1. INTEGRATED CIRCUITS Dr. Esam Yosry Lec. #4

2. Ion Implantation  Introduction  Ion Implantation Process  Advantages Compared to Diffusion  Disadvantages Compared to Diffusion  Implantation Doping Profiles Compared to Diffusion  Implantation Doping Profiles Parameters  Multiple Implant Process  Ion Implantation Technology

3. Introduction ( Chip Fabrication Cycle)

4. Introduction ( Processes)  Oxidation  Diffusion  Ion Implantation  Deposition  Etching  Lithography  Deposition  Removal  Patterning  Modification of electrical properties

5. Ion Implantation Process  Ion Implantation: is a method of introducing impurities in a controlled manner into wafer.  Dopant ions are accelerated by a high electric field and directed at the substrate.  They enter the crystal at high kinetic energy, collide with host atoms, gradually lost energy and finally come to rest at some depth.

6. Ion Implantation Process  Room Temp process.  High energy ion bombardment (10 - 500 KeV)  The penetration depth and dopant profile are be controlled by the accelerating electric field.

7. Advantages compared to Diffusion  Better control on profile Amount of dose and profile (position and area) are accurately obtainable.  Broad range of doping levels 10 11 – 10 18 cm -3 By low doping we can make fine tune the values of some electrical parameters.  Arbitrary doping profile Placing the peak anywhere under the wafer surface.

8. Advantages compared to Diffusion  Low contamination  Shallow depths with uniform profiles  Low temperature processing The growth of masking oxide layer is no longer needed. Also low temperature processing allows us to maintain the shape of any previously introduced profiles.  Less lateral dopant diffusion Dopant ions have no momentum in the horizontal direction.

9. Disadvantages compared to Diffusion Only for shallow junctions Incident ions damage the semiconductor lattice Silicon damage (anneal at 500 - 1000 o C) Very expensive and complex equipment Profiles can have tails (channeling) 1 wafer at a time vs. up to 200 for diffusion Long processing time

10. Implantation Doping Profiles Compared to Diffusion Projected range (mean penetration depth) Standard deviation Higher implantation energy Ξ deeper penetration R p and wider distribution ∆ R p

11. Implantation Doping Profiles Compared to Diffusion

13. Implantation Doping Profiles Parameters

15. Example  A boron dose of 1x10 13 cm -3 is implanted into 5x10 15 cm -3 n-type Si at 100 kev. Find the junction depth.  Solution  From charts for B into Si at 100 kev, one gets R p =0.3µ and ∆R p =0.07µ N peak =0.4x 10 13 /0.07x10 -4 = 5.7x10 17 cm -3

16. Multiple Implant Process  Fairly flat, deep dopant profiles can be made by multiple implants of different energies.

17. Ion Implantation Technology

18. Many thanks to Prof. Hany Fikry and Prof Wael Fikry for their useful materials that help me to prepare this presentation. Thanks