Gas cluster assisted plasma processing

Abstract

To provide a system and a method for gas cluster assisted plasma processing for increasing the density of radicals deep inside a high aspect ratio cavity.SOLUTION: A method for processing a substrate includes: forming a patterned layer over the substrate, the layer including an opening where a surface of the opening includes a sidewall and a bottom wall; and processing the patterned layer using an anisotropic process by generating a flux of gas clusters over the substrate in a first process chamber, where the gas clusters include radical precursors. The processing includes; exposing the substrate to the flux of gas clusters; sustaining plasma including ions in a second process chamber; and exposing the substrate to the ions by directing the ions toward the bottom wall of the opening.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of the filing date of U.S. Non-Provisional Patent Application No. 17 / 008,314, filed August 31, 2020, which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to plasma processing, and in particular embodiments to systems and methods for gas-cluster assisted plasma processing. [Background technology]

[0003] Typically, semiconductor devices, such as integrated circuits (ICs), are fabricated by sequentially depositing and patterning layers of dielectric, conductive, and semiconducting materials on a substrate to form a network of monolithically integrated electronic components and interconnect elements (e.g., transistors, resistors, capacitors, metal lines, contacts, and vias). Many of the deposition and etching steps used to form the constituent structures of semiconductor devices are performed using plasma processing. Plasma processing techniques include chemical dry etching (CDE) (e.g., plasma ashing), physical or sputter etching, reactive ion etching (RIE), plasma enhanced chemical vapor deposition (PECVD), plasma enhanced atomic layer etching (PEALE), and atomic layer deposition (PEALD).

[0004] Each successive technology node reduces costs by shrinking minimum feature sizes and roughly doubling component packing density. The demand for high-performance, low-cost electronics has driven feature sizes down to a few nanometers. As lateral dimensions approach molecular and atomic scales, plasma technology faces the challenge of fabricating very high aspect ratio structures using processes that can also meet the stringent precision, uniformity, stability, and repeatability required for IC manufacturing. Further innovations in plasma processing systems and methods may be required to overcome obstacles along the way to successful semiconductor device manufacturing. Summary of the Invention

[0005] According to one embodiment, a method for processing a substrate includes forming a patterned layer on the substrate, the layer including an opening, the opening having a surface including a sidewall and a bottom wall. The method includes processing the patterned layer using an anisotropic process by generating a flux of gas clusters above the substrate in a first processing chamber, the gas clusters including radical precursors, and exposing the substrate to the flux of gas clusters. The method also includes maintaining a plasma including ions in a second processing chamber and exposing the substrate to the ions by directing the ions toward the bottom wall of the opening.

[0006] According to one embodiment, a system for processing a substrate includes a first subsystem including a plenum including a gas inlet, a nozzle assembly including a plurality of nozzles, each nozzle having an inlet aperture disposed within the plenum, a gas-cluster processing chamber connected to the plenum via the plurality of nozzles of the nozzle assembly, and a gas flow system connected to the gas inlet and a gas outlet of the gas-cluster processing chamber, the gas flow system being configured to generate a flux of gas-clusters in the gas-cluster processing chamber, the system including a second subsystem including a plasma processing chamber and a power supply for powering a plasma in the plasma processing chamber.

[0007] According to one embodiment, a system for processing a substrate includes a plenum, a substrate processing chamber disposed outside the plenum and configured to sustain a plasma, and a nozzle having an intake aperture coupled to the plenum and an exhaust aperture coupled to the substrate processing chamber. [Brief explanation of the drawings]

[0008] For a more complete understanding of the present invention and its advantages, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

[0009] [Figure 1A] 1 is a flow diagram of a method for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 1B] 1B is a flow diagram of a method for processing a substrate using the gas-cluster assisted anisotropic plasma process shown in FIG. 1A using a cyclical process flow utilizing two processing chambers. [Figure 1C] 1B is a flow diagram of a method for processing a substrate using the gas-cluster assisted anisotropic plasma processing shown in FIG. 1A using a cyclical process flow utilizing one processing chamber. [Figure 2A]1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2B] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2C] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2D] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2E] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2F] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2G] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2H] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 2I] 1A-1D illustrate cross-sectional views of a substrate at various intermediate stages in the processing of the substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 3A] 1 shows a cross-sectional view of a subsystem including a plenum and a gas-cluster processing chamber of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 3B] 1 shows a cross-sectional view of a subsystem including a plasma processing chamber of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 4]1 shows a cross-sectional view of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 5A] 1A-1C show cross-sectional views of various design types of nozzles of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 5B] 1A-1C show cross-sectional views of various design types of nozzles of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 5C] 1A-1C show cross-sectional views of various design types of nozzles of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 5D] 1A-1C show cross-sectional views of various design types of nozzles of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 6] 1 shows a cross-sectional view of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 7A] 1 shows a top plan view of a nozzle system with a recessed electrode of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 7B] 1 shows a bottom plan view of a nozzle system with a recessed electrode of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 7C] 1 shows a cross-sectional view of a nozzle system with a recessed electrode of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 7D] 1 shows a cross-sectional view of a nozzle system with a recessed electrode of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 7E]1 shows an exploded view of a nozzle system with a recessed electrode of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. [Figure 8] 1 shows a cross-sectional view of a system for processing a substrate using gas-cluster assisted anisotropic plasma processing, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] This disclosure describes the processing of substrates using gas-cluster assisted anisotropic plasma processing. The gas-cluster assisted anisotropic plasma processing technique described in various embodiments herein is a hybrid gas-cluster and plasma processing method. In various embodiments of this method, radicals are delivered to the vicinity of the etching surface by a flux of gas-clusters, and positively charged ions from the plasma are directed toward the substrate to remove material from the etching surface.

[0011] Generally, the velocity of neutral radicals in anisotropic plasma etching processes has a wide angular distribution, while positively charged ions can be more easily directed, for example, perpendicular to the substrate by a vertical electric field to form vertical holes or trenches. Thus, radicals entering a narrow-opening cavity are more likely to collide with and adsorb onto the sidewalls than ions entering the cavity at near-perpendicular velocities. This phenomenon causes the ratio of radicals to ions to decrease rapidly with cavity depth and may also limit the maximum aspect ratio achievable by a respective etching process.

