Abstract:
A method and apparatus for processing semiconductor wafer blanks comprises an enclosed chamber with upper and lower plates with a plurality of fluid openings leading from a source of chemical cleaning fluids, flushing fluid and dry nitrogen gas. The top plate also acts as a vacuum chuck to hold the wafer after the top surface has been cleaned and may rotate or oscillate to enhance the cleaning of the lower wafer surface. The method includes a chemical cleaning of the wafer top followed by processing the lower surface by pumping appropriate chemicals through the lower plate center toward the wafer periphery while the wafer is extremely close to the surface so that the outward moving fluids cover the wafer surface and are sparingly used. As the chemicals flow toward the periphery, their strength is renewed by the addition of new chemicals pumped through additional holes.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. patent application Ser. No. 08/543,071, filed Oct. 13, 1995 now abn. This continuation-in-part application includes descriptions of preferred embodiments of the present invention as set forth in the disclosure document number 383,408, filed in the U.S. Patent and Trademark Office on Oct. 14, 1995. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to the surface preparation of objects with fine surfaces such as semiconductor wafers and particularly to a method and apparatus for both wet and dry processing of such wafers. 
     BACKGROUND OF THE INVENTION 
     Microelectronics processing is a matter of surfaces. Processing techniques are concerned with modifying properties less than a few microns below or above the surface of a substrate material. Present complex electronic integrated circuits are formed by using planar processes in which an ultraclean, flat wafer of silicon is used as a substrate upon which a large number of identical devices are built by various oxidation, photolithography, removal, ion bombardment and deposition processes. Therefore, the integrated circuit manufacturing is essentially a sequence of chemical processes. 
     An ultraclean surface preparation before and after the processes necessary for the patterning of microelectronics devices is now more important than ever before as the surface diameter extends toward 300 mm. and the structure dimension shrink below microns. It is well known that the device performance, reliability and product yield of silicon circuits are critically affected by the presence of chemical contaminants and particulate impurities on the wafer of device surface. 
     Current existing methods for ultraclean surface preparation can be divided into two main categories: wet processes, such as immersion and spray techniques, and dry processes such as chemical vapor and plasma based techniques. 
     Wet processing consists of a series of steps of immersing or spraying the wafers with appropriate chemical solutions. The wet processes for ultraclean wafer surface preparation has been successfully used for the past twenty-five years and are still the predominant methods used in manufacturing circuits. However, the high cost of the large amount of ultrapure chemicals required in the current wet processes and the treatment of hazardous waste resulting from the processes, together with its incompatibility with the advanced concepts of integrated processing such as cluster tooling, are the main reason for searching for gas processing methods that are less affected by these limitations. 
     Although dry processing has shown several advantages in the chemical processing of advanced sub-micron features integrated circuits with high aspect ratio structures, numerous advantages of wet chemical processing often outweigh their “generic” problems in many production applications. 
     There is a real need in today&#39;s semiconductor fabrication industry to tailor the chemical processes to minimize the manufacturing costs in order to remain competitive in the ever increasing demands of the semiconductor market, while at the same time, to meet the increasing quality demands of the devices. The best answer for that is to combine the wet and dry techniques into the processes. 
     Thus, there is a need of a method and apparatus for the ultraclean surface preparation that is capable of performing both wet and dry chemical processes. 
     There is also a strong need for a method and apparatus to reduce chemical consumption, to reduce processing steps, and to increase equipment utilization without losing the effectiveness of the process. 
     There is further need for a method and a system that can be fully automated, well controlled, and integrated with cluster tool environments. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus capable of either liquid or gas processing of semiconductor wafers or other objects having fine surfaces. 
     The apparatus of the invention includes an enclosed housing of a material unaffected by the chemicals used in the process. The housing has an internal cavity that contains a rotatable and vertically movable upper plate having apertures for either admitting chemical fluids or to apply a vacuum for venting the housing or for grasping a wafer which is positioned between the upper plate and a lower plate having apertures appropriately placed in its surface for admitting processing fluids and drying gas. 
