Hybrid flow measurement for improved chamber matching

Abstract

SOLUTION: A gas delivery system for a substrate processing system includes a gas box including mass flow controllers controlling a flow of gas from gas sources. A gas flow path is in fluid communication with the gas box. A hybrid flow measurement system is in fluid communication with the gas flow path, and includes a controller configured to perform first flow measurement. The first flow measurement is for calibrating at least one of the mass flow controllers on the basis of a differential mass of gas in the gas flow path between the gas box and the flow measurement system during a predetermined period when a desired flow rate for gas supplied by the at least one of the mass flow controllers is less than a predetermined flow rate. The controller is configured to perform second flow measurement when the desired flow rate is greater than the predetermined flow rate.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Patent Application No. 16 / 056,980, filed August 7, 2018. The entire disclosures of the above-referenced applications are incorporated herein by reference.

[0002] FIELD OF THE DISCLOSURE The present disclosure relates to flow measurement for substrate processing systems, and more particularly to hybrid flow measurement for substrate processing systems. [Background technology]

[0003] The background description provided herein is intended to present the contents of the present disclosure generally. Work by the presently named inventors within the scope of what is described in this Background section, as well as aspects of the description that may not otherwise be considered prior art at the time of filing, are not admitted, expressly or impliedly, as prior art against the present disclosure.

[0004] Substrate processing systems can be used to perform etching, deposition, and / or other processing of substrates, such as semiconductor wafers. Examples of processes that can be performed on a substrate include, but are not limited to, etching, deposition, and cleaning processes. During processing, the substrate is placed on a substrate support, such as a pedestal or electrostatic chuck (ESC), in a processing chamber of the substrate processing system. A gas delivery system supplies a gas mixture to the processing chamber to process the substrate. A plasma may be struck to enhance chemical reactions in the processing chamber. An RF bias may also be supplied to the substrate support to control ion energy.

[0005] To improve quality and reduce defects, one or more metrology systems can be used to verify the operation of a processing chamber. For example, a flow measurement system can be used to verify the flow rate of a gas delivery system that supplies a gas mixture. When multiple substrate processing chambers are disposed within a substrate processing tool, gas lines are used to connect the gas delivery system of each processing chamber to the multiplexed flow measurement system.

[0006] The flow measurement system may include an orifice-based steady-state flow measurement device. Gas delivery systems are typically required to calibrate and deliver flow rates between 10 and 3,000 sccm. Gas entering the gas line at low flow rates takes a long time to reach the flow measurement device and build up sufficient pressure for measurement, adversely affecting measurement time during tool startup. In other words, calibration of flow rates between 10 and several hundred sccm takes a long time. Recently, process recipes have also required calibration and delivery of flow rates between 0.1 and 10 sccm. As can be appreciated, unacceptable time delays can occur during calibration or chamber alignment for flow rates as low as 0.1 to 10 sccm using orifice-based methods. Summary of the Invention

[0007] A measurement system for a substrate processing system includes N primary valves that selectively flow gases from N gas sources, respectively, where N is an integer. N mass flow controllers are connected to the N primary valves, respectively, and flow N gases from the N gas sources. N secondary valves selectively flow gases from the N mass flow controllers, respectively. A gas flow path connects the N secondary valves to a flow measurement system located remotely from the N secondary valves. The gas flow path includes a gas line. A controller is configured to perform a first flow measurement on a selected gas flowed at a desired flow rate from one of the N mass flow controllers, and is configured to perform the first flow measurement by evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass in the gas flow path; flowing the selected gas at the desired flow rate from one of the N mass flow controllers for a predetermined period of time; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time.

[0008] In other features, the controller is further configured to determine an effective volume of the gas flow path for the selected gas and a desired flow rate. The controller is further configured to determine a flow rate based on the effective volume. The gas flow path further comprises a manifold and a valve. The controller is configured to use the first flow measurement in determining the actual flow rate if the desired flow rate is less than a predetermined flow rate. The predetermined flow rate is in the range of 5 sccm to 15 sccm.

[0009] In other features, the controller is configured to determine the actual flow rate using a second flow rate measurement different from the first flow rate measurement if the desired flow rate exceeds a predetermined flow rate, the predetermined flow rate being in a range of 5 sccm to 15 sccm.

[0010] In other features, the second flow rate measurement includes an orifice-based measurement. A valve is connected to an outlet of the orifice. A pressure sensor senses pressure at an inlet of the orifice. The controller is configured to determine the actual flow rate using the valve, pressure sensor, and orifice if the desired flow rate exceeds a predetermined flow rate.

[0011] In other features, the controller is configured to wait a first predetermined dwell period after evacuating the gas flow path before measuring an initial pressure in the gas flow path, and the controller is configured to wait a second predetermined dwell period after flowing the selected gas at a desired flow rate through one of the N mass flow controllers for a predetermined period before measuring a final pressure in the gas flow path.

[0012] The gas delivery system of the substrate processing system includes a gas box including N mass flow controllers each controlling a flow of gas from N gas sources, where N is an integer. A gas flow path is in fluid communication with the gas box. The hybrid flow measurement system includes a controller in fluid communication with the gas flow path and configured to perform a first flow measurement. The first flow measurement calibrates at least one of the N mass flow controllers based on a mass difference of gas in the gas flow path between the gas box and the flow measurement system during a predetermined time period Δt if a desired flow rate for the gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate. The controller is configured to perform a second flow measurement to calibrate at least one of the N mass flow controllers if the desired flow rate for the at least one of the N mass flow controllers exceeds the predetermined flow rate.

[0013] In other features, the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at a desired flow rate. The first flow measurement further determines a mass difference based on the effective volume of the gas flow path for the gas at the desired flow rate. The second flow measurement is an orifice-based method.

[0014] In other features, the hybrid flow meter system includes a controller configured to determine an effective volume of the gas flow path for a selected gas and a selected flow rate. The controller is further configured to determine the flow rate based on the effective volume. The gas flow path further includes a manifold and a valve. The predetermined flow rate is in the range of 5 sccm to 15 sccm.

