System and method for detecting flow in a mass flow controller

Systems and methods are provided for detecting flow in a mass flow controller (MFC). The position of a gate in the MFC is sensed or otherwise determined to monitor flow through the MFC and to immediately or nearly immediately detect a flow failure. In one embodiment of the present invention, a novel MFC is provided. The MFC includes an orifice, a mass flow control gate, an actuator and a gate position sensor. The actuator moves the control gate to control flow through the orifice. The gate position sensor determines the gate position and/or gate movement to monitor flow and immediately or nearly immediately detect a flow failure. According to one embodiment of the present invention, the gate position sensor includes a transmitter for transmitting a signal and a receiver for receiving the signal such that the receiver provides an indication of the position of the gate based on the signal received. Other embodiments of the gate position sensor are described herein, as well as systems and methods that incorporate the novel MFC within a semiconductor manufacturing process.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally to the detection of flow and flow failure in a mass flow controller, and more particularly to the delivery of semiconductor process gas in semiconductor manufacturing processes and the monitoring thereof for flow and flow failure.

BACKGROUND OF THE INVENTION

An integrated circuity is formed in and on a wafer in semiconductor manufacturing processes. Forming an integrated circuit on a wafer involves a number of sub-steps such as thermal oxidation, masking, etching and doping. In the thermal oxidation sub-step, the wafers are exposed to ultra-pure oxygen under carefully controlled conditions to form a silicon dioxide film, for example, on the wafer surface. In the masking sub-step, a photoresist or light-sensitive film is applied to the wafer, an intense light is projected through a mask to expose the photoresist with the mask pattern, the exposed photoresist is removed, and the wafer is baked to harden the remaining photoresist pattern. In the etching sub-step, the wafer is exposed to a chemical solution or gas discharge to etch away or remove areas not covered by the hardened photoresist. In the doping sub-step, atoms with either one less or one more electron than silicon are introduced into the area exposed by the etching process to alter the electrical character of the silicon. These sub-steps are repeated for each layer. Most of or all of these processes require the controlled introduction of gases into a processing chamber, and mass flow controllers are used to control the same. Each chip on the wafer is finally tested after the remaining metals, films and layers have been deposited. Subsequently, the wafer is sliced into individual chips that are assembled into packages.

Semiconductor gases are used in the above-described manufacturing process, and include, but are not limited to gases which serve as precursors, etchants and dopants. These gases are applied to the semiconductor wafer in a processing chamber. Precursor gases provide a source of silicon atoms for the deposition of polycrystalline silicon, epitaxial silicon, silicon dioxide and silicon nitride film within the thermal oxidation step. Etchant gases provide fluorocarbons and other fluorinated materials that react with silicon, silicon dioxide and silicon nitride. Dopants provide a source of controllable impurities that modify the local electrical properties or characteristics of the semiconductor material. A reliable supply of high purity process gases is required for advanced semiconductor manufacturing. As the semiconductor industry moves to smaller feature sizes, a greater demand is placed on the control technologies to accurately and reliably deliver the semiconductor process gases.

Mass Flow Controllers (MFCs) are placed in an inflow line to control the delivery of the semiconductor process gas. Conventional MFCs have an iris-like restricted orifice for controlling flow, and deliver gas or other mass at a low velocity. This low velocity allows interfering feedback in the MFC; i.e. the pressure differentials occurring in the chamber travel back upstream through the gas and perturb the delivery velocity of the gas. Therefore, a problem associated with conventional MFCs is that they are dependent on the characteristics of the specific chamber into which the gas is being delivered, and require trial and error methods to find the proper valve position for delivering a desired flow of material into the chamber. An obvious drawback to this approach is that the experimentation is very time consuming.

