U.S. patent application number 11/421701 was filed with the patent office on 2006-10-05 for system and method for detecting flow in a mass flow controller.
This patent application is currently assigned to Micron Technology, Inc.. Invention is credited to Allen P. Mardian, Neal R. Rueger, Gurtej Singh Sandhu, Sujit Sharan.
Application Number | 20060218762 11/421701 |
Document ID | / |
Family ID | 25482730 |
Filed Date | 2006-10-05 |
United States Patent
Application |
20060218762 |
Kind Code |
A1 |
Sandhu; Gurtej Singh ; et
al. |
October 5, 2006 |
SYSTEM AND METHOD FOR DETECTING FLOW IN A MASS FLOW CONTROLLER
Abstract
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.
Inventors: |
Sandhu; Gurtej Singh;
(Boise, ID) ; Sharan; Sujit; (Chandler, AZ)
; Rueger; Neal R.; (Boise, ID) ; Mardian; Allen
P.; (Boise, ID) |
Correspondence
Address: |
SCHWEGMAN, LUNDBERG, WOESSNER & KLUTH, P.A.
P.O. BOX 2938
MINNEAPOLIS
MN
55402
US
|
Assignee: |
Micron Technology, Inc.
|
Family ID: |
25482730 |
Appl. No.: |
11/421701 |
Filed: |
June 1, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10674963 |
Sep 29, 2003 |
|
|
|
11421701 |
Jun 1, 2006 |
|
|
|
09945161 |
Aug 30, 2001 |
6627465 |
|
|
10674963 |
Sep 29, 2003 |
|
|
|
Current U.S.
Class: |
29/25.01 ;
118/715; 156/345.33 |
Current CPC
Class: |
G05D 7/0635 20130101;
G01P 13/0006 20130101; G01P 13/0033 20130101; Y10T 137/0396
20150401; G01P 13/0013 20130101; G01F 1/42 20130101; G01F 1/40
20130101; Y10T 137/8242 20150401; Y10T 137/7722 20150401; Y10T
137/775 20150401 |
Class at
Publication: |
029/025.01 ;
156/345.33; 118/715 |
International
Class: |
H01L 21/00 20060101
H01L021/00; H01L 21/306 20060101 H01L021/306; C23C 16/00 20060101
C23C016/00 |
Claims
1. A gate position sensor, comprising: an orifice and a gate
adapted to adjust flow through the orifice; a light source to
generate a light signal; and a light detector adapted to receive
the light signal, the light detector being operably positioned with
respect to the light source and the orifice such that movement of
the gate with respect to the orifice affects a received light
signal.
2. The sensor of claim 1, wherein gate movement interrupts the
light signal.
3. The sensor of claim 1, wherein the orifice and the gate are an
orifice and a gate from an ultrasonic mass flow controller adapted
to control gas flow from a semiconductor gas source to a
semiconductor processing chamber.
4. The system of claim 1, wherein the gate is adapted to oscillate
between an open and closed position with respect to the
orifice.
5. A gate position sensor, comprising: a transmitter for
transmitting a signal in a flow controller, wherein a position of a
gate in the flow controller affects the signal; and a receiver for
receiving the signal, wherein the receiver is adapted to provide a
signal output for the sensor to indicate a gate position within the
flow controller based on the signal received, wherein the
transmitter is a light source, the signal is a light signal
transmitted by the light source, and the receiver is a light
detector operably positioned with respect to the light source and
an orifice such that movement of the gate oscillating between an
opened position and a closed position interrupts the light signal
from being received by the light detector.
6. The sensor of claim 5, wherein the transmitter includes a
transmitter for transmitting a signal in a mass flow
controller.
7. The sensor of claim 5, wherein the transmitter includes a
transmitter for transmitting a signal in an ultrasonic mass flow
controller.
8. A gate position sensor for a flow controller having an orifice
and a gate for closing the orifice, comprising: a light source
positioned on a first side of the orifice; and a light detector
positioned with respect to the light source and the orifice such
that movement of the gate oscillating between an opened position
and a closed position interrupts a light signal generated by the
light source from being received by the light detector.
9. The sensor of claim 8, wherein the sensor is adapted to sense
gate movement for an ultrasonic mass flow controller.
10. The sensor of claim 8, wherein the sensor is adapted for use in
monitoring a frequency of gate oscillations.
11. The sensor of claim 8, wherein the sensor is adapted for use in
detecting a position of the gate.
