Gas transport delay resolution for short etch recipes

In one embodiment, an apparatus for providing a gas mixture of a plurality of gases, may have a plurality of mass flow controllers (MFCs), a mixing manifold in fluid connection with each plurality of MFCs, a plurality of mixing manifold exits positioned on the mixing manifold; and an isolation device in fluid connection with each of the plurality of mixing manifold exits.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 (e) to U.S. Provisional Patent Application No. 61/016,908, filed on Dec. 27, 2007, entitled “Gas Transport Delay Resolution for Short Etch Recipes”, which is incorporated by reference herein for all purposes.

FIELD OF THE INVENTION

The present disclosure relates generally to gas delivery systems. More particularly, the present invention relates to a gas delivery system to reduce gas transport delays. Even more particularly, the present invention relates to a gas delivery system to reduce gas transport delays to efficiently mixing process gases.

BACKGROUND OF THE INVENTION

Process gasses are delivered from a gas box to a process chamber for various applications, such as reactive ion etching applications for building transistors on silicon wafers. Process gases are mixed downstream of the mass flow controllers (MFCs) to a mixing manifold prior to delivery to the process chamber, such as a plasma reaction chamber. Therefore, it is necessary to achieve good mixing of very low flow and high flow rate carrier gases in the mixing manifold and deliver them without significant delays (within allowed gas settlement times) to the process chamber to perform the various applications, such as etching.

Transient gas flow delays to the process chamber, which are greater than the allowed gas settlement times, affect etch rates adversely for short process recipes (30 seconds to 60 seconds processes) due to non-stabilized or unsteady flows to the chamber. The problem is further enhanced due to hardware differences in various gas boxes causing different transport delays to process chambers to create etch rate matching issues. In a gas-box with multiple gas feeds of low and high flow rate gases, spatially separated in a random gas order from various MFCs, are bound to be delivered at different times to the process chamber depending upon their diffusivity and flow velocities (momentum or inertia).

The gas delay delivery problems may be attributed to the volume through which low flow gases flow to mix with the higher flow carrier gas(es). Delayed delivery of key process etching gases to the reaction chamber impacts wafer etch rates and critical dimensions on silicon wafers. In a mixing manifold with an isolated low flow gas, located away from a high flow gas, will take some physical length of time to mix with higher flow gas used to speed-up the deliver of the gas mixture to the chamber. The time required to fill the low flow gas volume from the MFC until it mixes with the high flow gas, as well as its diffusion through the high flow gas, determines the total transport delay to the reaction chamber.

OVERVIEW

The present invention provides for an apparatus, method, and system to reduce gas transport delays and to efficiently mix process gases in a gas delivery system. In one embodiment, an apparatus for providing a gas mixture of a plurality of gases, may have a plurality of mass flow controllers (MFCs), a mixing manifold in fluid connection with each plurality of MFCs, a plurality of mixing manifold exits positioned on the mixing manifold; and an isolation device in fluid connection with each of the plurality of mixing manifold exits.

In another embodiment, a method for dynamically mixing a plurality of gases, may comprise receiving a first gas at a first gas inlet to a mixing manifold, the first gas being received at a first flow rate, receiving a second gas at a second gas inlet to the mixing manifold, the second gas being received at a second flow rate, determining whether the first flow rate is less than the second flow rate, and automatically opening a first mixing manifold exit proximate to the first gas inlet when the determining determines that the first flow rate is less than the second flow rate.

The present invention provides other hardware configured to perform the methods of the invention, as well as software stored in a machine-readable medium (e.g., a tangible storage medium) to control devices to perform these methods. These and other features will be presented in more detail in the following detailed description of the invention and the associated figures.

DESCRIPTION OF EXAMPLE EMBODIMENTS

Embodiments are described herein in the context of gas transport delay resolution for short etch recipes. The following detailed description is illustrative only and is not intended to be in any way limiting. Other embodiments will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations as illustrated in the accompanying drawings. The same reference indicators will be used throughout the drawings and the following detailed description to refer to the same or like parts.

