Method for removing low dielectric constant material layer
By employing oxygen plasma dry etching and isotropic etching solution wet etching with decreasing concentration, the problems of cumbersome cleaning and high particulate matter content in low dielectric constant material layers have been solved, achieving efficient and low-cost cleaning results and increasing the number of wafer reuses.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GEKKO SEMICON (SHANGHAI) CO LTD
- Filing Date
- 2023-03-22
- Publication Date
- 2026-06-19
AI Technical Summary
Existing cleaning methods for low dielectric constant material layers are cumbersome and complex, have low cleaning efficiency, and leave a large number of residual particles on the wafer surface after cleaning, resulting in high costs and limited reuse.
Oxygen plasma dry etching was used to reduce the methyl content in the low dielectric constant material layer. This was combined with a wet etching method that used two isotropic etching solutions with decreasing concentrations and durations, starting with a high concentration and ending with a low concentration. Finally, the material was cleaned with a mixture of ozone and deionized water.
It simplifies the cleaning process, reduces costs, improves cleaning efficiency, significantly reduces the number of particles on the wafer surface, and increases the number of times the wafer can be reused.
Smart Images
Figure CN116403895B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and in particular to a method for removing a low dielectric constant material layer. Background Technology
[0002] With the continuous development of integrated circuit manufacturing technology, the increasing circuit integration density, and the continuous reduction of feature size, the resistance-capacitance delay phenomenon between metal interconnects has become increasingly significant. Since the dielectric constant of the dielectric layer between metal interconnects is proportional to the interlayer parasitic capacitance, low-k dielectric materials are widely used in the integrated circuit industry to reduce the resistance-capacitance delay between metal interconnects.
[0003] In the low-k dielectric layer (hereinafter referred to as "low-k layer" or "low-k thin film") formation process, a photocell wafer is typically selected for process quality monitoring. Specifically, to monitor the quality of the low-k thin film deposited in the equipment chamber (e.g., whether the thickness of the deposited low-k thin film meets requirements), the photocell wafer is placed in the equipment chamber, a low-k thin film is deposited, and then the relevant parameters of the low-k thin film (e.g., thickness, refractive index, stress, etc.) are checked to ensure they meet the requirements for product manufacturing. After each process quality monitoring, the deposited low-k thin film on the photocell wafer needs to be removed to recycle the wafer for the next process monitoring. In this process, the cleaning effect of the low-k thin film on the surface of the photocell wafer (e.g., whether the low-k film is completely removed, and whether the number of particles on the cleaned photocell wafer meets the requirements for reuse) determines the number of times the photocell wafer can be reused in the process quality monitoring process, and thus determines the process monitoring cost and the effectiveness of the process monitoring.
[0004] In existing technologies, commonly used low-k thin film cleaning methods typically involve at least four steps: dry etching, wet etching, dry etching again, and wet etching again (i.e., at least two rounds of "dry etching + wet etching"). Furthermore, the same cleaning method is usually used for low-k films with different methyl contents and dielectric constants. Practice shows that after one round of "dry etching + wet etching," the low-k film is almost completely removed, but the number of residual particles on the wafer remains very high (potentially hundreds to thousands). This is likely due to insufficient optimization of the cleaning process. Therefore, a second round of repeated "dry etching + wet etching" is required to further remove the remaining particles. It is evident that the above cleaning method involves a relatively cumbersome and complex process, resulting in high time and equipment costs, and the cleaning efficiency needs improvement. Summary of the Invention
[0005] The technical problem solved by the embodiments of the present invention is: how to quickly and effectively remove the low dielectric constant material layer on the wafer surface, while significantly reducing the number of particles on the wafer surface after cleaning, so that the wafer meets the requirements for reuse.
[0006] To address the aforementioned technical problems, embodiments of the present invention provide a method for removing a low-dielectric-constant material layer, specifically comprising: providing a wafer to be cleaned, the surface of which has a low-dielectric-constant material layer; dry etching the wafer to be cleaned using oxygen plasma to reduce the methyl content in the low-dielectric-constant material layer; performing a first isotropic etching of the wafer to be cleaned for a first duration using an etching solution of a first concentration; and performing a second isotropic etching of the wafer to be cleaned for a second duration using the etching solution of a second concentration; wherein the second concentration is less than the first concentration, and the second duration is less than the first duration.
[0007] Optionally, the smaller the dielectric constant of the low dielectric constant material layer, the higher the oxygen plasma concentration during the dry etching process, and / or the longer the dry etching time.
