CN1341276A - Method and apparatus for cleaning semiconductor wafer - Google Patents

Abstract

A method for improving chemical cleaning efficiency by utilizing a gaseous chemical cleaning fluid in combination with a post chemical mechanical planarization cleaning process. Another advantage is that the amount of chemical solution used is also reduced accordingly. In accordance with an embodiment of the present invention, the vapor generator introduces vapors of a chemical solution (e.g., hydrofluoric acid) into the sealed brush station during various cleaning steps and for various time periods. These vapors interact with impurities or defects on the wafer surface. Since these defects provide preferential sites or denser vapors for chemical reactions, these vapors preferentially react with defects or impurities, thus increasing the efficiency of the chemical cleaning. Since the cleaning process is performed in a sealed scrubbing station, it is possible to save a certain amount of the chemicals used. In another embodiment, deionized water may be introduced along with the chemical vapors if it is desired to keep the wafer surface wet. The use of gaseous chemicals provides advantages from the flow control point of view, since control of the chemical reactions on the wafer surface can be easily achieved.

Description

Method and apparatus for cleaning semiconductor wafers

field of invention

The present invention relates to methods and apparatus for cleaning semiconductor wafers during semiconductor manufacturing. More specifically, the present invention relates to a post-CMP (Chemical Mechanical Planarization) wafer cleaning method and apparatus using vapor cleaning.

Background of the invention

Much of the functionality and utility of today's digital integrated circuits can be attributed to increased levels of integration. More and more components (such as resistors, diodes, transistors, etc.) are continuously integrated in the basic chip, ie, the integrated circuit. Typical integrated circuits are based on very high-purity silicon. This material is grown as a solid cylindrical single crystal of silicon. This crystal (like a loaf of bread) is divided into wafers with a diameter of 10-30 cm and a thickness of 250 μm.

The geometry of the details of integrated circuit components is usually determined photographically by a process known as photolithography. With this technique, very fine surface geometries can be reproduced precisely. This photolithographic method is used to define areas of components and form components one layer on top of another. Complex integrated circuits often have many different built-up layers, each layer has components, each layer has different interconnects, and each layer is stacked on top of the previous layer. Since the components of integrated circuits are manufactured on the base surface of silicon wafers, the surface of each layer of these complex integrated circuits is as uneven as the familiar land mountains with many "mountains" and "valleys".

During photolithography, ultraviolet light is used to focus a mask image or pattern of various elements onto a photosensitive layer. These images are passed through a photolithography tool, focused optically and printed on the photosensitive layer. If smaller components are to be made, a finer image must be focused on the surface of the photosensitive layer, for example, the optical resolution must be increased. As the optical resolution increases, the depth of focus of the mask image is correspondingly narrowed. This is because the large numerical aperture lenses used in lithography tools narrow the range of depth of focus. The narrowing of the depth of focus is often the limiting factor in achieving high resolution and the smallest features achievable with lithographic tools. The uneven surface of complex integrated circuits, the "hills" and "valleys", amplifies the effect of narrowing the depth of focus. Thus, a precisely planar surface is required in order to focus the mask image defining the submicron geometry on the photosensitive layer. Such a precisely flat surface (eg fully planarized) allows a very small depth of focus, which in turn allows the definition and subsequent fabrication of very small components.

Chemical-mechanical planarization (CMP) is the best way to achieve full planarization of wafers. It utilizes the mechanical contact between the wafer and the moving polishing disc, with the help of the chemical action of the polishing paste to remove the protective layer of insulating material or metal. Polishing eliminates height differences because the raised parts of the surface (protrusions) are more easily ground off than the lower parts (depressions). Chemical-mechanical planarization (CMP) is the only technology capable of polishing topography over millimeter-scale planarization distances, producing maximum angles far less than 1° after polishing.

