Reaction cavity, high aspect ratio structure and forming method thereof

Abstract

The invention discloses a reaction chamber, a high aspect ratio structure and a forming method thereof, and the reaction chamber comprises a lower electrode which is disposed in the reaction chamber and is used for supporting a substrate; the at least one high-frequency radio frequency source is applied to the lower electrode so as to form and maintain plasma in the reaction cavity; the at least one low-frequency radio frequency source is applied to the lower electrode; in the process of etching the substrate, the radio frequency of the low-frequency radio frequency source is less than or equal to 300kHz; the gas inlet device is used for conveying etching gas and fluorocarbon gas into the reaction cavity, and the etching gas comprises hydrogen halide gas and gas capable of generating hydrogen halide; the number of carbon atoms in the fluorocarbon gas is less than or equal to 3, and the flow ratio of the etching gas to the fluorocarbon gas is greater than 9: 1; the temperature of the substrate is less than 30 DEG C; and performing etching treatment on the substrate by using the reaction cavity, wherein the depth-to-width ratio of the high depth-to-width ratio is greater than 70: 1. The high aspect ratio structure formed by using the reaction chamber is good in morphology.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and particularly to a reaction chamber, a high aspect ratio structure and a method for forming the same. Background Art

[0002] With the vigorous development of semiconductor technology and the increasing integration of devices, the size of chips is getting smaller and smaller. To ensure the quality of chips, the process requirements for semiconductors are becoming more and more stringent. Size reduction is one of the driving forces for the development of integrated circuit processing. By reducing the size, synchronous improvement of cost effectiveness and device performance can be achieved.

[0003] With the increasing integration of devices, the recessed structures formed in the chip have a very high aspect ratio (HAR). Although the high aspect ratio structure can break through the capacity limitation on the plane, it also greatly increases the difficulty of etching the high aspect ratio structure, posing great challenges in terms of both process and equipment. Summary of the Invention

[0004] The object of the present invention is to provide a reaction chamber, a high aspect ratio structure and a method for forming the same, which can form a high aspect ratio structure with good morphology.

[0005] To achieve the above object, the present invention provides a reaction chamber for etching a high aspect ratio structure. The high aspect ratio structure is a recessed structure recessed downward from the surface of the substrate, and includes: a lower electrode disposed in the reaction chamber, the lower electrode being used to support the substrate; at least one high-frequency radio frequency source applied to the lower electrode to form and maintain a plasma in the reaction chamber; at least one low-frequency radio frequency source applied to the lower electrode; during the etching of the substrate, the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz; an air inlet device for delivering an etching gas and a carbon fluoride gas into the reaction chamber, the etching gas including a hydrogen halide gas and a gas capable of generating a hydrogen halide; the number of carbon atoms in the carbon fluoride gas is less than or equal to 3, and the flow ratio of the etching gas to the carbon fluoride gas is greater than 9:1; the substrate is etched by using the reaction chamber to form the recessed structure in the substrate. During the etching process, the temperature of the substrate is less than 30°C; after the etching is completed, the aspect ratio of the recessed structure is greater than 70:1.

[0006] Optionally, the peak power of the low-frequency radio frequency source is less than 30 kW.

[0007] Optionally, the net power of the low-frequency radio frequency source is less than 12.8 kW.

[0008] Optionally, the ratio range of the peak power of the low-frequency radio frequency source to the peak power of the high-frequency radio frequency source is 3:1 to 5:1.

[0009] Optionally, the peak power of the high-frequency radio frequency source is less than 10 kW.

[0010] Optionally, the average power of the low-frequency radio frequency source is less than 10 kW.

[0011] Optionally, the radio frequency of the high-frequency radio frequency source is 100 times higher than that of the low-frequency radio frequency source.

[0012] Optionally, the radio frequency of the low-frequency radio frequency source is greater than 10 kHz and less than or equal to 300 kHz.

[0013] Optionally, the radio frequency of the high-frequency radio frequency source is greater than or equal to 40 MHz and less than or equal to 120 MHz.

[0014] Optionally, the substrate includes a substrate and an etching layer located above the substrate, and the material of the etching layer is an alternating stack of any two of SiO 2 , SiN, and polysilicon.

[0015] Optionally, the hydrogen halide gas includes at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

[0016] Optionally, the gas capable of generating hydrogen fluoride includes a hydrogen source and a fluorine source; the gas capable of generating hydrogen chloride includes a hydrogen source and a chlorine source; the gas capable of generating hydrogen bromide includes a hydrogen source and a bromine source; the gas capable of generating hydrogen iodide includes a hydrogen source and an iodine source; the hydrogen source includes: H 2 , CH 4 , CH 3 F, CH 2 F 2 , C 2 H 2 F 2 , C 2 HF 5 , C 3 HF 5 , C 3 H 2 F 6 , C 3 H 2 F 4 and C 4 H 2 F 6 and at least one of the following; the fluorine source includes: NF 3 , CF 4 , SF 6 , CHF 3 , F 2 , ClF 3 , CF 3 I, C 2 F 6 , C 2HF 5 and C 3 H 2 F 6 at least one of; the chlorine source includes: Cl 2 、HCl、ClF 3 and CH 2 Cl 2 at least one of; the bromine source includes: HBr, Br 2 、BrF 3 、CBr 2 F 2 、CF x Br y 、PBr 3 and PBr 5 at least one of; the iodine source includes: CF 3 I、HI、I 2 、PI 3 、IF 5 、IF 7 、C 2 F 5 I and C 3 F 7 I among at least one of.

[0017] Optionally, the fluorocarbon gas includes CH 3 F、C 2 H 2 F 2 、C 3 HF 5 、C 4 H 2 F 6 and CF 4 among at least one of.

[0018] Optionally, the gas transported by the intake device to the reaction chamber further includes: PF 3 、O 2 、H 2 、NF 3 、WF 6 、Ar、He、BF 3 、BCL 3 and Cl 2 among at least one of.

[0019] Optionally, the high-frequency RF source and / or the low-frequency RF source is pulsed.

[0020] Optionally, the duty cycle of the pulse is less than 50%.

[0021] Optionally, the high-frequency RF source and / or the low-frequency RF source is continuous.

[0022] Optionally, the radio frequency of the low-frequency radio frequency source is one of 100 kHz, 200 kHz, and 300 kHz.

[0023] The present invention also provides a reaction chamber for etching high aspect ratio structures. The high aspect ratio structure is a concave structure recessed downward from the substrate surface, and includes: a lower electrode disposed in the reaction chamber for supporting the substrate; at least one high-frequency radio frequency source applied to the reaction chamber to form and maintain plasma in the reaction chamber; at least one low-frequency radio frequency source applied to the lower electrode; during the etching of the substrate, the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz; an air inlet device for delivering an etching gas and a carbon fluoride gas into the reaction chamber, the etching gas including a hydrogen halide gas and a gas capable of generating a hydrogen halide; the number of carbon atoms in the carbon fluoride gas is less than or equal to 3, and the flow ratio of the etching gas to the carbon fluoride gas is greater than 9:1; the substrate is etched using the reaction chamber to form the concave structure in the substrate. During the etching process, the temperature of the lower electrode is less than -30°C; after the etching is completed, the aspect ratio of the concave structure is greater than 70:1.