[0012] Highly anisotropic plasma etching processes often utilize an adsorbed passivation layer along vertical sidewalls to promote anisotropy and control sidewall profile, while simultaneously bombarding the bottom wall with a highly directed ion flux. Anisotropic chemical plasma etching processes involve a combination of adsorption and desorption fluxes, with net removal of substrate material as volatile gaseous reaction by-products. These fluxes are understood to occur simultaneously within a reaction volume of several monolayers at the surface, referred to as the intermixed layer. The removal rate decreases with increasing intermixed layer thickness, and the removal process may even cease in the absence of an energetic ion flux, as discussed above for vertical sidewalls. Energetic ions directed at the substrate can be interpreted as being driven into the intermixed layer at the bottom wall with sufficient energy to promote chemical reaction between the substrate and the etch reactants, for example, by breaking chemical bonds. In controlled anisotropic plasma etching processes, it is desirable to achieve a condition in which the removal rate is directly proportional to the incident ion flux. This condition is known as Γ r / Γ i is generally achieved when Γ>>1, where Γ r denotes the radical flux, and Γ i denotes the ion flux. r / Γ i If the ratio of is too small, e.g., Γ r / Γ i If Γ is below 10, it may not be possible to produce fluorine-based etch chemistries. Radicals are also utilized as scavenger species, forming volatile gaseous by-products with sufficient vapor pressure to be pumped out by the vacuum system. For example, in an RIE step using carbon tetrafluoride (CF4) to etch silicon, adding a small amount of oxygen can scavenge carbon residues from the dissociation of CF4. Oxygen radicals react with carbon to form volatile gaseous oxides of carbon (e.g., CO and CO2). As explained above, injecting a sufficient supply of radicals through the top opening of a narrow, deep hole, e.g., a via 30 nm in diameter and 3 microns deep, can produce a large value of Γ near the bottom etch surface. r / Γ iis difficult to achieve.

[0013] The systems and methods described in this disclosure offer the advantage of increasing the density of radicals deep within high aspect ratio cavities. Accordingly, a target application that may effectively utilize gas-cluster assisted anisotropic plasma processing techniques is etching high aspect ratio openings in semiconductor device structures, such as contacts, vias, and trench capacitors for dynamic random access memory (DRAM) cells. In this disclosure, the gas-cluster assisted anisotropic plasma processing (CLAAPP) technique, referred to as CLAAPP, is described in the context of first patterning a layer using conventional anisotropic plasma techniques (e.g., RIE) to form narrow openings with moderate aspect ratios (e.g., aspect ratios of about 30 to about 60), and then extending this depth using the CLAAPP technique to form very high aspect ratio features. For example, by using embodiments of CLAAPP described in this disclosure, it is possible to achieve a maximum aspect ratio (AR) of 1000 nm. max can be increased from about 60 to about 100, or even up to 150.

[0014] A general CLAAPP method 100 will first be described using the flow diagram of FIG. 1A. Two embodiments of the general method 100 are illustrated in the flow diagrams of FIGS. 1B and 1C. FIG. 1B illustrates a two-chamber CLAAPP method 130, and FIG. 1C illustrates a single-chamber CLAAPP method 140. Next, an application of the general CLAAPP method 100 will be described with reference to the cross-sectional views of FIGS. 2A-2I, which illustrate the formation of high aspect ratio openings (e.g., holes or trenches) in a layer (e.g., a dielectric layer such as silicon oxide). The two chambers of the two-chamber CLAAPP method 130 will be described with reference to the cross-sectional and schematic views of FIGS. 3A and 3B, and the single chamber of the single-chamber CLAAPP method 140 will be described with reference to FIG. 4. Various aspects of the design of the gas-cluster assisted plasma processing system (described with reference to FIGS. 3A-3B and 4) are discussed using the diagrams of FIGS. 5A-5D, 6, 7A-7E, and 8.

[0015] 1A shows a flow diagram of a general CLAAPP method 100. First, an incoming substrate (e.g., a semiconductor substrate) is prepared by forming a patterned layer on the substrate. As shown in block 110, this patterned layer includes narrow openings formed using appropriate photolithography and etching techniques, as known to those skilled in the art.

[0016] The patterned layer is then processed using a CLAAPP etching technique. As indicated by block 120, the CLAAPP etching includes several parts: generating a flux of gas clusters above the substrate (box 122), exposing the substrate to the flux of gas clusters (box 124), maintaining the plasma using radio frequency (RF) power (box 126), and exposing the substrate to a vertically directed flux of ions extracted from the plasma (box 128).

[0017] Gas clusters are formed from condensable gases, known as radical precursors, which are radical sources. Examples of radical precursors include oxygen, carbon monoxide, hydrogen, chlorine, carbon tetrachloride, silicon tetrachloride, boron trichloride, fluorine, carbon tetrafluoride, nitrogen trifluoride, sulfur hexafluoride, trifluoromethane, fluorocarbons, and hydrofluorocarbons. Gas clusters can be formed by injecting a condensable gas into a vacuum chamber through a nozzle. Radical precursor gases injected into the process chamber through a nozzle at several times the speed of sound can cool and condense by adiabatic expansion to form loosely bound gas clusters. Average cluster sizes can range from about 1,000 to about 10,000 molecules per cluster, depending on various process and equipment parameters, such as the temperature of the radical precursor gas, the nozzle design, and the pressure gradient between the nozzle inlet and outlet. The flux of gas clusters thus generated in the process chamber can then travel further toward the substrate placed on the underlying substrate holder. The processing chamber may be loaded with an incoming substrate with openings in the patterned layer and evacuated to a low pressure using a vacuum system. Upon reaching the substrate, the clusters enter the cavities exposed to a flux of gas clusters by the masking layer and can subsequently participate in a CLAAPP etching process, as described in more detail below.

[0018] The substrate is also exposed to ions extracted from the plasma to perform a CLAAPP etch, as shown in block 120 of the flow diagram of Figure 1A. The ions are directed normal to the bottom wall of the opening and may remove material as they strike the bottom wall and interact with the surface.

[0019] FIG. 1B shows a flow diagram of a two-chamber method 130. In the two-chamber method 130, the CLAAPP process is performed as a cyclical process carried out in two separate processing chambers. In the flow diagram of the two-chamber cyclical method 130, steps unique to the method are indicated by solid rectangles. As shown in box 121 of FIG. 1B, the cyclical CLAAPP process begins with a substrate being loaded into a gas-cluster processing chamber where a flux of gas clusters is formed. After the substrate is exposed to the gas-cluster flux (box 124), the substrate is transferred to the plasma processing chamber via a transfer chamber, as shown in box 131 of FIG. 1B. The transfer chamber may be designed to have a small volume to facilitate rapid transfer between the two processing chambers. In the plasma chamber, electrodes coupled to an RF power source sustain the plasma, and ions are extracted from the plasma (box 126). One cycle of the cyclical CLAAPP process is completed by exposing the substrate to the ion flux (box 128). After exposing the substrate to ions (box 128), the substrate may be returned to the gas-cluster processing chamber (box 132) for another cycle, and multiple cycles may be performed to complete the formation of high aspect ratio features.

[0020] In some embodiments, the CLAAPP process may be performed in a single chamber by simultaneously exposing the substrate to a flux of gas clusters and a flux of perpendicularly directed ions. The process parameter space (e.g., chamber pressure, substrate temperature, gas flow rates, RF power, etc.) for simultaneous processing is more limited compared to cyclic processing. Depending on the application, this may limit the ability of each CLAAPP process to form very high aspect ratio features. Using a cyclic CLAAPP process allows for greater process flexibility in a single chamber implementation.

