In a semiconductor device manufacturing process, various chemical liquids such as, for example, a resist, is supplied to a semiconductor wafer (hereinafter, referred to as a “wafer”) as a substrate, using a coating apparatus that is one of liquid processing apparatuses. The chemical liquid, scattered or overflowing from the wafer, flows to the bottom portion of, for example, a cup that forms the coating apparatus and is installed to surround the wafer. Then, the chemical liquid flows, as waste liquid, in a liquid discharge pipe connected to the bottom portion of the cup to be removed. The liquid discharge pipe is installed to be inclined, for example, downwardly so that the chemical liquid naturally flows by weight. Japanese Patent Laid-Open Publication No. 2012-33886 discloses a coating apparatus the cup and the liquid discharge pipe as described above.
In some cases, a chemical liquid having a relatively high viscosity may be used as the chemical liquid. In order to ensure that the chemical liquid flows in the liquid discharge pipe even if the viscosity of the chemical liquid is so high, the liquid discharge pipe is installed at a relatively large angle with respect to a horizontal plane. However, when the liquid discharge pipe is installed in this way, the height occupied by the liquid discharge pipe at the lower side of the cup is increased, which makes it difficult to miniaturize the coating apparatus.
While descriptions have been made on the waste liquid from the cup, in some cases, the coating apparatus may supply a chemical liquid to a place other than the cup, and the chemical liquid becomes the waste liquid, as will be described in detail in the description of exemplary embodiments of the present disclosure. A liquid discharge pipe configured to allow the waste liquid to flow therein also has an increased height due to a reason that is the same as the liquid discharge pipe connected to the cup, which may disturb miniaturization of the coating apparatus. The problems encountered in discharging the chemical liquid having a high viscosity as described above is not limited to an apparatus that performs a processing on a wafer like the aforementioned coating apparatus, i.e. an apparatus that performs a so-called pre-processing of a semiconductor manufacturing process. In a post-processing of the semiconductor manufacturing process, a wafer is cut to form a chip, then a chemical liquid such as, for example, a liquid resin is supplied to the chip, and the chemical liquid is cured to form a package that covers the chip. In general, the chemical liquid for forming a package also has a high viscosity. Therefore, when a liquid discharge pipe for discharging the chemical liquid is installed, the height may be increased like the liquid discharge pipe that is connected to the cup as described above.
Japanese Patent Laid-Open Publication No. 2012-33886 discloses a system that is provided with the liquid discharge path as described above and a tank that collects waste liquid, but does not disclose a means for solving the problems as described above. Japanese Patent Laid-Open Publication No. H5-7674 discloses a technique for mixing mixing-target materials within a tank by forming vortex flows within the tank, but does not disclose the problems as described above. The mixing target materials flow in a pipe connected to the lower side of the tank and is discharged from the tank by opening/closing a valve installed in the pipe, which requires burdens in opening/closing the valve and manufacturing costs due to the installation of the valve.