Methods and tools for etching titanium-containing films

Abstract

Examples are disclosed that relate to etching titanium-containing films using a cyclic process. One example provides a method of etching a titanium-containing film. The method comprises placing a substrate comprising the titanium-containing film in a process chamber. The method further comprises performing a plurality of etching cycles. Each etching cycle of the plurality of etching cycles comprises a first stage and a second stage. The first stage comprises exposing the titanium-containing film to a BCl3-containing plasma for a first period of time. The second stage comprises exposing the titanium-containing film to a Cl2-containing plasma for a second period of time.

Description

METHODS AND TOOLS FOR ETCHING TITANIUM-CONTAINING FILMSBACKGROUND

[0001] Traditional camera lenses are space consuming. As they rely on refractive principles, there is a tradeoff between focal length and lens thickness. To combat such shortcomings, multi-lens systems are often used, which can take up even more space.

[0002] Metalenses are flat lenses that use meta surfaces to manipulate light. The flat surfaces and reduced thicknesses of metalenses compared to conventional lenses make them attractive for various applications such as smartphones, augmented / virtual reality, wearables, automotive, and robotics.SUMMARY

[0003] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. Furthermore, the claimed subject matter is not limited to implementations that solve any or all disadvantages noted in any part of this disclosure.

[0004] One example provides a method of etching a titanium-containing film. The method comprises placing a substrate comprising the titanium-containing film in a process chamber. The method further comprises performing a plurality of etching cycles. Each etching cycle of the plurality of etching cycles comprises at least a first stage and a second stage. The first stage comprises exposing the titanium-containing film to a BCh-containing plasma for a first period of time. The second stage comprises exposing the titanium-containing film to a Ch-containing plasma for a second period of time.

[0005] In some such examples, the Ch-containing plasma comprises BCh.

[0006] Additionally or alternatively, in some such examples, the Ch-containing plasma comprises methane.

[0007] Additionally or alternatively, in some such examples, the second stage comprises applying a higher direct current (DC) bias than the first stage.

[0008] Additionally or alternatively, in some such examples, no purge is performed between the first stage and the second stage.

[0009] Additionally or alternatively, in some such examples, no purge is performed between etching cycles.

[0010] Additionally or alternatively, in some such examples, the first stage comprises a continuous application of the BCh-containing plasma.

[0011] Additionally or alternatively, in some such examples, the second stage comprises a pulsed application of the Ch-containing plasma.

[0012] Additionally or alternatively, in some such examples, the titanium- containing film is a titanium oxide-containing film.

[0013] Additionally or alternatively, in some such examples, performing the plurality of etching cycles forms a metalens.

[0014] Additionally or alternatively, in some such examples, the method comprises following the plurality of cycles, and prior to etching a second titanium- containing film, adjusting one or more parameters of one or more of the first stage and the second stage based on an etching profile of the titanium-containing film.

[0015] In another example, a processing tool comprising a processing chamber and a substrate holder disposed in the processing chamber. The processing tool further comprises a plasma source configured to form a plasma for processing substrates in the processing chamber, and flow control hardware to control processing chemical flows into the processing chamber. The processing tool further comprises a controller configured to control the processing tool to perform an etching process comprising a plurality of etching cycles. For each etching cycle of the plurality of etching cycles the controller is configured to operate a first stage and a second stage. In the first stage, the controller is configured to control the flow control hardware and the plasma source to form a BCh containing plasma in the processing chamber. In the second stage, the controller is configured to control the flow control hardware and the plasma source to form a Ch containing plasma in the processing chamber.

[0016] In some such examples, the controller is further configured to, in the second stage, control the flow control hardware to flow BCh into the Ch-containing plasma.

[0017] Additionally or alternatively, in some such examples, the controller is further configured to, in the second stage, control the flow control hardware to flow methane into the Ch-containing plasma.

[0018] Additionally or alternatively, in some such examples, the controller is further configured to form a continuous BCh-containing plasma in the first stage.

[0019] Additionally or alternatively, in some such examples, the controller is further configured to form a pulsed Ch-containing plasma in the second stage.

[0020] In another example, a method of etching a titanium oxide-containing film to form a metalens is presented. The method comprises placing a substrate comprising the titanium oxide-containing film in a process chamber. The method further comprises performing a plurality of etching cycles. Each etching cycle of the plurality of etching cycles comprises a first stage and a second stage. The first stage comprises exposing the titanium oxide-containing film to a BCh -containing plasma for a first period of time. The second stage comprises exposing the titanium oxide- containing film to a Ch -containing plasma for a second period of time.

