Endpoint energy reduction etching method for silver-based noble metal low energy inert ion beam etching

Abstract

The application provides an endpoint energy reduction etching method for silver-based noble metal low-energy inert ion beam etching, which comprises the following steps: firstly, providing a structure to be etched, which comprises, from bottom to top, a substrate, a lower barrier layer or a dielectric layer, a silver-based noble metal layer and a composite hard mask structure, wherein the composite hard mask structure comprises, from bottom to top, a sacrificial capture layer and a conductive suspension layer in sequence; secondly, performing selective lateral trimming on the sacrificial capture layer to make the sacrificial capture layer produce lateral shrinkage relative to the sidewall of the conductive suspension layer; thirdly, performing main etching on the silver-based noble metal layer by an inert ion beam in an inert environment to form a silver pattern, stopping the main etching when the remaining thickness of the silver-based noble metal layer meets a preset thickness, and performing endpoint suppression etching on the silver-based noble metal layer with the remaining thickness; and finally, removing the composite hard mask structure.

Description

Technical Field

[0001] This application relates to the field of micro-nano fabrication technology, and specifically to an endpoint de-energy etching method for low-energy inert ion beam etching of silver-based noble metals. Background Technology

[0002] Silver and its alloys are widely used as display electrodes, reflective electrodes, transparent conductive layers, and functional layers in micro / nano optical devices due to their excellent conductivity and reflectivity. However, silver is difficult to generate highly volatile etching products in conventional reactive plasma environments. Therefore, related technologies typically rely on physical etching methods such as ion beam etching or ion milling to pattern silver thin films. Ion beam etching utilizes inert gas ions to physically sputter the silver layer, achieving a relatively ideal anisotropic etching profile.

[0003] However, the physical etching process itself introduces unavoidable process defects. On the one hand, the silver atoms sputtered by the ion beam have a certain angular distribution, and some of them will redeposit on the sidewall surface of the etched pattern, forming conductive residues that may lead to leakage or short circuits between device electrodes. Related technologies improve the sidewall morphology by adjusting the ion beam incident angle or rotating the sample stage, but it is difficult to ensure that the redeposited material falls into an area that can be effectively removed. On the other hand, when the silver layer is etched to near the underlying barrier layer or dielectric layer, if high-energy ions are used for over-etching, the residual silver atoms will be back-implanted into the underlying material under the ion bombardment, causing interface contamination and device performance degradation. While extending the over-etching time in related technologies helps remove residual silver, it increases back-implantation damage to the bottom interface, and conventional hard masks can only protect the top of the pattern and cannot actively control the distribution of sidewall redeposited material.

[0004] Therefore, how to effectively suppress silver redeposition on the sidewalls and silver backflush injection at the bottom interface while ensuring the quality of silver pattern etching is a technical problem that urgently needs to be solved in related technologies. Summary of the Invention

[0005] In view of this, to solve at least one technical problem in related technologies and other aspects, this application proposes an endpoint reduction etching method for low-energy inert ion beam etching of silver-based noble metals, comprising: first, providing a structure to be etched, including a substrate, a lower barrier layer or dielectric layer, a silver-based noble metal layer and a composite hard mask structure arranged from bottom to top, wherein the composite hard mask structure includes a sacrificial trapping layer and a conductive suspension layer from bottom to top; then, selectively laterally trimming the sacrificial trapping layer to cause the sacrificial trapping layer to laterally retract relative to the sidewall of the conductive suspension layer, thereby forming a prefabricated trapping groove open to the outside etching space below the edge of the conductive suspension layer; then, in an inert environment, performing main etching on the silver-based noble metal layer by an inert ion beam to form a silver pattern; stopping the main etching when the remaining thickness of the silver-based noble metal layer meets a preset thickness, and performing endpoint suppression etching on the remaining thickness of the silver-based noble metal layer; finally, removing the composite hard mask structure to remove the silver redeposited material deposited in the prefabricated trapping groove.

[0006] According to embodiments of this application, the composite hard mask further includes a sputter-resistant hard mask layer disposed above the conductive shroud layer, suitable for maintaining pattern boundary integrity during main etching and endpoint suppression etching processes.

[0007] According to an embodiment of this application, after the prefabricated capture groove is formed and before the main etching begins, a continuous sidewall layer that closes the opening of the prefabricated capture groove is not deposited.

[0008] According to an embodiment of this application, the thickness of the sacrificial trapping layer is 5~20nm, and the lateral retraction distance is 5~40nm; the ratio of the lateral retraction distance to the thickness of the sacrificial trapping layer is 1.0~3.5.

