Abstract:
A process for the coating of substrates comprising insertion of a substrate into a process oven, plasma cleaning of the substrate, dehydration of the substrate, withdrawal of a metered amount of one or more chemicals from one or more chemical reservoirs, vaporizing the withdrawn chemicals in one or more vapor chambers, and transfer of the vaporized chemicals into a process oven, thereby reacting with the substrate. An apparatus for the coating of substrates comprising a process oven, a gas plasma generator, a metered chemical withdrawal subsystem, and a vaporization subsystem.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation in part of U.S. patent application Ser. No. 10/656,840 to Moffat et al., filed Sep. 5, 2003. 
     
    
     BACKGROUND  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates to the coating of substrates, and in particular to an apparatus and process for the efficient coating of substrates using chemical vapor reaction and gas plasma cleaning.  
         [0004]     2. Description of the Related Art  
         [0005]     The application of coatings onto substrates and other workpieces is required as a process step in many industrial fields. An example of such a process is the coating of a silicon wafer with a layer of Hexamethyldisalizane (HMDS). This coating process is used to promote the adhesion of organic layers such as photoresist to the inorganic silicon wafer. The HMDS molecule has the ability to adhere to the silicon wafer and also to be adhered to by an organic additional layer. For example, silicon wafers would be baked for 30 minutes in a 150C oven for 30 minutes to dehydrate them. The silicon wafers would then be sprayed with HMDS. The excess HMDS would then be spun off of the silicon wafer. A typical process of this type would result in a HMDS monolayer on the surface of the silicon wafer.  
         [0006]     A problem encountered with the above mentioned process was that if the silicon wafer was not sufficiently dry prior to the application of HMDS, then residual moisture would interfere with the reaction of the HMDS to the silicon wafer. This would result in variations in the HMDS layer reaction and then could lead to voids in the subsequently applied next layer. Another problem with a process of this type is that HMDS would rapidly deteriorate when exposed to air and moisture, and thus such a process required a large amount of HMDS to provide a small amount of reaction.  
         [0007]     Because of the problems relating to variations in the HMDS monolayer, processes for the coating of substrates with HMDS evolved. Later processes more thoroughly dehydrated the silicon wafer substrate prior to the application of HMDS, and limited the HMDS from much, if any, exposure to air and moisture. An example of such a process would be as follows. Silicon wafers would be placed in a vacuum chamber and cycled back and forth between vacuum and preheated hot dry nitrogen in order to dehydrate the silicon wafer. For example, the silicon wafer would be exposed to a vacuum of 10 Torr for 2 minutes. At this pressure water boils at about 11 C. The vacuum chamber would then be flooded with preheated nitrogen at 150 C. This part of the process would heat the surface of the silicon wafer so that the high temperature of the wafer would assist in the dehydration process as vacuum was once again applied. After 3 complete cycles, a vacuum of 1 Torr would be applied to complete the dehydration process.  
         [0008]     The next step in such a process is to open a valve between the vacuum chamber and a canister of HMDS. At room temperature the HMDS boils at approximately 14 Torr and thus the chamber is flooded with 14 Torr of HMDS vapor. In this process the HMDS is not exposed to air or moisture and the silicon wafer is significantly dryer prior to being coated.  
         [0009]     Some coating processes based on the above mentioned type of process require a higher pressure. The HMDS is preheated to create a higher vapor pressure. Typical figures are preheating of the HMDS to 100 C to produce up to 400 Torr pressure or HMDS vapor while limiting the pressure in the process oven at 300 Torr to avoid condensation of the HMDS.  
         [0010]     Processes involving the preheating of the deposition chemicals have the drawback that if the deposition chemicals degrade with exposure to heat then the bulk preheating of these chemicals may result in the loss of the unused residual chemical. These chemicals are often very expensive. Also, many of these chemicals are hazardous materials. The less of these chemicals actually being used in the process at any time reduces the potential risk for processing facilities.  
