Plasma processing apparatus and etching method thereof

Abstract

This invention discloses a plasma processing apparatus and its etching method. The plasma processing apparatus includes a vacuum reaction chamber containing: a lower electrode with a support surface for supporting a substrate; an upper electrode opposite to the lower electrode, the upper electrode having a gas spray head for introducing process gas into the chamber, and a reaction region formed between the upper and lower electrodes; and a magnetic field element surrounding the reaction region, configured to generate a magnetic field to regulate charged particles in the reaction region. The magnetic field includes a magnetic field perpendicular to the support surface and a divergent magnetic field inclined to the lower surface of the gas spray head. Its advantages are: the apparatus can precisely control the process by regulating the distribution and movement direction of charged particles in the reaction region at specific times through the magnetic field element, which helps to obtain ideal etching morphology, and can also improve the ability to etch recessed structures without increasing the peak power.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to a plasma processing apparatus and its etching method. Background Technology

[0002] With the advent of the big data era, the demand for data storage has grown exponentially. To meet this demand, memory chip technology, driven by major manufacturers such as Samsung, Hynix, Micron, and Toshiba, has transformed from 2D NAND to 3D NAND, which boasts higher storage density but a more complex structure. 3D NAND is formed by multi-layer stacking. As device integration increases, the number of stacked layers in 3D NAND also increases, and the depth of the recessed structures—the feature areas serving as word lines and contacts—also increases. Currently, the mainstream stacked layer count for 3D NAND is 128 layers, and its corresponding recessed structures have a very high aspect ratio (HAR). This high aspect ratio design can overcome the capacity limitations of planar structures, but it also significantly increases the difficulty of etching the recessed structures, posing significant challenges in both process technology and equipment.

[0003] As is well known, a typical substrate requires thousands of process steps from silicon wafer to final packaging, and these multiple process steps inevitably introduce complexity. Among these, the etched recesses on the substrate form the basis of these multiple process steps, and the etching quality of these recesses is crucial to the quality of subsequent self-aligned multi-patterned finished devices. However, the etching of existing recesses still faces many challenges. For example, as the aspect ratio of the recesses increases, the peak power required for etching becomes increasingly higher, making the cavity's internal breakdown protection design increasingly challenging. Furthermore, as the etching depth increases, the processing effect of the recesses becomes difficult to guarantee. In practical applications, various factors affect the etching of recesses, thereby affecting the formation of subsequent multi-patterned finished devices, reducing device yield, and impacting the output and scale of integrated circuit manufacturing. Therefore, improvements to existing production equipment and methods are necessary.

[0004] It is understood that the above statements only provide background information related to the present invention and do not necessarily constitute prior art. Summary of the Invention

[0005] Based on the aforementioned technical problems, the purpose of this invention is to provide a plasma processing device and its etching method. This plasma processing device adjusts the distribution and movement direction of charged particles in the reaction region at a specific time through a magnetic field element, thereby achieving precise control of the process. This device can not only constrain the scattering of incident ions and improve the collimation of ions entering the recessed structure, but also enhance the ability to etch the recessed structure under the same power intensity. It can also increase the dissociation ability of the process gas, thereby increasing the charge neutralization ability in the recessed structure, effectively controlling the positive ion residue at the bottom of the deep hole in the microscopic process, so as to facilitate the advancement of subsequent processes, and help to make the formed recessed structure have a better vertical cross section and bottom roundness, thus obtaining an ideal etching morphology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A plasma processing apparatus includes a vacuum reaction chamber, wherein the vacuum reaction chamber contains:

[0008] The lower electrode includes a bearing surface for supporting the substrate;

[0009] An upper electrode is disposed opposite to the lower electrode. The upper electrode has a gas spray head that introduces process gas into the cavity. A reaction zone is formed between the upper electrode and the lower electrode.

[0010] A magnetic field element is disposed around the reaction region and is configured to generate a magnetic field to modulate charged particles in the reaction region, wherein the magnetic field comprises a magnetic field perpendicular to the bearing surface and a divergent magnetic field inclined to the lower surface of the gas spray head.

[0011] Optionally, the magnetic field element comprises:

[0012] A first magnetic field element, surrounding the lower part of the reaction region, can generate a magnetic field perpendicular to the bearing surface;

[0013] The second magnetic field element, which surrounds the upper part of the reaction region, can generate a divergent magnetic field that is inclined to the lower surface of the gas spray head.

[0014] Optionally, the first magnetic field element includes a plurality of coils arranged vertically with the same inner diameter, and the second magnetic field element includes a plurality of coils arranged vertically with their inner diameters gradually increasing from bottom to top.

[0015] Optionally, in the vertical cross-section of the second magnetic field element, the arrangement direction of the multiple coils is at an angle α with the vertical line, and the range of the angle α is 0°<α<90°.

[0016] Optional, also includes:

[0017] A controller, connected to the first magnetic field element and the second magnetic field element, supplies pulse current to the first magnetic field element and the second magnetic field element, causing the high potential of the current in the first magnetic field element and the second magnetic field element to change alternately.

[0018] Optionally, the first magnetic field element and the second magnetic field element have pulsed currents. The first magnetic field element includes an inner loop coil and an outer loop coil. The inner diameter of the inner loop coil is smaller than the inner diameter of the outer loop coil. The high potential of the current in the outer loop coil changes synchronously with the high potential of the current in the second magnetic field element. The high potential of the current in the inner loop coil changes alternately with the high potential of the current in the second magnetic field element.

[0019] Optional, also includes:

[0020] A lifting ring surrounds the reaction region, and the magnetic field element is disposed within the lifting ring.

