A method and device for measuring gas mass flow rate and a mass flow controller

Abstract

The embodiments of the present application are applicable to the field of manufacturing process technology, and provide a method, device and mass flow measurement device of gas, wherein the method is applied to a mass flow controller, wherein the mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series on the gas channel, and the method comprises: obtaining mass flow measurement values ​​of each group of the measuring units; determining a target measuring unit according to the mass flow measurement values ​​and a preset corresponding relationship; the corresponding relationship comprises each of the measuring units and its corresponding measurement range; determining the mass flow measurement value of the target measuring unit as a mass flow calculation value; wherein the measuring unit is composed of a flow restrictor and a pressure sensor, and the embodiments of the present application can realize that within the measuring range of the mass flow controller, a high-precision measuring unit is used to output a mass flow calculation value.

Description

Technical Field

[0001] The embodiments of the present application belong to the field of manufacturing process technology, and in particular, relate to a gas mass flow measurement method, device and mass flow controller. Background Art

[0002] In the semiconductor manufacturing process, there are many links involving drastic changes in mass flow, which places extremely high demands on the performance of mass flow controllers (MFCs). In the multi-step chemical vapor deposition (Multi-step CVD) process, different chemical reactions may need to be performed alternately in the same reaction chamber, and the mass flow requirements of these reactions for precursor gases vary greatly. For example, when growing high-k dielectric layers or metal gate electrodes, the gas mass flow requirements for different chemical reaction steps can vary from a few SCCM (standard cubic centimeter per minute) to hundreds or even thousands of SCCM. During the ion implantation process and in the preparation and processing steps before and after it, the silicon wafer may need to be preheated, annealed, or cleaned, and the mass flow requirements for inert gases (such as argon or nitrogen) in these steps may have a wide range. For example, a lower mass flow may be required in the preheating stage, while a significantly increased gas mass flow may be required in the cleaning or annealing stage.

[0003] In some processes, it may be necessary to switch between ALD (Atomic Layer Deposition) and CVD (Chemical Vapor Deposition) processes on the same manufacturing line. The ALD process involves pulsed gas mass flow control with a very small mass flow rate, while the CVD process may require a continuous and large gas mass flow rate. This switching places higher requirements on the dynamic response range and accuracy of the MFC. Summary of the invention

[0004] In view of this, embodiments of the present application provide a gas mass flow measurement method, device and mass flow controller to improve the dynamic response range and accuracy of gas mass flow measurement.

[0005] A first aspect of an embodiment of the present application provides a method for measuring the mass flow rate of a gas applied to a mass flow controller, wherein the mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series and located on the gas channel, the method comprising:

[0006] Obtaining mass flow measurement values ​​of each group of the measurement units;

[0007] Determining a target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range;

[0008] Determining the mass flow measurement value of the target measurement unit as a mass flow calculation value;

[0009] Wherein, the measuring unit is composed of a flow limiter and a pressure sensor.

[0010] A second aspect of an embodiment of the present application provides a gas mass flow measurement device, the device is located in a mass flow controller, the mass flow controller is provided with a gas channel, and a plurality of groups of measuring units connected in series and located on the gas channel, the device comprising:

[0011] A mass flow measurement value acquisition module, used to acquire the mass flow measurement value of each group of the measurement units;

[0012] A target measurement unit determination module, used to determine the target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range;

[0013] A mass flow calculation value determination module, used to determine the mass flow measurement value of the target measurement unit as the mass flow calculation value;

[0014] Wherein, the measuring unit is composed of a flow limiter and a pressure sensor.

[0015] A third aspect of an embodiment of the present application provides a terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the gas mass flow measurement method as described in the first aspect above is implemented.

[0016] A fourth aspect of an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the gas mass flow measurement method as described in the first aspect above is implemented.

[0017] A fifth aspect of the embodiments of the present application provides a computer program product. When the computer program product is run on a computer, the computer executes the gas mass flow measurement method described in the first aspect.

[0018] Compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0019] In the embodiment of the present application, the mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series on the gas channel; wherein the measuring units are composed of a flow restrictor and a pressure sensor; by setting flow restrictors of different geometric structures in different measuring units, the range of measuring gas mass flow of the mass flow controller is improved, and the mass flow measurement values ​​of each group of the measuring units are obtained; the target measuring unit is determined according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measuring units and its corresponding measurement range; the mass flow measurement value of the target measuring unit is determined as the mass flow calculation value; and within the above-mentioned range, the mass flow calculation value is output by using a measuring unit with higher precision. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments or prior art descriptions. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a structural diagram of a differential pressure mass flow controller in the prior art;

[0022] Figure 2 is the mass flow controller accuracy curve of the prior art;

[0023] Figure 3 is a schematic diagram of a gas mass flow measurement method provided in an embodiment of the present application;

[0024] Figure 4 is a schematic diagram of another gas mass flow measurement method provided in an embodiment of the present application;

[0025] Figure 5 It is a structural diagram of a mass flow controller provided in an embodiment of the present application;

[0026] Figure 6 It is a schematic diagram of the accuracy of each group of measurement units provided in the embodiment of the present application;

[0027] Figure 7 is a control block diagram of a mass flow controller provided in an embodiment of the present application;

[0028] Figure 8 is a structural diagram of another mass flow controller provided in an embodiment of the present application;

[0029] Fig. 9 is a schematic diagram of a gas mass flow measurement device provided in an embodiment of the present application;

[0030] Fig.10 It is a schematic diagram of a terminal device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0031] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0032] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or combinations thereof.

[0033] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0034] As used in the specification and appended claims of this application, the term "if" can be interpreted as "when" or "uponce" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" can be interpreted as meaning "uponce it is determined" or "in response to determining" or "uponce [described condition or event] is detected" or "in response to detecting [described condition or event]", depending on the context.

[0035] In addition, in the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0036] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0037] Reference Figure 1 , shows a structure diagram of a differential pressure mass flow controller in the prior art, which consists of a control valve 101, a pressure sensor 102 and another pressure sensor 103, and a flow limiter 104. After the two pressure sensors measure the pressure values ​​to obtain the mass flow, the control signal is fed back to the control valve 101 for control. The flow limiter 104 is a section of pipe with a certain flow resistance. When the fluid flows through the flow limiter 104, a large pressure loss will be generated. Common flow limiters 104 include capillaries, annular slits between a cylinder and a coaxial hollow ring, etc.

[0038] The pressure loss of the fluid flowing through the restrictor 104 is proportional to the flow velocity v of the fluid, which is expressed as: v~P1-P2, where P1 is the pressure value measured by the pressure sensor 102, and P2 is the pressure value measured by the pressure sensor 103.

[0039] The average density ρ of the fluid flowing through the restrictor 104 is related to the average pressure at the inlet and outlet of the restrictor 104, which is expressed as: ρ~0.5*(P1+P2).

[0040] Since the mass flow rate is equal to the product of average density, velocity and cross-sectional area, the mass flow rate Q = ρVA ~ 0.5*(P1+P2)*(P1-P2)*A, V is the velocity and A is the cross-sectional area.

[0041] When the geometric structure of the restrictor 104 is fixed, the mass flow rate is only related to the pressure difference across the restrictor 104, so it can be obtained that Q = K*(P1 2 -P2 2 )(Formula 1). Wherein, K is a coefficient related only to the geometric structure of the flow restrictor 104. As can be seen from Formula 1, the pressure values ​​at both ends of the flow restrictor 104 can be measured by the pressure sensor 102 and the pressure sensor 103, and then the mass flow rate can be calculated by the above formula.

[0042] For (Formula 1), MFC needs to meet specific working conditions. The following example illustrates: for a mass flow meter with a full scale of 100 SCCM, if the measured value of P2 is 10 kPa, the measured value of P1 is 40 kPa when the full scale is 100 SCCM, then the geometric coefficient K is 0.06; according to the geometric coefficient, when the measured value of P2 is 70 kPa, the measured value of P1 is 80 kPa, but the accuracy of flow measurement will be reduced under this working condition. The specific reasons are as follows:

[0043] Since MFC directly calculates the flow rate through pressure, the accuracy of the flow measurement can be obtained from the accuracy of the pressure sensor through error transfer. The following analysis is based on (Equation 1) as an example. (Equation 1) is derived for P1 and P2 respectively, and the error transfer calculation formula is obtained as follows:

[0044]

[0045] Where [] represents the error of the physical quantity, and its unit is consistent with the physical quantity. Usually, P1 and P2 use sensors of the same specifications, so [P1] = [P2]. ​​The above formula can be further rewritten as:

[0046]

[0047] (Equation 3) shows the error transfer formula from the accuracy of the pressure sensor to the accuracy of the flow sensor. The flow accuracy is positively correlated with the geometric coefficient K, the accuracy of the pressure sensor [P1], and the sum of the squares of P1 and P2. In other words, in order to obtain high-precision flow measurement, it is necessary to reasonably design the geometric structure, select a high-precision pressure sensor, and control the range of pressures P1 and P2. Therefore, when designing such a differential pressure MFC, the preferred strategy is to place the flow measurement unit downstream of the MFC, that is, Figure 1 In the shown architecture, the control valve 101 is located upstream and the flow measurement unit is located downstream, so that the values ​​of P1 and P2 can be made smaller.

[0048] Because differential pressure MFC is mostly used under vacuum, P2 is much smaller than P1. Therefore, P2 can be ignored in the following two steps of derivation, and (Equation 3) can be simplified to [Q] = 2*K*[P1]*P1.

[0049] Divide both sides of the above equation (Equation 1) and we get [Q] / Q=2*[P1] / P1 (Equation 4).

[0050] The physical meaning of (Equation 4) is that the reading error of the mass flow is proportional to the reading error of the pressure sensor. The downstream pressure P2 is related to the customer scenario, and P2 can be considered to be constant. In (Equation 1), when the flow Q increases, P2 and K remain unchanged, then P1 should increase. For a certain set point Qc, it corresponds to P1c. When the set point Q value is greater than Qc, the corresponding P1 is greater than P 1c Combining the right side of (Equation 4), we can see that [Q] / Q = {2*[P1] / P1} < {2*[P1] / P 1c}=const (constant). The mass flow reading error is controlled within a certain constant value. Therefore, in the product specifications, the mass flow accuracy given by MFC manufacturers within a larger range is a fixed reading error.

[0051] However, when the flow rate is less than Qc, P1 <P 1c. Especially when the flow rate is very small, P1 will be close to P2. At this time, it is difficult to accurately characterize the accuracy of MFC using the reading error. Therefore, the full-scale error needs to be used to describe it in the small flow section. The above only explains the accuracy characteristics of MFC from the perspective of the pressure sensor accuracy value transfer. In addition to the pressure sensor accuracy value transfer, the MFC accuracy is also affected by other reasons such as sampling accuracy, noise influence, temperature deviation and other errors. Taking various factors into consideration, the accuracy given by the MFC manufacturer is the segmented accuracy. The full-scale accuracy is used at small flow rates, and the reading accuracy is used when the flow rate increases to a certain value. For example, the MFC accuracy description usually given by the manufacturer is: at 25% to 100% of the full scale, the accuracy is ±1% of the set value, recorded as ±1% SP (setpoint); at 0% to 25% of the full scale, the accuracy is ±0.25% of the full scale, recorded as ±0.25% FS (full scale). Reference Figure 2 , shows the accuracy curve of mass flow controller in the prior art. Figure 2 As shown in the figure, the accuracy curve can be drawn as a graph of accuracy versus flow rate. Within the range of 0 to 25%, the full-scale accuracy of the set value does not increase with the increase of the set value, so the figure shows a dotted line with a slope of 0; within the range of 25% to 100%, the accuracy of the set value is the reading accuracy, and the corresponding error will increase linearly with the increase of the set point, so the figure shows a slope of ±1%, and the outline of the error is shown as the dotted line in the figure.

[0052] The figure also shows that the measurement range of MFC is limited, and it can only maintain high accuracy (reading accuracy) within the appropriate flow range. However, the flow demand in the semiconductor manufacturing process has jumped from 1e1 SCCM (standard cubic centimeter per minute) to 1e5 SCCM. In order to meet the demand, MFC manufacturers need to develop dozens of ranges to cover the above measurement requirements. This makes the use and maintenance costs of MFC in the semiconductor manufacturing industry very high.

[0053] In order to solve the problem that a single MFC in the prior art cannot meet the requirement of high-precision measurement of gas flow mass of different magnitudes, the present application provides a mass flow controller and corresponding gas mass flow measurement. The technical solution of the present application is described below through specific embodiments.

[0054] Reference Figure 3, shows a schematic diagram of a gas mass flow measurement method provided by an embodiment of the present application. The embodiment of the present application can be applied to a mass flow controller, wherein the mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series on the gas channel; wherein the measuring unit is composed of a restrictor and a pressure sensor; and specifically may include the following steps:

[0055] Step 301, obtaining mass flow measurement values ​​of each group of measurement units;

[0056] The measuring units are connected in series and located on the gas channel. Therefore, when the gas flows in the gas channel, the gas can pass through the restrictors of each measuring unit in turn, and the pressure value measured by the pressure sensor contained in each measuring unit is measured, thereby obtaining the mass flow measurement value corresponding to each measuring unit.

[0057] The mass flow measurement value is obtained by measuring the pressure at both ends of the restrictor according to the geometric structure of each group of measuring units.

[0058] Step 302, determining a target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range;

[0059] In this embodiment, the geometric structures of the current limiters in different measuring units are different. Combined with the above discussion, it can be seen that the accuracy of different measuring units in different measuring ranges in this embodiment is different. In the same measuring range, a measuring unit with higher accuracy is determined to correspond to the measuring unit, and the corresponding relationship is determined in this way, that is, each measuring range corresponds to the measuring unit with higher accuracy in the measuring range.

[0060] The measurement range of the mass flow measurement value is determined, and the measurement unit corresponding to the measurement range is determined as the target measurement unit.

[0061] Step 303: determine the mass flow measurement value of the target measurement unit as the mass flow calculation value.

[0062] The mass flow measurement value determined by the target measurement unit is the mass flow calculation value of the mass flow controller, and the target measurement unit is the one with higher accuracy within the measurement range where the mass flow measurement value is located, so the mass flow calculation value of the mass flow controller is always the measurement value output by the measurement unit with higher accuracy within the current measurement range. Since the embodiment of the present application includes multiple groups of measurement units, and the combination structure of the restrictors in the measurement units is different, compared with the prior art, the embodiment of the present application also has a wider high-precision measurement range, and the mass flow calculation value can be output by the measurement unit with higher accuracy within the high-precision measurement range.

[0063] For example, a mass flow controller in the prior art includes only a measuring unit A, and the full scale of the measuring unit A is 100 SCCM. When the flow rate is greater than 25% of the full scale (25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the full scale (25 SCCM), the measurement accuracy is ±0.25% FS. Therefore, the high-precision measurement range of the mass flow controller is 25 to 100 SCCM.

[0064] A mass flow controller obtained based on the embodiment of the present application includes a measuring unit A and a measuring unit B, wherein the full scale of the measuring unit B is 25 SCCM, when the flow rate is greater than 25% of the full scale (6.25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the full scale (6.25 SCCM), the measurement accuracy is ±0.25% FS, and the high-precision measurement range of the mass flow controller is 6.25 to 100 SCCM, which expands a larger high-precision measurement range relative to the prior art. In addition, based on the content disclosed in the embodiment of the present application, different flow limiters are configured to provide different high-precision measurement ranges, or more measuring units are set to further broaden the high-precision measurement range.

[0065] In an embodiment of the present application, a mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series on the gas channel; wherein the measuring units are composed of a flow restrictor and a pressure sensor; by setting flow restrictors of different geometric structures in different measuring units, the range of measuring gas mass flow of the mass flow controller is improved, and by obtaining the mass flow measurement values ​​of each group of the measuring units; a target measuring unit is determined based on the mass flow measurement values ​​and a preset corresponding relationship; the corresponding relationship includes each of the measuring units and its corresponding measurement range; the mass flow measurement value of the target measuring unit is determined as a mass flow calculation value; and within the range of the mass flow controller, a high-precision measuring unit is used to output the mass flow calculation value.

[0066] In an embodiment of the present application, the mass flow controller is provided with a valve; the embodiment of the present application may further include the following steps: determining mass flow control information based on the mass flow calculation value and a preset algorithm; controlling the valve according to the mass flow control information to control the gas mass flow in the gas channel.

[0067] The mass flow control information for the valve is determined based on the measured mass flow calculation value and the preset algorithm. In specific applications, different voltages can be output to the valve to control the working state of the valve, and the mass flow control information is the voltage output to the valve.

[0068] By controlling the valve according to the mass flow control information, the gas mass flow in the gas channel is controlled, and then the gas mass flow of the mass flow controller output gas is controlled.

[0069] In an optional embodiment, the corresponding relationship is determined by the following method, including: obtaining the measurable mass flow value of each of the measuring units and the measurement accuracy of the measurable mass flow value; determining the one with the highest measurement accuracy under the same measurable mass flow value as the target measurement accuracy; dividing the measurable mass flow value into multiple measurement ranges; wherein a measurement range is composed of measurable mass flow values ​​corresponding to a target measurement accuracy; for the same target measurement accuracy, determining that the measurement unit corresponds to the measurement range.

[0070] The measuring range is determined by determining the maximum measurable mass flow value of the measuring unit, and the measurement accuracy corresponding to each measurable mass flow value within the measuring range is determined. For example: the full scale of measuring unit A is 100 SCCM, when the flow rate is greater than 25% of the full scale (25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the full scale (25 SCCM), the measurement accuracy is ±0.25% FS (FS = 100 SCCM); the full scale of measuring unit B is 25 SCCM, when the flow rate is greater than 25% of the full scale (6.25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the full scale (6.25 SCCM), the measurement accuracy is ±0.25% FS (FS = 25 SCCM). It should be noted that the accuracy in this embodiment (flow rate <25% FS, accuracy ±0.25% FS; flow rate >25% FS, accuracy ±1% SP) is only an example and is not limited to this accuracy; the actual parameters will be higher than this accuracy.

[0071] 0-100 SCCM is divided into measurement range I: less than 6.25 SCCM; measurement range II: greater than or equal to 6.25 SCCM and less than 25 SCCM; measurement range III: greater than or equal to 25 SCCM and less than 100 SCCM.

[0072] Based on the measurement accuracy of measurement unit A and measurement unit B in different ranges, the corresponding relationship is determined as follows: the target measurement accuracy corresponding to measurement range I is the measurement accuracy of measurement unit B, and the corresponding target measurement unit is measurement unit B; it is determined that the target measurement accuracy corresponding to measurement range II is the measurement accuracy of measurement unit B, and the corresponding target measurement unit is measurement unit B; it is determined that the target measurement accuracy corresponding to measurement range III is the measurement accuracy of measurement unit A, and the corresponding target measurement unit is measurement unit A.

[0073] Reference Figure 4, showing a schematic diagram of another gas mass flow measurement method provided in an embodiment of the present application, referring to Figure 5 , showing a mass flow controller structure diagram provided by an embodiment of the present application, the embodiment of the present application can be applied to Figure 5 The mass flow controller shown in the figure is provided with a gas channel 500 and a plurality of groups of measuring units connected in series on the gas channel; the plurality of groups of measuring units are composed of a first measuring unit and a second measuring unit; the first measuring unit comprises a first restrictor 501 and a first pressure sensor 511 and a second pressure sensor 512 located at both ends of the first restrictor 501; the second measuring unit comprises a second restrictor 502 and a second pressure sensor 512 and a third pressure sensor 513 located at both ends of the second restrictor 502; the first range of the first measuring unit is greater than the second range of the second measuring unit; the following steps may be specifically included:

[0074] Step 401, obtaining mass flow measurement values ​​of each group of the measuring units; the first mass flow measurement value of the first measuring unit is determined according to the first pressure value detected by the first pressure sensor 511, the second pressure value of the second pressure sensor 512 and the first preset coefficient; the second mass flow measurement value of the second measuring unit is determined according to the second pressure value detected by the second pressure sensor 512, the third pressure value of the third pressure sensor 513 and the second preset coefficient;

[0075] The first pressure sensor 511 and the second pressure sensor 512 are respectively used to measure the pressure at both ends of the first limiter 501, and obtain the corresponding first pressure value and the second pressure value, and the first preset coefficient is a coefficient that is only related to the geometric structure of the first limiter 501; the second pressure sensor 512 and the third pressure sensor 513 are respectively used to measure the pressure at both ends of the second limiter 502, and obtain the corresponding second pressure value and the third pressure value, and the second preset coefficient is a coefficient that is only related to the geometric structure of the second limiter 502.

[0076] By combining the above formula 1 with the first pressure value, the second pressure value, and the first preset parameter, the first mass flow measurement value can be calculated; by combining the above formula 1 with the second pressure value, the third pressure value, and the second preset parameter, the second mass flow measurement value can be calculated.

[0077] Step 402, determining a target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes a first measurement range corresponding to the first measurement unit and a second measurement range corresponding to the second measurement unit; the first measurement range and the second measurement range are obtained by dividing the first measurement range; within the second measurement range, the accuracy of the second measurement unit is higher than the accuracy of the first measurement unit;

[0078] Since the first range is larger than the second range, the first range can be used as the total measurement range of the mass flow controller. Since the measurement accuracy of the first measuring unit and the second measuring unit in different measurement ranges are not exactly the same, the first range can be divided into multiple measurement ranges, and the measurement unit with higher accuracy corresponding to the range can be determined.

[0079] The following takes the measurement unit A as the first measurement unit and the measurement unit B as the second measurement unit as an example to further illustrate step 402. Figure 6 , showing the accuracy diagram of each group of measurement units provided in the embodiment of the present application. The first range ( Figure 6 The area between the middle dotted lines), the second range ( Figure 6 The area between the dotted lines is the measurement range with known accuracy. The first range of the first measurement unit is 100 SCCM. When the flow rate is greater than 25% of the first range (25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the first range (25 SCCM), the measurement accuracy is ±0.25% FS (FS = 100 SCCM); the second range of the second measurement unit is 25 SCCM. When the flow rate is greater than 25% of the second range (6.25 SCCM), the measurement accuracy is ±1% SP; when the flow rate is less than 25% of the second range (6.25 SCCM), the measurement accuracy is ±0.25% FS (FS = 25 SCCM). Since the accuracy of the second measurement unit is higher than that of the first measurement unit within the range of 0 to 25 SCCM, and in the range of 25 to 100 SCCM, the mass flow measurement value measured by the second measurement unit is unknown at this time, the accuracy of the first measurement unit is higher than that of the second measurement unit. Therefore, the first measuring range can be divided into a first measuring range corresponding to the first measuring unit and a second measuring range corresponding to the second measuring unit, wherein the first measuring range is greater than or equal to 0 SCCM and less than 25 SCCM; the second measuring range is greater than or equal to 25 SCCM and less than 100 SCCM.

[0080] In this embodiment, step 402 may include: if the second mass flow measurement value is within the first measurement range, determining the first measurement unit as the target measurement unit; if the second mass flow measurement value is within the second measurement range, determining the second measurement unit as the target measurement unit;

[0081] Since the second mass flow measurement value has a higher precision than the first mass flow measurement value within the second measurement range, the target measurement unit can be determined based on the second mass flow measurement value. If the second mass flow measurement value is within the first measurement range, the first measurement unit is determined to be the target measurement unit; if the second mass flow measurement value is within the second measurement range, the second measurement unit is determined to be the target measurement unit.

[0082] In an optional embodiment, the target measurement unit may also be determined based on the first mass flow measurement value. If the first mass flow measurement value is within the first measurement range, the first measurement unit is determined to be the target measurement unit; if the first mass flow measurement value is within the second measurement range, the second measurement unit is determined to be the target measurement unit.

[0083] Step 403: determine the mass flow measurement value of the target measurement unit as the mass flow calculation value.

[0084] In this embodiment, step 403 may include: if the first measurement unit is a target measurement unit, determining the first mass flow measurement value as a mass flow calculation value; if the second measurement unit is a target measurement unit, determining the second mass flow measurement value as a mass flow calculation value.

[0085] After the target measurement unit is determined, the mass flow measurement value of the target measurement unit is determined as the mass flow calculation value obtained by combining the groups of measurement units.

[0086] Reference Figure 7 , showing a control block diagram of a mass flow controller provided in an embodiment of the present application; the flow measurement unit can pre-store a first preset coefficient and a second preset coefficient, and when it receives a first pressure value and a second pressure value, calculates to obtain a first mass flow measurement value; when it receives a second pressure value and a third pressure value, calculates to obtain a second mass flow measurement value.

[0087] The flow calculation unit transmits the mass flow calculated by each unit to the flow calculation unit, and the flow calculation unit performs threshold comparison analysis on the mass flow measurement values ​​corresponding to the two groups of measurement units. When the second mass flow measurement value is within a small flow range, a typical case is that the mass flow < 25% of the full scale (the second range), the flow calculation unit adopts the mass flow measurement value obtained by the flow measurement unit and transmits it to the flow control unit, and the flow control unit controls the valve voltage accordingly. On the contrary, when the second mass flow measurement value exceeds a certain threshold, such as the mass flow > 25% of the full scale, the flow in the second restrictor may have exceeded the laminar flow range. At this time, the flow calculation unit considers that the second mass flow measurement value is unreliable, and adopts the first mass flow measurement value as the mass flow calculation value in this range and transmits it to the flow control unit. If the second mass flow measurement value is greater than the first range, the mass flow calculation value is the first mass flow measurement value, but the accuracy value cannot be determined at this time.

[0088] In the embodiment of the present application, the range of the measuring unit located upstream of the gas channel is greater than the range of the measuring unit downstream, and the measuring unit downstream selects a measuring unit with a small range. When the large-range measuring unit is working, if the small-range measuring unit is upstream of the large-range measuring unit, since the small-range measuring unit has entered turbulence at this time, it will affect the flow in the large-range flow limiter downstream thereof to be turbulent or a transitional flow state from turbulence to laminar flow, affecting the accuracy of the large-range measuring unit. On the contrary, if the large-range measuring unit is located upstream of the small-range measuring unit, this problem will not occur.

[0089] In the embodiment of the present application, the mass flow controller is provided with a valve 520; the embodiment of the present application may further include the following steps: determining mass flow control information according to the mass flow calculation value and a preset algorithm; controlling the valve 520 according to the mass flow control information to control the gas mass flow in the gas channel. The specific description may refer to the relevant description of the previous embodiment, which will not be repeated here.

[0090] Reference Figure 8 , shows another mass flow controller structure diagram provided in an embodiment of the present application. Figure 5 Compared to the mass flow controller structure shown, Figure 8 In the mass flow controller structure shown, the valve 520 is located between the outlet of the gas channel 500 and the second measuring unit. The above steps 401-403 can also be applied to Figure 8 In the mass flow controller shown, the specific implementation process will not be repeated here.

[0091] It should be noted that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0092] Reference Fig. 9 , shows a schematic diagram of a gas mass flow measurement device provided in an embodiment of the present application, the device is located in a mass flow controller, the mass flow controller is provided with a gas channel, and a plurality of groups of measurement units connected in series on the gas channel, the device may specifically include a mass flow measurement value acquisition module 901, a target measurement unit determination module 902 and a mass flow calculation value determination module 903, wherein:

[0093] A mass flow measurement value acquisition module 901 is used to acquire the mass flow measurement value of each group of the measurement units;

[0094] A target measurement unit determination module 902 is used to determine a target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range;

[0095] A mass flow calculation value determination module 903, configured to determine the mass flow measurement value of the target measurement unit as a mass flow calculation value;

[0096] Wherein, the measuring unit is composed of a flow limiter and a pressure sensor.

[0097] In an optional embodiment, the mass flow controller is provided with a valve; the device comprises:

[0098] A mass flow control information determination module, used to determine the mass flow control information according to the mass flow calculation value and a preset algorithm;

[0099] The valve control module is used to control the valve according to the mass flow control information to control the gas mass flow in the gas channel.

[0100] In an optional embodiment, the plurality of measurement units are composed of a first measurement unit and a second measurement unit; the first measurement unit includes a first flow restrictor and a first pressure sensor and a second pressure sensor located at both ends of the first flow restrictor; the second measurement unit includes a second flow restrictor and a second pressure sensor and a third pressure sensor located at both ends of the second flow restrictor;

[0101] The first mass flow measurement value of the first measurement unit is determined according to the first pressure value detected by the first pressure sensor, the second pressure value of the second pressure sensor and a first preset coefficient;

[0102] The second mass flow measurement value of the second measurement unit is determined according to the second pressure value detected by the second pressure sensor, the third pressure value of the third pressure sensor, and a second preset coefficient.

[0103] In an optional embodiment, the first range of the first current limiter is greater than the second range of the second current limiter;

[0104] The corresponding relationship includes a first measurement range corresponding to the first measurement unit and a second measurement range corresponding to the second measurement unit; the first measurement range and the second measurement range are obtained by dividing the first measurement range;

[0105] The accuracy of the second measurement unit is higher than the accuracy of the first measurement unit within the second measurement range.

[0106] In an optional embodiment, the target measurement unit determination module 902 is used to determine the first measurement unit as the target measurement unit if the second mass flow measurement value is within the first measurement range; if the second mass flow measurement value is within the second measurement range, determine the second measurement unit as the target measurement unit.

[0107] In an optional embodiment, the mass flow calculated value determination module 903 is used to determine the first mass flow measurement value as the mass flow calculated value if the first measurement unit is a target measurement unit; if the second measurement unit is a target measurement unit, determine the second mass flow measurement value as the mass flow calculated value.

[0108] In an optional embodiment, the corresponding relationship is determined by the following modules, including:

[0109] A measurable mass flow value acquisition module, used to acquire the measurable mass flow value of each of the measuring units, and the measurement accuracy of the measurable mass flow value;

[0110] A target measurement accuracy determination module is used to determine the highest measurement accuracy under the same measurable mass flow value as the target measurement accuracy;

[0111] A measurement range division module, used to divide the measurable mass flow value into a plurality of measurement ranges; wherein one measurement range is composed of a measurable mass flow value corresponding to a target measurement accuracy;

[0112] The corresponding relationship determination module is used to determine the correspondence between the measurement unit and the measurement range for the same target measurement accuracy.

[0113] An embodiment of the present application provides a gas mass flow measurement device, and by using the device, each step in the aforementioned method embodiments can be implemented.

[0114] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiment part.

[0115] Reference Fig.10 , shows a schematic diagram of a mass flow controller provided in an embodiment of the present application. Fig.10 As shown, the mass flow controller 1000 in the embodiment of the present application includes: a gas channel, a plurality of groups of measuring units connected in series on the gas channel, a processor 1010, a memory 1020, and a computer program 1021 stored in the memory 1020 and executable on the processor 1010. When the processor 1010 executes the computer program 1021, the steps in each embodiment of the above-mentioned gas mass flow measurement method are implemented, such as Figure 3 Alternatively, when the processor 1010 executes the computer program 1021, the functions of each module / unit in the above-mentioned device embodiments are realized, for example Fig. 9 Functions of modules 901 to 903 are shown.

[0116] Exemplarily, the computer program 1021 may be divided into one or more modules / units, which are stored in the memory 1020 and executed by the processor 1010 to complete the present application. The one or more modules / units may be a series of computer program instruction segments capable of completing specific functions, which may be used to describe the execution process of the computer program 1021 in the mass flow controller 1000. For example, the computer program 1021 may be divided into a mass flow measurement value acquisition module, a target measurement unit determination module, and a mass flow calculation value determination module, and the specific functions of each module are as follows:

[0117] A mass flow measurement value acquisition module, used to acquire the mass flow measurement value of each group of the measurement units;

[0118] A target measurement unit determination module, used to determine the target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range;

[0119] A mass flow calculation value determination module, used to determine the mass flow measurement value of the target measurement unit as the mass flow calculation value;

[0120] Wherein, the measuring unit is composed of a flow limiter and a pressure sensor.

[0121] The mass flow controller 1000 may include, but is not limited to, a gas channel, a plurality of measurement units connected in series on the gas channel, a processor 1010, and a memory 1020. Those skilled in the art will appreciate that Fig.10The mass flow controller 1000 is only an example and does not constitute a limitation on the mass flow controller 1000. The mass flow controller 1000 may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the mass flow controller 1000 may also include Figure 5 Included components, input and output devices, network access devices, buses, etc.

[0122] The processor 1010 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0123] The memory 1020 may be an internal storage unit of the mass flow controller 1000, such as a hard disk or memory of the mass flow controller 1000. The memory 1020 may also be an external storage device of the mass flow controller 1000, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (Secure Digital, SD) card, a flash card (Flash Card), etc. equipped on the mass flow controller 1000. Further, the memory 1020 may also include both an internal storage unit of the mass flow controller 1000 and an external storage device. The memory 1020 is used to store the computer program 1021 and other programs and data required by the mass flow controller 1000. The memory 1020 may also be used to temporarily store data that has been output or is to be output.

[0124] The embodiments of the present application further disclose a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the gas mass flow measurement method as described in the above embodiments is implemented.

[0125] The embodiments of the present application further disclose a computer program product. When the computer program product is run on a computer, the computer is enabled to execute the gas mass flow measurement method described in the above embodiments.

[0126] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application is described in detail with reference to the above-mentioned embodiments, a person skilled in the art should understand that the technical solutions described in the above-mentioned embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for measuring the mass flow rate of a gas, characterized in that: Applied to a mass flow controller, the mass flow controller is provided with a gas channel and a plurality of groups of measuring units connected in series and located on the gas channel, the method comprising: Obtaining mass flow measurement values ​​of each group of the measurement units; Determining a target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range; Determining the mass flow measurement value of the target measurement unit as a mass flow calculation value; Wherein, the measuring unit is composed of a flow limiter and a pressure sensor; The corresponding relationship is determined by the following steps, including: Obtaining a measurable mass flow value of each of the measuring units and a measurement accuracy of the measurable mass flow value; Determine the highest measurement accuracy under the same measurable mass flow value as the target measurement accuracy; Dividing the measurable mass flow value into a plurality of measurement ranges; wherein one measurement range is composed of a measurable mass flow value corresponding to the target measurement accuracy; For the same target measurement accuracy, it is determined that the measurement unit corresponds to the measurement range.

2. The method according to claim 1, characterized in that The mass flow controller is provided with a valve; the method further comprises: Determining mass flow control information according to the mass flow calculation value and a preset algorithm; The valve is controlled according to the mass flow control information to control the gas mass flow in the gas channel.

3. The method according to claim 1 or 2, characterized in that: The plurality of measurement units are composed of a first measurement unit and a second measurement unit; the first measurement unit includes a first flow restrictor and a first pressure sensor and a second pressure sensor located at both ends of the first flow restrictor; the second measurement unit includes a second flow restrictor and a second pressure sensor and a third pressure sensor located at both ends of the second flow restrictor; The first mass flow measurement value of the first measurement unit is determined according to the first pressure value detected by the first pressure sensor, the second pressure value of the second pressure sensor and a first preset coefficient; The second mass flow measurement value of the second measurement unit is determined according to the second pressure value detected by the second pressure sensor, the third pressure value of the third pressure sensor, and a second preset coefficient.

4. The method according to claim 3, characterized in that The first measuring range of the first measuring unit is greater than the second measuring range of the second measuring unit; The corresponding relationship includes a first measurement range corresponding to the first measurement unit and a second measurement range corresponding to the second measurement unit; the first measurement range and the second measurement range are obtained by dividing the first measurement range; The accuracy of the second measurement unit is higher than the accuracy of the first measurement unit within the second measurement range.

5. The method according to claim 4, characterized in that The determining of the target measurement unit according to the mass flow measurement value and the preset corresponding relationship includes: If the second mass flow measurement value is within the first measurement range, determining the first measurement unit as a target measurement unit; If the second mass flow measurement value is within the second measurement range, the second measurement unit is determined to be a target measurement unit.

6. The method according to claim 5, characterized in that Determining the mass flow measurement value of the target measurement unit as the mass flow calculation value comprises: If the first measurement unit is a target measurement unit, determining the first mass flow measurement value as a mass flow calculation value; If the second measurement unit is a target measurement unit, the second mass flow measurement value is determined to be a mass flow calculation value.

7. A gas mass flow measurement device, characterized in that: The device is located in a mass flow controller, the mass flow controller is provided with a gas channel, and a plurality of groups of measuring units connected in series and located on the gas channel, the device comprising: A mass flow measurement value acquisition module, used to acquire the mass flow measurement value of each group of the measurement units; A target measurement unit determination module, used to determine the target measurement unit according to the mass flow measurement value and a preset corresponding relationship; the corresponding relationship includes each of the measurement units and its corresponding measurement range; A mass flow calculation value determination module, used to determine the mass flow measurement value of the target measurement unit as the mass flow calculation value; Wherein, the measuring unit is composed of a flow limiter and a pressure sensor; The corresponding relationship is determined by the following modules, including: A measurable mass flow value acquisition module, used to acquire the measurable mass flow value of each of the measuring units, and the measurement accuracy of the measurable mass flow value; A target measurement accuracy determination module, used to determine the highest measurement accuracy under the same measurable mass flow value as the target measurement accuracy; A measurement range division module, used for dividing the measurable mass flow value into a plurality of measurement ranges; wherein one measurement range is composed of a measurable mass flow value corresponding to the target measurement accuracy; The corresponding relationship determination module is used to determine the correspondence between the measurement unit and the measurement range for the same target measurement accuracy.

8. A mass flow controller, the mass flow controller is provided with a gas channel, a plurality of groups of measuring units connected in series on the gas channel, a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the gas mass flow measurement method according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the method for measuring the mass flow rate of gas according to any one of claims 1 to 6 is implemented.

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