Thin-film resistor (TFR) formed under a metal layer and method of fabrication
A method for manufacturing a thin film resistor (TFR) module includes forming a TFR element over a substrate; annealing the TFR element to reduce the temperature coefficient of resistance (TCR) of the TFR element; and after forming and annealing the TFR element, forming a pair of conductive TFR heads in contact with the TFR element. By forming the TFR element before the TFR heads, the TFR element may be annealed without affecting the TFR heads, and thus may be formed from various materials with different annealing properties, e.g., SiCCr and SiCr. Thus, the TFR element may be annealed to achieve a near 0 ppm TCR, without affecting the later-formed TFR heads. The TFR module may be formed using a damascene CMP approach and using only a single added mask layer. Further, vertically-extending “ridges” at edges of the TFR element may be removed or eliminated to further improve the TCR performance.
1. A method for manufacturing a thin film resistor (TFR) module in an integrated circuit (IC) structure, the method comprising:
forming a TFR element over a substrate, the TFR element including an upwardly-extending TFR ridge that extends upwardly from a laterally-extending region of the TFR element;
performing an annealing process to reduce a temperature coefficient of resistance (TCR) of the TFR element; and
performing a ridge removal process to remove the upwardly-extending TFR ridge;
forming an oxide layer over the TFR element having the removed upwardly-extending TFR ridge;
performing at least one etch through the oxide layer to define an opening exposing both (a) a top surface of the laterally-extending region of the TFR element and (b) a lateral side surface of the laterally-extending region of the TFR element;
forming a conductive TFR head in the opening, wherein the TFR head conductively contacts both the top surface and the lateral side surface of the laterally-extending region of the TFR element.
2. The method of claim 1 , wherein the TFR element comprises SiCr or SiCCr.
3. The method of claim 1 , wherein the annealing process comprises annealing the TFR element to achieve a TCR value of 0+−700 ppm/° C. for the TFR element.
4. The method of claim 1 , wherein the annealing process comprises annealing the TFR element to achieve a TCR value of 0+−300 ppm/° C. for the TFR element.
5. The method of claim 1 , wherein the annealing process comprises annealing the TFR element to achieve a TCR value of 0+−100 ppm/° C. for the TFR element.
6. The method of claim 1 , wherein the annealing process comprises annealing the TFR element to achieve a TCR value of 40+−20 ppm/° C. for the TFR element.
7. The method of claim 1 , wherein the annealing process comprises annealing the TFR element at a temperature in a range of 450° C. to 550° C.
8. The method of claim 1 , wherein forming the conductive TFR head comprises forming a metal 1 layer.
9. The method of claim 1 , wherein forming the conductive TFR head comprises forming a conductive structure using a dual damascene process.
10. The method of claim 1 , wherein the ridge removal process to remove the upwardly-extending TFR ridge comprises at least one etch.
11. The method of claim 10 , wherein the ridge removal process includes a wet etch.