Plasma Etch Tool for High Aspect Ratio Etching

Abstract

To provide a plasma etching tool for high aspect ratio etching.SOLUTION: Provided is a plasma etching apparatus 400a that etches high aspect ratio features by alternating between accelerating negative ions of reactive species at low energy and accelerating positive ions of inert gas species at high energy. The plasma etching apparatus includes a plasma generating source 410 for generating a plasma, an ionization space 420 coupled to the plasma generating source and configured to generate ions; and an acceleration space 430 coupled to the ionization space and configured to deliver the ions to a substrate 436 installed in the acceleration space. Negative ions of the reactive species can be generated by electron attachment ionization in the ionization space when a plasma is ignited in the plasma generating space, and positive ions of the inert gas species can be generated by Penning ionization in the ionization space when the plasma is quenched in the plasma generating space.SELECTED DRAWING: Figure 4A

Description

[Background technology]

[0001] [Incorporated by reference] PCT applications are being filed contemporaneously herewith as a part of this application. Each application to which this application claims the benefit or priority of a contemporaneously filed PCT application is hereby incorporated by reference in its entirety for all purposes.

[0002] Plasma etching processes are commonly used in the manufacture of semiconductor devices. More and more semiconductor devices are being scaled to ever-decreasing design rules. Feature sizes are shrinking and more features are being packed onto a single wafer to form denser structures. As device features shrink and structure density increases, the aspect ratio of etched features increases. Effectively etching high aspect ratio (HAR) features can be important in meeting the design requirements of many semiconductor devices.

[0003] The Background Art provided herein is intended to present the contents of the present disclosure generally, and the inventions of the presently named inventors are not admitted expressly or impliedly as prior art to the present disclosure to the extent that they are described in this Background Art section and in a manner that is not prior art at the time of filing. Summary of the Invention

[0004] Described herein is a plasma etching apparatus comprising a plasma generation source, an ionization space coupled to the plasma generation source and configured to generate ions, a first grid between the ionization space and the plasma generation source, an acceleration space coupled to the ionization space and configured to supply ions to a substrate therein, a substrate support configured to be biased and for supporting the substrate within the acceleration space, and a controller. The controller is configured with instructions to perform operations of: introducing reactive species into the ionization space and applying a positive bias to the substrate support to accelerate negative ions of the reactive species to the substrate in the acceleration space; and introducing non-reactive species into the ionization space and applying a negative bias to the substrate support to accelerate positive ions of the non-reactive species to the substrate in the acceleration space.

[0005] In some embodiments, the negative bias is substantially greater in absolute value than the positive bias. In some embodiments, the positive bias is about 0.5V to about 10V, and the negative bias is about -50kV to about -1kV. In some embodiments, the controller is further configured with instructions for igniting a plasma in the plasma source when accelerating negative ions of reactive species, and extinguishing a plasma in the plasma source when accelerating positive ions of non-reactive species. In some embodiments, the controller is further configured with instructions for extracting electrons from the plasma into the ionization space in association with accelerating negative ions of reactive species to ionize the reactive species and form negative ions of reactive species in the ionization space. In some embodiments, the controller is further configured with instructions for causing diffusion of metastable species from the plasma into the ionization space in association with accelerating positive ions of non-reactive species to ionize the non-reactive species and form positive ions of non-reactive species in the ionization space. In some embodiments, the plasma etching apparatus further comprises a second grid between the ionization space and the acceleration space. The pressure in the ionization space may be greater than the pressure in the acceleration space.

[0006] Another aspect includes a plasma etching apparatus including a plasma generation source, an ionization space coupled to the plasma generation source and configured to generate ions, a first grid between the ionization space and the plasma generation source, an acceleration space coupled to the ionization space and configured to provide ions to a substrate therein, a substrate support configured to be biased and for supporting the substrate within the acceleration space, and a controller, the controller configured with instructions to perform operations of introducing reactive and non-reactive species into the ionization space, igniting a plasma in the plasma generation source, applying a positive bias to the substrate support to ionize the reactive species to form negative ions of the reactive species and accelerating the negative ions of the reactive species to the substrate when the plasma is ignited, extinguishing the plasma in the plasma generation source, and applying a negative bias to the substrate support to form positive ions of the non-reactive species and accelerating the positive ions of the non-reactive species to the substrate when the plasma is extinguished.

[0007] In some embodiments, the positive bias is about 0.5V to about 10V and the negative bias is about -50kV to about -1kV. In some embodiments, the second grid is between the ionization space and the acceleration space, the first grid is configured to be biased, and the second grid is configured to be biased, and the pressure in the ionization space is greater than the pressure in the acceleration space. In some embodiments, the plasma source is an inductively coupled plasma (ICP) reactor or a capacitively coupled plasma (CCP) reactor. In some embodiments, the controller is further configured with instructions to perform an alternating operation between applying a positive bias to the substrate support when the plasma is ignited and applying a negative bias to the substrate support when the plasma is extinguished. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an exemplary plasma etching apparatus for generating an inductively coupled plasma for etching.

[0009] [Diagram 2] 1 is a schematic diagram of an exemplary plasma etching apparatus for generating a capacitively coupled plasma for etching.

[0010] [Figure 3A] Schematic diagram of an exemplary reaction mechanism for etching silicon dioxide (SiO2). [Figure 3B] Schematic diagram of an exemplary reaction mechanism for etching silicon dioxide (SiO2). [Figure 3C] Schematic diagram of an exemplary reaction mechanism for etching silicon dioxide (SiO2).

[0011] [Figure 4A] FIG. 1 is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids to generate an inductively coupled plasma in accordance with some embodiments and to provide alternating ion beams of positive and negative ions for etching.

[0012] [Figure 4B] FIG. 1 is a schematic diagram of an exemplary plasma etching apparatus divided into a single grid for generating an inductively coupled plasma in accordance with some embodiments and providing alternating ion beams of positive and negative ions for etching.

[0013] [Figure 4C] FIG. 1 is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids to generate an inductively coupled plasma in a remote plasma source according to some embodiments and to provide alternating ion beams of positive and negative ions for etching.

[0014] [Figure 4D] FIG. 1 is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids to generate a capacitively coupled plasma in accordance with some embodiments and to provide alternating ion beams of positive and negative ions for etching.

[0015] [Diagram 5] 2 is a flow diagram of an exemplary plasma etching method using alternating ion beams of positive and negative ions in accordance with some embodiments.

[0016] [Figure 6A] 1 is a schematic diagram of an exemplary plasma etching process that performs a modifying operation in accordance with some embodiments. [Figure 6B] 1 is a schematic diagram of an exemplary plasma etching process for performing a removal operation in accordance with some embodiments.

[0017] [Figure 7] 2 is an exemplary timing sequence diagram of applied voltages to a plasma source and a substrate support in a plasma etching process that alternates between modification and removal operations in accordance with some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In this disclosure, the terms "semiconductor wafer," "wafer," "substrate," "wafer substrate," and "partially fabricated integrated circuit" are used interchangeably. Those skilled in the art will appreciate that the term "partially fabricated integrated circuit" can refer to a silicon wafer at any of the many stages of integrated circuit manufacturing. Wafers or substrates used in the semiconductor device industry typically have diameters of 200 mm, or 300 mm, or 450 mm. The following detailed description assumes that the disclosure is implemented on a wafer. However, the disclosure is not so limited. Workpieces may have a variety of shapes, sizes, and materials. In addition to semiconductor wafers, other workpieces that may utilize the present disclosure include various articles such as printed circuit boards. Introduction

[0019] Plasma has long been used to process substrates. Plasma etching involves etching material deposited on a substrate to form a desired pattern. Specifically, reactive ion etching (RIE) uses a chemically reactive plasma to remove material deposited on the substrate. The plasma is generated by supplying reactive gases to a plasma generation chamber and applying an electromagnetic field. For example, plasma generation may use capacitively coupled plasma technology, inductively coupled plasma technology, electron cyclotron technology, or microwave technology. High energy ions and radicals from the plasma are delivered to the substrate surface and react with the material deposited on the substrate.