         [0011]     The coating of substrates for biotech applications may require sufficiently dehydrated substrates and insertion into the process chamber of one or more deposition chemicals which have been preheated and/or vaporized prior to insertion. Some coatings for biotech applications are quite expensive. Some coatings are difficult to vaporize and vaporization requires a combination of low pressure and high temperature. Without reduced pressure, the temperature required for vaporization may be too high to retain stability of the chemical to be vaporized. Biotech applications may require silane deposition onto glass and/or other substrates as a bridge to organic molecules. Among the silanes used are amino silanes, epoxy silanes, and mercapto silanes. These silanes are used in the adhesion layer between glass substrates and oligonucleotides. Oligonucleotides are a short DNA monomer. Substrates are coated with a monolayer of silane as a bridge between the inorganic substrate and the organic oligonucleotide. A silane coated substrate with an oligonucleotide layer is now a standard tool used in biotech test regimens. One area where this oligonucleotide layer is used is in the formation of DNA microarrays. A uniform and consistent silane layer leads to a more uniform and consistent top surface of the oligonucleotide layer, which in turn leads to more useful test results.  
         [0012]     What is called for is a process and apparatus which withdraws deposition chemicals from a bulk storage container and then preheats and/or vaporizes this portion separately prior to delivery into the process chamber, allowing for the introduction of deposition chemicals at high temperatures and/or vapor pressures into a process chamber, without requiring preheating of bulk amounts of the deposition chemicals. What is also called for is an apparatus which is able to plasma clean substrates in the chamber into which the vaporized chemicals will be delivered, and an apparatus which can clean itself after such production runs using plasma.  
         [0013]     Substrates coated with such a process have reduced contamination, have more consistent monolayers with better bonds to the substrate, allowing for a more consistent oligonucleotide layer. This consistent substrate, used in DNA microarray tests, leads to more accurate test results  
       SUMMARY  
       [0014]     A process for the coating of substrates comprising insertion of a substrate into a process oven, dehydration of the substrate, plasma cleaning of the substrate, withdrawal of a metered amount of one or more chemicals from one or more chemical reservoirs, vaporizing the withdrawn chemicals in one or more vapor chambers, and transfer of the vaporized chemicals into a process oven, thereby coating the substrate. An apparatus for the coating of substrates comprising a process oven, a gas plasma subsystem, a metered chemical withdrawal subsystem, a vacuum subsystem, and a vaporization subsystem. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a pictorial representation of portions of one embodiment of the invention highlighting the chemical withdrawal, infuse, and vaporization subsystems.  
         [0016]      FIG. 2  is a pictorial representation of portions of one embodiment of the invention highlighting the chemical withdrawal and infuse subsystems.  
         [0017]      FIG. 3  is a representational piping schematic of one embodiment of the present invention.  
         [0018]      FIG. 4  is a pictorial representation of portions of one embodiment of the present invention highlighting the vacuum and gas delivery subsystems.  
         [0019]      FIG. 5  is a front isometric view of one embodiment of the present invention.  
         [0020]      FIG. 6  is a rear isometric view of one embodiment of the present invention.  
         [0021]      FIG. 7  is a partial cutaway side view of one embodiment of the present invention.  
         [0022]      FIG. 8  is a blown up section of the partial side view of  FIG. 7 .  
         [0023]      FIG. 9  is a side view of one embodiment of the present invention.  
         [0024]      FIG. 10  is a rear view of one embodiment of the present invention.  
         [0025]      FIG. 11  is a top view of one embodiment of the present invention.  
         [0026]      FIG. 12  is a rear view of one embodiment of the present invention.  
         [0027]      FIG. 13  is a partial cutaway view of one embodiment of the present invention.  
         [0028]      FIG. 14  is a view of the process oven interior according to one embodiment of the present invention.  
         [0029]      FIG. 15  is a view of the process oven interior according to one embodiment of the present invention.  
         [0030]      FIG. 16  is a view of the process oven interior according to one embodiment of the present invention.  
         [0031]      FIG. 17  is a view of the process oven with its door open according to some embodiments of the present invention.  
         [0032]      FIG. 18  is a partial view of one embodiment of the present invention displaying the metering pumps.  
         [0033]      FIG. 19  is a partial view of one embodiment of the present invention displaying the metering pumps. 
