Atomic layer etching method, apparatus, and semiconductor device for hafnium oxide

Abstract

This invention provides a method, apparatus, and semiconductor device for atomic layer etching of hafnium oxide. The method includes performing multiple cycles of etching on the hafnium oxide layer on the top surface of the device to be etched within a reaction chamber until the hafnium oxide layer reaches the target etching requirement. Each cycle includes: adjusting the temperature of the device to be etched to a target reaction temperature; providing a process gas containing a chlorine-based gas; dissociating the process gas into a plasma containing ions and chlorine radicals; filtering the ions in the plasma to obtain chlorine radicals, and reacting the chlorine radicals with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer; and heating the device to be etched to a target sublimation temperature to vaporize and discharge the hafnium tetrachloride layer. This invention can reduce the damage to hafnium oxide during etching and achieve higher etching uniformity and precision.

Description

Technical Field

[0001] This invention relates to the field of hafnium oxide etching technology, and more particularly to an atomic layer etching method, apparatus, and semiconductor device for hafnium oxide. Background Technology

[0002] With the development of semiconductor technology, HfO2 (hafnium oxide, also known as hafnium dioxide) is often used to replace traditional silicon oxide in semiconductor devices due to its high dielectric constant (high-k) characteristics. For example, it is used as the gate dielectric layer in field-effect transistors and the resistive switching layer in memory.

[0003] Currently, plasma etching is the primary method for atomic-level etching of hafnium oxide, removing atomic-level thickness layer by layer through cyclic chemical reactions and physical bombardment. During plasma etching, the process gas is excited by a high-frequency electromagnetic field under vacuum to form plasma. This plasma creates a sheath layer on the top surface of the hafnium oxide. Ions within this sheath possess high energy, and these high-energy ions physically bombard the hafnium oxide surface, thus achieving etching. However, high-energy ion bombardment easily causes damage to the hafnium oxide film, which affects film properties, such as lattice damage and valence state changes.

[0004] For hafnium oxide, when used as a gate dielectric layer and resistive switching layer, the film is usually relatively thin. When using plasma etching to achieve atomic layer etching, the damage caused by high-energy ion bombardment can easily affect its electrical performance, such as increasing gate leakage current. Therefore, hafnium oxide etching requires extremely low damage.

[0005] Therefore, how to reduce the damage caused by hafnium oxide during etching is a problem that this invention urgently needs to solve. Summary of the Invention

[0006] To address the problem of hafnium oxide being easily damaged during atomic layer etching, this invention provides an atomic layer etching method, apparatus, and semiconductor device for hafnium oxide.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides an atomic layer etching method for hafnium oxide, the method comprising performing multiple cyclic processes on a hafnium oxide layer on the top surface of a device to be etched until the hafnium oxide layer reaches the target etching requirement, wherein each cyclic process comprises:

[0009] Adjust the temperature of the device to be etched to the target reaction temperature;

[0010] Provide a process gas, said process gas comprising a chlorine-based gas;

[0011] The process gas is dissociated into a plasma containing ions and chlorine radicals;

[0012] Ions in the plasma are filtered to obtain chlorine radicals, which are then reacted with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer.

[0013] The device to be etched is heated to the target sublimation temperature so that the hafnium tetrachloride layer is vaporized and discharged.

[0014] Preferably, the target reaction temperature is in the range of 50°C to 100°C, so that the chlorine free radicals can react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer, and the hafnium tetrachloride layer remains solid.

[0015] Preferably, during the process of generating a hafnium tetrachloride layer, the method further includes: measuring the concentration of oxygen generated during the reaction using a tunable laser absorption spectroscopy detection module; and determining that the process of generating a hafnium tetrachloride layer ends when the concentration of oxygen gradually increases to convergence.

[0016] Preferably, when the target etching requirement is to etch the hafnium oxide layer to a target etching thickness, the method further includes: pre-obtaining the atomic layer thickness of the hafnium oxide layer after a single cycle of the process;

[0017] The target number of executions for the loop process is determined based on the ratio of the target etching thickness to the atomic layer thickness.

[0018] Preferably, when the target etching requirement is to etch the hafnium oxide layer to expose the next layer of the hafnium oxide layer, the method further includes: using an endpoint detection device to detect whether etching has reached the next layer of the hafnium oxide layer; when etching to expose the next layer is detected, it is determined that the hafnium oxide layer has met the target etching requirement.

[0019] In a second aspect, the present invention provides a plasma etching apparatus, including a reaction chamber, a stage disposed in the reaction chamber to support a device to be etched, a temperature control component disposed at the bottom of the stage, an ion filter disposed above the stage, a gas injection device disposed at the top of the reaction chamber, a first pumping device communicating with the reaction chamber, and a radio frequency generator for providing radio frequency signals to the reaction chamber.

[0020] When it is necessary to etch the hafnium oxide layer on the top surface of the device to be etched, the etching equipment is used to perform multiple cycles until the hafnium oxide layer reaches the target etching requirement, wherein each cycle includes:

[0021] The temperature control component is used to adjust the device to be etched to the target reaction temperature.

[0022] The gas injection device supplies process gas into the reaction chamber, the process gas containing chlorine-based gas;

[0023] The radio frequency generator provides a radio frequency signal to dissociate the process gas into a plasma containing ions and chlorine radicals.

[0024] The plasma is filtered by the ion filter device, and the chlorine radicals are allowed to pass through the ion filter device and react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer.

[0025] The temperature control component heats the device to be etched to the target sublimation temperature to vaporize the hafnium tetrachloride layer.

[0026] The gas in the reaction chamber is extracted by the first extraction device.

[0027] Thirdly, the present invention provides a plasma etching apparatus, including a reaction chamber, a stage disposed in the reaction chamber to support the device to be etched, an ion filter disposed above the stage, a gas injection device disposed at the top of the reaction chamber, a radio frequency generator for providing radio frequency signals to the reaction chamber, a heating chamber, and a second pumping device communicating with the heating chamber.

