Universal atomic layer etching device and method

Abstract

A universal atomic layer etching (ALE) device for both isotropic and anisotropic etching is disclosed The universal ALE device includes a holder configured hold a substrate, an ALE chamber enclosing the holder to conceal the substrate internally and hermetically, and a plasma source configured to supply plasma into the ALE chamber. An integrated showerhead is positioned between the holder and the plasma source, dividing the ALE chamber into a first compartment configured to receive the plasma and a second chamber configured to distribute reactive gas to the substrate. The integrated showerhead includes a first tier having at least one first inlet configured to receive an inert gas, a second tier having at least one second inlet configured receive a reactive gas, and a plurality of common outlets for distributing the inert gas and the reactive gas towards the substrate directly.

Description

UNIVERSAL ATOMIC LAYER ETCHING DEVICE AND METHOD

[0001] The present disclosure relates to material removal processes and equipment, and more specifically, to material removal processes based on atomic layer etching, and device and method for atomic layer etching.

[0002] Atomic layer etching (ALE) is an advanced etching technique used in microfabrication and nanotechnology for precise and controlled removal of material at the atomic scale. ALE enables layer-by-layer removal with atomic-level precision, making it ideal for applications requiring high precision and high uniformity. ALE involves a cyclic or repeated process where a reactive species selectively reacts with the substrate surface to remove a single atomic layer at a time. Once the surface is saturated with the reactive species or the surface reacted layer is completely removed, the etching process stops, resulting in precise control over the etch depth. Further, isotropic and anisotropic ALE techniques are used in microfabrication and nanotechnology for precise removal of material at the atomic scale. Isotropic ALE involves the removal of material from a substrate in all directions, resulting in uniform etching across the surface. In isotropic ALE, reactive species are introduced to the substrate surface, where they react with the material to remove atomic layers uniformly. As such, isotropic ALE is particularly useful for applications where uniform etching or surface modification is desired, such as surface cleaning, smoothing, or form complex 3D structures. On the other hand, anisotropic ALE selectively removes material from a substrate in specific directions, resulting in directional etching with well-defined sidewalls. Accordingly, anisotropic ALE is essential for creating high-resolution features with precisely defined sidewalls, such as trenches, vias, and nanopores, required inadvanced semiconductor devices and nanotechnology applications. Anisotropic etch is required to reduce the damage to the underlayer in directional etch.

[0003] Due to the above differences in etch process directionality control, the isotropic and anisotropic ALE typically processes require different sets of hardware equipment features. As a result, in manufacturing industries where both the isotropic and anisotropic processes are required to performed, it proves costly and time consuming to acquire and utilise different equipment configurations for both application needs.

[0004] For etching 3D device structures, both isotropic and anisotropic ALE may be required in separate process steps or sequential process steps. Therefore, there is need for a device and method that has the capability to effectively perform both isotropic and anisotropic etching in the same equipment, and thereby provide offer efficiency, costeffectiveness, and flexibility in microfabrication and semiconductor processing.

[0005] This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the application. This summary is neither intended to identify key or essential inventive concepts of the invention or application and nor is it intended for determining the scope of relevant invention or application.

[0006] In an implementation of the present disclosure, a universal atomic layer etching (ALE) device for both isotropic and anisotropic etching is disclosed. The universal ALE device may include a holder configured hold a substrate at a predetermined position and orientation, and an atomic layer etching (ALE) chamber. The ALE chamber may include an inlet and an outlet. Further, the ALE chamber may enclose the holder in order to conceal the substrate internally and hermetically. The universal ALE device may further include a plasma source connected to the inlet configured to supply plasma into the atomic layer etching chamber, and an integrated showerhead positioned between theholder and the plasma source, dividing the atomic layer etching chamber into a first compartment or chamber configured to receive the plasma and a second compartment or chamber configured to distribute reactive gas to the substrate, thereby separating the holder from the plasma source. The universal ALE device may further include an ion flux controller connected to holder. The ion flux controller may be operable to selectively apply one or more programmed or predetermined waveforms to the holder. The integrated showerhead may include a first tier having at least one first inlet configured to receive an inert gas. The integrated showerhead may further include a second tier having at least one second inlet configured receive a reactive gas. The integrated showerhead may additionally include a plurality of common outlets at a bottom side of the integrated showerhead for distributing the inert gas and the reactive gas towards the substrate directly.

[0007] In an embodiment, the ion flux controller may be operable to apply the programmed waveform to the holder, in response to an instruction to perform anisotropic etching.

[0008] In an embodiment, the at least one second inlet of the second tier of the showerhead may be positioned along or at a lateral side of the showerhead. In an embodiment, the plurality of common outlets may be positioned at a side of the second tier of the integrated showerhead.

[0009] In an embodiment, the showerhead of the Universal ALE device may include a first inlet, a second inlet and an outlet. The first inlet and the second inlet may be operated independently from each other for receiving the respective inert gas and the reactive gas independently.

[0010] The showerhead may be configurable to operate between a first configuration and a second configuration. In the first configuration, the showerhead may be configuredto receive the inert gas from the first inlet exclusively for permeation towards the substrate near the outlet. In the second configuration, the showerhead may be configured to receive the inert gas from the first inlet and the reactive gas from the second inlet for permeation towards the substrate.

[0011] In an embodiment, the showerhead may be positioned directly next to the holder at a predetermined height or distance from the substrate. In an embodiment, the height (H) or distance (D) may be tuneable or adjustable in accordance with the required etching rate, uniformity and other process metrics.

[0012] The Universal ALE device may further include a bias generator to apply a bias voltage of a predefined waveform to the substrate. The predefined waveform associated with the bias voltage may include a time-varying negative voltage followed by a positive voltage pulse. The bias generator may perform a discrete ion energy control between a first energy range and a second energy range corresponding to the needed energy window to perform anisotropic etching. For example, the first energy range may be between 0 to 5 electron volts (eV), and the second energy range may be between 5 to 10 eV.

[0013] In an embodiment, the etching may be performed in cycles. Each cycle may be of a predefined cycle length, such that cycle length may be from a range of 5 seconds to 50 seconds, a range of 1 second to 5 seconds, or less than 5 seconds.

[0014] In an embodiment, the plasma source may include a dielectric tube, and a coil wrapped around the dielectric tube. The plasma source may generate plasma by flowing Argon gas through the dielectric tube and applying an electric power to the coil wrapped around the dielectric tube. For example, the dielectric tube may be a dielectric alumina tube, and the coil may be a Copper coil. Further, the applied electric power may be200W with 13.56 MHz radio frequency. In an alternate embodiment, the plasma source may include a remote plasma source (RPS).

[0015] In another implementation of the present disclosure, a method of selectively performing isotropic and anisotropic etching by a universal ALE device is disclosed. The method may include receiving an instruction to perform one of the isotropic etchings and the anisotropic etching on the substrate. The method may further include configuring a showerhead of the Universal ALE device in a second configuration based on the instruction. In the second configuration, the showerhead may be configured to receive the inert gas from the first inlet and a reactive gas from a second inlet for permeation towards the substrate. The showerhead may distribute at least one of the inert gas and the reactive gas towards the substrate at a first side of the substrate, via a plurality of common outlets at a bottom side of the showerhead. The method may further include causing a plasma source to excite the inert gas and the reactive gas to generate corresponding radicals for performing etching at the substrate. The method may further include causing an ion flux controller connected to a second side opposite to the first side of the substrate to selectively apply a programmed waveform to the holder, to perform ion flux control, to perform etching on the substrate, based on the instruction.

[0016] In an embodiment, the ion flux controller may be caused to apply the programmed waveform to the holder, to perform the anisotropic etching on the substrate.

[0017] In an embodiment, the showerhead may be positioned directly next to the holder at a predetermined height or distance from the substrate to minimize the loss of radicals reaching the substrate.

