Patent ID: 12228435

DETAILED DESCRIPTION

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention or inventions. The description of illustrative embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of the exemplary embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “left,” “right,” “top,” “bottom,” “front” and “rear” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated as such. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” “secured” and other similar terms refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. The discussion herein describes and illustrates some possible non-limiting combinations of features that may exist alone or in other combinations of features. Furthermore, as used herein, the term “or” is to be interpreted as a logical operator that results in true whenever one or more of its operands are true.

The disclosure is divided into four sections. Section I discusses a device and method for delivering process gas using a remote pressure measurement device. Section II discusses an MFC device with space saving layouts and improved functionalities. Section III discusses a gas delivery apparatus to output a process gas as rapid square waves of flow. Section IV discusses an electronic regulator utilizing reverse flow for fast bleed down of gas pressure in a gas delivery apparatus supplying a process gas at specific mass flow rates to a process. Different embodiments disclosed in the respective sections can be used together as part of a gas delivery apparatus, method, or system. To the extent a term, reference number, or symbol is used differently in different sections, context should be taken from the relevant section and not the other sections.

Section I

FIG.1Ais a schematic diagram illustrating a pressure based MFC1100with a volume (V1) in conduit1198A that is used to measure pressure. MFC1100has an inlet port1101A, an outlet port1102A, a proportional inlet valve1103A, a first pressure transducer1104A, a restrictor1105A, a second pressure transducer1106A and a temperature sensor1107A. The first pressure transducer1104A measures pressure over V1 as an input for pressure regulation and is operates so that pressure at the first pressure transducer1104A closely matches the pressure at an inlet of the restrictor1105A. The second pressure transducer1106A is located downstream and a temperature sensor1107A is used to increase accuracy.

FIG.1Bis a block diagram ofFIG.1Aillustrating a flow order for a process gas through the pressure based MFC1100B. As shown, a process gas moves through a proportional valve1103B to a conduit containing V11198B where the process gas is measured by a first pressure transducer1104B. Next the gas passes through restrictor1105B into a conduit with volume V2,1199B, where the pressure representative of the pressure at the outlet of the restrictor is measured. Finally, the process gas often exhausts from the MFC1100B to a process through an isolation valve actuator and seat1110.

Problematically, the space consumed by V1 hinders further efficiencies in accuracy, bleed down performance, space consumption and costs of gas delivery systems used for processing. Furthermore, when an external control directs the MFC to stop or reduce the magnitude of the gas flow to a lower rate of flow, V1 produces undesirable slow bleed down times to the new flow value.

What is needed is a flow node to provide an accurate delivery of process gas without the inefficiencies of MFCs having a local pressure measurement directly on V1, by utilizing a remote pressure measurement of V1 pressure to reduce the bleed down volume while still providing pressure measurements that represent the pressure of the gas inlet to the restrictor with sufficient accuracy to maintain the specified accuracy of the flow device.

A device and method for a flow node to control gas flow utilizing a remote pressure measurement device are disclosed. In general, the flow node disclosed herein eliminates the local pressure measurement directly on V1 needed by MFCs because a resulting pressure drop across conduits and poppet and valve seat of the flow node is designed to be insignificant relative to the remote measurement. The disclosed techniques can be implemented in a semiconductor fabrication process, or any other environment requiring flow rates of gas or fluid (e.g., low flow, high flow, 0.1 sccm, or 30,000 sccm) within tight tolerance limits or where reduced equipment cost is desired.

FIG.2Ais a block diagram illustrating a gas stick1200A that includes a flow node1201A making use of a remote pressure measurement, according to an embodiment. The gas stick1200A also includes an electronic regulator1202A and an inlet1203A and outlet1204A to a conduit.

The inlet1203A of a VCR fitting (e.g., as produced by Parker Corporation) receives a process gas into a conduit. Nitrogen is an exemplary process gas, but any suitable gas or fluid could be substituted. The conduit(s) can be any suitable tubing or plumbing, either rigid or flexible, to move the process gas through and to the electronic regulator1202A and the flow node1201A. The conduit can have an outside diameter of, for example, ¼ inch and inside diameter of 3/16 inch. K1S substrate blocks1203, as manufactured by Hytron Corporation, serve as an interconnecting platform for the electronic regulator1202A, the flow node1201A and the inlet conduit1203A and outlet1204A conduit.

The outlet1204A of a VCR fitting delivers the process gas to a next conduit for eventual use by the process. In some embodiments, additional processing is performed on the process gas, such as mixing with other gases, or the like.

The flow node1201A includes a valve seat and poppet assembly1205A, an actuator1222(represented by the arrow up/down arrow), internal conduits1207(can represent one or more portions of conduit), interface sealing surfaces1208and a characterized restrictor1209A. The flow node1201A is connected in series with an upstream electronic regulator1202A having a pressure transducer1206A. Generally, the flow node1201A limits a mass flow of gas or liquids that is in accordance with a pressure of a gas or liquids as measured upstream. Optionally a pressure measurement and/or temperature assumed, measured or communicated by other instrumentation elsewhere in the system can be used to improve the accuracy of the flow if available.

The valve seat and poppet assembly1205A includes an opening for gas flow and a movable poppet to preclude gas flow. In operation, the poppet moves between on and off by opening to allow process gas to flow into the conduit and closing to stop the process gas. In one embodiment, the valve seat has a high conductance relative to the characterized restrictor1209A (or alternatively, has low impedance relative to the characterized restrictor), for example, a ratio of 10:1, 200:1 (preferred) or higher. The conductance of an on/off valve such as used in the flow node, can be the maximum practical amount for a design envelope. With an MFC using a proportional valve as opposed to an on/off isolation valve, conductance has to be balanced with (and thus, is limited by) flow resolution needs.

The characterized restrictor1209A is located, in one embodiment, directly adjacent to and in series with the valve seat and poppet assembly1205A. The characterized flow restrictor1209A can be a laminar flow element (compressible or in-compressible flow), an orifice (sonic, sub sonic or molecular), a venturi nozzle (sonic, sub sonic or molecular), or the like. As discussed, the characterized restrictor1209A is selected to provide the desired full-scale flow at or slightly below the target full scale pressure to be delivered to the flow node1201A and still have a low conductance relative to a conductance of the valve seat. A resulting pressure drop from the pressure regulator output, through the conduits to the flow node1201A and across the valve seat of the flow node1201A is small enough to be ignored so that a pressure measurement within the flow node1201A is not required to achieve a desired accuracy.

For example, a characterized restrictor designed to flow 5,000 sccm at P1=2000 Torr is placed in the throat of an air valve with a flow impedance and associated plumbing that generates, for instance, a 0.15 Torr pressure drop when delivering the 5000 sccm flow through the restrictor at 2000 Torr. The induced flow error would be roughly 0.15% of reading if the characterized restrictor is a compressible laminar flow element. The 0.15% is well within the 1% reading of the device and is acceptable allowing the device to maintain it specified accuracy.

An electronic regulator1202A with the pressure1206A transducer and a proportional valve1211A measures and correspondingly controls a pressure of the process gas within the conduit. A proportional valve1211A of the electronic regulator1202A modulates to control a pressure of the process gas inlet in accordance with pressure set points. The pressure set points can be received automatically from a controller or manually input. In some embodiments, the pressure set points are externally calculated to cause a desired mass flow rate. In some embodiments, the electronic regulator can maintain accuracy from an upstream location for flows up to 8 SLM (standard liter per minute) on N2 (nitrogen) or 4 SLM on SF6 (sulfur hexafluoride) for flow nodes using a ¼″ air valve commonly used in the industry. In other embodiments, flow rates can be higher if larger standard components or non-standard modified components are used. At a certain point as flow rate gets larger, parasitic losses of pressure across the valve seat make the overall pressure drop larger, relative to the pressure delivered to the restrictor1209A, than manageable to maintain flow measurement accuracy.

FIG.2Bis a block diagram ofFIG.2Aillustrating a flow order for a process gas though a gas stick1200B that includes a flow node1201B with a remote pressure measurement, according to an embodiment.

