Mask structure, preparation method thereof and semiconductor equipment
By employing a double-layer mask material preparation method in semiconductor manufacturing, and utilizing hardness differences and extremely low frequency radio frequency, the problems of inaccurate pattern transfer and bow-shaped defects in high aspect ratio aperture etching are solved, achieving better aperture profile and etching selectivity.
Patent Information
- Application Number
- CN202510293764.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-08-05
- Filing Date
- 2025-03-12
- Publication Date
- 2026-02-10
AI Technical Summary
In semiconductor manufacturing, during the etching process of high aspect ratio apertures, the pattern transfer of traditional mask layers is prone to undesirable deformation and bow-shaped defects, resulting in the inability to transfer the pattern accurately.
A method for preparing a double-layer mask material is adopted. By forming first and second mask material layers with different hardness under different plasma atmospheres, the ion bombardment energy and collimation are increased by using extremely low frequency radio frequency. Combined with the hardness difference design, the pattern transfer accuracy is ensured and the bow-shaped defect is prevented.
It improves the accuracy of the aperture profile and the etching selectivity, reduces the etching difficulty, prevents the generation of bow-shaped defects, and enhances the etching effect of the mask structure.
Smart Images
Figure CN121496321A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular to a mask structure, a preparation method thereof and a semiconductor device. BACKGROUND
[0002] In a semiconductor manufacturing process, a multilayer stacked layer stack needs to be formed on a substrate. The layer stack is usually patterned by a mask layer on its surface to form an opening in the layer stack.
[0003] With the increase of chip storage density, the number of layers of the layer stack is also increasing, and the aspect ratio of the opening is also increasing. The high aspect ratio opening etching has higher and higher requirements for the mask layer.
[0004] How to prepare a mask layer that can meet the high aspect ratio etching is the focus of current research. In the process of preparing the mask layer by using the traditional method, the following problems may occur: when pattern transfer is performed, the side wall of the opening is prone to undesirable deformation, which causes the pattern to be unable to be accurately transferred to the mask layer. SUMMARY
[0005] In view of the deficiencies of the prior art, the technical solutions adopted by the embodiments of the present application are as follows:
[0006] A preparation method of a mask structure, comprising: providing a substrate; forming a first mask material layer with a first hardness on the substrate under a first plasma atmosphere, the first plasma atmosphere comprising a first high-frequency radio frequency and a first low-frequency radio frequency; forming a second mask material layer with a second hardness on the first mask material layer under a second plasma atmosphere, the second plasma atmosphere comprising a second high-frequency radio frequency and a second low-frequency radio frequency; wherein the first hardness is less than the second hardness, the first low-frequency radio frequency and the second low-frequency radio frequency are both less than or equal to 5MHz, and the first low-frequency radio frequency is greater than or equal to the second low-frequency radio frequency.
[0007] In the above-described mask structure fabrication method, during the formation of the first and second mask material layers, a low-frequency radio frequency (RF) of less than or equal to 5 MHz is applied. This extremely low RF frequency increases the plasma acceleration time, thereby increasing the bombardment energy and collimation of ions during their movement towards the film layer, thus improving the density of the deposited thin film. Furthermore, by controlling the first RF frequency to be greater than the second RF frequency, the hardness of the second mask material layer is made greater than that of the first mask material layer. The harder second mask material layer is more resistant to etching, but it is prone to aperture contour deformation when the aperture depth is large. The softer first mask material layer is easier to etch and remove, resulting in a better aperture contour. In addition, since bow-shaped defects tend to occur in the upper layer (i.e., near the photoresist layer), placing the harder second mask material layer on the upper layer and the softer first mask material layer on the lower layer not only fully utilizes the hardness difference between the two mask material layers to improve pattern transfer accuracy and maintain a high etching selectivity of the mask structure, but also effectively prevents the formation of bow-shaped defects and improves the aperture contour.
[0008] As an optional implementation, the second low-frequency radio frequency is less than or equal to 400 kHz.
[0009] As an optional implementation, the second low-frequency radio frequency is less than or equal to 200 kHz.
[0010] As an optional implementation, the second low-frequency radio frequency is less than or equal to 100 kHz.
[0011] As an optional implementation, the second high-frequency radio frequency is greater than or equal to 13.56MHz.
[0012] As an optional implementation, the second high-frequency radio frequency is greater than or equal to 60MHz.