     The preferred method is to force a thin layer of processing fluid, either gas or liquid, through the narrow space between the surfaces of a semiconductor wafer and plates of the processing apparatus. While the fluid passes through the narrow space, it contacts and interacts both chemically and physically with the semiconductor wafer surfaces. The narrow space may be from 0.01 mm. to 10 mm, depending on the nature of the chemical processes. 
     In a preferred embodiment, the particular choice of spacing will be one where an optimum fluid flow is created to simultaneously bring fresh chemicals into contact with the surface of the semiconductor wafer and remove unwanted reaction products away from the surface of the semiconductor wafer toward the drain in order to prevent the unwanted reaction products from redepositing on the surface of the semiconductor wafer. In this regard, the chemical flow can be turbulent or laminar, depending on the nature of the process being carried out. In the preferred embodiment, the particular choice of narrow space will additionally result in the desired processing of the semiconductor wafer surface using a minimum of chemicals, as well as minimize the costs of treating the resulting hazardous wastes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a section elevation view of the chemical processor; 
     FIG. 2 is an illustration of the chemical processor with the associated equipment and supplies necessary for chemical processing; 
     FIG. 3 is a plan view taken along the lines  3 — 3  of FIG. 1; 
     FIG. 4 is a plan view taken along the lines  4 — 4  of FIG. 1; and 
     FIGS. 5 and 6 are plan views of alternate embodiments of the plates of FIGS. 3 and 4 showing slots in the plate surface. 
     FIGS. 7-11 show preferred embodiment of a single wafer processing system according to the present invention. 
     FIGS. 12-15 show a preferred embodiment of a multiple wafer semiconductor processing system according to the present invention. 
     FIGS. 16-19 show an apparatus embodying the present invention used in photolithography. 
     FIGS. 21 and 22 depict an apparatus embodying the present invention which can be used in chemical vapor deposition (CVD). 
     FIGS. 23 and 24 depict an apparatus embodying the present invention which can be used in the metallization process. 
     FIG. 25 depicts a surface chemical analysis system embodying the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the processing apparatus may be used for different applications, it probably will have its greatest application in the processing of semiconductor wafers. 
     In FIG. 1 a semiconductor wafer  12  is shown positioned within a chamber having a base  14 , sidewalls  16 , and a removable top cover  18 . The wafer is located between a lower plate  20  and a rotatable and vertically movable upper plate  22 . The wafer is generally a thin silicon circular disc between about four and twelve inches in diameter. In the illustrated processing apparatus the wafer  12  is to be processed on both upper and lower surfaces with the lower surface being more thoroughly treated for construction of integrated circuitry. 
     The lower plate  20 , and preferably the entire structure, is formed of a material unaffected by the various chemical fluids used in the process (e.g., a synthetic resin polymer sold under the trademark TEFLON) and the plate  20  has a flat circular central surface having a diameter equal to or larger than the diameter of the wafer  12  and with a high edge rim or sidewall  16 . Between the central surface of plate  20  and rim  16  is a drain slot  24  having a valve  25  at the effluent outlet at its lowest point. 
     The top surface of the lower plate  20  has two or three circular concentric grooves spaced around a central fluid opening  26  which may be a circular hole or may be a slit. Each of the circular concentric grooves has eight to ten fluid openings  28  which, as with opening  26 , extend through the lower plate  20  and base  14  and terminate in a valve  30 . The valves are connected through a fluid heater  54  to a common fluid conduit  32  leading from a source of aqueous and gaseous processing chemicals shown in the system diagram of FIG.  2 . 
     Upper plate  22  is formed of the same material as lower plate  40 , and is circular with a diameter substantially equal to that of the flat circular surface of the lower plate  20  so that it will fit and rotate within the side walls  16  of the lower plate. Upper plate  22  may have a single central fluid entry opening  34  leading through a valve  36  and heater  38  to the source of processing chemicals, or there may be several entry openings leading to valve  36 . 