12. The sensor of claim 11, wherein the sensor is adapted to detect
a light intensity.
13. A system, comprising: an ultrasonic mass flow controller with
an orifice and a gate adapted to close the orifice; a sensor,
including: a light source positioned on a first side of the
orifice; and a light detector positioned with respect to the light
source and the orifice such that movement of the gate oscillating
between an opened position and a closed position affects light
received by the light detector from the light source.
14. The system of claim 13, further comprising: a semiconductor gas
source; a semiconductor processing chamber; and a gas flow line
connecting the gas source to the processing chamber, the ultrasonic
mass flow controller being adapted to control gas flow through the
line from the gas source to the processing chamber.
15. The system of claim 13, further comprising a processor
connected to the ultrasonic mass flow controller, the light source,
and the light detector.
16. The system of claim 13, wherein the sensor is adapted to sense
gate movement.
17. The system of claim 13, wherein the sensor is adapted for use
in monitoring a frequency of gate oscillations.
18. The system of claim 13, wherein the sensor is adapted for use
in detecting a position of the gate.
19. The system of claim 18, wherein the sensor is adapted to detect
a light intensity.
20. A system, comprising: an inflow line; a flow controller
positioned in the inflow line for controlling flow, the flow
controller including a gate and an actuator for moving the gate to
control flow; a gate position sensor for monitoring whether the
gate is in an opened position or a closed position, the sensor
including means for transmitting a signal in the flow controller
such that a position of the gate in the flow controller affects the
signal, and means for receiving the signal and providing a signal
output for the sensor to indicate a gate position within the flow
controller based on the signal received; and a processor for
controlling the position of the gate and for interfacing with the
sensor, wherein the sensor includes a light source and a light
detector, and wherein the light source and the light detector are
operably positioned with respect to each other and an orifice such
that movement of the gate oscillating between an opened position
and a closed position interrupts the light signal from being
received by the light detector.
21. The system of claim 20, further comprising: a semiconductor gas
source; and a semiconductor processing chamber, wherein the
ultrasonic mass flow controller is adapted to control gas flow
through the inflow line from the gas source to the processing
chamber.
22. The system of claim 20, wherein the sensor is adapted to sense
gate movement.
23. The system of claim 20, wherein the sensor is adapted for use
in monitoring a frequency of gate oscillations.
24. The system of claim 20, wherein the sensor is adapted for use
in detecting a position of the gate.
25. The system of claim 24, wherein the sensor is adapted to detect
a light intensity.
Description
RELATED APPLICATION(S)
[0001] This application is a Divisional of U.S. application Ser.
No. 10/674,963 filed Sep. 29, 2003, which is a Divisional of U.S.
application Ser. No. 09/945,161 filed Aug. 30, 2001, now U.S. Pat.
No. 6,627,465, both of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] 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
[0003] An integrated circuit 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.
[0004] 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.
[0005] 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.
[0006] 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.
[0007] Therefore, there is a need in the art to provide improved
MFC which overcomes these problems.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 illustrates a novel MFC and electronic system for
delivering a mass and for detecting a flow failure according to the
teachings of the present invention.
[0009] FIG. 2 illustrates a current detector embodiment of a gate
position sensor used in the MFC of FIG. 1.
[0010] FIG. 3 illustrates a physical wave generator/receiver
embodiment of a gate position sensor used in the MFC of FIG. 1, and
a direct detection method of using the same.
[0011] FIG. 4 illustrates a physical wave generator/receiver
embodiment of a gate position sensor used in the MFC of FIG. 1, and
a signal interference detection method of using the same.
[0012] FIG. 5 illustrates an optical detector embodiment of a gate
position sensor used in the MFC of FIG. 1.
[0013] FIG. 6 illustrates an electromagnetic pulse detector
embodiment of a gate position sensor used in the MFC of FIG. 1.
DETAILED DESCRIPTION
[0014] In the following detailed description of the invention,
reference is made to the accompanying drawings which form a part
hereof, and in which is shown, by way of illustration, specific
embodiments in which the invention may be practiced. In the
drawings, like numerals describe substantially similar components
throughout the several views. These embodiments are described in
sufficient detail to enable those skilled in the art to practice
the invention. Other embodiments may be utilized and structural,
logical, and electrical changes may be made without departing from
the scope of the present invention.
[0015] 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.
[0016] 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.
[0017] 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.
[0018] 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.
