Abstract:
A processor for cleaning, rinsing, and drying workpieces includes a process vessel, an ozone injection system for introducing ozone gas into the process vessel, a liquid injection system for introducing a processing fluid into the process vessel, and a drying system for delivering a drying fluid to the process vessel. The processing fluid is introduced into the process vessel such that the processing fluid lies beneath a workpiece. Ozone gas is introduced into the process vessel. The workpiece is then bathed in the processing fluid. A drying fluid is introduced into the process vessel while the processing fluid is evacuated from the process vessel. Microelectronic workpieces can be cleaned and dried in a single vessel, reducing the equipment and space used in manufacturing.

Description:
FIELD OF THE INVENTION  
         [0001]    The field of the invention is cleaning, rinsing, and drying a microelectronic workpiece. More specifically, the field of the invention relates to methods and devices that use vapor-phase processes to clean contaminants from the surface of a microelectronic workpiece, and liquid-phase treatment to rinse and the workpiece. A microelectronic workpiece is defined here to include a workpiece formed from a substrate on which microelectronic circuits or components, data storage elements or layers, or micro-mechanical or optical elements are formed.  
         BACKGROUND OF THE INVENTION  
         [0002]    During the processing of microelectronic workpieces into e.g., electronic devices such as integrated circuits, it is necessary to clean, rinse, and dry the workpieces. The cleaning process can involve the stripping of photoresist or contaminants that remain on the surface of the workpiece. In some cleaning processes, a vapor-phase is used to clean the workpiece. The vapor-phase typically includes ozone, O 3 , which is introduced into a process vessel or chamber. The O 3  can be injected into the process vessel as a dry gas, or alternatively, the O 3  can be bubbled through water to produce a moist vapor. The O 3  that is introduced into the process vessel chemically reacts with photoresist and contaminants on the surface of the workpiece.  
           [0003]    The cleaning process removes, to the greatest extent possible, residual chemicals such as photoresist, particulate matter, organic species and contaminants that adhere to the surface of the workpiece. Chemical residue and contaminants that are not removed during the cleaning and drying steps reduce the overall yield of the manufacturing process. This reduces the number of usable electronic components, such as integrated circuits, microprocessors, memory devices, etc. that can be obtained from a workpiece.  
           [0004]    To reduce the contamination, various surface tension effect cleaning and drying techniques have been used. Two of the most widely used technologies include thermocapillary and solutocapillary techniques. An example of a thermocapillary technique is disclosed in U.S. Pat. No. 4,722,752 (Steck). Steck teaches that the use of warm or hot water, with the subsequent reduction in surface tension, can aid in the drying of a semiconductor wafer through a combination of evaporation and low surface tension.  
           [0005]    U.S. Pat. Nos. 4,911,761 (McConnell et al.), 5,271,774 (Leenaars et al.), 5,807,439 (Akatsu et al.), 5,571,337 (Mohindra et al.), and European Patent Specification No. 0 385 536 B1 (Lenarrs et al.) describe solutocapillary techniques.  
           [0006]    These solutocapillary techniques typically clean and dry semiconductor wafers by introducing an organic solvent such as isopropyl alcohol (IPA) on the surface of a liquid such as deionized water. In some applications, the layer of solvent is then allowed to recede over the semiconductor wafers. In other applications, the semiconductor wafers are lifted out of the water bath. In either case, the organic solvent creates a displacement of the water on the liquid surface, effectively diluting the water near the surface. This reduces the surface tension of the surface region, causing displacement of water on the wafer surface by the organic solvent. The reduced surface tension located adjacent to the face of the semiconductor wafer promotes the removal of water and contaminants from the work piece.  
           [0007]    Currently, vapor-phase cleaning process and the liquid-phase rinsing and drying processes are carried out in separate processing vessels. Workpieces are cleaned with the vapor-phase process in a first vessel or chamber. They are transferred to a second vessel for completion with the rinsing and drying steps. Since the cleaning and rinsing processes are performed in two separate pieces of equipment, more floor space is required for the overall process. It is desirable, however, to reduce the overall floor space needed to process microelectronic workpieces, due to the high cost required to house, maintain, and operate a semiconductor manufacturing facility under extremely clean conditions.  
