AMMONIA ABATEMENT FOR IMPROVED ROUGHING PUMP PERFORMANCE

In a process chamber connected with a process roughing pump via a pump foreline, pumping from the process chamber to the foreline ammonia and a deposition precursor, introducing into the foreline hydrogen fluoride gas to react with the ammonia to form ammonium fluoride, and maintaining the process roughing pump and pump foreline at at least the ammonium fluoride sublimation temperature during the pumping provides ammonia abatement for improved roughing pump performance.

BACKGROUND

Ammonia (NH3) is frequently used as a co-reactant in various semiconductor processing operations. Ammonia can react with various deposition precursors, such as transition metal (e.g., tungsten, molybdenum, etc.) and silicon containing vapor deposition precursors, to form irreversible solids in the roughing pump used to pump or purge depositions reactant gases from a process chamber. These irreversible solids can adversely affect the roughing pump and tool throughput, and it is therefore desirable to mitigate the formation of these irreversible solids in the roughing pump.

SUMMARY

In some embodiments, a method may be provided. The method may include in an apparatus comprising a process chamber connected with a process roughing pump via a pump foreline, pumping from the process chamber to the foreline ammonia and a deposition precursor, introducing into the foreline hydrogen fluoride gas to react with the ammonia to form ammonium fluoride, and maintaining the process roughing pump and pump foreline at at least the ammonium fluoride sublimation temperature during the pumping.

In some embodiments, the process roughing pump and pump foreline may be maintained at a temperature of at least 100° C. during the pumping.

In some embodiments, the hydrogen fluoride may be introduced to the pump foreline in an amount at least stoichiometrically equal to the amount of ammonia pumped to the foreline.

In some such embodiments, the hydrogen fluoride may be introduced to the pump foreline in a ratio of about 1.1 hydrogen fluoride to 1 ammonia.

In some such embodiments, the hydrogen fluoride flow may be about 700 to 800 SCCM.

In some embodiments, the deposition precursor may include a transition metal species.

In some embodiments, the deposition precursor may include a transition metal halide.

In some embodiments, the deposition precursor may include tungsten fluoride.

In some embodiments, the deposition precursor may include tungsten chloride.

In some embodiments, the deposition precursor may include molybdenum fluoride.

In some embodiments, the deposition precursor may include molybdenum chloride.

In some embodiments, the deposition precursor may include a silicon-containing species.

In some embodiments, the deposition precursor may include a silicon halide.

In some embodiments, the deposition precursor may include a silicon chloride.

In some embodiments, the deposition precursor may include a silicon bromide.

In some embodiments, the deposition precursor may include a silicon iodide.

In some embodiments, the apparatus may further include a process exhaust abatement device connected with the process roughing pump via an exhaust line, and the exhaust line may be maintained at at least the ammonium fluoride sublimation temperature during the pumping.

In some such embodiments, the exhaust line may be maintained at a temperature of at least 100° C. during the pumping.

In some such embodiments, the ammonium fluoride may desublimate as solid ammonium fluoride and may be captured in the process exhaust abatement device for removal from the apparatus.

In some further embodiments, the removal of the solid ammonium fluoride may include dissolving the solid ammonium fluoride in the process exhaust abatement device in an aqueous solution.

In some embodiments, the pump foreline may further include a mixing area, and the hydrogen fluoride gas may be introduced into the foreline at or upstream of the mixing area such that the hydrogen fluoride mixes and reacts with the ammonia to form the ammonium fluoride prior to entering the process roughing pump.

In some embodiments, the maintaining the process roughing pump and pump foreline at at least the ammonium fluoride sublimation temperature during the pumping may include flowing a heated gas into the pump foreline and/or into the process roughing pump.

In some such embodiments, the heated gas may include nitrogen or argon.

In some embodiments, the maintaining the process roughing pump and pump foreline at at least the ammonium fluoride sublimation temperature during the pumping may include causing one or more heating elements to heat the pump foreline and/or the process roughing pump.

In some embodiments, an apparatus may be provided. The apparatus may include a process chamber connected with a process roughing pump via a pump foreline, a deposition precursor and ammonia gas source connected with the process chamber, a hydrogen fluoride gas source connected with the process roughing pump, gas flow-control hardware associated with the gas sources, and a controller having a processor and a memory. The processer and the memory are communicatively connected with one another, the processor is at least operatively connected with the flow-control hardware, and the memory stores computer-executable instructions for causing the process roughing pump to pump ammonia and a deposition precursor from the process chamber to the pump foreline, causing hydrogen fluoride gas to be introduced into the foreline to react with the ammonia to form ammonium fluoride, and causing the process roughing pump and the pump foreline to be maintained at at least the ammonium fluoride sublimation temperature during the pumping.

In some embodiments, the apparatus may further include a process exhaust abatement device connected with the process roughing pump via an exhaust line, and the memory stores computer-executable instructions for causing the exhaust line to be maintained at at least the ammonium fluoride sublimation temperature during the pumping.

In some embodiments, the pump foreline may further include a mixing area, and the memory further stores computer-executable instructions for introducing the hydrogen fluoride gas into the foreline at or upstream of the mixing area such that the hydrogen fluoride mixes and reacts with the ammonia to form the ammonium fluoride prior to entering the process roughing pump.

In some embodiments, the hydrogen fluoride gas may be connected to the process roughing pump via a connection to the pump foreline between the process chamber and the process roughing pump.

In some embodiments, the apparatus may further include a throttle valve connected to the pump foreline and configured to control gas flow through the pump foreline, and the hydrogen fluoride gas may be connected to the pump foreline between the throttle valve and the process roughing pump.

In some embodiments, the causing the process roughing pump and the pump foreline to be maintained at at least the ammonium fluoride sublimation temperature during the pumping may include causing a heated gas to be flowed into the pump foreline, into the process roughing pump, or into the pump foreline and the process roughing pump.

In some such embodiments, the heated gas may include nitrogen or argon.

In some embodiments, the apparatus may include one or more heating elements configured to heat the pump foreline to at least the ammonium fluoride sublimation temperature, and the causing the process roughing pump and the pump foreline to be maintained at at least the ammonium fluoride sublimation temperature during the pumping may include causing the one or more heating elements to heat the pump foreline to at least the ammonium fluoride sublimation temperature.

DETAILED DESCRIPTION

Ammonia (NH3) is frequently used as a co-reactant in various semiconductor processing operations, such as metal nitride or silicon nitride deposition processes. However, ammonia can react with various deposition precursors, such as transition metal (e.g., tungsten, molybdenum, etc.) and silicon containing vapor deposition precursors, to form irreversible solids in the roughing pump used to pump or purge depositions reactant gases from a process chamber. This can dramatically shorten the life of the roughing pump without excessively short periodic maintenance (PM) cycles. Short PM cycles result in decreased tool uptime and therefore reduced throughput.

A current ammonia mitigation technology is to react the ammonia with excess fluorine, generated from nitrogen trifluoride (NF3) with a remote plasma source (e.g., MKS Astron). However, introducing fluorine to process streams containing high levels of hydrogen (H2) or high levels of silane (SiH4) or some other silicon-based and/or hydrogen-containing precursors can produce a highly exothermic reaction, which results in an undesirable hazard.

This challenge can be addressed by introducing hydrogen fluoride (HF) gas into the foreline of the roughing pump to react with ammonia (NH3). The reaction of HF with NH3forms ammonium fluoride (NH4F). The reaction is a not highly exothermic, so this hazard is not created. And HF does not react with H2- or silane-based precursors.

NH4F is a solid at room temperature. However, the NH4F solid sublimes at temperatures of 100° C. or higher. With the appropriate heating of the pump foreline, pump and pump exhaust line, the accumulation of NH4F solids can be controlled so that the deposition precursors pass through the pump and can be captured and removed from the system in an abatement device.

This approach prevents ammonia from reacting with deposition precursors to form irreversible solids in the pump, which increases life of the pump and lengthens the time between PM cycles.

Referring toFIG.1, a process flow is depicted for one aspect of the present disclosure, a method conducted in an apparatus having a process chamber connected with a process roughing pump via a pump foreline. At101, ammonia and a deposition precursor are pumped from the process chamber to the foreline, such as upon pumping down or purging the process chamber following a deposition operation conducted in the process chamber. The ammonia and deposition precursor may be among other process gases pumped from the chamber. The deposition precursor may include a transition metal species, such as a transition metal halide. For example, the deposition precursor may include tungsten halide, such as tungsten or molybdenum chloride or fluoride. Other deposition precursors may include a silicon-containing species, such as a silicon halide, for example, silicon chloride, bromide or iodide. And contemplated deposition precursors may also include other elements, such as oxygen, nitrogen, etc., that are commonly incorporated in films deposited in semiconductor fabrication operations. Some samples process chemistries include:WF6+NH3MoX, where X includes a halide+NH3+H2SiH2X2/SiHX3/SiX4, where X includes a halide+NH3

Referring again toFIG.1, at103, hydrogen fluoride gas is introduced into the foreline to react with the ammonia to form ammonium fluoride. The hydrogen fluoride may be introduced to the pump foreline in an amount at least stoichiometrically equal to the amount of ammonia pumped to the foreline. For example, the hydrogen fluoride may be introduced to the pump foreline in a ratio of about 1.1 hydrogen fluoride to 1 ammonia. In a particular example, a suitable hydrogen fluoride flow rate may be about 700 to 800 standard cubic centimeters per minute (SCCM).

Referring again toFIG.1, at105, the process roughing pump and pump foreline are maintained at at least the ammonium fluoride sublimation temperature during the pumping so that the ammonium fluoride can pass to and through the pump in the gas phase to prevent fouling of the pump. For example, the process roughing pump and pump foreline may be maintained at a temperature of at least 100° C. during the pumping. In some embodiments, the process roughing pump and/or the pump foreline may be heated in order to maintain the temperature at at least 100° C. during pumping. This may include using one or more heating elements to heat the process roughing pump and/or the pump foreline. These heating elements may include resistive heaters or heating fluids positioned on or within the process roughing pump and/or the pump foreline. These heating elements are configured to heat the process roughing pump and/or the pump foreline to at least 100° C.

Additionally or alternatively, in some embodiments a heated gas may be flowed into the process roughing pump and/or the pump foreline in order to heat the process roughing pump and/or the pump foreline. This may be a heated inert gas, such as nitrogen or argon. In some implementations, this gas may be heated by one or more heaters configured to heat this gas, which may include one or more heating elements, such as a resistive heater or fluid conduits through which a heated fluid flows, positioned on or within one or more gas lines through which the gas flows. In some instances, this heated gas may be flowed from a gas source into the pump foreline through a connection point along the pump foreline. In some embodiments, this heated gas may be co-flowed with the hydrogen fluoride gas into the foreline. As described below, the heated gas may be flowed into the process roughing pump.

FIG.2depicts a simplified schematic of an apparatus such as described herein. The apparatus200includes a process chamber204connected with a process roughing pump208(e.g., a vacuum pump) via a pump foreline206. A deposition precursor and ammonia gas source202(i.e., process gas source) is connected with the process chamber204. As noted above, the ammonia and deposition precursor may be among other process gases pumped to and/or from the process chamber204. Arrows indicate the direction of gas flow through the apparatus200.

A hydrogen fluoride gas source212is connected with the pump208via the pump foreline206. The foreline206may include a throttle valve210to control gas flow through the foreline206drawn by the process roughing pump208. The process roughing pump208may have an associated pump purge gas source218, such as a source of nitrogen (N2) gas. This pump purge gas source218may be connected to the process roughing pump208and/or to an exhaust line214and configured to flow purge gas into the process roughing pump208and/or to the exhaust line214. In some embodiments, this purge gas may be heated

The pump foreline may also optionally include a mixing area207in a configuration to provide for thorough reaction of the ammonia and HF in the event the a straight foreline is insufficient to achieve this. If the foreline206incorporates a mixing area207, the HF gas source212may be connected with the foreline206via the mixing area207. In either arrangement, the hydrogen fluoride gas is introduced into the foreline at or upstream of the mixing area, if present, and the pump such that the hydrogen fluoride mixes and reacts with the ammonia to form the ammonium fluoride prior to entering the process roughing pump.

As stated above, the process roughing pump and pump foreline are maintained at at least the ammonium fluoride sublimation temperature during the pumping. In some embodiments, the temperature may be maintained by using one or more heating elements to heat the process roughing pump and/or the pump foreline. InFIG.2, a heating element209is illustrated on the pump foreline206and this heating element209is configured to heat the pump foreline206to at least 100° C. This heating element209also represents one or more heating elements, such as resistive heaters or heating fluids within fluid conduits positioned on or within the pump foreline206.FIG.2also includes a second heating element211that is configured to heat the process roughing pump208to at least 100° C. This heating element209also represents one or more heating elements, such as resistive heaters or heating fluids within fluid conduits positioned on or within the process roughing pump208.

As also stated above, in some embodiments, a portion of the pump foreline and/or the process roughing pump208may be heated to and maintained at at least the ammonium fluoride sublimation temperature during the pumping by flowing a heating gas from another gas source215, such as a heated nitrogen or argon, into the pump foreline at a location between the process chamber204and the process roughing pump208. This may include a point upstream or downstream from the connection point of the hydrogen fluoride into the pump foreline206. In some instances, this heating gas may be co-flowed with the hydrogen fluoride into the pump foreline206. In some embodiments, the other gas source215may be purge gas source218described herein such that purge gas source218may be configured to flow heated purge gas. In some implementations, this heating gas may be heated using another heater230configured to heat this gas, which may include one or more heating elements, such as a resistive heater or fluid conduits through which a heated fluid flows, positioned on or within one or more gas lines through which the gas flows. Although this heater230is illustrated on one gas line, it may be considered positioned on or within any gas line or gas plenum.

In some implementations that use a heated gas flowed from the additional gas source215, the heating gas may be flowed into the line connected the hydrogen fluoride to the mixing area207, into the foreline206upstream or downstream of the mixing area207, or into the mixing area207. This heated gas may maintain the portion of the foreline206between the mixing area207and the process roughing pump208, and/or the process roughing pump at a temperature at at least the ammonium fluoride sublimation temperature, such as at least 100° C.

The apparatus200further includes gas flow-control hardware associated with the gas sources202and212and, and a controller220having a processor and a memory. The processer and the memory are communicatively connected with one another, the processor is at least operatively connected with the flow-control hardware, and the memory stores computer-executable instructions for conducting the at least the method operations described above with reference toFIG.1and elsewhere herein.

The apparatus200depicted inFIG.2further includes a process exhaust abatement device216connected with the process roughing pump208via an exhaust line214. In one implementation of a method in accordance with this disclosure, the exhaust line214is maintained at at least the ammonium fluoride sublimation temperature during the pumping of gases through the apparatus, including the pumping of ammonium fluoride formed by the reaction of the ammonia and deposition precursor from the process chamber204in the foreline206and through the pump208and exhaust line214to the abatement device216. For example, the exhaust line may be maintained at a temperature of at least 100° C. during the pumping. Similar to above, in some embodiments the exhaust line may be heated in order to maintain its temperature at at least 100° C. during pumping. This may include using one or more heating elements, illustrated inFIG.2as optional element213, to heat the exhaust line214and these one or more heating elements213may include resistive heaters or heating fluids positioned on or within the exhaust line214. These one or more heating elements213are configured to heat the exhaust line to at least 100° C.

Further in this regard and as provided herein, an additional heated purge gas (e.g., N2) source215may be provided to facilitate the purging of gases from the pump208through the exhaust line214to the abatement device216. As stated herein, this heated purge gas may be configured to heat the exhaust line214to at least the ammonium fluoride sublimation temperature, such as at least 100° C. In some embodiments, this heated purge gas may maintain the process roughing pump208and/or the exhaust line213at at least the ammonium fluoride sublimation temperature.

In the abatement device216, the ammonium fluoride desublimates as solid ammonium fluoride and is captured for removal from the apparatus200. For example, the removal of the solid ammonium fluoride may involve dissolving the solid ammonium fluoride in the process exhaust abatement device216in an aqueous solution. The controller220memory may store computer-executable instructions for conducting the operations described above in connection with pumping the gases through the pump208and exhaust line214, to and through the abatement device216, in the apparatus200.

A suitable abatement device is known in the industry as a wet-burn-wet abatement unit. See, e.g., www.airgard.net/encompass.html. In such a device, a first section of the abatement unit is water-based, used to dissolve the ammonium fluoride. A second section of the abatement unit is burner/combustion-based to handle other effluents from the process chamber, such as chamber cleans. A third section of the abatement unit is wet-based, to capture the combustion by-products of the second section of the abatement unit.

Exhaust from the abatement device216may be directed to a facility scrubbed exhaust.

FIG.3depicts a more specific architecture of a particular example of an apparatus as described herein, to provide additional details of one specific embodiment of an implementation in accordance with the disclosure.

InFIG.3, process chamber304, the process gas source and hardware302, and the throttle valve310are the same as inFIG.2. Here, the mixing area307is included, is connected to the pump foreline306, and is interposed between the throttle valve310and the process roughing pump308. The hydrogen fluoride gas source312is connected with the foreline306via the mixing area307, and the hydrogen fluoride gas is introduced into the foreline306at the mixing area307. The hydrogen fluoride mixes and reacts with the ammonia to form the ammonium fluoride prior to entering the process roughing pump. Additional gas sources315may be used and connected to the hydrogen fluoride gas source312, piping between the mixing area and the hydrogen fluoride gas source312, and/or the mixing area307as illustrated with dashed optional lines.

One or more of these additional gases from gas sources315may assist with flowing the hydrogen fluoride into the mixing area307and/or to assist with maintaining the temperature of the mixing area307, the foreline306between the mixing area307and the process roughing pump308, and/or the process roughing pump308. In some implementations, as discussed above with respect to gas source215, a gas from gas source315may be a heated gas, such as a heated purge gas which may include argon or nitrogen. These gases may be heated in order to cause the temperature of the mixing area307, the foreline306between the mixing area307and the process roughing pump308, and/or the process roughing pump308at at least the ammonium fluoride sublimation temperature during the pumping, such as at least 100° C. These gases may include argon or nitrogen gas, for example. In some embodiments, the other gas source315may be purge gas source318described herein such that purge gas source318may be configured to flow heated purge gas.

In some embodiments, such as illustrated inFIG.3, one or more heating elements309may be included to heat at least a part of the pump foreline306. In some embodiments, alternatively or additionally, a gas from gas source315may be heated and flowed into the mixing area307to heat the mixing area307, the pump foreline306between the mixing area and the process roughing pump308, and/or the process roughing pump308. This heating may be performed by one or more heating elements, or fluid conduits in which heated fluid flows, on or within gas lines, as represented by heating element330.

As also seen inFIG.3, the purge gas source318may be connected to the process roughing pump308and configured to flow purge gas into the process roughing pump308. This gas may be heated nitrogen as described above. In some instances, apparatus300may also include a secondary gas line317connected to the exhaust line314and having a detector319and another pump321. This detector319may be an infrared and/or gas detector configured to detect various aspects of the gases in the exhaust line314, such as whether the ammonium fluoride is remaining in a gas state.

The remaining features ofFIG.3may be the same as described with respect toFIG.2.

Chamber Apparatus

The methods and apparatus described herein may be implemented and/or integrated with any suitable deposition chamber apparatus. Suitable apparatuses include various systems, e.g., ALTUS®, SPEED®, Striker®, and VECTOR®, available from Lam Research Corporation, Fremont, Calif., or any of a variety of other commercially available processing systems.

FIG.4Aillustrates a schematic representation of an apparatus400for processing a partially fabricated semiconductor substrate in accordance with certain embodiments. The apparatus400includes a chamber418with a pedestal420, a showerhead414, and an in-situ plasma generator416. The apparatus400also includes a system controller422to receive input and/or supply control signals to various devices.

Process gases, including deposition and/or etch precursors, ammonia inert gases and others, are supplied from a source402which may be one or more storage tank or a gas box. Process gases may be activated with a remote plasma generator406before being introduced into the chamber418. Any suitable remote plasma generator may be used. For example, a Remote Plasma Cleaning (RPC) unit, such as an ASTRON® unit available from MKS Instruments of Andover, Mass., may be used.

In certain embodiments, deposition precursors, etchant and other process gases can be flown from the source402through a remote plasma generator406and a connecting line408into the chamber418, where the mixture is distributed through the showerhead414. Alternatively, the remote plasma generator406may be absent or turned off while flowing the etchant into the chamber418, for example, because activation of the process gases is not needed.

The showerhead414or the pedestal420typically may have an internal plasma generator416attached to it. In one example, the generator416is a High Frequency (HF) generator capable of providing between about 0 W and 10,000 W at frequencies between about 1 MHz and 100 MHz. In a more specific embodiment, the HF generator may deliver between about 0 W to 5,000 W at about 13.56 MHz.

The chamber418may include a sensor424for sensing various process parameters, such as degree of deposition and etching, concentrations, pressure, temperature, and others. The sensor424may provide information on chamber conditions during the process to the system controller422. Examples of the sensor424include mass flow controllers, pressure sensors, thermocouples, and others. The sensor424may also include an infrared detector or optical detector to monitor presence of gases in the chamber and control measures.

Deposition and selective removal operations generate various volatile species that are evacuated from the chamber418. Moreover, processing is performed at certain predetermined pressure levels the chamber418. Both of these functions are achieved using a vacuum outlet426, which may be a vacuum pump. An apparatus as described with reference toFIGS.2and3herein may be integrated here.

In certain embodiments, a system controller422is employed to control process parameters. The system controller422typically includes one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc. Typically, there will be a user interface associated with system controller422. The user interface may include a display screen, graphical software displays of the apparatus and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.

In certain embodiments, the system controller422controls the substrate temperature, etchant flow rate, power output of the remote plasma generator406, pressure inside the chamber418and other process parameters. The system controller422executes system control software including sets of instructions for controlling the timing, mixture of gases, chamber pressure, chamber temperature, and other parameters of a particular process. Other computer programs stored on memory devices associated with the controller may be employed in some embodiments.

The computer program code for controlling the processes in a process sequence can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program. The system software may be designed or configured in many different ways. For example, various chamber component subroutines or control objects may be written to control operations of the chamber components used to carry out the described processes. Examples of programs or sections of programs for this purpose include process gas control code, pressure control code, and plasma control code.

The controller parameters relate to process conditions such as, for example, timing of each operation, pressure inside the chamber, substrate temperature, etchant flow rates, etc. These parameters are provided to the user in the form of a recipe and may be entered utilizing the user interface. Signals for monitoring the process may be provided by analog and/or digital input connections of the system controller422. The signals for controlling the process are output on the analog and digital output connections of the apparatus400.

FIG.4Bshows another example plasma reactor that may be used to deposit or etch materials in accordance with certain semiconductor fabrication processes.FIG.4Bschematically shows a cross-sectional view of an inductively coupled plasma apparatus490, an example of which is a SPEED® Max reactor, produced by Lam Research Corporation of Fremont, Calif. Although ICP reactors are described herein, in some embodiments, it should be understood that capacitively coupled plasma reactors may also be used.

The inductively coupled plasma apparatus490includes an overall process chamber structurally defined by chamber walls491and a dome492for igniting a plasma. The chamber walls491may be fabricated from stainless steel or aluminum. Elements for plasma generation include a coil494, which is positioned around the dome492and above the showerhead495. In some embodiments, a coil is not used in disclosed embodiments. The coil494is fabricated from an electrically conductive material and includes at least one complete turn. The example of a coil494shown inFIG.4Bincludes three turns. The cross-sections of coil494are shown with symbols, and coils having an “X” extend rotationally into the page, while coils having a “e” extend rotationally out of the page. Elements for plasma generation also include an RF power supply441configured to supply RF power to the coil494. In general, the RF power supply441is connected to matching circuitry439through a connection445. The matching circuitry439is connected to the coil494through a connection443. In this manner, the RF power supply441is connected to the coil494. Radio frequency power is supplied from the RF power supply441to the coil494to cause an RF current to flow through the coil494. The RF current flowing through the coil494generates an electromagnetic field about the coil494. The electromagnetic field generates an inductively coupled plasma within the dome492. The physical and chemical interactions of various generated ions and radicals with the wafer497etch features on the semiconductor substrate or wafer497.

Likewise, RF power supply441may provide RF power of any suitable frequency. In some embodiments, RF power supply441may be configured to control high- and low-frequency RF power sources independently of one another. Example low-frequency RF frequencies may include, but are not limited to, frequencies between 0 kHz and 500 kHz. Example high-frequency RF frequencies may include, but are not limited to, frequencies between 1 MHz and 2.45 GHz, or between 1.8 MHz and 2.45 GHz, or greater than about 13.56 MHz, or greater than 27 MHz, or greater than 40 MHz, or greater than 60 MHz. It will be appreciated that any suitable parameters may be modulated discretely or continuously to provide plasma energy for the surface reactions.

The RF power may be programmed to be ramped and/or pulsed during an etching operation performed in accordance with certain embodiments. For example, RF power may be ramped between an ON and OFF state, where the RF power during the OFF state is OW and the RF power during the ON state is between about 50 W and about 3000 W. RF power may be pulsed at a frequency between about 1 Hz and about 400 kHz, or between 1 Hz and about 100 KHz, or between about 10 Hz and about 100 kHz, or between about 100 Hz and about 10 kHz. The duty cycle may be between about 1% and about 99% or between about 10% and about 90%. The duration of RF power ON during a pulse may be between about 100 milliseconds and about 10 seconds, or between about 100 milliseconds and about 5 seconds.

Showerhead495distributes process gases toward substrate497. In the embodiment shown inFIG.4B, the substrate497is located beneath showerhead495and is shown resting on a pedestal496. Showerhead495may have any suitable shape and may have any suitable number and arrangement of ports for distributing process gases to substrate497.

A pedestal496is configured to receive and hold a substrate497upon which the etching is performed. In some embodiments, pedestal496may be raised or lowered to expose substrate497to a volume between the substrate497and the showerhead495. It will be appreciated that, in some embodiments, pedestal height may be adjusted programmatically by a suitable computer controller499.

In another scenario, adjusting a height of pedestal496may allow a plasma density to be varied during plasma activation cycles included in the process. At the conclusion of the process phase, pedestal496may be lowered during another substrate transfer phase to allow removal of substrate497from pedestal496. In some embodiments, a position of showerhead495may be adjusted relative to pedestal496to vary a volume between the substrate497and the showerhead495. Further, it will be appreciated that a vertical position of pedestal496and/or showerhead495may be varied by any suitable mechanism within the scope of the present disclosure. In some embodiments, pedestal496may include a rotational axis for rotating an orientation of substrate497. It will be appreciated that, in some embodiments, one or more of these example adjustments may be performed programmatically by one or more suitable computer controllers499.

Process gases (e.g. halogen-containing gases, NF3, argon, WF6, ammonia, nitrogen, etc.) may be flowed into the process chamber through one or more main gas flow inlets493positioned in the dome and/or through one or more side gas flow inlets (not shown). Likewise, though not explicitly shown, similar gas flow inlets may be used to supply process gases to a capacitively coupled plasma processing chamber. In some embodiments for a capacitively coupled plasma processing chamber, gas may be injected through a showerhead via the center and/or the edge of the showerhead. A vacuum pump, e.g., a one or two stage mechanical dry pump and/or turbomolecular pump498a, may be used to draw process gases out of the process chamber491and to maintain a pressure within the process chamber491. A valve-controlled conduit may be used to fluidically connect the vacuum pump to the process chamber491so as to selectively control application of the vacuum environment provided by the vacuum pump. This may be done employing a closed-loop-controlled flow restriction device, such as a throttle valve (not shown) or a pendulum valve (not shown), during operational plasma processing. Likewise, a vacuum pump and valve controlled fluidic connection to the capacitively coupled plasma processing chamber may also be employed. Volatile etching and/or deposition byproducts may be removed from the process chamber491through port498b.

In some embodiments, a system controller499(which may include one or more physical or logical controllers) controls some or all of the operations of a process chamber499. The system controller499may include one or more memory devices and one or more processors. In some embodiments, the apparatus490includes a switching system for controlling flow rates and durations when disclosed embodiments are performed. In some embodiments, the apparatus490may have a switching time of up to about 500 ms, or up to about 750 ms. Switching time may depend on the flow chemistry, recipe chosen, reactor architecture, and other factors.

Results

The techniques and apparatuses herein were found to reduce ammonia at the roughing pump exhaust. In one experiment, the inventors found that before any hydrogen fluoride (HF) was flowed into the system, ammonia was flowing at a flowrate of about 1 SLPM and a concentration above 6,000 ppm. Once the HF was flowed into the system at about 1.1 SLPM, the ammonia concentration was reduced to less than 2,000 ppm, or reduced by about 85%.

CONCLUSION