Patent Publication Number: US-6988932-B2

Title: Apparatus of sealing wafer backside for full-face processing

Description:
This application is a continuation of U.S. application Ser. No. 09/910,686 filed on Jul. 20, 2001, U.S. Pat. No. 6,855,037, and is related to and claims priority from U.S. Provisional Application No. 60/275,406 filed on Mar. 12, 2001 and entitled Wafer Carrier For Wet Processes, all incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to semiconductor processing technologies and, more particularly, to a versatile wafer carrier. 
     2. Description of the Related Art 
     Conventional semiconductor devices generally include a semiconductor substrate, usually a silicon substrate, and a plurality of sequentially formed dielectric interlayers such as silicon dioxide and conductive paths or interconnects made of conductive materials. The interconnects are usually formed by filling a conductive material in trenches etched into the dielectric interlayers. In an integrated circuit, multiple levels of interconnect networks laterally extend with respect to the substrate surface. The interconnects formed in different layers can be electrically connected using vias or contacts. A conductive material filling process of such features, i.e., via openings, trenches, pads or contacts can be carried out by depositing a conductive material over the substrate including such features. 
     Copper and copper alloys have recently received considerable attention as interconnect materials because of their superior electromigration and low resistivity characteristics. The preferred method of copper deposition is electrodeposition. During fabrication, copper or another conductive material is deposited on a substrate that has been previously coated with a conductor, typically a barrier layer and then a seed layer. Typical seed layers are made of copper and its alloys. Typical barrier materials generally include tungsten, tantalum, titanium, their alloys, and their nitrides. The deposition process can be carried out using a variety of processes. 
     After depositing copper into the features on the semiconductor wafer surface, a removal process, such as an etching, an electro polishing or a chemical mechanical polishing (CMP) step, may be employed. Such removal processes remove the conductive materials off the surface of the wafer, particularly the field regions, thereby leaving the conductive materials primarily disposed within the features, such as vias, trenches and the like. 
     During the deposition process or the removal process the wafer is generally held by a carrier head. As shown in  FIG. 1A , a conventional carrier head  10  having a rotatable shaft  12  holds a wafer  14  during the electrodeposition process. The wafer  14  is placed on a surface  16  of a carrier base  18  (chuck) of the carrier head  10 . During the deposition and/or material removal step, the carrier head  10  secures the wafer  14  to the surface  16  of the base  18  of the carrier head  10  by applying vacuum to the back of the wafer and using clamps  20 . The vacuum is applied using vacuum lines  22  extending through the carrier base  18  and the body of the carrier head  10 . Clamps  20  may also seal electrical contacts  24  to the wafer  14 . In such a conventional carrier head, because of the clamp around the periphery of the wafer, no deposition or material removal occurs at the edge of the wafer. 
     In use, the carrier head is immersed into a solution, typically an electrolyte in a deposition and certain material removal processes, or a slurry in a CMP material removal process, for example. In processes where moveable contact with a pad is desired, such as for polishing, such a pad will be included. During any such process, it is important to prevent leakage of the solution to the backside of the wafer. Such leakages to the backside of the wafer contaminate the wafer backside and the electrical contacts. Removal of contaminants from the wafer backside requires an extra process step that is time consuming and increases manufacturing costs. 
     Another conventional wafer carrier design does not use vacuum suction on the back of the wafer to retain the wafer on the carrier and attempts to reduce contamination of the wafer backside and wafer edge during processing. Referring to  FIG. 1B , with such a wafer carrier  28 , the back surface  30  of the wafer  32  is pressed against an o-ring  34  to form a seal between the back surface  30  of the wafer and the o-ring  34 . Also, a clamp  36  including a seal  38  seals a perimeter of the front surface  40  of the wafer  32  while housing the plurality of contacts  42  to the front surface  40 . In this prior art system, a region  44  behind the seal can be pressurized with gas to further prevent contamination at the wafer backside. In such designs, because of the clamp around the periphery of the wafer, no deposition or material removal occurs at the edge of the wafer. 
