Advanced isolation process for large memory arrays
AssigneeMicron Technology, Inc.
InventorSalman Akram
Life of this patent
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Abstract
A process for creating silicon isolation regions which utilizes silicon islands or pillars as sources of silicon for silicon dioxide (or silicon oxide) fields. These silicon oxide fields separate active areas within a device. By providing multiple sources of silicon for silicon oxide formation, the described invention minimizes the use of trench wall edges as silicon sources for silicon oxide growth. This reduction in stress helps to minimize encroachment and undergrowth or bird's beak formation. This process also leads to a reduced step height between the field oxide and active areas, thus providing a more planar wafer surface.
Claims30
A method of isolating devices within a silicon substrate, the method comprising:
- defining a field isolation region between two active area regions on a substrate;
- forming at least one silicon source protrusion within the isolation region by a photolithography and etch process, the protrusion spaced from the active areas by a surrounding trench within the substrate;
- and
- oxidizing substantially all of the silicon source protrusion to form a field oxide within the field isolation region.
A method for isolating devices within a semiconductor substrate, the method comprising:
- forming a mask by a photolithographic process defining an island region spaced from an active area;
- etching a surrounding trench within the substrate around the perimeter of the island, thereby creating a pillar spaced from the active area by the trench;
- and
- exposing the trench and pillar to an oxygen-containing ambient and substantially converting all of the piller to silicon oxide.
A method of isolating devices within a silicon substrate, the method comprising:
- recessing a field isolation region of the substrate between two active areas;
- forming at least two silicon source protrusions within the recessed field isolation region;
- and
- oxidizing the silicon source protrusions.
A method of isolating devices within a silicon substrate, the method comprising:
- forming at least one silicon source protrusion recessed within a surrounding cavity between active areas;
- and
- oxidizing the silicon source protrusion.
A process for creating a field isolation region, the process comprising the steps of:
- forming a patterned nitride mask layer on a silicon substrate, the mask defining at least two active areas, at least one island there between, and an unmasked trench region surrounding the island;
- anisotropically etching portions of the silicon substrate corresponding to the unmasked trench regions such that a trench is formed around a first pillar of silicon;
- exposing the walls and floor of the trench to an oxygen-containing ambient;
- and
- controlling the exposure time of the trench to the oxygen-containing ambient such that substantially all of said silicon pillar is converted to silicon oxide.
Dependencies are inferred from the claim text.