Proceedings of MUCEET2009

Malaysian Technical Universities Conference on Engineering and Technology

June 20-22, 2009, MS Garden, Kuantan, Pahang, Malaysia
MUCEET2009

Design, Simulation and Characterization of 50nm p-well MOSFET Using

Sentaurus TCAD Software

Marlia Morsin, Mohd Khairul Amriey, Abdul Majeed Zulkipli and Rahmat Sanudin

The MOS transistor contains two types, the p –channel

Abstract—Device 50nm p-well MOSFET was MOSFET (PMOS) and n- channel MOSFET (NMOS). Both
of these MOS transistors have their own characterization
designed, developed and optimized based on
that differentiates each other. The p – channel transistor
90nm recipe using Sentaurus TCAD Software. In (PMOS), based on aluminum – gate technology, was the
this project, there are two sub-programs used earliest practical MOS device structure [3]. The PMOS
which are Sentaurus Process and Sentaurus transistor consists of two categories which are depletion
Device. Sentaurus Process is a simulation process (DMOS) and enhancement (EMOS).
which in designing the semiconductor technology. A transistor is considered as depletion type if both
source and drain are connected by a channel. This channel is
While Sentaurus Device work as a device created by implantation ion or diffusion process. If there are
simulator to find the characteristic for each no channel exists, the operation of transistor is known as
semiconductor design. The simulation results are depletion operation. The depletion mode is used mainly in
shown in two dimensions (2D) in INSPECT and analog circuit. A p- channel depletion mode transistor,
TECPLOT SV. The threshold voltages (Vth) for although in conceptually possible, has never been used in
practical circuits.
NMOS and PMOS of 50nm are 0.187V and - In this project, the enhancement PMOS and NMOS
0.071V, the drain saturation current (Idsat) are transistor are used to design p-well MOSFET. It is relatively
6.897e-04A and 1.22e-03A with the leakage easy to make as an enhancement mode device, which is the
current (Ioff) are 2.799e-07A and 2.507e-08A. preferred choice for digital applications since it minimize
The simulation results are almost the same with the standby power dissipations [4].
the theoretical.
Keywords: P-well MOSFET, Sentaurus Process, Sentaurus Device
II. 50NM P-WELL MOSFET DESIGN

Designing p-well CMOS semiconductor must go

I. INTRODUCTION through several processes. The designing process involves
modifying the recipe of MOSFET 90nm to MOSFET50nm.
The MOS (Metal Oxide Semiconductor) transistor is The first process is the simulation of fabrication process
the most promising active component for silicon VLSI 50nm MOSFET which is done using Sentaurus Process.
circuits at the present time. There are a number of reasons Then, the process for structure and mesh are done onto
for this choice. First, it is self – isolating, so that the devices fabricated MOSFET using Sentaurus Structure Editor. The
can placed side by side on a chip without the needs for final step is electrical testing using Sentaurus Device.
providing isolation tubs. As a result, it is considerably The development of the CMOS starts with the
smaller than its bipolar counterpart, and requires less formation of p-well (for n-substrate), where the n-substrate
processing steps [1]. Furthermore, it can be made in bulk is layered with a 100Å thick oxide layer by oxidation
silicon, thus avoiding the costly epitaxial growth. However, process. Forming of active area with oxide layer with this
epitaxial structures are increasingly used in high – density thickness will act as a protector when doing ion
application, to minimize latch–up problems, caused by implantation process. Furthermore, phosphorus will be
devices interactions through a common substrate [2]. implanted with the positive resistive which act as a mask
during the annealing process in 900-1200 ۫ Celsius
temperature.
The formation of active area process of transistor
Marlia Morsin, Abdul Majeed and Rahmat Sanudin are with Faculty of
Electrical and Electronic Engineering, University of Tun Hussein Onn NMOS and PMOS are defined using photolithography. The
Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia, Tel:07- active edge of NMOS which is p-well is normally covered
4537524,Fax:07-4536060,e-mail:{marlia,mejeed,rahmats}@uthm.edu.my) by lithography. It is followed by the implantation of boron
ion to increase the density of n-type surface which is act as
Mohd Khairul Amriey is a B.Eng’s student at University of Tun Hussein
Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia,
obstacle of p-channel under the field oxide.

1
 The next process is the formation of the polysilicon
gate where the oxide layer will be growth and also
implantation of boron ion. The pattern of the gate is
designated by lithography action for drain (D) and source
(S). The formation process of drain (D) and source(S) for
MOSFET is carried with resistive electron layer by all over
the wafer for S and D pattern.
The final process for development of MOSFET is
metallization. The aluminum materials are doped on wafer
surface. The resistive layer is coated and the related patterns
are made by lithography process.
In process simulation, processing steps such as etching,
deposition, ion implantation, thermal annealing and
oxidation are simulated based on physical equations, which
govern the respective processing steps. The simulated part
of the silicon wafer is discretized (meshed) and represented Figure 2: Layout for 50nm PMOS transistor
as a finite-element structure. After the fabrication processes
are completed, the electrical testing called device simulation The electrical DC analysis are done for both transistors
is done onto the fabricated MOSFET. and the results are shown using TECPLOT SV tools.
Device simulations can be thought of as a virtual There are two electrical DC analyses done onto the
measurement of the electrical behavior of a semiconductor NMOS and PMOS transistors to obtain the curve for ID
device, such as a transistor or diode. The device is (Drain Current) versus VGS (Gate to Source Voltage) and ID
represented as a meshed finite-element structure. Each node (Drain Current) versus VD (Drain Voltage). The results for
of the device has properties associated with it, such as each graph are depicted in figure 3-6.
material type and doping concentration. For each node, the
carrier concentration, current densities, electric field,
generation and recombination rates, and so on are
computed.