[0008] Optionally, the dry etching duration satisfies any one of the following: the dielectric constant of the low dielectric constant material layer is selected from a first dielectric constant range [2.7, 3.5], and the dry etching duration is selected from [8s, 12s]; or the dielectric constant of the low dielectric constant material layer is selected from a second dielectric constant range [2.2, 2.7], and the dry etching duration is selected from [12s, 30s].
[0009] Optionally, the dielectric constant of the low dielectric constant material layer is selected from the first dielectric constant range [2.7, 3.5], the oxygen flow rate of the dry etching is selected from [10000 sccm, 12000 sccm], the carrier gas flow rate is selected from [1000 sccm, 1500 sccm], the pressure is selected from [750 mTorr, 1000 mTorr], the temperature is selected from [100℃, 400℃], and the radio frequency power is selected from [4400W, 4600W].
[0010] Optionally, the dielectric constant of the low dielectric constant material layer is selected from the second dielectric constant range [2.2, 2.7], the oxygen flow rate of the dry etching is selected from [12000 sccm, 15000 sccm], the carrier gas flow rate is selected from [1000 sccm, 1500 sccm], the pressure is selected from [750 mTorr, 1000 mTorr], the temperature is selected from [100℃, 400℃], and the radio frequency power is selected from [4600W, 5000W].
[0011] Optionally, the concentration ratio of the first concentration to the second concentration is selected from 5 to 100 times.
[0012] Optionally, one or more of the following conditions must be met: the first concentration is selected from [40%, 49%]; the second concentration is selected from [0.5%, 5%].
[0013] Optionally, the ratio of the first duration to the second duration is selected from 2 to 8 times.
[0014] Optionally, one or more of the following conditions must be met: the first duration is selected from [25s, 60s]; the second duration is selected from [8s, 30s].
[0015] Optionally, after performing a second isotropic etching of a second duration on the wafer to be cleaned, the method further includes cleaning the wafer to be cleaned with a mixture of ozone and deionized water.
[0016] Optionally, the low dielectric constant material layer satisfies one or more of the following: the constituent elements of the low dielectric constant material layer include: C, H, O, and Si; the thickness of the low dielectric constant material layer is selected from...
[0017] Optionally, the etching solution is a hydrofluoric acid solution.
[0018] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:
[0019] This invention employs a cleaning method that combines dry etching followed by wet etching. Specifically, in the dry etching section, oxygen plasma is used to perform dry etching on the wafer to be cleaned. The plasma can combine with methyl groups (mainly containing carbon elements) in the low-k layer on the surface of the wafer to form carbonyl groups, thereby effectively reducing the methyl content in the low-k layer. In the wet etching section, a first isotropic etching of the wafer to be cleaned is performed for a first duration using an etching solution of a first concentration, mainly to remove the remaining low-k film on the surface of the wafer through chemical reaction. Then, a second isotropic etching of the wafer to be cleaned is performed for a second duration using an etching solution of a second concentration, to further clean the residual low-k film on the wafer surface through chemical reaction and immersion and rinsing with the etching solution, effectively removing particulate matter on the wafer surface, making the wafer ready for reuse. The second concentration is less than the first concentration, and the second duration is less than the first duration.
[0020] In this embodiment of the invention, the concentration of the etching solution decreases in the two isotropic etching processes. In the first isotropic etching, the higher concentration of the etching solution enables the rapid removal of most of the low-k layer material in a short time, thereby improving etching efficiency. In the second isotropic etching process, the use of a lower concentration of the etching solution helps to reduce the damage of the etching solution to the wafer surface (the greater the damage to the wafer by the etching solution, the more particles may be generated), improve the uniformity of the wafer surface after cleaning, and thus effectively reduce the number of particles on the wafer surface.
[0021] Furthermore, in this embodiment of the invention, the etching time of the two isotropic etching processes also decreases progressively. Since the reaction between the higher concentration etching solution and the low-k layer is stronger, a longer etching time is correspondingly used for the higher concentration etching solution, which helps to improve the cleaning effect and achieve the effect of basically removing the remaining low-k film after dry etching. Based on the fact that most of the low-k layer material has been removed by dry etching and the first isotropic etching, a relatively lower concentration etching solution and a relatively shorter etching time are used in the second isotropic etching. This can avoid increasing the damage to the wafer surface due to the etching solution acting for too long, thereby helping to greatly reduce the number of particles on the wafer surface. In addition, using a shorter etching time also helps to reduce the total etching time and improve the overall etching efficiency.
