A semiconductor process and apparatus includes forming first and second gate electrodes ( 151, 161 ) by forming the first gate electrode ( 151 ) over a first high-k gate dielectric ( 121 ) and forming the second gate electrode ( 161 ) over at least a second high-k gate dielectric ( 122 ) different from the first gate dielectric ( 121 ). Either or both of the high-k gate dielectric layers ( 121, 122 ) may be formed by depositing and selectively etching an initial layer of high-k dielectric material (e.g., 14 ). As deposited, the initial layer ( 14 ) has an exposed surface ( 18 ) and an initial predetermined crystalline structure. An exposed thin surface layer ( 20 ) of the initial layer ( 14 ) is prepared for etching by modifying the initial crystalline structure in the exposed thin surface layer. The modified crystalline structure in the exposed thin surface layer may be removed by applying a selective etch, such as HF or HCl.
1. A semiconductor fabrication process, comprising:
forming a high-k gate dielectric layer with a material selected from the group consisting of oxides, silicates or aluminates of hafnium, zirconium, aluminum, lanthanum, strontium, titanium, or any combination thereof, said gate dielectric layer having an exposed surface and an initial crystalline structure;
preparing an exposed thin surface layer of the gate dielectric layer having a thickness of approximately 5-10 Angstroms for etching by modifying the initial crystalline structure in the exposed thin surface layer; and
etching the exposed thin surface layer by pulsing an etchant to remove the thin surface layer from the gate dielectric layer.
2. The process of claim 1 , wherein the preparing and etching steps are repeated until a desired amount of the gate dielectric layer having a predetermined thickness is removed.
3. The process of claim 1 , wherein preparing an exposed thin surface layer comprises pulsing the initial layer with ions so that only the exposed thin surface layer is amorphized.
4. The process of claim 3 , further comprising removing the ions prior to the etching step by introducing an inert gas.
5. The process of claim 1 , wherein etching the exposed thin surface layer comprises pulsing the exposed thin surface layer with HF to remove the exposed thin surface layer from the gate dielectric layer.
6. The process of claim 1 , further comprising removing the etchant by introducing an inert gas.
7. The process of claim 1 , wherein preparing an exposed thin surface layer comprises using a directional ion beam source to pulse the gate dielectric layer with heavy ions so that only the exposed thin surface layer on a predetermined surface of the gate dielectric layer is amorphized.
8. The process of claim 1 , wherein preparing an exposed thin surface layer comprises flowing a reactive species over the gate dielectric layer so that the reactive species are chemically absorbed in only the exposed thin surface layer.
9. The process of claim 8 , wherein etching the exposed thin surface layer comprises pulsing the exposed thin surface layer with high energy ion beams to remove the exposed thin surface layer from the gate dielectric layer.
10. A method of making an integrated circuit structure, comprising:
providing a substrate comprising a first well region and a second well region; and
forming transistors over the first and second well regions so that a first plurality of the transistors, each comprising a first gate electrode overlying a first high-k gate dielectric layer, is formed over the first well region, and so that a second plurality of the transistors, each comprising a second gate electrode overlying a second high-k gate dielectric layer, is formed over the second well region, wherein the first and second high-k gate dielectric layers differ in composition and further wherein an atomic layer etch process is performed on either or both of the first and second high-k gate dielectric layers, wherein the atomic layer etch process comprises removing a thin surface layer having a thickness of approximately 5-8 Angstroms of either or both of the first and second high-k gate dielectric layers by pulsing an exposed portion of either or both of the first and second high-k gate dielectric layers with ions to modify an initial crystalline structure of the thin surface layer and by subsequently pulsing the exposed portion of either or both of the first and second high-k gate dielectric layers with an etchant.
11. The method of claim 10 , wherein the first high-k gate dielectric layer comprises hafnium oxide and the second high-k gate dielectric layer comprises aluminum oxide.
12. The method of claim 10 , wherein forming transistors comprises:
forming the first high-k gate dielectric layer over the substrate; and
forming the first gate electrodes over the first high-k gate dielectric layer,
wherein the atomic layer etch process comprises removing a thin surface layer of the first high-k gate dielectric layer after the first gate electrode is formed by pulsing an exposed portion of the first high-k gate dielectric layer with ions and by subsequently pulsing the exposed portion of the first high-k gate dielectric layer with an etchant.
13. The method of claim 10 , wherein forming transistors comprises:
forming the first high-k gate dielectric layer over the substrate;
forming the first gate electrodes over the first high-k gate dielectric layer;
forming the second high-k gate dielectric layer over the first gate electrodes and the first high-k gate dielectric layer;
forming the second gate electrodes over at least part of the second high-k gate dielectric layer; and
removing at least an exposed thin surface layer of the second high-k gate dielectric layer by pulsing an exposed portion of the second high-k gate dielectric layer with ions and by subsequently pulsing the exposed portion of the second high-k gate dielectric layer with an etchant.
14. A method for fabricating a gate dielectric layer comprising:
forming a high-k gate dielectric layer of hafnium oxide, said high-k gate dielectric layer having an exposed surface;
preparing an exposed thin surface layer of the high-k gate dielectric layer having a thickness of approximately 5-10 Angstroms for removal by pulsing the exposed surface of the high-k gate dielectric layer with a chemically reactive species for absorption into the exposed thin surface layer; and
removing the exposed thin surface layer from the high-k gate dielectric layer.
15. The method of claim 14 , wherein the preparing step comprises pulsing the exposed thin surface layer with HCl for absorption into the exposed thin surface layer.
16. The method of claim 14 , wherein the removing step comprises applying energy to react the absorbed species in the exposed thin surface layer and remove the exposed thin surface layer from the high-k gate dielectric layer.
17. The method of claim 14 , wherein the preparing and removing steps remove a monolayer of material from the high-k gate dielectric layer, and wherein the preparing and removing steps are repeated until a desired thickness of the high-k gate dielectric layer remains.