Method for selectively forming silicon nitride film on sidewall or flat surface of trench

Abstract

A method for fabricating a layer structure in a trench includes simultaneously forming a dielectric film containing Si-N bonds on an upper surface, and a bottom surface and sidewalls of the trench, wherein a top / bottom portion of the film formed on the upper surface and the bottom surface and a sidewall portion of the film formed on the sidewall are imparted different chemical resistance properties by bombardment of a plasma excited by applying a voltage between two electrodes, the substrate is parallel to the two electrodes and is placed between the two electrodes; and substantially removing either, but not both, of the top / bottom portion and the sidewall portion of the film by wet etching that removes one of the top / bottom portion and the sidewall portion of the film more predominantly than the other according to the different chemical resistance characteristics.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201810447158.1, filed on May 11, 2018 (Applicant: ASM IP Holdings Limited; Invention Title: Method for Selectively Forming a Silicon Nitride Film on a Sidewall or a Flat Surface of a Trench). Technical Field

[0002] The present invention generally relates to a method for fabricating a layer structure composed of a dielectric film containing Si-N bonds in a trench formed in an upper surface of a substrate. Background Art

[0003] In the manufacturing process of large-scale integrated circuits (LSIs), there are several processes for forming sidewalls in trenches. The sidewalls are used as spacers or for blocking structures etched from the side surfaces of the trenches. Conventionally, a conformal film is formed on the surface of the trench, and then the portions formed on the upper surface (where the trench is formed) and the portions formed on the bottom surface of the trench are removed by anisotropic etching to form the sidewalls. However, when using this forming method, over-etching is required to remove the foot of the sidewall, where the thickness of the sidewall increases near and at the bottom, thereby forming a bevel. The over-etching causes etching of the underlying layer and damage to the layer structure.

[0004] Any discussion of problems and solutions related to the related art has been included in this disclosure only for the purpose of providing background to the present invention and should not be construed as an admission that any or all of the discussion was known at the time of making the present invention. Summary of the Invention

[0005] In some embodiments, the films formed on the top surface of the substrate in which the trench is formed, on the bottom surface of the trench, and on the sidewalls of the trench have different film characteristics related to wet etching (i.e., direction control of film characteristics). By wet etching the substrate, the film formed on the top / bottom surface of the trench or the film formed on the sidewalls of the trench can be selectively removed, i.e., a film extending in the horizontal direction or a film extending in the vertical direction in the trench structure can be selectively formed. According to the above method, a horizontal layer or a vertical layer in the trench structure can be selectively formed only by wet etching without using dry etching as an etching means (i.e., direction control of film formation).

[0006] In some embodiments, a film having directionally controlled film properties can be a silicon nitride film deposited by plasma enhanced chemical vapor deposition (PECVD) or plasma enhanced atomic layer deposition (PEALD). Alternatively, in some embodiments, a silicon nitride film is deposited without direction control, and then the film is processed to provide directionality of the film properties. That is, when ion bombardment is applied to the silicon nitride film during or after film deposition, impurities can be removed from the film, resulting in densification of the film and improved film quality; however, when the ion bombardment is enhanced in a direction perpendicular to the film and asymmetrically applied to the dielectric film, the film quality deteriorates, dissociating Si-N bonds, reducing the film density, and increasing the wet etching rate. The above phenomena are completely unexpected because it is generally believed that ion bombardment results in densification of the film and a reduction in the wet etching rate. The intensity of the ion bombardment can be controlled directionally by a plasma generated using a parallel plate electrode configuration (e.g., capacitively coupled plasma where the incident direction of ions, ion dose, and ion energy can be controlled). Based on the above principles, which are not intended to limit the present invention, the directionality of the film properties can be controlled.

[0007] For the purpose of summarizing aspects of the present invention and the advantages achieved over the related art, certain objects and advantages of the present invention are described in this disclosure. Of course, it should be understood that not necessarily all of these objects or advantages can be achieved in any particular embodiment of the present invention. Thus, for example, those skilled in the art will recognize that the present invention can be practiced or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein, without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0008] Other aspects, features, and advantages of the present invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other features of the present invention will now be described with reference to the drawings of the preferred embodiments, which are intended to illustrate and not limit the present invention. The drawings are greatly simplified for illustrative purposes and are not necessarily to scale.

[0010] Figure 1A is a schematic diagram of a PEALD (plasma enhanced atomic layer deposition) apparatus for depositing a protective film that can be used in embodiments of the present invention.

[0011] Figure 1B shows a schematic diagram of a precursor supply system using a flow - pass system (FPS) that can be used in embodiments of the present invention.

[0012] Figure 2Flow chart showing steps of manufacturing a layer structure according to an embodiment of the present invention.

[0013] Figure 3 Flow chart showing steps of manufacturing a layer structure according to another embodiment of the present invention.

[0014] Figure 4 Flow chart showing steps of manufacturing a layer structure according to another embodiment of the present invention.

[0015] Figure 5 Flow chart showing steps of manufacturing a layer structure according to another embodiment of the present invention.

[0016] Figure 6 Flow chart showing steps of manufacturing a layer structure according to different embodiments of the present invention.

[0017] Figure 7 Graph showing the relationship between RF power and wet etching rate of a film formed on the top surface and the relationship between RF power and wet etching rate of a film formed on the sidewall of a trench according to an embodiment of the present invention, which shows the threshold (reference) RF power.

[0018] Figure 8 Scanning electron microscope (SEM) photograph showing a cross-sectional view of a silicon nitride film formed according to an embodiment of the present invention.

[0019] Figure 9 Scanning electron microscope (SEM) photograph showing a cross-sectional view of a silicon nitride film formed according to an embodiment of the present invention.

[0020] Figure 10 Cross-sectional view showing a silicon nitride film formed according to an embodiment of the present invention.

[0021] Figure 11 Cross-sectional view showing a silicon nitride film formed according to another embodiment of the present invention.

[0022] Figure 12 Graph showing the relationship between RF power and Si-N peak intensity [au] of a SiN film according to an embodiment of the present invention.

[0023] Figure 13 Graph showing the relationship between RF power and density [g / cm 3 of a SiN film according to an embodiment of the present invention.

[0024] Figure 14A graph showing the relationship between the plasma density of a film formed on the top surface and the wet etching rate, and the relationship between the plasma density of a film formed on the sidewall of a trench and the wet etching rate, according to an embodiment of the present invention.

[0025] Figure 15 Scanning electron microscope (SEM) photograph showing a cross-sectional view of a silicon nitride film formed according to an embodiment of the present invention.

[0026] Figure 16 Scanning electron microscope (SEM) photograph showing a cross-sectional view of a silicon nitride film formed according to other embodiments of the present invention.

