Mass Flow Controllers for Substrate Handling

Abstract

This invention relates to a mass flow controller for substrate processing. A method and apparatus for delivering process gases to a processing chamber are provided. One mass flow controller includes: a first delivery line for introducing a process fluid; and an inlet valve disposed along the first delivery line for controlling the flow rate of the process fluid. The mass flow controller further includes: a second delivery line for introducing a carrier fluid into the mass flow controller; and a microelectromechanical system (MEMS) Coriolis sensor for providing a density signal and a mass flow rate signal for a mixture of the process fluid and the carrier fluid. The provided mass flow controller includes: an outlet valve for controlling the mass flow rate of the mixture output by the mass flow controller; and a controller for operating the inlet valve based on the density signal and for operating the outlet valve based on the mass flow rate signal.

Description

Technical Field

[0001] Embodiments of the present invention relate generally to substrate processing systems and, more particularly, to methods, systems, and computer programs for controlling the delivery of fluids to substrate processing systems. Background Art

[0002] Substrate processing in semiconductor manufacturing involves various processes, such as deposition processes, etching processes, etc. Substrate processing is usually carried out in a vacuum chamber, and various gases are introduced into the vacuum chamber to process the substrate. Mass flow controllers based on heat or pressure can be used to control the mass flow rate of the gas introduced into the substrate processing chamber. However, current mass flow controllers cannot reliably control the low gas flow desired for certain substrate processing steps.

[0003] It is against this background that these implementation plans emerge. Summary of the invention

[0004] Methods, apparatus, systems and computer programs for controlling the flow of process gases delivered to a processing chamber are presented. It should be understood that embodiments of the present invention can be implemented in a variety of ways, such as methods, apparatus, systems, devices or computer programs on computer readable media. Several embodiments are described below.

[0005] In one embodiment, a mass flow controller is provided. The mass flow controller includes: a first flow line for introducing a process fluid into the mass flow controller; and an inlet valve arranged along the first flow line for controlling the flow rate of the process fluid. The mass flow controller also includes: a second flow line for introducing a carrier fluid into the mass flow controller; and a microelectromechanical system (MEMS) Coriolis sensor for providing a density signal and a mass flow rate signal for a mixture of the process fluid and the carrier fluid. In addition, the mass flow controller includes: an outlet valve for controlling the mass flow rate of the mixture output by the mass flow controller; and a controller for operating the inlet valve based on the density signal, and operating the outlet valve based on the mass flow rate signal.

[0006] In another embodiment, a method for controlling the delivery of a process fluid is provided. The method includes operations for receiving a density signal and a mass flow rate signal for a mixture of a process fluid and a carrier fluid from a Coriolis sensor of a mass flow controller (MFC). The method also includes operations for calculating a fluid mixing ratio of the mixture based on the density signal and for adjusting the flow rate of the process fluid entering the MFC based on the fluid mixing ratio. In addition, the method includes operations for calculating a mass flow rate of the mixture based on the mass flow rate signal and for adjusting an output flow rate of the mixture leaving the MFC based on the mass flow rate of the mixture.

[0007] In another embodiment, a mass flow controller is provided. The mass flow controller includes: a mixing and sensing module, which is used to mix a process fluid and a carrier fluid into a mixture, and the mixing and sensing module provides a density signal and a mass flow rate signal for the mixture. The mass flow controller also includes: an inlet valve, which is used to control the flow rate of the process fluid entering the mixing and sensing module; and an outlet valve, which is used to control the output flow rate of the mixture leaving the mixing and sensing module. In addition, the mass flow controller includes: a controller, which is used to calculate the fluid mixing ratio of the process fluid and the carrier fluid based on the density signal, and is used to calculate the mass flow rate of the mixture based on the mass flow rate signal for the mixture. According to these and other embodiments, the controller is configured to adjust the inlet valve based on the fluid mixing ratio and to adjust the outlet valve based on the mass flow rate of the mixture.

[0008] Specifically, some aspects of the present invention can be described as follows:

[0009] 1. A mass flow controller, comprising:

[0010] a first flow line for introducing a process fluid into the mass flow controller;

[0011] an inlet valve disposed along the first flow line for controlling a flow rate of the process fluid;

[0012] a second flow line for introducing a carrier fluid into the mass flow controller;

[0013] a microelectromechanical system (MEMS) Coriolis sensor for providing a density signal and a mass flow rate signal for a mixture of the process fluid and the carrier fluid;

[0014] an outlet valve for controlling the mass flow rate of the mixture output by the mass flow controller; and

[0015] A controller is provided for operating the inlet valve based on the density signal and operating the outlet valve based on the mass flow rate signal.

[0016] 2. The mass flow controller according to clause 1, further comprising:

[0017] A connector connects the first flow line and the second flow line disposed downstream of the inlet valve and upstream of the MEMS Coriolis sensor, the connector mixing the process fluid and the carrier fluid into the mixture.

[0018] 3. A mass flow controller according to clause 1, wherein the process fluid is a process gas and the carrier fluid is a carrier gas.

[0019] 4. A mass flow controller according to clause 1, wherein the flow rate of the process fluid introduced into the mass flow controller is defined by a low flow rate.

[0020] 5. A mass flow controller according to clause 4, wherein the low flow rate is defined by a rate of 2 standard cubic centimeters per minute (sccm) or less.

[0021] 6. A mass flow controller according to clause 1, wherein the controller is configured to adjust the outlet valve based on the mass flow rate signal to achieve a desired mass flow rate of the mixture.

[0022] 7. A mass flow controller according to claim 1, wherein the controller is configured to calculate a fluid mixing ratio of a process fluid to a carrier fluid, and wherein the controller is further configured to adjust the inlet valve based on the calculated fluid mixing ratio to achieve a desired fluid mixing ratio.

[0023] 8. A mass flow controller according to claim 7, wherein the controller is further configured to calculate a mass flow rate specific to the process fluid based on the fluid mixing ratio and based on the mass flow rate signal, and wherein the controller is further configured to adjust the outlet valve based on the calculated mass flow rate specific to the process fluid to achieve a desired mass flow rate specific to the process fluid.

[0024] 9. The mass flow controller of clause 1, wherein the mass flow controller is in fluid communication with a process chamber via the outlet valve such that the mass flow controller controls delivery of the mixture of process fluid and carrier fluid into the process chamber.

[0025] 10. A method for controlling a mass flow controller (MFC), comprising:

[0026] receiving a density signal and a mass flow rate signal for a mixture of process fluid and carrier fluid from a Coriolis sensor of the MFC;

[0027] calculating a fluid mixing ratio of the mixture based on the density signal;

[0028] adjusting a flow rate of the process fluid entering the MFC based on the fluid mixing ratio;

[0029] calculating a mass flow rate of the mixture based on the mass flow rate signal; and

[0030] An output flow rate of the mixture exiting the MFC is adjusted based on the mass flow rate of the mixture.

[0031] 11. The method of clause 10, wherein the density signal is associated with a measurement of a change in a vibration frequency of a conduit of the Coriolis sensor.

[0032] 12. The method of clause 10, wherein the flow signal is associated with a measurement of a phase shift in a vibration frequency between two arms of a conduit of the Coriolis sensor.

[0033] 13. The method of clause 10, wherein the calculating the fluid mixing ratio comprises determining a density of the process fluid and a density of the carrier fluid.

[0034] 14. The method according to clause 10, further comprising:

[0035] A mass flow rate specific to the process fluid is calculated based on the fluid mixing ratio and the mass flow rate of the mixture, wherein the adjusting the output flow rate of the mixture is further based on the mass flow rate specific to the process fluid.

[0036] 15. A method according to claim 10, wherein when the fluid mixing ratio indicates that the ratio of process fluid to carrier fluid is greater than a desired ratio, adjusting the flow rate of the process fluid reduces the flow rate of the process fluid, and wherein when the fluid mixing ratio indicates that the ratio of process fluid to carrier fluid is less than the desired ratio, adjusting the flow rate of the process fluid increases the flow rate of the process fluid.