[0018] The method may further include triggering a bias generator to apply a bias voltage of a predefined waveform to the substrate. The predefined waveform associated withthe bias voltage may include a time-varying negative voltage followed by a positive voltage pulse.

[0019] In an embodiment, causing the ion flux controller to control ion flux may include causing the bias generator to perform a discrete ion energy control between a first energy range and a second energy range corresponding to the required energy window to perform the anisotropic etching. For example, the first energy range is between 0 to 5 electron volts (eV), and the second energy range is between 05 to 10 eV. The etching may be performed in cycles, such that each cycle may be of a predefined cycle length. For example, each cycle length may be selected from: a range of 05 seconds to 50 seconds, a range of 01 second to 05 seconds, or less than 05 seconds.

[0020] In an embodiment, the plasma source may include a dielectric tube, and a coil wrapped around the dielectric tube. The plasma source may generate plasma by flowing Argon gas through the dielectric tube and applying an electric power to the coil wrapped around the dielectric tube. The dielectric tube may a dielectric alumina tube, and the coil may a Copper coil. The applied electric power, for example, may be substantially 200W of 13.56 MHz radio frequency.

[0021] To further clarify the advantages and features of the present application, a more particular description of the application will be rendered by reference to specific implementations thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical implementations of the application and are therefore not to be considered limiting of its scope. The application will be described and explained with additional specificity and detail with the accompanying drawings.

[0022] These and other features, aspects, and advantages of the present application will become better understood when the following detailed description is read with referenceto the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

[0023] FIG. 1 illustrates a schematic diagram depicting a universal ALE device for both isotropic and anisotropic etching, according to an implementation of the present disclosure.

[0024] FIGS. 2-3 depict a perspective view and a sectional view of a showerhead of the universal ALE device of FIG. 1 , accordance with some embodiments.

[0025] FIG. 4 depicts a graphical representation of etch per cycle of a target material as a function of the ion energy during anisotropic plasma-enhanced atomic layer etching (ALE).

[0026] FIG. 5 depicts a graphical representation of ion energy distribution functions (lEDFs) for different bias voltage waveforms applied to a substrate during plasma exposure.

[0027] FIG. 6 depicts graphical representation ALE windows (in eVs) of different materials shown in a plot of the etch per cycle vs the ion energy.

[0028] FIG. 7 depicts a schematic view of an apparatus for isotropic and anisotropic etching, according to an implementation of the present disclosure.

[0029] FIG. 8 depicts an exploded view of the universal ALE device for both isotropic and anisotropic etching, according to an implementation of the present disclosure.

[0030] FIG. 9 is flowchart of a method of selectively performing isotropic and anisotropic etching by the universal ALE device, in accordance with an implementation of the present disclosure.

[0031] FIG. 10 is flowchart of another method of selectively performing isotropic and anisotropic etching by the universal ALE device, in accordance with an implementation of the present disclosure.

[0032] Further, skilled artisans will appreciate that elements, components or parts in the drawings or figures are illustrated for simplicity and may not have necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present application. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the implementations of the present application so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

[0033] For the purpose of promoting an understanding of the principles of the application, reference will now be made to the implementation illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the application is thereby intended, such alterations and further modifications in the illustrated apparatus, and such further applications of the principles of the application as illustrated therein being contemplated as would normally occur to one skilled in the art to which the application relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this application belongs. The apparatus, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0034] Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element." Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature orelement, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more...” or “one or more element is required.”

[0035] Unless otherwise defined, all terms and especially any technical and / or scientific terms, used herein may be taken to have the same meaning as commonly understood by a person ordinarily skilled in the art.

[0036] Reference is made herein to some “implementations.” It should be understood that an implementation is an example of a possible implementation of any features and / or elements of the present disclosure. Some implementations have been described for the purpose of explaining one or more of the potential ways in which the specific features and / or elements of the proposed disclosure fulfil the requirements of uniqueness, utility, and non-obviousness.

[0037] Use of the phrases and / or terms including, but not limited to, “a first implementation,” “a further implementation,” “an alternate implementation,” “one implementation,” “an implementation,” “multiple implementations,” “some implementations,” “other implementations,” “further implementation”, “furthermore implementation”, “additional implementation” or other variants thereof do not necessarily refer to the same implementations. Unless otherwise specified, one or more particular features and / or elements described in connection with one or more implementations may be found in one implementation, or may be found in more than one implementation, or may be found in all implementations, or may be found in no implementations. Although one or more features and / or elements may be described herein in the context of only a single implementation, or in the context of more than one implementation, or in the context of all implementations, the features and / or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, anyfeatures and / or elements described in the context of separate implementations may alternatively be realized as existing together in the context of a single implementation.

[0038] Any particular and all details set forth herein are used in the context of some implementations and therefore should not necessarily be taken as limiting factors to the proposed disclosure.

[0039] Implementations of the present application will now be described below in detail with reference to the accompanying drawings.

[0040] The present disclosure provides for a universal ALE device for universal isotropic and anisotropic etching. The universal ALE device is capable of performing both the isotropic and anisotropic etching in a range of pressure and chemistry environments, without requiring any change in the hardware configuration. The universal ALE device includes a showerhead and an atomic layer etching chamber. The showerhead is connected to a first gas inlet (supplying inert gas) positioned at the centre of the showerhead and a second inlet (supplying reactive gas) positioned at the lateral side of the showerhead. This enables an instantaneous switching between inert and reactive gas for different operations, such as functionalization prior to etching, etc. A plasma source excites and deliver both inert and reactive gasses for the above-mentioned operations. The showerhead has a labyrinth of the two-tier design that enables it showerhead to deliver the gases selectively, speedily, and directly to a substrate, via common outlets provided at a bottom side of the showerhead.

[0041] The conventional solutions in this technology area are limited by a significant radical loss through the conventional design structures (e.g., multiple layers of shower head(s) that are sequentially aligned). To this end, in the present atomic layer etching device, the single piece of integrated showerhead is positioned and designed in a waythat allows radicals to be generated directly above the substrate wafer to minimize the radical loss to the exposed surface area, hence enhancing its efficiency and etch rate.

[0042] Further, in some conventional device, ions are controlled by a relatively slow and unstable bias from a conventional radiofrequency (RF) generator. This causes an inaccurate ion energy control (30-50 electron volt (eV), or 50-80 eV). The present Universal ALE device includes a new RF generator with a discrete level of ion energy control (<5 eV, or 5-10 eV). Furthermore, switching of RF bias requires less stabilization time (<1 second (s), or 1 -5 s) and results in a more accurate ion flux control. Moreover, the conventional solutions require a longer switching time (> 1 second or s) to ignite the plasma and stabilize the pressure due the difference in functionalization steps and removal steps. The present Universal ALE device provides fast chemical delivery (switching time of <1 s) and fast cycle of etching (5-50 s, or 1 -5 s, or in some forms, <1 s) to improve throughput along with a bigger atomic layer etching (ALE) energy window which may yield improved etch rate and selectivity.

[0043] FIG. 1 illustrates a schematic diagram depicting a universal atomic layer etching (ALE) device 100 for both isotropic and anisotropic etching, according to an implementation of the present disclosure. In an implementation of the present disclosure, the universal ALE device 100 may include a holder 110 configured hold a substrate 108 at a predetermined position and orientation. The substrate 108, for example, may include a semiconductor or silicon wafer. The universal ALE device 100 may further include an atomic layer etching (ALE) chamber 106 that may define an inlet and an outlet. The ALE chamber 106 may enclose the holder 110 in order to conceal the substrate 108 securely, internally and hermetically. Further, the universal ALE device 100 may include a plasma source 104 connected to the inlet and may be configured to supply plasma into the ALE chamber 106. Furthermore, the universal ALEdevice 100 may include an integrated showerhead 102 (or simply, showerhead 102) that may be implemented as a single piece. The showerhead 102 may be positioned between the holder 110 and the plasma source 104. As such, the showerhead 102 may divide the ALE chamber 106 into a first compartment 126 above the showerhead 102 and a second compartment 128 below the showerhead 102, which are distinctly separated from each other. The first compartment 126 may be configured to receive the plasma and the second compartment 128 configured to distribute reactive gas to the substrate, thereby separating the holder 110 from the plasma source 104.

