Etching method
By forming passivation layers of varying thicknesses during semiconductor manufacturing and controlling the turnover efficiency of etching gases, the problem of uneven trench depths of different widths was solved, thereby improving the yield of semiconductors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- BEIJING NAURA MICROELECTRONICS EQUIP CO LTD
- Filing Date
- 2022-06-30
- Publication Date
- 2026-06-26
AI Technical Summary
In the semiconductor manufacturing process, due to the influence of aspect ratio, the uniformity of trench depth of different widths is poor, resulting in a low semiconductor yield.
An etching method is employed in which passivation layers of different thicknesses are first formed in the regions where first and second trenches are formed on the etched part. The passivation layer is formed by reacting the passivation gas with the etched part. By controlling the replacement efficiency of the etching gas and the etching rate, trenches of different widths can reach the same depth in the same time.
This technology enables the formation of trenches of varying widths on the etched surface to reach the same depth within the same timeframe, thereby improving the yield rate of semiconductors.
Smart Images
Figure CN114914156B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor manufacturing technology, and more particularly to an etching method. Background Technology
[0002] Trench etching is a common process in semiconductor manufacturing. During trench etching, the aspect ratio is a crucial factor affecting the etching depth. Compared to narrower trenches, wider trenches are more easily etched deeper. Furthermore, if the trench width is on the order of magnitude smaller, the aspect ratio has a greater impact on the etching depth, resulting in poor uniformity of trench depth across different widths and consequently, lower semiconductor yield. Summary of the Invention
[0003] This invention discloses an etching method to solve the problem that the depth uniformity of trenches of different widths is poor due to the influence of aspect ratio in the current semiconductor etching process, resulting in a low yield of semiconductors.
[0004] To solve the above problems, the present invention adopts the following technical solution:
[0005] This invention discloses an etching method for etching a first trench and a second trench on a workpiece, wherein the width of the longitudinal section of the first trench is greater than the width of the longitudinal section of the second trench, and the etching method includes:
[0006] Passivating gas is introduced into the process chamber until, after a first preset time, a first passivation layer and a second passivation layer are formed at the bottom of the corresponding areas on the etched part used to form the first trench and the second trench, respectively. The passivating gas reacts with the original etched material on the etched part to form the first passivation layer and the second passivation layer. The formation rate of the first passivation layer is greater than the formation rate of the second passivation layer, and the etching rates of the first passivation layer and the second passivation layer are both less than the etching rate of the etched material.
[0007] Turn on the RF power supply and introduce the first etching gas into the process chamber until the depths of the first trench and the second trench both meet the preset depth. The first plasma formed by the ionization of the first etching gas is used to continue etching the first trench and the second trench after penetrating the first passivation layer and the second passivation layer.
[0008] The technical solution adopted in this invention can achieve the following beneficial effects:
[0009] This application discloses an etching method, which specifically includes a passivation process and an etching process. During the passivation process, a passivation gas can be introduced into the process chamber, so that the passivation gas interacts with the original material on the etched part to form a passivation layer. Because the width of the longitudinal section of the first trench on the etched part is relatively large, the replacement efficiency of the passivation gas in this area is also relatively large. This results in the formation rate of the first passivation layer being greater than that of the second passivation layer. Consequently, within the same passivation time, the thickness of the first passivation layer is greater than that of the second passivation layer. Therefore, in the subsequent etching process, even if the replacement efficiency of the first etching gas (or first plasma) in the area corresponding to the first trench is greater than that in the area corresponding to the second trench, the etching time of the first passivation layer can still be greater than that of the second passivation layer. This allows the area corresponding to the second trench to begin etching the original material on the etched part before the area corresponding to the first trench. Consequently, when the first passivation layer is etched, the depth change of the first trench is less than that of the second trench, meaning the depth of the second trench is greater than that of the first trench.
[0010] When the original material to be etched on the workpiece begins to be etched in the regions corresponding to the first trench and the second trench, the first trench has a relatively large longitudinal cross-sectional width, and the replacement efficiency of the first etching gas and the discharge efficiency of by-products in the first trench are relatively high. As a result, after the first passivation layer is etched through, the etching rate of the first trench will be greater than that of the second trench. Under these circumstances, after a certain period of time, the first trench can "catch up" with the etching progress of the second trench at a certain depth. At this time, the etching depths of the first trench and the second trench are equal.
[0011] In summary, this etching method can form a first trench with a larger longitudinal cross-section and a second trench with a smaller longitudinal cross-section on the workpiece. Moreover, within the same processing time, the etching depths of the first and second trenches with different longitudinal cross-section widths can be the same, and both meet the preset depth. Attached Figure Description
[0012] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:
[0013] Figure 1 This is a flowchart of the etching method disclosed in the embodiments of this application;
[0014] Figures 2-8This is a schematic diagram illustrating different stages of etching a workpiece using the etching method disclosed in the embodiments of this application;
[0015] Figure 9 The image shows an electron microscope (EM) image of an etched part formed by etching using the etching method disclosed in the embodiments of this application.
