Reducing effects of parasitic transistors in thyristor-based memory using an isolation or damage region
View Patent ↗An integrated circuit having memory, including thyristor-based memory cells, is described, where each of the thyristor-based memory cells includes a thyristor-based storage element and an access transistor. Where the thyristor-based storage element includes an anode region and a cathode region, a pair of the thyristor-based memory cells are commonly coupled via a bitline associated with the access transistor or via a reference voltage line coupled to the anode region. Bitline or anode regions are separated from one another by an isolation region. In another configuration, a bitline region has a locally implant-damaged region to inhibit charge transfer between the pair. In yet another configuration, a storage node contact or contacts respectively can extend over or are coupled to a storage node line extending over an isolation region. In this latter configuration, a source/drain region and the cathode region are separated from one another by an isolation region.
1. An integrated circuit having memory, comprising:
thyristor-based memory cells, each of the thyristor-based memory cells including a thyristor-based storage element and an access transistor, the thyristor-based storage element including an anode region and a cathode region;
a pair of the thyristor-based memory cells commonly coupled via a bitline region associated with the access transistor;
the pair of the thyristor-based memory cells defining a parasitic bipolar junction transistor therebetween responsive to the bitline region being common;
the bitline region having a locally implant-damaged region to inhibit charge transfer between the pair of the thyristor-based memory cells via the parasitic bipolar junction transistor;
the locally implant-damaged region extending to and in contact with an insulator layer of a silicon-on-insulator wafer on which the integrated circuit is formed; and
the locally implant-damaged region formed with lateral control for at least some separation from p-n junctions of the bitline region.
2. The integrated circuit according to claim 1 , wherein the bitline region includes a portion on each side of the locally implant-damaged region to provide a source/drain region for the access transistor of each thyristor-based memory cell of the pair.
3. The integrated circuit according to claim 2 , wherein the locally implant-damaged region is formed using an implant angle in a range of approximately perpendicular to 45 degrees from a top surface of the silicon-on-insulator wafer.
4. The integrated circuit according to claim 1 , wherein the locally implant-damaged region is formed by implanting heavy ions having an atomic mass of at least 28 atomic mass units.
5. The integrated circuit according to claim 4 , wherein the heavy ions are part of a cluster or compound.