     
    
     DETAILED DESCRIPTION  
       [0034]     In one embodiment of the present invention, as seen in  FIG. 1 , chemical vapor deposition apparatus  101  has a fluid input portion  102 , a vaporization portion  103 , and a process oven  104 . Process oven  104  may be controlled with regard to both temperature and pressure. Fluid reservoirs  106 ,  107  provide the chemicals for the fluid input portion  102 . Fluid reservoirs  106 ,  107 , may be manufacturer&#39;s source bottles in some embodiments. Fluid reservoirs may contain the same fluid, allowing for the easy replacement of one reservoir if empty without disruption of the deposition process, or may contain separate chemicals. In some applications, water may be used as one of the chemicals in order to facilitate some rehydration of the substrate.  
         [0035]     Chemicals in the fluid reservoirs  106 ,  107 , are withdrawn into fluid input portion  102  by syringe pumps  108 ,  109 . Although syringe pumps are used in this embodiment, other methods of withdrawal may be used, including peristaltic pumps and other appropriate methods. Chemical withdraw valves  116 ,  117 , provide isolation between fluid reservoirs  106 ,  107 , and syringe pumps  108 ,  109 . Chemical withdraw valves  116 ,  117 , are opened prior to withdrawal of chemicals from fluid reservoirs  106 ,  107 .  
         [0036]     Chemical infusion valves  113 ,  114  provide isolation between syringe pumps  108 ,  109 , and the vapor chamber  110 . The vapor chamber  110  is surrounded by vapor chamber heater  118 . Although the vapor chamber heater is external to the vapor chamber in this embodiment, the vapor chamber heater may be internal to the vapor chamber or integral to the vapor chamber. The vapor chamber heater  110  may be P/N MBH00233 manufactured by Tempco, of Wood Dale, Ill., or other suitable heater. The vapor chamber  110  is fluidically coupled to process oven  104  by heated vapor line  111 . The vapor chamber  110  may be isolated from process oven  104  by the operation of heated vapor valve  115 . An example of such a heated vapor valve is valve P/N SS-8BK-VV-1C by Swagelok of Sunnyvale, Calif., with heater P/N 030630-41 by Nor-Cal Products of Yreka, Calif. The vapor chamber manometer  112  monitors the pressure inside vapor chamber  110 . The process oven  104  may contain one or more trays  105 .  
         [0037]     In one embodiment of the present invention, as seen in  FIG. 2 , fluid input portion  102  routes chemicals from the fluid reservoir  106  through a delivery pipe  203  to the chemical withdraw valve  116 . An example of such a chemical withdraw valve  116  is P/N 6LVV-DP 11811-C manufactured by Swagelok of Sunnyvale, Calif. A fluidic coupler  211  is inserted into fluid reservoir  106  to allow fluid withdrawal from the fluid reservoir  106 . In this embodiment, the fluid reservoirs  106 ,  107 , are chemical source bottles. The fluidic coupler  211  also allows fluid such as dry nitrogen gas from pipe  202  to be inserted into the chemical reservoir  106  to fill the volume voided by the removal of chemical from the chemical reservoir  106 . Exposure of the chemical to air and/or moisture is thus minimized. The syringe pump  206  may withdraw chemicals from fluid reservoir  106  when the chemical withdraw valve  116  is opened. An example of the syringe pump  206  is P/N 981948 manufactured by Harvard Apparatus, of Holliston, Mass. Actuation of the syringe pump mechanism  207  withdraws chemicals from the fluid reservoir  106  by partially or fully withdrawing the syringe plunger  208  from the syringe body  209 . The amount of chemical withdrawn may be pre-determined, and also may be pre-determined with accuracy. The chemical is routed from the fluid reservoir  106 , through the fluidic coupler  211  and the delivery pipe  203  to the chemical withdraw valve  116 , through a pipe  214  and a T-coupler  205  to the syringe body  209  in this embodiment. In general, fluidic coupling can be referring to liquid or gas coupling in this embodiment.  
