High aspect ratio etching structure and manufacturing method thereof

Abstract

The invention discloses a high-aspect-ratio etching structure and a manufacturing method thereof, and the method comprises the steps: executing an etching process at a first temperature, and carrying out the etching of the surface of a substrate exposed between adjacent organic masks, and forming the high-aspect-ratio etching structure; the etching process comprises a plurality of periodic circulation steps formed according to a deposition step and an etching step in sequence, a first gas is used as a deposition gas in the deposition step and used for forming a polymer layer, and a second gas is used as an etching gas in the etching step and used for etching the polymer layer and the substrate; the first gas comprises gas with the molecular weight smaller than that of C4F8, the second gas comprises gas with the molecular weight smaller than that of SF6, so that the diffusion coefficient is increased, the gas transmission efficiency is improved, and the first temperature is lower than-10 DEG C, so that the density and uniformity of the polymer layer are improved, and lateral etching is inhibited. According to the invention, the uniform protection of the side wall under the conditions of smaller size and higher aspect ratio can be realized, and the etching rate can be improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor processing technology, and in particular to a method for manufacturing a high aspect ratio etched structure and a high aspect ratio etched structure manufactured using this method. Background Technology

[0002] In the rapidly developing field of advanced packaging, higher-density interconnects are required, driving deep silicon etching (DSE) to meet nanometer-scale linewidths (less than 50 nm) and higher aspect ratios (greater than 100:1). Traditional periodic cyclic etching processes are increasingly constrained by physical limitations (such as ion shadowing effects and reactive gas transport efficiency), making it difficult to meet these critical aspect ratio requirements. Furthermore, nanometer-scale linewidths are more sensitive to variations in the thickness of sidewall passivation layers (such as CF polymers). Significant variations in the sidewall passivation layer thickness can easily lead to linewidth shifts and etching tilt (for 3D vias and memory stacking, the etching verticality error must be less than ±0.2°). In addition, existing etching processes suffer from plasma chemical residues and localized roughness peaks (Ra > 5 nm) caused by random deposition of CF polymers on the sidewalls. These factors significantly impact the achievement of higher aspect ratios and nanometer-scale deep silicon etching. Furthermore, with the requirements of higher aspect ratios and nanometer-scale linewidths, it is particularly important to improve the etching rate and the uniformity of protecting the bottom sidewalls during the etching process. Therefore, it is necessary to study a process method that can significantly improve the above problems. Summary of the Invention

[0003] The purpose of this application is to overcome the aforementioned problems in the prior art and to provide a high aspect ratio etched structure and its manufacturing method.

[0004] To achieve the above objectives, the technical solution of this application is as follows: According to a first aspect of this application, embodiments of this application provide a method for manufacturing a high aspect ratio etched structure, comprising: Provide substrate; Multiple organic masks are formed on the surface of the substrate; At a first temperature, an etching process is performed to etch the surface of the substrate exposed between adjacent organic masks, forming a high aspect ratio etched structure on the substrate; The etching process includes multiple periodic cyclic steps formed sequentially by deposition and etching steps. The deposition step uses a first gas as the deposition gas to form a polymer layer on the sidewalls of the high aspect ratio etched structure and the exposed surface of the organic mask during the etching process, so as to protect the sidewalls and the organic mask during etching; the etching step uses a second gas as the etching gas to etch the polymer layer and the substrate. The first gas includes gases with a molecular weight less than that of C4F8, and the second gas includes gases with a molecular weight less than that of SF6, in order to increase the diffusion coefficient and improve the gas transport efficiency. The first temperature is less than -10°C to improve the density and uniformity of the polymer layer and suppress lateral etching.

[0005] In some embodiments, the first gas includes hydrocarbon gases, fluorocarbon gases, and reducing gases, and the polymer layer includes an amorphous hydrocarbon fluoropolymer layer.

[0006] In some embodiments, the hydrocarbon gas includes CH4, the fluorocarbon gas includes CHF3, the reducing gas includes H2, and the amorphous hydrocarbon fluoropolymer layer includes an aC:H:F crosslinked polymer layer having a crosslinked three-dimensional network structure.

[0007] In some embodiments, the first gas includes sulfur and fluorine gases and oxidizing gases, and the polymer layer includes a SiCOF compound layer.

[0008] In some embodiments, the sulfur-fluorine gas includes SF6, the oxidizing gas includes O2, the substrate material includes Si, and the SiCOF compound layer is formed by reacting the O2 with the SF6 and the substrate material respectively, and the resulting active groups of F, O, and S reacting with CO groups sputtered from the organic mask, and co-depositing at the first temperature.

[0009] In some embodiments, the method further includes: during the deposition step, using the O2 to perform a first treatment on the exposed surface of the organic mask, causing the exposed surface of the organic mask to oxidize at the first temperature and be triggered by deep ultraviolet light in the environment to form a hardened layer.

[0010] In some embodiments, the second gas includes a halogen gas, or the second gas includes a halogen gas and a fluorine-containing gas.

[0011] In some embodiments, the halogen gas includes F2, and the fluorine-containing gas includes at least one of NF3, BF3, PF3, CF4, and C2F6.

[0012] In some embodiments, the first temperature is -80℃ to -10℃, or -80℃ to -15℃, or -80℃ to -20℃, or -80℃ to -30℃, or -80℃ to -40℃, or -80℃ to -50℃, or -80℃ to -60℃, or -80℃ to -70℃, or -70℃ to -15℃, or -70℃ to -20℃, or -70℃ to -30℃, or -60℃ to -15℃, or -60℃ to -20℃, or -60℃ to -40℃, or -45℃ to -35℃.

[0013] According to a second aspect of this application, embodiments of this application also provide a high aspect ratio etched structure, which is obtained using the manufacturing method of a high aspect ratio etched structure provided in any of the embodiments of the first aspect above.

[0014] The embodiments of this application may have, or at least have, the following advantages: (1) By using small molecule gases (first gas and second gas) instead of traditional large molecule gases such as C4F8 and SF6 as deposition and etching gases, the diffusion coefficient can be increased and the gas transport efficiency can be improved. This allows the etching gas to diffuse more uniformly and is more conducive to entering the nanoscale high aspect ratio etched structure (trench or via) for etching reaction, achieving superior small-size high aspect ratio etching. It also allows the deposition gas to smoothly enter the bottom of the high aspect ratio etched structure, achieving more uniform protection of the sidewalls at a smaller size. Furthermore, by keeping the temperature (first temperature) during the etching process below -10°C, the chemical kinetics can be changed to enhance physical adsorption and reduce the reaction rate. This allows the polymer layer (passivation layer) to be more densely and uniformly adsorbed on the sidewalls. Even at the bottom of the high aspect ratio etched structure, it can effectively protect the sidewalls and effectively suppress lateral etching, obtaining an extremely vertical sidewall morphology. Therefore, this application can solve the problems of thickness fluctuations in polymers deposited using macromolecular C4F8 affecting the control of nanoscale linewidth, as well as the ion shadowing effect (nanoscale involves atomic size). It effectively improves the uniformity and roughness of local CF polymers, achieving better uniformity (uniform size at the top, middle, and bottom positions of high aspect ratio etched structures) and better sidewall smoothness, thereby enabling the etching of nanoscale deep silicon structures with higher aspect ratios. Simultaneously, small-molecule etching gases can significantly improve the etching rate and etching behavior at high depths (>100µm).

[0015] (2) By using a combination of CH4, CHF3, and H2 as the deposition gas, it is easier to penetrate and uniformly deposit on the bottom of the sidewalls of ultra-narrow and ultra-deep etched structures. This allows for the formation of an amorphous hydrocarbon fluoropolymer layer (aC:H:F crosslinked polymer layer) with a lower fluorocarbon ratio, higher density, greater rigidity, and higher crosslinking degree on the sidewalls at ultra-low temperatures (first temperature). This layer exhibits excellent resistance to physical sputtering and chemical etching, providing better blocking effects and effectively preventing lateral etching. Furthermore, the addition of H2 to the deposition gas reduces the physical bombardment and chemical erosion of the organic mask by high-energy ions, thereby minimizing damage to the organic mask and protecting critical dimensions. This maintains the vertical sidewall morphology.

[0016] (3) By using a combination of SF6 and O2 as the deposition gas, O2 reacts with SF6 and silicon (Si) of the substrate material respectively. The resulting active groups of F, O and S react with CO groups sputtered from the organic mask and co-deposit on the sidewall surface at ultra-low temperature (first temperature) to form a SiCOF compound layer with higher etch resistance, which improves the protection of the sidewall. At low temperature, the SiCOF compound layer will be denser, more uniform and better covered. It can form effective protection even at the bottom of the high aspect ratio etched structure, thus effectively suppressing lateral etching and obtaining an extremely vertical sidewall morphology. Furthermore, by using O2 to perform a first treatment on the exposed surface of the organic mask, the exposed surface of the organic mask undergoes slight oxidation at a first temperature and is triggered by deep ultraviolet light present in the environment, forming a thin and durable "crust" (hardening layer) on the surface of the organic mask. Simultaneously, a SiCOF compound layer is also deposited on the surface of the organic mask, thus forming a composite protective layer. This significantly slows down the erosion rate of the organic mask by F free radicals, greatly reducing the consumption rate of the organic mask and thus significantly improving the selectivity. This means that thinner organic masks can be used to etch deeper, high aspect ratio structures.

