Abstract:
A method for cleaning a wafer with a drip nozzle being configured for use in a drip manifold that is oriented over a brush of a wafer cleaning system is provided. The drip nozzle has a first end and a second end with a passage defined there between where the passage includes a wall that extends longitudinally between the first end and the second end. An orifice is defined within the passage and located at the first end of the drip nozzle. The method includes inputting a fluid into the drip nozzle at an acute angle relative to a longitudinal extension of the wall and reflecting the fluid stream off an internal wall of the drip nozzle at least twice in a direction that is toward the second end. The method further includes outputting at least one substantially uniform drop from the second end of the passage.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a continuation and claims priority from co-pending U.S. patent application Ser. No. 09/538,865 filed on Mar. 29, 2000 and entitled “DRIP MANIFOLD FOR UNIFORM CHEMICAL DELIVERY” which is hereby incorporated by reference in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to semiconductor wafer cleaning and, more particularly, to techniques for applying fluids over a cleaning brush and improving wafer cleaning throughput and efficiency.  
           [0004]    2. Description of the Related Art  
           [0005]    In the semiconductor chip fabrication process, it is well-known that there is a need to clean a wafer where a fabrication operation has been performed that leaves unwanted residuals on the surface of the wafer. Examples of such a fabrication operation include plasma etching (e.g., tungsten etch back (WEB)) and chemical mechanical polishing (CMP). If left on the surface of the wafer for subsequent fabrication operations, the unwanted residual material and particles may cause, among other things, defects such as scratches on the wafer surface and inappropriate interactions between metallization features. In some cases, such defects may cause devices on the wafer to become inoperable. In order to avoid the undue costs of discarding wafers having inoperable devices, it is therefore necessary to clean the wafer adequately yet efficiently after fabrication operations that leave unwanted residue on the surface of the wafer.  
           [0006]    [0006]FIG. 1A shows a high level schematic diagram of a wafer cleaning system  50 . The cleaning system  50  typically includes a load station  10  where a plurality of wafers in a cassette  14  may be inserted for cleaning through the system. Once the wafers are inserted into the load station  10 , a wafer  12  may be taken from the cassette  14  and moved into a brush station one  16   a , where the wafer  12  is scrubbed with selected chemicals and water (e.g., de-ionized (DI) water). The wafer  12  is then moved to a brush station two  16   b.  After the wafer has been scrubbed in brush station  16 , the wafer is moved into a spin, rinse, and dry (SRD) station  20  where DI water is sprayed onto the surface of the wafer and spun to dry. During the rinsing operation in the SRD station, the wafer rotates at about 100 rotations per minute or more. After the wafer has been placed through the SRD station  20 , the wafer is moved to an unload station  22 .  
           [0007]    [0007]FIG. 1B shows a simplified view of a cleaning process performed in a brush station  16 . In brush station  16 , the wafer  12  is inserted between a top brush  30   a  and a bottom brush  30   b  with top surface  12   a  facing up. The wafer  12  is capable of being rotated with rollers (not shown) to enable the rotating brushes  30   a  and  30   b  to adequately clean the entire top and bottom surfaces of the wafer  12 . In certain circumstances, the bottom surface of the wafer is required to be cleaned as well because contaminants from the bottom may migrate to the top surface  12   a.  Although both the top surface  12   a  and the bottom surface of the wafer  12  are scrubbed with the brushes  30 , the top surface  12   a  that is scrubbed with the top brush  30   a  is the primary surface targeted for cleaning, since the top surface  12   a  is where the integrated circuit devices are being fabricated. To more effectively clean the wafer  12 , a cleaning solution can be applied onto the top brush  30   a  by the use of a drip manifold  13   a.  In this example, the drip manifold  13   a  is attached to a drip control  13  which is in turn connected to a fluid source  24 . The fluid source  24  pumps fluid (e.g., any cleaning chemical or DI water) through the fluid control  13  which controls the amount of fluid entering the drip manifold  13   a.  After receiving the fluid from the fluid control  13 , the drip manifold  13   a  then expels a non-uniform drip  32  onto the top brush  30   a.  As will be discussed below, this non-uniform drip  32  has been observed to cause problems in cleaning operations.  