[0015] In other features, a valve is connected to the outlet of the orifice. A pressure sensor senses pressure at the inlet of the orifice. The controller is configured to determine the actual flow rate using the valve, pressure sensor, and orifice if the desired flow rate exceeds a predetermined flow rate.

[0016] In other features, the controller is configured to perform a first flow measurement by evacuating the gas flow path, measuring an initial pressure in the gas flow path, determining an initial mass in the gas flow path, flowing a select gas at a desired flow rate from one of the N mass flow controllers for a predetermined period of time, measuring a final pressure in the gas flow path, determining a final mass in the gas flow path, and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time.

[0017] In other features, the controller is configured to wait a first predetermined dwell period after evacuating the gas flow path before measuring an initial pressure in the gas flow path, and the controller is configured to wait a second predetermined dwell period after flowing the selected gas at a desired flow rate through one of the N mass flow controllers for a predetermined period before measuring a final pressure in the gas flow path.

[0018] A method for performing gas flow metering in a substrate processing system includes providing a gas box including N mass flow controllers, where N is an integer, each controlling a flow of gas from N gas sources, and providing a gas flow path in fluid communication with the gas box. The method includes calibrating at least one of the N mass flow controllers based on a mass difference of gas in the gas flow path between the gas box and the flow metering system during a predetermined time period using a first flow measurement if a desired flow rate for the gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate. The method includes calibrating at least one of the N mass flow controllers using a second flow measurement if the desired flow rate for the at least one of the N mass flow controllers exceeds the predetermined flow rate.

[0019] In other features, the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at a desired flow rate.

[0020] In other features, the first flow measurement further determines a mass difference based on an effective volume of the gas flow path for the gas at the desired flow rate.

[0021] In another feature, the second flow rate measurement is an orifice type method, and the predetermined flow rate is in the range of 5 sccm to 15 sccm.

[0022] In other features, the first flow measurement includes evacuating the gas flow path, measuring an initial pressure in the gas flow path, determining an initial mass in the gas flow path, flowing a selected gas at a desired flow rate from one of N mass flow controllers for a predetermined period of time, measuring a final pressure in the gas flow path, determining a final mass in the gas flow path, and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time.

[0023] In other features, the method includes waiting a first predetermined dwell period after evacuating the gas flow path before measuring an initial pressure in the gas flow path, and waiting a second predetermined dwell period after flowing a selected gas at a desired flow rate from one of the N mass flow controllers for a predetermined period before measuring a final pressure in the gas flow path.

[0024] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief explanation of the drawings]

[0025] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0026] [Figure 1] FIG. 1 is a functional block diagram of an example of a substrate processing system.

[0027] [Figure 2] FIG. 2 is a functional block diagram of an example substrate processing tool.

[0028] [Figure 3] FIG. 3 is a functional block diagram of a gas delivery system according to the present disclosure that can be used in the systems of FIGS.

[0029] [Figure 4] FIG. 4 is a functional block diagram of an example gas box according to the present disclosure.

[0030] [Figure 5] FIG. 5 is a functional block diagram of an example hybrid flow measurement system according to the present disclosure.

[0031] [Figure 6]FIG. 6 is a functional block diagram of an example hybrid flow measurement controller according to the present disclosure.

[0032] [Figure 7A] FIG. 7A is a flow chart illustrating an example method for implementing hybrid flow measurement according to the present disclosure. [Figure 7B] FIG. 7B is a flowchart illustrating an example method for implementing hybrid flow measurement according to the present disclosure.

[0033] [Figure 8] FIG. 8 is a flow chart illustrating an example of a mass difference method according to the present disclosure.

[0034] [Figure 9] FIG. 9 is a graph showing pressure as a function of time in a mass difference method according to the present disclosure.

[0035] [Figure 10] FIG. 10 is a flow chart illustrating an example of a method for using time-dependent changes in effective volume calculations for a given gas as an additional metrology check according to the present disclosure.

[0036] In the drawings, reference numbers may be reused to refer to similar and / or identical elements. DETAILED DESCRIPTION OF THE INVENTION

[0037] In orifice-based flow metering systems, such as absolute flow verifiers (AFVs), gas is delivered to a pump from a mass flow controller (MFC) through an orifice bank. The orifice bank contains multiple precision orifices that can be selected using corresponding valves. Pressure builds up upstream of one selected orifice and is monitored by a pressure sensor, such as a manometer. The pressure value is used to determine the flow rate based on empirically developed gas tables that relate orifice pressure to gas flow rate for each gas. Temperature compensation can also be applied to account for temperature changes and determine the actual gas flow rate of the MFC.

[0038] Measurement times for AFVs are significantly longer at low flow rates due to the time required to fill and pressurize the gas flow path downstream of the MFC and upstream of the selected orifice. The gas flow path typically includes gas supply lines, manifolds, valves, etc. (located between the gas box and the flow measurement system). Longer calibration periods result in longer downtime required to perform gas flow calibrations during initial setup and subsequent chamber alignment. At very low flow rates and with longer gas supply lines, it is difficult to detect when the orifice flow rate has stabilized (and steady-state pressure has been achieved). The increased volume of the gas line makes it difficult to detect small changes in pressure rise.

[0039] The hybrid flow metering systems and methods disclosed herein use a differential mass measurement (DMM) method for flow rates below a predetermined flow rate and another flow metering method for flow rates above the predetermined flow rate. In some examples, the predetermined flow rate is 10 sccm, although other flow rate values ​​can be used. In some examples, an orifice-based flow metering method is used for flow rates above the predetermined flow rate, although other flow metering methods can be used.

[0040] As further described below, the DMM method fills a gas volume in a gas line, valve, manifold, etc. between a gas box and a flow measurement system. In some examples, the gas volume is evacuated and an initial pressure is measured after a settling period. The initial mass is determined based on the initial pressure and effective volume of the flow path through the gas line, manifold, valve, and / or other volume located between the gas box and the flow measurement system.

[0041] After determining the initial mass, the valve is opened and the MFC flows gas at the desired flow rate (to be calibrated) for a predetermined period of time, Δt. The pressure in the gas volume between the gas box and the flow measurement system steadily increases. After the predetermined period of time, Δt, the valve is closed and the final pressure is measured. The final mass is calculated based on the final pressure. The flow rate is calculated by dividing the difference between the final mass and the initial mass by Δt.