FIG. 1 shows a top view of a typical prior art CMP machine 100; Put the wafer to be polished into the CMP machine. The CMP machine 100 picks up wafers with an arm 101 and places them on a rotating polishing plate 102 . The polishing disk 102 is made of elastic material, and its typical common structure has many pre-made grooves 103 for assisting the polishing process. The polishing disc 102 is rotated at a predetermined speed on a table 104 located below the polishing disc 102 , that is, a turntable. Wafer 105 is held in place on polishing plate 102 and arm 101 by carrier ring 112 and carrier 106 . The lower surface (eg, the “front” side) of the wafer 105 rests on the polishing pad 102 . The upper surface of the wafer 105 rests against the lower surface of the carrier 106 of the arm 101 . As the polishing disc rotates, the arm 101 rotates the wafer 105 at a predetermined speed. Arm 101 presses wafer 105 onto polishing pad 102 with a predetermined amount of downwardly directed force. The CMP machine 100 also includes a paste dispensing arm 107 extending a length the radius of the polishing disk 102 that distributes the flow of paste over the polishing disk 102 .

The paste is a mixture of deionized water and a polishing agent to chemically assist in smoothing and predictable planarization of the wafer. The rotation of the polishing disc 102 and the wafer 105, in combination with the polishing action of the paste, planarizes, ie polishes, the wafer 105 at a nominal rate. This rate is called the removal rate. A constant and predictable removal rate has a significant impact on the consistency of the wafer fabrication process and the performance of the wafer. With an appropriate removal rate, precisely planarized wafers without surface asperities can be produced. If the removal rate is too slow, the yield of planarized wafers within a certain period of time will be reduced, reducing throughput. If the removal rate is too fast, the CMP planarization process will be inconsistent across the wafer surface and the quality of the production process will be difficult to assure.

In order to maintain a constant removal rate, the CMP machine 100 has a regulating device 120 . The adjustment device 120 includes an adjustment arm 108 that extends the radius of the polishing disc 102 . An end effector 109 is connected to the adjustment arm 108 . The end effector 109 includes a lapping conditioner disc 110 which is used to roughen the surface of the polishing disc 102 . The grinding adjusting disc 110 rotates under the effect of the rotating adjusting arm 108, and translates to the center of the polishing disc 102, and then translates outward from the center of the polishing disc 102, so that the adjusting disc 110 covers the radius of the polishing disc 102, so that The surface of the polishing disc 102 is almost completely covered during rotation. Under the action of the adjusting device 120, a large number of tiny pits and circular grooves are added on the rough surface of the polishing disc, thereby increasing the transfer of the paste to the crystal surface and due to the more effective downward polishing pressure , resulting in a faster removal rate. If there is no grinding adjustment disc, the surface of the polishing disc 102 will be ground flat during the polishing process, and the removal rate will be significantly reduced. Conditioning device 120 roughens the surface of polishing disc 102 again, which facilitates slurry delivery and increases removal rate.

The combination of the rough surface action of the polishing pad 102, the chemical softening action of the paste, and the abrasive action of the paste polishes the wafer surface to nearly completely smooth the wafer topography over millimeter planarization distances. Once the CMP process is complete, the wafer 105 is removed from the polishing pad 102 by the arm 101, ready for the next step in the integrated circuit fabrication process. However, before the next process starts, impurities remaining on the surface of the wafer 105 during the CMP process (such as particles on the polishing disc 102, trace residues of paste/grinding disc, metal ions, etc.) must be cleaned.

After the CMP process is complete, the surface of the wafer 105 must be cleaned to remove particles, metal ions and other impurities. Those skilled in the art know that before the wafer 105 enters the next manufacturing process, the impurities remaining on the wafer during the CMP process must be removed. For example: the presence of impurity particles may damage the next step of the photolithography process, which can lead to situations such as disconnection and short circuit. The most widely used post-CMP cleaning technique today involves scrubbing the wafer surface with deionized water or wet chemicals.

In practice, scrubbing uses a solution containing chemicals and a brush made of polymeric material. FIG. 3 shows a bristle brush 300 used on a semiconductor wafer 310 . As shown, the bristle brush 300 rotates in the direction of arrow 301 . As the bristle brush 300 rotates, the wafer 310 frictionally rotates (eg, spins) under the bristle brush 300 such that the bristle brush 300 makes frictional contact with the entire surface of the wafer 310 .

