Silicon nitride film with high nitrogen content

Abstract

To provide a method for depositing silicon nitride films with higher nitrogen content.SOLUTION: Certain methods comprise exposing a substrate to a silicon-nitrogen precursor and ammonia plasma to form a flowable polymer, and then curing the polymer to form a silicon nitride film. Certain methods cure the flowable polymer without the use of a UV-cure process.SELECTED DRAWING: Figure 2B

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to methods for depositing thin films, and more particularly to processes for depositing high nitrogen content silicon nitride films. [Background technology]

[0002] The deposition of thin films onto substrate surfaces is an important process in a variety of industries, including semiconductor processing, diffusion barrier coatings, and dielectrics for read / write magnetic heads. In the semiconductor industry, miniaturization benefits are especially realized by controlling thin film deposition to produce conformal coatings on high aspect structures. One method for depositing thin films with relatively controlled and conformal deposition is chemical vapor deposition (CVD). CVD involves exposing a substrate (e.g., a wafer) to one or more precursors that react to deposit a film on the substrate. Flowable chemical vapor deposition (FCVD) is a type of CVD that allows for the deposition of flowable films, especially for gap-fill applications.

[0003] SiN flowable films are commonly used for gap-fill applications. Currently, such films are produced by trisilylamine (TSA) with the radical form of NH3 as a co-reactant. The deposited films resulting from this TSA process contain primarily Si and N as is. These films typically have a nitrogen to silicon ratio in the range of 0.4:1 to 0.7:1. Films with relatively high nitrogen content can be useful in patterning applications to solve etch selectivity problems.

[0004] Thus, there is a need for new deposition chemistries that enable the deposition of SiN films with relatively high nitrogen content. Summary of the Invention

[0005] One or more embodiments of the present disclosure are directed to a method of depositing a SiN film. The method includes exposing a substrate to a silicon-nitrogen precursor and an NH3 plasma to deposit a flowable SiN polymer and curing the flowable SiN polymer to form a hardened SiN film. In these embodiments, the silicon-nitrogen precursor is one or more of the following: TIFF2025004005000002.tif35170 [wherein R1 to R5 are independently H or C1 to C4 alkyl] Includes.

[0006] Further embodiments of the present disclosure are directed to a method for depositing a SiN film. The method includes exposing a substrate, maintained at 25° C. or below, to a silicon-nitrogen precursor and NH3 plasma to deposit a flowable SiN polymer, and curing the flowable SiN polymer to form a cured SiN film, wherein the ratio of nitrogen atoms to silicon atoms in the cured SiN film is greater than about 1.0. In these embodiments, the silicon-nitrogen precursor is one or more of the following: TIFF2025004005000003.tif36170 [wherein R1 to R5 are independently H or methyl, provided that at least one of R1 to R5 is methyl] Includes.

[0007] Further embodiments of the present disclosure are directed to cured SiN films formed without UV curing by exposing a substrate to a silicon-nitrogen precursor and NH3 plasma at a temperature of about 25° C. or less. In these embodiments, the ratio of nitrogen atoms to silicon atoms in the cured SiN film ranges from about 1.0 to about 1.5, and the silicon nitrogen precursor is one or more of the following: TIFF2025004005000004.tif37170 [wherein R1 to R5 are independently H or C1 to C4 alkyl] Includes.

[0008] So that the foregoing features of the present invention may be understood in detail, a more particular description of the present invention summarized above may be made by reference to several embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings are only intended to illustrate exemplary embodiments of the present invention and should not be considered as limiting the scope of the present invention, since the present invention may leave room for other equally effective embodiments. [Brief description of the drawings]

[0009] [Figure 1] 1 shows a schematic diagram of a cross-section of a substrate in accordance with one or more embodiments of the present disclosure. [Figure 2A] 1 illustrates deposition of a flowable film in accordance with one or more embodiments of the present disclosure. [Figure 2B] 1 illustrates the formation of a cured film in accordance with one or more embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Before describing some example embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or process set forth in the following description. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0011] As used herein and in the appended claims, the term "substrate" refers to a surface or a portion of a surface on which a process is performed. It will be understood by those skilled in the art that a reference to a substrate may refer to only a portion of the substrate (unless the context clearly indicates otherwise). Furthermore, a reference to deposition on a substrate may refer to both a bare substrate and a substrate having one or more films or features deposited or formed on the films.

