Method for etching a substrate using a hybrid wet atomic layer etching process - Patents.com

Abstract

The present disclosure provides a hybrid atomic layer etching (ALE) process that combines a gas-phase surface modification step with a liquid-phase dissolution step to etch exposed material on a substrate disposed in a process chamber. In the hybrid ALE process disclosed herein, a gas-phase reactant is used to modify the exposed surface of the material to form a surface modification layer, and one or more liquid-phase reactants are used to selectively dissolve the surface modification layer without dissolving the material underlying the surface modification layer. Once the surface modification layer has been selectively dissolved, the substrate may be dried, and the gas-phase surface modification step and the liquid-phase dissolution step may be repeated for one or more ALE cycles until a desired amount of material has been etched.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 151,579, entitled "HYBRID WET ATOMIC LAYER ETCHING", filed February 19, 2021, and U.S. Provisional Patent Application No. 17 / 580,879, entitled "METHODS FOR ETCHING A SUBSTRATE USING A HYBRID WET ATOMIC LAYER ETCHING PROCESS", filed January 21, 2022, the disclosures of which are expressly incorporated by reference in their entireties into this specification.

[0002] The present disclosure relates to processing of a substrate. In particular, the present disclosure provides a method for etching a layer on a substrate. [Background technology]

[0003] As substrate structure geometries continue to shrink and the types of structures evolve, the challenges of etching substrates increase. One technique that has been utilized to address these challenges is atomic layer etching (ALE). ALE processes are generally known to involve processes that sequentially remove thin layers through one or more self-limiting reactions. For example, ALE typically refers to techniques that can etch with atomic precision, i.e., by removing material one or a few monolayers at a time. In general, ALE processes rely on chemical modification of the surface to be etched and then selective removal of the modified layer. Thus, ALE processes improve performance by separating the etching process into successive steps of surface modification and removal of the modified surface. Such processes often involve a series of layer modification and etching steps that are repeated multiple times, where the modification step modifies the exposed surface and the etching step selectively removes the modified layer. Thus, in some ALE processes, a series of self-limiting reactions may occur, and the cycle may be carried out repeatedly.

[0004] Various ALE processes are known, including plasma ALE, thermal ALE, and wet ALE techniques. In plasma ALE, a target substrate disposed in a process chamber is exposed to reactive precursors that adsorb and react with the exposed surface of the target substrate to modify the surface in a surface modification step. The exposed surface of the target substrate is then bombarded with low-energy non-reactive ions (e.g., ions from an inert gas) to remove the surface modification layer in a subsequent etching step. Some plasma ALE processes use periodic pulsing of process gases (e.g., reactive precursor gas(es) and inert gas(es)) in one or more ALE cycles (each ALE cycle consisting of at least one surface modification step and an etching step) to remove material from the surface of the target substrate. In plasma ALE, operating variables (e.g., chamber temperature, chamber pressure, flow rate of process gas, type of process gas, and / or other operating variables) can be adjusted to control the surface modification and etching process steps. In some cases, plasma ALE processes can be performed at relatively high temperatures and / or pressures. In plasma ALE, the process chamber is often purged after each surface modification step and after each etching step to avoid mixing of the reactive precursors and inert gases in the process chamber, which increases cycle time and reduces throughput.

[0005] In thermal ALE, the modified layer is removed by volatilization when the material is taken from the solid phase to the gas phase. This phase change requires additional latent heat and is limited by the vapor pressure of the modified layer. Thermal energy is used to replace the intermolecular interactions that stabilize the modified layer on the surface. In thermal ALE, high temperatures are often required to remove the modified layer.

[0006] In wet ALE, material is removed from a surface in a cyclic process that utilizes self-limiting and selective reactions. The name "wet ALE" indicates that some, if not all, of the reactions take place in the liquid phase. One advantage of wet ALE over thermal or plasma ALE techniques is that the wet ALE process can be carried out at ambient temperature and pressure.

[0007] The wet ALE process begins with a self-limiting surface modification step that can be achieved by oxidation, reduction, ligand binding, or ligand exchange. Ideally, the modified layer is limited to the top monolayer of material and acts as a passivation layer that prevents further modification reactions. The second step of the wet ALE process is the selective dissolution of the modified layer. The process must dissolve the modified layer without removing the underlying unmodified material. This can be achieved by using a different solvent in the second step than that used in the first step, by changing the pH, or by changing the concentration of other components in the first solvent.

[0008] In wet ALE, a purging step is usually performed between the surface modification step and the selective dissolution step by washing the surface modification layer with a purging solution to remove excess reactants. The purpose of the purging step is to ensure that no mixing occurs between the solution used for surface modification and the solution used for dissolution. If these two solutions mix, it is possible that the mixed solution can both modify and dissolve the substrate. When the solutions mix, the modification reaction is no longer self-limiting and continuous etching occurs. Continuous etching tends to etch preferentially at grain boundaries, resulting in a rough surface after etching.

[0009] Being an atomic layer process, wet ALE tends to be time consuming. Each reaction must be long enough to reach saturation, and each purge step must be long enough to completely separate the surface modification solution from the dissolution solution. This can lead to low throughput for high volume manufacturing (HVM), making wet ALE an expensive process. Summary of the Invention [Means for solving the problem]

[0010] One advantage of wet ALE over thermal or plasma ALE techniques is that wet ALE processes can be performed at ambient temperature and pressure. Gas phase reactants, condensates, sprays, or mist can be used in wet ALE processes while maintaining these advantages, as long as the reactants are delivered near room temperature and pressure. In ALE of metals, oxidation is often used as a surface modification step, and many self-limiting oxidation processes are performed on metal surfaces using room temperature and pressure reactants.

[0011] As further described herein, the present disclosure provides a hybrid wet ALE process that combines a gas-phase surface modification step with a liquid-phase dissolution step to etch a substrate disposed in a process chamber, thereby avoiding the disadvantages of wet ALE (e.g., low throughput, high cost, etc.) while maintaining the advantages of wet ALE (e.g., self-limiting reaction near ambient pressure and temperature, smoothing of the surface after etching, digital control of the total etch amount, etc.). In the hybrid ALE process described herein, a gas-phase reactant is used to modify the exposed surface of the material to form a surface modification layer, and one or more liquid-phase reactants are used to selectively dissolve the surface modification layer without dissolving the material underneath the surface modification layer. Once the surface modification layer is selectively dissolved, the substrate may be dried, and the gas-phase surface modification step and the liquid-phase dissolution step may be repeated for one or more ALE cycles until the desired amount of material is etched.

[0012] In some embodiments, the exposed surface of the material may be exposed to the gas-phase reactant and the liquid-phase reactant(s) sequentially. In other embodiments, the exposed surface of the material may be exposed to the liquid-phase reactant(s) while the gas-phase reactant is being delivered to the process chamber. When the liquid-phase reactant is delivered in the presence of the gas-phase reactant, the liquid-phase reactant delivered onto the exposed surface of the material displaces the gas-phase reactant from the exposed surface to prevent further surface modification of the exposed surface. Delivered in this manner, the liquid-phase reactant not only dissolves the surface modification layer, but also separates the gas-phase surface modification step from the liquid-phase dissolution step. This reduces cycle time and improves throughput of the hybrid ALE process described herein compared to other ALE techniques by eliminating the need to perform a purge step between the surface modification step and the dissolution step.

[0013] Cycle time and throughput may be further improved in the hybrid ALE process described herein by performing the gas-phase surface modification step and the liquid-phase dissolving step in the same process chamber. In one exemplary embodiment, the gas-phase surface modification step and the liquid-phase dissolving step may both be performed in a spin chamber. In some embodiments, the gas-phase surface modification step and the liquid-phase dissolving step may be performed in the same process chamber at approximately the same temperature and pressure. In one exemplary embodiment, the gas-phase surface modification step and the liquid-phase dissolving step may be performed at (or near) ambient room pressure. Performing the gas-phase surface modification step and the liquid-phase dissolving step in the same process chamber at approximately the same temperature and pressure reduces cycle time and improves throughput of the hybrid ALE process described herein by avoiding unnecessary chamber transitions and temperature / pressure changes.

[0014] The hybrid ALE process described herein may be used to etch a wide variety of materials, including polycrystalline, single crystalline, and amorphous materials. In some embodiments, the hybrid ALE process described herein may be used to etch polycrystalline materials, such as transition metals (e.g., molybdenum (Mo) and the like), and a gas-phase oxidizer (e.g., oxygen (O2) or ozone (O3)) may be used to oxidize the exposed surface of the transition metal to form a self-limiting oxide layer (e.g., MoO3 and the like). The oxidation of transition metals, such as molybdenum, is self-limiting at (or near) room temperature. After the exposed surface of the transition metal is exposed to the gas-phase oxidizer and an oxide layer is formed, a liquid-phase reactant may be delivered onto the substrate to selectively dissolve the oxide layer, such that the oxide layer may be removed without etching the underlying polycrystalline material. Several chemistries may be used to selectively dissolve molybdenum oxide (e.g., MoO3) without dissolving metallic Mo, which are described in more detail below.

[0015] Exemplary process conditions (e.g., etching chemistries, temperatures, pressures, etc.) are provided herein for etching transition metals, and more specifically for etching molybdenum, using the hybrid ALE processes described herein. However, those skilled in the art will recognize that the disclosed processes are not strictly limited to the exemplary process conditions described herein, and may be carried out using a wide variety of process conditions depending on the material being etched. In general, the hybrid ALE processes described herein may use a minimum pressure that is higher than the vapor pressure of the liquid-phase reactant used to remove and / or dissolve the surface modification layer. However, the temperatures used in the hybrid ALE processes described herein may generally range between the melting and boiling points of the liquid-phase reactants.

[0016] Thus, in some embodiments of the present disclosure, ambient pressure and room temperature gas phase reactants (or condensates, sprays, or mist) can be added to a wet ALE process to form a hybrid ALE process, which improves on other ALE techniques by reducing cycle time and increasing throughput while maintaining the advantages of traditional wet ALE.

[0017] Provided herein is a method for etching a substrate using a hybrid atomic layer etching (ALE) process according to a first embodiment of the present disclosure. In the first embodiment, the method includes receiving a substrate, the substrate having an exposed material, and selectively etching the material by performing multiple cycles of a hybrid ALE process, each cycle including: a) performing a gas-phase surface modification step to chemically modify the exposed surface of the material and provide a surface modification layer, the gas-phase surface modification step including exposing the substrate to a gas-phase reactant to chemically modify the exposed surface of the material; and b) performing a liquid-phase dissolution step to selectively dissolve the surface modification layer of the material, the liquid-phase dissolution step including providing one or more liquid-phase reactants on the surface of the substrate to dissolve the surface modification layer. In the first embodiment, the one or more liquid-phase reactants are provided on the surface of the substrate while the substrate is exposed to the gas-phase reactants. In so doing, one or more liquid phase reactants displace the gas phase reactants from the surface of the substrate, thereby separating the gas phase surface modification step from the liquid phase dissolution step.

[0018] In some embodiments, performing the gas-phase surface modification step a) may include exposing the substrate to a gas-phase oxidizing agent to oxidize the exposed surface of the material and form a self-limiting oxidation layer. In such embodiments, performing the liquid-phase dissolution step b) may include providing a complexing agent dissolved in a first liquid solvent on the surface of the substrate, where the complexing agent binds to the self-limiting oxidation layer to form a ligand-metal complex. In addition, performing the liquid-phase dissolution step b) may include providing a second liquid solvent on the surface of the substrate to dissolve the ligand-metal complex and remove the self-limiting oxidation layer. In some embodiments, the first liquid solvent and the second liquid solvent may be the same solvent. In other embodiments, the first liquid solvent and the second liquid solvent may be different solvents.

[0019] In some embodiments, each cycle of the hybrid ALE process may further include drying the surface of the substrate after a liquid-phase dissolution step is performed that selectively dissolves the surface-modified layer of the material. For example, said drying the surface of the substrate may include spin-drying the substrate to rinse one or more liquid-phase reactants from the surface of the substrate and re-exposing the exposed surface of the material to the gas-phase reactants in a subsequent gas-phase surface modification step.

[0020] Provided herein is another method for etching a substrate using a hybrid atomic layer etching (ALE) process according to a second embodiment of the present disclosure. In the second embodiment, the method includes receiving a substrate, the substrate having exposed polycrystalline material, and selectively etching the polycrystalline material by performing multiple cycles of a hybrid ALE process, each cycle including: a) chemically modifying an exposed surface of the polycrystalline material to provide a surface-modified layer, the exposed surface being chemically modified by oxidation of the polycrystalline material using a gas-phase oxidizing agent; b) binding a complexing agent to the surface-modified layer of the polycrystalline material to provide a complexed surface-modified layer; and c) selectively removing the complexed surface-modified layer of the polycrystalline material by exposing the complexed surface-modified layer to a liquid solvent, the liquid solvent dissolving the complexed surface-modified layer without dissolving the polycrystalline material underlying the complexed surface-modified layer. In some embodiments, steps a)-c) may be repeated at least once.

[0021] Provided herein is yet another method for etching a substrate using a hybrid atomic layer etching (ALE) process according to a third embodiment of the present disclosure. In the third embodiment, the method includes receiving a substrate, the substrate having exposed molybdenum (Mo) metal, and selectively etching Mo metal by performing multiple cycles of a hybrid ALE process, each cycle including: a) chemically modifying an exposed surface of Mo metal to provide a surface modification layer, the exposed surface being chemically modified by oxidation of Mo metal using a gas-phase oxidizing agent comprising ozone; b) binding a complexing agent to the surface modification layer of Mo metal to provide a complex-bonded surface modification layer; and c) selectively removing the complex-bonded surface modification layer of Mo metal by exposing the complex-bonded surface modification layer to a liquid solvent, the liquid solvent dissolving the complex-bonded surface modification layer without dissolving Mo metal underlying the complex-bonded surface modification layer. In some embodiments, steps a)-c) may be repeated at least once.

[0022] In the methods disclosed in the second and third embodiments, the order and / or timing of steps a) to c) performed in each cycle of the hybrid ALE process may differ in some cases. In one embodiment, for example, steps b) and c) may be performed consecutively without overlap in time in each cycle of the hybrid ALE process. In such an embodiment, the complexing agent may be dissolved in a first liquid solvent different from the liquid solvent used to dissolve the complex-bonded surface-modified layer, and the complex-bonded surface-modified layer may be insoluble in the first liquid solvent and soluble in the liquid solvent.

[0023] In other embodiments, two or more of steps a)-c) may be combined in each cycle of the hybrid ALE process. For example, steps b) and c) may be performed with at least partial time overlap in each cycle of the hybrid ALE process. In such embodiments, the liquid solvent may include a complexing agent, and the complex-bonded surface modification layer may be soluble in the liquid solvent.

[0024] In some embodiments, the methods disclosed in the second and third embodiments may further include d) washing the substrate to remove excess liquid solvent and unbound complexing agent, and e) drying the substrate using a gas flow, a spin-drying process, and / or a desiccant. In some embodiments, steps a) to e) may be repeated at least one time.

[0025] The methods disclosed herein can be used to etch a wide variety of materials, including polycrystalline, single crystalline, and amorphous materials. In some embodiments, the methods disclosed herein can be used to etch polycrystalline metal materials, such as transition metals. Examples of transition metals that can be etched using the methods disclosed herein include, but are not limited to, molybdenum (Mo), tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), and chromium (Cr).

[0026] A more complete understanding of the present invention and its advantages can be obtained by referring to the following description taken in conjunction with the accompanying drawings in which like reference numbers indicate like features, in which: It should be noted, however, that the accompanying drawings depict only exemplary embodiments of the disclosed concepts and therefore should not be considered limiting in scope, as the disclosed concepts may admit of other equally effective embodiments. [Brief description of the drawings]

[0027] [Figure 1] 1 illustrates an example of a cyclic hybrid atomic layer etching (ALE) process according to the present disclosure. [Figure 2A] FIG. 1 is a graph showing exemplary etching amounts (given in nanometers (nm)) that can be achieved over time (given in minutes (min)) when attempting to etch a molybdenum (Mo) surface using (a) UV ozone oxidation alone, and (b) a solution of α-benzoin oxime and DMSO. [Figure 2B] FIG. 1 is a graph showing an exemplary etch amount (nm) that can be achieved as a function of cycle number when a UV ozone oxidation step, an α-benzoin oxime ligand binding (complexation) step, and a DMSO dissolution step are used to etch a Mo surface using the hybrid ALE process disclosed herein. [Figure 3A] FIG. 1 is a block diagram illustrating one embodiment of a processing system capable of etching material on a surface of a substrate using the hybrid ALE process disclosed herein. [Figure 3B] FIG. 3B is an enlarged view of a portion of the substrate shown in FIG. 3A illustrating how the gas-phase surface modification and liquid-phase dissolution steps are split within the hybrid ALE process disclosed herein. [Figure 4] FIG. 1 is a flow diagram illustrating one embodiment of a method that utilizes the techniques described herein. [Diagram 5] FIG. 11 is a flow diagram illustrating another embodiment of a method utilizing the techniques described herein. [Figure 6]FIG. 11 is a flow diagram illustrating yet another embodiment of a method utilizing the techniques described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Chemical reactions on a surface may proceed using gas-phase reactants or liquid-phase reactants in contact with the surface. Wet ALE typically relies on reactions between a surface and a liquid-phase reactant, but gas-phase reactants can also be used to deliver reactants to the surface. Sequential reactions can also be achieved by utilizing reactants in different phases, such as a gas-phase reactant followed by a liquid-phase reactant (or vice versa). The present disclosure utilizes these concepts to provide a hybrid ALE process that avoids the disadvantages of wet ALE while maintaining its advantages.

[0029] In the hybrid ALE process described herein, a gas phase reactant is used to modify the exposed surface of a material to form a surface modification layer, and a liquid phase reactant is used to selectively dissolve the surface modification layer without dissolving the material underlying the surface modification layer. Once the surface modification layer has been selectively dissolved, the substrate may be dried, and the gas phase surface modification and liquid phase dissolution steps may be repeated for one or more ALE cycles until a desired amount of material has been etched.

[0030] In some embodiments, the exposed surface of the material may be exposed to a gas-phase reactant and a liquid-phase reactant sequentially. In other embodiments, the exposed surface of the material may be exposed to a liquid-phase reactant while a gas-phase reactant is being delivered to the process chamber. When a liquid-phase reactant is delivered in the presence of a gas-phase reactant, the liquid-phase reactant delivered onto the exposed surface of the material displaces the gas-phase reactant from the exposed surface to prevent further surface modification of the exposed surface. Delivered in this manner, the liquid-phase reactant not only dissolves the surface modification layer, but also separates the gas-phase surface modification step from the liquid-phase dissolution step. This reduces cycle time and improves throughput of the hybrid ALE process described herein compared to other ALE techniques by eliminating the need to perform a purge step between the surface modification step and the dissolution step.

[0031] Cycle time and throughput may be further improved in the hybrid ALE process described herein by performing the gas-phase surface modification step and the liquid-phase dissolving step in the same process chamber. In one exemplary embodiment, the gas-phase surface modification step and the liquid-phase dissolving step may both be performed in a spin chamber. In some embodiments, the gas-phase surface modification step and the liquid-phase dissolving step may be performed in the same process chamber at approximately the same temperature and pressure. In one exemplary embodiment, the gas-phase surface modification step and the liquid-phase dissolving step may be performed at (or near) ambient room pressure. Performing the gas-phase surface modification step and the liquid-phase dissolving step in the same process chamber at approximately the same temperature and pressure reduces cycle time and improves throughput of the hybrid ALE process described herein by avoiding unnecessary chamber transitions and temperature / pressure changes.

[0032] The techniques described herein offer several advantages over other etching techniques. For example, the techniques described herein offer the advantages of ALE, such as precise control of total etching volume, control of surface roughness, and improved wafer-scale uniformity. The techniques described herein also offer various advantages of wet etching, such as simplified etching chamber, self-limiting reactions at or near ambient etching conditions, and reduced surface roughness. Unlike traditional wet ALE processes, which tend to be time-consuming, the techniques described herein offer a hybrid ALE process that improves cycle time and throughput by combining a gas-phase surface modification step with a liquid-phase dissolution step.

[0033] The techniques described herein may be performed on a wide variety of substrates having a wide variety of layers and features formed thereon. In general, the substrate used in the techniques disclosed herein may be any substrate on which it is desired to etch a material. For example, the substrate may be a semiconductor substrate having one or more semiconductor processing layers formed thereon (all of which together may constitute the substrate). In one embodiment, the substrate may be a substrate that has been subjected to multiple semiconductor processing steps resulting in a wide variety of structures and layers (all of which are well known in the substrate processing art). In one embodiment, the substrate may be a semiconductor wafer that includes various structures and layers formed thereon.

[0034] The techniques described herein may be used to etch a wide variety of materials. Such materials include polycrystalline materials, single crystal materials, and amorphous materials. In some embodiments, the techniques described herein may be used to etch metallic materials, such as, but not limited to, transition metals and noble metals. In one exemplary embodiment, the material to be etched may be a polycrystalline transition metal, such as, for example, molybdenum (Mo). Although the techniques described herein are discussed below with respect to etching molybdenum, those skilled in the art will recognize that such examples are illustrative only and that the techniques described herein may be used to etch a wide variety of other materials. For example, the techniques described herein may be used to etch other transition metals, such as, but not limited to, tungsten (W), vanadium (V), niobium (Nb), tantalum (Ta), and chromium (Cr).

[0035] FIG. 1 illustrates an example of a hybrid ALE process according to the present disclosure. More specifically, FIG. 1 illustrates exemplary steps performed in one cycle of a hybrid ALE process. In the process illustrated in FIG. 1, a polycrystalline material 105 surrounded by a dielectric material 110 is exposed to a gas phase reactant 115 in a surface modification step 100 that modifies an exposed surface of the polycrystalline material 105 and forms a surface modification layer 120. In some embodiments, the polycrystalline material 105 to be etched can be, for example, a transition metal. In one exemplary embodiment, the polycrystalline material 105 can include molybdenum (Mo). In some embodiments, the gas phase reactant 115 can be included in an oxygen-containing gas environment. For example, the gas phase reactant 115 can be a gas phase oxidizer including, for example, oxygen (O2), ozone (O3), nitrogen dioxide (NO2), and / or a halogen gas. When the exposed surface of the polycrystalline material 105 is exposed to an oxygen-containing gas environment, i.e., the gas-phase oxidizing agent contained therein, the exposed surface is oxidized to form a self-limiting oxide layer (e.g., a molybdenum oxide such as MoO3) on the unmodified polycrystalline material.

[0036] Oxidation is often used as a surface modification step in ALE. Many oxidizing agents, such as oxygen (O2) and ozone (O3), are readily available at room temperature and atmospheric pressure. These oxidizing agents form self-limiting oxide layers at room temperature on many materials, such as metals. Although not strictly limited in this way, these metals can include transition metals, and more specifically, polycrystalline transition metals, such as molybdenum (Mo) metal.

[0037] 1, a chemical reaction (e.g., oxidation) occurs at the exposed surface of the polycrystalline material 105 to form a surface modification layer 120 (e.g., a self-limiting oxide layer such as molybdenum oxide). In some cases, the reaction may be fast and self-limiting, i.e., the reaction products may modify one or more monolayers of the exposed surface of the polycrystalline material 105, but may prevent further reaction between the gas-phase reactants 115 and the underlying polycrystalline material 105.

[0038] In some embodiments, the surface modification layer 120 may be exposed to one or more liquid phase reactants to selectively dissolve the surface modification layer 120. For example, the surface modification layer 120 may be exposed to a complexing agent 125 dissolved in a liquid solvent 135 (e.g., an aqueous or non-aqueous solution) in a complexing step 130. In the complexing step 130, the complexing agent 125 (e.g., a carboxylate-based ligand) binds to the surface modification layer 120 (e.g., a self-limiting oxidation layer) to form a ligand-metal complex 140. In some embodiments, the complexing agent 125 is a ligand of a higher oxidation state of the polycrystalline material 105 (e.g., Mo 6+ ) and react with the ligand dissolved in the liquid solvent 135 to form a ligand-metal complex 140 that is soluble in a subsequent dissolution step 150 of the surface modification layer 120 (e.g., MoO3). However, as described in more detail below, non-selective ligands may also be used to bind to the surface modification layer 120 and form the ligand-metal complex 140.

[0039] After oxidation and complexation, the polycrystalline material 105 is contacted with a liquid solvent 145 in a dissolution step 150 to selectively dissolve the surface modification layer 120 (e.g., MoO3) without dissolving the underlying polycrystalline material 105 (e.g., metallic Mo). This is accomplished by one of two different methodologies: reactive dissolution, or ligand binding followed by dissolution.

[0040] In reactive dissolution, the ligand is dissolved in a liquid solvent 135 capable of dissolving both the ligand and the ligand-metal complex 140 in a dissolution step 150. This allows for ligand binding and dissolution to be achieved using a single solvent 135 / 145. Thus, in reactive dissolution, the ligand binding and dissolution steps at least partially overlap in time.

[0041] In the reactive dissolution method, the surface modification layer 120 (e.g., MoO3) reacts with the ligands in the liquid solvent 135 / 145 to form soluble ligand-metal complexes 140 that dissolve in the liquid solvent 135 / 145 to remove the surface modification layer 120. Any thickness of the surface modification layer 120 (e.g., MoO3) can be removed using this method. Selectivity is achieved by determining whether the ligands are in a higher oxidation state (e.g., MoO3). 6+ ) to the polycrystalline material 105 but not to the polycrystalline material 105 of a lower oxidation state or to unmodified portions of the polycrystalline material 105. Since reactive dissolution is not self-limiting, the oxidation step must be self-limiting to keep the overall process self-limiting.

[0042] In the method of ligand binding followed by dissolution, the ligand binding and dissolution steps do not overlap in time. In this method, the ligand is dissolved in a liquid solvent 135 in which the ligand-metal complex 140 is insoluble. The ligand in the liquid solvent 135 reacts with the surface modification layer 120 (e.g., MoO3) to form an insoluble layer of the ligand-metal complex 140. This layer is dissolved in the dissolution step 150 when the surface is washed with a different liquid solvent 145 in which the ligand-metal complex 140 is soluble. In the method of ligand binding followed by dissolution, the removal of the surface modification layer 120 (e.g., MoO3) is limited by the packing density of the ligand on the surface. The ligand binding in the complexation step 130 and thus the dissolution of the ligand-metal complex 140 in the dissolution step 150 are self-limiting.

[0043] Once the surface modification layer 120 is dissolved, the ALE etching cycle may be completed by drying the surface of the substrate in a drying step 160. In one embodiment, the surface of the substrate may be dried in step 160 by providing a gas flow of air or nitrogen to the substrate. In another embodiment, the surface of the substrate may be dried in step 160 by performing a spin-dry step. In some embodiments, a drying aid (such as isopropyl alcohol (IPA)) may be provided on the surface of the substrate (not shown in FIG. 1) to further aid in drying the substrate before performing the spin-dry step. Once the surface of the substrate is dry, the surface modification step 100, complexing step 130, dissolving step 150, and drying step 160 shown in FIG. 1 may be repeated for one or more ALE cycles until a desired amount of polycrystalline material 105 is removed.

[0044] As mentioned above, in some embodiments, the hybrid ALE cycle shown in FIG. 1 may be used for Mo etching. In this etching regime, oxidation may be achieved by exposing the Mo surface to a gas-phase oxidant such as ozone. Ozone is a more oxidizing and reactive agent than molecular oxygen, and forms a self-limiting oxide that differs from the layer formed upon exposure to air. In particular, exposure to ozone results in the formation of a self-limiting molybdenum trioxide (MoO3) layer on the exposed Mo surface. After oxidation, the self-limiting molybdenum trioxide (MoO3) layer may be selectively removed by ligand-assisted dissolution in an appropriate solvent.

[0045] One good choice of ligand for Mo etching process is α-benzoin oxime. α-benzoin oxime ligand is Mo 6+To selectively bind ions, MoO3 reacts with the ligand to form molybdenum α-benzoin oximate (i.e., ligand-metal complex), but not with metallic molybdenum. This chemical selectivity allows ligand binding and dissolution to be achieved in a single solvent, such as dimethyl sulfoxide (DMSO). By exposing the MoO3 surface layer to a solution of α-benzoin oxime dissolved in DMSO, the MoO3 surface layer is converted to molybdenum α-benzoin oximate, which is then dissolved in DMSO. In this example, metallic molybdenum does not react with α-benzoin oxime, so the ligand binding and dissolution steps are self-limiting. For other non-selective ligands, the self-limiting behavior can be maintained by separating the ligand binding and dissolution steps into consecutive steps, using different solutions (i.e., different liquid solvents 135 and 145) for each process step.

[0046] The self-limiting and selective behavior of each of the above reaction steps is shown in FIG. 2A. More specifically, FIG. 2A shows a graph 200 illustrating exemplary etching amounts (in nanometers (nm)) that can be achieved with time (in minutes (min)) when etching a molybdenum (Mo) surface using (a) UV-ozone oxidation alone and (b) a solution of α-benzoin oxime and DMSO. As shown in FIG. 2A, even after 20 minutes of exposure to ozone in a UV ozone cleaner, the Mo surface is not etched. This indicates that the reaction between Mo and ozone is self-limiting at room temperature. Similarly, the Mo surface is not etched with a solution of α-benzoin oxime in DMSO. Even after 20 minutes of exposure, no etching is observed. This indicates that α-benzoin oxime does not react with metal or low oxidation states of Mo.

[0047] FIG. 2B shows a graph 250 illustrating an exemplary etch amount (nm) that can be achieved as a function of cycle number when the UV ozone oxidation, α-benzoin oxime ligand binding (complexation), and DMSO dissolution steps are used to etch a Mo surface using the hybrid ALE process disclosed herein. In the example shown in FIG. 2B, one ALE cycle consists of placing the Mo sample in a UV ozone cleaner for 1 minute, followed by a 10-second dip in a 50 mM α-benzoin oxime solution in DMSO. After removing excess DMSO and unbound α-benzoin oxime (complexing agent) with an acetone wash, the sample was dried using compressed air. In another example, another drying gas, such as nitrogen (N2), can be used. The thickness of the Mo layer was calculated from four-terminal resistivity measurements performed every 5 cycles. As shown in FIG. 2B, the etching is substantially linear with cycle number after the first nanometer of etching. Etching was observed in samples exposed to both UV and ozone in the oxidation step, as well as ozone only. This indicates that ozone, but not UV irradiation, is required for the hybrid ALE process of Mo. Figures 2A and 2B further show that the Mo material is not removed by exposure to either reactant alone (Figure 2A), but is removed in the cyclic hybrid ALE process shown in Figure 1 and described herein (Figure 2B).

[0048] The hybrid ALE process shown in Figure 1 smoothens the etched surface. To observe the etched surfaces, scanning electron microscope (SEM) images were acquired of the as-deposited Mo film and the Mo film etched using the hybrid ALE scheme described above. No pitting or preferential grain boundary etching was observed in the etched samples. In addition, it was observed that the thickness of the etched samples calculated from four-terminal resistivity measurements was consistent with the thickness measured in the SEM cross section. The roughness of the Mo film did not increase when etched using the hybrid ALE process described above, but particulate contamination (probably from the acetone washing step) was observed.

[0049] The hybrid ALE process described herein may be used to etch a wide variety of materials, including polycrystalline, single crystalline, and amorphous materials. In some embodiments, the hybrid ALE process described herein may be used to etch polycrystalline materials, such as transition metals (e.g., molybdenum (Mo)), as described above, and a gas-phase oxidizer (e.g., oxygen (O2) or ozone (O3)) may be used to oxidize the exposed surface of the transition metal to form a self-limiting oxide layer (e.g., MoO3, etc.). The oxidation of transition metals, such as molybdenum, is self-limiting when carried out at (or near) room temperature. After the exposed surface of the transition metal is exposed to the gas-phase oxidizer and a self-limiting oxide layer is formed, one or more liquid-phase reactants are delivered onto the surface of the substrate to selectively dissolve the self-limiting oxide layer, such that the self-limiting oxide layer may be removed without etching the underlying polycrystalline material. To selectively dissolve molybdenum oxide (e.g., MoO3) without dissolving metallic Mo, several different chemicals can be used, which are described in more detail below.

[0050] In some embodiments, for example, the MoO3 surface layer can be exposed to a ligand (such as α-benzoin oxime) dissolved in a non-aqueous solution (such as DMSO). By exposure to α-benzoin oxime dissolved in DMSO, the MoO3 surface layer is converted to molybdenum α-benzoin oximate, which is then dissolved in DMSO. However, in addition to DMSO, α-benzoin oxime is also soluble in water, alcohol, acetone, methyl ethyl ketone (MEK), and other ketones. The α-benzoin oxime ligand can be used to convert the MoO3 containing surface layer to molybdenum α-benzoin oximate. 6+It selectively binds ions to form Mo-α-benzoin oxime complexes that are soluble in acetone, DMSO, and other ketones, but insoluble in alcohols or water. This chemical selectivity allows ligand binding and dissolution to be achieved in a single solvent, for example, acetone, DMSO, and other ketones. Alternatively, ligand binding and dissolution can be performed in successive, non-overlapping steps, for example, using water or alcohols in a first step and acetone, DMSO, and other ketones in a second step.

[0051] Besides α-benzoin oxime, other ligands have been used to 6+ to form alternative ligand-metal complexes without binding to metallic molybdenum (Mo) or low oxidation states of Mo. Examples of such ligands include, but are not limited to, toluenedithiol, cupferrone, and 8-hydroxyquinoline. Like α-benzoin oxime, these ligands selectively bind to Mo. 6+ MoO3 selectively binds to form ligand-metal complexes that are soluble in non-aqueous solutions. For example, Mo-toluenedithiol complexes are soluble in acetates (e.g., ethyl acetate, butyl acetate, and amyl acetate) and carbon tetrachloride. Toluenedithiol is soluble in aqueous solutions and alcohol, but the Mo complex is insoluble. Mo-cupferron complexes are soluble in chloroform, concentrated nitric acid, or concentrated ammonium hydroxide. Cupferron is soluble in neutral aqueous solutions, but the Mo complex is insoluble. Mo-8-hydroxyquinoline complexes are soluble in concentrated mineral acids. 8-hydroxyquinoline is soluble in ethanol, acetone, chloroform, and benzene, but the Mo complex is insoluble. Any of the above-mentioned ligands can be used in the above-mentioned ligand-binding post-dissolution method to selectively dissolve the MoO3 surface layer.

[0052] Reactive dissolution of the MoO3 surface layer can also be achieved in aqueous solutions. For example, concentrated hydrochloric acid (HCl) can be used to selectively dissolve molybdenum oxide over metallic Mo. The measured Mo etch rates for 0.1 M, 1 M, 5 M, and 12 M HCl are below the normal detection threshold (e.g., <0.01 nm / min). These same concentrations of HCl dissolve a monolayer of MoO3 in less than 2 seconds, giving a selectivity ratio of over 800:1. Besides HCl, other mineral acids (such as sulfuric acid) can be used to dissolve molybdenum oxide. In some cases, sulfuric acid (H2SO4) may be preferred over HCl from a material compatibility standpoint. The availability of HCl and sulfuric acid (and other mineral acids) at high purity and low cost, their use in many other semiconductor processes, and their performance in selectively removing MoO3 may make mineral acids one of the preferred aqueous chemicals used for selective dissolution of MoO3 in the hybrid ALE process described herein. Concentrated ammonium hydroxide (NH4OH) can also be used to dissolve molybdenum oxides, but the selectivity to Mo metal with concentrated NH4OH is not as good as with HCl.

[0053] The use of water-soluble chemistries for selective dissolution of MoO3 offers several advantages. Water-soluble chemistries use cheap commodity chemicals, are environmentally friendly enough, and do not pose the risk of flammability of organic solvents. However, aqueous solutions of ammonium hydroxide (NH4OH) and concentrated mineral acids (such as HCl) react with many different metals. This can raise concerns about selectivity in Mo etching when multiple metals are present on the wafer surface. This leads to the advantage of non-water-soluble chemistries, namely that the ligand-metal complex formation can be very selective between metals. For example, α-benzoin oxime selectively dissolves Mo over most other metals. 6+α-Benzoin oxime is used to separate Mo from solutions containing many other metal ions in quantitative analysis. However, the selectivity advantage of using these ligands comes at the cost of additional chemical costs and flammability risks from using organic solvents.

[0054] Although Mo etching has been described thus far, one skilled in the art will readily understand how the hybrid ALE process shown in FIG. 1 can be used to etch other transition metals. For example, α-benzoin oxime binds to other ions as well as molybdenum. This includes ligand-metal complexes of tungsten, palladium, vanadium, niobium, tantalum, and chromium. There is inherent selectivity for other metals that do not bind with α-benzoin oxime. Selectivity for other metals that form complexes with α-benzoin oxime can still be achieved. Although α-benzoin oxime binds to the transition metals listed above, the ligand-metal complexes formed with such metals have different solubilities in different solutions. Selectivity is achieved in the dissolution step because molybdenum oximate is soluble in DMSO, whereas, for example, tungsten oximate is insoluble. However, both molybdenum oximate and tungsten oximate complexes are soluble in chloroform.

[0055] Room temperature processing is a major advantage of wet hybrid ALE over thermal ALE. This advantage is due to the mechanism by which the modified layer is removed. In thermal ALE, the modified layer is removed by volatilization when the material is taken from the solid phase to the gas phase. This phase change requires additional latent heat and is limited by the vapor pressure of the modified layer. High temperatures are often required to remove the modified layer because the thermal energy is used to replace the intermolecular interactions that stabilize the modified layer on the surface.

[0056] Unlike thermal ALE, in wet hybrid ALE the modified layer is dissolved in a solution. This process forms a solvation shell around the molecules as they dissolve. The interactions between the solvent and the solute are replaced by the intermolecular interactions in the solid state. This solvation energy, not thermal energy, drives the dissolution. The fundamental difference between the energy required for dissolution and the energy required for vaporization explains why wet hybrid ALE can be performed at room temperature while thermal ALE cannot. Since the solvation energy is highly dependent on the solvent species, an appropriate solvent must be selected to dissolve the modified layer in the hybrid ALE process described herein. For surfaces made of multiple materials, the different solvation energies of different components provide another route to derive selectivity.

[0057] The hybrid ALE process described herein may be realized using many different process chambers, tools, and equipment, but processing equipment used to perform the hybrid ALE process may preferably operate at (or near) room temperature and at (or near) atmospheric pressure. In one exemplary embodiment, the hybrid ALE process described herein may be performed in a spin chamber. When a spin chamber is utilized, liquid-phase reactants are provided from a nozzle located above the substrate and dispersed by the rotational motion of a spin chuck on which the substrate is located. Gas-phase reactants (e.g., gas-phase oxidizers such as oxygen or ozone) may also be provided from a nozzle that may be moved across the substrate surface so that the entire surface receives the same amount of gas-phase reactant. Alternatively, the gas-phase reactants may be provided from a gas inlet that introduces the gas-phase reactants into the spin chamber to form an oxygen-containing gas environment. The use of gas-phase reactants requires that the spinner (also called a spin chuck) be housed in an airtight enclosure with an exhaust and appropriate exhaust cleanup equipment, such as an ozone depletion module. In some embodiments, the spinner may be housed in an airtight enclosure that contains the gas phase reactants at static pressure.

[0058] FIG. 3A illustrates one embodiment of a processing system 300 that may etch material on a surface of a substrate 330 using the hybrid ALE techniques described herein. As illustrated in FIG. 3A, the processing system 300 includes a process chamber 310, which may be a pressure-controlled chamber in some embodiments. In the embodiment illustrated in FIG. 3A, the process chamber 310 is a spin chamber having a spinner 320 (or spin chuck) configured to spin or rotate at a controlled rate. A substrate 330 is held on the spinner 320, for example, by electrostatic forces or vacuum pressure. In one example, the substrate 330 may be a semiconductor wafer with a material (e.g., a polycrystalline material, etc.) formed on or in the substrate 330.

[0059] The processing system 300 shown in FIG. 3A further comprises a nozzle 340 disposed above the substrate 330 to deliver a liquid-phase reactant 342 onto the surface of the substrate 330, and a gas inlet 350 to deliver a gas-phase reactant 352 into the process chamber 310. In some embodiments, the polycrystalline material formed on or in the substrate 330 may be a transition metal (e.g., molybdenum (Mo) or the like), and a gas-phase reactant 352, such as a gas-phase oxidizer (e.g., O2 or O3, or the like), may be delivered to the process chamber 310 via the gas inlet 350 to form an oxygen-containing gas environment. The oxygen-containing gas environment oxidizes the exposed surface of the transition metal to form a self-limiting oxide layer (e.g., MoO3, or the like). After the oxide layer is formed, one or more liquid-phase reactants 342 may be delivered onto the surface of the substrate 330 via the nozzle 340 to selectively dissolve the oxide layer, such that the oxide layer may be removed without etching the underlying polycrystalline material. Examples of liquid phase reactants 342 that can be used to selectively bind and dissolve the oxide layer are discussed in more detail above.

[0060] The liquid phase reactant(s) 342 may be stored in a chemical delivery system 346, which may comprise one or more reservoirs for holding various liquid phase reactant(s) 342 and a chemical injection manifold fluidly coupled to the process chamber 310 via liquid supply lines 344. In operation, the chemical delivery system 346 may selectively apply a desired chemical to the process chamber 310 via the liquid supply lines 344 and nozzles 340 disposed in the process chamber 310. In this manner, the chemical delivery system 346 may be used to deliver the liquid phase reactant(s) 342 onto the surface of the substrate 330.

[0061] The gas-phase reactant(s) 352 may be stored in a gas supply system 356, which may comprise one or more reservoirs for holding various gas-phase reactant(s) 352 and a gas injection manifold coupled to the process chamber 310 via gas supply lines 354. In operation, the gas supply system 356 may selectively apply a desired gas-phase reactant to the process chamber 310 via the gas supply lines 354 and gas inlets 350 disposed in the process chamber 310. In this manner, the gas supply system 356 may be used to introduce the gas-phase reactants 352 to the process chamber 310.

[0062] Because a gas-phase reactant 352 is used, the process chamber 310 may comprise an airtight enclosure capable of maintaining a static pressure of the gas-phase reactant. The process chamber 310 may further comprise a gas exhaust 370 for removing the gas-phase reactant 352 and a drain 380 for removing the liquid-phase reactant 342 from the process chamber 310. In some embodiments, the gas exhaust 370 may be coupled to a suitable exhaust cleaning device (not shown), such as an ozone depletion module.

[0063] The components of the processing system 300 may be coupled to and controlled by a controller 360, which may be coupled to corresponding memory storage units and a user interface (not shown). Various processing operations may be performed via the user interface, and various processing recipes and operations may be stored in the storage unit. Thus, a given substrate 330 may be processed in the process chamber 310 according to a particular recipe. In some embodiments, a given substrate 330 may be processed in the process chamber 310 according to an etch recipe that utilizes the hybrid ALE techniques described herein.

[0064] The controller 360, shown in block diagram form in FIG. 3A, can be implemented in a wide variety of ways. In one example, the controller 360 can be a computer. In another example, the controller 360 can include one or more programmable integrated circuits programmed to provide the functionality described herein. For example, one or more processors (e.g., microprocessors, microcontrollers, central processing units, etc.), programmable logic devices (e.g., complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), etc.), and / or other programmable integrated circuits can be programmed with software or other programming instructions to implement the functionality of a defined plasma process recipe. It is further noted that the software or other programming instructions can be stored in one or more non-transitory computer-readable media (e.g., memory storage devices, flash memory, dynamic random access memory (DRAM), reprogrammable storage devices, hard drives, floppy disks, DVDs, CD-ROMs, etc.) and that the software or other programming instructions, when executed by the programmable integrated circuit, cause the programmable integrated circuit to perform the processes, functions, and / or capabilities described herein. Other variations may also be implemented.

[0065] 3A, a controller 360 may be coupled to receive inputs from and provide outputs to various components of the processing system 300. For example, the controller 360 may be coupled to the process chamber 310 to control the temperature and / or pressure therein, coupled to the spinner 320 to control the rotational speed of the spinner 320, coupled to a chemical delivery system 346 to control various liquid-phase reactants 342 delivered onto the substrate 330, and coupled to a gas delivery system 356 to control various gas-phase reactants 352 introduced to the process chamber 310.

[0066] In some embodiments, the controller 360 may control various components of the processing system 300 according to an etching recipe that utilizes the hybrid ALE technique described herein. For example, the controller 360 may provide various control signals to the gas supply system 356, which may cause the gas supply system 356 to introduce gas-phase reactants 352 into the process chamber 310 to form a surface modification layer on the substrate 330. Similarly, the controller 360 may provide various control signals to the chemical supply system 346, which may cause the chemical supply system 346 to provide one or more liquid-phase reactants 342 onto the surface of the substrate 330 to selectively dissolve the surface modification layer without dissolving the material underlying the surface modification layer. Exemplary gas-phase reactants 352 and liquid-phase reactants 342 for modifying an exposed surface of a polycrystalline molybdenum (Mo) material and for selectively dissolving the Mo surface modification layer are discussed above.

[0067] Once the surface modification layer is selectively dissolved, the substrate 330 may be dried, and the gas-phase surface modification and liquid-phase dissolution steps may be repeated for one or more ALE cycles until a desired amount of polycrystalline material is etched. In some embodiments, the controller 360 may provide control signals to the spinner 320 and / or the chemical delivery system 346 to dry the substrate 330. In one example, the controller 360 may control the rotation speed of the spinner 320 to dry the substrate 330 in a spin-dry step. In another example, the control signal provided from the controller 360 to the chemical delivery system 346 may cause a desiccant (e.g., isopropyl alcohol, etc.) to be provided on the surface of the substrate 330 to further help dry the substrate before performing the spin-dry step.

[0068] In some embodiments, the gas-phase surface modification, liquid-phase dissolution, and spin-drying steps of the hybrid ALE processes described herein may each be performed at approximately the same temperature and pressure in the same process chamber 310. In one exemplary embodiment, the gas-phase surface modification, liquid-phase dissolution, and spin-drying steps may be performed at (or near) ambient pressure and room temperature. Performing the processing steps in the same process chamber at approximately the same temperature and pressure reduces cycle time and improves throughput of the hybrid ALE processes described herein by avoiding unnecessary chamber transitions and temperature / pressure changes.

[0069] However, it should be noted that the embodiments described herein are not strictly limited to ambient pressure and room temperature, nor are they limited to a particular process chamber. In other embodiments, one or more of the process steps of the hybrid ALE process described herein may be carried out in a pressure vessel above ambient pressure or at reduced pressure in a vacuum chamber. Liquid phase reactants may be provided in these environments as long as the vapor pressure of the liquid is lower than the chamber pressure. In these embodiments, a spinner with a liquid delivery nozzle is placed in the pressure vessel or vacuum chamber. The temperature of the delivered liquid may be raised to any temperature below the boiling point at the pressure of the process. Higher liquid temperatures may increase the rate of dissolution.

