Patent Publication Number: US-2023142009-A1

Title: Split valve air curtain

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This patent application claims benefit of U.S. Provisional Patent Application No. 63/277,037 filed on Nov. 8, 2021 and titled “Slit Valve Air Curtain,” which is incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     With advances in semiconductor technology, there has been increasing demand for higher storage capacity, faster processing systems, higher performance, and lower costs. To meet these demands, the semiconductor industry continues to scale down the dimensions of semiconductor devices, such as metal oxide semiconductor field effect transistors (MOSFETs), including planar MOSFETs and fin field effect transistors (FinFETs). Such scaling down has increased the complexity of semiconductor manufacturing processes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with common practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG.  1 A  is a cross-sectional view of a via on a semiconductor wafer, in accordance with some embodiments. 
         FIG.  1 B  is an example surface chemical reaction for creating layers of the via shown in  FIG.  1 A , in accordance with some embodiments. 
         FIG.  2    is an illustrated flow diagram of a method for forming the via shown in  FIG.  1 A , in accordance with some embodiments. 
         FIG.  3    is a side elevation view of an interior of a processing chamber, in accordance with some embodiments. 
         FIG.  4 A  is a top plan view of an interior of a multi-chamber deposition equipment set, in accordance with some embodiments. 
         FIG.  4 B  is a series of cross-sectional views illustrating a process that occurs in the equipment set shown in  FIG.  4 A , in accordance with some embodiments. 
         FIG.  5    is a side elevation view of an interior of a processing chamber with a dual air curtain, in accordance with some embodiments. 
         FIG.  6 A  is a side elevation view of the processing chamber of  FIG.  5    during processing and while a slit valve is closed, in accordance with some embodiments. 
         FIG.  6 B  is a side elevation view of the processing chamber of  FIG.  5    during wafer unloading and while a slit valve is open, in accordance with some embodiments. 
         FIG.  7    is a simulated pressure map associated with a dual air curtain, in accordance with some embodiments. 
         FIG.  8    is a top plan view of an interior of a multi-chamber deposition equipment set with hardware enhancements for reducing contamination, in accordance with some embodiments. 
         FIG.  9    is a flow diagram of a method for implementing an automatic feedback control system to reduce contamination of a multi-chamber deposition equipment set, in accordance with some embodiments. 
         FIG.  10    is a block diagram of a computer system that can serve to implement various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed that are between the first and second features, such that the first and second features are not in direct contact. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     The term “nominal” as used herein refers to a desired, or target, value of a characteristic or parameter for a component or a process operation, set during the design phase of a product or a process, together with a range of values above and/or below the desired value. The range of values is typically due to slight variations in manufacturing processes or tolerances. 
     In some embodiments, the terms “about” and “substantially” can indicate a value of a given quantity that varies within 5% of a target value (e.g., ±1%, ±2%, ±3%, ±4%, and ±5% of the target value). 
     The term “vertical,” as used herein, means nominally perpendicular to the surface of a substrate. 
     It is to be appreciated that the Detailed Description section, and not the Abstract of the Disclosure section, is intended to be used to interpret the claims. The Abstract of the Disclosure section may set forth one or more but not all possible embodiments of the present disclosure as contemplated by the inventor(s), and thus, are not intended to limit the subjoined claims in any way. 
     During deposition of films in a process chamber, volatile substances can outgas and coat surfaces of the process chamber with chemical residues. When the coated surfaces cover moving parts of the process chamber, there can be a higher risk of disturbing accumulated residues and causing residue defects on the exposed surfaces of wafers during the semiconductor manufacturing process. Moving parts of the process chamber can include, for example, pressure valves or flow valves that open and close during processing, and entry/exit doors through which wafers pass during load and unload procedures. Through the use of in-situ particle monitoring and preventive measures that avoid or reduce changes in pressure and flow, the probability of generating residue defects can be reduced or eliminated, according to some embodiments of the present disclosure. Such improvements have multiple benefits, by increasing time between equipment maintenance events, improving product quality and yield, and increasing output efficiency. 
