Method and apparatus for processing a substrate

Abstract

Methods and apparatuses for processing a substrate are provided herein. For example, a method of processing a substrate includes: applying at least one of low frequency RF power or DC power to an upper electrode disposed adjacent to a processing volume, the upper electrode formed of a high secondary electron emission coefficient material; generating a plasma in the processing volume, the plasma including ions; bombarding the upper electrode with the ions to cause the upper electrode to emit electrons and form an electron beam; and applying a bias power to a lower electrode disposed in the processing volume to accelerate the electrons in the electron beam toward the lower electrode, the bias power including at least one of low frequency RF power or high frequency RF power.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to methods and apparatus for processing substrates, and more specifically, to methods and apparatus for configuring electron beam reactive plasma etching for substrates. Background Technology

[0002] Based on current substrate (e.g., wafer) manufacturing processes, etching rates, etching profiles, and etching selectivity can be controlled to reduce manufacturing costs and increase the density of circuit elements on the substrate. However, etched features on the substrate (e.g., memory vias, slits, etc.) continue to shrink in size or increase in aspect ratio (e.g., the ratio of feature depth to width). For example, in the manufacture of three-dimensional (3D) NAND devices, the substrate (wafer) can include up to 96 layers and can be expanded to up to 128 layers. Furthermore, for example, the aspect ratio of memory vias and / or slits can be between 100 and 200, with memory via depths ranging from approximately 6 μm to 8 μm, thus making memory via etching one of the most critical and challenging steps in the manufacture of 3D NAND devices. For example, such high aspect ratio (HAR) etching not only requires high etching speed and high etching selectivity (e.g., to mask material on the substrate), but HAR etching also requires straight profiles without bending and twisting, no under-etching and minimal micro-load, minimal aspect ratio-dependent etching (ARDE), and uniformity across the entire substrate (e.g., critical dimension (CD) variation 3σ < 1%).

[0003] Similarly, for FinFET manufacturing targeting logic applications, it is often necessary to perform chemical etching on similar materials with a selectivity ratio greater than 20 (e.g., etching between silicon oxide and silicon nitride).

[0004] Therefore, the inventors provide an improved method and apparatus for electron beam reactive plasma etching configured for a substrate. Summary of the Invention

[0005] This document provides a method and apparatus for electron beam reactive plasma etching of a substrate. In some embodiments, one method includes: applying at least one of low-frequency RF power or DC power to an upper electrode disposed adjacent to a processing space, the upper electrode being formed of a material with a high secondary electron emission coefficient; generating a plasma comprising ions in the processing space; bombarding the upper electrode with ions to cause the upper electrode to emit electrons and form an electron beam; and applying a bias power to a lower electrode disposed in the processing space to accelerate electrons in the electron beam toward the lower electrode, the bias power comprising at least one of low-frequency RF power or high-frequency RF power.

[0006] According to one or more embodiments, an apparatus for processing a substrate includes: a controller configured to: apply at least one of low-frequency RF power or DC power to an upper electrode disposed adjacent to a processing space, the upper electrode being formed of a material with a high secondary electron emission coefficient; generate a plasma in the processing space, the plasma comprising ions; bombard the upper electrode with ions to cause the upper electrode to emit electrons and form an electron beam; and apply a bias power to a lower electrode disposed in the processing space to accelerate electrons in the electron beam toward the lower electrode, the bias power comprising at least one of low-frequency RF power or high-frequency RF power.

[0007] According to one or more embodiments, a non-transitory computer-readable storage medium stores instructions thereon that, when executed by a processor, configure a processor to perform a method for processing a substrate. The method includes: applying at least one of low-frequency RF power or DC power to an upper electrode disposed adjacent to a processing space, the upper electrode being formed of a material with a high secondary electron emission coefficient; generating a plasma comprising ions in the processing space; bombarding the upper electrode with ions to cause the upper electrode to emit electrons and form an electron beam; and applying a bias power to a lower electrode disposed in the processing space to accelerate electrons in the electron beam toward the lower electrode, the bias power comprising at least one of low-frequency RF power or high-frequency RF power.

[0008] Other and further embodiments of this disclosure are described below. Attached Figure Description

[0009] Embodiments of this disclosure, which are briefly summarized above and discussed in more detail below, can be understood by referring to the illustrative embodiments depicted in the accompanying drawings. However, the drawings illustrate only typical embodiments of this disclosure and should therefore not be considered as limiting the scope of this disclosure, as other equivalent embodiments are permissible.

[0010] Figure 1 This is a schematic diagram of a device according to one or more embodiments of the present disclosure.

[0011] Figure 2 This is a flowchart of a method for processing a substrate according to one or more embodiments of the present disclosure.