An advantage of the bristle brush 300 is that as the bristle brush 300 abrasively sweeps across the surface of the wafer 310, it efficiently removes all impurities that come into direct contact with it. The bristle brush 300 may be a porous brush filled with a specially tailored cleaning fluid. As shown in FIG. 3 , the cleaning liquid flows into the scrubbing station 305 from the inlet 320 . The cleaning solution is specially prepared according to the materials that make up the surface of the wafer 310 (such as metal lines covered with oxide, tungsten in oxide via plugs, copper, etc.). These chemicals contained in the cleaning solution chemically react with impurities on the wafer surface. This cleaning solution reacts with the impurities to form a reaction product. This reaction product is washed off the wafer surface by the wiping force of the bristle brush 300 and the flow of the cleaning solution.

Cleaning solutions used to remove reaction products and debris cannot be reused or recycled because they contain impurities and reaction products. Therefore, conventional post-CMP cleaning methods require a large amount of cleaning fluid. Chemical cleaning fluids contain toxic substances and may contaminate the environment even with proper disposal. The use of large quantities of chemical solutions also increases the production cost of integrated circuit devices. Also, removing debris remaining on the wafer surface requires considerable pressure on the bristle brush. This increases the risk of damage to the wafer surface. Therefore, we need a post-CMP cleaning method that requires less chemical solution and does not increase the risk of damaging the crystal surface.

In addition, integrated circuit devices have entered the submicron era. It is increasingly important to ensure that the wafer surface is free of impurities. Although the existing bristle brush method can effectively remove surface impurities, it may not remove impurities embedded in the crystal surface. Moreover, the existing hard brush technology cannot effectively remove the impurities attached to the back of the wafer. Accordingly, there is also a need for a method and system that more effectively removes CMP impurities and by-products from the wafer surface following completion of the CMP process.

Overview of the invention

The present invention provides a method utilizing gaseous chemical cleaning fluids in combination with post-CMP to enhance the cleaning efficiency of these chemicals. The amount of chemical solutions is also reduced. According to an embodiment of the present invention, the steam generator sends the steam of the chemical cleaning liquid (such as hydrofluoric acid) into the sealed scrubbing station during various cleaning steps and different time periods. The vapor reacts with impurities or defects on the crystal surface. Since the defects of the semiconductor wafer provide preferential sites for chemical reaction and condensation of the vapor, the vapor preferentially chemically reacts with these defects and impurities. Therefore, cleaning efficiency is improved. Since the cleaning process takes place in a sealed scrub station, it is possible to save a certain amount of chemicals in use.

The next step in one embodiment of the present invention is to place a chemical mechanical planarized semiconductor wafer with an oxide surface into a sealed scrub station. Hydrofluoric acid (HF) vapor is then sent into a sealed scrub station. Hydrofluoric acid HF vapor etches away the thin oxide layer (<50 Angstroms) containing embedded impurities on the wafer surface. This vapor also contacts the backside of the wafer, removing impurities from the backside of the wafer without having to dispense chemicals directly on the backside of the wafer. After a certain time limit, the steam generator is switched off. A quantity of solution or deionized water is delivered to the wafer surface via a bristle brush to remove impurities or their reaction products with the vapor. The flow of the solution will also help prevent loading of the bristle brush. In one embodiment, the timing of turning on and off the steam can be varied according to specific treatment requirements.

In an alternate embodiment, if desired to keep the wafer surface wet, vapors of the chemical cleaning solution may be delivered along with the deionized water. Using gaseous chemicals also has advantages in terms of flow control, since the chemical reactions on the wafer surface can be easily and precisely controlled during post-CMP cleaning.

Brief description of the drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description explain the principles of the invention.

Prior Art Figure 1 shows a top view of a conventional CMP machine.

Prior Art FIG. 2 shows a side view of the conventional CMP machine shown in FIG. 1 .

PRIOR ART Figure 3 shows a side view of a conventional scrubbing station.

Figure 4 shows a wafer being cleaned according to the post-CMP cleaning method of the present invention.

FIG. 5 is a flowchart illustrating various steps of a post-CMP cleaning method according to an embodiment of the present invention.

Introduction to Best Practices

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method and system for post-CMP wafer cleaning as preferred embodiments of the present invention will now be described in detail, examples of which are illustrated in the accompanying drawings. Although the present invention has been described using preferred embodiments, it does not mean that the present invention is limited to these preferred embodiments. On the contrary, the invention includes all changes, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the invention, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one of ordinary skill in the art that the present invention may be practiced without these specific details. Additionally, well-known methods, procedures, components, and circuits have not been described in detail since they would unnecessarily obscure aspects of the present invention.

