Degas system using inert purge gas at controlled pressure for a liquid delivery system of a substrate processing system

Abstract

The degassing system includes a housing comprising a liquid inlet, a gas inlet, a liquid outlet, and a gas outlet. A piping system is configured to receive liquid containing air bubbles. The piping includes a plurality of loops, a first end fluidly connected to the liquid inlet of the housing, and a second end fluidly connected to the liquid outlet of the housing. The piping is gas-permeable but liquid-impermeable. A gas supply system is configured to supply gas to the gas inlet of the housing. A first conduit and a first limiting orifice are configured to fluidly connect the gas outlet of the housing to an exhaust system.

Description

Technical Field

[0001] This disclosure relates to degassing systems, and more particularly to degassing systems for liquid delivery systems used in substrate processing systems. Prior Technology

[0002] The prior art description provided herein is intended to provide a general overview of the content of this disclosure. The achievements of the inventors listed in this case, as well as the embodiments of the specification that were not qualified as prior art at the time of application, described in this prior art section are all implicitly or implicitly acknowledged as prior art relative to the content of this disclosure.

[0003] Substrate processing systems can be used to perform deposition, etching, and / or other processing on substrates (e.g., semiconductor wafers). The substrate may be disposed on a pedestal within a processing chamber. During deposition, a deposition gas mixture containing one or more precursors is supplied to the processing chamber. In some applications, plasma can be excited within the processing chamber to initiate a chemical reaction.

[0004] During film deposition on the substrate, a gaseous or liquid precursor is delivered to the processing chamber. If a liquid precursor is used, the liquid is degassed, metered, and vaporized in an evaporator. A carrier gas system is used to entrain and deliver the vapor to the processing chamber. The liquid delivery system needs to deliver the liquid to the evaporator at a uniform pressure and / or a predetermined flow rate. The liquid should be free of particulate impurities and / or bubbles.

[0005] Some liquid delivery systems include pumps that transport liquids. However, pumps contain dynamic seals that deteriorate over time and introduce unwanted impurities into the pumped liquid. Pump-based liquid delivery systems may not have uniform pressure due to the variable pumping force involved.

[0006] Instead of using pumps, some liquid delivery systems supply liquid from a liquid container pressurized with an inert gas. When using this method, some components of the gas may dissolve into the liquid. Dissolved gas bubbles can cause problems downstream. For example, under lower pressure conditions, dissolved gas may be released from the liquid. Bubbles displace the liquid, resulting in inconsistent flow rates. Bubbles also alter the thermal conductivity of the liquid. If a liquid mass flow controller is used, bubbles can adversely affect its operation. If a limiting orifice is used to control flow, bubbles can also cause inaccurate liquid flow metering. Understandably, variations in liquid flow rate can cause substrate inhomogeneities, such as variations in deposition thickness and / or quality. Summary of the Invention

[0007] The degassing system includes a housing comprising a liquid inlet, a gas inlet, a liquid outlet, and a gas outlet. A piping system is configured to receive liquid containing air bubbles. The piping includes a plurality of loops, a first end fluidly connected to the liquid inlet of the housing, and a second end fluidly connected to the liquid outlet of the housing. The piping is gas-permeable but liquid-impermeable. A gas supply system is configured to supply gas to the gas inlet of the housing. A first conduit and a first limiting orifice are configured to fluidly connect the gas outlet of the housing to an exhaust system.

[0008] Among other features, the gas supply system and the first limiting orifice system are configured to generate a first predetermined pressure in the housing, which is greater than a second predetermined pressure of the exhaust system and less than a third predetermined pressure of bubbles in the liquid.

[0009] Among other features, the gas supply system includes a gas source. The second conduit and the second limiting orifice have an inlet that is fluidly connected to the gas source and an outlet that is fluidly connected to the gas inlet of the housing.

[0010] Among other features, a gas source supplies gas at a first predetermined pressure. A second restrictive orifice system is sized to supply gas from the gas source at a predetermined flow rate. The second restrictive orifice system is configured to maintain pressure within the housing at a second predetermined pressure.

[0011] Among other features, the first predetermined pressure is in the range of 40 to 70 psig. The second predetermined pressure is in the range of 20 to 40 Torr. The first limiting orifice has a size in the range of 300 to 550 micrometers. The second limiting orifice has a size in the range of 25 to 55 micrometers.

[0012] Among other features, the gas supply system includes a gas source. The pressure regulator has an inlet fluidly connected to the gas source and an outlet fluidly connected to a gas inlet in the housing. The gas source supplies gas at a first predetermined pressure. The pressure regulator and the first limiting orifice system are configured to maintain the pressure in the housing at a second predetermined pressure.

[0013] Among other features, the first predetermined pressure is in the range of 40 to 70 psig. The second predetermined pressure is in the range of 20 to 40 Torr.

[0014] Among other features, the gas supply system includes a gas source. The gas mass flow controller has an inlet that is fluidly connected to the gas source. The valve has an inlet that is connected to the outlet of the gas mass flow controller and an outlet that is fluidly connected to the gas inlet of the housing.

[0015] Among other features, the gas source supplies gas at a first predetermined pressure. The gas flow controller, valve, and first limiting orifice system are configured to maintain the pressure in the housing at a second predetermined pressure.

[0016] Among other features, the first predetermined pressure is in the range of 40 to 70 psig. The second predetermined pressure is in the range of 20 to 40 Torr. The first limiting orifice has a size in the range of 300 to 550 micrometers. The bubble contains an inert gas. The liquid contains silicon alkoxides. The gas contains an inert gas.

[0017] The liquid delivery system for a substrate processing system includes a degassing system, a liquid container for storing liquid, a gas source for pressurizing the liquid container, and a conduit for connecting the liquid outlet of the liquid container to the liquid inlet of the outer casing.

[0018] Among other features, the liquid mass flow controller includes an inlet that is fluidly connected to the liquid outlet of the housing. The evaporator is fluidly connected to the outlet of the liquid mass flow controller.

[0019] Among other characteristics, the bubbles contain helium (He). The liquid contains tetraethyl orthosilicate (TEOS). The gas contains argon (Ar).

[0020] Among other features, the outer casing is sealed relative to the atmosphere. In the event of a seal failure, gas prevents the liquid from reacting with the atmosphere through the pipe.

[0021] Further applications of this disclosure will become apparent from the embodiments, the claims, and the drawings. The embodiments and specific examples are intended for illustrative purposes only and are not intended to limit the scope of this disclosure. Simple Explanation of the Diagram

[0022] This disclosure will become more fully understood from the embodiments and accompanying drawings, wherein:

[0023] Figure 1 is a functional block diagram of the substrate processing system, which includes a liquid delivery system with a degassing system;

[0024] Figure 2 is a functional block diagram illustrating a substrate processing system according to the present disclosure, which includes a liquid delivery system with a degassing system;

[0025] Figure 3 is a functional block diagram of another exemplary substrate processing system according to the present disclosure, which includes a liquid delivery system with a degassing system; and

[0026] Figure 4 is a functional block diagram of another exemplary substrate processing system according to the present disclosure, which includes a liquid delivery system with a degassing system.

[0027] In the diagram, reference numbers may be used repeatedly to indicate similar and / or identical elements. Implementation

[0028] According to this disclosure, the liquid delivery system for a substrate processing system includes a degassing system. The degassing system is configured to remove air bubbles from the liquid to be used in the substrate processing system.

[0029] The degassing system comprises a housing and coils disposed within the housing. The coils provide a tortuous pathway and are made of a gas-permeable but liquid-impermeable material. Permeability is a measure of a porous material's ability to allow fluids (e.g., gases and liquids) to pass through it. The permeability of a medium is related to its porosity, the shape of the pores within the medium, and the degree of connectivity of the pores. The coils are made of a material that allows gas to pass through but not liquids. Therefore, this material is described as gas-permeable but liquid-impermeable. An inert gas system is supplied to the housing to control the pressure within and prevent backflow of products from the pre-exhaust piping into the degassing system housing. An outlet restrictor orifice is used to maintain a higher pressure in the degassing system housing than in the pre-exhaust piping.

[0030] Inert gas can be supplied to the degassing system in several different ways, including using an inlet restrictor orifice, a pressure regulator, and / or a mass flow controller and valve located at the gas inlet of the housing. In use, the inlet restrictor orifice sets the mass flow rate of the gas. The outlet restrictor orifice sets the degassing pressure and maintains a controlled pressure inside the housing of the degassing system to prevent backflow. Generally, a restrictor orifice is a fluid control device that restricts fluid flow to achieve a controlled or limited flow rate. Due to this restriction, a pressure drop is observed from upstream to downstream of the orifice. Similar effects can be achieved using a pressure regulator and / or a mass flow controller and valve.

[0031] Referring now to FIG1, the substrate processing system 100 includes a liquid delivery system 104 and a degassing system 106. The liquid delivery system 104 includes a liquid container 105 connected to a gas source 112. The gas source 112 increases the pressure in the liquid container 105 and propels the liquid 114 stored in the liquid container 105 to the degassing system 106 via a conduit 116.

[0032] The degassing system 106 includes a housing 110 having a liquid inlet, a liquid outlet, and a gas outlet. The degassing system 106 includes a pipe 120 having one end fluidly connected to a conduit 116 (via the liquid inlet) and the other end fluidly connected to a mass flow controller (MFC) 126 (via the liquid outlet). The pipe 120 is gas-permeable but liquid-impermeable.

[0033] The outlet of the liquid MFC 126 is fluidly connected to an evaporator 130, which can be connected to a gas source 134. The evaporator 130 may include an atomizer (not shown) for vaporizing the liquid, and the gas source 134 supplies a carrier gas to carry the vapor. The outlet of the evaporator 130 is connected to a processing chamber 136.

[0034] Valves 140, 142, 144, and 146 may be configured to selectively connect components of the substrate processing system 100 to the exhaust system 150 (e.g., during decontamination). In some examples, gas sources 112 and 134 are fluidly connected to the liquid container 105 and / or the evaporator 130 via shut-off valves (shown) and / or restricting orifices (not shown).

[0035] The housing 110 is connected to the exhaust system 150 via a conduit 152 and a limiting orifice 154. In some examples, the limiting orifice 154 is sized to restrict the flow rate of liquid in the event of a catastrophic failure. For example, the limiter in the limiting orifice 154 is typically sized to be relatively small (e.g., less than or equal to about 150 μm (e.g., 127 μm (.005”))).

[0036] In some examples, valve 140 is fluidly connected to the outlet of pipe 120, the inlet of liquid MFC 126, and the venting system 150. Valve 142 is fluidly connected to the outlet of liquid MFC 126, the inlet of evaporator 130, and the venting system 150. Valve 144 is fluidly connected to the outlet of evaporator 130, the inlet of processing chamber 136, and the venting system 150. Valve 146 is fluidly connected to the outlet of processing chamber 136 and the inlet of venting system 150. Valves 140, 142, 144, and 146 can be used during system purge.

[0037] In some examples, an overflow sensor 162 is disposed within housing 110 to detect a fault in tube 120. In some examples, housing 110 may include a window 164 to allow view inside housing 110. Controller 166 may be used to control one or more components of the substrate processing system 100. For example, controller 166 may be used to control the formulation and / or other system parameters used in system valves, liquid MFC 126, evaporator 130, processing chamber 136.

[0038] During use, gas source 112 provides pressure to liquid container 105 to advance liquid 114 to liquid MFC 126 via conduit 116 and tube 120. As the liquid flows through tube 120, air bubbles are removed because tube 120 is gas-permeable and at a lower pressure.

[0039] In some examples, liquid container 105 is maintained at approximately the same pressure as venting system 150 (e.g., approximately 0 Torr). As will be understood, valves 140, 142, 144, and 146 are connected downstream of restricting orifice 154 to venting system 150. Pressure changes may occur in venting system 150. This may cause a temporary pressure difference in liquid container 105 relative to the venting system. This may cause vapors, reactants, or other materials (connected downstream of restricting orifice 154 to venting system 150) to flow back into liquid container 105 and eventually back through restricting orifice 154. This effect may cause blockage of restricting orifice 154.

[0040] The limiting orifice 154 was originally intended to protect against catastrophic failures of pipe 120 and has a relatively small limiter. However, since the overflow sensor 162 can be used to detect failures in pipe 120, the limiting orifice 154 is no longer necessary for this function. Simply removing the limiting orifice 154 would increase backflow of the product from the exhaust system 150 to the liquid container 105. Some systems attempt to use a large gap between the fore-pipe connection and the outlet of the degassing system housing to prevent backflow from the fore-pipe. Even with a narrow fore-pipe of non-linear length, simple separation is insufficient to completely eliminate backflow.

[0041] Referring now to Figure 2, the substrate processing system 200 includes a liquid delivery system 204, a degassing system 206, and a gas supply system 208. The degassing system 206 includes a housing 211 comprising a liquid inlet, a liquid outlet, a gas inlet, and a gas outlet. The gas supply system 208 includes a gas source 210 connected to the gas inlet of the housing 211 via a valve 212 and a limiting orifice 214. The gas outlet of the housing 211 is connected to an exhaust system 150 via a limiting orifice 224. In some examples, to prevent backflow of product from the exhaust system 150 into the housing 211, the limiting orifices 214 and 224 are sized to provide a predetermined pressure within the housing 211.

[0042] In some examples, the predetermined pressure in housing 211 is greater than the pressure in the exhaust system and less than the partial pressure of the bubbles in liquid 114. In some examples, the predetermined pressure in housing 211 is in the range of 15 to 45 Torr (e.g., 30 Torr) and the pressure in exhaust system 150 is less than 10 Torr (e.g., approximately 0 Torr).

[0043] In some examples, the limiting orifice 224 is specifically sized to achieve a predetermined pressure differential relative to the exhaust system 150. For instance, when the gas source 210 supplies argon (Ar) at 55 psig, the limiting orifice 214 includes a 40 μm limiter providing a flow rate of 50 sccm Ar. The limiting orifice 224 includes a 430 μm limiter to control a predetermined pressure within the housing at approximately 30T; however, other limiter sizes, pressures, and flow rates can be used.

[0044] In some examples, the gas supplied by gas source 210 is at a predetermined pressure range of 40 to 70 psig (e.g., 55 psig), however other pressures may be used. The predetermined pressure in housing 211 is in the range of 20 to 40 Torr (e.g., 30T), however other pressures may be used. The size of inlet restricting orifice 214 is in the range of 25 to 55 micrometers (e.g., 40 μm), however other sizes may be used. The size of outlet restricting orifice 154 is in the range of 300 to 550 micrometers (e.g., 430 μm), however other sizes may be used.

[0045] In some examples, gas source 112 supplies helium (He), gas source 210 supplies argon (Ar), and the liquid contains tetraethyl orthosilicate (TEOS); however, other inert gases and / or liquids can be used. TEOS is an ethyl ester of orthosilicate, Si(OH)4. TEOS is an alkoxide of silicon. TEOS is a tetrahedral molecule prepared by the alcoholysis of silicon tetrachloride. In some examples, the degassing system removes He propellant gas in the form of bubbles from the TEOS liquid. The degassing mechanism is through diffusion through the membrane of tube 120 via partial pressure difference. When using He propellant gas, using argon at 30 Torr does not reduce the degassing performance of the degasser.

[0046] Referring now to Figure 3, the substrate processing system 300 includes a liquid delivery system 304, a degassing system 306, and a gas supply system 308. The gas supply system 308 includes a gas source 310 connected to the inlet of the housing 211 via a valve 314, a gas mass flow controller (MFC) 318, and a valve 322. The outlet of the housing 211 is connected to the exhaust system 150 via a conduit and a limiting hole 224.

[0047] Pressure sensor 326 can be used to detect the pressure in housing 211. Controller 166 differentiates the operation of gas MFC 318, valve 314, and / or valve 322 to adjust the flow rate of gas flowing to the gas inlet of housing 211, thereby providing a predetermined pressure within housing 211 and preventing backflow of products from exhaust system 150. In some examples, the predetermined pressure in housing 211 is greater than the pressure in exhaust system 150 and less than the partial pressure of bubbles in liquid 114.

[0048] Referring now to Figure 4, the substrate processing system 400 includes a liquid delivery system 404, a degassing system 406, and a gas supply system 408. The gas supply system 408 includes a gas source 410 connected to the inlet of the housing 211 via a valve 412 and a pressure regulator 414. The outlet of the housing 211 is connected to the exhaust system 150 via a limiting orifice 224. The pressure regulator 414 adjusts the pressure of the gas flowing to the inlet of the housing 211 to provide a predetermined pressure within the housing 211 to prevent backflow from the exhaust system 150. The outlet of the housing 211 is connected to the exhaust system 150 via a conduit 152 and a limiting orifice 224. In some examples, the predetermined pressure in the housing 211 is greater than the pressure in the exhaust system 150 and less than the partial pressure of the bubbles in the liquid 114.

[0049] Furthermore, the inert gas (also known as the purge gas) used in the degasser (the degassing system shown in Figures 2-4) protects the reactive precursor (e.g., the liquid 114 supplied to liquid container 105) from reacting with the atmosphere through the membrane of pipe 120. Specifically, the inert purge gas generates an inert atmosphere within the degasser. The pressure in housing 211 is lower than the partial pressure of the inert purge gas and higher than the pressure of the upstream conduit (conduit 152) connecting the degasser to exhaust system 150. The pressure in housing 211 helps prevent material from flowing back from the upstream conduit into liquid container 105.

[0050] Although the housing 211 is sealed relative to the atmosphere, the purging function provided by the inert purging gas helps prevent atmospheric contamination of the liquid precursor in the event of seal failure. Without the inert purging gas, if the seal fails, atmosphere may permeate into the degasser volume (housing 211), potentially contaminating the liquid precursor in the liquid container 105 due to the low partial pressure of atmospheric products in the precursor and then across the membrane of the degasser (tube 120). The purging gas prevents contamination of the liquid precursor by diluting any potential small amount of leakage from the degasser volume (housing 211) that could allow atmosphere to enter the degasser volume (housing 211). Therefore, the inert purging gas helps prevent reactive precursors from reacting with the atmosphere through the membrane of tube 120.

[0051] The foregoing description is illustrative in nature and is not intended to limit the scope of this disclosure, its application, or its uses. The broad teachings of this disclosure can be implemented in various forms. Therefore, while this disclosure includes specific examples, its true scope should not be so limited, as other modifications will become apparent upon reading the drawings, specifications, and the following claims. It should be understood that one or more steps within the method may be performed in different orders (or simultaneously) without altering the principles of this disclosure. Furthermore, while the embodiments described above possess certain features, any one or more of these features described with respect to any embodiment of this disclosure may be implemented in features of any other embodiment and / or combined with features of any other embodiment, even if such combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitutions of one or more embodiments with each other remain within the scope of this disclosure.

[0052] Spatial and functional relationships between components (e.g., modules, circuit elements, semiconductor layers, etc.) are described using a variety of terms, including "connection," "joint," "coupled," "adjacent," "next to," "above," "below," and "set." When describing the relationship between a first and a second component in the foregoing disclosure, unless explicitly stated as "direct," the relationship may be a direct relationship between the first and second components without any other intermediate components, or it may be an indirect relationship between the first and second components with one or more intermediate components (whether spatial or functional). As used herein, the terms A, B, and C, at least one of which should be interpreted as meaning the logic of using non-exclusive OR (A OR B OR C), and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C."

[0053] In some embodiments, the controller is part of a system, which may be part of the above-described examples. Such a system may include semiconductor processing equipment, comprising one or more processing tools, one or more chambers, one or more processing platforms, and / or specific processing components (wafer pedestals, gas flow systems, etc.). These systems may be integrated with electronic components to control their operation before, during, and after the processing of semiconductor wafers or substrates. These electronic components may be referred to as "controllers," which control various components or sub-components of the system or system. The controller may be programmed, depending on the processing requirements and / or system type, to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and operation settings, wafer transfer tools and other transfer tools, and / or loading locks connected to or coupled to a specific system.

[0054] Broadly speaking, a controller can be defined as an electronic component having numerous integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, etc. Integrated circuits may include chips in the form of firmware storing program instructions, digital signal processors (DSPs), chips defined as application-specific integrated circuits (ASICs), and / or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of numerous individual settings (or program files), defining operating parameters for performing specific processes on or for a semiconductor wafer or for a system. In some embodiments, operating parameters may be part of a recipe defined by a process engineer to complete one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0055] In some embodiments, the controller may be part of or coupled to a computer that is integrated with, coupled to, or otherwise networked to the system, or a combination thereof. For example, the controller may be located in the cloud or in all or part of a wafer fab host system, allowing remote access to wafer processing. The computer may enable remote access to the system to monitor the current progress of manufacturing operations, examine the history of past manufacturing operations, examine trends or performance metrics from multiple manufacturing operations, change parameters of the current process, set processing steps to follow the current process, or initiate a new process. In some examples, the remote computer (e.g., a server) may provide process recipes to the system via a network, which may include a local area network or the Internet. The remote computer may include an input or programmed user interface for implementing parameters and / or settings, which are then communicated from the remote computer to the system. In some examples, the controller receives instructions in the form of data specifying parameters for each of the processing steps to be performed during one or more operations. It should be understood that parameters can be specific to the type of process to be performed and the type of tool to which the controller is configured to interface with or control. Therefore, as described above, the controller can be distributed, for example, by comprising one or more discrete controllers networked together and operating for a common purpose (e.g., the process and control described herein). An example of a distributed controller for such a purpose would be one or more integrated circuits on a chamber that communicate with one or more integrated circuits located remotely (e.g., at the platform level or as part of a remote computer), which in turn control the process on the chamber.

[0056] Without limitation, the illustrated system may include a plasma etching chamber or module, a deposition chamber or module, a rotary flushing chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel etching chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, an orbital chamber or module, and any other semiconductor processing system that may be associated with or used in the manufacture and / or fabrication of semiconductor wafers.

[0057] As described above, depending on one or more process steps to be performed by the tool, the controller may communicate with one or more of the following: other tool circuits or modules, other tool components, cluster tools, other tool interfaces, neighboring tools, adjacent tools, tools located at various locations in the plant, a host computer, another controller, or tools for transporting materials, which transport wafer containers to tool locations and / or loading ports in the semiconductor manufacturing plant.

[0058] 100: Substrate Processing System 104: Liquid Delivery System 105: Liquid containers 106: Degassing System 110: Outer shell 112: Gas Source 114: Liquid 116: Catheter 120: pipe 126: Liquid Mass Flow Controller 130: Evaporator 134: Gas Source 136: Processing Chamber 140: Valve 142: Valve 144: Valve 146: Valve 150: Exhaust System 152: Catheter 154: Restriction Hole 162: Overflow Sensor 164: Window 166: Controller 200: Substrate Processing System 204: Liquid Delivery System 206: Degassing System 208: Gas Supply System 210: Gas source 211: Outer shell 212: Valve 214: Restriction Hole 224: Restriction Hole 300: Substrate Processing System 304: Liquid delivery system 306: Degassing System 308: Gas Supply System 310: Gas Source 314: Valve 318: Gas Mass Flow Controller 322: Valve 326: Pressure sensor 400: Substrate Processing System 404: Liquid delivery system 406: Degassing System 408: Gas Supply System 410: Gas source 412: Valve 414: Pressure Regulator

Claims

1. A degassing system comprising: A housing comprising a liquid inlet, a gas inlet, a liquid outlet, and a gas outlet; a tube configured to receive a liquid containing air bubbles, wherein: the tube includes a plurality of loops, a first end fluidly connected to the liquid inlet of the housing, and a second end fluidly connected to the liquid outlet of the housing, and the tube is gas-permeable but liquid-impermeable; a gas supply system configured to supply gas to the gas inlet of the housing; and a first conduit and a first limiting orifice configured to fluidly connect the gas outlet of the housing to an exhaust system; wherein the housing is sealed relative to the atmosphere; and wherein, in the event of a failure of the seal, the gas prevents the liquid from reacting with the atmosphere through the tube.

2. The degassing system of claim 1, wherein the gas supply system and the first limiting orifice system are configured to generate a first predetermined pressure in the housing, the first predetermined pressure being greater than a second predetermined pressure of the exhaust system and less than a third predetermined pressure of the bubble in the liquid.

3. The degassing system of claim 1, wherein the gas supply system comprises: a gas source; and a second conduit and a second limiting orifice having an inlet fluidly connected to the gas source and an outlet fluidly connected to the gas inlet of the housing.

4. The degassing system of claim 3, wherein the gas source supplies gas at the first predetermined pressure; the second restricting orifice system is sized to supply gas from the gas source at a predetermined flow rate; and the first restricting orifice system is configured to maintain pressure in the housing at the second predetermined pressure.

5. As in request item 4, the degassing system, wherein: The first predetermined pressure is in the range of 40 to 70 psig; the second predetermined pressure is in the range of 20 to 40 Torr; the first limiting orifice has a size in the range of 300 to 550 micrometers; and the second limiting orifice has a size in the range of 25 to 55 micrometers.

6. The degassing system of claim 1, wherein the gas supply system comprises: a gas source; and a pressure regulator having an inlet fluidly connected to the gas source and an outlet fluidly connected to the gas inlet of the housing.

7. As in request item 6, the degassing system, wherein: The gas source supplies gas at a first predetermined pressure; and the pressure regulator and the first limiting orifice system are configured to maintain the pressure in the housing at a second predetermined pressure.

8. As in request item 4, the degassing system, wherein: The first predetermined pressure is in the range of 40 to 70 psig; and the second predetermined pressure is in the range of 20 to 40 Torr.

9. The degassing system of claim 1, wherein the gas supply system comprises: a gas source; a gas mass flow controller having an inlet fluidly connected to the gas source; and a valve having an inlet connected to an outlet of the gas mass flow controller and an outlet fluidly connected to a gas inlet of the housing.

10. As in request item 9, the degassing system, wherein: The gas source supplies gas at a first predetermined pressure; and the gas flow controller, the valve, and the first limiting orifice system are configured to maintain the pressure in the housing at a second predetermined pressure.

11. The degassing system as described in request item 10, wherein: The first predetermined pressure is in the range of 40 to 70 psig; and the second predetermined pressure is in the range of 20 to 40 Torr.

12. The degassing system of claim 11, wherein the first limiting orifice has a size in the range of 300 to 550 micrometers.

13. The degassing system of claim 1, wherein the bubble contains an inert gas.

14. The degassing system of claim 1, wherein the liquid contains alkyl silane oxides.

15. The degassing system of claim 1, wherein the gas contains an inert gas.

16. The degassing system of claim 1, wherein the bubble contains helium (He).

17. The degassing system of claim 1, wherein the liquid comprises tetraethyl orthosilicate (TEOS).

18. The degassing system of claim 1, wherein the gas contains argon (Ar).

19. A liquid delivery system for a substrate processing system, comprising: the degassing system of claim 1; a liquid container for storing the liquid; a gas source for pressurizing the liquid container; and a conduit for fluidly connecting the liquid outlet of the liquid container to the liquid inlet of the housing.

20. The liquid delivery system of claim 19 further includes: A liquid mass flow controller, comprising an inlet that is fluidly connected to the liquid outlet of the housing; And an evaporator, whose fluid is connected to the outlet of the liquid mass flow controller.

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