# Patent

## Title
Aluminum oxide selective etch

## Abstract

Methods of selectively etching aluminum oxide from the surface of a patterned substrate are described. The etch selectively removes aluminum oxide relative to other metal oxides and silicon-containing films such as silicon, polysilicon, silicon oxide, silicon germanium and/or silicon nitride. The methods include exposing aluminum oxide to plasma effluents formed in a remote plasma from a chlorine-containing precursor and a hydrocarbon. A remote plasma is used to excite the precursors and a local plasma is used to further excite the plasma effluents and accelerate ions toward the patterned substrate.

## Background
FIELD
This invention relates to selectively removing aluminum oxide.
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 of the first material. As a result of the diversity of materials, circuits and processes, etch processes have been developed that selectively remove one or more of a broad range 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 a variety of dielectrics relative to one another. However, relatively few dry-etch processes have been developed to selectively remove aluminum oxide with high selectivity.
SUMMARY
Methods of selectively etching aluminum oxide from the surface of a patterned substrate are described. The etch selectively removes aluminum oxide relative to other metal oxides and silicon-containing films such as silicon, polysilicon, silicon oxide, silicon germanium and/or silicon nitride. The methods include exposing aluminum oxide to plasma effluents formed in a remote plasma from a chlorine-containing precursor and a hydrocarbon. A remote plasma is used to excite the precursors and a local plasma is used to further excite the plasma effluents and accelerate ions toward the patterned substrate.
Embodiments of the invention include methods of etching aluminum oxide. The methods include placing a patterned substrate in a substrate processing region of a substrate processing chamber. The patterned substrate includes an exposed aluminum oxide portion. The methods further include flowing a chlorine-containing precursor into a remote plasma region fluidly coupled to the substrate processing region. The methods further include flowing a hydrogen-and-carbon-containing precursor into the remote plasma region. The methods further include forming a remote plasma in the remote plasma region from the chlorine-containing precursor and the hydrogen-and-carbon-containing precursor to produce plasma effluents. The methods further include flowing the plasma effluents into the substrate processing region through through-holes in a showerhead. The showerhead is disposed between the remote plasma region and the substrate processing chamber. The methods further include forming a bias plasma in the substrate processing region to further excite the plasma effluents. The methods further include etching the exposed aluminum oxide portion from the patterned substrate. A temperature of the patterned substrate is 130° C. or below during the operation of etching the exposed aluminum oxide portion.
Embodiments of the invention include methods of etching aluminum oxide. The methods include placing a patterned substrate in a substrate processing region of a substrate processing chamber. The patterned substrate includes an exposed aluminum oxide portion. The methods further include flowing radical-chlorine into the substrate processing region. The methods further include flowing radical-hydrogen-carbon into the substrate processing region. The methods further include forming a bias plasma in the substrate processing region to excite the radical-chlorine and the radical-hydrogen-carbon. The methods further include etching the exposed aluminum oxide portion from the patterned substrate. A temperature of the patterned substrate is below 130° C. during the operation of etching the exposed aluminum oxide portion.
Embodiments of the invention include methods of etching aluminum oxide. The methods include placing a patterned substrate in a substrate processing region of a substrate processing chamber. The patterned substrate includes an exposed aluminum oxide portion and a second exposed portion of silicon nitride, silicon or hafnium oxide. The methods further include combining molecular chlorine with methane in a remote plasma region fluidly coupled to the substrate processing region. The methods further include forming a remote plasma in the remote plasma region from the molecular chlorine and the methane to produce plasma effluents which flow into the substrate processing region through through-holes in a showerhead. The showerhead is disposed between the remote plasma region and the substrate processing chamber. The methods further include forming a bias plasma in the substrate processing region to further excite the plasma effluents. A pressure in the substrate processing region is between 0.01 Torr and 1.0 Torr during the operation of forming the bias plasma. The methods further include etching the exposed aluminum oxide portion from the patterned substrate. A temperature of the patterned substrate is below 130° C. during the operation of etching the aluminum oxide. The exposed aluminum oxide portion etches at greater than twenty times an etch rate of the second exposed portion.
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 disclosed embodiments. The features and advantages of the disclosed 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 disclosed embodiments may be realized by reference to the remaining portions of the specification and the drawings.
FIG. 1 is a flow chart of an aluminum oxide selective etch process according to embodiments.
FIGS. 2A, 2B, 2C and 2D are charts of etch rate dependence on process parameters according to disclosed embodiments.
FIG. 3A shows a schematic cross-sectional view of a substrate processing chamber according to embodiments.
FIG. 3B shows a schematic cross-sectional view of a portion of a substrate processing chamber according to embodiments.
FIG. 3C shows a bottom view of a showerhead according to embodiments.
FIG. 4 shows a top view of an exemplary substrate processing system according to embodiments.