[0013] As an optional implementation, the first high-frequency radio frequency is less than or equal to the second high-frequency radio frequency.
[0014] As an optional implementation, the second plasma atmosphere further includes a first dopant, which includes at least one of W, Mo, B, Si or N.
[0015] As an optional implementation, the first plasma atmosphere further includes a second dopant, which includes at least one of W, Mo, B, Si, or N.
[0016] As an optional implementation, the first plasma atmosphere includes a first high-frequency radio frequency power; the second plasma atmosphere includes a second high-frequency radio frequency power and a second low-frequency radio frequency power.
[0017] As an optional implementation, the first high-frequency radio frequency power is less than or equal to the second high-frequency radio frequency power.
[0018] As an optional implementation, the first plasma atmosphere further includes a first low-frequency radio frequency power, wherein the first low-frequency radio frequency power is less than or equal to the second low-frequency radio frequency power.
[0019] As an optional implementation, the second low-frequency radio frequency power is pulsed radio frequency power.
[0020] As an alternative implementation, both the first low-frequency radio frequency power and the second low-frequency radio frequency power pulsate between two different power levels.
[0021] As an optional implementation, when preparing the first mask material layer, the pressure in the reaction chamber is a first pressure; when preparing the second mask material layer, the pressure in the reaction chamber is a second pressure; wherein, the first pressure is greater than or equal to the second pressure.
[0022] As an optional implementation, when preparing the first mask material layer, a first film-forming temperature is present in the reaction chamber; when preparing the second mask material layer, a second film-forming temperature is present in the reaction chamber; wherein, the first film-forming temperature is less than or equal to the second film-forming temperature.
[0023] As an optional implementation, the first mask material layer and the second mask material layer are amorphous carbon layers or diamond-like layers.
[0024] As an optional implementation, the total thickness of the mask structure is 0.1μm-9μm.
[0025] As an optional implementation, the ratio between the thickness of the first mask material layer and the total thickness of the mask structure is 5%-60%.
[0026] As an optional implementation, the flow rate of the reactive gas used to form the mask structure is in the range of 100 sccm to 20000 sccm.
[0027] As an optional implementation, the spacing between the upper and lower electrodes in the device used to form the mask structure is 3mm-35mm.
[0028] As an optional implementation, the method for preparing the mask structure further includes: forming a third mask material layer having a third hardness on the second mask material layer, wherein the third hardness is greater than or less than the second hardness.
[0029] The present invention also discloses a mask structure, which is prepared by the method in any of the above embodiments.
[0030] The present invention also discloses a semiconductor device for fabricating a mask structure using the method described in any of the above embodiments. Attached Figure Description
[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0032] Figure 1 This is a flowchart of a method for preparing a mask structure according to an embodiment of the present invention;
[0033] Figure 2 This is a schematic diagram of the substrate structure in one embodiment of the present invention;
[0034] Figure 3 This is a schematic diagram of the structure after the first mask material layer is formed in one embodiment of the present invention.
[0035] Figure 4 This is a schematic diagram of the structure after the second mask material layer is formed in one embodiment of the present invention.
[0036] Figure 5 This is a schematic diagram of the structure after the graphic layer is formed in one embodiment of the present invention.
[0037] Figure 6 This is a schematic diagram of the structure after etching holes in the first mask material layer and the second mask material layer in one embodiment of the present invention.
[0038] Figure 7 This is a schematic diagram of the mask structure in one embodiment of the present invention.
[0039] Icon labels:
[0040] 10. Substrate; 20. Mask structure; 21. First mask material layer; 22. Second mask material layer; 30. Pattern layer. Detailed Implementation
[0041] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the method for preparing the mask structure and the wearable device proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, used only to facilitate and clearly illustrate the embodiments of this invention. Please refer to the drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.
[0042] As described in the background section, during the fabrication of hard masks using traditional methods, undesirable deformation of the aperture sidewalls can easily occur, resulting in the inaccurate transfer of the pattern into the mask layer. The applicant's research has revealed that the deformation of the aperture sidewalls is due to at least two reasons: 1. As the plasma etching depth increases, the energy of the plasma gradually decreases upon reaching the etched area, making it difficult to maintain good collimation and causing the aperture to easily become distorted; 2. The opening of the pattern layer is tilted, creating a sloping surface. The vertically downward-moving plasma is reflected after impacting the sloping surface and then impacts the aperture sidewall at an angle, thus forming an arc-shaped defect on the aperture sidewall.
