In-SITU calibration of gas flows in substrate processing systems

Abstract

A method of calibrating gas flow includes selecting a mass flow controller (MFC) to supply a gas, dividing a volume including gas lines between the MFC and an exhaust pump into a first volume and a second volume using a first valve located between the first volume and the second volume and located upstream from a second valve connected to the exhaust pump; supplying the gas from the MFC into the volume at a flow rate to be calibrated; controlling the first and second valves to perform multiple cycles of (i) supplying the gas from the first volume into the second volume, (ii) isolating the second volume from the first volume, and (iii) removing the gas from the second volume using the exhaust pump; and calibrating the flow rate of the MFC based on a mass of the gas removed from the second volume in the multiple cycles.

Description

IN-SITU CALIBRATION OF GAS FLOWS IN SUBSTRATE PROCESSING SYSTEMSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 612,480, filed on December 20, 2023. The entire disclosure of the application referenced above is incorporated herein by reference.FIELD

[0002] The present disclosure relates generally to substrate processing systems and more particularly to in-situ calibration of gas flows in substrate processing systems.BACKGROUND

[0003] The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.

[0004] Substrate processing systems may be used to perform etching, deposition, and / or other treatment of substrates such as semiconductor wafers. Examples of the processes that may be performed on a substrate include, but are not limited to, etching, deposition, and cleaning processes. Substrate processing systems (also called tools) may comprise multiple processing chambers (also called process modules). Some processing chambers in a tool may perform the same process on different substrates. In some tools, different processes may be performed in different processing chambers. For example, different processes may be performed sequentially on the same substrate by moving the substrate from one processing chamber to another. During processing, a substrate is arranged on a substrate support such as a pedestal or an electrostatic chuck (ESC) in a processing chamber of a tool. A gas delivery system supplies a gas mixture to the processing chamber to treat the substrate. Plasma may be struck to enhance chemical reactions in the processing chamber.SUMMARY

[0005] A method of calibrating gas flow in a substrate processing system comprises selecting a mass flow controller (MFC) to supply a gas, dividing a volume comprisinggas lines between the MFC and an exhaust pump into a first volume and a second volume using a first valve located between the first volume and the second volume and located upstream from a second valve connected to the exhaust pump, and supplying the gas from the MFC into the volume at a flow rate to be calibrated. The method comprises while supplying the gas from the MFC at the flow rate, controlling the first and second valves to perform multiple cycles of (i) supplying the gas from the first volume into the second volume, (ii) isolating the second volume from the first volume, and (iii) removing the gas from the second volume using the exhaust pump; and calibrating the flow rate of the MFC based on a mass of the gas removed from the second volume in the multiple cycles.

[0006] In additional features, the method further comprises determining the volume and the second volume using the gas, and calibrating a second MFC configured to supply a second gas using the volume and the second volume.

[0007] In additional features, the method further comprises calibrating the flow rate of the MFC regardless of a value of the flow rate.

[0008] In additional features, the method further comprises, before performing the multiple cycles, opening the first and second valves, evacuating the volume with the MFC turned off, closing the second valve, setting the MFC to supply the gas into the volume at any flow rate to pressurize the volume until pressure in the volume stabilizes, and recording a first pressure and a first temperature of the gas in the volume.

[0009] In additional features, the method further comprises, after recording the first pressure and the first temperature, while supplying the gas from the MFC at the flow rate, performing each of the multiple cycles by: with the second valve closed, closing the first valve to isolate the second volume from the first volume; recording a first set of pressure and temperature in the second volume; opening the second valve to remove the gas from the second volume using the exhaust pump while the first valve is closed; recording a second set of pressure and temperature in the second volume; closing the second valve; and opening the first valve to supply the gas from the first volume into the second volume.

[0010] In additional features, the method further comprises determining the mass of the gas removed from the second volume in the multiple cycles based on the first and second sets of pressure and temperature recorded in each of the multiple cycles.

[0011] In additional features, the method further comprises, after performing the multiple cycles, while supplying the gas from the MFC at the flow rate: with the first valve open and the second valve closed, setting the MFC to a zero setpoint; recording a second pressure and a second temperature of the gas in the volume; opening the first and second valves to evacuate the volume; and determining a second mass of the gas in the volume before and after the performing the multiple cycles based on the first and second sets of pressure and temperature.

[0012] In additional features, the method further comprises calibrating the flow rate based on the mass of the gas removed from the second volume in the multiple cycles, the second mass of the gas in the volume before and after the performing the multiple cycles, the volume, and the second volume.

[0013] In additional features, the method further comprises increasing the first volume in response to the flow rate being greater than or equal to a threshold.

[0014] In additional features, the method further comprises calibrating a second MFC to supply the gas at the flow rate, supplying the gas from the MFC at the calibrated flow rate to a first process module of the substrate processing system, and supplying the gas from the second MFC at the calibrated flow rate to a second process module of the substrate processing system.

[0015] In still other features, a system for calibrating gas flow in a substrate processing system, the system comprises a first valve and a controller. The first valve is configured to divide a volume comprising gas lines between a mass flow controller (MFC) and an exhaust pump into a first volume and a second volume. The first valve is located between the first volume and the second volume and located upstream from a second valve connected to the exhaust pump. The controller is configured to supply a gas from the MFC into the volume at a flow rate to be calibrated. The controller is configured to, while supplying the gas from the MFC at the flow rate, control the first and second valves to perform multiple cycles of (i) supplying the gas from the first volume into the second volume, (ii) isolating the second volume from the first volume, and (iii) removing the gas from the second volume using the exhaust pump. The controller is configured to calibrate the flow rate of the MFC based on a mass of the gas removed from the second volume in the multiple cycles.

[0016] In additional features, the controller is configured to determine the volume and the second volume using the gas, and calibrate a second MFC configured to supply a second gas using the volume and the second volume.

[0017] In additional features, the controller is configured to calibrate the flow rate of the MFC regardless of a value of the flow rate.

[0018] In additional features, the controller is configured to, before performing the multiple cycles, open the first and second valves, evacuate the volume with the MFC turned off, close the second valve, set the MFC to supply the gas into the volume at any flow rate to pressurize the volume until pressure in the volume stabilizes, and record a first pressure and a first temperature of the gas in the volume.