           [0008]    [0008]FIG. 1C shows a cross sectional view of the elements depicted in FIG. 1B. When the wafer  12  has been placed on the bottom brush  30   b , the top brush  30   a  is lowered onto the wafer  12 . As the top brush  30   a  is lowered onto the wafer  12 , drip control  13  starts the flow of fluid to the drip manifold  13   a  which releases the non-uniform drip onto the top brush  30   a.  During this time, both the bottom brush  30   a  and  30   b  turn to create the mechanical scrubbing action.  
           [0009]    [0009]FIG. 1D shows a more detailed side view of the wafer cleaning structure depicted in FIG. 1B. In general, it is a goal to have the fluid provided to the drip manifold  13   a  expel “droplets” of fluid evenly over the entire length of the brush  32   a.  To do this, it is common practice to introduce the fluid into the drip manifold  13   a  at reduced flow rates and pressures. To accomplish this, the fluid source  24  supplies the cleaning fluid through the drip control  13  which regulates the amount of fluid injected into a near end  31   a  of the drip manifold  13   a.  Unfortunately, as the fluid enters into the near end  31   a , the fluid tends to flow out of the drip manifold faster at that end than at a far end  31   b.  This differential fluid expulsion occurs because most of the fluid is released through the drip holes at the near end  31   a  before the fluid can reach the drip holes at the far end  31   b.  Therefore, if the drip manifold  13   a  were totally horizontal, more near end drops  32   a  will be expelled than far end drops  32   b.  In the prior art, the drip manifold  13   a  was sometimes tilted downward slightly at a manifold angle φ  42  to allow more fluid to reach the far end  31   b.  The manifold angle  42  is determined by finding the optimal angle of the drip manifold  13   a  which produces the equivalent amount of drip from both the near end  31   a  and the far end  31   b.  This manifold angle  42  is measured relative to a y-axis  40   a  and an x-axis  40   b.  As the drip manifold  13   a  expels the far end drops  32   a  and near end drops  32   b  onto the top brush  30   a , the brushes  30  turn to scrub the wafer  12 .  
           [0010]    Unfortunately, calibrating the drip manifold  13   a  to produce the right amount of fluid flow can be a very time consuming and a difficult process. By guesswork and trial and error, numerous manifold angles φ  42  must be tried to find the optimal flow rate of the cleaning fluid. Even after the optimal flow rate has been found, the drip manifold may need re-calibrating every time the cleaning apparatus is moved to another location. This problem occurs because each different location (even a different section of the same room) can have a floor angle that is different from the previous location. Therefore, as is often the case, if the cleaning apparatus must be moved frequently, the need for constant re-calibration can create large wastes of time and reduce wafer cleaning throughput. In addition, further problems in the maintenance of manifold angle φ  42  may occur if the drip manifold is moved by a bump or nudging of the cleaning apparatus because even a slight movement of the drip manifold can have the effect of altering the manifold angle φ  42 . Therefore, the prior art drip manifold  13   a  must often be re-calibrated far more often than is desirable or practical.  
           [0011]    [0011]FIG. 1E depicts a more detailed cross-sectional view of the drip manifold  13   a  which is expelling the non-uniform drip  32  through a drip hole  13   b.  As is common practice, the drip hole  13   b  is formed by drilling a hole into the drip manifold  13   a.  Unfortunately, the drilling process is known to leave hole shavings  13   c  in and around the drip holes  13   b.  These shavings can potentially be introduced over wafers as particulates causing damage to circuits or retard the flow of fluid, thus causing un-even fluid sprays along the drip manifold  13   a.  To compensate for potential hole shavings  13   c  and un-even fluid delivery, it is common practice to deliver fluids to the drip manifold  13   a  at high pressures and flow rates. This is believed to improve the distribution of fluid out of all of the drip holes  13   b  along the drip manifold  13   a.  As consequence, however, this high pressure delivery and flows tend to produce high pressure jets  32 ′.  
           [0012]    Although the distribution of fluids out of the drip holes  13   b  improved, the high pressure jets  32 ′ have the disadvantageous effects of damaging the delicate surface of the brush  32   a.  In some cases, after relatively few cleaning operations, it was noticed that the brush  32   a  became somewhat shredded or frayed. Consequently, the solution of simply increasing fluid delivery flow and pressures caused additional problems beyond those of un-even fluid delivery.  
           [0013]    Because of these inherent problems in the present drip manifold  13   a , additional devices such as pressure regulators, pressure gauges, and flow meters, which are part of the drip control  13 , have been used in a largely unsuccessful attempt to prevent over spraying. Unfortunately, even with seemingly proper drip control, unforeseen fluctuations in fluid pressure can occur which may result in the high pressure jet  32 ′ which have been known to damage the top brush  30   a  and/or the wafer  12 .  