[0021] FIG. 1C shows a flow diagram of a single-chamber method 140 in which exposing the substrate to a flux of gas clusters and exposing the substrate to ions are part of one cycle of a cyclical CLAAPP process. Steps unique to the single-chamber cyclical method 140 are indicated by solid rectangles. After exposing the substrate to a flux of gas clusters (box 124), the pressure in the process chamber and the RF power to the electrodes may be set to obtain a stable plasma above the substrate, as shown in box 141 of FIG. 1C. Exposing the substrate to an ion flux (box 128) completes one cycle of the cyclical CLAAPP process. The process chamber may then be prepared for the next cycle by resetting the chamber pressure and resetting the RF power to generate a stable flux of gas clusters, as shown in box 142.

[0022] The application of a cyclical CLAAPP process to form very high aspect ratio openings in a target layer 210 of a substrate will now be described with reference to the cross-sectional views shown in Figures 2A-2I.

[0023] 2A shows a mask layer 202 patterned over a target layer 210. In various embodiments, the target layer 210 may include silicon oxide, silicon oxynitride, alternating layers of silicon oxide and silicon nitride, silicon, germanium, a silicon-germanium alloy, or the like, and in one embodiment, may include silicon dioxide. In one embodiment, the mask layer 202 may be a stack of multiple layers, with a bottom layer of SOC, a middle layer of silicon nitride, and a top layer of metal oxide photoresist. In another embodiment, the mask layer 202 may include, for example, a stack of a top organic photoresist layer adjacent to an inorganic antireflective coating (ARC) and / or hard mask layer.

[0024] Photoresists can be photosensitive organic polymers, polymer precursors dissolved in organic solvents, or molecular systems based around small molecules, such as hafnium-core nanoparticles, metal oxides, and molecular glasses.

[0025] The hard mask may include materials such as silicon-containing antireflective coatings (SiARCs), silicon nitride, silicon carbide, titanium nitride, tantalum nitride, silicon boride, hafnium oxide, organic layers such as spin-on carbon (SOC), or combinations thereof.

[0026] In one exemplary embodiment shown in FIG. 2A, the target layer 210 may include silicon oxide, and the mask layer 202 may be a stack including a bottom layer of silicon oxide, a middle layer of silicon nitride, and a top layer of metal oxide photoresist. A narrow opening 230 (e.g., a via having a width of about 10 nm to about 30 nm) is shown in the mask layer 202 exposing a portion of the surface of the target layer 210. The opening 230 may be formed using suitable photolithography and etching techniques, such as EUV lithography and anisotropic plasma etching techniques. In various embodiments, the plasma etching chemistry may use, for example, methane, tetrafluoromethane, trifluoromethane, nitrogen trifluoride, oxygen, sulfur dioxide, or the like, or combinations thereof. The gas mixture may include an inert gas (e.g., argon and helium). In some embodiments, the plasma may be a capacitively coupled plasma (CCP) maintained using RF source power of about 300 W to about 1 kW, for example at a frequency of 40 MHz, coupled to the top disk-shaped electrode and low RF bias power not exceeding 100 W, for example at a standard frequency of 13.56 MHz, coupled to the substrate holder within the plasma processing chamber. In another embodiment, RF source power may be coupled to a helical resonator coil to maintain an inductively coupled plasma (ICP).

[0027] FIG. 2B shows an initial patterned layer 240 formed by etching the target layer 210 using an anisotropic plasma etch, such as RIE using fluorine chemistry. In various embodiments, the plasma may use a gas mixture including, for example, tetrafluoromethane, hexafluorocyclobutene, octafluorocyclobutane, or nitrogen trifluoride. Other gases may include oxygen and inert gases such as argon or helium. The plasma may be maintained using an RF bias power of about 10 kW to about 20 kW, for example, at a standard frequency of 13.56 MHz. The resulting RF source power may be about 1 kW to about 5 kW, for example, at a frequency of 40 MHz or 60 MHz. Additionally, a DC bias of about 500 V to about 1000 V may be present. In some embodiments, a pulsed DC bias having a duty cycle of about 10% to about 50% may be used at a low frequency in the range of 1 kHz to 10 kHz, and in one embodiment, 5 kHz. The chamber pressure may be between 10 mTorr and 100 mTorr in various embodiments, and 25 mTorr in one embodiment, and the chamber temperature may be controlled to a temperature in the range of 80°C to 100°C.

[0028] In FIG. 2B, a vertical flux of ions 220 is used to anisotropically remove silicon dioxide from the exposed surface of target layer 210, increasing the cavities of openings 230 to a depth d. In various exemplary embodiments, the aspect ratio of openings 230 in patterned layer 240 of FIG. 2B can be about 30 to about 60 for the smallest width features, and the smallest width can be about 10 nm to about 30 nm. Formation of the initial patterned layer 240 is complete upon completion of the etching step. The substrate having patterned layer 240 with a plurality of openings 230, each having a cavity of depth d etched into mask layer 202 and target layer 210, becomes the next substrate for the gas-cluster step of the cyclic CLAAPP process.

[0029] Figures 2C-2H show one cycle of an exemplary cyclic CLAAPP etching process: Figures 2C-2F show treating the surface with gas clusters, and Figures 2G-2H show using directed ions to increase the cavity depth. The cross-sectional view in Figure 2I shows the substrate at the start of the next cycle.

[0030] In FIG. 2C, the incoming substrate is exposed to a flux of gas clusters 222 generated by condensation of a radical precursor gas, as described above with reference to FIG. 1A. The radical precursor gas may be a fluorocarbon, e.g., tetrafluoromethane, and the gas clusters 222 may include clusters of various sizes. In various embodiments, the average cluster size is about 1,000 to about 10,000 molecules. As shown in FIG. 2C, gas clusters entering the cavity of an opening 230 (e.g., a hole or trench) are likely to collide with the cavity walls and break down into smaller particles, similar to the dirt that splatters on a car windshield. Radicals (e.g., fluorine radicals) thus released from the gas clusters are delivered into the cavity of the hole.

[0031] As shown schematically in FIG. 2D , the decomposed clusters can release thousands of radicals, greatly increasing the number of radicals and, therefore, the local molar density of the gas deep within the cavity of the opening 230. As indicated by the ideal gas equation, an increase in molar density is accompanied by a proportional increase in the ratio (P / T), where P represents pressure and T represents absolute temperature. The process of gas cluster decomposition by collision with the side or bottom walls of the opening 230 is largely isothermal because the relatively large heat capacity makes the substrate equivalent to a heat sink. Thus, the local pressure within the cavity can increase by several orders of magnitude.

[0032] 2E shows how many of the released radicals are adsorbed onto the walls of the opening 230, either by physisorption or by chemisorption facilitated by the increased pressure within the cavity. During exposure to a flux of gas clusters, the cluster decomposition and adsorption process continues to coat the surface of the wall of the opening 230, which may comprise, for example, silicon dioxide, with a layer of radicals (e.g., fluorine radicals).

[0033] As shown in Figure 2F, by the time the gas cluster exposure step is complete, the walls of the opening 230 may be saturated with radicals.

