Plasma beam lithography system and method

Abstract

Various examples are provided related to Plasma Beam Lithography (PBL). In one example, a PBL system includes a source of plasma and a pattern generation substrate (PGS) including at least one aperture formed therein. The PGS can receive the plasma and form one or more plasma beam directed at a target substrate for patterning or etching, each plasma beam shaped the same as or similar to a corresponding aperture. In another example, a method includes positioning a PGS adjacent to a target substrate opposite a source of plasma; forming one or more plasma beam directed at the target substrate with each plasma beam shaped the same as or similar to a corresponding aperture; and performing a simultaneous expose-and-etch or single-step writing with the one or more plasma beam to pattern the target substrate. A substrate or pattern or product can be formed using the disclosed system and methodology.

Description

PLASMA BEAM LITHOGRAPHY SYSTEM AND METHODCROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and the benefit of, U.S. provisional applications entitled “Plasma Beam Lithography Systems, Methods and Devices” having serial no. 63 / 547,081 , filed November , 2023, and serial no. 63 / 609,913, filed December 14, 2023, both of which are hereby incorporated by reference in their entireties.BACKGROUND

[0002] Conventional semiconductor manufacturing involves lithography processes using UltraViolet light, Deep- or Extreme-UltraViolet light, electron beams, x-ray or ion beams. However, these processes involve a two-step sequence to pattern thin-films on a substrate: an exposure step to create patterns on a resist or template layer, and a subsequent pattern transfer step from the resist to the target thin-film layer. The resolution or minimum printable feature size of these processes is limited by factors such as the wavelength of the radiation used during lithography, lenses used to focus the radiation, and radiation-matter interactions on the substrate. As a consequence, new processes that improve pattern resolution and reduce process complexity in comparison to conventional lithography processes could advance the field of lithography.SUMMARY

[0003] Aspects of the present disclosure are related to Plasma Beam Lithography (P- beam lithography or PBL). In accordance with the principles herein, PBL provides a new semiconductor nanomanufacturing methodology using plasma beams for directly writing patterns in diverse thin-film materials in the nano- to microscale size regimes, extending down to near the ultimate limits of solid-state miniaturization. PBL enables a disruptive performance regime where users will benefit from substantial efficiencies in patterning resolution as well as throughput, process scalability, manufacturing complexity, and equipment I operational costs.

[0004] PBL is transformative in two aspects: (i) it involves the use of focused plasma beams to perform lithography for the first time, and (ii) it uses nano-aperture arrays, which are miniaturized to up to a few nanometers (nm) in widths, to form and direct plasma beams and selectively dry-etch or pattern material at the deep-nm regime. The use of reactive radicals and energetic ions, which are generated within a plasma, enables the direct single- istep writing of nano-patterns via physical and / or chemical etching in diverse thin-film materials such as polymeric resists, dielectrics, semiconductors and metals, for example. This is a substantial simplification of the multi-step patterning process associated with extreme ultraviolet (EUV), photolithography or electron beam lithography (EBL) techniques, which involves: (i) a first pattern writing step followed by wet chemical development in resist thin films, and (ii) subsequent pattern transfer step(s) onto the eventual target materials (dielectrics, semiconductors or metals) through additional additive or subtractive IC- nanomachining techniques.

[0005] This single-step pattern writing process can be accomplished using a lithography system that involves all-on-a-wafer plasma beam formation, focusing, and pattern etching I writing inside a plasma-chamber that employs commercial processes such as reactive ion etching (RIE) and inductively coupled plasma - reactive ion etching (ICP-RIE). Such plasma chambers are ubiquitous and widely used in IC nanomanufacturing cleanrooms, thereby enabling the seamless integration of PBL into commercial IC nanomanufacturing facilities.

[0006] In accordance with the principles herein, devices that yield etching of diverse thin-film materials can be achieved. For example, a wide range of materials including, but not limited to polymeric resists, dielectrics, semiconductors and metals can undergo PBL processes to achieve a wide range of devices. A substrate or pattern or product can be formed via a PBL process. Further, any product that can be formed using direct writing (i.e., simultaneous exposure and pattern formation) of features on a surface on a target substrate is contemplated in accordance with the principles herein.

[0007] In one aspect, among others, a plasma beam lithography system comprises a source of plasma; and a pattern generation substrate (PGS) comprising at least one aperture formed therein, the PGS configured to receive the plasma from the source and form one or more plasma beam directed at a target substrate positioned on a side of the PGS opposite the source for patterning or etching, the one or more plasma beam formed via the at least one aperture with each of the one or more plasma beam shaped the same as or similar to a corresponding aperture of the at least one aperture. In one or more aspects, the plasma beam lithography system can comprise the target substrate in a fixed or variable position adjacent to the PGS opposite the source. The plasma beam lithography system can comprise a clamping fixture that secures the PGS between the target substrate and the source. The plasma beam lithography system can comprise a plurality of pattern generation substrates (PGSs) secured between corresponding target substrates and the source by the clamping fixture.

[0008] In various aspects, the target substrate can comprise an etchable film layer disposed on a substrate or the substrate in itself can be etched. The etchable film layer can comprise at least one dry etchable material. The target substrate can comprise a plurality ofetchable film layers disposed on the substrate. The PGS can comprise one or more electrostatic lens (e-lens) electrode disposed on a side adjacent to the target substrate. The plasma beam lithography system can comprise at least one feedthrough coupled to the one or more e-lens electrode for delivery of electrical signals from an external power source. The one or more e-lens electrode can be electrically biased with a positive or negative voltage to focus and / or adjust size of the one or more plasma beam to perform focused-plasma beam lithography (F-PBL). Electrically biasing with a positive voltage can reduce a footprint of the one or more plasma beam on the target substrate and electrically biasing with a negative voltage can increase the footprint of the one or more plasma beam on the target substrate. The one or more electrostatic lens (e-lens) electrode can be a single e-lens electrode or can comprise a plurality of e-lens electrodes. The plurality of e-lens electrodes can be configured to individually adjust size of each of a plurality of plasma beams. The source of the plasma can comprise a plasma generation chamber. The PGS can comprise an etch mask coating at least a portion of the PGS. The PGS can comprise a SNAP-Chip with the etch mask coating at least a portion of the SNAP-Chip. The etch mask can comprise chromium or aluminum. The at least one aperture can comprise a plurality of nano-apertures. The at least one aperture can comprise an aperture opening with a thickness between a single atomic- layer to 10 nanometers or more.