[0016] Explanation of reference numerals in the attached figures:
[0017] 101-Metal capping layer, 102-Protective layer, 103-Patterned mask layer, 104-Substrate, 105-Atoms, 106-Impurities, 107-Deposited layer, 108-First passivation layer, 109-Second passivation layer, 110-Metal filler layer. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0019] The technical solutions disclosed in the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0020] like Figures 1-9 As shown, an embodiment of the present invention discloses an etching method. When the etching method is used to etch a workpiece, a first trench and a second trench can be formed on the workpiece. The width of the longitudinal section of the first trench is greater than the width of the longitudinal section of the second trench, or in other words, the area of the cross section of the first trench is greater than the area of the cross section of the second trench.
[0021] Of course, in order to ensure that the etching method disclosed in this application can form the first trench and the second trench at the preset position on the etched part, a mask layer can be formed on the etched part in advance using a mask material before the etching process, and the mask layer can be patterned by means of exposure and development, that is, the area on the mask layer corresponding to the area on the etched part where the first trench and the second trench need to be formed is removed, so that the part on the etched part where the first trench and the second trench need to be formed can be exposed outside the mask layer, thereby ensuring that the passivating gas used to passivate the etched part and the etching gas used to etch the etched part can interact with the original material of the etched part, and finally achieve the purpose of etching the first trench and the second trench on the etched part.
[0022] Furthermore, since different etched parts may have different uses, a patterned mask layer 103 can be used to pre-form multiple trench structures on the substrate 104 of the etched part, and fill the multiple trench structures with conductive materials such as metal, so that the conductive materials such as metal refill the trench structures to form a metal filling layer 110. Then, the metal filling layer 110 is etched to remove some of the metal filling material, so that the etching depth of the multiple trench structures is equal (that is, the process of etching at the corresponding positions of the multiple filled trench structures to re-form the first trench and the second trench); at the same time, the conductive material filled at the bottom of the original trench structure is retained so that the conductive material can perform its conductive function. Of course, in order to prevent damage to the original sidewalls of the trench structure on the substrate 104 of the etched part during the etching of the metal filling layer 110, a protective layer 102 can be formed on the etched part with multiple trench structures before filling with conductive materials such as metal. The protective layer 102 covers the surface of the etched part (or the surface of the patterned mask layer on the top of the etched part that has not been completely etched), as well as the sidewalls and bottom walls of the trench structure. Thus, during the etching of the metal filling layer 110, it can be ensured that the passivation reaction and the etching reaction both occur in the area where the metal filling layer 110 is located, and the substrate of the etched part itself will not be etched.
[0023] Based on the above, the etching method disclosed in this application includes:
[0024] S1. Passivating gas is introduced into the process chamber until, after a first preset time, the bottom of the corresponding areas on the etched part used to form the first and second trenches are respectively formed with a first passivation layer and a second passivation layer. The specific value of the first preset time can be selected comprehensively based on various factors such as the depth requirements of the first and second trenches, and the difference in etching rate between the passivation material and the original etched material on the etched part.
[0025] Specifically, the passivating gas can be an oxidizing gas such as oxygen or nitrogen. The passivating gas reacts with the original etched material on the workpiece, forming a first passivation layer and a second passivation layer in the regions corresponding to the areas where the first and second trenches will be formed. To improve the reaction efficiency and effect of the passivation process, optionally, the upper radio frequency power supply can be kept on while the passivating gas is introduced into the process chamber. That is, during step S1, the upper radio frequency power supply is kept on, thereby ionizing the passivating gas into plasma. This can greatly improve the reaction efficiency and effect of the passivation process, shorten the passivation time, and improve process efficiency.
[0026] It should be noted that, since the first passivation layer and the second passivation layer are respectively formed at the bottom of the positions on the etched part where the first trench and the second trench are to be formed, and are protected by the mask layer or protective layer on the etched part, the etched part has a certain depth of groove at the position where the first trench and the second trench are to be formed. The groove can be formed by the mask layer, or the groove can be formed by the metal filling material not filling the groove structure pre-etched on the etched part. Furthermore, since the width of the longitudinal section of the first trench is greater than that of the longitudinal section of the second trench, the passivation gas can more easily enter the pattern structure of the mask layer corresponding to the relatively larger first trench (or the interior of the groove formed by the protective layer) and react with the filling material in the first trench. Therefore, the replacement efficiency of the passivation gas in the first trench is also relatively high, which makes the formation rate of the first passivation layer corresponding to the first trench greater than that of the second passivation layer corresponding to the second trench. As a result, within the same passivation time, the thickness of the first passivation layer formed in the region corresponding to the first trench is greater than that of the second passivation layer formed in the region corresponding to the second trench.
[0027] Therefore, during the subsequent etching process, even if the replacement efficiency of the first etching gas in the relatively large first trench is relatively high, the larger thickness of the first passivation layer means that the first passivation layer takes longer to be etched through than the second passivation layer. This results in a situation where the second passivation layer has already been etched in the area corresponding to the second trench, and the etching of the original material on the workpiece begins, while the area corresponding to the first trench has not yet completed the etching of the first passivation layer. Consequently, during the etching of the first and second trenches with the same initial depth, the area corresponding to the second trench can etch the original material on the workpiece before the area corresponding to the first trench, compensating for the time difference caused by the relatively faster etching rate of the first trench in subsequent etching of the original material on the workpiece.
