Nanogrids and Beehive-Like Nanostructures Formed by Plasma Etching the Self-Organized SiGe Islands

Abstract

A lithography-free method for fabricating the nanogrids and quasi-beehive nanostructures on Si substrates is developed. It combines sequential treatments of thermal annealing with reactive ion etching (RIE) on SiGe thin films grown on (100)-Si substrates. The SiGe thin films deposited by ultrahigh vacuum chemical vapor deposition form self-assembled nanoislands via the strain-induced surface roughening (Asaro-Tiller-Grinfeld instability) during thermal annealing, which, in turn, serve as patterned sacrifice regions for subsequent RIE process carried out for fabricating nanogrids and beehive-like nanostructures on Si substrates. The scanning electron microscopy and atomic force microscopy observations confirmed that the resultant pattern of the obtained structures can be manipulated by tuning the treatment conditions, suggesting an interesting alternative route of producing self-organized nanostructures.

Figure 1

Fabrication procedures of quasi-beehive Si nanostructures and self-organized nanogrids: a SiGe thin film is deposited on Si substrate; b SiGe islands arrays are formed via the annealing treatment; c then plasma etching (RIE); d finally the self-organized nanostructures are fabricated

Figure 2

The cross-sectional HRTEM image of SiGe/Si sample prior to thermal annealing. Inset compositions of Si and Ge elements are confirmed by Auger analysis

Figure 3

SEM observation the surface morphological image of SiGe thin film at an annealing temperature of 900°C. Inset the XTEM image of SiGe nanoislands on Si substrate

Figure 4

The depth of the self-organized nanoislands as a function of the annealing temperature. Inset the shape analysis of SiGe thin film with the annealing treatment at 900°C

Figure 5

Asymmetric (113) HRRSM of a the as-grown SiGe thin film and, b the annealed SiGe thin film at 900°C for 30 min

Figure 6

The HRTEM images of the a as-grown SiGe film and b SiGe film annealed at 900°C for 30 min. The results clearly indicate the degradation of crystalline structure resulted from the ATG instability-induced surface roughening driven by strain relaxation

Figure 7

SEM top-view images of SiGe thin films with a as-grown sample, b 900°C annealed and 1 min RIE, c 900°C annealed and 5 min RIE, and d 900°C annealed and 10 min RIE. e The SEM and f AFM image of the quasi-beehive Si nanostructures

Figure 8

SEM top-view images of SiGe thin films with a 900°C annealed and 1 min Ar plasma, b 900°C annealed and 3 min Ar plasma. c 2-D and d 3-D AFM images of the self-organized nanogrids (a)