[0042] The DMM method is similar to chamber ROR (rate of rise: a method of measuring flow rate from the rate of pressure rise in a chamber), but the DMM method uses the volumes of gas lines, valves, manifolds, etc., rather than the volume of the chamber / tank, to calculate the mass flow rate. In ROR, the governing equation for calculating the mass flow rate is obtained after taking the time derivative of the equation of state. During gas compression in the ROR tank, transient pressure and transient temperature are sampled over time, and the rate of change of pressure / temperature is calculated.

[0043] More specifically, when implementing the DMM method for low flow rates, the MFC gas flow is used to pressurize an enclosure of known volume V for a predetermined time period Δt. The initial and final gas pressures and temperatures within the enclosure are used to calculate the net gas mass delivered to the enclosure based on the gas equation of state:

number

[0044] The equation for absolute gas flow rate Q is:

number

[0045] The effect of compressibility becomes significant only for polyatomic gases as pressure and temperature approach atmospheric (ATM) conditions. However, even for polyatomic gases, the effect of compressibility can be neglected because the pressure downstream of the MFC is lower than atmospheric pressure and can be maintained an order of magnitude lower than ATM pressure when pressurizing the gas volume with the DMM method. Therefore, the flow equation simplifies to:

number

[0046] In some examples, the gas in the enclosure is allowed to rest for a predetermined settling period before measuring the initial and final values ​​of p and T. This settling period reduces the effect of the gas's kinetic energy and eliminates pressure gradients due to gas flow. This settling period also allows the gas temperature to stabilize with the environment. In other words, the gas is heated or cooled by the surrounding enclosure (wall temperature Tw), eliminating the effects of gas expansion or compression, respectively.

[0047] The gas expansion phenomenon occurs at the start of a measurement calibration when the enclosure is evacuated to remove any gas residue (from the previous measurement). When the gas is fed into the enclosure, it is compressed and heated, causing its temperature to rise. It is not possible to accurately measure the gas temperature directly, as it is not practical to use a high-speed temperature sensor in the gas path (due to the risk of potential sensor damage from exposure to corrosive gases).

[0048] When the gas is stabilized during the settling period, the initial and final gas temperatures are the initial wall temperature T W1and the final wall temperature T W2 Similarly, the initial and final pressures (p1 and p2) are equal to, respectively, due to the elimination of pressure gradients along the length of the gas supply line and changes in gas temperature. TIFF0007733203000004.tif14170 and TIFF0007733203000005.tif12170. As a result, the flow equation simplifies to:

number

[0049] As mentioned above, the enclosure (internal volume of gas lines, valves, manifolds, etc.) in the DMM method behaves differently from the enclosure in the ROR method. V eff is the same as the actual volume of the tank. However, experimental testing of the enclosure (gas lines, valves, manifolds, etc.) with the DMM method introduced errors. In other words, the effective volume V (calculated using the known flow rate) eff differs significantly from the expected internal volume.

[0050] Part of the volume difference is due to variations in geometric manufacturing tolerances. Also, the calibrated effective volume V eff Experiments have shown that the can vary depending on the gas and flow rate. These differences may be due to a variety of other factors. For example, these differences may be due to the relatively small volume of the gas supply lines (which is further influenced by variations in manufacturing tolerances of the gas lines, internal valves, and / or substrate volume). Differences may also be due to the overall complex geometry of the supply volume assembly (long tubular shape with internal valves) compared to the simple, uniform geometry of the tanks used in ROR.

[0051] The ROR method uses a tank with a much larger volume than the gas flow path, including the gas supply line. The pressure gradient in the gas supply line due to the viscous effect of the gas flow has a significant effect and, if not properly taken into account, will lead to inaccurate calculations of the mass flow rate. Therefore, the ROR method cannot be applied when the volume of the gas line is used as the enclosure and a single pressure measurement point is used.

[0052] However, this problem can be solved by determining the calibrated effective volume V (as opposed to the theoretical actual volume) for each gas and / or flow rate. eff As further described below, orifice technology or another flow measurement method can be employed to calculate the calibrated effective volume.

[0053] More specifically, the effective volume V eff can be calculated using Equation 4. First, the corresponding MFC is set to one of several low flow rate set points and the DMM method is performed. During the DMM method, the initial and final pressure and temperature are measured. The MFC is operated at the same flow rate set point (with the same gas) using the orifice method. The orifice method gives the absolute flow rate (true flow rate) Q of the MFC. Effective volume V eff is determined using Equation 4, the absolute flow rate Q, and the initial and final pressures and temperatures.

[0054] The effective volume calculation is required only once, at the initial tool startup, and only for low gas flow rates. This one-time calibration also accounts for variations in manufacturing tolerances of the gas delivery lines from tool to tool for chamber flow matching. Therefore, chamber matching can be performed more quickly using the hybrid method. Furthermore, by calibrating the DMM method (used for low flow rates) with the orifice technology method (used for high flow rates), mismatches or overlaps at the flow junction can be eliminated when switching between the two methods. Another advantage of the proposed hybrid flow measurement is that the calculation at the flow junction can be tracked and monitored as an additional system health check, eliminating drift in accuracy over time.

[0055] AFV is described in further detail in commonly assigned U.S. Patent No. 7,822,570, entitled "Methods for Performing Actual Flow Verification," issued October 26, 2010, and incorporated herein by reference in its entirety. ROR is described in further detail in commonly assigned U.S. Patent No. 9,778,083.

[0056] Reference is now made to FIG. 1 , which illustrates an exemplary substrate processing system 120. While the illustrated example is a processing chamber for etching, chemical vapor deposition, or atomic layer deposition (ALD) using capacitively coupled plasma (CCP), the flow measurement systems and methods described herein can be used in any other type of system or substrate processing system. For example, the flow measurement systems and methods described herein can be used in substrate processing systems that use remote plasma or inductively coupled plasma (ICP). Additionally, the systems and methods described herein can be used in any other semiconductor equipment requiring accurate flow measurement.