The present invention provides for an apparatus, method, and system to reduce gas transport delays and to efficiently mix process gases in a gas delivery system.FIGS. 1A and 1Billustrate an exemplary gas stick. Although illustrated with certain components, the specific components are not intended to be limiting as different components may be used and/or less or more components may be used to form the gas stick. Additionally, although described with a single gas stick, the number of gas sticks is not intended to be limiting. As discussed above, a plurality of gas sticks, form a gas box or panel. In an embodiment, the valve on the components is an integrated surface mount valve. In general, an integrated surface mount component is a gas control component (e.g., valve, filter, etc.) that is connected to other gas control components through channels on a substrate assembly, upon which the gas control components are mounted. This is in contrast to gas control components that are generally attached through bulky conduits with VCR attachments (vacuum coupled ring).

Referring toFIG. 1A, the gas stick100may have a gas stick input port102to input a supply gas. The term gas used herein is not intended to be limiting and is meant to include any liquid, gas, or a combination of liquid and gas. A manual valve104may be used for carrying out the supply or isolation of the supply of supply gas. The manual valve104may also have a lockout/tagout device106above it. Worker safety regulations often mandate that plasma processing manufacturing equipment include activation prevention capability, such as a lockout/tagout mechanism. Generally a lockout is a device that uses positive means such as a lock, either key or combination type, to hold an energy-isolating device in a safe position. A tagout device is generally any prominent warning device, such as a tag and a means of attachment that can be securely fastened to energy-isolating device in accordance with an established procedure.

A regulator108may be used to regulate the gas pressure or the supply gas and a pressure gauge110may be used to monitor the pressure of the supply gas. In one embodiment, the pressure may be preset and not need to be regulated. In another embodiment, a pressure transducer (not illustrated) having a display to display the pressure may be used. The pressure transducer may be positioned next to the regulator108. A filter112may be used to remove impurities in the supply gas. A primary shut-off valve114may be used to prevent any corrosive supply gasses from remaining in the gas stick. The primary shut-off valve114may be two-port valve having an automatic pneumatically operated valve assembly that causes the valve to become deactivated (closed), which in turn effectively stops plasma gas flow within the gas stick. Once deactivated, a non-corrosive purge gas, such as nitrogen, may be used to purge the gas stick. The purge valve116may have three-ports to provide for the purge process—an entrance port, an exit port and a discharge port.

Adjacent the purge valve116may be an MFC118. The MFC118accurately measures the flow rate of the supply gas. Positioning the purge valve116next to the MFC118allows a user to purge any corrosive supply gasses in the MFC118. A mixing valve120next to the MFC118may be used to control the amount of supply gas to be mixed with other supply gasses on the gas panel.

Each component of the gas stick may be positioned above a manifold block. A plurality of manifold blocks form a substrate122, a layer of manifold blocks that creates the flow path of gasses through the gas stick100. The gas delivery components may be positioned on the manifold blocks by any known means such as with a pressure fitting sealant (e.g., C-seal) and the like.

FIG. 1Billustrates the current flow of gases through the gas stick100. The gas may flow out of from the purge valve116and into the MFC118in the direction of flow path A. The gas may then flow out of the MFC118into the substrate122, through the mixing valve120and into the mixing manifold226as illustrated by flow path D.

FIG. 2is a block diagram ofFIG. 1Bto illustrate the delay time of a low flow gas. The gas box200may have a plurality of MFCs118a,118b,118c,118n(where n is an integer). Each MFC may be a high flow MFC or a low flow MFC. A low flow gas may have a flow rate of less than or equal to 7 sccm. A high flow gas may have a flow rate greater than 7 sccm. For exemplary purposes only and not intended to be limiting, as illustrated inFIG. 2, MFC118cis illustrated as a low flow MFC and MFC118ais illustrated as a high flow MFC. However, any MFC may be either a high flow MFC or a low flow MFC.

Each MFC118a-118n, may be in fluid communication with the mixing manifold126via gas inlet142a,142b,142c,142n. The gas inlet may be any type of inlet that may be manually or remotely controlled. For example, the gas inlet may be any known junction that may be manually positioned in an open or closed position. In another example, the gas inlet may be any known valve that may be controlled via a remote server or controller to be remotely and/or automatically positioned in an open or closed position. The volume of gas from the MFC118a-118nto the gas inlet142a-nmay be represented by V1. Once the gas enters the mixing manifold126, it may flow in the direction of flow path B to a mixing manifold exit140near the high flow MFC118a. The high flow carrier gas causes a high forced convection to drive the low flow gas toward the mixing manifold exit140thereby attempting to minimizing delay of the mixing with the low flow gas. The volume of gas from the gas inlet142cto the mixing manifold exit140may be represented by V2.

