Semiconductor structure etching method and semiconductor process equipment
By employing a two-step etching method, the silicide layer is first removed, and then the tungsten layer is etched using a carbon material layer as a mask. This solves the problem of poor etching directionality of tungsten material, and achieves precise control and improved yield of the tungsten layer.
Patent Information
- Application Number
- CN202410551791.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-06
- Publication Date
- 2025-11-07
AI Technical Summary
In existing technologies, tungsten materials have poor etching directionality, which leads to the etching of sidewalls, affecting product performance and yield.
A two-step etching method is adopted. First, the silicide layer is removed, and then the tungsten layer is etched using a carbon material layer as a mask layer. The carbon-based deposit is used to protect the sidewalls of the tungsten layer and avoid lateral etching.
To ensure that the dimensional accuracy of the tungsten layer remains uncontrolled during the etching process, reduce the risk of solid particle residue, and improve product yield.
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Figure CN120914101A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of semiconductor, and particularly relates to a semiconductor structure etching method and a semiconductor process equipment. BACKGROUND
[0002] In the related art, a silicide mask layer is used to etch tungsten material, wherein the etching gas is NF3 or the like. However, the plasma generated by the etching gas mainly uses chemical etching to etch tungsten. In the chemical reaction process, due to the poor longitudinal directionality of the plasma, the directionality of etching tends to be isotropic, so that the sidewall of the tungsten material is easily etched, causing the size precision of the tungsten material to be difficult to control, thereby affecting the product performance and product yield. SUMMARY
[0003] The application aims to provide a semiconductor structure etching method and a semiconductor process equipment, which can solve the problem that the tungsten material sidewall is etched to affect the product performance and product yield.
[0004] To solve the above technical problems, the application is implemented as follows:
[0005] The application provides a semiconductor structure etching method, the semiconductor structure comprising a tungsten layer and a carbon material layer and a silicide layer which are sequentially stacked on the tungsten layer, the carbon material layer and the silicide layer having the same pattern topography, and the etching method comprising:
[0006] A first etching step, using a plasma etching process to etch only the silicide layer, removing the silicide layer to expose the carbon material layer;
[0007] A second etching step, using the carbon material layer as a mask layer, using a plasma etching process to etch the tungsten layer, and carbon-based deposits generated by the carbon material layer being attached to the side surface of the tungsten layer.
[0008] The application further provides a semiconductor process equipment, comprising a process chamber, a gas inlet assembly and a controller, the controller comprising at least one processor and at least one memory, the memory storing a computer program, and the computer program being executed by the processor to implement the above semiconductor structure etching method.
[0009] The etching method of the semiconductor layer in the embodiment of the present application is mainly divided into two steps for the etching process of the tungsten layer. The first step is to remove the silicide layer, and only the silicide layer is etched, and the tungsten layer is not etched, which can avoid the deposition without side wall protection caused by etching the tungsten layer at the same time of removing the silicide layer, and the horizontal etching of the tungsten material side wall by the plasma. The second step is to etch the tungsten layer. In this process, the carbon-based deposition generated by the carbon material layer itself protects the side wall of the tungsten layer, so as to ensure that the tungsten layer will not be etched by the etching side wall during the etching process, and further ensure that the size accuracy of the tungsten layer will not be out of control during the etching process. BRIEF DESCRIPTION OF DRAWINGS
[0010] Figure 1 An etching effect schematic diagram in the tungsten etching process;
[0011] Figure 2 A tungsten material etching film layer schematic diagram;
[0012] Figure 3 A result schematic diagram of the tungsten etching using high lower electrode power under the scanning electron microscope;
[0013] Figure 4 A tungsten material physical diagram after etching in the case of using silicon oxide film to protect the tungsten material;
[0014] Figure 5 A Bosch process schematic diagram;
[0015] Figure 6 A semiconductor structure and etching step schematic diagram in the related art;
[0016] Figure 7 A flowchart of the etching method of the semiconductor structure disclosed in the embodiment of the present application;
[0017] Figure 8 A semiconductor structure and each step schematic diagram disclosed in the embodiment of the present application;
[0018] Figure 9 A semiconductor process equipment schematic diagram disclosed in the embodiment of the present application. DETAILED DESCRIPTION
[0019] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.
[0020] The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and are not used to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances so that the embodiments of the present application can be implemented in an order other than that illustrated or described herein, and the objects distinguished by "first", "second", etc. are generally of a kind and are not limited in number, for example, the first object can be one or more. In addition, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the front and rear associated objects are in an "or" relationship.
