Oxide deglaze before sidewall oxidation of mesa or trench
AssigneeTexas Instruments Incorporated
InventorKeith Joyner
Life of this patent
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Abstract
A shallow trench isolation (STJ) (10) is used to isolate two active regions (12) from each other. The advantage of STI (10) is that the upper corners (14) are rounded. Rounding of the upper corners (14) is accomplished using an oxide deglaze prior to sidewall oxidation of the trench which undercuts the pad oxide (20) from the pad nitride (22). The allows the sidewall oxidation process to form a thicker oxide at upper corners (14) which in turn, rounds the corners. Rounded corners (14) minimum the electric field strength induced by the geometry. As a result, the Vt lowering that occurs in prior art STI structures is minimized and off-state leakage due to the inherent parasitic transistor at the upper corner is reduced.
Claims17
A method of forming an isolation structure in a semiconductor body, comprising the steps of:
- forming a pad oxide on said semiconductor body;
- forming a pad nitride on said pad oxide;
- patterning and etching said pad oxide and pad nitride to form a hard mask;
- undercutting said pad oxide from said pad nitride using an oxide deglaze;
- etching a trench in said semiconductor body using said hard mask;
- oxidizing said semiconductor body in the presence of said hard mask to create a sidewall oxide, wherein said oxidizing step creates a thicker oxide at an upper corner of said trench rounding the upper corner of said trench;
- and
- filling said trench with a dielectric material.
A method of forming a shallow trench isolation structure in a semiconductor body, comprising the steps of:
- forming a pad oxide on said semiconductor body;
- forming a pad nitride on said pad oxide;
- patterning and etching said pad nitride and pad oxide to form a hard mask;
- etching a trench in said semiconductor body using said hard mask;
- isotropically etching said pad oxide to undercut the pad oxide from said pad nitride a distance approximately equal to the thickness of said pad oxide;
- oxidizing said semiconductor body to form a sidewall oxide in said trench, wherein the radius of curvature of an upper corner of said trench is increased during said oxidizing step due to said isotropically etching step;
- and
- filling said trench with a dielectric material.
Dependencies are inferred from the claim text.