[0020] In the plasma generation chamber, a reactive gas is introduced and a plasma is generated by applying a strong radio frequency (RF) electromagnetic field. Electrons are accelerated by an oscillating electric field, colliding with reactive gas molecules, which are ionized and lose their electrons, thereby generating a plasma of ions and more electrons. The plasma generally includes ions, radicals, neutral species, and electrons. With each cycle of the oscillating electric field, free electrons are electrically accelerated and decelerated in the plasma generation chamber. Many of the free electrons may induce a negative bias on an electrode, such as the substrate surface. The slow moving ions accelerate towards the biased electrode and react with the material on the substrate surface being etched. The slow moving ions may form a region that may be called a sheath or plasma sheath. A typical sheath thickness is on the order of a few millimeters. The ion flux is generally perpendicular to the surface of the substrate being processed.

[0021] Plasma reactors, such as inductively coupled plasma reactors and capacitively coupled plasma reactors, can generate plasmas with different characteristics. In general, inductively coupled plasma reactors may be effective for performing conductor etch processes, and capacitively coupled plasma reactors may be effective for performing dielectric etch processes.

[0022] In an inductively coupled plasma reactor, a high RF current in an external coil may generate an RF magnetic field in the plasma region, which in turn generates an RF electric field in the plasma region. Inductively coupled plasma reactors may use two RF generators to independently control the plasma density and ion energy. In capacitively coupled plasma reactors, energy is provided to the electrons in the plasma discharge by applying an RF voltage to the electrodes. Multiple RF excitation frequencies may be used individually or simultaneously to modify the plasma characteristics. Capacitively coupled plasma reactors can typically achieve higher ion energies than inductively coupled plasma reactors, and plasma density and ion energy are coupled whereas in inductively coupled plasma reactors they are decoupled.

[0023] 1 is a schematic diagram of an exemplary plasma etching apparatus for generating an inductively coupled plasma for etching. The plasma etching apparatus 100 includes an upper electrode 102 and a lower electrode 104 between which a plasma 140 may be generated. A substrate 106 may be placed on the lower electrode 104 and held in place by an electrostatic chuck (ESC). Other clamping mechanisms may also be used.

[0024] 1, plasma etching apparatus 100 includes two RF sources, RF source 110 connected to upper electrode 102 and RF source 112 connected to lower electrode 104. Plasma etching apparatus 100 may be an inductively coupled plasma reactor. Although plasma etching apparatus 100 is depicted as an inductively coupled plasma reactor, it will be appreciated that plasma etching apparatus 100 may be a capacitively coupled plasma reactor with a single RF power source.

[0025] 1, each of the RF sources 110 and 112 may include one or more sources of any suitable frequency, including 2 MHz, 13.56 MHz, 27 MHz, and 60 MHz. Reactant gases may be introduced into the process chamber 120 from one or more gas sources 114. For example, the gas sources 114 may include an inert gas, such as argon (Ar), an oxygen-containing gas (e.g., O2), a fluorine-containing gas (e.g., CF4), or combinations thereof. The reactant gases may be introduced into the process chamber 120 through an inlet 122, and excess gases and reaction by-products are exhausted through an exhaust pump 124.

[0026] The controller 130 is connected to valves associated with the RF sources 110 and 112, and the gas source 114. The controller 130 may further be connected to the exhaust pump 124. In some embodiments, the controller 130 controls all operations of the plasma etcher 100.

[0027] FIG. 2 is a schematic diagram of an exemplary plasma etching apparatus for generating a capacitively coupled plasma for etching. The plasma etching apparatus 200 includes an upper electrode 202 and a lower electrode 204. The lower electrode 204 may include additional components, such as a chuck or other clamping mechanism for holding a substrate 206. The lower electrode 204 may be RF powered by an RF source 212. The RF source 212 may provide any suitable frequency, including 2 MHz, 13.56 MHz, 27 MHz, and 60 MHz. The RF source 212 may provide an RF bias to the lower electrode 204 during etching. The RF source 212 provides power to excite a process gas in a gap 220 between the upper electrode 202 and the lower electrode 204 to generate a plasma 240. The RF source 212 may be a single RF source that generates a high density plasma 240 in the gap 220. A process gas may be supplied to the gap 220 from a gas source 214. Process gases may be supplied to the showerhead arrangement 216 and flow through the passages into the gap 220 .

[0028] The controller 230 may be implemented in the plasma etcher 200. The controller 230 may control some or all of the operation of the plasma etcher 200. In some embodiments, the controller may be connected to valves associated with the lower electrode 204, the RF source 212, and the gas source 214.

[0029] Plasmas typically contain a mixture of ions and neutral species (e.g., radicals). The neutral species tend to lack directionality and provide a wide angular distribution. The neutral species tend to be useful for isotropic etching and sidewall etching. Ions, on the other hand, tend to have directionality in a direction substantially perpendicular to the substrate surface and provide a narrow angular distribution. Ions tend to be useful for anisotropic etching. A mixture of ions and neutral species is used for aspect ratio dependent etching. Although the ratio, density, and other properties of the plasma can be controlled in the plasma reactor, the aspect ratio dependent etching is still driven by both ions and neutral species.

[0030] Ion beam etching reactors use an ion beam to etch material by sputtering. This type of etching is highly anisotropic and non-selective. Chemical etching reactors use an etching gas to etch material by chemical reaction and formation of volatile products at the substrate surface. This type of etching is highly isotropic and selective. Plasma etching reactors generally use ions and neutral species (e.g., radicals) to etch material by ion bombardment and chemical reaction on the substrate surface. This may be referred to as ion-enhanced etching. This type of etching may be moderately anisotropic and moderately selective. Etch directionality and etch profile may be influenced by controlling ion flux, ion energy, neutral species / ion flux ratio, deposition or passivation chemistry, substrate surface temperature, and pressure. However, for increasingly higher aspect ratio features, conventional plasma etching techniques and reactors do not provide sufficient control of etch directionality and etch profile in aspect ratio dependent etching.

[0031] 3A-3C show schematics of an exemplary reaction mechanism for etching silicon dioxide (SiO2). Many applications of aspect ratio dependent etching involve a combination of reactive and non-reactive species. A plasma may be generated from the reactive and non-reactive species and may include reactive radicals and non-reactive ions. The reactive species may be a fluorocarbon precursor (C x F y ), exemplary fluorocarbon precursors may include CF4 and C4F8. The non-reactive species may include one or more inert gases, such as helium (He), argon (Ar), xenon (Xe), and krypton (Kr).

[0032] In Figure 3A, C x F y The radicals may diffuse to the surface of the substrate having a SiO2 layer, and Ar + The ions may be accelerated under a bias to the surface of the substrate. The radicals and ions may be mixed. As shown in Figures 3A-3C, the radicals lack directionality, with a horizontal component equal in magnitude to the vertical component. The ions may have directionality in a direction substantially perpendicular to the substrate surface, with the vertical component being greater than the horizontal component. The radicals move to the substrate surface slower than the ions.

[0033] In FIG. 3B, the radicals under ion bombardment react with the SiC x F y O z The radicals may tend to saturate on the substrate surface and chemically react with the substrate surface. The radicals may also tend to condense and form a film on the substrate surface. Without being limited by theory, C x F y Ion beams mixed with radicals may play an important role in the formation of chemically reactive layers.

[0034] In Figure 3C, Ar + The energetic ions collide with the substrate surface and penetrate the substrate surface. This causes the SiC x Fy O z These etching by-products cause the SiC of the chemically reactive layer to desorb. x F y O z By removing the SiO2 from the substrate, some of the SiO2 may be etched away.

[0035] In a conventional plasma etch reactor, such as the plasma etch apparatus of FIG. 1 or the plasma etch apparatus of FIG. 2, a plasma is generated that contains a mixture of ions and neutral species. Etching of high aspect ratio features may occur by providing an increased amount of RF power during plasma generation, which generates higher ion energies through electron bombardment. A thick ion sheath is formed, and ions may be accelerated through the thick sheath by RF bias. However, this method of generating higher ion energies and accelerating ions is ineffective and expensive, yet still results in a wide ion energy distribution function (IEDF) and a wide ion angular distribution function (IADF). Thus, conventional plasma etch reactors may be of limited effectiveness for high aspect ratio etch applications.

[0036] Although a conventional plasma etch reactor may be replaced with an ion beam etch reactor so that the ions are completely dissociated for etching, reactive species (e.g., neutral species) from the plasma are often also required to etch high aspect ratio features, and thus the use of an ion beam etch reactor would be impractical for many high aspect ratio etch applications.

