Atomic layer deposition method for depositing layer on substrate and related method

Abstract

To provide an atomic layer deposition method, a method of depositing a layer on a substrate, and a related atomic layer deposition system.SOLUTION: A disclosed method includes pulsing a reactant gas into a reactor assembly, holding the reactant gas in the reactor assembly for a certain period, and purging the reactant gas from the reactor assembly.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates generally to the fields of semiconductor processing methods and device and integrated circuit manufacturing. More specifically, the present disclosure relates generally to atomic layer deposition methods and related methods for depositing layers on a substrate. [Background technology]

[0002] Atomic layer deposition (ALD) is a method for growing highly uniform thin layers on a substrate. In a time-resolved ALD reaction gas valve, the substrate is placed in an impurity-free reaction space, and at least two different volatile precursors (reactant gases) are alternately and repeatedly supplied in the vapor phase into the reaction space. Layer growth is based on self-limiting surface reactions that occur on the substrate's surface and form a solid layer of atoms or molecules. Reactants are supplied to the reactor assembly of the ALD apparatus at doses large enough to practically saturate the surface during each injection cycle. Therefore, the ALD method is highly self-regulating and independent of the starting material concentrations. Therefore, it is possible to achieve extremely high layer uniformity and thickness precision of single atomic or molecular layers. Reactants (precursors, co-reactants, etc.) can contribute to the growing layer and / or perform other functions, such as removing ligands from adsorbed species of precursors and facilitating the reaction or adsorption of subsequent reactants.

[0003] ALD methods can be used to grow both elemental and compound thin films. ALD methods can involve alternating two or more reactants repeated in cycles, with different cycles having different numbers of reactants. Pure ALD reactions tend to deposit less than a monolayer per cycle, but ALD can be modified to deposit more than a monolayer per cycle.

[0004] Depositing films using the ALD method can be a slow process due to its step-by-step (layer-by-layer) nature. At least two gas reactant pulses are alternated to form one layer of the desired material, and the reactant pulses are kept separated from each other to prevent uncontrolled film growth and contamination of the ALD reactor. After each pulse, gaseous reaction products of the thin film growth process and excess reactants in the gas phase are removed from the reaction space. This can be achieved by pumping down the reaction space, or by purging the reaction space with an inert (e.g., inert) gas flow between successive reactant pulses, or both. Purging is widely used at production scales due to its efficiency and its ability to form an effective diffusion barrier between successive pulses. Typically, the inert gas purge is also used as a carrier gas during the reactant pulses to dilute the reactant vapor before it is delivered into the reaction space.

[0005] For an ALD process to be successful, sufficient substrate exposure and good purging of the reaction space are desirable. That is, the pulse should be strong enough to actually saturate the substrate (at the flat portion of the saturation asymptotic curve), and the purge should be efficient enough to actually remove all precursor residues and undesired reaction products from the reactor. However, certain reactants may exhibit inherently slow reaction rates that may require long reactant pulse times and result in inefficient precursor utilization. Thus, there remains a continuing need for improved atomic layer deposition methods.

[0006] Any discussion set forth in this section, including the discussion of problems and solutions, is included in this disclosure solely for the purpose of providing a context for the disclosure, and should not be construed as an admission that any or all of the discussion was known at the time the invention was made or that it constitutes prior art. Summary of the Invention [Means for solving the problem]

[0007] This Summary is intended to introduce some concepts in a simplified form that are described in more detail below. This Summary is not necessarily intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0008] Various embodiments of the present disclosure relate to atomic layer deposition methods, ALD apparatuses, and related methods for depositing layers on substrates disposed within a reactor assembly.

[0009] According to an example of the present disclosure, a method for performing atomic layer deposition (ALD) is provided. The method includes pulsing a first reactant gas into a reactor assembly. In such a method, the pulsing step includes supplying the first reactant gas to a first reactant gas line, supplying a first inert gas at a first flow rate to a first inert gas line, and delivering the first reactant gas and the first inert gas through the first supply line to the reactor assembly. The method also includes holding the first reactant gas in the reactor assembly. In such a method, the holding step includes supplying the first inert gas to the first inert gas line and delivering the first inert gas to the reactor assembly. The method also includes purging the first reactant gas from the reactor assembly. In such a method, the purging step includes the steps of supplying a first inert gas to a first inert gas line, supplying a second inert gas to a second inert gas line at a second flow rate higher than the first flow rate, and delivering the first inert gas and the second inert gas through the first supply line to the reactor assembly.

[0010] In some embodiments, a method for performing atomic layer deposition (ALD) includes continuously supplying a first inert gas to a reactor assembly.

[0011] In some embodiments, a method of performing atomic layer deposition (ALD) includes controlling a supply of a first reactant gas to a first supply line with a first valve and controlling a supply of a second inert gas to the first supply line with a second valve, wherein the first valve and the second valve are two-state valves.

[0012] In some embodiments, a method for performing atomic layer deposition (ALD) includes continuously evacuating a reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

[0013] In some embodiments, a method for performing atomic layer deposition (ALD) includes maintaining a substantially constant pressure in a first supply line. In some embodiments, maintaining the substantially constant pressure includes producing a pressure control signal from a pressure sensor disposed upstream of the reactor assembly and varying a conductance of the exhaust line by communicating the pressure control signal to an active non-zero flow restrictor, the active non-zero flow restrictor varying a degree of flow restriction in response to the pressure control signal.

[0014] In some embodiments, a method of performing atomic layer deposition (ALD) includes pulsing a second reactant into a reactor assembly, holding the second reactant in the reactor assembly, and purging the second reactant from the reactor assembly. In some embodiments, a first inert gas is supplied at a first flow rate during the pulsing, holding, and purging steps, and a second inert gas is supplied at a second flow rate greater than the first flow rate during the purging step.

[0015] According to an example of the present disclosure, a method for depositing a layer on a substrate disposed within a reactor assembly is provided. The method includes performing an atomic layer deposition process including a plurality of repeated deposition cycles. In such a method, each deposition cycle includes performing a first half-cycle, the first half-cycle including supplying a first reactant gas to the reactor assembly, retaining the first reactant gas within the reactor assembly, and purging the first reactant gas from the reactor assembly. In such a method, each deposition cycle includes performing a second half-cycle, the second half-cycle including supplying a second reactant gas to the reactor assembly, and purging the second reactant gas from the reactor assembly. In such methods, a first inert gas is supplied at a first flow rate during the steps of performing a first half-cycle and performing a second half-cycle, and a second inert gas is supplied at a second flow rate greater than the first flow rate during the step of purging. In some embodiments, performing the second half-cycle also includes maintaining a second reactant gas in the reactor assembly.

[0016] In some embodiments, a method of depositing a layer on a substrate includes controlling a supply of a first reactant gas to a first supply line with a first valve and controlling a supply of a second inert gas to the first supply line with a second valve, wherein the first valve and the second valve are two-state valves.

[0017] In some embodiments, a method of depositing a layer on a substrate includes continuously evacuating the reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

[0018] In some embodiments, a method for depositing a layer on a substrate includes maintaining a substantially constant pressure in a first supply line. In some embodiments, maintaining the substantially constant pressure includes producing a pressure control signal from a pressure sensor disposed upstream of the reactor assembly and varying a conductance of the exhaust line by communicating the pressure control signal to an active non-zero flow restrictor, the active non-zero flow restrictor varying a degree of flow restriction in response to the pressure control signal.

[0019] According to an example of the present disclosure, an atomic layer deposition method is provided. The method includes pulsing a first reactant gas into a reactor assembly. In such a method, the pulsing step includes supplying a first inert gas at a first flow rate to a first inert gas line, initiating the flow of the first reactant gas into the first reactant gas line by opening a first valve, terminating the flow of a second inert gas into the second inert gas line by closing a second valve, and delivering the first reactant gas and the first inert gas through the first supply line to the reactor assembly. The method also includes retaining the first reactant gas in the reactor assembly. In such a method, the retaining step includes supplying the first inert gas into the first inert gas line, terminating the flow of the first reactant gas into the first reactant gas line by closing the first valve, and delivering the first inert gas into the reactor assembly. The method also includes purging the reactor assembly. In such a method, the purging step includes the steps of supplying a first inert gas to a first inert gas line, initiating a flow of a second inert gas into the second inert gas line at a second flow rate higher than the first flow rate by opening a second valve, and delivering the first inert gas and the second inert gas through the first supply line to the reactor assembly.

[0020] In some embodiments, the atomic layer deposition method includes continuously evacuating the reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

[0021] In some embodiments, the atomic layer deposition method includes maintaining a substantially constant pressure in the first supply line, wherein maintaining the substantially constant pressure includes producing a pressure control signal from a pressure sensor disposed upstream of the reactor assembly and varying a conductance of the exhaust line by communicating the pressure control signal to an active non-zero flow restrictor, the active non-zero flow restrictor varying a degree of flow restriction in response to the pressure control signal.

[0022] In some embodiments, the atomic layer deposition method includes pulsing a second reactant into a reactor assembly, retaining the second reactant in the reactor assembly, and purging the second reactant from the reactor assembly.

[0023] In some embodiments, the first inert gas is supplied at a first flow rate during the pulsing of the second reactant, the holding of the second reactant, and the purging of the second reactant, and the second inert gas is supplied at a second flow rate greater than the first flow rate during the purging of the second reactant.

[0024] In some embodiments, the first inert gas forms a diffusion barrier, the diffusion barrier preventing back-diffusion of the first reactant gas.

[0025] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above in this disclosure. Of course, it should be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, it should be recognized by those skilled in the art that the invention may be embodied or carried out in a manner that achieves or optimizes one or more advantages that may be taught or suggested in the present disclosure, without necessarily achieving other objects or advantages that may be taught or suggested in the present disclosure.

[0026] All of these embodiments are intended to be within the scope of the invention(s) disclosed in this disclosure. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments, taken in conjunction with the accompanying drawings, although the invention is not limited to any particular embodiment(s) disclosed.

[0027] To easily identify the description of any particular element or operation, the most significant digit(s) of a reference number refers to the figure number in which that element is first introduced.

[0028] A more complete understanding of the embodiments of the present disclosure may be obtained by reference to the detailed description and claims when considered in connection with the following illustrative drawings. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 illustrates exemplary gas flows typically used during one half-cycle of an atomic layer deposition process. [Figure 2] FIG. 1 illustrates exemplary gas flows used during a half-cycle of an atomic layer deposition process in accordance with one or more embodiments of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram of an atomic layer deposition apparatus according to one or more embodiments of the present disclosure. [Figure 4] FIG. 1 illustrates an atomic layer deposition process in accordance with one or more embodiments of the present disclosure. [Figure 5] FIG. 1 illustrates an additional atomic layer deposition process according to one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0030] It should be understood that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of the illustrated embodiments of the present disclosure.

[0031] The descriptions of exemplary embodiments of methods and configurations provided below are merely exemplary and intended for illustrative purposes only. The following descriptions are not intended to limit the scope of the present disclosure or the claims. Moreover, the recitation of multiple embodiments having stated features or steps is not intended to exclude other embodiments having additional features or steps, or other embodiments incorporating different combinations of the stated features or steps.

[0032] As used herein, the term "substrate" may refer to any underlying material that can be used to form a device, circuit, or film, or on which a device, circuit, or film can be formed by a method according to an embodiment of the present disclosure. The substrate may include a bulk material such as silicon (e.g., single crystal silicon), other Group IV materials such as germanium, or other semiconductor materials such as Group II-VI or Group III-V semiconductor materials, and may include one or more layers overlying or underlying the bulk material. The substrate may include various topologies, such as gaps, including spaces between recesses, lines, trenches, or raised portions such as fins, formed within or on at least a portion of a layer of the substrate. As an example, the substrate may include a bulk semiconductor material and an insulating or dielectric material layer overlying at least a portion of the bulk semiconductor material. Furthermore, the term "substrate" may refer to any underlying material that may be used, or on which a device, circuit, or film may be formed. A "substrate" may be continuous or discontinuous, rigid or flexible, solid or porous. The "substrate" may be in any form, such as a powder, plate, or workpiece. Substrates in the form of plates may include wafers of various shapes and sizes. Substrates may be constructed from materials such as silicon, silicon germanium, silicon oxide, gallium arsenide, gallium nitride, and silicon carbide. A continuous substrate may extend beyond the boundaries of the process chamber in which the deposition process occurs or may be moved through the process chamber so that the process continues until the end of the substrate is reached. A continuous substrate may be supplied from a continuous substrate supply system, which allows for the production and output of a continuous substrate in any suitable form. Non-limiting examples of continuous substrates may include sheets, nonwoven films, rolls, foils, webs, flexible materials, and bundles of continuous filaments or fibers (i.e., ceramic or polymer fibers). A continuous substrate may also include a carrier or sheet to which a non-continuous substrate is attached.

[0033] As used herein, the term "layer" can refer to any continuous or discontinuous structure and material. For example, a layer can include two-dimensional materials, three-dimensional materials, nanoparticles, or even partial or complete molecular layers, or partial or complete atomic layers, or clusters of atoms and / or molecules. A layer can also include materials or layers with pinholes that may be at least partially continuous.

[0034] The term "atomic layer deposition" can refer to a deposition process in which deposition cycles, typically multiple successive deposition cycles, are performed in a process chamber. As used herein, the term atomic layer deposition is also meant to include processes designated by related terms, such as chemical vapor deposition atomic layer deposition, atomic layer epitaxy (ALE), molecular beam epitaxy (MBE), gas source MBE, metalorganic MBE, and chemical beam epitaxy, when performed using alternating pulses of precursor / reactive gases and purge (e.g., inert carrier) gases.

[0035] Generally, for an ALD process, during each deposition cycle, a precursor is introduced into the reaction chamber and chemisorbed to the deposition surface (e.g., a substrate surface, which may include previously deposited material or other materials from a previous ALD cycle) and forms a monolayer or sub-monolayer of material therearound that does not readily react with additional precursors (i.e., self-limiting reaction). In some cases, a reactant (e.g., another precursor or reactant gas) may then be introduced into the process chamber for use in converting the chemisorbed precursor to the desired material on the deposition surface. The reactant may be capable of further reaction with the precursor. Purging steps may be utilized during one or more deposition cycles, e.g., during each step of each cycle, to remove any excess precursor from the process chamber and / or to remove any excess reactants and / or reaction by-products from the reaction chamber.

[0036] In this disclosure, any two numbers for a variable can constitute a workable range for that variable, and any range stated may include or exclude endpoints. In addition, any value for a stated variable (whether or not it is stated with "about") may refer to an exact or approximate value, including its equivalent, and in some embodiments, may refer to an average, median, representative value, key value, etc. Furthermore, in this disclosure, the terms "including," "constituted by," and "having" can, in some embodiments, independently refer to "typically or broadly comprising," "comprising," "consisting essentially of," or "consisting of." In this disclosure, any stated meaning does not necessarily exclude the ordinary and customary meaning in some embodiments. In some cases, percentages stated herein may be relative or absolute percentages.

[0037] It should be noted that many exemplary materials are provided throughout the embodiments of this disclosure, and the chemical formulas provided for each of the exemplary materials should not be construed as limiting, nor should the non-limiting exemplary materials provided be limited by any exemplary stoichiometry.

[0038] It should be understood that the terms "on" or "over" may be used herein to describe relative location relationships. Another element, film, or layer may be directly on top of a stated layer, or another layer (intermediate layer) or element may be interposed therebetween, or a layer may be disposed on top of a stated layer but not completely cover the surface of the stated layer. Thus, unless the term "directly" is used separately, the terms "on" or "over" should be interpreted as relative concepts. Similarly, it should be understood that the terms "under," "underlying," or "below" should be interpreted as relative concepts.

[0039] A commonly used atomic layer deposition (ALD) method can include sequentially and alternately supplying reactant gases (i.e., precursors and / or co-reactants) and an inert purge gas into a reactor assembly by performing one or more ALD deposition cycles. In such methods, each ALD deposition cycle includes a pulsing step (to introduce reactant gas into the reactor assembly) followed by a purging step (to remove excess reactant gas and any reaction by-products from the reactor assembly).

[0040] To illustrate embodiments of the present disclosure, gas flows for a first half-cycle 100 typically used in an ALD method are shown in FIG. 1 , and exemplary gas flows for a second half-cycle 200 of an ALD method of the present disclosure are shown in FIG. 2 . Both FIGS. 1 and 2 show a single half-cycle gas flow, i.e., a pulse and purge sequence, although a complete deposition cycle can include multiple half-cycles. In both FIGS. 1 and 2 , the horizontal axis represents the time parameter, but not necessarily the actual length of time of the individual steps, and the vertical axis represents the on or off state of the reactant and inert gas flows, with a high level on the vertical axis for each parameter representing the on state. However, the vertical axis of each line does not necessarily represent the actual amount of the associated parameter, while the bottom level of each line on the vertical axis represents the off state, i.e., a state where the reactant flow / inert gas flow is zero.

[0041] Referring to the drawings, FIG. 1 illustrates an exemplary first half-cycle 100 of a commonly used ALD method. In this example, a first reactant is supplied to the reactor assembly during a period from 102 to 106 (the pulse period), and an inert gas is supplied to the reactor assembly during a period from 106 to 108 (the purge period). In certain examples, the first reactant is a reactant that exhibits a slow reaction rate and / or a low sticking coefficient. As a result, the pulse period of the first reactant is longer than that typically observed with reactants having faster reaction rates and / or higher sticking coefficients. A long pulse period for such a “slow-reacting” reactant may be required to ensure sufficient time for full saturation of the substrate surface and / or completion of the reaction between absorbing species on the substrate and the incoming first reactant. However, a sufficient concentration of the first reactant can be introduced into the reactor assembly early in the pulse period (e.g., at time 104), and an additional pulse period (104 to 106) may be required to ensure saturation / completion of the reaction. The additional pulse duration of the first reactant can have several adverse effects, including, but not limited to, inefficient utilization of the first reactant, increased parasitic deposition, and degradation in the lifetime of the ALD apparatus.

[0042] In comparison, FIG. 2 illustrates a second half-cycle 200 of the ALD method of the present disclosure. In this example, a first reactant gas is supplied to the reactor assembly during a period from 202 to 204 (the pulse period). Furthermore, a first inert gas is supplied to the reactor assembly continuously throughout the second half-cycle 200 at a first flow rate, and a second inert gas is supplied to the reactor assembly during a period from 206 to 208 (the purge period) at a second flow rate greater than the first flow rate. The period between the pulsing and purging steps (i.e., from 204 to 206) is referred to as the hold step. During the hold step, the first reactant gas flow and the second inert gas flow are zero, and only the first inert gas is supplied to the reactor assembly at a relatively low flow rate compared to the second inert gas flow used during the purge step. In this example, the first reactant gas is also a reactant that exhibits a slow reaction rate and / or a low sticking coefficient. However, comparing the first half-cycle 100 with the second half-cycle 200, it is clear that the pulse periods (e.g., 202 to 204) of the disclosed method are shorter than the pulse periods (e.g., 102 to 106) of commonly used methods. In the disclosed second half-cycle 200, a sufficient concentration of the first reactant gas is supplied to the reactor assembly during the shorter pulse periods (202 to 204). However, to allow adequate time for complete saturation / reaction, a hold period (204 to 206) retains the first reactant gas within the reactor assembly. Thus, the second half-cycle 200 supplies a lower concentration of the first reactant gas to the reactor assembly (compared to the first half-cycle 100) while still maintaining complete saturation / reaction as a result of the hold step, thereby improving utilization of the first reactant gas. Additionally, during the hold period, a low flow rate of the first inert gas is maintained that does not significantly affect the hold period but ensures a continuous flow of inert gas through the reactor assembly throughout the second half-cycle 200.The reduction in the concentration of the first reactant gas supplied to the reactor assembly, along with the continuous evacuation of the reactor assembly (as described below), along with the continuous flow of inert gas throughout the second half-cycle 200, can improve utilization of the first reactant gas, prevent parasitic deposition within the reactor assembly, extend the life of the reactor assembly components (e.g., supply lines, exhaust lines, pumps, etc.), and prevent back-diffusion of the reactant gas.

[0043] 3 is a schematic diagram of an ALD apparatus 300 according to an embodiment of the present disclosure. The ALD apparatus 300 can be utilized to perform the ALD methods of the present disclosure.

[0044] The reactant gas source 304 is configured to supply a first reactant gas (e.g., vaporized precursor and / or reactant / co-reactant vapor) to the first reactant gas line 308. The reactant gas may include a volatile material capable of reacting with the substrate surface or with a reactant previously left on the substrate surface. The reactant may be a solid, liquid, or gas in nature under standard conditions; therefore, the reactant gas source 304 may include a vaporizer.

[0045] The first valve 316 is configured to be turned on or off to control the supply of the first reactant gas from the first reactant gas line 308 to the first supply line 314. The first valve 316 can be any suitable type of valve, including, for example, a solenoid-type valve, a pneumatic valve, a piezoelectric valve, etc. In some embodiments, the first valve 316 is a two-state valve (e.g., including only an on or off state), sometimes referred to as a binary valve. As shown in FIG. 3 , the first valve 316 can comprise a three-way valve that operates as a two-state valve to control the flow of the first reactant gas to the first supply line 314 and also allows for the flow (and mixing) of the first inert gas and the second inert gas sequentially, as described in more detail below. In a particular example, the two-state valve portion of the first valve 316 may comprise a high-speed diaphragm valve or a high-speed pneumatic valve that operates as a two-state valve for rapidly switching the flow of the first reactant gas on or off, as described in detail below, in which case the two-state valve portion of the first valve 316 is turned on when pulsing the first reactant gas into the reactor assembly.

[0046] According to an example of the present disclosure, the ALD apparatus 300 includes an inert gas source 302 configured to supply a first inert gas to a first inert gas line 310 and a second inert gas to a second inert gas line 312. Both the first inert gas and the second inert gas are reactive gases, or gases that do not react with the substrate on which a layer is being deposited. The first inert gas and the second inert gas also serve to prevent reactions between materials of different reactant groups, for example, by providing a diffusion barrier in the supply lines to the reactor assembly during the reactant phase. Any suitable type of inert gas can be used in the embodiments disclosed herein, including inert gases such as nitrogen gas and noble gases such as argon. The first inert gas and the second inert gas can also be inherently reactive gases, such as hydrogen gas, which function to prevent undesired reactions, such as oxidation reactions, from occurring on the substrate surface depending on their relative reactivities with other reactants. In some embodiments, both the first inert gas and the second inert gas can have the same gas composition. In a particular example, both the first inert gas and the second inert gas are inert gases such as, for example, N2 or Ar.

[0047] The first inert gas is continuously supplied to the first inert gas line 310 (and subsequently to the first supply line 314 and reactor assembly 306). The supply of the second inert gas to the second inert gas line 312 (and subsequently to the first supply line 314 and reactor assembly 306) is controlled by a second valve 318 configured to be turned on or off to control the supply of the second inert gas from the second inert gas line 312 to the first supply line 314. The second valve 318 can be any suitable type of valve, including, for example, a solenoid-type valve, a pneumatic valve, a piezoelectric valve, etc. In some embodiments, the second valve 318 is a two-state valve (e.g., including only an on or off state), also referred to as a binary valve. As shown in FIG. 3, the second valve 318 may comprise, for example, a high-speed diaphragm valve that operates as a two-state valve to quickly switch the flow of the second inert gas on or off, where the second valve 318 is turned on when purging the reactor assembly 306, as described in detail below.

[0048] According to examples of the present disclosure, flow control of the first and second inert gases to the first supply line 314 (and reactor assembly 306) is achieved without the use of mass flow controllers on either of the inert gas lines (310, 312). Mass flow controllers (and the like) generally slow the flow of gas, especially when alternating between high and low flow regimes, as used in the pulse, hold, and purge methods of the present disclosure.

[0049] Process gases (reactants and inerts) sequentially supplied to first supply line 314 are introduced into reactor assembly 306 to perform atomic layer deposition on a substrate disposed within reactor assembly 306. In various arrangements, reactor assembly 306 may include a reaction chamber including a substrate support (not shown) configured to support a substrate (not shown).

[0050] The ALD apparatus 300 of FIG. 3 includes an exhaust system 324. According to examples of the present disclosure, the exhaust system 324 can be configured to continuously evacuate the reactor assembly 306. The exhaust system 324 includes a vacuum source 328 (e.g., a vacuum pump) in fluid communication with the reactor assembly 306 via an exhaust line 326. The flow of exhaust gas and / or the level of vacuum (i.e., pressure) within the reactor assembly 306 can be controlled using a flow restrictor 322 disposed on the exhaust line 326 between the reactor assembly 306 and the vacuum source 328. In particular examples, the flow restrictor 322 is an active flow restrictor, where the term “active” can refer to a flow restriction device that can control the degree of restriction within the device. In even more particular examples, the flow restrictor 322 is a non-zero flow restrictor, where the term “non-zero” in this example can refer to a flow restrictor that does not completely prevent exhaust gas flow; i.e., the non-zero flow restrictor allows at least some process gas to be continuously evacuated from the reactor assembly 306. In some embodiments, the flow restrictor 322 is an active non-zero flow restrictor, i.e., a device that controllably restricts gas flow (e.g., exhaust gas flow) without completely preventing it. In such embodiments, the flow restrictor 322 may include a throttle valve.

[0051] According to examples of the present disclosure, the ALD apparatus 300 of FIG. 3 can be configured to perform an isobaric ALD process. In such examples, one or more deposition cycles of a provided ALD method can be performed at a constant pressure. In such exemplary ALD methods, the pressure within at least the reactor assembly 306 and / or the first supply line 314 is maintained at a constant or substantially constant value, where “substantially” in this example can refer to a percent change in pressure during the ALD process of less than 0.5%, less than 1%, less than 2%, less than 5%, less than 10%, or less than 20%, or between 0.5% and 20%.

[0052] According to examples of the present disclosure, isobaric operation of ALD apparatus 300 may include monitoring the pressure within ALD apparatus 300. As a non-limiting example, pressure sensor 320 may be disposed upstream of reactor assembly 306, for example, to monitor the pressure within reactor assembly 306 and / or first supply line 314. In a particular example, pressure sensor 320 is disposed on second inert gas line 312 between first valve 316 and second valve 318, as shown in FIG. 3 . In some embodiments, pressure sensor 320 is linked to controller 330 (e.g., via example links 344 and 346, which may be wired and / or wireless) to enable communication / control between at least pressure sensor 320, flow restrictor 322, and controller 330.

[0053] An exemplary method for performing atomic layer deposition according to the present disclosure is shown in Figure 4 and described in detail below with reference to the ALD apparatus 300 of Figure 3. Briefly, Figure 4 shows an ALD method 400 (e.g., a deposition half cycle) that includes pulsing a first reactant gas into a reactor assembly 306 (step 402), holding the first reactant gas in the reactor assembly 306 (step 404), and purging the reactor assembly 306 (step 406).

[0054] According to examples of the present disclosure, the ALD method 400 includes pulsing (step 402) a first reactant gas into the reactor assembly 306. In such examples, the pulsing (402) may include supplying the first reactant gas to the first reactant gas line 308. For example, the first reactant gas is supplied from the reactant gas source 304. In such examples, the pulsing (step 402) also includes supplying a first inert gas at a first flow rate to the first inert gas line 310. In such examples, the pulsing (step 402) may also include delivering the first reactant gas and the first inert gas through the first supply line 314 into the reactor assembly 306.

[0055] According to examples of the present disclosure, the ALD method 400 includes a step of holding (Step 404) a first reactant gas within the reactor assembly 306. In such examples, the holding step (Step 404) may include providing a first inert gas to the first inert gas line 310. In such examples, the holding step (Step 404) also includes delivering the first inert gas to the reactor assembly 306.

[0056] According to examples of the present disclosure, the ALD method 400 includes purging (step 406) a first reactant gas from the reactor assembly 306. In such examples, the purging (step 406) may include supplying a first inert gas to the first inert gas line 310 and supplying a second inert gas to the second inert gas line 312. In particular examples, the second inert gas is supplied at a second flow rate that is higher than the first flow rate (i.e., the flow rate of the first inert gas). Further, in such examples, the purging (406) may include delivering the first inert gas and the second inert gas to the reactor assembly 306 through the first supply line 314.

[0057] As described above, the first inert gas is continuously supplied to the reactor assembly 306. The continuous flow of the first inert gas (i.e., the low-flow inert gas shown in the second half-cycle 200 of FIG. 2 ), along with the continuous evacuation of the reactor assembly 306 (as described below), can prevent or reduce “dead space” within the ALD apparatus 300, i.e., areas within the ALD apparatus 300 where process gas (reactants, precursors, co-reactants, etc.) can reside for extended periods of time. Such residual process gas within the ALD apparatus 300 can result in undesirable parasitic deposition and degradation of both deposition quality and the lifetime of the apparatus (and associated components).

[0058] According to examples of the present disclosure, controlling the flow rate of a first reactant gas (from the reactant gas source 304) can include controlling the supply of the first reactant gas to the first supply line 314 using a first valve 316 (as described above). Controlling the flow rate of a second inert gas (from the inert gas source 302) can include controlling the supply of the second inert gas to the first supply line 314 using a second valve (as described above). In such examples, the first valve 316 and the second valve 318 can include two-state valves (i.e., binary valves that are on or off). Controlling process gases using two-state valves can eliminate the need for slow mass flow controllers, thereby increasing the gas switching speed and efficiency of the ALD apparatus 300.

[0059] According to further examples of the present disclosure, ALD method 400 ( FIG. 4 ) can be implemented as an isobaric process in which the pressure in reactor assembly 306 and / or first feed line 314 is maintained at a substantially constant pressure. In such examples, maintaining the substantially constant pressure can include producing a pressure control signal from a pressure sensor 320 disposed upstream of reactor assembly 306 and communicating the pressure control signal (via controller 330 and links 344, 346) to flow restrictor 322 (e.g., an active non-zero flow restrictor such as a throttle valve) to vary the conductance of exhaust line 326. In such examples, flow restrictor 322 varies the degree of flow restriction (and thus the conductance in exhaust line 326) in response to the pressure control signal.

[0060] The present disclosure also provides additional atomic layer deposition (ALD) deposition methods that utilize the pulse, hold, and purge sequence described in detail above. According to such examples of the present disclosure (and with continued reference to the ALD apparatus 300 of FIG. 3 ), the additional ALD methods provided include: (A) pulsing a first reactant gas into the reactor assembly 306; (B) holding the first reactant gas in the reactor assembly 306; and (C) purging the reactor assembly.

[0061] More specifically, and according to examples of the present disclosure, pulsing the first reactant gas into the reactor assembly 306 includes starting the flow of the first reactant gas into the first reactant gas line 308 by opening the first valve 316, terminating the flow of the second inert gas into the second inert gas line 312 by closing the second valve 318 (i.e., stopping the high flow purge gas), and delivering the first reactant gas and the first inert gas into the reactor assembly 306 through the first supply line 314. In such examples, one or more of the steps may be performed simultaneously or with at least some overlap in time.

[0062] According to a further example of the present disclosure, maintaining the first reactant gas within the reactor assembly 306 includes supplying the first inert gas to the first inert gas line 310, terminating the flow of the first reactant gas to the first reactant gas line 308 by closing the first valve 316, and delivering the first inert gas to the reactor assembly 306. Furthermore, in such an example, one or more of the steps may be performed simultaneously or with at least some overlap in time.

[0063] According to a further example of the present disclosure, purging the reactor assembly 306 of a first reactant gas includes supplying a first inert gas to the first inert gas line 310, initiating a flow of a second inert gas into the second inert gas line 312 at a second flow rate higher than the first flow rate by opening the second valve 318 (i.e., introducing a high flow purge gas), and delivering the first inert gas and the second inert gas through the first supply line 314 to the reactor assembly 306. Furthermore, in such an example, one or more of the steps may be performed simultaneously or with at least some overlap in time.

[0064] Various embodiments of the present disclosure also provide methods for depositing a layer on a substrate disposed within a reactor assembly. As a non-limiting example, FIG. 5 illustrates an exemplary method 500 for depositing a layer. In such an example, the exemplary deposition method 500 includes performing an atomic layer deposition process including multiple repeated deposition cycles. In a particular example, each deposition cycle includes performing a first half-cycle 518 and a second half-cycle 520.

[0065] According to an example of the present disclosure, performing the first half-cycle 518 includes supplying a first reactant gas to the reactor assembly (step 502), retaining the first reactant gas in the reactor assembly (step 504), and purging the first reactant gas from the reactor assembly (step 504). Details of supplying the first reactant (step 502), retaining the first reactant (step 504), and purging the first reactant (step 506) are described in detail above.

[0066] According to additional examples of the present disclosure, performing the second half-cycle 520 includes supplying a second reactant gas to the reactor assembly (step 510), optionally retaining the second reactant gas within the reactor assembly (optional step 510), and purging the second reactant gas from the reactor assembly (step 512). In such examples, the second reactant gas can be sourced from reactant gas source 304 of ALD apparatus 300 (FIG. 3) and can be provided to the reactor assembly through first supply line 314 or, alternatively, through a separate second supply line (with associated valving and purges, as described above).

[0067] In some embodiments, the exemplary method 500 includes supplying a first inert gas at a first flow rate while performing the first half-cycle 518 and the second half-cycle 520, and supplying a second inert gas at a second flow rate greater than the first flow rate while performing the purging steps (steps 506 and 512).

[0068] According to examples of the present disclosure, each deposition cycle (e.g., first half cycle 518 and second half cycle 520) is repeated one or more times (as indicated by deposition cycle loop 516) until a desired termination criterion is reached (decision block 514). In such examples, the termination criterion for deposition method 500 may be reached when a desired thickness of a layer is deposited on the substrate, or alternatively, when a predetermined number of deposition cycles have been performed.

[0069] According to examples of the present disclosure, the individual half-cycles (518 and 520) of the exemplary method 500 can be performed in parallel (or at least partially in parallel) in any order or sequence, with or without additional process steps or omitting steps shown in Figure 5. As a non-limiting example, in some deposition processes, the second reactant gas may include a "slow reactant" and the first reactant may include a "fast reactant," in which case the holding step (step 504) can be omitted from the first half-cycle 518, and an optional holding step (step 510) can be included in the second half-cycle 520 to increase utilization of the second reactant gas. As a further non-limiting example, in some deposition processes, both the first reactant vapor and the second reactant gas can both include “slow-reacting” reactants, in which case the holding step (step 504 and optional step 510) can be used in both the first half-cycle 518 and the second half-cycle 520.

[0070] According to examples of the present disclosure, ALD apparatus 300, in conjunction with the ALD methods described above (e.g., methods 400 and 500), enables rapid inert gas flow purging. Such rapid adjustment of ALD apparatus 300 from low-flow inert gas purging to high-flow inert gas purging is achieved by utilizing pressure control (as described above) of a high-flow purge gas (e.g., N or Ar) in conjunction with rapid switching of second valve 318 (e.g., a pneumatic diaphragm valve, etc.) positioned upstream of first valve 316 (e.g., a pulsed valve on a pulsed valve manifold). According to examples of the present disclosure, the inert purge gas flow can be set high during the purging step (406) (by introducing a second inert gas from the second inert gas line 312) and low during both the pulsing step (402) and the holding step (404) by activating or deactivating (on vs. off) the second valve 318 (e.g., a rapid purge gas air pressure valve). In certain examples, the continuous supply of a low flow rate of the first inert gas can also control a flow restrictor 322 (e.g., a throttle valve) to reduce conductance in the exhaust line 326 to maintain pressure, thereby reducing the pumping speed to the vacuum source in the exhaust system 342 and further improving reactant gas utilization.

[0071] According to examples of the present disclosure, the ALD methods provided herein include steps utilizing pressure control, whereby excess pressure in first supply line 314 is eliminated by methods and associated apparatus that allow the pressure in first supply line 314 to be controlled at a substantially constant value (i.e., constant pressure), regardless of the state of second valve 318 (i.e., a high-speed, high-flow purge valve) or the cycle times between various steps of the ALD method described above. Furthermore, the provided methods also increase chemical utilization (e.g., of the first reactant gas) by employing a holding step 404 ( FIG. 4 ) (i.e., when a low flow rate of the first inert gas is supplied to the reactor assembly after pulsing step 402).

[0072] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described hereinabove. Of course, it will be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, it will be appreciated by those skilled in the art that the invention may be embodied or carried out in a manner that achieves or optimizes one or more advantages that may be taught or suggested in the present disclosure, without necessarily achieving other objects or advantages that may be taught or suggested in the present disclosure.

[0073] All of these embodiments are intended to be within the scope of the invention disclosed in this disclosure. These and other embodiments will be readily apparent to those skilled in the art from the following detailed description of certain specific embodiments, which refer to the accompanying drawings, but the invention is not limited to any particular embodiment disclosed.