           [0008]    Accordingly, there is a need for an apparatus and method that combines the vapor-phase cleaning process with the liquid-phase rinsing and drying process into a single process vessel, to reduce the floor space and equipment required to process semiconductor wafers, or microelectronic workpieces in general.  
         SUMMARY OF THE INVENTION  
         [0009]    In a first aspect of the invention, a processor for cleaning, rinsing, and drying a microelectronic workpiece includes a process vessel, an ozone or reactive gas or vapor supply system, a liquid injection system, and a drying system. The process vessel holds one or more workpieces. The ozone supply system introduces ozone gas into the process vessel. The liquid supply system introduces a processing liquid into the process vessel. The drying system provides a drying gas, vapor, or liquid.  
           [0010]    In a second aspect of the invention, the processor according to the first aspect includes a gas bubbler for introducing ozone gas into the process vessel.  
           [0011]    In a third aspect of the invention, a method for cleaning, rinsing, and drying a microelectronic workpiece inside a single process vessel includes the steps of first introducing a processing fluid into the process vessel with the processing fluid lying beneath the workpiece. Ozone gas is then preferably introduced into the process vessel. The workpiece is then immersed in the processing fluid. The processing fluid is removed from the process vessel and a drying fluid is then introduced into the process vessel. Use of a single vessel reduces floor space and handling requirements, and can expedite processing.  
           [0012]    It is an object of the invention to provide an improved method and apparatus for cleaning, rinsing, and drying of a microelectronic workpiece. It is a further object of the invention to provide an improved method and apparatus that combines a vapor-phase cleaning process with a liquid-phase rinsing and drying process in a single processor or equipment.  
           [0013]    The invention resides as well in subcombinations of the features and steps described. While use of ozone is preferred, it is not essential to the invention. Rather, the invention more broadly contemplates performing vapor phase process and then an immersion process and a drying process, in a single vessel regardless of the fluid chemicals used. A fluid here can be a liquid, a gas, or a vapor.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0014]    [0014]FIG. 1 is a cut away perspective view of the cleaner/rinser/dryer system or processor. 
     
    
     DETAILED DESCRIPTION  
       [0015]    Referring now to the FIG. 1, a processor  2  includes a process vessel or tank  4 . The processor  2  is used as a cleaner, rinser, and dryer for the processing of microelectronic workpieces  6 , including, for example, semiconductor substrates. The processor  2  is adapted to clean, rinse, and dry one or more workpieces  6 . Preferably, a batch of workpieces  6  are held within a cassette or holder  8  positioned within the process vessel  4 . The cassette  8  preferably contacts each workpiece  6  with a minimum number of contact locations.  
         [0016]    In a preferred embodiment, the cassette  8  and the one or more workpieces  6  are held stationary within the process vessel  4  during the cleaning, rinsing, and drying process. The cassette  8 , however, may also be raised and lowered within the process vessel  4  during processing using known techniques. For stationary processing, the cassette or holder  8  may be held in place by a rack  10  located inside of the process vessel  4 . The processor  2  can also employ a motor  60  to spin the cassette or holder  8 , to provide more uniform processing. The spinning of the workpiece  6  is shown by the arrow  9  in FIG. 1. The workpieces are loaded and unloaded into the vessel  4  by opening or removing the vessel lid  5 . The lid  5  can, but need not, seal the vessel. Rather, the lid  5  helps to contain and control the vapor phase processing.  
         [0017]    The process vessel  4  includes a liquid supply or injection system  11  that introduces, extracts, and replenishes processing fluid  16  within the process vessel  4 . The liquid injection system  11  includes one or more inlets  12 , and one or more outlets  14 , in the process vessel  4  for supplying and removing a processing fluid  16 . Preferably, the processing fluid is deionized (DI) water. The level of processing fluid  16  within the process vessel  4  may be controlled by varying the flow rates through the inlet  12  and outlet  14 . The flow rates are preferably controlled by a microprocessor-based controller.  