[0012] To facilitate understanding, the same reference numerals are used to designate common elements in the figures where possible. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated into other embodiments without further description. Detailed Implementation

[0013] This document provides embodiments of methods and apparatuses for configuring electron beam reactive plasma etching for substrates. More specifically, according to this disclosure, the inventors have found that, compared to conventional etching apparatus (e.g., reactive ion etching (RIE)), the etching apparatus described herein: (a) increases the etching rate, for example, by 30 percent, for the same incident ion energy level used by conventional etching apparatus; (b) provides an increased source electron beam to increase the etching rate without having to increase the bias power, which conventional etching apparatus sometimes requires to increase the bias power to compensate for (e.g., due to blockage) a reduction in ion energy, which can sometimes generate a thermal load on the substrate (e.g., a wafer); (c) eliminates microtrenches, which are caused, for example, by charging effects that result in faster etching at the corners of the non-planar etch front; (d) provides an increased etching depth while minimizing ARDE effects (e.g., due to charging effects); and (e) provides increased contour control, for example, reducing (if not eliminating) bending and / or twisting caused by charging effects at the top of the etched features.

[0014] Figure 1 This is a schematic diagram of an apparatus according to one or more embodiments of the present disclosure. The apparatus is suitable for etching one or more substrates (wafers) using an electron beam. Thus, in at least some embodiments, the apparatus is a processing chamber 100 (e.g., an electron beam processing chamber) configured to perform electron beam induced etching (EBIE). The processing chamber 100 has a chamber body 102 that defines a processing space 101. In one embodiment, the chamber body 102 has a substantially cylindrical shape and may be made of a material suitable for maintaining a vacuum pressure environment therein, such as a metallic material, for example, aluminum or stainless steel.

[0015] A top plate 106 is coupled to the chamber body 102 and forms a processing space 101. The top plate 106 is formed of a conductive material, such as the material used to manufacture the chamber body 102. The top plate 106 is coupled to and supports an electrode 108 (e.g., an upper electrode). In some embodiments, the electrode 108 is coupled to the top plate 106 such that the electrode 108 is positioned adjacent to or within the processing space 101. The electrode 108 is formed of a process-compatible material having a high secondary electron emission coefficient (e.g., a secondary electron emission coefficient of about 5 to about 10). Materials with a relatively high secondary emission coefficient may include, but are not limited to, silicon, carbon, silicon carbide, or silicon oxide. Alternatively, the electrode 108 may be formed of a metal oxide material such as aluminum oxide (Al₂O₃), yttrium oxide (Y₂O₃), or zirconium oxide (ZrO₂). A dielectric ring 109 formed of an electrically insulating material is coupled to the chamber body 102 and surrounds the electrode 108. As shown in the figure, the dielectric ring 109 is disposed between the chamber body 102 and the top plate 106 and supports the electrode 108.

[0016] The top plate 106 may include an insulating layer 150, which includes an adsorption electrode 152 facing the electrode 108. In at least some embodiments, a DC voltage source 154 may be coupled to the adsorption electrode 152 via a feed conductor 155 for electrostatically adsorbing the electrode 108 to the top plate 106, and coupled to the electrode 108 for applying DC power (e.g., potential) to the electrode 108. In such embodiments, a DC blocking capacitor 156 may be connected in series with the output of an impedance matching circuit 124. A controller 126 is used to control the DC voltage source 154.

[0017] The mechanical contact between electrode 108 and top plate 106 is sufficient to maintain high thermal conductivity between them. Additionally, the force of the mechanical contact can be adjusted by the electrostatic attraction provided by DC voltage source 154.

[0018] In one or more embodiments, the top plate 106 is conductive and in electrical contact with the electrode 108. Power from the impedance matching circuit 124 is conducted to the electrode 108 through the top plate 106. In one or more embodiments, the chamber body 102 may be maintained at a ground potential. In one or more embodiments, the grounded inner surface inside the processing chamber 100 (i.e., the chamber body 102) may be coated with a process-compatible material, such as silicon, carbon, silicon carbide, or silicon oxide, alumina (Al₂O₃), yttrium oxide (Y₂O₃), or zirconium oxide (ZrO₂).

[0019] In some embodiments, an internal channel (not shown) for conducting a heat-conducting liquid or medium within the top plate 106 is connected to a heat medium circulation supply. The heat medium circulation supply serves as a radiator or heat source.