[0034] As shown in FIG. 2G, after the opening 230 is coated with radicals, the substrate may be exposed to a vertical flux 233 of ions extracted from a straight plasma maintained above the substrate using a gas mixture, such as, for example, a mixture of approximately equal parts inert gas (e.g., argon) and fluorocarbon (e.g., tetrafluoromethane (CF4)) with a small amount of oxygen. In an exemplary embodiment, the plasma may be maintained by an RF source power of about 100 W coupled to a coiled electrode, with 50 W to 200 W in various embodiments. The RF bias power coupled to the substrate holder may be about 5 kW in an exemplary embodiment, with 1 kW to 10 kW in various other embodiments. The RF source power and RF bias power may have, for example, a nominal frequency of 13.56 MHz. The chamber pressure may be in the range of 0.1 mTorr to about 10 mTorr.

[0035] In the exemplary embodiment shown in FIG. 2G, the ions 233 are argon (Ar + ) and trifluoromethyl cation (CF3 +) The vertically accelerated ions 233 interact with the material (e.g., silicon dioxide) of the target layer 210, imparting sufficient energy to, for example, break silicon-oxygen bonds when they strike the bottom wall of the opening 230. During this process, material near the surface may be removed. Silicon atoms removed from the silicon dioxide react with fluorine radicals to form SiF4 gas, and oxygen atoms released from the broken Si-O bonds react with fluorine radicals to form CF3 + The ions react with carbon present in the etched silicon dioxide to form CO and CO gases. These volatile gases may be evacuated by a vacuum system. The ion exposure completes one cycle of a cyclical CLAAPP etch process flow, such as the two-chamber CLAAPP method 130 shown in FIG. 1B or the single-chamber CLAAPP method 140 shown in FIG. 1C.

[0036] At the end of the cycle, as shown in Figure 2H, exposure of the substrate to vertically directed ions 233 anisotropically removes material (e.g., silicon dioxide) from the bottom wall of opening 230, expanding the initial depth d by an amount Δd, and the chemical reactions associated with this removal leave opening 230 largely depleted of radicals. The substrate is then re-exposed to gas clusters, thereby initiating a second cycle, as shown in Figure 2I. This process alternates between gas cluster and plasma steps, expanding the depth of the cavity over a predetermined number of cycles until the very high target aspect ratio of opening 230 is achieved.

[0037] 3A and 3B show cross-sectional views of two subsystems of a CLAAPP system in which the chamber described with reference to FIG. 1B can be used to perform the two CLAAPP methods 130. FIG. 3A shows a gas-cluster subsystem 300, and FIG. 3B shows a plasma subsystem 370.

[0038] 3A includes a first processing chamber 303 and a gas flow system 330. The first processing chamber 303 includes a plenum 310, a nozzle assembly 308, and a gas-cluster processing chamber 320, and is capable of processing a substrate 301. The gas flow system 330, connected to gas inlets and outlets of the CLAAPP system, controls the flow of various gases through the plenum 310 and the gas-cluster processing chamber 320. The first processing chamber 303 may also include an optional cooling system 340 coupled to the plenum 310.

[0039] During gas-cluster processing, the radical precursor gas may be introduced into the plenum 310 through the gas inlet 302 in a gas flow at a relatively high pressure, between about 100 Torr and about 760 Torr. At other times, a minimum plenum pressure is applied to prevent backflow, which may be as low as 0.1 Torr, depending on the pressure in the gas-cluster processing chamber 320. The various gas pressures in the first processing chamber 303 are controlled by a gas flow system 330. As known to those skilled in the art, the gas flow system may include various components, such as high-pressure gas canisters, valves (e.g., throttle valves), pressure sensors, gas flow sensors, vacuum pumps, piping, and an electronically programmable controller. In the exemplary embodiment shown in FIG. 3A, the gas inlet 302 is coupled to the top cover 305 of the plenum 310. In another embodiment, the radical precursor gas may be introduced through a gas inlet coupled to the sidewall 304 of the plenum 310.

[0040] The relatively high pressure within the plenum 310 causes radical precursor gases to flow into the inlet apertures of the array of nozzles 306 of the nozzle assembly 308 and out through the exhaust apertures of the nozzles 306. As shown in FIG. 3A , the inlet apertures of the nozzle assembly 308 are coupled to a cavity within the plenum 310, while the exhaust apertures of the nozzle assembly 308 are coupled to a lower-pressure gas-cluster processing chamber 320 located on the opposite side. In various embodiments, the nozzles 306 can be of various shapes, such as a tube, a truncated cone, a funnel with a stem coupled to the plenum, or a convergent-divergent de Laval nozzle. Nozzle geometric parameters are discussed in more detail below with reference to FIGS. 5A-5D .

[0041] As shown in FIG. 3A , the gas-cluster processing chamber 320 adjacent to the nozzle assembly 308 includes a substrate holder 312 and a gas outlet 318. The substrate 301 is shown mounted on the substrate holder 312. The gas-cluster processing chamber 320 may be maintained at a low pressure by a gas flow system 330 using a vacuum pump. As explained above, the pressure differential across the nozzle assembly is designed to rapidly cool the radical precursor gas by adiabatic expansion, condensing the gas and forming nanometer-scale clusters of gas molecules weakly bound by van der Waals forces. In various embodiments, the target pressure in the gas-cluster processing chamber 320 may be selected to be between about 0.1 mTorr and about 10 mTorr, depending on the target gas flow rate for the CLAAPP process. During gas-cluster formation, the ratio of the pressure at the inlet to the pressure at the outlet of each nozzle 306 of the nozzle assembly 308 must be high, e.g., greater than 10, with this ratio typically exceeding 1000.

[0042] The plasma subsystem 370 of FIG. 3B includes a second processing chamber 371 and a gas flow system 330. The second processing chamber 371 includes a plasma processing chamber 350 and an electrical system 372 including power sources, such as a source RF power supply 358 and an RF bias power supply 364, for powering a plasma in the plasma processing chamber 350. The electrical system 372 may also include an optional DC bias source 368. As described above with reference to FIGS. 2G and 2H, the plasma subsystem 370 may be configured to perform anisotropic etching using a directed ion flux. The plasma processing chamber 350 may maintain a plasma directly above the substrate 301 disposed on a substrate holder 362. A gas mixture used to generate ions for plasma etching may be introduced into the plasma processing chamber 350 through a gas inlet 352, and gaseous byproducts may be exhausted through a gas outlet 359. Gas flow rates and chamber pressure are controlled by a gas flow system 330 coupled to the gas inlet 352 and the gas outlet 359. Bias power from an RF bias power supply 364 and RF source power from an RF power supply 358 may be supplied to the respective electrodes of the plasma processing chamber 350. In the exemplary embodiment shown in FIG. 3B, the RF bias electrode is also the substrate holder 362, and RF source power is supplied to a helical resonator 356 that is spirally wound around the dielectric sidewall 354. A pulsed DC bias may also be used instead of the RF bias power supply 364. An optional DC bias source 368 is also shown coupled to the substrate holder 362. In FIG. 3B, the gas inlet 352 is coupled to a conductive top plate 355, and the gas outlet is coupled to a conductive bottom plate 366. The conductive top plate 355 and bottom plate 366 may be electrically connected to a system ground (reference potential).