[0009] In another aspect, a method of manufacturing plasma beam lithography components comprises providing a pattern generation substrate (PGS) comprising at least one aperture formed therein; positioning the PGS adjacent to a target substrate opposite a source of plasma; forming one or more plasma beam directed at the target substrate, the one or more plasma beam formed from plasma from the source via the at least one aperture with each of the one or more plasma beam shaped the same as or similar to a corresponding aperture of the at least one aperture; and performing a simultaneous expose- and-etch or single-step writing with the one or more plasma beam to pattern the target substrate. In one or more aspects, the source of the plasma can comprise a plasma generation chamber. The method can comprise fixing the PGS in position adjacent to the target substrate using a clamping fixture. The method can comprise fixing a plurality PGS in position adjacent to a plurality of corresponding target substrates using the clamping fixture. The method can comprise applying an electrical bias to one or more electrostatic lens (e- lens) electrode to dynamically tune a size of the one or more plasma beam. The electrical bias can be applied via one or more electrostatic lens (e-lens) electrode disposed adjacent to the target substrate. Electrically biasing with a positive voltage can reduce a footprint of the one or more plasma beam on the target substrate and electrically biasing with a negative voltage can increase the footprint of the one or more plasma beam on the target substrate. The method can comprise asymmetrically applying an electrical bias to electrostatic lens (e-lens) electrodes to deflect at least one plasma beam. The size of the one or more plasma beam can be adjusted to perform focused-plasma beam lithography (F-PBL). An aspect ratio of an etched pattern can be in a range from 1 :1 to 20:1 , or more. In some aspects, a substrate or pattern or product can be formed using the disclosed method.

[0010] Other systems, methods, features, and advantages of the present disclosure will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present disclosure, and be protected by the accompanying claims. In addition, all optional and preferred features and modifications of the described embodiments are usable in all aspects of the disclosure taught herein. Furthermore, the individual features of the dependent claims, as well as all optional and preferred features and modifications of the described embodiments are combinable and interchangeable with one another.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

[0012] FIGS. 1A and 1 B illustrate examples of plasma beam etching of a target substrate (TS), in accordance with various embodiments of the present disclosure.

[0013] FIGS. 2A and 2B illustrate examples of plasma beam lithography (PBL) of a TS, in accordance with various embodiments of the present disclosure.

[0014] FIGS. 3A and 3B illustrate examples of plasma generation substrates (PGS) over a TS, in accordance with various embodiments of the present disclosure.

[0015] FIG. 4 illustrates an example of an electrostatic lens used with the PGS, in accordance with various embodiments of the present disclosure.

[0016] FIGS. 5A-5B and 6 illustrate examples of clamping fixtures and bias voltage to the electrostatic lens for the PGS, in accordance with various embodiments of the present disclosure.

[0017] FIGS. 7A and 7B illustrate examples of a PBL system, in accordance with various embodiments of the present disclosure.

[0018] FIGS. 8A-8C illustrate examples of electrostatic focusing, de-focusing and deflection effects, in accordance with various embodiments of the present disclosure.

[0019] FIG. 8D illustrates an example of lateral movement of the PGS or target substrate to form an array of patterns, in accordance with various embodiments of the present disclosure.

[0020] FIG. 9A includes a table illustrating a comparison of PBL to other sub-50nm nanomanufacturing technologies, in accordance with various embodiments of the present disclosure.

[0021] FIGS. 9B and 9C illustrate comparisons of patterning processes vs. PBL, in accordance with various embodiments of the present disclosure.'

[0022] FIGS. 10-17 illustrate an example of PGS PBL manufacturing, in accordance with various embodiments of the present disclosure.

[0023] FIGS. 18A and 18B illustrate an example of vertical anisotropy in PBL, in accordance with various embodiments of the present disclosure.

[0024] FIG. 19 illustrates an example of an example of array operation in PBL, in accordance with various embodiments of the present disclosure.

[0025] FIGS. 20A and 20B illustrate examples of differences between the PBL PGS and SNAP-Chip nanodroplet generation substrates, respectively, in accordance with various embodiments of the present disclosure.

[0026] FIGS. 21 A and 21 B illustrate examples of patterned substrates, in accordance with various embodiments of the present disclosure.

[0027] FIG. 22 illustrates an example of PBL system operation with a PBL Al processor, in accordance with various embodiments of the present disclosure.DETAILED DESCRIPTION

[0028] Disclosed herein are various embodiments of methods related to Plasma Beam Lithography (PBL). Reference will now be made in detail to the description of the embodiments as illustrated in the drawings, wherein like reference numbers indicate like parts throughout the several views.

[0029] Over the past decades, the IC industry has remained a predominant driver for progressive miniaturization of components in order to achieve efficiencies in computing power, cost, and scale. Beyond the IC industry, such deeply miniaturized elements are also essential to enable next-generation products in diverse application areas such as nanoporebased devices for molecular detection I water and gas purification / energy storage I DNA sequencing, single-electron transistors, capacitive touch screens (in mobile phones, displays, etc.), flexible electronics, sensors, and nano-optics, nanocatalysis, among others.

[0030] Much of the nanomanufacturing approaches of today have evolved predominantly from the lithography technology that has fueled the IC industry.Photolithography involves the formation of micron or nanometer scale shapes in photosensitive materials called resists through the use of UV light and their subsequent transfer on to other conductive, insulating, or functional material layers on substrates that often involve silicon. The resolution or half-pitch of the minimum resolvable feature in projection lithography is given by Abbie’s Law asR- ^ ^ / NA’ where 2 is the wavelength of the light source, NA is the numerical aperture of the projection mediumis a constant. Progressive IC technological nodes over the past decades have employed increasingly shorter-wavelength light sources in order to improve resolution and the current immersion lithography techniques employ 193nm ArF excimer lasers with multiple patterning steps (up to 4) to achieve sub-20nm resolution.