[0028] When it is necessary to etch the hafnium oxide layer on the top surface of the device to be etched, the etching equipment is used to perform multiple cyclic processes until the hafnium oxide layer reaches the target etching requirement, wherein each cyclic process includes:

[0029] After the device to be etched is transferred to the stage and the temperature of the device to be etched reaches the target reaction temperature, process gas is supplied to the reaction chamber through the gas injection device. The process gas contains chlorine-based gas.

[0030] The radio frequency generator provides a radio frequency signal to dissociate the process gas into a plasma containing ions and chlorine radicals.

[0031] The plasma is filtered by the ion filter device, and the chlorine radicals are allowed to pass through the ion filter device and react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer.

[0032] After the device to be etched is transferred to the heating chamber, the device to be etched is heated to the target sublimation temperature through the heating chamber so that the hafnium tetrachloride layer is vaporized.

[0033] The gas inside the heating chamber is extracted using the second extraction device.

[0034] Preferably, when the temperature of the device to be etched after being transferred to the stage is higher than the target reaction temperature, cooling gas is introduced into the area where the device to be etched is located to adjust the temperature of the device to be etched to the target reaction temperature.

[0035] Fourthly, the present invention provides a semiconductor device comprising a substrate and a hafnium oxide layer, wherein the hafnium oxide layer is obtained by etching using the aforementioned atomic layer etching method.

[0036] Preferably, the semiconductor device is a field-effect transistor or a memory; and / or, the substrate material includes Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, or InP.

[0037] By adopting the above technical solution, the present invention has the following advantages over the prior art:

[0038] In this invention, during atomic layer etching of a hafnium oxide layer, the process gas is first dissociated to generate plasma containing ions and chlorine radicals. Ion filtration effectively prevents high-energy ions in the plasma from physically bombarding the hafnium oxide layer, providing an environmental basis for subsequent precise atomic layer etching based on self-limiting properties. The filtered chlorine radicals react rapidly with the top surface of the hafnium oxide layer at a relatively low temperature (target reaction temperature) to generate a hafnium tetrachloride layer. The generated hafnium tetrachloride layer covers the top surface of the hafnium oxide layer. Through self-limiting properties, the chlorine radicals are prevented from continuing to contact and react with the hafnium oxide layer below. Therefore, the reaction automatically stops after only an atomic layer thickness of hafnium oxide reacts on the top surface of the hafnium oxide layer. Then, the hafnium tetrachloride layer is vaporized and discharged at a higher temperature (target sublimation temperature), thereby removing the generated hafnium tetrachloride layer without damage and exposing the top surface of the hafnium oxide layer below for the next cycle, thus completing precise atomic layer etching.

[0039] As can be seen, this invention combines ion filtration with low-temperature reaction and high-temperature desorption. Under the self-limiting effect of the hafnium tetrachloride layer, it can achieve high etching uniformity and etching precision, ensuring a low surface roughness of the hafnium oxide layer. This reduces the surface damage of the remaining hafnium oxide layer after etching and improves the device etching yield. It is particularly suitable for etching hafnium oxide in high-end semiconductor devices. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of a plasma etching apparatus in one embodiment of the present invention;

[0041] Figure 2 This is a schematic diagram of the plasma etching apparatus in another embodiment of the present invention;

[0042] Figure 3This is a schematic diagram illustrating the implementation principle of the atomic layer etching method for hafnium oxide in this invention. Detailed Implementation

[0043] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0044] It should be noted that the illustrations provided in the embodiments are only schematic representations of the basic concept of the present invention. Although the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components, the shape, quantity, positional relationship and proportion of each component can be arbitrarily changed under the premise of realizing the technical solution, and the layout of the components may also be more complex.

[0045] As mentioned earlier, the main method currently used is plasma etching to achieve atomic-level etching of hafnium oxide. Through cyclic chemical reactions and physical bombardment steps, the atomic-level thickness of hafnium oxide is removed layer by layer. However, high-energy ion bombardment can easily damage the hafnium oxide film, thereby affecting its electrical properties.

[0046] In view of this, the inventors, through in-depth research and improvement of the atomic layer etching process for hafnium oxide, discovered that:

[0047] Reactive chlorine radicals (chemical symbol Cl•) can react rapidly with the top surface of a hafnium oxide layer at low temperatures (e.g., 50-100℃) to form a solid hafnium tetrachloride layer. This hafnium tetrachloride layer covers the top surface of the hafnium oxide layer. Since the solid hafnium tetrachloride layer does not react with the chlorine radicals, and the top surface of the hafnium oxide layer is covered by the hafnium tetrachloride layer, the chlorine radicals are prevented from continuing to contact and react with the hafnium oxide layer below. Therefore, the top surface of the hafnium oxide layer automatically stops reacting after only an atomic layer thickness of hafnium oxide has reacted, thus achieving a precise self-limiting reaction process. That is, each reaction precisely consumes an atomic layer thickness of hafnium oxide.

[0048] After the reaction is complete, when the temperature is raised to the point that the hafnium tetrachloride layer vaporizes, the hafnium tetrachloride layer generated by the reaction can be removed without damage. The top surface of the hafnium oxide layer below will be exposed. The exposed hafnium oxide layer will not vaporize or react at this high temperature, thus achieving a precise self-limiting reaction process, allowing the hafnium oxide layer to be ready for the next cycle of reaction.

[0049] Due to its self-limiting effect, the hafnium oxide layer participating in a single reaction is precisely atomically thick. Therefore, a single cycle of low-temperature reaction and high-temperature desorption can accurately complete the atomic-level etching of hafnium oxide. By alternately executing the etching process of low-temperature reaction and high-temperature desorption, high etching uniformity and etching precision can be achieved, ensuring a low surface roughness of the hafnium oxide layer, thereby reducing the surface damage of the remaining hafnium oxide layer after etching.

