FABRICATION OF MEMS

1. MEMS
FBRICATION
METHODS
MADE BY: Amit . K. Parcha
Roll No:2K13E21
Department of Electronic Science
Uinversity Of Pune

2. TABLE OF CONTENTS
Abstract of work undertaken
3) Introduction to the problem
4) Fabricating MEMS and Nanotechnology
a) Deposition Processes
b) Lithography
c) Etching
MEMS and Nanotechnology Applications
6) Current Challenges
Reference sites

3. MEMS: MICRO-ELECTRO-MECHANICAL
SYSTEMS
COMBINATION OF MECHANICAL
FUNCTIONS
(SENSING,MOVING,HEATING) AND
ELECTRICAL FUNCTIONS
(SWITCHING ,DECIDING) ON THE SAME
CHIP USING MICRO FABRICATION
TECHNOLOGY.

4. INTRODUCTION TO THE PROBLEM
 Imagine a machine so small that it is imperceptible to the
human eye. Imagine working machines no bigger than a
grain of pollen. Imagine thousands of these machines batch
fabricated on a single piece of silicon, for just a few pennies
each. Imagine a world where gravity and inertia are no
longer important, but atomic forces and surface science
dominate. Imagine a silicon chip with thousands of
microscopic mirrors working in unison, enabling the all optical
network and removing the bottlenecks from the global
telecommunications infrastructure. You are now entering the
microdomain, a world occupied by an explosive technology
known as MEMS. A world of challenge and opportunity,
where traditional engineering concepts are turned upside
down, and the realm of the "possible" is totally redefined.

5. FABRICATING MEMS AND
NANOTECHNOLOGY
 MEMS technology is based on a number of tools and
methodologies, which are used to form small structures with
dimensions in the micrometer scale (one millionth of a meter).
Significant parts of the technology has been adopted from
integrated circuit (IC) technology. For instance, almost all devices
are build on wafers of silicon, like ICs. The structures are realized
in thin films of materials, like ICs. They are patterned using
photolithographic methods, like ICs. There are however several
processes that are not derived from IC technology, and as the
technology continues to grow the gap with IC technology also
grows.
 There are three basic building blocks in MEMS technology, which
are the ability to deposit thin films of material on a substrate, to
apply a patterned mask on top of the films by photolithograpic
imaging, and to etch the films selectively to the mask. A MEMS
process is usually a structured sequence of these operations to
form actual devices.

6. DEPOSITION PROCESSES
MEMS Thin Film Deposition Processes
One of the basic building blocks in MEMS processing is the ability to deposit thin films of material.
In this text we assume a thin film to have a thickness anywhere between a few nanometer to
about 100 micrometer.
MEMS deposition technology can be classified in two groups:
1. Depositions that happen because of a chemical reaction:
a) Chemical Vapor Deposition (CVD)
b) Electrodeposition
c) Epitaxy
d) Thermal oxidation
These processes exploit the creation of solid materials directly from chemical reactions in gas
and/or liquid compositions or with the substrate material. The solid material is usually not the only
product formed by the reaction. Byproducts can include gases, liquids and even other solids.
2) Depositions that happen because of a physical reaction:
a) Physical Vapor Deposition (PVD)
b) Casting

7. LITHOGRAPHY
Various steps involved in Lithography:
1) Pattern Transfer
Lithography in the MEMS context is typically the transfer of a pattern to a photosensitive material
by selective exposure to a radiation source such as light. A photosensitive material is a material
that experiences a change in its physical properties when exposed to a radiation source. If we
selectively expose a photosensitive material to radiation (e.g. by masking some of the radiation)
the pattern of the radiation on the material is transferred to the material exposed, as the
properties of the exposed and unexposed regions differs.
2) Alignment
In order to make useful devices the patterns for different lithography steps that belong to a single
structure must be aligned to one another. The first pattern transferred to a wafer usually
includes a set of alignment marks, which are high precision features that are used as the
reference when positioning subsequent patterns, to the first pattern.
3) Exposure
The exposure parameters required in order to achieve accurate pattern transfer from the mask to
the photosensitive layer depend primarily on the wavelength of the radiation source and the
dose required to achieve the desired properties change of the photoresist. Different photoresists
exhibit different sensitivities to different wavelengths. The dose required per unit volume of
photoresist for good pattern transfer is somewhat constant; however, the physics of the
exposure process may affect the dose actually received. For example a highly reflective layer
under the photoresist may result in the material experiencing a higher dose than if the
underlying layer is absorptive, as the photoresist is exposed both by the incident radiation as
well as the reflected radiation. The dose will also vary with resist thickness.

