High-Energy Atomic Layer Etching

Abstract

To provide a method and an apparatus for processing a substrate for performing high energy atomic layer etching.SOLUTION: A method includes the steps of providing a substrate having material to be etched, exposing the surface of the material to a modifying gas to modify the surface and form a modified surface, and exposing the modified surface to energetic particles to preferentially remove the modified surface relative to an underlying unmodified surface. The energetic particle has ion energy sufficient to overcome an average surface binding energy of the underlying unmodified surface. The energy of the energetic particles used is very high in some cases, and the power applied to a bias used when exposing the modified surface to the energetic particles is at least 150 eV.SELECTED DRAWING: Figure 3B

Description

Technical Field

[0001] (Cross - Reference to Related Applications) This application claims the benefit of U.S. Non - Provisional Application No. 16 / 148,939, filed on October 1, 2018, entitled "HIGH ENERGY ATOMIC LAYER ETCHING", which claims priority to both U.S. Provisional Patent Application No. 62 / 569,443, filed on October 6, 2017, entitled "PULSING ATOMIC LAYER ETCHING", and U.S. Provisional Patent Application No. 62 / 599,613, filed on December 15, 2017, entitled "HIGH ENERGY ATOMIC LAYER ETCHING", which are hereby incorporated by reference in their entireties for all purposes as if fully set forth herein.

Background Art

[0002] Semiconductor fabrication processes include steps of etching various materials. As the three - dimensional structures shrink towards nodes less than 10 nm, conventional etching processes face unprecedented challenges. For example, pitch loading becomes a problem when the etching rate is affected by the increasing aspect ratio. Challenges related to the transport of neutral species and ions to the etching front, the surface reaction rate at each etching front, and the removal of etching products from the etching front become prominent as the device shrinks.

Summary of the Invention

[0003] This specification provides methods and apparatuses for performing high-energy atomic layer etching. One aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface, and exposing the modified surface to energy particles to preferentially remove the modified surface relative to an underlying unmodified surface, the energy particles having an ion energy sufficient to overcome the average surface bond energy of the underlying unmodified surface.

[0004] In various embodiments, the ion energy of the energy particles is sufficient to break the bonds of the underlying unmodified surface. The energy particles may be delivered in temporally separated doses having a duty cycle between about 1% and about 10%.

[0005] In various embodiments, a bias voltage is applied to a substrate support holding the substrate while the modified surface is exposed to the energy particles.

[0006] In some embodiments, the energy particles remove an amount of the modified surface, and the amount of the modified surface removed is given by the following equation:

Equation

[0007] In various embodiments, the energy particles do not significantly sputter the underlying unmodified material. For example, the modified surface may be exposed to the energy particles for a duration sufficient to remove the modified surface in a self-limiting manner.

[0008] Another aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and applying a bias while exposing the modified surface to energy particles to remove the modified surface, wherein the power applied to the bias is at least 150 eV.

[0009] In various embodiments, the power applied to the bias is at least 500 eV.

[0010] Another aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and delivering a dose of energy particles to the modified surface to remove the modified surface, wherein the dose is insufficient to remove the modified surface when delivered using a bias voltage less than the surface binding energy of the underlying unmodified surface.

[0011] Another aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and exposing the modified surface to energy particles and preferentially removing at least 80% of the modified surface relative to the underlying unmodified surface for a duration longer than a duration sufficient to remove the modified surface and the underlying unmodified surface by ion bombardment.

[0012] Another aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and exposing the modified surface to energy particles in the form of pulses having a duty cycle of less than 100%.

[0013] Another aspect involves a method of processing a substrate, the method including providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and exposing the modified surface to energy particles having a reduced dose of irradiation, such that the dose of irradiation without attenuation has an energy greater than the surface binding energy of the material to be etched when continuously delivered to the modified surface.

[0014] In various embodiments, the dose of irradiation is attenuated by varying the ion flux of the active species.

[0015] In some embodiments, the dose of irradiation is attenuated by varying the duration of exposure of the modified surface to the active species.

[0016] In various embodiments, the reduced dose of irradiation includes two or more temporally separated pulses of the active species reaching the modified surface to remove at least a portion of the modified surface.

[0017] In some embodiments, the dose of irradiation is attenuated by varying the ion acceleration of the active species reaching the modified surface.

[0018] In various embodiments, the dose of irradiation is attenuated by varying a bias voltage applied to a substrate support holding the substrate to deliver the active species to the modified surface in a specific direction.

[0019] Another aspect involves a method of processing a substrate. The method includes providing a substrate including a material to be etched, exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, exposing the modified surface to energy particles in the form of pulses that are temporally separated, and modulating the ion energy and dose between the temporally separated pulses. In some embodiments, the step of modulating the ion energy and dose includes increasing the ion energy and compensating for the increase in ion energy with a reduced dose.

[0020] Another aspect involves a method of processing a substrate. The method includes exposing the substrate to a modifying gas to modify a surface of the substrate and form a modified surface, exposing the modified surface of the substrate to a removal gas, and providing a plurality of temporally separated pulses of energy generated from an activation source while exposing the modified surface to the removal gas to remove at least a portion of the modified surface from the substrate.

[0021] In some embodiments, the method also includes repeating the steps of exposing the substrate to the modifying gas and exposing the modified surface to the removal gas in two or more cycles, such that in each cycle, a plurality of temporally separated pulses of energy are provided while exposing the modified surface to the removal gas.

[0022] In various embodiments, the plurality of temporally separated pulses of energy includes at least 100 temporally separated pulses of energy per cycle.

[0023] In various embodiments, the temporally separated pulses of energy are sufficient to remove the modified surface and insufficient to physically sputter the modified surface.

[0024] In various embodiments, the energy provided is defined by a bias window that consists of a minimum voltage applied to the substrate while exposing it to a removal gas sufficient to remove the modified surface, and a maximum voltage applied to the substrate while exposing it to a removal gas insufficient to sputter the modified surface.

[0025] In various embodiments, a plurality of temporally separated energy pulses are pulsed between about 10 Hz and about 200 Hz.

[0026] In various embodiments, a plurality of temporally separated energy pulses are pulsed with a duty cycle between about 1% and about 10%.

[0027] In some embodiments, the activation source includes two or more supply sources.

[0028] In some embodiments, the activation source is selected from the group consisting of radio frequency plasma, a bias applied to the substrate, ultraviolet radiation, photons, and combinations thereof.

[0029] In some embodiments, the activation source includes a voltage applied to bias the substrate. The bias voltage may be between at least about 500 V and about 1500 V. The bias may be pulsed between 0 V and a bias voltage between about 500 V and about 1500 V.

[0030] In some embodiments, the bias is pulsed between a low bias voltage between about 100 V and about 300 V and a high bias voltage between about 500 V and about 1500 V.

[0031] In some embodiments, the bias is pulsed using a pulsing frequency between about 10 Hz and about 200 Hz.

[0032] In some embodiments, the bias is pulsed using a duty cycle between about 1% and about 20%.

[0033] In some embodiments, the activation source includes a radio frequency plasma.

[0034] In some embodiments, radio frequency plasma is generated by applying power and applying a pulsed radio frequency plasma power between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

[0035] In some embodiments, the radio frequency plasma generated by applying power and radio frequency plasma power is pulsed between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W and the high plasma power being between about 900 W and about 1500 W.

[0036] In some embodiments, a pulsed frequency between about 10 Hz and about 200 Hz is used to pulse the radio frequency plasma.

[0037] In some embodiments, the duty cycle of the radio frequency plasma pulsing is between about 1% and about 20%.

[0038] As a result, in some embodiments, the activation source includes a radio frequency plasma and a bias applied to the substrate. The bias may be pulsed between 0 V and a bias voltage between about 500 V and about 1500 V. The bias may be pulsed between a low bias voltage between about 100 V and about 300 V and a high bias voltage between about 500 V and about 1500 V. Radio frequency plasma may be generated by applying power and applying a pulsed radio frequency plasma power between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W. The radio frequency plasma may be pulsed between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W and the high plasma power being between about 900 W and about 1500 W.

[0039] In various embodiments, the substrate includes one or more narrow features and one or more wide features.

[0040] In some embodiments, the substrate is processed at a substrate temperature between about 0 °C and about 120 °C.

[0041] In some embodiments, while exposing the substrate to a modifying gas, the substrate is processed in a processing chamber having a chamber pressure between about 5 mTorr and about 1 Torr.

[0042] In some embodiments, while exposing the substrate to a removal gas, the substrate is processed in a processing chamber having a chamber pressure between about 5 mTorr and about 200 mTorr.

[0043] Another aspect involves a method of processing a substrate, the method including exposing the substrate to a modifying gas to modify a surface of the substrate to form a modified surface, exposing the modified surface of the substrate to a removal gas, and periodically igniting a plasma in the form of two or more temporally separated pulses while exposing the modified surface to the removal gas to remove at least a portion of the modified surface from the substrate.

[0044] The method also includes repeating the steps of exposing the substrate to the modifying gas and exposing the modified surface to the removal gas in two or more cycles, such that in each cycle, while exposing the modified surface to the removal gas, two or more temporally separated pulses of plasma are provided.

[0045] In some embodiments, the plurality of temporally separated pulses of plasma comprise at least 100 energy pulses per cycle.

[0046] The method may also include applying a bias in the form of pulses while exposing the modified surface to a removal gas. In some embodiments, the method also includes repeating the steps of exposing the substrate to a modification gas and exposing the modified surface to a removal gas in two or more cycles, such that in each cycle, while exposing the modified surface to the removal gas, two or more temporally separated pulses of plasma and bias are provided.

[0047] In some embodiments, the plurality of temporally separated pulses of plasma and bias comprise at least 100 pulses per cycle, and the cycle includes the step of exposing the substrate to a modification gas and the step of exposing the modified surface to a removal gas.

[0048] In some embodiments, the plasma and the bias are pulsed at the same frequency.

[0049] In some embodiments, the same duty cycle is used to pulse the plasma and the bias.

[0050] Another aspect involves a method of processing a substrate, the method including exposing the substrate to a modification gas to modify the surface of the substrate to form a modified surface, exposing the modified surface of the substrate to a removal gas, igniting a plasma while exposing the modified surface, and periodically applying a bias to the substrate in the form of two or more temporally separated pulses while exposing the modified surface to the removal gas to remove the modified surface from the substrate.

[0051] The method may also include igniting the plasma in the form of pulses while exposing the modified surface to the removal gas.

[0052] In some embodiments, the method includes repeating, in two or more cycles, the steps of exposing a substrate to a modifying gas and exposing the modified surface to a removal gas, such that, in each cycle, while exposing the modified surface to the removal gas, two or more temporally separated pulses of bias power are provided.

[0053] In some embodiments, the plurality of temporally separated pulses of bias power comprise at least 100 pulses per cycle, and the cycle includes the steps of exposing a substrate to a modifying gas and exposing the modified surface to a removal gas.

[0054] Another aspect involves an apparatus for processing a substrate, the apparatus including a processing chamber having a showerhead and a substrate support for holding a substrate having a material, a plasma generator, and a controller having at least one processor and a memory, such that the at least one processor and the memory are communicatively coupled to each other, the at least one processor is at least operably coupled to flow control hardware, and the memory stores machine-readable instructions for introducing a modifying gas into the processing chamber, introducing a removal gas into the processing chamber, and pulsing an activation source during introduction of the removal gas.

[0055] In some embodiments, the memory further stores machine-readable instructions for setting a pulse frequency of the activation source between about 10 Hz and about 200 Hz during introduction of the removal gas.

[0056] In some embodiments, the memory further stores machine-readable instructions for setting a duty cycle of the activation source between about 1% and about 10% during introduction of the removal gas.

[0057] In some embodiments, the activation source is a plasma generated within the processing chamber using plasma power, and the memory further stores machine-readable instructions for pulsing the activation source between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

[0058] In some embodiments, the activation source is a plasma generated within the processing chamber, and the memory further comprises machine-readable instructions for pulsing the activation source between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W, and the high plasma power being between about 900 W and about 1500 W.

