High energy atomic layer etching of carbon-containing layers.

Abstract

The method comprises a plurality of cycles, where each cycle comprises exposing the carbon-containing etch layer to oxygen radicals to modify a portion of the carbon-containing etch layer, where the carbon-containing etch layer is exposed to bombarding ions having an energy greater than 100 eV for less than 0.5 seconds, where the bombarding ions remove the modified portion of the carbon-containing etch layer to form an etched feature.

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, and U.S. Application No. 63 / 345,655, filed May 25, 2022, which are 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 etching may be used to achieve a highly selective etch. Because atomic layer etching may remove several atomic layers for 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.

[0006] Additionally, U.S. Patent No. 10,685,836, entitled "Etching Substrates Using ALE and Selective Deposition" by Tan et al., issued June 16, 2020, which is incorporated by reference for all purposes, discloses a process for atomic layer etch (ALE) of carbon-containing layers using a low voltage bias. U.S. Patent No. 10,304,659, entitled "ALE Smoothness: In and Outside Semiconductor Industry" by Kanarik et al., issued May 28, 2019, which is incorporated by reference for all purposes, discloses a process for atomic layer etch (ALE) of carbon-containing layers, such as amorphous carbon, using a low voltage bias. The low bias is used to reduce or prevent physical sputtering.

[0007] An oxygen-containing reactive ion etch may be used to etch the carbon-containing layer beneath the hard mask. The reactive ion etch may use high energy ions at low pressure to etch the etch layer. The reactive ion etch may not provide the desired etch selectivity. Summary of the Invention

[0008] To achieve the above, and in accordance with an object of the present disclosure, a method is provided for etching a carbon-containing etch layer, the method comprising a plurality of cycles, wherein each cycle comprises exposing the carbon-containing etch layer to oxygen radicals to modify a portion of the carbon-containing etch layer, the carbon-containing etch layer being exposed to bombarding ions having an energy greater than 100 eV for less than 0.5 seconds, wherein the bombarding ions remove the modified portion of the carbon-containing etch layer to form an etched feature.

[0009] In another aspect, an etching system for etching a carbon-containing 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. An oxygen radical source is adapted to provide oxygen 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 oxygen radical source, and the bombardment gas source. The controller is configured to provide a plurality of cycles, where each cycle includes exposing the carbon-containing etch layer to oxygen radicals, where the oxygen radicals are absorbed in the carbon-containing etch layer to form a modified portion of the carbon-containing etch layer, and exposing the etch layer to bombardment ions having an energy greater than 100 eV for a time less than 0.5 seconds, where the bombardment ions remove the modified portion of the carbon-containing etch layer.

[0010] 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]

[0011] 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.

[0012] [Figure 1] 1 is a high-level flowchart according to some embodiments.

[0013] [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.

[0014] [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.

[0015] [Figure 4A] 1 is a graph illustrating the number of angstroms (Å) etched per cycle during ALE etching for only a modification step and for only a removal step at different pulsed bias voltages according to some embodiments.

[0016] [Figure 4B] FIG. 4B is a graph of synergy from the data in FIG. 4A.

[0017] [Figure 5A] 13 is a graph illustrating the number of angstroms (Å) etched per cycle during ALE etching for only a modification step and for only a removal step at different pulsed bias voltages in accordance with another embodiment.

[0018] [Figure 5B] FIG. 5B is a graph of synergy from the data in FIG. 5A.

[0019] [Figure 6A] 1A-1C are cross-sectional side views of example carbon-containing etch layers etched in accordance with some embodiments.

[0020] [Figure 6B] FIG. 6B is a perspective view of the carbon-containing etched layer shown in FIG. 6A.

[0021] [Figure 7A] 1A-1C are cross-sectional side views of example carbon-containing etch layers etched in accordance with other embodiments without passivation.

[0022] [Figure 7B] FIG. 7B is a perspective view of the carbon-containing etched layer shown in FIG. 7A.