[0057] The substrate processing system 120 includes a processing chamber 122 that encloses the other components of the substrate processing system 120 and contains an RF plasma (if used). The substrate processing system 120 includes an upper electrode 124 and a substrate support 126, such as an electrostatic chuck (ESC). During operation, a substrate 128 is positioned on the substrate support 126.

[0058] By way of example only, the upper electrode 124 can include a gas distribution device 129, such as a showerhead, for introducing and distributing process gases. The gas distribution device 129 can include a stem portion connected at one end to the upper surface of the processing chamber. A base portion is generally cylindrical and extends radially outward from the other end of the stem portion at a location spaced from the upper surface of the processing chamber. The substrate-facing surface or faceplate of the showerhead base portion includes a plurality of holes through which precursors, reactants, etching gases, inert gases, carrier gases, other process gases, or purge gases flow. Alternatively, the upper electrode 124 can include a conductive plate, or process gases can be introduced in other ways.

[0059] The substrate support 126 includes a base plate 130 that acts as a bottom electrode. The base plate 130 supports a heating plate 132, which may correspond to a ceramic multi-zone heating plate. A thermal resistance layer 134 may be disposed between the heating plate 132 and the base plate 130. The base plate 130 may include one or more channels 136 for flowing a coolant through the base plate 130.

[0060] When a plasma is used, an RF generation system 140 generates and outputs an RF voltage to either the upper electrode 124 or the lower electrode (e.g., the base plate 130 of the ESC 126). The other of the upper electrode 124 and the base plate 130 may be DC grounded, AC grounded, or floating. By way of example only, the RF generation system 140 may include an RF generator 142 that generates RF power supplied to the upper electrode 124 or the base plate 130 by a matching and distribution network 144. In other examples, the plasma may be generated inductively or remotely.

[0061] A typical gas delivery system 150 includes one or more gas sources 152-1, 152-2, ..., and 152-N (collectively, gas sources 152), where N is an integer greater than zero. The gas sources 152 are connected to a manifold 160 by valves 154-1, 154-2, ..., and 154-N (collectively, valves 154) and MFCs 156-1, 156-2, ..., and 156-N (collectively, MFCs 156). Secondary valves may be used between the MFCs 156 and the manifold 160. Although one gas delivery system 150 is shown, more than one gas delivery system may be used.

[0062] A temperature controller 163 may be connected to a plurality of thermal control elements (TCEs) 164 disposed within the heating plate 132. The temperature controller 163 may be used to control the plurality of TCEs 164 to control the temperature of the substrate support 126 and the substrate 128. The temperature controller 163 may be in communication with a coolant assembly 166 to control the flow of coolant through the channels 136. For example, the coolant assembly 166 may include a coolant pump, a reservoir, and / or one or more temperature sensors. The temperature controller 163 operates the coolant assembly 166 to selectively flow coolant through the channels 136 to cool the substrate support 126. A valve 170 and a pump 172 may be used to evacuate reactants from the processing chamber 122. A system controller 180 may be used to control the components of the substrate processing system 120.

[0063] 2, the flow measurement systems and methods described herein can be used to provide cost-saving flow measurement of gases supplied to one or more substrate processing tools 210. Illustrated is one example of a substrate processing tool 210, although other substrate processing tools may be used.

[0064] The substrate processing tool 210 includes a robot 212 disposed at a central location. The robot 212 can operate at vacuum or atmospheric pressure. The substrate processing tool 210 includes multiple stations (or substrate processing chambers) 216-1, 216-2, ..., and 216-S (collectively, stations 216) (where S is an integer greater than 1) disposed around the robot 212. The stations 216 can be disposed around the center of the substrate processing tool 210 with uniform or irregular angular offsets. Examples of the stations 216 can include one or more of deposition, etch, pre-clean, post-clean, spin-clean, etc.

[0065] The substrates may initially be placed in a cassette 234. A robot and load lock, generally indicated at 238, may be used to move the substrates from the cassette 234 to the substrate processing tool 210. Once processing is complete, the robot and load lock 238 may return the substrates to the cassette 234 and / or another cassette 239. As described further below, a gas delivery system supplies gas to the stations and a flow measurement system calibrates the gas flow rates.

[0066] 3, the illustrated gas delivery system 300 includes multiple gas boxes 310-1, 310-2, ... 310-10 (collectively, gas boxes 310). While ten gas boxes are shown, the gas delivery system 300 may include more or fewer gas boxes. The gas boxes 310-1, 310-2, ... 310-10 are connected to a hybrid flow measurement system 320 by first gas lines 312-1, 312-2, ... 312-10 (collectively, first gas lines 312). The first gas lines 312 may be connected to the hybrid flow measurement system 320 via a manifold 313. Return gas from hybrid flow metering system 320 is connected to gas boxes 310-1, 310-2, ... 310-10 by second gas lines 314-1, 314-2, ... 314-10 (collectively second gas lines 314). Second gas lines 314 exit hybrid flow metering system 320 into manifold 315 and are separated into individual lines connected to gas boxes 310-1, 310-2, ... 310-10.

[0067] Gas lines 316-1, 316-2, ... 316-10 (collectively gas lines 316) connect the outputs of gas boxes 310-1, 310-2, ... 310-10 to the processing chambers. In some examples, a clean dry air (CDA) source 330 is also connected to gas boxes 310-1, 310-2, ... 310-10. As can be appreciated, hybrid flow metering system 320 is shared or time multiplexed by gas boxes 310-1, 310-2, ... 310-10, thereby reducing costs.