[0012] As used herein, "substrate" refers to a substrate on which a film process is performed during the fabrication process, or a material surface formed on the substrate. For example, substrate surfaces that can be treated include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxide, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and other materials such as metals, metal nitrides, metal alloys, and other conductive materials depending on the application. Substrates include, but are not limited to, semiconductor wafers. Substrates can be exposed to pre-treatment steps that polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure, and / or bake the substrate surface. In addition to performing film treatments directly on the surface of the substrate itself, the present invention also allows any of the disclosed film treatment steps to be performed on underlying layers formed on the substrate, as disclosed in detail below, and the term "substrate surface" is intended to include such underlying layers as indicated by the context. Thus, for example, if a film / layer or partial film / layer is being deposited on a substrate surface, the exposed surface of the newly deposited film / layer becomes the substrate surface.

[0013] One or more embodiments of the present disclosure are directed to a method of depositing silicon nitride films by using a novel silicon-nitrogen precursor. The embodiments of the disclosure utilize various CVD methods. In some embodiments, a plasma enhanced chemical vapor deposition (PECVD) process is used. A PECVD process is similar to CVD processes well known in the art, where one or more reactants are provided as a plasma. Without wishing to be bound by theory, a PECVD process uses radicals present in the plasma reactants to facilitate reactions that are not available through conventional thermal reactions. In some embodiments, a flowable chemical vapor deposition (FCVD) process is used. An FCVD process is similar to CVD processes well known in the art, except that the material deposited is "flowable" and moves along the substrate surface to fill substrate features. The flowable material deposited in an FCVD process is typically cured to solidify the flowable material into a hardened film that can no longer move along the substrate surface.

[0014] In some embodiments, the film deposition process includes exposing the substrate to a silicon-nitrogen precursor and an NH3 plasma to deposit a flowable SiN polymer, which is cured to form a hardened SiN film.

[0015] FIG. 1 is a cross-sectional view of a substrate 100 having two features 110 (e.g., trenches or vias). The number of features in the drawing is provided for illustrative purposes only and should not be construed as limiting the scope of the present disclosure. Those skilled in the art will understand that there may be no features or any number of features. The shape of the features 110 may be any suitable shape, including but not limited to trenches and cylindrical vias. As used in this context, the term "feature" refers to an irregular shape of the intended surface having an aspect ratio of about 2:1 or greater. The aspect ratio of a feature is the ratio of the depth D of the feature to the width W of the feature. A feature with a relatively large aspect ratio will have a thinner / longer shape than a feature with a relatively small aspect ratio. In some embodiments, the features have an aspect ratio equal to or greater than 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 15:1, 20:1, 25:1, or 30:1. For purposes of this disclosure, a trench comprises a top and two sidewalls extending from a surface to a bottom. As shown, each of the sidewalls may be substantially perpendicular to the bottom, or may be sloped at an angle other than 90° to the bottom such that the opening at the surface is larger than the opening at the bottom of the feature.

[0016] 1, the substrate 100 may be composed of two materials: a first material 120 and a second material 130. In some embodiments, the first material 120 and the second material 130 are the same such that the feature 110 is bonded at the sides and bottom by the same material. In some embodiments, the first material 120 and the second material 130 are different such that the bottom 115 of the feature is of a different material than the sidewalls 111, 112 of the feature 110.

