Etching method of high aspect ratio structure and plasma processing device thereof

Abstract

The invention discloses an etching method of a high aspect ratio structure and a plasma processing device thereof. The etching method of the high aspect ratio structure comprises the following steps: introducing required process gas into a vacuum reaction cavity; applying radio frequency power into the cavity in a pulse mode so as to etch the substrate; wherein the etching process comprises a plurality of pulse periods, each pulse period comprises a first etching stage and a second etching stage, and the first etching stage comprises the steps of applying high-frequency radio-frequency power and low-frequency radio-frequency power into a cavity, and etching a substrate; the second etching stage comprises the steps of reducing high-frequency radio-frequency power and low-frequency radio-frequency power, and starting an auxiliary light source to provide auxiliary light for the substrate. According to the method, the problem of positive ion residue in the high-aspect-ratio structure and the distribution of byproducts in the etching process can be effectively improved, so that the etching effect in the high-aspect-ratio structure is ensured, the subsequent process is further facilitated, and the yield of subsequent finished devices is favorably improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to an etching method for a high aspect ratio structure and a plasma processing device thereof. Background Art

[0002] With the advent of the big data era, the demand for data storage has increased exponentially. 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, driven by major manufacturers such as Samsung, Hynix, Micron, and Toshiba. 3D NAND is formed by multi-layer stacks. As the integration of devices increases, the number of stacking layers of 3D NAND also increases, and the depth of the recessed structure, which is the characteristic area of ​​word lines and contacts, also increases. At present, the mainstream stacking layer number of 3D NAND is 128 layers, and its corresponding recessed structure has a very high aspect ratio (HAR). The recessed structure with a high aspect ratio design can break through the capacity limitation on the plane, but it also greatly increases the difficulty of etching the recessed structure, which brings great challenges in terms of process and equipment.

[0003] As we all know, a normal substrate requires thousands of process flows from silicon wafer to final packaging, and multiple process flows inevitably create complexity in the processing process. The recessed structure etched on the substrate is the basis of multiple process flows, and the etching quality of the recessed structure is crucial to the quality of the subsequent self-aligned multiple pattern finished devices. However, the existing recessed structure etching method cannot guarantee the processing effect, which may cause problems such as uneven inner wall of the recessed structure or premature closure, which in turn leads to defects in the multiple pattern finished devices, reduces product productivity, and affects the output and preparation scale of integrated circuits. Therefore, it is necessary to improve the existing production equipment or production methods.

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

[0005] Based on the above technical problems, the purpose of the present invention is to provide an etching method for a high aspect ratio structure and a plasma processing device thereof. The method coordinates auxiliary light with high-frequency RF power and low-frequency RF power to form a high aspect ratio structure by etching on a substrate in a pulsed manner. The auxiliary light enhances electron energy and excites photogenerated electrons, thereby enhancing the neutralization ability of positive ions at the bottom of the high aspect ratio structure. At the same time, the byproducts at the bottom of the high aspect ratio structure absorb photon energy and obtain better migration and diffusion capabilities, which helps to improve their distribution state in the high aspect ratio structure. The method can effectively improve the problem of uneven etching inside the high aspect ratio structure, ensure the etching effect, and facilitate the advancement of subsequent processes, which helps to improve the yield rate of subsequent finished devices.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0007] An etching method for a high aspect ratio structure, comprising:

[0008] Introducing required process gas into the vacuum reaction chamber;

[0009] Applying radio frequency power into the cavity in a pulsed manner to etch the substrate;

[0010] Among them, the etching process includes multiple pulse cycles, and the pulse cycle includes a first etching stage and a second etching stage. The first etching stage includes: applying high-frequency RF power and low-frequency RF power into the cavity to etch the substrate; the second etching stage includes: reducing the high-frequency RF power and the low-frequency RF power, and turning on the auxiliary light source to provide auxiliary light to the substrate.

[0011] Optionally, in the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, the auxiliary light source is turned on again after a preset time period to provide auxiliary light to the substrate.

[0012] Optionally, the preset time period is zero seconds.

[0013] Optionally, the first etching stage accounts for 5% to 50% of the time, and the second etching stage accounts for 50% to 95% of the time.

[0014] Optionally, the preset time period is greater than zero.

[0015] Optionally, the first etching stage accounts for 5% to 50% of the time, the preset time period accounts for 10% to 30% of the time, and the auxiliary light source is turned on for 20% to 85% of the time.

[0016] Optionally, the etching process is divided into several timing stages, and the process parameters in at least two timing stages are not completely the same, and the process parameters include at least one of gas pressure, process gas, gas flow, high-frequency RF power and low-frequency RF power.

[0017] Optionally, in the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, the auxiliary light source is turned on after a preset time period to provide auxiliary light to the substrate, and the length of the preset time period is different in at least two timing stages.

[0018] Optionally, the preset time period in at least one timing stage is greater than the preset time period in at least one subsequent timing stage.