[0043] To solve the above problems, such as Figures 1-4 As shown, the present invention provides a method for fabricating a mask structure 20, comprising:
[0044] S11: Provides substrate 10;
[0045] S12: Under a first plasma atmosphere, a first mask material layer 21 with a first hardness is formed on the substrate 10. The first plasma atmosphere includes a first high-frequency radio frequency and a first low-frequency radio frequency.
[0046] S13: Under a second plasma atmosphere, a second mask material layer 22 with a second hardness is formed on the first mask material layer 21. The second plasma atmosphere includes a second high-frequency radio frequency and a second low-frequency radio frequency. The first low-frequency radio frequency and the second low-frequency radio frequency are both less than or equal to 5MHz, and the first low-frequency radio frequency is greater than or equal to the second low-frequency radio frequency.
[0047] Please refer to Figure 2In step S11, the substrate 10 can be a base and a stacked structure located on the surface of the base. The stacked structure includes alternating silicon oxide layers and silicon nitride layers. The total number of silicon oxide layers and silicon nitride layers can reach more than one hundred or even several hundred layers.
[0048] Optionally, the substrate 10 may also be a base and other layers to be etched located on the base.
[0049] Please refer to Figure 3 and Figure 4 In steps S12 and S13, plasma-enhanced chemical vapor deposition (PECVD) can be used to prepare the first mask material layer 21 and the second mask material layer 22. The reaction gases used to form the first mask material layer 21 and the second mask material layer 22 include: hydrocarbons, such as: alkanes, including methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane, and similar alkanes; olefins (such as hexene, propylene, butene, pentene, and similar olefins); dienes (such as hexadiene, butadiene, isoprene, pentadiene, and similar dienes); alkynes (such as acetylene, vinylacetylene, and similar alkynes); aliphatic hydrocarbons (e.g., cyclopropane, cyclobutane, cyclopentane, cyclopentadiene, toluene, and similar aliphatic hydrocarbons); and aromatic hydrocarbons (e.g., benzene, styrene, toluene, xylene, pyridine, ethylbenzene, acetophenone).
[0050] The first mask material layer 21 and the second mask material layer 22 are amorphous carbon layers (ACL). Optionally, in other embodiments, the first mask material layer 21 and the second mask material layer 22 may also be diamond-like carbon layers.
[0051] It should be noted that the first mask material layer 21 and the second mask material layer 22 are prepared under different plasma atmospheres to form mask structures 20 with layers of different hardness. As an optional embodiment, the first plasma atmosphere includes a first high-frequency radio frequency and a first low-frequency radio frequency, and the second plasma atmosphere includes a second high-frequency radio frequency and a second low-frequency radio frequency, both of which are less than or equal to 5 MHz. For example, the first low-frequency radio frequency and the second low-frequency radio frequency can be 5 MHz, 2 MHz, or less than 1 MHz. Wherein, the first low-frequency radio frequency is greater than or equal to the second low-frequency radio frequency.
[0052] In the fabrication method of the aforementioned mask structure 20, during the formation of the second mask material layer 22, a second low-frequency radio frequency (RF) of less than or equal to 5 MHz is applied. This extremely low RF frequency increases the plasma acceleration time, thereby increasing the bombardment energy and collimation of ions during their movement towards the film layer, thus improving the density of the deposited thin film. Furthermore, the first low-frequency RF frequency is set to be greater than the second low-frequency RF frequency, making the hardness of the second mask material layer 22 greater than that of the first mask material layer 21. The harder second mask material layer 22 is more resistant to etching, but it is prone to aperture contour deformation when the aperture depth is large. The softer first mask material layer 21 is easier to etch and remove, resulting in a better aperture contour. Therefore, the harder second mask material layer 22 is designed as the upper layer, and the softer first mask material layer 21 is designed as the lower layer. When creating openings in the mask material layer, the harder second mask material layer 22 is etched at the shallowest etching depth. As the etching depth increases, the etching switches to the softer first mask material layer 21. This not only reduces the etching difficulty and accelerates the etching rate but also makes it easier to obtain a better opening profile. Furthermore, since bow-shaped defects tend to occur in the upper layer (i.e., near the photoresist layer), placing the harder second mask material layer on the upper layer can effectively prevent the formation of bow-shaped defects and improve the opening profile.