[0021] The embodiments of the present application will be described in detail below with specific examples and their application scenarios in conjunction with the accompanying drawings.
[0022] Since tungsten material has good electrical conductivity and thermal stability, it is used in the manufacturing process of metal interconnection in the field of integrated circuit manufacturing, and it is one of the important materials of integrated circuits. Among the many processes for processing tungsten material, etching of tungsten material is a key and difficult process. As shown in Figure (1a), a schematic diagram in the state of no protection side wall, in the etching process of tungsten material, the main etching gas can be NF3 and other fluorine-based gases. The directionality of the plasma generated by such gases is less affected by the lower electrode. Therefore, the etching of tungsten material by the plasma generated by such gases is mainly chemical etching. In the chemical reaction process, due to the poor longitudinal directionality of NF3 and other fluorine-based gas plasma, the directionality of etching tends to be isotropic. When etching the side wall of tungsten material, it is difficult to control the dimensional accuracy of tungsten material in integrated circuits, and even directly affects the structural features of tungsten material. However, the dimensional accuracy and structural accuracy of tungsten material are key factors affecting product performance and yield.
[0023] Therefore, in the design of integrated circuit process flow, carbon mask layer is used to etch tungsten material, because carbon mask will sputter CH long-chain polymer and other deposits under the bombardment of plasma, and adhere to the side wall of tungsten material, protecting the side wall of tungsten material, as shown in Figure (1b), a schematic diagram in the state of side wall protection.
[0024] However, silicide mask layer is also essential in the design of film layer. For example, in most tungsten etching processes such as tungsten material landing pad, in order to obtain better electrical properties, the thickness of tungsten material to be etched is large, so a carbon mask layer with a thickness of hundreds of nanometers needs to be laid by spin coating and other methods, as shown in Figure (2a), a schematic diagram before the silicide mask layer transfers the pattern to the carbon mask layer.
[0025] For the carbon mask layer with a thickness of hundreds of nanometers, the diffraction of light and the scattering of interlayer medium affect the accurate pattern obtained by lithography alone and the transmission of the pattern to the underlying tungsten material. Therefore, in the integrated circuit process flow, a layer of silicon oxide is further deposited above the carbon mask layer, and the pattern is transmitted to the carbon mask layer through the upper layer of silicon oxide, as shown in the schematic diagram of the state after the silicide transmits the pattern to the carbon mask layer in Fig. (2b).
[0026] In the process of etching the carbon material (or the carbon mask layer), considering the differences between the wafer center and the edge and the differences between different patterns inside the wafer, a certain etching selectivity ratio of the silicon oxide to the carbon material needs to be ensured in the etching of the carbon material, so as to avoid the risk of out-of-control feature size in a local area caused by the complete depletion of the silicon oxide mask layer at the end of the carbon material etching, as shown in Fig. (2c) which is a real object diagram of the tungsten material to be etched.
[0027] For some tungsten material etching methods, in order to reduce the lateral etching of plasma, the lower electrode power is increased to make the plasma load more kinetic energy, so that the plasma migrates to the bottom of the area to be etched with stronger directionality, thereby reducing the plasma concentration of the tungsten material sidewall and realizing anisotropic etching. However, in the advanced process of integrated circuits, the tungsten material is etched at the same time as the logic control area of the integrated circuit. After the lower electrode power is increased, the kinetic energy of the plasma is enhanced, which will increase the bombardment of the plasma on other area materials, affecting the electrical properties of the area, and thus affecting the product performance. In addition, after the lower electrode power is increased to 80W-300W, the selectivity ratio of the tungsten material to the mask layer will decrease significantly during the etching process, causing a large amount of mask layer to be consumed during the tungsten material etching process, so that the thickness of the mask layer is not enough to support the subsequent etching process, as shown in Fig. (2d). Figure 3
[0028] Another method to enhance the protection of the tungsten material sidewall in the etching process is to add silicon tetrachloride gas and a small amount of oxygen. Silicon tetrachloride gas and oxygen can effectively form a thin layer of silicon oxide film on the surface of the tungsten material, thereby achieving the purpose of protecting the tungsten material sidewall. However, after the etching is completed, silicon oxide particles are easily left over, which are difficult to remove and can easily cause defects in the structure of the wafer surface.
