FAB, Bring-Up, and Post-Silicon - How Does the Chip Come to Life?

We’ve come a long way:

• Designed the chip
• Wrote RTL
• Did Verification
• Performed Synthesis
• Went through Place & Route
• Approved STA
• Did Tapeout

And the chip left our hands.

Now it’s at the manufacturing plant - the FAB.

This is the last and most exciting stage:

Turning the design into actual hardware.

What Is a FAB?

FAB = Fabrication Facility Or: chip manufacturing plant.

These are enormous facilities where:

• Chips are manufactured from pure silicon
• The world’s most advanced equipment is used
• Work is done in rooms cleaner than operating rooms
• Billions of dollars are invested in processes

FAB is where the design becomes actual atoms.

How Does the Manufacturing Process Work?

1. Creating the Masks

The GDSII sent at Tapeout becomes physical masks.

Each layer in the chip:

• Needs its own mask
• The mask determines where there will be material and where not
• The Photolithography process uses light to create patterns

A modern chip requires dozens of masks.

2. Creating the Wafer (Silicon Disc)

Take:

• A large silicon disc (300mm diameter in modern processes)
• Place thin layers of materials on it
• Use masks to create patterns
• Repeat the process dozens of times

In the end, you get a Wafer with hundreds (sometimes thousands) of identical chips.

3. Dicing (Cutting)

After the Wafer is ready:

• Cut it into individual chips
• Test each chip to see if it’s functional
• Failed chips are discarded
• Functional chips move to the next stage

Yield - how many functional chips there are - is critical for costs.

4. Packaging

The small chip:

• Receives an external casing
• Is connected to pins allowing connection to a system
• Is tested again
• And packaged for shipping

This is the final chip that arrives to customers.

How Long Does the Manufacturing Process Take?

• Old processes (28nm and above): About a month
• Advanced processes (7nm, 5nm, 3nm): 2-3 months
• Especially complex processes: Up to 4 months

After Tapeout, you wait months until receiving the first chips.

First Silicon - The First Samples

After all the waiting, the first samples arrive:

First Silicon The first chips manufactured from the factory.

This is an exciting and stressful moment simultaneously:

• Will the chip even work?
• Are there bugs we missed?
• Are the timings correct?
• Are the performance metrics as planned?

In most cases - there are some issues.

Bring-Up - First Power-On

Bring-Up is the process where:

1. Connect the chip for the first time
2. Power it on
3. Check if it’s “alive”
4. Run test software
5. Try different interfaces
6. Ensure it responds

This is a moment of truth.

If the chip doesn’t work at all - there’s a big problem. If it works partially - need to find what’s wrong. If it works as planned - it’s great joy.

Post-Silicon Validation - Testing on the Actual Chip

After Bring-Up passed:

Deep testing begins:

• Functional tests: Does each unit work?
• Performance tests: Is the chip as fast as planned?
• Power consumption tests: Does it consume energy as expected?
• Reliability tests: Is it stable over time?
• Temperature tests: How does it behave at high heat?

This is the final Validation stage.

What Happens If There Are Bugs?

Usually bugs are discovered at the Post-Silicon stage.

There are several options:

1. Software Fix

If the bug can be worked around in code - do a Workaround.

2. Firmware Fix

Sometimes things can be fixed at the microcode or settings level.

3. Respin - Another Tapeout

If the bug is severe - need to do a new Tapeout.

It’s expensive and takes time, but sometimes there’s no choice.

4. Release Anyway

If the bug doesn’t affect most users - sometimes the chip is released with notes.

What Happens After the Chip Works?

After all tests pass:

1. Mass production begins
2. The chip goes to market
3. Is integrated into products
4. Reaches customers

And the chip begins its real life.

An Analogy to Clear Things Up

Think about launching a rocket:

FAB: Building the rocket at the factory.

First Silicon: The rocket arrived at the launch site.

Bring-Up: Engine ignition for the first time.

Post-Silicon: Checking all systems work before actual launch.

Mass production: Launching rockets regularly.

Summary

FAB, Bring-Up, and Post-Silicon are:

• The physical manufacturing process of the chip
• The moment when the design becomes actual hardware
• First power-on and final testing
• Discovering bugs not caught in simulation
• Final confirmation the chip is ready for market

This is the last stage in the long journey of creating a chip.

From initial idea, through RTL, Synthesis, Place & Route, Tapeout - to an actual physical chip working in billions of devices worldwide.

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This is the “Chip Design Journey” series - a complete journey from idea to manufacturing. In the summary post, we’ll review all stages together and see the complete picture.