which can be attached and/or fabricated using one of many techniques. The devices may be used in both embedded and directly perceived applications, the latter providing multiple viewing modes as well as a multitude of product concepts ranging in size from microscopic to architectural in scope.

Interferometric modulation of radiation

Plasma emission actinometry has been used to study the mechanism by which small additions of oxygen (∼0.5%) enhance the rate of diamond deposition in a dilute (4%) CH4/H2 discharge at high temperature (900–1300 K). Increasing amounts of CH4 in the feed depress [H], while increasing the O2 concentration, up to ∼5%, produces a fivefold increase in atomic hydrogen in the discharge zone. Invoking a mechanism where diamond growth competes with the formation of an amorphous/graphitic inhibiting layer, these results and earlier studies suggest that oxygen (1) increases [H] which selectively etches amorphous/graphitic carbon, (2) accelerates reaction of this layer with molecular hydrogen, and (3) may itself act as a selective etchant of nondiamond carbon. As a result, the number of active diamond growth sites is increased and enhanced growth rates are observed. We also have grown diamond by alternating a CH4/He discharge with a H2/O2/He discharge and results are consistent with this mechanism. Instantaneous growt...

On the role of oxygen and hydrogen in diamond-forming discharges

Silicon gasification by XeF2 is compared with F‐atom etching under conditions typical of those used in plasma etching. Temperatures ranged from −17 to 360 °C and XeF2 pressures were between 0.05 and 2 Torr. Silicon etching by XeF2 shows a sharply different etch rate/temperature dependence than the Si/F or Si/F2 reaction systems; there is no detectable reaction between XeF2 and SiO2 in contrast to the F‐atom/SiO2 system. These data indicate that physisorption can limit silicon etching by XeF2 and show that basic studies which use XeF2 as a model compound for the etching of silicon and SiO2 by F atoms should be interpreted with caution.

Comparison of XeF2 and F‐atom reactions with Si and SiO2

We have grown diamond crystals and polycrystalline diamond films from CH4/H2/O2 gas feeds in a simple, high‐power density, 2450‐MHz discharge tube reactor. Single‐crystal growth rates over 20 μm/h have been achieved. The material has been analyzed using Raman spectroscopy, Auger spectroscopy, and x‐ray diffraction. Control of nucleation is a major problem for growing sound films, and the high temperatures currently required for growth will limit applications. Oxygen additions were necessary to deposit diamonds over the range of feed composition we studied.

Diamond crystal growth by plasma chemical vapor deposition

Silicon is rapidly etched by the gas‐phase halogen fluorides ClF3, BrF3, BrF5, and IF5, in analogy to XeF2 etching silicon. Nearly complete selectivity over SiO2 is achieved in all cases. By contrast, ClF and Groups III and V fluorides such as NF3, BF3, PF3, and PF5 do not spontaneously etch either Si or SiO2 under the same experimental conditions. These relatively inexpensive interhalogens can be applied to pattern silicon and more generally to remove silicon or polysilicon layers without a plasma. Low‐temperature plasmaless gasification of substrates by these fluorine‐containing interhalogens is an economically attractive alternative to fluorine‐based plasma etching.

Plasmaless dry etching of silicon with fluorine‐containing compounds

Anisotropic plasma etching is accomplished utilizing a helical resonator operated at relatively low gas pressure. The use of this combination yields an extremely high flux of ionic species with resulting rapid anisotropic etching. A helical resonator in conjunction with suitable precursors is also quite useful for plasma induced deposition.

Dale E. Ibbotson

Papers

On the role of oxygen and hydrogen in diamond-forming discharges

Comparison of XeF2 and F‐atom reactions with Si and SiO2

Diamond crystal growth by plasma chemical vapor deposition

Plasmaless dry etching of silicon with fluorine‐containing compounds

Processes depending on plasma generation using a helical resonator