[0021] In some such examples, the Ch -containing plasma comprises BCh.

[0022] Additionally or alternatively, in some such examples, the first stage comprises a continuous application of the BCh-containing plasma.

[0023] Additionally or alternatively, in some such examples, the second stage comprises a pulsed application of the Ch-containing plasma.BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 shows a highly magnified schematic illustration of an example metalens array.

[0025] FIG. 2 schematically shows an example imaging device comprising a metalens array.

[0026] FIGS. 3 A-3D schematically show an example nanopillar plasma etching process.

[0027] FIG. 4 shows a flow diagram illustrating an example method of etching a titanium-containing film.

[0028] FIGS. 5A-5C schematically show an example cyclic nanopillar plasma etching process.

[0029] FIG. 6 schematically shows an example processing tool.

[0030] FIG. 7 schematically shows an example computing device.DETAILED DESCRIPTION

[0031] The term “DC bias” generally represents a voltage generated due to the difference in mobility between electrons and ions in a plasma.

[0032] The term “continuous plasma” generally represents maintaining an RF power used to form a plasma at a substantially constant power level over time.

[0033] The term “controller” generally represents a computing system configured to control a machine, such as a processing tool.

[0034] The terms “etching” and “etching process ” generally refer to processes in which materials are removed from a substrate using chemical and / or physical processes.

[0035] The term “etching cycle” generally represents a multi-stage etching process that is repeated.

[0036] The term “etching profile” generally represents a three-dimensional structure of a film produced by etching the film.

[0037] The term “film” generally represents a layer of material deposited on a substrate.

[0038] The term “flow control hardware” generally represents components configured to place one or more chemical sources in fluid connection with a processing chamber. Flow control hardware can comprise one or more mass flow controllers and / or valves, for example.

[0039] The term “metalens” generally represents a flat optical device comprising optical waveguides configured to manipulate an amplitude, phase, and / or polarization of incident light.

[0040] The term “plasma” generally represents a gas comprising ions and free electrons.

[0041] The term “plasma source” generally represents a device configured to generate a plasma to provide reactive species and / or energetic ions for substrate processing in a processing chamber.

[0042] The term “processing chamber” generally represents an enclosure in which chemical and / or physical processes are performed on substrates.

[0043] The term “processing tool” generally represents a machine comprising a processing chamber and other hardware configured to enable processing to be carried out on a substrate.

[0044] The term “pulsed plasma” varying RF power used to produce a plasma as a function of time, such as periodically.

[0045] The term “purge” and variants thereof generally represent processes in which unwanted species are removed from a processing chamber.

[0046] The term “substrate” generally represents any object that can be etched in a processing chamber.

[0047] The term “substrate holder” generally represents any structure for supporting a substrate in a processing chamber.

[0048] Metalenses comprise a flat substrate supporting a semiconductor layer. Etched in the semiconductor layer is a quasi-periodic array of subwavelength nanopillars on the order of several hundred nanometers high. FIG. 1 shows a highly magnified depiction of an example metalens 100. Metalens 100 comprises a substrate base 102, and a plurality of nanopillars 104. Substrate base 102 can be fabricated out of glass, while nanopillars 104 can be fabricated out of a semiconductor such as titanium oxide.

[0049] Properties of individual nanopillars, including their height, thickness, and position next to other nanopillars, impact the distribution of light emerging from the lens. Generally, metalens nanopillars are on the order of 400-500 nm in height (A), but can range up to 700-800 nm, or even 1 pm or more in some examples. The width for metalens nanopillars can be on the order of 120-150 nm, but also can be larger or smaller depending on the wavelengths of light that are to be captured.

[0050] Nanopillar arrays can redirect, alter, and sort light in numerous ways. The nanopillars are pointed outward, toward the scene being captured. Photons incident on the tops of the nanopillars transfer their energy into vibrations called plasmons, which travel down the nanopillars. When that energy reaches the bottom of a pillar, it exits as photons, which can then be captured by an image sensor.

