Cyclic etch / deposition plasma process using a tungsten-based precursor gas

Abstract

A method of plasma etching a substrate, the method comprising performing a first etch step in a cyclical manner to etch a target material, the substrate comprising a patterned mask disposed on the target material and having openings in the patterned mask, performing the first etch step comprising generating a first plasma from a carbon-containing precursor gas and exposing the substrate to the first plasma to form a first passivation layer and etch the target material, the first passivation layer comprising a polymeric material on sidewalls of the openings. Further, the method further comprises performing a second etch step in a cyclical manner to remove a portion of the first passivation layer, performing the second etch step comprising generating a second plasma from a tungsten-containing precursor gas and exposing the substrate to the second plasma.

Description

Cross-reference to related applications

[0001] This application claims the benefit of U.S. non-provisional application No. 18 / 603,049, filed March 12, 2024, which is incorporated herein by reference in its entirety. Technical Field

[0002] The present invention generally relates to methods of plasma etching, and in certain embodiments, to methods, apparatus, and systems for removing polymer build-up and depositing a passivation layer using a cyclic etching process. Background Technology

[0003] Microelectronic device manufacturing typically involves a range of fabrication techniques that include forming, patterning, and removing multiple layers of material on a substrate. Etching masks can be formed (e.g., deposited, grown) to protect areas of the substrate and allow pattern transfer via etching. Wet or dry etching processes can be used, with plasma etching being an example of a dry etching process.

[0004] Etching processes are used in various semiconductor fabrication fields, such as memory manufacturing. One category of etching processes is high aspect ratio (HAR) etching, which includes processes such as high aspect ratio contact (HARC) etching for contact formation. Achieving a high aspect ratio during etching is useful for various semiconductor processes, such as during NAND formation (e.g., 3D-NAND) or NORgate formation.

[0005] Defects may occur when transferring a pattern to the underlying layer. For example, features transferred to the underlying layer may have any number of undesirable defects, such as widening or narrowing, inconsistent size or position, distortion (e.g., deviation from the initial circular shape), and non-vertical sidewalls. Additionally, the edges of the transferred pattern may not be as smooth as the mask pattern; this metric is called edge roughness.

[0006] During the etching process, polymers can accumulate on the sidewalls of the mask. For example, polymers may accumulate in the openings of the mask. This polymer reduces the aperture size, thereby decreasing the area through which ions and free radicals can pass. The critical size (CD) of the mask can be undesirably altered by the polymer, leading to feature defects. Furthermore, the reduced flux of particles reaching the etching front undesirably slows down the etching rate and may exacerbate detrimental effects such as aspect ratio-dependent etch rate (ARDE). Therefore, etching processes that control polymer accumulation during the etching process are desirable. Summary of the Invention

[0007] A method for plasma etching a substrate includes cyclically performing a first etching step to etch a target material, the substrate including a patterned mask disposed on the target material and having openings in the patterned mask, the first etching step including generating a first plasma from a carbon-containing precursor gas and exposing the substrate to the first plasma to form a first passivation layer and etching the target material, the first passivation layer comprising a polymer material on the sidewalls of the openings. Furthermore, the method further includes cyclically performing a second etching step to remove a portion of the first passivation layer, the second etching step including generating a second plasma from a tungsten-containing precursor gas and exposing the substrate to the second plasma.

[0008] A method for plasma etching a substrate includes cyclically etching a target material with a first plasma, the substrate including a patterned mask disposed on the target material and having openings in the patterned mask, the etching of the target material including forming a first passivation layer comprising a polymer material on the sidewalls of the openings while etching the target material. Furthermore, the method further includes cyclically etching a portion of the first passivation layer deposited in the etching of the target material with a second plasma and depositing a second passivation layer comprising tungsten.

[0009] Furthermore, the plasma etching system includes a plasma chamber; a substrate holder disposed in the plasma chamber and configured to support the substrate; and a controller operatively coupled to the plasma chamber and to a memory storing a program to be executed in the controller, the program including instructions to: generate a first plasma in a cyclic manner from a carbon-containing precursor gas to etch the target material and form a first passivation layer comprising a polymer material on the sidewall of the opening, and generate a second plasma from a tungsten-containing precursor gas to remove a portion of the first passivation layer. Attached Figure Description

[0010] To gain a more complete understanding of the invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

[0011] Figure 1 An example substrate comprising a mask material covering the target material is schematically illustrated according to an embodiment of the invention, and polymer accumulation over time during a plasma etching process is qualitatively shown.

[0012] Figure 2 An example substrate comprising a polymer material having both a primary facet and a secondary facet, and another example substrate comprising a polymer material having only a primary facet, are schematically illustrated according to embodiments of the present invention.

[0013] Figure 3 A timing diagram and a corresponding substrate of an example method for etching a target material according to an embodiment of the present invention are schematically illustrated. The method includes a plurality of first etching steps and a plurality of second etching steps performed in a cyclic manner to remove polymer material accumulated at the opening during the first etching steps and passivate the sidewalls during the second etching steps.

[0014] Figure 4 An example plasma etching system according to an embodiment of the present invention is schematically illustrated. The plasma etching system includes a controller operatively coupled to a plasma chamber and configured to deliver a first precursor gas during a first etching step and a second precursor gas during a second etching step.

[0015] Figure 5 Two timing diagrams of an example method for etching a target material according to an embodiment of the present invention are schematically illustrated, wherein the total first etching time is the same between the two timing diagrams;

[0016] Figure 6 Two timing diagrams of an example method for etching a target material according to an embodiment of the present invention are schematically illustrated, wherein the total first etching time and the total second etching time are the same between the two timing diagrams, but the number of second etching steps varies;

[0017] Figure 7 Qualitative illustrations show example pits exhibiting more severe defects according to embodiments of the present invention, and contrasting example pits exhibiting less severe defects; and

[0018] Figures 8A to 8B An example method for etching a target substrate according to an embodiment of the present invention is illustrated.

[0019] Unless otherwise indicated, corresponding numbers and symbols in different figures generally refer to corresponding parts. These figures are drawn to clearly illustrate relevant aspects of the embodiments, and these figures are not necessarily drawn to scale. The edges of features drawn in the figures do not necessarily indicate the termination of the feature's extent. Detailed Implementation

[0020] The manufacture and use of various embodiments are discussed in detail below. The various embodiments described herein are applicable to a wide variety of specific situations. The specific embodiments discussed are merely illustrative of specific ways of manufacturing and using the various embodiments and should not be interpreted in a limited manner.

[0021] Polymer formation typically occurs during plasma etching processes. For example, when using fluorocarbons as etchants (e.g., compounds with the formula C...),... x F yIn the plasma etching process of the compound (also abbreviated as CF) in this paper, dissociation within the plasma leads to the formation of CF polymers. This polymer formation reduces the size of the openings in the mask layer, resulting in fewer plasma species (such as ions and radicals) reaching the bottom of the mask features. Polymer formation also passivates the sidewalls of the openings, and this passivation reduces distortion as the plasma etching process continues.

[0022] A major drawback of polymer accumulation is a reduction in etch rate over time during the etching process, as fewer ions and radicals reach the bottom of mask features such as holes and trenches. Accumulated polymers deflect plasma species entering mask features from their original trajectories, thus reducing their verticality. Furthermore, the reduction in etchant species at the feature bottom becomes increasingly severe as the aspect ratio increases. Therefore, polymer accumulation at mask sidewalls (e.g., necking) can also be a major source of common undesirable effects in aspect ratio-dependent etch rate (ARDE).

