The process of manufacturing semiconductors or integrated circuits (commonly called ICs or chips) typically consists of hundreds of steps, during which hundreds of copies of an integrated circuit are formed on a single wafer.
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Generally, the process involves the creation of 8 to 20, and frequently more, patterned layers on (and into) the wafer, ultimately forming the complete integrated circuit. This layering process creates (interconnected) electrically active regions on the semiconductor wafer surface.
Silicon Wafer Manufacturing
Semiconductor manufacturing begins with production of the wafer, i.e., a thin, round slice of a semiconductor material varying in size 6 inches to 12 inches in diameter. The finished wafer is approximately 15 mil thick. The materials are primarily silicon; however, gallium arsenide, silicon carbide, germanium, and others undergo similar processes. Purified polycrystalline silicon is created from sand, one of the most abundant materials available on our planet, is heated to a molten liquid. In a process similar to repeatedly dipping a wick in wax to make a candle, a small piece of solid silicon (seed) is dipped in molten liquid. As the seed is slowly withdrawn (by mechanical means) from the melt, the liquid quickly cools to form a single crystal ingot.
This cylindrical crystal ingot is then ground to a uniform diameter. A diamond saw blade slices the ingot into thin wafers. The cut wafers are then processed through a series of machines where they are ground (optically) smooth and chemically polished.
The wafers are now ready to be sent to the wafer fabrication area fab, where they are used as the foundation for manufacturing integrated circuits (ICs).
The heart of any semiconductor manufacturing business is the fab, where the integrated circuit is formed on the wafer. The fabrication process, which takes place in an environmentally controlled clean room, involves a series of principle repetitive steps described below. Typically, it takes from 10-30 days, but frequently much longer, to complete the fabrication process.
Thermal oxidation–wafers are pre-cleaned using high-purity deionized water and various low-particulate chemicals, a must for high-yield production. The silicon wafers are heated to approximately c and exposed to ultra-pure oxygen in the oxidation furnace. Under carefully controlled conditions, a silicon dioxide insulator film of uniform thickness is formed on the surface of the wafer.
Patterning–masking is used to protect one area of the wafer while working on another. This process is referred to as photolithography. A photo resist, light-sensitive film is spin-coated onto the wafer, giving it characteristics similar to a photographic film. A (micro) aligner aligns the wafer to a glass mask and then projects an intense ultraviolet light through the mask, exposing the photo resist with the mask pattern, thereby transferring the image from the mask into the light-sensitive film.
Etching–the wafer image is then developed (like a photo negative). The exposed photo resist is chemically removed and baked to harden the remaining photo resist pattern, which now is no longer light sensitive. It is then exposed to a chemical wet solution or plasma (gas discharge) so that areas not covered by the hardened photo resist are etched away. The remaining photo resist is now removed using either wet or plasma chemistry. The wafer is optically inspected to assure that the image transfer from the mask to the top silicon layer is correct, and then goes on to the next step.
Doping/diffusion–atoms with one less electron than silicon (such as boron) or one more electron than silicon (such as phosphorus) are introduced into the area exposed by the etch process, to alter the electrical character (conductivity) of the silicon. These areas are called p type or n type, respectively, which reflects their conducting characteristics.
Complete front end layer— Repeating the above steps: the thermal oxidation, masking, etching, and doping steps are repeated many times until the last “Front end” layer is completed (all active devices have been formed).
Dielectric deposition and metallization–following completion of the “Front end,” the individual devices are interconnected “Backend” (like on a pc board) using a series of alternating metal depositions, dielectric films, with their respective patterning. Current semiconductor fabrication includes as many as 5 to 7 metal layers for logic, and fewer for memory, separated by dielectric layers (insulators).
Passivation–after the last metal is patterned, a final insulating layer (passivation) is deposited to protect the circuit from damage and contamination. Openings are etched in this film to allow access to the top metal later by electrical probes and subsequent wire bonds.
Electrical test–an automatic, computer-driven test system checks for functionality of each chip on the wafer. Chips that do not pass the test are marked for automatic rejection. For simpler devices a mechanical probe is used.
Assembly–a diamond saw slices the wafer into single chips. Sizes can vary from 1 x 1 mm to 10 x 10 mm. The rejected chips are discarded and the remaining chips are visually inspected under a high-power microscope before packaging.