[0037] 16. A method according to clause 10, wherein when the mass flow rate of the mixture is greater than a desired mass flow rate, the adjusting the output flow rate of the mixture reduces the output flow rate of the mixture, and wherein when the mass flow rate of the mixture is less than the desired mass flow rate, the adjusting the output flow rate of the mixture increases the output flow rate of the mixture.

[0038] 17. A mass flow controller comprising:

[0039] a mixing and sensing module for mixing a process fluid and a carrier fluid into a mixture, the mixing and sensing module providing a density signal and a mass flow rate signal for the mixture;

[0040] an inlet valve for controlling the flow rate of process fluid entering the mixing and sensing module;

[0041] an outlet valve for controlling an output flow rate of the mixture exiting the mixing and sensing module; and

[0042] a controller for calculating a fluid mixing ratio of a process fluid to a carrier fluid based on the density signal and for calculating a mass flow rate of the mixture based on the mass flow rate signal for the mixture, wherein the controller is configured for regulating the inlet valve based on the fluid mixing ratio and for regulating the outlet valve based on the mass flow rate of the mixture.

[0043] 18. A mass flow controller according to claim 17, wherein the controller is also configured to calculate a mass flow rate specific to the process fluid based on the fluid mixing ratio and the mass flow rate of the mixture, and wherein the adjustment of the outlet valve is further based on the mass flow rate specific to the process fluid.

[0044] 19. A mass flow controller according to claim 17, wherein the mixing and sensing module includes a Coriolis sensor for providing the density signal and the mass flow rate signal for the mixture, and the mixing and sensing module also includes a connector arranged downstream of the inlet valve and upstream of the Coriolis sensor, the connector defining a mixing point for mixing the process fluid and the carrier fluid into the mixture.

[0045] 20. The mass flow controller of clause 17, wherein the mass flow controller is part of a system further comprising a processing chamber for processing a substrate using the mixture output by the mass flow controller.

[0046] Other aspects will become apparent from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The embodiments may be best understood by referring to the following description taken in conjunction with the accompanying drawings.

[0048] Figure 1 is a schematic diagram of a system for controlling delivery of a mixture of a first fluid and a second fluid to a processing chamber, according to an embodiment.

[0049] Figure 2 is a schematic diagram of a system for controlling delivery of a mixture of process gas and carrier gas to a processing chamber using a single Coriolis sensor according to an embodiment.

[0050] Figure 3 is a schematic diagram of a system for controlling delivery of a mixture of process gas and carrier gas to a processing chamber using two Coriolis sensors according to an embodiment.

[0051] Figure 4 is a schematic diagram of a system for controlling delivery of a mixture of first and second process gases and a carrier gas to a processing chamber using two Coriolis sensors according to an embodiment.

[0052] Figure 5A is a schematic diagram of a mass flow controller for controlling the mass flow rate of a mixture of process gas and carrier gas supplied to a processing chamber according to one embodiment.

[0053] Figure 5B and 5C Exemplary embodiments of Coriolis sensors that may be used with the systems and methods described herein are shown, according to some embodiments.

[0054] Figure 6 An overall flow diagram of a method of controlling gas delivery using the system described herein, according to one embodiment, is shown.

[0055] Figure 7 An overall flow diagram of a method of controlling the delivery of a gas using the system described herein according to further embodiments is shown. DETAILED DESCRIPTION

[0056] Embodiments provide a mass flow controller for substrate processing in semiconductor manufacturing. For some substrate processing steps, a process gas with a lower flow rate is required, for example, a process gas with a flow rate of about 2 standard cubic centimeters per minute (sccm) or lower. The processing steps involving low-flow gases include deposition processes such as chemical vapor deposition (CVD), atomic layer deposition (ALD), and etching processes such as plasma etching and atomic layer etching (ALE). Current controllers including heat-based flow meters and pressure-based flow meters cannot reliably control gases with lower flow rates (e.g., about 2 sccm or lower flow rates).

[0057] For certain processing steps involving low flow rates of process gases, a larger flow rate of a carrier gas, such as argon (Ar), may be used. In conventional processes, separate mass flow controllers for each of the process gas and the carrier gas are used to ensure precise gas flows to the process chamber. The process gas and the carrier gas are mixed together at a mixing point and then delivered to the process chamber.

[0058] Embodiments described herein include gas delivery systems and mass flow controllers (MFCs) that can measure, control, and deliver low flow rates of process gases (e.g., less than 2 sccm) in a mixture with a carrier gas. Some of the described embodiments use one or more micro-electromechanical systems (MEMS) based Coriolis sensors. In some embodiments, the gas delivery system is capable of measuring and controlling the respective mass flow rates of both the process gas and the carrier gas using a single mass flow controller. In these and other embodiments, the gas delivery system is capable of ensuring that an accurate amount of process gas is delivered to the processing chamber even when the flow rate of the process gas is relatively low (e.g., less than about 2 sccm). As used herein, a low flow rate may include a flow rate range of about 2 sccm or less.

[0059] Figure 1 1 is a schematic diagram of a system for controlling the delivery of a mixture of a first fluid and a second fluid to a process chamber according to an embodiment. The system shown includes a mass flow controller (MFC) 100 that controls the delivery of a first fluid supplied by a first fluid supply source 102 and a second fluid supplied by a second fluid supply source 104 to a process chamber 101. In various embodiments, the first fluid may include a process gas and the second fluid may include a carrier gas.

[0060] The first fluid supply source 102 supplies the first fluid to the MFC 100 via the flow line 122, and the second fluid supply source 104 supplies the second fluid to the MFC 100 via the flow line 124. An inlet valve 106 is provided along the flow line 122 to control the flow rate of the first fluid supplied to the MFC 100. Figure 2 In the illustrated embodiment, the carrier gas inlet valve is not used to control the flow rate of the carrier gas because the MFC 100 is relatively unaffected by the carrier gas flow rate, as will be described below with reference to Figure 6 However, in other embodiments, an inlet valve disposed along the supply line may also be included to control the flow rate of the carrier gas entering the MFC 100 .

[0061] The first fluid and the second fluid are both flowed into the mixing and sensing module 108. The mixing and sensing module 108 is particularly used to mix the first fluid and the second fluid into a mixture. For example, if the first fluid is a process gas and the second fluid is a carrier gas, the mixing and sensing module 108 will produce a mixture containing the process gas and the carrier gas. The mixture leaves the mixing and sensing module 108 via the outlet line 126 to be introduced into the processing chamber 101. The outlet valve 110 arranged along the outlet line 126 controls the total flow rate of the mixture leaving the MFC 100 and being introduced into the processing chamber 101.

[0062] In addition to mixing the first and second fluids, the mixing and sensing module 108 also provides a density signal 114 and a flow signal 116 to a controller 112 of the MFC 100. The density signal 114 is related to the respective densities of the first fluid, the second fluid, or a mixture of the first fluid and the second fluid. The controller 112 processes the density signal 114 into, for example, a mass divided by a volume (e.g., kg / m 3 or g / L, or any other unit expressing mass units / volume units).

[0063] according to Figure 1 In the embodiment shown in FIG. 1 , the controller 112 uses the density signal 114 to provide a density signal feedback 118 to control the inlet valve 106. The density signal feedback 118 is used to control the flow rate of the first fluid introduced into the MFC 100 via the pipeline 122 for the first fluid. As a result, the density signal feedback 118 provided by the controller 112 can control the proportion of the first fluid mixed with the second fluid. For example, the density signal feedback 118 can control the relative density (fractional density) of the first fluid in the mixture between the first fluid and the second fluid.

[0064] according to Figure 1 , the mixing and sensing module 108 also provides a flow signal 116 related to the respective flow rates of the first fluid, the second fluid, or the mixture of the first fluid and the second fluid. The flow signal 116 is processed by the controller 112 to obtain a flow rate measurement of the mixture expressed as volume divided by time (e.g., standard cubic centimeters per minute, or any other unit representing volume units / time units), or a flow rate measurement of the mixture expressed as mass divided by time (e.g., g / minute, or g / hour, or any other unit representing mass units / time units).

[0065] The controller 112 uses the flow rate data provided by the flow signal 116 to generate a flow signal feedback 120 to control the outlet valve 110, thereby controlling the total flow rate of the mixture of the first and second fluids exiting the MFC 100 and entering the process chamber 101. Because the controller 112 controls the relative densities of the first and second fluids in the mixture through the inlet valve 106, and controls the total flow rate of the mixture through the outlet valve 110, the MFC 100 is able to precisely and accurately control the true mass flow rate of the first fluid and / or the second fluid introduced into the process chamber 101.

[0066] For example, if the first fluid is a process gas and the second fluid is a carrier gas, then Figure 1 The MFC 100 shown in FIG. 1 is capable of controlling the relative density of the process gas with respect to the mixture through the inlet valve 106. That is, for example, even when the flow rate of the process gas through the flow line 122 is low, such as 2 sccm or less, the MFC 100 is capable of producing a mixture of the process gas and the carrier gas having a desired ratio or ratio (process gas to carrier gas). In addition, the MFC 100 is also capable of controlling the flow rate of the mixture of the process gas and the carrier gas having a desired ratio (process gas to carrier gas) through the outlet valve 110, and thus is capable of precisely and accurately controlling the true mass flow rate of the process gas introduced into the processing chamber 101.

[0067] In some embodiments, Figure 1 The mixing and sensing module 108 shown in FIG. 1 may include a single sensor that provides a density signal 114 and a flow signal 116 . Figure 2 1 shows an embodiment of an MFC 100 having a mixing and sensing module that uses a single micro-electromechanical system (MEMS) Coriolis sensor (or simply MEMS Coriolis sensor) to obtain a density signal 114 and a flow signal 116 of a mixture of the first and second fluids. In other embodiments, the mixing and sensing module 108 may include two or more sensors that provide the density signal 114 and the flow signal 116. For example, in Figure 3 , the MFC 100 is shown to include a first MEMS-based Coriolis sensor for the process gas and a second MEMS-based Coriolis sensor for the carrier gas.

[0068] Figure 21 is a schematic diagram of a mass flow controller (MFC) 100 in fluid communication with a process chamber 101 according to one embodiment. The MFC 100 supplies a mixture of a process gas supplied by a process gas supply source 202 and a carrier gas supplied by a carrier gas supply source 204 to the process chamber 101. The mixture may be introduced into the process chamber 101 via a showerhead, a gas distribution ring, or any other suitable delivery device (not shown). As described above, the mixture introduced into the process chamber 101 may be used in various processing steps, including, as non-limiting examples, plasma etching, chemical etching, atomic layer etching (ALE), chemical vapor deposition (CVD), atomic layer deposition (ALD), etc.

[0069] according to Figure 2 In the embodiment shown in, MFC 100 receives process gas from process gas supply source 202 via flow line 122, and receives carrier gas from carrier gas supply source 204 via flow line 124. Inlet valve 106 is arranged along flow line 122 and controls the flow rate of process gas introduced into MFC 100. Inlet valve 106 can be any type of flow restriction device, such as fixed orifice or needle valve, etc. Inlet valve can provide a flow rate range of about 0sccm to about 10sccm, or about 0.1sccm to about 2sccm, to meet the needs of various applications. In some embodiments, the flow rate of carrier gas can be higher than the flow rate of process gas, for example, about 2 times to about 100 times or more. Therefore, in various embodiments, the carrier gas in the supply line can have a flow rate between 1sccm and about 200sccm or between about 2sccm and about 20sccm.

[0070] according to Figure 2 , flow lines 122 and 124 enter the mixing and sensing module 108, where the contents of the flow lines 122 and 124 are mixed and metered for density signal 114 and flow signal 116. More specifically, the flow line 122 carrying the process gas and the flow line 124 carrying the carrier gas are connected at the connector 208. The connector 208 serves as a mixing point 206, where the process gas is mixed into the carrier gas and mixed with the carrier gas to form a mixture. The connector 208 can be any type of suitable connector or coupling that connects the flow lines 122 and 124.

[0071] exist Figure 2In the illustrated embodiment, the inlet valve 106 is shown as being disposed downstream of the process gas supply source 202, but upstream of the connector 208 and the mixing point 206. As a result, the inlet valve 106 controls only the flow rate of the process gas, but not the flow rate of the carrier gas. It should be noted that an optional inlet valve for the carrier gas may be disposed upstream of the connector 208 and the mixing point 206 along the flow line 124 to control the flow rate of the carrier gas. However, in some embodiments, such an inlet valve for controlling the flow rate of the carrier gas may not be necessary, because the MFC 100 is relatively unaffected by the precise flow rate of the carrier gas entering the MFC, as long as the flow rate is within the operating range. In some embodiments, the operating flow rate range of the carrier gas is between about 1 sccm and about 200 sccm, or between about 2 sccm and about 50 sccm, or between about 5 sccm and about 15 sccm, depending on various applications.

[0072] The mixture then enters the MEMS Coriolis sensor 210 from the connector 208 and the mixing point 206. The MEMS Coriolis sensor 210 provides a density signal 114 and a flow signal 116 to the controller 112. The density signal 114 will be related to the density of the mixture of the process gas and the carrier gas, and the ratio of the process gas to the carrier gas can be obtained based on the density. The flow signal 116 is related to the mass flow of the mixture entering the MEMS Coriolis sensor 210. The density signal 114 and the flow signal 116 can be used together to specifically determine, for example, the true mass flow rate of the process gas. In addition, the MFC 100 is capable of controlling the true mass flow rate of the process gas introduced into the processing chamber 101 via the inlet valve 106 and the outlet valve 110.

[0073] In one embodiment, the MEMS Coriolis sensor 210 is a micromechanical Coriolis sensor that is capable of obtaining signals for both the mass flow rate of the fluid flowing through the sensor and the density of the fluid. In some embodiments, the MEMS Coriolis sensor 210 will include a silicon-based tube formed into a curved loop, but other materials and other shapes may be used. The tube is then driven to a resonant frequency of oscillation or vibration. In some embodiments, the tube is electrostatically driven, while in other embodiments, the tube may be piezoelectrically or electromagnetically driven.

[0074] When fluid is introduced into the tube, the resonant frequency of the oscillation changes (e.g., decreases) due to the increased inertia associated with the contents of the tube and conduit. The change in the resonant frequency of the oscillation Δf B It is proportional to the density ρ of the fluid, as shown in formula (1).

[0075] Δf B ∝ρ (1)

[0076] It is conceivable that Δf can be obtained BThe measured values ​​of ρ are accurate enough to be related to the density ρ with an accuracy of at least 10 -5 Δρ / ρ. As a result, the accuracy of the fluid density measurements provided by the MEMS Coriolis sensor 210 is accurate enough to also be used for fluid identification.

[0077] As the fluid travels through the bending ring, the fluid traveling away from the oscillation axis exerts a force on a first portion of the bending ring extending away from the oscillation axis near the inlet of the bending ring. The force applied in the opposite direction to the fluid causes the fluid to experience an increase in angular momentum to match the angular momentum of the bending ring. As the fluid travels back toward the oscillation axis through a second portion of the bending ring extending back toward the oscillation axis near the outlet, the fluid exerts a force on the second portion, whose angular momentum decreases. As a result, the first portion of the bending ring experiences a negative phase shift relative to the center portion of the bending ring (e.g., the first portion lags), while the second portion of the bending ring experiences a positive phase shift relative to the center portion of the bending ring (e.g., the second portion oscillates before the center portion of the bending ring). The degree of the phase difference between the first portion and the second portion is proportional to the amount of mass of the pipe flowing through the MEMS Coriolis sensor 210. The mass flow rate of the fluid through the MEMS Coriolis sensor 210 can be related to the phase shift or time lag given in equation (2):

[0078]

[0079] In equation (2), K u is the temperature-dependent stiffness of the pipe, K is the shape-dependent factor, d is the width of the bending loop, τ is the time lag, ω is the oscillation or vibration frequency, and I u is the inertia of the pipe. The time lag τ can be measured in a variety of ways, such as electrostatically, piezoelectrically, or electromagnetically. In addition, the measured value of the time lag τ can be measured with a certain accuracy so that it can be measured with a precision of at least about 5×10 -4 ΔQ m / Q m The mass flow rate Q is obtained with an accuracy of m The measured value of

[0080] Using the Δf associated with the density signal 114 by examining B The measured density of the fluid can be used to calculate the inertia I u , thereby accurately reading the true mass flow rate of the fluid traveling through the MEMS Coriolis sensor. Therefore, the MEMS Coriolis sensor 210 is able to provide an accurate signal so that the MFC 100 can accurately determine both the density and mass flow rate of the process gas.

[0081] In one embodiment, the MEMS Coriolis sensor 210 provides at least a density signal 114 and a flow signal 116 to the controller 112 of the MFC 100. The density signal 114 may include a measurement of the oscillation frequency of the conduit of the MEMS Coriolis sensor 210. And the flow signal 116 may include phase shift or time lag information. The controller 112 processes the density signal 114 and the flow signal 116 to calculate the density and mass flow rate of the fluid traveling through the MEMS Coriolis sensor 210. The controller 112 operates the inlet valve 106 based on the density signal 114 received from the MEMS Coriolis sensor 210 to adjust the ratio of the process gas to the carrier gas in the mixture delivered to the process chamber 101. That is, for example, the controller 112 adjusts the fraction of the total density of the mixture measured by the MEMS Coriolis sensor 210 by adjusting the flow rate of the process gas entering the MFC 100.

[0082] The controller 112 also operates the outlet valve 110 to adjust the total mass flow rate of the mixture delivered to the process chamber 101. By controlling the ratio of the process gases in the mixture and the total mass flow rate of the mixture, the MFC 100 is able to precisely control the mass flow rate of the process gases specifically delivered to the process chamber 101. The MFC 100 is able to precisely adjust the actual mass flow rate of the process gases to a desired rate by individually adjusting the inlet valve 106 to adjust the ratio of the process gases in the mixture and by adjusting the total mass flow rate of the mixture introduced into the process chamber 101.

[0083] An embodiment for determining the ratio of process gas to carrier gas and how such determination is used to achieve a precise flow of process gas delivered to the processing chamber 101 is described below. When the inlet valve 106 is in a certain open state, a steady flow of process gas is mixed with a larger flow of carrier gas. For example, the process gas can be chlorine (Cl2) with a flow rate of about 1 sccm, and the carrier gas can be argon (Ar) with a flow rate of about 10 sccm. In this example, when the mixture of chlorine and argon enters the MEMS Coriolis sensor 210, the MEMS Coriolis sensor 210 can provide a density signal 114 associated with the mixture. The controller 112 can then calculate the density of the mixture as, for example, about 2.00000 g / L. As described above, the density of the measured fluid can be calculated to 10 -5 Then, based on the density reading, the controller 112 or an associated computing system can calculate the ratio of the mixture, for example, by using the following expression:

[0084] (3)

[0085] where ρ mis a measure of the density of the mixture, and ρ Ar and are the densities of Ar and Cl2, respectively, and x and y are the fractional densities of Ar and Cl2 in the mixture, respectively, and where x+y=1. When the pressure and temperature of the MEMS Coriolis sensor 210 are known, ρ can be found from the lookup table Ar and Alternatively, the density ρ can be calculated using, for example, the following relationship:

[0086] (4)

[0087] Where P is the pressure inside the tube of the MEMS Coriolis sensor 210, R sp is the specific gas constant of the gas, and T is the temperature of the gas. For clarity, assume that ρ Ar and Calculated or found to be and Therefore, according to equation (3), x will be found to be x = 0.84745, and y will be found to be y = 0.15255. m The value of can be associated with high precision, so the accuracy of the calculated density ratio of x and y can have similarly high precision, depending on the precision of the other variables shown in equation (4).

[0088] According to this example, if the relative density y=0.15255 of Cl2 in the mixture is higher than the desired ratio, the controller 112 can adjust the inlet valve 106 to reduce the flow of Cl2 until the desired ratio is achieved through the density signal feedback 118. If the relative density of Cl2 in the mixture is lower than the desired ratio, the controller 112 can adjust the inlet valve 106 to increase the flow of Cl2 until the desired ratio is achieved through the density signal feedback 118.

[0089] In some embodiments, it may be desirable to control the precise amount of process gas introduced into the processing chamber 101. One way to precisely control the amount of process gas introduced into the processing chamber 101 is to precisely control the mass flow rate of the process gas by precisely controlling the total flow rate of the mixture and the time over which the mixture can flow into the processing chamber 101 (e.g., when the ratio of the process gases in the mixture is accurately known). This may be the case, for example, in applications involving atomic layer deposition and / or etching. Continuing with the above example, assume that a desired gas mixture ratio has been met, where x = 0.84745 and y = 0.15255. If the MEMS Coriolis sensor 210 provides a flow signal 116, which results in a calculated mass flow rate of the argon-chlorine mixture of Then the mass flow rate of Cl2 can be specifically calculated as Again, because the mass flow rate values ​​can be at least about 5×10 -4 The accuracy of the specific mass flow rate of Cl2 can be determined with similar accuracy.

[0090] If the mass flow rate of the process gas is higher than the desired mass flow rate, the controller 112 may send a flow signal feedback 120 to the outlet valve 110 to reduce the total mass flow rate of the mixture leaving the MFC 100. If the mass flow rate of the process gas is lower than the desired mass flow rate, the controller 112 may send a flow signal feedback 120 to the outlet valve 110 to increase the total mass flow rate of the mixture introduced into the process chamber 101. The above steps may be repeated until the desired mass flow rate of the process gas is achieved. Alternatively or additionally, the controller 112 may send a density signal feedback 118 to the inlet valve 106 to adjust the flow rate of the process gas entering the MFC 100. In this way, the ratio of the process gas may also be adjusted in parallel with adjusting the total mass flow rate of the mixture entering the process chamber 101.

[0091] As described above, an optional second inlet valve (not shown) for the carrier gas may also be used to adjust the flow rate of the carrier gas entering the MFC 100. However, it should be noted that Figure 2 The embodiment shown in can be implemented without an inlet valve for the carrier gas because the density signal of the MFC 100 is relatively independent of the flow rate of the carrier gas. Moreover, the accuracy of the density signal 114 and the flow signal 116 of the MFC 100 is relatively unaffected by the flow rate of the carrier gas. For example, it is expected that the MFC 100 has an operating range of about 1 sccm to about 100 sccm, or about 2 sccm to 20 sccm, or about 5 sccm to about 10 sccm with respect to the carrier gas flow rate.

[0092] Figure 3 is a schematic diagram of a system for controlling the delivery of a mixture of process gas and carrier gas to a processing chamber using two Coriolis sensors according to one embodiment. In this embodiment, the mixing and sensing module 108' includes a MEMS Coriolis sensor 210 for the process gas supplied by the process gas supply source 202 and a MEMS Coriolis sensor 300 for the carrier gas supplied by the carrier gas supply source 204. Similar to Figure 2 In the embodiment of the present invention, the inlet valve 106 is arranged along the flow line 122 for controlling the flow rate of the process gas entering the MFC 100. Figure 2 Unlike the MFC 100 shown in Figure 3The mixing and sensing module 108 in the embodiment of includes a MEMS Coriolis sensor 210, which provides a density signal 114 and a flow signal 116 specific to the process gas, while a MEMS Coriolis sensor 300 for the carrier gas provides a density signal 302 and a flow signal 304 specific to the carrier gas. Figure 2 The mixing and sensing module 108 shown in FIG. Figure 3 The mixing and sensing module 108 ′ shows the connector 208 ′ and mixing point 206 ′ located downstream of the MEMS Coriolis sensors 210 and 300 .

[0093] exist Figure 3 In the illustrated embodiment, the density of the process gas and the density of the carrier gas may be obtained via density signals 114 and 302, respectively. Based on these signals, the ratio of the process gas to the carrier gas may be calculated by the controller 112. In addition, if the desired ratio of the process gas to the carrier gas is not met, the controller 112 may send a density signal feedback 118 to the inlet valve 106 to adjust the flow of the process gas until the desired ratio is achieved.

[0094] Since the flow signals 116 and 304 of the process gas and the carrier gas are obtained respectively, the total mass flow rate of the mixture produced after the process gas and the carrier gas are mixed can be obtained by the controller 112. In some embodiments, the total mass flow rate of the mixture is derived from the sum of the mass flow rate of the process gas and the mass flow rate of the carrier gas as provided by the flow signals 116 and 304 respectively. If the desired mass flow rate of the process gas entering the processing chamber 101 is higher or lower than the desired rate, the controller 112 can adjust the outlet valve 110 through the flow signal feedback 120 to achieve the desired total mass flow rate of the mixture. When the ratio of the process gas to the carrier gas is known, the desired mass flow rate of the process gas can also be achieved by adjusting the outlet valve 110 to achieve the desired total mass flow rate of the mixture.

[0095] Figure 4 is a schematic diagram of a system for controlling the delivery of first and second process gases mixed with a carrier gas to a processing chamber 101 using two Coriolis sensors according to one embodiment. Figure 4 The MFC 100 shown in the figure expands Figure 2 The principles and technical advantages of the system shown in , including the precise delivery of two process gases to the processing chamber 101. The MFC 100 receives a first process gas from a first process gas supply source 202 via a flow line 122 and a first carrier gas from a first carrier gas supply source via a flow line 124. Similar to Figure 2In the MFC 100 shown in FIG. 1 , an inlet valve 106 is disposed along a flow line 122 for controlling the flow rate of a first process gas. The first process gas and the first carrier gas are mixed at a mixing point 206 where a connector 208 couples the flow lines 122 and 124. The mixing point 206 and the connector 208 are downstream of the inlet valve 106 and upstream of a MEMS Coriolis sensor 210. The mixture of the first process gas and the first carrier gas enters the MEMS Coriolis sensor 210, which provides a density signal 114 and a flow signal 116 to the controller 112 for the mixing of the first process gas and the first carrier gas.

[0096] Figure 4 The MFC 100 shown in FIG. 1 also receives a second process gas from a second process gas supply 402 via a flow line 406, and receives a second carrier gas from a second carrier gas supply 404 via a flow line 408. An inlet valve 410 is shown disposed along the flow line 406 for controlling the flow rate of the second process gas. The second process gas and the second carrier gas are mixed at a mixing point 206" where a connector 208" couples the flow lines 406 and 408. The mixing point 206" and the connector 208" are shown downstream of the inlet valve 410 and upstream of the MEMS Coriolis sensor. The mixture of the second process gas and the second carrier gas enters the MEMS Coriolis sensor 400, which provides a density signal 412 and a flow signal 414 for the mixture of the second process gas and the second carrier gas. It should be noted here that in some embodiments, the second carrier gas may be the same as the first carrier gas. For example, in some embodiments, the first carrier gas supply may supply carrier gas for both the first process gas and the second process gas.

[0097] A mixture of the first process gas and the first carrier gas and a mixture of the second process gas and the second carrier gas are shown mixing at a mixing point 206' where a connector 208' couples lines leading from the MEMS Coriolis sensor 210 and the MEMS Coriolis sensor 400. If the first carrier gas and the second carrier gas are not the same, the resulting final mixture will include the first process gas, the second process gas, and the first carrier gas and the second carrier gas. If the first carrier gas and the second carrier gas are the same, the resulting final mixture will include the first process gas and the second process gas and the carrier gas. The final mixture of the first process gas and the second process gas and one or both carrier gases flows to the processing chamber 101 via an outlet line 126. An outlet valve 110 is disposed along the outlet line 126 for controlling the total flow of the final mixture of the first process gas and the second process gas and one or both carrier gases leaving the MFC 100 and entering the processing chamber 101.

[0098] according to Figure 4In the embodiment shown, the ratio of the first process gas to the first carrier gas can be calculated based on the density signal 114, and the ratio of the second process gas to the second carrier gas can be calculated based on the density signal 114. In addition, the gas mixing ratio of the first or second process gas relative to the final mixture can be obtained. For example, the density signal 114 can provide that the first mixture of the first process gas and the first carrier gas has a density of 2 g / L. According to equation (3), the relative density of the first process gas can be calculated as, for example, y=0.1, and the relative density of the first carrier gas can be calculated as x=0.9. As a result, the density of the process gas can be calculated to be 0.2 g / L. In addition, the density signal 412 can provide that the second mixture of the second process gas and the second carrier gas has a density of 8 g / L. According to equation (3), the relative density of the second process gas relative to the second mixture can be calculated as, for example, y=0.2, and the relative density of the second carrier gas will be x=0.8. Therefore, the density of the second process gas in the second mixture and the final mixture is 1.6 g / L. The ratio of the first process gas to the final mixture can be calculated as (0.2 g / L) / (2 g / L+8 g / L)=0.02. The ratio of the second process gas to the final mixture can also be calculated as (1.6 g / L) / (2 g / L+8 g / L)=0.16. If the ratio of the first process gas or the second process gas is higher or lower than the desired ratio, the inlet valve 106 and the inlet valve 410 can be adjusted respectively to obtain the desired ratio.

[0099] For example, if the desired ratio of the first process gas to the final mixture is 0.04 and the desired ratio of the second process gas to the final mixture is 0.16, the controller 112 may send the density signal feedback 118 to the inlet valve 106 to increase the flow rate of the first process gas flowing into the MFC 100. However, the increase in the flow rate of the first process gas flowing into the MFC 100 may change the ratio of the second process gas to the final mixture. As a result, the controller 112 may calculate the density signal feedback 118 and the density signal feedback that will result in a ratio of the first process gas in the final mixture of 0.04 while maintaining a ratio of the second process gas in the final mixture of 0.16.

[0100] according to Figure 4 In the illustrated embodiment, the mass flow rate of the mixture of the first process gas and the first carrier gas is provided by the flow signal 116, and the mass flow rate of the mixture of the second process gas and the second carrier gas is provided by the flow signal 414. For example, the mass flow rate of the mixture between the first process gas and the first carrier gas can be calculated based on the flow signal 116 as follows: In addition, the mass flow rate of the mixture between the second process gas and the second carrier gas can be calculated based on the flow signal 414: The mass flow rate of the final mixture can be calculated as Continuing with the example provided above, the mass flow rate characteristic of the first process gas can be calculated as (0.1)(0.02 g / min)=0.002 g / min, or alternatively, (0.02)(0.1 g / min)=0.002 g / min. The mass flow rate characteristic of the second process gas can be calculated as (0.2)(0.08 g / min)=0.016 g / min, or alternatively, (0.16)(0.1 g / min)=0.016 g / min. If the desired mass flow rates of the first process gas and the second process gas are higher or lower than 0.002 g / min and 0.016 g / min, respectively, the controller 112 can send a flow signal feedback 120 to reduce or increase the total mass flow rate of the mixture that can pass through the outlet valve 110.

[0101] Figure 5A 100 according to various embodiments described herein. The MFC 100 includes an inlet 502 for process gas and an inlet 504 for carrier gas. The process gas travels through the pipe flow line 122 and then reaches the mixing point 206 defined by the connector 208. The inlet valve 106 is arranged along the flow line 122 for controlling the flow rate of the process gas flowing into the MFC 100. The carrier gas enters the MFC 100 through the inlet 504 and travels through the flow line 124 and then reaches the mixing point 206. The process gas and the carrier gas become a mixture before entering the MEMS Coriolis sensor 210. The mixture leaves the MEMS Coriolis sensor 210 via the outlet line 126, and the outlet line 126 leads to the outlet 516. The mixture can then be transported to a processing chamber in fluid communication with the MFC 100. An outlet valve is arranged along the conduit 216 for controlling the total flow rate of the mixture leaving the MFC 100.

[0102] The MEMS Coriolis sensor 210 used in the various embodiments described herein can be any type of suitable Coriolis sensor that provides a signal related to the density of the measured fluid and a signal related to the flow rate of the measured fluid. Some examples of suitable Coriolis sensor configurations are described in Figure 5B and 5C Shown in. Figure 5A The MEMS Coriolis sensor 210 shown in FIG. 1 provides density feedback 508 for driving or operating the inlet valve 106 to control the flow of process gas entering the MFC 100. Additionally, the MEMS Coriolis sensor 210 provides flow feedback 506 for driving or operating the outlet valve 110 to control the total flow rate of the mixture exiting the MFC 100.

[0103] The MEMS Coriolis sensor 210 includes a tube through which the mixture travels. As described above, the density signal provides a signal to the controller 112 related to the density of the mixture. The density signal is generated by examining the change in the frequency of the MEMS Coriolis sensor 210 tube vibration when the fluid is introduced into the tube compared to the frequency of the MEMS Coriolis sensor 210 tube vibration when the fluid is introduced into the tube. The density signal can be used to calculate the relative density of the process gas or carrier gas in the mixture, which is also indicative of the gas mixture ratio of the mixture. The controller 112 uses the density feedback 508 to adjust the inlet valve 10 until the desired gas mixture ratio is achieved.

[0104] In addition, when the mixture travels through the MEMS Coriolis sensor 210, the flow feedback 506 provides a signal related to the mass flow rate of the mixture to the controller 112. When the mixture travels through the MEMS Coriolis sensor 210, a flow signal is generated by detecting the phase shift or time delay between the inlet arm and the outlet arm of the pipeline. The flow feedback 506 is used to calculate the mass flow rate of the mixture traveling through the MFC 100. In addition, the unique mass flow rate of the process gas or carrier gas can be determined using the gas mixture ratio and the mass flow rate. The controller 112 uses the flow feedback 506 to adjust the outlet valve 110 until the desired mass flow rate of the process gas is achieved.

[0105] Figure 5A Also shown is an optional on-off valve 512 that can be used to switch the flow of the mixture between a line delivered to the process chamber (e.g., via outlet 516) and an exhaust line 514. For applications such as atomic layer deposition and atomic layer etching, the on-off valve 512 provides the opportunity to pulse the output of the MFC 100 while maintaining a small constant or near-constant inlet flow of process gas into the MFC 100.

[0106] Figure 5B An embodiment of a Coriolis sensor 210A in a curved conduit configuration is shown. The Coriolis sensor 210A includes an inlet 524 and an outlet 526 for measuring the flow of, for example, a mixture of a process gas and a carrier gas. The flow is divided into two conduits, each of which includes an inlet portion 518a and 518b, a center portion 520a and 520b, and an outlet portion 522a and 522b. The center portions 520a and 520b are excited to a resonant frequency by an electrostatic, piezoelectric, or electromagnetic mechanism, and are Figure 5B The vibration is shown in the figure with the direction indicated by the double-headed arrow.

[0107] Figure 5C5 shows another embodiment of a Coriolis sensor 210B that can be used with various embodiments of mass flow controllers described herein. The Coriolis sensor 210B includes an inlet 530 and an outlet 532 for measuring the flow of, for example, a mixture of a process gas and a carrier gas. In this embodiment, the flow is divided into two parallel pipes 528a and 528b. The flow is controlled by a drive mechanism 534 to Figure 5C The tube is driven to the resonant frequency in the direction indicated by the double-headed arrow in FIG. The drive mechanism 534 can use electrostatic, electromagnetic, and piezoelectric forces to drive the tube, and the frequency change experienced by the tube can be measured electrostatically, electromagnetically, piezoelectrically, or optically.

[0108] Figure 6 The overall flow of a method for controlling a fluid delivery system or a gas delivery system according to an embodiment is shown. The fluid delivery system may be a mass flow controller and a gas mixer, such as Figure 1-3 As used herein, the term fluid is intended to include any substance in a liquid or gaseous state. Operation 600 includes monitoring the density and flow rate of a mixture of a first fluid and a second fluid using, for example, a Coriolis sensor. To monitor the density of the mixture of operation 600, the density signal may be used to calculate the density of the mixture, which may be calculated with high accuracy (e.g., 10 -5 The gas mixture ratio can also be obtained from the measured value of the density of the mixture, for example by using equations (3) and (4).

[0109] For example, ρ in equation (3) mixture =xρ carrier +yρ process ρ can be obtained from the density signal mixture , and obtain ρ from the lookup table carrier and ρ process Or by solving equation (4) Thus solving for x and y. In other embodiments, carrier and ρ process can be obtained empirically. For example, the inlet valve for the process gas can be closed so that only the carrier gas flows through the Coriolis sensor. The resulting density signal will reflect the carrier gas-specific density ρ carrier Similarly, the inlet valve for the carrier gas can be closed so that only the process gas flows through the Coriolis sensor. The resulting density signal will reflect the characteristic density ρ of the process gas. process Therefore, in some embodiments for gas mixture ratio calculations, ρ carrier and ρ process Both can be acquired empirically.

[0110] To monitor the flow of the mixture in operation 600, the flow rate may be calculated based on a flow signal provided by a Coriolis sensor. The flow signal is based on a phase shift or time lag in vibration between an inlet portion of the pipe of the Coriolis sensor and an outlet portion of the pipe. Figure 5B , the flow signal will be based on the phase shift or time lag between the inlet portion 518a and the outlet portion 522a or between the inlet portion 518b and the outlet portion 522b. In many cases, the phase shift or time lag between the inlet portion 518a and the outlet portion 522a and the phase shift or time lag between the inlet portion 518b and the outlet portion 522b will be almost the same. Then, by operation 600, the flow rate of the mixture is calculated by using an equation such as equation (1). The flow rate obtained in operation 600 can be a mass flow rate or a volume flow rate. However, in many embodiments, a mass flow rate may be required.

[0111] In operation 602, the method includes controlling the ratio of the first fluid and the second fluid by adjusting the inlet flow of the first fluid based on the density signal. For example, if it is found in operation 600 that the ratio of the process gas to the carrier gas is greater than the desired ratio, the inlet valve of the process gas can be signaled to reduce the flow of the process gas. The signal to reduce the flow can be calculated based on the difference between the desired gas mixture ratio and the current or actual gas mixture ratio. Therefore, if the difference between the desired gas mixture ratio and the actual gas mixture ratio is large, the signal can be operable to reduce the flow to a greater extent than in the case where the difference is small. Once the inlet valve is adjusted, the Coriolis sensor will send a signal indicating that the density has changed due to an increase or decrease in the flow of the process gas. The process can be repeated until the ratio of the process gas to the carrier gas reaches the desired ratio, or is within the desired range.

[0112] The method proceeds to operation 604, which includes precisely controlling the total flow of the mixture exiting a gas delivery system (e.g., an MFC). As described above, certain applications of gas delivery for substrate processing require precise control of the flow rate of process gas admitted into a processing chamber, and it is desirable to precisely control the total amount of process gas introduced into the processing chamber. This may be true for applications such as atomic layer etching and deposition, where only the top atomic layer of the substrate surface is affected by each step. Operation 604 provides a desired level of accuracy for delivering process gases based on the accuracy of the density and flow signals obtained from the Coriolis sensor and the precise control of the inlet and outlet valves. For example, the mass flow rate measurements provided by the Coriolis sensor are believed to be accurate to at least 5×10 -4 ΔQ m / Q m .

[0113] It should also be noted here that the accuracy of the density and flow measurements is relatively unaffected by the flow rate of the carrier gas entering the gas delivery system. In most embodiments, the carrier gas flow is relatively constant. However, even if it is not, operation 600 is able to provide real-time or near real-time density and flow signals, which result in a non-constant flow of the carrier gas. For example, if the flow rate of the carrier gas changes over a 60 second time period, the gas mixture ratio of the process gas to the carrier gas will also change over the same time period. However, in some embodiments, operation 600 monitors the density of the mixture traveling through the gas delivery system in real time, and can therefore determine what the gas mixture ratio of the process gas to the carrier gas is at any given point within the 60 seconds. Similarly, operation 600 can also determine the mass flow rate of the mixture at any given point within the 60 second time period. As a result, Figure 6 The method shown in can be used to determine the amount of process gas that has been delivered to the process chamber and how much process gas is expected to be delivered. Therefore, even when the flow rate of the carrier gas is not constant, the method can accurately deliver a certain amount of process gas to the process chamber.

[0114] Figure 7 700 is a flow chart showing the method operations that can be performed by a mass flow controller according to one embodiment. In operation 700, the settings for the desired gas mixture ratio of the process gas to the carrier gas and the desired settings for the mass flow rate of the process gas are obtained. These settings can be manually entered by the operator, or they can be calculated or looked up based on the substrate processing step (e.g., recipe) being performed. In other embodiments, the settings for the total amount of process gas to be delivered to the processing chamber for a given step or process can be received. In operation 700, the desired gas mixture ratio and mass flow rate settings can be calculated based on the total amount of process gas set to be delivered to the processing chamber. In addition, operation 700 can also calculate the amount of time that the mixture can flow into the processing chamber. For example, if the total amount of process gas set to be delivered to the processing chamber is 0.01 grams, and the mass flow rate of the process gas is 0.1 grams per minute, then the total time that the mixture should be able to enter the processing chamber should be about 6 seconds.

[0115] In operation 702, density values ​​of the process gas and the carrier gas are determined based on the corresponding specific gas constants, pressure values, and temperature values. For example, these density values ​​can be obtained by using equation (4). In other embodiments, the density values ​​can be determined empirically by measuring the process gas and the carrier gas separately.

[0116] In operation 704, a density signal for a mixture of process gas and carrier gas is obtained from a MEMS Coriolis sensor. In some embodiments, the density signal is related to the frequency measurement of the pipeline of the MEMS Coriolis sensor. Operation 704 is configured to calculate the difference between the current resonant frequency measurement and the baseline resonant frequency value (e.g., the resonant frequency of the pipeline without any contents). The density of the mixture is then calculated using the difference between the current resonant frequency measurement and the baseline resonant frequency. In operation 706, the gas mixture ratio and / or relative density value of the gas is calculated, for example, by using equation (3) and the density value calculated for the mixture in operation 704. Based on the gas mixture ratio calculation value obtained in operation 706, operation 708 is used to adjust the inlet valve of the flow rate of the process gas introduced into the MFC. Operations 704 to 708 can be repeated until the desired gas mixture ratio is reached. In some embodiments, operation 708 can also adjust the inlet valve controlling the inflow of the carrier gas to obtain the desired gas mixture ratio between the process gas and the carrier gas.

[0117] In operation 710, the method includes obtaining a mass flow rate signal from a MEMS Coriolis sensor to determine the mass flow rate of the mixture. As described above, the mass flow rate signal can be related to a phase shift or time lag measurement between opposite ends of a vibrating conduit of the MEMS Coriolis sensor. Then, operation 710 uses the phase shift or time lag measurement to calculate the mass flow rate of the mixture flowing through the MEMS Coriolis sensor. In operation 712, the method calculates a mass flow rate specific to the process gas based on the mass flow rate obtained in operation 710 and the gas mixture ratio calculated in operation 706. For example, by obtaining the product of the total mass flow rate of the mixture and the ratio of the process gas to the mixture, the mass flow rate specific to the process gas can be calculated. Based on the calculated value obtained in operation 712, operation 714 is used to adjust the fluid rate of the outlet valve output by the MFC and delivered to the processing chamber. Operations 710 to 714 can be repeated until the desired mass flow rate specific to the process gas is obtained.

[0118] In some embodiments, two mass flow controllers are used to control the flow rates of process gas and carrier gas delivered to the process chamber, one MFC for each of the process gas and carrier gas. Figure 2 The embodiment shown in provides additional advantages for systems having an MFC for each gas. For example, Figure 2 The embodiment shown in is capable of controlling both the gas mixing ratio and mass flow rate of two gases with a single MFC, which reduces the cost and footprint of the gas delivery system. It is also contemplated that Figure 2 The embodiment shown in provides more accurate measurements of the mass flow rate of process gases (eg, low flow gases) than a dual MFC configuration.

[0119] For example, suppose the desired process gas flow rate is about 0.1 sccm, and the carrier gas is about 10 sccm. Using a dual MFC system, one of the MFCs will be responsible for measuring 0.1 sccm, which may be outside the optimal range in which flow rates can be accurately measured. Instead, using Figure 2 In the embodiment shown in FIG. 1 , the MFC 100 essentially measures a flow rate of 0.1 sccm in a mixture having a flow rate in the range of 10 sccm, which is within a more optimized flow rate range that can be measured more accurately. As a result, a flow rate such as Figure 2 Embodiments such as the one shown in are able to accurately measure low flow rates (eg, below about 2 seem) in a manner that many MFC systems are unable to accurately measure.

[0120] It is also expected that Figure 2 Embodiments such as the embodiment shown in make it possible to reduce the delay associated with the time it takes for the gas to reach the process chamber from the output valve of the MFC. For example, the time delay for the gas to reach the process chamber can be expressed as follows:

[0121] (5)

[0122] In certain embodiments, such as those with two MFCs for controlling process gas and carrier gas, respectively, the pipe length may be about 100 mm or greater. If the flow rate of the gas is relatively low (e.g., less than 2 sccm), it may take up to 50 seconds for the gas to travel from the output valve of the MFC to the process chamber. Because the mixing of the gases at the mixing point occurs downstream of the MFC, the pipe length cannot be much shorter.

[0123] Described here and for example in Figure 2 The embodiment shown in FIG. 1 can shorten the length of the pipeline between the outlet valve 110 of the MFC 100 and the process chamber 101 to about 1 / 10 or less. Figure 2 For example, mixing at mixing point 206 occurs before the gas enters MEMS Coriolis sensor 210. As a result, the length of tubing between outlet valves 110 of MFC 100 can be reduced, so that the time delay is reduced to between about 30 seconds and about 1 second, or between about 20 seconds and about 2 seconds, or between about 10 seconds and about 5 seconds.

[0124] The computer program for controlling the delivery of process gases may be written in any conventional computer-readable programming language: for example, assembly language, C, C++, Pascal, Fortran, or others. The processor executes the compiled object code or script to perform the tasks identified in the program.

[0125] The system software may be designed or configured in many different ways. For example, various chamber and MFC component subroutines or control objects may be written to control the operation of the MFC components necessary to perform the flow control process.

[0126] In view of the above-mentioned embodiments, it should be understood that the embodiments can adopt various computer-implemented operations involving data stored in a computer system. These operations are operations that require physical manipulation of physical quantities. Any operation described herein that forms a part of the embodiments is an effective machine operation. The embodiments also relate to equipment or devices for performing these operations. The device can be specially constructed for a specific purpose, such as a special-purpose computer. When defined as a special-purpose computer, the computer can also perform other processing, program execution or routines that do not belong to the special purpose, while still being able to operate for a special purpose. Alternatively, the operation can be processed by a general-purpose computer, which is selectively activated or configured by one or more computer programs stored in a computer memory, a cache or obtained through a network. When data is obtained through a network, the data can be processed by other computers on the network, such as by a computing resource cloud.

[0127] One or more embodiments may also be manufactured as computer readable code on a computer readable medium. A computer readable medium is any data storage device that can store data, which can then be read by a computer system. Examples of computer readable media include hard drives, network attached storage (NAS), read-only memories, random access memories, CD-ROMs, CD-Rs, CD-RWs, magnetic tapes, and other optical and non-optical data storage devices. Computer readable media may include computer readable tangible media distributed on a network coupled computer system so that computer readable code is stored and executed in a distributed manner.

[0128] Although the method operations are described in a particular order, it should be understood that other housekeeping operations may be performed between the operations, or the operations may be adjusted so that they occur at slightly different times, or may be distributed in the system so that the processing operations can occur at different intervals associated with the processing, so long as the processing of the superimposed operations is performed in the desired manner.

[0129] Although the foregoing embodiments have been described in considerable detail for the purpose of clear understanding, it is apparent that certain changes and modifications may be implemented within the scope of the disclosed embodiments. It should be noted that there are many alternative ways to implement the processes, systems, and devices of the present embodiments. Therefore, the present embodiments are considered to be illustrative rather than restrictive, and the embodiments are not limited to the details given herein.

Claims

1. A mass flow controller, comprising: a first flow line for introducing a process fluid into the mass flow controller; an inlet valve disposed along the first flow line for controlling a flow rate of the process fluid; a second flow line for introducing a carrier fluid into the mass flow controller, wherein the mass flow controller is connected to receive both the first flow line and the second flow line; a microelectromechanical system (MEMS) Coriolis sensor for providing a density signal and a mass flow rate signal for a mixture of the process fluid and the carrier fluid; an outlet valve for controlling the mass flow rate of the mixture output by the mass flow controller; as well as A controller is provided for operating the inlet valve based on the density signal and operating the outlet valve based on the mass flow rate signal.

2. The mass flow controller according to claim 1, further comprising: A connector connects the first flow line and the second flow line disposed downstream of the inlet valve and upstream of the micro-electromechanical system (MEMS) Coriolis sensor, the connector mixing the process fluid and the carrier fluid into the mixture.

3. The mass flow controller of claim 1, wherein the process fluid is a process gas and the carrier fluid is a carrier gas.

4. The mass flow controller of claim 1, wherein the flow rate of the process fluid introduced into the mass flow controller is defined by a low flow rate.

5. A mass flow controller according to claim 4, wherein the low flow rate is defined by a rate of 2 standard cubic centimeters per minute (sccm) or less.

6. The mass flow controller of claim 1, wherein the controller is configured to adjust the outlet valve based on the mass flow rate signal to achieve a desired mass flow rate of the mixture.

7. The mass flow controller of claim 1 , wherein the controller is configured to calculate a fluid mixing ratio of a process fluid to a carrier fluid, and wherein the controller is further configured to adjust the inlet valve based on the calculated fluid mixing ratio to achieve a desired fluid mixing ratio.

8. A mass flow controller according to claim 7, wherein the controller is further configured to calculate a mass flow rate specific to the process fluid based on the fluid mixing ratio and based on the mass flow rate signal, and wherein the controller is further configured to adjust the outlet valve based on the calculated mass flow rate specific to the process fluid to achieve a desired mass flow rate specific to the process fluid.

9. The mass flow controller of claim 1, wherein the mass flow controller is in fluid communication with a process chamber via the outlet valve such that the mass flow controller controls delivery of the mixture of process fluid and carrier fluid into the process chamber.

10. A method for controlling a mass flow controller (MFC), comprising: receiving a density signal and a mass flow rate signal for a mixture of a process fluid and a carrier fluid from a Coriolis sensor of the MFC, the MFC being connected to both a first flow line for the process fluid and a second flow line for the carrier fluid; calculating a fluid mixing ratio of the mixture based on the density signal; operating an inlet valve to adjust a flow rate of the process fluid entering the MFC through the inlet valve based on the fluid mixing ratio; calculating a mass flow rate of the mixture based on the mass flow rate signal; as well as Operating an outlet valve regulates an output flow rate of the mixture exiting the MFC through the outlet valve based on the mass flow rate of the mixture.

11. The method of claim 10, wherein the density signal is associated with a measurement of a change in a vibration frequency of a conduit of the Coriolis sensor.

12. The method of claim 10, wherein the mass flow rate signal is associated with a measurement of a phase shift in a vibration frequency between two arms of a conduit of the Coriolis sensor.

13. The method of claim 10, wherein said calculating said fluid mixing ratio comprises determining a density of said process fluid and a density of said carrier fluid.

14. The method according to claim 10, further comprising: A mass flow rate specific to the process fluid is calculated based on the fluid mixing ratio and the mass flow rate of the mixture, wherein the adjusting the output flow rate of the mixture is further based on the mass flow rate specific to the process fluid.

15. The method of claim 10, wherein when the fluid mixing ratio indicates that the ratio of process fluid to carrier fluid is greater than a desired ratio, adjusting the flow rate of the process fluid is decreasing the flow rate of the process fluid, and wherein when the fluid mixing ratio indicates that the ratio of process fluid to carrier fluid is less than the desired ratio, adjusting the flow rate of the process fluid is increasing the flow rate of the process fluid.

16. The method of claim 10, wherein when the mass flow rate of the mixture is greater than a desired mass flow rate, the adjusting the output flow rate of the mixture is to reduce the output flow rate of the mixture, and wherein when the mass flow rate of the mixture is less than the desired mass flow rate, the adjusting the output flow rate of the mixture is to increase the output flow rate of the mixture.

17. A mass flow controller comprising: a mixing and sensing module for mixing a process fluid and a carrier fluid into a mixture, the mixing and sensing module providing a density signal and a mass flow rate signal for the mixture, the mixing and sensing module being connected to both a first flow line for the process fluid and a second flow line for the carrier fluid; an inlet valve for controlling the flow rate of process fluid entering the mixing and sensing module; an outlet valve for controlling an output flow rate of the mixture exiting the mixing and sensing module; as well as a controller for calculating a fluid mixing ratio of a process fluid to a carrier fluid based on the density signal and for calculating a mass flow rate of the mixture based on the mass flow rate signal for the mixture, wherein the controller is configured for regulating the inlet valve based on the fluid mixing ratio and for regulating the outlet valve based on the mass flow rate of the mixture.

18. The mass flow controller of claim 17, wherein the controller is further configured to calculate a mass flow rate specific to the process fluid based on the fluid mixing ratio and the mass flow rate of the mixture, and wherein the adjusting the outlet valve is further based on the mass flow rate specific to the process fluid.

19. A mass flow controller according to claim 17, wherein the mixing and sensing module includes a Coriolis sensor for providing the density signal and the mass flow rate signal for the mixture, and the mixing and sensing module also includes a connector disposed downstream of the inlet valve and upstream of the Coriolis sensor, the connector defining a mixing point for mixing the process fluid and the carrier fluid into the mixture.

20. The mass flow controller of claim 17, wherein the mass flow controller is part of a substrate processing system, the substrate processing system further comprising a processing chamber for processing a substrate using the mixture output by the mass flow controller.

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