[0043] The configuration of the plasma subsystem 370 described above with reference to FIG. 3B is merely exemplary. In alternative embodiments, various alternative configurations of the plasma subsystem 370 may be used. For example, an inductively coupled plasma (ICP) may be used with RF source power coupled to a planar coil on the top dielectric cover, or a capacitively coupled plasma (CCP) generated using a disk-shaped upper electrode within the plasma processing chamber 350, gas inlets and / or gas outlets may be coupled to the sidewalls, etc. In some embodiments, pulsed RF power and pulsed DC power (as opposed to continuous wave RF power) may also be used. In various embodiments, the RF power, chamber pressure, substrate temperature, gas flow rates, and other plasma processing parameters may be selected according to a respective process recipe.

[0044] FIG. 4 illustrates a single-chamber CLAAPP system 400 for implementing a gas-cluster assisted anisotropic plasma processing system. The single-chamber CLAAPP system 400 may be used to perform the single-chamber cyclic CLAAPP method 140 described with reference to the flow diagram of FIG. 1C. In the single-chamber cyclic CLAAPP method 140, a substrate (e.g., semiconductor substrate 301) is alternately exposed to a flux of gas clusters and a flux of directed ions. Furthermore, the single-chamber CLAAPP system 400 may enable a simultaneous CLAAPP method, eliminating time-consuming chamber resets between gas-cluster processing steps and plasma processing steps. In the simultaneous CLAAPP method, exposing the substrate to a flux of gas clusters and exposing the substrate to ions may be performed simultaneously using the single-chamber CLAAPP system 400.

[0045] 4, a single-chamber CLAAPP system 400 integrates, with minor adjustments, two subsystems 300 and 370 (described above with reference to FIGS. 3A and 3B). The single-chamber CLAAPP system 400 includes a plenum 310 and a substrate processing chamber 450, in which a substrate 301 may be subjected to gas cluster processing and plasma processing. Additionally, the single-chamber CLAAPP system 400 includes a gas flow system 330, an optional cooling system 340, and an electrical system 372 that includes one or more power sources, such as an RF bias power supply 364, a source RF power supply 358, and an optional DC bias source 368.

[0046] The substrate processing chamber 450 may be described as a combination of the gas-cluster processing chamber 320 (shown in FIG. 3A ) and the plasma processing chamber 350 (shown in FIG. 3B ), where the substrate processing chamber 450 has been modified from the plasma processing chamber 350. The modifications include coupling the plenum 310 to the substrate processing chamber 450 via the nozzle assembly 308 and including an additional gas inlet 452 for introducing a gas mixture that can be used to generate a plasma. These modifications enable the single-chamber CLAAPP system 400 to perform the single-chamber cyclic CLAAPP method 140 (described above with reference to FIG. 1C ) and the simultaneous CLAAPP method.

[0047] During a single-chamber cyclical implementation of the CLAAPP method 140, the process parameters selected for the plenum 310 and the substrate processing chamber 450 alternate between two sets of values. During exposure of the substrate 301 to a flux of gas clusters, in various embodiments, the gas pressure in the plenum 310 is selected to be between 100 Torr and 760 Torr, and in the substrate processing chamber 450 is selected to be between 0.1 mTorr and 10 mTorr. However, during exposure of the substrate 301 to a flux of ions, the gas pressure in the plenum 310 may decrease but remain high enough to prevent backflow. For example, the plenum pressure may be between about 0.1 Torr and about 10 Torr in various embodiments, and about 1 Torr in one embodiment. In various embodiments, the pressure in the substrate processing chamber 450 may be between 0.1 mTorr and 10 mTorr, depending on the requirements of the plasma etch process.

[0048] The process conditions for simultaneous processing may be more constrained than those for cyclic processing. For example, the pressure in the combined gas-cluster and plasma processing chamber, referred to herein as the substrate processing chamber 450, may need to accommodate a low-pressure constraint for generating gas-clusters of a reasonable average cluster size and maintain a reasonable flux of gas-clusters passing through the plasma discharge and reaching the substrate 301. At the same time, this pressure must be controlled within the window required to perform each plasma etch process. In various embodiments, when performing the simultaneous CLAAPP method, the pressure in the substrate processing chamber 450 may be maintained at approximately 10 mTorr or less and 0.1 mTorr or more. The pressure in the plenum 310 may be maintained in the range of 100 Torr to 760 Torr in various embodiments, and in one embodiment, at approximately 380 Torr. The gas-cluster formation process may be facilitated by pre-cooling the plenum 310 to a temperature in the range of 100 K to 310 K using the cooling system 340. If it is desirable to select a relatively low plenum pressure, for example, a pressure of 380 Torr or less, it may be advantageous to have a lower temperature within the plenum 310 .

[0049] The process of forming van der Waals-bonded molecular gas clusters is known to be very sensitive to the absolute temperature T0 of the gas at the nozzle inlet. The average number of molecules in a cluster (N c ) can be estimated from a semi-empirical scaling law called Hagena's formula. Within the pressure range of interest, Hagena's formula states that N c ∝(Γ * ) 2.35 where the Hagener parameter Γ * ∝T0 -2.29 and therefore N c ∝T0 -5.38 According to the Hagena equation, if the gas is pre-cooled from room temperature by 100°C (from T0=300K to T0=200K), the cluster size (N c ) increases by almost an order of magnitude, or half the plenum pressure results in the same average cluster size. These estimates are approximate, but demonstrate that in some embodiments, it may be advantageous to include a cooling system 340, despite the added cost and complexity. In various embodiments, the temperature of the gas in the plenum may be selected to be controlled to a target value above 100 K and below 310 K.

[0050] 5A-5D show cross-sectional views of various nozzle designs that may be used to generate gas-clusters in various embodiments of the gas-cluster-assisted plasma processing system described above, such as the nozzle 306 in the nozzle assembly 308 of the system shown in FIGS. 3A and 4. Nozzles shaped like a tube 500, a truncated cone 530, a funnel with a stem 560, and a converging-diverging Laval nozzle 590 are shown in the cross-sectional views of FIGS. 5A, 5B, 5C, and 5D, respectively. The nozzle structure is a hole formed in a substrate 540, with an inlet aperture 510 and an exhaust aperture 520. In some embodiments, the substrate 540 may comprise a dielectric (e.g., ceramic), while in other embodiments, the substrate 540 may comprise a metal (e.g., aluminum or copper). The narrowest region of the nozzle is called the throat and is indicated by the double-headed arrow in FIGS. 5A-5D. The tube 500 has a uniform width, as indicated by the multiple double-headed arrows. Geometric parameters describing the nozzles shown in Figures 5A-5D include height h, throat width d, divergence ratio ε, and cone half angle α (or two cone half angles in the case of the Laval nozzle 590). The divergence ratio ε, defined as the ratio of the area of ​​the exhaust aperture to the area of ​​the throat, is an important design parameter for nozzle design because it is advantageous for the gas to adiabatically expand and cool before exiting the nozzle through the exhaust aperture. Typically, ε ≥ 1 is used, including for the nozzle designs shown in Figures 5A-5D. However, nozzles with large α (very wide exhaust apertures) may be undesirable because, according to Hagena's equation for a conical nozzle, Γ * ∝(0.74d / tan α) 0.85 Therefore, the cluster size N c may become too small for a given throat width d. In various embodiments, the cone half angle is about 30° or less, and in one embodiment may be between 5° and 30°.

