Mini FM Transmitter
Mini FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps. When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance. I've seen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc.
Here is the last step of this evolution, the most stable, smallest, problemless, and energy saving champion of this race. Circuit given below will serve as a durable and versatile FM transmitter till you break or crush it's PCB. Frequency is determined by a parallel L-C resonance circuit and shifts very slow as battery drains out.
Simple FM Transmitter involves on a single transistor oscillator
Technical datas:
Supply voltage : 1.1 - 3 Volts
Power consumption : 1.8 mA at 1.5 Volts
Range : 30 meters max. at 1.5 Volts
Main advantage of this circuit is that power supply is a 1.5Volts cell (any size) which makes it possible to fix PCB and the battery into very tight places. Transmitter even runs with standard NiCd rechargeable cells, for example a 750mAh AA size battery runs it about 500 hours (while it drags 1.4mA at 1.24V) which equals to 20 days. This way circuit especially valuable in amateur spy operations :)
Transistor is not a critical part of the circuit, but selecting a high frequency / low noise one contributes the sound quality and range of the transmitter. PN2222A, 2N2222A, BFxxx series, BC109B, C, and even well known BC238 runs perfect. Key to a well functioning, low consumption circuit is to use a high hFE / low Ceb (internal junction capacity) transistor.
Not all of the condenser microphones are the same in electrical characteristics, so after operating the circuit, use a 10K variable resistance instead of the 5.6K, which supplies current to the internal amplifier of microphone, and adjust it to an optimum point where sound is best in amplitude and quality. Then note the value of the variable resistor and replace it with a fixed one.
The critical part is the inductance L which should be handmade. Get an enameled copper wire of 0.5mm (AWG24) and round two loose loops having a diameter of 4-5mm. Wire size may vary as well. Rest of the work is much dependent on your level of knowledge and experience on inductances: Have an FM radio near the circuit and set frequency where is no reception. Apply power to the circuit and put a iron rod into the inductance loops to chance it's value. When you find the right point, adjust inductance's looseness and, if required, number of turns. Once it's OK, you may use trimmer capacitor to make further frequency adjustments. You may get help of a experienced person on this point. Do not forget to fix inductance by pouring some glue onto it against external forces. If the reception on the radio lost in a few meters range, than it's probably caused by a wrong coil adjustment and you are in fact listening to a harmonic of the transmitter instead of the center frequency. Place radio far away from the circuit and re-adjust. An oscilloscope would make it easier, if you know how to use it in this case. Unfortunately I don't have any :(
Every part should fit on the following PCB easily. Pay attention to the transistor's leads which should be connected right. Also try to connect trimmer capacitor's moving part to the + side, which may help unwanted frequency shift while adjusting. PCB drawing should be printed at 300DPI, here is a TIFF file already set.
PCB design for the FM Transmitter
The one below is a past PCB work of mine, which was prepared to fit into a pocket flashlight. Since it was so crowded, use the new computerized PCB artwork instead, yet very small. Take a look at my PCB design page to get information on my work style.
Transmitter PCB compared in size with an AA battery
Here is a completed and perfectly running circuit, mounted in a pocket light, taking the advantage of the 1.5V AA cell slot near it. Microphone is fixed into the bulb's place and antenna is made out of a 30cm soft cable. When cover is placed, it becomes very handy!
Transmitter placed in a pocket flashlight
Do not forget, restrictions on radio frequency transmitting devices may differ in your local area. This circuit has a power output that should be less than 1mW so have to be safe under many kinds of legal conditions but particular attempts such as listening to other people's private life will always be disapproved everywhere.
Wireless Power Transmission
Though the physics of both are related, this is distinct from wireless transmission for the purpose of transferring information (such as radio) through waves, where the percentage of the power that is received is only important if it becomes too low to successfully recover the signal. With wireless energy transfer, the efficiency is a more critical parameter and this creates important differences in these technologies
Introduction
Wireless is one of those hot tech catch-all of the new millennium. There are wireless broadcasters and receivers, utilizing such technology as WiMax, 802.11n, and Bluetooth. There are wireless gaming controllers. There's just about wireless everything -- except power transmission.
Wireless power transmission is something that inventor Nikolai Tesla came up with over a century ago and claimed to have perfected. However, his mysterious work vanished with his death, and for decades the
topic was left untouched. Now there has been resurgence in interest with several
Companies competing to becoming the first to offer commercially broadcast wireless power.