[0050] Meanwhile, considering that active chlorine radicals are generally obtained by dissociating chlorine gas, and the plasma obtained by dissociation must contain high-energy ions, if these ions reach the device surface and physically bombard it, the hafnium tetrachloride layer will not be able to play a self-limiting role, that is, the above-mentioned atomic layer etching process cannot be achieved. Therefore, it is necessary to filter the ions.

[0051] Based on this, the present invention provides an atomic layer etching method, apparatus, and semiconductor device for hafnium oxide. Utilizing a processing approach of "low-temperature reaction + high-temperature removal of reaction products," it achieves high-precision atomic layer etching of hafnium oxide, improving etching accuracy and reducing damage to hafnium oxide during etching, thus ensuring etching quality and electrical performance. Specifically, in the low-temperature step, the newly formed solid HfCl4 layer covering HfO2 acts as a "protective layer," preventing the underlying HfO2 from continuing to contact with chlorine radicals Cl•. Therefore, the reaction automatically stops after consuming one atomic layer of Hf. Furthermore, in the high-temperature step, because HfO2 is very stable at this temperature and will not volatilize or decompose, it ensures that only the reaction byproduct HfCl4 is removed, while the underlying HfO2 layer is exposed intact, preparing for the next cycle.

[0052] In summary, the key to the technical concept of this invention lies in the significant differences in the physical state and reactivity of the reactant (chlorine radical Cl•) and the reaction product (hafnium tetrachloride HfCl4) at different temperatures, thereby achieving the "self-limiting" nature of each of the two steps.

[0053] Specifically, the atomic layer etching method for hafnium oxide of the present invention includes performing multiple cycles of etching on the hafnium oxide layer on the top surface of the device to be etched until the hafnium oxide layer reaches the target etching requirement, wherein each cycle includes:

[0054] Adjust the temperature of the device to be etched to the target reaction temperature;

[0055] Provide process gases, which include chlorine-based gases;

[0056] The process gas is dissociated into a plasma containing ions and chlorine radicals;

[0057] Chlorine radicals are obtained by filtering ions from the plasma, and then the chlorine radicals react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer.

[0058] The device to be etched is heated to the target sublimation temperature so that the hafnium tetrachloride layer is vaporized and then extracted.

[0059] The core advantages of this invention include one or more of the following aspects:

[0060] Atomic precision: Through a self-limiting reaction, the atomic layer thickness is precisely removed in each cycle, achieving high-precision etching control at the nanometer or even atomic level;

[0061] Excellent uniformity and consistency: The cyclic process is carried out synchronously in all areas, avoiding local over-etching or under-etching;

[0062] Low damage: Pure chemical process, without high-energy particle physical bombardment, maintaining the integrity of the material;

[0063] High conformality: For devices with three-dimensional structures, this method can uniformly etch all surfaces, making it ideal for advanced semiconductor manufacturing;

[0064] High selectivity: Low-temperature reaction or high-temperature desorption is only related to the target material and has minimal impact on other materials, which helps to improve the process window;

[0065] Good repeatability: Since only atomic layer thickness is etched in each cycle, the cycle process is stable and controllable, with good process repeatability and reliability.

[0066] The technical solutions provided by the various embodiments of the present invention are described below with reference to the accompanying drawings.

[0067] Example 1

[0068] This embodiment provides an atomic layer etching method for hafnium oxide, based on, for example, Figure 1 or Figure 2 The plasma etching apparatus shown achieves atomic layer etching of the hafnium oxide layer on top of the device 10 to be etched.

[0069] Figure 1The plasma etching apparatus shown mainly includes a reaction chamber 21, a stage 22 disposed within the reaction chamber 21, an ion filter 23 disposed above the stage 22, a gas injection device 25 disposed at the top of the reaction chamber 21 and connecting the gas source 24 and the reaction chamber 21, a first pumping device 26 communicating with the reaction chamber 21, and a radio frequency generator 27 for providing radio frequency signals to the reaction chamber 21. The stage 22 is preferably a chuck, such as an electrostatic chuck (E-Chuck), used to support and fix the device 10 to be etched, preventing movement of the device 10 during the etching process. A temperature control component (not shown) is integrated at the bottom of the stage 22. This temperature control component includes a cooler and a heater for cooling or heating the stage 22, thereby achieving temperature control of the device 10 to be etched.

[0070] Figure 2 The plasma etching equipment shown is Figure 1 The difference in the equipment is that a heating chamber 41, which is set independently of the reaction chamber 21, is added to replace the temperature control component at the bottom of the stage 22, and the heating chamber 41 is connected to the second exhaust device 42.

[0071] In one feasible manner, such as Figure 3 As shown, the device to be etched 10 is a front-end device fabricated by a front-end process. A hafnium oxide layer 11 is formed on its top during the front-end process. In order to form the final semiconductor device, this embodiment needs to etch the hafnium oxide layer 11.

[0072] After the device 10 to be etched is placed on the stage 22 within the reaction chamber 21, the atomic layer etching method of this embodiment includes performing multiple cycles of etching on the hafnium oxide layer 11 on the top surface of the device 10 to be etched until the hafnium oxide layer 11 reaches the target etching requirement. Specifically, in conjunction with Figure 3 As shown, each loop process includes the following steps:

[0073] Step S1: Adjust the temperature of the device 10 to be etched to the target reaction temperature.