           [0014]    It should be apparent that using the aforementioned drip manifold is unduly inefficient. Such a drip manifold has the downside of taking more time to setup, and requiring a large amount of maintenance time to keep the drip manifold at the perfect manifold angle φ  42 . Moreover, the fluid application must be carefully monitored because of the possible damage to brushes and wafers caused by flow altering effects of fluctuations in fluid pressure and hole shavings  13   c.  Therefore, using prior art dripping mechanisms can cause lower throughput of wafer cleaning and/or cause damage to the brushes and wafers.  
           [0015]    In view of the foregoing, there is a need for a drip manifold that avoids the problems of the prior art by improving cleaning fluid dripping and increasing wafer cleaning efficiency and output.  
         SUMMARY OF THE INVENTION  
         [0016]    Broadly speaking, the present invention fills these needs by providing an improved method for providing uniform chemical delivery over brushes of a wafer cleaning system. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, a system, a device, or a method. Several inventive embodiments of the present invention are described below.  
           [0017]    In one embodiment, a method for cleaning a wafer with a drip nozzle being configured for use in a drip manifold that is oriented over a brush of a wafer cleaning system is provided. The drip nozzle has a first end and a second end with a passage defined there between where the passage includes a wall that extends longitudinally between the first end and the second end. An orifice is defined within the passage and located at the first end of the drip nozzle. The method includes inputting a fluid into the drip nozzle at an acute angle relative to a longitudinal extension of the wall and reflecting the fluid stream off an internal wall of the drip nozzle at least twice in a direction that is toward the second end. The method further includes outputting at least one substantially uniform drop from the second end of the passage.  
           [0018]    In another embodiment, a method for cleaning a wafer with a manifold including at least one drip nozzle is provided. The method includes inputting a fluid into a first end of the at least one drip nozzle at an acute angle relative to a wall that extends longitudinally between the first end and a second end of the at least drip nozzle. The method further includes reflecting the fluid stream off an internal wall of the at least one drip nozzle at least twice in a direction that is toward the second end of the at least one drip nozzle. The method also includes outputting at least one substantially uniform drop from the second end of the passage at a consistent rate, and applying the at least one substantially uniform drop onto a brush.  
           [0019]    In yet another embodiment, a method for cleaning a wafer with a manifold including at least one drip nozzle is provided. The method includes inputting a fluid into a first end of the drip nozzle at an acute angle relative to a wall that extends longitudinally between the first end and a second end of the drip nozzle and reflecting the fluid stream off an internal wall of the drip nozzle at least twice in a direction that is toward the second end of the drip nozzle. The method also includes outputting at least one substantially uniform drop from the second end of the passage at a consistent rate and applying the at least one substantially uniform drop onto a brush. The method further includes scrubbing a wafer with the brush.  
           [0020]    The advantages of the present invention are numerous. Most notably, by designing a drip manifold which produces consistent dripping of uniform drops, the wafer cleaning efficiency and throughput may be improved. The claimed invention removes the problems of variable cleaning chemical flow which causes problems such as brush and/or wafer damage.  
           [0021]    The present drip manifold does not have to be oriented at a specific manifold angle to properly apply the cleaning fluid in the proper manner. This advancement obviates the need for continual re-calibrations of drip manifold systems to obtain and maintain the perfect manifold angle. This feature reduces time spent on maintaining the drip manifold and allows increased wafer cleaning throughput. Moreover, the present drip manifold is nearly immune to fluctuations in cleaning fluid dripped caused by small fluid pressure variations. Further, due to the design of the drip nozzle, flow alterations normally caused by hole shavings are also eliminated. Therefore the drip manifold will allow new drip systems to more easily produce and maintain the type of dripping preferable in the wafer cleaning process.  
           [0022]    Other aspects and advantages of the invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principle invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]    The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings. To facilitate this description, like reference numerals designate like structural elements.  
         [0024]    [0024]FIG. 1A shows a high level schematic diagram of a wafer cleaning system.  
         [0025]    [0025]FIG. 1B shows a simplified view of a cleaning process performed in a brush station.  
         [0026]    [0026]FIG. 1C shows a cross sectional view of the elements depicted in FIG. 1B.  
