Mems for Sysem on Chip Conectivtety

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BYK.PRASHANTH KUMAR

(08AN1A0432)

BALAJI INSTITUTE OF ENGINEERING & SCIENCESLAKNEPALLY , NARSAMPET , WARANGAL



Micromechanical systems can be combined with microelectronics, photonicsor wireless capabilities new generation of Microsystems can be developed

which will offer far reaching efficiency regarding space, accuracy,

precision and so forth. Micromechanical systems (MEMS) technology

can be used fabricate both application specific devices and the associatedmicro packaging systems that will allow for the integration of devices or

circuits, made with non-compatible technologies, with a System- on-Chip

environment. The MEMS technology can be used for permanent, semi

permanent or temporary interconnection of sub modules in a System- on-

Chip implementation. The interconnection of devices using MEMS

technology is described with the help of a hearing instrument application

and related micropackaging.



INTRODUCTION

MEMS ACCOUSTICAL SENSOR ARRAY FOR A HEARING INSTRUMENT

BEAM FORMING USING MICROPHONE ARRAY

MEMS MICROPACKAGING SOLUTION

DIE TESTING CONFIGURATION

ADVANTAGES AND DISADVANTAGES

CONCLUSION

REFERENCES

BIBLIOGRAPHY



MEMS technology has enabled us to realize advanced micro

devices by using processes similar to VLSI technology.

When MEMS devices are combined with other technologies new

generation of innovative technology will be created.

MEMS DEVICES + OTHER TECHNOLOGIES

||

NEW GENERATION OF INNOVATION TECHNOLOGY

Such technologies will have wide scale applications in fields

ranging from automotive, aerodynamics, hydrodynamics, bio-medical

and so forth.

INTRODUCTIN



In this application an array of capacitive type sensors are

used in a hearing instrument to provide dynamic directional

sensitivity and speaker tracking and can be completelyimplanted in the ear canal. The directional sensitivity is

obtained by the method of beam forming. The microphone

array is developed using MEMS technology and which can beused to form beam to provide directional sensitivity.



The microphone array consists of nine capacitor type

microphones arranged in a 3*3 array and utilizes the classical

phased array technique for beam forming.

In this technique, the relative delay or advance in signal

reception is eliminated by applying a delay or advance is that

the signal out puts from different microphones can be added to

form a beam as shown in figure .



Beam pattern of a transducer array: normal beam



It is also possible to steer the direction of the beam by

providing additional delay factor that is equal to the negative

of the relative delay to the out put of each microphone in thearray when a signal arrives from that direction. Figure .

illustrates the beam steering concept .



Similarly, it is possible to form multiple beams out of the single

array employing different delay factors and use such beams to

scan the direction of the potential speaker. This scanning beam can

easily realized by continuously steering the beam from top to

bottom or from left to right by dynamically changing the steering

delay using digital filters. An algorithm will detect a speech

signal above some threshold level and will steer the main beam

towards that direction. The block diagram for such a system is

shown in figure .



Block Diagram of Hearing Aid Instrument



To avoid spatial aliasing at all steering angles the spacing d between

the microphones of the array is required to be

D < πc/ω

= πc/2πf

= λ/2

Where λ is the wavelength of the incident acoustical signal and f is

the frequency in Hz. c is the velocity.

If the sensor array is to be inserted inside the ear canal, the spacing

between the microphones will be much smaller than the required.

This constraint can be overcome by introducing additional delay

factor to compensate for the difference in delay due to the required

spacing d

and the delay due to physical microphone spacing.



MEMS MICROPACKAGINGSOLUTION

The MEMS technology can be used to create necessary structures for

die level integration of MEMS devices or components and CMOS

or non-CMOS, like BJT, GaAs, and Silicon-germanium devices.

The basic structure of the proposed mechanism is a socket

submodule ( figure ) that holds a die or device. The required no

of submodules can be stacked vertically or horizontally to realize

a completely system in a micropackage.







Connectivity between submodules is achieved by means

of microbus card ( figure .) constructed with heat deformed,

gold coated polysilicon cantilever microspring contacts and

platinum coated microrails fabricated inside an

interconnection channel that is presented in each socket

submodule. An illustration of the micropackaging system

is shown in figure







Microorganisms and moisture inside the ear canal may

contaminate the microsensor array. This can be helped by the

submodule type sensor array, which can be removed easily for

cleaning or replacement.

The submodules are connected by means of a MEMS

microbus with gold coated polysilicon cantilever microspring

contacts and platinum coated microrails fabricated inside

an interconnection channel that is presented in each socketsubmodule. Figure shows the 3D model of microbus





The concept of socket submodules and connectivity can alsobe used in a die testing platform. The establishment of

temporary connectivity for testing a die without exposing

the die to otherwise harmful energy sources or contaminationsduring the test cycles is a major technological challenge. The

MEMS submodule can be reconfigured to establish

temporary connectivity for die testing with out exposing thedie to any contamination while carrying out necessary test

procedures





In this set up, two different type of MEMS sockets are used: a fixed

one connected permanently to a Tester-on-Chip (ToC),which is a die

testing SoC using an enabling gold – to-gold thermo sonic

bonding technology and a removable socket that acts a die

specific carrier. The contact springs on both sides of the removable

socket undergo deformation due to a compression mass on the topof the die and generate the necessary contact force. The removable

MEMS socket can be redesigned to connect a die that is larger than

the ToC. This makes the system a flexible one. The major designobjectives of contact spring mechanism is to develop a proper



contact force, low-contact resistance, small area, and short

contact path while having the ability to tolerate some torsional

misalignment. Another important requirement is to maintain the

contact surface that will remain reasonably flat even under

torsional deformation to realize a higher contact area. Based on

these constraints designs two of contact springs are given in

figure .





High efficiency

Cost effective

Flexible

High accuracy precision



Complex designComplex fabrication procedures



MEMS technology offers wide range application in fields

like biomedical, aerodynamics, thermodynamics and

telecommunication and so forth. MEMS technology can be

used to fabricate both application specific devices and the

associated micropackaging system that will allow for the

integration of devices or circuits, made with non compatible

technologies, with a SoC environment.



Sazzadur Choudhury,M. Ahmadi, and W.C. Miller ,Micromechanical system for System-on-Chip Connectivity’,

IEEE Circuits and Sytems, September 2002

New battery may jump-start MEMS usage, ISA InTech April

2002



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Mems for Sysem on Chip Conectivtety

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