Claims

1. 1. A method of performing atomic layer deposition, comprising: pulsing a first reactant gas into the reactor assembly, said pulsing comprising: supplying the first reactant gas to a first reactant gas line; supplying a first inert gas to a first inert gas line at a first flow rate; pulsing the first reactant gas and the first inert gas through a first supply line into the reactor assembly; maintaining the first reactant gas within the reactor assembly, said maintaining comprising: supplying the first inert gas to the first inert gas line; delivering the first inert gas to the reactor assembly; purging the first reactant gas from the reactor assembly, the purging comprising: supplying the first inert gas to the first inert gas line; supplying a second inert gas to a second inert gas line at a second flow rate higher than the first flow rate; feeding the first inert gas and the second inert gas into the reactor assembly through the first supply line.

2. 10. The method of claim 1, further comprising the step of continuously supplying said first inert gas to said reactor assembly.

3. controlling the supply of the first reactant gas to the first supply line using a first valve; and controlling the supply of the second inert gas to the first supply line using a second valve; The method of claim 2 , wherein the first valve and the second valve are two-state valves.

4. 4. The method of claim 3, further comprising continuously evacuating the reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

5. 5. The method of claim 4, further comprising the step of maintaining a constant pressure in the first supply line.

6. The step of maintaining a constant pressure comprises: generating a pressure control signal from a pressure sensor disposed upstream of the reactor assembly; 6. The method of claim 5, further comprising: varying the conductance of the exhaust line by communicating the pressure control signal to the active non-zero flow restrictor, the active non-zero flow restrictor changing a degree of flow restriction in response to the pressure control signal.

7. pulsing a second reactant into the reactor assembly; retaining the second reactant within the reactor assembly; 10. The method of claim 1, further comprising the step of: purging the second reactant from the reactor assembly.

8. the first inert gas is supplied at the first flow rate during the steps of pulsing the second reactant, holding the second reactant, and purging the second reactant; 8. The method of claim 7, wherein the second inert gas is supplied at the second flow rate greater than the first flow rate during the step of purging the second reactant.

9. 1. A method for depositing a layer on a substrate disposed in a reactor assembly, comprising: performing an atomic layer deposition process comprising a plurality of repeated deposition cycles, each deposition cycle comprising: performing a first half cycle, supplying a first reactant gas to the reactor assembly; maintaining the first reactant gas within the reactor assembly; conducting a first half-cycle, the first half-cycle comprising: performing a second half cycle, supplying a second reactant gas to the reactor assembly; performing a second half-cycle comprising purging the second reactant gas from the reactor assembly; a first inert gas is supplied at a first flow rate during the step of performing the first half-cycle and the step of performing the second half-cycle; A method wherein a second inert gas is supplied at a second flow rate greater than the first flow rate during the purging step.

10. controlling the supply of the first reactant gas to a first supply line using a first valve; and controlling the supply of the second inert gas to the first supply line using a second valve; 10. The method of claim 9, wherein the first valve and the second valve are two-state valves.

11. 11. The method of claim 10, further comprising continuously evacuating the reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

12. The method of claim 11 further comprising maintaining a constant pressure in the first supply line.

13. The step of maintaining a constant pressure comprises: generating a pressure control signal from a pressure sensor disposed upstream of the reactor assembly; 13. The method of claim 12, further comprising: varying the conductance of the exhaust line by communicating the pressure control signal to the active non-zero flow restrictor, the active non-zero flow restrictor changing a degree of flow restriction in response to the pressure control signal.

14. 10. The method of claim 9, wherein conducting the second half-cycle further comprises retaining the second reactant gas within the reactor assembly.

15. 1. An atomic layer deposition method comprising: pulsing a first reactant gas into the reactor assembly, said pulsing comprising: supplying a first inert gas to a first inert gas line at a first flow rate; initiating a flow of the first reactant gas into a first reactant gas line by opening a first valve; terminating the flow of the second inert gas to the second inert gas line by closing the second valve; pulsing the first reactant gas and the first inert gas through a first supply line into the reactor assembly; maintaining the first reactant gas within the reactor assembly, said maintaining comprising: supplying the first inert gas to the first inert gas line; terminating the flow of the first reactant gas to the first reactant gas line by closing the first valve; delivering the first inert gas to the reactor assembly; purging the reactor assembly, said purging comprising: supplying the first inert gas to the first inert gas line; commencing flow of the second inert gas into the second inert gas line at a second flow rate higher than the first flow rate by opening the second valve; feeding the first inert gas and the second inert gas into the reactor assembly through the first supply line.

16. 16. The method of claim 15, further comprising continuously evacuating the reactor assembly with a vacuum source in fluid communication with the reactor assembly by an exhaust line and an active non-zero flow restrictor disposed on the exhaust line between the reactor assembly and the vacuum source.

17. further comprising maintaining a constant pressure in the first supply line, wherein the maintaining a constant pressure comprises: generating a pressure control signal from a pressure sensor disposed upstream of the reactor assembly; 17. The method of claim 16, further comprising: varying the conductance of the exhaust line by communicating the pressure control signal to the active non-zero flow restrictor, wherein the active non-zero flow restrictor changes a degree of flow restriction in response to the pressure control signal.

18. pulsing a second reactant into the reactor assembly; retaining the second reactant within the reactor assembly; 20. The method of claim 17, further comprising purging the second reactant from the reactor assembly.

19. the first inert gas is supplied at the first flow rate during the steps of pulsing the second reactant, holding the second reactant, and purging the second reactant; 20. The method of claim 18, wherein the second inert gas is supplied at a second flow rate greater than the first flow rate during the step of purging the second reactant.

20. the first inert gas forms a diffusion barrier; 20. The method of claim 19, wherein the diffusion barrier prevents back-diffusion of the first reactant gas.

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