[0023] [Figure 8A] 1A-1C are cross-sectional side views of example carbon-containing etch layers etched in accordance with other embodiments using passivation.

[0024] [Figure 8B] FIG. 8B is a perspective view of the carbon-containing etch layer shown in FIG. 8A.

[0025] [Figure 9] FIG. 1 is a schematic diagram of an exemplary plasma processing chamber that may be used in some embodiments.

[0026] [Figure 10] FIG. 1 is a schematic diagram of an example computer system that can be used in practicing some embodiments.

[0027] [Figure 11A] 1 is a schematic diagram of a stack processed according to some embodiments. [Figure 11B] 1 is a schematic diagram of a stack processed according to some embodiments. [Figure 11C] 1 is a schematic diagram of a stack processed according to some embodiments. [Figure 11D] 1 is a schematic diagram of a stack processed according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] 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.

[0029] 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 a few 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 few atomic layers 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.

[0030] ALE processes used to etch carbon-containing etch layers, such as amorphous carbon, use a low bias voltage. In such processes, a low bias voltage may be applied for several seconds to perform ALE while preventing or reducing sputtering caused by higher bias. Some of the disadvantages of such processes using low bias are that such ALE processes are slower and the ions under low bias for ALE processes are not highly directional. Because the ions are not highly directional, the resulting features do not have a high aspect ratio of height to width.

[0031] To facilitate understanding, FIG. 1 is a high-level flow chart illustrating a process used in some embodiments. As shown, a carbon-containing 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, a carbon-containing etch layer 208 disposed thereunder, and an exemplary wafer 204 thereunder. In some embodiments, the carbon-containing etch layer 208 is a carbon-based layer. In various embodiments, the mask may be formed from a photoresist, such as 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 cross-sectional view of an enlarged portion of an exposed portion of the carbon-containing etch layer 208 showing carbon atoms 304 therein.

[0032] The carbon-containing 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 carbon-containing etch layer 208 is modified (step 112). In some embodiments, a modifying gas is provided. In various embodiments, the modifying gas includes an oxygen-containing component. The oxygen-containing component is oxygen gas (O 2 ), carbon dioxide (CO 2 ), carbon monoxide (CO), carbonyl sulfide (COS), sulfur dioxide (SO 2 ), and water (H 2 In some embodiments, the aryl group may be at least one of the following: (O) 2 ) may provide an improved ALE process. In some embodiments, CO 2is used to provide oxygen-containing components and to provide carbon for sidewall passivation to reduce sidewall undercutting. The modification gas is converted into a plasma containing oxygen radicals. In some embodiments, the plasma is formed by providing about 100 watts of RF power at 13.56 megahertz (MHz). In various embodiments, RF power of more than 100 watts or more than 2000 watts is provided. In some embodiments, the pressure is between 10 mTorr and 500 mTorr. For example, a pressure of about 40 mTorr is provided. Higher pressure increases the number of ions that are converted to neutral radicals. In some embodiments, the oxygen radicals can be oxygen ions or neutral oxygen radicals. A charge can be used to repel ions from the carbon-containing etch layer 208. If a bias is provided, in some embodiments, the bias is less than 50 eV. Since the modification process is not removing any material, a low bias or no bias is provided during the surface modification. For example, some embodiments do not provide a bias during the modification step (step 112). With a low or no bias applied, neutral oxygen radicals effect the modification instead of oxygen ions. The oxygen radicals form bonds with carbon from the carbon etch layer, resulting in modification of the carbon etch layer regions.

[0033] FIG. 2B is a schematic cross-sectional view of the mask 212, the carbon-containing etch layer 208 disposed thereunder, and the exemplary wafer 204 thereunder after the exposed portion of the carbon-containing etch layer 208 has been modified. The modified portion is illustrated diagrammatically by the shaded region 216. In this example, only a few atomic layers are modified, so the shaded region 216 is not drawn to scale to facilitate understanding. 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 portion of the carbon-containing etch layer 208 after the portion of the exposed portion of the etch layer 208 has been modified. Some of the radical oxygen atoms 308 form bonds with the exposed carbon atoms 304. In some embodiments, a portion of the carbon-containing etch layer 208 may be etched away during the modification step.

