Plasma processing device and etching method thereof

Abstract

The invention discloses a plasma processing device and an etching method thereof, the plasma processing device comprises a vacuum reaction chamber, and the vacuum reaction chamber comprises a lower electrode which comprises a bearing surface used for bearing a substrate; the upper electrode and the lower electrode are oppositely arranged, the upper electrode is provided with a gas spraying head for introducing process gas into the cavity, and a reaction area is formed between the upper electrode and the lower electrode; the magnetic field element is arranged around the reaction area, the magnetic field element is configured to generate a magnetic field to adjust the charged particles in the reaction area, and 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. The device has the advantages that the distribution and the movement direction of the charged particles in the reaction area are adjusted through the magnetic field element at a specific moment, accurate control over the technological process can be achieved, ideal etching morphology can be obtained, and meanwhile the capacity of etching the sunken structure can be improved under the condition that the power peak value is not increased.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a plasma processing apparatus and an etching method thereof. Background Art

[0002] With the advent of the big data era, the demand for data storage has shown a geometric order of magnitude growth. To meet this demand, the technology of storage chips has been transformed from 2D NAND to 3D NAND with higher storage density but more complex structure under the promotion of large manufacturers such as Samsung, Hynix, Micron, and Toshiba. 3D NAND is formed by multiple layers of stacking. With the increasing device integration, the number of stacked layers of 3D NAND also increases, and the depth of the recessed structure, which is the feature area of the word line and the contact, also increases day by day. Currently, the mainstream number of stacked layers of 3D NAND is 128 layers, and the corresponding recessed structure has a very high aspect ratio (HAR). The recessed structure designed with a high aspect ratio can break through the capacity limit on the plane, but it also greatly increases the difficulty of etching the recessed structure, bringing great challenges in terms of process and equipment.

[0003] As is well known, a normal substrate requires thousands of process steps from a silicon wafer to the final packaging. The multiple process steps generate inevitable complexity during the processing. Among them, the recessed structure etched on the substrate is the basis of the multiple process steps, and the etching quality of the recessed structure is crucial for the quality of the subsequent self-aligned multiple-pattern finished devices. However, the existing etching of the recessed structure still faces many problems. For example, as the aspect ratio of the recessed structure increases, the peak power required for etching becomes higher and higher, making the challenge of the anti-breakdown design inside the chamber greater and greater. In addition, as the etching depth deepens, it is difficult to guarantee the processing effect of the recessed structure. In practical applications, various factors will affect the etching of the recessed structure, thereby affecting the formation of the subsequent multiple-pattern finished devices, reducing the yield of device production, and affecting the production volume and preparation scale of integrated circuits. Therefore, it is necessary to improve the existing production equipment or production method.

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

[0005] Based on the aforementioned technical problems, the object of the present invention is to provide a plasma processing apparatus and an etching method thereof. The plasma processing apparatus adjusts the distribution and movement direction of charged particles in the reaction region through a magnetic field element at a specific moment, enabling precise control of the process. The apparatus can not only restrain the scattering of incident ions, improve the collimation of ions entering the concave structure, and enhance the etching ability of the concave structure under the same power intensity, but also increase the dissociation ability of the process gas, thereby increasing the charge neutralization ability in the concave structure, effectively controlling the positive ion residue at the bottom of the deep hole in the microscopic process for the subsequent process to proceed, helping the formed concave structure to have a better vertical cross-section and bottom roundness, and thus obtaining an ideal etching morphology.

[0006] To achieve the above object, the present invention is realized through the following technical solutions:

[0007] A plasma processing apparatus, which includes a vacuum reaction chamber, and the vacuum reaction chamber includes:

[0008] A lower electrode, which includes a bearing surface for carrying a substrate;

[0009] An upper electrode, which is disposed opposite to the lower electrode. The upper electrode has a gas shower head for introducing a process gas into the chamber, and a reaction region is formed between the upper electrode and the lower electrode;

[0010] A magnetic field element, which is disposed around the reaction region. The magnetic field element is configured to generate a magnetic field to adjust the charged particles in the reaction region. Among them, the magnetic field includes a magnetic field perpendicular to the bearing surface and a divergent magnetic field inclined to the lower surface of the gas shower head.

[0011] Optionally, the magnetic field element includes:

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

[0013] A second magnetic field element, which surrounds the upper part of the reaction region and can generate a divergent magnetic field inclined to the lower surface of the gas shower head.

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

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

[0016] Optionally, it further includes:

[0017] A controller, which is connected to the first magnetic field element and the second magnetic field element. The controller passes pulsed current into the first magnetic field element and the second magnetic field element, which can cause the high potential of the current in the first magnetic field element and the second magnetic field element to alternate.

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

[0019] Optionally, it further includes:

[0020] A lifting ring, which surrounds the reaction area, and the magnetic field element is arranged inside the lifting ring.

[0021] Optionally, it further includes:

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

[0023] A source RF power supply, which is used to apply source RF power to the cavity;

[0024] The bias RF power supply, the current in the first magnetic field element, and the current in the second magnetic field element are in pulsed 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 alternates with the high potential of the current output by the bias RF power supply.