Ultrasonic MFCs meter gas flowing through an orifice of a known size at a velocity higher than the speed of sound. The mass flow is controlled using a gated orifice by oscillating a gate between an opened and closed position with respect to the orifice. The amount of material delivered into the chamber is adjusted by adjusting the duty cycle of the oscillations; i.e. by adjusting the amount of time per oscillation period that the gate is opened rather than closed. Because pressure differentials can only travel through the gas at the speed of sound, pressure variations in the chamber do not travel upstream quickly enough to perturb the ultrasonic delivery velocity. Thus, ultrasonic MFCs have feed forward control as they are able to deliver exactly the desired amount of material into the chamber without being affected by any feedback from the chamber. However, a problem associated with ultrasonic MFCs is that control gates regulating the precision flow may fail by becoming stuck either in an opened position, a closed position, or in some position in between the opened and closed positions. And in the case of the above-described process for manufacturing semiconductors, this failure may not be detected for a considerable amount of time causing considerable losses in both processing time and resources.

Therefore, there is a need in the art to provide improved MFC which overcomes these problems.

SUMMARY OF THE INVENTION

The above mentioned problems with MFCs and other problems are addressed by the present invention and will be understood by reading and studying the following specification. Systems and methods are provided for detecting flow and flow failure in a MFC. These systems and methods are particularly useful in delivering semiconductor gas in a semiconductor manufacturing process using an ultrasonic MFC. The mass flow through the MFC is monitored by sensing or otherwise determining the position and/or motion of the gate in an ultrasonic MFC. Therefore, the system is able to immediately or nearly immediately detect a flow failure, and provide an indication of the same, caused by a gate being stuck in an opened position, a closed position, or a position in between the opened and closed positions. Given the relatively long time horizon for semiconductor manufacturing processes and the fact that the testing is conducted late in the process, significant losses of manufacturing time and material are avoided through the early detection of flow failure.

In one embodiment of the present invention, a novel MFC is provided. The MFC includes an orifice, a mass flow control gate, an actuator and a gate position sensor. The mass flow control gate controls flow through the orifice, and the actuator moves the gate to control flow through the orifice. The gate position sensor senses or otherwise determines the gate position to monitor flow and immediately or nearly immediately detect a flow failure caused by a stuck gate. The novel MFC may be incorporated into an electronic system such as a semiconductor manufacturing system.

In a further embodiment of the present invention, a novel method is provided. The method comprises the steps of providing a mass flow controller in an ultrasonic mass flow line, oscillating a gate in the mass flow controller at a desired frequency between an opened and closed position, and monitoring gate movement. This method may be incorporated into a method for delivering a semiconductor gas in a semiconductor manufacturing process, and into a method for detecting a gas flow failure in a semiconductor manufacturing process.

DETAILED DESCRIPTION OF THE INVENTION

The term wafer, as used in the following description, includes any structure having an exposed surface with which to form the integrated circuit (IC) structure of the invention. The term wafer also includes doped and undoped semiconductors, epitaxial semiconductor layers supported by a base semiconductor or insulator, as well as other semiconductor structures well known to one skilled in the art. The term conductor is understood to include semiconductors, and the term insulator is defined to include any material that is less electrically conductive than the materials referred to as conductors. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

According to the teachings of the present invention, a novel choke-orifice or gated-orifice MFC capable of detecting flow and flow failure in the MFC is described. The MFC uses an oscillating control gate to control or otherwise regulate the delivery of an ultrasonic gas or other substance. A gate position sensor senses or otherwise determines the position and/or the motion of the control gate. Thus, the gate position sensor can detect a stuck gate and thus detect flow failure in the MFC. The gate position sensor may also be used to monitor the oscillations of the control gate, and the duty cycle thereof, to continuously monitor the flow through the MFC by verifying that the control gate is operating as anticipated and desired.

The MFC is described below first with respect to a general electronic system, and then in particular with respect to a semiconductor manufacturing system. Subsequently, the MFC itself and the gate position sensor of the MFC is described in detail. Finally, specific methods utilizing the MFC of the present invention are provided.