[0021] Optional, also includes:

[0022] Bias RF power supply, which is used to apply bias RF power into the cavity;

[0023] Source radio frequency power supply, which is used to apply source radio frequency power into the cavity;

[0024] The current in the bias RF power supply, the current in the first magnetic field element, and the current in the second magnetic field element are in pulse mode. The high potential of the current in the first magnetic field element changes synchronously with the high potential of the current output by the bias RF power supply, and the high potential of the current in the second magnetic field element changes alternately with the high potential of the current output by the bias RF power supply.

[0025] Optionally, an etching method for the aforementioned plasma processing apparatus, the method comprising:

[0026] The required process gas is introduced into the vacuum reaction chamber;

[0027] The etching process includes: applying a pulsed source radio frequency to the cavity to form plasma, applying a pulsed bias radio frequency to accelerate charged particles toward the substrate, and adjusting the distribution and direction of movement of charged particles in the reaction region through a magnetic field element.

[0028] The etching process includes multiple etching cycles, and each etching cycle includes:

[0029] First etching stage: The source RF and bias RF are at high potentials, and the substrate is etched.

[0030] Second etching stage: The power of the source RF and bias RF is at a low potential to neutralize the charge on the substrate.

[0031] Optionally, the magnetic field element comprises:

[0032] A first magnetic field element is used to generate a magnetic field perpendicular to the bearing surface;

[0033] The second magnetic field element is used to generate a divergent magnetic field that is inclined to the lower surface of the gas spray head.

[0034] During the etching process, a pulsed current is passed through the first magnetic field element and the second magnetic field element.

[0035] Optionally, during the first etching stage, a current at a high potential is passed through the first magnetic field element.

[0036] Optionally, the current value range when the current in the first magnetic field element is at a high potential is: greater than 0A and less than or equal to 200A.

[0037] Optionally, during the second etching stage, a current at a high potential is supplied to the second magnetic field element.

[0038] Optionally, the current value range when the current in the second magnetic field element is at a high potential is: greater than 0A and less than or equal to 200A.

[0039] Optionally, during the first etching stage, a current at a low potential is supplied to the second magnetic field element.

[0040] Optionally, the current value range when the current in the second magnetic field element is at a low potential is: greater than or equal to 0A and less than 200A.

[0041] Optionally, during the second etching stage, a current at a low potential is supplied to the first magnetic field element.

[0042] Optionally, the current value range when the current in the first magnetic field element is at a low potential is: greater than or equal to 0A and less than 200A.

[0043] Optionally, during the second etching stage, the current in the first magnetic field element is at a high potential.

[0044] Optionally, within the same etching cycle, the second etching stage may last longer than the first etching stage.

[0045] Compared with the prior art, the present invention has the following advantages:

[0046] In a plasma processing apparatus and etching method of the present invention, the plasma processing apparatus includes a magnetic field element that can generate a magnetic field perpendicular to the substrate and a divergent magnetic field inclined to the lower surface of the gas spray head. At a specific moment, the specific magnetic field provided by the magnetic field element can adjust the distribution and movement direction of charged particles in the reaction region, achieving precise control of the process. This apparatus not only constrains the scattering of incident ions and improves the collimation of ions entering the recessed structure, thereby enhancing the ability to etch high aspect ratio structures without increasing the power peak, but it also increases the dissociation capability of the process gas, thereby increasing the charge neutralization capability in the recessed structure. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the local microscopic particle state during the etching of a semiconductor device according to the present invention.

[0048] Figure 2 This is a schematic diagram of a plasma processing device according to the present invention;

[0049] Figure 3 This is a top view of a magnetic field element according to the present invention;

[0050] Figure 4 This is a schematic diagram of the scattering angle distribution of charged particles in a plasma according to the present invention.

[0051] Figure 5 This is a schematic diagram of an etching method for a plasma processing apparatus according to the present invention;

[0052] Figure 6 This is a control timing diagram of the present invention. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] It should be noted that, in this document, the terms "comprising," "including," "having," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." or "including..." does not exclude the presence of additional elements in the process, method, article, or terminal device that includes said element.

[0055] It should be noted that the accompanying drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clearly illustrate the purpose of the embodiments of the present invention.

[0056] like Figure 1 The diagram shows a partial schematic of a semiconductor device according to the present invention. The semiconductor device includes a substrate 100, which includes a stacked layer formed by alternating layers of different materials. The stacked layer includes a first material layer 110 and a second material layer 120, and includes an etched recessed structure 130. During the etching process, a patterned mask 140 is applied to the stacked layer of the substrate 100. The openings of the mask 140 form corresponding target patterns. Through etching of the stacked layer, a recessed structure 130 corresponding to the pattern of the mask 140 is finally formed, facilitating the subsequent fabrication of a self-aligned multi-patterned device. In this embodiment, the first material layer 110 and the second material layer 120 are an oxide layer and a nitride layer, respectively. These layers are fabricated using an oxide / nitride (O / N) stacking process to create stacked layers ranging from several micrometers to tens of micrometers in size. A recessed structure 130 is formed on the stacked layers using an etching method on a substrate 100. This substrate 100 etching method uses amorphous carbon (several micrometers) as a mask 140. Plasma is generated by dissociating the process gas, which is then used to etch the stacked layers, creating deep holes or trenches to form the recessed structure 130, while meeting very stringent morphology requirements. In practical applications, different process gases can be used for etching based on different stacked layer material types to achieve optimal etching results. In this embodiment, C... x F y H z C x F y Ar, N2, O2 and other reactive gases are used as process gases introduced into the vacuum reaction chamber.

[0057] Of course, the types of materials for the first material layer 110, the second material layer 120, the mask 140, and the process gas are not limited to those described above. In other embodiments, other materials may be used, and the present invention does not impose any limitations on this. For example, in another embodiment, the first material layer 110 and the second material layer 120 are a polycrystalline silicon (Si) layer and a silicon oxide layer, respectively. Furthermore, the present invention does not limit the number of stacked layers of the substrate 100; the more stacked layers, the higher the integration density of the device.