[0023] Polymer deflection can also undesirably increase the lateral etch rate relative to the vertical etch rate and cause undesirable effects such as the bowing effect of the sidewalls. The shape of the polymer on top of the mask (which may be referred to as the sub-facet or 2) ° Facets typically have irregular (e.g., smooth, lateral, but non-circular) shapes. This irregularity can be projected into the underlying layer, resulting in undesirable distortions and feature edge roughness (e.g., contact edge roughness (CER)) in the pits within the underlying layer.

[0024] Conventional methods for preventing undesirable effects from polymer buildup involve tuning parameters such as high-frequency (HF) power, pressure, and relative gas flow rates. For example, gas flow rates can be adjusted by reducing the flow rate of fluorocarbons (CFs) (e.g., C4F6) and / or increasing other flow rates such as oxygen (O2). This can make the plasma rarefied and alter the plasma's gas chemistry to include fewer large CF plasma species. For instance, smaller CF plasma species can penetrate deeper into the mask openings than larger CF species that might tend to adhere near the top of the mask.

[0025] However, this conventional gas tuning method has several drawbacks. Conventional gas tuning inherently involves a trade-off between increasing the overall etch rate and reducing mask erosion. That is, gas tuning methods that increase the etch rate also reduce polymer buildup. For example, as the etch rate increases, mask selectivity may be undesirably reduced, leading to negative effects propagating to underlying layers, such as large bow critical dimensions (CD).

[0026] Another conventional approach is to use a cyclic etching process, which includes a first etching step and a second etching step, switching between the two steps to form device features. The first etching step uses a first precursor gas to form a first plasma to etch the target material to a specific etch depth. Subsequently, a second etching step is used to etch the polymer buildup at the opening, using a second precursor gas to form a second plasma. Unfortunately, during the second etching step of a conventional cyclic method, the benefits of sidewall passivation achieved through the polymer may be lost, potentially increasing distortion of the features being etched in the opening and resulting in a reduction in mask height due to the removal of passivation from the mask material.

[0027] Therefore, it is desirable to remove polymer buildup in the top region of the mask while maintaining sidewall passivation during etching. For example, polymer buildup in the top region of the mask may be achieved by forming 2 ° Faceting results in a narrower mask opening (smaller neck CD). However, during etching, the polymer flux reaching the sidewalls (e.g., oxide sidewalls) can be desirable for passivation. The inventors have determined that polymer accumulation and sidewall passivation in the top region of the mask can be removed, and that new passivation of the sidewalls can be achieved by incorporating a tungsten-containing precursor gas (such as tungsten fluoride (WF6)) into the second etching step of the cyclic etching process. In other words, although the second etching step still removes the passivated polymer on the sidewalls, the incorporation of a tungsten-containing precursor gas (such as WF6) leads to tungsten passivation of the mask and sidewalls while removing excess polymer accumulation at the mask opening. The inventors have determined that including a tungsten-containing precursor gas (such as WF6) in the second etching step contributes to the passivation of the sidewalls and the mask, which can further improve roundness, improve mask selectivity, reduce distortion, facilitate charge accumulation, and reduce contact edge roughness.

[0028] The embodiments described herein introduce one or more second etching steps to manage polymer accumulation and perform tungsten passivation of the sidewalls during the plasma etching process. The second etching step allows the first etching step to achieve higher polymer throughput, with the advantage of avoiding clogging, tapering, distortion, and / or CER. Specifically, the second etching step includes a second plasma generated by a second precursor gas containing a second etchant species that contains a tungsten-containing precursor gas, to remove polymer material without damaging the mask material and to perform tungsten passivation of the sidewalls. The second etchant species differs from the first etchant species contained in the first precursor gas used to generate the first plasma for the first etching step. For example, the second etchant species may further contain oxygen (i.e., oxygen-containing compounds). A bias power may be applied during the second etching step to increase ion perpendicularity, thereby improving subfacet removal. The target material may be a dielectric material, such as an oxide, nitride, or a stacked structure thereof (e.g., ONO). The mask material may be a hard mask material such as silicon nitride and may contain carbon. For example, the mask material may be an amorphous carbon layer (ACL).

[0029] By implementing a cyclic etching process, polymer accumulation can be advantageously controlled without directly affecting sidewall passivation during the second etching step. In many etching applications (such as HAR etching, e.g., HARC etching), polymer accumulation can be the driving force behind such undesirable effects as distortion and CER. That is, distortion and CER are persistent problems in dielectric HARC etching processes. Therefore, controlling polymer accumulation during the cyclic etching process has the advantage of controlling distortion and CER.

[0030] Another advantage is the consistent and selective removal of polymer buildup. ° The ability to facet (i.e., smooth, irregular subfacets). This is beneficial for achieving the desired sidewall passivation provided by tungsten passivation of the sidewalls during the second etching step, while removing unwanted polymer buildups on top of the mask features. Removal 2 ° Faceting also advantageously reduces the amount of plasma species (e.g., ions) deflected to the sidewalls during the first etching step. With fewer species impacting the sidewalls, lateral etching effects such as undesirable bowing effects can also be reduced.

[0031] Variations in the second etching parameters can provide optimization benefits for a given cyclic etching process. The second etching chemistry can be customized independently of the first etching chemistry as needed (e.g., to react more strongly with the polymer or to increase ion sputtering). The duration of each second etching step and / or the total second etching duration throughout the cyclic etching process can also be customized to optimize etching rate, total etching time, bottom-to-top ratio (B / T ratio), pit density (CD), distortion, and contact edge roughness (CER) improvement, among other things.

[0032] The inventors have also determined that, in some embodiments, the effectiveness of the second etching step in removing polymer may face diminishing marginal returns as the duration of the second etching step increases. That is, the early stages of each second etching step may have the greatest impact on mitigating negative effects such as B / T ratio, distortion, and CER. As the duration of the second etching step increases, the incremental benefit diminishes until no further benefit is gained from extending the second etching duration (e.g., because all polymer has been removed and / or there are chamber effects, substrate cooling, etc.).

[0033] Therefore, when utilizing multiple second etching steps, there may be additional controls over the efficiency of the cyclic etching process. For example, including more short second etching steps can advantageously maximize the high efficiency of the early stages of each second etching step and avoid inefficiencies in the second etching steps. For instance, the second etching step near the end of the etching process can be shorter than the second etching step at the beginning of the etching process. As an example, the duration of the second etching step near the end of the etching process can be 30% to 70% of the duration of the second etching step at the beginning of the etching process. Furthermore, controlling the frequency of the second etching steps in a given cyclic etching process has the benefit of tuning the second etching steps to be applied only when there is an optimal amount of polymer accumulation, thereby achieving maximum benefit.

[0034] Other conventional methods have already used cleaning steps in contexts other than those described herein. For example, polymer buildup is a problem encountered in various processes, including other etching processes. Therefore, conventional etching methods have used cleaning steps to remove polymer buildup, with varying degrees of success. For instance, in the specific instance of silicon oxynitride (SiON) masks, CF4-based cleaning steps have been used to remove silicon oxide or silicon oxynitride buildup during ACL etching and silicon etching (to form shallow trench isolation).

