Recrystallization of Si-, As- And BF 2 -Implanted, Bonded SOI
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micrograph of a typical sample structure having an amorphized SOI layer on 500-nm -thick SiO2 after Si implantation. The samples after implantation were mainly annealed at 600*C for times ranging from 30 s to 100 h. TEM observations were carried out at 200 keV. GROWTH SEQUENCE Figure 2 shows conventional XTEM micrographs of the L-SPE regrowth sequence of the amorphized SOI layer of the Fig. I sample along the + [110] directions at 600*C. After annealing for 10 min (Fig.2(a)), (11 )]facets were observed to have formed at the growth front of L-SPE layers and then L-SPE growth gradually proceeded with the increase in annealing time. The fIII) facet formation phenomenon at the L-SPE front along the direction has previously been observed in VLSPE processes, where the facet was already formed at the oxide window edge during V-SPE growth [3]. In the present case,
Fig. 1 XTEM micrograph of a sample structure with an amorphized SOI layer by Si implantation.
we observed through HRXTEM that two f 111 ) facet planes at the
growth front appeared even after annealing for 30 s at 600°C, independent of implantation species. This suggests that the upper (screen oxide) and lower SiO2 materials contacting the SOI layers act as a pinning site for LSPE growth and that the slowergrowing f111) faces are generated during the initial growth stages along the direction. The fI111 twins were also generated on these ( 111 facet
planes
(dark
regions
of
n
12111
Fig. 2 XTEM micrographs of the L-SPE growth sequence of the amorphized SOI layer in the Fig. I sample along the direction after annealing for (a) 10 min, (b) 2 h, (c) 4 h, (d) 4.5 h and (e) 6 h at 6000C. The enlarged micrographs in (c) and (e) show a micro crystallite and a residual defect below the original (a/c) interface, respectively.
recrystallized ones) as will be described in the next section. After annealing for 4 h, small crystallites in a-Si SOI layers began to form (Fig. 2(c)). For annealing periods under 4 h, the growth length from the mask edges was almost constant in each patterned area. However, after annealing between 4.5 h and 5 h, the growth front suddenly advanced (Fig.2(d)). This increased growth is probably due to the much greater crystallite formation in a-Si layers. Almost the whole area of patterned SOI was recrystallized after annealing for 6h (Fig.2(e)), although the thus recrystallized area consisted of rotated I111 Itwins. 466
The other samples implanted
10 .
with As and BF2 ions were studied using the same procedure
as a function of annealing time at .-, 600'C. General phenomena E during L-SPE growth such as (111) facet formation, the E generation of high density 111) P twins and small crystallite formation
were
similarly
observed, the same as for Si implanted SOI layers. However,
I
i
I
i
I
Annealing Temp.: 600t direction
0.5
As2 S
m o.S
_ 0
the growth rate and the annealing • 0.05 time at which small crystallites
were generated, were different for Si-, BF2- and As-implanted layers. Figure 3 shows the change in
L-SPE length with
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