[0020] A base 110 is disposed within a processing space 101. The base 110 supports a substrate 111 (e.g., a semiconductor wafer, such as a silicon wafer, or a glass panel or other substrate, such as for solar cells, displays, or other applications) and has a substrate support surface 110a oriented parallel to the electrode 108. In one embodiment, the base 110 can be moved axially by a lifting servo motor 112. During operation, the upper electrode (such as electrode 108) is held at one or more distances (e.g., processing positions) from the substrate support surface 110a. For example, in at least some embodiments, the electrode 108 is held at a distance of approximately 1 inch to approximately 20 inches from the processing position for processing the substrate. For example, in at least some embodiments, the distance may be approximately 6 inches to approximately 10 inches.

[0021] A controller 126 is provided and coupled to various components of the processing chamber 100 to control the operation of the processing chamber 100 for processing the substrate. The controller 126 includes a central processing unit (CPU) 127, support circuitry 129, and memory or non-transitory computer-readable medium 131. The controller 126 is operatively coupled to and controls one or more power sources, either directly or via a computer (or controller) associated with the processing chamber 100 and / or support system components. The controller 126 may be any form of general-purpose computer processor that can be used in an industrial environment to control various chambers and subprocessors. The memory or non-transitory computer-readable medium 131 of the controller 126 may be one or more of readily available memory such as random access memory (RAM), read-only memory (ROM), disk, hard disk, optical storage media (e.g., compact disk or digital video disk), flash drive, or any other form of local or remote digital storage. The support circuitry 129 is coupled to the CPU 127 for conventionally supporting the CPU 127. Support circuitry 129 may include cache, power supply, clock circuitry, input / output circuitry systems, and subsystems. The inventive methods described herein (such as methods for processing a substrate (e.g., EBIE of the substrate)) may be stored as software routine 133 in memory 131, which may be executed or invoked to control the operation of one or more power sources in a manner described herein. Software routine 133 may also be stored and / or executed by a second CPU (not shown), located remotely from the hardware controlled by CPU 127.

[0022] In one or more embodiments, the base 110 may include an insulating disk 142 forming a substrate support surface 110a, a lower electrode 144 disposed within the insulating disk 142, and an adsorption voltage source 148 connected to the electrode 144. Additionally, in at least some embodiments, a base layer 146 located below the insulating disk 142 may include one or more internal channels (not shown) for circulating a heat transfer medium (e.g., a liquid) from a circulating supply. In such embodiments, the circulating supply may function as a radiator or heat source.

[0023] A high-frequency RF power generator 120, having a frequency of approximately 20 MHz to approximately 200 MHz, and a low-frequency RF power generator 122, having a frequency of approximately 100 kHz to approximately 20 MHz, are coupled to electrode 108 via an RF feed conductor 123, for example, an impedance matching circuit 124. In one or more embodiments, the RF feed conductor 123 from the impedance matching circuit 124 may be connected to an electrode support or top plate 106, rather than directly to electrode 108. In such embodiments, RF power from the RF feed conductor 123 may be capacitively coupled from the electrode support to electrode 108. The impedance matching circuit 124 is adapted to provide impedance matching at different frequencies of the high-frequency RF power generator 120 and the low-frequency RF power generator 122, and to perform filtering to isolate the high-frequency RF power generator 120 and the low-frequency RF power generator 122 from each other. The output power levels of the high-frequency RF power generator 120 and the low-frequency RF power generator 122 may be independently controlled by a controller 126, as will be described in more detail below.

[0024] Using a high-frequency RF power generator 120 and a low-frequency RF power generator 122, the radial plasma uniformity in the processing space 101 can be controlled by selecting the distance between the electrode 108 and the base 110 (e.g., from approximately 6 inches to approximately 10 inches). For example, in some embodiments, a lower VHF frequency produces a radially high distribution of plasma ion density at the edges of the processing space 101, while a higher VHF frequency produces a radially high distribution of plasma ion density at the center. Through this selection, the power levels of the high-frequency RF power generator 120 and the low-frequency RF power generator 122 can produce a plasma with a substantially uniform radial plasma ion density.

[0025] An upper gas injector 130 supplies process gas to the processing space 101 via a first valve 132, and a lower gas injector 134 supplies process gas to the processing space 101 via a second valve 136. The upper gas injector 130 and the lower gas injector 134 may be disposed in the sidewall of the chamber body 102. The process gas is supplied from a process gas supply array, such as a gas supply 138, via a valve array 140 coupled to the first valve 132 and the second valve 136. The type and flow rate of the process gas supplied to the processing space 101 can be controlled independently. For example, the airflow through the upper gas injector 130 may be different from the airflow through the lower gas injector 134. A controller 126 controls the valve array 140.

