Thin film resistor methods of making contacts

1. A method comprising:

forming a first interlayer dielectric (ILD) over a substrate;

forming a second ILD over the first ILD;

forming a first metal layer in the second ILD;

forming a first nitride layer over the second ILD and the first metal layer;

forming a third ILD over the first nitride layer;

forming vias through the third ILD and the first nitride layer, coupled to the first metal layer;

forming a thin film resistor (TFR) layer over two of the vias and the third ILD between the two vias;

forming a second nitride layer over the TFR layer and the third ILD, wherein the second nitride layer covers an upper surface and side surfaces of the TFR layer in their entirety;

forming a fourth ILD over the second nitride layer; and

forming a second metal layer in the fourth ILD and the second nitride layer, wherein the second metal layer extends through the second nitride layer, and wherein the second metal layer is in direct contact with the third ILD and a third via.

2. A method according to claim 1 , comprising forming the first metal layer by a single damascene process.

3. A method according to claim 1 , comprising forming the second metal layer by a single or dual damascene process.

4. A method according to claim 1 , comprising forming each of the first and second metal layers to a thickness of 2,000 Angstrom (Å) to 10,000 Å.

5. A method according to claim 1 , comprising forming each of the first and the second nitride layers of silicon nitride (Si 3 N 4 ) and to a thickness of 300 Å to 1,000 Å.

6. A method according to claim 1 , comprising forming the TFR layer of tantalum (Ta), tantalum nitride (TaN), silicon chromium (SiCr), or nickel chromium (NiCr) and to a thickness of 50 Å to 2,000 Å.