High aspect ratio etched structures and methods of making same

Abstract

The application discloses a high aspect ratio etching structure and a manufacturing method thereof, comprising: performing an etching process at a first temperature to etch the surface of the substrate exposed between adjacent organic masks to form a high aspect ratio etching structure; the etching process comprises a plurality of periodic cycle steps formed in sequence by a deposition step and an etching step, the deposition step uses a first gas as a deposition gas to form a polymer layer, and the etching step uses a second gas as an etching gas to etch the polymer layer and the substrate; the first gas comprises a gas with a molecular weight less than that of C4F8, and the second gas comprises a gas with a molecular weight less than that of SF6, so as to increase the diffusion coefficient and improve the gas transmission efficiency; the first temperature is less than -10 DEG C, so as to improve the density and uniformity of the polymer layer and inhibit lateral etching. The application can realize uniform protection of the sidewall at a smaller size and a higher aspect ratio, and can improve the etching rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor processing, and in particular to a manufacturing method of a high aspect ratio etching structure and a high aspect ratio etching structure manufactured by using the method. BACKGROUND

[0002] In the field of advanced packaging which is developing rapidly, higher density interconnection is required, and deep silicon etching (DSE) should be able to meet the requirement of nanometer level line width (less than 50 nm) and higher aspect ratio (greater than 100:1). The traditional periodic cyclic etching process has been difficult to meet the requirement of the extreme aspect ratio due to the influence of the corresponding physical limitations (such as ion shadow effect, reaction gas transmission efficiency). Meanwhile, the nanometer level line width is more sensitive to the thickness fluctuation of the sidewall passivation layer (such as C-F polymer), and when the thickness fluctuation of the sidewall passivation layer is large, it is easy to cause line width deviation and etching tilt (three-dimensional through silicon via and memory stack require etching verticality error less than ±0.2°) problems. In addition, the existing etching process also has the problems of plasma chemical residue and local rough peak (Ra>5nm) caused by random deposition of C-F polymer on the sidewall, which have important influence on the realization of higher aspect ratio and nanometer level deep silicon etching. And under the requirement of higher aspect ratio and nanometer level line width, how to improve the etching rate and how to improve the uniformity of the protection of the bottom sidewall during the etching process are particularly important. Therefore, it is necessary to study a process method which can significantly improve the above problems. SUMMARY

[0003] The present application aims to overcome the above problems existing in the prior art, and provides a high aspect ratio etching structure and a manufacturing method thereof.

[0004] To achieve the above-mentioned purpose, the technical solutions of the present application are as follows:

[0005] According to a first aspect of the present application, the present application provides a manufacturing method of a high aspect ratio etching structure, comprising:

[0006] providing a substrate;

[0007] forming a plurality of organic masks on the surface of the substrate;

[0008] performing an etching process at a first temperature to etch the surface of the substrate exposed between adjacent organic masks to form a high aspect ratio etching structure on the substrate;

[0009] wherein the etching process comprises a plurality of periodic cyclic steps formed in sequence by deposition steps and etching steps;

[0010] The deposition step uses a first gas as a deposition gas to form a polymer layer on the sidewall of the high aspect ratio etching structure being formed and the exposed surface of the organic mask, so as to protect the sidewall and the organic mask during etching; and the etching step uses a second gas as an etching gas to etch the polymer layer and the substrate.

[0011] The first gas comprises a gas with a molecular weight less than that of C4F8, and the second gas comprises a gas with a molecular weight less than that of SF6, so as to increase the diffusion coefficient and improve the gas transmission efficiency.

[0012] The first temperature is less than -10°C, so as to improve the density and uniformity of the polymer layer and inhibit lateral etching.

[0013] In some embodiments, the first gas comprises a hydrocarbon gas, a fluorocarbon gas, and a reducing gas, and the polymer layer comprises an amorphous carbon-hydrogen-fluorine polymer layer.

[0014] In some embodiments, the hydrocarbon gas comprises CH4, the fluorocarbon gas comprises CHF3, the reducing gas comprises H2, and the amorphous carbon-hydrogen-fluorine polymer layer comprises an a-C:H:F cross-linked polymer layer with a three-dimensional network structure of cross-linking.

[0015] In some embodiments, the first gas comprises a sulfur-fluorine gas and an oxidizing gas, and the polymer layer comprises a SiCOF compound layer.

[0016] In some embodiments, the sulfur-fluorine gas comprises SF6, the oxidizing gas comprises O2, and the substrate material comprises Si, and the SiCOF compound layer is formed by co-deposition of active groups of F, O, and S generated by reactions of the O2 with the SF6 and the substrate material, respectively, and C-O groups sputtered from the organic mask at the first temperature.

[0017] In some embodiments, the method further comprises, when the deposition step is performed, using the O2 to perform a first treatment on the exposed surface of the organic mask, so as to oxidize the exposed surface of the organic mask at the first temperature and trigger a reaction of the exposed surface of the organic mask by ambient deep ultraviolet light to form a hardened layer.

[0018] In some embodiments, the second gas comprises a halogen element gas, or the second gas comprises a halogen element gas and a fluorine-containing gas.

[0019] In some embodiments, the halogen element gas comprises F2, and the fluorine-containing gas comprises at least one of NF3, BF3, PF3, CF4, and C2F6.

[0020] In some embodiments, the first temperature is -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.

[0021] According to a second aspect of the present application, the embodiments of the present application also provide a high aspect ratio etching structure obtained by using the manufacturing method of the high aspect ratio etching structure according to any one of the embodiments of the first aspect.

[0022] The embodiments of the present application can / at least have the following advantages:

[0023] (1) By using small molecule gas (first gas and second gas) to replace traditional large molecule gas such as C4F8 and SF6 as deposition gas and etching gas, the diffusion coefficient can be increased, the gas transmission efficiency can be improved, the etching gas can be more uniformly diffused and more easily enter the nanoscale high aspect ratio etching structure (trench or via hole) for etching reaction, and more excellent small size high aspect ratio etching can be realized. The deposition gas can smoothly enter the bottom of the high aspect ratio etching structure, and more uniform protection of the sidewall at a smaller size can be realized. By making the temperature (first temperature) during the etching process less than -10°C, the chemical kinetics can be changed, the physical adsorption can be enhanced, and the reaction rate can be reduced, so that the polymer layer (passivation layer) can be more dense and uniformly adsorbed on the sidewall. Even at the bottom of the high aspect ratio etching structure, effective protection of the sidewall can be formed, and lateral etching can be effectively inhibited, and an extremely vertical sidewall morphology can be obtained. Therefore, the present application can solve the problem of the influence of the thickness fluctuation of the polymer formed by using large molecule C4F8 deposition on the control of nanoscale line width, and the ion shadow effect problem (nanoscale involves atomic size level), effectively improve the uniformity and roughness of the local C-F polymer, realize more excellent uniformity (uniformity of the upper, middle and lower positions of the high aspect ratio etching structure), better sidewall smoothness, and further realize higher aspect ratio nanoscale size deep silicon structure etching. At the same time, the small molecule etching gas can significantly improve the etching rate and etching behavior at high depth (> 100µm).