         [0027]    [0027]FIG. 1D shows a more detailed side view of the wafer cleaning structure depicted in FIG. 1B.  
         [0028]    [0028]FIG. 1E depicts a more detailed cross-sectional view of the drip manifold which is expelling the non-uniform drip through a hole.  
         [0029]    [0029]FIGS. 2A and 2B show a side view and a top view, respectively, of a cleaning system, in accordance with one embodiment of the present invention.  
         [0030]    [0030]FIG. 3A shows a cross-sectional view of a drip nozzle, in accordance with one embodiment of the present invention.  
         [0031]    [0031]FIG. 3B depicts a cross-sectional view of a drip manifold in accordance with one embodiment of the present invention.  
         [0032]    [0032]FIG. 3C shows an exploded view of the sapphire orifice manifold in accordance with one embodiment of the present invention.  
         [0033]    [0033]FIG. 3D shows a view of an alternative orifice in accordance with one embodiment of the present invention.  
         [0034]    [0034]FIG. 4 depicts a side view of the drip manifold containing a plurality of the drip nozzles in accordance with one embodiment of the present invention.  
         [0035]    [0035]FIG. 5 illustrates a cleaning system using the drip manifold containing a plurality of the drip nozzles in accordance with one embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0036]    An invention of method and systems presenting an improved method for providing uniform chemical delivery over brushes of a wafer cleaning system. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be understood, however, by one of ordinary skill in the art, that the present invention may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention.  
         [0037]    [0037]FIGS. 2A and 2B show a side view and a top view, respectively, of a cleaning system  120 . The cleaning system  120  typically includes an input station  100  where a plurality of wafers may be inserted for cleaning through the system. Once the wafer  12  is inserted into the input station  100 , the wafer  12  may be taken from the input station  100  and moved into a brush station one  102   a , where the wafer  12  is scrubbed with selected chemicals and water (e.g., de-ionized water) before being moved to a brush station two  102   b.  In the brush stations, a drip manifold including a drip nozzle of the present invention is contained. The features of the drip manifold and drip nozzle will be described in greater detail below.  
         [0038]    After the wafer  12  has been scrubbed in the brush stations  102 , the wafer  12  is moved into a spin, rinse, and dry (SRD) station  104 , where de-ionized (DI) water is sprayed onto the surface of the wafer and spun to dry. After the wafer has been placed through the SRD station  104 , the wafer  12  is moved to an output station  106 . The cleaning system  120  is configured to be programmed and controlled from system electronics  108 . Of course, this cleaning system is only exemplary in nature, and any other type of cleaning system that uses brush technology coupled with drip manifolds will also benefit from the advantages of the present invention. For instance, the system can be a standalone brush station for scrubbing wafers horizontally or vertically, or part of a chemical mechanical polishing (CMP) system and clean system combination.  
         [0039]    [0039]FIG. 3A shows a cross-sectional view of a drip nozzle  200 , in accordance with one embodiment of the present invention. The drip nozzle  200  is configured to provide more consistent dripping of more uniform drops.  
         [0040]    In one embodiment, the drip nozzle  200  has a first end  201   a  and a second end  201   b.  The drip nozzle  200  has a tubular segment  201   c  connected to a nozzle head  200   c.  The drip nozzle  200  contains a passageway between the first end  201   a  and the second end  201   b  where fluid can travel. Generally, a passage  205  is defined by a cylindrical shape having an inner surface  200 ′. In one embodiment, the first end  201   a  of the drip nozzle  200  will preferably have an angled wall  200   a.  It should be understood that the angle of the angled wall  200   a  can be varied depending on fluid flow requirements or any other calibration parameter. The drip nozzle  200  also has an outer nozzle wall  200   b.  To secure the drip nozzle  200  to a drip manifold (as will be shown below), the outer nozzle wall will preferably have threads (not shown).  
         [0041]    In one embodiment, a sapphire orifice  202  is preferably inserted into the angled wall  200   a  at the first end  201   a.  In an alternative embodiment, the sapphire orifice can made from any suitable material that is hard enough and compatible with cleaning solutions, and therefore, the sapphire orifice can be made from any material to define an insert orifice. Because a passage  200 ″ is angled into the angled wall  200   a , the sapphire orifice  202  is also angled to fit into the passage  200 ″. Thus, the sapphire orifice  202  will include an orifice inner surface  202 ′ that defines an angled path into the passage  205 . This angled path serves to create an angled fluid stream that is directed against the drip nozzle inner surface  200 ′ at a stream contact surface  206 .  