[0019] These and other embodiments, aspects, advantages, and
features of the present invention will be set forth in part in the
description which follows, and in part will become apparent to
those skilled in the art by reference to the following description
of the invention and referenced drawings or by practice of the
invention. The aspects, advantages, and features of the invention
are realized and attained by means of the instrumentalities,
procedures, and combinations particularly pointed out in the
appended claims.
[0020] 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.
[0021] 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.
[0022] An electronic delivery system 110 incorporating a mass flow
controller 112 is generally illustrated in FIG. 1. The system 110
generally comprises a source 114, a flow controller 112 connected
to the source 114 through an inflow line 116, a sensor 118, a
processor 120, and an outflow line 122 connected to a chamber 124.
The inflow line 116 delivers the substance from the source 114 to
mass flow controller 112, which in turn regulates the flow of the
substance out through the outflow line 122. This delivered
substance may comprise any material. Therefore, the flow controller
112 is often referred to as a mass flow controller (MFC). The flow
controller 112 may be referred to as a liquid flow controller (LFC)
if a liquid substance is being delivered by the system 110, 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.
[0023] The MFC 112 is positioned in the flow, and is adapted for
controlling or regulating the flow out through the outflow line
122. An ultrasonic MFC 112 passes a high velocity flow (higher than
the speed of sound) through an orifice 226, specifically through a
gated orifice. As described throughout this specification and as
shown in the Figures, the term orifice 226 is 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 gate 228 is closed. A gate 228 and
corresponding actuator 230 for moving the gate 228, as generally
illustrated in FIG. 2 and is also illustrated in FIGS. 3-6 using
like numbers, is operably positioned proximate to the orifice 226
such that the gate 228 may oscillate between a closed position in
which the flow through the orifice 226 is prevented, and an opened
position in which the flow through the orifice 226 is allowed. The
actuator 230 oscillates or shutters the gate 228 between the opened
and closed positions to regulate the ultrasonic flow through the
orifice 226. The amount of substance that is delivered through the
MFC 212 is therefore dependent upon the duty cycle of the gate 228,
which corresponds to the relative amount of time that the gate 228
is opened rather than closed for each opened-to-closed-to-opened
cycle.
[0024] Referring again to FIG. 1, the gate position sensor 118
senses, detects or otherwise monitors the position of the gate 128.
In one embodiment of the present invention, the gate position
sensor 118 determines whether the gate 128 is in an opened position
or is in a closed position. In other embodiments, the sensor 118 is
designed to determine whether the gate 128 is moving as expected so
as to verify proper operation. Additionally, the gate position
sensor 118 may be designed to accurately detect the position that
the gate 128 is in between the opened and closed positions.
[0025] The electronic system 110 includes the processor 120 that is
interfaced with the actuator 130 of the control gate 128 to control
the duty cycle of the gate 128. That is, the processor sends a
control signal to oscillate the control gate 128 for the purpose of
regulating the flow through the MFC 112. The processor 120 further
may be interfaced with the gate position sensor 118, and thus is
able to determine the position and/or motion of the control gate
128. The processor 120 may include appropriate software programs to
provide a number of functions, including but not limited to,
verifying that the desired position of the control gate 128
corresponds with the actual position of the control gate 128 as
sensed by the gate position sensor 118, 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 sensor 118 to the
processor 120, the sensor 118 may provide an output to an audio or
visual device, or may otherwise provide a signal to other control
circuitry.
[0026] FIG. 1 illustrates the electronic system 110 as a
semiconductor manufacturing system in which the inflow line 116 is
connected to a semiconductor process gas source 114. For an
ultrasonic MFC, the inflow line 16 provides an ultrasonic gas flow
to the MFC 112. As indicated above, the MFC 112 regulates the
ultrasonic gas flow by oscillating the control gate 128 between
closed and opened positions with respect to the orifice 126. The
regulated or controlled gas flow is delivered to a processing
chamber 124 in which various semiconductor processes are performed
on the wafer. These processes may include, for example, deposition,
etching, and doping. Also as illustrated in FIG. 1, the MFC 112 may
include a pressure and temperature transducer 132 interfaced with
the processor 120 to monitor the characteristics of the gas and
provide appropriate feedback control to the control gate 128.
