Abstract:
Provided herein is a double dual slot load lock chamber. The double dual slot load lock chamber includes two isolated load lock regions that are vertically stacked and share a common wall, wherein each isolated load lock region comprises two substrate slots.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 11/278,318, filed Mar. 31, 2006 now U.S. Pat. No. 7,316,966 which is a divisional of U.S. patent application Ser. No. 09/957,784, filed Sep. 21, 2001, now U.S. Pat. No. 7,105,463, which claims benefit of U.S. patent application Ser. No. 09/663,862, filed Sep. 15, 2000, now abandoned. Each of the aforementioned related patent applications is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the fields of semiconductor manufacturing. More specifically, the present invention relates to a semiconductor wafer or glass substrate processing system comprising a double dual slot load lock and uses thereof. 
     2. Description of the Related Art 
     The need for greater throughput and yield in the manufacture of semiconductor devices has driven the development and use of more highly automated wafer processing machines. Also, the desire to minimize wafer particulate contamination during processing has led to the use of vacuum load locks and wafer transport mechanisms which operate in vacuum. 
     In continuous throughput systems, wafers must be introduced into the vacuum chamber through a load lock in order to prevent exposing the vacuum condition in the chamber to the air outside the chamber. When a wafer is to be loaded into the chamber, the inner closure means, such as a sealing plate, is activated to seal the inner side of the opening, and then the outer closure means, such as a sealing door, is opened. Next the door is opened, a wafer is inserted through the opening, and the door is again closed. The load lock chamber now containing the wafer is pumped down to contain an atmosphere compatible with the atmosphere in the processing vacuum chamber, and then the inner sealing plate is moved away from the opening to expose the wafer for processing in the main vacuum chamber. To increase the throughout, some systems employ two load lock chambers so that processing of wafers can continue uninterrupted by a delay caused by the need to open, empty, reload and re-equilibrate a single load lock chamber. 
     Despite the increased vacuum isolation, the state-of-the-art systems typically have difficulty providing commercially acceptable throughput for high vacuum processes. Presently, typical load lock chambers employ sliding or rotating valves to isolate a single wafer. Such load locks require a pumpdown cycle for each wafer processed and thus inhibit throughput. In addition, the load locks are typically in-line devices; that is, wafers pass in a straight line through the load lock. This substantially contributes to the overall width of the wafer processing machine. Furthermore, in the prior art designs, mechanical feedthroughs, which are used to transmit motion through a vacuum seal, have not been adequate to the task of simultaneously operating a load lock valve and indexing an internal wafer cassette. 
     Therefore, the prior art is deficient in the lack of effective system/means of processing substrates in a high throughput fashion and meanwhile minimizing particulate contamination during processing. Specifically, the prior art is deficient in the lack of a highly automated substrate processing system comprising double dual slot load locks constructed at one body. The present invention fulfills this long-standing need and desire in the art. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, there is provided herein a double dual slot load lock chamber. The double dual slot load lock chamber includes two isolated load lock regions that are vertically stacked and share a common wall, wherein each isolated load lock region comprises two substrate slots. 
     In another aspect of the present invention, there is provided a substrate processing system, which comprises a cassette load station; a load lock chamber; a centrally located transfer chamber; and one or more process chambers located about the periphery of the transfer chamber. In this system, the load lock chamber comprises two dual slot load locks constructed at same location. 
     In another aspect of the present invention, there is provided a method of processing substrates in the system disclosed herein for semiconductor manufacturing. This method comprises the following steps: first, moving substrates from the cassette load station to the transfer chamber through the load lock chamber; secondly, transferring the substrates from the transfer chamber to the process chambers; thirdly, processing the substrates in the process chambers; and lastly, unloading the processed substrates from the process chambers to the same cassette load station through the same load lock chamber. In this method, one load lock is in a vacuum condition and the other load lock is in an atmospheric/venting condition at the same time. 
     Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the embodiments of the invention given for the purpose of disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features, advantages and objects of the invention, as well as others which will become clear, are attained and can be understood in detail, more particular descriptions of the invention, briefly summarized above may be had by reference to certain embodiments thereof which are illustrated in the appended drawings. These drawings form a part of the specification. It is to be noted, however, that the appended drawings illustrate embodiments of the invention and therefore are not to be considered limiting in their scope. 
         FIG. 1  is an overview of the presently disclosed system, i.e., AKT Gen4 with AGV/MGV interface and atmospheric cassette load station (ACLS), comprising a cassette load station  101 , a load lock chamber  102 , a central transfer chamber  103 , one or more process chambers  104 , a heat chamber  105 , and control towers and gas chamber  106 . 
         FIG. 2  is an overview of system AKT Gen4 with a substrate transferring link  107 . 
         FIG. 3  is a side view of double dual slot load lock and transfer chamber construction in system AKT Gen4. 
         FIG. 4  is a schematic drawing demonstrating loading and unloading of a pre-processed substrate using the double dual slot load lock, wherein the substrate is loaded from ACLS to the upper load lock, and then unloaded to the transfer chamber through the lower load lock. 
         FIG. 5  is a schematic drawing demonstrating loading and unloading of a pre-processed substrate using the double dual slot load lock, wherein the substrate is loaded from ACLS to the lower load lock, and then unloaded to the transfer chamber through the upper load lock. 
         FIG. 6  is a schematic drawing demonstrating loading and unloading of a processed substrate using the double dual slot load lock, wherein the substrate is loaded from the transfer chamber to the lower load lock, and then unloaded to ACLS through the upper load lock. 
         FIG. 7  is a schematic drawing demonstrating pumping and venting processes which take place in the double dual slot load lock. Specifically, filtered diffuser N 2  vent is used for cooling a processed substrate when venting. 
         FIGS. 8A-8C  show system size comparison among AKT5500  150  (state-of-art system) (Figure A), AKT stretch  160  (Figure B), and AKT Gen4  170  (Figure C). The AKT stretch  160  is 133% stretch of AKT5500  150  and a traditional approach to AKT Gen4  170 . Both AKT5500  150  and AKT stretch  160  have two dual slot load locks which are constructed at two locations, whereas AKT Gen4  170  has one double dual slot load lock. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Provided herein is a semiconductor wafer processing system, comprising a cassette load station  101 , load lock chamber  102 , a central transfer chamber  103 , one or more process chambers  104 , a heat chamber  105 , and control towers and gas chamber  106  ( FIG. 1 ). 
     The load lock chamber  102  is provided for transferring wafers between the transfer chamber  103 , which is typically at high vacuum, and the outside, typically a clean room at atmospheric pressure. The central transfer chamber  103  is provided with a vacuum transfer robot located therein for transferring wafers between the load lock chamber  102  and the process chambers  104 /heat chamber  105 , which are located about the periphery of the transfer chamber  103 .  FIG. 2  is an over view of the system with substrate transferring link  107 . 
     Specifically, the load lock chamber  102  comprises double dual slot load lock constructed at one body (i.e., one location, in one chamber). Each load lock has dual slot load lock (DSL) function: upper slot for loading pre-processed substrate from cassette load station  101  (atmospheric side); and lower slot for unloading processed substrate to cassette load station  101  (atmospheric side). In most cases, the substrate is a wafer or a glass substrate. 
     Substrates are loaded/unloaded by both vacuum robot and atmospheric robot. Vacuum robot in the central transfer chamber  103  passes substrates through slit valves in the various connected processing chambers  104  or heater chamber  105  and retrieves them after processing in the chambers is complete. Access between the individual process chambers  104  and between the transfer chamber  103  and the load lock chamber  102  is via flip door type slit valves which selectively isolate the process chambers  104  or heat chamber  105  from the robot (in transfer chamber  103 ) and the robot from the load lock chamber  102 . However, the load lock chamber at the atmospheric side may have other than flip door type slit valves. Other doors may also be used to separate the vacuum condition in the load lock chamber from the atmospheric condition outside the chamber. 