         [0042]    Although sapphire is used in an exemplary embodiment, other materials may be used such as materials that are compatible with various cleaning fluids. Such cleaning fluids may include basic solutions, acidic solutions (e.g., HF), and other fluids. The sapphire material can also be defined with passage ways (e.g., holes) that are defined to tight tolerances, and once formed, leave a very clean unobstructed surface (e.g., smooth surface). Moreover, it should be appreciated by one of ordinary skill in the art that the sapphire orifice  202  may be oriented differently as long as the resultant configuration produces an angled stream of fluid that is directed at the drip nozzle inner surface  200 ′.  
         [0043]    When orifice input fluid  204 ′ first enters the drip nozzle  200 , it travels through the sapphire orifice  202 . As the resultant angled stream leaves the sapphire orifice  202  and enters the inner passage  205  of drip nozzle  200 , it begins to expand and is defined by a stream boundary  206   a  and a stream boundary  206   b.  This initial stream then hits against the stream contact surface  206  which is a section of the drip nozzle inner surface  200 ′. Because the initial stream hits the stream contact surface  206  at an angle, the initial stream reflects off of the stream contact surface  206  and is angled towards the second end  201   b  of the drip nozzle  200 . When this reflection occurs, the initial stream loses velocity and expands to form a first reflected spray with a spray boundary  208   a  and a spray boundary  208   b.  When this expansion occurs, portions of the first reflected spray having boundaries  208   a  and  208   b  contact portions of the incoming initial stream having boundaries  206   a  and  206   b.  This contact serves to decrease the velocities of both the initial stream and the first reflected spray.  
         [0044]    The first reflected spray then hits spray contact surface  208 . By this time, the first reflected spray has expanded so the area of the spray contact surface  208  is larger than the spray contact surface  206 . When this contact occurs, the first reflected spray is reflected a second time towards the second end  201   b  of the drip nozzle  200 . When the reflection occurs, the first reflected spray loses velocity and a slower moving second reflected spray is produced. This loss in velocity causes a further expansion of the spray boundaries to form a spray boundary  210   a  and a spray boundary  210   b.  As the second reflected spray expands, it comes into contact with the incoming first reflected spray. This contact further reduces the velocities of both the first reflected spray and the second reflected spray.  
         [0045]    The second reflected spray then contacts a spray contact surface  210 . Once again, because of the expansion of the spray in transit, the spray contact surface  210  is larger than the spray contact surface  208 . When this contact occurs, the spray is once again reflected at an angle towards the second end  201   b  of the drip nozzle  200  to produce a third reflected spray. When this reflection occurs, the velocity of the spray is decreased again and further expansion of the spray occurs. This expansion forms a spray boundary  212   a  and a spray boundary  212   b.  Moreover, when this spray expansion occurs, the third reflected spray comes into contact with the incoming second reflected spray. When this contact occurs, the velocities of both the second reflected spray and the third reflected spray are decreased.  
         [0046]    Therefore, each spray reflection produces a decrease in fluid velocity. These spray reflections continue until the fluid reaches the periphery of a nozzle head  200   c  at the second end  201   b.  By this time, the fluid velocity has slowed significantly. This decrease in velocity creates an accumulation of liquid towards the second end  201   b  of the drip nozzle  200  which creates back forces  207  in the direction of the first end  201   a.  The creation of these back forces  207  serves to further slow down the fluid traveling through the passage  205  of the drip nozzle  200 . Therefore, uniform droplets slowly form at the opening of the nozzle head  200   c  creating a controlled, consistent, and uniform dripping action.  