[0027] Figure 17 Scanning electron microscope (SEM) photograph showing a cross-sectional view of a silicon nitride film formed according to other embodiments of the present invention. Detailed Description

[0028] In the present disclosure, "gas" may include vaporized solids and / or liquids and may consist of a single gas or a gas mixture. In the present disclosure, the process gas introduced into the reaction chamber through a showerhead may include a precursor gas and an additive gas, consist essentially of them, or consist of them. The precursor gas and the additive gas are generally introduced into the reaction space as a mixed gas or separately. The precursor gas may be introduced using a carrier gas such as a noble gas. The additive gas may include a reactive gas and a dilution gas such as a noble gas, consist essentially of them, or consist of them. The reactive gas and the dilution gas may be introduced into the reaction space as a mixed gas or separately. The precursor may include two or more precursors, and the reactive gas may include two or more reactive gases. The precursor is a gas that chemisorbs on the substrate and generally contains a quasi-metal or metal element that forms the main structure of the matrix of the dielectric film, and the reactive gas for deposition is a gas that reacts with the precursor chemisorbed on the substrate when the gas is excited to fix an atomic layer or a monolayer on the substrate. "Chemisorption" refers to chemical saturation adsorption. The gas that is not used as the process gas, i.e., the gas that is not introduced through the showerhead, may be used, for example, to seal the reaction space, and such gas includes a sealing gas such as a noble gas. In some embodiments, a "film" refers to a substantially pinhole-free layer that continuously extends in a direction perpendicular to the thickness direction to cover the entire target or related surface, or simply refers to a layer that covers the target or related surface. In some embodiments, a "layer" refers to a structure having a certain thickness formed on a surface or is a synonym for a film or non-film structure. The film or layer may be composed of discrete single films or layers having certain characteristics or multiple films or layers, and the boundary between adjacent films or layers may be transparent or may be opaque, and may be established based on physical, chemical, and / or any other characteristics, formation processes or procedures, and / or the functions or purposes of adjacent films or layers.

[0029] In the present disclosure, "containing Si-N bonds" may refer to being characterized by one or more Si-N bonds, having a main skeleton substantially composed of one or more Si-N bonds, and / or having substituents substantially composed of one or more Si-N bonds. Dielectric films containing Si-N bonds include, but are not limited to, SiN films and SiON films having a dielectric constant of about 2 to 10, typically about 4 to 8.

[0030] In the present disclosure, "annealing" refers to a process in which a material is treated to enter its stable form. For example, end groups present in the components (such as alcohol groups and hydroxyl groups) are replaced by more stable groups (such as Si-Me groups) and / or a more stable form is formed (such as Si-O bonds), which generally causes densification of the film.

[0031] In addition, in the present disclosure, unless otherwise specified, the article "a" or "an" refers to a particular species or a genus including multiple species. In some embodiments, the terms "consisting of" and "having" independently refer to "typically or broadly including", "including", "substantially consisting of", or "consisting of". In addition, in the present disclosure, in some embodiments, any defined meaning does not necessarily exclude the ordinary and customary meanings.

[0032] In addition, in the present disclosure, since the operable range can be determined based on conventional operations, any two numbers of a variable can constitute the operable range of the variable, and any indicated range may include or exclude the endpoints. Additionally, any value of the indicated variable (whether or not indicated by "about") can refer to an exact value or an approximate value and includes equivalent values, and in some embodiments can refer to an average value, a median value, a representative value, a majority value, etc.

[0033] In the present disclosure, when conditions and / or structures are not specified, those skilled in the art can easily provide such conditions and / or structures according to the present disclosure through conventional experiments. In all disclosed embodiments, for a predetermined purpose, any element used in an embodiment can be replaced by any equivalent element, including those explicitly, necessarily, or inherently disclosed herein. In addition, the present invention can be equally applied to devices and methods.

[0034] Embodiments will be described with reference to preferred embodiments. However, the present invention is not limited to these preferred embodiments.

[0035] Some embodiments provide a method for fabricating a layer structure composed of a dielectric film containing Si-N bonds in a trench formed in an upper surface of a substrate, comprising: (i) simultaneously forming a dielectric film containing Si-N bonds on an upper surface, as well as a bottom surface and sidewalls of the trench, wherein a top / bottom portion of the dielectric film formed on the upper and bottom surfaces and a sidewall portion of the dielectric film formed on the sidewalls are imparted with different chemical resistance characteristics by bombardment of a plasma excited by applying a voltage between two electrodes, with the substrate placed between the electrodes parallel to the two electrodes; and (ii) substantially removing by wet etching either the top / bottom portion or the sidewall portion of the dielectric film, but not both, the wet etching removing one of the top / bottom portion and the sidewall portion of the dielectric film more predominantly than the other based on the different chemical resistance characteristics. The term "simultaneously forming" may refer to forming at approximately or substantially the same time, in the same process, or in the same step, which includes depositing at approximately or substantially the same time, in the same process, or in the same step, and / or treating at approximately or substantially the same time, in the same process, or in the same step. In the present disclosure, the term "substantially" may refer to an amount of material, a dimension, a time, or a space that is sufficient, considerable, or considered by those skilled in the art to be sufficient for the intended purpose or function (e.g., at least 70%, 80%, 90%, or 95% of a total value or a reference value).

[0036] Figure 2 FIG. is a flowchart showing steps of fabricating a layer structure according to an embodiment of the present invention. Step S1 and step S2 correspond to step (i) and (ii), respectively. In step S1, a dielectric film having a film property directionality is formed on the trench by using plasma bombardment. The plasma bombardment can be applied during a film deposition process or after completion of the film deposition. In step S2, based on a film property difference between a top / bottom portion of the film and a sidewall portion of the film, one portion of the film is etched more predominantly than the other portion by wet etching, so that only one portion remains in the layer structure.

[0037] In step S2, wet etching is performed using, for example, a solution of hydrogen fluoride (HF).

