Browse Prior Art Database

Recirculating Overflow Etch Tank

IP.com Disclosure Number: IPCOM000045590D
Original Publication Date: 1983-Apr-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Gatov, LA: AUTHOR

Abstract

Contaminants tend to accumulate at the surface of buffered hydrofluoric acid solutions through which the wafers must pass when they are removed from the tank. Other debris settles to the bottom of the tank.

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Recirculating Overflow Etch Tank

Contaminants tend to accumulate at the surface of buffered hydrofluoric acid solutions through which the wafers must pass when they are removed from the tank. Other debris settles to the bottom of the tank.

The surface contamination is removed by overflow separation which occurs through six slots (three on each side) labeled 1 in the diagram. Overflow from both sides allows for a rapid surface cleaning time. The solution is collected in the overflow chambers 2 and drains out through the lines 3. It is then pumped through a filter and returned to the tank through the four inlet ports (two on each side) 4. Four ports are used to provide a large inlet area so that jetting and turbulence in the tank are minimized.

Debris that has settled to the bottom of the tank is removed through the drain
5. 0nce a pump flow rate is chosen, the ratio of drainage from the overflow chambers to drainage from the bottom of the tank is regulated by the throttling valve 6.

The overflow chambers have a sloping bottom to facilitate drainage and have a large volume to allow for "drag-out". Drag-out refers to the solution which is carried by the wafers, boats, and tray during the transfer from one tank to another.

The overflow chambers are to be filled at the same time the tank is filled. They act as a reservoir to replenish the acid volume in the tank when drag-out occurs. The liquid levels in the chambers drop in order to maintain a constant level in the m...