An electronic delivery system110incorporating a mass flow controller112is generally illustrated inFIG. 1. The system110generally comprises a source114, a flow controller112connected to the source114through an inflow line116, a sensor118, a processor120, and an outflow line122connected to a chamber124. The inflow line116delivers the substance from the source114to mass flow controller112, which in turn regulates the flow of the substance out through the outflow line122. This delivered substance may comprise any material. Therefore, the flow controller112is often referred to as a mass flow controller (MFC). The flow controller112may be referred to as a liquid flow controller (LFC) if a liquid substance is being delivered by the system110, or even a gas flow controller (GFC) if a gas substance is being delivered. However, for the purposes of this application and the teaching contained herein, the terms MFC, LFC and GFC are deemed equivalent as they both deliver a substance.

The MFC112is positioned in the flow, and is adapted for controlling or regulating the flow out through the outflow line122. An ultrasonic MFC112passes a high velocity flow (higher than the speed of sound) through an orifice226, specifically through a gated orifice. As described throughout this specification and as shown in the Figures, the term orifice226is intended to cover not only the opening through which the mass flows, but also the surrounding structure that forms or defines the opening and that contacts the gate when the gate228is closed. A gate228and corresponding actuator230for moving the gate228, as generally illustrated inFIG. 2and is also illustrated inFIGS. 3–6using like numbers, is operably positioned proximate to the orifice226such that the gate228may oscillate between a closed position in which the flow through the orifice226is prevented, and an opened position in which the flow through the orifice226is allowed. The actuator230oscillates or shutters the gate228between the opened and closed positions to regulate the ultrasonic flow through the orifice226. The amount of substance that is delivered through the MFC212is therefore dependent upon the duty cycle of the gate228, which corresponds to the relative amount of time that the gate228is opened rather than closed for each opened-to-closed-to-opened cycle.

Referring again toFIG. 1, the gate position sensor118senses, detects or otherwise monitors the position of the gate128. In one embodiment of the present invention, the gate position sensor118determines whether the gate128is in an opened position or is in a closed position. In other embodiments, the sensor118is designed to determine whether the gate128is moving as expected so as to verify proper operation. Additionally, the gate position sensor118may be designed to accurately detect the position that the gate128is in between the opened and closed positions.

The electronic system110includes the processor120that is interfaced with the actuator130of the control gate128to control the duty cycle of the gate128. That is, the processor sends a control signal to oscillate the control gate128for the purpose of regulating the flow through the MFC112. The processor120further may be interfaced with the gate position sensor118, and thus is able to determine the position and/or motion of the control gate128. The processor120may include appropriate software programs to provide a number of functions, including but not limited to, verifying that the desired position of the control gate128corresponds with the actual position of the control gate128as sensed by the gate position sensor118, providing feedback control to adjust the duty cycle to obtain the desired flow, and warning operators of flow failure. Alternatively, in lieu of sending an indication signal from the gate position sensor118to the processor120, the sensor118may provide an output to an audio or visual device, or may otherwise provide a signal to other control circuitry.

FIG. 1illustrates the electronic system110as a semiconductor manufacturing system in which the inflow line116is connected to a semiconductor process gas source114. For an ultrasonic MFC, the inflow line16provides an ultrasonic gas flow to the MFC112. As indicated above, the MFC112regulates the ultrasonic gas flow by oscillating the control gate128between closed and opened positions with respect to the orifice126. The regulated or controlled gas flow is delivered to a processing chamber124in which various semiconductor processes are performed on the wafer. These processes may include, for example, deposition, etching, and doping. Also as illustrated inFIG. 1, the MFC112may include a pressure and temperature transducer132interfaced with the processor120to monitor the characteristics of the gas and provide appropriate feedback control to the control gate128.

Generally, the gate position sensor118includes a transmitter134for transmitting a signal136and a receiver138for receiving the signal140. The receiver138provides an indication of whether the control gate128is in an opened position, a closed position, or is in another position based on the signal140received. The receiver138may also provide a signal that the control gate is moving, either in addition to or in place of the position signal. The processor120, or other control circuitry, interprets the signal140received by the receiver138to provide an immediate or nearly immediate warning if there has been a flow failure or if the control gate128has otherwise malfunctioned. As is described in more detail below with respect to the detailed description of the MFC112and the gate position sensor118, there are a number of embodiments for the gate position sensor118. The following embodiments provide a non-exhaustive list of sensor118designs for determining the gate position and/or gate movement that fall within the teachings of the present invention for determining flow and flow failure.