     Yet another conventional CMP head is similar to the head shown in  FIG. 1A , but it holds the wafer from the back side by vacuum when positioning the wafer for processing and from the circumference of the wafer by a retaining ring during processing, thereby fully exposing the front surface of the wafer. While the CMP process is done over the front surface of the wafer, the slurry from the CMP process can nevertheless migrate toward the back surface of the wafer. 
     To this end, there is a need for a wafer carrier design that that may be used throughout either one or more process steps and be able to seal back of the wafer from the process solutions. There is also a need for a wafer carrier design that seals back of the wafer from the process solutions while exposing the entire front surface of the wafer for processing without excluding processing at the edge of the wafer. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved wafer carrier. 
     It is another object of the present invention to provide a wafer carrier that prevents processing liquids and contaminants resulting therefrom from reaching a backside inner region of the wafer. 
     It is a further object of the present invention to provide a wafer carrier that prevents processing liquids and contaminants resulting therefrom from reaching an inner region of the base and a backside inner region of the wafer. 
     The present invention attains the above objects, considered singly or in combination, among others, by providing a wafer carrier that includes an opening, which in one embodiment is a plurality of holes, disposed along the periphery of the wafer carrier. A gas emitted through the holes onto a peripheral back edge of the wafer assists in preventing the processing liquids and contaminants resulting therefrom from reaching the inner region of the base and the backside inner region of the wafer. In another embodiment, a plurality of concentric sealing members are used to provide a better seal, and the outer seal is preferably independently movable to allow cleaning of a peripheral backside of the wafer to occur while the wafer is still attached to the wafer carrier. 
     Further, a sealing member, which are alternatively an o-ring, gasket, or inflatable member are used in specific embodiments to assist in preventing the processing liquids and contaminants resulting therefrom from reaching the backside inner region of the wafer. 
     As noted in more detail below, the above-described characteristics of the wafer carrier can be used on different wafer carriers that are used in various processing environments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objectives, features, and advantages of the present invention are further described in the detailed description which follows, with reference to the drawings by way of non-limiting exemplary embodiments of the present invention, wherein like reference numerals represent similar parts of the present invention throughout several views and wherein: 
         FIGS. 1A and 1B  illustrate various conventional carrier heads; 
         FIG. 2  illustrates an exemplary processing system on which carrier heads according to the present invention may be used. 
         FIGS. 3A and 3B  illustrate more detailed views of wafer carriers according to two embodiments of the present invention; 
         FIGS. 4A and 4B  illustrate injected gas and process fluid flow using the wafer carriers according to the two embodiments illustrated in  FIGS. 3A and 3B  of the present invention. 
         FIG. 5  illustrates a gasket member used in the embodiment of the present invention illustrated in  FIGS. 3B and 4B ; 
         FIGS. 6A and 6B  illustrate usage of the gasket member illustrated in  FIG. 5  in more detail; 
         FIGS. 7A and 7B  illustrate another embodiment of a the present invention using an inflatable gasket member; 
         FIGS. 8A–8D  illustrate another embodiment of the present invention using a pair of concentric gasket members; and 
         FIGS. 9A–9C  illustrate another embodiment of the present invention using a pair of concentric gasket members. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE PRESENT INVENTION 
     Reference will now be made to the drawings wherein like numerals refer to like parts throughout.  FIG. 2  shows an exemplary processing system  100 . When used for electrodeposition, the system  100  may, for example, include a cathode assembly  102  and an anode assembly  104  and can then deposit a conductive material such as copper on a workpiece or substrate, such as semiconductor wafer. When used for material removal, the system  100  may, for example, have the polarity of the anode and cathode reversed, or instead use other processing chemicals, such as a CMP slurry. It should be understood that the particular process in which the present invention is used is not of particular importance. What is significant, as illustrated hereinafter, is prevention of contamination of a processing solution from reaching a backside of a wafer. And in certain embodiments, also allowing for full face processing of the wafer to occur. 