Each chip is then assembled into an appropriate package that provides the contact leads for the chip. In one type of interconnect a wire bonding machine attaches wires, a fraction of the width of a human hair, to the leads of the package. The packaged chip is tested again prior to delivery to the customer. Alternatively, the chip can be assembled in a ceramic package for certain high-performance applications.
3G/4G
Industry term for third and fourth generation wireless mobile communications networks.
A/D
Analog-to-Digital Converter. This device is what all digital imaging systems use to get real-world pictures from a TV camera, for example into a computer.
Adapter Card
Circuit board or other hardware in Data Terminal Equipment (DTE) that provides the physical interface to the communications network.
Analog Signals
Analog is a continuous signal, measuring features that are difficult to break into digital components, such as pressure, temperature, voltage, current and air and water-flow. The circuits are used in products that involve sound (radios, TVs) and pressure (automotive air bags, anti-lock brakes).
Angstrom
One ten-billionth of a meter. Some chip layers are only 100 angstroms thick.
ASIC
Application Specific Integrated Circuits. Designed to suit a customer’s particular requirement, as opposed to DRAMs or microprocessors, which are general-purpose semiconductors.
Application Specific Integrated Circuits
Designed to suit a customer’s particular requirement, as opposed to DRAMs or microprocessors, which are general-purpose semiconductors.
Assembly
A step in semiconductor manufacturing in which the chip (die) is either encased in a plastic, ceramic or other package or assembled directly on a printed circuit board.
ASSP
Application-Specific Standard Products. An integrated circuit that performs functions for a single application.
Bandwidth
An analog measure derived from the difference between the highest and lowest frequency on a carrier wave. Also used to describe the amount of data that can be sent through a given communications circuit.
BiCMOS
Bipolar Complementary Metal Oxide Semiconductors. This relatively new process combines both bipolar and CMOS technologies on the same chip, yielding products with the benefits of both technologies.
Binary
Characteristic of having only two states, such as current on and current off. The binary number system uses only ones and zeros.
Bipolar
A type of transistor noted for its speed where a flow of both conduction electrons and holes determine the device characteristics.
Bit
Binary digit
The basic unit of all digital communications. A bit is a “1” or “0” in a binary language.
Bluetooth™
A wireless Personal Area Network (PAN) technology from the Bluetoothtm Special Interest Group, founded in by Ericsson, TBM, Intel, Nokia and Toshiba. It is an open standard for short-range transmission of digital voice and data between mobile and desktop devices.
Broadband
Originally described the frequency bandwidth of analog circuits. The term has evolved to specify 56 KBps, then 1.5 Mbps capability.
Buckyball*
A sphere of 60 carbon atoms in an arrangement that looks like a soccer ball. A popular name for a buckminsterfullerene (named after Buckminster Fuller, inventor of the geodesic dome). This nanostructure’s unique properties could be useful in nanotechnology.
Byte
A data unit of eight bits.
CAD
Computer-Aided Design. Sophisticated, computerized workstations and software used to design integrated circuit chips.
CDMA
Code Division Multiple Access, also called Spread Spectrum, a term for a form of digital spread spectrum cellular service that assigns a code to all speech bits, sends a scrambled transmission of the encoded speech over the air and reassembles the speech into its original format. CDMA has up to 20 times the capacity of analog cellular service and is best known for its superior call quality and long battery life.
Chip
An individual integrated circuit built in a tiny, layered rectangle or square on a silicon wafer.
Cleanroom
The sterile rooms where chips are fabricated. The air in these rooms is thousands of times cleaner than in a typical hospital operating room.
Circuit Board
Same as printed circuit board. A board with microprocessors, transistors and other electronic components. Also called a circuit card.
CMOS
Complementary Metal Oxide Semiconductors. Combine both positive- and negative-channel transistors on the same circuit design. CMOS circuits consume relatively low amounts of power.
Defect
A chemical or structural irregularity that degrades the product. Defects can affect the product over time or interfere with manufacturing the chip correctly. Common causes of defects are flakes from skin or cosmetics, and droplets from a person’s sneeze.
Digital
The method of representing information as numbers with discrete (non-continuous) values, usually expressed as a sequence of binary digits (ones and zeros).
Die
A single integrated circuit (or chip) cut from the wafer on which it was manufactured.
Digital Cellular
Cellular communications technology. Transmitting digital data with over 15 times the capacity of analog technology with significantly less static, loss/interruption of the signal when passing between cells and connection problems because of congested relays.
