Hybrid flow metrology for improved chamber matching

Abstract

A gas delivery system for a substrate processing system includes a gas chamber comprising a mass flow controller for controlling airflow from a gas source. An airflow path is fluidly connected to the gas chamber. A mixed flow metering system is fluidly connected to the airflow path and includes a controller configured to perform a first flow metering to calibrate at least one of the mass flow controllers based on differential mass of gas in the airflow path between the gas chamber and the flow metering system during a predetermined time period when the desired flow rate of gas supplied by at least one of the mass flow controllers is less than a predetermined flow rate. The controller is configured to perform a second flow metering when the desired flow rate is greater than the predetermined flow rate.

Description

Mixed flow metering for improved chamber matching The present disclosure relates to flow metering in substrate processing systems, and more particularly to mixed flow metering in substrate processing systems. The prior art section provided here is for the purpose of generally presenting the present disclosure. The scope of the work of the inventors named in this application, as well as the embodiments described in this prior art section that do not qualify as prior art at the time of filing, are not intended to be admitted, either expressly or impliedly, as prior art against the present disclosure. Substrate processing systems can be used to perform etching, deposition, and / or other processing of substrates such as semiconductor wafers. Example processes that can be performed on substrates include, but are not limited to, etching, deposition, and cleaning processes. During processing, the substrate is positioned on a substrate support, such as a pedestal or electrostatic chuck (ESC), within a processing chamber of the substrate processing system. A gas delivery system supplies a gas mixture into the processing chamber to process the substrate. Plasma can be ignited to enhance chemical reactions within the processing chamber. An RF bias can also be applied to the substrate support to control ion energy. To improve quality and reduce defects, one or more metrology systems may be used to verify the operation of a processing chamber. For example, a flow metering system may be used to verify the flow rate of a gas mixture supplied by a gas delivery system. When multiple substrate processing chambers are arranged in a substrate processing tool, gas lines are used to connect the gas delivery systems of the processing chambers to the multiplexed flow metering system. Flow metering systems may include orifice-based, steady-state flow measurement devices. Gas delivery systems typically require calibration and supply of flow rates from 10-3000 sccm. Gas flowing into the gas line at low flow rates takes a long time to reach the flow metering device and build up sufficient pressure for measurement, which adversely affects measurement time during tool startup. In other words, calibrating flow rates from 10 to several hundred sccm takes a long time. More recently, process recipes also require calibration and supply of flow rates from 0.1-10 sccm. As can be appreciated, unacceptable time delays can occur during chamber matching or calibration at lower flow rates from 0.1 to 10 sccm using orifice-based methods. A flow metering system for a substrate processing system comprises: N primary valves for selectively flowing gases from N gas sources, where N is an integer; N mass flow controllers, each connected to the N primary valves, for flowing N gases from the N gas sources; N secondary valves, each connected to the N mass flow controllers, for selectively flowing gases from the N mass flow controllers; a gas flow path connecting the N secondary valves to a flow metering system remote from the N secondary valves; the gas flow path comprising a gas pipeline; and a controller configured to perform a first flow metering operation on a selected gas at a desired flow rate from one of the N mass flow controllers 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 from one of the N mass flow controllers at the desired flow rate 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. In other features, the controller is further configured to determine an effective volume of the gas flow path for the selected gas and the desired 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 controller is configured to use the first flow metric when determining the actual flow rate when the desired flow rate is less than a predetermined flow rate. The predetermined flow rate is in a range of 5 sccm to 15 sccm. In other features, the controller is configured to determine the actual flow rate using a second flow rate metric different from the first flow rate metric when the desired flow rate is greater than the predetermined flow rate. The predetermined flow rate is in a range from 5 seem to 15 seem. In other features, the second flow meter comprises an orifice-based meter. 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 use the valve, the pressure sensor, and the orifice to determine the actual flow rate when the desired flow rate is greater than the predetermined flow rate. In other features, the controller is configured to wait a first predetermined settling period after evacuating the gas flow path and before measuring the initial pressure in the gas flow path. The controller is configured to wait a second predetermined settling period after flowing the selected gas from the one of the N mass flow controllers at the desired flow rate during the predetermined period and before measuring the final pressure in the gas flow path. A gas delivery system for a substrate processing system comprises: a gas box including N mass flow controllers for controlling gas flows from N gas sources, respectively, where N is an integer; a gas flow path in fluid communication with the gas box; a hybrid flow metering system in fluid communication with the gas flow path and comprising a controller configured to perform the following operations: a first flow metering system for calibrating at least one of the N mass flow controllers based on a differential mass of gas in the gas flow path between the gas box and a flow metering system during a predetermined period Δt when a desired flow rate of gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate; and a second flow metering system for calibrating at least one of the N mass flow controllers when the desired flow rate of the at least one of the N mass flow controllers is greater than the predetermined flow rate. In other features, the first flow metric and the second flow metric are used to determine an effective volume of the gas flow path for the gas at the desired flow rate. The first flow metric further determines the differential mass based on the effective volume of the gas flow path for the gas at the desired flow rate. The second flow metric is an orifice-based method. In other features, 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. 