An in-situ self-cleaning tungsten oxide etching method, semiconductor structure and chip

Abstract

This application relates to the field of semiconductor manufacturing technology, and discloses an in-situ self-cleaning tungsten oxide etching method, a semiconductor structure, and a chip. The method includes: forming an organic polymer soft mask layer on a tungsten oxide film; etching the tungsten oxide film with the organic polymer soft mask layer using a trifluoromethane-based etching gas in an ICP etching apparatus to form a tungsten oxide etched structure; during the etching process, the trifluoromethane flow rate is in the range of 35 sccm to 90 sccm, and the ratio of ICP source power to bias power is in the range of 1.53:1 to 3.3:1 to achieve in-situ self-cleaning; the sidewall tilt angle of the tungsten oxide etched structure is 85 degrees to 90 degrees, and the percentage of carbon atoms at the bottom of the trenches of the tungsten oxide etched structure does not exceed 1.02%. Its beneficial effect is that it simultaneously achieves precise morphology etching and in-situ self-cleaning.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to an in-situ self-cleaning tungsten oxide etching method, semiconductor structure, and chip. Background Technology

[0002] Tungsten oxide, as an important functional material, is widely used in micro / nanoelectronic devices, electrochromic windows, and sensors. The fabrication quality of its micro / nano structures directly determines device performance. Currently, inductively coupled plasma etching (ICP-E) based on a trifluoromethane and argon mixture is the mainstream technique for fabricating tungsten oxide structures. This technique follows the technical bias that "Ar gas must be added to provide physical bombardment to suppress polymer deposition and maintain etching." However, while the intense physical sputtering of argon ions achieves anisotropic etching, it inevitably bombards and damages organic masks such as photoresists, generating a large number of carbon-based debris byproducts. These debris fall into the etching trenches, forming contaminants that are difficult to remove in situ during the etching process, leading to deterioration of the etching morphology, increased defects, and even etching termination. Subsequent wet or dry cleaning steps cannot repair the structural damage caused by these byproducts, severely limiting the manufacturing yield and reliability of high-performance tungsten oxide devices. Summary of the Invention

[0003] This application provides an in-situ self-cleaning tungsten oxide etching method, a semiconductor structure, and a chip, which solves the technical problem of severe mask carbon contamination in related tungsten oxide etching and achieves the technical effect of simultaneously realizing precise morphology etching and in-situ self-cleaning.

[0004] To achieve the above objectives, the main technical solutions adopted in this application include:

[0005] In a first aspect, embodiments of this application provide an in-situ self-cleaning tungsten oxide etching method, the method comprising: forming an organic polymer soft mask layer on a tungsten oxide film; in an ICP etching apparatus, using an etching gas mainly composed of trifluoromethane to etch the tungsten oxide film having the organic polymer soft mask layer to form a tungsten oxide etched structure; during the etching process, the flow rate of the trifluoromethane is in the range of 35 sccm to 90 sccm, and the ratio of ICP source power to bias power is in the range of 1.53:1 to 3.3:1, so as to achieve in-situ self-cleaning; the sidewall tilt angle of the tungsten oxide etched structure is 85 degrees to 90 degrees, and the percentage of carbon atoms at the bottom of the trench of the tungsten oxide etched structure does not exceed 1.02%.

[0006] This application employs an organic polymer soft mask and precisely controls the flow rate of trifluoromethane-based etching gas within the range of 35 sccm to 90 sccm during ICP etching, while simultaneously adjusting the ratio of ICP source power to bias power between 1.53:1 and 3.3:1. By optimizing the balance between physical bombardment and chemical reaction, a high-verticality etching morphology with sidewall tilt angles of 85° to 90° is obtained, ensuring accurate pattern transfer and high anisotropy. Furthermore, the carbon atomic percentage at the bottom of the trenches in the tungsten oxide etching structure does not exceed 1.02%, allowing for the immediate removal of carbon-containing byproducts from the trench bottom during etching. This achieves effective in-situ self-cleaning, suppresses defect formation, and improves the interface quality, electrical performance, and reliability of tungsten oxide micro / nano devices.

[0007] Optionally, the etching gas is composed of trifluoromethane.