[0038] By adjusting the bombardment of a plasma excited by applying a voltage between two electrodes (with the substrate disposed therebetween parallel to the two electrodes), different chemical resistance characteristics can be imparted to a top / bottom portion of the dielectric film formed on the upper and bottom surfaces and a sidewall portion of the dielectric film formed on the sidewalls. A plasma is a partially ionized gas having a high free electron content (about 50%), and when a plasma is excited by applying an alternating voltage between parallel electrodes, ions are formed by a DC self-bias voltage (V DC)Accelerate and bombard the film on the substrate placed on the lower electrode in a direction perpendicular to the film (ion incident direction). The bombardment of the plasma can be represented by the plasma density or the kinetic energy of the ions (ion energy). The plasma density can be mainly adjusted by tuning the pressure and RF power (the lower the pressure and the higher the power, the higher the plasma density becomes). The plasma density can also be adjusted by applying a DC bias voltage or an AC voltage with a lower frequency (<1 MHz) set to make the ions follow. The plasma density can be measured using a probe method (for example, "High accuracy plasma density measurement using hybrid Langmuir probe and microwave interferometer method", Deline C et al., Rev. Sci. Instrum. November 2007; 78(11): 113504, the full text of whose disclosure is incorporated herein by reference). When a probe is inserted into the plasma and a voltage is applied to it, a current flows through the probe, which is called the "ion saturation current" (I i ), the ion saturation current can be calculated as follows, and then the plasma density (N p ) can be calculated as follows:

[0039] I i =e x N e √(kT e / M) x exp(1 / 2)eA; N p =I i √(M / kT e ) / exp(1 / 2)eA, where I i : ion saturation current [A]; A: surface area of the probe [m 2 ; e: electron charge [C]; Ne: electron density [m -3 ; k: Boltzmann constant [J / K]; T e : electron temperature [K]; M: ion mass [kg].

[0040] Figure 14A graph showing the relationship between the plasma density and the wet etching rate of the film formed on the top surface and the relationship between the plasma density and the wet etching rate of the film formed on the sidewalls of the trench according to an embodiment of the present invention. In this graph, the chemical resistance property is represented by the wet etching rate. On the top / bottom surface of the film, plasma bombardment is applied substantially in a direction perpendicular to the film surface, while on the sidewall surface of the film, plasma bombardment is applied substantially in a direction parallel to the film surface. When the plasma density is low, the wet etching rate of the film formed on the top / bottom surface of the trench is low because the ions included in the plasma applied to the film remove impurities and cause densification of the film. However, as Figure 14 shown, as the plasma density increases, the wet etching rate of the film formed on the top / bottom surface increases because the dose of ions is so high that it enhances the dissociation of the Si-N bonds. On the other hand, when the plasma density is low, the wet etching rate of the film formed on the sidewall surface of the trench is high because the dose of ions included in the plasma applied to the film is not sufficient to remove impurities and cause densification of the film. However, as Figure 14 shown, as the plasma density increases, the wet etching rate of the film formed on the sidewall surface decreases. In other words, as the plasma density increases, the film quality of the film formed on the top / bottom surface decreases, while as the plasma density increases, the film quality of the film formed on the sidewall surface increases. Therefore, there is a threshold point in the plasma density at which the film quality (or film characteristics) of the film on the top / bottom surface and the film on the sidewalls is substantially equivalent, that is, the line showing the relationship between the plasma density and the wet etching rate of the film formed on the top / bottom surface and the line showing the relationship between the plasma density and the wet etching rate of the film formed on the sidewalls intersect at the threshold point, as Figure 14 shown. The film characteristics of the film on the top / bottom surface and the film characteristics of the film on the sidewall surface are reversed at the threshold point. Therefore, by adjusting the plasma density, a film with directional film characteristics can be formed. When the plasma density is set below the threshold point, the film on the sidewalls can be removed more predominantly by wet etching compared to the film on the top / bottom surface, and when the plasma density is set above the threshold point, the film on the top / bottom surface can be removed more predominantly by wet etching compared to the film on the sidewalls. Therefore, a desired layer structure can be fabricated.

[0041] In Figure 14Among them, the intersection point (threshold point) is changed according to the duration, frequency, pressure, distance between electrodes, temperature, etc. of the voltage application. Generally speaking, the longer the duration of the voltage application and the lower the pressure, the lower the plasma density at the intersection point. It should be noted that when the pressure, RF power, voltage, etc. are constant, a relationship substantially similar to that shown in Figure 14 can be obtained between the wet etching rate and the RF power between the parallel electrodes. Based on the present disclosure and conventional experiments, the threshold point can be determined before steps (i) and (ii). Therefore, in some embodiments, the method for manufacturing a layer structure further includes repeating the following steps to determine the threshold point (reference point) before steps (i) and (ii): (a) simultaneously forming a dielectric film under the same conditions as in step (i), except that the voltage varies as a variable; and (b) removing either the top / bottom portion or the sidewall portion of the dielectric film substantially by wet etching under the same conditions as in step (ii), but not both.

[0042] Figure 3 FIG. is a flowchart showing the steps of manufacturing a layer structure according to an embodiment of the present invention. Step S11 corresponds to steps (a) and (b), and steps S12 and S13 correspond to steps (i) and (ii) respectively. In step S11, the threshold voltage of plasma bombardment for inverting the film characteristics of the top / bottom portion and the sidewall portion of the film is determined. In step S12, a dielectric film having a directionality of film characteristics is formed on the trench by using plasma bombardment at a voltage adjusted with reference to a predetermined threshold voltage. For example, when a voltage higher than the threshold voltage is applied between the electrodes in step S12, the wet etching rate of the top / bottom portion of the film becomes higher than that of the sidewall portion of the film, resulting in mainly removing the top / bottom portion of the film rather than the sidewall portion of the film by wet etching in step S13. On the other hand, when a voltage lower than the threshold voltage is applied between the electrodes in step S12, the wet etching rate of the sidewall portion of the film becomes higher than that of the top / bottom portion of the film, resulting in mainly removing the sidewall portion of the film rather than the top / bottom portion of the film by wet etching in step S13.

[0043] When ion bombardment is applied to the film without using a parallel electrode configuration (for example, by using reactants in low-pressure chemical vapor deposition (LPCVD)), effects such as Figure 14The threshold points shown, because the reactants in LPCVD do not produce asymmetric ion bombardment, i.e., do not produce directionality of film properties. For example, U.S. Patent Application Publication No. 2003 / 0029839 discloses LPCVD, in which nitrogen-containing ions such as N2+ are implanted to form a nitrogen-rich layer, followed by thermal annealing to promote Si-N and N-H bonds in the layer in order to reduce the wet etching rate of the layer. In contrast, in some embodiments of the present invention, asymmetric plasma bombardment using nitrogen is applied to the top / bottom layer, which does not enrich nitrogen in the layer but dissociates Si-N bonds and reduces the density of the layer, thereby increasing the wet etching rate of the layer formed on the top / bottom surface relative to the wet etching rate of the layer formed on the sidewalls of the trench. In the above, when the Si-N bond is dissociated, Si dangling bonds and N dangling bonds are formed, and the bonds are finally hydrogen-terminated to form N-H bonds and Si-H bonds. As a consequence of dissociating the Si-N bond, the density of the layer is reduced and the wet etching rate is increased. Therefore, in some embodiments, no thermal annealing (such as at 900 °C) is performed between steps (i) and (ii) to avoid densification of the top / bottom layer (i.e., to avoid reducing the wet etching rate of the top / bottom layer). In addition, in some embodiments, the incident energy of the ions is less than about 200 eV (the plasma potential is about 100 to 200 V), which is lower than the ion incident energy (0.5 to 20 keV) in U.S. Patent Application Publication No. 2003 / 0029839. Like the reactants in LPCVD, the reactants in thermal atomic layer deposition (ALD) and the plasma of remote plasma deposition do not form such as Figure 14 The threshold points shown, because the plasma of thermal ALD and remote plasma deposition also does not produce asymmetric ion bombardment, i.e., does not produce directionality of film properties. Additionally, when using a plasma such as a surface wave plasma (SWP) with a low electron temperature and low incident ion kinetic energy, the effect of ion bombardment is very limited, so film degradation does not occur, and thus it is difficult to produce directionality of film properties. Furthermore, even when plasma bombardment is applied to a film composed of silicon oxide, the film quality of the silicon oxide film does not deteriorate, and thus it is difficult to produce directionality of film properties.