The new tech was first developed by Massachusetts Institute of Technology physicist Marin Soljacic. Professor Soljacic came up with the idea of transmitting wireless power via resonant magnetic fields. He calls the invention WiTricity, a blend of the words wireless and electricity. The work relies heavily on the electric concept of induction. Induction is already used commercially on a limited scale, to recharge certain powered toothbrushes.
Intel helped improve upon MIT's design, bringing the efficiency up from 50 percent to 75 percent. Internally, Intel is speculating that the device may permit and work with the shift from batteries to super capacitors. While currently more expensive, super capacitors could allow faster recharging. Mr. Rattner states, "In the future, your kitchen counters might do it. You’d just drop your espresso maker down on them and you would never have to plug it in."
Intel calls its new technology a "wireless resonant energy link". It uses transmitting loop antennas, less than 2 feet in diameter.
It is competing with a couple scrappy startups, which are also looking to improve upon MIT's technology. Startups Wild Charge, based in Boulder, Colo., and WiPower, based in Altamonte Springs, Fla. both are looking to make their name in wireless power history. While both have announced consumer devices based on their upcoming technologies, their devices currently require the item to be touching the transmitter.
Application in space (transmitting solar power):
Space Solar Power gathers energy from sunlight in space and transmits it wirelessly to Earth. Space solar power can solve our energy and greenhouse gas emissions problems. Not just help, not just take a step in the right direction, but solve. Space solar power can provide large quantities of energy to each and every person on Earth with very little environmental impact.
The solar energy available in space is literally billions of times greater than we use today. The lifetime of the sun is an estimated 4-5 billion years, making space solar power a truly long-term energy solution. As Earth receives only one part in 2.3 billion of the Sun's output, space solar power is by far the largest potential energy source available, dwarfing all others combined. Solar energy is routinely used on nearly all spacecraft today. This technology on a larger scale, combined with already demonstrated wireless power transmission can supply nearly all the electrical needs of our planet.
Another need is to move away from fossil fuels for our transportation system. While electricity powers few vehicles today, hybrids will soon evolve into plug-in hybrids which can use electric energy from the grid. As batteries, super-capacitors, and fuel cells improve, the gasoline engine will gradually play a smaller and smaller role in transportation — but only if we can generate the enormous quantities of electrical energy we need. It doesn't help to remove fossil fuels from vehicles if you just turn around and use fossil fuels again to generate the electricity to power those vehicles. Space solar power can provide the needed clean power for any future electric transportation system.
While all viable energy options should be pursued with vigor, space solar power has a number of substantial advantages over other energy sources.
Advantages of Space Solar Power
• Unlike oil, gas, ethanol, and coal plants, space solar power does not emit greenhouse gases.
• Unlike coal and nuclear plants, space solar power does not compete for or depend upon increasingly scarce fresh water resources.
• Unlike bio-ethanol or bio-diesel, space solar power does not compete for increasingly valuable farm land or depend on natural-gas-derived fertilizer. Food can continue to be a major export instead of a fuel provider.
• Unlike nuclear power plants, space solar power will not produce hazardous waste, which needs to be stored and guarded for hundreds of years.
• Unlike terrestrial solar and wind power plants, space solar power is available 24 hours a day, 7 days a week, in huge quantities. It works regardless of cloud cover, daylight, or wind speed.
• Unlike nuclear power plants, space solar power does not provide easy targets for terrorists.
• Unlike coal and nuclear fuels, space solar power does not require environmentally problematic mining operations.
• Space solar power will provide true energy independence for the nations that develop it, eliminating a major source of national competition for limited Earth-based energy resources.
• Space solar power will not require dependence on unstable or hostile foreign oil providers to meet energy needs, enabling us to expend resources in other ways.
• Space solar power can be exported to virtually any place in the world, and its energy can be converted for local needs — such as manufacture of methanol for use in places like rural India where there are no electric power grids. Space solar power can also be used for desalination of sea water.
• Space solar power can take advantage of our current and historic investment in aerospace expertise to expand employment opportunities in solving the difficult problems of energy security and climate change.
• Space solar power can provide a market large enough to develop the low-cost space transportation system that is required for its deployment. This, in turn, will also bring the resources of the solar system within economic reach.
Disadvantages of Space Solar Power
• High development cost. Yes, space solar power development costs will be very large, although much smaller than American military presence in the Persian Gulf or the costs of global warming, climate change, or carbon sequestration. The cost of space solar power development always needs to be compared to the cost of not developing space solar power.
