Charge trapping split gate device and method of fabricating same
View Patent ↗Embodiments provide a split gate device, methods for fabricating a split gate device, and integrated methods for fabricating a split gate device and a periphery device. In an embodiment, the split gate device is a charge trapping split gate device, which includes a charge trapping layer. In another embodiment, the split gate device is a non-volatile memory cell, which can be formed according to embodiments as standalone or embedded with a periphery device.
1. A method of fabricating a split gate device, comprising:
disposing a first conductor layer over a substrate;
disposing, using a non-photolithographic process, a hardmask layer over the first conductor layer;
etching, in an etch process, the hardmask layer to form a first hardmask gate pattern over a first region of the substrate and a second hardmask gate pattern over a second region of the substrate, wherein the first hardmask gate pattern and the second hardmask gate pattern are both formed by the etch process;
forming a first photoresist layer over the second region of the substrate, wherein the first region of the substrate remains uncovered by the first photoresist layer;
etching, in the uncovered first region of the substrate, the first conductor layer according to the first hardmask gate pattern to form a first gate of the split gate device, wherein the second region of the substrate is covered by the first photoresist layer while the first conductor layer is etched in the first region;
removing the first photoresist layer from the second region of the substrate;
forming a dielectric over the first gate and the second hardmask gate pattern;
disposing a second conductor layer over the dielectric;
forming a second photoresist layer over the second conductor layer in the second region of the substrate, wherein the first region of the substrate remains uncovered by the second photoresist layer; and
etching the second conductor layer, in the uncovered first region of the substrate, to form a second gate of the split gate device, wherein the second region of the substrate is covered by the second photoresist layer while the second conductor layer is etched in the first region.
2. The method of claim 1 , further comprising:
removing exposed portions of the dielectric;
forming a third photoresist layer over the first region and a portion of the second region; and
etching the first conductor layer according to the second hardmask gate pattern to form a gate of a periphery device in the second region.
3. The method of claim 2 , wherein the etching of the first conductor layer according to the first hardmask gate pattern and the etching of the first conductor layer according to the second hardmask gate pattern are performed at different times.
4. The method of claim 2 , wherein the etching of the first conductor layer according to the first hardmask gate pattern is performed before the etching of the first conductor layer according to the second hardmask gate pattern.
5. The method of claim 2 , wherein etching the first conductor layer according to the first hardmask gate pattern to form the first gate of the split gate device comprises:
forming a photo resist mask over the second region only of the substrate.
6. The method of claim 2 , wherein etching the first conductor layer according to the second hardmask gate pattern to form the gate of the periphery device comprises:
forming a photo resist mask over the first region only of the substrate.
7. The method of claim 2 , wherein the first gate and the second gate of the split gate device are formed before the gate of the periphery device.
8. The method of claim 1 , wherein etching the first conductor layer according to the first hardmask gate pattern to form the first gate of the split gate device comprises:
forming a photo resist mask over the second region only of the substrate.
9. The method of claim 1 , further comprising:
growing a thick oxide layer over the substrate;
forming a device isolation trench in the substrate after growing the thick oxide layer over the substrate; and
forming a high voltage periphery device using the thick oxide layer as a gate oxide of the high voltage periphery device.
10. The method of claim 1 , wherein etching the second conductor layer to form the second gate of the split gate device comprises:
etching the second conductor layer to create first and second formations of the second conductor layer on first and second sidewalls respectively of the first gate;
forming a photo resist mask over the first formation; and etching the conductor layer to remove the second formation,
wherein the first formation corresponds to the second gate of the split gate device.
11. The method of claim 1 , further comprising:
forming a spacer over the first gate, the spacer covering a portion of an inner sidewall of the second gate that extends above a top surface of the first gate.
12. The method of claim 1 , wherein forming the dielectric comprises:
forming a bottom oxide layer over the first gate, an exposed region of the substrate, and the second hardmask pattern;
forming a nitride layer over the bottom oxide layer; and
forming a top oxide layer over the nitride layer.
13. The method of claim 12 , further comprising:
removing the top oxide layer and the nitride layer from a top surface of the first gate of the split gate device.
14. The method of claim 1 , further comprising:
forming first and second spacers on first and second sidewalls on the split gate device.
15. The method of claim 1 , further comprising:
forming a silicide layer over the first gate and the second gate.
16. A method for fabricating a split gate device and a periphery device, the method comprising:
disposing, using a non-photolithographic process, a hardmask layer above a substrate;
etching, in an etch process, the hardmask layer to form a first hardmask gate pattern over a first region of the substrate and a second hardmask gate pattern over a second region of the substrate, wherein the first hardmask gate pattern and the second hardmask gate pattern are both formed by the etch process;
forming a first photoresist layer over the second region of the substrate, wherein the first region of the substrate remains uncovered by the first photoresist layer;
etching, in the uncovered first region of the substrate, a first conductor layer according to the first hardmask gate pattern to form a first gate of the split gate device, wherein the second region of the substrate is covered by the first photoresist layer while the first conductor layer is etched in the first region;
forming a dielectric over the first gate and an exposed region of the substrate;
forming a second conductor layer over the dielectric;
forming a second photoresist layer over the second conductor in the second region of the substrate, wherein the first region of the substrate remains uncovered by the second photoresist layer;
etching the second conductor layer, in the uncovered first region of the substrate, to form a second gate of the split gate device, wherein the second region of the substrate is covered by the second photoresist layer while the second conductor layer is etched in the first region; and
etching the first conductor layer according to the second hardmask gate pattern to form a gate of the periphery device.
17. The method of claim 16 , further comprising:
disposing the first conductor layer over the substrate; and
disposing the hardmask layer over the first conductor layer.
18. The method of claim 16 , wherein the etching of the first conductor layer according to the first hardmask gate pattern and the etching of the first conductor layer according to the second hardmask gate pattern are performed at different times.
19. The method of claim 16 , wherein the etching of the first conductor layer according to the first hardmask gate pattern is performed before the etching of the first conductor layer according to the second hardmask gate pattern.