Modern computer microprocessor chips are marvels of engineering complexity. For the current 45 nm technology node, there may be nearly a billion transistors on a chip barely 1 cm2 and more than 10 000 m of wiring connecting and powering these devices distributed over 9-10 wiring levels. This represents quite an advance from the first INTEL 4004B microprocessor chip introduced in 1971 with 10 μm minimum dimensions and 2 300 transistors on the chip! It has been disclosed that advanced microprocessor chips at the 32 nm node will have more than 2 billion transistors.1 For instance, Figure 1 shows a sectional 3D image of a 90 nm IBM microprocessor, containing several hundred million integrated devices and 10 levels of interconnect wiring, designated as the back-end-of-the-line (BEOL). Since the invention of microprocessors, the number of active devices on a chip has been exponentially increasing, approximately doubling every two years. This trend was first described in 1965 by Gordon Moore,2 although the original discussion suggested doubling the number of devices every year, and the phenomenon became popularly known as Moore’s Law. This progress has proven remarkably resilient and has persisted for more than 50 years. The enabler that has permitted these advances is known as scaling, that is, the reduction of minimum device dimensions by lithographic advances (photoresists, tooling, and process integration optimization) by ∼30% for each device generation.3 It allowed more active devices to be incorporated in a given area and improved the operating characteristics of the individual transistors. It should be emphasized that the earlier improvements in chip performance were achieved with very few changes in the materials used in the construction of the chips themselves. The increase of performance with scaling * Corresponding author. E-mail: gdubois@us.ibm.com. † IBM Almaden Research Center. ‡ Stanford University. Willi Volksen received his B.S. in Chemistry (magna cum laude) from New Mexico Institute of Mining and Technology in 1972 and his Ph.D. in Chemistry/Polymer Science from the University of Massachusetts, Lowell, in 1975. He then joined the research group of Prof. Harry Gray/Dr. Alan Rembaum at the California Institute of Technology as a postdoctoral fellow and upon completion of the one-year appointment joined Dr. Rembaum at the Jet Propulsion Laboratory as a Senior Chemist in 1976. In 1977 Dr. Volksen joined the IBM Research Division at the IBM Almaden Research Center in San Jose, CA, where he is an active research staff member in the Advanced Materials Group of the Science and Technology function.

Low dielectric constant materials.

Plasma enhanced chemical vapor deposition(PECVD) is being increasingly used for the fabrication of transparent dielectric optical films and coatings. This involves single-layer, multilayer, graded index, and nanocomposite optical thin filmsystems for applications such as optical filters, antireflective coatings, optical waveguides, and others. Beside their basic optical properties (refractive index, extinction coefficient, optical loss), these systems very frequently offer other desirable “functional” characteristics. These include hardness, scratch, abrasion, and erosion resistance, improved adhesion to various technologically important substrate materials such as polymers, hydrophobicity or hydrophilicity, long-term chemical, thermal, and environmental stability, gas and vapor impermeability, and others. In the present article, we critically review the advances in the development of plasma processes and plasmasystems for the synthesis of thin film high and low index optical materials, and in the control of plasma–surface interactions leading to desired film microstructures. We particularly underline those specificities of PECVD, which distinguish it from other conventional techniques for producing optical films (mainly physical vapor deposition), such as fabrication of graded index (inhomogeneous) layers, control of interfaces, high deposition rate at low temperature, enhanced mechanical and other functional characteristics, and industrial scaleup. Advances in this field are illustrated by selected examples of PECVD of antireflective coatings, rugate filters, integrated optical devices, and others.

Plasma deposition of optical films and coatings: A review

To extend the scaling limit of thermal SiO/sub 2/ in the ultrathin regime when the direct tunneling current becomes significant, members of this author's research team at Yale University, in collaboration with the Jet Process Corporation, embarked on a program to explore the potential of silicon nitride as an alternative gate dielectric. In this paper, high-quality silicon nitride (or oxynitride) films made by a novel jet vapor deposition (JVD) technique are described. The JVD process utilizes a high-speed jet of light carrier gas to transport the depositing species onto the substrate to form the desired films. The film composition has been determined to consist primarily of Si and N, with some amounts of O and H. Metal-nitride-Si (MNS) capacitors based on the JVD nitride films deposited directly on Si exhibit relatively low densities of interface traps, fixed charge, and bulk traps. The interface traps at the nitride/Si interface exhibit different properties from those at the SiO/sub 2//Si interface in several aspects. In contrast to the conventional CVD silicon nitride, the high-field I-V characteristics of the JVD silicon nitride fit the Fowler-Nordheim (F-N) tunneling theory over four to five orders of magnitude in current, but do not fit at all the Frenkel-Poole (F-P) transport theory. This is consistent with the much lower concentration of electronic traps in the JVD silicon nitride. Results from the carrier separation experiment indicate that electron current dominates the gate current with very little hole contribution. Both theoretical calculation and experimental data indicate that the gate leakage current in JVD silicon nitride is significantly lower than that in silicon dioxide of the same equivalent oxide thickness. The breakdown characteristics of the JVD nitride are also respectable. Compared to their MOSFET counterparts, MNS transistors exhibit reduced low-field transconductance but enhanced high-field transconductance, perhaps due to the presence of border traps. As expected, the JVD silicon nitride films exhibit very strong resistance to boron penetration and oxidation at high temperatures. These properties, coupled with its room-temperature deposition process, make JVD silicon nitride an attractive candidate to succeed thermal SiO/sub 2/ as an advanced gate dielectric in future generations of ULSI devices.