Once the gas mixture exits the mixing manifold126, the gas mixture may be flowed and retained in an isolation chamber144until it is used in a process chamber. The isolation chamber may be any type of chamber used to isolate the gas prior to being used, such as a dual gas feed, or the like.

The total delay time of a low flow gas to mix with a high flow carrier gas (Total Delay TimeLow Flow Gas) may be calculated as the time it takes for the low flow gas to reach the mixing manifold (Tmm) plus the time it takes the gas to diffuse (Tdiffusion) with the high flow carrier gas, as illustrated in the following equation:
Total Delay TimeLow Flow Gas=Tmm+Tdiffusion(1)

The time for the low flow gas to reach the mixing manifold126, or the inertial delay of the low flow gas (illustrated as V1), may be calculated as follows:
Tmm=(V/φm)*(Pmm/Pambient)  (2)

Wherein V=volume of the gasφm=mass flow rate of the low flow gasPmm=pressure in the mixing manifoldPambient=ambient pressure

The time it takes the low flow gas to diffuse (Tdiffusion) with the high flow carrier gas, may be calculated as follows:
TdiffusionαL2/Deffective(3)

Wherein L2=diffusion coefficient of the low flow gasDeffective=effective rate of diffusion

The examples provided herein are merely for exemplary purposes and are not intended to be limiting. The current volume of a low flow gas from the MFC to the mixing manifold may be between about 4-5 cubic centimeters (cc), the pressure in the mixing manifold may be about 100 Torr, and Pambientmay be 760 Torr. Thus, the delay time for a low flow gas to reach the mixing manifold (Tmm) may be calculated as follows:

Thus, a 40 second delay in the flow of a gas to the mixing manifold would adversely affect etch rates for short process recipes that are 30 seconds to 60 seconds long, such as in reactive ion etching or gas modulated applications as the process gases may not be mixed properly or the process gases may not even be mixed together in the mixing manifold. Additionally, the slower the flow rate, the greater the delay will be. Thus, a way to reduce the time delay may be to lower the gas volume from the MFC118a-nto the mixing manifold126or locate the mixing manifold exit140near a low flow MFC.

FIG. 3is a block diagram of an exemplary mixing manifold having a plurality of mixing manifold exits. The mixing manifold126may have a plurality of mixing manifold exits148a,148b,148c,148n. This allows for the flexibility to locate the mixing manifold exit148a-nproximate or substantially close to a low flow MFC, illustrated as MFC118cinFIG. 3, thereby minimizing delay of the low flow gas when mixing with the high flow gas. In use, the high flow gas in MFC118a, may enter the mixing manifold126via gas inlet142a. The high flow gas may then flow in the direction of flow path C toward the low flow gas entering into the mixing manifold via gas inlet142c. The gas mixture may then exit the mixing manifold126via mixing manifold exit148c. V2Newmay be the volume of gas from the gas inlet142cto the mixing manifold exit148c, which may be less than V2illustrated inFIG. 2.

By having multiple mixing manifold exits148a-nand opening the mixing manifold exit148a-nproximate or closest to the low flow MFC, this ensures that the low flow gases will mix with the high flow gases prior to exiting the mixing manifold126. In other words, having multiple manifold exits may minimize the delay or flow time for the low flow gas to the mixing manifold exit such that the low flow gas may be able to mix with the high flow gas prior to exiting the mixing manifold126.

As illustrated inFIG. 3, mixing manifold exits148a, b, nmay be closed and mixing manifold exit148cmay be opened as it is proximate or closer to the low flow MFC118cthan the other mixing manifold exits148a, b, n. As the low flow gas flows from the MFC118cto the mixing manifold126, the high flow gas may simultaneously flow from the MFC118ato the mixing manifold exit148c. Just as the high flow gas reaches the mixing manifold exit148c, it may mix with the low flow gas entering the mixing manifold via gas inlet142c. The gas mixture may then exit the mixing manifold126via mixing manifold exit148c. Thus, the delay time or lag time for the low flow gas to flow to the mixing manifold exit may be minimized.