[0024] (2) By using a combination of CH4, CHF3 and H2 as the deposition gas, it is easier to enter and uniformly deposit on the sidewall bottom of the ultra-narrow, ultra-deep etching structure, and form an amorphous carbon hydrogen fluorine polymer layer (a-C:H:F cross-linked polymer layer) with a lower fluorocarbon ratio, a denser, harder, and higher cross-linking three-dimensional network structure on the sidewall at an ultra-low temperature (first temperature), which has excellent anti-physical sputtering and chemical etching capability, and better barrier effect, so as to effectively avoid lateral etching. Moreover, by adding H2 in the deposition gas, the physical bombardment and chemical erosion of high-energy ions on the organic mask can be reduced, thereby reducing the damage to the organic mask and protecting the critical dimension. Thus, the vertical sidewall morphology can be maintained.

[0025] (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 active groups of F, O and S generated by the reaction react with the C-O groups sputtered from the organic mask, and co-deposition occurs on the sidewall surface at an ultra-low temperature (first temperature), forming a SiCOF compound layer with higher etching resistance, improving the protection capability of the sidewall, and at a low temperature, the SiCOF compound layer will be denser, more uniform, and have better coverage, and can form effective protection even at the bottom of the high aspect ratio etching structure, so as to effectively inhibit lateral etching and obtain an extremely vertical sidewall morphology. Moreover, O2 is also used for the first treatment of the exposed surface of the organic mask, so that the exposed surface of the organic mask is slightly oxidized at the first temperature and is triggered to react by the deep ultraviolet light existing in the environment, forming a thin and durable "crust" (hardened layer) on the surface of the organic mask, and at the same time, the SiCOF compound layer is also deposited on the surface of the organic mask, thereby forming a composite protective layer, greatly slowing down the erosion rate of F radicals on the organic mask, greatly reducing the consumption rate of the organic mask, and significantly improving the selectivity ratio. This means that a thinner organic mask can be used to etch a deeper high aspect ratio etching structure.

[0026] (4) By using F2 (or F2 and fluorine-containing gas) as the etching gas, the high reactivity of F2 can provide abundant main etching agents, reduce the dependence on physical bombardment, and improve the etching rate. Among them, the small molecule reactants and products have a longer average free path, can directly reach the bottom of the high aspect ratio etching structure, ensure the bottom etching rate, and avoid "etching stop"; the generated ions have lighter mass and more concentrated energy distribution, realize extremely anisotropic etching, and can reduce the damage to the organic mask, and obtain a more vertical sidewall.

[0027] Other advantages of the present application will be described in the specific embodiments below. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 A flow chart of a method for manufacturing a high aspect ratio etching structure according to an embodiment of the present application.

[0029] Figure 2 A schematic diagram of a structure after forming an organic mask on a substrate according to an embodiment of the present application.

[0030] Figure 3 A schematic diagram of a structure after depositing a polymer layer on the substrate and the organic mask according to an embodiment of the present application.

[0031] Figure 4 A schematic diagram of a structure after forming a first etching structure on the substrate according to an embodiment of the present application.

[0032] Figure 5 A schematic diagram of a structure after depositing a polymer layer on the substrate and the organic mask again according to an embodiment of the present application.

[0033] Figure 6 A schematic diagram of a structure after forming a second etching structure on the substrate according to an embodiment of the present application.

[0034] Figure 7 A schematic diagram of a structure after forming a high aspect ratio etching structure on the substrate according to an embodiment of the present application.

[0035] Figure 8 A schematic diagram of a structure after removing the organic mask according to an embodiment of the present application.

[0036] Figure 9 A schematic diagram of a structure after performing a second treatment on the sidewall according to an embodiment of the present application. Wherein Figure 9 (a) is adsorption and reaction, Figure 9 (b) is desorption.

[0037] Fig. 10. Substrate; 11. Opening; 12. Organic mask; 13. Carbon-based protective film; 14. Polymer layer; 15. First etching structure; 16. Second etching structure; 17. High aspect ratio etching structure; 18. Protruding portion; 19. Concave portion. DETAILED DESCRIPTION

[0038] In order to solve the problems existing in the prior art, the embodiments of the present application provide a method for manufacturing a high aspect ratio etching structure, which comprises the following steps:

[0039] providing a substrate;

[0040] forming a plurality of organic masks on the surface of the substrate;

[0041] at a first temperature, performing an etching process to etch the surface of the substrate exposed between the adjacent organic masks to form a high aspect ratio etching structure on the substrate;

[0042] wherein the etching process comprises a plurality of periodic cycle steps formed in sequence by a deposition step and an etching step;

[0043] the deposition step uses a first gas as a deposition gas to form a polymer layer on the sidewall of the high aspect ratio etching structure being formed and the exposed surface of the organic mask, so as to protect the sidewall and the organic mask during etching; and the etching step uses a second gas as an etching gas to etch the polymer layer and the substrate;

[0044] the first gas comprises a gas with a molecular weight less than that of C4F8, and the second gas comprises a gas with a molecular weight less than that of SF6, so as to increase the diffusion coefficient and improve the gas transmission efficiency;

[0045] the first temperature is less than -10℃, so as to improve the density and uniformity of the polymer layer and inhibit lateral etching.

[0046] The embodiments of the present application use small molecule first gas and second gas to replace the traditional large molecule gas C4F8 and SF6 as the deposition gas and etching gas respectively, effectively increase the diffusion coefficient, improve the transmission efficiency of the reaction gas, solve the influence of the thickness fluctuation of the large molecule C4F8 polymer on the control of the nanoscale line width and the ion shadow effect problem, effectively improve the uniformity and roughness of the local C-F polymer, and therefore can realize more optimal uniformity, better sidewall smoothness, and higher aspect ratio nanoscale size deep silicon structure etching. At the same time, the use of small molecule etching gas can significantly improve the etching rate and etching behavior under high depth (>100µm).

[0047] The embodiments of the present application also provide a high aspect ratio etching structure obtained by using the manufacturing method of the high aspect ratio etching structure.

[0048] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0049] Reference Figure 1 According to a first aspect of the present application, the embodiments of the present application provide a manufacturing method of a high aspect ratio etching structure, which comprises the following steps in sequence:

[0050] Step S11: providing a substrate.

[0051] Reference Figure 2 In some embodiments, the material of the substrate 10 includes silicon (i.e., a silicon substrate).

[0052] In some embodiments, a silicon wafer can be used as the substrate 10 to form the desired high aspect ratio etching structure on the substrate 10 by performing an etching process.

[0053] In some embodiments, the high aspect ratio etching structure includes a deep trench, a Deep Via or a Through Via, etc.

[0054] In some embodiments, the silicon wafer can be doped to provide the substrate 10 with desired electrical properties.

[0055] In some embodiments, integrated circuits such as transistor structures can be fabricated on the substrate 10 to achieve desired vertical interconnections by filling conductive materials after the high aspect ratio etching structure is formed.

[0056] Step S12: Forming a plurality of organic masks on the surface of the substrate.

[0057] Reference 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. Any two adjacent organic masks 12 have an opening 11 as an etching window between them, and the surface of the substrate 10 between the two adjacent organic masks 12 is exposed at the bottom of the opening 11.

[0058] It should be noted that, Figure 2 In some embodiments, only two organic masks 12 are formed on the upper surface of the substrate 10. However, it should be understood that more organic masks can be formed on the upper surface of the substrate 10, such as three organic masks, four organic masks, ten organic masks, etc., and the number of organic masks is not limited to the above.

[0059] In some embodiments, the organic material includes photoresist. That is, the organic mask layer includes a photoresist layer, and the organic mask 12 includes a photoresist mask.