[0035] However, the inclusion of fluorocarbons (such as CF4) in the flash evaporation steps described herein often has the opposite effect, resulting in polymer accumulation rather than polymer removal. Furthermore, many conventional cleaning steps do not use bias power during the cleaning process (e.g., to avoid substrate damage), and therefore have poor overall performance and are less effective for morphologies such as subfacets. Conventional cleaning steps may also use cleaning chemistry systems that cannot be mixed with the etching step chemistry systems, requiring the plasma chamber to be emptied between each step, which increases the overall fabrication time.

[0036] The method described in this paper improves upon these conventional methods by incorporating one or more features (such as a tungsten-based, fluorocarbon-free second etch chemistry, bias power during the second etch step, heavy inert gas bombardment, no purge gas switching, and selectivity of the first etch target (e.g., oxides, ONO, etc.)) and by enhancing control over polymer accumulation through customizing the second etch frequency, the ratio of the first to the second etch, the total second etch time, and the total etch time.

[0037] The embodiments provided below describe various methods, apparatus, and systems for plasma etching, and in particular, methods, apparatus, and systems using a cyclic etching process comprising a first etching step and a second etching step, wherein the second etching step includes WF6 and is used to remove polymer and passivate sidewalls during the plasma etching process. Examples are described in the following description. Figure 1 An example substrate is described. (Using...) Figure 2 Two example substrates are described, comparing the effects of subfacets on polymer materials. Using... Figure 3 An example method for etching a target material is described. Using... Figure 4 An example plasma etching system configured to perform a method for etching a target material is described. Using... Figure 5 and Figure 6 Two additional example methods for etching the target material are described, demonstrating the effect of keeping the total first etching time and the total second etching time constant. Figure 7 Qualitative illustrations show the differences between more severe and less severe defects in the pits. Furthermore, using... Figures 8A to 8B Two other example embodiments of the method for etching the target material in a cyclic manner as disclosed herein are illustrated.

[0038] Figure 1 An example substrate comprising a mask material covering the target material is schematically illustrated according to an embodiment of the invention, and polymer accumulation over time during a plasma etching process is qualitatively shown.

[0039] refer to Figure 1Side view 101 and top view 102 show a substrate 110 containing a mask material 16 covering a target material 112. The mask material 16 is patterned to form openings 26 for transferring the desired pattern from the mask layer containing the mask material 16 to the target material 112 and optionally in the underlying layer 18 beneath the target material 112. The substrate 110 can be any suitable substrate, such as an insulating substrate, a conductive substrate, or a semiconductor substrate on which one or more layers are disposed. An example category of possible substrates would be one of many types of semiconductor wafers (silicon, silicon-on-insulator, germanium, gallium arsenide, etc.).

[0040] This configuration can represent a general etching process and is not limited to any specific material or pattern. For example, the target material 112 can be any suitable material, but in various embodiments it is a dielectric material. In one embodiment, the target material 112 is a dielectric material comprising an oxide. For example, the dielectric material may comprise silicon dioxide (SiO2). In various other embodiments, other oxides, such as aluminum oxide (Al2O3, commonly known as sapphire), may be used. In one embodiment, the dielectric material comprises a nitride, such as silicon nitride (Si3N4).

[0041] The target material 112 can be a homogeneous material (such as SiO2), or it can be a stacked structure of any number of materials. In some embodiments, the target material 112 is a stacked structure comprising oxides and nitrides, and is an alternating stacked structure of oxides and nitrides (commonly referred to as an ONO stacked structure). For example, the target material 112 can be an ONO stacked structure comprising tens to hundreds of alternating SiO2 layers and Si3N4 layers. This configuration can be used for various applications, such as HARC etching for memories (e.g., 3D-NAND, DRAM, etc.). In a specific instance of HARC etching, the bottom layer 18 can be a semiconductor layer (e.g., a device layer), with which an electrical contact is established using a plasma etching process.

[0042] The mask material 16 can also be any suitable material, such as a material having properties that allow the patterned mask material to etch away the exposed portion of the target material 112 (i.e., in the opening 26) during the plasma etching process while protecting the underlying portion of the target material 112. In various embodiments, the mask material 16 is a hard mask material, such as that used for HAR etching. In some embodiments, the mask material 16 comprises carbon and is ACL. Other possible materials for the mask material 16 include polysilicon, tungsten-containing materials, etc. In a specific instance where the target material 112 is a dielectric material, the mask material 16 can be selected to be resistant to fluorocarbon (CF) chemistry, as fluorocarbons (especially higher molecular weight fluorocarbons having at least two carbon atoms) can be used to etch the target material 112.

[0043] During the first etching step of the cyclic etching process, polymer material 22 accumulates on the mask material 16 over time, particularly on top of features, such as on and around the opening 26. Furthermore, polymer material 22 can also passivate the sidewalls of the mask material 16 and the target material 112, and a first passivation layer 252 containing the polymer is formed on the sidewalls of the mask material 16 and the target material 112. Figure 1 Several examples are shown where polymer material 22 accumulates to varying degrees around opening 26. Each example may represent a different first etching step in a cyclic process. Figure 1 The bottom diagram illustrates the possible qualitative effects of polymer buildup at different average levels during the etching process.

[0044] Depending on the properties of the target material 112 and the type of the first precursor gas used to generate the first plasma, there are many different types of polymer materials 22 that may accumulate. In various embodiments, the polymer material 22 is an organic polymer (i.e., containing carbon). For example, the carbon may be introduced by a fluorocarbon etchant (e.g., C4F6, C4F8, C3F8, CHF3, CH2F2, CH3F, etc.) or may come from the mask material 16, such as that used for an ACL mask. In some cases, the fluorocarbons present during the first etching step interact with various materials of the substrate 110 to form the polymer material 22.

[0045] As shown, polymer material 22 can accumulate at the opening 26 of the mask material 16 in a specific manner to produce a substantially flat primary facet 21 and a smooth secondary facet 23 protruding into the opening 26. Initially, the opening 26 is clean and has a mask width 31, allowing maximum flux of plasma species of the first plasma to enter the opening 26 and reach the bottom of the feature being etched. However, over time, polymer material 22 accumulates and reduces the minimum size of the opening 26, which is referred to as the NCD 30 (neck CD). As the first etching step proceeds, the NCD 30 becomes increasingly smaller relative to the mask width 31, and various undesirable effects may occur.

[0046] For example, in extreme cases, NCD 30 becomes zero and opening 26 closes (as indicated by arrow 35). This may cause etching of the target material 112 to stop and the desired etching depth (e.g., bottom layer 18) may not be achieved. Although this worst-case scenario may not always occur (depending on several factors related to the first etching step parameters), for many plasma etching processes (such as those using fluorocarbons), the first etching step parameters cannot be used to prevent the accumulation of polymer material 22. Furthermore, even a small amount of polymer accumulation can have undesirable effects on the results of the cyclic etching process.

[0047] For example, various CDs can be affected by polymer accumulation, such as TCD 34 (top CD, measured near the top of opening 26 (e.g., between 80% and 100% of the feature height)), BCD 36 (bottom CD, similarly measured near the bottom of opening 26 (e.g., between 0% and 20% of the feature height)), and DCD 38 (pit CD, such as measuring the average diameter or maximum size of pits 28 formed in the bottom layer 18). One specific CD that may be affected and lead to degradation of other CDs is the bow-shaped CD 32, which is caused by plasma species deflection (e.g., by the subfacet 23). The bow-shaped CD 32 is the maximum width of the feature and can also be measured sideways (shown as a single-sided bow 33).

[0048] In practice, the pit 28 will deviate from the ideal shape and size of the feature that the patterned mask material 16 is designed to transfer. Minimizing these deviations is desirable and can be achieved by reducing the amount of time that polymer accumulates in the opening 26. Some common measures of deviation for the pit 28 are distortion (which can be expressed in various ways that measure the uniformity of the pit 28, such as ellipticity, expressed as minimum diameter divided by maximum diameter or minimum radius divided by maximum radius), and CER, which is a measure of the smoothness of the boundary of the pit 28 (e.g., expressed as a three-sigma deviation of radius or diameter). As shown, the pit 28 becomes increasingly distorted and coarse as polymer material 22 accumulates in the opening 26.

[0049] Figure 2 The illustrations schematically depict an example substrate comprising a polymer material having both a primary facet and a secondary facet, and another example substrate comprising a polymer material having only a primary facet, according to embodiments of the present invention. For example, Figure 2 The substrate can be any other substrate described herein (such as...). Figure 1 Specific embodiments of the substrate. Elements marked similarly may be as previously described.

[0050] refer to Figure 2 The substrate 210 comprises a polymer material 22 covering the target material 212 as described above. Although an example shape of the polymer material 22 with primary facets 21 and secondary facets 23 is shown, its shape can vary while the polymer still has primary facets 21 and secondary facets 23. Therefore, a conceptually simplified version of the polymer material 22 is provided to highlight the fundamental effects accumulated by the polymer material 22 at the opening 26.

[0051] For the sake of brevity and clarity, convention is used herein and hereinafter to refer to elements [x10] (where 'x' is a figure number) attached to a pattern as relevant embodiments of the substrate in various examples. For example, unless otherwise stated, substrate 210 may be similar to substrate 110. Similar convention is used for other elements, as clearly indicated by using similar terminology in conjunction with the numbering system described above.

[0052] In the first example 201, polymer material 22 has been accumulated and formed into a shape comprising both the primary facet 21 and the polymer material 22. Notably, the secondary facet 23 extends into the opening 26 and has a smooth surface (in contrast to the substantially linear surface of the primary facet 21). In various embodiments, the primary facet 21 may be entirely polymer, contain mask material, or be entirely mask material (e.g., if the polymer accumulated on top of the mask is continuously etched away).

[0053] During the first etching step, ions 24 are accelerated toward substrate 210 (i.e., at a given vertical velocity relative to substrate 210) with the aim of introducing a vertical flux of ions 24 to the bottom of the feature and increasing the etching depth. However, as the subfacet 23 grows, ions 24 may deflect with a gradually increasing probability, resulting in fewer ions 24 reaching the bottom of the feature and more ions 24 impacting the sidewalls of the feature. This is one source of the undesirable bowing effect (as shown in the figure, bow CD 32 and single-sided bow 33), highlighting the benefit of sidewall passivation in mitigating distortion.

[0054] In the second example 202, some of the polymer material 22 remains, but only the primary facet 21 is present (i.e., the secondary facet 23 has been removed using a second etching step, which also deposits a second passivation layer 373 containing tungsten). In this case, fewer ions 24 deflect to the sidewalls, and the vertical flux of ions 24 reaching the bottom of the feature is greater. Therefore, this may be the desired goal for polymer removal, with additional advantages over simply removing all the polymer. For example, polymer that does not negatively affect the etching process remains on top of the opening 26 and protects the mask material (not shown) from erosion during the first etching step. In another embodiment, the first passivation layer 252 containing polymer is removed using a second etching step, and a second passivation layer 373 containing tungsten is deposited to protect the mask material. Generally, a certain amount of polymer or tungsten is desired as the first or second passivation layer to improve selectivity and passivate the sidewalls to reduce distortion.

[0055] Figure 3A timing diagram and a corresponding substrate are schematically illustrated for an example method of etching a target material using a cyclic etching process according to an embodiment of the present invention. This cyclic etching process switches between a first etching step that etches the target material and a second etching step that removes polymer material accumulated at the opening during the first etching step, passivates the sidewalls, and forms a second passivation layer. For example, Figure 3 The method can be used with any substrate as described herein (e.g., Figure 1 and Figure 2 (The substrate) is used to perform the operation. The elements are similarly labeled as previously described.

[0056] refer to Figure 3 The method 300 for etching a target material 312 (such as a dielectric material) using different plasmas includes repeatedly performing a cycle 350, which is performed in the first etching step E. i With the second etching step F i (This can also be referred to as a flash evaporation step) alternates between these steps until n first etch steps have been performed (e.g., a series of steps constituting cycle 350 are performed in a cyclic manner until n first etch steps have been performed). Although the last cycle (e.g., the nth cycle) is shown as not including the second etch step F. n However, a final second etching step can be included if necessary. The number of cycles, n, can be any suitable value and can depend on various factors, such as the desired etching depth, d. f The accumulation rate and removal rate of polymer material 22, etching rate, chemical system (both the first etching chemical system and the second etching chemical system), etc.

[0057] Perform the first etching step E i The first etching step continues for a duration of 351, during which a first precursor gas 341 is provided near the substrate 310 containing the target material 312. A first plasma is generated by the first precursor gas 341 (e.g., by using a first etching source power level SP). E A first etch source power 371 (SP) is applied. A first precursor gas 341 contains a first etchant species that has a selected selectivity to etch the target material 312 exposed in the openings 26 of the patterned mask material 16. For example, the reactivity of the first etchant species with respect to the target material 312 (e.g., a dielectric material, such as an oxide) may be greater than its reactivity with respect to the mask material 16 (e.g., a hard mask material, such as ACL).

[0058] Figure 3 The effect of the first etching step E1 is shown. During the first etching step E1, the bias power (BP) can be set at the first etching bias power level BP. EAn etching bias power 381 is applied to impart a vertical velocity to the charged species of the first plasma (such as positive ions of the first etchant species). The first plasma species containing ions etches the target material 312 to a first etch depth d1 during the first etch step duration 351. As previously discussed, polymer material 22 is accumulated on the mask material 16 to form a shape that reduces the size of the opening 26 and includes a primary facet 21 and a secondary facet 23. The polymer material 22 can also passivate the target material 312 and pattern the sidewalls of the mask material 16 and form a first passivation layer 252 containing the polymer.

[0059] Perform the second etching step F i (Or flash evaporation step) The second etching step continues for a duration of 352. During the second etching step duration of 352, a second precursor gas 342 is provided near the substrate 310 to remove the precursor gas from the substrate in the first etching step. i During this process, polymer material 22 accumulates at the opening 26, and the sidewalls of the target material 312 are passivated, forming a second passivation layer 373 containing tungsten to improve distortion. In the embodiment, the second etching step F i It can also replace the first etching step E i The first passivation layer 252 of polymer deposited during this period due to the accumulation of polymer material 22 on the sidewalls further controls the distortion of the target material 312. Furthermore, in those embodiments, replacing the first passivation layer 252 of the sidewalls with a second passivation layer 373 by depositing a material of a second plasma species can also reach the bottom of the forming feature, which can reduce charge accumulation at the etch front and thus further reduce bending and other charge-accumulation-driven defects.

[0060] The second plasma is generated by the second precursor gas 342 (e.g., by using SP at the second etching source power level). F The second etching source power 372 is coupled to the second precursor gas 342. As shown in the figure, in various embodiments, SP F Less than SP E For example, this can prevent damage to materials other than polymer material 22 (such as mask material 16) (or even prevent excessive damage to polymer material 22, since, as mentioned above, certain polymers or other passivating materials are generally beneficial to the etching process). In various embodiments, from the first etching step E i Switch to the second etching step F i This involves stopping the first plasma and the first precursor gas, then pumping in the second precursor gas and igniting the second precursor gas to generate the second plasma.

[0061] The second precursor gas 342 contains a second etchant species, which is selected to interact with the polymer material 22 such that the second etchant species is used in the flash evaporation step F i During this process, polymer material 22 is removed, and the first passivation layer 252 on the sidewall of the target material 312 is replaced with a second passivation layer 373. For example, the second etchant species can react with polymer material 22. Furthermore, the second etchant species can exhibit selectivity towards polymer material 22, such as greater reactivity towards polymer material 22 than towards the target material 312. During the second etching step, the second etchant species removes the passivated polymer on the sidewall of the opening 26, and a tungsten passivation layer (second passivation layer 373) is deposited to replace the polymer passivation layer (first passivation layer 252). Therefore, Figure 3 The method 300 illustrated in the middle retains the benefits of polymer passivation by using a tungsten-containing precursor gas (such as WF6) in the second etchant species to form tungsten passivation of the mask material 16 and the target material 312.

[0062] In all embodiments, the second precursor gas 342 comprises a tungsten-containing precursor gas mixed with other gases. The second precursor gas 342 may comprise a mixture containing a precursor gas containing halogens and tungsten (e.g., tungsten fluoride (WF6)). In some embodiments, the second precursor gas 342 comprises a precursor gas containing tungsten, chlorine, and fluorine. As mentioned above, tungsten (W) contributes to charge mitigation and forms a second passivation layer 373 on the sidewalls of the target material 312. The inclusion of tungsten fluoride (WF6) in the second precursor gas 342 also helps reduce distortion of features forming in the substrate while cleaning the opening 26 with accumulated polymer material 22. In one embodiment, the second precursor gas 342 comprises oxygen (O2), carbonyl sulfide (COS), and tungsten fluoride (WF6). In another embodiment, the second precursor gas 342 comprises oxygen (O2) and tungsten fluoride (WF6). In another embodiment, the second precursor gas 342 comprises nitrogen (N2), hydrogen (H2), and tungsten fluoride (WF6).

[0063] The effect of the first second etching step F1 is also shown. During the first second etching step F1, the bias power can also be at the second etching bias power level BP. FThe second etch bias power 382 is applied. A certain amount of bias power can advantageously impart a vertical velocity to the ions of the second plasma and improve the selectivity of the second etch step for the sub-facet 23 (e.g., the smooth protrusions of the sub-facet 23 are less stable than the supported main facet 21 and may therefore be more susceptible to bombardment effects, causing the polymer of the sub-facet 23 to be knocked off). However, as with the source power (and to a greater extent in many embodiments), the BP... F Less than BP E .

[0064] The overall effect of the second etching step F1 is to remove the polymer material 22 and deposit a second passivation layer 373 containing tungsten (W) on the sidewalls of the target material 312 and the mask material 16. The second passivation layer 373 on the mask material 16 also prevents the mask height of the mask material 16 from decreasing. Specifically, the secondary facets 23 of the polymer material 22 can be removed or reduced such that the distortion of the target material 312 is improved using the resulting second passivation layer 373 containing tungsten (W), while the opening 26 is widened to be closer to the original mask width (e.g., increasing the NCD of the opening 26 during the flash evaporation step). The primary facets 21 may also be affected. Advantageously, it is not necessary to completely remove the primary facets 21 (and in fact, it may be beneficial, as shown, to leave them on the sidewalls along with, for example, a certain amount of a first passivation layer 252 containing polymer and a certain amount of a second passivation layer 373 containing tungsten). In this qualitative example, the reduction in polymer height 27 does not result in the exposure of the original mask material 16 (i.e., the mask height can be protected by the second passivation layer 373 generated by the second etching step). Furthermore, even if the primary facet 21 is completely removed, its prior presence, combined with the preferential removal of the secondary facet 23 and the second passivation layer 373 on the sidewalls, can advantageously reduce or limit the reduction in mask height during the first and second etching steps.

[0065] As shown in the figure, the second first etching step E2 causes the target material 312 to be etched to a second etching depth d2, and the polymer material 22 accumulates to form a familiar structure with a primary facet 21 and a secondary facet 23. Polymer accumulation may also result in an increase in polymer height 29 (conceptually shown as equal to a decrease in polymer height 27, but could of course be smaller or larger). Then, the second etching step F2 again removes the secondary facet 23, as well as a portion of the primary facet 21 and the first passivation layer 252, and forms another second passivation layer 373 on the sidewalls of both the mask material 16 and the target material 312. Cycle 350 is repeated to achieve the desired etching depth.

[0066] In this ideal scenario, there would never be a mask removal cost for repeatedly performing the second etching step. However, in practice, the rate of polymer accumulation may be less than the rate of polymer removal, and mask removal may eventually occur, but the second passivation layer 373 containing tungsten can help reduce mask removal. For example, the inventors have determined that, at least under some conditions, up to 10 second etching steps can be performed without sacrificing selectivity, but these results will depend heavily on the specific details of a given application. Other benefits of the second passivation layer 373 containing tungsten on the sidewalls include improved sidewall smoothness and improved selectivity of the mask material 16. In embodiments, the polymerization of the gas occurs continuously during the first etching step to form the first passivation layer 252. In various embodiments, the second passivation layer 373 is formed due to the surface reaction between WF6 and the mask material 16. Furthermore, WF6 can react with SiN to form WN, thereby passivating the upper portion of the target material 312. It can also undergo a gas phase reaction between WF6 and other gases in the plasma (such as N2, CO, O2, etc.), resulting in W being further deposited on the feature to form a second passivation layer 373.

[0067] Cyclic etching processes can achieve the desired final etching depth d. f Then terminated. For applications where the goal is to breach the underlying layer 18 using etching, the method 300 for etching the target material 312 can end once the desired pattern has been transferred to the underlying layer 18 (e.g., a semiconductor device layer as during HARC etching) after n first etch steps. Several potential advantages achieved as a result of implementing method 300 are improved deformability, CER, DCD (dimpled CD), and bow CD. Additionally, method 300 can also reduce ARDE due to the increase in average NCD (neck CD), thereby allowing the first etchant species to reach the bottom of the feature more consistently during the cyclic etch process. Furthermore, the addition of WF6 can improve the selectivity of the mask material 16.

[0068] As illustrated in this specific example, method 300 can be performed without a purge step between the first and second etching steps (e.g., without needing to empty the plasma chamber between steps). This can advantageously reduce the overall process time and simplify the manufacturing process. For example, the purge step can be omitted due to the selection of the first etching chemical system, the second etching chemical system, and etching parameters (such as power settings, step duration, and the material of substrate 310).

[0069] While an optimized process formulation will gain some benefits from method 300, an unoptimized formulation can gain even more, as the ability to effectively remove polymer allows for the generation of more polymer during the first etching step with fewer negative consequences. Therefore, the process formulation can be advantageously optimized in different ways; optimization can consider the generation of more polymer and can optimize other aspects such as etching rate or selectivity.

