how to layout bondpad?

[leohart]

Someone told me to draw all metal layers,poly,nwell under pad,then make vias and contacts in pad area interleaved...

why use so many layers?we only use top metal to connect the input/output signal...

The Art of analog layout said use m1 and m2 then a big via same size as pad(the book said this is to remove the interlevel oxeide between metals ,so the ballbond lands on the stacked metal layers,but if the oxide exists,the ballbond still lands on the stack metal...really confused). The problem is DRC won't allow such big via!!!

Help me,it is better if you can upload a layout to illustrate the concept...

 

[acbalbason]

hi!

that someone who told you was correct! we make bond pads as big as 60um by 60 um. use only minimum via size just make lots of them! imagine a checker board. contacts are black and vias are white.

- al

 

[leohart]

Thx! now I'm sure how to draw...but Anyone konws why so many layers ,vias,contacts are used? any reason?

 

[acbalbason]

hi!

i think it is for metal density. your band pads are where copper or gold is attached to connect the actual ic to the "legs" of the package.

- al

 

[CK815]

Of course you have to stick to your design rules when it comes to via size. Most CMOS processes will only allow a fixed via size.
The stack of a bond pad should always be made up of at least all metal layers available in order to withstand vertical forces during the bond process and to add stability to the pad. Single layer bond pads are prone to simply lift off if force is applied to the bond wire. The "chess board" or brick- step layout of vias and contacts adds additional stability compared to a regular matrix layout. This helps to withstand the lateral forces during the bond process.

Hope that helps.
Regards,

C.

 

[leohart]

Of course you have to stick to your design rules when it comes to via size. Most CMOS processes will only allow a fixed via size.
The stack of a bond pad should always be made up of at least all metal layers available in order to withstand vertical forces during the bond process and to add stability to the pad. Single layer bond pads are prone to simply lift off if force is applied to the bond wire. The "chess board" or brick- step layout of vias and contacts adds additional stability compared to a regular matrix layout. This helps to withstand the lateral forces during the bond process.

Hope that helps.
Regards,

C.

THX, when doing wiring from pad,should I use both metal1 and metal2(m3,m4 if the process have other metal layer) ? I think this can make the pad wiring more robust(like counteract the m2 liftoff said above).Someone tell just use top metal to do the wiring from bondpad,is it enough?

 

[CK815]

Hi leohart,

generally, if you have a robust bond stack, it shoud be sufficient to use just one metal to connect the pad. For supply pads, the topmost (usually the thickest) metal should be used. On another note: in some processes it is advisable not to use a minimum width metal trace to connect probepads (or analysis- pads, whatever you call them), but to use a tapered construction or just a wider trace. Sometimes when placing a needle on a probepad, a minimum wire may just tear off as the probepad will be slightly deformed by the force of the needle. We have also seen probepads to slide away and eventually even "lift off" the IMD. So for a robust probepad design, use two layers of metal and connect them with a via array. In this case, even a minimum trace will be sufficient to connect the pad.

Regards,

C

 

[leohart]

Hi leohart,

generally, if you have a robust bond stack, it shoud be sufficient to use just one metal to connect the pad. For supply pads, the topmost (usually the thickest) metal should be used. On another note: in some processes it is advisable not to use a minimum width metal trace to connect probepads (or analysis- pads, whatever you call them), but to use a tapered construction or just a wider trace. Sometimes when placing a needle on a probepad, a minimum wire may just tear off as the probepad will be slightly deformed by the force of the needle. We have also seen probepads to slide away and eventually even "lift off" the IMD. So for a robust probepad design, use two layers of metal and connect them with a via array. In this case, even a minimum trace will be sufficient to connect the pad.

Regards,

C

I think now I totally understand the purpose of using via array here:it is used to make the top metal more robust to "liftoff" when bonding or probing.
Usually,use top metal as wiring out for supply(the thick top metal can handle more current ).Also we can use metal under top metal for wiring(non-supply pad),becuase it is under the top metal so more robust.

 

[huangxf517]

hi,we make bond pads as big as 100um by 100 um.

Added after 51 seconds:

hi,we make bond pads as big as 100um by 100 um.

 

[research235]

Hello every one,

May be this is a very silly question but sinec i never worked on this kind before i am stuck up here.

The question is on bound pads and theire external connections.

i have a top level layout which has cerrtain number of pads on it .. wen i see the wire diagram the number of pads are more and these are further conencted through wires .. i ahve no idea wat it is .. can some body provide me with soem material which has soem information abt this ..

some books are also OK ..

thank u in advance

Sing-

 

[leo_o2]

Some process design rule requires POLY is must if AL wire is employed while POLY is not necessary if gold wire is used.

 

[jamesfeng1981]

Just follow the design rule. Then it is ok

Added after 1 minutes:

Who can tell me how to add my points. As I can not download some usefule material

 

[acbalbason]

hi!

post, post and post! but be sure to post sensible stuff. the forums is here to help people not just to rack up points so we can download. Ü

- al

 

[jamesfeng1981]

Just follow the design rule. And make sure in your bondpad you have the top metal. That is enough

 

[leohart]

Just follow the design rule. And make sure in your bondpad you have the top metal. That is enough

My design rule didnt give bondpad rules and example...