[0022] Therefore, compared to existing technologies that employ two rounds of "dry etching + wet etching," resulting in high costs and low etching efficiency, the solution of this invention uses a single round of "dry etching + wet etching." This reduces process steps, lowers cleaning costs, and improves cleaning efficiency. Furthermore, it effectively removes low-k films and significantly reduces particulate matter generated during cleaning through a more streamlined process. Moreover, compared to existing technologies that may use the same concentration of etching solution or the same etching time in each step of wet etching, leading to poor cleaning results, the solution of this invention combines both concentration and time, with both decreasing. This achieves a better balance between etching efficiency and residual particulate matter on the wafer surface, thus improving the cleaning effect.
[0023] Furthermore, the smaller the dielectric constant of the low-k material layer, the higher the oxygen plasma concentration during the dry etching process, and / or the longer the dry etching time. In this embodiment of the invention, since the dielectric constant of the low-k layer on the surface of the wafer to be cleaned is mainly affected by the methyl group content therein, the higher the methyl group content in the low-k layer (which also means a higher carbon content), the smaller the dielectric constant. Therefore, in this embodiment of the invention, for low-k layers with smaller dielectric constants, a higher concentration of oxygen plasma and / or a longer dry etching time are used during the dry etching process. Thus, for low-k layers with different dielectric constants, the etching efficiency can be improved as much as possible and the etching effect can be enhanced by appropriately controlling the oxygen plasma concentration and / or the dry etching time.
[0024] Furthermore, after performing a second isotropic etching of a second duration on the wafer to be cleaned, the method further includes cleaning the wafer with a mixture of ozone and deionized water. Based on the removal of the low-k layer via dry etching and two isotropic etching processes, the cleaning with the mixture helps to further remove particulate matter (e.g., particulate matter generated during etching) from the wafer surface, improving the cleanliness of the wafer surface after cleaning. On the other hand, the cleaning with the mixture can form an extremely thin oxide layer (e.g., approximately 1 Å thick) on the cleaned wafer surface, repairing minor damage caused by etching, thereby further reducing the number of particulate matter on the wafer surface and repairing the damage. Attached Figure Description
[0025] Figure 1 This is a flowchart of the first method for removing a low dielectric constant material layer in an embodiment of the present invention;
[0026] Figure 2 This is a flowchart of the second method for removing a low dielectric constant material layer in an embodiment of the present invention. Detailed Implementation
[0027] As mentioned in the background section, in the quality monitoring process of using optical wafers for depositing low-k thin films, the effectiveness of removing the low-k thin film from the wafer surface after each process quality monitoring directly determines the number of times the optical wafer can be reused in the process quality monitoring, and thus determines the process monitoring cost and the reliability of the process monitoring data.
[0028] In existing technologies, commonly used low-k thin film cleaning methods typically involve at least four steps: dry etching, wet etching, dry etching, and wet etching again. The same cleaning method is usually used for low-k films with different methyl content and dielectric constants. Practice shows that after one round of "dry etching + wet etching," the low-k film is almost completely removed, but a large number of particles remain on the wafer (potentially hundreds to thousands). This is likely due to insufficient optimization of the cleaning process. Therefore, a second round of repeated "dry etching + wet etching" is needed to further remove the remaining particles. Thus, the above cleaning methods involve a relatively cumbersome and complex process, resulting in high time and equipment costs, and the cleaning efficiency needs improvement.
[0029] To address the aforementioned technical problems, embodiments of the present invention provide a method for removing a low-dielectric-constant material layer, specifically comprising: providing a wafer to be cleaned, the surface of which has a low-dielectric-constant material layer; dry etching the wafer to be cleaned using oxygen plasma to reduce the methyl content in the low-dielectric-constant material layer; performing a first isotropic etching of the wafer to be cleaned for a first duration using an etching solution of a first concentration; and performing a second isotropic etching of the wafer to be cleaned for a second duration using the etching solution of a second concentration; wherein the second concentration is less than the first concentration, and the second duration is less than the first duration.