In one embodiment, as generally illustrated inFIG. 2and will be discussed in more detail below, the gate position sensor218may include a device242that applies an electrical potential across the orifice226and the gate228in the MFC212. The sensor218further may include a current detector244that is able to detect a current flow through a junction formed when the orifice226contacts the gate228when the gate228is closed, i.e. an orifice/gate junction. Thus, in this embodiment, the transmitter134shown inFIG. 1is the device242for applying electric potential across the gate228and an orifice226in the MFC212, the signal136and140shown inFIG. 1is electric current246flowing through the orifice/gate junction formed when the gate228is closed, and the receiver138shown inFIG. 1is a current detector244for detecting current flowing through the orifice/gate junction.

In another embodiment, as generally illustrated inFIGS. 3 and 4using like numbers and will be discussed in more detail below, the gate position sensor318may include a physical wave generator348and at least one physical wave receiver350. The physical wave generator348generates a physical signal352in the MFC312. The physical wave receiver350detects the physical signal352propagating from the generator348through an orifice/gate junction formed when the gate328is closed. Thus, in this embodiment, the transmitter134ofFIG. 1is the physical wave generator348, the signals136and140ofFIG. 1are the physical signal352propagating through the orifice/gate junction formed when the gate328is closed, and the receiver138ofFIG. 1is the physical wave receiver350for detecting the physical signal352propagating through the orifice/gate junction.

In another embodiment, as generally illustrated inFIG. 5and will be discussed in more detail below, the gate position sensor518includes a light source556and a light detector558. The light source556is positioned on a first side of an orifice526in the MFC512, and the light detector558is positioned on a second side of the orifice526. The light source556and light detector558are positioned and arranged so that, as the control gate528oscillates between an opened position a closed position with respect to the orifice526, a light signal560received by the light detector558and transmitted by the light source556will be interrupted such that the gate position can be determined by the interrupted signal. In one embodiment, the light source556and light detector558are placed on opposing inflow and outflow ends of the orifice526. Thus, in this embodiment, the transmitter134ofFIG. 1is the light source556, the signals136and140ofFIG. 1are the light signal560transmitted by the light source556, and the receiver138ofFIG. 1is the light detector558operably positioned with respect to the light source556and the orifice526such that movement of the control528gate oscillating between an opened position and a closed position interrupts the light signal560from being received by the light detector558.

In another embodiment, as generally illustrated inFIG. 6and will be discussed in more detail below, the gate position sensor618includes a magnet662, a cooperating induction coil664, and an electromagnetic pulse detector666. Movement of the control gate628generates a magnetically induced signal in the induction coil664detectable by the electromagnetic pulse detector666. Thus, in this embodiment, the transmitter134ofFIG. 1is the magnet662, the signals136and140ofFIG. 1are magnetic flux668from the magnet662, and the receiver138ofFIG. 1is the combination of the cooperating induction coil664and the electromagnetic pulse detector666for detecting a magnetically induced signal in the induction coil664. The control gate628movement induces the signal in the coil by providing relative movement between the magnet662and the coil664.

The MFC112ofFIG. 1is illustrated in more detail inFIG. 2and inFIGS. 3-6using like numbers. The illustrated MFC has a generally cylindrical structure268, somewhat akin to the shape of a conventional gas inflow line. However, the illustrated structure268, and the arrangement of the elements within, is not intended to describe any specific MFC or MFC structure, but rather is intended solely for the purpose of illustrating the present invention.

