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.

Abstract: A method is provided for forming buried source line in semiconductor devices. It is known in the art to form buried contacts on the surface of a semiconductor substrate. The present invention discloses a method of fabricating a semiconductor device, particularly a memory cell, having both the source region and the source line buried within the substrate. The source line is formed in a trench in the substrate over the source region. The trench walls are augmented with voltage anti-punch-through protection. The trench also provides the attendant advantages of extended sidewall area, smaller sheet resistance, and yet smaller cell area, therefore, smaller chip size, and faster access time as claimed in the embodiments of this invention. The buried source disclosed here is integrated with source line which is also buried within the substrate.

Abstract: A semiconductor memory device is formed on a doped semiconductor substrate, and covered with a tunnel oxide layer covered in turn with a doped first polysilicon layer. The first polysilicon layer is patterned into a pair of floating gate electrodes. An interelectrode dielectric layer covers the floating gate electrodes, the sidewalls of the floating gate electrodes and the edges of the tunnel oxide below the floating gate electrodes. A second polysilicon layer overlies the interelectrode dielectric layer and is in turn covered by a tungsten silicide layer. A second dielectric layer covers the tungsten silicide layer. A control gate electrode which spans the pair of floating gate electrodes is formed by the second polysilicon layer, the tungsten silicide and the first and second dielectric layers patterned into a gate electrode stack providing a control gate electrode spanning across the pair of floating gate electrodes.

Abstract: A method of forming split gate electrode MOSFET devices comprises the following steps. Form a tunnel oxide layer over a semiconductor substrate. Form a floating gate electrode layer over the tunnel oxide layer. Form a masking cap over the floating gate electrode layer. Pattern a gate electrode stack formed by the tunnel oxide layer and the floating gate electrode layer in the pattern of the masking cap. Form intermetal dielectric and control gate layers over the substrate covering the stack and the source regions and the drain regions. Pattern the intermetal dielectric and control gate layers into adjacent mirror image split gate electrode pairs. Pattern a source line slot in the center of the gate electrode stack down to the substrate. Form source regions through the source line slot. Form drain regions self-aligned with the split gate electrodes and the gate electrode stack.

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 split-gate flash memory cell having self-aligned source and floating gate self-aligned to control gate is disclosed as well as a method of forming the same. This is accomplished by depositing over a gate oxide layer on a silicon substrate a poly-1 layer to form a vertical control gate followed by depositing a poly-2 layer to form a spacer floating gate adjacent to the control gate with an intervening intergate oxide layer. The source is self-aligned and the floating gate is also formed to be self-aligned to the control gate, thus making it possible to reduce the cell size. The resulting self-aligned source alleviates punch-through from source to control gate while the self-aligned floating gate with respect to the control gate provides improved programmability. The method also replaces the conventional poly oxidation process thereby yielding improved sharp peak of floating gate for improved erasing and writing of the split-gate flash memory cell.

Abstract: A new method of fabricating a stacked gate Flash EEPROM device having an improved stacked gate topology is described. Isolation regions are formed on and in a semiconductor substrate. A tunneling oxide layer is provided on the surface of the semiconductor substrate. A first polysilicon layer is deposited overlying the tunneling oxide layer. The first polysilicon layer is polished away until the top surface of the polysilicon is flat and parallel to the top surface of the semiconductor substrate. The first polysilicon layer is etched away to form the floating gate. The source and drain regions are formed within the semiconductor substrate. An interpoly dielectric layer is deposited overlying the first polysilicon layer. A second polysilicon layer is deposited overlying the interpoly dielectric layer. The second polysilicon layer and the interpoly dielectric layer are etched away to form a control gate overlying the floating gate. An insulating layer is deposited overlying the oxide layer and the control gate.

Abstract: A layer of well oxide is grown over the n-well or p-well region of the semiconductor substrate. A deep n-well implant is performed in high voltage device region, followed by a deep n-well drive-in of the deep n-well implant. The well oxide is removed; the field oxide (FOX) region is created in the high voltage device region. A layer of sacrificial oxide is deposited on the surface of the semiconductor substrate. A low voltage cluster n-well implant is performed in the high voltage PMOS region of the semiconductor substrate followed, for the high voltage NMOS region, by a low voltage cluster p-well implant which is followed by a buried p-well cluster implant.