[0019] In additional features, the controller is configured to, after recording the first pressure and the first temperature, while supplying the gas from the MFC at the flow rate, perform each of the multiple cycles by: with the second valve closed, closing the first valve to isolate the second volume from the first volume; recording a first set of pressure and temperature in the second volume; opening the second valve to remove the gas from the second volume using the exhaust pump while the first valve is closed; recording a second set of pressure and temperature in the second volume; closing the second valve; and opening the first valve to supply the gas from the first volume into the second volume.

[0020] In additional features, the controller is configured to determine the mass of the gas removed from the second volume in the multiple cycles based on the first and second sets of pressure and temperature recorded in each of the multiple cycles.

[0021] In additional features, the controller is configured to, after performing the multiple cycles, while supplying the gas from the MFC at the flow rate: with the first valve open and the second valve closed, set the MFC to a zero setpoint; record a second pressure and a second temperature of the gas in the volume; open the first and second valves to evacuate the volume; and determine a second mass of the gas in the volume before and after the performing the multiple cycles based on the first and second sets of pressure and temperature.

[0022] In additional features, the controller is configured to calibrate the flow rate based on the mass of the gas removed from the second volume in the multiple cycles,the second mass of the gas in the volume before and after the performing the multiple cycles, the volume, and the second volume.

[0023] In additional features, the controller is configured to add a third volume to the first volume in response to the flow rate being greater than or equal to a threshold.

[0024] In additional features, the controller is configured to calibrate a second MFC to supply the gas at the flow rate, supply the gas from the MFC at the calibrated flow rate to a first process module of the substrate processing system, and supply the gas from the second MFC at the calibrated flow rate to a second process module of the substrate processing system.

[0025] Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:

[0027] FIG. 1 shows an example of a substrate processing system comprising an in- situ dual-volume gas flow calibration system according to the present disclosure;

[0028] FIG. 2 schematically shows an example of the in-situ dual-volume gas flow calibration system according to the present disclosure;

[0029] FIG. 3 shows an example of a timing diagram of steps performed in an in-situ dual-volume gas flow calibration method according to the present disclosure; and

[0030] FIG. 4 shows an example of the in-situ dual-volume gas flow calibration method according to the present disclosure.

[0031] In the drawings, reference numbers may be reused to identify similar and / or identical elements.DETAILED DESCRIPTION

[0032] In substrate processing systems (tools), metrology systems may be used to verify operation of processing chambers of the tools. For example, in a tool, a flow metrology system may be used to verify flow rates of gas delivery systems supplyinggases to the processing chambers. The flow metrology system is connected to the gas delivery systems of the processing chambers using gas lines. When the tool is powered up, the flow metrology system calibrates flow rates of mass flow controllers (MFCs) of the gas delivery systems used to supply gases to the processing chambers. Calibration can reduce defects and improve chamber matching. Some processes performed in the processing chambers may require calibration of the MFCs and supply of gases at low flow rates such as 0.1 -10 standard cubic centimeters per minute (seem) and / or high flow rates such as a few hundred scorn’s or more. Currently used flow metrology systems for calibrating flow rates of MFCs use a rate of rise (ROR) method, an orificebased absolute flow verification (AFV) method, and a differential mass measurement (DMM) method, which are briefly described below.

[0033] In the ROR method, a gas supplied by a gas delivery system via an MFC flows into a known chamber volume, and mass flow rate is calculated by taking time derivative of a state equation. In the orifice method, a gas supplied by a gas delivery system via an MFC flows through a bank of orifices to a pump. The pump is used to evacuate or purge contents of the processing chambers of the tool into a foreline of an exhaust system of the tool. As the pressure builds up upstream of an orifice, the pressure is monitored, and a steady-state pressure value is used to determine a flow rate based on an empirically developed gas table that relates orifice pressure to gas flow rate. A temperature correction can also be applied to account for temperature variations and to determine the correct gas flow rate of the MFC. In the DMM method, a gas is supplied by a gas delivery system via an MFC to a known volume for a known amount of time, and a difference between final and initial masses in the known volume is measured to determine a gas flow rate of the MFC. The known volume in the DMM method is calculated using actual flow rate determined by the orifice method. Some tools use a hybrid flow metrology system comprising a combination of the orifice method and the DMM method. For example, the orifice method is used for higher flow rates, and the DMM method is used for lower flow rates.

[0034] The orifice method has many limitations. For example, the orifice method is gas dependent. That is, the orifice method requires generation of empirical gas tables (pressure vs. flow rate) for each gas. Additionally, the orifice method requires multiple orifices (e.g., a bank of orifices) for different flow rates for each gas. Further, the measurement times for the orifice method are longer for lower flow rates. Unlike the orifice method, the ROR method and the DMM method for calculating flow rate areindependent of gas properties and can be used for any gas once the volume is determined using a known flow rate of any gas from other methods like the orifice method. However, the limitation of the ROR and DMM method is that a maximum flow rate that can be measured by the ROR and DMM methods is limited by the size of available wetted flow volume or tank size. A wetted volume is volume in contact with a fluid flowing through the volume. The DMM and ROR methods involve initial and final mass measurements or measurement of pressure gradient with time and are therefore limited by the size of the tank volume. Therefore, at higher flow rates, the orifice method is used instead, which has the disadvantages described above.

[0035] In recent years, semiconductor manufacturing has seen rapid introduction of new gases due to various factors such as process technology advancement, environmental impact, and so on, and it has become challenging for flow metrology to timely support new gases using the above methods. Specifically, the orifice method requires gas specific data generation, which is time consuming, while the DMM and ROR methods are limited to low flow rates based on size of wetted volume and have other limitations such as maximum operating pressure of equipment.

[0036] The present disclosure provides an in-situ flow metrology system that solves the above problems associated with the other methods and that does not have the above limitations of the other methods. The in-situ flow metrology system of the present disclosure uses a dual volume-based method for calibrating gas flows that is independent of gas properties. The dual-volume method can be used to calibrate flow rates that are low as well as multiple times higher than the flow rates that can be calibrated using other volume-based methods such as the ROR and DMM methods for similar volume size. Additionally, unlike the orifice method, the dual-volume method is independent of gas properties, which eliminates the need to generate new gas tables for each new gas. Further, since the dual-volume method does not use the gas tables, the dual-volume method can calibrate flow rates for any new gas in minutes.

