Yasuo Tarui

Investigation on Leakage Current Reduction of Photo‐CVD Tantalum Oxide Films Accomplished by Active Oxygen Annealing

Previously, the authors demonstrated that photo‐CVD films formed on a Si substrate using and acquire very low leakage current by active oxygen annealing. This paper investigates in detail the mechanism of the leakage current reduction. Low‐leakage‐current films are produced provided there is a sufficient UV‐activation of molecules during CVD, an abundant supply of electronically excited oxygen, O(1D) and , during annealing, and Si migration from the substrate into the films during annealing, or CVD. A phenomenological model of the leakage current reduction is proposed. In the model, a certain void in the Ta‐O network is compensated by chemically incorporating a Si atom and several excited oxygen species; O(1D) or . This model can consistently interpret a series of phenomena on leakage current reduction reported in this paper and in our previous papers.

Preparation and properties of microcrystalline silicon films using photochemical vapor deposition

Abstract microcrystalline silicon films have been prepared through mercury photosensitized decomposition of monosilane at low gas pressures. The dark and light conductivities of the silicon films tend to increase at reactant pressures lower than 65 Pa and become 10 −2 Ω −1 · cm −1 at 26 Pa. From the Raman scattering and x-ray diffraction, silicon films were found to consist of a mixed phase structure including both microcrystalline and amorphous regions.

Photochemical vapor deposition of amorphous silicon through 185 nm excitation of monosilane

Abstract Photochemical vapor deposition of a-Si films at a high rate using SiH 4 and a 185 nm low pressure mercury lamp is described. A maximum rate of 1 nm/sec was attained using the 185 nm lamp. This rate was about ten times higher than that using a 254 nm lamp. Assuming that there is no interaction between the effects of the two wavelengths, the deposition rate per light output power of 184.9 nm light is 160 times larger than that for 253.7 nm light. The absorption cross-section of the 184.9 nm light is ten times greater than that for the 253.7 nm light.

Synchronously excited discrete chemical vapor deposition of Ta[sub 2]O[sub 5]

A versatile chemical vapor deposition (CVD) technique is proposed which has two noteworthy technical features: (1) alternate or intermittent introduction of source vapors followed by evacuation and (2) one or more excitations synchronized with the sequences of vapor introduction. Since it can select and identify the place and time for the occurrence of reactions and excitation among source molecules, this technique also promises to be valuable in investigating the use of conventional CVD processes with unfamiliar materials. In this work, the technique is used to investigate the conventional photo and thermal CVD processes of tantalum pentoxide film using tantalum pentachloride and oxygen. The results indicate that significant deposition occurs even without the vapor phase reactions among source vapors and that photoexcitation of the substrate surface greatly enhances film deposition. In the course of the investigation, it was observed that temporary photoexcitation and ozone supply produced a high rate of film deposition even at temperature lower than 300 C.

Mask Inspection Technology

With the advent of masks, an inspection technology had to be developed. Initially it relied on the human eye, but in VLSI technology high-speed, highprecision inspection became necessary to handle large amounts of fine patterns.

Fundamentals of Test and Evaluation

With increasing integration level and circuit complexity toward VLSI, an advanced high technology is required in every part of the production of integrated circuits. Consequently, concerning test and evaluation technology there are several new problems, and it is required to establish new basic technologies for VLSI-testing.

Electron Beam Lithography

To develop greater LSIs, it is necessary to increase the number of pattern elements per unit area by reducing circuit patterns. The increase of pattern elements per chip needs high-speed pattern writing. The electron-beam lithography system has stepped into the limelight as one of the systems for meeting the demand of fine and high-speed writing. The electron-beam technology utilized in such a system is immature from the viewpoint of semiconductor production. In addition, it essentially requires modern technologies, such as electrooptics, precision machinary and Controlling electronics, a precision moving table, computers and software.

Basic Device Technology

One of the most important features of VLSI technique, especially in view of VLSI devices, is the change from the conventional integration of circuits (Integrated Circuit: IC) to the integration of systems itself (Integrated System: IS) as the result of an increased level of integration.

Pattern Replication Technology

In semiconductor device fabrication, optical lithography has widely been employed as the pattern replication method. Today, three methods are used: the shadow casting method, the imaging method, and the holographic method.