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 a range of 5 sccm to 15 sccm. In other features, a valve is connected to an outlet of an orifice. A pressure sensor senses pressure at an inlet of the orifice. The controller is configured to use the valve, the pressure sensor, and the orifice to determine the actual flow rate when the desired flow rate is greater than the predetermined flow rate. In other features, the controller 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 from one of the N mass flow controllers at the desired flow rate during 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. In other features, the controller is configured to wait a first predetermined adaptation period after evacuating the gas flow path and before measuring the initial pressure in the gas flow path. The controller is configured to wait a second predetermined adaptation period after flowing the selected gas from the one of the N mass flow controllers at the desired flow rate during the predetermined period and before measuring the final pressure in the gas flow path. A method for performing gas flow metering in a substrate processing system comprises: providing a gas box comprising N mass flow controllers for controlling gas flows from N gas sources, wherein N is an integer; and providing a gas flow path in fluid communication with the gas box. The method comprises using a first flow meter to calibrate at least one of the N mass flow controllers based on a differential mass of gas in the gas flow path between the gas box and a flow meter system during a predetermined period of time when a desired flow rate of the gas supplied by at least one of the N mass flow controllers is less than a predetermined flow rate. The method comprises using a second flow meter to calibrate at least one of the N mass flow controllers when the desired flow rate of the at least one of the N mass flow controllers is greater than the predetermined flow rate. In other features, the first flow metric and the second flow metric are used to determine an effective volume of the gas flow path for the gas at the desired flow rate. In other features, the first flow metric further determines the differential mass based on the effective volume of the gas flow path for the gas at the desired flow rate. In other features, the second flow meter is an orifice-based method. The predetermined flow rate is in a range from 5 sccm to 15 sccm. 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 from one of the N mass flow controllers at the desired flow rate during 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. In other features, the method further includes waiting a first predetermined adaptation period after evacuating the gas flow path and before measuring the initial pressure in the gas flow path. The method further includes waiting a second predetermined adaptation period after flowing the selected gas from the one of the N mass flow controllers at the desired flow rate during the predetermined period and before measuring the final pressure in the gas flow path. Further areas of applicability of the present disclosure will become apparent from the detailed description, the appended claims and the accompanying drawings. The detailed description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. Orifice-based flow metering systems, such as Absolute Flow Verification (AFV), supply gas from a mass flow controller (MFC) to a pump through an orifice bank. The orifice bank contains multiple precision orifices that can be selected using corresponding valves. Pressure is established upstream of one of the selected orifices and monitored with a pressure sensor, such as a manometer. A pressure valve is used to determine the flow rate based on an empirically developed gas table that correlates orifice pressure to gas flow rate on a gas-by-gas basis. Temperature correction can also be applied to account for temperature variations and determine the true gas flow rate of the MFC. Due to the time required to fill and pressurize the gas flow path downstream of the MFC and upstream of the selected orifice, the measurement time of the AFV is greatly increased at lower flow rates. The gas flow path generally includes gas supply lines, manifolds, valves, etc. (located between the gas box and the flow metering system). The long calibration period increases the downtime required to perform gas flow calibration during initial setup and later during chamber matching. At very low flow rates and using long gas supply lines, it is difficult to detect when the orifice flow stabilizes (to obtain a steady-state pressure). Due to the increased volume of the gas line, it is difficult to detect small changes in pressure accumulation. According to the hybrid flow metering system and method disclosed herein, a differential mass measurement (DMM) method is used for flow rates below a predetermined flow rate, and another flow metering method is used for flow rates above the predetermined flow rate. In some examples, the predetermined flow rate is 10 sccm, although other flow values ​​may be used. In some examples, orifice-based flow metering is used for flow rates above the predetermined flow rate, although other flow metering methods may be used. As described further below, the DMM method fills a gas volume in gas lines, valves, manifolds, and the like between the gas tank and the flow metering system. In some cases, the gas volume is emptied and an initial pressure is measured after an acclimatization period. The initial mass is determined based on the initial pressure and the effective volume of the gas flow path through the gas lines, manifolds, valves, and / or other volumes between the gas tank and the flow metering system. After determining the initial mass, the valve is opened and the MFC flows gas at a desired flow rate (to be calibrated) for a predetermined period Δt. The pressure