DSL
Digital Subscriber Line. A technology that increases the digital speed of ordinary lines by a substantial factor over common dial-up modems. Offers symmetrical and asymmetrical operation. Asymmetrical versions (ADSL, RADSL, VDSL, etc.) provide higher downstream transmission than upstream and are better suited for Internet usage and video on demand applications. Symmetric DLS (HDLS, SDSL, IDSL, etc.) provide the same speed in both directions. All DSL have distance limitations of around two or three miles between the company’s central office and the customer site.
Digital Signal Processing (DSP)
Digital circuits designed to address a broad class of problems in signal reception and analysis that have traditionally been solved using analog components. DSP is used to enhance, analyze, filter, modulate or otherwise manipulate standard analog functions, such as images, sounds, radar pulses, and other such signals by analyzing and transforming wave-forms (e.g., transmitting data over lines via modem).
Diode
A signal and switching device that allows current in one direction and blocks it in the opposite direction. One use: regulating load voltages.
Discrete Device
A device that contains one active element, such as a transistor or diode, although a hybrid might contain more than one active element. In comparison, an integrated circuit could contain billions of active elements on a single chip.
DRAM
Dynamic Random Access Memory. A type of memory component. “Dynamic” means the device’s memory cells must be recharged periodically. Information stored in the memory cells is accessed randomly. Memory is a key component of most electronic products.
Doping
A wafer fabrication process in which exposed areas of silicon are bombarded with chemical impurities to alter the way the silicon conducts electricity in those areas.
E-Beam
Electron Beam refers to a machine that produces a stream of electrons that can be used to expose photoresists directly on a wafer or on a mask. Electron-beam lithography is a microprinting technique.
EEPROM
Electronically-Erasable Programmable Read-Only Memory.
Embedded Processor
A computer chip that controls the function of its product. While embedded processors sometimes refer to the type of chips used in simple electronic toys, “talking” greeting cards and similar consumer products, they are also high-functioning microcontrollers that are the brains of products such as laser printers.
Etch
The removal of selected portions of materials to define patterned layers on chips.
EPROM
Erasable Programmable Read Only Memory. Allows stored information to be erased by exposure to ultraviolet light.
Ethernet
A local area network used for connecting computer, printers, workstations, terminals, servers and other computer hardware within the same company. Ethernet operates over twisted wire and over coaxial cable at speeds up to 10 million bits per second (Mbps).
Extreme Ultraviolet Technology
A technology for extending ultraviolet lithography by manufacturing a lens with concave and convex mirrors. This type of manufacturing allows the lens to focus patterns on a chip that are too small to be lithographed.
Fab
The fabrication facility, or fab, is the manufacturing plant where the front-end process of making semiconductors on silicon wafers is completed. The package and assembly (back end) stages are typically completed at other facilities.
Fabless
A semiconductor company with no wafer fabrication capability.
Flash Memory
A faster form of EPROM that permits more erase/write cycles. Flash memory allows large amounts of non-volatile program memory.
Focus Center
The Focus Center Research Program has six Focus Centers that are university centers leading a consortium of other universities in researching a particular challenge to the long-term advancement of semiconductor technologies.
Foundry
A factory that manufactures semiconductor chips on wafers. Usually used to denote a facility that is available on a contract basis to companies that do not have wafer fab capability of their own, or that wish to supplement their own capabilities.
GaAs
Gallium Arsenide. A III-V compound semiconductor material used for making optoelectronic devices and high-frequency ICs. GaAs has a higher electron mobility than silicon, thus having the capability of producing higher-speed devices. III-V refers to the third and fifth columns of the periodic table.
Gate Array
A semi-custom chip. The integrated circuit is preprocessed to the first interconnect level. The remainder of the interconnect is customized to meet specific requirements of the customer.
IC
Integrated Circuit. A chip etched or imprinted with network or electronic components such as transistors, diodes and resistors along with their interconnections.
IEEE
Institute of Electrical and Electronics Engineers. A world-wide engineering publishing and standards-making body for the electronics industry.
Integrated Circuit (IC)
Semiconductor chip in which many active or passive elements are fabricated and connected together on a continuous substrate, as opposed to discrete devices, such as transistors, resistors, capacitors and diodes that exist individually.
Ion Implatation
One way that the surface of a chip is transformed. It is a method that fires beams of charged atoms at the surface of the wafer. The high level of energy of these ions allows them to penetrate the silicon to produce the desired doping effect.
