Self-aligned thin capacitively-coupled thyristor structure
View Patent ↗A semiconductor memory device having a thyristor is manufactured in a manner that makes possible self-alignment of one or more portions of the thyristor. According to an example embodiment of the present invention, a gate is formed over a first portion of doped substrate. The gate is used to mask a portion of the doped substrate and a second portion of the substrate is doped before or after a spacer is formed. After the second portion of the substrate is doped, the spacer is then formed adjacent to the gate and used to mask the second portion of the substrate while a third portion of the substrate is doped. The gate and spacer are thus used to form self-aligned doped portions of the substrate, wherein the first and second portions form base regions and the third portion form an emitter region of a thyristor. In another implementation, the spacer is also adapted to prevent formation of salicide on the portion of the thyristor beneath the spacer, self-aligning the salicide to the junction between the second and third portions. In addition, dimensions such as width and other characteristics of the doped portions that are used to form a thyristor can be controlled without necessarily using a separate mask.
1. A method for manufacturing a thyristor, the method comprising:
forming a control port over a first base region in a semiconductor substrate;
forming a spacing material laterally adjacent to a first side of the control port and over the first base region;
implanting a dopant at an acute angle between the control port and the first base region to form a second base region using the control port and spacing material to mask a portion of the first base region, the formed second base region being laterally offset from the control port and at least a portion of the second base region being underneath the spacing material; and
forming first and second emitter regions respectively coupled to the first and second base regions, the emitter and base regions forming a thyristor body, wherein the control port and the thyristor body are arranged such that the control port is adapted for capacitively coupling at least one edge of a voltage pulse at least to the first base region.
2. The method of claim 1 further comprising forming a first salicide over one of the first and the second emitter regions.
3. The method of claim 2 further comprising forming a second salicide over another of the first and the second emitter regions.
4. The method of claim 1 farther comprising forming a salicide over the gate.
5. The method of claim 1 further comprising forming a second spacer positioned contiguously adjacent to the first spacer.
6. The method of claim 1 further comprising forming a salicide block layer covering at least a portion of the gate and the first spacer.
7. The method of claim 1 wherein the first base region and the first emitter region is doped with an N-type dopant and the second base region and the second emitter region is doped with a P-type dopant.