阅读说明：本技术 流通压力传感器 (Flow-through pressure sensor ) 是由 丹尼尔·穆德 穆罕默德·萨利姆 阿伦·纳加良 于 2020-08-28 设计创作，主要内容包括：给出了一种用于去除质量流量控制器的传感器组件中的死区体积的系统。所述系统包括可连通地连接到传感器组件的阀组件。该阀组件与主流动路径中的流体处于流体连通,并且该传感器组件与该主流动路径中的流体处于流体连通。该传感器组件包括具有第一贮存器的压力换能器和具有第二贮存器的另一压力换能器。该第一贮存器具有与采样流动路径中的流体处于流体连通的端口。该第二贮存器连接到第二压力换能器,并且通过流通路径流体地连接到该第一贮存器。该第二贮存器还包括另一端口,用于将流体流从该流通路径传送到另一流动路径。流速限流器布置在该流通路径中。(A system for removing dead volume in a sensor assembly of a mass flow controller is presented. The system includes a valve assembly communicably connected to a sensor assembly. The valve assembly is in fluid communication with fluid in the main flow path, and the sensor assembly is in fluid communication with fluid in the main flow path. The sensor assembly includes a pressure transducer having a first reservoir and another pressure transducer having a second reservoir. The first reservoir has a port in fluid communication with fluid in the sampling flow path. The second reservoir is connected to a second pressure transducer and is fluidly connected to the first reservoir by a flow path. The second reservoir further comprises a further port for conveying the fluid flow from the flow path to a further flow path. A flow rate restrictor is disposed in the flow path.)

1. An apparatus for removing dead volume in a sensor assembly, the apparatus comprising:

a first reservoir connected to the first pressure transducer and having a port in fluid communication at a location in the sampling flow path;

a second reservoir connected to a second pressure transducer, fluidly connected to the first reservoir by a flow path, and having another port in fluid communication at another location of another sampling flow path; and

a flow restrictor disposed in the flow path.

2. The apparatus of claim 1, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is one selected from the group consisting of another absolute pressure transducer and a differential pressure transducer.

3. The apparatus of claim 1, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is one selected from the group consisting of an absolute pressure transducer and another differential pressure transducer.

4. The device of claim 1, wherein the flow path is between the first reservoir and the second reservoir.

5. The device of claim 1, wherein the flow path fluidly connects one end of the first reservoir with another end of the second reservoir.

6. The apparatus of claim 1, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by a full scale flow rate of the MFC.

7. The apparatus of claim 1, wherein the volume of the second reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by a full scale flow rate of the MFC.

8. A system for removing dead volume in a sensor assembly of a mass flow controller, the system comprising:

a valve assembly in fluid communication with fluid in the main flow path;

a pressure sensor assembly in fluid communication with fluid in the primary flow path, the pressure sensor assembly comprising:

a first reservoir connected to the first pressure transducer and having a port in fluid communication at a location in the sampling flow path;

a second reservoir connected to a second pressure transducer, fluidly connected to the first reservoir by a flow path, and having another port in fluid communication at another location of another sampling flow path;

wherein the first and second pressure transducers are communicably connected with the valve assembly.

9. The system of claim 8, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is one selected from the group consisting of another absolute pressure transducer and a differential pressure transducer.

10. The system of claim 8, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is one selected from the group consisting of an absolute pressure transducer and another differential pressure transducer.

11. The system of claim 8, wherein the flow path is between the first reservoir and the second reservoir.

12. The system of claim 8, wherein the flow path fluidly connects one end of the first reservoir with another end of the second reservoir.

13. The system of claim 8, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by a full scale flow rate of the MFC.

14. The system of claim 8, wherein the volume of the second reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by a full scale flow rate of the MFC.

15. A method for removing dead volume in a sensor assembly of a mass flow controller, the method comprising:

pumping fluid from the primary flowpath through a port into a first reservoir connected to a first pressure transducer; and

fluid is pumped from the first reservoir to a second reservoir connected to a second pressure transducer through a flow path and through another port.

16. The method of claim 15, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is one selected from the group consisting of another absolute pressure transducer and a differential pressure transducer.

17. The method of claim 15, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is one selected from the group consisting of an absolute pressure transducer and another differential pressure transducer.

18. The method of claim 15, further comprising: pumping fluid from the first reservoir through the flow path, wherein the flow path is between the first reservoir and the second reservoir.

19. The method of claim 15, further comprising: pumping fluid from the first reservoir through the flow path, wherein the flow path fluidly connects one end of the first reservoir with another end of the second reservoir.

20. The method of claim 15, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by a full scale flow rate of the MFC.

Background

In many manufacturing operations that use chemicals to manufacture electronic devices, Mass Flow Controllers (MFCs) are used to measure and control the flow rate of fluids delivered to a process chamber. In the manufacture of semiconductor devices, more than 50 gases are used in etching and Chemical Vapor Deposition (CVD) processes, and other 150 gases are known in the industry. On a production line flow, one semiconductor fabrication chamber may contain 9 to 16 MFCs, and each production line may contain 1 to 6 chambers. The use of MFCs is prevalent and they control gases ranging from inert gases, to corrosive gases, to pyrophoric gases, and/or to highly toxic gases; wherein the allowable exposure limit is below one part per million. Therefore, the ability to completely remove stagnant gas from a failed MFC is a critical safety requirement when replacing the failed MFC with a new MFC.

In addition to the safety issues of replacing a failed MFC, there is a strong demand for "dry down" of the internal flow channels of a new MFC to remove atmospheric moisture adhering to the channel walls. All devices exposed to air with any relative humidity, including MFC, will attract H2O at the molecular level to its surface walls. At a given time, stable temperature and humidity, the amount of H2O on the wall reaches equilibrium, i.e. molecules adhering to the surface and molecules leaving the surface remain in equilibrium. However, when the device is initially installed in a semiconductor processing tool, these atmospheric H2O molecules remain on the interior surfaces and will begin to fall off the walls and into the dry process gas stream, causing corrosion problems or process chemistry problems downstream of the MFC.

Thus, it is common in the marketplace to quantify the rate at which a new MFC will "dry" as part of its performance specification file when circulating dry inert "purge" gas (typically nitrogen or argon) through the MFC to remove atmospheric water from its walls. A typical "dry out" test will establish a known level of moisture on the walls of the MFC and then record the moisture level in the device exhaust over time as a specified flow rate of dry purge gas flows through the MFC until the detected moisture level reaches a few parts per billion level.

To remove moisture on the walls of new MFCs or to ensure removal of "harmful gases" from replaced MFCs, the industry has in practice "flow" and "cycle" purging of MFCs and other devices with dry purge gases. Typically, the purge gas flow will be directed to the MFC, flow through the MFC, and then be diverted to a non-process location. After a period of flow purge, the valve positions are changed and the device is repeatedly and alternately evacuated to a moderate vacuum level and then repressurized again with a purge gas for hundreds of cycles, eventually bringing the moisture level or concentration of harmful gases to sub-ppm levels.

In addition to the current "safe" and process "dry" advantages described above, additional advantages are created in that one gas is efficiently and quickly replaced with another gas. These additional advantages stem from the continuing trend to reduce hardware costs and space by flowing multiple gas species through a single MFC. As an example, in a gas box containing 16 gas lines delivering gases to the etch process tool, each line having its own dedicated MFC, 2 to 4 gases can flow simultaneously. Many of these 16 gases belong to the same gas family and can be directed to and flow through the same MFC as long as the old gas can be easily replaced by a new gas.

One example is to flow oxygen, nitrogen or argon through the same MFC. Similarly, multiple freon gases may be grouped together. This approach provides significant opportunities to reduce hardware costs and associated costs by reducing the number of gas lines from 16 to possibly 8. However, there is a need for an efficient method of changing the type of gas; such as a flow purge or a cycle purge, in which fresh gas is circulated through the MFC to vent old gas. Without an effective purge, a stagnant volume (known as dead head) may form in the small passage of the MFC. While purging is an effective practical means when used with heat-based MFCs, it is ineffective when used with pressure-based MFCs. The purge effectively removes dead volume of gas due to the natural flow design of the heat-based MFC. However, pressure-based MFCs do not share the same or similar flow design, and therefore purging is not an effective practical means of removing the dead volume of gas.

Drawings

For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description and to the accompanying drawings in which corresponding reference numerals in the different drawings represent corresponding parts, and in which:

FIGS. 1A and 1B are illustrations of various MFC configurations having sensor assemblies designed to include a flow path and a reservoir passage having a selected volume in accordance with certain exemplary embodiments; and

fig. 2A-2D are illustrations of a sensor assembly having a flow path and various MFC configurations, according to certain example embodiments.

Detailed Description

While the making and using of various embodiments of the present disclosure are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not limit the scope of the disclosure. In the interest of clarity, not all features of an actual implementation may be described in this disclosure. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

Pressure-based MFCs are typically closed-loop designs in which a pressure sensor assembly includes a port and a small reservoir so that fluid pressure can be sampled and measured from the main flow path to determine fluid flow rate. In practice, the sensor assembly may include one or more absolute pressure transducers and one or more differential pressure transducers. Each transducer includes a port for sampling fluid pressure from the primary flow path and a reservoir. The primary flow path may include a flow restrictor having certain characteristics, and fluid pressure may be sampled upstream and downstream of the flow restrictor. Because the reservoir of the transducer does not include a flow path, i.e., is closed with respect to the main flow path, dead spaces may be formed in the reservoir, i.e., stagnant volumes where the gas flow does not readily displace old gas. Also, this configuration results in dead zones, which are volumes that the gas stream cannot efficiently sweep. Dead volume (i.e., stagnant fluid) is not vented from the reservoir as gas flows through the flow restrictor in the MFC base. Thus, the reservoir is not purged when new gas is circulated to replace old gas. The effect of this dead volume on MFC operation is the introduction of undesirable gas mixtures that can affect downstream processes.

A system, method, and apparatus for inducing a gas flow to sweep through the volume of a reservoir of a sensor, thereby eliminating the stagnant nature of previous designs, thereby removing the dead volume in the transducer assembly of the MFC is presented herein. The transducer assembly includes a first reservoir connected to a first pressure transducer, a second reservoir connected to another pressure transducer, and a flow restrictor disposed in a flow path connecting the first reservoir with the second reservoir. The flow path provides a path for fluid to flow between and through the two reservoirs. The effect of this is to have new gas sweep/vent the previous gas from the reservoir, thereby preventing the old gas from slowly bleeding into the mainstream gas resulting in delivery of the unknown mixture to the process for a significant period of time after the gas for the MFC begins to change (e.g., switch from one gas type to another in a semiconductor manufacturing operation).

Referring now to fig. 1A and 1B, various MFC configurations are illustrated with sensor components designed to include a flow path and a reservoir passage having a selected volume, according to some example embodiments. The location of the total volume of the reservoir and the flow path in the sensor assembly depends on the type of MFC application. For low flow rate applications, a reduced reservoir volume may be required. For high flow rate applications, an increased reservoir volume may be required. However, the volume of the reservoir may also be based on the purge time. Additionally, each reservoir in the sensor assembly may have a unique volume size.

In fig. 1A, two MFC configurations, generally designated 10A and 10B, are illustrated with sensor components having at least one flow path and a reservoir passage with a defined volume. The MFC configuration 10A includes a valve assembly 12A, a base having a main flow path 14A in which a main flow path obstruction 28A is disposed, and a sensor assembly 16A. The sensor assembly 16A includes: two absolute pressure transducers 18A, 20A, reservoirs 22A, 24A, at least one flow path 26A, and a characterized flow restrictor (not shown). The MFC configuration 10B includes a valve assembly 12B, a base having a main flow path 14B and a characterized flow restrictor 28B disposed in the main flow path, and a sensor assembly 16B. The sensor assembly 16B includes: two absolute pressure transducers 18B, 20B, reservoirs 22B, 24B, at least one flow path 26B, and a characterized flow restrictor (not shown).

The MFC configuration 10A is configured to process a fluid at a relatively low flow rate, for example, 0.15 seem to 500 seem (standard cubic centimeters per minute). The specific sccm depends on the gas velocity and the specific value of the target pressure drop across the flow restrictor and may vary according to the specific design and application. MFC configuration 10B is configured to handle higher flow rates (e.g., greater than 500sccm) of fluid. The flow restrictors not shown and the flow restrictor 28B may be designed based on the desired flow rate. In the sensor assemblies 16A, 16B, the volumes of the reservoirs 22A, 24A and 22B, 24B may be configured to have a defined volume based on the application. As an example, for the lowest full scale flow, the volume of 22A may be reduced such that in response to the closing of the upstream valve (e.g., when switching between gases), the purge time (the time it takes for the pressure in the reservoir 22A to decay as it vents through the flow restrictor 26) is also reduced. The purge time constant is proportional to the volume of the reservoir divided by the MFC full scale flow rate. Thus, a larger full-scale MFC may have a larger reservoir volume required for higher flow without being adversely affected by longer drain times. A well-designed purge time may also reduce or eliminate dead volume in the sensor assemblies 16A, 16B.

In fig. 1B, two other MFC configurations, generally designated 30A and 30B, are illustrated with sensor components having at least one flow path and a reservoir channel having a volume for certain MFC applications. MFC configuration 30A may include a valve assembly 32A, a base having a main flow path 34A, and a sensor assembly 36A. The sensor assembly 36A may include: either two absolute pressure transducers or one absolute pressure transducer-one differential pressure transducer 38A, 40A, reservoirs 42A, 44A, at least one flow path 46A, and a flow restrictor (not shown). The MFC configuration 30A includes a sensor assembly 36A having reservoirs 42A, 44A whose volumes are more suitable for higher flow rate applications because a large portion of the flow passes through the larger passage 42A-1 and a smaller portion of the flow passes through 42A-2 to sweep across the sensor surface. MFC configuration 30B may include a valve assembly 32B, a base having a main flow path 34B, and a sensor assembly 36B. The sensor assembly 36B may include: either two absolute pressure transducers or one absolute pressure transducer-one differential pressure transducer 38B, 40B, reservoirs 42B, 44B, at least one flow path 46B, and a flow restrictor (not shown). MFC configuration 30B includes a sensor assembly 36B having reservoirs 42B and 44B of reduced volumetric sizes, and thus is more suitable for lower flow rate applications due to bleed-off issues. As illustrated, the internal diameter, and thus the total volume, of reservoirs 42A, 44A is greater than the volume of reservoirs 42B, 44B. In the MFC application 30A, the volume of the reservoirs 42A, 44A is considered to be an internal flow path that is fluidly connected and in series with the primary flow path 34A, and within the structure of the sensor assembly 36A, the flow from 34B is split into two parallel paths, with the majority of the flow continuing directly through 42A-1, and a small portion of the flow being diverted to sweep across the surface of the transducer 38A via the passage 42A-2. The flows in 42A-1 and 42A-2 merge at the channel entrance of channel 46A, flow through a characterized flow restrictor, and exit to channel 44A, where the flow is again split into parallel paths 44A-1 and 44A-2, where the flow in 44A-2 is diverted to sweep across the sensor surface and again merges with 44A-1 and exits to the main flow path in MFC base 34B. In MFC application 30B, the lower flow rate does not require shunting of flow paths 42B and 44B, and the entire flow sweeps across the surface of sensors 38B and 40B. In this particular embodiment, the flow velocity is low enough that the entire flow can be directed over the sensor surface without causing velocity related problems.

It should also be understood that any of the primary flow paths 14 may have a featured flow restrictor disposed therein. It should also be understood that the sensor assemblies 16 and 36 may include a combination of absolute and differential pressure transducers. It should also be understood that the pressure transducers 18, 20, 38 and 44 described herein may in practice comprise a semiconductor-based transducer, an oil sump and an isolation diaphragm, wherein fluid traversing the diaphragm generates a force on the diaphragm that is transferred through the oil sump to the transducer for measurement.

Referring now to fig. 2A-2D, block diagrams of sensor assemblies 16, 36 with flow paths and various MFC configurations are shown. In fig. 2A, the sensor assembly 16 includes pressure transducers 18 and 20. In this particular embodiment, transducers 18 and 20 are absolute pressure transducers. The reservoirs 22, 24 include ports 60, 62 for receiving fluid sampled from the main flow path 14 through sampling flow paths 64, 66. In this particular embodiment, the flow path 26 is disposed between the reservoirs 22 and 24, and the featured reservoir 68 is disposed in the flow path. In fig. 2B, the sensor assembly 36 includes: pressure transducers 38, 40, flow path 46, and ports 60A-B, 62A-B. The pressure transducers 38, 40 are an absolute pressure transducer 18 and a differential pressure transducer 40, or two absolute pressure transducers with the pressure sensing surface of the pressure transducer 40 facing 44. The flow path 46 fluidly connects a port 60B on one end of the reservoir 42 with another port 62B on the other end of the reservoir 44. A characterized flow restrictor 68 is disposed within the flow path 46. In both embodiments, the characteristic flow restrictor 70 is disposed within the primary flow path 14, 34 and carries the majority of the flow. However, in fig. 2C and 2D, the primary flow paths 14, 34 do not include the flow restrictors 70. In some applications, neither of the flow restrictors 68 and 70 is required. In MFC applications where lower flow rates do not create gas velocity problems, no flow restrictor 70 is needed. Thus, the design of the MFC is cheaper. In this particular embodiment, the upstream portion of the main flow path 14, 34 continues through the sampling flow path 64, the flow paths 26, 46, the sampling flow path 66, and returns to the downstream portion of the main flow path 14, 34. In this case, the flow restrictor 68 may be designed as desired for a particular application. As used herein, sampling flow paths 64, 66 relate to flow paths that carry the fluid to be measured and are in fluid communication with pressure transducers 38, 40 and traverse transducer ports 60, 62. Although the sensor assemblies 16, 36 are described in a particular transducer configuration, it should be understood that other configurations are possible. Although the primary flow paths 14, 34 have been illustrated and described as flowing from upstream to downstream, it should be understood that the flow of fluid along the primary flow paths 14, 34 may be from downstream to upstream. Obviously, this would mean that the fluid would traverse the reservoirs 22, 24 and the flow paths 26, 46 in opposite directions.

The embodiments of the foregoing disclosure have been presented for purposes of illustration and to enable one of ordinary skill in the art to practice the disclosure, but are not intended to be exhaustive or limited to the disclosure in the form disclosed. Numerous insubstantial modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the disclosure. The scope of the claims is intended to broadly cover the disclosed embodiments and any such modifications. Furthermore, the following clauses represent additional embodiments of the present disclosure and are to be considered within the scope of the present disclosure:

clause 1, an apparatus for removing dead volume in a sensor assembly, the apparatus comprising: a first reservoir connected to the first pressure transducer and having a port in fluid communication at a location in the sampling flow path; a second reservoir connected to a second pressure transducer, fluidly connected to the first reservoir by a flow path, and having another port in fluid communication at another location of another sampling flow path; and a flow restrictor disposed in the flow path;

clause 2, the apparatus of clause 1, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is a transducer selected from the group consisting of another absolute pressure transducer and a differential pressure transducer;

clause 3, the apparatus of clause 1, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is a transducer selected from the group consisting of an absolute pressure transducer and another differential pressure transducer;

clause 4, the apparatus of clause 1, wherein the flow path is between the first reservoir and the second reservoir;

clause 5, the apparatus of clause 1, wherein the flow path fluidly connects one end of the first reservoir with the other end of the second reservoir;

clause 6, the apparatus of clause 1, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by the full scale flow rate of the MFC;

clause 7, the apparatus of clause 1, wherein the volume of the second reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by the full scale flow rate of the MFC;

clause 8, a system for removing dead volume in a sensor assembly of a mass flow controller, the system comprising: a valve assembly in fluid communication with fluid in the main flow path; a pressure sensor assembly in fluid communication with fluid in the primary flow path, the pressure sensor assembly comprising: a first reservoir connected to the first pressure transducer and having a port in fluid communication at a location in the sampling flow path; a second reservoir connected to a second pressure transducer, fluidly connected to the first reservoir by a flow path, and having another port in fluid communication at another location of another sampling flow path; wherein the first pressure transducer and the second pressure transducer are communicably connected to the valve assembly;

clause 9, the system of clause 8, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is a transducer selected from the group consisting of another absolute pressure transducer and a differential pressure transducer;

clause 10, the system of clause 8, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is a transducer selected from the group consisting of an absolute pressure transducer and another differential pressure transducer;

clause 11, the system of clause 8, wherein the flow path is between the first reservoir and the second reservoir;

clause 12, the system of clause 11, wherein the flow path fluidly connects one end of the first reservoir with the other end of the second reservoir;

clause 13, the system of clause 8, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by the full scale flow rate of the MFC;

clause 14, the system of clause 13, wherein the volume of the second reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by the full scale flow rate of the MFC;

clause 15, a method for removing dead volume in a sensor assembly of a mass flow controller, the method comprising: pumping fluid from the primary flowpath through a port into a first reservoir connected to a first pressure transducer; and pumping fluid from the first reservoir to a second reservoir connected to a second pressure transducer through a flow path and through another port;

clause 16, the method of clause 15, wherein the first pressure transducer is an absolute pressure transducer and the second pressure transducer is a transducer selected from the group consisting of another absolute pressure transducer and a differential pressure transducer;

clause 17, the method of clause 15, wherein the second pressure transducer is a differential pressure transducer and the second pressure transducer is a transducer selected from the group consisting of an absolute pressure transducer and another differential pressure transducer;

clause 18, the method of clause 15, further comprising: pumping fluid from the first reservoir through the flow path, wherein the flow path is between the first reservoir and the second reservoir;

clause 19, the method of clause 18, further comprising: pumping fluid from the first reservoir through the flow path, wherein the flow path fluidly connects one end of the first reservoir with another end of the second reservoir; and

clause 20, the method of clause 15, wherein the volume of the first reservoir is determined based on a purge time determined by dividing the volume in the respective reservoir by the full scale flow rate of the MFC.