A fab plant manufactures Integrated Circuits (ICs) by working on raw wafers through a complex process. The manufacturing involves 500 machines. There are some 700-1500 processes, some of which require heating to 1100 degree centigrade, at times as many as 27 times. The process requires 300 plus gases, and chemicals such as acetone. Many of the inputs depend on imports as these are not made in India. A fab plant requires a minimum investment of $3-4 billion.
The raw material most commonly used is silicon. Some materials are combination of elements –compound semiconductors. These materials are gallium nitride and silicon carbide. These are more heat resistant and compact. The material plants are set up with an investment of an investment below $500 million.
There are different kinds of chip makers. Some are called IDMs — integrated device manufacturers. Samsung and Intel too both design and manufacture chips. Some manufacturers are foundries — they make chips under contract for others, e.g. TSMC. Some organisations are fabless firms — they only design the chips, e.g. Qualcomm, Media Tek and Nvidia. These designers then get them manufactured by foundries.
Stages of Making a Chip
To begin with, wafers are carved out from a salami-shaped bar of 99.99 per cent pure silicon. These are polished to ensure smooth texture. The films of conducting materials are deposited on the wafer.
The second step is to cover the wafers with a light-sensitive coating (photo resist). Those areas which are exposed to UV light change their structure. Thus they become ready for etching.
As a third step, these are put through a lithography machine. It decides just how small the transistor on a chip could be.
As a fourth step, the wafer is etched. It is then baked to reveal the 3D pattern of open channels. It creates a cavity in the wafer with exact depth. Lastly, the wafer is subjected to bombing with ions to facilitate the control of the flow of electricity.
There are two models after this. Foundries or IDMs might do the few processes left themselves or they can outsource to third parties to reduce the investment.
The player involved is outsourced semiconductor assembly and test (OSAT) who do the assembly, packing and testing of the ICs for others. There are companies such as Micro which can set up an assembly, testing, marking and packaging (ATMP) operation. Micron can use its own fabs produced abroad. The chips are then taken out of the wafer, sliced and diced with a diamond saw. These become individual chips.
Wafers can contain a few chips or thousands of chips.
IC packaging is also done — wire bonding and laser marking. The wafers and ICs are tested.
Types of Chips
First there are logic chips.They process information to complete a task. These are used to optimize visual display. They also do processing of ML and deep learning apps. They also act as processors in CPUs.
Secondly, there are memory chips used to store information and save data when machines are switched on and also when they are off.
Thirdly, there are application specific ICs. They are single purpose chips used for repetitive, routine processing.
Lastly, there are chips which carry a system on them. These integrate and combine many chips and circuits into one chip, e.g. a camera, video or Wi-Fi.
Chip Designers
Companies such as Qualcomm, Medi Tek design the chip and get it made by the foundries.
Some Comments
Initially, there will be limited buyers for wafers of any fab plant in India. There are hardly any companies in India which can place orders. India lacks fabless design companies such as Qualcomm to place orders. India must have a foreign partner who can buy back and offtake agreement with the fab company.
Fab plant requires complex technology. However, it is not enough to pay and get technology and drawings to make a fab plant. There should be desirable yields — the total number of chips produced to the maximum chip count on one wafer, ideally it should be 90-95 per cent.
Fabless design companies are ready to buy provided the prices are competitive and the quality is on par with other foreign firms.
Some IDM players can make their own design and fabricate the chips in their own fab plants. However, big IDMs have not shown much interest in India.
Micron is ready to shift its ATMP functions to India to test wafers. Its global plants will import the wafers at agreed transfer price.
Some experts suggest India should have compound semiconductor plants (based on gallium nitride or silicon carbide, rather than pure silicon). These require investments of $100 million-$500 million. But these can be built quickly and have a growing market in automobiles, telecom and power electronics.