in the gas volume between the gas tank and the flow metering system steadily rises. After the predetermined period 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 taking the difference between the final mass and the initial mass and dividing it by Δt. Although similar to the rate of change (ROR) method, the DMM method uses the volumes of gas lines, valves, manifolds, etc., rather than the volumes of the chamber / tank, to calculate mass flow. In ROR, the governing equation for calculating mass flow is derived by taking the time derivative of the equation of state. In the ROR tank, the instantaneous pressure and temperature are sampled over time during the compression of the gas, and the rate of change of pressure / temperature is calculated. More specifically, when performing the DMM method for low flow rates, the MFC gas flow is used to pressurize a chamber of known volume V for a predetermined period of time Δt. The initial and final gas pressures and temperatures within the chamber are used to calculate the net mass of gas supplied to the chamber based on the following gas state equation: PV = m RTZ / MW (1) where P is pressure, V is volume, m is mass, MW is molecular weight, R is the universal gas constant, and Z is the compressibility of the gas under the conditions (p, T). The equation for absolute gas flow Q is: (2) The subscripts 1 and 2 represent the initial and final states, respectively. Compressibility effects are important only for polyatomic gases and when pressure and temperature are close to atmospheric (ATM) conditions. Since the pressure downstream of the MFC is subatmospheric and can be maintained at an order of magnitude less than the ATM pressure when pressurizing the gas volume in the DMM method, compressibility effects can be ignored even for polyatomic gases. Therefore, the flow equation is simplified to: (3) In some cases, the gas within the enclosure is allowed to settle for a predetermined acclimatization period before measuring the initial and final p and T. This acclimatization period reduces the effects of the gas's kinetic energy, eliminating pressure gradients caused by gas flow. This acclimatization period also allows the gas temperature to stabilize with respect to the surrounding environment. In other words, the gas is heated or cooled by the surrounding enclosure (wall temperature Tw), eliminating effects caused by gas expansion or compression, respectively. Gas expansion occurs at the start of a metrology calibration when the enclosure is evacuated to purge gas residues (from previous measurements). As gas is supplied to the enclosure, it undergoes compression, which raises its temperature. Because the use of fast temperature sensors in the gas path is impractical (due to the potential risk of sensor damage from exposure to corrosive gases), accurate direct gas temperature measurement is not possible. If the gas is allowed to stabilize during the acclimation period, the initial and final gas temperatures will be and Similarly, due to the elimination of pressure gradients along the length of the gas supply line and changes in gas temperature, the initial and final pressures (p1 and p2) are adjusted to and Therefore, the flow equation is simplified to: (4) As mentioned above, the volume of the enclosure used in the DMM method (gas lines, valves, manifolds, etc.) behaves differently than the enclosure used in the ROR method. In the ROR method, the effective volume V is the same as the actual volume of the tank. However, experimental testing of the enclosure used in the DMM method (gas lines, valves, manifolds, etc.) leads to errors. In other words, the effective volume V (calculated using known flow rates) is eff The volume is significantly different from what was expected. Some of the differences in volume can be attributed to variations in geometric manufacturing tolerances. Furthermore, experiments have shown that the calibrated effective volume V eff The volumetric pressure can vary depending on the gas and flow rate. These differences can be attributed to a variety of other factors. For example, this difference can be attributed to the relatively small volume of the gas supply line (which is more significantly affected by variations in manufacturing tolerances of the gas line, internal valve, and / or substrate volume). This difference can also be attributed to the overall complex geometry of the supply volume assembly (a long tube with an internal valve) compared to the simple, uniform geometry of the tank used in the ROR method. The ROR method uses a tank with a larger volume than the gas flow path, including the gas supply line. If not properly accounted for, pressure gradients in the gas supply line due to gas viscosity effects can significantly affect mass flow calculations and cause inaccuracies. Therefore, the ROR method is not applicable when using the gas line volume as a containment volume and measuring pressure at a single point. However, this problem can be solved by using the calibrated effective volume V of each gas. eff As will be described further below, the calibrated effective volume can be calculated using an orifice technique or another flow measurement method. More specifically, the effective volume V can be calculated using Equation 4. Initially, the corresponding MFC is set to one of the low flow settings and the DMM method is performed. During the DMM method, the initial and final pressures and temperatures are measured. The MFC is operated at the same flow setting (with the same gas) using the orifice method. The orifice method provides the absolute (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 pressures and temperatures. Calculations for the effective volume are only required once, during initial tool startup and only for gases with low flow rates. This single calibration also accounts for variations in manufacturing tolerances of gas supply lines between tools used for chamber flow matching. Therefore, chamber matching can be performed more quickly using the hybrid approach. Furthermore, calibrating the DMM method (for low flows) with the orifice technique method (for higher flows) ensures that there is no deviation at flow transitions or overlaps when switching between the two methods. Another advantage of the proposed hybrid flow metering is that calculations at flow transitions can be tracked and monitored as an additional system health check to ensure accuracy has not drifted over time. Additional details regarding AFVs can be found in commonly