Fabrication method
View Patent ↗A process and an architecture related to a vertical MOSFET device and a capacitor for use in integrated circuits. The integrated circuit structure includes a semiconductor layer with a major surface and further including a first doped region formed in the surface. A second doped region of a different conductivity type than the first doped region is positioned over the first region. A third doped region of a different conductivity type than the second region is positioned over the second region. The integrated circuit includes a capacitor having a bottom plate, dielectric layer and a top plate. In an associated method of manufacture, a first device region. is formed on a semiconductor layer. A field-effect transistor gate region is formed over the first device region. A capacitor comprising top and bottom layers and a dielectric layer is formed on the semiconductor layer.
1. A process for fabricating an integrated circuit structure comprising:
forming a first device region selected from the group consisting of a source region and a drain region of a semiconductor device in a semiconductor substrate;
forming a multilayer stack comprising at least three layers of material over the first device region in the semiconductor substrate, wherein the second layer is interposed between the first and the third layers, and wherein the first layer is adjacent the first device region;
forming a window in the at least three layers of material, wherein the window terminates at the first device region formed;
forming a doped semiconductor plug in the window, wherein the semiconductor plug has a first end and a second end, and wherein the first end is in contact with the first device region;
forming a second device region selected from the group consisting of a source region and a drain region in the second end of the semiconductor plug, wherein one of the first and second device regions is a source region and the other is a drain region;
removing the second layer, thereby exposing a portion of the semiconductor plug;
forming gate dielectric material on the exposed portion of the semiconductor plug;
forming a conductive layer comprising a horizontal capacitor segment and a vertical gate segment, wherein the vertical gate segment contacts the gate dielectric material to form a gate of a MOSFET device, and the horizontal capacitor segment forms a first capacitor plate;
forming a capacitor dielectric layer over the first capacitor plate; and
forming a second capacitor plate over the capacitor dielectric layer.
2. The process of claim 1 wherein the second layer is removed by etching in an etchant, characterized by a first layer etch rate, a second layer etch rate, and a third layer etch rate, and wherein the second layer etch rate is at least ten times faster than one of the first layer etch rate and the third layer etch rate.
3. The process of claim 1 wherein the semiconductor plug comprises a doped crystalline semiconductor material, and wherein the dopant is selected from the group consisting of n-type dopants and p-type dopants, and wherein the crystalline semiconductor material selected from the group consisting of silicon, silicon germanium, and silicon-germanium-carbon.
4. The process of claim 1 further comprising forming a layer of insulating material over either the first layer of material and the second layer of material, or both the first and second layers of material, wherein the layer of insulating material comprises an etch stop layer.
5. The process of claim 4 wherein the material of the first and the third layers comprises a doped insulating material, and wherein source and drain region extensions are formed within the semiconductor plug by the diffusion of dopants from the first and the third layers into the adjacent semiconductor plug material, and wherein the layer of insulating material comprises an offset spacer for controlling the extent of vertical diffusion of dopants from the first and the third layers.
6. The process of claim 1 wherein the substrate is selected from the group comprising silicon substrates and silicon-on-insulator substrates.
7. The process of claim 1 wherein the conductive material is selected from the group consisting of doped polycrystalline silicon, doped amorphous silicon, doped silicon germanium, doped silicon-germanium-carbon, metals and metal compounds.
8. The process of claim 1 further comprising the steps of:
forming an insulating layer over the second capacitor plate; and
forming a window in the insulating layer for accessing the second capacitor plate.
9. The process of claim 8 wherein the insulating layer is selected from the group consisting of silicon nitride and silicon dioxide.
10. The process of claim 1 wherein the first and the second capacitor plates are formed of a material selected from the group comprising doped polysilicon, metal, and metal compounds.
11. The process of claim 1 wherein the capacitor dielectric layer is formed of material selected from the group comprising silicon dioxide and silicon nitride.
12. The process of claim 1 further comprising insulating the horizontal and the vertical segments of the conductive layer.
13. The process of claim 12 wherein an insulative trench insulates the horizontal and vertical segments of the conductive layer.