[0030] Therefore, in this embodiment of the invention, a cleaning method consisting of dry etching followed by wet etching is adopted. In the dry etching section, oxygen plasma is used for dry etching. Since the plasma can combine with methyl groups (mainly containing carbon elements) in the low-k layer to form carbonyl groups, the methyl content in the low-k layer can be effectively reduced. In the wet etching section, a first isotropic etching of a first concentration of etching solution is performed on the wafer to be cleaned for a first duration to remove the remaining low-k film on the wafer surface primarily through chemical reactions. Then, a second isotropic etching of the same solution is performed on the wafer for a second duration using a second concentration of etching solution. This further cleans the residual low-k film on the wafer surface through chemical reactions and immersion and rinsing with the etching solution, while significantly reducing particulate matter on the wafer surface caused by etching, thus enabling the wafer to meet reuse requirements.
[0031] On the one hand, the concentration of the etching solution decreases in the two isotropic etching processes. Specifically, in the first isotropic etching, the higher concentration of the etching solution allows for the rapid removal of most of the low-k layer material in a short time, thereby improving etching efficiency. In the second isotropic etching process, the use of a lower concentration of the etching solution helps to reduce the damage of the etching solution to the wafer surface, improves the uniformity of the wafer surface after cleaning, and thus effectively reduces the number of particles on the wafer surface.
[0032] On the other hand, the etching time of the two isotropic etching processes also decreases. Specifically, since the higher concentration of the etching solution reacts more strongly with the low-k layer, a longer etching time is used for the higher concentration of the etching solution, which helps to improve the cleaning effect and achieve the effect of basically removing the remaining low-k film after dry etching. After dry etching and the first isotropic etching have removed most of the low-k layer material, using a relatively lower concentration of etching solution and a relatively shorter etching time in the second isotropic etching can avoid increasing the damage to the wafer surface due to the etching solution acting for too long. This helps to greatly reduce the number of particles on the wafer surface. In addition, using a shorter etching time also helps to reduce the total etching time, thereby improving the overall etching efficiency.
[0033] In summary, compared to existing technologies that employ a two-stage "dry etching + wet etching" process, resulting in high costs and low etching efficiency, the solution of this invention uses a single-stage "dry etching + wet etching" process. This reduces process steps, lowers cleaning costs, and improves cleaning efficiency. Furthermore, it effectively removes low-k films and significantly reduces particulate matter generated during cleaning through a more streamlined process. Moreover, unlike existing technologies that may use the same concentration of etching solution or the same etching time in each step of the wet etching process, leading to poor cleaning results, the solution of this invention combines both concentration and time, with both decreasing. This achieves a better balance between etching efficiency and residual particulate matter on the wafer surface, thus improving the cleaning effect.
[0034] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
[0035] Reference Figure 1 , Figure 1 This is a flowchart of a method for removing a low-dielectric-constant material layer according to an embodiment of the present invention. The first method for removing a low-dielectric-constant material layer may include steps S11 to S14:
[0036] Step S11: Provide a wafer to be cleaned, the surface of which has a low dielectric constant material layer;
[0037] Step S12: Dry etching is performed on the wafer to be cleaned using oxygen plasma to reduce the methyl content in the low dielectric constant material layer;
[0038] Step S13: Using an etching solution of the first concentration, perform a first isotropic etching on the wafer to be cleaned for a first duration;
[0039] Step S14: Using the etching solution of the second concentration, perform a second isotropic etching on the wafer to be cleaned for a second duration.
[0040] Wherein, the second concentration is less than the first concentration, and the second duration is less than the first duration.
[0041] In a specific implementation of step S11, the wafer to be cleaned may be a wafer that has already been used for process quality monitoring. The low dielectric constant material layer on the surface of the wafer to be cleaned may be deposited (e.g., chemical vapor deposition) on the optical wafer during the process quality monitoring.
[0042] Specifically, in applications monitoring the effectiveness of depositing low-dielectric-constant material layers (also known as low-k layers, typically low-k thin films) in equipment chambers, such as monitoring whether the deposited low-k thin film meets process quality requirements, a wafer is typically placed in the equipment chamber to deposit the low-k thin film. Then, relevant parameters of the low-k thin film (e.g., thickness, refractive index, stress, etc.) are evaluated. After each process quality monitoring session, the deposited low-k thin film on the wafer needs to be removed to recycle the wafer for the next process monitoring.
[0043] The low dielectric constant material layer described in this invention mainly comprises carbon (C), silicon (Si), oxygen (O), and hydrogen (H). C and H combine to form a methyl group, with the chemical formula -CH3 (a single hyphen "-" represents a single electron), abbreviated as -Me. Specifically, it refers to the electrically neutral monovalent group remaining after removing a hydrogen atom from a methane molecule.
