Deposition method using high aspect ratio structures of inhibitor molecules

Abstract

A deposition method for improving thickness control of a film deposited on a high aspect ratio (HAR) hole in a substrate is disclosed. The method comprises: i) exposing the substrate sequentially or simultaneously to a vapor of an inhibitor, a vapor of a precursor, and a vapor of a co-reactant; and ii) depositing a film having desired thickness control on the HAR hole by a vapor deposition process, wherein the inhibitor contains O, N, S, P, B, C, F, Cl, Br, or I.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of U.S. Application No. 17,072,882, filed October 16, 2020, which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] A deposition method for high aspect ratio structures using inhibitor molecules and precursors in semiconductor applications is disclosed. In particular, the disclosed method involves a vapor deposition process using organometallic precursors and inhibitor molecules containing O, N, S, P, B, C, F, Cl, Br, or I to improve thickness control in substrates, including step coverage and gap filling. Background Technology

[0004] As devices in semiconductors scale down, precise thickness control becomes a critical challenge. In some respects, atomic layer deposition (ALD) may be superior to chemical vapor deposition (CVD) because the growth per cycle (GPC) of ALD is much lower than the growth rate per unit time of CVD, making it relatively easy to achieve the desired thickness. This is limited by layer-by-layer deposition, resulting in a very pronounced linear relationship between thickness and the number of ALD cycles. However, even in ALD, GPC is highly dependent on the type of precursor, process type, and the material being deposited. To date, no universal or easy way has been reported to control the deposition rate or thickness in a given process while maintaining ALD behavior. To reduce GPC in ALD, small amounts of precursors or co-reactants can be applied to induce a sub-ALD state, but this results in a very unstable process due to the lack of precursors, as GPC can vary significantly depending on the process temperature.

[0005] As device dimensions in semiconductors continue to shrink proportionally, step coverage is a critical factor in the integration of high aspect ratio (HAR) structures. For example, narrow, deep trenches are formed in a semiconductor substrate, and gaps are filled with an insulating material to form an insulating film deposited sequentially from the bottom surface of the trench, ensuring complete trench coverage. Deposition on the HAR step surface faces the challenge of uneven gap filling, which can result in poor step coverage and may contain voids and / or weak points.

[0006] As device dimensions in semiconductors continue to shrink proportionally, vapor deposition (ALD) has become one of the most important techniques for depositing thin films of new materials. ALD, in particular, has become a key enabling factor for highly conformal deposition and gap filling. A major challenge in gap filling is sealing two layers so that there are no empty spaces between them, known as voids or seams (which are narrow openings during the deposition process). Filling gaps in high aspect ratio structures or complex 3D structures is often even more challenging.

[0007] Various attempts have been made to improve thickness control, step coverage, and gap filling.

[0008] US 20070141779 by Abelson et al. discloses a method for coating and filling high aspect ratio (HAR) recessed features and for coating and / or uniformly filling structures with continuous, conformal or superconformal layers, wherein a bottom-up CrB2 film is deposited on a trench substrate using conventional chemical vapor deposition (CVD) methods with the aid of hydrogen plasma as a suppressor.

[0009] Henri et al.'s US 9564312 discloses silicon-containing films (e.g., SiN). x Selective inhibition in atomic layer deposition (ALD) of a film. This selective inhibition involves exposing an adsorbed layer containing a silicon precursor to a hydrogen-containing inhibitor, followed by exposure of the adsorbed layer to a second reactant. Exposure to the hydrogen-containing inhibitor can be performed using plasma.

[0010] Moon et al.’s US 10103026 and US 20170040172 disclose methods for forming material layers, and more specifically, methods for forming material layers that can stably manufacture material layers with good step coverage, regardless of variations in other process parameters.

[0011] Talukdar TK (PhD dissertation, University of Illinois at Urbana-Champaign, 2018) disclosed the use of CVD to coat and fill nanoscale structures, in which oxides are used to provide bottom-up trench filling via a superconformal CVD method.

[0012] Jin et al.’s KR 102095710 discloses a method for forming a thin film using a surface protective material to achieve good step coverage, the method comprising a surface protective material supply step for supplying the surface protective material to adsorb onto a substrate.

[0013] In the field of semiconductor processes, the development of processes with good step coverage has attracted attention, and the use of atomic layer deposition (ALD) processes has received particular attention. Summary of the Invention

[0014] A deposition method for improving thickness control of films deposited on high aspect ratio (HAR) holes in a substrate is disclosed, the method comprising:

[0015] i) Expose the substrate sequentially or simultaneously to the vapors of the inhibitor, the precursor, and the co-reactant; and

[0016] ii) Deposit a film with desired thickness control on the HAR pores by a vapor deposition process, wherein the inhibitor contains O, N, S, P, B, C, F, Cl, Br or I.

[0017] The disclosed deposition methods may include one or more of the following aspects:

[0018] Further, this includes maintaining the substrate temperature within a range from room temperature to 650°C;

[0019] • Inhibitors are selected from one or more of the following:

[0020] a) Oxygen-based aliphatic and aromatic inhibitors, including alcohols, glycols, ethers, epoxides, aldehydes, ketones, carboxylic acids, enols, esters, acid anhydrides, phenols, and substituted phenols.