[0044] In some embodiments, the plasma is a capacitively coupled plasma (CCP), which is excited by applying RF power to one of two electrodes. Additionally, in some embodiments, an inductively coupled plasma (ICP), an electron cyclotron resonance (ECR) plasma, a microwave surface wave plasma, a helicon wave plasma, etc. can be used as the plasma, and a bias voltage is applied to the electrode as needed to increase the DC bias voltage between the plasma and the electrode.

[0045] In some embodiments, the RF power is higher than a reference RF power at which the chemical resistance characteristics of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent, where wet etching selectively removes the top / bottom portion of the dielectric film relative to the sidewall portion of the dielectric film.

[0046] In some embodiments, the plasma is Ar, N 2 and / or O 2 or a plasma of other atoms having an atomic number higher than that of hydrogen or helium.

[0047] In some embodiments, the trench has a width of 10 nm to 50 nm (typically 15 nm to 30 nm) (where when the trench has a length substantially the same as the width, it is referred to as a hole / via and has a diameter of 10 nm to 50 nm), a depth of 30 nm to 200 nm (typically 50 nm to 150 nm), and an aspect ratio of 3 to 20 (typically 3 to 10).

[0048] In some embodiments, the dielectric film can be used as an etch stopper, a low-k spacer, or a gap filler. For example, when only the sidewall portion remains, this portion can be used as a spacer for spacer-defined double patterning (SDDP), or when only the top / bottom portion remains, this portion can be used as a mask for solid-state doping (SSD) dedicated to the sidewall layer.

[0049] In some embodiments, step (i) includes: (ia) placing a substrate having trenches in its upper surface between electrodes; and (ib) depositing a dielectric film on the substrate by plasma-enhanced atomic layer deposition (PEALD) using nitrogen as a reaction gas, where the plasma is a capacitively coupled plasma (CCP) that is excited by applying RF power to one of the two electrodes in each cycle of the PEALD, where the RF power is higher than a reference RF power at which the chemical resistance characteristics of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent, such that the wet etching in step (ii) selectively removes the top / bottom portion of the dielectric film relative to the sidewall portion of the dielectric film. Above, a film having a directionality of film properties is formed while the film deposition is in progress, rather than after the film deposition is completed.

[0050] Figure 4A flowchart showing the steps of manufacturing a layer structure according to another embodiment of the present invention. Step S21 corresponds to step (ib), and step S22 corresponds to step (ii). In step S21, a dielectric film having a directionality of film characteristics is deposited on the trench by using plasma bombardment at a voltage higher than the threshold voltage, and in step S22, the top / bottom portion of the film is removed more predominantly than the sidewall portion of the film so that substantially only the sidewall portion remains in the layer structure.

[0051] In some embodiments, step (i) includes: (ia) placing a substrate having trenches on its upper surface between electrodes; and (ic) depositing a dielectric film on the substrate by plasma enhanced atomic layer deposition (PEALD) using nitrogen as a reaction gas, wherein the plasma is capacitively coupled plasma (CCP) which is excited by applying RF power to one of the two electrodes in each cycle of PEALD, wherein the RF power is lower than a reference RF power at which the chemical resistance characteristics of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent, such that the wet etching in step (ii) selectively removes the sidewall portion of the dielectric film relative to the top / bottom portion of the dielectric film. Above, a film having a directionality of film characteristics is formed while the film deposition is in progress, rather than after the film deposition is completed.

[0052] Figure 5 A flowchart showing the steps of manufacturing a layer structure according to another embodiment of the present invention. Step S31 corresponds to step (ic), and step S32 corresponds to step (ii). In step S31, a dielectric film having a directionality of film characteristics is deposited on the trench by using plasma bombardment at a voltage lower than the threshold voltage, and in step S32, the sidewall portion of the film is removed more predominantly than the top / bottom portion of the film so that substantially only the top / bottom portion remains in the layer structure.

[0053] In some embodiments, the dielectric film is a SiN film or a SiON film or other films containing Si-N bonds.

[0054] In some embodiments, PEALD or other deposition methods use one or more compounds selected from the group consisting of aminosilanes, halosilanes, silane, and disilane as precursors. Aminosilanes and halosilanes include, but are not limited to, Si 2 Cl 6 、SiCl 2 H2、SiI 2 H 2, bis(diethylamino)silane, bis(dimethylamino)silane, hexaethylaminodisilane, tetraethylaminosilane, tert-butylaminosilane, bis(tert-butylamino)silane, trimethylsilyldiethylamine, trimethylsilyldiethylamine, and bis(dimethylamino)dimethylsilane.

[0055] In some embodiments, step (i) includes: (iA) depositing a dielectric film on a substrate having trenches in its upper surface; (iB) placing the substrate between two electrodes; and (iC) exciting a plasma between the electrodes to treat the surface of the deposited dielectric film without depositing a film, wherein the plasma is a capacitively coupled plasma (CCP) excited by applying RF power to one of the two electrodes, where the RF power is higher than a reference RF power at which the chemical resistance characteristics of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent, such that the wet etching in step (ii) selectively removes the top / bottom portion of the dielectric film relative to the sidewall portion of the dielectric film. Herein, a film having a directionality of film properties is formed by treating the film after the deposition of the film is completed. Herein, step (ii) is a post-deposition treatment that does not require cycling.

