GAS CAPACITOR FOR SEMICONDUCTOR TOOL

Abstract

A system is provided which includes a gas supply; a fluidic circuit which includes first and second sub-circuits, wherein said first sub-circuit includes a first one-way valve, and wherein said second sub-circuit includes a second one-way valve and a gas capacitor disposed downstream of said second one-way valve; and a pneumatically operated semiconductor tool in fluidic communication with said gas supply by way of said fluidic circuit.

Claims

1. A gas capacitor in combination with a semiconductor tool, wherein said semiconductor tool comprises: a gas supply line which supplies gas from a remote gas source and which is equipped with a first one-way valve, a central chamber, and a plurality of process chambers, wherein each of said plurality of process chamber is equipped with a pneumatically actuated valve which is in fluidic communication with the gas supply line and which transforms the process chamber from a first state in which the process chamber is in fluidic communication with said central chamber, to a second state in which the process chamber is fluidically isolated from said central chamber; and wherein said gas capacitor comprises: a pressurized gas reservoir which is disposed downstream from said one-way valve, and which is in fluidic communication with said plurality of process chambers.

2. The apparatus of claim 1, wherein said gas reservoir is disposed in said semiconductor tool.

3. The apparatus of claim 1, wherein said gas reservoir is disposed proximal to said semiconductor tool.

4. The apparatus of claim 1, wherein said first one-way valve is characterized by a cracking pressure P.sub.crack; wherein, at pressures above the cracking pressure, the first one-way valve assumes an open state in which fluidic flow between the gas reservoir and the gas supply line occurs; and wherein, at pressures below the cracking pressure, the first one-way valve assumes a closed state in which no fluidic flow between the gas reservoir and the gas supply line occurs.

5. The apparatus of claim 4, wherein the gas supply line experiences operating pressure fluctuations while the semiconductor tool is in operation, and wherein the operating pressure fluctuations are characterized by a maximum pressure P.sub.max and a minimum pressure P.sub.min, and wherein 0<P.sub.crack<P.sub.min.

6. The apparatus of claim 5, wherein P.sub.min>50 psi.

7. The apparatus of claim 5, wherein P.sub.min≥60 psi.

8. The apparatus of claim 5, wherein P.sub.max<100 psi.

9. The apparatus of claim 5, wherein P.sub.max≤90 psi.

10. The apparatus of claim 5, wherein 10 psi<P.sub.crack<60 psi.

11. The apparatus of claim 5, wherein 20 psi<P.sub.crack<50 psi.

12. A system, comprising: a gas supply; a fluidic circuit which includes first and second sub-circuits, wherein said first sub-circuit includes a first one-way valve, and wherein said second sub-circuit includes a second one-way valve and a gas capacitor disposed downstream of said second one-way valve; and a pneumatically operated semiconductor tool in fluidic communication with said gas supply by way of said fluidic circuit.

13. The system of claim 12, wherein said first and second one-way valves impart a one-way flow of fluid between said gas supply and said semiconductor tool.

14. The system of claim 12, wherein said semiconductor tool includes a central chamber and a plurality of process chambers, and wherein each of said plurality of process chamber is equipped with a pneumatically actuated valve which is in fluidic communication with the fluidic circuit.

15. The system of claim 12, wherein each pneumatically actuated valve is transformable between a first state in which the process chamber associated with the pneumatically actuated valve is in fluidic communication with said central chamber, to a second state in which the process chamber associated with the pneumatically actuated valve is fluidically isolated from said central chamber.

16. The system of claim 12, wherein said gas capacitor includes a pressurized gas reservoir which is disposed downstream from said second one-way valve, and which is in fluidic communication with said plurality of process chambers.

17. The system of claim 12, wherein said first and second sub-circuits are in fluidic communication with each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which like reference numerals indicate like features.

[0017] FIG. 1 is an illustration of a prior art cluster tool equipped with a robotic wafer handling system.

[0018] FIG. 2 is an illustration of the arm assembly of the robot depicted in FIG. 1, and illustrates the retracted and extended positions of the arm assembly.

[0019] FIG. 3 is a front view of a prior art slit valve.

[0020] FIG. 4 is a side view of the slit valve of FIG. 3.

[0021] FIG. 5 is an illustration of a semiconductor fab layout featuring a remote gas supply and a plurality of cluster tools.

[0022] FIG. 6 is a schematic illustration of a system which includes a gas supply and a semiconductor tool and which is equipped with a gas capacitor in accordance with the teachings herein.