[0068] 4, which illustrates one of the gas boxes 310. Gas sources 410-1, 410-2, ..., and 410-G (collectively, gas sources 410) are connected to flow control devices including primary valves 420-1, 420-2, ..., and 420-G (where G is an integer greater than 1) (collectively, primary valves 420), mass flow controllers (MFCs) 430-1, 430-2, ..., 430-G (collectively, MFCs 430), and secondary valves 434-1, 434-2, ..., and 434-G (collectively, secondary valves 434). The output of secondary valve 434 is connected to mixing manifold 435 and input to valves 440, 442, and 448. Valves 440 and 442 are connected to hybrid flow metering system 320. Valve 442 is associated with gas flowing through gas line 312 to hybrid flow metering system 320. Valve 440 is associated with gas returning from hybrid flow metering system 320 through gas line 314. Valve 448 is associated with gas flowing through gas line 316 to a processing chamber associated with gas box 310. One or more temperature sensors 480 can be used to sense the temperature of the gas lines. In some examples, portions of the gas lines are heated by resistive heaters (not shown).

[0069] Reference is now made to Figure 5, which shows a portion of a hybrid flow measurement system. 320 Inlet B to gas boxes GB1, GB2, GB3, GB4, GB5, GB6, GB7, and GB8 is connected to valve 510. Inlet B' associated with gas boxes GB2, GB4, GB6, GB8, and GB10 is connected to valve 511. The outlets of valves 510 and 511 are connected by manifold 513 to a plurality of gas lines 518-1, 518-2, ..., and 518-O (where O is an integer greater than or equal to 1) (collectively, gas lines 518). Gas lines 518 are connected to precision orifices 520-1, 520-2, ..., and 520-O (collectively, precision orifices 520).

[0070] In some examples, the precision orifices 520 have various orifice sizes. The precision orifices 520 are considered "precise" when the orifices have a predetermined, known size and shape and are unobstructed. One or more pressure sensors 530 sense the pressure upstream from the precision orifice 520 when the precision orifice is operating in a choked flow condition. A choked flow condition occurs when gas exits the precision orifice at the speed of sound. One of the precision orifices is selected based on the flow rate to be calibrated.

[0071] Pressure sensor 530 is connected to the outlets of valves 510 and 511 and the inlet of precision orifice 520. For example, first pressure sensor 530 operates in a first pressure range and second pressure sensor 530 operates in a second pressure range that may be the same or different from the first pressure range. For example, first pressure sensor 530 measures pressures up to 50 T and second pressure sensor 530 measures pressures up to 500 T, although other pressure ranges may be used. Precision orifice 520 is connected to the inlets of valves 524-1, 524-2, ..., and 524-O (collectively valves 524). The outlets of valves 524 are connected together and output to pump 540.

[0072] Reference is now made to Figure 6, which illustrates a hybrid flow measurement controller 610. In some examples, the hybrid flow measurement controller 610 includes an AFV table 620 and a V eff Table 622 and V eff and an estimation module 624. The AFV table 620 is an empirically developed table relating orifice pressure to flow rate for each gas. eff Table 622 is a V table that is calibrated and indexed by gas and / or desired flow rate. eff Contains a value.

[0073] The hybrid flow measurement controller 610 is in communication with the valve 634, the mass flow controller 636, the pressure sensor 530, and the temperature sensor 480. flow rateThe measurement controller 610 controls the valve 634 based on feedback from the temperature sensor 480 and the pressure sensor 530, as described further below. eff The estimation module 624 may use interpolation, formulas, or other techniques to estimate other V eff Based on the value of V eff may be used to estimate

[0074] Reference is now made to Figures 7A and 7B, which illustrate a method for implementing hybrid flow measurement. In Figure 7A, a method 700 for determining a calibrated effective volume for a low flow rate gas is implemented. In other words, the calibrated effective volume need only be determined for gases delivered at flow rates below a predetermined flow rate for which the DMM method is used. Furthermore, a calibration may be performed for each of the flow rates and gases used. Alternatively, one or more calibrations may be performed for one or more gases and one or more flow rates. For other gases and / or other flow rates (below the predetermined flow rate), the flow rate may be determined using interpolation, a formula, or other compensation without individual calibration.

[0075] At 710, a gas and flow rate for which to calibrate the effective volume are selected. At 714, first and second flow measurement techniques are used to determine the effective volume at the selected flow rate for the selected gas.

[0076] In some examples, the effective volume V can be calculated using Equation 4. First, the corresponding MFC is set to one of several low flow rate set points and the DMM method is performed. During the DMM method, the initial and final pressure and temperature are measured. The MFC is operated at the same flow rate set point (with the same gas) using the orifice method. The orifice method provides the absolute flow rate (true flow rate) Q of the MFC. The effective volume V is determined using Equation 4, the absolute flow rate Q, and the initial and final pressure and temperature.

[0077] If additional samples are needed, the method proceeds to 718 to calibrate another flow rate for the selected gas. Once all flow rates have been calibrated for the selected gas, the method proceeds to 722 to determine whether to calibrate another gas. If 722 is true, the method returns to 710. If not true, the method ends.

[0078] 7B illustrates a method 750 of operating a hybrid flow measurement system according to the present disclosure. At 760, it is determined whether to perform a flow measurement. If 760 is true, it is determined whether the desired flow rate to be calibrated is less than or equal to a first flow rate threshold TH1. If 764 is true, a DMM method is used and a calibrated effective volume corresponding to the selected gas and / or selected flow rate is used. If 764 is false, a second flow measurement method is used. In some examples, the second flow measurement method includes an orifice-based method.

[0079] Reference is now made to FIG. 8, which illustrates a method 800 for performing flow measurements. At 810, the gas line is pumped from the gas box to the orifice. At 814, a valve is closed, isolating the gas line from the outlet of the MFC to the orifice. At 816, a settling period is waited to allow kinetic energy to subside and the gas line to reach wall temperature. In some examples, the settling period ranges from 10 seconds to 60 seconds. At 820, pressure sensor noise is filtered, pressure is measured, and an initial mass is determined based on the measured pressure. At 824, a secondary valve of the MFC is opened to provide flow at a desired flow rate. During a predetermined time period Δt, the gas line, manifold, and other structures are filled with the desired flow rate output by the MFC. At 830, the secondary valve of the MFC is closed, stopping the flow. At 834, a settling period is waited. At 838, pressure sensor noise is filtered, pressure is measured, and a final mass is determined based on the measured pressure and effective volume (for the selected gas and / or selected flow rate). At 842, a flow rate is determined based on the final mass, the initial mass, and Δt.

