Barton Lane

Relationship between center-peaked plasma density profiles and harmonic electromagnetic waves in very high frequency capacitively coupled plasma reactors

An understanding of the factors that control radial plasma uniformity in very high frequency (VHF) capacitively coupled plasma (CCP) sources is important for many plasma processes in semiconductor device manufacturing. Here, we report experimental measurements and high-resolution self-consistent numerical simulations that illustrate the plasma density profile and the higher harmonic wave content in two types of VHF-CCP test-bench reactors. A distinct sharp center peak superimposed on a broad center peak in argon plasma was observed for driving frequencies of 60 and 106 MHz. Experimental measurements and numerical simulations of the electric field power spectrum reveal the presence of UHF waves when the electron density is over 5 × 1016 (#/m3). The presence of UHF waves closely correlates with the occurrence of a distinct and sharp-center-peaked electron density. The numerical simulations show that specific frequency bands in the UHF spectrum are amplified in the plasma and lead to the evolution of the sharp-center-peaked electron density.

Global minimization line-edge roughness analysis of top down SEM images

Line edge placement error is a limiting factor in multipatterning schemes which are required for advanced nodes in high volume manufacturing for the semiconductor industry. Thus, we aim to develop an approach which provides both a quantitative estimate of whether a segment of a feature edge is in the ideal location and a quantitative estimate of the long wavelength roughness. The method is described, numerical simulation models its application to the issue of distortion caused by SEM aberrations, and the method is applied to a sample data set of SEM images. We show that the method gives a robust estimate of a major component leading to feature edge placement error. Long wavelength distortions either from SEM aberrations or from long wavelength noise have a clear statistical signature. This methodology applied to a large, consistently acquired SEM data set allows estimates as to important elements required to assess the line edge placement error issue and to whether there is underlying long wavelength roughness which arises from physical sources

Measurement of spatial and temporal evolution of electromagnetic fields in a 100 MHz plasma source using B dot and double dipole probes

Very high frequency plasma sources are often accompanied by plasma density nonuniformities associated with a standing-wave effect. Electron density measurements using a plasma absorption probe show density nonuniformities that can be larger than predicted by a standing wave model. These structures have been associated with harmonics of the electric fields in the plasma. The authors present the first time and phase-resolved measurements of the spatial structure of the electromagnetic waves in a 100 MHz plasma source using argon at 40 mTorr employing a B dot probe. The authors show that the harmonic structure is related to a current reversal and subsequent circulation that appears when the sheath collapses during the radio frequency cycle. The circulation is driven by inward traveling waves that are electromagnetic in nature, not plasma waves traveling at the electron thermal velocity. Double dipole probe measurements were used to validate the B dot probe electric field measurements derived from the time de...