Accelerating chamber; The B+ ions will come with a moderate speed. In order to ensure that they penetrate the wafer, they must be accelerated. For this, a set of ring electrodes are used (Figure 7.4). If negative charge is applied on the plates, the ions will get accelerated considerably. They form what is called as “ion beam”. The ionizing chamber must be kept under high vacuum. If any neutral molecules are there, the boron ion (B+) may hit them and take up an electron and become neutral boron  atom (B). We should not dope the wafer with boron atom, but should use only the boron ion. We will see the reason shortly.

Figure 7.4. Acceleration