Thursday 9 August 2012

Research Paper on DIODE


INDUSTRIAL ENGINNERING ASSIGNMENT


TOPIC OF RESEARCH PAPER:
THERMAL MANAGEMENT OF LED’S (LIGHT EMMITTING DIODE)
BY ANITA LAFOND
Constructive Communication, Inc.









INTRODUCTION

In the continuing quest for energy-efficient lighting products, light-emitting diodes (LEDs) offer many advantages such as low-energy consumption, long service life, and compact size. These beneficial characteristics make LEDs very popular with fixture designers who want to expand into the lucrative and burgeoning energy-efficient lighting market. And with new federal energy standards coming into effect this year, LED light bulbs are becoming more prevalent. The United States Department of Energy (DoE) estimates that switching to LEDs lighting over the next 20 years could save $120 million in energy costs, reduce electricity consumption for lighting by one-fourth, and avoid 246 million metric tons of carbon. LEDs, therefore, have the promising capability to significantly reduce lighting energy use and impact climate change solutions in the U.S.


SWITCHING TO LED’S

In January 2012, the first phase of the Energy Independence and Security Act of 2007 (EISA) went into effect. The “Energy Bill” is an energy policy intended to make better use of our nation’s resources and help the U.S. become more energy independent. Part of the law sets energy efficiency standards for light bulbs.
Under the new law, screw-based light bulbs must use fewer watts for a similar lumen output.
Common household light bulbs that traditionally used between 40 and 100 watts must be redesigned to use at least 27% less energy by 2014. The second part of the law, which will go into effect in 2020, requires most light bulbs to be 60 to 70% more efficient than current standard incandescent bulbs. Many LEDs can meet this requirement today, and the industry is poised to provide viable, cost-efficient alternatives to standard lighting products. As a substitute for incandescent lighting, compact fluorescent lighting (CFL) has also become more popular. Compared to a typical incandescent bulb (which lasts approximately 1,000 hours), a CFL has a life expectancy of nearly 8,000 hours. These statistics, though, are “dim” in comparison to an LED bulb with its life span of 30,000 to 50,000 hours. CFLs, however, contain mercury, a toxic substance that makes disposal a potentially hazardous situation. LEDs contain no toxic materials, while offering high-quality illumination that is superior to incandescent and CFLs.

MANAGING EXCESS HEAT

Manufacturers are eager to meet the demand for energy-efficient LED designs and are looking for methods to make LED packages more cost efficient. Thermal management is one of the most important aspects of successful LED systems design. LEDs convert only 20 to 30% of their electric power into visible light. The remainder of the light is converted to heat that must be conducted away from the LED die. Excess heat is an unwanted by product of LED design because it reduces light output and shortens the life span of the LED bulb. Therefore, managing thermal output to dissipate heat is crucial to maximizing an LED’s performance potential. This is especially important for high-power/high-brightness LED applications such as streetlamps, traffic lights, and automotive head lights where long operating life is essential.

LESS HEAT, MORE LIGHT

According to Mitsuru Kondo, global LED project manager for Heraeus Precious Metals’ Thick Film Division, thermal management really is the key to good LED design. “The LED light is relatively cool; it is the LED die itself that generates excessive heat and it is this heat that must be dissipated into the substrate,” Kondo said. “The more heat you can dissipate into the substrate, the longer life will be generated from the LED light.” Long life expectancy is one of the LED advantages that is of particular interest to municipalities looking to save money and maintenance time on streetlight purchases. For example, in a typical streetlight outfitted with incandescent or fluorescent bulbs, the bulbs must be changed every six months to one year. Contrast this with an LED streetlamp fixture where the bulbs will last from three to four years. Less time spent maintaining streetlamps translates into immediate cost savings.
Although LEDS are currently more expensive to purchase, the long life expectancy makes them a worthwhile investment. An LED that costs $30 can last for up to three years, while a $5 incandescent bulb has to be changed every five to six months. The total cost of LED ownership is cheaper and electrical costs are less expensive, along with the time savings in not having to change bulbs as frequently. LED manufacturers are working to get their costs down, so that the price of LEDs can be lowered also.

