Yttrium and titanium high-k dielectric films
This disclosure provides (a) methods of making an oxide layer (e.g., a dielectric layer) based on yttrium and titanium, to have a high dielectric constant and low leakage characteristic and (b) related devices and structures. An oxide layer having both yttrium and titanium may be fabricated either as an amorphous oxide or as an alternating series of monolayers. In several embodiments, the oxide is characterized by a yttrium contribution to total metal that is specifically controlled. The oxide layer can be produced as the result of a reactive process, if desired, via either a PVD process or, alternatively, via an atomic layer deposition process that employs specific precursor materials to allow for a common process temperature window for both titanium and yttrium reactions.
1. A method of forming a capacitor stack, comprising:
depositing a first conductive layer above a substrate;
depositing a dielectric above the conductive layer using a physical vapor deposition (PVD) process, the dielectric including both yttrium and titanium, the PVD process comprising reactive co-sputtering of a first source and a second source,
wherein the first source comprises metallic yttrium, and
wherein the second source comprises metallic titanium;
controlling the relative deposition for each of titanium and yttrium so as to deposit the dielectric to have a yttrium-to-total-metal (Y/(Y+Ti)) constituency of between 16% and 41% yttrium; and
depositing a second conductive layer above the dielectric.
2. The method of claim 1 , wherein the yttrium-to-total-metal constituency is between about 20% and 40% yttrium.
3. The method of claim 2 , wherein the yttrium-to-total-metal constituency is 40% yttrium.
4. The method of claim 1 , wherein the dielectric has a dielectric constant of above 60.
5. The method of claim 1 , wherein the dielectric has leakage characteristics approximately the same as the leakage characteristics of crystalline Y 2 O 3 .
6. The method of claim 1 , further comprising using an oxygen source subsequent to the sputtering process to form a single oxide layer.
7. The method of claim 6 , wherein oxygen of the oxygen source reacts with metallic yttrium sputtered from the first source and with metallic titanium sputtered from the second source to form an yttrium-titanium oxide deposited on the substrate.
8. The method of claim 1 , wherein the sputtering comprises reactive sputtering in an oxygen-containing gas.
9. The method of claim 8 , wherein oxygen of the oxygen source reacts with metallic yttrium sputtered from the first source and metallic titanium sputtered from the second source to form an yttrium-titanium oxide after the metallic yttrium is sputtered from the first source and the metallic titanium is sputtered from the second source and before the metallic yttrium and the metallic titanium are deposited on the substrate.
10. The method of claim 1 , where at least one of depositing the first conductive layer or depositing the second conductive layer includes depositing an electrode having a material selected from the group of titanium nitride (TiN), platinum, iridium, iridium oxide, tungsten, tungsten oxide, molybdenum, molybdenum oxide, ruthenium and ruthenium oxide.
11. The method of claim 1 , wherein the dielectric comprises amorphous TiYOx.
12. The method of claim 1 , wherein the dielectric is less than 20 nm in thickness.
13. The method of claim 1 , further comprising controlling deposition for each of titanium and yttrium so as to suppress the formation of crystalline titanium oxide and so as to suppress the formation of crystalline yttrium oxide.
14. The method of claim 1 , further comprising annealing the deposited dielectric at between 500° C. and 600° C. in an atmosphere comprising oxygen.
15. The method of claim 1 , wherein the reactive co-sputtering simultaneously transfers yttrium and titanium from the first source and the second source and reacts yttrium and titanium with an oxygen-containing gas.