[0025] Optionally, an etching method for the foregoing plasma processing device, the method includes:

[0026] Introducing the required process gas into the vacuum reaction chamber;

[0027] Performing an etching process, which includes: applying pulsed source RF to form plasma in the chamber, applying pulsed bias RF to accelerate charged particles to move towards the substrate, and adjusting the distribution and movement direction of charged particles in the reaction area through the magnetic field element;

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

[0029] The first etching stage: The power of the source RF and the bias RF is at a high potential to etch the substrate;

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

[0031] Optionally, the magnetic field element includes:

[0032] A first magnetic field element for generating a magnetic field perpendicular to the bearing surface;

[0033] A second magnetic field element for generating a divergent magnetic field inclined to the lower surface of the gas shower head;

[0034] During the etching process, a pulsed current is applied to 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 applied to the first magnetic field element.

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

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

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

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

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

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

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

[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 time of the second etching stage is longer than the time of the first etching stage.

[0045] The present invention has the following advantages compared with the prior art:

[0046] In a plasma processing apparatus and an etching method thereof according to the present invention, the magnetic field element included in the plasma processing apparatus can generate a magnetic field perpendicular to the substrate and a divergent magnetic field inclined to the lower surface of the gas shower 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, realizing precise control of the process. This apparatus can not only constrain the scattering of incident ions, improve the collimation of ions entering the recessed structure, and enhance the ability to etch high aspect ratio structures without increasing the peak power, but also increase the dissociation ability of the process gas, thereby increasing the charge neutralization ability in the recessed structure. Description of the Drawings

[0047] Figure 1 It 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 It is a schematic diagram of a plasma processing apparatus according to the present invention;

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

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

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

[0052] Figure 6 It is a schematic diagram of a control timing sequence according to the present invention. Detailed Embodiments

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] It should be noted that in this article, the terms "include", "comprise", "have" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or terminal device. Without further limitation, the elements defined by the statement "including..." or "comprising..." do not exclude the presence of additional elements in the process, method, article or terminal device including the said elements.

[0055] It should be noted that the accompanying drawings are in a very simplified form and use non-precise ratios, only for the purpose of conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0056] As Figure 1 shown, it is a partial schematic diagram of a semiconductor device of the present invention. The semiconductor device includes a substrate 100. The substrate 100 includes a stacked layer formed by alternately arranging different material layers. The stacked layer includes a first material layer 110 and a second material layer 120. The stacked layer contains an etched recessed structure 130. During the etching process, a patterned mask 140 is covered on the stacked layer of the substrate 100. The opening position of the mask 140 forms a corresponding target pattern. Through the etching process of the stacked layer, a recessed structure 130 corresponding to the pattern of the mask 140 is finally formed for the subsequent preparation of a self-aligned multiple patterning device. In this embodiment, the first material layer 110 and the second material layer 120 are an oxide layer and a nitride layer respectively. It is necessary to use an oxide / nitride (Oxide / Nitride) overlapping process to prepare a stacked layer of several microns to more than ten microns, and form a recessed structure 130 on the stacked layer by the substrate 100 etching method. In this substrate 100 etching method, amorphous carbon of several microns is used as the mask 140. By dissociating the process gas to generate plasma, the stacked layer is etched to prepare very deep holes (Hole) or trenches (Trench) in the stacked layer to form the recessed structure 130, and meet very strict topography requirements. In practical applications, based on different types of stacked layer materials, different process gases can be used for etching to achieve the optimal etching effect. In this embodiment, C x F y H z 、C x F y 、Ar、N 2 、O 2 and other reaction gases are used as the process gases introduced into the vacuum reaction chamber.

[0057] Of course, the material types of 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 restrictions thereon. By way of example, in another embodiment, the first material layer 110 and the second material layer 120 are a polysilicon layer (Si) and a silicon oxide layer, respectively. Further, the present invention does not limit the number of stacked layers of the substrate 100. The more stacked layers there are, the higher the device integration level.

[0058] As can be seen from the foregoing, the etching of the recessed structure 130 with a high aspect ratio design, i.e., the deep hole, is the most critical step in device production. The etching quality of the recessed structure 130 is crucial for the subsequent preparation of the self-aligned multiple patterning device. Moreover, with the development of semiconductor nodes, the processing requirements for the high aspect ratio recessed structure 130 are getting higher and higher. Ideally, the recessed structure 130 on the substrate 100 needs to have a vertical profile, and the sidewalls of the recessed structure 130 should not exhibit bending or bowing 131. The horizontal profile at the bottom of the recessed structure 130 should be as close to circular as possible without distortion or other deformation conditions. As the aspect ratio increases, it is generally required that the ion collimation incident on the microstructure (hole or groove) be higher and higher, so as to promote high-energy ions to reach the bottom of the high aspect ratio hole or groove to achieve etching. In practical applications, in order to obtain a recessed structure 130 with an ideal morphology, very high low-frequency radio frequency power can be used in a very short time to obtain 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 radio frequency power peak becomes higher and higher. Although the desired recessed structure 130 can be obtained based on this power peak, this also makes the challenge of the anti-voltage breakdown design inside the chamber increasingly large.

