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Ion Implantation Process Presentation Transcript
1.Ion Implantation –
2 2.Channeling Effect
3.Channeling after collision
4.Value of Channeling is characterized by a critical angle ?1 which is the maximum angle between ion and channel for a glancing collision to occur. If we neglect thermal vibrations, then for KeV energy range, 1 is given by: ?1 = 9.73 {Z1Z2/Ed}-0.5 (degrees) d = atomic spacing along the ion direction (Å) E = ion energy (KeV)
5.Recoils In the I.I. process, oxygen atoms are displaced from oxide into silicon, giving a profile composed of two roughly exponential regions. This is called recoils mixing. This recoil mixing can be used for introducing dopant atoms by automatic implantation machines.
6.Sketch of an Ion Implanter
7.Campbell p.101
8.Campbell p.101
9.3 quantities define I.I. steps Ion Type Energy Dose
10.Ion Type ? mag field of analyzer magnet B = mag field strength R = Radius of circle in which ion of charge ? moves.
11.Oxide Barrier Thickness
12.Dose ?d = Total number of ions per unit area during exposure time te .
13.I(t) = ion beam current incident on a single location qi = charge per ion Abeam = area of implanting beam N(x) = resultant impurity conc. /unit vol. in the wafer
14.DOSE 15.total dose F =2.5* no * sp no is the peak concentration in atoms/c.c. sp is in cm Straggle sp is the same as ?Rp F is in atoms/sq. cm of surface area
16.Total Dose F = I*t/(qnA) I is current in Amperes A is area in sq. cm. n is the charge on ion q is electronic charge q = 1.6 * 10-19 coulombs
17.Controlling Dopant Conc. and Depth
18.Dopant Distribution
19.Damage caused by one ion
20.Why does the wafer need annealing?
21.Why are the wafers usually tilted
22.Comparison between Diffusion and I.I. 23. Comparison of I.I. And Diffusion
24. h159
25.Ion Implantation At its heart Ion Implantation is a random process. High energy ions (1 – 1000 keV) bombard the substrate and loose energy through nuclear collisions and electronic drag forces
. 26.Why does the wafer need annealing
27.Figure 8.14
28.Total Dose F = I*t/(qnA) I is current in Amperes A is area in sq. cm. n is the charge on ion q is electronic charge in coulombs q = 1.6 * 10-19 coulombs
29.Straggle sp is the same as ?Rp F =2.5* no * sp no is the peak concentration in atoms/c.c. sp is in cm total dose F is in atoms/sq. cm of surface area .
30.Average donor concentration in n-type layer = Nd = Qd /xj
31.Ion Type ? mag field of analyzer magnet B = mag field strength R = Radius of circle in which ion of charge ? moves.
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