[0070] Various second etching step options can improve the time efficiency of the second etching step or the entire etch cycle process. For example, the inventors have determined that the greatest benefit of removing the subfacet occurs during the initial phase of the second etching step. This may be because the top portion of the subfacet is removed rapidly, allowing more ions to quickly enter the opening without being deflected. Additionally, the inventors have observed that, under certain conditions, diminishing marginal benefits may exist for second etching steps that are too long. For example, the benefits for CD, distortion, CER, and ARDE may be weakened (or even impaired). Of course, longer second etching steps also result in longer overall process times.

[0071] In various embodiments, the duration of the second etching step 352 is less than about 40 s and in some embodiments less than about 20 s. In some applications, 20 s can achieve a desired balance, and therefore in one embodiment, the duration of the second etching step 352 is about 20 s. However, a faster second etching step also appears to be advantageous (as opposed to a shorter, longer second etching step). Therefore, in other embodiments, the duration of the second etching step 352 is less than about 10 s, and in one embodiment it is about 10 s.

[0072] The number of second etching steps performed during a cyclic etching process can influence the degree of benefit to almost all parameters. For example, distortion, DCD, BT ratio (BCD / TCD), and CER can all be improved by simply increasing the number of second etching steps. Some metrics, such as the bowing effect, can generally benefit from the second etching steps through the second passivation layer on the sidewalls of the target material 312 and the mask material 16, but cannot be further improved by simply adding more second etching steps.

[0073] Figure 4 An example plasma etching system according to an embodiment of the present invention is schematically illustrated. The plasma etching system includes a controller operatively coupled to a plasma chamber and configured to deliver a first precursor gas during a first etching step and a second precursor gas during a second etching step. For example, Figure 4The plasma etching system can be used to perform any of the methods described herein, such as Figure 3 The method is similar. Elements can be labeled as previously described.

[0074] refer to Figure 4 The plasma etching system 400 includes a controller 40 operatively coupled to a plasma chamber 44 and a memory 41 coupled to the controller 40 and storing a set of instructions (or programs) to be executed by the controller 40. When executed, the instructions cause the controller 40 to supply a first precursor gas 441 and a second precursor gas 442 into the plasma chamber 44. When further executed, the instructions may cause the controller 40 to perform a first etching step by supplying the first precursor gas 441 and a second etching step by supplying the second precursor gas 442 in a cyclical manner, without purging the plasma chamber 44 between steps. The memory 41 can be any suitable means for storing instructions to be executed by the controller 40.

[0075] The controller 40 is further coupled to a source power supply 46, which is configured to couple source power to the gas within the plasma chamber 44. For example, the source power supply 46 can be any suitable type of source power supply, such as an RF power supply. The source power supply 46 is configured to generate plasma 20 in the plasma chamber 44 by igniting a first precursor gas 441 to generate a first plasma or by igniting a second precursor gas 442 to generate a second plasma. Plasma 20 can be inductively coupled plasma (ICP), capacitively coupled plasma (CCP), or any other desired type.

[0076] A substrate 410 comprising a patterned mask material having openings exposing the target material can be loaded into a plasma chamber 44. A substrate holder 45 can be included in the plasma chamber 44 to support the substrate 410. The substrate holder 45 can be any suitable type of holder, including a mechanical chuck, a vacuum chuck, or an electrostatic chuck. A controller 40 can be operatively coupled to a bias power supply 49, which is in turn coupled to the substrate 410 (e.g., via the substrate holder 45) and configured to deliver bias power 48 at the substrate 410.

[0077] The source power supply 46 can be configured to deliver a higher wattage of power during the first etching step and a lower wattage of power during the second etching step. In various embodiments, SP E The power output is between approximately 3 kW and approximately 8 kW, and in some embodiments between approximately 4 kW and approximately 5 kW. In contrast, during the second etching step, the source power supply 46 is configured to deliver lower power. In various embodiments, SP FIt is between approximately 500 W and approximately 2 kW, and in one embodiment it is approximately 1 kW.

[0078] Similarly, the bias power supply 49 can also be configured to deliver a higher wattage of power (e.g., even higher than the source power) during the first etching step and a lower wattage of power during the second etching step. In some embodiments, BP E Greater than approximately 2 kW, while BP F Less than approximately 500 W. For example, BP. E In various embodiments, the power output is between about 10 kW and about 25 kW, and in some embodiments, it is between about 15 kW and 18 kW. In contrast, BP... F In some embodiments, it is between about 100 W and about 1 kW, and in one embodiment it is about 200 W.

[0079] The bias power supply 49 can also be an RF power supply and can be configured to provide RF power in the low-frequency (LF) to mid-frequency (MF) range. In one embodiment, the bias power supply 49 is configured to supply approximately 400 kHz of RF bias power. For example, during the second etching step, an RF frequency of 400 kHz and approximately 200 W of bias power (SP) can be used. F The bias power 48 is provided to the substrate 410. Other bias power strategies can also be used, such as square waveform (which can be called high-energy rectangular bias).

[0080] The first precursor gas 441 contains a first etchant species that is selective for the target material. For example, in a specific application of dielectric etching involving oxides, the first etchant species may be a chemical formula C x F y Fluorocarbons. In various embodiments, the fluorocarbon is a higher molecular weight fluorocarbon having at least two carbon atoms and (therefore) a higher carbon-to-fluorine ratio. For example, the first etchant species may be CF4, C4F8, C5F8, C2F6, C4F6, C5F6, etc.

[0081] The second precursor gas 442 contains a second etchant species used as an etchant and includes WF6. The second etchant species is targeted at organic materials, such as polymer materials. In one embodiment, the second etchant species includes oxygen (O2), carbonyl sulfide (COS), and tungsten fluoride (WF6). In another embodiment, the second etchant species includes oxygen (O2) and tungsten fluoride (WF6). Furthermore, in another embodiment, the second etchant species includes nitrogen (N2), hydrogen (H2), and tungsten fluoride (WF6).

[0082] The second precursor gas 442 may also contain various additional components, such as inert species or additives, designed to improve the desired results. In one embodiment, the second precursor gas 442 contains carbonyl sulfide (COS) and tungsten fluoride (WF6). For example, including COS can further reduce the bowing effect, thereby producing other beneficial effects.

[0083] Figure 5 Two timing diagrams schematically illustrate an example method for etching a target material according to an embodiment of the present invention, wherein the total first etching time is the same between the two timing diagrams. For example, Figure 5 The method can be any of the other methods described herein (such as...) Figure 3 The specific implementation of the method is as follows. Similarly, the labeled elements can be as described previously.

[0084] refer to Figure 5 Method 500 is similar to Method 300, but demonstrates varying the number of second etch steps without changing the total first etch time. The source power and bias power can also be varied as in Method 300, but are not shown here for simplicity. This is desirable when the desired total first etch time is known or capped and the goal is to optimize other effects using an appropriate number of second etch steps. As shown, the first configuration 501 repeats cycle 550, which includes a first etch step using a first precursor gas 541 and a first etch step duration 551 (or a first duration) and a second etch step using a second precursor gas 542 and a second etch step duration 552 (or a second duration). As shown, the first configuration 501 has five first etch steps and four second etch steps.

[0085] In the second configuration 502, the number of second etching steps is reduced to two, resulting in only three first etching steps. To keep the total first etching time the same, the first etching steps are extended to a first etching step duration 556, resulting in a longer cycle 555. Depending on the desired outcome, the second etching step duration 557 can be the same or different. Here, the second etching step duration 557 is the same as the second etching step duration 552, which is desirable when the optimal second etching step duration is determined and only the number of second etching steps is optimized.