[0017] The feature 110 extends into the substrate 100 over a distance D from the substrate surface 125 to a bottom 115. The feature 110 has a first sidewall 111 and a second sidewall 112 that define a width W of the feature 110. The open area formed by the sidewalls and the bottom is also referred to as a gap. The material that fills the gap is referred to as a gap fill.

[0018] 2A and 2B, one or more embodiments of the present disclosure are directed to a film deposition method utilizing a silicon-nitrogen precursor and a plasma (e.g., ammonia). In some embodiments, the silicon-nitrogen precursor and the plasma reactant are flowed simultaneously into the process chamber. The silicon-nitrogen precursor and the plasma can be mixed in the process chamber or prior to entering the process chamber. In some embodiments, the reactants are flowed sequentially into the process chamber to avoid gas-phase mixing of the precursor and the plasma reactant.

[0019] In some embodiments, the silicon-nitrogen precursor comprises a compound having the general formula (I): TIFF2025004005000005.tif33170, wherein the R substituents (R1-R5) are each independently selected from H or C1-C4 alkyl. For purposes of this disclosure, C1-C4 alkyl means any group having 1-4 carbon atoms. Examples of C1-C4 alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and t-butyl groups. In some embodiments, all of the R groups are the same. In some embodiments, at least one of the R substituents is a methyl group. In some embodiments, at least one of the R groups is not a hydrogen atom. In some embodiments, at least one of the R groups includes an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a t-butyl group.

[0020] In some embodiments, the silicon-nitrogen precursor consists essentially of a compound of formula (I), where R1-R5 are each independently H or C1-C4 alkyl. As used herein, the term "consists essentially of" means that the reactive species in the silicon-nitrogen precursor is about 95% or more of the desired species by weight. In some embodiments, the silicon-nitrogen precursor consists essentially of one or more of the following: Includes TIFF2025004005000006.tif64170.

[0021] In some embodiments, the silicon-nitrogen precursor comprises a compound having the general formula (II): TIFF2025004005000007.tif36170 wherein the R substituents (R1-R5) are each independently selected from H or C1-C4 alkyl. Examples of C1-C4 alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and t-butyl groups. In some embodiments, all of the R groups are the same. In some embodiments, at least one of the R substituents is a methyl group. In some embodiments, at least one of the R groups is not a hydrogen atom. In some embodiments, at least one of the R groups comprises an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a t-butyl group.

[0022] In some embodiments, the silicon-nitrogen precursor consists essentially of a compound of formula (II), where R1-R5 are each independently H or C1-C4 alkyl. In some embodiments, the silicon-nitrogen precursor consists essentially of one or more of the following: Includes TIFF2025004005000008.tif71170.

[0023] In some embodiments, the silicon-nitrogen precursor comprises a compound having the general formula (III): TIFF2025004005000009.tif24170 wherein the R substituents (R1-R2) are each independently selected from H or C1-C4 alkyl. Examples of C1-C4 alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and t-butyl groups. In some embodiments, all of the R groups are the same. In some embodiments, at least one of the R substituents is a methyl group. In some embodiments, at least one of the R groups is not a hydrogen atom. In some embodiments, at least one of the R groups comprises an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, or a t-butyl group.

[0024] In some embodiments, the silicon-nitrogen precursor consists essentially of a compound of formula (III), where R1-R2 are independently H or C1-C4 alkyl. In some embodiments, the silicon-nitrogen precursor consists essentially of one or more of the following: Includes TIFF2025004005000010.tif22170.

[0025] The silicon-nitrogen precursor can be delivered in one or more pulses or continuously. The flow rate of the precursor can be any suitable flow rate, including, but not limited to, flow rates in the range of about 1 to about 1000 sccm, or about 2 to about 500 sccm, or about 3 to about 200 sccm, or about 5 to about 100 sccm, or about 10 to about 50 sccm, or about 15 to 25 sccm. In some embodiments, the flow rate of the precursor is about 50 sccm or less, 45 sccm or less, 40 sccm or less, 35 sccm or less, 30 sccm or less, 25 sccm or less, 20 sccm or less, or 15 sccm or less. The precursors can be delivered at any suitable pressure, including, but not limited to, pressures in the range of about 5 mTorr to about 25 Torr, or about 100 mTorr to about 20 Torr, or about 5 Torr to about 20 Torr, or about 50 mTorr to about 2000 mTorr, or about 100 mTorr to about 1000 mTorr, or about 200 mTorr to about 500 mTorr.