[0051] FIG. 2 schematically shows an example image capturing system 200 comprising a metalens 202 having a plurality of nanopillars 205. Metalens 202 including nanopillars 205 is not shown to scale, but rather is exaggerated for illustration. Metalens 100 can be an example of metalens 202. Metalens 202 can be supported by barrels, which can orient metalens 202 both axially and radially towards the environment and towards image sensor 210. Other image capture elements, such as filters and a controller to control the image sensor 210 and to process images from image sensor, are not shown can also be included in image capturing system 200. Imagecapture system 200 can schematically represent any device that utilizes a metalens to capture images. Examples include smartphones, augmented / virtual reality devices, other wearable device, vehicles comprising image sensing capabilities, and robotics.

[0052] Nanopillar arrays can be produced, for example, using patterning and etching techniques. In an example process, a layer of semiconductor is deposited on a substrate. A layer of a mask material (e.g. photoresist or hard mask material) is then deposited on the desired areas of the semiconductor surface. Next, the layer of the mask material is patterned to remove the layer of the mask material from some areas of the substrate but not others. Then, an etching process is used to remove substrate material from areas not covered by the mask. To form the pillars of a metalens, a directional etching process can be used. Directional etching processes, such as reactive ion etching (RIE), can utilize a plasma formed under such conditions as to etch vertically (normal to a substrate surface) at a substantially higher rate than horizontally (parallel to a substrate surface). Etching parameters as plasma power, pressure, gas flow rates, can be controlled to achieve a directional etch to form vertical pillars.

[0053] FIGS. 3A-3D schematically show an example substrate 300 that can be etched into a plurality of nanopillars using a plasma etching process. As shown in FIG. 3A, substrate 300 comprises substrate base 302, which can be a glass substrate. Titanium-containing film 304 is layered on a side of substrate base 302. Titanium- containing film 304 can be a titanium oxide film, for example. A bottom anti -reflective coating (BARC) 306 is layered on a side of titanium-containing film 304 opposite substrate base 302. A photoresist 308 is layered on a side of BARC 306 opposite titanium-containing film 304. In FIG. 3A, the photoresist 308 has been previously patterned using photolithography. In other examples, a mask layer other than photoresist can be used.

[0054] To pattern photoresist 308, a layer of photoresist 308 is deposited (e.g. by spin-on coating) on BARC 306 and exposed to light filtered by a reticle. After passing through the reticle, the light contacts the surface of photoresist 308, changing the chemical composition of photoresist 308 such that a developer can remove a portion of photoresist 308. In the case of positive photoresist materials, the exposed regions are removed, while in the case of negative photoresist materials, the unexposed regions are removed. The result of this process is shown in FIG. 3 A.

[0055] BARC 306 absorbs the light that travels through photoresist 308 during exposure to light to minimize reflectivity. BARC 306 can be inorganic or organic. Forexample, an inorganic BARC layer can be composed of at least silicon oxynitride (SION). Organic BARC layers can comprise carbon-based organic compounds that absorb light, such as polyvinylphenol, acrylate polymers, isocyanurate compounds, polymers containing ester bonds, etc. The composition of BARC 306 can be selected based on the composition of photoresist 308, the thickness of photoresist 308, light treatment wavelengths used to process photoresist 308, etc. In some examples, substrate 300 can include a dielectric material between the BARC layer and the titanium - containing film.

[0056] Next, an etching step is performed to remove regions of the BARC that are not protected by the photoresist. When an organic BARC is applied to the bottom of photoresist 308, various gas mixtures can be used to etch the organic BARC. Examples include a mixture of tetrafluoromethane (CF4), fluoroform (CHF3), and oxygen (O2); a mixture of chlorine (Ch), hydrogen bromide (HBr), and nitrogen (N2); or a mixture of HBr and O2. The sulfur-containing gas can include carbonyl sulfide (COS) gas or sulfur dioxide (SO2) gas. The sulfur-containing gas can also include a mixed gas of SO2and O2. Inorganic BARC materials can be removed via methods such as an HF acid dip followed by a hot phosphoric acid strip. FIG. 3B shows substrate 300 following removal of excess BARC 306.

[0057] Next, titanium-containing film 304 can be plasma-etched to remove the underlying material from the areas that are no longer protected by photoresist 308, and thereby define the desired features in substrate 300. As mentioned above, plasma etching processes use a combination of physical bombardment and chemical reaction to remove selected portions of the titanium-containing film. The surface of titanium- containing film 304 is exposed to fluxes of atoms, molecules, ions, electrons, and photons, which break the chemical bonds and react with elements at the interface of the gas and the solid. As will be described, the composition of the plasma influences the resultant structures of titanium-containing film 304.