[0037] As discussed above, control of parameters such as ion / neutral flux ratio may affect etch directionality and etch profile. In aspect ratio dependent etching, the ion / neutral flux ratio may be adjusted according to the aspect ratio. A high ion / neutral flux ratio may provide a more anisotropic etch, and a low ion / neutral flux ratio may provide a more selective etch. The ion / neutral flux ratio may be changed during the etch. For example, in a conventional plasma etch reactor, the ion / neutral flux ratio may be adjusted by mixed mode pulsing (MMP). Each pulse of a gas cycle may have a different amount of reactive species (e.g., neutral species) relative to non-reactive species (e.g., inert gas). The plasma power and / or frequency may be different during each pulse of a gas cycle. That is, RF settings and flow rate settings may be changed with each pulse to change the ion / neutral flux ratio. With mixed mode pulsing, the ratio of ions to neutral species may be temporarily changed. However, mixed-mode pulses can be relatively slow due to the constant gas switching between reactive and non-reactive species. Additionally, mixed-mode pulses can provide different RF powers / frequencies for each pulse, but the different RF powers / frequencies do not essentially change the chemistry. Due to the electron impact ionization that occurs in conventional plasma etch reactors, neutral species and ions do not completely separate during etching, even with mixed-mode pulses.

[0038] Conventional plasma etch reactors that rely on both ions and neutral species for aspect ratio dependent etching also pose the challenge that neutral species diffuse very slowly towards the bottom of the feature. Etching a high aspect ratio feature may include flowing neutral species to adsorb to the exposed surface and form a reaction layer, and accelerating ions towards the surface to remove the reaction layer. Plasmas generated in conventional plasma etch reactors typically have a wide IEDF and a wide IADF. Neutral species have energies on the order of a few eV, and ions have energies on the order of tens or hundreds of eV. Neutral species lack directionality, making it difficult to etch high aspect ratio features (e.g., deep trenches) with a wide IEDF and a wide IADF. Ions with high ion energy are accelerated by the bias pulse, while neutral species with low ion energy diffuse very slowly in all directions. Neutral species may not necessarily reach the bottom of the feature, but may impinge on the sidewalls of the feature. This results in a low etch rate.

[0039] In etching high aspect ratio features, accelerating ions in a conventional plasma etch reactor can result in charge accumulating on the mask. Charge accumulation on the mask can prevent ions from reaching the bottom of the feature. This reduces etching at the bottom of the feature and increases etching on the sidewalls, resulting in "bowback." Conventional plasma etch reactors may increase ion energy to overcome charge repulsion and reach the bottom of high aspect ratio features, but this increases cost.

[0040] Conventional plasma etch reactors may also generate various etch by-products while removing material from the substrate. The etch by-products are typically pumped out of the plasma etch reactor by one or more pumping mechanisms. However, the etch by-products may not be completely removed. When the plasma is ignited, such etch by-products may be ionized and redeposited on the substrate. Waferless automatic cleaning (WAC) may be performed between operations to remove the etch by-products, but this increases costs. Plasma etching equipment

[0041] The plasma etching apparatus of the present disclosure can address the aforementioned challenges of high aspect ratio etching. The plasma etching apparatus can be divided into two or more volumes that separate the plasma generation space and the ionization space. In some embodiments, the plasma etching apparatus can be divided into at least three volumes that separate the plasma generation space, the ionization space, and the acceleration space. In some embodiments, a grid separates the plasma generation space and the ionization space, and the grid can be biased or grounded. An electrode or substrate support for supporting the substrate can be biased by a DC voltage to form an electric field with the grid. In the first stage of the etching process, electrons generated in the plasma generation space react with reactive species to form negative ions in the ionization space by electron attachment ionization, and the negative ions accelerate to the substrate surface to modify the material on the substrate surface. In the second stage of the etching process, the plasma is extinguished, and the remaining metastable neutral species can react with inert gas species to form positive ions in the ionization space by Penning ionization, and the positive ions accelerate to the substrate surface to etch the modified material on the substrate surface. The first and second stages of the etching process may be alternately repeated to complete the etching process. In this specification, negative ions may be referred to as "fast neutral species," "accelerated neutral species," "non-dissociated reactive ions," or "reactive ions." Positive ions may be referred to as "non-reactive ions" or "inert gas ions." The plasma etcher may perform high aspect ratio etching by completely separating the fast neutral species and the non-reactive ions.

[0042] 4A is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids to generate an inductively coupled plasma and provide an alternating ion beam of positive and negative ions for etching according to some embodiments. The plasma etching apparatus 400a includes a plasma source 410 for generating plasma, an ionization space 420 coupled to the plasma source 410 and configured to generate ions, and an acceleration space 430 coupled to the ionization space 420 and configured to provide ions to a substrate 436 placed therein. The plasma etching apparatus 400a may include a first grid 424 between the plasma source 410 and the ionization space 420. In some embodiments, the plasma etching apparatus 400a may further include a second grid 434 between the ionization space 420 and the acceleration space 430. The plasma source 410 may be upstream of the ionization space 420, and the ionization space 420 may be upstream of the acceleration space 430.

[0043] A first gas or a first gas mixture may be introduced to the plasma generation source 410 from a first gas source 412. The first gas source 412 may be in fluid communication with the plasma generation source 410. One or more valves, mass flow controllers (MFCs), and / or mixing manifolds may be associated with the first gas source 412 to control the flow of the first gas to the plasma generation source 410. The first gas may include a noble gas, such as helium, argon, xenon, or krypton. In some embodiments, the first gas may be supplied continuously during the etching process. In some embodiments, the first gas may be pulsed at different stages of the etching process.

[0044] RF power may be provided to the plasma source 410 to generate a plasma of the first gas in the plasma source 410. In some embodiments, the plasma source 410 may include an RF antenna 414 coupled to an RF generator 416. In some embodiments, the RF generator 416 may include an RF power source coupled to a matching network. In some embodiments, the RF antenna 414 may include a planar spiral coil. In some embodiments shown in FIG. 4A, the plasma source 410 of the plasma etching apparatus 400a is an inductively coupled plasma (ICP) reactor. However, it will be appreciated that the present disclosure may use a capacitively coupled plasma (CCP) reactor, or other types of plasma reactors to generate plasma. In use, the first gas is provided to the plasma source 410 and RF power is provided from the RF generator 416 to the RF antenna 414 to generate plasma in the plasma source 410. Electrons collide with the first gas by electron impact ionization, which removes electrons and generates ions and more electrons. In a first stage of the etching process, RF power may be supplied to generate a plasma of the first gas in the plasma generation source 410. In a second stage of the etching process, the RF power may be turned off to extinguish the plasma in the plasma generation source 410.

[0045] As will be explained in more detail below, the etching process may constitute an etching cycle divided into two stages: a first stage may constitute a modification stage during which the plasma is switched on, and a second stage may constitute a removal stage during which the plasma is switched off.

[0046] The plasma source 410 is coupled to the ionization volume 420 via a first grid 424. Ions, electrons, or intermediate species may be extracted from the plasma generated in the plasma source 410 through the first grid 424. In some embodiments, the first grid 424 may comprise a number of openings or holes through which the ions, electrons, or intermediate species may pass. In some embodiments, the first grid 424 may comprise a conductive plate having a number of openings or holes, which may be biased or grounded. In some embodiments shown in FIG. 4A, the first grid 424 may be grounded by an electrical ground 446. However, it will be understood that in some embodiments, the first grid 424 may be biased. The first grid 424 may form an electric field with the second grid 434 or the substrate support 438. Depending on the potential gradient of the electric field, certain charged and / or neutral species may be extracted from the plasma through the first grid 424. The electrons may be extracted during a first stage of the etching process due to electron attachment ionization, and the metastable neutral species may be extracted during a second stage of the etching process due to Penning ionization. The first stage may constitute a modification stage in which electrons are extracted from the plasma through the first grid 424, and the second stage may constitute a removal stage in which metastable neutral species are extracted from the plasma afterglow through the first grid 424.

