Void-Free Low-Stress Filling

Abstract

Described herein are methods and associated apparatus for depositing low-stress, void-free metal films in deep features. An embodiment of this method includes treating the sidewalls of the hole to inhibit metal deposition while leaving the bottom of the feature untreated. In a subsequent deposition operation, metal precursor molecules diffuse to the bottom of the feature for deposition. This process is repeated, with a subsequent inhibition operation treating the remaining exposed sidewalls. Repeating the inhibition and deposition operations results in high-quality, void-free fill. This allows for high-temperature, low-stress deposition to be performed.

Description

Background Art

[0001] [Cross - Reference to Related Applications] As part of this application, a PCT application is filed simultaneously with this specification. Each application that this application claims the benefit or priority recognized in the simultaneously filed PCT application is hereby incorporated by reference into this specification for all purposes.

[0002] The deposition of conductive materials such as tungsten films is an essential part of many semiconductor manufacturing processes. These materials may be used for horizontal interconnects, vias between adjacent metal layers, contacts between metal layers and devices on silicon substrates, and high aspect ratio features. In this industry, as devices are miniaturized and more complex patterning schemes are used, the deposition of thin films has become an issue. These issues include the deposition of void - free, low - stress films.

[0003] The description of the background art and content included in this specification is provided only for the purpose of generally presenting the content of the present disclosure. Most of the present disclosure represents the inventions of the inventors, and just because such inventions are described in this background art section or presented as technical content elsewhere in this specification does not mean that they are recognized as prior art.

Summary of the Invention

[0004] One aspect of the present disclosure relates to a method that includes providing a three-dimensional structure including metal lines disposed in a stepped pattern, a dielectric material covering the stepped pattern, and vertical alignment features providing fluid access to the metal lines; depositing a metal conformal layer on the vertical alignment features; exposing the metal conformal layer features to an etchant species at a first flow rate and a first exposure time in a first etch operation; after the first etch operation, depositing metal preferentially on the bottom of the vertical alignment features in a first non-conformal deposition operation, wherein the substrate temperature during the first non-conformal deposition operation is at least 400° C.; after the first non-conformal deposition operation, exposing the features to an etchant species at a second flow rate and a second exposure time in a second etch operation, wherein the second flow rate is less than the first flow rate and / or the second exposure time is shorter than the first exposure time; and after the second etch operation, depositing metal on the features at a substrate temperature of at least 400° C. in a second non-conformal deposition operation.

[0005] In some embodiments, the metal is one of tungsten, cobalt, molybdenum, and ruthenium. In some embodiments, the step of depositing metal preferentially on the bottom of the features includes exposing the features to a metal precursor and a reducing agent, and the volume ratio of the reducing agent to the metal precursor is at least 30:1. In some embodiments, the step of depositing metal preferentially on the bottom of the features includes exposing the features to a metal precursor at a flow rate of 100 sccm or less. In some embodiments, the features are interconnect features of a 3D NAND device. In some embodiments, the metal is tungsten and the substrate temperature during deposition is at least 430° C. In some embodiments, the metal is molybdenum and the substrate temperature during deposition is at least 600° C.

[0006] In some embodiments, the suppression species is a nitrogen-containing gas or a plasma species. In some embodiments, the first suppression operation processes most of the features. The first suppression operation processes at least 70% of the feature depth. In some embodiments, the substrate temperature is different during the first suppression operation and the second suppression operation.

[0007] Another aspect of the present disclosure relates to an apparatus for processing a substrate, the apparatus comprising: (a) a processing chamber comprising at least one station having a pedestal configured to hold the substrate; (b) at least one outlet for coupling to a vacuum; (c) one or more processing gas inlets coupled to one or more processing gas sources; (d) a controller for controlling the operation of the apparatus, the controller injecting a suppression species into the processing chamber at a first flow rate and a first exposure time in a first suppression operation, and after the first suppression operation, injecting a metal precursor and a reducing agent in a first non-conformal deposition operation to deposit a metal, the temperature of the pedestal on which the substrate is placed being at least 400° C., and after the first non-conformal deposition operation, injecting a suppression species into the processing chamber at a second flow rate and a second exposure time in a second suppression operation, the second flow rate being less than the first flow rate and / or the second exposure time being shorter than the first exposure time, and after the second suppression operation, injecting a metal precursor and a reducing agent to deposit a metal, the temperature of the pedestal on which the substrate is placed being at least 400° C., the controller comprising machine-readable instructions for implementing the method. In some embodiments, in the second non-conformal deposition operation, the metal is tungsten and the substrate temperature during deposition is at least 430° C. In some embodiments, the volume ratio of the reducing agent to the tungsten precursor during the first non-conformal deposition operation and the second non-conformal deposition operation is at least 30:1.

[0008] Another aspect of the present disclosure relates to a method that includes depositing a metal conformal layer on a feature on a substrate, treating a portion of the conformal layer to suppress subsequent tungsten nucleation, and after treating the portion of the conformal layer, preferentially depositing tungsten at the bottom of the feature, wherein the substrate temperature during deposition is at least 400° C., and repeating the treatment operation and the deposition operation one or more times to fill the feature with metal.

[0009] These and other aspects are described below with reference to the drawings.

Brief Description of the Drawings

[0010]

FIG. 1A

[0011]

FIG. 1B

[0012]

FIG. 2

[0013]

FIG. 3

[0014]

FIG. 4

[0015]

FIG. 5

Modes for Carrying Out the Invention

[0016] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to obscure the present invention needlessly. The present invention is described in connection with specific embodiments, but it will be understood that the intention is not to limit the present invention to these embodiments.

[0017] This specification describes methods of feature filling and related systems and devices. Examples of applications include contact filling of logic and memory, DRAM embedded word line filling, vertical integrated memory gate / word line filling, and three-dimensional integration by through-silicon vias (TSVs). In some embodiments, these methods may be used for tungsten feature filling. Such features can include vertical features such as vias, and horizontal features such as vertical NAND (VNAND) word lines.