Requirements for Space Solar Power
The technologies and infrastructure required to make space solar power feasible include:
• Low-cost, environmentally-friendly launch vehicles: Current launch vehicles are too expensive, and at high launch rates may pose atmospheric pollution problems of their own. Cheaper, cleaner launch vehicles are needed.
• Large scale in-orbit construction and operations: To gather massive quantities of energy, solar power satellites must be large, far larger than the International Space Station (ISS), the largest spacecraft built to date. Fortunately, solar power satellites will be simpler than the ISS as they will consist of many identical parts.
• Power transmission: A relatively small effort is also necessary to assess how to best transmit power from satellites to the Earth’s surface with minimal environmental impact.
All of these technologies are reasonably near-term and have multiple attractive approaches. However, a great deal of work is needed to bring them to practical fruition.
In the longer term, with sufficient investments in space infrastructure, space solar power can be built from materials from space. The full environmental benefits of space solar power derive from doing most of the work outside of Earth's biosphere. With materials extraction from the Moon or near-Earth asteroids, and space-based manufacturer of components, space solar power would have essentially zero terrestrial environmental impact. Only the energy receivers need be built on Earth.
Space solar power can completely solve our energy problems long term. The sooner we start and the harder we work, the shorter "long term" will be.
Areas of Future use:
The advantage of this technology is it can transmit power even when not in contact. And the receiver antenna is about the size of a laptop base. It could be that cell phones and P.D.A.’s are even more compelling and it would be more useful for laptops.
In robotic technology, sensors using the power transmission and reception technologies could use electric fields to detect objects.
Transmission of Information -it would not interfere with radio waves and thus could be used as a cheap and efficient communication device without requiring a license or a government permit.
Counterpoise Conductors
LIGHTNING PROTECTION SYSTEM
- GENERAL
- RELATED DOCUMENTS
- General: Drawings and general provisions of the Contract, including General and Supplementary Conditions and Division 1 Specification sections, apply to work specified of this section.
- DESCRIPTION
- General: Provide a complete lightning protection system as indicated on the drawings and as specified herein. The lightning protection system shall be installed by a firm presently engaged in installations of Master Labeled or LPI certified lightning protection systems. The system as completed shall comply with the latest edition of UL96A, Installation Requirements for Lightning Protection Systems, and NFPA-780 "Standard for the Installation of Lightning Protection Systems." The system shall meet all requirements of these standards and the Lightning Protection Institute Standard of Practice LPI-175. All components required for a UL master label and a full LPI certification plate shall be provided whether or not such materials are specifically addressed by the contract drawings or described herein.
- Qualification: All installers shall be experienced with installing UL master labeled and LPI certified systems or of equivalent qualification, as accepted in writing by the engineer of record. A UL/LPI certified installer shall be on the project site at all times during installation of the systems and shall supervise all of the installation.
- COUNTERPOISE CONDUCTOR
- General: Where indicated on the drawings or required by NFPA 780, the structure shall be provided with a below-grade continuous counterpoiseconductor, equal in size to the largest conductor in the building lightning protection system, or sized as indicated on the drawing. This conductorshall be installed at a minimum depth of two feet below finished grade and a minimum of two feet from the exterior foundation wall of the building. Thecounterpoise conductor shall be copper and extend continuously around the entire perimeter of the building. All joints and connections shall be exothermically welded.
MACRO: DESIGNER TO DELETE WHERE BUILDING IS LESS THAN 60’ HIGH.
- Counterpoise: As a minimum, the counterpoise conductor shall be connected to each of the following system components utilizing appropriate exothermic welds:
- Each down conductor or steel column ground.
- All counterpoise conductors on power and communications ducts which enter the building.
- The building electrical service ground.
- All metallic water and gas services entering the building (ahead of meter).
- Counterpoise conductor on adjacent buildings (within fifty feet).
- All metallic fence posts, safety railings, etc., or any other metallic item within ten feet of the project building.
- SUBMITTALS
- General: Shop drawings identifying all system wiring and component placement, including all details, shall be submitted to the Engineer for review. The Contractor shall not perform any portion of the Work until the respective submittal has been accepted. All work shall be in accordance with accepted submittals.
- Detail Submission: Details shall be submitted to the Engineer for review indicating the method of cabling connections and attachments starting at the top of the project building to the ground rods at the counterpoise. All details shall be appropriate for the project.
