diffusion time vs ramping time

[haswath]

diffusion ramping time

hi ,
can anyone tell what will be the effect if
diffusion time is much greater than the time at which the wafer temperature is ramped
?

i.e diffusion time >>>> ramping time ??


for .2 micron junction depth

 

[srivatsan]

ramping time

Lets take DNW (Deep NWELL) fab step as an example, because it is one of the earliest fab steps.

DNW fab step is ion implantation. It goes in Si and things are great.

After some steps, you can have oxide growth and etch or cleaning the Si surface. During oxdatoin step, the temp is increased (ramping time). Usually ions like to diffuse through any medium after certain temperature. Now, you dont want the DNW to move "around". You loose all its intended purpose. So if its diffusion time is longer than ramping tme needed to start oxidation, then things are nice otherwise you gotta problem.

Hope it helps...

Srivats.