Pulse Breakdown in Sub-20 nm Organic Dielectrics for Nanoscale-Electromachining (nano-EM)

[+] Author and Article Information
Kumar R. Virwani

Department of Microelectronics Photonics, University of Arkansas, Fayetteville, AR 72701kvirwan@us.ibm.com

Ajay P. Malshe

Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701apm2@uark.edu

Kamlakar P. Rajurkar

Department of Industrial and Management Systems Engineering, University of Nebraska, Lincoln, NE 6858krajurka@unlnotes.unl.edu

J. Manuf. Sci. Eng 132(3), 030915 (Jun 09, 2010) (8 pages) doi:10.1115/1.4001718 History: Received December 10, 2009; Revised May 02, 2010; Published June 09, 2010; Online June 09, 2010

Nano-electromachining (nano-EM) is a process in which electric fields applied across sub-20 nm tool-workpiece gaps in organic dielectrics (n-decane C10H22 and n-undecane C12H26) are used to produce nanometer size features (8–80 nm) in electrically conductive materials. In order to improve the speed of nano-EM for manufacturing, utilization of pulse breakdown phenomena is studied. Linear behavior of Paschen curves for pulse breakdown demonstrated the predictability of pulse nano-EM process. The discharge current in the machining gap showed exponential decay behavior in the post-breakdown regime with certain delay. This delay in current recovery may present a limit to improving nano-EM production speeds and suggests a need for external pressurized dielectric flow over self-guided diffusion. Other notable effects such as adsorption compression limited dielectric diffusion and the variation in the recovery current with the tool-workpiece gap along with their engineering implications are discussed.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Schematic of the nano-EM set-up. The pulse bias was applied to the sample while the tool was maintained at ground potential. The zero offset of 30 mV on the pulse generator was used to obtain topographical scans of the surface as well as to quantify the quality of the tools with current-displacement spectroscopy. Inset A shows the meniscus formed on the gold surface and inset B shows a series of 52 features written in the outline of the map of Arkansas with pulse nano-EM. The machining and metrology were performed with the same tool.

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Figure 2

Current-voltage curve for 10 nm gap pulsed breakdown in n-decane; inset A shows the exponential behavior of the recovery current. The arrows mark the percentage of current recovery.

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Figure 3

Paschen curve for pulsed breakdown in sub-20 nm confined n-decane molecules

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Figure 4

TEM (a) and diffraction analysis (b) of a tool subjected to 67.5% of the breakdown field strength showing the surface reconstruction. The circular area in (a) shows the region of the tool from which the diffraction pattern in (b) was obtained. The presence of tungsten oxide nanocrystals and graphite in the matrix was deduced from the analysis of diffraction pattern.

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Figure 5

EDS and EELS analysis of a tool subjected to 80% of the breakdown field strength during pulse breakdown. The EDS analysis clearly shows the migration of Au atoms before breakdown. The EELS analysis confirms the presence of graphitic form of carbon close to the machining interface and none at the interior of the tool.

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Figure 6

Feature machined with 15 nm tool-workpiece gap with 2 ms pulse breakdown. The reference features show the location of the feature post-breakdown. The cross-sectional analysis shows an approximate depth of the feature. The ability of the tool to resolve atomic steps on the gold surface prove the quality factor of tool to be unity.

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Figure 7

Oscillatory behavior of the current upon the removal of the voltage pulse due to possible adsorption compression of the nanoconfined n-decane molecules and ionized species for 5 nm tool-workpiece separation

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Figure 8

Variation in the dielectric recovery times with an increase in the tool-workpiece gap



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