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Question: q1 a for a boron diffusion in silicon at 1000c...

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Q1 a) For a boron diffusion in silicon at 1000°C, the surface concentration, Cs, is maintained at 1019 cm3 and the diffusion time is 1 hour. Find the total number of dopant atoms per unit area of the semiconductor, O(t), and the gradient of the diffusion profile. cc/ax, at x 0 and a location where the dopant concentration reaches 1015 cm3 Assume that the diffusion coefficient of boron at 1000°C is 2x10-14 cm, s. The expressions of the dopant concentration distribution, the total number of dopants per unit area, and the gradient of the diffusion profile are, respectively, )C(x,t)dr-1.130 \Dt . and 6c C exp 4Dt [Hint: erfc(104 2.75.] (8 marks) Q1 b) What are the advantages of ion implantation as a doping technology? (9 marks) Q1 c) Explain why annealing is an essential process step after ion implantation in CMOS techniques, and state what are the advantages of rapid thermal annealing (8 marks) Q1 d) What is ion channeling and how can it be minimised? (8 marks)

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