METHODS TO ENHANCE EFFECTIVE WORK FUNCTION OF MID-GAP METAL BY INCORPORATING OXYGEN AND HYDROGEN AT A LOW THERMAL BUDGET
First Claim
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1. A method of forming an integrated circuit comprising:
- forming a PMOS gate dielectric layer on a substrate;
forming a PMOS gate work function metal layer on the PMOS gate dielectric layer, such that;
said PMOS gate work function metal layer includes oxygen atoms such that said oxygen atoms have a distribution of at least 1×
1015 atoms/cm2 within 1 nanometer of a top surface of said PMOS gate dielectric layer; and
said PMOS gate work function metal layer includes oxygen such that an effective work function of said PMOS gate work function metal layer is above 4.85 eV; and
forming a PMOS metal fill gate over and in direct electrical connection with said PMOS gate work function metal layer.
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Abstract
A process is disclosed of forming metal replacement gates for PMOS transistors with oxygen in the metal gates such that the PMOS gates have effective work functions above 4.85. Metal work function layers in the PMOS gates are oxidized at low temperature to increase their effective work functions to the desired PMOS range. Hydrogen may also be incorporated at an interface between the metal gates and underlying gate dielectrics. Materials for the metal work function layers and processes for the low temperature oxidation are disclosed.
11 Citations
14 Claims
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1. A method of forming an integrated circuit comprising:
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forming a PMOS gate dielectric layer on a substrate; forming a PMOS gate work function metal layer on the PMOS gate dielectric layer, such that; said PMOS gate work function metal layer includes oxygen atoms such that said oxygen atoms have a distribution of at least 1×
1015 atoms/cm2 within 1 nanometer of a top surface of said PMOS gate dielectric layer; andsaid PMOS gate work function metal layer includes oxygen such that an effective work function of said PMOS gate work function metal layer is above 4.85 eV; and forming a PMOS metal fill gate over and in direct electrical connection with said PMOS gate work function metal layer. - View Dependent Claims (2, 3, 4, 5)
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6. A process of forming an integrated circuit, comprising the steps of:
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forming a gate dielectric layer on a substrate; forming a metal layer on the gate dielectric layer, such that said metal layer has an effective work function between 4.5 and 4.7 eV; forming a dummy gate layer on the metal layer; forming a gate photoresist pattern over said dummy gate layer, such that said gate photoresist pattern defines an area for a PMOS gate of a PMOS transistor; using the gate photoresist pattern, removing said dummy gate layer, said metal layer and said gate dielectric layer outside of said area for said PMOS gate; forming a fill oxide layer over the substrate including over the dummy gate layer; removing said fill oxide layer from said PMOS gate area over said dummy gate layer; removing said dummy gate layer in said areas for said PMOS gate; performing a low temperature oxidation process on said metal layer to form a PMOS gate work function metal layer, such that said effective work function of the metal layer is increased to a value above 4.85 eV; and forming a metal fill gate layer over said PMOS gate work function metal layer. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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Specification