[0074] In one feasible approach, the target reaction temperature ranges from 50°C to 100°C, for example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C. At this temperature, chlorine radicals can react with the top surface of the hafnium oxide layer 11 to generate a solid hafnium tetrachloride layer 12. This prevents the generated hafnium tetrachloride layer 12 from directly volatilizing due to excessively high reaction temperatures, thus affecting its self-limiting properties. It ensures that the hafnium tetrachloride layer 12 remains solid, covering the surface of the hafnium oxide layer 11, thereby preventing chlorine radicals from contacting and reacting with the hafnium oxide layer 11 below the hafnium tetrachloride layer 12.

[0075] In this embodiment, when using Figure 1When using the etching apparatus shown, this step can adjust the temperature of the device 10 to be etched to the target reaction temperature using a temperature control component integrated at the bottom of the stage 22. Specifically, when the current temperature of the device 10 to be etched is lower than the target reaction temperature, the temperature control component heats the device 10 to the target reaction temperature; conversely, when the current temperature of the device 10 to be etched is higher than the target reaction temperature, the temperature control component cools the device 10 to the target reaction temperature.

[0076] In this embodiment, when using Figure 2 In the etching apparatus shown, the temperature inside the reaction chamber 21 is typically set to the target reaction temperature, and the temperature inside the heating chamber 41 is typically set to the target sublimation temperature (higher than the target reaction temperature). In this step, when the current temperature of the device 10 to be etched is lower than the target reaction temperature, the device 10 to be etched is heated to the target reaction temperature by the temperature of the reaction chamber 21 itself; conversely, when the current temperature of the device 10 to be etched is higher than the target reaction temperature, the device 10 to be etched is cooled to the target reaction temperature by introducing cooling gas.

[0077] Step S2: Provide process gas into reaction chamber 21, the process gas containing chlorine-based gas.

[0078] Specifically, process gas is supplied through gas source 24, and the process gas is sprayed downward into the reaction chamber 21 through gas injection device 25 at the top of the reaction chamber 21.

[0079] In one feasible embodiment, chlorine-based gases serve as the primary source of chlorine radicals 32, including but not limited to at least one of Cl2 (chlorine) and BCl3 (boron trichloride).

[0080] In one feasible approach, in addition to chlorine-based gases, the process gas may also contain other auxiliary gases, such as helium or argon, to promote gas dissociation.

[0081] In one feasible embodiment, the gas injection device 25 is positioned directly above the stage 22, and its bottom is provided with a spray head for uniformly spraying process gas downwards.

[0082] Step S3, as follows Figure 3 As shown in (a), the process gas is dissociated into plasma 30 containing ions 31 and chlorine radicals 32.

[0083] In one feasible manner, such as Figure 1 or Figure 2As shown, reaction chamber 21 is an inductively coupled plasma (ICP) chamber, and coil 28 is provided on the top surface of reaction chamber 21. When a radio frequency signal provided by radio frequency generator 27 is passed through coil 28, a time-varying magnetic field will be induced in reaction chamber 21. The magnetic field will then induce a circumferential electric field, thereby dissociating the process gas into plasma 30. Since the process gas contains chlorine-based gas, the resulting plasma 30 contains ions 31 and chlorine free radicals 32.

[0084] The frequency of the radio frequency (RF) signal used in this step affects the density and distribution of the plasma. Higher frequencies can increase plasma density, thereby improving process efficiency. Therefore, the RF signal frequency can be selected from 13.56MHz, 27MHz, 40MHz, 60MHz, 100MHz, or 2.45GHz, depending on the specific process requirements and environment.

[0085] The power of the radio frequency signal used in this step determines the energy level of the plasma. In this embodiment, the power range of the radio frequency signal can be, for example, 1000W~2000W, such as 1000W, 1100W, 1200W, 1500W, 1800W or 2000W, etc., which can be selected according to actual process requirements and environment.

[0086] During this step, the pressure range within reaction chamber 21 is 500 mtorr to 1 torr, for example, 500 mtor, 600 mtor, 700 mtor, 800 mtor, 900 mtor, or 1 tor. Maintaining the process pressure within this range prevents a low concentration of chlorine free radicals due to insufficient process pressure, ensuring high reaction efficiency.

[0087] In step S4, ions 31 in plasma 30 are filtered through ion filter device 23 to obtain chlorine free radicals 32, so that chlorine free radicals 32 react with the top surface of hafnium oxide layer 11 at the target reaction temperature to generate solid hafnium tetrachloride layer 12.

[0088] Specifically, such as Figure 3 As shown in (b), when the plasma 30 moves downward, the ions 31 in it are blocked and filtered by the ion filter device 23, while the chlorine free radicals 32 pass through the ion filter device 23 to reach the top surface of the hafnium oxide layer 11, and react with the top surface of the hafnium oxide layer 11 at the target reaction temperature to generate the hafnium tetrachloride layer 12.

[0089] In this embodiment, chlorine radical 32 is an active group with very high chemical reactivity. At a relatively low temperature (target reaction temperature), it can react with the top surface of hafnium oxide layer 11 to generate solid hafnium tetrachloride layer 12. The chemical reaction equation is as follows:

[0090] HfO2 + 4Cl• → HfCl4 + O2

[0091] The generated hafnium tetrachloride layer 12 will cover the top surface of the hafnium oxide layer 11. Due to its self-limiting effect, the hafnium tetrachloride layer 12 can prevent chlorine free radicals 32 from continuing to contact and react with the hafnium oxide layer 11 below it. Therefore, the top surface of the hafnium oxide layer 11 will automatically stop reacting after only reacting with a layer of hafnium oxide of atomic thickness. That is, each reaction will precisely consume a layer of hafnium oxide of atomic thickness.

[0092] In one feasible embodiment, the ion filtering device 23 includes at least one layer of spaced-apart filter plates, which are grounded metal filter plates and include a plurality of longitudinally penetrating filter holes. The outer peripheral surface of the metal filter plate is shaped to fit the inner wall of the reaction chamber 21 and is insulated from the inner wall of the reaction chamber 21. After being grounded, it can filter charged ions 31 in the plasma 30 to prevent ions 31 from passing through, thereby preventing ions 31 from reaching the area where the device 10 to be etched is located and causing physical bombardment.