[0059] Based on the above, the present invention provides a plasma processing apparatus. The plasma processing apparatus includes a magnetic field element disposed around a reaction region between an upper electrode and a lower electrode. The magnetic field element is configured to generate a magnetic field to regulate charged particles in the reaction region. Among them, 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 shower head. At a specific moment 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, improve the collimation of ions entering the recessed structure 130, achieve precise control of the process, and thus obtain an ideal etching profile. At the same time, the magnetic field element can also enhance the dissociation ability of the process gas, thereby increasing the charge neutralization ability in the recessed structure. Therefore, the plasma processing apparatus improves the ability to control the angular distribution of plasma ion scattering and the ability to etch recessed structures with a high aspect ratio under the same intensity of radio frequency power, helps to generate standardized recessed structures 130 with a high aspect ratio, and at the same time reduces the impact on the inside of the chamber, avoids electrical breakdown of the inside of the chamber caused by too high radio frequency power, and ensures the stability of the chamber environment. Through experimental verification, when using the plasma processing apparatus of the present invention, when the aspect ratio of the obtained recessed structure 130 is greater than or equal to 50, the required collimation and good profile can still be maintained. 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. In the production requirements of recessed structures 130 with an aspect ratio less than 50, the apparatus can also meet the process requirements.

[0060] Specifically, as Figure 2As shown in the figure, a plasma processing device of the present invention includes a vacuum reaction chamber 200, which is surrounded by a reaction chamber cavity and a cavity end cover 201. The reaction chamber cavity is usually made of a metal material and includes a cavity side wall 202 and a cavity bottom wall 203. A substrate transfer port (not shown in the figure) is provided on the cavity side wall 202, and this substrate transfer port is used to realize the transfer of the substrate 100 between the inside and outside of the vacuum reaction chamber 200. Inside the vacuum reaction chamber 200, there is a lower electrode 210, which is arranged at the inner bottom of the vacuum reaction chamber 200. The lower electrode 210 includes a bearing surface for bearing the substrate 100, and the substrate 100 to be processed introduced into the vacuum reaction chamber 200 is placed on this bearing surface. Inside the vacuum reaction chamber 200, there is also an upper electrode 220 arranged opposite to the lower electrode 210. A reaction area is formed between the upper electrode 220 and the lower electrode 210. The upper electrode 220 includes an installation base 221, and the installation base 221 is arranged through a through hole of the cavity end cover 201. A plurality of gas channels 222 are arranged inside the installation base 221, and the gas channels 222 are communicated with a gas buffer 230 located above the cavity end cover 201. At the bottom of the installation base 221, there is a gas spray head 223 including a plurality of spray holes 224, and the spray holes 224 are communicated with the gas channels 222. The process gas in the gas supply device is sequentially injected into the vacuum reaction chamber 200 through the gas buffer 230, the gas channels 222 and the spray holes 224.

[0061] Furthermore, this plasma processing device also includes a source radio frequency power supply 240 and a bias radio frequency power supply 250. The source radio frequency power supply 240 and the bias radio frequency power supply 250 apply radio frequency energy to the lower electrode 210 through a matching network 260. Among them, the source radio frequency power supply 240 is used to apply a source radio frequency to the chamber to ignite the process gas to generate plasma and then form a concave structure 130. The bias radio frequency power supply 250 is used to apply a bias radio frequency power to the chamber to accelerate the charged particles in the plasma to increase their moving speed towards the substrate 100 and enhance their directionality of moving towards the substrate 100. In this embodiment, the source radio frequency power supply 240 and the bias radio frequency power supply 250 apply their radio frequency power to the lower electrode 210. In other embodiments, it can also be applied to the upper electrode 220 or applied to the upper electrode 220 and the lower electrode 210 respectively.

[0062] During the process, first transfer the substrate 100 to be processed to the bearing surface of the lower electrode 210, and then x F y H z 、O 2After the reaction gases such as those are mixed well through the gas buffer 230, they are injected into the chamber through the gas passage 222 of the mounting base 221 and the spray holes 224 of the gas shower head 223. Then, the RF powers of the source RF power supply 240 and the bias RF power supply 250 are input to the lower electrode 210 through the matching network 260, and a large amount of plasma is dissociated from the process gas by means of capacitive coupling, so that the space between the upper electrode 220 and the lower electrode 210 is a plasma environment for etching (please refer to Figure 1 and Figure 2 ). This plasma environment contains a large number of active particles such as positive ions, radicals and electrons ( Figure 1 where + represents positive ions, - represents electrons, and О represents radicals). The above-mentioned active particles can undergo various physical and / or chemical reactions with the surface of the substrate 100 to be processed, causing the morphology of the substrate 100 to be processed to change, thereby completing the processing of the substrate 100 to be processed. Among them, electrons reach the surface of the substrate 100 first due to their relatively fast speed, forming an electric field between the substrate 100 and the plasma. This electric field accelerates the positive ions. After the electrons and positive ions finally stabilize, a very high sheath structure is formed between the plasma and the substrate 100. The positive ions are accelerated under the bias voltage of the sheath structure and reach the deep holes of the substrate 100, bombarding the bottom of the deep holes to promote the progress of etching; the dissociated radicals reach the surface of the substrate 100 and the deep holes (the bottom of the concave structure 130) through diffusion, undergoing surface reactions and generating by-products.