[0028] As described above, the first and second passivation layers are formed by the interaction between the passivation gas and the etched material on the etched component. In other words, during the formation of the first and second passivation layers, the original etched material at corresponding locations is consumed, and corresponding passivation is formed. Due to the influence of the structural composition, the etching rate of the passivation is less than the etching rate of the original etched material on the etched component; that is, the etching rates of both the first and second passivation layers are less than the etching rate of the original etched material on the etched component.
[0029] Furthermore, as explained above, because the thickness of the first passivation layer is greater than that of the second passivation layer, even if the replacement efficiency of the first etching gas in the first trench is relatively high, the process result of the first passivation layer not being completely etched through when the second passivation layer is etched through can still occur. Therefore, when the first trench and the second trench with the same initial depth are further etched, when the area corresponding to the second trench has begun to etch the original etched material on the etched part, the area corresponding to the first trench is still etching the first passivation layer. Simultaneously, since the etching rate of the first passivation layer is lower than the etching rate of the original etched material on the etched part, the difference between the depth variation of the second trench and the depth variation of the first trench can be further increased during the time period from the completion of etching of the second passivation layer to the completion of etching of the first passivation layer. Therefore, when etching of the original etched material on the etched part begins in the area corresponding to the first trench, the difference between the depth of the second trench and the depth of the first trench can be further expanded. This compensates for the difference in etching depth variation between the first trench and the second trench within the same time period when etching the same material (i.e., the original etched material on the etched part) in the areas corresponding to the first and second trenches, due to their different width dimensions. Subsequently, after the first passivation layer is etched through, a second preset etching process can be performed to bring the etching progress of the first and second trenches to a level position, making the etching depths of the first and second trenches equal.
[0030] In the above process, based on the difference in etching rate between the passivation layer and the original etched material on the etched part, and the difference in etching rate between the regions corresponding to the first trench and the second trench when etching the original etched material on the etched part, etc., by setting the corresponding passivation time (i.e. the first preset time and the second preset time mentioned above), it can theoretically be guaranteed that after a single passivation process and etching process, the etching depth of the first trench and the second trench is equal or substantially equal, and the specific value when the two depths are equal is equal to the preset depth. The preset depth is the actual depth of the first trench and the second trench formed by (re)etching at the corresponding position.
[0031] In detail, the above etching process includes:
[0032] S2: Turn on the lower RF power supply and introduce the first etching gas into the process chamber until the depths of the first trench and the second trench both meet the preset depth. Furthermore, during the etching process of the workpiece with the first passivation layer and the second passivation layer formed, the first plasma formed by the ionization of the first etching gas can continue to etch the first trench and the second trench to a deeper location after penetrating the first and second passivation layers. As described above, by utilizing the time difference between the penetration of the first passivation layer and the second passivation layer, which have different thicknesses, and the difference in etching rate between the passivation layer (including the first and second passivation layers) and the original etched material on the workpiece, the depths of the (re)etched first trench and the second trench can be made the same after a second preset time period following the penetration of the first passivation layer. Specifically, the specific type of the first etching gas can be determined based on the original etched material on the etched part, ensuring that the first plasma formed by the ionization of the first passivation gas has the ability to etch the original etched material on the etched part, as well as the first passivation layer and the second passivation layer formed by the etched material.
[0033] This application discloses an etching method in which a first passivation layer and a second passivation layer are formed on the etched part in the regions corresponding to the areas where the first and second trenches are to be formed. Furthermore, by using a patterned mask layer or by etching first and then filling, it can be ensured that both the first and second passivation layers are formed in "grooves", and the grooves correspond to the regions on the etched part where the first and second trenches are to be formed. Because the width of the longitudinal section of the "sinking" region corresponding to the first trench on the etched part is relatively large, the replacement efficiency of the passivation gas in this region is also relatively large. This results in the formation rate of the first passivation layer being greater than that of the second passivation layer. Consequently, within the same passivation time, the thickness of the first passivation layer is greater than that of the second passivation layer. Therefore, in the subsequent etching process, even if the replacement efficiency of the first etching gas in the region corresponding to the first trench is greater than that in the region corresponding to the second trench, the etching time of the first passivation layer can still be greater than that of the second passivation layer. This allows the region corresponding to the second trench to begin etching the original material on the etched part before the region corresponding to the first trench. Consequently, when the first passivation layer is etched, the depth change of the first trench is less than that of the second trench.
[0034] As mentioned above, since the etching time of the first passivation layer is longer than that of the second passivation layer, the original material to be etched on the workpiece has already begun to be etched in the area corresponding to the second trench before the first passivation layer has been etched through. Furthermore, since the etching rates of passivation materials such as the first and second passivation layers are both less than the etching rate of the original material to be etched on the workpiece, the difference between the depth change of the first trench and the depth change of the second trench can be further amplified during the time period from when the second passivation layer is etched through to when the first passivation layer is etched through.
