Ion selection chamber: The next section is the selecting chamber. We would like to dope the wafer with boron only and not with fluorine. Hence only B+ must be selected from the mixture of ions and added to the wafer. In order to select the required ion (B+), electric field and magnetic field are used. If we send the stream of ions between two electric plates, which have positive and negative connection as shown in Fig 7.2, the ions will be attracted to the negative plate and move towards the negative plate. If a magnetic field is also applied at the same time, the direction of the movement will change. The speed and the direction of the movement will depend on the charge and the mass of the ions. A plate with a hole in the appropriate place can be used to block all the ions except the desired one (Figure 7.3). Thus B+ ion can be separated from the mixture of ions.