Abstract: A new method to form MOS gates in an integrated circuit device is achieved. The method is particularly useful for forming floating gates in split gate flash transistors. The method comprises providing a substrate. A dielectric layer is formed overlying the substrate. A conductor layer is formed overlying the dielectric layer. A first masking layer is deposited overlying the conductor layer. The first masking layer is patterned to selectively expose the conductor layer. A second masking layer is deposited overlying the first masking layer and the conductor layer. The second masking layer is etched back to form spacers on sidewalls of the first masking layer. The conductor layer is etched through where exposed by the first masking layer and the spacers to thereby form MOS gates in the manufacture of the integrated circuit device.

Abstract: A new method to form MOS gates in an integrated circuit device is achieved. The method is particularly useful for forming floating gates in split gate flash transistors. The method comprises providing a substrate. A dielectric layer is formed overlying the substrate. A conductor layer is formed overlying the dielectric layer. A first masking layer is deposited overlying the conductor layer. The first masking layer is patterned to selectively expose the conductor layer. A second masking layer is deposited overlying the first masking layer and the conductor layer. The second masking layer is etched back to form spacers on sidewalls of the first masking layer. The conductor layer is etched through where exposed by the first masking layer and the spacers to thereby form MOS gates in the manufacture of the integrated circuit device.

Abstract: A memory cell including a substrate having a source region; a floating gate structure disposed over the substrate and associated with the source region; and a source coupling enhancement structure covering an exposed portion of the floating gate structure and extending to the source region. The flash memory cell can be fabricated in a method including the steps of forming the floating gate structure over a substrate; forming the source coupling enhancement structure on an exposed portion of the floating gate structure; and forming the source region in the substrate.

Abstract: Methods of fabricating semiconductor devices using separate periphery and cell region etching steps are provided. A substrate is provided, wherein the substrate has a cell region and a periphery region separated by a shallow trench isolation (STI). The STI is filled with a dielectric material. A protective layer is formed on the periphery region, allowing semiconductor structures to be formed in the cell region without damaging the surface of the periphery region. Upon forming the semiconductor structures in the cell region, a portion of the dielectric material in the STI adjacent to the cell region is partially removed. The dielectric material adjacent to the periphery region is substantially unetched.

Abstract: A new method to form MOS gates in an integrated circuit device is achieved. The method is particularly useful for forming floating gates in split gate flash transistors. The method comprises providing a substrate. A dielectric layer is formed overlying the substrate. A conductor layer is formed overlying the dielectric layer. A first masking layer is deposited overlying the conductor layer. The first masking layer is patterned to selectively expose the conductor layer. A second masking layer is deposited overlying the first masking layer and the conductor layer. The second masking layer is etched back to form spacers on sidewalls of the first masking layer. The conductor layer is etched through where exposed by the first masking layer and the spacers to thereby form MOS gates in the manufacture of the integrated circuit device.

Abstract: A method is provided for forming a flash memory cell having an amorphous silicon floating gate capped by a CVD oxide, and a control gate formed over an intergate oxide layer formed over the oxide cap. Amorphous silicon is first formed over a gate oxide layer over a substrate, followed by the forming of a silicon nitride layer over the amorphous silicon layer. Silicon nitride is patterned to have a tapered opening so that the process window for aligning the floating gate with the active region of the cell is achieved with a relatively wide margin. Next, an oxide cap is formed over the floating gate. Using an oxide deposition method in place of the conventional polyoxidation method provides a less bulbous oxide formation over the floating gate, thus, yielding improved erase speed for the cell. The invention is also directed to a flash memory cell fabricated by the disclosed method.

Abstract: A method of fabricating an embedded flash memory device. A substrate having a memory area is provided. A device is formed on the substrate in the memory area. A conductive layer is formed over the substrate to cover the device in the memory area. A conformal insulating layer is formed on the conductive layer and the substrate. The insulating layer is removed at an edge of the memory area. By anisotropic etching, the insulating layer and part of the conductive layer is removed to form a control gate on the sidewall of the device. Thus, polysilicon residue caused by the conventional control gate process does not occur.

