On the scaling of rf and dc self-bias voltages with pressure in electronegative capacitively coupled plasmas

Journal Article · Thu Mar 15 00:00:00 EDT 2012 · Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films

DOI:https://doi.org/10.1116/1.3676182· OSTI ID:22051368

Agarwal, Ankur; Dorf, Leonid; Rauf, Shahid; Collins, Ken ^[1]

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1. Applied Materials Inc., 974 E. Arques Avenue, M/S 81312, Sunnyvale, California 94085 (United States)

Higher gas densities and lower diffusion losses at higher operating pressures typically lead to increased charged species densities (and hence flux) for a constant power deposition in capacitively coupled plasmas (CCP). As a result, one would expect that the bias radio-frequency (rf) voltage required to deposit a given power in a CCP reactor decreases with increasing operating pressure. These observations may not hold true in multiple frequency CCPs, commonly used for dielectric etching in microelectronics fabrication, due to nonlinear interactions between the rf sources. Wafer-based measurements of the rf and self-generated direct current (dc) bias voltages in a dual-frequency capacitively coupled electronegative plasma were made, which indicate that the rf and dc voltages vary nonmonotonically with pressure. These experimental results are presented in this paper and a computational plasma model is used to explain the experimental observations for varying 60 MHz and 13 MHz powers in the Ar/CF{sub 4}/CHF{sub 3} plasma over a pressure range of 25 to 400 mTorr. The authors found that while the ion density increases with pressure, the increase is most dominant near the electrode with the high frequency source (60 MHz). The rf and dc bias voltages are ultimately influenced by both charged species density magnitudes and spatial profiles.

• OSTI ID: 22051368
• Journal Information: Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 30, Issue 2; Other Information: (c) 2012 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ARGON
CARBON TETRAFLUORIDE
DEPOSITION
DIELECTRIC MATERIALS
DIFFUSION
DIRECT CURRENT
ELECTRIC POTENTIAL
ELECTRODES
ETCHING
FLUOROFORM
ION DENSITY
MHZ RANGE
MICROELECTRONICS
NONLINEAR PROBLEMS
PLASMA
PLASMA DIAGNOSTICS
PLASMA PRESSURE
PRESSURE RANGE
RADIOWAVE RADIATION
SCALING