[0059] As a result, in some embodiments, the memory further stores machine-readable instructions for applying a bias to the substrate support in the form of pulses. For example, the memory may also store machine-readable instructions for pulsing the bias between 0 V and a bias voltage between about 500 V and about 1500 V. In some embodiments, the memory further stores machine-readable instructions for pulsing the bias at the same pulsing frequency as the activation source. In some embodiments, the memory further stores machine-readable instructions for pulsing the bias at the same pulsing duty cycle as the activation source.

[0060] Another aspect may involve an apparatus for processing a substrate, the apparatus including a processing chamber including a showerhead and a substrate support for holding a substrate having a material, a plasma generator, and a controller having at least one processor and a memory, such that the at least one processor and the memory are communicatively coupled to each other, the at least one processor is at least operatively coupled to flow control hardware, and the memory stores machine-readable instructions for introducing a modifying gas into the processing chamber, introducing a removal gas into the processing chamber, and generating radio frequency plasma power within the processing chamber in the form of two or more temporally separated pulses during introduction of the removal gas.

[0061] In some embodiments, the memory further stores machine-readable instructions for setting the pulse frequency of the radio frequency plasma power between about 10 Hz and about 200 Hz during introduction of the removal gas.

[0062] In some embodiments, the memory further stores machine-readable instructions for causing the duty cycle of the radio frequency plasma power to be between about 1% and about 10% during the introduction of the scavenging gas.

[0063] In some embodiments, the memory further stores machine-readable instructions for pulsing the radio frequency plasma power between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

[0064] In some embodiments, the memory further stores machine-readable instructions for pulsing the radio frequency plasma power between a low plasma power and a high plasma power, where the low plasma power is between about 10 W and about 100 W and the high plasma power is between about 900 W and about 1500 W.

[0065] In some embodiments, the memory further stores machine-readable instructions for applying a bias to the substrate support in the form of a pulse.

[0066] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias between 0 V and a bias voltage between about 500 V and about 1500 V.

[0067] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias between a low bias voltage between about 100 V and about 300 V and a high bias voltage between about 500 V and about 1500 V.

[0068] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias at the same pulse frequency as the radio frequency plasma power.

[0069] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias at the same pulse duty cycle as the radio frequency plasma power.

[0070] Another aspect involves an apparatus for processing a substrate. The apparatus includes a processing chamber with a showerhead and a substrate support for holding a substrate having a material, a plasma generator, and a controller having at least one processor and a memory. As a result, the at least one processor and the memory are communicatively connected to each other, the at least one processor is at least operably connected to flow control hardware, and the memory stores machine-readable instructions for introducing a reforming gas into the processing chamber, introducing a removal gas into the processing chamber, and applying bias power to the substrate support in the form of pulses to the substrate during the introduction of the removal gas at two or more temporally separated times.

[0071] In some embodiments, the memory further stores machine-readable instructions for causing the pulse frequency of the bias power to be between about 10 Hz and about 200 Hz during the introduction of the removal gas.

[0072] In some embodiments, the memory further stores machine-readable instructions for causing the duty cycle of the bias power to be between about 1% and about 10% during the introduction of the removal gas.

[0073] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias power between an off state where the bias power is 0 V and an on state where the bias power is between about 500 V and about 1500 V.

[0074] In some embodiments, the memory further stores machine-readable instructions for pulsing the bias power between a low bias power and a high bias power, where the low bias power is between about 100 V and about 300 V and the high bias power is between about 500 V and about 1500 V.

[0075] In some embodiments, the memory further stores machine-readable instructions for igniting the plasma by applying plasma power in the form of pulses during the introduction of the removal gas.

[0076] In some embodiments, the memory further stores machine-readable instructions for pulsing the plasma power between 0W and a plasma voltage between about 50W and about 900W.

[0077] In some embodiments, the memory further stores machine-readable instructions for pulsing the plasma power at the same pulsing frequency as the bias power.

[0078] In some embodiments, the memory further stores machine-readable instructions for pulsing the plasma power at the same pulsing duty cycle as the bias power.

[0079] These and other aspects are further described below in conjunction with the drawings.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0103] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments presented. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail in order not to unnecessarily obscure the disclosed embodiments. While the disclosed embodiments are described in connection with specific embodiments, it will be understood that the disclosed embodiments are not intended to be limiting.

[0104] Semiconductor processing often involves various etching operations. One example of a technique for processing and forming 3D structures involves reactive ion etching (RIE) that produces directional etching and sidewall passivation. Generally, RIE produces reactive species such as halogen-containing species generated from fluorine-containing compounds, chlorine, hydrogen bromide, as well as ions such as hydrogen and / or argon for use in directional etching, and various species for passivating the sidewall surface. However, as the etching depth increases, depth loading occurs for features of different aspect ratios because, in part, species hit the sidewalls of the feature holes when the species are delivered to the bottom of the feature. Depth loading also occurs due to various isolated (iso) regions (e.g., features having wide feature openings) and high-density regions (e.g., features having narrow feature openings). A feature having a "narrow" opening may be defined as a feature having an opening diameter or linewidth smaller than that of a "wide" feature, which is a relative term. A wide feature may have an opening diameter or critical dimension that is at least 1.5 times, or at least 2 times, or at least 5 times, or at least 10 times or more that of the critical dimension of the narrow feature. Examples of "narrow" features include features having an opening diameter between about 1 nm and about 10 nm. Examples of "wide" features include features having an opening diameter on the order of several hundred nanometers to about 1 micron.

[0105] Etching processes often involve exposing a material to be etched to a combination of etching gases to remove the material. However, such removal is not self-limiting, and in some cases, over-etching or undesirable feature profiles may result. As feature sizes shrink, there is an increasing need for atomic-scale processes such as atomic layer etch (ALE). ALE is a technique that uses sequential self-limiting reactions to remove thin layers of material in a cycle of nominally self-limiting steps that result in a numerically small change in film thickness. This process is characterized by smoothness and isotropicity, and in some cases of ALE, also by directionality.

[0106] ALE can be used in advanced semiconductor manufacturing (e.g., technology nodes less than about 10 nm) for blanket removal of ultrathin layers of material or pattern-definition etching using atomic-scale depth resolution and control. In general, ALE can be performed using any suitable technique. Examples of atomic layer etching techniques are described in U.S. Patent No. 8,883,028, issued November 11, 2014, and U.S. Patent No. 8,808,561, issued August 19, 2014, which are incorporated herein by reference for the purpose of describing exemplary atomic layer etching and etching techniques. In various embodiments, ALE can be performed using plasma or thermally.

[0107] The ALE can be performed in cycles. The concept of "ALE cycle" is relevant to the discussion of various embodiments in this specification. Generally, an ALE cycle consists of a minimum set of operations used to perform an etching process once, such as monolayer etching. The result of one cycle is to etch at least a part of the film layer on the substrate surface. Typically, an ALE cycle includes a modification operation to form a reaction layer, followed by a removal operation to remove or etch only this modified layer. The cycle may include certain auxiliary operations, such as sweeping away and removing one of the reactants or by-products. Generally, a cycle encompasses one instance of a specific operation sequence. As an example, an ALE cycle may include (i) delivery of a reactant gas, (ii) purging of the reactant gas from the chamber, (iii) delivery of a removal gas and optional plasma, and (iv) purging of the chamber. In some embodiments, the etching may be performed anisotropically. FIG. 1 shows two exemplary schematic diagrams of an ALE cycle. FIGS. 171a - 171e show a general ALE cycle. In 171a, a substrate is provided. In 171b, the surface of the substrate is modified. In 171c, preparation for the next step is made. In 171d, the modified layer is being etched. In 171e, the modified layer is removed. Similarly, FIGS. 172a - 172e show an example of an ALE cycle for etching a silicon film. In 172a, a silicon substrate containing many silicon atoms is provided. In 172b, chlorine, a reactant gas that modifies the surface of the substrate, is introduced to the substrate. The schematic diagram of 172b shows, as an example, that some chlorine is absorbed on the surface of the substrate. Chlorine is depicted in FIG. 1, but any chlorine-containing compound or suitable reactant may be used. In 172c, the reactant gas chlorine is purged from the chamber. In 172d, Ar +As shown by the plasma species and the arrows, removal gas argon with a directional plasma is introduced to perform ion bombardment to remove the modified surface of the substrate. Ion bombardment is continuously performed with low-energy ALE under processing conditions that prevent the substrate from sputtering. For example, during this operation, a vice is applied to the substrate to attract ions toward the substrate. During this removal operation, since power is continuously applied, the bias power is typically set to a power that prevents sputtering. Thus, the power applied to the bias is typically on the order of less than about 100V. Since the bias power depends on the material to be etched, for example, for germanium, the bias power may be between about 20V and about 35V, while for silicon, the bias power may be between about 35V and about 65V. In these examples, germanium sputters at a bias power greater than 35V, and silicon sputters at a bias power greater than 65V. Thus, the bias power is typically kept low to prevent sputtering and also to prevent damage to the substrate and surrounding materials. The minimum bias power in the "bias window" of this example is the minimum bias power required to provide the substrate with sufficient energy to remove the modified material. Thus, with respect to the continuously applied bias power, at a bias power of less than 20V for germanium and less than 35V for silicon, the modified surface does not have sufficient energy to be removed from the substrate. At 172e, the chamber is purged to remove by-products.

[0108] A certain cycle may partially etch between about 0.1nm and about 50nm of the material, or between about 0.1nm and about 20nm of the material, or between about 0.1nm and about 2nm of the material, or between about 0.1nm and about 5nm of the material, or between about 0.2nm and about 50nm of the material, or only between about 0.2nm and about 5nm of the material. The amount of material etched in a certain cycle may depend on the purpose of etching with a self-limiting technique. In some embodiments, the ALE cycle may remove less than a monolayer of the material.

[0109] ALE processing conditions such as chamber pressure, substrate temperature, plasma power, frequency, and type, as well as bias power, depend on the material to be etched, the composition of the gas used to modify the material to be etched, the material underlying the material to be etched, and the composition of the removal gas used to remove the modified material. However, the combination of these factors makes it difficult to perform ALE for etching various materials.

[0110] Since the bias power is typically kept low to prevent sputtering and damage to the substrate, performing ALE in a self-controlled manner without sputtering for various materials is a challenge and is often limited by certain processing conditions.

[0111] As the feature width of the feature size shrinks to less than 10 nm, the 1 nm critical dimension variation between features causes a large variation in aspect ratio between features, and a depth loading effect is observed in the etching process performed by conventional ALE using continuous bias (low energy ALE). During the etching process, the etching amount of the material per cycle of ALE in a deeper trench is less than the etching amount of the material per cycle of ALE in a shallower trench. In some cases, the etching amount per cycle may be less at the bottom of the feature than at the top near the feature opening, even within a single feature. Without being limited to a particular theory, it is considered necessary to change the ion energy supplied from the plasma to satisfy the self-controlled features of ALE in an extreme 3D structure. However, when the ion energy is selected to be sufficient to etch a substrate having a large feature opening using ALE for a substrate having features with various aspect ratios, features having a narrower feature opening receive ions with reduced energy and flux, whereby the etching of smaller features is insufficient. However, when a larger ion energy is selected to effectively etch features having a narrow feature opening, larger features receive much higher ion energy, whereby the much higher ion energy sputters the surface of the larger features and the self-controlled aspect of ALE is eliminated. This depth loading effect revealed in the 3D structure suggests that the etching rate depends on the geometry of the features.

[0112] There are several reasons why geometric dependencies may exist during etching. One example of a problem that may occur is a charging effect that occurs when, due to the generation of cations, there is some accumulation of such positively charged ions at or near the feature openings of high aspect ratio features due to narrow feature openings, whereby a charging difference is brought about within the depth range of the feature where the feature opening is more positively charged than the bottom of the feature, resulting in a repulsive phenomenon between the positively charged incident ions used to remove the modified surface and the positively charged ions, and as a result, at the bottom of the feature, the removal of the modified surface becomes non-uniform.

[0113] Assuming that an increasing number of new materials are being introduced into integrated circuit processing and there are numerous combinations of process parameters (such as gas pressure, wafer temperature, plasma power, ion energy, etc.), it is a challenge to achieve an ALE process that etches each layer in a self-controlled manner without sputtering a given material while avoiding the charging effect at high aspect ratios.

