antenna ratio of thinox is bigger than thickox ?????

Hi,

I am confused by the drc antenna check. In my opinion, the antenna ratio of thick oxide transistors should be bigger than thin oxide transistors, because they are more voltage tolerant. But in my design rule, it is opposite, like this. Thinox is 5500 while thickox is only 600. Is this right?


//===============================================================================//
//========= Metal 1 Antenna Design Rule Checks =========//
//===============================================================================//

CONNECT MET1I Fpoly Sdi BY CONTACTI

Diode_Met = NET AREA RATIO Sdi MET1I > 0 // Island connected to Met1
Min_diode_Met = NET AREA Diode_Met >= 0.16 // Find real diode

6.18.1.2.1_M1
{
@ Maximum ratio of cumulative total Metal [Metal 1] area to poly
@ gate area (thinox wo/protection diode) is 5500
NET AREA RATIO MET1I Min_diode_Met ChannelThini > 5500
[ (AREA(MET1I)*!AREA(Min_diode_Met))/AREA(ChannelThini) ]
RDB drc_ant_met1thin.db MET1I ChannelThini
}

6.18.1.2.2_M1
{
@ Maximum ratio of cumulative total Metal [Metal 1] area to poly
@ gate area (thickox wo/protection diode) is 600
NET AREA RATIO MET1I Min_diode_Met ChannelThicki > 600
[ (AREA(MET1I)*!AREA(Min_diode_Met))/AREA(ChannelThicki) ]
RDB drc_ant_met1thick.db MET1I ChannelThicki
}

6.18.2.1.1_M1
{
@ Maximum ratio of cumulative total Metal [Metal 1] area to poly
@ gate area (thinox w/protection diode) = (Diode area x 460)+43000
NET AREA RATIO MET1I Min_diode_Met ChannelThini > 43000
[ ((AREA(MET1I)*!!AREA(Min_diode_Met))/AREA(ChannelThini))-(AREA(Min_diode_Met)*460) ]
RDB drc_ant_met1thin_wdiode.db MET1I Min_diode_Met ChannelThini
}

6.18.2.1.2_M1
{
@ Maximum ratio of cumulative total Metal [Metal 1] area to poly
@ gate area (thickox w/protection diode) = (Diode area x 460)+43000
NET AREA RATIO MET1I Min_diode_Met ChannelThicki > 43000
[ ((AREA(MET1I)*!!AREA(Min_diode_Met))/AREA(ChannelThicki))-(AREA(Min_diode_Met)*460) ]
RDB drc_ant_met1thick_wdiode.db MET1I Min_diode_Met ChannelThicki
}



Thank you!

Very thin oxides allow, and can take, more tunneling current
away from the antenna source. Thick oxides may just charge
until destructive breakdown. Of course this all depends on
just what you mean by "thin" and "thick"... I've worked in
technologies where the "thin" ox was 1kA and ones where
the "thick" was 90A or so.

It seems to me that perhaps these rules were derived from
actual testing. How lucky you are, to be working with that
kind of foundry. Sometimes all you get are blind assertions.

Now I know why the ratio is bigger. Thank you!