III. RESULT AND ANALYSIS

The results for process and device simulation are shown

in figure 1-6. The graphs display in two dimension (2D) in
INSPECT and TECPLOT SV tools in Sentaurus TCAD.
Figure 1 and 2 depict the layout for NMOS and PMOS
transistor. For both transistors, the metal used is aluminum.
Figure 3: ID (Drain Current) -VGS (Gate to Source
The metals are used for interconnection and routing. The
Voltage) graph for 50nm NMOS transistor
insulator used in this device is polysilicon. The source and
drain areas are shown in green color and placed in between
gate region for both transistors.

Figure 4: ID (Drain Current) -VGS (Gate to Source

Voltage) graph for 50nm PMOS transistor

Figure 1: Layout for 50nm NMOS transistor

2
 The opposite situation happens for leakage current.
For the operating of ideal MOS transistor, the current only
flow when it is in linear operation. When the transistor is
off, no current will flow. But due to some geometrical
effects, there is leakage current in small amount though the
transistor in cut –off operation.

IV. CONCLUSION

The development of 50nm p-well CMOS transistor

using Sentaurus TCAD software is successful. The design
Figure 5: ID (Drain Current)-VD (Drain Voltage) graph of 50nm p-well MOSFET transistor is done in two main
for 50nm NMOS transistor processes which are device simulation and process
simulation. Three main parameters are obtained and
analyzed which are Threshold Voltage (Vth), Drain
Saturation Current (Idsat) and Leakage Current (Ioff).
The downsizing of MOSFET is important due to the
technology demand. However, the parameters must be
scaled using Scaling Factor (S) to ensure the device can
operate well after fabrication process.

ACKNOWLEDGMENT
This project has been carried out with the support of the
Ministry of Higher Education Malaysia under FRGS Vot.
Figure 6: ID (Drain Current) -VD (Drain Voltage) graph 0401 grant.
for 50nm PMOS transistor
REFERENCES
The main parameters for 50nm p-well MOSFER are
shown in Table 1. The data obtained from the graph in
[1] Neamen, Donald A. “Semiconductor Physics And Devices : Basic
figure 3- 6. Principles” (Book style), University of New Mexico, McGraw Hill
Higher Education, 2002, pg 1-18, 367, 449-485.
Table 1: Simulation values for 50nm MOSFET
[2] Kenneth J. Wu, Krishna Seshan, and Timothy J. “The Quality and
Reliability of Intel’s Quarter Micron Process” (Journal style), Intel
Type NMOS PMOS Technology Journal Q3 1998, 1998, pg 1-11

Vth (V) 0.187296 -0.070747 [3] Hong Xiao, “Introduction to Semiconductor Manufacturing
6.897e-04 1.220e-03 Technology”, New Jersey, Prentice Hall, 2001, pg 2,380-86.53-
Idsat (A)
181,313-360, 447-501.
Ioff (A) 2.799e-07 2.507e-08
[4] Clein, Dan, “CMOS Layout, Concepts, Methodologies and Tools”
(Book style), Newnes, 2000, pg 7-9.
The threshold voltage (Vth) for transistor MOSFET is [5] Ng Jin Aun, Ibrahim Ahmad, and Burhanuddin Yeop Majlis,
also know as the voltage that was generated between get and “Rekabentuk, Simulasi dan Pencirian Teknologi 0.25µm Peranti
source at MOS device where current drain-source, drop MOSFET” (Published Conference Proceedings Style), 2003 IEEE
until zero value. Vth is the starting voltage to operate for National Symposium on Microelectronics (NSM 2003), pg 221-224.
certain MOS transistor. If the value of voltage that is being
use is below than Vth, the transistor will be in cut-off area.
The threshold voltage (Vth) for 50nm p-well MOSFET is
0.187296V for NMOS and -0.070740V for PMOS
transistor.
Majority carrier for NMOS transistor is electron, but for
PMOS transistor is hole. Speed operation for NMOS is two
(2) times faster comparing with PMOS transistor. This
happen because the effective mass at the hole is better
compared with electron, but electron has higher mobility
value compare with hole.
Table 1 show the value of drain saturation current
(Idsat) for NMOS transistor is 6.897e-04A while for PMOS
transistor is 1.220e-03A. The Idsat is increasing
proportionally with the increasing of gate length.