[0024] Optionally, the temperature of the lower electrode is: -130°C to -30°C.

[0025] Optionally, the peak power of the low-frequency radio frequency source is less than 30 kW.

[0026] Optionally, the net power of the low-frequency radio frequency source is less than 12.8 kW.

[0027] Optionally, the average power of the low-frequency radio frequency source is less than 10 kW.

[0028] Optionally, the high-frequency radio frequency source and / or the low-frequency radio frequency source is continuous.

[0029] Optionally, the radio frequency of the low-frequency radio frequency source is one of 100 kHz, 200 kHz, and 300 kHz.

[0030] Accordingly, the present invention further provides a method for forming a high aspect ratio structure by using the above reaction chamber, including: providing a substrate, placing the substrate on a lower electrode, a mask layer being provided on the surface of the substrate, the mask layer having a mask opening, the bottom of the mask opening exposing the top surface of the substrate; introducing an etching gas and a fluorocarbon gas, the flow ratio of the etching gas to the fluorocarbon gas being greater than 9:1, the etching gas and the fluorocarbon gas being excited by a high-frequency radio frequency source to form a plasma, the plasma processing the substrate under the action of a low-frequency radio frequency source to form a high aspect ratio structure in the substrate; the etching gas including a hydrogen halide gas and a gas capable of generating a hydrogen halide, the number of carbon atoms in the fluorocarbon gas being less than or equal to 3; during the process of etching the substrate, the temperature of the lower electrode being less than -30°C or the temperature of the substrate being less than 30°C, the radio frequency of the low-frequency radio frequency source being less than or equal to 300 kHz.

[0031] Optionally, it further includes: when forming a high aspect ratio structure with a first depth, the lower electrode has a first temperature; when forming a high aspect ratio structure with a second depth, the lower electrode has a second temperature, the second depth being greater than the first depth, and the second temperature being higher than the first temperature.

[0032] Optionally, it further includes: when forming a high aspect ratio structure with a first depth, the low-frequency radio frequency source has a first peak power; when forming a high aspect ratio structure with a second depth, the low-frequency radio frequency source has a second peak power, the second depth being greater than the first depth, and the second peak power being higher than the first peak power.

[0033] Accordingly, the present invention further provides a high aspect ratio structure, including: a substrate, a mask layer being provided on the surface of the substrate, the mask layer having a mask opening, the bottom of the mask opening exposing the top surface of the substrate; a high aspect ratio structure provided in the substrate, the high aspect ratio structure being a concave structure recessed downward from the surface of the substrate, the aspect ratio of the concave structure being greater than 70:1, and the perpendicularity of the concave structure being greater than 70%.

[0034] Optionally, along the depth direction of the high aspect ratio structure, the difference between the maximum width and the minimum width of the high aspect ratio structure is less than 30 nm.

[0035] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: In the reaction chamber provided by the present invention, the temperature of the lower electrode is set to be less than -30°C to control the temperature of the substrate during the process to be less than 30°C. At this relatively low temperature, the ultra-high active groups formed by the etching gas and the carbon fluoride gas can be preferably adsorbed on the surface of the substrate, and the lower temperature increases the residence time of these ultra-high active groups on the substrate surface. During this residence time, the etching gas is mainly used for etching the surface of the substrate, and the carbon fluoride gas is mainly used for protecting the sidewalls of the high aspect ratio structure concave structure. At low temperatures, when the number of carbon atoms in the carbon fluoride gas is less than or equal to 3, good sidewall protection can be achieved without the need to select carbon fluoride gases with a higher number of carbon atoms. Moreover, the carbon fluoride gas is only used as a sidewall protection gas without being used as an etching gas at the same time, so that the etching effect and the sidewall protection effect of the process gas are decoupled, facilitating the independent control of the flow rates of the etching gas and the sidewall protection gas respectively. At the same time, since the carbon fluoride gas is only used as a sidewall protection gas, the flow rate of the carbon fluoride gas is much less than that of the etching gas, that is, the flow rate ratio of the etching gas to the carbon fluoride gas is greater than 9:1. The radio frequency of the low-frequency radio frequency source of the present invention is less than or equal to 300 kHz, which is beneficial to increasing the energy of the plasma bombarding the bottom of the high aspect ratio structure and reducing the scattering angle of the plasma. Therefore, it is beneficial to form a high aspect ratio structure concave structure with a high aspect ratio. On the contrary, if the radio frequency of the low-frequency radio frequency source is greater than 300 kHz, the energy of the plasma bombarding the bottom of the high aspect ratio structure will be small, and the scattering angle of the plasma will be large, which is not conducive to continuous etching and difficult to form a high aspect ratio structure. It can be seen that through the mutual cooperation among the type of the etching gas, the flow rate ratio of the etching gas to the carbon fluoride gas, the number of carbon atoms in the carbon fluoride gas, the low temperature of the substrate, and the radio frequency of the low-frequency radio frequency source, it is beneficial to form a high aspect ratio structure meeting the process requirements.

[0036] Furthermore, the peak power of the low-frequency radio frequency source is less than 30 kW, so that the influence of the plasma on the temperature of the substrate is small, enabling the substrate to maintain a low temperature state to continuously maintain the adsorption capacity for the etching gas and the carbon fluoride gas, thereby ensuring a high etching rate. On the contrary, if the peak power of the low-frequency radio frequency source is greater than 30 kW, this will cause a large influence of the plasma on the temperature of the substrate, resulting in a high temperature of the substrate and making it difficult to maintain a low temperature state, which will lead to poor adsorption capacity of the substrate for the etching gas and the carbon fluoride gas, thus making it difficult to ensure the chemical etching effect of the etching gas and the carbon fluoride gas on the substrate. Description of the Drawings

[0037] Figure 1 is a schematic structural diagram of a reaction chamber of the present invention; Figure 2 is a schematic diagram of the etching principle using the etching gas of the present invention; Figure 3Schematic diagram of the substrate being processed by the plasma of the present invention when the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz; Figure 4 Schematic structural diagram of another reaction chamber of the present invention; Figure 5 Process flow chart of forming a high aspect ratio structure of the present invention; Figure 6 Schematic diagram of a high aspect ratio structure of the present invention. Detailed implementation manners

[0038] The following will combine the accompanying Figure 1 ~accompanying Figure 6 to elaborate in detail on the technical solutions, structural features, achieved objectives and effects in the embodiments of the present invention.

[0039] It should be noted that the accompanying drawings adopt a very simplified form and all use non-precise scales, and are only used to conveniently and clearly assist in explaining the purpose of the implementation manner of the present invention, and are not used to limit the limiting conditions for the implementation of the present invention. Therefore, they do not have technical essential significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0040] It should be noted that in the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements clearly listed, but also includes other elements not clearly listed, or also includes elements inherent to such process, method, article or device.

