Thermal atomic layer etching method
Patent Information
- Application Number
- CN202510551175.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-28
- Publication Date
- 2026-10-30
AI Technical Summary
但是，目前等离子体原子层刻蚀(Plasma Enhanced Atomic Layer Etching,PE-ALE)由于其各向异性的刻蚀特点，难以满足三维半导体器件的横向刻蚀需求
[0030]与现有技术相比，本发明提供的热型原子层刻蚀方法借助活性气体的吸附与解离循环蚀刻机制，能够实现对晶圆顶部单个原子层的精准化学修饰与去除，确保在刻蚀过程中维持优良的表面粗糙度与陡直度，显著降低对衬底表面的潜在损伤，具备各向同性的刻蚀特点，能够满足横向刻蚀需求，并且本发明提供的热型原子层刻蚀方法是在原子层沉积设备上实现的，通过直接利用原子层沉积设备有效满足了热型原子层刻蚀过程中严苛的反应条件。
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Figure CN123005347A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor device technology, and in particular to a thermal atomic layer etching method. Background Technology
[0002] As the functionality of microelectronic devices continues to shrink to below 10nm, and as more and more new devices adopt three-dimensional structures, the demand for higher etching precision and lateral etching is also increasing. However, the current Plasma Enhanced Atomic Layer Etching (PE-ALE) method, due to its anisotropic etching characteristics, is difficult to meet the lateral etching requirements of three-dimensional semiconductor devices.
[0003] Therefore, how to meet the lateral etching requirements of three-dimensional semiconductor devices is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention
[0004] The purpose of this invention is to provide a thermal atomic layer etching method to meet the lateral etching requirements of three-dimensional semiconductor devices.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] A thermal atomic layer etching method, employing an atomic layer deposition apparatus, the thermal atomic layer etching method comprising:
[0007] S100, a semiconductor substrate is provided, the semiconductor substrate having two opposing sides;
[0008] S200, a mask is deposited on a portion of at least one side of the semiconductor substrate using the atomic layer deposition apparatus, so that an etched area is formed on the portion of the semiconductor substrate not covered by the mask;
[0009] S300, the semiconductor substrate is placed in the vacuum environment of the atomic layer deposition equipment and heated to a preset temperature;
[0010] S400, the semiconductor substrate is oxidized to form a silicon oxide layer on the surface of the etched area;
[0011] S500, trimethylaluminum is introduced into the atomic layer deposition apparatus, so that the trimethylaluminum reacts with the silicon oxide layer to form an aluminum oxide layer;
[0012] S600, a hydrofluoric acid-pyridine mixture is introduced into the atomic layer deposition apparatus, such that the hydrofluoric acid-pyridine mixture reacts with the alumina layer to form an aluminum fluoride layer;
[0013] S700, trimethylaluminum is introduced into the atomic layer deposition apparatus, causing the trimethylaluminum to react with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride, thereby removing the aluminum fluoride layer and forming an etched pattern on the surface of the semiconductor substrate.
[0014] Optionally, in the above-described thermal atomic layer etching method, trimethylaluminum is introduced into the atomic layer deposition apparatus so that the trimethylaluminum reacts with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride, and the method further includes: allowing the trimethylaluminum to continue reacting with the silicon oxide layer that was not completely reacted in step S500 to form an aluminum oxide layer;
[0015] After step S700, steps S400, S600, and S700 are repeated cyclically until the etched pattern reaches the predetermined etch depth.
[0016] Optionally, in the above-described thermal atomic layer etching method, the oxidation treatment of the semiconductor substrate includes:
[0017] Oxygen is introduced into the atomic layer deposition apparatus to oxidize the etched area, wherein the pressure of the introduced oxygen is 240 torr-260 torr, and the oxidation reaction time between the etched area and the oxygen is 5s-15s.
[0018] Optionally, in the above-described thermal atomic layer etching method, the pressure of the hydrofluoric acid-pyridine mixture introduced into the atomic layer deposition equipment is 0.5 torr-2 torr, and the reaction time between the hydrofluoric acid-pyridine mixture and the alumina layer is 2s-8s.
[0019] Optionally, in the above-described thermal atomic layer etching method, the pressure of the trimethylaluminum gas introduced into the atomic layer deposition equipment is 0.5 torr-5 torr, and the reaction time of the trimethylaluminum with the silicon oxide layer and the reaction time of the trimethylaluminum with the aluminum fluoride layer are both 2s-8s.