[0056] Figure 6 FIG. is a flowchart showing the steps of manufacturing a layer structure according to different embodiments of the present invention. Step S41 corresponds to step (iA), step S42 corresponds to steps (iB) and (iC), and step S43 corresponds to step (ii). In step S41, a dielectric film is deposited on the trenches, and the film does not need to have a directionality of film properties, but it may already have a directionality of film properties. In step S42, plasma bombardment as a post-deposition treatment is applied to the film at a voltage higher than the threshold voltage, such that the wet etching rate of the top / bottom portion of the film is higher than the wet etching rate of the sidewall portion of the film. In step S43, the top / bottom portion of the film is mainly removed by wet etching compared to the sidewall portion of the film, so that substantially only the sidewall portion of the film remains in the layer structure. Since the film has been deposited before the post-deposition treatment, using a voltage lower than the threshold voltage may be ineffective because the wet etching rate of the sidewall portion does not become higher than the wet etching rate of the just-deposited film by applying plasma bombardment to the film, as discussed above. Figure 14 as shown.

[0057] In some embodiments, the deposited dielectric film has a thickness of about 10 nm or less (usually about 5 nm or less). If the film to be treated is thicker than about 10 nm, then the plasma bombardment does not reach the bottom of the film, that is, it is difficult to fully adjust the wet etching rate of the film in the thickness direction.

[0058] The dielectric film subjected to post-deposition treatment can be deposited on a substrate by any suitable deposition method, including plasma-enhanced atomic layer deposition (PEALD), thermal ALD, low-pressure chemical vapor deposition (PCVD), remote plasma deposition, PECVD, etc. Preferably, the dielectric film is deposited by ALD because ALD can provide high conformality such as greater than about 70% (or greater than 80% or 90%).

[0059] In some embodiments, annealing is not performed after depositing the dielectric film and before step (ii).

[0060] In some embodiments, the plasma in step (i) is a capacitively coupled plasma (CCP) which is excited by applying RF power to one of two electrodes, where the plasma density is higher than a reference plasma density at which the chemical resistance properties of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent, and where the wet etching in step (ii) selectively removes the top / bottom portion of the dielectric film relative to the sidewall portion of the dielectric film. As discussed above with respect to Figure 14 the wet etching rate of the film formed on the top surface and the wet etching rate of the film formed on the sidewalls of the trench can be adjusted by changing the plasma density, and the plasma density can be adjusted by tuning the pressure and / or RF power (the lower the pressure and / or the higher the power, the higher the plasma density), and / or by applying RF power with a low frequency (<1 MHz).

[0061] In some embodiments, the plasma density is adjusted by tuning the pressure in the reaction space, where the plasma density increases by reducing the pressure. In that case, the method further includes repeating the following steps to determine the reference plasma density before steps (i) and (ii): (a) simultaneously forming the dielectric film under the same conditions as in step (i) except that the pressure varies as a variable; and (b) removing substantially either the top / bottom portion or the sidewall portion of the dielectric film by wet etching under the same conditions as in step (ii), but not both.

[0062] In some embodiments, the pressure in step (i) is controlled below 350 Pa, including 300 Pa, 250 Pa, 200 Pa, 150 Pa, 100 Pa, 50 Pa, and 10 Pa, and any value between any two of the above values.

[0063] In some embodiments, the plasma density is adjusted by tuning the ratio of the high-frequency RF power to the low-frequency RF power that constitutes the RF power, wherein the plasma density increases by decreasing the ratio. In some embodiments, the high-frequency RF power has a frequency of 1 MHz or higher (e.g., 10 MHz to 60 MHz), and the low-frequency RF power has a frequency of less than 1 MHz (e.g., 200 kHz to 800 kHz). Above, the method further includes repeating the following steps to determine a reference plasma density before steps (i) and (ii): (a) simultaneously forming a dielectric film under the same conditions as in step (i), except that the ratio varies as a variable; and (b) removing, by wet etching, essentially any one but not both of the top / bottom portion and the sidewall portion of the dielectric film under the same conditions as in step (ii).

[0064] In some embodiments, the ratio of the high-frequency RF power (HRF) to the low-frequency RF power (LRF) is from 0 / 100 to 95 / 5 (e.g., 10 / 90 to 90 / 10). In some embodiments, the RF power consists of the low-frequency RF power. In some embodiments, for a 300 mm wafer, the total RF power is from 100 W to 600 W (this power is applicable to wafers of any size, in the form of watts per unit area, i.e., 0.14 W / cm 2 to 0.85 W / cm 2 ).

[0065] In some embodiments, when depositing the dielectric film, any one or more of the variables discussed in this disclosure can be used to manipulate the plasma density in order to control selective etching during the etching process.

[0066] In the above embodiments of controlling the HRF / LRF ratio, when depositing the dielectric film, low pressure and high RF power are not required as variables for manipulating the plasma density, thus making the process conditions less restricted. In addition, in the embodiments, abnormal discharges can be avoided by applying high RF power.

[0067] In other embodiments where the wet etching in step (ii) selectively removes the sidewall portion of the dielectric film relative to the top / bottom portion of the dielectric film, the plasma density is set to be lower than the reference plasma density at which the chemical resistance characteristics of the top / bottom portion of the dielectric film and the sidewall portion of the dielectric film are substantially equivalent.

[0068] In some embodiments, the deposition cycle is performed by PEALD, and one cycle is carried out under the conditions shown in Table 1 below.

[0069] Table 1 (the values are approximate)

[0070]

[0071] In some embodiments, post-deposition processing can be performed under the conditions shown in Table 2 below.

[0072] Table 2 (values are approximate)

[0073] In the above, no precursor is fed into the reaction chamber, and the carrier gas flows continuously.

[0074] In some embodiments, wet etching can be performed under the conditions shown in Table 3 below.

[0075] Table 3 (values are approximate)

[0076]

[0077] For wet etching, any suitable single-wafer or batch-type equipment including any conventional equipment can be used. Additionally, any solution suitable for wet etching can be used, including any conventional solution such as phosphoric acid.

[0078] In some embodiments, instead of wet etching, any other suitable etching can be performed, such as dry etching or plasma etching. Those skilled in the art can easily determine the etching conditions, such as temperature, duration, and etchant concentration, according to the present disclosure through routine experiments.

[0079] In some embodiments, the insulating film can be formed only on the sidewalls of the trenches as follows:

[0080] 1) Form an SiN film on a substrate having a trench pattern, where pulses of the precursor are repeatedly fed and the substrate is exposed to pulses of an ambient atmosphere containing plasma-excited nitrogen species, where the plasma is excited in a direction perpendicular to the substrate (the angle of incidence of the ions is perpendicular to the substrate) in such a way as to apply plasma bombardment to the substrate under conditions such that the wet etching rate of the sidewall portion of the film is lower than the wet etching rate of the top / bottom portion of the film; and

[0081] 2) Remove the top / bottom portion of the film by wet etching.