[0041] Figure 1 Schematic structural diagram of a reaction chamber of the present invention.

[0042] Please refer to Figure 1, a reaction chamber 11, which is provided with a lower electrode 12 therein, and the lower electrode 12 is used to support the substrate W; at least one high-frequency radio frequency source 14 is applied into the reaction chamber 11 to form and maintain the plasma in the reaction chamber 11; a low-frequency radio frequency source 15 outputs a bias radio frequency power to the lower electrode 12; during the process of etching the substrate, the radio frequency frequency of the low-frequency radio frequency source 15 is less than or equal to 300 kHz; an air inlet device 13 is used to transport etching gas and carbon fluoride gas into the reaction chamber 11, the etching gas includes hydrogen halide gas and gas capable of generating hydrogen halide, the number of carbon atoms in the carbon fluoride gas is less than or equal to 3, and the flow ratio of the etching gas to the carbon fluoride gas is greater than 9:1; the reaction chamber is used to etch the substrate to form a high aspect ratio structure in the substrate, the high aspect ratio structure is a concave structure recessed downward from the substrate surface, and the aspect ratio of the concave structure is greater than 70:1.

[0043] In this embodiment, the reaction chamber is a capacitively coupled plasma etching device, which is a device that generates plasma in the reaction chamber 11 by capacitive coupling of a radio frequency power source applied to the electrode plate and is used for etching. The reaction chamber 11 includes a substantially cylindrical reaction chamber side wall made of a metal material, and an opening (not marked in the figure) is provided on the reaction chamber side wall for accommodating the substrate to enter and exit. The reaction chamber is also provided with an air inlet device 13 and a lower electrode 12 disposed opposite to the air inlet device 13. The air inlet device 13 is connected to a gas supply device (not marked in the figure) for transporting gas into the reaction chamber 11. In this embodiment, the air inlet device 13 is a disk-shaped gas shower head and also serves as the upper electrode of the reaction chamber. In other embodiments, the air inlet device can also be a structure of one or more nozzles. An electrostatic chuck is disposed above the lower electrode 12 and also serves as the lower electrode of the reaction chamber 11. A reaction region is formed between the upper electrode and the lower electrode. At least one high-frequency radio frequency source 14 is applied to the reaction chamber through a matching network, such as one of the upper electrode or the lower electrode. In this embodiment, the high-frequency radio frequency source 14 is applied to the lower electrode 12. In other embodiments, the high-frequency radio frequency source 14 is applied to the air inlet device 13 to generate a radio frequency electric field between the upper electrode and the lower electrode to dissociate the etching gas and the carbon fluoride gas into plasma. A low-frequency radio frequency source 15 is applied to the lower electrode 12 to control the direction of the plasma. The plasma contains a large number of active particles such as electrons, ions, excited atoms, molecules and free radicals. The above active particles can undergo various physical and chemical reactions with the surface of the substrate to be processed, so that the surface morphology of the substrate is changed, that is, the etching process is completed. A exhaust pump is also disposed below the reaction chamber 11 to discharge reaction by-products from the reaction chamber and maintain the vacuum environment of the reaction chamber.

[0044] One application of the reaction chamber is the etching of high aspect ratio structures in 3D NAND memories. As the demand for data storage and logic processing capabilities gradually increases, the aspect ratio (the ratio of the depth to the radial width of the high aspect ratio structure) of the high aspect ratio structures formed on the substrate is also getting higher. In addition, other applications of the reaction chamber also include the etching of high aspect ratio structures in DRAM and / or logic devices. During the process of forming these high aspect ratio structures using plasma etching, the difference in the upper and lower radial dimensions of the high aspect ratio structure needs to be controlled within a small range. However, in the existing process, when the high aspect ratio etching progresses to a certain extent, there will be a large gap between the maximum radial size and the minimum radial size, resulting in defect morphologies such as bowing and bending. These high aspect ratio structures with such morphologies are not conducive to improving performance.

[0045] To solve this technical problem, the present invention sets the temperature of the lower electrode to be less than -30°C to control the temperature of the substrate to be less than 30°C. When the etching gas and the fluorocarbon gas are in this low-temperature environment, the ultra-high reactive groups formed can be well adsorbed on the surface of the substrate. The enhanced adsorption increases the residence time and promotes the reaction. The number of carbon atoms in the fluorocarbon gas is less than or equal to 3, the flow ratio of the etching gas to the fluorocarbon gas is greater than 9:1, and the radio frequency frequency of the low-frequency radio frequency source is less than 300 kHz, which is beneficial to increasing the energy of the plasma bombarding the bottom of the high aspect ratio structure and reducing the scattering angle of the plasma, having a high etching rate, and finally forming a high aspect ratio structure that meets the process requirements.

[0046] Figure 2 This is a schematic diagram of the etching principle of the present invention using an etching gas.

[0047] The substrate includes a substrate 100. In some embodiments, the substrate 100 can be made of Si. The layer to be etched is located above the substrate 100, and the layer to be etched can be a dielectric material, a semiconductor material, or a stack of multiple materials, or a doped mixture, such as a single layer of SiO 2 、Si 3 N 4 or polysilicon, and an alternating stack of SiO 2 and SiN, an alternating stack of SiO 2 and polysilicon. In this embodiment, the layer to be etched includes an alternating stack of a SiO 2 layer 101 and a SiN layer 102, as Figure 2 shown.

[0048] The gas delivered by the gas inlet device 13 to the reaction chamber 11 includes: etching gas and carbon fluorine gas, wherein the etching gas includes hydrogen halide gas and gas capable of generating hydrogen halide. The hydrogen halide gas includes: at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide. The gas capable of generating hydrogen fluoride includes: a hydrogen source and a fluorine source; the gas capable of generating hydrogen chloride includes: a hydrogen source and a chlorine source; the gas capable of generating hydrogen bromide includes: a hydrogen source and a bromine source; the gas capable of generating hydrogen iodide includes: a hydrogen source and an iodine source. The hydrogen source includes: H 2 , CH 4 , CH 3 F, CH 2 F 2 , C 2 H 2 F 2 , C 2 HF 5 , C 3 HF 5 , C 3 H 2 F 6 , C 3 H 2 F 4 and C 4 H 2 F 6 At least one of; the fluorine source comprises: NF 3 CF 4 , SF 6 , CHF 3 、F 2 , ClF 3 CF 3 I.C 2 F 6 , C 2 HF 5 and C 3 H 2 F 6 At least one of; the chlorine source comprises: Cl 2 , HCl, ClF 3 and CH 2 Cl 2 At least one of; the bromine source includes: HBr, Br 2 BrF 3 , CBr 2 F 2 CF x Br y , PBr 3 and PBr 5 At least one of; the iodine source comprises: CF 3 I, HI, I 2 ,PI3 , IF 5 , IF 7 , C 2 F 5 I and C 3 F 7 at least one of I

