METHODS OF ETCHBACK PROFILE TUNING

A method of controlling an etch profile includes introducing a tungsten containing gas into a processing chamber; depositing a first tungsten film lining sidewalls of a feature formed in a substrate using the tungsten containing gas in the processing chamber; and treating the first tungsten film in the processing chamber using the tungsten containing gas until a particular etch profile is attained by repeatedly alternating between etching the first tungsten film for a first interval and stopping the etching of the first tungsten film for a second interval by at least one of purging the tungsten containing gas from the process chamber or turning off a power supply that powers the etching of the first tungsten film.

FIELD

Embodiments of the present disclosure generally relate to the processing of substrates and, more particularly, to methods of controlling an etch profile of features formed in substrates.

BACKGROUND

The shrinking dimensions of the features of the circuits and devices used in integrated circuits have placed additional demands on processes for manufacturing the integrated circuits. For example, forming multilevel interconnects used in integrated circuit technology may include precise processing of high aspect ratio features, such as vias and other interconnects. Reliable formation of these interconnects may be used to increase circuit density and quality of individual substrates.

Metallization of features formed on substrates includes deposition of metals such as tungsten. Tungsten may be used for metal fill of source contacts, drain contacts, metal gate fill, and gate contacts as well as in other applications. With technology node shrinkage, tungsten films may be used to obtain low resistivity and low roughness of devices and for integration with subsequent process steps. Chemical vapor deposition (CVD) may be a process technology used for a metal fill of tungsten. A pattern may be etched in an underlying interlayer dielectric (ILD) material, and the tungsten may then be deposited to fill the etched material.

However, the reduction in feature sizes has often increased difficulty in the metal fill process. For example, when a dielectric material layer is formed on the sidewalls and bottom surface of a feature, the deposition process may deposit a greater thickness of dielectric material on a part of the sidewalls that is nearer to an opening of the feature. Then, the subsequent CVD formation of the tungsten on the side walls may close off the feature at the feature opening before the lower portion of the feature has completely filled resulting in a void forming within the feature. The presence of the void may change the material and operating characteristics of the interconnect feature and may eventually cause improper operation and premature breakdown of the device. For example, to be efficient, a conductive element or line may need to carry an almost practical maximum current density to achieve the same current flow density or higher in smaller features in future devices.

Therefore, the inventors have provided a process to control the profile of the sidewalls of high aspect ratio features so that subsequent void-free (or substantially void-free) filling of the high aspect ratio with a metal may be attained.

SUMMARY

Methods of controlling an etch profile are provided herein. In some embodiments, a method of controlling an etch profile includes; introducing a tungsten containing gas into a processing chamber; depositing a first tungsten film lining sidewalls of a feature formed in a substrate using the tungsten containing gas in the processing chamber; and treating the first tungsten film in the processing chamber using the tungsten containing gas until a particular etch profile is attained by repeatedly alternating between etching the first tungsten film for a first interval and stopping the etching of the first tungsten film for a second interval by at least one of purging the tungsten containing gas from the process chamber or turning off a power supply that powers the etching of the first tungsten film.

In some embodiments, a method of controlling an etch profile includes forming an adhesion layer along sidewalls of a feature formed in a substrate, wherein sidewalls of the feature slant towards each other at an upper part of the feature; introducing a tungsten containing gas into a processing chamber having the substrate disposed therein; forming a first tungsten film atop the adhesion layer in the processing chamber; treating the first tungsten film in the processing chamber using the tungsten containing gas until a particular etch profile is attained by repeatedly alternating between plasma etching the first tungsten film for a first interval of about 1 sec to about 5 sec and stopping the etching of the first tungsten film for a second interval of about 1 sec to about 10 sec by at least one of purging the tungsten containing gas from the process chamber or turning off RF power that generates the plasma; and forming a second tungsten film atop the first tungsten film after treating the first tungsten film.

In some embodiments, non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method of controlling an etch profile that includes; introducing a tungsten containing gas into a processing chamber; depositing a first tungsten film lining sidewalls of a feature formed in a substrate using the tungsten containing gas in the processing chamber; and treating the first tungsten film in the processing chamber using the tungsten containing gas until a particular etch profile is attained by repeatedly alternating between etching the first tungsten film for a first interval and stopping the etching of the first tungsten film for a second interval by at least one of purging the tungsten containing gas from the process chamber or turning off a power supply that powers the etching of the first tungsten film.

