Atomic layer deposition of selected molecular clusters
Energy bands of a thin film containing molecular clusters are tuned by controlling the size and the charge of the clusters during thin film deposition. Using atomic layer deposition, an ionic cluster film is formed in the gate region of a nanometer-scale transistor to adjust the threshold voltage, and a neutral cluster film is formed in the source and drain regions to adjust contact resistance. A work function semiconductor material such as a silver bromide or a lanthanum oxide is deposited so as to include clusters of different sizes such as dimers, trimers, and tetramers, formed from isolated monomers. A type of Atomic Layer Deposition system is used to deposit on semiconductor wafers molecular clusters to form thin film junctions having selected energy gaps. A beam of ions contains different ionic clusters which are then selected for deposition by passing the beam through a filter in which different apertures select clusters based on size and orientation.
1. A method, comprising:
forming a source region and a drain region in a substrate;
forming a channel region extending between the source region and the drain region; and
forming a gate structure on the channel region, wherein the forming the gate structure includes forming a gate electrode and a first molecular cluster thin film between the gate electrode and the channel region, the first molecular cluster thin film having ionic clusters that each includes at least two bonded atoms that are different.
2. The method of claim 1 comprising forming contacts that couple the source region, the drain region, and the gate structure to a multi-layer metal interconnect structure.
3. The method of claim 1 comprising forming a gate dielectric between the first molecular cluster thin film and the channel region.
4. The method of claim 1 , comprising:
forming a second molecular cluster thin film in the source region; and
forming a third molecular cluster thin film in the drain region.
5. The method of claim 4 , comprising:
forming a first contact on the second molecular cluster thin film; and
forming a second contact on the third molecular cluster thin film.
6. The method of claim 5 , comprising forming neutral cluster in the second molecular cluster thin film and the third molecular cluster thin film.
7. A method, comprising:
forming a first metal film in contact with a source region, the first metal film including first molecular clusters;
forming a second metal film in contact with a drain region, the second metal film including second molecular clusters; and
forming a strained channel region extending between the source region and the drain region.
8. The method of claim 7 , comprising forming a gate structure over the strained channel region; and
forming first and second contacts in contact with the first and second metal films, respectively.
9. The method of claim 8 , comprising forming the first metal film laterally surrounding the first contact and the second metal film laterally surrounding the second contact.
10. The method of claim 8 , comprising forming the channel region laterally surrounding the gate structure.
11. The method of claim 10 , comprising forming a multi-layer metal interconnect structure coupled, respectively, to one or more of the first and second contacts.
12. A method, comprising:
forming a channel region between a source region and a drain region and including a strained silicon interface; and
forming a first molecular cluster thin film including ionic clusters having at least two bonded atoms that are different between the source and drain regions; and
forming a gate electrode on the first molecular cluster thin film, the first molecular cluster thin film being between the gate electrode and the channel region.
13. The method of claim 12 wherein the ionic clusters impart a compressive stress at the strained silicon interface.
14. The method of claim 12 wherein the strained silicon interface is an interface between silicon and germanium.
15. The method of claim 12 wherein the ionic clusters of a gate stack include a selected orientation.
16. The method of claim 12 , comprising forming a second molecular cluster thin film in the source region.
17. The method of claim 16 , comprising forming a third molecular cluster thin film in the drain region.
18. The method of claim 17 wherein the second molecular cluster and the third molecular cluster thin film each includes neutral clusters.
19. The method of claim 12 , comprising forming a gate dielectric between the first molecular cluster thin film and the channel region.