[0021] b) Nitrogen-based aliphatic and aromatic inhibitors, including amines, imines, imides, amides, azides, cyanates, nitriles, nitrates, nitrites, and nitrogen-containing heterocyclic compounds;

[0022] c) Sulfur-based aliphatic and aromatic inhibitors, including thiols, sulfides, disulfides, sulfoxides, sulfones, thiocyanates, isothiocyanates, and thioesters.

[0023] d) Phosphorus-based aliphatic and aromatic inhibitors, including phosphine, phosphonic acid, and phosphodiester;

[0024] e) Boron-based aliphatic and aromatic inhibitors, including boric acid, borate esters, and dialkylboronic esters; carbon-based aliphatic inhibitors, including alkanes, alkenes, alkynes, and benzene derivatives.

[0025] f) Halides containing organic molecules and inorganic halides, including I2; or

[0026] g) H2O vapor, H2 gas, CO gas, CS gas, and nitrogen oxides (NOx) x )gas;

[0027] Combinations of h) and a)-g);

[0028] • The inhibitor is produced in the form of a vapor or gas of the inhibitor in the presence or absence of plasma, within a temperature range from room temperature to approximately 650°C.

[0029] The inhibitor is selected from tetrahydrofuran (THF), dimethoxyethane (DME), triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA), or tris(2-aminoethyl)amine;

[0030] The inhibitor is THF;

[0031] The inhibitor is DME;

[0032] The inhibitor is a TEA;

[0033] Tetramethylethylenediamine (TMEDA);

[0034] • Dimethylethylenediamine (DMEDA);

[0035] Tris(2-aminoethyl)amine;

[0036] • The precursor is an organometallic precursor selected from alkylamino and cyclopendadiendyl derivatives of transition metals and main group elements, which contain homogamic or heterogamic ligands selected from alkylamines, alkoxy groups, amidinates, or halides;

[0037] These transition metals and main group elements are selected from Hf, Zr, Nb, Ti, lanthanides, rare earth elements, Al, or Si;

[0038] The precursor is ZrCp(NMe2)3;

[0039] The precursor is HfCp(NMe2)3;

[0040] The precursor is Nb(=NtBu)Cp(NMe2)2;

[0041] The precursor is TiCp*(OMe)3;

[0042] • Thickness control is step coverage control;

[0043] • Thickness control is gap filling control;

[0044] • The control of the thickness of hope is the coverage of the steps of hope;

[0045] • Desired thickness control is desired gap filling;

[0046] • Step coverage ≥ 100%;

[0047] • Step coverage is greater than step coverage without inhibitors;

[0048] • The membrane is a seamless gap filler for HAR pores;

[0049] • The interstitial filler is formed by bottom-up deposition;

[0050] • HAR ranges from 5:1 to 200:1;

[0051] • The substrate is patterned or a 3D structure;

[0052] • A hole is a cavity, via, trench, gap, or opening formed in the substrate by previous manufacturing steps;

[0053] • The films deposited on the HAR structure are metal films, metal oxide films, silicon-containing films, alloys, etc.

[0054] The film deposited on the HAR structure is ZrO2;

[0055] The film deposited on the HAR structure is HfO2;

[0056] The film deposited on the HAR structure is Nb2O5;

[0057] The film deposited on the HAR structure is TiO2;

[0058] • The vapor deposition process is ALD, CVD, or a combination thereof;

[0059] • Vapor deposition processes include space ALD, thermal ALD, plasma-enhanced ALD, and plasma-enhanced CVD;

[0060] • Vapor deposition is a space-based ALD process;

[0061] • Vapor deposition is a thermal ALD process;

[0062] • Vapor deposition is a plasma-enhanced ALD process;

[0063] • Vapor deposition is a plasma-enhanced CVD process;

[0064] • The co-reactants are O3, O2, H2O, H2O2, D2O, alcohol, NH3, N2, N2H2, H2, or free radicals generated by plasma;

[0065] • The co-reactant is O3 or O3 free radicals generated through plasma;

[0066] The sequence of substrate exposure to inhibitors, precursors, and co-reactants includes:

[0067] i) Sequential exposure to the inhibitor, the precursor, and the co-reactant;

[0068] ii) Sequential exposure to the precursor, the inhibitor, and the co-reactant;

[0069] iii) Sequential exposure to the precursor, the co-reactant, and the inhibitor; or

[0070] iv) Simultaneous exposure to the inhibitor and the precursor, followed by exposure to the co-reactant;

[0071] • The substrate is exposed to the inhibitor, precursor, and co-reactant in the following order: inhibitor, precursor, and co-reactant.

[0072] • The order in which the substrate is exposed to the inhibitor, precursor, and co-reactant is, in the order of precursor, inhibitor, and co-reactant;

[0073] • The order in which the substrate is exposed to the inhibitor, precursor, and co-reactant is, in the order of precursor, co-reactant, and inhibitor.