DETAILED DESCRIPTION

Embodiments of the present disclosure advantageously provide for treating a first tungsten film by repeatedly alternating between etching the first tungsten film for a first interval and stopping the etching the first tungsten film for a second interval until a particular etch profile for the sidewalls of the material may be attained. Advantageously, by repeatedly alternating between etching the first tungsten film for the first interval and stopping the etching the first tungsten film for the second interval, an overhang portion of the first tungsten film may be removed. Advantageously, by removing the overhang portion of the first tungsten film and attaining a predetermined profile for the sidewalls of the first tungsten film, the formation of a void within a feature may be avoided. Advantageously, deposition of a second tungsten film may fill a lower portion of a feature starting from a bottom surface of the feature until an opening in the feature may be completely filled.

FIG. 1illustrates an example of a method100of controlling an etch profile on a substrate in accordance with some embodiments of the present disclosure. In some embodiments, the method100may be carried out on a substrate200with a feature208formed in the substrate as shown inFIGS. 2A-2Fand described below. In some embodiments, the method may be carried out using the process chamber ofFIG. 3, which is described below.

The method100is performed on a substrate having a feature formed in the substrate and a first tungsten film lining the sidewalls and bottom of the feature are provided in a processing chamber, such as using the process as shown inFIGS. 2A-2D.

For example,FIG. 2Adepicts substrate200that contains a dielectric layer210disposed on a substrate202and a feature208formed or otherwise contained within the dielectric layer210. The feature208has one or more sidewalls222and a bottom surface224. In some embodiments, features such as vias, trenches, lines, contact holes, or other features utilized in a semiconductor, solar, or other electronic devices, such as high aspect ratio contact plugs. In some embodiments, where the feature is a via, the via may have a high depth to width aspect ratio of, e.g., about 20-50. In some embodiments, substrate202is a silicon substrate or at least contains silicon or a silicon-based material. In some embodiments, the substrate200is a semiconductor substrate having a silicon substrate or wafer as the substrate202, and the dielectric layer210contains at least one dielectric material, such as silicon, monocrystalline silicon, microcrystalline silicon, polycrystalline silicon (polysilicon), amorphous silicon, hydrogenated amorphous silicon, silicon oxide materials, dopant derivatives thereof, or combinations thereof.

In some embodiments, an adhesion layer may be formed on the dielectric layer disposed on the substrate, as depicted inFIG. 2B. The adhesion layer220forms a relatively uniform layer of material on the planar upper surface204of the dielectric layer210, the sidewalls222of the feature208, and the bottom surface224of the feature208. In some embodiments, the adhesion layer220contains a metal or a metal nitride material, such as titanium, titanium nitride, alloys thereof, or combinations thereof. In some embodiments, the adhesion layer220may include tantalum (Ta), tungsten nitride (WN), titanium nitride (TiN), TiNxSiy, tantalum nitride (TaNx), silicon nitride (SiN), tungsten (W), CoWP, NiMoP, NiMoB, ruthenium (Ru), RuO2, molybdenum (Mo), MoxNy, where x and y are non-zero numbers, and combinations thereof. Adhesion layer220may have a thickness within a range from about 2 Å to about 100 Å, more narrowly within a range from about 3 Å to about 80 Å, more narrowly within a range from about 2 Å to about 50 Å, more narrowly within a range from about 5 Å to about 25 Å, more narrowly within a range from about 5 Å to about 20 Å, more narrowly within a range from about 5 Å to about 15 Å, and more narrowly within a range from about 5 Å to about 10 Å. Adhesion layer220is generally deposited by chemical vapor deposition (CVD), atomic layer deposition (ALD) or physical vapor deposition (PVD) processes.