[0044] Furthermore, the thickness of the low dielectric constant material layer is typically within... Within a range, for example, it can be or
[0045] In the specific implementation of step S12, the oxygen plasma is composed of positive and negative charged ions, molecules, atoms, and atomic groups generated after oxygen ionization. The main working principle of dry etching of the wafer to be cleaned using oxygen plasma is as follows: oxygen gas is transformed into oxygen plasma under the excitation of radio frequency power, and after ionization, excitation, dissociation, recombination and other reactions, positive and negative ions, free radicals, atoms, molecules and other active substances are generated. It mainly reacts with methyl groups in the low-k film to form carboxylated groups. These carboxylated groups are removed in a low-pressure vacuum chamber, thereby effectively reducing the methyl content in the low-k film.
[0046] Furthermore, the smaller the dielectric constant of the low dielectric constant material layer, the higher the oxygen plasma concentration during the dry etching process, and / or the longer the dry etching time.
[0047] In the dry etching process, the oxygen plasma concentration can be controlled by oxygen flow rate, carrier gas flow rate, radio frequency power, etc.
[0048] In some embodiments, the dielectric constant of the low dielectric constant material layer is selected from a first dielectric constant range [2.7, 3.5], the dry etching duration is selected from [8s, 12s], the oxygen flow rate of the dry etching is selected from [10000sccm, 12000sccm], the carrier gas flow rate is selected from [1000sccm, 1500sccm], the pressure is selected from [750mTorr, 1000mTorr], the temperature is selected from [100℃, 400℃], and the RF power is selected from [4400W, 4600W].
[0049] In other embodiments, the dielectric constant of the low dielectric constant material layer is selected from the second dielectric constant range [2.2, 2.7], the dry etching duration is selected from [12s, 30s], the oxygen flow rate of the dry etching is selected from [12000sccm, 15000sccm], the carrier gas flow rate is selected from [1000sccm, 1500sccm], the pressure is selected from [750mTorr, 1000mTorr], the temperature is selected from [100℃, 400℃], and the RF power is selected from [4600W, 5000W].
[0050] The carrier gas can be selected from nitrogen (N2), helium (He), argon (Ar) and other suitable inert gases.
[0051] In the low-dielectric-constant material layer described in this embodiment of the invention, the dielectric constant is mainly affected by the methyl group content. Specifically, the higher the methyl group content, the lower the dielectric constant of the low-dielectric-constant material layer; conversely, the lower the methyl group content, the higher the dielectric constant of the low-dielectric-constant material layer. Therefore, in this embodiment of the invention, for low-k layers with smaller dielectric constants, a higher concentration of oxygen plasma and / or a longer dry etching time are used during the dry etching process. Thus, by appropriately controlling the oxygen plasma concentration and / or the dry etching time, etching efficiency and etching effect can be improved as much as possible for low-k layers with different dielectric constants.
[0052] In the specific implementation of step S13, an etching solution of a first concentration is used to perform a first isotropic etching of a first duration on the wafer to be cleaned.
[0053] In the specific implementation of step S14, the etching solution of the second concentration is used to perform a second isotropic etching of the wafer to be cleaned for a second duration.
[0054] Wherein, the second concentration is less than the first concentration, and the second duration is less than the first duration.
[0055] In some embodiments, the etching solution may be a mixture of hydrofluoric acid stock solution and deionized water.
[0056] In other embodiments, the etching solution may be a mixture of hydrofluoric acid stock solution, other solutions with wet etching capabilities (e.g., ammonia water), and deionized water.
[0057] It should be noted that the concentration ratio of the first concentration to the second concentration should not be too small, otherwise it may result in insufficient intensity of the first isotropic etching, leading to a reduced etching rate and poor removal of the low-k film, or increased damage to the wafer during the second isotropic etching. Conversely, the concentration ratio of the first concentration to the second concentration should not be too large, otherwise it may result in excessive intensity of the first isotropic etching, causing over-etching and increased wafer damage, or a too low etching rate during the second isotropic etching, increasing etching time.
[0058] Furthermore, the concentration ratio of the first concentration to the second concentration can be selected from 5 to 100 times.