[0058] As mentioned above, the etching of the high aspect ratio recessed structure 130, i.e., the deep hole, is the most critical step in device manufacturing. The etching quality of the recessed structure 130 is crucial for the subsequent fabrication of self-aligned multi-patterned devices. Furthermore, with the development of semiconductor nodes, the processing requirements for the high aspect ratio recessed structure 130 are becoming increasingly stringent. Ideally, the recessed structure 130 on the substrate 100 needs to have a vertical profile. The sidewalls of the recessed structure 130 should not exhibit bending or bowing 131, while the horizontal profile at the bottom of the recessed structure 130 should be as close to circular as possible, without distortion or other deformation. With increasing aspect ratio, the collimation of ions incident on the microstructure (hole or trench) is typically required to be increasingly higher, prompting high-energy ions to reach the bottom of the high aspect ratio hole or trench for etching. In practical applications, to obtain the desired morphology of the recessed structure 130, very high low-frequency radio frequency power can be used in a very short time to generate high-energy ions to bombard the bottom of the microstructure (hole or groove) to form the recessed structure 130. However, as the aspect ratio of the recessed structure 130 increases, the required peak radio frequency power becomes increasingly higher. Although the desired recessed structure 130 can be obtained based on this peak power, this also makes the design of the cavity's internal voltage breakdown protection increasingly challenging.

[0059] Based on the above, this invention proposes a plasma processing apparatus comprising a magnetic field element arranged around a reaction region between an upper electrode and a lower electrode. This magnetic field element is configured to generate a magnetic field to regulate charged particles in the reaction region. The magnetic field includes a magnetic field perpendicular to the substrate 100 and a divergent magnetic field inclined to the lower surface of the gas spray head. At specific moments during the process, the specific magnetic field provided by the magnetic field element can regulate the distribution and movement direction of charged particles in the reaction region, improving the collimation of ions entering the recessed structure 130, achieving precise control of the process, and thus obtaining an ideal etching morphology. Simultaneously, the magnetic field element can also enhance the dissociation capability of the process gas, thereby increasing the charge neutralization capability in the recessed structure. Therefore, this plasma processing apparatus improves the ability to control the plasma ion scattering angle distribution and the ability to etch high aspect ratio recessed structures under the same RF power intensity, contributing to the generation of standardized high aspect ratio recessed structures 130, while reducing the impact on the cavity interior, avoiding electrical breakdown caused by excessive RF power, and ensuring the stability of the cavity environment. Experiments have verified that, using the plasma processing apparatus of the present invention, the resulting recessed structure 130 with an aspect ratio greater than or equal to 50 can still maintain the required collimation and good morphology. It should be noted that the apparatus of the present invention is not limited to generating recessed structures 130 with an aspect ratio greater than or equal to 50; it can also meet the process requirements for producing recessed structures 130 with an aspect ratio less than 50.

[0060] Specifically, such as Figure 2As shown, a plasma processing apparatus of the present invention includes a vacuum reaction chamber 200, which is surrounded by a reaction chamber body and a chamber end cap 201. The reaction chamber body is typically made of a metallic material and includes a chamber sidewall 202 and a chamber bottom wall 203. A substrate transfer port (not shown in the figure) is provided on the chamber sidewall 202 for transferring a substrate 100 between the inside and outside of the vacuum reaction chamber 200. The vacuum reaction chamber 200 includes a lower electrode 210, which is disposed at the bottom of the vacuum reaction chamber 200. The lower electrode 210 includes a bearing surface for supporting the substrate 100, and the substrate 100 to be processed is placed on the bearing surface. The vacuum reaction chamber 200 also includes an upper electrode 220 disposed opposite to the lower electrode 210. A reaction region is formed between the upper electrode 220 and the lower electrode 210. The upper electrode 220 includes a mounting base 221, which is disposed through a through hole in the end cap 201 of the chamber. The mounting base 221 is provided with multiple gas channels 222, which are connected to a gas buffer 230 located above the end cap 201 of the chamber. The bottom of the mounting base 221 is provided with a gas spray head 223 containing multiple spray holes 224, which are connected to the gas channels 222. The process gas in the gas supply device is injected into the vacuum reaction chamber 200 in sequence through the gas buffer 230, the gas channels 222 and the spray holes 224.

[0061] Furthermore, the plasma processing apparatus also includes a source RF power supply 240 and a bias RF power supply 250, which apply RF energy to the lower electrode 210 through a matching network 260. The source RF power supply 240 applies source RF to the cavity to ignite the process gas and generate plasma, thereby forming the recessed structure 130. The bias RF power supply 250 applies bias RF power to the cavity to accelerate charged particles in the plasma, increasing their speed of movement towards the substrate 100 and enhancing the directionality of their movement towards the substrate 100. In this embodiment, the source RF power supply 240 and the bias RF power supply 250 apply their RF power to the lower electrode 210. In other embodiments, they may also be applied to the upper electrode 220 or to both the upper electrode 220 and the lower electrode 210 respectively.

[0062] During the process, the substrate 100 to be processed is first transferred to the bearing surface of the lower electrode 210, and then C... x F y H zAfter being mixed by the gas buffer 230, reactive gases such as O2 are injected into the cavity through the gas channel 222 of the mounting base 221 and the spray hole 224 of the gas spray head 223. Then, the RF power from the source RF power supply 240 and the bias RF power supply 250 is input to the lower electrode 210 through the matching network 260, dissociating a large amount of plasma from the process gas via capacitive coupling, creating a plasma environment between the upper electrode 220 and the lower electrode 210 for etching (see [link to documentation]). Figure 1 and Figure 2 This plasma environment contains a large number of active particles such as positive ions (Ion), free radicals (Radical), and electrons (Electron). Figure 1 In this text, "+" represents a positive ion, "-" represents an electron, and "О" represents a free radical. These active particles can undergo various physical and / or chemical reactions with the surface of the substrate 100 to be treated, thereby altering the morphology of the substrate 100 and completing the treatment of the substrate 100. Electrons, due to their faster velocity, preferentially reach the surface of the substrate 100, forming an electric field between the substrate 100 and the plasma. This electric field accelerates the positive ions. After the electrons and positive ions stabilize, a high sheath structure is formed between the plasma and the substrate 100. Under the bias voltage of the sheath structure, the positive ions are accelerated to the deep holes of the substrate 100, bombarding the bottom of the deep holes to advance the etching process. Dissociated free radicals diffuse to the surface of the substrate 100 and into the deep holes (bottom of the recessed structure 130), undergoing surface reactions and generating byproducts.

[0063] Furthermore, in combination Figure 2 As shown, the vacuum reaction chamber 200 also includes a magnetic field element 270, which is arranged around the reaction region to allow for close-range control of the generated plasma, reducing the waste of magnetic field energy. The magnetic field element 270 is configured to generate a magnetic field to regulate charged particles in the reaction region. This magnetic field includes a magnetic field perpendicular to the bearing surface and a divergent magnetic field inclined to the lower surface of the gas spray head 223. During the process, according to the principle of force on charged particles in a magnetic field, charged particles moving parallel to the magnetic field lines are not affected by the magnetic force (e.g., charged particles whose original direction of motion is perpendicular to the substrate 100 for etching deep holes). However, charged particles with a horizontal component at a certain angle to the magnetic field lines are constrained by the magnetic field and rotate around the magnetic field lines. This reduces the displacement of these charged particles in the direction parallel to the substrate 100, making it easier for them to move in the direction perpendicular to the surface of the substrate 100. This results in a more concentrated distribution of the deflection angle of the charged particles entering the deep holes in the vertical direction (see [link to relevant documentation]). Figure 4(A schematic diagram of the scattering angle distribution of charged particles) allows more charged particles to reach the bottom of the deep hole for etching. On the other hand, based on the principle that charged particles move around magnetic field lines, the divergent magnetic field tilted to the lower surface of the gas spray head 223 can increase the motion component of charged particles in the direction parallel to the substrate 100, increase the collision probability of electrons, positive ions and process gas, further increase the degree of dissociation of process gas, and increase plasma density. This allows more electrons to enter the bottom of the deep hole, thereby increasing the neutralization ability of positive charges in the high aspect ratio structure, reducing the etching direction offset caused by charge accumulation at the bottom of the hole, and thus improving the consistency of the top and bottom morphology of the deep hole. As can be seen from the above, the magnetic field element 270 can not only constrain the scattering of incident ions in the sheath and improve the collimation of ions entering the recessed structure 130 to improve the ability to etch high aspect ratio structures under the same power intensity, but it can also increase the dissociation ability of process gas, thereby increasing the neutralization ability in the high aspect ratio structure. In practical applications, by applying DC currents of different directions and magnitudes to the magnetic field element 270, the particle state in the reaction region can be controlled by the magnetic field element 270. In other embodiments, alternating currents can also be added to coordinate with the etching and neutralization charge cycles according to process requirements, thereby enhancing the process effects of the two stages respectively.

[0064] like Figure 2 and Figure 3 As shown, in this embodiment, the magnetic field element 270 includes a first magnetic field element 271 and a second magnetic field element 272. The first magnetic field element 271 is disposed around the lower part of the reaction region, bringing it closer to the plasma in the region above the substrate 100. The plasma in this region directly etches the substrate 100. The first magnetic field element 271 can generate a magnetic field perpendicular to the bearing surface. In practical applications, this magnetic field perpendicular to the bearing surface can improve the collimation of charged particles within the recessed structure 130, increase the etching depth, and reduce damage to the sidewalls of the recessed structure 130. The second magnetic field element 272 is disposed around the upper part of the reaction region. The plasma in this region acts as a source of etching particles. The second magnetic field element 272 can generate a divergent magnetic field inclined to the lower surface of the gas spray head 223. This divergent magnetic field can increase the dissociation capability of the process gas, increase the plasma density, thereby increasing the charge neutralization capability at the bottom of the deep hole and advancing the etching of the deep hole. In actual use, both the first magnetic field element 271 and the second magnetic field element 272 are connected to an external DC power supply so that DC currents of different directions and magnitudes can be applied during the process to control the direction and intensity of their respective magnetic fields.

[0065] In this embodiment, the first magnetic field element 271 includes a plurality of coils arranged vertically with the same inner diameter. Each coil is connected to a DC power supply to generate a magnetic field perpendicular to the bearing surface, improving the collimation of charged particles and facilitating further increases in etching depth. The second magnetic field element 272 includes a plurality of coils arranged vertically with an inner diameter gradually increasing from bottom to top. Each coil is connected to a DC power supply to generate a magnetic field that diverges to both sides near the gas source. This magnetic field has an angle between the magnetic field lines near the gas source and the vertical line to enhance the dissociation capability of the process gas and thus increase the plasma density. In practical use, by adjusting the current applied to the first magnetic field element 271 and the second magnetic field element 272, the magnetic field formed by the three-dimensional structure composed of the first magnetic field element 271 and the second magnetic field element 272 can be such that the magnetic field lines near the substrate 100 are perpendicular to the surface of the substrate 100, while the magnetic field lines near the gas spray head 223 are divergent, thereby improving the etching efficiency and etching quality.

[0066] Optionally, in the vertical cross-section of the second magnetic field element 272, the arrangement direction of the plurality of coils forms an angle α with the vertical line (see [link to relevant documentation]). Figure 2 The included angle α is in the range of 0° < α < 90°. It is understood that the included angle α between the arrangement direction of the plurality of coils and the vertical line is not limited to the above data range; in other embodiments, it can be set to other data ranges, and this invention does not limit this.

[0067] Furthermore, such as Figure 2 and Figure 3As shown, the first magnetic field element 271 includes an inner loop coil 273 and an outer loop coil 274 arranged vertically with different inner diameters. The inner loop coil 273 is located near the substrate 100, and the outer loop coil 274 is located outside the inner loop coil 273. That is, the inner diameter of the inner loop coil 273 is smaller than the inner diameter of the outer loop coil 274. The outer loop coil 274 is arranged downwards from the bottom of the second magnetic field element 272. The surface formed by the second magnetic field element 272 is funnel-shaped, and the diameter of the second magnetic field element 272 near the gas spray head 223 is larger than its diameter near the substrate 100. It should be noted that the first magnetic field element 271 and the second magnetic field element 272 are not limited to the above-described coil structure; they can also be other structures, as long as they can achieve the corresponding function. This invention does not limit them. For example, in other embodiments, the first magnetic field element 271 and / or the second magnetic field element 272 are a single sheet of iron core or magnetic core, or they can be multiple coils formed by spiral arrangement of the same conductor. Similarly, the composition and arrangement of the first magnetic field element 271 and the second magnetic field element 272 are not limited to the above. As long as the first magnetic field element 271 is close to the lower part of the reaction region and the second magnetic field element 272 is close to the upper part of the reaction region, the present invention does not limit this, as long as the corresponding function can be achieved.

[0068] During the etching process, a pulsed current is supplied to the magnetic field element 270. The current potential of the inner loop coil 273 and the outer loop coil 274 of the first magnetic field element 271 can change synchronously or alternately. Optionally, the high potential of the inner loop coil 273 and the high potential of the outer loop coil 274 alternate. Specifically, the high potential of the outer loop coil 274 changes synchronously with the high potential of the second magnetic field element 272, while the high potential of the inner loop coil 273 changes alternately with the high potential of the second magnetic field element 272. That is, regardless of whether the current of the second magnetic field element 272 is in a high-potential state or a low-potential state, the first magnetic field element 271 will generate a magnetic field perpendicular to the bearing surface to constrain the scattering of charged particles entering the deep hole, thereby increasing the etching depth without increasing the power peak, which helps to reduce power loss, improve plasma utilization, and also reduces the pressure faced by the cavity breakdown protection design. Of course, the current flowing into the inner loop coil 273 and the outer loop coil 274 can also be in a high potential state at certain times, so as to further strengthen the magnetic field strength of the vertical magnetic field on the surface of the substrate 100 and enhance the constraint and guidance effect of the vertical magnetic field on charged particles.

[0069] Furthermore, the first magnetic field element 271 and the bias RF power supply 250 can be combined to enhance the guiding effect on charged particles. For example, in one embodiment, to enhance the etching effect, the current in the bias RF power supply 250, the first magnetic field element 271, and the second magnetic field element 272 are in pulse mode. The high potential of the current in the first magnetic field element 271 changes synchronously with the high potential of the current output by the bias RF power supply 250, i.e., the high intensity state of the bias RF power. This enhances the collimation and movement speed of charged particles under the influence of the bias electric field formed by the bias RF and the magnetic field generated by the first magnetic field element 271, further optimizing the etching effect and advancing the etching process. Furthermore, the high potential of the current in the second magnetic field element 272 alternates with the high potential of the current output by the bias RF power supply 250 to avoid wasting the bias power output by the bias RF power supply 250, while simultaneously improving the effect of the magnetic field generated by the second magnetic field element 272 in promoting the dissociation of process gases.

[0070] Furthermore, the plasma processing apparatus also includes a controller 280 connected to the first magnetic field element 271 and the second magnetic field element 272. The controller 280 supplies pulsed current to the first magnetic field element 271 and the second magnetic field element 272, which causes the high potential of the current in the first magnetic field element 271 and the second magnetic field element 272 to change alternately, so as to optimize the etching process of the recessed structure 130 on the substrate 100.

[0071] Furthermore, the plasma processing device also includes a lifting ring 290, which surrounds the reaction region, and the magnetic field element 270 is disposed within the lifting ring 290. In this embodiment, the lifting ring 290 can be considered as a liftable vacuum-sealed tube to protect the magnetic field element 270 from interference from the plasma environment within the cavity, thus helping to ensure its service life. Simultaneously, the lifting ring 290 can also drive the magnetic field element 270 to move up and down, adjusting the region corresponding to its magnetic field, and thereby adjusting the plasma state corresponding to that region. When the substrate 100 needs to enter or exit the vacuum reaction chamber 200, the lifting ring 290 can be raised above the substrate transfer port, without obstructing the robot's entry and exit path. It is understood that the first magnetic field element 271 and the second magnetic field element 272 can be jointly disposed within one lifting ring 290, or they can be separately disposed within two lifting rings 290, so that the first magnetic field element 271 or the second magnetic field element 272 can be raised and lowered individually to adjust their magnetic field distribution. This invention does not limit this.

[0072] Based on the same inventive concept, the present invention also provides an etching method for a plasma processing device, such as... Figure 5As shown, the etching method includes: introducing the required process gas into the vacuum reaction chamber 200; performing an etching process, the etching process including: applying a pulsed-mode source radio frequency to the chamber to form plasma, applying a pulsed-mode bias radio frequency to accelerate charged particles toward the substrate 100, and adjusting the distribution and direction of movement of charged particles in the reaction region by a magnetic field element 270. The etching process includes multiple etching cycles (see [link to documentation]). Figure 6 , Figure 6 (The HF intensity is the power intensity of the source radio frequency, and the LF intensity is the power intensity of the bias radio frequency). The etching cycle includes: a first etching stage (S310): the power of the source radio frequency and the bias radio frequency is at a high potential, and the substrate 100 is etched; a second etching stage (S320): the power of the source radio frequency and the bias radio frequency is at a low potential, and the charge on the substrate 100 is neutralized.

[0073] As described above, this invention employs a pulsed etching method combining a first etching stage and a second etching stage. In the first etching stage, the source RF power supply 240 and the bias RF power supply 250 apply high-potential source RF and bias RF to the cavity, respectively, to dissociate the process gas, generate plasma, and apply a bias electric field that moves positively charged particles toward the substrate, thereby generating a recessed structure 130 on the substrate 100. In the second etching stage, to reduce charge accumulation in the recessed structure 130, opposite charges need to enter and neutralize it. Therefore, by reducing the power of the source RF and bias RF, the concentration of the plasma generated by dissociation will decrease accordingly, and the thickness of the sheath structure between the substrate 100 and the plasma will also decrease. The confinement effect of the sheath structure on electrons will also decrease, so electrons can diffuse into the deep hole as much as possible to neutralize the positive charge at the bottom of the deep hole. However, as the depth of the recessed structure 130 increases, it becomes increasingly difficult for electrons to reach the bottom of the deep hole, and its neutralization effect on positive ions becomes increasingly limited. The probability of undesirable deformation of the sidewalls of the recessed structure 130 also increases. This application utilizes a magnetic field perpendicular to the bearing surface generated by the magnetic field element 270 and a divergent magnetic field inclined to the lower surface of the gas spray head 223 to increase the collimation of charged particles in the plasma and the plasma concentration, respectively. Increased plasma concentration leads to increased electron concentration, and the proportion of electrons entering the recessed structure 130 is also increased due to the effect of the first magnetic field element 271, thus preventing undesirable deformation of the recessed structure 130. Furthermore, it enhances the ability to etch high aspect ratio structures without increasing RF power, contributing to improved device production yield. In practical applications, a corresponding magnetic field environment can be generated at specific timing points according to actual needs to improve the etching efficiency of the substrate 100 and the etching quality of the recessed structure 130, obtaining an ideal etching morphology to facilitate subsequent process advancement and ensure device production yield. Compared to processes without the assistance of magnetic field element 270, this method does not require continuously increasing peak power to improve the ability to etch high aspect ratio structures. Therefore, this method helps to reduce energy consumption and avoids the problem of intracavity breakdown.

[0074] In this embodiment, source RF power is supplied to the cavity via source RF power supply 240 to generate plasma within the cavity, thereby promoting the formation of the recessed structure 130. Bias RF power is supplied to the cavity via bias RF power supply 250 to accelerate charged particles in the plasma, increasing their speed of movement towards the substrate 100 and enhancing their directionality. During etching, the distribution and direction of movement of charged particles in the reaction region are adjusted by regulating the current supplied to the magnetic field element 270 to match the timing changes of the RF pulses. It is understood that the operating timing of the source RF power supply 240, bias RF power supply 250, and magnetic field element 270 can be independently controlled to achieve different microscopic processes based on different etching processes.

[0075] like Figure 6 The diagram shows the timing of applying pulsed currents to the first magnetic field element 271 and the second magnetic field element 272 in this embodiment, along with the RF pulses from the source RF power supply 240 and the bias RF power supply 250. In this embodiment, during the first etching stage, a current at a high potential is supplied to the first magnetic field element 271 to generate a strong magnetic field perpendicular to the bearing surface. As mentioned above, during the first etching stage, both the source radio frequency (RF) and the bias RF are in a high-power state, resulting in a high plasma density. This provides high ion energy to bombard the surface of the substrate 100 to form a high aspect ratio recessed structure 130. At this time, the first magnetic field element 271 is supplied with a large current to generate a strong magnetic field perpendicular to the surface of the substrate 100. The confinement effect of this strong magnetic field on charged particles in the plasma can significantly reduce the horizontal deflection of charged particles as they move toward the surface of the substrate 100. This makes the deflection angle distribution of charged particles entering the deep hole more concentrated in the vertical direction. As a result, more charged particles will reach the bottom of the deep hole for etching and charge neutralization, which helps to advance the etching downward and increase the depth of the deep hole. At the same time, it avoids damage to the sidewalls of the deep hole and helps to obtain the recessed structure 130 with the best morphology. Optionally, during the first etching stage, when the current in the first magnetic field element 271 is at a high potential, the range of the current value is greater than 0A and less than or equal to 200A. That is, during the first etching stage, the current in the first magnetic field element 271 is at least partially at a high potential. This not only promotes the etching downward but also avoids adverse effects on the sidewalls of the recessed structure 130, improves the utilization efficiency of the plasma, and enhances the treatment effect on the recessed structure 130.

[0076] Furthermore, during the first etching stage, a low-potential current is supplied to the second magnetic field element 272. As mentioned above, during the first etching stage, a large amount of plasma is generated mainly by applying a high source radio frequency power to the cavity. The divergent magnetic field generated by the second magnetic field element 272 below the gas spray head 223 can increase the collision probability of active particles and process gases to a certain extent, which helps to increase the density of the generated plasma. Since the current supplied is at a low potential, its deflection effect on charged particles below the gas spray head 223 is limited. This stage is dominated by the effect of the vertical magnetic field. Therefore, this method can further increase the etching capability of the recessed structure 130. It is understood that during the first etching stage, when the second magnetic field element 272 is activated and current is supplied, the source RF and bias RF power supplied to the cavity can be appropriately reduced. The plasma concentration required for this stage is compensated and increased by the second magnetic field element 272. Since the second magnetic field element 272 is located in the RF-shielded vacuum ring, this method can effectively prevent arcing and breakdown due to excessive RF power in the cavity, thus helping to ensure the stability of the process and equipment. Of course, the second magnetic field element 272 can also be left off during the first etching stage to save current consumption. In practical applications, it can be adjusted according to actual needs, and this invention does not impose any limitations on this. Optionally, the current value range of the second magnetic field element 272 when it is at a low potential is: greater than or equal to 0A and less than 200A.