ITRS
International Technology Roadmap for Semiconductors. ITRS is an international effort involving industry, government and academic experts to identify technical barriers that must be overcome to continue semiconductor technology advances.
LAN
Local Area Network. A communications network that serves users within a confined geographical area, and made up of servers, workstations, a network operating system and a communications link.
Lead Frame
A stamped or etched metal frame, usually connected to the bonding pads of a die by wire bonding, that provides external electrical connections for a packaged electrical device.
Length Scale*
The size range within which an object falls; e.g. nanscale, millimeter scale.
Lithography
From the root “litho” meaning “stone” and “graph” meaning “writing”. Lithography is the transfer of a pattern or image from one medium to another, as from a mask to a wafer. If light is used to effect the transfer, the term “photolithography” applies. “Microlithography” refers to the process as applied to images with features in the micrometer range.
LSI
Large Scale Integration. The art of putting tens of thousands of transistors into a single integrated circuit.
Meter
A unit of measure equaling about 3.3 feet.
Macro Cell
Similar to a standard cell but larger. Macro cells contain predefined circuit elements that may be selected and arranged to create a custom or semi-custom integrated circuit more easily than through design. Designers building ASICs use macro and standard cells.
Microcontroller
A microcontroller is a stand-alone device that performs computer functions within an electronic system without the need of other support circuits. A microcontroller contains memory functions, unlike a microprocessor; which is typically paired with a chip that provides memory. Microcontrollers are used in TVs, VCRs, microwave ovens and automobile engines.
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Micron
A metric unit of linear measure which equals one millionth of a meter or one thousandth of a millimeter. A thousand times bigger than a nanometer. The diameter of a human hair is about 100 microns. Today’s semiconductors have lines etched at 0.065 microns.
Microperipheral
A device that works with a micro-controller or microprocessor. Microperipherals are used in modems, ISDN and ethernet lines, in imaging equipment such as printers, computer mice and keyboards.
Microprocessor
A central processing unit (CPU) fabricated on one or more chips, containing the basic arithmetic, logic and control elements required by a computer for processing data. Micro-processor also refers to an integrated circuit that accepts coded instructions, executes the instructions and delivers signals that describe its internal status.
Millimeter*
One thousandth of a meter. About 4/100 inch.
Mixed Signals
A class of ICs that have traditionally been considered analog semiconductors. They can also be defined as anything that combines analog and digital circuitry-and that includes many ASICs and DSPs.
Molecular Electronics*
Any system with atomically precise electronic devices of nanometer dimensions, especially if made of discrete molecular parts rather than the continuous materials found in today’s semiconductor devices.
Moore’s Law
In Intel co-founder Gordon Moore predicted that the number of transistors (and capacity) that can be squeezed onto a chip would double every 18 months. If this trend continued, he reasoned, computing power would rise exponentially with each new generation of chips. His published observation holds to this day.
MOSFET
Metal Oxide Semiconductor Field Effect Transistor. A device that does not require as much power as bipolar devices because of its insulation. The term can be applied either to transistors in an IC or to discrete power devices. MOSFETs are easier to manufacture than bipolar devices and are a building block in the fabrication of CMOS chips.
Nanocrystal*
A nanoscale crystal whose size, shape and atomic composition are carefully controlled to yield specific properties, like absorption of specific wavelengths of light.
Nanometer
A metric unit of linear measure which equals one billionth of a meter. A leading edge semiconductor today has line widths of 65 nanometers.
Nanoscale*
The size range of objects studied by nanotechnologists.
Nanotechnology*
The ability to see, measure and make objects that are within the same tiny size scale as atoms and molecules. The nanotechnology realm can be defined as being between 0.1 nanometer (about the size of a hydrogen atom) and 100 nanometers (about the size of a virus).
Nanotube*
A tube of nanoscale dimensions, but most frequently referring to carbon nanotubes. These tubes, which are stronger and lighter than steel, can have varying electrical properties with applications in computing, materials manufacturing and biotechnology.
Non-Volatile Memory
A storage device whose contents are preserved when its power is off. Storage using magnetic disks or tape is normally non-volatile. Some semiconductor memories (ROM, EPROM, Flash memory) are non-volatile while other semiconductor memories (static RAM and especially dynamic RAM) are normally volatile but can be made into non-volatile storage by permanently connecting a (rechargeable) battery.