In some embodiments, a nucleation layer230of predetermined thickness is deposited on adhesion layer220, as depicted inFIG. 2C. The nucleation layer230may be a thin layer of tungsten which acts as a growth site for subsequent film. In some embodiments, the nucleation layer230may be deposited by techniques such as atomic layer deposition (ALD), conventional chemical vapor deposition (CVD), or pulsed chemical vapor deposition (CVD). The nucleation layer deposition process may be performed in any suitable process chamber for performing the aforementioned ALD or CVD processes. In some embodiments, the nucleation layer may be deposited in the same process chamber used to deposit the adhesion layer. The nucleation layer230may comprise tungsten, tungsten alloys, tungsten-containing materials, e.g., tungsten boride or tungsten silicide, and combinations thereof. The nucleation layer230may be deposited to a thickness in a range of about 10 angstroms to about 200 angstroms, or about 50 angstroms to about 150 angstroms. The nucleation layer may be deposited by flowing a tungsten containing gas, e.g., a tungsten halide compound such as WF6, and a hydrogen containing gas, e.g., H2, B2H6, or SiH4, into a processing chamber having the substrate disposed in the processing chamber.

In some embodiments, a first layer, such as a first tungsten film240of a bulk tungsten layer260, is deposited on or over the nucleation layer230, as depicted inFIG. 2D. The first tungsten film240is generally formed by thermal CVD, pulsed-CVD, plasma enhanced CVD (PE-CVD), or pulsed PE-CVD. The deposition process may be performed in any suitable process chamber for performing the aforementioned CVD processes. The first tungsten film240may contain metallic tungsten, tungsten alloys, tungsten-containing materials, tungsten boride, tungsten silicide, tungsten phosphide, or combinations thereof.

In some embodiments, the first tungsten film240may be deposited on or over nucleation layer230on substrate200which is simultaneously exposed to a tungsten containing gas, e.g., tungsten hexafluoride (WF6), and a hydrogen containing gas, e.g., hydrogen (H2), during a CVD process.

In some embodiments, the first tungsten film240may be deposited using the same processing gases, tungsten containing gas and hydrogen containing gases as were used to deposit the nucleation layer230. In some embodiments, the first tungsten film240may be formed in the same process chamber as the nucleation layer230.

In some embodiments, following deposition of the nucleation layer230and any subsequent purging or post soak processes, the substrate may be positioned on a substrate support pedestal having a temperature in the range of about 100° C. to about 600° C., or in some embodiments, in the range of about 100° C. to 230° C., or in some embodiments, in the range of about 200° C. to 230° C. In some embodiments, the temperature may be about 200° C. Deposition of the first tungsten film240may be performed with the process chamber at a pressure in the range of about 10 Torr to about 300 Torr, for example, in the range of about 30 Torr to about 100 Torr. In some embodiments, the pressure may be about 90 Torr. The reducing gas can be introduced with a carrier gas, such as argon (Ar), at a flow rate in the range of about 0 sccm to about 20,000 sccm. In some embodiments, argon may be introduced at a total flow rate of 11,000 sccm. A second flow of argon may be flowed through a purge guide (not shown inFIG. 3) at a rate from about 0 sccm to 2,000 sccm to prevent deposition gases from contacting the edge and backside of the substrate. In some embodiments, the argon edge purge flow may be 500 sccm. Similarly, a second flow of hydrogen gas (H2) may be flowed through a purge guide (not shown inFIG. 3) at a rate from about 0 sccm to 6,000 sccm. In some embodiments, the hydrogen gas edge purge flow may be 2,500 sccm. In some embodiments, an additional flow of carrier gas, such as argon, may be introduced as a bottom purge in order to prevent deposition on the backside of the chamber heating elements. In some embodiments, the argon bottom purge flow may be 5,000 sccm. The tungsten-containing compound may be tungsten hexafluoride (WF6) and may be introduced at a continuous flow rate in the range of about 50 sccm to 500 sccm, such as in the range of about 300 sccm to 200 sccm.

As depicted inFIG. 2D, the growth of the first tungsten film240along the sidewalls222of the feature208tends to form an overhang portion243of the first tungsten film240. The presence of the overhang portion243would cause any further deposition of tungsten material to close off the opening242of the feature before the lower portion of the feature208has completely grown from the bottom surface224of the feature208, resulting in a void forming within the feature208.

Advantageously, the inventors have determined that treating the first tungsten film240by repeatedly alternating between etching the first tungsten film240for a first interval and stopping the etching the first tungsten film240for a second interval may remove the overhang portion243of the first tungsten film240. Advantageously, the inventors have also determined that treating the first tungsten film240by repeatedly alternating between etching the first tungsten film240for a first interval and stopping the etching the first tungsten film240for a second interval, a particular advantageous etch profile for the sidewalls of the first tungsten film240may be attained. Advantageously, by removing the overhang portion243of the first tungsten film240and attaining a predetermined profile for the sidewalls of the first tungsten film, the formation of a void within the feature208may be avoided. Advantageously, further deposition of tungsten material may fill the lower portion of the feature208starting from the bottom surface224of the feature208until the opening242may be completely filled.

