Methods and apparatus for enhanced flow detection repeatability of thermal-based mass flow controllers (mfcs)

Abstract

An electronic device manufacturing system includes a mass flow controller (MFC) that has a thermal flow sensor. The thermal flow sensor may measure a mass flow rate and may include a sensor tube having an inner surface coated with a material to form an inner barrier layer. The inner barrier layer may prevent or substantially reduce the likelihood of a corrosive reaction from occurring on the inner surface, which may prevent or reduce the likelihood of the MFC drifting beyond the MFC's mass flow rate accuracy specifications. This may improve the repeatability of flow detection by the MFC. Methods of measuring and controlling a mass flow rate in an electronic device manufacturing system are also provided, as are other aspects.

What is claimed is: 
     
         1 . A mass flow controller comprising:
 an inlet port;   an outlet port;   a thermal flow sensor configured to measure a mass flow rate of a gas flowing through the mass flow controller, the thermal flow sensor having a sensor tube, the sensor tube having an input coupled to the inlet port, the sensor tube also having an output, an inner surface, and an outer surface, the inner surface coated with an inner barrier layer comprising a first material and the outer surface coated with an outer barrier layer comprising at least one of the first material or a second material, wherein the first material comprises tantalum pentoxide or aluminum oxide;   a flow rate control valve coupled between the output of the sensor tube and the outlet port, the flow rate control valve configured to increase or decrease the mass flow rate of the gas flowing through the mass flow controller; and   a controller configured to receive sensor information from the thermal flow sensor and to operate the flow rate control valve.   
     
     
         2 . The mass flow controller of  claim 1 , wherein the outer barrier layer comprises the second material, and wherein the second material is different from the first material. 
     
     
         3 . The mass flow controller of  claim 1 , wherein the inner barrier layer is an atomic layer deposition (ALD) deposited layer. 
     
     
         4 . The mass flow controller of  claim 1 , wherein the inner barrier layer comprises a single layer. 
     
     
         5 . The mass flow controller of  claim 1 , wherein the inner barrier layer comprises a plurality of layers. 
     
     
         6 . The mass flow controller of  claim 1 , wherein the outer barrier layer comprises a single layer. 
     
     
         7 . The mass flow controller of  claim 1 , wherein the outer barrier layer comprises a plurality of layers. 
     
     
         8 . The mass flow controller of  claim 1 , wherein the first material comprises aluminum oxide. 
     
     
         9 . The mass flow controller of  claim 1 , wherein the first material comprises tantalum pentoxide. 
     
     
         10 . The mass flow controller of  claim 1 , wherein the outer barrier layer comprises the second material, and wherein the second material comprises tantalum pentoxide. 
     
     
         11 . The mass flow controller of  claim 1 , wherein the inner barrier layer has a thickness of 50 nm to 150 nm. 
     
     
         12 . The mass flow controller of  claim 1 , wherein the outer barrier layer has a thickness of 50 nm to 150 nm. 
     
     
         13 . The mass flow controller of  claim 1 , wherein the sensor tube has an inside diameter of 1.3 mm to 1.7 mm. 
     
     
         14 . The mass flow controller of  claim 1 , wherein the sensor tube comprises stainless steel. 
     
     
         15 . The mass flow controller of  claim 1 , further comprising a bypass flow path coupled between the inlet port and the flow rate control valve, the bypass flow path coupled parallel to the thermal flow sensor. 
     
     
         16 . An electronic device manufacturing system, comprising:
 a process chamber having a substrate support;   a gas delivery system including a gas supply and a mass flow controller, the mass flow controller including a thermal flow sensor having a sensor tube, the sensor tube having an input, an output, an inner surface, and an outer surface, the inner surface coated with an inner barrier layer comprising a first material and the outer surface coated with an outer barrier layer comprising at least one of the first material or a second material, wherein the first material comprises tantalum pentoxide or aluminum oxide; and   a system controller configured to operate the process chamber and the gas delivery system.   
     
     
         17 . The electronic device manufacturing system of  claim 16 , wherein the first material comprises aluminum oxide. 
     
     
         18 . The electronic device manufacturing system of  claim 16 , wherein the first material comprises tantalum pentoxide. 
     
     
         19 . The electronic device manufacturing system of  claim 16 , wherein the outer barrier layer comprises the second material, and wherein the second material comprises tantalum pentoxide. 
     
     
         20 . The electronic device manufacturing system of  claim 16 , wherein the outer barrier layer comprises the second material, and wherein the second material is different from the first material.