Split-channel antifuse array architecture
An anti-fuse memory cell having a variable thickness gate oxide. The variable thickness gate oxide has a thick gate oxide portion and a thin gate oxide portion, where the thing gate oxide portion has at least one dimension less than a minimum feature size of a process technology. The thin gate oxide can be rectangular in shape or triangular in shape. The anti-fuse transistor can be used in a two-transistor memory cell having an access transistor with a gate oxide substantially identical in thickness to the thick gate oxide of the variable thickness gate oxide of the anti-fuse transistor.
1. A method of forming a variable thickness gate oxide for an anti-fuse transistor having a channel region and a diffusion region, comprising the steps of:
a) forming a field oxide surrounding the channel region and the diffusion region;
b) growing an intermediate oxide in the channel region;
c) removing the intermediate oxide from a thin oxide region of the channel region;
d) growing a thin oxide over the thin oxide region and the intermediate oxide;
e) forming a common gate over the thin oxide, the intermediate oxide and the field oxide; and,
f) forming the diffusion region adjacent the intermediate oxide.
2. The method of claim 1 , wherein the anti-fuse transistor and one low voltage transistor are formed on a semiconductor material, the low voltage transistor having a dielectric structure being the same as the thin oxide.
3. The method of claim 1 , wherein the step of forming the diffusion region includes simultaneously forming a floating diffusion region adjacent the thin oxide region.
4. The method of claim 1 , wherein the intermediate oxide extends from a first edge of the common gate to a predetermined length of the channel region, and the thin gate oxide over the thin oxide region extends from the predetermined length of the channel region to a second edge of the common gate.
5. The method of claim 4 , wherein said predetermined length is defined through a masking step.
6. The method of claim 1 , wherein the thin oxide is formed with the same process steps as for forming a low voltage transistor gate oxide on the same semiconductor material.
7. The method of claim 1 , wherein a thick oxide consisting of the thin oxide and the intermediate oxide is formed with the same process steps as for forming a high voltage transistor gate oxide on the same semiconductor material.
8. The method of claim 1 , further including the steps of
selectively growing a salicidation protect oxide over the diffusion region; and,
saliciding a portion of the common gate and the diffusion region.