[0009] According to an embodiment of this application, the lateral retraction distance is no greater than one-quarter of the smaller of the line width of the silver pattern or the spacing between adjacent silver patterns.

[0010] According to an embodiment of this application, the material of the sacrificial trapping layer is amorphous carbon; the material of the conductive suspension layer is metal nitride, and the thickness of the conductive suspension layer is 5~20nm; the material of the sputter-resistant hard mask layer is silicon nitride or silicon oxide, and the thickness of the sputter-resistant hard mask layer is 20~120nm; in the selective lateral trimming process, the conductive suspension layer is used as a mask, and the two sides of the sacrificial trapping layer are isotropically etched by oxygen-containing plasma treatment to achieve lateral retraction.

[0011] According to an embodiment of this application, the first energy of the main etching output is 300~600eV, and the second energy of the endpoint suppression etching output is 100~350eV; the second energy is less than the first energy, and the ratio of the second energy to the first energy is 0.25~0.70.

[0012] According to the embodiments of this application, during the main etching process: the working gas of the inert ion beam is argon, krypton or xenon, the incident angle of the inert ion beam relative to the sample stage normal is 5°~20°, and the set total flow rate of oxygen, oxygen-containing reactive gas and halogen reactive gas accounts for no more than 1% of the total inlet flow rate.

[0013] According to an embodiment of this application, in the process of endpoint suppression etching: the preset thickness is that the remaining thickness of the silver-based noble metal layer is no more than 30 nm, and the output form of endpoint suppression etching is a short pulse ion beam or an intermittent ion beam.

[0014] According to an embodiment of this application, removing the composite hard mask structure includes: selectively removing the sacrificial trapping layer by means of at least one of low-bias oxygen plasma treatment, remote oxygen plasma treatment, or ozone treatment, utilizing the etching selectivity ratio between the sacrificial trapping layer and the conductive suspension layer, and causing the silver redeposited material to be stripped off synchronously along with the removal of the sacrificial trapping layer.

[0015] According to embodiments of this application, by providing a composite hard mask structure comprising a sacrificial trapping layer and a conductive suspension layer, and laterally trimming the sacrificial trapping layer before the main etching to form a pre-fabricated trapping groove, silver atoms sputtered during the main etching process can be guided into the groove for deposition, thereby reducing the amount of redeposited material adhering to the sidewalls of the silver pattern and lowering the risk of conductive residue. Maintaining an inert environment during the main etching process avoids additional changes in the size of the pre-fabricated trapping groove due to reactive gases, keeping the geometry of the trapping space stable. When the remaining thickness of the silver layer meets a preset condition, the main etching is stopped and switched to endpoint suppression etching, which can remove residual silver with lower energy, reduce the impact driving force of high-energy ions on the near-interface residual silver, and reduce the risk of silver atoms being back-injected into the underlying barrier layer or dielectric layer. After etching, the composite hard mask structure is removed, and the silver redeposited material deposited in the pre-fabricated trapping groove is removed along with the mask structure, eliminating the need for additional sidewall cleaning steps and resulting in high overall process compatibility. Attached Figure Description

[0016] Figure 1 This is a flowchart of the endpoint de-energization etching method for low-energy inert ion beam etching of silver-based noble metals in the embodiments of this application;

[0017] Figure 2 This is a schematic diagram of the initial stacked structure including the hard mask structure in Embodiment 1 of this application;

[0018] Figure 3 This is a graphical schematic diagram of the stacked structure in Embodiment 1 of this application;

[0019] Figure 4 This is a schematic diagram of the structure of the quantitative open prefabricated capture groove in Embodiment 1 of this application;

[0020] Figure 5 This is a schematic diagram of the etched structure in Embodiment 1 of this application;

[0021] Figure 6 This is a schematic diagram of the structure after removing the hard mask in Embodiment 1 of this application.

[0022] [Attached image labels]

[0023] In the accompanying drawings of this application, the reference numerals have the following meanings:

[0024] 1-Substrate; 2-Lower barrier layer; 3-Silver-based noble metal layer; 4-Sacrificial trap layer; 5-Conductive shroud layer; 6-Sputter-resistant hard mask layer. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0026] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this application.

[0027] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0028] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0029] It should be noted that, unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person with ordinary skill in the art to which this application pertains. Where the terms "first," "second," etc., are used throughout, they are used only to distinguish similar objects and should not be construed as indicating or implying their relative importance, order of precedence, or implicitly specifying the number of technical features indicated. It should be understood that the data in the descriptions of "first," "second," etc., can be interchanged where appropriate.