     The upper plate  22  also functions as a vacuum chuck for holding the wafer during part of the process or may be used for venting the chamber interior. Therefore the valve  36  is capable of selecting either a flow of fluid into the apparatus or a vacuum applied to the apparatus for securing a wafer disc during a part of the process. Upper plate  22  may also be rotated or oscillated around its axis and is vertically movable by a motor  40  attached to the top cover  18  of the apparatus. The oscillation of the upper plate  22  is for agitation during processing and for the elution of chemicals from a wafer being held by the vacuum chuck. 
     Although the apparatus described is well suited for production line type of processing a typical single wafer cleaning operation in an initially clean and dry apparatus will now be described. 
     The top cover  18  with the upper plate  22  is lifted and a wafer  12  is held to its vacuum chuck while the vacuum is applied. In the preferred embodiment, the plate  22  places the adhering wafer  12  on at least three equally spaced, radially adjustable beveled fingers  42  overlying the lower plate surface and in the side wall  16  which can adjust the height of the wafer  12  from about 0.005 mm. to 10 mm. above the lower plate  20 . The vacuum is released from the chuck, the upper plate  22  is raised 0.01 to 10 mm. and a flow of cleaning chemicals is applied to the top surface of the wafer  12  through the opening  34  in the upper plate  22 . 
     When the wafer top surface is thus cleaned and dried, valve  36  is closed and a flow of processing chemicals is applied to the bottom surface through the opening  26  and through one or more of the concentric grooves fed by opening  28 . An ultraclean wafer surface is obtained in the preferred process by an optimized velocity passage of appropriate chemicals over the wafer surface. To obtain the desired velocity and to achieve the best effectiveness of the dynamic fluids while conserving costly chemicals, the processing fluids are pumped through the openings  26  and  28  as the bottom surface of wafer  12  is positioned very close (e.g. 0.01-1.0 mm.) to the lower plate by forcing down the wafer, as needed, with the upper plate. 
     A flow of fluid pumped through only the central opening  26  will not assure that the entire lower surface of the wafer will receive adequate fluid, nor fluid received near the periphery of the wafer will have the same processing power as the fresh fluid emanating from the opening. The surface grooves and the plurality of openings in each groove in the lower plate  20  will assure both an adequate supply of fluid to float the wafer off the lower plate and will provide a fresh supply of fluids to all areas of the wafers bottom surface as the fluid rushes toward the periphery. It is noted that in other embodiments of the present invention varying the flow of fluids pumped through openings  26  and  28  to float the wafer to varying heights above the lower plate may be used in place of the radially adjustable beveled fingers  42 . 
     Some processing steps may require a soaking period which is provided by closing the valve  25  from the drain slot  24 . In such a case agitation of the wafer may be very important and locking the wafer to the vacuum chuck and engaging the motor  40  for slow rotation or oscillation of the upper plate and wafer will assure that the bottom surface becomes thoroughly processed. 
     Rinsing of a chemically washed wafer usually requires great quantities of deionized water for elution of all traces of chemical from the wafer and to thoroughly rinse the various crevices and wafer holding clamps of the equipment. It should be noted that the apparatus described has no crevices nor holding clamps in which contaminants or chemical solutions can deposit and hide; both the chemicals and the rinsing water merely flow in over the wafer and flow out through the drain. Hence, a relatively small amount of deionized rinse water is required and all possibility of cross-contamination can be eliminated. After the processing, the chemical supply is shut off and the water supply is passed through the same openings  26 ,  28  as used for the chemical solutions. This rinsing water passes over the surface of the wafer and through the drain slot  24 . 
     The processed and rinsed wafer is dried by passing a dry inert gas such as nitrogen, through the fluid conduits and the openings  26 ,  28 ,  34 . Then the vacuum chuck is again actuated to hold the cleaned wafer so that the top cover  18  with the upper plate  22  may be removed. Releasing the vacuum will then release the wafer. 