At102, the first tungsten film240of the bulk tungsten layer260is etched for a first interval. In some embodiments, the first interval is about 1 sec to about 5 sec. In some embodiments, shown inFIG. 2D, the arrows264′ represent the direction of the reactants formed of an etchant gas or gases during the etch process which causes the reactants to collide with the top (planar) surface of the first tungsten film240.

In some embodiments, the first tungsten film240of the bulk tungsten layer260is etched using the tungsten containing gas to remove a portion of the overhang portion243of the first tungsten film240. The etching process, also referred to as an etchback process, removes a portion of the first tungsten film240from along the sidewalls222of the feature208. The etching process may also be performed in the same processing chamber as the tungsten deposition process. The etching process is generally performed using the same tungsten containing gases, e.g., tungsten hexafluoride (WF6).

In some embodiments, the first tungsten film240is etched using a plasma etching process. The plasma may be formed by coupling RF power to a treatment gas such as helium (He), argon (Ar), oxygen (O2), nitrogen (N2), or combinations thereof. The plasma may be formed in the process chamber or by a remote plasma source (RPS) and delivered to the process chamber. In some embodiments, the tungsten containing gas is provided with the treatment gas. In some embodiments, the tungsten containing gas is provided to the process chamber separately from the treatment gas.

During the etch process, the pedestal (and, therefore, the substrate) may have a temperature in the range of about 100° C. to about 600° C., for example, in the range of about 300° C. to 230° C. In some embodiments, the temperature may be about 200° C. Etching of the first tungsten film240may be performed with the process chamber at a chamber pressure in the range of about 0.1 Torr to about 5 Torr, for example, in the range of about 0.5 Torr to about 2 Torr. In some embodiments, the pressure may be about 1 Torr. The treatment gas, e.g., argon (Ar), may be introduced at a flow rate in the range of about 100 sccm to about 3,000 sccm. In some embodiments, argon may be introduced at a total flow rate of 2,000 sccm. A second flow of argon may be flowed through a purge guide (not shown) at a rate from about 0 sccm to 2,000 sccm to prevent deposition gases from contacting the edge and backside of the substrate. In some embodiments, the argon edge purge flow may be 500 sccm. Similarly, a second flow of hydrogen gas (H2) may be flowed through a purge guide (not shown inFIG. 3) at a rate from about 0 sccm to 6,000 sccm. In some embodiments, the hydrogen gas edge purge flow may be 2,500 sccm. In some embodiments, an additional flow of treatment gas, such as argon, may be introduced as a bottom purge in order to prevent deposition on the backside of the chamber heating elements. In some embodiments, the argon bottom purge flow may be 5,000 sccm. The tungsten-containing gas may be tungsten hexafluoride (WF6) and may be introduced at a continuous flow rate in the range of about 1 sccm to 150 sccm, such as in the range of about 3 sccm to 100 sccm. The arrows264′ may represent the direction of atomic fluorine during the etch process which may cause the atomic fluorine to collide with the top (planar) surface of the first tungsten film240.

In some embodiments, where the plasma is formed by coupling RF power to the treatment gas, an RF power between about 50 watts (W) and about 100 W, such as about 75 W at an RF power frequency from about 10 MHz to about 30 MHZ. In some embodiments, about 13.56 MHz, may be used.

In some embodiments, where the plasma is formed in a remote plasma source (RPS) the power application may be from about 1,000 W to about 6,000 W, In some embodiments, from about 1,000 W to about 2,000 W, with a treatment gas flow rate, e.g., argon, from about 500 sccm to about 6,000 sccm.

Portions of the first tungsten film240may be removed at an etch rate from about 0.1 Å/second to about 10 Å/second. In some embodiments, the first tungsten film240may be removed at an etch rate from about 0.5 Å/second to about 3 Å/second.