[0030] Similarly, to simplify this application and aid in understanding one or more of the various disclosed aspects, in the above description of exemplary embodiments of this application, various features of this application are sometimes grouped together into a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicates that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0031] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0032] In the process of realizing this application, it was discovered that the sidewall redeposition and bottom interface implantation problems of silver during inert ion beam etching are rooted in the spatial distribution characteristics of sputtered particles and the interaction between high-energy ions and residual silver near the interface, respectively. For sidewall redeposition, since silver atoms have a certain angular distribution after sputtering, if a geometrically favorable trapping region can be constructed in the mask structure beforehand, the redeposited material may preferentially accumulate in this region rather than adhering to the sidewalls of the silver pattern. For bottom interface implantation, when the silver layer becomes thin to the nanoscale, the underlying barrier layer begins to be exposed. The impact of high-energy ions on residual silver will push silver atoms into the lower layer. Reducing the bombardment energy may mitigate the backflow implantation effect while removing residual silver.

[0033] Based on the above findings, this paper proposes to introduce a laterally adjustable sacrificial trapping layer into the hard mask to form a prefabricated groove, and at the same time, to combine it with an etching strategy that reduces ion energy at the endpoints, so as to solve the above problems simultaneously through the synergy of structure and process.

[0034] Figure 1 This is a flowchart of the endpoint de-energization etching method for low-energy inert ion beam etching of silver-based noble metals in the embodiments of this application.

[0035] This application proposes an endpoint de-energy etching method for low-energy inert ion beam etching of silver-based noble metals, such as... Figure 1 As shown, it includes the following steps S1 to S4.

[0036] Step S1: Provide the structure to be etched, including a substrate, a lower barrier layer or dielectric layer, a silver-based noble metal layer and a composite hard mask structure arranged from bottom to top. The composite hard mask structure includes a sacrificial trapping layer and a conductive suspension layer from bottom to top.

[0037] Step S2: Selectively laterally trim the sacrificial capture layer to cause the sacrificial capture layer to laterally retract relative to the sidewall of the conductive shield layer, thereby forming a prefabricated capture groove that opens to the external etching space below the edge of the conductive shield layer.

[0038] Step S3: In an inert environment, the silver-based noble metal layer is etched by an inert ion beam to form a silver pattern. When the remaining thickness of the silver-based noble metal layer meets the preset thickness, the main etching is stopped, and the remaining thickness of the silver-based noble metal layer is subjected to endpoint suppression etching.

[0039] Step S4: Remove the composite hard mask structure to remove the silver redeposited in the prefabricated capture groove.

[0040] According to embodiments of this application, a composite hard mask structure comprising a sacrificial trapping layer and a conductive suspension layer is provided. Before the main etching, the sacrificial trapping layer is laterally trimmed to form a pre-fabricated trapping groove. This allows silver atoms sputtered during the main etching process to be guided into the groove for deposition, thereby reducing the amount of redeposited material adhering to the sidewalls of the silver pattern and lowering the risk of conductive residue. Maintaining an inert environment during the main etching process avoids additional changes in the size of the pre-fabricated trapping groove due to reactive gases, ensuring the stability of the trapping space geometry. When the remaining thickness of the silver layer meets preset conditions, the main etching is stopped and switched to endpoint suppression etching, thereby removing residual silver with lower energy, reducing the impact driving force of high-energy ions on near-interface residual silver, and lowering the risk of silver atoms being back-injected into the underlying barrier layer or dielectric layer. After etching, the composite hard mask structure can be removed, allowing the silver redeposited material deposited in the pre-fabricated trapping groove to be removed along with the mask structure, eliminating the need for additional sidewall cleaning steps and resulting in high overall process compatibility.

[0041] In some specific embodiments, the silver-based noble metal layer can be a patterned silver (Ag) layer, an Ag alloy layer with an Ag atomic fraction of not less than 50 at.%, or a multilayer electrode containing Ag as an extended implementation. The lower barrier layer is a lower structure that needs to reduce the risk of Ag injection contamination. The substrate is used to support the entire film structure.

[0042] According to embodiments of this application, the composite hard mask further includes a sputter-resistant hard mask layer disposed above the conductive shroud layer, suitable for maintaining pattern boundary integrity during main etching and endpoint suppression etching processes.

[0043] According to embodiments of this application, a sputter-resistant hard mask layer is further disposed above the conductive suspension layer, which can provide effective protection against ion bombardment for the underlying sacrificial trapping layer and conductive suspension layer. During the main etching and endpoint suppression etching processes, the ion beam will continuously generate physical sputtering on the surface of the mask structure. If only the conductive suspension layer is relied upon to perform the mask function, its thickness needs to be significantly increased, which may affect the formation accuracy of the groove structure. The sputter-resistant hard mask layer is made of a material with strong sputter resistance, which can withstand ion beam bombardment for a long time while maintaining the integrity of the pattern boundary, thereby ensuring the linewidth accuracy and sidewall perpendicularity of the silver pattern. At the same time, this hard mask layer can be removed together with or in stages with the conductive suspension layer in subsequent removal processes without adding additional process complexity.

