BRIEF DESCRIPTION OF THE DRAWINGS
The features, aspects, and advantages of the present invention will become more fully apparent from the following detailed description, appended claims, and accompanying drawings in which:
FIG. 1 is a process flow chart for a conventional spin coating process on a wafer.
FIG. 2 is a cross-sectional view of a conventional spin coater used in spin coating a liquid on a wafer.
FIG. 3 is a cross-sectional view of a spin coater showing a wafer positioned on a vacuum chuck according to one aspect of the present invention.
FIG. 4 is a cross-sectional view of the spin coater of FIG. 3 showing steps of rotating the wafer and pre-wetting the inside surface of the cup according to one aspect of the present invention.
FIG. 5 is a cross-sectional view of the spin coater of FIG. 4 showing a further step of dispensing a liquid material on the wafer according to one aspect of the present invention.
FIG. 6 is a cross-sectional view of the spin coater of FIG. 5 showing some liquid material thrown off the wafer, splashed onto the inside surface of the cup but not adhering thereto, and drained away in drain pipe according to one aspect of the present invention.
FIG. 7 is a cross-sectional view of the spin coater of FIG. 6 showing little or none of the liquid material remaining on the inside surface of the cup according to one aspect of the present invention.
DETAILED DESCRIPTION
In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, one having an ordinary skill in the art will recognize that the invention can be practiced without these specific details. Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
The present invention discloses a spin coater that is equipped with a self-cleaning cup and a method for self-cleaning a spin coater. FIG. 3 is a cross-sectional view showing a spin coating apparatus 22 of the present invention. The spin coating cup 28 has a basin with sidewalls and a drain pipe 34 at the bottom of the basin. A rotatable platform 30 is situated inside the cup 28 and is adapted for holding and rotating a wafer 26 to be coated. Wafer 26 is mounted on a top surface 24 of the rotatable platform 30. The rotatable platform 30 may comprise a vacuum chuck. A liquid dispenser 18 is situated over the rotatable platform 30 for dispensing a liquid coating material, such as a photoresist material on top of the wafer 26. The rotatable platform 30 may be rotated at a predetermined speed by a shaft 32, which is connected to an electric motor (not shown). A solvent dispensing means 40 is mounted under the rotatable platform 30 for dispensing a cleaning solvent onto the backside of the wafer to pre-wet an interior surface of the sidewalls of the cup 28. In another embodiment, solvent dispensing means 40 may be configured to dispense cleaning solvent onto an interior surface of the sidewalls of the cup 28. Solvent dispensing means 40 may comprise of one or more spray nozzles (two spray nozzles are shown in FIG. 3) for spraying cleaning solvent. The spray nozzles may be fabricated of a material that is chemical resistant, such as stainless steel or Teflon. The nozzle spray(s) may be aimed upwards toward the edge and backside of wafer 26 and the flow rate of the cleaning solvent, such as isopropanol or acetone may flow at a flow rate of between about 2 ml/min and about 20 ml/min. The spray pattern of the cleaning solvent may be fan-shaped such that each nozzle spray may cover a wide area of the interior surface of cup 28. In another embodiment, the solvent dispensing means 40 comprises at least one spray nozzle and a solvent supply tube (not shown) for delivering the cleaning solvent to the spray nozzle. The drain pipe 34 funnels spent cleaning solvent and/or liquid coating material from the bottom of cup 28 to a waste solvent tank (not shown).
The present invention is further directed to a method for self-cleaning a spin coater used for coating a liquid material on a wafer. Referring now to FIG. 4, a cross-sectional view of the spin coater of FIG. 3 shows the steps of rotating the wafer and pre-wetting the inside surface of the cup according to one aspect of the present invention. The solvent dispensing means 40 dispenses a cleaning solvent 42 onto the backside of the wafer 26 to pre-wet an interior surface or side-walls of coater cup 28 to dissolve and rinse off any subsequently dispensed liquid coating material (e.g. photoresist) splattered thereon and to prevent the formation of solid contaminating particles from the splattered liquid coating material.
After the steps of rotating the wafer and dispensing cleaning solvent on the wafer backside to pre-wet the sidewalls of the cup, a liquid coating material 44 or photoresist is dispensed by liquid dispenser 18 onto the wafer 26, as shown in FIG. 5.
FIG. 6 is a cross-sectional view of the spin coater of FIG. 5 showing some liquid coating material 44 thrown off the wafer 26, splashed onto the inside surface of the cup 28 but not adhering thereto, and drained away in drain pipe 34 according to one aspect of the present invention. The liquid coating material 44 does not adhere to the sidewalls of the cup 28 because the cleaning solvent 42 continuously flows down the side-walls of coater cup 28 to rinse off any residual coating material 44 deposited, or splattered thereon.
FIG. 7 is a cross-sectional view of the spin coater of FIG. 6 showing little or none of the liquid coating material 44 remaining on the inside surface of the cup 28 according to one aspect of the present invention.
The present invention described a spin coating apparatus and method thereof, which greatly improves over conventional spin coaters, wherein the coater cups can be easily contaminated by dry photoresist material deposited thereon, thus becoming a major source of solid particle contamination. The dry photoresist material or powder on the sidewalls of the cup further causes blockage of a drain pipe, which may be very difficult and time-consuming to clean. The present invention spin coating apparatus greatly reduces the dry photoresist material remaining on the sidewalls of the cup. As such, the present invention eliminates the need for frequent replacement of the coater cup for cleaning purpose, thereby reducing fabrication costs, cycle time, and improving throughput.
In the preceding detailed description, the present invention is described with reference to specifically exemplary embodiments thereof. It will, however, be evident that various modifications, structures, processes, and changes may be made thereto without departing from the broader spirit and scope of the present invention, as set forth in the claims. The specification and drawings are, accordingly, to be regarded as illustrative and not restrictive. It is understood that the present invention is capable of using various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein.
Patent Application
20080066786