[0059] In some non-limiting embodiments, the first concentration can be selected from [40%, 49%]. For example, in some applications with high etching rate requirements, a 49% hydrofluoric acid stock solution can be used to quickly remove the remaining low-k film after dry etching in a short time. The second concentration can be selected from [0.5%, 5%]. For example, an etching solution with a hydrofluoric acid to deionized water ratio of 1:100 can be used.
[0060] In this embodiment of the invention, by setting the concentration of the etching solution to decrease in the two isotropic etching processes, the following technical effects are achieved: In the first isotropic etching, the higher concentration of the etching solution enables the rapid removal of most of the low-k layer material in a short time, thereby improving etching efficiency; In the second isotropic etching process, the use of the lower concentration of the etching solution helps to reduce the damage of the etching solution to the wafer surface (the greater the damage to the wafer by the etching solution, the more particles may be generated), improve the uniformity of the wafer surface after cleaning, and thus effectively reduce the number of particles on the wafer surface.
[0061] It should be noted that the ratio of the first time duration to the second time duration should not be too small, otherwise it may lead to poor removal of the low-k film by the first isotropic etching, or increased damage to the wafer by the second isotropic etching; the ratio of the first time duration to the second time duration should not be too large, otherwise it may lead to over-etching in the first isotropic etching, increasing damage to the wafer, or insufficient etching and cleaning by the second isotropic etching, resulting in poor removal of particles on the wafer surface.
[0062] Furthermore, the ratio of the first duration to the second duration is selected from 2 to 8 times.
[0063] In some non-limiting embodiments, the first duration may be selected from [25s, 60s], for example, it may be set to 30 seconds; the second duration may be selected from [8s, 30s], for example, it may be set to 10 seconds.
[0064] In this embodiment of the invention, not only is the concentration of the etching solution in the two isotropic etching processes reduced, but the etching time in the two isotropic etching processes is also reduced. This has the following technical effects: In the first isotropic etching, since the higher concentration of the etching solution reacts more strongly with the low-k layer, a longer etching time is used for the higher concentration of the etching solution, which helps to improve the cleaning effect and achieve the effect of basically removing the remaining low-k film after dry etching. Based on the fact that most of the low-k layer material has been removed by dry etching and the first isotropic etching, the use of a relatively lower concentration of etching solution and a relatively shorter etching time in the second isotropic etching can avoid increasing the damage to the wafer surface due to the etching solution acting for too long, thereby helping to greatly reduce the number of particles on the wafer surface. Furthermore, using a shorter etching time also helps to reduce the total etching time and improve the overall etching efficiency.
[0065] In summary, compared to the existing technology which uses two rounds of "dry etching + wet etching" resulting in high cost and low etching efficiency, the solution of this invention uses one round of "dry etching + wet etching", which reduces process steps, lowers cleaning costs, improves cleaning efficiency, and can effectively remove low-k films and significantly reduce particulate matter generated during cleaning through a more streamlined process.
[0066] Furthermore, compared to existing technologies that may use the same concentration of etching solution or the same etching time in each step of wet etching, resulting in poor cleaning effect, the solution of this invention combines both concentration and time, and sets both concentration and time to decrease, which can better achieve a balance between etching efficiency and residual particulate matter on the wafer surface, thus improving the cleaning effect.
[0067] Reference Figure 2 , Figure 2 This is a flowchart illustrating a second method for removing a low-dielectric-constant material layer according to an embodiment of the present invention. The second method for removing a low-dielectric-constant material layer may include... Figure 1 The steps S11 to S14 shown may further include step S21, wherein step S21 may be performed after step S14. The following describes... Figure 1 The different contents of the illustrated embodiments will be explained.
[0068] In step S21, a mixture of ozone and deionized water is used to clean the wafer to be cleaned.
[0069] In this embodiment of the invention, after removing the low-k layer via dry etching and two isotropic etching processes, the cleaning with the mixed solution helps to further remove particulate matter (e.g., particulate matter generated during etching) from the wafer surface, improving the cleanliness of the wafer surface after cleaning. Furthermore, the cleaning with the mixed solution can form an extremely thin oxide layer (e.g., approximately 1 angstrom thick) on the cleaned wafer surface, repairing minor damage caused by etching, thereby further reducing the number of particulate matter on the wafer surface and repairing the damage. Therefore, by adopting the solution of this embodiment of the invention, and further improving the cleaning effect, the goal of increasing the number of wafer recycling cycles can be achieved, thereby reducing costs.