[0035] Furthermore, when the etching of the original etched material on the workpiece begins in the regions corresponding to the first and second trenches, the relatively large width of the longitudinal section of the first trench results in relatively high replacement efficiency of the first etching gas and removal efficiency of byproducts within it. This causes the etching depth change rate of the region corresponding to the first trench to exceed that of the region corresponding to the second trench. Consequently, after penetrating the first passivation layer, the region corresponding to the first trench can "catch up" with the etching progress of the second trench at a certain depth after a second preset time, thus making the etching depths of the first and second trenches equal. Simultaneously, based on objective factors such as the etching rates of the passivation layer and the original etched material on the workpiece, and the etching rates of the original etched material in the regions corresponding to the first and second trenches, a first preset time for the passivation process and a second preset time for the etching process can be selected to ensure that the depths of both the first and second trenches meet the preset depth when their depths are equal.
[0036] In summary, this etching method can form a first trench with a larger longitudinal cross-section and a second trench with a smaller longitudinal cross-section on the workpiece. Moreover, within the same processing time, the etching depths of the first and second trenches with different longitudinal cross-section widths can be the same, and both meet the preset depth.
[0037] As described above, a patterned mask layer can be pre-formed to provide protection for areas on the etched part other than the areas where the first and second trenches need to be formed. This creates two "sinking" spaces on the etched part, each corresponding to the area where the first and second trenches are to be formed. By controlling the formation parameters of the patterned mask layer, the width of the two "sinking" spaces can be made different. This ensures that during step S1, the first passivation layer and the second passivation layer can be formed in the two "sinking" spaces (i.e., at the bottom of the corresponding areas on the etched part where the first and second trenches are to be formed). Due to the different turnover efficiencies of the passivation gas, the thickness of the first passivation layer is greater than the thickness of the second passivation layer.
[0038] Similarly, when using a technical solution that partially fills multiple pre-formed trench structures with metal filler material, multiple trenches can also have an initial depth greater than zero. This can also ensure that the first passivation layer and the second passivation layer can both be formed in the "sinking" structure, and ensure that the formation rate of the first passivation layer is greater than the formation rate of the second passivation layer, so as to achieve the purpose of the first passivation layer being thicker than the second passivation layer within the same passivation time.
[0039] However, in the process of filling the pre-formed multiple trench structures with metal filler material, the metal filler material may completely fill the trench structure, or even extend beyond the original trench structure, covering the upper surface of the etched part (specifically, the upper surface of the protective layer), forming a metal capping layer 101. In this case, to ensure that a first passivation layer and a second passivation layer of different thicknesses are formed on the etched part corresponding to the positions where the first and second trenches are to be formed, a pre-etching method can be used to remove the portion of the original material on the upper surface of the etched part, i.e., the metal capping layer 101, and to produce a certain over-etching effect in the aforementioned etching process, so that the positions on the etched part used to form the first and second trenches have an initial depth greater than zero. Based on this, performing the above steps S1 and S2 can ensure that after a preset time, the first and second trenches of the same depth can be formed on the etched part, and that some metal filler material remains at the bottom of both the first and second trenches.
[0040] In the etching method disclosed in the above embodiments, both steps S1 and S2 can be performed in one go. Considering that the width of the longitudinal section is relatively small, the difference between the etching rates of the trenches with different widths is relatively large. When using the passivation layer formed in one go to compensate for the difference between the etching rates, the control accuracy needs to reach a relatively high level, which makes the control difficult.
[0041] Based on this, in order to reduce the difficulty of control and improve the yield, the deposition process can be carried out simultaneously during the pre-etching process. After the regions corresponding to the first and second trenches have a "sinking" structure, the difference between the etching rate and the deposition rate of the first trench, which has a relatively large width, is relatively small. This achieves the goal of making the etching rate of the first trench less than that of the second trench, thereby further increasing the depth difference between the first and second trenches before the above step S2.
[0042] Simultaneously, during the pre-etching and deposition processes, a protective layer can be formed on the sidewalls of the first and second trenches. Correspondingly, due to the difference in the width of the longitudinal cross-section of the first and second trenches, the thickness of the deposition layer 107 formed on the sidewall of the first trench will be greater than the thickness of the deposition layer 107 formed on the second trench. In this case, the difference between the width of the longitudinal cross-section of the cavity in the first and second trenches can be reduced, making the difference between the gas replacement efficiency in the first and second trenches relatively smaller, so as to further reduce the etching depth change rate when etching the original material in the first and second trenches, and reduce the etching control difficulty of the first and second trenches.
[0043] Of course, in the above process, in order to ensure that the simultaneous etching and deposition processes can etch the first and second trenches to a deeper location, it is necessary to ensure that the flow rates of the gas used for etching and the gas used for deposition are greater than a certain preset value. The specific value of the aforementioned preset value can be determined based on parameters such as the material of the etched part, the power of the lower RF power supply, the deposition gas and the corresponding etching gas, so as to ensure that the etching rate at the bottom of the etched part is greater than the deposition rate at the bottom of the etched part, allowing the etching process to proceed to a deeper location on the etched part.