[0018] In some embodiments of this specification, methods and related devices for depositing a void-free metal film with low stress in deep features are described. Embodiments of these methods include a step of treating the sidewalls of the holes so as to suppress metal deposition while leaving the bottom of the feature untreated. In subsequent deposition operations, metal precursor molecules diffuse to the bottom of the feature for deposition. This process is repeated together with the next suppression operation of treating the remaining exposed sidewalls. By repeating the suppression operation and the deposition operation, high-quality void-free filling can be achieved. This enables the implementation of deposition with low stress at high temperatures.

[0019] FIG. 1A shows an exemplary structure that can be filled with a conductive material using the feature filling method described herein. In the example of FIG. 1A, structure 102 is a 3D NAND device in a semi-finished product. Oxide layers 111 and word lines 140 of tungsten or other metals that alternate on substrate 100 are shown in a staircase structure. Five word lines 140 are depicted for ease of explanation, but depending on various embodiments, structure 102 may include any number of word lines, such as 48 word lines, 256 word lines, 512 word lines, or 1024 word lines. In some embodiments, the feature to be filled has a depth of at least 10 microns and may be deeper (e.g., 30 microns deep).

[0020] Oxide layer 122 is deposited on the staircase structure, and features 137 are etched into oxide layer 122. These features 137 may be filled with tungsten or other metals using the method described herein to provide interconnects to word lines 140. FIG. 1B shows interconnect 142 after the filling process.

[0021] Figure 2 is a flowchart depicting certain operations in a method of filling a feature. The method begins with operation 202 of depositing a conformal material layer on the feature. This layer can be a nucleation layer or a bulk layer that conforms to the feature. In certain embodiments, operation 202 may be omitted, for example, if the underlying feature surface is susceptible to subsequent inhibitor chemicals. In the example of tungsten, operation 202 may include exposing the feature to a tungsten precursor such as tungsten hexafluoride (WF6) and a reducing agent such as hydrogen (H2). Figure 3 shows an example of the feature after conformal deposition (conformal deposition 1 in the figure). Returning to Figure 2, the feature is then exposed to an inhibitor chemical with the exception of the feature bottom for conformal nucleation suppression (204). An example of operation 204 is represented in Figure 3 by the circle indicating the suppression surface (conformal suppression in the figure). The suppression surface is a surface on which subsequent nucleation of tungsten or other materials is suppressed, delaying or preventing deposition thereon. As can be seen from Figure 3, most of the feature except for the feature bottom and the short sidewalls extending upward from the bottom is suppressed. Depending on various embodiments, the suppression may extend to 99%, 95%, 90%, 80%, 70%, or 60% of the feature depth.

[0022] In some embodiments, operation 204 includes exposing the feature to a nitrogen-containing compound such as nitrogen (N2) or ammonia (NH3) in a thermal (non-plasma) operation. In another embodiment, the inhibitor chemical may be provided as plasma species generated by a remote plasma generator or a direct plasma generator.

[0023] Returning to Figure 2, a low stress film is deposited on the feature bottom (206). To deposit the low stress film, the feature may be exposed to a precursor and a reducing agent in a high temperature low precursor state. The low precursor state may be considered to have a volume flow ratio of reducing agent:precursor of at least 30:1. In some embodiments, a substrate temperature of at least 400 °C is used.

[0024] For tungsten deposition using WF6, a substrate temperature of at least 400 °C or at least 430 °C may be used, and WF6 of 100 sccm or less may be used. The chamber pressure may be 5 to 200 Torr. WF6 is supplied together with H2 and a carrier gas (such as argon (Ar)). The H2 and carrier gas flows are at least 10 times greater than the precursor flow. An exemplary range is that the flow rate of WF6 is less than 100 sccm, the flow rate of H2 is 3000 to 6000 sccm, and the flow rate of Ar is 4000 to 8000 sccm.

[0025] For Mo deposition, the temperature may be at least 450 °C (for example, 450 to 800 °C such as 600 to 750 °C).

[0026] Operation 204 may simultaneously expose both reactants so that two reactants flow simultaneously during deposition. For example, bulk tungsten may be deposited by simultaneously exposing the substrate to hydrogen (H2) and tungsten hexafluoride (WF6). Hydrogen and WF6 (or other metal precursors) react during exposure to deposit tungsten on the feature. In a pulsed CVD process, one reactant is flowed continuously and the other reactant is pulsed, but the substrate is exposed to both reactants during deposition to deposit material between each pulse. For example, the substrate may be exposed to a continuous flow of H2 while WF6 is pulsed, and WF6 and H2 react during the pulse to deposit tungsten. In some embodiments, operation 204 may include separately exposing each reactant so that two reactants do not flow into the chamber simultaneously during deposition. Rather, each reactant stream is introduced in turn in discrete pulses temporarily separated in the chamber containing the substrate and repeated one or more times in a cycle. In such embodiments, a low precursor state may be practiced by using more reducing agent pulses and / or volumetric flow rates during the pulse.

[0027] Deposition at a low precursor state and high temperature results in a low stress film, but these conditions also make feature filling difficult because the small amount of precursor used in the reaction reacts on the nearest possible reaction surface. Without suppression, the precursor would be used up at the top of the feature, closing the feature to further diffusion and forming voids. Thus, suppression of the above operation prevents reaction on the sidewall surface and guides the precursor to the bottom of the feature for reaction. This is shown in Figure 3 by a second deposition (Deposition 2) that deposits material at the bottom of the feature (see suppression after Deposition 2). Returning to Figure 2, operations 204 and 206 are repeated one or more times (208). This is shown in Figure 3 (Deposition 2 + suppression and Deposition 3). As depicted in Figure 3, the suppression gradually disappears during deposition.

[0028] Each successive suppression may be considered "non-conformal" compared to the previous deposition in that it extends to a shallower depth to accommodate film growth at the bottom of the feature. To control the suppression depth, the temperature and suppression gas flow rate may be adjusted to a higher temperature and lower flow rate that results in a shallower depth. However, since the substrate temperature is generally determined by deposition requirements, the suppression flow rate may be varied.

[0029] In some embodiments, operations 204 and 206 are repeated until the feature is completely filled. In some embodiments, operations 204 and 206 may be repeated to partially fill the feature by bottom-up filling and then perform a longer CVD deposition for final feature filling. Non-conformal suppression may be implemented for suppression deposition at the top of a reentrant feature as depicted in Figure 3.

[0030] The deposition operation and the suppression operation may be performed in the same or different processing chambers. Further, when performed in a multi-station chamber, they may be performed in the same or different stations. In some embodiments, one or more deposition suppression cycles are performed at the same station of the multi-station chamber. For example, the feature filling operation includes six deposition / suppression cycles, and the final CVD filling operation may be performed in a four-station chamber with two deposition / suppression cycles at station 1, two deposition / suppression cycles at station 2, two deposition / suppression cycles at station 3, and CVD deposition and nucleation layer deposition at station 4.

[0031] In some embodiments, the method described herein includes the step of depositing a tungsten nucleation layer prior to the deposition of the bulk layer. In the examples described herein, the nucleation layer may be deposited as a first conformal deposition or as a seed layer for the first conformal deposition. The nucleation layer is a thin conformal layer that promotes the deposition of subsequent bulk tungsten-containing materials. According to various embodiments, the nucleation layer may be deposited before feature filling and / or at subsequent times during feature filling. In some embodiments of the method described herein, the nucleation layer is deposited only at the start of feature filling and is not required for subsequent depositions.

[0032] In certain embodiments, the nucleation layer is deposited using pulse nucleation layer (PNL) technology. In PNL technology, pulses of a reducing agent, any purge gas, and a tungsten-containing precursor are continuously injected into the reaction chamber and purged from the reaction chamber. This process is periodically repeated until the desired thickness is achieved. PNL generally embodies any cyclic process that sequentially adds reactants for reactions on a semiconductor substrate, including atomic layer deposition (ALD) technology. The thickness of the nucleation layer may depend on not only the nucleation layer deposition method but also the bulk deposition of the desired quality. Generally, the thickness of the nucleation layer is sufficient to support high-quality and uniform bulk deposition. An example thereof may be in the range of 10 to 100 Å.

[0033] Examples of PNL deposition have been described above, but the methods described herein are not limited to a particular tungsten nucleation layer deposition method and include the deposition of a bulk tungsten film onto a tungsten nucleation layer formed by any method including PNL, ALD, CVD, and physical vapor deposition (PVD). Also in certain embodiments, bulk tungsten may be deposited directly onto the feature without using a nucleation layer. For example, in some embodiments, the feature surface and / or an already deposited underlying layer support bulk tungsten deposition. In some embodiments, a bulk tungsten deposition process without using a nucleation layer may be implemented.

[0034] In various embodiments, tungsten nucleation layer deposition may include exposure to tungsten-containing precursors such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), and tungsten hexacarbonyl (W(CO)6). In certain embodiments, the tungsten-containing precursor is a halogen-containing compound such as WF6. Organometallic precursors and fluorine-free precursors such as MDNOW (methylcyclopentadienyl-dicarbonylnitrosyl-tungsten) and EDNOW (ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten) may also be used.

[0035] Examples of reducing agents can include boron-containing reducing agents including diborane (B2H6) and other boranes, silicon-containing reducing agents including silane (SiH4) and other silanes, hydrazine, and germanium. In some embodiments, pulses of the tungsten-containing precursor can be alternating with pulses of one or more reducing agents (e.g., S / W / S / W / B / W etc. (W is the tungsten-containing precursor, S is the silicon-containing precursor, B is the boron-containing precursor)). In some embodiments, another reducing agent may not be used (e.g., the tungsten-containing precursor may be subject to thermal decomposition or plasma-assisted decomposition).

[0036] In various embodiments, hydrogen may or may not be flowed on the back side. Further, in some embodiments, one or more processing operations may follow the deposition of the tungsten nucleation layer and precede the tungsten bulk deposition. Treating the deposited tungsten nucleation layer to a lower resistivity may include pulses of a reducing agent and / or a tungsten precursor.

[0037] Bulk deposition In many embodiments, tungsten bulk deposition can occur by a CVD process in which a reducing agent and a tungsten-containing precursor are flowed into a deposition chamber to deposit a bulk fill layer on a feature. An inert carrier gas may be used to supply one or more reactant streams, and the one or more reactant streams may or may not be premixed. Unlike a PNL or ALD process, this operation generally involves continuously flowing reactants until a desired amount is deposited. In certain embodiments, the CVD operation may be performed in multiple stages, and the multiple periods of continuous and simultaneous flow of reactants are separated by periods of one or more branched reactant streams.

[0038] Various tungsten-containing gases including, but not limited to, WF6, WCl6, and W(CO)6 can be used as the tungsten-containing precursor. In certain embodiments, the tungsten-containing precursor is a halogen-containing compound such as WF6. In certain embodiments, the reducing agent is hydrogen gas, although other reducing agents including silane (SiH4), disilane (Si2H6), hydrazine (N2H4), diborane (B2H6), and germane (GeH4) may be used. In many embodiments, hydrogen gas is used as the reducing agent in the CVD process. In some other embodiments, a tungsten precursor that can be decomposed to form a bulk tungsten layer can be used. Bulk deposition may occur using other types of processes including an ALD process.

[0039] The tungsten films described herein may contain some other compounds, dopants and / or impurities (such as nitrogen, carbon, oxygen, boron, phosphorous acid, sulfur, silicon, germanium, etc.) depending on the particular precursors and processes used. The tungsten content in the film may be 20 - 100 (atomic)% tungsten. In many embodiments, the film is high tungsten content having at least 50 (atomic)% tungsten, or at least about 60, 75, 90, or 99 (atomic)% tungsten.

[0040] The above description focuses on tungsten feature fill, but aspects of the present disclosure may be implemented in feature fill with other materials. For example, feature fill using one or more of the techniques described herein may be used to fill features with other tungsten-containing materials (such as tungsten nitride (WN) and tungsten carbide (WC)), titanium-containing materials (such as titanium (Ti), titanium nitride (TiN), titanium silicide (TiSi), titanium carbide (TiC), and titanium aluminum (TiAl)), tantalum-containing materials (such as tantalum (Ta) and tantalum nitride (TaN)), nickel-containing materials (such as nickel (Ni) and nickel silicide (NiSi)), cobalt-containing materials (such as cobalt (Co)), ruthenium-containing materials (such as ruthenium (Ru)), and molybdenum-containing materials (such as molybdenum (Mo)).

[0041] CVD and ALD deposition of these materials can include using any suitable precursors. For example, CVD and ALD deposition of tungsten nitride can include using tungsten-containing compounds and nitrogen-containing compounds. CVD and ALD deposition of titanium-containing layers can include using titanium-containing precursors such as tetrakis(dimethylamino)titanium (TDMAT) and titanium chloride (TiCl4), and can include using one or more co-reactants if necessary. CVD and ALD deposition of tantalum-containing layers can include using precursors such as pentakis-dimethylaminotantalum (PDMAT) and TaF5, and can include using one or more co-reactants if necessary. CVD and ALD deposition of cobalt-containing layers can include using precursors such as tris(2,2,6,6-tetramethyl-3,5-heptanedionato)cobalt, bis(cyclopentadienyl)cobalt, and dicobalt hexacarbonyl butylacetylene, and one or more co-reactants.

[0042] Examples of cobalt precursors include dicarbonyl cyclopentadienyl cobalt, cobalt carbonyl, cobalt amidinate precursors, cobalt diazadienyl complexes, and cobalt amidinate / guanidinato precursors.

[0043] Examples of ruthenium precursors that can be used in the oxidation reaction include (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)Ru(0), (2,3-dimethyl-1,3-butadienyl)Ru(0) tricarbonyl, (1,3-cyclohexadienyl)Ru(0) tricarbonyl, and (cyclopentadienyl)(ethyl)Ru(II) dicarbonyl. Examples of ruthenium precursors that can be used in the oxidation reaction include (ethylbenzyl)(1-ethyl-1,4-cyclohexadienyl)Ru(0), (1-isopropyl-4-methylbenzyl)(1,3-cyclohexadienyl)Ru(0), (2,3-dimethyl-1,3-butadienyl)Ru(0) tricarbonyl, (1,3-cyclohexadienyl)Ru(0) tricarbonyl, and (cyclopentadienyl)(ethyl)Ru(II) dicarbonyl. Examples of ruthenium precursors that react with non-oxidizing reactants are bis(5-methyl-2,4-hexanedionato)Ru(II) dicarbonyl and bis(ethylcyclopentadienyl)Ru(II).

[0044] Examples of nickel precursors include cyclopentadienylallylnickel (CpAllylNi) and MeCp2Ni.

[0045] Examples of molybdenum precursors include molybdenum hexafluoride (MoF6), molybdenum pentachloride (MoCl5), molybdenum dioxide dichloride (MoO2Cl2), molybdenum oxychloride tetrachloride (MoOCl4), and molybdenum hexacarbonyl (Mo(CO)6). Examples of co-reactants can include N2, NH3, N2H4, N2H6, SiH4, Si3H6, B2H6, H2, and AlCl3.

[0046] The metal-containing precursor may react with a reducing agent as described above. In some embodiments, H2 is used as a reducing agent for bulk layer deposition to deposit a high-purity film.

[0047] Suppression of nucleation Inhibition may involve exposure of the feature surface to reactive species that passivate the surface. For example, in certain embodiments, a tungsten (W) surface can be passivated by exposure to a nitrogen-based plasma or a hydrogen-based plasma. In some embodiments, inhibition may involve a chemical reaction between the reactive species and the feature surface to form a thin layer of a composite material such as tungsten nitride (WN) or tungsten carbide (WC). In some embodiments, inhibition may involve surface effects such as adsorption that passivate the surface without forming a layer of the composite material. The reactive species may be formed by any suitable method including plasma generation and / or exposure to ultraviolet (UV) light. In some embodiments, a substrate comprising the feature is exposed to a plasma generated from one or more gases supplied to the chamber on which the substrate is placed. In some embodiments, the one or more gases may be supplied to a remote plasma generator, and the reactive species formed in the remote plasma generator are supplied to the chamber on which the substrate is placed. The plasma source can be any type of source including a radio frequency (RF) plasma source or a microwave source. The plasma can be inductively and / or capacitively coupled. The reactive species can include atomic species, radical species, and ionic species. In certain embodiments, exposure to a remotely generated plasma involves exposure to radical species and sputtered species, and there are substantially no ionic species present in the plasma so that the inhibition process is not ion-mediated. In other embodiments, ionic species may be present in the remotely generated plasma. In certain embodiments, exposure to an in-situ plasma involves ion-mediated inhibition.

[0048] For the W surface, exposure to nitrogen-based plasma and / or hydrogen-based plasma suppresses subsequent tungsten deposition on the W surface. Other chemical substances that can be used for the suppression of the tungsten surface include oxygen-based plasma and hydrocarbon-based plasma. For example, oxygen molecules or methane molecules may be introduced into the plasma generator. Similarly, nitrogen-containing chemical substances may also suppress the nucleation of other metals described herein, including Mo, Co, and Al. The nitrogen-based plasma used herein is a plasma in which the main non-inert component is nitrogen. Inert components such as argon, xenon, or krypton may be used as carrier gases. In some embodiments, there are no other non-inert components in the gas in which the plasma is generated, except for trace amounts. In some embodiments, the suppression chemical substance may be nitrogen-containing, hydrogen-containing, oxygen-containing, and / or carbon-containing, and there may be one or more additional reactive species in the plasma.

[0049] For example, when active fluorine radicals react with tungsten in the feature opening to remove tungsten, the nitrogen generated from NF3 plasma using NF3 plasma can cause nitridation of the tungsten surface to form tungsten nitride. Subsequent deposition of tungsten on the nitrided surface is significantly delayed compared to normal bulk tungsten film. The longer delay allows the feature to remain open for a longer time before pinch-off, enabling more WF6 molecules to reach the inside of the feature and deposit tungsten, thus promoting improved filling. In addition to NF3, fluorocarbons such as CF4 or C2F8 may be used. However, in certain embodiments, the suppression species is fluorine-free to prevent etching during suppression.

[0050] In certain embodiments, UV light and / or thermal energy may be used instead of, or in addition to, a plasma generator to provide the active species. In addition to the tungsten surface, nucleation on the surface of a liner layer / barrier layer such as a TiN and / or WN surface may be suppressed. Any chemical substance that passivates these surfaces may be used. This may include exposure to nitrogen-based or nitrogen-containing chemical substances for TiN and WN. In certain embodiments, the chemical substances described above for W may be employed on the surface of TiN, WN, or other liner layers. In some embodiments, the suppression includes exposure to NH3 in non-plasma operation.

[0051] Adjustment of the suppression profile may include appropriate control of the suppression chemical, substrate bias power, plasma power, process pressure, exposure time, and other process parameters. In an in-situ plasma process (or other process where ionic species are present), a bias may be applied to the substrate. In some embodiments, the substrate bias significantly affects the suppression profile, and an increase in bias power can bring the active species deeper inside the feature. In a three-dimensional structure where selectivity is required in the lateral rather than the vertical direction (tungsten deposition is preferred inside the structure), increased bias power may be used to promote uniformity of deposition from top to bottom.

[0052] Bias power may be used as fundamental or as a knob only to adjust the suppression profile of ionic species in certain embodiments, but in certain situations, adjustment of the suppression profile uses other parameters in addition to, or instead of, bias power. These include remotely generated non-ionic plasma processes and non-plasma processes. Also, in many systems, the substrate bias can be easily applied to adjust lateral selectivity rather than vertical selectivity. Thus, in a three-dimensional structure where lateral selectivity is desired, parameters other than bias may be controlled as described above.

[0053] The inhibiting chemical is also used to adjust the inhibition profile, and different ratios of active inhibiting species can be used. For example, for the inhibition of the W surface, nitrogen may have a stronger inhibitory effect than hydrogen, and adjustment of the ratio of N2 to H2 in a forming gas plasma can be used to adjust the profile. Plasma power is also used to adjust the inhibition profile with different ratios of active species adjusted by the plasma power. For example, in certain embodiments described herein, nitrogen radical formation and resulting W-N formation, as well as the associated passivation effect, can be adjusted by changing the plasma power. Changing the plasma power also enables control of the resistivity of the final W film.

[0054] Pressure can be used to adjust the profile because it can not only cause more recombination (inactivation of active species), but also push the active species deeper into the feature. Process time may be used to adjust the inhibition profile, and an increase in the processing time results in deeper inhibition of the feature.

[0055] In some embodiments, non-conformal inhibition can be achieved in the mass transport rate-limiting regime. In this regime, the inhibition rate inside the feature is rate-limited by the amount and / or relative composition of different inhibiting material components (e.g., initial inhibiting species, active inhibiting species, and recombination inhibiting species) diffusing into the feature. In a specific example, the inhibition rate depends on the various component concentrations at different positions inside the feature.

[0056] The mass transport rate-limiting condition may be partially characterized by the overall suppression concentration change. In certain embodiments, the concentration is lower inside the feature than near the opening of the feature, resulting in a higher suppression rate near the opening than inside. This in turn results in preferential suppression near the feature opening. The mass transport rate-limiting process condition is achieved by supplying a limited amount of suppression species to the processing chamber while maintaining a relatively high suppression rate near the feature opening, since the suppression species consume some of the active species as they diffuse into the feature (e.g., using a low suppression gas flow rate relative to the cavity profile and dimensions). In certain embodiments, the concentration gradient may be large, causing relatively high suppression kinetics and relatively low suppression supply. In certain embodiments, the suppression rate near the opening may be mass transport rate-limited.

[0057] The suppression profile may be affected by the relative concentrations of different suppressing species across the feature, in addition to the overall suppression concentration change within the feature. These relative concentrations may similarly depend on the relative kinetics of the dissociation and recombination processes of the suppressing species. As described above, initial suppression materials such as nitrogen molecules can pass through a remote plasma generator and / or have in-situ plasma applied to generate active species (e.g., nitrogen atoms, nitrogen ions). However, the active species may recombine with recombination species of reduced activity (e.g., nitrogen molecules) and / or react with the W, WN, TiN, or other feature surfaces along the diffusion path. Therefore, different portions of the feature may be exposed to different concentrations of different suppression materials (e.g., initial suppression gas, active suppression species, and recombination suppression species). This provides additional opportunities to control the suppression profile. For example, active species are generally more reactive than the initial suppression gas and recombination suppression species. Additionally, in some cases, the active species may be less affected by temperature changes than the recombination species. Thus, the process conditions may be controlled such that removal is primarily brought about by the active species. As noted above, some species may be more reactive than others. Additionally, certain process conditions may result in a higher concentration of active species near the opening of the feature than within the feature. For example, some active species may be consumed (e.g., react with the feature surface material and / or adsorb to the surface) and / or recombine while diffusing deeper through particularly fine, high aspect ratio features. Recombination of the active species may also occur outside the feature (e.g., in the showerhead or process chamber) and may depend on the chamber pressure. Thus, the chamber pressure may be controlled to regulate the concentration of active species at various points in the chamber and feature.

[0058] In certain embodiments, the substrate can be heated or cooled prior to suppression. The predetermined temperature of the substrate can be selected to induce a chemical reaction between the feature surface and the suppression species and / or to promote the adsorption of the suppression species and control the rate of the reaction or adsorption. For example, the temperature may be selected to have a high reaction rate such that more suppression occurs near the opening than inside the feature. Further, the temperature may be selected to control the recombination of the active species (e.g., recombination of nitrogen atoms to nitrogen molecules) and / or to control the species that mainly contribute to suppression (e.g., active species or recombination species). In certain embodiments, the substrate is maintained at less than about 300 °C, or more specifically less than about 250 °C, or less than about 150 °C, or less than about 100 °C. In other embodiments, the substrate is heated from about 300 °C to 450 °C, and in more specific embodiments, from about 350 °C to 400 °C. Other temperature ranges may be used for different types of suppression chemicals. In some embodiments, the suppression temperature may be the same as the deposition temperature which may be relatively high to deposit a low stress film. However, in some embodiments, a multi-station chamber is used such that deposition and suppression are performed at different stations. Thereby, a temperature difference between operations can be promoted.

[0059] As described above, in some embodiments, a thermal suppression process is used. The thermal suppression process can include exposing the feature to a nitrogen-containing compound such as ammonia (NH3) or hydrazine (N2H4) to suppress the feature conformally or non-conformally. In some embodiments, the thermal suppression process is performed at a temperature of 250 °C to 450 °C. At these temperatures, exposure of the previously formed tungsten nucleation layer to NH3 results in a suppression effect. For thermal suppression at higher temperatures (e.g., 900 °C), other potential suppression chemicals such as nitrogen (N2) or hydrogen (H2) may be used. However, in many applications, these high temperatures exceed the thermal budget. In addition to ammonia, other hydrogen-containing nitriding agents such as hydrazine may be used at low temperatures suitable for back-end-of-line (BEOL) wiring formation applications.

[0060] Since the thermal suppression process does not use plasma, bias power on the substrate cannot be used to adjust the suppression profile. However, by appropriately adjusting one or more of the chamber pressure, flow rate, dose time, and temperature, the suppression profile can be adjusted as desired. As described above, in some embodiments, a mass transport rate-limiting region is employed. In some embodiments, the chamber pressure may be from 0.5 Torr to 40 Torr. As noted above, the flow rate of the suppression gas can depend on the size of the chamber, the reaction rate, and other parameters. The flow rate can be selected such that more suppression material concentrates near the openings rather than inside the features. In certain embodiments, these flow rates result in selective suppression of mass transport rate-limiting.

[0061] An increase in pressure and a decrease in flow rate and dose time result in a more non-conformal (i.e., more selective by feature openings) suppression profile. While high pressure results in a decrease in the mean free path, a decrease in flow rate and dose time limits the molecular weight consumed. An increase in temperature results in a more non-conformal suppression profile, with more suppression molecules being consumed at the top of the feature. The profile may be adjusted as described above depending on whether a pinching point is within the feature. An example of the dose time is from 0.5 seconds to 10 seconds.

[0062] In some embodiments, the suppression can include a chemical reaction between a thermal suppression species and the feature surface to form a thin layer of a WN composite material. In some embodiments, the suppression can include surface effects such as adsorption that passivate the surface without forming a layer of the composite material.

[0063] The metal nucleation layer, if present, may be exposed to NH3 or other suppressant vapors to suppress features. In some embodiments, if a bulk tungsten layer or tungsten-containing layer is present, a reducing agent / tungsten-containing precursor / nitrogen-containing suppressant chemical may be employed to form WN in the bulk layer. These reducing agents may be introduced in sequence (e.g., pulses of B2H6 / WF6 / NH3) or simultaneously. Any suitable reducing agent (e.g., diborane or silane) and any suitable tungsten-containing precursor (e.g., tungsten hexafluoride or tungsten hexacarbonyl) may be used. Thermal processes may be used to avoid damage that can occur with the use of plasma.

[0064] In the methods described herein, the suppression profile may be controlled by the temperature and / or flow rate of the suppressant gas. The high temperatures used for the deposition of low stress films can lead to more suppressant species being consumed at the top of the features. Higher flow rates may be used for deeper suppression (e.g., the suppression used in the early cycle suppression operations). The flow rate of the suppressant gas may depend on the size of the chamber, the reaction rate, and other parameters. The flow rate may be selected such that more suppressant material is concentrated near the openings rather than inside the features. The exposure time may likewise be selected to result in a particular suppression profile. Exemplary exposure times can range from about 10 seconds to 500 seconds, depending on the desired selectivity and feature depth. The flow rate and / or exposure time may decrease with successive cycles to produce shallower suppression.

[0065] Apparatus Any suitable chamber may be used to implement the disclosed embodiments. Exemplary deposition apparatuses include various systems (e.g., ALTUS® and ALTUS® Max available from Lam Research Corporation, Fremont, California), or any of a variety of other commercially available processing systems.

[0066] Figure 4 is a block diagram of a processing system suitable for performing a deposition process according to an embodiment. System 400 includes a transfer module 403. The transfer module 403 provides a clean pressurized environment to minimize the risk of contamination when the substrate being processed moves between various reactor modules. Attached to the transfer module 403 is a multi-station reactor 409 capable of performing ALD, CVD, and suppression processes according to an embodiment. The multi-station reactor 409 may include a plurality of stations, 411, 413, 415, and 417, that can continuously perform operations according to the disclosed embodiments. For example, the multi-station reactor 409 can be configured such that station 411 performs ALD nucleation and suppression, stations 413 and 415 each perform a plurality of CVD and suppression cycles, and station 417 performs CVD. In another example, the multi-station reactor 409 is configured such that station 411 performs ALD nucleation, station 413 performs suppression, station 415 performs ALD or CVD deposition, and station 417 performs CVD.

[0067] A station may include a heated pedestal or substrate support, one or more gas inlets, or a showerhead or dispersion plate. FIG. 5 depicts an example of a deposition station 500 including a substrate support 502 and a showerhead 503. The pedestal portion 501 may be provided with a heater. The pedestal 501 may include a chuck for clamping the wafer. In certain embodiments, an electrostatic chuck or a mechanical chuck rather than a vacuum chuck may be used to facilitate providing a low-pressure environment. The gas may be exhausted from the deposition station 500 through an exhaust port (not shown).

[0068] The transfer module 403 may be attached with one or more single or multiple station modules 407 capable of performing plasma pre - cleaning or chemical (non - plasma) pre - cleaning. This module may be used for various processes to prepare the substrate for, for example, the deposition process. The system 400 may include one or more wafer source modules 401 where wafers are stored before and after processing. The atmospheric robot (not shown) in the atmospheric transfer chamber 419 may first take the wafer out from the source module 401 and load it into the load lock 421. The wafer transfer device (generally, a robot arm unit) of the transfer module 403 transfers the wafer from the load lock 421 to the modules attached to the transfer module 403 and moves it between those modules.

[0069] In various embodiments, the system controller 429 is used to control the process conditions during deposition. The controller 429 will typically include one or more storage devices and one or more processors. The processor may include a CPU or a computer, analog and / or digital input / output connections, a stepper motor control board, etc.

[0070] The controller 429 may control all operations of the deposition apparatus. The system controller 429 executes system control software that includes a set of instructions for controlling timing, gas mixing, chamber pressure, chamber temperature, wafer temperature, wafer chuck or pedestal position, and other parameters of a particular process. In some embodiments, other computer programs stored in the storage device associated with the controller 429 may be used.

[0071] Typically, there will be a user interface associated with the controller 429. The user interface may include a display screen, an image software display device of the apparatus and / or process conditions, and a user input device (e.g., a pointing device, a keyboard, a touch screen, a microphone, etc.).

[0072] The system control logic may be configured in any suitable manner. Generally, the logic can be designed or configured in hardware and / or software. Instructions for controlling the drive circuit may be hard-coded or provided as software. The instructions may be provided by "programming". Such programming is understood to include any form of logic including hard-coded logic in a digital signal processor, an application specific integrated circuit, and other devices having specific algorithms implemented as hardware. Programming is also understood to include software or firmware instructions executable on a general purpose processor. The system control software may be coded in any suitable computer-readable programming language.

[0073] Computer program code for controlling pulses of germanium-containing reducing agent, hydrogen flow, pulses of tungsten-containing precursor, and other processes in the process sequence may be written in any conventional computer-readable programming language (e.g., assembly language, C, C++, Pascal, Fortran, or others). The compiled object code or script is executed by the processor to perform the tasks identified in the program. As described above, the program code may also be hard-coded.

[0074] The controller parameters relate to process conditions such as, for example, the composition and flow rate of the process gas, temperature, pressure, cooling gas pressure, substrate temperature, and chamber wall temperature. These parameters may be provided to the user in the form of a recipe and may be input using the user interface.

[0075] Signals for monitoring the process may be provided by the analog and / or digital input connections of the system controller 429. Signals for controlling the process are output at the analog-digital output connections of the system 400.

[0076] System software may be designed or configured in many different ways. For example, subroutines or control objects of various chamber components may be written to the control operations of the chamber components necessary to perform the deposition process according to the disclosed embodiments. Examples of programs or program sections for this may include substrate positioning code, process gas control code, pressure control code, and heater control code.

[0077] In some embodiments, the controller 429 is part of a system that may be part of the examples described above. Such a system may include a semiconductor processing apparatus having a processing tool, a chamber, a processing platform, and / or specific processing components (such as a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling the operation of the semiconductor wafer or substrate before, during, and after processing. These electronics are referred to as "controllers" and may control various components or sub-components of the system. The controller 429 may be programmed to control any process disclosed herein, including the supply of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, power settings, flow rate settings, fluid supply settings, position movement settings, wafer loading and unloading to the tool and other transfer tools, and / or wafer loading and unloading to a load lock connected or coupled to a particular system, depending on the processing conditions and / or the type of system.

[0078] Generally, a controller may be defined as an electronic device having various integrated circuits, logic, memory, and / or software that receives instructions, issues instructions, controls operations, enables a cleaning operation, enables endpoint measurement, etc. The integrated circuit may include a chip in the form of firmware that stores program instructions, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). The program instructions are instructions transmitted to the controller in the form of various individual settings (or program files) that may define operating parameters for performing a particular process on or for a semiconductor wafer or for a system. In some embodiments, the operating parameters may be part of a recipe defined by a process engineer to implement one or more processing steps during the manufacture of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and / or wafer dies.

[0079] In some embodiments, the controller 429 may be part of a computer that is integrated with or coupled to the system, otherwise network-connected to the system, or a combination thereof, or may be coupled to such a computer. For example, the controller 429 may be in a "cloud" that enables remote access to wafer processing, or may be all or part of a fab host computer system. The computer enables remote access to the system, monitors the progress of manufacturing operations, examines the history of past manufacturing operations, examines trends or implementation criteria from multiple manufacturing operations, changes the parameters of the current process, sets the process steps following the current process, or starts a new process. In some examples, a remote computer (e.g., a server) can provide a process recipe to the system through a network that can include a local network or the Internet. The remote computer may include a user interface that enables parameters and / or setting entries or programming to be transmitted from the remote computer to the system. In some examples, the controller receives instructions in a data format that specify the parameters of each process step performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool that the controller is configured to connect to or control. Thus, as described above, the controller may be distributed by, for example, including one or more separate controllers network-connected to each other and cooperating towards a common purpose such as the processes and controls described herein. An example of a controller distributed for such a purpose would be one or more integrated circuits of a chamber that are installed remotely (e.g., at the platform level or as part of a remote computer) and communicate with one or more integrated circuits to cooperate in controlling the process in the chamber.

[0080] Rather than being restrictive, the exemplary system may include a plasma etching chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etching chamber or module, a PVD chamber or module, a CVD chamber or module, an ALD chamber or module, an atomic layer etching (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and other semiconductor processing systems that may be related or used in the fabrication and / or manufacture of semiconductor wafers.

[0081] As described above, depending on the processing steps performed by the tool, the controller may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools installed throughout the factory, main computers, other controllers, or tools used for material transport for loading and unloading wafer containers with respect to tool positions and / or load ports in a semiconductor manufacturing facility.

[0082] The controller 429 may comprise various programs. The substrate positioning program may include program code for controlling chamber components used to load a substrate onto a pedestal or chuck and to control the space between the substrate and other chamber components (e.g., gas inlets and / or targets). The process gas control program may include code for controlling gas composition, flow rate, and pulse time, and may optionally include code for flowing gas into the chamber prior to deposition to stabilize the chamber pressure. The pressure control program may include code for controlling the chamber pressure, for example, by adjusting a throttle valve in the chamber's exhaust system. The heater control program may include code for controlling the current to a heating device used to heat the substrate. Alternatively, the heater control program may control the supply of a heat transfer gas, such as helium, to the wafer chuck.

[0083] Examples of chamber sensors that may be monitored during deposition include mass flow controllers, pressure sensors such as pressure gauges, and thermocouples installed on the pedestal or chuck. Feedback control algorithms appropriately programmed with data from these sensors may be used to maintain desired process conditions.

