METHODS OF FORMING CONFORMAL TRANSITION METAL DICHALCOGENIDE FILMS

Transition metal dichalcogenide (TMDC) films and methods for conformally depositing TMDC films on a substrate surface are described. The substrate surface may have one or more features formed therein, one or more layers formed thereon, and combinations thereof. The substrate surface is exposed to a transition metal precursor and an oxidant to form a transition metal oxide film in a first phase. The transition metal oxide film is exposed to a chalcogenide precursor to convert the transition metal oxide film to the TMDC film in a second phase.

TECHNICAL FIELD

Embodiments of the disclosure generally relate to methods of forming transition metal dichalcogenide (TMDC) films. More particularly, embodiments of the disclosure are directed to methods of forming TMDC films for high aspect ratio structures and for barrier and liner material applications in back-end-of-line (BEOL) processes.

BACKGROUND

The semiconductor processing industry continues to strive for larger production yields while increasing the uniformity of layers deposited on substrates having larger surface areas. These same factors in combination with new materials also provide higher integration of circuits per unit area of the substrate. As circuit integration increases, the need for greater uniformity and process control regarding layer thickness rises. As a result, various technologies have been developed to deposit layers on substrates in a cost-effective manner, while maintaining control over the characteristics of the layer.

Chemical vapor deposition (CVD) is one of the most common deposition processes employed for depositing layers on a substrate. CVD is a flux-dependent deposition technique that requires precise control of the substrate temperature and the precursors introduced into the processing chamber in order to produce a desired layer of uniform thickness. These requirements become more critical as substrate size increases, creating a need for more complexity in chamber design and gas flow technique to maintain adequate uniformity.

A variant of CVD that demonstrates excellent step coverage is cyclical deposition or atomic layer deposition (ALD). Cyclical deposition is based upon atomic layer epitaxy (ALE) and employs chemisorption techniques to deposit precursor molecules on a substrate surface in sequential cycles. The cycles include exposing the substrate surface to a first precursor, a purge gas, a second precursor, and the purge gas. The first and second precursors react to form a product compound as a film on the substrate surface. The cycles may be repeated to form the layer to a desired thickness.

The advancing complexity of advanced microelectronic devices is placing stringent demands on currently used deposition techniques. Unfortunately, there is a limited number of viable chemical precursors and processes to provide films with suitable crystallinity, grain size, continuity, and electrical conductivity.

Transition metal dichalcogenides (TMDCs) are known to be great candidates to mitigate the issue of metal migration associated with interconnect downscaling of films. Moreover, TMDCs possess better conductivity and carrier mobility compared to current processes in 3D-NAND devices. Typical TMDC deposition methods require high temperature processes which may not be compatible with device thermal budgets.

Accordingly, there is a need for improved TMDC deposition methods that can conformally grow TMDC films by low temperature thermal processes suitable for device integration in temperature sensitive structures.

SUMMARY

One or more embodiments of the disclosure are directed to a method of forming a transition metal dichalcogenide film. The method comprises depositing a transition metal oxide film on a semiconductor substrate surface by sequentially exposing the semiconductor substrate surface to a transition metal precursor and an oxidant, the oxidant comprising one or more of an alcohol or deionized/deoxygenated water; and converting the transition metal oxide film to the transition metal dichalcogenide film.

Additional embodiments of the disclosure are directed to a method of forming a transition metal dichalcogenide film on a semiconductor substrate surface comprising at least one feature. The method comprises sequentially exposing the semiconductor substrate surface to a transition metal precursor and an oxidant to directly deposit a transition metal oxide film without forming a transition metal film intermediate. The transition metal precursor comprises one or more of bis(t-butylimino) bis(dimethylamino) tungsten(VI), bis(isopropylcyclopentadienyl) tungsten(IV) dihydride, bis(cyclopentadienyl) tungsten dihydride, bis(t-butylimino) bis(dimethylamino) molybdenum(VI), pentakis (dimethylamino) tantalum (V), or tetrakis (dimethylamido) titanium (IV). The oxidant comprises one or more of an alcohol or deionized/deoxygenated water. The method further comprises exposing the transition metal oxide film to a chalcogenide precursor to convert the transition metal oxide film to the transition metal dichalcogenide film. The semiconductor substrate surface is maintained at a temperature in a range of about 150° C. to about 450° C. In some embodiments, converting the transition metal oxide film is performed at a pressure in a range of from 0.1 Torr to 100 Torr.

DETAILED DESCRIPTION

The term “about” as used herein means approximately or nearly and in the context of a numerical value or range set forth means a variation of ±15% or less, of the numerical value. For example, a value differing by ±14%, ±10%, ±5%, ±2%, ±1%, ±0.5%, or ±0.1% would satisfy the definition of about.

As used herein, the terms “substrate surface” or “semiconductor substrate surface” may be interchangeably used to refer to any substrate surface upon which a layer may be formed. The substrate (or substrate surface) may be pretreated prior to the disclosed methods, for example, by polishing, etching, reduction, oxidation, halogenation, hydroxylation, annealing, baking, or the like.