         [0038]     After withdrawal of chemicals into the syringe body  209 , the chemical withdraw valve  116  may be closed to isolate the delivery pipe  203 . The chemical infusion valve  113  may then be opened to link the syringe body  209  to the vapor chamber  110 . An example of such a chemical infusion valve  113  is P/N 6LVV-DP11811-C manufactured by Swagelok of Sunnyvale, Calif. The syringe pump mechanism  207  may then re-insert the syringe plunger  208  partially or fully into the syringe body  209 , forcing the chemical within the syringe body  209  through the T-coupler  205  and then through pipe  210 . With the chemical infusion valve  113  open, the chemical then may enter the vapor chamber  110  via pipe  215 . Pressure within the vapor chamber  110  is monitored with the vapor chamber manometer  112 . An example of such a manometer is a 0-100 Torr heated capacitance manometer P/N 631A12TBFP manufactured by MKS of Andover, Md.  
         [0039]     The fluid reservoir  106  is secured with a spring clamp  212  within a source bottle tray  213 . The source bottle tray  213  may also act as a spill containment vessel.  
         [0040]     In some embodiments of the present invention, the fluid input portion  102  delivers the desired amount of chemical in another way. The chemicals in the fluid reservoirs are withdrawn in a pre-determined amount using a metering pump. For example, the metering pump may withdraw and deliver 2 milliliters per stroke. To deliver a specific quantity of a chemical, the metering pump would be pumped repeatedly until the desired quantity had been delivered. In some embodiments using metering pumps, the chemical withdraw valve and the chemical infusion valve are not necessary. The metering pump itself acts to isolate the fluid reservoir from the vapor chamber. Such embodiments allow for the delivery of the chemical from the fluid reservoir with less required hardware.  
         [0041]      FIGS. 18 and 19  are partial cutaway views of an embodiment using metering pumps. The metering pumps  1801  are fluidically coupled to the vapor chamber. Chemical reservoirs  1802 ,  1803  are the source of supply of the liquid which the metering pumps  1801  pump into the vapor chamber (some piping is omitted in the Figures).  
         [0042]     One of skill in the art will understand that the fluid input portion may have other embodiments that may use the above described elements in different types of combinations, or may use different typed of elements.  
         [0043]     In one embodiment of the present invention, as seen in  FIG. 3 , piping and other hardware is arranged as illustrated in the piping schematic  401 . Vacuum and gas portion  402  illustrates the portion of the apparatus with inputs for gas and the provision of vacuum. In one embodiment of the present invention, a high pressure gas inlet  403  connects to 80-100 psig nitrogen, an inlet  404  connects to 5-15 psig of a process gas, and an inlet  405  connects to 15-40 psig nitrogen. A vacuum inlet  406  provides vacuum to the system.  
         [0044]     The high pressure gas inlet  403  provides gas via a line  464  to the chemical reservoirs  502 ,  503 , and also provides the pressure to actuate valves  463  and valves  480 - 484 . Solenoids  421 - 427  are directed by a logic controller at I/O locations  440 - 445  to actuate valves  480 - 485  using solenoids  421 - 427 . The gas from the high pressure gas inlet  403  is reduced in pressure to 4 psig by a pressure reducer  460  to be fed to the chemical reservoirs.  
         [0045]     The solenoid acutated valves  430 ,  431  are triggered by directions from a logic controller at I/O interfaces  454 ,  455  to allow for purging of the chemical source bottle feed line  490 .  
         [0046]     When the solenoid  421  is directed by the logic controller via the I/O interface  440 , high pressure gas is directed through a line  471  to actuate the chemical infusion valve  480 , which connects the fluid line  510  from the syringe pump  512  to the vaporization chamber  501 . When the solenoid  422  is directed by the logic controller via the I/O interface  441 , high pressure gas is directed through the line  470  to actuate the chemical infusion valve  481 , which connects the fluid line  511  from the syringe pump  513  to the vapor chamber  501 .  
         [0047]     When the solenoid  426  is directed by the logic controller via the I/O interface  444 , high pressure gas is directed through the line  467  to actuate valve  483  which allows for the introduction into the process chamber  500  of gas from the inlet  404 . When the solenoid  425  is directed by the logic controller via the I/O interface  443 , high pressure gas is directed through the line  465  to actuate the valve  485 , which allows for the introduction into the process chamber  500  of gas from the inlet  405 .  
         [0048]     When the solenoid  427  is directed by the logic controller via the I/O interface  445 , high pressure gas is directed through a line  468  to actuate the heated vapor valve  484 , which allows for the introduction into the process chamber  500  of vaporized chemical from the vapor chamber  501  via line  554 . Temperature indicating controller  524  and temperature alarm high switch are coupled to I/O interface  451 .  
