United Microelectronics Corp.

Promos Technologies, Inc

Jih W Chou

Joe Ko

Chun Yen Chang

Jai Hoon Sim

A memory cell structure comprises a semiconductor substrate, two stack structures positioned on the semiconductor substrate, two conductive spacers positioned on sidewalls of the two stack structures, a gate oxide layer covering a portion of the semiconductor substrate between the two conductive spacers and a gate structure positioned at least on the gate oxide layer. Particularly, each of two stack structures includes a first oxide block, a conductive block and a second oxide block, and the two conductive spacers are positioned at on the sidewall of the two conductive blocks of the two stack structures. The two conductive spacers are preferably made of polysilicon, and have a top end lower than the bottom surface of the second oxide block. In addition, a dielectric spacer is positioned on each of the two conductive spacers.

Method for fabricating memory cell

A new surface counter-doped lightly doped source and drain integrated circuit field effect transistor device is described. A gate silicon oxide layer is formed on the silicon substrate. A layer of polysilicon is deposited over the gate silicon oxide layer and etched to form a gate electrode structure. A first ion implantation is performed at a tilt angle to form lightly doped drain regions in the semiconductor substrate wherein the lightly doped drain regions are partially overlapped by the gate electrode structure. A second ion implantation is performed at a larger tilt angle and lower energy than the first ion implantation wherein the second ion implantation counter-dopes the surface of the lightly doped drain regions to form a very lightly doped drain layer thus making the lightly doped drain regions buried regions. A thin layer of silicon oxide is deposited over the surface of the polysilicon gate electrode structure and is anisotropically etched to form ultra thin spacers on the sidewalls of the polysilicon gate electrode structure. A third ion implantation is performed with no tilt angle to complete formation of the lightly doped drain regions. A glasseous layer is deposited over all surfaces of the substrate and flowed followed by metallization and passivation to complete manufacture of the integrated circuit.

Surface counter doped N-LDD for high carrier reliability

A method of forming an integrated circuit field effect transistor with surface counter-doped lightly doped drain regions is described. A gate silicon oxide layer is formed on the silicon substrate. A layer of polysilicon is deposited over the gate silicon oxide layer and etched to form a gate electrode structure. A first ion implantation is performed at a tilt angle to form lightly doped drain regions in the semiconductor substrate wherein the lightly doped drain regions are partially overlapped by the gate electrode structure. A second ion implantation is performed at a larger tilt angle and lower energy than the first ion implantation wherein the second ion implantation counter-dopes the surface of the lightly doped drain regions to form a very lightly doped drain layer thus making the lightly doped drain regions buried regions. A thin layer of silicon oxide is deposited over the surface of the polysilicon gate electrode structure and is anisotropically etched to form ultra thin spacers on the sidewalls of the polysilicon gate electrode structure. A third ion implantation is performed with no tilt angle to complete formation of the lightly doped drain regions. A glasseous layer is deposited over all surfaces of the substrate and flowed followed by metallization and passivation to complete manufacture of the integrated circuit.

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Hsinchu, Taiwan

Jih W Chou