[0063] Furthermore, as shown in Figure 2 , the vacuum reaction chamber 200 further includes a magnetic field element 270. The magnetic field element 270 is disposed around the reaction region to closely control the generated plasma and reduce the waste of magnetic field energy. The magnetic field element 270 is configured to generate a magnetic field to regulate the charged particles in the reaction region. Among them, the magnetic field includes a magnetic field perpendicular to the bearing surface and a divergent magnetic field inclined to the lower surface of the gas shower head 223. During the process, according to the force principle of charged particles in the magnetic field, the charged particles moving parallel to the magnetic field lines are not affected by the magnetic field force (for example, the charged particles whose original moving direction is perpendicular to the substrate 100 for etching deep holes), but the charged particles with a horizontal component and a certain angle with the magnetic field lines will be restricted by the magnetic field and rotate around the magnetic field lines, reducing the displacement of such charged particles in the direction parallel to the substrate 100 and making it easier for them to move in the direction perpendicular to the surface of the substrate 100, so that the deflection angle distribution of the charged particles entering the deep holes is more concentrated in the vertical direction (please refer to Figure 4(Schematic diagram of the scattering angle distribution of charged particles), so that more charged particles can reach the bottom of the deep hole for etching. On the other hand, also based on the principle that charged particles will move around the magnetic field lines, the divergent magnetic field inclined to the lower surface of the gas shower head 223 can increase the moving component of the charged particles in the direction parallel to the substrate 100, increase the collision probability of electrons, positive ions and process gas, further increase the dissociation degree of the process gas, and enhance the plasma density. In this way, more electrons can enter the bottom of the deep hole, thereby increasing the ability to neutralize the positive charges in the high aspect ratio structure, reducing the etching direction deviation caused by the charge accumulation at the bottom of the hole, and improving the consistency of the upper and lower topography of the deep hole. As can be seen from the above, the magnetic field element 270 can not only restrict the scattering of the incident ions in the sheath layer, improve the collimation of the ions entering the concave structure 130, and enhance the ability to etch the high aspect ratio structure under the same power intensity, but also increase the dissociation ability of the process gas, thereby increasing the neutralization ability in the high aspect ratio structure. In actual use, by applying DC currents with different directions and different magnitudes to the magnetic field element 270, the particle state in the reaction region can be controlled through the magnetic field element 270. In other embodiments, an alternating current can also be added according to the process requirements to cooperate with the periods of etching and neutralizing charges, respectively strengthening the process effects of the two stages.

[0064] As Figure 2 and Figure 3 shown, in this embodiment, the magnetic field element 270 includes a first magnetic field element 271 and a second magnetic field element 272. Among them, the first magnetic field element 271 is arranged around the lower part of the reaction region, making it closer to the plasma in the region above the substrate 100. The plasma in this region directly plays the role of etching the substrate 100. The first magnetic field element 271 can generate a magnetic field perpendicular to the bearing surface. In actual application, this magnetic field perpendicular to the bearing surface can improve the movement collimation of the charged particles in the concave structure 130, increase the etching depth and reduce the damage to the side walls of the concave structure 130. The second magnetic field element 272 is arranged around the upper part of the reaction region. The plasma in this region acts as the generation source of the etching particles. The second magnetic field element 272 can generate a divergent magnetic field inclined to the lower surface of the gas shower head 223. This divergent magnetic field can increase the dissociation ability of the process gas, improve the plasma density, thereby increasing the charge neutralization ability at the bottom of the deep hole and promoting 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 the peripheral DC power supply, so as to pass DC currents with different directions and different magnitudes according to the setting during the process, thereby controlling the magnetic field directions and intensities of each.

[0065] In this embodiment, the first magnetic field element 271 includes a plurality of vertically arranged coils with the same inner diameter, and each coil is connected to a DC power supply so that the first magnetic field element 271 generates a magnetic field perpendicular to the bearing surface, improving the collimation of charged particles and contributing to the continuous increase of the etching depth. The second magnetic field element 272 includes a plurality of vertically arranged coils with an inner diameter gradually increasing from bottom to top, and each coil is connected to a DC power supply so that the second magnetic field element 272 generates a magnetic field diverging to both sides near the gas source side. The magnetic field lines of this magnetic field have an angle with the vertical line near the gas source to enhance the dissociation ability of the process gas and thus increase the density of the plasma. In actual use, by adjusting the currents 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 have magnetic field lines perpendicular to the surface of the substrate 100 near the substrate 100 part and diverging magnetic field lines near the gas shower head 223 part, so as to improve its 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 has an angle α with the vertical line (please refer to Figure 2 ), and the range of the angle α is 0° < α < 90°. It can be understood that the 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 also be set to other data ranges, and the present invention does not limit this.