         [0018]    The processor  2  also includes a drying system  17  connecting into the process vessel  4 . The drying system  17  operates by delivering a drying fluid such as a drying gas  24  into the process vessel. The drying system  17  may include a gas diffuser  18  located at the top of the process vessel  4 . The gas diffuser  18  advantageously includes a plurality of holes  20  to permit gas flow from above and into the vessel  4 . While rectangular-shaped orifices  20  are shown in FIG. 1, other shapes can also be used. One or more gas delivery pipes  22  are preferably connected to the gas diffuser  18  (if used) to supply a drying gas  24  to the process vessel  4 . The drying gas  24  may include any number of gases or gas mixtures. For example, the drying gas  24  might include N 2 , air, N 2 /air mixture, or an organic vapor  26  mixed with a carrier gas  28 .  
         [0019]    [0019]FIG. 1 illustrates the gas delivery pipe  22  connected to separate sources for the organic vapor  26  and the carrier gas  28 , to provide surface tension effects for drying the workpieces  6 . The organic vapor  26  is preferably isopropyl alcohol (IPA). Of course, materials other than IPA may be used to promote drying. The carrier gas  28  is preferably N 2 , but other inert gases or even air can be used. The dilution of the combined organic vapor  26  and carrier gas  28  is preferably controlled by pressure regulators  30 . The combined gas stream is preferably pumped into the process vessel by pump  32 . A manifold  19  having spray nozzles may be used instead of the diffuser  18 .  
         [0020]    If a single gas component is used for the drying gas  24 , the branch structure  33  shown in FIG. 1 is not necessary. The drying gas  24  is preferably directly pumped into the process vessel  4 . As an alternative to introducing the drying gas to the process vessel  4  via a gas diffuser  18  or the top manifold  19 , the drying fluid can be directly injected through one or more side nozzles  33  at the sides of the process vessel  4 . The drying fluid can be injected or sprayed as either a liquid or a gas depending on the drying fluid used. Various other drying systems, with or without IPA or other chemicals, may be used, including drying systems using heat, air or gas movement, mechanical liquid removal, or other techniques.  
         [0021]    An overflow weir or wall  34  may be provided in the vessel, e.g., located on one side of the process vessel  4 . When the process fluid  16  rises to the level of the overflow weir  34 , the process fluid  16  passes over the overflow weir  34  and into a drain  36 . The overflow weir  34  ensures that the process vessel  4  does not overflow. In addition, the overflow weir  34  also serves as another outlet to remove processing fluid  16  that contains contaminants from the cleaning of the workpiece  6 . The overflow weir  34 , if used, can be located on any side of the process vessel  4 .  
         [0022]    One or more heaters  38  are preferably, but not necessarily, provided and located on the side of the process vessel  4 . The heaters  38  are preferably located at a position that permits heat to be transferred from the heaters  38  to the processing fluid  16 . The heaters  38 , if used, may be positioned inside, within, or outside of the process vessel  4 . The heaters  38  are preferably controlled by a microprocessor-based controller to control the temperature of the processing fluid  16  within the process vessel  4 .  
         [0023]    An ozone supply system  40  may be included for use in the vapor phase processing. If used, the ozone supply system  40  preferably includes a gas bubbler  46  connected via piping  47  to an ozone generator  42 . A pump  48  may be used to pump the ozone gas from the ozone generator  42  into the process vessel  4 . A flow control valve may also be used to control the flow of ozone gas into the process vessel  4 . A gas regulator  50  is preferably located upstream of the pump  48 . The ozone gas is preferably introduced into the process vessel  4  using the gas bubbler  46 . The gas bubbler  46  includes openings  52  that create bubbles  54  of ozone gas within the processing fluid  16 . As an alternative to the gas bubbler  46 , one or more ozone spray nozzles or even simple ports  56  can be positioned within the process vessel  4  to provide ozone gas directly into the process vessel  4 .  
         [0024]    The process vessel  4  also preferably includes a gas vent  58  that permits the evacuation of gas from the process vessel  4 . The gas vent  58  is located on the top of the processor  2  or on the lid  5 .  
         [0025]    In a preferred method, a cassette  8  containing a batch of workpieces is loaded into the processor  2 . Loading may be performed by opening or removing the lid  5 , and placing the cassette  8  onto a rack  10  within the process vessel  4 . The cassette  8  can also be loaded into the process vessel  4  via a robot. During the cleaning phase of the process, a processing fluid  16  such as DI water is introduced into the process vessel  4  via inlet  12 . The DI water level rises up from the bottom along the walls of the process vessel  4 . The level of the processing fluid  16  is raised to a first level shown by arrow A in FIG. 1. This first level is preferably below the bottom edge of the workpieces  6  held within the cassette  8 , so that the processing fluid  16  preferably does not contact the workpieces  6 .  