[0060] 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 perform photolithography on the photoresist layer to form a plurality of photoresist patterns, i.e., the organic masks 12, on the upper surface of the substrate 10.

[0061] In some embodiments, before performing the 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 in an ultra-low temperature range. Specifically, a plasma of a fifth gas is used to bombard the interface (the upper surface) of the substrate 10 to form a protective film at the interface between 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.

[0062] Due to the mask edge effect, the polymer layer is not deposited enough in the edge area during the subsequent main etching process using the etching process, thus intensifying the etching behavior at the top, and the ion bombardment is more concentrated at the top, thus intensifying the lateral etching of the area during the etching process, resulting in a deeper and rougher sidewall scallop at the top of the high aspect ratio etched structure. Therefore, by pre-forming the protective film at the interface between the bottom of the organic mask 12 and the upper surface of the substrate 10, the topography of the etching top can be effectively protected during the subsequent etching process on the substrate 10, preventing abnormal excessive lateral etching behavior at the top, and ensuring the uniformity of the size at different depths of the upper, middle and lower positions during the subsequent high aspect ratio etching, i.e. ensuring the verticality of the sidewall.

[0063] In some embodiments, the fifth gas comprises a noble gas.

[0064] In the present embodiment, argon is used as the fifth gas, and the photoresist material of the organic mask 12 and the upper surface of the substrate 10 are bombarded by the argon plasma (plasma of the fifth gas) formed thereby to form a carbon-based protective film 13 (protective film of carbon-based material containing C, N and O) at the interface between the bottom of the organic mask 12 and the upper surface of the substrate 10.

[0065] In some embodiments, the third temperature during the third treatment is in the range of -80℃ to -10℃. For example, the third temperature can be in the range of -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℃. For another 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 temperatures. However, the present application is not limited thereto.

[0066] In some embodiments, the pressure is 50 mTorr to 800 mTorr when the third process is performed. 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 foregoing pressure values. However, the application is not limited thereto.

[0067] In some embodiments, the source power is 50 W to 100 W when the third process is performed. For example, the source power can be 50 W, 55 W, 60 W, 65 W, 70 W, 75 W, 80 W, 85 W, 90 W, 95 W, or 100 W, or any value between any two of the foregoing source power values. However, the application is not limited thereto.

[0068] In some embodiments, the bias power is 10 W to 50 W when the third process is performed. For example, the bias power can be 10 W, 15 W, 20 W, 25 W, 30 W, 35 W, 40 W, 45 W, or 50 W, or any value between any two of the foregoing bias power values. However, the application is not limited thereto.

[0069] In some embodiments, the time is 5 s to 20 s when the third process is performed. For example, the time can be 5 s, 10 s, 15 s, or 20 s, or any value between any two of the foregoing time values. However, the application is not limited thereto.

[0070] Step S13: A polymer layer is deposited on the surface of the substrate and the exposed surface of the organic mask using a first gas of a small molecule as a deposition gas at an ultra-low temperature.

[0071] In some embodiments, a high aspect ratio etching structure is formed on the substrate 10 by performing an etching process and periodically cyclically etching the surface of the substrate 10 exposed in the openings 11 between the adjacent organic masks 12 using the organic mask 12 as a mask.

[0072] 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.

[0073] 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.

[0074] The first temperature is less than -10°C to improve the density and uniformity of the formed polymer layer 14 and suppress lateral etching.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] The deposition gas C4F8 used in the prior art is a macromolecular gas. In the process of realizing smaller CD (nanometer level line width) and higher aspect ratio (>100:1), the deposition of the macromolecular gas on the sidewall is mainly in the upper half of the trench and the deep hole, and it is difficult to enter the bottom of the deep silicon structure. Therefore, for the structure with high aspect ratio, the protection of the bottom sidewall is not very sufficient. In the embodiment of the present application, the small molecules CH4, CHF3 and H2 are used to replace the traditional macromolecular C4F8 as the deposition gas, and the first temperature during the etching process is less than -10℃. In the process of etching deep silicon with high aspect ratio, the core advantage is that:

[0079] (1) Better sidewall protection quality: a polymer layer 14 with lower fluorocarbon ratio, higher density and higher cross-linking degree can be formed.

[0080] (2) Better step coverage and penetration: small molecule deposition gas is easier to enter and uniformly deposit on the sidewall bottom of the ultra-narrow and ultra-deep structure (the average free path of small molecules such as CH3• and CF• is longer, and it is easier to reach the bottom of the deep hole without collision. The large groups generated by the traditional C4F8 dissociation (such as C2F5) are more likely to collide in the narrow channel and be consumed, and it is difficult to reach the bottom).

[0081] (3) Reduce damage to the organic mask 12: the use of small molecule deposition gas reduces the physical bombardment and chemical erosion of high-energy ions on the organic mask 12, and protects the critical dimension.

[0082] The embodiment of the present application uses a mixed gas system composed of CH4, CHF3 and H2 (without C4F8). In the plasma, an extremely rich chemical environment is generated, and the products are more complex and superior: a large number of small size radicals such as CH3•, CH2•, CF•, CF2• and H• can be generated; these active groups are adsorbed and reacted on the sidewall and bottom of the silicon material under the assistance of ion bombardment, forming a dense a-C:H:F cross-linked polymer film (amorphous carbon film). The a-C:H:F film is an amorphous carbon hydrogen fluoride polymer, and its structure is no longer linear, but a highly cross-linked three-dimensional network structure.

[0083] While the deposition step of traditional deep silicon etching uses C4F8 as deposition gas to form polymer, when it dissociates in plasma, it will produce a large amount of CF2 free radicals and other larger fluorocarbon groups (such as CF3, C2F5, etc.). This polymer is a "loose" Teflon-like structure mainly composed of linear -CF2-CF2- chains. This structure is relatively loose and has weak mechanical strength. In addition, the polymer formed by C4F8 deposition gas has a high F / C ratio, and contains a large amount of fluorine (F) in the polymer, making it more similar to Teflon, which has strong chemical inertness, but is not strong enough as an etching barrier.

[0084] The small molecule deposition system formed by the combination of CH4, CHF3 and H2 in the embodiments of the present application has a low F / C ratio and a high H / C ratio. The introduction of H can play the following key roles:

[0085] (a) Termination of dangling bonds: H atoms can combine with dangling bonds of carbon chains to form stable C-H bonds, making the polymer layer 14 structure more complete.

[0086] (b) Promote cross-linking: -CH2- and -CH- groups can be used as cross-linking points to tightly connect carbon chains together, so that the polymer layer 14 formed on the sidewall has better blocking effect and can effectively avoid lateral etching.

[0087] Therefore, the a-C:H:F cross-linked polymer layer formed by the embodiments of the present application has a highly cross-linked structure, which is more dense and hard when deposited on the sidewall, and has excellent resistance to physical sputtering and chemical etching.

[0088] When the small molecule deposition gas system of the embodiments of the present application cooperates with the organic mask 12, the following advantages will also be produced:

[0089] (1) Reduce the loss of organic mask 12:

[0090] Chemically: The traditional C4F8 deposition gas system will produce a large amount of F atoms, which will chemically erode the organic mask 12 (the main component of photoresist is a hydrocarbon polymer), causing the organic mask 12 to be consumed too quickly. In the small molecule system of CH4, CHF3 and H2 in the embodiments of the present application, the addition of H2 will "remove" a certain amount of F atoms to form stable HF, greatly reducing the chemical erosion of the organic mask 12.

