Solid phase epitaxy in uniaxially stressed (001) Si

Abstract

The effect of ͓110͔ uniaxial stresses up to 1.5 GPa on defect nucleation during solid phase epitaxy of amorphous ͑001͒ Si created via ion implantation was examined. The solid phase epitaxial regrowth velocity was slowed in compression. However, in tension, the velocity was unaffected. Both compression and tension resulted in an increase in regrowth defects compared to the stress-free case. The defects in compression appear to arise from roughening of the crystallizing interface whereas in tension it is proposed that reorientation of crystallites near the initial amorphous/ crystalline interface is responsible for defect formation. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2801518͔ Solid phase epitaxy ͑SPE͒ in amorphous ͑␣͒ Si created via ion implantation produces enhanced dopant activation and shallower junctions. 1 However, stresses found during typical device fabrication may influence the SPE process. 2,3 Early investigations revealed exponential enhancement of the ͓001͔ SPE using hydrostatic pressure while subsequent investigations revealed uniaxial stress in the plane of the regrowing ␣/crystalline interface caused smaller changes to SPE rates. [4][5][6] In-plane compression also caused significant roughening of the regrowing ␣/crystalline interface. 7 This is significant since interfacial roughening is known to cause SPE-related defect formation. 8,9 However, while BarvosaCarter et al. 7 quantified and modeled the roughness of the regrowing interface, they did not quantify the resulting defects or examine tensile stresses. Furthermore, the stresses used were fairly small in magnitude ͑Ͻ0.5 GPa͒ and the stresses present in Si-based technology can be ϳ1 GPa or more. 2 Thus, the goal of this study is to examine the effect of very high uniaxial ͓110͔ stresses on SPE in ͑001͒ Si.For this study, 50-m-thick polished ͑001͒ Si wafers were used. The specimens were first Si + implanted at 50 and 200 keV with doses of 1.0ϫ 10 15 cm −2 and subsequently As + implanted at 300 keV to a dose of 1.8ϫ 10 15 cm −2 . Samples were cleaved along ͗110͘ directions into ϳ0.3ϫ 1.8 cm 2 strips. Stress was applied by bending and inserting the strips into slots in a quartz tray spaced ϳ1.5 cm apart. A Philtec laser displacement measurement system accurate to 1 m measured the local radius of curvature along the strips. The bent strips were symmetric and parabolic in shape with the smallest radius of curvature at midlength. The ͓110͔ stress ͑ ͓110͔ ͒ was calculated using the ͓110͔ Young's modulus of Si near ϳ500°C ͑ϳ1.61ϫ 10 11 Pa͒, the wafer halfthickness, and the local radius of curvature as presented elsewhere. 10,11 Maximum repeatable stresses of 1.5± 0.1 GPa were attained. Specimens were annealed at 525°C in N 2 ambient for 0.7-3.2 h. Stress-free, tensile, and compressive specimens were annealed simultaneously for each anneal time. Upon removal from the quartz tray after annealing, the specimens exhibited no detectable radii of curvature ͑ӷ2.0 m͒ indicating no measurable plastic strain. Regrowth of the ␣-Si layers was ex...

Kinetics and Morphological Instabilities of Stressed Solid-Solid Phase Transformations

“…1(b)-1(d), 77 9, 72 8, and 68 9 nm of growth occurred which is less than the 11 0 case. Growth interface roughening was observed with 11 < 0, consistent with prior reports [9][10][11]. For cases of 11 0:5, 1.0, and 1.3 GPa, shown in Figs.…”

“…Subsequently, samples were cleaved along h110i directions into 0:2 1:8 cm 2 strips (with 1 and 2 directions taken to be [110] and 1 10 crystal directions) and uniaxially-stressed up to magnitude of 1:3 0:1 GPa along [110] ( 11 ) as presented elsewhere [11]. Stress-free, tensilely stressed, and compressively stressed strips were annealed simultaneously at 525 C in N 2 ambient for 1.0-4.0 h. No detectable stress relaxation occurred during annealing.…”

Dopant-stress synergy in Si solid-phase epitaxy

“…The wafer was subsequently cleaved along ͗110͘ directions into ϳ0.2 ϫ 1.8 cm 2 strips ͑with 1 and 2 directions taken to be ͓110͔ and ͓110͔ crystal directions͒ and uniaxially stressed up to magnitude of 1.0 GPa along ͓110͔ as presented elsewhere. 21 The error in all nonzero stress measurements is estimated to be Ϯ0.1 GPa. Stress-free, tensilely stressed, and compres- sively stressed strips were annealed simultaneously at 500Ϯ 1°C in N 2 ambient up to 11.2 h. No detectable stress relaxation occurred during annealing.…”

Lithium implantation at low temperature in silicon for sharp buried amorphous layer formation and defect engineering

“…From the strong black contrast on the TEM images, it can be assumed that the crystalline front layer is strained. The recrystallization of the front layer at such low temperature could be explained by a stress-enhanced recrystallization as already proposed by Holland et al 16 Although, recent results obtained by Rudawski et al 17 show that uniaxial stress has no effect on SPEG velocity of the planar interfaces for in-plane tension though compression does cause significant retardation. But in our case, recrystallization does not concern planar interfaces but more spherical amorphous zones.…”