Techniques for forming passive devices during semiconductor back-end processing
Fabrication of electronic devices in the “metal layers” of semiconductor devices. Each metal layer includes a dielectric layer that supports a conductive layer, which includes electrically conductive pathways and electronic devices. The metal layers are stacked on top of each other such that the dielectric layers separate the adjacent conductive layers. The electronic devices may be passive devices such as resistors. The resistors are formed by depositing metal onto the dielectric layer and then implanting the metal with oxygen. The conductive layer may be formed of materials such as copper and aluminum.
1. A method for forming a semiconductor device comprising:
forming a dielectric mask on a top surface of a semiconductor substrate, the semiconductor substrate containing a plurality of integrated devices;
etching recessed regions into a top surface of the dielectric mask;
filling the recessed regions with a conductive material to form a resistor in each recessed region;
selecting a dosage of oxygen for implanting into the resistor in order to give the resistors a desired level of resistance;
implanting the resistors with oxygen; and
annealing the resistors to cause the oxygen to react with the conductive material of the resistor such that the resistor transforms into a metal oxide material having a certain level of resistance wherein at least two resistors have different levels of resistance.
2. A method as recited in claim 1 further comprising operations that follow the operation of forming the dielectric mask, such operations including:
applying a photoresist layer over the dielectric mask;
exposing the photoresist layer to a pattern of light;
developing the photoresist layer to expose areas of the oxide mask that will form the respective recessed regions; and
then proceeding onto the etching process.
3. A method as recited in claim 1 further comprising:
etching recessed channels into the top surface of the dielectric mask wherein at least some of the recessed channels connect to respective recessed regions; and
filling in the recessed channels with the conductive material to form conductive traces wherein some of the traces are integrally formed wit the resistors that are fanned in the recessed regions, wherein the conductive traces and resistors connect integrated devices within the semiconductor substrate.
4. A method as recited in claim 3 wherein the operation of filling the recessed channels and regions is an electroplating, a physical vapor deposition, chemical vapor deposition, atomic layer deposition, or a dual damascene processes.
5. A method as recited in claim 1 wherein the conductive material is aluminum or copper.
6. A method as recited in claim 1 further comprising:
polishing the top surface of the dielectric mask and a top surface of the resistors such that the top surfaces of the dielectric mask and the resistors are substantially coplanar and flat.
7. A method as recited in claim 6 wherein the polishing operation is a chemical mechanical polishing operation.
8. A method as recited in claim 6 wherein the polishing operation removes a top layer off of the resistors until the resistors have a desired depth, wherein the depth of the resistors affects the level of resistance of the resistors.
9. A method as recited in claim 1 further comprising operations that precede the operation of implanting the resistors with oxygen, such operations including:
applying a photoresist layer over the dielectric mask and the resistors;
exposing the photoresist layer to a pattern of light;
developing the photoresist layer to expose the resistors; and
then proceeding onto the implanting process.
10. A method as recited in claim 1 wherein the etching operation creates recessed regions with varying depths, widths, and lengths suitable for creating resistors of different sizes and levels of resistance.