         [0047]    In this example, the drip nozzle head  200   c  is configured so it is larger in circumference than the outer nozzle wall  200   b.  The nozzle head  200   c  is also preferably controlled at surface  200   c ′ of drip nozzle  200  which further assists in the production of uniform drops. For example, the diameter D 263  contributes to the formation of a uniform droplet by defining an area of attachment of the uniform droplet to the nozzle head  200   c.  The uniform droplet grows in size until its mass causes it to separate from the surface  200   c ′. In addition, an angle θ  265  also contributes to the formation of the uniform droplet by preventing fluid from migrating up the nozzle. It should be appreciated that the drip nozzle may be configured in a variety of shapes and sizes to produce similar drops. Additionally, the drip nozzle  200  can be made without the drip nozzle head  200   c.  The actual shape of the drip nozzle  200  will primarily depend on the viscosity of fluid, drip rate, and the environment into which it is being installed. Also, the drip nozzle  200  is preferably manufactured from a material that is compatible with the chemistry of the fluid such as Teflon™ or polyethylene terephthalate (PET). PET materials are known for their high purity and are relatively easy to machine. In one embodiment, the length L 260  of the drip nozzle  200  can vary between about 0.02 inch and about 1 inch, and more preferably is about 0.437 inch long. This dimension can generally be varied to any length that will allow for one or more spray reflections off of the drip nozzle inner surface  200 ′. This will ensure that a more uniform drip is formed. In this embodiment, passage diameter D 262  of the drip nozzle  200  can be between about 0.02 inch and about 0.1 inch, and more preferably is about 0.062 inch. Of course, this dimension can be varied depending on the viscosity and desired fluid flow. Still further, the sapphire orifice is preferably angled once inserted into the orifice inner surface  200 ″. This angle can vary widely. For example, the angle θ  264  can be between about 15 degrees and about 75 degrees, and more preferably is set to about 45 degrees. In general, some angle must exist so long as one or more spray reflections off of the drip nozzle inner surface  200 ′ are produced.  
         [0048]    [0048]FIG. 3B depicts a cross-sectional view of a drip manifold  220  in accordance with another embodiment of the present invention. In this embodiment, the drip manifold  220  has a manifold inner surface  220   a  and a manifold outer surface  220   b.  The drip nozzle  200  is secured to the drip manifold  220  by threads  200   d.  It should be understood that the drip nozzle  200  may be fastened to the drip manifold  220  in a variety of other ways such as pressing the drip nozzle  200  into the drip manifold  220 . In one embodiment, the drip nozzle  200  is preferably oriented such that the first end  201   a  protrudes into an inner region  203  of the drip manifold  220 . Although any suitable diameter may be used for the inner part of the drip manifold  220 , a diameter ranging between about 0.250 inch and 1.00 inch, and more preferably about 0.375 inch may be used. By having the drip nozzle  200  extend into the inner region  203 , hole shavings  220   c  (created by the drilling of the hole) are less likely to clog the hole defined by the orifice surface  202 ′. The inner region  203  of the drip manifold  220  is preferably a cylindrical shape defined by the manifold inner surface  204   a.  When the cleaning fluid is pumped into the drip manifold  220 , the inner region  203  is filled by a manifold fluid  204 . A portion of the manifold fluid  204  enters the sapphire orifice  202  as orifice input fluid  204 ′. The orifice input fluid  204 ′ then goes through the numerous reflective actions as described above with reference to FIG. 3A, and a uniform drop  204   a  is released from the nozzle head  200   c.  Of course, in a true drip manifold  220 , there will actually be several drip nozzles  200 , as will be illustrated below.  
         [0049]    [0049]FIG. 3C shows an exploded view of the sapphire orifice  202 . In this embodiment, the sapphire orifice  202  includes the orifice inner surface  202 ′ defined generally as a cylindrical shape. At one end of the sapphire orifice  202 , the inner surface  202 ′ angles out to define an angled surface  202 ″. The angled surface  202 ″ is configured to feed into the passage  205  of the drip nozzle  200 . Therefore, in operation, the orifice input fluid  204 ′ enters the sapphire orifice  202  and exits out of one side as defined by the stream boundaries  206   a  and  206   b.  In one embodiment, it is preferable for an outer diameter D 266  of the sapphire orifice  202  to be about 0.087 inch. It should be appreciated that the diameter of the orifice inner surface  202 ′ may be varied to produce different flow rates as need. The dimensions of the orifice inner surface  202 ′ are closely controlled to a desired tolerance so that most all of the sapphire orifice  202  of a specific size are nearly identical. In one preferred embodiment, the orifice inner surface  202 ′ may have a diameter that is about 0.010. The length L 268  of the sapphire orifice  202  in this example is about 0.047 inch. Of course, the length L 268  may be varied depending upon the desired drip characteristics. FIG. 3D shows a view of an alternative orifice  202 ″.  