[0044] Based on the above embodiments, before introducing passivation gas into the process chamber, the etching method disclosed in this application further includes:
[0045] S3. Turn on the lower RF power supply and introduce the deposition gas and the second etching gas into the process chamber until the difference between the depth change of the second trench and the depth change of the first trench meets the preset difference value. Since the ions formed by the ionization of the second etching gas and the deposition gas can move towards the depth direction of the first and second trenches under the action of the lower RF power supply, the deposition process at the bottom of the first and second trenches will be interfered with by the etching process, increasing the difficulty of forming the deposition layer at the bottom. The specific type of the second etching gas can be determined according to the original material on the etched part, and the type of the second etching gas can be the same as or different from the type of the first etching gas; no limitation is made here.
[0046] Furthermore, during step S3, the ratio between the flow rate of the second etching gas and the flow rate of the deposition gas can be controlled so that when step S3 is performed, the etching rate at the bottom of the etched part is greater than the deposition rate, so that after step S3 is completed, the areas on the etched part used to form the first trench and the second trench both have a certain initial depth.
[0047] Meanwhile, due to the different characteristics of etching and deposition processes, the difference between the etching rate and deposition rate is relatively small for the first trench with a relatively large width, while the difference is relatively large for the second trench with a smaller width. Therefore, during step S3, the change in etching depth of the first trench per unit time can be less than the change in etching depth of the second trench. Furthermore, by setting the duration of step S3, the difference between the depth change of the second trench and the depth change of the first trench can be made to meet a preset difference after step S3 is completed.
[0048] Furthermore, in step S3 above, the third plasma formed by the ionization of the deposited gas can be deposited on the sidewalls of the first and second trenches. Due to the difference in the width of the longitudinal cross-section of the first and second trenches, the formation rate of the deposition layer on the sidewall of the first trench is greater than that on the sidewall of the second trench. As a result, when step S3 is completed, the thickness of the deposition layer 107 on the sidewall of the first trench is greater than that of the deposition layer 107 in the second trench. This can reduce the difference between the gas replacement efficiency in the first and second trenches, thereby reducing the etching rate of the original etched material in the corresponding areas of the first and second trenches, and further reducing the difficulty of etching control of the etched part.
[0049] In the above embodiments, optionally, the power of the lower radio frequency power supply when the first etching gas is introduced is greater than the power of the lower radio frequency power supply when the second etching gas is introduced; that is, the power of the lower radio frequency power supply when performing step S1 is greater than the power of the lower radio frequency power supply when performing step S3. In this case, the power of the lower radio frequency power supply when performing step S1 is relatively large, thereby increasing the magnitude of the downward pull on the first plasma, thereby enhancing the ability of the first plasma corresponding to the first trench and the second trench to move to the depth of the first trench and the second trench, reducing the proportion of the first plasma entering the second trench annihilated on the sidewall of the second trench, thereby reducing the difference between the effective number of first plasmas in the first trench and the second trench, reducing the difference in the etching rate of the original etched material in the region corresponding to the first trench and the second trench in the etched part, thereby further reducing the etching difficulty of the etched part.
[0050] In the above embodiments, optionally, the power of the upper radio frequency power supply when the first etching gas is introduced is less than the power of the upper radio frequency power supply when the second etching gas is introduced; that is, the power of the upper radio frequency power supply when performing step S1 is less than the power of the upper radio frequency power supply when performing step S3. In this case, the power of the upper radio frequency power supply when performing step S1 is relatively small, thereby reducing the generation rate of the first plasma during step S1 within a certain range. With the reduction in the generation amount of the first plasma per unit time, the difference between the amount of first plasma entering the first trench and the second trench per unit time is relatively smaller, thereby reducing the difference in the etching rate of the original etched material in the regions corresponding to the first trench and the second trench in the etched part, further reducing the etching difficulty of the etched part.
[0051] As described above, during step S1, the first etching gas can be ionized into the first plasma under the action of the upper radio frequency power supply, so as to use the first plasma to etch the first passivation layer, the second passivation layer and the original etched material on the etched part; at the same time, under the action of the lower radio frequency power supply, the first plasma can be made to move into the depth of the trench, and the by-products in the first trench and the second trench can be discharged as timely as possible in the gas environment flowing in the process chamber.
[0052] However, as the etching process continues, the depth of the first and second trenches increases, making it more difficult to remove byproducts from the first and second trenches. Furthermore, the lower RF power supply further exacerbates the difficulty of removing byproducts from the first and second trenches, thereby hindering the entry of new first plasma into the first and second trenches and making it difficult to carry out the replacement of the first plasma in the first and second trenches.
