The increasing adoption of digitization coupled
with enhanced connectivity is rapidly accelerating the demand for modern
electronics. The global consumer electronics market size was valued at over USD1
trillion and is anticipated to grow at a CAGR of 8% from
2021 to 2027 with increasing internet penetration. All modern electronics
require semiconductors that sit in the heart of integrated circuits and
specialized components, from the smartphone in your pocket to cutting-edge
vehicles. Made using raw materials such as silicon, germanium, and other pure
materials, semiconductor lies between a conductor and an insulator to manage
and control current flow in electronics.
Rapidly increasing appetite for consumer
electronics, expansion of 5G, and advancements in technology are exploding the
demand for processors. According to International Data Corporation
(IDC), the global semiconductor market is expected to reach a value
of USD600 billion by 2025. Currently, there is a huge global
shortage of semiconductors due to supply chain shortages and a sudden spike in
the usage of electronics since the pandemic. The semiconductor industry is
substantially ramping up its fab capacity utilization to meet the growing
demand for chips.
Semiconductor manufacturing is a costly, complex,
and highly disciplinary procedure which involves physics, chemistry,
electricity, metallurgy, and more. Manufacturing chips is one of the most
R&D- and capital-intensive manufacturing processes on earth. Around 1400 process
steps are involved in the overall manufacturing of just the semiconductor
wafers alone, and each phase includes the use of a variety of highly
sophisticated tools and machines. On average, manufacturing a semiconductor
wafer takes up to 12 weeks, whereas a finished chip can
require 26 weeks.
From Silicon to Semiconductor: An Overview
A semiconductor chip is an electric circuit built
up in a series of nanofabrication processes performed on the surface of
substrates (wafers) composed of highly pure single crystal silicon. The
production of a microchip involves adding impurities to the base element in a
process called “doping” to adjust the conductance or inductance of the outcome,
based on the type and intensity of impurities added. Here are the seven crucial
steps involved in the manufacturing of semiconductors.
·
Cleaning
Silicon wafers forming the base of the microchip
are cleaned by a solvent and followed by a deionized water (DI) rinse and
blow-dry. This is the first and most crucial step of semiconductor
manufacturing, as even slight contamination can cause defects in the circuit.
Generally, chemical agents remove the contamination, varying from ultra-fine
particles to minute amounts of metallic residues generated during the
production process or natural oxide layer formed due to air exposure. The final
wafer cleaning step involves a Hydrofluoric Acid dip for two minutes to remove
the silicon oxide layer. Then, the wafer is put under running DI water, and a
wettability test is conducted to confirm whether the cleaning was successful or
needed more. If the water turns into little beads and rolls off, then the
wafers are considered good to go for further processing.
The semiconductor chip manufacturing process
initiates with a silicon wafer. Wafers are sliced from a salami-shaped bar made
of 99.99% pure silicon and polished until they become highly
smooth. Depending on the type of structure being created, thin films of
dielectric (insulating) and metal (conducting) materials are deposited on the
wafer surface to build a microchip. This process is known as deposition. There
are multiple ways to perform deposition: sputtering, electrodeposition, chemical
vapor deposition, and thermal deposition. The kind of technique
used for deposition depends upon the process node, type of chip, and the amount
of time needed to do the deposition.
Sputtering involves the bombarding of ions on the
target materials, which knocks off atoms and molecules that are further
deposited on the wafer surface. Electrodeposition is used to form copper wire
layers. In contrast, chemical vapor deposition includes special gases that
cause a chemical reaction to generate molecules that are then deposited on the
wafer surface to form a film. Thermal oxidation includes heating up of wafer to
form a silicon oxide film on the wafer surface.
The semiconductor wafer is covered with a
light-sensitive coating called ‘photoresist’ or ‘resist’ that blocks everything
not meant to be exposed to ultraviolet light. The resist coating can be
positive or negative, depending upon the chemical structure of the material and
the way that the resist reacts with light. With positive resist, the area
exposed to light changes its structure, whereas with negative resist, the areas
hit by light polymerize and become more difficult to dissolve. Generally, a
positive resist is used in semiconductor manufacturing due to its higher
resolution capabilities. It is crucial to have a resist coating method to have
a uniform coating of photoresist over the surface of the substrate. Several
options available for resist coating include spin coating, spray coating, dip
coating, inkjet printing, and slot-die coating.
