Patent Publication Number: US-2023139777-A1

Title: Wafer cooling system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 17/125,191, titled “Wafer Cooling System,” filed Dec. 17, 2020, which is a divisional of U.S. patent application Ser. No. 15/719,027, titled “Wafer Cooling System,” filed Sep. 28, 2017, each of which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     In semiconductor manufacturing, many processes (e.g., depositions, implants, anneals, etc.) are performed at elevated temperatures (e.g., above 150° C.) or at temperatures below room temperature (e.g., 24° C.). Processed wafers may need to be cooled (or heated) before returning to a wafer carrier outside a processing cluster tool or prior to further processing. 
    
    
     
       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    is a cross-sectional view of an exemplary wafer cooling/heating system that includes a load-lock and a thermo module, according to some embodiments. 
         FIG.  2    is a top-view of an exemplary load-lock with an arcuate-shaped diffuser, according to some embodiments. 
         FIG.  3    is a top-view of an exemplary load-lock with diffuser rods in an arcuate configuration, according to some embodiments. 
         FIG.  4    is a top-view of an exemplary load-lock with an arcuate-shaped diffuser with nozzles, according to some embodiments. 
         FIG.  5    is a cross-sectional view of an exemplary wafer holder and diffuser with multiple nozzles, according to some embodiments. 
         FIG.  6    is a cross-sectional view of an exemplary thermoelectric module with a semiconductor material between a pair of copper sheets and a pair of ceramic plates, according to some embodiments. 
         FIG.  7    is a top-view of an exemplary arrangement of thermoelectric modules in a thermo module, according to some embodiments. 
         FIG.  8    is a cross-sectional view of an exemplary arrangement of thermoelectric modules in a thermo module where the thermoelectric modules are stacked with a gas flowing between them, according to some embodiments. 
         FIG.  9    is an exemplary method for cooling or heating one or more wafers, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many 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 over 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. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     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. 
     In semiconductor manufacturing, many processes (e.g., depositions, implants, anneals, etc.) are performed at elevated temperatures (e.g., above 150° C.) or at temperatures below room temperature (e.g., 24° C.). Therefore, wafers may need to be cooled (or heated) before returning to a wafer carrier outside a processing cluster tool or before entering a processing reactor for additional processing. A cool-down or a warm-up process may take hundreds or thousands of seconds and may depend on an initial wafer temperature and an “efficiency” of the cooling/heating system—e.g., cooling or heating rate. Wafer cooling or heating can take place in a part of a cluster tool that is referred to as “a load-lock.” Wafer cooling or heating can be performed via thermal conduction between a gas, which can flow constantly into the load-lock, and the wafer(s). A diffuser can be used to distribute the gas in the load-lock. The diffuser can be, for example, located at the top of the load-lock so the gas can flow from top to bottom in a downstream fashion. An exhaust line located, for example, at the bottom of the load-lock can remove the gas from the load-lock. The downstream design, however, can result in a temperature gradient of several degrees Celsius (e.g., up to 4° C. or more) across a batch (or load) of wafers as they cool down or heat up. The resulting temperature gradient can impact the load-lock&#39;s cooling or heating efficiency. Other factors that may impact the cooling or heating efficiency of the load-lock can be load-lock pressure, load-lock volume, cooling/heating gas temperature, flow rate of the heating/cooling gas, etc. 
     The efficiency of the load-lock can be measured in terms of wafer throughput, such as how many wafers the load-lock can “process” (e.g., cool-down or heat-up) per hour. The wafer throughput of the load-lock can also impact an overall wafer throughput of a processing tool (cycle time). If the temperature gradient between the wafers within a batch of wafers is high (e.g., 6° C. or 7° C.), the cooling or heat-up time may increase until all wafers are cooled down or warmed up to an appropriate temperature. 