     It should also be noted that in the description provided below in which copper is used as an example material that is deposited during a deposition process, other conductors can also be deposited during deposition processing, for example Ni, Pd, Pt, Au, Pb, Sn, Ag and their alloys. 
     The wafer holding assembly  102  of the system  100  includes a wafer carrier  106 , shown in  FIG. 2  holding an exemplary wafer  108 , which can be referred to as the cathode during deposition, the anode during electropolishing, or just the wafer if a process that does not require a current flow/voltage differential to exist. During deposition, for example, a front surface  112  of the wafer  108  is connected to a negative terminal of a power supply (not shown) by electrical contact members  114 . During electropolishing, for example, the front surface  112  of the wafer  108  is connected to a positive terminal of a power supply (not shown) by electrical contact members  114 . 
     As will be described more fully below, the wafer carrier  106  holds the wafer  108  from a back surface  113  of the wafer  108  using vacuum suction. In this embodiment, the wafer  108  is held by the wafer carrier  106  so that a front surface  112  of the wafer  108  is fully exposed. During the process, the wafer carrier  106  and hence the wafer  108  are moved by rotating a carrier shaft  110  about a rotation axis  115  or vertical axis and/or by laterally translating the carrier shaft  110 . 
     The electrode assembly  104  of the system  100  will typically have a different type of electrode  116 , depending upon whether assembly  104  is being used for deposition or electropolishing. When used for deposition, the electrode  116  is an anode, preferably a consumable copper anode, and when used for electropolishing, the electrode  116  is a cathode, and is preferably not consumable. The electrode  116  may preferably be placed into an enclosure such as an electrode cup  118 . The electrode  116  may have holes that allow the electrolyte to flow therethrough (not shown). The electrode cup  118  may have bleeding openings (not shown) to control the amount of the flow of solution, such as electrolyte when used for deposition and certain electropolishing techniques, or slurry if CMP is being used, for example. During processing, the solution  120  is pumped into the electrode cup  118  through a liquid inlet  130  to reach and wet the front surface  112  of the wafer  108 . The solution  120  flows in the direction of arrows and wets the front surface  112  of the wafer  108 . 
     During deposition or certain electropolishing processes, typically the solution  120  is an electrolyte that is used to deposit material on the front surface  112  of the wafer  108  under applied appropriate potential or remove material from the front surface  112  of the wafer  108  under applied appropriate potential. During CMP, such potential may or may not be applied. With all processes, however, the wafer front surface  112  is preferably rotated, as is known. 
     In the system  100 , electrical contact members  114  contact wafer  108  on a contact region  126 , as shown in  FIG. 2 . The contact region  126  is a peripheral ring region on the front surface of the wafer that has a portion thereof that is always exposed over the edge of the electrode cup  118  as the wafer is rotated. 
       FIGS. 3A and 3B  each illustrate a side view with a cut-away of the wafer carrier  106  of embodiments of the present invention in further detail. As will become apparent, the difference between the embodiments illustrated in  FIGS. 3A and 3B  is the type of sealing member  154  that is used. The wafer carrier  106  comprises a carrier body  140  having a lower and upper end  142  and  144 . The lower end  142  of the carrier  106  comprises a carrier base  146 , chuck, upon which the wafer  108  is held. The carrier base may be made of variety of materials, such as plastic, steel or titanium. And, as shown the carrier ring  147  can have a surface portion that extends below the surface of the wafer that contacts the support pad  166  described further below to prevent lateral movement of the wafer  108  beyond the surface portion that extends below the backside surface of the wafer  108 . The carrier base  146  is preferably surrounded by a carrier ring  147 . The carrier ring may be constructed separately or may be an integral part of the carrier base. The carrier ring may be made of plastic or any material that is stable in the process solutions. The wafer carrier  106  is rotated or moved through the shaft  110 . In this embodiment, a bottom surface  148  of the carrier base  146 , preferably disk shaped, includes a first surface portion  150  and a second surface portion  152 . The first surface portion  150  is a peripheral surface surrounding the second surface portion  152  that is an inner region. The first and second surface portions  150 ,  152  of the bottom surface  148  are established by a sealing member  154  of the present invention, described hereinafter. 