- Identification: All product data sheets submitted, for proposed system components, shall clearly identify the item being submitted and shall indicate the UL label.
- Suppression Device: All transient voltage surge suppressors for the project shall be submitted at the same time as the lightning protection floor plans, details and product data sheets are submitted. Each suppressor shall clearly indicate the item to be protected and shall comply with Section 16709 of these specifications. Suppressors shall be provided as required in NFPA 780 unless otherwise indicated on the drawings or otherwise specified.
- Deviations: The Contractor shall not be relieved of responsibility for deviations from requirements of the Contract Documents by the acceptance of shop drawings, product data, samples or similar submittals unless the Contractor has specifically informed the Engineer in writing of such deviation at the time of submittal and the Engineer has given written acceptance to the specific deviation.
- Certification: Provide documentation of UL master label, LPI certification or equivalent qualification of exact installer intended to do this particular job.
- PRODUCTS
- GENERAL REQUIREMENTS
- Labels: All materials used for the system installation shall comply in size, composition and weight to all requirements of NFPA U.L. and LPI for the class of system in which they are installed. All materials shall be labeled or listed by Underwriters Laboratories, Inc. for use in master labeled or LPI certified lightning protection systems.
- Material: Generally, the external lightning protection system at the roof level shall be constructed of copper cable and copper compatible components. The internal lightning protection system, starting with the down conductors and concluding at the ground termination system shall be constructed of copper cable and copper compatible components. Likewise, all bonding conductors, equipotential loop conductors, etc, shall also be constructed of compatible cable and components.
- Compatibility: All portions of the system, whether copper or aluminum, shall be galvanically compatible to the building material to which they are to be attached. Connections between copper and aluminum portions of the system shall be made with appropriate bimetallic coupling devices. In all areas, the conductor shall be supported to maintain clearance from all galvanically incompatible materials or shall be of the same material if permitted within these specifications.
- Components: All system components (i.e. air terminals, bases, connectors, cable, thru-roof fittings, ground rods, etc.) shall be, to the maximum extent possible, the product of a single manufacturer. All components shall be Class I or II as required by NFPA 780 or as noted. All air terminal bases shall be securely mounted to the building structure by means of mechanical fasteners. Adhesive type air terminal bases are acceptable only where hard setting epoxy adhesive is utilized, where mechanical fastening is prohibited by the roofing manufacturer and where acceptable to the code authority having jurisdiction. Submit shop drawings for all proposed air terminal mounting details.
- AIR TERMINALS
- General: Air Terminals shall be copper as required to match the building system to which they attach. Air terminals shall protrude a minimum of 10 inches above the object to be protected. Center roof terminals shall be 24” high. Air terminal points shall be blunt with the radius of curvature equal to the rod diameter.
- Base: Each air terminal shall be equipped with the correct type of base for the location in which it is mounted.
C. Roof Top Equipment: Air terminals and interconnecting cable shall be provided for all roof mounted equipment (fans, A/C equipment, etc.) subject to a direct strike as required by NFPA 780 and as shown.
- CONDUCTORS
- General: Main roof conductors shall be copper unless otherwise specified or required and shall provide a two-way path from each air terminal horizontally or downward to connections with down conductors. Conductors shall be free of excessive splices and bends. No bend of a conductorshall form an included angle of less than 90 degrees nor have a radius of bend of less than 8 inches. Conductors shall be secured to the structure at intervals not exceeding 3 feet with approved fasteners. Cables connected to “thru-roof” connectors may rise from the roof to the connector at a maximum slope of 3 inches per foot, not exceeding 3 feet horizontally in air.
- Down Conductors: Down conductors shall be copper and shall be concealed in the exterior wall construction or structural columns. Where run in or on reinforced concrete columns, bond down conductor to the re-bar at top and bottom of column. Down conductors shall be spaced at intervals averaging not more than 100 feet around the perimeter of the structure. If project structure is of structural steel frame construction, down conductors may be omitted and roof conductors shall be connected to the structural steel frame at intervals averaging not more than 100 feet around the perimeter of the structure. Connections to the steel frame shall be made with heavy duty bonding plates having 8 square inches of contact surface or with exothermic welds.
- Shop Drawing: Submit all conductor types in shop drawings. Each conductor shall be identified as to location in the lightning protection system.
