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Integrated Circuits
Semiconductor elements
Introduction Integrated circuits (ICs) are microelectronic elements. They are characterized by miniature size and weight, low power requirements and low cost, while having increased reliability and significant complexity. The production technology allows them to build a whole system in a single integrated circuit (chip), which contains tens of millions of transistors.
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Applications Modern electronics began with the discovery of the transistor in 1947 and the subsequent development of integrated circuits (ICs) in the early 1960s.
Thanks to ICs, modern computers, information technology, telecommunications, space and aircraft equipment, entertainment, automotive and medical electronics, navigation systems, audio and video devices and much more have become possible.
Goals and prerequisites
Basic concepts and classification of integrated circuits, key processes in their production and the structure of the elements are considered.
After studying the material you should: Познавате What is an integrated circuit Types of integrated circuits
Разбирате Planar technology The main processes in the production of silicon IC The structure of the elements implemented in the IC
Анализирате The need for insulation between the elements Problems in integrating passive components Оценявате Advantages and disadvantages of bipolar, MOS and CMOS ICs
Prerequisites: semiconductors, bipolar and MOS transistors
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What is an integrated circuit?
An integrated circuit (also called a chip or microchip) is defined as a combination of inextricably linked elements implemented on or in a common substrate. Many transistors, diodes, resistors and capacitors are manufactured as a whole and are enclosed in a common case. The whole scheme is considered as one indivisible component.
Integrated circuits classification
According to the technology for their production, the following IC types differ:
Types of integrated circuits
Monolithic Layered ICs
Hybrid
MOS Bipolar Thin-film ICs Thick-film ICs
NMOS PMOS
CMOS
Mixed
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Monolithic integrated circuits IC
Semiconductor Needle substrate
In monolithic integrated circuits, all elements are made inside of a common semiconductor substrate. They can be bipolar or MOS ICs according to the transistors available in them. There are also mixed monolithic ICs that contain both types of transistors.
Although they contain millions of transistors, these integrated circuits are several millimeters in size.
Layered Integrated Circuits
Capacitor
Al SiO2 NiCr
Dielectric substrate Resistor
Layered ICs are made of conductive or non-conductive material, which is applied on an insulating substrate. According to the layer thickness, they are divided into thin- layer and thick-layer ICs. They are used to make only passive elements - resistors and capacitors.
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Hybrid Integrated circuits
Resistor Case of layered IC
Dielectric substrate
IC Бобина Capacitor
Hybrid ICs combine layered passive elements with integrated circuits and other discrete components mounted on the insulation pad.
Linear and Digital ICs
According to their purpose, integrated circuits are classified as digital and linear. Linear ICs are used in analog circuits - audio amplifiers, voltage regulators, operational amplifiers and more. In them the signal is continuous in time.
In digital circuits, IC signals have two levels. They are used in computers, computer networks, digital clock calculators and others.
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History of Iс development
First Ge transistor with point contact
Bell Labs, 1947
John Bardeen, Walter First Si transistor – Гордън Тийл, Texas Brattain, William Shockley, Instruments, 1954 Winners of the 1956 Nobel Prize in physics First MOSFET
Bell Labs, 1959 Dawon Kahng, Mohamed M. Atalla
Revolution in microelectronics
First hybrid Ge IC, 1958 1 transistor and 4 other elements on 1 chip
Jack Kilby Winner of the 2000 Nobel Prize
Texas Instruments, 1958
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Planar process –1959
A more efficient method of manufacturing transistors Fairchild Electronics – Jean Hoerni and Robert Noyce
First commercial monolithic Si IC, implemented with planar process
Fairchild, 1959
One Binary Digital (Bit) Memory Device on a Chip, 4 Transistors and 5 Resistors
Start of Small Scale Integration (SSI) technology Robert Noyce
First Linear IC
mA 709 OPAMP, 1965 mA 702 OPAMP, 1964
Operational amplifier
Robert Widlar, Fairchild,
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First Semiconductor memories Intel Corporation DRAM, 1970 Fairchild 4100 SRAM, 1970
First 1,024 Bit Memory Chip – 1970 First 256-Bit Static RAM – 1970
Intel 1702, EPROM, 1971
First EPROM Memory chip
Birth of microprocessor – 1971 The first computer on a single chip – 2300 transistors,1MHz, MOS technology
Intel 4004, 4-bit microprocessor, 1971
Federico Faddin
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Minicomputer revolution
2901 Bit-Slice Microprocessor, 1975 Motorola 68000, 16-bit microprocessor
Advanced Micro Devices, 1975
Beginning of the Medium Scale Integration Motorola, 1979 (MSI) technology Beginning of the Large Scale Integration (LSI) technology
Minicomputer revolution
HP Focus Chip, 32-bit proc, 1981 Intel Pentium 4, 64-bit proc, 2000
Hewlett-Packard Co. 450,000 transistors Intel Corporation Beginning of Very Large Scale Integration (VLSI) technology
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Moor Law
Gordon Moor, Intel
According to the number of transistors in integrated circuits, they are classified as those with small, medium, large and very-large degree of integration.