       FIG.  1 A  illustrates an exemplary film stack of via layers  100  formed on a semiconductor wafer as part of a metal interconnect structure, according to some embodiments. Via layers  100  can be deposited on a substrate  102 . 
     Substrate  102  can be a bulk semiconductor wafer or the top semiconductor layer of a semiconductor-on-insulator (SOI) wafer (not shown), such as silicon-on-insulator. In some embodiments, substrate  102  can include a crystalline semiconductor layer with its top surface parallel to (100), (110), (111), or c-(0001) crystal plane. In some embodiments, substrate  102  can be a glass or plastic substrate. Substrate  102  can be made of a semiconductor material such as, but is not limited to, silicon (Si). In some embodiments, substrate  102  can include (i) an elementary semiconductor, such as germanium (Ge); (ii) a compound semiconductor including silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs), and/or indium antimonide (InSb); (iii) an alloy semiconductor including silicon germanium carbide (SiGeC), silicon germanium (SiGe), gallium arsenic phosphide (GaAsP), gallium indium phosphide (InGaP), gallium indium arsenide (InGaAs), gallium indium arsenic phosphide (InGaAsP), aluminum indium arsenide (InAlAs), and/ or aluminum gallium arsenide (AlGaAs); or (iv) a combination thereof. Further, substrate  102  can be doped with p-type dopants (e.g., boron (B), indium (In), aluminum (Al), or gallium (Ga)) or n-type dopants (e.g., phosphorus (P) or arsenic (As)). In some embodiments, different portions of substrate  102  can have opposite type dopants. 
     In some embodiments, substrate  102  is a wafer, e.g., a semiconductor wafer, in which transistors or other electronic devices have been fabricated. A top layer of substrate  102  can be, for example, a contact layer that helps to form a low-resistivity electrical contact to underlying devices. Such a contact layer can be made of, for example, cobalt, nickel, or silicides thereof. In some embodiments, substrate  102  further includes, above the contact layer, a liner made of e.g., titanium, titanium nitride, or a combination thereof. 
     Via layers  100  can include, for example, a seed layer  106 , and a bulk metal  108 , surrounded by a sidewall insulating material  110  and an inter-layer dielectric (ILD)  112 . In some embodiments, seed layer  106  and bulk metal  108  both include the same primary metal component, e.g., tungsten (W). Seed layer  106  can have a thickness between about 27 Å and about 33 Å. ILD  112  can include silicon dioxide (SiO 2 ) or a low-k dielectric material such as, for example, a fluorosilicate glass, a carbon-doped silicon dioxide, a porous silicon dioxide, a porous carbon-doped silicon dioxide, a polyimide, or a polytetrafluoroethylene (PTFE). Via layers  100  are used to illustrate the present disclosure by way of example. However, the present disclosure is not so limited. Other film stacks may pose a similar defect risk as the via layers described herein. 
       FIG.  1 B  illustrates formation of seed layer  106 , according to some embodiments. Seed layer  106  can be deposited onto substrate  102  under vacuum by, for example, chemical vapor deposition (CVD) or plasma enhanced chemical vapor deposition (PECVD), by exposing substrate  102  to a gas mixture containing boron hexafluoride (B 2 H 6 ) and tungsten hexafluoride (WF 6 ) gases. When the fluorine component of WF 6  dissociates and reacts chemically with B 2 H 6 , tungsten is deposited onto substrate  102 , and the fluorine, boron, and hydrogen components are released as volatile reaction products. Volatilized chemicals may then fill the vacuum chamber and coat interior walls during the reaction phase, before the chamber is evacuated. Seed layer  106  is used to illustrate the present disclosure by way of example. However, the present disclosure is not so limited. Deposition of other seed layers, or other types of layers, may pose a similar defect risk as seed layer  106  that is described herein. 
