Transcript File - Anmol Ramraika

POWER MOSFET
PROCESS AND DEVICE SIMULATION USING SILVACO-TCAD
TEAM MEMBERS

SOMITRA BALDUA
120108034

ANMOL RAMRAIKA
120102079

RAJESH KUMAR

JITENDRA KHATIK
120108016

PRAKHAR TOSHNIWAL
120108026
120108028
MOSFET---------introduction

The metal–oxide–semiconductor field-effect transistor (MOSFET) is a
transistor used for amplifying or switching electronic signals.

In MOSFET ,a voltage drop across the oxide induces a conducting channel
between the source and drain contacts via the field effect.

The channel can contain electrons (called an nMOSFET or nMOS), or holes
(called a pMOSFET or pMOS), opposite in type to the substrate.
MOSFET----------------structure(n-MOSFET)
BAND-DIAGRAM-------------
POWER MOSFET

If the gate-source voltage is at or above what is called the threshold voltage,
enough electrons accumulate under the gate to cause an inversion n-type
layer; forming a conductive channel across the body region. Electrons can
flow in either direction through the channel.

Switching speed is only limited by the rate that charge is supplied to or
removed from capacitances in the MOSFET. Therefore switching can be very
fast. This is what makes power MOSFETs so efficient at high switching
frequency.
POWER MOSFET-----structure (n-channel MOSFET)
SIMULATION---------steps involved

Developing a good simulation grid

Defining the initial substrate

Performing epitaxial growth

Performing layer deposition and geometrical etching
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Performing ion implantation

Removing implant mask

Performing diffusion

Specification of electrodes
1--------developing a simulation grid

The number of nodes in the grid has a direct influence on simulation accuracy
and time. A finer grid should exist in those areas of the simulation structure
where ion implantation will occur, where p-n junction will be formed.

In our simulation process ,Grid is kept finest in the surface active region of
the MOSFET.
2---------developing initial substrate

Selecting semiconductor material as Silicon and impurity material as
Phosphorous

Selecting orientation of silicon as <100> and concentration of impurity as
1 * 1018 atoms/cm3 .
3---------------epitaxial growth

Using process menu for performing deposition epitaxial layer on gate surface
of MOSFET

At the temperature of 1200 degree Celsius for 10 minutes.
4----------------deposition and etching

Oxide, polysilicon and photoresist layers are deposited along with layer
thickness

Shape of etch is defined and etching is performed
5-------------------ion implantation

Implantation of boron with dose of 1*1014 atom/cm2 and implant energy of
80 KeV is performed
6-------------removing implant mask

Removal of barrier mask by performing etching.

Removing photoresist material by selecting all option to remove the implant
mask
7----------------specification of electrodes

Using Structure menu for specifying the location of electrodes so that device
can be used by device simulator for electrical characterization.

Aluminium contact is established by deposition and etching beforehand.
Tonyplot
Device simulation…………

The modelled MOSFET is simulated using Atlas.

Device equations are solved to obtain electrical characteristics of power
MOSFET.
I-V curve of device
Applications of power MOSFET--------
Power MOSFETs with lateral structure are mainly used in high-end audio
amplifiers and high-power PA systems.

Power MOSFETs are well known for superior switching speed, and they
require very little gate drive power because of the insulated gate. In these
respects, power MOSFETs approach the characteristics of an "ideal switch".

The main drawback is on-resistance RDS(on) and its strong positive temperature
coefficient.