12.2 Heteroepitaxy
353
(a)
(b)
(c)
Fig. 12.1 a Silicon single crystal for 300-mm diameter wafers after opening of the crucible. From [1114] with permission.
b Historic development (first year of larger production) of silicon wafer diameter and ingot mass. Data from [1104]. c
GaAs single crystal (boule) for 4-inch wafers and some cut and polished wafers
Fig. 12.2 Schematic
semiconductor wafer
geometry for various
orientations and doping
with the primary (P) and
secondary (S) flats
indicated
S
P
P
S
P
(1
P
S
(1
speed of the material) and the heating power. For the growth of III–V compound semiconductors, liquid
encapsulated CZ (LEC) growth has been developed to counteract the high volatility of the group-V
component. During LEC growth the melt is completely covered with molten boric oxide (B 2 O 3 ). The
keys to optimization of the crystal growth process are numerical modeling and computer control.
In Fig. 12.1a,c a large CZ silicon crystal and a smaller LEC GaAs crystal (boule) are shown. Over
time wafer size and ingot mass have increased remarkably (Fig. 12.1b). For details on other important
fabrication methods for bulk crystals, including float-zone (FZ [291, 1112]) or vertical gradient freeze
(VGF), we refer to the literature [1113]. Significant expertise is necessary for cutting, grinding and
polishing (lapping) wafers for epitaxy.
For semiconductors, the wafer is marked with flats to indicate orientation and doping. In Fig. 12.2
the standard flats are shown for (100)- and (111)-oriented material. The primary (major) flat (OF,
orientation flat) defines the crystallographic orientation
1 is longer than the secondary (minor) flat which
defines the conductivity type (IF, identification flat). For a 4-inch (100 mm) diameter wafer the OF is
32 and the IF 12 mm long. The front surface, on which the epitaxy is performed, typically undergoes
1 In the ‘US’ flat definition, the primary flat is the (01 ¯
1) surface, in the ‘EJ’ definition, the primary flat is (0 ¯
1 ¯
1).
353
(a)
(b)
(c)
Fig. 12.1 a Silicon single crystal for 300-mm diameter wafers after opening of the crucible. From [1114] with permission.
b Historic development (first year of larger production) of silicon wafer diameter and ingot mass. Data from [1104]. c
GaAs single crystal (boule) for 4-inch wafers and some cut and polished wafers
Fig. 12.2 Schematic
semiconductor wafer
geometry for various
orientations and doping
with the primary (P) and
secondary (S) flats
indicated
S
P
P
S
P
(1
P
S
(1
speed of the material) and the heating power. For the growth of III–V compound semiconductors, liquid
encapsulated CZ (LEC) growth has been developed to counteract the high volatility of the group-V
component. During LEC growth the melt is completely covered with molten boric oxide (B 2 O 3 ). The
keys to optimization of the crystal growth process are numerical modeling and computer control.
In Fig. 12.1a,c a large CZ silicon crystal and a smaller LEC GaAs crystal (boule) are shown. Over
time wafer size and ingot mass have increased remarkably (Fig. 12.1b). For details on other important
fabrication methods for bulk crystals, including float-zone (FZ [291, 1112]) or vertical gradient freeze
(VGF), we refer to the literature [1113]. Significant expertise is necessary for cutting, grinding and
polishing (lapping) wafers for epitaxy.
For semiconductors, the wafer is marked with flats to indicate orientation and doping. In Fig. 12.2
the standard flats are shown for (100)- and (111)-oriented material. The primary (major) flat (OF,
orientation flat) defines the crystallographic orientation
1 is longer than the secondary (minor) flat which
defines the conductivity type (IF, identification flat). For a 4-inch (100 mm) diameter wafer the OF is
32 and the IF 12 mm long. The front surface, on which the epitaxy is performed, typically undergoes
1 In the ‘US’ flat definition, the primary flat is the (01 ¯
1) surface, in the ‘EJ’ definition, the primary flat is (0 ¯
1 ¯
1).