100
S. Leu and D. Sontag
Fig. 5.1 The Siemens reactor process, which extracts pure silicon from trichlorosilane. The pure
thin silicon rods, with a diameter of about 8 mm are electrically heated to about 1150 °C. Pure
trichlorosilane flows around these hot silicon rods and polycrystalline silicon is deposited until the
rod has a diameter of about 300 mm
so that Si atoms from the vapour are deposited on a silicon starting ‘seed’, usually
consisting of a cylindrically arranged array of thin Si rods. It is the most widespread
cleaning process for silicon—it results in pure silicon with a purity of 9 N–11 N,
depending on how pure the trichlorosilane is. Figure 5.1 shows, in a schematic way,
the process flow.
In the next step, the polycrystalline silicon rods grown in the Siemens reactor
process are broken down in pieces of different sizes (chunks and chips) so that the
various crucibles can be filled to produce either monocrystalline silicon or multicrystalline silicon. The aim of this process step is to produce, from the ultra-pure silicon, a
silicon crystal (ingot) with, on the one hand few dislocations, and, on the other hand a
material in which the desired concentration of the doping material is contained.
(e) Production of monocrystalline ingots
Czochralski Method
In the widely used Czochralski
4 method (CZ), which is shown in Fig. 5.2, ultrafine
silicon chunks are filled into a crucible, which consists of pure quartz glass SiO 2
and is coated with Si 3 N 4 . The quartz glass crucible is in its turn embedded in a
graphite crucible, which supports it. The temperature resistance of these crucibles is
over 1600 °C. The structure and coating of the crucible are crucial for the quality of
the silicon [2]. After the quartz glass crucible has been filled with ultra-pure silicon
4 Jan Czochralski was a Polish Chemist (1885–1953). He developed 1916 the Czochralski method
for pulling single crystals from the melt.
S. Leu and D. Sontag
Fig. 5.1 The Siemens reactor process, which extracts pure silicon from trichlorosilane. The pure
thin silicon rods, with a diameter of about 8 mm are electrically heated to about 1150 °C. Pure
trichlorosilane flows around these hot silicon rods and polycrystalline silicon is deposited until the
rod has a diameter of about 300 mm
so that Si atoms from the vapour are deposited on a silicon starting ‘seed’, usually
consisting of a cylindrically arranged array of thin Si rods. It is the most widespread
cleaning process for silicon—it results in pure silicon with a purity of 9 N–11 N,
depending on how pure the trichlorosilane is. Figure 5.1 shows, in a schematic way,
the process flow.
In the next step, the polycrystalline silicon rods grown in the Siemens reactor
process are broken down in pieces of different sizes (chunks and chips) so that the
various crucibles can be filled to produce either monocrystalline silicon or multicrystalline silicon. The aim of this process step is to produce, from the ultra-pure silicon, a
silicon crystal (ingot) with, on the one hand few dislocations, and, on the other hand a
material in which the desired concentration of the doping material is contained.
(e) Production of monocrystalline ingots
Czochralski Method
In the widely used Czochralski
4 method (CZ), which is shown in Fig. 5.2, ultrafine
silicon chunks are filled into a crucible, which consists of pure quartz glass SiO 2
and is coated with Si 3 N 4 . The quartz glass crucible is in its turn embedded in a
graphite crucible, which supports it. The temperature resistance of these crucibles is
over 1600 °C. The structure and coating of the crucible are crucial for the quality of
the silicon [2]. After the quartz glass crucible has been filled with ultra-pure silicon
4 Jan Czochralski was a Polish Chemist (1885–1953). He developed 1916 the Czochralski method
for pulling single crystals from the melt.