Ultrapure Process Research Articles

Diaphragm Durability Enhancement for Valves Supplying Gas for Atomic Layer Deposition

Semiconductor devices are manufactured from Silicon wafers via diverse processes and application-specific equipment that requires supply of various gases. The gas supply system consists of pressure regulators, pressure gauges, filters, flow controllers, valves, fittings etc. The valves in this system are important parts for controlling and stopping the flow of gases. A wide variety of valves are used throughout the industrial world, but those used for semiconductor manufacturing require special features such as external leak-free, particle-free and dead space-free, because the extremely fine patterns formed on the high grade wafers are made with ultrapure process gases. In addition to these features, the valves must be durable enough to operate several tens of millions of cycles because of faster processing requirements with ALD applications. This research work was done to develop a highly durable diaphragm valve and to verify its durability performance via stress analysis.

Growth Kinetics of Vertically Aligned Carbon Nanotube Arrays in Clean Oxygen-free Conditions

Vertically aligned carbon nanotubes (CNTs) are an important technological system, as well as a fascinating system for studying basic principles of nanomaterials synthesis; yet despite continuing efforts for the past decade many important questions about this process remain largely unexplained. We present a series of parametric ethylene chemical vapor deposition growth studies in a "hot-wall" reactor using ultrapure process gases that reveal the fundamental kinetics of the CNT growth. Our data show that the growth rate is proportional to the concentration of the carbon feedstock and monotonically decreases with the concentration of hydrogen gas and that the most important parameter determining the rate of the CNT growth is the production rate of active carbon precursor in the gas phase reaction. The growth termination times obtained with the purified gas mixtures were strikingly insensitive to variations in both hydrogen and ethylene pressures ruling out the carbon encapsulation of the catalyst as the main process termination cause.

Highly Efficient Ultra-Violet Luminescence from Low-Temperature Grown AlGdN

We have investigated the narrowband ultraviolet (UV) emission characteristics of Al0.94Gd0.06N grown by reactive magnetron sputtering in an ultra-pure process. A resolution limited, narrow band luminescence line from Gd3+ ions has been observed at ∼320nm. The crystallographic properties of the Al0.94Gd0.06N thin films are sensitive to the growth temperature. With a decrease in the growth temperature, the emission efficiency has been found to increase considerably. According to the crystallographic properties investigated by extended X-ray absorption fine structure analysis, fluctuation of the column-III sublattices around the Gd3+ ions plays a key role to enhance the luminescence intensity.

Production of ultrapure water by continuous electrodeionization

The process of continuous electrodeionization (CEDI) has now been in commercial use for over twenty years and has gained widespread acceptance in the production of ultrapure process water for industrial use. Likely the chief reason for its commercial success is that CEDI is a green process. It substitutes electricity for the hazardous chemicals normally used to regenerate ion exchange resins, and thereby eliminates the waste stream associated with resin regeneration. This paper describes the mechanisms of operation, types of device construction, and principal industrial applications of this relatively new water purification technology.

Organic contamination of silicon wafers by buffered oxide etching

Recently it has been shown that for present and future scales of integration in semiconductor devices even volatile organics have a strong negative impact on process yield and product performance. Therefore, new ultrasensitive analytical methods for the detection and identification of organic volatiles are needed in process control for monitoring and for failure analysis. Very promising in this field, especially for monitoring of ultrapure process gases, are methods involving atmospheric pressure ionization, like API-MS and IMS (ion mobility spectrometry). We present results from investigations into wafer contamination by wetting agents and surfactants that are used in buffered oxide etchings (BOE) and related processes. Depending upon the chemical class of the surfactant, considerably strong bindings are formed to the silicon surface. DI-water rinse is not able to remove the species. The residues strongly increase the tendency of the surface to adsorb particles and thus may lead to a higher defect density. On the other hand, only the persisting residues assure that the silicon surface remains wetted during following steps of processing. So the optimum selection of the surfactant is crucial to adjust parameters for etching and other wet processes.

Ultra-Pure Processing: a Key Challenge for Ion Implantation Processing for Fabrication of ULSI Devices

AbstractA key issue in modern ion implantation processing is the requirement for dramatic improvements in the purity of the incident ion beam and reductions in the deposition of foreign materials onto the wafer surface. These deposited materials include particles as well as sputtered and vapor deposited metals and dopants. Physical mechanisms which effect the elemental purity of atoms arriving at the surface of ion implanted wafers and progress towards achieving implantation purity levels of below 100 ppm of the implanted dose for sputtered metal and dopant films are discussed.

Catalyst-adsorption type purifiers for ultra-pure gas supply

In accordance with the increase in integrated precision, particle-free and ultrapure process gases containing no impurities, such as hydrogen, oxygen and nitrogen are demanded increasingly as material gases for semiconductors. To meet these needs the author and his colleagues have developed a catalyst adsorption type gas purifier. In this paper the purifying system adapted by this device will be explained. The measured results of ultramicroanalysis for impurity concentration in the gases emitted and the measured result of the particle using the laser type particle counter will be reported.