[0029] In the above tungsten material etching process, the silicon oxide film not only deposits on the sidewall of the tungsten material, but also deposits on the sidewall and top of the carbon mask layer. When a large amount of silicon oxide film is deposited on the carbon mask layer, two problems will occur: first, if a large amount of silicon oxide film is deposited on the top of the carbon mask layer, the film will gradually thicken and even expand laterally, thereby reducing the space for the longitudinal migration of plasma, making it difficult for the plasma to migrate to the area to be etched, and causing the termination of the etching process, as shown in Fig. (2e). Figure 4
[0030] Secondly, after the etching of the tungsten material is completed, the remaining carbon mask layer needs to be removed. In the process of removing the carbon mask layer, the silicon oxide film on the top of the carbon mask layer is relatively high in selectivity and is not easy to be removed. After the removal step of the carbon mask layer is completed, the silicon oxide will fall onto the wafer surface, finally reducing the yield of the product.
[0031] In addition, for the sidewall protection technology in the etching process, in some process flows, Bosch process is used for etching. The main principle of Bosch process technology is to split the etching process into multiple cycle steps, wherein each cycle step includes a deposition step and an etching step. As shown in the following figure, when an etching step is completed, a deposition step is immediately switched to, a protective layer is deposited on the sidewall of the material to be etched, and then etching is continued, and so on, so as to achieve the effect of minimizing the loss of the lateral size of the material to be etched when etching to the target depth. Figure 5
[0032] The above process mode has the disadvantages of sawtooth-shaped sidewall morphology, long process time, and narrow process window when Bosch process is used for etching in order to protect the sidewall of the material to be etched.
[0033] Firstly, because Bosch process needs to switch between deposition and etching steps multiple times, this will cause the sidewall of the material to be etched to have a "U" morphology at the position of each cycle. After multiple cycles of etching, the sidewall of the material to be etched becomes sawtooth-shaped. In the previous process, the continuity of the sidewall morphology of the material to be etched is required to be high, and the sawtooth-shaped morphology is easy to cause sharp end discharge phenomenon, especially in the landing pad manufacturing process, which will have a serious impact on the electrical properties.
[0034] Secondly, the etching method in the related art is one-step etching to the target depth, and the etching speed is relatively fast. In Bosch process, an additional deposition step is needed, and the etching step also needs to open the deposition on the bottom before etching, so the total time consumption will be much longer than that of the traditional etching technology, thereby increasing the production cost.
[0035] In addition, in the previous process, especially in the previous process of advanced processes, the line spacing size is small, but the mask layer is thick. For example, in the landing pad manufacturing process, the aspect ratio of the etching region can reach 10:1. If Bosch process is used for etching, this will cause the deposition to be unable to be deposited to the bottom of the etching region, and a large amount of deposition is deposited on the top and sidewall of the carbon mask layer. If the amount and deposition speed of the deposition are reduced to make it deposited to the bottom of the etching region, the sidewall protection effect of the material to be etched will be very limited. Therefore, in this process, the process window of adjusting the etching and deposition ratio is narrow, and it is difficult to achieve the expected effect of protecting the sidewall.
[0036] In addition, in the process of etching the tungsten material, it is difficult to avoid the plasma etching the sidewall of the tungsten material laterally, and therefore, the deposition in the process chamber is the key to protect the sidewall of the tungsten material. As shown in Fig. (6a), a schematic diagram of a film layer structure of the tungsten material to be etched, when the tungsten material is etched, the mask layer is a silicide layer such as silicon oxide and a carbon material layer. In the process of etching the tungsten material, the related art first takes the silicide layer as the mask layer, and then converts to take the carbon material layer as the mask layer. In the stage of taking the silicide layer as the mask layer, as shown in Fig. (6b), a schematic diagram of etching the tungsten material with the silicide as the mask layer, the main etching gas such as NF3 in the process chamber is dissociated to generate highly reactive atomic fluorine radicals, and these radicals generate silicon tetrafluoride gas in the process of reacting with the silicide layer. Since no deposition can be generated to adhere to the sidewall of the tungsten material in this stage, the sidewall of the tungsten material is in a protection-free stage in this stage, and the sidewall of the tungsten material is easily etched laterally in the process of plasma downward migration. When the silicide layer is etched completely, the process of etching the tungsten material takes the carbon material layer as the mask layer to etch, as shown in Fig. (6c), a schematic diagram of etching the tungsten material with the carbon material layer as the mask layer, at this time, the carbon material layer is bombarded by the plasma, and part of the deposition adheres to the sidewall of the tungsten material to protect the sidewall of the tungsten material. The actual photo of the tungsten material etched by this scheme is shown in Fig. (6d), since the sidewall deposition is not protected, the size of the black tungsten material is small, and the vertical etching speed is fast, the etching depth is large, and the line width of the tungsten material obtained by etching is 13 nm.