[0047] Electron attachment ionization and Penning ionization may occur in the ionization space 420. A second gas or a second gas mixture may be introduced into the ionization space 420 from one or more additional gas sources 422. The second gas may include a reactive gas or reactive species. Examples of reactive species include halogen gases such as chlorine (Cl2), bromine (Br2), fluorine (F2), or iodine (I2), perfluorocarbons such as tetrafluoromethane (CF4), octafluorocyclobutane (C4F8), and hexafluorocyclobutene (C4F6), hydrofluorocarbons such as trifluoromethane (CHF3), difluoromethane (CH2F2), and fluoromethane (CH3F), and oxygen (O2). In general, the second gas is an electronegative reactive gas. A third gas or a third gas mixture may be introduced into the ionization space 420 from one or more additional gas sources 422. The third gas may include a non-reactive species such as helium, argon, xenon, or krypton. In some embodiments, the third gas is different from the first gas. In some embodiments, the second gas and the third gas may be provided to the ionization space 420 through different gas inlets fluidly coupled to one or more additional gas sources 422. One or more valves, mass flow controllers (MFCs), and / or mixing manifolds may be associated with the one or more additional gas sources 422 to control the flow of the second gas and the third gas to the ionization space 420. In some embodiments, the second gas and the third gas may be provided continuously to the ionization space 420 during the first and second stages of the etching process. In some other embodiments, the second gas and the third gas may be provided in pulses to the ionization space 420 such that the second gas is provided in the first stage and the third gas is provided in the second stage.

[0048] The electrons extracted through the first grid 424 may cause electron attachment ionization of the second gas, which forms negative ions of the reactive species. The negative ions of the reactive species are formed without dissociation by electron attachment ionization. Electron attachment ionization may occur in a first stage of the etching process. Thus, electron attachment ionization to form negative ions of the reactive species occurs in a modification stage of the etching process. An exemplary equation for electron attachment ionization with C4F8 is e - +C4F8-->C4F8 - As shown in the figure.

[0049] The metastable neutral species extracted through the first grid 424 may cause Penning ionization of the third gas, which forms positive ions of the non-reactive species. The metastable neutral species may be extracted through the first grid 424 even after the plasma in the plasma source 410 is extinguished or turned off. In some embodiments, the metastable neutral species may be in an excited state. The metastable neutral species may have a long enough lifetime to diffuse through the first grid 424 and collide with the non-reactive species. The collisions may cause Penning ionization of the non-reactive species such that the non-reactive species loses electrons. The Penning ionization may occur in a second stage of the etching process. Thus, the Penning ionization to form positive ions of the non-reactive species may occur in the removal stage of the etching process. For Ar and metastable He * An example equation for Penning ionization by He * +Ar-->Ar + +He+e - As shown in the figure.

[0050] The substrate 436 may be supported on a substrate support 438 in the acceleration space 430. The substrate 436 may comprise a plurality of high aspect ratio features in some embodiments. The high aspect ratio features may include features having an aspect ratio of depth:width of at least 10:1, at least 20:1, at least 50:1, or at least 100:1. The substrate support 438 is configured to be biased by a DC voltage. The substrate support 438 may comprise a chuck or other clamping mechanism for holding the substrate 436. The substrate support 438 may comprise an electrode electrically coupled to a DC power supply 442 for applying a positive or negative DC voltage to the substrate support 438. The biased substrate support 438 may accelerate ions towards the substrate 436. Negative ions or fast neutral species may be accelerated to the substrate 436 by application of a positive bias during a first stage (the modification stage) of the etching process, and positive ions or non-reactive ions may be accelerated to the substrate 436 by application of a negative bias during a second stage (the removal stage) of the etching process.

[0051] The positive bias may create a weak electric field between the substrate support 438 and the second grid 434 or the first grid 424 such that the negative ions accelerate with low energy. The negative bias may create a strong electric field between the substrate support 438 and the second grid 434 or the first grid 424 such that the positive ions accelerate with high energy. In some embodiments, the negative bias may be substantially greater in absolute value than the positive bias. In some embodiments, the positive bias may be about 0.5V to about 10V and the negative bias may be about -50kV to about -1kV. The negative ions accelerated to the modification stage of the etching process may help modify or activate the substrate surface and form a reactive layer on the substrate surface. The positive ions accelerated to the removal stage of the etching process may help etch the reactive layer on the substrate surface.

[0052] In some embodiments shown in FIG. 4A, the ionization space 420 is coupled to the acceleration space 430 via a second grid 434. The first grid 424 may separate the plasma source 410 from the ionization space 420, and the second grid 434 may separate the ionization space 420 from the acceleration space 430. The first grid 424 and the second grid 434 may both be used to enhance ionization. The first grid 424 and the second grid 434 allow the ionization space 420 to operate at a different pressure than the acceleration space 430. In some embodiments, the pressure in the ionization space 420 is greater than the pressure in the acceleration space 430. A higher pressure in the ionization space 420 promotes more collisions and more ionization. In some embodiments, the pressure in the ionization space 420 is about 10 mTorr to about 1000 mTorr (e.g., about 500 mTorr). A lower pressure in the acceleration space 430 promotes acceleration with fewer collisions. In some embodiments, the pressure in the acceleration space 430 is from about 1 mTorr to about 50 mTorr (eg, about 4 mTorr).

[0053] The second grid 434 may be similar in appearance to the first grid 424. In some embodiments, the second grid 434 may comprise a plurality of openings or holes through which ions, electrons, or intermediate species can pass. In some embodiments, the second grid 434 may comprise a conductive plate having a plurality of openings or holes, which may be biased or grounded. In some embodiments shown in FIG. 4A, the second grid 434 comprises an electrode electrically connected to a DC power supply 444 for applying a positive or negative DC voltage to the second grid 434. For example, in a first stage of the etching process, the second grid 434 may be positively biased to draw electrons from the plasma generation source 410 into the ionization space 420. In a second stage of the etching process, the second grid 434 may be negatively biased to accelerate positive ions from the ionization space 420. Although the embodiment of FIG. 4A depicts a first grid 424 and a second grid 434, it will be understood that the plasma etching apparatus 400a may include any number of grids (e.g., three, four, five, or more grids).

[0054] The plasma etcher 400a may further include an exhaust pump 470. The exhaust pump 470 may include a roughing pump and / or a turbomolecular pump in fluid communication with the acceleration space 430. The exhaust pump 470 is used to control the pressure of the plasma etcher 400a, including the pressure of the acceleration space 430. The exhaust pump 470 is also used to evacuate various gases from the acceleration space 430.

[0055] The modification and removal stages of the etching process may be alternately repeated in the plasma etching apparatus 400a. In the modification stage, plasma is generated in the plasma generation source 410, electrons are extracted from the plasma through the first grid 424, electron attachment ionization occurs in the ionization space 420 to form reactive negative ions, the negative ions are accelerated by a positive bias applied to the substrate support 438 in the acceleration space 430, and the substrate surface is modified by the negative ions. In the removal stage, plasma is turned off in the plasma generation source 410, metastable neutral species are extracted from the plasma afterglow through the first grid 424, Penning ionization occurs in the ionization space 420 to form non-reactive positive ions, the positive ions are accelerated by a negative bias applied to the substrate support 438 in the acceleration space 430, and the modified layer on the substrate surface is removed by the positive ions.

[0056] The plasma etching apparatus 400a may further include a controller 450. The controller 450, which may include one or more physical or logical controllers, controls some or all of the operation of the plasma etching apparatus 400a. The controller 450 may be configured with instructions for performing the modification and removal phases of the etching process. The controller 450 may thereby selectively ionize reactive and non-reactive species in alternating phases and accelerate an ion beam of positive and negative ions in alternating phases. In some embodiments, the controller 450 may be used to control an RF generator 416 coupled to an RF antenna 414, a first gas source 412 for providing a first gas, one or more additional gas sources 422 for providing a second gas and a third gas, a DC power source 444 electrically coupled to a second grid 434, a DC power source 442 electrically coupled to a substrate support 438, an exhaust pump 470, or a combination thereof. In some embodiments, the controller 450 may be configured to apply RF power to the plasma source 410 during the modification phase and to turn off RF power to the plasma source 410 during the removal phase. In some embodiments, the controller 450 may be configured to apply a positive bias to the substrate support 438 during the modification phase to extract electrons from the plasma source 410 and accelerate negative ions of reactive species to the substrate 436 and to apply a negative bias to the substrate support 438 during the removal phase to accelerate positive ions of non-reactive species to the substrate 436. The application of a positive bias may extract electrons from the plasma to ionize the reactive species and form negative ions of the reactive species. The application of a negative bias may cause diffusion of metastable species from the plasma or its afterglow to ionize the non-reactive species and form positive ions of the non-reactive species.

