what is Antenna vioaltion and how to fix that

Hi,

Can anyone expalin what is Antenna vioaltions and how to fix them.


REGARDS
Qaul_Ti

aviod antenna violation using Jumpers are a short metal segment inserted onto a long route of another metal layer.
The Magma design system implements a powerful jumper-based antenna solution that effectively solves the majority of the antenna violations with little impact on the routing congestion. The remainder of the violations can be fixed using diode insertion.
Jumpertechniques are the most effective method of avoiding antenna-effect problems

---------- Post added at 17:42 ---------- Previous post was at 17:41 ----------

During the process of plasma etching, charges accumulate along the metal strips. The longer the strips are, the more charges are accumulated. IF a small transistor gate connected to these long metal strips, the gate oxide can be destroyed (large electric field over a very thin electric) , This is called as Antenna violation.

The ways to prevent is , by making jogging the metal line, which is atleast one metal above the layer to be protected. If we want to remove antenna violation in metal2 then need to jog it in metal3 not in metal1. The reason being while we are etching metal2, metal3 layer is not laid out. So the two pieces of metal2 got disconnected. Only the piece of metal connected to gate have charge to gate. When we laydown metal3, the remaining portion of metal got charge added to metal3. This is called accumulative antenna effect.

Another way of preventing is adding reverse Diodes at the gates.

During the Fabrication Process the large amount of charge is induced in plasma etching, ion implantation and in other processes. If a large interconnect (Poly or other Conducting material) is connected to the Gate of a MOSFET, then this larger conducting material will act as Antenna and will receive the induced charge of the Fabrication Process.
The charge due to these extra carriers might be too much for the thin gate to handle it, and it may also damage the thin oxide layer. So, Antenna effect may result in breakdown of Gate Oxide or degrade the I-V Characteristics.

How to fix antenna violation:
To avoid the antenna effect we need to avoid large Interconnect Area to Gate of a MOSFET or we can also use the diode placed near the MOSFET, so that the diode will provide a conductive path to substrate, if the induced charge is above a limit. Metal layer jogging can be done to avoid antenna violation. Layer jogging picture is given in this link Antenna effect fixing by metal jogging

Hi shivaram,

Thanks for ur reply.

charge accumulation can happen on long metal stripes due to plasma etching. How does that charge is transferred to gate. ?
correct me if i am wrong.

You have connection to the MOS transistor gate. This problem occurs only when the metal is connected to gate of the transistor.

In all std cells,the gates are connected to metal(follow pins),

my question is how that charge accumulated on long metal stripe can go to gate of transistor. what is the source for moving of those chargers ...

When routing is done than the gate of the transistor is connected to some metal for interconnection between different circuit elements. There is a antenna violation only if long metal layer is connected to the gate of the transistor. If the long metal layer is connected to the gate, it may damage the gate oxide the gate which is very thin now a days. See this pictures in this link. Antenna effect - Wikipedia, the free encyclopedia. I think it should clear now.

you told that " If the long metal layer is connected to the gate, it may damage the gate oxide the gate which is very thin now a days ", how does it damage menas ,during CMP, the accumulated charge can destroy gate of transistor.
If that charge is excessive then it damage the gate of transistor .

My question is how that charge is moved from metal to gate .

Correct me If I am wrong.

Chemical-mechanical planarization(CMP) is a process of smoothing surfaces with the combination of chemical and mechanical forces to ensure conformality in further grown layers. Chemical-mechanical planarization - Wikipedia, the free encyclopedia. It doesn't damage gate oxide.
Antenna Effect cause gate oxide's electrical breakdown
Yes, Only if there is sufficient charge on metal, only than it can damage gate oxide. If metal is connected to gate and it has some amount of charge on in it. It will be transferred to gate as both metal and poly silicon gate are conductors. There is antenna violation, If metal is large to accommodate enough charge which can produce high electric field to breakdown of oxide.

Hi,

You can refer following article.
Antenna Effects |VLSI Concepts