[0070] It should be noted that, in a specific application experiment of an embodiment of the present invention, a material with a thickness of... and Experimental data on the removal of the low-k material layer showed that after the optical wafer underwent seven repeated process quality monitoring processes (film deposition and film removal), the total number of large particles with a size of about 0.12 micrometers on the wafer was between 0 and 2, and the total number of particles with a size of about 0.5 micrometers was between 2 and 20. Both of these numbers are far less than the number of particles required for wafer reuse (the number of particles required for wafer reuse is usually less than 200).
[0071] However, in existing mature low-layer cleaning methods, the cleaned wafers can generally only be reused about 3 times. Therefore, the cleaning scheme of the present invention can not only improve efficiency and reduce process costs in the removal of the low-k layer, but also increase the number of wafer reuses due to the significant improvement in the low-layer removal effect, thereby significantly reducing costs.
[0072] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article indicates that the preceding and following related objects have an "or" relationship.
[0073] In the embodiments of this application, "multiple" refers to two or more.
[0074] The descriptions of "first," "second," etc., appearing in the embodiments of this application are for illustrative purposes and to distinguish the objects being described. They have no order and do not indicate any special limitation on the number of devices in the embodiments of this application, nor do they constitute any limitation on the embodiments of this application.
[0075] It should be noted that the sequence number of each step in this embodiment does not represent a limitation on the execution order of each step.
[0076] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.
Claims
1. A method for removing a low dielectric constant material layer, characterized by, include: A wafer to be cleaned is provided, the surface of which has a low dielectric constant material layer; The wafer to be cleaned is dry etched using oxygen plasma to reduce the methyl content in the low dielectric constant material layer; An isotropic etching process of a first duration is performed on the wafer to be cleaned using an etching solution of a first concentration. The wafer to be cleaned is subjected to a second isotropic etching for a second duration using the etching solution of a second concentration. Wherein, the second concentration is less than the first concentration, and the second duration is less than the first duration.
2. The method of claim 1, wherein, The smaller the dielectric constant of the low dielectric constant material layer, the higher the oxygen plasma concentration during the dry etching process, and / or the longer the dry etching time.
3. The method of claim 2, wherein, The duration of the dry etching process satisfies any one of the following: The dielectric constant of the low dielectric constant material layer is selected from the first dielectric constant range [2.7, 3.5], and the dry etching duration is selected from [8s, 12s]. The dielectric constant of the low dielectric constant material layer is selected from the second dielectric constant range [2.2, 2.7], and the dry etching duration is selected from [12s, 30s].
4. The method of claim 2, wherein, The dielectric constant of the low dielectric constant material layer is selected from the first dielectric constant range [2.7, 3.5], the oxygen flow rate of the dry etching is selected from [10000 sccm, 12000 sccm], the carrier gas flow rate is selected from [1000 sccm, 1500 sccm], the pressure is selected from [750 mTorr, 1000 mTorr], the temperature is selected from [100℃, 400℃], and the radio frequency power is selected from [4400W, 4600W].
5. The method of claim 2, wherein, The dielectric constant of the low dielectric constant material layer is selected from the second dielectric constant range [2.2, 2.7], the oxygen flow rate of the dry etching is selected from [12000 sccm, 15000 sccm], the carrier gas flow rate is selected from [1000 sccm, 1500 sccm], the pressure is selected from [750 mTorr, 1000 mTorr], the temperature is selected from [100℃, 400℃], and the radio frequency power is selected from [4600W, 5000W].
6. The method of claim 1, wherein, The concentration ratio of the first concentration to the second concentration is selected from 5 to 100 times.
7. The method of claim 6, wherein, Meet one or more of the following: The first concentration is selected from [40%, 49%]; The second concentration is selected from [0.5%, 5%].
8. The method of claim 1 or 6, wherein, The ratio of the first duration to the second duration is selected from 2 to 8 times.
9. The method of claim 8, wherein, Meet one or more of the following: The first duration is selected from [25s, 60s]; The second duration is selected from [8s, 30s].
10. The method of claim 1, wherein, After performing a second isotropic etching of a second duration on the wafer to be cleaned, the method further includes: The wafer to be cleaned is cleaned using a mixture of ozone and deionized water.
11. The method of claim 1, wherein, The low dielectric constant material layer satisfies one or more of the following: The constituent elements of the low dielectric constant material layer include: C, H, O, and Si. the thickness of the low dielectric constant material layer is selected from the group consisting of 12. The method of claim 1, wherein, The etching solution is a hydrofluoric acid solution.