[0091] Physically: The plasma conditions required for small molecule deposition are generally milder than those of macromolecules, with relatively low ion energy, reducing physical sputtering of the organic mask 12.

[0092] (2) Suppress the BOWING morphology:

[0093] Formation mechanism of drum defect: In the etching process, if the sidewall protection layer (polymer layer 14) is not strong enough, high-energy particles and radicals from the plasma will laterally etch the sidewall from the opening 11. The closer to the top of the opening 11, the stronger the bombardment and time accumulation effect, resulting in the sidewall being hollowed out and forming a drum.

[0094] Therefore, the small molecule deposition gas system of the embodiments of the present application can effectively resist such lateral etching. At the same time, since the polymer layer 14 can extend to the bottom of the hole, it ensures that the etching rate anisotropy from top to bottom is consistent, thereby maintaining the vertical sidewall morphology.

[0095] In some embodiments, the flow rate of CH4 in the deposition gas is 3-20 sccm. For example, the flow rate of CH4 can be 3-10 sccm, or 5-15 sccm, or 5-20 sccm. For 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 foregoing flow rates. However, it can not be limited thereto.

[0096] In some embodiments, the flow rate of CHF3 in the deposition gas is 10-50 sccm. For example, the flow rate of CHF3 can be 10-30 sccm, or 15-40 sccm, or 20-50 sccm. For 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 foregoing flow rates. However, it can not be limited thereto.

[0097] In some embodiments, the flow rate of H2 in the deposition gas is 10-100 sccm. For example, the flow rate of H2 can be 10-50 sccm, or 20-80 sccm, or 30-100 sccm. For 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 foregoing flow rates. However, it can not be limited thereto.

[0098] In some embodiments, the flow ratio of CH4, CHF3and H2in the deposition gas is CH4:CHF3:H2= 1 :2:3 ~ 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 CHF3may continuously vary between 2 and 5, and the flow ratio of H2may continuously vary between 3 and 10. But it can not be limited to this.

[0099] It should be noted that when CH4:CHF3:H2= 1 :2:3 is selected as the flow ratio reference, the process target is to focus on basic deposition and morphology control. That is, this flow ratio is used to balance the deposition of C and the etching of F, and is used as the starting point of process debugging. This flow ratio can be used for optimization of the carbon skeleton structure of amorphous hydrogenated fluorocarbon polymer.

[0100] When CH4:CHF3:H2= 1 :3:5 is selected as the flow ratio reference, the process target is to focus on side wall protection. That is, by increasing the proportion of H2and CHF3, the polymer formation and crosslinking degree are enhanced to optimize the side wall morphology.

[0101] When CH4:CHF3:H2= 1 :5: 10 is selected as the flow ratio reference, the process target is to focus on high etching selectivity. That is, by having a higher proportion of H2, the etching of silicon of the substrate 10 can be significantly inhibited, thereby improving the selectivity to the organic mask 12. Moreover, when the F / C ratio in the deposition gas is lower than 3, the etching process will change from "tending to etch" to "tending to form polymer", which is crucial for protecting the organic mask 12 and obtaining high anisotropy.

[0102] In some embodiments, when the deposition step is performed, the first gas includes a sulfur-fluorine type gas and an oxidizing gas, and the polymer layer 14 includes a SiCOF compound layer.

[0103] Further, the sulfur-fluorine type gas includes SF6, and the oxidizing gas includes O2. The combination of SF6and O2, which are small molecules (the molecular weight of SF6and O2 is less than the molecular weight of C4F8), is used as the deposition gas, and a SiCOF compound layer is deposited on the surface of the substrate 10 and the exposed surface of the organic mask 12 as the polymer layer 14 at an ultra-low temperature of less than -10°C.

[0104] By lowering the temperature of the substrate 10 to an ultra-low temperature of less than -10°C, the kinetics of the etching chemistry can be greatly changed. Low temperature makes the byproducts produced in the reaction and the added gas more likely to be physically adsorbed on the silicon material surface of the substrate 10, rather than being immediately desorbed or sputtered off, enhancing the physical adsorption ability. Moreover, the ultra-low temperature makes the reaction rate reduced, and all surface chemical reaction rates are significantly slowed down at the ultra-low temperature.

[0105] When a combination of SF6and O2is used as the deposition gas, it is easier to reach the bottom of the high aspect ratio etched structure. The reaction of O2with SF6will generate SO2F2, SOF4, and other sulfur oxyfluorides, as well as fluorine radicals; at the same time, O2will also react with silicon of the substrate 10 material to generate SiO2(SiO x F y ). Most importantly, the active groups of F, O, S generated will react with the C-O groups sputtered from the organic mask 12 (photoresist), and co-deposit on the ultra-low temperature sidewall surface to form a layer of SiCOF compound. This SiCOF compound is a more complex, more etch-resistant Si-C-O-F compound, commonly referred to as SiFO polymer or SiCOF glaze. This SiFO polymer formed at ultra-low temperature has superior performance compared to the CF x polymer at room temperature:

[0106] (1) Superior sidewall protection capability.

[0107] (2) Higher etch resistance: The SiFO polymer contains Si-O bonds (very strong and stable), making it more resistant to chemical attack by F radicals and physical bombardment by ions than pure CF x polymer.

[0108] (3) Better coverage and stability: The physical adsorption at low temperature makes this protective film denser, more uniform, and better able to cover the sidewall, even at the bottom of the high aspect ratio etched structure, to form effective protection. This effectively suppresses lateral etching and achieves an extremely vertical sidewall profile.

[0109] In some embodiments, when performing the deposition step, the O2in 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 to react by the deep ultraviolet light present in the environment, forming a hardened layer.

[0110] When performing the deposition step, the O2added 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. At the same time, during the deposition step, SiFO polymer (SiCOF compound) is also deposited on the surface of the organic mask 12, so that the SiFO polymer (polymer layer 14) and the hardened layer together form a composite protective layer. This composite protective layer greatly slows down the etching rate of the F radicals on the organic mask 12, thus significantly improving the selectivity of the organic mask 12. This means that a thinner photoresist can be used to etch a deeper silicon structure.

[0111] In some embodiments, the flow rate of SF6 in the deposition gas is 10-30 seem. For example, the flow rate of SF6 can be 10 seem, 12 seem, 15 seem, 20 seem, 25 seem, or 30 seem, or any value between any two of the aforementioned flow rates. However, the application is not limited thereto.

[0112] In some embodiments, the flow rate of O2 in the deposition gas is 30-100 seem. For example, the flow rate of O2 can be 30 seem, 35 seem, 40 seem, 50 seem, 75 seem, or 100 seem, or any value between any two of the aforementioned flow rates. However, the application is not limited thereto.

[0113] In some embodiments, the flow rate ratio of SF6 and O2 in the deposition gas is SF6:O2 = 1:3-1:10. For example, the flow rate ratio of SF6 and O2 can be 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10, and the flow rate ratio of O2 can continuously vary between 3 and 10. However, the application is not limited thereto.

[0114] Step S14: etching the polymer layer and the substrate using a second gas of small molecules as an etching gas at an ultra-low temperature.