The gas is received through an inlet1203B to a proportional valve1211B that is modulated in coordination with a pressure transducer1206B to control pressure to the1201B flow node. A volume1298for bleed down between the valve seat and poppet assembly1205B and the characterized restrictor1209B is minimized for faster bleed down (e.g., 50× faster). By minimizing the distance and geometry, the volume1298of gas between the components is minimized. An exemplary volume of the resulting bleed off volume can be a negligible at 0.02 cc, 0.01 cc or less. As shown inFIG.1B, an exemplary bleed off volume of an MFC can be 0.50 cc. Optionally, a temperature sensor1252provides an internal temperature measurement, although temperature can also be received from external components such as a gas box temperature controller or sensor.

Additionally, the MFC has typical measurements of 1.1″ (W)×4.1″ (L)×5″ (H), compared to a flow node constructed from an air valve having measurements of 1.1″ (W)×1.1″ (L)×4′ (H) for similar operational parameters. Further, the pressure based MFC can cost $2,500, while an air valve can cost $90 in volume and a characterized restrictor to press in the air valve and make a flow node from the air valve, can cost an additional $20.

FIGS.3A-3Bare schematic diagrams illustrating alternative configurations of a valve relative to a characterized restrictor, according to some embodiments.

In more detail, the valve seat and poppet assembly1301A of a first configuration inFIG.3Aare located upstream of the characterized restrictor1303A. In some cases, the characterized restrictor1303A can be exposed to the multiple gases from other flow nodes and MFCs exhausting to a common conduit. In a no flow condition, the isolation on the flow node is closed, and small amounts of these other gases can backflow into the restrictor1303A which can lead to reliability issues such as corrosion or particle generation in the case where the gases are incompatible or in reacting families. In an alternative configuration ofFIG.3B, a characterized restrictor1303B is located upstream of a valve seat and poppet assembly1301B. By locating the valve seat and poppet assembly1301B downstream, the backflow is remediated. On the other hand, the buildup of gas pressure between the restrictor1303B and the downstream valve seat can cause a microburst which may be objectionable in some cases. So long as the ratio of conductance remains, the flow node operates within tolerable error limits.

FIGS.4A-4Care schematic diagrams illustrating alternative configurations of multiple flow nodes, according to some embodiments.

Specifically,FIG.4Ashows a gas stick1400A with two flow nodes1401A,B in parallel. An additional K1S substrate1402is needed to support the additional flow nodes.

In operation, the process gas can flow through either flow node or both. When flow node1401A is open, the process gas flows to a conduit1403and when flow node1401B is open, the process gas flows to a conduit1404. For example, one flow node can be configured to accurately handle low flows while the other flow node accurately handles all non-low flows. The dual flow node thus increases an overall dynamic range that is superior to an MFC. Further efficiency is achieved because a single pressure transducer is shared between the flow nodes.

While the characterized restrictors are located downstream of the valve seat in theFIG.4A,FIG.4Bshows an example of characterized restrictors located upstream of the valve seat. When a flow node1413A is open, the process gas inlets through a conduit1411, and when a flow node1413B is open, the process gas inlets through a conduit1412.

A further example ofFIG.4Cshows an embodiment of a gas stick1400C with three flow nodes1421A-C in a parallel configuration. This configuration provides the equivalent capability as three separate MFCs, but only occupies one third the space while providing a cost savings. The embodiment also shows characterized restrictor located downstream of the valve seat and poppet assemblies, although the opposite configuration is also possible. When the flow node1421A is open, the process gas flows through a conduit1422, when the flow node1421B is open, the process gas flows through a conduit1423, and when the flow node1421C is open, the process gas flows through a conduit1424.

FIGS.5A-5Care schematic diagrams illustrating a flow node supplied by a self-venting electronic regulator, according to some embodiments.

The proportional dump valve, or optional on/off valve with flow limiting restrictor in series, allows process gas to be vented from the additional conduit routed to a vent. By quickly depressurizing the conduit in a low flow scenario, changes in mass flow rate are realized with reduced bleed times.

As shown inFIG.5A, an electronic regulator1501A includes a valve1502and optional flow limiting restrictor1503in series with a conduit to a vent. A feedback and control1599can coordinate components. The configuration can relieve a volume of gas between a proportional valve1504and a flow node1505(and coupled to a pressure transducer1506) allowing it to transition more quickly from a higher pressure set point to a new lower pressure set point than could occur without the venting of gas, thus avoiding intolerable slow bleed down.

In an embodiment ofFIG.5B, a proportional valve1511provides a controlled release of the process gas to a conduit1512for venting. In an embodiment ofFIG.5C, an on/off valve1531with a limiting flow restrictor is used release the process gas to a conduit1532for venting. The on/off valve1531and limiting flow restrictor are preferred in some cases due to lower cost and less complexity for control.

FIG.6is a flow chart illustrating a method for delivering a process gas with a remote pressure measurement, according to an embodiment. The method can be implemented by any of the flow nodes discussed above.

At step1610, pressure points associated with mass flow parameters of a process gas are received. For example, an electronic regulator can receive pressure set points from a controller that is aware of characteristics of the flow node and a temperature and pressure, P2 (assumed or measured).

At step1620, a process gas is received through a high conductance valve and poppet assembly. An actuator changes position to move the poppet, thereby allowing or preventing gas flow.

At step1630, a primary flow of the process gas is limited by the low conductance characterized restrictor. As the restrictor is characterized so that flow is known as a function of pressure to the restrictor, a mass flow through the restrictor is known if one knows the pressure delivered to the flow node. Correspondingly, one can change mass flow to a new desired value by changing the pressure delivered to the flow node. As discussed, a ratio of conductance between the valve seat and the characterized restrictor, along with a minimized volume between the two, produces a very low pressure drop allowing the remote pressure measurement to represent the pressure at the inlet of the restrictor with sufficient accuracy to allow sufficiently accurate flow measurement.

At step1640, the process gas is delivered to an exhaust. The process gas can move on to be mixed with other gases, heated, cooled, or the like.

Section II

As more refined manufacturing processes evolved with time, higher performance was needed from thermal and pressure based MFCs. The stability and accuracies of the past devices were bottlenecking semiconductor fabrication process. Process step durations shortened to 5 second steps seen now verses 30 minutes process steps of the past. The relatively long transient time to change gas flow rates to the process once acceptable with the longer process steps is problematic with the shorter process steps. Further, MFCs are lagging to meet the demand for controlling gas flows over a wider flow range with more accuracy and less costly hardware.

The pressure based MFC was introduced in the last decade and is now overtaking the use of the thermal MFC in critical etch applications. In2002, Fugasity introduced a pressure base MFC called the Criterion. The pressure based MFC was an improvement on the thermal MFC and hence was a commercial success. However, those same forces that pushed the development of the Criterion, the demand for improved performance and reduced price, are still pushing to improve the design of the pressure based MFC.

One of the issues common to thermal and pressure based MFCs is form factor. Space is very expensive in a modern semiconductor tool. The interface connecting the MFC to the other components in a gas box has been standardized by the industry to allow interchangeability of devices such as MFC and air operated shut off valve produce by a multiple different suppliers. The dominate interface standard in the industry is based on components being 1.1″ wide. MFC's are 1.1″ wide (28.6 mm) by 4.13″ (105 mm) in length with porting and other geometry details as describe in the Semi F82-0304 specification. Similarly a second interface specification, Semi F84-0304, defines the interface geometry for air operated valve as being 1.1″ wide by 1.1″ in length square interface.

Independent of the device type or manufacturer the vast majority of components (air valves, filters, check valves, regulators, etc.) found in the gas box of a modern semiconductor fabrication tool will comply with the 1.1″ square interface. MFC and Electronic regulators will fit the 1.1″×4.13″ rectangular interface.

These device interchangeability issues and the resulting interface standards have had the impact of preventing spontaneous component size reductions. About every 10 to 20 years the industry has seen a new smaller standard proposed and accepted, but in time periods between these adoptions, devices are, as a practical matter, forced to retain the external envelope defined by the standards.

However, internal device design improvements that allow smaller internal components, while not affecting the external envelope, have had the beneficial effect of allowing more instrumentation and functionality to be placed into the standard external envelope. For example a supply pressure transducer, typically a 1.1″ square interface, had been traditionally place upstream of an MFC. Component size reduction of the pressure transducer and similar reduction in the MFC's internal components has allow the function of the supply pressure transducer to be integrated into the MFC thus eliminating the need for the 1.1″ square interface formerly used by the pressure transducer.