[0082] In the above process sequence, the precursor is supplied in a pulsed manner using a continuously supplied carrier gas. This can be achieved using a flow-through system (FPS), where the carrier gas line has a bypass line with a precursor reservoir (bottle), and the main line and the bypass line are switched, where when it is intended to feed only the carrier gas to the reaction chamber, the bypass line is closed, and when it is intended to feed the carrier gas and the precursor gas to the reaction chamber, the main line is closed, and the carrier gas flows through the bypass line and exits the bottle together with the precursor gas. In this way, the carrier gas can continuously flow into the reaction chamber, and the precursor gas can be transported in a pulsed manner by switching the main line and the bypass line. Figure 1B Fig. shows a precursor supply system using a flow-through system (FPS) according to an embodiment of the present invention (the black valves indicate that the valves are closed). As Figure 1B shown in (a) of, when feeding the precursor to the reaction chamber (not shown), first, a carrier gas such as Ar (or He) flows through the gas line having valves b and c, and then enters the bottle (reservoir) 30. The carrier gas exits the bottle 30 while transporting the precursor gas corresponding to the vapor pressure inside the bottle 30, and flows through the gas line having valves f and e, and then is fed to the reaction chamber together with the precursor. Above, valves a and d are closed. When only the carrier gas (noble gas) is fed to the reaction chamber, as Figure 1B shown in (b) of, the carrier gas flows through the gas line having valve a while bypassing the bottle 30. Above, valves b, c, d, e, and f are closed.

[0083] The precursor can be provided by means of a carrier gas. Since ALD is a self-limiting adsorption reaction process, the number of deposited precursor molecules is determined by the number of reactive surface sites, and after saturation, it is independent of the precursor exposure. Thus, the supply of the precursor in each cycle saturates the reactive surface sites. The plasma for deposition can be generated in-situ, for example, in ammonia gas flowing continuously throughout the deposition cycle. In other embodiments, the plasma can be generated remotely and supplied to the reaction chamber.

[0084] As mentioned above, each pulse or stage of each deposition cycle is preferably self-limiting. An excess of reactant is supplied in each stage to saturate the sensitive structural surface. Surface saturation ensures that the reactant occupies all available reaction sites (e.g., limited by physical size or "steric hindrance"), thus ensuring excellent step coverage. In some embodiments, the pulse time of one or more reactants can be reduced such that complete saturation is not achieved and less than a monolayer adsorbs on the substrate surface.

[0085] For example, the process cycle can be carried out using any suitable equipment, including Figure 1A the equipment shown in. Figure 1AIt is a schematic diagram of a PEALD device. The device is preferably combined with a control device programmed to perform the processes described below and can be used in some embodiments of the present invention. In this figure, by providing a pair of parallel conductive plate electrodes 4 and 2 facing each other inside the reaction chamber 3 (reaction zone), HRF power (13.56 MHz or 27 MHz) 20 is applied to one side, and the other side 12 is electrically grounded, and a plasma is excited between the electrodes. A temperature regulator is provided in the lower platform 2 (lower electrode), and the temperature of the substrate 1 placed thereon is constantly maintained at a specified temperature. The upper electrode 4 also serves as a shower plate, and the reaction gas (and rare gas) and the precursor gas are respectively introduced into the reaction chamber 3 through the gas line 21 and the gas line 22 and pass through the shower plate 4. Additionally, in the reaction chamber 3, an annular duct 13 with an exhaust duct line 7 is provided, and the gas in the interior 11 of the reaction chamber 3 is discharged through the annular duct. Additionally, a dilution gas is introduced into the reaction chamber 3 through the gas line 23. Additionally, the transfer chamber 5 provided below the reaction chamber 3 has a sealed gas line 24 to introduce the sealed gas into the interior 11 of the reaction chamber 3 through the interior 16 (transfer zone) of the transfer chamber 5. An isolation plate 14 for isolating the reaction zone from the transfer zone is provided in the transfer chamber (the gate valve is omitted in this figure, and the wafer is transferred into or out of the transfer chamber 5 through the gate valve). The transfer chamber also has an exhaust duct line 6. In some embodiments, the deposition of a multi-element film and surface treatment are carried out in the same reaction space such that all steps can be carried out continuously without exposing the substrate to air or other oxygen-containing atmospheres. In some embodiments, a remote plasma unit can be used to excite the gas.

[0086] In some embodiments, in Figure 1A the device depicted in Figure 1B the system for switching the non-reactive gas flow and the precursor gas flow shown in (described previously) can be used to introduce the precursor gas in a pulsed manner while keeping the pressure in the reaction chamber substantially non-fluctuating.

[0087] In some embodiments, a dual-chamber reactor (for processing two parts or compartments of wafers arranged close to each other) can be used, where the reaction gas and the rare gas can be supplied through a shared line while the precursor gas is supplied through a non-shared line.

[0088] Those skilled in the art will understand that the device includes one or more controllers (not shown) programmed or otherwise configured such that the deposition and the reactor cleaning processes described elsewhere herein can be carried out. Those skilled in the art will understand that the controller is in communication with various power supplies, heating systems, pumps, robotic devices, and the gas flow controllers or valves of the reactor.

[0089] The present invention is further illustrated by reference to the following working examples. However, these examples are not intended to limit the present invention. In examples where conditions and / or structures are not specified, those skilled in the art can readily provide such conditions and / or structures according to the present disclosure through routine experiments. Similarly, in some embodiments, the numerical values applied in specific examples can be modified within a range of at least ±50%, and the numerical values are approximate values.

[0090] In some embodiments, the insulating film can be formed only on the sidewalls of the trenches as follows:

[0091] 1) Form a SiN film on a substrate having a trench pattern (the film may or may not have directionality of film properties);

[0092] 2) Treat the film with a plasma excited in a manner of applying plasma bombardment to the substrate in a direction perpendicular to the substrate (the incident angle of ions is perpendicular to the substrate) under conditions such that the wet etching rate of the sidewall portion of the film is lower than the wet etching rate of the top / bottom portion of the film; and

[0093] 3) Remove the top / bottom portion of the film by wet etching.

[0094] Examples

[0095] Example 1

[0096] A SiN film was formed on a Si substrate (Ф300 mm) having trenches by PEALD, using Figure 1A the PEALD equipment shown and Figure 1B the gas supply system (FPS) shown for one cycle under the conditions shown in Table 4 (deposition cycle) below.

[0097] After removing the substrate from the reaction chamber, the substrate was wet-etched under the conditions shown in Table 4 below.

[0098] Table 4 (numerical values are approximate values)

[0099]

[0100] The results are shown in Figure 7 . Figure 7 A graph showing the relationship between the RF power of the film formed on the top surface and the wet etching rate and the relationship between the RF power of the film formed on the sidewalls of the trenches and the wet etching rate, which shows the threshold (reference) RF power. As Figure 7As shown, as the RF power increases, the wet etching rate of the sidewall portion decreases, while the wet etching rate of the top / bottom portion increases as the RF power increases, and the line representing the former and the line representing the latter intersect at an RF power of approximately 600 W. That is, the threshold RF power is approximately 600 W, and it can be understood that when the RF power applied between the electrodes is higher than approximately 600 W, the top / bottom portion of the film can be selectively removed relative to the sidewall portion of the film, and when the RF power applied between the electrodes is lower than approximately 600 W, the sidewall portion of the film can be selectively removed relative to the top / bottom portion of the film.

