Work function adjustment in high-k metal gate electrode structures by selectively removing a barrier layer
In a replacement gate approach in sophisticated semiconductor devices, a tantalum nitride etch stop material may be efficiently removed on the basis of a wet chemical etch recipe using ammonium hydroxide. Consequently, a further work function adjusting material may be formed with superior uniformity, while the efficiency of the subsequent adjusting of the work function may also be increased. Thus, superior uniformity, i.e., less pronounced transistor variability, may be accomplished on the basis of a replacement gate approach in which the work function of the gate electrodes of P-channel transistors and N-channel transistors is adjusted after completing the basic transistor configuration.
1. A method, comprising:
forming a first gate electrode structure above a first semiconductor region of a semiconductor device and a second gate electrode structure above a second semiconductor region, said first and second gate electrode structures comprising a gate insulation layer including a high-k dielectric material, a metal-containing cap material formed on said gate insulation layer and a placeholder material, at least said second gate electrode structure comprising an etch stop liner located between said metal-containing cap material and said placeholder material;
removing said placeholder material in said first and second gate electrode structures;
forming one or more first material layers in said first and second gate electrode structures, said one or more first material layers comprising a work function metal for said first gate electrode structure;
removing said one or more first material layers selectively from said second gate electrode structure by using a wet chemical agent based on ammonium hydroxide to etch at least one of said one or more material layers; and
forming one or more second material layers in said second gate electrode structure, said one or more second material layers comprising a work function metal for said second gate electrode structure.
2. The method of claim 1 , wherein said one or more first material layers comprise at least tantalum nitride.
3. The method of claim 2 , wherein forming said one or more first material layers comprises depositing a tantalum nitride layer above said first and second gate electrode structures and depositing a metal-containing material layer above said tantalum nitride layer.
4. The method of claim 3 , wherein removing said one or more first material layers comprises removing said metal-containing material layer by using said tantalum nitride layer as an etch stop and removing said tantalum nitride layer by using said wet chemical agent.
5. The method of claim 4 , wherein removing said metal-containing material layer comprises performing a wet chemical etch process based on sulphuric acid and hydrogen peroxide.
6. The method of claim 1 , wherein said one or more first material layers are removed by using said wet chemical agent.
7. The method of claim 2 , wherein said one or more first material layers comprise a titanium nitride layer.
8. The method of claim 1 , further comprising forming drain and source regions in said first and second semiconductor regions and forming at least a portion of an interlayer dielectric material prior to removing said placeholder material.
9. The method of claim 1 , wherein forming said first and second gate electrode structures comprises forming a silicon dioxide base material and forming said high-k dielectric material on said silicon dioxide base material.
10. The method of claim 1 , wherein said etch stop liner is formed on the basis of a silicon dioxide material.
11. The method of claim 10 , wherein said etch stop liner is provided in said first and second gate electrode structures.
12. The method of claim 1 , further comprising forming an electrode metal in said first and second gate electrode structures after forming said one or more first and second material layers.