[0114] This specification provides a method for performing controlled atomic layer etching using high energy. The disclosed embodiments involve exposing the surface of the material to be etched to a modifying gas to modify the surface and form a modified surface, and exposing the modified surface to energy particles to remove the modified surface relative to the underlying unmodified surface, wherein the energy particles have an ion energy sufficient to overcome the average surface binding energy of the underlying unmodified surface.

[0115] For example, the substrate may include a material to be etched having an average surface binding energy. The material to be etched includes various material layers. Assuming the self-limiting aspect of atomic layer etching, during exposure to the modifying gas, the modifying gas modifies the surface of the material to be etched such that it modifies the exposed surface but not the underlying material. When the modified material is exposed to energy particles such as ions, electrons, neutrons, photons, or other species, the energy particles remove the modified surface, leaving the underlying unmodified surface and maintaining the self-limiting mode of ALE. The energy particles are delivered with high energy, and the high energy may be ion energy sufficient to overcome the average surface binding energy of the unmodified surface underlying the material to be etched. That is, in some embodiments, when the energy particles are delivered in a large dose, such as all at once with many energy particles, they break the bonds of the underlying material, thereby sputtering the material underlying the modified surface and minimizing the self-limiting aspect of ALE. In contrast, the disclosed embodiments involve modulating the energy of the energy particles with a dose for delivering the energy particles so as to compensate for the high energy by delivering a low dose. In low-energy ALE, the low energy is compensated by delivering a high dose, i.e., the energy particles are delivered at low energy but continuously at a high dose, still removing only the modified surface without affecting the underlying unmodified surface and maintaining only the self-limiting aspect of ALE. However, in high-energy ALE, the high energy is compensated by delivering a low dose, i.e., the energy particles are accompanied by a high energy much greater than the energy used in low-energy ALE (and would remove more than the modified surface if delivered at the same dose as low-energy ALE), but are delivered at a low dose such that the etching remains self-limiting.

[0116] Various embodiments involve modifying the surface of a material to be etched and exposing the modified surface to attenuated doses of active species generated by activating a removal gas to remove some or all of the modified surface. Various methods can be used to achieve an attenuated dose. One way to provide an attenuated dose of active species may involve delivering the active species in a temporally separated pulse, in the form of synchronized or asynchronous pulses, with steps of pulsing the plasma power, bias voltage, gas flow, etc., not only during high / low processing but also during on / off processing. The attenuated dose is defined as delivering a dose with reduced effectiveness that has an energy greater than the sputter threshold energy of the material to be etched when continuously delivered to the modified surface. In some cases, the sputter threshold is the surface binding energy of the material to be etched.

[0117] Another method for delivering an attenuated dose is by varying the ion flux of the active species, while the dose without attenuation has an energy greater than the surface binding energy. Yet another example of delivering an attenuated dose is by varying the duration of exposure of the modified surface to the attenuated dose of active species. The duration may be insufficient to remove the modified surface. For example, a single pulse of a given duration of an attenuated dose may be insufficient to remove the modified surface, but two or more pulses of the same duration delivered over time with an attenuated dose may be sufficient to remove the modified surface. Another example involves delivering an attenuated dose to the modified surface by varying the acceleration of the ions generated by the active species. Another example involves delivering an attenuated dose by varying the bias voltage applied to a substrate support holding the substrate to deliver the active species to the modified surface in a specific direction. In some embodiments, the attenuated dose is sufficient to remove the modified surface without sputtering the underlying unmodified material.

[0118] The techniques heretofore for performing ALE obtain an "ALE window" of the bias voltage applied to a substrate support that holds a substrate during the removal operation of ALE, and provide sufficient energy to the modified surface to remove the modified surface molecules from the substrate (lower limit of the ALE window), but provide less than the threshold energy of the modified surface that would result in material under the modified surface and / or physical sputtering of the surface if exceeded (upper limit of the ALE window). Such techniques that focus on providing a low bias voltage and low plasma power to prevent sputtering of the material on the surface and ensure removal by ALE are self-regulating and can thus be controlled on a layer-by-layer basis.

[0119] In contrast, the disclosed embodiments involve operating at high plasma power, high bias voltage, or both. In this specification, it should be understood that the terms "bias power" and "bias voltage" are used interchangeably to describe the voltage set on the substrate support when applying a bias to the substrate support. The threshold bias power or threshold bias voltage refers to the maximum voltage of the bias applied to the substrate support before sputtering the material on the surface of the substrate on the substrate support. Thus, the threshold bias power depends in part on the material to be etched, the gas used to generate the plasma, the plasma power for igniting the plasma, and the plasma frequency. The bias power or bias voltage as described in this specification is measured in volts denoted by "V" or "Vb", where b refers to bias. When described in this specification, an electron volt (eV) is the amount of energy acquired by one electron by being accelerated by a potential difference of 1 volt. An electron volt refers to the amount of energy acquired by one electron by being accelerated by a potential difference of 1 volt. The disclosed embodiments can operate with low-duty-cycle pulses, such as a duty cycle between 1% and 10%. The disclosed embodiments overcome the charging problem because the high energy added to the activated removal gas is sufficient to overcome the repulsive effect. In low-energy ALE, it can be assumed that higher bias power is used to try to overcome the repulsive effect, but higher bias power in low-energy ALE results in sputtering or damaging the substrate due to the long exposure time, thereby losing the self-limiting feature of ALE. In contrast, using high-energy pulsed ALE overcomes the repulsive effect while maintaining the self-limiting characteristics of ALE without sputtering.

[0120] As shown in FIG. 13, which is further described below, typically when using a short duty cycle, incomplete removal of the modified surface is expected.

[0121] However, the disclosed embodiments involve the step of using a short duty cycle as one technique for performing ALE using high energy. Without being limited to a particular theory, it is believed that there is a time dependence associated with the removal operation of ALE.

[0122] This example is assumed to involve the silicon surface being modified by chlorine plasma and the modified surface having SiCl that can be removed using argon plasma. This example is provided only as an example, however, the following expressions generally relate to any suitable plasma (instead of chlorine) and any suitable material for etching with high energy species (instead of argon plasma) for ALE, including both low energy ALE and high energy ALE.

[0123] N 0 is assumed to represent the total number of surface sites on the substrate. The total number of surface sites is given by the following equation, N 0 = N + S Equation 1 where N represents the total number of unreacted sites (sites where SiCl remains on the substrate), and S represents the total number of reacted sites (sites where only the underlying layer of Si remains).

[0124] The reaction for desorbing chlorine on the substrate is given by the following equation. Si - Si Cl (s) + Ar + ions → Si(s) + SiCl(g) Equation 2

[0125] This chemical reaction equation depicts ion-assisted desorption in the form of reaction per ion and does not assume a reverse reaction, and the rate efficiency Y = yield.

[0126] F is assumed to be the ion flux given in ions / m 2 ·s.

[0127] Therefore, the rate of the equation is given by the following equation.

Number

[0128] The derivative of [S] is given at time t by the following expression, assuming that k is dependent on [S] and t. [Number] The reacted surface portion is given by θ as follows. [Number]

[0129] Equation 5A is rewritten as Equation 5B. In Equation 5B, θ(t) represents the removal amount as a function of time, where Y(ε) is the ion yield for removing the product (0.1 ions at 0 eV), and according to this, [Number] where d is the surface density expressed in units of 1 / cm 2 and F is the ion flux, which may be, in some devices, about 1E16 / cm 2 per second at 50 eV, and t is the "on" time of argon ions, such as an irradiation dose of 0.2 seconds at a 10% duty cycle of a 2-second operation.

[0130] Figure 12B, described below, shows an example of etching per cycle using this inverse correlation function of Equation 5A for silicon ALE. Without being limited to a particular theory, it is considered that higher energy requires fewer ions due to more efficient momentum transfer at higher energy. An example is provided in FIGS. 4I and 4J. In FIG. 4I, a low ion energy of 50 eV applied to the modified surface uses argon delivered at a speed of 13,000 m / s to remove the modified surface, where Y ~ 0.1SiCl x / ions. In contrast, in FIG. 4J, the high ion energy of 300 eV applied to the modified surface removes the surface using argon delivered at a speed of 33000 m / sec, in which case Y~0.5SiCl x / ions. Thus, on a surface that required 10 ions to be removed using low ion energy, only 2 ions are required to remove the same surface using high ion energy.

[0131] Without being limited to a particular theory, sputtering increases with ion energy, while on the other hand, the SiCl surface etches faster than the underlying Si surface, and thus the contribution to the etch amount is small until the reaction layer is removed. When the exposure time is very short, the reaction layer exists for most of the removal time. For example, FIG. 15 shows an example of etching rate versus argon bias, according to which SiCl etches faster than Si(1502) at all energies (1501).

[0132] FIG. 16A shows an example of low energy ALE using a bias of 50 V at 1.5 seconds / cycle, which results in a smoother surface, a longer exposure time window, and a higher resolution per cycle, and as a result, there may be less damage to the underlying layer. The gray part represents TEOS on the substrate. The green part represents the underlying material. FIG. 16B shows an example of the same substrate structure exposed to pulsed ALE using high energy, which uses a similar synergistic effect to give a higher throughput due to a narrower ion angular distribution function (IADF) provided by 50 eV at 8° as opposed to 500 eV at 2°, improved aspect ratio dependent etching (ARDE), less charging effect, and less redeposition and ion scattering. High energy ALE can be achieved in the form of short pulses useful for use in a CCP reactor. High energy ALE allows for a larger ion energy window.

[0133] The disclosed embodiments are suitable for etching various materials including metals, metal-containing materials, dielectric materials, semiconductor materials, insulating materials, etc. Non-limiting examples include silicon, silicon oxide, silicon nitride, tungsten, carbon, germanium, metal oxides, and metal nitrides (such as titanium nitride, aluminum nitride, etc.). The examples provided herein are directed to the etching of silicon, but it will be understood that the disclosed embodiments can be used to etch various materials and that the modifying gas chemistry, removal gas chemistry, and processing conditions depend on the material to be etched.

[0134] The methods and apparatuses herein are directed to performing high-energy atomic layer etching. High-energy atomic layer etching (high-energy ALE) can be used by compensating for the high energy with a low dose. In contrast, conventional ALE performed at low energy (low-energy ALE) involves a high dose of low energy. The dose is defined as the number of ions used during the removal operation of ALE.

[0135] In some embodiments, high-energy ALE can be performed using an etching process referred to herein as pulsed atomic layer etching. In some cases, the terms “high-energy ALE” and “pulsed ALE” are used interchangeably. A single high-energy ALE cycle includes at least two operations, namely, 1) surface modification with continuous or pulsed plasma, and 2) removal of the modified surface using one or more pulsed energy sources such as bias power, or radio frequency plasma power, or both, or lattice energy. Multiple pulses may be used in either the surface modification operation and / or the removal operation in a single high-energy ALE cycle. For example, in some embodiments, during removal, pulsed bias power of 100 or more pulses may be performed. During removal, bias, or power, or both may be pulsed, and in some cases, other energies such as photon energy may be used. The pulses may be synchronous or asynchronous when using both pulsed bias power and pulsed plasma power. The frequencies for pulsing may be the same or different. Pulsing conditions, including on / off pulsing, or pulsing between low and high power, or between low and high voltage, the frequency of the pulse, the duty cycle of the pulse, and the duration of the pulse, may be carefully adjusted according to the modifying chemical, the removal gas chemical, the material to be etched, the substrate feature profile, and the application of the disclosed embodiments.

[0136] The disclosed embodiments can be performed during a high-energy ALE regime using an ion energy that is about 10 to about 20 times higher than that of low-energy ALE processing. Some embodiments are performed by synchronizing the pulsing of the inductively coupled plasma power with the bias to the substrate applied by applying a voltage to the substrate at a very low duty cycle between about 1% and about 10%. The new processing regime enables the etching of extremely narrow features with high aspect ratios, such as greater than about 30:1, with low loading effects and reduced or eliminated lateral etching.

[0137] Pulsed ALE may involve both pulsed plasma and ion bias pulsing such that pulsing is performed between both modification and removal.

[0138] Pulsing during surface modification can control the effective plasma time and can be adjusted to suit the apparatus or tool used to perform the modification. Pulsing during removal can be used to remove the modified surface using high energy. In some embodiments, pulsing during removal may include both pulsing of the RF plasma and pulsing of the bias power, and the pulsing may be synchronized such that the RF plasma power pulsing and the bias power pulsing are pulsed using the same duty cycle at the same pulse frequency.

[0139] Pulsed ALE using pulsed energy provides a method for extending the self-controlled synergy window. Synergy means that favorable etching occurs due to the interaction of both the surface modification operation and the removal operation. The synergy window extended to higher bias / energy regimes can compensate for the loss of ion energy / flux reaching the etching front due to ion scattering associated with extremely narrow 3D structures. Thus, high-energy ALE provides an operating regime that enables the same etching per cycle with a self-controlled reaction for a wide range of critical dimensions and aspect ratios.

[0140] High-energy ALE extends the self-controlled energy window for the synergistic behavior of atomic layer etching. In continuous ion bombardment, for example, the sputter threshold voltage of silicon can be greater than 100 V. That is, with a bias power greater than 100 V, the silicon surface will sputter. The pulsed mode generates plasma and ions at a given frequency and duty cycle. Using power / bias pulsing at a low duty cycle can increase the threshold sputter bias to a higher bias power. Therefore, bias pulsing increases the range and magnitude of the self-controlled energy window by at least an order of magnitude compared to low-energy ALE.

[0141] Without being limited to a particular theory, it is believed that pulsed atomic layer etching is achieved due to the reduced ion fluence associated with pulsing. Assuming that fluence = flux × time, fluence represents the ion exposure. As the simplest estimate, the reduction in exposure can be calculated by the duty cycle and the ratio of the step times. For example, at a 10% duty cycle, the exposure time is thereby 2 seconds instead of 5 seconds with pulsing, in which case the effective reduction in fluence is 94%. Therefore, in this example, the wafer is exposed to 0.06 times the original ion exposure used in low-energy ALE. The amount etched per cycle depends on the ion exposure and the ion energy. Generally, as a result of reducing the exposure, the amount etched becomes less. Without being limited to a particular theory, it is believed that a higher ion energy can compensate for a lower exposure.

[0142] Compared to reactive ion etching, high-energy ALE employs two self-controlled steps to independently control reactant transfer and surface reactions. The bias pulsing mode redefines the self-control window of ALE to provide a dominant period for etching 3D structures by ALE where the bias power or RF power is independent of the trench size and aspect ratio. The disclosed embodiments are suitable for etching on both blanket and patterned substrates. In some embodiments, the bias window of high-energy ALE may have a non-sharp maximum value, such that the maximum bias voltage used with high-energy ALE without causing sputtering is not a single set value but rather a range of values.

[0143] The disclosed embodiments extend the ALE energy window, which is referred to as the range of voltages at which etching becomes substantially self-controlled. In some embodiments, the ALE energy window is determined by evaluating a graph of etching versus voltage per cycle, and in some embodiments, involves identifying where in the etching per cycle is the flat region, and the energy window is calculated as ± about 10% of the values of the flat region. In some embodiments, this can be accomplished by determining the inflection points where the positive slope becomes the slope of 0 (minimum value) and the slope of 0 becomes the positive slope (maximum value). In some embodiments, the ALE energy window is the range of voltages that can be applied to the substrate to remove the modified surface of the material without sputtering the substrate. The range of voltages includes a minimum voltage, which is the minimum voltage required to provide sufficient energy on the modified surface to remove the modified material, and a maximum voltage, which is the maximum voltage that the substrate can withstand before the removal gas sputters the substrate.

[0144] In low-energy ALE, to prevent damage to the substrate caused by sputtering, the range of the bias voltage of the bias window, which tends to be lower, typically becomes narrower. By changing the duty cycle and thus the duration of the energy applied to the removal gas, as the duty cycle is reduced and, as a result, the duration of exposure to energy is reduced, the range and amplitude of the bias window increase such that the bias voltage that can be applied to the substrate can be increased up to 10 to 20 times greater than the bias voltage used during low-energy ALE. By using greater energy for the removal gas during removal, the damage becomes greater, and thus it may generally be expected to attempt to reduce the damage by reducing the amount of energy by reducing the bias voltage or RF plasma power. However, without being limited to a particular theory, it is conceivable to provide a bias window for removing the modified material using the amount of energy expended over time for each combination of the modifying chemical, the removal gas chemical, and the substrate material chemical. In low-energy ALE, it is observed that sputtering is prevented by a certain limitation on the bias power. However, in high-energy ALE, the bias power can be up to 10 to 20 times greater than the bias power used in low-energy ALE since the bias is applied in the form of pulses over time. It should be noted that in some embodiments, other techniques may be used to apply high energy during ALE while performing high-energy ALE in the form of pulses. With the bias power used in high-energy ALE, low-energy ALE results in sputtering, while high-energy ALE separates the high bias power over time, thereby preventing any sputtering of the substrate. When depending on the modifying chemical, the removal gas chemical, and the material to be etched, the combination of the applied energy, time (e.g., duty cycle), and flux can be modified to maximize the bias window using certain disclosed embodiments.

[0145] The disclosed embodiments may be particularly suitable for etching features in FinFET applications. FIG. 2 shows an exemplary FinFET structure (fin-shaped field effect transistor) 200. The substrate 202 may be a semiconductor substrate. In this structure, surfaces 214a and 204a correspond to the source regions, while 214b and 204b correspond to the drain regions. The liner 212 separates the semiconductor material of the substrate 202 from an insulating material 230 such as silicon oxide. Thin gate dielectric layers 206b and 206a may be deposited over the entire surface of the insulating material 230 and may separate the insulating material 230 from a gate including spacers 210, gate electrode 208, and gate electrode barrier 208a. An electrical contact 250 is formed over the entire top surface of the gate. Certain disclosed embodiments may be used to define fin / shallow trench isolation with minimal depth loading with respect to trenches formed in the substrate 202. Additionally, certain disclosed embodiments may be suitable for dummy gate removal for gate electrode deposition.

[0146] FIGS. 3A and 3B are flowcharts of a process depicting the operations of a method performed in accordance with certain disclosed embodiments. The operations of FIGS. 3A and 3B may be performed at a chamber pressure between about 1 mTorr and about 100 mTorr, such as, for example, between about 1 mTorr and about 1 Torr, such as about 50 mTorr. The operations of FIGS. 3A and 3B may be performed at a substrate temperature between about 0° C. and about 120°.

[0147] In the following discussion, it will be understood that operations 302, 304, 306, 310, and 312 of FIG. 3A may correspond to and / or be the same as operations 302, 304, 306, 310, and 312 of FIG. 3B. In operation 302, a substrate is provided to the processing reaction chamber. The substrate may include a silicon wafer having one or more layers of a material such as a dielectric, a conductive material deposited on the substrate, or a semiconductor material, for example, a 200 mm wafer, a 300 mm wafer, or a 450 mm wafer. The patterned substrate may have "features" such as vias or contact holes that may be characterized by one or more of narrow and / or concave corner openings, constrictions within the features, and high aspect ratios. Features may be formed within one or more of the aforementioned layers. An example of a feature is a hole or via in a semiconductor substrate, or a layer on the substrate. Another example is a trench in the substrate or layer. In various embodiments, the feature may have an underlying layer such as a barrier layer or an adhesion layer. Non-limiting examples of underlying layers include dielectric layers and conductive layers, for example, layers of silicon oxide, silicon nitride, silicon carbide, metal oxides, metal nitrides, metal carbides, and metals.

[0148] In some embodiments, the substrate has no features, and the surface of the substrate is a blanket layer of material. In some embodiments, the substrate includes features of various sizes. In various embodiments, the type of substrate fabricated by performing the disclosed embodiments may depend on the aspect ratio of the features on the substrate prior to performing the disclosed embodiments. In some embodiments, the features on the substrate provided in operation 301 may have an aspect ratio of at least about 2:1, at least about 3:1, at least about 4:1, at least about 6:1, at least about 10:1, at least about 30:1, or higher. The feature may also have a dimension near the opening, for example, an opening diameter or line width between about 5 nm and 500 nm, for example, between about 25 nm and about 300 nm. The disclosed method may be performed on a substrate with features having openings less than about 20 nm.

[0149] A via, trench, or other recessed feature may be referred to as an unfilled feature or feature. According to various embodiments, the feature profile may gradually narrow and / or may include overhangs at the feature opening. The profile of the concave corner is a profile that narrows from the bottom, closed end, or interior of the feature to the feature opening. The profile of the concave corner may be generated by asymmetric etching kinetics during patterning and / or by overhanging due to non-isotropic film step coverage in a preceding film deposition such as the deposition of a diffusion barrier. In various examples, the feature may have a width at the opening at the top of the feature that is smaller than the width at the center and / or bottom of the feature.

[0150] In operation 304, the substrate is exposed to a modifying gas for a duration sufficient to modify at least the surface of the substrate. An etching gas is introduced into the chamber in operation 304. In some embodiments involving atomic layer etching using a plasma in the operation of introducing a material into the chamber as described herein, the reactor or chamber may be stabilized by introducing a chemical into the chamber prior to processing the wafer substrate. The step of stabilizing the chamber may use the same flow rate, pressure, temperature, and other conditions as the chemical used in the operations that follow the stabilization. In some embodiments, the step of stabilizing the chamber may involve different parameters. In some embodiments, during operation 304, N 2 , carrier gases such as Ar, Ne, He, and combinations thereof are flowed continuously. In some embodiments, the carrier gas is used only during removal. As described below, the carrier gas may be used as a purge gas in some operations.

[0151] The modification operation forms a thin reactive surface layer with a thickness that can be more easily removed by a subsequent removal operation than the unmodified material. In the modification operation, the substrate may be chlorinated by introducing chlorine into the chamber. In the disclosed embodiments, chlorine is used as an exemplary etchant species, but it will be understood that in some embodiments, different etching gases may be introduced into the chamber. The etching gas may be selected according to the type and chemical properties of the substrate to be etched. In some embodiments, a plasma may be ignited, and chlorine reacts with the substrate during the etching process. In some embodiments, chlorine may react with the substrate or may be adsorbed on the surface of the substrate. In various embodiments, chlorine is introduced into the chamber in gaseous form and may optionally be accompanied by a carrier gas, which may be any of the carrier gases described above. The species generated from the chlorine plasma can be generated directly by forming a plasma in the processing chamber containing the substrate or can be generated remotely in a processing chamber not containing the substrate and supplied into the processing chamber containing the substrate. In some embodiments, chlorine may be introduced thermally into the chamber without using a plasma.

[0152] In various embodiments, the plasma may be an inductively coupled plasma or a capacitively coupled plasma. The inductively coupled plasma may be set to a plasma between about 50 W and about 2000 W. In some embodiments, a bias may be applied between about 0 V and about 500 V.

[0153] In various embodiments, a plasma is ignited to promote the modification of the substrate surface. In some embodiments, a modification gas is ignited in a remote plasma chamber to generate plasma species, and then the plasma species are delivered to the processing chamber containing the substrate. In some embodiments, the modification gas is ignited inside the processing chamber.

[0154] In various embodiments, the plasma may be pulsed during operation 304. The plasma may be pulsed between an on state where the plasma power is between about 50 W and about 2000 W and an off state where the plasma power is 0 W. In some embodiments, the plasma may be pulsed between a low state where the plasma power is between about 10 W and about 100 W and a high state where the plasma power is between about 900 W and about 1500 W.

[0155] Pulsing may be performed at a pulsing frequency between about 10 Hz and about 200 Hz. The duty cycle of the plasma pulsing of the reforming gas may be between about 1% and about 20%. It will be appreciated that the pulsing may involve a repetition of cycles each having a duration T. The duration T includes the duration of the pulse-on time (the duration that the plasma is in the on state) and the duration of the off time (the duration that the plasma is in the off state) during a given cycle. The pulse frequency is understood to be 1 / T. For example, for a pulsing cycle T = 100 μs, the frequency is 1 / T = 1 / 100 μs, i.e., 10 kHz. The duty cycle or duty ratio is the ratio or percentage within the cycle T during which the energy source is in the on state such that the duty cycle or duty ratio is pulse-on time / T. For example, for a pulsing cycle T = 100 μs, if the pulse-on time is 70 μs (such that the duration that the energy source is in the on state within a certain cycle is 70 μs) and the pulse-off time is 30 μs (such that the duration that the energy source is in the off state within a certain cycle is 30 μs), the duty cycle is 70%.

[0156] FIG. 4H provides examples of various duty cycles that may be used in an ALE cycle, including 3%, 10%, 40%, and 100% (100% involves sufficient synergistic action but ALE is performed with continuous low energy). The corresponding "on" times when Ar is on are provided in the schematic of FIG. 4H.

[0157] In some embodiments, the plasma is pulsed to deliver higher energy to the reforming gas. In some embodiments, the plasma may be pulsed so that the device used to generate the plasma can operate under certain conditions that address the limitations of the device. For example, in a device that cannot deliver plasma power during a continuous short duration, by separating the dose delivered within the continuous short duration into multiple pulses over a longer period such that the total plasma-on time is the same as the continuous short duration, it becomes easier to deliver sufficient plasma power to modify most or all of the active sites on the substrate surface. For example, the minimum amount of time required for chlorine to continuously modify the silicon surface is 400 ms, but if the device cannot deliver chlorine gas and apply plasma power during such a continuous short duration, 4 cycles consisting of a continuous flow of chlorine gas and 400 ms without plasma power and 100 ms pulses of plasma power can be used to add the 400 ms duration over 2 seconds.

[0158] In operation 306, optionally purge the process chamber to remove excess reforming gas molecules that did not modify the substrate surface. In the purge operation, reactive chlorine species not bound to the surface may be removed from the process chamber. This can be done by purging and / or evacuating the process chamber without removing the absorbed layer to remove the reactive species. Species generated in the chlorine plasma can be removed by simply stopping the plasma and allowing the decay of the remaining species, optionally in combination with purging and / or evacuating the chamber. 2 Purging can be performed using any inert gas such as N

[0159] In operation 308a, an activation gas is delivered to the substrate, active species are generated from the activation gas using an activation source, and the modified surface is removed using the active species. In operation 308a, the substrate may be exposed to active species of a high energy dose, in addition to by pulsing an energy source such as RF plasma power, bias power, photons, or other energy sources that etch the substrate. In some embodiments, during operation 308a, two or more high energy doses are provided in one ALE cycle. The high energy dose is provided with energy greater than the threshold energy for sputtering the modified surface, for a duration insufficient to remove the modified surface using a single energy dose. The activation gas may be an inert gas or a noble gas such as argon, helium, neon, krypton, xenon, or a combination thereof. In some embodiments, the energy of a single high energy dose is at least 2 times to at least 15 times greater than the sputtering threshold energy. For example, in some embodiments, to etch silicon using the disclosed embodiments, the high energy dose is provided with a bias power of at least 150 eV, or at least 500 eV, or at least 1000 eV, or between 100 eV and about 1500 eV, compared to an exemplary threshold sputter bias power of 65V.

[0160] In some embodiments, one or more energy sources are pulsed, while one or more energy sources are emitted continuously. For example, in some embodiments, the RF plasma power is continuous while the bias is pulsed. In some embodiments, the RF plasma power is pulsed and the bias power is pulsed. In some embodiments, the RF plasma power is pulsed and the bias power is continuous. In various embodiments, when pulsing the power, the pulsing may be performed between an on state and an off state, or between a low state and a high state.

[0161] The pulsed conditions of the plasma power and the bias power, including the frequency and the duty cycle, depend on the material to be etched. To etch silicon using chlorine as the modifying gas, the following ranges may be used. For the RF plasma power, when pulsing between the on-state and the off-state, the power during the on-state may be between about 50 W and about 900 W. For the RF plasma power, when pulsing between low power and high power, the power during the high power may be between about 900 W and about 1500 W, and the power during the low power may be between about 10 W and about 100 W. For the bias power, when pulsing between the on-state and the off-state, the bias power may be about 10 to about 20 times higher than the bias power of the low-energy ALE. For the etching of silicon, the bias power during the on-state may be between about 100 V and about 1500 V for a duty cycle between about 1% and about 10%. For the bias power, when pulsing between high power and low power, the bias power during the high power may be between about 500 V and about 1500 V for a duty cycle between about 1% and about 10%, and the low power may be between about 100 V and about 300 V for a duty cycle between about 1% and about 10%. In some embodiments, the vice power and the RF plasma power are pulsed at least 100 times during one ALE cycle.

[0162] In one example, the following processing conditions may be used to etch silicon. Table 1. Exemplary processing conditions for high-energy ALE of silicon [Table 1]

[0163] In some embodiments, the RF plasma power is continuous, while the bias power is pulsed between an on state and an off state. In some embodiments, the RF plasma power is continuous, while the bias power is pulsed between a high power and a low power. In some embodiments, the RF plasma power is pulsed between an on state and an off state, while the bias power is pulsed between an on state and an off state. In some embodiments, the RF plasma power is pulsed between a high power and a low power, while the bias power is pulsed between an on state and an off state. In some embodiments, the RF plasma power is pulsed between an on state and an off state, while the bias power is pulsed between a high power and a low power. In some embodiments, the RF plasma power is pulsed between a high power and a low power, while the bias power is pulsed between a high power and a low power. In some embodiments, the high bias power may be the maximum bias power for providing sufficient energy to remove the modified surface without sputtering, and the low bias power may be as low as the minimum bias power for providing sufficient energy to remove the modified surface at a given RF plasma power and duty cycle.

[0164] In some embodiments, the pulsing of the RF power and the bias power may be synchronized such that the RF power is on when the bias power is on and off when the bias power is off, or the RF power is on when the bias power is high and off when the bias power is low, or the RF power is high when the bias power is on and low when the bias power is off, or the RF power is high when the bias power is high and low when the bias power is low.

[0165] In some embodiments, the pulsing of the RF power and the bias power may be asynchronous, such that the RF power is off when the bias power is on and on when the bias power is off, or the RF power is off when the bias power is high and on when the bias power is low, or the RF power is low when the bias power is on and high when the bias power is on, or the RF power is low when the bias power is high and high when the bias power is low. In some embodiments, the frequency at which the RF power is pulsed and the frequency at which the bias power is pulsed are the same. In some embodiments, the frequency at which the RF power is pulsed and the frequency at which the bias power is pulsed are different.

[0166] Pulsing may be performed at a pulsing frequency between about 10 Hz and about 200 Hz, such as about 200 Hz. The duty cycle of the plasma pulsing of the activation gas may be between about 1% and about 10%. In various embodiments, reducing the duty cycle increases the range and size of the bias window, such that a lower duty cycle results in a larger bias power applied to the substrate with a wider bias window and tolerance range.

[0167] In FIG. 3B, in operation 308b, the modified surface is exposed to high-energy energy particles to etch the modified surface. The energy particles may have an ion energy greater than the average surface bond energy of the unmodified surface underlying the material to be etched. As described above for operation 308a, the high-energy energy particles may be delivered to the substrate in the form of pulses. In some embodiments, the energy particles do not significantly sputter the underlying unmodified material. For example, the amount of the underlying unmodified material sputtered by the energy particles during removal is less than about 10% of the total amount of material removed by the energy particles in one cycle.

[0168] In various embodiments, operation 308b involves exposing the modified surface for a duration insufficient to remove at least 80% of the surface that is modified when exposed to low ion energy.

[0169] In operation 310, optionally purge the chamber to remove excess activation gas and reaction by-products resulting from the removal operations of operation 308a or 308b.

[0170] In operation 312, optionally repeat operations 304 - 310 periodically. In various embodiments, the modification and removal operations may be repeated periodically, such as about 1 cycle to about 200 cycles, or about 1 cycle to about 150 cycles, or about 1 cycle to about 70 cycles, or about 1 cycle to about 40 cycles, or about 1 cycle to about 30 cycles, or about 1 cycle to about 20 cycles. Any suitable number of ALD cycles may be included to etch a desired amount of the film. In some embodiments, ALD is performed periodically to etch about 1 Å to about 50 Å of the surface of the layer on the substrate. In some embodiments, the ALD cycle etches about 2 Å to about 50 Å of the surface of the layer on the substrate.

[0171] Examples of various timing schematics are depicted in FIGS. 4A - 4G. In these figures, the RF plasma is depicted as being off during surface modification, while in various embodiments, the plasma is on during surface modification. In all of the examples of FIGS. 4A - 4G, the modification gas is on and constant during surface modification and off during the purge and removal stages, the removal gas is on and constant during removal, and off during the purge stage and Surface modification during. Although not depicted in the figures, it will be understood that a carrier gas may flow continuously during the etching cycle. In some embodiments, the gas for the purge stage is the same as the removal gas, and thus the removal gas may be turned on during the purge stage, while neither plasma nor bias power is delivered (not shown).

[0172] Figure 4A shows two etching cycles consisting of surface modification, purge, removal, and purge. In this case, the bias power is pulsed between on and off during the removal operation, while the RF plasma is constant during the removal operation. Only four on-pulses for the bias power are depicted during removal within one ALE cycle, although multiple pulses may be used with various duty cycles, such as between 1% and 10%.

[0173] Figure 4B shows two etching cycles consisting of surface modification, purge, removal, and purge. In this case, the bias power is pulsed between low power and high power during the removal operation, while the RF plasma is constant during the removal operation. Only four high-power pulses for the bias power are depicted during removal within one ALE cycle, although multiple pulses may be used with various duty cycles, such as between 1% and 10%.

[0174] Figure 4C shows two etching cycles consisting of surface modification, purge, removal, and purge. In this case, the bias power is pulsed between on and off during the removal operation, while the RF plasma is also pulsed between on and off during the removal operation. Only four on-pulses are depicted during removal within one ALE cycle, although multiple pulses may be used with various duty cycles, such as between 1% and 10%. In this example, the RF pulsing and the bias power pulsing are synchronized at the same frequency and duty cycle.

[0175] Figure 4D shows two etching cycles consisting of surface modification, purge, removal, and purge. In this case, the bias power is pulsed between high power and low power during the removal operation, while the RF plasma is also pulsed between on and off during the removal operation. Only four pulses are depicted during removal within one ALE cycle, although multiple pulses may be used with various duty cycles, such as between 1% and 10%. In this example, the RF pulsing and the bias power pulsing are synchronized at the same frequency and duty cycle.

[0176] FIG. 4E shows two etching cycles consisting of surface modification, purge, removal, and purge, where the bias power is pulsed between on and off during the removal operation, while the RF plasma is also pulsed between high and low power during the removal operation. Only four pulses are depicted during removal within one ALE cycle, while multiple pulses may be used with various duty cycles, such as between 1% and 10%. In this example, the RF pulsing and the bias power pulsing are synchronized at the same frequency and duty cycle.

[0177] FIG. 4F shows two etching cycles consisting of surface modification, purge, removal, and purge, where the bias power is pulsed between high and low power during the removal operation, while the RF plasma is also pulsed between high and low power during the removal operation. Only four pulses are depicted during removal within one ALE cycle, while multiple pulses may be used with various duty cycles, such as between 1% and 10%. In this example, the RF pulsing and the bias power pulsing are synchronized at the same frequency and duty cycle.

[0178] FIG. 4G shows two etching cycles consisting of surface modification, purge, removal, and purge, where the bias power is pulsed between on and off during the removal operation, while the RF plasma is also pulsed between on and off during the removal operation. Only four bias power pulses (and only three RF plasma pulses) are depicted during removal within one ALE cycle, while multiple pulses may be used with various duty cycles, such as between 1% and 10%. In this example, the RF pulsing and the bias power pulsing are asynchronous, such that the bias power is on when the RF plasma is off and the bias power is off when the RF plasma is on, but with the same frequency.

[0179] Figures 4A - 4G provide only examples of pulse timing in various pulsed ALE embodiments. It will be appreciated that in some of the disclosed pulsed ALE embodiments, many variations may be used.

[0180] This specification provides embodiments for achieving etch selectivity. For example, etch selectivity depends on the material to be etched, the removal gas and modification gas used, and the bias power used in pulses during the on - state. As a result, at lower bias powers, higher selectivity may be observed between two materials, while at higher bias powers, lower selectivity may be observed between two materials. The disclosed embodiments extend the bias window for operating self - controlled pulsed ALE, thereby allowing the use of various bias powers during pulsed ALE to adjust the etch selectivity of one material compared to that of another material to obtain desired etch characteristics and, in some embodiments, feature profiles.

[0181] Device Next, an inductively coupled plasma (ICP) reactor, which may be suitable for atomic layer etching (ALE) in some embodiments, is described. Such an ICP reactor is also described in U.S. Patent Application Publication No. 2014 / 0170853, filed on December 10, 2013, entitled "IMAGE REVERSAL WITH AHM GAP FILL FOR MULTIPLE PATTERNING", which is hereby incorporated by reference in its entirety. Although an ICP reactor is described herein, it should be understood that in some embodiments, capacitively coupled plasma reactors may also be used. In some embodiments, electron cyclotron resonance plasmas may be used.

[0182] FIG. 5 schematically shows a cross-sectional view of an inductively coupled plasma etching apparatus 500 suitable for implementing certain embodiments of the present specification. An example of such an embodiment is the Kiyo (registered trademark) reactor manufactured by Lam Research Corp. in Fremont, California. The inductively coupled plasma apparatus 500 includes an integrated processing chamber 501 structurally defined by a chamber wall 501 and a window 511. The chamber wall 501 may be fabricated from stainless steel or aluminum. The window 511 may be fabricated from quartz or other dielectric material. An optional internal plasma grid 550 divides the integrated processing chamber 501 into an upper sub-chamber 502 and a lower sub-processing chamber 503. In most embodiments, the plasma grid 550 may be removed, whereby the chamber space consisting of sub-chambers 502 and 503 is utilized. A chuck 517 is positioned near the lowermost inner surface inside the lower sub-chamber 503. The chuck 517 is configured to receive and hold a semiconductor wafer 519 on which an etching process and a deposition process are performed. The chuck 517 can be an electrostatic chuck for supporting the wafer 519 when the wafer 519 is present. In some embodiments, an edge ring (not shown) surrounds the chuck 517 and has a substantially planar upper surface together with the uppermost surface of the wafer 519 when the wafer 519 is present on the chuck 517. The chuck 517 also includes electrostatic electrodes for chucking and de-chucking the wafer. For this purpose, a filter and a DC clamp power supply (not shown) may be provided. Furthermore, another control system for lifting the wafer 519 away from the chuck 517 can be provided. The chuck 517 can be electrically charged using an RF power supply 523. The RF power supply 523 is connected to a matching circuit 521 through a connection 527. Bias power may be applied to the chuck 517 to bias the substrate. In various embodiments, the bias power may be set to a value between 0 V (no bias) and about 2000 V, or between 0 V and 1800 V, or between 0 V and 1500 V, or between 500 V and about 1500 V. The matching circuit 521 is connected to the chuck 517 through a connection 525.In this way, the RF power supply 523 is connected to the chuck 517.

[0183] The element for generating plasma includes a coil 533 positioned above the window 511. In some embodiments, no coil is used in the disclosed embodiments. The coil 533 is fabricated from a conductive material and includes at least one complete turn. The example of the coil 533 shown in FIG. 5 includes three turns. The cross-section of the coil 533 is shown symbolically, with the coil having an "X" rotating into the page and the coil having a "●" rotating out of the page. The element for generating plasma also includes an RF power supply 541 configured to supply RF power to the coil 533. Generally, the RF power supply 541 is connected to a matching circuit 539 through a connection 545. The matching circuit 539 is connected to the coil 533 through a connection 543. In this way, the RF power supply 541 is connected to the coil 533. The RF power supply 541 is configured to be pulsed at a frequency between 10 Hz and 200 Hz using a duty cycle between 1% and about 20% during the reforming operation and / or to be pulsed at a frequency between 10 Hz and 200 Hz using a duty cycle between 1% and about 20% during the removal operation of the ALE cycle. An optional Faraday shield 549 is positioned between the coil 533 and the window 511. The Faraday shield 549 is maintained in a spatially separated relationship with respect to the coil 533. The Faraday shield 549 is disposed directly above the window 511. The coil 533, the Faraday shield 549, and the window 511 are each configured to be substantially parallel to each other. The Faraday shield may prevent metal or other species from depositing on the dielectric window of the plasma chamber 501.

[0184] A processing gas (e.g., chlorine, argon, oxygen, etc.) may be flowed into the processing chamber 501 through the main gas flow inlet 560 positioned within the upper chamber 502 and / or through one or more side gas flow inlets 570. Similarly, although not explicitly shown, similar gas inlets may be used to supply the processing gas to the capacitively coupled plasma processing chamber. A vacuum pump, e.g., a single- or two-stage mechanical dry pump and / or a turbomolecular pump 540, may be used to extract the processing gas out of the processing chamber 501 and maintain the pressure inside the processing chamber 501. For example, a pump may be used to evacuate the chamber 501 during the purge operation of ALE. A valve control conduit may be used to fluidly connect the vacuum pump to the processing chamber 501 so as to selectively control the application of the vacuum environment provided by the vacuum pump. This may be done by employing a closed-loop control flow restriction device such as a throttle valve (not shown) or a pendulum valve (not shown) during the plasma processing in operation. Similarly, the vacuum pump and valve control fluid connections to the capacitively coupled plasma processing chamber may be further used.

[0185] During operation of the apparatus, one or more processing gases may be supplied through the gas inlets 560 and / or 570. In certain embodiments, the processing gas may be supplied only through the main gas flow inlet 560 or only through the side gas flow inlet 570. In some cases, the gas inlets shown in the figure may be replaced with more complex gas inlets, e.g., one or more showerheads. The Faraday shield 549 and / or the optional grid 550 may include internal channels and holes to enable the delivery of the processing gas to the chamber 501. Either, or both, of the Faraday shield 549 and the optional grid 550 may serve the role of a showerhead for delivering the processing gas. In some embodiments, a liquid vaporization and delivery system may be disposed upstream of the chamber 501, such that when a liquid reactant or precursor is vaporized, the vaporized reactant or precursor is introduced into the processing chamber 501 through the gas inlets 560 and / or 570. Exemplary liquid precursors are SiCl4 and includes silicon amide.

[0186] RF power 541 supplies radio frequency power to coil 533 to pass an RF current through coil 533. The RF current passing through coil 533 generates an electromagnetic field around coil 533. The electromagnetic field generates an induced current inside the upper sub-chamber 502. Through the physical and chemical interactions of the generated various ions and radicals with the wafer 519, the features of the wafer are selectively etched and a layer is selectively deposited on the wafer.

[0187] When using a plasma grid such that both the upper sub-chamber 502 and the lower sub-processing chamber 503 are present, the induced current acts on the gas present in the upper sub-chamber 502 to generate an electron-ion plasma in the upper sub-chamber 502. The optional internal plasma grid 550 limits the amount of hot electrons in the lower sub-chamber 503. In some embodiments, the apparatus is designed and operated such that the plasma present in the lower sub-chamber 503 becomes an ion-ion plasma.

[0188] Both the upper electron-ion plasma and the lower ion-ion plasma may include positive and negative ions, but the ion-ion plasma has a larger negative ion:positive ion ratio. Volatile etching and / or deposition by-products may be removed from the lower sub-chamber 503 through port 522. The chuck 517 described herein may operate at a temperature ranging from about -200°C to about 600°C, or from about -20°C to about 250°C, to process the substrate and etch tantalum, and the chuck 517 may be set to a temperature below about 0°C. The temperature depends on the processing operation, and the specific recipe, and the tools used.

[0189] When installing in a clean room or manufacturing facility, chamber 501 may be connected to a facility (not shown). The facility includes piping that provides process gas, vacuum, temperature control, and environmental particle control. These facilities are connected to chamber 501 when installed within the manufacturing facility of interest. Additionally, chamber 501 may be connected to a transfer chamber that uses typical automated control machinery to enable robotics to transfer semiconductor wafers into and out of chamber 501.

[0190] In some embodiments, system controller 530 (which may include one or more physical or logical controllers) controls some or all of the operation of the processing chamber. System controller 530 may include one or more storage devices and one or more processors. In some embodiments, the apparatus includes a switching system for controlling flow rate and duration when implementing the disclosed embodiments. In some embodiments, the apparatus may have a switching time of up to about 500 ms, or up to about 750 ms. The switching time may depend on the chemistry of the flow, the selected recipe, the reactor architecture, and other factors.

[0191] In some implementations, the controller 530 may be part of a system that may be part of the example described above. Such a system may comprise semiconductor processing equipment including one or more processing tools, one or more chambers, one or more platforms for processing, and / or specific processing components (such as wafer substrate supports, gas flow systems, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing a semiconductor wafer or semiconductor substrate. The electronics may sometimes be referred to as a “controller” that may control various components or subsections of one or more systems. Depending on the processing parameters and / or the type of system, the controller 530 may be programmed to control any of the processes disclosed herein, including delivery of process gases, temperature settings (e.g., heating and / or cooling), pressure settings, vacuum settings, output settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, position and motion settings, wafer transfer into and out of tools and other transfer tools, and / or load locks connected to or interfacing with specific systems.

[0192] Broadly speaking, the controller 530 may be defined as an electronic circuit having various integrated circuits, logic circuits, memories, and / or software that receives instructions, issues instructions, controls operations, enables cleaning operations, enables endpoint measurements, and the like. The integrated circuit may take the form of a chip storing program instructions in the form of firmware, a digital signal processor (DSP), a chip defined as an application specific integrated circuit (ASIC), and / or one or more microprocessors or microcontrollers that execute program instructions (e.g., software). The program instructions may be instructions transmitted to the controller in the form of various individual settings (or program files) that define operating parameters for performing specific processing on a semiconductor wafer, for a semiconductor wafer, or for a system. The operating parameters may, in some embodiments, be part of a recipe defined by a process engineer to achieve one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon oxide, surfaces, circuits, and / or dies of a wafer. In some embodiments, the controller 530 may be used to determine a temperature window for the modification operation of the ALE, or a processing condition window for the removal operation of the ALE, or both.

[0193] In some implementations, the controller 530 may be part of a computer integrated with, coupled to, networked to the system in some other way, or a combination thereof, or may be coupled to the computer. For example, the controller may be in the "cloud" or may be all or part of the host computer system of a semiconductor fabrication facility, thereby enabling remote access to wafer processing. The computer may enable remote access to the system to monitor the current progress of fabrication operations, examine the history of past fabrication operations, and examine trends or performance metrics from multiple fabrication operations, to change the parameters of the current process, set the process steps following the current process, or initiate a new process. In some examples, a remote computer (e.g., a server) can provide a process recipe to the system via a network that may include a local network or the Internet. The remote computer may include a user interface that enables input or programming of parameters and / or settings, and the parameters and / or settings are then communicated from the remote computer to the system. In some examples, the controller 530 receives instructions in the form of data that specify parameters for each of one or more process steps to be performed during an operation. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus, as described above, the controller 530 may be distributed, such as by comprising one or more separate controllers networked together and operating towards a common purpose, such as the processes and controls described herein. An example of such distributed controllers for such a purpose is one or more integrated circuits on a chamber that communicate with one or more remotely located integrated circuits (e.g., at the platform level or as part of a remote computer) combined to control the processing on the chamber.

[0194] Without limitation, the exemplary system may include a plasma etching chamber or module, a deposition chamber or module, a spin rinse chamber or module, a metal plating chamber or module, a cleaning chamber or module, a bevel edge etching chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an ALD chamber or module, an ALE chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing system that may be associated with or used in the fabrication and / or manufacture of semiconductor wafers.

[0195] As noted above, depending on one or more processing steps to be performed by the tool, the controller may communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, nearby tools, adjacent tools, tools located throughout the factory, the main computer, another controller, or tools used in material transport to carry the wafer container between the location of the tool and / or load port within the semiconductor manufacturing facility.

[0196] FIG. 6 depicts a semiconductor processing cluster architecture with various modules that interface with a vacuum transfer module (VTM) 638. An arrangement of transfer modules for "transferring" wafers between multiple storage facilities and processing modules is sometimes referred to as a "cluster tool architecture." An airlock 630, also known as a load lock or transfer module, is shown within the VTM 638 with four processing modules 620a - 620d that may be individually optimized to perform various fabrication processes. By way of example, the processing modules 620a - 620d may be implemented to perform substrate etching, deposition, ion implantation, wafer cleaning, sputtering, and / or other semiconductor processing. One or more of the substrate etching processing modules (any of 620a - 620d) may be implemented as disclosed herein, i.e., for introducing a modifying gas, for introducing a removal gas, and for other suitable functions in accordance with the disclosed embodiments. The airlock 630 and the processing modules 620 are sometimes referred to as "stations." Each station has a facet 636 that interfaces the station to the VTM 638. Inside each facet, sensors 1 - 18 are used to detect the passage of the wafer 626 as the wafer 626 moves between the corresponding stations.

[0197] Robot 622 transfers the wafer 626 between stations. In one embodiment, robot 622 has one arm, and in another embodiment, robot 622 has two arms, in which case each arm has an end effector 624 for picking out wafers such as wafer 626 for conveyance. In the atmospheric transfer module (ATM) 640, the front-end robot 632 is used to transfer the wafer 626 from the cassette or from the FOUP (Front Opening Unified Pod) 634 in the Load Port Module (LPM) 642 to the air lock 630. The module center 628 inside the processing module 620 is a place for placing the wafer 626. The exposure device 644 in the ATM 640 is used to align the wafer.

[0198] In a representative processing method, the wafer is placed in one of the FOUPs 634 in the LPM 642. The front-end robot 632 transfers the wafer from the FOUP 634 to the exposure device 644, so that the wafer 626 can be properly centered before being etched or processed. After aligning the wafer 626, the front-end robot 632 moves the wafer 626 into the air lock 630. Since the air lock module has the ability to reconcile the environment between the ATM and the VTM, the wafer 626 can move between the two pressure environments without being damaged. The wafer 626 is moved from the air lock module 630 by the robot 622 through the VTM 638 into one of the processing modules 620a - 620d. To achieve this wafer transfer, the robot 622 uses the end effector 624 on each of its arms. When the wafer 626 is processed, the robot 622 moves the wafer 626 from the processing modules 620a - 320d to the air lock module 630. From here, the front-end robot 632 moves the wafer 626 to one of the FOUPs 634 or to the exposure device 644.

[0199] Note that the computer that controls wafer movement can be present locally in the cluster architecture, or can be located outside the cluster architecture within the manufacturing site, or can be at a remote location and connected to the cluster architecture via a network. A controller as described above with respect to FIG. 5 may be implemented using the tool within FIG. 6.

[0200] Experimental Experiment 1 Experiments on SOI (silicon on insulator) materials on a substrate were conducted by exposing the substrate to 40 - cycle pulsed atomic layer etching. Each cycle included a 200 sccm chlorine dose for modification at 40 mTorr pulsed at a frequency of 100 Hz, a purge using argon, a 400 sccm helium flow with a 300 W plasma using a bias (on / off) pulsed at a frequency of 100 Hz, and a purge using argon. The etching per cycle was determined for each trial, and each trial used different bias powers in the range of 100 V to 500 V in 50 V increments in the on - state of the bias. In FIG. 7, the bias power is plotted against the etching per cycle in angstrom units. FIG. 7 shows a saturated etching rate, and the self - controlled regime is at a high bias power between 300 V and 500 V, which is substantially higher than the self - controlled bias power with continuous ALE. The scale of the Y - axis depicted in FIG. 7 is linear.

[0201] Experiment 2 Experiments were conducted to determine the etching per cycle for amorphous silicon and silicon oxide materials on a substrate. Both amorphous silicon and silicon oxide were exposed to 70 cycles of pulsed atomic layer etching using helium as the removal gas, and each cycle consisted of 180 sccm of chlorine with 180 sccm of helium for modification at 20 mTorr pulsed at a frequency of 100 Hz without bias, a purge using helium, a 400 sccm helium flow with 0 W of plasma power using a pulsed (on / off) bias at a frequency of 100 Hz, and a purge using helium. The etching per cycle was determined at various bias powers in the on state of the bias ranging from 100 V to 500 V in 100 V increments. In FIG. 8A, the bias power is plotted against the etching per cycle in angstroms, and FIG. 8A shows that the etching per cycle of amorphous silicon (triangles) is higher than that of silicon oxide (circles). The scale of the Y-axis depicted in FIG. 8A is linear. The etching selectivity of amorphous silicon with respect to silicon oxide was calculated and plotted in FIG. 8B, and FIG. 8B shows higher selectivity at lower bias powers and lower selectivity at higher bias powers. These results suggest that the etching selectivity can be achieved using pulsed ALE by adjusting a wider range of bias powers.

[0202] Experiment 3 Experiments were conducted to determine the per-cycle etching for amorphous silicon and silicon oxide materials on a substrate. Both amorphous silicon and silicon oxide were exposed to 200 cycles of pulsed atomic layer etching using argon as the removal gas. Each cycle consisted of 180 sccm of chlorine with 180 sccm of helium for modification at 20 mTorr, pulsed at a frequency of 100 Hz with 200 W of plasma power without bias, a purge using argon, a 400 sccm argon flow with 0 W of plasma power using a pulsed (on / off) bias at a frequency of 100 Hz, and a purge using argon. The per-cycle etching was determined at various bias powers in the on state of the bias ranging from 200 V to 400 V in 25 V or 50 V increments. In FIG. 9A, the bias power is plotted against the per-cycle etching in angstrom units, and FIG. 9A shows that the per-cycle etching of amorphous silicon (triangles) is higher than that of silicon oxide (circles). The scale of the Y-axis depicted in FIG. 9A is linear. The etching selectivity of amorphous silicon with respect to silicon oxide was calculated and plotted in FIG. 9B, and FIG. 9B shows higher selectivity at lower bias powers and lower selectivity at higher bias powers. These results suggest that the etching selectivity can be achieved using pulsed ALE by adjusting a wider range of bias powers.

[0203] Experiment 4 Experiments were conducted on a patterned substrate using pulsed ALE, where the removal gas used was helium. The patterns on the substrate included both iso-structures and high-density structures. The iso-structure had a feature width of 80 nm, the high-density structure had a feature width of approximately 5 nm near the opening of the feature, and the depth of the feature was on the order of 60 nm to 80 nm. The substrate was exposed to multiple cycles of pulsed ALE at a substrate temperature of 120 °C. Each cycle included chlorine irradiation using plasma, a purge using helium, exposure to helium removal gas with a pulsed bias at a duty cycle of 25% for 3 seconds per exposure at a bias power between plasma and 0 V to 65 V, and a purge using helium. For various trenches with a range of critical dimensions, the pitch-loading percentage was calculated and the results were plotted in FIG. 10A. As shown, as the trench size increases, the pitch loading decreases.

[0204] A pattern of a similar structure was exposed to multiple cycles of pulsed ALE at a substrate temperature of 120 °C. Each cycle included chlorine irradiation using plasma, a purge using helium, exposure to helium removal gas with a pulsed bias at a duty cycle of 10% for 3 seconds per exposure at a bias power between plasma and 0 V to 150 V, and a purge using helium. For various trenches with a range of critical dimensions, the pitch-loading percentage was calculated and the results were plotted in FIG. 10B. As shown, as the trench size increases, the pitch loading decreases.

[0205] An image of the substrate was generated. For trenches with a feature opening of less than 10 nm, the image showed that a higher helium bias pulsed between 0 V and 150 V using a 10% duty cycle achieved a similar etching depth for each feature across the entire substrate compared to a lower helium bias pulsed between 0 V and 65 V using a 25% duty cycle.

[0206] Experiment 4 Figure 11 shows a comparison of the etching vs. bias for each cycle during the removal operation for three different curves. Curve 1002 shows an example of the etching per cycle when performing ALE with 3% duty cycle pulsing during the removal operation using a 2 - second exposure time. Curve 1101 shows an example of the etching per cycle when performing ALE with 10% duty cycle pulsing during the removal operation using a 2 - second exposure time. These curves are compared to curve 1103 which performs ALE without pulsing (e.g., 100% duty cycle) using a 7 - second exposure time during removal. As shown, the pulsed embodiments saturate (the 10% duty cycle saturates at approximately 900 eV and the 3% duty cycle saturates at approximately 1500 eV), while the data provided by the non - pulsed embodiment does not have a specific saturation bias voltage.

[0207] Experiment 4 Figure 12A shows an example of experimental data collected for the etching vs. bias voltage per cycle during removal with consecutive exposures. Arrow 1201 shows an example of the ALE window consisting of the voltage at which the etching per cycle saturates.

[0208] Figure 12B shows an example of the time vs. etching per cycle for continuous ALE of silicon. In comparison, the literature shows that the etching amount of the ion beam in the etching reactor as a function of the duration of argon exposure increases between 100 seconds and 300 seconds of argon exposure, followed by a relatively flat slope of the etching amount up to about 650 seconds, and in some cases a slight increase during argon exposure exceeding 700 seconds.

[0209] Experiment 5 Figure 13 shows that the complete removal of ion energy depends on the "on" time of argon ions.

[0210] Figure 14A shows ALE windows for various on - times on a silicon substrate using chlorine as the reforming gas and argon as the removal gas, and the flux rate is F = F 0 (1 + a×V bias ^1.5), where F 0 is determined from experimental data. For example, curve 1401 represents the normalized etching per cycle where each pulse is 0.06 seconds, curve 1402 represents the normalized etching per cycle where each pulse is 0.2 seconds, curve 1403 represents the normalized etching per cycle where each pulse is 0.5 seconds, curve 1405 represents the normalized etching per cycle where each pulse is 1 second, curve 1407 represents the normalized etching per cycle where each pulse is 2 seconds, curve 1408 represents the normalized etching per cycle where each pulse is 3 seconds, and curve 1409 represents the normalized etching per cycle where each pulse is 7 seconds. Line 1410 indicates the amount by which one layer is etched.

[0211] Figure 14B shows an exemplary fit simulation to data showing the per - cycle etching of pulsed ALE that can enable complete removal using the synergistic effect of ALE with a constant on - time of argon. These results suggest that pulsed ALE can enable complete removal using a higher etching rate per cycle with substantially no sputtering, even if the duration of the "on" time during removal is much higher.

[0212] Conclusion 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 made within the scope of the appended claims. Note that there are many alternative ways to implement the processes, stems, and apparatuses of this embodiment. Therefore, this embodiment should be considered illustrative and not restrictive, and the embodiments should not be limited to the details shown herein.

Claims

1. A method for processing a substrate, comprising: providing a substrate having a material to be etched; exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; applying a bias while exposing the modified surface to energy particles to remove the modified surface; and wherein the power applied to the bias is at least 500 eV.

2. A method for processing a substrate, comprising: providing a substrate having a material to be etched; exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; applying a bias to deliver an irradiation dose of energy particles to the modified surface to remove the modified surface; and wherein the irradiation dose is insufficient to remove the modified surface when delivered using a bias voltage less than the surface binding energy of the underlying unmodified surface; and wherein the power applied to the bias is at least 500 eV.

3. A method for processing a substrate, comprising: providing a substrate having a material to be etched; exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; applying a bias to expose the modified surface to energy particles and preferentially removing at least 80% of the modified surface with respect to the underlying unmodified surface for a duration longer than a duration sufficient to remove the modified surface and the underlying unmodified surface by ion bombardment; and wherein the power applied to the bias is at least 500 eV.

4. A method for processing a substrate, comprising: providing a substrate having a material to be etched; exposing a surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; applying a bias with a duty cycle of less than 100% to expose the modified surface to energy particles in the form of pulses; and wherein the power applied to the bias is at least 500 eV.