     The sealing member  154  is placed into a circular groove  156  formed in the bottom surface  148  and between the first and second surfaces  150 ,  152  defines an inner region of the base  146 , and, when the sealing member  154  contacts the back side of the wafer  108 , establishes a backside inner region of the wafer  108 . Fluid lines  158  connect a fluid supply to a plurality of outlet ports  159  on the first surface portion  150  of the bottom surface  148 , as described further hereinafter. The outlet ports  159  are radially distributed around the first surface  150 , such that the outlet ports are formed concentrically around the sealing member  154 . Although it may be directly connected to the first surface portion  150 , a lower end  160  of the fluid lines  158  may run between the carrier base  146  and the carrier ring  147 . In these embodiments, the fluid lines  158  are used to blow a gas, preferably a non-oxidizing gas, onto a peripheral back edge  162  of the back surface  113  of the wafer  108 . The non-oxidizing gas may preferably be nitrogen gas. Holes may have any number and varied diameters, but preferably a diameter in the range of 0.5–1 mm found most preferable. In the preferred embodiment, at 16–64 holes are disposed around the edge of the wafer carrier, for wafer sizes of between 200 and 300 mm. Of course, the number of such holes can vary, and, instead of holes, a continuous slit or slits, or another shaped opening can be used instead. The gas flow rate can vary, with a flow rate preferably between 10–60 liters per minute. As will be described more fully below, the gas emitted from ports  159  continuously sweeps the peripheral back edge  162  and provides another seal that assists in preventing liquid, such as electrolyte, from reaching behind the wafer  108  and causing unwanted contamination. 
     The wafer  108  is retained by the carrier base  146  by the application of vacuum suction. For this purpose, a number of vacuum lines  164  are connected to the second surface  152  of the carrier base  146 . In order to support the back surface of the wafer, a support pad  166  or a backing pad is preferably, but not necessarily, attached on the second surface portion  152  to maintain the wafer in a substantially flat state while under the applied vacuum suction. When a support pad  166  is used, the vacuum lines  164  continue through holes in the support pad  166 . Although in this embodiment the wafer is held by vacuum applied through the lines  164 , the wafer may be held using a suction cup. In order for the seal to be created, the sealing member  154  must extend past the support pad  166 , typically by an amount that is in the range of 50–100 microns, so that the seal can be properly formed. As described hereinafter, the sealing member  154  will be relatively much softer than the support pad  166 . 
     The other components, such as mechanical components of the wafer carrier  106  may be conventionally constructed and well known in the art. The carrier head  106  may be provided with some form of gimbal mechanism and cooperating mechanical components. Such conventional components need not be further described. 
     In use, the wafer  108  is placed on the carrier base  146  as shown in  FIGS. 3A and 3B , using a wafer handling system (not shown). The wafer  108  is aligned with the sealing member  154  and under the applied vacuum, the sealing member  154  seals the space confined between the second surface portion  152  and the back  113  of the wafer, thereby retaining the wafer  108  on the wafer carrier  106  and fully exposing the front surface  112  of the wafer  108 . In the preferred embodiment, vacuum levels in the range of 400–650 Torr were employed. 
     Once the wafer  108  is held by the carrier  106 , gas is blown through the ports  159  onto the peripheral back edge  162  as the wafer is processed during deposition, in an amount as described above. 