[0017] (4) By using F2 (or F2 and fluorine-containing gases) as the etching gas, the high reactivity of F2 can be utilized to provide an abundant main etchant, reducing dependence on physical bombardment and increasing the etching rate. Among them, small molecule reactants and products have a longer mean free path, which can reach the bottom of the high aspect ratio etched structure, ensuring the bottom etching rate and avoiding "etching stop"; the generated ions are lighter and have a more concentrated energy distribution, achieving extreme anisotropic etching, and reducing damage to organic masks, resulting in more vertical sidewalls.

[0018] Other advantages of this application will be described in the following detailed description. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating a method for manufacturing a high aspect ratio etched structure according to a preferred embodiment of this application.

[0020] Figure 2 This is a schematic diagram of the structure after forming an organic mask on a substrate, which is a preferred embodiment of this application.

[0021] Figure 3 This is a schematic diagram of the structure after depositing a polymer layer on a substrate and an organic mask, according to a preferred embodiment of this application.

[0022] Figure 4 This is a schematic diagram of the structure after a first etched structure is formed on a substrate, according to a preferred embodiment of this application.

[0023] Figure 5 This is a schematic diagram of the structure after a polymer layer is redeposited on a substrate and an organic mask, according to a preferred embodiment of this application.

[0024] Figure 6 This is a schematic diagram of a structure after a second etched structure is formed on a substrate, according to a preferred embodiment of this application.

[0025] Figure 7 This is a schematic diagram of a high aspect ratio etched structure formed on a substrate, according to a preferred embodiment of this application.

[0026] Figure 8 This is a schematic diagram of the structure after removing the organic mask, which is a preferred embodiment of this application.

[0027] Figure 9 This is a schematic diagram illustrating the principle of a second treatment of the sidewall provided in a preferred embodiment of this application. Figure 9 (a) represents adsorption and reaction. Figure 9 (b) is desorption.

[0028] In the figure: 10. Substrate; 11. Opening; 12. Organic mask; 13. Carbon-based protective film; 14. Polymer layer; 15. First etched structure; 16. Second etched structure; 17. High aspect ratio etched structure; 18. Protrusion; 19. Recess. Detailed Implementation

[0029] To address the shortcomings of existing technologies, embodiments of this application provide a method for manufacturing a high aspect ratio etched structure, including: Provide substrate; Multiple organic masks are formed on the surface of the substrate; At a first temperature, an etching process is performed to etch the surface of the substrate exposed between adjacent organic masks, forming a high aspect ratio etched structure on the substrate; The etching process includes multiple periodic cyclic steps formed sequentially by deposition and etching steps. The deposition step uses a first gas as the deposition gas to form a polymer layer on the sidewalls of the high aspect ratio etched structure and the exposed surface of the organic mask during the etching process, so as to protect the sidewalls and the organic mask during etching; the etching step uses a second gas as the etching gas to etch the polymer layer and the substrate. The first gas includes gases with a molecular weight less than that of C4F8, and the second gas includes gases with a molecular weight less than that of SF6, in order to increase the diffusion coefficient and improve the gas transport efficiency. The first temperature is less than -10°C to improve the density and uniformity of the polymer layer and suppress lateral etching.

[0030] This application employs small-molecule first and second gases instead of traditional large-molecule gases like C4F8 and SF6 as deposition and etching gases, respectively. This effectively increases the diffusion coefficient, improves the transport efficiency of the reactant gases, and solves the problem of the influence of thickness fluctuations of large-molecule C4F8 polymers on the control of nanoscale linewidth, as well as the ion shadowing effect. It also effectively improves the uniformity and roughness of local CF polymers, thus enabling the etching of nanoscale deep silicon structures with better uniformity, better sidewall smoothness, and higher aspect ratio. Simultaneously, the small-molecule etching gas can significantly improve the etching rate and etching behavior at high depths (>100µm).

[0031] This application also provides a high aspect ratio etched structure obtained by the manufacturing method of the high aspect ratio etched structure described above.

[0032] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0033] refer to Figure 1 According to a first aspect of this application, embodiments of this application provide a method for manufacturing a high aspect ratio etched structure, comprising the following steps: Step S11: Provide a substrate.

[0034] refer to Figure 2 In some embodiments, the material of substrate 10 includes silicon (i.e., a silicon substrate).

[0035] In some embodiments, a silicon wafer may be used as substrate 10 to further form the desired high aspect ratio etched structure on substrate 10 by performing an etching process.

[0036] In some embodiments, the high aspect ratio etched structure includes deep trenches, deep vias, or through vias.

[0037] In some embodiments, the silicon wafer may be doped to provide a substrate 10 that meets the required electrical properties.

[0038] In some embodiments, an integrated circuit, such as a transistor structure, may be fabricated on the substrate 10 to achieve the desired vertical interconnection by filling it with conductive material after forming a high aspect ratio etched structure.

[0039] Step S12: Form multiple organic masks on the surface of the substrate.

[0040] refer to Figure 2 In some embodiments, an organic mask layer is formed on the upper surface of the substrate 10, and the organic mask layer is patterned to form a plurality of patterned organic masks 12 on the upper surface of the substrate 10. An opening 11, serving as an etching window, is provided between any two adjacent organic masks 12, and the surface of the substrate 10 located between the two adjacent organic masks 12 is exposed at the bottom of the opening 11.

[0041] It should be noted that, Figure 2 The diagram only schematically illustrates the case where two organic masks 12 are formed on the upper surface of the substrate 10. However, it is understood that more organic masks, such as three, four, or ten organic masks, can be formed on the upper surface of the substrate 10, and the diagram is not limited to this.

[0042] In some embodiments, the organic material includes photoresist. That is, the organic material mask layer includes a photoresist layer, and the organic material mask 12 includes a photoresist mask.

[0043] In some embodiments, a spin coating process is used to form a photoresist layer on the upper surface of the substrate 10. Then, a photolithography process is used to lithographically shape the photoresist layer, thereby forming a plurality of photoresist patterns, namely organic masks 12, on the upper surface of the substrate 10.

[0044] In some embodiments, before performing an etching process on the substrate 10, a third treatment is performed on the interface between the substrate 10 and the organic mask 12 at a third temperature at an ultra-low temperature. Specifically, a plasma of a fifth gas is used to bombard the interface (upper surface) of the substrate 10, forming a protective film at the junction of the bottom of the organic mask 12 and the upper surface of the substrate 10 (i.e., at the inner bottom corner of the opening 11). The plasma of the fifth gas is obtained by ionizing the fifth gas introduced into the process chamber.

[0045] Due to the mask edge effect, insufficient polymer layer deposition occurs in the edge region during subsequent etching processes, exacerbating the etching behavior at the top. Ion bombardment becomes more concentrated at the top, leading to intensified lateral etching in this area and resulting in deeper and coarser scallop-like ripples on the sidewalls of the high aspect ratio etched structure. Therefore, by pre-forming a protective film at the interface between the bottom of the organic mask 12 and the upper surface of the substrate 10, the morphology of the etched top can be effectively protected during subsequent etching processes on the substrate 10. This prevents abnormal excessive lateral etching at the top, ensuring dimensional uniformity at different depths (top, middle, and bottom) during subsequent high aspect ratio etching, thus guaranteeing the verticality of the sidewalls.

[0046] In some embodiments, the fifth gas includes a rare gas.

[0047] In this embodiment, the fifth gas is argon, and the argon plasma (the plasma of the fifth gas) is used to bombard the photoresist material of the organic mask 12 and the upper surface of the substrate 10, forming a carbon-based protective film 13 (a protective film containing carbon-based materials of C, N and O) at the junction of the bottom of the organic mask 12 and the upper surface of the substrate 10.

[0048] In some embodiments, when performing the third processing, the third temperature is -80°C to -10°C. For example, the third temperature can be -80°C to -10°C, or -80°C to -15°C, or -80°C to -20°C, or -80°C to -30°C, or -80°C to -40°C, or -80°C to -50°C, or -80°C to -60°C, or -80°C to -70°C, or -70°C to -15°C, or -70°C to -20°C, or -70°C to -30°C, or -60°C to -15°C, or -60°C to -20°C, or -60°C to -40°C, or -45°C to -35°C. For example, the third temperature can be -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -15℃, or -10℃, or any value between any two of the aforementioned temperature values. However, it is not limited to these.

[0049] In some embodiments, the pressure during the third processing is 50 mTorr to 800 mTorr. For example, the pressure can be 50 mTorr, 100 mTorr, 200 mTorr, 300 mTorr, 400 mTorr, 500 mTorr, 600 mTorr, 700 mTorr, or 800 mTorr, or any value between any two of the aforementioned pressure values. However, it is not limited to these.