What is needed is a robust MFC having various space-saving layouts that allows additional component integration within the standard envelope and which incorporates improved design, components and new functionalities to address the transient response issues and accuracy limitations inherent in the current devices. Additionally, a layout in an MFC allows for a smaller pressure based MFC package size that allow it to fit the smaller standard square interface envelope rather than requiring the larger rectangular interface that current MFCs require.

An MFC device, and methods therein, with various space saving layouts is described.

FIG.7is a schematic diagram illustrating a layout of a pressure based MFC2100with a P1 pressure transducer2104coupled to a base2110within a standard envelope. The MFC2100can be 4.13″ long to fit industry standards. It consists of a proportional flow control valve2105at an inlet2101of the device, followed by the P1 pressure transducer2104downstream of a proportional flow control valve2105, followed by a characterized laminar flow element (LFE)2115acting as a flow restrictor, and a P2 pressure transducer2106near the outlet2102of the device. The MFC2100also utilizes a printed circuit board (PCB) (not shown) containing supporting electronics, software and calibration coefficient for receiving, pressure signals, a temperature signal (e.g., from a temperature sensor2107embedded in the device) and an external set point indicating the target flow. Given these inputs the PCB drives a voltage to the proportional inlet valve2105until sufficient pressure was achieved in the volume between a poppet of a valve and the downstream restrictor, to achieve the needed flow through the restrictor. This particular pressurized volume is referred to herein as a P1 volume. Under this paradigm, the P1 pressure transducer2104is coupled to the base in order to monitor the pressure of P1 volume. Gas flow follows arrows in from inlet2101through device2103to volume2198through LFE2115to volume2199and out at outlet2102.

FIG.8Ais a schematic diagram illustrating a layout for a pressure based MFC2200A with a P1 pressure transducer2210A decoupled from a base2220, according to an embodiment. Because the P1 pressure transducer2210A no longer occupies space on the base2220, the envelope can be reduced from the standard size of 4.13″ or the freed up space on the base can be used to add additional components and functionality.

The inlet2211of the MFC2200A receives a process gas into a conduit (e.g., an inlet conduit). Nitrogen is an exemplary process gas, but any suitable gas or fluid could be substituted. The conduit can be any suitable tubing, plumbing or machined block, either rigid or flexible. A KS1 substrate block (not shown) as manufactured by Hytron Corporation, serves as an interconnecting platform for the base2220of the MFC2200A and other components for supplying gas to and receiving gas from the MFC2200A.

The proportional inlet valve2230A can be a solenoid or other appropriate component physically coupled to the base2220to control gas flow through an inlet2211of the MFC2200A. Process gas is received from the conduit (e.g., the inlet conduit) and sent back to the conduit after processing (e.g., the intermediate conduit). Rather than being directly connected to the base2220, the P1 pressure transducer2210is communicatively coupled to monitor process gas internally downstream of from the valve seat and poppet of proportional inlet valve2230A. In some embodiments, the proportional inlet valve2230A has a movable portion and a fixed portion, and the P1 pressure transducer2210A is coupled to the fixed portion.

More specifically, the proportional inlet valve2230A has a solid upper pole rigidly attached to an outer tube, also rigidly attached to the base of the valve which is sealed to the base2220of the MFC2200A. The mechanism contains the pressurized gas flowing through the proportional inlet valve2230A. Inside the outer tube a movable plunger is suspended via a radial spring. A conduit is bored through the fixed pole to communicate gas pressure to the P1 pressure transducer2210A attach to an end of the fixed pole, on top of the proportional inlet valve2230. As a result, the process gas and its associated pressure can communicate from the exits of the valve seat to the P1 pressure transducer2210A allowing the P1 pressure upstream of the restrictor to be sensed and controlled.

Details2201and2204are detail views showing the gas passages connecting the valve seat to the P1 pressure transducer2210. Detail2201shows the small passages that contain gas from the valve seat to the movable plunger. Detail2202illustrates the flow passage in the area of the movable plunger and orifice valve seat. Detail2203shows the gas passage past the radial spring and into the small annular gap between the movable plunger and the lower details of the fixed outer tube assembly. Detail2204illustrates the annular gap passage between the top section of the fixed outer tube assembly and the movable plunger and a second passage between the gap between the movable plunger and the fixed core where it enters the bore drilled through the length of the fixed plunger.

Although these passages are small, little flow is needed to pressurize or depressurize the small volume, hence, the pressure measured by the P1 pressure transducer2210effectively represents the pressure at an outlet2212of the valve seat and the inlet to the characterized restrictor.

A P2 pressure transducer2240measures process gas in the conduit (e.g., outlet conduit) between an LFE2225and the outlet2212. The outlet2212delivers the process gas to a next conduit for eventual use by the process. In some embodiments, additional processing is performed on the process gas, such as mixing with other gases, or the like. A temperature sensor2245provides temperature readings and a PCB2235processes the temperature readings and other information in controlling the components on the MFC2200A.

In an embodiment of an IGS style MFC, due to arranging the P1 pressure transducer on top, the MFC functionality can be provided by a smaller envelope (e.g., seeFIGS.14and15). In more detail, rather than complying with the traditional interface standard of Semi F82-0304 for a rectangular-shaped interface having a 4.13″ long base, the IGS style MFC can comply with the Semi F84-0304 standard for a square-shaped interface having a 1.1″ base. Both standards are hereby incorporated by reference in their entirety.

FIG.8Bis a schematic diagram illustrating a layout for a pressure based MFC2200B with a P1 pressure transducer2210B decoupled from the base over proportional inlet valve2230B and an additional component coupled to the base within a standard envelope, according to an embodiment.

Relative toFIG.8A, the newly available real estate along the base of MFC2200B is utilized for integrating one or more additional components2270within the standard size envelope rather than reducing the envelope (e.g., seeFIGS.9-13for examples of additional components).

FIG.9is a schematic diagram illustrating a layout for a pressure based MFC2300with a P1 pressure transducer2310decoupled from the base and a relief valve2370coupled to the base within a standard envelope, according to an embodiment. Space for the relief valve2370is enabled by the relocation of the P1 pressure transducer.

For MFCs having a small flow range, 500 sccm and below for example, the pressurized mass of gas between the valve seat of the proportional inlet valve and the inlet of the flow restrictor, the P1 volume, is significant compared to the desired flow rate to the process. Traditionally, when one gives the MFC a command to stop flow, via outputting a set point value of zero, the inlet proportional valve closes immediately but flow continues to bleed through the restrictor and to the process as the pressure in the P1 volume bleeds down to equalize with the pressure downstream of the restrictor. In the current pressure based MFC2300, the mass at P1 pressures that correspond to 100% full scale flow is roughly 1 to 2 standard cubic centimeters (i.e., 1 scc=1 cc of gas at 0 C and 1 atm). If the MFC is relatively large, say 1000 sccm at full scale, FS, (i.e., 1000 scc per minute) then the mass in the P1 volume is insignificant compared to the working flow rate and it bleeds off relatively quickly. However, flow rates below 1 sccm are now being requested. If the MFC is a 1 sccm FS device the P1 mass is very significant and the time constant of bleeding off the P1 mass is 1 minute. If the process is 5 seconds in length, then having an MFC that continues to flow gas to the process minutes after the command to stop flow, is not an acceptable situation. As a practical matter, the traditional mechanical full scale of pressure based MFC are limited to be above 250 sccm, to avoid this issue. Pressure based MFCs, which are built and labeled with full scales below this value, typically have the large 250 sccm laminar flow element restrictor but operate in the lower range operation by electronically or numerically scaling the flow calculation so that although the device is mechanically large its full scale reading is much smaller. The larger restrictor lowers the P1 pressure and bleeds down the P1 volume quicker, however this method induces larger device calibration drift.