     FIG. 2 illustrates the processing apparatus of FIG. 1 along with the equipment and supplies to make a computer controlled automated processing unit. Included are fluid supplies including three tanks of chemical liquids  44  and a tank of deionized water  46  and three tanks of dry processing gases  48  and a tank of nitrogen  50 . Obviously, other tanks of wet or dry fluids may be added. Each liquid chemical tank has its own valve where the liquid enters a mixing conduit or manifold at the input of a pump  52  followed by a switching valve  33 , then a heating element  54 . Each dry chemical tank has its own regulator and valve where the fluid is admitted into a mixing conduit or manifold at the input of a pump  53  followed by a switching valve  33  and the heating element  54 . The heating element is coupled directly to the mixing input conduit or manifold  32  of FIG. 1, which is shown connected to the selector valve  36  for admitting cleaning fluids to the top surface of the wafer through the top plate  22  in FIG.  2 . 
     A vacuum pump  56  is coupled to the vacuum terminal of the selector valve  36 . A second vacuum pump is coupled to the drain valve for the removal of dry chemicals and the effluent of both dry and liquid chemicals is monitored and recycled, as desired, by a monitor and recycle unit  58  coupled to the output of the drain valve  25 . 
     For full computer control, a digital computer  60  may be added to control the operation of the process. Each valve, pump, heater and motor is under the control of the computer which may be programmed according to timed sequences. For example, when a wafer has been installed, the computer may start at time, t 1 , with a three minute bath of heated deionized water through the top plate  22 , followed at time t 2  with one minute of a strong cleaning reagent to the top surface, followed at t 3  by three minutes of rinsing, then at t 4  a vacuum clamps the wafer to the top plate  22  and adjusts the fingers  42  to position the wafer 0.50 mm. above the surface of the lower plate  20 . Then follows a complete cleaning of the lower surface of the wafer, until probably at t 50 , heated nitrogen may be applied for drying. The procedure is variable, depending upon the nature and requirements of the process, the condition of the substrate wafer and the size of the wafer surface. The process steps can be completed sequentially. 
     FIG. 3 is a plan view of the lower plate  20  as taken along the lines  3 — 3  of FIG.  1  and shows the concentric grooves  62  in the plate surface linking the fluid openings  28  for evenly distributing the chemical reactants. If a processing liquid were admitted only through the central opening  26  it would be insufficient to cover the entire wafer surface and if a large quantity of liquid were to enter only through the central opening, the reactant strength would diminish as it flowed outward and covered a greater area. Hence, the grooves and the additional openings  28 , as shown in FIGS. 5 and 6, will provide additional, original strength fluid to the uniformity of the process. 
     FIG. 4 is a plan view of the upper plate  22  and shows a single central opening  34  with four narrow radial slits for admitting cleaning fluids and for applying a vacuum to clamp the wafer to the plate. Several holes or narrow slits could be employed and the single hole  34  with radial slits is for illustrative purposes only. 
     The foregoing description is of the preferred embodiment. it is apparent that by changing the location of the drainage channel, the apparatus may be used in an inverted position or may be used vertically. It is intended, therefore, to be limited only by the scope of the appended claims. 
     Automated Wafer Processing Apparatus 
     FIGS. 7 to  11 , shows an automated single-wafer processing system  100  which includes a framework  101  having a base portion  105  and upper chamber  110 . In the base portion  105 , there are chemical fluid delivery unit, effluent collector or recycling unit, on-line analyzer or sampling unit, vacuum unit and computer control unit. 
     As shown in FIGS. 7 and 8, the wafer processor is contained in the upper chamber  110  which functions as a mini-environment with the capabilities of inner gas purge, gases elevating and flow balance according to the requirements of a particular process. Along with the wafer processor in the upper chamber, there are wafer containers  115  and  116  for wafers going to be processed and the wafers having been processed respectively. The wafer containers  115  and  116  are loaded into the chamber through the access door  112  and  113  respectively and are positioned as shown in FIGS. 7 to  11 . The upper chamber further includes two robotic transfer units  118  and  119  for loading the wafer from wafer container  115  to the wafer processor and unloading the processed wafer from the processor to wafer container  116  as shown in FIGS. 7 to  8 . 