5. A method for processing a substrate, comprising: providing a substrate having a material to be etched; Exposing the surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; Applying a bias to expose the modified surface to energy particles with a reduced dose of irradiation; comprising; The dose without attenuation has an energy greater than the surface binding energy of the material to be etched when continuously delivered to the modified surface; The power applied to the bias is at least 500 eV. **Claim 6** The method according to claim 5, wherein the dose is attenuated by changing the ion flux of the active species. **Claim 7** The method according to claim 5, wherein the dose is attenuated by changing the duration during which the modified surface is exposed to the active species. **Claim 8** The method according to claim 5, wherein the attenuated dose comprises two or more temporally separated pulses of active species reaching the modified surface to remove at least a portion of the modified surface. **Claim 9** The method according to claim 5, wherein the dose is attenuated by changing the acceleration of the ions of the active species reaching the modified surface. **Claim 10** The method according to claim 5, wherein the dose is attenuated by changing the bias voltage applied to the substrate support holding the substrate to deliver the active species to the modified surface in a specific direction. **Claim 11** A method of processing a substrate, providing a substrate comprising a material to be etched; exposing the surface of the material to be etched to a modifying gas to modify the surface and form a modified surface; applying a bias in temporally separated pulses to expose the modified surface to energy particles; modulating the ion energy and dose during the temporally separated pulses; comprising; The power applied to the bias is at least 500 eV. **Claim 12** The method according to claim 11, wherein the step of modulating the ion energy and the dose comprises increasing the ion energy and compensating for the increase in ion energy with a reduced dose. **Claim 13** A method of processing a substrate, exposing the substrate to a modifying gas to modify the surface of the substrate and form a modified surface; Exposing the modified surface of the substrate to a removal gas; During the step of exposing the modified surface to the removal gas, applying a bias to provide a plurality of temporally separated pulses of energy generated from an activation source to remove at least a portion of the modified surface from the substrate; comprising; The power applied to the bias is at least 500 eV.

14. The method according to claim 13, further comprising repeating the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas in two or more cycles, wherein the plurality of temporally separated pulses of energy are provided during the step of exposing the modified surface to the removal gas in each cycle.

15. The method according to claim 14, wherein the plurality of temporally separated pulses of energy comprise at least 100 temporally separated pulses of energy per cycle.

16. The method according to claim 13, wherein the temporally separated pulse of energy is sufficient to remove the modified surface and insufficient to physically sputter the modified surface.

17. The method according to claim 13, wherein the energy provided is defined by a bias window consisting of a minimum voltage applied to the substrate during exposure to the removal gas sufficient to remove the modified surface and a maximum voltage applied to the substrate during exposure to the removal gas insufficient to sputter the modified surface.

18. The method according to any one of claims 13 to 17, wherein the plurality of temporally separated pulses of energy are pulsed at a frequency between about 10 Hz and about 200 Hz.

19. The method according to any one of claims 13 to 17, wherein the plurality of temporally separated pulses of energy are pulsed at a duty cycle between about 1% and about 10%.

20. The method according to any one of claims 13 to 17, wherein the activation source comprises two or more sources.

21. The method according to any one of claims 13 to 17, wherein the activation source is selected from the group consisting of radio frequency plasma, a bias applied to the substrate, ultraviolet radiation, photons, and combinations thereof.

22. The method according to any one of claims 13 to 17, wherein the activation source is a method comprising a voltage applied to bias the substrate.

23. The method according to claim 22, wherein the bias voltage is between at least about 20 V and about 2000 V.

24. The method according to claim 22, wherein the bias is pulsed between 0 V and the bias voltage between about 20 V and about 2000 V.

25. The method according to claim 22, wherein the bias is pulsed between a low bias voltage between about 100 V and about 300 V and a high bias voltage between about 20 V and about 2000 V.

26. The method according to claim 22, wherein the bias is pulsed using a pulsing frequency between about 10 Hz and about 200 Hz.

27. The method according to claim 22, wherein the bias is pulsed using a duty cycle between about 1% and about 20%.

28. The method according to any one of claims 13 to 17, wherein the activation source is a method comprising radio frequency plasma.

29. The method according to claim 28, wherein radio frequency plasma is generated by applying power and applying the radio frequency plasma power pulsed between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

30. The method according to claim 28, wherein the radio frequency plasma generated by applying the power and the radio frequency plasma power is pulsed between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W, and the high plasma power being between about 900 W and about 1500 W.

31. The method according to claim 28, wherein the radio frequency plasma is pulsed using a pulsing frequency between about 10 Hz and about 200 Hz.

32. The method according to claim 28, wherein the duty cycle of the pulsing of the radio frequency plasma is between about 1% and about 20%.

33. The method according to any one of claims 13 to 17, wherein the activation source comprises a radio frequency plasma and a bias applied to the substrate.

34. The method according to claim 33, wherein the bias is pulsed between 0 V and the bias voltage between about 20 V and about 2000 V.

35. The method according to claim 33, wherein the bias is pulsed between a low bias voltage between about 100 V and about 300 V and a high bias voltage between about 20 V and about 2000 V.

36. The method according to claim 33, wherein radio frequency plasma is generated by applying power and applying the pulsed radio frequency plasma power between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

37. The method according to claim 33, wherein the radio frequency plasma is pulsed between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W and the high plasma power being between about 900 W and about 1500 W.

38. The method according to any one of claims 13 to 17, wherein the substrate comprises one or more narrow features and one or more wide features.

39. The method according to any one of claims 13 to 17, wherein the substrate is processed at a substrate temperature between about 0 °C and about 120 °C.

40. The method according to any one of claims 13 to 17, wherein the substrate is processed in a processing chamber having a chamber pressure between about 5 mTorr (about 666.612 mPa) and about 1 Torr (about 133.322 Pa) during the step of exposing the substrate to the modifying gas.

41. The method according to any one of claims 13 to 17, wherein the substrate is processed in a processing chamber having a chamber pressure between about 5 mTorr (about 666.612 mPa) and about 200 mTorr (about 26664.5 mPa) during the step of exposing the substrate to the removing gas.

42. A method of processing a substrate, exposing the substrate to a modifying gas to modify the surface of the substrate to form a modified surface; exposing the modified surface of the substrate to a removing gas. During the step of exposing the modified surface to the removal gas, a bias is applied to periodically ignite a plasma in the form of two or more temporally separated pulses to remove at least a portion of the modified surface from the substrate; comprising; The power applied to the bias is at least 500 eV.

43. The method according to claim 42, further comprising repeating the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas in two or more cycles, and in each cycle, during the step of exposing the modified surface to the removal gas, providing the two or more temporally separated pulses of plasma.

44. The method according to claim 42, wherein the plurality of temporally separated pulses of plasma comprise at least 100 energy pulses per cycle.

45. The method according to any one of claims 42 to 44, further comprising applying a bias in the form of a pulse during the step of exposing the modified surface to the removal gas.

46. The method according to claim 45, further comprising repeating the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas in two or more cycles, and the two or more temporally separated pulses of the plasma and the bias are provided during the step of exposing the modified surface to the removal gas in each cycle.

47. The method according to claim 45, wherein the plurality of temporally separated pulses of the plasma and the bias comprise at least 100 pulses per cycle, and the cycle comprises the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas.

48. The method according to claim 45, wherein the plasma and the bias are pulsed at the same frequency.

49. The method according to claim 45, wherein the plasma and the bias are pulsed using the same duty cycle.

50. A method of processing a substrate, exposing the substrate to a modifying gas to modify the surface of the substrate to form a modified surface; Exposing the modified surface of the substrate to a removal gas; During the step of exposing the modified surface, igniting a plasma; During the step of exposing the modified surface to the removal gas, applying a bias to periodically apply the bias in the form of two or more temporally separated pulses to remove at least a portion of the modified surface from the substrate; Comprising; The power applied to the bias is at least 500 eV.

51. The method according to claim 50, further comprising, during the step of exposing the modified surface to the removal gas, igniting the plasma in the form of pulses.

52. The method according to claim 50, further comprising repeating the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas in two or more cycles, and in each cycle, providing the pulses of the two or more temporally separated bias powers while exposing the modified surface to the removal gas.

53. The method according to claim 50, wherein the plasma of the plurality of temporally separated bias powers comprises at least 100 pulses per cycle, and the cycle comprises the step of exposing the substrate to the modifying gas and the step of exposing the modified surface to the removal gas.

54. An apparatus for processing a substrate, comprising: A processing chamber comprising a showerhead and a substrate support for holding the substrate having a material; A plasma generator; A controller having at least one processor and a memory; Comprising; The at least one processor and the memory are communicatively connected to each other; The at least one processor is operably connected to flow control hardware; The memory stores; To introduce a modifying gas into the processing chamber; To introduce a removal gas into the processing chamber; During the introduction of the removal gas, applying a bias to generate radio frequency plasma power in the processing chamber in the form of two or more temporally separated pulses; Machine-readable instructions for; The power applied to the bias is at least 500 eV.

55. The apparatus according to claim 54, wherein the memory further stores machine-readable instructions for causing the pulse frequency of the radio frequency plasma power to be between about 10 Hz and about 200 Hz during the introduction of the removal gas.

56. The apparatus according to claim 54, wherein the memory further stores machine-readable instructions for causing the duty cycle of the radio frequency plasma power to be between about 1% and about 20% during the introduction of the removal gas.

57. The apparatus according to claim 54, wherein the memory further stores machine-readable instructions for pulsing the radio frequency plasma power between an off state where the plasma power is 0 W and an on state where the plasma power is between about 50 W and about 900 W.

58. The apparatus according to claim 54, wherein the memory further stores machine-readable instructions for pulsing the radio frequency plasma power between a low plasma power and a high plasma power, the low plasma power being between about 10 W and about 100 W and the high plasma power being between about 900 W and about 1500 W.

59. The apparatus according to any one of claims 54 to 58, wherein the memory further stores machine-readable instructions for applying a bias to the substrate support in the form of a pulse.

60. The apparatus according to claim 59, wherein the memory further stores machine-readable instructions for pulsing the bias between 0 V and a bias voltage between about 20 V and about 2000 V.

61. The apparatus according to claim 59, wherein the memory further stores machine-readable instructions for pulsing the bias between a low bias voltage between about 50 V and about 300 V and a high bias voltage between about 20 V and about 2000 V.

62. The apparatus according to claim 59, wherein the memory further stores machine-readable instructions for pulsing the bias at the same pulse frequency as the radio frequency plasma power.

63. The apparatus according to claim 59, wherein the memory further stores machine-readable instructions for pulsing the bias at the same pulse duty cycle as the radio frequency plasma power.

64. An apparatus for processing a substrate, a processing chamber comprising a showerhead and a substrate support for holding the substrate having a material, A plasma generator and, A controller having at least one processor and a memory Comprising, The at least one processor and the memory are communicably connected to each other, The at least one processor is operably connected to flow control hardware, The memory, To introduce a reformed gas into the processing chamber, To introduce a removal gas into the processing chamber, During the introduction of the removal gas, a bias is applied to the substrate to apply bias power to the substrate support in the form of two or more temporally separated pulses Stores machine-readable instructions for The power applied to the bias is at least 500 eV.

65. The apparatus according to claim 64, wherein the memory further stores machine-readable instructions for causing the pulse frequency of the bias power to be between about 10 Hz and about 200 Hz during the introduction of the removal gas.

66. The apparatus according to claim 64, wherein the memory further stores machine-readable instructions for causing the duty cycle of the bias power to be between about 1% and about 20% during the introduction of the removal gas.

67. The apparatus according to claim 64, wherein the memory further stores machine-readable instructions for pulsing the bias power between an off state where the bias power is 0 V and an on state where the bias power is between about 20 V and about 2000 V.

68. The apparatus according to claim 64, wherein the memory further stores machine-readable instructions for pulsing the bias power between a low bias power and a high bias power, the low bias power being between about 50 V and about 300 V, and the high bias power being between about 20 V and about 2000 V.

69. The apparatus according to any one of claims 64 to 68, wherein the memory further stores machine-readable instructions for igniting a plasma by applying plasma power in the form of pulses during the introduction of the removal gas.

70. The apparatus according to claim 69, wherein the memory further stores machine-readable instructions for pulsing the plasma power between 0 W and a plasma voltage between about 50 W and about 900 W.

71. The apparatus according to claim 69, wherein the memory further stores machine-readable instructions for pulsing the plasma power at the same pulsing frequency as the bias power.

72. The apparatus according to claim 69, wherein the memory further stores machine-readable instructions for pulsing the plasma power at the same pulsing duty cycle as the bias power.

73. The method according to claim 1, wherein the reformed gas comprises argon, helium, neon, krypton, xenon, or a combination thereof.

74. The method according to claim 1, wherein the energy particles have an ion energy greater than the average surface binding energy of the unmodified surface underlying the material to be etched.

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