High-speed atomic layer etch

Abstract

A method for etching an etch layer is provided, the method comprising a plurality of cycles, each cycle comprising: exposing the etch layer to neutral radicals for a time between 10 ms and 600 ms, where the neutral radicals are absorbed into the etch layer to form a modified portion of the etch layer, and exposing the etch layer to bombarding ions for a time between 10 ms and 600 ms, where the bombarding ions remove the modified portion of the etch layer.

Description

[Background technology]

[0001] [CROSS REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of priority to U.S. Application No. 63 / 322,535, filed March 22, 2022, which is incorporated by reference herein for all purposes.

[0002] The background description provided herein is intended to generally present the context of the present disclosure. Nothing described in this background section, and potentially any aspect of the present specification, is admitted explicitly or implicitly as prior art with respect to this application.

[0003] FIELD OF THE DISCLOSURE The present disclosure relates to methods of forming semiconductor devices on semiconductor wafers, and more particularly, the present disclosure relates to selective etching of semiconductor devices.

[0004] In the formation of semiconductor devices, various layers may be selectively etched. Atomic layer etches may be used to achieve highly selective etches. Because atomic layer etches may remove a monolayer with each cycle, the atomic layer etch rate depends on the duration of each cycle.

[0005] Atomic layer etching processes are described in U.S. Pat. No. 10,566,212 by Kanarik, entitled "Designer Atomic Layer Etching," issued on February 18, 2020; U.S. Pat. No. 10,763,083 by Yang et al., entitled "High Energy Atomic Layer Etching," issued on September 1, 2020; U.S. Patent Application Publication No. 2021 / 0005425A1 by Yang et al., entitled "Atomic Layer Etching and Smoothing of Refractory Metals and Other High Surface Binding Energy Materials," published on January 2, 2021; and WO 2020 / 223152 A1 by Yang et al., entitled "Atomic Layer Etching for Subtractive Metal Etch," published on November 5, 2020, all of which are incorporated by reference for all purposes. Summary of the Invention

[0006] To achieve the above, and in accordance with an object of the present disclosure, a method for etching an etch layer is provided, the method comprising a plurality of cycles, where each cycle comprises exposing the etch layer to neutral radicals for a time between 10 ms and 600 ms, where the neutral radicals are absorbed into the etch layer to form a modified portion of the etch layer, and exposing the etch layer to bombarding ions for a time between 10 ms and 600 ms, where the bombarding ions remove the modified portion of the etch layer.

[0007] In another aspect, an etching system for etching an etch layer over a substrate is provided. A substrate support supports a substrate in a processing chamber. An RF power source provides RF power to the etch chamber. A neutral radical source is adapted to provide neutral radicals in the processing chamber. A bombardment gas source is adapted to provide bombardment gas in the processing chamber. A controller is controllably connected to the RF power source, the neutral radical source, and the bombardment gas source. The controller is configured to: expose the etch layer to the neutral radicals for a time between 10 ms and 600 ms, where the neutral radicals are absorbed in the etch layer to form a modified portion of the etch layer; and expose the etch layer to bombardment ions for a time between 10 ms and 600 ms, where the bombardment ions remove the modified portion of the etch layer.

[0008] These and other features of the present disclosure are described in more detail below in the Detailed Description and in conjunction with the following Figures. [Brief description of the drawings]

[0009] The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numbers refer to similar elements.

[0010] [Figure 1] 1 is a high-level flowchart according to some embodiments.

[0011] [Figure 2A] 1 is a schematic cross-sectional view of an exemplary stack processed in accordance with some embodiments. [Figure 2B] 1 is a schematic cross-sectional view of an exemplary stack processed in accordance with some embodiments. [Figure 2C] 1 is a schematic cross-sectional view of an exemplary stack processed in accordance with some embodiments.

[0012] [Figure 3A] 2 is a detailed schematic diagram of an exemplary etch layer processed in accordance with some embodiments. [Figure 3B] 2 is a detailed schematic diagram of an exemplary etch layer processed in accordance with some embodiments. [Figure 3C] 2 is a detailed schematic diagram of an exemplary etch layer processed in accordance with some embodiments.

[0013] [Figure 4] 2A-2C are cross-sectional side views of exemplary etch layers processed in accordance with embodiments.

[0014] [Diagram 5] FIG. 1 is a schematic diagram of an exemplary plasma processing chamber that may be used in some embodiments.

