International Business Machines Corporation

Carol Galli

Louis L Hsu

Seiki Ogura

Joseph F Shepard

Nivo Rovedo

Joyce E Acocella

Ahmet Bindal

Improved packing density as well as improved performance and manufacturing yield is achieved in an electrically programmable memory by confining floating gate structures between isolation structures covered with a thin nitride layer. The confinement of the floating gate is achieved by planarization, preferably with a self-limiting chemical/mechanical polishing process, to the surface of the nitride layer covering the isolation structures. Gate oxide and control electrode connections can then be formed on a substantially planar surface without compromising the quality of the gate oxide or breakdown voltage the device must withstand for programming. Since severe topology is avoided over which these connections are formed, improved formation of low resistance connections, possibly including metal connections, are possible and allow scaling of transistors of the memory cells to be scaled to sizes not previously possible.

Packing density for flash memories

Packing density for flash memories by using a pad oxide

A shallow trench isolation structure is formed by a process having a reduced number of steps and thermal budget by filling trenches by liquid phase deposition of an insulating semiconductor oxide and heat treating the deposit to form a layer of high quality thermal oxide at an interface between the deposited oxide and the body of semiconductor material (e.g. substrate) into which the trench extends. This process yields an isolation structure with reduced stress and reduced tendency to develop charge leakage. The structure can be readily and easily planarized, particularly if a polish-stop layer is applied over the body of semiconductor material and voids and contamination of the deposited oxide are substantially eliminated by self-aligned deposition above the trench in the volume of apertures on a resist used to form the trench.

Isolation structure using liquid phase oxide deposition

A method of forming a SOI integrated circuit includes defining thin silicon mesas by etching a device layer down to the underlying insulator, forming a nitride bottom polish stop in the bottom of the apertures by a low temperature PECVD process, with nitride sidewalls on the silicon mesas being susceptible to easy removal, so that no hard material is present during a chemical-mechanical polishing step to thin the device layer down to less than 1000.ANG., and filling the apertures with a temporary layer of polysilicon to provide mechanical support to the edges of the device layer during the polishing operation.

Thin SOI layer for fully depleted field effect transistors

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Odenton, MD, United States of America

Carol Galli