[0080] Now, refer to FIG. 9, which shows the measured pressure as a function of time for an example of the DMM method. After evacuating the gas line, the gas is allowed to stand and the equilibrium temperature (T W2 ) which results in a slight increase in the initial pressure p1. The MFC is then set to the desired flow rate to be calibrated for a period Δt. After the period Δt, the gas is allowed to stand, eliminating the pressure gradient along the gas supply line and allowing the gas to reach an equilibrium temperature (T w2 ) as a result of which the final pressure p2 is slightly change do.

[0081] Reference is now made to FIG. 10 , which illustrates a method 1000 for performing additional checks on the calibration of an MFC. In some examples, during operation, the first and second flow measurement systems will have one or more comparable flow rates overlapping within a predetermined range. For example, the first flow measurement system may calibrate flow rates of 10 sccm or less, while the second flow measurement system may be used to calibrate flow rates of 10 sccm or more. In some examples, both the first and second flow measurement systems may be used to calibrate the same desired flow rate of the MFC. For example, both measurement systems may be used to perform a 10 sccm calibration.

[0082] The results of the calibration using the first and second flow measurement systems can be compared. If the comparison results are within a predetermined tolerance, the first and second flow measurement systems are functioning properly. If the comparison results are not within the predetermined tolerance, the system sends a notification, generates a warning message, turns on a warning light, and / or takes other action.

[0083] In 1010, the MFC is configured to flow the selected gas at a desired flow rate within a predetermined flow rate range. In some examples, the predetermined flow rate range is close to a predetermined flow rate at which the first and second measurement systems are switched. For example, the desired flow rate of the MFC can be in the range of 5 sccm to 15 sccm.

[0084] At 1020, a first flow rate MFR1 is measured using a first measurement system. At 1030, a second flow rate MFR2 is measured using a second measurement system. At 1040, the first flow rate MFR1 and the second flow rate MFR2 are compared. At 1050, the system determines whether the difference between the first flow rate MFR1 and the second flow rate MFR2 is less than a predetermined value or within a predetermined tolerance. If 1050 is true, the method ends. If not true, the system sends a notification at 1052, generates a warning message, turns on a warning light, or takes other action.

[0085] The foregoing description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the present disclosure can be embodied in a variety of forms. Accordingly, while the present disclosure includes specific examples, the true scope of the disclosure should not be limited to such examples, as other modifications will become apparent upon review of the drawings, the specification, and the following claims. It should be understood that one or more steps in a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure. Furthermore, although each embodiment is described above as having particular features, any one or more of these features described with respect to any embodiment of the present disclosure may be implemented in other embodiments and / or combined with any features of the other embodiments (even if such combination is not explicitly described). In other words, the described embodiments are not mutually exclusive, and substituting one or more embodiments for one another is within the scope of the present disclosure.

[0086] Spatial and functional relationships between elements (e.g., modules, circuit elements, semiconductor layers, etc.) are described using various terms such as "connected," "engaged," "coupled," "adjacent," "next to," "on," "above," "below," and "disposed." Also, when a relationship between a first element and a second element is described in the above disclosure, unless expressly described as "direct," the relationship may be a direct relationship where no other intervening elements exist between the first element and the second element, or an indirect relationship where one or more intervening elements (spatial or functional) exist between the first element and the second element. As used herein, the phrase "at least one of A, B, and C" should be interpreted in the sense of a logical (A or B or C) using a non-exclusive logical OR, and not in the sense of "at least one of A, at least one of B, and at least one of C."

[0087] In some embodiments, the controller is part of a system, and such a system may be part of the examples described above. Such systems may include semiconductor processing equipment, including one or more processing tools, one or more chambers, one or more processing platforms, and / or specific processing components (e.g., wafer pedestals, gas flow systems, etc.). These systems may be integrated with electronics for controlling system operation before, during, and after semiconductor wafer or substrate processing. Such electronics may be referred to as a "controller" and may control various components or subcomponents of one or more systems. The controller may be programmed to control any of the processes disclosed herein, depending on the processing requirements and / or type of system. Such processes may include process gas supply, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid supply settings, position and motion settings, wafer transfer to and from the tool, and wafer transfer to and from other transfer tools and / or load locks connected or interfaced with the particular system.

[0088] Broadly, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. Integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and / or one or more microprocessors, i.e., microcontrollers, that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files) that define operational parameters for performing a particular process on or for a semiconductor wafer or for a system. The operational parameters, in some embodiments, may be part of a recipe defined by a process engineer to implement one or more processing steps in the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0089] In some embodiments, the controller may be part of, coupled to, or a combination of a computer integrated with, coupled to, or otherwise networked to the system. For example, the controller may be in the “cloud” or all or part of a fab host computer system. This allows for remote access of wafer processing. The computer may provide remote access to the system to monitor the current progress of a fabrication operation, review the history of past fabrication operations, review trends or performance criteria from multiple fabrication operations, modify parameters of a current process, configure processing steps following a current process, or initiate a new process. In some examples, a remote computer (e.g., a server) can provide process recipes to the system over a network. Such a network may include a local network or the Internet. The remote computer may include a user interface that allows entry or programming of parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data. Such data identifies parameters for each processing step performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool the controller is configured to interface with or control. Thus, as discussed above, the controller may be distributed, for example, by having one or more individual controllers networked together and working together toward a common purpose (such as the processes and controls described herein). An example of a distributed controller for such purposes would include one or more integrated circuits on the chamber in communication with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer) and coupled to control the process in the chamber.

[0090] Exemplary systems may include, but are not limited to, a plasma etch chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a tracking chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacturing of semiconductor wafers.