       FIG. 3  is a system side view showing the construction of double dual slot load lock  102  and the transfer chamber  103 . The flip type valve  113  is closed from the atmospheric side, which makes it possible to keep load lock vacuum condition with small torque actuator. The valve  113  is always operated below the substrate transferring plane to reduce particle exposure and opens before loading and unloading of a substrate. 
     This system configuration permits processing in one or more chambers while wafers are being loaded or unloaded at other process chambers or at the load lock chamber  102  and permits wafer transfer from one processing chamber to another via the transfer chamber  103 . Different processes may be simultaneously performed on different substrates at different process chambers. Each wafer which is dispensed from load lock may be stepped through the same process steps to produce the same type of wafer. Alternatively, different wafers from the same load lock may be programmed to undergo a different ‘recipe” involving different steps and/or process times, such that different types of wafers are produced. 
     Specifically, the vacuum robot  118  was operated by Z-drive  117  in an up-and-down motion. The Z-drive shaft is a vacuum seal constructed in chambers with nitrogen purge and vacuum at the same time. 
     The above-disclosed system can be used for processing substrates for semiconductor manufacturing. In more specific detail, pre-processed substrates are loaded into the upper slot  120  via opening  110  in one of the load locks from the cassette load station ( FIGS. 4-5 ). The upper slot  120  optionally has a heating plate for heating up the substrates. The heating plate is either a stationary plate or a moving plate. It can approximate to the substrates by Z-drive to increase the heating efficiency. During pumping, the heating temperature can be up to 400° C. The heated substrates are then unloaded from the other load lock via opening  111  to the transfer chamber, and further to the process chambers for processing, or to the heat chamber for either preheating or annealing. 
     After processing in the chambers is complete, the processed substrates are then unloaded from the lower slot  124  in one of the load locks to the cassette load station ( FIG. 6 ). Lower slot has a cooling plate  125  for cooling down the processed substrates. The cooling plate  125  is either a stationary plate or moving plate and it can approximate to the substrates by Z-drive to increase the cooling efficiency. Also, a small amount of helium gas (He) can be supplied with nitrogen gas (N2) for cooling. Filtered diffuser N2 vent  133  is used to prevent particle generation in the load locks ( FIG. 7 ). During venting, the temperature can be cooled down from 350° C. to 80° C. When operated, each load lock loads and unloads substrates separately. Normally, one is venting and the other is pumping so that the vacuum pump can be shared between the two load locks. 
     The double dual slot load lock (DDSL) system disclosed herein provides several advantages in comparison with traditional one DSL system, such as AKT5500 or AKT stretch ( FIGS. 8A-8C ). First, constructing two dual slot load lock at one body (one location) can increase system cost performance, i.e., minimize system footprint and increase system throughput that was restricted by the load lock pumping/venting activity. For a traditional one dual slot load lock system (with 4 process chambers), the system maximum throughput determined by the load lock activity is approximately 30 substrate/hour. In contrast, for one embodiment of the double dual slot load lock system disclosed herein, the system maximum throughput is approximately 60 substrate/hour. For example, a single layer firm (passivation) process has a throughput of approximately 26 substrate/hour for traditional one DSL system, while for one embodiment of the double dual slot load lock system disclosed herein, the passivation process has a throughput of approximately 50 substrate/hour. Since the throughput is restricted by load lock activity, a traditional one DSL system with 3 process chambers has the same throughput as the one with 4 process chambers. For active layer process, a traditional one DSL system (with 4 process chambers) has a throughput of approximately 18 substrate/hour, the same as for one embodiment of the double dual slot load lock system disclosed herein. In this case, the system throughput is the same for both one and double DSL systems, therefore system can use one of the two dual slot load lock. Most customers prefer a system that is capable of switching the process based on the production situation, therefore the system has to be configured to handle quick process. For example, the system can be configured to have shorter process time, or change process time based on process data. 
