Semiconductor structures for latch-up suppression and methods of forming such semiconductor structures
View Patent ↗Semiconductor structures and methods for suppressing latch-up in bulk CMOS devices. The semiconductor structure comprises a shaped-modified isolation region that is formed in a trench generally between two doped wells of the substrate in which the bulk CMOS devices are fabricated. The shaped-modified isolation region may comprise a widened dielectric-filled portion of the trench, which may optionally include a nearby damage region, or a narrowed dielectric-filled portion of the trench that partitions a damage region between the two doped wells. Latch-up may also be suppressed by providing a lattice-mismatched layer between the trench base and the dielectric filler in the trench.
1. A method of fabricating a semiconductor structure in a substrate of a semiconductor material, the method comprising:
forming a trench in the semiconductor material with a plurality of vertical first sidewalls disposed between a base of the trench and a top surface of the substrate;
forming an oxygen-enriched region in the semiconductor material of the substrate bounding the first sidewalls of the trench near the base;
forming a spacer on each of the vertical first sidewalls of the trench; and
oxidizing the oxygen-enriched region to form an oxide region with a plurality of second sidewalls having a separation width greater than a separation width of the first sidewalls while each spacer protects the semiconductor material along a respective one of the vertical first sidewalls of the trench against oxidation.
2. The method of claim 1 further comprising:
forming a first doped well in the semiconductor material of the substrate; and
forming a second doped well in the semiconductor material of the substrate proximate to the first doped well such that the first and second sidewalls of the trench are located between the first and second doped wells and the oxide region extends into the first doped well.
3. The method of claim 1 wherein forming the oxygen-enriched region further comprises:
implanting oxygen ions into the semiconductor material of the substrate bounding the first sidewalls of the trench near the base to form the oxygen-enriched region.
4. The method of claim 3 wherein a peak atomic concentration for the oxygen ions in the oxygen-enriched region ranges from 5×10 19 cm −3 to 5×10 21 cm −3 .
5. The method of claim 3 wherein a peak atomic concentration for the oxygen ions in the oxygen-enriched region is 5×10 18 cm −3 or more.
6. The method of claim 3 further comprising:
co-implanting the oxygen-enriched region with germanium ions, silicon ions, arsenic ions, or boron difluoride ions.
7. The method of claim 1 further comprising:
at least partially filling the trench with a dielectric material to define an isolation region.
8. The method of claim 1 wherein the oxide region is composed of silicon dioxide.
9. The method of claim 1 wherein each spacer is formed from a dielectric material.
10. The method of claim 9 wherein the dielectric material is composed of a nitride and has a thickness of 5 nm to 15 nm.