The present invention provides a semiconductor wafer cleaning method and system based on a combination of etching and scrubbing for effectively removing CMP impurities and by-products from the wafer surface after completion of the CMP process. The invention is used in efficient post-CMP cleaning without increasing the risk of damage to the wafer surface. Chemical vapors are used to remove thin layers of the wafer surface, thereby removing hard-to-remove impurities, greatly reducing the amount of scrubbing required. Thereby, the amount of chemical solutions required and the cost of the CMP treatment itself can be reduced.

Chemical-mechanical planarization (CMP) is the best way to obtain fully planarized semiconductor crystals with fabrication equipment. The CMP process involves the removal of one or more layers of material (such as insulating material, aluminum, tungsten or copper layers, etc.) using abrasive contact between the wafer and a moving polishing pad filled with a polishing compound and the chemical reaction of the paste itself. Polishing during the CMP process eliminates the difference in height of the crystal surface because the raised portions (protrusions) of the crystal surface are ground down faster than the lower portions (depressions) of the crystal surface. CMP technology is the best method capable of smoothing the profile over a range of millimeter planarization distances, producing a maximum tilt angle of much less than 1° after polishing.

A large amount of impurities and polishing products are generated by the frictional contact with the surface of the polishing disc of the CMP machine, the chemical softening action of the paste, and the abrasive action of the paste when polishing the semiconductor wafer. These impurities/polishing products (eg, particles of the polishing disc 102, traces of paste/grinding residue, metal ions, etc.) are distributed over the entire wafer surface during the CMP process. Some impurities may even become embedded in the wafer surface. After the CMP process is over, the wafer is taken out of the CMP machine and ready to enter the next process of the chip manufacturing process. But before the next process, the remaining impurities/products in the CMP process on the wafer must be cleaned off. It is very important to clean the residues of the CMP process before the wafer goes to the next process. For example, the existence of impurity particles may damage the next photolithography process, resulting in situations such as disconnection and short circuit.

When the bristle brush moves on the surface of the wafer 310, FIG. 3 shows that the traditional scrubbing method can effectively remove those impurities that the bristle brush directly contacts. This is the advantage of traditional scrubbing methods. However, these conventional scrubbing methods have a disadvantage in that the spent cleaning solution cannot be reused or recovered due to impurities and chemical reaction products contained in it. Also, removal of impurities trapped in the wafer surface requires considerable pressure on the bristle brush. This may increase the risk of damage to the wafer surface.

The present invention provides a system for post-CMP scrubbing and an improved post-CMP scrubbing method: post-CMP scrubbing with a gaseous cleaning fluid. FIG. 4 illustrates a scrub station 400 for cleaning a semiconductor wafer 405 after chemical mechanical planarization, according to an embodiment of the present invention. As shown, a wafer 405 is placed in a sealed chamber 440 of a scrubbing station 400, where a bristle brush 430 and a cleaning fluid inlet 410 are located. As the bristle brush 430 rotates, the wafer 405 also spins abrasively under the bristle brush 430 so that the scrubbing operation removes impurities on the front surface 450 a of the wafer 405 . The cleaning liquid flows in from the liquid inlet 410, and the cleaning liquid can be specially prepared according to the different materials constituting the surface of the wafer 405 (such as metal lines covered with oxide film, tungsten and copper in oxide channel pins, etc.).

Obviously, as shown in FIG. 4 , the scrubbing station 400 includes a steam inlet 420 installed in the sealed cavity 440 , through which vaporized cleaning fluid can be introduced at different stages of the scrubbing process and for different periods of time. In this embodiment, the gaseous cleaning liquid is also specially prepared according to the different materials constituting the surface of the wafer 405 . The advantage of using a gaseous cleaning solution (such as gaseous hydrofluoric acid) is: the etching action of the gaseous cleaning solution can remove a very thin layer of deposition on the front surface 450a and the rear surface 450b of the wafer 405 and the impurities attached to it to form Easily removable or gaseous reaction products.