         [0049]     Solenoid operated valves  428 ,  429  allow the opening and closing of lines between the chemical reservoirs  502 ,  503  and the syringe pumps  512 ,  513 . I/O interfaces  458 ,  459  control the operation of the solenoid operated valves  428 ,  429 .  
         [0050]     The level of chemical left in the chemical reservoirs  502 ,  503  is monitored with level sensors  514 ,  515  and routed to the logic controller via the I/O interfaces  456 ,  457 . Level sensors  514 ,  515  are capacitance level switches P/N KN5105 by IFM Effector of Exton, Pa., in this embodiment.  
         [0051]     The vapor chamber pressure switch  464  is linked directly by a line  472  to a solenoid actuated valve  423 , which, when triggered, in turn triggers the gas actuated overpressurization limit relief valve  463 . The overpressurization limit relief valve  463  connects the vapor chamber  501  to the vacuum line inlet  406 . The vapor chamber pressure switch  464  triggers when the pressure in the vapor chamber  501  exceeds a preset pressure, which is 650 Torr in this embodiment.  
         [0052]     The process oven manometer  461  feeds its signal to the logic controller via an analog interface (not shown). Overtemperature alarm  551  feeds its signal to the logic controller via I/O interface  448 . An I/O interface  442  controls the solenoid actuated valve  424 , which in turn can trigger the gas actuated heated vacuum valve  482  via a line  466 , which links the process oven  500  to the vacuum inlet  406 . A temperature monitor  527  monitors the vacuum line temperature and is linked to the logic controller via an I/O interface  460 . Temperature alarm high switch  552  is linked to the logic controller via an I/O interface  460 .  
         [0053]     Temperature monitors  520 ,  521 ,  522 ,  523  monitor the temperature in the process oven  500 . Temperature monitors  520 ,  521 ,  522 ,  523  are linked to the logic controller by an RS-485 interface (not shown). Alarms are present in the temperature monitoring system and are linked to the logic controller by I/O interfaces  446 ,  447 ,  449 ,  450 .  
         [0054]     Temperature monitors  524 ,  525  connected to I/O interfaces  451 ,  453  are also used to monitor the temperature of the heated vapor line  526  and the vapor chamber  501 . A pressure monitor  462  is linked to the logic controller by an analog interface and overtemperature alarm  553  is linked to the logic controller by an I/O interface  452 .  
         [0055]     A logic controller may be used to control this apparatus in some embodiments. An example of such a controller is Control Technology Corporation Model 2700 of Hopinkton, Mass. One of skill in the art will understand that the apparatus may be controlled using a variety of suitable methods.  
         [0056]     In one embodiment of the present invention, as seen in  FIG. 4 , a chemical vapor deposition apparatus  101  has a vacuum subsystem  701 . Vacuum is applied to the vacuum subsystem  701  vacuum input supply line  735 . A heated vacuum valve  703  may be actuated to isolate the heated vacuum line  704  from the vacuum input supply line  735 . An example of the heated vacuum valve is P/N SS-8BK-VV- 1 C manufactured by Swagelok of Sunnyvale, Calif. The vacuum in the process chamber is measured using the chamber manometer  705 . An example of such a manometer is P/N 631A13TBFP manufacture by MKS of Andover, Md. Vacuum input supply line is fluidically coupled to the overpressurization limit relief valve  710 . An example of such a overpressurization limit relief valve is P/N SS-BNVS4-C manufactured by Swagelok of Sunnyvale, Calif. Overpressurization limit relief valve  710  couples vacuum input supply line  735  to line  709 . T-coupler  707  links line  708 , line  709 , and line  736 . Line  736  is fluidically coupled to vapor flask overpressurization limit switch  706 . The overpressurization limit switch  706  is electrically connected to a solenoid actuated valve which supplies high pressure gas that actuates the overpressurization limit relief valve  710 . An example of the vapor flask overpressurization limit switch is P/N51A13TCA2AF650 by MKS of Andover, Md. Line  708  is fluidically coupled to vapor chamber  110 .  