assigned U.S. Patent No. 7,822,570, issued on October 26, 2010, and entitled “Methods for Performing Actual Flow Verification,” which is incorporated herein by reference in its entirety. Additional details regarding RORs can be found in commonly assigned U.S. Patent No. 9,778,083. Referring now to FIG. 1 , an example substrate processing system 120 is shown. Although an example is shown of a process chamber using capacitively coupled plasma (CCP) for etching, chemical vapor deposition, or atomic layer deposition (ALD), the flow metering systems and methods described herein can be used with any other type of system or substrate processing system. For example, the flow metering systems and methods described herein can be used with substrate processing systems using remote plasma or inductively coupled plasma (ICP). Furthermore, the systems and methods described herein can be used in any other semiconductor equipment requiring precise flow metering. The substrate processing system 120 includes a processing chamber 122 that encloses the other components of the substrate processing system 120 and contains the 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 placed on the substrate support 126. By way of example only, the upper electrode 124 may include a gas distribution assembly 129, such as a showerhead, that introduces and distributes process gases. The gas distribution assembly 129 may include a rod portion including one end connected to the top surface of the processing chamber. A base portion is generally cylindrical and extends radially outward from the opposite end of the rod portion at a location spaced from the top surface of the processing chamber. The substrate-facing surface or faceplate of the showerhead base portion includes a plurality of through-holes through which precursors, reactants, etching gases, inert gases, carrier gases, other process gases, or purge gases flow. Alternatively, the upper electrode 124 may include a guide plate, and the process gases may be introduced in another manner. The substrate support 126 includes a pedestal 130 that serves as a lower electrode. The pedestal 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 pedestal 130. The pedestal 130 may include one or more channels 136 for flowing a coolant through the pedestal 130. If plasma is used, the RF generation system 140 generates and outputs an RF voltage to one of the upper electrode 124 and the lower electrode (e.g., the pedestal 130 of the ESC 126). The other of the upper electrode 124 and the pedestal 130 may be DC grounded, AC grounded, or floating. For example only, the RF generation system 140 may include an RF generator 142 that generates RF power that is fed to the upper electrode 124 or the pedestal 130 by a matching and distribution network 144. In other examples, the plasma may be generated inductively or remotely. 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. Gas sources 152 are connected to manifold 160 via valves 154-1, 154-2, ..., and 154-N (collectively, valves 154) and MFCs 156-1, 156-2, ..., and 156-N (collectively, MFCs 156). A secondary valve may be used between MFCs 156 and manifold 160. Although a single gas delivery system 150 is shown, two or more gas delivery systems may be used. A temperature controller 163 may be connected to a plurality of thermal control elements (TECs) 164 disposed within the heater plate 132. The temperature controller 163 may be configured to control the plurality of TECs 164 to control the temperature of the substrate support 126 and substrate 128. The temperature controller 163 may communicate with a coolant assembly 166 to control the flow of coolant through the channel 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 channel 136 to cool the substrate support 126. A valve 170 and a pump 172 may be configured to evacuate reactants from the processing chamber 122. A system controller 180 may be configured to control components of the substrate processing system 120. 2, the flow metering systems and methods described herein may be used to provide cost-effective flow metering of gases supplied to one or more substrate processing tools 210. Although an example substrate processing tool 210 is shown, other substrate processing systems may be used. Substrate processing tool 210 includes a centrally located robot 212. Robot 212 can operate under vacuum or atmospheric pressure. Substrate processing tool 210 includes a plurality of stations (or substrate processing chambers) 216-1, 216-2, ..., and 216-S (collectively referred to as stations 216) (where S is an integer greater than one) arranged around robot 212. Stations 216 can be arranged at regular or irregular angles around the center of substrate processing tool 210. Examples of stations 216 include one or more of deposition, etching, pre-clean, post-clean, spin clean, and the like. The substrate may initially be located in a cassette 234. A robot and load lock, generally identified at 238, may be used to move the substrate from the cassette 234 to the substrate processing tool 210. When processing is complete, the robot and load lock 238 may return the substrate to the cassette 234 and / or another cassette 239. As will be described further below, a gas delivery system supplies gases to the stations, and a flow metering system calibrates the gas flows. Referring now to FIG3 , a gas delivery system 300 is shown that includes a plurality of gas boxes 310 - 1 , 310 - 2 , ..., and 310 - 10 (collectively, gas boxes 310 ). Although ten (10) gas boxes are shown, the gas delivery system 300 may include additional or fewer gas boxes. The gas boxes 310 - 1 , 310 - 2 , ..., 310 - 10 are connected to a mixed flow metering 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 a manifold 313 and then delivered to the mixed flow metering system 320. Return gas from the mixed flow metering system 320 may be connected to the gas boxes 310 - 1 , 310 - 2 , ..., 310 - 10 by second gas lines 314 - 1 , 314 - 2 , ..., 314 - 10 (collectively, second gas lines 314 ). The second gas line 314 flows from the hybrid flow metering system 320 into the manifold 315 and is separated into independent lines connected to the gas boxes 310 - 1 , 310 - 2 , . . . , 310 - 10 . 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 chamber. 