[0074] The substrate is exposed to the inhibitor, precursor, and co-reactant in the following order: simultaneous exposure to the inhibitor and precursor, followed by exposure to the co-reactant; and

[0075] Further including

[0076] After each exposure, purge with purge gas to remove excess inhibitors, excess precursors, and excess co-reactants, or one or more of these.

[0077] The purging gas is an inert gas selected from N2, Ar, Kr, or a combination thereof;

[0078] • The membrane growth rate decreases continuously with the increase of precursor addition time;

[0079] • The membrane growth rate continuously decreases relative to the amount of precursor;

[0080] • The growth rate of this membrane is reduced compared to the growth rate of a membrane without inhibitors;

[0081] • Compared to the growth rate without inhibitors, the growth rate of this membrane decreased relative to the amount of precursor.

[0082] • The precursor, inhibitor, or both are plasma-activated; and

[0083] • The precursor, inhibitor, or both are not plasma activated.

[0084] A deposition method for improving thickness control of ZrO2, HfO2, Nb2O5, or TiO2 films deposited on pores in a substrate with an aspect ratio of about 5:1 to about 200:1 is also disclosed, the method comprising:

[0085] i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: tetrahydrofuran (THF), dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine;

[0086] ii) Expose the substrate to the vapor of a precursor selected from the group consisting of: ZrCp(NMe2)3, HfCp(NMe2)3, Nb(=NtBu)Cp(NMe2)2 and TiCp*(OMe)3;

[0087] iii) Exposing the substrate to the vapor of the co-reactant O3; and

[0088] iv) Repeat steps i) to iii) until the desired thickness of the ZrO2, HfO2, Nb2O5, or TiO2 film deposited on the pore is achieved by ALD process at temperatures ranging from room temperature to 650°C.

[0089] Among them, the step coverage of ZrO2, HfO2, Nb2O5 or TiO2 film is ≥100%;

[0090] The growth per cycle (GPC) of ZrO2, HfO2, Nb2O5 or TiO2 films decreases relative to the amount of precursor;

[0091] ZrO2, HfO2, Nb2O5, or TiO2 films are seamless gap fillers.

[0092] After each exposure, excess inhibitors, precursors, and co-reactants were removed by purging with N2.

[0093] A deposition method for improving thickness control of ZrO2 films deposited on pores in a substrate with an aspect ratio of about 5:1 to about 200:1 is also disclosed, the method comprising:

[0094] i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: tetrahydrofuran (THF), dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine;

[0095] ii) Expose the substrate to the vapor of a precursor selected from the group consisting of ZrCp(NMe2)3;

[0096] iii) Exposing the substrate to the vapor of the co-reactant O3; and

[0097] iv) Repeat steps i) to iii) until the desired thickness control of the ZrO2 film deposited on the pores is achieved by the ALD process at temperatures ranging from room temperature to 650°C.

[0098] The ZrO2 membrane has a step coverage of ≥100%;

[0099] The growth per cycle (GPC) of the ZrO2 membrane decreased relative to the amount of precursor.

[0100] The ZrO2 film is a seamless gap filler.

[0101] After each exposure, excess inhibitors, precursors, and co-reactants were removed by purging with N2.

[0102] A deposition method for improving thickness control of HfO2 films deposited on pores in a substrate with an aspect ratio of about 5:1 to about 200:1 is also disclosed, the method comprising:

[0103] i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: tetrahydrofuran (THF), dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine;

[0104] ii) Expose the substrate to the vapor of a precursor selected from the group consisting of HfCp(NMe2)3;

[0105] iii) Exposing the substrate to the vapor of the co-reactant O3; and

[0106] iv) Repeat steps i) to iii) until the desired thickness control of the HfO2 film deposited on the pores is achieved by the ALD process at temperatures ranging from room temperature to 650°C.

[0107] The HfO2 membrane has a step coverage of ≥100%;

[0108] The growth per cycle (GPC) of the HfO2 membrane decreases relative to the amount of precursor.

[0109] The HfO2 membrane is a seamless gap filler.

[0110] After each exposure, excess inhibitors, precursors, and co-reactants were removed by purging with N2.

[0111] A deposition method for improving thickness control of Nb₂O₅ films deposited on pores in a substrate with an aspect ratio of about 5:1 to about 200:1 is also disclosed, the method comprising:

[0112] i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: tetrahydrofuran (THF), dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine;

[0113] ii) Expose the substrate to the vapor of a precursor selected from the group consisting of Nb(=NtBu)Cp(NMe2)2;

[0114] iii) Exposing the substrate to the vapor of the co-reactant O3; and

[0115] iv) Repeat steps i) to iii) until the desired thickness control of the Nb2O5 film deposited on the pores is achieved by the ALD process at temperatures ranging from room temperature to 650°C.

[0116] The Nb2O5 membrane has a step coverage of ≥100%;

[0117] The growth per cycle (GPC) of the Nb2O5 membrane decreased relative to the amount of precursor.

[0118] The Nb2O5 membrane is a seamless gap filler.

[0119] After each exposure, excess inhibitors, precursors, and co-reactants were removed by purging with N2.

