The effects of dwell time on focused ion beam machining of silicon

Abstract

In this study, the effects of dwell time on Ga + focused ion beam machining at 30 keV for different milling currents were investigated. The surface topographies were analysed using atomic force microscopy (AFM) and the substrate structures were investigated by means of Raman spectroscopy. It has been observed that by increasing dwell time the total sputtering yield was increased even though the total dose was remained the same. Also the silicon damage by ion bombardment is reduced as the dwell time is increased. This is mainly due to catalyst behaviour of Ga inside Si which over a period of hours causes recrystallization of Si at room temperature by lowering the activation energy for crystallization. 2 IntroductionFocused ion beam (FIB) systems are widely used as a versatile tool for nanofabrication prototyping, device modification and ion beam lithography. Two main categories of FIB micromachining are sputtering and deposition. FIB sputtering is a maskless microfabrication technique where incident ions transfer momentum to the substrate and release atoms through cascades of collisions.

Template-assisted growth of Ga-based nanoparticle clusters on Si: effect of post-annealing process on the Ga ion beam exposed 2D arrays fabricated by focused ion beam nanolithography

“…Note that the sputtering yield depends on the atomic binding energy. As the amorphous Si has weaker bonds, sputtering yield increases with the fraction of amorphous Si [32]. Hence, etchpit size increases with dose (or dwell time), as shown in figure 2(f).…”

“…Ga ion beam exposure leads to the implantation of Ga into Si along with localized sputtering of Si atoms and other typical ion-induced processes. According to the stopping and range of ions in matter calculations, it is estimated that the stopping range of 30 kV accelerated Ga ions in crystalline Si (target material) is between 15 and 40 nm below the surface [31,32]. The extent of the thickness of the target material, from its surface and beneath, that is modified by the ion beam exposure is referred as the modified layer.…”

“…As the dwell time increases, the number of ions implanted in Si increases and in addition to that, the degree of damage that occurs to the substrate increases [32], which in fact leads to increase in sputtering yield. Therefore, the etchpit size increases with dose (or dwell time) as shown in figures 4(a)-(f).…”

Figuring Method of High Convergence Ratio for Pulsed Ion Beams Based on Frequency-Domain Parameter Control

“…This material removal method based on duty cycle adjustment enables the motion axis to move uniformly during the processing [ 14 , 15 , 16 ], completely avoids the restriction of the acceleration of the machine tool motion axis and reduces the requirement for the dynamic performance of the machine tool while having high machining convergence ability [ 17 , 18 , 19 ]. Previously, Zhou et al [ 13 ] only validated the stability and linearity of the PIB removal function; its actual shaping ability and advantages were not verified.…”

Selecting suitable image dimensions for scanning probe microscopy

“…Surface topography measurement also detects the marks left on a specimen in trying to achieve the shape, such as those created by machining or polishing. Surface metrology is also highly relevant to nanotechnology and micro/nanofabrication, for example assessing the structure of thin films manufactured using vapour deposition [2][3][4], or using focused ion beam to etch surfaces [5][6]. Researchers in these fields represent a range of scientific and engineering disciplines, and hence may be unfamiliar with the complexities of measuring surface topography.…”