Vertical replacement-gate junction field-effect transistor
An architecture for creating a vertical JFET. Generally, an integrated circuit structure includes a semiconductor area with a major surface formed along a plane and a first source/drain doped region formed in the surface. A second doped region forming a channel of different conductivity type than the first region is positioned over the first region. A third doped region is formed over the second doped region having an opposite conductivity type with respect to the second doped region, and forming a source/drain region. A gate is formed over the channel to form a vertical JFET. In an associated method of manufacturing the semiconductor device, a first source/drain region is formed in a semiconductor layer. A field-effect transistor gate region, including a channel and a gate electrode, is formed over the first source/drain region. A second source/drain region is then formed over the channel having the appropriate conductivity type.
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 first and a second window in the at least three layers of material, wherein said first and second windows terminate at the first device region formed in the semiconductor substrate;
forming a semiconductor material within the first and the second windows, thereby forming a first and a second semiconductor plug in the at least three layers of material, wherein each of the first and the second semiconductor plugs has a first end and a second end, and wherein the first end of each semiconductor plug is in contact with the first device region, and wherein the first semiconductor plug is of a first conductivity type;
forming a second device region selected from the group consisting of a source region and a drain region at the second end of the first semiconductor plug, wherein one of the first and second device regions is a source region and the other is a drain region;
forming a third device region selected from the group consisting of a source region and a drain region at the second end of the second semiconductor plug, wherein one of the first and the third device regions is a source region and the other is a drain region;
removing the second layer, thereby exposing a portion of the first and the second semiconductor plugs;
forming a layer of dielectric material on the exposed portion of the first semiconductor plug;
forming a region of a second conductivity type surrounding the first conductivity type region of the second semiconductor plug; and
forming a gate electrode having a first region in contact with the layer of dielectric material and having a second region in contact with the second conductivity type region of the second semiconductor plug.
2. The process of claim 1 wherein the gate is of a second conductivity type, and further comprising the step of doping a region of the second semiconductor plug from the gate to form a pn junction in the semiconductor plug.
3. The process of claim 1 wherein the second layer is removed by etching in an etchant, wherein the first layer has a first etch rate, the second layer has a second etch rate, and the third layer has a third etch rate, and wherein the second etch rate is at least ten times faster than the first etch rate and the third etch rate in the etchant.
4. The process of claim 2 wherein the etchant is selected from the group consisting of isotropic wet etchants and isotropic dry etchants.
5. The process of claim 1 wherein the first layer and the third layer are formed of electrically insulating material.
6. The process of claim 5 wherein the electrically insulating material is selected from silicon nitride, silicon dioxide, doped silicon dioxide, and doped silicon oxide.
7. The process of claim 5 wherein the electrically insulating material comprises doped silicon dioxide that is a dopant source for a source extension and a drain extension, and wherein the process further comprises the step of doping the semiconductor plug with dopant from the first layer and the third layer to form source and drain extensions in the semiconductor plug.
8. The process of claim 7 wherein the type of dopant in the doped silicon dioxide is selected from the group consisting of n-type and p-type, and wherein the dopant type is opposite the dopant type in the first and the second semiconductor plugs.
9. The process of claim 1 wherein the first and the second semiconductor plugs comprise doped semiconductor plugs, and wherein the dopant is selected from the group consisting of n-type dopants and p-type dopants.
10. The process of claim 9 wherein the doped first and second semiconductor plugs are formed by introducing the dopants into the semiconductor material in situ as the semiconductor material is deposited in the first and the second windows.
11. The process of claim 10 wherein the doped first and second semiconductor plugs are formed by implanting the dopant into the semiconductor material after deposition in the first and the second windows.
12. The process of claim 9 wherein the semiconductor material comprises a crystalline semiconductor material and is selected from the group consisting of silicon, silicon-germanium, and silicon-germanium-carbon.
13. The process of claim 1 further comprising the step of forming an etch stop layer over the first layer of material, or over the second layer of material, or over both of the first and second layers.
14. The process of claim 1 further comprising the step of forming a first insulating layer above the first layer of material and forming a second insulating layer above the second layer of material.
15. The process of claim 14 wherein the first and the second insulating layers comprise etch stop layers.
16. The process of claim 14 wherein the first and the second insulating layers comprise offset spacers.
17. The process of claim 1 further comprising the step of forming a diffusion barrier layer over the first device region before the at least three layers of material are formed thereover.
18. The process of claim 1 further comprising the step of forming a layer of thermal oxide on the exposed portion of the semiconductor plug and removing the layer of thermal oxide.
19. The process of claim 1 wherein the substrate is selected from the group consisting of silicon substrate and silicon on insulator substrates.
20. The process of claim 1 wherein a gate electrode material is selected from the group consisting of doped polycrystalline silicon, doped amorphous silicon, doped polycrystalline silicon-germanium, doped amorphous silicon-germanium, doped polycrystalline silicon-germanium-carbon, doped amorphous silicon-germanium-carbon, metals, and metal-containing compounds.
21. The process of claim 20 wherein the gate electrode is formed on the substrate by chemical vapor deposition, electroplating, or a combination thereof.
22. The process of claim 20 wherein the metals and metal-containing compounds are selected from the group consisting of titanium, titanium nitride, tungsten, tungsten silicide, tantalum, tantalum nitride, and molybdenum.