[0093] Specifically, the principle of ion filtration achieved by the metal filter plate is as follows: when the metal filter plate is grounded, positively charged ions will be adsorbed onto the metal filter plate; negatively charged ions will be prevented from moving downwards by the metal filter plate due to the mutual repulsion of like charges. Since the chlorine free radicals 32 in the plasma 30 are electrically neutral, they can pass downwards through the filter holes of the metal filter plate to reach the area where the device 10 to be etched is located, so as to react with the top surface of the hafnium oxide layer 11 to generate the hafnium tetrachloride layer 12.

[0094] In one feasible embodiment, the ion filtration device 23 includes two or more filter plates spaced apart, which, through multi-layer filtration, can obtain purer chlorine free radicals 32.

[0095] Step S5: Heat the device 10 to be etched to the target sublimation temperature to vaporize and discharge the solid hafnium tetrachloride.

[0096] It should be understood that the target sublimation temperature is higher than the target reaction temperature and higher than the vaporization point of hafnium tetrachloride under the current process conditions.

[0097] Preferably, the target sublimation temperature is 200℃~500℃, for example, it can be 200℃, 300℃, 400℃ or 500℃, etc., to provide temperature conditions for the conversion of hafnium tetrachloride layer 12 into gaseous hafnium tetrachloride. The specific temperature can be determined according to the etching rate requirements.

[0098] In this embodiment, when the following is used Figure 1When using the etching apparatus shown, this step specifically involves heating the device 10 to be etched to the target sublimation temperature using a temperature control component at the bottom of the stage 22; and extracting the gas from the reaction chamber 21 using a first evacuation device 26 connected to the reaction chamber 21.

[0099] In this embodiment, when the following is used Figure 2 When using the etching equipment shown, this step specifically involves transferring the device to be etched 10 into the heating chamber 41 and heating it to the target sublimation temperature; and then using a second evacuation device 42 connected to the heating chamber 41 to extract the gas from the heating chamber 41.

[0100] After vaporization is complete, the resulting device to be etched, 10, is as follows: Figure 3 As shown in (c), the dashed box represents the outline of the hafnium tetrachloride layer 12 before vaporization. It can be seen that after vaporization, the hafnium tetrachloride layer 12 generated by the reaction can be removed without damage, exposing the top surface of the hafnium oxide layer 11 below it, thus preparing for the self-limiting reaction in the next cycle.

[0101] This completes one cycle of precise atomic-level thickness removal of the hafnium oxide layer 11. By repeating this process multiple times, the target etching requirements can be achieved.

[0102] As can be seen, this embodiment first generates plasma 30 containing ions 31 and chlorine radicals 32 by dissociating the process gas, and effectively prevents the high-energy ions 31 in the plasma 30 from physically bombarding the hafnium oxide layer 11 by ion filtration, providing an environmental basis for subsequent precise atomic layer etching based on self-limiting effect; then, the chlorine radicals 32 react rapidly with the top surface of the hafnium oxide layer 11 at a relatively low temperature (target reaction temperature) to generate a hafnium tetrachloride layer 12, which will cover the hafnium oxide layer 11. The top surface of layer 11, through its self-limiting property, can prevent chlorine free radicals 32 from continuing to contact and react with the hafnium oxide layer 11 below it. Therefore, the top surface of hafnium oxide layer 11 automatically stops reacting after reacting with only an atomic layer thickness of hafnium oxide. Then, the device to be etched 10 is raised to a higher temperature (target sublimation temperature) and held to vaporize and remove the hafnium tetrachloride layer 12. This allows the hafnium tetrachloride layer 12 generated by the reaction to be removed without damage, exposing the top surface of the hafnium oxide layer 11 below it, thereby completing precise atomic layer etching.

[0103] In summary, this embodiment combines ion filtration with low-temperature reaction and high-temperature desorption. Under the self-limiting effect of the hafnium tetrachloride layer 12, it can achieve high etching uniformity and etching precision, ensuring that the surface roughness of the hafnium oxide layer 11 is low, thereby reducing the surface damage of the remaining hafnium oxide layer 11 after etching and improving the device etching yield.

[0104] In one feasible approach, the execution time of each of the above steps is a corresponding preset time, which is obtained in advance through experimental calibration.

[0105] In another feasible approach, during the formation of the hafnium tetrachloride layer 12 in step S4, the concentration of oxygen (O2) generated in the reaction chamber 21 can be measured using a tunable laser absorption spectroscopy detection module (not shown). When the oxygen concentration gradually increases until it converges, the process of forming the hafnium tetrachloride layer 12 is considered complete, and the next step can begin. This avoids insufficient reaction time based on a fixed time, or waiting for the next step after the reaction is completed, which would affect process efficiency.

[0106] The basis for the above judgment process is as follows: According to the preceding chemical reaction equation, oxygen will be produced as a byproduct during the reaction in step S4. As the reaction continues, the concentration of oxygen will gradually increase until the reaction ends. When the reaction ends, the concentration of oxygen will no longer change (i.e., convergence). Therefore, by detecting whether the oxygen concentration increases to the point of convergence, it is possible to accurately determine whether the reaction has ended.

[0107] Specifically, in this embodiment, the oxygen concentration can be detected non-contactly and in situ using a tunable laser absorption spectroscopy detection module, providing feedback for determining the end of the reaction. It should be understood that, in order to cooperate with the tunable laser absorption spectroscopy detection module, a viewing window needs to be configured in the corresponding position of the reaction chamber 21.