Abstract: In this invention bit lines are ion implanted into a semiconductor substrate in columns beside floating gates of an array of flash memory cells. A control gate overlays each row floating gates and operates as a word lines for the rows of flash memory cells. Each bit line serves a dual purpose of providing a drain for one cell and a source for the adjacent cell. The flash memory cells are programmed, erased and read depending upon the voltages applied to the buried bit lines and the word line structured as a control gate that extends the length of each row. By implanting the bit lines into the semiconductor substrate the flash memory cell can be made smaller improving the density of the flash memory.

Abstract: A method for forming a square oxide structure or a square floating gate without a rounding effect at its corners. A first dielectric layer is formed on a pad layer for a square oxide structure or a polysilicon layer overlying a gate oxide layer for a floating gate, and a second dielectric layer is formed on the first dielectric layer. The second dielectric layer is patterned to form parallel openings in a first direction using a first photosensitive mask. A second photosensitive mask, having a plurality of parallel openings in a second direction perpendicular to the first direction is formed over the second dielectric layer and the first dielectric layer. The first dielectric layer is etched through square openings where the openings in the second photosensitive mask and the openings in the second dielectric layer intersect, thereby forming square openings in the first dielectric layer. The second photosensitive mask and the second dielectric layer are removed.

Abstract: A flash EEPROM or split gate flash EEPROM is made on a doped silicon semiconductor N-well formed in a doped semiconductor substrate. A channel with a given width is formed in the N-well which is covered with a tunnel oxide layer, and an N+ doped polysilicon floating gate electrode layer, which can be patterned into a split gate floating gate electrode having a narrower width than the channel width. An interelectrode dielectric layer is formed over the floating gate electrode and the exposed tunnel oxide. A control gate electrode includes a layer composed of P+ doped polysilicon over the interelectrode dielectric layer. The tunnel oxide layer, the floating gate electrode layer, the interelectrode dielectric layer, and the control gate electrode are patterned into a gate electrode stack above the channel. A source region and a drain region are formed in the surface of the substrate with a P type of dopant, the source region and the drain region being self-aligned with the gate electrode stack.

Abstract: An ensemble of test structures comprising arrays of polysilicon plate MOS capacitors for the measurement of electrical quality of the MOSFET gate insulation is described. The test structures also measure plasma damage to these gate insulators incurred during metal etching and plasma ashing of photoresist. The structures are formed, either on test wafers or in designated areas of wafers containing integrated circuit chips. One of the test structures is designed primarily to minimize plasma damage so that oxide quality, and defect densities may be measured unhampered by interface traps created by plasma exposure. Other structures provide different antenna-to-oxide area ratios, useful for assessing plasma induced oxide damage and breakdown. The current-voltage characteristics of the MOS capacitors are measured by probing the structures on the wafer, thereby providing timely process monitoring capability.

Abstract: A method is disclosed for forming a split gate flash memory cell having a thin floating gate and a sharp poly tip in order to improve the erasing and programming speed of the cell. The method involves the use of an oxide other than the poly oxide that is conventionally employed in forming the floating gate, and also using to advantage a so-called “smiling effect” which is normally taught away. The smiling effect, or an uneven thickening of an oxide layer, comes into play while growing interpoly oxide where concurrently the oxidation of the polysilicon gate advances in such a manner so as to form a sharp and reliable poly tip. The invention is also directed to providing a split gate flash memory cell having a thin floating gate and a poly tip therein.

Abstract: A method is provided for forming a split-gate flash memory cell having a step poly supporting an interpoly oxide of varying thickness for the purposes of improving the over-all performance of the cell. Polyoxide is formed over portions of a first polysilicon layer which in turn is partially etched to form a step adjacent to the side-wall of a floating gate underlying the polyoxide. A spacer is next formed of a hot temperature oxide over the step poly. An interpoly oxynitride is then formed and control gate is patterned overlapping the floating gate with the intervening interpoly oxide. The step poly and the spacer thereon form proper distances between the control gate and the floating gate while keeping the distance between the poly tip and the control gate unchanged so that appropriate couplings between the control gate and the floating gate, and between the floating gate and the substrate are achieved, thus improving the over-all performance of the split-gate flash memory having a step poly.

