Method for fabricating a 3-D integrated circuit using a hard mask of silicon-oxynitride on amorphous carbon
A method for fabricating a 3-D monolithic memory device. Silicon-oxynitride (Si x O y N z ) on amorphous carbon is used an effective, easily removable hard mask with high selectivity to silicon, oxide, and tungsten. A silicon-oxynitride layer is etched using a photoresist layer, and the resulting etched Si x O y N z layer is used to etch an amorphous carbon layer. Silicon, oxide, and/or tungsten layers are etched using the amorphous carbon layer. In one implementation, conductive rails of the 3-D monolithic memory device are formed by etching an oxide layer such as silicon dioxide (SiO 2 ) using the patterned amorphous carbon layer as a hard mask. Memory cell diodes are formed as pillars in polysilicon between the conductive rails by etching a polysilicon layer using another patterned amorphous carbon layer as a hard mask. Additional levels of conductive rails and memory cell diodes are formed similarly to build the 3-D monolithic memory device.
1. A method for fabricating a 3-D monolithic memory device, comprising:
patterning a first silicon-oxynitride layer in a layered structure to provide a first patterned silicon-oxynitride layer, the layered structure includes a first amorphous carbon layer below the first silicon-oxynitride layer, and a first polycrystalline layer below the first amorphous carbon layer;
patterning the first amorphous carbon layer using the first patterned silicon-oxynitride layer to provide a first patterned amorphous carbon layer;
patterning the first polycrystalline layer using the first patterned amorphous carbon layer to provide a first plurality of pillars which comprise diodes in a first level of the 3-D monolithic memory device;
forming a second polycrystalline layer above the first plurality of pillars, a second amorphous carbon layer above the second polycrystalline layer, and a second silicon-oxynitride layer above the second amorphous carbon layer;
patterning the second silicon-oxynitride layer to provide a second patterned silicon-oxynitride layer;
patterning the second amorphous carbon layer using the second patterned silicon-oxynitride layer to provide a second patterned amorphous carbon layer; and
patterning the second polycrystalline layer using the second patterned amorphous carbon layer to provide a second plurality of pillars which comprise diodes in a second level of the 3-D monolithic memory device.
2. The method of claim 1 , wherein:
during the patterning of the first polycrystalline layer, a conductive layer which is provided between the first polycrystalline layer and the first patterned amorphous carbon layer is also patterned using the first patterned amorphous carbon layer.
3. The method of claim 1 , wherein the first plurality of pillars are electrically coupled from below to a first set of conductive rails, the method further comprising:
forming a second set of conductive rails above the first plurality of pillars and below the second plurality of pillars, the first plurality of pillars are electrically coupled from above to the second set of conductive rails, and the second plurality of pillars are electrically coupled from below to the second set of conductive rails.
4. The method of claim 1 , wherein:
the first silicon-oxynitride layer has a starting thickness of about 220 to 420 Angstroms; and
the first amorphous carbon layer has a starting thickness of approximately 2700 to 3300 Angstroms.
5. The method of claim 1 , wherein:
the patterning of the first polycrystalline layer using the first patterned amorphous carbon layer includes patterning one or more intermediate layers using the first patterned amorphous carbon layer and patterning the first polycrystalline layer using the one or more intermediate layers.
6. The method of claim 2 , wherein:
the conductive layer comprise at least one of tungsten and aluminum titanium nitride.
7. A method for fabricating a 3-D monolithic memory device, comprising:
in a layered structure, in a first level of the 3-D monolithic memory device:
transferring a first common pattern to a first silicon-oxynitride layer and a first amorphous carbon layer below the first silicon-oxynitride layer, to provide, together, first patterned silicon-oxynitride and amorphous carbon layers;
patterning a first oxide layer below the first amorphous carbon layer using the first patterned silicon-oxynitride and amorphous carbon layers together to provide a first patterned oxide layer;
forming a first set of conductive rails in the first patterned oxide layer;
forming a polycrystalline layer above the first set of conductive rails; and
patterning the polycrystalline layer to form a plurality of pillars which are electrically coupled to the first set of conductive rails, the first plurality of pillars comprise diodes; and
above the first level of the 3-D monolithic memory device, in a second level of the 3-D monolithic memory device:
transferring a second common pattern to a second silicon-oxynitride layer and a second amorphous carbon layer below the second silicon-oxynitride layer, to provide, together, second patterned silicon-oxynitride and amorphous carbon layers; and
patterning a second oxide layer below the second amorphous carbon layer using the second patterned silicon-oxynitride and amorphous carbon layers together to provide a second patterned oxide layer.
8. The method of claim 7 , further comprising, in the second level of the 3-D monolithic memory device:
forming a second set of conductive rails in the second patterned oxide layer;
forming a polycrystalline layer above the second set of conductive rails; and
patterning the polycrystalline layer to form a second plurality of pillars which are electrically coupled to the second set of conductive rails, the second plurality of pillars comprise diodes.
9. A method for fabricating a 3-D monolithic memory device, comprising:
in a layered structure, in a first level of the 3-D monolithic memory device:
transferring a common pattern to a first silicon-oxynitride layer and a first amorphous carbon layer below the first silicon-oxynitride layer, to provide, together, first patterned silicon-oxynitride and amorphous carbon layers; and
patterning a first polycrystalline layer below the first amorphous carbon layer using the first patterned silicon-oxynitride and amorphous carbon layers together to provide a first patterned polycrystalline layer, the patterning of the first polycrystalline layer forms a first plurality of pillars which comprise diodes; and
above the first level of the 3-D monolithic memory device, in a second level of the 3-D monolithic memory device:
transferring the common pattern to a second silicon-oxynitride layer and a second amorphous carbon layer below the second silicon-oxynitride layer, to provide, together, second patterned silicon-oxynitride and amorphous carbon layers; and
patterning a second polycrystalline layer below the second amorphous carbon layer using the second patterned silicon-oxynitride and amorphous carbon layers together to provide a second patterned polycrystalline layer, the patterning of the second polycrystalline layer forms a second plurality of pillars which comprise diodes.