[0058] One-step plasma etching has been explored to form short titanium oxide sidewall spacers using plasma etch chemistries. One-step plasma etching processes contain both an etching species and a passivation agent to minimize the difference of the etching rates of the spacer top and the spacer bottom. However, such an approach is not suitable for etching high aspect ratio titanium oxide nanopillars needed for metalens applications because one-step plasma etching cannot consistently tune the sidewall profile over an extended period. To create high aspect ratio nanopillars (e.g.,400-800 nm or even 1 m), the ability to consistently and precisely tune the etching profile for an extended period of time is important.

[0059] Accordingly, embodiments of the present disclosure disclose methods for forming high aspect nanopillars with uniform width by cyclically switching between Ch-based and BCh-based etching steps. Referring to FIGs. 3C and 3D, a cycle may start with BCh- based etch 310 for a first period of time then switch to Ch-based etch 320 that uses Ch based gases for a second period of time. Alternating between 310 and 320 for a set period of time enables continuous and precise control on the etching profile. The tendency for creating bottom tapering in the BCh- based etch 310 (e.g., tendency to create a smaller upper portion 314 than the lower portion 316) can be immediately tuned with more aggressive lateral etching from the Ch-based etch 320 in the subsequent cycle (e.g., tendency towards a larger width upper portion 324 than the lower portion 326). Simply mixing Ch and BCh does not provide the control over profile tuning that generates columnar nanopillars.

[0060] FIG. 4 shows a flow-diagram depicting an example method 400 of etching a titanium-containing film. FIG. 4 can be performed by a controller in conjunction with a processing tool, as described with regard to FIG. 6. In some examples, the titanium-containing film is a titanium oxide-containing film. While described with regard to the process for etching nanopillars for metalens applications, the process of method 400 can be used for any other suitable etching process. Examples include the etching of titanium oxide structures in self-aligned patterning applications (e.g., 10-20 nm spacers) and titanium-containing films for magnetic RAM, among other applications.

[0061] At 402, method 400 comprises placing a substrate comprising a titanium-containing film in a process chamber. At 404, method 400 comprises performing a plurality of etching cycles. In some examples, performing the plurality of etching cycles forms a metalens. In some such examples, the metalens can comprise nanopillars having depth between 200 nm and 1 m, and widths between 50 and 200 nm, depending on a desired effect on a predetermined wavelength of light. In other examples, a metalens can have one or more dimensions outside of this range.

[0062] Each etching cycle of the plurality of etching cycles comprises at least a first stage and a second stage. At 406, the first stage comprises exposing the titanium- containing film to a BCh-containing plasma for a first period of time. In this step, flowcontrol hardware and a plasma source are controlled to form a BCh containing plasma in the processing chamber, as indicated at 408.

[0063] In some examples, the first stage can comprise a continuous application of the BCh-containing plasma, where an RF power of the plasma is maintained at a substantially continuous level. In other examples, the RF power can be pulsed.

[0064] In some examples, the BCh-containing plasma can be a BCh-dominated plasma, wherein BCI3 comprises the majority of the gas flowed to generate the plasma. In some such examples, other chlorine-containing molecules outside of BCh can additionally or alternatively be included, such as alkyl chlorides, in order to provide passivation for the plasma etching. In other examples, such additional chlorine- containing molecules are omitted.

[0065] At 410, method 400 comprises a second stage comprising exposing the titanium-containing film to a Ch-containing plasma for a second period of time. As indicated at 412, this comprises controlling the flow control hardware and the plasma source to form a Ch containing plasma in the processing chamber. Although described with the first stage comprising BCh-containing plasma and the second stage comprising Ch-containing plasma, the order of the stages is interchangeable. The first and second periods of time may be of the same or different durations. One or more of the first and second periods of time may increase or decrease as cycling progresses.

[0066] This cyclic etching process is illustrated in FIGS. 5 A-5C. FIG. 5 A shows an example substrate 500 that can be etched into a plurality of nanopillars using a plasma etching process. As shown in FIG. 5A, substrate 500 comprises substrate base 502, which can be glass in some examples. Titanium-containing film 504 is layered on a side of substrate base 502. Titanium-containing film 504 can comprise a titanium oxide film in some examples. A mask material 506 is layered on a side of titanium- containing film 504 opposite substrate base 502. Mask material 506 can represent a photoresist / BARC layer, as described above with regard to FIGS. 3A-3D. Alternatively, mask material 506 can represent a hardmask material in other examples.

