STI region for small fin pitch in FinFET devices
View Patent ↗The present invention relates generally to semiconductor devices, and particularly to fabricating a shallow trench isolation (STI) region in fin field effect transistors (FinFETs) having a small fin pitch. According to one embodiment, a method of using selective etching techniques to remove a single fin to form a fin trench and to form an isolation trench having a width approximately equal to a width of the single fin below the removed fin is disclosed. The fin trench and the isolation trench may be filled with isolation material to form an isolation region.
1. A method, comprising:
forming an isolation layer between a plurality of caps on a plurality of fins, wherein an upper surface of the isolation layer is substantially flush with an upper surface of the plurality of caps;
forming a patterning layer on the isolation layer and on the plurality of caps;
removing a portion of the patterning layer to form an opening above one of the plurality of fins to expose at least a portion of one of the plurality of caps;
removing the one of the plurality of caps selective to the patterning layer, the isolation layer, and the one of the plurality of fins to expose the one of the plurality of fins;
removing one of the plurality of fins from a fin field effect transistor (FINFET) device using a selective etching process to form a fin trench in the isolation layer, the fin trench extending from an upper surface of the isolation layer to an upper surface of a semiconductor substrate;
forming an isolation trench in the semiconductor substrate directly below the fin trench, the isolation trench having a width that is approximately equal to a width of the one of the plurality of fins; and
filling the isolation trench and the fin trench with an insulating material to form an isolation region, the isolation region having an upper surface that is substantially flush with the upper surface of the isolation layer.
2. The method of claim 1 , wherein the semiconductor substrate is a bulk substrate.
3. The method of claim 1 , wherein the semiconductor substrate is a semiconductor on insulator (SOI) substrate.
4. The method of claim 1 , wherein the isolation trench is formed between a n-type field effect transistor (NFET) region of the semiconductor substrate and a p-type field effect transistor (PFET) region of the semiconductor substrate.
5. The method of claim 1 , further comprising:
widening the isolation trench using a lateral etch to form a wide isolation trench in the semiconductor substrate.
6. The method of claim 1 , wherein the opening has a minimum width approximately equal to a portion of the one of the plurality of caps and a maximum width approximately equal to a width of the one of the plurality of caps and a width of adjacent portions of the isolation layer on either side of the one of the plurality of caps.
7. The method of claim 1 , wherein the patterning layer comprises a hard mask material.
8. The method of claim 1 , wherein the width of the opening is greater than the width of the fin trench and the width of the isolation trench.