     FIG. 8 shows transfer unit  118  at the first position for loading the wafer from wafer container  115  and shows transfer unit  119  at the initial position. FIG. 9 shows the transfer unit  118  at the last position for loading the wafer to wafer processor. FIG. 10 shows the transfer unit  119  at the first position for unloading the wafer from the processor. FIG. 11 shows the transfer unit  119  at the last position for unloading the wafer from the processing unit. 
     FIGS. 12 to  15  show a preferred automated multi-wafer semiconductor processing system  200  embodying the present invention. The automated multi-wafer processing system  200  includes a wafer processor unit  201 , a back portion  220 , a base portion  230  as shown in FIG.  12 . In the base portion  230 , there are effluent collector or recycling unit, on-line analyzer or sampling unit, vacuum unit and computer unit. In the back portion  220 , there are chemical fluid delivery unit and computer interface. 
     The multi-wafer processor  201  is basically a set of single-wafer processors as shown in FIG. 1. A set of three is used as an example as shown in FIG.  12 . Each single-wafer processor consists of a wafer holding frame  203  with four movable lower teeth  205  and three movable upper teeth  207 . The frame  203  can be slid in and out from the working chamber for loading and unloading the wafer. The movable lower teeth  205  and upper teeth  207  are not only for securing the wafer, but also for defining the wafer position in the chamber. The front wall, or other appropriate side wall, can be adapted to function as an access door  209 . 
     Wafers are loaded into the processing chamber by opening the door, sliding out the frame  203 , inserting the wafer into the teeth  205 - 207 , securing and positioning the wafer with the movable teeth  205 - 207 , sliding frame with the wafer back into the processing chamber and closing the door  209 . The operation procedure is automated and programmed controlled by the computer control unit. After the process is completed, open the accessing door  209 , slide the wafer holding frame  203  out the working chamber, and unload the wafer  12 . 
     The number of the single-wafer processors can be more than three. The working chamber of processor is simplified compared to the wafer processor shown in FIG.  1 . The chemical fluid is injected and the vacuum is applied through the apertures on the top side of the processor chamber. 
     There are several advantages of this simplification: (1) less possibility of equipment contamination because of the simple structure and the less moving part in the working chamber; (2) smaller space of working chamber and lighter weight of the processor; and (3) easier in processors construction and simpler in operation. 
     The versatility in operation and simplicity in system construction are the very important characteristics of the automated multi-wafer processing system  200 . The system can be compacted into a structure fairly small in size and light in weight. Therefore the automated multi-wafer processing apparatus can not only be used as a processing system but also as a mini-environment storage for storing and transferring wafers. That will make the system very useful in the semiconductor processing. 
     Application in Etching and Cleaning Processes 
     It is now common to use a series of cleaning processes after etching of silicon wafers. For example, Blended Hydrogen Fluoride Acid (BHF) treatment for oxide etching followed by RCA—Hydrogen Fluoride Acid (RCA-HF) last cleaning. 
     The sequence of chemical solutions used to clean a wafer depends upon the contaminants presented and the requirement of the process. It is reasonable to take the well-known RCA clean as an example since the RCA wet clean method is still widely used in the wafer cleaning process. The RCA cleans are based on a two-step process, the Standard Clean-1, referred to as SC-1, followed by Standard Clean 2, SC-2. In the Standard Clean-1, the SC-1 solution is typically a 5:1:1 mixture of deionized water, “unstabilized” hydrogen peroxide (30%, “not stabilized”) and ammonium hydroxide (27 w/w% as NH 3 ). The working conditions are generally at 70 C. for 5-10 minute. In the Standard Clean-2, the SC-2 solution typically consists of 6:1:1 deionized water, hydrogen peroxide (30%, “not stabilized”), hydrochloric acid (37 w/w%), and the working conditions are at 70 C. for 510 minute. 
