FIELD

This disclosure relates to electronic device manufacturing and, more particularly, to verifying mass flow rates of mass flow controllers based on choked flow principles.

BACKGROUND

Electronic device manufacturing systems may include one or more mass flow controllers (MFCs). MFCs control the mass flow rates of process chemistries used in the manufacture of electronic devices. Process chemistries may include various gases (e.g., cleaning, deposition, and etchant gases) that are delivered to one or more process chambers in which electronic circuits may be fabricated on semiconductor wafers, glass plates, or the like. Precise mass flow control of process chemistries may be used in one or more steps of an electronic device's fabrication process. Precise mass flow control provided by MFCs may contribute to high yield production of electronic devices having microscopically small dimensions.

To ensure that process chemistries are delivered accurately, verification and calibration of MFC's may be performed periodically. However, verifying and calibrating MFCs may involve additional bulky and expensive equipment that may be time-consuming and inefficient to use, may be limited to low mass flow rate ranges (e.g., up to only 3000 seem (standard cubic centimeter per minute) nitrogen equivalent), may result in notable process downtime, and/or may not be sufficiently accurate to ensure precise mass flow control of process chemistries.

SUMMARY

According to a first aspect, a mass flow verification system is provided. The mass flow verification system comprises an inlet; a first pressure sensor and a temperature sensor each coupled downstream of the inlet; a plurality of isolation valves coupled downstream of the inlet; a plurality of differently-sized flow restrictors coupled in parallel and downstream of the inlet, each one of the plurality of differently-sized flow restrictors coupled in series with the inlet and a respective one of the plurality of isolation valves; an outlet coupled downstream of and in series with each one of the plurality of differently-sized flow restrictors; and a controller coupled to the first pressure sensor, the temperature sensor, and the plurality of isolation valves, wherein the controller is configured to determine a mass flow rate in response to a temperature measured by the temperature sensor under a choked flow condition and a first pressure measured by the first pressure sensor under the choked flow condition.

According to a second aspect, an electronic device manufacturing system is provided. The electronic device manufacturing system comprises a mass flow controller; a mass flow verification system having an inlet and an outlet, the inlet coupled to the mass flow controller; a controller; and a process chamber coupled to a flow path coupled to the mass flow controller and configured to receive one or more process chemistries via the mass flow controller. The mass flow verification system comprises a plurality of isolation valves coupled downstream of the inlet, and a plurality of differently-sized flow restrictors coupled in parallel and downstream of the inlet, each one of the plurality of differently-sized flow restrictors coupled in series with the inlet, a respective one of the plurality of isolation valves, and the outlet. The controller is coupled to the plurality of isolation valves and is configured to receive a pressure measurement and a temperature measurement upstream of the plurality of differently-sized flow restrictors under a choked flow condition through only one of the plurality of isolation valves. The controller is also configured to determine a mass flow rate in response to receiving the pressure measurement and the temperature measurement.

According to a third aspect, a method of verifying a mass flow rate is provided. The method comprises causing a gas to flow through only one of a plurality of differently-sized flow restrictors during a choked flow condition; measuring a pressure upstream of the one of the plurality of differently-sized flow restrictors to obtain a measured pressure value during the choked flow condition; measuring a temperature upstream of the one of the plurality of differently-sized flow restrictors to obtain a measured temperature value during the choked flow condition; and determining a mass flow rate by applying a predetermined flow restrictor coefficient, a predetermined gas correction factor, and a predetermined temperature value to the measured pressure value and the measured temperature value.

Still other aspects, features, and advantages in accordance with these and other embodiments of the disclosure may be readily apparent from the following detailed description, the appended claims, and the accompanying drawings. Accordingly, the drawings and descriptions herein are to be regarded as illustrative in nature, and not as restrictive.