[0108] In one feasible approach, when the target etching requirement is to etch the hafnium oxide layer 11 to a target etching thickness, this embodiment pre-obtains the atomic layer thickness of the hafnium oxide layer 11 after a single cycle of processing, and determines the target number of cycles based on the ratio of the target etching thickness to the atomic layer thickness, thereby enabling the hafnium oxide layer 11 to be etched to any target etching thickness with extremely high precision, meeting the etching requirements of different device structures.

[0109] In another feasible approach, when the target etching requirement is to etch the hafnium oxide layer 11 to the next layer below the exposed hafnium oxide layer 11 (i.e., the hafnium oxide layer 11 is etched to the bottom), this embodiment uses an endpoint detection device (not shown) to detect whether the etching has reached the next layer below the exposed hafnium oxide layer 11. When etching to the next layer is detected, it is determined that the hafnium oxide layer 11 has met the target etching requirement, and the above-mentioned cycle process is automatically terminated, thereby reducing over-etching damage to the underlying material.

[0110] In one feasible embodiment, after the formation of the hafnium tetrachloride layer 12 in step S4 and before step S5, each cycle process further includes performing the following step: purging the reaction chamber 21 with a purge gas. This purges excess chlorine radicals 32 and other contaminants from the reaction chamber 21 to the outside of the reaction chamber 21, improving etching accuracy.

[0111] In another feasible embodiment, after step S5 is completed, each cycle process further includes performing the following steps: using a purge gas to purge the reaction chamber 21 or heating chamber 41 where the hafnium tetrachloride layer 12 is vaporized, thereby cleaning up the gaseous hafnium tetrachloride and other residual gaseous hafnium tetrachloride in the reaction chamber 21 or heating chamber 41, and preventing gaseous hafnium tetrachloride from remaining on the chamber wall after cooling.

[0112] In this embodiment, the type of purging gas, purging duration, and gas flow rate can be determined according to the actual application scenario, and are not specifically limited here.

[0113] For example, the purging gas can be a protective gas such as nitrogen, helium, or argon.

[0114] Example 2

[0115] This embodiment provides a plasma etching apparatus for implementing the aforementioned atomic layer etching method, such as... Figure 1 As shown, the etching apparatus includes a reaction chamber 21, a stage 22 disposed in the reaction chamber 21 to support the device 10 to be etched, a temperature control component (not shown) disposed at the bottom of the stage 22, an ion filter device 23 disposed at a certain distance above the stage 22, a gas injection device 25 disposed at the top of the reaction chamber 21 and connected between an external gas source 24 and the reaction chamber 21, a first air extraction device 26 connected to the reaction chamber 21, and a radio frequency generator 27 for providing radio frequency signals to the reaction chamber 21.

[0116] When it is necessary to etch the hafnium oxide layer 11 on the top surface of the device 10, the etching equipment is used to perform multiple cycles until the hafnium oxide layer 11 reaches the target etching requirements. Each cycle includes:

[0117] First, the temperature control component adjusts the device 10 to be etched to the target reaction temperature. Then, the gas injection device 25 provides a process gas containing chlorine-based gas into the reaction chamber 21, and the radio frequency generator 27 provides a radio frequency signal to dissociate the process gas in the reaction chamber 21 into plasma 30 containing ions 31 and chlorine free radicals 32. The dissociated ions 31 are filtered by the ion filter device 23, while the chlorine free radicals 32 pass through the ion filter device 23 and react with the top surface of the hafnium oxide layer 11 at the target reaction temperature to generate a solid hafnium tetrachloride layer 12. Finally, the temperature of the device 10 to be etched is raised to the target sublimation temperature by the temperature control component, so that the solid hafnium tetrachloride layer 12 is vaporized into gaseous hafnium tetrachloride. At the same time, the gas in the reaction chamber 21 is extracted by the first gas extraction device 26, thus completing one atomic-level thickness removal cycle of the hafnium oxide layer 11.

[0118] In one feasible approach, the target reaction temperature ranges from 50°C to 100°C, providing the temperature conditions for the subsequent reaction to generate hafnium tetrachloride layer 12.

[0119] In one feasible approach, the target sublimation temperature is in the range of 200°C to 500°C, providing the temperature conditions for the conversion of the solid hafnium tetrachloride layer 12 into gaseous hafnium tetrachloride.

[0120] In one feasible embodiment, the ion filtering device 23 includes at least one filter plate spaced apart within the reaction chamber 21. This filter plate is, for example, a grounded metal filter plate and includes a plurality of longitudinally penetrating filter holes. The outer peripheral surface of the metal filter plate is shaped to fit the inner wall of the reaction chamber 21 and is insulated from it. After grounding, it can filter ions 31 in the plasma 30 to prevent ions 31 from passing through, thereby preventing ions from reaching the area where the device 10 is to be etched, and thus preventing ions 31 from physically bombarding the hafnium oxide layer 11. Since the chlorine free radicals 32 in the plasma 30 are electrically neutral, they can pass through the metal filter plate to reach the area where the device 10 is to be etched and react with the top surface of the hafnium oxide layer 11 to generate a solid hafnium tetrachloride layer 12.

[0121] In one feasible approach, multiple filter holes are evenly distributed on a metal filter plate, which helps chlorine radicals 32 to diffuse evenly and stably to the top surface of the entire device 10 to be etched, but this embodiment is not limited to this.

[0122] In one feasible embodiment, the outer peripheral surface of the metal filter plate and the inner wall of the reaction chamber 21 are both circular, and an annular insulating seal (not shown) is provided between them. This ensures electrical insulation between the metal filter plate and the inner wall of the reaction chamber 21, and forms an effective physical sealing space, clearly separating the upper part (plasma generation zone) and the lower part (reaction zone) of the reaction chamber 21. This helps maintain a pure chemical etching environment in the reaction zone and prevents active ions or process gases from entering the lower reaction zone without effective filtration.