NMOS
Negative-channel Metal Oxide Semiconductor. NMOS was the preferred technology for making leading-edge chips in the ’s and early ’s.
Optoelectronics
A device that is responsive to or that emits or modifies light waves. Examples are LEDs, optical couplers, laser diodes, and photo detectors.
Packaging
The protective container or housing for an electronic component or die, with external terminals to provide electrical access to the components inside. Packages provide for power and signal distribution, power dissipation, and physical and chemical protection of the circuits.
PCB
Printed Circuit Board. Flat material on which electronic components are mounted. Also provides electrical pathways that connect components.
PDA
Personal Digital Assistant
PLD
Programmable Logic Device. A digital IC that can be programmed by the user to perform a wide variety of logical operations. FPGAs and CPLDs are classes of PLDs.
Quantum Dots*
A class of nanocrystals that emit varying colors of light depending on their size. They can be used to label different biological structures.
RAM
Random Access Memory. May be written to, or read from, any address location in any sequence. Also called a read/write memory, RAM stores digital bits temporarily and can be changed rapidly as required. RAM constitutes the basic read/write storage element in computers.
RF
Radio Frequency. The rage of electromagnetic frequencies above the audio range and below the visible light. All broadcast transmission, from AM radio to satellites, falls into this range, between 30KHz to 300GHz.
ROM
Read Only Memory. Permanently stores information used repeatedly, such as tables of data, characters for electronic displays, etc. A popular type known as PROM is programmable in the field with the aid of programmer equipment. Programmed data stored in ROM is often called firmware.
Roadmap
An international reference document of requirements, potential solutions, and their timing for the semiconductor industry. It identifies needs and encourages innovative solutions to meet future technical challenges, and provides an ongoing emphasis on obtaining consensus industry drivers, requirements, and technology timelines.
Self-Replication*
The ability of an entity such as a living cell to make a copy of itself. Theoretically, nanotechnologists could invent self- replicating devices.
Self-Assembly*
The ability of objects to assemble themselves into an orderly structure. Routinely seen in living cells, this is a property that nanotechnology may extend to inanimate matter.
Semiconductor
This is the generic name for discrete devices and integrated circuits that can control the flow of electrical signals. Silicon is the basic material on which semiconductors are fabricated.
Signal Processing
Electronic functions that enhance the representations of physical or electrical phenomena. Temperature, pressure, vibration, acceleration and flow are examples of physical properties that rely on signal processing enhancements. The detection and conversion of RF, X-ray or ultrasonic energy into images and sound is another form of signal processing.
Solid State
Refers to the electronic properties of crystalline material, as opposed to vacuum and gas-filled tubes that transmit electricity. Compared with earlier vacuum-tube devices, solid-state components are smaller, less expensive, more reliable, use less power and generate less heat.
SRAM
Static Random Access Memory. Is an integrated circuit similar to a DRAM that requires no constant refreshing or recharging. It retains stored information as long as power is applied to the computer, hastening information-retrieval process time. In contrast to ROM, SRAM is still volatile and will lose its contents when the power is switched off. SRAM is usually faster than DRAM but usually costs more per bit because each bit requires several transistors. It is used for the most speed-critical parts of a computer or other circuit.
Standard Cell
Predefined circuit elements that may be selected and arranged to create a custom or semi-custom integrated circuit more easily than through design. Designers build ASICs using standard cells.
Substrate
The body or base layer of an integrated circuit, onto which other layers are deposited to form the circuit. The substrate is usually silicon, although sapphire is used for certain applications, particularly military, where radiation resistance is important. The substrate is originally part of the wafer from which the die is cut. It is used as the electrical ground for the circuit.
Synchrotron
A device used to produce high-energy X-rays that can inscribe features on a chip potentially as small as 100 nanometers.
System on a Chip
A chip that is a self-contained system, including processing, memory and input-output functions.
Transistor
An electronic device capable of amplifying electronic signals similar to the vacuum tube but made from a semiconductor material such as silicon or germanium.
VLSI
Very Large-Scale Integration. The art of putting hundreds of thousands of transistors onto a single quarter-inch integrated circuit.
Wafer Fab
A slang term for wafer fabrication facilities, ultra clean factories wherein silicon wafers are produced.
