info. regarding circuit under pad(CUP)

[harry_madaan]

can anybdy tell me wat is circuit under pad(CUP).

Actually i wants the proper guidelines to convert a nonCUP circuit in CUP.

Harry

 

[pawan_nayal]

Nothing much I can add except CUP is ( circuit under pad ) a circuit just below the I/O
bondpad.

 

[srivatsan]

Bondpad is a way to access the circuit in the chip. When it is being deposited, the stress can alter the characteristics of a circuit underneath it. Over a period of time (about 6 months) the fab will make it more roboust that you can start putting up circuits. But be very careful. If you do not follow the DRC rules exactly for the Vias and metal layers underneath bondpad, the circuit most probably will not work in reliable fashion.

Srivats

 

[mdcui]

I believe there is limited type of circuit which can be put under pad, mostly output driver and ESD diodes, since the mechanical stress may alter the characteristic of device and it is very hard to predict circuit behavior with/without stress, so we better put large drivers and diodes under to avoid un-necessary problems.

 

[vikaskm]

Hi,

Circuit under the pad (CUP) essentially means the same as it sounds, mainly done to save area in dsm processes usually, the drivers and esd protection structures are placed under the pad. But the bondpad must be able to handle the stress at the same time so there are special structures the via placements done in groupings and stacked to tackle the stress under the bondpad, some foundries call it ' copper line via support structures' clvs structures which are added to tackle mechanical stress. In geometries like 45nm the entire logic + esd + drivers etc all come under the bondpad...essentially the entire pad is the bondpad in whole !!