SUCESSFUL DESIGN

Four areas of thermal management are important to LED designers: Increased LED life, higher output of lumens, reduced heat sink size, and less LED chips. Effective heat dissipation helps to keep the temperature of LEDs lower which in turn improves brightness and life span. The ability to use less expensive substrates, such as aluminium, can also help to lower the overall cost of LEDs.
“If you can reduce the temperature by just 10°C, you can double the life of an LED,” explained Kondo. “Lumen power can be increased and designers can reduce the number of LEDs needed without restricting performance. If you can reduce the amount of LEDs needed, while still producing the same output, you save money on the overall design cost.”
MCPCB’s require large heat spreading layers to dissipate heat. This increases the overall size of the substrate, and consequently the size of the heat sink, which is expensive. With the Celcion system, the circuit is constructed directly on the heat sink, reducing the thermal interfaces between the LED and the heat sink. This enables the designer to eliminate the large heat spreaders, and thereby reduce the size of the overall substrate. One of the materials in the Celcion material set is a silver paste that is used in place of a heat spreader, and allows printing directly on the aluminium substrate or the heat sink. Heat sink size can be reduced while lowering the temperature of the LED chip.

According to the EISA, LED bulbs have the potential to last up to 22 years and can save up to 75% or more in energy costs. However, the initial cost is currently more expensive than other alternatives. As manufacturing costs decrease through better thermal management techniques, LEDs are expected to increase in performance and become more affordable. Effective thermal management is the key to making a brighter future for LEDs.

Research Paper on Environmental Ergonomics


NATIONAL INSTITUTE OF INDUSTRIAL ENGINEERING
PGDIE-42

INDUSTRIAL ENGINEERING


Summary of Research Paper on:

Environmental ergonomics: a review of principles, methods and models
K.C. Parsons
Department of Human Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
Received 1 June 2000; accepted 14 July 2000







                                                                                                   SUBMITTED BY
JAYANT PATWARE
                                                                                          ROLL NO 38


ABSTRACT

A review of the principles, methods and models used in environmental ergonomics is provided in terms of the effects of heat and cold, vibration, noise and light on the health, comfort and performance of people. Environmental ergonomics is an integral part of the discipline of ergonomics and should be viewed and practised from that perspective. Humans do not respond to the environment in a way monotonically related to direct measures of the physical environment. There are human characteristics which determine human sensitivities and responses. Practical methods for assessing responses to individual environmental components are presented as well as responses to &total' environments and current and proposed International Standards concerned with the ergonomics of the physical environment.

INTODUCTION

Ergonomics can be defined as the application of knowledge of human characteristics to the design of systems. People in systems operate within an environment and environmental ergonomics is concerned with how they interact with the environment from the perspective of ergonomics. Although there have been many studies, over hundreds of years, of human responses to the environment (light, noise, heat, cold, etc.) and much is known, it is only with the development of ergonomics as a discipline that the unique features of environmental ergonomics are beginning to emerge. In principle, environmental ergonomics will encompass the social, psychological, cultural and organisational environments of systems, however to date it has been viewed as concerned with the individual components of the physical environment. Typically, ergonomists have considered the environment in a mechanistic way in terms such as the lighting or noise survey rather than as an integral part of ergonomics investigation.

There is a continuous and dynamic interaction between people and their surroundings that produce physiological and psychological strain on the person. This can lead to discomfort, annoyance, subtle and direct affects on performance and productivity, affects on health and safety, and death. Discomfort in offices can be due to glare, noisy equipment, draughts, or smells. In the cold people experience frostbite and die from hypothermia. In the heat they collapse or die from heat stroke. People exposed to vibrating tools have damage to their hands. Performance can be dramatically affected by loss of manual dexterity in the cold, noise interfering with speech communication or work time lost because the environment is unacceptable or distracting. Accidents can occur due to glare on displays, missed signals in a warm environment or disorientation due to exposure to extreme environments.

There are numerous factors that can make up a working environment. These include noise, vibration, light, heat and cold, particulates in the air, gases, air pressures, gravity, etc. The applied ergonomist must consider how these factors, in the integrated environment, will affect the human occupants. Three effects are usually considered; those on the health, comfort and performance of the occupants. The factors of the environment are usually considered separately. Some attempt at integration of effects can be made. However, there is insufficient objective knowledge to allow an accurate quantification.