         [0057]     A low pressure gas distribution manifold  733  distributes gas such as dry nitrogen for use in dehydration cycles. Inert gas such as dry nitrogen may be used in these lines. A purge manifold  732  allows for the purging of the fluid reservoirs and lines. The low pressure gas input line  522  is split at a T-coupler  723  into two serpentine lines  720 . Gas line heaters  721  allow for the pre-heating of the gas prior to delivery of the process chamber. T-couplers  724 ,  729  further divide the delivery lines prior to input to the chamber at the gas inlets  725 ,  726 ,  727 ,  728 .  
         [0058]     A high pressure gas distribution manifold  731  provides gas for purge manifold  732  which inserts low pressure nitrogen into the fluid reservoirs  106 ,  107 . A line  730  routes gas to a fluidic coupler  211  in order to replace the volume voided by chemical withdrawal. Inert gas such as dry nitrogen may be used in these lines. The low pressure regulator  741  reduces the pressure from the high pressure gas distribution manifold  731  upstream from purge manifold  732 . The low pressure regulator  741  then provides gas to the purge manifold  732 .  
         [0059]     High pressure gas distribution manifold  731  provides high pressure gas that is routed to the gas actuated valves by the triggering of solenoid actuated valves in valve bank  740 .  
         [0060]     An alternative process gas distribution inlet  734  provides another inlet for process gas that may be used in some processes using this embodiment of the present invention. In this embodiment, the process gas lines are fluidically coupled to the low pressure gas lines upstream of the serpentine lines  720 .  
         [0061]     As seen in  FIG. 5 , chemical vapor reaction apparatus  1001  has a touchpanel interface  1002 . The light tower  1003  signals status of the apparatus to persons in the vicinity. Door  1004  provides access to the process chamber.  
         [0062]     In some embodiments of the present invention, as seen in  FIGS. 14 through 16 , the process oven  104  houses a plasma gas generation system. The plasma gas generation system resides predominantly within the process oven chamber walls  1401 . The gas plasma generation system is adapted to generate gas plasma within the process oven  104 .  
         [0063]     FIGS.  14  to  16  show several variations of capacitive plasma generation. Plasma may be generated with an appropriate gas in the presence of a strong electric field at an appropriate pressure. Capacitive plasma generation typically uses parallel plate electrodes to create the electric field. Electrodes may also be used to reduce the charging potential of a plasma and to concentrate the plasma in selected areas.  
         [0064]     Capacitive plasma electrodes are commonly referred to as being electrically active, electrically grounded, or electrically floating. An electrically active electrode has a high voltage, typically 400-600 volts, placed on it to create an electric field with respect to other electrodes. The voltage is typically alternating current at a high frequency. The industry standard frequency for plasma equipment is 13.56 MHz. There are advantages to using a lesser frequency in the 40 to 50 KHz range. An electrically grounded electrode is connected to ground with a appropriate conductor so that it remains at ground voltage potential. An electrically floating electrode is isolated from all other electrical potentials and will be at some voltage level that depends on the influence of the plasma upon it.  
         [0065]      FIG. 14  shows a horizontal electrode configuration that spans the process oven  104 . Plasma is generated primarily between active electrodes  1402  and grounded electrodes  1403 . Product material to be processed is typically place on the floating electrodes  1404 . To reach the product, plasma must pass through the perforated grounded electrode  1403 . Passing through the grounded electrode  1403  reduces the charging influence of the plasma and therefore reduces the charge that may be induced on the surface of product material by exposure to the plasma.  
         [0066]      FIG. 15  shows a vertical electrode configuration with grounded product trays  1411 . Plasma is primarily generated between active electrodes  1410  and grounded electrodes  1412 . Plasma passes through the perforated, grounded electrodes  1412  and reduces it charging influence. The region between the grounded electrodes  1412  has no electric field and therefore no plasma generation. However, plasma concentrates in regions with zero electric fields when plasma generation is at relatively low frequencies, 40-50 KHz. The configuration of  FIG. 15  therefore concentrates plasma with low charging influence around grounded product trays  1411 .  
         [0067]      FIG. 16  shows a configuration similar to that of  FIG. 15  with an additional plasma generation region in the center of the chamber  104 . Plasma is primarily generated between active electrodes  1420  and grounded electrodes  1422 , Once again, product trays  1421  are electrically grounded and in a region where plasma is concentrated but with low charging influence.  