[0101] In addition, before wet etching, an additional analysis is performed on the top portion of the film: the Si-N peak intensity and density. Figure 12 Is a graph showing the relationship between the RF power of the SiN film and the Si-N peak intensity [au]. Figure 13 Is a graph showing the relationship between the RF power of the SiN film and the density [g / cm 3 . As can be seen from Figure 12 and 13 , contrary to common technical knowledge (i.e., when the RF power is gradually increased, densification of the film occurs), when the RF power increases, the asymmetric plasma bombardment of the SiN film breaks the Si-N bonds, and due to the dissociation of the Si-N bonds, the density of the film decreases (the density is generally in the range of 2.6 to 3.2 g / cm 3 ), and the density of the film portion to be removed by wet etching is lower than the density of the film portion to be retained in the wet etching).

[0102] Example 2

[0103] A SiN film is deposited under the conditions shown in Table 5, where the threshold RF power is determined to be approximately 400 W in the same manner as in Example 1. Then, the SiN film is wet-etched under the conditions shown in Table 5. Figure 8 A scanning transmission electron microscope (STEM) photograph showing a cross-sectional view of the silicon nitride film. As can be seen from Figure 8 , when the RF power is 700 W, the top / bottom portion of the film is selectively removed by wet etching, and there is substantially no film retained on the top surface and at the bottom of the trench (no residual film is observed). When the RF power is 500 W, the top / bottom portion of the film is removed more predominantly by wet etching compared to the sidewall portion of the film, but a residual film remains on the top surface and at the bottom of the trench, while most of the sidewall portion of the film is retained. When the RF power is 300 W, the sidewall portion of the film is removed more predominantly by wet etching compared to the top / bottom portion of the film, and there is no residual film retained in some areas of the sidewall, while most of the top / bottom portion of the film is retained.

[0104] Table 5 (Values are approximate)

[0105]

[0106] Example 3

[0107] A SiN film was deposited in the same manner as in Example 1 except that the RF power was 880 W. Then, the SiN film was wet-etched under the same conditions as in Table 1. Figure 9 A scanning transmission electron microscope (STEM) photograph showing a cross-sectional view of the SiN film after wet etching. As can be seen from Figure 9 it, there is substantially no film remaining on the top surface and the bottom of the trench (no residual film was observed).

[0108] Example 4 (Predictive Example)

[0109] A SiN film was formed on a Si substrate (Φ300 mm) with trenches by PEALD in the same manner as in Example 1 except that the RF power was 600 W. Thereafter, in the same reactor, the film was treated with plasma under the conditions shown in Table 6 below, where the RF power was 800 W, which is higher than the threshold RF power, thereby causing damage to the top surface of the substrate and the bottom surface of the trench and reducing the film quality. After the substrate was taken out of the reaction chamber, the substrate was wet-etched under the conditions shown in Table 6 below.

[0110] Table 6 (Values are approximate)

[0111]

[0112] Figure 10 A cross-sectional view of the silicon nitride film is shown. Since a part 52 of the film formed on the sidewall 51 of the trench formed in the substrate 51 did not receive substantial plasma bombardment, this part 52 retained the film characteristics and remained after wet etching. In contrast, since a part of the film formed on the top surface 51b and a part of the film formed on the bottom surface 51a received plasma bombardment, these parts had reduced film characteristics and were removed after wet etching.

[0113] Example 5 (Predictive Example)

[0114] A SiN film was formed on a Si substrate (Ф300 mm) with trenches by PEALD, using Figure 1A the PEALD equipment shown Figure 1B and the gas supply system (FPS) shown under the conditions shown in Table 7 (deposition cycle) below for one cycle thereof.

[0115] After taking out the substrate from the reaction chamber, the substrate is wet-etched under the conditions shown in Table 7 below.

[0116] Table 7 (The values are approximate)

[0117]

[0118] Figure 11 A cross-sectional view of the silicon nitride film is shown. Since the RF power is 100 W, which is lower than the threshold RF power (expected to be 600 W), the sidewall portion of the film is selectively removed by wet etching relative to the top portion 53b and the bottom portion 53a of the film, and only the top / bottom portions 53a, 53b remain after wet etching. Such a film can be used as a capping layer.

[0119] Example 6

[0120] A SiN film is deposited under the conditions shown in Table 8, where the threshold pressure is determined to be approximately 300 Pa in a manner substantially similar to that in Example 1. Then the SiN film is wet-etched under the conditions shown in Table 8. Figure 15 A scanning transmission electron microscope (STEM) photograph showing a cross-sectional view of the silicon nitride film is shown. As can be seen from Figure 15 When the pressure is 150 Pa, the top / bottom portions of the film are selectively removed by wet etching, and there is substantially no film remaining on the top surface and at the bottom of the trench (no residual film is observed). When the pressure is 250 Pa, the top / bottom portions of the film are removed more predominantly by wet etching compared to the sidewall portion of the film, but a residual film remains on the top surface and at the bottom of the trench, while most of the sidewall portion of the film is retained. When the pressure is 350 Pa, the sidewall portion of the film is removed more predominantly by wet etching compared to the top / bottom portions of the film, and there is no residual film remaining in some regions of the sidewall, while most of the top / bottom portions of the film are retained.

[0121] Table 8 (The values are approximate)

[0122]

[0123] Example 7

[0124] A SiN film is deposited under the conditions shown in Table 9, where the threshold RF power (only HRF) is determined to be approximately 550 W in a manner substantially similar to that in Example 1. Then the SiN film is wet-etched under the conditions shown in Table 9. Figure 16 A scanning transmission electron microscope (STEM) photograph showing a cross-sectional view of the silicon nitride film is shown. As can be seen from Figure 16It can be seen that when the HRF power (13.56 MHz) is 880 W without LRF power, the top / bottom part of the film is selectively removed by wet etching, and there is substantially no film remaining on the top surface and at the bottom of the trench (no residual film is observed). When the HRF power is 550 W without LRF power, the top / bottom part of the film and the sidewall part of the film are etched approximately equally and mostly retained. When the HRF power is 550 W and 50 W of LRF power (400 kHz) is added thereto, the top / bottom part of the film is removed more predominantly by wet etching compared to the sidewall part of the film, and there is no residual film remaining in some areas of the top / bottom part, while the sidewall part of the film is mostly retained.