[0026] In one embodiment, one or more inert gases such as helium (He), argon (Ar) (or other inert gases) and / or one or more reactive gases such as hydrogen (H2), hydrogen bromide (HBr), ammonia (NH3), silane (Si2H6), methane (CH4), acetylene (C2H2), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), sulfur hexafluoride (SF6), carbon monoxide (CO), carbonyl sulfide (COS), trifluoromethane (CHF3), hexafluorobutadiene (C4F6), chlorine (Cl2), nitrogen (N2), oxygen (O2), combinations thereof, etc., can be supplied to the processing space 101 through either or both of the upper gas injector 130 and the lower gas injector 134. In some embodiments, the processing gas delivered to the processing space 101 adjacent to the electrode 108 can accelerate secondary electrons toward the substrate 111, as will be described in more detail below, and / or protect the electrode 108 from the reactive plasma formed in the processing space 101, thereby increasing the lifespan of the electrode 108.

[0027] According to this disclosure, plasma is generated in the processing space 101 through various body and surface treatments, such as capacitive coupling 170 (e.g., capacitively coupled plasma (CCP)) and / or inductive coupling 172 (e.g., inductively coupled plasma (ICP)). In addition to bias power controlling ion energy, inductively coupled power or high-frequency capacitively coupled power can also be used to achieve independent control of plasma density. Therefore, when the processing chamber 100 is configured for use with capacitive coupling 170 (e.g., configured as a CCP reactor), the source power may refer to the higher-frequency power (compared to the bias voltage) applied to the bias electrode (e.g., electrode 144) or upper electrode (e.g., electrode 108) of the support substrate 111. Alternatively or additionally, when the processing chamber 100 is configured for use with inductive coupling 172 (e.g., configured as an ICP reactor), the source power refers to the power applied to the coil 173 (in... Figure 1The power (shown in dashed lines). When the processing chamber 100 is configured as an ICP reactor, a dielectric window 175 (also shown in dashed lines) is provided on one side of the chamber body 102 of the processing chamber 100. The dielectric window 175 is configured to provide a vacuum boundary and a window for electromagnetically excited plasma.

[0028] The inventors have discovered that ions generated by CCP or ICP are influenced by an electric field that promotes the ion bombardment of electrode 108 by plasma-generated ions, as will be described in more detail below. Furthermore, depending on the operating mode of the processing chamber 100, the ion bombardment energy of electrode 108 can be a function of the power supplied to electrode 108 (e.g., provided by one or more of DC voltage source 154, low-frequency RF power generator 122, or high-frequency RF power generator 120). For example, in at least some embodiments, the ion bombardment energy of electrode 108 can be provided by applying a voltage from one or both of DC voltage source 154 and low-frequency RF power generator 122. In at least some embodiments, in addition to using one or both of DC voltage source 154 and low-frequency RF power generator 122, high-frequency RF power generator 120 can also be used to increase plasma density and electron beam flux.

[0029] When the DC voltage source 154 is used to supply power (e.g., bias) to the electrode 108, the power supplied by the DC voltage source 154 can be approximately 1W to approximately 30kW (e.g., approximately -1560V to approximately -1440V). Similarly, when the low-frequency RF power generator 122 is used to supply power (e.g., bias) to the electrode 108, the power supplied by the low-frequency RF power generator 122 can be approximately 1W to approximately 30kW at a frequency of approximately 100kHz to approximately 20MHz. Likewise, when the high-frequency RF power generator 120 is used in combination with either or both of the DC voltage source 154 and the low-frequency RF power generator 122, the power supplied by the high-frequency RF power generator 120 can be approximately 1W to approximately 10kW at a frequency of approximately 20MHz to approximately 200MHz.

[0030] The ion bombardment energy and plasma density of electrode 108 can be a function of the high-frequency RF power generator 120, the low-frequency RF power generator 122, and the DC voltage source 154. For example, in at least some embodiments, the ion bombardment energy of electrode 108 is substantially controlled by the low-frequency power from the low-frequency RF power generator 122 (or the DC voltage source 154), and the plasma density in the processing space 101 is substantially controlled (enhanced) by the power from the high-frequency RF power generator 120. In at least some embodiments, the ion bombardment of electrode 108 causes electrode 108 to emit secondary electrons. High-energy secondary electrons with negative charges are emitted from the inner surface of electrode 108 and accelerated away from electrode 108 due to the negative bias voltage of electrode 108, as will be described in more detail below. Additionally, to increase the electron beam bombardment dose at the substrate surface, the relative power provided by each of the low-frequency RF power generator 122 and / or the DC voltage source 154 can be varied to change the corresponding voltage provided at electrode 108 and / or electrode 144, as will be described in more detail below.