[0026] As used herein, "pulse" or "dose" is intended to refer to an amount of a reactant that is intermittently or non-continuously introduced into a process chamber. The amount of a particular compound in each pulse may vary over time depending on the duration of the pulse. Any particular reactant may include one compound or a mixture / combination of two or more compounds.

[0027] The duration of each pulse / dose is variable and can be adjusted, for example, to the volume of the process chamber and the capabilities of the vacuum system connected to that process chamber. Furthermore, the reactant dose time can be varied depending on the reactant flow rate, the reactant temperature, the type of control valve, the type of process chamber used, and the nature of the reactant components that react to form the appropriate film. The dose time can also be varied depending on the type of film to be formed and the geometry of the substrate. The dose time should be long enough to allow a sufficient volume of reactant to adsorb / chemisorb substantially over the entire surface of the substrate to form a layer of reactive species on the substrate.

[0028] In some embodiments, the reactants include an inert, dilution, and / or carrier gas. The inert, dilution, and / or carrier gas can be mixed with the reactants and can be pulsed or in a constant flow. In some embodiments, the carrier gas is flowed into the process chamber at a constant flow in the range of about 1 to about 20,000 sccm. The carrier gas can be any gas that does not interfere with the film deposition. The carrier gas can include, for example, one or more of argon, helium, hydrogen, nitrogen, neon, and the like, or combinations thereof. In one or more embodiments, the carrier gas is mixed with the reactants before flowing into the process chamber.

[0029] The ammonia plasma can be generated at any suitable location. The plasma can be generated or ignited within the processing chamber (e.g., direct plasma techniques) or can be generated outside the processing chamber and flowed into the processing chamber (e.g., remote plasma techniques). In some embodiments, the plasma is generated outside the processing chamber, for example, by a remote plasma source. In some embodiments, the remote plasma can be generated upstream of the deposition chamber such that reactive species are in direct contact with the deposited film.

[0030] The plasma is described in the context of an ammonia plasma. However, one skilled in the art will appreciate that the plasma may have reactive species other than ammonia. The plasma may include, for example, nitrogen or hydrazine. The ammonia plasma may be generated by any suitable plasma generation process or technique known to those skilled in the art. The plasma may be generated, for example, by one or more microwave (MW) generators or radio frequency (RF) generators. The plasma frequency may be adjusted depending on the particular reactive species used. Suitable frequencies include, but are not limited to, 2 MHz, 13.56 MHz, 40 MHz, 60 MHz, and 100 MHz.

[0031] In some embodiments, the NH3 plasma is generated by a remote plasma source. In some embodiments, the plasma power is about 300 W or less. In one or more embodiments, the plasma power is about 250 W or less, 200 W or less, 150 W or less, 100 W or less, 50 W or less, or 25 W or less. In some embodiments, the plasma power is in the range of about 10 W to about 200 W, or in the range of about 25 W to about 175 W, or in the range of about 50 W to about 150 W.

[0032] In some embodiments, a plasma is generated in a remote plasma source and flowed into a processing region of the processing chamber such that radicals present in the plasma can react with the silicon-nitrogen precursor, or with the substrate, or with a film on the substrate. In some embodiments, the remote plasma is configured such that there are more radicals than ions in the processing region of the processing chamber.