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 of selectively etching aluminum oxide from the surface of a patterned substrate are described. The etch selectively removes aluminum oxide relative to other metal oxides and silicon-containing films such as silicon, polysilicon, silicon oxide, silicon germanium and/or silicon nitride. The methods include exposing aluminum oxide to plasma effluents formed in a remote plasma from a chlorine-containing precursor and a hydrocarbon. A remote plasma is used to excite the precursors and a local plasma is used to further excite the plasma effluents and accelerate ions toward the patterned substrate. The selective etch process may remove aluminum oxide at significant etch rates even at room temperature and below.
In order to better understand and appreciate the invention, reference is now made to FIG. 1 which is a flow chart of an aluminum oxide selective etch process 101 according to embodiments. The aluminum oxide may have a variety of stoichiometries which may be determined by the method of forming the aluminum oxide. Prior to the first etch operation, aluminum oxide is formed on a patterned substrate. The aluminum oxide forms exposed portions of the patterned substrate. The substrate is placed in a substrate processing region (operation 110).
A flow of molecular chlorine (Cl2) is introduced into a remote plasma region separate from the substrate processing region during operation 120. Methane is also flowed into the remote plasma region and combined with the molecular chlorine (operation 120). Other sources of chlorine may be used to augment or replace the molecular chlorine. In general, a chlorine-containing precursor may be flowed into the remote plasma region in embodiments. The chlorine-containing precursor may include one or more of atomic chlorine, molecular chlorine (Cl2), hydrogen chloride (HCl), or boron trichloride (BCl3) in embodiments. The chlorine-containing precursor may be a boron-and-chlorine-containing precursor according to embodiments, such as boron trichloride (BCl3), BCl(CH3)2 or BCl2(CH3). The chlorine-containing precursor may be a carbon-and-chlorine-containing precursor according to embodiments, such as BCl(CH3)2, BCl2(CH3) or CCl4. The chlorine-containing precursor may be devoid of carbon and/or boron in embodiments. The chlorine-containing precursor may be devoid of fluorine according to embodiments.
Generally speaking, a hydrocarbon may be used to augment or replace the methane of etch process 101. The hydrocarbon may be a hydrogen-and-carbon-containing precursor which may contain elements other than hydrogen and carbon in embodiments. The hydrogen-and-carbon-containing precursor may be halogen-free, chlorine-free or fluorine-free in embodiments. According to embodiments, the hydrogen-and-carbon-containing precursor may consist only of hydrogen and carbon. The hydrogen-and-carbon-containing precursor may be one of methane, ethane, propane or a higher order saturated alkane. The radical-hydrogen-carbon is the portion of the plasma effluents produced from the excitation of the hydrogen-and-carbon-containing precursor. The radical-hydrogen-carbon may be halogen-free, chlorine-free or fluorine-free according to embodiments.
Including fluorine in the chlorine-containing precursor or the hydrogen-and-carbon-containing precursor may form Al—F complexes on the patterned substrate. Al—F complexes may not be volatile and so may stay of the surface of the patterned substrate and inhibit aluminum oxide selective etch process 101. Al—F complexes are also thought to be energetically very favorable and so will likely form with high reaction probability.
The separate plasma region may be referred to as a remote plasma region herein and may be within a distinct module from the substrate processing chamber or a compartment within the substrate processing chamber. The separate plasma region may is fluidly coupled to the substrate processing region by through-holes in a showerhead disposed between the two regions. The hardware just described may also be used in all processes discussed herein.
The plasma effluents formed in the remote plasma region are then flowed into the substrate processing region (operation 130) through the through-holes the showerhead separating the remote plasma region and the substrate processing region. A local plasma power is applied to the substrate processing region in operation 140 and aluminum oxide on the substrate is selectively etched (operation 150) such that aluminum oxide may be removed more rapidly than a variety of other materials in embodiments. The reactive chemical species and any process effluents are removed from the substrate processing region and then the substrate is removed from the substrate processing region (operation 160).
