Low-density, high-resistivity titanium nitride layer for use as a contact for low-leakage dielectric layers and method of making
A low-density, high-resistivity layer of a PVD sputter-deposited material, preferably titanium nitride, when coupled with a dielectric, makes a superior low-leakage insulating barrier for use in semiconductor devices. The material is created by sputtering methods that cause the ions to strike the deposition surface with reduced energy, for example in an ion metal plasma chamber with no self-bias accelerating ions normal to the deposition surface, or in a standard PVD chamber with pressure increased.
1 . A method for forming titanium nitride in a semiconductor device comprising:
providing a surface for a semiconductor device; and
depositing a film of titanium nitride on the surface by physical vapor deposition wherein, for any portion of the film more than about 20 angstroms thick, the density of the titanium nitride is less than about 4.0 grams per cubic cm.
2 . The method of claim 1 wherein, for any portion of the film more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms.
3 . The method of claim 1 wherein, for any portion of the titanium nitride film more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 1000 microOhm-cms.
4 . The method of claim 1 wherein, for any portion of the titanium nitride film more than about 20 angstroms thick, the density of the titanium nitride is less than about 4.0 grams per cubic cm.
5 . The method of claim 4 wherein, for any portion of the titanium nitride film more than about 20 angstroms thick, the pressure during physical vapor deposition is greater than about 15 mTorr.
6 . The method of claim 5 wherein, for any portion of the titanium nitride film more than about 20 angstroms thick, the pressure during physical vapor deposition is greater than about 18 mTorr.
7 . The method of claim 6 wherein, for any portion of the titanium nitride film more than about 20 angstroms thick, the pressure during physical vapor deposition is greater than or equal to about 20 mTorr.
8 . The method of claim 1 wherein the titanium nitride film is in contact with a dielectric.
9 . The method of claim 8 wherein the dielectric is disposed between the titanium nitride film and a conductive or semiconductive layer.
10 . A method for making a thin film transistor comprising:
forming a polysilicon layer;
forming a silicon dioxide layer in contact with the polysilicon layer;
forming a titanium nitride layer in contact with the silicon dioxide layer wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the density of the titanium nitride is less than about 4.25 grams per cubic cm; and
patterning and etching the titanium nitride.
11 . The method of claim 10 wherein the step of forming the silicon dioxide layer comprises thermally growing silicon dioxide.
12 . The method of claim 10 , wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the step of forming the titanium nitride layer comprises physical vapor deposition of titanium nitride with substantially no self-bias and pressure greater than about 15 mTorr.
13 . The method of claim 10 , wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, density of the titanium nitride is less than about 4.0 grams per cubic cm.
14 . A method for forming titanium nitride in a semiconductor device comprising:
providing a surface for a semiconductor device; and
depositing on the surface a film of titanium nitride by physical vapor deposition wherein, for any portion of the film more than about 20 angstroms thick, the deposition is performed with substantially no self-bias and with pressure greater than about 15 mTorr.
15 . The method of claim 14 , wherein the titanium nitride is in contact with a dielectric layer.
16 . The method of claim 15 , wherein the dielectric layer is silicon dioxide.
17 . The method of claim 15 , wherein the dielectric layer is silicon nitride.
18 . A method for forming titanium nitride for use in a semiconductor device comprising:
providing a surface for a semiconductor device;
on the surface, depositing titanium nitride wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 300 microOhm-cms and the ratio of nitrogen to titanium is greater than about 1.2:1.
19 . The method of claim 18 wherein, for any portion of the titanium nitride layer more than about 20 angstroms thick, the resistivity of the titanium nitride is greater than about 1000 microOhm-cms.