Tung & Associates
Method and apparatus for dispensing a liquid
 The present invention discloses a system and method for controlling the dispensing of a fine liquid for coating or other applications, by detecting the volume of liquid dispensed when coating a single workpiece and sending a signal to a controller to disable the dispensing when an insufficient volume of liquid is being dispensed. In a preferred embodiment, the fine liquid is spin-on-glass (SOG) used in semiconductor processing machinery during wafer fabrication and the the SOG volume dispensed when coating a semiconductor wafer is measured using a weight measurement instrument, e.g., an electronic scale capable of 0.1 gm. accuracy, which outputs a weight signal that is input, along with a dispenser condition signal from the SOG dispensing machine, to a programmable logic controller (PLC). A set point is selected to produce a desired weight of dispensed liquid, e.g., 1.7 gms. when 2 ccs. are desired, and is programmed into the PLC. The PLC detects and controls the dispenser and counts the weight reduction recorded by the scale from the beginning of dispensing until reaching the set point. The weight difference is directly related to the volume of SOG dispensed. The scale is reset to 0 after each dispensing period so that the reading is positive. When the set point is reached, the PLC stops counting and the weight difference is checked. If the weight is insufficient, a signal is sent to cause an alarm and interlock to prevent further machine operation until restarted by an operator. 
Taiwan Semiconductor Manufacturing Co., Ltd.
H B B B
H01L B05C B05C B05C
inventional additional inventional inventional
Yu L. Wen Y. Tun L. Shih S.
Ma Wang Lee Jang