Abstract: A split-gate flash memory cell having self-aligned source and floating gate self-aligned to control gate is disclosed as well as a method of forming the same. This is accomplished by depositing over a gate oxide layer on a silicon substrate a poly-1 layer to form a vertical control gate followed by depositing a poly-2 layer to form a spacer floating gate adjacent to the control gate with an intervening intergate oxide layer. The source is self-aligned and the floating gate is also formed to be self-aligned to the control gate, thus making it possible to reduce the cell size. The resulting self-aligned source alleviates punch-through from source to control gate while the self-aligned floating gate with respect to the control gate provides improved programmability. The method also replaces the conventional poly oxidation process thereby yielding improved sharp peak of floating gate for improved erasing and writing of the split-gate flash memory cell.

Abstract: A method is provided for forming a source line self-aligned to adjacent transistor device. This is accomplished by a forming a self-aligned polysilicon as a source line in an opening formed in a doped polysilicon layer separated from the source line by a spacer. The alignment of the poly source line with the transistor is provided by employing still another thin polysilicon layer as a mask for etching the source opening in the doped polysilicon layer which already has an outside wall aligned with respect to the contact hole for the drain of the device. An additional spacer is provided between the outside wall of the doped poly and the drain contact.

Abstract: A method of forming split gate electrode MOSFET devices comprises the following steps. Form a tunnel oxide layer over a semiconductor substrate. Form a floating gate electrode layer over the tunnel oxide layer. Form a masking cap over the floating gate electrode layer. Pattern a gate electrode stack formed by the tunnel oxide layer and the floating gate electrode layer in the pattern of the masking cap. Form intermetal dielectric and control gate layers over the substrate covering the stack and the source regions and the drain regions. Pattern the intermetal dielectric and control gate layers into adjacent mirror image split gate electrode pairs. Pattern a source line slot in the center of the gate electrode stack down to the substrate. Form source regions through the source line slot. Form drain regions self-aligned with the split gate electrodes and the gate electrode stack.

Abstract: A method is provided for forming buried source line in semiconductor devices. It is known in the art to form buried contacts on the surface of a semiconductor substrate. The present invention discloses a method of fabricating a semiconductor device, particularly a memory cell, having both the source region and the source line buried within the substrate. The source line is formed in a trench in the substrate over the source region. The trench walls are augmented with voltage anti-punch-through protection. The trench also provides the attendant advantages of extended sidewall area, smaller sheet resistance, and yet smaller cell area, therefore, smaller chip size, and faster access time as claimed in the embodiments of this invention. The buried source disclosed here is integrated with source line which is also buried within the substrate.

Abstract: A method is disclosed for forming a split-gate flash memory cell where the floating gate of the cell is self-aligned to isolation, to source and to word line. This multi-self-aligned structure, which provides the maximum shrinkage of the cell that is possible, is also disclosed. The multi-self-alignment is accomplished by first defining the floating gate at the same time the trench isolation is formed, and then self-aligning the source to the floating gate by using a nitride layer as a hard mask in place of the traditional polyoxide, and finally forming a polysilicon spacer to align the word line to the floating gate. Furthermore, a thin floating gate is used to form a thin and sharp poly tip through the use of a “smiling effect” to advantage.

Abstract: A new method of fabricating a stacked gate Flash EEPROM device having an improved stacked gate topology is described. Isolation regions are formed on and in a semiconductor substrate. A tunneling oxide layer is provided on the surface of the semiconductor substrate. A first polysilicon layer is deposited overlying the tunneling oxide layer. The first polysilicon layer is polished away until the top surface of the polysilicon is flat and parallel to the top surface of the semiconductor substrate. The first polysilicon layer is etched away to form the floating gate. The source and drain regions are formed within the semiconductor substrate. An interpoly dielectric layer is deposited overlying the first polysilicon layer. A second polysilicon layer is deposited overlying the interpoly dielectric layer. The second polysilicon layer and the interpoly dielectric layer are etched away to form a control gate overlying the floating gate. An insulating layer is deposited overlying the oxide layer and the control gate.