
55Importance of Single Crystals for Integrated Circuit Fabrication
impurities in silicon is relatively small, but it depends on the temperature of the system.
The highest concentration of boron in silicon, for example, is less than 1% [1] of the total
number of silicon atoms. The solubility value initially increases in response to temperature
and then begins to decrease as the crystal melting temperature is approached [6], as shown
in Figure 3.5. When the maximum solubility is achieved at a certain temperature, the crys-
tal is said to be saturated with the impurity at that temperature only. If the crystal is cooled
to a lower temperature withou ...