The semiconductor substrate surface may have one or more features formed therein, one or more layers formed thereon, and combinations thereof. The feature may define any suitable shape including, but not limited to, peaks, trenches, holes and vias (circular or polygonal). As used in this regard, the term “feature” refers to any intentional surface irregularity. Suitable examples of features include but are not limited to trenches, which have a top, two sidewalls and a bottom extending into the substrate, vias which have one or more sidewall extending into the substrate to a bottom, and slot vias. The features described herein can have any suitable aspect ratio (ratio of the depth of the feature to the width of the feature). In one or more embodiments, the aspect ratio of the features described herein is greater than or equal to about 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, or 40:1.

According to one or more embodiment, the term “on”, with respect to a film or a layer of a film, includes the film or layer being directly on a surface, for example, a semiconductor substrate surface, as well as there being one or more underlayers between the film or layer and the surface, for example the substrate surface. Thus, in one or more embodiments, the phrase “on the substrate surface” is intended to include one or more underlayers. In other embodiments, the phrase “directly on” refers to a layer or a film that is in contact with a surface, for example, a substrate surface, with no intervening layers. Thus, the phrase “a layer directly on the substrate surface” refers to a layer in direct contact with the substrate surface with no layers in between.

“Atomic layer deposition” or “cyclical deposition” as used herein refers to the sequential exposure of two or more reactive compounds to deposit a layer of material on a substrate surface. As used in this specification and the appended claims, the terms “reactive compound”, “reactive gas”, “reactive species”, “precursor”, “process gas” and the like are used interchangeably to mean a substance with a species capable of reacting with the substrate surface or material on the substrate surface in a surface reaction (e.g., chemisorption, oxidation, reduction). The substrate, or portion of the substrate is exposed sequentially to the two or more reactive compounds which are introduced into a reaction zone of a processing chamber. In a time-domain ALD process, exposure to each reactive compound is separated by a time delay to allow each compound to adhere and/or react on the substrate surface. In a spatial ALD process, different portions of the substrate surface, or material on the substrate surface, are exposed simultaneously to the two or more reactive compounds so that any given point on the substrate is only substantially exposed to one reactive compound at a time. As used in this specification and the appended claims, the term “substantially” used in this respect means, as will be understood by those skilled in the art, that there is the possibility that a small portion of the substrate may be exposed to multiple reactive gases simultaneously due to diffusion, and that the simultaneous exposure is unintended.

In one aspect of a time-domain ALD process, a first reactive gas (i.e., a first precursor or compound A) is pulsed into the reaction zone followed by a first time delay. Next, a second precursor or compound B is pulsed into the reaction zone followed by a second delay. During each time delay a purge gas, such as argon, is introduced into the processing chamber to purge the reaction zone or otherwise remove any residual reactive compound or by-products from the reaction zone. Alternatively, the purge gas may flow continuously throughout the deposition process so that only the purge gas flows during the time delay between pulses of reactive compounds. The reactive compounds are alternatively pulsed until a desired film or film thickness is formed on the substrate surface.

In some embodiments, the ALD process of pulsing compound A, purge gas, compound B and purge gas is a cycle. A cycle can start with either compound A or compound B and continue the respective order of the cycle until achieving a film with the desired thickness. In some embodiments, there may be two reactants, A and B, that are alternatingly pulsed and purged.

In some embodiments, there may be three or more reactants, A, B, and C, that are alternatingly pulsed and purged. In some embodiments, each reactant is utilized during each deposition cycle (e.g., A-B-C). In some embodiments, a series of alternating exposures to compounds A and B may be performed before exposure to compound C (e.g., A-B-A-B-C).

In a spatial ALD process, a first reactive gas and a second reactive gas are delivered simultaneously to the reaction zone but are separated by an inert gas curtain and/or a vacuum curtain. The substrate is moved relative to the gas delivery apparatus so that any given point on the substrate is exposed to the first reactive gas and the second reactive gas.

According to one or more embodiments, the disclosed method utilize an atomic layer deposition (ALD) process. In such embodiments, the substrate surface is exposed to the precursors (or reactive gases) sequentially. As used herein, throughout the specification, “sequentially” means that the duration of a precursor exposure does not intentionally overlap with the exposure to a reactant in a manner intended to create a gas phase reaction. It is understood that while some overlap may occur, this overlap is unintentional.

Embodiments of the disclosure advantageously provide a pathway to grow TMDC films at lower temperatures, such as in a range of from about 150° C. to about 500° C., or in a range of from about 150° C. to about 450° C., which is suitable for device integration in temperature sensitive structures and devices. Embodiments of the disclosure provide methods of forming high-quality TMDC films in terms of crystallinity, grain size, continuity, and electrical conductivity for use as a channel material, liner, or barrier layer in the miniaturization and scaling of integrated circuits. Embodiments of the disclosure provide methods of forming high-quality2D-TMDC films for temperature-sensitive device architectures.

