Correlation between conductivity and ph measurements for koh texturing solutions and additives
AssigneeAkrion Systems, LLC
InventorsISMAIL KASHKOUSH, Jennifer Rieker, Gim-Syang Chen, Dennis Nemeth
Life of this patent
Estimating the term…
Abstract
The variability of an etchant concentration in an immersion processes for treatment of semiconductor devices can be significantly lowered by continuously measuring the conductivity of an etchant solution and comparing against predetermined thresholds. The etchant concentration can be maintained by a feed and bleed process based on conductivity measurements of the etchant solution and the conductivity measurements being correlated with premeasured pH values of an etchant solution.
Claims18
A method of etching material from at least one substrate, the method comprising:
- a) immersing the at least one substrate in an etchant solution within a process chamber, the process chamber operably coupled to a recirculation line to form a closed-loop circulation system;
- b) circulating a circulation volume of the etchant solution through the closed-loop circulation system;
- c) repetitively measuring conductivity of the circulation volume of the etchant solution that is circulating through the closed-loop circulation system with a conductivity sensor;
- and
- d) upon detecting that the circulation volume of the etchant solution has an average measured conductivity over a predetermined period of time that is at or below a lower threshold of conductivity, automatically performing a feed-and-bleed event that comprises:
- (i) bleeding a volume of contaminated etchant solution from the circulation volume of the etchant solution;
- and (ii) adding fresh etchant solution to the circulation volume of the etchant solution to increase the conductivity of the circulation volume of the etchant solution to a value that is greater than the lower threshold of conductivity but less than or equal to an upper threshold of conductivity.
A system for etching at least one substrate comprising:
- a closed-loop circulation system having a process chamber and a recirculation line fluidly coupled to the process chamber, the closed-loop circulation system configured to circulate a circulation volume of an etchant solution;
- means for bleeding contaminated etchant solution from the circulation volume of the etchant solution;
- means for adding fresh etchant solution to the circulation volume of the etchant solution;
- a conductivity sensor operably coupled to the closed-loop circulation system and configured to repetitively measure conductivity of the circulation volume of the etchant solution;
- and
- a controller configured so that upon detecting that the circulation volume of the etchant solution has an average measured conductivity over a predetermined period of time that is at or below a lower threshold of conductivity, the controller automatically:
- (1) activates the means for the bleeding contaminated etchant solution to bleed a volume of the contaminated etchant solution from the circulation volume of the etchant solution;
- and (2) activates the means for adding fresh etchant solution to add fresh etchant solution to the circulation volume of the etchant solution to increase the conductivity of the circulation volume of the etchant solution to a value that is greater than the lower threshold of conductivity but less than or equal to an upper threshold of conductivity.
A method of generating a control process for maintaining concentration of an etchant solution based on conductivity of the etch solution, the method comprising:
- a) circulating a circulation volume of an etchant solution through a closed-loop circulation system and in contact with at least one substrate to etch material from the at least one substrate, the circulation volume of the etchant solution being at a known temperature;
- b) measuring conductivity of the circulation volume of the etchant solution circulating through the closed-loop circulation system;
- c) measuring pH of the circulation volume of the etchant solution circulating through the closed-loop circulation system;
- and
- d) assign an etchant concentration value to the measured conductivity based on the measured pH.
Dependencies are inferred from the claim text.