[0115] Reference Figure 4 This step is used to continue to perform the etching step included in the etching process at an ultra-low temperature (first temperature) of less than -10°C after the deposition step described above is performed, and to etch the polymer layer 14 and the substrate 10 formed in the previous step by using a second gas of small molecules as an etching gas, to form a first etching structure 15 on the substrate 10 (after the etching step is completed, there is still residual polymer on the side of the organic mask 12, Figure 4 which is omitted). The plasma of the second gas is obtained by ionizing the second gas introduced into the process chamber, and is used to etch the polymer layer 14 and the substrate 10. Further, by the first etching step and by the bombardment of the plasma of the second gas, the polymer layer 14 on the bottom of the opening 11 is removed, and by the second etching step, the exposed substrate 10 is further etched downward by the plasma of the second gas. By implementing multiple periodic cycle steps of the etching process, a high aspect ratio etching structure 17 can be finally formed on the substrate 10 (reference Figure 7 ).

[0116] When etching the substrate 10, due to the presence of the carbon-based protective film 13, when the first etching structure 15 is etched, the top is prevented from being excessively laterally etched, so that the size of the first etching structure 15 is relatively uniform, thereby laying a foundation for ensuring that the size of the entire high aspect ratio etching structure at different positions on the top, middle and bottom is uniform.

[0117] In some embodiments, the second gas includes a halogen elemental gas. For example, the halogen elemental gas includes F2, and nitrogen (N2) can be used as a dilution and dissociation gas in the second gas. That is, the second gas includes a mixed gas of F2 and N2.

[0118] In some embodiments, the second gas includes a halogen elemental gas and a fluorine-containing gas. For example, the halogen elemental 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 mixed gas of F2 and NF3, or a mixed gas of F2 and BF3, or a mixed gas of F2 and PF3, or a mixed gas of F2 and CF4, or a mixed gas of F2 and C2F6.

[0119] In some embodiments, the second gas includes a halogen elemental gas and a fluorine-containing gas. For example, the halogen elemental gas includes F2, and the fluorine-containing gas includes at least one of NF3, BF3, PF3, CF4, and C2F6.

[0120] When a fluorine gas with a smaller molecule and a mixed gas thereof are used as an etching gas instead of a conventional SF6 large molecule gas, diffusion can be more uniform, and it is more beneficial to enter a nanoscale deep trench or hole for etching reaction. Among them, F2 can be mixed with other gases (nitrogen or fluorine-containing gas) to form various mixed gases, which can achieve more excellent small-size high-aspect-ratio etching. In addition, although SF6 has 6 F, only one F ion can be dissociated for etching reaction, and the remaining SF5 does not participate in the reaction and is then pumped away. F2 gas dissociation can produce two F ions, more reactants than SF6, which can improve the etching rate, especially for etching structures with high depth (more than 100 µm), which can significantly improve the throughput of the machine.

[0121] Therefore, by using the small molecule etching gas and deposition gas, the diffusion coefficient is effectively increased, the reaction gas transmission efficiency is improved, the influence of the thickness fluctuation of the previous macromolecular C4F8 polymer on the control of the nanoscale line width and the ion shadow effect problem are solved, the uniformity and roughness of the local C-F polymer are effectively improved, and thus the nanoscale size deep silicon structure etching with better uniformity, better sidewall smoothness and higher aspect ratio is realized. Meanwhile, the mixed gas of F2 is used as the etching gas, and the etching rate and the etching behavior at high depth (greater than 100 µm) can be significantly improved.

[0122] By switching the etching gas from the traditional SF6 to the mixed gas of the small molecule F2, the demand of the advanced process can be better met, the performance is significantly improved in molecular transport, reaction efficiency and morphology control through optimizing the reaction chemistry and plasma physics, and it is a key technical path to realize the ultra-high aspect ratio etching.

[0123] The difference of using the mixed gas of F2 as the etching gas compared with using the traditional SF6 as the etching gas can include:

[0124] (1) High-density F atoms can be efficiently generated: through a more efficient dissociation path, abundant main etching agent (F atoms) is provided.

[0125] (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 to ensure the bottom etching rate.

[0126] (3) Precise ion energy and angle control: the generated ions are lighter and have a more concentrated energy distribution, which realizes extreme anisotropic etching and reduces damage to the organic mask 12.

[0127] (4) Inhibition of side reactions and morphology distortion: through specific gas combination (such as the combination of F2 and NF3), defects such as bowing can be inhibited, and a more vertical sidewall can be obtained.

[0128] When the etching gas uses the combination of F2 and N2, the main reaction groups are: F•, N + , N2 + . N2 can dilute F2 to prevent overreaction; N + , N2 + is a light ion that can efficiently transfer energy to the bottom with little sputtering damage; the N element can also form a very thin nitride layer on the sidewall to play an auxiliary passivation role.

[0129] When the etching gas uses the combination of F2 and NF3, the main reaction groups are: F•, NF2•, NF +The dissociation energy of NF3 is lower than that of SF6, and more F ions can be generated, thus providing a high-efficiency fluorine source; and the NF2 group helps to passivate the sidewall and inhibit the drum-shaped defects.

[0130] When the etching gas uses a combination of F2 and BF3, the main reaction groups are F• and BF2 + . + x + is a light ion, which is beneficial to bottom etching and sidewall modification. The B element can also be doped into the polymer on the sidewall to change the properties of the polymer, thereby further enhancing the etching resistance of the polymer layer 14 (the case when a combination of F2 and PF3 is used is similar).

[0131] When the etching gas uses a combination of F2 and CF4, the main reaction groups are F• and CF3 + . CF4 can provide a carbon source, and a small amount of C is introduced in the etching step, which can be coordinated with the deposition step to achieve more precise control of the sidewall morphology, thereby playing a role in balancing deposition and etching.

[0132] When the etching gas uses a combination of F2 and C2F6, the main reaction groups are F• and CF3 + , and C2F5 + . C2F6 can provide a higher C / F ratio than CF4, and can be used for etching conditions that require stronger passivation.

[0133] The common advantage mechanism of the small molecule groups in the etching gas of the above embodiments of the present application in the etching step can include:

[0134] (1) Higher F atomic density and deep hole penetration capability: The dissociation energy of small molecule gases (such as NF3, BF3, etc.) is generally 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 NF + , BF2 + ) are light in mass and have a long mean free path, and can effectively diffuse to the bottom of the deep hole to maintain the etching rate of the bottom and avoid “etching stop”.

[0135] (2) Better ion-assisted etching: The essence of etching is “ion-enhanced chemical etching”. The removal of the bottom silicon requires: a) F atoms for chemical reaction; and b) ion bombardment to provide energy to break the Si-Si bond and sputter the byproduct. Light ions (such as NF + , BF2 + ) can more effectively transfer energy to the bottom surface than SF x + heavy ions, thereby enhancing the etching reaction; at the same time, due to their light mass, the physical sputtering yield of the material is low, thereby reducing the physical damage to the bottom silicon and the back sputtering of the top organic mask 12.​

[0136] (3) Inhibition of drumming: The cause of drumming includes partial sidewall passivation failure, which leads to lateral etching of silicon from the sidewall by F atoms and ions. The advantage of small molecule system is that: a) higher F atom density means that it can switch to deposition step faster, avoiding long etching step time causing lateral etching; b) some gases (such as NF3) produce groups (NF2•) that can assist sidewall passivation; c) more concentrated vertical ion beam reduces the lateral scattering of ions. The three work together to ensure that etching is basically in the vertical direction.

[0137] (4) Reduction of organic mask 12 consumption caused by physical bombardment: the ions produced by small molecule system are lighter in mass, and at the same bias, their momentum is lower than that of heavy ions produced by SF6. Therefore, the physical sputtering rate of the organic mask 12 is significantly reduced, and the consumption of the organic mask 12 is reduced, and the pattern fidelity is improved.

