Articles you may be interested inCharacterization of damage induced by FIB etch and tungsten deposition in high aspect ratio vias J. Vac. Sci. Technol. B 29, 011026 (2011); 10.1116/1.3539204 Purification and crystallization of tungsten wires fabricated by focused-ion-beam-induced deposition Low resistance metal deposition in deep submicron vias is required for circuit rewiring in focused ion beam ͑FIB͒-based integrated circuit modification. Voids in high aspect ratio deposition, associated with the application of traditional FIB process to tungsten deposition in vias with aspect ratios beyond 10:1 contribute substantially to the resistance of the via. Pinch off of the via aperture is frequently observed. The dynamics of tungsten deposition within vias was studied through a series of via cross sections with variable deposition dose, and revealed accelerated deposition growth on the walls at the top of the vias. Accelerated deposition on the sidewalls, where the primary beam interacts with the substrate at a glancing angle, suggested that the deposition growth is initiated by secondary charged particles generated at the point of primary beam impact rather than by the primary beam itself. The results are in agreement with mechanisms previously proposed and confirmed by experiments. In order to prevent the generation of secondary particles on the walls of the via, and the consequent pinch off closure of the via aperture, confining the primary beam to an area much smaller than the aperture of the via was attempted. With this process, secondary particles are generated at the bottom of the via and trapped within the via, which was expected to lead to bottom-up deposition growth. A dose series study of the deposition produced by the proposed process confirmed the uniform growth of the tungsten fill from the bottom of the via. Void-free depositions were made in 5 m deep vias ranging in size from 0.5 m by 0.5 m to 0.2 m by 0.2 m, corresponding to aspect ratios from 10:1 to 25:1, respectively.
Gas Assisted Etching (GAE) is the enabling technology for High Aspect Ratio (HAR) circuit access via milling in Focused Ion Beam (FIB) circuit modification. Metal interconnect layers of microelectronic Integrated Circuits (ICs) are separated by Inter-Layer Dielectric (ILD) materials, therefore HAR vias are typically milled in dielectrics. Most of the etching precursor gases presently available for GAE of dielectrics on commercial FIB systems, such as XeF2, Cl2, etc., are also effective etch enhancers for either Si, or/and some of the metals used in ICs. Therefore use of these precursors for via milling in dielectrics may lead to unwanted side effects, especially in a backside circuit edit approach. Making contacts to the polysilicon lines with traditional GAE precursors could also be difficult, if not impossible. Some of these precursors have a tendency to produce isotropic vias, especially in Si. It has been proposed in the past to use fluorocarbon gases as precursors for the FIB milling of dielectrics. Preliminary experimental evaluation of Trifluoroacetic (Perfluoroacetic) Acid (TFA, CF3COOH) as a possible etching precursor for the HAR via milling in the application to FIB modification of ICs demonstrated that highly enhanced anisotropic milling of SiO2 in HAR vias is possible. A via with 9:1 aspect ratio was milled with accurate endpoint on Si and without apparent damage to the underlying Si substrate.
Widespread adoption and significant developments in Focused Ion Beam technology has made FIB/SEM instrumentation a commonplace sample preparation tool. Fundamental limitations inherent to Ga ion species complicate usage of Ga+ FIB instruments for the modification of semiconductor devices on advanced technology nodes. Said limitations are fueling interest in exploring alternative primary species and ion beam technologies for circuit edit applications. Exploratory tests of etching typical semiconductor materials with Xe ion beams generated from two plasma ion sources confirmed advantages of Xe+ as a potential ion species for gas-assisted etching of semiconductor materials, but also revealed potential complications including, swelling of metal and Xe+ retention within the material arising from excessive Xe ion beam current density.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.