Method for self-aligning a stop layer to a replacement gate for self-aligned contact integration
Semiconductor devices with replacement gate electrodes and integrated self aligned contacts are formed with enhanced gate dielectric layers and improved electrical isolation properties between the gate line and a contact. Embodiments include forming a removable gate electrode on a substrate, forming a self aligned contact stop layer over the removable gate electrode and the substrate, removing a portion of the self aligned contact stop layer over the removable gate electrode and the electrode itself leaving an opening, forming a replacement gate electrode of metal, in the opening, transforming an upper portion of the metal into a dielectric layer, and forming a self aligned contact. Embodiments include forming the contact stop layer of a dielectric material, e.g., a hafnium oxide, an aluminum oxide, or a silicon carbide and transforming the upper portion of the metal into a dielectric layer by oxidation, fluorination, or nitridation. Embodiments also include forming a hardmask layer over the removable gate electrode to protect the electrode during silicidation in source/drain regions of the semiconductor device.
1. A method comprising:
forming a removable gate electrode over a substrate;
forming a self aligned contact (SAC) stop layer over the removable gate electrode and the substrate;
removing a portion of the SAC stop layer over the removable gate electrode;
removing the removable gate electrode leaving an opening;
forming a replacement gate electrode, comprising a metal, in the opening;
transforming an upper portion of the metal into a dielectric layer; and
forming an SAC.
2. The method according to claim 1 , comprising:
forming spacers on side surfaces of the removable gate electrode; and
forming the SAC stop layer over the spacers.
3. The method according to claim 1 , comprising transforming the upper portion of the metal into a dielectric layer by oxidation or nitriding or fluorinating.
4. The method according to claim 3 , wherein the metal comprises aluminum, the method comprising anodizing an upper portion of the aluminum to form aluminum oxide (Al 2 O 3 ).
5. The method according to claim 1 , wherein the SAC stop layer comprises a dielectric material.
6. The method according to claim 5 , wherein the dielectric material comprises a hafnium oxide, aluminum oxide, or a silicon carbide.
7. The method according to claim 6 , wherein the dielectric material comprises a hafnium oxide.
8. The method according to claim 5 , comprising depositing the dielectric material by atomic layer deposition at a thickness of about 1 to about 10 nm.
9. The method according to claim 2 , further comprising:
forming a hardmask layer on the removable gate electrode; and
forming a silicide in a substrate region spaced from the removable gate electrode by the spacers, prior to depositing the SAC stop layer.
10. The method according to claim 9 , further comprising:
providing an isolation material on the region after forming the SAC stop layer;
forming the replacement gate electrode;
transforming the upper portion of the metal into the dielectric layer; and
etching, with a high etch selectivity to the isolation material with respect to the dielectric layer, to remove isolation material to form a contact hole.
11. The method according to claim 10 , wherein the etch selectivity to the isolation material with respect to the dielectric layer is about 4:1 or greater.
12. A method comprising:
forming a first gate electrode over a substrate, the first gate electrode comprising a high-K gate dielectric layer, a metal layer on the gate dielectric layer, and polysilicon;
forming spacers on side surfaces of the first gate electrode;
forming a hardmask over the polysilicon;
forming a silicide on the substrate;
depositing an SAC stop layer over the hardmask layer, the spacers, and the silicide;
depositing an isolation material over the SAC stop layer;
forming a replacement gate electrode by:
removing the hardmask layer and the polysilicon from the first gate electrode to form an opening;
depositing a metal lining in the opening; and
depositing aluminum on the metal lining in the opening;
anodizing an upper portion of the aluminum to form a layer of aluminum oxide (Al 2 O 3 );
etching, with a high etch selectivity to the isolation material with respect to the Al 2 O 3 layer, to remove isolation material to form the contact hole and/or to remove the Al 2 O 3 from the replacement gate electrode; and
forming an SAC on the silicide and/or the replacement gate electrode.