[0077] In the second etching stage, reducing the source RF power and bias RF power decreases the concentration of plasma generated by dissociation, and consequently reduces the thickness of the sheath structure. This reduces the sheath structure's confinement of electrons, making it easier for electrons to enter the deep holes and neutralize accumulated positive ions. However, as the plasma concentration decreases and the depth of the recessed structure 130 increases, it becomes increasingly difficult for electrons to reach the bottom of the deep holes, thus limiting their neutralization effect on positive ions. Based on this, as... Figure 6 As shown, in this embodiment, during the second etching stage, a high-potential current (i.e., a larger current) is supplied to the second magnetic field element 272 to generate a divergent strong magnetic field below the gas spray head 223. This divergent strong magnetic field increases the collision probability between electrons, positive ions, free radicals, and process gases, further increasing the dissociation capability of the process gases and increasing the plasma concentration, thereby increasing the neutralization capability of positive charges in the deep holes. Optionally, during the second etching stage, the current value range of the second magnetic field element 272 when it is at a high potential is greater than 0A and less than or equal to 200A. That is, during the second etching stage, the current in the second magnetic field element 272 is at least partially at a high potential to enhance the dissociation capability of the process gases and strengthen the treatment effect on the recessed structure 130.

[0078] Furthermore, in the second etching stage, a low-potential current is supplied to the first magnetic field element 271. As mentioned above, the second etching stage mainly involves neutralizing the charge on the substrate 100 to facilitate subsequent processes. In this stage, the magnetic field generated by the first magnetic field element 271, perpendicular to the surface of the substrate 100, further enhances the collimation of charged particle motion, allowing more electrons to reach the bottom of the deep holes. This increases the electron concentration at the bottom of the deep holes, thereby promoting the neutralization of positive ions in the deep holes and improving the control of residual positive ions at the bottom of the deep holes during microscopic processes. Optionally, in the second etching stage, the current value of the first magnetic field element 271 at a low potential range is greater than or equal to 0A and less than 200A. It should be noted that during the second etching stage, the current in the first magnetic field element 271 can also be at a high potential. The first magnetic field element 271 generates a strong magnetic field perpendicular to the substrate 100, which improves the collimation of charged particles entering the recessed structure 130, helps to deepen the recessed structure 130, and avoids affecting the sidewalls of the recessed structure 130. This results in the formed recessed structure 130 having a better vertical cross section and bottom roundness, thereby obtaining an ideal etching morphology.

[0079] Optionally, the time percentage of the first etching stage ranges from 5% to 50% of the entire cycle, and the time percentage of the second etching stage ranges from 50% to 95% of the entire cycle. In practical applications, the time percentage of each etching stage can be adjusted according to the different etching effects produced by the first and second etching stages and the actual application requirements to achieve the optimal etching effect with low power consumption. For example, in one embodiment, within the same etching cycle, the time of the second etching stage is longer than that of the first etching stage to provide sufficient charge neutralization time, minimize positive ion accumulation, improve the charge neutralization effect at the bottom of the deep hole, facilitate subsequent process steps, and thus obtain the ideal morphology of the recessed structure 130. Furthermore, in the first and second etching stages, regardless of whether the current in the first magnetic field element 271 and the second magnetic field element 272 is at a high potential or a low potential, its current range is not limited to the aforementioned data range. In other embodiments, it can also be other data ranges. The present invention does not limit this, as long as the corresponding function can be achieved.

[0080] Optionally, in the first etching stage, the peak power range of the source RF power is 50W to 10000W, and the peak power range of the bias RF power is 0W to 100000W. Further optionally, in the second etching stage, the peak power range of the source RF power is 0 to 50W; and the value of the bias RF power is greater than zero or equal to zero. Of course, the ranges of source RF power and bias RF power in each stage are not limited to the above. In other embodiments, they can be set according to actual application requirements and site conditions, and this invention does not impose any limitations on this. In practical applications, since the restart process of the source RF power source is relatively time-consuming, preferably, this invention does not repeatedly start and stop the source RF power source during the etching process. Instead, in the second etching stage, it generates a lower source RF power that can maintain plasma continuity, thereby reducing operational complexity, increasing throughput, and simplifying operation steps, while also helping to ensure its service life. It should be noted that when transitioning from the first etching stage to the second etching stage, the source RF power and bias RF power can be rapidly reduced to very low levels or even zero, so that the thickness of the sheath structure between the plasma and the substrate 100 is reduced to a minimum. This allows electrons in the plasma to diffuse more easily to the surface of the substrate 100, increasing the probability of neutralizing positive ions in the recessed structure 130.

[0081] In summary, the plasma processing apparatus and etching method of the present invention include a magnetic field element 270 that generates a magnetic field perpendicular to the substrate 100 and a divergent magnetic field inclined to the lower surface of the gas spray head 223. At a specific moment, the specific magnetic field provided by the magnetic field element 270 can adjust the distribution and movement direction of charged particles in the reaction region, achieving precise control of the process. This apparatus not only constrains the scattering of incident ions in the sheath and improves the collimation of ions entering the recessed structure 130, thereby enhancing the etching capability of the recessed structure 130 without increasing the power peak, but it also increases the dissociation capability of the process gas, thereby increasing the charge neutralization capability of the recessed structure 130.

[0082] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A plasma processing apparatus characterized by comprising: It includes a vacuum reaction chamber, which contains: The lower electrode includes a bearing surface for supporting the substrate; An upper electrode is disposed opposite to the lower electrode. The upper electrode has a gas spray head that introduces process gas into the cavity. A reaction zone is formed between the upper electrode and the lower electrode. Source radio frequency power supply, which is used to apply source radio frequency power into the cavity to ignite the process gas and generate plasma; Bias RF power supply, which is used to apply bias RF power into the cavity; A magnetic field element is disposed around the reaction region. The magnetic field element is configured to generate a magnetic field to regulate charged particles in the reaction region. The magnetic field includes a magnetic field perpendicular to the bearing surface located in the reaction region and a divergent magnetic field inclined to the lower surface of the gas spray head. The magnetic field perpendicular to the bearing surface is used to improve the collimation of the charged particle motion, and the divergent magnetic field is used to increase the collision probability of the charged particles and increase the degree of dissociation of the process gas. A controller, connected to the magnetic field element, is used to control the current flowing through the magnetic field element to adjust the magnetic field perpendicular to the bearing surface and the divergent magnetic field, respectively.

2. The plasma processing apparatus of claim 1, wherein, The magnetic field element comprises: A first magnetic field element, which surrounds the lower part of the reaction region, can generate a magnetic field perpendicular to the bearing surface; The second magnetic field element, which surrounds the upper part of the reaction region, can generate a divergent magnetic field that is inclined to the lower surface of the gas spray head. The controller is connected to the first magnetic field element and the second magnetic field element respectively, and the controller is used to control the current flowing through the first magnetic field element and the second magnetic field element.

3. The plasma processing apparatus as described in claim 2, characterized in that, The first magnetic field element includes a plurality of coils arranged vertically with the same inner diameter, and the second magnetic field element includes a plurality of coils arranged vertically with their inner diameters gradually increasing from bottom to top.

4. The plasma processing apparatus as described in claim 3, characterized in that, In the vertical cross-section of the second magnetic field element, the arrangement direction of the multiple coils is at an angle α with the vertical line, and the range of the angle α is 0°<α<90°.

5. The plasma processing apparatus of claim 2, wherein, Also includes: A controller, connected to the first magnetic field element and the second magnetic field element, supplies pulse current to the first magnetic field element and the second magnetic field element, causing the high potential of the current in the first magnetic field element and the second magnetic field element to change alternately.

6. The plasma processing apparatus as described in claim 2, characterized in that, The first magnetic field element and the second magnetic field element have pulse currents. The first magnetic field element includes an inner loop coil and an outer loop coil. The inner diameter of the inner loop coil is smaller than the inner diameter of the outer loop coil. The high potential of the current in the outer loop coil changes synchronously with the high potential of the current in the second magnetic field element. The high potential of the current in the inner loop coil changes alternately with the high potential of the current in the second magnetic field element.

7. The plasma processing apparatus of claim 1, wherein, Also includes: A lifting ring surrounds the reaction region, and the magnetic field element is disposed within the lifting ring.

8. The plasma processing apparatus of claim 2, wherein, Also includes: The current in the bias RF power supply, the current in the first magnetic field element, and the current in the second magnetic field element are in pulse mode. The high potential of the current in the first magnetic field element changes synchronously with the high potential of the current output by the bias RF power supply, and the high potential of the current in the second magnetic field element changes alternately with the high potential of the current output by the bias RF power supply.

9. An etching method using the plasma processing apparatus according to any one of claims 1 to 8, characterized by, The method includes: The required process gas is introduced into the vacuum reaction chamber; The etching process includes: applying a pulsed source radio frequency to the cavity to form plasma, applying a pulsed bias radio frequency to accelerate charged particles toward the substrate, and adjusting the distribution and direction of movement of charged particles in the reaction region through a magnetic field element. The etching process includes multiple etching cycles, and each etching cycle includes: First etching stage: The source RF and bias RF are at high potentials, and the substrate is etched. Second etching stage: The power of the source RF and bias RF is at a low potential to neutralize the charge on the substrate.

10. The etching method of claim 9, wherein, The magnetic field element comprises: A first magnetic field element is used to generate a magnetic field perpendicular to the bearing surface; The second magnetic field element is used to generate a divergent magnetic field that is inclined to the lower surface of the gas spray head. During the etching process, a pulsed current is passed through the first magnetic field element and the second magnetic field element.

11. The etching method as described in claim 10, characterized in that, During the first etching stage, a current at a high potential is passed through the first magnetic field element.

12. The etching method as described in claim 11, characterized in that, The current value range when the current in the first magnetic field element is at a high potential is: greater than 0A and less than or equal to 200A.

13. The etching method as described in claim 10, characterized in that, In the second etching stage, a current at a high potential is passed through the second magnetic field element.

14. The etching method as described in claim 13, characterized in that, The current value range when the current in the second magnetic field element is at a high potential is: greater than 0A and less than or equal to 200A.

15. The etching method as described in claim 11 or 12, characterized in that, During the first etching stage, a current at a low potential is passed through the second magnetic field element.

16. The etching method as described in claim 15, characterized in that, The current value range when the current in the second magnetic field element is at a low potential is: greater than or equal to 0A and less than 200A.

17. The etching method as described in claim 13 or 14, characterized in that, In the second etching stage, a current at a low potential is passed through the first magnetic field element.

18. The etching method as described in claim 17, characterized in that, The current value range when the current in the first magnetic field element is at a low potential is: greater than or equal to 0A and less than 200A.

19. The etching method as described in claim 10, characterized in that, During the second etching stage, the current in the first magnetic field element is at a high potential.

20. The etching method as described in claim 9, characterized in that, Within the same etching cycle, the second etching stage lasts longer than the first etching stage.

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