- ROOF PENETRATIONS
- General: Roof penetrations required for down conductors or for connections to structural steel framework shall be made using pre-manufactured U.L. approved thru-roof type assemblies with solid rods, PVC sleeves and appropriate roof flashing. Roof flashing shall be compatible with the roofing system and shall be provided under this contract and installed by the roofing contractor. Submit roof flashing data sheets and letter of acceptance from roofing contractor in shop drawing package.
- COMMON GROUNDING
- General: Common grounding of all ground mediums within the project building shall be made by interconnecting with main size conductors, fittings as required or exothermic welds.
- Bonding: Grounded metal bodies located within the required bonding distance (as determined by the bonding distance formulas in NFPA 780) shall be bonded to the system using bonding conductors and fittings. Bond to rebar utilizing exothermic weld connections.
- GROUND TERMINATIONS
- General: One ground termination shall be provided for each down conductor and shall consist of one ¾” inch x 10 foot copper-clad ground rod.. Each down conductor shall be connected to the ground rod by an exothermic weld connection. Tops of ground rods shall be located 2 feet below finished grade and 2 feet from the foundation wall and shall extend a minimum of 10 feet vertically into the earth. Where a counterpoise is provided, rods shall be interconnected with the counterpoise.
- General: Where the structural steel framework is utilized as the down conductor for the system, every other perimeter steel column shall be grounded but no more than 60 feet apart. Steel columns shall be grounded using bonding plates having 8 square inches of surface contact area or with exothermic welds. Conductors from the steel column connections to the ground terminations shall be full size copper lightning conductors.
- FASTENERS
- General: Conductor fasteners shall be manufactured of a material which is compatible with the type of conductor being supported. Fasteners shall be of sufficient strength to properly support each conductor or terminal base, etc.
- ACCEPTABLE MANUFACTURERS
- Manufacturers: Equipment manufactured by ERICO, INC.
- Certified Installer: BONDED LIGHTNING PROTECTION SYSTEMS, INC.
2080 W. INDIANTOWN ROAD, SUITE 100
JUPITER, FL 33458 561/746-4336
- EXECUTION
- INSTALLATION OF CONDUCTORS
- General: Conductors shall be installed to interconnect all air terminals to the system of grounding electrodes, and in general provide a minimum of at least 2 paths to ground from any air terminal on the system. Conductors shall provide a horizontal or downward path between the system air terminals and grounding electrode system.
- Routing: Conductors shall be routed in such a manner that maximum concealment from public view is achieved. Down conductors may be installed in one-inch PVC conduit from roof to grade.
- Counterpoise Conductors: Counterpoise conductors shall be installed after finished grades are established to insure specified depth and to minimize the possibility of damage. Any counterpoise conductor which is cut or damaged shall be repaired or replaced with no additional cost to the contract.
- Connections: All connections between conductors below grade shall be exothermically welded. Improper application of weld shall be replaced at no additional cost to the contract.
- INSTALLATION OF GROUND RODS
- General: Ground rods shall be installed vertically at each down conductor position at a minimum of 2 feet from the building foundation wall. Inspection and documentation at each grounded location, weld, depth of counterpoise, etc., shall be made prior to backfill. Contractor shall notify engineer in writing to request inspection of underground work and for L.P.I. inspection before backfill. Allow a minimum of one week for engineer to make the inspection after notification from contractor.
- Test/Inspection Wells: Provide prefabricated test and inspection wells for all ground rods installed in paved or concrete areas.
- BONDING OF SECONDARY METALLIC BODIES
A. Structure Grounding: Provision shall be made at the roof level on reinforced concrete structures for bonding between the roof or down conductors, metallic elements of the roof system and metallic exterior wall systems.
- Bonding: All down conductors run in concrete columns shall be bonded to the reinforcing steel at the top and the bottom of the column.
- GENERAL WORKMANSHIP
- General: All elements of the Lightning Protection System shall be installed in a professional and workmanlike manner consistent with the best industry practices.
- Concealed Installation: All system components shall be concealed to the maximum extent possible to preserve the aesthetic appearance of the project building on which the system is installed.
- COORDINATION WITH OTHER TRADES
- Coordination: The Contractor shall coordinate his work with all trades, to insure the use of proper materials and procedures in and around the roof in order not to jeopardize the roofing warranty.
- Fasteners: Where fasteners are to be embedded in masonry or the structural system, they shall be coordinated to insure installation at the proper time of construction.
- Certification: Upon completion of the installation the Contractor shall provide to the owner the Master Label issued by Underwriters Laboratories, Inc. for the installation, and the LPI certification issued by LPI.