[0049] The etching principle is described below using hydrogen fluoride as the etching gas as an example: Please refer to Figure 1 and Figure 2 , the substrate further includes a mask layer 104 on the surface of the layer to be etched. The mask layer 104 has a mask opening, and the mask opening is used to define the position and size of the subsequent formation of the high aspect ratio structure. The hydrogen fluoride gas is dissociated under the action of the high-frequency radio frequency source 14 to form H plasma and F plasma. The H plasma and F plasma move towards the bottom of the mask opening under the action of the low-frequency radio frequency source 15. The substrate is at a low temperature. Specifically, the temperature of the substrate is less than 30 °C. One way to achieve a low temperature of the substrate is to control the temperature of the lower electrode so that the temperature of the lower electrode is less than -30 °C. In one embodiment, the temperature of the lower electrode is: -120 °C to -30 °C, or the temperature of the lower electrode is: -90 °C to -30 °C, or the temperature of the lower electrode is: -70 °C to -40 °C. At a low temperature of the substrate, the H plasma and F plasma can be better adsorbed on the sidewalls of the high aspect ratio structure 103, and the following chemical reactions occur: SiO 2 The chemical reaction occurring in layer 101 is: HF + SiO 2 + H 2 O → SiF 4 + 3H 2 O The chemical reaction occurring in the SiN layer 102 is: SiN + 8HF → (NH 4 ) 2 SiF 6 (NH 4 ) 2 SiF 6 → SiF 4 + HF + NH 3 When etching the SiO 2 layer 101, HF first reacts with SiO 2 to generate a small amount of water. The gas transported by the gas inlet device into the reaction chamber further includes: PF 3 , PF 3 can solidify the generated small amount of water, which is beneficial to SiO 2The chemical reaction in layer 101 continues in the forward direction, i.e., it is conducive to the continuous etching of SiO 2 layer 101.

[0050] When the SiN layer 102 undergoes a chemical reaction in a low-temperature environment, a relatively large amount of (NH 4 ) 2 SiF 6 is generated. A relatively large amount of (NH 4 ) 2 SiF 6 accumulates on the inner sidewalls of the high aspect ratio structure as a sidewall protection layer for etching the SiO 2 layer 101, preventing the morphology of the high aspect ratio structure formed by etching the SiO 2 layer 101 with hydrogen fluoride gas from being too wide and large. Moreover, the layer to be etched is not entirely a silicon nitride layer, but an alternating stack of the SiO 2 layer 101 and the SiN layer 102. Due to the restrictive effect of the SiO 2 layer 101 on the upper and lower surfaces of the SiN layer 102, when etching with hydrogen fluoride gas, it prevents the formed high aspect ratio structure from being too deep and sharp, i.e., when etching the SiO 2 layer 101 and the SiN layer 102 complement each other, and finally the morphology of the formed high aspect ratio structure can better meet the process requirements.

[0051] During the etching process of the SiO 2 layer 101 and the SiN layer 102, in addition to hydrogen fluoride as the etching gas, it also includes carbon fluoride gas. Specifically, the carbon fluoride gas includes: CH 3 F, C 2 H 2 F 2 , C 3 HF 5 and CF 4At least one of them. Such fluorocarbon gases usually react to form fluorocarbon polymers, which serve as sidewall protection. The number of carbon atoms in such fluorocarbon gases is less than or equal to 3, so that the thickness of the formed fluorocarbon polymer is not too thick. Therefore, it is beneficial to prevent the over-protection of the sidewalls from blocking the high aspect ratio structure. At the same time, by adjusting the flow rate of the fluorocarbon gas, a fluorocarbon polymer with an appropriate thickness is formed on the sidewalls of the high aspect ratio structure to prevent the unnecessary expansion of the lateral dimension of the formed high aspect ratio structure, which is beneficial to forming a high aspect ratio structure that meets the process requirements. Moreover, when the fluorocarbon gas is an unsaturated fluorocarbon gas, the fluorocarbon polymer is formed faster and has a longer chain at low temperature. In this way, the fluorocarbon polymer is not easy to move to the bottom of the high aspect ratio structure due to its large mass, so that the fluorocarbon polymer is more likely to aggregate on the top surface of the mask layer 104 and the inner sidewalls of the high aspect ratio structure 103, which is beneficial to improving the selectivity of the mask layer to the layer to be etched, and can also better control the critical dimension of the high aspect ratio structure, and only a small amount needs to be added to play this role.

[0052] More importantly, in the present invention, the etching gas is mainly used for etching the layer to be etched, and the fluorocarbon gas is mainly used for protecting the sidewalls of the high aspect ratio structure during the etching process. Their functions are independent of each other and do not overlap. Different from the usual etching process, the selected etching gas not only plays an etching role but also forms a polymer to protect the sidewalls of the high aspect ratio structure, that is: the functions of the etching gas and the fluorocarbon gas in the present invention are not coupled to each other. If you want to adjust the etching situation, only adjust the content of the etching gas, and when adjusting the content of the etching gas, it will not affect the protection of the sidewalls of the high aspect ratio structure; if you want to adjust the lateral dimension of the high aspect ratio structure, only adjust the content of the fluorocarbon gas, and when adjusting the content of the fluorocarbon gas, it is not easy to affect the etching situation. The decoupling of the functions of the etching gas and the fluorocarbon gas in the present invention makes it simple and easy to adjust the morphology of the high aspect ratio structure. Moreover, the fluorocarbon gas does not need to be used as an etching gas, so that the flow rate of the fluorocarbon gas is small, while the flow rate of the etching gas is large, which is beneficial to protecting the sidewalls of the high aspect ratio structure well while meeting the high etching rate.

[0053] In this embodiment, the flow rate ratio of the etching gas to the fluorocarbon gas is greater than 9:1. By adjusting the flow rate ratio of the etching gas and the fluorocarbon gas, the etching rate and sidewall protection can be better controlled to form a high aspect ratio structure that meets the process requirements. If the flow rate ratio of the etching gas to the fluorocarbon gas is less than 9:1, the flow rate of the fluorocarbon gas is too much, and there is a risk of blocking the high aspect ratio structure at the position of the shallow high aspect ratio structure, making it difficult to continue etching, which is not conducive to forming a high aspect ratio structure.

[0054] In other embodiments, the flow rate ratio of the etching gas to the carbon fluoride gas is: 10:1, 11:1, 12:1, 14:1, which is not limited herein. A larger flow rate of the etching gas is beneficial to improving the etching rate.

[0055] In addition, the gas delivered by the gas inlet device to the reaction chamber further includes: O 2 , H 2 , NF 3 , WF 6 , Ar, BF 3 , BCL 3 , HBr and Cl 2 at least one of. These gases can modify and adjust the morphology of the high aspect ratio structure to balance the selectivity between the mask layer and the layer to be etched, the roundness of the high aspect ratio structure, and the perpendicularity of the high aspect ratio structure.

[0056] During the etching of the SiO 2 layer 101 and the SiN layer 102, the formed SiF 4 , HF and NH 3 are all gases. The air pressure in the reaction chamber is relatively low. In one embodiment, the air pressure range in the reaction chamber is less than 25 mT, so that the generated SiF 4 , HF and NH 3 can be quickly pumped away from the bottom of the high aspect ratio structure 103, achieving continuous etching of the SiO 2 layer 101 and the SiN layer 102 to form a high aspect ratio structure.