[0019] Optionally, the wavelength of the auxiliary light provided to the substrate in at least one timing stage is greater than the wavelength of the auxiliary light provided to the substrate in at least one subsequent timing stage.

[0020] Optionally, in the second etching stage, the auxiliary light source is turned on to asynchronously provide a first auxiliary light and a second auxiliary light to the substrate, and the first auxiliary light and the second auxiliary light have different wavelengths.

[0021] Optionally, the time range of the pulse period is 500 μs to 10 ms.

[0022] Optionally, the wavelength of the auxiliary light is less than 380 nm.

[0023] Optionally, in the first etching stage, the peak power of the high-frequency RF power is greater than 3 kW, and the peak power of the low-frequency RF power is greater than 10 kW.

[0024] Optionally, in the second etching stage, the peak power range of the high-frequency radio frequency power is 0 to 2000W.

[0025] Optionally, in the second etching stage, the value of the low-frequency RF power is greater than zero or equal to zero.

[0026] Optionally, a plasma processing device comprises:

[0027] A vacuum reaction chamber, in which a base for carrying a substrate to be processed is arranged;

[0028] A high-frequency radio frequency power source, which is used to provide high-frequency radio frequency power into the cavity;

[0029] A low-frequency radio frequency power source, which is used to provide low-frequency radio frequency power into the cavity;

[0030] An auxiliary light source, which is used to provide auxiliary light to the substrate at a specific moment;

[0031] A controller is used to control various components to execute the above-mentioned etching method of the high aspect ratio structure.

[0032] Optionally, the plasma processing apparatus includes at least two auxiliary light sources with different wavelengths.

[0033] Optionally, the auxiliary light source provides auxiliary light in a circumferential direction around the substrate.

[0034] Optionally, the wavelength of the auxiliary light is less than 380 nm.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] In an etching method for a high aspect ratio structure and a plasma processing device thereof of the present invention, the etching method for a high aspect ratio structure combines auxiliary light with high-frequency radio frequency power and low-frequency radio frequency power, and forms an ideal high aspect ratio structure, i.e., a recessed structure, on a substrate in a pulsed manner. In the first etching stage, the method forms a deep hole on the substrate by high-frequency radio frequency power and low-frequency radio frequency power, and in the second etching stage, pulsed high- and low-frequency radio frequency power and auxiliary light are combined, which can effectively enhance the neutralization capability of positive ions accumulated at the bottom of the recessed structure and improve the distribution of by-products, so as to ensure the etching effect inside the recessed structure, avoid excessive expansion of the critical size of the recessed structure, and facilitate the advancement of subsequent processes, so that the formed recessed structure has better vertical side and bottom morphology, which helps to improve the yield rate of subsequent finished devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1A A partial schematic diagram of a semiconductor device of the present invention;

[0038] Figure 1B-1C It is a partial schematic diagram of different etching states of a semiconductor device of the present invention;

[0039] Figure 2 It is a schematic diagram of an etching method of a high aspect ratio structure of the present invention;

[0040] Figure 3 A control timing diagram of the present invention;

[0041] Figure 4 for Figure 3 Schematic diagram of the corresponding microscopic particle state in the pulse period;

[0042] Figure 5 Another control timing diagram of the present invention;

[0043] Figure 6 for Figure 5 Schematic diagram of the corresponding microscopic particle state in the pulse period;

[0044] Figure 7 It is another control timing schematic diagram of the present invention;

[0045] Figure 8 It is a schematic diagram of turning on an auxiliary light source at different times according to the present invention;

[0046] Fig. 9 It is a schematic diagram of a plasma processing device of the present invention. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] It should be noted that, in this article, the terms "include", "comprises", "has" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of further restrictions, the elements defined by the sentence "includes..." or "comprising..." do not exclude the existence of other elements in the process, method, article or terminal device including the elements.

[0049] It should be noted that the drawings are all in very simplified form and use inaccurate ratios, and are only used to conveniently and clearly assist in explaining the embodiments of the present invention.

[0050] like Figures 1A to 1C FIG. 1 is a partial schematic diagram of a semiconductor device of the present invention, wherein the semiconductor device comprises a substrate 100, wherein the substrate 100 comprises a stacked layer formed by alternating different material layers, wherein the stacked layer comprises a first material layer 110 and a second material layer 120, wherein the stacked layer comprises a recessed structure 130 formed by etching (see FIG. 1 ). Figure 1BDuring the etching process, a patterned mask 140 (Mask) is covered on the stacked layer of the substrate 100, and the opening 141 of the mask 140 forms a corresponding target pattern. The stacked layer is etched to finally form a recessed structure 130 having a pattern corresponding to the pattern of the mask 140, so as to facilitate the subsequent preparation of a self-aligned multi-patterning device. In this embodiment, the first material layer 110 and the second material layer 120 are respectively an oxide layer and a nitride layer, which require an oxide / nitride overlapping process to prepare a stacked layer of several microns to more than ten microns, and a recessed structure 130 is formed on the stacked layer by a substrate 100 etching method. In the substrate 100 etching method, amorphous carbon of several microns is used as a mask 140, and plasma is generated by dissociating the process gas, and then the stacked layer is etched to prepare a very deep hole (Hole) or trench (Trench) in the stacked layer to form a recessed structure 130, and meet very demanding morphology requirements. In practical applications, different process gases can be used for etching based on different types of stacked layer materials to achieve the best etching effect. In this embodiment, C is used. x F y H z , C x F y , Ar, N2, O2 and other reaction gases are used as process gases introduced into the vacuum reaction chamber.