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, which reduces costs. Referring now to FIG. 4 , one of the gas boxes 310 is shown. Gas sources 410-1, 410-2, ..., and 410-G (collectively, gas sources 410) are connected to a flow control device comprising 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 a mixing manifold 435 and input to valves 440, 442, and 448. Valves 440 and 442 are connected to a mixing flow metering system 320. Valve 442 is associated with the gas flowing in gas line 312 to the mixing flow metering system 320. Valve 440 is associated with the return gas from the mixing flow metering system 320 in gas line 314. Valve 448 is associated with the gas flowing in gas line 316 to the processing chamber associated with gas box 310. One or more temperature sensors 480 can be used to sense the temperature of the gas line. In some examples, portions of the gas line are heated by resistive heaters (not shown). Referring now to FIG5 , a portion of a hybrid flow metering system is shown. Inlet B of hybrid flow metering system 320 is connected to valve 510. Inlet B' associated with gas boxes GB2, GB4, GB6, GB8, and GB10 is connected to valve 511. The outputs 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 one) (collectively, gas lines 518). Gas lines 518 are connected to precision orifices 520-1, 520-2, ..., and 520-O (collectively, precision orifices 520). In some cases, the precision orifice 520 has varying orifice sizes. A precision orifice 520 is considered "precision" if the orifice has a predetermined, known size and shape and is unobstructed. When the precision orifice operates in a choked flow state, one or more pressure sensors 530 sense the pressure upstream of the precision orifice 520. A choked flow state 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. Pressure sensors 530 are connected to the outputs of valves 510 and 511 and to the inlet of precision orifice 520. For example, a first pressure sensor 530 operates within a first pressure range, while a second pressure sensor 530 operates within a second pressure range that is the same as or different from the first pressure range. For example, the first pressure sensor 530 measures pressures up to 50°F, while the second pressure sensor 530 measures pressures up to 500°F, 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. Referring now to FIG6 , a hybrid flow metering controller 610 is shown. In some examples, the hybrid flow metering controller 610 includes an AFV table 620, a V eff Table 622 and V eff Estimation module 624. AFV table 620 is an empirically established table that relates orifice pressure to flow rate on a per-gas basis. eff Table 622 contains V values ​​that are calibrated and indexed by gas and / or desired flow rate. eff value. The hybrid flow meter controller 610 communicates with the valve 634, the mass flow controller 636, the pressure sensor 530, and the temperature sensor 480. As will be described further below, the hybrid flow meter controller 610 controls the valve 634 based on feedback from the temperature sensor 480 and the pressure sensor 530. In some examples, V eff The estimation module 624 may be used to estimate V based on other calibrations using interpolation, formulas, or other techniques. eff value to estimate V eff . Referring now to Figures 7A and 7B, a method for performing mixed flow metering is shown. In Figure 7A, method 700 is performed to determine the calibrated effective volume for a low flow gas. In other words, the calibrated effective volume only needs to be determined for the gas to be supplied at a flow rate below the predetermined flow rate, where the DMM method will be used. In addition, calibrations can be performed for each of the gases and flow rates to be used. Alternatively, one or more calibrations can be performed for one or more gases and one or more flow rates. Interpolation, formulas, or other compensation methods can be used to determine the flow rates of other gases and / or other flow rates (below the predetermined flow rate) without requiring separate calibrations for these. At 710, a gas and flow rate are selected for calibration of the effective volume. At 714, the effective volume of the selected gas at the selected flow rate is determined using the first and second flow metering methods. In certain examples, the effective volume V can be calculated using Equation 4. Initially, the corresponding MFC is set to one of the low flow settings and the DMM method is performed. During the DMM method, the initial and final pressures and temperatures are measured. The MFC is operated at the same flow setting (with the same gas) using the orifice method. The orifice method provides the absolute (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 pressures and temperatures. If additional samples are needed, the method continues at 718 and calibrates another flow rate of the selected gas. When all flow rates of the selected gas have been calibrated, the method continues at 722 and determines whether to calibrate another gas. If 722 is true, the method returns to 710. Otherwise, the method ends. FIG7B illustrates a method 750 for operating a hybrid flow metering system according to the present disclosure. At 760, the method determines whether to perform flow metering. If 760 is true, the method determines whether the desired flow rate to be calibrated is less than or equal to a first flow threshold TH1. If 764 is true, the method utilizes a DMM method and a calibrated effective volume corresponding to the selected gas and / or flow rate. If 764 is false, the method utilizes a second flow metering method. In some examples, the second flow metering method comprises an orifice-based method. Referring now to FIG. 8 , a method 800 for performing flow metering is shown. At 810 , a gas line is drawn from a gas box to an orifice. At 814 , a valve is closed to isolate the gas line from the MFC outlet to the orifice. At 816 , the method waits for an acclimation period to allow kinetic energy to dissipate and the gas to reach wall temperature. In some examples, the acclimation period ranges from 10 to 60 seconds. At 820 , noise from the pressure sensor is filtered, the pressure is measured, and an initial mass is determined based on the measured pressure. At 824 , the secondary valve of the MFC is opened and flow is supplied at the desired flow rate. The gas line, manifold, and other structures are filled with the desired flow rate output by the MFC for a predetermined period Δt. At 830 , the secondary valve of the MFC is closed and flow is stopped. At 834 , the method waits for an acclimation period. At 838 , noise from the pressure sensor is filtered, the pressure is measured, and a final mass