8.31 Sspd_chapter 6_part 10_simulation of mosfet  (Page 4/5)

We select Process → Implant….. in command menu and open the Implant Menu.

#Impurities: B, P, As, Bf2, Sb, Si, Zn, Se, Be, Mg, Al, Ga, C############################

#Dose (ions/cm^2):#############################################################

#Energy (KeV);################################################################

#Model: Dual Pearson-Gauss-Predict-Montecarlo######################################

#Tilt:#########################################################################

#Rotaion:######################################################################

#Material Type: Crystalline-Amorphous;#############################################

#Point Defects: None-Unit Damage-Damage;#########################################

#Comment:####################################################################

After setting the parameters and the models for Boron Implant in P-well we get the following statement:

#P-well Implant

#

implant boron dose=8e12 energy=100 pears

In P-Well implant we have used 8×10 ¹² Boron ions/cm ² at 100 KeV and Dual Pearson Model has been invoked. With these parameters the peak of the implant will occur at 0.25µm.

#

diffus temp=950 time=100 weto2 hcl=3

Now wet Oxidation done at 950°C for 100 minutes with 3% HCl. This gives 0.5µm thick oxide layer which covers P-Well again

#

#N-well implant not shown -

#

Now we do thermal annealing to heal the damage as well as to drive the Boron atoms deep into P well.

# welldrive starts here

diffus time=50 temp=1000 t.rate=4.000 dryo2 press=0.10 hcl=3

Drive in takes place at 1000°C for 50 minutes at ramp rate of 4°C per minute with HCl 3% and dry oxygen ambient at 0.1 atmosphere pressure..

#

diffus time=220 temp=1200 nitro press=1

#

diffus time=90 temp=1200 t.rate=- 4.444 nitro press=1

#

Then damage annealing is done at 1200°C for 220 minutes in Nitrogen Ambient at 1 atmosphere pressure. The goal of damage annealing is is to remove the primary damage created by the implant and restore the silicon lattice to its perfect crystalline state leaving the dopents in active substitutional sites. This annealing removes the damage as well as activates the dopents. Activaion means dopents contribute to electrical conductivity and this can happen only after they occupy substitutional sites.

Next it is ramped down from 1200°C to Room Temperature at a rate of

– 4.444°C/min in Nitrogen Ambient at 1 atmosphere.

etch oxide all

#

#sacrificial "cleaning" oxide

Next by geometrical etching all oxide is removed from P-Well.

diffus time=20 temp=1000 dryo2 press=1 hcl=3

Next 0.03µm Oxide is grown over P-Well at temperature 1000°C in a period of 20 minutes in dry oxygen at a pressure of 1 atmosphere with HCl 3%.

#

etch oxide all

#

#gate oxide grown here:-

diffus time=11 temp=925 dryo2 press=1.00 hcl=3

#

# Extract a design parameter

extract name="gateox" thickness oxide mat.occno=1 x.val=0.05

A thin oxide layer is grown and again etched. This is done to improve the silicon surface which has received considerable battering due to Boron implants. This is in addition to anneal step.