     This disclosure is directed to a wafer cooling/heating system that includes a load-lock and a thermo module. The load-lock utilizes a level stream design that can improve wafer temperature uniformity during the cooling/heating process and can accelerate wafer cooling or heating compared to a load-lock with a downstream design. According to some embodiments, the level stream cooling/heating system can reduce the wafer cooling/heating time by about 82% and improve the wafer throughput by about 45%. The level stream design includes a diffuser, which is positioned on a side surface of a load-lock and can flow a gas parallel to the surface of the wafer(s) through multiple nozzles. A series of gas exhaust lines at the wafer level can control a gas removal rate and detect potential nozzle malfunctions. Additionally, the thermo module of the cooling/heating system can provide a wide range of gas temperatures. For example, the temperature of the gas supplied to the load-lock via the thermo module can range from about −50° C. to about 50° C. 
       FIG.  1    is a cross-sectional view of an exemplary wafer cooling/heating system  100 , according to some embodiments. Exemplary wafer cooling/heating system  100  includes a load-lock  110 , a thermo module unit  120 , and a control module  125 . Load-lock  110  can include multiple exhaust lines or exhaust lines  130 , a diffuser  140 , and a wafer holder  150 . A gas from a semiconductor fabrication facility can be delivered to thermo module unit  120  through inlet  160 . The gas can be heated or cooled in thermo module unit  120  and subsequently delivered to diffuser  140  via outlet  170 . 
     Wafer cooling/heating system  100  can be, for example, a unit on a processing cluster tool that can receive individual wafers or wafer batches in wafer holder  150 . By way of example and not limitation, wafer holder  150  can be configured to hold up to 25 wafers. Wafer cooling/heating system  100  can cool-down/warm-up wafers before releasing them to a wafer carrier outside the cluster tool or before releasing them to the cluster tool for further processing. Wafer cooling/heating system  100  may include additional components. These additional components may or may not be depicted in  FIG.  1   ; however, they are within the spirit and scope of this disclosure. Such components may be additional reactors or modules, robotic arms, controllers, valves, pedestals, internal and external electrical connections to other modules of the cluster tool such as computers, valves, pumps, and the like. 
     In some embodiments, load-lock  110  can be a chamber with a cubical shape, an orthogonal shape, a cylindrical shape, a polyhedron shape, or any other suitable shape. Load-lock  110  can have one or more side surfaces. Load-lock  110  can also have a front surface with a door valve (or slit valve) used to transfer wafers in and out of load-lock  110 . Wafers can be transferred in and out of load-lock  110  via a robotic arm (not shown in  FIG.  1   ) that can be located outside wafer cooling/heating system  100 . The robotic arm can be located, for example, in a transfer module, which can be part of the processing cluster tool (not shown in  FIG.  1   ). 
     Exhaust lines  130  may be located on one or more side surfaces of load-lock  110 , according to some embodiments. In some embodiments, exhaust lines  130  may include up to 25 individual lines, where each exhaust line may correspond to a single wafer on wafer holder  150 . In some embodiments, each exhaust line is connected, via a respective exhaust valve (not shown in  FIG.  1   ), to an external exhaust pump (not shown in  FIG.  1   ). In some embodiments, a gas flow through each of exhaust lines  130  towards the exhaust pump can be controlled by a respective exhaust valve for exhaust lines  130 . By way of example and not limitation, each exhaust valve may adjust its opening from 0 to about 100%. In some embodiments, depending on a “heat load” of load-lock  110  (e.g., a number of wafers and a starting wafer temperature), wafer cooling/heating system  100  may activate one or more exhaust valves and may control the gas flow through each exhaust line (e.g., the opening position of each exhaust valve) for optimal cooling or heating performance. In some embodiments, exhaust lines  130  may detect a clogged nozzle on diffuser  140 . For example, a flow controller connected to each exhaust line may be calibrated to anticipate a certain flow for a particular valve position. When that flow is not met, an alarm can notify a user. 
     In some embodiments, diffuser  140  can be located on a back side surface of load-lock  110 , a side surface of load-lock  110 , or a combination thereof. A back side surface of load-lock  110  can be defined as a surface that is opposite to a front side surface of load-lock  110 . By way of example and not limitation,  FIG.  2    is a top-view of load-lock  110 , according to some embodiments. In this exemplary view, load-lock  110  is a chamber with a front surface  200 , a back surface  210 , and a pair of side surfaces  220  and  230 . In some embodiments, diffuser  140  can have an arcuate shape, which can be any fraction of a cylinder (e.g., semi-cylindrical, ¾ of a cylinder, etc.) as long as diffuser  140  does not obstruct a path of an incoming or outgoing wafer through front surface  200 . Based on the above description, diffuser  140  may be located on back side surface  210 , side surfaces  220  and  230 , or a combination of thereof. Diffuser  140 , due to its arcuate shape, can partially surround stacked wafers  240  on wafer holder  150 . 
