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PMOS Tuning

PMOS devices are a special case since the boron doped Source/Drain implants overall tend to absorb interstitials rather than emit them. The reverse short channel effect in buried channel PMOS devices can be caused by high angle implants. If high angle implants are used, the reverse short channel effect can be tuned using the LAT.RATIO1 parameter in the IMPLANT statement.

7.8.5: Related Issues on using the Device Simulator ATLAS for MOS Process Tuning

It should now be known that calibrating an ATHENA process file involves using the device simulator ATLAS to a significant extent. Hence, it’s imperative that the use of the device simulator doesn’t create additional errors, rendering the process calibration results invalid.

Fortunately, the device physics involved in simulating the conditions required to extract a threshold voltage are not demanding. The drain voltage required to extract a threshold voltage is only 50-100mV so effects such as impact ionization can be neglected. The field perpendicular to the gate is also relatively low around the threshold voltage so field effects in this direction will do little effect. We recommend, however, using at least the models SRH and CVT during the calculation. Other parameters for silicon are sufficiently well known for silicon to the point that the results from the device simulator are reliable.

The first important point is to ensure that you let the device simulator calculate the work function of the gate electrode from the simulated doping profile rather than assigning a value to it. This means, making sure that the polysilicon gate is not itself defined as an electrode but rather a layer of metal, usually aluminum, is deposited on top of the polysilicon gate. Therefore, this metal layer is the film defined as the electrode. Do not assign a work function to this deposited metal electrode to ensure that it behaves as an ohmic contact rather than a Schottky contact. The effective work function of the poly gate will then be correctly calculated from the doping profile in the polysilicon.

An important area for accuracy in MOSFETs is modeling the inversion region under the gate. As it is, this charge that is responsible for current conduction in the device. The inversion region charge under the gate-only extends approximately 30 Angstroms into the silicon. The inversion region charge density under the gate falls off rapidly with depth into the silicon. It is imperative that there are several mesh points in the Y direction in this inversion region to model the drain current correctly. Accordingly, we recommend that the mesh spacing under the gate be no more than 10 Angstroms (1 nm).

You would think that a 10 Angstrom mesh under the gate would result in a huge number of mesh points. But, there only needs to be approximately three mesh points within the inversion region in the Y direction. The grid spacing can increase rapidly in spacing away from the oxide-silicon interface.

Figure 7.43 shows the effects of changing the mesh spacing at the interface on the simulated drain current. You can see from this figure that too coarse of a mesh always results in too high of a current simulated.

Figure 7.43: The effect of changing the mesh spacing at the interface on the simulated drain current

If contact resistance is a problem, then include it in the CONTACT statement. The resistance added to the CONTACT statement should be the measured resistance per contact divided by the number of contacts on each individual electrode. Obviously for D.C. measurements, the resistance on the gate contact will have no effect on the results since no current flows in this direction.

Checking the Predictive Powers of Tuned Process Parameters

If the process simulation has been correctly tuned, the process and device simulators should have predictive powers. To check the validity of the tuning process, use a new set of electrical data that was not used during the tuning process. For example, a good alternative set of data is to check the threshold voltage versus gate length for a non-zero voltage applied to the MOSFET body contact.

Conclusion

Using just one set of easily obtained measured electrical data, namely a plot of threshold voltage versus gate length, you can obtain most of the tuning parameters required for accurate process simulation. The other most important piece of data required is an accurate measurement of the gate oxide thickness, which is routinely measured in any instance.

You have been given specific advice as to which process and device models to use for each process in order to get the best results out of the simulation software. In particular, the correct use of models for the implantation and diffusion processes is stressed, as this has a dramatic effect on MOSFET characteristics, especially as anneal times and device dimensions decrease.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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