[0120] A deposition method for improving thickness control of TiO2 films deposited on pores in a substrate with an aspect ratio of about 5:1 to about 200:1 is also disclosed, the method comprising:

[0121] i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: tetrahydrofuran (THF), dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine;

[0122] ii) Expose the substrate to the vapor of a precursor selected from the group consisting of TiCp*(OMe)3;

[0123] iii) Exposing the substrate to the vapor of the co-reactant O3; and

[0124] iv) Repeat steps i) to iii) until the desired thickness of the TiO2 film deposited on the pores is achieved by the ALD process at temperatures ranging from room temperature to 650°C.

[0125] The TiO2 film has a step coverage of ≥100%;

[0126] The growth per cycle (GPC) of the TiO2 film decreased relative to the amount of precursor.

[0127] The TiO2 film is a seamless gap filler.

[0128] After each exposure, excess inhibitors, precursors, and co-reactants were removed by purging with N2.

[0129] Annotations and naming

[0130] The following detailed description and claims utilize many abbreviations, symbols, and terms commonly known in the art, and include:

[0131] As used in this article, the indefinite article “a or an” means one or more species.

[0132] As used herein, “about” or “around or approximately” in the text or claims means ±10% of the stated value.

[0133] As used herein, “room temperature” in the text or claims means from about 20°C to about 25°C.

[0134] As used in the disclosed embodiments, the term "independently" when used in the context of describing an R group should be understood to mean that the subject R group is chosen independently not only relative to other R groups with the same or different subscripts or superscripts, but also independently relative to any other kind of the same R group. For example, in the formula MR 1 x (NR 2 R 3 ) (4-x) In the case where x is 2 or 3, two or three R 1 Groups may (but need not) be identical to each other or with R 2 or R 3 The same. Furthermore, it should be understood that, unless otherwise specified, the values ​​of the R group are independent of each other when used in different formulas.

[0135] This article uses standard abbreviations of elements from the periodic table. It should be understood that elements may be referred to by these abbreviations (e.g., Si for silicon, N for nitrogen, O for oxygen, C for carbon, H for hydrogen, F for fluorine, etc.).

[0136] As used herein, the abbreviation “Me” refers to methyl; the abbreviation “Et” refers to ethyl; the abbreviation “Pr” refers to propyl (i.e., n-propyl or isopropyl); the abbreviation “iPr” refers to isopropyl; the abbreviation “Bu” refers to any butyl (n-butyl, isobutyl, tert-butyl, sec-butyl); the abbreviation “tBu” refers to tert-butyl; the abbreviation “sBu” refers to sec-butyl; the abbreviation “iBu” refers to isobutyl; and the abbreviation “Ph” refers to phenyl.

[0137] The term "substrate" refers to one or more materials on which processes are performed. A substrate can refer to a wafer having one or more materials on which processes are performed. A substrate can be any suitable wafer used in the manufacture of semiconductor, photovoltaic, flat panel, or LCD-TFT devices. A substrate can also have one or more different material layers deposited thereon from previous manufacturing steps. For example, a wafer can include silicon layers (e.g., crystalline, amorphous, porous, etc.), silicon-containing layers (e.g., SiO2, SiN, SiON, SiCOH, etc.), metal-containing layers (e.g., copper, cobalt, molybdenum, tungsten, platinum, palladium, nickel, ruthenium, gold, etc.), organic layers such as amorphous carbon, or photoresist, or combinations thereof. Furthermore, a substrate can be planar or patterned. The substrate may include an oxide layer used as a dielectric material (e.g., ZrO2-based materials, HfO2-based materials, TiO2-based materials, rare earth oxide-based materials, ternary oxide-based materials, etc.) in MEMS, 3D NAND, MIM, DRAM, or FeRam device applications, or a nitride-based film (e.g., TaN, TiN, NbN) used as an electrode. Those skilled in the art will recognize that the terms "film" or "layer" as used herein refer to a material of a certain thickness laid or spread on a surface, and that surface may be trenches or lines. Throughout this specification and claims, the wafer and any associated layers thereon are referred to as the substrate.

[0138] The term "wafer" or "patterned wafer" refers to a wafer having a stack of silicon-containing films on a substrate and a patterned hard mask layer on the formed stack of silicon-containing films for pattern etching. The term "wafer" or "patterned wafer" can also refer to a trench wafer with a certain aspect ratio.

[0139] The term "aspect ratio" refers to the ratio of the height of a groove (or hole) to the width of the groove (or the diameter of the hole).

[0140] It should be noted in this article that the terms “aperture,” “gap,” “via,” “hole,” “opening,” “trench,” and “structure” are used interchangeably to refer to openings formed in a semiconductor substrate.

[0141] It should be noted in this document that the terms "film" and "layer" are used interchangeably. It should be understood that a film can correspond to or be associated with a layer, and a layer can refer to the film. Furthermore, those skilled in the art will recognize that, as used herein, the terms "film" or "layer" refer to a material of a certain thickness deposited or spread on a surface, and that surface can range from as large as an entire wafer to as small as a trench or line. Additionally, the terms "film" or "layer" as used herein can also refer to interstitial filling, more specifically, interstitial filling formed by a bottom-up deposition process. In this document, "interstitial filling" refers to holes, vias, pores, openings, trenches, etc.