[0020] Optionally, in the above-described thermal atomic layer etching method, after the silicon oxide layer is formed on the surface of the etched area and before the trimethylaluminum is introduced into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove the residual oxygen.
[0021] And / or, after the formation of the alumina layer and before the introduction of the hydrofluoric acid-pyridine mixture into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove any residual trimethylaluminum;
[0022] And / or, after the formation of the aluminum fluoride layer and before the introduction of the trimethylaluminum into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove any residual hydrofluoric acid-pyridine mixture.
[0023] Optionally, in the above-described thermal atomic layer etching method, the flow rate of the purge gas introduced into the atomic layer deposition equipment is 20 sccm-100 sccm, and the time for introducing the purge gas is 10 s-60 s.
[0024] Optionally, in the above-described thermal atomic layer etching method, a mask is deposited on a portion of at least one side of the semiconductor substrate using the atomic layer deposition apparatus to form an etchable region on the portion of the semiconductor substrate not covered by the mask, including:
[0025] A metal mask is deposited on at least one side of the semiconductor substrate, the metal mask having a covered area and a cutout area;
[0026] Physical vapor deposition of a mask material is performed on one side of the semiconductor substrate on which the metal mask is deposited using the atomic layer deposition equipment. The mask material covers the covered area and the cut-out area of the metal mask.
[0027] The metal mask is removed, so that the mask material remaining on the surface of the semiconductor substrate corresponding to the cutout area forms a mask, and the part of the semiconductor substrate not covered by the mask forms the etched area.
[0028] Optionally, in the above-described thermal atomic layer etching method, before depositing a metal mask on at least one side of the semiconductor substrate, the thermal atomic layer etching method further includes: cleaning the surface of the semiconductor substrate with a cleaning solution to remove the natural oxide layer on the surface of the semiconductor substrate.
[0029] Optionally, in the above-described thermal atomic layer etching method, the preset temperature range is 285°C to 300°C.
[0030] Compared with existing technologies, the thermal atomic layer etching method provided by this invention utilizes the adsorption and dissociation cyclic etching mechanism of active gases to achieve precise chemical modification and removal of a single atomic layer on the top of the wafer. This ensures excellent surface roughness and steepness during the etching process, significantly reduces potential damage to the substrate surface, and possesses isotropic etching characteristics, meeting the requirements of lateral etching. Furthermore, the thermal atomic layer etching method provided by this invention is implemented on an atomic layer deposition equipment, effectively meeting the stringent reaction conditions during the thermal atomic layer etching process by directly utilizing the atomic layer deposition equipment. Attached Figure Description
[0031] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:
[0032] Figure 1 This is a schematic flowchart of the thermal atomic layer etching method disclosed in an embodiment of the present invention. Detailed Implementation
[0033] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.
[0034] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.
[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.
[0036] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.
[0038] The core of this invention is to provide a thermal atomic layer etching method to meet the lateral etching requirements of three-dimensional semiconductor devices.
[0039] like Figure 1 As shown, this embodiment of the invention discloses a thermal atomic layer etching method that employs an atomic layer deposition device to perform etching. The thermal atomic layer etching method disclosed in this embodiment of the invention includes:
[0040] Step S100: Provide a semiconductor substrate, the semiconductor substrate having two opposing sides;
[0041] The size of the semiconductor substrate can be adjusted according to actual needs. The double-sided polishing of the semiconductor substrate reduces roughness and needs to be kept clean to prepare for subsequent processes such as coating, ensuring that the subsequent processes have high forming quality.
[0042] Step S200: A mask is deposited on a portion of at least one side of the semiconductor substrate using an atomic layer deposition apparatus, so that an etched area is formed on the portion of the semiconductor substrate not covered by the mask;
[0043] A semiconductor substrate is placed in an atomic layer deposition apparatus, and a mask is deposited on a portion of one side of the semiconductor substrate. The mask protects the covered surface from being etched during subsequent etching processes, while the portion of the surface not covered by the mask is etched in subsequent etching processes, forming etched areas on the surface of the semiconductor substrate, thus creating the pattern required by the design on the surface of the semiconductor substrate.
