Buckling suppression of SiGe islands on compliant substrates

Abstract

A cap layer was used to suppress buckling during the relaxation of compressively strained 30 nm Si 0.7 Ge 0.3 islands on borophosphorosilicate glass. The lateral expansion and buckling of a bilayer structure made of SiGe and a cap layer were studied by both modeling and experiment. Both epitaxial silicon and amorphous silicon dioxide (SiO 2) caps were investigated. Caps stiffen the islands to reduce buckling and accelerate the lateral relaxation, so that larger, flat, relaxed SiGe islands can be achieved. Using a 31 nm silicon cap, flat Si 0.7 Ge 0.3 islands up to 200 mϫ200m were achieved. However, germanium diffusion in the SiGe/Si structure took place during relaxation anneals and lowered the germanium fraction of the final fully relaxed SiGe film. Silicon dioxide caps, which are not prone to germanium diffusion, allowed suppression of SiGe buckling without lowering the germanium percentage. Full relaxation of SiGe islands was achieved by a controlled multicycle silicon dioxide removal and anneal procedure. Large, fully relaxed, smooth SiGe islands obtained using cap layers indicate that this approach could be of potential use for electronic device applications.

Wrinkle patterns of anisotropic crystal films on viscoelastic substrates

“…For many applications of the integrated material structures, wrinkling is undesirable as it may lead to failure by delamination or fracture (e.g., Suo, 1995;Martin et al, 2000;Mumm et al, 2001;Yin et al, 2003;Peterson, 2006). On the other hand, wrinkling has also been exploited as an enabling mechanism for a variety of applications, such as stretchable electronics (Watanabe et al, 2002;Lacour et al, 2003;Choi et al, 2007), micro/nanoscale surface patterning (Huck et al, 2000;Serrano and Cahill, 2002;Ohzono and Shimomura, 2004;Chan and Crosby, 2006), optical phase grating , microfluidic sieves (Efimenko et al, 2005), smart adhesion (Chan et al, 2008), and metrology aid for measuring mechanical properties of thin films .…”

Buckling modes of elastic thin films on elastic substrates

“…A frequent failure mechanism in these materials is buckling of the thin films, resulting in interfacial delamination and fracture [1,2]. Recently, understanding of buckle patterns has also led to applications in metrology [3][4][5], stretchable interconnects [6,7], and optical gratings [8].…”

Fracture, delamination, and buckling of elastic thin films on compliant substrates

“…Upon compression, buckling of thin films may lead to failure of integrated structures interfacial delamination and fracture [8,9]. Recently, understanding of buckle patterns has also led to applications in metrology [26,27], stretchable interconnects [28,29], and optical gratings [30].…”

“…The former pertains to the brittleness of the low-k materials subjected to tension, and the latter manifests due to poor adhesion between low-k and surrounding materials. Furthermore, a thin film layer under compression can buckle, which leads to failure due to uneven surfaces, buckle-driven delamination and/or fracture [8,9]. These failure mechanisms are schematically illustrated in Figure 1.…”