[0070] In some embodiments of the hybrid ALE process described herein, the substrate 330 may be exposed to the gas-phase reactant(s) 352 and the liquid-phase reactant(s) 342 sequentially. However, in other embodiments, the substrate 330 may be exposed to one or more liquid-phase reactants 342 while the gas-phase reactants 352 are being supplied to the process chamber 310. When the liquid-phase reactants 342 are supplied in the presence of the gas-phase reactants 352, the liquid-phase reactants 342 supplied on the surface of the substrate 330 displace the gas-phase reactants 352 from the surface to prevent further modification of the surface. When supplied in this manner, the liquid-phase reactants 342 not only dissolve the surface modification layer, but also split the gas-phase surface modification step from the liquid-phase dissolution step. This is shown diagrammatically in FIG. 3B and improves the cycle time and throughput of the hybrid ALE process described herein compared to other ALE techniques by eliminating the need to perform a purge step between the surface modification step and the dissolution step.

[0071] To illustrate the division between the gas-phase surface modification and liquid-phase dissolution steps, a close-up of a portion 390 of the substrate 330 is shown in FIG. 3B. In the hybrid ALE process described herein, gas-phase reactant(s) 352 are introduced into the process chamber 310 to form, for example, an oxygen-containing gas environment. The gas-phase reactant(s) 352 react with the exposed surface of the substrate 330 to form a self-limiting surface modification layer 335. One or more liquid-phase reactants 342 are then delivered onto the surface of the substrate 330 in the presence of the gas-phase reactants 352 while the spinner 320 is rotating. As the spinner 320 rotates, the liquid-phase reactant(s) 342 spread outward (in the direction shown in FIG. 3B) and dissolve the surface modification layer 335. The liquid phase reactant(s) 342 prevent the gas phase reactants 352 from reaching the surface of the substrate 330, thereby dissolving the surface modification layer 335 while preventing the underlying portions of the substrate 330 from being re-oxidized.

[0072] As the liquid-phase reactant(s) 342 spread outward (in the direction shown in FIG. 3B ), the gas-phase reactant(s) 352 are expelled from the surface of the substrate 330. This expulsion occurs because the liquid-phase reactant(s) 342 form a continuous film on the surface, which makes it difficult or substantially prevents the gas-phase reactant(s) 352 from reaching the surface of the substrate 330. For example, the gas-phase reactant 352 must diffuse through the liquid-phase reactant(s) 342 to reach the surface of the substrate 330. However, if the surface modification layer 335 is dissolved by the liquid-phase reactant(s) 342, the liquid-phase reactant(s) 342 may be washed away from the surface of the substrate 330, re-exposing the surface to the gas-phase reactant(s) 352 and forming a new surface modification layer. Exposure to the gas-phase reactant(s) 352 may, in some embodiments, be accomplished by spin-drying the substrate 330. Repeated applications of the liquid-phase reactant(s) 342 effectively separate the gas-phase surface modification process from the liquid-phase dissolution process, since the liquid-phase reactant(s) 342 may be washed off the surface of the substrate 330 at a rate faster than the diffusion timescale of the gas-phase reactant(s) 352 into the liquid.

[0073] The techniques described herein offer several advantages over other etching techniques. For example, the techniques described herein offer the advantages of ALE, such as precise control of total etch volume, control of surface roughness, and improved wafer-scale uniformity. The techniques described herein also offer various advantages of wet etching, such as simplified etch chamber, self-limiting reactions at or near atmospheric and room temperature etching conditions, and reduced surface roughness.

[0074] Unlike conventional wet ALE processes, which tend to be time-consuming, the techniques described herein provide a hybrid ALE process that improves cycle time and throughput by combining a gas-phase surface modification step with a liquid-phase dissolution step. As described above, cycle time and throughput are improved in the hybrid ALE process described herein by performing the gas-phase surface modification step and the liquid-phase dissolution step in the same process chamber at approximately the same temperature and pressure. In some embodiments, cycle time and throughput are further improved by delivering liquid-phase reactant(s) onto the surface of the substrate in the presence of gas-phase reactant(s) such that the liquid-phase reactant(s) displace the gas-phase reactant(s) from the surface, and splitting the gas-phase surface modification step and the liquid-phase dissolution step.

[0075] 4-6 illustrate exemplary methods of using the hybrid ALE technique described herein. More specifically, FIGS. 4-6 illustrate various embodiments of methods used to provide a hybrid ALE process that maintains the advantages of wet ALE while avoiding its drawbacks by combining a gas-phase surface modification step with a liquid-phase dissolution step to etch a substrate disposed in a process chamber. It should be understood that the embodiments of FIGS. 4-6 are merely exemplary and that additional methods may utilize the hybrid ALE technique described herein. Additionally, additional process steps may be added to the methods illustrated in FIGS. 4-6, as the process steps described are not intended to be exclusive. Additionally, the order of steps is not limited to the order shown in the figures, as different orders may occur and / or various steps may be performed in combination or simultaneously.

[0076] FIG. 4 illustrates one embodiment of a method 400 that can be used to etch a substrate using a hybrid atomic layer etching (ALE) process. The method 400 illustrated in FIG. 4 includes receiving (at step 410) a substrate, the substrate having an exposed material. Then, at step 420, the method 400 includes selectively etching the material by performing multiple cycles of the hybrid ALE process, each cycle including: a) performing a gas-phase surface modification step to chemically modify an exposed surface of the material and provide a surface modification layer, the gas-phase surface modification step including exposing the substrate to a gas-phase reactant to chemically modify the exposed surface of the material, and b) performing a liquid-phase dissolution step to selectively dissolve the surface modification layer of the material, the liquid-phase dissolution step including providing one or more liquid-phase reactants on the surface of the substrate to dissolve the surface modification layer. In the method 400 illustrated in FIG. 4, one or more liquid-phase reactants are provided on the surface of the substrate while the substrate is exposed to the gas-phase reactants. In such methods, one or more liquid phase reactants displace the gas phase reactants from the surface of the substrate, thereby separating the gas phase surface modification step from the liquid phase dissolution step.

[0077] FIG. 5 illustrates another embodiment of a method 500 that may be used to etch a substrate using a hybrid atomic layer etching (ALE) process. The method 500 illustrated in FIG. 5 includes receiving (at step 510) a substrate, the substrate having an exposed polycrystalline material. Then, at step 520, the method 500 includes selectively etching the polycrystalline material by performing multiple cycles of the hybrid ALE process, each cycle including: a) chemically modifying an exposed surface of the polycrystalline material to provide a surface-modified layer, the exposed surface being chemically modified by oxidation of the polycrystalline material using a gas-phase oxidizing agent; b) binding a complexing agent to the surface-modified layer of the polycrystalline material to provide a complexed surface-modified layer; and c) selectively removing the complexed surface-modified layer of the polycrystalline material by exposing the complexed surface-modified layer to a liquid solvent, the liquid solvent dissolving the complexed surface-modified layer without dissolving the polycrystalline material underlying the complexed surface-modified layer.

[0078]

[0023] Figure 6 illustrates yet another embodiment of a method 600 that may be used to etch a substrate using a hybrid atomic layer etching (ALE) process. The method 600 illustrated in Figure 6 includes receiving a substrate (at step 610), the substrate having exposed molybdenum (Mo) metal. Then, in step 620, the method 600 includes selectively etching the Mo metal by performing multiple cycles of a hybrid ALE process, each cycle including: a) chemically modifying an exposed surface of the Mo metal to provide a surface modification layer, wherein the exposed surface is chemically modified by oxidation of the Mo metal using a gas phase oxidizing agent comprising ozone; b) binding a complexing agent to the surface modification layer of the Mo metal to provide a complex-bonded surface modification layer; and c) selectively removing the complex-bonded surface modification layer of the Mo metal by exposing the complex-bonded surface modification layer to a liquid solvent, wherein the liquid solvent dissolves the complex-bonded surface modification layer without dissolving the Mo metal underlying the complex-bonded surface modification layer, and wherein b) and c) at least partially overlap in time.

[0079] It should be noted that throughout this specification, references to "one embodiment" or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention, but do not indicate that they are present in all embodiments. Thus, the appearance of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily refer to the same embodiment of the invention. Moreover, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. In other embodiments, various additional layers and / or structures may be included and / or described features may be omitted.