[0031] Further miniaturization down to the about 10nm and smaller regime is being implemented through EUV systems, which employ 13.5nm wavelength light. While EUV offers substantially better resolution, critical challenges centered on resist line width roughness, mask defect controls, and an enormous amount of complexity involving a bulky and expensive system still remain. For instance, each EUV machine has over 100,000 components, requires four jumbo jets to ship and costs about $200M. Thus, manufacturing solutions such as PBL that meet or exceed the performance features of EUV systems while at the same time offering efficiencies in cost and system complexity are desirable.

[0032] On the other hand, EBL, helium-ion beam lithography and focused ion beam (FIB) machining are mask-free, writing tools with sub-50nm resolution involving electron and ion beams, respectively. However, these tools are limited in their throughput (involve very slow, serial writing) and capital costs apart from being impacted by space charging and proximity effects. Other reported sub-50nm techniques include dip-pen nanolithography (DPN) and nanoimprint lithography (NIL). However, DPN suffers from slow patterning speed and lack of scalability. Similarly, NIL presents challenges in terms of mask wear, overlay and pattern reproducibility due to mechanical contact of the imprinting hard-mask template with the underlying printing resist. Thus, current processes have not yet overcome the deficiencies discussed above.

[0033] An exemplary plasma beam lithography system is set forth. The system comprises components configured to selectively form, focus and / or direct plasma beams delivered thereto and perform a lithography and / or etch process thereby. The system can comprise a pattern generation substrate (PGS) or wafer-scale array, and at least one aperture formed therein. The PGS can be configured to receive the plasma from a plasma generation chamber, and to form plasma beams that are shaped the same as or similar to the aperture therein in order to pattern underlying material(s) on a target substrate therethrough, with or without selectivity. The target substrate can be further defined by atleast one dry etchable material on top of a substrate to form the target substrate. The PGS can comprise at least one nano-pattern shaped in the form of at least one aperture. The PGS can be configurable to perform a simultaneous expose-and-etch or single-step writing to pattern the etchable material of the target substrate.

[0034] The PGS can comprise at least one nano-pattern shaped in the form of at least one aperture. The PGS can be configurable to perform a simultaneous expose-and-etch or single-step writing to pattern the etchable material of the target substrate. The plasma can be generated and delivered to the device by a plasma generation chamber. The system can comprise one or more platforms with: a PGS assembled on top of the target substrate using a clamping fixture with or without alignment thereto. The plasma generation substrate can comprise a SNAP-Chip with suitable modifications thereon. In some exemplary systems, an electrical bias can be applied to dynamically tune (i.e., increase or decrease) the size of the plasma beams and perform focused-plasma beam lithography (FPBL). This electrical bias can also be used to deflect the plasma beam laterally and write patterns on the target substrate in locations that are not directly beneath the aperture.

[0035] The system can further comprise one or more electrodes (e-lens) that can be biased to focus the plasma beams and dynamically tune the width or size of the plasma beams. The system platform(s) can be electrically connected to feedthroughs on the plasma chamber for delivery of electrical signals from an external power source to the e-lens. The system can further comprise a processor and at least one controller or user interface both operatively connectable to the PBL system and / or PBL component(s) / component(s) generator for automating the plasma lithography process via instructions stored therein and operating a selectable pattern plasma beam lithography process via the processor / controller.

[0036] The PGS can be configured wherein passive masking of a lateral footprint of a target substantially matches a lateral footprint of the at least one aperture. The system can include e-lens electrodes and positive (or negative) bias in order to selective tune the size of the plasma beam where the size of the plasma beam is smaller (or larger) than the size of the at least one aperture. The system can be configured wherein magnitude and polarity of electrode biasing is configurable to tune the size of the plasma beam.

[0037] In an exemplary Plasma Beam Lithography (PBL) system, an aspect ratio of an etched pattern (depth to width) can be configured to below 10:1 , between 10:1 and 20: 1 or more for a selected process. An exemplary system herein can be configured to comprise a calibration of aspect ratio and feature size I shape for a selectable process that is predictable via an output function of an Al or other processor based on an input into the processor and can be generated via a machine learning or other suitable algorithm. The system can further comprise an e-lens on the PGS for further focusing the plasma beam by providing an electrical bias.

[0038] An exemplary plasma beam lithography platform can comprise a pattern generation substrate comprising at least one aperture assembled on top of a target substrate with or without alignment and housed in a clamping fixture. Further, exemplary systems herein can be configured for the system configured for miniaturization of the pattern, which is created on the etchable material on top of the target substrate, down to a single nanometer or a few nanometers.

[0039] An exemplary method of manufacturing PBL components can comprise the steps of forming at least one of a target substrate for a plasma etching process and a plasma generator substrate for a plasma etching process; and optionally, forming a clamping fixture configured to dispose the target substrate thereon and connect the plasma generation substrate during use; and packaging the PBL components formed above. For exemplary systems herein, different plasma chemistries can produce etching of different films on target substrates. In certain exemplary systems, a target material for a selected PBL process can be a part of a substrate which can include silicon, polymers, or other metallic, semiconductor or ceramic substrates.

[0040] An exemplary PBL device herein can comprise: a target substrate comprising at least one plasma etchable surface. The PBL device can further comprise a clamping fixture connecting one or more target substrates indirectly to one or more PGS. The PBL device can comprise a PGS further comprising an aperture opening with a thickness that extends between a single atomic layer to 10 nanometers. A PBL etching device can comprise a PGS comprising one or more apertures for directing plasma therethrough. In an exemplary PBL etching device, the PGS can further comprise an etch mask coating on at least a portion of the PGS. The etch mask coating can comprise chromium, aluminum, or other suitable coating materials.

