US20180102259A1

US20180102259A1 - Cobalt-containing material removal

Info

Publication number: US20180102259A1
Application number: US15/332,849
Authority: US
Inventors: Xikun Wang; Zhenjiang Cui; Soonam Park; Nitin K. Ingle
Original assignee: Applied Materials Inc
Current assignee: Applied Materials Inc
Priority date: 2016-10-10
Filing date: 2016-10-24
Publication date: 2018-04-12
Anticipated expiration: 2036-10-24
Also published as: US9947549B1

Abstract

Methods are described herein for etching cobalt films which are difficult to volatize. The methods include exposing a cobalt film to a bromine or chlorine-containing precursor with a concurrent local plasma which applies a bias to the impinging etchants. Cobalt halide is formed on the surface at the same time an amorphized cobalt layer is formed near the surface. A carbon-and-nitrogen-containing precursor is later delivered to the substrate processing region to form volatile cobalt complexes which desorb from the surface of the cobalt film. Cobalt may be selectively removed. The concurrent production of cobalt halide and amorphized regions was found to markedly increase the overall etch rate and markedly improve surface smoothness upon exposure to the carbon-and-nitrogen-containing precursor. All the recited steps may now be performed in the same substrate processing chamber.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 62/406,368, filed Oct. 10, 2016 entitled “COBALT-CONTAINING MATERIAL REMOVAL”. The disclosure of 62/406,368 is hereby incorporated by reference in its entirety for all purposes.

FIELD

Embodiments disclosed herein relate to gas-phase etching cobalt-containing materials.

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 yet quickly remove metals which have limited or no previously known chemically volatile pathways.