[0051] The nozzle height h and throat width d may be adjusted in the nozzle design to position the design flow rate and plenum pressure within a desired range. As expected, reducing d or increasing h reduces the flow rate for a given back pressure P in the plenum. The average cluster size N c It is advantageous for a system configuration if the plenum pressure does not need to exceed 1 standard atmosphere without reducing Nc ∝ P0 below 1,000. 2.35 It is estimated from the Hagena equation that: In various embodiments, gas flow rates of about 50 sccm to about 1000 sccm may be achieved using an array of about 200 to about 1000 nozzles with throat widths d of about 0.5 mm to about 1 mm and nozzle heights h of about 1 cm to about 5 cm.

[0052] Gas clusters of various sizes are propelled from the exhaust aperture at exit velocities several times the speed of sound in a spray that spreads over a solid angle relatively large for a parallel beam. In the gas-cluster assisted plasma processing system and method embodiments described above, the clusters are not ionized and accelerated by an electromagnetic field, as is typically done in gas-cluster ion beam (GCIB) systems. However, because in simultaneous processing methods some of the clusters may be scattered and broken down as they pass through the combined gas-cluster and plasma maintained in the plasma processing chamber 450 during processing, the single-chamber CLAAPP system 400 may be modified to accelerate the clusters toward the substrate. This modification is described with reference to FIGS. 6, 7A-7E, and 8.

[0053] 6 illustrates an embodiment of a single-chamber CLAAPP system 600 with an electron beam ionizer 601 coupled to the processing chamber, configured to direct a beam of energetic electrons to intercept a flux of gas clusters within a combined gas-cluster and plasma processing chamber 650. Features of the single-chamber CLAAPP system 600 are similar to those of the single-chamber CLAAPP system 400 (described above with reference to FIG. 4), except for the addition of the electron beam ionizer 601. The energetic electrons from the electron beam ionizer 601 can ionize a portion of the gas clusters. The ionized gas clusters may then be accelerated by a bias electric field generated using an RF bias power supply 364 (or a pulsed DC bias source) or an optional DC bias source 368 coupled to the substrate holder 362.

[0054] 7A-7E show a polarization nozzle 700 in which conductive films 710 and 720 are embedded in a substrate 540. The substrate 540 of the polarization nozzle 700 is a dielectric material (e.g., ceramic) with sufficient dielectric strength to insulate the conductive film 710 from the conductive film 720. Contacts may be provided to connect the embedded conductive films 710 and 720 to electrodes, electrically coupling the conductive films 710 and 720 to a pulsed DC bias source. In the embodiment shown in FIGS. 7A-7E, the polarization nozzle 700 has a shape similar to the stem-shaped funnel 560 shown in FIG. 5C. Other shapes may be used in other embodiments. The top plan view in FIG. 7A shows the inlet aperture 510, which has a width equal to the throat width d, and the bottom plan view in FIG. 7B shows the exhaust aperture 520 of the polarization nozzle 700. It can be seen that these apertures are surrounded by the substrate 540, which comprises a dielectric material, such as a ceramic. Dashed lines 7C and 7D indicate the cutting planes used to obtain the cross-sectional views shown in Figures 7C and 7D, respectively.

[0055] The cross-sectional view of FIG. 7C shows that the conductive films 710 and 720 contain gaps. The nozzle holes, which are laterally surrounded by the dielectric substrate 540, pass through these gaps in the conductive films 710 and 720. The cross-sectional view of FIG. 7D shows that the conductive films 710 and 720 maintain electrical continuity through the continuous conductive regions between adjacent nozzle holes. The structure of the polarized nozzle 700 described with reference to the plan views of FIGS. 7A-7B in conjunction with the cross-sectional views of FIGS. 7C-7D is further illustrated by the exploded view shown in FIG. 7E. In FIG. 7E, four plan views are shown aligned perpendicular to one another. Two vertical double-headed arrows are shown passing through the centers of the nozzle holes of two adjacent nozzles 700. Material between the four plan views showing the exploded view of FIG. 7E has been removed for clarity. Note that the conductive films 710 and 720 are electrically insulated from one another by the dielectric substrate 540.

[0056] 8 shows an embodiment of a single-chamber CLAAPP system 800 in which a polarized nozzle 700 is used in a nozzle assembly 808. Embedded conductive films 710 and 720 are shown schematically by two solid lines. Electrical contacts may be made to the conductive films 710 and 720 to use them as electrodes. In FIG. 8, the conductive films 710 and 720 are shown schematically as being used as electrodes connected to a pulsed DC bias source 801.

[0057] Neutral gas clusters, including polarizable atoms or molecules, may be accelerated by an electric field gradient according to the laws of electromagnetic theory. It should be appreciated that due to the conical geometry of the nozzle hole, a vertical electric field gradient may be generated by biasing the embedded conductive films 710 and 720 with a potential difference. Therefore, a pulsed DC source may be electrically coupled to the two embedded conductive films 710 and 720, thereby accelerating the polarized clusters vertically downward.

[0058] This disclosure has described a method for using gas clusters to deliver radicals deep into high aspect ratio holes or trenches. The embodiments described herein are applicable to contact / via holes with maximum aspect ratio (AR) that are etched using a single photolithographic patterning step followed by one or more pattern transfer etch steps. max The performance of 100<(AR) max <150. Without the aid of gas cluster treatment, it can be difficult to obtain reasonable etching efficiencies (e.g., >100 nm / min) on the bottom walls of cavities with high aspect ratios (e.g., aspect ratios >100). Similarly, the rapid decrease in radical flux with depth (compared to vertically directed ion flux) can lead to high ion flux-to-radical ratios, e.g., Γ r / Γ i This severely limits the ability to maintain the desired ratio of >10. Despite the complex processing configuration, r / Γ i It can be very difficult to achieve this and provide enough ions with sufficient kinetic energy (e.g., >10 keV) to etch the bottom of narrow features with high aspect ratios (e.g., holes or trenches about 20 nm wide and a few microns deep).

[0059] In contrast, by using embodiments of the gas-cluster assisted plasma process described in this disclosure, the capabilities of the etch process can be extended to form openings having widths of about 10 nm to about 30 nm and aspect ratios of about 100 to about 150 using a single photolithographic patterning step (e.g., EUV photolithography) followed by an anisotropic pattern transfer etch process using relatively simple plasma processing conditions, thereby reducing process costs and improving process yields.

[0060] Various implementations of embodiments of the present application are discussed below.