[0041] How does patterning with a plasma work? Plasmas are ionized gases that contain a neutral collection of charged particles such as ions and electrons. In the IC and nanomachining industries, plasmas are widely employed to faithfully reproduce a mask pattern on to a target material via dry etching processes. These processes are grouped into the following categories:(i) ion etching or physical etching of materials via bombardment of inert and energetic ions that erodes the surface through momentum transfer. Since it is a purely physical process, this type of etching is very slow and is also non-selective in terms of the materials being etched;(ii) RIE employs a reactive gas and uses a combination of physical and chemical processes to etch materials. Specifically, ion bombardment makes the surface more reactive towards etching by the neutral species in the plasma. RIE is highly material selective and offers some degree of anisotropy; and(iii) ICP-RIE represents a variant of RIE where two RF power sources are employed: an RF antenna which generates the plasma via inductive coupling and a separate RF table bias to attract the ions to the cathode. This serves to decouple the ion flux (through RF antenna) and ion energy applied to the target substrate, thereby widening the process window.As a result, ICP-RIE offers advantages in comparison to RIE that include lower chamber pressure (improves anisotropy), higher plasma density (increases etch rate), and improved material selectivity.

[0042] It is important to note that material selectivity in a plasma etch is achieved through the selection of a suitable feed gas. On the other hand, vertical anisotropy is achieved through one of two mechanisms: (i) selective activation of horizontally exposed surfaces (as opposed to sidewalls) for chemical etching via directional ion bombardment, and (ii) passivation of sidewalls via the formation of an etch inhibiting species that originate from involatile etching products.

[0043] In accordance with the principles herein, PBL can be used in a number of processes, such as in commercial cleanrooms that manufacture Integrated Circuits (ICs), semiconductor chips, microelectromechanical systems (MEMS), lab-on-a-chip devices, etc. PBL has the potential to replace current tools for performing lithography such as photolithography, e-beam lithography, Deep UltraViolet (DUV) and Extreme UltraViolet (EUV) lithography. Furthermore, PBL can be used as a mask-writer to create masks used in lithography tools such as EUC, DUV and photolithography, among others. Systems and methods herein will improve the capabilities of current tools by offering substantial efficiencies in patterning resolution as well as throughput, process scalability, manufacturing complexity, and equipment / operational costs.

[0044] Systems and methods herein address the societal need for new silicon (Si) as well as beyond-Si nanomanufacturing methodologies in the deep-nanometer to micrometer regime, where feature sizes extend as low as a few-nm or near the ultimate limits of solid- state miniaturization. This manufacturing process can be used in diverse products and markets such as Integrated Circuits (ICs), flexible electronics, nanoelectromechanical systems (NEMS), nanopore-based devices for molecular detection I water and gas purification I energy storage I DNA sequencing, single-electron transistors, capacitive touch screens (in mobile phones, displays, etc.), sensors, and nano-optics / nanocatalysis, among others.

[0045] Systems, devices and methods constructed in accordance with the principles herein can facilitate directly writing patterns in diverse thin-film materials near the ultimate limits of solid-state miniaturization. They enable a disruptive performance regime where customers will benefit from substantial efficiencies in patterning resolution as well asthroughput, process scalability, manufacturing complexity, and equipment / operational costs.

[0046] PBL is transformative in two aspects (as will be discussed below): (i) it involves the use of focused plasma beams to perform lithography for the first time, and (ii) it uses nano-aperture arrays, which are miniaturized to up to a few nm in width and represent the smallest reported till-date, to direct plasma beams and selectively dry-etch material at the deep-nm regime. The use of reactive radicals and energetic ions, which are generated within a plasma, enables the direct single-step writing of nano-patterns via physical and / or chemical etching in diverse thin-film materials such as polymeric resists, dielectrics, semiconductors and metals. This is a substantial simplification of the multi-step patterning process associated with the current extreme ultraviolet (EUV), photolithography or electron beam lithography (EBL) techniques, which involves: (i) a first pattern writing step followed by wet chemical development in resist thin films, and (ii) subsequent pattern transfer step(s) onto the eventual target materials (dielectrics, semiconductors or metals) through additional additive or subtractive IC-nanomachining techniques.

[0047] This single-step pattern writing process can be accomplished using an all-on-a- wafer lithography system that is performed inside commercially available plasma-based material etching equipment such as reactive ion etching (RIE) and inductively coupled plasma - reactive ion etching (ICP-RIE). Such tools are ubiquitous and widely used in IC nanomanufacturing cleanrooms, thereby enabling the seamless integration of PBL into commercial IC nanomanufacturing facilities.

[0048] Plasma Beam Lithography (PBL): PBL involves the use of focused plasma beams to directly pattern thin film materials on Si and beyond-Si substrates. While lithography based on radiation of different types such as light, electrons, and ions have been commercialized before, the use of plasma beams offers a disruptive new lithographic performance regime near the ultimate limits of solid-state miniaturization and is being advanced for the first time.

[0049] FIGS. 1 A and 1 B illustrate a target substrate (TS) comprised of an etchable film layer 103 over a substrate 106. Plasma beams 109 containing ions and radicals can etch or pattern the film on the target substrate using Plasma Beam Lithography (PBL). The PBL process can be performed passively or focused, as desired. Regardless of how the plasma is created, if the plasma is electrified, a plasma beam 109 can be focused and dynamically tuned from a larger width (as shown in FIG. 1A) to a smaller width (as shown in FIG. 2A) in order to perform focused plasma beam lithography.

[0050] To this end, an energy field, such as electric field, can be applied so that the feature size or width of the etched pattern can become smaller from top to bottom, enable the process to form chips / chip components, flexible electronics and the like. In fact, anumber of commercial products can be formed or enhanced by devices incorporating PBL components constructed in accordance with the principles herein.