[0051] 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 the above. In other embodiments, other materials may also be used, and the present invention is not limited to this. For example, in another embodiment, the first material layer 110 and the second material layer 120 are a polysilicon layer (P-Si) 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 there are, the higher the integration of the device.

[0052] As can be seen from the above, etching of the high aspect ratio recessed structure 130 is the most critical step in device production. The etching quality of the recessed structure 130 is crucial to the subsequent preparation of self-aligned multiple patterning devices, and with the development of semiconductor nodes, the processing requirements for the high aspect ratio recessed structure 130 are getting higher and higher. Figure 1BAs shown, it is a schematic diagram of a desired high aspect ratio recessed structure 130. Ideally, the recessed structure 130 on the substrate 100 needs to have a vertical profile, and the sidewall of the recessed structure cannot be bent or bowed, while the horizontal profile of the bottom of the recessed structure 130 needs to be as close to a circle as possible, and no distortion or other deformations can occur. To form the high aspect ratio recessed structure 130 required by the above, it is necessary to perform very fine control on the ions, by-products, and etchants at the bottom of the high aspect ratio recessed structure 130 during the etching process. The dry etching process currently used in the industry uses a pulsed radio frequency method, using a very high low-frequency radio frequency power in a very short duty cycle to obtain high-energy ions to bombard the bottom of the high aspect ratio recessed structure 130, and then using a very low radio frequency power in a longer duty cycle to allow electrons to neutralize the residual ions at the bottom of the recessed structure 130. However, as the aspect ratio of the recessed structure 130 increases, the ability of electrons to neutralize high-energy ions at the bottom will decrease, and it will become more difficult to achieve more precise control of the bottom material through conventional macroscopic parameters (such as pressure, temperature, etc.). As the etching progresses, the ability to control the bottom material of the recessed structure is weakened, which can easily lead to over-etching of the bottom of the recessed structure 130 and its sidewalls, resulting in bending 131 and bowing 132 (see Figure 1C ), the bow 132 and other conditions will make the stacked layers around the recessed structure 130 too thin. When the conductive layer is filled in the recessed structure 130, it is easy to cause a short circuit or breakdown between adjacent conductive layers, resulting in instability of the device at that location.

[0053] Based on the above, the present invention proposes an etching method for a high aspect ratio structure, which can avoid undesired deformation of the recessed structure 130 during the etching process, and is helpful to generate a standardized high aspect ratio recessed structure 130. It has been verified by experiments that the recessed structure 130 obtained by the etching method for a high aspect ratio structure of the present invention can still maintain the required collimation when the aspect ratio is greater than or equal to 50.

[0054] like Figure 2 As shown, the etching method of the high aspect ratio structure includes: introducing the required process gas into the vacuum reaction chamber; applying radio frequency power to the chamber in a pulsed manner to etch the substrate 100; wherein the etching process includes a plurality of pulse cycles, the pulse cycle includes a first etching stage and a second etching stage, the first etching stage includes: applying high-frequency radio frequency power (HF) and low-frequency radio frequency power (LF) into the chamber to etch the substrate 100; the second etching stage includes: reducing the high-frequency radio frequency power and the low-frequency radio frequency power, and turning on an auxiliary light source to provide auxiliary light to the substrate 100.

[0055] As can be seen from the above, the present invention adopts a pulsed etching method combining the first etching stage and the second etching stage. In the first etching stage, by applying high high-frequency radio frequency power and low-frequency radio frequency power to the chamber, a large amount of plasma (Plasma) is dissociated from the process gas. The plasma contains positive ions (Ion), free radicals (Radical) and electrons (Electron). Due to the faster rate, the electrons preferentially reach the surface of the substrate 100, and an electric field is formed between the substrate 100 and the plasma. The electric field accelerates the positive ions and decelerates the electrons. After the electrons and positive ions are finally stabilized, a very high sheath (Sheath) structure is formed between the plasma and the substrate 100. Under the action of the sheath structure, the positive ions bombard the surface of the substrate 100 to generate a concave structure 130, i.e., a deep hole; the free radicals reach the surface of the substrate 100 and the deep hole by diffusion, and react on the surface to generate by-products. As the etching proceeds, the by-products and positive charges accumulated in the deep hole gradually increase. After more positive ions reach the deep hole, they cannot be neutralized with the surface electrons and accumulate.

