Kurt L. Haller

Bio: Kurt L. Haller is an academic researcher from IBM. The author has contributed to research in topics: Plasma & Particle. The author has an hindex of 8, co-authored 9 publications receiving 656 citations.

Particle trapping phenomena in radio frequency plasmas

Abstract: Particles generated in an argon plasma and suspended at the plasma/sheath boundary are localized by lateral trapping fields. In the commercial rf etching reactor used in this work, the particles and their motion in real time are observed by laser light scattering with the laser beam rapidly rastered in a plane parallel to the rf electrode. Repulsion between individual, relatively large particles is observed, verifying that there is significant negative charge on the particles. Two types of trapping regions are commonly seen: rings of particles around the outside edge of silicon wafers, and domes of particles over the centers of the wafers. It is shown that these effects are influenced by the topography of the electrode. In addition, particle densities >107 cm−3 for particles of diameter 0.2 μm are inferred from transmission studies for certain plasma conditions.

In situ plasma contamination measurements by HeNe laser light scattering: A case study

Abstract: Using a simple, inexpensive HeNe laser and a video camera to measure light scattering intensity and location, particulate contamination in an SiO2 sputtering process used in semiconductor manufacturing has been studied under actual process conditions in a class 10 cleanroom. Particulates were observed during all aspects of the sputtering process. It was seen that portions of the process which resulted in mechanical stress on the tool walls produced the greatest flux of particles inside the tool. However, the sputtering step was the major contributor to contamination in this chemically simple process, because of its long duration and the stress‐inducing nature of the plasma. The contamination level in this plasma is estimated to exceed the cleanroom ambient by three orders of magnitude. As in other process plasmas, the particles were suspended at the sheath/plasma boundary. It is argued that a relatively weak electrostatic field is required for gravitational counterbalance of these highly charged particles...

Rastered laser light scattering studies during plasma processing: Particle contamination trapping phenomena

Abstract: The distribution and transport of particles in materials processing plasmas has been studied with a rastered laser light scattering technique. Contrary to expectation, the distribution of particles in a plasma processing tool is rarely random. Instead, structured clouds of particles form at the plasma/sheath boundary. The effect is attributed to trapping of the particles by weak electric field nonuniformities and the characteristic negative charge of isolated particles in a plasma. Field nonuniformities appear to be influenced by the topography and material design of the tool. For example, the presence of a Si wafer often induces significant particle trapping. Examples of particle trapping in a laboratory system are given, and similar phenomena are also verified in a manufacturing sputter deposition tool operating in a class 100 cleanroom. The implications of particle trapping in plasma processing are discussed.

Double-beam laser absorption spectroscopy: shot noise-limited performance at baseband with a novel electronic noise canceler

Abstract: In a high J-value scheme (photo-excitation sequence), the authors investigate the characteristics of three-step photo-ionization, through an autoionizing level, of a complex atom using three single-mode pulsed dye lasers. The report covers (1) ion yield dependence on the balance of three laser intensities; (2) AC Stark effect, observed in intermediate excitation; and (3) multi-photon-resonance effect in a stepwise near-resonant excitation. The experimental results are discussed through comparison with the theoretical analyses, that include the effects of magnetic sublevel degeneracy.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Method and apparatus for contamination control in processing apparatus containing voltage driven electrode

Abstract: A process chamber having voltage driven electrodes, e.g. plasma chamber, can be made self cleaning of particle contamination by appropriate design of the workpiece or electrode surface to provide protuberances, grooves or tapers thereon which result in a predetermined pattern in the electrostatic potential within the process chamber which can trap particulate contamination in preselected regions within the plasma chamber. These particles can then be channeled out of the process chamber through a pump port.

Observation of Coulomb-Crystal Formation from Carbon Particles Grown in a Methane Plasma

Abstract: A Coulomb crystal was successfully formed as a result of the growth of spherical and monodisperse carbon particles suspended in a methane plasma. The crystal structure was confirmed to be hexagonal from top- and side-view photographs. The particle growth was monitored by Mie-scattering ellipsometry and correlated with the formation process of the Coulomb crystal. The liquid-to-solid phase transition occurred when particle diameter grew to 1.3 µm, and when the Wigner-Seitz radius was about 90 µm.

Ultrasensitive detections in atomic and molecular physics: demonstration in molecular overtone spectroscopy

Abstract: We consider several highly sensitive techniques commonly used in detection of atomic and molecular absorptions. Their basic operating principles and corresponding performances are summarized and compared. We then present our latest results on the ultrasensitive detection of molecular overtone transitions to illustrate the principle and application of the cavity-enhanced frequency-modulation (FM) spectroscopy. An external cavity is used to enhance the molecular response to the light field, and an FM technique is applied for shotnoise-limited signal recovery. A perfect match between the FM sideband frequency and the cavity free spectral range makes the detection process insensitive to the laser-frequency noise relative to the cavity, and, at the same time, overcomes the cavity bandwidth limit. Working with a 1.064-mm Nd:YAG laser, we obtained sub-Doppler overtone resonances of C2HD, C2H2, and CO2 molecules. A detection sensitivity of 5 3 10 213 of

Dust plasma crystals, drops, and clouds

Abstract: The experimental and theoretical aspects of the dust particle phenomenon are discussed. The subjects include dust particle attraction in open systems ( in spite of charges of up to 105e on individual particles); dust molecule formation; large (100 eV and higher) values of the dust-plasma crystal binding energy; self-contraction instabilities (similar to and operating together with gravitational instability in cosmic structures); free boundary dust-plasma crystals; new dust attraction mechanisms; the growth and agglomeration of dust particles; and the development of long order in dust plasmas. New estimates for understanding the fireball phenomenon and star production are given.

Nonthermal Plasma Synthesis of Nanocrystals: Fundamental Principles, Materials, and Applications

Abstract: Nonthermal plasmas have emerged as a viable synthesis technique for nanocrystal materials. Inherently solvent and ligand-free, nonthermal plasmas offer the ability to synthesize high purity nanocrystals of materials that require high synthesis temperatures. The nonequilibrium environment in nonthermal plasmas has a number of attractive attributes: energetic surface reactions selectively heat the nanoparticles to temperatures that can strongly exceed the gas temperature; charging of nanoparticles through plasma electrons reduces or eliminates nanoparticle agglomeration; and the large difference between the chemical potentials of the gaseous growth species and the species bound to the nanoparticle surfaces facilitates nanocrystal doping. This paper reviews the state of the art in nonthermal plasma synthesis of nanocrystals. It discusses the fundamentals of nanocrystal formation in plasmas, reviews practical implementations of plasma reactors, surveys the materials that have been produced with nonthermal pla...