[0053] When the first low-frequency radio frequency is equal to the second low-frequency radio frequency, other parameters, such as pressure, doping concentration, or power, can be adjusted to make the first hardness less than the second hardness.
[0054] In some embodiments, to further enhance ion bombardment energy and collimation, and increase the density of the deposited thin film, a lower frequency radio frequency source can be used, such as a second low-frequency radio frequency of less than or equal to 400 kHz. As an example, the second low-frequency radio frequency can also be 200 kHz, 100 kHz, or 50 kHz.
[0055] By employing extremely low-frequency radio waves, ions can be given a longer acceleration time, thereby increasing ion bombardment energy and collimation, which is beneficial for improving the density and hardness of the deposited film.
[0056] In some embodiments, the second high-frequency radio frequency is greater than or equal to 13.56 MHz.
[0057] As an example, the apparatus for fabricating the mask structure 20 is configured with a first high-frequency radio frequency source, a second high-frequency radio frequency source, and a second low-frequency radio frequency source. The first high-frequency radio frequency source provides a first high-frequency radio frequency, the second high-frequency radio frequency source provides a second high-frequency radio frequency, and the second low-frequency radio frequency source provides a second low-frequency radio frequency.
[0058] For example, the first high-frequency radio frequency and the second high-frequency radio frequency can be 13.56MHz, 27MHz, or 30MHz. The first high-frequency radio frequency is less than or equal to the second high-frequency radio frequency. By increasing the frequency of the high-frequency radio frequency source, the dissociation degree of the process gas and precursor can be improved, the quality of the deposited film can be improved, the hardness can be increased, and the hydrogen content entering the film can be reduced, thereby improving the etching selectivity of the film.
[0059] In some embodiments, the second high-frequency radio frequency is greater than or equal to 40MHz.
[0060] To further enhance the dissociation degree of process gases and precursors and reduce the hydrogen content entering the thin film, a high-frequency radio frequency (RF frequency) greater than or equal to 40 MHz can be used. As an example, the second high-frequency RF frequency can be 40 MHz, 60 MHz, 80 MHz, or 100 MHz.
[0061] As an example, the apparatus for fabricating the mask structure 20 is equipped with a first low-frequency radio frequency source. The first low-frequency radio frequency source is used to provide a first low-frequency radio frequency.
[0062] Extremely low radio frequency frequencies can increase plasma acceleration time, ion bombardment energy, and collimation, thereby increasing the density of the deposited thin film. Therefore, a first low-frequency radio frequency can be added to the first plasma atmosphere to increase the hardness of the first mask material layer 21. Simultaneously, to ensure that the first hardness is less than the second hardness, the first low-frequency radio frequency can be set to be greater than the second low-frequency radio frequency. For example, the first low-frequency radio frequency is greater than the second low-frequency radio frequency but less than or equal to 5 MHz.
[0063] Optionally, when the first high-frequency radio frequency is less than the second high-frequency radio frequency, the first low-frequency radio frequency can be equal to the second low-frequency radio frequency.
[0064] In some embodiments, the first high-frequency radio frequency is less than or equal to the second high-frequency radio frequency.
[0065] As an example, the apparatus for fabricating the mask structure 20 is configured with a first high-frequency radio frequency (RF) source, a second high-frequency RF source, a first low-frequency RF source, and a second low-frequency RF source. The first high-frequency RF source provides a first high-frequency RF frequency, the second high-frequency RF source provides a second high-frequency RF frequency, the first low-frequency RF source provides a first low-frequency RF frequency, and the second low-frequency RF source provides a second low-frequency RF frequency.
[0066] By increasing the frequency of the high-frequency radio frequency source, the dissociation degree of the process gas and precursor can be improved, thereby enhancing the quality and hardness of the deposited film. Simultaneously, the hydrogen content entering the film can be reduced, thus improving the etching selectivity. Therefore, a second high-frequency radio frequency can be added to the first plasma atmosphere to improve the film quality and etching selectivity of the first mask material layer 21. Furthermore, to ensure that the first hardness is less than the second hardness, the second high-frequency radio frequency can be set to be less than or equal to the second high-frequency radio frequency.