The etch processes disclosed herein remove aluminum oxide without relying on high substrate temperatures. The presence of the hydrogen-and-carbon-containing precursor and the chlorine-containing precursor has been found to remove the aluminum oxide selectively when the substrate temperature is below 130° C., below 100° C., below 70° C., below 40° C. or even below 30° C. according to embodiments. The etch rate of aluminum oxide selective etch process 101 at 20° C. was observed to only be 30% less than the etch rate at 90° C. Aluminum oxide selective etch process 101 is a non-thermal process according to embodiments. The carbon may be weakening the Al—O bond in the aluminum oxide, allowing the chlorine to bond with aluminum to form volatile Al—Cl complexes. The simultaneous availability of the carbon and the chlorine may result in an aluminum oxide etch rate greater than 50 Å/min, greater than 70 Å/min or greater than 90 Å/min in embodiments for a low temperature substrate at about 90° C. or less. The aluminum oxide portions may be in the form of a conformal aluminum oxide layer prior to aluminum oxide selective etch process 101 in embodiments. The conformal aluminum oxide layer may be functional and not simply a byproduct of exposing aluminum to atmosphere in embodiments. As such, the thickness of the conformal aluminum oxide layer may be greater than 100 Å, greater than 200 Å or greater than 400 Å according to embodiments.
The processes disclosed herein display etch selectivities of aluminum oxide relative to a variety of other materials even at the low patterned substrate temperatures. The etch selectivity of aluminum oxide relative to silicon (including single crystal, polysilicon or amorphous silicon) may be greater than or about 10:1, greater than or about 15:1, greater than or about 20:1 or greater than or about 25:1 in embodiments. The etch selectivity of aluminum oxide relative to silicon nitride may be greater than or about 10:1, greater than or about 15:1, greater than or about 20:1 or greater than or about 25:1 in embodiments. The etch selectivity of aluminum oxide relative to select metal oxides (e.g. hafnium oxide) may be greater than or about 15:1, greater than or about 20:1, greater than or about 25:1 or greater than or about 40:1 in embodiments. High etch selectivities of aluminum oxide relative to these materials are helpful in enabling new process flows which may include forming aluminum oxide spacers or other novel features. The achievement of high etch selectivities at low substrate temperatures enables the thermal budget to be allocated elsewhere in the semiconductor manufacturing process flow.
In embodiments, the chlorine-containing precursor (e.g. Cl2) is supplied at a flow rate of between 5 sccm and 500 sccm, between 10 sccm and 300 sccm, between 25 sccm and 200 sccm, between 50 sccm and 150 sccm or between 75 sccm and 125 sccm. The hydrogen-and-carbon-containing precursor (e.g. CH4) is supplied at a flow rate of between 1 sccm and 200 sccm, between 2 sccm and 100 sccm, between 5 sccm and 75 sccm, between 10 sccm and 50 sccm or between 20 sccm and 40 sccm according to embodiments. The hydrogen-and-carbon-containing precursor (e.g. CH4) is supplied at a flow rate (or partial pressure) of between 1% and 100%, between 5% and 75%, between 10% and 50%, or between 20% and 40% of the chlorine-containing precursor flow rate (or partial pressure) in embodiments. Too low or too high a hydrogen-and-carbon-containing precursor flow rate/partial pressure results in an undesirably low etch rate of the aluminum oxide as discussed in more detail shortly. However, the latitude in choosing the flow rate ratio (known as the process window) is high and a large process window is desirable for manufacturing processes such as these.
The method also includes applying energy to the combination of the hydrogen-and-carbon-containing precursor and the chlorine-containing precursor in the remote plasma region to generate the plasma effluents. The remote plasma may be generated using known techniques (e.g., radio frequency excitations, capacitively-coupled power, inductively-coupled power). In an embodiment, the remote plasma power is applied capacitively. The remote plasma power may be between about 100 watts and about 3000 watts, between about 200 watts and about 2000 watts, between about 300 watts and about 1000 watts in embodiments.
A low-intensity plasma is also applied in the substrate processing region to create a low ion density and direct the ions toward the substrate to remove the aluminum oxide. A plasma in the substrate processing region may also be referred to as a bias plasma because ions are accelerated towards the substrate to assist the process. The bias plasma in the substrate processing region may be applied capacitively, in embodiments. The bias plasma may be applied concurrently with the remote plasma according to embodiments. The bias plasma may be applied with a bias power which is between 10% and 100% of the remote plasma power, between 20% and 90% of the remote plasma power or between 25% and 70% of the remote plasma power in embodiments. In embodiments, the bias power may be between 50 watts and 1500 watts, between 100 watts and 1000 watts or between 150 watts and 500 watts according to embodiments.
FIG. 2A is a chart of aluminum oxide etch rate dependence on methane flow rate into the remote plasma region during aluminum oxide selective etch process 101. The etch rate is immeasurable if methane is not included as indicated by the etch rate at the extreme left of the figure. The etch rate increases monotonically up to a point and then is reduced possibly due to the formation of polymers on the exposed aluminum oxide portions of the patterned substrate. The rate of formation of polymers on the surface of the patterned substrate may be removed (and the process may proceed) but only when the hydrogen-and-carbon-containing precursor is flowed or present in specific ranges relative the chlorine-containing precursor as indicated previously.