[0056] In the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, 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 accordingly, and the confinement effect of the sheath structure on the electrons will also decrease, so that the 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 becomes deeper and deeper, it becomes increasingly difficult for the electrons to reach the bottom of the deep hole, and the neutralization effect on the positive ions becomes increasingly limited. In the present application, providing auxiliary light to the substrate 100 through an auxiliary light source can effectively improve the above-mentioned problems. On the one hand, the auxiliary light can enhance the energy of the electrons so that the diffused electrons have a better chance to enter the bottom of the deep holes and neutralize the positive ions. On the other hand, after the high-energy photons of the auxiliary light enter the deep holes and are absorbed by the substances at the bottom of the deep holes, it can not only promote the by-products to excite photogenerated electron-hole pairs, but also form a path between the electrons on the surface of the substrate 100 and the positive ions in the deep holes, which is beneficial to enhance the electron concentration at the bottom of the deep holes, and then promote the neutralization of the positive ions in the deep holes. The high-energy photons of the auxiliary light can also increase the temperature of the by-products in the deep holes, so that they obtain higher migration and diffusion capabilities, promote their thermal motion diffusion, and help improve their uniformity at the bottom of the deep holes. The method forms a recessed structure 130, i.e., a deep hole, on the substrate 100 in the first etching stage, and combines pulsed high- and low-frequency RF power with auxiliary light in the second etching stage, thereby effectively controlling the residual positive ions and the distribution of by-products at the bottom of the recessed structure 130, i.e., the deep hole, during the microscopic process, so as to facilitate the advancement of subsequent processes and help the formed recessed structure 130 have better vertical side and bottom morphologies, thereby obtaining an ideal etching morphology.

[0057] In this embodiment, a high-frequency RF power source is used to provide high-frequency RF power to the cavity to generate plasma in the cavity and form the recessed structure 130; a low-frequency RF power source is used to provide low-frequency RF power to the cavity to accelerate positive ions in the plasma and speed up their movement toward the substrate 100; an auxiliary light source is used to provide auxiliary light to the substrate 100 at a specific time to provide energy for electrons or substances in the recessed structure 130. It can be understood that the working timing of the high-frequency RF power source, the low-frequency RF power source and the auxiliary light source can be independently controlled to achieve different microscopic processes based on different etching processes.

[0058] Optionally, in the first etching stage, the peak power of the high-frequency RF power is above 3kW, and the peak power of the low-frequency RF power is above 10kW. Further optionally, in the second etching stage, the peak power range of the high-frequency RF power is 0 to 2000W; the value of the low-frequency RF power is greater than zero or equal to zero. Further optionally, the wavelength λ of the auxiliary light is less than 380nm, and for example, the auxiliary light is short-wavelength ultraviolet light. Of course, the wavelength λ of the auxiliary light and the range of the high-frequency RF power and the low-frequency RF power in each stage are 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. Since the restart process of the high-frequency RF power source is relatively time-consuming, preferably, the present invention does not repeatedly start and shut down the high-frequency RF power source during the etching process, but generates a lower high-frequency RF power that can maintain the plasma in the second etching stage to improve throughput, simplify the operating steps, and also help to ensure its service life. It should be noted that in the second etching stage, the high-frequency RF power and the low-frequency 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 an extremely 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 neutralization of the positive ions in the recessed structure 130.

[0059] Furthermore, in the etching method of the high aspect ratio structure of the present invention, after reducing the high-frequency RF power and the low-frequency RF power in the second etching stage, the auxiliary light source is turned on again after a preset time period to provide auxiliary light to the substrate 100. As can be seen from the above, in the first etching stage, a large amount of plasma is generated in the cavity by the high-frequency RF power and the low-frequency RF power to etch the substrate 100 to form a deep hole, i.e., a recessed structure 130. In the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, the thickness of the sheath structure is reduced, and electrons are more likely to enter the deep hole and neutralize the accumulated positive ions. At the same time, the auxiliary light provided by the auxiliary light source in the second stage can further alleviate the imbalance between positive ions and electrons and the accumulation of by-products. In practical applications, the turn-on time of the auxiliary light source, i.e., the length of the preset time period, can be set according to actual needs.

[0060] like Figure 3 and Figure 4 As shown, in one embodiment, the preset time period is zero seconds, that is, while reducing the high-frequency RF power and the low-frequency RF power, the auxiliary light source is turned on to generate auxiliary light, and the entire pulse cycle includes two periods, namely period 1S210 (Stage 1) of the first etching stage and period 2S220 (Stage 2) of the second etching stage. Figure 4 In the equation, + represents positive ions, - represents electrons, and О represents free radicals. represents the excited photogenerated electrons, λ represents the high-energy photons of the auxiliary light, and the U-shaped material at the bottom of the recessed structure 130 represents the byproduct ( Figure 6 and Figure 8 The same representation method is used in the figure). In period 2S220, the restraining ability of the sheath structure on the electrons is reduced, and the electrons in the free state can quickly have higher electron energy under the action of the high-energy photons of the auxiliary light, which accelerates their movement into the deep holes. At the same time, the substances in the deep holes (by-products and unreacted free radicals) can stimulate photogenerated electrons or obtain higher migration and diffusion capabilities after absorbing high-energy photons, which helps to reduce the positive ions accumulated in the deep holes and improve the distribution uniformity of the by-products, which is convenient for the subsequent process to obtain the ideal morphology of the recessed structure 130.