[0061] Example 1. A method for processing a substrate includes forming a patterned layer on the substrate, the layer including an opening, the surface of the opening including a sidewall and a bottom wall. The method includes treating the patterned layer using an anisotropic process by generating a flux of gas clusters above the substrate in a first processing chamber, the gas clusters including radical precursors, and exposing the substrate to the flux of gas clusters. The method includes maintaining a plasma including ions in a second processing chamber and exposing the substrate to the ions by directing the ions toward the bottom wall of the opening.

[0062] Example 2. The method of Example 1, wherein the first processing chamber further includes a plenum, a nozzle assembly, and a gas-cluster processing chamber, and the second processing chamber includes a plasma processing chamber and a power supply for powering a plasma in the plasma processing chamber.

[0063] Example 3. The method of any one of Examples 1 or 2, wherein generating a flux of gas clusters and exposing a substrate to the flux of gas clusters includes loading the substrate into a gas cluster processing chamber, introducing a gas under pressure into the plenum through a gas inlet in the plenum, and flowing the gas from the plenum to the gas cluster processing chamber through a nozzle having an intake aperture coupled to the plenum and an exhaust aperture coupled to the gas cluster processing chamber, the nozzle having a divergence ratio of 1 or more, and flowing the gas includes applying a gas pressure of 760 Torr or less in the plenum, and flowing the gas causes the gas to cool and form gas cluster condensate in the gas cluster processing chamber.

[0064] Example 4. The method of any one of Examples 1-3, wherein the first processing chamber and the second processing chamber are integrated as part of a single processing chamber.

[0065] Example 5. The method of any one of Examples 1-4, wherein exposing the substrate to a flux of gas clusters and exposing the substrate to ions is part of a cycle of a cyclical etching process including a plurality of cycles, each cycle of the plurality of cycles further comprising: stabilizing a plasma after exposing the substrate to the flux of gas clusters, wherein stabilizing the plasma includes introducing a gas under pressure into the plenum through a gas inlet of the plenum, setting a pressure in the single processing chamber, setting a pressure in the plenum, and coupling an electrode of the processing chamber to a radio frequency (RF) power source; and stabilizing the flux of gas clusters after exposing the substrate to the ions, wherein stabilizing the flux of gas clusters includes resetting the pressure in the single processing chamber, resetting the pressure in the plenum, and resetting the RF power coupled to the electrode of the processing chamber.

[0066] Example 6. The method of any one of Examples 1-5, further comprising simultaneously exposing the substrate to a flux of gas clusters and exposing the substrate to ions, and maintaining a pressure in the single processing chamber at or below 10 mTorr and above 0.1 mTorr.

[0067] Example 7. The method of any one of Examples 1-6, wherein exposing the substrate to a flux of gas clusters and exposing the substrate to ions is part of a cycle of a cyclical etching process including a plurality of cycles, each cycle of the plurality of cycles further comprising: transferring the substrate from a first processing chamber to a second processing chamber after exposing the substrate to a flux of gas clusters; and transferring the substrate from the second processing chamber to the first processing chamber after exposing the substrate to the ions.

[0068] Example 8. The method of any one of Examples 1-7, wherein the gas clusters comprise oxygen, carbon monoxide, hydrogen, chlorine, carbon tetrachloride, silicon tetrachloride, boron trichloride, fluorine, carbon tetrafluoride, nitrogen trifluoride, sulfur hexafluoride, trifluoromethane, perfluorocarbons, hydrofluorocarbons, or any combination thereof, or in combination with an inert gas.

[0069] Example 9. A system for processing a substrate includes a first subsystem including a plenum including a gas inlet, a nozzle assembly including a plurality of nozzles, wherein an intake aperture of each nozzle of the plurality of nozzles is disposed within the plenum, a gas-cluster processing chamber connected to the plenum via the plurality of nozzles of the nozzle assembly, and a gas flow system connected to the gas inlet and a gas outlet of the gas-cluster processing chamber, the gas flow system configured to generate a flux of gas-clusters in the gas-cluster processing chamber. The system includes a second subsystem including a plasma processing chamber and a power supply for powering a plasma in the plasma processing chamber.

[0070] Example 10. The system of Example 9, wherein the exhaust aperture of each nozzle of the plurality of nozzles is located outside the plenum, and each nozzle of the plurality of nozzles is shaped like a tube, a truncated cone, a funnel with a stem coupled to the plenum, or an hourglass-shaped Laval nozzle.

[0071] Example 11. The system of any one of Examples 9 or 10, wherein each nozzle of the nozzle assembly has a length of 1 cm or more and 10 cm or less, a throat width of 0.5 mm or more and 1 mm or less, and a divergence ratio of 1 or more and 10 or less.

[0072] Example 12. The system of any one of Examples 9-11, wherein the first subsystem further includes a cooling system coupled to the plenum, the cooling system configured to control the temperature of the gas in the plenum to a target value of 100K or greater and 310K or less.

[0073] Example 13. A system for processing a substrate includes a plenum, a substrate processing chamber disposed outside the plenum and configured to sustain a plasma, and a nozzle having an intake aperture coupled to the plenum and an exhaust aperture coupled to the substrate processing chamber.

[0074] Example 14. The system of example 13, wherein the nozzle has a divergence ratio of 1 or greater, and the nozzle is shaped like a tube, a truncated cone, a funnel with a stem connected to a plenum, or a converging-diverging Laval nozzle.

[0075] Example 15. The system of any one of Examples 13 or 14, wherein the nozzle is a polarized nozzle, the polarized nozzle further comprising a dielectric substrate having embedded therein two conductive layers electrically insulated by the dielectric substrate, the two conductive layers configured to be electrically coupled to a pulsed DC bias source.

[0076] Example 16. The system of any one of Examples 13-15, further comprising a cooling system coupled to the plenum, the cooling system configured to control the temperature of the gas in the plenum to a target value of 100K or greater and 310K or less.

[0077] Example 17. The system of any one of Examples 13-16, further comprising a plurality of nozzles disposed adjacent to the nozzle, the nozzle and the plurality of nozzles forming a nozzle assembly connecting the plenum to the substrate processing chamber.

[0078] Example 18. The system of any one of Examples 13-17, wherein the plenum includes a first gas inlet, the substrate processing chamber includes a second gas inlet, a substrate holder, and a gas outlet, the system further including a gas flow system connected to the first gas inlet, the second gas inlet, and the gas outlet, the gas flow generating a flux of gas clusters within the substrate processing chamber.

[0079] Example 19. The system of any one of Examples 13-18, wherein the substrate holder is coupled to a pulsed DC bias source or a radio frequency (RF) bias source.

[0080] Example 20. The system of any one of Examples 13-19, further comprising an electrode coupled to a radio frequency (RF) power source, the electrode shaped like a coil positioned outside the substrate processing chamber, the electrode configured to maintain an inductively coupled plasma (ICP) inside the substrate processing chamber.

[0081] Example 21. The system of any one of Examples 13-20, further comprising an electron beam ionizer coupled to the processing chamber, the electron beam ionizer configured to direct a beam of energetic electrons to intercept a flux of gas clusters within the processing chamber.