Abstract: A process for forming a high voltage oxide (HV) and a select gate poly for a split-gate flash memory is disclosed. The general difficulty of forming oxides of two different thicknesses for two different areas on the same substrate is alleviated by forming an HV oxide layer over the entire substrate just prior to the forming of the control gate of a cell area after the forming of a gate oxide layer over the peripheral area of the substrate. At an immediate subsequent step, a peripheral gate is formed over the HV oxide over the peripheral area, and, as a final step, the forming of the control gate, or the select gate of the cell area follows next.

Abstract: A method to suppress bit-line leakage in a nonvolatile memory cell is achieved. The method comprises providing an array of nonvolatile memory cells comprising source and bulk terminals. The array comprises a plurality of subarrays. The sources of all the nonvolatile cells in each subarray are coupled together to form a common subarray source. Bulks of all the nonvolatile cells in the array are coupled together to form a common array bulk. A first, non-zero voltage is forced between the common subarray source and the common array bulk for a first subarray that is selected for an access operation. A second, non-zero voltage is forced between the common subarray source and the common array bulk for a second subarray that is not selected for an access operation. The second, non-zero voltage inhibits bit line leakage in the second subarray.

Abstract: A memory cell including a substrate having a source region; a floating gate structure disposed over the substrate and associated with the source region; and a source coupling enhancement structure covering an exposed portion of the floating gate structure and extending to the source region. The flash memory cell can be fabricated in a method including the steps of forming the floating gate structure over a substrate; forming the source coupling enhancement structure on an exposed portion of the floating gate structure; and forming the source region in the substrate.

Abstract: A new method is provided for the etch of polysilicon spacers that form part of split-gate flash memory devices. Under a first embodiment of the invention, a conventional polysilicon gate etch is augmented with an oxide based plasma treatment of the layer of polysilicon that is being etched as part of this etch.

Abstract: A method is provided for forming a split-gate flash memory cell having a shallow trench isolation without the intrusion of a “smiling” gap near the edge of the trench encompassing the first polysilicon layer. This is accomplished by forming two conformal layers lining the interior walls of the trench. An exceptionally thin nitride layer overlying the first conformal oxide layer provides the necessary protection during the oxidation of the first polysilicon layer so as to prevent the “smiling” effect normally encountered in fabricating ultra large scale integrated circuits.

Abstract: A method to suppress bit-line leakage in a nonvolatile memory cell is achieved. The method comprises providing an array of nonvolatile memory cells comprising source and bulk terminals. The array comprises a plurality of subarrays. The sources of all the nonvolatile cells in each subarray are coupled together to form a common subarray source. Bulks of all the nonvolatile cells in the array are coupled together to form a common array bulk. A first, non-zero voltage is forced between the common subarray source and the common array bulk for a first subarray that is selected for an access operation. A second, non-zero voltage is forced between the common subarray source and the common array bulk for a second subarray that is not selected for an access operation. The second, non-zero voltage inhibits bit line leakage in the second subarray.

Abstract: A PIP (Poly-Interpoly-Poly) capacitor with high capacitance is provided in a split-gate flash memory cell. A method is also disclosed to form the same PIP capacitor where the bottom and top plates of the capacitor are formed simultaneously with the floating gate and control gate, respectively, of the split-gate flash memory cell. Furthermore, the thin interpoly oxide of the cell, rather than the thick poly-oxide over the floating gate is used as the insulator between the plates of the capacitor. The resulting capacitor yields high storage capacity through high capacitance per unit area.