[0057] Moreover, the etching gas in the present invention is a carbon-free gas. Although the carbon fluoride gas contains carbon, the amount of the carbon fluoride gas is very small, and the generated gas is also a carbon-free gas. Therefore, the technical solution of the present invention is low-carbon and environmentally friendly, which is beneficial to promoting the green production and sustainable development of enterprises, helps to establish a green, environmentally friendly and low-carbon corporate image, and makes a positive contribution to the sustainable development of society.

[0058] Meanwhile, in order to remove more (NH 4 ) 2 SiF 6 , the radio frequency of the bias power supply is relatively low, which is beneficial to increasing the energy of the plasma and is beneficial to removing (NH 4 ) 2 SiF 6 . In addition, the gas delivered to the reaction chamber further includes an inert gas with a relatively heavy atomic mass. The inert gas with a relatively heavy atomic mass includes: at least one gas among argon, krypton, xenon and radon. The mass of the inert ions dissociated from the inert gas is relatively heavy, and it can better penetrate to the bottom of the high aspect ratio structure to bombard and remove the (NH4 ) 2 SiF 6 , enabling the etching of silicon nitride to proceed continuously.

[0059] The above is an illustration of the etching principle with hydrogen fluoride gas as the etching gas. In fact, the etching principles of other hydrogen halide gases or gases that can produce hydrogen halide through reactions on the substrate are similar. These gases are dissociated under the action of the high-frequency radio frequency source 14 to form H plasma and halogen plasma. The H plasma and halogen plasma move towards the bottom of the mask opening under the action of the low-frequency radio frequency source 15. The substrate is at a low temperature, and the H plasma and halogen plasma can be well adsorbed on the sidewalls of the high aspect ratio structure 103 and undergo chemical reactions similar to those described above, thereby realizing the etching of the SiO 2 layer 101 and the SiN layer 102.

[0060] As Figure 3 shown, as the etching progresses, the depth of the formed high aspect ratio structure 103 continuously increases, making the aspect ratio of the high aspect ratio structure 103 continuously increase. In order to be able to transport the plasma to the bottom of the high aspect ratio structure 103 to continue etching the substrate, it is necessary to apply a low-frequency radio frequency source 15 to the lower electrode (please refer to Figure 1 ). The plasma 200 represents the above-mentioned fluoride ions and / or hydrogen ions. During the etching process, the radio frequency of the low-frequency radio frequency source 15 is less than or equal to 300 kHz. For example, the radio frequency of the low-frequency radio frequency source 15 is one of 100 kHz, 200 kHz, and 300 kHz, making the energy of the plasma 200 relatively high, which is beneficial for bombarding the plasma to the bottom of the high aspect ratio structure 103 to carry out the etching process. Figure 3 The arrows in represent the movement direction of the plasma. The radio frequency of the low-frequency radio frequency source 15 being less than or equal to 300 kHz also makes the scattering angle of the plasma relatively small, enabling the plasma to be transported to the bottom of the high aspect ratio structure 103 more vertically, preventing the bending of the sidewall morphology of the high aspect ratio structure caused by multiple reflections of the plasma on the inner wall of the high aspect ratio structure due to a large scattering angle of the plasma. A smaller scattering angle of the plasma is beneficial for forming a high aspect ratio structure, and the morphology of the high aspect ratio structure is good. If the radio frequency of the low-frequency radio frequency source 15 is greater than 300 kHz, on the one hand, the energy of the plasma bombarded to the bottom of the high aspect ratio structure is relatively small, making it difficult to continue etching and not conducive to forming a high aspect ratio structure. On the other hand, it will make the scattering angle of the plasma relatively large, so that a large number of plasmas no longer move vertically downward, but a considerable part are obliquely incident on the inner sidewall of the high aspect ratio structure and undergo multiple reflections on the inner sidewall of the high aspect ratio structure, which will make the formed high aspect ratio structure have a poor perpendicularity and it is difficult to meet the process requirements.

[0061] In another embodiment, the radio frequency of the low-frequency radio frequency source is greater than 10 kHz and less than or equal to 300 kHz. The relatively low radio frequency of the low-frequency radio frequency source is conducive to increasing the energy of the plasma bombarding the bottom of the high aspect ratio structure and reducing the scattering angle of the plasma. Therefore, it is conducive to forming a high aspect ratio structure with a high aspect ratio.

[0062] The radio frequency of the high-frequency radio frequency source is greater than or equal to 40 MHz and less than or equal to 120 MHz.

[0063] In one embodiment, the radio frequency of the high-frequency radio frequency source is 100 times higher than that of the low-frequency radio frequency source, which can generate more sheath collapse points, facilitating the elimination of accumulated charges. In this way, ultra-high aspect ratio etching can be better achieved, and the morphology of the high aspect ratio structure can be improved.

[0064] In summary, through the mutual cooperation among the type of etching gas, the flow ratio of the etching gas to the fluorocarbon gas, the number of carbon atoms in the fluorocarbon gas, the low temperature of the substrate, and the radio frequency of the low-frequency radio frequency source, the present invention is conducive to forming a high aspect ratio structure that meets the process requirements.

[0065] To achieve the low temperature of the substrate, in addition to the method of controlling the temperature of the lower electrode 12 (see Figure 1 ), it can also be achieved by setting a relatively low power of the low-frequency radio frequency source 15. The relatively low power of the low-frequency radio frequency source 15 results in a relatively low temperature of the substrate, enabling the ultra-highly active groups formed by the etching gas and the fluorocarbon gas to be better adsorbed on the surface of the substrate. Moreover, the low temperature increases the residence time of these ultra-highly active groups on the substrate surface. During this residence time, through the mutual cooperation among the type of etching gas, the flow ratio of the etching gas to the fluorocarbon gas, the number of carbon atoms in the fluorocarbon gas, the low temperature of the substrate, the radio frequency of the low-frequency radio frequency source, and the power of the low-frequency radio frequency source, it is conducive to forming a high aspect ratio structure that meets the process requirements. The following is a detailed description: First, the etching gas in the present invention is more inclined to chemical reaction etching of the substrate. Therefore, high ion energy is not required to assist the reaction. Thus, the power of the low-frequency radio frequency source 15 is small. The power characterization parameters of the low-frequency radio frequency source 15 include: the peak power of the low-frequency radio frequency source 15, the net power of the low-frequency radio frequency source 15, and the average power of the low-frequency radio frequency source 15. Among them, the peak power of the low-frequency radio frequency source 15 refers to the maximum power that the low-frequency radio frequency source 15 can reach within one cycle. The net power of the low-frequency radio frequency source 15 is equal to the output power of the low-frequency radio frequency source 15 multiplied by the duty cycle. When the duty cycle is equal to 1, it indicates that the low-frequency radio frequency source 15 outputs power continuously, making the process relatively simple, with a lower peak power of the low-frequency radio frequency source 15, which is friendly to the hardware. When the duty cycle is less than 1, it indicates that the low-frequency radio frequency source 15 outputs power in a pulsed manner. In this embodiment, the duty cycle of the low-frequency radio frequency source 15 is less than 50%, making the low-frequency radio frequency source 15 have a smaller impact on the temperature of the substrate. And the average power of the low-frequency radio frequency source 15 refers to the average output power of the low-frequency radio frequency source 15 within a complete cycle.

