12.6 Wafer Bonding
381
Fig. 12.45 a Atomic displacements [Ga (filled dots) and P (open circles)] of odd-index LO modes in a 69 Ga 16 P/ 71 Ga 16 P
superlattice unit cell. These modes have even parity with respect to midlayer planes, which are at atom numbers 16
and 48 in this example. The labels on the left identify the predominant character of the mode, those on the right give
the relative Raman intensities with respect to that of the 69 LO 1 mode. The tick marks on the vertical axis indicate zero
displacement of the respective mode. b Upper panel: Energies and characters of odd-index LO phonon modes in GaP
isotope SLs as calculated within the planar bond charge model for the case of ideal interfaces. 69 LO m modes are shown
as open symbols; 71 LO m modes as full symbols. The shaded area marks n = 16 for which the atomic displacements of
the modes are shown in part (a). Lower panel: Calculated intensities of the modes relative to that of the 69 LO 1 phonon
mode. Adapted from [379], reprinted with permission, ©1999 APS
12.6 Wafer Bonding
Wafer bonding is a fairly recently developed method to join different and dissimilar materials. Two
wafers of the respective materials are put together face to face and are adequately fused. The idea is to
not only ‘glue’ the wafers together with a sticky (and compliant) organic material, but to form strong
atomic bonds between the two materials with possibly a perfect interface. In some cases, the interface
needs to allow charge-carrier transport through it. Less stringent conditions need to be met for photon
transport.
Mechanical deficiencies such as surface roughness, dust particles and the like must be avoided in
the wafer-bonding process since they result in voids. Several methods have been developed for bonding
various materials [1220–1222]. Such processes are successful for large substrate sizes. With proper
processing, ideal interfaces can be created, as shown in Fig. 12.46. Such structures, if made between a
p-doped and a n-doped semiconductor, show diode characteristics.
381
Fig. 12.45 a Atomic displacements [Ga (filled dots) and P (open circles)] of odd-index LO modes in a 69 Ga 16 P/ 71 Ga 16 P
superlattice unit cell. These modes have even parity with respect to midlayer planes, which are at atom numbers 16
and 48 in this example. The labels on the left identify the predominant character of the mode, those on the right give
the relative Raman intensities with respect to that of the 69 LO 1 mode. The tick marks on the vertical axis indicate zero
displacement of the respective mode. b Upper panel: Energies and characters of odd-index LO phonon modes in GaP
isotope SLs as calculated within the planar bond charge model for the case of ideal interfaces. 69 LO m modes are shown
as open symbols; 71 LO m modes as full symbols. The shaded area marks n = 16 for which the atomic displacements of
the modes are shown in part (a). Lower panel: Calculated intensities of the modes relative to that of the 69 LO 1 phonon
mode. Adapted from [379], reprinted with permission, ©1999 APS
12.6 Wafer Bonding
Wafer bonding is a fairly recently developed method to join different and dissimilar materials. Two
wafers of the respective materials are put together face to face and are adequately fused. The idea is to
not only ‘glue’ the wafers together with a sticky (and compliant) organic material, but to form strong
atomic bonds between the two materials with possibly a perfect interface. In some cases, the interface
needs to allow charge-carrier transport through it. Less stringent conditions need to be met for photon
transport.
Mechanical deficiencies such as surface roughness, dust particles and the like must be avoided in
the wafer-bonding process since they result in voids. Several methods have been developed for bonding
various materials [1220–1222]. Such processes are successful for large substrate sizes. With proper
processing, ideal interfaces can be created, as shown in Fig. 12.46. Such structures, if made between a
p-doped and a n-doped semiconductor, show diode characteristics.