[0044] Step S300: Place the semiconductor substrate in the vacuum environment of the atomic layer deposition equipment and heat it to a preset temperature;
[0045] After the semiconductor substrate surface is coated with a mask, the masked semiconductor substrate is placed in the reaction vacuum chamber of the atomic layer deposition equipment. The reaction vacuum chamber is then evacuated to place the semiconductor substrate in a vacuum environment, preventing air from interfering with the subsequent introduction of reaction gases and preventing contamination from dust or other particles in the air. Simultaneously, the vacuum system allows for precise regulation of the gas pressure within the reaction chamber, ensuring good etching rate and uniformity, and improving etching quality. After evacuation, the reaction vacuum chamber is heated using a heating device to adjust the temperature within the chamber to the preset temperature required for the etching process. The specific preset temperature range is 285℃ to 300℃ to ensure proper operation of the etching reaction within the reaction vacuum chamber. Of course, those skilled in the art will understand that the preset temperature can be adjusted accordingly based on actual etching requirements.
[0046] Step S400: Oxidize the semiconductor substrate to form a silicon oxide layer on the surface of the etched area;
[0047] After the vacuuming and temperature adjustment, the delivery system in the equipment is started to deliver the oxidant to the atomic layer deposition equipment. The etched areas of the semiconductor substrate not covered by the mask react with the oxidant, and a silicon oxide layer is formed on the surface of the etched area. The surface of the silicon oxide layer covered by the mask is blocked from the oxidant and does not react with the oxidant.
[0048] Step S500: Trimethylaluminum is introduced into the atomic layer deposition apparatus to react with the silicon oxide layer to form an aluminum oxide layer;
[0049] After the semiconductor substrate undergoes oxidation treatment and a silicon oxide layer is formed in the etched area of the semiconductor substrate, the control delivery system transports trimethylaluminum to the reaction chamber. Trimethylaluminum reacts with the silicon oxide layer in the following reaction formula: SiO2 + 4Al(CH3)3 → 2Al2O3 + 3Si(CH4)3. An aluminum oxide layer is generated on the surface of the etched area of the semiconductor substrate, along with the byproduct tetramethylsilane.
[0050] Step S600: A hydrofluoric acid-pyridine mixture is introduced into the atomic layer deposition equipment, so that the hydrofluoric acid-pyridine mixture reacts with the alumina layer to form an aluminum fluoride layer;
[0051] After the alumina layer is formed on the semiconductor substrate, a hydrofluoric acid-pyridine mixture can be introduced into the reaction chamber. The hydrofluoric acid in the hydrofluoric acid-pyridine mixture reacts with the alumina layer in the form of Al2O3 + 6HF → 2AlF3 + 3H2O, thereby generating an aluminum fluoride layer on the surface of the etched area of the semiconductor substrate.
[0052] Step S700: Trimethylaluminum is introduced into the atomic layer deposition equipment, so that trimethylaluminum reacts with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride, thereby removing the aluminum fluoride layer and forming an etch pattern on the surface of the semiconductor substrate.
[0053] After an aluminum fluoride layer is formed on the surface of the semiconductor substrate, trimethylaluminum is introduced into the atomic layer deposition equipment again. The trimethylaluminum reacts with the aluminum fluoride layer in the form of 2AlF3 + 4Al(CH3)3 → 6AlF(CH3)2, producing dimethylaluminum fluoride. The dimethylaluminum fluoride is removed from the surface of the semiconductor substrate in liquid state, and then the aluminum fluoride layer on the semiconductor substrate is removed. At this time, the surface of the etched area is etched with grooves, realizing the formation of the etched pattern.
[0054] The thermal atomic layer etching method provided in this embodiment not only significantly reduces potential damage to the substrate surface and has isotropic etching characteristics, which can meet the requirements of lateral etching, but also directly utilizes atomic layer deposition equipment to effectively meet the stringent reaction conditions in the thermal atomic layer etching process, realizing a higher precision three-dimensional etching process, such as etching of gate-around transistors and three-dimensional flash memory, and is also applicable to etching substrate materials such as silicon, silicon dioxide or silicon germanium.