According to Moore's Law, the number of transistors in the IC doubles in approximately 2 years (1.96). This law is illustrated by the evolution of Intel's microprocessors.
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Manufacturing of monolithic ICs
Monolithic ICs are built in layers on a silicon wafer and in a single technological process hundreds of ICs are produced simultaneously. All operations are performed in "clean rooms", where a low level of dust and impurities is maintained, which would damage the entire chip.
Planar process
Structure of the surface
Layers
he structure of IC is complex. It consists of many layers that are created sequentially in a certain plane in the so-called planar process. The planar process will be illustrated by the production of one MOS transistor, despite the fact that millions of transistors are produced simultaneously.
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Oxidation
SiO2
Substrate
Initially, a p-silicon substrate is covered with SiO2 by oxidizing at high temperature in pure oxygen medium. The resulting insulation layer protects the surface in subsequent operations.
Photolithography
UV light Mask
Photoresist
SiO2
Images on SiO2 are created by an operation called photolithography. A photosensitive layer – photoresist – is applied on the surface. A corresponding mask is used for each image. When irradiated with UV, the unprotected area of the photoresist is polarized, which changes its solubility.
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Etching
Window Window SiO2
The exposed (soluble) photoresist is removed with hydrofluoric acid. The operation is called etching. This opens a window to the silicon substrate in a shape determined by the mask. Subsequently, the remaining photoresist is removed.
Gate formation
Polysilicon Polysilicon UV light gate
Mask
A sequence of the same operations is used to form the next layer - oxidation, coating the oxidized surface with polysilicon, applying a photoresist, a second mask to form an image, irradiation with UV light and etching. As a result, two silicon windows are created. The remaining polysilicon serves as the gate of the transistor.
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Ion implantation
Сорс
Дрейн
Introduction of impurities in the windows open to silicon is performed with the doping operation. In this case, phosphorus or boron atoms are introduced into the substrate to create regions with N- or P-conductivity, respectively. The impurity atoms are ionized, accelerated and by bombarding the surface are implanted in it. This creates the drain and source areas.
Contacts
Contact holes
The same operations are used to form contact holes - oxidation of the entire surface, photolithography with a mask for the holes to the areas of the source, gate and drain and etching to remove the photoresist.
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Metallization Metal pads
Metal (aluminum) atoms are deposited on the entire surface, filling the contact holes. Photolithography with an appropriate mask is then used and, after etching, metal pads are formed to connect electrical conductors. The operation is called metallization.
Testing
During production, precise control of all operations is performed. The plates are tested with computer-controlled equipment in clean rooms, where staff have suits similar to those of astronauts.
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Assembling Gold wires
Contact pads
Wafer cutting Base for mounting
Transistors and integrated circuits are manufactured together with hundreds of neighbors on a single wafer. After testing the wafer, it is cut with diamond cutters and each IC is mounted in a metal, plastic or ceramic case. The chip is connected to the case with gold wires, which are pressed under pressure to the contact pads (the operation is called bonding).