[0015] [Figure 6] FIG. 1 is a schematic diagram of an example computer system that can be used in practicing some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present disclosure will now be described in detail with reference to several preferred embodiments thereof, as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that the present disclosure may be practiced without some or all of these specific details. In other instances, well-known process steps and / or structures have not been described in detail in order not to unnecessarily obscure the present disclosure.

[0017] In the formation of semiconductor devices, various layers may be selectively etched. Atomic layer etching may be used to achieve a highly selective etch. In atomic layer etch (ALE), a cyclic process is performed. The cyclic process may have a first step of modifying a portion of the etch layer and a second step of removing the modified portion of the etch layer. Such an ALE may use a self-limiting process to modify a portion of the etch layer. The self-limiting process may modify several monolayers of the etch layer to form a self-limiting layer. In such a case, removing the modified portion of the etch layer may remove only a monolayer of the etch layer. As a result, many cycles are required to etch a substantial portion of the etch layer. Each cycle may be more than 12 seconds in length. As a result, the ALE process may take a long time to etch a substantial portion of the etch layer.

[0018] To facilitate understanding, FIG. 1 is a high level flow chart illustrating a process used in some embodiments. As shown, an etch layer above a substrate and below a mask is placed in a processing chamber (step 104). FIG. 2A is a schematic cross-sectional view of a mask 212, an etch layer 208 disposed thereunder, and an exemplary wafer 204 thereunder. In some embodiments, the etch layer 208 is silicon and the photoresist mask 212 is a polymer-containing photoresist mask 212. In various embodiments, the photoresist mask may be formed from one or more of an extreme ultraviolet (EUV) photoresist, a metal-containing photoresist, an organometallic photoresist, a tin-containing photoresist, a tin oxide-containing photoresist, and an organotin photoresist. In other embodiments, the mask may not be made from a photoresist material. FIG. 3A is a schematic diagram of an enlarged cross-section of an exposed portion of the etch layer 208 showing atoms 304 therein.

[0019] The etch layer 208 is etched using an atomic layer etch (step 108). The atomic layer etch (step 108) is a cyclic process in which in each cycle, the exposed surface of the etch layer 208 is modified (step 112). The modifying gas is converted to neutral radicals. The neutral radicals may be created by forming a plasma from the modifying gas. In some embodiments, the plasma is formed by providing RF power of greater than 2000 Watts at 13.56 megahertz (MHz). In some embodiments, a pressure between 10 mTorr and 500 mTorr is provided. For example, a pressure of about 35 mTorr may be provided. A higher pressure increases the number of ions that are converted to neutral radicals. A charge may be used to repel the ions from the etch layer 208. In some embodiments where a bias is provided, the bias may be less than 50 eV. In other embodiments, a bias may not be provided during the surface modification (step 112). If a bias is provided, the bias may be either pulsed or continuous. If a pulsed bias is provided, the pulsed bias may have a duty cycle greater than 10% to reduce the time required for surface modification (step 112). The duty cycle may be adjusted to increase neutral radicals and decrease ions. In some embodiments, this surface modification (step 112) occurs for less than 0.5 seconds (s). In some embodiments, the surface modification occurs for a time between 10 milliseconds (ms) and 600 ms. In other embodiments, the surface modification occurs for a time between 50 ms and 300 ms. In various embodiments, various methods may be used to inhibit ions from reaching the etch layer 208. In some embodiments, the flux of neutral radicals near the exposed etch layer is greater than 10 ms. 18 Neutral radicals per square centimeter (cm) per second (s / cm 2 In various embodiments, the flux of neutral radicals is greater than about 10 17 Neutral radicals / cm 2 s~10 20 Neutral radicals / cm2 s. A higher flux of neutral radicals helps reduce the time required for the modification step. A higher flux of neutral radicals can be provided by using one or more of higher pressure, higher RF power, and / or higher flow rate, as well as possibly other factors.

[0020] 2B is a schematic cross-sectional view of the mask 212, the etch layer 208 disposed thereunder, and the exemplary wafer 204 thereunder after the exposed portions of the etch layer 208 have been modified. The modified portions are illustrated diagrammatically by the shaded regions 216. In this example, the shaded regions 216 are not drawn to scale to facilitate understanding, since a few atomic layers are modified. In various embodiments, from about 1 to 30 atomic or molecular layers are modified. FIG. 3B is a schematic diagram of an enlarged cross-section of the exposed portions of the etch layer 208 after a portion of the exposed portions of the etch layer 208 have been modified. Some of the neutral radical atoms 308 form bonds with the exposed atoms 304.

[0021] After reformulation (step 112), a first transition occurs (step 114). The first transition removes the reformulated gas and provides a bombardment gas (also referred to as a stripping gas). In some embodiments, the bombardment gas comprises argon (Ar). In some embodiments, the first transition is achieved in less than 0.5 s. In various embodiments, the first transition is achieved within a range of 1 ms to 500 ms. In some embodiments, the first transition is achieved within a range of 0.2 s to 0.5 s.

[0022] After the first transition (step 114), a removal step is performed (step 116). In some embodiments, the bombardment gas is provided at a pressure of about 20 mTorr. In various embodiments, the pressure is between 1 mTorr and 25 mTorr. In some embodiments, the pressure of the modification gas exceeds the pressure of the bombardment gas by at least 10 mTorr. In some embodiments, the bombardment gas can be converted to a plasma by providing RF power of greater than 500 Watts at 13.56 MHz. In some embodiments, the bias is in the range of 200 eV to 2000 eV. In various embodiments, the bias is greater than 700 eV. In some embodiments, the bias voltage during the removal step is at least 10 times the bias voltage during the modification step. In some embodiments, this removal step (step 116) is performed for less than 0.5 s. In some embodiments, the removal step is performed for a time between 10 ms and 600 ms. In other embodiments, the removal step is performed for a time between 10 ms and 300 ms. In other embodiments, the removal step occurs for a time between 10 ms and 50 ms. In some embodiments, the removal step occurs for a time less than 25 ms. In some embodiments, the bias power is supplied as a continuous wave. In embodiments using a continuous wave, the removal step (step 116) may be for 20 ms in some examples. In some embodiments, the bias power may be pulsed. In a pulsed embodiment, an exemplary pulsed RF bias power may be supplied at a pulsed frequency of 100 Hz, where the RF bias power has a 10% duty cycle during the removal step. In such a pulsed embodiment using a 10% duty cycle, the removal step (step 116) is about 200 ms. In various embodiments, the pulsed bias has a duty cycle between 10% and 100%. In other embodiments, the pulsed bias has a duty cycle between 40% and 100%. A continuous wave bias for 20 ms can provide the same results as a pulsed bias at a 10% duty cycle for 200 ms, if other parameters are the same.Therefore, an embodiment using a continuous bias during the removal step (step 116) for 20 ms can achieve the same removal as a pulsed bias process using a 10% duty cycle for 200 ms. To achieve a short removal step, the bias increase time must be short. In some embodiments, the bias can be increased in less than 100 ms. In some embodiments, the bias can be increased from 0.1 ms to 10 ms. In some embodiments, the flux of bombarding ions near the modified layer can be increased in less than 10. 17 ions / cm 2 In some embodiments, the flux of ions is greater than about 10 17 ions / cm 2 s~10 21 ions / cm 2 s. Higher flux and higher energy ion bombardment reduces the time required for the removal step.

[0023] Figure 2C is a schematic cross-sectional view of the mask 212, the etch layer 208 disposed thereunder, and the wafer 204 thereunder after the removal step (step 116). The modified portions have been removed. Figure 3C is a schematic close-up cross-sectional view of the exposed portion of the etch layer 208 during the removal step. Ions 312 bombard the etch layer, causing the modified atoms 304 associated with the neutral radical atoms 308 to be removed.

[0024] After the removal step (step 116), a second transition occurs (step 118). The second transition removes the bombardment gas and provides the modified gas. In some embodiments, the second transition is achieved in less than 0.5 s. In various embodiments, the second transition is achieved within a range of 1 ms to 500 ms. In some embodiments, the first transition is achieved within a range of 0.2 s to 0.5 s.

[0025] The cycle of steps of modifying (step 112), first transition (step 114), removing (step 116), and second transition (step 118) is repeated multiple times until the feature is etched to a desired depth. In some embodiments, 70 Å is etched in each cycle.

[0026] Some embodiments are capable of increasing the etch rate by more than 10 times over prior art ALE processes. The use of one or more of the neutral radicals, faster transition times, the use of continuous wave or high duty cycle bias, and / or a larger ion flux during bombardment enable such faster embodiments. In an example, each cycle may be less than 35 ms. In some embodiments, each cycle is between about 20 ms and 1500 ms. In other embodiments, each cycle is between about 30 ms and 1000 ms.

[0027] 4 is a cross-sectional side view of the etch layer 208 etched in accordance with some embodiments. Note that the depth of the narrow features is approximately equal to the depth of the wide features. In addition, the bottom of the wide features is relatively flat. In addition, most of the patterned photoresist mask 212 remains, indicating that the etch is highly selective.

[0028] The use of neutral radicals in combination with high flux and low bias has been found to provide a monolayer in less than 0.5 s. The time for absorption of neutral radicals in forming a monolayer can be modeled accordingly in the following relationship:

number

[0029] It has been found that the use of higher energy ions in combination with a high flux allows removal of the modified monolayer in less than one second. The time to remove the modified layer can be modeled according to the following relationship:

number

number

[0030] In various embodiments, the modifying gas is chlorine gas (Cl2) and the neutral radicals are chlorine neutral radicals. When the modifying gas is chlorine gas, in some embodiments, the etch layer is a silicon etch layer. The silicon etch layer can be doped silicon. In other embodiments, the etch layer can be other silicon-containing etch layers, such as silicon germanium (SiGe), silicon nitride (SiN), or silicon oxide (SiO2). In other embodiments, the etch layer can be a metal etch layer. The metal etch layer can be ruthenium (Ru), molybdenum (Mo), tungsten (W), tantalum (Ta), or titanium (Ti). In other embodiments, the etch layer can be a metal-containing etch layer, such as titanium nitride (TiN) or tantalum nitride (TaN). In other embodiments, the etch layer can be a metalloid or metalloid-containing layer, such as germanium (Ge) or a germanium-containing layer.

[0031] In other embodiments, the modifying gas is an oxygen-containing gas and the radical neutrals are oxygen atoms. In such embodiments, the mask may be SiO2 or SiN. When the modifying gas is an oxygen-containing gas, the etch layer may be a carbon-containing layer, such as an amorphous carbon layer with some hydrogen or pure carbon, or a ruthenium-containing layer. In various embodiments, the oxygen-containing gas is oxygen gas (O2), carbon dioxide (CO2), carbon monoxide (CO), sulfur dioxide (SO2), and water (H2O). In various embodiments, the modifying gas consists essentially of chlorine gas or an oxygen-containing gas. In various embodiments, the bombardment gas may include Ar, helium (He), neon (Ne), krypton (Kr), and xenon (Xe). In some embodiments, the bombardment gas consists essentially of one or more of Ar, He, Ne, Kr, and Xe. For example, Ar+ bombardment ions may be generated from an Ar bombardment gas.

[0032] To provide an example of a processing chamber that may be used in some embodiments, Figure 5 illustrates generally an example of a plasma processing chamber system 500 that may be used for a plasma treatment process. The plasma processing chamber system 500 includes a plasma reactor 502 having a plasma processing confinement chamber 504 therein. A plasma power supply 506, tuned by a plasma matching network 508, powers a transformer coupled plasma (TCP) coil 510 positioned near a dielectric inductive power window 512 to create a plasma 514 in the plasma processing confinement chamber 504 by providing inductively coupled power.

[0033] The TCP coil (upper power supply) 510 may be configured to provide a uniform diffusion profile in the plasma processing confinement chamber 504. For example, the TCP coil 510 may be configured to generate an annular power distribution in the plasma 514. A dielectric induction power window 512 is provided to isolate the TCP coil 510 from the plasma processing confinement chamber 504 while allowing energy to be transferred from the TCP coil 510 to the plasma processing confinement chamber 504. The TCP coil 510 acts as an electrode to provide radio frequency (RF) power to the plasma processing confinement chamber 504. A wafer bias voltage power supply 516 tuned by a bias matching network 518 provides power to an electrode 520 to set a bias voltage on a substrate 566. The substrate 566 is supported by the electrode 520, and thus the electrode acts as a substrate support. A controller 524 controls the plasma power supply 506 and the wafer bias voltage power supply 516.

[0034] The plasma power source 506 and the wafer bias voltage power source 516 may be configured to operate at a particular radio frequency, such as, for example, 13.56 megahertz (MHz), 27 MHz, 2 MHz, 60 MHz, 400 kilohertz (kHz), 2.54 gigahertz (GHz), or a combination thereof. The plasma power source 506 and the wafer bias voltage power source 516 may be appropriately sized to provide a range of power to achieve a desired process performance. For example, in some embodiments, the plasma power source 506 may provide power in the range of 50-5000 watts, and the wafer bias voltage power source 516 may provide a bias voltage in the range of 20-2000 V. In addition, the TCP coil 510 and / or the electrode 520 may be comprised of two or more sub-coils or sub-electrodes. The sub-coils or sub-electrodes may be powered by a single power source or may be powered by multiple power sources.

