Micron Technology Incorporated

Round Rock Research, LLC

Xianfeng Zhou

Mark Alan Helm

Michael A Smith

Graham Richard Wolstenholme

Sukesh Sandhu

Gurtej S Sandhu

Shubneesh Batra

Howard Kirsch

Chih-Chen Cho

An oxide layer is formed over a substrate having a smaller isolation trench and a large isolation trench. A nitride layer is formed over the oxide layer such that it completely fills the smaller isolation trench and lines the larger isolation trench. The nitride layer is etched back to form a recess in the nitride layer in the smaller isolation trench while at least a portion of the nitride layer lining the larger isolation trench is completely removed. A layer of HDP oxide is deposited over the substrate, completely filling the smaller and larger isolation trenches. The HDP oxide layer is planarized to the upper surface of the substrate. The deeper larger isolation trench may be formed by performing an etching step after the nitride layer has been etched back, prior to depositing HDP oxide.

Isolation trench fill using oxide liner and nitride etch back technique with dual trench depth capability

An integrated circuit and gate oxide forming process are disclosed which provide a gate structure that is simple to integrate with conventional fabrication processes while providing different gate oxide thicknesses for different transistors within the integrated circuit. For a flash memory, which may utilize the invention, the different gate oxide thicknesses may be used for lower voltage transistors, memory array transistors, and higher voltage transistors.

Method of fabricating different gate oxides for different transistors in an integrated circuit

Different gate oxides thicknesses for different transistors in an integrated circuit

Wells are formed in a substrate where standard Vt and low Vt devices of both a first and second type are to be fabricated. Wells defining the locations of first type standard Vt devices are masked, and a first voltage threshold implant adjustment is performed within wells defining the second type standard Vt devices, and each of the first and second type low Vt devices. Wells that define the locations of second type standard Vt devices are masked, and a second voltage threshold implant adjustment is performed to the wells defining the first type standard Vt devices, and each of the first and second type low Vt devices. Doped polysilicon gate stacks are then formed over the wells. Performance characteristics and control of each device Vt is controlled by regulating at least one of the first and second voltage threshold implant adjustments, and the polysilicon gate stack doping.

Formation of standard voltage threshold and low voltage threshold MOSFET devices

The invention includes methods of forming oxide structures under corners of transistor gate stacks and adjacent trenched isolation regions. Such methods can include exposure of a semiconductor material to steam and H, with the Hbeing present to a concentration of from about 2% to about 40%, by volume. An oxide structure formed under the bottom corner of a transistor gate stack can have a bottom surface with a topography that includes a step of at least about 50 &#x212b;, and an upper surface directly over the bottom surface and having a topography that is substantially planar. Methodology of the present invention can be utilized to form semiconductor constructions suitable for incorporation into highly integrated circuitry. The highly integrated circuitry can be incorporated into electronic systems, and can, for example, be utilized in processors and/or memory storage devices.

Semiconductor constructions

Multiple trench depths within an integrated circuit device are formed by first forming trenches in a substrate to a first depth, but of varying widths. Formation of a dielectric layer can cause some of the trenches to fill or close off while leaving other, wider trenches open. Removal of a portion of the dielectric material can then be tailored to expose a bottom of the open trenches while leaving remaining trenches filled. Removal of exposed portions of the underlying substrate can then be used to selectively deepen the open trenches, which can subsequently be filled. Such methods can be used to form trenches of varying depths without the need for subsequent masking.

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Meridian, ID, United States of America

Xianfeng Zhou