[0055] In one specific embodiment, in step S500, trimethylaluminum is introduced into the atomic layer deposition equipment. During the reaction between trimethylaluminum and the silicon oxide layer on the semiconductor substrate, not all of the silicon oxide layer participates in the reaction to form an aluminum oxide layer; some silicon oxide remains on the semiconductor substrate. Therefore, after trimethylaluminum is introduced again in step S700, it not only reacts with the aluminum fluoride layer on the semiconductor substrate to form dimethylaluminum fluoride, but also reacts with the remaining silicon dioxide on the semiconductor substrate to form an aluminum oxide layer. At this point, the semiconductor substrate has both a silicon oxide layer and an aluminum oxide layer, with the silicon oxide layer located between the aluminum oxide layer and the semiconductor substrate. When it is necessary to etch the pattern to a predetermined etching depth to meet design requirements, oxygen is introduced into the equipment again, i.e., step S400 is repeated. Because the remaining silicon dioxide layer on the semiconductor substrate and The alumina layers are relatively thin, allowing oxygen in the reaction chamber to permeate through the silicon dioxide and alumina layers and react with silicon to generate more silicon dioxide. This results in a thicker silicon dioxide layer on the semiconductor substrate. Since the semiconductor substrate has an alumina layer, step S500 can be omitted, and the process can proceed directly to step S600, where a hydrofluoric acid-pyridine mixture is introduced into the reaction chamber. This allows the hydrofluoric acid to react with the alumina layer to generate an aluminum fluoride layer. Then, step S700 involves introducing trimethylaluminum, which reacts with the aluminum fluoride layer to generate dimethylaluminum fluoride. Simultaneously, trimethylaluminum reacts with silicon dioxide to generate more alumina. Since step S700 includes the reaction in step S500, step S500 can be omitted. The subsequent cyclic steps are steps S400, S600, and S700, respectively, until the etched pattern reaches the predetermined etching depth.
[0056] In some embodiments, the oxidation treatment of the etched area in the semiconductor substrate in step S400 specifically includes the following steps: introducing oxygen into the atomic layer deposition equipment to oxidize silicon. When oxygen is introduced, the oxidation reaction is Si + O2 → SiO2, and the oxygen pressure is 240 torr-260 torr. For example, the pressure can be set to 240 torr, 245 torr, 250 torr or 260 torr, so that oxygen can penetrate into the single crystal silicon layer better, ensuring the balanced reaction rate and uniformity of the oxidation reaction. When the pressure is less than this range, the oxygen penetration effect is poor, and when the pressure is greater than this range, it may affect the oxidation reaction rate. The oxidation reaction time between the etched area and oxygen is controlled at 5s-15s to ensure that silicon and oxygen have sufficient reaction time and the oxidation reaction proceeds smoothly.
[0057] In the thermal atomic layer etching method provided in this embodiment, the pressure of the hydrofluoric acid-pyridine mixture introduced into the atomic layer deposition equipment in step S600 is 0.5 torr-2 torr. The specific pressure can be set to 0.5 torr, 1 torr, 1.5 torr, or 2 torr. The reaction chamber is in a low-pressure environment to ensure the uniformity of the gas phase reaction. Of course, it is understandable that when etching semiconductor substrates of different materials, the pressure should be adjusted accordingly according to the actual needs. The reaction time between the hydrofluoric acid-pyridine mixture and the alumina layer is 2s-8s, which provides a good reaction time for the hydrofluoric acid-pyridine mixture and the alumina layer. By controlling the time, the etching depth can be controlled. Appropriately extending the time can result in a deeper etching depth. In addition, the hydrofluoric acid in the hydrofluoric acid-pyridine mixture accounts for 70% of the mixture, which not only ensures a high etching rate but also improves the stability of gas phase transport, which is beneficial to enhancing process stability and ensuring good process safety, thus improving the protection and safety of the workers.
[0058] In a specific embodiment, the pressure of trimethylaluminum introduced into the atomic layer deposition equipment is 0.5 torr-5 torr, specifically 0.5 torr, 1 torr, 3 torr, or 5 torr. The pressure can be adjusted according to actual needs. The reaction chamber in the atomic layer deposition equipment is in a suitable pressure state, which is suitable for surface reaction control, reduces gas phase side reactions, and improves precursor coverage efficiency. At the same time, the reaction time of trimethylaluminum with the silicon oxide layer and the reaction time of trimethylaluminum with the aluminum fluoride layer can be carried out in one step. The reaction time can be controlled between 2s and 8s to ensure that the reaction sites are fully saturated and to avoid the problem of oversaturation adsorption due to excessive time.
