Metal contacts to group IV semiconductors by inserting interfacial atomic monolayers
Techniques for reducing the specific contact resistance of metal—semiconductor (group IV) junctions by interposing a monolayer of group V or group III atoms at the interface between the metal and the semiconductor, or interposing a bi-layer made of one monolayer of each, or interposing multiple such bi-layers. The resulting low specific resistance metal—group IV semiconductor junctions find application as a low resistance electrode in semiconductor devices including electronic devices (e.g., transistors, diodes, etc.) and optoelectronic devices (e.g., lasers, solar cells, photodetectors, etc.) and/or as a metal source and/or drain region (or a portion thereof) in a field effect transistor (FET). The monolayers of group III and group V atoms are predominantly ordered layers of atoms formed on the surface of the group IV semiconductor and chemically bonded to the surface atoms of the group IV semiconductor.
1. A method of forming a metal semiconductor contact with a monolayer of one of group V or group III atoms at the metal-semiconductor interface, wherein the monolayer is an ordered monolayer formed by segregation of group V or group III atoms, as applicable, out of a layer of material in contact with a surface of the semiconductor with the group V or group III atoms, as applicable, bonded in epitaxial coordination with atoms of a top layer of the semiconductor.
2. The method of claim 1 , wherein the group V or group III atoms of the monolayer are introduced into the layer of material by ion implantation.
3. The method of claim 1 , wherein the layer of material is deposited on the semiconductor surface by one of chemical vapor deposition (CVD) or physical vapor deposition (PVD).
4. The method of claim 3 , wherein the group V or group III atoms of the monolayer are introduced into the layer of material by including said atoms as a dopant in the CVD or PVD deposition process or by ion implantation.
5. A method of forming a metal semiconductor contact with a monolayer of one of group V or group III atoms at a metal-semiconductor interface, comprising forming the monolayer by segregation of group V or group III atoms, as applicable, out of a layer of material in contact with a surface of the semiconductor, wherein the layer of material is deposited as a thin film of doped silicon oxide containing a high concentration of a group V element.
6. A method of forming a metal semiconductor contact with a monolayer of one of group V or group III atoms at a metal-semiconductor interface, comprising forming the monolayer by segregation of group V or group III atoms, as applicable, out of a layer of material in contact with a surface of the semiconductor, wherein the layer of material is deposited as a thin film of doped silicon oxide containing a high concentration of a group III element.
7. A method of forming a metal semiconductor contact with a monolayer of one of group V or group III atoms at a metal-semiconductor interface, comprising forming the monolayer by segregation of group V or group III atoms, as applicable, out of a layer of material in contact with a surface of the semiconductor, wherein the group V or group III atoms of the monolayer are introduced into the layer of material, and thereafter, the contact is annealed at a sufficiently high temperature to cause the group V or group III atoms to segregate and form an ordered monolayer of group V or group III atoms at the interface, with the group V or group III atoms bonded in epitaxial coordination with a top layer of atoms of the semiconductor.
8. The method of claim 7 , wherein the layer of material is a doped silicon oxide or silicon nitride layer, and wherein after annealing has caused segregation of some group V or group III element to the semiconductor-silicon oxide or semiconductor-silicon nitride interface, as applicable, the silicon oxide or silicon nitride is subsequently removed by selective wet chemical etching, leaving behind a coordinated monolayer of the group V or group III atoms at the semiconductor surface, and a metal is deposited to form a metal contact to the group V or group III atoms.
9. The method of claim 7 , wherein the layer of material is a metal silicide, and wherein, after annealing has caused segregation of the group V or group III atoms to form an interfacial ordered monolayer, the metal silicide is removed.
10. The method of claim 7 , wherein the layer of material is a metal silicide, and wherein, after annealing has caused segregation of the group V or group III atoms to form an interfacial ordered monolayer, the metal silicide is retained in place to function as a metal contact to the group V or group III atoms.