[0050] In some embodiments, when performing the third processing, the source power is 50W to 100W. For example, the source power can be 50W, 55W, 60W, 65W, 70W, 75W, 80W, 85W, 90W, 95W, or 100W, or any value between any two of the aforementioned source power values. However, it is not limited to these.

[0051] In some embodiments, the bias power is 10W to 50W when performing the third processing. For example, the bias power can be 10W, 15W, 20W, 25W, 30W, 35W, 40W, 45W, or 50W, or any value between any two of the aforementioned bias power values. However, it is not limited to this.

[0052] In some embodiments, the time for performing the third processing is 5s to 20s. For example, the time can be 5s, 10s, 15s, or 20s, or any value between any two of the aforementioned time values. However, it is not limited to these.

[0053] Step S13: At ultra-low temperature, a polymer layer is deposited on the surface of the substrate and the exposed surface of the organic mask using a small molecule first gas as the deposition gas.

[0054] In some embodiments, by performing an etching process and using an organic mask 12 as a mask, the surface of the substrate 10 exposed in the opening 11 between adjacent organic masks 12 is periodically etched to form a high aspect ratio etched structure on the substrate 10.

[0055] The etching process includes multiple periodic cyclic steps, sequentially consisting of a deposition step and an etching step. The deposition step uses a first gas as the deposition gas to form a polymer layer 14 on the sidewalls (surface of substrate 10) and exposed surfaces (side and top surfaces) of the organic mask 12 of the high aspect ratio etched structure, protecting the sidewalls and organic mask 12 during etching. The etching step uses a second gas as the etching gas to etch the polymer layer 14 and the substrate 10. The etching step may further include a first etching step and a second etching step; the first etching step removes the polymer layer 14 on the bottom to allow the second etching step to continue etching the substrate 10 downwards. By implementing multiple periodic cyclic steps, a high aspect ratio etched structure is formed on the substrate 10.

[0056] The first gas includes gases with a molecular weight less than C4F8 (small molecule gases), and the second gas includes gases with a molecular weight less than SF6 (small molecule gases) to increase the diffusion coefficient and improve gas transport efficiency.

[0057] The first temperature is less than -10°C to improve the density and uniformity of the formed polymer layer 14 and suppress lateral etching.

[0058] refer to Figure 3 This step involves performing a deposition step within the etching process at an ultra-low temperature (first temperature) below -10°C. A polymer layer 14 is deposited on the surface of the substrate 10 and the exposed surface of the organic mask 12 using a small-molecule first gas as the deposition gas. This protects the sidewalls and the organic mask 12 during the subsequent etching step. A plasma of the first gas is obtained by ionizing the first gas introduced into the process chamber, which is then used to deposit the polymer layer 14.

[0059] In some embodiments, the first gas includes hydrocarbon gases, fluorocarbon gases, and reducing gases, and the polymer layer 14 includes an amorphous hydrocarbon fluoropolymer layer.

[0060] In some embodiments, hydrocarbon gases include CH4, fluorocarbon gases include CHF3, and reducing gases include H2. A combination of small molecules of CH4, CHF3, and H2 (excluding C4F8) is used as the deposition gas (the molecular weights of CH4, CHF3, and H2 are all smaller than the molecular weight of C4F8). An aC:H:F crosslinked polymer layer with a highly crosslinked three-dimensional network structure is deposited on the exposed surface of the substrate 10 and the exposed surface of the organic mask 12 as an amorphous hydrocarbon fluoropolymer (amorphous hydrogenated fluorocarbon polymer) layer.

[0061] Traditionally used deposition gas C4F8 is a large molecule gas. In achieving smaller linewidths (CD) and higher aspect ratios (>100:1), its deposition on the sidewalls is mainly limited to the upper half of trenches and deep holes, making it difficult to penetrate to the bottom of the deep silicon structure. Therefore, for high aspect ratio structures, it does not provide sufficient protection for the bottom sidewalls. This application, by using small molecules CH4, CHF3, and H2 instead of the traditional large molecule C4F8 as the deposition gas, and by keeping the initial etching temperature below -10°C, offers the following core advantages in high aspect ratio deep silicon etching: (1) Better sidewall protection quality: It can form a polymer layer 14 with a lower fluorocarbon ratio, higher density and higher degree of cross-linking.

[0062] (2) Better step coverage and penetration: Small molecule deposited gases are more likely to enter and be uniformly deposited on the bottom of the sidewalls of ultra-narrow and ultra-deep structures (small molecules such as CH3• and CF• have a longer mean free path and are more likely to reach the bottom of the deep pore without collision. In contrast, the large groups generated by the dissociation of traditional C4F8 (such as C2F5) are more likely to be consumed by gas phase collisions in narrow channels and are difficult to reach the bottom).

[0063] (3) Reduce damage to organic mask 12: The use of small molecule deposition gas reduces the physical bombardment and chemical erosion of organic mask 12 by high-energy ions, protecting critical dimensions.

[0064] This application uses a mixed gas system of CH4, CHF3, and H2 (excluding C4F8), which generates an extremely rich chemical environment in plasma, producing more complex and superior products: it can generate a large number of small-sized free radicals such as CH3•, CH2•, CF•, CF2•, and H•. These active groups, aided by ion bombardment, adsorb and react on the sidewalls and bottom of the silicon material, forming a dense aC:H:F cross-linked polymer film (amorphous carbon film). The aC:H:F film is an amorphous hydrocarbon fluoropolymer whose structure is no longer linear but a highly cross-linked three-dimensional network structure.

[0065] Traditional deep silicon etching uses C4F8 as the deposition gas to form a polymer. When this polymer dissociates in the plasma, it generates a large number of CF2 free radicals and other large fluorocarbon groups (such as CF3, C2F5, etc.). This polymer has a "loose" Teflon-like structure, mainly composed of linear -CF2-CF2- chains. This structure is relatively loose and has weak mechanical strength. Furthermore, the polymer formed by C4F8 deposition gas has a high F / C ratio and contains a large amount of fluorine (F), making it more similar to Teflon and chemically inert, but not robust enough as an etching barrier layer.

[0066] This application's embodiments utilize a small-molecule deposition system formed by a combination of CH4, CHF3, and H2, exhibiting a low F / C ratio and a high H / C ratio. The introduction of H plays a crucial role in the following aspects: (a) Termination of dangling bond: H atoms can combine with dangling bonds in the carbon chain to form stable CH bonds, making the polymer layer 14 structure more complete.

[0067] (b) Promote cross-linking: -CH2- and -CH- groups can be used as cross-linking points to tightly connect the carbon chains together. Therefore, the polymer layer 14 formed on the sidewall has a better blocking effect and can effectively avoid lateral etching.

[0068] Therefore, the aC:H:F crosslinked polymer layer formed through the embodiments of this application has a highly crosslinked structure, which will be more dense and hard when deposited on the sidewall, and has excellent resistance to physical sputtering and chemical etching.

[0069] When the small molecule deposition gas system of this application embodiment cooperates with the organic mask 12, the following advantages will also be achieved: (1) Reduce organic matter mask 12 loss: In terms of chemistry: the traditional C4F8 deposition gas system generates a large number of F atoms, which chemically erode the organic mask 12 (the main component of the photoresist is a hydrocarbon polymer), causing the organic mask 12 to be consumed too quickly. However, in the small molecule system of CH4, CHF3 and H2 in the embodiments of this application, the addition of H2 "removes" a certain amount of F atoms, forming stable HF, which greatly reduces the chemical erosion of the organic mask 12.

[0070] From a physical perspective: the plasma conditions required for small molecule deposition are generally milder than those for large molecules, and the ion energy is relatively low, which reduces the physical sputtering of the organic material mask 12.

[0071] (2) Suppressing the bowing morphology: The formation mechanism of drum-shaped defects: During the etching process, if the sidewall protective layer (polymer layer 14) is not strong enough, high-energy particles and free radicals from the plasma will laterally erode the sidewall from the opening 11. The closer to the top of the opening 11, the stronger the bombardment and the cumulative effect over time, which leads to the sidewall being hollowed out and forming a drum shape.

[0072] Therefore, the robust protective layer (aC:H:F cross-linked polymer layer) formed by the small molecule deposition gas system in this embodiment can effectively resist this lateral erosion. At the same time, since the polymer layer 14 can extend all the way to the bottom of the hole, it ensures that the etching rate is anisotropic from top to bottom, thereby maintaining the vertical sidewall morphology.