     The apparatus of FIG. 2 can be used to sequentially perform the steps of the BFH etching and RCA clean. In the process, the lower teeth  42  and the upper plate  22  are set at positions to define proper processing space heights. A processing protocol is generated in the computer unit  60 . For example, 
     At time- 1 , connect valves  30  and  36  to the chemical fluid line for double-side clean, start to inject deionized water to clean the working chamber. 
     At time- 2 , load the wafer on the lower teeth 1 mm above the lower plate  20  and position the upper plate  22  at 1 mm above the wafer  12 . 
     At time- 3 , start to inject deionized water from valves  30  and  36  to clean both side of the wafer. 
     At time- 4 , purge nitrogen into the upper narrow space to dry the back surface of the wafer. 
     At time- 5 , switch valve  36  to the vacuum line and chuck the wafer by applying vacuum. 
     At time- 6 , wet the surface with deionized water containing surfactant reagent if it is needed. 
     At time- 7 , introduce the BHF mixture which is pre-mixed right before being pumped out the chemical fluid delivery unit and pushed into the lower narrow space for etching the wafer. 
     At time- 8 , inject deionized water to rinse out BHF. 
     At time- 9 , inject SC-1 solution at 70 degrees C. to clean the wafer. 
     At time- 10 , inject deionized water to rinse out SC-1 solution. 
     At time- 11 , inject SC-2 solution at 70 degrees C. to further clean the wafer. 
     At time- 12 , inject deionized water for rinsing. 
     At time- 13 , inject dilute hydrofluoric acid for positive -surface preparation. 
     At time- 14 , inject ultrapure nitrogen gas to push the water out the wafer surface. 
     At time- 12 , spin the wafer while the a hot nitrogen gas is injected to further dry the wafer. 
     At time- 13 , initial the position of the holding teeth  42  and the upper plate  22  and unload the wafer. 
     After the processing parameters have been carefully set up, the chemicals needed in the process are loaded in the proper containers, and then the processing program is started. 
     The optimum parameters for the best processing result according to specification of product and cost of the process can be obtained by adjusting the processing program. For example, to avoid micro-roughening of the silicon surface, it may be achieved by reducing the ammonia and hydrogen peroxide concentration in SC-1 to a minimum level without losing the effectiveness of cleaning. 
     Many advantages of the invention can be easily seen and understood through the example given above. The entire processing steps are conducted in one working chamber and carried out by a programmable sequence. This eliminates the transfer of wafers between baths, therefore prevent the re-contamination commonly occurred during the transfer. It substantially reduce the processing time and consumption of chemicals which includes the deionized water. It also reduces the cost for the equipment footprint and utilities&#39; maintenance. The operation is very simple and much safer. 
     The processing quality can be well controlled because of the fully automated programming procedure and the ability of real-time process monitoring or on-line analyzing. The reproducibility is also expected to be improved. 
     Most existing techniques, for instance, megasonic treatment, brush scrubbing and photochemical techniques can be adopted into the system. The system can be easily implemented in the production environment and adapted into those well-established fabrication processes. 
     The system&#39;s capability of combining dry and wet processes permits the creation and development of new methods and techniques, and will aid the improvement of existing methodologies, such as HF-based cleaning, sulfuric-based cleaning, ozone treatment and chelating agents cleaning. 
     Application in Photolithography 
     In general, the photolithography process consists the following steps: 
     Step 1, cleaning, rinsing and drying the wafer to assure a utraclean surface. 
     Step 2, baking the wafer to remove both molecular water and silanol group (Si—OH) for good adhesion between the substrate and resist film by heating the wafer at 200-250 degrees C. for 30 minutes. 
     Step 3, priming the wafer to promote adhesion with an adhesion promoter such as hexamethyl disilazane (HMDS) for silicon dioxide. 