[0037] Through analysis, the inventors found that in the related art, the process of etching the tungsten material adopts a one-step etching method to etch the tungsten material, and in the same process step, the tungsten material is etched with the silicide layer and the carbon material layer as the mask layer. In the stage of etching the tungsten material with the silicide layer as the mask layer, the silicide layer reacts with the fluorine-based plasma to generate SiF4 gas, and no deposition can be formed on the sidewall of the tungsten material to reduce the lateral etching of the tungsten material by the plasma. Therefore, the stage of taking the silicide layer as the mask layer is the most serious stage of lateral etching of the tungsten material, and the main reason for the serious lateral etching in this stage is that no deposition adheres to the sidewall of the tungsten material in the etching process. Therefore, in order to solve this problem, the embodiments of the present application disclose a new etching method to protect the sidewall of the tungsten material and prevent it from being etched laterally.
[0038] The embodiments of the present application disclose an etching method of a semiconductor structure, wherein the semiconductor structure comprises a tungsten layer, a carbon material layer and a silicide layer, the carbon material layer and the silicide layer are sequentially stacked on the tungsten layer, as shown in Fig. (8a), a schematic diagram of a film layer structure of the semiconductor structure to be etched, and the carbon material layer and the silicide layer have the same pattern topography.
[0039] To alleviate the problem of insufficient sidewall deposition of the tungsten layer in the process of etching the tungsten layer with the silicide layer as a mask layer, the etching method of the embodiments of the present application divides the etching process of the tungsten layer into a first etching step and a second etching step, as shown in Figure 7
[0040] S100, the first etching step: using a plasma etching process to etch only the silicide layer, removing the silicide layer to expose the carbon material layer;
[0041] S200, the second etching step: using a plasma etching process to etch the tungsten layer with the carbon material layer as a mask layer, and the carbon-based deposition generated by the carbon material layer is attached to the side of the tungsten layer.
[0042] In the etching method of the semiconductor layer of the embodiments of the present application, the etching process of the tungsten layer is mainly divided into two steps. The first step removes the silicide layer and only etches the silicide layer without etching the tungsten layer, which can avoid the problem of horizontal etching of the tungsten material sidewall caused by the absence of sidewall protection deposition when the silicide layer is removed while etching the tungsten layer. The second step etches the tungsten layer. In this process, no gas such as silicon tetrachloride that can easily produce solid particles is introduced. Instead, the carbon-based deposition generated by the carbon material layer itself as a mask layer is fully utilized to protect the sidewall of the tungsten layer. Therefore, it can be ensured that the tungsten layer will not be etched during the etching process, thereby ensuring that the size accuracy of the tungsten layer will not be out of control during the etching process. This makes it easier to control the size accuracy when etching the tungsten layer, and the phenomenon of significant reduction in the line width of the tungsten layer will not occur. Moreover, it can effectively reduce the risk of solid particle residue.
[0043] Optionally, the plasma etching process is used to etch the silicide layer, including:
[0044] The plasma etching process uses a first process gas to etch the silicide layer, wherein the etching selectivity of the first process gas to the tungsten layer and the etching selectivity of the first process gas to the carbon material layer are both greater than the etching selectivity of the first process gas to the silicide layer. Based on this setting, only the silicide layer can be etched without etching the carbon material layer and the tungsten layer in the first etching step, thereby alleviating the problem of etching the carbon material layer and the tungsten layer.
[0045] In the embodiments of the present application, the first etching step can be used as a pretreatment step before etching the tungsten layer, which is used to remove the silicide layer. The main purpose of the first etching step for removing the silicide layer is to remove the silicide layer as a mask layer without etching the tungsten layer. In the embodiments of the present application, the first process gas is used as the main etching gas, which has a higher selectivity to the tungsten layer, so that the silicide layer can be removed without etching the tungsten layer, thereby ensuring that the tungsten layer will not appear depth loading effect when etching the tungsten layer in the subsequent second etching step.
[0046] Benefited from the first etching step does not have to etch the tungsten layer, and the first process gas has a relatively high selectivity to the tungsten layer, in the step of removing the silicide layer, the chamber pressure can have a relatively large selection range, wherein the chamber pressure can be set to 3mT-10mT; in addition, the upper and lower electrode power thresholds can also have a relatively large process window, which can be set to the upper electrode power range of 200W-800W, and the lower electrode power range of 50W-300W; the current ratio range is controlled to be 0.25-0.75. The selection of these parameters only affects the etching rate of the silicide layer, and in the actual etching process, a suitable etching rate can be adjusted according to the thickness of the silicide layer and the above parameters.
[0047] In addition, compared with the etching of the tungsten layer, the etching of the silicide layer is not sensitive to the process temperature, so that the temperature of the first etching step can have a relatively large adjustment range, which can be set to 30℃-60℃, and the time length can be set to 10s-30s, so that the problem of too long process time caused by temperature change between process steps can be alleviated as much as possible.
[0048] In the embodiment of the application, the first etching step can remove the silicide layer as a mask layer before etching the tungsten layer, so as to expose the carbon material layer, so that the whole process of etching the tungsten layer is with the carbon material layer as a mask layer, such as Figure 8 (b) shows a schematic diagram of removing the silicide layer.
[0049] Optionally, the first process gas can include fluorocarbon gas, which has a relatively high etching selectivity to the tungsten layer, so as to alleviate the problem of etching the tungsten layer in the process of removing the silicide layer.
[0050] The fluorocarbon gas can include any one of CF4, C2F6, C4F8. Of course, it can also be other gases, which are not limited here.
[0051] Taking CF4 as the main etching gas as an example, the silicide layer etched by this kind of gas has a higher etching selectivity to the tungsten layer than NF3 gas, and can achieve the removal of only the silicide layer without etching the tungsten layer.
[0052] Exemplarily, the flow rate of CF4 can be 20sccm-100sccm, for example, including 20sccm, 40sccm, 60sccm, 80sccm, 100sccm, etc., and of course, it can also be other values, which are not limited here.
[0053] Optionally, the first etching step further comprises: using a protective gas to protect the portion of the carbon material layer and the tungsten layer exposed to the plasma while etching the silicide layer by using the plasma etching process. Based on this configuration, the protective gas can be attached to the surface of the carbon material layer and the tungsten layer, so as to provide more deposition, and by virtue of the presence of the deposition, the carbon material layer and the tungsten layer can be effectively prevented from being etched.
[0054] Of course, the protective gas can also be attached to the sidewall of the process chamber, so as to change the etching environment of the process chamber from a relatively clean environment without deposition to an etching environment with a large amount of long-chain polymer attached, so as to prepare for the etching of the tungsten layer in the next step.
[0055] In addition, in actual process practice, when the opening rate is small, a small amount of protective gas can also be added or no protective gas can be added during the removal of the silicide layer, so as to avoid the phenomenon of "plugging" or even process termination.
[0056] Optionally, the protective gas can comprise a hydrocarbon fluoride gas, which can be attached to the surface of the carbon material layer, the surface of the tungsten layer, and the sidewall of the process chamber during the removal of the silicide layer, so as to not only protect the carbon material layer and the tungsten layer, but also prepare for the subsequent etching of the tungsten layer.
[0057] For example, the hydrocarbon fluoride gas of the protective gas can comprise CH2F2 or CHF3, and in addition, other gas types can also be included, which are not limited herein.
[0058] For example, the flow rate of CH2F2 can be 10sccm-200sccm, for example, 10sccm, 50sccm, 80sccm, 100sccm, 120sccm, 150sccm, 180sccm, 200sccm, and the like, and of course, other values can also be used, which are not limited herein.
[0059] In some more specific embodiments, the first process gas can comprise CF4 and CH2F2, and in addition, the flow rate ratio of CF4 and CH2F2 can be controlled to be 2:1 to meet the etching requirement of the silicide layer, and of course, other ratios can also be used, which are not limited herein.
[0060] In addition, the first process gas can flow into different regions in the process chamber, including a center region, an intermediate region, and an edge region, and the flow rate ratio of the first process gas flowing into the center region, the intermediate region, and the edge region can be 33:33:34, and of course, other ratios can also be used, which are not limited herein, as long as the process requirement is met.
[0061] In the embodiments of the present application, the second etching step is the tungsten layer etching step, for example,Figure 8 (c) the schematic diagram of etching the tungsten layer using the carbon material layer as a mask layer. The carbon material layer is bombarded by ions in the plasma in the process chamber, and part of the carbon-based deposits are generated. Figure (8d) is a physical diagram of the tungsten material after etching. Due to the protection of the sidewall deposits, the black tungsten material has a larger size, and the etching speed in the vertical direction is slower. With the same etching time, the etching depth is shallower, and the protection effect on the lateral size of the tungsten material is better.
[0062] In addition, during the removal of the silicide layer through the first etching step, a large amount of carbon-based deposits generated by the dissociation of the protective gas (such as CH2F2, etc.) on the surface of the carbon material layer and the tungsten layer and the sidewall of the process chamber will also be partially attached to the sidewall of the tungsten layer under the bombardment of the plasma. These carbon-based deposits are not easy to react with the first process gas (such as fluorocarbon gas, etc.), and can provide better protection effect for the sidewall of the tungsten layer during the etching of the tungsten layer.