     As shown in  FIGS. 4A and 4B , during the above exemplified deposition process, the gas flow from the ports  159 , in the direction of the arrow  168 , sweeps away the electrolyte  120  flowing in the direction of the arrow  170  (delivered to the frontside of the wafer  108  through pad  200  that contains channels  202  therein) and assists in preventing the electrolyte solution from reaching the peripheral back edge  162  of the wafer  108 . In cooperation with the sealing member  154 , the wafer carrier of the present invention advantageously prevents the electrolyte from reaching the back surface  113  of the wafer  108  while rotating the wafer  108  relative to the pad  200  and fully exposing the front surface  112  of the wafer to the processing solutions. 
     During a subsequent cleaning step, however, the gas can be turned off so that it does not blow through the ports  159 , thereby allowing for access to the backside of the wafer  108  to a liquid cleaning solution, a gas fluid such as air, or both. 
     In accordance with the principles of the present invention, the sealing member  154  is designed such that the sealing function is efficiently achieved with the application of minimum vacuum suction. 
     The sealing member  154 A illustrated in  FIGS. 3A and 4A  is an o-ring made of an insulating material. The o-ring  154 A may or may not be hollow inside, but as shown in  FIG. 4A , it will tend to retain its shape under pressure. It has been found that preferably the o-ring  154 A is hollow, having a diameter of 1–4 mm, and a thickness of between 0.5 and 1.5 mm. Put in other terms, there is softness to the hollow o-ring, such that it has a durometer rating of less than 70, and preferably within the range of 30–50 durometers, in contrast to typical o-rings that are much harder, and have a higher durometer rating, and support pads  166  that will have a durometer rating (which is a hardness rating) that typically are at least 5 times greater than that of the hollow o-ring. This softness advantageously allows for the desired seal to occur, without the detrimental side effect of causing bowing on the wafer due to the pressure of a hard seal exerting too much pressure onto the backside of the wafer. The o-ring  154 A, particularly when hollow, is preferably made of an ethylene propylene material. 
     The gasket  154 B illustrated in  FIGS. 3B and 4B  is an alternative to the o-ring  154 A. As shown in  FIG. 5  in partial perspective view, the gasket  154 B has a circular body  300  having a bulb shape cross section. The body  300  has a first portion  302  or an attachment portion and a second portion  304  or a sealing portion. The sealing portion  304  may preferably be slanted outwardly to offer more sealing surface when the vacuum is applied, which will be described more fully below. 
       FIG. 6A  shows the gasket  154 B in cross section and with no compressive force applied upon it or no wafer held on it. Referring to  FIG. 6A , the gasket  154 B is placed on the wafer carrier by inserting the attachment portion  302  into the circular groove  156 . The sealing portion  304  of the gasket  154 B defines a sealing surface  306  which is a slanted surface generally facing the back surface  113  of the wafer  108 . The sealing portion  304  is a compression distance, denoted with ‘h’, higher than the top of the support pad  166 . The compression distance may be in the range of 0.1 mm to 0.3 mm, preferably 0.2 mm. In sealing stage, the compression distance ‘h’ is reduced to zero, allowing full usage of the sealing surface  306 . 
       FIG. 6B  shows the gasket  154 B when sealing the back surface  113  of the wafer  108 . As illustrated in  FIG. 6B , as vacuum suction is applied to the back surface  113  of the wafer  108 , the wafer  108  presses against the sealing surface  306  and causes the sealing portion  304  to collapse thereby achieving sealing function. The gasket  154 B achieves sealing function with ease, i.e., by the collapse of the sealing portion  306  and with providing larger sealing surface. 
     In this embodiment, the gasket  154 B can be made of an elastic material such as elastomer. One such material is commercially available under the brand name KalreZ™, which can be available from DuPont. It is understood, however, that although in the preferred embodiment the gasket member of the present invention is described above, the gasket member may be made of any compressible material, membrane, or tube, or the like, as long as it performs the above given sealing functions, and is within the scope of the present invention. 