[0084] The foregoing has described the implementation of embodiments of the disclosure in a single-chamber or multi-chamber semiconductor processing tool. The apparatuses and processes described herein may be used in conjunction with, for example, lithography patterning tools or lithography patterning processes for the fabrication or manufacture of semiconductor devices, display devices, LEDs, solar cell panels, and the like. Typically, but not necessarily, such tools / processes will be used together or executed in a common manufacturing facility. Lithographic patterning of a film typically includes some or all of the following steps: (1) applying a photoresist to a workpiece (i.e., a substrate) using a spin-on tool or a spray-on tool; (2) curing the photoresist using a hot plate, a furnace, or a UV curing tool; (3) exposing the photoresist to visible light, UV light, or X-ray light using a tool such as a wafer stepper; (4) patterning the resist by developing the resist and selectively removing the resist using a tool such as a wet bench; (5) transferring the resist pattern to an underlying film or workpiece using a dry etching tool or a plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF plasma resist stripper or a microwave plasma resist stripper. Each step may be performed using several possible tools. The present disclosure may be implemented in the following forms. [Form 1] A method comprising: providing a three-dimensional structure on a substrate, the three-dimensional structure including metal lines arranged in a stepped pattern, a dielectric material covering the stepped pattern, and vertical alignment features having feature sidewalls and a feature bottom, the vertical alignment features providing fluid access to the metal lines at the feature bottom; depositing a metal conformal layer on the vertical alignment features; exposing the metal conformal layer to a suppressing species at a first flow rate and a first exposure time in a first suppression operation; after the first suppression operation, preferentially depositing metal on the bottom of the vertical alignment features in a first non-conformal deposition operation, the temperature of the substrate during the first non-conformal deposition operation being at least 400° C.; after the first non-conformal deposition operation, exposing the vertical alignment features to a suppressing species at a second flow rate and a second exposure time in a second suppression operation, the second flow rate being less than the first flow rate and / or the second exposure time being shorter than the first exposure time; after the second suppression operation, depositing metal on the features at a substrate temperature of at least 400° C. in a second non-conformal deposition operation; A method comprising the above steps. [Form 2] The method according to Form 1, wherein the metal is one of tungsten, cobalt, molybdenum, and ruthenium. [Form 3] The method according to Form 1 or Form 2, wherein the step of preferentially depositing metal on the bottom of the features includes exposing the features to a metal precursor and a reducing agent, and the volume ratio of the reducing agent to the metal precursor is at least 30:1. [Form 4] The method according to Forms 1 to 3, wherein the step of preferentially depositing metal on the bottom of the features includes exposing the features to a metal precursor at a flow rate of 100 sccm or less. [Form 5] The method according to any one of Forms 1 to 4, wherein the features are interconnect features of a 3D NAND device. [Form 6] The method according to any one of Forms 1 to 5, wherein the metal is tungsten and the temperature of the substrate during deposition is at least 430° C. [Form 7] A method according to any one of Forms 1 to 5, wherein the metal is molybdenum and the substrate temperature during deposition is at least 600 °C. [Form 8] A method according to any one of Forms 1 to 7, wherein the suppressing species is a nitrogen-containing gas or a plasma species. [Form 9] A method according to any one of Forms 1 to 8, wherein the first suppressing operation processes most of the features. [Form 10] A method according to any one of Forms 1 to 9, wherein the first suppressing operation processes at least 70% of the depth of the feature. [Form 11] A method according to any one of Forms 1 to 10, wherein the substrate temperature during the first suppressing operation is different from that during the second suppressing operation. [Form 12] An apparatus for processing a substrate, comprising: (a) a processing chamber including at least one station having a pedestal configured to hold the substrate; (b) at least one outlet for coupling to a vacuum; (c) one or more processing gas inlets coupled to one or more processing gas sources; (d) a controller for controlling the operation of the apparatus, the controller including: machine-readable instructions for injecting a suppressing species into the processing chamber at a first flow rate and a first exposure time in a first suppressing operation; machine-readable instructions for injecting a metal precursor and a reducing agent in a first non-conformal deposition operation to deposit a metal after the first suppressing operation, wherein the temperature of the pedestal on which the substrate is placed is at least 400 °C; machine-readable instructions for injecting a suppressing species into the processing chamber at a second flow rate and a second exposure time in a second suppressing operation after the first non-conformal deposition operation, wherein the second flow rate is less than the first flow rate and / or the second exposure time is shorter than the first exposure time; machine-readable instructions for injecting a metal precursor and a reducing agent in a second non-conformal deposition operation to deposit a metal after the second suppressing operation, wherein the temperature of the pedestal on which the substrate is placed is at least 400 °C. The apparatus comprising the same. [Form 13] The apparatus according to Form 12, wherein the volume ratio of the reducing agent to the tungsten precursor between the first non-conformal deposition operation and the second non-conformal deposition operation is at least 30:1. [Form 14] A method, A step of depositing a metal conformal layer on a feature of a substrate; A step of treating a part of the metal conformal layer to suppress subsequent tungsten nucleation; A step of preferentially depositing tungsten at the bottom of the feature after treating the part of the conformal layer, wherein the temperature of the substrate during the deposition is at least 400 °C; A step of repeating the treatment operation and the deposition operation one or more times to fill the feature with metal; A method comprising the above steps.

Claims

1. A method comprising: depositing a metal conformal layer on a feature of a substrate; processing a portion of the metal conformal layer to suppress subsequent tungsten nucleation; after processing the portion of the conformal layer, preferentially depositing metal at the bottom of the feature, wherein the temperature of the substrate during deposition is at least 400 °C; repeating the processing operation and the deposition operation one or more times to fill the feature with metal; wherein the step of preferentially depositing metal at the bottom of the feature includes exposing the feature to a metal precursor and a reducing agent, and the volume ratio of the reducing agent to the metal precursor is at least 30:1; the step of preferentially depositing metal at the bottom of the feature includes simultaneously supplying the metal precursor and the reducing agent, including continuously supplying one of the metal precursor and the reducing agent and supplying the other in a pulsed manner.

2. The method according to claim 1, wherein the metal is one of tungsten, cobalt, molybdenum, and ruthenium.

3. The method according to claim 1, wherein the step of preferentially depositing metal at the bottom of the feature includes exposing the feature to the metal precursor at a flow rate of 100 sccm or less.

4. The method according to claim 1, wherein the feature is an interconnect feature of a 3D NAND device.

5. The method according to claim 1, wherein the metal is tungsten and the temperature of the substrate during deposition is at least 430 °C.

6. The method according to claim 1, wherein the metal is molybdenum and the temperature of the substrate during deposition is at least 600 °C.

7. The method according to claim 1, wherein the feature has a depth of at least 10 microns.

8. The method according to claim 1, wherein the feature has a depth of at least 30 microns.

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