[0063] Based on the above, in order to reduce the chemical reaction between the free radicals and the sidewall of the tungsten layer, thereby reducing the loss of the sidewall of the tungsten layer, the embodiments of the present application adopt a technical solution different from the related art, that is, to solve the problem from the aspect of reducing the lateral chemical etching angle.
[0064] Optionally, the tungsten layer is etched by using a plasma etching process, comprising:
[0065] The tungsten layer is etched by using a plasma etching process using a second process gas, wherein the second process gas can include Ar, NF3 and a fluorocarbon gas.
[0066] Wherein, Ar and NF3 are both main etching gases, and the fluorocarbon gas can be used as a protective gas, wherein the fluorocarbon gas can include CH2F2 or CHF3, in addition to other gas types, which are not limited here.
[0067] Exemplarily, the flow rate of Ar can range from 100sccm to 500sccm, for example, including 100sccm, 200sccm, 300sccm, 400sccm, 500sccm, etc.; the flow rate of NF3 can range from 5sccm to 50sccm, for example, including 5sccm, 10sccm, 20sccm, 40sccm, 50sccm, etc.
[0068] For example, the flow rate of the fluorocarbon gas including CH2F2 can range from 10sccm to 50sccm, for example, including 10sccm, 20sccm, 30sccm, 40sccm, 50sccm, etc.
[0069] In some specific embodiments, the second process gas can include Ar, NF3 and CH2F2, and the flow ratio of the three can be 10:1:1 to meet the etching requirement of the tungsten layer, but can also be other ratios, which are not limited herein.
[0070] In addition, the second process gas can flow into different regions in the process chamber, including a center region, an intermediate region and an edge region, and the flow ratio of the second process gas flowing into the center region, the intermediate region and the edge region can be 33:33:34, but is not limited thereto and can also be other ratios as long as the process requirement is met.
[0071] In addition, a higher lower electrode power is used in the related art, so that the migration direction of fluorine-based plasma and radicals is as little as possible to deviate under the action of a higher electric field, so that better longitudinal directionality is obtained, and the anisotropic etching of the tungsten layer is realized as much as possible. However, the higher lower electrode power can consume a large amount of carbon material layer, so that the thickness of the carbon material layer is insufficient for subsequent processes.
[0072] Compared with the related art, the silicide layer is removed in advance in the embodiments of the present application, and then the etching environment is converted into a deposition-rich environment, and then the tungsten layer is etched. In this environment, the sidewall of the tungsten layer is protected by a large amount of deposition. Therefore, when the second etching step of the embodiments of the present application is performed, a higher lower electrode power is not required. Even if the directionality of the plasma and the fluorine-containing radicals is not strong under a lower lower electrode power, the deposition on the sidewall of the tungsten layer has a high selectivity to the fluorine-containing radicals. These depositions can consume a large amount of fluorine-containing radicals, thereby reducing the loss of the sidewall of the tungsten layer.
[0073] Optionally, in the second etching step, the lower electrode power can range from 80W to 300W, for example, including 80W, 100W, 150W, 200W, 250W, 300W, and the like, but can also be other values, which are not limited herein. Compared with the related art, the lower electrode power in the second etching step in the embodiments of the present application is relatively low, but a large amount of fluorine-containing radicals can still be consumed by the deposition to reduce the loss of the sidewall of the tungsten layer. Therefore, the sidewall of the tungsten layer can be protected.
[0074] Therefore, in the tungsten layer etching process, the etching effect of the plasma on the sidewall of the tungsten layer is weakened without using a higher lower electrode power, and the etching selectivity ratio of the mask layer is not reduced, so that the mask layer is sufficient to support the subsequent etching process, and the consumption of other region materials such as logic circuit control by the plasma under a high lower electrode power can also be avoided.
[0075] The process formula of the second etching step in the embodiments of the present application includes:
[0076] The chamber pressure of the process chamber ranges from 3 mT to 12 mT, the upper electrode power ranges from 400 W to 1000 W, the current ratio ranges from 0.25 to 0.75, the temperature of the second etching step can be set to 35 DEG C to 60 DEG C, and the time length is set to 30 s to 70 s.