FIG. 2B is a chart of aluminum oxide etch rate dependence on pressure in the substrate processing region during aluminum oxide selective etch process 101. The etch rate reduces as the process pressure is increased across the approximate range from 0.1 Torr to 10 Torr. This dependence indicates that the process depends on a large mean free path and the removal mechanism may be activated by impingement energy of the etchants activated, lastly, in the bias plasma. Lower process pressures are preferred for the aluminum oxide etch processes described herein. During aluminum oxide selective etch process 101, the pressure within the substrate processing region may be below 10 Torr, below 3 Torr, below 2 Torr, or below 1 Torr according to embodiments. The pressure may be between 0.01 Torr and 1.0 Torr, or between 0.02 Torr and 0.5 Torr or preferably between 0.05 Torr and 0.2 Torr in embodiments.
FIGS. 2C and 2D are charts of aluminum oxide etch rate dependence on plasma power in the remote plasma region and in the substrate processing region during aluminum oxide selective etch process 101, respectively. While varying the remote plasma power for FIG. 2C, the bias plasma power was maintained at 180 watts. While varying the bias plasma power for FIG. 2D, the remote plasma power was maintained at 300 watts. Both values were selected to achieve at least 80% of the maximum aluminum oxide etch rate shown in the FIGS. 2C and 2D. Inferring from FIGS. 2C-2D, both the remote plasma power and the bias plasma power are necessary (must be non-zero) to enable aluminum oxide selective etch process 101 to proceed. The remote plasma power saturates the aluminum oxide etch rate after about 300 watts and the bias plasma power exhibits shows a second-order component indicating an accelerating influence of the aluminum oxide etch rate with bias plasma power.
The etch rate may increase using etch-purge-etch and etch-purge-etch cycles. Therefore, the etching operations of all processes may have a pause in the flow and/or concentration of precursors in the remote plasma and the substrate processing region during the processes disclosed and claimed herein. The remote plasma region and/or the substrate processing region may be actively purged using a gas which displays essentially no chemical reactivity to the exposed materials on the patterned substrate. After purging the regions the flows of precursors may be resumed to restart the removal of aluminum oxide from the patterned substrate at a rejuvenated or renewed etch rate (which may be the same or similar to the initial etch rate of the etch process).
The aluminum oxide portions etched herein may contain aluminum and oxygen (and not just any specific example of stoichiometric aluminum oxide). The remote plasma etch processes may remove aluminum oxide which includes an atomic concentration of about 20% or more aluminum and about 60% or more oxygen in embodiments. The aluminum oxide may consist essentially of aluminum and oxygen, allowing for small dopant concentrations and other undesirable or desirable minority additives, in embodiments. Aluminum oxide may have roughly an atomic ratio 2:3 (Al:O). The aluminum oxide may contain between 30% and 50% aluminum and may contain between 50% and 70% oxygen in embodiments.
Advantages of the processes described herein relate to tuning the anisotropy of aluminum oxide selective etch 101. Aluminum oxide selective etch 101 may be conformal with some process parameter combinations (e.g. higher pressure and/or lower bias power/voltage) or directional (e.g. with lower pressures and/or higher bias power/voltage). This flexibility is enabled because aluminum oxide selective etch 101 does not rely on a traditionally high bias power to accelerate etchants towards the substrate. The anisotropic etch process disclosed herein may open the door to new process sequences which use aluminum oxide as a spacer material. Anisotropic/directional etch processes can remove material from the top of features and from the bottom of trenches while leaving sidewall material behind. In contrast, a conformal etch process refers to a generally uniform removal rate of material from a patterned surface regardless of the shape of the surface. In a conformal etch process the aluminum oxide on the top, the bottom and on the sidewalls may all be removed according to embodiments. The surface of the layer before and after the etch process are generally parallel. A person having ordinary skill in the art will recognize that the etch process likely cannot be 100% conformal and thus the term “generally” allows for acceptable tolerances. A conformal etch may be interchangeably referred to as an isotropic etch. Generally speaking, increasing pressure in the substrate processing region will increase conformality and increasing bias plasma power as a percentage of remote plasma power will increase anisotropy of aluminum oxide selective etch process 101.
