Method and apparatus for plating solution analysis and control

A system for controlling the composition of a plating solution, the system comprising:

• a visible light spectrometer configured to measure an absorbance of the plating solution, the absorbance of the plating solution being an indication of the concentration of at least one metal in the plating solution;
• a Raman spectrometer configured to measure a concentration of a reducing agent in the plating solution;
• a pH probe configured to measure a pH level of the plating solution;
• and
• a controller configured to utilize the measurements of the visible light spectrometer, the Raman spectrometer, and the pH probe to determine dosing additions of a chemical makeup solution, the reducing agent, a pH adjusting solution, and deionized (DI) water to the plating solution, the dosing additions functioning to replace plating solution components diminished by a plating process, the controller further configured to determine replenishment additions of the chemical makeup solution, the reducing agent, the pH adjusting solution, and deionized (DI) water to the plating solution, the replenishment additions functioning to maintain a target volume of the plating solution.

A method of operating a controller to add dosing and replenishment chemicals to a plating solution, the method comprising:

• measuring a visible light absorbance of the plating solution with a visible light spectrometer to determine a concentration of at least one metal in the plating solution;
• measuring the plating solution with a Raman spectrometer to determine a concentration of a reducing agent in the plating solution;
• measuring a pH level of the plating solution with a pH probe;
• providing the visible light absorbance, the reducing agent concentration, and the pH level to the controller;
• computing a volume for a dosing addition of the reducing agent to the plating solution;
• computing a volume for a dosing addition of a pH adjuster solution to the plating solution;
• computing a volume for a dosing addition of deionized (DI) water to the plating solution;
• and
• computing a volume for a replenishment solution addition to the plating solution when the total dosing volume is less-than a minimum dosing volume.

A method of operating a controller to add dosing and replenishment chemicals to a plating solution, the method comprising:

• measuring a visible light absorbance of the plating solution with a visible light spectrometer to determine a concentration of at least one metal in the plating solution;
• measuring the plating solution with a Raman spectrometer to determine a concentration of a reducing agent in the plating solution;
• measuring a pH level of the plating solution with a pH probe;
• and
• providing the visible light absorbance, the reducing agent concentration, and the pH to the controller.

A system for controlling the composition of an electroless plating solution, the system comprising:

• a sampling means for diverting a sample portion of the electroless plating solution to a Raman spectrometer to measure a concentration of an reducing agent in the sample portion, to a visible spectrometer to measure an absorbance of the sample portion, and to a pH probe to measure a pH value of the sample portion,
• a first controller means for computing a dosing solution volume, the dosing solution comprising portions of the reducing agent, deionized (DI) water, a pH adjusting solution, and a chemical makeup solution, the dosing solution volume acting to maintain a target composition of the electroless plating solution;
• a second controller means for computing a replenishment solution volume, the replenishment solution comprising portions of the reducing agent, deionized (DI) water, a pH adjusting solution, and a chemical makeup solution, the replenishment solution volume acting to maintain a target volume of the electroless plating solution;
• and
• a delivery means for adding any of the dosing solution volume and the replenishment solution volume to the electroless plating solution.

A system used to measure a plating solution, the system comprising:

• a solution sampling apparatus having a solution manifold including:
• a plurality of process solution tubes including throttling valves with at least one of the process solution tubes configured to be coupled to the plating solution;
• and
• a first sample tube coupled to the solution manifold and to a flow cell, the first sample tube configured to convey a sample of the plating solution from the solution manifold to the flow cell;
• a visible light spectrometer coupled to the flow cell and having a light source configured to measure an absorbance of the plating solution;
• a Raman spectrometer coupled to the flow cell and having a light source configured to measure a concentration of a component of the plating solution;
• and
• a second sample tube coupled to a flow cell and to a pH probe, the second sample tube configured to convey the sample of the plating solution from the flow cell to the pH probe, the pH probe configured to measure a pH value of the plating solution.

A method to compute a dosing solution composition, the method comprising:

• sampling an electroless plating solution to determine a concentration of at least one solution component and a visible light absorbance;
• selecting a first method of computing the dosing solution composition when the at least one solution component exceeds a threshold concentration;
• selecting a second method of computing the dosing solution composition when the visible light absorbance exceeds a threshold absorbance;
• and
• selecting a third method of computing the dosing solution composition when the visible light absorbance is either equal to or less than the threshold absorbance.