Wafer
A thin slice, typically 10-30 mils thick, sawed from a cylindrical ingot (boule) of extremely pure, crystalline silicon, typically six to eight inches in diameter. Arrays of ICs or discrete devices are fabricated in the wafers during the manufacturing process.
X-ray Lithography
The lithographic process for transferring patterns to a silicon wafer. The electromagnetic radiation used is X-ray, rather than visible radiation.
Yield
Yield refers to the percentage or absolute number of defect-free die on a silicon wafer or of packaged units that pass all device specifications. Because it costs the same to process a wafer with 10% good die and 90% good die, eliminating defects and improving yield become the critical variable in determining the cost per chip.
From engineering advances to medical applications to geopolitics, semiconductors are big news. And for good reason, says Stanford University semiconductor researcher, Srabanti Chowdhury. “Semiconductors are incredibly impactful in our life,” said Chowdhury, who is an associate professor of electrical engineering, materials science and engineering (by courtesy) and a senior fellow at the Precourt Institute for Energy. “We’re always among them, either using them directly or getting benefits from them.”
Chowdhury’s lab focuses on studying semiconductors that can support more efficient, sustainable, and heatproof electronics. On Sept. 11, the Semiconductor Research Corporation awarded Chowdhury the Technical Excellence Award, recognizing her expertise in semiconductors that are designed to withstand extreme heat environments and her prolific and transparent data sharing practices.
Short answer: Semiconductors can conduct electricity in some situations but block it in others.
Chowdhury: A semiconductor is a chemical element or compound that conducts electricity under certain conditions and blocks it in other conditions. If you think of a metal, like a copper wire, and you think about electricity flowing through it, you cannot generally switch it off without taking away the source or supply – like using a wall switch to stop the flow of current through the wiring of your room into your light bulb. Copper will always conduct and wood will never conduct (because it’s an insulator). A semiconductor is something in between. You can make it conduct or block current by design!
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Short answer: Any electronics that you see, hold, or touch all have a chip – or several chips – inside that is made out of semiconductors.
Chowdhury: We’re always among semiconductors. They are in your computer, your cell , your watch, your car, and even in LED lights. Semiconductors are so important because you cannot run your daily life without them. The smarter the world gets, the more the need for semiconductors will increase.
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Short answer: To a materials scientist, a semiconductor is a crystal with atoms and defects; to a physicist, it has a conduction band and valence band; and to an electrical engineer, it has electrons and holes.
Chowdhury: You can see semiconductors in the frame of energy, which typically device physicists do. They see two energy bands – a conduction band and a valence band – and a very important energy gap (aka bandgap) that separates the two. The bands are full of “rooms” for electrons, which are called states. In the conduction band, only some of the states are filled with electrons and the others remain empty, where the electrons can jump into. This is how a semiconductor conducts current. A valence band, which otherwise is full of electrons, has some empty states that are called “holes”. Holes are positive in charge and electrons are negative. They can combine to emit light or generate heat!
If you see through the lens of charges, like an electrical engineer, the current in a semiconductor is generally carried by electrons or holes, or both.
Last but not least, through the lens of a material scientist, we have lattices – a repeated geometrical pattern – of atoms that create a very crystalline structure. Sometimes you will have one or two atoms or more missing from a given set of lattices and those give vacancies, or defects.
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Short answer: Semiconductors can be made of a single element or combination of elements in the form of a compound. Si is an elemental semiconductor and GaN is a compound semiconductor.
Chowdhury: Some elements are semiconductors by themselves, or they can be mixed with another element to become semiconductors. These are actually categorized as elemental and compound semiconductors. Silicon and diamond are elemental semiconductors. Gallium nitride, gallium arsenide, cadmium telluride, zinc oxide, molybdenum disulfide, and silicon carbide are compound semiconductors to name a few. The periodic table provides us with many permutations and combinations of elements to form a semiconductor.
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Short answer: Transistors and diodes are the building blocks of circuits that go in a computer, and these are made out of semiconductors. Once upon a time transistors or diodes in computers were made out of vacuum tubes, but not since semiconductors emerged.
Chowdhury: Everything. No computer can function without the semiconductor (device) in it. All information in a computer is transmitted or stored in forms of binary digits – zeros and ones – and these zeros and ones are ‘voltages’ that are generated, transmitted and stored using little switches made out of transistors and diodes, and those are made of semiconductors. Powering up a computer to function also happens through semiconductor switches.