The relief valve2370ofFIG.9, by contrast, routes the P1 volume mass to a non-process abatements system via a vent or vacuum pump (also seeFIGS.10,12,13and15). In operation, a PCB controls a proportional valve controlled by a PCB. When it is desired to reduce the flow from the MFC2300faster than the natural bleed down time constant of the bleed off through the restrictor to the process, the proportional P1 relief valve will open and control the P1 pressure to a lesser pressure. The lesser pressure can be controlled to quickly reduce to a lower flow rate or to stop flow. In the IGS2900ofFIG.15, an orifice2910replaces the proportional valve for cost and space savings. The orifice2910is sized to bleed off a mass flow rate typically between 50 and 500 sccm (give a 1 cc P1 volume) to allow the speedy depressurization, relative to the intended process time, of the P1 area. It is noted that an on/off valve might be placed downstream and in series with the vent line if it is desired to reduce the quantity of gas vented. In this case continuous venting is avoided and gas is only vented when it is desired to reduce the P1 pressure.

FIG.10is a schematic diagram illustrating a layout for a pressure based MFC2400with a P2 pressure transducer2440decoupled from the base and located remote to the envelope, and a relief valve2470coupled to the base, according to an embodiment.

The gas box of a modern semiconductor fabrication tool controls and mixes the flows of multiple gas species. Typically these gases combine at a common header connected to the exhaust of each of different gas sticks contain the different MFCs. Although there is typically a shut off air valve at the end of each MFC, its conductance is sufficiently high compared to the flow rate of the MFC that the pressure of the common header is sufficiently indicative of the P2 pressure seen by the individual MFCs when the shut off air valve is open and gas is flowing from the MFC. As a result, the P2 pressure information from a single pressure transducer located on this exhaust header (via analog or digital connections) can be shared with the PCBs of the individual MFCs to provide the P2 pressure information without the need for individual P2 pressure transducers located on each MFC. Optionally the P2 information may be read by the tool controller and sent electronically to the MFCs. In this layout, space is gained by removing the second pressure transducer allowing a smaller envelope or additional integrated components. Moreover, cost savings is realized because P2 pressure transducers are not needed on each MFC.

In one embodiment, as shown byFIGS.14and15, the P2 pressure transducer2840,2940can be located remotely to an IGS style MFC2800,2900. In other embodiments, the P1 pressure transducer2810,2910can be placed on top of the proportional inlet valve as described herein. Furthermore, other embodiments can add a second LFE or a self-relieving valve.

FIG.11is a schematic diagram illustrating a layout for a pressure based MFC2500with a P1 pressure transducer2510decoupled from the base and a second LFE2525B, according to an embodiment. InFIG.13, the MFC with a P1 pressure transducer2710decoupled from the base and a second LFE2725B also has a remotely-located P2 pressure transducer2740.

Returning toFIG.11, the second LFE2525B is configured in series with a high conductance valve2575. The high conductance valve2575for this embodiment can be characterized by a pressure drop through the valve sufficiently small compared to a pressure drop across the second LFE2225B, such that the flow calculation error induced by ignoring the valve pressure drop is acceptably small. For example, ignoring the pressure drop a standard ¾″ valve used in the industry in series with a LFE typically induces a 0.15% R error at 5,000 sccm flow of N2. It is noted that this error can be further reduced, or flow rates increased without loss of accuracy, by numerically correcting the flow calculation based on the characterization of the valve used.

This additional LFE2525B and valve are placed in parallel with the initial LFE2525A. When the high conductance valve is closed the MFC2500has the full scale of the single initial LFE. When the high conductance valve is open, the MFC2500has the full scale of the two LFEs2525A,2525B in parallel. By making the added LFE2525B markedly larger (i.e., much more flow at the same P1 and P2 pressures) than the initial LFE2525A, the MFC2500will have a markedly higher full scale flow capability. Effectively, the MFC2500has the novel aspect of operating as a high flow and a low flow MFC that shares the same inlet valve, transducers and PCB in the same package size as other MFCs. The MFC2500allows the replacement of multiple gas lines and MFCs for a single gas species, a situation commonly seen in a modern gas box, by a single gas line and MFC saving both space and cost.

The present MFC2500meets dueling industry demands for accurate flow control and wider ranges than current MFCs can support. The O2 flow rates from 0.1 sccm to 10,000 sccm are now achievable on the same tool. In other devices, separate O2 MFCs of different full scale values are configured to cover the desired flow range at the intended accuracy. The additional LFE2525B with the high conductance on/off valve in series can cut the number of O2 (or other gas) MFCs in half, saving space and money. While the initial LFE2525A of the pressure based MFC2500can maintain 1% reading accuracy over a dynamic range of 20 to 1, the dual LFE operation of the MFC2500, with the proper ratio between the LFE's2525A,2525B, can maintain a 1% of reading accuracy over a dynamic range of 20×20 to 1 or 2400 to 1. One of ordinary skill in the art will recognize that a dynamic range of 20 to 1 and a reading accuracy of 1% are just examples that can be varied for different implementations.

Optionally, the two LFEs2525A,2525B may be sized to focus on separate flow ranges that are not adjacent but that are further apart. For example, the smaller restrictor controlling flow accurately from 0.5 sccm to 10 sccm and the larger LFE sized to control flows from 200 sccm to 4000 when the high.

In other embodiments a third or more LFEs can be added for additional range.

In the layout embodiment ofFIG.12, a pressure based MFC2600with a second LFE2625B (in addition to a first LFE2625A) also includes a P1 pressure transducer2610decoupled from the base, and a relief valve. Additionally, in the layout embodiment ofFIG.13, a pressure based MFC2700with a second LFE2725B (in addition to a first LFE2725A) with a P1 pressure transducer decoupled and a relief also includes a P2 pressure transducer decoupled from the base and located remote to the envelope. As described above, the P2 pressure transducer can be locate downstream, for example, at a common exhaust header shared by several MFCs.

Section III

MFCs and electronic regulators are important components of delivering process gasses (e.g., N2, O2, SF6, C4F8 . . . etc.) for semiconductor fabrication. Of particular interest are the atomic layer deposition (ALD) and three-dimensional integrated circuit (3DIC) processes which require the rapid and repeated changing or the gas species in the process chamber thousands of times to achieve the needed feature.

Changing the gas species in the chamber requires the interruption of the flow on one gas species and beginning the flow of a second gas species. One alternately turns on a Gas A and off a Gas B, and then turns off Gas B and turns on Gas A again. MFCs are normally used to turn on, turn off, and control process gas flows, however commercially available MFCs are slow to turn on and achieve controlled flow, typically having response times between 0.3 and 1.0 seconds, thereby creating a bottleneck in semiconductor processing, particularly for ADL and 3DIC processing.

Other techniques mitigate the processing bottleneck by using an MFC operating at a steady state and flowing into an on-off valve that opens and closes more rapidly (e.g., every 10 to 50 msec). With this approach, pressure builds up behind the on-off valve when closed during an off cycle because of the MFC continuously flows into an accumulation volume between the MFC and the on-off valve. Unfortunately, as shown inFIG.16, when the on-off valve is opened at the beginning of an on cycle, the built up pressure in the accumulation volume initially causes a large flow of gas that quickly decays in magnitude to the steady state flow of the MFC as the stored pressure and mass is released, due to a small time constant from a low flow resistance (or nearly no flow resistance) in the on-off valve.

FIG.16shows a graph100of test data collected using special instrumentation to show an output wave produced by a system using an embodiment of the current method. During normal processing of semiconductors, instrumentation to observe the output wave in not available and thus actual flow profiles are unseen and often unknown. Problematically, a large, initial spike120is produced at the beginning of an on cycle. Due to the pressure build up when the on-off valve is closed, and high conductance of the on-off valve when opened, the process gas rushes through quickly in a ramp up110before peaking and then settling to a steady-state flow level130as desired. The magnitude ramps down140when the on-off valve is again closed during the off cycle.

The initial spike120, however, is undesirable because it introduces an unseen, unintended, and uncontrolled event. This event can vary from system to system depending on the specific of the plumbing, air valves and supply pressure actuating the on-off valve (assuming the on-off valve is an air operated valve), and introduces a random element introducing variation in a process in which repeatability is desired. In addition, the presence of this large transient gas flow has been largely unknown and generally, large overshoots in gas flow are undesirable.

Therefore, what is needed is a technique in gas delivery systems to overcome the above shortcomings by repeatable outputting fast square waves of flow, which is reproducible from system to system, while minimizing an initial spike.