[0066] The peak power of the low-frequency radio frequency source 15 is small. Specifically, the peak power of the low-frequency radio frequency source is less than 30 kW, making the low-frequency radio frequency source have a smaller impact on the temperature of the substrate, enabling the substrate to maintain a low temperature state to continuously maintain the adsorption capacity for the etching gas and the fluorocarbon gas, thereby ensuring a high etching rate. If, as is the common understanding in the industry, the peak power of the low-frequency radio frequency source is usually set relatively high for the purpose of increasing the ion energy bombarding the bottom of the high aspect ratio structure. However, with such a design, the plasma will be heated by the low-frequency radio frequency source, and the plasma contacting the substrate will also heat the substrate, making it difficult to maintain a low temperature environment where the temperature of the substrate is less than 30°C. As the temperature of the substrate rises, the adsorption capacity of the substrate for the plasma will decrease, and the contact time between the plasma and the substrate will become shorter, which is not conducive to increasing the etching rate. Moreover, the peak power of the low-frequency radio frequency source in the prior art is relatively high, consuming a large amount of electric energy and easily causing energy waste. While the peak power of the low-frequency radio frequency source in the present invention is low, which is conducive to saving energy and reducing the production cost of enterprises.

[0067] Similarly, the net power of the low-frequency radio frequency source 15 is small. Specifically, the net power of the low-frequency radio frequency source 15 is less than 12.8 kW, making the low-frequency radio frequency source have a smaller impact on the temperature of the substrate, enabling the substrate to maintain a low temperature state to continuously maintain the adsorption capacity for the etching gas and the fluorocarbon gas, thereby ensuring a high etching rate.

[0068] Similar to the peak power of the low-frequency RF source 15 and the net power of the low-frequency RF source 15 described above, the average power of the low-frequency RF source 15 is small, and the temperature of the substrate is low, enabling the substrate to continuously maintain the adsorption capacity for the etching gas and the fluorocarbon gas, thereby ensuring a high etching rate.

[0069] In addition to the fact that the low-frequency RF source 15 is likely to affect the temperature of the plasma, the power of the high-frequency RF source 14 is also likely to affect the temperature of the plasma. In order to reduce the influence of the power of the high-frequency RF source 14 on the plasma, the ratio range between the peak power of the low-frequency RF source 15 and the peak power of the high-frequency RF source 14 is 3:1 to 5:1. Specifically, the peak power range of the high-frequency RF source 14 is: 6 kW to 10 kW, that is: the peak power of the high-frequency RF source 14 is also small. Therefore, the high-frequency RF source 14 has a small influence on the temperature of the substrate, enabling the substrate to maintain a low-temperature state to continuously maintain the adsorption capacity for the etching gas and the fluorocarbon gas, thereby ensuring a high etching rate. The working mode of the high-frequency RF source 14 can be pulsed or continuous. In addition, both the net power and the average power of the high-frequency RF source 14 are also low. Since the peak power, net power, and average power of the high-frequency RF source 14 are all low, it is also beneficial to save energy, avoid waste, further reduce the production cost of the enterprise, and improve the product advantage.

[0070] In summary, through the cooperation of the type of etching gas, the flow rate ratio of the etching gas and the fluorocarbon gas, the number of carbon atoms in the fluorocarbon gas of the fluorocarbon gas, the low temperature of the substrate, the peak power of the low-frequency radio frequency source, and the radio frequency of the low-frequency radio frequency source, it is beneficial to quickly form a high aspect ratio structure. The temperature of the substrate is less than 30 °C, that is, the substrate placed on the lower electrode is at a low temperature, and the ultra-high active groups formed by the etching gas and the fluorocarbon gas can be better adsorbed on the surface of the substrate. And the low temperature increases the residence time of these ultra-high active groups on the substrate surface. During the residence time, the ultra-high active groups tend to chemically react and etch with the substrate. The radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz, which is beneficial to increasing the energy of the plasma bombarding the bottom of the high aspect ratio structure and reducing the scattering angle of the plasma. Therefore, it is beneficial to form a high aspect ratio structure. On the contrary, if the radio frequency of the low-frequency radio frequency source is greater than 300 kHz, the energy of the plasma bombarding the bottom of the high aspect ratio structure will be small, and the scattering angle of the plasma will be large, which is not conducive to continuous etching and it is difficult to form a high aspect ratio structure. In addition, the peak power of the low-frequency radio frequency source is less than 30 kW, so that the plasma has a small impact on the temperature of the substrate, enabling the substrate to maintain a low temperature state to continuously maintain the adsorption capacity for the etching gas and the fluorocarbon gas, thereby ensuring a high etching rate. On the contrary, if the peak power of the low-frequency radio frequency source is greater than 30 kW, this will cause the plasma to have a greater impact on the temperature of the substrate, resulting in a higher temperature of the substrate and it is difficult to maintain a low temperature state, which will lead to poor adsorption capacity of the substrate for the etching gas and the fluorocarbon gas, thus making it difficult to ensure the chemical etching effect of the etching gas and the fluorocarbon gas on the substrate.

[0071] In addition, when the peak power and the net power of the low-frequency radio frequency source 15 and the high-frequency radio frequency source 14 of the present invention are both low, the etching of the high aspect ratio structure can be achieved. This not only reduces the requirements for the reaction chamber hardware, but also helps to reduce energy consumption, contributes to enterprises reducing energy costs and obtaining more profits, and can also enhance international competitiveness and strengthen the competitiveness of enterprises in the international market.

[0072] The above Figures 1 to 3 are all described with the reaction chamber being a capacitively coupled plasma etching device. In fact, the reaction chamber can also be an inductively coupled plasma etching device, such as Figure 4 As shown, the inductively coupled plasma etching device is a device that enters the energy of the radio frequency power supply into the interior of the reaction chamber 21 in the form of magnetic field coupling through the inductance coil 26, thereby generating plasma and being used for etching. The reaction chamber includes a reaction chamber side wall. An insulating window 27 is provided above the reaction chamber side wall, and an inductively coupled coil 26 is provided above the insulating window 27. The high-frequency radio frequency source 24 applies a radio frequency voltage to the inductively coupled coil 26 through a radio frequency matching network.