Although illustrated with the use of two gases, the number of gases used is not intended to be limiting as any number of gases may be used to form a gas mixture. For example, MFC118aand118bmay both be high flow gases and MFC118cmay be a low flow gas. In another example, MFC118amay be a high flow MFC and MFC118band MFC118cmay both be low flow gases.

In one embodiment, the mixing manifold exits148a-nmay be any known junction that may be manually positioned in an open or closed position. In another embodiment, the mixing manifold exits148a-nmay be valves controlled via a remote server or controller, as further described with reference toFIGS. 10A and 10B. Thus, the mixing manifold exits148a-nmay be remotely and automatically controlled to be in an opened or closed position.

Additionally, MFCs may also be controlled by a remote server or controller. The MFCs may be a wide range MFC having the ability to be either a high flow MFC or a low flow MFC. The controller may be configured to control and change the flow rate of a gas in each of the MFCs. As such, the controller may be configured to monitor the flow rates of each MFC, having the ability to change the flow rate of each MFC, determine which MFC has the slowest flow rate, and control the mixing manifold exits to open the mixing manifold exit proximate the lowest flow rate MFC. This may be useful in processes such as gas modulation processes. Such a process is further described in detail in co-owned U.S. Pat. No. 6,916,746, entitled “High-Performance Etching of Dielectric Films Using Periodic Modulation of Gas Chemistry”, filed Apr. 9, 2003 and is incorporated herein by reference for all purposes.

The controller may also be configured to close the mixing manifold exits that are not proximate the lowest flow MFC. However, the controller may be configured to open and close the exits as determined by a user as the user may desire to have multiple exits opened as there may be more than one low flow MFC, the user may desire to have a mixing manifold exit open proximate a high flow MFC, and the like.

The following example is for exemplary purposes only and not intended to be limiting as any combination of gasses, flows, processes and the like may be used. In a first process the following requirement may be desired:

Any time thereafter, such as between about 20-60 seconds later, a second process may be desired. The second process may have the following requirements:

MFC 118a:low flow gas AMFC 118bhigh flow gas BMFC 118chigh flow gas C
Thus, mixing manifold exit (MME)148b, c, nmay be closed and MME148amay be opened. The MFCs and the MMEs may be automatically changed via a remote computer or controller.

After the second process is complete, such as between about 20-60 second, the user may desire to revert back to the first process and/or start a third process. As will now be known, any combination of flow rates, processes, and the like may be performed using the various embodiments of the present invention.

FIGS. 4A and 4Billustrate an exemplary flange to reduce the volume of a gas flow from the MFC to the mixing manifold. As discussed above, reducing the volume of gas from the MFC to the mixing manifold may reduce the flow time of a low flow gas from the MFC to the mixing manifold.FIG. 4Aillustrates a front perspective view of the exemplary flange andFIG. 4Billustrates a back perspective view of the exemplary flange. The flange400may have a mating member402to mate with a gas delivery component, such as a mixing valve120(illustrated inFIG. 5). Although illustrated as a circular mating member402, it will now be known that the mating member may be any shape and/or configuration as necessary to mate with any desired gas delivery component. The flange400may have a gas inlet port406in fluid communication with the gas delivery component and a gas outlet port408in fluid communication with the mixing manifold126.

FIG. 5illustrates the flow of gas in a gas stick using the flange ofFIGS. 4A and 4B. The flow of gas from the purge valve116to the MFC118ain the direction of flow path A is similar to the flow path as illustrated inFIG. 1B. However, the flow path from the MFC118to the mixing manifold126in the direction of flow path E has a lower volume, V1New. The gas flows directly to the mixing manifold126from the MFC118rather than through a substrate122(as illustrated inFIGS. 1A and 1B). Thus, V1Newis less than V1. Additionally, V1Newis less than 1 cc, and preferably between about 0.01 cc to 1 cc. By reducing V1, the flow time delay of a low flow gas may be decreased.

