Method of increasing the gettering effect in the bulk of semiconductor bodies utilizing a preliminary thermal annealing step

DETAILED DESCRIPTION In brief, and in reference to the prior art, the part taken by oxygen precipitates to ensure the internal impurity gettering effect is well-known but the formation of these oxygen precipitates requires thermal processes which are carried out at high temperatures and which are time-consuming.
In addition, the prior art gives no information about both the quantity of the oxygen precipitates existing in a silicon material and the behavior of the same during the following thermal cycles carried out at high temperatures.
This invention proposes a method of increasing the internal gettering effect in semiconductor bodies by increasing the number of oxygen atom precipitates through the generation of small clusters which though too small to be detected, act as nucleation sites for these precipitates.
This method is characterized in that the semiconductor body is subject to a thermal annealing step at temperatures within 750.
degree.
and 900.
degree.
C.
and for a length of time between 1 and 8 hours.
This invention proposes also a method of characterizing the precipitation capability of the oxygen atoms in semiconductor bodies, a method which includes the following steps: measuring the initial concentration (0.
sub.
O) of the oxygen in the body; annealing the body at a temperature T within 950.
degree.
and 1200.
degree.
C.
for a time length extending between 5 and 100 hours.
cleaning the body in an appropriate solution, measuring the oxygen concentration (0) and computing the precipitation characteristic k.
sub.
T according to the relation ##EQU1## Therefore, one object of this invention is to provide for a low temperature method capable of creating small clusters around which the oxygen atoms will precipitate during the following thermal cycles carried out at high temperatures, in order to ensure an internal gettering effect.
Another object of this invention is to provide for a method of characterizing semiconductor bodies, which gives advantageously the user the information about the oxygen precipitation phenomenon at different processing temperatures of the wafers, and helps him to choose at best the processing which corresponds to a determined material, in order to obtain optimization of the manufacturing throughputs of the final test