[0051] As illustrated in FIG. 1A, the target substrate can include a suitable substrate and an etchable film. One specific example of a TS can be formed of a Silicon substrate and an etchable film is shown in FIG. 1 B. Other substrates can include but are not limited to other semiconductors, metals or polymers and combinations thereof, for example.

[0052] FIGS. 2A and 2B show examples of focused PBL on a general device TS, FIG. 2A, and an exemplary Silicon device TS, FIG. 2B. In both cases, the ions from the plasma beam 109 are focused and directed to a smaller width to pattern the substrate in a focused manner.

[0053] A typical PBL set-up, which is schematically illustrated in FIGS. 3A and 3B, is described as follows. The pattern generation substrate can include, but is not limited to, a nanodroplet generation substrate of a SNAP-Chip or other suitable device. Embodiments herein are contemplated that are configured for the use of plasma beams through any aperture embodiment (i.e. , not limited by substrate, manufacturing process, aperture size, etc.) and not just the nanodroplet generation substrate of a SNAP-Chip example set forth herein. Exemplary embodiments of the nanodroplet generation substrate of a SNAP-Chip are described in, for example, US patent application number 17 / 608,020, filed November 1 , 2021 (US patent application publication No. US 2022 / 0347749), which is hereby incorporated by reference herein in its entirety.

[0054] FIGS. 3A and 3B illustrate an example of a plasma generation substrate (PGS) over a target substrate (FIG. 3A) and with an optional conductive electrostatic lens (e-lens) layer 303 between the PGS and the TS (FIG. 3B). The materials selected to form the various components of the system can vary and can be selected based on component parameters I processing conditions. As illustrated in FIG. 4, an electrostatic lens 303 can be provided in the system and operated in an unbiased fashion for passive PBL (as shown in FIG. 3B), or in a biased fashion as shown in FIG. 4 to achieve a focused plasma beam.

[0055] As shown in FIGS. 3A-3B and 4, the exemplary nanodroplet generation substrate can be coated with a plasma resistant thin film such as chromium or aluminum or other suitable etch-resistant material (e.g., a material with a lower etch rate in comparison to the material being etched on the target substrate) on the reservoir side to form the pattern generation substrate (PGS), or beam generation substrate (BGS), for plasma beam lithography. The PGS has two important elements among others: (a) a deeply miniaturized aperture (e.g., nano-aperture 306) with an opening shaped and sized similar to the pattern that is desired to be created on the film on top of the target substrate, and (b) a conductive electrode called an electrostatic lens (e-lens) 303 that can be separated from the aperture by nanoscopic to microscopic gaps. The PGS can be assembled and secured on top of a targetwafer / substrate (TS) with or without a spacing between the PGS and the target substrate (TS). It is important to note that the target substrate already has a thin-film coating 103 of the material to be patterned on its surface. This thin-film 103 may be made of metals, dielectrics, semiconductors and polymers. In some implementations, the TS can be etched without an etchable film layer 103 being disposed over the substrate 106. In this case, the substrate 106 would be directly etched by the process.

[0056] As illustrated in FIGS. 5A and 5B, a PGS-TS system assembly can include one or more clamping fixtures 503 to position PGS over the TS. The PGS can be spaced apart from the TS, FIG. 5A, or placed directly on the TS (not shown). In some embodiments, an electrostatic lens 303 can be positioned between the PGS and the TS, as illustrated in FIG. 5B. A clamping fixture 503 can be provided to facilitate the positioning, alignment and assembly of the PGS and TS components for the PBL process. The PGS and TS components, and clamping fixture(s) 503 can be constructed prior to processing into a single customizable platform and can be selected to provide a customized platform for a particular manufacturing process. Further, one or more devices can be manufactured simultaneously as illustrated in FIGS. 5A and 5B.

[0057] As illustrated in FIG. 6, one or more metal clamps 603 or another suitable electrical connector can provide a bias voltage to the electrostatic lens 303 for focused plasma beam lithography (FPBL) processes. Again, the PGS and TS can be in direct contact, have a gap or space between them, or have a lens or other structure between them as desired for FPBL.

[0058] FIGS. 7A and 7B show examples of a PBL system comprising a plasma chamber 703, such as but not limited to ICP-IRE or RIE, an RF antenna 706, an inductively powered plasma power (ICP) power source 709, a cathode 712, and a table bias 715. The system can further comprise one or more custom pattern carrier devices therein. Further, an electrical feedthrough can be provided and operable / connected to an external power supply in order to provide power to the e-lens via the metal clamp for F-PBL processes.

[0059] Once secured in place, the substrate assembly is placed inside a suitable plasma generator such as but not limited to an Inductively Coupled Plasma Reactive Ion Etcher (ICP-RIE) or a Reactive Ion Etcher. Other types of plasma chambers including custom-built systems are also envisioned for such use. FIGS. 7A and 7B show the use of an ICP-RIE system. FIG. 7A shows a passive PBL system, while FIG. 7B shows a focused-PBL System. When a suitable feed gas is introduced into the low-pressure chamber (such as 1- 100 mtorr) from the top, it is ionized by the RF bias supplied to the RF antenna 706 to create a high-density plasma. This plasma contains positive ions, neutral molecules, radicals, electrons and photons.

[0060] FIG. 8A illustrates the electrostatic focusing effect where a positive bias applied to the e-lens electrodes 303 exerts a repulse force on the positive ions within the plasma beam and thereby, results in electrostatic focusing of the beam into lateral dimensions that are smaller than that of the aperture. FIG. 8B illustrates the electrostatic de-focusing effect where a negative bias applied to the e-lens electrodes 303 exerts an attractive force on the positive ions within the plasma beam and thereby, results in electrostatic focusing of the beam into lateral dimensions that are larger than that of the aperture. This example may also be used to perform passive PBL without the external power supply or the electrical feedthrough. FIGS. 8A and 8B illustrate the dynamic tunability of the beam size and thereby, the pattern sizes created on the film on top of the target substrate.