     As shown in  FIG. 7A , in an alternative embodiment, a gasket member  154 C may be an inflatable membrane.  FIG. 7A  shows the inflatable membrane in deflated stage. The inflatable membrane  154 C is attached to and seals the perimeter edge of opening  402  of the circular grove  156 . In this embodiment the circular groove is connected to a fluid line  404  through at least one inlet port  406  so that a fluid such as air can be used to inflate the inflatable membrane  154 C. The fluid line  404  is further connected to a fluid supply system (not shown) such that the fluid pressure can be controlled. 
       FIG. 7B  shows the inflatable member  154 C in inflated stage and when sealing the back surface  113  of the wafer  108 . As vacuum suction is applied, the wafer  108  presses against the inflatable membrane thereby achieving sealing function. By controlling the fluid pressure, the force applied by the member  154 C to the back of the wafer  108  may be optimized. This, in turn, provides efficient sealing without causing the above explained prior art wafer sinking problem. The inflatable member  154 C may be made of any rubber or elastomer material. 
     It is also noted that it is within the scope of the present invention, as described above with reference to  FIGS. 3A–7B  to use any of the sealing members  154  as described injecting gas through the ports  159 . 
       FIGS. 8A–8D  illustrate another embodiment of the present invention using a pair of concentric sealing members. In this embodiment, as illustrated, a carrier head  500  comprises a carrier body  502  and a carrier base  504  where a wafer or other workpiece  505  is held. The carrier head  500  is rotated or moved through the shaft  508 . The carrier base  504  comprises a bottom surface  506  that is preferably a surface that conforms to the shape of the workpiece, typically circular for a wafer. A first sealing member  508  and a second sealing member  509  are concentrically placed adjacent outer circumference  510  of the bottom surface  506 . 
     The first sealing member  508  is preferably an inflatable gasket membrane having a circular strip shape. The membrane  508  is attached to the bottom surface  506  of the carrier base  504  from its inner and outer circumferential edges  512  and  514 , respectively, such that an inner pocket  516  of the membrane  508  is formed. The inner pocket  516  of the membrane  508  is connected to a fluid source (not shown), such as a gas source, through fluid lines  518 . As will be described below, the fluid from the fluid lines  518  is used to inflate the inflatable membrane  508  during the process. The second sealing member  509  is preferably made such as one of the sealing members  154  described above. In a particularly preferred embodiment, the second sealing member is made as the hollow o-ring  154 A as described in  FIGS. 3A and 4A . The second sealing member  509  is preferably placed in a circular groove  520 . A support member  522  may be concentrically placed within the circular area formed by the o-ring  509 . A number of vacuum lines  524  are formed through the carrier base  504  and through the support member  522  so that when the wafer  505  is placed on the support member  522 , vacuum suction can be created on back side  526  of the wafer  505 , which is sealed by the second sealing member  509 . 
     As shown in  FIGS. 8A–8D , in operation, described in the preferred embodiment of the first sealing member  508  being an inflatable member and the second sealing member  509  being an o-ring, the back side  526  of the wafer  505  is placed on the o-ring  509  and vacuum suction is applied to hold the wafer  505  on the carrier  500 . It is understood that in this embodiment, front surface  528  of the wafer  505  is fully exposed. As shown in  FIG. 8C , next the inflatable membrane  508  is inflated by supplying gas into the inner pocket  516 . In inflated state the inflatable membrane  509  effectively seals edge region  530  of the wafer  505 . In this respect, the combination of both the inflatable membrane  508  and the o-ring  509  form a double seal along the circumference/edge of the wafer  505 . Such combination advantageously prevents leakage of the process solutions, such as electrolyte, through both the inflatable member  508 , and the o-ring  509  and prevents contamination of the backside  526  of the wafer as well as of the support member  522 . And, even if there is some leakage within the inflatable member  508  of the process solution into the edge region  530  that exists between the inflatable member  508  and the o-ring  509 , this edge region  530  can be easily cleaned, such as during a cleaning step after a plating step, as explained hereinafter. 