is determined based on the measured pressure and the 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. Referring now to FIG9 , for an example of the DMM method, the measured pressure is shown as a function of time. After the gas line is evacuated, the gas is allowed to settle and reach equilibrium temperature with a surface such as the inner wall of the gas line ( ), which creates an initial pressure p 1. Next, the MFC is set to the desired flow rate to be calibrated for a period of time Δt. After the period Δt, the gas is allowed to settle to eliminate the pressure gradient along the gas supply line and to reach equilibrium temperature with the surface such as the inner wall of the gas line ( ), which creates a final pressure p 2 slight changes. Referring now to FIG. 10 , a method 1000 for providing additional confirmation of MFC calibration is shown. In certain examples, during operation, a first flow metering system and a second flow metering system will have one or more flow rate overlaps within a comparable predetermined range. For example, the first flow metering system may be used to calibrate flow rates less than or equal to 10 sccm, while the second flow metering system may be used to calibrate flow rates greater than or equal to 10 sccm. In certain examples, both the first and second flow metering systems may be used to calibrate the same desired MFC flow rate. For example, both metering systems may be used to calibrate 10 sccm. The results of calibration using the first flow metering system and the second flow metering system can be compared. If the results are within a predetermined tolerance, the first and second flow metering systems are operating correctly. If the results are not within the predetermined tolerance, the system sends a notification, generates an alarm message, activates a warning light, and / or takes other actions. At 1010, the MFC is configured to flow the selected gas at a desired flow rate within a predetermined flow range. In some examples, the predetermined flow range approximates a predetermined flow rate for switching between the first metering system and the second metering system. For example, the desired flow rate of the MFC may be in the range of 5 sccm to 15 sccm. At 1020, a first flow rate MFR is measured using a first metering system. 1. At 1030, a second flow rate MFR is measured using a second metering system 2. At 1040, the first and second flow MFR 1 and MFR 2. At 1050, the system determines the first and second flow MFRs 1 and MFR 2 is less than a predetermined value or is within a predetermined tolerance. If 1050 is true, the method ends. Otherwise, the system sends a notification, generates an alarm message, turns on a warning light, or takes other actions at 1052. The foregoing description is intended to be illustrative only and is not intended to limit the present disclosure, its application, or use. The broad teachings of this disclosure can be implemented in many forms. Therefore, although this disclosure includes specific examples, the true scope of the disclosure should not be limited thereto as other modifications will become apparent upon study of the drawings, the specification, and the following patent claims. It should be understood that one or more steps in a method can 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 and / or in combination with the features of any other embodiment, even if such combination is not explicitly described. In other words, the embodiments described are not mutually exclusive, and substitution of one or more embodiments with another remains within the scope of this disclosure. Various terms are used to describe spatial and functional relationships between components (e.g., between modules, circuit elements, semiconductor layers, etc.), including "connected," "engaged," "coupled," "adjacent," "adjacent," "on top of," "above," "below," and "disposed." Unless explicitly described as "directly," when describing a relationship between a first and second component in the above disclosure, that relationship can be a direct relationship with no other intervening components between the first and second components, or an indirect relationship with one or more intervening components between the first and second components (spatially or functionally). As used herein, the phrase "at least one of A, B, and C" should be construed to mean a logical (A or B or C) using a non-exclusive "or" and should not be construed to mean "at least one of A, at least one of B, and at least one of C." In some instances, a controller is part of a system, which may be one of the examples above. The system may include semiconductor processing equipment, including processing tools, chambers, platforms, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems may incorporate electronics to control their operations before, during, and after processing semiconductor wafers or substrates. This electronics, referred to as a "controller," can control various system components or subcomponents. The controller may be designed to control any of the processes disclosed herein, including process gas delivery, 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 settings, fluid delivery settings, position and operation settings, wafer access tools and other handling tools, and / or load locks that connect to or interface with the specific system, depending on the processing requirements and / or system type. Broadly speaking, a controller can be defined as an electronic product with various integrated circuits, logic, memory, and / or software that accepts and sends commands, controls operations, initiates cleaning operations, initiates endpoint measurements, and so on. These integrated circuits may include chips that store program instructions in the form of firmware, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). Program instructions may be communicated to the controller in the form of various individual configurations (or program files) that define the operating parameters for a specific process performed on a semiconductor wafer or system. In some embodiments, these operating parameters may be part of a recipe defined by a process engineer for performing one or more process steps in the fabrication of one or more layers, material layers, metal layers, oxide layers, silicon crystal layers, silicon dioxide layers, surfaces, circuits, and / or dies on a wafer. In some embodiments, the controller may be part of or coupled to a computer that is integrated with the