     Step 4, coating the wafer by dynamic dispense, for example, in which the resist is dispensed on rotating wafer. 
     Step 5, soft baking or postbaking to remove remaining solvents by heating the wafer at 90-100 degrees C. 
     Step 6, exposing the resist. 
     Step 7, developing the film by washing, or immersing, or spraying method. 
     Step 8, etching the film by wet or dry processes. 
     Step 9, removing the resist and cleaning the surface for a next process such as ion implantation and or dopant diffusion. 
     FIG.  16  and FIG. 17 show an apparatus  300  based upon the present invention which can be used to sequentially perform the step 1 to step 5 listed. 
     The wafer is loaded into the processing chamber by sliding out the holding frame  303 , inserting and securing the wafer between the movable teeth  305 - 307 , and sliding the frame with the secured wafer back into the processing chamber, where the wafer is positioned on the lower plate  322  which is rotatable and vertically movable, and secured by a vacuum chuck. 
     The wafer surface is cleaned and dried with fluid introduced from the aperture  326  on the upper plate  320  while the wafer is heated using the heating elements  334  in the lower plate  322 . Drying the surface with hot nitrogen gas while heating up the wafer from the bottom may help the removal of molecular water and the silanol group. After cleaning and drying, the surface is primed by flowing the adhesion promoter over the surface if it is required. Resist is dispensed from the resist &amp; solvent inlet  332  in the center of the upper plate on to the surface of the wafer while the wafer is spinning. Purging the chamber using an inert gas from the fluid opening  326  through the space between the surface of the wafer and the upper plate may help the remove of the volatile solvent and improve the adhesion of the resist. After the wafer is soft baked or postbaked by heating the wafer using heating elements  334  in the lower plate  322  while keeping the inert gas flow over the film, the wafer is ready for exposure. 
     FIG.  18  and FIG. 19 show an apparatus based upon the present invention which can be used to sequentially perform the step 7 to step 9 listed above. 
     After the resist exposure, the wafer is loaded into the chamber on the lower plate  344  which is rotatable and vertically movable as shown in FIG.  18 . The wafer is secured by the vacuum chuck, and the wafer surface is sequentially developed, rinsed, etched, stripped of resist, cleaned and dried by the programmed introduction of various chemical fluids into the narrow space between the wafer and the upper plate from the apertures  326  and  328  on the upper plate. The quality of processing may be improved by rotating, oscillating, or vertically moving the wafer during processing. 
     FIG. 20 illustrates a diagram of cluster-tools for photolithography and etching. 
     Application in Chemical Vapor Deposition (CVD) 
     A CVD process is designed to supply reactive gasses to the surface under conditions that encourage surface reaction and discourage reaction elsewhere. In CVD, one or more gasses react on a surface to form a film. The main requirements in CVD are to provide a uniform supply of gaseous reactant to the substrate surface and energy to activate the reactant and promote the reaction. 
     FIG.  21  and FIG. 22 shown an apparatus  400  based upon the present invention which can be used in the CVD process. 
     The wafer is loaded into the working chamber and secured on the upper plate  422  with vacuum chuck. The distance of the wafer to the surface of the lower plate  420  is adjusted by moving the upper plate  422  which is rotatable and vertically movable. The wafer is cleaned and dried if needed using a chemical fluid admitted from the openings  426  and  428  on the lower plate. The wafer and the working chamber are then heated with the heating elements  430 , and the desired fluid is introduced into the chamber from the openings on the lower plate into the narrow space between the wafer and the surface of the lower plate. The temperature of the fluid can be controlled by the heating units  432 . The “V” shape of the lower plate surface is designed for better uniformity of the process. Spinning or oscillating the wafer during processing results in a better quality film. 
     Application in Thin-film Deposition of Metals 
     The vacuum deposition method works best for elements or highly stable compounds of moderate melting points, especially when high purity is required; it is most useful with metallic conductors. In the process, the film material is transferred from a solid source, through a vacuum, to the substrate forming a metallic thin film on the surface. Vacuum deposition of a film requires two things: a vacuum and a source of film material. 