[0142] It should be noted in this document that the terms “deposition temperature,” “substrate temperature,” and “process temperature” are used interchangeably. It should be understood that substrate temperature may correspond to or be related to deposition temperature or process temperature, and deposition temperature or process temperature may refer to substrate temperature.

[0143] It should be noted in this document that when the precursor is in a gaseous state at room temperature and ambient pressure, the terms "precursor," "deposited compound," and "deposited gas" are used interchangeably. It should be understood that a precursor can correspond to, or be associated with, a deposited compound or deposited gas, and a deposited compound or deposited gas can refer to a precursor.

[0144] As used herein, the abbreviation “NAND” refers to a “Negated AND” or “Not AND” gate; the abbreviation “2D” refers to a 2D gate structure on a planar substrate; and the abbreviation “3D” refers to a 3D or vertical gate structure in which the gate structures are stacked in the vertical direction.

[0145] As used herein, the term "inhibitor" refers to modifiers, inhibitors, or promoters, encompassing the concept of inhibiting, suppressing, or promoting to improve step coverage. Inhibitors are additives or inserted chemicals during the vapor deposition process that are removed after film deposition. Inhibitors enhance the conformability of films deposited on HAR structures and / or help remove voids or weak points in gap-filling applications. The thickness of inhibitors on HAR structures can be a very thin layer, possibly a monolayer or thinner.

[0146] Please note that silicon-containing films, such as SiN and SiO, are listed throughout this specification and claims without mentioning their appropriate stoichiometry. Silicon-containing films may include pure silicon (Si) layers, such as crystalline Si, polycrystalline silicon (p-Si or polycrystalline Si), or amorphous silicon; silicon nitride (SiO2)... k N l ) layer; or silicon dioxide (Si) n O mA layer; or a mixture thereof, wherein k, I, m, and n range from 0.1 to 6 (inclusive of the endpoints). Preferably, silicon nitride is Si. k N l Where k and I each range from 0.5 to 1.5. More preferably, silicon nitride is Si3N4. In this document, SiN as described below can be used to represent Si-containing silicon. k N l The layer. Preferably, the silicon oxide is Si. n O m Where n ranges from 0.5 to 1.5 and m ranges from 1.5 to 3.5. More preferably, the silicon oxide is SiO2. In this document, SiO as described below can be used to represent Si-containing... n O m The silicon-containing film can also be a silicon oxide-based dielectric material, such as an organic-based or silicon oxide-based low-k dielectric material, such as Applied Materials, Inc.'s Black Diamond II or III materials (with the formula SiOCH). The silicon-containing film may also include Si... a O b N c , where a, b, and c range from 0.1 to 6. The silicon-containing film may also include dopants such as B, C, P, As, and / or Ge.

[0147] In this document, a range may be expressed as from about one specific value and / or to about another specific value. When such a range is expressed, it should be understood that another embodiment is from that one specific value and / or to that other specific value, together with all combinations within the range. Any and all ranges listed in the disclosed embodiments include their endpoints (i.e., x = 1 to 4 or x in the range from 1 to 4 includes x = 1, x = 4, and x = any value between them), regardless of whether the term "including endpoints" is used.

[0148] In this document, references to "an embodiment" or "embodiment" mean that a particular feature, structure, or characteristic described with respect to that embodiment may be included in at least one embodiment of the invention. The phrase "in an embodiment" appearing in different places in the specification does not necessarily refer to the same embodiment in all instances, and individual or alternative embodiments are not necessarily mutually exclusive with other embodiments. The foregoing also applies to the term "implementation".

[0149] As used herein, the term “exemplary” is used to mean serving as an instance, example, or illustration. Any aspect or design described herein as “exemplary” is not necessarily to be construed as superior to or advantageous to other aspects or designs. Rather, the use of the term “exemplary” is intended to present the concept in a concrete manner.

[0150] The term "comprising" in the claims is an open-ended transitional term that means the subsequently defined claim elements are a non-exclusive list, i.e., anything else can be additionally included and remain within the scope of "comprising". "Comprising" is defined herein as necessary to encompass the more restrictive transitional terms "substantially consists of" and "consisting of"; therefore, "comprising" can be replaced by "substantially consists of" or "consisting of" and remain within the clearly defined scope of "comprising".

[0151] Furthermore, the term "or" is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless otherwise stated or clear from the context, "X adopts A or B" is intended to mean any natural inclusive arrangement. That is, if X adopts A; X adopts B; or X adopts both A and B, then "X adopts A or B" is satisfied in any of the foregoing cases. Additionally, the article "a / an" as used in this application and the appended claims should generally be interpreted as meaning "one or more" unless otherwise stated or clearly indicated from the context to the singular form. Attached Figure Description

[0152] To further understand the nature and purpose of the present invention, reference should be made to the following detailed description in conjunction with the accompanying drawings, in which similar elements are given the same or similar reference numerals, and wherein:

[0153] Figure 1 This is a schematic diagram showing the stepped coverage of the difference in HAR holes;

[0154] Figure 2 This is a schematic diagram illustrating the inhibitory effect of the inhibitor according to the disclosed method on step coverage of HAR pores;

[0155] Figure 3a This is a schematic diagram showing perfect conformal step coverage of HAR holes at 100% film thickness ratio (bottom thickness / top thickness * 100%).

