Fabrication of Spindt-Type Nanometer-Sized Chromium Tips for Application as Field-Electron Emitters by Releasing the Stress of the Deposited Thin Film

Abstract

Metal cone-shaped nanotip field-electron emitters which are fabricated by directional thin-film deposition (so-called Spindt-type tips) have shown promising potential for application in modern vacuum micro-/nanoelectronics. Although the fabrication processes of Spindt-type tips have been well established, the in situ release of the initial stress in the deposited metal thin film is still an open issue. Herein, an in situ stress-release process was developed to fabricate chromium (Cr) tip arrays. Patterned photoresist microcavities with surrounding trenches were designed. The microcavities were used as templates for forming the metal tips. Trenches were employed for the in situ internal stress release of the Cr film on the top of the resist. The trenches not only separated the deposited Cr film into small-sized slices (square film on the photoresist) for decreasing the deformation but also provided sufficient space for possible deformation. High-aspect-ratio (∼2) tips were achieved by plasma etching the Si substrate using the Cr tip as the mask, forming a Cr tip on a Si pillar. The Cr tips maintaining a good tip shape demonstrated that the Cr nanotips possessed good etch resistance to the SF6/O2 plasma. The gated Cr-tip array was fabricated following a self-aligned microfabrication procedure. The fabrication process was compatible with the semiconductor manufacturing technology. The gated devices showed an emission current of 33 μA at a gate voltage of 137 V. This work provides a well-developed in situ stress-releasing fabrication process to obtain Spindt-type Cr-tip field-electron emitters, which has potential for application in ionization vacuum gauges and neutralizers for propulsion.