[0034] After reformulation (step 112), a first transition is performed (step 114). The first transition removes the reformulated gas and provides a shock gas (also called a removal gas). In various embodiments, the shock gas is hydrogen (H 2 ), nitrogen (N 2 The bombardment gas may be one or more of Ar, Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), and Xenon (Xe). For example, the bombardment gas may include Ar, which is readily available and has a higher mass than He and Ne. In various embodiments, the first transition is achieved within a range of 1 ms to 500 ms. In some embodiments, the first transition is completed within a range of 0.1 s to 3 s. For example, the first transition is achieved in less than 0.5 s.

[0035] After the first transition (step 114), a removal step is performed (step 116). In some 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. For example, the bombardment gas is provided at a pressure of about 5 mTorr. A lower pressure of the bombardment gas results in fewer collisions in the bombardment plasma, allowing for a more directional ion flow. It is more important that the bombardment ions are more directional than the modification ions, so that the bombardment ions can provide higher aspect ratio features. In some embodiments, RF power greater than 500 Watts is provided. For example, the bombardment gas is converted into a plasma by providing 300 Watts of RF power at 13.56 MHz. In some embodiments, the bias is in the range of 100 eV to 2000 eV. In various embodiments, the bias is in the range of 400 eV to 1500 eV. In other embodiments, the bias is greater than 500 eV. A higher energy bias provides more directional ions. In some embodiments, the ions are highly directional in the vertical direction to form vertical features with high depth to width ratios. Previously, such high biases were avoided to prevent physical sputtering because physical sputtering is not selective. Some embodiments avoid or reduce physical sputtering by providing a bias for a short period of time. The bias is applied for a period of time long enough to effect removal of the modified portions of the etch layer and short enough to reduce or eliminate physical sputtering. In some embodiments, the bias is provided for a period of time between 0.3 ms and 500 ms. In some embodiments, the bias is provided for a period within the range of 5 ms to 300 ms.

[0036] In some embodiments, the bias is applied as a continuous bias for a period of 0.3 ms to 500 ms for the cyclic removal step (step 116). Thus, in some embodiments, the removal step occurs for a period of 0.3 ms to 500 ms. In some embodiments, a pulsed bias is provided. For example, the bias may be pulsed at 100 Hz with a 10% duty cycle. In such an example, the bias is applied for 1 ms for each bias pulse at 100 Hz. In this example, if the removal step occurs for 2 seconds, the bias is applied for 10% of 2 seconds, which is 0.2 seconds or 200 ms. With a pulsed bias, some embodiments provide a bias for a period of 0.3 ms to 500 ms in total during the cyclic removal step (116) to reduce physical sputtering. At a 10% duty cycle, the removal step (step 116) of each cycle is from 3 ms to 5000 ms in length. Different embodiments may provide different duty cycles from 1% to 100%, and different frequencies. In some embodiments, the removal step occurs for a time between 10 ms and 6000 ms. In some embodiments, the removal step occurs for a time between 100 ms and 6000 ms.

[0037] Having a higher ion flux allows for a faster removal step (step 116) without increasing physical sputtering. However, the flux should be low enough to minimize collisions between the bombarding ions, thereby making the ions directional. In some embodiments, the flux of ions is about 10 15 ions / cm 2 s~10 20 ions / cm 2 In some embodiments, the flux of ions near the modified layer is between 10 17 ions / cm 2 s. Higher flux and higher energy ion bombardment reduces the time required for the removal step.

[0038] FIG. 2C is a schematic cross-sectional view of the mask 212, the carbon-containing etch layer 208 disposed thereunder, and the wafer 204 thereunder after the removal step (step 116). The modified portions have been removed. FIG. 3C is a schematic close-up cross-sectional view of the exposed portion of the carbon-containing etch layer 208 during the removal step. Argon ions (Ar + ) 312 bombards the carbon-containing etch layer, causing the modified carbon atoms 304 associated with oxygen atoms 308 to be removed.

