National Semiconductor Corporation

Jiankang Bu

David Courtney Parker

Li-Heng Chou

Lee James Jacobson

Andre Paul Labonte

William S Belcher

Thanas Budri

Heather McCulloh

Henry G Prosack, Jr

Mark Rathmell

Kenneth M Lewis

A method includes forming at least one control gate over a semiconductor substrate. The method also includes depositing a layer of conductive material over the at least one control gate and the semiconductor substrate. The method further includes etching the layer of conductive material to form multiple spacers adjacent to the at least one control gate, where at least one of the spacers forms a floating gate in at least one memory cell. Two spacers could be formed adjacent to the at least one control gate, and one of the spacers could be etched so that a single memory cell includes the control gate and the remaining spacer. Also, two spacers could be formed adjacent to the at least one control gate, and the at least one control gate could be etched and separated to form multiple control gates associated with different memory cells.

Non-volatile memory cell with asymmetrical split gate and related system and method

A memory cell includes a control gate and a transistor having a gate, a source junction, and a drain junction. The gate is coupled to the control gate, and the source junction and the drain junction are asymmetrical. For example, a channel doping associated with the source junction may be different than a channel doping associated with the drain junction. The memory cell also includes a write line coupled to the control gate, a source line coupled to the source junction of the transistor, and a bit line coupled to the drain junction of the transistor. The control gate could represent a second transistor, where the gates of the transistors are coupled together to form a floating gate. The memory cell could be programmed to store a single-bit value or a multiple-bit value, such as by storing the appropriate charge on the floating gate.

High-performance CMOS-compatible non-volatile memory cell and related method

A system and method is disclosed for providing a low voltage high density multi-bit storage flash memory. A dual bit memory cell of the invention comprises a substrate having a common source, a first drain and first channel, and a second drain and a second channel. A common control gate is located above the source. A first floating gate and a second floating gate are located on opposite sides of the control gate. Each floating gate is formed with a sharp tip adjacent to the control gate and an upper curved surface that follows a contour of the surface of the control gate. The sharp tips of the floating gates efficiently discharge electrons into the control gate when the memory cell is erased. The curved surfaces increase capacitor coupling between the control gate and the floating gates.

System and method for providing low voltage high density multi-bit storage flash memory

A system and method is disclosed for improving complementary metal oxide semiconductor (CMOS) compatible non volatile memory (NVM) retention reliability in memory cells. A memory cell of the invention comprises a backend layer that reduces charge leakage from a floating gate of the memory cell. A first bottom portion of the backend layer is formed from a first layer of silicon oxynitride having a low value of defect/trap density. A second top portion of the backend layer is formed from a second layer of silicon oxynitride having a high value of defect/trap density. The first layer of silicon oxynitride inhibits electron transport and the second layer of silicon oxynitride protects CMOS devices from plasma induced damage.

System and method for improving CMOS compatible non volatile memory retention reliability

A system and method are disclosed for increasing the reliability of a channel erase procedure in an electrically erasable programmable read only memory (EEPROM) memory cell. A memory cell of the present invention comprises a program gate, a control gate, and a floating gate that erase data using a channel erase procedure. An erase capacitor is coupled to the floating gate to provide a low voltage bias that decreases the voltage that is required to perform a Fowler-Nordheim erase process in the memory cell. The erase capacitor of the present invention is formed without adding a step in the manufacturing process of the memory cell. Memory cells of the present invention are low cost, high endurance, low voltage memory cells.

System and method for providing low cost high endurance low voltage electrically erasable programmable read only memory

A non-volatile memory cell includes a program transistor and a control capacitor. A portion of a substrate associated with the program transistor is exposed to multiple implantations (such as DNW, HiNWell, HiPWell, and P-well implantations). Similarly, a portion of the substrate associated with the control capacitor is exposed to multiple implantations (such as DNW, HiNWell, HiPWell, P-well, and N-well implantations). These portions of the substrate may have faster oxidation rates than other portions of the substrate, allowing a thicker front-end gate oxide to be formed over these portions of the substrate. In addition, a rapid thermal process anneal can be performed, which may reduce defects in the front-end gate oxide and increase its quality without having much impact on the oxide over the other portions of the substrate.

Method for fabricating higher quality thicker gate oxide in a non-volatile memory cell and associated circuits

A method for scaling channel length in a semiconductor device is provided. The method includes increasing a pitch to reduce a development inspection critical dimension (DICD) for a plurality of polysilicon lines. The polysilicon lines are trimmed to provide a reduced-size channel length, based on the reduced DICD, for each polysilicon line. For a particular embodiment, the semiconductor device is fabricated using a photolithography tool having a wavelength of 248 nm, the pitch is about 800 nm, and the reduced-size channel length is about 0.11 &#x3bc;m.

Method and system for scaling channel length

A method for forming a transistor gate includes performing a first exposure of a photo-resist material on a semiconductor device. The first exposure defines a line pattern in the photo-resist material. The method also includes performing a second exposure of the photo-resist material, where the second exposure trims a resist profile of the line pattern. The method further includes etching a conductive material on the semiconductor device to form a transistor gate based on the line pattern. The first exposure could represent a best focus exposure of the photo-resist material, and the second exposure could represent a positive focus exposure of the photo-resist material. The trimming of the line pattern's resist profile may cause the transistor gate to have at least one of a rounded edge and a rounded corner. This may allow a thicker insulating material, such as tetraethylorthosilicate, to be deposited around portions of the transistor gate.

Photo-focus modulation method for forming transistor gates and related transistor devices

A system and method are disclosed for increasing retention reliability of a floating gate of a CMOS compatible memory cell. A mask structure is formed with a plurality of apertures near the edges of the mask structure. The size of the apertures is less than a resolution limitation of a photo exposure system. The mask structure is placed over a resist material and the resist material is exposed to light through the apertures of the mask structure. Zero order diffraction light passes though the apertures and imparts energy to the exposed portions of the resist material. A develop process is then used to remove portions of the resist material to form a sloped edge resist pattern. A sloped edge floating gate that is formed from the pattern facilitates the deposition of a thicker oxide layer at the sloped edge of the floating gate and reduces backend leakage current.

System and method for providing process compliant layout optimization using optical proximity correction to improve CMOS compatible non volatile memory retention reliability

A system and method are disclosed for providing an electrically programmable read only memory (EPROM) in which each memory cell comprises an NMOS select transistor with a thick gate oxide and a PMOS breakdown transistor with a thin gate oxide. The source of the NMOS transistor and the source, drain and N well of the PMOS transistor are connected. The gate of the PMOS transistor is grounded. Under the control of the NMOS transistor, a programming voltage pulse is passed to the N well of the PMOS transistor of a selected memory cell. The magnitude of the voltage is sufficient to break the thin gate oxide of the PMOS transistor without damaging the NMOS transistor. Because the memory state of the memory cell depends on the breakdown status of the PMOS transistor, the data may be retained in the memory cell for an unlimited period of time.

System and method for providing an EPROM with different gate oxide thicknesses

A method includes forming a release layer of a semiconductor device being fabricated, where the release layer has a trapezoidal shape. The method also includes forming a cantilever, which has a cantilever arm formed over the release layer. The method further includes removing at least part of the release layer from under the cantilever arm. The release layer could be formed using a photo-resist material. The photo-resist material can be patterned by exposing the photo-resist material using multiple exposures. A first exposure could expose a portion of the photo-resist material, where the exposed portion has substantially vertical sides. A second exposure could give the exposed portion of the photo-resist material slanted sides. A wet etch could be performed to remove the release layer from under the cantilever arm.

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Windham, ME, United States of America

Jiankang Bu