ENVIRANMENTAL AND HUMAN RESPONSE

Most of the energy that makes up our environment originally comes as electromagnetic radiation from the sun. Around 1373Wm~2 (the solar constant) enters the outer limits of the earth's atmosphere and this arrives on the earth in modified form where it is transformed from place to place and from one form to another (heat, mechanical, light, chemical, electrical). The wide diversity of environments to which people are exposed is therefore defined by that energy which varies in level, characteristic and form. It is the human condition to interact and survive in those environments and part of that has been the creation of &local' optimum environments (e.g. buildings).The human body is not a passive system that responds to an environmental input in a way that is monotonically related to the level of the physical stimulus. Any response depends upon a great number of factors. If viewed in engineering terms the & transducers' of the body (sensors eyes, ears, etc.) have their own specification in terms of responses to different types of physical stimuli (e.g. the eyes have spectral sensitivity characteristics). In addition, the body does not behave as a passive system; for example, the body responds to a change in environmental temperature by reacting in a way consistent with maintaining internal body temperature (e.g. by sweating to lose heat by evaporation). The body therefore senses the environment with a &transducer' system that has its own characteristics and it reacts in a dynamic way to environmental stimuli


ENVIRANMENTAL ERGONOMICS METHODS

There are four principal methods of assessing human response to environments. These are: subjective methods; where those representative of the user population actually report on the response to the environment; objective measures, where the occupant's response is directly measured (e.g. body temperature, hearing ability, performance at a task); behavioural methods; where the behaviour of a person or group is observed and related to responses to the environment (e.g. change posture, move away, switch on lights); and modelling methods. Modelling methods include those where predictions of human response are made from models that are based on experience of human response in previously investigated environments (empirical models) or rational models of human response to environments that attempt to simulate the underlying system and hence can be used to relate cause and effect.


ENVIRONMENTAL ERGONOMICS MODELS

Thermal environments and human response
There are six main factors that should be quantified in order to assess human response to thermal environments; these are air temperature, radiant temperature, air velocity, humidity, the activity of the occupants, and the clothing worn by the occupants. A thermal index integrates these values in a way that will provide a single value that is related to the effects on the occupants.

Humans are homeotherms-that means that they attempt to maintain their internal (core) temperature within an optimum range (around 373C). If the body is subjected to thermal stress then the thermoregulatory system responds by changing its state in a way which is consistent with maintaining core temperature within this range. This response of the body has consequences for the health, comfort, and working efficiency of a person.

Rational indices are derived from mathematical models that describe the behaviour of the human body in thermal environments. If the body is to remain at approximately a constant temperature then, on average, the heat outputs from the body must be equivalent to heat inputs to the body. This is known as heat balance and a usual starting point for derivation is the heat balance equation
M=E+R+C+K+S,
Where M is the energy produced by the metabolic processes of the body and W is the energy required for physical work; C is the heat loss by convection; R is the heat loss by radiation; K is the heat loss by conduction; E is the heat loss by evaporation; and S is the heat stored.
By identifying the practical ways in which heat is exchanged between the body and its environment, equations can be derived and values of heat transfer can be calculated from the parameters measured in the physical environment (air temperature, humidity, etc.).

Thermal environments- health When the body becomes &too hot' or &too cold' it reacts in a way that is consistent with maintaining core temperature at a relatively constant level. When the body is under heat stress the two main mechanisms for losing heat are controlled by the anterior hypothalamus. The initial reaction is vasodilatation, where the peripheral blood vessels dilate and transfer blood, and hence heat, to the surface of the body where it can be lost to the surrounding environment. If core temperature continues to rise, sweating occurs and considerable heat loss by evaporation can occur. If these heat loss mechanisms are insufficient to maintain heat balance then core temperature rises

Thermal environments-comfort Thermal comfort can be defined as `that condition of mind which expresses satisfaction with the thermal environment a (ASHRAE, 1966). The reference to &mind' indicates that it is essentially a subjective term; however, there has been extensive research in this area and a number of indices exist which can be used to assess environments for thermal comfort. Although simple values of air temperature or globe temperature can be used to provide conditions for comfort in rooms a more detailed, practical approach is usually taken.

Thermal environments- performance Accurate predictions of the effects of environments on performance at a specific &real' task are difficult to make. This is because there are many variables that relate to specific tasks in specific contexts and all cannot be accounted for. However, using task analysis, components of tasks can be determined. General guidance can then often be provided from studies of similar tasks or studies of similar task components. A simple example would be the division of a task (or job) into mental and manual components. The effects of a given environment on similar mental tasks could be derived from previous studies; similarly for the manual task components. A useful overall prediction can often then be made

Vibration and human response Vibration can significantly affect the health, comfort and performance of people, particularly in vehicles. A full review of the subject is provided in Griffin (1990). This paper can present only a summary and concentrates on human responses to the built environment. The study of human response to building vibration can be divided into two areas: one area is concerned with the effects of low-frequency (often large displacement) vibration (motion) that would occur at the top of tall buildings (due to the buildings' response to wind for example); the other area is concerned with vibration transmitted to buildings from such things as road traffic, trains, or aircraft passing nearby or the operation of heavy machinery or blasting operations, etc. This type of vibration has relatively high-frequency content and can have a different effect on the building occupants.