system, coupled to the system, or otherwise networked to the system, or a combination thereof. For example, the controller may be in the "cloud" or part of or all of a mainframe computer system in a factory, allowing remote access to wafer processes. The computer may be able to remotely connect to the system to monitor the progress of current manufacturing operations, view historical records of past manufacturing operations, view trends or performance metrics for multiple manufacturing operations, modify current process parameters, set process steps to continue the current process, or initiate a new process. In some examples, a remote computer (e.g., a server) may provide process recipes to the system via a network, which may include a local area network (LAN) or the Internet. The remote computer may include a user interface for entering or configuring parameters and / or settings, which are then connected to the system from the remote computer. In some examples, the controller receives instructions in the form of data specifying parameters for each process step to be performed in one or more operational processes. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool with which the controller is configured to interface or control. Thus, as described above, the controller may be decentralized, such as by combining one or more individual controllers that collaborate and work toward a common purpose, such as process and control, as described herein. An example of a decentralized controller for this purpose may be one or more integrated circuits located on a chamber coupled to one or more remotely located integrated circuits (e.g., at the stage level or as part of a remote computer) to control the process in that chamber. Without limitation, example systems may include plasma etch chambers or modules, deposition chambers or modules, spin rinse chambers or modules, metal plating chambers or modules, cleaning chambers or modules, bevel etch chambers or modules, physical vapor deposition (PVD) chambers or modules, chemical vapor deposition (CVD) chambers or modules, atomic layer deposition (ALD) chambers or modules, atomic layer etch (ALE) chambers or modules, ion implantation chambers or modules, track chambers or modules, and any other semiconductor processing system that may be associated with or used in the production and / or fabrication of semiconductor wafers. As described above, the controller may communicate with one or more other tool circuits or modules, other tool components, group tools, other tool interfaces, adjoining tools, neighboring tools, tools throughout the factory, a host computer, another controller, or a material handling tool to transport wafer containers to or from tool locations and / or load ports in the semiconductor manufacturing facility, depending on the process steps being performed by the tool. 120: Substrate processing system 122: Processing chamber 124: Upper electrode 126: Substrate support 128: Substrate 129: Gas distribution device 130: Base 132: Heating plate 134: Thermal resistance layer 136: Channel 140: RF generation system 142: RF generator 144: Matching and distribution network 150: Gas delivery system 152: Gas source 152-1: Gas source 152-2: Gas source 152-N: Gas source 154-1: Valve 154-N: Valve 156-1: MFC 156-N: MFC 160: Manifold 163: Temperature controller 164: TEC 166: Coolant assembly 170: Valve 172: Pump 180: System controller 210: Substrate processing tool 212: Robot 216-1: Station 216-2: Station 216-S: Station 234: Cassette 238: Robot and load lock 239: Cassette 300: Gas delivery system 310: Gas box 310-1: Gas box 310-2: Gas box 310-3: Gas box 310-10: Gas box 312: Gas line 312-1: Gas line 312-2: Gas line 312-3: Gas line Line 313: Manifold 314: Second Gas Line 314-1: Second Gas Line 314-2: Second Gas Line 314-3: Second Gas Line 315: Manifold 316: Gas Line 316-1: Gas Line 316-2: Gas Line 316-3: Gas Line 320: Mixed Flow Metering System 330: Clean Dry Air Source 410-1: Gas Source 410-2: Gas Source 410-G: Gas Source 420-1: Primary Valve 420-2: Primary Valve 420-G: Primary Valve 430-1: MFC 430-2: MFC 430-G: MFC 434-1: Secondary valve 434-2: Secondary valve 434-G: Secondary valve 435: Manifold 440: Valve 442: Valve 448: Valve 480: Temperature sensor 510: Valve 511: Valve 513: Manifold 518-1: Gas line 518-2: Gas line 518-O: Gas line 520-1: Precision orifice 520-2: Precision orifice 520-O: Precision orifice 524-1: Valve 524-2: Valve 524-O: Valve 530: Pressure sensor 540: Pump 610: Mixed flow metering controller 620: AFV meter 622: V eff Table 624: V eff Estimation module 634: valve 636: mass flow controller B: inlet B': inlet GB2: gas box GB4: gas box GB6: gas box GB8: gas box GB10: gas box The present disclosure will become more fully understood from the detailed description and the accompanying drawings, in which: FIG1 is a functional block diagram of an example substrate processing system; FIG2 is a functional block diagram of an example substrate processing system; FIG3 is a functional block diagram of a gas delivery system according to the present disclosure that may be used in the systems of FIG1 and FIG2 ; FIG4 is a functional block diagram of an example of an air box according to the present disclosure; FIG5 is a functional block diagram of an example of a hybrid flow metering system according to the present disclosure; FIG6 is a functional block diagram of an example of a hybrid flow metering controller according to the present disclosure; 7A and 7B are flow charts illustrating an example of a method for performing hybrid flow metering according to the present disclosure; FIG8 is a flow chart illustrating an example of a differential quality method according to the present disclosure; FIG9 is a graph depicting pressure as a function of time during a differential mass method according to the present disclosure; and 10 is a flow chart depicting an example of a method for using the calculation of the effective volume of a given gas over time as additional metrological confirmation according to the present disclosure. Among the drawings, reference numerals may be repeated to identify similar and / or identical components. 312: Gas pipeline 314: Second gas pipeline 320: Mixed flow metering system 480: Temperature sensor 510: Valve 511: Valve 513: Manifold 518-1: Gas pipeline 518-2: Gas pipeline 518-O: Gas pipeline 520-1: Precision Orifice 520-2: Precision Orifice 520-O: Precision Orifice 524-1: Valve 524-2: Valve 524-O: Valve 530: Pressure sensor 540: Pump B: Entrance B': Entrance