[0031] The electron beam flux of high-energy electrons emanating from the emitting surface of electrode 108 can be oriented substantially perpendicular to the inner surface of electrode 108. The beam energy of the electron beam can be approximately equal to the ion bombardment energy of electrode 108, which is typically in the range of approximately 100 eV to 20,000 eV. At least a portion of the electron beam, consisting of the secondary electron flux emitted from electrode 108 due to high-energy ion bombardment of the surface of electrode 108, propagates through processing space 101 and reacts with a processing gas near substrate 111. By utilizing one or more previously described processing gases (such as Ar), the inventors have found that the electron beam bombardment effect on substrate 111 can be used in a variety of ways. First, as described above, the inventors have found that electron beam bombardment on surfaces adsorbed with reactive materials can induce etching reactions (e.g., EBIE), which provides the substrate with damage-free etching and high etching selectivity.

[0032] Secondly, since the electric field on the substrate surface is always directed towards the substrate, the charging effect negatively impacts substrate processing. More specifically, electrons may only approach the substrate for charge neutralization at the moment the sheath (e.g., an electrostatic sheath) collapses (e.g., at the positive peak of the RF cycle). Furthermore, with increasing aspect ratio, fewer electrons from bulk plasma can reach the bottom of the etched feature. Therefore, positive charge can accumulate at the bottom of the etched feature, creating an electric field that blocks incident ions. For example, based on empirical data, for a memory via with an aspect ratio of 50:1, more than 50 percent of ions fail to reach the bottom of the memory via, resulting in a significant reduction in ion energy due to positive field delay. The charging effect, along with neutral transport limitation, can reduce the etching rate with increasing aspect ratio (e.g., the ARDE effect). Moreover, the charging effect can cause ion trajectory deflection (e.g., ions bombard sidewalls instead of vertically downwards), posing challenges to etching profile control, such as bending, twisting, under-etching, and microtrenching. Therefore, the inventors have discovered that electron beam bombardment can be used to neutralize the positive ion charge accumulated on the bottom and / or sidewalls of etched features (such as memory holes), thereby eliminating the charging effect.

[0033] In some embodiments, the RF bias power generator 162 may be coupled to the electrode 144 of the base 110 via an impedance matching device 164. The RF bias power generator 162 (if used) is configured to accelerate ions onto the substrate 111. The RF bias power generator 162 may be configured to provide low-frequency RF power and / or high-frequency RF power. For example, in at least some embodiments, the RF bias power generator 162 may be configured to supply 1W to 30kW of power to the electrode 144 at one or more frequencies, for example, from about 100kHz to about 200MHz. In some embodiments, for example, the RF bias power generator 162 may be configured to supply 1W to 30kW of power to the electrode 144 at frequencies from about 100kHz to about 100MHz.

[0034] A waveform adjustment processor 147 can be connected between electrode 144 and the output of impedance matching circuit 164 and / or electrode 108 and the output of impedance matching circuit 124. The waveform adjustment processor 147 controller can be configured to modify the waveform generated by RF bias power generator 162 and / or high-frequency RF power generator 120 and low-frequency RF power generator 122 to a desired waveform. The ion energy of the plasma near substrate 111 and / or electrode 108 can be controlled by the waveform adjustment processor 147. For example, in some embodiments, the waveform adjustment processor 247 generates a waveform in which the amplitude is maintained at a level corresponding to the desired ion energy level during a specific portion of each RF cycle. Controller 126 controls the waveform adjustment processor 147.

[0035] The etching of substrate 111 may also be affected by one or more factors. For example, pressure (in addition to electron beam energy, electron beam plasma power, and bias power (if used)) can affect the etching of substrate 111. Therefore, in one embodiment, the pressure maintained in processing space 101 during EBIE of substrate 111 can be between approximately 0.1 mTorr and approximately 300 mTorr. For example, in at least some embodiments, such as when electron beam neutralization and etch profile control are required, the pressure maintained in processing space 101 during EBIE of substrate 111 can be between approximately 0.1 mTorr and approximately 30 mTorr. Similarly, in at least some embodiments, such as when electron beam neutralization and etch profile control are not required and bias power is not required, the pressure maintained in processing space 101 during EBIE of substrate 111 can be between approximately 0.1 mTorr and approximately 100 mTorr. The pressure is generated by vacuum pump 168 in fluid communication with processing space 101. The pressure is regulated by gate valve 166 disposed between processing space 101 and vacuum pump 168. The controller 126 controls the vacuum pump 168 and / or the gate valve 166.