In each remote plasma or local plasma described herein, the flows of the precursors into the remote plasma region may further include one or more relatively inert gases such as He, N2, Ar. The inert gas can be used to improve plasma stability, ease plasma initiation, and improve process uniformity. Argon is helpful, as an additive, to promote the formation of a stable plasma. Process uniformity is generally increased when helium is included. These additives are present in embodiments throughout this specification. Flow rates and ratios of the different gases may be used to control etch rates and etch selectivity.
In embodiments, an ion suppressor as described in the exemplary equipment section may be used to provide radical and/or neutral species for selectively etching substrates. The ion suppressor may also be referred to as an ion suppression element. In embodiments, for example, the ion suppressor is used to filter chlorine-containing plasma effluents and hydrogen-and-carbon-containing plasma effluents to selectively etch aluminum oxide. The ion suppressor may be included in each exemplary process described herein. Using the plasma effluents, an etch rate selectivity of aluminum oxide to a wide variety of materials may be achieved.
The ion suppressor may be used to provide a reactive gas having a higher concentration of radicals than ions. The ion suppressor functions to dramatically reduce or substantially eliminate ionically charged species traveling from the plasma generation region to the substrate. The electron temperature may be measured using a Langmuir probe in the substrate processing region during excitation of a plasma in the remote plasma region on the other side of the ion suppressor. In embodiments, the electron temperature may be less than 0.5 eV, less than 0.45 eV, less than 0.4 eV, or less than 0.35 eV. These extremely low values for the electron temperature are enabled by the presence of the showerhead and/or the ion suppressor positioned between the substrate processing region and the remote plasma region. Uncharged neutral and radical species may pass through the openings in the ion suppressor to react at the substrate. Because most of the charged particles of a plasma are filtered or removed by the ion suppressor, the substrate is not necessarily biased during the etch process. Such a process using radicals and other neutral species can reduce plasma damage compared to conventional plasma etch processes that include sputtering and bombardment. The ion suppressor helps control the concentration of ionic species in the reaction region at a level that assists the process. Embodiments of the present invention are also advantageous over conventional wet etch processes where surface tension of liquids can cause bending and peeling of small features.
FIG. 3A shows a cross-sectional view of an exemplary substrate processing chamber 1001 with a partitioned plasma generation region within the processing chamber. During film etching, a process gas may be flowed into chamber plasma region 1015 through a gas inlet assembly 1005. 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 1005. The process gas may be excited within RPS 1002 prior to entering 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.
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. 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 −20° C. to 200° C. Pedestal 1065 may also be resistively heated to relatively high temperatures, such as between 100° C. and 1100° C., using an embedded heater element.
Exemplary configurations may include having the gas inlet assembly 1005 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 1005, 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.
The plurality of holes in the ion suppressor 1023 may be configured to control the passage of the activated gas: 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. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with the substrate.
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 power may be between about 10 watts and about 5000 watts, between about 100 watts and about 2000 watts, between about 200 watts and about 1500 watts, or between about 200 watts and about 1000 watts in embodiments. 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 embodiments. The plasma power may be capacitively-coupled (CCP) or inductively-coupled (ICP) into the remote plasma region.
A precursor, for example a chlorine-containing precursor, may be flowed into substrate 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 substrate 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. A small bias plasma may be present in substrate processing region 1033 during the remote plasma etch process. Excited derivatives of the precursors may combine in the region above the substrate and/or on the substrate to etch structures or remove species from the substrate.
The processing gases may be excited in chamber plasma region 1015 and may be passed through the showerhead 1025 to substrate processing region 1033 in the excited state. While a plasma may be generated in substrate 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 substrate processing region 1033. As previously discussed, this may be to protect the structures patterned on substrate 1055.