[0077] Compared with the Bosch process in the related art, the embodiment of the present application first performs a pretreatment step, i.e., the first etching step, before etching the tungsten layer, and then performs the second etching step. The Bosch process, however, inserts a plurality of deposition processes in the etching process, thereby dividing the etching process into a plurality of steps. The difference makes the sidewall of the tungsten layer etched by the embodiment of the present application smoother and more continuous, and the phenomenon of the jagged sidewall generated by the Bosch process does not occur.
[0078] In addition, the embodiment of the present application adds a pretreatment step (i.e., the first etching step) on the basis of one-step etching (i.e., the second etching step), and the process time is only increased by 10 s to 30 s, which is about 25% of the time of the entire etching step. The Bosch process, however, needs to go through a plurality of deposition-etching cycles, and the process time is much longer than the time of one-step etching. In addition, after the first etching step, the process environment is changed to an environment rich in deposits. At this time, the second etching step is only an etching step, and the deposition and etching ratio does not need to be considered, thereby making the process window larger.
[0079] Optionally, the etching method further comprises:
[0080] The third etching step uses a plasma etching process to etch the carbon material layer by using a third process gas to remove the carbon material layer, wherein the third process gas comprises O2.
[0081] In the embodiment of the present application, after the tungsten layer is etched, the remaining carbon material layer on the tungsten layer is removed through a debonding step, i.e., the third etching step described above. The main purpose of this step is to remove the remaining carbon material layer after the tungsten layer is etched. The main etching gas used in this step can be O2. When this gas etches the carbon material layer, it has a high etching selectivity to the tungsten layer and will not etch the tungsten layer. In the environment with a large amount of O2, a thin layer of oxide will be formed on the surface of the tungsten layer. The oxide does not react with O2 and can further protect the tungsten layer from being etched by O2.
[0082] Exemplarily, in the third etching step, the flow rate of O2 can range from 200 sccm to 500 sccm, for example, including 200 sccm, 300 sccm, 400 sccm, 500 sccm, etc.
[0083] In addition, the third etching step can be performed without the lower electrode power, and only the upper electrode is used to dissociate the oxygen-containing plasma and radicals. Therefore, the chamber pressure and temperature of the third etching step can be adjusted in a relatively large range, and these parameters only affect the removal rate. In the actual process, the appropriate parameters can be selected according to the thickness of the remaining carbon material layer, so as to determine the removal rate and process time.
[0084] In some embodiments, in the third etching step, the chamber pressure of the process chamber ranges from 10 mT to 30 mT, the upper electrode power ranges from 500 W to 1200 W, the current ratio ranges from 0.25 to 0.75, the temperature of the third etching step ranges from 30°C to 60°C, and the time length ranges from 50 s to 120 s.
[0085] In addition, the third process gas can flow into different regions in the process chamber, including a central region, an intermediate region, and an edge region. The flow ratio of the third process gas flowing into the central region, the intermediate region, and the edge region can be 33:33:34, but is not limited thereto and can be other ratios as long as the process requirements are met.
[0086] In addition, in addition to the above-mentioned step of removing the carbon material layer, an additional stripping step is performed between the process flows to complete the tungsten layer etching and enter the next process. The remaining carbon material layer is further removed, so that the wafer surface is free of residual carbon material layer and carbon-containing deposit particles.
[0087] To reduce the risk of falling particles in the process chamber, after the stripping step in the last step of the tungsten layer etching process, most of the carbon-containing deposits (such as the carbon material layer) are removed, and the process chamber is cleaned after the tungsten layer etching process is completed. The residual particles in the process chamber are removed, the process chamber is restored to the initial state, and the risks of process repetition, change of etching process environment, and falling particles are avoided. In addition, the chamber cleaning process WAC is a necessary chamber cleaning process after each etching process. The time length of the process does not affect the overall process time of the tungsten layer etching process, and has little effect on the production efficiency.
[0088] Optionally, the etching method further comprises:
[0089] In the pattern transfer step before the first etching step, the pattern morphology of the silicide layer is transferred to the carbon material layer, so that the carbon material layer and the silicide layer have the same pattern morphology.
[0090] Based on the above-mentioned etching method of the semiconductor structure, the embodiments of the present application also disclose a semiconductor process equipment, such as Figure 9As shown, the disclosed semiconductor process equipment includes a process chamber, a gas inlet assembly, and a controller, wherein the controller includes at least one processor and at least one memory having stored therein a computer program which, when executed by the processor, implements the above-mentioned etching method for semiconductor structure.
[0091] In addition, the semiconductor process equipment can further include an upper electrode assembly and a lower electrode assembly.
