Method for fabricating dual-metal gate device
A method of fabricating a MOS transistor that comprises a dual-metal gate that is formed from heterotypical metals. A gate dielectric ( 34 ), such as HfO 2 , is deposited on a semiconductor substrate. A sacrificial layer ( 35 ), is next deposited over the gate dielectric. The sacrificial layer is patterned so that the gate dielectric over a first (pMOS, for example) area ( 32 ) of the substrate is exposed and gate dielectric over a second (nMOS, for example) area ( 33 ) of the substrate continues to be protected by the sacrificial layer. A first gate conductor material ( 51 ) is deposited over the remaining sacrificial area and over the exposed gate dielectric. The first gate conductor material is patterned so that first gate conductor material over the second area of the substrate is etched away. The sacrificial layer over the second area prevents damage to the underlying dielectric material as the first gate conductor material is removed.
1. A method comprising:
providing a semiconductor substrate having a first area of a first conductivity type and a second area of a second conductivity type;
forming a dielectric material on a surface of the substrate over the first area and over the second area;
forming a sacrificial layer so that the dielectric material over the first area is exposed and dielectric material over the second area is protected by a remaining portion of the sacrificial layer;
depositing a first gate conductor material over the exposed dielectric material and the remaining portion of the sacrificial layer;
forming patterned photoresist over the first gate conductor material to cover a first portion of the first gate conductor material and expose a second portion of the first gate material over the remaining portion of the sacrificial layer;
etching the second portion of the first gate conductor material to expose the remaining portion of the sacrificial layer ( 352 ) using a first etchant technique and stopping etching prior to etching through the remaining portion of the sacrificial layer so that the first etchant technique is precluded from attacking the dielectric material;
removing the remaining portion of the sacrificial layer so as to expose the dielectric material over the second area using a second etchant technique, so that the remaining portion of the sacrificial layer is removed without comprising the dielectric layer; and
depositing a second gate conductor material on the exposed dielectric material over the second area.
2. The method of claim 1 , wherein the dielectric material is a MeOx.
3. The method of claim 2 , wherein the MeOx is selected from the group consisting of HfO 2 and oxides or oxynitrides of zirconium, hafnium, aluminum, lanthanum, strontium, titanium, silicon and combinations thereof.
4. The method of claim 3 , wherein the sacrificial layer is silicon dioxide.
5. The method of claim 2 , wherein the first gate conductor material and the second gate conductor material have distinguishably different work functions.
6. The method of claim 5 , wherein the first area of the substrate accommodates the formation of a pMOS transistor and the second area of the substrate accommodates the formation of an nMOS transistor.
7. The method of claim 6 , wherein the first gate conductor material has a work function that approximates the valence band of silicon and the second gate conductor material has a work function that approximates the conduction band of silicon.
8. The method of claim 7 , wherein the first gate conductor material is selected from the group of materials consisting of rhenium, iridium, platinum, and molybdenum, ruthenium and ruthenium oxide.
9. The method of claim 1 , wherein the step of removing comprises a wet chemical etch in HF solution.
10. The method of claim 1 , wherein the first etchant technique is a dry, gaseous plasma etch.