FIG. 3B shows a detailed view of the features affecting the processing gas distribution through 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 system of FIGS. 3A-3C 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 substrate 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 RPS 1002 and/or chamber plasma region 1015 may contain chlorine, e.g., Cl2 or BCl3. 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-chlorine 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 in 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.
The chamber plasma region 1015 or a region in an RPS may be referred to as a remote plasma region. In embodiments, the radical precursor, e.g., a radical-chlorine precursor, is created in the remote plasma region and travels into the substrate processing region where it may or may not combine with additional precursors. In embodiments, the additional precursors are excited only by the radical-chlorine precursor. Plasma power may essentially be applied only to the remote plasma region in embodiments to ensure that the radical-chlorine precursor provides the dominant excitation.
Combined flow rates of precursors into the chamber may account for 0.05% to about 20% by volume of the overall gas mixture; the remainder being carrier gases. The chlorine-containing precursor may be flowed into the remote plasma region, but the plasma effluents may have the same volumetric flow ratio in embodiments. In the case of the chlorine-containing precursor, a purge or carrier gas may be first initiated into the remote plasma region before the chlorine-containing gas to stabilize the pressure within the remote plasma region. 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.
Embodiments of the dry etch systems may be incorporated into larger fabrication systems for producing integrated circuit chips. FIG. 4 shows one such processing system (mainframe) 1101 of deposition, etching, baking, and curing chambers in 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 be configured for depositing, annealing, curing and/or etching a film on the substrate wafer. In one configuration, all three pairs of chambers, e.g., 1108a-f, may be configured to etch a film on the substrate, for example, chambers 1108a-d may be used to etch the gapfill silicon oxide to create space for the airgap while chambers 1108e-f may be used to etch the polysilicon.
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” or “polysilicon” of the patterned substrate is predominantly Si but may include minority concentrations of other elemental constituents such as nitrogen, oxygen, hydrogen and carbon. Exposed “silicon” or “polysilicon” may consist of or consist essentially of silicon. Exposed “silicon nitride” of the patterned substrate is predominantly silicon and nitrogen but may include minority concentrations of other elemental constituents such as oxygen, hydrogen and carbon. “Exposed silicon nitride” may consist essentially of or consist of silicon and nitrogen. Exposed “silicon oxide” of the patterned substrate is predominantly SiO2 but may include minority concentrations of other elemental constituents (e.g. nitrogen, hydrogen, carbon). In some embodiments, silicon oxide films etched using the methods disclosed herein consist essentially of silicon and oxygen. “Aluminum oxide” is predominantly aluminum and oxygen but may include minority concentrations of other elemental constituents (e.g. nitrogen, hydrogen, carbon). Aluminum oxide may consist essentially of aluminum and oxygen. “Aluminum” is predominantly aluminum but may include minority concentrations of other elemental constituents (e.g. nitrogen, hydrogen, oxygen, carbon). Aluminum oxide may consist essentially of aluminum. Analogous definitions will be understood for other metal-containing materials such as hafnium oxide.
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. “Radical-hydrogen-carbon” are radical precursors which contain hydrogen and carbon 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. 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 disclosed 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 aluminum oxide, the method comprising:
placing a patterned substrate in a substrate processing region of a substrate processing chamber, wherein the patterned substrate comprises an exposed aluminum oxide portion;
flowing a chlorine-containing precursor into a remote plasma region fluidly coupled to the substrate processing region;
flowing a hydrogen-and-carbon-containing precursor into the remote plasma region;
forming a remote plasma in the remote plasma region from the chlorine-containing precursor and the hydrogen-and-carbon-containing precursor to produce plasma effluents;
flowing the plasma effluents into the substrate processing region through through-holes in a showerhead, wherein the showerhead is disposed between the remote plasma region and the substrate processing chamber;
forming a bias plasma in the substrate processing region to further excite the plasma effluents; and
etching the exposed aluminum oxide portion from the patterned substrate, wherein a temperature of the patterned substrate is below 130° C. during the operation of etching the exposed aluminum oxide portion.