According to this embodiment, the gaseous cleaning fluid interacts with impurities or defects found on wafer surfaces 450a and 450b. The gaseous cleaning fluid preferentially interacts with these defects or impurities because these defects provide preferential sites for chemical reactions or a greater density of vapor. The chemical cleaning efficiency is thus increased. When combined with the scrubbing action of the bristle brush 430, the use of a gaseous cleaning fluid can significantly reduce the amount of scrubbing required. The reduced amount of scrubbing correspondingly reduces the risk of damaging the front surface 450a of the wafer 405 . In addition, the amount of cleaning fluid used will be reduced. In this way, post-CMP cleaning time and cleaning costs will be significantly reduced. It should be pointed out that the chemical composition of the gas cleaning liquid and the cleaning liquid in this embodiment may be different.

Another advantage of the present invention is that the gaseous cleaning solution can easily contact the lower surface 450b of the wafer 405, so that the impurities on the surface can be easily removed without directly adding chemicals to the lower surface 450b. The use of a gaseous cleaning fluid also has advantages in terms of flow control, since the precise control of the chemical reactions on the wafer surfaces 450a and 450b can be easily controlled using gases.

5 is a flowchart of a post-CMP cleaning process according to an embodiment of the present invention. For purposes of illustration, the steps represented by process 500 include the operation of a post-oxide CMP cleaning system using a scrub station, such as scrub station 400 shown in FIG. 4 . However, it does not mean that the present invention is only applicable to post-oxide CMP cleaning processes. Rather, it is evident to those skilled in the art that different compound vapors can be similarly introduced for different post-CMP cleaning processes or for different surface cleaning applications.

Process 500 begins with step 510 of receiving a wafer that has been processed by a CMP machine and is ready for cleaning. As mentioned above, chemical mechanical planarization involves the use of a paste and abrasive contact with a polishing disk. The CMP process generates large amounts of impurities that must be removed from the wafer surface.

In step 515, the wafer is placed in a sealed chamber of a scrubbing station (eg, scrubbing station 400) in a post-CMP wafer cleaning system according to the present invention. The scrubbing station preferably includes a bristle brush (eg, bristle brush 300), a cleaning fluid inlet (eg, inlet 410) for the cleaning fluid to flow in, and a steam inlet (eg, inlet 420) for the gaseous cleaning fluid to flow into.

In step 520, according to the present embodiment, a gaseous cleaning fluid containing hydrofluoric acid (HF) is introduced into the sealed chamber of the scrub station. In this embodiment, the amount of vapor introduced and the time the wafer is in contact with the vapor are controlled by the vapor generator. The reason why the gaseous cleaning solution containing HF is selected in this embodiment is that the gaseous HF can etch away the oxide film (with a thickness not greater than 50 angstroms) on the surface of the wafer. Impurities embedded in the wafer surface can also be etched away along with the oxide film. HF vapor can also come into contact with the backside of the wafer and remove impurities from that surface without the chemicals having to come into direct contact. In other embodiments, other compound vapors of the cleaning solution can be selected according to the composition of the wafer surface.

In another embodiment, chemical vapors can also be fed along with deionized water if desired to keep the wafer surface wet.

In step 525, a cleaning solution containing hydrofluoric acid is sprinkled on the wafer surface. In one embodiment, the cleaning fluid may be delivered to the wafer surface by a bristle brush. The flow of the solution helps prevent loading of the bristle brush. In other embodiments, the cleaning solution may include a specialized cleaning solution containing various chemicals or deionized water specially formulated for the chemical makeup of the wafer surface. Also, the cleaning fluid and the gaseous cleaning fluid (introduced in step 520) may have different chemical compositions.

In step 530, the surface of the wafer is scrubbed with a bristle brush mounted within the sealed chamber. As mentioned above, the scrubbing brush removes impurities from the surface of the wafer by wiping.

Continuing with step 535 in FIG. 5, impurities are removed from the wafer surface under the combined action of the bristle brushes and the flow of cleaning fluid. As mentioned earlier, since the surface of the wafer is etched away in a thin layer by gaseous hydrofluoric acid to remove all impurities embedded in the surface of the wafer, fewer scrubbing operations and lower cleaning fluid flow rates are required to be effective clean the wafer. The scrub station has a very effective cleaning action and allows lower pressure on the bristle brushes compared to prior art cleaning methods.

In step 540, the surface of the wafer is rinsed with deionized water. This rinsing can remove all the cleaning fluid remaining on the wafer after the cleaning process.