SUMMARY

Methods are described herein for etching cobalt films which are difficult to volatize. The methods include exposing a cobalt film to a chlorine-containing precursor (e.g. Cl₂) with a concurrent local plasma which applies a bias to the impinging etchants. Cobalt chloride (e.g. CoCl₂) is formed on the surface at the same time an amorphized cobalt layer is formed near the surface. 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 cobalt complexes which desorb from the surface of the cobalt film. The methods presented remove cobalt while retaining the other exposed materials. The concurrent production of cobalt chloride and amorphized regions was found to markedly increase the overall etch rate as well as to markedly improve surface smoothness upon exposure to TMEDA. A thin cobalt oxide layer is typically present on the surface of the metal layer, in which case a local hydrogen plasma may be used to reduce or remove the cobalt oxide. All the recited steps may now be performed in the same substrate processing chamber.
Embodiments disclosed herein include methods of etching cobalt and cobalt oxide. The methods include transferring a substrate into a substrate processing region. The substrate includes cobalt and a thin cobalt oxide layer thereon. The methods further include removing the thin cobalt oxide layer by flowing a hydrogen-containing precursor into the substrate processing region while forming a local plasma from the hydrogen-containing precursor. The methods further include forming cobalt chloride and amorphizing a portion of the cobalt by flowing a chlorine-containing precursor into the substrate processing region while forming a plasma from the chlorine-containing precursor to form chlorine-containing plasma effluents. Forming cobalt chloride and amorphizing the portion of the cobalt further comprises accelerating the chlorine-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate. Forming the cobalt chloride occurs after reducing or removing the thin cobalt oxide layer. The methods further include purging the substrate processing region with an inert gas to remove the halogen-containing precursor from the substrate processing region. The methods further include removing the cobalt from the substrate by 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 include transferring the substrate out of the substrate processing region.
The substrate may be maintained at a same substrate temperature during the removing the thin cobalt layer and removing the cobalt. The substrate may remain inside the substrate processing throughout the method.
Embodiments disclosed herein include methods of etching cobalt from a substrate. The methods include placing the substrate into a first substrate processing region. The substrate includes cobalt and an overlying cobalt oxide. The methods further include removing the cobalt oxide and exposing the cobalt by flowing a hydrogen-containing precursor into a first substrate processing region housing the substrate while forming a hydrogen plasma in the substrate processing region. The methods further include placing the substrate into a second substrate processing region. The methods further include forming cobalt halide and amorphizing a portion of the cobalt by flowing a halogen-containing precursor into the second substrate processing region while forming a local plasma from the halogen-containing precursor to form halogen-containing plasma effluents. Forming the cobalt halide and amorphizing the portion of the cobalt further comprises accelerating the halogen-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate. 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 and flowing of the carbon-and-nitrogen-containing precursor occurs after flowing the halogen-containing precursor. The methods further include removing cobalt from the substrate. The methods further include removing the substrate from the second substrate processing region.
The cobalt may consist only of cobalt. The hydrogen-containing precursor may include H₂. The carbon-and-nitrogen-containing precursor may include tetramethylethylenediamine (TMEDA). The carbon-and-nitrogen-containing precursor may include a carbon-nitrogen single bond. The carbon-and-nitrogen-containing precursor may include at least two methyl groups. The halogen-containing precursor may include at least one of chlorine or bromine. The halogen-containing precursor may be a homonuclear diatomic halogen. The first substrate processing region and the second substrate processing region may be the same substrate processing region. The first substrate processing region and the second substrate processing region may be the different substrate processing regions in separate substrate processing chambers. The carbon-and-nitrogen-containing precursor may consist only of carbon, nitrogen and hydrogen. A pressure within the substrate processing region may be 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. The cobalt halide may be one of cobalt chloride or cobalt bromide. The plasma to treat the thin metal oxide layer may include applying a local capacitive plasma RF power between a showerhead and the substrate. A processing temperature of the substrate may be greater than 80° C. during the forming the cobalt halide and amorphizing the portion of the cobalt.
Embodiments disclosed herein include methods of removing cobalt from a substrate. The methods include placing the substrate into a substrate processing region. The substrate includes exposed cobalt. The methods further include forming cobalt halide and amorphizing a portion of the cobalt by flowing a halogen-containing precursor into the second substrate processing region while forming a local plasma from the halogen-containing precursor to form halogen-containing plasma effluents. Forming the cobalt halide and amorphizing the portion of the cobalt further comprises accelerating the halogen-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate. The cobalt halide is formed from cobalt from the substrate and halogen from the halogen-containing precursor. The methods further include removing cobalt from the substrate by 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 and flowing of the carbon-and-nitrogen-containing precursor occurs after flowing the halogen-containing precursor. The methods further include removing the substrate from the substrate processing region. A temperature of the substrate while removing the cobalt may be between 80° C. and 600° C. during the removing cobalt from the substrate. The substrate may be maintained at a same substrate temperature during the forming the cobalt halide and amorphizing the portion of the cobalt.
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. 1A is a side view of a substrate during a cobalt etch process.

FIG. 1B is a side view of a substrate during a cobalt etch process.

FIG. 1C is a side view of a substrate during a cobalt etch process.

FIG. 1D is a side view of a substrate during a cobalt etch process.

FIG. 2A is a side view of a substrate during a cobalt etch process according to embodiments.

FIG. 2B is a side view of a substrate during a cobalt etch process according to embodiments.

FIG. 2C is a side view of a substrate during a cobalt etch process according to embodiments.

FIG. 2D is a side view of a substrate during a cobalt etch process according to embodiments.

FIG. 3 is a flow chart of a cobalt etch process according to embodiments.

FIG. 4 is a flow chart of a cobalt etch process according to embodiments.

FIG. 5 shows a schematic cross-sectional view of a substrate processing chamber according to the disclosed technology.