Abstract: A method of etch polysilicon adjacent to a recessed STI structure feature is described. A substrate is provided with a dielectric layer thereon and a polysilicon layer on the dielectric layer. A shallow trench is formed that extends through the polysilicon and dielectric layers into the substrate. An insulating material is used to fill the trench and is then recessed in the trench below the surface of the substrate by polishing and etching steps. A conformal buffer layer is deposited which covers the polysilicon and sidewalls of the trench above the recessed insulating layer. The buffer layer is etched back to expose the insulating layer and the polysilicon is removed by a plasma etch. A spacer comprised of a portion of the buffer layer protects the substrate during the polysilicon etch to prevent unwanted trenches from being formed adjacent to the STI structure, thereby increasing the etch process window.

Abstract: A method is provided to form a sharp poly tip to improve the speed of a split-gate flash memory. The sharp poly tip is provided in place of the conventional gate bird's beak (GBB) because the latter requires the forming of thick poly-oxide which is more and more difficult in the miniaturized circuits of the ultra scale integrated technology. Furthermore, it is well known that GBB encroaches under the gate edge in a split-gate flash and degrades the programmability of submicron memory cells. The sharp poly tip of the invention is provided by forming a tapered floating gate through a high pressure etch such that the tip of the upper edge of the floating gate under the poly oxide is sharper and more robust, and, therefore, less susceptible to damage during the manufacture of the cell. The invention is also directed to a semiconductor device fabricated by the disclosed method.

Abstract: A method is provided for forming a flash memory cell having an amorphous silicon floating gate capped by a CVD oxide, and a control gate formed over an intergate oxide layer formed over the oxide cap. Amorphous silicon is first formed over a gate oxide layer over a substrate, followed by the forming of a silicon nitride layer over the amorphous silicon layer. Silicon nitride is patterned to have a tapered opening so that the process window for aligning the floating gate with the active region of the cell is achieved with a relatively wide margin. Next, an oxide cap is formed over the floating gate. Using an oxide deposition method in place of the conventional polyoxidation method provides a less bulbous oxide formation over the floating gate, thus, yielding improved erase speed for the cell. The invention is also directed to a flash memory cell fabricated by the disclosed method.

Abstract: A split gate P-channel flash memory cell and method of forming a split gate P-channel flash memory cell which avoids of high erasing voltage, reverse tunneling during programming, drain disturb and over erase problems, and permits shrinking the cell dimensions. The control gate has a concave top surface which intersects with the sidewalls to form a sharp edge. The cell is programmed by charging the floating gate with electrons by means of hot electron injection from the channel into the floating gate. The cell is erased by discharging the excess electrons from the floating gate into the control gate using Fowler-Nordheim tunneling. The sharp edge at the intersection of the concave top surface and the sidewalls of the floating gate produces a high electric field between the control gate and the floating gate to accomplish the Fowler-Nordheim tunneling with only moderate voltage differences between the floating gate and control gate.

Abstract: A method for forming square polysilicon spacers on a split gate flash memory device by a multi-step polysilicon etch process is described. The method can be carried out by depositing a polysilicon layer on the flash memory device structure and then depositing a sacrificial layer, such as silicon oxide, on top of the polysilicon layer. The sacrificial layer has a slower etch rate than the polysilicon layer during a main etch step. The sacrificial layer overlies the flash memory device is then removed, while the sacrificial layer on the sidewall is kept intact. The polysilicon layer that overlies the flash memory device is then etched away followed by a step of removing all residual sacrificial layers. The exposed polysilicon layer is then etched to define the square polysilicon spacers on the split gate flash memory device.

Abstract: A method is disclosed for forming a split-gate flash memory cell having a salicidated control gate and self-aligned contacts. Salicidation is normally performed with single gate devices, such as logic devices. In a split-gate where the control gate overlays the floating gate with an intervening intergate oxide layer, it is conventionally incompatible to form self-aligned silicides over the control gate due to its position at a different level from that of the floating gate. Furthermore, oxide spacers that are normally used are inadequate when applied to memory cells. It is shown in the present invention that by a judicious use of an additional nitride/oxide layer over the control gate, oxide spacers can now be used effectively to delineate areas on the control gate that can be silicided and also self-aligned.