What is a semiconductor fab
A semiconductor fab, short for fabrication plant, is the specialised factory where silicon wafers are turned into finished microchips through hundreds of precise chemical and physical steps carried out in an ultra-clean environment. Fabs are among the most expensive and complex facilities humans build, which is why the Tata Electronics and PSMC fab at Dholera, a Rs 91,000 cr (about US$11B) plant with a target of up to 50,000 wafers per month, is such a significant project for India.
What a fab does
A fab is where the physical chip is made. It takes a blank, polished disc of ultra-pure silicon, called a wafer, and builds circuits onto its surface layer by layer. The process is subtractive and additive at once. Thin films of conducting, insulating and semiconducting material are deposited, patterns are printed onto them using light, and unwanted material is etched away, over and over, until a complete three-dimensional circuit exists on the wafer. A single wafer can carry hundreds of identical chips, and a leading-edge chip may require several hundred separate process steps and take weeks to move through the line. The fab is only the front end of the story. After the wafer is finished it goes to a separate assembly and test operation, often called OSAT, where individual chips are cut out, packaged and tested. The fab handles the delicate business of creating the transistors and wiring at nanometre scale.
Why fabs are so expensive
A modern fab is one of the most capital-intensive facilities in any industry. A single advanced plant can cost billions of dollars, and the Dholera fab carries a reported investment of Rs 91,000 cr, about US$11B. The cost comes from several places at once. The cleanroom itself, with its air filtration, vibration isolation and utility systems, is enormously expensive to build. The process tools, especially the lithography systems that print the circuit patterns, are among the most sophisticated machines ever made and cost tens of millions of dollars each. On top of that, a fab consumes vast quantities of ultrapure water, specialty gases, chemicals and electricity, all delivered to exacting standards. Because these fixed costs are so high, a fab has to run at high utilisation to be economical, which is why capacity numbers like Dholera's up to 50,000 wafers per month matter so much. The India Semiconductor Mission covers 50 percent of eligible cost for approved fabs precisely because the upfront bill is so heavy.
Inside a fab: the cleanroom
The heart of a fab is its cleanroom, a sealed environment where the air is filtered to remove almost all dust particles. This matters because the features on a chip are far smaller than a speck of dust, so a single stray particle landing on a wafer at the wrong moment can ruin the chips beneath it. Air is pushed down from the ceiling through high-efficiency filters and drawn out through the floor, so contaminants are constantly swept away. Staff wear full coverall suits, often called bunny suits, not to protect themselves but to stop skin flakes, hair and fibres from reaching the wafers. Temperature, humidity and vibration are all tightly controlled, because even tiny changes can throw off the precision steps. Much of the wafer handling is automated, with wafers travelling between tools in sealed carriers along overhead tracks, so human contact is minimised. The cleanroom fit-out is one of the final and most demanding stages of building a fab, and at Dholera this stage is reported to be underway in 2026.
The main process areas
A fab is organised around a handful of repeated operations, each with its own dedicated equipment. Deposition lays down thin films of material onto the wafer. Lithography coats the wafer with a light-sensitive layer and projects a circuit pattern onto it, defining where features will be. Etching removes material where it is not wanted, transferring the printed pattern into the film below. Ion implantation and diffusion introduce the dopant atoms that give silicon its electrical behaviour. Chemical mechanical planarisation polishes the wafer flat between layers so the next layer can be built accurately. Cleaning and inspection happen constantly between steps. These operations are not done once but repeated dozens of times, because a chip is built up as many stacked layers, first the transistors themselves and then the metal wiring that connects them. The order and recipe of these steps is the fab's core intellectual property, which is why partnering with an experienced foundry like PSMC matters at Dholera.
Front end and back end
The industry splits chip making into two broad halves. The front end of line is everything that happens inside the fab on the whole wafer, creating the transistors and the wiring. The back end, handled in assembly and test facilities known as OSAT, is where the finished wafer is cut into individual chips, each is placed into a protective package with electrical connections to the outside world, and every chip is tested to confirm it works. A fab and an OSAT are different kinds of facility with different skills, cleanliness needs and cost structures. A country building a chip ecosystem usually needs both, along with suppliers of materials, gases, chemicals and equipment maintenance. Dholera's strategy reflects this, with the large Tata fab as the anchor and a broader cluster forming around it, including two additional semiconductor units cleared on 5 May 2026, one in Dholera and one in Surat, worth over Rs 3,900 cr combined.
What a fab needs from its location
A fab is picky about where it sits, which explains why sites are chosen carefully and supported by heavy infrastructure. It needs a large, stable supply of electricity, because a fab runs continuously and a power interruption can spoil wafers worth a great deal. It needs enormous volumes of water, purified to ultrapure standards, along with the ability to treat and recycle wastewater. It needs excellent logistics for moving delicate equipment and materials in and finished wafers out, which is where an expressway, airport and rail link become relevant. It needs a workforce of engineers and technicians, so proximity to talent and training matters. Dholera was planned as a greenfield industrial smart city with trunk utilities, a dedicated solar park, an expressway operational since 31 Mar 2026, an airport with its first trial landing on 4 Jun 2026, and a semi-high-speed rail cleared in May 2026, all of which are the kind of enabling backbone a fab depends on.
FAQ
What does fab stand for?
Fab is short for fabrication plant, the factory where silicon wafers are processed into microchips. The name distinguishes the wafer-processing facility from the later assembly and test operation. People also call it a wafer fab or simply a fabrication facility.
Why does a fab need a cleanroom?
Chip features are far smaller than a speck of dust, so a single stray particle can ruin the chips it lands on. A cleanroom filters the air to remove almost all particles, controls temperature, humidity and vibration, and requires staff to wear full coverall suits. This keeps contamination away from the wafers during the hundreds of process steps.
How is a fab different from an OSAT?
A fab performs the front-end work, building transistors and wiring onto whole silicon wafers. An OSAT performs the back-end work, cutting the finished wafer into individual chips, packaging each one and testing it. They are separate facilities with different skills and cost structures, and a full chip ecosystem usually needs both.
Why are fabs so expensive to build?
Costs come from the cleanroom itself, the extremely sophisticated process tools such as lithography systems, and the demanding supply of ultrapure water, gases, chemicals and continuous power. The Dholera fab carries a reported investment of Rs 91,000 cr, about US$11B, and the India Semiconductor Mission covers 50 percent of eligible cost for approved fabs.
What is the Dholera fab's capacity?
The Tata Electronics and PSMC fab at Dholera is designed for up to 50,000 wafers per month on 300 mm wafers, which puts it in the high-volume tier. High utilisation matters because a fab's fixed costs are enormous whether it runs full or half empty.