Discussed below is a gas delivery apparatus, and methods, to output a process gas as rapid square waves by increasing a time constant of a gas flowing to a process during an on cycle, by installing flow restrictor having a specific high impedance.

Square Wave Output Characteristics of a Gas Delivery System

FIG.17Ais a graph3200illustrating the results of a computer simulation showing a series of square output waves produced by a gas delivery system with a properly sized and installed flow restrictor, in accordance with an embodiment of the present invention. Given the gas pressures used and the conductance of the on-off valves typically used with the current method, the addition of a flow restrictor can increases the flow impedance and hence the a time constant of the flow out of the on-off valve up to, for example, 60,000 times. The resulting square waves (such as square wave3210) are characterized by an on cycle at a desired magnitude of flow (and only minor decay which is affected by the sizing of the restrictor impedance for process gas flow), and an off cycle at a zero magnitude. During the on cycle, the magnitude ramps up over a leading edge, outputs at the desired magnitude during steady-state flow, and then ramps down to the zero magnitude over a trailing edge. During the off cycle, the magnitude preferably remains at zero.

Output waves are referred to as square waves, as an ideal, because of a desired consistent, steady-state magnitude during an on cycle. In implementation, the output waves are only substantially square or quasi-square waves because of limitations from physical characteristics of the system. Specifically, decay while outputting at the desired magnitude is referred to as droop and results from a time constant of the system as configured, as discussed below. An increased pressure, and hence accumulation mass, maintained in an accumulation volume during the on cycle, due to the increased flow impendence by adding the restrictor, keeps the output magnitude more consistent than the original rapidly decreasing pressure due to the low flow impendence. Relative to the output wave3110ofFIG.16, the undesirable spike at ramp up been eliminated due to the drastically increased time constant designed from installation of a flow restrictor. Accordingly, during the on cycle, flow from an accumulation volume is relatively constant.

FIG.17Bis a graph3250of square output waves produced by a gas delivery system with a property sized and installed flow restrictor, and an increased accumulation volume, 5 times the value ofFIG.17A, in accordance with an embodiment of the present invention. The square waves (such as wave3260) possess the same advantage as the square waves ofFIG.17Ain eliminating the large spike at ramp up. The droop, however, in the MFC embodiment is less prominent because the increased accumulation volume further increases the time constant relative toFIG.17A.

Methods for producing the improved fast square waves, and hardware for producing such square waves, are discussed below.

Methods for Square Wave Output of Gas Delivery

FIG.18is a flow chart illustrating a method3300for producing square waves in a gas delivery system, according to an embodiment of the present invention.

At step3310, a flow restrictor is sized and installed in a throat of an on-off valve. A proper size primarily depends on the available supply pressure, a desired output flow (e.g., a maximum flow target), and a ratio of the on-cycle time to the total on-cycle and off-cycle time, and the desired time constant (which determines droop). For instance, the lower the selected flow coefficient, i.e. higher flow impendence, of a flow restrictor, the higher the resulting pressure drop across the combination of the on-off valve and the flow restrictor. The relationship of time constant to wave shape is described in association withFIGS.19A-D.

During an off cycle at step3320, the on-off valve is closed, so the process gas builds pressure in an accumulation volume of conduit located upstream from a wave generation component. For example, an MFC in the wave generation component can deliver a continuous predefined mass flow to the accumulation volume, or an electronic regulator in the wave generation component can pressurize the accumulation volume, based on set points calculated by processors. As a result, pressure builds in the accumulation volume until the on-off valve opens.

During an on cycle at step3330, the on-off valve is opened, allowing the process gas to pass through a throat of the on-off valve, through the flow restrictor. Because the on-off valve essentially has nearly infinite impedance when closed and nearly zero impedance when open, gas delivery is unregulated at this point, leading to a spike if a restrictor of markedly higher impedance has not been placed in series with the on-off valve.

However, under the present technique, the flow restrictor is characterized with a significantly higher impedance, relative to the on-off valve, to further regulate gas flow. In some embodiments, the impedance is selected to drastically increase a time constant during a specific duration of the on cycle by decreasing a flow capacity on the order of, for example, 60,000 times or more while still delivering gas at an appropriate magnitude of flow, as described more fully below.

At step3340, process gas is output from the gas delivery apparatus as a series of (quasi) square waves responsive to opening and closing of the on-off valve.

FIGS.19A-Dare graphs illustrating time constant decay for a linear gas delivery system, according to one embodiment of the present invention. One of ordinary skill in the art will understand, given the disclosure herein, application of the same principles to a non-linear gas delivery system.

InFIG.19A, a time constant is defined as the amount of time required for an initial variable (pressure or mass flow) to decay by 63.2% in route to steady state flow at 0%. The time constant is a defined as: Tc=(V*DP)/m, where V is an accumulation volume, DP is a total variable drop (pressure or mass flow) between an initial time and infinity, and m is the initial mass flow rate (or pressure drop rate) out of the accumulation volume. Therefore, the time constant is a function of the initial mass flow rate which is drastically reduced by a flow restrictor to drastically increase the time constant. Furthermore, the time constant is also a function of accumulation volume and can be increased to further raise the time constant. Accumulation volume, however, is limited to the available space for the device and, as such, cannot be viably increased to have the same order of affect as the flow restrictor impedance.

In contrast toFIG.19A, inFIG.19B, a 20% flow into the volume is superimposed on the decay as described inFIG.19Awhich results in a 20% flow at steady state flow after several time constants have passed.

InFIG.19C, the decay ofFIG.19Bto 20% flow is shown over a large span of time constants for a 1 second on cycle. From this perspective, the decay to steady state resembles the system ofFIG.16, with a large spike3421at ramp up before reaching steady state. In other words, a time decay of the spike is small relative to an on cycle. On the other hand,FIG.19Dshows a time decay that is large relative to the same 1 second on cycle. Fewer time constants elapse inFIG.19Dthan 19C over the same amount of time, so the spike3421is reduced to a modest droop3431. The period of interest for the on cycle of a square wave according toFIG.19Dends before significant pressure decay from the large time constant. The pressure decay from the smaller time constant ofFIG.19Cis undesirable.

Accordingly, a flow restrictor is introduced to a gas delivery system markedly increases the decay time in order to bring droop, during an on cycle, within tolerance of a specific semiconductor process.

Systems for Gas Delivery a Square Wave Output

FIG.20is a high-level schematic diagram conceptually illustrating a system3500to produce a square wave using an MFC, according to one embodiment of the present invention.

A wave generation system or component includes an MFC3501coupled to an on-off valve3504within component3503. An accumulation volume3502is shown conceptually as an aggregate of volume between the MFC3501and the on-off valve3504. For instance, conduit volume, spacing within components, and even additional accumulation chambers can all add to a total accumulation volume.

The on-off valve3504can be air actuated to move up and down to open and close during on and off cycles, respectively. When the on-off valve3504moves up to open, process gas in the conduit is markedly unrestricted by the open valve seat of the on off valve but is primarily restricted by flow restrictor3505. The flow restrictor3505is sized and installed in a throat of an on-off valve seat3506. The restrictor3505can be selected so that the flow impendence provides a predefined amount of restriction to gas flow from the accumulation volume3502. Sizing can refer to a size of an opening, porosity of a sintered media, or diameter of a long capillary tube. In some embodiments, a flow node is implemented in component3503, as shown inFIG.21.

FIG.21is a schematic diagram illustrating a system3600to produce a square wave optionally using a flow node, according to one embodiment of the present invention. In general, a flow node can be used along with a pressure reading from the electronic regulator3601to measure pressure at the inlet of the restrictor, even if the restrictor is downstream of the valve seat of the on-off valve, because the flow resistance is negligible between the on-off valve seat in component3603and the upstream electronic regulator3601. In alternative embodiments, electronic regulator3601is replaced with a proportional valve operating in conjunction with a pressure transducer coupled to accumulation volume3602. Note that the downstream pressure transducer3620may be needed for laminar and molecular flow restrictors but typically is not needed when using a sonic flow restrictor.