[0057] The controller 450 may comprise one or more memory devices and one or more processors. The processor may comprise a central processing unit (CPU) or computer, analog and / or digital input / output connections, a stepper motor controller board, and other similar components. Instructions for performing suitable control operations are executed in the processor. These instructions may be stored in a memory device associated with the controller 450 and provided over a network. In certain embodiments, the controller 450 executes system control software. The system control software may include instructions for controlling the timing and / or magnitude of application of any one or more of the following chamber operating conditions: gas mixture and / or composition, gas flow rate, chamber pressure, room temperature, substrate / substrate support temperature, substrate position, substrate support tilt, substrate support rotation, voltage applied to grid, voltage applied to substrate support, frequency and power applied to coils, antennas, or other plasma generating components, and other parameters of the particular process being performed by the tool. The system control software may further control purging and cleaning operations through the exhaust pump 470. The system control software may be configured in any suitable manner. For example, various process tool component subroutines or control objects may be written to control the operation of the process tool components necessary to perform the various process tool processes. The system control software may be coded in any suitable computer readable programming language.

[0058] In some embodiments, the system control software includes input / output control (IOC) sequence instructions for controlling the various parameters described above. For example, each stage of a semiconductor manufacturing process may include one or more instructions for execution by the controller 450. Instructions for setting process conditions for a stage may be included in the corresponding recipe stage, for example. In some embodiments, the recipe stages may be sequentially arranged such that operations in the plasma etch process are performed in a specific order for that process stage. For example, a recipe may be configured to perform plasma generation and acceleration of negative ions in a first stage and positive ion acceleration with plasma power off in a second stage.

[0059] In some embodiments, other computer software and / or programs may be used. Examples of programs or program sections for this purpose include a substrate positioning program, a process gas composition control program, a pressure control program, a heater control program, and an RF power supply control program.

[0060] The controller 450 may control these and other aspects based on sensor outputs (e.g., when power, potential, pressure, gas levels, etc. reach certain thresholds), based on the timing of actions (e.g., the action of providing power at a particular time in the process), or based on instructions received from a user.

[0061] In general, the controller 450 may be defined as electronic equipment having various integrated circuits, logic, memory, and / or software that receive instructions, issue instructions, control operations, enable cleaning operations, enable endpoint measurements, etc. The integrated circuits may include chips in firmware format that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and / or one or more microprocessors or microcontrollers that execute the program instructions (e.g., software). The program instructions may be instructions communicated to the controller in the form of various personalizations (or program files) that define the operating parameters for performing a particular process on or for a semiconductor wafer or for a system. In some embodiments, the operating parameters may be part of a recipe defined by a process engineer to achieve one or more process steps during plasma etching.

[0062] In some embodiments, the controller 450 may be part of or coupled to a computer that is integrated or coupled to the system, or otherwise network-coupled to the system, or a combination thereof. For example, the controller 450 may be in the "cloud" that allows remote access of wafer processing, or may be all or part of a fab host computer system. The computer may allow remote access to the system to monitor the progress of a manufacturing operation, examine the history of past manufacturing operations, examine trends or performance metrics from multiple manufacturing operations, modify parameters of a current process, set processing steps following a current process, or start a new process. In some examples, a remote computer (e.g., a server) may provide a process recipe to the system over a network that may include a local network or the Internet. The remote computer may include a user interface that allows entry or programming of parameters and / or settings that are then communicated from the remote computer to the system. In some examples, the controller 450 receives instructions in the form of data that specify parameters for each processing step to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process being performed and the type of tool that the controller 450 is configured to couple to or control. Thus, as described above, controller 450 may be distributed, for example by including one or more separate controllers networked together and cooperating towards a common purpose, such as a process or control as described herein. An example of a controller 450 distributed for such purposes would be one or more integrated circuits in a room that are located remotely (e.g., at the platform level or as part of a remote computer) and communicate with one or more integrated circuits that cooperate to control a process in the room.

[0063] As described above, depending on the processing steps being performed by the tool, the controller 450 may be in communication with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, nearby tools, tools installed throughout the factory, a main computer, another controller, or tools used to transport materials to and from tool locations and / or load ports in a semiconductor manufacturing factory.

[0064] In some embodiments, the controller 450 is configured with instructions to accelerate negative ions of the reactive species in the acceleration space 430 to the substrate 436 by introducing reactive species into the ionization space 420 and applying a positive bias to the substrate support 430, and to accelerate positive ions of the non-reactive species in the acceleration space 430 to the substrate 436 by introducing non-reactive species into the ionization space 420 and applying a negative bias to the substrate support 438. The controller 450 may further be configured with instructions to ignite a plasma in the plasma source 410 when accelerating the negative ions of the reactive species, and to extinguish a plasma in the plasma source 410 when accelerating the positive ions of the non-reactive species. The controller 450 may further be configured with instructions to extract electrons from the plasma into the ionization space 420 to ionize the reactive species and form negative ions of the reactive species in the ionization space 420 in association with the acceleration of the negative ions of the reactive species. This may occur by applying a positive bias to the substrate support 438. The controller 450 may further be configured with instructions to perform an operation associated with the acceleration of the non-reactive positive ions to cause diffusion of metastable species from the plasma into the ionization volume 420 to ionize the non-reactive species and form the non-reactive positive ions in the ionization volume 420. This may occur by applying a negative bias to the substrate support 438. The controller 450 may further be configured with instructions to perform an operation associated with the acceleration of the reactive negative ions to form a reactive layer on the material layer of the substrate 436, and an operation associated with the acceleration of the non-reactive positive ions to etch the material layer of the substrate 436, including a dielectric material or a conductive material. The controller 450 may further be configured with instructions to perform an operation of alternating between accelerating the reactive negative ions and accelerating the non-reactive positive ions.

[0065] FIG. 4B is a schematic diagram of an exemplary plasma etching apparatus divided by a single grid, which generates an inductively coupled plasma according to some embodiments and provides alternating ion beams of positive and negative ions for etching. The embodiment of the plasma etching apparatus 400b of FIG. 4B may be the same as the plasma etching apparatus 400a of FIG. 4A, except that the second grid is not present in the plasma etching apparatus 400b. Thus, the ionization space 420 and the acceleration space 430 occupy a combined volume and are not separated by a physical structure. The pressures in the ionization space 420 and the acceleration space 430 may be the same. Ions are efficiently generated and accelerated within the same combined volume of the plasma etching apparatus 400b.

[0066] FIG. 4C is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids, which generates an inductively coupled plasma at a remote plasma source and provides an alternating ion beam of positive and negative ions for etching, according to some embodiments. The plasma etching apparatus 400c of FIG. 4C may be the same as the plasma etching apparatus 400a of FIG. 4A, except that the plasma generation source 410 is coupled to a remote inductive source 472 of the plasma etching apparatus 400c. RF current from an RF generator 476 may be applied to a coil 474 to form an RF electric field at the remote inductive source 472, forming a downstream plasma at the plasma generation source 410. An inductively coupled remote plasma reactor can generate a higher density plasma than a capacitively coupled plasma reactor. Thus, an inductively coupled remote plasma reactor may be used to increase the electron density and metastable species density. This may be the same for a capacitively coupled remote plasma reactor versus a capacitively coupled plasma reactor. In some embodiments, the plasma etching apparatus 400c may include a single grid instead of two or more grids.

[0067] FIG. 4D is a schematic diagram of an exemplary plasma etching apparatus divided by at least two grids to generate a capacitively coupled plasma and provide alternating ion beams of positive and negative ions for etching according to some embodiments. The aspects of the plasma etching apparatus 400d of FIG. 4D may be the same as the plasma etching apparatus 400a of FIG. 4A, except that the plasma generation source 410 is a capacitively coupled plasma reactor in the plasma etching apparatus 400d. RF power may be provided from an RF generator 416 to an electrode 418 to generate a plasma in the plasma generation source 410. The first grid 424 may be biased or grounded, and a plasma may be formed between the electrode 418 and the first grid 424 in the capacitively coupled plasma reactor. In some embodiments, the plasma etching apparatus 400d may include a single grid rather than two or more grids. It will also be appreciated that the plasma etching apparatus 400a-400d of Figures 4A-4D may use any number of grids and may use any suitable plasma generation technology, such as CCP technology, ICP technology, electron cyclotron technology, or microwave technology.