[0044] According to an embodiment of this application, after the prefabricated capture groove is formed and before the main etching begins, a continuous sidewall layer that closes the opening of the prefabricated capture groove is not deposited.

[0045] According to embodiments of this application, by adding a layer of material with low ion sputtering yield above the conductive shroud layer as a sputter-resistant hard mask layer, this layer can bear the main load of ion beam bombardment, effectively dissipating ion energy, thereby reducing the bombardment damage to the underlying conductive shroud layer and sacrificial trapping layer. During the endpoint suppression etching stage, although the ion energy is reduced, there is still continuous sputtering effect on the mask structure. The sputter-resistant hard mask layer can also continue to play a protective role during this stage, ensuring the stability of the pattern boundary throughout the etching process, which is beneficial for obtaining a silver pattern profile with high conformability.

[0046] According to an embodiment of this application, the thickness (T) of the sacrificial trapping layer is 5~20nm, for example, it can be 5nm, 10nm, 15nm, 20nm, or any two of them, preferably 5~15nm; the lateral retraction distance (R) is 5~40nm, for example, it can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, or any two of them, preferably 8~25nm; the ratio of the lateral retraction distance to the thickness of the sacrificial trapping layer is 1.0~3.5, preferably 1.2~3.0nm.

[0047] According to embodiments of this application, the thickness of the sacrificial trapping layer and the lateral retraction distance jointly determine the size of the prefabricated trapping groove's accommodating space. A sacrificial trapping layer thickness within this range helps ensure sufficient groove depth while avoiding increased processing difficulty for pattern transfer due to excessive thickness. The lateral retraction distance is also within this range, with its ratio to the sacrificial trapping layer thickness limited to 1.0 to 3.5. This ratio characterizes the lateral extension of the groove relative to its longitudinal depth. When this ratio is within the aforementioned range, the groove has a suitable aspect ratio, providing sufficient space to accommodate a certain amount of silver redeposited material while maintaining the mechanical stability of the conductive shield layer's overhanging edges, preventing collapse or deformation of the overhanging portion due to excessive suspension.

[0048] In some specific embodiments, if the lateral retraction distance is less than the lower limit of this range, the lateral extension of the groove is insufficient, making it difficult for silver sputtered particles to effectively enter the groove, resulting in a decrease in capture efficiency. If the lateral retraction distance is greater than the upper limit of this range or the ratio is too large, the overhang length of the conductive shielding layer edge relative to its underlying support increases significantly, reducing the structural stability of the shielding layer. This may lead to deformation or breakage during subsequent ion beam bombardment, and excessive retraction may also cause the grooves of adjacent patterns to connect. If the thickness of the sacrificial capture layer deviates from the above range, if it is too thin, the groove depth is insufficient, and silver particles are prone to overflow after entering. If it is too thick, it increases the burden of etching pattern transfer and the difficulty of process control.

[0049] In some specific embodiments, after forming a stacked structure including a hard mask structure, the hard mask layer structure is patterned to subsequently form a silver pattern.

[0050] According to an embodiment of this application, the lateral retraction distance is no greater than one-quarter of the smaller of the line width of the silver pattern or the spacing between adjacent silver patterns.

[0051] According to embodiments of this application, when the silver pattern linewidth is narrow or the spacing between adjacent patterns is small, if the lateral retraction distance is too large, the overhanging edges on both sides of the conductive mask layer may approach or even overlap each other, causing the groove structure to interfere with each other between adjacent patterns. Furthermore, an excessively large retraction distance will reduce the effective pattern width of the sputter-resistant hard mask layer, affecting the precise control of the silver pattern linewidth. This constraint ensures that the composite hard mask structure provides capture functionality without sacrificing pattern resolution.

[0052] In some specific embodiments, the lateral retraction distance (R) can be calibrated by changing the O2 treatment time, O2 flow ratio, plasma power, bias voltage, and cavity pressure, and can be measured by cross-sectional scanning electron microscopy (SEM) or projection electron microscopy (TEM).