The space consumption and cost of a second local pressure transducer on the accumulation volume is not needed to know the pressure at the inlet to the restrictor. It is needed when using only a proportional valve but not with the e-reg present. A temperature sensor3606(located within component3603) detects temperature (e.g., a flow restrictor and/or temperature of the process gas) and allows for accommodation of temperature measurement typically used in a massflow calculation utilizing pressure based methods. A PCB3610includes electronics to calculate flow and to adjust operation of the electronic regulator3601(or other device) based on feedbacks from the temperature sensor and pressure sensor(s)3606, and the optional downstream pressure transducer3620.

FIG.22is a schematic diagram illustrating a system to produce a square wave of a gas mixture, according to one embodiment of the present invention. A first MFC3701A and a second MFC3702A are both connected to an accumulation volume3702feeding component3703. A PCB3710controls the first and second MFCs3701A,B. In one example, the first MFC3701A feeds oxygen at a mass flow rate while the second MFC3701B feeds nitrogen. The relative concentration of the two gases can be adjusted by controlling the relative set point sent to MFCs3701A to3701B by the PCB3710.

FIG.23is a more detailed schematic diagram illustrating an example system3800to produce a square wave, according to one embodiment of the present invention.

The system3800includes an electronic regulator3810coupled by a first conduit section3801to a gas supply and coupled to a second conduit section3802. A local pressure transducer, at the top of3810, tracks pressure in the second conduit section3802.

A relief valve3820is coupled to the second conduit portion3802and a third conduit portion3803and a fourth conduit portion3804. The relief vale3820is an optional implementation for faster bleed off from an accumulation volume. Depending on the desired flow rate for the specific process, required output pressure in3804can vary widely, and the conduit portion3803can be activated to quickly send extra mass to a vacuum. When not needed, the relief valve3820can remain in a closed position.

An accumulation chamber3830is coupled to the fourth conduit portion3804. The accumulation chamber3830adds to a total accumulation volume for improved performance, as described above. For example, the accumulation chamber3830can add 40 cc to an existing 4 cc that might be typical of the volume between the valve seats of3810and3840. Time constant is a function of accumulation volume, albeit to a much lesser extent than time constant is a function of the impendence of the flow restrictor (which determines the pressure in the accumulation volume). For example, the square waves ofFIG.17Bdisplay approximately ⅕th the drop of the square waves ofFIG.17A, due to a fivefold increase in accumulation volume from 20 cc inFIG.17Ato 100 cc inFIG.17B. Thus, additional accumulation volume can further increase a time constant as needed.

An on-off valve3840is coupled to the fourth conduit portion3804and to a fifth conduit portion3805that exhausts through a flow restrictor3815to the process and a downstream pressure transducer3850, as described herein. In other embodiments, the flow restrictor3815is located upstream from the on-off valve3840.

A PCB3860is electronically coupled to one or more of the electronic regulator3810, the relief valve3820, the on-off valve3840, a temperature sensor3845and the downstream pressure transducer3850. Note that the downstream pressure transducer3850may be needed for laminar and molecular flow restrictors but typically is not needed when using sonic restrictor.

FIG.24shows a graph3910with a series of square output waves produced by a gas delivery system with an electronic regulator while graph3920, whereas graph3950shows a series of square output waves produced by a gas delivery system with an MFC. As can be seen, an electronic regulator reaches a steady-state of output characteristics almost immediately while the MFC does not. Once the MFC reaches steady-state, the performance is similar. Some implementations may not have tolerance for the ramp up time of an MFC.

In some embodiments, a higher set point is initially given to an MFC so that pressure in the accumulation volume can reach steady-state more quickly. Once at steady-state, the set points are reduced to what is necessary to maintain the desired steady-state flow. The higher set points can be used for a predetermined amount of time, or alternatively, responsive to a pressure transducer coupled to measure pressure in the accumulation volume.

Section IV

The MFC typically functions as a subsystem within a larger capital equipment apparatus referred to as a tool. However, commercially available pressure based MFCs are slow to transition between gases or to transition from higher to lower flow rates of a single gas, particularly for lower full scale flow rated devices, because of space within conduits of MFCs that are depressurized during transitions (also known as an accumulation volume). Typical response times can be between 0.2 and 4.0 seconds. Response times longer than 4.0 seconds are typically not allowed on many applications as monitoring systems on some equipment alarm at 4 seconds. The smaller the device's full scale rating the slower the depressurization response time. The 4 second limit currently excludes devices with full scale flow rating 100 SCCM (standard cubic centimeter per minute) or below. This slow response either creates a bottleneck in semiconductor processing, particularly for ALD and 3D-IC processing and/or forces poorer accuracies on flow rates below 50 SCCM as larger full scale devices are used to avoid unacceptable response times. Other techniques such as natural bleed off are slower than desired. Additionally, downstream purging or diverting techniques can require undesirable hardware modifications or additions.

Of particular interest are the accumulation volumes in pressure based MFCs and flow measurement systems that delivery process gas at low flow rates. With smaller mass flows, the depressurization process of the accumulated volumes can slow down the transition of the MFC to an intolerable amount of time.

Therefore, what is needed is a robust technique in gas delivery apparatus to overcome the above shortcomings by evacuating process gas in an accumulation volume upstream of a characterized flow resistance to a non-process location.

Gas delivery apparatus, gas delivery methods, non-transitory computer-readable media with source code, for reversing gas flow from an accumulation volume for pressure regulation with fast pressure bleed down, are disclosed. One of ordinary skill in the art will recognize, given the below description, variations available to one of ordinary skill in the art, such as the application of these principles to fluid, or a mix of gasses and fluid, in an accumulation volume.

Fine chemical synthesis, pharmaceutical production, optical fiber processing, nano material manufacturing, and similar high purity fluid delivery applications will also benefit from the disclosed techniques. General industrial applications can also benefit where a single device can act as both a standard forward pressure regulator and a back pressure regulator thereby replacing the need for extra hardware and providing a cost reduction.

I. Gas Delivery Apparatus Using Both Forward and Reverse Flow Mode for Pressure Regulation of an Accumulation Volume

FIG.25is a perspective diagram illustrating a gas delivery apparatus5100utilizing a reverse flow mode for fast bleed down of an accumulation volume5199, according to one embodiment. The gas delivery apparatus5100can be, for example, an MFC, a flow node and associated hardware, or the like. In one example, a low flow MFC delivers oxygen or nitrogen to a semiconductor fabrication process in a clean room. A flow path of the gas delivery apparatus5100includes a conduit inlet5105receiving downstream to conduits5115A-D, accordingly, and exhausting downstream to a process at a conduit outlet5125. A preferred embodiment of the gas delivery apparatus5100involves low flow gas delivery which can be characterized as less than 5100 SCCM (standard cubic centimeters per minute) or approximately 4/1000 chemical mole per minute. Although gas is referred to throughout the description for simplicity, some embodiments handle liquid or a dynamic mixture of gas and liquid (e.g., droplets). Some embodiments comprise more than one characterized restrictor for wider dynamic accuracy (e.g., in a parallel configuration).

An accumulated (accumulation) volume includes at least a portion of space within the conduit5115C between a proportional valve5120and a characterized restrictor5130. A pressure transducer5121A measures an associated pressure (i.e., pressure P1 in volume V1). Some embodiments also include space within the conduit5115B upstream of the proportional valve5120. Spacing within and between components can also be included.FIGS.28A and28Bshow an abstraction of the gas delivery apparatus5100including the accumulated volume5199(P1 volume). However, space within the upstream conduit5115A and the downstream conduit5115D can be effectively separated from the accumulated volume5199and considered as a second accumulated volume and have a different pressure as measured by a second pressure transducer5121B (i.e., volume V2 held at pressure P2). A second downstream cycle purge valve5106can be used to regulate pressure within the second accumulated volume of conduit5115D. In some cases, the second accumulated volume does affect pressurization of the first accumulated volume5199. The conduits5115A-D can be any suitable tubing or plumbing, either rigid or flexible, to deliver gas (or fluid) to the next stage. The conduits5115A-D can have a diameter of, for example, ¼ inch.