FIG. 6 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 cobalt films which are difficult to volatize. The methods include exposing a cobalt film to a chlorine-containing precursor (e.g. Cl₂) with a concurrent local plasma which applies a bias to the impinging etchants. Cobalt chloride (e.g. CoCl₂) is formed on the surface at the same time an amorphized cobalt layer is formed near the surface. 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 cobalt complexes which desorb from the surface of the cobalt film. The methods presented remove cobalt while retaining the other exposed materials. The concurrent production of cobalt chloride and amorphized regions was found to markedly increase the overall etch rate as well as to markedly improve surface smoothness upon exposure to TMEDA. A thin cobalt oxide layer is typically present on the surface of the metal layer, in which case a local hydrogen plasma may be used to reduce or remove the cobalt oxide. All the recited steps may now be performed in the same substrate processing chamber.
In order to better understand and appreciate the embodiments disclosed herein, reference is now made to FIGS. 2A, 2B, 2C and 2D which are side views of a substrate during a cobalt etch process according to embodiments. For comparison, references will be interleaved with references to FIGS. 1A, 1B, 1C and 1D which are side views of a substrate during a conventional cobalt etch process. FIGS. 1A, 1B, 1C and 1D show effects occurring on the substrate which were not known before the present disclosure. FIG. 1A shows a substrate 101 having a cobalt portion (cobalt 104) with a thin cobalt oxide 120. Cobalt oxide 120 often forms on cobalt 104 upon exposure to atmosphere, for example. FIG. 2A also shows a cobalt portion (cobalt 204) having a thin cobalt oxide 220 for both the conventional process (FIG. 1A) and the process according to embodiments disclosed herein (FIG. 2A). Both processes begin from the same starting point. In both processes, cobalt oxide 120 and cobalt oxide 220 are exposed to hydrogen (H₂) to remove the cobalt oxides in a chemical reduction reaction. Following removal of cobalt oxide (120, 220) cobalt 104 is shown exposed for further processing in FIG. 1B and cobalt 204 is shown exposed in FIG. 2B.
Exposed cobalt 104 is exposed to chlorine (Cl₂) in a chlorination operation in FIG. 1B to form cobalt chloride 140 (e.g. CoCl₂) as shown in FIG. 1C. A small portion of cobalt 104 is consumed during the chlorination to form cobalt 105 whose topmost border is shown receded from the topmost border of cobalt 104. A benefit of the methods described herein involve the formation of a flat cobalt surface. A flat cobalt surface benefits processes which will later be electrically attached to form a contact or gate, for example. FIG. 2B indicates with darker straight arrows that the chlorination is biased in a local plasma to simultaneously chlorinate cobalt 204 and amorphize the cobalt region near the surface (amorphized cobalt 260). Amorphizing cobalt 204 at this stage may redistribute cobalt as shown in FIG. 2C, providing the benefit that the chlorination does not preferentially follow grain boundaries 210 of cobalt 204 on substrate 201 shown in FIG. 2B. In contrast, cobalt 104 (including grain boundary 110) is exposed to chlorine without a plasma bias power in FIG. 1B. Little or no beneficial redistribution of cobalt is shown following the purely thermal chlorination as shown in FIG. 1C. Applying bias to the chlorine has also been found to satisfactorily replace the conventional separate operation of using a biased hydrogen plasma to amorphize polycrystalline cobalt. Grain boundary 110 is still as pronounced in FIG. 1C and walls of grain boundary 110 may be chlorinated to form cobalt chloride 140. Following the biased plasma shown in FIG. 2B, cobalt 205 is shown with a relatively flat amorphized cobalt 260 layer underlying a similarly flat cobalt chloride 240 layer. “Top” and “Up” will be used herein to describe portions/directions perpendicularly distal from the substrate plane and further away from the center of mass of the substrate in the perpendicular direction. “Vertical” will be used to describe items aligned in the “Up” direction towards the “Top”. Other similar terms may be used whose meanings will now be clear. The vertical memory hole may be circular as viewed from above.
Both cobalt chloride 140 on substrate 101 and cobalt chloride 240 on substrate 201 are chelated by exposing the substrates to a carbon-and-nitrogen-containing precursor. Chelation involves the formation of volatile complexes. Chelation may only remove the cobalt chloride but not the amorphized cobalt or the polycrystalline cobalt films (cobalt 105, cobalt 205). Amorphization is still necessary in the conventional process to maintain an appreciable overall etch rate and patterned substrate 101 is shown in FIG. 1D after amorphization with a biased local plasma formed from hydrogen (H₂). A separate amorphization operation is not necessary and is not present in the methods described herein according to embodiments. The widening of grain boundary 101 shown in FIG. 1D may result in a non-uniform surface of exposed cobalt after all the etch operations are completed. Additional amorphization is not necessary following amorphization with the bias-plasma of the chlorine-containing precursor (e.g. Cl₂) shown in FIG. 2B. FIG. 2D shows a uniform amorphized cobalt layer which may be left on cobalt 205 at the conclusion of the etch process. A benefit of the processes described herein involve the uniformity of the etched cobalt layer which may include or consist of both amorphized cobalt 260 and cobalt 205 in embodiments.