[0027] Generally, the gate position sensor 118 includes a
transmitter 134 for transmitting a signal 136 and a receiver 138
for receiving the signal 140. The receiver 138 provides an
indication of whether the control gate 128 is in an opened
position, a closed position, or is in another position based on the
signal 140 received. The receiver 138 may also provide a signal
that the control gate is moving, either in addition to or in place
of the position signal. The processor 120, or other control
circuitry, interprets the signal 140 received by the receiver 138
to provide an immediate or nearly immediate warning if there has
been a flow failure or if the control gate 128 has otherwise
malfunctioned. As is described in more detail below with respect to
the detailed description of the MFC 112 and the gate position
sensor 118, there are a number of embodiments for the gate position
sensor 118. The following embodiments provide a non-exhaustive list
of sensor 118 designs for determining the gate position and/or gate
movement that fall within the teachings of the present invention
for determining flow and flow failure.
[0028] In one embodiment, as generally illustrated in FIG. 2 and
will be discussed in more detail below, the gate position sensor
218 may include a device 242 that applies an electrical potential
across the orifice 226 and the gate 228 in the MFC 212. The sensor
218 further may include a current detector 244 that is able to
detect a current flow through a junction formed when the orifice
226 contacts the gate 228 when the gate 228 is closed, i.e. an
orifice/gate junction. Thus, in this embodiment, the transmitter
134 shown in FIG. 1 is the device 242 for applying electric
potential across the gate 228 and an orifice 226 in the MFC 212,
the signal 136 and 140 shown in FIG. 1 is electric current 246
flowing through the orifice/gate junction formed when the gate 228
is closed, and the receiver 138 shown in FIG. 1 is a current
detector 244 for detecting current flowing through the orifice/gate
junction.
[0029] In another embodiment, as generally illustrated in FIGS. 3
and 4 using like numbers and will be discussed in more detail
below, the gate position sensor 318 may include a physical wave
generator 348 and at least one physical wave receiver 350. The
physical wave generator 348 generates a physical signal 352 in the
MFC 312. The physical wave receiver 350 detects the physical signal
352 propagating from the generator 348 through an orifice/gate
junction formed when the gate 328 is closed. Thus, in this
embodiment, the transmitter 134 of FIG. 1 is the physical wave
generator 348, the signals 136 and 140 of FIG. 1 are the physical
signal 352 propagating through the orifice/gate junction formed
when the gate 328 is closed, and the receiver 138 of FIG. 1 is the
physical wave receiver 350 for detecting the physical signal 352
propagating through the orifice/gate junction.
[0030] In another embodiment, as generally illustrated in FIG. 5
and will be discussed in more detail below, the gate position
sensor 518 includes a light source 556 and a light detector 558.
The light source 556 is positioned on a first side of an orifice
526 in the MFC 512, and the light detector 558 is positioned on a
second side of the orifice 526. The light source 556 and light
detector 558 are positioned and arranged so that, as the control
gate 528 oscillates between an opened position a closed position
with respect to the orifice 526, a light signal 560 received by the
light detector 558 and transmitted by the light source 556 will be
interrupted such that the gate position can be determined by the
interrupted signal. In one embodiment, the light source 556 and
light detector 558 are placed on opposing inflow and outflow ends
of the orifice 526. Thus, in this embodiment, the transmitter 134
of FIG. 1 is the light source 556, the signals 136 and 140 of FIG.
1 are the light signal 560 transmitted by the light source 556, and
the receiver 138 of FIG. 1 is the light detector 558 operably
positioned with respect to the light source 556 and the orifice 526
such that movement of the control 528 gate oscillating between an
opened position and a closed position interrupts the light signal
560 from being received by the light detector 558.
[0031] In another embodiment, as generally illustrated in FIG. 6
and will be discussed in more detail below, the gate position
sensor 618 includes a magnet 662, a cooperating induction coil 664,
and an electromagnetic pulse detector 666. Movement of the control
gate 628 generates a magnetically induced signal in the induction
coil 664 detectable by the electromagnetic pulse detector 666.
Thus, in this embodiment, the transmitter 134 of FIG. 1 is the
magnet 662, the signals 136 and 140 of FIG. 1 are magnetic flux 668
from the magnet 662, and the receiver 138 of FIG. 1 is the
combination of the cooperating induction coil 664 and the
electromagnetic pulse detector 666 for detecting a magnetically
induced signal in the induction coil 664. The control gate 628
movement induces the signal in the coil by providing relative
movement between the magnet 662 and the coil 664.
[0032] The MFC 112 of FIG. 1 is illustrated in more detail in FIG.
2 and in FIGS. 3-6 using like numbers. The illustrated MFC has a
generally cylindrical structure 268, somewhat akin to the shape of
a conventional gas inflow line. However, the illustrated structure
268, 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.