[0123] In one feasible embodiment, the side wall of the reaction chamber 21 has a transfer port 29 for a robotic arm (not shown) to transfer the device 10 to be etched. The height difference between the ion filter device 23 and the bottom surface of the reaction chamber 21 is greater than the height difference between the transfer port 29 and the bottom surface of the reaction chamber 21. Therefore, when the robotic arm feeds the device 10 to be etched into or removes the device 10 from the reaction chamber 21 through the transfer port 29, there will be no motion interference with the ion filter device 23.

[0124] The etching apparatus of this embodiment incorporates an ion filter 23, which serves two purposes: firstly, to filter ions 31, effectively blocking the physical bombardment of high-energy ions 31; and secondly, to allow chlorine free radicals 32 to pass through. These chlorine free radicals 32 pass through the ion filter 23 and react with the top surface of the hafnium oxide layer 11 at the target reaction temperature to generate a solid hafnium tetrachloride layer 12. Then, a temperature control component heats the device 10 to be etched to the target sublimation temperature and maintains it, causing the hafnium tetrachloride layer 12 to vaporize and be extracted from the reaction chamber 21. Due to the self-limiting nature of the hafnium tetrachloride layer 12, atomic-level etching of the hafnium oxide layer 11 can be achieved. Therefore, this embodiment combines ion filtration with low-temperature reaction and high-temperature desorption. Under the self-limiting effect of the hafnium tetrachloride layer 12, it can achieve high etching uniformity and etching precision, ensuring a low surface roughness of the hafnium oxide layer, thereby reducing the surface damage of the remaining hafnium oxide layer after etching and improving the device etching yield.

[0125] See again Figure 1 As shown, the reaction chamber 21 in this embodiment is preferably an inductively coupled plasma (ICP) reaction chamber. Compared with a capacitively coupled plasma (CCP) reaction chamber, the plasma density obtained by the dissociation of the ICP reaction chamber is higher and has lower energy. When filtered by the ion filter device 23, the lower energy ions are less likely to damage the ion filter device 23.

[0126] Example 3

[0127] This embodiment also provides a plasma etching apparatus for implementing the aforementioned atomic layer etching method. Compared with embodiment 2, this embodiment adds a heating chamber 41, which is set independently of the reaction chamber 21, to replace the temperature control component at the bottom of the stage 22, and the heating chamber 41 is connected to a second air extraction device 42.

[0128] Specifically, such as Figure 2 As shown, the etching apparatus of this embodiment mainly includes a reaction chamber 21, a stage 22 disposed in the reaction chamber 21 to support the device 10 to be etched, an ion filter 23 disposed at a certain distance above the stage 22, a gas injection device 25 disposed at the top of the reaction chamber 21 and connected between an external gas source 24 and the reaction chamber 21, a first suction device 26 connected to the reaction chamber 21, a radio frequency generator 27 for providing radio frequency signals to the reaction chamber 21, a heating chamber 41, and a second suction device 42 connected to the heating chamber 41.

[0129] When it is necessary to etch the hafnium oxide layer 11 on the top surface of the device 10, the temperature in the reaction chamber 21 is set at the target reaction temperature (50℃~100℃), and the temperature in the heating chamber 41 is set at the target sublimation temperature (200℃~500℃). This etching equipment is used to perform multiple cycles until the hafnium oxide layer 11 is etched to meet the target etching requirements. Each cycle includes:

[0130] First, the device to be etched 10 is transferred to the stage 22 and the temperature of the device to be etched 10 reaches the target reaction temperature. Then, a process gas containing chlorine-based gas is supplied to the reaction chamber 21 through the gas injection device 25, and a radio frequency signal is provided through the radio frequency generator 27 to dissociate the process gas in the reaction chamber 21 into plasma 30 containing ions 31 and chlorine free radicals 32. The dissociated ions 31 are filtered through the ion filter device 23, while the chlorine free radicals 32 pass through the ion filter device 23 and react with the top surface of the hafnium oxide layer 11 at the target reaction temperature to generate a solid hafnium tetrachloride layer 12. Finally, the device to be etched 10 is transferred to the heating chamber 41, and the temperature of the device to be etched 10 is raised to the target sublimation temperature through the heating chamber 41 to vaporize the solid hafnium tetrachloride layer 12 into gaseous hafnium tetrachloride. At the same time, the gas in the heating chamber 41 is extracted through the second gas extraction device 42, thus completing one atomic-level thickness removal cycle of the hafnium oxide layer 11.

[0131] In the next cycle, the device to be etched 10 is transferred back to the stage 22 in the reaction chamber 21 to repeat the above process. When the current temperature of the device to be etched 10 after being transferred to the stage 22 is higher than the target reaction temperature, cooling gas can be introduced into the area where the device to be etched 10 is located to adjust the temperature of the device to be etched 10 to the target reaction temperature; when the current temperature of the device to be etched 10 after being transferred to the stage 22 is lower than the target reaction temperature, the device to be etched 10 is heated to the target reaction temperature by the temperature of the reaction chamber 21 itself.

[0132] Compared with Example 2, in this embodiment, the device to be etched 10 is transferred to the heating chamber 41 for heating, which results in faster heating efficiency. Moreover, the reaction chamber 21 and the heating chamber 41 can work in parallel, reducing the waiting time caused by the circulating heating and cooling in the same chamber, thereby significantly improving the working efficiency of the equipment.

[0133] Example 4

[0134] This embodiment provides a semiconductor device, which includes a substrate and a hafnium oxide layer etched using the atomic layer etching method provided in Embodiment 1. Since the hafnium oxide layer is obtained by the atomic layer etching method of Embodiment 1, high etching uniformity and etching precision can be achieved.

[0135] In one feasible embodiment, the substrate material includes, but is not limited to, any one of Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, and InP.