[0044] The universal ALE device 100 may further include an ion flux controller 1 12 that may be connected to the substrate 108. The ion flux controller (IFC) 112 may be operable to selectively apply a programmed waveform to the substrate holder 1 10. An electrical field may be coupled or applied to the substrate 108, and the IFC 112 may modulate the ion acceleration to the substrate surface. The IFC 112 may have a waveform that is shaped to deliver a narrow single-peaked ion energy distribution (IED), which is favourable for ALE. The ALE chamber 106 may be hermetically sealed when in use, and may include an exhaust 114 (also, referred to as outlet 114). The ALE chamber 106 may enclose and securely hold the substrate 108 and the ion flux controller 112 in an airtight manner.

[0045] In an embodiment, the showerhead 102 may be configured in a substantially circular profile, defining a top side 102A and a bottom side 102B. The showerhead 102 may define a first tier 130 that may include at least one first inlet 116 configured to receive an inert gas. The at least one first inlet 116 may be positioned along a centre or middle 134 of the showerhead 102. The at least one first inlet 116 may be connected to an inert gas source for receiving an inert gas. In one embodiment, the inert gas is Argon. In alternate embodiments, the inert gas may be selected from Helium, (He), Krypton(Kr), and Xenon (Xe). For example, as shown in FIG. 1 , the first tier 130 of the showerhead 102 may include the first inlet 116. Further, as shown in FIG. 1 , the first inlet 1 16 may be positioned along the middle / centre 134 of the showerhead 102. The first inlet 1 16 may connect to the showerhead 102 via the top side 102A.

[0046] The showerhead 102 may further define a second tier 132 that may include at least one second inlet 118 that may be connected to a reactive gas source for receiving a reactive gas. In an embodiment, the reactive gas may be selected from Halogen gases such as Florine (F2), Chlorine (CI2), Bromine (Br2), or Iodine (I2), or Halogen compounds such as Nitrogen Trifluoride (NF3), Carbon Tetrafluoride (CF4), Sulphur Hexafluoride (SF6), Hydrogen Chloride (HCI), and Hydrogen Bromide (HBr). Each of the at least one second inlet 118 may be positioned along a lateral side 136 of the showerhead 102. For example, as shown in FIG. 1 , the second tier of the showerhead 102 may include a pair of second inlets 1 18 that may be connected to a reactive gas source, and each positioned along the lateral side 136 of the showerhead 102. Therefore, the first inlet 116 and the second inlets 118 are independent from each other, for receiving the respective inert gas and the reactive gas exclusively.

[0047] It should be noted that, in some embodiments, the first inlet 116 may be connected to the reactive gas source (instead of inert gas source) for receiving the reactive gas, whilst the second inlet 118 may be connected to the inert gas source (instead of reactive gas source) for receiving the inert gas. By way of the reactive gas and the inert gas being received in the showerhead 102, both the gases may be uniformly or completely mixed with each other within the showerhead 102 in one embodiment.

[0048] The showerhead 102 may further include a plurality of common outlets 120 at the bottom side 102B of the showerhead 102. The plurality of common outlets 120 areprovided for distributing the inert gas and the reactive gas towards the substrate 108 directly, and, in particular, at a first side 108A of the substrate 108. The substrate 108 may define the first side 108A (also referred to as top side) and a second side 108B (also referred to as bottom side) opposite to the first side 108A. The substrate 108 may be positioned within the ALE chamber 106, such that the showerhead 102 faces the first side 108A of the substrate 108 and the ion flux controller 112 is towards the second side 108B of the substrate 108. In particular, the ion flux controller 112 may be connected to the second side 108B of the substrate 108.

[0049] During operation, the plasma source 104 may excite the inert gas and the reactive gas to generate corresponding radicals for performing etching at the substrate 108. Accordingly, radicals are directly distributed to the substrate 108 (i.e., without hindrance of any obstacle, element or object), making etching much more efficient. Plasma, often referred to as the fourth state of matter, may include an ionized gas consisting of positively charged ions, electrons, and neutral particles. For example, inert gases like Argon or Helium may be used as the carrier gas for the plasma.

[0050] In order to generate plasma, a low-pressure environment may be created within a chamber (not shown in FIG. 1 ) associated with the plasma source 104 that contains the inert gas. An electric field may be applied to the gas, causing the gas to ionize and form a plasma. As such, the plasma is characterized by high temperatures and energetic particles. Within the plasma, energetic collisions occur between the gas molecules, electrons, and ions, leading to the dissociation of gas molecules, and thereby resulting in the formation of radicals. Radicals are highly reactive species with unpaired electrons. The conditions within the ALE chamber 106, such as gas composition, pressure, temperature, and applied electric field, may be controlled and optimized to tailor the properties of the generated radicals. This allows for precise manipulation of radicalspecies and their reactivity, enabling fine-tuning of the desired chemical processes. The radicals generated within the plasma may be introduced into the ALE chamber 106 for carrying out etching operation on the substrate 108.

[0051] In an embodiment, the showerhead 102 may be configurable to operate between a first configuration and a second configuration. In the first configuration, the showerhead 102 may be configured to receive the inert gas from the first inlet 116 for permeation towards the substrate 108 at the plurality of common outlets 120. It should be noted that, in the first configuration, the showerhead 102 may exclusively receive the inert gas from the first inlet 116 and may not receive the reactive gas from the second inlets 118 at the same time. As such, when the showerhead 102 is configured in the first configuration, only the inert gas is introduced in the ALE chamber 106. Accordingly, only radicals corresponding to the inert gas may be generated within the ALE chamber 106 that may cause the etching to be performed at the substrate 108.

[0052] In an embodiment, the showerhead 102 may be configured in the first configuration by activating the first inlet 116 to supply inert gas from the inert gas source. In other words, the inert gas supply from the inert gas source may be channelised to the showerhead 102 and as a result the inert gas may be permeated inside the ALE chamber 106 via the plurality of common outlets 120 associated with the showerhead 102. Further, it should be noted that it may be possible to deactivate or shut off the first inlet 116 to stop supply of the inert gas into the ALE chamber 106 whenever necessary, for example, when the Universal ALE device 100 is not in use.

[0053] In the second configuration, the showerhead 102 may be configured to receive both inert gas from the first inlet 116 and the reactive gas from the second inlets 118 for permeation towards the substrate 108 simultaneously. As such, in the second configuration, both the inert gas and the reactive gas may be received in the ALEchamber 106. Accordingly, radicals corresponding to both the inert gas and the reactive gas may be generated within the ALE chamber 106, which causes the ALE etching to be performed at the substrate 108.

[0054] In the isotropic etching, material from a surface of the substrate 108 may be selectively by inert and reactive ions and radicals generated in a plasma. Within plasma (introduced from the plasma source 104 into the ALE chamber 106) energetic collisions between electrons, ions, and gas molecules result in the generation of radicals corresponding to the inert gas. These radicals upon contacting the surface of the substrate 108 may cause to break chemical bonds on the surface of the substrate 108. This may further lead to chemical reactions resulting in the removal of material. In isotropic etching, the radicals attack the material of the substrate 108 uniformly from all directions, causing materia! to be removed isotropically. Isotropic etching may result in the formation of rounded or sloped etch profiles, as material is etched away uniformly from all sides of the substrate 108. Isotropic etching, therefore, may be performed on the substrate 108 in scenarios where precise control over feature dimensions or sidewall profiles is not critical, such as roughening surfaces or creating curved structures.

