Method for fabricating stacked capacitors with increased capacitance in a DRAM cell

Claim 1

Method for fabricating a dynamic random access memory having a capacitor comprising: selectively forming field oxide areas on the surface of a semiconductor substrate while leaving device areas for fabrication of field effect devices; forming a gate dielectric layer on said substrate in the said device areas; depositing a first layer of polysilicon on the said field oxide areas and said device areas; removing portions of said first polysilicon layer while leaving portions thereof for the gate structure in said device areas, and portions over said field oxide areas; forming source/drain structures within said device areas of said semiconductor substrate associated with said gate structures; forming a first oxide layer over said device and field oxide areas; and forming said capacitors by, depositing a second polysilicon layer over the device and field oxide areas, depositing a second oxide layer over said second polysilicon layer, forming openings to said source/drain structures by etching through said second oxide, second polysilicon, and first oxide layers, forming cavities between said first oxide layer and said second oxide layer by lateral etch of said second polysilicon layer; depositing a third polysilicon layer over said cavities, device and field oxide, patterning and anisotropical etching said second and third polysilicon layers and said second oxide layers so as to have their remaining portions over the planned capacitor areas whereat said capacitor is to be formed, said patterning and etching leaves a portion of said second polysilicon layer under said second oxide layer, removing by isotropic etching said first and second oxide layers whereby said remaining second and third polysilicon layers construct the bottom storage node electrode of said capacitor, forming a capacitor dielectric layer over the said bottom storage node electrode, and depositing a fourth polysilicon layer as the top plate electrode, and patterning said fourth polysilicon layer and said dielectric layer.

Claim 14

A method for fabricating a dynamic random access memory having a capacitor comprising: selectively forming field oxide areas on the surface of a semiconductor substrate while leaving device areas for fabrication of semiconductor devices; forming device structures within said device areas of said semiconductor substrate; forming a first oxide layer over said device and field oxide areas; and forming said capacitors by, depositing a second polysilicon layer over the device and field oxide areas, depositing a second oxide layer over said second polysilicon layer, depositing a third polysilicon layer over said second oxide layer, depositing a third oxide over said third polysilicon layer, forming openings to said source/drain structures by etching through said first, second, and third oxide layers and said second and third polysilicon layers, forming cavities between said first and second oxide layers and between said second and third oxide layers by lateral etch; depositing a fourth polysilicon layer over said cavities, device and field oxide, patterning and anisotropical etching said second, third, and fourth polysilicon layers and said second and third oxide layers with an etch stop at said first oxide layer so as to have their remaining portions over the planned capacitor areas whereat said capacitor is to be formed, said patterning and etching leaves a portion of said second and third polysilicon layers under said second and third oxide layers, removing by isotropic etching said first, second, and third oxide layers whereby said second, third, and fourth polysilicon layers construct the bottom storage node electrode of said capacitor, forming a capacitor dielectric layer over the said bottom storage node electrode, and depositing a fifth polysilicon layer as the top plate electrode, and patterning said fifth polysilicon layer and said dielectric layer to complete said capacitor.

Claim 15

A method for fabricating a dynamic random access memory having a capacitor comprising: selectively forming field oxide areas on the surface of a semiconductor substrate while leaving device areas for fabrication of semiconductor devices; forming device structures within said device areas of said semiconductor substrate; forming a first oxide layer over said device and field oxide areas; and forming said capacitors by, depositing a second polysilicon layer over the device and field oxide areas, depositing a second oxide layer over said second polysilicon layer, depositing a third polysilicon layer over said second oxide layer, depositing a third oxide over said third polysilicon layer, forming openings to said source/drain structures by etching through said first, second, and third oxide layers and said second and third polysilicon layers, forming cavities between said first and second oxide layers and between said second and third oxide layers by lateral etch; depositing a fourth polysilicon layer over said cavities, device and field oxide, patterning and anisotropical etching said second, third, and fourth polysilicon layers and said second and third oxide layers with an etch stop at said first oxide layer so as to have their remaining portions over the planned capacitor areas whereat said capacitor is to be formed, said patterning and etching leaves a portion of said second and third polysilicon layers under said second and third oxide layers, removing by isotropic etching said first, second, and third oxide layers whereby said second, third, and fourth polysilicon layers construct the bottom storage node electrode of said capacitor, forming a capacitor dielectric layer over the said bottom storage node electrode, and depositing a fifth polysilicon layer as the top plate electrode, and patterning said fifth polysilicon layer and said dielectric layer to complete said capacitor.