Articles you may be interested inLow-pressure inductively coupled plasma etching of benzocyclobutene with SF6/O2 plasma chemistry J. Vac. Sci. Technol. B 30, 06FF06 (2012); 10.1116/1.4758765Reduction of silicon recess caused by plasma oxidation during high-density plasma polysilicon gate etching Level set approach to simulation of feature profile evolution in a high-density plasma-etching system Profile evolution during polysilicon gate etching has been investigated with low-pressure high-density Cl 2 /HBr/O 2 plasma chemistries. Etching was performed in electron cyclotron resonance Cl 2 /HBr/O 2 plasmas as a function of HBr percentage in a Cl 2 /HBr mixture, using oxide-masked poly-Si gate structures. The linewidth was nominally 0.18 m, and the spacing between the two neighboring poly-Si lines was varied in the range ϳ0.2-10 m. In addition, the macroscopic open space of the oxide-masked sample was also varied over a wide range from Ϸ28% to Ϸ76%. As the HBr percentage in Cl 2 /HBr is increased from 0 to 100%, the linewidth shift ⌬L of poly-Si relative to the mask width ͑or the degree of sidewall tapering of poly-Si lines͒ first decreased linearly, passed through a minimum, and then increased considerably at above ϳ80%. In Cl 2 /O 2 plasmas without HBr addition, ⌬L was almost independent of the microscopic and macroscopic poly-Si open spaces although its value was relatively large; on the contrary, in HBr/O 2 plasmas, ⌬L increased with an increase of microscopic line spacing and/or the macroscopic open space of the sample. Comparisons of the etched profiles obtained in Cl 2 /HBr/O 2 plasmas with numerical profile simulations indicate that the strongly tapered sidewalls observed at high HBr percentages ͑տ80%͒ result from the simultaneous etch inhibitor deposition onto sidewalls during etching; moreover, such inhibitors are predicted to come from the plasma with a large sticking probability of ϳO(0.1). On the other hand, the relatively large ⌬L obtained in Cl 2 /O 2 plasmas is considered to be due to intrinsic sidewall tapering, rather than inhibitor deposition arriving from the plasma or redeposition of etch products desorbed from the surface in microstructures. Such intrinsic tapering is discussed in terms of the angular dependence of the Si etch yield.

Ion trajectories near a submicron-patterned surface were investigated using numerical simulations including the effects of local charging on the patterned surface and ion drift velocity toward the wafer. The simulation results were also discussed relative to the etched profile characteristics in electron cyclotron resonance (ECR) plasmas with a divergent magnetic field. Since the pattern size was much smaller than the Debye length, charge neutrality was not satisfied on the submicron-patterned surface. The simulated ion trajectories were largely deflected at the inside of the outermost lines of line-and-space patterns. Moreover, the ion trajectory deflection was reduced with increasing ion drift velocity. These simulation results showed a similar tendency as the etching characteristics.

This article describes a large-diameter, surface-wave excited plasma (SWP) source designed for materials processing. The plasma reactor employs a launcher of 2.45 GHz azimuthally symmetric surface waves in the field-free region of 24-pole line-cusp magnetic fields, generated by a set of permanent magnets surrounding the reactor chamber walls; the magnets also provide an electron cyclotron resonance (ECR) magnetic field of 875 G near the chamber wall surfaces. Langmuir probe and optical emission measurements were made for characterizing the plasma produced in Ar. After the microwave power was turned on, the discharge was observed to start near the ECR region and then propagate toward the field-free region in the central area of the chamber. Moreover, the discharge was also observed to be excited by ECR at low microwave-power levels, and by surface waves in the field-free region at above a critical power strongly depending on the gas pressure. Such a transition of plasma excitation from ECR to SWP was found to occur under conditions where the plasma electron density exceeds a 2.45 GHz microwave cutoff value of ≈7.4×1010 cm−3. As a result, overdense plasmas with large diameters could be successfully produced with moderate microwave input powers ≲1 kW; the electron density was measured to be Ne∼1−3.5×1011 cm−3 in Ar plasmas, with its spatial variation being ≲5% over a 26-cm-diam area. Furthermore, preliminary experiments of SiO2 etching in pure CF4 plasmas showed that the SiO2 etch rate was typically ∼300 nm/min with a good uniformity ≲3% over an 8-in.-diam wafer.

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Electron cyclotron resonance (ECR) discharge plasmas in Cl2 and Ar have been investigated over a pressure range of 0.2–10 mTorr, using microwave interferometry, optical emission spectroscopy, electrostatic probes, and charge collectors. The plasma parameters measured were spatially nonuniform along the magnetic field. The plasma electron density and the plasma potential had their maxima around the ECR region and decreased in going forward the position of the substrate, giving rise to a broadened energy distribution of positive ions incident on the substrate. The plasma density in Ar increased monotonously with increasing pressure, while the density in Cl2 had its maximum around 0.3–0.4 mTorr.