[0053] According to embodiments of this application, the material of the sacrificial trapping layer is amorphous carbon; the material of the conductive suspension layer is metal nitride, and the thickness of the conductive suspension layer is 5~20nm, for example, 5nm, 10nm, 15nm, 20nm, etc., or any two thereof; the material of the sputter-resistant hard mask layer is silicon nitride or silicon oxide, and the thickness of the sputter-resistant hard mask layer is 20~120nm, for example, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, etc., or any two thereof; in the selective lateral trimming process, the conductive suspension layer is used as a mask, and isotropic etching is performed on both sides of the sacrificial trapping layer by oxygen-containing plasma treatment to achieve lateral retraction.

[0054] According to embodiments of this application, the combination of these three types of materials has a synergistic effect in terms of process compatibility and selectivity. Amorphous carbon has a high etching rate in oxygen-containing plasma, while metal nitrides and silicon nitride / silicon oxide have extremely low etching rates under the same oxygen plasma conditions. Therefore, using a metal nitride conductive slack layer as a mask and isotropically etching the amorphous carbon layer through oxygen-containing plasma treatment can achieve relatively precise lateral retraction control. The lateral retraction distance can be calibrated by adjusting parameters such as the processing time and power of the oxygen plasma. The thickness range of each layer is also rationally configured according to their respective process functions. The sacrificial trapping layer provides an appropriate groove depth within this range, the thickness of the conductive slack layer balances the strength of the overhang structure and the conductive discharge function, and the thickness of the sputter-resistant hard mask layer helps to provide sufficient bombardment resistance to protect the integrity of the underlying layers throughout the entire etching cycle.

[0055] In some specific embodiments, if the thickness of each layer deviates from the above range or the material selection is inappropriate, it will be difficult to balance the etching selectivity, structural stability and process synergy between the layers. Problems may occur such as uneven shrinkage of the sacrificial capture layer during the lateral trimming process, oxidation failure of the conductive suspension layer in oxygen plasma, or complete consumption of the sputter-resistant hard mask layer before the main etching is completed.

[0056] According to embodiments of this application, the first energy of the main etching output is 300~600eV, for example, it can be 300eV, 350eV, 400eV, 450eV, 500eV, 550eV, 600eV, or any two of them, preferably 350~450eV; the second energy of the endpoint suppression etching output is 100~350eV, for example, it can be 100eV, 150eV, 200eV, 250eV, 300eV, 350eV, or any two of them, preferably 120~280eV; the second energy is less than the first energy, and the ratio of the second energy to the first energy is 0.25~0.70, preferably 0.30~0.60.

[0057] According to embodiments of this application, the first energy output during the main etching stage, within this range, is beneficial for providing sufficient sputtering yield during the main etching process of the silver-based noble metal layer, ensuring a high etching rate and process throughput. Simultaneously, it avoids excessively high energy leading to an excessively large lateral velocity component in the silver sputtered particles, which is beneficial for controlling the distribution range of sidewall redepositions. The second energy during the endpoint suppression etching stage is lower than the main etching energy in this range, but still retains sufficient physical sputtering capability to remove residual silver from the thin layer. The ratio of the second energy to the first energy ensures that the endpoint suppression etching stage has a clear energy reduction, effectively distinguishing it from the main etching stage. By limiting the above energy range and ratio range, a good match can be achieved between main etching efficiency and endpoint interface protection.

[0058] In some specific embodiments, if the first energy of the main etching is higher than 600 eV, the silver recoil implantation depth and cascade collision region caused by ion bombardment are significantly increased. Even if the energy is subsequently reduced, the damage to the underlying layer caused by the high-energy etching in the early stage is irreversible. If the first energy of the main etching is lower than 300 eV, the silver etching rate is low, the process efficiency is insufficient, and the directionality of the ion beam decreases at low energy, which may lead to an increase in the tilt of the pattern sidewalls. If the second energy of the endpoint suppression etching is higher than 350 eV or the ratio of the energy to the main etching is higher than 0.70, the energy reduction is insufficient, and high-energy ions will still push the residual silver into the underlying material. If the second energy of the endpoint suppression etching is lower than 100 eV or the ratio of the energy to the main etching is lower than 0.25, the ion energy is too low, and the physical sputtering removal ability of the residual silver is insufficient, which may cause silver residue to remain at the bottom of the pattern, affecting the electrical performance of the device.

[0059] According to embodiments of this application, during the main etching process: the working gas of the inert ion beam is argon, krypton, or xenon, and the incident angle of the inert ion beam relative to the sample stage normal is 5° to 20°, for example, it can be 5°, 10°, 15°, 20°, or any two of them, preferably 8°–15°; the set total flow rate of oxygen, oxygen-containing reactive gas, and halogen reactive gas accounts for no more than 1% of the total inlet flow rate, preferably no more than 0.5%, more preferably no more than 0.1%.