[0067] Furthermore, as Figure 2 and Figure 3As shown, the first magnetic field element 271 includes an inner ring coil 273 and an outer ring coil 274 arranged vertically with different inner diameters. The inner ring coil 273 is disposed close to the substrate 100, and the outer ring coil 274 is disposed outside the inner ring coil 273, that is, the inner diameter of the inner ring coil 273 is smaller than that of the outer ring coil 274. The outer ring coil 274 is arranged downward from the bottom of the second magnetic field element 272. The surface formed by the overall enclosure of the second magnetic field element 272 is in a horn-shaped structure. The diameter of the second magnetic field element 272 close to the gas shower head 223 is larger than the diameter thereof close to 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 coil structures, and they can also be other structures as long as the corresponding functions can be achieved. The present invention does not limit this. For example, in other embodiments, the first magnetic field element 271 and / or the second magnetic field element 272 is a single-piece sheet-shaped iron core or magnetic core, or can also be a plurality of coils formed by arranging the same conductor in a spiral. Similarly, the composition and arrangement manner 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 area and the second magnetic field element 272 is close to the upper part of the reaction area. The present invention does not limit this, as long as the corresponding functions can be achieved.

[0068] During the etching process, a current in a pulse mode is passed into the magnetic field element 270. The current potentials of the inner ring coil 273 and the outer ring coil 274 included in the first magnetic field element 271 can change synchronously or alternately. Optionally, the high current potentials of the inner ring coil 273 and the outer ring coil 274 change alternately. Specifically, the high current potential of the current in the outer ring coil 274 changes synchronously with the high current potential of the current in the second magnetic field element 272, and the high current potential of the current in the inner ring coil 273 changes alternately with the high current potential of the current in the second magnetic field element 272. That is, regardless of whether the current in 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 incident on the deep holes, thereby increasing the etching depth without increasing the power peak value, helping to reduce power loss, improve the utilization rate of the plasma, and at the same time reducing the pressure faced by the anti-breakdown design in the cavity. Of course, the currents passed into the inner ring coil 273 and the outer ring coil 274 can also be in a high potential state at certain moments to further strengthen the magnetic field intensity of the vertical magnetic field on the surface of the substrate 100 and enhance the constraint and guiding effect of the vertical magnetic field on charged particles.

[0069] Further, the first magnetic field element 271 and the bias RF power supply 250 can be combined to enhance the guiding effect on charged particles. Exemplarily, in one embodiment, to enhance the etching effect, the currents in the bias RF power supply 250, the first magnetic field element 271, and the second magnetic field element 272 are in a pulsed mode. The high potential of the current in the first magnetic field element 271 synchronously changes 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, so as to enhance the collimation and moving speed of charged particles under the action 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 promoting the etching process. Further, 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 waste of the bias power output by the bias RF power supply 250, and at the same time enhances the effect of the magnetic field generated by the second magnetic field element 272 in promoting the dissociation of process gases.

[0070] Further, the plasma processing apparatus further includes a controller 280, which is connected to the first magnetic field element 271 and the second magnetic field element 272. The controller 280 passes pulsed current into the first magnetic field element 271 and the second magnetic field element 272, enabling the high potentials of the currents in the first magnetic field element 271 and the second magnetic field element 272 to alternate, so as to optimize the etching process of the recessed structure 130 on the substrate 100.

[0071] Further, the plasma processing apparatus further includes a lifting ring 290, which is arranged to surround the reaction area, and the magnetic field element 270 is arranged inside the lifting ring 290. In this embodiment, the lifting ring 290 can be regarded as a liftable vacuum sealing tube to protect the magnetic field element 270 from the plasma environment interference in the chamber, which helps to ensure its service life; at the same time, the lifting ring 290 can also drive the magnetic field element 270 to lift to adjust the area corresponding to its magnetic field, and further adjust the plasma state corresponding to this area. When the substrate 100 needs to enter and exit the vacuum reaction chamber 200, the lifting ring 290 can be raised above the substrate transfer port without hindering the access path of the manipulator. It can be understood that the first magnetic field element 271 and the second magnetic field element 272 can be jointly arranged in one lifting ring 290, or they can be separately arranged in two lifting rings 290 to separately lift the first magnetic field element 271 or the second magnetic field element 272 to adjust their magnetic field distribution. The present invention does not limit this.

[0072] Based on the same inventive concept, the present invention also provides an etching method for a plasma processing apparatus, as Figure 5As shown, the etching method includes: introducing the required process gas into the vacuum reaction chamber 200; performing an etching process, which includes: applying a pulsed source radio frequency to form a plasma in the chamber, applying a pulsed bias radio frequency to accelerate charged particles towards the substrate 100, and adjusting the distribution and movement direction of charged particles in the reaction area through the magnetic field element 270. Among them, the etching process includes multiple etching cycles (please refer to Figure 6 , Figure 6 where 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), and 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 to etch the substrate 100; a second etching stage (S320): the power of the source radio frequency and the bias radio frequency is at a low potential to neutralize the charge carried on the substrate 100.