10. ETCHING PROCESSES
In order to form a functional MEMS structure on a
substrate, it is necessary to etch the thin films
previously deposited and/or the substrate itself. In
general, there are two classes of etching
processes:
1) Wet etching where the material is dissolved when
immersed in a chemical solution.
2) Dry etching where the material is sputtered or
dissolved using reactive ions or a vapor phase
etchant.

14. Other Microfabrication
Processes
1)Soft lithography
2)Micro-Imprint
Lithography
3)Microstereolithography
(MSTL

15. Base material of MEMS
¾ Single crystal wafers
- Diameter of 4‘‘ to 6‘‘
- Thickness 200 μm to 1 mm
- Orientation mostly <110> and <100>

16. COMPARISON OF
MICROELECTRONICS AND
MICROSYSTEMS
Microelectronics Microsystems (silicon
 Fabrication
techniques are proven
and well documented
 Packaging technology
is relatively well
established
 Primarily 2-
dimensional
structures
 Stationary structures
based)
 Many microfabrication
techniques are used for
production, but with no
standard procedures
 Packaging technology is
Complex
 3-dimensional structure
at the infant stage
 May involve moving
components

17. ADVANTAGES:
Less material usage
Lower power requirements
Greater functionality per unit space
Accessibility to regions that are forbidden to
larger products
In most cases, smaller products should mean
lower prices because less material is used

18. MATERIALS FOR MEMS
1)Materials are the basic things
required to develop micro
sensors
2)Metals
3)Polymers
4)Ceramic materials
5)Semiconductors
6)Composite materials

19. mems product is always based on
silicon.why.??????
Silicon has good mechanical
properties:
High strength and elasticity, good hardness, and
relatively low density
Techniques to process silicon are well established
from processing of ICs

20. CURRENT CHALLENGES
MEMS and Nanotechnology is currently used in low- or medium-volume
applications.
Some of the obstacles preventing its wider adoption are:
1) Limited Options
Most companies who wish to explore the potential of MEMS and
Nanotechnology have very limited options for prototyping or
manufacturing devices, and have no capability or expertise in
microfabrication technology. Few companies will build their own
fabrication facilities because of the high cost. A mechanism giving
smaller organizations responsive and affordable access to MEMS and
Nano fabrication is essential.

21. 2) Packaging
The packaging of MEMS devices and systems needs to improve considerably from its
current primitive state. MEMS packaging is more challenging than IC packaging due to the
diversity of MEMS devices and the requirement that many of these devices be in contact with
their environment. Currently almost all MEMS and Nano development efforts must develop a
new and specialized package for each new device. Most companies find that packaging is the
single most expensive and time consuming task in their overall product development program.
As for the components themselves, numerical modeling and simulation tools for MEMS
packaging are virtually non-existent. Approaches which allow designers to select from a
catalog of existing standardized packages for a new MEMS device without compromising
performance would be beneficial.
3) Fabrication Knowledge Required
Currently the designer of a MEMS device requires a high level of fabrication
knowledge in order to create a successful design. Often the development of even
the most mundane MEMS device requires a dedicated research effort to find a
suitable process sequence for fabricating it. MEMS device design needs to be
separated from the complexities of the process sequence.
4)CAD Design tool inaccuracies

22. FUTURE:
It has the potential to change our daily life as
much as computer
As with all emerging technologies, the MEMS
industry had been predicted to revolutionize
technology and our lives.

23. •Microorganisms act as tiny machines in future MEMS
devices

25. REFERENCE SITES
1) Memx.org
2) Google.com

26. Queries……..
Thank
u………