[0033] In some embodiments, the NH3 radicals are generated by a hot wire instead of or in addition to a plasma source. As used herein and in the appended claims, the term "hot wire" refers to any element that can be heated to a temperature sufficient to generate radicals in a fluid flowing across the element. In some embodiments, the hot wire is one or more metal filaments (e.g., tungsten). In some embodiments, the hot wire is one or more tungsten, tantalum, or ruthenium-containing filaments. In some embodiments, the filament temperature is maintained in the range of about 200°C to about 1500°C, or in the range of about 1000°C to about 1500°C, or in the range of about 1100°C to about 1400°C. In some embodiments, the filament temperature is maintained at a temperature less than about 1500°C, less than 1400°C, less than 1300°C, or less than 1200°C. In some embodiments using a hot wire to generate radical species, the substrate is kept at a low temperature (i.e., about 25°C or less).

[0034] During deposition, the temperature of the substrate 100 can be controlled. In some embodiments, the substrate 100 is cooled to a temperature of about 25° C. or less. Such cooling can be achieved by any suitable means, including, but not limited to, varying the temperature of the substrate support or flowing a cooled gas over the substrate surface. In some embodiments, the substrate support includes a controllable cooling device to conductively vary the substrate temperature. In one or more embodiments, the gases used, including reactant and / or carrier gases, are cooled to locally vary the substrate temperature. In some embodiments, a cooling device is located inside the chamber adjacent to the substrate surface to conductively vary the substrate temperature.

[0035] With reference to Figure 2A, the substrate 100 is exposed to silicon-nitrogen precursors and reactants to form a flowable film 210 on the substrate. Although the flowable film 210 is depicted in Figure 2A only within features, one of ordinary skill in the art will appreciate that this is merely an illustrative example.

[0036] The flowable film 210 can be deposited on a substrate maintained at any suitable temperature. In some embodiments, the substrate is maintained at a temperature in the range of about -100°C to about 25°C, or in the range of about -75°C to about 20°C, or in the range of about -50°C to about 10°C, or in the range of about -25°C to about 0°C. Without wishing to be bound by theory, the temperature is kept low to promote polymerization of the silicon nitrogen precursor. In some embodiments, the substrate is maintained at a temperature below about 25°C, below 20°C, below 15°C, below 10°C, below 5°C, below 0°C, below -10°C, below -20°C, below -30°C, below -40°C, below -50°C, below -60°C, below -70°C, below -80°C, or below -90°C.

[0037] Flowable film 210 can be formed at any suitable pressure. In some embodiments, the pressure used to form flowable film 210 is in the range of about 0.5T (Torr) to about 50T, or in the range of about 0.75T to about 25T, or in the range of about 1T to about 10T, or in the range of about 2T to about 8T, or in the range of about 3T to about 6T.

[0038] Referring to FIG. 2B, after deposition, the flowable film 210 is cured to form a hardened film 220. The flowable film 210 may be cured by any suitable means. In some embodiments, the flowable film 210 is cured by exposing it to radicals in a plasma or from a thermal radiation. In some embodiments, the flowable film 210 is cured by exposing it to ultraviolet (UV) light. In some embodiments, the flowable film 210 is cured without the use of ultraviolet (UV) light. In some embodiments, the flowable film 210 is cured substantially only by exposure to radicals. As used herein and in the appended claims, the term "cured substantially only by exposure to radicals" means that about 90% or more, 95% or more, 98% or more, or 99% or more of the flowable film 210 is cured by radicals.

[0039] In some embodiments, the cured film is subjected to a post-deposition treatment process, which in some embodiments includes at least one process for polishing, etching, reducing, oxidizing, hydroxylating, annealing, UV curing, e-beam curing, or baking the substrate surface or the deposited film.

[0040] Referring to FIG. 2B, a cured film 220 is formed on the substrate 100. Within the gap, a partial film of gap fill is formed along the sidewalls 111, 112 and bottom 115. As this film forms, a seam may form if the top of the gap closes before the bottom is filled with the gap fill material. Seam formation is more likely in features with higher aspect ratios because the film at the top of the feature tends to pinch close, causing a void to become enclosed within the deposited gap fill. As used in this context, the term "seam" means any space or void between the sidewalls 111 and 112, where the volume of the void volume is greater than 1% of the volume of the gap or other feature. In some embodiments, the deposited and cured SiN film is substantially seam-free.