An electronic regulator (or electronic pressure regulator)5110communicatively couples to a valve system and the proportional valve5120. Based on inputs of set points and sensor feedback (e.g., from pressure transducer5121A), commands are sent from the electronic regulator5110to the valve system to open or close valves. Also commands can be sent to the proportional valve5120which can further open, further close, or stop adjustments. When sensor feedback indicates that the accumulated volume pressure is too low, a forward flow mode is implemented to intake a mass of the process gas with a downstream flow (e.g., by opening the proportional valve5120). When sensor feedback indicates that the accumulated volume pressure is near a target range, a halt or rate reduction is implemented (e.g., by stopping or slowing down adjustments of the proportional valve5120). Finally, when sensor feedback indicates that the accumulated volume pressure is too high, some embodiments implement a reverse flow mode to evacuate a mass of the process gas (e.g., by closing the gas supply shut-off valve5102, opening the upstream cycle purge valve5104, and controlling the proportional valve5120). In some embodiments, a control system of the electronic regulator5110may function in the forward flow mode as a standard pressure reducing regulator and may function in the reverse flow mode as a back pressure regulator. In both instances the electronic regulator5110will actively adjust and control the pressure in the accumulated volume5199according to inputs of set points and sensor feedback.

The electronic regulator5110can switch modes periodically or in near real-time responsive to changing inputs. In some implementations, the electronic regulator5110may switch control strategy responsive to more inputs than just pressure. For example, a flow command below a threshold can require a relatively large accumulation volume pressure drop, or a pressure drop in a short amount of time (i.e., short bleed down time), accomplished by resorting to the reverse flow mode. In such a situation the electronic regulator5110may close the gas supply shut-off valve5102, open the upstream cycle purge valve5104, and set the proportional valve5120to a fully open condition (not subject to customary PID control) to quickly achieve a desired large pressure drop. Another example involves switching from one type of gas to another in which the entire accumulated volume is bled. Still another embodiment factors in temperature feedback from sensors for additional control functions. A more detailed view of the electronic regulator5110is set forth below with respect toFIGS.26-27.

The valve system ofFIGS.25,28A and28Bmay be controlled by a controller of the electronic regulator5110to implement the forward and reverse flow modes, as shown inFIGS.28A and28B. In the forward flow mode ofFIG.28A, a gas supply valve5102can be opened and a purge valve5104closed. This arrangement allows pressure to build up behind the proportional valve5120upstream for pressurizing the accumulation volume5199as the proportional valve5120is further opened. However, in the reverse flow mode ofFIG.28B, the gas supply valve5102can be closed and the purge (or dump) valve5104opened. This depressurizes space in the conduit5115B held behind the proportional valve5120notionally upstream of the accumulated volume. As the proportional valve5120further opens, reverse flow from the accumulated volume transits into the open purge valve5104which evacuates gas to a non-process location using a vacuum pump. Additional valves are possible (e.g., outlet valve5108). Alternatively, the semiconductor capital equipment tool (not shown), within which the gas delivery apparatus5100is installed, may control the configuration of the supply valve5102and the purge valve5104while adjusting set point commands to the electronic regulator5110and thereby directing suitable control of the proportional valve5120to implement the forward and reverse flow modes.

The proportional valve5120, responsive to the electronic regulator5110, may function as the primary adjustable control element in both the forward and reverse flow modes. To enable control of flow in both the forward and reverse flow modes the proportional valve5120is located within a conduit upstream of the accumulated volume5199and downstream from both the gas supply line valve5102that supplies the process gas and the purge line valve5104that evacuates process gas.

A characterized restrictor5130impedes (or resists) the process gas from exhausting in accordance with component sizing. Specific impedance characteristics are designed by sizing components therein. In one embodiment, the accumulated volume exists in a space downstream of the proportional valve5120and upstream of the characterized restrictor5130. In other words, the characterized restrictor5130can effectively separate the accumulated volume from an exhaust pathway. Another embodiment includes the space upstream of the proportional valve5120. Generally, various aggregates of conduit space and/or spacing within components can contribute to the accumulated volume. As the accumulation volume pressurizes or depressurizes, a resulting mass flow rate increases and decreases. In an embodiment, the characterized restrictor5130further comprises a valve seat and poppet or other valve and seat mechanisms.

FIG.26-27are block diagrams illustrating a view of an electronic regulator of a gas delivery apparatus, according to an embodiment. The electronic regulator5110comprises a communication interface5210, a proportional valve controller5220, a processor5230and a memory5240.

The communication interface5210receives data used for determination of forward and reverse flow modes, and sends data for adjustment of the proportional valve5120. The received data can include external set points that define a desired mass flow rate for delivery of the process gas to the semiconductor process. Additional received data can be pressure sensor and/or temperature sensor feedbacks. Other embodiments of the communication interface5210involve sending and receiving data that is only peripherally related to determination of forward and reverse flow modes, as well as unrelated data.

The communication interface5210comprises hardware and/or software. Hardware can be male or female connections for inputs and/or outputs, such as a serial port, a parallel port, a USB port, a FireWire port, an IEEE 802.11 Wi-Fi radio, an Ethernet port, a Bluetooth radio, a radio jack, radios, or any other appropriate port capable of electrical or electro-magnetic signaling. The software can include network communication modules, operation systems, applications, daemons, coders, decoders, memory, source code, and any other appropriate aspects of communication, stored on a non-tangible computer readable media

For example, detail5290illustrates a schematic of various ports used for communication in an embodiment. An R45 jack5292provides an Ethernet receptacle for connecting to an enterprise network for remotely sending external set points from a controller computer. A signaling port5294connects to a proportional valve for sending control signals for further opening, further closing, and stop, for instance. Another signaling port5296receives pressure and/or temperature sensor feedback. Other ports are available for other types of connections, such as a direct connection from an administrator.

The proportional valve controller5220, responsive to the external set points, may determine whether to operate in a forward mode or a reverse mode for meeting a target pressure in an accumulated volume, and perform algorithms for PID valve control and flow calculations based in part upon existing sensed conditions. In forward mode the process gas flows in a usual downstream direction through an electronic regulator into an accumulated volume. In reverse mode the process gas flows in an unusual locally upstream direction through the electronic regulator out of the accumulated volume.

The processor5230can be, without limitation, a microprocessor, a customized ASIC, or any appropriate mechanism for executing source code, in accordance with embodiments described herein. For example, the processor5230can detect when a threshold has been exceeded leading to the reverse flow mode. Also, the processor5230can map specific commands from external set points.

The memory5240can be, without limitation, RAM, ROM, cache, virtualized memory, queues, instruction stacks, flash memory, or any appropriate hardware and/or software for storing source code, values, and the like, in accordance with embodiments described herein.

II. Methods for Using Reverse Flow Mode for Pressure Regulation of an Accumulated Volume

FIG.29is a flowchart diagram illustrating a method5400for utilizing a reverse flow mode for fast bleed down of an accumulated volume, according to an embodiment of the present invention. In one case, the method5400is implemented in the electronic regulator5110of the system5100ofFIG.25, and in other cases, is implemented in alternative systems. Further, the order of steps can be interchanged, and there can be more or less steps than shown in implementations.

External set points that define a desired mass flow rate for delivery of process gas are received (step5410). Pressure readings are received from a pressure transducer within an accumulated volume (e.g., periodically or on demand) (step5420). Other sensor feedback can include temperature readings. Next, it is determined whether to operate a proportional valve in forward mode or reverse mode based on the set points and sensor feedback (step5430). In turn, commands are sent to the proportional valve for pressurizing or depressurizing the accumulated volume in accordance with the set points and current pressure readings (step5440).

FIG.30is a more detailed flowchart diagram illustrating a step5430of transitioning from a forward flow mode to a reverse flow mode, according to an embodiment of the present invention. The step5430can be implemented, without limitation, in the proportional valve controller5220of the electronic regulator5110ofFIG.26.

A valve system initially operates in forward flow mode (step5510). Based on pressure readings received from a pressure transducer, it is determined whether the pressure reading is greater than a target pressure (step5520). If the pressure is greater, the valve system is adjusted to operate in reverse flow mode (step5530). If the pressure is not greater, an opening of the proportional valve can optionally be adjusted as needed (e.g., further opened, further closed, or halted) (step5525).

If the pressure reading is less than the target pressure while operating in a reverse flow mode (step5540), and the process continues (step5550), the valve system is adjusted to operate in the forward flow mode (step5510). On the other hand, if the pressure is not less than the target pressure, the proportional valve opening can be optionally adjusted to change the depressurization rate (step5545).