[0073] Inside the reaction chamber 21, a liner 28 is provided to protect the inner wall of the reaction chamber from being corroded by the plasma. An air inlet device 23 is provided at one end of the side wall of the reaction chamber close to the insulating window. In other embodiments, the air inlet device can also be provided in the central area of the insulating window 27. The air inlet device is used to inject reaction gases into the reaction chamber 21. The radio frequency power of the high-frequency radio frequency source 24 drives the inductively coupled coil 26 to generate a strong high-frequency alternating magnetic field, so that the low-pressure reaction gases in the reaction chamber are ionized to generate plasma. A lower electrode 22 is provided at the downstream position of the reaction chamber 21, and the lower electrode is used to carry the substrate W. The plasma is used to process the surface of the substrate to form a concave structure that depresses downward from the surface of the substrate. A low-frequency radio frequency source 25 applies a bias radio frequency voltage to the base through a radio frequency matching network to control the bombardment direction of charged particles in the plasma. An exhaust pump is also provided below the vacuum reaction chamber 200 to discharge reaction by-products from the reaction chamber and maintain the vacuum environment of the reaction chamber.

[0074] When the reaction chamber is an inductively coupled plasma etching device, the type of etching gas, the flow ratio of the etching gas to the fluorocarbon gas, the number of carbon atoms in the fluorocarbon gas, the low temperature of the substrate, the radio frequency of the low-frequency radio frequency source, and the power of the low-frequency radio frequency source are Figure 1 the same as the characteristic parameters corresponding to the embodiment. Through the mutual cooperation among the type of etching gas, the flow ratio of the etching gas to the fluorocarbon gas, the number of carbon atoms in the fluorocarbon gas, the low temperature of the substrate, the radio frequency of the low-frequency radio frequency source, and the power of the low-frequency radio frequency source, it is beneficial to form a high aspect ratio structure that meets the process requirements.

[0075] Correspondingly, the present invention also provides a method for forming a high aspect ratio structure using the above reaction chamber. Please refer to Figure 5 , step S1: Provide a substrate, the substrate is placed on a lower electrode, a mask layer is provided on the surface of the substrate, the mask layer has a mask opening, and the bottom of the mask opening exposes the top surface of the substrate; step S2: Introduce an etching gas and a fluorocarbon gas, the flow ratio of the etching gas to the fluorocarbon gas is greater than 9:1, the etching gas and the fluorocarbon gas are excited by a high-frequency radio frequency source to form plasma, and the plasma processes the substrate under the action of a low-frequency radio frequency source to form a high aspect ratio structure in the substrate; the etching gas includes hydrogen halide gas and gases that can generate hydrogen halide, and the number of carbon atoms in the fluorocarbon gas is less than or equal to 3; during the process of etching the substrate, the temperature of the lower electrode is less than -30°C or the temperature of the substrate is less than 30°C, and the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz.

[0076] During the etching process, when the high aspect ratio structure initially has a first depth, the aspect ratio of the high aspect ratio structure is not large at this time. Since the carbon fluoride polymer at the bottom of the high aspect ratio structure is relatively easy to remove, therefore, when the lower electrode has a first temperature, the substrate can continue to be etched; as the etching progresses, the high aspect ratio structure has a second depth. At this time, the generated carbon fluoride polymer is likely to accumulate at the bottom of the high aspect ratio structure and is difficult to remove. In order to be able to remove these carbon fluoride polymers, one solution is to increase the temperature of the lower electrode, that is: when the high aspect ratio structure has a second depth, the lower electrode has a second temperature, and the second temperature is greater than the first temperature.

[0077] Another solution is to increase the peak power of the low-frequency radio frequency source. Specifically, when forming a high aspect ratio structure with a first depth, the low-frequency radio frequency source has a first peak power; when forming a high aspect ratio structure with a second depth, the low-frequency radio frequency source has a second peak power. The second depth is greater than the first depth, and the second peak power is higher than the first peak power.

[0078] Correspondingly, the present invention also provides a high aspect ratio structure formed by using the above method. Please refer to Figure 6 , the high aspect ratio structure includes: a substrate 300, a mask layer 301 is provided on the surface of the substrate 300, the mask layer 301 has a mask opening 302, and the bottom of the mask opening 302 exposes the top surface of the substrate 300; a high aspect ratio structure 303 is provided in the substrate 300. The high aspect ratio structure is a concave structure that is recessed downward from the substrate surface, and the aspect ratio of the high aspect ratio structure 303 is greater than 70:1.

[0079] Regarding whether the high aspect ratio structure 303 meets the process requirements, it needs to be characterized and verified from multiple perspectives. One dimensional characterization method is the perpendicularity of the high aspect ratio structure 303. The perpendicularity refers to the ratio of the minimum dimension to the maximum dimension of the high aspect ratio structure along the depth direction of the high aspect ratio structure. In one embodiment, the perpendicularity of the high aspect ratio structure 303 is greater than 80%. The perpendicularity of the high aspect ratio structure 303 being greater than 80% indicates that the difference between the minimum dimension and the maximum dimension of the high aspect ratio structure is relatively small, that is: during the high aspect ratio process, there is no serious bottom necking phenomenon, and the morphology of the formed high aspect ratio structure is good.

[0080] Another characterization method is: calculate the difference between the maximum width dimension and the minimum width dimension of the high aspect ratio structure 302. In one embodiment, the difference between the maximum width and the minimum width of the high aspect ratio structure is less than 30 nm. The difference between the maximum width and the minimum width of the high aspect ratio structure is relatively small, indicating that during the high aspect ratio process, there is no serious bottom necking phenomenon, and the morphology of the formed high aspect ratio structure is good.

[0081] The high aspect ratio structure may be a high aspect ratio hole or a high aspect ratio groove, which is not limited herein.

[0082] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be construed as a limitation of the present invention. After those skilled in the art have read the above content, various modifications and alternatives to the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A reaction chamber for etching a high aspect ratio structure, wherein the high aspect ratio structure is a concave structure concave downward from a substrate surface, characterized in that: include: A lower electrode is disposed in the reaction chamber, and the lower electrode is used to support the substrate; at least one high frequency radio frequency source, applied to the lower electrode to form and maintain a plasma in the reaction chamber; at least one low frequency radio frequency source applied to the lower electrode; During the etching of the substrate, the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz; A gas inlet device, used for delivering etching gas and carbon fluorine gas into the reaction chamber, wherein the etching gas includes hydrogen halide gas and gas capable of generating hydrogen halide; The number of carbon atoms in the carbon fluorine gas is less than or equal to 3, and the flow ratio of the etching gas to the carbon fluorine gas is greater than 9:1; The substrate is etched by the reaction chamber to form the recessed structure in the substrate, wherein the temperature of the substrate is less than 30° C. during the etching process; After etching, the depth-to-width ratio of the recessed structure is greater than 70:

1.

2. The reaction chamber according to claim 1, characterized in that: The peak power of the low-frequency radio frequency source is less than 30 kW.

3. The reaction chamber according to claim 1, characterized in that: The net power of the low-frequency radio frequency source is less than 12.8kw.

4. The reaction chamber according to claim 1, characterized in that: The ratio of the peak power of the low-frequency radio frequency source to the peak power of the high-frequency radio frequency source is in the range of 3:1 to 5:

1.

5. The reaction chamber according to claim 4, characterized in that: The peak power of the high-frequency radio frequency source is less than 10 kW.

6. The reaction chamber according to claim 1, characterized in that: The average power of the low-frequency radio frequency source is less than 10 kW.