[0138] (5) Reduction of organic mask 12 consumption caused by chemical attack: although F atoms will attack the organic mask 12, the small molecule system shortens the overall process time by higher etching efficiency, which indirectly reduces the cumulative exposure time of the organic mask 12. In addition, the C element of the combination such as CF4 / F2 can also form a light C-containing protective layer on the surface of the organic mask 12.

[0139] In some embodiments, when the etching gas uses a combination of F2 and N2, the flow rate of F2 is 100sccm-500sccm, and the flow rate of N2 is 10sccm-100sccm. For example, the flow rate of F2 can be 100sccm, 120sccm, 150sccm, 200sccm, 300sccm, 400sccm or 500sccm, or any value between any two of the aforementioned flow rates. The flow rate of N2 can be 10sccm, 20sccm, 30sccm, 50sccm, 60sccm, 80sccm or 100sccm, or any value between any two of the aforementioned flow rates. But it can not be limited to this.

[0140] In some embodiments, when the etching gas uses a combination of F2 and N2, the flow ratio of F2 and N2 is F2:N2=5:1-10:1. For example, the flow ratio of F2 and N2 can be 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, and the flow ratio of F2 can be continuously varied between 5 and 10. But it can not be limited to this. N2 plays a role in providing light ions and stabilizing plasma, but the proportion should not be too high, otherwise F2 will be diluted too much, reducing the rate.

[0141] In some embodiments, when the etching gas uses a combination of F2and NF3, the flow rate of F2is 50 sccm to 300 sccm, and the flow rate of NF3is 50 sccm to 200 sccm. For example, the flow rate of F2may 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 NF3may 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, the present application is not limited thereto.

[0142] In some embodiments, when the etching gas uses a combination of F2and NF3, the flow rate ratio of F2and NF3is F2:NF3= 1 : 1 to 1 : 2. For example, the flow rate ratio of F2and NF3may be 1 : 1 or 1 : 2, and the flow rate ratio of NF3may continuously vary between 1 and 2. However, the present application is not limited thereto. NF3provides a high-efficiency fluorine source.

[0143] In some embodiments, when the etching gas uses a combination of F2and BF3, the flow rate of F2is 100 sccm to 400 sccm, and the flow rate of BF3is 5 sccm to 50 sccm. For example, the flow rate of F2may 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 BF3may 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, the present application is not limited thereto.

[0144] In some embodiments, when the etching gas uses a combination of F2and BF3, the flow rate ratio of F2and BF3is F2:BF3= 8 : 1 to 20 : 1. For example, the flow rate ratio of F2and BF3may be 8 : 1, 9 : 1, 10 : 1, 12 : 1, 15 : 1, 18 : 1, or 20 : 1, and the flow rate ratio of F2may continuously vary between 8 and 20. However, the present application is not limited thereto. BF3is mainly used to introduce B elements and light ions.

[0145] In some embodiments, when the etching gas uses a combination of F2and PF3, the flow rate of F2is 100 sccm to 400 sccm, and the flow rate of PF3is 5 sccm to 50 sccm. For example, the flow rate of F2may 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 rate values. The flow rate of PF3may 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 rate values. However, the application is not limited thereto.

[0146] In some embodiments, when the etching gas uses a combination of F2and PF3, the flow rate ratio of F2and PF3is F2:PF3= 8: 1 to 20: 1. For example, the flow rate ratio of F2and PF3may be 8: 1, 9: 1, 10: 1, 12: 1, 15: 1, 18: 1, or 20: 1, and the flow rate ratio of F2may continuously vary between 8 and 20. However, the application is not limited thereto. PF3is mainly used to introduce P element and light ions.

[0147] In some embodiments, when the etching gas uses a combination of F2and CF4, the flow rate of F2is 100 sccm to 400 sccm, and the flow rate of CF4is 10 sccm to 80 sccm. For example, the flow rate of F2may 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 rate values. The flow rate of CF4may 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 rate values. However, the application is not limited thereto.

[0148] In some embodiments, when the etching gas uses a combination of F2and CF4, the flow rate ratio of F2and CF4is F2:CF4= 5: 1 to 10: 1. For example, the flow rate ratio of F2and CF4may be 5: 1, 6: 1, 7: 1, 8: 1, 9: 1, or 10: 1, and the flow rate ratio of F2may continuously vary between 5 and 10. However, the application is not limited thereto. CF4is used to provide carbon for slight passivation. Within the above ratio range, the phenomenon of switching from etching mode to deposition mode and causing etching to stop can be avoided.

[0149] In some embodiments, when the etching gas uses a combination of F2 and C2F6, the flow rate of F2 is 100-400 seem, and the flow rate of C2F6 is 5-40 seem. For example, the flow rate of F2 can be 100 seem, 130 seem, 150 seem, 180 seem, 200 seem, 300 seem, or 400 seem, or any value between any two of the aforementioned values. The flow rate of C2F6 can be 5 seem, 10 seem, 15 seem, 20 seem, 25 seem, 30 seem, 35 seem, or 40 seem, or any value between any two of the aforementioned values. However, the application is not limited thereto.

[0150] In some embodiments, when the etching gas uses a combination of F2 and C2F6, the flow rate ratio of F2 and C2F6 is F2:C2F6 = 10:1-20:1. For example, the flow rate ratio of F2 and C2F6 can be 10:1, 11:1, 13:1, 15:1, 19:1, or 20:1, and the flow rate ratio of F2 can continuously vary between 10 and 20. However, the application is not limited thereto. C2F6 has stronger deposition, so it can be used in smaller amounts than CF4, and the problem of polymer clogging at the opening 11 can be avoided.

[0151] Step S15: Steps S13-S14 are repeatedly performed until a high aspect ratio etching structure is formed on the substrate.

[0152] By repeatedly performing the above steps S13-S14, a high aspect ratio etching structure 17 with a target aspect ratio can finally be formed on the substrate 10, as shown in Figure 7 .

[0153] Specifically, by performing the deposition step in the etching process at the first temperature and using the first gas of the above small molecule as the deposition gas, the polymer layer 14 is again deposited on the surface of the substrate 10 (i.e. the inner wall of the first etching structure 15 formed in the previous step) and the exposed surface of the organic mask 12, as shown in Figure 5 , so as to protect the sidewall of the first etching structure 15 and the organic mask 12 when the etching step is subsequently performed. Then, at the first temperature, the etching step in the etching process is performed using the second gas of the above small molecule as the etching gas, and the polymer layer 14 and the substrate 10 are etched, i.e. through the first etching step, and by the bombardment effect of the plasma of the second gas, the polymer layer 14 on the bottom of the first etching structure 15 (the bottom of the opening 11) is first removed, and then through the second etching step, the exposed silicon material at the bottom of the first etching structure 15 is continuously etched downward by the plasma of the second gas, and a second etching structure 16 is formed below the first etching structure 15, as shown in Figure 6 .Figure 6 The original bottom of the first etching structure 15 is indicated by a horizontal dotted line. After the etching step, there is still some polymer remaining on the side of the organic mask 12 and on the sidewall of the first etching structure 15, Figure 6 By analogy, a third etching structure, a fourth etching structure, etc. (not shown) can be successively formed below the second etching structure 16, and finally a high aspect ratio etching structure 17 composed of the successively formed etching structures (the first etching structure 15 to the fourth etching structure, etc.) can be formed on the substrate 10, as shown in Figure 7 .