Projection Printing
Projection printing is the technique employed by most modern optical lithography equipment. Projection printers use a well-designed objective lens between the mask and the wafer, which collects diffracted light from the mask and projects it onto the wafer. The capability of a lens to collect diffracted light and project this onto the wafer is measured by its numerical aperture (NA). The NA values of lenses used in projection printers typically range from 0.16 to 0.40.
The resolution achieved by projection printers depends on the wavelength and coherence of the incident light and the NA of the lens. The resolution achievable by a lens is governed by Rayleigh's criterion, which defines the minimum distance between two images for them to be resolvable. Thus, for any given value of NA, there exists a minimum resolvable dimension.
Using a lens with a higher NA will result in better resolution of the image, but this advantage has a price. The depth of focus of a lens is inversely proportional to the square of the NA, so improving the resolution by increasing the NA reduces the depth of focus of the system. Poor depth of focus will cause some points of the wafer to be out of focus, since no wafer surface is perfectly flat. Thus, proper design of any aligner used in projection printing considers the compromise between resolution and depth of focus.
Proximity Printing
Proximity printing is another optical lithography technique. As its name implies, it involves no contact between the mask and the wafer, which is why masks used with this technique have longer useful lives than those used in contact printing. During proximity printing, the mask is usually only 20-50 microns away from the wafer.
The resolution achieved by proximity printing is not as good as that of contact printing. This is due to the diffraction of light caused by its passing through slits that make up the pattern in the mask, and traversal across the gap between the mask and the wafer.
This type of diffraction is known as Fresnel diffraction, or near-field diffraction, since it results from a small gap between the mask and the wafer. Proximity printing resolution may be improved by diminishing the gap between the mask and the wafer and by using light of shorter wavelengths.
Contact Printing in Photolithography
Photolithpgraphy
Photolithography
Photolithography is the process of transferring geometric shapes on a mask to the surface of a silicon wafer. The steps involved in the photolithographic process are wafer cleaning; barrier layer formation; photoresist application; soft baking; mask alignment; exposure and development; and hard-baking.
Wafer Cleaning, Barrier Formation and Photoresist Application
In the first step, the wafers are chemically cleaned to remove particulate matter on the surface as well as any traces of organic, ionic, and metallic impurities. After cleaning, silicon dioxide, which serves as a barrier layer, is deposited on the surface of the wafer. After the formation of the SiO2 layer, photoresist is applied to the surface of the wafer. High-speed centrifugal whirling of silicon wafers is the standard method for applying photoresist coatings in IC manufacturing. This technique, known as "Spin Coating," produces a thin uniform layer of photoresist on the wafer surface.
Positive and Negative Photoresist
There are two types of photoresist: positive and negative. For positive resists, the resist is exposed with UV light wherever the underlying material is to be removed. In these resists, exposure to the UV light changes the chemical structure of the resist so that it becomes more soluble in the developer. The exposed resist is then washed away by the developer solution, leaving windows of the bare underlying material. In other words, "whatever shows, goes." The mask, therefore, contains an exact copy of the pattern which is to remain on the wafer.
Negative resists behave in just the opposite manner. Exposure to the UV light causes the negative resist to become polymerized, and more difficult to dissolve. Therefore, the negative resist remains on the surface wherever it is exposed, and the developer solution removes only the unexposed portions. Masks used for negative photoresists, therefore, contain the inverse (or photographic "negative") of the pattern to be transferred. The figure below shows the pattern differences generated from the use of positive and negative resist.
Negative resists were popular in the early history of integrated circuit processing, but positive resist gradually became more widely used since they offer better process controllability for small geometry features. Positive resists are now the dominant type of resist used in VLSI fabrication processes.
Soft-Baking
Soft-baking is the step during which almost all of the solvents are removed from the photoresist coating. Soft-baking plays a very critical role in photo-imaging. The photoresist coatings become photosensitive, or imageable, only after softbaking. Oversoft-baking will degrade the photosensitivity of resists by either reducing the developer solubility or actually destroying a portion of the sensitizer. Undersoft-baking will prevent light from reaching the sensitizer. Positive resists are incompletely exposed if considerable solvent remains in the coating. This undersoft-baked positive resists is then readily attacked by the developer in both exposed and unexposed areas, causing less etching resistance.