Use of the flange400may also result in an efficient gas delivery. The gas delivery component, the mixing valve120as illustrated inFIG. 5, may be positioned in a horizontal position along the x-axis. Positioning the mixing valve120in a horizontal position allows for the low flow gas to be quickly measured and flowed vertically to the mixing manifold126. This position not only reduces the volume, V1New, of gas, but also allows the gas to flow quicker and uninterrupted to the mixing manifold126.

FIGS. 6A and 6Bare perspective views illustrating exemplary universal fluid flow adaptors. The gas stick may also be used with a universal fluid flow adaptor600(also illustrated inFIG. 5) to decrease the volume of gas flow from the MFC118to the mixing manifold126.FIG. 6Ais a perspective view of a two-port universal fluid flow adaptor andFIG. 6Bis a perspective view of a three-port universal fluid flow adaptor. Referring toFIGS. 6A and 6B, the universal fluid flow adaptor600may be a single structure having a top surface602opposite a bottom surface604, a first side610opposite a second side612, and a first end608opposite a second end606. The adaptor600may have a plurality of vertical channels or conduits616to receive and communicate a gas (i.e. a gas, liquid, or combination thereof). As the term is used herein, a conduit refers to a channel, tube, routing port, pipe, or the like that permits gaseous or fluid communication between two locations. The vertical conduits616may extend through the adaptor600from the top surface602to the bottom surface604in the interior of the adaptor600. Although the vertical conduits616are illustrated extending through the adaptor600in a straight line along the same vertical axis, it will be appreciated that the vertical conduit may having an opening on the top surface that is different that the opening on the bottom surface. For example, the vertical conduit616may have an opening on the top surface602, intersect a horizontal conduit614within the adaptor600, and exit the adaptor600at the bottom surface604at a location that is different from the vertical axis of the opening at the top surface602.

As illustrated inFIG. 6A, one of the vertical conduits616may be an entrance port and the other vertical conduit616may be an exit port. As illustrated inFIG. 6B, one vertical conduit616may be an entrance port, another vertical conduit616may be an exit port, and the last vertical conduit616may be a discharge port. Gas delivery components, such as valves (see, e.g.FIG. 1A), may be coupled to the top surface602of the adaptor600such that gases enter into the valve through the entrance port and exit through the exit port.

The adaptor600may also have a plurality of horizontal channels or conduits614to receive and communicate the gas. The horizontal conduits614may extend through the first side610to the second side612and/or from the first end608to the second end606in the interior of the adaptor600. As illustrated, the vertical conduits616may converge with the horizontal conduit614at the interior of the adaptor600and the horizontal conduits614may converge with each other to form at least one cross-shaped or t-shaped conduit. Thus, a gas may have at least four different flow paths from which to flow.

The adaptor600may also have a plurality of apertures620. Although illustrated with the apertures620extending through the top surface602to the bottom surface604, the apertures may only extend partially through the top surface602or the bottom surface604. Additionally, the apertures620may be threaded or designed to receive an attachment means, such as a screw, to couple the adaptors600to a gas delivery component or a flange400(FIG. 5).

Additional universal fluid flow adaptors that may be used with the various embodiments discussed herein are further discussed in detail in co-pending application Ser. No. 60/979,788, entitled “Universal Fluid Flow Adaptor”, filed on Oct. 12, 2007, and co-pending application Ser. No. 11/761,326, entitled “Flexible Manifold For Integrated Gas System Gas Panels”, filed on Jun. 11, 2007, both of which are incorporated herein by reference for all purposes.

FIG. 7is a flow diagram of a method for dynamically mixing a plurality of gases. Although illustrated with the use of two gases, it will now be known that any number of gases may be used to form any desired gas mixture. Additionally, the term gas used herein is not intended to be limiting and is meant to include any liquid, gas, or a combination of liquid and gas. A first gas may be received at a first gas inlet to a mixing manifold, the first gas being received at a first flow rate at700. A second gas may be received at a second gas inlet to the mixing manifold, the second gas being received at a second flow rate at702.

The first and second gases may be flowed into a mixing manifold having a plurality of mixing manifold exits. This allows for the flexibility to locate the mixing manifold exit near a low flow MFC to minimizing the delay of the low flow gas from mixing with the high flow gas to ensure that the low flow gases will mix with the high flow gases prior to exiting the mixing manifold. In other words, having multiple manifold exits and/or having a manifold exit located proximate or substantially close to a low flow MFC provides the low flow gas time to flow into the mixing manifold such that it will flow into the mixing manifold in time to mix with the high flow gas prior to exiting the mixing manifold exit.

