Latent image diffraction from submicron photoresist gratings

Light scattering from latent images in photoresist is useful for lithographic tool characterization, process monitoring, and process control. In particular, closed‐loop control of lithographic processes is critical for high yield, low cost device manufacturing. In this work, we report use of pulsed laser diffraction from photoresist latent images in 0.24 μm pitch distributed feedback laser gratings. Gated detection of pulsed light scattering permits high spatial resolution probing using ultraviolet light without altering the latent image. A correlation between latent image and etched grating diffraction efficiencies is demonstrated and shows the value of "upstream" monitoring

Ion velocity distributions in helicon wave plasmas: Magnetic field and pressure effects

Consideration of ion transport in high density, low pressure plasma systems is important for meeting process requirements in the manufacturing of ultra-large-scale integrated circuits. The ion energy and angular distributions at the boundary between the plasma and the wafer, the sheath, influence etching selectivity, linewidth control, plasma-induced damage, and microscopic etching uniformity. These distributions, in turn, are easily altered by changing the magnetic field profile and/or the neutral gas pressure. Using Doppler-shifted laser-induced fluorescence, metastable ion velocity distribution functions in helicon-wave-excited Ar plasmas are measured. Two magnetic field configurations are examined. For a magnetic "mirror," where the field exhibits a maximum and a saddle point in the source, the plasma is observed to be asymmetric and nonuniform: this leads to broadened velocity distributions and significant ion drift from one region of the plasma to another. As the pressure is increased in the mirror field configuration, the transverse ion "temperature" exhibits a maximum as a function of pressure and, when etching is ion-flux limited, either decreasing or increasing the pressure should result in improved linewidth control. The plasma is more symmetric when the magnetic field is reversed in the source and again downstream. With this double cusp configuration, the transverse ion temperature decreases monotonically with pressure, and improved linewidth control in the ion-flux limit would be obtained by operating at higher pressure

Microscopic and macroscopic uniformity control in plasma etching

By cooling substrates to low temperatures (–40 °C), plasma etching of AlGaAs/AlAs/GaAs structures is performed in an ion-activated, surface reaction limited regime. As a result, microscopic and macroscopic uniformity are vastly improved and etching is independent of gas flow patterns, plasma geometry, and reactor loading. Because the reactant is concentrated on the surface, etching rates remain large

Ion acceleration in plasmas emerging from a helicon-heated magnetic-mirror device

Using laser-induced fluorescence, measurements have been made of metastable argon-ion, Ar{sup +}*(3d{sup 4} f{sub 7/2}), velocity distributions on the major axis of an axisymmetric magnetic-mirror device whose plasma is sustained by helicon wave absorption. Within the mirror, these ions have sub-eV temperature and, at most, a subthermal axial drift. In the region outside the mirror coils, conditions are found where these ions have a field-parallel velocity above the acoustic speed, to an axial energy of {approx}30 eV, while the field-parallel ion temperature remains low. The supersonic Ar{sup +}*(3d{sup 4} f{sub 7/2}) are accelerated to one-third of their final energy within a short region in the plasma column, {le}1 cm, and continue to accelerate over the next 5 cm. Neutral gas density strongly affects the supersonic Ar{sup +}*(3d{sup 4} f{sub 7/2}) density

The Gaseous Electronics Conference radio‐frequency reference cell: A defined parallel‐plate radio‐frequency system for experimental and theoretical studies of plasma‐processing discharges

A ‘‘reference cell’’ for generating radio‐frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self‐bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70394/2/RSINAK-65-1-140-1.pd