[0055] In anisotropic etching, within the plasma, energetic collisions between electrons, ions, and inert and reactive gas molecules result in the generation of radicals corresponding to both inert and reactive gas. These radicals cause breaking chemical bonds on the surface of the substrate 108. Anisotropic etching relies on the directionality of the bombardment of radicals onto the surface of the substrate 108. As such, to achieve anisotropic etching, the plasma is engineered to preferentially bombard the substrate 108 as exposed from certain directions, typically perpendicular to the surface or a broad exposed area of the substrate 108. The radicals with the plasma selectively react with the material on the substrate 108, leading to chemical reactions that result inthe removal of material. In anisotropic etching, the directional bombardment of the radicals cause material to be removed preferentially along certain crystallographic planes or orientations, resulting in the formation of vertical sidewalls or trenches. Anisotropic etching using plasma may result in the formation of features with well- defined, vertical sidewalls, as the material of the substrate 108 is preferentially etched along certain crystallographic directions. This enables the creation of high-resolution patterns and structures essential for semiconductor devices, integrated circuits, MEMS (Microelectromechanical Systems), and photonic devices.

[0056] It should be noted that that conventional ALE techniques may include various process steps, amongst them being two discrete steps of modification and removal. It should be further noted that other than the steps of modification and removal, all the remaining steps are common in both the isotropic and anisotropic etching processes. In other words, for isotropic and anisotropic etching processes, the steps of modification and removal differ in the way how they are performed. For example, the modification step may be one of chemisorption, deposition, conversion, or extraction. The chemisorption process may be associated with Silicon (Si), Germanium (Ge), semiconductor materials that are made by combining elements from the third and fifth columns of the periodic table (I ll-Vs), graphene, polymers, and materials having high-K (dielectric constant (K, kappa)). The deposition process may be associated with dir Silicon Dioxide (SiO2), Silicon (Si), and graphene. The conversion process may be associated with iso SiO2, Si, Tungsten (W), Molybdenum (Mo), Gallium nitride (GaN), Aluminium gallium nitride (AIGaN), lll-Vs. The extraction process may be associated with silicon nitride (Si3N4), materials made from the combination of Cadmium (Cd) and Tellurium (Te), Gold-Tin (AuSn) alloy.

[0057] Therefore, depending on isotropic or anisotropic etching to be performed, the modification and removal steps may be configured accordingly. However, even if one of the modification and removal steps is configured according to the anisotropic (i.e. directional) etching, the overall etching process may result in anisotropic (i.e. directional) etching.

[0058] As will be understood by those skilled in the art, aspect ratio dependent etching (ARDE) may be observed in anisotropic etching processes where the etch rate of a material varies depending on the aspect ratio (depth-to-width ratio) of the etched feature. This effect can be beneficial or detrimental, depending on the desired outcome of the etching process. Some of the possible causes of ARDE may include ion shadowing (ions in the plasma being shadowed by the sidewalls as the etched features become deeper, leading to a reduced etch rate at the bottom of the feature), neutral gas trapping (neutral gas molecules getting trapped within the etched feature, reducing the effectiveness of the etching process and leading to tapered or undercut profiles), etc. A common cause for ARDE in reactive-ion etching is flux attenuation. To this end, the present techniques of ALE work with saturated steps, thereby helping in eliminating ARDE during etching.

[0059] In an example embodiment, the showerhead 102 may be configured in the second configuration by activating the second inlets 118 to supply reactive gas from the reactive gas source as well as activating the first inlet 116 to supply inert gas from the inert gas source. In other words, both the inert gas supply and the reactive gas supply from the inert gas source and the reactive gas source, respectively, may be channelised to the showerhead 102. As a result, the both inert gas and the reactive gas may be permeated inside the ALE chamber 106 via the plurality of common outlets 120 associated with the showerhead 102. It is therefore possible to selectively activate anddeactivate the second inlets 118. The showerhead 102 is further explained in detail in conjunction with FIGs. 2-3.

[0060] Referring now to FIGs. 2-3, a perspective view and a sectional view (along a line A-A’ of FIG. 2), respectively, of the showerhead 102 are illustrated in accordance with some embodiments. The showerhead 102, in some embodiments as shown in FIG. 2, may be configured in a circular profile. The showerhead 102, may include an upper mesh 202 and a lower mesh 204 with a gap 206 therebetween. As such, each of the upper mesh 202 and the lower mesh 204 may have a circular profile. The upper mesh 202 may have a plurality of holes that may act as the first inlet 116. As shown in FIG. 1 , the inert gas may percolate through showerhead 102 via the one or more first inlets 116 of the upper mesh 202. The upper mesh 202 may be made from a rigid material, for example, a metal such as Aluminium (Al) and Nickel (Ni), or an alloy such as an Aluminium, a Silicon, or a Magnesium-based alloy. It should be noted that, in some embodiments, the plasma entering from the plasma source may also enter percolate through the holes of the upper mesh 202. In some embodiments, the upper mesh 202 may be treated to form a ceramic coating, for example, by performing anodization, Chemical Vapor Deposition (CVD), or Atomic Layer Deposition (ALD) methods. The formed coating layer may include an Aluminium Oxide (AI2O3), a Yttrium Oxide (Y2O3), or a Yttrium Oxyfluoride (YOF) containing chemical resistance layer.

[0061] The lower mesh 204 may also have a plurality of holes that may act as the plurality of common outlets 120. The lower mesh 204 may be made from a rigid material, for example, a metal such as Aluminium and Nickel, an alloy such as an Aluminium, a Silicon, or a Magnesium-based alloy. The upper mesh 202 and the lower mesh 204 may be positioned adjacent to each with the gap 206 therebetween. In some embodiments, the lower mesh 204 may be treated to form a ceramic coating, for example, byperforming anodization, CVD, or ALD methods. The formed coating layer may include an AI2O3 (i.e., AI2O3), a Y2O3 (i.e., Y2O3), or a YOF containing chemical resistance layer.

[0062] As mentioned above, the showerhead 102 may further include the second inlets 118 that may supply reactive gas to the showerhead 102 from the reactive gas source. The second inlets 118 may be positioned at the lateral sides 136 of the showerhead 102, i.e. lateral sides of the upper mesh 202 and the lower mesh 204. As such, the second inlets 118 may open in the gap 206 between the upper mesh 202 and the lower mesh 204. As such, the reactive gas may be introduced in the in the gap 206 between the upper mesh 202 and the lower mesh 204 by the second inlets 118.

[0063] When the showerhead is configured in the second configuration, both the inert gas and the reactive gas may be introduced simultaneously in the showerhead 102. In particular, both the inert gas and the reactive gas may be mixed with each other in the gap 206 between the upper mesh 202 and the lower mesh 204. As such, once the inert gas and / or the reactive gas are received in the gap 206, the inert gas and / or the reactive gas may pass through the plurality of common outlets 120 to enter the ALE chamber 106. In particular, as mentioned above, in the first configuration of the showerhead 102, only the inert gas may be received in the gap 206 and therefore allowed to pass through the plurality of common outlets 120 to enter the ALE chamber 106. And, in the second configuration of the showerhead 102, both the inert gas and the reactive gas may be received in the gap 206 and therefore allowed to pass through the plurality of common outlets 120 to enter the ALE chamber 106.

[0064] The showerhead 102 may be adapted to switch between the first configuration and the second configuration based on different operations, such as functionalization prior to etching, etc.

[0065] Referring once again to FIG. 1 , in some implementations, the radicals may be formed below the showerhead 102 (i ,e. , between the showerhead 102 and the substrate 108), as the inert gas and / or reactive gas are emitted from the showerhead 102 via the plurality of common outlets 120. The showerhead 102 may be positioned directly next to or adjacent to the holder 110 at a predetermined height (H) or distance from the substrate 108 to minimize the loss of radicals reaching the substrate 108. In some example embodiments, the predetermined height (H) may be selected from one of the following ranges: 10 - 20 millimetres (mm), 15-35 mm, or 10-50 mm. In some embodiment, the height (H) may be tuneable or adjustable in accordance with the required etching rate, uniformity and other process metrics. In other words, the height (H) or distance can be increased or decreased as per the requirement.