Embodiments of the disclosure advantageously provide conformally deposited crystalline TMDC films which can be used in memory and logic applications, such as, for example, barrier and liner material applications in back-end-of-line (BEOL) processes. For example, the TMDC film acting as a barrier/liner may enable nucleation of a subsequently deposited metal, adhesively bind a metal to underlying dielectric materials, and block diffusion of metal elements to underlying dielectric materials. The TMDC films can advantageously be used in high aspect ratio structures.

Some embodiments provide methods of forming TMDC films by thermal or plasma-based processes.

Embodiments of the disclosure advantageously provide methods of forming TMDC films via a low energy barrier pathway. In some embodiments, in the low energy barrier pathway, the transition metal precursors are used in their various forms (metal, metal oxide, metal chloride, metal oxychloride, and the like). In one or more embodiments, the methods include depositing an ultrathin layer to a few nm thick, followed by oxidation, then exposure to a chalcogenide precursor, (e.g., sulfurization), which forms high-quality TMDC films. Advantageously, the methods described herein provide a low energy barrier pathway for sulfurization of transition metals or their precursors to metal sulfides. Based on this low energy barrier pathway, the methods advantageously form a conformal and continuous TMDC film, such as a WS2film, in all regions of a high aspect ratio structure, such as a trench.

The embodiments of the disclosure are described by way of the Figures, which illustrate processes and substrates in accordance with one or more embodiments of the disclosure. The processes, schemes, and resulting substrates shown are merely illustrative of the disclosed processes, and the skilled artisan will recognize that the disclosed processes are not limited to the illustrated applications.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments. It will be apparent to one skilled in the art that embodiments may be practiced without these specific details. In other instances, well-known aspects are not described in detail in order to not unnecessarily obscure embodiments. Furthermore, it is to be understood that the various embodiments shown in the accompanying drawings are illustrative representations and are not necessarily drawn to scale.

FIG.1illustrates a process flow diagram of a method100of forming a transition metal dichalcogenide film.FIGS.2and3illustrate cross-sectional views of a semiconductor substrate200in accordance with one or more embodiments of the disclosure. The method100can be used to form a transition metal dichalcogenide film on a substrate, such as, for example, the semiconductor substrate200shown inFIGS.2and3.

The method100illustrated inFIG.1is representative of an atomic layer deposition (ALD) process in which the semiconductor substrate or semiconductor substrate surface is exposed sequentially to the reactive gases in a manner that prevents or minimizes gas phase reactions of the reactive gases. In so doing, the method100advantageously avoids a chemical vapor deposition (CVD) process in which the reactive gases are mixed in the processing chamber to allow gas phase reactions of the reactive gases.

In one or more embodiments, the method100comprises optionally pre-treating the substrate at operation105. A transition metal dichalcogenide film is formed on the substrate in a deposition process cycle110. The deposition process cycle110can be understood in two phases112,120. A first phase112comprising operations113,114,115,116, and decision117, forms a transition metal oxide film on the substrate surface. In the first phase112, the transition metal oxide film is directly formed without forming a transition metal film intermediate. A second phase120comprising operations121and122converts the transition metal oxide film formed in the first phase112to a transition metal dichalcogenide film.

In some embodiments, the second phase120is performed after the first phase112has deposited the transition metal oxide film to a predetermined thickness. In some embodiments, the second phase120is performed after a single cycle of the first phase112. In some embodiments, the second phase120is performed after multiple cycles of the first phase112.

The first phase112comprises sequentially exposing the substrate to a transition metal precursor at operation113, optionally purging the substrate surface at operation114, exposing the substrate to an oxidant at operation115, and optionally purging the substrate surface at operation116to deposit the transition metal oxide film.

The second phase120comprises sequentially exposing the substrate to a chalcogenide precursor at operation121and, optionally, purging the substrate surface at operation122to convert the transition metal oxide film to the transition metal dichalcogenide film.

In some embodiments, the method100optionally includes a pre-treatment operation105. In one or more embodiments, method100includes pre-treating the substrate surface at operation105prior to depositing the transition metal oxide film (first phase112). The pre-treatment can be any suitable pre-treatment process known to the skilled artisan. Suitable pre-treatments include, but are not limited to, pre-heating, cleaning, soaking, native oxide removal, or the like.

It has been observed that the substrate surface, such as, for example, a low-κ dielectric substrate surface, is sensitive to strong oxidants while growing the transition metal oxide film in the first phase112. It remains a challenge for the transition metal precursors to adsorb on inherently highly hydrophobic alkyl-group terminated dielectric surfaces. In some embodiments, the method100comprises pre-treating the substrate surface at operation105with a plasma treatment or ultraviolet (UV) radiation exposure to remove surface alkyl groups and make the low-K dielectric surface suitable for precursor adsorption. Advantageously, the oxidant comprising one or more of an alcohol or deionized/deoxygenated water does not damage the low-K dielectric surface. Additionally, use of the transition metal precursors and the oxidant comprising one or more of an alcohol or deionized/deoxygenated water advantageously enables uniform growth of the transition metal oxide film without modifying the properties of, or damaging, the low-κ dielectric surface.