[0053] Therefore, in one specific embodiment of this application, during the introduction of the first etching gas, the lower RF power supply operates with a preset duty cycle. The specific value of the preset duty cycle can be determined according to the specific etching operation conditions and is not limited here. When this technical solution is adopted, if the lower RF power supply is in the off state, that is, when the power of the lower RF power supply is 0, the byproducts in the first and second trenches no longer have the tendency to move deeper. Therefore, under the action of the flowing gas environment, the byproducts in the first and second trenches can be discharged as quickly and thoroughly as possible, ensuring that the first plasma can be replenished in both the first and second trenches, and ensuring that the etching operation can be carried out stably and continuously.
[0054] In addition, when the etching method includes the above step S3, the lower radio frequency power supply can also be operated with a preset duty cycle, thereby ensuring that the byproducts in the first and second trenches with relatively small depths on the etched part can also be discharged in time, and that the second plasma can be replenished in the first and second trenches in time, so that the etching work of the first and second trenches can be carried out stably.
[0055] Optionally, before introducing the passivation gas into the process chamber, i.e., before step S1 above, the etching method disclosed in this application embodiment further includes:
[0056] S4. Surface-activating gas is introduced into the process chamber until the third preset time is met. During the aforementioned process, the fourth plasma formed by the ionization of the surface-activating gas can bombard the surface of the original etched material on the etched part to remove non-etched material adhering to the surface of the etched material. Specifically, the surface-activating gas can be an inert gas; of course, other gases with relatively stable chemical properties can also be used as surface-activating gases.
[0057] In detail, before the etching process, the atoms 105 of the original etchable material on the etched part may react with oxidation or weak acids in the air to form oxides or other compounds and impurities 106. The etching rate (or passivation rate) of these impurities 106 is necessarily different from the etching rate (or passivation rate) of the original etchable material atoms on the etched part. As a result, during the etching or passivation process on such a etched part, the aforementioned impurities 106 will cause differences in the etching rate at different locations on the etched part, which will have a great adverse effect on the accuracy of the etching process. This will result in the etching process based on preset parameters failing to form the first and second trenches of the same depth after completing the corresponding steps.
[0058] Therefore, before performing step S1, step S4 is performed first to pre-etch the surface of the workpiece using the fourth plasma formed by the ionization of surface-activated gas. This removes non-etchable materials such as oxides and compounds, i.e., impurities 106, that are not originally etchable materials on the workpiece. This prevents these non-etchable materials from hindering the subsequent passivation and etching processes. On the one hand, this ensures that the etching work can be carried out reliably, and on the other hand, it can improve the accuracy of the etching process, thereby increasing the yield.
[0059] As described above, during the etching process of the first passivation layer, the second passivation layer, and the original etched material on the etched part, corresponding byproducts are generated. These byproducts can be discharged from the exhaust port of the process chamber in a flowing gas environment. However, over time, a small amount of byproducts may still adhere to the inner walls of the first trench and / or the second trench. To improve the cleanliness of the etched part, after the depths of both the first and second trenches meet a preset depth, the etching method disclosed in this application embodiment optionally further includes:
[0060] S5. A cleaning gas is introduced into the process chamber until the fourth preset time is met. Furthermore, the fifth plasma formed by the ionization of the cleaning gas can react with the byproducts attached to the surface of the etched part, thereby achieving the purpose of cleaning the etched part. Specifically, the type of cleaning gas can also be determined according to the actual situation such as the passivation layer of the etched part and the specific type of the original etched material, and is not limited here.
[0061] After completing the etching of the first and second trenches, by performing the above step S5, the byproducts attached to the surface of the etched part can be cleaned using the fifth plasma formed by the ionization of the cleaning gas. Furthermore, compared to the technical solution of cleaning the etched part after it is removed from the process chamber, the above technical solution can also prevent fluorides and / or chlorides that may be present on the surface of the etched part from reacting with water vapor in the atmospheric environment to form weak acids, which would corrode the surface of the etched part, damage the etched part, and affect the yield of the etched part.
[0062] As described above, by performing steps S1 and S2 in a single operation, a first trench and a second trench with different longitudinal cross-sectional widths but the same depth can be formed on the etched part. In order to further reduce the processing difficulty and improve the yield, the etching process and passivation process can be cycled multiple times to etch the material in the first trench and the second trench in small batches. This can also improve the processing accuracy.
[0063] Specifically, after turning on the RF power supply and introducing the first etching gas into the process chamber, until the depths of both the first and second trenches meet the preset depth, the etching method disclosed in this application embodiment may further include:
[0064] S6. Turn on the lower RF power supply and introduce the first etching gas into the process chamber. Correspondingly, under the action of the upper RF power supply, the first etching gas can be ionized into the first plasma, and the first plasma is used to etch the workpiece. In this case, the first plasma can etch the first passivation layer and the second passivation layer on the workpiece, and after both are etched through, the etching process continues for a preset time so that the first trench and the second trench extend to a deeper position.