[0037] The dual-volume method involves flowing a gas (any gas; e.g., nitrogen) from an MFC into a combined volume that is separated (split) by an isolation valve into two parts or volumes. For example, the two volumes can be called a storage volume (V_Storage) and a scoop volume (V_Scoop), which are together called the combined volume or a total volume. The dual-volume method is called an in-situ method because the dual-volume method uses the volume of the gas lines, manifold, and so on betweenthe MFC and the pump itself as the combined volume. While the gas from the MFC keeps flowing into the storage volume, the scoop volume is emptied (evacuated) iteratively (repeatedly) a number of times. In each iteration, a known scoop of mass QJ,sccop is extracted from the scoop volume by intermittently closing the isolation valve and opening a foreline valve connecting the scoop volume to the pump. Throughout the present disclosure, the foreline valve is also called an exhaust valve. Using iterative scooping, the maximum flow rate that can be achieved and calibrated by the dual-volume method can be multiple times higher than that achievable by the DMM and ROR methods for a similar size of the combined volume.

[0038] In the dual-volume method, the wetted volume upstream of the isolation valve to a selected MFC is called the storage volume (V_storage), and the wetted volume downstream of isolation valve to the pump valve is called scoop volume, V_scoop. Initially, the isolation valve is opened and the foreline valve is closed. The MFC is turned on and set to any flow rate, and initial pressure and temperature (P1 , T1 ) in the total volume are recorded. Then the MFC is set to a desired setpoint (i.e., the setpoint for which the MFC is to be calibrated), and the gas is allowed to flow for a desired (selectable predetermined) duration, tjotal.

[0039] As the pressure in the storage and scoop volumes rises, the isolation valve is closed after some (selectable predetermined) duration to isolate the scoop volume from storage volume while the gas from the MFC continues to flow into the storage volume. Once the pressure stabilizes in the isolated scoop volume, the pre-scoop stabilized pressure and temperature (PJ, pre-scoop; TJ, pre-scoop) are recorded, and the foreline valve is opened to empty the scoop volume and is then closed. Once the foreline valve closes, the post-scoop pressure and temperature (PJ, post-scoop; TJ, post-scoop) are recorded when pressure stabilizes in the isolated scoop volume. The mass QJ,sccop dumped into the foreline is given by the equation of state as follows: P V = m R T Z / MW, where R is the Universal Gas Constant, Z is the gas compressibility at condition (P,T), MW is the molecular weight of the gas, and Z=1 at sub-atmospheric operating conditions.

[0040] The equation for the mass scooped in each iteration QJ, scoop is given by:QJ, scoop = Delta_mDelta_m = (V_Scoop* MW / R) [PJ, pre-scoop I TJ, pre-scoop - PJ, post-scoop I TJ, post-scoop]QJ, scoop = (V_Scoop* MW / R) [PJ, pre-scoop / TJ, pre-scoop - PJ, post-scoop / TJ, post-scoop]

[0041] During the time when the isolation valve is kept closed, the pressure in the storage volume rises. After taking the post scoop measurements (PJ, post-scoop; TJ, post-scoop), the isolation valve is opened, which allows for the pressure that is built-up in the storage volume to relieve as the gas flows from the storage volume into the emptied scoop volume while the gas from the MFC continues to flow into the storage volume. Once again, with the isolation valve open, the pressure in scoop and storage volumes starts to rise. Then after some duration (selectable predetermined) tjso-close (iso=isolation valve), the isolation valve is closed, and the same cycle of emptying and filling the scoop volume is iteratively repeated n (selectable predetermined) number of times.

[0042] Once the total amount of time for which the gas flows from the MFC reaches the desired total duration (selectable predetermined) tjotal, the cycle is no longer repeated (i.e., the cycle is stopped), the isolation valve is kept open, the foreline valve is closed, the MFC is turned off, and the gas from the MFC stops flowing. The final stabilized pressure and temperature (P2, T2) in the total volume are recorded.

[0043] The total mass scooped out in n iterations called Q_scoop (also called first mass) is given by:Q_scoop = Q_1 , scoop + Q_2, scoop + Q_n, scoop,Q_scoop = SUM {(QJ, scoop), for i = 1 to n}

[0044] The balance mass not scooped out in n iterations (i.e., mass of gas in the total volume before and after the iterations of scooping operations or before t=0 and after t=tjotal shown in FIG. 3) is called QJcalance (also called second mass) and is given by:QJcalance = Delta_m_balanceDelta_m_balance = (VJotal* MW / R) [P2 / T2 - P1 / T1]QJcalance = (VJotal* MW / R) [P2 / T2 - P1 / T1]

[0045] The equation for absolute volumetric gas flow rate q in seem is given by: q * tjotal * P_STP*MW / (R*T_STP) = Delta_mDelta_m = Delta_m Jealance + Delta_m_scoopDelta_m = Q_balance + Q, scoop q * tjotal * P_STP*MW / (R*T_STP) = (V Jotal* MW / R) [P2 / T2 - P1 / T1] + SUM{(QJ, scoop), for i = 1 to n}

[0046] Therefore, q * t_ total * P_STP I T_STP = VJotal * [P2 / T2 - P1 / T1] + V_scoop* SUM{[PJ, pre-scoop I TJ, pre-scoop - PJ, post-scoop I TJ, post-scoop], for i = 1 to n}, where V_total = V_scoop + V_storage, and STP is standard pressure and standard temperature (e.g., atmospheric pressure and zero degrees Celsius).

