Willt
Member level 5
Hi friends,
In the old days, metal was used as the gate of MOS.
But now, polysilicon is used.
Metal has a lower resistivity than polysilicon.
What is the reason for using polysilicon now?
I think of a few reason:
1. Polysilicon is easier to stick to silicon oxide.
2. Polysilicon can achieve self-alignment but metal cannot.
(Metal will melt when S/D dopant is being doped [HIGH TEMPERATURE!]
under self-alignment.)
Disadv. of using polysilicon as the gate:
1. Higher resistivity
2. Higher cap.
I heard that metal will be used as the gate again
in the near future under 45nm-process. Is this true?
Please feel free to discuss together.
Your friend
Will
In the old days, metal was used as the gate of MOS.
But now, polysilicon is used.
Metal has a lower resistivity than polysilicon.
What is the reason for using polysilicon now?
I think of a few reason:
1. Polysilicon is easier to stick to silicon oxide.
2. Polysilicon can achieve self-alignment but metal cannot.
(Metal will melt when S/D dopant is being doped [HIGH TEMPERATURE!]
under self-alignment.)
Disadv. of using polysilicon as the gate:
1. Higher resistivity
2. Higher cap.
I heard that metal will be used as the gate again
in the near future under 45nm-process. Is this true?
Please feel free to discuss together.
Your friend
Will