At104, the etching of the first tungsten film240is stopped for a second interval. In some embodiments, the second interval is about 1 sec to about 10 sec. The etching of the first tungsten film240may be stopped by purging an etchant gas from the processing chamber, by turning off a power supply that powers the etching of the first tungsten film240, or by both purging an etchant gas from the process chamber and turning off the power supply. In some embodiments, an inert gas may be introduced into the process chamber prior to purging the etchant gas from the processing chamber. The inert gas may be at least one of helium or argon. In some embodiments, the inert gas may be introduced in the manner described above.

In some embodiments, the etching the first tungsten film240may be a plasma process, and turning off the power supply that powers the etching of the first tungsten film240may include removing RF power from the power supply that generates the plasma.

At106, the first tungsten film is treated until a particular etch profile is attained. In some embodiments,102and104are repeated (e.g., etching and stopping the etch process are repeated). In some embodiments, as depicted inFIG. 2E, the particular etch profile is slanted sidewalls244of the first tungsten film240. The slanted sidewalls244may slant outwardly such that the sidewalls244are nearer to each other proximate the bottom of the feature and further from each other proximate the opening of the feature.

Next, at108, a second layer, such as second tungsten film of the bulk tungsten layer260, is deposited over the first layer, such as the remaining portion of the first tungsten film240, as depicted inFIG. 2F. The second tungsten film of the bulk tungsten layer260may be deposited in the same process chamber as the processes described above. The second tungsten film of the bulk tungsten layer260may be deposited using the same tungsten containing gases as used above.

The deposition of the second tungsten film of the bulk tungsten layer260may be performed on a pedestal having a temperature in the range of about 100° C. to about 600° C., for example, in the range of about 300° C. to about 230° C. In some embodiments, the temperature may be about 200° C. Deposition of the second tungsten film of the bulk tungsten layer260may be performed with the process chamber at a pressure in the range of about 10 Torr to about 300 Torr, or in some embodiments, in the range of about 30 Torr to about 100 Torr. In some embodiments, the pressure may be about 90 Torr. The reducing gas, for example, hydrogen gas (H2), may be introduced at a continuous flow rate between 1,000 sccm and about 8,000 sccm, such as 5,000 sccm. The reducing gas can be introduced with a carrier gas, such as argon (Ar), at a flow rate in the range of about 0 sccm to about 20,000 sccm. In some embodiments, argon may be introduced at a total flow rate of 11,000 sccm. A second flow of argon may be flowed through a purge guide (not shown inFIG. 3) at a rate from about 0 sccm to 2,000 sccm to prevent deposition gases from contacting the edge and backside of the substrate. In some embodiments, the argon edge purge flow may be 500 sccm. Similarly, a second flow of hydrogen gas (H2) may be flowed through a purge guide (not shown inFIG. 3) at a rate from about 0 sccm to 6,000 sccm. In some embodiments, the hydrogen gas edge purge flow may be 2,500 sccm. In some embodiments, an additional flow of carrier gas, such as argon, may be introduced as a bottom purge in order to prevent deposition on the backside of the chamber heating elements. In some embodiments, the argon bottom purge flow may be 5,000 sccm. The tungsten-containing compound may be tungsten hexafluoride (WF6) and may be introduced at a continuous flow rate in the range of about 50 sccm to 500 sccm, such as in the range of about 300 sccm to 200 sccm.

If the predetermined thickness of bulk tungsten layer260has been achieved, the method100ends. If the predetermined thickness of the bulk tungsten layer260has not been achieved any of the aforementioned deposition and etching processes may be performed again. In some embodiments, the determination of the thickness of the of the tungsten bulk layer may be performed using conventional processes such as spectroscopic measurements.

FIG. 3depicts a schematic diagram of a process chamber300of the kind that may be used to practice embodiments of the disclosure as discussed herein. The particular configuration of the process chamber300is illustrative and not limiting of the scope of the present disclosure. The process chamber300may be utilized alone or, more typically, as a processing module of an integrated semiconductor substrate processing system, or cluster tool, such as a ENDURA®, CENTURA®, or PRODUCER® integrated semiconductor substrate processing system, available from Applied Materials, Inc. of Santa Clara, Calif. In some embodiments, the process chamber300may be a deposition chamber, such as a chemical vapor deposition (CVD) chamber suitable for depositing materials, such as tungsten, on a substrate. Suitable deposition processing chambers include, but are not limited to, certain single wafer chambers on the ENDURA® platform and twin wafer chambers on the PRODUCER® platform, also available from Applied Materials, Inc. Methods of processing substrates in accordance with the present disclosure can be utilized on other chambers and platforms as well.