[0061] In this embodiment, the auxiliary light source is turned on when the high-frequency RF power and the low-frequency RF power are reduced. Compared with the auxiliary light source being turned on all the time during the process, the following problems can be avoided: turning on the auxiliary light source in period 1S210 will affect the plasma dissociation process designed for the process conditions in period 1S210, causing the process conditions to deviate. On the other hand, due to the presence of high low-frequency RF power, there is a very thick sheath between the plasma and the substrate surface, and the electrons excited or accelerated by the auxiliary light source have no way to reach the surface of the substrate for charge neutralization and cannot play a role. Therefore, there is no need to turn on the auxiliary light source in period 1S210.

[0062] Optionally, in this embodiment, the first etching stage, i.e., period 1S210, accounts for 5% to 50% of the time, and the second etching stage, i.e., period 2S220, accounts for 50% to 95% of the time. In practical applications, the time proportion of each etching stage can be adjusted according to the different etching effects produced by the first etching stage and the second etching stage, as well as actual application requirements, to achieve the optimal etching effect.

[0063] It should be noted that the duration of the preset time period is not limited to zero seconds. In practical applications, it can also be adjusted according to practical application requirements or experimental conditions. For example, in another embodiment, the preset time period is greater than zero seconds, and the entire pulse cycle includes three periods, namely, period 1 S310 (Stage 1) of the first etching stage, period 2 S320 (Stage 2) of the second etching stage, and period 3 S330 (Stage 3). Figure 5 and Figure 6 As shown, it is a pulse control timing diagram of this embodiment and a corresponding particle microscopic state diagram. The period 1S310 is the first etching stage, during which a large number of positive ions, electrons and free radicals are dissociated under the action of high-frequency RF power and low-frequency RF power to form a deep hole structure. The period 2S320 is a preset time period in the second etching stage, during which the high-frequency RF power and the low-frequency RF power are reduced, and the sheath height between the substrate 100 and the plasma is reduced accordingly. During this period, electrons continue to diffuse into the deep holes to neutralize the positive ions in the deep holes. The period 3S330 is the time period when the auxiliary light source is turned on in the second etching stage. During this period, the high-energy photons of the auxiliary light enter the surface of the substrate 100 and the deep holes, which can not only increase the energy of electrons and thus enhance their ability to enter the deep holes, but also prompt the by-products and other substances in the deep holes to excite photogenerated electrons under the action of high-energy photons to promote the neutralization of positive ions in the deep holes, so as to minimize the accumulation of positive ions, and at the same time help the diffusion and distribution of by-products. This method has an improvement effect on the distortion and other morphologies of the bottom of the recessed structure 130.

[0064] A preset time period greater than zero seconds has the following beneficial effects relative to a preset time period of zero seconds: (1) after the RF power is reduced after the end of period 1S310, the plasma sheath does not immediately decrease, so a given period of time (i.e., period 2S320) of low-power RF can ensure that the plasma sheath is completely reduced to a very low level to complete the state switching, so that the electrons in the plasma can diffuse more freely to the deep hole structure in the substrate to neutralize the charge; (2) a given period of low power can allow the low-energy electrons generated by the plasma to first neutralize a portion of the positive charges at a shallow depth, and then the auxiliary light source is turned on, so that the accelerated electrons will not be consumed at a shallow depth prematurely, and will more effectively reach the bottom of the deep hole, thereby increasing the charge neutralization efficiency at the bottom of the deep hole.

[0065] Optionally, in this embodiment, the first etching stage accounts for 5% to 50% of the time, the preset time period accounts for 10% to 30% of the time, and the auxiliary light source is turned on for 20% to 85% of the time. In practical applications, the time proportion of each etching stage can be adjusted according to actual needs to achieve the best etching effect.

[0066] Further, in yet another embodiment, if Figure 7As shown, it is another pulse control timing schematic diagram. In this embodiment, the preset time period is greater than zero seconds, and in the second etching stage, auxiliary light of at least two wavelengths is provided to the substrate 100. Specifically, the entire pulse cycle includes four periods, namely, period 1S410 (Stage 1) of the first etching stage, period 2S420 (Stage 2) included in the second etching stage, period 3S430 (Stage 3) and period 4S440 (Stage 4). The period 1S410 is the first etching stage, and the particle state of this period is the same as that in other embodiments. The period 2S420 is a preset time period in the second etching stage. During this period, due to the reduction of the sheath thickness, the possibility of electrons diffusing into the deep holes and neutralizing positive ions increases. The period 3S430 and period 4S440 are the time periods for turning on the auxiliary light source 530 in the second etching stage. After the preset time period of the second etching stage, the auxiliary light source 530 asynchronously provides the first auxiliary light (period 3S430) and the second auxiliary light (period 4S440) to the substrate 100. The wavelength of the first auxiliary light is greater than the wavelength of the second auxiliary light, that is, from period 3S430 to period 4S440, another auxiliary light source 530 with a different wavelength is converted to excite electrons of different energies, thereby enhancing the neutralization ability of positive ions of different energy levels and different depths. This method can further enhance the effect of neutralizing positive ions in deep holes, thereby alleviating or even eliminating the imbalance between positive ions and electrons to obtain an ideal etching morphology. Optionally, in this embodiment, the time proportions of the first auxiliary light and the second auxiliary light are 20% to 85% respectively.