[0033] In addition to the structure 268, the MFC 12 generally
comprises an orifice 226 defined herein to include the surrounding
structure that defines an opening, a mass flow control gate 228, an
actuator 230, and a gate position sensor 218. The control gate 228
is movable toward and away from the orifice 226 to control flow
through the orifice 226. In response to a control signal from the
microprocessor 120, for example, the actuator 230 moves the control
gate 228 as desired either toward the orifice 226 into a closed
position or away from the orifice 226 into an opened position. In
this manner, the actuator 230 oscillates the control gate 228
through a desired duty cycle between a closed position and an open
position to control flow through the orifice 226. The duty cycle
controls the flow, and is determined by the total time that the
control gate 228 is in an open position in comparison to the entire
period of time it takes to move the control gate 228 from an open
position to a closed position and back to the open position. The
gate position sensor 118 is adapted to determine the position
and/or movement of the control gate 228. And as illustrated above
with respect to FIG. 1, the gate position sensor 118 generally can
be considered to include a transmitter 134 for transmitting a
signal 136 and a receiver 138 for receiving the signal 140. The
receiver 138 provides 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 processor 120, to other control
circuitry, or to audio or visual indicators.
[0034] According to the teachings of the present invention as
indicated above and as generally illustrated in FIG. 1, a gate
position sensor 118 is used to sense or detect the position and/or
the movement of the control gate 128 of the MFC 112. The sensor 118
may either form part of the MFC 112, or may be a separate component
of an electronic system 110 that contains a MFC 112. 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
sensor 118 may vary. That is, the specific transmitter 134 and
receiver 138 that 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 sensor 118 is 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.
[0035] Referring now to FIG. 2, the illustrated gate position
sensor 218 includes a device 242 for applying an electrical
potential across the orifice 226 and the control gate 228. The
device 242 may 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 device 242
for applying electric potential. An orifice/gate junction is formed
to complete a circuit when the control gate 228 is closed. A
current detector 244 is able to detect the current flow 246, or an
increase in current flow, through the orifice/gate junction. Based
on the detection of this current 246, the system 110 is able to
determine that the control gate is closed 228. 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 gate 228
and at the orifice 226. Therefore, the gate 228 and orifice 226
form a conductor through which current may pass when the control
gate 228 is closed and the orifice/gate junction is formed.
[0036] When the control gate 228 is open, no current other than
leakage currents through alternative pathways within the entire
structure 268 will be detected. The MFC 212 may 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 structure 268 and the specific
characteristics of the actuator 230 vary, 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.
[0037] Referring now to FIGS. 3-4, the gate position sensor 318 is
illustrated to include a physical wave generator 348 for generating
a physical signal 352 and at least one physical wave receiver 350
for receiving the physical signal 352. As one skilled in the art
would recognize based on the teachings of the present invention,
the positions of the generator 348 and receiver 350 may vary. The
receiver 350 may be considered to be a transducer that forms a
vibration sensor or switch. The physical wave generator 348 and the
physical wave receiver 350 may be formed using piezoelectric
crystals. However, this embodiment of the invention is not so
limited to the use of piezoelectric crystals.
[0038] The physical wave generator 348 is driven with an ultrasonic
frequency and sends ultrasonic physical waves through the structure
368. The receiver 350 receives the ultrasonic wave form 352 through
the orifice/gate junction formed when the control gate 328 is
closed. When the control gate 328 is open, the wave energy can only
be received by the receiver 350 via a secondary pathway, i.e.
physical signal 454 in FIG. 4 for example, throughout the structure
368, and therefore will register as a much lower intensity or
amplitude. The system 110 is able to determine that the control
gate 328 is in a closed position when the physical signal receiver
350 provides an indication that it has detected the physical signal
352 which propagated through the gate/orifice junction.
[0039] A direct physical wave detection method is illustrated in
FIG. 3; namely, the physical wave receiver 350 directly detects the
closed gate by sensing an increased amplitude in the physical
signal received by the receiver 350 caused by the signal 352 being
directly transmitted through the orifice/gate junction. When the
control gate 328 is closed, the signal detected by the receiver 350
will be strong due to the direct connection between the generator
348 and the receiver 350. When the control gate 328 is open, the
signal will be weak due to a non-existent or weak signal 354 being
transmitted elsewhere throughout the structure 368, depending on
the physical construction of the system. In other words, a portion
of the generated physical wave may be transmitted as signal 454 of
FIG. 4 throughout the structure and as signal 352 through the
orifice/gate junction. The received physical signal will be
significantly higher if a direct signal path 352 is provided
between the physical wave generator 348 and physical wave receiver
350.