[0156] Figure 3b This is a schematic diagram showing the conformal step coverage of HAR holes with a film thickness ratio of >100%;

[0157] Figure 3c This is a schematic diagram illustrating a gap-filling process using bottom-up deposition;

[0158] Figure 3d This is a schematic diagram illustrating the interstitial filling material deposited from the bottom up;

[0159] Figure 4a This is an exemplary timeline of the sequence in which the inhibitor, precursor, and co-reactant are introduced according to the disclosed method;

[0160] Figure 4b This is another exemplary timeline of the sequence in which the inhibitor, precursor, and co-reactant are introduced according to the disclosed method;

[0161] Figure 4c This is another exemplary timeline of the sequence in which the inhibitor, precursor, and co-reactant are introduced according to the disclosed method;

[0162] Figure 4d This is another exemplary timeline of the sequence in which the inhibitor, precursor, and co-reactant are introduced according to the disclosed method;

[0163] Figure 5 This is a SEM image showing approximately 60% step coverage of a 20:1 aspect ratio well without inhibitor;

[0164] Figure 6 This is a SEM image showing approximately 100% step coverage of a 25:1 aspect ratio well containing the inhibitor dimethoxyethane (DME);

[0165] Figure 7 This is a SEM image showing approximately 100% step coverage of a 25:1 well containing the inhibitor triethylamine (TEA);

[0166] Figure 8 This is a SEM image showing approximately 100% step coverage of a pore with an aspect ratio of 20:1 containing the inhibitor tetrahydrofuran (THF);

[0167] Figure 9 The growth rate at 300℃ under saturated conditions decreases continuously with the duration of precursor addition.

[0168] Figure 10 This is a comparison of GPC with and without an inhibitor (DMEDA) under ALD saturation conditions;

[0169] Figure 11 It is a bottom-up growth process in an 11:1 aspect ratio structure at 300℃; and

[0170] Figure 12 It is a complete gap fill in a patterned structure with a 25:1 aspect ratio. Detailed Implementation

[0171] A high aspect ratio (HAR) structure deposition method using inhibitor molecules and precursors in semiconductor applications is disclosed. More specifically, the disclosed inhibitor deposition method involves a vapor phase deposition process using organometallic precursors and inhibitor molecules containing O, N, S, P, B, C, F, Cl, Br, or I to improve thickness control of the deposited film, such as step coverage and gap filling in the substrate. The disclosed inhibitor deposition method includes a vapor phase deposition process involving inhibitors to improve thickness control, step coverage, and gap filling. Furthermore, the disclosed inhibitor deposition method includes an ALD process involving inhibitors to improve thickness control, step coverage, and gap filling. The disclosed inhibitors include the concepts of deposition inhibition, suppression, or promotion to improve the thickness of the resulting deposited film (including step coverage and gap filling). More specifically, the disclosed inhibitor deposition method includes the selection of inhibitor molecules and inhibitor dosage to improve thickness control of the deposited film (e.g., step coverage, gap filling), thereby preventing overhang films, so-called "pinchoffs," in HAR structures, and preventing the formation of voids and / or weak points in the deposited film and / or gap filler. HAR structures include HAR holes, gaps, voids, vias, trenches, openings, etc., which are fabricated in a substrate by prior manufacturing processes. The substrate typically has one or more different material layers deposited thereon from the prior manufacturing process.

[0172] The disclosed deposition precursors may be organometallic precursors. More specifically, the disclosed precursors may include alkylamino and cyclopentadienyl derivatives of transition metals and main group elements, containing homogamic or heterogamic ligands selected from alkylamines, alkoxy groups, amido groups, or halides. Transition metals and main group elements may be Hf, Zr, Nb, Ti, lanthanides, rare earth elements, Al, Si, etc. The disclosed precursors are suitable for vapor deposition processes.

[0173] The disclosed depositional precursors include typical and well-known precursors used in vapor deposition, for example,

[0174] M(CpR 1 R 2 R 3 R 4 R 5 )(NR'2)3, where M = the fourth group element, R 1 R 2 R 3 R 4 and R 5 Each is independently H or a C1 to C6 straight-chain or branched alkyl group, and R' is a C1 to C4 straight-chain or branched alkyl group;

[0175] M(CpR 1 R2 R 3 R 4 R 5 (OR')3, where M = the element of group 4, R 1 R 2 R 3 R 4 and R 5 Each is independently H or a C1 to C6 straight-chain or branched alkyl group, and R' is a C1 to C4 straight-chain or branched alkyl group;