[0091] As described above, depending on the process step or steps being performed by the tool, the controller may communicate with one or more other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools located throughout the factory, a main computer, another controller, or tools used in material transport to and from tool locations and / or load ports in a semiconductor fabrication factory. Application example 1: 1. A gas flow measurement system for a substrate processing system, comprising: N primary valves, each of which selectively flows gas from N gas sources, where N is an integer; N mass flow controllers each connected to the N primary valves and each configured to flow N types of gas from the N gas sources; N secondary valves each selectively flow gas from the N mass flow controllers; a gas flow path connecting the N secondary valves to a flow measurement system installed remotely from the N secondary valves, the gas flow path including a gas line; a controller configured to perform a first flow measurement on a selected gas flowed at a desired flow rate from one of the N mass flow controllers, the first flow measurement comprising: evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass within the gas flow path; flowing the selected gas at the desired flow rate through the one of the N mass flow controllers for a predetermined period of time; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time; a controller configured to implement A gas flow measurement system comprising: Application example 2: The gas flow measurement system of claim 1, The gas flow metering system, wherein the controller is further configured to determine an effective volume of the gas flow path for the selected gas and the desired flow rate. Application example 3: The gas flow measurement system of claim 2, The gas flow measurement system, wherein the controller is further configured to determine the actual flow rate based on the effective volume. Application example 4: The gas flow measurement system of claim 1, The gas flow measurement system, wherein the gas flow path further comprises a manifold and a valve. Application example 5: The gas flow measurement system of claim 1, The gas flow measurement system, wherein the controller is configured to use the first flow measurement in determining the actual flow rate if the desired flow rate is less than a predetermined flow rate. Application example 6: The gas flow measurement system of claim 5, A gas flow measurement system, wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm. Application example 7: The gas flow measurement system of claim 5, The gas flow measurement system, wherein the controller is configured to determine the actual flow rate using a second flow measurement different from the first flow measurement if the desired flow rate exceeds the predetermined flow rate. Application example 8: The gas flow measurement system of claim 7, A gas flow measurement system, wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm. Application example 9: The gas flow measurement system of claim 7, A gas flow measurement system, wherein the second flow measurement includes an orifice-type measurement. Application example 10: The gas flow measurement system of claim 5, An orifice; a valve connected to the outlet of the orifice; a pressure sensor that detects the pressure at the inlet of the orifice; Furthermore, the controller is configured to determine the actual flow rate using the valve, the pressure sensor, and the orifice if the desired flow rate exceeds the predetermined flow rate. Gas flow measurement system. Application example 11: The gas flow measurement system of claim 1, The gas flow measurement system, wherein the controller is configured to wait a first predetermined dwell period after evacuating the gas flow path before measuring the initial pressure in the gas flow path. Application example 12: The gas flow measurement system of claim 1, the controller is configured to wait a second predetermined quiescent period after flowing the selected gas at the desired flow rate from the one of the N mass flow controllers during the predetermined period and before measuring the final pressure in the gas flow path. Application example 13: 1. A gas flow measurement system for a substrate processing system, comprising: a gas box including N mass flow controllers for respectively controlling the flow of gas from N gas sources, where N is an integer; a gas flow path in fluid communication with the gas box; a hybrid flow measurement system including a controller in fluid communication with the gas flow path and configured to perform a first flow measurement and a second flow measurement; the first flow measurement is calibrating at least one of the N mass flow controllers based on a mass difference of gas in the gas flow path between the gas box and a flow measurement system during a predetermined time period when a desired flow rate for the gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate; The second flow measurement is for calibrating at least one of the N mass flow controllers if the desired flow rate for the at least one of the N mass flow controllers exceeds the predetermined flow rate. Hybrid flow measurement system A gas flow measurement system comprising: Application 14: The gas flow measurement system of claim 13, A gas flow metering system, wherein the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at the desired flow rate. Application example 15: 15. The gas flow measurement system of claim 14, The gas flow measurement system, wherein the first flow measurement further determines the mass difference based on the effective volume of the gas flow path for the gas at the desired flow rate. Application 16: The gas flow measurement system of claim 13, A gas flow measurement system, wherein the second flow measurement is an orifice type method. Application 17: 15. The gas flow measurement system of claim 14, The hybrid flow metering system includes a controller configured to determine an effective volume of the gas flow path for a selected gas and a selected flow rate. Application 18: 18. The gas flow measurement system of claim 17, The gas flow measurement system, wherein the controller is further configured to determine an actual flow rate based on the effective volume. Application 19: The gas flow measurement system of claim 13, The gas flow measurement system, wherein the gas flow path further comprises a manifold and a valve. Example 20: The gas flow measurement system of claim 13, A gas flow measurement system, wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm. Example 21: The gas flow measurement system of claim 13, An orifice; a valve connected to the outlet of the orifice; a pressure sensor that detects the pressure at the inlet of the orifice; Furthermore, the controller is configured to determine an actual flow rate using the valve, the pressure sensor, and the orifice if the desired flow rate exceeds the predetermined flow rate. Gas flow measurement system. Application example 22: 18. The gas flow measurement system of claim 17, The controller evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass within the gas flow path; flowing the selected gas at the desired flow rate through the one of the N mass flow controllers for a predetermined period of time; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time; configured to perform the first flow measurement by Gas flow measurement system. Application 23: 23. The gas flow measurement system of claim 22, The gas flow measurement system, wherein the controller is configured to wait a first predetermined dwell period after evacuating the gas flow path before measuring the initial pressure in the gas flow path. Application 24: 23. The gas flow measurement system of claim 22, the controller is configured to wait a second predetermined quiescent period after flowing the selected gas at the desired flow rate from the one of the N mass flow controllers during the predetermined period and before measuring the final pressure in the gas flow path. Example 25: 1. A method for performing gas flow measurements in a substrate processing system, comprising: providing a gas box including N mass flow controllers respectively controlling the flow of gas from N gas sources, where N is an integer; providing a gas flow path in fluid communication with the gas box; if a desired flow rate for the gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate, calibrating the at least one of the N mass flow controllers based on a mass difference of the gas in the gas flow path between the gas box and a flow measurement system during a predetermined time period using a first flow measurement; calibrating the at least one of the N mass flow controllers using a second flow measurement if the desired flow rate for the at least one of the N mass flow controllers exceeds the predetermined flow rate. A method comprising: Application 26: 26. The method of claim 25, The method, wherein the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at the desired flow rate. Application 27: 27. The method of claim 26, The method, wherein the first flow measurement further determines the mass difference based on the effective volume of the gas flow path for the gas at the desired flow rate. Application 28: 26. The method of claim 25, The method wherein the second flow measurement is an orifice-based method. Example 29: 26. The method of claim 25, The method wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm. Example 30: 26. The method of claim 25, The first flow rate measurement includes: evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass within the gas flow path; flowing a selected gas at the desired flow rate through said one of said N mass flow controllers for a predetermined period of time; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining an actual flow rate based on the initial mass, the final mass, and the predetermined period of time; A method comprising: Example 31: 31. The method of claim 30, The method further comprising waiting a first predetermined dwell period after evacuating the gas flow path before measuring the initial pressure in the gas flow path. Application 32: 32. The method of claim 31, the method further comprising, after flowing the selected gas at the desired flow rate from the one of the N mass flow controllers during the predetermined period of time, waiting a second predetermined dwell period before measuring the final pressure in the gas flow path.

