Method of measuring gas flow and method of calibrating a flow controller

Abstract

The present application relates to a method for measuring gas flow, comprising the following steps: S1, providing a chamber with a fixed volume for processing wafers, providing at least a first flow controller with high measurement accuracy and at least a second flow controller, the first flow controller and the second flow controller are connected in parallel; S2, using only the first flow controller to provide a first gas with a known flow to the chamber, and obtaining a calibration factor; S3, using only the second flow controller to provide a second gas to the chamber, 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 gas flow provided by the present application can be applied to the calibration of flow controllers with large flow, and the flow calibration can be carried out in a high temperature environment.

Description

Technical Field

[0001] This invention relates to the field of semiconductor gas flow detection, and more specifically to a method for measuring gas flow and a method for calibrating a flow controller. Background Technology

[0002] In the semiconductor manufacturing process, it is necessary to accurately control and monitor the flow rate of various process gases.

[0003] Commonly used gas flow control devices in semiconductor equipment include mass flow controllers (MFCs) and flow restrictors (FRs). MFCs have the following problems: an accuracy error of ±2% of the set value exists within the measurement range, and this error is non-linearly distributed within the range, changing with usage time. FRs have the following problems: due to manufacturing errors, the accurate flow rate limited during use cannot be obtained.

[0004] Currently, the most common equipment for calibrating MFCs, the Mass Flow Verifier (MFV), can only calibrate small-flow MFCs or FRs (below 3000 sccm) and has high requirements for ambient temperature (300K). It cannot meet the calibration needs of large-flow MFCs, FRs, and high-temperature environments. Furthermore, FRs need to be calibrated before use to determine the accurate flow rate limit during use. Summary of the Invention

[0005] To address the flow calibration and measurement issues of high-flow-rate flow controllers, this invention proposes a method for measuring gas flow rate, comprising the following steps: S1. A chamber with a fixed volume for processing wafers is provided, at least one first flow controller with accurate measurement is provided, and at least one second flow controller is provided, wherein the first flow controller and the second flow controller are connected in parallel; S2. Using only the first flow controller, supply the chamber with a first gas at a known flow rate to obtain a calibration factor; S3. The second gas is supplied to the chamber using only one of the second flow controllers, and the flow rate of the second flow controller is obtained based on the pressure change of the chamber over time and the calibration factor.

[0006] Furthermore, the calibration factor is a mathematical relationship between the known flow rate of the first gas under the current conditions and the reciprocal of the pressure change of the chamber over time, obtained by deriving from the ideal gas law.

[0007] Furthermore, the calibration factor is: ; Among them, the The known flow rate of the first gas is... It is the reciprocal of the change in chamber pressure of the first gas within the chamber over time.

[0008] Furthermore, the flow rate of the second flow controller Through formula Obtain, wherein, the It is the calibration factor, the It is the change in pressure of the second gas in the chamber over time.

[0009] Furthermore, the first gas and the second gas are the same gas.

[0010] Furthermore, there is one first flow controller and two second flow controllers.

[0011] Furthermore, the first flow controller with accurate measurement is calibrated using a mass flow detector.

[0012] Furthermore, the chamber is at least one of an epitaxial chamber, a CVD chamber, a rapid thermal processing chamber, and an etching chamber.

[0013] Furthermore, the calibration factor is a constant related to the gas type and gas temperature.

[0014] Furthermore, the calibration factor is: ; V It is the volume of the chamber. T It is the temperature of the gas inside the chamber. R It is the molar gas constant. It is a coefficient related to the type of gas.

[0015] The present invention also proposes a method for calibrating a flow controller, wherein the flow rate obtained by the method for measuring gas flow rate is used to calibrate the flow controller.

[0016] The method for measuring gas flow provided by this invention is applicable to the calibration of flow controllers with large flow rates and can be used for flow calibration in high-temperature environments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of an epitaxial device structure provided in an embodiment of the present invention; Figure 2 This is a flowchart of the method for measuring gas flow rate according to the present invention. Detailed Implementation

[0018] The method for measuring gas flow rate and the method for calibrating a mass flow controller proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] This invention proposes a method for measuring gas flow rate and a method for calibrating a flow controller. The method is primarily applied to measuring gas flow rate on semiconductor equipment. The semiconductor equipment should have a chamber of fixed volume, which can be at least one of an epitaxial chamber, a CVD chamber, a rapid thermal processing chamber, and an etching chamber. Taking an epitaxial device as an example, such as… Figure 1As shown, this example provides an epitaxial device to illustrate the content of the present invention. The epitaxial device includes a chamber, a gas supply line, a heating device 104, a thermometer 105, connecting lines, a gas supply device 110, a pressure sensor 12, a mass flow detector 13 (MFV), an exhaust line, and a pump 109. The chamber includes a quartz upper dome 101 and a lower dome 102, which are connected by a flange 106 to form a sealed chamber. A base 103 for supporting a wafer is also provided in the chamber, and the base 103 is horizontally supported in the chamber by a support body. The heating device 104 and the thermometer 105 are located at the top and bottom of the chamber, respectively. The heating device 104 is used to radiate infrared rays into the chamber to heat the wafer, and the thermometer 105 is used to monitor the temperature inside the chamber. An air inlet 107 and an exhaust outlet 108 are provided on the side of the chamber. The air inlet 107 is connected to one end of a parallel air supply pipeline, and the other end of the air supply pipeline is connected to the air supply device 110 via a connecting pipeline. Each air supply pipeline is equipped with a flow controller and a first valve, the first valve being used to control the on / off state of the corresponding air supply pipeline. The number of flow controllers is the same as the number of air supply pipelines, so as to achieve zoned air control on the wafer surface. Optionally, there are at least two air supply pipelines; for example, four air supply pipelines, each equipped with a flow controller, then the wafer surface will form four zones with independently controlled airflow. The exhaust outlet 108 is connected to the pump 109 via an exhaust pipeline, used to discharge the process gas after processing from the chamber. The pressure sensor 12 is located at the exhaust outlet 108, used to measure the pressure value inside the chamber.

[0021] In this example, the gas supply lines are configured with three lines, and at least one of the gas supply lines is equipped with a first flow controller 10 for accurate measurement, used to supply gas with a known flow rate to the chamber. At least one gas supply line is equipped with a second flow controller 11, the flow rate of which is measured and calibrated by the first flow controller 10. Optionally, there may be one first flow controller 10 and two second flow controllers 11. Alternatively, there may be more than one first flow controller 10 and one or more second flow controllers 11. It should be noted that the device provided in this example is only used to exemplify the device structure for implementing the gas flow measurement method of the present invention, and does not specifically limit the type or structure of the device.

[0022] The first flow controller 10 is also connected to a mass flow detector 13, and is connected to the pump 109 through the mass flow detector 13. The first flow controller 10 can calibrate its flow rate at low flow rates through the mass flow detector 13 to achieve accurate flow measurement. The calibrated gas is then drawn away by the pump 109. Optionally, one end of the mass flow detector 13 is connected to a gas supply line with the first flow controller 10 via a gas path, and the other end of the mass flow detector 13 is connected to an exhaust line via a gas path. The gas path upstream of the mass flow detector 13 is located downstream of the first flow controller 10. The gas path upstream of the mass flow detector 13 is also equipped with a second valve, and the gas path downstream of the mass flow detector 13 is equipped with a third valve. The second and third valves are used to control whether gas is introduced into the mass flow detector 13.

[0023] In this invention, the first flow controller 10 can be calibrated by the mass flow detector 13, but the accuracy of the second flow controller 11 changes after a period of use, so it also needs to be calibrated.

[0024] In response, this invention also proposes a method for measuring gas flow rate, which can be used to calibrate high-flow-rate flow controllers, such as... Figure 2 As shown, the method includes the following steps: S1. A chamber with a fixed volume for processing wafers is provided, along with at least one first flow controller 10 with accurate measurement and at least one second flow controller 11, wherein the first flow controller 10 and the second flow controller 11 are connected in parallel; wherein the chamber is... Figure 1 The chamber of the semiconductor device described herein.

[0025] S2. Using only the first flow controller 10, supply the chamber with a first gas at a known flow rate to obtain a calibration factor; S3. The second gas is supplied to the chamber using only one second flow controller 11, and the flow rate of the second flow controller is obtained based on the change of pressure in the chamber over time and the calibration factor.

[0026] The method for measuring gas flow rate proposed in this invention can measure and calibrate MFC or FR with any range, especially a large range, and is not limited by temperature, and can perform flow rate measurement and calibration over a wide temperature range.

[0027] Optionally, in step S1, the specific method for providing at least one accurate first flow controller 10 is as follows: calibrating the flow rate of the first flow controller 10 using a mass flow detector 13, thereby providing an accurate first flow controller 10. Specifically, the first valve on the gas supply line where the first flow controller 10 is installed is opened, the first valves on other gas supply lines are closed, and the second and third valves are opened simultaneously. Gas is introduced into the mass flow detector 13 through only one gas supply line where the first flow controller 10 is installed. At this time, the gas does not enter the chamber but only enters the mass flow detector 13, and is then pumped away, thereby calibrating the first flow controller 10.

[0028] In step S2, specifically, as follows: Figure 1 As shown, the first valve on the gas supply line equipped with the first flow controller 10 is opened, the first valves on other gas supply lines are closed, and the second and third valves are closed. Only one gas supply line equipped with the first flow controller 10 is used to supply the chamber with the first gas. Since the first flow controller 10 is accurate, it can measure the accurate flow rate at this time, i.e., the known flow rate. The calibration factor can be obtained through the above steps.

[0029] In step S3, specifically, as follows: Figure 1 As shown, the first valve on a gas supply line equipped with a second flow controller 11 is opened, the first valve on other gas supply lines is closed, and the second and third valves are closed. The second gas is supplied to the chamber using only the gas supply line equipped with the second flow controller 11. The pressure change of the chamber over time is obtained, and the flow rate of the second flow controller 11 is obtained based on the pressure change of the chamber over time and the calibration factor.

[0030] Optionally, the calibration factor is a mathematical relationship between the known flow rate of the first gas under current conditions and the reciprocal of the pressure change in the chamber over time, derived from the ideal gas law. The specific derivation process is as follows: According to the ideal gas law We obtain the following formula: (1); Therefore, from the above equation (1), we can obtain: (2) And because, (3) Therefore, from equations (2) and (3), we can obtain: (4); therefore, (5); in, P It is the pressure in the chamber. V It is the volume of the chamber. T It is the temperature of the gas inside the chamber. n It is the amount of substance of the gas. R It is the molar gas constant. Indicates in The change in chamber pressure over time, It is a coefficient related to the type of gas. Indicates flow rate. This represents the calibration factor.

[0031] As can be seen from equation (5) above, the calibration factor k can be the known flow rate of the first gas ( ) and the reciprocal of the pressure change in the chamber over time ( The mathematical relationship between them, namely ; As can be seen from equation (5) above, the calibration factor k can also be a constant related to the gas type and gas temperature, i.e. .

[0032] The flow rate of the second flow controller 11 Through formula Obtain, wherein, the It is the above calibration factor (which can be) or ), the It is the change in pressure of the second gas in the chamber over time.

[0033] For calibration factor Among them, the known flow rate The reciprocal of the change in chamber pressure over time All of these are readily available, the aforementioned The pressure is obtained through pressure sensor 12, and therefore the flow rate of the second flow controller 11 can be easily calculated using this calibration factor. .

[0034] For calibration factor Among them, the molar gas constant R, the temperature T of the gas in the chamber, and the coefficient a related to the gas type are easily obtained; the temperature T of the gas in the chamber is obtained by a thermometer 105, but the volume of the chamber... V Precise values ​​are not easily obtained, therefore the flow rate of the second flow controller 11 obtained through this calibration factor is... Inaccurate, but the volume of the chamber. V It can be achieved through calibration factor The calibration factor is calculated, specifically through equation (5). It can achieve secondary auxiliary calibration, that is, first through calibration factor Calibration, and then through calibration factor Auxiliary calibration.

[0035] Furthermore, the calibration factor can be determined from the above formula. This is a constant related to the gas type and gas temperature. Based on this, the first gas and the second gas should be the same gas. Preferably, both the first gas and the second gas are hydrogen, which can further increase the obtained flow rate. This improves the accuracy of the calibration of the second flow controller 11.

[0036] In this invention, through formula The calculated flow rate of the second flow controller 11 It can be used to calibrate the flow rate of the second flow controller 11.

[0037] 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 limiter (FR).

[0038] The method for measuring gas flow provided by this invention is applicable to the calibration of flow controllers with large flow rates and can be used for flow calibration in high-temperature environments.

[0039] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for measuring gas flow rate, characterized in that, Includes the following steps: S1. A chamber with a fixed volume for processing wafers is provided, at least one first flow controller with accurate measurement is provided, and at least one second flow controller is provided, wherein the first flow controller and the second flow controller are connected in parallel; S2. Using only the first flow controller, supply the chamber with a first gas at a known flow rate to obtain a calibration factor; the calibration factor is: ; wherein, the The known flow rate of the first gas is... It is the reciprocal of the change in pressure of the first gas in the chamber over time; S3. Using only one of the second flow controllers, supply the second gas to the chamber, and obtain the flow rate of the second flow controller based on the pressure change of the chamber over time and the calibration factor; the flow rate of the second flow controller... Through formula Obtain, wherein, the It is the calibration factor, the It is the change in pressure of the second gas in the chamber over time; the first gas and the second gas are the same gas.

2. The method for measuring gas flow rate as described in claim 1, characterized in that, There is one first flow controller and two second flow controllers.

3. The method for measuring gas flow rate as described in claim 1, characterized in that, The first flow controller, which measures accurately, is calibrated using a mass flow detector.

4. The method for measuring gas flow rate as described in claim 1, characterized in that, The chamber is at least one of an epitaxial chamber, a CVD chamber, a rapid thermal processing chamber, and an etching chamber.

5. The method for measuring gas flow rate as described in claim 1, characterized in that, The calibration factor is a constant related to the gas type and gas temperature.

6. The method for measuring gas flow rate as described in claim 5, characterized in that, The calibration factor is: ; V It is the volume of the chamber. T It is the temperature of the gas inside the chamber. R It is the molar gas constant. It is a coefficient related to the type of gas.

7. A method for calibrating a flow controller, characterized in that, The flow rate of the second flow controller is obtained using the gas flow measurement method according to any one of claims 1-6. And based on the acquired traffic Calibrate the second flow controller.

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