     FIG.  23  and FIG. 24 show an apparatus  500  based upon the present invention which can be used in the metallization process. The wafer is loaded into the working chamber and secured on the upper plate  522  with a vacuum chuck. The distance of the wafer to the surface of the lower plate  520  is then adjusted by moving the upper plate which is rotatable and vertically movable. The working chamber is heated using heating elements  521 , then the lower plate, which has a thin layer of the film material on the surface, is heated using heating elements  521 . A steam of inert gas is introduced into the working chamber from the openings  526  on the lower plate into the narrow space between the wafer and the lower plate to enhance the step side coating and the uniformity of the overall coating of the film material onto the wafer. Step side coating refers to the coating of the sides of depressions etched into the wafer. A better quality film may be obtained by spinning or oscillating the wafer during processing. 
     Application in Surface Chemical Analysis 
     The ever-decreasing dimensions of microelectronics devices demands the refinement of traditional surface and materials characterization techniques and the inception of novel methodologies. 
     Direct surface analyses techniques such as Total Reflection X-Ray Fluorescence (TXRF), and Secondary Ion Mass Spectrometry (SIMS) have been the common methods for the determination of trace metal ions on a silica surface. The detection limits for these methods are ranged from 10 10  to 10 15  atoms/cm 2 . 
     In the past few years, vapor phase decomposition (VPD) method, an indirect surface analysis method, have been extensively studied and applied to the analysis of metal ion contamination on a silicon surface in combination with Graphite Furnace Atomic Absorption Spectroscopy (GFAAS), Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), TXRF or SIMS to achieve lower detection limit. 
     Vapor Phase Decomposition (VPD) involves wet-HF vapor preconcentration of contaminant of metals in the oxide layer on the very surface of wafer into a very small volume of solution. The measurement of the metals in the pre-concentrated liquid residue is accomplished by sensitive analytical instruments such as GFAA, TXRF, ICP-MS and SIMS. 
     The VPD method permits better detection limit which is very demanded in the semiconductor industry. But there are several disadvantages with the VPD extraction method. The method is limited to extraction of metal elements on silicon oxide layer only. The pre-concentration procedure is very time consuming. The performance is very labor intensive and is difficult to automate and standardize. The extraction efficiency is chemistry dependent and can vary dramatically for different metallic elements and substrates. The operator is constantly exposed to the HF vapor which is known harmful to human health. 
     FIG. 25 shows a surface chemical analysis system  600  for surface chemical analysis designed based on the present invention. 
     The component of the surface chemical extraction system  600  is almost the same as the surface chemical processing system FIG.  2 . Except the monitoring unit and effluent collection unit or the chemical recycle unit in FIG. 2 is replaced by an analyzing unit  605  in FIG.  33 . 
     The analyzing unit  605  in FIG. 25 consists of a sampler  601  for extract collection, a concentrator  602  for sample concentration and analyzers  603  for sample analyses such as ion chromatography and ICP-MS. 
     The wafer is chucked by applying the vacuum to the upper plate  22  and placed 0.005 mm-0.500 mm above the lower plate by the removable head  18  and vertically movable upper plate  22 . Desired chemical fluids are introduced into the narrow space between the wafer surface and the lower plate surface, the extraction solution is collected by the sample collector, and the solution is concentrated by the concentrator. Then the concentrated residue is analyzed by an appropriate instrument, for example, by ICP-MS for metal contaminants and by High Performance Liquid Chromatography (HPLC) for organic contaminants. 
     The surface analysis system  600  shown in FIG. 25 can be used not only for extraction of metal impurities in the oxide layer of the wafer surface, but also for other inorganic and organic impurity species on the wafer surface and in the substrate, because of the wide choices of the chemistry of chemical fluids. The performance is simple, fast and easily automated. It also provides better extraction selectivity and efficiency. 
     While a number of preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.