[0047] To calculate the flow rate q of the MFC, the only unknowns are V_total and V_scoop, which can be calculated one time during tool startup by using known flow rates from another method such as the DMM method or the orifice method by using a known gas such as nitrogen. For example, V_total in the dual-volume method is the same as volume calibration factor in the DMM method, which can be initially determined once after tool startup using the DMM method. These calculations can also account for manufacturing tolerances of the gas lines and other implements used in the gas delivery systems of the processing chambers. Then the calculated flow rate q of the MFC can be compared to the desired setpoint of the MFC used during the desired total duration t otal, and any difference (offset) between the two quantities can be used to calibrate the MFC. Once the unknowns V_total and V_scoop are determined using an MFC supplying a known gas (e.g., an MFC supplying nitrogen) in a gas box 16, the dual-volume method can be used to calibrate other symmetrically located MFC’s in the gas box 16 and supplying other gases using the same V_total and V_scoop. That is, V_total and V_scoop are independent of gas properties.

[0048] The dual-volume method provides many other advantages in addition to those described above. For example, the dual-volume method can be implemented by retrofitting an isolation valve and manometers into an existing volume (i.e., existing gas distribution system) of the tool. The location of the isolation valve can be selected to define the V_storage and V_scoop volumes such that higher maximum flow rates can be achieved. For example, V_storage can be generally greater than V_scoop. The location of the isolation valve can be selected to ensure that when the isolation valve is closed intermittently for a short duration, the pressure in the storage volume stays within equipment operating limits at maximum flow rates, and the scoop volume is not too small to ensure that a measurable scoop (amount of gas) is extracted from the scoop volume. In some tools, an additional volume (e.g., a cylinder) can be added tothe combined volume to cover the entire flow rate range for all MFCs. The dual-volume method uses the existing hardware, which is simplistic and includes isolation valves, transducers, temperature sensors, and properly sized volumes, which can include wetted flow volume downstream of the MFC, including the gas supply lines, weldments, valves, and other components of the tool. The dual-volume method eliminates the challenges associated with the orifice method, which include complicated fabrication process of the orifices that often suffers from yield loss and is therefore costly. These and other features of the present disclosure are described below in further detail.

[0049] FIG. 1 shows an example of a tool 10. For example, the tool 10 comprises a plurality of process modules 12-1 , 12-2, 12-3, and 12-4 (collectively called the process modules 12). The tool comprises a plurality of gas sources 14. The gas sources 14 supply various gases (e.g., process gases, precursors, reactants, purge gases, cleaning gases, etc.). The tool 10 comprises a plurality gas boxes 16-1 , 16-2, 16-3, and 16-4 (collectively called the gas boxes 16). Each gas box 16 supplies the gases received from the gas sources 14 to a respective process module 12. Each gas box 16 comprises a plurality of MFCs and valves. The valves in each gas box 16 can be controlled to select and mix the gases received from the gas sources 14. The MFCs in each gas box 16 are calibrated using the dual-volume method of the present disclosure to supply the gases and / or gas mixtures at calibrated flow rates to the respective process modules 12.

[0050] The process modules 12 are connected to an exhaust pump (hereinafter called the pump) 18. The pump 18 evacuates the contents of the process modules 12 (e.g., residual gases and reaction byproducts) into an exhaust system (not shown) of the tool 10. The gas sources 14, gas boxes 16, the process modules 12, and the pump 18 are connected to each other as shown by various gas lines, manifolds, weldments, and valves (hereinafter collectively called gas lines).

[0051] The tool 10 comprises a calibration device 20. The calibration device 20 is disposed centrally in the tool 10 relative to the process modules 12 (e.g., equidistant from the gas boxes 16). The calibration device 20 is connected to the pump 18 via an exhaust valve 56 (see FIG. 2). For example, the exhaust valve 56 may be selected from an exhaust valve connecting a process module 12 to the pump 18 or can be a separate exhaust valve connecting the calibration device 20 to the pump 18. The calibration device 20 is connected to the gas boxes 16, the process modules 12, and isolation andexhaust valves (see FIG. 2). An example of the isolation valve is shown at 52 in FIG. 2. Specifically, the calibration device 20 is connected to the gas lines downstream from the gas boxes 16 (and therefore downstream from the MFCs) and to the gas lines upstream from the exhaust valve 56. The isolation valves are disposed in the gas lines between the gas boxes 16 and the exhaust valves as shown in FIG. 2. Specifically, the isolation valves are disposed in the gas lines downstream from the MFCs and upstream from the exhaust valve 56 as shown in FIG. 2.

[0052] The calibration device 20 comprises a calibration controller 21 (shown in FIG. 2) that calibrates the MFCs in the gas boxes 16 using the dual-volume method of the present disclosure as described below in detail. The calibration controller 21 controls the isolation valves and the exhaust valve 56 and performs the various measurements and calculations of the dual-volume method to calibrate the MFCs of the gas boxes 16 as described below in detail.

[0053] For example, the calibration device 20 comprises one or more pressure sensors and one or more temperature sensors to measure various pressures and temperatures during the dual-volume method as described below in detail. Alternatively, the calibration controller 21 may communicate with one or more pressure sensors and one or more temperature sensors disposed in the total volume (described below with reference to FIG. 2) that measure the various pressures and temperatures during the dual-volume method.

[0054] The tool 10 comprises a system controller 22. The system controller 22 controls the gas boxes 16, various components (e.g., pedestals and showerheads) of the process modules 12, the exhaust pump 18, and the calibration device 20. For example, during startup of the tool 10, the system controller 22 activates the calibration device 20. After the calibration device 20 calibrates the MFCs of the gas boxes 16, the calibration device 20 provides the calibration data for each MFC of the gas boxes 16 to the system controller 22. The system controller 22 sets the setpoints for flow rates of the MFCs of the gas boxes 16 according to the calibration data.

[0055] FIG. 2 schematically shows the total volume, storage volume, scoop volume, and the isolation and exhaust valves used by the dual-volume method of the present disclosure to calibrate the MFCs in the gas boxes 16. The dual-volume method is described below with reference to FIGS. 3 and 4. For calibration of an MFC 17 of a gas box 16 supplying a gas to a process module 12, a volume between the MFC 17 and thepump 18 constitutes a total volume as shown in FIG. 2. For example, the total volume comprises a first gas line 50 connecting the MFC 17 being calibrated to the calibration device 20, including any valves present in the first gas line 50, an isolation valve 52 connecting the first gas line 50 to a second gas line 54, an exhaust valve 56 connected to the second gas line 54, and a third gas line 58 connecting the exhaust valve 56 to the pump 18. In some examples, the first, second, and third gas line 50, 54, 58 may be a single gas line. One or more pressure sensors and one or more temperature sensors may be located in the total volume to measure the various pressures and temperatures during the dual-volume method.