[0040] A physical wave signal interference detection method is
illustrated in FIG. 4; namely, the physical wave receiver 450 is
adapted for detecting and distinguishing a complex wave formed from
a superposition of a first physical signal 454 and a second
physical signal 452. It simplifies this analysis to consider that
the structure 468 has at least two separate pathways 452 and 454
for the physical wave transmission to be detected at the receiver
450. The required time for each transmission is a function of the
entire structure 468, and the interferences between the signals 452
and 454 from all possible paths will give a complex waveform at the
receiver 450. The first physical signal 454 is propagated
throughout the structure 468 when the control gate 428 is open. For
a given generator 448/receiver 450 arrangement on a given structure
468, the first physical signal 454 will have a signature wave form.
The second physical signal 452 is directly propagated from the
physical wave generator 448 to the physical wave receiver 450
through the orifice/gate junction formed when the control gate 428
is closed. Similarly, for a given generator 448/receiver 450
arrangement on a given structure 468, the second physical signal
will have a signature wave form. It follows that the superposition
of the first and second signals 454 and 452 will also have a
signature wave form. These signature waveforms are repeatable.
Therefore, for physical wave signal interference detection method,
the system 110 includes circuitry capable of distinguishing the
first signal 454 from the superposition of the first and second
signals 454 and 452 in order to determine whether the control gate
428 is closed.
[0041] Alternatively, other receivers/transducers could be located
at intermediate positions between the generator 348 and the
receiver 350. The generator 348 may send a coded signal, and the
arrival time of the coded signal at each receiver/ transducer would
indicate whether the control gate 328 is opened or closed.
[0042] As another alternative, the physical wave generator may be
considered to be the control gate 328 itself as it produces a
physical wave throughout the structure 368 each time it closes. In
this situation, the physical wave receiver 350 is positioned and
arranged to detect, and if necessary distinguish from other
physical signals, the physical signal generated by the gate 328
when it closes. This embodiment monitors the self-generated sound
wave of a gated orifice.
[0043] Referring now to FIG. 5, the gate position sensor 518 is
illustrated to include a light source 556 positioned on a first
side of the orifice 526 and a light detector 558 positioned on a
second side of the orifice 526. Movement of the control gate 528
oscillating between an opened position and a closed position
interrupts the light signal 560 from being received by the light
detector 558. As one of ordinary skill would understand from
reading this disclosure, there are a number of possible layouts of
the light source 556 and the light detector 558 that could be used
to detect a gate position or gate motion. One, as illustrated in
FIG. 5, shows the light source 556 and the light detector 558 on
opposing inflow and outflow ends of the orifice 526 such that the
light detector 558 receives the light signal 560 from the light
source 556 through the orifice 526. Another possible arrangement is
to have the light source 556 and the light detector 558 across the
control gate 528 from each other. A light detector 558 with a fast
response will be able to directly monitor the frequency of the
opening and closing of the gate 528, and thus give a direct measure
of the gas flow through the MFC 512 in addition to simply detecting
whether the gate 528 is 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 signal 560 in order to detect the position of a partially
closed or partially opened gate 528.
[0044] Referring now to FIG. 6, the gate position sensor 618 is
illustrated to include a magnet 662, a cooperating induction coil
664, and an electromagnetic pulse detector 666. Movement of the
gate 628 generates a magnetically induced signal in an induction
coil 664 detectable by the electromagnetic pulse detector 666. 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 magnet 662 may either be a permanent magnet, as
illustrated, or an electrically activated magnetic coil. Either the
magnet 662 or the induction coil 664 may be attached to the moving
arm of the gate 628, with the other operably located nearby so that
the changing magnetic flux 668 caused by the motion of the control
gate 628 will induce an electromagnetic signal in the induction
coil 664.
[0045] 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that any arrangement which is calculated to achieve the
same purpose may be substituted for the specific embodiment shown.
This application is intended to cover any adaptations or variations
of the present invention. It is to be understood that the above
description is intended to be illustrative, and not restrictive.
Combinations of the above embodiments, and other embodiments will
be apparent to those of skill in the art upon reviewing the above
description. The scope of the invention includes any other
applications in which the above structures and fabrication methods
are used. The scope of the invention should be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled.
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