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.
The damage induced by CO2 and O2 plasmas to an ultra low-k (ULK) dielectric film with a dielectric constant (κ) of 2.2 was investigated. The dielectric constant was observed to increase due to methyl depletion, moisture uptake, and surface densification. A gap structure was used to delineate the role of ions, photons and radicals in inducing the damage, where the experimental variables included an optical mask (MgF2, fused silica, and Si), a gap height, an inductively coupled plasma power source, a bias power on the bottom electrode, variable chamber pressure, and variable substrate temperature. The plasma radical density distribution inside the gap between the optical mask and the ULK film was simulated. The simulation was based on radical diffusion, reaction, and recombination inside the gap. The experimental results and the numerical simulation showed that the oxygen radicals played an important role in plasma induced damage which was found to be proportional to the oxygen radical density and enhanced byvacuum ultraviolet (VUV) photon radiation. Under certain experimental conditions, ion bombardment can induce surface densification and suppress radical diffusion. The role of UV and VUV photons in induced damage was investigated with Ar plasma using the gap structure and it was found that the photons can induce surface damage directly.
Study of the impact of the time-delay effect on the critical dimension of a tungsten silicide/polysilicon gate after reactive ion etching Magnetic field optimization in a dielectric magnetically enhanced reactive ion etch reactor to produce an instantaneously uniform plasma A constant concern in semiconductor manufacturing is plasma induced damage. A non-uniform etching plasma can induce a dc current at the wafer surface that can damage the film and therefore the device. The magnetic field in an Applied Materials magnetically enhanced reactive ion etch chamber has been enhanced to provide minimal self-bias non-uniformity. The objective of this article is to characterize the magnetic field through a comparison of experimental etch data and modeling. Both analytical and empirical modeling have been used to gain a better understanding of the particular magnetic field configuration under investigation. At low pressure the etch rate pattern correlated well with the calculated stationary magnetic field gradient. For higher pressure this model failed to predict the etch rate uniformity behavior because of contributions from other effects in the plasma. In order to characterize these effects, experiments were conducted for both stationary and rotating magnetic fields. This was done to aid process optimization with respect to the potential for damage.
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