In one or more embodiments, the plasma treatment of operation105comprises exposing the substrate surface to a plasma of carbon dioxide (CO2). In one or more embodiments, the plasma of CO2further comprises an inert gas, including, but not limited to, argon (Ar), helium (He), or nitrogen (N2). In one or more embodiments, the substrate surface is exposed to the plasma of CO2for a time period in a range of from about 0.5 seconds to about 20 seconds.

Without intending to be bound by theory, it is thought that the κ-value of the low-κ dielectric substrate surface, such as silicon oxycarbide (SiOC), is dependent on the oxidant used during the method100. It has been advantageously found that the oxidant described herein does not change the κ-value and is suitable for deposition on a low-κ dielectric substrate surface.

In one or more embodiments, the stoichiometry of the TMDC film was measured by x-ray photoelectron spectroscopy (XPS). In one or more embodiments, a TMDC film comprising WS2and having a stoichiometric ratio of sulfur:tungsten in a range of from 1:1 to 1:2 with impurities, e.g., carbon (C), nitrogen (N2), and/or oxygen (O2), such as about 5% nitrogen (N2), does not change the κ-value and is suitable for deposition on a low-κ dielectric substrate surface.

In specific embodiments, it has advantageously been found that exposing the substrate surface to the plasma of CO2for a time period in a range of from about 0.5 seconds to about 20 seconds does not modify the properties of, or damage, the substrate surface, such as a low-κ dielectric surface, where there is no change in κ-value.

In one or more embodiments, the pre-treatment of operation105comprises exposing the substrate surface to ultraviolet (UV) radiation. In one or more embodiments, the pre-treatment of operation105comprises exposing the substrate surface to UV radiation for a time period in a range of from about 0.5 seconds to about 30 seconds. In one or more embodiments, exposing the substrate surface to UV radiation includes using a UV lamp that generates the UV radiation.

In one or more embodiments, the method100comprises, consists essentially of, or consists of pre-treating the substrate (operation105), deposition process cycle110including the first phase112[comprising sequentially exposing the substrate to a transition metal precursor at operation113, purging the substrate surface at operation114, exposing the substrate to an oxidant at operation115, and purging the substrate surface at operation116to deposit the transition metal oxide film], the second phase [comprising sequentially exposing the substrate to a chalcogenide precursor at operation121and purging the substrate surface at operation122to convert the transition metal oxide film (formed in the first phase112) to the transition metal dichalcogenide film].

In the first phase112of the deposition process cycle110, in one or more embodiments, at operation113, the substrate (or substrate surface) is exposed to a transition metal precursor to form a reactive metal species on the substrate surface. The transition metal precursor can be any suitable transition metal containing compound that can react (i.e., adsorb or chemisorb onto) the substrate surface to leave a transition metal containing species on the substrate surface. It is thought that any transition metal containing compound, which, based on its size, can inhibit diffusion through pores in the substrate surface, where each pore has a size in a range of from 5 Å to 20 Å, is suitable.

In one or more embodiments, the transition metal precursor does not comprise oxygen or halogen atoms. In some embodiments, the transition metal precursor does not comprise, consist essentially of, or consist of oxygen or halogen atoms.

In one or more embodiments, the transition metal precursor comprises one or more of tungsten (W), molybdenum (Mo), tantalum (Ta), titanium (Ti), or ruthenium (Ru).

At operation114, the processing chamber or substrate surface is optionally purged to remove unreacted transition metal precursor, reaction products, and byproducts. As used in this manner, the term “processing chamber” also includes portions of a processing chamber adjacent the substrate surface without encompassing the complete interior volume of the processing chamber. For example, in a sector of a spatially separated processing chamber, the portion of the processing chamber adjacent the substrate surface is purged of the transition metal precursor by any suitable technique including, but not limited to, moving the substrate through a gas curtain to a portion or sector of the processing chamber that contains none or substantially none of the transition metal precursor.

In one or more embodiments, purging the processing chamber comprises applying a vacuum. In some embodiments, purging the processing chamber comprises flowing a purge gas over the substrate. In some embodiments, the portion of the processing chamber refers to a micro-volume or small volume process station within a processing chamber. The term “adjacent” referring to the substrate surface means the physical space next to the surface of the substrate which can provide sufficient space for a surface reaction (e.g., precursor adsorption) to occur. In one or more embodiments, the purge gas is selected from one or more of nitrogen (N2), helium (He), and argon (Ar).

The descriptors of the purge operations described herein, both in operation and composition, may apply to any of the purge operations of the method100: operation114,116, and122.

