Integrated circuit with a trench capacitor structure and method of manufacture
View Patent ↗An integrated circuit device having a capacitor structure. In one form of the invention, an integrated circuit device includes a capacitor structure formed along a surface of a semiconductor layer. The capacitor structure includes a region formed in the semiconductor surface, a layer of dielectric material formed along a trench wall of the trench region and a first layer of doped polysilicon formed over the layer of dielectric material in the trench region. The capacitor structure further includes a second layer of doped polysilicon formed over the first layer of polysilicon.
1. A method of forming an integrated circuit device, comprising:
providing a semiconductor layer having an upper surface;
forming a trench in the semiconductor layer upper surface, the trench having a bottom portion and a wall portion extending from the upper surface to the bottom portion;
growing by thermal oxidation a layer of silicon oxide on said bottom portion and along the wall portion,
depositing a high density plasma silicon oxide over the thermal oxidation layer of silicon oxide and filing the trench with the high density plasma silicon oxide;
removing a portion of the high density plasma silicon oxide from the trench to leave a remaining layer of the high density plasma silicon oxide on the bottom portion, the removing including removing the thermal oxidation layer of silicon oxide from the wall portion;
implanting ions in the semiconductor layer in the region adjacent said wall portion to form a first capacitor plate;
forming a layer of dielectric material on the wall portion;
forming an in-situ doped first polysilicon layer along the wall portion to form a second capacitor plate having a substantially uniform dopant concentration along the remaining layer of the high density plasma and along the layer of dielectric material on the wall portion; and
depositing a second doped polysilicon layer over the doped first polysilicon layer,
wherein the second doped polysilicon layer is formed over the doped first polysilicon layer within the trench and is patterned to form both a conductive layer over the first layer and a gate runner for a transistor.
2. The method of claim 1 wherein the second layer of polysilicon is doped by ion implantation.
3. The method of claim 1 wherein a layer of silicon oxide is formed along a lower portion of the trench with the doped first conductive polysilicon layer formed thereover.
4. The method of claim 1 wherein the doped first conductive polysilicon layer is formed to have a thickness of at least 100 Angstroms and by an in situ doped deposition providing a net dopant concentration of at least 5 ×10 18 cm −3 in said polysilicon layer, said method further including the step of implanting dopant into said second polysilicon layer.
5. The method of claim 1 further including formation of a transistor device having a gate oxide layer and a gate runner wherein the step of depositing said second polysilicon Layer includes depositing of material which forms the gate runner.
6. The method of claim 1 wherein the second layer of polysilicon is characterized by a dopant implant profile.
7. The method of claim 6 wherein the doped first conductive polysilicon layer has a dopant profile produced by inducing diffusion from the implant profile of the second layer of polysilicon.