[0073] In some embodiments, the flow rate of CH4 in the deposition gas is 3 sccm to 20 sccm. For example, the flow rate of CH4 can be 3 sccm to 10 sccm, or 5 sccm to 15 sccm, or 5 sccm to 20 sccm. As another example, the flow rate of CH4 can be 3 sccm, 5 sccm, 8 sccm, 10 sccm, 15 sccm, or 20 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0074] In some embodiments, the flow rate of CHF3 in the deposition gas is 10 sccm to 50 sccm. For example, the flow rate of CHF3 can be 10 sccm to 30 sccm, or 15 sccm to 40 sccm, or 20 sccm to 50 sccm. As another example, the flow rate of CHF3 can be 10 sccm, 15 sccm, 20 sccm, 30 sccm, 40 sccm, or 50 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0075] In some embodiments, the flow rate of H2 in the deposition gas is 10 sccm to 100 sccm. For example, the flow rate of H2 can be 10 sccm to 50 sccm, or 20 sccm to 80 sccm, or 30 sccm to 100 sccm. As another example, the flow rate of H2 can be 10 sccm, 20 sccm, 30 sccm, 50 sccm, 80 sccm, or 100 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0076] In some embodiments, the flow ratio of CH4, CHF3, and H2 in the deposition gas is CH4:CHF3:H2 = 1:2:3 to 1:5:10. For example, CH4:CHF3:H2 = 1:2:3, or CH4:CHF3:H2 = 1:3:5, or CH4:CHF3:H2 = 1:5:10, and the flow ratio of CHF3 can vary continuously between 2 and 5, and the flow ratio of H2 can vary continuously between 3 and 10. However, it is not limited to these.

[0077] It should be noted that when the flow ratio of CH4:CHF3:H2 = 1:2:3 is selected as the baseline, the process objective focuses on basic deposition and morphology control. This flow ratio is used to balance C deposition and F etching, and serves as a starting point for process tuning. This flow ratio can be used to optimize the carbon framework structure of amorphous hydrogenated fluorocarbon polymers.

[0078] When the flow ratio of CH4:CHF3:H2 = 1:3:5 is selected as the baseline, the process objective is to focus on sidewall protection. That is, by increasing the ratio of H2 and CHF3, the formation and crosslinking degree of the polymer are enhanced, thereby optimizing the sidewall morphology.

[0079] When the flow ratio of CH4:CHF3:H2 = 1:5:10 is selected as the baseline, the process objective is to focus on high etch selectivity. That is, by increasing the proportion of H2, the etching of silicon on the substrate 10 can be significantly suppressed, thereby improving the selectivity for the organic mask 12. Furthermore, when the F / C ratio in the deposition gas is below 3, the etching process shifts from "preferring etching" to "preferring polymer formation," which is crucial for protecting the organic mask 12 and achieving high anisotropy.

[0080] In some embodiments, when performing the deposition step, the first gas includes sulfur and fluorine gases and oxidizing gases, and the polymer layer 14 includes a SiCOF compound layer.

[0081] Furthermore, the sulfur and fluorine gases include SF6, and the oxidizing gases include O2. A combination of small-molecule SF6 and O2 (the molecular weights of SF6 and O2 are both less than the molecular weight of C4F8) is used as the deposition gas, and a SiCOF compound layer as a polymer layer 14 is deposited on the surface of the substrate 10 and the exposed surface of the organic mask 12 at an ultra-low temperature of less than -10°C.

[0082] By lowering the temperature of substrate 10 to an ultra-low temperature of less than -10°C, the kinetics of etching chemistry can be significantly altered. The low temperature allows byproducts and added gases generated during the reaction to more readily physical adsorb onto the silicon surface of substrate 10, rather than being immediately desorbed or sputtered away, thus enhancing physical adsorption capacity. Furthermore, the ultra-low temperature reduces the reaction rate; all surface chemical reaction rates are significantly slowed down at ultra-low temperatures.

[0083] When using a combination of SF6 and O2 as the deposition gas, it is easier to reach the bottom of high aspect ratio etched structures. The reaction of O2 with SF6 generates sulfur-containing oxyfluorides such as SO2F2 and SOF4, as well as fluorine radicals; simultaneously, O2 also reacts with silicon in the substrate 10 to generate SiO2 (SiO2). x F y Most importantly, the generated F, O, and S active groups react with the CO groups sputtered from the organic mask 12 (photoresist), co-depositing on the ultra-low temperature sidewall surface to form a SiCOF compound layer. This SiCOF compound is a more complex and etch-resistant Si-COF compound, commonly referred to as SiFO polymer or SiCOF glaze. This SiFO polymer formed at ultra-low temperatures, compared to CF at room temperature... x Polymers with excellent properties: (1) Excellent sidewall protection capability.

[0084] (2) Higher etching resistance: SiFO polymer contains Si-O bonds (which are very strong and stable), making it more resistant to etching than pure CF. x Polymers are more resistant to chemical attack by F free radicals and physical bombardment by ions.

[0085] (3) Better coverage and stability: Physical adsorption at low temperature makes the protective film denser and more uniform, and can better cover the sidewalls, forming effective protection even at the bottom of high aspect ratio etched structures. This can effectively suppress lateral etching and obtain extremely vertical sidewall morphology.

[0086] In some embodiments, during the deposition step, O2 in the deposition gas is also used to perform a first treatment on the exposed surface of the organic mask 12, causing the exposed surface of the organic mask 12 to oxidize at a first temperature and be triggered by deep ultraviolet light present in the environment to form a hardened layer.

[0087] During the deposition step, the O2 added to the deposition gas slightly oxidizes and hardens the surface of the organic mask 12 (photoresist), forming a thin and durable "crust," i.e., a hardened layer on the surface of the organic mask 12. Simultaneously, a SiFO polymer (SiCOF compound) is also deposited on the surface of the organic mask 12 during the deposition step, thus forming a composite protective layer together with the hardened layer. This composite protective layer significantly slows down the erosion rate of F free radicals on the organic mask 12, thereby significantly improving the selectivity of the organic mask 12. This means that a thinner photoresist can be used to etch deeper silicon structures.

[0088] In some embodiments, the flow rate of SF6 in the deposition gas is 10 sccm to 30 sccm. For example, the flow rate of SF6 can be 10 sccm, 12 sccm, 15 sccm, 20 sccm, 25 sccm, or 30 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these values.

[0089] In some embodiments, the flow rate of O2 in the deposition gas is 30 sccm to 100 sccm. For example, the flow rate of O2 can be 30 sccm, 35 sccm, 40 sccm, 50 sccm, 75 sccm, or 100 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these values.

[0090] In some embodiments, the flow ratio of SF6 to O2 in the deposition gas is SF6:O2 = 1:3 to 1:10. For example, the flow ratio of SF6 to O2 can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10, and the flow ratio of O2 can vary continuously between 3 and 10. However, it is not limited to this.

[0091] Step S14: At ultra-low temperature, a small molecule second gas is used as the etching gas to etch the polymer layer and the substrate.

[0092] refer to Figure 4This step is used to perform the etching step included in the etching process after the above-described deposition step at an ultra-low temperature (first temperature) below -10°C. A small-molecule second gas is used as the etching gas to etch the polymer layer 14 and substrate 10 formed in the previous step, forming a first etched structure 15 on the substrate 10. (After the etching step, there is still residual polymer on the side surface of the organic mask 12.) Figure 4 (Omitted in the text). By ionizing the second gas introduced into the process chamber, a plasma of the second gas is obtained, which is used to etch the polymer layer 14 and the substrate 10. Further, through the first etching step and the bombardment of the plasma of the second gas, the polymer layer 14 on the bottom of the opening 11 is removed, and then through the second etching step, the exposed substrate 10 is etched downward through the plasma of the second gas. By implementing multiple periodic cycles of the etching process, a high aspect ratio etched structure 17 can finally be formed on the substrate 10 (see reference). Figure 7 ).

[0093] When etching the substrate 10, the presence of the carbon-based protective film 13 prevents the top from being excessively laterally etched when the first etched structure 15 is formed, making the size of the first etched structure 15 more uniform. This lays a good foundation for ensuring the uniform size of the entire high aspect ratio etched structure at different positions in the upper, middle and lower parts.

[0094] In some embodiments, the second gas comprises a halogen gas. For example, the halogen gas includes F2, and nitrogen (N2) may be used as a diluting and dissociating gas in the second gas. That is, the second gas comprises a mixture of F2 and N2.

[0095] In some embodiments, the second gas includes a halogen gas and a fluorine-containing gas. For example, the halogen gas includes F2, and the fluorine-containing gas includes any one of NF3, BF3, PF3, CF4, and C2F6. For example, the second gas can be a mixture of F2 and NF3, or a mixture of F2 and BF3, or a mixture of F2 and PF3, or a mixture of F2 and CF4, or a mixture of F2 and C2F6.

[0096] In some embodiments, the second gas includes a halogen gas and a fluorine-containing gas. For example, the halogen gas includes F2, and the fluorine-containing gas includes at least one of NF3, BF3, PF3, CF4, and C2F6.

[0097] When smaller fluorine molecules and their mixtures are used as etching gases instead of traditional large SF6 molecules, diffusion becomes more uniform, facilitating etching reactions in nanoscale deep trenches or pores. F2 can be mixed with other gases (nitrogen or fluorine-containing gases) to form various mixed gases, enabling superior etching of small dimensions with high aspect ratios. Furthermore, although SF6 has six F atoms, only one F ion can dissociate for etching; the remaining SF5 does not participate in the reaction and is extracted. F2, on the other hand, dissociates to produce two F ions, resulting in more reactants than SF6, thus increasing the etching rate, especially for etching deep structures (greater than 100µm), significantly improving the machine's throughput.