At operation115, the substrate (or substrate surface) is exposed to an oxidant to form a transition metal oxide film on the substrate. The oxidant (which may also be referred to as an oxide reactant) may be any suitable compound for oxidizing the adsorbed transition metal precursor to form a transition metal oxide film. As described herein, it has been observed that the substrate surface, such as, for example, a low-κ dielectric substrate surface, is sensitive to strong oxidants while growing the transition metal oxide film in the first phase112. It remains a challenge for the transition metal precursors to adsorb on inherently highly hydrophobic alkyl-group terminated dielectric surfaces. In some embodiments, pre-treating the substrate surface at operation105comprises a plasma treatment or ultraviolet (UV) radiation exposure to remove surface alkyl groups and make the low-κ dielectric surface suitable for precursor adsorption.

Advantageously, the oxidant comprising one or more of an alcohol or deionized/deoxygenated water does not damage the low-κ dielectric surface. In some embodiments, the oxidant does not comprise a plasma, which, without intending to be bound by any particular theory, is also thought to damage the low-κ dielectric surface.

The alcohol can be any suitable alcohol. In one or more embodiments, the alcohol used for the oxidant comprises one or more of methanol, ethanol or isopropyl alcohol. In one or more embodiments, the alcohol used for the oxidant comprises isopropyl alcohol.

As used herein, “deionized/deoxygenated water” includes any water composition in which dissolved oxygen (DO) has been removed. In embodiments where the oxidant comprises deionized/deoxygenated water, DO can be removed by any suitable process known to the skilled artisan, and it is to be understood that the disclosure is not limited to any specific process.

At operation116, the processing chamber or substrate surface is optionally purged to remove unreacted oxidant, reaction products, and byproducts. The purge process of operation116may be the same purge process or a different purge process as operation114.

In one or more embodiments, the first phase112includes exposing the substrate surface to the transition metal precursor (operation113), the purge gas (operation114), the oxidant (operation115), and the purge gas (operation116). The transition metal precursor and the oxidant react to form a product compound as a film, such as the transition metal oxide film, on the substrate surface. The first phase112may be repeated to form the transition metal oxide film to a desired thickness (decision117).

In one or more embodiments, the transition metal oxide film is formed to a thickness in a range of 5 Å to 50 Å, in a range of 5 Å to 35 Å, in a range of 5 Å to 25 Å, or in a range of 5 Å to 10 Å. In accordance with decision117, the first phase112, e.g., exposing the substrate surface to the transition metal precursor (operation113), the purge gas (operation114), the oxidant (operation115), and the purge gas (operation116), may be repeated until the transition metal oxide film is formed to the desired thickness.

The inventors have advantageously found that purging the processing chamber at operation116enhances the adsorption of the transition metal precursor if returning to the beginning of the first phase112to deposit additional transition metal oxide film. Without being bound by theory, it is believed that the purge at operation116provides a “clean” substrate surface, which enhances the adsorption of the transition metal precursor in operation113.

In some embodiments, the transition metal oxide film formed in the first phase112is directly formed without forming a transition metal film intermediate. The inventors have surprisingly found that the formation of certain metals (e.g., tungsten) on dielectric surfaces is more difficult (e.g., longer processing times, elevated temperatures) than the formation of metal oxides. Further, the formation of a metal layer which is subsequently oxidized requires more processing time and decreases processing throughput. Accordingly, embodiments of the disclosure advantageously provide methods of forming a transition metal oxide film without the formation of a metal film intermediate.

In some embodiments, the substrate surface does not include a barrier layer. Without being bound by theory, it is believed that the formation of a metal layer without a barrier layer leads to the possible diffusion of the metal into the underlying material(s). The inventors have surprisingly found that diffusion from metal oxide materials is significantly lower. In some embodiments, the diffusion of metal atoms from metal oxide materials is low enough that the benefits of a barrier layer are negligible. Accordingly, the elimination of the barrier layer from a process flow is expected to decreasing processing time, increase throughput, and decrease resistance of the metal fill since the fill will be larger in volume. Additionally, it is thought that any transition metal containing compound, which, based on its size, can inhibit diffusion through pores in the substrate surface, where each pore has a size in a range of from 5 Å to 20 Å, is suitable as the transition metal precursor.

Once the first phase112is completed, and the transition metal oxide film has reached a predetermined thickness or a predetermined number of process cycles have been performed, the method100moves to the second phase120.

In the second phase120, the transition metal oxide film formed in the first phase112is converted to a transition metal dichalcogenide (TMDC) film. In some embodiments, converting the transition metal oxide film comprises exposing the transition metal oxide film to a chalcogenide precursor at operation121. The chalcogenide precursor comprises one of more of sulfur (S), selenium (Se), tellurium (Te), polonium (Po), or livermorium (Lv). In some embodiments, the chalcogenide precursor comprises one of more of sulfur (S), selenium (Se), tellurium (Te). In some embodiments, the chalcogenide precursor comprises H2S. In some embodiments, the chalcogenide precursor further comprises an inert gas, including, but not limited to, argon (Ar), helium (He), or nitrogen (N2). In some embodiments, the chalcogenide precursor further comprises hydrogen (H2). In some embodiments, the chalcogenide precursor does not comprise a plasma.