[0176] M(CpR 1 R 2 R 3 R 4 R 5 )X3, where M = the fourth group element, R 1 R 2 R 3 R 4 and R 5 Each is independently an H or a C1 to C6 straight-chain or branched alkyl group, X = halide;

[0177] M(=NtBu)(NR2)3, where M=a group 5 element and R=C1 to C6 alkyl;

[0178] M(=NtBu)(CpR 1 R 2 R 3 R 4 R 5 )(NR'2)3, where M = the fifth group element, R 1 R 2 R 3 R 4 and R 5 Each is independently H or a C1 to C6 straight-chain or branched alkyl group, and R' is a C1 to C4 straight-chain or branched alkyl group;

[0179] M(NR2)5, where M = a group 5 element and R = C1 to C6 alkyl;

[0180] AlR3, wherein R = C1 to C6 alkyl;

[0181] Ln(CpR 1 R 2 R 3 R 4 R 5 )3, where Ln = lanthanide elements, R 1 R 2 R 3 R 4 and R 5 Each is independently an H or a C1 to C6 straight-chain or branched alkyl group;

[0182] Ln(CpR 1 R 2 R 3 R 4 R 5 )2(R'-amd), where Ln = lanthanide elements, R 1 R 2 R 3 R 4 and R 5 Each is independently H or a C1 to C6 straight-chain or branched alkyl group, and R' is a C1 to C4 straight-chain or branched alkyl group;

[0183] Ln(CpR 1 R 2 R 3 R 4 R 5 )2(R'-fmd), where Ln = lanthanide element, R 1 R 2 R 3 R 4 and R 5 Each is independently H or a C1 to C6 straight-chain or branched alkyl group, and R' is a C1 to C4 straight-chain or branched alkyl group;

[0184] Ln(NR2)3, where Ln = lanthanide element and R = C1 to C6 alkyl;

[0185] (3,3-Dimethyl-1-butynedi)hexacarbonyldicobalt (CCTBA, CAS No.: 56792-69-9);

[0186] Ru(CpR 1 R 2 R 3 R 4 R 5 )2, where R 1 R 2 R 3 R 4 and R 5 Each is independently an H or a C1 to C6 straight-chain or branched alkyl group;

[0187] Ru(R-cyclohexadiene)(CO)3, wherein R = C1 to C6 alkyl;

[0188] The compound of oxygen and chlorine with molybdenum, MoO x Cl y Where x>0, y>0;

[0189] Organometallic molybdenum compounds; and

[0190] Other silicon-containing precursors.

[0191] Exemplary examples of the disclosed deposition precursors include organometallic precursors of alkylamino and cyclopentadienyl derivatives selected from transition metals and main group elements, which contain homogamic or heterogamic ligands selected from alkylamines, alkoxys, amidoyls, or halides, wherein the transition metals and main group elements are selected from Hf, Zr, Nb, Ti, lanthanides, rare earth elements, Al, or Si.

[0192] Exemplary examples of the disclosed deposition precursors include HfCp(NMe2)3, ZrCp(NMe2)3, NbCp(NMe2)3 and TiCp(NMe2)3.

[0193] The most important feature of the disclosed inhibitor deposition method is the selection of the inhibitor. The inhibitor should not react with the precursors used in the deposition process and should be physically adsorbed onto the surface of the HAR structure, but not too strongly (mild adsorption), so that the physically adsorbed inhibitor can subsequently be purged and removed by a subsequent purging step. Furthermore, to avoid any unnecessary reactions with incoming co-reactants, the inhibitor addition and subsequent purging steps should be separate from the precursor addition and purging steps. In the HAR structure, the inhibitor layer can form a vertical gradient adsorption along the pores, with high adsorption near the top inlet and low adsorption at the bottom depths (see [link to relevant documentation]). Figure 1 This may compete with the introduced precursor for active binding sites on the surface, resulting in improved and / or perfect step coverage, such as ≥100% step coverage. See [link to relevant documentation]. Figure 2 and Figure 3a as well as Figure 3b .

[0194] The disclosed inhibitors may contain O, N, S, P, B, C or halogen elements (e.g., F, Cl, Br, I).

[0195] The disclosed inhibitors include oxygen-based inhibitors, nitrogen-based inhibitors, sulfur-based inhibitors, phosphorus-based inhibitors, boron-based inhibitors, carbon-based inhibitors, halides containing organic molecules and inorganic halides, H2O vapor, H2 gas, CO gas, CS gas, and nitrogen oxides (NOx). x (Gas, and any free radical form of gas at room temperature or higher.)

[0196] The disclosed oxygen-based inhibitors include aliphatic and aromatic inhibitors, such as alcohols, glycols, ethers, epoxides, aldehydes, ketones, carboxylic acids, enols, esters, acid anhydrides, phenols, and substituted phenols. Exemplary examples of disclosed oxygen-based inhibitors include tetrahydrofuran (THF), dimethoxyethane (DME), diethyl ether, and dioxane.

[0197] The disclosed nitrogen-based inhibitors include aliphatic and aromatic inhibitors, such as amines, imines, imides, amides, azides, cyanates, nitriles, nitrates, nitrites, and nitrogen-containing heterocyclic compounds. Exemplary examples of disclosed nitrogen-based inhibitors include triethylamine (TEA), trimethylamine, dimethylethylenediamine (DMEDA), tetramethylethylenediamine (TMEDA), and NH3.