[0035] As shown in FIG. 5, the plasma processing chamber system 500 further includes a gas source / gas supply mechanism 530. The gas source 530 is in fluid communication with the plasma processing confinement chamber 504 through a gas inlet, such as a gas injector 540. The gas injector 540 may be located at any advantageous location in the plasma processing confinement chamber 504 and may take any form for injecting gas. However, preferably, the gas inlet may be configured to provide a “tunable” gas injection profile. The adjustable gas injection profile allows for independent adjustment of the respective flow of gas to multiple zones in the plasma process confinement chamber 504. More preferably, the gas injector is mounted to the dielectric induction power window 512. The gas injector may be mounted on, in, or form a part of the power window. Process gases and by-products are removed from the plasma process confinement chamber 504 via a pressure control valve 542 and a pump 544. The pressure control valve 542 and the pump 544 also serve to maintain a particular pressure in the plasma processing confinement chamber 504. A pressure control valve 542 can maintain a pressure of less than 1 Torr during processing. An edge ring 560 is positioned around the substrate 566. The gas source / gas delivery mechanism 530 is controlled by a controller 524. An example of such a plasma processing chamber system 500 is described in PCT Application PCT / US21 / 31490, entitled Distributed Plasma Source Array, filed May 10, 2021, which is incorporated by reference for all purposes. An example of such a plasma processing chamber is the Syndion® Etch System manufactured by Lam Research, Fremont, California.

[0036] 6 is a high-level block diagram illustrating a computer system 600. The computer system 600 is suitable for implementing the controller 524 used in the embodiments. The computer system 600 can have many physical forms ranging from integrated circuits, printed circuit boards, and small handheld devices to large supercomputers. The computer system 600 includes one or more processors 602 and can further include an electronic display device 604 (for displaying graphics, text, and other data), a main memory 606 (e.g., random access memory (RAM)), a storage device 608 (e.g., a hard disk drive), a removable storage device 610 (e.g., an optical disk drive), a user interface device 612 (e.g., a keyboard, touch screen, keypad, mouse or other pointing device, etc.), and a communication interface 614 (e.g., a wireless network interface). The communication interface 614 allows software and data to be transferred between the computer system 600 and external devices over a link. The system may also include a communication infrastructure 616 (eg, a communication bus, crossover bar, or network) to which the above-mentioned devices / modules are connected.

[0037] Information transferred via communication interface 614 may be in the form of signals, such as electronic, electromagnetic, optical, or other signals, that carry signals and can be received by communication interface 614 over a communication link, which may be implemented using wire or cable, fiber optics, telephone line, cellular phone link, radio frequency link, and / or other communication channel. It is contemplated that using such communication interface 614, one or more processors 602 may receive information from a network or output information to a network in the course of performing the method steps described above. Moreover, method embodiments may execute solely on the processor or may execute over a network, such as the Internet, with a remote processor sharing a portion of the processing.

[0038] The term "non-transitory computer-readable medium" is used generally to refer to media such as main memory, secondary memory, removable storage, and storage devices, such as hard disks, flash memory, disk drive memory, CD-ROMs, and other forms of persistent memory, and should not be interpreted to encompass transitory subject matter, such as carrier waves or signals. Examples of computer-readable code include machine code, such as that produced by a compiler, and files containing higher level code that is executed by a computer using an interpreter. The computer-readable medium may also be computer code transmitted to a processor by a computer data signal.

[0039] In some embodiments, the computer readable medium may comprise computer readable code for performing a reformulation step in less than 0.5 seconds (Step 112), computer readable code for performing a first transition from the reformulated gas to the shock gas in less than 0.5 seconds (Step 114), computer readable code for performing a removal step in less than 0.5 seconds (Step 116), and computer readable code for performing a second transition from the shock gas to the reformulated gas in less than 0.5 seconds (Step 118).

[0040] In other embodiments, instead of forming the plasma in the reactor in which the substrate is placed, the plasma can be formed remotely for the modification step. Radical neutrals can be provided by a remote plasma source. In some embodiments, charged ions are prevented from entering the reactor during the modification step.

[0041] While the present disclosure has been described with respect to several preferred embodiments, there are changes, modifications, substitutions, and various substitute equivalents that fall within the scope of the present disclosure. It should also be noted that there are many alternative ways of implementing the methods and apparatuses of the present disclosure. It is therefore intended that the following appended claims be interpreted to include all such changes, modifications, substitutions, and various substitute equivalents that fall within the true spirit and scope of the present disclosure.