[0098] Therefore, by employing the aforementioned small-molecule etching and deposition gases, this embodiment effectively increases the diffusion coefficient and improves the transport efficiency of the reactive gas. It solves the problems of thickness fluctuations in large-molecule C4F8 polymers affecting the control of nanoscale linewidth and the ion shadowing effect, effectively improving the uniformity and roughness of local CF polymers. This results in nanoscale deep silicon structure etching with superior uniformity, better sidewall smoothness, and a higher aspect ratio. Simultaneously, using a mixed gas of F2 as the etching gas significantly improves the etching rate and etching behavior at high depths (greater than 100µm).

[0099] This application embodiment, by changing the etching gas from the traditional SF6 to a combination of small-molecule F2 mixed gases, can better adapt to the needs of advanced processes. By optimizing reaction chemistry and plasma physics, significant performance improvements are achieved in molecular transport, reaction efficiency, and morphology control, which is a key technical path to achieve ultra-high aspect ratio etching.

[0100] The differences between using a mixture of F2 and other gases as an etching gas and using traditional SF6 as an etching gas include: (1) It can efficiently generate high-density F atoms: it provides abundant main etchant (F atoms) through a more efficient dissociation path.

[0101] (2) Excellent deep-hole transport capability: Small molecule reactants and products have a longer mean free path, which can reach the bottom of the deep hole and ensure the bottom etching rate.

[0102] (3) Precise control of ion energy and angle: The generated ions are lighter and have a more concentrated energy distribution, achieving the ultimate anisotropic etching and reducing damage to the organic mask 12.

[0103] (4) Suppressing side reactions and morphological distortion: By using specific gas combinations (such as the combination of F2 and NF3), defects such as bowing can be suppressed and more vertical sidewalls can be obtained.

[0104] When the etching gas uses a combination of F2 and N2, the main reactive groups are: F•, N• + N2 + N2 can dilute F2 and prevent excessive reaction; N + N2 + It is a light ion, which can efficiently transfer energy to the bottom and minimize sputtering damage; the nitrogen element can also form an extremely thin nitride layer on the sidewall, which plays an auxiliary role in passivation.

[0105] When the etching gas uses a combination of F2 and NF3, the main reactive groups are: F•, NF2•, NF + NF3 has a lower dissociation energy than SF6, which can generate more F ions, thus providing a highly efficient fluorine source; groups such as NF2 help passivate the sidewalls and suppress drum-shaped defects.

[0106] When the etching gas uses a combination of F2 and BF3, the main reactive groups are: F•, BF2. + BF + BF x + It is a light ion, which is beneficial for bottom etching and sidewall modification. Element B can also be incorporated into the polymer on the sidewall to change its properties and further enhance the etching resistance of polymer layer 14 (similar to the case when using a combination of F2 and PF3).

[0107] When the etching gas uses a combination of F2 and CF4, the main reactive groups are: F•, CF3. + CF4 can provide a carbon source, introducing a small amount of C into the etching step. This can work in conjunction with the deposition step to achieve finer control over the sidewall morphology, thus balancing deposition and etching.

[0108] When the etching gas uses a combination of F2 and C2F6, the main reactive groups are: F•, CF3. + C2F5 + It can provide a higher C / F ratio than CF4 and can be used in etching conditions that require stronger passivation.

[0109] The common advantage mechanism of small molecule groups in the etching gas of the above-described embodiments of this application in the etching step may include: (1) Higher F atom density and deep-pore penetration capability: The dissociation energy of small molecule gases (such as NF3, BF3, etc.) is usually lower than that of SF6, and under the same plasma conditions, a higher concentration of F atoms can be generated. F atoms and small molecule ions (such as NF3, BF3, etc.) + BF2 + Lightweight and with a long mean free path, it can effectively diffuse to the bottom of deep holes, maintain the etching rate at the bottom, and avoid "etching stop".

[0110] (2) Improved Ion-Assisted Etching: The essence of etching is "ion-enhanced chemical etching." Removal of the bottom silicon requires: a) chemical reaction by F atoms; b) ion bombardment to provide energy, break Si-Si bonds, and sputter away byproducts. Light ions (such as N...) + BF2 + ) compared to SF x + Heavy ions can transfer energy to the bottom surface more effectively, enhancing the etching reaction; at the same time, due to their light weight, the physical sputtering yield of the material is lower, reducing physical damage to the bottom silicon and back-side sputtering of the top organic mask 12.

[0111] (3) Suppressing drum-shaped morphology: Drum-shaped morphology is caused by local failure of the sidewall protective layer, leading to lateral etching of silicon by F atoms and ions from the sides. The advantages of small molecule systems are: a) Higher F atom density means that the deposition step can be switched more quickly, avoiding lateral etching caused by long etching steps; b) Groups (NF2•) generated by certain gases (such as NF3) can assist in sidewall passivation; c) A more concentrated vertical ion beam reduces laterally scattered ions. The combined effect of these three factors ensures that etching is carried out primarily in the vertical direction.

[0112] (4) Reduced consumption of organic mask 12 due to physical bombardment: The ions generated by the small molecule system are lighter and have lower momentum than the heavy ions generated by SF6 under the same bias voltage. Therefore, the physical sputtering rate of organic mask 12 is significantly reduced, resulting in less consumption of organic mask 12 and improved pattern fidelity.

[0113] (5) Reduced consumption of organic mask 12 due to chemical etching: Although F atoms will erode organic mask 12, the small molecule system shortens the overall process time through higher etching efficiency, indirectly reducing the cumulative exposure time of organic mask 12. In addition, combinations like CF4 / F2 can also form a slight C-containing protective layer on the surface of organic mask 12.

[0114] In some embodiments, when the etching gas uses a combination of F2 and N2, the flow rate of F2 is 100 sccm to 500 sccm, and the flow rate of N2 is 10 sccm to 100 sccm. For example, the flow rate of F2 can be 100 sccm, 120 sccm, 150 sccm, 200 sccm, 300 sccm, 400 sccm, or 500 sccm, or any value between any two of the aforementioned flow rates. The flow rate of N2 can be 10 sccm, 20 sccm, 30 sccm, 50 sccm, 60 sccm, 80 sccm, or 100 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0115] In some embodiments, when the etching gas uses a combination of F2 and N2, the flow rate ratio of F2 to N2 is F2:N2 = 5:1 to 10:1. For example, the flow rate ratio of F2 to N2 can be 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, and the flow rate ratio of F2 can vary continuously between 5 and 10. However, it is not limited to this. N2 serves to provide light ions and stabilize the plasma, but its proportion should not be too high to avoid over-diluting F2 and reducing the plasma rate.

[0116] In some embodiments, when the etching gas uses a combination of F2 and NF3, the flow rate of F2 is 50 sccm to 300 sccm, and the flow rate of NF3 is 50 sccm to 200 sccm. For example, the flow rate of F2 can be 50 sccm, 60 sccm, 80 sccm, 100 sccm, 150 sccm, 200 sccm, or 300 sccm, or any value between any two of the aforementioned flow rates. The flow rate of NF3 can be 50 sccm, 60 sccm, 80 sccm, 90 sccm, 100 sccm, 150 sccm, or 200 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0117] In some embodiments, when the etching gas uses a combination of F2 and NF3, the flow ratio of F2 to NF3 is F2:NF3 = 1:1 to 1:2. For example, the flow ratio of F2 to NF3 can be 1:1 or 1:2, and the flow ratio of NF3 can vary continuously between 1 and 2. However, it is not limited to this. NF3 provides a highly efficient fluorine source.

[0118] In some embodiments, when the etching gas uses a combination of F2 and BF3, the flow rate of F2 is 100 sccm to 400 sccm, and the flow rate of BF3 is 5 sccm to 50 sccm. For example, the flow rate of F2 can be 100 sccm, 110 sccm, 150 sccm, 180 sccm, 200 sccm, 300 sccm, or 400 sccm, or any value between any two of the aforementioned flow rates. The flow rate of BF3 can be 5 sccm, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 45 sccm, or 50 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0119] In some embodiments, when the etching gas uses a combination of F2 and BF3, the flow rate ratio of F2 to BF3 is F2:BF3 = 8:1 to 20:1. For example, the flow rate ratio of F2 to BF3 can be 8:1, 9:1, 10:1, 12:1, 15:1, 18:1, or 20:1, and the flow rate ratio of F2 can vary continuously between 8 and 20. However, it is not limited to this. BF3 is mainly used to introduce boron (B) and light ions.

