Wafer fabrication
Encyclopedia
Wafer fabrication is a procedure composed of many repeated sequential processes to produce complete electrical or photonic
circuits
. Examples include production of radio frequency (RF
) amplifiers, LED
s, optical computer components, and CPU
s for computer
s. Wafer fabrication is used to build components with the necessary electrical structures.
The main process begins with electrical engineers designing the circuit and defining its functions, and specifying the signals, inputs, outputs and voltage
s needed. These electrical circuit specifications are entered into electrical circuit design software, such as SPICE
, and then imported into circuit layout programs, which are similar to ones used for computer aided design. This is necessary for the layers to be defined for wafer mask production. The resolution of the circuits increases rapidly with each step in design, as the scale of the circuits at the start of the design process is already being measured in fractions of micrometers. Each step thus increases circuit density for a given area.
The silicon wafers start out blank and pure. The circuits are built in layers in clean rooms. First, photo-sensitive resistance patterns are photo-masked in micrometer detail onto the wafers' surface. The wafers are then exposed to short-wave ultraviolet
light and the unexposed areas are thus etched away and cleaned
. Hot chemical vapor
s are deposited on to the desired zones and baked in high heat
, which permeate the vapors into the desired zones. In some cases, ions, such as O2+ or O+, are implanted in precise patterns and at a specific depth by using RF-driven ion sources.
These steps are often repeated many hundreds of times, depending on the complexity of the desired circuit and its connections.
New processes to accomplish each of these steps with better resolution and in improved ways emerge every year, with the result of constantly changing technology in the wafer fabrication industry. New technologies result in denser packing of minuscule surface features such as transistors and micro-electro-mechanical systems (MEMS). This increased density continues the trend often cited as Moore's Law
.
A fab is a common term for where these processes are accomplished. Often the fab is owned by the company that sells the chips, such as AMD, Intel, Texas Instruments
, or Freescale. A foundry is a fab at which semiconductor chips or wafers are fabricated to order for third party companies that sell the chip, such as fabs owned by Taiwan Semiconductor Manufacturing Company (TSMC), United Microelectronics Corporation
(UMC) and Semiconductor Manufacturing International Corporation
(SMIC).
Photonics
The science of photonics includes the generation, emission, transmission, modulation, signal processing, switching, amplification, detection and sensing of light. The term photonics thereby emphasizes that photons are neither particles nor waves — they are different in that they have both particle...
circuits
Electrical network
An electrical network is an interconnection of electrical elements such as resistors, inductors, capacitors, transmission lines, voltage sources, current sources and switches. An electrical circuit is a special type of network, one that has a closed loop giving a return path for the current...
. Examples include production of radio frequency (RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
) amplifiers, LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s, optical computer components, and CPU
Central processing unit
The central processing unit is the portion of a computer system that carries out the instructions of a computer program, to perform the basic arithmetical, logical, and input/output operations of the system. The CPU plays a role somewhat analogous to the brain in the computer. The term has been in...
s for computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s. Wafer fabrication is used to build components with the necessary electrical structures.
The main process begins with electrical engineers designing the circuit and defining its functions, and specifying the signals, inputs, outputs and voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
s needed. These electrical circuit specifications are entered into electrical circuit design software, such as SPICE
SPICE
SPICE is a general-purpose, open source analog electronic circuit simulator.It is a powerful program that is used in integrated circuit and board-level design to check the integrity of circuit designs and to predict circuit behavior.- Introduction :Unlike board-level designs composed of discrete...
, and then imported into circuit layout programs, which are similar to ones used for computer aided design. This is necessary for the layers to be defined for wafer mask production. The resolution of the circuits increases rapidly with each step in design, as the scale of the circuits at the start of the design process is already being measured in fractions of micrometers. Each step thus increases circuit density for a given area.
The silicon wafers start out blank and pure. The circuits are built in layers in clean rooms. First, photo-sensitive resistance patterns are photo-masked in micrometer detail onto the wafers' surface. The wafers are then exposed to short-wave ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light and the unexposed areas are thus etched away and cleaned
RCA clean
The RCA clean is a standard set of wafer cleaning steps which needs to be performed before high temp processing steps of silicon wafers in semiconductor manufacturing. RCA cleaning includes RCA-1 and RCA-2 cleaning procedures...
. Hot chemical vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical point....
s are deposited on to the desired zones and baked in high heat
Heat
In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...
, which permeate the vapors into the desired zones. In some cases, ions, such as O2+ or O+, are implanted in precise patterns and at a specific depth by using RF-driven ion sources.
These steps are often repeated many hundreds of times, depending on the complexity of the desired circuit and its connections.
New processes to accomplish each of these steps with better resolution and in improved ways emerge every year, with the result of constantly changing technology in the wafer fabrication industry. New technologies result in denser packing of minuscule surface features such as transistors and micro-electro-mechanical systems (MEMS). This increased density continues the trend often cited as Moore's Law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
.
A fab is a common term for where these processes are accomplished. Often the fab is owned by the company that sells the chips, such as AMD, Intel, Texas Instruments
Texas Instruments
Texas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
, or Freescale. A foundry is a fab at which semiconductor chips or wafers are fabricated to order for third party companies that sell the chip, such as fabs owned by Taiwan Semiconductor Manufacturing Company (TSMC), United Microelectronics Corporation
United Microelectronics Corporation
UMC was founded as Taiwan's first semiconductor company in 1980 as a spin-off of the government-sponsored Industrial Technology Research Institute .-Overview:...
(UMC) and Semiconductor Manufacturing International Corporation
Semiconductor Manufacturing International Corporation
Semiconductor Manufacturing International Corporation, is a semiconductor foundry in mainland China, providing integrated circuit manufacturing services at 350 nm to 45nm technologies...
(SMIC).