Joseph Skinner Logan

Copper deposition by electron cyclotron resonance plasma

An electron cyclotron resonance plasma reactor has been built in order to study the filling of high aspect‐ratio features on semiconductor devices with metal. The reactor produces a plasma of copper which is nearly 100% ionized at the substrate, without the use of any buffer or carrier gas. The ion flux is dependent on both the feed rate of copper neutrals into the plasma region, and on the microwave power absorbed in the plasma. Solid filling of features having aspect ratios as high as 4.2 is demonstrated, and a simple model is derived to explain the fill characteristics.

Mechanism of silicon etching by a CF4 plasma

The mechanisms for the reactive ion etching of silicon by CF4 plasma are investigated. A model is proposed whereby silicon is etched by chemical reaction with free fluorine to produce a volatile species, and also by physical sputtering. The chemical etching is shown to be enhanced by ion bombardment of the reacting surface. This etching process, together with a model for cracking CF4 in the plasma, is evaluated by comparison to actual etch rates. Experimentally, the silicon etch rate is observed to decrease with increasing silicon area, by what is called the loading effect. The functional form of the loading effect, as predicted by the model, is fitted to experimental loading curves. The contributions of the various etching components are separated, to yield empirical values for the enhancement of the chemical reaction by physical sputtering.

Study of particle emission in vacuum from film deposits

This study was carried out to determine how much material can be accumulated on vacuum process chamber walls and shields before excessive particle generation occurs, and how the chamber wall materials influence particle generation. Samples of aluminum, stainless steel, titanium, and anodized aluminum were coated with successive layers of sputtered SiO2. Between each layer deposit, samples were transferred in vacuum to proximity with a particle counter and allowed to cool down. Particles were found to be emitted from the surfaces for times as long as 30 min, typically, before emission rates dropped to zero. The total numbers of particles emitted in a fixed time period increased with the accumulated film layers, until massive delamination was observed. Titanium was found to give the lowest particle rates for a given accumulated thickness, followed by stainless steel, and then aluminum. Anodized aluminum was found to give extremely high particle emissions. Residual stress measurements were made by measuring ...

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.

Reactant supply in reactive ion etching

In reactive ion etching, the etch rate may be reactant limited, so that a measurement of reactant supply is neccessary to understand the details of the etching process. A quantitative determination of reactant supply can be obtained by measuring the total dissociation of the etching gas. In particular, this paper reports the total dissociation of CF4 as a function of input power and pressure in a diode system. A quadrupole mass spectrometer measuring the CF3+ peak indicates the presence of CF4 as well as other molecules containing the (CF3) radical. A transient technique is used to separate the contributions of the other molecules from CF4 so that the total CF4 number density can be calculated. The production of reactant by the dissociation of Cf4 causes etching of silicon and SiO2 on the cathode of the system. Possible reaction sequences of these etching processes are modelled by using the known supply of reactant. The partial pressures of the etching products are calculated and correlated with the etch ...

A study of voids in sputtered SiO2

Voids have been observed in sputtered SiO2 films when deposited over substrate topographies with high aspect ratios (depth/width). This report describes experimental results which show the conditions under which voids are found, and the response of void formation to available deposition parameter variations, such as resputtering bias, power, and frequency. A simple model for void formation is used to predict quantitatively the limits of the process with respect to void formation. The results show that it is possible to obtain void‐free coatings up to an aspect ratio of ∼2.0, and that the controlling factor is the sputtering yield versus angle of incidence curve. Data suggest that 40‐MHz conditions are slightly more favorable than 13 MHz.

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...

R.F. diode sputtering

Abstract A review of r.f. sputtering principles is presented with reference to recent plasma models and sample calculations. Typical modern sputtering equipment is described and methods of measurement of important process variables. Application to the sputtering of SiO 2 is described, with data on film properties as a function of bias, rate and oxygen additions.

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.