Vibration- health There are levels of vibration that can cause physical damage to the body; for example, those found in aircraft in severe turbulence, long-term exposure of tractor operators to vibration, or vibration to the hand from some vibrating tools. It is highly unlikely that the occupants of buildings would be exposed to vibration levels that would directly cause physical damage to the body. Methods by which building vibration can affect health are therefore indirect; causing a loss of balance in persons, for example, or simply as an additional environmental stressor that can affect mental health and emotional state. In practice, it is difficult to provide a model which will predict these effects and subjective, objective and behavioural methods of investigation are more appropriate.

Vibration-comfort The term vibration discomfort is used in studies of human response to vibration. However, this relates more towards the effects of vibration on the occupants of vehicles and is not appropriate in the context of building vibration. In practice, the building designer or transport system operator wish to know at what level of vibration occupants will be disturbed and complain. Whether occupants complain about an environmental stress is highly context dependent and can be based on such factors as fear of building collapse or structural damage, the perceived source of vibration and the attitude of the occupant to the source. Accurate predictions are therefore difficult to make for individuals, however general guidance can be provided for populations of occupants.

Vibration- performance Vibration can have large effects on human performance at simple tasks (e.g. reading, writing, and drinking) and many studies have shown major effects on manual control and vision. These effects occur at levels found mainly in vehicles and are unlikely to occur in buildings. Low frequency vibrations often create large displacements in tall buildings and can cause loss of orientation and balance in subjects. However, these effects have yet to be quantified and their effects on tasks (e.g. typing) cannot be easily predicted.

Noise-human response The human ear detects sound pressure changes in the air and transmits a signal, which is related to the sound pressure changes, to the brain where it is perceived as sound. The signal which is &perceived' by the person is not directly proportional to the sound pressure stimulus which first entered the ear. There is a human perception transfer function. For a given sound pressure level, for example, a single frequency noise (pure tone) at one frequency may sound &louder' than a pure tone sound at a different frequency even though they are at the same physical sound pressure levels. The relative effect of sound frequency on loudness (for example) has been quantified in experimentation and &equal loudness contours ' have been produced. Based on &equal loudness (annoyance, noisiness, etc.) contours' weighting functions have been proposed which approximate the average perceived response of a population.

Noise-health Noise can have direct and indirect effects on workers health. Long-term exposure to noise causes noise-induced hearing loss. This is due to damage to sensors in the inner ear. The effect is in terms of reduced sensitivity to certain frequencies of noise. Reduced sensitivity occurs initially, usually in the region of 4 kHz and, as the condition becomes more severe, sensitivity is further reduced and this occurs over a broader frequency band. A practical approach to assessing the noise health hazard is to use the index dB(A) L%2 (Burns and Robinson, 1970). Limiting values of around 85}90 dB(A) L%2 have been proposed for 8 h exposure in industrial environments.

Noise-comfort The term comfort is not usually used when assessing the effects of noise on the occupants of buildings. In practice, annoyance levels are the most useful criterion, although loudness, perceived noisiness, and nuisance are also terms used. There are many indices that can be used to provide a value that is related to ratings of the terms described and no one index is generally used. However dB(A) L%2 is a widely used index. A simple practical approach to assessing noise in offices, for example, would be to measure the noise throughout the office and take the average dB(A) value. If a more detailed analysis is required then the noise could be analysed in the frequency domain that would also help identify the causes of the noise.

Noise-performance The effects of noise on human physical and mental performance can be divided into effects on non-auditory task performance and effects on auditory task performance (e.g. interference with speech communication, etc.). The effects of noise on non-auditory task performance have been inconclusive, different studies indicating that noise reduces task performance, has no effect on task performance or increases task performance. No obvious general predictions can therefore be made. A major consideration appears to be the level of arousal of persons as compared with that required for optimum performance at tasks. Performance at vigilance tasks, for example, can be improved by increasing noise levels, hence increasing arousal to an optimum level. In practical application the variation in results has not been sufficiently explained to allow accurate predictions of the effects of noise on the performance of the occupants of buildings. Some general predictions can be made, however, based on models of human response to noise and previous laboratory and field investigations.

