AB etch endpoint by ABFILL compensation
AssigneeInternational Business Machines Corporation
InventorsPaul C. Buschner, Timothy G. Dunham, Howard S. Landis
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Abstract
A method for determining the AB etch endpoint during an silicon trench isolation fabrication process requires the introduction into the STI design a sufficient quantity of “dummy” diffusion structures that provide a strong endpoint signal during normal STI fabrication and, that which endpoint signal may be controlled by adjustment of the planarization shapes associated with the dummy diffusion structures.
Claims10
A method of co-planarizing at least one material on the surface of a semiconductor substrate having a first region including trenches for isolating a plurality of diffusion shapes, said method comprising the steps of:
- providing second region including trenches for isolating a plurality of dummy diffusion shapes on said surface,
- providing oxide deposition above said first and second regions;
- applying a first coating of photoresist to said first and second regions above said oxide layer at a predetermined thickness, an amount of photoresist material being patterned and retained in said second region being insufficient to completely planarize said second region in a subsequent planarizing step;
- applying a second coating of photoresist on top of said first layer of photoresist in said first and second regions, a thickness and leveling properties of said applied second layer of photoresist being sufficient to allow local planarization within said first and second regions, said applied second coating forming a substantially flat surface over said first region, and a substantially flat surface over said second region, with a height of said flat surface being lower in said second region than in said first region;
- and,
- etching said second photoresist, first photoresist, and those sections of said oxide layer not recessed within said trenches, to planarize the oxide within said first and second regions, wherein the second region having said dummy diffusion shapes is planarized prior to the first region by terminating said etching upon detection of an emission endpoint signal arising from the dummy diffusion structures during said etching.
A method for determining a surface etch endpoint during a planarization step of a silicon trench isolation (STI) fabrication process, said method comprising the steps of:
- a) fabricating real diffusion structures according to a semiconductor design and fabricating a plurality of dummy diffusion structures in an unused region of the same semiconductor, each said real and dummy diffusion structures including a pad nitride layer remaining on top of said structures, and a conforming oxide deposition layer formed above said pad nitride layer and trench regions surrounding said structures;
- b) constructing a planarization photoresist pattern over said trench regions on said oxide layer about said real and dummy diffusion structures and applying a resist material to said real and dummy diffusion structures, said pattern being designed such that an amount of resist retained above said real diffusion structures is at a first level and, an amount of resist retained above said plurality of dummy diffusion shapes is at a second level, said first level being greater than said second level;
- and,
- c) proceeding with standard STI processing including an oxide-etch step for removing said conformal oxide deposition not rendered in photoresist;
- and,
- d) during said oxide-etch step, detecting a nitride emission endpoint signal arising from the dummy diffusion structures, and terminating said oxide-etch step based on said nitride emission endpoint signal.
Dependencies are inferred from the claim text.