[0036] Figure 2 This is a flowchart of a method 200 for processing a substrate according to one or more embodiments of the present disclosure. Method 200 can be performed using a processing chamber (e.g., processing chamber 100) configured, for example, to perform EBIE on the substrate. For illustrative purposes, it is assumed that the processing chamber is configured as a CCP reactor for EBIE on a substrate (e.g., substrate 111), which may be, for example, a 150mm, 200mm, 300mm, 450mm substrate, etc. For example, in at least some embodiments, the substrate may be a 300mm substrate, such as a semiconductor wafer. As will be understood, the power / voltage and / or pulse / duty cycle described herein may be scaled accordingly (e.g., for substrates with a diameter greater than or less than 300mm). Initially, one or more of the above-described processing gases may be introduced into the processing space of the processing chamber (e.g., processing space 101). For example, in at least some embodiments, the processing gas may be one or more of He, Ar, etc. (or other inert gases), and / or H2, HBr, NH3, Si2H6, CH4, C2H2, NF3, CF4, SF6, CO, COS, CHF3, C4F6, Cl2, N2, O2, etc. (or other reactive gases). Additionally, the processing space may be maintained at one or more operating pressures ranging from approximately 0.1 mTorr to approximately 300 mTorr. For example, in at least some embodiments, the pressure may be maintained from 0.1 mTorr to approximately 100 mTorr.

[0037] At point 202, one or both of low-frequency RF power and DC power can be applied to an upper electrode (e.g., electrode 108) disposed adjacent to the processing space. As described above, the upper electrode can be formed of a material with a high secondary electron emission coefficient. For example, in at least some embodiments, an RF power generator (e.g., low-frequency RF power generator 122) can be used to supply low-frequency RF power to the upper electrode. As described above, the low-frequency RF power applied to the upper electrode can be from approximately 1 W to approximately 30 kW and can be provided at a frequency from approximately 100 kHz to approximately 20 MHz.

[0038] Alternatively or additionally, at 202, DC power, for example using DC voltage source 154, can be supplied to the upper electrode. For example, up to about 20 kW of DC power can be provided (e.g., corresponding to a supply voltage of about 0 to about 20 kV). The inventors have found that using DC power at 202 results in the formation of a narrow electron beam (e.g., a narrow electron energy distribution).

[0039] In at least some embodiments, at 202, a high-frequency RF power generator (e.g., high-frequency RF power generator 120) may also be used to supply high-frequency RF power in combination with low-frequency RF power and / or DC power to the upper electrode. As described above, the high-frequency RF power can be used to increase plasma density or electron beam flux.

[0040] Next, 204, a plasma containing ions can be generated in the processing space using, for example, the power supplied to the upper electrode. For example, DC power, low-frequency RF power, and / or high-frequency RF power supplied to the upper electrode can be used to ignite the processing gas introduced into the processing space to generate plasma.

[0041] Next, at 206, the upper electrode is bombarded with ions to cause it to emit secondary electrons and form an electron beam. More specifically, low-frequency RF power (or DC power) at the upper electrode is used to generate a high sheath voltage, such that the ion bombardment at the upper electrode (e.g., using ions formed from plasma) has sufficient energy to release secondary electrons from the upper electrode. In some embodiments, and as described above with respect to 202, high-frequency RF power may also be applied to the upper electrode to increase the plasma density or electron beam flux.

[0042] At 208, bias power is provided to the lower electrode (e.g., electrode 144). For example, in at least some embodiments, an RF bias power generator (e.g., RF bias power generator 162) can be used to supply bias power to the lower electrode, the RF bias power generator being configured to supply low-frequency or high-frequency RF power to the lower electrode for accelerating electrons in the electron beam toward the lower electrode. More specifically, the high sheath voltage at the upper electrode and the relatively low bias potential at the lower electrode provide sufficient energy to accelerate secondary electrons into the main plasma to overcome the substrate sheath potential and reach the substrate surface (e.g., substrate 111).

[0043] In at least some embodiments, one or more gases may be used to enhance heat transfer from the base (and / or lower electrode) to the substrate. For example, in at least some embodiments, He or other suitable gases for heat transfer may be applied between the base (and / or lower electrode) and the substrate using, for example, one or more gas supply sources (e.g., gas supply source 138), to enhance heat transfer.

[0044] The generated electron beam can be used to etch a substrate to form one or more features on the substrate. For example, in some embodiments, the generated electron beam can be used to form one or more memory holes in the substrate. More specifically, the inventors have found that the electron beam can be used to form memory holes with an etching depth of about 200 nm to about 500 nm without ARDE effects, defining the sidewalls of the memory holes without bending or twisting, and having better CD (e.g., a flat bottom) and a relatively straight profile.

[0045] The inventors have also discovered that the balance between electron beam flux and ion flux can be controlled using one or more pulse schemes (e.g., controlling the pulse duty cycle, pulse synchronization, duty cycle, and delay). For example, in method 200, any supplied RF power can be used in pulsed or continuous wave (CW) modes to achieve the desired results for different applications (e.g., high or low aspect ratio, logic, or memory, etc.). Alternatively or in combination, in method 200, any supplied DC power can be used in pulsed or continuous modes to achieve the desired results for different applications (e.g., high or low aspect ratio, logic, or memory, etc.). More specifically, to maximize the electron beam bombardment dose incident on the substrate, one or more pulse schemes can be used as described below.

[0046] In at least some embodiments, for example, one or both of low-frequency RF power or DC power may be continuously supplied to the upper electrode (as described above with respect to 202), and low-frequency RF power may be supplied to the lower electrode (as described above with respect to 208). In some embodiments, during at least a portion of the sinusoidal period of the low-frequency RF power, the DC power voltage supplied to the upper electrode is greater than the low-frequency RF power voltage supplied to the lower electrode. Additionally, in some embodiments, the low-frequency RF power voltage supplied to the lower electrode may be pulsed at a low duty cycle (e.g., from about 10% to about 70%, such as about 50%). The pulse frequency can range from about 50 Hz to about 100 kHz. Using such a pulse scheme reduces the substrate sheath potential (e.g., during periods when the low-frequency RF power of the lower electrode is off), thereby increasing the electron beam bombardment dose to the substrate surface. That is, only electron beam electrons with energies higher than the substrate sheath potential can reach the substrate surface.

[0047] In embodiments where low-frequency RF power is supplied to the upper electrode, the pulse can be configured such that when power is supplied to the upper electrode, low-frequency RF power is not supplied to the lower electrode, and vice versa. Alternatively, as described above, low-frequency RF power can be supplied to the upper electrode in CW mode and low-frequency RF power can be supplied to the lower electrode in a pulsed low duty cycle.

[0048] In at least some embodiments, both low-frequency RF power and DC power can be supplied to the upper and lower electrodes in a pulsed mode, but synchronized in such a way that when power is supplied to the upper electrode, power to the lower electrode is turned off. For example, when one or both of the low-frequency RF power and DC power are supplied to the upper electrode, low-frequency RF power is not supplied to the lower electrode. In such embodiments, the on / off pulse period can be set to a frequency of approximately 100 Hz to approximately 100 kHz. In such embodiments, alternating ion flux and electron beam flux are applied to the substrate, thereby increasing the electron beam bombardment dose on the substrate surface.

[0049] While the foregoing describes embodiments of this disclosure, other and further embodiments of this disclosure may be designed without departing from the basic scope of this disclosure.

Claims

1. A method of processing a substrate, the method comprising: applying at least one of low frequency RF power or DC power to an upper electrode disposed adjacent to a processing volume, the upper electrode formed of a high secondary electron emission coefficient material; generating a plasma in the processing volume, the plasma comprising ions; bombarding the upper electrode with the ions to cause the upper electrode to emit electrons and form an electron beam; applying a bias power to a lower electrode disposed in the processing volume to accelerate electrons in the electron beam toward the lower electrode, the bias power comprising at least one of low frequency RF power or high frequency RF power; and wherein applying the at least one of low frequency RF power or DC power to the upper electrode is in a continuous mode, and wherein applying the bias power comprises applying low frequency RF power to the lower electrode in a pulsed mode such that during at least a portion of a sinusoidal cycle of the low frequency RF power, a given pulse of low frequency RF power provides a voltage to the lower electrode that is less than a voltage applied to the upper electrode.

3. The method of claim 1, wherein generating the plasma comprising the electrons comprises introducing at least one of helium (He), argon (Ar), hydrogen (H2), hydrogen bromide (HBr), ammonia (NH3), disilane (Si2H6), methane (CH4), acetylene (C2H2), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), sulfur hexafluoride (SF6), carbon monoxide (CO), carbonyl sulfide (COS), trifluoromethane (CHF3), hexafluorobutadiene (C4F6), chlorine (Cl2), nitrogen (N2), or oxygen (O2) into the processing volume.

2. The method of claim 1, wherein the high secondary electron emission coefficient material is at least one of silicon (Si), silicon nitride (SiN), silicon oxide (SiO x ), or carbon (C).

4. The method of claim 1, further comprising maintaining the upper electrode at a distance of 1 inch to 20 inches from a processing position for processing a substrate.

5. The method of claim 1, further comprising maintaining a pressure within the processing volume at 0.1 mTorr to 300 mTorr.

6. The method of claim 1, further comprising applying high frequency RF power in combination with the at least one of low frequency RF power or DC power to the upper electrode.

7. The method of any of claims 1-6, further comprising applying the at least one of low frequency RF power or DC power to the upper electrode in a pulsed mode, and wherein applying the bias power comprises applying low frequency RF power to the lower electrode in the pulsed mode such that when the at least one of low frequency RF power or DC power to the upper electrode is pulsed on, the pulse of low frequency RF power to the lower electrode is off.

