Flush system for dry film photoresist remover

#The present invention relates to the packaging of semiconductor integrated circuits. More particularly, the present invention relates to an auto flush system for a dry film photoresist remover which is used to remove a photoresist film from a semiconductor chip after the formation of ball grid array (BGA) solder bumps on the chip.

#One of the last processes in the production of semiconductor integrated circuits (IC) is multi-leveled packaging, which includes expanding the electrode pitch of the IC chips containing the circuits for subsequent levels of packaging; protecting the chip from mechanical and environmental stress; providing proper thermal paths for channeling heat dissipated by the chip; and forming electronic interconnections. The manner in which the IC chips are packaged dictates the overall cost, performance, and reliability of the packaged chips, as well as of the system in which the package is applied.

#Package types for IC chips can be broadly classified into two groups: hermetic-ceramic packages and plastic packages. A chip packaged in a hermetic package is isolated from the ambient environment by a vacuum-tight enclosure. The package is typically ceramic and is utilized in high-performance applications. A chip packaged in a plastic package, on the other hand, is not completely isolated from the ambient environment because the package is composed of an epoxy-based resin. Consequently, ambient air is able to penetrate the package and adversely affect the chip over time. Recent advances in plastic packaging, however, has expanded their application and performance capability. Plastic packages are cost-effective due to the fact that the production process is typically facilitated by automated batch-handling.

#The invention will now be described, by way of example, by reference to the accompanying drawings, wherein:

#FIG. 1 is a cross-sectional view of a portion of a semiconductor IC chip, illustrating a DFR (dry film photoresist) layer formed on the chip substrate and solder bumps formed on the substrate using the DFR layer as a mold;

#FIG. 2 is a schematic view of a conventional dry film photoresist layer remover system;

#The present invention has particularly beneficial utility in flushing particles from a solvent in a dry film photoresist remover system used in the processing of semiconductor IC chips. However, the invention is not so limited in application and while references may be made to such dry film photoresist remover systems, the invention is more generally applicable to flushing particles from liquids in a variety of industrial and product applications.

#Referring to FIGS. 4 and 5 of the drawings, a flush system of the present invention, suitable for implementation in a dry film photoresist (DFR) remover system used in the semiconductor production industry, is generally indicated by reference numeral 25. The flush system 25 is interposed between the inner tank 13 of the upstream process container 11 and the downstream solvent re-claim tank 16 of the DFR remover system and is designed to prevent excessive clogging of a particle filter 18, which is connected to the solvent re-claim tank 16 by means of a tank outlet conduit 17, as described above with respect to the conventional DFR remover system 10 of FIG. 2. The particle filter 18 is connected to a circulation pump 20 by a filter outlet conduit 19, and the circulation pump 20 is connected to the outer tank 12 of the process container 11 by a pump outlet conduit 21, in conventional fashion. The flush system 25 of the present invention includes an elongated, sloped circulation conduit 26, the rear, upstream or upper end of which is provided in fluid communication with a container outlet conduit 15 that drains the inner tank 13, and the opposite front, downstream or lower end of which circulation conduit 26 is disposed in fluid communication with the solvent re-claim tank 16. A flush loop 29 of the flush system 25 includes a flush loop intake conduit 30 which is connected to the circulation conduit 26 through a loop entry valve 35; a flush loop pump 31 provided in fluid communication with the flush loop intake conduit 30; a pump conduit 32 extending from the flush loop pump 31; and a circulation re-entry conduit 33 which extends from the pump conduit 32 and is connected to the circulation conduit 26. A circulation valve 28 is provided in the circulation conduit 26, between the loop entry valve 35 and the circulation re-entry conduit 33 of the flush loop 29. A loop screen 34, having screen openings or pore sizes of typically about 12 μm, is further provided in the circulation conduit 26, between the circulation valve 28 and the circulation re-entry conduit 33. A backflow valve 37 is provided in the circulation conduit 26, between the discharge end of the circulation re-entry conduit 33 and the solvent re-claim tank 16.

#The flush system 25 further includes a particle discharge unit 39, having a vertical particle drain conduit 40 extending downwardly from a particle drain valve 41 which is provided in fluid communication with the circulation conduit 26, at a point between the circulation valve 28 and the loop screen 34. The horizontal bottom portion of the particle drain conduit 40 is fitted with an outlet valve 42 which is connected to the bottom end portion of a vertical particle screen conduit 44. A particle screen 45, having screen or pore sizes of typically about 12 μm, is mounted in the particle screen conduit 44. A solvent re-entry valve 51 connects the upper end of the particle screen conduit 44 to the rear end of a horizontal solvent re-entry conduit 50, the front end of which terminates in fluid communication with the circulation conduit 26, just upstream of the entry point of the circulation conduit 26 into the solvent re-claim tank 16. A particle discharge valve 46 connects the bottom end of the particle screen conduit 44 to a particle discharge conduit 48.