A determination may be made as to which of the first flow rate and the second flow rate is slower. A mixing manifold exit proximate to the first gas inlet may be automatically opened when it is determine that the first flow rate is less than the second flow rate at704. Otherwise, the mixing manifold exit proximate to the second gas inlet may be automatically opened when it is determine that the second flow rate is less than the first flow rate at706. The mixing manifold exits may be manually controlled or remotely controlled in an opened or closed position. The mixing manifold exits may be valves controlled via a remote server or controller, as further described with reference toFIGS. 10A and 10B. Thus, the mixing manifold exits may be remotely and automatically controlled to be in an opened or closed position.

If the process is not complete at708, the gas flow rates may be monitored at710. Each MFCs may be controlled by a remote server or controller. Each MFC may be a wide range MFC having the ability to be either a high flow MFC or a low flow MFC. The controller may be configured to control and change the flow rate of a gas in each of the MFCs. As such, the controller may be configured to monitor the flow rates of each MFC, having the ability to dynamically change the flow rate of each MFC, determine which MFC has the slowest flow rate, and control the mixing manifold exits to open the mixing manifold exit proximate the lowest flow rate MFC and/or close the mixing manifolds that are not proximate the lowest flow rate MFC. Should the controller detect a change in the flow rate at712, the process may repeat from706. As such, the second inlet proximate to a second mixing manifold exit may automatically be opened when it is determined that the second flow rate is less than the first flow rate.

The embodiments described above may be used in various applications. For example,FIG. 8is a schematic view of an exemplary gas feed device for semiconductor processing. A plasma processing chamber810is supplied processing gas through gas supply line814. The gas supply line812may provide process gas to a showerhead or other gas supply arrangement arranged in the upper portion of the chamber. Additionally, gas supply line814may supply processing gas to a lower portion of the chamber such as, for example, to a gas distribution ring surrounding the substrate holder or through gas outlets arranged in the substrate support. However, an alternative dual gas feed arrangement can supply gas to the top center and top perimeter of the chamber. Processing gas may be supplied to gas line814from gas supplies816,818,820,830the process gasses from supplies816,818,820,830being supplied to MFC822,824,826,832respectively. The MFC822,824,826,832supply the process gasses to a mixing manifold828having a plurality of mixing manifold exits802a,802b,802c,802nafter which the mixed gas is directed to an isolation chamber804. The mixed gas may then be directed to gas flow line814.

In operation, the user may select the fraction of mixed flow to be delivered to the plasma processing chamber. For example, the user might select a flow of 250 sccm Ar/30 sccm C4F8/15 sccm C4F6/22 sccm O2delivered through line814. By comparing the total flow, which in this case could be measured by summing all of the flow readouts of the MFC822,824,826,832in the gas box, the controller can adjust the degree of throttling in line814to achieve the desired flow distribution. Alternatively, an optional total flow meter could be installed just downstream of the mixing manifold828to measure the total flow of mixed gas, rather than determining the total flow by summing the readouts of the MFCs822,824,826,832in the gas box.

In another example,FIG. 9illustrates a schematic view of another exemplary plasma processing chamber900that may be used in embodiments of the invention. The plasma processing chamber900may comprise confinement rings902, an upper electrode904, a lower electrode908, a gas source910, and an exhaust pump920. The gas source910may be substantially similar to the gas source910discussed with reference toFIG. 8and will not be discussed herein. Within plasma processing chamber900, the substrate wafer980, over which the oxide layer is deposited, is positioned upon the lower electrode908. The lower electrode908incorporates a suitable substrate chucking mechanism (e.g., electrostatic, mechanical clamping, or the like) for holding the substrate wafer980. The reactor top928incorporates the upper electrode904disposed immediately opposite the lower electrode908. The upper electrode904, lower electrode908, and confinement rings902define the confined plasma volume940. Gas is supplied to the confined plasma volume by gas source910through a gas inlet943and is exhausted from the confined plasma volume through the confinement rings902and an exhaust port by the exhaust pump920. The exhaust pump920forms a gas outlet for the plasma processing chamber. An RF source948is electrically connected to the lower electrode908. Chamber walls952define a plasma enclosure in which the confinement rings902, the upper electrode904, and the lower electrode908are disposed. The RF source948may comprise a 27 MHz power source and a 2 MHz power source. Different combinations of connecting RF power to the electrodes are possible.