[0067] FIG. 5B depicts cycling (or alternating) between a first stage, BCh- containing plasma etch 510, and a second stage, Ch-containing plasma etch 512 for a number (n) of cycles 514. As shown in FIG. 5C, this process yields nanopillars 520 that have a lower portion 522 of relatively equal width to an upper portion 524. Once the etching process has been completed, the remaining mask material 506 can be removed.

[0068] Cyclic etching between the BCh-containing plasma and Ch-containing plasma helps to fabricate taller nanopillars, produce a vertical nanopillar profile, and can provide more control over profile tuning, as compared to non-cyclic etching. As shown in FIG. 3C, BCh etching on its own generates nanopillars with a lower portion having a larger width than the upper portion. As shown in FIG. 3D, CI2 etching on its own generates nanopillars with an upper portion having a larger width than the lower portion. Cycling between the two chemistries balances passivation with photoresist selectivity and lateral etching. This yields relatively taller, more vertical nanopillars following the plurality of etching cycles than using either etching process alone.

[0069] In some examples, the RF power of the plasma formed in the second stage 410 can be pulsed to form a pulsed Ch-containing plasma. The Ch-containing plasma can be a Ch-dominated plasma, wherein Ch comprises the majority of the gas flowed to generate the plasma. In some examples, the Ch-containing plasma comprises BCh as a minority component. For example, the controller can control the flow control hardware to flow BCh into the Ch-containing plasma. Further, in some examples, the Ch-containing plasma comprises methane as a minority component. For example, the controller can control the flow control hardware to flow methane into the Ch-containing plasma. In other examples, BCh and / or methane can be omitted as minority components.

[0070] In some examples, the second stage comprises a higher DC bias than the first stage. Ch-based etching can have a wider process window for high DC bias than does BCh, which can be more sensitive to DC bias. In various examples, the first stage 406 and the second stage 410 can comprise different durations of exposure, or a same duration of exposures. In some examples, no purge is performed between the first stage and the second stage. Additionally or alternatively, in some examples no purge is performed between cycles. Rather, the chemistry for the next stage can be blended into the current stage. In this way, the process time can be decreased. In some examples, one or more of the BCh-containing plasma and Ch-containing plasma can comprise inert gas. Example inert gases include helium, neon, argon, krypton, and xenon.

[0071] In some examples, following the plurality of cycles, and prior to etching a second titanium-containing film, one or more parameters of one or more of the first stage and the second stage are adjusted based on an etching profile of the titanium- containing film. The etching profile can be evaluated based on images obtained via scanning electron microscope, for example. Parameters can be controlled separately forthe first stage and the second stage and can thus be adjusted independently following the plurality of cycles. For example, parameters can include pressure (e.g., ranging from 1 to 20 millitorr), RF power (e.g., ranging from 250-2500 W), gas flow rates, flow ratios for multiple gases, DC bias, plasma exposure time, and temperature.

[0072] FIG. 6 schematically shows an example processing tool 600 that can be used to perform plasma-etching of titanium-containing films as described above with regard to FIGS. 4 and 5A-5C. Processing tool 600 comprises a processing chamber 602 and a substrate support 604 within the processing chamber. The substrate support 604 is configured to support a substrate 606 disposed within the processing chamber 602. The substrate support 604 comprises a substrate heater 608. In other examples, a heater can be omitted, or can be located elsewhere within processing chamber 602.

[0073] The processing tool 600 further comprises a showerhead 610 configured for introducing gas into processing chamber 602. In other examples, a processing tool can comprise a nozzle or other apparatus for introducing gas into processing chamber 602, as opposed to or in addition to a showerhead 610. The processing tool 600 further comprises flow control hardware 612. The flow control hardware 612 connects processing gas source(s) to the processing chamber. In the depicted example, the flow control hardware 612 connects a chlorine gas source 616, a boron trichloride gas source 618, an inert gas source 620, and a methane gas source 622 to the processing chamber 602. Example inert gases include helium, neon, argon, krypton, and xenon. In some examples, chlorine gas source 616 can comprise metered amounts of boron trichloride and / or methane. FIG. 6 illustrates a single processing station for processing a single substrate at a time. In some examples, a processing tool can have two, three, four, or more processing stations, each with a showerhead and substrate holder, in a same processing chamber. Further, in some examples, a processing tool can have two, three, four or more processing chambers, each with one or more processing stations.