FIG.31is a perspective diagram illustrating a gas delivery apparatus5600utilizing a reverse flow mode for fast bleed down of an accumulation volume5699, according to another alternative embodiment. The gas delivery apparatus5600may be used to provide controlled delivery of a reactant to a semiconductor manufacturing process, for example. The illustrated alternative gas delivery apparatus5600includes a gas supply shut-off valve5602, an upstream cycle purge valve5604, an electronic pressure regulator5610, and a flow node5629. A flow path of the alternative gas delivery apparatus5600includes a conduit inlet5605receiving downstream to conduits5615A-D, accordingly, and exhausting downstream to a process at a conduit outlet5625. A preferred embodiment of the gas delivery apparatus5600involves low flow gas delivery which can be characterized as less than 5100 SCCM (standard cubic centimeters per minute) or approximately 4/1000 chemical mole per minute. Some alternative embodiments comprise more than one flow node for wider dynamic accuracy (e.g., in a parallel configuration).

An accumulated (accumulation) volume5699includes at least a portion of space within the conduit5615B between the gas supply shut-off valve5602and the electronic pressure regulator5610combined with at least a portion of space within the conduit5615C between the electronic pressure regulator5610and a flow node5629. The electronic pressure regulator5610includes a pressure transducer5621which measures an associated pressure and also a proportional valve5620. Spacing within and between components may also be included in consideration of the accumulated volume5699. The flow node5629includes a characterized restrictor5630in series and directly adjacent with a valve seat and diaphragm which together may function as a downstream outlet shut-off valve. The illustrated gas delivery apparatus5600has a form factor comprising decentralized components making up a gas stick using a flow node and associated electronic regulator, sensors and control system, as opposed to the gas stick ofFIG.25. The alternative gas delivery apparatus5600illustrates use of metallic tubing and machined surface mount fluid delivery substrates as known in the semiconductor capital equipment industry.

A process control system (not shown) may use the gas delivery apparatus5600in a forward flow mode in the following manner. Process gas enters through the inlet conduit5605and passes through the gas supply valve5602into the conduit5615B upstream of the electronic pressure regulator5610while the upstream cycle purge valve5604is in a closed condition. A target pressure set point is provided by the process control system to the electronic pressure regulator5610based at least in part upon a desired mass flow rate to be provided to the process by the flow node5629. The electronic pressure regulator5610includes the pressure transducer5621which measures a pressure within the conduit5615C upstream of the flow node5629, and adjusts the proportional valve5620to keep the measured pressure approximately equal to the target pressure (opening the proportional valve5620more if the measured pressure is too low or reducing the opening of the proportional valve5620if the pressure is too high). Process gas flows from the conduit5615C upstream of the flow node5629, into the flow node5629, and through the characterized restrictor5630and exhausting downstream to a process at a conduit outlet5625.

The process control system (not shown) may in the following manner use the gas delivery apparatus5600in a reverse flow mode in response to inputs. Changing to reverse flow mode may be done when needing a fast reduction of gas delivery flow rate, for example. The gas supply valve5602is placed into a closed condition and the upstream cycle purge valve5604is placed into an open condition thereby connecting the conduit5615B upstream of the electronic pressure regulator5610to a vacuum suction (sink) thereby reversing the flow supplied to the electronic pressure regulator5610and rapidly reducing the supplied process gas pressure. Strategies for removing process gas from the conduit5615C between the electronic pressure regulator5610and the flow node5629may depend upon design of the electronic pressure regulator5610. For example, temporarily providing a large target pressure set point to the electronic regulator5610will cause a forward pressure regulator control system to further open the proportional valve5620thereby allowing process gas to reverse flow leaving the conduit5615C and pass into the vacuum suction (sink) through the cycle purge valve5604. Alternatively, the electronic pressure regulator5610may be reconfigurable to operate in a back pressure regulation mode. In such instance the process control system may provide a new reduced target pressure set point to the reconfigured pressure regulator5610whereby the pressure transducer5621, which measures a pressure within the conduit5615C upstream of the flow node5629, provides local feedback and the reconfigured electronic pressure regulator5610adjusts the proportional valve5620to keep the measured pressure approximately equal to the target pressure (reducing the opening of the proportional valve5620if the measured pressure is too low or increasing the opening of the proportional valve5620if the pressure is too high).

FIG.32is a perspective diagram illustrating a gas delivery apparatus5700utilizing a reverse flow mode for fast bleed down of an accumulation volume5799, according to yet another embodiment. The gas delivery apparatus5700may be used to provide controlled delivery of a reactant to a semiconductor manufacturing process, for example. The illustrated another gas delivery apparatus5700includes a gas supply shut-off valve5702, an upstream cycle purge valve5704, a control valve5720, a pressure transducer5721, and a flow node5729. A flow path of the alternative gas delivery apparatus5700includes a conduit inlet5705receiving downstream to conduits5715A-D, accordingly, and exhausting downstream to a process at a conduit outlet5725. A preferred embodiment of the gas delivery apparatus5700involves low flow gas delivery which can be characterized as less than 100 SCCM (standard cubic centimeters per minute) or approximately 4/1000 chemical mole per minute. Some alternative embodiments comprise more than one flow node for wider dynamic accuracy (e.g., in a parallel configuration).

An accumulated (accumulation) volume5799includes at least a portion of space within the conduit5715B between the gas supply shut-off valve5702and the control valve5720combined with at least a portion of space within the conduit5715C between the pressure transducer5721and a flow node5729. Spacing within and between components may also be included in consideration of the accumulated volume5799. The flow node5729includes a characterized restrictor5730in series and directly adjacent with a valve seat and diaphragm which together may function as a downstream outlet shut-off valve. The illustrated gas delivery apparatus5700has a form factor comprising decentralized components making up a gas stick using a flow node and associated valves, sensors and control system, as opposed to the gas stick ofFIG.25. The alternative gas delivery apparatus5700illustrates use of metallic tubing and machined surface mount fluid delivery substrates as known in the semiconductor capital equipment industry.

A process control system (not shown) may use the gas delivery apparatus5700in a forward flow mode in the following manner. Process gas enters through the inlet conduit5705and passes through the gas supply valve5702into the conduit5715B upstream of the control valve5720while the upstream cycle purge valve5704is in a closed condition. A target pressure set point may be calculated by the process control system based at least in part upon a desired mass flow rate to be provided to the process by the flow node5729. Signals from the pressure transducer5721, which measures a pressure within the conduit5715C upstream of the flow node5729, are used by the process control system to determine adjustments to the proportional valve5720intended to keep the measured pressure approximately equal to the target pressure (opening the proportional valve5720more if the measured pressure is too low or reducing the opening of the proportional valve5720if the pressure is too high). Process gas flows from the conduit5715C upstream of the flow node5729, into the flow node5729, and through the characterized restrictor5730and exhausting downstream to a process at a conduit outlet5725.

The process control system (not shown) may in the following manner use the gas delivery apparatus5700in a reverse flow mode in response to inputs. Changing to reverse flow mode may be done when needing a fast reduction of gas delivery flow rate, for example. The gas supply valve5702is placed into a closed condition and the upstream cycle purge valve5704is placed into an open condition thereby connecting the conduit5715B upstream of the control valve5720to a vacuum suction (sink) thereby reversing the flow supplied to the control valve5720and rapidly reducing the supplied process gas pressure. Strategies for removing process gas from the conduit5715C between the control valve5720and the flow node5729may depend upon the inputs which led to use of the reverse flow mode. For example, the process control system may maximally open the proportional valve5720thereby allowing process gas to very rapidly reverse flow leaving the conduit5715C and pass into the vacuum suction (sink) through the cycle purge valve5704. Alternatively, the process control system may calculate a new reduced target pressure set point and adjust the proportional valve5720to keep the measured pressure approximately equal to the new reduced target pressure (reducing the opening of the proportional valve5720if the measured pressure is too low or increasing the opening of the proportional valve5720if the pressure is too high).

While the invention has been described with respect to specific examples, those skilled in the art will appreciate that there are numerous variations and permutations of the above described invention. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Thus, the spirit and scope should be construed broadly as set forth in the appended claims.