In one or more embodiments, the transition metal oxide film is exposed to a chalcogenide precursor comprising thermal Ar/H2S or H2/H2S gas. In one or more embodiments, the transition metal oxide film is exposed to a chalcogenide precursor comprising a plasma formed from Ar/H2S or H2/H2S gas. In one or more embodiments, the transition metal oxide film comprising tungsten (W) is converted to WS2by exposing the substrate surface to the chalcogenide precursor. In one or more embodiments, the transition metal oxide film comprising molybdenum (Mo) is converted to MoS2by exposing the substrate surface to the chalcogenide precursor.

In one or more embodiments, converting the transition metal oxide film to the TMDC film is conducted at a plasma power in a range of from 25 watts (W) to 500 watts (W).

In one or more embodiments, converting the transition metal oxide film to the transition metal dichalcogenide film is conducted at a temperature in a range of from about 150° C. to about 500° C., in a range of from about 150° C. to about 450° C., or in a range of from about 300° C. to about 450° C.

In some embodiments, converting the transition metal oxide film to the transition metal dichalcogenide film is performed at a pressure in a range of from 0.1 Torr to 100 Torr. In some embodiments, converting the transition metal oxide film to the transition metal dichalcogenide film is performed at a pressure in a range of from, for example, 1 Torr to 100 Torr, in a range of from 1 Torr to 50 Torr, in a range of from 1 Torr to 30 Torr, or in a range of from 1 Torr to 10 Torr. In some embodiments, the transition metal oxide film is exposed to a chalcogenide precursor comprising thermal or plasma Ar/H2S or H2/H2S gas in a range of from 1 Torr to 100 Torr.

In one or more embodiments, converting the transition metal oxide film to the transition metal dichalcogenide film is conducted for a time period in a range of from 1 minute to 60 minutes.

In one or more embodiments, the TMDC film is substantially free of oxygen. As used herein, “substantially free” means that there is less than or equal to about 5%, including less than or equal to about 4%, less than or equal to about 3%, less than or equal to about 2%, less than or equal to about 1%, or less than or equal to about 0.5% of oxygen, on an atomic basis, in the TMDC film. It is thought that the TMDC film that is formed without producing oxygen as a byproduct, thus advantageously minimizing the potential to etch/corrode underlying metal layers.

At operation122, the processing chamber or substrate surface is optionally purged to remove unreacted chalcogenide precursor, reaction products, and by products.

At decision130, the method100includes determining whether the thickness of the TMDC film, and/or number of cycles of the deposition process cycles110has been reached. If the TMDC film has reached a predetermined thickness or a predetermined number of cycles have been performed, the method100moves to an optional post-processing operation140. If the thickness of the TMDC film or the number of cycles has not reached the predetermined threshold, the method100returns to the beginning of the deposition process cycle110to form additional TMDC film.

In one or more embodiments, the method100further comprises repeating forming the transition metal oxide film in the first phase112and converting the transition metal oxide film to form a TMDC film in the second phase120with a final thickness of greater than or equal to 200 Å. In one or more embodiments, the TMDC film has a final thickness of greater than or equal to 150 Å, greater than or equal to 100 Å, or greater than or equal to 50 Å. In some embodiments, the TMDC film has a final thickness in a range of from 5 Å to 10 Å.

The optional post-processing operation140can be any suitable semiconductor manufacturing process known to the skilled artisan such as, for example, a process to modify film properties (e.g., annealing) or a further film deposition process (e.g., additional ALD or CVD processes) to grow additional films.

Advantageously, the transition metal oxide film can be deposited on the substrate surface (first phase112) and the transition metal oxide film can be converted to the TMDC film (second phase120) in situ or ex situ.

As used herein, the term “in situ” refers to processes that are all performed in the same processing chamber or within different processing chambers that are connected as part of an integrated processing system, such that each of the processes are performed without an intervening vacuum break. As used herein, the term “ex situ” refers to processes that are performed in at least two different processing chambers such that one or more of the processes are performed with an intervening vacuum break. In some embodiments, processes are performed without breaking vacuum or without exposure to ambient air.

The method100can be performed at any suitable temperature depending on, for example, the transition metal precursor, oxidant, chalcogenide precursor, or thermal budget of the device. In one or more embodiments, the use of high temperature processing may be undesirable for temperature-sensitive substrates, such as logic devices. In one or more embodiments, the substrate surface is maintained at a temperature in a range of about 150° C. to about 500° C., in a range of about 150° C. to about 450° C., or in a range of about 300° C. to about 450° C. during the entirety of the method100.