[0023] FIG. 7 is a detailed illustration of the gas capacitor of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

[0024] The trend toward operating cluster tools at higher speeds has resulted in more slit valve actuations occurring simultaneously. Cluster tools are typically equipped with a long length of piping that supplies the working gas for the pneumatic system. Since this piping has a finite flow capacity, the simultaneous operation of an increasing number of slit valves (as necessary to accommodate higher throughput speeds) places increasing demands on the pneumatic system. This frequently results in dramatic fluctuations in pneumatic pressure at the cluster tool, which can lead to tool alarms, chamber leaks and slow actuations of the slit valves. In order to reduce such pressure fluctuations and to accommodate the necessary flow requirements, the clean dry air (CDA) pressure at the tool is frequently increased beyond the suggested limitations of the slit valves.

[0025] It has been found that, as a result of their frequent exposure to CDA pressures that exceed their design capabilities, the slit valves in a cluster tool suffer frequently exhibit premature wear. This is often manifested as a breakdown of the O-ring material in the valve, which may lead to particle generation.

[0026] On the other hand, if CDA pressures in the tool drop below the required level, the slit valves may not fully actuate, which may leave them in an unknown open/closed state. If these faults occur during wafer transfer, the robot and wafer may be left in an unknown position. Similarly, if the CDA supply is depleted, tool technicians may have no options for wafer recovery, and may be forced to wait for the CDA supply to recover. Either of these scenarios may lead to wafer scrap that may have been averted if the tool technicians had been able to quickly remove the wafers from the tool.

[0027] It has now been found that some or all of the foregoing issues may be addressed with the systems and methodologies disclosed herein. In a preferred embodiment of such a system, a gas capacitor, preferably in the form of a pressurized vessel, is added locally to the cluster tool at a location near (and upstream from) the slit valves. The gas capacitor, which is in fluidic communication with the slit valves, provides an additional local reservoir of working gas (preferably CDA) local to the tool. The availability of this additional reservoir local to the tool increases the effective volume of CDA available to the tool, while also decreasing the effective length of pipe supplying the CDA. This arrangement significantly reduces or eliminates the pressure fluctuations which otherwise arise from the simultaneous operation of an increasing number of slit valves. Consequently, the operating pressure may be set at lower values (e.g., those recommended by the tool manufacturer), even if the remote supply of CDA is servicing multiple tools and/or a large number of slit valves simultaneously.

[0028] Moreover, the gas capacitor may be configured to allow the tool to cease operation if the facility CDA pressure drops sufficiently (as is currently the case), but to maintain a reservoir of CDA of sufficient volume and pressure to allow for manual operation of the slit valves in the tool. This provides a means by which in-process wafers may be recovered, thus avoiding some of the cost and waste attendant to CDA disruptions.

[0029] In some embodiments, the auxiliary gas supply may be configured to be removable from (or fluidically or pneumatically isolated from) the tool. This may be accomplished, for example, through the provision of a bypass line. This feature allows the auxiliary gas supply to be removed for maintenance or replacement without disrupting the operation of the associated tool, and without introducing moisture or other contaminants into the gas circuit.

[0030] FIG. 5 depicts a particular, non-limiting embodiment of a semiconductor fab layout. As seen therein, the layout 201 comprises a plurality of cluster tools 203 that are in fluidic communication with a remote gas supply 205 via a gas supply line 207. Each of the cluster tools 203 is equipped with a one-way check valve 209 which isolates the tool from the gas supply line 207 in the event of a sufficiently large pressure drop. The check valve 209 preferably serves as a pneumatic lock-up valve which functions to shut off the signal pressure line of pneumatic actuators when the pressure in the gas supply line falls below a predetermined threshold value. This typically causes the pneumatically activated actuators in the tool (including those in the slit valves) to remain in their last position.

[0031] The check valve 209 is characterized by a cracking pressure P.sub.crack. At pressures above the cracking pressure, the valve assumes an open state in which fluidic flow between the remote gas supply and the tool occurs. Similarly, at pressures below the cracking pressure, the valve assumes a closed state in which no fluidic flow between the gas reservoir and the gas supply line occurs. The gas supply line will typically experience operating pressure fluctuations while the semiconductor tool is in operation. These operating pressure fluctuations are characterized by a maximum pressure P.sub.max and a minimum pressure P.sub.min. Preferably, the check valve is designed such that 0<P.sub.crack<P.sub.min. Typically, P.sub.min>30 psi, and preferably, P.sub.min≥60 psi. Typically, P.sub.max<100 psi, and preferably, P.sub.max≤90 psi. Moreover, typically, 10 psi<P.sub.crack<60 psi, and preferably, 20 psi<P.sub.crack<50 psi.