Conventionally, a substrate having exposed cobalt (and a thin layer of cobalt oxide thereon) is placed into a first substrate processing region. Hydrogen (H₂) is flowed into the first substrate processing region and a plasma is ignited to form plasma effluents. The plasma effluents react with the cobalt oxide to reduce or remove the cobalt oxide from atop the exposed cobalt. The substrate is next placed into a second substrate processing region where chlorine (Cl₂) is flowed into the second substrate processing region to form cobalt chloride on the exposed cobalt. A portion of the exposed cobalt is consumed in the process of forming the cobalt chloride. The substrate is then exposed to a carbon-and-nitrogen-containing precursor to remove the cobalt chloride from atop the exposed cobalt. The substrate is then placed into a third substrate processing region (this one is equipped with a plasma biasing capability) where the substrate is exposed to a biased plasma formed from hydrogen and helium. Plasma effluents include ions which are accelerated into the substrate to amorphize a portion of the exposed cobalt but leaving behind some polycrystalline cobalt. Amorphization enables the process to continue so the substrate may be transferred back to the second substrate processing region to enable repetition of that portion of the process.
FIG. 3 is a flow chart of a cobalt etch process 301 according to embodiments. Benefits of the processes described herein include a more uniform cobalt surface than the conventional process just described. The cobalt etch process also results in a much more rapid removal rate during the etching operations. The rapidity of the etch is caused by the concurrent exposure to the chlorine and the amorphization operation. The etch is also hastened because the chemical reactions are promoted not only by thermal substrate effects but also the kinetic energy supplied by the ions in the plasma effluents during chlorination. A further benefit of the cobalt etch processes described herein results from using the same substrate processing region for both the amorphization and chlorination operations. A further potential benefit of the cobalt etch processes described herein results from embodiments wherein the same substrate processing region is used for amorphization/chlorination as well as exposure to the carbon-and-nitrogen-containing precursor. Rather than using three separate substrate processing chambers, the operations described herein may be performed in two or even one substrate processing chamber (e.g. in two or even one substrate processing regions) according to embodiments. The benefits resulting from these methods include much higher throughput resulting from reduced wafer handling and increased etch rate. The higher throughput garners a lower cost-of-ownership resulting from the greater throughput and the reduced square footage required to house the various substrate processing chambers.
Substrate 201 is placed into a first substrate processing region in operation 310. Substrate 201 has portions of cobalt 204 and cobalt oxide 220. Hydrogen (H₂) is flowed into the first substrate processing region in operation 320. A plasma is ignited in the first substrate processing region to react plasma effluents with substrate 201. The plasma effluents react with cobalt oxide 220 in operation 330. Cobalt oxide 220 is reduced or removed from atop cobalt 204 in the process. Substrate 201 is transferred into a second substrate processing region in operation 340. In embodiments, no substrate 201 transfer is necessary because the same substrate processing region may be used for all etch operations described herein. Chlorine (Cl₂) is flowed into the second substrate processing region to form cobalt chloride 240 on cobalt 205 in operation 350 during which a biased local plasma is formed from the chlorine in the second substrate processing region. The plasma bias directs ionized species in the plasma effluents toward substrate 201. The bias-accelerated chlorine plasma effluents amorphize near-surface portions of cobalt 204 and even out the chlorine reactions to avoid the grain boundary effects which widened the grain boundary shown in FIGS. 1A-1D. Substrate 201 is then exposed to a carbon-and-nitrogen-containing precursor to remove cobalt chloride 240 from atop cobalt 205 in operation 360. Substrate 201 is then removed from the second substrate processing region in operation 370. A further benefit of the embodiments described herein include reduced wafer handling and much higher throughput because amorphization and chlorination occur in the same chamber whereas conventional processes conducted chlorination and amorphization in separate substrate processing chambers.