[0073] As can be seen from the above, the present invention adopts a pulsed etching method combining a first etching stage and a second etching stage. In the first etching stage, the source radio frequency power supply 240 and the bias radio frequency power supply 250 respectively apply a high-potential source radio frequency and a bias radio frequency to the cavity to dissociate the process gas to generate plasma and apply a bias electric field that moves positive charged particles towards the substrate, thereby generating a concave structure 130 on the substrate 100. In the second etching stage, in order to reduce the charge accumulation in the concave structure 130, opposite charges need to enter to neutralize it. Therefore, after reducing the power of the source radio frequency and the bias radio frequency, the concentration of the dissociated plasma 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. Therefore, electrons can diffuse into the deep holes as much as possible to neutralize the positive charges at the bottom of the deep holes. However, as the depth of the concave structure 130 becomes deeper and deeper, it becomes more and more difficult for electrons to reach the bottom of the deep holes, and its neutralization effect on positive ions becomes more and more limited. The probability of unwanted deformation occurring on the sidewalls of the concave structure 130 also increases accordingly. In this application, the magnetic field perpendicular to the bearing surface generated by the magnetic field element 270 and the divergent magnetic field inclined to the lower surface of the gas shower head 223 can respectively increase the collimation of charged particles in the plasma and the concentration of the plasma. With the increase in the concentration of the plasma, the concentration of electrons will also increase. At the same time, electrons will also be affected by the first magnetic field element 271 to increase the proportion of entering the concave structure 130, so as to avoid unwanted deformation of the concave structure 130. At the same time, it also improves the ability to etch high aspect ratio structures without increasing the radio frequency power, which helps to improve the yield of device production. In practical applications, a corresponding magnetic field environment can be generated at a specific timing moment according to actual needs to improve the etching efficiency of the substrate 100 and the etching quality of the concave structure 130, obtain an ideal etching morphology, facilitate the progress of subsequent processes, and help ensure the yield of device production. Compared with the process without the assistance of the magnetic field element 270, this method does not need to continuously increase the peak power to improve the ability to etch high aspect ratio structures. Therefore, this method helps to reduce energy consumption and avoid the problem of anti-breakdown in the cavity.

[0074] In this embodiment, the source radio frequency power supply 240 is used to provide source radio frequency power to the cavity to generate plasma in the cavity and then promote the generation of the concave structure 130; the bias radio frequency power supply 250 is used to provide bias radio frequency power to the cavity to accelerate the charged particles in the plasma to increase their moving speed towards the substrate 100 and increase their movement directionality; during the etching process, the distribution state and movement direction of the charged particles in the reaction region are adjusted by adjusting the current passed through the magnetic field element 270 to cooperate with the timing change of the radio frequency pulse. It can be understood that the working timings of the source radio frequency power supply 240, the bias radio frequency power supply 250, and the magnetic field element 270 can be independently controlled to realize different microscopic processes based on different etching processes.

[0075] As Figure 6 shown, it is a timing diagram of applying pulsed current to the first magnetic field element 271 and the second magnetic field element 272 in cooperation with the radio frequency pulses of the source radio frequency power supply 240 and the bias radio frequency power supply 250 in this embodiment. In this embodiment, in the first etching stage, a current at a high potential is passed through the first magnetic field element 271 to generate a strong magnetic field perpendicular to the bearing surface. As can be seen from the foregoing, in the first etching stage, both the source radio frequency and the bias radio frequency are in a high power state, and the plasma density in this stage is relatively high. They provide high ion energy to bombard the surface of the substrate 100 to form a recessed structure 130 with a high aspect ratio. At this time, a relatively large current is passed through the first magnetic field element 271 to generate a strong magnetic field perpendicular to the surface of the substrate 100. The confinement effect of this strong magnetic field on the charged particles in the plasma can greatly reduce the deflection amplitude of the charged particles in the horizontal direction when moving towards the surface of the substrate 100, so that the deflection angle distribution of the charged particles entering the deep hole is more concentrated in the vertical direction. Therefore, more charged particles will reach the bottom of the deep hole for etching and charge neutralization, which helps to promote the continuous downward etching, deepen the depth of the deep hole, and at the same time avoid damaging the side walls of the deep hole, which helps to obtain a recessed structure 130 with the best morphology. Optionally, in the first etching stage, when the current in the first magnetic field element 271 is at a high potential, the value range of the current passed through it is: greater than 0 A and less than or equal to 200 A, that is, in the first etching stage, the current in the first magnetic field element 271 is in a high potential state at least part of the time, which not only promotes the downward etching but also avoids having an adverse effect on the side walls of the recessed structure 130, improves the utilization efficiency of the plasma, and enhances the processing effect on the recessed structure 130.

[0076] Further, in the first etching stage, a current at a low potential is applied to the second magnetic field element 272. As described above, in the first etching stage, a large amount of plasma is mainly generated by applying a relatively high source RF power to the chamber. The divergent magnetic field generated by the second magnetic field element 272 below the gas showerhead 223 can increase the collision probability between active particles and process gases to a certain extent, which helps to increase the density of the generated plasma. Also, since the current applied to it is in a low-potential state, the deflection effect on charged particles below the gas showerhead 223 is limited. In this stage, the effect of the vertical magnetic field is dominant. Therefore, this method can further increase the etching ability of the recessed structure 130. It can be understood that in the first etching stage, when the second magnetic field element 272 is started and a current is applied, the source RF power and bias RF power applied to the chamber can be appropriately reduced. The second magnetic field element 272 compensates to increase the plasma concentration required in this stage. Since the second magnetic field element 272 is arranged in the vacuum ring of the RF shield, this method can effectively avoid the occurrence of arc breakdown in the chamber due to excessive RF power, which helps to ensure the stability of the process and equipment. Of course, the second magnetic field element 272 may not be turned on in the first etching stage to save current consumption. In practical applications, it can be adjusted according to actual needs, and the present invention does not limit this. Optionally, the current value range when the current in the second magnetic field element 272 is at a low potential is: greater than or equal to 0 A and less than 200 A.