[0067] Generally speaking, the etching time of the high aspect ratio recessed structure 130 is relatively long (>10 minutes), which includes multiple pulse cycles. Optionally, the time range of the pulse cycle is 500μs to 10ms. Of course, the time range of the pulse cycle is not limited to the above. In other embodiments, it can also be other data ranges, which can be adjusted according to actual application conditions, and the present invention is not limited to this.

[0068] On the other hand, during the process, as the etching depth of the substrate 100 increases, the entire etching process can be divided into several sequential stages (steps) in sequence. Optionally, the process parameters in at least two sequential stages are not exactly the same. Different process parameters will be adjusted in each different sequential stage based on the requirements of the etching morphology, that is, the specific process conditions required for each sequential stage will be different, so that the plasma state of each sequential stage is different, the sheath thickness between the plasma and the substrate 100 will also be different, and the charge distribution in the deep hole will be different. The best charge neutralization effect is achieved by optimizing and adjusting the process conditions, so that the final etching morphology is optimized. Optionally, the process parameters include at least one of gas pressure, process gas, gas flow, high-frequency RF power and low-frequency RF power. It can be understood that the process parameters are not limited to the above. In other embodiments, other parameters can also be adjusted according to actual needs.

[0069] Further, in different sequential stages of the process, auxiliary light of different wavelengths may be used to optimize the process conditions, that is, the wavelengths of the auxiliary light provided to the substrate 100 in at least two sequential stages are different. For example, as the etching depth increases, the etching process includes a first stage (step1), a second stage (step2), and a third stage (step3) that develop in chronological order. In the first stage, the etching depth is shallow, and a light source with a relatively large wavelength (for example, a wavelength of 360nm) may be selected at this time. In the third stage, the etching depth is deep, and a light source with a relatively small wavelength (for example, a wavelength of 290nm) may be selected at this time. That is, the wavelength of the auxiliary light provided to the substrate 100 in at least one sequential stage is greater than the wavelength of the auxiliary light provided to the substrate 100 in at least one subsequent sequential stage. The etching depth in the first stage is less than the etching depth in the third stage, and the accumulated positive charge in the recessed structure 130 in the first stage is less than the accumulated positive charge in the third stage. In the third stage, the use of auxiliary light with a shorter wavelength can provide higher energy for the electrons, which helps to improve the ability of electrons to diffuse downward and increase the ability to neutralize the charges at the bottom of the recessed structure 130. Different auxiliary light wavelengths are optimized by different steps before and after to match the different positive ion distributions in different etching stages, so as to obtain an optimal etching morphology. As can be seen from the above, different wavelengths can be used in different timing stages and different control timings of the etching process, that is, different wavelengths are optimized and used in conjunction with the specific process conditions in each step to obtain an ideal etching morphology. Of course, in practical applications, the process parameters used in each timing stage or control timing may also be the same, and the present invention is not limited to this.

[0070] On the other hand, as the etching depth increases, the turn-on time of the auxiliary light source may be different in different timing stages of the process, that is, the best charge neutralization effect is achieved by optimizing and adjusting the turn-on time of the auxiliary light source in different timing stages. As mentioned above, in the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, the auxiliary light source is turned on after a preset time period to provide auxiliary light to the substrate 100. Optionally, in at least two timing stages, the length of the preset time period is different to match the different positive ion distribution states in different etching stages to maximize the utilization of the auxiliary light source energy.

[0071] For example, the total etching depth of the recessed structure 130 is divided into multiple depth ranges from top to bottom, and each depth range is achieved by an etching process in a corresponding timing stage. Figure 8 As shown, in one embodiment, the depth of the recessed structure 130 includes a first depth (depth1) and a second depth (depth2), and the corresponding timing stages are a first process stage and a second process stage. In the process of the first process stage, the pulse cycle includes a period 1S510 (Stage 1) of the first etching stage, a period 2S520 (Stage 2) and a period 3S530 (Stage 3) of the second etching stage; in the process of the second process stage, the pulse cycle includes a period 1S610 (Stage 1) of the first etching stage, a period 2S620 (Stage 2) and a period 3S630 (Stage 3) of the second etching stage, and the time length of the period 2S620 of the second process stage is shorter than the time length of the period 2S520 of the first process stage.