7. The reaction chamber according to claim 1, characterized in that: The radio frequency of the high-frequency radio frequency source is 100 times higher than the radio frequency of the low-frequency radio frequency source.

8. The reaction chamber according to claim 1, characterized in that: The radio frequency of the low-frequency radio frequency source is greater than 10 kHz and less than or equal to 300 kHz.

9. The reaction chamber according to claim 1, characterized in that: The radio frequency of the high-frequency radio frequency source is greater than or equal to 40M and less than or equal to 120M.

10. The reaction chamber according to claim 1, characterized in that: The base plate comprises a substrate and a layer to be etched located above the substrate, and the material of the layer to be etched is an alternating stack of any two of SiO2, SiN and polysilicon.

11. The reaction chamber according to claim 10, characterized in that: The hydrogen halide gas includes at least one of hydrogen fluoride, hydrogen chloride, hydrogen bromide and hydrogen iodide.

12. The reaction chamber according to claim 11, characterized in that: Gases capable of producing hydrogen fluoride include: a hydrogen source and a fluorine source; gases capable of producing hydrogen chloride include: a hydrogen source and a chlorine source; gases capable of producing hydrogen bromide include: a hydrogen source and a bromine source; gases capable of producing hydrogen iodide include: a hydrogen source and an iodine source; the hydrogen source includes: at least one of H2, CH4, CH3F, CH2F2, C2H2F2, C2HF5, C3HF5, C3H2F6, C3H2F4 and C4H2F6; the fluorine source includes: at least one of NF3, CF4, SF6, CHF3, F2, ClF3, CF3I, C2F6, C2HF5 and C3H2F6; the chlorine source includes: at least one of Cl2, HCl, ClF3 and CH2Cl2; the bromine source includes: HBr, Br2, BrF3, CBr2F2, CF x Br y , PBr3 and PBr5; the iodine source includes: at least one of CF3I, HI, I2, PI3, IF5, IF7, C2F5I and C3F7I.

13. The reaction chamber according to claim 1, characterized in that: The carbon fluorine gas includes at least one of CH3F, C2H2F2, C3HF5 and CF4.

14. The reaction chamber according to claim 13, characterized in that: The gas delivered into the reaction chamber by the gas intake device further includes at least one of PF3, O2, H2, NF3, WF6, Ar, He, BF3, BCL3 and Cl2.

15. The reaction chamber according to claim 1, characterized in that: The high-frequency radio frequency source and / or the low-frequency radio frequency source are pulsed.

16. The reaction chamber according to claim 15, characterized in that: The pulse duty cycle is less than 50%.

17. The reaction chamber according to claim 1, characterized in that: The high-frequency radio frequency source and / or the low-frequency radio frequency source are continuous.

18. The reaction chamber according to claim 1, characterized in that: The radio frequency of the low-frequency radio frequency source is one of 100 kHz, 200 kHz and 300 kHz.

19. A reaction chamber for etching a high aspect ratio structure, wherein the high aspect ratio structure is a concave structure concave downward from a substrate surface, characterized in that: include: A lower electrode is disposed in the reaction chamber, and the lower electrode is used to support the substrate; at least one high frequency radio frequency source, applied to the reaction chamber to form and maintain a plasma in the reaction chamber; at least one low frequency radio frequency source applied to the lower electrode; During the etching of the substrate, the radio frequency of the low-frequency radio frequency source is less than or equal to 300 kHz; A gas inlet device, used for delivering etching gas and carbon fluorine gas into the reaction chamber, wherein the etching gas includes hydrogen halide gas and gas capable of generating hydrogen halide; The number of carbon atoms in the carbon fluorine gas is less than or equal to 3, and the flow ratio of the etching gas to the carbon fluorine gas is greater than 9:1; The substrate is etched by the reaction chamber to form the recessed structure in the substrate, wherein the temperature of the lower electrode is less than -30°C during the etching process; After etching, the depth-to-width ratio of the recessed structure is greater than 70:

1.

20. The reaction chamber according to claim 19, characterized in that: The temperature of the lower electrode is: -130°C~-30°C.

21. The reaction chamber according to claim 19, characterized in that: The peak power of the low-frequency radio frequency source is less than 30 kW.

22. The reaction chamber according to claim 19, characterized in that: The net power of the low-frequency radio frequency source is less than 12.8kw.

23. The reaction chamber according to claim 19, characterized in that: The average power of the low-frequency radio frequency source is less than 10 kW.

24. The reaction chamber according to claim 19, characterized in that: The high-frequency radio frequency source and / or the low-frequency radio frequency source are continuous.

25. The reaction chamber according to claim 19, characterized in that: The radio frequency of the low-frequency radio frequency source is one of 100 kHz, 200 kHz and 300 kHz.

26. A method for forming a high aspect ratio structure using the reaction chamber according to any one of claims 1 to 25, characterized in that: include: Providing a substrate, the substrate is placed on a lower electrode, a mask layer is provided on the surface of the substrate, the mask layer has a mask opening, and the bottom of the mask opening exposes the top surface of the substrate; Passing etching gas and carbon fluorine gas, wherein the flow ratio of the etching gas to the carbon fluorine gas is greater than 9:1, the etching gas and the carbon fluorine gas are excited by a high-frequency radio frequency source to form plasma, and the plasma processes the substrate under the action of a low-frequency radio frequency source to form a high aspect ratio structure in the substrate; The etching gas includes hydrogen halide gas and gas capable of generating hydrogen halide, and the number of carbon atoms in the carbon fluorine gas is less than or equal to 3; During the etching process of the substrate, the temperature of the lower electrode is less than -30°C or the temperature of the substrate is less than 30°C, and the radio frequency of the low-frequency radio frequency source is less than or equal to 300kHz.

27. The method for forming a high aspect ratio structure according to claim 26, wherein: Also includes: When forming a high aspect ratio structure having a first depth, the lower electrode has a first temperature; When forming a high aspect ratio structure with a second depth, the lower electrode has a second temperature, the second depth is greater than the first depth, and the second temperature is higher than the first temperature.

28. The method for forming a high aspect ratio structure according to claim 26, wherein: Also includes: When forming a high aspect ratio structure having a first depth, the low frequency RF source has a first peak power; When forming a high aspect ratio structure with a second depth, the low-frequency RF source has a second peak power, the second depth is greater than the first depth, and the second peak power is higher than the first peak power.

29. A high aspect ratio structure formed by the method according to any one of claims 26 to 28, characterized in that: include: A substrate, a surface of the substrate is provided with a mask layer, the mask layer has a mask opening, and the bottom of the mask opening exposes the top surface of the substrate; A high aspect ratio structure is arranged in the substrate. The high aspect ratio structure is a concave structure that is concave downward from the surface of the substrate. The aspect ratio of the concave structure is greater than 70:1, and the verticality of the concave structure is greater than 70%.

30. The high aspect ratio structure according to claim 29, wherein: Along the depth direction of the high aspect ratio structure, the difference between the maximum width and the minimum width of the high aspect ratio structure is less than 30 nm.

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