Methods of fabricating high density mask ROM cells
AssigneeMacronix International Co., Ltd.
InventorChing-Yu Chang
Life of this patent
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Abstract
Methods for making integrated circuit devices, such as high density memory devices and memory devices exhibiting dual bits per cell, include forming multiple oxide fences on a semiconductor substrate between multiple polybars. The oxide fences create a hole pre-code pattern that facilitates ion implantation into trenches disposed between the polybars. The holes, or voids, formed by the oxide fences provide greater control of the critical dimension of ion implantation, for example, the critical dimension of the trench sidewalls. Semiconductor devices used in the manufacture of memory devices include the oxide fences during the manufacturing process.
Claims22
A method for making an integrated circuit on a semiconductor substrate, the method comprising the steps of:
- (a) providing a semiconductor substrate having a plurality of polybars disposed on a gate oxide layer, each of the polybars oriented parallel to the other polybars and disposed on either side of at least one trench defined by a sidewall which is formed in the semiconductor substrate thereby creating a channel between the polybars;
- (b) forming a plurality of reflective dielectric fences between the plurality of polybars to create a plurality of voids bounded by the plurality of polybars and the reflective dielectric fences;
- (c) implanting a dopant into at least one of the voids;
- (d) removing the reflective dielectric fences;
- and
- (e) implanting a dopant into a base of the trench.
A method for making an integrated circuit on a semiconductor substrate, the method comprising the steps of:
- (a) providing a semiconductor substrate having a plurality of polybars disposed on a gate oxide layer, each of the polybars oriented parallel to the other polybars and disposed on either side of at least one trench formed in the semiconductor substrate thereby creating a channel between the polybars;
- (b) forming a reflective dielectric fence between the plurality of polybars to create a plurality of voids bounded by the plurality of polybars and the reflective dielectric fence;
- (c) filling the voids with photoresist and removing the photoresist from select voids using a first photoresist mask having a pattern for a first ROM code;
- (d) implanting a dopant into the voids having the photoresist removed in step (c);
- (e) filling the voids implanted in step (d) with photoresist and removing the photoresist from select voids using a second photoresist mask having a pattern for a second ROM code;
- and
- (f) implanting a dopant into the voids having the photoresist removed in step (e).
A method for making an integrated circuit on a semiconductor substrate, the method comprising the following steps:
- (a) forming a plurality of polybars on the semiconductor substrate, each polybar having a length and comprising a gate oxide layer, a polybar conductive layer, and a polybar dielectric layer, and each polybar being disposed parallel to each of the other polybars on the semiconductor substrate;
- (b) forming at least one trench in the semiconductor substrate between the plurality of polybars, thereby creating a channel between the polybars;
- (c) filling the trench and the channel with a reflective dielectric layer;
- (d) removing portions of the reflective dielectric layer in the trench to form a pattern perpendicular to the length of the polybars, and to form a plurality of voids on the semiconductor substrate with each void being bounded by the polybars and portions of the reflective dielectric layer not removed;
- (e) filling the voids with a first photoresist;
- (f) selectively removing the first photoresist from certain voids;
- (g) implanting a dopant into the voids without photoresist;
- (h) filling the voids without the first photoresist with a second photoresist;
- (i) selectively removing photoresist from certain voids;
- (j) implanting the dopant into the voids without photoresist;
- (k) removing the remaining photoresist from the semiconductor substrate;
- (l) removing the remaining reflective dielectric layer from the trench;
- and
- (m) implanting a dopant into a base of the trench.
Dependencies are inferred from the claim text.