METAL GATE in the mos transistor

[beckwang]

In the old process , some was appied to metal gate in the mos transistor , but with development of Si gate, Metal ( AL) gate process was replaced by SI gate? Who could tell me the disadvantages in the AL gate process? TNANKS!

 

[yjkwon57]

Hi.

You will use polysilicon as a gate material with some metal elements doped to improve the conductivity of the gate electrode. Metal atoms including aluminium atoms can easily penetrate into the defeccts in the silicon dioxide material to form the spikes, which causes the shorts beteen the gate and the channel.

Bye~~

 

[Hughes]

Another advantage of polysilicon is that it is suit for self-aligned gate.

 

[Humungus]

Due to the work function of Al and Si, poly gates give lower threshold voltages. See the Tsividis book.