[0066] As mentioned above, the ion flux controller 112 may be connected to the second side 108B of the substrate 108. The ion flux controller 112 may be coupled to a bias generator 122 to apply a bias voltage of a predefined waveform to the substrate 108. The ion flux controller 112 may apply the bias voltage of the predefined waveform to the substrate 108, only when performing anisotropic etching. In other words, for isotropic etching, the ion flux controller 112 may not be required. The predefined waveform associated with the bias voltage may include a time-varying negative voltage followed by a positive voltage pulse.

[0067] The bias generator 122 may be a low-frequency (LF: 100 kHz) voltage waveform generator. The bias generator 122 may be fitted to the holder 110 The bias generator 122 may include compact power electronics components. The bias generator 122 may perform a discrete ion energy control between a first energy range and a second energy range corresponding to the needed energy window to perform anisotropic etching. By way of an example, the first energy range may be between 0 to 5 electron volts (eV),and the second energy range may be between 5 to 10 eV, Further, in some embodiments, the etching may be performed in cycles, such that each cycle is of a predefined cycle length. For example, the cycle length may be between a range of 5 seconds to 50 seconds, or a range of 1 second to 5 seconds, or less than 5 seconds.

[0068] In an embodiment, the plasma source 104 may be an inductive coupling plasma (ICP)). As such, the plasma source 104 may include a dielectric tube and a coil wrapped around the dielectric tube (not shown in FIG. 1 ). The plasma source may generate plasma by flowing a plasma gas, such as Argon (Ar) gas, through the dielectric tube and applying an electric power to the coil wrapped around the dielectric tube. The dielectric tube, for example, may be a dielectric alumina tube, and the coil may be a Copper coil. Further, the applied electric power, for example, may be 200W of 13.56 MHz radio frequency. In particular, a remote inductively coupled plasma (ICP) may be used with Ar as the plasma gas. The plasma may be generated by flowing 25 Standard Cubic Centimeter per Minute (SCCM) of Ar gas through the dielectric tube and applying the radio-frequency (RF: 13.56 MHz) power of 200W to the copper coil wrapped around the dielectric tube. A low pressure of about 3 millitorr (mTorr) may be maintained in the ALE chamber 106 during plasma exposure. This may yield collision-less plasma sheaths.

[0069] In another embodiment, the plasma source 104 may be a remote plasma source (RPS). The RPS may generate and control plasma away from the main processing area. The RPS may include a plasma generation chamber which may be chamber separated from the ALE chamber. In the plasma generation chamber, the plasma may be created by applying high-frequency radio frequency (RF) or microwave power to a gas, which ionizes the gas and creates a plasma. A gas supply system may regulate the type and flow rate of gases used to create the plasma. The plasma or reactive species may be delivered to the ALE chamber via one or more channels (conduits or pipes). A controlsystem may manage the plasma generation, gas flow, and transport to ensure precise and repeatable processing conditions.

[0070] As mentioned above, anisotropic etching requires selectively removing one material with respect to the other from the substrate 108. As such, there may exist a selectivity window in terms of the ion energy for removing only the targeted material during the anisotropic ALE. For example, the lower limit of the ALE window for Silicon (Si) may be at 40 eV, while that for Gallium Nitride (GaN) may occur at 50 eV. Selective removal of Si with respect to GaN by anisotropic ALE, therefore, may require the incident ions to have an energy distribution lying within a narrow window of only 10 eV. However, such a narrow energy window for precise ion energy control cannot be achieved when using conventional radio-frequency (RF) sinusoidal waveform biasing.

[0071] To this end, the above-mentioned non-sinusoidal voltage waveform may be applied on the dielectric substrate 108 to generate a time-independent sheath voltage that can yield ions with a narrow, mono-modal energy distribution. The low frequency (LF) (for example, 100 kHz) bias voltage waveform may be applied on dielectric substrate 108 for accurate control of the ion energy, independent of the ion flux. An additional external RF power supply 124 may be connected to the substrate 108 for applying RF sinusoidal waveform biasing during Ar plasma exposure. For example, the RF power supply 124 may be rated at 13.56 MHz, and up to 100 Watts.

[0072] The techniques of the present disclosure are based on atomic scale processing that provide high selectivity and precise thickness control of material removal. As will be appreciated by those skilled in the art, etching is the process of removal of atoms from a material by bond dissociation, by overcoming an energy barrier called the binding energy. To this end, ALE aims to weaken the binding energy between the surface of the substrate so that it becomes easier to remove the surface atoms. This is achieved byexposing the material to reactive species (e.g., plasma radicals, precursor gas molecules, etc.) that form a modified surface region preferably through self-limiting chemical reactions.

[0073] In anisotropic plasma-enhanced ALE, the modified surface region is removed in the next step of the ALE cycle using energetic and directional ions. Further, selflimitation may be ensured by operating in a process window where the incident ions have enough energy to remove the modified surface region but not the underlying bulk. Energetic ions dissociate the relatively weak bonds between the modified surface and the underlying bulk, while simultaneously inducing chemical reactions that create volatile reaction products.

[0074] FIG. 4 depicts a graphical representation 400 of etch per cycle of a target material as a function of the ion energy during anisotropic plasma-enhanced atomic layer etching (ALE). An ALE window and respective sputter etch thresholds are indicated in FIG. 4. FIG. 5 depicts a graphical representation 500 of ion energy distribution functions (lEDFs) for different bias voltage waveforms applied to a substrate during plasma exposure. The area under the curves and hence the ion flux is the same for all lEDFs. Line 502 indicates a conventional low frequency (LF) sinusoidal waveform, line 504 indicates a conventional radio frequency (RF) sinusoidal waveform, and line 506 indicates the waveform according to the present disclosure. FIG. 6 depicts graphical representation 600 ALE windows (in eVs) of different materials shown in a plot of the etch per cycle vs the ion energy.

[0075] When the ion energy is high enough to break bonds in the unmodified bulk, atoms are physically displaced from their equilibrium positions and can eventually be ejected from the target material. This type of material removal is known as physical sputtering for which the threshold, as shown in FIG. 4, is approximately a factor of 5 to 10 higherthan the binding energy (2 to 12 eV) of a material, since the energy delivered by an impinging ion gets dissipated in a collision cascade. Therefore, etch control with atomic scale precision requires the impinging ion flux to have a well-defined energy lying between the chemical and physical sputter etch thresholds of a target material, as shown in FIGs. 4-6.

[0076] In inductively coupled plasma (ICP) etching system, the ion energy is traditionally controlled by applying a radio-frequency (RF: 13.56 MHz) sinusoidal bias voltage waveform to the substrate undergoing plasma exposure. However, this generates a time-varying plasma sheath that is known to yield ion fluxes having broad and bimodal energy distributions, as shown in FIG. 5. Therefore, the ions impinging on a material surface have a range of energies instead of a single value. Such ions can lead to undesired scenarios; for instance, the ion energy exceeding the physical sputter etch threshold of a target material results in a contribution of a physical sputter etching component and consequently, compromised etch control. Furthermore, the use of high frequency RF bias voltages often entails electron heating mechanisms that do not allow for controlling the ion energy independent of the ion flux. On the other hand, low- frequency (LF: kHz) bias voltages yield ion fluxes with even broader energy distributions when the bias waveform remains sinusoidal, as shown in FIG. 5.