Mask Alignment and Exposure
One of the most important steps in the photolithography process is mask alignment. A mask or "photomask" is a square glass plate with a patterned emulsion of metal film on one side. The mask is aligned with the wafer, so that the pattern can be transferred onto the wafer surface. Each mask after the first one must be aligned to the previous pattern.
Once the mask has been accurately aligned with the pattern on the wafer's surface, the photoresist is exposed through the pattern on the mask with a high intensity ultraviolet light. There are three primary exposure methods: contact, proximity, and projection. They are shown in the figure below.
Contact Printing
In contact printing, the resist-coated silicon wafer is brought into physical contact with the glass photomask. The wafer is held on a vacuum chuck, and the whole assembly rises until the wafer and mask contact each other. The photoresist is exposed with UV light while the wafer is in contact position with the mask. Because of the contact between the resist and mask, very high resolution is possible in contact printing (e.g. 1-micron features in 0.5 microns of positive resist). The problem with contact printing is that debris, trapped between the resist and the mask, can damage the mask and cause defects in the pattern.
Proximity Printing
The proximity exposure method is similar to contact printing except that a small gap, 10 to 25 microns wide, is maintained between the wafer and the mask during exposure. This gap minimizes (but may not eliminate) mask damage. Approximately 2- to 4-micron resolution is possible with proximity printing.
Projection Printing
Projection printing, avoids mask damage entirely. An image of the patterns on the mask is projected onto the resist-coated wafer, which is many centimeters away. In order to achieve high resolution, only a small portion of the mask is imaged. This small image field is scanned or stepped over the surface of the wafer. Projection printers that step the mask image over the wafer surface are called step-and-repeat systems. Step-and-repeat projection printers are capable of approximately 1-micron resolution.
Development
One of the last steps in the photolithographic process is development. The figure below shows response curves for negative and positive resist after exposure and development.
At low-exposure energies, the negative resist remains completely soluble in the developer solution. As the exposure is increased above a threshold energy Et, more of the resist film remains after development. At exposures two or three times the threshold energy, very little of the resist film is dissolved. For positive resists, the resist solubility in its developer is finite even at zero-exposure energy. The solubility gradually increases until, at some threshold, it becomes completely soluble. These curves are affected by all the resist processing variables: initial resist thickness, prebake conditions, developer chemistry, developing time, and others.
Hard-Baking
Hard-baking is the final step in the photolithographic process. This step is necessary in order to harden the photoresist and improve adhesion of the photoresist to the wafer surface.
Engineering books-Electronics
Non Linear Fibre Optics 3rd edition ~G.P Aggarwal
Power Electronic Control In Electrical Engg. ~E Acha
Radio & Electronics Cookbook ~G. Brown
Erbium Dope Fibre Technology ~P. C. Becker
Millman Halkias, Electronic Device & Circuits, Tata McGraw Hill
Control Systems Engineering - NORMAN NISE
Circuit Analysis ,Theory & Practice
CMOS IC Layout Concepts, Methodologies and Tools
Practical Analog and Digital Filter Design
Part 1: Semiconductor Physics and Devices
Part 2: Semiconductor Physics and Devices
The Illustrated Dictionary of Electronics [password is www.ebooksclub.org]
Electronic Navigation
Fiber Optic Cabling
Handbook Digital Signal Processing
Introduction to Statistical Pattern Recognition
Tunable Lasers Handbook
WDM Technologies - Active Optical Components
Radio Frequency Transistors - Principles & Practical Applications
Designing Embedded Internet Devices
The Art of Designing Embedded Systems