Cases Types
Cases are essential for the effective isolation of IC from the environment and to facilitate its use and installation in electronic systems. Some of the most commonly used cases are shown in the figure.
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Bipolar Integrated Circuits
Diffusion furnace Silicon wafers
Bipolar ICs contain bipolar transistors and other passive components. They are produced in a common technological process, which covers a sequence of a larger number of operations compared to those required for the manufacturing of MOS integrated circuits.
Manufacturing of bipolar ICs
SiO2 Enlargement of the epitaxial layer Epitaxial Layer
Substrate Substrate
The plate (p pad) is placed in a furnace through which a gas of silicon atoms and donor impurities (P or As) is passed at high temperature. A thin layer of monocrystalline silicon (called the epitaxial layer) grows on the substrate. The process is called epitaxy. The plate is then coated by oxidation with a layer of SiO2 .
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Formation of the insulating island
Diffusion of р- impurities Each element is prepared in a separate island
SiO2 SiO2
Epitaxial layer Island
Substrate Substrate
Part of SiO2 is etched to reveal part of the epitaxial layer. The Si wafer is then placed in a furnace and atoms of acceptor impurities (B or Ga) enter the epitaxial layer by diffusion. This is how an n-type island is formed.
Formation of the base
Diffusion of р- impurities
SiO2
Island В C
Substrate
Oxidation, photolithography, etching and doping processes are used repeatedly to form different areas of the transistor. A window in the n-epitaxial layer is opened for the base and diffusion of acceptor impurities is performed.
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Formation of the emitter
Diffusion of n-impurities
SiO2 Е Islandl В C
Substrate
A window in the p-base is opened for the emitter and diffusion is performed with donor impurities to form an n-region.
Terminals
Е В C
View from above
Vertical cross section of the structure
The terminals for the emitter, base and collector are formed by metallization.
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Passive components
Simultaneously with the transistors, the passive components are formed, for which part of the operations are used, as shown in the figure. Because the processes are optimized to obtain good transistor parameters, this imposes limitations on the values of the passive elements.
Passive components
Passive components with large values of resistance and capacity occupy a significant area of the chip surface. For this reason, such resistors, capacitors and coils are usually not integrated.
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Isolation with PN junction
Al Metallization
Isolation with PN junction Substrate
The elements are interconnected by metal interconnections on the oxide. An inverse PN junction is used for their electrical insulation. For this purpose, the substrate is connected to the most negative voltage in the circuit. No current flows through the resulting depleted layer, which provides effective insulation.
Comparison of Bipolar and MOS ICs
MOS ICs are manufactured with a smaller number of operations than bipolar ICs.
MOS transistors are self-isolated from the substrate, while bipolar ICs require isolation for each element. For this reason, MOS ICs have a much higher scale of integration (they contain a larger number of transistors in the chip) than bipolar ones.
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Comparison of Bipolar and MOS ICs
In MOS technology, passive components take up much less space than in bipolar circuits. A depletion mode MOS transistor (with a built-in channel) can be used as a resistor, and the gate capacitance serves as a capacitor with a larger value per unit area.
For this reason, all modern ICs with an extremely high scale of integration (Ultra Large Scale of Integration – ULSI) use MOS technology.
Moor Law – for how long?
It was thought that Moore's law for CMOS would end at dimensions below 100 nm, because then more power would have to be dissipated in W/cm2 than that of a rocket nozzle. And the industry has declared this a lost battle. The solution was found with the invention of the FinFET transistor – a 3-D transistor structure.
Chenming Hu, Berkeley University
Each transistor has S, D, a conductive channel that connects them and G, which controls the current in the channel. In FinFET, the channel rises above the surface of the chip - like a shark's fin, allowing the gate to wrap around it on three sides, giving more control over the current. FinFET helps Moore's law stay in place for decades and not end at 25 nm, although his death is still regularly predicted.
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What is FinFET?
Planar 2-D transistor 3-D FinFET transistor https://www.youtube.com/watch?v=Jctk0DI7YP8
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