Method with CMP for Metal Ion Prevention

A method, comprising:

• providing a workpiece including a semiconductor substrate, a first dielectric layer over the semiconductor substrate, and a first cap layer over the first dielectric layer;
• forming a first metal layer over the first dielectric layer including a first metal feature in a first region having a first critical dimension (CD) and a second metal feature in a second region having a second CD less than the first CD;
• performing a first CMP process on the first metal layer forming a first recess in the first metal feature having a first maximum depth and a second recess in the second metal feature having a second maximum depth less than the first maximum depth;
• depositing a second dielectric layer over the first and second metal features;
• and
• forming a second metal layer over the second dielectric layer including a third metal feature in the first region having a third CD and a fourth metal feature in the second region having a fourth CD greater than the third CD.

A method, comprising:

• providing a workpiece including a semiconductor substrate, a first dielectric layer over the semiconductor substrate, and a first cap layer over the first dielectric layer;
• forming a first metal feature in the first dielectric layer;
• performing a first chemical mechanical polishing/planarization (CMP) process on the first metal feature using a first rotation rate and a first slurry having a first pH value;
• performing a second CMP process on the first metal feature using a second rotation rate slower than the first rotation rate and a second slurry having a second pH value being greater than the first pH value, wherein the second CMP process stops on the first cap layer;
• and
• after the performing of the second CMP process, removing the first cap layer by wet etching.