FIG. 4 is a flow chart of a cobalt etch process 401 according to embodiments. Benefits of the processes represented in FIG. 4 also include a more uniform cobalt surface, less wafer handling and a much more rapid etch rate than conventional processes. The rapidity of the etch is again caused by the concurrent exposure to chlorine and amorphization. The etch rate is further hastened by the higher kinetic energy of the impinging precursors compared to conventional chlorination operations. Substrate 201 is placed into a substrate processing region in operation 410. All of the operations occur in the same substrate processing region in embodiments. Substrate 201 has portions of cobalt 204 and cobalt oxide 220 potentially overlying cobalt 204 in embodiments. Hydrogen (H₂) is flowed into the substrate processing region in operation 420. Operation 420 is optional and used if cobalt oxide 220 is present on cobalt 204. An absence of atmospheric exposure in advanced wafer handling configurations could conceivably result in an absence of cobalt oxide 220 according to embodiments. If cobalt oxide 220 is present, a plasma is ignited in the first substrate processing region to react plasma effluents with substrate 201. The plasma effluents may react with cobalt oxide 220 in (optional) operation 430. Cobalt oxide 220 is reduced or removed from atop cobalt 204 in the process and cobalt 204 becomes exposed.
Substrate 201 may then remain in the same substrate processing region or transferred to another substrate processing region for the chlorine operation. Chlorine (Cl₂) is flowed into the substrate processing region to form cobalt chloride 240 on cobalt 205. A biased local plasma is formed from the chlorine in the substrate processing region. The biased local plasma bias directs ionized species in the plasma effluents toward substrate 201. The bias-accelerated chlorine plasma effluents amorphize near-surface portions of cobalt 204 (amorphized cobalt 260) and even out the chlorination to avoid the grain boundary effects which widened the grain boundary shown in FIGS. 1A-1D. Substrate 201 is not transferred out of the substrate processing region between operations 440 and 450 in embodiments. Substrate 201 may remain in the same placement for operation 450 according to embodiments. Substrate 201 is then exposed to a carbon-and-nitrogen-containing precursor to remove cobalt chloride 240 from atop cobalt 205 in operation 450. Operations 440 and 450 may be repeated as a sequence (see dashed line) to remove additional material but are both carried out in the same substrate processing chamber so transfer overhead does not slow down the throughput. Substrate 201 may then be removed from the substrate processing region in operation 460 once a target amount of exposed cobalt 205 has been removed.
Additional aspects of the processes described herein will be presented before and during the description of exemplary substrate processing hardware. Other sources of hydrogen may be used to augment or replace the molecular hydrogen used to reduce the cobalt oxide and expose the cobalt. 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. The hydrogen reduction may be formed in a local plasma and results in a faster subsequent cobalt etch rate in cobalt etch process described herein, either by removing oxygen and exposing cobalt or otherwise transforming the cobalt oxide layer to promote the cobalt etch rate.
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 substrate processing region after the operation of flowing the chlorine-containing precursor in embodiments. Chlorine may be removed from the substrate processing region before flowing the carbon-and-nitrogen-containing precursor into the substrate processing region to maintain a beneficial separate between the precursors. The substrate processing region may be actively purged with a relatively inert gas before flowing the carbon-and-nitrogen-containing precursor or after flowing the carbon-and-nitrogen-containing precursor to avoid having the carbon-and-nitrogen-containing precursor react with the halogen-containing precursor. Operations 450 and 460 may be repeated, with these precautions, between 2 and 7 times to remove additional material rapidly and still maintain the uniform post-etch surface. Operations 440 and 450 may be repeated to the same ends. 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.
In general, a halogen-containing precursor may be used in place of the chlorine-containing precursor (e.g. Cl₂) of cobalt etch processes described herein. 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.
The carbon-and-nitrogen-containing precursor may be TMEDA (C₆H₁₆N₂) as in the example, but may be other precursors. In general, the carbon-and-nitrogen-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, C₂H₅or a higher order hydrocarbon.
