International Business Machines Corporation

Robert W Zigner, Jr

Charles Jesse Taft

Richard O Henry

David F Hilscher

Sandi E Merritt

David Lee Rath

Kenneth John McCullough

George Francis Ouimet, Jr

A recyclable fluid cleaning system wafers includes a cleaning vessel configured to clean semiconductor wafers immersed in a bath of persulfuric acid cleaning solution, the cleaning solution circulated through a primary process tool fluid path; a secondary fluid path that diverts a portion of the persulfuric acid cleaning solution for electrolysis treatment thereof; an electrolysis reactor within the secondary fluid path that receives oxidant depleted sulfuric acid, the electrolysis reactor having electrodes that, when activated causes sulfate ions in the solution to be oxidized and form persulfate ions that are recombined with fluid from the primary fluid path and fed back to the cleaning vessel; and one or more controller devices in operative communication with the cleaning vessel and with the electrolysis reactor.

Partial solution replacement in recyclable persulfuric acid cleaning systems

A method of implementing cleaning solution replacement in a recyclable fluid cleaning system for semiconductor wafers includes activating electrode current for an electrolysis reactor included in the cleaning system. At least one of electrode voltage and operating time for the electrolysis reactor is monitored, until a trigger point has been reached. The trigger point includes one of the electrode voltage reaching a predetermined threshold voltage value, a process time counter reaching a predetermined counter value, and a time value that the electrode voltage has been at the threshold voltage value reaching predetermined value. The process time counter is incremented based on one or more of actual wafer processing time, wafer type, number of wafers processed, and thickness of material to be stripped. Upon reaching the trigger point, the electrode current is deactivated, and at least a portion of cleaning system fluid is drained and replaced with fresh cleaning fluid.

An apparatus and method is described for cleaning semiconductor wafers using a dilute aqueous solution including at least 80% deionized water, sulfuric acid, an oxidant such as hydrogen peroxide, and a small amount of hydrofluoric acid (HF), preferably in the range of about 5 ppm to about 12 ppm. The automated system mixes the water, sulfuric acid, hydrogen peroxide, and HF to form a cleaning solution having a target HF concentration within the preferred range, for example at 8 ppm. Subsequently, the system maintains the HF concentration at least within about 0.5 ppm to about 1 ppm of the target HF concentration. Thus the system allows effective and predictable cleaning of semiconductor wafers while minimizing damage to metal features, and minimizing cost and waste disposal impacts.

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Hyde Park, NY, United States of America

Robert W Zigner, Jr