8. An apparatus for processing a substrate, the apparatus comprising: a controller configured to: apply at least one of low frequency RF power or DC power to an upper electrode disposed adjacent to a processing volume, the upper electrode formed of a high secondary electron emission coefficient material; ​ generating a plasma in the processing volume, the plasma including ions; bombarding the upper electrode with the ions to cause the upper electrode to emit electrons and form an electron beam; applying a bias power to a lower electrode disposed in the processing volume to accelerate electrons in the electron beam toward the lower electrode, the bias power including at least one of low frequency RF power or high frequency RF power; and applying the at least one of low frequency RF power or DC power to the upper electrode in a continuous mode, and when the bias power includes low frequency RF power, applying the low frequency RF power to the lower electrode in a pulsed mode such that during at least a portion of a sinusoidal cycle of the low frequency RF power, a given pulse of low frequency RF power provides a voltage to the lower electrode that is less than a voltage applied to the upper electrode.

9. The apparatus of claim 8, wherein the high secondary electron emission coefficient material is at least one of silicon (Si), silicon nitride (SiN), silicon oxide (SiO x ), or carbon (C).

10. The apparatus of claim 8, wherein the plasma including the electrons includes at least one of helium (He), argon (Ar), hydrogen (H2), hydrogen bromide (HBr), ammonia (NH3), disilane (Si2H6), methane (CH4), acetylene (C2H2), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), sulfur hexafluoride (SF6), carbon monoxide (CO), carbonyl sulfide (COS), trifluoromethane (CHF3), hexafluorobutadiene (C4F6), chlorine (Cl2), nitrogen (N2), or oxygen (O2) into the processing volume.

11. The apparatus of claim 8, wherein the controller is further configured to maintain the upper electrode at a distance of 1 inch to 20 inches from a processing position for processing a substrate.

12. The apparatus of claim 8, wherein the controller is further configured to maintain a pressure within the processing volume at 0.1 mTorr to 300 mTorr.

13. The apparatus of claim 8, wherein the controller is further configured to apply high frequency RF power in combination with the at least one of low frequency RF power or DC power to the upper electrode.

14. The apparatus of any of claims 8 to 13, wherein the controller is further configured to apply the at least one of low frequency RF power or DC power to the upper electrode in a continuous mode, and when the bias power includes low frequency RF power, the controller is further configured to apply the low frequency RF power to the lower electrode in a pulsed mode such that when the at least one of low frequency RF power or DC power to the upper electrode is pulsed on, the low frequency RF power pulse to the lower electrode is off.

15. A non-transitory computer readable storage medium having instructions stored thereon that, when executed by a processor, configure the processor to perform a method for processing a substrate, the method comprising the steps of: applying at least one of low frequency RF power or DC power to an upper electrode disposed adjacent a processing volume, the upper electrode formed of a high secondary electron emission coefficient material; generating a plasma in the processing volume, the plasma including ions; bombarding the upper electrode with the ions to cause the upper electrode to emit electrons and form an electron beam; applying a bias power to a lower electrode disposed in the processing volume to accelerate electrons in the electron beam toward the lower electrode, the bias power including at least one of low frequency RF power or high frequency RF power; and applying the at least one of low frequency RF power or DC power to the upper electrode in a continuous mode, and wherein applying the bias power includes applying low frequency RF power to the lower electrode in a pulsed mode such that, during at least a portion of a sinusoidal cycle of the low frequency RF power, a given pulse of low frequency RF power provides a voltage to the lower electrode that is less than a voltage applied to the upper electrode.

16. The non-transitory computer-readable storage medium of claim 15, wherein the high secondary electron emission coefficient material is at least one of silicon (Si), silicon nitride (SiN), silicon oxide (SiO x ), or carbon (C).

17. The non-transitory computer readable storage medium of claim 15, wherein generating the plasma including the electrons includes introducing at least one of helium (He), argon (Ar), hydrogen (H2), hydrogen bromide (HBr), ammonia (NH3), disilane (Si2H6), methane (CH4), acetylene (C2H2), nitrogen trifluoride (NF3), tetrafluoromethane (CF4), sulfur hexafluoride (SF6), carbon monoxide (CO), carbonyl sulfide (COS), trifluoromethane (CHF3), hexafluorobutadiene (C4F6), chlorine (Cl2), nitrogen (N2), or oxygen (O2) into the processing volume.

18. The non-transitory computer readable storage medium of any of claims 15 to 17, further including maintaining the upper electrode at a distance of 1 inch to 20 inches from a processing position for processing a substrate.

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