An 2300 Exelan™ dielectric etch system made by Lam Research Corporation™ of Fremont, Calif. modified to provide the cycle time required by the invention may be used in a preferred embodiment of the invention. A controller935is controllably connected to the RF source948, the exhaust pump920, and the plurality of mixing manifold exits802a-nand gas inlets850a-n(FIG. 8) of gas source910. A showerhead may be connected to the gas inlet943. The gas inlet943may be a single inlet for each gas source or a different inlet for each gas source or a plurality of inlets for each gas source or other possible combinations.

FIGS. 10A and 10Billustrate a computer system1000, which is suitable for implementing a controller used in embodiments of the present invention.FIG. 10Ashows one possible physical form of the computer system. Of course, the computer system may have many physical forms ranging from an integrated circuit, a printed circuit board, and a small handheld device up to a huge super computer. Computer system1000includes a monitor1002, a display1004, a housing1006, a disk drive1008, a keyboard1010, and a mouse1012. Disk1014is a computer-readable medium used to transfer data to and from computer system1000.

FIG. 10Bis an example of a block diagram for computer system1000. Attached to system bus1020are a wide variety of subsystems. Processor(s)1022(also referred to as central processing units, or CPUs) are coupled to storage devices, including memory1024. Memory1024includes random access memory (RAM) and read-only memory (ROM). As is well known in the art, ROM acts to transfer data and instructions uni-directionally to the CPU and RAM is used typically to transfer data and instructions in a bi-directional manner. Both of these types of memories may include any suitable of the computer-readable media described below. A fixed disk1026is also coupled bi-directionally to CPU1022; it provides additional data storage capacity and may also include any of the computer-readable media described below. Fixed disk1026may be used to store programs, data, and the like and is typically a secondary storage medium (such as a hard disk) that is slower than primary storage. It will be appreciated that the information retained within fixed disk1026may, in appropriate cases, be incorporated in standard fashion as virtual memory in memory1024. Removable disk1014may take the form of any of the computer-readable media described below.

CPU1022is also coupled to a variety of input/output devices, such as display1004, keyboard1010, mouse1012and speakers1030. In general, an input/output device may be any of: video displays, track balls, mice, keyboards, microphones, touch-sensitive displays, transducer card readers, magnetic or paper tape readers, tablets, styluses, voice or handwriting recognizers, biometrics readers, or other computers. CPU1022optionally may be coupled to another computer or telecommunications network using network interface1040. With such a network interface, it is contemplated that the CPU might receive information from the network, or might output information to the network in the course of performing the above-described method steps. Furthermore, method embodiments of the present invention may execute solely upon CPU1022or may execute over a network such as the Internet in conjunction with a remote CPU that shares a portion of the processing.

FIG. 11is a flow diagram of an exemplary method for controlling a plurality of mixing manifold exit valves. As stated above, the gas source may be controlled by a remote controller. The remote controller may be configured to communicate with the plurality of MFCs in the gas source to determine whether each MFC is opened or closed and determine the flow rate of each MFC. The remote controller may have computer readable code for determining which of the plurality of MFCs has a lowest flow rate at1100.

The remote controller may also be configured to communicate with the plurality of mixing manifold exit valves in the gas source to open and/or close each of the plurality of mixing manifold exits on the mixing manifold. The remote controller may have computer readable code for opening at least one mixing manifold exit valves to minimize a delay flow time or lag time of the MFC with the lowest flow rate at1102. Thus, the delay time or lag time for the low flow gas to flow from the MFC to the mixing manifold exit may be minimized.

The remote controller may continue to monitor the flow rate of each of the plurality of MFCs and have computer readable code for determining when there is a change in any of the MFC flow rates at1104. In another embodiment, the remote controller may automatically change the flow rate of any of the plurality of MFCs. Should the remote controller detect a chance in a flow rate, the remote controller may repeat the process from step1100.

While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein.