# Patent

## Title
Oxide and metal removal

## Abstract

Methods are described herein for etching metal films which are difficult to volatize. The methods include exposing a metal film to a chlorine-containing precursor (e.g. Cl2). Chlorine is then removed from the substrate processing region. A carbon-and-nitrogen-containing precursor (e.g. TMEDA) is delivered to the substrate processing region to form volatile metal complexes which desorb from the surface of the metal film. The methods presented remove metal while very slowly removing the other exposed materials. A thin metal oxide layer may be present on the surface of the metal layer, in which case a local plasma from hydrogen may be used to remove the oxygen or amorphize the near surface region, which has been found to increase the overall etch rate.

## Background
FIELD
Embodiments of the invention relate to gas-phase etching metal.
BACKGROUND
Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process which etches one material faster than another helping e.g. a pattern transfer process proceed. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits and processes, etch processes have been developed with a selectivity towards a variety of materials.
Dry etch processes are often desirable for selectively removing material from semiconductor substrates. The desirability stems from the ability to gently remove material from miniature structures with minimal physical disturbance. Dry etch processes also allow the etch rate to be abruptly stopped by removing the gas phase reagents. Some dry-etch processes involve the exposure of a substrate to remote plasma by-products formed from one or more precursors. For example, remote plasma excitation of ammonia and nitrogen trifluoride enables silicon oxide to be selectively removed from a patterned substrate when the plasma effluents are flowed into the substrate processing region. Remote plasma etch processes have recently been developed to selectively remove several dielectrics relative to one another. However, dry-etch processes are still needed, which delicately remove metals which have limited or no previously known chemically volatile pathways.
SUMMARY
Methods are described herein for etching metal films which are difficult to volatize. The methods include exposing a metal film to a chlorine-containing precursor (e.g. Cl2). Chlorine is then removed from the substrate processing region. A carbon-and-nitrogen-containing precursor (e.g. TMEDA) is delivered to the substrate processing region to form volatile metal complexes which desorb from the surface of the metal film. The methods presented remove metal while very slowly removing the other exposed materials. A thin metal oxide layer may be present on the surface of the metal layer, in which case a local plasma from hydrogen may be used to remove the oxygen or amorphize the near surface region, which has been found to increase the overall etch rate.
Embodiments of the invention include methods of etching metal from a substrate. The methods include flowing a hydrogen-containing precursor into a first substrate processing region housing the substrate while forming a plasma in the plasma substrate processing region to treat a thin metal oxide layer formed on a metal layer. The methods further include flowing a halogen-containing precursor into a second substrate processing region. The second substrate processing region is plasma-free during the flowing of the halogen-containing precursor. The methods further include flowing a carbon-and-nitrogen-containing precursor into the second substrate processing region. The second substrate processing region is plasma-free during the flowing of the carbon-and-nitrogen-containing precursor. Flowing of the carbon-and-nitrogen-containing precursor occurs after flowing the halogen-containing precursor.
Embodiments of the invention include methods of etching metal from a substrate. The methods include transferring the substrate into the substrate processing region. The methods further include flowing a hydrogen-containing precursor into a substrate processing region while forming a plasma to treat a thin metal oxide layer formed on a metal layer. The methods further include flowing a halogen-containing precursor into the substrate processing region. The substrate processing region is plasma-free during the flowing of the halogen-containing precursor. Flowing the halogen-containing precursor occurs after flowing the hydrogen-containing precursor. The methods further include purging the substrate processing region with a relatively inert gas to remove the halogen-containing precursor from the substrate processing region. The methods further include flowing a carbon-and-nitrogen-containing precursor in to the substrate processing region. The substrate processing region is plasma-free during the flowing of the carbon-and-nitrogen-containing precursor and flowing of the carbon-and-nitrogen-containing precursor occurs after purging the substrate processing region. The methods further include removing the substrate from the substrate processing region.
Additional embodiments and features are set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the specification or may be learned by the practice of the embodiments. The features and advantages of the embodiments may be realized and attained by means of the instrumentalities, combinations, and methods described in the specification.



DESCRIPTION OF THE DRAWINGS
A further understanding of the nature and advantages of the embodiments may be realized by reference to the remaining portions of the specification and the drawings.
FIG. 1 is a flow chart of a cobalt etch process according to embodiments.
FIG. 2 is a flow chart of a cobalt etch process according to embodiments.
FIG. 3A shows a schematic cross-sectional view of a substrate processing chamber according to the disclosed technology.
FIG. 3B shows a schematic cross-sectional view of a portion of a substrate processing chamber according to the disclosed technology.
FIG. 3C shows a bottom plan view of a showerhead according to the disclosed technology.
FIG. 4 shows a top plan view of an exemplary substrate processing system according to the disclosed technology.



In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.
DETAILED DESCRIPTION
Methods are described herein for etching metal films which are difficult to volatize. The methods include exposing a metal film to a chlorine-containing precursor (e.g. Cl2). Chlorine is then removed from the substrate processing region. A carbon-and-nitrogen-containing precursor (e.g. TMEDA) is delivered to the substrate processing region to form volatile metal complexes which desorb from the surface of the metal film. The methods presented remove metal from the substrate while very slowly removing the other exposed materials. A thin metal oxide layer may be present on the surface of the metal layer, in which case a local plasma from hydrogen may be used to remove the oxygen or amorphize the near surface region, which has been found to increase the overall etch rate.
In order to better understand and appreciate the invention, reference is now made to FIG. 1 which is a flow chart of a cobalt etch process 100 according to embodiments. The cobalt film of this example has a thin native oxide layer on its surface due to atmospheric exposure. Cobalt may be in the form of a blanket layer on a substrate or cobalt may reside in discrete regions of a patterned substrate surface. In either case, the cobalt forms exposed surfaces of the surface of the substrate once the cobalt oxide layer is modified/removed. The substrate is delivered into a substrate processing region (operation 110).
A flow of hydrogen (H2) is introduced into the substrate processing region (operation 120). Other sources of hydrogen may be used to augment or replace the molecular hydrogen. In general, a hydrogen-containing precursor may be flowed into the substrate processing region and the hydrogen-containing precursor may be oxygen-free and/or carbon-free according to embodiments. A local plasma is formed, in operation 130, from the hydrogen-containing precursor in the substrate processing region to process the cobalt oxide layer. The local plasma treatment results in a faster subsequent cobalt etch rate in cobalt etch process 100, either by removing oxygen and exposing cobalt or otherwise transforming the cobalt oxide layer to promote the cobalt etch rate in operation 140. The substrate is removed, following cobalt etching operation 140, in operation 150 of cobalt etch process 100.
Reference is now made to FIG. 2 which is a flow chart of another cobalt etch process 200 according to embodiments. The cobalt film of this example has a cobalt oxide layer on top of cobalt. The substrate is delivered into a substrate processing region (operation 210). A flow of hydrogen (H2) is introduced into the substrate processing region (operation 220). As before, a hydrogen-containing precursor may generally be flowed into the substrate processing region and the hydrogen-containing precursor may be oxygen-free and/or carbon-free according to embodiments. In operation 225, a local plasma is formed from the hydrogen-containing precursor in the substrate processing region to process the cobalt oxide layer. The local plasma treatment results in a faster subsequent cobalt etch rate, possibly by removing oxygen and exposing cobalt or otherwise transforming/modifying the cobalt oxide layer to promote the cobalt etch rate. Cobalt may be exposed in operation 225 or during subsequent operations depending on the removal mechanism.
A flow of chlorine (Cl2) is introduced into a substrate processing region in operation 230. Other sources of chlorine may be used to augment or replace the chlorine. More generally, a chlorine-containing precursor may be flowed into the substrate processing region, such as chlorine (Cl2), xenon dichloride or boron trichloride. A halogen-containing precursor may also be used instead or to augment the chlorine-containing precursor as described shortly. Exposing the cobalt to chlorine may occur with plasma or without any plasma in the substrate processing region in embodiments. In other words, the substrate processing region may be plasma-free during operation 230 of cobalt etch process 200. The cobalt (or thin modified cobalt oxide layer initially) reacts with the chlorine to presumably form cobalt-chloride adsorbates on or near the surface of the substrate. The cobalt-chloride adsorbates facilitate the subsequent removal of cobalt from the substrate.
A carbon-and-nitrogen-containing precursor is flowed into the substrate processing region in operation 235 of cobalt etch process 200. The carbon-and-nitrogen-containing precursor may possess at least one carbon-nitrogen bond and the bond may be a single bond in embodiments. The carbon-and-nitrogen-containing precursor comprises at least two nitrogen atoms according to embodiments. The carbon-and-nitrogen-containing precursor may consist of carbon, nitrogen and hydrogen in embodiments. The carbon-and-nitrogen-containing precursor comprises at least two, three or four methyl groups according to embodiments. An exemplary carbon-and-nitrogen-containing precursor is tetramethylethylenediamine (aka TMEDA or C6H16N2). The carbon-and-nitrogen-containing precursor is flowed into the plasma region after the operation of flowing the chlorine-containing precursor in embodiments. Chlorine may be removed from the substrate processing region prior to operation 235 and the substrate processing region may be actively purged with a relatively inert gas between operations 230 and 235 to avoid having the carbon-and-nitrogen-containing precursor react with the halogen-containing precursor. The reaction between the carbon-and-nitrogen-containing precursor and the chlorine-containing precursor may produce undesirable deposition and accumulation on the substrate or processing system hardware in embodiments. The substrate is removed in operation 245 of cobalt etch process 200.
In general, a halogen-containing precursor may be used in place of the chlorine-containing precursor (e.g. Cl2) of cobalt etch process 200. The halogen-containing precursor may include at least one of chlorine or bromine in embodiments. The halogen-containing precursor may be a diatomic halogen, a homonuclear diatomic halogen or a heteronuclear diatomic halogen according to embodiments.
A reaction between the carbon-and-nitrogen-containing precursor and the halogen-containing precursor has been found to not only reduce the efficacy of the etch process, but also produces solid residue which can clog chamber features and impede flow rates. To avoid forming solid residue, the substrate processing region may be purged between the operations of flowing the halogen-containing precursor (operation 230) and flowing the carbon-and-nitrogen-containing precursor (operation 235) into the substrate processing region. Flowing the carbon-and-nitrogen-containing precursor 235 occurs after flowing the halogen-containing precursor 230 which occurs after the operation of flowing the hydrogen 220 (and igniting the hydrogen plasma 225) in embodiments. The operations may be repeated (in an “etch cycle” as referred to herein) in several ways to remove additional cobalt when desired. The substrate processing region may be purged with a relatively inert gas following operation 235, at which point operation 230 may be repeated to rechlorinate the cobalt surface. Operation 235 may then be repeated again with another optional purging operation between operations 230 and 235. A relatively inert gas may be, for example, helium and/or argon.
A different etch cycle has been found to be beneficial as well alone or in combination with the etch cycle just described. The substrate processing region may be purged following operation 235 and cobalt etch process 200 may repeat operations 220-235 to remove additional cobalt. Operation 220/225, 230 and 235 occur as an ordered series according to embodiments. Repeating operations 220-235 has been found to produce a more uniform cobalt surface in some cases. Cobalt etch process 100 may use this type of etch cycle by repeating operations 120/130 and operation 140 an integral number of times before removing the substrate from the substrate processing region in operation 150.
The term “pretreatment” will be used to describe operations 220 and 225 in their general form. The term “etch cycle” will be used to describe operation 230 (involving the halogen-containing precursor) followed by operation 235 (involving the carbon-and-nitrogen-containing precursor). The pretreatment has been found to increase the cobalt etch rate. Each etch cycle may remove between about 2 Å and about 8 Å or between about 3 Å and about 6 Å according to embodiments. Performing a pretreatment followed by multiple etch cycles (e.g. 30 or 60) has been found to remove cobalt at these appreciable etch rates. However, an improvement in etch rate smoothness has been found if the pretreatment is periodically repeated. The pretreatment is repeated every 2 to 25 etch cycles or every 5 to 15 etch cycles in embodiments. Periodically repeating the pretreatment appears to clear the surface of any residual reactants and increase the uniformity and activity of reaction sites. The improvement in etch uniformity has been observed for blanket substrate and also for patterned substrates where cobalt has been deposited within gaps in the pattern. In such gapfill applications, cobalt may need to be “recessed” to below the top of the gap. The pretreatment may be repeated 2 to 5 times and each pretreatment may be followed by 2 to 25 or 5 to 15 etch cycles. In this way, cobalt etch process 200 has been found to produce an even recess of gapfill cobalt.
The carbon-and-nitrogen-containing precursor may be TMEDA (C6H16N2) as in the example, but may be other precursors. In general, the carbon-and-hydrogen-containing precursor may include carbon and nitrogen and may consist only of carbon, nitrogen and hydrogen. The carbon-and-nitrogen-containing precursor may possess at least one carbon-nitrogen bond and the bond may be a single bond in embodiments. The carbon-and-nitrogen-containing precursor comprises at least two nitrogen atoms according to embodiments. The carbon-and-nitrogen-containing precursor may include a phenyl group in embodiments. For example, the carbon-and-nitrogen-containing precursor may include o-phenylenediamine, p-phenylenediamine and/or m-phenylenediamine according to embodiments. Chemically linear options are also possible, the carbon-and-nitrogen-containing precursor may be of the form R2—N—[CH2]m—N—R2, where m is 1, 2 or 3 and R is H, CH3, C2H5 or a higher order hydrocarbon.
Creating volatile reaction products from cobalt removes material during cobalt etch process 100 or cobalt etch process 200. The volatile reaction products are thought to include methyl cobalt complexes such as Co(CH3)4. Exposing cobalt first to chlorine (operation 230) and then to the carbon-and-nitrogen-containing precursor (operation 235) has been found to produce the production worthy etch rate of cobalt and presumably makes volatile reaction products which leave the surface by desorption. Cobalt chloride complexes have been found to be nonvolatile with or without plasma treatment. However, the formation of cobalt chloride complexes have been found to be a conducive intermediate state toward volatization and desorption.
In embodiments, the chlorine-containing precursor (e.g. Cl2) may be flowed into the substrate processing region at a flow rate of between about 3 sccm (standard cubic centimeters per minute) and about 50 sccm or between about 5 sccm and about 20 sccm in embodiments. The carbon-and-nitrogen-containing precursor may be flowed at a flow rate of between about 10 sccm and about 300 sccm or between about 20 sccm and about 200 sccm according to embodiments. The carbon-and-nitrogen-containing precursor may be a liquid prior to entering the substrate processing region, in which case a bubbler and carrier gas may be used to flow the precursor into the substrate processing region. The bubbler may heat the precursor above room temperature, for example to between about 25° C. and about 60° C., to increase the vapor pressure while the carrier gas is flowed through the liquid. The carrier gas may be relatively inert in comparison to the carbon-and-nitrogen-containing precursor. Helium may be used as the carrier gas. The carrier gas may be flowed at between about 1 slm (standard liters per minute) and about 5 slm according to embodiments. One of ordinary skill in the art would recognize that other gases and/or flows may be used depending on a number of factors including processing chamber configuration, substrate size, geometry and layout of features being etched.
The substrate processing region may be devoid of plasma or “plasma-free” during the cobalt etch operation 140, during the flow of the halogen-containing precursor (e.g. operation 230) and/or during the flow of the carbon-and-nitrogen-containing precursor (e.g. operation 235). The substrate processing region may be plasma-free during an etch cycle according to embodiments. In embodiments, a plasma-free substrate processing region means there is essentially no concentration of ionized species and free electrons within the substrate processing region.
In embodiments, the hydrogen-containing precursor (e.g. H2) may be flowed into the substrate processing region at a flow rate of between about 50 sccm and about 2,000 sccm or between about 100 sccm and about 1,000 sccm in embodiments. The method also includes applying energy to the hydrogen-containing precursor in the substrate processing region during operations 130 and 225 to form a hydrogen plasma. The plasma in the substrate processing region may be generated using a variety of techniques (e.g., radio frequency excitations, capacitively-coupled power and/or inductively coupled power). In an embodiment, the energy is applied using a capacitively-coupled plasma unit. The plasma power applied to the hydrogen-containing precursor may be between about 25 watts and about 1500 watts, between about 100 watts and about 1200 watts or between about 150 watts and about 700 watts according to embodiments. A sputtering component of the plasma may be included to help remove cobalt oxide which covers the cobalt to be etched. The plasma in the substrate processing region may be referred to herein as a local plasma.
During the operations of processing the cobalt oxide (e.g. operations 120-130 and 220), the operations of flowing the halogen-containing precursor (e.g. operation 230), and/or the operation of flowing the carbon-and-nitrogen-containing precursor (e.g. operation 235), the substrate may be maintained may be between about −30° C. and about 400° C. in general. In embodiments, the temperature of the substrate during the operations described may be greater than or about −30° C., greater than or about −10° C., greater than or about 10° C., or greater than or about 25° C. The substrate temperatures may be less than or about 400° C., less than or about 350° C., less than or about 250° C. in embodiments. The pressure in the substrate processing region may be about or below 20 Torr during each of the operations (e.g. operations 120-130, 220, 230 and/or 235), and may be about or below 15 Torr, 5 Torr or 3 Torr. For example, the pressure may be between about 10 mTorr and about 10 Torr.
Generally speaking, the cobalt is a “metal” and may be one of cobalt or nickel. Both cobalt and nickel have been found to etch using the methods described herein. The metal layer may consist of or consist essentially of cobalt and may consist of or consist essentially of nickel according to embodiments. The metal layer may consist of or consist essentially of a single element according to embodiments.
Additional process parameters are disclosed in the course of describing an exemplary processing chamber and system.
Exemplary Processing System
FIG. 3A shows a cross-sectional view of an exemplary substrate processing chamber 1001 with partitioned plasma generation regions within the processing chamber. During film etching, a process gas may be flowed into chamber plasma region 1015 through a gas inlet assembly 1105. A remote plasma system (RPS) 1002 may optionally be included in the system, and may process a first gas which then travels through gas inlet assembly 1105. The inlet assembly 1105 may include two or more distinct gas supply channels where the second channel (not shown) may bypass the RPS 1002, if included. Accordingly, in embodiments the precursor gases may be delivered to the processing chamber in an unexcited state. In another example, the first channel provided through the RPS may be used for the process gas and the second channel bypassing the RPS may be used for a treatment gas in embodiments. The process gas may be excited within the RPS 1002 prior to entering the chamber plasma region 1015. Accordingly, the chlorine-containing precursor as discussed above, for example, may pass through RPS 1002 or bypass the RPS unit in embodiments. Various other examples encompassed by this arrangement will be similarly understood.
A cooling plate 1003, faceplate 1017, ion suppressor 1023, showerhead 1025, and a substrate support 1065 (also known as a pedestal), having a substrate 1055 disposed thereon, are shown and may each be included according to embodiments. The pedestal 1065 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate. This configuration may allow the substrate 1055 temperature to be cooled or heated to maintain relatively low temperatures, such as between about −20° C. to about 200° C., or there between. The heat exchange fluid may comprise ethylene glycol and/or water. The wafer support platter of the pedestal 1065, which may comprise aluminum, ceramic, or a combination thereof, may also be resistively heated to achieve relatively high temperatures, such as from up to or about 100° C. to above or about 1100° C., using an embedded resistive heater element. The heating element may be formed within the pedestal as one or more loops, and an outer portion of the heater element may run adjacent to a perimeter of the support platter, while an inner portion runs on the path of a concentric circle having a smaller radius. The wiring to the heater element may pass through the stem of the pedestal 1065, which may be further configured to rotate.
The faceplate 1017 may be pyramidal, conical, or of another similar structure with a narrow top portion expanding to a wide bottom portion. The faceplate 1017 may additionally be flat as shown and include a plurality of through-channels used to distribute process gases. Plasma generating gases and/or plasma excited species, depending on use of the RPS 1002, may pass through a plurality of holes, shown in FIG. 3B, in faceplate 1017 for a more uniform delivery into the chamber plasma region 1015.
Exemplary configurations may include having the gas inlet assembly 1105 open into a gas supply region 1058 partitioned from the chamber plasma region 1015 by faceplate 1017 so that the gases/species flow through the holes in the faceplate 1017 into the chamber plasma region 1015. Structural and operational features may be selected to prevent significant backflow of plasma from the chamber plasma region 1015 back into the supply region 1058, gas inlet assembly 1105, and fluid supply system 1010. The structural features may include the selection of dimensions and cross-sectional geometries of the apertures in faceplate 1017 to deactivate back-streaming plasma. The operational features may include maintaining a pressure difference between the gas supply region 1058 and chamber plasma region 1015 that maintains a unidirectional flow of plasma through the showerhead 1025. The faceplate 1017, or a conductive top portion of the chamber, and showerhead 1025 are shown with an insulating ring 1020 located between the features, which allows an AC potential to be applied to the faceplate 1017 relative to showerhead 1025 and/or ion suppressor 1023. The insulating ring 1020 may be positioned between the faceplate 1017 and the showerhead 1025 and/or ion suppressor 1023 enabling a capacitively coupled plasma (CCP) to be formed in the first plasma region. A baffle (not shown) may additionally be located in the chamber plasma region 1015, or otherwise coupled with gas inlet assembly 1105, to affect the flow of fluid into the region through gas inlet assembly 1105.
The ion suppressor 1023 may comprise a plate or other geometry that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of chamber plasma region 1015 while allowing uncharged neutral or radical species to pass through the ion suppressor 1023 into an activated gas delivery region between the suppressor and the showerhead. In embodiments, the ion suppressor 1023 may comprise a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed.
The plurality of holes in the ion suppressor 1023 may be configured to control the passage of the activated gas, i.e., the ionic, radical, and/or neutral species, through the ion suppressor 1023. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor 1023 is reduced. The holes in the ion suppressor 1023 may include a tapered portion that faces chamber plasma region 1015, and a cylindrical portion that faces the showerhead 1025. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to the showerhead 1025. An adjustable electrical bias may also be applied to the ion suppressor 1023 as an additional means to control the flow of ionic species through the suppressor.
The ion suppression element 1023 may function to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Showerhead 1025 in combination with ion suppressor 1023 may allow a plasma present in chamber plasma region 1015 to avoid directly exciting gases in substrate processing region 1033, while still allowing excited species to travel from chamber plasma region 1015 into substrate processing region 1033. In this way, the chamber may be configured to prevent the plasma from contacting a substrate 1055 being etched. This may advantageously protect a variety of intricate structures and films patterned on the substrate, which may be damaged, dislocated, or otherwise warped if directly contacted by a generated plasma. Additionally, when plasma is allowed to contact the substrate or approach the substrate level, the rate at which oxide species etch may increase. Accordingly, if the exposed second material is oxide, this material may be further protected by maintaining the plasma remotely from the substrate.
The processing system may further include a power supply 1040 electrically coupled with the processing chamber to provide electric power to the faceplate 1017, ion suppressor 1023, showerhead 1025, and/or pedestal 1065 to generate a plasma in the chamber plasma region 1015 or processing region 1033. The power supply may be configured to deliver an adjustable amount of power to the chamber depending on the process performed. Such a configuration may allow for a tunable plasma to be used in the processes being performed. Unlike a remote plasma unit, which is often presented with on or off functionality, a tunable plasma may be configured to deliver a specific amount of power to chamber plasma region 1015. This in turn may allow development of particular plasma characteristics such that precursors may be dissociated in specific ways to enhance the etching profiles produced by these precursors.
A plasma may be ignited in chamber plasma region 1015 above showerhead 1025 and/or substrate processing region 1033 below showerhead 1025. A plasma may be present in chamber plasma region 1015 to produce plasma-excited hydrogen-containing precursors from an inflow of a hydrogen-containing precursor. A local plasma has also been found to work for the pretreatment and the hydrogen-containing precursor may be flowed into in substrate processing region 1033 and a local plasma may be formed to effect the pretreatment. The etch cycle may be performed in the same substrate processing region and the substrate processing region may be plasma-free during each operation of the etch cycle (for example during flowing of the halogen-containing precursor and the subsequent flowing of the carbon-and-nitrogen-containing precursor). An AC voltage typically in the radio frequency (RF) range may be applied between the conductive top portion of the processing chamber, such as faceplate 1017, and showerhead 1025 and/or ion suppressor 1023 to ignite a plasma in chamber plasma region 1015 during processes. An RF power supply may generate a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.
Plasma power can be of a variety of frequencies or a combination of multiple frequencies. In the exemplary processing system the plasma may be provided by RF power delivered to faceplate 1017 relative to ion suppressor 1023 and/or showerhead 1025. The RF frequency applied in the exemplary processing system may be low RF frequencies less than about 200 kHz, high RF frequencies between about 10 MHz and about 15 MHz, or microwave frequencies greater than or about 1 GHz in different embodiments. The plasma power may be capacitively-coupled (CCP) or inductively-coupled (ICP) into the remote plasma region.
Plasma power may also be simultaneously applied to both chamber plasma region 1015 and substrate processing region 1033 during etching processes described herein. The frequencies and powers above apply to both regions. Either region may be excited using either a capacitively-coupled plasma (CCP) or an inductively-coupled plasma (ICP).
Chamber plasma region 1015 (top plasma in figure) may be left at low or no power when a bottom plasma in the substrate processing region 1033 is turned on to, for example, cure a film or clean the interior surfaces bordering substrate processing region 1033. A plasma in substrate processing region 1033 may be ignited by applying an AC voltage between showerhead 1055 and the pedestal 1065 or bottom of the chamber. A cleaning gas may be introduced into substrate processing region 1033 while the plasma is present.
A fluid, such as a precursor, for example a chlorine-containing precursor, may be flowed into the processing region 1033 by embodiments of the showerhead described herein. Excited species derived from the process gas in chamber plasma region 1015 may travel through apertures in the ion suppressor 1023, and/or showerhead 1025 and react with an additional precursor flowing into the processing region 1033 from a separate portion of the showerhead. Alternatively, if all precursor species are being excited in chamber plasma region 1015, no additional precursors may be flowed through the separate portion of the showerhead. Little or no plasma may be present in the processing region 1033. Excited derivatives of the precursors may combine in the region above the substrate and, on occasion, on the substrate to etch structures or remove species on the substrate in disclosed applications.
Exciting the fluids in the chamber plasma region 1015 directly, or exciting the fluids in the RPS units 1002, may provide several benefits. The concentration of the excited species derived from the fluids may be increased within the processing region 1033 due to the plasma in the chamber plasma region 1015. This increase may result from the location of the plasma in the chamber plasma region 1015. The processing region 1033 may be located closer to the chamber plasma region 1015 than the remote plasma system (RPS) 1002, leaving less time for the excited species to leave excited states through collisions with other gas molecules, walls of the chamber, and surfaces of the showerhead.
The uniformity of the concentration of the excited species derived from the process gas may also be increased within the processing region 1033. This may result from the shape of the chamber plasma region 1015, which may be more similar to the shape of the processing region 1033. Excited species created in the RPS 1002 may travel greater distances to pass through apertures near the edges of the showerhead 1025 relative to species that pass through apertures near the center of the showerhead 1025. The greater distance may result in a reduced excitation of the excited species and, for example, may result in a slower growth rate near the edge of a substrate. Exciting the fluids in the chamber plasma region 1015 may mitigate this variation for the fluid flowed through RPS 1002, or alternatively bypassed around the RPS unit.
The processing gases may be excited in chamber plasma region 1015 and may be passed through the showerhead 1025 to the processing region 1033 in the excited state. While a plasma may be generated in the processing region 1033, a plasma may alternatively not be generated in the processing region. In one example, the only excitation of the processing gas or precursors may be from exciting the processing gases in chamber plasma region 1015 to react with one another in the processing region 1033. As previously discussed, this may be to protect the structures patterned on the substrate 1055.
In addition to the fluid precursors, there may be other gases introduced at varied times for varied purposes, including carrier gases to aid delivery. A treatment gas may be introduced to remove unwanted species from the chamber walls and/or the substrate. A treatment gas may be excited in a plasma and then used to reduce or remove residual content inside the chamber. In other embodiments the treatment gas may be used without a plasma. When the treatment gas includes water vapor, the delivery may be achieved using a mass flow meter (MFM), an injection valve, or by commercially available water vapor generators. The treatment gas may be introduced to the processing region 1033, either through the RPS unit or bypassing the RPS unit, and may further be excited in the first plasma region.
FIG. 3B shows a detailed view of the features affecting the processing gas distribution through faceplate 1017. As shown in FIG. 3A and FIG. 3B, faceplate 1017, cooling plate 1003, and gas inlet assembly 1105 intersect to define a gas supply region 1058 into which process gases may be delivered from gas inlet 1105. The gases may fill the gas supply region 1058 and flow to chamber plasma region 1015 through apertures 1059 in faceplate 1017. The apertures 1059 may be configured to direct flow in a substantially unidirectional manner such that process gases may flow into processing region 1033, but may be partially or fully prevented from backflow into the gas supply region 1058 after traversing the faceplate 1017.
The gas distribution assemblies such as showerhead 1025 for use in the processing chamber section 1001 may be referred to as dual channel showerheads (DCSH) and are additionally detailed in the embodiments described in FIG. 3A as well as FIG. 3C herein. The dual channel showerhead may provide for etching processes that allow for separation of etchants outside of the processing region 1033 to provide limited interaction with chamber components and each other prior to being delivered into the processing region.
The showerhead 1025 may comprise an upper plate 1014 and a lower plate 1016. The plates may be coupled with one another to define a volume 1018 between the plates. The coupling of the plates may be so as to provide first fluid channels 1019 through the upper and lower plates, and second fluid channels 1021 through the lower plate 1016. The formed channels may be configured to provide fluid access from the volume 1018 through the lower plate 1016 via second fluid channels 1021 alone, and the first fluid channels 1019 may be fluidly isolated from the volume 1018 between the plates and the second fluid channels 1021. The volume 1018 may be fluidly accessible through a side of the gas distribution assembly 1025. Although the exemplary chamber of FIG. 3A includes a dual-channel showerhead, it is understood that alternative distribution assemblies may be utilized that maintain first and second precursors fluidly isolated prior to the processing region 1033. For example, a perforated plate and tubes underneath the plate may be utilized, although other configurations may operate with reduced efficiency or not provide as uniform processing as the dual-channel showerhead as described.
In the embodiment shown, showerhead 1025 may distribute via first fluid channels 1019 process gases which contain plasma effluents upon excitation by a plasma in chamber plasma region 1015. In embodiments, the process gas introduced into the RPS 1002 and/or chamber plasma region 1015 may contain hydrogen. The process gas may also include a carrier gas such as helium, argon, nitrogen (N2), etc. Plasma effluents may include ionized or neutral derivatives of the process gas and may also be referred to herein as a radical-hydrogen precursor referring to the atomic constituent of the process gas introduced.
FIG. 3C is a bottom view of a showerhead 1025 for use with a processing chamber according to embodiments. Showerhead 1025 corresponds with the showerhead shown in FIG. 3A. Through-holes 1031, which show a view of first fluid channels 1019, may have a plurality of shapes and configurations to control and affect the flow of precursors through the showerhead 1025. Small holes 1027, which show a view of second fluid channels 1021, may be distributed substantially evenly over the surface of the showerhead, even amongst the through-holes 1031, which may help to provide more even mixing of the precursors as they exit the showerhead than other configurations.
Substrate processing region 1033 can be maintained at a variety of pressures during the flow of precursors, any carrier gases, and plasma effluents into substrate processing region 1033. The pressure may be maintained between about 0.1 mTorr and about 20 Torr or between about 10 mTorr and about 10 Torr in different embodiments.
Embodiments of the processing chambers may be incorporated into larger fabrication systems for producing integrated circuit chips. FIG. 4 shows one such processing system 1101 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (load lock chambers 1102) supply substrates of a variety of sizes that are received by robotic arms 1104 and placed into a low pressure holding area 1106 before being placed into one of the substrate processing chambers 1108a-f. A second robotic arm 1110 may be used to transport the substrate wafers from the holding area 1106 to the substrate processing chambers 1108a-f and back. Each substrate processing chamber 1108a-f, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.
The substrate processing chambers 1108a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric film on the substrate wafer. In one configuration, two pairs of the processing chamber, e.g., 1108c-d and 1108e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 1108a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 1108a-f, may be configured to etch a dielectric film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments.
In the preceding description, for the purposes of explanation, numerous details have been set forth to provide an understanding of various embodiments of the present invention. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.
As used herein “substrate” may be a support substrate with or without layers formed thereon. The patterned substrate may be an insulator or a semiconductor of a variety of doping concentrations and profiles and may, for example, be a semiconductor substrate of the type used in the manufacture of integrated circuits. Exposed “silicon” of the patterned substrate is predominantly Si but may include minority concentrations of other elemental constituents such as nitrogen, oxygen, hydrogen or carbon. Exposed “cobalt” of the patterned substrate is predominantly cobalt but may include minority concentrations of other elemental constituents such as oxygen, hydrogen and carbon. Of course, “exposed cobalt” may consist of only cobalt. Exposed “silicon nitride” of the patterned substrate is predominantly Si3N4 but may include minority concentrations of other elemental constituents such as oxygen, hydrogen and carbon. “Exposed silicon nitride” may consist of silicon and nitrogen. Exposed “silicon oxide” of the patterned substrate is predominantly SiO2 but may include minority concentrations of other elemental constituents such as nitrogen, hydrogen and carbon. In some embodiments, silicon oxide films etched using the methods disclosed herein consist of silicon and oxygen. “Cobalt oxide” is predominantly cobalt and oxygen but may include minority concentrations of other elemental constituents such as nitrogen, hydrogen and carbon. Cobalt oxide may consist of cobalt and oxygen.
The term “precursor” is used to refer to any process gas which takes part in a reaction to either remove material from or deposit material onto a surface. “Plasma effluents” describe gas exiting from the chamber plasma region and entering the substrate processing region. Plasma effluents are in an “excited state” wherein at least some of the gas molecules are in vibrationally-excited, dissociated and/or ionized states. A “radical precursor” is used to describe plasma effluents (a gas in an excited state which is exiting a plasma) which participate in a reaction to either remove material from or deposit material on a surface. “Radical-chlorine” are radical precursors which contain chlorine but may contain other elemental constituents. The phrase “inert gas” refers to any gas which does not form chemical bonds when etching or being incorporated into a film. Exemplary inert gases include noble gases but may include other gases so long as no chemical bonds are formed when (typically) trace amounts are trapped in a film.
The terms “gap” and “trench” are used throughout with no implication that the etched geometry has a large horizontal aspect ratio. Viewed from above the surface, trenches may appear circular, oval, polygonal, rectangular, or a variety of other shapes. A trench may be in the shape of a moat around an island of material. The term “via” is used to refer to a low aspect ratio trench (as viewed from above) which may or may not be filled with metal to form a vertical electrical connection. As used herein, a conformal etch process refers to a generally uniform removal of material on a surface in the same shape as the surface, i.e., the surface of the etched layer and the pre-etch surface are generally parallel. A person having ordinary skill in the art will recognize that the etched interface likely cannot be 100% conformal and thus the term “generally” allows for acceptable tolerances.
Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described to avoid unnecessarily obscuring the present invention. Accordingly, the above description should not be taken as limiting the scope of the invention.
Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.
As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a process” includes a plurality of such processes and reference to “the dielectric material” includes reference to one or more dielectric materials and equivalents thereof known to those skilled in the art, and so forth.
Also, the words “comprise,” “comprising,” “include,” “including,” and “includes” when used in this specification and in the following claims are intended to specify the presence of stated features, integers, components, or steps, but they do not preclude the presence or addition of one or more other features, integers, components, steps, acts, or groups.

## Claims

1. A method of etching metal from a substrate, the method comprising:
flowing a hydrogen-containing precursor into a first substrate processing region housing the substrate while forming a plasma in the first substrate processing region to treat a thin metal oxide layer formed on a metal layer;
flowing a halogen-containing precursor into a second substrate processing region, wherein the second substrate processing region is plasma-free during the flowing of the halogen-containing precursor;
flowing a carbon-and-nitrogen-containing precursor into the second substrate processing region, wherein the second substrate processing region is plasma-free during the flowing of the carbon-and-nitrogen-containing precursor and flowing of the carbon-and-nitrogen-containing precursor occurs after flowing the halogen-containing precursor; and
removing at least a portion of the metal layer from the substrate.

2. The method of claim 1 wherein the metal comprises at least one of cobalt and nickel.

3. The method of claim 1 wherein the metal consists of a single element.

4. The method of claim 1 wherein the hydrogen-containing precursor comprises H2.

5. The method of claim 1 wherein the carbon-and-nitrogen-containing precursor comprises tetramethylethylenediamine.

6. The method of claim 1 wherein the carbon-and-nitrogen-containing precursor comprises a carbon-nitrogen single bond.

7. The method of claim 1 wherein the carbon-and-nitrogen-containing precursor comprises at least two methyl groups.

8. The method of claim 1 wherein the halogen-containing precursor comprises at least one of chlorine or bromine.

9. The method of claim 1 wherein the halogen-containing precursor is a homonuclear diatomic halogen.

10. The method of claim 1 wherein the first substrate processing region and the second substrate processing region are the same substrate processing region.

11. The method of claim 1 wherein the carbon-and-nitrogen-containing precursor consists of carbon, nitrogen and hydrogen.

12. The method of claim 1 wherein a pressure within the substrate processing region is between about 0.01 Torr and about 10 Torr during one or more of flowing the hydrogen-containing precursor, flowing the halogen-containing precursor or flowing the carbon-and-nitrogen-containing precursor.

13. The method of claim 1 wherein forming the plasma to treat the thin metal oxide layer comprises applying a remote RF power between about 25 watts and about 1500 watts to the substrate processing region.

14. The method of claim 1 wherein forming the plasma to treat the thin metal oxide layer comprises applying a local capacitive plasma RF power a showerhead and the substrate.

15. The method of claim 1 wherein a processing temperature of the substrate is greater than or about −30° C. and less than or about 400° C. during the etching operation.

16. The method of claim 1, further comprising purging the second substrate processing region with an inert gas prior to flowing the carbon-and-nitrogen-containing precursor into the second substrate processing region to remove residual halogen-containing precursor from the second substrate processing region.

17. A method of etching metal from a substrate, the method comprising:
transferring the substrate into a substrate processing region;
flowing a hydrogen-containing precursor into the substrate processing region while forming a plasma to treat a thin metal oxide layer formed on a metal layer;
flowing a halogen-containing precursor into the substrate processing region, wherein the substrate processing region is plasma-free during the flowing of the halogen-containing precursor and wherein flowing the halogen-containing precursor occurs after flowing the hydrogen-containing precursor;
purging the substrate processing region with a relatively inert gas to remove the halogen-containing precursor from the substrate processing region;
flowing a carbon-and-nitrogen-containing precursor in to the substrate processing region, wherein the substrate processing region is plasma-free during the flowing of the carbon-and-nitrogen-containing precursor and flowing of the carbon-and-nitrogen-containing precursor occurs after purging the substrate processing region;
removing at least a portion of the metal layer from the substrate; and
removing the substrate from the substrate processing region.

18. The method of claim 17 further comprising purging the substrate processing region with a relatively inert gas to remove the carbon-and-nitrogen-containing precursor from the substrate processing region and then repeating the operations of flowing the hydrogen-containing precursor, flowing the halogen-containing precursor, purging to remove the halogen-containing precursor and flowing the carbon-and-nitrogen-containing precursor.