[0008] By eliminating the conventional addition of argon gas, the main source of mask carbon contamination caused by argon ion physical sputtering is fundamentally eliminated. High verticality of the tungsten oxide etching structure and in-situ self-cleaning of the trench bottom are achieved without the need for external inert gas assistance, overcoming the technical bias in this field that necessitates the addition of inert gas.

[0009] Optionally, the ratio of the ICP source power to the bias power is 1.53:1.

[0010] When the ratio of ICP source power to bias power is controlled at the optimal value of 1.53:1, a perfect balance between physical bombardment and chemical reaction can be achieved. At this ratio, the vertical ion bombardment energy provided by the bias power is strong enough to effectively remove the polymer generated at the bottom of the etching process, ensuring that the etching reaction continues downward and avoiding the formation of conical sidewalls. At the same time, the high-density plasma maintained by the ICP source power provides sufficient active groups, ensuring a sufficient chemical reaction rate and the formation of sidewall-protective polymers, thereby suppressing lateral etching. Since mask damage is controlled to a minimum, carbon contamination originating from the mask is fundamentally suppressed, and etching byproducts can be removed in a timely and effective manner, thus achieving optimal in-situ self-cleaning effect at the bottom of the trench.

[0011] Optionally, the ICP source power ranges from 600 W to 700 W, and the bias power ranges from 200 W to 500 W.

[0012] If the bias power is too low (below 200 W), the ion bombardment energy is insufficient to effectively remove the polymer film deposited at the bottom of the etching process. If the bias power is too high (above 500 W), the excessive physical bombardment will severely damage the photoresist mask, sputtering out a large amount of carbon-based debris. Accordingly, the ICP source power is set in the range of 600 W to 700 W to ensure that the plasma density is high enough across the entire bias power range to provide sufficient reactive groups.

[0013] Optionally, the ICP source power is 660 W and the bias power is 430 W.

[0014] A 660 W ICP source power generated a high density of active groups, while a 430 W bias power provided precisely targeted ion bombardment. This specific power combination ensured high-speed chemical reactions and a sufficient sidewall-protected polymer source. By precisely controlling the ion bombardment energy, polymer at the etch bottom was effectively removed to maintain the continuous vertical etching process, while the intensity was controlled precisely below a threshold that would not cause severe sputtering damage to the photoresist mask. This allowed for the simultaneous achievement of vertical morphology and in-situ self-cleaning of the tungsten oxide etched structure without the need for inert gas assistance.

[0015] Optionally, the flow rate of the trifluoromethane is 90 sccm.

[0016] Setting the flow rate of the etching gas trifluoromethane to a high value of 90 sccm significantly increases the concentration of fluorine radicals and fluorocarbon polymer precursors generated by plasma decomposition. This ensures the formation of a sufficiently thick and stable polymer protective layer on the sidewalls, thereby strongly suppressing lateral etching, which is key to achieving high verticality. By creating a plasma environment with high chemical activity and low physical damage, the generation of contaminants is mechanistically suppressed and their removal is promoted to the maximum extent, thus achieving optimal in-situ self-cleaning of the etched trenches.

[0017] Optionally, the organic polymer soft mask layer is a photoresist mask.

[0018] Compared to hard masks (such as metals, silicon nitride, and aluminum oxide), photoresist masks offer a significantly simplified fabrication process, eliminating the complex steps required for hard masks, including deposition, etching, and final hard mask removal. By combining low-cost, standardized photoresist processes with high-performance, highly vertical, and residue-free tungsten oxide etching, the economics and efficiency of the process are greatly improved while ensuring optimal device performance.

[0019] Optionally, the etching process is carried out at a gas pressure of 0.9 Pa.

[0020] By setting a moderately low-pressure environment, in conjunction with optimized power and gas parameters, the strong directionality of plasma bombardment and sufficient diffusion capacity of active groups are ensured. This not only directly contributes to obtaining highly vertical etching morphologies, but also facilitates in-situ self-cleaning by maintaining the effective volatilization and removal of etching byproducts.

[0021] Secondly, embodiments of this application provide a semiconductor structure, the semiconductor structure including a tungsten oxide etched structure formed by the above-described tungsten oxide etching method.

[0022] Thirdly, embodiments of this application provide a chip, the chip comprising the semiconductor structure described above.