In addition to the structure268, the MFC12generally comprises an orifice226defined herein to include the surrounding structure that defines an opening, a mass flow control gate228, an actuator230, and a gate position sensor218. The control gate228is movable toward and away from the orifice226to control flow through the orifice226. In response to a control signal from the microprocessor120, for example, the actuator230moves the control gate228as desired either toward the orifice226into a closed position or away from the orifice226into an opened position. In this manner, the actuator230oscillates the control gate228through a desired duty cycle between a closed position and an open position to control flow through the orifice226. The duty cycle controls the flow, and is determined by the total time that the control gate228is in an open position in comparison to the entire period of time it takes to move the control gate228from an open position to a closed position and back to the open position. The gate position sensor118is adapted to determine the position and/or movement of the control gate228. And as illustrated above with respect toFIG. 1, the gate position sensor118generally can be considered to include a transmitter134for transmitting a signal136and a receiver138for receiving the signal140. The receiver138provides an indication of a gate position or a gate movement based on the signal received. This indication may be provided as an input to the processor120, to other control circuitry, or to audio or visual indicators.

According to the teachings of the present invention as indicated above and as generally illustrated inFIG. 1, a gate position sensor118is used to sense or detect the position and/or the movement of the control gate128of the MFC112. The sensor118may either form part of the MFC112, or may be a separate component of an electronic system110that contains a MFC112. Also according to the teachings of the present invention and as one skilled in the art would understand, the specific design of the gate position sensor118may vary. That is, the specific transmitter134and receiver138that is selected, and the arrangement thereof, may vary according to the particular characteristics of the actual physical devices. Therefore, the following embodiments of the gate position sensor118is intended as a non-exhaustive list of sensor designs that would enable one skilled in the art to design and build the same or equivalent sensor.

Referring now toFIG. 2, the illustrated gate position sensor218includes a device242for applying an electrical potential across the orifice226and the control gate228. The device242may include, but is not limited to, a battery or an electronic voltage supply. For example, it is anticipated that it may be desirable to use a switchable power device as the device242for applying electric potential. An orifice/gate junction is formed to complete a circuit when the control gate228is closed. A current detector244is able to detect the current flow246, or an increase in current flow, through the orifice/gate junction. Based on the detection of this current246, the system110is able to determine that the control gate is closed228. Any number of current detection means may be used to detect the current. Therefore, one skilled in the art would be able to design or provide an appropriate detection circuit for a particular device. Electrical connections are illustrated at the arm of the gate228and at the orifice226. Therefore, the gate228and orifice226form a conductor through which current may pass when the control gate228is closed and the orifice/gate junction is formed.

When the control gate228is open, no current other than leakage currents through alternative pathways within the entire structure268will be detected. The MFC212may be designed such that adequate electrical insulation is maintained for all alternative pathways so that leakage current intensities will be orders of magnitude lower than the closed orientation current. As the conductivity of the structure268and the specific characteristics of the actuator230vary, it is anticipated that one skilled in the art would be able to determine these characteristics and design an appropriate electrical circuit that permits the system to detect current through the orifice/gate junction and otherwise operate as intended without causing any damage to the equipment.

Referring now toFIGS. 3–4, the gate position sensor318is illustrated to include a physical wave generator348for generating a physical signal352and at least one physical wave receiver350for receiving the physical signal352. As one skilled in the art would recognize based on the teachings of the present invention, the positions of the generator348and receiver350may vary. The receiver350may be considered to be a transducer that forms a vibration sensor or switch. The physical wave generator348and the physical wave receiver350may be formed using piezoelectric crystals. However, this embodiment of the invention is not so limited to the use of piezoelectric crystals.

The physical wave generator348is driven with an ultrasonic frequency and sends ultrasonic physical waves through the structure368. The receiver350receives the ultrasonic wave form352through the orifice/gate junction formed when the control gate328is closed. When the control gate328is open, the wave energy can only be received by the receiver350via a secondary pathway, i.e. physical signal454inFIG. 4for example, throughout the structure368, and therefore will register as a much lower intensity or amplitude. The system110is able to determine that the control gate328is in a closed position when the physical signal receiver350provides an indication that it has detected the physical signal352which propagated through the gate/orifice junction.