Creating volatile reaction products from cobalt removes material during cobalt etch processes described herein. The volatile reaction products are thought to include methyl cobalt complexes such as Co(CH₃)₄. Exposing cobalt first to accelerated chlorine plasma effluents and then to the carbon-and-nitrogen-containing precursor has been found to produce a high etch rate of cobalt and presumably makes volatile reaction products which leave the surface by desorption. Hypotheses about mechanisms are not included to limit the claims in any way but to enhance the understanding of the embodiments discussed herein.
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 method also includes applying energy to the chlorine-containing precursor in the substrate processing region to form the biased chlorine 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 chlorine-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 is included to help even out the net cobalt etch rate and to hasten the chlorine reaction with the cobalt on the surface. The chlorine plasma in the substrate processing region may be referred to herein as a local plasma.
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 before 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 1 slm (standard liters per minute) and 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 flow of the carbon-and-nitrogen-containing precursor. 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. Stated another way, the electron temperature in the substrate processing region may be less than 0.5 eV, less than 0.45 eV, less than 0.4 eV, or less than 0.35 eV according to embodiments. Moreover, the carbon-and-nitrogen-containing precursor may have not been excited in any remote plasma before entering the substrate processing region in embodiments.
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 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 which biases ions relative to the substrate and accelerates the ions towards the substrate. 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 and chlorinate/amorphize cobalt in the appropriate operations described previously. The hydrogen plasma and the biased chlorine plasma in the substrate processing regions may be referred to herein as local plasmas.
During the operations of processing the cobalt oxide, the operations of flowing the halogen-containing precursor to form the cobalt halide, and/or the operation of flowing the carbon-and-nitrogen-containing precursor to remove the cobalt halide, the substrate may be maintained at a same substrate temperature in embodiments. During the operations of reducing the cobalt oxide, forming the cobalt chloride or removing the cobalt chloride, the substrate temperature may be between 80° C. and 600° C. in general. In embodiments, the temperature of the substrate during the operations described may be greater than 80° C., greater than 100° C., greater than 120° C., or greater than 150° C. . The substrate temperatures may be less than 600° C., less than 550° C., less than 500° C. according to embodiments. The pressure in the substrate processing during any or all of the steps may be below 20 Torr, and may be below 15 Torr, below 5 Torr or below 3 Torr. For example, the pressure may be between 10 mTorr and 10 Torr during processing.
Additional process parameters are disclosed in the course of describing an exemplary processing chamber and system. FIG. 5 is a partial cross sectional view showing an exemplary substrate processing chamber 1201 which may be used to perform portions of processes described herein. The various precursors (e.g. the hydrogen-containing precursor, the chlorine-containing precursor or the carbon-and-nitrogen-containing precursor) may be introduced through one or more apertures 1251 into remote plasma region 1265. The precursors may or may not be excited by remote plasma power source 1246, in embodiments, as appropriate for the process operations described in detail above. RF power from remote plasma power source 1246 may be applied between remote electrode 1245 and showerhead 1220 to form a remote plasma in remote plasma region 1265. Substrate processing chamber 1201 includes chamber body 1212 and substrate pedestal 1210. The substrate pedestal 1210 is at least partially disposed within chamber body 1212. Showerhead 1220 is disposed between remote plasma region 1265 and substrate processing region 1240. A local plasma may be formed and biased relative to substrate 1211 by applying RF power from local plasma power source 1248 to showerhead 1220 relative to substrate pedestal 1210 in embodiments.