[0077] As mentioned above, the voltage waveform as per to the present disclosure may include a time-varying negative voltage (i.e., a linear voltage ramp) followed by a positive voltage pulse. Applying the non-sinusoidal voltage waveform according to the present disclosure, as indicated by the line 506 in FIG. 5, on the substrate 108 generates a timeindependent sheath voltage that can yield ions with a narrow, mono-modal energy distribution. The sheath voltage remains constant under this condition yielding a narrow, mono-modal IEDF. The subsequent positive voltage pulse attracts electrons toward thesubstrate which then discharge the surface. The ion energy may be enhanced for the above waveform biasing by increasing the amplitude of the respective voltage waveforms. The FWHM for the above waveform biasing remains at 7 ± 1 eV. This value lies well within the narrow ALE windows of, for example, 10 and 20 eV for Ge and Si, respectively. Such narrow lEDFs ensure that the ion flux impinging on a surface of the substrate 108 is efficiently utilized for complete removal of only the modified surface layer (i.e., no incomplete or bulk etching components).

[0078] The present techniques, therefore, thereby enable both self-limiting surface reactions and a higher throughput. In addition, the 7 ± 1 eV wide lEDFs enable new selective anisotropic plasma ALE processes by exploiting narrow selectivity windows [e.g., 10 eV selective ALE window of Si with respect to GaN. Further, the above- mentioned voltage waveforms do not cause any electron heating, demonstrating ion energy control independent of the ion flux.

[0079] The above waveform biasing during collision-less plasma exposure enables precise ion energy control, independent of the ion flux, on dielectric substrates. The use of the above waveform generator in a remote plasma reactor yields ions with narrow and mono-modal lEDFs (7 ± 1 eV FWHM). The techniques provide capability to accurately control the ion energy. The techniques can be implemented in materials processing as well. The above waveform biasing offers numerous opportunities for advancing selective atomic scale processing techniques. Ions with low ion energies and narrow lEDFs may be used for atomic scale cleaning, for example, selective removal of ultrathin native oxide or damaged surface layers with respect to the underlying material. Mono-energetic ions can also allow for topographically selective deposition on 3D substrates. Furthermore, using the mono-modal lEDFs generated by the above waveform biasing offer better control over the growth and properties.

[0080] Referring now to FIG. 7, a schematic view of an apparatus 700 for universal isotropic and anisotropic etching is depicted, according to an implementation of the present disclosure. The apparatus 700 may include the Universal ALE device 100 that is already explained above. The apparatus 700 may further include an inert gas source 702 and a reactive gas source 704. Each of the inert gas source 702 and a reactive gas source 704, for example, may include gas cylinders that store the respective gas. Further, the inert gas source 702 may be coupled with a valve 706 that may be used for opening and closing the supply of the inert gas from the inert gas source 702. The reactive gas source 704 may be coupled with a valve 708 that may be used for opening and closing the supply of the reactive gas from the reactive gas source 704.

[0081] In some embodiments, when the showerhead 102 is configured in the first configuration, the inert gas source 702 may exclusively supply the inert gas to the Universal ALE device 100 (i.e. the reactive gas source 704 does not supply the reactive gas to the Universal ALE device 100). Further, when the showerhead 102 is configured in the second configuration, the inert gas source 702 and the reactive gas source 704 may supply the inert gas and the reactive gas, respectively, to the Universal ALE device 100. Therefore, in order to selectively supply the inert gas exclusively or along with the reactive gas, the apparats may include a controller 720.

[0082] The controller 720 may be a computing device having data processing capability. In particular, the controller 720 may have the capability for selectively switching the showerhead between the first configuration and second configuration. The controller 720 may be implemented in as a desktop, a laptop, a notebook, a netbook, a tablet, a smartphone, a mobile phone, an application server, a web server, or the like.

[0083] The controller may implement various modules for performing one or more functionalities. For example, the one or more functionalities may include flow controlmodules 710 and 712, a temperature control module 714, a pressure control module 716, and coolant control module 718.

[0084] The flow control modules 710 and 712 may interact with the valves 706 and 708 associated with the inert gas source 702 and the reactive gas source 704, respectively. And accordingly, the flow control modules 710 and 712 may cause to configure the valves 706 and 708 in open and close condition. In particular, when the showerhead 102 is configured in the first configuration, the flow control module 710 may open the valve 706 to thereby supply the inert gas from the inert gas source 702 to the Universal ALE device 100. However, the valve 708 may remain closed in the first configuration. When the showerhead 102 is configured in the second configuration, the flow control module 710 may open the valve 706 to thereby supply the inert gas from the inert gas source 702 to the Universal ALE device 100, and the flow control module 712 may open the valve 708 to thereby supply the reactive gas from the reactive gas source 704 to the Universal ALE device 100. Depending on an instruction received by the controller 720 for an operation such as functionalization prior to etching, , the controller 720 may cause only the valve 706 or both valves 706 and 708 to open.

[0085] The temperature control module 714 may interact with a temperature control coil 722 that may be configured to increase or decrease the temperature of the inert and reactive gases supplied to the Universal ALE device 100. Additionally, the temperature control module 714 may also interact with the coolant control module 718 and a coolant supply 726 to control an amount of supply of the coolant to the Universal ALE device 100 to control the temperature of the ALE chamber 106. The pressure control module 716 may interact with a pressure release valve 724 to control the pressure of the inert gas and the reactive gas in the piping manifold leading to the Universal ALE device 100. For example, when the pressure in the piping manifold increased beyond a threshold,the pressure control module 716 may cause to open the pressure release valve 724 to release the excess pressure in the piping manifold.

[0086] To perform the above functionalities, the controller 720 may include a processor and a memory (not shown in FIG. 7). The memory may be communicatively coupled to the processor, and stores a plurality of instructions, which upon execution by the processor, cause the processor to perform the above functionalities. The controller 720 may further include a user interface which may further implement a display, keypad, microphone, audio speakers, vibrating motor, LED lights, etc. The user interface may receive input (e.g. an instruction for switching the configuration of the showerhead) from a user.

[0087] In an embodiment, the universal ALE device 100 may further include a valve and pump assembly that includes one or more valves 728 and one or more pumps 730. The one or more valves 728 may control the introduction of inert and reactant gases into the ALE chamber, regulate pulsed delivery of the gases within the ALE chamber, maintain the desired pressure within the ALE chamber, and facilitate switching between the gases. To this end, the controller 720 may further incorporate a valve control module 732 to control the one or more valves 728 to perform the above functionalities. The one or more pumps 730 may create and maintain vacuum conditions within the ALE chamber, remove byproducts from the ALE chamber, help purge the ALE chamber of residual gases and byproducts, and stabilize pressure within the etching chamber. To this end, the controller 720 may further incorporate a pump control module 734 to control the one or more pumps 730 to perform the above functionalities.

[0088] Referring now to FIG. 8, an exploded view of the universal ALE device 100 for both isotropic and anisotropic etching is illustrated, in accordance with an embodiment. As shown in FIG. 8, the universal ALE device 100 may include the ALE chamber 106,the holder 110, and the showerhead 102. As mentioned above, the substrate 108 to be etched upon may be positioned on the holder 110. The ALE chamber 106 may include a chamber liner 802 that may be mounted within the ALE chamber 106, and may be configured to enclose or assist in enclosing the holder 110 in order to conceal the substrate 108 internally and hermetically. The holder 110 may further define a RF bowl that may be connected to the RF power supply 124. The constructional features of the ALE chamber 106, the holder 110, and the showerhead 102 are already explained in conjunction with FIG. 1 .

[0089] The universal ALE device 100 may further include a chamber stand 804 on which the ALE chamber 106 may be positioned. The chamber stand 804 may be manufactured from a rigid material, for example, a metal or an alloy. By way of positioning of the ALE chamber 106 on the chamber stand 804, the ALE chamber 106 may be elevated from the ground level. Further, the universal ALE device 100 may include a cover lid 806 that may be configured to be positioned atop the ALE chamber 106, and may enclose the holder 110 to conceal the substrate 108 internally and hermetically.

[0090] The universal ALE device 100 may further include a valve and pumping assembly 808 that may include one or more valves and pumps. The one or more valves of the valve and pumping assembly may control the introduction of inert and reactant gases into the ALE chamber. The one or more valves may further regulate pulsed delivery of the gases within the ALE chamber, ensuring that the gases are introduced into the ALE chamber in a controlled and timely manner. Further, by opening or closing (e.g., in response to pressure sensors), the valves help maintain the desired pressure within the ALE chamber, which is crucial for consistent and repeatable etching processes. Moreover, the one or more valves may facilitate switching between the gases, ensuring that the correct gas is delivered at the right time. The pumps of the valve and pumpingassembly may be responsible for creating and maintaining vacuum conditions within the ALE chamber. A high vacuum is essential for preventing unwanted reactions and ensuring that the etching process is clean and controlled. Further, the pumps remove byproducts from the ALE chamber, thereby preventing them from interfering with subsequent etching cycles. The pumps may further help purge the ALE chamber of residual gases and byproducts, preparing it for the next cycle. This purging ensures that the environment is reset for each atomic layer etching step. Further, the pumps work in conjunction with valves to stabilize the pressure within the etching chamber. This stability is crucial for the precision and uniformity of the etching process.

[0091] The universal ALE device 100 may further include a gas box 810. The gas box 810 may house the inert gas source and the reactive gas source that may supply the inert gas and the reactive gas to the ALE chamber.

[0092] Referring now to FIG. 9, a flowchart of a method 900 of selectively performing isotropic and anisotropic etching by the universal ALE device 100, in accordance with an implementation of the present disclosure. For example, the method 900 may be performed by the controller 720 (of FIG. 7). The flowchart of the method 900 is explained in conjunction with FIGs. 1-8.

[0093] At step 902, an instruction may be received to perform one of the isotropic etchings and the anisotropic etching on the substrate 108.

[0094] At step 904, the showerhead 102 of the universal ALE device 100 may be configured in the second configuration. As explained above, in the second configuration, the showerhead 102 may be configured to receive the inert gas from the first inlet 116 and the reactive gas from the second inlets 118 for permeation towards the substrate 108. As such, at step 904A, further, the showerhead 102 may receive the inert gas from the first inlet 116 and the reactive gas from the second inlets 118 for permeation towardsthe substrate 108. The showerhead 102 may distribute the inert gases and / or the reactive gas towards the substrate 108 at the first side 108A of the substrate 108, via the plurality of common outlets 120 at the bottom side 102B of the showerhead 102.

[0095] At step 906A, the plasma source 104 may be caused to excite the inert gas and the reactive gas to generate corresponding radicals for performing etching at the substrate 108. In particular, at step 906A, the plasma source 104 may be caused to excite the inert gas and the radical gas to generate corresponding radicals for performing isotropic etching at the substrate 108.

[0096] If, at step 902, the received instruction is for performing anisotropic etching, then, at step 906B, the plasma source 104 may be caused to excite the inert gas and the reactive gas to generate corresponding radicals.

[0097] Subsequently, at step 908B, the ion flux controller 112 connected to the second side 108B opposite to the first side 108B of the substrate 108 may be caused to apply a programmed waveform to the holder, to thereby perform etching on the substrate 108.

[0098] Additionally, at step 910B, the bias generator 122 may be triggered to apply a bias voltage of a predefined waveform to the substrate 108. The predefined waveform associated with the bias voltage may include a time-varying negative voltage followed by a positive voltage pulse. As a result, the bias generator 122 may perform a discrete ion energy control between a first energy range and a second energy range corresponding to the energy window required to perform anisotropic etching. The first energy range may lie between 0 to 5 electron volts (eV), and the second energy range may be between 5 to 10 eV. The etching may be performed in cycles, such that each cycle is a predefined cycle length. The cycle length may be selected from one of: a range of 5 seconds to 50 seconds, a range of 1 second to 5 seconds, or less than 5 seconds.

[0099] Referring now to FIG. 10, a flowchart of another method 1000 of selectively performing isotropic and anisotropic etching by the universal ALE device 100 is illustrated, in accordance with an implementation of the present disclosure. For example, the method 1000 may be performed by the controller 720 (of FIG. 7). The flowchart of the method 1000 is explained in conjunction with FIGs. 1-8.

[0100] At step 1002, an instruction may be received to perform one of the isotropic etchings and the anisotropic etching on the substrate 108.

[0101] In some embodiments, additionally, at step 1004, conditions for an etch cycle may be configured. For example, the conditions for the etch cycle may correspond to a pressure and temperature to be maintained within the ALE chamber 106 during the process of etching. Further, at step 1004, a number of etch cycles may be configured. For example, the number of etch cycles may be configured corresponding to an amount of etch required. As such, for a greater amount of required etch, a higher number of etch cycles may be configured. At step 1006, an amount of over-etch may be configured to accommodate an etch-margin. The over-etch may include an additional time or depth allowed during the etching process to ensure complete removal of material in the target areas of the substrate 108, thereby compensating for any non-uniformities or variations in the etch rate.

[0102] At step 1008, the showerhead 102 of the universal ALE device 100 may be configured in the second configuration. As explained above, in the second configuration, the showerhead 102 may be configured to receive the inert gas from the first inlet 116 and the reactive gas from the second inlets 118 for permeation towards the substrate 108. The showerhead 102 may distribute at least one of the inert gases and the reactive gas towards the substrate 108 at the first side 108A of the substrate 108, via the plurality of common outlets 120 at the bottom side 102B of the showerhead 102.

[0103] If, at step 1002, the instruction received is for performing isotropic etching, the method 1000 may follow steps 1010A - 1014A. On the other hand, if, at step 1002, , the instruction received is for performing anisotropic etching, the method 1000 may follow steps 1010B - 1018B.

[0104] When the instruction received is for performing isotropic etching, then, at step 1010A, the plasma source 104 may be caused to excite the inert gas and the reactive gas to generate corresponding radicals for performing isotropic etching at the substrate 108.

[0105] Additionally, once the etching is performed at the substrate, at step 1012A, the distribution of the reactive gas to the substrate 108 may be stopped. Further, at step 1012A, the remaining gas may be purged out from the ALE chamber 106. At step 1014A, once the remaining gas is purged out from the ALE chamber 106, the reactive gas may be supplied to remove by-product of etching. It should be noted that the above steps 1010A-1014A may be iteratively performed multiple times, till a desired amount of etch is obtained on the substrate 108 to achieve a steady state. Once the desired amount of etch is obtained on the substrate 108, the method 1000 may be stopped and the substrate 108 (i.e. wafer) may be returned to transfer module, and the ALE chamber 106 may be prepared for the next wafer for etching.

[0106] When the instruction received is for performing anisotropic etching, then, at step 1010B, the plasma source 104 may be caused to excite the inert gas and the reactive gas to generate corresponding radicals for performing etching at the substrate 108. At step 1012B, the ion flux controller 112 connected to the second side 108B opposite to the first side 108B of the substrate 108 may be caused to apply a programmed waveform to the holder, to thereby perform modification on the substrate 108.

[0107] Additionally, at step 1014B, the bias generator 122 may be triggered to apply a bias voltage of a predefined waveform to the substrate 108. The predefined waveform associated with the bias voltage may include a time-varying negative voltage followed by a positive voltage pulse. As a result, the bias generator 122 may perform a discrete ion energy control between a first energy range and a second energy range corresponding to the energy window required to perform anisotropic etching. The first energy range may lie between 0 to 5 electron volts (eV), and the second energy range may be between 5 to 10 eV. The etching may be performed in cycles, such that each cycle is a predefined cycle length. The cycle length may be selected from one of: a range of 5 seconds to 50 seconds, a range of 1 second to 5 seconds, or less than 5 seconds.