       FIG.  2    shows an exemplary method  200  that can be executed in a multi-chamber deposition equipment set  220 , according to some embodiments. Method  200  can be used to form the conductive seed and bulk tungsten layers of the stack of via layers  100  shown in  FIG.  1 A . A top-down view of multi-chamber deposition equipment set  220  is provided in  FIG.  2    for each operation in method  200 . In some embodiments, multi-chamber deposition equipment set  220  includes a plurality of load stations  221  (for example, three load stations,  221   a - 221   c , are shown in  FIG.  2   ), an entrance load lock  222 , a buffer chamber  223 , a plurality of process chambers  224  (for example, four process chambers,  224   a - 224   d , are shown in  FIG.  2   ), and an exit load lock  226 . Multi-chamber deposition equipment set  220  can further include one or more robots for automated transfer of wafers to and from the various stations and chambers, or modules. In some embodiments, buffer chamber  223  and process chambers  224  stay under vacuum, while load locks  222  and  226 , adjoining both buffer chamber  223  and load stations  221 , alternate between atmospheric pressure and vacuum. Process chambers  224  are plumbed with process gases to chemically alter the surface of the wafer being processed, while buffer chamber  223  is used for transferring wafers among process chambers  224 . In some embodiments, one or more process chambers  224  can be configured for CVD or for PECVD, with the addition of an energy source that can ionize process gases to create a plasma. In some embodiments, one or more process chambers  224  can be configured as a variant of CVD, such as atomic layer deposition (ALD) or spatial atomic layer deposition (SALD), in which surface reactions create films on the wafer in process, one atomic layer at a time. An exemplary equipment configuration for multi-chamber deposition equipment set  220  is used to illustrate the present disclosure by way of example. However, the present disclosure is not so limited. Other equipment configurations, or other equipment sets used for deposition and/or etching of films on wafers, can pose a similar defect risk as the examples described herein. 
     In accordance with exemplary method  200 , an automated robot can be programmed to transfer a single wafer through multi-chamber deposition equipment set  220 . At operation  202 , the wafer can be transferred from a front opening unified pod (FOUP) positioned at load station  221   a  of multi-chamber deposition equipment set  220  to a seed layer deposition chamber  224   c  via entrance load lock  222  and buffer chamber  223 . Entrance load lock  222  can have two doors (not shown) so that a wafer enters entrance load lock  222  at atmospheric pressure, from load station  221   a  through a first door, then entrance load lock  222  is evacuated, and the wafer exits entrance load lock  222  under vacuum, into buffer chamber  223  through a second door. At operation  204 , seed layer  106  is deposited onto the wafer in seed layer deposition chamber  224   c . At operation  206 , the wafer is transferred from seed layer deposition chamber  224   c  to bulk layer deposition chamber  224   d  via buffer chamber  223 . At operation  208 , bulk metal  108  is deposited onto the wafer in bulk layer deposition chamber  224   d . At operation  210 , the wafer is transferred from bulk layer deposition chamber  224   d  via buffer chamber  223  and exit load lock  226 , back to the FOUP at load station  221   a  of multi-chamber deposition equipment set  220 . Exit load lock  226  can have two doors (not shown) so that the wafer enters exit load lock  226  from buffer chamber  223  under vacuum, through a first door, exit load lock  226  is pressurized, and the wafer is removed from exit load lock  222 , at atmospheric pressure, through a second door for loading back into the FOUP at load station  221   a.    