Substrate processing chamber 1201 may include a vacuum pump 1225 and a throttle valve 1227 to regulate the flow of gases through the processing chamber 1201 and substrate processing region 1240 therein. The vacuum pump 1225 is coupled through the chamber body 1212 and in fluid communication with the interior of substrate processing chamber 1201. The RF power, when applied between remote electrode 1245 and showerhead 1220, generates a plasma of reactive species in remote plasma region 1265. Remote electrode 1245 is supported by top plate 1250 and is electrically isolated therefrom by electrically isolating ring(s) 1247. Substrate 1220 is supported by showerhead flange 1222 and is electrically isolated therefrom by showerhead isolator 1221. RF power, when applied between showerhead 1220 and substrate pedestal 1210, generates a plasma of reactive species in substrate processing region 1240. The plasma in substrate processing region 1240 may be referred to as a local plasma and may be biased to accelerate ions in substrate processing region 1240 towards substrate 1211 during processing.
A local plasma may be formed to excite the hydrogen-containing precursor in embodiments. Another local plasma may be formed to excite the chlorine-containing precursor according to embodiments. A remote plasma may or may not be used to further pre-excite the hydrogen-containing precursor and/or the chlorine-containing precursor in embodiments. On the other hand, no local plasma and/or no remote plasma is used to excite the carbon-and-nitrogen-containing precursor according to embodiments. The carbon-and-nitrogen-containing precursor may be delivered through remote plasma region 1265 into substrate processing region 1240 or directly into substrate processing region 1240 in embodiments. In either case, the carbon-and-nitrogen-containing precursor may not be excited in any plasma before entering the substrate processing region 1240 according to embodiments. Substrate processing region 1240 may be “plasma-free” while exposing substrate 1211 to the carbon-and-nitrogen-containing precursor according to embodiments.
The substrate temperature may be controlled by applying heat to or cooling substrate pedestal 1210. Substrate temperatures during the various operations were given previously. Flowrates of the various precursors and process pressures in substrate processing region 1240 and remote plasma region 1265 were given previously. Apertures in showerhead 1220 may be large enough that the pressures in substrate processing region 1240 and remote plasma region 1265 may be about the same in embodiments. Plasma power (remote and local) can be supplied from remote plasma power source 1246 and local plasma power source 1248 at a variety of frequencies or a combination of multiple frequencies. The RF frequency applied in the exemplary processing system may be an RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency. The RF frequency applied in the exemplary processing system may be an RF frequency less than 200 kHz, an RF frequency between 5 MHz and 25 MHz, or a microwave frequency greater than 1 GHz in embodiments. The remote and/or local plasma power may be capacitively-coupled (CCP) or inductively-coupled (ICP) into the remote plasma region and/or the substrate processing region, respectively. Plasma power may also be simultaneously applied to both remote plasma region 1265 and substrate processing region 1240 during etching operations described herein. The frequencies and powers above apply to both regions.
A plasma may be ignited in remote plasma region 1265 above showerhead 1220 and/or substrate processing region 1240 below showerhead 1220 in embodiments. A plasma may be present in remote plasma region 1265 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 used to remove cobalt oxide. The hydrogen-containing precursor may be flowed into substrate processing region 1240 and a local plasma may be formed to perform the pretreatment. The etch cycle may be performed in the same substrate processing region and the substrate processing region may be plasma-free during the flowing of the carbon-and-nitrogen-containing precursor.
Embodiments of the processing chambers may be incorporated into larger fabrication systems for producing integrated circuit chips. FIG. 6 shows one such processing system 2101 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (load lock chambers 2102) supply substrates of a variety of sizes that are received by robotic arms 2104 and placed into a low pressure holding area 2106 before being placed into one of the substrate processing chambers 2108 a-f. A second robotic arm 2110 may be used to transport the substrate wafers from the holding area 2106 to the substrate processing chambers 2108 a-f and back. Each substrate processing chamber 2108 a-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.
In the preceding description, for the purposes of explanation, numerous details have been set forth to provide an understanding of various embodiments disclosed herein. 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 Si₃N₄but 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 SiO₂but 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 disclosure. Accordingly, the above description should not be taken as limiting the scope of the claims.
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 disclosure, 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 cobalt and cobalt oxide, the method comprising:

transferring a substrate into a substrate processing region, wherein the substrate comprises cobalt and a thin cobalt oxide layer thereon;

removing the thin cobalt oxide layer by flowing a hydrogen-containing precursor into the substrate processing region while forming a local plasma from the hydrogen-containing precursor;

forming cobalt chloride and amorphizing a portion of the cobalt by flowing a chlorine-containing precursor into the substrate processing region while forming a plasma from the chlorine-containing precursor to form chlorine-containing plasma effluents, wherein forming cobalt chloride and amorphizing the portion of the cobalt further comprises accelerating the chlorine-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate, wherein forming the cobalt chloride occurs after removing the thin cobalt oxide layer;

purging the substrate processing region with an inert gas to remove the chlorine-containing precursor from the substrate processing region;

removing the cobalt from the substrate by 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; and

transferring the substrate out of the substrate processing region.

2. The method of claim 1 wherein the substrate is maintained at a same substrate temperature during the removing the thin cobalt layer and removing the cobalt.

3. The method of claim 1 wherein the substrate remains inside the substrate processing throughout the method.

4. A method of etching cobalt from a substrate, the method comprising:

placing the substrate into a first substrate processing region, wherein the substrate comprises cobalt and an overlying cobalt oxide;

reducing the cobalt oxide and exposing the cobalt by flowing a hydrogen-containing precursor into a first substrate processing region housing the substrate while forming a hydrogen plasma in the substrate processing region;

placing the substrate into a second substrate processing region;

forming cobalt halide and amorphizing a portion of the cobalt by flowing a halogen-containing precursor into the second substrate processing region while forming a local plasma from the halogen-containing precursor to form halogen-containing plasma effluents, wherein forming the cobalt halide and amorphizing the portion of the cobalt further comprises accelerating the halogen-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate;

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;

removing cobalt from the substrate; and

removing the substrate from the second substrate processing region.

5. The method of claim 4 wherein the cobalt consists of cobalt.

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

7. The method of claim 4 wherein the carbon-and-nitrogen-containing precursor comprises tetramethylethylenediamine.

8. The method of claim 4 wherein the carbon-and-nitrogen-containing precursor comprises a carbon-nitrogen single bond.

9. The method of claim 4 wherein the carbon-and-nitrogen-containing precursor comprises at least two methyl groups.

10. The method of claim 4 wherein the halogen-containing precursor comprises at least one of chlorine or bromine.

11. The method of claim 4 wherein the halogen-containing precursor is a homonuclear diatomic halogen.

12. The method of claim 4 wherein the first substrate processing region and the second substrate processing region are the same substrate processing region.

13. The method of claim 4 wherein the carbon-and-nitrogen-containing precursor consists of carbon, nitrogen and hydrogen.

14. The method of claim 4 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.

15. The method of claim 4 wherein the cobalt halide is one of cobalt chloride or cobalt bromide.

16. The method of claim 4 wherein forming the plasma to treat the thin metal oxide layer comprises applying a local capacitive plasma RF power between a showerhead and the substrate.

17. The method of claim 4 wherein a processing temperature of the substrate is greater than 80° C. during the forming the cobalt halide and amorphizing the portion of the cobalt.

18. A method of etching cobalt from a substrate, the method comprising:

placing the substrate into a substrate processing region, wherein the substrate comprises exposed cobalt;

forming cobalt halide and amorphizing a portion of the cobalt by flowing a halogen-containing precursor into the substrate processing region while forming a local plasma from the halogen-containing precursor to form halogen-containing plasma effluents, wherein forming the cobalt halide and amorphizing the portion of the cobalt further comprises accelerating the halogen-containing plasma effluents towards the substrate by biasing the plasma relative to the substrate, and wherein the cobalt halide is formed from cobalt from the substrate and halogen from the halogen-containing precursor;

removing cobalt from the substrate by flowing a carbon-and-nitrogen-containing precursor into the (same) 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 flowing the halogen-containing precursor; and

removing the substrate from the substrate processing region.

19. The method of claim 18 wherein a temperature of the substrate while removing the cobalt is between 80° C. and 600° C. during the removing cobalt from the substrate.

20. The method of claim 18 wherein the substrate is maintained at a same substrate temperature during the forming the cobalt halide and amorphizing the portion of the cobalt.