Claims

1. 1. A method for performing gas flow metering in a substrate processing system, the substrate processing system comprising: a gas box including N mass flow controllers controlling respective flows of gas from N gas sources, where N is an integer; and a gas flow path in fluid communication with the gas box, the method comprising: setting a desired flow rate for a gas supplied by at least one of the N mass flow controllers; calibrating the at least one of the N mass flow controllers using a first flow measurement and a second flow measurement selected based on a comparison between a predetermined flow rate and the desired flow rate; A method comprising:

2. 10. The method of claim 1 further comprising: selecting the first flow measurement if the desired flow rate is less than or equal to the predetermined flow rate; selecting the second flow measurement if the desired flow rate exceeds the predetermined flow rate; A method comprising:

3. 10. The method of claim 1 further comprising: performing the first flow measurement based on a mass difference of the gas in the gas flow path between the gas box and a flow measurement system during a predetermined period of time.

4. 4. The method of claim 3, The method, wherein the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at the desired flow rate.

5. 5. The method of claim 4, The method of claim 1, wherein the first flow measurement further determines the mass difference based on the effective volume of the gas flow path for the gas at the desired flow rate.

6. 10. The method of claim 1, The method wherein the second flow measurement is an orifice-based method.

7. 10. The method of claim 1, The method wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm.

8. 4. The method of claim 3, The first flow measurement includes: evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass in the gas flow path; flowing a selected gas at the desired flow rate through said at least one of said N mass flow controllers during said predetermined time period; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; determining an actual flow rate based on the initial mass, the final mass, and the predetermined time period; A method comprising:

9. 9. The method of claim 8, further comprising: The method includes waiting a first predetermined dwell period after evacuating the gas flow path before measuring the initial pressure in the gas flow path.

10. 10. The method of claim 9, further comprising: after flowing the selected gas at the desired flow rate through the at least one of the N mass flow controllers during the predetermined period of time, waiting a second predetermined dwell period before measuring the final pressure in the gas flow path.

11. A hybrid flow measurement system, comprising: a gas flow path in fluid communication with a gas box containing N mass flow controllers that respectively control the flow of gas from N gas sources, where N is an integer; a controller configured to calibrate the at least one of the N mass flow controllers using a first flow measurement and a second flow measurement selected based on a comparison between a predetermined flow rate and a desired flow rate for the gas supplied by the at least one of the N mass flow controllers; A hybrid flow measurement system comprising:

12. 12. The hybrid flow measurement system of claim 11, The controller selecting the first flow measurement if the desired flow rate is less than or equal to the predetermined flow rate; Selecting the second flow measurement if the desired flow rate exceeds the predetermined flow rate. A hybrid flow measurement system configured as follows.

13. 12. The hybrid flow measurement system of claim 11, The hybrid flow measurement system, wherein the controller is configured to perform the first flow measurement based on a mass difference of the gas in the gas flow path between the gas box and the hybrid flow measurement system during a predetermined period of time.

14. 14. The hybrid flow measurement system of claim 13, A hybrid flow measurement system, wherein the first flow measurement and the second flow measurement are used to determine an effective volume of the gas flow path for the gas at the desired flow rate.

15. 15. The hybrid flow measurement system of claim 14, The hybrid flow measurement system, wherein the first flow measurement further determines the mass difference based on the effective volume of the gas flow path for the gas at the desired flow rate.

16. 12. The hybrid flow measurement system of claim 11, A hybrid flow measurement system, wherein the second flow measurement is an orifice-type method.

17. 12. The hybrid flow measurement system of claim 11, The hybrid flow meter system, wherein the controller is configured to determine an effective volume of the gas flow path for a selected gas and a selected flow rate.

18. 18. The hybrid flow measurement system of claim 17, The hybrid flow measurement system, wherein the controller is further configured to determine an actual flow rate based on the effective volume.

19. 12. The hybrid flow measurement system of claim 11, The hybrid flow measurement system, wherein the gas flow path further comprises a manifold and a valve.

20. 12. The hybrid flow measurement system of claim 11, The hybrid flow measurement system, wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm.

21. 12. The hybrid flow measurement system of claim 11, further comprising: An orifice; a valve connected to the outlet of the orifice; a pressure sensor that detects the pressure at the inlet of the orifice; Equipped with The hybrid flow measurement system, wherein the controller is configured to determine an actual flow rate using the valve, the pressure sensor, and the orifice if the desired flow rate exceeds the predetermined flow rate.

22. 18. The hybrid flow measurement system of claim 17, The controller evacuating the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass in the gas flow path; flowing the selected gas at the desired flow rate through the one of the N mass flow controllers for a predetermined period of time; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; determining an actual flow rate based on the initial mass, the final mass, and the predetermined time period; a hybrid flow measurement system configured to perform the first flow measurement by

23. 23. The hybrid flow measurement system of claim 22, The hybrid flow measurement system, wherein the controller is configured to wait a first predetermined dwell period after evacuating the gas flow path before measuring the initial pressure in the gas flow path.

24. 24. The hybrid flow measurement system of claim 23, the controller is configured to wait a second predetermined dwell period after flowing the selected gas at the desired flow rate from the one of the N mass flow controllers during the predetermined period and before measuring the final pressure in the gas flow path.

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