A direct physical wave detection method is illustrated inFIG. 3; namely, the physical wave receiver350directly detects the closed gate by sensing an increased amplitude in the physical signal received by the receiver350caused by the signal352being directly transmitted through the orifice/gate junction. When the control gate328is closed, the signal detected by the receiver350will be strong due to the direct connection between the generator348and the receiver350. When the control gate328is open, the signal will be weak due to a non-existent or weak signal354being transmitted elsewhere throughout the structure368, depending on the physical construction of the system. In other words, a portion of the generated physical wave may be transmitted as signal454ofFIG. 4throughout the structure and as signal352through the orifice/gate junction. The received physical signal will be significantly higher if a direct signal path352is provided between the physical wave generator348and physical wave receiver350.

A physical wave signal interference detection method is illustrated inFIG. 4; namely, the physical wave receiver450is adapted for detecting and distinguishing a complex wave formed from a superposition of a first physical signal454and a second physical signal452. It simplifies this analysis to consider that the structure468has at least two separate pathways452and454for the physical wave transmission to be detected at the receiver450. The required time for each transmission is a function of the entire structure468, and the interferences between the signals452and454from all possible paths will give a complex waveform at the receiver450. The first physical signal454is propagated throughout the structure468when the control gate428is open. For a given generator448/receiver450arrangement on a given structure468, the first physical signal454will have a signature wave form. The second physical signal452is directly propagated from the physical wave generator448to the physical wave receiver450through the orifice/gate junction formed when the control gate428is closed. Similarly, for a given generator448/receiver450arrangement on a given structure468, the second physical signal will have a signature wave form. It follows that the superposition of the first and second signals454and452will also have a signature wave form. These signature waveforms are repeatable. Therefore, for physical wave signal interference detection method, the system110includes circuitry capable of distinguishing the first signal454from the superposition of the first and second signals454and452in order to determine whether the control gate428is closed.

Alternatively, other receivers/transducers could be located at intermediate positions between the generator348and the receiver350. The generator348may send a coded signal, and the arrival time of the coded signal at each receiver/transducer would indicate whether the control gate328is opened or closed.

As another alternative, the physical wave generator may be considered to be the control gate328itself as it produces a physical wave throughout the structure368each time it closes. In this situation, the physical wave receiver350is positioned and arranged to detect, and if necessary distinguish from other physical signals, the physical signal generated by the gate328when it closes. This embodiment monitors the self-generated sound wave of a gated orifice.

Referring now toFIG. 5, the gate position sensor518is illustrated to include a light source556positioned on a first side of the orifice526and a light detector558positioned on a second side of the orifice526. Movement of the control gate528oscillating between an opened position and a closed position interrupts the light signal560from being received by the light detector558. As one of ordinary skill would understand from reading this disclosure, there are a number of possible layouts of the light source556and the light detector558that could be used to detect a gate position or gate motion. One, as illustrated inFIG. 5, shows the light source556and the light detector558on opposing inflow and outflow ends of the orifice526such that the light detector558receives the light signal560from the light source556through the orifice526. Another possible arrangement is to have the light source556and the light detector558across the control gate528from each other. A light detector558with a fast response will be able to directly monitor the frequency of the opening and closing of the gate528, and thus give a direct measure of the gas flow through the MFC512in addition to simply detecting whether the gate528is opened, is closed, or is moving between the opened and closed positions. Additionally, the detection circuitry may be such as to detect the change in intensity of the detected light signal560in order to detect the position of a partially closed or partially opened gate528.

Referring now toFIG. 6, the gate position sensor618is illustrated to include a magnet662, a cooperating induction coil664, and an electromagnetic pulse detector666. Movement of the gate628generates a magnetically induced signal in an induction coil664detectable by the electromagnetic pulse detector666. As one skilled in the art would understand from reading this disclosure, there are an number of designs that may be used within this embodiment that still falls within the teaching of this invention. The magnet662may either be a permanent magnet, as illustrated, or an electrically activated magnetic coil. Either the magnet662or the induction coil664may be attached to the moving arm of the gate628, with the other operably located nearby so that the changing magnetic flux668caused by the motion of the control gate628will induce an electromagnetic signal in the induction coil664.