[0072] When etching the first depth, the etching depth is shallow and a shallow hole structure is formed. The peak power used in the process of the corresponding first process stage is usually low, and the time of period 1S510 is relatively long. Most of the positive ions are distributed in the mask plate 140 and the shallow hole. In period 2S520, most of the positive ions can be neutralized by normal diffusion of electrons. Finally, a short period 3S530 is used to further ensure that all positive ions at the bottom of the hole are neutralized, which helps to reduce the energy loss of the auxiliary light source. When etching the second depth, the etching depth is deep and a deep hole structure is further formed. The peak power used in the process of the corresponding second process stage is usually high, but the time of period 1S610 of this stage is relatively short. Most of the positive ions are distributed in the deep hole. After the plasma sheath thickness is reduced or collapsed by a short period 2S620, a long period 3S630 is used to ensure that the positive ions in the deep hole are neutralized. From the above, it can be seen that during the process, as the process continues to advance, the preset time period in at least one timing stage is greater than the preset time period in at least one subsequent timing stage, so as to match the different charge distribution and neutralization conditions in different etching stages, thereby saving energy loss while ensuring the neutralization effect on positive ions.

[0073] Further, based on the same inventive concept, the present invention also provides a plasma processing device, such as Fig. 9As shown, the plasma processing device includes: a vacuum reaction chamber 500, a high-frequency radio frequency power source 510, a low-frequency radio frequency power source 520, an auxiliary light source 530 and a controller 540, etc. The vacuum reaction chamber 500 comprises a reaction chamber body 501 and a chamber end cover 502, wherein the chamber end cover 502 is provided with a through hole, and a base 550 for carrying a substrate 100 to be processed and an upper electrode assembly 560 arranged opposite to the base 550 are arranged in the vacuum reaction chamber 500, and the upper electrode assembly 560 comprises a mounting base 561, wherein the mounting base 561 passes through the through hole of the chamber end cover 502, and a plurality of gas channels 562 are arranged in the mounting base 561, wherein the gas channels 562 are connected to a gas buffer 570 located above the chamber end cover 502, and a gas shower head 563 comprising a plurality of shower holes 564 is arranged at the bottom of the mounting base 561, wherein the gas shower head 563 is connected to the gas channel 562, and the process gas in the gas supply device is injected into the vacuum reaction chamber 500 through the gas buffer 570, the gas channel 562 and the shower hole 564 in sequence. The high-frequency RF power source 510 is used to provide high-frequency RF power into the cavity, and the low-frequency RF power source 520 is used to provide low-frequency RF power into the cavity. The high-frequency RF power source 510 and the low-frequency RF power source 520 apply RF energy to the base 550 through a matcher 580. The auxiliary light source 530 is used to provide auxiliary light to the substrate 100 at a specific moment. The controller 540 is used to control various components to execute the aforementioned etching method of the high aspect ratio structure.

[0074] In practical applications, the substrate 100 to be processed is first transferred to the base 550 in the vacuum reaction chamber 500, and then the C x F y H z , C x F y , Ar, N2, O2 and other reaction gases are buffered by the gas buffer 570 and then injected into the cavity through the gas channel 562 of the mounting base 561 and the spray hole 564 of the gas shower head 563. Next, the RF energy of the high-frequency RF power source 510 and the low-frequency RF power source 520 is applied to the base 550 through the matcher 580 to dissociate the process gas introduced into the cavity to generate plasma in order to start etching. During the etching process, the controller 540 controls the high-frequency RF power source 510, the low-frequency RF power source 520 and the auxiliary light source 530 to work according to a specific timing.

[0075] In this embodiment, the auxiliary light source 530 provides auxiliary light around the circumference of the substrate 100, that is, there is a circle of vacuum light sources with a specific frequency around the periphery of the substrate 100. In this embodiment, one light source is arranged around the circumference of the substrate 100 to provide auxiliary light to the substrate 100, so as to ensure the uniformity of the surface treatment of the substrate 100. Of course, in other embodiments, auxiliary light can also be provided to the substrate 100 by multiple light sources, and the multiple light sources are arranged around the circumference of the substrate 100 to provide uniform auxiliary light to the substrate 100.

[0076] Furthermore, the plasma processing device includes at least two auxiliary light sources 530 with different wavelengths, so that different wavelengths can be used in different timing stages and different control timings of the etching process, thereby optimizing the process conditions and obtaining an ideal etching morphology.

[0077] In summary, in an etching method for a high aspect ratio structure and a plasma processing device thereof of the present invention, the etching method for a high aspect ratio structure comprises the following steps: introducing the required process gas into a vacuum reaction chamber 500; applying radio frequency power to the chamber in a pulsed manner to etch the substrate 100; wherein the etching process comprises a plurality of pulse cycles, the pulse cycle comprising a first etching stage and a second etching stage, the first etching stage comprising: applying high-frequency radio frequency power and low-frequency radio frequency power to the chamber to etch the substrate 100; the second etching stage comprising: reducing the high-frequency radio frequency power and the low-frequency radio frequency power, and turning on the auxiliary light source 530 to provide auxiliary light to the substrate 100. The method forms a recessed structure 130 on the substrate 100 by using high-frequency RF power and low-frequency RF power in the first etching stage, and combines pulsed high- and low-frequency RF power with auxiliary light in the second etching stage. This can effectively control the residual positive ions at the bottom of the recessed structure 130 and the distribution of by-products in the microscopic process, so as to facilitate the advancement of subsequent processes, help the formed recessed structure 130 to have better vertical side and bottom morphology, avoid excessive expansion of the critical size of the recessed structure 130, and help improve the yield rate of subsequent finished devices.