[0086] Additionally, in some cases, the duration of both the first and second etching steps can be dynamically changed, which can be useful when there is an effect that changes with increasing etching depth or the passage of time during a cyclic etching process.

[0087] A relevant parameter that can have an effect similar to the number of second etching steps is the frequency of the second etching steps. Specifically, as the number of second etching steps increases, the frequency of the second etching steps (equal to the reciprocal of the cycle or period) typically also increases, because for a given process, the total first etching time remains substantially the same. As shown in the first configuration 501 and the second configuration 502, the frequency of the second etching steps increases with the number of second etching steps. In various embodiments, the frequency of the second etching steps is greater than about one second etching step every two minutes. In one embodiment, the frequency of the second etching steps is greater than about one second etching step per minute.

[0088] Figure 6 Two timing diagrams schematically illustrate an example method for etching a target material according to an embodiment of the present invention, wherein the total first etching time and the total second etching time are the same between the two timing diagrams, but the number of second etching steps varies. For example, Figure 6 The method can be any of the other methods described herein (such as...) Figure 3 The specific implementation of the method is as follows. Similarly, the labeled elements can be as described previously.

[0089] refer to Figure 6 Method 600 is similar to Method 500, but demonstrates varying the number of second etching steps without changing the total first etching time or the total second etching time. Specifically, the first configuration 601 repeats cycle 650, which includes a first etching step using a first precursor gas 641 and a first etching step duration 651, and a second etching step using a second precursor gas 642 and a second etching step duration 652. As shown, the first configuration 601 has eight first etching steps and seven second etching steps.

[0090] In the second configuration 602, the number of second etching steps is reduced to two, resulting in only three first etching steps. To keep both the total first etching time and the total second etching time the same, both the first and second etching steps are extended to the durations 656 and 657 of the first etching step, resulting in a much longer cycle 655. This is desirable when the desired total second etching time is known or has been capped, and other desired results can be achieved even by reducing the frequency of the second etching steps.

[0091] Figure 7 Qualitative illustrations show example pits exhibiting more severe defects according to embodiments of the present invention, and contrasting example pits exhibiting less severe defects. For example, Figure 7 This can be used as a concrete qualitative example to visually demonstrate the potential advantages of the methods disclosed herein in transferring defects to the underlying layer.

[0092] refer to Figure 7 The qualitative illustrations 700 of the two underlying layers are configured with an underlying layer 701 showing a pit 77 with more severe defects and another underlying layer 702 showing a pit 78 with less severe defects. Although the goal is to transfer highly regular (e.g., circular) pits into the underlying layers, this ideal result may not be achievable in practice. Therefore, example pits are provided to illustrate the difference between more severe defects (such as height distortion and CER in pit 77) and less severe defects (such as a quasi-circular shape with smooth edges in pit 78).

[0093] Dent 78 is closer to dent 77. Figure 1 The image shows an ideal, perfectly circular recess 28 transferred to the bottom layer 18 when the sub-facet 23 is absent. The recess 78 is much smoother (e.g., lower CER), much more uniform (e.g., less distorted), and much larger (e.g., a larger B / T ratio, resulting in a larger recess size that more accurately reflects the desired pattern).

[0094] Figures 8A to 8B An example method for etching a target substrate according to an embodiment of the present invention is illustrated. Figures 8A to 8B The method can be combined with other methods and executed using systems and devices as described herein. For example, Figures 8A to 8B The method can be with Figures 1 to 6 Any combination of the embodiments. Although shown in logical order, Figures 8A to 8B The arrangement and numbering of the steps are not intended to be restrictive. Figures 8A to 8B The steps can be performed in any suitable order or simultaneously with each other.

[0095] refer to Figure 8A In step 810 of method 801 for etching a target material, a first etching step is performed to etch the target material of a substrate, the substrate including a patterned mask disposed on the target material and having an opening in the patterned mask. Performing step 810 of the first etching step includes generating a first plasma to form a first passivation layer comprising a polymer material on the sidewalls of the opening and etching the target material. Step 820 of method 801 for etching the target material includes performing a second etching step to remove a portion of the first passivation layer. Performing step 820 of the second etching step includes generating a second plasma from a tungsten-containing precursor gas and exposing the substrate to the second plasma. Method 801 is then performed cyclically by repeating steps 810 and 820, as indicated in step 830.

[0096] Now for reference Figure 8BIn step 850 of method 802 for etching a target material, the target material is etched using a first plasma. The substrate includes a patterned mask disposed on the target material and has openings in the patterned mask. The etching of the target material in step 850 includes forming a first passivation layer comprising a polymer material on the sidewalls of the openings while etching the target material. In step 860 of method 802 for etching the target material, a portion of the first passivation layer deposited in the etching of the target material is etched using a second plasma, and a second passivation layer comprising tungsten is deposited. Method 802 is then performed cyclically by repeating steps 850 and 860, as indicated in step 870.

[0097] In various embodiments, the etching of a portion of the first passivation layer in step 860 of method 802 and the removal of a portion of the first passivation layer in step 820 of method 801 can be described as Figure 3 The second etching step of method 300, as illustrated, involves cleaning the opening. Similarly, step 810 of method 801 and step 850 of method 802 can be... Figure 3 The first etching step of method 300 is illustrated in the figure.

[0098] Example embodiments of the present invention are described below. Other embodiments can also be understood based on the entire specification and the claims set forth herein.

[0099] Example 1. A method for plasma etching a substrate, the method comprising cyclically performing a first etching step to etch a target material, the substrate including a patterned mask disposed on the target material and having openings in the patterned mask, the first etching step comprising generating a first plasma from a carbon-containing precursor gas and exposing the substrate to the first plasma to form a first passivation layer and etching the target material, the first passivation layer comprising a polymer material on the sidewalls of the openings. Furthermore, the method further comprises cyclically performing a second etching step to remove a portion of the first passivation layer, the second etching step comprising generating a second plasma from a tungsten-containing precursor gas and exposing the substrate to the second plasma.

[0100] Example 2. The method as described in Example 1, wherein the second plasma is further generated from a precursor gas mixture comprising nitrogen (N2) and hydrogen (H2), and wherein the tungsten-containing precursor gas comprises tungsten fluoride (WF6).

[0101] Example 3. The method as described in either Example 1 or 2, wherein the second plasma is further generated from a precursor gas mixture comprising oxygen (O2) and carbonyl sulfide (COS), and wherein the tungsten-containing precursor gas comprises tungsten fluoride (WF6).

[0102] Example 4. The method as described in any one of Examples 1 to 3, wherein the second plasma is further generated from a precursor gas mixture containing oxygen (O2), and wherein the tungsten-containing precursor gas contains tungsten fluoride (WF6).

[0103] Example 5. The method described in any one of Examples 1 to 4, wherein the patterned mask comprises an amorphous carbon layer (ACL).

[0104] Example 6. The method as described in any one of Examples 1 to 5, wherein the carbon-containing precursor gas comprises a fluorocarbon.

[0105] Example 7. The method as described in any one of Examples 1 to 6, wherein the second etching step is performed after the first etching step without an intermediate purging step.

[0106] Example 8. The method as described in any one of Examples 1 to 7, wherein the second etching step forms a second passivation layer comprising tungsten on the patterned mask.

[0107] Example 9. The method as described in any one of Examples 1 to 8, wherein the first etching step is performed for a first duration and the second etching step is performed for a second duration, the second duration being shorter than the first duration.