[0082] While the present invention has been described with reference to exemplary embodiments, this specification is not intended to be construed in a limiting sense. Various modifications and combinations of those exemplary embodiments, as well as other embodiments of the present invention, will become apparent to those skilled in the art upon reference to this specification. It is therefore intended that the appended claims cover any and all such modifications or embodiments.

Claims

1. 1. A system for processing a substrate, comprising: a first subsystem, a plenum including a first gas inlet; a nozzle assembly including a plurality of nozzles, an intake aperture of each nozzle of the plurality of nozzles disposed within the plenum, a first nozzle of the plurality of nozzles being a polarized nozzle, the polarized nozzle further including a dielectric substrate having embedded therein two conductive layers electrically isolated by the dielectric substrate, the two conductive layers being configured to be electrically coupled to a pulsed DC bias source; a gas-cluster processing chamber connected to the plenum via the plurality of nozzles of the nozzle assembly, the gas-cluster processing chamber coupled with a second gas inlet, the second gas inlet being located below the nozzle assembly; and a first subsystem including a gas flow system connected to the first gas inlet, the second gas inlet, and a gas outlet of the gas-cluster processing chamber, the gas flow system configured to generate a flow of gas clusters within the gas-cluster processing chamber and to introduce a gas mixture via the second gas inlet; a second subsystem, a second subsystem including a power supply for powering a plasma from the gas mixture in the gas-cluster processing chamber.

2. 2. The system of claim 1, wherein an exhaust aperture of each nozzle of the plurality of nozzles is located outside the plenum, and each nozzle of the plurality of nozzles has the shape of a tube, a truncated cone, a funnel having a stem coupled to the plenum, or a convergent-divergent de Laval nozzle.

3. Each nozzle of the nozzle assembly is Length of 1 cm or more and 10 cm or less, a throat width of 0.5 mm or more and 1 mm or less, and Spread ratios of 1 or more and 10 or less The system of claim 1 , comprising:

4. 10. The system of claim 1, wherein the first subsystem further comprises a cooling system coupled to the plenum, the cooling system configured to control a temperature of the gas in the plenum to a target value greater than or equal to 100 K and less than or equal to 310 K.

5. 10. The system of claim 1, wherein the gas mixture comprises tetrafluoromethane, hexafluorocyclobutene, octafluorocyclobutane, nitrogen trifluoride, oxygen, argon, or helium.

6. 1. A system for processing a substrate, comprising: a first subsystem, a plenum containing a gas inlet; a nozzle assembly including a plurality of nozzles and a first nozzle disposed adjacent to the plurality of nozzles, the first nozzle being a polarized nozzle, the polarized nozzle further including a dielectric substrate having embedded therein two conductive layers electrically insulated by the dielectric substrate, the two conductive layers being configured to be electrically coupled to a pulsed DC bias source, and wherein a respective intake aperture of the first nozzle and a respective intake aperture of each nozzle of the plurality of nozzles are disposed within the plenum; and a first subsystem including a gas-cluster processing chamber connected to the plenum via the plurality of nozzles of the nozzle assembly; a gas flow system connected to the gas inlet and to a gas outlet of the gas-cluster processing chamber, the gas flow system configured to generate a flow of gas-clusters within the gas-cluster processing chamber; a second subsystem, a substrate processing chamber disposed outside the plenum and configured to sustain a plasma, the first nozzle having an exhaust aperture coupled to the substrate processing chamber; and a second subsystem including a power supply for powering a plasma in the substrate processing chamber.

7. 7. The system of claim 6, wherein the first nozzle has one or more divergence ratios, and the first nozzle has the shape of a tube, a truncated cone, a funnel with a stem connected to the plenum, or a convergent-divergent de Laval nozzle.

8. 7. The system of claim 6, further comprising a cooling system coupled to the plenum, the cooling system configured to control the temperature of the gas in the plenum to a target value of 100 K or greater and 310 K or less.

9. 7. The system of claim 6, wherein the substrate processing chamber includes a second gas inlet and a substrate holder, and the gas flow system is further connected to the second gas inlet and the gas outlet.

10. The system of claim 9 , wherein the substrate holder is coupled to a pulsed DC bias source or a radio frequency (RF) bias source.

11. 10. The system of claim 9, further comprising an electrode coupled to a radio frequency (RF) power source, the electrode having a shape of a coil disposed outside the substrate processing chamber, the electrode configured to maintain an inductively coupled plasma (ICP) inside the substrate processing chamber.

12. 10. The system of claim 9, further comprising an electron beam ionizer coupled to the substrate processing chamber, the electron beam ionizer configured to direct a beam of energetic electrons to intercept the flow of gas clusters within the substrate processing chamber.

13. 1. A system for processing a substrate, comprising: a first subsystem, a plenum containing a gas inlet; a nozzle assembly including a plurality of nozzles, a first nozzle of the plurality of nozzles being a polarized nozzle, the polarized nozzle further including a dielectric substrate having embedded therein two conductive layers electrically insulated by the dielectric substrate, the two conductive layers being configured to be electrically coupled to a pulsed DC bias source, and an intake aperture of each nozzle of the plurality of nozzles being disposed within the plenum; and a first subsystem including a gas-cluster processing chamber connected to the plenum via the plurality of nozzles of the nozzle assembly; a gas flow system connected to the gas inlet and to a gas outlet of the gas-cluster processing chamber, the gas flow system comprising: generating a flow of gas clusters in the gas-cluster processing chamber, the gas clusters comprising radical precursors; and a gas flow system configured to effectuate exposing a substrate disposed within the gas-cluster processing chamber to the flow of gas-clusters; a second subsystem, a plasma processing chamber; and a second subsystem including a power supply for powering a plasma in the plasma processing chamber, the plasma including ions, and the plasma processing chamber configured to expose the substrate to the ions.

14. generating a flow of gas clusters and exposing the substrate to the flow of gas clusters; loading the substrate into the gas-cluster processing chamber; introducing a gas under pressure into the plenum through the gas inlet of the plenum; 14. The system of claim 13, further comprising: flowing the gas from the plenum to the gas-cluster processing chamber through nozzles of the plurality of nozzles, the nozzles having a divergence ratio of one or more.

15. 15. The system of claim 14, wherein the flowing of the gas comprises applying a gas pressure of 760 Torr or less in the plenum.

16. 15. The system of claim 14, wherein said flowing said gas cools said gas and forms gas-cluster condensate within said gas-cluster processing chamber.

17. 14. The system of claim 13, wherein the gas-cluster processing chamber and the plasma processing chamber are integrated as part of a combined gas-cluster and plasma processing chamber.

18. The system of claim 13 , wherein the first nozzle of the plurality of nozzles has a tubular shape.

19. The system of claim 13 , wherein the first nozzle of the plurality of nozzles has a frusto-conical shape.

20. The system of claim 13 , wherein the first nozzle of the plurality of nozzles has a funnel shape with a stem coupled to the plenum.

21. The system of claim 13 , wherein the first nozzle of the plurality of nozzles has a convergent-divergent de Laval nozzle shape.

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