[0060] According to embodiments of this application, the working gas of the inert ion beam is argon, krypton, or xenon. The ions of these inert gases do not chemically react with silver during physical sputtering of the silver layer, ensuring the purely physical nature of the etching process. This helps maintain the stability of the pre-fabricated trapping groove dimensions and avoids changes in the groove geometry due to chemical reactions. Simultaneously, limiting the ion beam incident angle helps balance etching efficiency and the effectiveness of the trapping geometry. Furthermore, limiting the total flow rate of reactive gases ensures a high purity and inertness of the main etching environment. Even if trace amounts of background reactive gases may exist in the process chamber, their content is strictly controlled to a low level, not substantially affecting the lateral dimensions of the amorphous carbon sacrificial trapping layer. This means the geometry of the pre-fabricated trapping groove is primarily determined by the lateral trimming steps before the main etching, improving process controllability and repeatability.

[0061] In some specific embodiments, when the incident angle is too low, the direction of the ion beam tends to be close to the vertical sample stage surface, and the angular distribution range of the sputtered silver atoms is relatively narrow, which is not conducive to the effective entry of silver atoms into the groove; when the incident angle is too high, the shadowing effect is enhanced, and the overhang of the conductive shroud layer may block the groove opening, reducing the actual capture opening size of the groove.

[0062] In some specific embodiments, the main etching employs at least one low-energy inert ion beam selected from Ar, Kr, or Xe.

[0063] According to an embodiment of this application, in the process of endpoint suppression etching: the preset thickness is that the remaining thickness of the silver-based noble metal layer is no more than 30 nm, preferably no more than 15 nm, and the output form of endpoint suppression etching is a short pulse ion beam or an intermittent ion beam.

[0064] According to embodiments of this application, a remaining thickness of no more than 30 nm is used as a preset condition for initiating endpoint suppression etching. This is based on the judgment of interface state changes when the silver layer approaches the underlying barrier layer or dielectric layer. When the remaining thickness of the silver layer is below this threshold, the underlying barrier layer or dielectric layer may have been exposed in local areas. In this case, continuing etching with the main etching energy would result in silver atoms being directly implanted into the lower layer. Switching to low-energy etching under this thickness condition can both utilize low-energy ions to continue removing the remaining thin layer of silver and avoid interface damage caused by high-energy bombardment, achieving a smooth transition from the main etching stage to the over-etching stage. Specifically, the short-pulse or intermittent ion beam output further optimizes the energy application method for endpoint suppression etching. Compared to continuous ion beam bombardment, pulsed or intermittent output delivers a lower total ion dose to the sample surface per unit time. During each pulse interval, the sample surface has sufficient cooling and relaxation time, which can reduce the accumulation of heat in the interface region. At the same time, each pulse of ion bombardment removes only a small number of silver atoms, resulting in a shallower impact on the underlying material. This is beneficial for further reducing the probability of silver atoms being injected by recoil and the range of impact of collisional cascade mixing effects.

[0065] In some specific embodiments, the endpoint determination of the preset thickness can be based on a pre-calibrated Ag etching rate, Ag film thickness, etching time, optical endpoint signal, secondary ion signal, or a combination thereof.

[0066] According to an embodiment of this application, removing the composite hard mask structure includes: selectively removing the sacrificial trapping layer by means of at least one of low-bias oxygen plasma treatment, remote oxygen plasma treatment, or ozone treatment, utilizing the etching selectivity ratio between the sacrificial trapping layer and the conductive suspension layer, and causing the silver redeposited material to be stripped off synchronously along with the removal of the sacrificial trapping layer.

[0067] According to embodiments of this application, the core of this removal method lies in utilizing the significantly different reaction rates of the amorphous carbon sacrificial trapping layer, the metal nitride conductive suspension layer, and the silicon nitride / silicon oxide sputter-resistant hard mask layer in an oxidizing atmosphere. Under low bias or remote oxygen plasma conditions, amorphous carbon reacts with oxygen-active species to generate volatile carbon oxides and is thus removed, while the reaction rates of metal nitride and silicon nitride / silicon oxide are extremely low under these conditions. Therefore, the sacrificial trapping layer can be preferentially removed without significantly corroding the conductive suspension layer and the sputter-resistant hard mask layer. Since most of the silver atoms sputtered during the main etching process are deposited on the sidewalls and bottom surface of the sacrificial trapping layer within the prefabricated trapping groove, when the sacrificial trapping layer is selectively etched away, the silver redeposited material attached to it loses its support and detaches from the structure along with the decomposition products of the sacrificial trapping layer, achieving simultaneous removal of silver contaminants from the sidewalls. Compared with related technologies that employ additional wet cleaning or residue removal processes after pattern etching, this removal method avoids a separate cleaning step for silver redeposition, reduces the potential corrosion risk of wet solutions to silver patterns, and the removal process is completed in a plasma chamber, which has good compatibility with the front-end etching process.