         [0068]     In some embodiments, the product trays  1404  span the process oven  104 . Active electrodes  1402  and ground electrodes  1403  span the process oven  104  horizontally. The RF power supply, cabling, and RF power feed through are known in the art.  
         [0069]     In some embodiments, the plasma cleaning cycle may occur before the dehydration process. In an exemplary process, the chamber is evacuated. A gas is then introduced into the chamber and the pressure is stabilized at a low pressure, such as 150-200 milliTorr. In some embodiments, the introduced gas in oxygen. In some embodiments, the introduced gas is a combination of oxygen and argon. In some embodiments, other gasses are used.  
         [0070]     The plasma gas generation system allows for plasma gas cleaning of a work piece, such as a slide or substrate, in the same chamber as that in which subsequent process steps will take place. This gives many advantages, including reducing possible contamination that may occur if the work piece is exposed to the environment after plasma cleaning. Also, the plasma gas generation system can be used to clean the oven after the work pieces have been processed and removed. Many of the chemicals that may be used in processes that this chamber supports may leave residues that can interfere with subsequent runs. The plasma gas generation system may be utilized to clean the chamber after a process run and prior to loading the chamber with the work pieces for the next run.  
         [0071]     In some embodiments, as seen in  FIG. 15 , the active electrodes  1410  and the ground electrodes  1412  may span the interior of the process oven  104  vertically. The product trays  1411  may span the process oven  104  horizontally between the ground electrodes  1412 .  
         [0072]     In some embodiments, as seen in  FIG. 16 , there may be a plurality of vertical segments within the process oven  104 . The ground electrodes  1422  and the active electrodes  1420  reside vertically within the process oven  104 . The product trays  142  reside horizontally between ground electrodes  1422 .  
         [0073]      FIG. 6  shows a rear isometric view of apparatus  1001 .  FIG. 7  is a partial cutaway side view of one embodiment of the present invention.  FIG. 8  is a blown up section of the partial side view of  FIG. 7 .  FIG. 9  is a side view of one embodiment of the present invention.  FIG. 10  is a rear view of one embodiment of the present invention.  FIG. 11  is a top view of one embodiment of the present invention with the process door open.  FIG. 12  is a rear view of one embodiment of the present invention.  
         [0074]      FIG. 13  is a cutaway view of the vacuum subsystem and the chemical reservoir purge subsystem. A manufacturer&#39;s chemical source bottle  1304  is the chemical reservoir in this embodiment. The purge regulator  1307  feeds the purge manifold  1306  with a gas such as nitrogen. A 5 psi relief valve  1308  is located downstream from the purge manifold in this embodiment. Gas is routed to the bottle  1304  via a line  1301 . Line  1301  connects to a fitting  1303  which routes the gas from line  1301  into the head portion of the source bottle  1304 . The withdrawal line  1302  couple to the fitting  1305  for withdrawal of the chemical from the source bottle  1304 . The tube supplying chemical to the withdrawal line  1302  terminates near the bottom of the inside of source bottle  1304 . Line  1301  is delivered gas from the purge manifold  1306 .  
         [0075]     A process for the coating of substrates in a process chamber, which may include dehydrating the substrate, gas plasma cleaning of the substrate, and vaporizing the chemical to be reacted prior to its entry into the process chamber. Subsequent to the processing of the substrate, the chamber may be cleaned using gas plasma.  
         [0076]     A substrate for the chemical deposition of different chemicals may be of any of a variety of materials. For biotech applications, a glass substrate, or slide, is often used. Glass substrates may be borosilicate glass, sodalime glass, pure silica, or other types. Substrate dehydration may be performed as part of some processes. The glass slide is inserted into the process chamber. The slide is then dehydrated. Residual moisture interferes with the adhesion of chemicals during the deposition process. Alternatively, dehydration of the slide allows for later rehydration in a controlled fashion. The dehydration process alternates exposing the glass slide to vacuum and then to heated nitrogen, either once or multiple times. For example, the glass slide would be exposed to a vacuum of 10 Torr for 2 minutes. At this pressure water boils at about 11C. The vacuum chamber would then be flooded with preheated nitrogen at 150C. This part of the process would heat the surface of the glass slide so that the high temperature of the slide would assist in the dehydration process as vacuum was once again applied. After 3 complete cycles, a vacuum of 1 Torr would be applied to complete the dehydration process.  