[0059] The thermal atomic layer etching method provided in this embodiment further includes the step of introducing purge gas into the atomic layer deposition equipment. After each step of the reaction is completed, to prevent residual gas from the previous step from interfering with or affecting the reaction in the next step, a purging process is also included. Specifically, after the surface of the etched area reacts with oxygen to form a silicon oxide layer, and before introducing trimethylaluminum into the atomic layer deposition equipment, purge gas is introduced to remove residual oxygen; after forming an aluminum oxide layer, and before introducing a hydrofluoric acid-pyridine mixture into the atomic layer deposition equipment, purge gas is introduced again to remove residual trimethylaluminum; similarly, after forming an aluminum fluoride layer, and before introducing trimethylaluminum into the atomic layer deposition equipment, purge gas is introduced to remove residual hydrofluoric acid-pyridine mixture, thereby ensuring that each reaction proceeds efficiently and smoothly, improving reaction quality and efficiency. Alternatively, the purging step can be set after the reaction of any one or two steps is completed, and then the purging gas is introduced into the atomic layer deposition equipment for purging. Of course, it is understood that it is preferable to perform purging after each step is completed, so that the residual gas can be removed in time and the purging effect is better.
[0060] Specifically, during the process of purging residual gases into the atomic layer deposition equipment, the purge gas flow rate is 20 sccm-100 sccm. The flow rate can be set to 20 sccm, 50 sccm, 70 sccm, or 100 sccm, depending on the volume of the reaction chamber to ensure purging efficiency. The purge gas introduction time can be controlled between 10 s and 60 s, adjusted according to factors such as reaction complexity, chamber size, and purge flow rate. For simple reactions, small chambers, or high purge flow rates, the purge time can be set to 10 s-30 s. For complex precursors, larger chambers, and lower purge flow rates, the purge time can be set to 30 s-60 s. After purging, it can be further verified whether the residual gases in the chamber have been completely purged. Additionally, inert gases such as nitrogen or argon can be used as the purge gas to avoid chemical reactions between the purge gas and the residual gases or semiconductor substrate.
[0061] In some embodiments, step S200, which involves depositing a mask on a portion of at least one side of the semiconductor substrate using an atomic layer deposition apparatus, to form an etchable region on the portion of the semiconductor substrate not covered by the mask, specifically includes the following steps:
[0062] Step S201: A metal mask is deposited on at least one side of a semiconductor substrate. The metal mask has a covered area and a cutout area.
[0063] A metal photomask is fabricated, the specific dimensions of which can be designed according to the size of the semiconductor substrate. The metal photomask has through holes that penetrate both sides, so that the metal photomask has a covered area and a cutout area. Then the metal photomask is placed on one side of the semiconductor substrate. Part of the surface of the semiconductor substrate is covered by the covered area of the metal photomask, while the other part of the surface of the semiconductor substrate is exposed through the cutout area of the metal photomask.
[0064] Step S202: Physical vapor deposition of mask material is performed on one side of the semiconductor substrate on which the metal mask is deposited using an atomic layer deposition device. The mask material covers the covered area and the cut-out area of the metal mask.
[0065] A semiconductor substrate with a metal mask is placed in an atomic layer deposition apparatus. A mask material is deposited on the side of the substrate covered by the metal mask using physical vapor deposition. The mask material directly covers the surface of the semiconductor substrate through the cutout area of the metal mask, while the covered area of the metal mask isolates the deposited mask material from the rest of the semiconductor substrate surface.
[0066] Step S203: Remove the metal mask, so that the mask material remaining on the surface of the corresponding cutout area of the semiconductor substrate forms a mask, and the part of the semiconductor substrate not covered by the mask forms an etched area.
[0067] After the mask material is deposited and stabilized using physical vapor deposition, the semiconductor substrate is removed from the atomic layer deposition equipment, and then the metal mask on the semiconductor substrate is removed. At this point, the mask material on the surface of the semiconductor substrate corresponding to the cutout area forms a mask, while the part of the semiconductor substrate not covered by the mask forms an etched area.
[0068] In addition, before laying the metal mask on the surface of the semiconductor substrate, the surface of the semiconductor substrate is cleaned with a cleaning solution to remove the natural oxide layer on the surface of the semiconductor substrate. This ensures that the single crystal silicon layer of the semiconductor substrate is not blocked by the natural oxide layer, so that the oxidation reaction of the subsequent etching process can run efficiently and also helps to improve the quality of the etching process. The cleaning solution can be a 5% hydrofluoric acid solution to clean the surface of the semiconductor substrate and remove the natural oxide layer on the surface of the semiconductor substrate.