Claims

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

2. The method for performing gas flow metering in a substrate processing system as claimed in claim 1 further includes: selecting the first flow metering when the desired flow rate is less than the predetermined flow rate; and selecting the second flow metering when the desired flow rate is greater than the predetermined flow rate.

3. The method for performing gas flow measurement in a substrate processing system as claimed in claim 1 further includes: performing the first flow measurement based on a differential mass of gas in the airflow path between the gas tank and a flow measurement system during a predetermined time period.

4. The method for performing gas flow metering in a substrate processing system as claimed in claim 3, wherein the first flow metering and the second flow metering are used to determine an effective volume for the gas flow path at the desired flow rate.

5. The method for performing gas flow metering in a substrate processing system as claimed in claim 4, wherein the first flow metering is further based on the effective volume of the gas flow path for the gas at the desired flow rate to determine the differential mass.

6. The method for performing gas flow measurement in a substrate processing system as claimed in claim 1, wherein the second flow measurement is an orifice-based method.

7. The method for performing gas flow metering in a substrate processing system as claimed in claim 1, wherein the predetermined flow rate is in the range of 5 sccm to 15 sccm.

8. The method for performing gas flow metering in a substrate processing system as claimed in claim 3, wherein the first flow metering comprises: purging the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass in the gas flow path; allowing a selected gas to flow at least one of the N mass flow controllers at the desired flow rate during a predetermined time period; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining a true flow rate based on the initial mass, the final mass, and the predetermined time period.

9. The method for performing gas flow measurement in a substrate processing system as claimed in claim 8 further includes: waiting for a first predetermined adjustment period after purging the gas flow path and before measuring the initial pressure in the gas flow path.

10. The method for performing gas flow measurement in a substrate processing system as claimed in claim 9 further comprises: waiting for a second predetermined settling period after the selected gas flows at the desired flow rate during the predetermined time period from at least one of the N mass flow controllers and before measuring the final pressure in the gas flow path.

11. A hybrid flow metering system comprising: an airflow path in fluid communication with a gas chamber, the gas chamber including N mass flow controllers for controlling airflows from N gas sources, wherein N is an integer; and a controller configured to calibrate the at least one of the N mass flow controllers using a first flow meter and a second flow meter selected based on a comparison between a predetermined flow rate and a desired flow rate for gas supplied by at least one of the N mass flow controllers.

12. The hybrid flow metering system of claim 11, wherein the controller is configured to: select the first flow meter when the desired flow is less than the predetermined flow; and select the second flow meter when the desired flow is greater than the predetermined flow.

13. The mixed flow metering system of claim 11, wherein the controller is configured to perform the first flow metering based on a differential mass of gas in the airflow path between the gas tank and the mixed flow metering system during a predetermined time period.

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

15. The mixed flow metering system of claim 14, wherein the first flow metering is further based on the effective volume of the gas flow path for the desired flow rate to determine the differential mass.

16. The hybrid flow metering system of claim 11, wherein the second flow metering is an orifice-based method.

17. The mixed flow metering system of claim 11, wherein the controller is configured to: determine an effective volume for the flow path of a selected gas and a selected flow rate.

18. The hybrid flow metering system of claim 17, wherein the controller is further configured to determine a true flow rate based on the effective volume.

19. The mixed flow metering system of claim 11, wherein the airflow path further includes a manifold and a valve.

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

21. The hybrid flow metering system of claim 11 further includes: an orifice; a valve connected to an outlet of the orifice; and a pressure sensor for sensing pressure at an inlet of the orifice, wherein the controller is configured to use the valve, the pressure sensor, and the orifice to determine a true flow rate when the desired flow rate is greater than the predetermined flow rate.

22. The hybrid flow metering system of claim 17, wherein the controller is configured to perform the first flow metering by: purging the gas flow path; measuring an initial pressure in the gas flow path; determining an initial mass in the gas flow path; allowing the selected gas to flow from one of the N mass flow controllers at the desired flow rate over a predetermined time period; measuring a final pressure in the gas flow path; determining a final mass in the gas flow path; and determining a true flow rate based on the initial mass, the final mass, and the predetermined time period.

23. The mixed flow metering system of claim 22, wherein the controller is configured to wait for a first predetermined settling period after the airflow path is emptied and before the initial pressure in the airflow path is measured.

24. The mixed flow metering system of claim 23, wherein the controller is configured to wait for a second predetermined settling period after the selected gas flows at the desired flow rate during the predetermined time period from one of the N mass flow controllers and before measuring the final pressure in the gas flow path.

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