[0077] In the second etching stage, after reducing the source RF power and bias RF power, the concentration of the dissociated generated plasma will decrease, and the thickness of the sheath structure will also decrease accordingly. The confinement effect of the sheath structure on electrons will also decrease, and electrons are more likely to enter the deep holes to neutralize the accumulated positive ions. However, as the plasma concentration decreases and the depth of the recessed structure 130 increases, it becomes more and more difficult for electrons to reach the bottom of the deep holes, and its neutralization effect on positive ions becomes more and more limited. Based on this, as Figure 6 shown, in this embodiment, in the second etching stage, a current at a high potential, that is, a relatively large current, is applied to the second magnetic field element 272 to generate a strong divergent magnetic field below the gas showerhead 223. This strong divergent magnetic field can increase the collision probability between electrons, positive ions, free radicals and process gases, further increase the dissociation ability of the process gases, improve the plasma concentration, and thus increase the neutralization ability of the positive charges in the deep holes. Optionally, in the second etching stage, the current value range when the current in the second magnetic field element 272 is at a high potential is: greater than 0 A and less than or equal to 200 A, that is, in the second etching stage, the current in the second magnetic field element 272 is at a high potential state at least for some time to improve the dissociation ability of the process gases and enhance the processing effect on the recessed structure 130.

[0078] Further, in the second etching stage, a current at a low potential is applied to the first magnetic field element 271. As described above, in the second etching stage, the process of neutralizing the charges carried on the substrate 100 is mainly carried out to facilitate the subsequent process. In this stage, the magnetic field perpendicular to the surface of the substrate 100 generated by the first magnetic field element 271 can further improve the collimation of the movement of charged particles, enabling more electrons to reach the bottom of the deep hole, which is beneficial to further increasing the electron concentration at the bottom of the deep hole, thereby promoting the neutralization of positive ions in the deep hole and enhancing the control of positive ion residues at the bottom of the deep hole in the microscopic process. Optionally, in the second etching stage, the current value range of the first magnetic field element 271 when the current is at a low potential is: greater than or equal to 0 A and less than 200 A. It should be noted that in the second etching stage, the current in the first magnetic field element 271 can also be at a high potential. By generating a strong magnetic field perpendicular to the substrate 100 through the first magnetic field element 271, the collimation of charged particles entering the concave structure 130 is improved, which helps to deepen the depth of the concave structure 130. At the same time, it also avoids affecting the sidewalls of the concave structure 130, making the formed concave structure 130 have a better vertical cross-section and bottom roundness, and thus obtaining an ideal etching morphology.

[0079] Optionally, the time ratio range of the first etching stage is 5% - 50% of the entire cycle, and the time ratio range of the second etching stage in the entire cycle is 50% - 95%. In practical applications, according to the different etching effects generated in the first etching stage and the second etching stage, as well as the actual application requirements, the time ratios of each etching stage can be adjusted to achieve the optimal etching effect with lower power loss. For example, in an 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 the accumulation of positive ions as much as possible, improve the charge neutralization effect at the bottom of the deep hole, facilitate the subsequent process, and thus obtain an ideal morphology of the concave structure 130. Further, in the first etching stage and the second etching stage, regardless of whether the currents in the first magnetic field element 271 and the second magnetic field element 272 are at a high potential or a low potential, their current ranges are not limited to the aforementioned data ranges. In other embodiments, they can also be other data ranges, and the present invention does not limit this, as long as the corresponding functions 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; the value of the bias RF power is greater than zero or equal to zero. Of course, the range of the source RF power and the bias RF power in each stage is not limited to the above. In other embodiments, it can also be set according to actual application requirements and field conditions, and the present invention is not limited to this. In practical applications, since the restart process of the source RF power source is relatively time-consuming, preferably, the present invention does not repeatedly start and shut down the source RF power source during the etching process, but generates a lower source RF that can maintain the plasma in the second etching stage, so as to reduce the complexity of operation, improve throughput and simplify the operation steps, while also helping to ensure its service life. It should be noted that when the first etching stage is turned into the second etching stage, the source RF power and the bias RF power can be quickly reduced to a very low level or even zero, so that the thickness of the sheath structure between the plasma and the substrate 100 is reduced to a very small level, thereby making it easier for the electrons in the plasma to diffuse to the surface of the substrate 100, thereby increasing the probability of neutralizing the positive ions in the recessed structure 130.