Lithography is a crucial step in the chipmaking
process which involves transferring patterns of geometric shapes in a mask to a
thin layer of radiation-sensitive material called resist. This process
determines just how small the transistors on the chips can be. The geometric
shapes and patterns on a semiconductor make up the complex structures that
allow dopants to complete a circuit to fulfill a technological purpose. During
this process, the semiconductor wafer is inserted into a lithography machine,
where it is exposed to deep UV lights to produce the finest details of a chip.
The light projected through the ‘reticle’ causes a chemical change that enables
the pattern to be replicated on the resist. A complementary
metal-oxide-semiconductor (CMOS) wafer can undergo the photolithographic cycles
as many as 50 times.
The etching process is used to eliminate the
degraded resist to reveal the intended pattern. During this procedure, the
wafer is baked and developed. A developer is sprayed on the water, which
dissolves the areas exposed to the light and reveals a 3D pattern of open
channels. Etching process can be done in two ways, wet etching and dry etching.
During wet etching, the exposed thin film on the surface layer is dissolved using
chemicals such as hydrofluoric or phosphoric acid, which is then later removed.
In dry etching, the wafer is exposed to dry gases with ionized atoms to remove
the film layer. Etching must be done in a way that it precisely and
consistently forms increasingly conductive features and does not hinder the
integrity and stability of the chip. Advanced etch technology enables
semiconductor manufacturers to use double, quadruple, and spacer-based
patterning to create tiny features.
This step involves the implantation of impurities
to provide the silicon substrate semiconducting properties. Generally,
impurities such as phosphor, arsenic, or boron are implanted in the wafers that
are shot into the wafer in a bullet-like fashion. Sacrificial films prevent the
ions from being shot at the unwanted places of the wafer. Directing
electrically charged ions (positive or negative) into the silicon crystal
controls the flow of electricity and allows the creation of transistors. After
this procedure, the remaining sections of resist are not etched or
ionized.
Packaging is a crucial part of semiconductor
manufacturing and design as it can affect the power, performance, and cost on a
macro level and functionality on a micro level. The semiconductor wafer is
sliced and diced with a diamond saw to get the individual chips out of the
wafer. Semiconductor chips are cut from the wafer and are referred to as
‘dies,’ which can vary in different sizes. The chip die is placed into a
substrate, a type of baseboard that uses metal foils to direct the input and
output signals of a chip to other parts of the system. A heat spreader is
placed on the top of the lid to ensure that the microchip stays cool during
operation.
The microchip becomes ready to be used in
electronic equipment such as smartphones, TV, tablets, or other devices.
Although the semiconductor’s size is less than a thumb, one chip can contain
billions of transistors that power up your device.
Silicon wafers are manufactured at fabrication plants
that are often termed as fab or foundry. Fabs require high investments to
function, and most of these are located across Asia, mainly in Taiwan.
Semiconductor foundries are at the core of modern-day society as every
electronic equipment that we use today is made from chips. Fabs are rapidly
increasing in number worldwide to solve the global shortage of microchips and fulfil
the expanding demand for electronic units. With the growth of IoT, the demand
for microchips will expand further, which will highly impact the growth of the
semiconductor foundry industry.
How is USA overcoming its microchip shortage?
The semiconductor shortage in the USA due to supply
chain issues and geopolitical rivalry with China has led to calls for more chip
production within the country. As USA resets to post-pandemic life, the
semiconductor problem has been aggravating, affecting automaker industry
drastically. Since microchips have become the brains of modern society, being a
crucial component of so many strategic technologies-from renewable energy to
artificial intelligence to cybersecurity-their manufacturing has become the
focus of economic planning. In June 2021, USA’s Senate passed a bipartisan bill
with USD52 billion in funding to increase the domestic microchip production and
expand R&D efforts to become a global champion in semiconductor manufacturing.
In 1990, around 37% of chips were manufactured in
the USA, however that number declined to 12% in 2020 as the semiconductor
manufacturing industries proliferated in Asian countries like Taiwan, South
Koreas, and China. In March, Intel announced a plan for USD20 billion expansion
of its factory, whereas Taiwan Semiconductor Manufacturing Company (TSMC) is currently
building a new factory, which is estimated to cost around USD10-12 billion in
Arizona for semiconductor chip production. Additionally, Apple, Tesla,
Facebook, Baidu are all bringing certain aspects of in-house chip development
to decrease reliance on microchip imports.