Light and human response Light is that part of the electromagnetic spectrum that is detected by the human eye. The eye is, however, not equally sensitive to all wavelengths of light and there is a human perception transfer function. This function depends upon the level of light present. A consequence of the dynamic response of the eye to a change in light level is that when there is a wide range of luminance within a visual field, glare can occur. This depends upon the luminance of a source compared with its background and its position within the angle of sight of the observer. Using these variables a glare constant can be calculated for a single glare source and, if integrated over the visual field, this provides a glare index. It is important to note that there are large individual differences in human response to light. In addition, defects occur in the visual system (colour defects, myopia, etc.).

Light-health Excessive exposure to light can cause direct effects on health. Ultra violet, infrared, and visible radiation can cause health problems in the eye. In addition, this radiation can also damage skin. In addition to these direct effects on health, eyestrain can be caused by inadequate lighting conditions. Too little or too much light, veiling rejections, disability, and discomfort glare and flicker can all cause eyestrain (Boyce, 1981). This can cause irritation in the eyes, a breakdown of vision and headaches, indigestion, giddiness, etc.

Light-comfort Light can cause discomfort to the occupants of an environment as well as positive sensations such as pleasure and emotional sensations (cold, warm, etc.). Human response to light is a very complex subject and, despite a great deal of research, accurate predictions of subjective impressions are still difficult to make. However, this area of human response to the environment has employed sophisticated psychophysical scaling techniques (e.g. multidimensional scaling) and it may be possible in the future to provide more accurate models of subjective impressions of lighting environments.

Light-performance Although light can affect human performance at general tasks, glare can cause a distraction effect; for example, the main effects of light are on visual performance. Visual performance is related to a combination of the efficiency of the eye in receiving and conditioning light and the interpretation of what is seen by the person. While training can influence workers' interpretation of what is seen, in practice lighting guidelines are required to provide the desired visual performance at particular tasks.

CONCLUSION

It is clear from the above discussions that there has been a great deal of work on the effects of light, noise, vibration, and thermal environments on the health, comfort, and working efficiency of the occupants of buildings. Models exist which can provide realistic predictions of the effects or probable effects of components of environments. In addition, general guidance on interactive effects and the effects of total environments can be provided. The effects of &total' environments include `2the sum of the physiological, psychological and social sensations experienced by people in or around buildings which follow from their use of the buildings. Models of these &integrated effects are not available and buildings should also still be evaluated using subjective (and also possibly objective) methods.


REFERENCES



IE component design

NATIONAL INSTITUTE OF INDUSTRIAL ENGINEERING
PGDIE-42


INDUSTRIAL ENGINEERING


ASSIGNMENT
Selected Component: DIODE (Electronics)
















     SUBMITTED BY:
ANKITA CHAUHAN (14)
                                                                                       JAYANT PATWARE (38)
                                                                                              


1)    Write down its design process and come out with a design (Assume the required data)
 Fabrication Technology

1.      Introduction
2.      Fabrication processes
a.       Thermal
b.      Oxidation
c.       Etching techniques
d.      Diffusion
3.      Expressions for diffusion of dopant concentration
4.      Ion implantation
5.      Photomask generation
6.      Photolithography
7.      Epitaxial growth
8.      Metallization and interconnections,
9.      Ohmi ccontacts
10.  Planar PN junction diode fabrication,
11.  Fabrication of resistors and capacitors in IC's.
1. INTRODUCTION
·         The microminiaturization of electronics circuits and systems and then concomitant application to computers and communications represent major invasions of the twentieth century. These have led to the introduction of new applications that were not possible with discrete devices.

·         Integrated circuits on a single silicon wafer followed by the increase of the size of the wafer to accommodate many more such circuits served to significantly reduce the costs while increasing there liability of these circuits.

·        

1.    Silicon From Sand
                       
2.    Fabrication Process
a.     Oxidation
 The process of oxidation consists of growing a thin film of silicon dioxide on the surface of the silicon wafer.
Silicon dioxide, as we shall see later, plays an important role in shielding of the surface so that dopant atoms, by diffusion or ion implantation, may be driven into other selected regions

b.    Diffusion
This process consists of the introduction of a few tenths to several micrometers of impurities by the solid-state diffusion of dopants into selected regions of a wafer to form junctions.

c.      Ion Implantation
This is a process of introducing dopants into selected areas of the surface of the wafer by bombarding the surface with high-energy ions of the particular dopant.
d.     Photolithography
In this process, the image on the reticle is transferred to the surface of the wafer.

e.      Epitaxy
Epitaxy is the process of the controlled growth of a crystalline doped layer of silicon on a single crystal substrate.