     Referring to  FIG.  2   , in operation  204 , contaminants  300  are formed within seed layer deposition chamber  224   c  as shown in  FIG.  3   .  FIG.  3    illustrates an interior view of seed layer deposition chamber  224   c , according to some embodiments. Seed layer deposition chamber  224   c  can have components such as a pump  302 , a heated chuck  304 , a showerhead  306 , and a slit valve  308 . Slit valve  308  serves as a doorway for loading and unloading wafers onto heated chuck  304  for processing. Gas phase reactants enter seed layer deposition chamber  224   c  through showerhead  306 , and react at the surface of substrate  102  to form seed layer  106 . Residual gases and reaction products exit seed layer deposition chamber  224   c  via pump  302 . In some embodiments, the temperature of heated chuck  304  is between about 270 degrees C. and about 330 degrees C. Heated chuck  304  may catalyze surface reactions, and/or increase a deposition rate of seed layer  106 . The temperature of heated chuck  304  can affect the smoothness of the surface of seed layer  106 . Heated chuck  304  may also cause evaporation or outgassing of chemicals from the surface of seed layer  106 , which chemicals can condense into contaminants  300 . In some embodiments, contaminants  300  are as large as about  10  nm in diameter. The composition of contaminants  300  can include tungsten, titanium, and nitrogen, with tungsten being the most prevalent species. Although pump  302  is intended to remove residual gases from seed layer deposition chamber  224   c , contaminants  300  that are not captured by pump  302  can accumulate on slit valve  308 . After some period of time, when a thick enough layer forms on slit valve  308 , motion of slit valve  308  while opening and closing can dislodge contaminants  300 , creating a particle source that can impact wafers as they pass through slit valve  308 . 
     Referring to  FIG.  2   , in operations  204  and  206 , formation and migration of contaminants  300  can occur as shown in  FIG.  4 A .  FIG.  4 A  shows an enlarged view of multi-chamber deposition equipment set  220  during operations  204  and  206 .  FIG.  4 A  further illustrates contaminants  300 , which may be generated during operation  204  as described above, migrating out of seed layer deposition chamber  224   c , into buffer chamber  223 , during wafer transfer to bulk layer deposition chamber  224   d  in operation  206 . As the wafer moves out of seed layer deposition chamber  224   c  through slit valve  308 , in addition to residues being dislodged by motion of slit valve  308 , changes in gas flows and/or chamber pressure may further disturb residues and spread contaminants to other areas of multi-chamber deposition equipment set  220 . Such residues can impact wafers, causing contaminants  300  to accumulate on the top surface of seed layer  106 . Contaminants  300  may also be swept out from seed layer deposition chamber  224   c  as the wafer passes along a transfer path  400  into buffer chamber  223 . In addition, wafers may continue to outgas volatile reaction products from seed layer  106  while they are being transported through buffer chamber  223 , thus contaminating buffer chamber  223 . 
     Referring still to  FIG.  2   , in operations  204  and  206 , an effect of contaminants  300  at the interface between seed layer  106  and bulk metal  108  on a wafer is illustrated in  FIG.  4 B .  FIG.  4 B  shows the wafer at three successive times during operations  204 - 206 . In a top frame of  FIG.  4 B , at time t 1 , the wafer is shown after deposition of seed layer  106  has been completed, while the wafer is still in seed layer deposition chamber  224   c . In a middle frame of  FIG.  4 B , at time t 2 , contaminants  300  land on seed layer  106  as the wafer exits process chamber  224   c  through slit valve  308  and into buffer chamber  223 . In a bottom frame of  FIG.  4 B , contaminants  300  remain on the surface of the wafer as it continues along transfer path  400 , into bulk layer deposition chamber  224   d  for processing at operation  206 . Bulk metal  108  is then deposited over contaminants  300 , which intervene between seed layer  106  and bulk metal  108 . The presence of contaminants  300  at the interface between the two tungsten layers will thus obstruct electrical contact at the interface and will introduce via resistance that can result in reduced device performance. 
       FIG.  5    illustrates an interior view of seed layer deposition chamber  224   c  shown in  FIG.  3   , following implementation of a dual air curtain  500 , according to some embodiments. Dual air curtain  500  can be disposed between slit valve  308  and pump  302 , so that wafers pass through dual air curtain  500  while loading and unloading from seed layer deposition chamber  224   c . When it is positioned above pump  302 , dual air curtain  500  produces a region of laminar flow that separates the processing area of seed layer deposition chamber  224   c  between heated chuck  304  and showerhead  306  from the wafer transfer area near slot valve  308 . Dual air curtain  500  can be designed to flow first and second inert gases,  502  and  504 , respectively at flow rates in the range of about 500 standard cubic centimeters per minute (sccm) to about 1000 sccm. In some embodiments, nitrogen gas (N 2 ) is used as first inert gas  502  and argon (Ar) us used as second inert gas  504 . Alternatively, other inert gases, e.g., helium (He) or oxygen (O 2 ), can be used. In some embodiments, the same gas can be used as both first and second inert gases  502  and  504 . 
     Dual air curtain  500  can alter the motion of contaminants  300  by directing outgassed reaction products toward pump  302  for removal from seed layer deposition chamber  224   c . Dual air curtain  500  therefore can prevent contaminants  300  from accumulating on slit valve  308 . When only a thin layer of contaminants  300  accumulates on slit valve  308 , the thin layer is more likely to stay intact. Thus, the likelihood of flaking and causing defects on processed wafers is lowered. In addition, the presence of dual air curtain  500  increases pressure inside seed layer deposition chamber  224   c , which allows increasing pressure in the buffer chamber to balance the chamber pressure and prevent contaminants from rushing out of seed layer deposition chamber  224   c  during wafer transfer. In some embodiments, the buffer chamber pressure can be set to about 250 mTorr. 
     Referring to  FIGS.  6 A and  6 B , dual air curtain  500  can be implemented to flow different inert gases at different times, in accordance with some embodiments.  FIG.  6 A  shows an operation of dual air curtain  500  at time t A  when a wafer is present on heated chuck  304  and is being processed in seed layer deposition chamber  224   c , while slit valve  308  is closed. At time t A , dual air curtain  500  can be programmed to initiate flow of second inert gas  504 , e.g., Ar, to direct reaction byproducts and contaminants  300  toward pump  302 . As chemicals outgas from the surface of seed layer  106 , dual air curtain  500  blocks motion of volatilized species from contaminating slit valve  308  or migrating to buffer chamber  123 . 
       FIG.  6 B  shows an operation of dual air curtain  500  at time t B  when a wafer is being unloaded from seed layer deposition chamber  224   c  and slit valve  308  is open. At time t B , dual air curtain  500  can be programmed to turn off the flow of second gas  504  and turn on the flow of first inert gas  502 , e.g., N 2 , to direct reaction byproducts and contaminants  300  toward pump  302 . As the wafer is transported out of the chamber towards open slit valve  308 , the flow of inert gas  502  through dual air curtain  500  sweeps volatilized species from the surface of seed layer  106 , confining contaminants  300  to the chamber, where they can be removed by pump  302 . 
     In some embodiments, different gases can be plumbed to dual air curtain  500 , and flow control can be tailored to specific processes other than the example of depositing seed layer  106 . For example, dual air curtain  500  can be programmed to flow any combination of first and second inert gases at various times, as needed for the process that is being used in the chamber. In some embodiments, dual air curtain  500  can be implemented on other types of semiconductor process equipment with etching chambers instead of, or in addition to, deposition chambers. In some embodiments, dual air curtain  500  can be implemented on other platforms that may not include vacuum chambers, such as a solvent station for a lithography track where outgassing of volatile solvent chemicals can pose a similar problem to the outgassing described herein. 
       FIG.  7    shows a magnified view of dual air curtain  500  in operation, with first inert gas  502  providing laminar flow.  FIG.  7    corresponds to region indicated in  FIG.  6 B  by a dotted line box  700 , in which dual air curtain  500  is implemented on seed layer deposition chamber  224   c , as described above with respect to  FIG.  6 B . In  FIG.  7   , the wafer is not in transit, allowing for laminar flow to proceed unobstructed.  FIG.  7    shows simulated pressure gradients in the vicinity of slit valve  308 , defined in  FIG.  7    as slit valve channel  702 .  FIG.  7    also shows simulated pressure gradients in a laminar flow region  704  between dual air curtain  500  and the inlet of pump  302 . 
     In  FIG.  7   , regions of lowest pressure are in laminar flow region  704  and to the right of laminar flow region  704 , where the pressure can be less than 100 mTorr. A medium pressure region exists where slit valve channel  702  joins laminar flow region  704 , on the left side of laminar flow region  704 , where the pressure can be in the range of about 100-150 mTorr. The highest pressures are in slit valve channel  702 , farthest away from pump  302 , where pressure values can be greater than about 200 mTorr. 
       FIG.  8    shows the multi-chamber deposition equipment set  220  of  FIG.  4 A , implemented with additional hardware solutions to further reduce contamination from outgassing due to deposition of seed layer  106 , according to some embodiments. Additional hardware solutions shown in  FIG.  8    include a chamber throttle valve  800  for improving control of pump  302 , a buffer chamber throttle valve  802  for regulating pressure in buffer chamber  223 , and a residual gas analyzer (RGA) monitor  804  installed in buffer chamber  223 . Additionally or alternatively, RGA monitor  804  can be installed in other chambers of multi-chamber deposition equipment set  220 . RGA monitor  804  measures gas composition of contaminants  300  using mass spectrometry. When installed in buffer chamber  223 , RGA monitor  804  can act as an in-situ process monitor to help determine, from the composition of detected contaminants, which chamber of multi-chamber deposition equipment set  220  is the source of detected contaminants. 
     Throttle valves  800  and  802  can be configured separately, or in a coordinated fashion, to regulate a differential pressure between buffer chamber  223  and a chamber of multi-chamber deposition equipment set  220  with slit valve  308 , e.g., seed deposition chamber  224   c . With improved pressure regulation provided by throttle valves  800  and  802 , changes in pressure can be avoided, reducing the probability of disturbing residue buildup on slit valve  308 . In addition, the action of pump  302  and a separate buffer chamber pump (not shown) can be varied using throttle valves  800  and  802 , respectively, according to process needs, to more quickly evacuate volatilized species, thereby preventing residues from forming on equipment surfaces. 
     RGA monitor  804  and throttle valves  800  and  802  can be implemented together as a feedback control system to reduce effects of contaminants  300 , and to reduce contamination of buffer chamber  223  and bulk deposition chamber  224   d . Using RGA monitor  804  in-situ, while wafers are in process and in transit, throttle valves  800  and  802  can be adjusted in accordance with detected contaminant levels. Operation of dual air curtain  500  can also be implemented within the feedback control system 
       FIG.  9    illustrates an exemplary method  900  for providing real-time feedback control of hardware solutions shown in  FIG.  8   , during execution of steps  204  and  206  within method  200 , in accordance with some embodiments. Method  900  uses data from multiple types of monitors, in combination, for controlling multiple hardware elements installed in multi-chamber deposition equipment set  220  to reduce contamination from outgassing. 
     At operation  902 , an in-situ RGA measurement is performed to detect contaminants in buffer chamber  123 . 
     At operation  904 , a level of contaminants, e.g., contaminants having tungsten composition, determined in operation  902  is compared against a standard for failure data collection (FDC) to determine whether or not the contaminant level is within a maximum allowed limit. When the contaminant level is below a threshold value, method  200  continues and subsequent RGA measurements continue to be performed at operation  902  at prescribed time intervals. 
     At operation  906 , when the level of contaminants determined in operation  902  exceeds the threshold value, which may indicate, for example, a burst of contaminants following opening of slit valve  308 , the status of an equipment particle monitor is checked using a tool automation program (TAP) to see if there is a commensurate increase in particle trend data. 
     Equipment particle data may be stored on a tool server and may be used for statistical process control (SPC) of multi-chamber deposition equipment set  220 . In some embodiments, SPC refers to collecting equipment particle data on test wafers and/or collecting in-line defect data on product wafers, at regular time intervals, and monitoring particle trends in real time. Using SPC, outliers in the data can be recognized to control the process. Automated statistical control, using 3-sigma or 6-sigma (double-sided) threshold values, flags anomalies in particle data trends so that action can be taken to contain product and to address equipment failures. SPC can be used to monitor either equipment sets, individual chambers, or both. 
     At operation  908 , numerical values of the RGA and equipment monitors can be combined to determine a composite particle score. Based on the composite particle score and/or a relative contribution of various particle monitor values to the overall particle score, equipment adjustment values can be determined and, if needed, can be codified in a recipe modification summary (RMS). For example, when the composite score exceeds a predetermined threshold, further investigation can be carried out to determine whether the largest contribution is from the RGA monitor in buffer chamber  223  or from specific automated tool monitors of individual process chambers  224 . If the contribution can be narrowed down to a specific chamber, e.g., process chamber  224   c , maintenance can be done on the chamber to confirm the particle signature and eliminate the root cause of particles, for example, slit valve accumulation and flaking. The response to an out-of-control particle monitor may be to replace a contaminated slit valve  308 . On the other hand, if the RGA monitor is the larger contributor, the root cause may be narrowed down to facilities contamination, e.g., gas lines or pumps, or to contaminants coming from the product itself, e.g., outgassing. The response to an out-of-control RGA monitor may be to adjust the operation of dual air curtain  500 . One advantage of using the RGA monitor and/or the RMS monitor is that the RGA monitor operates continuously, whereas SPC data is intermittent or periodic. So, the RGA monitor may flag a problem earlier than a periodic equipment particle monitor would. 
     At operation  910 , adjustments to hardware elements are made according to the determined equipment adjustment values. Based on one or more of an RGA value, a TAP value, and an RMS value, relative flow rates of first and second inert gases  502  and  504  of dual air curtain  500  can be modified. For example, in response to an RGA value indicating an increase in contaminants  300  within buffer chamber  223 , the flow of first inert gas  502  through dual air curtain  500  can be increased. This would ensure that when wafers are transferred from process chamber  224   c , outgassed contaminants  300  do not enter buffer chamber  223 . In response to a TAP value indicating an increase in particles within process chamber  224 , the flow of second inert gas  504  through dual air curtain  500  can be increased. This would ensure that while wafers are being processed in chamber  224   c , outgassed contaminants  300  are swept into the draft of pump  302  before they can accumulate on slit valve  308 . 
     Additionally or alternatively, settings for chamber throttle valve  800  can be adjusted, or settings for buffer chamber throttle valve  802  can be adjusted based on one or more of the RGA value, TAP value, and RMS value. For example, in response to an equipment particle monitor or TAP value increasing beyond a threshold value, throttle valves  800  and/or  802  can be opened so as to evacuate the chambers more quickly, thereby reducing the particulate load. 
     Method  900  can be implemented with any combination of monitors contributing to the RMS calculation in operation  908 , and any combination of adjustments made at operation  910 , in response to the monitor data. Any or all of the equipment adjustments made at operation  910  can be made in real time, in response to real-time measurements. Thus, processing of wafers can be adjusted based on varying contamination levels, as they occur, without sacrificing yield. 
       FIG.  10    is an illustration of an example computer system  1000  in which various embodiments of the present disclosure can be implemented. Computer system  1000  can be any well-known computer capable of performing the functions and operations described herein. Computer system  1000  can be used, for example, to execute one or more operations in method  200  of  FIG.  2    and method  900  of  FIG.  9   . 
     Computer system  1000  includes one or more processors (also called central processing units, or CPUs), such as a processor  1004 . Processor  1004  is connected to a communication infrastructure or bus  1006 . Computer system  1000  also includes input/output device(s)  1003 , such as monitors, keyboards, pointing devices, etc., that communicate with communication infrastructure or bus  1006  through input/output interface(s)  1002 . Computer system  1000  also includes a main or primary memory  1008 , such as random access memory (RAM). Main memory  1008  can include one or more levels of cache. Main memory  1008  has stored therein control logic (e.g., computer software) and/or data. In some embodiments, the control logic (e.g., computer software) and/or data can include one or more of the operations described above with respect to method  200  of  FIG.  2    and method  900  of  FIG.  9   . 
     Computer system  1000  can also include one or more secondary storage devices or memory  610 . Secondary memory  1010  can include, for example, a hard disk drive  1012  and/or a removable storage device or drive  1014 . Removable storage drive  1014  can be a floppy disk drive, a magnetic tape drive, a compact disk drive, an optical storage device, tape backup device, and/or any other storage device/drive. 
