Why do we use polysilicon gate in VLSI?

[@stm3252]

Thank you bro!! Very informative video! Keep them comping please!

[@rayanjamil5328]

Could you please suggest me an article or review about why we use polysilicon as a gate instead of metal gate . Thank you

[@shivanilahariya7017]

Why we can't use self Aligned process for Al gate?

[@jairamgouda]

Hi @shivani, aluminum can be used for self alignment process but if we use it what happens? Think of it. We will deposit aluminum first, then we do ion implantation to create p and n diffusion regions. Then, we do annealing process for the proper diffusion to happen and the impurity atoms settle down in the best lattice points. Annealing happens at atleast 1000 degree Celsius. Aluminum melts at 660 degree Celsius. It just melts. So, aluminum has to be deposited at the end. After the formation of diffusion regions. Which means, it's not available for self alignment process. Hope it clarifies.