[0023] Fourthly, embodiments of this application provide a circuit comprising the semiconductor structure described above. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the specific embodiments or related technologies of this application, the drawings used in the description of the specific embodiments or related technologies will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0025] Figure 1 A flowchart illustrating an in-situ self-cleaning tungsten oxide etching method provided in this application embodiment;

[0026] Figure 2 A schematic diagram of the curves relating bias power to etching rate and etching sidewall angle provided for embodiments of this application;

[0027] Figure 3(a) is a SEM image of the tungsten oxide etching cross section provided in Embodiment 1 of this application;

[0028] Figure 3(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 1 of this application;

[0029] Figure 3(c) is an EDS data diagram of the tungsten oxide etching trench provided in Embodiment 1 of this application;

[0030] Figure 3(d) is an EDS data diagram of the photoresist mask provided in Embodiment 1 of this application;

[0031] Figure 4(a) is a SEM image of the tungsten oxide etching cross section provided in Embodiment 2 of this application;

[0032] Figure 4(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 2 of this application;

[0033] Figure 4(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment 2 of this application;

[0034] Figure 4(d) is an EDS data diagram of the photoresist mask provided in Embodiment 2 of this application;

[0035] Figure 5(a) is a SEM image of the tungsten oxide etching cross section provided in Embodiment 3 of this application;

[0036] Figure 5(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 3 of this application;

[0037] Figure 5(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment 3 of this application;

[0038] Figure 5(d) is an EDS data diagram of the photoresist mask provided in Embodiment 3 of this application;

[0039] Figure 6 A graph showing trifluoromethane versus etching rate and etching sidewall angle provided for embodiments of this application;

[0040] Figure 7(a) is a SEM image of the tungsten oxide etching cross section provided in Embodiment 4 of this application;

[0041] Figure 7(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 4 of this application;

[0042] Figure 8(a) is a SEM image of the tungsten oxide etching cross section provided in Example 5 of this application;

[0043] Figure 8(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 5 of this application;

[0044] Figure 9(a) is a SEM image of the tungsten oxide etching cross section provided in Example 6 of this application;

[0045] Figure 9(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment Six of this application;

[0046] Figure 9(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment Six of this application;

[0047] Figure 9(d) is an EDS data diagram of the photoresist mask provided in Embodiment 6 of this application;

[0048] Figure 10(a) is a SEM image of the unetched tungsten oxide surface provided in the embodiment of this application;

[0049] Figure 10(b) is an EDS data diagram of the unetched tungsten oxide surface provided in the embodiments of this application. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] Tungsten oxide (WO3), as an important functional material, has shown broad application prospects in micro / nanoelectronic devices, smart windows, and sensors due to its excellent electrochromic, gas-sensitive, and catalytic properties. In these applications, dry etching, especially inductively coupled plasma (ICP) etching, is often required to fabricate tungsten oxide micro / nanostructures with high aspect ratios and vertical sidewalls to meet the requirements of device performance and integration.

[0052] In relevant ICP dry etching technologies, fluorocarbon gases, especially a mixture of trifluoromethane (CHF3) and the inert gas argon (Ar), are commonly used as etchants. In this conventional approach, the two gases play different roles: CHF3 decomposes in the plasma, generating fluorine (F•) radicals to achieve chemical etching of tungsten oxide, while the resulting carbon-fluorine (CF2) radicals... x The groups form a polymer protective layer on the sidewalls of the structure to suppress lateral etching and obtain anisotropic profiles; while Ar gas does not directly participate in the chemical reaction, its main role is to facilitate the process. + The physical bombardment of ions enhances the reaction rate in the etching direction and sputters away any polymer that may be over-deposited at the bottom of the etching, preventing it from causing the etching to terminate.

[0053] It is widely recognized in the art that in pure CHF3 plasma, the system is highly susceptible to shifting from "etching-dominated" to "deposition-dominated." Excessive polymer can coat the surface to be etched, hindering contact between the active etching groups and the material, ultimately leading to a sharp decrease in the etching rate or even process failure. Therefore, "the addition of Ar gas to CHF3 to physically bombard and suppress excessive polymer deposition, thereby maintaining a stable etching process," has become a deeply ingrained technical consensus and operational practice in the field. This technical bias has directly resulted in the lack of successful reports on etching systems using pure CHF3 gas, especially in applications requiring high vertical etching.