[0056] The isolation valve 52 divides (splits) the total volume into two volumes: a storage volume and a scoop volume. While the storage and scoop volumes are schematically shown as boxes in FIG. 2, the entire volume between the MFC 17 and the isolation valve 52 constitutes the storage volume, and the entire volume between the isolation valve 52 and the pump 18 constitutes the scoop volume. Thus, the storage volume comprises the first gas line 50 connecting the MFC 17 to the isolation valve 52, and the scoop volume comprises the second and third gas lines 54, 58 and the exhaust valve 56. The location of the isolation valve 52 is selected such that when the isolation valve 52 is closed as described below, the pressure in the storage volume stays within operating limits at maximum flow rates, and the scoop volume is not too small to ensure that a measurable scoop (amount of gas) is extracted from the scoop volume. For example, the storage volume can be generally greater than the scoop volume.

[0057] The total volume comprises the storage volume and the scoop volume. The storage volume is a volume upstream of the isolation valve 52 and includes the volume between the MFC 17 and the isolation valve 52. The scoop volume is a volume downstream of the isolation valve 52 and includes the volume between the isolation valve 52 and the pump 18. The storage volume may be called the upstream volume relative to the isolation valve 52 (or a first volume). The scoop volume may be called the downstream volume relative to the isolation valve 52 (or a second volume). The two volumes are separated by the isolation valve 52.

[0058] The isolation valve 52 is located between the storage volume and the scoop volume. The isolation valve 52 is located upstream from the exhaust valve 56. The exhaust valve 56 is located downstream from the isolation valve 52 and upstream from the pump 18. The total volume is contiguous between the MFC 17 and the pump 18.The storage volume is contiguous between the MFC 17 and the isolation valve 52. The scoop volume is contiguous between the isolation valve 52 and the pump 18. The storage volume and the scoop volume are contiguous. The isolation valve 52 and the exhaust valve 56 may be called a first valve and a second valve, respectively.

[0059] The calibration device 20 taps into the total volume. In some examples, the isolation valve 52 may be disposed within the calibration device 20. Since the calibration device 20 is located centrally relative to the process modules 12 (e.g., equidistant from the gas boxes 16 associated with the process modules 12), the isolation valve 52 in the calibration device 20 can divide a total volume between any MFC in any of the gas boxes 16 and the pump 18 such that the storage volume can be generally greater than the scoop volume.

[0060] Alternatively, the calibration device 20 can select any valve downstream from a gas box 16, which comprises the MFC being calibrated, and upstream of the exhaust valve 56 as the isolation valve 52. The selected valve can function as the isolation valve 52 provided that the selected valve divides the total volume between the MFC being calibrated and the pump 18 into storage and scoop volumes such that the storage volume can be generally greater than the scoop volume. Thus, depending on the gas box 16 in which the MFC being calibrated is located, the calibration device 20 can select different valves as the isolation valve 52 provided that the selected valves satisfy the above criteria.

[0061] In addition, the calibration device 20 can add an additional volume V+ 60 (also called a third volume) to the storage volume depending on the flow rate for which an MFC is being calibrated. For example, if the MFC is calibrated for a high flow rate (e.g., a flow rate greater than a threshold), the storage volume may need to be increased to perform calibration. One or more cylindrical containers represented by the additional volume V+ 60 may be disposed in the gas lines between the gas boxes 16 and the isolation valves 52. The cylindrical containers of various known volumes may be connected to the gas lines between the gas boxes 16 and the isolation valves 52 by respective valves. The calibration device 20 can control the valves connecting the cylindrical containers to the gas lines between the gas boxes 16 and the isolation valves 52. By controlling the valves that connect the cylindrical containers to the gas lines between the gas boxes 16 and the isolation valves 52, the calibration device 20 can increase the storage volume depending on the flow rate for which an MFC is beingcalibrated. In some examples, for very high flow rates, the calibration device 20 can add more than one cylindrical device to the storage volume.

[0062] FIG. 3 graphically shows the cycling of the isolation and exhaust valves 52, 56 and the pressure changes in the storage and scoop volumes in the dual-volume method of calibrating the MFCs in the gas boxes 16. The dual-volume method of calibrating the MFCs in the gas boxes 16 is described below in detail with reference to FIG. 4. The description of FIG. 4 also references FIGS. 2 and 3 as needed and describes the reference numerals shown in FIG. 3.

[0063] FIG. 4 shows a dual-volume method 100 of calibrating MFCs in the gas boxes 16. For example, calibration of only one MFC is described. Each MFC in each gas box 16 is similarly selected and calibrated by the calibration device 20 when the tool 100 is powered up. After the calibration of the MFCs in the gas boxes 16, processes such as deposition, etching, and cleaning can be performed in the process modules 12. The operations described below can be performed by the calibration controller 21 of the calibration device 20. For example, the calibration controller 21 can comprise a processor and memory storing instructions, which when executed by the processor, configure the processor to perform the following operations. In the following description of the method 100, references to the method 100 should be understood as references to the processor of the calibration controller 21 . Alternatively, the operations described below can be performed by the system controller 22 of the tool 10.

[0064] At 102, the method 100 selects an MFC to be calibrated (e.g., the MFC 17 shown in FIG. 2) and turns off the selected MFC 17. Accordingly, no gas flows from the selected MFC 17 into the total volume (see FIG. 2). At 104, the method 100 connects the selected MFC 17 to the pump 18 of the exhaust system of the tool 10 via manifolds, gas lines, and valves. For example, the method 100 selects one or more valves to connect the gas lines from the selected MFC 17 to the exhaust pump 18 to establish the total volume between the selected MFC 17 and the pump 18.