     Another advantage of using the presently disclosed double dual slot load lock system is its compact size. The double dual slot load lock system requires narrower atmospheric cassette load station than two DSL systems. For grand transportation, there is an equipment size limitation of approximate 3.0 m in dimension. In one embodiment of the double dual slot load lock system, the transfer chamber is designed in a shape of heptagon and the maximum process chamber quantity is 5. To meet the same size requirement, for two DSL systems, the maximum process chamber quantity would be 3. 
     Therefore, a substrate processing system is hereby provided, which comprises a cassette load station  101 , a load lock chamber  102 , a transfer chamber  103 , and one or more process chambers  104 . The transfer chamber  103  is centrally located, and the multiple process chambers  104  are located about the periphery of the transfer chamber  103 . The load lock chamber  102  comprises two dual slot load lock  108 ,  109  constructed at one location. 
     Specifically, each dual slot load lock  108 ,  109  has a heating plate and a cooling plate  125  located in different slots. The heating plate is a stationary plate or moving plate operated by Z-drive, and can heat the temperature up to 400° C. during pumping. Similarly, the cooling plate  125  is a stationary plate or moving plate operated by Z-drive, and can cool the temperature down from about 350° C. to about 80° C. during venting. More specifically, the cooling is achieved by water or by venting using nitrogen gas mixed with helium. 
     The substrate processing system described herein may further comprise a vacuum robot  118 , which is located in the transfer chamber  103  for transferring substrates. The vacuum robot  118  is operated by Z-drive  117 . Still, the system may further comprise a flip type door located between the cassette load station  101  and the load lock chamber  102 . Flip type slit valves  113  may also be constructed between the load lock chamber  102  and the transfer chamber  103 . Such slit valves are closed from atmospheric side and always operated below substrate transferring plane to reduce particle exposure. Still yet, the substrate processing system may further comprise filter diffusers vents  133 , which are located in the both dual slot load locks to prevent particle generation. 
     Further provided is a method of processing substrates using the above-disclosed system for semiconductor manufacturing. This method comprises the steps of moving substrates from the cassette load station to the transfer chamber through the load lock chamber; transferring the substrates from the transfer chamber to the process chambers; processing the substrates in the process chambers; and unloading the processed substrates from the process chambers to the cassette load station through the load lock chamber. In this method, one of the dual slot load locks is in a vacuum condition for unloading preprocessed substrates from the load lock chamber to the transfer chamber, whereas at the same time the other dual slot load lock is in an atmospheric condition for unloading processed substrates from the load lock chamber to the cassette load station. 
     Furthermore, the pre-processed substrates are heated up to about 400° C. before loading to the transfer chamber. The heated substrates are then transferred to the transfer chamber by a vacuum robot which is driven by Z-drive. After processing, the processed substrates are cooled down from about 350° C. to about 80° C. before loading to the cassette load station. To increase cooling efficiency, a small amount of helium gas is supplied with nitrogen gas. Alternatively, the cooling can be achieved by water. 
     In this method, one load lock is in a vacuum condition and at the same time, the other load lock is in an atmospheric/venting condition. One vacuum pump is shared between the two load locks. Additionally, filter diffusers are located on both load locks to prevent particle generation. Increased vent speed may also be used to further prevent particle generation. 
     The system/method disclosed herein provides an improved wafer support and transport means to enable automatic and repetitive moving of individual wafers into and from load locks into, through and between processing chambers while minimizing damage and contamination of wafers. Additionally, using two dual slot load lock constructed in the same chamber increases system cost performance, i.e., minimizes system footprint and increases system throughput that was restricted by the load lock pumping/venting activity. 
     Any patents or publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. These patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. It will be apparent to those skilled in the art that various modifications and variations can be made in practicing the present invention without departing from the spirit or scope of the invention. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention as defined by the scope of the claims.