[0068] In some specific embodiments, the conductive suspension layer and the sputter-resistant hard mask layer can be removed by at least one of the following methods: DI water rinsing, IPA replacement, low-power megohmmetry, N2 drying, stripping, selective wet etching, or selective dry etching.

[0069] It should be noted that the described embodiments are merely some, not all, of the embodiments described in this application. Other embodiments obtained by those skilled in the art based on the embodiments described in this application without inventive effort are all within the scope of protection of this application.

[0070] Example 1

[0071] The technical solution of this application will be described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of this application is not limited thereto.

[0072] This embodiment 1 provides an endpoint reduction etching method for low-energy inert ion beam etching of silver-based noble metals. Specifically, this embodiment 1 uses the silver-based noble metal layer 3 to be etched as the target layer. The silver-based noble metal layer 3 is a silver alloy layer with a silver atomic fraction of not less than 50 at.%. The specific process flow is as follows:

[0073] Figure 2 This is a schematic diagram of the initial stacked structure including the hard mask structure in Embodiment 1 of this application.

[0074] Step s101: Provide a structure to be etched, such as Figure 2As shown, the structure, from bottom to top, includes a substrate 1, a lower barrier layer 2, a silver-based noble metal layer 3, and a composite hard mask structure. The lower barrier layer 2 is made of titanium nitride and has a thickness of 30 nm; the silver-based noble metal layer 3 is made of silver and has a thickness of 60 nm. The composite hard mask structure, from bottom to top, includes a laterally retractable sacrificial trapping layer 4, a conductive suspension layer 5, and a sputter-resistant hard mask layer 6. Specifically, the laterally retractable sacrificial trapping layer 4 is made of amorphous carbon and has a thickness of 10 nm; the conductive suspension layer 5 is made of titanium nitride and has a thickness of 10 nm; and the sputter-resistant hard mask layer 6 is made of silicon oxide and has a thickness of 60 nm.

[0075] Figure 3 This is a graphical schematic diagram of the stacked structure in Embodiment 1 of this application. Figure 4 This is a schematic diagram of the structure of the quantitative open prefabricated capture groove in Embodiment 1 of this application.

[0076] Step s102: Through photolithography and dry etching processes, such as Figure 3 As shown, the pattern is transferred to the sputter-resistant hard mask layer 6 and the conductive shroud layer 5, exposing the sidewalls of the amorphous carbon sacrificial trap layer 4. Figure 4 As shown, before the main etching of the silver-based noble metal layer 3, the amorphous carbon sacrificial trapping layer 4 is selectively laterally trimmed. Specifically, using a conductive suspension layer 5 as a mask, isotropic etching is performed on the exposed sidewalls of the sacrificial trapping layer 4 through oxygen-containing plasma treatment, causing the amorphous carbon sacrificial trapping layer 4 to laterally retract relative to the sidewalls of the conductive suspension layer 5, thereby forming a prefabricated trapping groove open to the external etching space below the edge of the conductive suspension layer 5. The lateral retraction distance R is 25 nm, the thickness T of the amorphous carbon sacrificial trapping layer 4 is 10 nm, and the ratio of R to T is 2.5. Simultaneously, after the formation of the prefabricated trapping groove and before the start of the main etching of the silver-based noble metal layer 3, a continuous sidewall layer sealing the opening of the groove is not deposited.

[0077] Step s103: In an inert environment, the silver-based noble metal layer 3 is etched using an inert ion beam to form a silver pattern. Argon is used as the working gas for the inert ion beam, and the incident angle of the ion beam relative to the sample stage normal is 12°. The ion energy E1 output from the main etching is 400 eV. During the main etching process, oxygen, oxygen-containing reactive gases, or halogen reactive gases are not actively introduced, or the total flow rate of these reactive gases is controlled to be no more than 0.5% of the total inlet flow rate, to ensure a high purity and inertness of the etching environment and maintain the stability of the lateral dimensions of the pre-fabricated trapping groove.

[0078] Step s104: When the remaining thickness of the silver-based noble metal layer 3 is no greater than 15 nm, the main etching is stopped, and the endpoint suppression etching stage begins. In this stage, the ion beam energy is reduced from the main etching energy E1 to a second energy E2, where E2 is 200 eV and the ratio of E2 to E1 is within the range of 0.5. Simultaneously, the endpoint suppression etching employs a short-pulse ion beam output to reduce the continuous bombardment dose per unit time on the residual silver near the lower layer and the lower layer surface. The endpoint determination can be based on one or more combinations of pre-calibrated silver etching rate, silver film thickness, etching time, optical endpoint signal, or secondary ion signal.