[0120] In some embodiments, when the etching gas uses a combination of F2 and PF3, the flow rate of F2 is 100 sccm to 400 sccm, and the flow rate of PF3 is 5 sccm to 50 sccm. For example, the flow rate of F2 can be 100 sccm, 110 sccm, 150 sccm, 180 sccm, 200 sccm, 300 sccm, or 400 sccm, or any value between any two of the aforementioned flow rates. The flow rate of PF3 can be 5 sccm, 10 sccm, 20 sccm, 30 sccm, 40 sccm, 45 sccm, or 50 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0121] In some embodiments, when the etching gas uses a combination of F2 and PF3, the flow ratio of F2 to PF3 is F2:PF3 = 8:1 to 20:1. For example, the flow ratio of F2 to PF3 can be 8:1, 9:1, 10:1, 12:1, 15:1, 18:1, or 20:1, and the flow ratio of F2 can vary continuously between 8 and 20. However, it is not limited to this. PF3 is mainly used to introduce phosphorus (P) and light ions.

[0122] In some embodiments, when the etching gas uses a combination of F2 and CF4, the flow rate of F2 is 100 sccm to 400 sccm, and the flow rate of CF4 is 10 sccm to 80 sccm. For example, the flow rate of F2 can be 100 sccm, 120 sccm, 150 sccm, 180 sccm, 200 sccm, 300 sccm, or 400 sccm, or any value between any two of the aforementioned flow rates. The flow rate of CF4 can be 10 sccm, 20 sccm, 30 sccm, 40 sccm, 50 sccm, 60 sccm, 70 sccm, or 80 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0123] In some embodiments, when the etching gas uses a combination of F2 and CF4, the flow ratio of F2 to CF4 is F2:CF4 = 5:1 to 10:1. For example, the flow ratio of F2 to CF4 can be 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1, and the flow ratio of F2 can vary continuously between 5 and 10. However, it is not limited to this. CF4 is used to provide carbon for slight passivation. Within the above ratio range, the phenomenon of switching from the etching mode to the deposition mode and causing etching to stop can be avoided.

[0124] In some embodiments, when the etching gas uses a combination of F2 and C2F6, the flow rate of F2 is 100 sccm to 400 sccm, and the flow rate of C2F6 is 5 sccm to 40 sccm. For example, the flow rate of F2 can be 100 sccm, 130 sccm, 150 sccm, 180 sccm, 200 sccm, 300 sccm, or 400 sccm, or any value between any two of the aforementioned flow rates. The flow rate of C2F6 can be 5 sccm, 10 sccm, 15 sccm, 20 sccm, 25 sccm, 30 sccm, 35 sccm, or 40 sccm, or any value between any two of the aforementioned flow rates. However, it is not limited to these.

[0125] In some embodiments, when the etching gas uses a combination of F2 and C2F6, the flow rate ratio of F2 to C2F6 is F2:C2F6 = 10:1 to 20:1. For example, the flow rate ratio of F2 to C2F6 can be 10:1, 11:1, 13:1, 15:1, 19:1, or 20:1, and the flow rate ratio of F2 can vary continuously between 10 and 20. However, it is not limited to this. C2F6 has stronger deposition properties, so a smaller amount can be used than CF4, and the problem of polymer clogging at the opening 11 can be avoided.

[0126] Step S15: Repeat steps S13 to S14 until a high aspect ratio etched structure is formed on the substrate.

[0127] By repeating steps S13 to S14 above, a high aspect ratio etched structure 17 with a target aspect ratio can finally be formed on the substrate 10, such as... Figure 7 As shown.

[0128] Specifically, by performing the deposition step in the etching process at a first temperature and using the aforementioned small-molecule first gas as the deposition gas, a polymer layer 14 is deposited again on the surface of the substrate 10 (i.e., the inner wall of the first etched structure 15 formed in the previous step) and the exposed surface of the organic mask 12, as shown below. Figure 5As shown, this is to protect the sidewalls of the first etched structure 15 and the organic mask 12 during subsequent etching steps. Then, at a first temperature, the aforementioned small-molecule second gas is used as the etching gas to perform the etching steps in the etching process, etching the polymer layer 14 and the substrate 10. That is, through the first etching step, and through the bombardment of the plasma of the second gas, the polymer layer 14 on the bottom of the first etched structure 15 (bottom of the opening 11) is first removed. Then, through the second etching step, the plasma of the second gas continues to etch downwards to the exposed silicon material at the bottom of the first etched structure 15, and the second etched structure 16 is formed below the first etched structure 15, as shown. Figure 6 As shown ( Figure 6 The horizontal dashed line in the image represents the original bottom of the first etched structure 15. After the etching process is complete, residual polymer remains on the sides of the organic mask 12 and the sidewalls of the first etched structure 15. Figure 6 (The details are omitted). Similarly, a third etching structure, a fourth etching structure, etc., can be continuously formed below the second etching structure 16 (figures omitted), ultimately forming a high aspect ratio etching structure 17 on the substrate 10, composed of successive etching structures (first etching structure 15 to fourth etching structure, etc.), such as... Figure 7 As shown.

[0129] In some embodiments, the first temperature is -80°C to -10°C. For example, the first temperature can be -80°C to -10°C, or -80°C to -15°C, or -80°C to -20°C, or -80°C to -30°C, or -80°C to -40°C, or -80°C to -50°C, or -80°C to -60°C, or -80°C to -70°C, or -70°C to -15°C, or -70°C to -20°C, or -70°C to -30°C, or -60°C to -15°C, or -60°C to -20°C, or -60°C to -40°C, or -45°C to -35°C. For example, the first temperature can be -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -15℃, or -10℃, or any value between any two of the aforementioned temperature values. However, it is not limited to these.

[0130] In some embodiments, when etching the substrate 10 using an etching process, the times for the deposition step, the first etching step, and the second etching step are all limited to very short intervals, within the range of 0.1s to 2s, with rapid switching between the three steps. For example, the time for the deposition step can be 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.7s, 0.9s, 1s, 1.2s, 1.5s, 1.8s, or 2s, or any value between any two of the aforementioned time values. The time for the first etching step can be 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.7s, 0.9s, 1s, 1.2s, 1.5s, 1.8s, or 2s, or any value between any two of the aforementioned time values. The time for performing the second etching step can be 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.7s, 0.9s, 1s, 1.2s, 1.5s, 1.8s, or 2s, or any value between any two of the aforementioned time values.

[0131] In some embodiments, the pressure during the etching process is 5 mTorr to 200 mTorr. For example, the pressure can be 5 mTorr, 10 mTorr, 20 mTorr, 50 mTorr, 80 mTorr, 100 mTorr, 130 mTorr, 150 mTorr, 190 mTorr, or 200 mTorr, or any value between any two of the aforementioned pressure values.

[0132] In some embodiments, the source power during the etching process is 500W to 3000W. For example, the source power can be 500W, 1000W, 1500W, 2000W, 2500W, or 3000W, or any value between any two of the aforementioned source power values. The source power for the deposition step, the first etching step, and the second etching step can be different.

[0133] In some embodiments, the bias power is 10W to 200W when performing the etching process. For example, the bias power can be 10W, 20W, 50W, 70W, 100W, 130W, 160W, 180W, or 200W, or any value between any two of the aforementioned bias power values. Pulsing etching can be achieved by setting the bias power.

[0134] Because the etching process involves repeated deposition and etching steps, regular, multi-scallop-shaped stripes are formed on the sidewalls during multiple cyclic etching processes, such as... Figure 9As shown in (a), each cyclic etching process, which includes a deposition step and an etching step, generates a scallop-shaped stripe on the sidewall. Each scallop-shaped stripe has a recess 19 at its bottom and a protrusion 18 at the junction of two scallop-shaped stripes, resulting in a rough surface morphology on the sidewall. Therefore, in this embodiment, after each cyclic step, a second treatment step is embedded at a second temperature. That is, after each of the above-mentioned etched structures is formed (for example, after the formation of the first etched structure 15 and the formation of the second etched structure 16, and so on), a second treatment is performed on the sidewall at a second temperature to remove excess polymer on the sidewall in a timely manner, prevent uneven etching caused by excessive polymer thickness, and reduce the roughness and improve the smoothness of the sidewall through the second treatment.

[0135] In the second process, a portion of the polymer layer 14 on the sidewall is removed by reacting a reactive gas with the polymer layer 14, thereby adjusting the uniformity of the polymer layer 14's thickness on the sidewall. As the thickness of the polymer layer 14 gradually decreases due to removal, the protrusions 18 on the sidewall gradually become exposed from the surface of the polymer layer 14. During this process, a reaction product layer is generated by reacting the reactive gas with the substrate 10 material on the surface of the exposed protrusions 18. By removing the reaction product layer, at least a portion of the protrusions 18 can be removed, resulting in a smoother sidewall after the removal of the protrusions 18.

[0136] In some embodiments, the second process specifically includes: using a third gas to remove a portion of the thickness of the polymer layer 14 deposited on the sidewall and reacting it with the substrate 10 material on the surface of the protrusion 18 present and exposed on the sidewall to generate a reaction product layer; and then using a fourth gas to remove the reaction product layer to remove at least a portion of the protrusion 18.