[0054] However, the inventors of this application have discovered through in-depth research that the conventional method for introducing Ar gas has inherent defects: Ar +The physical bombardment removes the underlying polymer while also violently impacting organic masks such as photoresist, causing mask damage and generating carbon-based debris. These debris fall into the etching trenches, forming byproduct residues that are difficult to remove in situ during the etching process, known as the "micromask" effect. This introduces defects and severely affects the morphological quality of the etched structure and the performance of the final device.

[0055] Therefore, there is an urgent need in the field for an etching method that can overcome the above-mentioned technical biases and achieve high verticality etching of tungsten oxide without the introduction of Ar gas, while simultaneously solving the problem of by-product residue.

[0056] This application provides an in-situ self-cleaning tungsten oxide etching method. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0057] Please refer to Figure 1 , Figure 1 A flowchart of an in-situ self-cleaning tungsten oxide etching method provided in this application embodiment is shown below. Figure 1 As shown, the process includes the following steps:

[0058] Step S1: An organic polymer soft mask layer is formed on the tungsten oxide film.

[0059] Tungsten oxide thin films refer to a uniform layer of tungsten oxide material deposited on the surface of a substrate material (such as silicon wafers, glass, etc.), with a thickness ranging from nanometers to micrometers. An organic polymer soft mask layer with a specific pattern is formed on the tungsten oxide thin film. The organic polymer soft mask layer can be photoresist, polyimide, etc. During the etching process, the organic polymer soft mask provides a controllable carbon source, reacting with the etching gas to generate an appropriate amount of polymer. In the embodiments of this application, by precisely controlling the etching parameters, the polymer at the bottom of the trench that hinders etching can be selectively removed, while a thin layer of polymer on the sidewalls is retained to achieve vertical protection, and a smooth corner that naturally forms improves the electrical performance of the device.

[0060] Step S3: In the ICP etching equipment, trifluoromethane-based etching gas is used to etch the tungsten oxide film containing the organic polymer soft mask layer to form a tungsten oxide etched structure. During the etching process, the flow rate of trifluoromethane is in the range of 35 sccm to 90 sccm, and the ratio of ICP source power to bias power is in the range of 1.53:1 to 3.3:1 to achieve in-situ self-cleaning. The sidewall tilt angle of the tungsten oxide etched structure is 85 degrees to 90 degrees, and the percentage of carbon atoms at the bottom of the trenches of the tungsten oxide etched structure does not exceed 1.02%.

[0061] In-situ self-cleaning refers to the fact that during the etching process, the rate of the etching reaction (including physical sputtering and chemical reaction) is greater than or equal to the deposition rate of the carbon-containing polymer, thereby avoiding the residue and accumulation of carbon-containing polymer in the etching trench.

[0062] Trifluoromethane is key to achieving the optimal balance between high etching selectivity and controllable polymer generation. It provides the appropriate amount of polymer to effectively protect the mask and sidewalls for high selectivity and verticality, while maintaining a generation rate that can be controlled through "in-situ self-cleaning" via subsequent ion bombardment. Trifluoromethane is the dominant component of all gases introduced into the ICP etching chamber, accounting for the highest flow rate, and it plays a leading role in the chemical reactions.

[0063] To ensure sufficient fluorine radicals react with tungsten oxide and maintain a reasonable etching rate, a low trifluoromethane flow rate results in a slow etching rate and insufficient polymer formation, potentially leading to inadequate sidewall protection and decreased selectivity. Therefore, the lower limit for trifluoromethane flow rate is set at 35 sccm. A higher flow rate promotes the formation of more volatile fluorides, while the provided carbon source is effectively removed under optimized ion bombardment, achieving a clean trench bottom. The upper limit for trifluoromethane flow rate is set at 90 sccm. Excessive flow rate beyond this range may lead to excessive polymer formation, exceeding the upper limit of the "self-cleaning" capability.

[0064] The ratio of ICP source power to bias power is crucial for controlling the balance between chemical and physical processes during etching. It directly and synergistically determines the final etching morphology (verticality) and cleaning effect. A ratio that is too high (e.g., exceeding 3.3) indicates insufficient physical bombardment (removal capability). Excessive polymer deposition on the sidewalls and bottom results in conical sidewalls and bottom residue. Conversely, a ratio that is too low (e.g., less than 1.53) indicates excessive physical bombardment. This not only removes the bottom polymer but also violently bombards the photoresist mask, generating a large amount of carbon debris, ultimately forming a carbon film that prevents etching and terminates the process. Setting the ICP source power to bias power ratio between 1.53:1 and 3.3:1 ensures that the energy of ion bombardment effectively removes polymer from the bottom of the trench (achieving in-situ self-cleaning) while minimizing damage to the sidewalls protected by the polymer film (achieving vertical sidewalls).

[0065] This application employs an organic polymer soft mask and precisely controls the flow rate of trifluoromethane-based etching gas within the range of 35 sccm to 90 sccm during ICP etching, while simultaneously adjusting the ratio of ICP source power to bias power between 1.53:1 and 3.3:1. By optimizing the balance between physical bombardment and chemical reaction, a high-verticality etching morphology with sidewall tilt angles of 85° to 90° is obtained, ensuring accurate pattern transfer and high anisotropy. Furthermore, the carbon atomic percentage at the bottom of the trenches in the tungsten oxide etching structure does not exceed 1.02%, allowing for the immediate removal of carbon-containing byproducts from the trench bottom during etching. This achieves effective in-situ self-cleaning, suppresses defect formation, and improves the interface quality, electrical performance, and reliability of tungsten oxide micro / nano devices.

[0066] In some specific embodiments, the etching gas is composed of trifluoromethane.

[0067] During the ICP etching process, the etching gas introduced into the reaction chamber is only trifluoromethane, with no other gas added, especially argon, which is usually considered necessary.

[0068] By eliminating the conventional addition of argon gas, the main source of mask carbon contamination caused by argon ion physical sputtering is fundamentally eliminated. High verticality of the tungsten oxide etching structure and in-situ self-cleaning of the trench bottom are achieved without the need for external inert gas assistance, overcoming the technical bias in this field that necessitates the addition of inert gas.

[0069] In some specific embodiments, the ratio of the ICP source power to the bias power is 1.53:1.

[0070] When the ratio of ICP source power to bias power is controlled at the optimal value of 1.53:1, a perfect balance between physical bombardment and chemical reaction can be achieved. At this ratio, the vertical ion bombardment energy provided by the bias power is strong enough to effectively remove the polymer generated at the bottom of the etching process, ensuring that the etching reaction continues downward and avoiding the formation of conical sidewalls. At the same time, the high-density plasma maintained by the ICP source power provides sufficient active groups, ensuring a sufficient chemical reaction rate and the formation of sidewall-protective polymers, thereby suppressing lateral etching. Since mask damage is controlled to a minimum, carbon contamination originating from the mask is fundamentally suppressed, and etching byproducts can be removed in a timely and effective manner, thus achieving optimal in-situ self-cleaning effect at the bottom of the trench.

[0071] In some specific embodiments, the ICP source power ranges from 600 W to 700 W, and the bias power ranges from 200 W to 500 W.

[0072] ICP source power primarily controls plasma density. Higher power results in a higher concentration of ionized active groups, determining the upper limits of chemical etching rate and polymer formation rate. Bias power primarily controls the energy of ions perpendicularly bombarding the wafer surface. Higher bias power results in stronger physical bombardment, directly affecting the degree of anisotropy, bottom polymer removal efficiency, and the degree of damage to the mask.

[0073] If the bias power is too low (below 200 W), the ion bombardment energy is insufficient to effectively remove the polymer film deposited at the bottom of the etching process. If the bias power is too high (above 500 W), the excessive physical bombardment will severely damage the photoresist mask, sputtering out a large amount of carbon-based debris. Accordingly, the ICP source power is set in the range of 600 W to 700 W to ensure that the plasma density is high enough across the entire bias power range to provide sufficient reactive groups.

[0074] In some specific embodiments, the ICP source power is 660 W and the bias power is 430 W.

[0075] A 660W ICP source generated a high density of active groups, while a 430W bias power provided precisely targeted ion bombardment. This specific power combination ensured high-speed chemical reactions and a sufficient sidewall-protected polymer source. By precisely controlling the ion bombardment energy, polymer at the etch bottom was effectively removed to maintain the continuous vertical etching process, while the intensity was controlled precisely below a threshold that would not cause severe sputtering damage to the photoresist mask. This allowed for the simultaneous achievement of vertical morphology and in-situ self-cleaning of the tungsten oxide etched structure without the need for inert gas assistance.

[0076] In some specific embodiments, the flow rate of the trifluoromethane is 90 sccm.

[0077] Setting the flow rate of the etching gas trifluoromethane to a high value of 90 sccm significantly increases the concentration of fluorine radicals and fluorocarbon polymer precursors generated by plasma decomposition. This ensures the formation of a sufficiently thick and stable polymer protective layer on the sidewalls, thereby strongly suppressing lateral etching, which is key to achieving high verticality. By creating a plasma environment with high chemical activity and low physical damage, the generation of contaminants is mechanistically suppressed and their removal is promoted to the maximum extent, thus achieving optimal in-situ self-cleaning of the etched trenches.

[0078] In some specific embodiments, the organic polymer soft mask layer is a photoresist mask.

[0079] Compared to hard masks (such as metals, silicon nitride, and aluminum oxide), photoresist masks offer a significantly simplified fabrication process, eliminating the complex steps required for hard masks, including deposition, etching, and final hard mask removal. By combining low-cost, standardized photoresist processes with high-performance, highly vertical, and residue-free tungsten oxide etching, the economics and efficiency of the process are greatly improved while ensuring optimal device performance.

[0080] In some specific embodiments, the etching process is performed at a gas pressure of 0.9 Pa.

[0081] By setting a moderately low-pressure environment, in conjunction with optimized power and gas parameters, the strong directionality of plasma bombardment and sufficient diffusion capacity of active groups are ensured. This not only directly contributes to obtaining highly vertical etching morphologies, but also facilitates in-situ self-cleaning by maintaining the effective volatilization and removal of etching byproducts.

[0082] The following is a detailed description with reference to specific embodiments.

[0083] The following Examples 1, 2, 3, 4, 5, and 6 all include the following steps in the sample preparation stage: A glass slide with a tungsten oxide thin film magnetron sputtered on its surface is provided. Photoresist (ZEP520A) is coated onto the tungsten oxide thin film using spin coating. A trench pattern with a linewidth of 1 μm is formed through photolithography and development processes. The patterned sample is placed into the reaction chamber of an inductively coupled plasma (ICP) etching apparatus.

[0084] To investigate the impact of carbon contamination introduced by the photoresist mask on the etching process under different etching conditions, this application established control experiments for Examples 1, 2, and 3. Specifically, during the etching processes of Examples 1, 2, and 3, patterned photoresist mask samples (experimental group) and unpatterned tungsten oxide samples using high-temperature tape as masks (control group) were placed in the same ICP reaction chamber and etched synchronously under identical process parameters. The high-temperature tape exhibited structural stability under the aforementioned etching conditions and produced almost no carbon-based debris or other contaminants, serving as a clean reference standard for evaluating the intrinsic characteristics of the process. Experimental results showed that in Example 3, the photoresist mask sample (experimental group) experienced etching termination due to carbon debris deposition, while the high-temperature tape (control group) could still be etched normally. This comparison demonstrates that etching termination was not caused by systematic factors such as the chamber environment or process parameter settings, but rather by the photoresist mask being violently bombarded under high bias power, generating carbon contaminants sufficient to hinder the etching reaction.

[0085] The etching parameter settings and result analysis for Examples 1, 2, and 3 are shown in Table 1 below:

[0086] Table 1

[0087]

[0088] Please refer to Figure 2 , Figure 2 This is a schematic diagram showing the curves of bias power versus etching rate and etching sidewall angle provided in the embodiments of this application. When the bias power is 500 W, the etching of the patterned tungsten oxide sample terminates (Example 3), while the unpatterned tungsten oxide sample with the high-temperature tape as a control group can still continue etching. This indicates that when the bias power is 500 W, the fundamental reason for the etching termination is not the failure of the chemical ability of the etching environment, but the damage to the photoresist mask caused by physical bombardment, resulting in excessive carbon fragment contaminants that cannot be removed in situ. This, in turn, highlights that optimizing the bias power to 430 W (Example 2) is a key parameter for suppressing mask damage and achieving in-situ self-cleaning.