[0108] Once the etching is performed at the substrate, at step 1016B, the distribution of the reactive gas to the substrate 108 may be stopped. Further, at step 1016B, the remaining gas may be purged out from the ALE chamber 106. At step 1018B, once the remaining gas is purged out from the ALE chamber 106, the reactive gas may be supplied and the ion flux controller 112 may be activated to remove by-product of etching. The above steps 1012B, 1014B, 1016B, 1018B may be iteratively performed multiple times, till a desired amount of etch is obtained on the substrate 108. Once the desired amount of etch is obtained on the substrate 108, the method 1000 may be stopped and the substrate 108 (i.e. wafer) may be returned to transfer module, and the ALE chamber 106 may be prepared for the next wafer for etching.

[0109] While specific language has been used to describe the present subject matter, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of implementations. Those skilled in the art will appreciatethat one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one implementation may be added to another implementation.Reference Numerals

Claims

CLAIMS1. A universal atomic layer etching (ALE) device (100) for both isotropic and anisotropic etching, the universal ALE device (100) comprising: a holder (110) configured hold a substrate (108) at a predetermined position and orientation; an atomic layer etching (ALE) chamber (106) comprising an inlet and an outlet, the ALE chamber (106) enclosing the holder (110) in order to conceal the substrate (108) internally and hermetically; a plasma source (104) connected to the inlet configured to supply plasma into the ALE chamber (106); an integrated showerhead (102) positioned between the holder (110) and the plasma source (104), dividing the ALE chamber (106) into a first compartment (126) configured to receive the plasma and a second chamber (128) configured to distribute reactive gas to the substrate (108), thereby separating the holder (110) from the plasma source (104); wherein the integrated showerhead (102) comprises: a first tier (130) having at least one first inlet (116) configured to receive an inert gas; and a second tier (132) having at least one second inlet (118) configured receive a reactive gas; and a plurality of common outlets (120) at a side of the integrated showerhead (102) for distributing the inert gas and the reactive gas towards the substrate (108) directly; andan ion flux controller (112) connected to holder (110) and operable to selectively apply a programmed waveform to the holder (1 10), in response to an instruction to perform isotropic or anisotropic etching.

2. The universal ALE device (100) of claim 1 , wherein the ion flux controller (112) is operable to apply the programmed waveform to the holder (1 10), in response to an instruction to perform anisotropic etching.

3. The universal ALE device (100) of claim 1 , wherein the at least one second inlet (118) of the second tier (132) of the showerhead (102) is positioned along a lateral side of the showerhead (102), and wherein the plurality of common outlets (120) are positioned at a bottom side of the second tier (132) of the integrated showerhead (102).

4. The universal ALE device (100) of claim 3, wherein the showerhead (102) is configurable to operate between a first configuration and a second configuration, wherein in the first configuration, the showerhead (102) is configured to receive the inert gas from the first inlet (116) exclusively for permeation towards the substrate (108) at the outlet; and wherein in the second configuration, the showerhead (102) is configured to receive the inert gas from the first inlet (1 16) and the reactive gas from the at least one second inlet (118) for permeation towards the substrate (108).

5. The universal ALE device (100) of claim 1 , wherein the showerhead (102) is positioned directly next to the holder (110) at a predetermined height from the substrate (108) to minimize the loss of radicals reaching the substrate (108).

6. The universal ALE device (100) of claim 1 further comprising: a bias generator (122) to apply a bias voltage of a predefined waveform to the substrate (108), wherein the predefined waveform associated with the bias voltage comprises a time-varying negative voltage followed by a positive voltage pulse.

7. The universal ALE device (100) of claim 6, wherein the bias generator (122) is to perform a discrete ion energy control between a first energy range and a second energy range corresponding to a needed energy window to perform the anisotropic etching.

8. The universal ALE device (100) of claim 7, wherein the first energy range is between 0 to 5 electron volts (eV), and wherein the second energy range is between 5 to 10 eV.

9. The universal ALE device (100) of claim 7, wherein the etching is performed in cycles, each of a predefined cycle length, wherein each cycle length is selected from one of: a range of 5 seconds to 50 seconds, a range of 1 second to 5 seconds, or less than 5 seconds.

10. The universal ALE device (100) of claim 1 , wherein the plasma source (104) comprises: a dielectric tube; and a coil wrapped around the dielectric tube, wherein the plasma source generates plasma by flowing Argon gas through the dielectric tube and applying an electric power to the coil wrapped around the dielectric tube.11 . The universal ALE device (100) of claim 9, wherein the dielectric tube is a dielectric alumina tube, and wherein the coil is a Copper coil.

12. The universal ALE device (100) of claim 9, wherein the applied electric power is 200W of 13.56 MHz radio frequency.

13. A method of selectively performing isotropic and anisotropic etching by a universal ALE device (100), the method comprising: receiving, by a controller (720), an instruction to perform one of the isotropic etchings and the anisotropic etching on the substrate (108); configuring a showerhead (102) of the universal ALE device (100) in a second configuration, wherein in the second configuration, the showerhead (102) is configured to receive the inert gas from the at least one first inlet (116) and a reactive gas from at least one second inlet (118) for permeation towards the substrate (108), andwherein the showerhead (102) is to distribute the inert gas and the reactive gas towards the substrate (108) at a first side of the substrate, via a plurality of common outlets (120) at a bottom side of the integrated showerhead (102); and causing a plasma source (104) to excite the inert gas and the reactive gas to generate corresponding radicals for performing etching at the substrate (108); and causing an ion flux controller (112) connected to a second side opposite to the first side of the substrate (108) to selectively apply a programmed waveform to the holder (110), to perform one of the isotropic and anisotropic etching on the substrate, in response to the instruction.

14. The method of claim 13, wherein the ion flux controller (112) is caused to apply the programmed waveform to the holder (110), when the instruction is to perform the anisotropic etching on the substrate.

15. The method of claim 13, further comprising: upon configuring the showerhead (102) in the second configuration, configuring conditions for an etch cycle and a number of etch cycles corresponding to an amount of etch required; and configuring an amount of over-etch to accommodate an etch-margin.

16. The method of claim 15, wherein, for performing isotropic etching, the method further comprises:upon performing of etching at the substrate, stopping distribution of the reactive gas to the substrate (108) and purging out remaining gas from the ALE chamber (106); and upon purging out of the remaining gas from the ALE chamber (106), supplying the reactive gas to remove by-product of etching.

17. The method of claim 15, wherein, for performing anisotropic etching, the method further comprises: upon performing of etching at the substrate, stopping distribution of the reactive gas to the substrate (108) and purging out remaining gas from the ALE chamber (106); and upon purging out of the remaining gas from the ALE chamber (106), supplying the reactive gas and activating the ion flux controller (112) to remove by-product of etching.

18. The method of claim 13, wherein the showerhead (102) is positioned directly next to the holder (110) at a predetermined height from the substrate to minimize the loss of radicals reaching the substrate (108).

19. The method of claim 13 further comprising: triggering a bias generator (122) to apply a bias voltage of a predefined waveform to the substrate (108), wherein the predefined waveform associated with the bias voltage comprises a time-varying negative voltage followed by a positive voltage pulse.

20. The method of claim 19, wherein the bias generator (122) is to perform a discrete ion energy control between a first energy range and a second energy range corresponding to the required energy window to perform anisotropic etching.

21. The method of claim 20, wherein the first energy range is between 0 to 5 electron volts (eV), and wherein the second energy range is between 5 to 10 eV.

22. The method of claim 20, wherein the etching is performed in cycles, each of a predefined cycle length, wherein each cycle length is selected from one of: a range of 5 seconds to 50 seconds, a range of 1 second to 5 seconds, or less than 5 seconds.

23. The method of claim 13, wherein the plasma source (104) comprises: a dielectric tube; and a coil wrapped around the dielectric tube, wherein the plasma source (104) generates plasma by flowing Argon gas through the dielectric tube and applying an electric power to the coil wrapped around the dielectric tube.

24. The method of claim 23, wherein the dielectric tube is a dielectric alumina tube, and wherein the coil is a Copper coil.

25. The method of claim 23, wherein the applied electric power is 200W of 13.56 MHz radio frequency.

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