Fiber Optic Data Communications - Technological Trends & Advances
Handbook of Fiber Optics Data Communication
The Digital Consumer Technology Handbook
Multimedia Communications - Directions & Innovations
Modern Dictionary of Electronics
Essential Java for Scientist & Engineers
Analog Circuits Cookbook
Application of Nonlinear Fiber Optics
Telecommunications Demystified
Antenna Toolkit
RF Components & Circuits
Embedded FreeBSD Cookbook
Non-Linear Fiber Optics
Analog Interfacing to Embedded Microprocessors
Optical Fibre Telecomm. ~I.P. Kaminow
power electronics handbook~ M.H. Rashid
The Art Of Designing Embedded Systems ~J.G. Ganssle
Erbium Dope Fiber Amplifiers - Fundamentals & Technology
Understanding Telephone Electronics
Computer Busses - Design & Application
Electrical Circuits Theory & Technology
Handbook of Image & Video Processing
RF Circuits Design
Guide to Digital TV
Radio & Electronics Cookbook
Embedded Microprocessor Systems - Real World Design
Fundamentals and Applications of Ultrasonic Waves
Very Large Scale Integration Handbook
Electromagnetics Handbook
Introduction to Fiber Optics
High Frequency & Microwave Engineering
OPERATIONAL AMPLIFIERS - CLAYTON WINDER
OP AMPS - TERREL
SATELLITE COMMUNICATION ENGINEERING - KOLAWOLE
SATELLITE COMMUNICATION - DENNIS RODDY
WIRELESS COMMUNICATIONS - ANDREA GOLDSMITH
WIRELESS COMMUNICATION - THEODORE RAPPAPORT
MODERN WIRELESS COMMUNICATIONS - SIMON HAYKIN MICHAEL MOHER
FUNDAMENTALS OF TELECOMMUNICATIONS - ROGER FREEMAN
WIRELESS NETWORKS - P.Nicopolitidis, M.S.Obaidat, G.I. papadimitria, A.S. Pomportsis JHON WILLEY & SONS
WIRELESS INTERNET AND MOBILE BUSINESS - DEITEL
MOBILE ADHOC NETWORKING - BASAGNI CONTI GIORDANO IVAN
ANTENNAS - KRAUS
ANTENNAS AND RADIOWAVE PROPAGATION - COLLIN
MICROWAVE ENGINEERING - DAVID M POZAR MIRROR
OPTICAL COMMUNICATIONS ESSENTIALS - GERD KEISER
FIBER OPTIC COMMUNICATION SYSTEMS - AGARWAL
INTRODUCTION TO RADAR SYSTEMS - MERRIL SKOLNIK
digital logic and computer design morris mano
Digital Logic Design
Fundamentals of Logic Design-SOLUTION MANUAL
Electronic Circuit Analysis and Design 2nd edt. by Donald A. Neamen - solution manual
Analog and Digital Circuits for Electronic Control System Applications
integrated electronics; analog and digital circuits and systems - jacob millman, christos c halkias - mcgraw hill
Schaum's Outline of Basic Circuit Analysis (Paperback) by John O'Malley (Author)
Elements of Electromagnetics (Oxford Series in Electrical and Computer Engineering)
Microelectronic Circuits (Oxford Series in Electrical Engineering)
Microelectronics-Fabrication
ELECTRIC CIRCUITS - SCHAUMS OUTLINE
MICROELECTRONIC CIRCUITS - SEDRA SMITH
MICROELECTRONIC DEVICES AND CIRCUITS - FONSTAD
ELECTRONIC DEVICES AND CIRCUITS - SCHAUM
CMOS LOGIC CIRCUIT DESIGN - UYEMURA
Schaum's Outline of Digital Signal Processing
DIGITAL IMAGE PROCESSING - GONZALEZ WOODS
ENGINEERING ELECTROMAGNETICS - HAYT BUCK
ELEMENTS OF ELECTROMAGNETICS - MATTHEW N.O. SADIKU
Electronic Devices - Thomas L Floyd
Part2:
Practical Radio Frequency Handbook 1.89 MB
Video Demystified - A Handbook for the Digital Engineer 5.07 MB
Dictionary of Video & Television Technology 1.45 MB
Introduction to Medical Electronics Applications 7.18 MB
Optical Fiber Telecommunication III 28.97 MB
Optical Fiber Telecommunication IV 33.46 MB
Fiber Bragg Gratings 29.25 MB
Mixed Signal & DSP Design Techniques 3.93 MB
RF & Microwave Radiation Safety Handbook 4.24 MB
Radar Systems Peak Detection & Tracking 1.98 MB
Telecommunications Circuits & Technology 2.20 MB
Electronic Packaging Handbook 13.19 MB
A Wavelet Tour of Signal Processing 18.94 MB
Op Amps for Everyone 2.09 MB
Third Generation CDMA Systems for Enhanced data Services 7.72 MB
Practical Handbook of Photovoltaic's - Fundamentals & Applications 16.39 MB
Bebop to the Boolean Boogie 21.88 MB
NMR-Spectroscopy: Data Acquisition 1.82 MB
Feature Extraction & Image Processing
Building A Successful Board Test Strategy
Photoreactive Organic Thin Films
Audio & Hi-Fi Handbook
Sensors & Transducers
Digital Signal Processing 16.65 MB
SMT Soldering Handbook - Surface Mount Technology
Intelligent Communication Systems