Abstract
We discuss how the emission of electrons and ions during electron-beam-induced physical vapor deposition can cause problems in micro- and nanofabrication processes. After giving a short overview of different types of radiation emitted from an electron-beam (e-beam) evaporator and how the amount of radiation depends on different deposition parameters and conditions, we highlight two phenomena in more detail: First, we discuss an unintentional shadow evaporation beneath the undercut of a resist layer caused by the one part of the metal vapor which got ionized by electron-impact ionization. These ions first lead to an unintentional build-up of charges on the sample, which in turn results in an electrostatic deflection of subsequently incoming ionized metal atoms toward the undercut of the resist. Second, we show how low-energy secondary electrons during the metallization process can cause cross-linking, blisters, and bubbles in the respective resist layer used for defining micro- and nanostructures in an e-beam lithography process. After the metal deposition, the cross-linked resist may lead to significant problems in the lift-off process and causes leftover residues on the device. We provide a troubleshooting guide on how to minimize these effects, which e.g. includes the correct alignment of the e-beam, the avoidance of contaminations in the crucible and, most importantly, the installation of deflector electrodes within the evaporation chamber.
Highlights
Electron-beam-induced physical vapor deposition (e-beam deposition) has developed into a versatile tool in the field of micro- and nanofabrication:[1,2,3] Compared to resistive evaporation techniques, e-beam deposition allows the evaporation of a larger variety of materials, including many oxides and metals with very low vapor pressures
After giving a short overview of different types of radiation emitted from an electron-beam (e-beam) evaporator and how the amount of radiation depends on different deposition parameters and conditions, we highlight two phenomena in more detail: First, we discuss an unintentional shadow evaporation beneath the undercut of a resist layer caused by the one part of the metal vapor which got ionized by electron-impact ionization
In this article we first give an overview on different types of radiation that are emitted during e-beam evaporation and how the amount of radiation depends on different deposition parameters and conditions
Summary
Electron-beam-induced physical vapor deposition (e-beam deposition) has developed into a versatile tool in the field of micro- and nanofabrication:[1,2,3] Compared to resistive evaporation techniques, e-beam deposition allows the evaporation of a larger variety of materials, including many oxides and metals with very low vapor pressures. There are drawbacks in using e-beam deposition, which include the generation of X-rays, the emission of electrons over a large energy range, and the creation of ions by electron-impact ionization, which all can lead to problems in device fabrication.[1,2,3] Especially in the field of semiconductor technology, it is well documented that radiation emitted by an e-beam evaporator can induce defects in the semiconductor material.[4,5,6,7,8] Possible side-effects of e-beam evaporation on other aspects of micro- and nanofabrication, e.g., lift-off problems of resist defined patterns,[9,10] are far less reported.
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