[0079] Figure 5 This is a schematic diagram of the etched structure in Embodiment 1 of this application. Figure 6 This is a schematic diagram of the structure after removing the hard mask in Embodiment 1 of this application.

[0080] Step s105: The structure after endpoint suppression etching is as follows Figure 5 As shown, the composite hard mask structure was removed to remove the silver redeposited within the prefabricated trap groove, resulting in the following: Figure 6 The composite structure shown.

[0081] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for end-point de-energizing etching of silver-based noble metals using low-energy inert ion beam etching, comprising: The structure to be etched is provided, including a substrate, a lower barrier layer or dielectric layer, a silver-based noble metal layer and a composite hard mask structure arranged from bottom to top. The composite hard mask structure includes a sacrificial trapping layer and a conductive suspension layer from bottom to top. The sacrificial trapping layer is selectively laterally trimmed to cause the sacrificial trapping layer to retract laterally relative to the sidewall of the conductive shielding layer, thereby forming a prefabricated trapping groove that opens to the external etching space below the edge of the conductive shielding layer. In an inert environment, the silver-based noble metal layer is etched by an inert ion beam to form a silver pattern. When the remaining thickness of the silver-based noble metal layer meets the preset thickness, the main etching is stopped, and the remaining thickness of the silver-based noble metal layer is subjected to endpoint suppression etching. Remove the composite hard mask structure to remove the silver redeposited material deposited in the prefabricated capture groove.

2. The endpoint de-energizing etching method according to claim 1, wherein, The composite hard mask also includes a sputter-resistant hard mask layer disposed above the conductive shroud layer, which is suitable for maintaining the integrity of the pattern boundary during the main etching and the endpoint suppression etching processes.

3. The endpoint de-energizing etching method according to claim 1, wherein, After the prefabricated trapping groove is formed and before the main etching begins, no continuous sidewall layer is deposited to seal the opening of the prefabricated trapping groove.

4. The endpoint de-energizing etching method according to claim 1, wherein, The thickness of the sacrificial trapping layer is 5~20nm, and the lateral retraction distance is 5~40nm; The ratio of the lateral retraction distance to the thickness of the sacrificial capture layer is 1.0 to 3.

5.

5. The endpoint de-energizing etching method according to claim 4, wherein, The lateral retraction distance is no greater than one-quarter of the smaller of the line width of the silver pattern or the spacing between adjacent silver patterns.

6. The endpoint de-energizing etching method according to claim 2, wherein, The material of the sacrificial trapping layer is amorphous carbon; The conductive shielding layer is made of metal nitride, and the thickness of the conductive shielding layer is 5~20nm; The sputter-resistant hard mask layer is made of silicon nitride or silicon oxide, and the thickness of the sputter-resistant hard mask layer is 20~120nm; In the selective lateral trimming process, the conductive shroud layer is used as a mask, and isotropic etching is performed on both sides of the sacrificial trapping layer by oxygen-containing plasma treatment to achieve the lateral retraction.

7. The endpoint de-energizing etching method according to claim 1, wherein, The first energy of the main etching output is 300~600eV, and the second energy of the endpoint suppression etching output is 100~350eV; The second energy is less than the first energy, and the ratio of the second energy to the first energy is 0.25 to 0.

70.

8. The endpoint de-energizing etching method according to claim 1, wherein, During the main etching process: The working gas of the inert ion beam is argon, krypton or xenon, the incident angle of the inert ion beam relative to the sample stage normal is 5° to 20°, and the total flow rate of oxygen, oxygen-containing reactive gas and halogen reactive gas accounts for no more than 1% of the total inlet flow rate.

9. The endpoint de-energizing etching method according to claim 1, wherein, In the process of suppressing etching at the endpoints: The preset thickness is that the remaining thickness of the silver-based noble metal layer is no more than 30 nm. The output form of the endpoint suppression etching is a short-pulse ion beam or an intermittent ion beam.

10. The endpoint de-energizing etching method according to claim 1, wherein, The removal of the composite hard mask structure includes: selectively removing the sacrificial trapping layer by means of at least one of low-bias oxygen plasma treatment, remote oxygen plasma treatment, or ozone treatment, utilizing the etching selectivity ratio between the sacrificial trapping layer and the conductive shielding layer, and causing the silver redeposited material to be stripped off synchronously along with the removal of the sacrificial trapping layer.

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