Ion implantation
Singly charged ions are implanted into a wafer area of 100 cm² at a dose of 1×10¹⁵ ions/cm². With a beam current of 1 mA, approximately how long does the implant take? (Elementary charge 1.6×10⁻¹⁹ C)
- AAbout 160 seconds
- BAbout 1.6 seconds
- CAbout 16 seconds
Show answer and explanation
Answer: C. About 16 seconds
The total number of ions is 1×10¹⁵ × 100 = 1×10¹⁷, with a charge of 1×10¹⁷ × 1.6×10⁻¹⁹ = 1.6×10⁻² C. Dividing by the current, 1 mA = 1×10⁻³ C/s, gives 16 seconds. In practice, beam that falls outside the wafer is also taken into account.