摘要:
A split gate EEPROM memory device formed on a doped silicon semi-conductor substrate starting with an initial oxide layer with an undoped first polysilicon layer formed thereon. A polysilicon oxide hard mask over the undoped first polysilicon layer for use in patterning the initial oxide layer and the undoped first polysilicon layer which are then etched to form a floating gate electrode stack from the undoped first polysilicon layer and the initial oxide layer on the substrate. Then form a tunnel oxide layer and a doped polysilicon and pattern them into control gate electrode stack, with the control gate electrode stack being located in a split-gate configuration with respect to the floating gate electrode stack.
摘要:
Form a split gate EEPROM memory device on a doped silicon semiconductor substrate starting with an initial oxide layer and form an undoped first polysilicon layer thereon. Then form a polysilicon oxide hard mask over the undoped first polysilicon layer for use in patterning the initial oxide layer and the undoped first polysilicon layer which are then etched to form a floating gate electrode stack from the undoped first polysilicon layer and the initial oxide layer on the substrate. Then form a tunnel oxide layer and a doped polysilicon and pattern them into control gate electrode stack, with the control gate electrode stack being located in a split-gate configuration with respect to the floating gate electrode stack.
摘要:
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.
摘要:
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.
摘要:
A split-gate flash memory cell having a three-dimensional source capable of three-dimensional coupling with the floating gate of the cell, as well as a method of forming the same are provided. This is accomplished by first forming an isolation trench, lining it with a conformal oxide, then filling with an isolation oxide and then etching the latter to form a three-dimensional coupling region in the upper portion of the trench. A floating gate is next formed by first filling the three-dimensional region of the trench with polysilicon and etching it. The control gate is formed over the floating gate with an intervening inter-poly oxide. The floating gate forms legs extending into the three-dimensional coupling region of the trench thereby providing a three-dimensional coupling with the source which also assumes a three-dimensional region. The leg or the side-wall of the floating gate forming the third dimension provides the extra area through which coupling between the source and the floating gate is increased. In this manner, a higher coupling ratio is achieved without an increase in the cell size while at the same time alleviating the punchthrough and junction break-down of source region by sharing gate voltage along the side-wall.
摘要:
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. The P-channel flash memory cell has a higher impact ionization rage for creating hot electrons so that the distance between the source and drain junctions and the length of the floating gate can be kept small thereby permitting the dimensions of the flash memory cell to be shrunk.
摘要:
A novel method of forming a first polysilicon gate tip (poly-tip) for enhanced F-N tunneling in split-gate flash memory cells is disclosed. The poly-tip is formed in the absence of using a thick polysilicon layer as the floating gate. This is made possible by forming an oxide layer over the poly-gate and oxidizing the sidewalls of the polygate. Because the starting thickness of polysilicon of the floating gate is relatively thin, the resulting gate beak, or poly-tip, is also necessarily thin and sharp. This method, therefore, circumvents the problem of oxide thinning encountered in scaling down devices of the ultra large scale integration technology and the fast programmability and erasure performance of EEPROMs is improved.
摘要:
A method is disclosed for forming a split-gate flash memory cell having a protruding source in place of the conventional flat source. The vertically protruding source structure has a top portion and a bottom portion. The bottom portion is polysilicon while the top portion is poly-oxide. The vertical wall of the protruding structure over the source is used to form vertical floating gate and spacer control gate with an intervening inter-gate oxide. Because the coupling between the source and the floating gate is now provided through the vertical wall, the coupling area is much larger than with conventional flat source. Furthermore, there is no longer the problem of voltage punch-through between the source and the drain. The vertical floating gate is also made thin so that the resulting thin and sharp poly-tip enhances further the erasing and programming speed of the flash memory cell. The vertical orientation of the source structure and the floating gate and the self-alignment of the spacer control gate to the floating gate together makes it possible to reduce the memory cell substantially.
摘要:
A method is disclosed to form a split-gate flash memory cell having nitride spacers formed on a pad oxide and prior the forming of an inter-poly oxide layer thereover. In this manner, any damage that would normally occur to the inter-poly oxide during the etching of the nitride spacers subsequent to the forming of the inter-poly oxide is avoided. Consequently, the variation in the thickness of the inter-poly oxide due to the unpredictable damage to the underlying spacers is also avoided by reversing the order in which the spacers and the inter-poly oxide are formed, including the forming of the pad oxide first. As a result, variation in the erase speed of the inter-gate flash memory cell is prevented, both for cells fabricated on the same wafer as well as on different wafers on same or different production lines.
摘要:
A split-gate flash memory cell having a three-dimensional source capable of three-dimensional coupling with the floating gate of the cell, as well as a method of forming the same are provided. This is accomplished by first forming an isolation trench, lining it with a conformal oxide, then filling with an isolation oxide and then etching the latter to form a three-dimensional coupling region in the upper portion of the trench. A floating gate is next formed by first filling the three-dimensional region of the trench with polysilicon and etching it. The control gate is formed over the floating gate with an intervening inter-poly oxide. The floating gate forms legs extending into the three-dimensional coupling region of the trench thereby providing a three-dimensional coupling with the source which also assumes a three-dimensional region. The leg or the side-wall of the floating gate forming the third dimension provides the extra area through which coupling between the source and the floating gate is increased. In this manner, a higher coupling ratio is achieved without an increase in the cell size while at the same time alleviating the punchthrough and junction break-down of source region by sharing gate voltage along the side-wall.