[0061] Asymmetric bias of the e-lens electrodes 303 can also allow for deflection of the plasma beam as illustrated in FIG. 8C. An example of a PBL system is shown where the e- lens electrodes 303 on either side of the aperture 306 are asymmetrically biased to laterally deflect the beam towards the e-lens electrode 303 carrying the lower (or less positive) of the two voltages and thereby achieve lateral scanning of the plasma beam for formation of etched patterns on the target substrate that are offset from the center of the aperture opening.

[0062] FIG. 8D illustrates an example of a PBL system where an array of patterns is formed on the target substrate by lateral movement of the target substrate in the x- and / or y- directions with respect to the PGS through a cyclical sequence of operations that involve PBL etching, lateral movement, and PBL etching steps. In an alternative example, an array of patterns can be formed on the target substrate by lateral movement of the PGS in the x- and / or y-directions with respect to the target substrate through a cyclical sequence of operations.

[0063] Once generated, the ions and neutral species I radicals in the plasma are transported to the PBL substrate assembly (which is placed on the cathode of the ICP-RIE system) due to the applied table bias and diffusion, respectively. Here, the plasma can form arrays of nanoscopic beams that are selectively transmitted through the nanoscopic aperture arrays defined on the pattern generation substrate and reach the thin-film layer on the target substrate (see, e.g., FIG. 19). The shape and size of the resultant plasma beam is defined by those of the aperture from which it is generated. At the other regions outside of the apertures, the plasma is blocked by an etch-resistant layer such as but not limited to Cr or Al, which is coated on the top side of the pattern generation substrate.

[0064] Upon reaching the surface of the thin-film layer 103 on the target substrate, the positive ions in the plasma beam make the surface more reactive towards the neutral species by ion bombardment. As a result, the thin-film material reacts with the neutral species to form a volatile product that is pumped away from the reactor chamber. Animportant aspect of ICP-RIE is the directionality of the plasma due to the low chamber pressure (for example, 1 to 100 mtorr) and its resulting long mean-free paths. As a result, the positive ions in the plasma species maintain vertical trajectories as they move towards the cathode 712. It is important to note that even though the neutral species (or radicals) diffuse randomly in all directions, they etch the target material only in regions that are activated by the positive ions and hence yield anisotropic etches with perfectly straight sidewalls. It thus follows that even though the radicals may reach the portions of the surface of the target substrate that are not desired to be etched, they do not yield etching due to those portions not being activated by bombardment via the positive ions. Hence, PBL performed inside an ICP-RIE system does not require the application of a beam focusing bias at the e- lens electrodes 303 unless the width of the P-beam needs to be miniaturized beyond the width of the aperture on the PGS (as is the case with focused PBL).

[0065] However, when PBL is performed inside other conventional RIE systems that yield an isotropic etch due to higher chamber pressures, a positive bias will be applied to focus the plasma beam and deliver anisotropy during patterning. Here, the magnitude and polarity of the applied bias will determine the size of the resultant plasma beam. For instance, with increasing positive bias applied at the e-lens 303, the resultant electrostatic focusing force will yield beam sizes that are equal to or smaller than the footprints of the aperture. On the other hand, a negative bias applied at the e-lens 303 will result in a beam size that is larger than that of the aperture footprints. This enables a dynamic, on-the-fly tuning of the pattern size through the use of electric potentials that are applied to the e-lens. Such lithography performed through on-the-fly tuning of the plasma beam via electrostatic focusing is called as focused-plasma beam lithography (F-PBL). F-PBL can be implemented in plasma chambers such as but not limited to RIE, ICP-RIE, or any other standard as well as custom-built plasma chambers.

[0066] Customizations for the plasma chemistry and its parameters such as but not limited to source gases I chamber pressure will be based upon the properties of the film material(s) selected to undergo the PBL process. For example, PBL can be performed on a poly-methyl-methacrylate (PMMA) resist layer coated on top of a silicon wafer. The lithographic pattern transfer in this example can be accomplished through an oxygen plasma generated inside an ICP-RIE system. This PBL process can involve the following parameters: (a) ICP and RF powers of 600W and 20W, respectively, (b) chamber pressure of 50 mtorr, (c) O2feed-gas at a flow rate of 60 seem, and (d) an RF frequency of 13.7MHz. Other parameters and materials are contemplated in accordance with the principles herein.

[0067] Why is PBL an ideal solution for nanomanufacturinq? The benefits of using plasma beams to define dry-etched patterns at the nanoscale to microscale size regime (and extending up to single-digit nm) include:(i) the ability to form plasma beams with nanometrically small widths as defined and focused by physical apertures; and(ii) direct writing of patterns into the target material as opposed to most other lithographic techniques. For instance, photolithography and EBL involve pattern writing through chemical modification of a masking resist layer prior to its chemical development and subsequent pattern transfer into the target material. The chemical modification of the resist layer through radiation such as light or electron beams involves scattering in the resist resulting in lithographic bias in the created features.The key differentiators of PBL in comparison to the other sub-50nm nanomanufacturing technologies that are currently in the market are summarized in the table of FIG. 9A.

[0068] FIG. 9B illustrates a comparison of the etch-based or subtractive patterning process between photo- or EUV lithography vs. PBL. In prior art involving photo- or EUV lithography, three steps are involved as illustrated: selective exposure of a light-sensitive polymeric resist (step 1), development of the resist to form the pattern in the resist (step 2), and transfer of the pattern to the target film via dry or wet etch followed by removal of the resist (step 3). In PBL, the desired pattern is directly written on to the target film in a single step as shown.

[0069] FIG. 9C illustrates a comparison of the lift-off based or additive patterning process between photo- or EUV lithography vs. PBL. In prior art involving photo- or EUV lithography, three steps are involved as illustrated: selective exposure of a light-sensitive polymeric resist (step 1), development of the resist to form the pattern in the resist (step 2), and transfer of the pattern to the target film via dry or wet etch followed by removal of the resist (step 3). In PBL, the desired pattern is created using two steps: direct writing of a desired pattern on to an etchable film (step 1), and transfer of the pattern ot the target film via metal deposition followed by lift-off (step 2). An important innovation in PBL is that the etchable film, which serves the role of a resist in the first step of PBL, is not limited to just the polymeric, light-sensitive resists used in photo- or EUV lithography. This film can be made of any additional plasma-etchable material such as but not limited to dielectrics, semiconductors, metals, and polymers.