In step 545, the wafer is spun dry. Once the cleaning solution is rinsed off in step 507, a completely clean wafer without any impurities can be obtained through spinning and drying.

In step 550, the completely clean wafer is removed from the cleaning equipment and sent from the post chemical mechanical planarization cleaning equipment to the next step in the integrated circuit fabrication process.

Thus, the present invention provides methods and systems for efficiently removing CMP impurities and reaction products from the wafer surface after completion of the chemical mechanical planarization process. The present invention provides for efficient post-CMP cleaning without the risk of damaging the wafer surface. The invention effectively cleans away the impurities and by-products on the surface of the post-CMP wafer without causing damage.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They do not limit the invention to a certain scope, and many modifications and variations based on the invention are obviously possible. The embodiment selected for introduction is to better explain the principle of the present invention and its application in practice, so that those skilled in the art can better apply the present invention and make some changes for different usage requirements. The scope of the present invention is determined by the appended claims and their equivalents.

Claims (20)

1. A method for cleaning a semiconductor wafer, comprising the following steps: a) putting the semiconductor wafer into a sealed chamber; b) feeding gaseous cleaning liquid into the sealed chamber, the gaseous cleaning liquid is suitable for interacting with the surface of the semiconductor wafer in the sealed chamber and suitable for chemical reaction with the impurity particles attached to the surface; c) introducing a chemical cleaning solution into the sealed chamber; and d) brushing off foreign particles on said semiconductor wafer with a bristle brush adapted to come into contact with said surface of said semiconductor wafer. 2. The method of claim 1, further comprising the step of spin drying said semiconductor wafer after said scrubbing step. 3. The method of claim 1, wherein said semiconductor wafer is a chemically and mechanically planarized semiconductor wafer. 4. The method of claim 3, wherein the chemically and mechanically planarized semiconductor wafer includes an oxide layer. 5. The method of claim 4, wherein said gaseous cleaning fluid comprises gaseous hydrofluoric acid. 6. The method of claim 5, wherein said gaseous cleaning fluid is adapted to remove thin oxide layers from said semiconductor wafer. 7. The method of claim 6, wherein said thin oxide layer has a thickness of less than 50 Angstroms. 8. The method of claim 1, further comprising the step of introducing deionized water onto said semiconductor wafer simultaneously with said step b. 9. The method of claim 1, wherein said foreign particles comprise by-products of chemical mechanical planarization. 10. A device for cleaning semiconductor wafers, comprising: a) a sealed chamber for placing said semiconductor wafer; b) means for introducing a gaseous cleaning liquid into said sealed chamber, said gaseous cleaning liquid being adapted to interact with the surface of said semiconductor wafer in said sealed chamber and suitable to interact with foreign particles adhering to said surface chemical reaction; c) means for introducing said chemical cleaning solution into said sealed chamber; and d) A device for scrubbing foreign particles from said semiconductor wafer. 11. The apparatus of claim 10, wherein said semiconductor wafer is a chemical mechanical planarized semiconductor wafer. 12. The apparatus of claim 11, wherein the chemically mechanically planarized semiconductor wafer includes an oxide layer. 13. The apparatus of claim 12, wherein said gaseous cleaning fluid comprises gaseous hydrofluoric acid. 14. The apparatus of claim 13, wherein said gaseous cleaning fluid is adapted to remove thin oxide layers from said semiconductor wafer. 15. The device of claim 14, wherein said thin oxide layer has a thickness of less than 50 Angstroms. 16. The apparatus of claim 10, further comprising means for introducing deionized water into said sealed chamber simultaneously with the introduction of said gaseous cleaning fluid. 17. The device of claim 10, wherein said foreign particles comprise by-products of chemical mechanical planarization. 18. The apparatus of claim 10, wherein said means for introducing gaseous cleaning fluid into said sealed chamber is a first inlet adapted to introduce gaseous cleaning fluid into said sealed chamber. 19. The apparatus of claim 10, wherein said means for introducing chemical cleaning solution into said sealed chamber is a second inlet adapted to introduce chemical cleaning solution into said sealed chamber. 20. The apparatus of claim 10, wherein said means for brushing off foreign particles from said semiconductor wafer is adapted to contact said semiconductor wafer so as to brush off foreign particles from said semiconductor wafer brushes.

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