Making silicon nitride film a viable gate dielectric

A plasma jet has been developed which deposits silica films at up to at 760 Torr and 115 to C. The jet operates by feeding oxygen and helium gas between two coaxial electrodes that are driven by a 13.56 MHz radio frequency source at 40 to 500 W. Tetraethoxysilane is mixed with the effluent of the plasma jet and directed onto a substrate located 1.7 cm downstream. The properties of the silica films, as determined by infrared spectroscopy and capacitance measurements, are comparable to those of thermally grown silicon dioxide films at C.

/pdf/deposition-of-silicon-dioxide-films-with-an-atmospheric-3zh40l71zt.pdf

Deposition of silicon dioxide films with an atmospheric-pressure plasma jet

Silicon alloys and doped silicon films are prepared by chemical vapor deposition and ion implantation processes using Si-containing chemical precursors as sources for Group III and Group V atoms. Preferred dopant precursors include (H3Si)3-xMRx, (H3Si)3N, and (H3Si)4N2, wherein R is H or D, x = 0, 1 or 2, and M is selected from the group consisting of B, P, As, and Sb. Preferred deposition methods produce non-hydrogenated silicon alloy and doped Si-containing films, including crystalline films.

Dopant precursors and processes

A gas‐phase reaction mechanism is proposed for the chemical vapor deposition (CVD) of amorphous silicon from silane or disilane at atmospheric pressure. The gas stream in the CVD reactor is populated by silanes, silylenes, and disilenes in a variety of sizes. Silylenes form by the decomposition of silanes, and they rapidly insert into other silanes to form larger silanes. Although silylenes are expected to stick to growth surfaces to which they diffuse, they are too reactive in the gas phase to deliver a large flux onto the growth surface. Larger silylenes (SiH3SiH and larger) also isomerize to form less reactive disilenes, which we propose to be principally responsible for film growth. Film profiles observed in depositions from silane and disilane are presented, and computed film profiles are compared to these observations. Deposition from silane is explained quite well by the mechanism, as are some qualitative features of deposition from disilane.

Gas‐phase kinetics in the atmospheric pressure chemical vapor deposition of silicon from silane and disilane

The qualities of plasma-enhanced chemical vapor deposited (PECVD) silicon nitride films can be improved by increasing the deposition temperature. This report compares PECVD silicon nitride films to low pressure chemical vapor deposited (LPCVD) films. The dependence of the film properties on process parameters, specifically power and temperature, are investigated. The stress is shown to shift from tensile to compressive with increasing temperature and power. The deposition rate, uniformity, wet etch rate, index of refraction, composition, stress, hydrogen content, and conformality are considered to evaluate the film properties. Temperature affects the hydrogen content in the films by causing decreased incorporation of N-H containing species whereas the dependence on power is due to changes in the gas-phase precursors. All PECVD film properties, with the exception of conformality, are comparable to those of LPCVD films.

https://iopscience.iop.org/article/10.1149/1.2220766/pdf

High Quality Plasma‐Enhanced Chemical Vapor Deposited Silicon Nitride Films

Kinetic Modeling of the Chemical Vapor Deposition of Silicon Dioxide from Silane or Disilane and Nitrous Oxide

We have studied the incorporation of hydrogen in films of silicon nitride deposited by remote electron‐cyclotron‐resonance chemical vapor deposition using silane (SiH4) as the silicon precursor and both ammonia (NH3) and deuteroammonia (ND3) as nitrogen precursors. Nearly stoichiometric films of silicon nitride, with a refractive index ranging from 1.84 to 2.08, were obtained at substrate temperatures from 50 to 550 °C, microwave powers from 0.5 to 2.5 kW, and NH3 (ND3) to SiH4 flow ratios from 2.5 to 10. The total hydrogen incorporation decreased linearly with increasing temperature from a maximum value of 2×1022 to 6×1021 cm−3. The amount of hydrogen incorporated in the film was independent of the microwave power and the NH3/SiH4 flow ratio, though both variables strongly influenced the hydrogen bonding configuration. The majority of the hydrogen ends up bound to the excess species in the film. Films deposited from deuteroammonia show that 70%–80% of the incorporated hydrogen originates from the ammonia precursor. Optical emission spectroscopy shows the formation of both SiD and NH in the gas phase indicating that an isotopic exchange takes place during the downstream excitation of SiH4. The relative number of N—H and Si—H bonds measured in the gas phase and in the film, as a function of the NH3 to SiH4 flow ratio, are similar. These results suggest that the hydrogen configuration in the film may be determined primarily by gas phase chemistry. Temperature programmed desorption analysis on deposited films shows that hydrogen starts to evolve from the film at a temperature of 620 °C. Films deposited at temperatures ≳350 °C were found to be stable after a 920 °C anneal.

Hydrogen incorporation in silicon nitride films deposited by remote electron-cyclotron-resonance chemical vapor deposition

A mechanistic study of oxide deposition from silane and nitrous oxide between 495{sup 0}C and 690{sup 0}C was performed in a laminar flow, cool wall reactor. Results indicate the existence of two distinct chemical pathways. At high nitrous oxide concentrations, the deposition reaction is dominated by radical chain chemistry initiated by the decomposition of N/sub 2/O. At lower N/sub 2/O concentrations, the decomposition of silane to form silylene (SiH/sub 2/) initiates the deposition. Studies of the reaction of disilane and nitrous oxide confirmed the role of SiH/sub 2/ in the deposition. Reactions involving SiH/sub 2/ are used to explain the observed growth of sub-stoichiometric oxides under low N/sub 2/O conditions.

A Kinetics Study of the Atmospheric Pressure CVD Reaction of Silane and Nitrous Oxide

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