         [0077]     A gas plasma cleaning cycle may also be used in preparation of the substrate for coating. In a typical process, the substrate is cleaned using gas plasma after the dehydration process. In some embodiments, the plasma cleaning cycle may occur before the dehydration process. In an exemplary process, the chamber is evacuated. A gas is then introduced into the chamber and the pressure is stabilized at a low pressure, such as 150-200 milliTorr. In some embodiments, the introduced gas in oxygen. In some embodiments, the introduced gas is a combination of oxygen and argon. In some embodiments, other gasses are used. After the stabilization of the pressure in the process chamber, the electrodes are powered to generate the plasma. In an exemplary process, the electrodes are powered to 450 Volts cycled at 40 kiloHertz. The power cycle may last for 2 minutes in some embodiments.  
         [0078]     After the completion of the dehydration and plasma cleaning cycles, the slide or substrate is ready for chemical reaction. Chemical reservoirs, such as manufacturer&#39;s source bottles, provide the chemical for the deposition process. For many processes, silanes are used. Among the silanes used are amino silanes, epoxy silanes, and mercapto silanes. Chemical may be withdrawn directly from the reservoir. A metered amount of chemical is withdrawn from the chemical reservoir. This may be done by opening a valve between the chemical reservoir and a withdrawal mechanism. The withdrawal mechanism may be a syringe pump. Chemical is withdrawn from the reservoir, enters the syringe pump, and then the valve between the chemical reservoir and the syringe pump is closed. The chemical reservoirs may be purged with an inert gas such as nitrogen. This purging allows for the filling of the volume of fluid removed with an inert gas, minimizing contact between the chemical in the reservoir and any air or moisture.  
         [0079]     Next, a valve between the syringe pump and a vaporization chamber is opened. The vapor chamber may be pre-heated. The vapor chamber may be a reduced pressure. The syringe pump then pumps the previously withdrawn chemical from the syringe pump to the vaporization chamber. The vapor chamber may be at the same vacuum level as the process oven. In parallel to this delivery of chemical to the vaporization chamber, a second chemical may be undergoing the same delivery process. The two chemicals may vaporize at substantially the same time. Additionally, more chemicals may also be delivered to the vaporization chamber, or to another vaporization chamber.  
         [0080]     In some embodiments, the chemical or chemicals to be vaporized may be withdrawn from the reservoir or reservoirs in a specific metered amount. This specific amount of withdrawal and delivery to the vapor chamber may be repeated until the desired amount of chemical or chemicals has been delivered into the vapor chamber. For example, a metering pump may be used. The metering pump may deliver a pre-determined amount of chemical per stroke of the metering pump. The number of pump strokes may be selected, thus delivering a specified amount of chemical.  
         [0081]     The reduced pressure in the vapor chamber, and/or the elevated temperature in the vapor chamber may allow for the vaporization of chemicals at pre-determined pressure levels and temperatures.  
         [0082]     The vaporized chemical, or chemicals, are then delivered to the process chamber. This may be done by opening a valve between the vaporization chamber and the process oven after the chemical has vaporized in the vaporization chamber. Alternatively, the valve between the vaporization chamber and the process oven may already be open when the chemical, or chemicals, are delivered to the vaporization chamber. The chemical then proceeds into the process chamber and reacts with the substrate.  
         [0083]     In some embodiments, the chemical may be added into the vapor chamber with the valve between the vapor chamber and the process chamber open. The chemical may be continued to be added into the vapor chamber until the vapor pressure in the process chamber reaches a desired level. At that time, the valve between the vapor chamber and the process chamber may be closed. The chemical may then remain in the process chamber for the desired amount of time for reaction.  
         [0084]     In some embodiments, the chamber may be cleaned using gas plasma subsequent to the processing steps. The chamber may be emptied of all workpieces and then cleaned. The gas plasma cleaning step subsequent to the processing steps helps prepare the process chamber for subsequent processing.  
         [0085]     As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details, representative apparatus and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant&#39;s general invention.