     Removable storage drive  1014  can interact with a removable storage unit  1018 . Removable storage unit  1018  includes a computer usable or readable storage device having stored thereon computer software (control logic) and/or data. Removable storage unit  1018  can be a floppy disk, magnetic tape, compact disk, DVD, optical storage disk, and/ any other computer data storage device. Removable storage drive  1014  reads from and/or writes to removable storage unit  1018  in a well-known manner. 
     According to some embodiments, secondary memory  1010  can include other means, instrumentalities or other approaches for allowing computer programs and/or other instructions and/or data to be accessed by computer system  1000 . Such means, instrumentalities or other approaches can include, for example, a removable storage unit  1022  and an interface  1020 . Examples of the removable storage unit  1022  and the interface  1020  can include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM or PROM) and associated socket, a memory stick and USB port, a memory card and associated memory card slot, and/or any other removable storage unit and associated interface. In some embodiments, secondary memory  1010 , removable storage unit  1018 , and/or removable storage unit  1022  can include one or more of the operations described above with respect to method  900  of  FIG.  9   . 
     Computer system  1000  can further include a communication or network interface  1024 . Communication interface  1024  enables computer system  1000  to communicate and interact with any combination of remote devices, remote networks, remote entities, etc. (individually and collectively referenced by reference number  1028 ). For example, communication interface  1024  can allow computer system  1000  to communicate with remote devices  1028  over communications path  1026 , which can be wired and/or wireless, and which can include any combination of LANs, WANs, the Internet, etc. Control logic and/or data can be transmitted to and from computer system  1000  via communication path  1026 . 
     The operations in the preceding embodiments can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding embodiments—e.g., method  200  of  FIG.  2    and method  900  of  FIG.  9   —can be performed in hardware, in software or both. In some embodiments, a tangible apparatus or article of manufacture comprising a tangible computer useable or readable medium having control logic (software) stored thereon is also referred to herein as a computer program product or program storage device. This includes, but is not limited to, computer system  1000 , main memory  1008 , secondary memory  1010  and removable storage units  1018  and  1022 , as well as tangible articles of manufacture embodying any combination of the foregoing. Such control logic, when executed by one or more data processing devices (such as computer system  1000 ), causes such data processing devices to operate as described herein. 
     Semiconductor processing equipment can be configured with specialty hardware to reduce the effects of contamination that arises from the process itself, for example, from outgassing following film deposition. Such hardware can include throttle valves for regulating pump speed and efficiency, and air curtains such as a dual air curtain installed at the entrance to a process chamber. The dual air curtain can be programmable, and each of the hardware items can be controlled automatically in real time using in-situ monitoring of the process, combined with data from periodic equipment monitors that is stored on a server. A feedback control system can be used to make equipment adjustments that are tailored for certain processes, as needed. 
     In some embodiments, a method includes: loading a wafer into a buffer chamber; transferring the wafer from the buffer chamber to a process chamber including a slit valve, a pump, and a dual air curtain disposed between the slit valve and the pump; processing the wafer in the process chamber; and transferring the wafer from the process chamber to the buffer chamber. 
     In some embodiments, a system includes: a wafer station; a load lock adjoining the wafer station, the load lock configured to alternate between atmospheric pressure and vacuum; a buffer chamber adjoining the load lock; a vacuum chamber adjoining the buffer chamber and including a showerhead and a slit valve, the vacuum chamber configured to expose a wafer to a vaporized chemical from the showerhead; and a dual air curtain between the slit valve and the showerhead and configured to flow a plurality of gases. 
     In some embodiments, a method includes: detecting a level of contaminants in a buffer chamber using an in-situ residual gas analyzer (RGA) monitor; collecting data from a tool server; analyzing the level of contaminants together with the data from the tool server to determine one or more adjustment values; and in response to the level of contaminants being above a first threshold, adjust relative flow rates of different inert gases flowing through a dual air curtain based on the one or more adjustment values. 
     The foregoing disclosure outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art will appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art will also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.