Claims

1. 1. A method for etching an etch layer, the method comprising a plurality of cycles, each cycle comprising: exposing the etch layer to neutral radicals for a time between 10 ms and 600 ms, wherein the neutral radicals are absorbed into the etch layer to form a modified portion of the etch layer; exposing the etch layer to bombardment ions for a time between 10 ms and 600 ms, the bombardment ions removing the modified portion of the etch layer; A method comprising:

2. 10. The method of claim 1, wherein said exposing said etch layer to bombarding ions provides a bias greater than 700 eV.

3. 2. The method of claim 1 , wherein the neutral radical is 10 17 Neutral radicals / cm 2 s.

4. 2. The method of claim 1, wherein the bombarding ions are 17 ions / cm 2 s.

5. 10. The method of claim 1, wherein the exposing the etch layer to bombarding ions is for a time between 10 ms and 250 ms.

6. 10. The method of claim 1, wherein the exposing the etch layer to bombarding ions is for a time between 10 ms and 25 ms.

7. 2. The method of claim 1, wherein the exposing the etch layer to bombarding ions comprises providing a bias in a range of 200 eV to 2000 eV.

8. The method of claim 7 , wherein the bias is a continuous wave bias.

9. 8. The method of claim 7, wherein the bias is a pulsed bias.

10. 8. The method of claim 7, wherein the bias is increased in less than 100 ms.

11. 2. The method of claim 1 , performing a first transition from a modified gas to a bombardment gas in less than 0.5 seconds, the modified gas being converted to provide the neutral radicals and the bombardment gas being converted to bombarding ions, the first transition being after the exposure of the etch layer to neutral radicals and prior to exposing the etch layer to bombardment ions; performing a second transition from the bombardment gas to the modified gas, the second transition being after the exposure of the etch layer to the bombardment ions and before the exposure of the etch layer to neutral radicals; The method further comprises:

12. 2. The method of claim 1, wherein the neutral radical is a chlorine atom or an oxygen atom.

13. 2. The method of claim 1, wherein the bombarding ions are ions of argon, helium, neon, krypton, and xenon.

14. 10. The method of claim 1, wherein the exposing the etch layer to bombarding ions comprises providing an RF power of greater than 2000 W.

15. 1. An etching system for etching an etch layer above a substrate, the etching system comprising: a processing chamber; a substrate support for supporting a substrate in the processing chamber; an RF power source for supplying RF power to the etch chamber; a neutral radical source adapted to provide neutral radicals into the processing chamber; an impingement gas source adapted to supply an impingement gas into the processing chamber; a controllable connection to the RF power source, the neutral radical source, and the bombardment gas source; a) exposing the etch layer to neutral radicals for a time between 10 ms and 600 ms, wherein the neutral radicals are absorbed into the etch layer to form a modified portion of the etch layer; b) exposing the etch layer to bombardment ions for a time between 10 ms and 600 ms, the bombardment ions removing the modified portion of the etch layer; A controller configured to: An etching system comprising:

16. 16. The etching system of claim 15, wherein said exposing said etch layer to bombarding ions provides a bias greater than 700 eV.

17. 16. The etching system of claim 15, wherein the neutral radicals are 10 17 Neutral radicals / cm 2 s is a flux greater than s.

18. 16. The etching system of claim 15, wherein the bombarding ions are 17 ions / cm 2 s is a flux greater than s.

19. 16. The etching system of claim 15, wherein said exposing said etch layer to bombarding ions comprises providing a bias in a range of 200 eV to 2000 eV.

20. 20. The etching system of claim 19, wherein the bias is a continuous wave bias.

21. 20. The etching system of claim 19, wherein the bias is a pulsed bias.

22. 20. The etching system of claim 19, wherein the bias is increased in less than 100 ms.

23. 16. The etching system of claim 15, wherein the controller: performing a first transition from a modified gas to a bombardment gas in less than 0.5 seconds, the modified gas being converted to provide the neutral radicals and the bombardment gas being converted to bombarding ions, the first transition being after the exposure of the etch layer to neutral radicals and prior to exposing the etch layer to bombardment ions; performing a second transition from the bombardment gas to the modified gas, the second transition being after the exposure of the etch layer to the bombardment ions and before the exposure of the etch layer to neutral radicals; The etching system is further configured to:

24. 16. The etching system of claim 15, wherein said exposing said etch layer to bombarding ions comprises providing an RF power of greater than 2000 W.

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