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Short answer: Moore’s Law is an observation (not a law!) made by Gordon Earle Moore, the co-founder of Intel Corporation. In , he observed, “The complexity for minimum component costs has increased at a rate of roughly a factor of two per year,” and that this trend should continue for 10 years or more.
Chowdhury: Moore’s Law is an observation; it’s a household name for semiconductor engineers and electrical engineers. In , Gordon Moore, who at the time was working as the director of research and development at Fairchild, postulated that the number of components that can be packed onto a chip will double every two years – and this relates to semiconductors because these components are made of semiconductors. Moore’s Law is often used as an indicator of potential computing power.
Moore’s “prophecy” has been used by the semiconductor industry to guide long-term goals and to set roadmaps. Semiconductor component cost only goes down over time, not up. For performance and functionality, we pack more and more on a chip but cannot increase the price of it. So, Gordon Moore was trying to predict how it would stay profitable. Often I joke, that if the semiconductors folks had cut themselves some slack, Moore’s Law wouldn’t have come true.
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Short answer: Producing semiconductor chips involves access to fabrication plants, but the main piece of the puzzle is our workforce. In addition to issues like insufficient capacity at semiconductor fabs, the COVID-19 pandemic severely affected those people.
Chowdhury: Whenever supply falls short of the demand, you have a shortage. The shortage could be because of regional issues, like a drought in Taiwan – which reduces the availability of pure water needed to make semiconductors – or it could be something like what we’re seeing today, which was purely COVID-19-related. The workforce suffered significantly from the pandemic, and we are seeing the consequences still in the form of labor shortages. I think if robots were running the whole process, we probably wouldn’t see shortages anymore, but I hope that’s not coming soon.
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Short answer: Modern life is dependent on semiconductors – similar to our dependence on oil – and producing semiconductors is an international effort.
Chowdhury: Semiconductors are like an economic backbone of society. They are a measure of prosperity and advancement. Like other backbones – water or clean air or land or oil – it is a political entity because countries will defend their access to semiconductors. They do this, in part, because there is a responsibility towards their people and their prosperity. And, in some cases, you want to use your power to make sure your country is more advanced than others.
On top of that, we’re a very global economy and very interdependent. We don’t manufacture chips as much in the U.S. as we used to; we depend on other countries. Similarly, other countries depend on us for the research and development regarding chips. Basically, whenever countries try to control their stake in the process of creating semiconductors, it’s an international situation. And that is why you see semiconductors in political news.
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Short answer: There is a lack of people going into semiconductor science, and we need to think more about sustainability.
Chowdhury: Number one is workforce. We are falling short of people who make semiconductors their career. The hardware side of things often tests your patience and doesn’t offer instant gratification. For example, Julius Lilienfeld patented the field-effect transistor in the s, but no one could make it until around . So, sometimes, you’re not even there to see your work realized and recognized.
The second one is industry-academia partnership (or lack thereof) to inspire students to solve real problems. The notion of academic semiconductor research being far out in time often turns off students who want to make a difference now. However, this is mostly untrue. There are many problems to choose from and you can always find those that matches your expectation. Career opportunities in semiconductors are also extensive and fulfilling and we are not saying it loud enough.
One other major challenge is sustainability. When it comes to helping our planet, semiconductors are part of the solution, but they can also be part of the problem. We are producing semiconductors and products with semiconductors at a fast pace, and we have catching up to do in terms of our thinking about sustainability.
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Short answer: Some of the biggest advancements that are coming are adding an emotional piece to AI, remote access to high-quality medical care, and energy security being tied to semiconductors.
Chowdhury: Artificial intelligence is one of the biggest revolutions of our time. We are adding AI into electronics and making them smart. We are also trying to introduce emotions in them, and trying to build robots that are like you and me. That is tough because human brains are extremely complicated systems to model. We cannot yet make robots – or should I say the chips needed for such robots – that are as efficient as human beings, but we are moving in that direction.
I am also very intrigued by what will happen in clinical and non-clinical medical applications. In some parts of the world where there isn’t access to a good surgeon, 6G could enable a surgeon from somewhere else to control surgical instruments remotely with extreme precision. Right now, with 5G, I think the latency is a few milliseconds, which is very small but may not be little enough for intricate operations like a life-saving surgery done remotely. If we can do those kinds of things, the world will benefit from expertise from anywhere.
Another thing that is very interesting is energy security, which currently comes from oil. I think energy security will significantly come to depend on semiconductors because of dependence on renewables – to convert that energy from one form to another, you need semiconductors.