[0067] In some embodiments, the second plasma atmosphere further includes a first dopant, which includes at least one of W, Mo, B, Si, or N.
[0068] The applicant discovered through research that the film hardness can be improved by metal doping or non-metal doping during the fabrication of the second mask material layer 22. Specifically, the second plasma atmosphere may include a second low-frequency radio frequency and a first dopant, which may be at least one of W, Mo, B, Si, or N. For example, the doping concentration of the first dopant may be 5%-60%. For instance, the doping concentration of the first dopant may be 5%, 10%, 20%, 30%, 40%, 50%, or 60%.
[0069] In some embodiments, the first plasma atmosphere further includes a second dopant, the second dopant including at least one of W, Mo, B, Si or N.
[0070] For example, the doping concentration of the second dopant can be 5%-60%. For instance, the doping concentration of the second dopant can be 5%, 10%, 20%, 30%, 40%, 50%, or 60%. Both the first and second plasma atmospheres contain dopant, and the type and concentration of the dopant can be the same. The difference is that the first plasma atmosphere does not contain a low-frequency radio frequency (RF) frequency, while the second plasma atmosphere does contain a second RF frequency, which is less than or equal to 5MHz, for example, 400kHz or 200kHz. This configuration can both increase the hardness of the first mask material layer 21 and the second mask material layer 22, and ensure that the first hardness is less than the second hardness.
[0071] As an optional embodiment, the first dopant and the second dopant are of the same type, but the doping concentration of the first dopant is lower than that of the second dopant, so as to prepare a second mask material layer 22 with higher hardness.
[0072] In some embodiments, the first plasma atmosphere includes a first high-frequency radio frequency power; the second plasma atmosphere includes a second high-frequency radio frequency power and a second low-frequency radio frequency power.
[0073] As an example, the apparatus for fabricating the mask structure 20 is configured with a high-frequency radio frequency (RF) source and a low-frequency RF source. The high-frequency RF source is used to provide a first high-frequency RF power when fabricating the first mask material layer 21 and a second high-frequency RF power when fabricating the second mask material layer 22, and the low-frequency RF source is used to provide a second low-frequency RF power when fabricating the second mask material layer 22.
[0074] The applicant discovered through research that higher power results in greater energy gain for the plasma, leading to a denser and harder deposited film. Therefore, compared to the first mask material layer 21, the fabrication conditions of the second mask material layer 22 include both high-frequency and low-frequency radio frequency power, thus resulting in greater hardness.
[0075] For example, the first high-frequency radio frequency power can be 100W-3000W, the second high-frequency radio frequency power can be 100W-3000W, and the second low-frequency radio frequency power can be 50W-3000W.
[0076] In some embodiments, the first high-frequency radio frequency power is less than or equal to the second high-frequency radio frequency power.
[0077] As an example, the first high-frequency radio frequency power is equal to the second high-frequency radio frequency power. This configuration allows the high-frequency radio frequency source to provide a constant power output, eliminating the need to adjust the power when fabricating different layers and reducing process complexity.
[0078] As an example, the first high-frequency radio frequency power is less than the second high-frequency radio frequency power. When fabricating the second mask material layer 22, the power of the high-frequency radio frequency source is increased to obtain a second mask material layer 22 with greater hardness.
[0079] In some embodiments, the first plasma atmosphere further includes a first low-frequency radio frequency power, wherein the first low-frequency radio frequency power is less than or equal to the second low-frequency radio frequency power.
[0080] In this embodiment, the low-frequency radio frequency (RF) source has adjustable power, providing a first low-frequency RF power when fabricating the first mask material layer 21 and a second low-frequency RF power when fabricating the second mask material layer 22. The high-frequency RF source can provide the same power in both the first and second plasma atmospheres, i.e., the first high-frequency RF power is equal to the second high-frequency RF power. In this case, the first low-frequency RF power can be set to be less than the second low-frequency RF power.
[0081] Alternatively, the high-frequency radio frequency source can provide a smaller power in the first plasma atmosphere and a larger power in the second plasma atmosphere, i.e., the first high-frequency radio frequency power is less than the second high-frequency radio frequency power. In this case, the first low-frequency radio frequency power can be set to be equal to the second low-frequency radio frequency power.
[0082] In some embodiments, the second low-frequency radio frequency power pulsates between two different power levels.
[0083] For example, two different power levels can be one zero power and one non-zero power. When the pulse signal is high, the output is non-zero power; when the pulse signal is low, the output is zero power. Alternatively, the two different power levels can be two non-zero powers of different magnitudes. When the pulse signal is high, the first non-zero power is output; when the pulse signal is low, the second non-zero power is output, where the first non-zero power is greater than the second non-zero power. The second low-frequency RF power can be provided by a pulsed RF source, which can provide a pulsed RF signal with a duty cycle ranging from 5% to 90% and a signal power range of 100W to 3000W.
[0084] The pulsating low-frequency power can make the surface of the formed film have more relaxed ions and atoms, optimize the densification of the film, reduce the stress of the film, and also reduce the hydrogen content in the film, thereby improving the etching selectivity of the film.
[0085] In some embodiments, the second high-frequency radio frequency power can be pulsed synchronously with the second low-frequency radio frequency power. It is important to note that during the pulsed operation of the second high-frequency radio frequency power, it is necessary to ensure that plasma shell collapse does not occur. For the formation of a stable plasma, a second high-frequency radio frequency power with constant power is preferred.
[0086] In some embodiments, both the first low-frequency radio frequency power and the second low-frequency radio frequency power pulsate between two different power levels. For example, both the first low-frequency radio frequency power and the second low-frequency radio frequency power can be provided by a pulsed radio frequency source, which can provide a pulsed radio frequency signal with a duty cycle ranging from 5% to 90% and a signal power ranging from 100W to 3000W.
[0087] The value of the second low-frequency radio frequency power is greater than the value of the first low-frequency radio frequency power to ensure that the second hardness is greater than the first hardness.
[0088] In some embodiments, when the first mask material layer 21 is prepared, the pressure in the reaction chamber is a first pressure; when the second mask material layer 22 is prepared, the pressure in the reaction chamber is a second pressure; wherein the first pressure is greater than or equal to the second pressure.
[0089] The lower the pressure in the reaction chamber, the larger the intermolecular distance. This makes it less likely for ions to collide with other molecules during acceleration, resulting in higher ion bombardment energy and collimation, thus increasing the density and hardness of the deposited film. Therefore, by configuring the first pressure to be greater than the second pressure, a first mask material layer 21 and a second mask material layer 22 with different hardness can be prepared, with the second mask material layer 22 exhibiting greater hardness.
[0090] When the first low-frequency radio frequency is greater than the second low-frequency radio frequency, the first pressure can be equal to the second pressure.
[0091] As an example, when preparing the first mask material layer 21, the first pressure ranges from 1 Torr to 20 Torr; when preparing the second mask material layer 22, the second pressure ranges from 0.5 Torr to 15 Torr.
[0092] In some embodiments, when the first mask material layer 21 is prepared, a first film-forming temperature is present in the reaction chamber; when the second mask material layer 22 is prepared, a second film-forming temperature is present in the reaction chamber; wherein the first film-forming temperature is less than or equal to the second film-forming temperature.
[0093] Because the second film-forming temperature is higher, the plasma has greater kinetic energy, making it easier for the plasma to reach the surface of the film layer, thereby increasing the density of the deposited film. This, in turn, is beneficial for improving the hardness of the second mask material layer 22. Furthermore, the higher second film-forming temperature and greater kinetic energy mean that after the plasma reaches the film surface, it has sufficient kinetic energy to migrate and adjust to a suitable position to settle, which is beneficial for improving the film-forming uniformity of the second mask material layer 22. In addition, the higher second film-forming temperature facilitates the desorption of hydrogen from the second mask material layer 22, resulting in a lower hydrogen content in the formed second mask material layer 22, which is beneficial for improving the etching selectivity of the second mask material layer 22.
[0094] When the first low-frequency radio frequency is greater than the second low-frequency radio frequency, the first film-forming temperature can be equal to the second film-forming temperature.
[0095] As an example, the range of the first film-forming temperature and the second film-forming temperature is 250℃-700℃.
[0096] In some embodiments, the total thickness of the mask structure 20 is 0.1 μm-9 μm.
[0097] In some embodiments, the ratio between the thickness of the first mask material layer 21 and the total thickness of the mask structure 20 is 5%-60%.
[0098] The flow rate of the reaction gas used to form the mask structure 20 is in the range of 100 sccm to 20000 sccm.
[0099] The spacing between the upper and lower electrodes in the device used to form the mask structure 20 is 3mm-35mm.
[0100] In some embodiments, considering both etching efficiency and the degree of sidewall morphology protection, the hardness range of the first mask material layer 21 is 1 GPa to 20 GPa; and the hardness range of the second mask material layer 22 is 10 GPa to 50 GPa. Simultaneously, to ensure that the mask structure as a whole does not bulge or crack, stress balance needs to be considered. The relative thickness and relative hardness of the first mask material layer 21 and the second mask material layer 22 both affect the stress. Therefore, the hardness of the first mask material layer 21 is 2% to 90% of the hardness of the second mask material layer 22, and the thickness of the second mask material layer 22 is 5% to 60% of the overall thickness of the mask structure 20. Finally, the stress range of the first mask material layer 21 is -80 MPa to 800 MPa; and the stress range of the second mask material layer 22 is -80 MPa to 800 MPa.
[0101] In some embodiments, please refer to Figures 5 to 6 The method for fabricating the mask structure 20 also includes:
[0102] S14: A patterned layer 30 is formed on the upper surface of the second mask material layer 22;
[0103] S15: The second mask material layer 22 and the first mask material layer 21 are etched according to the pattern layer 30 until the substrate 10 is exposed.
[0104] For example, pattern layer 30 includes a photoresist layer and a BARC layer (bottom anti-reflective coating) stacked sequentially from top to bottom. The etching gases used to etch the first mask material layer 21 and the second mask material layer 22 include C4F6, CHF3, O2 and Ar, or the etching gases include C4H8, CH2F2, O2 and Ar.
[0105] Since the first mask material layer 21 and the second mask material layer 22 with different hardness were prepared using the method described in the previous embodiment, when performing step S15, the second mask material layer 22 with higher hardness can be etched at a lower etching depth stage. As the etching depth increases, the etching can switch to the first mask material layer 21 with lower hardness. This not only reduces the etching difficulty but also makes it easier to obtain a better aperture profile. Furthermore, since bow-shaped defects usually form in the upper middle part of the mask structure, the hardness of the upper second mask material layer 22 can be set to be relatively high to effectively prevent bow-shaped defects from occurring on the aperture sidewall. In addition, the first mask material layer 21 with lower hardness is closer to the layer to be etched below. Since the mask material layer and the layer to be etched are usually completely different materials, the lower density makes it easier to promote the stability of their adhesion and improve the bonding force between them.
[0106] like Figure 7As shown, after completing steps S14 and S15, it is also necessary to remove the graphic layer 30 to obtain the mask structure 20.
[0107] In some embodiments, the method for preparing the mask structure 20 further includes: forming a third mask material layer having a third hardness on the second mask material layer 22, wherein the third hardness is greater than or less than the second hardness.
[0108] In some embodiments, after forming the third mask material layer, the method further includes: forming a pattern layer 30 on the upper surface of the third mask material layer; and etching the third mask material layer, the second mask material layer 22, and the first mask material layer 21 according to the pattern layer 30 until the substrate 10 is exposed.
[0109] During the production or use of the mask structure 20, more complex process conditions are often encountered, which may lead to complex and diverse contour deformations. A double-layer mask structure 20 may not meet the requirements. Therefore, a method for fabricating a mask structure 20 with more than two layers is provided.
[0110] The foregoing embodiments described how to form two mask material layers with different hardnesses. The preparation of the third mask material layer can be achieved by adjusting different parameters to make the third hardness greater than or less than the second hardness, which will not be elaborated here.
[0111] When the third hardness is greater than the second hardness, the hardness of the mask structure 20 increases sequentially from bottom to top. When the third hardness is less than the second hardness, the hardness of the mask structure 20 first increases and then decreases from bottom to top.
[0112] Optionally, the position of the layer with the highest hardness can be adjusted specifically according to the location that is prone to over-etching during the aperture opening process, thereby reducing the degree of deformation of the aperture sidewall. Optionally, the number of layers of the mask structure 20 is not limited to two or three layers. Those skilled in the art can flexibly adjust the number of layers, thickness, and hardness variation trend of the mask structure 20 according to actual process requirements.
[0113] The present invention also discloses a mask structure 20, such as Figure 7 As shown.