[0092] Exemplarily, the controller can be a host computer or a lower computer. The controller can control the valve of the gas inlet assembly to open to introduce the corresponding process gas into the interior of the process chamber. The controller can also control the opening degree of the valve of the gas inlet assembly to control the flow of the process gas. The controller can also control the gas extraction assembly to extract the interior of the process chamber to control the pressure in the interior of the process chamber, discharge the reaction by-products, etc.
[0093] The upper electrode assembly can include a radio frequency coil, an upper radio frequency power source, and an upper matching device. The controller is further configured to control the upper radio frequency power source to provide upper electrode power to the radio frequency coil through the upper matching device, so that the radio frequency coil excites the process gas in the interior of the process chamber to generate plasma.
[0094] The lower electrode assembly includes a wafer supporting device, a lower radio frequency power source, and a lower matching device. The controller is further configured to control the lower radio frequency power source to provide lower electrode power to the lower electrode of the wafer supporting device through the lower matching device, so that the lower electrode of the wafer supporting device provides a radio frequency bias to attract the plasma above the object to be etched to bombard the object to be etched.
[0095] Exemplarily, the semiconductor process equipment of the embodiments of the present application can be an inductively coupled plasma (ICP) etching device.
[0096] It should be noted that the specific structure of the semiconductor process equipment and its working principle can refer to the prior art, which will not be described in detail here.
[0097] In summary, the embodiments of the present application optimize the process steps, and according to the type difference of the mask layer in the tungsten layer etching process, the etching process steps are divided into two steps. The first etching step is mainly to remove the remaining silicide layer in the process of transferring the pattern and morphology of the silicide layer to the carbon material layer, to expose the carbon material layer, so that a large amount of carbon appears on the wafer surface, creating a carbon-containing environment for the next etching step. The second etching step etches the tungsten layer with the carbon material layer as the mask layer, so that the tungsten layer is etched in the environment with the carbon material layer as the mask layer. In addition, in the process of removing the silicide layer, a high carbon-fluorine ratio gas which is easy to dissociate carbon-based deposits is added, so that the content of carbon-based deposits in the process chamber is further increased, providing sufficient protection for the sidewall of the tungsten layer.
[0098] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims.
Claims
1. A method of etching a semiconductor structure, comprising: The semiconductor structure includes a tungsten layer, a carbon material layer and a silicide layer which are sequentially stacked on the tungsten layer, the carbon material layer and the silicide layer have the same pattern topography, and the etching method includes: A first etching step of etching only the silicide layer by using a plasma etching process to remove the silicide layer to expose the carbon material layer; A second etching step of etching the tungsten layer by using a plasma etching process with the carbon material layer as a mask layer, and carbon-based deposits generated by the carbon material layer are attached to the side surface of the tungsten layer.
2. The etching method according to claim 1, wherein The etching of the silicide mask layer by using a plasma etching process includes: The etching of the silicide layer by using a plasma etching process with a first process gas, wherein the etching selectivity of the first process gas to the tungsten layer and the etching selectivity of the first process gas to the carbon material layer are both greater than the etching selectivity of the first process gas to the silicide layer.
3. The etching method according to claim 2, wherein The first process gas includes a fluorocarbon gas, and the fluorocarbon gas includes any one of CF4, C2F6 and C4F8.
4. The etching method according to claim 2, wherein The first etching step further includes, while etching the silicide layer by using a plasma etching process, protecting the carbon material layer and the part of the tungsten layer exposed to the plasma by using a protective gas.
5. The etching method according to claim 4, wherein The protective gas includes a hydrofluorocarbon gas, and the hydrofluorocarbon gas includes CH2F2 or CHF3.
6. The etching method of claim 1, wherein The etching of the tungsten layer by using a plasma etching process includes: The etching of the tungsten layer by using a plasma etching process with a second process gas, wherein the second process gas includes Ar, NF3 and a hydrofluorocarbon gas.
7. The etching method of claim 1, wherein In the second etching step: The power range of the lower electrode is 80 W to 300 W.
8. The etching method of claim 1, wherein, The etching method further includes: A third etching step of etching the carbon material layer by using a plasma etching process with a third process gas to remove the carbon material layer, wherein the third process gas includes O2.
9. The etching method of claim 1, wherein The etching method further includes: A pattern transfer step before the first etching step of transferring the pattern topography of the silicide layer to the carbon material layer.
10. A semiconductor process apparatus comprising a process chamber, a gas inlet assembly, and a controller, wherein, The controller includes at least one processor and at least one memory, the memory stores a computer program, and the computer program is executed by the processor to implement the etching method of the semiconductor structure according to any one of claims 1 to 9.