1). Field of the Invention
This invention relates to a solvent bath and drain, in particular a solvent bath and drain for use on a semiconductor substrate processing apparatus, and a method of draining a dispense head.
2). Discussion of Related Art
Integrated circuits are formed on semiconductor wafers. The formation of the integrated circuits may include numerous processing steps such as deposition of various layers, etching some of the layers, and multiple bakes.
Often the processing of semiconductor wafers takes place in large wafer processing machines. One of the components found in these machines are known as modules. These modules may receive a semiconductor wafer from another component, place the wafer on a wafer support, and dispense a solution, such as photoresist, onto the wafer as one of the many steps included in wafer processing. The photoresist may be dispensed onto the wafers from a dispense head attached to a dispense arm that is moveably connected to the module. Typically, the photoresist is fed into inlets of the dispense head where is passes through a chamber within the dispense head before it is dispensed onto the wafer through nozzles on the dispense head.
While the dispense head is not in use, the dispense head may be moved off to the side of the module. Often, some of the photoresist dries within the dispense head and is later dispensed onto the wafer, causing defects on the wafer. In order to prevent the photoresist from drying within the dispense head, some of the photoresist may be occasionally dispensed, or purged, into a small drain, typically approximately every thirty minutes. The small size of the drain allows only one nozzle to be purged at a time. The nozzles of the dispense head may also be placed, on or directly into an open solvent bath, separate from the drain, which keeps the nozzles moist and further prevents the photoresist from drying within the dispense head.
Because of the small size of the drain and the fact that the solvent bath is separate from the drain, the dispense arm must repeatedly move the dispense head back and forth between the solvent bath and the drain in order to prevent the photoresist from drying in the dispense head. This extra movement reduces the speed at which wafers can be processed and increases the wear on the dispense arm, thereby decreasing the longevity, durability, and reliability of the dispense arm. Additionally, because the solvent bath is open to the air, much of the volatile solvent evaporates and is lost. The photoresist and the solvent are often very expensive and having to waste photoresist and replace the solvent so often greatly increase the cost of semiconductor wafer processing.