Fletcher Jones

Effect of gas impurity and ion bombardment on stresses in sputter‐deposited thin films: A molecular‐dynamics approach

Intrinsic stresses in sputter‐deposited thin films are studied via a two‐dimensional molecular‐dynamics model. Two‐body potential functions, periodic boundary conditions, and a generalized Langevin equation are applied to determine the microstructure of the film. The intrinsic stresses are then calculated using a stress method. 12 layers of substrate atoms are arranged in the (111) plane at the beginning of the film growth simulation. The molecular‐dynamics simulations using the constant pressure and constant temperature ensemble are first carried out to obtain the zero stress state of the substrate. A thin film of Ni atoms is deposited in the presence of a background of argon and energetic ions in order to obtain a reasonable representation of the film structure. After the deposition process is completed, the film and the substrate are allowed to contract or expand in accordance with the elastic energies. It is found that the microstructure and intrinsic stresses of the film depend upon the incident ener...

High‐rate reactive sputter deposition of aluminum oxide

Using a new reactive sputter deposition approach, we are able to consistently deposit stoichiometric Al2O3 films at a rate of 220 nm/min with±6% thickness variations across 82‐mm‐diam substrates. Thus a 10‐μm‐thick aluminum film could be deposited in 40 min. Deposition rates as high as 500 nm/min have been demonstrated. However, at these deposition rates, the voltage levels were high and the system was prone to arc during long runs. This paper describes the system and some of the properties of the films deposited at rates of ∼220 nm/min. It is shown that there is a range of experimental parameters over which the properties of films deposited at 220 nm/min show small variations.

Molecular dynamics modeling of microstructure and stresses in sputter‐deposited thin films

A molecular dynamics model to study thin film formation processes is presented. In this model, the Lennard‐Jones and Moliere potential functions are used to describe the interaction between the atoms, and ions and atoms, respectively, and determine the atomic forces among the atoms. A third‐order, nonuniform time step integration scheme is used to determine the new position and velocity of each particle within the film and the substrate. The use of nonuniform time interval results in significant savings in CPU time. The force evaluation is performed in a short cutoff range which requires that the list of neighbor particles be known. A ‘‘position index method’’ which is much more efficient than the previous schemes, is proposed and implemented in order to sort the table of atoms locally. The frictional force originating from the heat bath is represented by using the generalized Langevin equation such that the temperature of the substrate can be kept constant during the film growth. A moveable periodic boun...

Morphology‐enhanced metal‐alumina adhesion by depositing textured alumina films on textured Teflon substrates

An enhanced adhesion between metals and alumina has been achieved by texturing the alumina films. The Al2O3 films are deposited on textured Teflon substrate; the latter was presputtered to provide a textured surface for the alumina deposition. For thin alumina layers of about 500‐A, a textured surface is obtained which is nearly identical to that of the starting Teflon. On such an alumina surface, an increase in peel strength of about 40–50 times is obtained for both Cu and Cu90%‐Cr10%, from those deposited on nontextured alumina using nontextured Teflon substrates. With an increasing thickness of alumina, the height of the surface texture is reduced, resulting in less enhancements in peel strength than those on the 500‐A alumina. The results are in agreement with the model for the morphology‐enhanced adhesion, which was proposed to explain the previously observed enhancement in adhesion between Cu and textured Teflon. The work also provides a simple way of generating a textured surface for the ceramic ma...

High rate radio frequency sputtering using in‐phase plasma confinement

A new new radio frequency sputtering system single‐wafer (125 mm diam) design has been developed to achieve low‐voltage sputtering at high power density without magnetic confinement. The low voltage operation was achieved by using in‐phase target and substrate sheath voltages, 40.68 MHz excitation, and a controlled‐area confining wall electrode. A single generator was used with a simple bias adjustment circuit to obtain in‐phase excitation. Observed rf voltages were about 65% of that observed for a conventional tuned substrate (180° phase) at equal input power density and frequency. A manually loaded version used a 150 mm diam SiO2 target and a load‐locked version used a 178 mm diam target for better uniformity. SiO2 films have been deposited at rates as high as 4300 A/min in a low‐resputtering mode. In a planarizing mode, rates of 1750 A/min were observed. Resputtering could be smoothly adjusted from near zero to at least as high as 70%. Temperature was controlled by gas conduction cooling to temperature...

Radio frequency sputter deposition of SiO2 films at high rate

SiO2 films have been deposited by rf sputtering in a conventional tuned substrate rf diode system at 40.68 MHz. Deposition rates as high as 2690 A/min were achieved on a single 125‐mm‐diam silicon substrate, as compared to a typical rate of 250 A/min for large manufacturing batch tools. Substrates were cooled using gas conduction, to limit temperatures to below 150 °C. These films were nonabsorbing and had stress and refractive indexes in the normal range for conventionally sputtered films, without the need for added oxygen to the argon gas. Temperatures were measured using a Luxtron FluoropticTM Thermometer. Deposition rates were compared to those predicted from a simple computer model of the system, using published sputter‐yield data and measured electrode voltages. Good agreement was obtained using a weak plasma approximation for the sheath voltage at the system wall. Films were deposited at low and high (planarizing) resputtering conditions using simple substrate tuning adjustment.

A new method for determining electron beam proximity correction parameters in a double layer siloxane‐diazo resist system

Double layer resist systems have recently become very popular in electron beam lithography because of the ease of defining a high quality, high density very large scale integrated circuit (VLSI) pattern in the thin top layer of resist. However, in order to delineate high density VLSI patterns of high quality using electron beams, the electron scattering processes or proximity effects must be accurately characterized and appropriate steps taken to compensate for them. In this paper, theoretical considerations are combined with experimental observations in order to show how proximity correction parameters can be measured in a double layer system where the top layer is a thin (1200 A) electron beam sensitive, negative resist.