[0137] In some embodiments, the second temperature is -80°C to -10°C. For example, the second temperature can be -80°C to -10°C, or -80°C to -15°C, or -80°C to -20°C, or -80°C to -30°C, or -80°C to -40°C, or -80°C to -50°C, or -80°C to -60°C, or -80°C to -70°C, or -70°C to -15°C, or -70°C to -20°C, or -70°C to -30°C, or -60°C to -15°C, or -60°C to -20°C, or -60°C to -40°C, or -45°C to -35°C. For example, the second temperature can be -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -15℃, or -10℃, or any value between any two of the aforementioned temperature values. However, it is not limited to these.

[0138] In some embodiments, the third gas, comprising HBr and O2, reacts with the polymer layer 14 to remove a portion of its thickness, thereby adjusting the thickness uniformity of the polymer layer 14 on the sidewalls, and reacts with the silicon of the substrate 10 material to generate a silicon tetrabromide layer and a silicon dioxide layer as reaction product layers. The fourth gas, comprising CF4 and Ar, removes the silicon tetrabromide layer and the silicon dioxide layer by bombarding the sidewalls, thereby removing at least a portion of the protrusions 18 and smoothing the sidewalls.

[0139] Specifically, during the second process, a mixed-state plasma of HBr and O2 is first used to adsorb onto the sidewall surface and react with the polymer layer 14, removing a portion of the thickness of the polymer layer 14 deposited on the sidewall to prevent it from becoming too thick and thus adjust the uniformity of the polymer layer 14 thickness on the sidewall. Then, the O2 plasma reacts with the substrate material (silicon) on the exposed surface of the protrusions 18 from the remaining polymer layer 14 surface to form a silicon dioxide (SiO2) layer in situ. Simultaneously, the HBr plasma undergoes a displacement reaction with the substrate material on the exposed surface of the protrusions 18 to form a low-volatility silicon tetrabromide (SiBr4) layer on the sidewall surface. The oxygen ions (O2) in the plasma... 2- ) and bromide ions (Br - It can be adsorbed onto the surface of the exposed protrusion 18 and can penetrate into the exposed protrusion 18 from multiple directions to react with the silicon (Si) material of the substrate 10, such as... Figure 9 As indicated by the arrow in (a), after oxygen ions react with the silicon (Si) material of the substrate 10, a silicon dioxide layer is formed in situ on the surface of the exposed protrusion 18. This causes the silicon material interface to gradually recede towards the outside of the sidewall, thereby allowing the new interface of the silicon material formed after the reaction (i.e., the new sidewall surface to be formed subsequently, see reference) to be formed. Figure 9 (b) The fluctuations become smoother. The low-volatility tetrabromosilane layer generated by the reaction of bromide ions with the silicon (Si) material of substrate 10 can be adsorbed at the recesses 19 on the sidewalls at low temperatures, making the entire sidewall surface smoother. This facilitates the smoothing process during subsequent removal of the reaction product layer and the continuous cyclic processing steps. HBr plasma and O2 plasma are obtained by ionizing HBr and O2 (reaction gases) introduced into the process chamber. Nitrogen gas can also be used simultaneously as a dilution gas.

[0140] It is worth noting that the adsorption and reaction of oxygen ions on the silicon surface of the sidewall is a self-limiting reaction. Therefore, once the silicon surface on the sidewall has oxidized to a certain extent, the reaction will stop, thus preventing the silicon material on the sidewall surface at protrusion 18 from being over-etched away. This effectively achieves longitudinal cyclic etching and transverse atomic-level precision surface treatment. When protrusion 18 is sufficiently removed, making the sidewall surface smoother, the passivation layer redeposited in subsequent cycles can protect the treated upper sidewall, thereby preventing loss of width.

[0141] In some embodiments, when plasma of a third gas is used for adsorption and reaction, the time is 0.5 s to 2 s. For example, the time can be 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.1 s, 1.3 s, 1.5 s, 1.7 s, or 2 s, or any value between any two of the aforementioned time values.

[0142] In some embodiments, when using plasma with a third gas for adsorption and reaction, the pressure is 10 mTorr to 50 mTorr. For example, the pressure can be 10 mTorr, 15 mTorr, 20 mTorr, 25 mTorr, 30 mTorr, 35 mTorr, 40 mTorr, 45 mTorr, or 50 mTorr, or any value between any two of the aforementioned pressure values.

[0143] In some embodiments, when plasma of a third gas is used for adsorption and reaction, the source power is 200W to 2000W. For example, the source power can be 200W, 500W, 800W, 1000W, 1200W, 1500W, 1800W, or 2000W, or any value between any two of the aforementioned source power values.

[0144] In some embodiments, when using plasma of a third gas for adsorption and reaction, the bias power is 5W to 30W. For example, the bias power can be 5W, 6W, 8W, 10W, 15W, 20W, 25W, or 30W, or any value between any two of the aforementioned bias power values.

[0145] In some embodiments, during the second treatment, HBr is also used to perform a fourth treatment on the exposed surface of the organic mask 12, causing the chemical bonds in the organic mask 12 material to break and recombine, forming polymer chains. This improves the etching resistance of the organic mask 12 by changing the C / H ratio of the organic mask 12 material surface. The principle is as follows: through the action of hydrogen bromide plasma, the C=O, CO, and CH chemical bonds in the photoresist material of the organic mask 12 break and recombine, turning CH3 groups into two CH2 groups. These two CH2 groups are more likely to recombine chemical bonds, forming polymer chains and changing the C / H ratio of the photoresist material. This makes the photoresist material structurally more stable, thereby improving the etching resistance of the photoresist. Therefore, it improves the etching barrier capability of the organic mask 12 during deep silicon etching, i.e., it improves the etching selectivity of the organic mask 12. The fourth treatment is completed simultaneously with the adsorption and reaction processes of the second treatment.

[0146] Subsequently, the sidewall surface is bombarded with a mixed plasma of CF4 and Ar to remove the silicon tetrabromide and silicon dioxide layers, which are reaction product layers, thereby removing at least a portion of the protrusions 18 and smoothing the sidewall. The CF4 and Ar plasmas are obtained by ionizing the CF4 and Ar introduced into the process chamber.

[0147] In this embodiment, low-energy fluoride ions (F) are used. - ) and argon ions (Ar + The sidewall surface is bombarded to etch and remove the silicon dioxide on the protrusion 18, and tetrabromosilane is desorbed and removed from the sidewall to form a smoother new sidewall. Fluoride ions react with the silicon dioxide on the protrusion 18, causing the silicon dioxide to decompose and generate gaseous silicon tetrafluoride (SiF4), which is then removed from the sidewall.

[0148] In some embodiments, when plasma of a fourth gas is used to remove the reaction product layer, the time is 0.5 s to 2 s. For example, the time can be 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.1 s, 1.3 s, 1.5 s, 1.7 s, or 2 s, or any value between any two of the aforementioned time values.

[0149] In some embodiments, when plasma of a fourth gas is used to remove the reaction product layer, the pressure is 2 mTorr to 10 mTorr. For example, the pressure can be 2 mTorr, 3 mTorr, 4 mTorr, 5 mTorr, 6 mTorr, 7 mTorr, 8 mTorr, 9 mTorr, or 10 mTorr, or any value between any two of the aforementioned pressure values.

[0150] In some embodiments, when plasma of a fourth gas is used to remove the reaction product layer, the source power is 50W to 500W. For example, the source power can be 50W, 80W, 100W, 200W, 300W, 400W, or 500W, or any value between any two of the aforementioned source power values.

[0151] In some embodiments, when plasma of a fourth gas is used to remove the reaction product layer, the bias power is 5W to 30W. For example, the bias power can be 5W, 6W, 8W, 10W, 15W, 20W, or 30W, or any value between any two of the aforementioned bias power values.

[0152] In some embodiments, when plasma of the fourth gas is used to remove the reaction product layer, the total flow rate of the fourth gas (CF4 and Ar) is 20 sccm to 200 sccm. For example, the flow rate can be 20 sccm, 50 sccm, 80 sccm, 100 sccm, 130 sccm, 160 sccm, or 200 sccm, or any value between any two of the aforementioned flow rate values.

[0153] In some embodiments, when using plasma with a fourth gas to remove the reaction product layer, the flow ratio of CF4 to Ar is 1:1 to 1:3. For example, the flow ratio can be 1:1, 1:2, or 1:3, and is not limited to these.

[0154] After the reaction product layer is removed by plasma using the fourth gas, the newly formed sidewall surface becomes smooth, thereby reducing the roughness of the sidewall surface. Figure 9 As shown in (b). In this way, the polymer layer 14 deposited in subsequent cycles can cover the treated smooth upper sidewall surface more uniformly, so that the deposition thickness does not need to be very thick to play a good sidewall protection role, and can effectively avoid the local rough peaks (Ra>5nm) caused by the random deposition of polymer on the sidewall in the past.

[0155] In some other embodiments, a second treatment of the sidewalls may be incorporated at a second temperature after every two cyclic steps. Specifically, after every two of the aforementioned etched structures are formed (e.g., after the consecutive formation of the first etched structure 15 and the second etched structure 16, and after the consecutive formation of the third and fourth etched structures, and so on), the sidewalls are treated at a second temperature. Please refer to the foregoing embodiments for further understanding.