[0065] Accordingly, after step S6 above, the etching method disclosed in this application further includes:
[0066] S7. When the first passivation layer is etched through, and the depths of both the first and second trenches do not meet the preset depth, passivation gas is introduced into the process chamber to form new first and second passivation layers at the bottom of the first and second trenches. During this process, due to the different longitudinal cross-sectional widths of the first and second trenches, the thicknesses of the first passivation layer 108 and the second passivation layer 109 formed at the bottom of the first and second trenches are still different. Therefore, in subsequent etching processes, it is still possible to produce a process result where the second passivation layer 109 has been etched through, but the first passivation layer 108 has not been etched through.
[0067] Therefore, by repeatedly compensating the etching process of the first and second trenches using first and second passivation layers of different thicknesses, it can be ensured that after a preset number of cycles, the depths of the first and second trenches with different longitudinal cross-sectional widths can be balanced and both meet the preset depth.
[0068] Based on the technical solutions disclosed in the above embodiments, in a specific embodiment of this application, the original etchable material on the etched part can be tungsten metal. The tungsten metal is formed in the original trench structure on the etched part by filling. After etching, a tungsten metal layer of a preset thickness can be left at the bottom of the first trench and the second trench, so as to use this device to prepare dynamic random access memory.
[0069] When the material to be etched is tungsten, the passivation gas can specifically be oxygen to reduce passivation costs while ensuring passivation effect and efficiency. Furthermore, to improve passivation effect and efficiency and ensure the stable formation of the first and second passivation layers, the passivation gas flow rate can be 50–300 sccm, and the pressure within the process chamber can be 5–10 mT during step S1. Additionally, to further ensure the reliability and efficiency of the passivation process, the upper RF power supply can be kept on during passivation, operating as a continuous wave with a power of 200–1500 W. Correspondingly, the lower RF power supply is also a continuous wave with a power of 0–50 W. Furthermore, devices such as electrostatic chucks can be used to provide heating to the etched part, improving the efficiency of the etching process. Optionally, the temperature range of the electrostatic chuck is 20–90°C, and the current ratio Ir is 0.2–0.8. Figure 6 This is a cross-sectional schematic diagram of the etched part after step S3 and then step S1.
[0070] As described above, steps S4 and S3 may be included before step S1, namely the surface activation process and the etching deposition process, respectively. Therefore, when the material to be etched is tungsten, the surface activation gas used to provide surface activation can be argon, with a flow rate of 100–300 sccm, and the surface activation process can last for 10–30 seconds. Furthermore, the power of the upper RF power supply used to ionize the surface activation gas can be 600–1500 W, the power of the lower RF power supply can be 0 W, the gas pressure range within the process chamber can be 5–20 mT, and the current ratio between the inner and outer coils of the concentric circular inductor spiral coil can be 0.2–0.8. Figure 3 This is a cross-sectional view of the etched part before step S4. Figure 4 This is a cross-sectional schematic diagram of the etched part before step S4.
[0071] Following step S4, step S3 may also be included. When the material to be etched is tungsten, the type of the second etching gas can be similar to that of the first etching gas, specifically SF6 and / or NF3, and the deposition gas can specifically be SiCl4. Furthermore, during the simultaneous introduction of the second etching gas and the deposition gas, the total flow rate can be 300–1000 sccm, and the ratio of the flow rate of the second etching gas to the flow rate of the deposition gas can be less than 3:1, to further increase the difference between the depth change of the second trench and the depth change of the first trench.
[0072] Meanwhile, during step S3, both the upper and lower RF power supplies can be continuous waves, and the power of the upper RF power supply can be 200-800W, the power of the lower RF power supply can be 0-30W, the air pressure range in the process chamber can be 2-6mT, the temperature range of the electrostatic chuck can be 20-90℃, and the current ratio Ir of the inner and outer coils of the concentric circular inductor spiral coil can be 0.2-0.8. Figure 5 This is a cross-sectional schematic diagram of the etched part after step S4 and then step S3.
[0073] When the material to be etched is tungsten, the first etching gas used to etch the first passivation layer, the second passivation layer, and the material to be etched can specifically be an etching gas containing halogen elements. This allows the halogen particles to react with the material to be etched and the passivation, thereby removing the first and second passivation layers and continuing to etch the tungsten at the bottom of the first and second trenches. To ensure a stable and efficient etching process, the flow rate of the first etching gas can optionally be in the range of 100–300 sccm, and the pressure within the process chamber can be in the range of 2–6 mT.
[0074] Additionally, during step S2, both the upper and lower RF power supplies can remain on. To achieve this, both power supplies can operate in a pulsed manner, with a synchronization pulse frequency of 1000–7000 Hz and a duty cycle of 5–25%. This utilizes the zero-output time periods of the upper and lower RF power supplies to accelerate the removal of byproducts from the first and second trenches, thereby improving etching efficiency and etching effect. Optionally, the power of the upper RF power supply can be 200–600 W, and the power of the lower RF power supply can be 100–250 W.
[0075] The first etching gas may specifically include at least one of SF6, NF3 and Cl2. During step S2, the temperature range of the electrostatic chuck can be maintained between 20 and 90°C, and the current ratio Ir ranges between 0.2 and 0.8. Figure 7 This is a cross-sectional schematic diagram of the etched part after steps S3 and S1, and then step S2.
