To use the calculator, simply enter the various parameters — times and temperatures — for your CyMOS process. All entries have default values included, these are not suggested values — just typical numbers that are used as place holders. You should design your process according the requirements of the class instructor.
For diffusion drive steps that include an oxidation phase, the listed drive time is the total drive time — the oxidation time is included. For example, if your PMOS drive consists of 20 minutes of wet oxidation and 40 more minutes of drive with a nitrogen ambient, the correct entries should be t2 = 60 min for the drive and t = 20 min for the oxidation.
All diffusions include the effects of subsequent high-temperature steps. For example, the Dt2 of the PWELL diffusion includes the effects of the PMOS deposition and drive steps, the NMOS deposition and drive steps, and the gate oxidation step. The addition of these extra steps will not a have huge effect on the end results. But, the calculator will give slightly different values from hand calculations if those do not include the extra effects.
This calculator is not a substitue for a proper SUPREM simulation. All of the calculations here use the exact formulas and parameters given in the class notes. The calculated results should be identical to what you could do by hand. (In fact, you should confirm these results with hand calculations.) Other than the accumulated Dt effects described above, there are no other higher-level effects included — consumption of the substrate during oxidation, dopant segregation, doping-dependent oxidation, concentration-dependent diffusion coefficients, enhanced thin-oxide growth, etc. To see those more subtle effects, use SUPREM.
For the diffusions, the calculator assumes that the deposition steps are done with the surface concentration held at the solid-solubility limit. The calculator uses the SSL values given in the class notes, interpolating between listed values when needed.
The figures shown in the results section come from the CyMOS process traveler. The five figures included depict the test wafers and a CyMOS device wafer after each oxidation step. Refer to the process traveler to see the complete set of figures. Of course, the vertical dimensions in the figures are wildly out of scale.
There is minimal error checking in the script. (Our software test group has limited resources.) It is possible that some combination of entries may cause the script to fail. If it seems that the script is not working, try refreshing the page and starting from scratch.
If you think you've found an error in the calculations — and you've checked it at least five times — send a screen shot of the suspected erroneous result to G. Tuttle.
Enter the constant background doping concentration of the n-type wafer: NB = cm-3.
Field oxidation temperature and time: T = °C and t = min.
PWELL boron diffusion temperatures and times.
deposition: T1 = °C and t1 = min.
drive: T2 = °C and t2 = min.
For the oxide growth: t = min.
PMOS boron diffusion temperatures and times.
deposition: T1 = °C and t1 = min.
drive: T2 = °C and t2 = min.
For the oxide growth: t = min.
NMOS phosphorus diffusion temperatures and times.
deposition: T1 = °C and t1 = min.
drive: T2 = °C and t2 = min.
For the oxide growth: t = min.
Gate oxidation temperature and time (dry oxide): T = °C and t = min.
After the field oxidation, the test wafer oxide thicknesses are:
TW1
TW2
TW3
TW4
nm
nm
nm
nm
After the PWELL diffusion, the test wafer oxide thicknesses are:
TW1
TW2
TW3
TW4
nm
nm
nm
nm
For the PWELL diffusion,
The dose is Q = cm-2
The surface concentration is N(0) = cm-3.
The junction depth is xj = µm. (Between PWELL diffusion and substrate doping.)
The sheet resistance of the PWELL diffusion is Rs = Ω per square.
After the PMOS diffusion, the test wafer oxide thicknesses are:
TW1
TW2
TW3
TW4
nm
nm
nm
nm
For the PMOS diffusion,
The dose is Q = cm-2.
The surface concentration is N(0) = cm-3.
The junction depth is xj = µm. (Between PMOS diffusion and substrate doping.)
The sheet resistance of the PMOS diffusion is Rs = Ω per square.
After the NMOS diffusion, the test wafer oxide thicknesses are:
TW1
TW2
TW3
TW4
nm
nm
nm
nm
(Note that TW1 was etched clean of oxide prior to the diffusion in order to measure the PWELL sheet resistance. So the TW1 thickness is equal to TW3 thickness.)
For the NMOS diffusion,
The dose is Q = cm-2.
The surface concentration is N(0) = cm-3.
The junction depth is xj = µm. (Between NMOS diffusion and PWELL diffusion!)
The sheet resistance of the NMOS diffusion is Rs = Ω per square.
After the gate oxidation, the test wafer oxide thicknesses are:
