Multi-stage flow control apparatus

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of an embodiment of a track lithography tool according to an embodiment of the present invention;

FIG. 2 is a simplified cross-sectional diagram of a multi-stage flow control apparatus according to an embodiment of the present invention;

FIG. 3 is a simplified perspective view of a multi-stage flow control apparatus according to an embodiment of the present invention;

FIG. 4 is a simplified cross-sectional diagram of an multi-stage flow control apparatus according to an additional embodiment of the present invention;

FIG. 5 is a simplified exemplary diagram showing exhaust pressure with and without a multi-stage flow control apparatus according to an embodiment of the present invention;

FIG. 6 is a simplified exemplary process flow showing processes used to maintain a constant exhaust flow according to an embodiment of the present invention;

FIG. 7 is a simplified cross-sectional diagram of a multi-stage flow control apparatus according to an embodiment of the present invention; and

FIG. 8 is a simplified perspective view of a multi-stage flow control apparatus according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, an apparatus related to semiconductor manufacturing equipment are provided. More particularly, the present invention relates to an apparatus for maintaining a constant exhaust flow through an exhaust line coupled to a semiconductor processing chamber. Merely by way of example, the invention can be applied by using a multi-stage flow control apparatus to control and regulate the exhaust flow. While some embodiments of the invention are particularly useful in eliminating fluctuations and back streaming of house exhaust for a lithography chamber, other embodiments of the invention can be used in other applications where it is desirable to manage air flow in a highly controllable manner.

FIG. 1 is a plan view of an embodiment of a track lithography tool 100 in which the embodiments of the present invention may be used. As illustrated in FIG. 1, track lithography tool 100 contains a front end module 110 (sometimes referred to as a factory interface or FI) and a process module 111. In other embodiments, the track lithography tool 100 includes a rear module (not shown), which is sometimes referred to as a scanner interface. Front end module 110 generally contains one or more pod assemblies or FOUPS (e.g., items 105A-D) and a front end robot assembly 115 including a horizontal motion assembly 116 and a front end robot 117. The front end module 110 may also include front end processing racks (not shown). The one or more pod assemblies 105A-D are generally adapted to accept one or more cassettes 106 that may contain one or more substrates or wafers, “W,” that are to be processed in track lithography tool 100. The front end module 110 may also contain one or more pass-through positions (not shown) to link the front end module 110 and the process module 111.

Process module 111 generally contains a number of processing racks 120A, 120B, 130, and 136. As illustrated in FIG. 1, processing racks 120A and 120B each include a coater/developer module with shared dispense 124. A coater/developer module with shared dispense 124 includes two coat bowls 121 positioned on opposing sides of a shared dispense bank 122, which contains a number of nozzles 123 providing processing fluids (e.g., bottom anti-reflection coating (BARC) liquid, resist, developer, and the like) to a wafer mounted on a substrate support 127 located in the coat bowl 121. In the embodiment illustrated in FIG. 1, a dispense arm 125 sliding along a track 126 is able to pick up a nozzle 123 from the shared dispense bank 122 and position the selected nozzle over the wafer for dispense operations. Of course, coat bowls with dedicated dispense banks are provided in alternative embodiments.

Processing rack 130 includes an integrated thermal unit 134 including a bake plate 131, a chill plate 132, and a shuttle 133. The bake plate 131 and the chill plate 132 are utilized in heat treatment operations including post exposure bake (PEB), post-resist bake, and the like. In some embodiments, the shuttle 133, which moves wafers in the x-direction between the bake plate 131 and the chill plate 132, is chilled to provide for initial cooling of a wafer after removal from the bake plate 131 and prior to placement on the chill plate 132. Moreover, in other embodiments, the shuttle 133 is adapted to move in the z-direction, enabling the use of bake and chill plates at different z-heights. Processing rack 136 includes an integrated bake and chill unit 139, with two bake plates 137A and 137B served by a single chill plate 138.

One or more robot assemblies (robots) 140 are adapted to access the front-end module 110, the various processing modules or chambers retained in the processing racks 120A, 120B, 130, and 136, and the scanner 150. By transferring substrates between these various components, a desired processing sequence can be performed on the substrates. The two robots 140 illustrated in FIG. 1 are configured in a parallel processing configuration and travel in the x-direction along horizontal motion assembly 142. Utilizing a mast structure (not shown), the robots 140 are also adapted to move in a vertical (z-direction) and horizontal directions, i.e., transfer direction (x-direction) and a direction orthogonal to the transfer direction (y-direction). Utilizing one or more of these three directional motion capabilities, robots 140 are able to place wafers in and transfer wafers between the various processing chambers retained in the processing racks that are aligned along the transfer direction.

Referring to FIG. 1, the first robot assembly 140A and the second robot assembly 140B are adapted to transfer substrates to the various processing chambers contained in the processing racks 120A, 120B, 130, and 136. In one embodiment, to perform the process of transferring substrates in the track lithography tool 100, robot assembly 140A and robot assembly 140B are similarly configured and include at least one horizontal motion assembly 142, a vertical motion assembly 144, and a robot hardware assembly 143 supporting a robot blade 145. Robot assemblies 140 are in communication with a system controller 160. In the embodiment illustrated in FIG. 1, a rear robot assembly 148 is also provided.

The scanner 150, which may be purchased from Canon USA, Inc. of San Jose, Calif., Nikon Precision Inc. of Belmont, Calif., or ASML US, Inc. of Tempe Ariz., is a lithographic projection apparatus used, for example, in the manufacture of integrated circuits (ICs). The scanner 150 exposes a photosensitive material (resist), deposited on the substrate in the cluster tool, to some form of electromagnetic radiation to generate a circuit pattern corresponding to an individual layer of the integrated circuit (IC) device to be formed on the substrate surface.

Each of the processing racks 120A, 120B, 130, and 136 contain multiple processing modules in a vertically stacked arrangement. That is, each of the processing racks may contain multiple stacked coater/developer modules with shared dispense 124, multiple stacked integrated thermal units 134, multiple stacked integrated bake and chill units 139, or other modules that are adapted to perform the various processing steps required of a track photolithography tool. As examples, coater/developer modules with shared dispense 124 may be used to deposit a bottom antireflective coating (BARC) and/or deposit and/or develop photoresist layers. Integrated thermal units 134 and integrated bake and chill units 139 may perform bake and chill operations associated with hardening BARC and/or photoresist layers after application or exposure.

In one embodiment, a system controller 160 is used to control all of the components and processes performed in the cluster tool 100. The controller 160 is generally adapted to communicate with the scanner 150, monitor and control aspects of the processes performed in the cluster tool 100, and is adapted to control all aspects of the complete substrate processing sequence. The controller 160, which is typically a microprocessor-based controller, is configured to receive inputs from a user and/or various sensors in one of the processing chambers and appropriately control the processing chamber components in accordance with the various inputs and software instructions retained in the controller's memory. The controller 160 generally contains memory and a CPU (not shown) which are utilized by the controller to retain various programs, process the programs, and execute the programs when necessary. The memory (not shown) is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits (not shown) are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like all well known in the art. A program (or computer instructions) readable by the controller 160 determines which tasks are performable in the processing chamber(s). Preferably, the program is software readable by the controller 160 and includes instructions to monitor and control the process based on defined rules and input data.

Referring to FIG. 1, a variable process module 198 is provided in the track lithography tool 100. Variable process module 198 is serviced by one or both of the robot assemblies 140. The use of the variable process module may occur before or after several of the wafer processes performed within the track lithography tool 100. These wafer processes include coat, develop, bake, chill, exposure, and the like. In a particular embodiment, variable process module may be used for wafer particle detection, or for performing one or more of the wafer processes described above. One of ordinary skill in the art would recognize many variations, modifications, and alternatives.

It is to be understood that embodiments of the invention are not limited to use with a track lithography tool such as that depicted in FIG. 1. Instead, embodiments of the invention may be used in any track lithography tool including the many different tool configurations described in U.S. patent application Ser. No. 11/315,984, entitled “Cartesian Robot Cluster Tool Architecture” filed on Dec. 22, 2005, which is hereby incorporated by reference for all purposes and including configurations not described in the above referenced application.

FIG. 2 is a simplified cross-sectional diagram of a multi-stage flow control apparatus according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. A multi-stage flow control apparatus 200 is provided for use between a semiconductor processing chamber (not shown) and an exhaust device (not shown). For example, the semiconductor processing chamber may be a lithography device including one or more bowls used within lithography processing steps such as a track lithography tool described in FIG. 1. In another example, the exhaust device may be house exhaust present in a semiconductor manufacturing facility which is shared between several processing apparatus. Alternatively, the exhaust device may be a turbopump, roughing pump, cryopump, or other stand-alone vacuum device capable of generating an exhaust flow. The multi-stage flow control apparatus 200 may comprise two stages: a throttle valve stage 204 used to control a desired flow rate or set point from the bowl, and a floating plunger stage 206 used to reduce or eliminate the fluctuations and back streaming from the house exhaust. Of course, there can be other variations, modifications, and alternatives.

Throttle valve stage 204 is coupled with an inlet 202, which receives a flow input from the semiconductor processing chamber. Inlet 202 may be coupled to the semiconductor processing chamber through an exhaust line (not shown). Furthermore, inlet 202 provides an opening to throttle valve stage 204. Throttle valve stage 204 may be shaped in a variety of configurations depending upon the specific implementation. For example, throttle valve stage 204 may include a seat 208 with upward sloping faces. The base of the seat may reveal an internal orifice 210 employed to allow exhaust flow 216 from the semiconductor processing chamber to progress from throttle valve stage 204 to floating plunger stage 206.

Throttle valve stage 204 further includes throttle valve plug 212, which may be controlled by a linear actuator (not shown) to control a desired flow rate or set point from the bowl. Of course, other devices could be used to provide throttle valve plug 212 with a desired range of motion. For example, the linear actuator may be coupled with throttle valve plug 212 at its stem 213 which protrudes from throttle valve stage 204. The desired flow rate may be set by modulating the distance 214 between throttle valve plug 212 and upward sloping faces of seat 208. A larger distance between throttle valve plug 212 and upward sloping faces of seat 208 can allow for an increased flow rate, and a smaller distance between throttle valve plug 212 and upward sloping faces of seat 208 can allow for a reduced flow rate. Throttle valve plug 212 may be modulated by the linear actuator to move in a substantially vertical motion, thus allowing for a varied amount of exhaust flow to progress between throttle valve plug 212 and upward sloping faces of seat 208. In another example, upward sloping faces of seat 208 and the portion of throttle valve plug 212 opposite from upward sloping faces of seat 208 may possess the same gradient to allow for minimal obstruction in the exhaust flow path.

Other throttle configurations could also be used as well, such as a throttle with downwards sloping faces and a similarly shaped throttle valve plugs. However, one additional advantage to utilizing upward sloping faces within throttle valve stage 204 is that the exhaust device (not shown) pulls the throttle valve closed during operation. For example, during conventional operation of the device, the desired flow rates may be low, necessitating a small gap between the throttle valve plug and the faces to restrict exhaust flow. By utilizing the exhaust flow stream to partially close the throttle valve in an upward sloping face design, a reduced amount of force can be expended in setting the desired flow rate for the device.

A floating plunger stage 206 is coupled to throttle valve stage 204, and exhaust flow 216 proceeds from throttle valve stage 204 through floating plunger stage 206 and exits flow control apparatus 200 through an outlet 224. A floating plunger 218 moves vertically to vary the opening to opening 222, with the motion being a function of the weight of floating plunger 218, the pressure in the region 230 below the flexible membrane 220, and the vacuum level above the plunger. Among other functions, floating plunger 218 is designed to reduce or eliminate the fluctuations in the exhaust from an exhaust device and potential back streaming from the exhaust device. An opening 222 may be defined between a top surface of floating plunger 218 and an upper portion of outlet 224. As floating plunger 218 rises in a vertical direction, opening 222 is reduced in size, and opening 222 is enlarged when floating plunger 218 is lowered in a vertical direction. This can greatly reduce the amount of backflow and exhaust that can progress upstream and affect the operation of the semiconductor processing chamber coupled with flow control apparatus 200. In addition, the floating plunger implementation further helps to eliminate variations in the exhaust level by providing a controlled area through which exhaust flow 216 can flow. In addition, if an exhaust device is shared among different processing apparatus, crosstalk between different processing apparatus can also be reduced.

A vent 226 providing a controlled pressure below floating plunger 218 causes the floating plunger 218 to rise to a desired level. Floating plunger 218 may be secured by flexible membranes 220, which may be attached to an interior surface of floating plunger stage 206. Of course, other attachment methods could also be used, such as attaching flexible membrane 220 to posts located on the interior perimeter of floating plunger stage 206. While flexible membrane 220 is shown as having a straight profile, the shape of flexible membrane 220 should not be restricted as thus. For example, flexible membrane 220 may also have a wavy or curved profile. Flexible membrane 220 may be made from a rubber or silicone material that allows the membrane to contract and expand with the movement of floating plunger 218. The stroke of floating plunger 218 may be limited by the size, attachment location, and material of flexible membrane 220. In addition, two separate pressure regions may be maintained within floating plunger stage 206: a first pressure region 228 located above floating plunger 218 and flexible membrane 220, and a second pressure region 230 located below floating plunger 218 and flexible membrane 220. By maintaining a separation between two pressure regions 228 and 230, any particulates generated by controlled pressure through vent 226 being applied to floating plunger 218 can be contained within the second pressure region 230 and prevented from entering exhaust flow 216.

Floating plunger 218 may be made from a variety of materials, including plastic, aluminum, or other lightweight materials that are buoyant under a controlled pressure through vent 226. For example, floating plunger 218 may be hollow so that the weight of the plunger can be modified by partial filling of the plunger with fluids or solids, thereby customizing the plunger to a particular house exhaust.

The movement of floating plunger 218 under the controlled pressure through vent 226 may be in a substantially vertical position. To reduce the size of an opening 222 between a top surface of floating plunger 218 and an upper portion of outlet 224, outlet 224 may be recessed into floating plunger stage 206. By doing so, the horizontal distance between floating plunger 218 and outlet 224 can be reduced and exhaust flows more accurately maintained.

FIG. 3 is a simplified perspective view of a multi-stage flow control apparatus according to an embodiment of the present invention. A flow control apparatus 300 is shown in a 3-dimensional layout. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. For example, aspects of flow control apparatus 300 may be similar to flow control apparatus shown in FIG. 2.

Throttle valve stage 304 and floating plunger stage 306 are shown using a dual-wall design where an external layer is used to secure exterior surfaces of the stages together. For example, attaching devices 332 may be used within both stages 304, 306 to attach top and bottom sections to the stages. A separate inside wall within both stages 304, 306 contains the areas through which exhaust will flow within the stages. The addition of a second wall adds to the robustness of the design against physical damage which could cause leakage of the exhaust into the wafer fabrication environment and contamination of the semiconductor processing chamber. Alternatively, a single-wall design could also be used where attaching devices 332 are also contained within the exhaust flow area. Throttle valve plug 312 is attached to a mounting attachment 330, which couples throttle valve plug 312 to a linear actuator (not shown) or other device providing throttle valve plug 312 with a desired range of motion. Additionally, outlet 324 may extend into floating plug stage 306 to allow for a desired opening size between outlet 324 and floating plunger 318 when the floating plunger 318 is extended in a vertical direction. Flexible attachment 320 is shown as securing floating plunger 318 to an inner wall of floating plunger stage 306.

FIG. 4 is a simplified cross-sectional diagram of an multi-stage flow control apparatus according to an additional embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. For example, flow control apparatus 400 shown in FIG. 4 may share similar elements with flow control apparatus 200 shown in FIG. 2. Flow control apparatus 400 utilizes a multi-stage design, comprising a throttle valve stage 404 and a floating plunger stage 406. Throttle valve stage 404 and throttle valve plug 412 may provide similar functions to the components described in regards to flow control apparatus 200 shown in FIG. 2. In addition, flow control apparatus 400 could also employ a dual-wall design as shown in FIG. 3.

Floating plunger stage 406 is configured with a floating plunger 418, which may be hollow so that the weight of the plunger can be modified by partial filling of the plunger with fluids or solids, thereby customizing the plunger to a particular house exhaust. However floating plunger 418 is coupled with a surface of floating plunger stage 406 through flexible membrane 420. Flexible membrane 420 utilizes an accordion-style design which allows the membrane to expand and contract to accommodate variable amounts of controlled pressure through vent 426. For example, the membrane may be made of silicone, rubber, or other nonpermeable materials. In addition, the stroke of floating plunger 418 is not limited by the material properties of the material chosen for flexible membrane 420, as additional amounts of the material may be incorporated within flexible membrane 420 to allow floating plunger 418 to achieve its full stroke. For example, the stroke of floating plunger 418 may extend to a top face of floating plunger stage 406. Two different pressure regions 430 and 428 are provided, with pressure region 428 above and to the sides of flexible membrane 420 and floating plunger 418, and pressure region 430 below and contained by floating membrane 420 and floating plunger 418. This can allow for improved particulate content within the exhaust flow, as any particulates generated by controlled pressure through vent 426 are maintained within pressure region 430.

The opening 422 being varied by the movement of floating plunger 418 may between an upper inwards surface of floating plunger stage 406 and a top surface of floating plunger 418. For example, a floating plunger 418 may have a large top surface area to guide exhaust flow in a more controlled manner. As the movement of the opening 422 between the floating plunger 418 and a surface of floating plunger stage 406 occurs away from outlet 424, recession of outlet 424 into floating plunger stage 406 is no longer needed.

A guide pin 434 may be employed to improve the lateral stability of floating plunger 418. During operation, floating plunger 418 may shift laterally during operation, which can detract from the flow control of the exhaust. Guide pin 434 and guide pin housing 432 are included to ensure that the motion of floating plunger 418 is maintained in a substantially vertical direction. Guide pin 434 may be coupled to a lower face of floating plunger stage 406, and guide pin housing 432 may be coupled to a bottom face of floating plunger 418. Guide pin housing 432 and guide pin 434 are coupled together to allow for a minimum amount of lateral motion while ensuring floating plunger 418 can extend to its full stroke.

FIG. 5 is a simplified exemplary diagram showing exhaust pressure as a function of time with and without a multi-stage flow control apparatus according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. Signal 500 shows the exhaust pressure vs. time for the exhaust of a semiconductor processing chamber without a flow controlled valve during operation. As an example, the exhaust pressure represented by the signal may be measured at the inlet of inlet 202 as shown in FIG. 2. Signal 502, in comparison, shows the exhaust pressure vs. time for the exhaust of a semiconductor processing chamber with a flow controlled valve during operation. The amount of fluctuation within the exhaust pressure can be greatly minimized and the pressure cycles can be greatly reduced due to the dampening effect of a flow control apparatus on exhaust flow according to an embodiment of the present invention.

FIG. 6 is a simplified exemplary process flow showing processes used to maintain a constant exhaust flow according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. Process flow 600 includes process 602 for providing an exhaust flow through the multi-stage flow control apparatus from a semiconductor processing chamber to a exhaust device, process 604 for determining a set point for the semiconductor processing chamber in the throttle valve stage, process 606 for detecting a deviation in the exhaust flow or pressure, process 608 for moving the position of the plunger to increase the exhaust flow rate and/or decrease pressure in the flow control apparatus, process 610 for moving the position of the plunger to decrease the exhaust flow rate and/or decrease the pressure in the flow control apparatus, process 612 for rechecking the exhaust flow, process 614 for returning to process 606, and process 616 for returning the exhaust flow to equilibrium. For example, process flow 600 may be used in conjunction with the flow control apparatus shown in FIGS. 2-4.

In process 602, an exhaust flow is provided through a flow control apparatus from a semiconductor processing chamber to an exhaust device. During this process, the exhaust flow level through the flow control apparatus is monitored on a periodic or continuous basis to detect variations or deviations from a predetermined exhaust flow level. For example, the exhaust flow rate may be monitored to determine if the measured exhaust flow rate is outside a predetermined window of desired exhaust flow rates. The monitoring can take place at the semiconductor processing chamber, within either stage of the flow control apparatus, or within an exhaust line coupling the semiconductor processing chamber to the flow control apparatus. In an embodiment, a flow or pressure monitor may be utilized to monitor the exhaust flow level through or pressure within the flow control apparatus. In process 604, a set point is determined for the semiconductor processing chamber within the throttle valve stage in the flow control apparatus. When a change, for example, a deviation of exhaust flow rate greater than the desired variability defined by the predetermined window, is detected in the exhaust flow in process 606, steps are taken to address the variation. In addition, the pressure within the flow control apparatus may also be monitored to determine if a deviation in pressure greater than the desired variability defined by the predetermined window is detected. For example, the exhaust flow and pressure may be monitored concurrently with each other.

If the exhaust flow is too low or the pressure within the flow control apparatus is too high, the position of the plunger shifts to increase the exhaust flow rate through the flow control apparatus and/or decrease the pressure in the flow control apparatus in process 608. For example, the floating plunger may be lowered to increase the opening between the top surface of the floating plunger and an upper portion of the output tube in accordance with an embodiment of the invention shown in FIG. 2. Alternatively, the floating plunger may be lowered to increase the opening between the top surface of the floating plunger and a top surface of the floating plunger stage in accordance with an embodiment of the invention shown in FIG. 4. This process may self-regulated by the flow control apparatus without any direct control from a user. For example, control of the vent or applied pressure used to move the floating plunger may be coupled to the pressure and exhaust monitors coupled with the flow control apparatus to form a self-regulated monitoring loop. By coupling these items together, pressure and exhaust flow deviations can be reduced to lower levels by the flow control apparatus.

If the exhaust flow is too high or the pressure within the flow control apparatus is too low, the position of the plunger shifts to decrease the exhaust flow rate through the flow control apparatus and/or increase the pressure in the flow control apparatus in process 610. For example, the floating plunger may be raised to decrease the opening between the top surface of the floating plunger and an upper portion of the output tube in accordance with an embodiment of the invention shown in FIG. 2. Alternatively, the floating plunger may be raised to decrease the opening between the top surface of the floating plunger and a top surface of the floating plunger stage in accordance with an embodiment of the invention shown in FIG. 4. This process may self-regulated by the flow control apparatus without any direct control from a user. For example, control of the vent or applied pressure used to move the floating plunger may be coupled to the pressure and exhaust monitors coupled with the flow control apparatus to form a self-regulated monitoring loop. By coupling these items together, pressure and exhaust flow deviations can be reduced to lower levels by the flow control apparatus.

In process 612, the exhaust flow and pressure are rechecked to ensure that any deviation in exhaust flow or pressure has subsided to be within a predetermined window. If so, the exhaust flow and pressure return to an acceptable equilibrium level in process 616. If deviations are still detected, the system returns to process 606 until an equilibrium level is reached.

FIG. 7 is a simplified cross-sectional diagram of a multi-stage flow control apparatus according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. A multi-stage flow control apparatus 700 is provided for use between a semiconductor processing chamber (not shown) and an exhaust device (not shown). For example, the semiconductor processing chamber may be a lithography device including one or more bowls used within lithography processing steps such as a track lithography tool described in FIG. 1. In another example, the exhaust device may be house exhaust present in a semiconductor manufacturing facility which is shared between several processing apparatus. Alternatively, the exhaust device may be a turbopump, roughing pump, cryopump, or other stand-alone vacuum device capable of generating an exhaust flow. The multi-stage flow control apparatus 700 may comprise two stages: a throttle valve stage 704 used to control a desired flow rate or set point from the bowl, and a floating plunger stage 706 used to reduce or eliminate the fluctuations and back streaming from the house exhaust. Of course, there can be other variations, modifications, and alternatives.

The design of throttle valve stage 704 may be similar to that of throttle valve stages 204 and 404. For example, throttle valve stage 704 is coupled with an inlet 702, which receives a flow input from the semiconductor processing chamber. Furthermore, inlet 702 provides an opening to throttle valve stage 704. Throttle valve stage 704 may be shaped in a variety of configurations depending upon the specific implementation. For example, throttle valve stage 704 may include a seat 708 with upward sloping faces. The base of the seat 708 may reveal an internal orifice 710 employed to allow exhaust flow 716 from the semiconductor processing chamber to progress from throttle valve stage 704 to floating plunger stage 706.

Throttle valve stage 704 further includes throttle valve plug 712, which may be controlled by a linear actuator (not shown) to control a desired flow rate or set point from the bowl. Of course, other devices could be used to provide throttle valve plug 712 with a desired range of motion. For example, the linear actuator may be coupled with throttle valve plug 712 at its stem 713 which protrudes from throttle valve stage 704. The desired flow rate may be set by modulating the distance 714 between throttle valve plug 712 and upward sloping faces of seat 708. A larger distance between throttle valve plug 712 and upward sloping faces of seat 708 can allow for an increased flow rate, and a smaller distance between throttle valve plug 712 and upward sloping faces of seat 708 can allow for a reduced flow rate. Throttle valve plug 712 may be modulated by the linear actuator to move in a substantially vertical motion, thus allowing for a varied amount of exhaust flow to progress between throttle valve plug 712 and upward sloping faces of seat 708. In another example, upward sloping faces of seat 708 and the portion of throttle valve plug 712 opposite from upward sloping faces of seat 708 may possess the same gradient to allow for minimal obstruction in the exhaust flow path.

Other throttle configurations could also be used as well, such as a throttle with downwards sloping faces and a similarly shaped throttle valve plugs. However, one additional advantage to utilizing upward sloping faces within throttle valve stage 704 is that the exhaust device (not shown) pulls the throttle valve closed during operation. For example, during conventional operation of the device, the desired flow rates may be low, necessitating a small gap between the throttle valve plug and the faces to restrict exhaust flow. By utilizing the exhaust flow stream to partially close the throttle valve in an upward sloping face design, a reduced amount of force can be expended in setting the desired flow rate for the device.

A floating plunger stage 706 is coupled to throttle valve stage 704, and exhaust flow 716 proceeds from throttle valve stage 704 through floating plunger stage 706 and exits flow control apparatus 700 through an outlet 724. A floating plunger 718 moves vertically to vary the opening 722 to outlet 724, with the motion being a function of the weight of floating plunger 718, the pressure in the region 730 below the floating plunger 718, and the vacuum level above the floating plunger 718. Among other functions, floating plunger 718 is designed to reduce or eliminate the fluctuations in the exhaust from an exhaust device and potential back streaming from the exhaust device. An opening 722 may be defined between a top surface of floating plunger 718 and outlet 724. As floating plunger 718 rises in a vertical direction, opening 722 is reduced in size, and opening 722 is enlarged when plunger 718 is lowered in a vertical direction. This can greatly reduce the amount of backflow and exhaust that can progress upstream and affect the operation of the semiconductor processing chamber coupled with flow control apparatus 700. In addition, the floating plunger implementation further helps to eliminate variations in the exhaust level by providing a controlled area through which exhaust 716 can flow. In addition, if an exhaust device is shared among different processing apparatus, crosstalk between different processing apparatus can also be reduced.

A vent 726 providing a controlled pressure below floating plunger 718 causes the floating plunger 718 to rise to a desired level. Floating plunger 718 may float and not be in contact with any other surfaces during operation of flow control apparatus 700 when a controlled pressure is applied through vent 726. Floating plunger 718 may have a primarily flat surface facing the lower surface of floating plunger stage 706 to optimize the upwards movement of floating plunger 718 in response to the applied pressure through vent 726. Side regions 740 of floating plunger 718 may be elevated on one or both sides to reduce the amount of movement of floating plunger 718 needed to close opening 722. Of course, there can be other variations, modifications, and alternatives.

Floating plunger 718 may be centered upon a guide pin 732, which may be attached to an interior surface of floating plunger stage 706. For example, floating plunger 718 may be designed so that at least a portion of its surface is elevated to accommodate guide pin 732. Of course, other attachment methods could also be used, such utilizing a multiple guide pin design. The inclusion of guide pin 732 within floating plunger stage 706 allows for floating plunger 718 to move in a substantially vertical direction without incurring lateral or rotational movement. A physical coupling may be made between floating plunger 718 and guide pin 732, or a gap maintained between guide pin 732 and floating plunger 718 that is closed when floating plunger 718 experiences lateral or rotational movement. For example, floating plunger 718 may rest upon guide pin 732 when no controlled pressure is provided through vent 726. Alternatively, guide pin 732 may also protrude from floating plunger 718. Support posts 734 may be provided to prevent floating plunger 718 from contacting a top surface of floating plunger stage 706. For example, support posts 734 may be coupled to an interior surface of floating plunger stage 706. For example, support posts 734 may be made from an rubber or soft material that allows for contact with floating plunger 718 without damage. In addition, the height of support post 734 may be set to provide an upper limit for the stroke of floating plunger 718. Correspondingly, the height of guide pin 732 may be set to provide a lower limit for the stroke of floating plunger 718. For example, the upper and lower limits of floating plunger 718 may be correspond with the upper and lower surfaces of outlet 724. Of course, there can be other variations, modifications, and alternatives.

A small gap 736 may be present between floating plunger 718 and a side surface of floating plunger stage 706. Unlike the embodiments described in regards to FIGS. 2 and 4, a separate vacuum is not maintained above and below floating plunger 718. Instead, gas can flow from below floating plunger 718 through gap 736. The gas can then be exhausted through outlet 724 to leave flow control apparatus 700. A pressure differential Δp is present between region 730 and region 720, as a result of the gap 736 and controlled pressure through vent 726 being applied to the bottom of floating plunger 718. The size of the gap 736 must be chosen to fit the desired flow characteristics of the flow control apparatus, as a gap 736 that is too large will not maintain a pressure differential Δp above and below the floating plunger 718 due to large outflows through gap 736. Additionally, a overly large gap 736 can also lead to increased particulates moving through vent 726 reaching into region 720 above floating plunger 718. An additional benefit towards having a flow of gas through gap 736 is that it can contribute to the lateral stability of floating plunger 718 in operation. Of course, there can be other variations, modifications, and alternatives.

Floating plunger 718 may be made from a variety of materials, including plastic, aluminum, or other lightweight materials that are buoyant under a controlled pressure through vent 726. For example, floating plunger 718 may be hollow so that the weight of the plunger can be modified by partial filling of the plunger with fluids or solids, thereby customizing the plunger to a particular house exhaust.

The movement of floating plunger 718 under controlled pressure through vent 726 may be in a substantially vertical position. To reduce the size of an opening 722 between a top surface of floating plunger 718 and an upper portion of outlet 724, outlet 724 may be recessed into floating plunger stage 706. By doing so, the horizontal distance between floating plunger 718 and outlet 724 can be reduced and exhaust flows more accurately maintained.

FIG. 8 is a simplified perspective view of a multi-stage flow control apparatus according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize many other variations, modifications, and alternatives. For example, aspects of flow control apparatus 800 may be similar to flow control apparatus shown in FIG. 7 and FIG. 3.

Throttle valve stage 804 and floating plunger stage 806 are shown using a dual-wall design where an external layer is used to secure exterior surfaces of the stages together. For example, attaching devices 832 may be used within both stages 804, 806 to attach top and bottom sections to the stages. A separate inside wall within both stages 804, 806 contains the areas through which exhaust will flow within the stages. The addition of a second wall adds to the robustness of the design against physical damage which could cause leakage of the exhaust into the wafer fabrication environment and contamination of the semiconductor processing chamber. Alternatively, a single-wall design could also be used where attaching devices 832 are also contained within the exhaust flow area.

Throttle valve plug 812 is attached to a mounting attachment 830, which couples throttle valve plug 812 to a linear actuator (not shown) or other device providing throttle valve plug 812 with a desired range of motion. In addition, guide pin 820 is shown coupled to floating plunger 818 to restrict the lateral or rotational movement of floating plunger 818 and allow floating plunger 818 to move in a substantially vertical direction. Floating plunger 818 is also shown within its rest position, where no pressure is provided underneath floating plunger 818 to move floating plunger 818 in a substantially vertical direction. For example, the position of side regions 834 of floating plunger 818 may be below an inner orifice of outlet 836 at the rest position so that when pressure is applied to floating plunger 818, the exhaust flow through outlet 836 may be controlled. Of course, there can be other variations, modifications, and alternatives.

While the present invention has been described with respect to particular embodiments and specific examples thereof, it should be understood that other embodiments may fall within the spirit and scope of the invention. The scope of the invention should, therefore, be determined with reference to the appended claims along with their full scope of equivalents.

Multi-stage flow control apparatus

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