[0108] Example 10. The method of any one of Examples 1 to 9, further comprising performing an intermediate step between the first etching step and the second etching step, wherein, during the intermediate step, the carbon-containing precursor gas and the tungsten-containing precursor gas are simultaneously injected.

[0109] Example 11. A method for plasma etching a substrate, the method comprising cyclically etching a target material with a first plasma, the substrate including a patterned mask disposed on the target material and having openings in the patterned mask, the etching of the target material including forming a first passivation layer comprising a polymer material on the sidewalls of the openings while etching the target material. Furthermore, the method further includes cyclically etching a portion of the first passivation layer deposited in the etching of the target material with a second plasma and depositing a second passivation layer comprising tungsten.

[0110] Example 12. The method as described in Example 11, wherein the second plasma is generated from a precursor gas mixture comprising nitrogen (N2), hydrogen (H2) and tungsten fluoride (WF6).

[0111] Example 13. The method as described in any one of Examples 11 or 12, wherein the second plasma is generated from a precursor gas mixture comprising oxygen (O2), carbonyl sulfide (COS), and tungsten fluoride (WF6).

[0112] Example 14. The method as described in any one of Examples 11 to 13, wherein the second plasma is generated from a precursor gas mixture containing oxygen (O2) and tungsten fluoride (WF6).

[0113] Example 15. The method as described in any one of Examples 11 to 14, wherein the patterned mask comprises an amorphous carbon layer (ACL).

[0114] Example 16. The method as described in any one of Examples 11 to 15, wherein the first plasma is generated from a precursor gas mixture containing a fluorocarbon compound.

[0115] Example 17. The method of any one of Examples 11 to 16, wherein the etching with the second plasma is performed after the etching with the first plasma without an intermediate purging step.

[0116] Example 18. The method of any one of Examples 11 to 17, wherein the etching performed with the first plasma lasts for a first duration, and the etching performed with the second plasma lasts for a second duration, the second duration being shorter than the first duration.

[0117] Example 19. A plasma etching system comprising a plasma chamber; a substrate holder disposed in the plasma chamber and configured to support a substrate; and a controller operatively coupled to the plasma chamber and to a memory storing a program to be executed in the controller, the program comprising instructions to: generate a first plasma in a cyclic manner from a carbon-containing precursor gas to etch a target material and form a first passivation layer comprising a polymer material on the sidewall of an opening, and generate a second plasma from a tungsten-containing precursor gas to remove a portion of the first passivation layer.

[0118] Example 20. The plasma etching system as described in Example 19, wherein the instructions include instructions to generate the second plasma from a precursor gas mixture comprising nitrogen (N2), hydrogen (H2) and the tungsten-containing precursor gas, and wherein the tungsten-containing precursor gas comprises tungsten fluoride (WF6).

[0119] Example 21. A plasma etching system as described in any one of Examples 19 or 20, wherein the instructions include instructions to generate the second plasma from a precursor gas mixture comprising oxygen (O2), carbonyl sulfide (COS) and the tungsten precursor gas, and wherein the tungsten precursor gas comprises tungsten fluoride (WF6).

[0120] Although the invention has been described with reference to illustrative embodiments, this specification is not intended to be limiting. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to those skilled in the art upon reference to this specification. Therefore, the appended claims are intended to cover any such modifications or embodiments.

Claims

1. A method for plasma etching a substrate, the method comprising: in a cyclic manner: A first etching step is performed to etch a target material. The substrate includes a patterned mask disposed on the target material and having openings in the patterned mask. Performing the first etching step includes generating a first plasma from a carbon-containing precursor gas and exposing the substrate to the first plasma to form a first passivation layer and etching the target material. The first passivation layer comprises a polymer material on the sidewalls of the openings. A second etching step is performed to remove a portion of the first passivation layer. The second etching step includes generating a second plasma from a tungsten-containing precursor gas and exposing the substrate to the second plasma.

2. The method as described in claim 1, wherein, The second plasma is further generated from a precursor gas mixture containing nitrogen (N2) and hydrogen (H2), wherein the tungsten-containing precursor gas contains tungsten fluoride (WF6).

3. The method as described in claim 1, wherein, The second plasma is further generated from a precursor gas mixture containing oxygen (O2) and carbonyl sulfide (COS), wherein the tungsten-containing precursor gas contains tungsten fluoride (WF6).

4. The method of claim 1, wherein, The second plasma is further generated from a precursor gas mixture containing oxygen (O2), wherein the tungsten-containing precursor gas contains tungsten fluoride (WF6).

5. The method of claim 1, wherein, The patterned mask comprises an amorphous carbon layer (ACL).

6. The method of claim 1, wherein, The carbon-containing precursor gas contains fluorocarbons.

7. The method of claim 1, wherein, The second etching step is performed after the first etching step without an intermediate purging step.

8. The method of claim 1, wherein, The second etching step forms a second passivation layer containing tungsten on the patterned mask.

9. The method of claim 1, wherein, The first etching step is performed for a first duration, and the second etching step is performed for a second duration, the second duration being shorter than the first duration.

10. A method for plasma etching a substrate, the method comprising: in a cyclic manner: Etching a target material using a first plasma, the substrate including a patterned mask disposed on the target material and having openings in the patterned mask, the etching of the target material including forming a first passivation layer comprising a polymer material on the sidewalls of the openings while etching the target material; and A portion of the first passivation layer deposited in the etching of the target material is etched using a second plasma, and a second passivation layer containing tungsten is deposited.

11. The method of claim 10, wherein, The second plasma is generated by a precursor gas mixture containing nitrogen (N2), hydrogen (H2) and tungsten fluoride (WF6).

12. The method of claim 10, wherein, The second plasma is generated by a precursor gas mixture containing oxygen (O2), carbonyl sulfide (COS), and tungsten fluoride (WF6).

13. The method of claim 10, wherein, The second plasma is generated from a precursor gas mixture containing oxygen (O2) and tungsten fluoride (WF6).

14. The method of claim 10, wherein, The patterned mask comprises an amorphous carbon layer (ACL).

15. The method of claim 10, wherein, The first plasma is generated from a precursor gas mixture containing fluorocarbons.

16. The method of claim 10, wherein, The etching performed with the second plasma is carried out after the etching performed with the first plasma without an intermediate purging step.

17. The method of claim 10, wherein, The etching performed with the first plasma lasts for a first duration, and the etching performed with the second plasma lasts for a second duration, the second duration being shorter than the first duration.

18. A plasma etching system comprising: Plasma chamber; A substrate holder is disposed in the plasma chamber and configured to support the substrate; and A controller, operatively coupled to the plasma chamber and to a memory storing a program to be executed within the controller, the program comprising instructions to cyclically... A first plasma is generated from a carbon-containing precursor gas to etch the target material and form a first passivation layer containing a polymer material on the sidewall of the opening. A second plasma is generated from a tungsten-containing precursor gas to remove a portion of the first passivation layer.

19. The plasma etching system of claim 18, wherein, These instructions include instructions for generating the second plasma from a precursor gas mixture comprising nitrogen (N2), hydrogen (H2) and the tungsten-containing precursor gas, wherein the tungsten-containing precursor gas comprises tungsten fluoride (WF6).

20. The plasma etching system of claim 18, wherein, These instructions include instructions for generating the second plasma from a precursor gas mixture containing oxygen (O2), carbonyl sulfide (COS) and the tungsten-containing precursor gas, wherein the tungsten-containing precursor gas contains tungsten fluoride (WF6).

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