[0065] At 106, the method 100 divides (splits) the total volume between the selected MFC 17 and the pump 18 comprising the manifolds, gas lines, and valves into a storage volume and a scoop volume (called the two volumes) by arranging the isolation valve 52 between the two volumes. For example, the isolation valve 52 may be already present in the calibration device 20, which is already centrally located in the tool 10 relative to the process modules 12. Accordingly, the isolation valve 52 in the calibrationdevice 20 may divide the total volume between the selected MFC 17 and the pump 18 into the two volumes. Alternatively, the method 100 can select one of the valves in the total volume between the selected MFC 17 and the pump 18 as the isolation valve 52 and can control the isolation valve 52 as described below. Either way, the location of the isolation valve 52 is such that when the isolation valve 52 is closed as described below, the pressure in the storage volume stays within operating limits at maximum flow rates, and the scoop volume is large enough to ensure that a measurable scoop (amount of gas) is extracted from the scoop volume.

[0066] At 108, the method 100 arranges (e.g., selects) the exhaust valve 56 between the scoop volume and the pump 18. For example, the exhaust valve 56 may be a dedicated exhaust valve coupled to the calibration device 20, which connects the scoop volume to the pump 18. Alternatively, the method 100 may select an exhaust valve associated with the process module 12 for which the selected MFC 17 is being calibrated as the exhaust valve 56.

[0067] At 110, the method 100 opens all valves between the selected MFC 17 and the pump 18, including the isolation valve 52 and the exhaust valve 56. The method 100 evacuates (emptied) the total volume between the selected MFC 17 and the pump 18, with the selected MFC 17 turned off in step 102, into the exhaust system of the tool 10. Thus, at this point, the pressure in the total volume is nearly zero (vacuum) as shown at 150 in FIG. 3.

[0068] At 112, the method 100 closes the exhaust valve 56 (also called the foreline valve), opens the isolation valve 52, sets the selected MFC 17 to any flow rate, and pressurizes the total volume to a pressure P1 . At this point, the gas from the selected MFC 17 flows into the total volume, and pressure in the total volume increases as shown at 152 in FIG. 3.

[0069] At 114, when the pressure in the total volume stabilizes at P1 as shown at 154 in FIG. 3 (SP=stabilized pressure), the method 100 sets the selected MFC 17 to a zero setpoint to stop the gas flow into the total volume, and records the initial stabilized pressure P1 and temperature T1 in the total volume. For example, the method 100 can store the initial stabilized pressure P1 and temperature T1 in the memory of the calibration controller 21 of the calibration device 20 or the system controller 22 of the tool 10.

[0070] At 1 16, with the gas in the total volume at the initial stabilized pressure P1 and temperature T1 , the selected MFC 17 set to a zero setpoint, the exhaust valve 56 closed, and the isolation valve 52 open, the iterative scooping operations begin at time t=0. The iterative scooping operations are performed as described below for a time t=t_total, which is selectable predetermined time period. At time t=0, the method 100 sets the selected MFC 17 to a desired setpoint that is to be calibrated (i.e., a flow rate for which the selected MFC 17 is to be calibrated). At this point, gas continues to flow from the selected MFC 17 into the total volume, and pressure in the total volume begins to increase.

[0071] At 1 18, at time t=t1 , where t1 is a selectable predetermined time period (i.e., after the selected MFC 17 is set to the desired setpoint at time t=0 in step 1 16 and gas has flowed into the total volume for time t1 ), the method 100 closes the isolation valve 52 to isolate the scoop volume from the storage volume. Since gas continues to flow into the storage volume and since the isolation valve 52 and the exhaust valve 56 are closed, the pressure in the storage volume continues to increase as shown at 160. However, since the isolation valve 52 and the exhaust valve 56 are closed, gas does not flow into the scoop volume, and the pressure in the scoop volume stabilizes as shown at 162. The method 100 records the pre-scoop stabilized pressure P1 i and temperature T1 i of the gas in the scoop volume, where i is the index denoting the number of the iteration of the scooping operation. For example, the method 100 can store the pre-scoop stabilized pressure P1 i and temperature T1 i of the gas in the scoop volume in the memory of the calibration controller 21 of the calibration device 20 or the system controller 22 of the tool 10.

[0072] At 120, at time t=t2, where t2 is a selectable predetermined time period, the method 100 opens the exhaust valve 56 to empty (evacuate) the scoop volume while the isolation valve 52 remains closed. The emptying of the scoop volume or evacuating gas from the scoop volume is called scooping the gas from the scoop volume, and hence the name scoop volume.

[0073] At 122, at time t=t3, where t3 is a selectable predetermined time period, the method 100 closes the exhaust valve 56 while the isolation valve 52 remains closed. The method 100 records the post-scoop stabilized pressure P2i and temperature T2i of the gas in the scoop volume, where i is the index denoting the number of the iteration of the scooping operation. For example, the method 100 can store the post-scoopstabilized pressure P2i and temperature T2i of the gas in the scoop volume in the memory of the calibration controller 21 of the calibration device 20 or the system controller 22 of the tool 10.

[0074] At 124, at time t=t4, where t4 is a selectable predetermined time period, the method 100 opens the isolation valve 52 allowing the gas from the storage volume to flow into the scoop volume while the exhaust valve 56 remains closed. While gas continues to flow into the storage volume, the pressure in the storage volume decreases since the gas from the storage volume flows into the empty scoop volume through the open isolation valve 52. However, since the exhaust valve 56 is closed, the pressure in the scoop volume increases. The decrease in pressure in the storage volume and the increase in pressure in the scoop volume is shown at 170 in FIG. 3.

[0075] At 126, the method 100 determines if the time that has elapsed since t=0 is less than t_total. If t < t_total, the method 100 returns to step 118, and repeats the scooping operation in the steps 118-124 (i.e., performs another iteration of the scooping operation as described in steps 118-124). If t > t_total, the method 100 proceeds to step 128.

[0076] At 128, with the isolation valve 52 open and the exhaust valve 56 closed from step 124, the method 100 sets the selected MFC 17 to a zero setpoint to stop the gas flow into the total volume , and the pressure in the total volume stabilizes at P2 as shown at 180 in FIG. 3 (SP=stabilized pressure). The method 100 records the final stabilized pressure P2 and temperature T2 in the total volume. For example, the method 100 can store the final stabilized pressure P2 and temperature T2 in the memory of the calibration controller 21 of the calibration device 20 or the system controller 22 of the tool 10.