[0074] The flow control hardware 612 can include any suitable components. For example, the flow control hardware 612 can comprise one or more conduits and valves controllable to place a selected gas source or selected gas sources in fluid connection with showerhead 610. The flow control hardware 612 also can comprise one or more mass flow controllers or other controllers for controlling a flow rate of one or more processing chemicals.

[0075] The processing tool 600 further comprises an exhaust system 626. The exhaust system 626 is configured to exhaust gases from the processing chamber 602.The exhaust system 626 can comprise any suitable hardware, including one or more low vacuum pumps and one or more high vacuum pumps. Together, flow control hardware 612 and exhaust system 626 can be operated to achieve a selected pressure in processing chamber 602 during substrate processing.

[0076] The processing tool 600 further comprises a radiofrequency power source 628 that is electrically connected to showerhead 610. Radiofrequency power source 628 is configured to form a plasma using a gas mixture. For example, during a modification step, the radiofrequency power source 628 can be operated to form a plasma to dissociate a volatilizable terminal leaving group from a film material. In some examples, the radiofrequency power source 628 can be controlled to form a directional plasma to enable the etching of relatively high aspect ratio features. Conditions that can be used to form a directional plasma are described below. The substrate support 604 is configured as a grounded opposing electrode in this example. In other examples, the radiofrequency power source 628 can supply radiofrequency power to substrate support 604, or to another suitable electrode structure. Thus, the radiofrequency power source 628 forms a capacitively coupled plasma when operated. In other examples, radiofrequency power source 628 can be used to form an inductively coupled plasma.

[0077] The processing tool 600 further includes a matching network 630 for impedance matching of the radiofrequency power source 628. The radiofrequency power source 628 can be configured to provide RF energy of any suitable frequency and power. Any suitable RF power conditions can be used to form a plasma in a processing chamber for controlled carbon deposition. In some examples, a plasma can be formed by application of a relatively higher frequency (HF) RF power. The HF RF power can comprise a frequency in a frequency band of 5 megahertz (MHz) or greater. In some examples, a relatively lower frequency (LF) RF power component can also be used. The terms “relatively higher frequency” and “relatively lower frequency” are with reference to one another. In some examples, the LF RF power can comprise a frequency in a frequency band of less than 5 MHz. HF RF and LF RF power levels can be varied in any suitable manner to help achieve a desired carbon film profile. In some examples, HF RF power can comprise power in a range of 100 W to 6,000 W. The power can be directed to a single processing station or can be shared between multiple processing stations and / or multiple processing chambers (two, three four, or more processing stations in a single chamber, and / or two, three, four or more processing chambers each having one or more processing stations in various examples). In some examples, LF RFpower can comprise power in a range of 0 W to 5,000 W. The HF RF and LF RF powers can have the same power level, or different power levels, in various examples. More specific examples of RF frequencies include 400 kHz, 13.56 MHz, 27 MHz, 60 MHz, and 90 MHz.

[0078] In some examples, a DC bias is applied to one or both electrodes of the electrode pair. Applying a DC bias can help increase the directionality of the directional plasma. In further examples, a processing tool can comprise a remote plasma chamber for forming a remote plasma.

[0079] The processing tool 600 further comprises a controller 640 configured to control operation of the processing tool. The controller 640 is operatively coupled to the substrate heater 608, the flow control hardware 612, the exhaust system 626, and the radiofrequency power source 628. The controller 640 is configured to control various functions of processing tool 600 to perform an etching process as disclosed by example herein, among other possible processes. For example, the controller 640 is configured to operate the substrate heater 608 to heat a substrate to a desired temperature. The controller 640 also is configured to operate the flow control hardware 612 to flow a selected processing chemical or mixture of processing chemicals at a selected rate into the processing chamber 602. The controller 640 is further configured to operate the exhaust system 626 to remove processing chemicals and byproducts from processing chamber 602. The controller 640 further can control the exhaust system 626 and / or the flow control hardware 612 to purge the processing chamber 602.