[0068] FIG. 5 illustrates a flow diagram of an exemplary method of plasma etching using alternating ion beams of positive and negative ions, according to some embodiments. The operations of process 500 of FIG. 5 may include additional, fewer, or different operations. The description of process 500 of FIG. 5 is accompanied by a series of simplified cross-sectional views illustrating a modification operation of FIG. 6A and a removal operation of FIG. 6B. FIGS. 6A and 6B illustrate schematic diagrams of an exemplary plasma etching process that alternates between the modification operation of FIG. 6A and the removal operation of FIG. 6B, according to some embodiments. The operations of process 500 may be performed using a plasma etching apparatus, such as one of plasma etching apparatuses 400a-400d of FIGS. 4A-4D.

[0069] In block 510 of the process 500, reactive and non-reactive species are introduced into the ionization space. The reactive and non-reactive species may flow directly into the ionization space of the plasma etcher in the gas phase. The ionization space may be a separate volume from the plasma source, and a first grid may separate the ionization space from the plasma source. The ionization space may be downstream of the plasma source. The first grid may comprise a conductive plate having a plurality of openings or holes through which the ions, electrons, and neutral species of the noble gas may pass. The reactive species may include an electronegative reactive gas species, such as a halogen, a perfluorocarbon, a hydrofluorocarbon, or oxygen. For example, the reactive species includes C4F8. The non-reactive species may include an inert gas, such as helium, argon, xenon, or krypton. The non-reactive species may be different from the noble gas provided to the plasma source. In some embodiments, the reactive and non-reactive species may be introduced continuously throughout the process 500 or during a particular period of the process 500. In some embodiments, the reactive and non-reactive species may be introduced in separate pulses during process 500. For example, either or both of the reactive and non-reactive species may be introduced in a first stage of process 500, and either or both of the reactive and non-reactive species may be introduced in a second stage of process 500.

[0070] The first stage comprises a modification stage and may include at least blocks 520 and 530 of process 500. In some embodiments, the first stage further comprises block 510. The second stage comprises a removal stage and may include at least blocks 540 and 550 of process 500. In some embodiments, the second stage further comprises block 510.

[0071] In block 520 of process 500, a plasma of a noble gas is ignited in a plasma source. In some embodiments, the noble gas is introduced into the plasma source prior to or during block 520. The noble gas may include helium, argon, xenon, or krypton. For example, the noble gas includes helium. The plasma of the noble gas may include a mixture of ions, electrons, and neutral species of the noble gas. In some embodiments, the plasma source may be a CCP reactor or an ICP reactor. During the plasma ignition in block 520, the plasma is turned on.

[0072] In block 530 of process 500, a positive bias is applied to the substrate support to extract electrons from the plasma source and accelerate negative ions of the reactive species to the substrate. The substrate may be supported on the substrate support in an acceleration space, which may represent a volume integrated with or separated from the ionization space in a plasma etching apparatus. The acceleration space may be downstream of the ionization space. The substrate may comprise a layer of material to be etched, which may include a dielectric material or a conductive material. In some embodiments, the substrate may comprise a plurality of high aspect ratio features having a depth:width aspect ratio of at least 10:1, at least 20:1, at least 50:1, or at least 100:1.

[0073] Electrons may be extracted from the plasma in the plasma source through a first grid. In some embodiments, the first grid may be electrically grounded and a substrate support external to the plasma source is positively biased to extract electrons through the first grid. In some embodiments, the first grid may be negatively biased and a substrate support external to the plasma source is positively biased to extract electrons through the first grid. Electrons are extracted from the plasma as a result of an electric field established between the positively biased substrate support and the grounded or negatively biased grid. The electrons are extracted while the plasma is turned on. Without being limited by theory, the extracted electrons may collide with reactive species to form negative ions of the reactive species by electron attachment ionization. The ions of the reactive species are not dissociated. The electrons are extracted with an energy that causes electron attachment ionization by reactive species but not non-reactive species. For example, electrons are extracted with an energy of about 1 eV to about 5 eV for electron attachment of C4F8 to form negative ions of C4F8. - In some embodiments, the positive bias applied to the substrate support is from about 0.5V to about 10V, or from about 1V to about 5V.

[0074] As negative ions of reactive species are formed by electron attachment ionization, a positive bias applied to the substrate support causes acceleration of the negative ions to the substrate. The negative ions of reactive species are accelerated to the substrate to limit or prevent sputtering at the substrate surface. Specifically, the positive bias applied to the substrate support may be maintained at about 0.5 V to about 10 V, or about 1 V to about 5 V. By applying a small positive bias, the accelerating negative ions can modify or activate the substrate surface instead of sputtering atoms / molecules from the substrate surface. In some embodiments, the accelerating negative ions adsorb to the substrate surface to form a reactive layer for etching. A material layer on the substrate may be converted to a reactive layer, and the reactive layer may be etched during the removal phase of the process 500.

[0075] The operations of blocks 520 and 530 of the reformulation stage may be performed simultaneously or sequentially. The operation of block 510 may be performed before or during the operations of blocks 520 and 530.

[0076] FIG. 6A shows a schematic diagram of an exemplary plasma etching apparatus during a modification stage of an etching process. Such a modification stage may include the operations of blocks 510, 520, and 530 of process 500 of FIG. 5. Helium gas is provided to a plasma generation source, such as a CCP reactor. Although the plasma generation source is shown as a CCP reactor, it will be understood that the plasma generation source may be any suitable plasma reactor. A helium plasma is generated by the plasma generation source. A positive DC voltage is applied to a substrate support on which a substrate is supported. A positive bias causes electrons to be extracted through a grid between the plasma generation source and the ionization space. A reactive gas, such as C4F8, and a non-reactive gas, such as Ar, are introduced into the ionization space. The extracted electrons cause ionization without dissociation of the reactive gas to form negative ions of the reactive gas. As shown in FIG. 6A, C4F8 is ionized by electron attachment ionization to produce C4F8. - The negative ions of the reactive gas are accelerated to the substrate by the positive bias to activate or modify the substrate surface. - may form a reactive layer on the substrate surface. Although a single grid is shown in the plasma etching apparatus, it will be understood that the plasma etching apparatus may be provided with a second grid to divide the ionization space between an ionization space where ionization occurs and an acceleration space where the substrate is placed. Thus, the modification stage of the etching process may include turning on the plasma to ignite the plasma, applying a positive bias to the substrate support, extracting electrons from the plasma, ionizing reactive species to form negative ions of the reactive species, and accelerating the negative ions to the substrate to modify the substrate surface.

[0077] Returning to FIG. 5, in block 540 of process 500, the plasma is extinguished in the plasma source. No RF power is applied to the plasma source to ignite or maintain the plasma. That is, the plasma is turned off. Charged species of the noble gas are not generated without a plasma discharge. However, metastable species, such as metastable neutral species of the noble gas, may remain in the plasma source even after the plasma is turned off. The metastable species of the noble gas may have a long enough lifetime to diffuse through the first grid into the ionization space. Specifically, the metastable species of the noble gas may diffuse into the ionization space during the afterglow.

[0078] Metastable species that diffuse into the ionization space after the plasma is turned off may collide with non-reactive species to form positive ions of the non-reactive species. The metastable species may be in an excited state. Without being limited by theory, the excited state metastable species may cause Penning ionization by the non-reactive species but not by the reactive species. For example, an excited state metastable helium radical (He * ) may have a lifetime of several seconds and an energy of several eV. This lifetime is long enough for collisions to occur before the decay, and the metastable helium radical has enough excited-state energy to ionize an inert gas species such as Ar. The metastable helium radical can ionize Ar to produce Ar + may be formed.

[0079] In block 550 of the process 500, a negative bias is applied to the substrate support to accelerate positive ions of non-reactive species to the substrate. Since the positive ions of the inert gas species are formed by Penning ionization, the negative bias applied to the substrate support causes the acceleration of the positive ions to the substrate. The non-reactive positive ions are accelerated to the substrate to promote ion bombardment and chemically enhanced sputtering at the substrate surface. The positive ions may impinge and penetrate the substrate surface with energies of about 1000 eV to about 50000 eV. In some embodiments, the negative bias applied to the substrate support may be about -50 kV to about -1 kV, or about -10 kV to about -1 kV. By applying a large negative bias, the accelerated positive ions can etch the material formed on the substrate surface. In some embodiments, the accelerated positive ions mix with the reactive layer such that the reactive layer is etched.

