Why do we put Reverse biased diode close to gate which is violating Antenna check ?

[vikramc98406]

Can anybody tell me the reason for Why do we put Reverse biased doide
close to gate which is voilating Antenna check ?

My understanding is, if static charge depsited on the length of the poly, it can break the gate if we put reverse biased doide either near or far from the Gate.

 

[chinnisunny]

Re: Antenna check

We insert reverse bias diode to provide the path to discharge the collected charges,so that the gate wont gets damaged.

This is my understanding plz correct me if i am wrong.

Thanks.

 

[vikramc98406]

Re: Antenna check

You are right, But my question is why do we have to place the diode close to Gate?

 

[joe2moon]

Re: Antenna check

Since the current will always follow the path of lowest resistance.

If the antenna diode has been placed far away from the desired location, then the discharge path will not go through inserted diode .

 

[msaadrahman]

Re: Antenna check

Antenna errors occur when a large metal structure is connected to a gate. When the metal is etched in the fabrication a large amount of charge might be induced in the metal. This can cause the gate to break if there is no discharging path for high voltages (like a drain/source or a reversed diode).

Antenna errors can be fixed by adding a reversed diode connected to the metal wire causing the problem. A N+ doped nwell contact will function as a reversed diode if it is connected to the substrate.

Ref: TSEK01 - VLSI Deisgn Project 2006, Third Edition, Rev. 2005, Linkoping University, Sweden