[0032] Each cluster tool 203 is also equipped with a gas capacitor 211 of the type disclosed herein, which is preferably located downstream of the check valve 209. As described below, the gas capacitor 211 serves as a local supply of gas, in contrast to the remote gas supply 205 from the facility. It will be appreciated that, while the check valve 209 is depicted as a separate component from the gas capacitor 211 in FIG. 5, in some embodiments, the check valve will actually be a component of the gas capacitor.

[0033] FIGS. 6-7 depict a first particular, non-limiting embodiment of a system 301 incorporating a gas capacitor 307 in accordance with the teachings herein. As seen therein, the system 301 comprises a pneumatically powered semiconductor tool 303 which is in fluidic communication with a facility gas supply 305 via a fluidic circuit 306 that includes first 308 and second 310 sub-circuits. The first 308 and second 310 sub-circuits are in fluidic communication with each other via first 309 and second 311 T-joints. The first sub-circuit 308 includes check valve 313, and the second sub-circuit includes gas capacitor 303. Check valve 313 maintains a one-way flow in the first sub-circuit 308 in the direction going from the first T-joint 309 to the second T-joint 311. The semiconductor tool 303 is equipped with a plurality of slit valves 323 that are in fluidic communication with fluidic circuit 306 via a manifold 321.

[0034] The gas capacitor 303 is depicted in greater detail in FIG. 7. As seen therein, the gas capacitor 307 comprises a gas reservoir 314 equipped with a pressure gauge 343. The gas reservoir 314 is preferably a gas cylinder, and more preferably, an aluminum gas cylinder. The use of aluminum in the construction of the gas reservoir 314 is preferred here because aluminum poses a lower contamination threat than other metals commonly used in the construction of gas cylinders. The pressure gauge 343 is preferably fitted with a filtered exhaust. The pressure gauge 343 is useful during initial installation and charging of the gas reservoir 314 to ensure that the initial pressure remains steady (i.e., there are no leaks present in the gas capacitor 307).

[0035] The gas capacitor 307 further comprises first 335 and second 337 manually operated isolation valves. The first isolation valve 335 is associated with fittings 331 and 339, and the second isolation valve 337 is associated with fitting 333. The first 335 and second 337 isolation valves are preferably disposed immediately upstream and immediately downstream, respectively, from the gas reservoir 314, and thus provide a means to readily remove the gas reservoir 314 from the pneumatic circuit 306 as, for example, for repair or maintenance. The gas capacitor 307 is further equipped with a check valve 341, which maintains a one-way flow in the direction going from the first isolation valve 335 to the second isolation valve 337.

[0036] In some embodiments, the gas capacitor 307 may include additional components. Thus, for example, in some embodiments, the gas capacitor 307 or the fluidic circuit 306 may include a gas dryer, which is preferably a modular adsorption dryer. The gas dryer serves to remove water vapor from the gas supply, thus preventing condensation, corrosion and the growth of microorganisms. In some embodiments, the gas dryer may be equipped with a suitable desiccant. One or more filters may also be provided in the gas capacitor 307 or the fluidic circuit 306 to remove impurities therefrom such as, for example, liquid water, water aerosols, oil, particulates, or microorganisms.

[0037] In normal use of the system 301, as pressure fluctuations are propagated through fluidic circuit 306, the check valve 313 remains open so long as the pressure in fluidic sub-circuit 308 upstream of the check valve 313 does not fall below P.sub.min. These pressure fluctuations are compensated for by the gas capacitor 307 as a result of the additional, localized reservoir of pressurized gas it provides via gas reservoir 314.

[0038] However, if the pressure in fluidic sub-circuit 308 upstream of the check valve 313 line falls below P.sub.crack, the check valve 313 is activated (that is, moves from an open position in which fluidic flow through the check valve 313 is permitted, to a closed position in which fluidic flow through the check valve 313 is not permitted), and the gas supply to the tool 303 is cut off. Since the check valve 313 is a one-way valve, the portion of the first sub-circuit 318 upstream of the check valve 313 remains fluidically isolated from the tool 303, and hence, working gas pressure is maintained in the portion of the first sub-circuit 308 downstream of the check valve 313. Similarly, the one-way flow provided by check valve 341 (see FIG. 7) ensures that the portion of the second sub-circuit 310 upstream of the check valve 341 remains fluidically isolated from the tool 303, and hence, working gas pressure is maintained in the portion of the second sub-circuit 310 downstream of the check valve 313. Since check valves 313 and 341 provide a one-way flow of fluid, and since the gas reservoir 314 of the gas capacitor 307 is downstream from the check valve 341, the additional, localized reservoir of pressurized gas provided by gas reservoir 314 may be utilized to manually operate slit valves 323 or other pneumatically operated components of the tool 303. This allows for wafer recovery and temporary operation of the slit valves, even if the facility gas supply 305 remains offline.

[0039] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.