[0156] Step S16: Remove the organic mask.

[0157] In some embodiments, after forming the high aspect ratio etched structure 17, the surface of the substrate 10 is bombarded using a plasma of a sixth gas to remove the organic mask 12 and the carbon-based protective film 13 from the surface of the substrate 10. The plasma of the sixth gas is obtained by ionizing the sixth gas introduced into the process chamber. After removing the organic mask 12 and the carbon-based protective film 13, a substrate 10 with the high aspect ratio etched structure 17 exposed is obtained, as shown below. Figure 8 As shown.

[0158] In some embodiments, the sixth gas includes an oxidizing gas. The oxidizing gas may be, for example, oxygen, and nitrogen may be introduced simultaneously as a diluent gas.

[0159] In some other embodiments, the etching process may include a first etching stage, a second etching stage, and a third etching stage that are sequentially connected, for forming the top, middle, and bottom of the high aspect ratio etched structure 17, respectively. The first etching stage may use F2 and N2 as etching gases, the second etching stage may use F2 and PF3 (or F2 and BF3) as etching gases, and the third etching stage may use F2 and C2F6 (or F2 and CF4) as etching gases. During the first etching stage, the addition of N2 can form a stable plasma, which can mitigate the severe etching behavior in the top region caused by sheath instability and mask edge effects in the early stages of etching, effectively ensuring the stability of the critical dimensions at the top. It can also reduce ion sputtering damage during the etching process, improve the protection of the organic mask, and form an extremely thin nitride layer on the sidewalls to assist in passivation of the sidewall surface, preventing excessive lateral etching and improving the verticality of the top of the sidewalls. By using a combination of F2 and PF3 (or F2 and BF3) as the etching gas in the second etching stage, the properties of the polymer layer can be altered through the incorporation of P (or B) elements, thereby enhancing the polymer layer's resistance to lateral etching and further improving the verticality and dimensional uniformity of the sidewalls. Using a combination of F2 and C2F6 (or F2 and CF4) as the etching gas in the third etching stage provides a higher carbon-to-fluorine ratio, enhances deposition, and effectively suppresses lateral etching of the bottom of the sidewalls, thus eliminating the problem of bottom side-cutting. Therefore, by performing the etching process in stages, not only are the limitations of traditional single etching processes in achieving high-precision control overcome, but a more refined and controllable etching scheme is also provided for the fabrication of high-performance devices, effectively expanding the etching process window.

[0160] According to a second aspect of this application, embodiments of this application also provide a high aspect ratio etched structure, which is obtained using a manufacturing method for a high aspect ratio etched structure as provided in any of the embodiments of the first aspect above.

[0161] refer to Figure 8In some embodiments, a high aspect ratio etched structure 17 is formed on the surface of the substrate 10. The critical dimension of the high aspect ratio etched structure 17 can be less than 50 nm, and the aspect ratio can be greater than or equal to 100:1. The high aspect ratio etched structure 17 can be, for example, a deep trench, a deep via, or a through-hole.

[0162] In some embodiments, the high aspect ratio etched structure 17 can be applied to MEMS devices (such as accelerometers, gyroscopes, pressure sensors, etc.), 3D integration and advanced packaging (such as through-silicon via (TSV) fabrication, chip stacking, etc.), optical devices (such as optical waveguides, diffraction gratings, etc.), and power devices (such as trench structures of insulated gate bipolar transistors (IGBTs) and power metal-oxide-semiconductor field-effect transistors (MOSFETs, etc.).

[0163] In a third aspect, embodiments of this application also provide a plasma processing apparatus for performing the manufacturing method of the high aspect ratio etched structure corresponding to the above embodiments to form the high aspect ratio etched structure 17 corresponding to the above embodiments. The plasma processing apparatus includes inductively coupled plasma (ICP) etching apparatus or capacitively coupled plasma (CCP) etching apparatus, etc.

[0164] In other aspects, embodiments of this application also provide an electronic device, including a high aspect ratio etched structure 17 (e.g., deep trench, deep hole, or through hole, etc.) obtained using the manufacturing method of the high aspect ratio etched structure of the above embodiments. The electronic device can be a storage device, mobile phone, computer, tablet computer, electronic instrument, television, artificial intelligence device, etc.

[0165] In summary, by using small molecule gases (first gas and second gas) instead of traditional large molecule gases such as C4F8 and SF6 as deposition and etching gases, this application increases the diffusion coefficient and improves gas transport efficiency. This allows for more uniform diffusion of the etching gas, facilitating its entry into the nanoscale high aspect ratio etched structure 17 for etching reactions. This results in superior small-size high aspect ratio etching and allows the deposition gas to smoothly enter the bottom of the high aspect ratio etched structure 17, achieving more uniform protection of the sidewalls at a smaller size. Furthermore, by keeping the etching process temperature below -10°C, chemical kinetics are altered, physical adsorption is enhanced, and the reaction rate is reduced. This allows the polymer layer 14 to be more densely and uniformly adsorbed on the sidewalls, effectively protecting the sidewalls even at the bottom of the high aspect ratio etched structure 17 and effectively suppressing lateral etching, resulting in an extremely vertical sidewall morphology. Ultimately, this enables the etching of nanoscale deep silicon structures with even higher aspect ratios. Meanwhile, small molecule etching gases can significantly improve etching rate and etching behavior at high depths (>100µm).

[0166] The above are merely preferred embodiments of this application. These embodiments are not intended to limit the scope of protection of this application. Therefore, any equivalent changes made based on the description and drawings of this application should also be included within the scope of protection of this application.

Claims

1. A method for manufacturing a high aspect ratio etched structure, characterized in that, include: Provide substrate; Multiple organic masks are formed on the surface of the substrate; At a first temperature, an etching process is performed to etch the surface of the substrate exposed between adjacent organic masks, forming a high aspect ratio etched structure on the substrate; The etching process includes multiple periodic cyclic steps formed sequentially by deposition and etching steps. The deposition step uses a first gas as the deposition gas to form a polymer layer on the sidewalls of the high aspect ratio etched structure and the exposed surface of the organic mask during the etching process, so as to protect the sidewalls and the organic mask during etching; the etching step uses a second gas as the etching gas to etch the polymer layer and the substrate. The first gas includes gases with a molecular weight less than that of C4F8, and the second gas includes gases with a molecular weight less than that of SF6, in order to increase the diffusion coefficient and improve the gas transport efficiency. The first temperature is less than -10°C to improve the density and uniformity of the polymer layer and suppress lateral etching.

2. The method for manufacturing a high aspect ratio etched structure according to claim 1, characterized in that, The first gas includes hydrocarbon gases, fluorocarbon gases, and reducing gases, and the polymer layer includes an amorphous hydrocarbon fluoropolymer layer.

3. The method for manufacturing a high aspect ratio etched structure according to claim 2, characterized in that, The hydrocarbon gas includes CH4, the fluorocarbon gas includes CHF3, the reducing gas includes H2, and the amorphous hydrocarbon fluoropolymer layer includes an aC:H:F crosslinked polymer layer with a crosslinked three-dimensional network structure.

4. The method for manufacturing a high aspect ratio etched structure according to claim 1, characterized in that, The first gas includes sulfur and fluorine gases and oxidizing gases, and the polymer layer includes a SiCOF compound layer.

5. The method for manufacturing a high aspect ratio etched structure according to claim 4, characterized in that, The sulfur-fluorine gas includes SF6, the oxidizing gas includes O2, and the substrate material includes Si. The SiCOF compound layer is formed by reacting O2 with SF6 and the substrate material respectively, and the resulting active groups of F, O, and S react with CO groups sputtered from the organic mask, and co-deposit at the first temperature.

6. The method for manufacturing a high aspect ratio etched structure according to claim 5, characterized in that, Also includes: During the deposition step, the O2 is also used to perform a first treatment on the exposed surface of the organic mask, causing the exposed surface of the organic mask to oxidize at the first temperature and be triggered by deep ultraviolet light in the environment to form a hardened layer.

7. The method for manufacturing a high aspect ratio etched structure according to claim 1, characterized in that, The second gas includes a halogen gas, or the second gas includes a halogen gas and a fluorine-containing gas.

8. The method for manufacturing a high aspect ratio etched structure according to claim 7, characterized in that, The halogen gas includes F2, and the fluorine-containing gas includes at least one of NF3, BF3, PF3, CF4, and C2F6.

9. The method for manufacturing a high aspect ratio etched structure according to claim 1, characterized in that, The first temperature is -80℃ to -10℃, or -80℃ to -15℃, or -80℃ to -20℃, or -80℃ to -30℃, or -80℃ to -40℃, or -80℃ to -50℃, or -80℃ to -60℃, or -80℃ to -70℃, or -70℃ to -15℃, or -70℃ to -20℃, or -70℃ to -30℃, or -60℃ to -15℃, or -60℃ to -20℃, or -60℃ to -40℃, or -45℃ to -35℃.

10. A high aspect ratio etched structure, characterized in that, It is obtained using the manufacturing method of the high aspect ratio etched structure as described in any one of claims 1-9.

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