[0069] In one specific embodiment, the mask material can be made of metal materials such as platinum or gold. It should be noted that the material used to make the mask needs to be resistant to hydrofluoric acid corrosion, so as to avoid the hydrofluoric acid reacting with the mask and destroying the integrity of the mask structure during the reaction of the hydrofluoric acid-pyridine mixture with the alumina layer.
[0070] In a specific embodiment, the etching steps using the thermal atomic layer etching method provided in this embodiment on a silicon-germanium substrate in an atomic layer deposition apparatus are as follows:
[0071] The first step is to provide a silicon-germanium substrate having two opposing sides;
[0072] The second step involves depositing a mask on at least one side of a silicon-germanium substrate using an atomic layer deposition (ALD) apparatus. This creates etchable areas on the unmasked portions of the silicon-germanium substrate. Before depositing the mask, the substrate surface is cleaned with a 5% hydrofluoric acid solution to remove the natural oxide layer. A metal mask with covered and cutout areas is then fabricated and placed over one side of the silicon-germanium substrate. The substrate with the metal mask is then placed in an ALD apparatus, and a platinum mask is deposited on the side covered by the metal mask using physical vapor deposition (PVD) to form a platinum mask.
[0073] The third step involves placing the silicon-germanium substrate in the vacuum environment of the atomic layer deposition equipment and heating the reaction chamber to a preset temperature of 295°C.
[0074] The fourth step is to open the oxygen valve and introduce oxygen into the atomic layer deposition equipment after the environment in the reaction chamber has stabilized. After the oxygen pressure reaches 250 torr, the valve is closed to stop the gas supply. The oxygen reacts with the etched area for 2 seconds, and a silicon dioxide layer is formed on the surface of the silicon-germanium substrate.
[0075] Fifth step: After the oxidation reaction is complete, nitrogen gas is introduced into the atomic layer deposition equipment for purging. The flow rate of nitrogen gas is 80 sccm and the purging time is 40 s. After the purging is completed, the vacuum system is started to evacuate the reaction chamber.
[0076] Step 6: Open the trimethylaluminum valve to introduce trimethylaluminum into the atomic layer deposition equipment. After the pressure of the introduced trimethylaluminum is 1 torr, close the gas valve to stop the gas supply. The reaction time of trimethylaluminum with the silicon oxide layer is 0.4s, and an aluminum oxide layer is generated.
[0077] Step 7: After the reaction is complete, nitrogen gas is introduced into the atomic layer deposition equipment for purging. The flow rate of nitrogen gas is 80 sccm and the purging time is 40 s. After the purging is completed, the vacuum system is started to evacuate the reaction chamber.
[0078] Step 8: Open the delivery valve of the hydrofluoric acid-pyridine mixture and introduce the hydrofluoric acid-pyridine mixture into the reaction chamber of the atomic layer deposition equipment. After the pressure of the hydrofluoric acid-pyridine mixture is 1 torr, close the gas valve to stop the gas supply. The hydrofluoric acid in the hydrofluoric acid-pyridine mixture reacts with the alumina layer for 5 seconds to generate an aluminum fluoride layer. The hydrofluoric acid content of the hydrofluoric acid-pyridine mixture is 70%.
[0079] Step 9: After the reaction is complete, nitrogen gas is introduced into the atomic layer deposition equipment for purging. The flow rate of nitrogen gas is 80 sccm and the purging time is 40 s. After the purging is completed, the vacuum system is started to evacuate the reaction chamber.
[0080] Step 10: Open the trimethylaluminum valve to introduce trimethylaluminum into the atomic layer deposition equipment. After the pressure of the introduced trimethylaluminum is 1 torr, close the gas valve to stop the gas supply. The trimethylaluminum reacts with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride. The reaction time is 0.4s.
[0081] Finally, repeat steps four, eight, and ten until the etched pattern reaches the predetermined etch depth.
[0082] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.
[0083] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A thermal atomic layer etching method, characterized in that, The thermal atomic layer etching method, employing atomic layer deposition equipment, includes: S100, a semiconductor substrate is provided, the semiconductor substrate having two opposing sides; S200, a mask is deposited on a portion of at least one side of the semiconductor substrate using the atomic layer deposition apparatus, so that an etched area is formed on the portion of the semiconductor substrate not covered by the mask; S300, the semiconductor substrate is placed in the vacuum environment of the atomic layer deposition equipment and heated to a preset temperature; S400, the semiconductor substrate is oxidized to form a silicon oxide layer on the surface of the etched area; S500, trimethylaluminum is introduced into the atomic layer deposition apparatus, so that the trimethylaluminum reacts with the silicon oxide layer to form an aluminum oxide layer; S600, a hydrofluoric acid-pyridine mixture is introduced into the atomic layer deposition apparatus, such that the hydrofluoric acid-pyridine mixture reacts with the alumina layer to form an aluminum fluoride layer; S700, trimethylaluminum is introduced into the atomic layer deposition apparatus, causing the trimethylaluminum to react with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride, thereby removing the aluminum fluoride layer and forming an etched pattern on the surface of the semiconductor substrate.
2. The thermal atomic layer etching method according to claim 1, characterized in that, The process of introducing trimethylaluminum into the atomic layer deposition apparatus, causing the trimethylaluminum to react with the aluminum fluoride layer to form gaseous dimethylaluminum fluoride, further includes: causing the trimethylaluminum to continue reacting with the silicon oxide layer that was not completely reacted in step S500 to form an aluminum oxide layer; After step S700, steps S400, S600, and S700 are repeated cyclically until the etched pattern reaches the predetermined etch depth.
3. The thermal atomic layer etching method according to claim 1, characterized in that, The oxidation process of the semiconductor substrate includes: Oxygen is introduced into the atomic layer deposition apparatus to oxidize the etched area, wherein the pressure of the introduced oxygen is 240 torr-260 torr, and the oxidation reaction time between the etched area and the oxygen is 5s-15s.
4. The thermal atomic layer etching method according to claim 1, characterized in that, The pressure of the hydrofluoric acid-pyridine mixture introduced into the atomic layer deposition equipment is 0.5 torr-2 torr, and the reaction time of the hydrofluoric acid-pyridine mixture with the alumina layer is 2s-8s.
5. The thermal atomic layer etching method according to claim 1, characterized in that, The pressure of the trimethylaluminum gas introduced into the atomic layer deposition equipment is 0.5 torr-5 torr, and the reaction time of the trimethylaluminum with the silicon oxide layer and the reaction time of the trimethylaluminum with the aluminum fluoride layer are both 2s-8s.
6. The thermal atomic layer etching method according to claim 3, characterized in that, After the silicon oxide layer is formed on the surface of the etched area, and before the trimethylaluminum is introduced into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove any residual oxygen; And / or, after the formation of the alumina layer and before the introduction of the hydrofluoric acid-pyridine mixture into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove any residual trimethylaluminum; And / or, after the formation of the aluminum fluoride layer and before the introduction of the trimethylaluminum into the atomic layer deposition apparatus, the thermal atomic layer etching method further includes: introducing a purge gas into the atomic layer deposition apparatus to purge and remove any residual hydrofluoric acid-pyridine mixture.
7. The thermal atomic layer etching method according to claim 6, characterized in that, The flow rate of the purge gas introduced into the atomic layer deposition apparatus is 20 sccm-100 sccm, and the time for introducing the purge gas is 10 s-60 s.
8. The thermal atomic layer etching method according to claim 1, characterized in that, A mask is deposited on a portion of at least one side of the semiconductor substrate using the atomic layer deposition apparatus to form etchable regions on the portion of the semiconductor substrate not covered by the mask, including: A metal mask is deposited on at least one side of the semiconductor substrate, the metal mask having a covered area and a cutout area; Physical vapor deposition of a mask material is performed on one side of the semiconductor substrate on which the metal mask is deposited using the atomic layer deposition equipment. The mask material covers the covered area and the cut-out area of the metal mask. The metal mask is removed, so that the mask material remaining on the surface of the semiconductor substrate corresponding to the cutout area forms a mask, and the part of the semiconductor substrate not covered by the mask forms the etched area.
9. The thermal atomic layer etching method according to claim 8, characterized in that, Before depositing a metal mask on at least one side of the semiconductor substrate, the thermal atomic layer etching method further includes cleaning the surface of the semiconductor substrate with a cleaning solution to remove the natural oxide layer on the surface of the semiconductor substrate.
10. The thermal atomic layer etching method according to any one of claims 1-9, characterized in that, The preset temperature range is 285℃ to 300℃.