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Short answer: I don’t think we’ll be replacing silicon as the basis of computer chips.
Chowdhury: An idea you hear often is replacing silicon or making a non-silicon computer. That’s not happening. Our entire concept of modern computers is based on silicon and silicon continues to surprise us in a very good way.
At the same time, the silicon industry is increasingly open to welcoming new semiconductors to complement silicon, and that is the key. Theoretically, we should be able to make silicon more efficient by adding non-silicon semiconductors to do stuff that silicon cannot do. For example, my group works on diamond for thermal benefits that now we are mixing with silicon on chips to make it function better with more thermal management. Oxides, Nitrides, 1D, 2D – all these semiconductors can be carefully mixed (called “heterogenous integration”) to make the overall performance go up. But it is not trivial and will take time.
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Short answer: We’re working on developing solutions based on semiconductors that lead to more efficient performance and allow energy to be more sustainable and accessible.
We work on developing materials, and make devices with them, while often adding stretch goals to demonstrate their potential in an application with our collaborators.
Chowdhury: My group works on wide bandgap materials, which are best thought of as materials that can give you 10-100 times the power density of silicon. They can also handle harsher environment, like high temperature, where they don’t fail when silicon does. One of our specialties is “power electronics” – all the AC-to-DC power conversions required to get power from the grid to your home or into your favorite electric vehicle rely on semiconductors. If power goes through oil refineries, you need semiconductors that can adjust to very high pressure and geothermal temperatures. Electronics in space also need very rugged semiconductors that can handle radiation, the cosmic rays. What we’re doing is we’re bringing in wide bandgap materials along with silicon, and to get more power out of less silicon. It is extremely important to offer more power density to make things compact and efficient at the same time.
We also work on radio-frequency (RF) electronics for 5G, 6G, and beyond. One of the biggest challenges in electronics right now is managing temperature. This is a necessity in computation and in RF applications, which include radar. We are studying a novel approach of integrating thin film diamond, which is a semiconductor, at the material level to help spread more heat and reduce temperature spikes in the chip. If you can spread the heat out, you can avoid some degradation of the performance. It helps chips operate more reliably and live longer.
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Short answer: I believe this is a thriving industry and it’s becoming increasingly interdisciplinary, which is compelling. But I encourage people to decide for themselves how they feel about what is happening in semiconductors by spending enough time with the topic. It’s ok to take your time to decide, rather than rushing.
Chowdhury: There are some people worried that semiconductors are done advancing. So, I just want to say that no matter what they read or what they hear, they should explore the situation for themselves. I teach my group and undergrads to be curious and to not worry about imposing on anyone by asking questions. It’s so important for them to get a true picture of what is happening in their chosen field.
This is what I see: If you look at the big tech companies, all of them have their own semiconductor efforts in their backyard. They’re developing and researching semiconductors on site. So, jobs are very attractive in semiconductor engineering. Also, people don’t always realize that semiconductors is a very interdisciplinary topic. It has chemistry in it and physics and engineering, and you can apply it to your favorite domain: energy, sustainability, medical or biological applications. In the case of my group, heterogenous integration – that careful mixing of materials – to offer more efficiency to electronics compels us to explore new materials and devices.
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Short answer: I’m very optimistic and excited about the future because we have made the tent much bigger with interdisciplinary research, and we have the opportunity to benefit people worldwide.
Chowdhury: I’m not the only person who would say this: we have never felt so excited about semiconductors as we are today. And there are two main reasons for that.
For one, our industry is accepting that silicon, alone, is not enough. We’re used to silicon and we know everything about it. We feel more free to explore different and new materials for logic, memory, power conversion, thermal management, and more. What used to be a “silicon community” has broadened. We’re collaborating, we’re talking, we’re criticizing, and all of these are an indicator of a very healthy society.
A more general point: As we look to the future, it’s important to me, personally, that the benefits of semiconductors are accessible to the world as a whole. A great example is the Nobel Prize in physics in , which was given for “the invention of efficient blue light-emitting diodes [LEDs] which has enabled bright and energy-saving white light sources.” That was one of the most engineering-centric Nobel Prizes and it recognized beautiful work that changed how humankind advances in a way that’s accessible everywhere. In the most optimistic future, our work can have a deep societal impact. The closer we get to those applications, the more exciting our industry will be.
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