The processing chamber300may be part of a processing system that includes multiple processing chambers connected to a central transfer chamber and serviced by a robot (seeFIG. 5). The processing chamber300includes walls306, a bottom308, and a lid310that define a processing volume312. The walls306and bottom308are typically fabricated from a unitary block of aluminum. The walls306may have conduits (not shown) within through which a fluid may be passed to control the temperature of the walls306. The processing chamber300may also include a pumping ring314that couples the processing volume312to an exhaust port316as well as other pumping components (not shown).

A substrate support assembly338, which may be heated, may be centrally disposed within the processing chamber300. The substrate support assembly338supports a substrate303during a deposition process. The substrate support assembly338generally is fabricated from aluminum, ceramic or a combination of aluminum and ceramic and typically includes a vacuum port (not shown) and at least one or more heating elements332.

The vacuum port may be used to apply a vacuum between the substrate303and the substrate support assembly338to secure the substrate303to the substrate support assembly338during the deposition process. The one or more heating elements332may be, for example, electrodes disposed in the substrate support assembly338, and coupled to a power source330, to heat the substrate support assembly338and substrate303positioned on to a predetermined temperature.

Generally, the substrate support assembly338is coupled to a stem342. The stem342provides a conduit for electrical leads, vacuum and gas supply lines between the substrate support assembly338and other components of the processing chamber300. Additionally, the stem342couples the substrate support assembly338to a lift system344that moves the substrate support assembly338between an elevated position (as shown inFIG. 3) and a lowered position (not shown). Bellows346provides a vacuum seal between the processing volume312and the atmosphere outside the process chamber300while facilitating the movement of the substrate support assembly338.

The substrate support assembly338additionally supports a circumscribing shadow ring348. The shadow ring348is annular in form and typically comprises a ceramic material such as, for example, aluminum nitride. Generally, the shadow ring348prevents deposition at the edge of the substrate303and substrate support assembly338.

The lid310is supported by the walls306and may be removable to allow for servicing of the processing chamber300. The lid310may generally be comprised of aluminum and may additionally have heat transfer fluid channels324formed within. The heat transfer fluid channels324are coupled to a fluid source (not shown) that flows a heat transfer fluid through the lid310. Fluid flowing through the heat transfer fluid channels324regulates the temperature of the lid310.

A showerhead318may generally be coupled to an interior side320of the lid310. A perforated blocker plate336may optionally be disposed in the space322between the showerhead318and lid310. Gases (i.e., process and other gases) that enter the processing chamber300are first diffused by the blocker plate336as the gases fill the space322behind the showerhead318. The gases then pass through the showerhead318and into the processing chamber300. The blocker plate336and the showerhead318are configured to provide a uniform flow of gases to the processing chamber300. Uniform gas flow advantageously promotes uniform layer formation on the substrate303.

A gas source360is coupled to the lid310to provide gas through gas passages in the showerhead318to a processing area between the showerhead318and the substrate303. A vacuum pump (not shown) may be coupled to the processing chamber300to control the processing volume at a predetermined pressure. An RF source370is coupled through a match network390to the lid310and/or to the showerhead318to provide an RF current to the showerhead318. The RF current creates an electric field between the showerhead318and the substrate support assembly338so that plasma may be generated from the gases between the showerhead318and the substrate support assembly338.

A remote plasma source380, such as an inductively coupled remote plasma source, may also be coupled between the gas source360and the lid310. Between processing substrates, a cleaning gas may be provided to the remote plasma source380so that remote plasma is generated. The radicals from the remote plasma may be provided to the processing chamber for a plasma etching process. The etching gas may be further excited by the RF source370provided to the showerhead318.

The process chamber300includes a controller340. The controller340comprises a central processing unit (CPU)354, a memory352, and support circuits356for the CPU354and facilitates control of the components of the process chamber300and, as such, of the method100, as discussed herein in further detail. To facilitate control of the process chamber300as described above, the controller340may be any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory352, or computer-readable medium, of the CPU354may be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The support circuits356are coupled to the CPU354for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. The inventive method described herein is generally stored in the memory352as a software routine. The software routine may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU354.