[0154] In some embodiments, the first temperature is -80℃ to -10℃. For example, the first temperature can be -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℃. For another example, the first temperature can be -80℃, -70℃, -60℃, -50℃, -40℃, -30℃, -20℃, -15℃ or -10℃, etc., or any value between any two of the aforementioned temperature values. But it is not limited thereto.

[0155] In some embodiments, when the substrate 10 is etched using the etching process, the time for performing the deposition step, the first etching step and the second etching step is limited to be very short, and is limited to be in the range of 0.1s to 2s, and the three steps are switched quickly. For example, the time for performing 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 performing 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.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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 9 As 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.

[0160] During the second processing, a portion of the thickness of the polymer layer 14 is removed by reacting the reaction gas with the polymer layer 14 on the sidewall to adjust the thickness uniformity of the polymer layer 14 on the sidewall. As the thickness of the polymer layer 14 is gradually thinned by the removal, the protrusions 18 on the sidewall are gradually exposed from the surface of the polymer layer 14. During this process, by reacting the reaction gas with the substrate 10 material on the surface of the exposed protrusions 18 to form a reaction product layer, at least a portion of the protrusions 18 can be removed by removing the reaction product layer, and the sidewall after the removal of the protrusions 18 is smoothed.

[0161] In some embodiments, the second processing specifically includes: using a third gas to remove a portion of the thickness of the polymer layer 14 deposited on the sidewall, and to react with the substrate 10 material present on and exposed on the surface of the protrusions 18 on the sidewall to form a reaction product layer; and then using a fourth gas to remove the reaction product layer to remove at least a portion of the protrusions 18.

[0162] 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 another example, the second temperature can be -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -15°C, or -10°C, or any value between any two of the foregoing temperatures. However, the disclosure is not limited thereto.

[0163] In some embodiments, the third gas includes HBr and O2, which is used to react with the polymer layer 14 to remove a portion of the thickness of the polymer layer 14 to adjust the thickness uniformity of the polymer layer 14 on the sidewall, and to react with silicon of the substrate 10 material to form a silicon tetrabromide layer and a silicon dioxide layer as the reaction product layer. The fourth gas includes CF4 and Ar, which is used to remove the silicon tetrabromide layer and the silicon dioxide layer by bombarding the sidewall to remove at least a portion of the protrusions 18 to smooth the sidewall.

[0164] Specifically, when performing the second processing, first, the plasma of HBr and the plasma of O2 in a mixed state are used to adsorb on the sidewall surface and react with the polymer layer 14, to remove part of the thickness of the polymer layer 14 deposited on the sidewall, so that the thickness of the polymer layer 14 is not too thick, to adjust the thickness uniformity of the polymer layer 14 on the sidewall. And, the plasma of O2 is used to oxidize the substrate 10 material (silicon) on the surface of the protrusion 18 exposed from the remaining polymer layer 14 surface, to generate a silicon dioxide (SiO2) layer in situ on the exposed surface of the protrusion 18. At the same time, the plasma of HBr is used to displace the substrate 10 material on the surface of the protrusion 18 exposed, to generate a low-volatility silicon tetrabromide (SiBr4) layer on the sidewall surface. Oxygen ions (O 2- ) and bromine ions (Br - ) in the plasma can adsorb on the surface of the protrusion 18 exposed and penetrate into the protrusion 18 from multiple directions, to react with the silicon (Si) material of the substrate 10, as shown by the arrows in Figure 9 (a). Among them, after the oxygen ions react with the silicon (Si) material of the substrate 10, a silicon dioxide layer is generated in situ on the surface of the protrusion 18 exposed, so that the silicon material interface gradually recedes in the direction of the outside of the sidewall, so that the undulation of the new interface of the silicon material formed after the reaction (i.e. the new sidewall surface to be formed subsequently, refer to Figure 9 (b)) becomes relatively flat. And the low-volatility silicon tetrabromide layer generated by the reaction of bromine ions with the silicon (Si) material of the substrate 10 can adsorb at the recess 19 on the sidewall at low temperature, so that the entire sidewall surface is flattened, which is beneficial to the smooth processing and the continuous processing steps when removing the reaction product layer. The plasma of HBr and the plasma of O2 are obtained by ionizing HBr and O2 (reaction gas) introduced into the process chamber. And nitrogen can be used as a dilution gas at the same time.

[0165] It is worth noting that the adsorption and reaction of oxygen ions on the silicon material surface of the sidewall is a self-limiting reaction. Therefore, when the silicon material on the sidewall surface of the protrusion 18 is oxidized to a certain extent, the reaction will not continue, thereby avoiding the silicon material on the sidewall surface of the protrusion 18 being etched too much, effectively realizing longitudinal cyclic etching and horizontal atomic-level precision surface processing. When the protrusion 18 is sufficiently removed and the sidewall surface after removal is relatively flattened, the passivation layer deposited again in the subsequent cycle can be used to protect the upper sidewall that has been processed, so that the loss of width size can be avoided.

[0166] In some embodiments, the time for adsorption and reaction using the plasma of the third gas is 0.5s to 2s. For example, the time can be 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 1.1s, 1.3s, 1.5s, 1.7s, or 2s, or any value between any two of the aforementioned time values.

[0167] In some embodiments, the pressure for adsorption and reaction using the plasma of the third gas is 10mTorr to 50mTorr. For example, the pressure can be 10mTorr, 15mTorr, 20mTorr, 25mTorr, 30mTorr, 35mTorr, 40mTorr, 45mTorr, or 50mTorr, or any value between any two of the aforementioned pressure values.

[0168] In some embodiments, the source power for adsorption and reaction using the plasma of the third gas 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.

[0169] In some embodiments, the bias power for adsorption and reaction using the plasma of the third gas 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.

[0170] In some embodiments, when performing 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 on the surface to break and recombine to form high-molecular polymer chains, so as to improve the etching resistance of the organic mask 12 by changing the C / H ratio on the surface of the organic mask 12 material. The principle is that, through the action of the hydrogen bromide plasma, the C=O, C-O, and C-H chemical bonds in the photoresist material of the organic mask 12 break and recombine, causing the CH3 group to become two CH2 groups. The two CH2 groups are more likely to recombine chemical bonds, form high-molecular polymer chains through recombination, change the C / H ratio of the photoresist material, and make the photoresist material more structurally stable, thereby improving the etching resistance of the photoresist, and thus improving the etching resistance of the organic mask 12 in the deep silicon etching process, i.e., improving the etching selectivity of the organic mask 12. The fourth treatment is completed simultaneously during the adsorption and reaction process of the second treatment.

[0171] Afterwards, the sidewall surface is bombarded with a plasma of CF4 and a plasma of Ar to remove the silicon tetrabromide layer and the silicon dioxide layer as the reaction product layer to remove at least part of the protrusion 18 and to smooth the sidewall. The plasma of CF4 and the plasma of Ar are obtained by ionizing CF4 and Ar introduced into the process chamber.

[0172] In this embodiment, low-energy fluorine ions (F - ) and argon ions (Ar + ) are used to bombard the sidewall surface to etch away the silicon dioxide on the protrusion 18 and to desorb the silicon tetrabromide to be removed from the sidewall to form a new sidewall that is relatively smooth. The fluorine ions react with the silicon dioxide on the protrusion 18 to decompose the silicon dioxide to generate gaseous silicon tetrafluoride (SiF4) to be removed from the sidewall.