2. The method of claim 1 wherein the chlorine-containing precursor comprises one or more of atomic chlorine, molecular chlorine (Cl2), hydrogen chloride (HCl), or boron trichloride (BCl3).

3. The method of claim 1 wherein the chlorine-containing precursor is devoid of carbon.

4. The method of claim 1 wherein the hydrogen-and-carbon-containing precursor is an alkane.

5. The method of claim 1 wherein a bias plasma power of the bias plasma is between 25% and 70% of a remote plasma power of the remote plasma.

6. The method of claim 1 wherein the hydrogen-and-carbon-containing precursor is chlorine-free.

7. The method of claim 1 further comprising purging reactants from the substrate processing region and reintroducing the reactants to the substrate processing region to etch the exposed aluminum oxide portion again, wherein the etch rate of the exposed aluminum oxide portion is restored to previous levels.

8. The method of claim 1 wherein a pressure in the substrate processing region is between 0.01 Torr and 1.0 Torr during the operation of etching the exposed aluminum oxide portion.

9. The method of claim 1 wherein the hydrogen-and-carbon-containing precursor is fluorine-free.

10. A method of etching aluminum oxide, the method comprising:
placing a patterned substrate in a substrate processing region of a substrate processing chamber, wherein the patterned substrate comprises an exposed aluminum oxide portion;
flowing radical-chlorine into the substrate processing region;
flowing radical-hydrogen-carbon into the substrate processing region;
forming a bias plasma in the substrate processing region to excite the radical-chlorine and the radical-hydrogen-carbon; and
etching the exposed aluminum oxide portion from the patterned substrate, wherein a temperature of the patterned substrate is below 130° C. during the operation of etching the exposed aluminum oxide portion.

11. The method of claim 10 wherein the radical-hydrogen-carbon is halogen-free.

12. The method of claim 10 wherein the operation of etching the exposed aluminum oxide portion is an isotropic etch.

13. The method of claim 10 wherein the operation of etching the exposed aluminum oxide portion is an anisotropic etch.

14. A method of etching aluminum oxide, the method comprising:
placing a patterned substrate in a substrate processing region of a substrate processing chamber, wherein the patterned substrate comprises an exposed aluminum oxide portion and a second exposed portion of silicon nitride, silicon or hafnium oxide;
combining molecular chlorine with methane in a remote plasma region fluidly coupled to the substrate processing region;
forming a remote plasma in the remote plasma region from the molecular chlorine and the methane to produce plasma effluents which flow into the substrate processing region through through-holes in a showerhead, wherein the showerhead is disposed between the remote plasma region and the substrate processing chamber;
forming a bias plasma in the substrate processing region to further excite the plasma effluents, wherein a pressure in the substrate processing region is between 0.01 Torr and 1.0 Torr during the operation of forming the bias plasma; and
etching the exposed aluminum oxide portion from the patterned substrate, wherein a temperature of the patterned substrate is below 130° C. during the operation of etching the aluminum oxide, and wherein the exposed aluminum oxide portion etches at greater than twenty times an etch rate of the second exposed portion.

15. The method of claim 14 wherein the pressure in the substrate processing region is between 0.05 Torr and 0.2 Torr during the operation of forming the bias plasma.