[0080] The controller 640 further can operate the flow control hardware 612 and the radiofrequency power source 628 to form a plasma and control a directionality of the plasma. For example, a directionality of a plasma can be increased (i.e. an ion angular distribution made to be more narrowly concentrated about a vertical direction relative to a substrate surface) by using a relatively lower pressure, a relatively higher RF power, including a DC bias, and / or by include both HF and an LF RF energy components. Likewise, a directionality of a plasma can be decreased by using a relatively higher pressure, a relatively lower RF power, and / or omitting an LF RF energy component. These parameters thus can be used to control a directionality of an etching process. Other parameters also can be used to control the directionality, including relative cycle times of BCh-dominant and Ch-dominant etching steps in each etching cycle of an etching process.

[0081] FIG. 7 schematically shows an example of a computing system 700 that can enact one or more of the methods and processes described above. Computing system 700 is shown in simplified form. Computing system 700 can take the form of one or more personal computers, workstations, computers integrated with substrate processing tools, and / or network accessible server computers.

[0082] Computing system 700 includes a logic machine 702 and a storage machine 704. Computing system 700 can optionally include a display subsystem 706, input subsystem 708, communication subsystem 710, and / or other components not shown in FIG. 7. Controller 640 is an example of computing system 700.

[0083] Logic machine 702 includes one or more physical devices configured to execute instructions. For example, the logic machine can be configured to execute instructions that are part of one or more applications, services, programs, routines, libraries, objects, components, data structures, or other logical constructs. Such instructions can be implemented to perform a task, implement a data type, transform the state of one or more components, achieve a technical effect, or otherwise arrive at a desired result.

[0084] The logic machine can include one or more processors configured to execute software instructions. Additionally or alternatively, the logic machine can include one or more hardware or firmware logic machines configured to execute hardware or firmware instructions. Processors of the logic machine can be single-core or multi-core, and the instructions executed thereon can be configured for sequential, parallel, and / or distributed processing. Individual components of the logic machine optionally can be distributed among two or more separate devices, which can be remotely located and / or configured for coordinated processing. Aspects of the logic machine can be virtualized and executed by remotely accessible, networked computing devices configured in a cloud-computing configuration.

[0085] Storage machine 704 includes one or more physical devices configured to hold instructions 712 executable by the logic machine to implement the methods and processes described herein. When such methods and processes are implemented, the state of storage machine 704 can be transformed — e.g., to hold different data.

[0086] Storage machine 704 can include removable and / or built-in devices. Storage machine 704 can include optical memory (e.g., CD, DVD, HD-DVD, Blu-Ray Disc, etc.), semiconductor memory (e.g., RAM, EPROM, EEPROM, etc.), and / or magnetic memory (e.g., hard-disk drive, floppy-disk drive, tape drive, MRAM, etc.),among others. Storage machine 704 can include volatile, nonvolatile, dynamic, static, read / write, read-only, random-access, sequential-access, location-addressable, file- addressable, and / or content-addressable devices.

[0087] It will be appreciated that storage machine 704 includes one or more physical devices. However, aspects of the instructions described herein alternatively can be propagated by a communication medium (e.g., an electromagnetic signal, an optical signal, etc.) that is not held by a physical device for a finite duration.

[0088] Aspects of logic machine 702 and storage machine 704 can be integrated together into one or more hardware-logic components. Such hardware-logic components can include field-programmable gate arrays (FPGAs), program- and application-specific integrated circuits (PASIC / ASICs), program- and applicationspecific standard products (PSSP / ASSPs), system-on-a-chip (SOC), and complex programmable logic devices (CPLDs), for example.

[0089] When included, display subsystem 706 can be used to present a visual representation of data held by storage machine 704. This visual representation can take the form of a graphical user interface (GUI). As the herein described methods and processes change the data held by the storage machine, and thus transform the state of the storage machine, the state of display subsystem 706 can likewise be transformed to visually represent changes in the underlying data. Display subsystem 706 can include one or more display devices utilizing virtually any type of technology. Such display devices can be combined with logic machine 702 and / or storage machine 704 in a shared enclosure, or such display devices can be peripheral display devices.

[0090] When included, input subsystem 708 can comprise or interface with one or more user-input devices such as a keyboard, mouse, or touch screen. In some examples, the input subsystem can comprise or interface with selected natural user input (NUI) componentry. Such componentry can be integrated or peripheral, and the transduction and / or processing of input actions can be handled on- or off- board. Example NUI componentry can include a microphone for speech and / or voice recognition, and an infrared, color, stereoscopic, and / or depth camera for machine vision and / or gesture recognition.

