Embedded ROM device using substrate leakage
AssigneeMicron Technology, Inc.
InventorsCasey Kurth, Scott Derner, Phillip G. Wald
Life of this patent
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Abstract
A ROM embedded DRAM provides ROM cells that can be programmed to a single state. The ROM cells include capacitors having a storage node. The storage node is processed to have a substantially high substrate leakage. The ROM cells, therefore, are hard programmed to a logic zero state. Bias techniques can be used to read un-programmed ROM cells accurately. As described, sense amplifier circuitry can be offset in one embodiment to default to the un-programmed state. In another embodiment, bias circuitry is coupled to bit lines to favor the un-programmed state. A differential pre-charge operation can also be used in another embodiment.
Claims18
A method of fabricating a read only memory (ROM) cell comprising:
- forming a doped active area in an integrated circuit substrate;
- counter doping the active area to increase conductivity between the active area and the substrate;
- and
- forming a cell capacitor having a storage plate electrically coupled to the active area.
A method of forming a read only memory (ROM) embedded dynamic random access memory (DRAM), comprising:
- forming an array of dynamic memory cells, each dynamic memory cell comprising a storage capacitor having a storage plate coupled to first active area regions of a substrate, wherein the first active areas are doped to reduce a leakage current from the first active area to the substrate;
- and
- forming an array of read only memory (ROM) cells, each ROM cell comprising a storage capacitor having a storage plate coupled to second active area regions of a substrate, wherein the second active areas are doped to enhance a leakage current from the second active area to the substrate.
Dependencies are inferred from the claim text.