[0089] Figure 3(a) is a SEM image of the tungsten oxide etched cross section provided in Embodiment 1 of this application. Figure 3(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 1 of this application. Figure 3(c) is an EDS data image of the tungsten oxide etched trench provided in Embodiment 1 of this application. Figure 3(d) is an EDS data image of the photoresist mask provided in Embodiment 1 of this application. EDS (Energy Dispersive X-ray Spectroscopy) is used to detect the carbon (C) content at different locations at the bottom of the etched trench and compare it with the carbon content at the photoresist mask, thereby proving whether the surface byproduct residues in the trench have been effectively removed. As shown in Figures 3(a) and 3(b), the tungsten oxide trench contains nanoparticles. As shown in Figure 3(a), the sidewall angle of the tungsten oxide etched structure is approximately 85°, exhibiting a distinct conical shape. In an ideal, clean tungsten oxide etched structure, the bottom of the trench should contain only tungsten oxide (W, O) and should not contain carbon (C). Therefore, any carbon detected within the trench can be considered a byproduct or contaminant. As shown in Figures 3(c) and 3(d), the atomic percentage of carbon in the trench is 3.55%, while the atomic percentage of carbon at the photoresist mask is 90.96%. The significantly higher carbon content at the bottom of the etched trench confirms the presence of residual polymer byproducts. Due to insufficient bias power (200 W), the ion bombardment capability was inadequate, failing to effectively remove the polymer deposited on the trench sidewalls and bottom, resulting in conical sidewalls and severe byproduct residue.

[0090] Figure 4(a) is a SEM image of the tungsten oxide etched cross section provided in Embodiment 2 of this application. Figure 4(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 2 of this application. Figure 4(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment 2 of this application. Figure 4(d) is an EDS data diagram of the photoresist mask provided in Embodiment 2 of this application. As shown in Figure 4(b), when the bias power is 430 W, the technical effect of vertical sidewalls is obtained. As shown in Figures 4(a) and 4(b), the tungsten oxide trench contains large particles. As shown in Figure 4(c), the percentage of carbon atoms in the trench is 5.23%, and as shown in Figure 4(d), the percentage of carbon atoms at the photoresist mask is 74.8%.

[0091] Figure 5(a) is a SEM image of the tungsten oxide etched cross section provided in Embodiment 3 of this application. Figure 5(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 3 of this application. Figure 5(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment 3 of this application. Figure 5(d) is an EDS data diagram of the photoresist mask provided in Embodiment 3 of this application. As shown in Figure 5(a), since the etching process has ended, there is a whole carbon film in the tungsten oxide trench. As shown in Figure 5(c), the percentage of carbon atoms in the trench is 59.9%, and as shown in Figure 5(d), the percentage of carbon atoms at the photoresist mask is 70.82%.

[0092] The above analysis shows that as the bias power gradually increases, the carbon content in the trench gradually increases, while the carbon content at the photoresist mask gradually decreases. This indicates that there is an optimal power window for the bias power, such as 430 W. Within this window, the ion bombardment energy is sufficient to maintain vertical etching, and the small amount of mask debris generated does not accumulate into a dense carbon film. In the extreme case of a bias power of 500 W, the mask is severely damaged, and a large amount of carbon debris forms a dense carbon film at the bottom of the trench. This film completely blocks the contact between the etchant and tungsten oxide, thus causing the etching to terminate.

[0093] Please refer to Figure 6 , Figure 6 The graph shows the relationship between trifluoromethane and etching rate and etching sidewall angle in the embodiments of this application.

[0094] The etching parameter settings and result analysis for Examples 4, 5, and 6 are shown in Table 2 below:

[0095] Table 2

[0096]

[0097] Please refer to Figure 7(a), which is a SEM image of the tungsten oxide etched cross section provided in Embodiment 4 of this application. Figure 7(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 4 of this application. As shown in Figures 7(a) and 7(b), the sidewall angle of the etched trench is approximately 90 degrees, and a large number of large particle-like residues are visible at the bottom of the trench.