[0080] As used herein, the term "substrate" means and includes a base material or structure on which a material is formed. It should be understood that a substrate may include a single material, multiple layers of different materials, one or more layers having regions of different materials or structures therein, and the like. These materials may include semiconductors, insulators, conductors, or combinations thereof. For example, the substrate may be a semiconductor substrate, a base semiconductor layer on a supporting structure, a metal electrode, or a semiconductor substrate having one or more layers, structures, or regions formed thereon. The substrate may be a conventional silicon substrate or other bulk substrate including a layer of semiconducting material. As used herein, the term "bulk substrate" means and includes not only silicon wafers, but also silicon-on-insulator ("SOI") substrates such as silicon-on-sapphire ("SOS") substrates and silicon-on-glass ("SOG") substrates, epitaxial layers of silicon on a base semiconductor substrate, and other semiconductor or optoelectronic materials such as silicon germanium, germanium, gallium arsenide, gallium nitride, and indium phosphide. The substrate may be doped or undoped.

[0081] Systems and methods for processing a substrate are described in various embodiments. The substrate may include any material portion or structure of a device, particularly a semiconductor or other electronic device, and may be, for example, a base substrate structure, such as a semiconductor substrate, or a layer on or overlying the base substrate structure, such as a thin film. Thus, the substrate is not intended to be limited to any particular base structure, underlying layer, or overlying layer, patterned or unpatterned, but rather is intended to include any such layer or base structure, and any combination of layers and / or base structures.

[0082] As will be appreciated by those skilled in the art, various embodiments may be practiced without one or more of the specific details, or with other alternative and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring aspects of the various embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth to provide a thorough understanding of the invention. However, the invention may be practiced without the specific details. Furthermore, it should be understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

[0083] Further modifications and alternative embodiments of the described systems and methods should be apparent to those skilled in the art upon review of this specification. It is therefore understood that the described systems and methods are not limited by these exemplary configurations. It should be understood that the forms of the systems and methods shown and described herein should be construed as exemplary embodiments. Various modifications can be made to the embodiments. Thus, although the hybrid ALE technique is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the disclosure. Thus, the specification and drawings should be regarded in an illustrative rather than a restrictive sense, and such modifications are intended to be included within the scope of the disclosure. Moreover, any benefits, advantages, or solutions to problems described herein with respect to specific embodiments are not intended to be construed as any or all essential, necessary, or essential features or elements of the claims.

Claims

1. 1. A method of etching a substrate using a hybrid atomic layer etching (ALE) process, the method comprising: receiving the substrate, the substrate having exposed material; Selectively etching the material by performing multiple cycles of the hybrid ALE process, each cycle comprising: a) performing a gas-phase surface modification process to chemically modify an exposed surface of the material and provide a self-limiting surface modification layer on the material, the gas-phase surface modification process comprising exposing the substrate to a gas-phase reactant to chemically modify the exposed surface of the material and form the self-limiting surface modification layer on the material via a self-limiting reaction; b) performing a liquid phase dissolution process to selectively dissolve the self-limiting surface modification layer of the material, the liquid phase dissolution process comprising providing one or more liquid phase reactants on a surface of the substrate to dissolve the self-limiting surface modification layer; Including, the one or more liquid phase reactants are delivered onto the surface of the substrate while the substrate is exposed to the gas phase reactants; the one or more liquid phase reactants displace the gas phase reactants from the surface of the substrate, thereby separating the gas phase surface modification step from the liquid phase dissolution step; Steps a)-b) are repeated one or more times until a desired amount of the material is removed from the substrate. A method comprising:

2. The method of claim 1 , wherein the material comprises a transition metal.

3. 10. The method of claim 1, wherein said performing a gas-phase surface modification step comprises exposing said substrate to a gas-phase oxidizing agent to oxidize said exposed surface of said material to form a self-limiting oxide layer.

4. 4. The method of claim 3, wherein said performing a liquid phase dissolution step comprises providing a complexing agent dissolved in a first liquid solvent onto said surface of said substrate, said complexing agent binding to said self-limiting oxidation layer to form a ligand-metal complex.

5. 5. The method of claim 4, wherein said performing a liquid phase dissolution step comprises providing a second liquid solvent onto said surface of said substrate to dissolve said ligand-metal complexes and remove said self-limiting oxidation layer.

6. The method of claim 5 , wherein the first liquid solvent and the second liquid solvent are the same.

7. The method of claim 5 , wherein the first liquid solvent and the second liquid solvent are different solvents.

8. 10. The method of claim 1, wherein each cycle further comprises drying the surface of the substrate after the liquid phase dissolution process is performed that selectively dissolves the self-limiting surface modification layer of the material.

9. 9. The method of claim 8, wherein said drying the surface of the substrate comprises spin-drying the substrate to rinse the one or more liquid phase reactants from the surface of the substrate and re-exposing the exposed surface of the material to the gas phase reactants in a subsequent gas phase surface modification step.

10. 1. A method of etching a substrate using a hybrid atomic layer etching (ALE) process, comprising: receiving the substrate, the substrate having exposed polycrystalline material; Selectively etching the polycrystalline material by performing multiple cycles of the hybrid ALE process, each cycle comprising: a) chemically modifying an exposed surface of the polycrystalline material to provide a surface modification layer, the exposed surface being chemically modified by oxidizing the polycrystalline material using a gas phase oxidizing agent to form a self-limiting oxidation layer on the polycrystalline material via a self-limiting oxidation reaction; b) binding a complexing agent to the self-limiting oxidation layer formed on the polycrystalline material to provide a complex-bound surface modification layer; c) selectively removing the complex-bonded surface-modified layer of the polycrystalline material by exposing the complex-bonded surface-modified layer to a liquid solvent, the liquid solvent dissolving the complex-bonded surface-modified layer without dissolving the polycrystalline material underlying the complex-bonded surface-modified layer; Including, A method comprising:

11. The method of claim 10 , wherein in each cycle b) and c) are performed with at least partial overlap in time.

12. The method of claim 11 , wherein the liquid solvent comprises the complexing agent, and the complex-bonded surface modification layer is soluble in the liquid solvent.

13. The method of claim 10 , wherein in each cycle, b) and c) are performed consecutively with no overlap in time.

14. 14. The method of claim 13, wherein the complexing agent is dissolved in a first liquid solvent different from the liquid solvent used to dissolve the complex-bonded surface-modified layer, and the complex-bonded surface-modified layer is insoluble in the first liquid solvent and soluble in the liquid solvent.

15. The method of claim 10 , wherein the polycrystalline material comprises a transition metal.

16. The method of claim 10, further comprising repeating steps a) through c) at least once until a desired amount of the polycrystalline material is removed from the substrate.

17. 1. A method of etching a substrate using a hybrid atomic layer etching (ALE) process, comprising: receiving the substrate, the substrate having exposed molybdenum (Mo) metal; Selectively etching the Mo metal by performing multiple cycles of the hybrid ALE process, each cycle comprising: a) chemically modifying an exposed surface of the Mo metal to provide a surface modification layer, the exposed surface being chemically modified by oxidizing the Mo metal using a gas phase oxidizing agent comprising ozone to form a self-limiting molybdenum oxide layer on the Mo metal via a self-limiting oxidation reaction; b) binding a complexing agent to the self-limiting molybdenum oxide layer formed on the Mo metal to provide a complex-bound surface modification layer; c) selectively removing the complex-bonded surface modification layer of the Mo metal by exposing the complex-bonded surface modification layer to a liquid solvent, the liquid solvent dissolving the complex-bonded surface modification layer without dissolving the Mo metal underlying the complex-bonded surface modification layer, and b) and c) at least partially overlap in time; Including, A method comprising:

18. The method of claim 17, further comprising repeating steps a) through c) at least once until a desired amount of the Mo metal is removed from the substrate.

19. The method of claim 17 , wherein the liquid solvent comprises the complexing agent, and the complex-bonded surface modification layer is soluble in the liquid solvent.

20. d) washing the substrate to remove excess liquid solvent and unbound complexing agent; e) drying the substrate using a gas flow, a spin-dry process, and / or a desiccant; 20. The method of claim 17, further comprising:

21. The method of claim 20, further comprising repeating steps a) through e) at least once until a desired amount of the Mo metal is removed from the substrate.

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