[0041] The cured films for the disclosed embodiments have a relatively high ratio of nitrogen atoms to silicon atoms. In some embodiments, the cured SiN film has a ratio of nitrogen atoms to silicon atoms of about 0.7 or more, 0.8 or more, 0.9 or more, or 1.0 or more. In some embodiments, the cured SiN film has a ratio of nitrogen atoms to silicon atoms ranging from a lower limit of about 1.0, 1.1, 1.2, or 1.33 to an upper limit of about 1.33, 1.4, or 1.5. In some embodiments, the cured SiN film is substantially free of carbon atoms. As used in this context, the term "substantially free of carbon atoms" means that carbon atoms are about 5% or less, 2% or less, or 1% or less in the cured film on an atomic basis.

[0042] Throughout this specification, references to "one embodiment," "an embodiment," "one or more embodiments," or "embodiments" mean that a particular feature, structure, material, or characteristic described in connection with an embodiment is included in at least one embodiment disclosed. Thus, the appearance of phrases such as "in one or more embodiments," "in an embodiment," "in an embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the disclosure. Furthermore, particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0043] Although the present disclosure has been described with reference to specific embodiments, those skilled in the art will understand that the described embodiments are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope of the present disclosure. Thus, the present disclosure includes modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. 1. A method for depositing a SiN film, the method comprising: The substrate was treated with a silicon-nitrogen precursor and NH ３ exposing to a plasma to deposit a flowable SiN polymer; and curing the flowable SiN polymer to form a hardened SiN film. Including, The silicon-nitrogen precursor is one or more of the following: [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl. [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl; or [In the formula, R １ ~R ２ are independently H or C1-C4 alkyl. A method comprising:

2. The method of claim 1 , wherein at least one R group in the silicon-nitrogen precursor is a methyl group.

3. The silicon-nitrogen precursor is one or more of the following: The method of claim 1 , comprising:

4. The silicon-nitrogen precursor is [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl. The method of claim 1 , consisting essentially of

5. The silicon-nitrogen precursor is one or more of the following: The method of claim 4 , comprising:

6. The silicon-nitrogen precursor is [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl. The method of claim 1 , consisting essentially of

7. The silicon-nitrogen precursor is one or more of the following: The method of claim 6, comprising:

8. The silicon-nitrogen precursor is [In the formula, R １ ~R ２ are independently H or C1-C4 alkyl. The method of claim 1 , consisting essentially of

9. The silicon-nitrogen precursor is one or more of the following: The method of claim 8 , comprising:

10. 10. The method of claim 1, wherein the plasma is generated by a remote plasma source.

11. 10. The method of claim 1, wherein the flowable SiN polymer is cured by exposure to radicals in a plasma.

12. 10. The method of claim 1 further comprising a post-treatment comprising UV exposure or annealing.

13. 10. The method of claim 1, wherein the hardened SiN film has a nitrogen atomic to silicon atomic ratio of about 0.7 or greater.

14. 10. The method of any one of claims 1 to 9, wherein the substrate is maintained at a temperature of about 25°C or less.

15. The substrate was treated with a silicon-nitrogen precursor and NH ３ A cured SiN film formed without UV curing by exposure to a plasma at a temperature of about 25° C. or less, wherein the ratio of nitrogen atoms to silicon atoms in the cured SiN film ranges from about 1.0 to about 1.5, and the silicon-nitrogen precursor is one or more of the following: [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl. [In the formula, R １ ~R ５ are independently H or C1-C4 alkyl; or [In the formula, R １ ~R ２ are independently H or C1-C4 alkyl. A hardened SiN film comprising:

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