Question

The advantage of twin tub process in CMOS fabrication is ________.

• A. ensuring standard latch-up condition
• B. prevention of latch-up condition
• C. avoidance of post lithography etching
• D. overcoming short channel effects

Hint:

Twin-tub CMOS reduces latch-up risk by creating separate n-well and p-well regions for NMOS and PMOS transistors.

Answer 1

The Correct Option is B

Step 1: What is latch-up?
Latch-up is a condition in CMOS where a parasitic thyristor structure (PNPN) conducts heavily, potentially destroying the device.
Step 2: Understand Twin-tub process
The twin-tub (or twin-well) process:
- Creates both n-well and p-well on the same substrate.
- This allows independent optimization of NMOS and PMOS.
Step 3: Advantage of isolation
The separate wells reduce parasitic interactions between NMOS and PMOS transistors, minimizing the chances of forming a parasitic latch-up path.
Thus, the twin-tub process prevents latch-up by better isolation and layout control.
\[ \boxed{\text{Advantage: Prevention of latch-up condition}} \]