[0076] After completing the above steps, some byproducts may adhere to the surface of the etched part. At the same time, since there are also deposited layers on the sidewalls of the first and second trenches, the etched part can be cleaned before it is removed from the process chamber, i.e., step S5 above.
[0077] When the etched material is tungsten, the cleaning gas used to clean byproducts and the deposited layer can be hydrogen gas with relatively high purity, and the hydrogen flow rate is 50-100 sccm. Furthermore, during step S5, both the upper and lower RF power supplies are continuous waves, with the upper RF power supply powering at 600-1500W and the lower RF power supply powering at 0W. The gas pressure inside the process chamber ranges from 5 to 30 mT, the temperature of the electrostatic chuck ranges from 20 to 90°C, and the current ratio Ir ranges from 0.2 to 0.8. Figure 8 This is a schematic diagram of the cross-section of the etched part after step S5.
[0078] Figure 9 For example, electron microscope images of the etched part formed by etching using the technical solutions disclosed in the above embodiments of this application, such as Figure 9 As shown, the etched part has multiple trench structures (the first trench and the second trench, respectively), and the bottom of each trench structure is still deposited with a metal filling layer, and the depth of the trench structures formed by re-etching is basically equal.
[0079] The above embodiments of the present invention focus on describing the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be described in detail here.
[0080] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.
Claims
1. An etching method for etching a first trench and a second trench on a workpiece, wherein the width of the longitudinal section of the first trench is greater than the width of the longitudinal section of the second trench, characterized in that, The etching method includes: Turn on the RF power supply and introduce deposition gas and second etching gas into the process chamber until the difference between the depth change of the second trench and the depth change of the first trench meets a preset difference. The deposition gas is ionized to form a third plasma that is deposited on the sidewalls of the first trench and the second trench. The second plasma formed by the ionization of the second etching gas is used to etch the bottom walls of the first trench and the second trench. Passivating gas is introduced into the process chamber until, after a first preset time, a first passivation layer and a second passivation layer are formed at the bottom of the corresponding areas on the etched part used to form the first trench and the second trench, respectively. The passivating gas is an oxidizing gas used to react with the original etched material on the etched part to form the first passivation layer and the second passivation layer. The formation rate of the first passivation layer is greater than the formation rate of the second passivation layer, and the etching rates of the first passivation layer and the second passivation layer are both less than the etching rate of the etched material. Turn on the RF power supply and introduce the first etching gas into the process chamber until the depths of the first trench and the second trench both meet the preset depth. The preset depth is a specific value when the depths of the first trench and the second trench are equal. The first plasma formed by the ionization of the first etching gas is used to continue etching the first trench and the second trench after penetrating the first passivation layer and the second passivation layer.
2. The etching method according to claim 1, characterized in that, The power of the lower radio frequency power supply when the first etching gas is introduced is greater than the power of the lower radio frequency power supply when the second etching gas is introduced. And / or the power of the upper radio frequency power supply when the first etching gas is introduced is less than the power of the upper radio frequency power supply when the second etching gas is introduced.
3. The etching method according to claim 1, characterized in that, During the introduction of the first etching gas, the lower radio frequency power supply operates at a preset duty cycle.
4. The etching method according to claim 1, characterized in that, Before introducing the passivation gas into the process chamber, the etching method further includes: Surface-activating gas is introduced into the process chamber until a third preset time is met, wherein the fourth plasma formed by the ionization of the surface-activating gas is used to bombard the surface of the original etched material on the etched part to remove non-etched material adhering to the surface of the etched material.
5. The etching method according to claim 1, characterized in that, After the depths of both the first trench and the second trench meet the preset depth, the etching method further includes: Cleaning gas is introduced into the process chamber until a fourth preset time is met, wherein the fifth plasma formed by the ionization of the cleaning gas is used to react with byproducts attached to the surface of the etched part to clean the etched part.
6. The etching method according to claim 1, characterized in that, The etching method further includes: turning on the RF power supply and introducing a first etching gas into the process chamber until the depths of the first trench and the second trench both meet a preset depth; Turn on the lower radio frequency power supply and introduce the first etching gas into the process chamber; When the first passivation layer is etched through and the depths of the first trench and the second trench do not meet the preset depth, the passivation gas is introduced into the process chamber to form a new first passivation layer and a new passivation layer at the bottom of the first trench and the second trench, respectively.
7. The etching method according to claim 1, characterized in that, During the process of introducing passivation gas into the process chamber, the upper RF power supply is kept on.
8. The etching method according to claim 1, characterized in that, The material to be etched is tungsten metal, the passivation gas is oxygen, the flow rate of the passivation gas is 50~300 sccm, and the pressure in the process chamber is 5~10 mT.
9. The etching method according to claim 1, characterized in that, The material to be etched is tungsten metal, the first etching gas is an etching gas containing halogen elements, the flow rate of the first etching gas is in the range of 100~300 sccm, and the pressure in the process chamber is in the range of 2~6 mT.