         [0050]    In this embodiment, alternative orifice  202 ″ is preferably also made out of a sapphire material. The orifice inner surface  202 ′ of the alternative orifice  202 ′ keeps a constant configuration and does not angle out into the passage  205  of the drip nozzle  200 . In one embodiment, the diameter D 266  of the alternative orifice  202 ″ is also about 0.087 inch. It should be appreciated that the diameter of the orifice inner surface  202 ′ may be varied to produce different flow rates as needed. The dimensions of the orifice inner surface  202 ′ are closely controlled to a desired tolerance so that most all of the sapphire orifice  202  of a specific size are nearly identical. In yet another embodiment, it is preferable for length L 268  of the alternative orifice  202 ″ to be about 0.047 inch. The length L 268  of the alternative orifice  202 ″ may be varied depending upon the drip characteristics desired. The orifice input fluid  204 ′ enters the alternative orifice  202 ″ and exits out of the other side as defined by the stream boundaries  206   a  and  206   b.  As mentioned above, the sapphire orifice  202  and the alternative orifice  202 ″ may be made out of other materials that are compatible with different cleaning fluids and that can be defined to exact tolerances and leave a smooth surface after it is formed. The smooth surface thus enables the generation of a more uniform entry point for fluid and gives rise to more controlled droplets from each of the drip nozzles  200  that may be integrated into a drip manifold  220 .  
         [0051]    [0051]FIG. 4 depicts a side view of the drip manifold  220  containing a plurality of the drip nozzles  200  in accordance with one embodiment of the present invention. In this embodiment, a fluid source  258  is connected by a tubing  252  to a pressure regulator  256 . A pressure gauge  254  is then attached to a portion of the tubing  252  connecting the pressure regulator  256  to one end of the drip manifold  220 . A plurality of the drip nozzles  200  are secured to the drip manifold  220  as explained above with reference to FIG. 3B. In one embodiment, the drip manifold  220  is preferably a cylindrical structure manufactured out of a Teflon™ material or any other material that is compatible with cleaning chemicals.  
         [0052]    In this embodiment, the fluid source  258  generally supplies fluid to the pressure regulator  256  where the pressure of the fluid leading to the drip manifold can be controlled. A pressure gauge  254  monitors the fluid pressure in the tubing  252 . By the use of both the pressure regulator  256  and the pressure gauge  254 , the fluid pressure (and the resultant dripping) of the cleaning fluids can be controlled. The fluid then passes from the tubing  252  into the drip manifold  220 . Once inside the drip manifold  220 , the pressurized fluid flows equally into a plurality of the drip nozzles  200 . Because the drip manifold  220  may be filled with pressurized fluid, the flow of fluid into all of the drip nozzles  200  is substantially equal. As described above, after the fluid has passed through the drip nozzles  200 , the uniform drops  204   a  drip from the drip nozzles  200  at a constant and controlled rate. Advantageously, the flow of fluid through the drip manifold  220  may be regulated with only the use of the pressure gauge  254  and the pressure regulator  256  without the need for implementing a a flow meter or additional hardware.  
         [0053]    [0053]FIG. 5 illustrates a cleaning system using the drip manifold  220  containing a plurality of the drip nozzles  200  in accordance with one embodiment of the present invention. The tubing  252  is connected to one end of the drip manifold  220 . In one embodiment, the drip manifold  220  is preferably positioned over the top brush  30   a  so the cleaning fluid can be dripped onto the top brush  30   a.  It is should be appreciated that the drip manifold  220  may be positioned in any orientation which would allow for consistent application of cleaning liquid onto the top brush  30   a  (or any other brush that is positioned below the drip manifold  220 ). The wafer  12  is placed on top of the bottom brush  30   b  and below the top brush  30   a.  The tubing  252  transports fluid into the drip manifold  220 . The fluid passes through the drip nozzles  200  and is released in the form of the uniform drops  204   a.  As the uniform drops  204   a  are applied to the top brush  30   a  at a consistent rate, the brushes  30  can turn thus scrubbing the wafer  12 . Therefore, the drip manifold  220  applies precisely the correct amount of cleaning fluid at the desired rate to the top brush  30   a  which results in optimal cleaning of the wafer  12 .  
         [0054]    While this invention has been described in terms of several preferred embodiments, it will be appreciated that those skilled in the art upon reading the preceding specifications and studying the drawings will realize various alterations, additions, permutations and equivalents thereof. It is therefore intended that the present invention includes all such alterations, additions, permutations, and equivalents as fall within the true spirit and scope of the invention.