[0070] FIGS. 10-17 illustrate an example of method steps for complete PGS PBL device manufacturing. FIG. 10 illustrates a cross-sectional view of an exemplary pattern generation substrates PGS. The PGS can include a silicon-on-insulator (SOI) substrate, which can be further optimized by polishing, and / or selecting the silicon resistivity to be ultralow, and by a desired crystallographic orientation which can be optimized for a particular process. Exemplary layer thicknesses in the SOI substrate can include a thin device layer 1003 (e.g., Si) of approximately 100 nm to 10 pm above an insulating layer 1006 (e.g., SiO2) and a thicker handle layer 1009 (e.g., Si) of approximately 100 to 500 pm or more below theinsulating layer 1006, although these rates can be optimized for a selected manufacturing process.

[0071] As illustrated in FIG. 11 , a low stress etchable film 1012 (e.g., Si3N4) can be deposited on both sides of the PGS to prevent membrane buckling after etching. Electrodes 1015 can then be formed in a suitable manner, such as for example a gold (Au) film layer over a thinner adhesion layer (such as, for example chromium or titanium, not shown), if desired, as illustrated in FIG. 12. In the example of FIG. 12, the e-lens electrodes 1015 are drawn to be common and global to all apertures on the PGS. Variations are envisioned where the e-lens electrode 1015 is uniquely addressable to each aperture via electrical isolation. A nozzle-etch opening can then be formed using dry-etch or other suitable process, as shown in the example of FIG. 13.

[0072] FIG. 14 illustrates back-side trenches formed on the opposite (back) side of the structure from the electrodes 1015 via wet or dry etching. This involves the first opening of windows on the back-side nitride film 1012 using photolithography and a dry-etch. Next, a second photolithography step can be employed to create a resist or metal mask film followed by dry-etching (such as with the Bosch process) of silicon 1009. The silicon dioxide layer 1006 of the SOI wafer can serve as the etch stop. Alternatively, the last few tens of microns or the entire thickness of the handle silicon layer 1009 may be etched using a TMAH etch in which case the sidewalls will be sloped as in pattern generation substrate of FIG. 4.

[0073] As illustrated in FIG. 15, a wet etch of the buried silicon dioxide layer 1006 of the silicon-on-insulator (SOI) substrate can be performed using etchants such as HF or Buffered HF. Next, aperture creation through etching of silicon 1003 using a wet (TMAH or KOH) or dry etch as shown in FIG. 16. In the example of FIG. 16, the e-lens electrodes 1015 are drawn to be common and global to all apertures on the PGS. Variations are envisioned where the e-lens electrode 1015 is uniquely addressable to each aperture 306 via electrical isolation. While a wet etch can yield pyramidal sidewalls with, e.g., a 54.7° angle, a dry etch can yield vertical sidewalls. Other sidewall angles can also be used to achieve the desired aperture 306, e.g., in a range from about 30° to about 75°, about 30° to about 60°, about 45° to about 60°, etc. Then, a PBL etch mask layer 1018 can be formed, as shown in FIG. 17, using thin films, such as, but not limited to Cr or Au thin-films on the back-side. The thickness of the etch mask layer 1018 can be selected based on dimensions for the etch and can be selected to be as little as 50 to 100 nanometers, if desired. The etch mask layer can also be formed on the sidewalls as illustrated in FIGS. 3A-3B, 4 and 8A-8B.

[0074] Further, as illustrated in FIGS. 18A and 18B, vertical anisotropy in the PBL process can be achieved through one of two mechanisms: (i) selective activation of horizontally exposed surfaces (as opposed to sidewalls) for chemical etching via directionalion bombardment [FIG. 18A], and (ii) passivation of sidewalls via the formation of an etch inhibiting species that originate from involatile etching products [FIG. 18B],

[0075] FIG. 19 shows an example of array operation in PBL enables plasma beams with differently shaped / orientated aperture / openings. As illustrated in FIG. 19, apertures of different geometries can be included on the PGS, if desired. FIGS. 20A and 20B illustrate the differences between the PBL PGS and the SNAP-Chip nanodroplet generation substrates, respectively. Finally, FIGS. 21 A and 21 B illustrate exemplary products in the form of patterned substrates. FIG. 21 A shows that the shape, lateral dimensions and depth of the etched patterns for PBL processing can vary. FIG. 21 B shows the depth of the PBL etch in the TS can vary and also that the etch can be performed in multiple material layers on the target substrate.

[0076] FIG. 22 illustrates a PBL system operatively connected to an optional PBL Al processor in order to optimize the PBL process, select optimum materials and conditions for a particular PBL process, and predict the accuracy of the patterns on a selected target substrate. To this end a user interface can be connected to the PBL Al processor to provide inputs regarding available materials, desired components and the like. The PBL Al processor can calibrate the process for a given environment and optimize the parameters and materials for a selected process.

[0077] As illustrated in FIGS. 1A and 1B, the method of plasma beam lithography (PBL) can be achieved by delivering plasma, such as via plasma beams of a suitable size, such as less than 10 microns, to an etchable (or patternable) film on a target substrate. This yields an etched pattern on the film on top of the target substrate with a width that is substantially the same as that of the plasma beam width. Plasma beams can vary in width, such as below 5 nanometers, or between 5 nanometers to 100 nanometers, or between 500 nanometers to 10 microns. In addition, other features, devices, systems and methods from which a technical benefit is achieved in accordance with the principles herein are contemplated as well.

[0078] It should be emphasized that the above-described embodiments of the present disclosure are merely possible examples of implementations set forth for a clear understanding of the principles of the disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the disclosure. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

[0079] The term "substantially" is meant to permit deviations from the descriptive term that don't negatively impact the intended purpose. Descriptive terms are implicitly understood to be modified by the word substantially, even if the term is not explicitly modified by the word substantially.

