Advanced transistors (FinFET and GAA)

Which correctly describes the gate-last (replacement metal gate) process?

  1. AThe metal gate is made first, and then all high-temperature steps are performed
  2. BThe transistor is first formed with a dummy gate, and after high-temperature steps the dummy is removed and replaced with a metal gate
  3. CA transistor without a gate is made
Show answer and explanation

Answer: B. The transistor is first formed with a dummy gate, and after high-temperature steps the dummy is removed and replaced with a metal gate

High-temperature steps such as source/drain activation annealing can degrade high-k films and metal gates. In gate-last, the high-temperature steps are completed with a dummy gate such as polysilicon, after which the dummy is removed and the high-k film and metal gate are filled in.

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More Advanced transistors (FinFET and GAA) questions

  1. What is an advantage of fully depleted SOI (FD-SOI) transistors?
  2. In very small transistors, what is the phenomenon called in which the threshold voltage varies because of statistical variation in the number and positions of dopant atoms in the channel?
  3. Compared with FinFETs, what is a design advantage of nanosheet GAA transistors?
  4. Which technique, used to make the thin fins of FinFETs, uses sidewall spacers to create patterns finer than the lithography limit?
  5. In manufacturing nanosheet GAA transistors, why is only the SiGe selectively removed from stacked alternating Si and SiGe layers?