[0039] After the removal step (step 116), a second transition is performed (step 118). The second transition removes the bombardment gas and provides the modified gas. In some embodiments, the second transition is accomplished in less than 0.5 s. In various embodiments, the second transition is accomplished within a range of 1 ms to 0.5 s. In some embodiments, the first transition is completed within a range of 0.1 s to 3 s.

[0040] 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 the desired depth.

[0041] In some embodiments, an optional passivation (step 122) is performed. During the passivation step, a passivation gas is provided. In some embodiments, the passivation gas is tungsten hexafluoride (WF 6). In some embodiments, the passivation gas is converted to a plasma. A passivation is formed on the sidewalls of the etched features to passivate the sidewalls to reduce undercutting during a subsequent etch step. In some embodiments, the passivation (step 122) is performed in a separate step at a different time than the atomic layer etch (step 108). In other embodiments, the passivation (step 122) is performed simultaneously with the atomic layer etch (step 108). In some embodiments where the passivation (step 122) is performed simultaneously with the atomic layer etch (step 108), the passivation gas is provided simultaneously with at least one of exposing the carbon-containing etch layer to oxygen radicals and exposing the carbon-containing layer to bombarding ions. In some embodiments, the carbon-containing layer is a carbon hard mask, e.g., an amorphous carbon layer. In other embodiments, the carbon-containing layer is not a carbon hard mask, which is weaker carbon with dangling bonds. For example, the carbon-containing layer can be an underlayer under the mask. Such carbon-containing materials that are not hardmasks with weak dangling bonds are more susceptible to sidewall etching and undercutting. As a result, passivation is more effective at protecting sidewalls when the carbon-containing layer is not a hardmask carbon material. In some embodiments, CO is used as the modifying gas. 2 The use of CO provides carbon for sidewall passivation. 2 When toluene is used as the modifying gas, the resulting plasma provides oxygen radicals to modify the carbon etch layer and carbon species that provide passivation of the sidewalls of the etch features. In some embodiments, methane (CH 4 ), fluoromethane (CH 3 Other carbon-containing gases, such as nitrogen (N) with methane, and CO, can be added to provide carbon for sidewall passivation. The ratio of carbon-containing gas to oxygen-containing gas can be used as a knob to adjust sidewall passivation. In some embodiments, passivation is performed using nitrogen with methane (N 2This can be done by supplying a 2500 sulphur dioxide (2500 sulphur) gas. The nitrogen combines with the carbon from the methane to form a carbon and nitrogen based passivation layer. In some embodiments, boron trichloride (BCl 3 ) and N 2 may be used to provide a boron nitride passivation. In some embodiments, a silicon-based passivation may be provided.

[0042] FIG. 4A is an exemplary graph illustrating the number of angstroms (Å) of a carbon-containing etch layer etched per cycle during ALE etching only for a modification step and only for a removal step at different pulsed bias voltages according to some embodiments. FIG. 4A shows that at bias voltages ranging from 100 volts to 800 volts using the parameters in the above embodiment, the modification step only etches about 0.8 Å per cycle, and the removal step without the modification step etches within the range of about 0.7 Å to 1.3 Å per cycle. FIG. 4A further shows that at a bias of about 800 volts, ALE cycling between a modification step (step 112) followed by a removal step (step 116) etches about 10 Å per cycle, and the removal step without the modification step at a bias of about 800 volts etches about 1.3 Å. Thus, at a bias of about 800 volts, the modification step alone etches about 0.8 Å, and the removal step alone etches about 1.3 Å, for a total of about 2.1 Å. However, an ALE cycle of a modification step followed by a removal step at a bias of about 800 volts removes about 10 Å. As a result, ALE etches about 5 times the amount etched by the individual modification and removal steps alone. This means that the modification and removal steps combined in a cyclic ALE process have a synergistic effect of about 80%, where synergistic effect is defined by the following formula:

number

[0043] Figure 4B is a graph of the synergy from the data in Figure 4A. At bias voltages in the range of 400 volts to 800 volts, the synergy is approximately 80%.

[0044] In some embodiments, the reformulated gas is CO supplied at a pressure of about 40 millitorr. 2 100W of TCP power is provided for about 1 second for each cycle. The parameters of the removal step are the same as in the previous embodiment. FIG. 5A is a graph illustrating the number of Å etched per cycle during ALE etching only for the modification step and only for the removal step at different pulse bias voltages in some embodiments. FIG. 5B is a graph of synergy from the data in FIG. 5A. At bias voltages in the range of 200 volts to 800 volts, synergy of greater than 80% is obtained.

[0045] Using an atomic layer etch process allows for a highly selective etch of the carbon-containing etch layer 208 relative to the mask 212. Etching by physical sputtering has lower selectivity than an atomic layer etch process, which first modifies the carbon etch layer and then selectively removes the modified portions of the carbon etch layer.

[0046] FIG. 6A shows that the reformed gas is CO 2 6A is a cross-sectional side view of a carbon-containing etch layer 208 etched according to an embodiment in which a passivation gas is not provided, and the carbon-containing etch layer 208 is a carbon hard mask. FIG. 6B is a perspective view of the carbon-containing etch layer 208 shown in FIG. 6A.

[0047] 11A is a schematic diagram of a stack 1100 that may be etched in some embodiments. In some embodiments, the stack 1100 comprises an extreme ultraviolet (EUV) mask 1120, an underlayer 1116 disposed thereunder, a carbon hardmask layer 1112 disposed thereunder, an etch layer 1108 disposed thereunder, and a wafer 1104 underneath. In some embodiments, one or more layers may be between the various layers. In some embodiments, the underlayer 1116 is a material that provides improved performance of the EUV mask 1120 by enabling a reduced EUV dose for patterning the EUV mask 1120. In some embodiments, the carbon hardmask layer 1112 is amorphous carbon. Examples of carbon hard mask layer 1112, EUV mask 1120, and underlayer 1116 that may be used in some embodiments are described in WO2021 / 146138A1 by Xue et al., entitled “Underlayer for Photoresist Adhesion and Dose Reduction,” published July 22, 2021, which is incorporated by reference for all purposes.

[0048] In some embodiments, the underlayer 1116 is etched to transfer the pattern of the EUV mask 1120 to the underlayer 1116. Figure 11B is a schematic diagram of the stack 1100 after the underlayer 1116 has been etched. The pattern of the EUV mask 1120 has been transferred to the underlayer 1116.

[0049] After the pattern is transferred to the underlayer 1116, in some embodiments, the sidewalls of the underlayer 1116 are passivated. 6 A plasma formed from WF is used to provide sidewall passivation of the underlayer 1116. FIG. 11C shows that the sidewalls of the underlayer 1116 are passivated by WF 6 11 illustrates generally how the plasma component 1124 may be exposed to plasma from a plasma formed from the.

[0050] During or after the passivation of the sidewalls of the underlayer 1116, the carbon hardmask layer 208 is etched using the atomic layer etch (step 108) shown in FIG. 1. In some embodiments, the etching of the carbon hardmask layer 208 occurs after the passivation of the sidewalls of the underlayer 1116. In some embodiments, the etching of the carbon hardmask layer 208 occurs during the passivation of the sidewalls of the underlayer 1116. In some embodiments, the passivation of the sidewalls of the underlayer 1116 occurs both before and during the etching of the carbon hardmask layer 208.

[0051] In some embodiments, the atomic layer etch (step 108) is a cyclic process where in each cycle the exposed surface of the carbon-containing etch layer 208 is modified (step 112). In some embodiments, a modification gas is provided. In various embodiments, the modification gas includes an oxygen-containing component. In some embodiments, the modification gas further includes a passivation component. In some embodiments, the passivation component is WF 6 In some embodiments, the modifying gas is converted into a plasma containing oxygen radicals. In some embodiments, the oxygen radicals or ions form bonds with carbon from the carbon etch layer, resulting in modification of the carbon etch layer region. In some embodiments, the passivation component WF 6 provides passivation on the sidewalls of the underlayer 1116 during the modification step (step 112).

[0052] In some embodiments, after the modification step (step 112), a removal step is performed (step 116). In some embodiments, a bombardment gas is provided and RF power is used to form the bombardment gas into a plasma. In some embodiments, a passivation gas is provided during the modification step (step 112). In some embodiments, the passivation gas is WF 6In some embodiments, components from the passivation gas provide passivation on the sidewalls of the underlayer 1116 during the removal step (step 116). In some embodiments, a bias in the range of 100 eV to 2000 eV is provided. A higher energy bias provides more directional ions. In some embodiments, the ions are highly directional in the vertical direction to form vertical features with high depth-to-width ratios. The bias is applied for a period of time long enough to effect removal of the modified portions of the etch layer and short enough to reduce or eliminate physical sputtering. In some embodiments, the bias is provided for a period of time between 0.3 ms and 500 ms.

[0053] 11B is a schematic diagram of stack 1100 after the atomic layer etch (step 108) has completed etching of etch layer 1108. The atomic layer etch (step 108) etches feature 1132 in etch layer 1108.

[0054] WF 6 To show how the use of a passivation gas containing O improves the results, FIG. 7A shows a modified gas containing O 2 7A and 7B are cross-sectional side views of a carbon-containing etch layer 208 etched according to an embodiment including a passivation gas and no passivation gas is provided. FIG. 7B is a perspective view of the carbon-containing etch layer 208 shown in FIG. 7A. The ALE process causes undercutting of the carbon-containing etch layer 208 as shown in FIG. 7A and FIG. 7B.

[0055] FIG. 8A shows the reformed gas. 2 Including WF 6FIG. 8B is a cross-sectional side view of a carbon-containing etch layer 208 etched according to an embodiment in which a passivation gas including is provided during the passivation step (step 122). FIG. 8B is a perspective view of the carbon-containing etch layer 208 shown in FIG. 8A. The passivation step (step 122) reduces undercutting of the carbon-containing etch layer 208 caused by ALE, as shown in FIGS. 8A and 8B. As a result, the etched features and resulting ridges are more uniform and vertically straight.

[0056] The ion dose required to remove the modified surface is defined by the ion flux, ion energy, and exposure time. The reacted fractional surface is given by θ as follows:

number

number

[0057] 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 Ar, He, Ne, Kr, and Xe. The bombardment ions must have sufficient energy to sputter the oxygen-modified carbon surface with minimal or no sputtering of the unmodified carbon surface.

[0058] In various embodiments, the carbon-containing layer may be an amorphous carbon layer with some hydrogen. The carbon-containing layer may be used as a mask to etch a stack comprising at least one of a silicon-containing layer, such as silicon oxide, silicon carbide, silicon nitride or polysilicon, an oxide layer, or a nitride layer, such as titanium nitride. In some embodiments, the stack may comprise alternating layers. The alternating layers may be alternating layers of silicon oxide and polysilicon forming an OPOP stack, or alternating layers of silicon oxide and silicon nitride forming an ONON stack, or alternating layers of silicon oxide and tin nitride.

[0059] To provide an example of a processing chamber that may be used in an embodiment, Figure 9 illustrates generally an example of a processing chamber system 900, such as an etch system, that may be used for a plasma treatment process. The processing chamber system 900 includes a plasma reactor 902 having a plasma processing confinement chamber 904, such as an etch chamber, therein. A plasma power source 906, such as an RF power source, tuned by a plasma matching network 908, supplies power to a transformer coupled plasma (TCP) coil 910 positioned near a dielectric inductive power window 912 to create a plasma 914 in the plasma processing confinement chamber 904 by providing inductively coupled power.

[0060] The TCP coil (upper power supply) 910 may be configured to provide a uniform diffusion profile in the plasma processing confinement chamber 904. For example, the TCP coil 910 may be configured to generate an annular power distribution in the plasma 914. A dielectrically inductive power window 912 is provided to isolate the TCP coil 910 from the plasma processing confinement chamber 904 while allowing energy to be transferred from the TCP coil 910 to the plasma processing confinement chamber 904. The TCP coil 910 acts as an electrode to provide radio frequency (RF) power to the plasma processing confinement chamber 904. A wafer bias voltage power supply 916 tuned by a bias matching network 918 provides power to an electrode 920 to set a bias voltage on a substrate 966. The substrate 966 is supported by the electrode 920, and thus the electrode acts as a substrate support. A controller 924 controls the plasma power supply 906 and the wafer bias voltage power supply 916.

[0061] The plasma power source 906 and the wafer bias voltage power source 916 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 906 and the wafer bias voltage power source 916 may be appropriately sized to provide a range of power to achieve a desired process performance. For example, in one embodiment, the plasma power source 906 may provide power in the range of 50-5000 watts, and the wafer bias voltage power source 916 may provide a bias voltage in the range of 20-2000 V. In addition, the TCP coil 910 and / or the electrode 920 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.

[0062] As shown in FIG. 9, the processing chamber system 900 further includes a gas source / gas supply mechanism 930, such as a bombardment gas source, an oxygen radical source, and a passivation gas source. The gas source 930 is in fluid communication with the plasma processing confinement chamber 904 through a gas inlet, such as a gas injector 940. The gas injector 940 may be located at any advantageous location in the plasma processing confinement chamber 904 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 each flow of gas to multiple zones in the plasma process confinement chamber 904. More preferably, the gas injector is mounted to the dielectric induction power window 912. The gas injector may be mounted on, in, or form a part of the power window. The process gases and by-products are removed from the plasma process confinement chamber 904 via a pressure control valve 942 and a pump 944. A pressure control valve 942 and a pump 944 also serve to maintain a particular pressure within the plasma processing confinement chamber 904. The pressure control valve 942 can maintain a pressure of less than 1 Torr during processing. An edge ring 960 is positioned around the substrate 966. The gas source / gas delivery mechanism 930 is controlled by a controller 924. 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.

[0063] 10 is a high-level block diagram illustrating a computer system 1000. The computer system 1000 is suitable for implementing the controller 924 used in the embodiments. The computer system 1000 may have many physical forms ranging from integrated circuits, printed circuit boards, and small handheld devices to large supercomputers. The computer system 1000 includes one or more processors 1002 and may further include an electronic display device 1004 (for displaying graphics, text, and other data), a main memory 1006 (e.g., random access memory (RAM)), a storage device 1008 (e.g., hard disk drive), a removable storage device 1010 (e.g., optical disk drive), a user interface device 1012 (e.g., keyboard, touch screen, keypad, mouse or other pointing device, etc.), and a communication interface 1014 (e.g., wireless network interface). The communication interface 1014 allows software and data to be transferred between the computer system 1000 and external devices over a link. The system may also include a communication infrastructure 1016 (eg, a communication bus, crossover bar, or network) to which the above-mentioned devices / modules are connected.

[0064] Information transferred via communications interface 1014 may be in the form of signals, such as electronic, electromagnetic, optical, or other signals, that carry signals and can be received by communications interface 1014 over a communications link, which may be implemented using wire or cable, fiber optics, a telephone line, a cellular phone link, a radio frequency link, and / or other communications channels. It is contemplated that using such communications interface 1014, one or more processors 1002 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.

[0065] 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.

[0066] 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).

[0067] 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.

[0068] 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 features in a carbon-containing etch layer, the method comprising a plurality of cycles, each cycle comprising: exposing the carbon-containing etch layer to oxygen radicals, the oxygen radicals modifying a portion of the carbon-containing etch layer; exposing the carbon-containing etch layer to bombardment ions having an energy greater than 100 eV for less than 0.5 s for each cycle, the bombardment ions removing the modified portion of the carbon-containing etch layer to form an etched feature; A method comprising:

2. 10. The method of claim 1, wherein the exposing the carbon-containing etch layer to the bombarding ions does not cause physical sputtering.

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

4. 2. The method of claim 1, wherein the bombarding ions are hydrogen (H 2 ), nitrogen (N 2 ), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) ions.

5. 2. The method of claim 1, wherein the exposing the carbon-containing etch layer to bombarding ions comprises exposing the carbon-containing etch layer to bombarding ions having an energy in a range of 400 eV to 1500 eV for a period in a range of 0.3 ms to 500 ms for each cycle.

6. 2. The method of claim 1, wherein the oxygen radicals form a self-limiting layer on the etch layer.

7. 10. The method of claim 1, further comprising passivating sidewalls of the etched features.

8. 8. The method of claim 7, wherein the passivating the sidewalls of the etched features comprises: 6 providing a passivation gas comprising:

9. 9. The method of claim 8, wherein the supplying of the passivation gas is at a different time than the exposing of the carbon-containing etch layer to the oxygen radicals and the exposing of the carbon-containing layer to the bombarding ions.

10. 9. The method of claim 8, wherein the supplying of the passivation gas is simultaneous with at least one of exposing the carbon-containing etch layer to the oxygen radicals and exposing the carbon-containing layer to the bombarding ions.

11. 9. The method of claim 8, wherein the supplying of the passivation gas is simultaneous with exposing the carbon-containing etch layer to the oxygen radicals.

12. 2. The method of claim 1, wherein the exposing the carbon-containing etch layer to the oxygen radicals comprises: providing a reformed gas, the reformed gas comprising an oxygen-containing component; converting the modified gas into a plasma containing the oxygen radicals; A method comprising:

13. 13. The method of claim 12, wherein the oxygen-containing component is O 2 , CO 2 , CO, COS, SO 2 , and H 2 O.

14. 10. The method of claim 1, further comprising etching at least one layer below the carbon-containing etch layer, wherein the carbon-containing etch layer is used as a mask.

15. 2. The method of claim 1, wherein the methane (CH 4 ), fluoromethane (CH 3 F), carbon monoxide (CO), carbon dioxide (CO 2 ), nitrogen (N 2 ), and boron trichloride (BCl 3 ), wherein the sidewalls of the etched feature are passivated by supplying a passivation gas comprising at least one of:

16. 10. The method of claim 1, further comprising passivating sidewalls of the etched feature by supplying a passivation gas to form a passivation layer, the passivation layer being at least one of carbon-based, silicon-based, boron nitride-based, and carbon and nitrogen-based.

17. 1. An etching system for etching features in a carbon-containing 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; an oxygen radical source adapted to provide oxygen radicals into the processing chamber; an impingement gas source adapted to supply an impingement gas into the processing chamber; a controllably connected to the RF power source, the oxygen radical source, and the bombardment gas source for a plurality of cycles; a) exposing the carbon-containing etch layer to oxygen, wherein the oxygen radicals are absorbed by the carbon-containing etch layer to form a modified portion of the carbon-containing etch layer; b) for each cycle, exposing the carbon-containing etch layer to bombarding ions having an energy greater than 100 eV for less than 0.5 s, the bombarding ions removing the modified portion of the carbon-containing etch layer; A controller configured to: An etching system comprising:

18. 20. The etching system of claim 17, wherein the exposing the carbon-containing etch layer to bombarding ions provides a bias in the range of 400 eV to 1500 eV for a period in the range of 0.3 ms to 500 ms for each cycle.

19. 20. The etching system of claim 17, wherein the exposing the carbon-containing etch layer to bombarding ions does not cause physical sputtering.

20. 18. The etching system of claim 17, wherein the bombardment gas source is hydrogen (H 2 ), nitrogen (N 2 ), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) in an etching system.

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