[0080] The operations of blocks 540 and 550 of the removal stage may be performed simultaneously or sequentially. The operation of block 510 may be performed before or during the operations of blocks 540 and 550.

[0081] FIG. 6B illustrates a schematic diagram of an exemplary plasma etching apparatus during a removal phase of the etching process. Such a removal phase may include the operations of blocks 510, 540, and 550 of process 500 of FIG. 5. No power is applied to the plasma generation source such that the plasma in the plasma generation source is extinguished. The helium plasma is turned off, leaving only metastable helium radicals in the plasma afterglow. The metastable helium radicals may be in an excited state and may diffuse through the grid. A reactive gas, such as C4F8, and a non-reactive gas, such as Ar, are introduced into the ionization space. The extracted metastable helium radicals cause ionization of the non-reactive gas to form positive ions of the non-reactive gas. As shown in FIG. 6B, Ar is ionized by Penning ionization to form Ar +A negative DC voltage is applied to the substrate support on which the substrate is supported. The negative bias accelerates positive ions of a non-reactive gas, e.g. Ar, to the substrate in order to remove the reactive layer on the substrate surface by chemically enhanced sputtering. + is the C4F8 adsorbed on the substrate surface. - Thus, the removal phase of the etching process may include turning off the plasma to extinguish the plasma, applying a negative bias to the substrate support, extracting metastable neutral species, ionizing the non-reactive species to form positive ions of the non-reactive species, and accelerating the positive ions to the substrate to etch material from the substrate surface.

[0082] Returning to FIG. 5, the process 500 may further include alternating between the modification phase at blocks 520 and 530 and the removal phase at blocks 540 and 550. The modification phase and the removal phase may be continuously alternating to complete the process 500 for plasma etching. In some embodiments, the modification phase and the removal phase may be continuously alternating to complete the process 500 for plasma etching high aspect ratio features on a substrate. The process 500 may alternate between electron attachment ionization in the modification phase and Penning ionization in the removal phase. The process 500 may also alternate between accelerating fast neutral species at low energy in the modification phase and accelerating positive ions at high energy in the removal phase. The process 500 may also alternate between plasma on in the modification phase and plasma off in the removal phase.

[0083] FIG. 7 illustrates an exemplary timing sequence diagram of the applied power to the plasma source and the applied voltage to the substrate support in a plasma etching process alternating between modification and removal operations according to some embodiments. The modification and removal operations may constitute an etching cycle. In some embodiments, the etching cycle may last from about 1 ms to about 50 ms. The duration of the modification operation may be from about 1 ms to about 10 ms, and the duration of the removal operation may be from about 1 ms to about 10 ms. The modification operation and its duration may occur in conjunction with the acceleration of negative ions of reactive species or in conjunction with the application of a positive bias to the substrate support. The removal operation and its duration may occur in conjunction with the acceleration of positive ions of non-reactive species or in conjunction with the application of a negative bias to the substrate support.

[0084] As shown in Figure 7, during a modification operation, power is applied to the plasma source and the substrate support is slightly biased with a positive DC voltage. The positive DC voltage may be about 1 V to about 5 V. As shown in Figure 7, during a removal operation, no power is applied to the plasma source and the substrate support is substantially biased with a negative DC voltage. The negative DC voltage may be about -50 kV to -1 kV. The controller may be configured to provide instructions for the applied power to the plasma source and the applied voltage to the substrate support when alternating between the modification and removal operations.

[0085] The plasma etching apparatus of the present disclosure provides an alternating ion beam of reactive negative ions and non-reactive positive ions for plasma etching. The fast neutral species may modify the substrate surface by DC acceleration at low energy, and the positive ions may etch material from the substrate surface by DC acceleration at high energy. The fast neutral species are provided with a narrow IEDF and narrow IADF. Acceleration of positive and negative ions occurs separately by DC acceleration, instead of sheath acceleration by RF bias in conventional plasma etching reactors that results in a wide IEDF and wide IADF. The present disclosure can separate ion flux and neutral flux by separating high energy positive ions and low energy negative ions, instead of mixed mode pulsing in conventional plasma etching reactors to balance the ion / neutral flux ratio. While conventional plasma etching reactors ionize by electron impact ionization, the present disclosure can achieve selective ionization by selecting between electron attachment ionization to form negative ions and Penning ionization to form positive ions. Fast neutral species with low energy and narrow IADF may be generated by electron attachment ionization, which avoids very slow diffusion of neutral species to the bottom of high aspect ratio features. Additionally, alternating ion beams of positive and negative ions avoid charge build-up on the mask. Separating the plasma generation region from the etching region by one or more grids also avoids redeposition of etching by-products and prevents backflow of etching by-products into the plasma generation region. Additionally, dielectric and conductor etching may be performed by the plasma etching apparatus of the present disclosure, regardless of whether the plasma reactor is a CCP reactor or an ICP reactor. ·Conclusion

[0086] In the foregoing description, several specific details have been set forth to provide a thorough understanding of the present embodiments. The embodiments of the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail so as not to unnecessarily obscure the embodiments of the present disclosure. While the embodiments of the present disclosure will be described in conjunction with specific embodiments, it will be understood that they are not intended to limit the embodiments of the present disclosure.

[0087] Although the foregoing embodiments have been described in some detail for clarity of understanding, it will be apparent that certain changes and modifications may be implemented within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Thus, the present embodiments should be considered as illustrative rather than restrictive, and are not limited to the details described herein. The present disclosure may be realized in the following forms. [Form 1] 1. A plasma etching apparatus comprising: A plasma generating source; an ionization space coupled to the plasma generation source and configured to generate ions; a first grid between the ionization space and the plasma generation source; an acceleration space coupled to the ionization space and configured to supply the ions to a substrate therein; a substrate support for supporting the substrate in the acceleration space, the substrate support being configured to be biased; A controller, an operation of introducing a reactive species into the ionization space and accelerating negative ions of the reactive species toward the substrate in the acceleration space by applying a positive bias to the substrate support; a controller configured with instructions to perform the operations of introducing a non-reactive species into the ionization space and accelerating positive ions of the non-reactive species in the acceleration space toward the substrate by applying a negative bias to the substrate support; and A plasma etching apparatus comprising: [Form 2] 2. The plasma etching apparatus according to claim 1, The negative bias is substantially greater in absolute value than the positive bias. [Form 3] 3. The plasma etching apparatus according to claim 2, The positive bias is from about 0.5V to about 10V, and the negative bias is from about -50kV to about -1kV. [Form 4] 2. The plasma etching apparatus according to claim 1, The controller further comprises: forming a reaction layer on a material layer of the substrate in association with accelerating the negative ions of the reactive species; an operation of etching the material layer of the substrate in association with accelerating the positive ions of the non-reactive species, the material layer comprising a dielectric material or a conductive material; A plasma etching apparatus configured with instructions for performing the steps of: [Form 5] 2. The plasma etching apparatus according to claim 1, The controller further comprises: igniting a plasma in the plasma source when accelerating the negative ions of the reactive species; extinguishing a plasma in the plasma source when accelerating the positive ions of the non-reactive species; A plasma etching apparatus configured with instructions for performing the steps of: [Form 6] 6. The plasma etching apparatus according to claim 5, The controller further comprises: A plasma etching apparatus, comprising instructions configured to perform an operation of extracting electrons from the plasma into the ionization space to ionize the reactive species in association with the acceleration of the negative ions of the reactive species, and an operation of forming the negative ions of the reactive species in the ionization space. [Form 7] 6. The plasma etching apparatus according to claim 5, The controller further comprises: A plasma etching apparatus, comprising instructions configured to perform an operation of causing diffusion of metastable species from the plasma into the ionization space to ionize the non-reactive species in association with acceleration of the positive ions of the non-reactive species, and an operation of forming the positive ions of the non-reactive species in the ionization space. [Form 8] 2. The plasma etching apparatus according to claim 1, The first grid is configured to be biased or grounded, and the controller further comprises: forming a weak electric field between the first grid and the substrate support in association with accelerating the negative ions; and forming a strong electric field between the first grid and the substrate support in conjunction with accelerating the positive ions. [Form 9] A plasma etching apparatus according to any one of aspects 1 to 8, The substrate includes a plurality of high aspect ratio features having a depth-to-width aspect ratio of at least 10:1. [Form 10] The plasma etching apparatus according to any one of aspects 1 to 8, further comprising: A plasma etching apparatus comprising: a second grid between the ionization space and the acceleration space. [Form 11] 11. The plasma etching apparatus according to claim 10, A plasma etching apparatus, wherein a pressure in the ionization space is greater than a pressure in the acceleration space. [Form 12] 11. The plasma etching apparatus according to claim 10, The second grid is configured to be biased. [Form 13] A plasma etching apparatus according to any one of aspects 1 to 8, The plasma etching apparatus, wherein the plasma generation source is an inductively coupled plasma (ICP) reactor or a capacitively coupled plasma (CCP) reactor. [Form 14] A plasma etching apparatus according to any one of aspects 1 to 8, The controller is further configured with instructions to perform an operation of alternating between accelerating the negative ions of the reactive species and accelerating the positive ions of the non-reactive species. [Form 15] A plasma etching apparatus according to any one of aspects 1 to 8, The controller further comprises: accelerating the negative ions of the reactive species for a first duration of about 1 ms to about 10 ms associated with accelerating the negative ions of the reactive species; accelerating the positive ions of the non-reactive species for a second duration of about 1 ms to about 10 ms associated with accelerating the positive ions of the non-reactive species; A plasma etching apparatus configured with instructions for performing the steps of: [Form 16] 1. A plasma etching apparatus comprising: A plasma generating source; an ionization space coupled to the plasma generation source and configured to generate ions; a first grid between the ionization space and the plasma generation source; an acceleration space coupled to the ionization space and configured to supply the ions to a substrate therein; a substrate support configured to be biased and for supporting the substrate in the acceleration space; A controller, An operation of introducing reactive and non-reactive species into the ionization space; igniting a plasma in the plasma source; applying a positive bias to the substrate support to ionize the reactive species to form negative ions of the reactive species, and accelerating the negative ions of the reactive species to the substrate when the plasma is ignited; an operation of extinguishing the plasma in the plasma generation source; applying a negative bias to the substrate support to ionize the non-reactive species to form positive ions of the non-reactive species, and accelerating the positive ions of the non-reactive species to the substrate when the plasma is extinguished; a controller configured with instructions to perform the A plasma etching apparatus comprising: [Form 17] 17. The plasma etching apparatus according to claim 16, The positive bias is from about 0.5V to about 10V, and the negative bias is from about -50kV to about -1kV. [Form 18] The plasma etching apparatus according to claim 16, further comprising: a second grid between the ionization space and the acceleration space; the first grid is configured to be biased and the second grid is configured to be biased; A plasma etching apparatus, wherein a pressure in the ionization space is greater than a pressure in the acceleration space. [Form 19] 19. The plasma etching apparatus of any one of aspects 16 to 18, The plasma etching apparatus, wherein the plasma generation source is an inductively coupled plasma (ICP) reactor or a capacitively coupled plasma (CCP) reactor. [Form 20] 19. The plasma etching apparatus of any one of aspects 16 to 18, the controller is further configured with instructions to perform an alternating operation between applying the positive bias to the substrate support when the plasma is ignited and applying the negative bias to the substrate support when the plasma is extinguished.

