What Is A Fab?
In the world of electronics, a fab refers to a fabrication facility. This is a specialised factory that manufactures semiconductors. Fabs manufacture semiconductor devices, most commonly integrated circuits (ICs) like computer processors, memory chips, and microcontrollers.
These facilities are expensive to build and operate and require strictly controlled environments to avoid contamination, even at the microscopic level.
How Does A Fab Work?
Manufacturing silicon-based ICs in a fab is a highly complex process, but here is a simplified overview of the steps that take place within a fab:
- Design And Mask Making: The groundwork starts with engineers crafting the blueprint for the chip. This design is then translated into a photomask, essentially a high-resolution stencil containing the intricate circuit patterns.
- Wafer Prep And Oxidation: Ultra-pure silicon ingots are grown using Czochralski growth (CZ) and sliced into thin wafers. These wafers undergo a high-temperature oxidation step to grow a thin layer of silicon dioxide (SiO2) on the surface. This oxide layer serves as an insulator and plays a crucial role in transistor formation.
- Lithography And Patterning: A layer of light-sensitive photoresist is deposited on the wafer. Then, the photomask is aligned and UV light is shone through its transparent areas. This light exposure alters the chemical properties of the photoresist, making the exposed regions either soluble or hard depending on the type of photoresist used. This creates the desired circuit pattern on the photoresist.
- Etching: The wafer is then dipped into an etching solution that selectively removes either the exposed or unexposed photoresist. This essentially ‘etches’ the circuit pattern onto the underlying oxide or silicon layer, depending on the desired outcome.
- Deposition And Doping: Materials like silicon nitride, polysilicon or metals are deposited onto the wafer using techniques like Chemical Vapor Deposition (CVD) or Physical Vapor Deposition (PVD). Specific regions are then ‘doped’ by introducing carefully controlled impurities to alter the electrical conductivity of the silicon. This doping creates p-type and n-type regions, the building blocks of transistors.
- Metallisation And Interconnects: Metal layers are deposited to form the electrical pathways (interconnects) that connect various circuit elements on the chip.
- Chemical-Mechanical Polishing (CMP): After each layer deposition or etch step, the wafer surface is meticulously polished using a CMP process to achieve a perfectly flat and smooth topography for subsequent layers.
- Repeat And Refine: These core processes (lithography, etch, deposition, and doping) are repeated numerous times, meticulously building up the intricate layers of the circuit with incredible precision.
- Testing And Packaging: Once the final layer is formed, the wafer undergoes rigorous electrical testing to identify and isolate any malfunctioning circuits. The wafer is then diced into individual chips, which are encapsulated in protective packages to shield them from the environment and provide connections for external circuitry.
Are Fabs Expensive To Set Up?
Fabs are incredibly expensive to set up and operate because of the following factors:
- High-Tech Equipment: Fabs rely on a vast array of sophisticated machinery. These include photolithography scanners that cost tens or even hundreds of millions of dollars each, along with complex deposition and etching tools.
- Cleanroom Construction: Maintaining an ultra-clean environment is paramount in a fab. Building and maintaining specialised clean rooms with air filtration systems and controlled temperature/humidity require significant investment.
- Research & Development: The semiconductor industry is constantly evolving. Developing advanced fabrication processes and staying at the forefront of technology demands continuous research and development efforts, adding to the cost.
- Skilled Workforce: Operating a fab requires a highly trained workforce with expertise in various disciplines like physics, chemistry, and engineering. Attracting and retaining this talent pool contributes to the overall expense.
Cost Estimates: Providing a single cost figure is difficult because fab complexity varies. However, estimates for a new fab can range anywhere from:
- $1 Bn: For a basic fab producing less advanced chips.
- $3-4 Bn: This is a more typical range for a modern fab with mid-range capabilities.
- $10 Bn+: Cutting-edge fabs pushing the boundaries of chip technology can cost significantly more.
The costs can vary significantly, depending on the location, fab size and capacity and the type of chips produced.
Which Are Some Of The Largest Fabs In The World?
According to Blackridge Research, Taiwan-based TSMC boasts the world’s largest fabs, making it the largest chipmaker globally. Further, seven of the ten largest chipmakers and fabs are in the United States. These include the likes of Intel, Qualcomm, Micron, Nvidia, Broadcom, AMD and Texas Instruments.
All of these fabs have different production priorities. For instance, Intel produces silicon chips, including CPUs, GPUs, wireless products, and server products. On the other hand, Qualcomm produces chips for smartphones.
Which Are Some Indian Companies Developing Fabs?
This February, India approved an allocation of up to $15.2 Bn (INR 1,260 Cr) to build three new semiconductor plants, including the country’s first semiconductor fab facility. This facility is being set up by the Tata Group and Taiwan’s Power Chip in the Dholera region of Gujarat.
The fab facility expects to have the capacity to produce 50,000 wafers per month, and it aims to manufacture 3 Bn chips annually for a variety of market segments, including high-power computers, electric vehicles, telecom and power electronics.
Alongside the fab, the Indian government also approved the investment of $3.2 Bn in a semiconductor assembly, testing, marking and packaging unit planned to be set up in Assam by Tata Semiconductor Assembly and Test.