The Figures presented and described in detail above are similarly useful in describing the method embodiments for operating MFCs, systems incorporating MFCs, and gate position sensors incorporated in MFCs.

Therefore, according to the teachings of the present invention, a method is taught comprising providing a mass flow controller in an ultrasonic mass flow line, oscillating a gate in the mass flow controller at a desired frequency between an opened position and a closed position to regulate the mass flow, and monitoring gate movement. In one embodiment, monitoring gate movement may include verifying an actual gate position against a desired gate position, and/or transmitting a signal in the mass flow controller, receiving the signal, and determining whether the gate is opened or closed based on the signal received. Additionally, oscillating a gate at a desired frequency may include varying a duty cycle to adjust mass flow through the mass flow controller.

Furthermore, according to the teachings of the present invention, a method for delivering a semiconductor gas for a semiconductor manufacturing process is taught, comprising providing a mass flow controller in an ultrasonic semiconductor gas flow line, oscillating a gate in the mass flow controller between an opened position and a closed position, and monitoring operation of the gate by transmitting a signal, receiving the signal, and determining whether the gate is opened or closed based on the signal received.

In one embodiment, transmitting a signal may include applying electric potential across the gate and an orifice in the flow controller, and receiving the signal may include detecting current flowing through an orifice/gate junction formed when the gate is closed.

In another embodiment, transmitting a signal may include generating a physical wave in the mass flow controller using a physical wave generator, receiving the signal may include receiving a physical wave in the mass flow controller using a physical wave receiver, and determining whether the gate is opened or closed may include determining whether at least a component of the received physical wave was propagated through an orifice/gate junction formed when the gate is closed.

In another embodiment, transmitting a signal may include transmitting a light signal in the mass flow controller, receiving a signal may include receiving the light signal, and determining whether the gate is opened or closed may include determining whether the light signal is received.

In another embodiment, transmitting a signal may include producing magnetic flux, receiving a signal may include detecting a magnetically induced signal in a cooperating induction coil positioned within the magnetic flux, and determining whether the gate is opened or closed may include determining that the gate has moved if a magnetically induced signal is detected in the induction coil.

Additionally, according to the teachings of the present invention, a method for detecting a gas flow failure in a semiconductor manufacturing process is taught, comprising providing a flow controller in a semiconductor gas inflow line, oscillating a gate in the flow controller to control flow, and monitoring the gate to detect flow failure. In one embodiment, monitoring the gate may include verifying an actual gate position against a desired gate position. In another embodiment, monitoring the gate may include transmitting a signal, receiving the signal, and determining whether the gate has moved or is moving based on the signal received. In another embodiment, monitoring the gate may include determining that the gate is either stuck in an open position or stuck in a closed position.

CONCLUSION

Thus, the present invention provides novel systems and methods for detecting flow and flow failure in a mass flow controller. These systems and methods are particularly useful as used within semiconductor manufacturing processes. The invention is not limited to these processes, however. The novel mass fluid controller (MFC) of the present invention provides an ultrasonic delivery using a gated orifice, and further provides a gate position sensor for detecting flow and flow failure in the MFC. Unlike conventional MFCs, the ultrasonic MFC of the present invention has feed forward control, and is not susceptible to feedback interference caused by pressure differentials in the chamber. As such, the ultrasonic MFC provides an accurate delivery of a substance. The ultrasonic MFC has an oscillating gate that moves between an opened position and a closed position to regulate or control flow through the MFC. Additionally, the ultrasonic MFC of the present invention includes a gate position sensor that senses or otherwise detects the position and/or movement of the oscillating gate. As such, the gate position sensor determines if the gate is stuck or has otherwise failed without notice, and thus guards against the considerable loss of process time and material that would likely occur without an immediate or nearly immediate detection and indication of a flow failure.