[0114] The present invention also discloses a semiconductor device that can be used to prepare a mask structure 20 by applying the method described in any of the above embodiments.
[0115] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A method for fabricating a mask structure, characterized in that, include; Provide substrate; In a first plasma atmosphere, a first mask material layer with a first hardness is formed on the substrate. The first plasma atmosphere includes a first high-frequency radio frequency and a first low-frequency radio frequency. In a second plasma atmosphere, a second mask material layer with a second hardness is formed on the first mask material layer. The second plasma atmosphere includes a second high-frequency radio frequency and a second low-frequency radio frequency. Wherein, the first hardness is less than the second hardness, the first low-frequency radio frequency and the second low-frequency radio frequency are both less than or equal to 5MHz, and the first low-frequency radio frequency is greater than or equal to the second low-frequency radio frequency.
2. The method for preparing the mask structure as described in claim 1, characterized in that, The second low-frequency radio frequency is less than or equal to 400kHz.
3. The method for preparing the mask structure as described in claim 1, characterized in that, The second high-frequency radio frequency is greater than or equal to 13.56MHz.
4. The method for preparing the mask structure as described in claim 1, characterized in that, The second high-frequency radio frequency is greater than or equal to 40MHz.
5. The method for preparing the mask structure as described in claim 3, characterized in that, The first high-frequency radio frequency is less than or equal to the second high-frequency radio frequency.
6. The method for preparing the mask structure as described in claim 1, characterized in that, The second plasma atmosphere also includes a first dopant, which includes at least one of W, Mo, B, Si, or N.
7. The method for preparing the mask structure as described in claim 7, characterized in that, The first plasma atmosphere further includes a second dopant, which includes at least one of W, Mo, B, Si, or N.
8. The method for preparing the mask structure as described in claim 1, characterized in that, The first plasma atmosphere includes a first high-frequency radio frequency power; the second plasma atmosphere includes a second high-frequency radio frequency power and a second low-frequency radio frequency power.
9. The method for preparing the mask structure as described in claim 9, characterized in that, The first high-frequency radio frequency power is less than or equal to the second high-frequency radio frequency power.
10. The method for preparing the mask structure as described in claim 9, characterized in that, The second low-frequency radio frequency power pulsates between two different power levels.
11. The method for preparing the mask structure as described in claim 9, characterized in that, The first plasma atmosphere also includes a first low-frequency radio frequency power, which is less than or equal to the second low-frequency radio frequency power.
12. The method for preparing the mask structure as described in claim 12, characterized in that, Both the first low-frequency radio frequency power and the second low-frequency radio frequency power pulsate between two different power levels.
13. The method for preparing the mask structure as described in claim 1, characterized in that, When preparing the first mask material layer, the pressure in the reaction chamber is a first pressure; when preparing the second mask material layer, the pressure in the reaction chamber is a second pressure; wherein, the first pressure is greater than or equal to the second pressure.
14. The method for preparing the mask structure as described in claim 1, characterized in that, When preparing the first mask material layer, a first film-forming temperature is present in the reaction chamber; when preparing the second mask material layer, a second film-forming temperature is present in the reaction chamber; wherein, the first film-forming temperature is less than or equal to the second film-forming temperature.
15. The method for preparing the mask structure as described in claim 1, characterized in that, The first mask material layer and the second mask material layer are amorphous carbon layers or diamond-like layers.
16. The method for preparing the mask structure as described in claim 1, characterized in that, The total thickness of the mask structure is 0.1μm-9μm.
17. The method for preparing the mask structure as described in claim 17, characterized in that, The ratio between the thickness of the second mask material layer and the total thickness of the mask structure is 5%-60%.
18. The method for preparing the mask structure as described in claim 1, characterized in that, The flow rate of the reactive gas used to form the mask structure is in the range of 100 sccm to 20000 sccm.
19. The method for preparing the mask structure as described in claim 1, characterized in that, The spacing between the upper and lower electrodes in the device used to form the mask structure is 3mm-35mm.
20. The method for preparing the mask structure as described in claim 1, characterized in that, Also includes: A third mask material layer with a third hardness is formed on the second mask material layer, wherein the third hardness is greater than or less than the second hardness.
21. A mask structure, characterized in that, It is prepared by any one of claims 1-20.
22. A semiconductor device, characterized in that, The mask structure is prepared by any one of claims 1-20.