Claims

1. 1. A plasma etching apparatus comprising: a plasma source configured to ignite or extinguish a plasma of a rare gas therein; an ionization space coupled to the plasma generation source, the ionization space being coupled to one or more gas sources configured to supply reactive and non-reactive gases to the ionization space, the ionization space being configured to form negative ions of the reactive gases and positive ions of the non-reactive gases; a first grid between the ionization space and the plasma generation source; an acceleration space coupled to the ionization space and configured to supply the negative ions of the reactive gas and the positive ions of the non-reactive gas to a substrate therein; a second grid between the ionization space and the acceleration space; a substrate support for supporting the substrate in the acceleration space, the substrate support being configured to be positively biased or negatively biased; A plasma etching apparatus comprising:

2. 2. The plasma etching apparatus of claim 1, The ionization space is configured to form the negative ions of the reactive gas in response to the substrate support being positively biased.

3. 3. The plasma etching apparatus according to claim 2, The ionization space is configured to form the positive ions of the non-reactive gas in response to the plasma of the rare gas being extinguished at the plasma generation source.

4. 4. The plasma etching apparatus according to claim 3, a first ion generating section configured to generate a first ion of the reactive gas toward the substrate in response to the substrate support being positively biased, and a second ion generating section configured to generate a second ion of the reactive gas toward the substrate in response to the substrate support being negatively biased.

5. 2. The plasma etching apparatus of claim 1, A plasma etching apparatus, wherein a noble gas source is coupled to the plasma generation source and configured to supply the noble gas to the plasma generation source, the noble gas being different from the non-reactive gas.

6. 2. The plasma etching apparatus of claim 1, The first grid comprises a conductive plate having a plurality of holes and is configured to be biased.

7. 2. The plasma etching apparatus of claim 1, The second grid comprises a conductive plate having a plurality of holes and is configured to be biased.

8. 2. The plasma etching apparatus of claim 1, further comprising: A controller, modifying a material layer of the substrate using the negative ions of the reactive gas; etching the material layer of the substrate with the positive ions of the non-reactive gas; A plasma etching apparatus comprising a controller configured with instructions to perform the steps of:

9. 1. A plasma etching apparatus comprising: A plasma generating source; an ionization space coupled to the plasma generation source and configured to generate ions; a first grid between the ionization space and the plasma generation source; an acceleration space coupled to the ionization space and configured to supply the ions to a substrate therein; a substrate support configured to be biased and for supporting the substrate in the acceleration space; A controller, directing negative ions of a reactive gas at the substrate in the acceleration space to modify a material layer on the substrate; directing positive ions of a non-reactive gas at the substrate in the acceleration space to etch the material layer of the substrate; a controller configured with instructions to perform the one or more gas sources coupled to the ionization volume, the one or more gas sources configured to supply reactive and non-reactive gases to the ionization volume; A plasma etching apparatus comprising:

10. 10. The plasma etching apparatus of claim 9, The controller further comprises: applying a positive bias to the substrate support, the negative ions of the reactive gas being directed toward the substrate in response to applying the positive bias; applying a negative bias to the substrate support, the positive ions of the non-reactive gas being directed toward the substrate in response to applying the negative bias; A plasma etching apparatus configured with instructions for performing the steps of:

11. 11. The plasma etching apparatus of claim 10, The controller further comprises: an operation of igniting a plasma in the plasma generation source, the negative ions of the reactive gas being formed in the ionization space when the plasma is ignited; an operation of extinguishing a plasma in the plasma generation source, the positive ions of the non-reactive gas being formed in the ionization space when the plasma is extinguished; An order is framed to implement Plasma etching equipment.

12. 11. The plasma etching apparatus of claim 10, The negative bias is substantially greater in absolute value than the positive bias.

13. 10. The plasma etching apparatus of claim 9, further comprising: A plasma etching apparatus comprising: a second grid between the ionization space and the acceleration space.

14. 1. A method of etching a layer of material on a substrate, comprising: introducing reactive and non-reactive species; applying a positive bias to a substrate support to direct negative ions of the reactive species at a substrate disposed on the substrate support to modify the material layer of the substrate; applying a negative bias to the substrate support to accelerate positive ions of the non-reactive species onto the substrate to etch the layer of material of the substrate; igniting a plasma of a rare gas in a plasma generation space prior to applying the positive bias to the substrate support; extinguishing the plasma of the noble gas after applying the positive bias to the substrate support and before applying the negative bias to the substrate support; A method comprising:

15. 15. The method of claim 14, The method, wherein introducing the reactive species and the non-reactive species comprises introducing the reactive species and the non-reactive species into an ionization space coupled to the plasma generation space.

16. 16. The method of claim 15, The method of claim 1, wherein applying the positive bias to the substrate support comprises accelerating the negative ions of the reactive species to the substrate in an acceleration space coupled to the ionization space, and applying the negative bias to the substrate support comprises accelerating the positive ions of the non-reactive species to the substrate in the acceleration space.

17. 15. The method of claim 14, The method of claim 1, wherein applying the positive bias to the substrate support comprises extracting electrons from the plasma of the noble gas to form the negative ions of the reactive species.

18. 15. The method of claim 14, The method of claim 1, wherein applying the negative bias to the substrate comprises causing diffusion of metastable species from the plasma of the noble gas to form the positive ions of the non-reactive species.

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