[0077] At 130, the method 100 opens all valves between the selected MFC 17 and the pump 18, including the isolation valve 52 and the exhaust valve 56. The method 100 evacuates (empties) the total volume between the selected MFC 17 and the pump 18, with the selected MFC 17 set to a zero setpoint in step 128, into the exhaust system of the tool 10. Thus, at this point, the pressure in the total volume is nearly zero (vacuum) as shown at 190 in FIG. 3.

[0078] At 132, the method 100 calibrates the selected MFC 17 based on the total mass of the gas scooped out of the scoop volume during t_total in the i iterations ofsteps 118-124, the balance mass of the gas not scooped out before t=0 and after t=t_total, the total volume, and the scoop volume using the equations described above.

[0079] Specifically, the method 100 calculates an actual flow rate of the selected MFC 17 and compares the actual calculated (measured) flow rate to the setpoint (i.e., the desired setpoint to be calibrated) set in step 116. The method 100 provides any difference (offset) between the calculated flow rate and the setpoint set in step 116 to the system controller 22. The system controller 22 adjusts the setpoint of the selected MFC 17 based on the offset. For example, if the calculated flow rate is greater than the setpoint set in step 116, the system controller 22 subtracts the offset from the setpoint of the selected MFC 17. If the calculated flow rate is less than the setpoint set in step 116, the system controller 22 adds the offset from the setpoint of the selected MFC 17.

[0080] In the method 100, the time t_total can be selected to allow a predetermined number of iterations i of the scooping operation. For example, a longer t_total can allow more number of iterations of the scooping operation, which in turn can increase the calibration accuracy of the MFCs. Alternatively, a shorter t_total can allow fewer iterations of the scooping operation, which in turn can increase the calibration speed of the MFCs.

[0081] The method 100 is performed to calibrate the flow rate of each MFC of each gas box 16 when the tool 10 is initially powered up. Subsequently, the calibrated MFCs can supply respective gases to the process modules 12 at the calibrated flow rates. Further, with the flow rates of the MFCs in the gas boxes 16 calibrated, the performance of two or more process modules 12 can be matched. For example, the same gas can be supplied at the same flow rate from two different calibrated MFCs in two different gas boxes 16 to two process modules 12 in which the same process is performed. Since the calibrated MFCs in two different gas boxes 16 can supply the same gas at the same flow rate to two process modules 12, two different substrates can be processed in identical manner in two different process modules 12 to produce the same result in both substrates.

[0082] To calculate the flow rate q of the MFC using the equations described above, the only unknowns are V_total and V_scoop, which can be calculated once during tool startup using the orifice method and the DMM method as follows. The tool 10 may additionally comprises an orifice bank through which a gas (e.g., nitrogen) can be supplied from an MFC to a pump (e.g., the pump 18) via the gas lines (the total volumedescribed above) used by the dual-volume method. The orifice bank includes multiple orifices that can be selected using corresponding valves (e.g., by the calibration controller 21 or the system controller 22). Pressure builds upstream from a selected orifice and is measured by a pressure sensor. The measured pressure is used to measure a flow rate of the MFC based on an empirically developed gas table that relates orifice pressure to gas flow rate for the gas used (e.g., nitrogen). Thus, by using an MFC supplying nitrogen, setting the MFC at a selected setpoint, and supplying nitrogen at the selected setpoint from the MFC through the selected orifice into the total volume used by the dual-volume method, an actual flow rate q of the MFC can be obtained using the orifice method.

[0083] After measuring the actual flow rate of the MFC using the orifice method, the calibration controller 21 or the system controller 22 performs the DMM method using the same MFC set at the same setpoint and supplying the same gas at the same setpoint used in the orifice method to determine the total volume as follows. In the DMM method, the total volume is initially evacuated, and initial pressure and temperature are measured after a settling period. Then the DMM method fills the total volume between the MFC and the pump 18 at the measured flow rate (i.e., with the MFC set at the same selected setpoint used in the orifice method as described above) for a duration t_total used in the dual-volume method. Then the final pressure and temperature are measured. The total volume V_total is calculated based on the initial and final pressures and temperatures, and the measured flow rate q using the following equation.

[0084] Then the scoop volume V_scoop is determined as follows. The calibration controller 21 or the system controller 22 performs the dual-volume method using the same MFC set at the same setpoint and supplying the same gas at the same setpoint used in the DMM and orifice method. Since the flow rate q and V_total are known from the orifice method and the DMM method as described above, V_scoop can be obtained from the equation: q * t_ total * P_STP I T_STP = VJotal * [P2 / T2 - P1 / T1] + V_scoop* SUM{[PJ, prescoop / TJ, pre-scoop - PJ, post-scoop / TJ, post-scoop], for i = 1 to n}

[0085] While the calibration device 20 may be centrally located in the tool 10, the total volume of the gas lines between the calibration device 20 and each gas box 16 used in the dual-volume method may not be the same. Therefore, V_total and V_scoop may be initially determined for each gas box 16 as described above before performing the dualvolume method. Then the MFCs in the gas boxes 16 can be calibrated using the dualvolume method as described above.

[0086] The foregoing description is merely illustrative in nature and is not intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims.

[0087] It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the examples is described above as having certain features, any one or more of those features described with respect to any one of the examples of the disclosure can be implemented in and / or combined with features of any of the other examples, even if that combination is not explicitly described. In other words, the described examples are not mutually exclusive, and permutations of one or more examples with one another remain within the scope of this disclosure.

[0088] Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. 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 logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.”

[0089] In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and / or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate.

[0090] The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and / or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, 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 delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and / or load locks connected to or interfaced with a specific system.

[0091] Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The 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, or microcontrollers that execute program instructions (e.g., software).

[0092] Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some examples, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or dies of a wafer.

[0093] The controller, in some implementations, may be a part of or coupled to a computer that is integrated with the system, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may bein the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process.

[0094] In some examples, a remote computer (e.g., a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and / or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control.

[0095] Thus, as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

[0096] Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean 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 track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and / or manufacturing of semiconductor wafers.