[0136] In one feasible embodiment, the semiconductor device is a field-effect transistor, and its gate dielectric layer is a hafnium oxide layer etched using the atomic layer etching method of Example 1. Since the gate dielectric layer is etched using the atomic layer etching method of Example 1, it suffers less damage compared to etching using a plasma etching method, and thus has a lower gate leakage current.

[0137] In another possible implementation, the semiconductor device is a memory, and its resistive switching layer is a hafnium oxide layer etched using the atomic layer etching method of Example 1. Since the resistive switching layer is etched using the atomic layer etching method of Example 1, it suffers less damage and thus has higher reliability compared to etching using a plasma etching method.

[0138] In this specification, the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the descriptions of the embodiments described later are relatively simple, and relevant parts can be referred to the descriptions of the foregoing embodiments.

[0139] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. An atomic layer etching method for hafnium oxide, characterized in that, The method includes performing multiple cycles of etching on the hafnium oxide layer on the top surface of the device to be etched until the hafnium oxide layer reaches the target etching requirement, wherein each cycle includes: Adjust the temperature of the device to be etched to the target reaction temperature; Provide a process gas, said process gas comprising a chlorine-based gas; The process gas is dissociated into a plasma containing ions and chlorine radicals; Ions in the plasma are filtered to obtain chlorine radicals, which are then reacted with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer. The device to be etched is heated to the target sublimation temperature so that the hafnium tetrachloride layer is vaporized and discharged.

2. The atomic layer etching method as described in claim 1, characterized in that, The target reaction temperature range is 50℃~100℃, so that the chlorine free radicals can react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer, and keep the hafnium tetrachloride layer in a solid state.

3. The atomic layer etching method as described in claim 1, characterized in that, In the process of generating a hafnium tetrachloride layer, the method further includes: measuring the concentration of oxygen generated during the reaction using a tunable laser absorption spectroscopy detection module; and determining that the process of generating a hafnium tetrachloride layer ends when the concentration of oxygen gradually increases to convergence.

4. The atomic layer etching method according to any one of claims 1-3, characterized in that, When the target etching requirement is to etch the hafnium oxide layer to a target etching thickness, the method further includes: pre-obtaining the atomic layer thickness of the hafnium oxide layer after a single cycle of the process; The target number of executions for the loop process is determined based on the ratio of the target etching thickness to the atomic layer thickness.

5. The atomic layer etching method according to any one of claims 1-3, characterized in that, When the target etching requirement is to etch the hafnium oxide layer to expose the next layer of the hafnium oxide layer, the method further includes: using an endpoint detection device to detect whether etching has reached the next layer of the hafnium oxide layer; when etching to expose the next layer is detected, it is determined that the hafnium oxide layer has met the target etching requirement.

6. A plasma etching apparatus, characterized in that, The device includes a reaction chamber, a stage disposed within the reaction chamber to support the device to be etched, a temperature control component disposed at the bottom of the stage, an ion filter disposed above the stage, a gas injection device disposed at the top of the reaction chamber, a first pumping device communicating with the reaction chamber, and a radio frequency generator for providing radio frequency signals to the reaction chamber. When it is necessary to etch the hafnium oxide layer on the top surface of the device to be etched, the etching equipment is used to perform multiple cycles until the hafnium oxide layer reaches the target etching requirement, wherein each cycle includes: The temperature control component is used to adjust the device to be etched to the target reaction temperature. The gas injection device supplies process gas into the reaction chamber, the process gas containing chlorine-based gas; The radio frequency generator provides a radio frequency signal to dissociate the process gas into a plasma containing ions and chlorine radicals. The plasma is filtered by the ion filter device, and the chlorine radicals are allowed to pass through the ion filter device and react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer. The temperature control component heats the device to be etched to the target sublimation temperature to vaporize the hafnium tetrachloride layer. The gas in the reaction chamber is extracted by the first extraction device.

7. A plasma etching apparatus, characterized in that, It includes a reaction chamber, a stage disposed in the reaction chamber to support the device to be etched, an ion filter device disposed above the stage, a gas injection device disposed at the top of the reaction chamber, a radio frequency generator for providing radio frequency signals to the reaction chamber, a heating chamber, and a second pumping device communicating with the heating chamber. When it is necessary to etch the hafnium oxide layer on the top surface of the device to be etched, the etching equipment is used to perform multiple cyclic processes until the hafnium oxide layer reaches the target etching requirement, wherein each cyclic process includes: After the device to be etched is transferred to the stage and the temperature of the device to be etched reaches the target reaction temperature, process gas is supplied to the reaction chamber through the gas injection device. The process gas contains chlorine-based gas. The radio frequency generator provides a radio frequency signal to dissociate the process gas into a plasma containing ions and chlorine radicals. The plasma is filtered by the ion filter device, and the chlorine radicals are allowed to pass through the ion filter device and react with the top surface of the hafnium oxide layer at the target reaction temperature to generate a hafnium tetrachloride layer. After the device to be etched is transferred to the heating chamber, the device to be etched is heated to the target sublimation temperature through the heating chamber so that the hafnium tetrachloride layer is vaporized. The gas inside the heating chamber is extracted using the second extraction device.

8. The plasma etching apparatus as described in claim 7, characterized in that, When the temperature of the device to be etched after being transferred to the stage is higher than the target reaction temperature, cooling gas is introduced into the area where the device to be etched is located to adjust the temperature of the device to the target reaction temperature.

9. A semiconductor device comprising a substrate and a hafnium oxide layer, characterized in that, The hafnium oxide layer is obtained by etching using any one of the atomic layer etching methods described in claims 1 to 5.

10. The semiconductor device as claimed in claim 9, characterized in that, The semiconductor device is a field-effect transistor or a memory. And / or, the substrate material includes Si, Ge, SiGe, SiC, SiGeC, InAs, GaAs, or InP.

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