Oxygen reservoir for low threshold voltage P-type MOSFET
View Patent ↗A p-type FinFET has an oxygen reservoir disposed on the gate stack. The oxygen reservoir provides an oxygen rich environment during processing steps of manufacturing the device to help the work function metal retain or obtain oxygen to maintain or increase the work function and keep the Vth of the device lower.
1. A p-type FinFET comprising:
a channel;
a source electrically connected to a source side of the channel; a drain electrically connected to a drain side of the channel;
a gate stack comprising a high k dielectric material disposed on the channel and a work function metal disposed on the high k dielectric material; and
an oxygen reservoir disposed on the gate stack, the oxygen reservoir made of a reservoir material, the reservoir material containing oxygen, the oxygen reservoir having a top surface; and
a metal liner or a low resistivity metal fill directly connected to the top surface.
2. The p-type FinFET, as in claim 1 , where the channel is made of Silicon (Si).
3. The p-type FinFET, as in claim 1 , where the reservoir material is one of: Silicon Dioxide (SiO2) and Silicon Oxynitride (SiON).
4. The p-type FinFET, as in claim 1 , where the work function metal (WFM) is one of: Titanium Nitride (TiN), Titanium Oxynitride (TiON), Tantalum Nitride (TaN), and Tantalum Oxynitride (TaON).
5. The p-type FinFET, as in claim 1 , where the work function metal (WFM) is formed with layers of two or more deposition layers.
6. The p-type FinFET, as in claim 5 , where each of the deposition layers is between 2 and 20 angstroms thick.
7. The p-type FinFET, as in claim 5 , where one or more pairs of adjacent deposition layers has an oxygen containing layer between the layers of two or more deposition layers.
8. The p-type FinFET, as in claim 1 , where a top of the oxygen reservoir is recessed below a top surface of the replacement metal gate.
9. The p-type FinFET, as in claim 8 , where the top of the oxygen reservoir is recessed below the top surface of the replacement metal gate between 20 nanometers (nm) and 200 nm.
10. The p-type FinFET, as in claim 1 , where the work function metal has an effective work function (EWF) of 5.0 electron Volts (eV) or greater.
11. A p-type FinFET comprising:
a channel;
a source electrically connected to a source side of the channel;
a drain electrically connected to a drain side of the channel;
a gate stack comprising a high k dielectric material disposed on the channel and a work function metal (WFM) disposed on the high k dielectric material;
an oxygen reservoir disposed on the gate stack, the oxygen reservoir made of a reservoir material, the reservoir material containing oxygen; and
a low resistivity metal layer contact electrically connected to the work function metal (WFM) as well as being physically disposed above a top of the oxygen reservoir.
12. The p-type FinFET, as in claim 11 , where the low resistivity metal layer contact is made of one or more of the following: tungsten (W), Aluminum (Al), Copper (Cu), and Cobalt (Co).
13. The p-type FinFET, as in claim 11 , further comprising a conductive liner, the conductive liner disposed between the low resistivity metal layer contact and the work function metal (WFM) and being on the top of the oxygen reservoir.
14. The p-type FinFET, as in claim 13 , where the conductive liner is Titanium Nitride (TiN).
15. The p-type FinFET, as in claim 11 , that is one of the following: a planar FET, a Gate-All-Around (GAA) structure, and a Stacked Nanosheet structure.
16. A method of making a p-type FinFET, comprising the steps of:
forming a gate trench between a first and second spacer disposed on a fin,
forming a source on a source side of the first spacer and a drain on a drain side of the second spacer, a channel being a region of the fin between the first and second spacer;
depositing a high-k dielectric within the gate trench on the channel and on one side of each of the spacers exposed within the gate trench;
depositing a work function metal (WFM) on the high-k dielectric to form a gate stack above the channel;
depositing an oxygen reservoir on the gate stack; and
depositing a low resistivity metal layer contact electrically connected to the work function metal as well as being physically disposed above a top of the oxygen reservoir.
17. The method of making the p-type FinFET, as in claim 16 , where the WFM is deposited in two or more deposition layers.
18. The method of making the p-type FinFET, as in claim 17 , where there is a layer of oxygen containing material formed between two of the deposition layers.
19. The method of making the p-type FinFET, as in claim 18 , where the oxygen containing material is formed by one of the following:
a. exposing a first deposition layer to air before depositing a second deposition layer, and
b. oxidizing the deposition layer before depositing the second deposition layer.
20. The method of making the p-type FinFET, as in claim 16 , further comprising the step of etching back a top of the oxygen reservoir into the gate stack so the top of the oxygen reservoir is recessed below a top surface of the replacement metal gate between 20 nm and 200 nm.