Antenna diodes breakdown

[srihari465]

Hi all,

During plasma processing Antenna diodes provides a path for accumulated charges in the conductor to the substrate, My doubt is that if the diode connected in reverse biased mode has to provide a path for the charge to the substrate it has to breakdown, so this breakdowned diode will affect the normal circuit operation or not?? please explain in detail.

 

[yadavvlsi]

Antenna diode is connected to the gate of the MOSFET. Breakdown of diode takes place when the accumulated charge is high. But typical operating voltages are typically 1.0V or below. So breakdown of diode can't take place. So it doesn't effect normal operation but protect transistor from damaging by antenna effect.

 

[srihari465]

Hi,
Please check para 3 under Background of invention of the following document.
**broken link removed**

there they are explaining about breakdown of diode

 

[erikl]

... it has to breakdown, so this breakdowned diode will affect the normal circuit operation or not??

This antenna diode breakdown is in no case destructive, so the diode is totally intact after having protected its gate. It doesn't affect the normal circuit operation, because Vgs(normal_operation) < V(antenna_diode_breakdown) < Vgs(breakdown) .

 

[dick_freebird]

You don't need it to break down, the soft X-rays, UV
and/or heat of the plasma etch will light up the reverse
leakage adequately. The current involved is low.

 

[Teddy]

a) if you look at any diode characteristic you will see that even reverse biased diode is still letting some current through. Not much but enough - you can actually use it for your design if you are careful. Very often it is used for biasing of substrate in case of "overvoltage" circuits. That said diode does not have to break down to provide current path - if currents are small.

b) in case of the antenna diodes - if the accumulated voltage is high enough for diode to go through destructive breakdown then you will have much bigger issues.
Breakdown for the diodes is about 10V - since diodes are connected through metal to the gate - and gate oxide breakdown is max 5V(sure depends on technology) for thin oxide then obviously you don't worry about the diode to go bad.....