         [0026]    Next, the heaters  38  are preferably used to heat the processing fluid  16  within the process vessel  4 . The processing fluid  16  is preferably heated to enhance the cleaning effect of the ozone gas on the workpiece  6 . Of course, the processing fluid  16  can also be heated before or while the processing fluid  16  is introduced into the process vessel  4  by the drying system. Once the appropriate temperature of the processing fluid  16  has been established, the ozone injection system  40  begins to inject ozone gas into the process vessel  4 . If used, the gas bubbler  46  bubbles ozone gas through the preferably heated processing fluid  16 . The ozone gas becomes heated and moist, thereby enhancing the cleaning effects of the ozone gas on the workpieces  6 . The ozone gas, if used, may alternatively be injected directly into the process vessel  4  via one or more nozzles  56 . The ozone gas is introduced into the process vessel  4  for a period of time sufficient to strip or remove any remaining photoresist or other contaminants from the workpieces  6 . Processing may also be performed at room temperature, without any heating, although heating is preferred.  
         [0027]    After the vapor-phase cleaning step, the liquid-phase rinsing begins. Rinsing is important because the vapor phase cleaning step may not completely remove all contaminants. The level of the processing fluid  16  within the process vessel  4  is gradually increased to completely immerse the workpieces  6 . The processing fluid  16  stops rising when it reaches the top of the overflow weir  34 . This level is shown by arrow B in FIG. 1. At this point, the processing fluid  16  is preferably continuously refreshed to supply clean processing fluid  16  to the process vessel  4 . Processing fluid  16  containing contaminants passes out of the process vessel  4  via the overflow weir  34  and drain  36 , and optionally, the outlet  14 .  
         [0028]    The processing fluid  16  used in this rinsing step is preferably, but not necessarily, the same fluid or the same type of fluid as used in the preceding cleaning step. This immersion step may also not necessarily be a rinsing step. Rather, if a process chemical liquid is provided into the vessel, this step may be a process step which chemically processes the workpieces. A rinsing step (using a rinsing liquid such as water) may then be subsequently performed, preferably in the vessel, but potentially also in another vessel.  
         [0029]    After rinsing the workpiece, the drying step begins with the gradual reduction of the level of processing fluid  16  within the process vessel  4  via the outlet  14 . A drying gas  24  is preferably introduced into the process vessel  4  by the drying system  17 . The drying gas  24  may be introduced via the gas diffuser  18  located at the top of the process vessel  4 . If a liquid is used as the drying fluid, the liquid may be injected via injectors  33 . The drying gas  24  may alternatively be introduced via injectors  33  in the process vessel  4 . If surface tension effects are used, the drying gas  24  preferably includes an organic vapor component such as IPA to increase surface tension effect drying of the workpiece  6 .  
         [0030]    At the end of the cleaning/rinsing/drying process, when the processing fluid  16  has been removed from the process vessel  4 , the workpieces  6  are removed from the processor  2 . While DI water has been described as the preferred processing fluid, other processing fluids  16  can also be used. In addition, multiple processing fluids  16  can be introduced into the process vessel  4  in a continuous or near-continuous manner. This allows different processing fluids  16  to replace each other. The processing fluid  16  inside the process vessel  4  is removed from the process vessel  4  either by the overflow weir  34  or the outlet  14 . The removed processing fluid  16  can then be returned to a process tank for recovery and reuse. Alternatively, the processing fluid  16  can be directed to a waste drain.  
         [0031]    In another aspect of the invention a processor  2  of the type disclosed in pending U.S. patent application Ser. No. 09/590,724, filed Jun. 8, 2000, is used. This Application is incorporated by reference as if set forth fully herein. U.S. patent application Ser. No. 09/950,724 discloses a processor  2  that uses an outer containment vessel and a porous process vessel  4  to enhance drying.  
         [0032]    While embodiments of the present invention have been shown and described, various modifications may be made without departing from the scope of the invention. The invention, therefore, should not be limited, except to the following claims, and their equivalents.