CN117810130A - Method for measuring gas flow and method for calibrating flow controller - Google Patents
Method for measuring gas flow and method for calibrating flow controller Download PDFInfo
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- CN117810130A CN117810130A CN202311862625.4A CN202311862625A CN117810130A CN 117810130 A CN117810130 A CN 117810130A CN 202311862625 A CN202311862625 A CN 202311862625A CN 117810130 A CN117810130 A CN 117810130A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
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Abstract
The invention relates to a method for measuring gas flow, comprising the following steps: s1, providing a chamber with a fixed volume for processing a wafer, providing at least one first flow controller with accurate measurement and at least one second flow controller, wherein the first flow controller is connected with the second flow controller in parallel; s2, providing a first gas with a known flow rate to the chamber by using only one first flow rate controller to obtain a calibration factor; and S3, providing a second gas for the chamber by only using one second flow controller, and obtaining the flow of the second flow controller according to the time-dependent change of the pressure of the chamber and the calibration factor. The method for measuring the gas flow is applicable to the calibration of a high-flow controller, and can be used for flow calibration in a high-temperature environment.
Description
Technical Field
The invention relates to the field of semiconductor gas flow detection, in particular to a method for measuring gas flow and a method for calibrating a flow controller.
Background
In the semiconductor manufacturing process, accurate control and monitoring of the gas flow of various process gases are required.
Common Flow control devices for gases in semiconductor devices include mass Flow controllers (Mass Flow Controller, MFC) and Flow Restrictors (FR). Among them, MFC has the following problems: the accuracy error of +/-2% of the set value exists in the range, the error is distributed in a nonlinear manner in the range, and the accuracy error can change along with the increase of the service time. FR has the following problems: due to manufacturing errors, accurate flow rates limited during use cannot be obtained.
The current common mass flow detector (Mass Flow Verifier, MFV) for equipment with calibrated MFC can only calibrate small-flow MFC or FR (below 3000 sccm), has high requirement on ambient temperature (300K), cannot meet the calibration requirements of large-flow MFC, FR and high-temperature environment, and requires calibration before FR use to determine the accurate flow limited in the use process.
Disclosure of Invention
In order to solve the problems of flow calibration and measurement of a large-flow controller, the invention provides a method for measuring gas flow, which comprises the following steps:
s1, providing a chamber with a fixed volume for processing a wafer, providing at least one first flow controller with accurate measurement and at least one second flow controller, wherein the first flow controller is connected with the second flow controller in parallel;
s2, providing a first gas with a known flow rate to the chamber by using only one first flow rate controller to obtain a calibration factor;
and S3, providing a second gas for the chamber by only using one second flow controller, and obtaining the flow of the second flow controller according to the time-dependent change of the pressure of the chamber and the calibration factor.
Further, the calibration factor is a mathematical relationship between the known flow rate of the first gas and the inverse of the pressure of the chamber over time under the current conditions derived from an ideal gas state equation.
Further, the calibration factor is:
k＝f 1 ·Δt 1 /ΔP 1 ；
wherein said f 1 Is the known flow of the first gas, Δt 1 /ΔP 1 Is the inverse of the pressure of the first gas in the chamber over time.
Further, the flow f of the second flow controller 2 By formula f 2 ＝(ΔP 2 /Δt 2 ) K, wherein k is the calibration factor, ΔP 2 /Δt 2 Is the pressure of the second gas in the chamber over time.
Further, the first gas and the second gas are the same gas.
Further, the number of the first flow controllers is one, and the number of the second flow controllers is two.
Further, the first flow controller with accurate measurement is calibrated through a mass flow detector.
Further, the chamber is at least one of an epitaxial chamber, a CVD chamber, a rapid thermal processing chamber, and an etch chamber.
Further, the calibration factor is a constant related to the gas type and the gas temperature.
Further, the calibration factor is: k=v/(r·t·a); v is the volume of the chamber, T is the temperature of the gas within the chamber, R is the molar gas constant, and a is a coefficient related to the gas type.
The invention also provides a method for calibrating the flow controller, and the flow calibration flow controller obtained by adopting the method for measuring the gas flow.
The method for measuring the gas flow is applicable to the calibration of a high-flow controller, and can be used for flow calibration in a high-temperature environment.
Drawings
Fig. 1 is a schematic structural diagram of an epitaxy apparatus according to an embodiment of the present invention;
FIG. 2 is a flow chart of a method of measuring gas flow according to the present invention.
Detailed Description
The method of measuring gas flow and the method of calibrating a mass flow controller according to the present invention are described in further detail below with reference to the accompanying drawings and detailed description.
It is noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The invention provides a method for measuring gas flow and a method for calibrating a flow controller, which are mainly applied to semiconductor equipment, wherein the semiconductor equipment is provided with a chamber with a fixed volume, and the chamber can be at least one of an epitaxial chamber, a CVD chamber, a rapid thermal processing chamber and an etching chamber. Taking an epitaxial apparatus as an example, as shown in fig. 1, this example provides an epitaxial apparatus for illustrating the content of the present invention, the epitaxial apparatus includes a chamber, a gas supply pipeline, a heating device 104, a thermometer 105, a connection pipeline, a gas supply apparatus 110, a pressure sensor 12, a mass flow detector 14 (MFV), a gas exhaust pipeline, and a pump 109, the chamber includes an upper dome 101 and a lower dome 102 made of quartz, and the upper dome 101 and the lower dome 102 are connected by a flange 106 to form a sealed chamber. A susceptor 103 for carrying a wafer is also provided in the chamber, the susceptor 103 being horizontally supported in the chamber by a support body. The heating device 104 and the thermometer 105 are arranged at the top and the bottom of the chamber, the heating device 104 is used for radiating infrared rays to the chamber to heat the wafer, and the thermometer 105 is used for monitoring the temperature in the chamber. The side of the chamber is provided with an air inlet 107 and an air outlet 108 opposite to the air inlet, the air inlet 107 is connected with one end of an air supply pipeline connected in parallel, and the other end of the air supply pipeline is connected with an air supply device 110 through a connecting pipeline; each air supply pipeline is provided with a flow controller and a first valve, and the first valve is used for controlling the on-off of the corresponding air supply pipeline; the number of the flow controllers is the same as that of the air supply pipelines so as to realize regional air control on the surface of the wafer. Optionally, the air supply pipeline is at least two paths; for example, four gas supply lines, each with a flow controller, will form four zones on the wafer surface that each independently control the gas flow. The exhaust port 108 is connected to the pump 109 via an exhaust line for exhausting the processed process gas from the chamber. The pressure sensor 12 is disposed at the exhaust port 108 for measuring a pressure value in the chamber.
In this example, the gas supply lines are arranged in three ways, and at least one of the gas supply lines is provided with a first flow controller 10 with accurate measurement for supplying a known flow of gas to the chamber, and at least one of the gas supply lines is provided with a second flow controller 11, the flow of the second flow controller 11 being measured and calibrated by the first flow controller 10. Alternatively, the number of first flow controllers 10 is one, and the number of second flow controllers 11 is two. Of course, alternatively, the first flow controller 10 may be more than one, and the second flow controller 10 may be one or more than two. The apparatus provided in this example is merely for illustrating the construction of an apparatus for implementing the method for measuring a gas flow rate of the present invention, and the kind and structure of the apparatus are not particularly limited.
The first flow controller 10 is also connected to a mass flow detector 14 and to the pump 109 via the mass flow detector 14. The first flow controller 10 can calibrate its flow rate at small flow rates via the mass flow detector 14 to achieve accurate flow rates, and the calibrated gas is pumped away by the pump 109. Optionally, one end of the mass flow detector 14 is connected with an air supply pipeline provided with the first flow controller 10 through an air path, and the other end of the mass flow detector 14 is connected with an air exhaust pipeline through an air path; the gas circuit upstream of the mass flow detector 14 is arranged downstream of the first flow controller 10; the gas path upstream of the mass flow detector 14 is further provided with a second valve, the gas path downstream of the mass flow detector 14 is provided with a third valve, and the second valve and the third valve are used for controlling whether the mass flow detector 14 is filled with gas.
In the present invention, the first flow controller 10 can be calibrated by the mass flow detector 14, but the second flow controller 11 will change its accuracy after a period of use, and therefore also require calibration.
In this regard, the present invention also proposes a method for measuring a gas flow rate, which can be used to calibrate a high-flow rate controller, as shown in fig. 2, the method comprising the steps of:
s1, providing a chamber with a fixed volume for processing a wafer, providing at least one first flow controller 10 with accurate measurement and at least one second flow controller 11, wherein the first flow controller 10 is connected with the second flow controller 11 in parallel; wherein the chamber is the chamber of the semiconductor device described in fig. 1.
S2, providing a first gas with a known flow rate to the chamber by using only one first flow controller 10 to obtain a calibration factor;
and S3, supplying a second gas to the chamber by using only one second flow controller 11, and obtaining the flow of the second flow controller according to the change of the pressure of the chamber with time and the calibration factor.
The method for measuring the gas flow can measure and calibrate the MFC or FR of any measuring range, especially wide measuring range, is not limited by temperature, and can measure and calibrate the flow in a wide temperature range.
Optionally, in the step S1, the specific method for providing at least one first flow controller 10 with accurate measurement is as follows: the flow of the first flow controller 10 is calibrated by the mass flow detector 14 to provide a measured accurate first flow controller 10. Specifically, a first valve on the gas supply pipeline provided with the first flow controller 10 is opened, the first valves on other gas supply pipelines are closed, the second valve and the third valve are opened simultaneously, gas is introduced into the mass flow detector 14 only by using one gas supply pipeline provided with the first flow controller 10, and at the moment, the gas does not enter the chamber, only enters the mass flow detector 14 and is pumped away, so that the calibration of the first flow controller 10 is realized.
In the step S2, specifically, as shown in fig. 1, a first valve on the gas supply line provided with the first flow controller 10 is opened, the first valves on the other gas supply lines are closed, the second valve and the third valve are closed, and the first gas is supplied to the chamber only by using one gas supply line provided with the first flow controller 10, and since the first flow controller 10 is accurate in measurement, it can measure the accurate flow at this time, that is, the known flow. The calibration factor can be obtained by the above steps.
In the step S3, specifically, as shown in fig. 1, a first valve on a gas supply line provided with a second flow controller 11 is opened, first valves on other gas supply lines are closed, the second valve and a third valve are closed, and only a gas supply line provided with the second flow controller 11 is used to supply the second gas to the chamber, so as to obtain the change of the pressure of the chamber with time, and the flow of the second flow controller 11 is obtained according to the change of the pressure of the chamber with time and the calibration factor.
Optionally, the calibration factor is a mathematical relationship between the known flow rate of the first gas and the inverse of the pressure of the chamber over time under current conditions derived from an ideal gas state equation. The specific deduction process is as follows:
the following formula is obtained from the ideal gas state equation p·v=n·r·t,
Δn/Δt＝(ΔP·V)/(Δt·R·T)＝a·F (1)；
thus, it can be obtained from the above formula (1):
F＝(ΔP·V)/(Δt·R·Ta) (2)
and because of the fact that,
F＝(ΔP/Δt)·k (3)
then, from the formula (2) and the formula (3):
F＝(ΔP·V)/(Δt·R·T·a)＝(ΔP/Δt)·K (4)；
thus, the first and second substrates are bonded together,
k＝V/(R·T·a)＝F·Δt/AP (5)；
where P is the pressure of the chamber, V is the volume of the chamber, T is the temperature of the gas in the chamber, n is the amount of substance of the gas, R is the molar gas constant, Δp represents the variation of the chamber pressure over a time Δt, a is a coefficient related to the gas type, F represents the flow rate, and k represents the calibration factor.
As can be seen from equation (5) above, the calibration factor k may be the known flow rate (f 1 ) Reciprocal of the pressure of the chamber over time (Δt 1 /ΔP 1 ) Mathematical relationship between, i.e. k=f 1 ·Δt 1 /ΔP 1 ；
As can be seen from the above equation (5), the calibration factor k may also be a constant related to the gas type and the gas temperature, i.e., k=v/(r·t·a).
The flow f of the second flow controller 11 2 By formula f 2 ＝(ΔP 2 /Δt 2 ) K, where k is the above calibration factor (may be f 1 ·Δt 1 /ΔP I Or V/(R.T.a)), the ΔP 2 /Δt 2 Is the pressure of the second gas in the chamber over time.
For the calibration factor k=f 1 ·Δt 1 /ΔP 1 Wherein the flow rate f is known 1 And the inverse Δt of the pressure of the chamber over time 1 /ΔP 1 Are all readily available, said ΔP 1 Obtained by means of the pressure sensor 12, the flow f of the second flow controller 11 can thus be calculated conveniently by means of this calibration factor 2 。
For the calibration factor k=v/(r·t·a), where the molar gas constant R, the temperature T of the gas in the chamber, the coefficient a related to the gas type are easily obtained; the temperature T of the gas in the chamber is obtained by the thermometer 105, but the volume V of the chamber is not easily obtained with an accurate value, so the flow f of the second flow controller 11 is obtained by the calibration factor 2 Inaccuracy, but the volume V of the chamber may be adjusted by a calibration factor k=f 1 ·Δt 1 /ΔP 1 The calculation is carried out in particular by means of the formula (5), so that the calibration factor k=v/(r·t·a) makes it possible to carry out a secondary auxiliary calibration, i.e. by means of the calibration factor k=f first 1 ·Δt 1 /ΔP 1 Calibration is assisted by a calibration factor k=v/(r·t·a).
Further, it is understood from the above equation that the calibration factor k=v/(r·t·a) is a constant related to the type of gas and the temperature of the gas, and based on this, the first gas and the second gas should be the same gas, and preferably, the first gas and the second gas are both hydrogen gas, so that the obtained flow rate f can be further increased 2 Thereby improving the accuracy of the calibration of the second flow controller 11.
In the present invention, the formula f is used 2 ＝(ΔP 2 /Δt 2 ) The flow f of the second flow controller 11 obtained by calculation of k 2 May be used to calibrate the flow of the second flow controller 11.
In this example, the first flow controller is a Mass Flow Controller (MFC), and the second flow controller is at least one of a Mass Flow Controller (MFC), a Mass Flow Meter (MFM), or a Flow Restrictor (FR).
The method for measuring the gas flow is applicable to the calibration of a high-flow controller, and can be used for flow calibration in a high-temperature environment.
While the present invention has been described in detail through the foregoing description of the preferred embodiment, it should be understood that the foregoing description is not to be considered as limiting the invention. Many modifications and substitutions of the present invention will become apparent to those of ordinary skill in the art upon reading the foregoing. Accordingly, the scope of the invention should be limited only by the attached claims.
Claims (11)
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118567328A (en) * | 2024-05-16 | 2024-08-30 | 大连皓宇电子科技有限公司 | A mass flow controller calibration method and system |
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| CN118567328A (en) * | 2024-05-16 | 2024-08-30 | 大连皓宇电子科技有限公司 | A mass flow controller calibration method and system |
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