[0091] When included, communication subsystem 710 can be configured to communicatively couple computing system 700 with one or more other computing devices. Communication subsystem 710 can include wired and / or wireless communication devices compatible with one or more different communicationprotocols. As non-limiting examples, the communication subsystem can be configured for communication via a wireless telephone network, or a wired or wireless local- or wide-area network. In some examples, the communication subsystem can allow computing system 700 to send and / or receive messages to and / or from other devices via a network such as the Internet.

[0092] It will be understood that the configurations and / or approaches described herein are exemplary in nature, and that these specific examples or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein can represent one or more of any number of processing strategies. As such, various acts illustrated and / or described can be performed in the sequence illustrated and / or described, in other sequences, in parallel, or omitted. Likewise, the order of the above-described processes can be changed.

[0093] The subject matter of the present disclosure includes all novel and non- obvious combinations and sub-combinations of the various processes, systems and configurations, and other features, functions, acts, and / or properties disclosed herein, as well as any and all equivalents thereof.

Claims

CLAIMS:

1. A method of etching a titanium-containing film, comprising: placing a substrate comprising the titanium-containing film in a process chamber; and performing a plurality of etching cycles, wherein each etching cycle of the plurality of etching cycles comprises a first stage comprising exposing the titanium-containing film to a BCh- containing plasma for a first period of time; and a second stage comprising exposing the titanium-containing film to a Ch-containing plasma for a second period of time.

2. The method of claim 1, wherein Ch-containing plasma comprises BCh.

3. The method of claim 1, wherein the Ch-containing plasma comprises methane.

4. The method of claim 1, wherein the second stage comprises a higher DC bias than the first stage.

5. The method of claim 1, wherein no purge is performed between the first stage and the second stage.

6. The method of claim 1, wherein no purge is performed between cycles.

7. The method of claim 1, wherein the first stage comprises a continuous application of the BCh-containing plasma.

8. The method of claim 1, wherein the second stage comprises a pulsed application of the Ch-containing plasma.

9. The method of claim 1 , wherein the titanium-containing film is a titanium oxidecontaining film.

10. The method of claim 9, wherein performing the plurality of etching cycles forms a metalens.

11. The method of claim 1, further comprising: following the plurality of cycles, and prior to etching a second titanium- containing film, adjusting one or more parameters of one or more of the first stage and the second stage based on an etching profile of the titanium-containing film.

12. A processing tool, comprising: a processing chamber; a substrate holder disposed in the processing chamber; a plasma source configured to form a plasma for processing substrates in the processing chamber; flow control hardware to control processing chemical flows into the processing chamber; and a controller configured to control the processing tool to perform an etching process comprising a plurality of etching cycles, wherein the controller is configured to, for each etching cycle of the plurality of etching cycles: in a first stage, control the flow control hardware and the plasma source to form a BCh-containing plasma in the processing chamber; and in a second stage, control the flow control hardware and the plasma source to form a Ch-containing plasma in the processing chamber.

13. The processing tool of claim 12, where the controller is further configured to, in the second stage, control the flow control hardware to flow BCh into the Ch- containing plasma.

14. The processing tool of claim 12, where the controller is further configured to, in the second stage, control the flow control hardware to flow methane into the Ch- containing plasma.

15. The processing tool of claim 12, wherein the controller is further configured to form a continuous BCh-containing plasma in the first stage.

16. The processing tool of claim 12, wherein the controller is further configured to form a pulsed Ch-containing plasma in the second stage.

17. A method of etching a titanium oxide-containing film to form a metalens, the method comprising: placing a substrate comprising the titanium-oxide containing film in a process chamber; and performing a plurality of etching cycles, wherein each etching cycle of the plurality of etching cycles comprises a first stage comprising exposing the titanium oxide-containing film to a BCh-containing plasma for a first period of time; and a second stage comprising exposing the titanium oxide-containing film to a Ch-containing plasma for a second period of time.

18. The method of claim 17, wherein the Ch-containing plasma comprises BCh.

19. The method of claim 17, wherein the first stage comprises a continuous application of the BCh-containing plasma.

20. The method of claim 17, wherein the second stage comprises a pulsed application of the Ch-containing plasma.

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