The difference between diffusion ROM and Via ROM

[pawan_nayal]

Can anyone help me understand the difference between diffusion ROM and Via ROM.
If we want to move from diffusion ROM to Via ROM, which mask layers needed to chage?

 

[cougar168]

diffusion rom

Diffusion ROM is based on VT change (using VT implant mask) => Hihg VT transistors not conducting, low VT ones conducting

VIA ROM is using via to "connect" or "not connect", resulting 0 and 1

VIA ROM may have bigger cell size

 

[mists]

via rom

diffusion rom also can be programed with whether diffusion layer exist, please see attached map, in genera, the two diffusion rom bit cell can share the same drain area, so lt lhas little bitcell size.

via rom means programed with via connect or not conencted, in general more higher via layer iss prefered for small fabicate time, often used is via2, please see attached map.

 

[laglead]

diffusion rom 和 via rom

thanks a lot