In some embodiments, exposure to the transition metal precursor (operation113) occurs at a different temperature than the exposure to the oxidant (operation115) or the chalcogenide precursor (operation121). In some embodiments, the substrate is maintained at a first temperature in a range of about 150° C. to about 300° C. for the exposure to the transition metal precursor and/or the oxidant, and at a second temperature in the range of about 300° C. to about 500° C. for the exposure to the chalcogenide precursor. In some embodiments, both the transition metal precursor and the chalcogenide precursor are delivered at the same substrate temperature.

According to one or more embodiments, the substrate is subjected to processing prior to and/or after forming the TMDC film. This processing can be performed in the same chamber or in one or more separate processing chambers. In some embodiments, the substrate is moved from the first chamber to a separate, second chamber for further processing. The substrate can be moved directly from the first chamber to the separate processing chamber, or it can be moved from the first chamber to one or more transfer chambers, and then moved to the separate processing chamber. Accordingly, the processing apparatus may comprise multiple chambers in communication with a transfer station. An apparatus of this sort may be referred to as a “cluster tool” or “clustered system,” and the like.

Generally, a cluster tool is a modular system comprising multiple chambers which perform various functions including substrate center-finding and orientation, degassing, annealing, deposition and/or etching. According to one or more embodiment, a cluster tool includes at least a first chamber and a central transfer chamber. The central transfer chamber may house a robot that can shuttle substrates between and among processing chambers and load lock chambers. The transfer chamber is typically maintained at a vacuum condition and provides an intermediate stage for shuttling substrates from one chamber to another and/or to a load lock chamber positioned at a front end of the cluster tool. Two well-known cluster tools which may be adapted for the present disclosure are the Centura® and the Endura®, both available from Applied Materials, Inc., of Santa Clara, Calif. However, the exact arrangement and combination of chambers may be altered for purposes of performing specific steps of a process as described herein. Other processing chambers which may be used include, but are not limited to, cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, chemical clean, thermal treatment such as RTP, plasma nitridation, degas, orientation, hydroxylation, and other substrate processes. By carrying out processes in a chamber on a cluster tool, surface contamination of the substrate with atmospheric impurities can be avoided without oxidation prior to depositing a subsequent film.

According to one or more embodiment, the substrate is continuously under vacuum or “load lock” conditions and is not exposed to ambient air when being moved from one chamber to the next. The transfer chambers are thus under vacuum and are “pumped down” under vacuum pressure. Inert gases may be present in the processing chambers or the transfer chambers. In some embodiments, an inert gas is used as a purge gas to remove some or all of the reactants (e.g., reactant). According to one or more embodiment, a purge gas is injected at the exit of the deposition chamber to prevent reactants (e.g., reactant) from moving from the deposition chamber to the transfer chamber and/or additional processing chamber. Thus, the flow of inert gas forms a curtain at the exit of the chamber.

The substrate can be processed in single semiconductor processing chamber, where a single substrate is loaded, processed, and unloaded before another substrate is processed. The substrate can also be processed in a continuous manner, similar to a conveyer system, in which multiple substrates are individually loaded into a first part of the chamber, move through the chamber, and are unloaded from a second part of the chamber. The shape of the chamber and associated conveyer system can form a straight path or curved path. Additionally, the processing chamber may be a carousel in which multiple substrates are moved about a central axis and are exposed to deposition, etch, annealing, cleaning, etc. processes throughout the carousel path.

During processing, the substrate can be heated or cooled. Such heating or cooling can be accomplished by any suitable means including, but not limited to, changing the temperature of the substrate support, and flowing heated or cooled gases to the substrate surface. In some embodiments, the substrate support includes a heater/cooler which can be controlled to change the substrate temperature conductively. In one or more embodiment, the gases (either reactive gases or inert gases) being employed are heated or cooled to locally change the substrate temperature. In some embodiments, a heater/cooler is positioned within the chamber adjacent the substrate surface to convectively change the substrate temperature.

The substrate can also be stationary or rotated during processing. A rotating substrate can be rotated (about the substrate axis) continuously or in discrete steps. For example, a substrate may be rotated throughout the entire process, or the substrate can be rotated by a small amount between exposures to different reactive or purge gases. Rotating the substrate during processing (either continuously or in steps) may help produce a more uniform deposition by minimizing the effect of, for example, local variability in gas flow geometries.

Referring now toFIG.2, a substrate200including a base material210having at least one feature220formed from a material230is shown. The surfaces of the base material210and the material230form the substrate surface. In some embodiments, the base material210and the material230are the same. In some embodiments, the base material210is a metal or other conductive material. In some embodiments, the material230is a dielectric material.

The Figures show a substrate200having three features for illustrative purposes; however, those skilled in the art will understand that there can be more or fewer than three features. In one or more embodiments, the substrate200comprises at least one feature220.

The feature220may define any suitable shape including, but not limited to, trenches and cylindrical vias. As used in this regard, the term “feature” means any intentional surface irregularity. Suitable examples of features include but are not limited to trenches, which have a top, two sidewalls and a bottom extending into the substrate, vias which have one or more sidewall extending into the substrate to a bottom, and slot vias. The features described herein can have any suitable aspect ratio (ratio of the height/depth to the width). In some embodiments, the aspect ratio is greater than or equal to about 5:1, 10:1, 15:1, 20:1, 25:1, 30:1, 35:1 or 40:1. In one or more embodiments, the aspect ratio is greater than or equal to about 10:1.