     In some embodiments, wafer holder  150  can have a rectangular shape as shown in  FIG.  2   . The rectangular shape of wafer holder  150  in  FIG.  2    is exemplary and is not intended to be limiting. Therefore, additional shapes are within the spirit and scope of this disclosure. For example, wafer holder  150  can have a square shape, a cylindrical shape, or any other shape that fits load-lock  110 . In some embodiments, wafer holder  150  can have slots configured to receive respective wafers. By way of example and not limitation, each slot may further include multiple slats  250  (e.g., four opposing slats  250  as shown in  FIG.  2   ), which are configured to hold a single wafer in a horizontal position. Each slat  250  may have a temperature sensor  260  and a flow rate sensor  270  thereon. By way of example and not limitation, temperature sensor  260  may be in contact with a wafer&#39;s back surface (e.g., a wafer surface without semiconductor elements formed thereon), while flow rate sensors  270  may not be in contact the wafer. In some embodiments, each temperature sensor  260  on each slat  250  can provide a wafer temperature reading so that a four-corner temperature map for each wafer can be obtained. By way of example and not limitation, temperature sensors  260  may transmit a radio frequency (RF) signal that can contain a temperature reading to an external control unit (e.g., control module  125  of  FIG.  1   ). In some embodiments, temperature sensor  260  can read wafer temperatures within a range of about −150° C. to about 500° C. By way of example and not limitation, temperature sensor  260  can be a thermocouple that produces a temperature-dependent voltage or a resistance temperature detector (e.g., a thermistor). 
     Similarly, flow rate sensors  270  can provide a flow rate reading for a gas flown through diffuser  140  at their respective locations. In some embodiments, each flow rate sensor  270  may provide a gas flow rate reading so that a four-corner gas flow rate map for each wafer can be obtained. In some embodiments, flow rate sensors  270  may transmit a radio frequency (RF) signal that can contain a gas flow rate reading to an external control unit, such as control module  125  of  FIG.  1   . In some embodiments, flow rate sensors  270  may be able to read a range of gas flow rates (e.g., between about 2 ml/min to about 200 ml/min and between about 4 l/min to about 350 l/min). 
     In some embodiments, the temperature and flow rate readings from the flow and temperature sensors  260  and  270 , respectively, can be used by control module  125  and other units of cooling/heating system  100  to further optimize the wafer cooling or heating process. For example, as a result of the temperature and flow rate readings, cooling/heating system  100  may increase or decrease the flow of cooling/heating gas, increase or decrease the gas temperature, activate or deactivate one or more exhaust lines  130 , etc. In some embodiments, the temperature and flow rate readings can be used to detect a system malfunction, such as a deactivated exhaust line  130  or a clogged nozzle on diffuser  140 . 
     According to some embodiments, diffuser  140  can be made of individual cylindrical, square, rectangular, or polygon diffuser “rods” which can be arranged in a arcuate configuration, such as diffuser rods  300  as shown, for example, in  FIG.  3   . The aforementioned shapes of diffuser rods  300  are exemplary and not intended to be limiting. Therefore, additional shapes are within the spirit and scope of this disclosure. The arcuate configuration of diffuser rods  300  may not be limited to the number of diffuser rods  300  shown in  FIG.  3   . Therefore, additional or fewer diffuser rods  300  are possible as long as the diffuser rods  300  do not obstruct the path of an incoming or outgoing wafer via front surface  200  of load-lock  110 . 
     As discussed above, diffuser  140  may include multiple nozzles along its surface.  FIG.  4    is the diffuser arrangement of  FIG.  2    with an exemplary row of nozzles  400  thereon. Nozzles  400  are facing a stack of wafers  240  and may cover an inner surface of diffuser  140  in several possible arrangements. By way of example and not limitation, the arrangement may include a row of nozzles  400  across an x-y plane (according to x-y axes shown  FIG.  4   ) that can be repeated along a z-direction, where the z-direction can be perpendicular to the x-y plane. Further, each row of nozzles  400  along the x-y plane may be aligned in the z-direction to a space between two neighboring wafers  240  as shown in  FIG.  5   .  FIG.  5    can be, for example, a cross sectional view of  FIG.  4    along the z-axis (e.g., perpendicular to x-y plane of  FIG.  4   ). As discussed above, alternative arrangements of nozzles  400  on diffuser  140  can be possible depending on, for example, the chamber geometry (e.g., rectangular, orthogonal, cylindrical, etc.), the volume of load-lock  110 , the flow kinetics of the gas, etc. 
     In  FIG.  5   , a gas spray angle θ of each nozzle  400  may be controlled by cooling/heating system  100  depending, for example, on the number of wafers  240  in wafer holder  150 , the space between wafers  240  in wafer holder  150 , the volume of load-lock  110 , or a combination thereof. According to some embodiments, gas flow angle θ for each nozzle  400 , may range from 0° (narrow) to about 90° (wide), such as a range between 0.01° and 89.9°. As a result, the flow for each nozzle  400  may be directional (e.g., about 0.01°) or wide (e.g., about 89.9°). In some embodiments, an output gas pressure of each nozzle  400  can also be controlled by cooling/heating system  100 . For example, and according to some embodiments, the output gas pressure for each nozzle  400  can range from about 0.1 psi to about 100 psi. In some embodiments, nozzles  400  can be activated individually or as a group. In addition, each nozzle may have a different spray angle θ. For example, if a slot is not occupied by a wafer, its corresponding nozzle(s) may have a wider spray angle θ compared to a nozzle located between slots with wafers. Alternatively, each nozzle may have a similar or the same spray angle θ. 
     In some embodiments, load-lock  110  can also include pressure sensors (not shown in the figures), which can provide pressure readings from about 1×10 −9  Torr to about 1000 Torr. By way of example and not limitation, the pressure sensors can be located at the corners of load-lock  110 , if load-lock  110  has a cubical or a rectangular shape. Alternatively, the pressure sensors can be located in the top and bottom perimeter of load-lock  110 , if load-lock  110  has, for example, a cylindrical shape. The number or arrangement of pressure sensors disclosed herein is exemplary and is not intended to be limiting. Therefore, additional or fewer pressure sensors and their respective location in load-lock  110  are possible. In some embodiments, the pressure sensors may provide feedback to cooling/heating system  100  and based on the feedback adjustments can be made to gas flow angle θ, output pressure of nozzles  400 , etc. 
     In some embodiments, the gas used to cool or heat the wafers in load-lock  110  is a noble or an inert gas. The noble or inert gas can prevent chemical reactions between, for example, the gas and wafers  240 . Chemical reactions between the gas and wafers  240  can inadvertently alter the physical, chemical, and/or electrical properties of structures formed on wafers  240 . In some embodiments, the gas can be nitrogen (N 2 ). By way of example and not limitation, other gases include helium (He), argon (Ar), neon (Ne), xenon (Xe), krypton (Kr), and radon (Rn). In referring to  FIG.  1   , the gas can be delivered to thermo module unit  120  from an external source (e.g., a source located elsewhere in a semiconductor fabrication facility). According to some embodiments, the gas delivered from the external source can be at room temperature (e.g., about 24° C.) and at a pressure of about 20 psi. According to some embodiments, thermo module unit  120  can be configured to adjust the temperature of the gas delivered to a diffuser  140 , via outlet  170 , to a range between about −50° C. to about 50° C. In some embodiments, control module  125  may control the operations of thermo module unit  120 . Control module  125  may connect to thermo module unit  120  via a wire or wireless communication and may be able to receive temperature readings from multiple sources and multiple locations of wafer cooling/heating system  100  (e.g., inlet  160 , outlet  170 , temperature sensors  270 , etc.). 
     According to some embodiments, thermo module unit  120  includes a thermoelectric module. The thermoelectric module is a semiconductor-based electronic component that functions as a heat pump. By applying a direct current (DC) voltage (e.g., 24 Volts) to a thermoelectric module, heat can be moved through the module from one side to the other. As a result, one side of the module can be cooled while an opposite side of the module can be heated. If a change in the polarity (plus and minus) of the applied DC voltage occurs, the cooling and heating sides of the module can be reversed. Consequently, a gas can be cooled when it is exposed to a cold side of the thermoelectric module or heated when it is exposed to the hot side of the thermoelectric module. For example, in some embodiments, cooling or heating of a gas is achieved by channeling the incoming gas over the cold or hot side of the thermoelectric module. In other embodiments, the gas can be exposed to a single side of the thermoelectric module and the polarity of the applied DC voltage can be changed to switch from cooling to heating. In some embodiments, control module  125  can control the DC voltage applied to thermo module unit  120 . 
     Referring to  FIG.  6   , an exemplary thermoelectric module  600  is depicted. Thermoelectric module  600  can include semiconductor material  610  that is electrically connected to a DC power supply (not shown) through electrical connections  620 . Semiconductor material  610  can include a multiple PN junctions electrically connected in series. By way of example and not limitation, semiconductor material  610  can include P- and N-doped bismuth telluride (Bi 2 Te 3 ). The electrical connections of semiconductor material  610  can be made such that a top side A of thermoelectric module  600  is the cold side and a bottom side B is the hot side, or vice versa. For example purposes, top side A can be the cold side and bottom side B can be the hot side of semiconductor material  610 . Semiconductor material  610  can be disposed between two copper sheets  630 . Copper sheets  630  can improve the heat transfer from each side of semiconductor material  610  to the surrounding layers. The aforementioned elements (semiconductor material  610  and copper sheets  630 ), along with their electrical interconnects, can be enclosed between two ceramic plates  640 , which can mechanically hold the overall structure together. In some embodiments, ceramic plates  640  can function as external mounting surfaces. 
     According to some embodiments, thermoelectric module  600  can include additional layers, which are not depicted in  FIG.  6   . For example, thermoelectric module  600  may include an adhesion medium (e.g., a glue layer) between ceramic plates  640  and copper sheets  630 , and an alloy material (e.g., solder) between semiconductor material  610  and copper sheets  630  or between copper sheets  630  and ceramic plates  640 . 
     In some embodiments, a finned heat sink may be attached on ceramic plate  640  located on the hot side, B, of thermoelectric module  600 . In some embodiments, finned heat sinks may be attached on both ceramic plates  640 . Finned heat sinks can have a greater surface area than a flat surface and can therefore accelerate the heat exchange process between the gas and thermoelectric module  600 . By way of example and not limitation, the heat sink can be made of metals with high thermal conductivity, such as aluminum (Al) or copper (Cu). In some embodiments, the gas is forced through the heat sink so that it can be cooled or heated. 
     In some embodiments, a thermo module unit  120  may include more than one thermoelectric module  600 . For example, in some embodiments, a thermo module unit  120  may include multiple thermoelectric modules  600  in a variety of arrangements. By way of example and not limitation,  FIG.  7    shows an exemplary arrangement of thermoelectric modules  600  in thermo module unit  120 . A gas is delivered from an external source (e.g., a source located elsewhere in a fabrication facility through inlet  160  inside thermo module unit  120 . The gas passes through a top or a bottom surface of the thermoelectric modules before it exits thermo module unit  120  via outlet  170 . The arrangement of thermoelectric modules  600  described in  FIG.  7    is exemplary and should not be considered limiting. Additional arrangements of thermoelectric modules  600  are possible with a larger or smaller number of thermoelectric modules  600 . Additionally, the path of the gas inside thermo module unit  120  is not limited to the depiction of  FIG.  7   . Therefore, additional arrangements, gas paths inside thermo module unit  120 , and number of thermoelectric modules  600  are within the spirit and scope of this disclosure. In some embodiments, arrangements of thermoelectric modules  600  can be stacked on top of each other with the gas flowing between them. For example, an additional arrangement of thermoelectric modules  600  can be stacked over the arrangement of thermoelectric modules  600  of  FIG.  7    so that the gas can travel between them. By way of example and not limitation,  FIG.  8   , which is a cross-sectional view of thermo module unit  120  across line AB, shows such an exemplary stacked configuration, where the path of the gas is in the x-direction and between an upper arrangement  800  of thermoelectric modules  600  and a lower arrangement  810  of thermoelectric modules  600 . In the example of  FIG.  8   , the gas enters thermo module unit  120  through inlet  160  and exits from outlet  170 . 
       FIG.  9    is an exemplary method  900  for cooling or heating one or more wafers, according to some embodiments. This disclosure is not limited to this operational description. Rather, other operations are within the spirit and scope of the present disclosure. It is to be appreciated that additional operations may be performed. Moreover, not all operations may be needed to perform the disclosure provided herein. Further, some of the operations may be performed simultaneously, or in a different order than shown in  FIG.  9   . In some implementations, one or more other operations may be performed in addition to or in place of the presently described operations. For illustrative purposes, method  900  is described with reference to the embodiments of  FIGS.  1 - 8   . However, method  900  is not limited to these embodiments. 
     Exemplary method  900  starts with operation  910 , where one or more wafers are transferred to available slats  250  on a wafer holder  150  in load-lock  110 . According to some embodiments, load-lock  110  is housed in cooling/heating system  100 . Each wafer is positioned in a respective slot of wafer holder  150  so that it rests on slats  250 . Temperature sensors  260  on each slat  250  make contact to the back side of the wafer. 
     In operation  920 , the one or more wafers are “mapped” so that the slot position of the one or more wafers is identified and stored in a memory of a computer system that can be accessed by control module  125 . In some embodiments, the number of wafers can range from 1 to 25. In some embodiments, the wafers may or may not occupy consecutive slots. 
     In operation  930 , cooling/heating system  100  may adjust the spray angle θ of nozzles  400  on diffuser  140 . In some embodiments, the spray angle adjustment can be based on the slot position of the one or more wafers on wafer holder  150  and the spacing between neighboring wafers, so that nozzles  400  on diffuser  140  can flow the gas parallel to the one or more wafers. In some embodiments, spray angle θ of nozzles  400  can be controlled independently for each nozzle. By way of example and not limitation, if two consecutive slots are occupied, the spray angle θ of the corresponding nozzle can be narrow (e.g., 0.01°). In another example, where two consecutive slots are not occupied, the spray angle θ of the corresponding nozzle can be wide (e.g., 89.9°). According to some embodiments, nozzles  400  can be positioned on diffuser  140  between the slots of wafer holder  150 . According to some embodiments, if some slots are not occupied by a wafer, the corresponding nozzles may be turned off by cooling/heating system  100 . 
     In operation  940 , based on an initial temperature of the one or more wafers in load-lock  100 , thermo module unit  120  can adjust the temperature of an incoming gas prior to its delivery to load-lock  110  through outlet  170 . In some embodiments, the gas is delivered to thermo module unit  120  through inlet  160  from an external source. In some embodiments, the gas can be N 2 . By way of example and not limitation, other gases that can be used include He, Ar, Ne, Xe, Kr, and Rn. According to some embodiments, the gas delivered from the external source can be at room temperature (e.g., about 24° C.) and at a pressure of about 20 psi. According to some embodiments, thermo module unit  120  can be configured to adjust the temperature of the gas delivered to a diffuser  140 , via outlet  170 , to a range between about −5° C. to about 50° C. In some embodiments, control module  125  can control operations of thermo module unit  120 . Control module  125  may connect to thermo module unit  120  via a wire or wireless communication and may be able to receive temperature readings from multiple sources and multiple locations of cooling/heating system  100  (e.g., inlet  160 , outlet  170 , temperature sensors  270 , etc.). 
     According to some embodiments, thermo module unit  120  includes a thermoelectric module, which is a semiconductor-based electronic component that functions as a heat pump. By applying a DC voltage (e.g., 24 Volts) to a thermoelectric module, heat can be moved through the module from one side to the other. As a result, one side of the module can be cooled while an opposite side of the module can be heated. Consequently, a gas can be cooled when it is exposed to a cold side of the thermoelectric module or heated when it is exposed to the hot side of the thermoelectric module. For example, in some embodiments, cooling or heating of a gas is achieved by channeling the incoming gas over the cold or hot side of the thermoelectric module. In other embodiments, the gas can be exposed to a single side of the thermoelectric module and the polarity of the applied DC voltage can be changed to switch from cooling to heating. In some embodiments, control module  125  can control the DC voltage applied to thermo module unit  120 . 
     In operation  950 , one or more exhaust lines  130  of load-lock  110  can be activated to remove the gas from load-lock  110  once it has flown through the one or more wafers. Exhaust lines  130  may be located on one or more side surfaces of load-lock  110 , according to some embodiments. In some embodiments, exhaust lines  130  may include up to 25 individual lines, where each exhaust line may correspond to a single wafer. In some embodiments, each exhaust line can be connected, via a respective exhaust valve, to an external exhaust pump. In some embodiments, the gas flow through each of exhaust lines  130  towards the exhaust pump can be controlled by its respective exhaust valve. By way of example and not limitation, each exhaust valve may change its opening cross section from 0 (e.g., fully closed position) to about 100% (e.g., fully open open). According to some embodiments, cooling/heating system  100  may determine which exhaust valves may be activated depending on a number of parameters such as: (i) the number of wafers in load-lock  110  and each of the wafer&#39;s slot position; (ii) the spray angle θ of each nozzle; (iii) the flow rate of the gas through the nozzles; (iv) the temperature of the wafers; and (v) the temperature of the gas. In some embodiments, exhaust lines  130  may be used as a troubleshooting tool to detect a clogged nozzle on diffuser  140 . 
     This disclosure is directed to a wafer cooling/heating system that includes a load-lock and a thermo module. The load-lock uses a level stream design to improve temperature uniformity across a batch of wafers during a cooling/heating process. In this level stream design, a diffuser is placed on a side surface of a load-lock and can flow a gas in a direction parallel to the wafer&#39;s surface through a series of nozzles. The gas spray angle of the nozzles can be adjusted between 0.01° to about 89.9°. Exhaust lines at the wafer level can control the gas removal rate and detect any nozzle malfunctions. A number of flow and temperature sensors on the wafer holder of the load-lock provide temperature and gas flow information for each wafer. Additionally, the thermo module of the cooling/heating system utilizes a series of thermoelectric modules in a variety of configurations to effectively cool or heat the incoming gas. According to some embodiments, the thermo module of the cooling/heating system can provide a wide range of gas temperatures. For example, the temperature of the gas supplied to the load-lock can range from about −50° C. to about 50° C. 
     In some embodiments, a wafer cooling system includes (i) a load-lock and (ii) a thermo module configured to control a temperature of a gas provided to the load-lock. Further, the load-lock includes (i) a wafer holder configured to receive wafers at a front side of the load-lock; (ii) a gas diffuser with one or more nozzles along a back side of the load-lock, a side surface of the load-lock, or a combination thereof; and (iii) one or more exhaust lines. 
     In some embodiments, a wafer cooling system includes a load-lock and a thermo module configured to provide a gas to the load-lock, where the thermo module comprises a semiconductor material with top and bottom surfaces configured to be heated or cooled to different temperatures. The load-lock further includes: (i) a wafer holder configured to receive wafers at a front side of the load-lock; (ii) a gas diffuser along a back side of the load-lock, a side surface of the load-lock, or a combination thereof, where the gas diffuser comprises one or more diffuser rods with one or more nozzles thereon; (iii) and one or more exhaust lines along the side surface of the load-lock, the back side of the load-lock, or a combination thereof. 
     In some embodiments, a method of cooling wafers includes transferring one or more wafers to slats on a wafer holder that is housed in a load-lock. Adjusting a spray angle for one or more nozzles of a gas diffuser that is located in the load-lock, where the one or more nozzles provides a gas in a direction parallel to the one or more wafers. Adjusting a temperature of the gas with a thermo module, and activating one or more exhaust lines in the load-lock based on at least the spray angle of the one or more nozzles. 
     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. 
     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.