[0125] Table 9 (values are approximate)

[0126]

[0127] Example 8

[0128] A SiN film is deposited under the conditions shown in Table 10, where the threshold RF power (only HRF) is determined to be approximately 400 W in a manner substantially similar to that in Example 1. Then, the SiN film is wet-etched under the conditions shown in Table 10. Figure 17 A scanning transmission electron microscope (STEM) photograph showing a cross-sectional view of the silicon nitride film. As can be seen from Figure 17 It can be seen that when the HRF power (13.56 MHz) is 200 - 250 W without LRF power, the sidewall part of the film is selectively removed by wet etching, and there is substantially no film remaining on the sidewall surface of the trench (no residual film is observed). When the LRF power (430 kHz) is 300 W without HRF power, the top / bottom part of the film is selectively removed by wet etching, and there is substantially no film remaining on the top surface and at the bottom of the trench (no residual film is observed), while the sidewall part of the film is mostly retained.

[0129] Table 10 (values are approximate)

[0130]

[0131] Example 9

[0132] As Figure 17As shown, reverse topology selectivity (RTS) can be effectively achieved by manipulating the HRF / LRF ratio. When using LRF power, the reason for selectively removing the top / bottom part of the film by wet etching seems to lie in the amount of impurities such as hydrogen contained in the resulting film. It appears that the LRF power process generates more hydrogen radicals than the HRF power process and supplies more hydrogen atoms to the film, thus increasing the wet etching rate. Table 11 below shows the hydrogen content of the SiN film deposited on a blank (flat) wafer in the same manner as in Example 8. As shown in Table 11, the SiN film formed by the LRF power process contains more hydrogen atoms than the SiN film formed by the HRF power process, resulting in a higher WER in the SiN film for the LRF power process than for the HRF power process. Therefore, it can be understood that the hydrogen content in the film is one of the main factors for RTS.

[0133] Table 11 (Values are approximate)

[0134]

[0135] Example 10 (Predictive Example)

[0136] As shown in Example 2 ( Figure 8 ), reverse topology selectivity (RTS) can be effectively achieved by manipulating the RF power (HRF). Additionally, as Figure 17 shown, reverse topology selectivity (RTS) can be effectively achieved by manipulating the HRF / LRF ratio. In the wet etching step after the deposition step, as the etching solution (etchant solution), not only hydrogen fluoride (HF) can be used, but also phosphoric acid (H 3 PO 4 ) or any other suitable solution can be used to achieve RTS. However, the type of etching solution can affect the degree of RTS. For example, Table 12 shows that the etching rates at the top surface and the sidewalls of the trenches vary according to the type of etchant solution, where the deposited dielectric film is formed in a manner similar to Example 2 or Example 8.

[0137] Table 12 (Values are approximate)

[0138]

[0139] *: Manufactured by Daikin Industries, Ltd., Japan (hydrogen fluoride containing 5% ammonium bifluoride, 37% ammonium fluoride, and 58% water)

[0140] Those skilled in the art should understand that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the form of the present invention is merely illustrative and is not intended to limit the scope of the present invention.

Claims

1. A method for fabricating a layer structure composed of a dielectric film containing Si-N bonds in a trench formed in an upper surface of a substrate, the method comprising: (i) simultaneously forming a dielectric film containing Si-N bonds on the upper surface, the bottom surface, and the sidewalls of the trench, wherein the top / bottom portions of the dielectric film already formed on the upper surface and the bottom surface and the sidewall portions of the dielectric film already formed on the sidewalls are imparted with different chemical resistance characteristics by bombardment with nitrogen-based plasma excited by applying a voltage in a reaction space between two electrodes, the substrate being placed between the electrodes parallel to the two electrodes; and (ii) etching to substantially remove either the top / bottom portions or the sidewall portions of the dielectric film, but not both, the etching removing one of the top / bottom portions and the sidewall portions of the dielectric film more predominantly than the other according to the different chemical resistance characteristics, wherein no annealing is performed between step (i) and step (ii); wherein the plasma in step (i) is a capacitively coupled plasma (CCP) which is excited by applying RF power to one of the two electrodes, wherein the plasma density is higher than a reference plasma density at which the chemical resistance characteristics of the top / bottom portions of the dielectric film and the sidewall portions of the dielectric film are substantially equivalent, and wherein the etching in step (ii) selectively removes the top / bottom portions of the dielectric film with respect to the sidewall portions of the dielectric film, wherein the width of the trench is 10 nm to 50 nm, the depth is 30 nm to 200 nm, and the aspect ratio is 3 to 20, the distance between the two electrodes is 5 mm to 30 mm, the dielectric film is formed by plasma enhanced atomic layer deposition (PEALD) in step (i), wherein the pressure in step (i) is controlled to be lower than 350 Pa; and wherein the plasma density is adjusted by tuning the ratio of high-frequency RF power to low-frequency RF power constituting the RF power, wherein the plasma density increases by decreasing the ratio.

2. The method according to claim 1, wherein in step (i), the dielectric film is formed by plasma enhanced atomic layer deposition (PEALD).

3. The method according to claim 1, wherein the plasma is a plasma of Ar, N 2 or O 2 .

4. The method according to claim 1, wherein the dielectric film is a SiN film.

5. The method according to claim 4, wherein in step (i), a halogenated silane is used as a precursor.

6. The method according to claim 1, wherein the etching is wet etching which is performed using a solution of hydrogen fluoride (HF) or phosphoric acid.

7. The method according to claim 1, wherein the plasma density is adjusted by tuning the pressure in the reaction space, wherein the plasma density increases by decreasing the pressure.

8. The method according to claim 7, further comprising repeating the following steps before steps (i) and (ii) to determine the reference plasma density: While varying the pressure as a variable, forming a dielectric film simultaneously under the same conditions as in step (i); and Under the same conditions as in step (ii), removing substantially any one of the top / bottom portions and the sidewall portions of the dielectric film by etching, but not both.

9. The method according to claim 7, wherein the pressure in step (i) is controlled to be below 300 Pa.

10. The method according to claim 1, wherein the high-frequency RF power has a frequency of 1 MHz or higher, and the low-frequency RF power has a frequency of less than 1 MHz.

11. The method according to claim 1, further comprising repeating the following steps before steps (i) and (ii) to determine the reference plasma density: While varying the ratio as a variable, forming a dielectric film simultaneously under the same conditions as in step (i); and Under the same conditions as in step (ii), removing substantially any one of the top / bottom portions and the sidewall portions of the dielectric film by wet etching, but not both.

12. The method according to claim 1, wherein the ratio of the high-frequency RF power to the low-frequency RF power is from 10 / 90 to 90 / 10.

13. The method according to claim 1, wherein no annealing is performed between steps (i) and (ii).

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