EEE413_Assignment-1 in the field of biosensor

Nanotechnology

1. Group-01 Assignment-01 EEE413(1) Fundamentals of Nanotechnology Course Instructor Mohammad Ryyan Khan Associate Professor Department of EEE East West University Group Members Naquibuddin Sarkar ID: 2018-2-80-004 Md Mehedi Hassan ID: 2018-2-80-008 Abrar Shahriyar ID: 2018-2-80-026 MD Ashik Mahmud ID: 2018-3-80-022 Title: Dopant diffusion of Phosphorus in Silicon 01

2. Dopant diffusion is a process to change the electrical, optical, or structural properties of a material for controlled impurities that can be uniformly distributed throughout the material during the deposition process. The following formula can be used to determine the impurity concentration profile after diffusion, N(x,t) = Diffusivity at any temperature (T), D = D o   What is Dopant Diffusion? 02

3. For Calculation we need the following parameters, = 10 15 /cm 2 [Given] D o =3.85 cm 2 s -1 [Given] E a = 3.66 eV [Given] k B = 8.617 × 10 5 eV/K We also need temperature, time and value of depth.   Phosphorus Doping in Silicon 03

4. Algorithm START CALCULATE DIFFUSIVITY CALCULATE DIFFUSIVITY For 1200K For 800K CALCULATE IMPURITY CONCENTRATION PLOT N Vs x FOR, t = 5 min, t-= 10 min PLOT N Vs x FOR, t = 5 years CALCULATE IMPURITY CONCENTRATION MERGE THE PLOTS END 04

5. Calculation (Q1) Question 1 : Assume that we anneal the device at 1200 K. In the same figure, show the dopant distribution N vs x at time t = 5min and 10min. Here, T = 1200 K . We need to calculate impurity concentration @ t = 5min and t = 10 min . We assume the range for the depth of doping in silicon, x = cm, We can calculate the diffusivity and the impurity concentration using MATLAB .   05

6. MATLAB code (Q1) 06

7. Result Analysis (Q1) The X-axis represents the depth of doped phosphorus in silicon. Y- axis represents the impurity concentration per cm^3. If the phosphorus is diffused for longer period at the same temperature, then the depth is higher. 07

8. Calculation (Q2) Question 2 : (2) Now assume that the device operates at 800 K for 5 years. We want to see how far the dopant will diffuse under operation: in the same figure in (1), now plot N vs x after 5 years. Here, T = 800 K . We need to calculate impurity concentration @ t = 5 years. We assume the range for the depth of doping in silicon, x = cm, We can calculate the diffusivity and the impurity concentration using MATLAB .   08

9. MATLAB code (Q2) 09

10. Result Analysis (Q2) Impurity concentration depends on diffusivity and diffusivity depends on temperature. Here, at T=800K, diffusivity is low compared to diffusivity at T= 1200K. Which means the diffusion process will be slow. Here the depth of phosphorus is very much low at 800K for 5 years compared to 1200K for 5min and 10 min. 10

11. THANK YOU 1 1