5.4 Plasticity
133
Fig. 5.44 Cleaving planes
of the a diamond and b
zincblende lattice
(a)
(b)
Fig. 5.45 Scanning
tunneling microscopy
images of a cleaved GaAs
(110) surface with a good
cleave and b bad cleave
with defects dominating.
Adapted from [446]
10 nm
(a)
(b)
nescence (or X-ray imaging) offer a quite high sensitivity for plastic relaxation since a small number
of dislocations can be detected in relatively large areas (while TEM finds defects but only within small
areas and X-ray diffraction looks at large area but has only a low strain sensitivity).
5.4.2 Cleaving
The cleavage planes of the diamond structure are {111} planes (Fig. 5.44a). It is easiest to break the
bonds connecting the double layers in the 111 directions.
The cleavage planes of the zincblende structure are {110} planes (Fig. 5.44b). Due to the ionic
character, breaking the bonds connecting the double layers in the 111 directions would leave charged
surfaces, which is energetically unfavorable. The {100} planes contain only one sort of atom and would
also leave highly charged surfaces. The {110} planes contain equal amounts of A- and B-atoms and are
neutral. Ideally, the cleaving plane is atomically flat (Fig. 5.45a) or exhibits large mono-atomically flat
terraces. However, certain dopants in high concentrations, e.g. GaAs:Te, can induce a rough surface
due to lattice distortion [444].
The natural cleavage planes of wurtzite (GaN) are {1 ¯
1.0} (m-type) planes [445].
5.4.3 Wafer Breakage
The thickness and thus strength of wafers for semiconductor production (cmp. Sect. 12.2.2) is an
important issue. The wafer should be as thin as possible for saving expensive materials but thick
enough to avoid loss due to stress during handling, in particular during the later steps in a process since
the value of a wafer increases with number of process steps it has undergone.
133
Fig. 5.44 Cleaving planes
of the a diamond and b
zincblende lattice
(a)
(b)
Fig. 5.45 Scanning
tunneling microscopy
images of a cleaved GaAs
(110) surface with a good
cleave and b bad cleave
with defects dominating.
Adapted from [446]
10 nm
(a)
(b)
nescence (or X-ray imaging) offer a quite high sensitivity for plastic relaxation since a small number
of dislocations can be detected in relatively large areas (while TEM finds defects but only within small
areas and X-ray diffraction looks at large area but has only a low strain sensitivity).
5.4.2 Cleaving
The cleavage planes of the diamond structure are {111} planes (Fig. 5.44a). It is easiest to break the
bonds connecting the double layers in the 111 directions.
The cleavage planes of the zincblende structure are {110} planes (Fig. 5.44b). Due to the ionic
character, breaking the bonds connecting the double layers in the 111 directions would leave charged
surfaces, which is energetically unfavorable. The {100} planes contain only one sort of atom and would
also leave highly charged surfaces. The {110} planes contain equal amounts of A- and B-atoms and are
neutral. Ideally, the cleaving plane is atomically flat (Fig. 5.45a) or exhibits large mono-atomically flat
terraces. However, certain dopants in high concentrations, e.g. GaAs:Te, can induce a rough surface
due to lattice distortion [444].
The natural cleavage planes of wurtzite (GaN) are {1 ¯
1.0} (m-type) planes [445].
5.4.3 Wafer Breakage
The thickness and thus strength of wafers for semiconductor production (cmp. Sect. 12.2.2) is an
important issue. The wafer should be as thin as possible for saving expensive materials but thick
enough to avoid loss due to stress during handling, in particular during the later steps in a process since
the value of a wafer increases with number of process steps it has undergone.