[0098] Please refer to Figure 8(a), which is a SEM image of the tungsten oxide etched cross section provided in Embodiment 5 of this application. Figure 8(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 5 of this application. As shown in Figures 8(a) and 8(b), the sidewall angle of the etched trench is approximately 90 degrees, and a large number of small particulate residues are visible at the bottom of the trench.

[0099] Please refer to Figures 9(a), 9(b), 9(c), and 9(d). Figure 9(a) is a SEM image of the tungsten oxide etched cross section provided in Embodiment 6 of this application. Figure 9(b) is a SEM image of the tungsten oxide etched surface provided in Embodiment 6 of this application. As shown in Figures 9(a) and 9(b), the sidewall angle of the etched trench is approximately 90 degrees, and the bottom of the trench is a smooth surface. Figure 9(c) is an EDS data diagram of the tungsten oxide etched trench provided in Embodiment 6 of this application, and Figure 9(d) is an EDS data diagram of the photoresist mask provided in Embodiment 6 of this application. As shown in Figure 9(c), the percentage of carbon atoms in the trench is 0%, and as shown in Figure 9(d), the percentage of carbon atoms in the photoresist mask is 83.93%. Please refer to Figures 10(a) and 10(b). Figure 10(a) is a SEM image of the unetched tungsten oxide surface provided in the embodiment of this application, and Figure 10(b) is an EDS data image of the unetched tungsten oxide surface provided in the embodiment of this application. As shown in Figure 10(b), the percentage of carbon atoms on the unetched tungsten oxide surface is 1.02%, while the percentage of carbon atoms in the trench in Example 6 is significantly lower than 1.02%. This confirms that Example 6 of this application achieves no by-product residue in the trench and realizes in-situ self-cleaning.

[0100] The sixth embodiment provided in this application is a preferred embodiment. By using pure trifluoromethane as the etching gas and combining it with optimized ICP power and bias power, a balance between physical etching and chemical etching is achieved. It can provide sufficient ion energy to ensure verticality and remove by-products, and the fluorine-rich environment generates more volatile reaction products. High verticality and self-cleaning within the cavity are achieved simultaneously during the etching process. This successfully breaks the technical prejudice that argon must be added to maintain etching. Under the premise of using low-cost photoresist masks, the process flow is significantly simplified and the manufacturing cost is reduced by eliminating the complex process of hard masks and the additional cleaning steps after etching.

[0101] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and all such modifications and variations fall within the scope defined by the appended claims.

[0102] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0103] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0104] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

[0105] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. An in-situ self-cleaning tungsten oxide etching method, characterized in that, The method includes: An organic polymer soft mask layer is formed on a tungsten oxide thin film; In the ICP etching apparatus, the etching gas is composed of trifluoromethane and is used to etch the tungsten oxide film having the organic polymer soft mask layer to form a tungsten oxide etched structure. During the etching process, the flow rate of the trifluoromethane ranges from 35 sccm to 90 sccm, and the ratio of ICP source power to bias power ranges from 1.53:1 to 3.3:1 to achieve in-situ self-cleaning. The sidewall tilt angle of the tungsten oxide etched structure is from 85 degrees to 90 degrees, and the percentage of carbon atoms at the bottom of the trenches of the tungsten oxide etched structure does not exceed 1.02%.

2. The method according to claim 1, characterized in that, The ratio of the ICP source power to the bias power is 1.53:

1.

3. The method according to claim 1, characterized in that, The ICP source power ranges from 600 W to 700 W, and the bias power ranges from 200 W to 500 W.

4. The method according to claim 3, characterized in that, The ICP source power is 660 W, and the bias power is 430 W.

5. The method according to claim 1 or 4, characterized in that, The flow rate of the trifluoromethane is 90 sccm.

6. The method according to claim 1, characterized in that, The organic polymer soft mask layer is a photoresist mask.

7. The method according to claim 1, characterized in that, The etching process is carried out at a pressure of 0.9 Pa.

8. A semiconductor structure, characterized in that, The semiconductor structure includes a tungsten oxide etched structure formed by the tungsten oxide etching method as described in any one of claims 1-7.

9. A chip, characterized in that, The chip includes the semiconductor structure as described in claim 8.

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