Takahiko Moriya

High aspect ratio hole filling by tungsten chemical vapor deposition combined with a silicon sidewall and barrier metal for multilevel interconnection

A newly developed processing for high aspect ratio hole filling by tungsten chemical vapor deposition, combined with a Si sidewall technique and resist etch back is proposed. A high aspect ratio hole (around 3) was completely filled with W and W‐Si alloy without voids. It is also proposed to interpose a TiN/TiSi2 layer between W and Si, in order to suppress rapid silicidation of W at high temperatures above 800 °C. Silicidation rates for W/TiN/TiSi2/Si systems were 2–2.5 orders of magnitude lower than W/Si systems. Electrical contact resistivity was kept to be lower than 1×10−5 Ω cm2 even after 900 °C annealing by suppressing rapid silicidation of W.

A planar metallization process—Its application to tri-level aluminum interconnection

A planar metallization process has been proposed, where contact windows or via holes of a high aspect ratio are refilled with tungsten by selective CVD enloloying WF6. In tungsten selective CVD, an appropriate choice of substrate material and surface cleaning prior to tungsten deposition is a key factor to success. For selective deposition onto Al, Al surface is coated with MoSi2thin layer, and contact resistivities of refilling tungsten with n+Si and MoSi2coated Al are comparable to those of conventional Al metallization. Combining a interlevel insulator surface planarization process and a planar metallization process, a tri-level aluminum interconnection process of 1 micron feature size has been constructed, which has a scheme extensive to submicron feature size.

Cleaning by Brush-Scrubbing of Chemical Mechanical Polished Silicon Surfaces Using Ozonized Water and Diluted HF

A new process for scrubbing chemical-mechanical-polished silicon wafer surfaces with a brush (brush-scrubbing process) was developed. The scrubbing is performed in two stages; the first stage involves a wet treatment using ozonized water and dilute HF. The second stage involves scrubbing with a Poly(vinyl alcohol)(PVA) brush. After scrubbing, the number of residual particles, metal and carbonaceous contamination, and surface roughness of the silicon wafer surface were evaluated. It was determined that this new brush-scrubbing process efficiently removed particles from chemical mechanical polished silicon surfaces. Finally, a model explaining the new brush-scrubbing process is constructed.

Tungsten photochemical vapor deposition mechanism in WF6+H2 system. I: Adspecies excitation model

The tungsten film deposition rate in the WF6+H2 system increases in proportion to the reaction time under light irradiation, while it remains constant in thermal deposition. This phenomenon is analyzed kinetically on the basis of the adspecies excitation model. Light is assumed to suppress adsorption but to enhance desorption, and to promote the excitation of adspecies. The rate equations are solved analytically without assuming steady states. The deposition rate obtained reproduces the observed time-dependence for both thermal and photochemical processes, though qualitatively. One difficulty still remains with this model, and a guideline for resolving it is presented.

Reduced pressure deposited arsenic‐doped silicon film and its properties as a diffusion source

Extremely thin (50∼550 A) and high‐concentration (1×1021∼1×1022 cm−3) arsenic‐doped silicon (ADS) films are deposited at a reduced pressure by means of pyrolysis of SiH4 and AsH3. The ADS films are used as an improved diffusion source, which can be alternative to ion implantation. Arsenic drive‐in diffusion from ADS film is carried out in an O2 ambient, and the desired junctions are achieved. When the arsenic concentration is above 8×1021 cm−3 and the film thickness above 200 A, however, arsenic atom pileup at the Si‐SiO2 interface, reverse dependence of junction depth on the ADS thickness, and high‐density hillocks are observed. The increase in junction depth and the decrease in surface concentration during the subsequent heat treatment at 1000 °C in N2 are remarkable for high arsenic concentration and thick ADS films at low diffusion temperature. A modified simulation program is developed with Si‐SiO2 interface moving and concentration‐dependent diffusion coefficient. The calculated profiles are in sati...

Tungsten Photochemical Vapor Deposition Mechanism in WF6+H2 System II. Gas-Molecule Adspecies Collision Model

Two new models are proposed for the W photochemical vapor deposition mechanism; one is the gas-phase intermediate formation model and the other is the gas-molecule adspecies collision (GAC) model. The GAC model, a modification of the adspecies excitation model proposed in a previous paper, is the most promising. A collision term between an excited WF6 gas molecule and an intermediate M adsorbed on the W surface is added to the decomposition of M. This collision reaction is dominant under light irradiation. It produces a W atom and a new intermediate M and does not limit the time constant of the intermediate concentration. The new model completely reproduces the observed time and light-intensity dependences of the W deposition rate.

High Aspect Ratio Hole Filling with CVD Tungsten for Multi-level Interconnection

For realizing reliable quarter micron VLSI and three dimensional LSIs , planarlzing the interlevel insulator and filling high aspect ratio holes with metal are indispensible. RF bias sputt.ring(1) , serective cvD w Q-41 and blankei cVD w/v{Si^ (5) combined with in situ z etch-back to form planarized via-hole filing have been reported. However, complete hole filling without voids for an aspect ratio over one has not yet been reported. In this paper, a newly developed processing for high aspect ratio (about 3) hole filling by W-CVD combined with Si sidewall technique and resist etch back is proposed. The underlying layer can be any conductive material and can be applied to fitling holes of various depths at the same time. Moreover, a novel w/TiN/TiSi2 structure lras applied in order to suppress rapid silicidation of W at temperatures higher than