[0078] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. An etching method for a high aspect ratio structure, characterized in that: Include: Introducing required process gas into the vacuum reaction chamber; Applying radio frequency power into the cavity in a pulsed manner to etch the substrate; Among them, the etching process includes multiple pulse cycles, and the pulse cycle includes a first etching stage and a second etching stage. The first etching stage includes: applying high-frequency RF power and low-frequency RF power into the cavity to etch the substrate; the second etching stage includes: reducing the high-frequency RF power and the low-frequency RF power, and turning on the auxiliary light source to provide auxiliary light to the substrate.

2. The etching method of the high aspect ratio structure according to claim 1, characterized in that: In the second etching stage, after reducing the high-frequency radio frequency power and the low-frequency radio frequency power, the auxiliary light source is turned on again after a preset time period to provide auxiliary light to the substrate.

3. The etching method of the high aspect ratio structure according to claim 2, characterized in that: The preset time period is zero seconds.

4. The etching method of the high aspect ratio structure according to claim 3, characterized in that: The first etching stage accounts for 5% to 50% of the time, and the second etching stage accounts for 50% to 95% of the time.

5. The etching method of the high aspect ratio structure according to claim 2, characterized in that: The preset time period is greater than zero.

6. The etching method of the high aspect ratio structure according to claim 5, characterized in that: The first etching stage accounts for 5% to 50% of the time, the preset time period accounts for 10% to 30% of the time, and the auxiliary light source is turned on for 20% to 85% of the time.

7. The etching method of the high aspect ratio structure according to claim 1, characterized in that: The etching process is divided into several timing stages, and the process parameters in at least two timing stages are not completely the same. The process parameters include at least one of gas pressure, process gas, gas flow, high-frequency radio frequency power and low-frequency radio frequency power.

8. The etching method of the high aspect ratio structure according to claim 7, characterized in that: In the second etching stage, after reducing the high-frequency RF power and the low-frequency RF power, the auxiliary light source is turned on after a preset time period to provide auxiliary light to the substrate, and the length of the preset time period is different in at least two timing stages.

9. The etching method of the high aspect ratio structure according to claim 7, characterized in that: The preset time period in at least one timing stage is greater than the preset time period in at least one subsequent timing stage.

10. The etching method of the high aspect ratio structure according to claim 7, characterized in that: The wavelength of the auxiliary light provided to the substrate in at least one timing stage is greater than the wavelength of the auxiliary light provided to the substrate in at least one subsequent timing stage.

11. The etching method of a high aspect ratio structure according to claim 1, characterized in that: In the second etching stage, the auxiliary light source is turned on to asynchronously provide a first auxiliary light and a second auxiliary light to the substrate, and the wavelengths of the first auxiliary light and the second auxiliary light are different.

12. The etching method of a high aspect ratio structure according to claim 1, characterized in that: The time range of the pulse period is 500 μs to 10 ms.

13. The etching method of a high aspect ratio structure according to claim 1, characterized in that: The wavelength of the auxiliary light is less than 380 nm.

14. The etching method of a high aspect ratio structure according to claim 1, characterized in that: In the first etching stage, the peak power of the high-frequency RF power is greater than 3 kW, and the peak power of the low-frequency RF power is greater than 10 kW.

15. The etching method of a high aspect ratio structure according to claim 1, characterized in that: In the second etching stage, the peak power range of the high-frequency radio frequency power is 0-2000W.

16. The etching method of a high aspect ratio structure according to claim 1, characterized in that: In the second etching stage, the value of the low-frequency RF power is greater than zero or equal to zero.

17. A plasma processing device, characterized in that: Include: A vacuum reaction chamber, in which a base for carrying a substrate to be processed is arranged; A high-frequency radio frequency power source, which is used to provide high-frequency radio frequency power into the cavity; A low-frequency radio frequency power source, which is used to provide low-frequency radio frequency power into the cavity; An auxiliary light source, which is used to provide auxiliary light to the substrate at a specific moment; A controller is used to control various components to execute the etching method of the high aspect ratio structure according to any one of claims 1 to 16.

18. The plasma processing apparatus according to claim 17, wherein: The plasma processing device comprises at least two auxiliary light sources with different wavelengths.

19. The plasma processing apparatus according to claim 17, wherein: The auxiliary light source provides auxiliary light in a circumferential direction around the substrate.

20. The plasma processing apparatus according to claim 17, wherein: The wavelength of the auxiliary light is less than 380 nm.

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