     As shown in  FIG. 8D , it becomes apparent why the first sealing member  508  is preferably an inflatable member. After a plating step, in which both the first sealing member  508 , and the second sealing member  509  are providing a seal, is completed, the first sealing member  508 , when an inflatable member, can be deflated, as shown. This exposes a potentially contaminated edge region  530  while the wafer is still being held by the carrier  500  and the vacuum suction is still being applied to the area sealed by the o-ring  509 . Thus, in this configuration, cleaning of the edge region  530  can occur by applying a cleaning fluid or fluids (such as either a liquid cleaning fluid, or both a liquid cleaning fluid and thereafter a gas such as air for drying) in the direction of arrow into the edge region  530  from a cleaning system (not shown) into the area that had previously been protected to the inflated inflatable member  508 . During the cleaning and a subsequent drying step the carrier  500  may also be spun. Although in this embodiment the first sealing member  508  is preferably an inflatable membrane, for the reasons described above, other alternative seals, for example an o-ring, can also be used. 
       FIGS. 9A–9C  illustrate another embodiment of the present invention using a pair of concentric gasket members. This embodiment is similar to the  FIG. 8  embodiment, as shown in the overview of  FIG. 9A , in using a first seal member  908  and a concentric second seal member  909  to provide a seal for the backside of the wafer  905  within the interior region formed by the second seal member  909 , which interior region includes a support member  922 . As in the previous embodiments the backside of the wafer  905  is preferably held on the second sealing member  909  and the support member  922  through the usage of a vacuum that is applied through vacuum lines  924 . In contrast to the  FIG. 8  embodiment, however, instead of having an inflatable first sealing member, the first sealing member  908  is preferably an o-ring, which may or may not be hollow inside, but preferably has a softness that is softer than that of the second sealing member  909 . The seal with the first sealing member  908  is also formed by having a vertically moveable annular housing  904  on the outside of the carrier head  900 . The vertical movability can be achieved in a variety of manners, including a motorized sprocket along the inner radius of the annular housing  904 , other mechanical mechanisms, or otherwise. 
       FIG. 9B  illustrates in more detail the sealed position, in which both the first seal member  908  and the second seal member  909  provide the sealing function. In this sealed position, the vertically moveable annular housing  904  is moved downward, to establish the seal between the first sealing member  908  and the wafer  905 . The wafer is processed in the chemical environment when both sealing members  908  and  909  seal the wafer  905 . It is noted that there is no carrier ring with a surface portion that extends below the backside surface of the wafer  906 , as is shown in  FIG. 3A , to assist in preventing lateral movement of the wafer  905 , and thus, the vacuum applied through vacuum lines  924  is solely used to prevent lateral movement of the wafer  905  relative to the carrier head  900 . In the unsealed position, which allows a cleaning fluid, or gas, to be injected into the backside of the wafer outside of the second sealing member  909 , as shown by the arrows in  FIG. 9C , the vertically moveable annular housing is moved upward, thereby disengaging the first sealing member  908  and providing a gap through which the cleaning fluid or gas can be injected to the peripheral backside of the wafer  905 , outside of the second sealing member  909 . 
     With respect to the various sealing members described herein, it is further noted that each is preferably coated with a material that allows for chemical compatibility with the process being performed, such as Teflon® for chemical compatibility with plating that uses an electrolyte as well as cleaning with conventional cleaning solutions. 
     Although various preferred embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications of the exemplary embodiment are possible without materially departing from the novel teachings and advantages of this invention. For example, although an o-ring, gasket, and inflatable member are described to provide the vacuum seal, any material or device that may provide this sealing may replace o-ring and be within the scope of this invention. It will thus be appreciated that in some instances some features of the invention will be employed without a corresponding use of other features without departing from the spirit and scope of the invention as set forth in the appended claims.