p–n junction isolation is a method used to electrically isolate
electronic component
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are mostly industrial products, available in a singular form and are not ...
s, such as
transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
s, on an
integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Large numbers of tiny ...
(IC) by surrounding the components with
reverse bias
Reverse or reversing may refer to:
Arts and media
* ''Reverse'' (Eldritch album), 2001
* ''Reverse'' (2009 film), a Polish comedy-drama film
* ''Reverse'' (2019 film), an Iranian crime-drama film
* ''Reverse'' (Morandi album), 2005
* ''Reverse'' ...
ed
p–n junction
A p–n junction is a boundary or interface between two types of semiconductor materials, p-type and n-type, inside a single crystal of semiconductor. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contains ...
s.
Introduction
By surrounding a transistor, resistor, capacitor or other component on an IC with semiconductor material which is doped using an opposite species of the substrate
dopant
A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optical properties. The amount of dopant necessary to cause changes is typically very low. When ...
, and connecting this surrounding material to a voltage which reverse-biases the
p–n junction
A p–n junction is a boundary or interface between two types of semiconductor materials, p-type and n-type, inside a single crystal of semiconductor. The "p" (positive) side contains an excess of holes, while the "n" (negative) side contains ...
that forms, it is possible to create a region which forms an electrically isolated "well" around the component.
Operation
Assume that the
semiconductor wafer
In electronics, a wafer (also called a slice or substrate) is a thin slice of semiconductor, such as a crystalline silicon (c-Si), used for the fabrication of integrated circuits and, in photovoltaics, to manufacture solar cells. The wafer serv ...
is
p-type material. Also assume a ring of
n-type material is placed around a transistor, and placed beneath the transistor. If the p-type material within the n-type ring is now connected to the
negative terminal of the power supply and the n-type ring is connected to the
positive terminal, the '
holes
A hole is an opening in or through a particular medium, usually a solid body. Holes occur through natural and artificial processes, and may be useful for various purposes, or may represent a problem needing to be addressed in many fields of en ...
' in the p-type region are pulled away from the p–n junction, causing the width of the
nonconducting depletion region
In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile ...
to increase. Similarly, because the n-type region is connected to the positive terminal, the electrons will also be pulled away from the junction.
This effectively increases the
potential barrier
In quantum mechanics, the rectangular (or, at times, square) potential barrier is a standard one-dimensional problem that demonstrates the phenomena of wave-mechanical tunneling (also called "quantum tunneling") and wave-mechanical reflection. ...
and greatly increases the
electrical resistance
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
against the flow of
charge carrier
In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes. The term is used ...
s. For this reason there will be no (or minimal)
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
across the junction.
At the middle of the junction of the p–n material, a
depletion region
In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile ...
is created to stand-off the reverse voltage. The width of the
depletion region
In semiconductor physics, the depletion region, also called depletion layer, depletion zone, junction region, space charge region or space charge layer, is an insulating region within a conductive, doped semiconductor material where the mobile ...
grows larger with higher voltage. The electric field grows as the reverse voltage increases. When the electric field increases beyond a critical level, the junction breaks down and current begins to flow by
avalanche breakdown
Avalanche breakdown (or avalanche effect) is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good ...
. Therefore, care must be taken that circuit voltages do not exceed the breakdown voltage or electrical isolation ceases.
History
In an article entitled "Microelectronics", published in ''
Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many famous scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it. In print since 1845, it i ...
'', September 1977 Volume 23, Number 3, pp. 63–9, Robert Noyce wrote:
"The integrated circuit, as we conceived and developed it at Fairchild Semiconductor in 1959, accomplishes the separation and interconnection of transistors and other circuit elements electrically rather than physically. The separation is accomplished by introducing pn diodes, or rectifiers, which allow current to flow in only one direction. The technique was patented by Kurt Lehovec at the Sprague Electric Company".
Sprague Electric Company
Sprague Electric Company was an electronic component maker founded by Robert C. Sprague in 1926.
Sprague was best known for making a large line of capacitors used in a wide variety of electrical and electronic in commercial, industrial and milit ...
engineer
Kurt Lehovec
Kurt Lehovec (June 12, 1918 – February 17, 2012) was one of the pioneers of the integrated circuit. While also pioneering the photo-voltaic effect, light-emitting diodes and History of the battery#Invention, lithium batteries, he innovated ...
filed for p–n junction isolation in 1959, and was granted the patent in 1962. He is reported (during his lectures on semiconductor memory cells) to have said "I never got a dime out of it
he patent" However, I T Histor
stateshe was paid (''pro forma'') at least one dollar for what is possibly the most important invention in history, as it also was instrumental in the invention of the
LED
A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
and the
solar cell
A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon. , both of which
Lau Wai Shing
Lau Wai Shing (; born 29 July 1955 in Hong Kong), also known as Wai Shing Lau or Michael Lau, is a Hong Kong electrical engineer and materials scientist. He worked on both Si-based and III-V based microelectronics.
Biography
Lau was born in Hong ...
says Lehovec als
pioneeredthe research of.
When
Robert Noyce
Robert Norton Noyce (December 12, 1927 – June 3, 1990), nicknamed "the Mayor of Silicon Valley", was an American physicist and entrepreneur who co-founded Fairchild Semiconductor in 1957 and Intel Corporation in 1968. He is also credited wit ...
invented the
monolithic integrated circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, usually silicon. Transistor count, Large ...
in 1959, his idea of p–n junction isolation was based on Hoerni's planar process.
In 1976, Noyce stated that, in January 1959, he did not know about the work of Lehovec.
See also
*
LOCOS
LOCOS, short for LOCal Oxidation of Silicon, is a microfabrication process where silicon dioxide is formed in selected areas on a silicon wafer having the Si-SiO2 interface at a lower point than the rest of the silicon surface. As of 2008 it was ...
*
Shallow trench isolation
Shallow trench isolation (STI), also known as box isolation technique, is an integrated circuit feature which prevents electric current leakage between adjacent semiconductor device components. STI is generally used on CMOS process technology no ...
References
{{DEFAULTSORT:P-n junction isolation
Semiconductor structures
Integrated circuits
Czech inventions