In one or more embodiments, the at least one feature220is a trench. In one or more embodiments, the at least one feature220comprises a dielectric material and a conductive material. In one or more embodiments, a transition metal oxide film forms selectively on the dielectric material (not shown).

Referring now toFIG.3, each of the at least one feature220shown inFIG.2has a transition metal dichalcogenide (TMDC) film240deposited thereon. The TMDC film240is deposited on or directly on the at least one feature220. In one or more embodiments, the TMDC film240is the TMDC film formed by the method100shown inFIG.1.

In one or more embodiments, the TMDC film240is conformally deposited on the at least one feature220. As used herein, as will be understood by the skilled artisan, a layer which is “conformal” or “conformally deposited” refers to a layer where the thickness is about the same throughout. A layer/film which is conformal varies in thickness by less than or equal to about 5%, 2%, 1% or 0.5%.

InFIGS.2and3, the substrate200having three features220has a gap between each of the features220. Gap fill processes are integral to several semiconductor manufacturing processes. A gap fill process can be used to fill a gap (or feature) with an insulating or conducting material. For example, shallow trench isolation, inter-metal dielectric layers, passivation layers, dummy gate, are all typically implemented by gap fill processes.

In one or more embodiments, the substrate200includes a metal fill250that is deposited on the TMDC film240to fill the gaps between each of the features220. In one or more embodiments, the metal fill250comprises a high-conductivity metal. In some embodiments, the metal fill250comprises one or more of copper (Cu), cobalt (Co), tungsten (W), molybdenum (Mo), or ruthenium (Ru).

In some embodiments, the metal fill250is substantially free of seams and/or voids. As used in this regard, “substantially free” means that less than about 5%, including less than about 4%, less than about 3%, less than about 2%, less than about 1%, less than about 0.5%, and less than about 0.1% of the total composition of the metal fill250on an atomic basis, comprises seams and/or voids.

The disclosure is now described with reference to the following examples. Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways.

EXAMPLES

Comparative Example 1

A transition metal dichalcogenide (TMDC) film was formed by depositing a transition metal oxide film on a substrate surface by sequentially exposing the substrate surface to a transition metal precursor and an oxidant, and converting the transition metal oxide film to the TMDC film. The transition metal precursor used includes bis(t-butylimino) bis(dimethylamino) tungsten(VI). The oxidants used include oxygen (O2), O2plasma, and ozone (O3), which may be referred to as “strong” oxidants. The substrate surface was purged after each exposure to remove unreacted transition metal precursor and oxidant, and byproducts. The substrate surface was maintained at a temperature of about 350° C. throughout the process. In specific experiments where the TMDC film was formed on a low-κ dielectric substrate surface, it was found that this process lowers the carbon (C) content of the low-κ dielectric substrate surface, resulting in a greater κ-value (from 2.7 to 3.3) and damage to the low-κ dielectric substrate surface. Accordingly, the TMDC film formed by the process was found to not be compatible for deposition on low-κ dielectric substrate surfaces.

A process following the operations of method100was performed to form a transition metal dichalcogenide (TMDC) film. The process included pre-treating a substrate surface, depositing a transition metal oxide film on the substrate surface by sequentially exposing the substrate surface to a transition metal precursor and an oxidant, and converting the transition metal oxide film to the TMDC film. The transition metal precursor used includes bis(t-butylimino) bis(dimethylamino) tungsten(VI). The oxidants used include one or more of an alcohol or deionized/deoxygenated water, which may be referred to as “mild” oxidants. In one or more experiments, isopropyl alcohol was used as the oxidant. The substrate surface was purged after each exposure to reacted transition metal precursor and oxidant and byproducts. The substrate surface was maintained at a temperature of about 350° C. throughout the process.

As described herein and with respect to Conventional Example 1, it has been observed that the substrate surface, such as, for example, a low-κ dielectric substrate surface, is sensitive to strong oxidants while growing the transition metal oxide film. It remains a challenge for the transition metal precursors to adsorb on inherently highly hydrophobic alkyl-group terminated dielectric surfaces. The process of Inventive Example 1, as in method100, comprises pre-treating the substrate surface at operation comprises a plasma treatment or ultraviolet (UV) radiation exposure to remove surface alkyl groups and make the low-κ dielectric surface suitable for precursor adsorption. Advantageously, the oxidant comprising one or more of an alcohol or deionized/deoxygenated water does not damage the low-κ dielectric surface. Additionally, use of the transition metal precursors and the oxidant comprising one or more of an alcohol or deionized/deoxygenated water advantageously enables uniform growth of the transition metal oxide film without modifying the properties of, or damaging the low-κ dielectric surface.