f.      Metallization and interconnections
After all semiconductor fabrication steps of a device or of an integrated circuit are
completed, it becomes necessary to provide metallic interconnections for the integrated circuit and for external connections to both the device and to the IC.
2. Design Assumming data of planer PN junction diode
1.            An N+ substrate grown by the Czochralski process is the starting metal of approximately 150μm thick.
2.            A layer of N-type silicon (1-5μm) is grown on the substrate by epitaxy.
3.            Silicondioxide layer deposited by oxidation.
4.            Surface is coated with photoresist (positive).
5.            Mask is placed on surface of silicon, aligned, and exposed to UV light.
6.            Mask is removed, resist is removed, and SiOz under the exposed resist is etched.
7.            Boron is diffused to form Pregion.Boron diffuses easily in silicon but noting SiO2
8.            Thin aluminum film is deposited over surface.
9.            Metallized area is covered with resist and an other mask isused to identify areas where metal is to be preserved.Wafer is etched to remove unwanted metal.Resist is then dissolved.
10.        Contact metal is deposited on the back surface and ohmic contacts are made by heat treatment.
3. Supply Chain at chip level

Presently, most of the raw and intermediate materials used in the LED packaging process are imported. If the intermediate material is purchased locally, the supplier company that is operating locally has imported the raw material to add value
Materials used in LED Packaging
·         Wafer
·         Lead frame
·         Single sided PCB
·         Gold wire
·         Ceramic substrate
·          Aluminium substrate
·         Epoxy / silicone
Although some of the materials may be available locally, companies are importing pricing and meeting specifications and requirement

4. Manufacturing process of diode
1.      Die Bond: when semiconductor chip is attached to the substrate
2.      Wire Bond: where internal connections of diode is made
3.      Modelling: to protect the chip from internal connections
4.      Marking: using laser marking code on the tab
5.      Slicing: cutting the finished die into individual pieces
6.      Test and Tapping: each die tested individually and put on the tap reel
7.      Testing Equipment: reliability test for customer satisfaction
8.      Measure microscopic9.                                  

Process
Control item
Control point
              Purchase of material
 

wafer
                     Diffusion
                     Film thickness               
                     Inspection
mask
Photolithography
Inspection

Metallization                   
PQC

       
Scribbling
Chip inspection
Pallet washing
PQC
Lead glass
Assembling
Sealing
Soldering
PQC

Screening
Total electrical
Inspection
PQC

Marking
Taping & packing

Shipment
Inspection
Warehouse


                    
          shipping

Type no.

Film thickness, resistivity



Appearance of wafer

Film thickness
Appearance of wafer


Appearance of chip



Type no.


Appearance , solder thickness


Electrical characteristics failure analysis


Assurance of tapping

Electrical characteristic appearance





Part confirmation

Assurance of basic film thickness


Scratch and position deviation

Monitor scratch and metallization


Selection of good / bad chip


Part confirmation


Appearance of outline



Feedback of analysis information

References
2. Comchip technology’s flat chip diode manufacturing process
3. Fabrication technology by B.G. Balagangadhar (Ghousia college of enggineering)

Paper 1: PN-DIODE TRANSDUCED 3.7-GHZ SILICON RESONATOR
Summary: We present in this paper the design and fabrication of a homogeneous silicon micromechanical resonator actuated using forces acting on the immobile charge in the depletion region of a symmetrically doped pndiode. The proposed resonator combines the high quality factor (Q) of airgap transduced resonators with the frequency scaling benefits of internal dielectrically transduced resonators. Using this transduction method, we demonstrate a thickness longitudinal mode micromechanical resonator with Q ~ 18,000 at a resonant frequency of 3.72 GHz, yielding an f·Q product of 6.69 x 1013, which is close to the intrinsic f·Q product of 1014 for (100)-Si.

This work combines the pioneering work of and to develop a micromechanical resonator with the benefits of high quality factor at GHz frequencies. This is made possible by the use of pn-diode transduction, which allows efficient transduction at high frequencies without using a separate transducer material. Using this method, we present a thickness longitudinal mode micromechanical resonator with resonant frequency of 3.72 GHz and an f·Q product of 6.69 x 1013. This is close to the theoretical limit in (100)-Si of ~1014. In addition, the proposed device results in a CMOS-compatible fabrication process and higher device yield as compared to traditional air-gap or dielectrically transduced resonators.

References: PN-DIODE TRANSDUCED 3.7-GHZ SILICON RESONATOR
Eugene Hwang and Sunil A. Bhave
Cornell University, Ithaca, NY, USA