[0097] As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits ormodules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and / or load ports in a semiconductor manufacturing factory.

Claims

CLAIMSWhat is claimed is:1 . A method of calibrating gas flow in a substrate processing system, the method comprising: selecting a mass flow controller (MFC) to supply a gas; dividing a volume comprising gas lines between the MFC and an exhaust pump into a first volume and a second volume using a first valve located between the first volume and the second volume and located upstream from a second valve connected to the exhaust pump; supplying the gas from the MFC into the volume at a flow rate to be calibrated; while supplying the gas from the MFC at the flow rate, controlling the first and second valves to perform multiple cycles of (i) supplying the gas from the first volume into the second volume, (ii) isolating the second volume from the first volume, and (iii) removing the gas from the second volume using the exhaust pump; and calibrating the flow rate of the MFC based on a mass of the gas removed from the second volume in the multiple cycles.

2. The method of claim 1 further comprising: determining the volume and the second volume using the gas; and calibrating a second MFC configured to supply a second gas using the volume and the second volume.

3. The method of claim 1 further comprising calibrating the flow rate of the MFC regardless of a value of the flow rate.

4. The method of claim 1 further comprising, before performing the multiple cycles: opening the first and second valves; evacuating the volume with the MFC turned off; closing the second valve; setting the MFC to supply the gas into the volume at any flow rate to pressurize the volume until pressure in the volume stabilizes; and recording a first pressure and a first temperature of the gas in the volume.

5. The method of claim 4 further comprising, after recording the first pressure and the first temperature, while supplying the gas from the MFC at the flow rate, performing each of the multiple cycles by: with the second valve closed, closing the first valve to isolate the second volume from the first volume; recording a first set of pressure and temperature in the second volume; opening the second valve to remove the gas from the second volume using the exhaust pump while the first valve is closed; recording a second set of pressure and temperature in the second volume; closing the second valve; and opening the first valve to supply the gas from the first volume into the second volume.

6. The method of claim 5 further comprising determining the mass of the gas removed from the second volume in the multiple cycles based on the first and second sets of pressure and temperature recorded in each of the multiple cycles.

7. The method of claim 5 further comprising, after performing the multiple cycles, while supplying the gas from the MFC at the flow rate: with the first valve open and the second valve closed, setting the MFC to a zero setpoint; recording a second pressure and a second temperature of the gas in the volume; opening the first and second valves to evacuate the volume; and determining a second mass of the gas in the volume before and after the performing the multiple cycles based on the first and second sets of pressure and temperature.

8. The method of claim 7 further comprising calibrating the flow rate based on the mass of the gas removed from the second volume in the multiple cycles, the second mass of the gas in the volume before and after the performing the multiple cycles, the volume, and the second volume.

9. The method of claim 1 further comprising increasing the first volume in response to the flow rate being greater than or equal to a threshold.

10. The method of claim 1 further comprising: calibrating a second MFC to supply the gas at the flow rate; supplying the gas from the MFC at the calibrated flow rate to a first process module of the substrate processing system; and supplying the gas from the second MFC at the calibrated flow rate to a second process module of the substrate processing system.

11. A system for calibrating gas flow in a substrate processing system, the system comprising: a first valve configured to divide a volume comprising gas lines between a mass flow controller (MFC) and an exhaust pump into a first volume and a second volume, the first valve being located between the first volume and the second volume and located upstream from a second valve connected to the exhaust pump; and a controller configured to: supply a gas from the MFC into the volume at a flow rate to be calibrated; while supplying the gas from the MFC at the flow rate, control the first and second valves to perform multiple cycles of (i) supplying the gas from the first volume into the second volume, (ii) isolating the second volume from the first volume, and (iii) removing the gas from the second volume using the exhaust pump; and calibrate the flow rate of the MFC based on a mass of the gas removed from the second volume in the multiple cycles.

12. The system of claim 11 wherein the controller is configured to: determine the volume and the second volume using the gas; and calibrate a second MFC configured to supply a second gas using the volume and the second volume.

13. The system of claim 11 wherein the controller is configured to calibrate the flow rate of the MFC regardless of a value of the flow rate.

14. The system of claim 11 wherein the controller is configured to, before performing the multiple cycles: open the first and second valves; evacuate the volume with the MFC turned off; close the second valve;set the MFC to supply the gas into the volume at any flow rate to pressurize the volume until pressure in the volume stabilizes; and record a first pressure and a first temperature of the gas in the volume.

15. The system of claim 14 wherein the controller is configured to, after recording the first pressure and the first temperature, while supplying the gas from the MFC at the flow rate, perform each of the multiple cycles by: with the second valve closed, closing the first valve to isolate the second volume from the first volume; recording a first set of pressure and temperature in the second volume; opening the second valve to remove the gas from the second volume using the exhaust pump while the first valve is closed; recording a second set of pressure and temperature in the second volume; closing the second valve; and opening the first valve to supply the gas from the first volume into the second volume.

16. The system of claim 15 wherein the controller is configured to determine the mass of the gas removed from the second volume in the multiple cycles based on the first and second sets of pressure and temperature recorded in each of the multiple cycles.

17. The system of claim 15 wherein the controller is configured to, after performing the multiple cycles, while supplying the gas from the MFC at the flow rate: with the first valve open and the second valve closed, set the MFC to a zero setpoint; record a second pressure and a second temperature of the gas in the volume; open the first and second valves to evacuate the volume; and determine a second mass of the gas in the volume before and after the performing the multiple cycles based on the first and second sets of pressure and temperature.

18. The system of claim 17 wherein the controller is configured to calibrate the flow rate based on the mass of the gas removed from the second volume in the multiple cycles, the second mass of the gas in the volume before and after the performing the multiple cycles, the volume, and the second volume.

19. The system of claim 11 wherein the controller is configured to add a third volume to the first volume in response to the flow rate being greater than or equal to a threshold.

20. The system of claim 11 wherein the controller is configured to: calibrate a second MFC to supply the gas at the flow rate; supply the gas from the MFC at the calibrated flow rate to a first process module of the substrate processing system; and supply the gas from the second MFC at the calibrated flow rate to a second process module of the substrate processing system.

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