[0080] It should be noted that ratios, concentrations, amounts, and other numerical data may be expressed herein in a range format. It is to be understood that such a range format is used for convenience and brevity, and thus, should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. To illustrate, a concentration range of “about 0.1% to about 5%” should be interpreted to include not only the explicitly recited concentration of about 0.1 wt% to about 5 wt%, but also include individual concentrations (e.g., 1%, 2%, 3%, and 4%) and the sub-ranges (e.g., 0.5%, 1.1%, 2.2%, 3.3%, and 4.4%) within the indicated range. The term “about” can include traditional rounding according to significant figures of numerical values. In addition, the phrase “about ‘x’ to ‘y’” includes “about x’ to about ‘y’”.

Claims

CLAIMSTherefore, at least the following is claimed:

1. A plasma beam lithography system, comprising: a source of plasma; and a pattern generation substrate (PGS) comprising at least one aperture formed therein, the PGS configured to receive the plasma from the source and form one or more plasma beam directed at a target substrate positioned on a side of the PGS opposite the source for patterning or etching, the one or more plasma beam formed via the at least one aperture with each of the one or more plasma beam shaped the same as or similar to a corresponding aperture of the at least one aperture.

2. The plasma beam lithography system of claim 1 , comprising the target substrate in a fixed or variable position adjacent to the PGS opposite the source.

3. The plasma beam lithography system of claim 2, comprising a clamping fixture that secures the PGS in the fixed position between the target substrate and the source.

4. The plasma beam lithography system of claim 3, comprising a plurality of pattern generation substrates (PGSs) secured between corresponding target substrates and the source by the clamping fixture.

5. The plasma beam lithography system of any of claims 1-4, wherein the target substrate comprises an etchable film layer disposed on a substrate.

6. The plasma beam lithography system of claim 5, wherein the etchable film layer comprises at least one dry etchable material.

7. The plasma beam lithography system of claim 5, wherein the target substrate comprises a plurality of etchable film layers disposed on the substrate.

8. The plasma beam lithography system of any of claims 1 -7, wherein the PGS comprises one or more electrostatic lens (e-lens) electrode disposed on a side adjacent to the target substrate.

9. The plasma beam lithography system of claim 8, comprising at least one feedthrough coupled to the one or more e-lens electrode for delivery of electrical signals from an external power source.

10. The plasma beam lithography system of claim 9, wherein the one or more e-lens electrode is electrically biased with a positive or negative voltage to focus or adjust size of the one or more plasma beam to perform focused-plasma beam lithography (F-PBL).11 . The plasma beam lithography system of claim 10, wherein electrically biasing with a positive voltage reduces a footprint of the one or more plasma beam on the target substrate and electrically biasing with a negative voltage increases the footprint of the one or more plasma beam on the target substrate.

12. The plasma beam lithography system of claim 8, wherein the one or more electrostatic lens (e-lens) electrode is a single e-lens electrode.

13. The plasma beam lithography system of claim 8, wherein the one or more electrostatic lens (e-lens) electrode comprises a plurality of e-lens electrodes.

14. The plasma beam lithography system of claim 13, wherein the plurality of e-lens electrodes is configured to individually adjust size of each of a plurality of plasma beams.

15. The plasma beam lithography system of any of claims 1-14, wherein the source of the plasma comprises a plasma generation chamber.

16. The plasma beam lithography system of any of claims 1-15, wherein the PGS comprises an etch mask coating at least a portion of the PGS.

17. The plasma beam lithography system of claim 16, wherein the PGS comprises a SNAP-Chip with the etch mask coating at least a portion of the SNAP-Chip.

18. The plasma beam lithography system of claim 16, wherein the etch mask comprising chromium or aluminum.

19. The plasma beam lithography system of any of claims 1-18, wherein the at least one aperture comprises a plurality of nano-apertures.

20. The plasma beam lithography system of any of claims 1-18, wherein the at least one aperture comprises an aperture opening with a thickness between a single atomic- layer to 10 nanometers.21 . A method of manufacturing plasma beam lithography components, comprising: providing a pattern generation substrate (PGS) comprising at least oneaperture formed therein; positioning the PGS adjacent to a target substrate opposite a source of plasma; forming one or more plasma beam directed at the target substrate, the one or more plasma beam formed from plasma from the source via the at least one aperture with each of the one or more plasma beam shaped the same as or similar to a corresponding aperture of the at least one aperture; and performing a simultaneous expose-and-etch or single-step writing with the one or more plasma beam to pattern the target substrate.

22. The method of claim 21 , wherein the source of the plasma comprises a plasma generation chamber.

23. The method of any of claims 21 and 22, comprising fixing the PGS in position adjacent to the target substrate using a clamping fixture.

24. The method of claim 23, comprising fixing a plurality PGS in position adjacent to a plurality of corresponding target substrates using the clamping fixture.

25. The method of any of claims 21-24, comprising applying an electrical bias to one or more electrostatic lens (e-lens) electrode to dynamically tune a size of the one or more plasma beam.

26. The method of claim 25, wherein the electrical bias is applied via one or more electrostatic lens (e-lens) electrode disposed adjacent to the target substrate.

27. The method of claim 25, wherein electrically biasing with a positive voltage reduces a footprint of the one or more plasma beam on the target substrate and electrically biasing with a negative voltage increases the footprint of the one or more plasma beam on the target substrate.

28. The method of any of claims 21-24, comprising asymmetrically applying an electrical bias to electrostatic lens (e-lens) electrodes to deflect at least one plasma beam.

29. The method of claim 25, wherein the size of the one or more plasma beam is adjusted to perform focused-plasma beam lithography (F-PBL).

30. The method of claim 29, wherein an aspect ratio of an etched pattern is in a range from 1 :1 to 20: 1 , or more.31 . A substrate or pattern or product formed using the method of any of claims 21-30.

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