[0081] In summary, in a plasma processing device and an etching method thereof of the present invention, the magnetic field element 270 included in the plasma processing device can generate a magnetic field perpendicular to the substrate 100 and a divergent magnetic field inclined to the lower surface of the gas shower 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 the charged particles in the reaction area, thereby achieving precise control of the process. The device can not only constrain the scattering of the incident ions in the sheath layer and improve the collimation of the ions entering the recessed structure 130, so as to improve the ability to etch the recessed structure 130 without increasing the power peak, but also increase the dissociation ability of the process gas, thereby increasing the charge neutralization ability in the recessed structure 130.

[0082] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as limiting the present invention. After reading the above content, various modifications and substitutions of the present invention will be obvious to those skilled in the art. Therefore, the protection scope of the present invention should be defined by the attached claims.

Claims

1. A plasma processing device, characterized in that: It comprises a vacuum reaction chamber, wherein the vacuum reaction chamber contains: A lower electrode including a supporting surface for supporting a substrate; An upper electrode, which is arranged opposite to the lower electrode, the upper electrode has a gas shower head for introducing process gas into the chamber, and a reaction area is formed between the upper electrode and the lower electrode; A magnetic field element is disposed around the reaction area and is configured to generate a magnetic field to adjust the charged particles in the reaction area, wherein the magnetic field includes a magnetic field perpendicular to the carrying surface and a divergent magnetic field inclined to the lower surface of the gas shower head.

2. The plasma processing device according to claim 1, characterized in that The magnetic field element comprises: A first magnetic field element, which surrounds the lower part of the reaction area and can generate a magnetic field perpendicular to the carrying surface; The second magnetic field element, which surrounds an upper portion of the reaction region, can generate a divergent magnetic field inclined to a lower surface of the gas shower head.

3. The plasma processing device according to claim 2, characterized in that: The first magnetic field element includes a plurality of coils arranged vertically and having the same inner diameter, and the second magnetic field element includes a plurality of coils arranged vertically and having inner diameters gradually increasing from bottom to top.

4. The plasma processing apparatus according to claim 3, wherein: In the vertical cross section of the second magnetic field element, an angle α is formed between the arrangement direction of the plurality of coils and the vertical line, and the range of the angle α is 0°<α<90°.

5. The plasma processing apparatus according to claim 2, wherein: Also includes: A controller is connected to the first magnetic field element and the second magnetic field element. The controller passes pulse current into the first magnetic field element and the second magnetic field element, so that the high potential of the current of the first magnetic field element and the second magnetic field element can be changed alternately.

6. The plasma processing apparatus according to claim 2, wherein: There is a pulse current in the first magnetic field element and the second magnetic field element. The first magnetic field element includes an inner ring coil and an outer ring coil. The inner diameter of the inner ring coil is smaller than the inner diameter of the outer ring coil. The high potential of the current in the outer ring 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 ring coil changes alternately with the high potential of the current in the second magnetic field element.

7. The plasma processing apparatus according to claim 1, wherein: Also includes: A lifting ring surrounds the reaction area, and the magnetic field element is arranged in the lifting ring.

8. The plasma processing apparatus according to claim 2, wherein: Also includes: A bias radio frequency power supply, which is used to apply bias radio frequency power to the cavity; A source radio frequency power supply, which is used to apply source radio frequency power into the cavity; 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 for a plasma processing device according to any one of claims 1 to 8, characterized in that: The method comprises: Introducing required process gas into the vacuum reaction chamber; Performing an etching process, which includes: applying a source radio frequency in a pulse mode into the cavity to form a plasma, applying a bias radio frequency in a pulse mode to accelerate charged particles to move toward the substrate, and adjusting the distribution and movement direction of the charged particles in the reaction area by a magnetic field element; The etching process includes multiple etching cycles, and the etching cycles include: The first etching stage: the power of the source radio frequency and the bias radio frequency is at a high potential to etch the substrate; The second etching stage: the power of the source RF and the bias RF is at a low potential to neutralize the charge on the substrate.

10. The etching method of the plasma processing device according to claim 9, characterized in that: The magnetic field element comprises: A first magnetic field element, used to generate a magnetic field perpendicular to the bearing surface; a second magnetic field element, used to generate a divergent magnetic field inclined to a lower surface of the gas shower head; During the etching process, a pulse current is supplied to the first magnetic field element and the second magnetic field element.

11. The etching method of the plasma processing device according to claim 10, characterized in that: In the first etching phase, a current at a high potential is supplied to the first magnetic field element.

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

13. The etching method of the plasma processing device according to claim 10, characterized in that: In the second etching phase, a current at a high potential is supplied to the second magnetic field element.

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

15. The etching method of the plasma processing device according to claim 11 or 12, characterized in that: In the first etching phase, a current at a low potential is supplied to the second magnetic field element.

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

17. The etching method of the plasma processing device according to claim 13 or 14, characterized in that: In the second etching phase, a current at a low potential is supplied to the first magnetic field element.

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

19. The etching method of the plasma processing device according to claim 10, characterized in that: In the second etching stage, the current in the first magnetic field element is at a high potential.

20. The etching method of the plasma processing device according to claim 9, characterized in that: In the same etching cycle, the duration of the second etching stage is longer than that of the first etching stage.

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