[0173] In some embodiments, the time for removing the reaction product layer using the plasma of the fourth gas is 0.5s to 2s. For example, the time can be 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, Is, 1.1s, 1.3s, 1.5s, 1.7s, or 2s, or any value between any two of the foregoing time values.

[0174] In some embodiments, the pressure for removing the reaction product layer using the plasma of the fourth gas is 2mTorr to 10mTorr. For example, the pressure can be 2mTorr, 3mTorr, 4mTorr, 5mTorr, 6mTorr, 7mTorr, 8mTorr, 9mTorr, or 10mTorr, or any value between any two of the foregoing pressure values.

[0175] In some embodiments, the source power for removing the reaction product layer using the plasma of the fourth gas 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 foregoing source power values.

[0176] In some embodiments, the bias power for removing the reaction product layer using the plasma of the fourth gas 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 foregoing bias power values.

[0177] In some embodiments, the total flow rate of the fourth gas (CF4and Ar) is 20 sccm to 200 sccm when the plasma of the fourth gas is used to remove the reaction product layer. 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 rates.

[0178] In some embodiments, the flow rate ratio of CF4to Ar is 1:1 to 1:3 when the plasma of the fourth gas is used to remove the reaction product layer. For example, the flow rate ratio can be 1:1, 1:2, or 1:3, and can not be limited thereto.

[0179] After the aforementioned removal of the reaction product layer using the plasma of the fourth gas, the newly formed sidewall surface is smoothed, thereby reducing the roughness of the sidewall surface, as shown in Figure 9 Thus, the polymer layer 14 deposited in the subsequent cycle can be evenly coated on the smoothed sidewall surface after the treatment, so that the deposition thickness does not need to be very thick to achieve a good sidewall protection effect, and the local rough peaks (Ra>5nm) caused by the random deposition of the polymer on the sidewall can be effectively avoided.

[0180] In other embodiments, a second treatment of the sidewall at the second temperature can also be performed after every two periodic cycle steps, i.e., after every two aforementioned etching structures are formed (for example, after the first etching structure 15 and the second etching structure 16 are continuously formed, and after the third etching structure and the fourth etching structure are continuously formed, and so on). Please refer to the aforementioned embodiments for further understanding.

[0181] Step S16: removing the organic mask.

[0182] In some embodiments, after the high aspect ratio etching structure 17 is formed, the surface of the substrate 10 is bombarded by the plasma of the sixth gas to remove the organic mask 12 and the carbon-based protective film 13 on 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 the organic mask 12 and the carbon-based protective film 13 are removed, the substrate 10 with the surface exposed and the high aspect ratio etching structure 17 formed is obtained, as shown in Figure 8 .

[0183] In some embodiments, the sixth gas includes an oxidizing gas. The oxidizing gas can be, for example, oxygen, and nitrogen can be introduced as a dilution gas at the same time.

[0184] In some other embodiments, the etching process can include sequentially connected first, second and third etching stages for forming sequentially connected top, middle and bottom portions of the high aspect ratio etching structure 17, respectively, and the first etching stage can use F2 and N2 as etching gases, the second etching stage can use F2 and PF3 (or F2 and BF3) as etching gases, and the third etching stage uses F2 and C2F6 (or F2 and CF4) as etching gases. When performing the first etching stage, a stable plasma can be formed by adding N2, which can reduce the severe etching behavior in the top region caused by the instability of the sheath layer and the mask edge effect in the initial stage of etching, effectively ensure the stability of the top critical dimension, and reduce ion sputtering damage during etching, improve the protection of the organic mask, and also form an extremely thin nitride layer on the sidewall to assist in passivation of the sidewall surface to prevent excessive lateral etching and improve the verticality of the sidewall top. By using a combination of F2 and PF3 (or F2 and BF3) as etching gases in the second etching stage, the properties of the polymer layer can be changed by the incorporation of P (or B) elements to enhance the lateral etching resistance of the polymer layer, thereby further improving the verticality of the sidewall and the uniformity of the size. By using a combination of F2 and C2F6 (or F2 and CF4) as etching gases in the third etching stage, a higher fluorocarbon ratio can be provided to enhance the deposition, which can effectively suppress the lateral etching of the sidewall bottom, thereby eliminating the problem of bottom side digging. Therefore, by performing the etching process in stages, not only does it overcome the limitations of traditional single etching processes that cannot achieve high-precision control, but it also provides a more precise and controllable etching solution for the manufacture of high-performance devices, effectively expanding the etching process window.

[0185] According to a second aspect of the present application, the embodiments of the present application also provide a high aspect ratio etching structure obtained by using the manufacturing method of the high aspect ratio etching structure according to any one of the embodiments of the first aspect.

[0186] Reference Figure 8 In some embodiments, the high aspect ratio etching structure 17 is formed on the surface of the substrate 10. The critical dimension of the high aspect ratio etching structure 17 can be 50 nm or less, and the aspect ratio can be greater than or equal to 100:1. The high aspect ratio etching structure 17 can be, for example, a deep trench, a deep hole, or a via, etc.

[0187] In some embodiments, the high aspect ratio etching 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) preparation, chip stacking, etc.), optical devices (such as optical waveguides, diffraction gratings, etc.), power devices (such as insulated gate bipolar transistors (IGBT), trench structures of power metal-oxide-semiconductor field-effect transistors (MOSFET), etc.).

[0188] In a third aspect, the embodiments of the present application also provide a plasma processing device for performing the manufacturing method of high aspect ratio etched structure as described in the above embodiments to form the high aspect ratio etched structure 17 as described in the above embodiments. The plasma processing device includes an inductively coupled plasma (ICP) etching device or a capacitively coupled plasma (CCP) etching device, etc.

[0189] In other aspects, the embodiments of the present application also provide an electronic device including the high aspect ratio etched structure 17 (e.g., deep trench, deep hole or via, etc.) obtained by using the manufacturing method of high aspect ratio etched structure as described in the above embodiments. The electronic device can be a storage device, a mobile phone, a computer, a tablet computer, an electronic instrument, a television, an artificial intelligence device, etc.

[0190] In summary, by using small molecule gas (first gas and second gas) instead of traditional large molecule gas such as C4F8 and SF6 as deposition gas and etching gas, the diffusion coefficient can be increased, the gas transmission efficiency can be improved, the etching gas can be more uniformly diffused and more easily enter the nanoscale high aspect ratio etched structure 17 for etching reaction, a more excellent small size high aspect ratio etching can be achieved, the deposition gas can smoothly enter the bottom of the high aspect ratio etched structure 17, and more uniform protection of the sidewall at a smaller size can be achieved. By making the temperature during etching process less than -10℃, the chemical kinetics can be changed, the physical adsorption can be enhanced, and the reaction rate can be reduced, so that the polymer layer 14 can be more dense and uniformly adsorbed on the sidewall, effective protection of the sidewall can be formed even at the bottom of the high aspect ratio etched structure 17, lateral etching can be effectively inhibited, an extremely vertical sidewall morphology can be obtained, and a higher aspect ratio nanoscale size deep silicon structure etching can be achieved. At the same time, the small molecule etching gas can significantly improve the etching rate and etching behavior at high depth (>100µm).

[0191] The above only describes the preferred embodiments of the present application, and the embodiments are not intended to limit the protection scope of the present application. Therefore, any equivalent changes made according to the content of the specification and drawings of the present application should also be included in the protection scope of the present 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℃.

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.

Images