[0198] The disclosed sulfur-based inhibitors include aliphatic and aromatic inhibitors, such as thiols, sulfides, disulfides, sulfoxides, sulfones, thiocyanates, isothiocyanates, thioesters, etc. Exemplary examples of the disclosed sulfur-based inhibitors include H2S, Me2S, Et2S, Me2S-SMe2, and Et2S-SEt2.

[0199] The disclosed phosphorus-based inhibitors include aliphatic and aromatic inhibitors, such as phosphine, phosphonic acid, and phosphodiester. Exemplary examples of the disclosed phosphorus-based inhibitors include PH3, PMe3, and P(OMe)3.

[0200] The disclosed boron-based inhibitors include aliphatic and aromatic inhibitors, such as boric acid, borate esters, and dialkylboronic esters. Exemplary examples of disclosed boron-based inhibitors include BMe3, BEt3, borazine, B(OMe)3, and B(OEt)3.

[0201] The disclosed carbon-based inhibitors include aliphatic inhibitors, such as alkanes, alkenes, alkynes, and benzene derivatives. Exemplary examples of the disclosed carbon-based inhibitors include acetylene and alkenes.

[0202] The disclosed halides containing organic molecules and inorganic halides include I2.

[0203] The disclosed inhibitor can be a gaseous free radical form at room temperature. The disclosed inhibitor is any gaseous free radical form at temperatures ranging from room temperature to approximately 650°C; preferably, the disclosed inhibitor is a compound capable of interacting with surfaces having relatively high electronegativity or lone pairs of electrons. Examples include THF, DME, and TEA.

[0204] The disclosed precursors and inhibitors have a purity greater than 95% w / w (i.e., 95.0% w / w to 100.0% w / w), preferably greater than 98% w / w (i.e., 98.0% w / w to 100.0% w / w), and more preferably greater than 99% w / w (i.e., 99.0% w / w to 100.0% w / w). Those skilled in the art will recognize that purity can be determined by ¹H NMR and gas-liquid chromatography in conjunction with mass spectrometry. The disclosed precursors and inhibitors may contain organic, inorganic, and metal-containing impurities. The total amount of these impurities is preferably less than 5% w / w (i.e., 0.0% w / w to 5.0% w / w), preferably less than 2% w / w (i.e., 0.0% w / w to 2.0% w / w), and more preferably less than 1% w / w (i.e., 0.0% w / w to 1.0% w / w). The disclosed precursors and inhibitors can be obtained by recrystallization, sublimation, distillation, and / or by passing the gas or liquid through a suitable adsorbent (e.g., Molecular sieve purification.

[0205] The purification of the disclosed precursors and inhibitors may also result in metallic impurities at levels ranging from 0 ppbw to 1 ppmw, preferably 0-500 ppbw (parts per million by weight). These metallic impurities may include, but are not limited to, aluminum (Al), arsenic (As), barium (Ba), beryllium (Be), bismuth (Bi), cadmium (Cd), calcium (Ca), chromium (Cr), cobalt (Co), copper (Cu), gallium (Ga), germanium (Ge), hafnium (Hf), zirconium (Zr), iron (Fe), lead (Pb), lithium (Li), magnesium (Mg), manganese (Mn), tungsten (W), nickel (Ni), potassium (K), sodium (Na), strontium (Sr), thorium (Th), tin (Sn), titanium (Ti), uranium (U), zinc (Zn), etc.

[0206] In addition to the disclosed precursors and inhibitors, co-reactants may be used. Co-reactants may be O3, O2, H2O, H2O2, D2O, alcohols, NH3, N2, N2H2, H2, or their radicals. Preferably, the co-reactant is O3 or NH3. Preferably, the radical is any radical form of a gas generated by plasma and formed at room temperature or higher. For ALD processes not involving plasma, the radicals of the co-reactant may be formed prior to introducing the co-reactant into the reactor. Preferably, the co-reactant is in gaseous or vapor form. In the case of using liquid co-reactants, a vapor form of the co-reactant needs to be generated prior to introducing the co-reactant into the reactor. In some embodiments, the co-reactant and inhibitor may be the same molecule, such as ammonia. For example, ammonia may be used as a co-reactant for forming a SiNx film together with a metal-organic precursor, and then ammonia may be used as an inhibitor in a separate step of the deposition sequence.

[0207] The purity of the disclosed co-reactant is greater than 95% v / v (or by volume) (i.e., 95.0% v / v to 100.0% v / v), preferably greater than 98% v / v (i.e., 98.0% v / v to 100.0% v / v), and more preferably greater than 99% v / v (i.e., 99.0% v / v to 100.0% v / v). Those skilled in the art will recognize that purity can be determined by H NMR and gas-liquid chromatography in conjunction with mass spectrometry. The disclosed co-reactant may contain impurities of organic molecules. The total amount of these impurities is preferably less than 5% v / v (i.e., 0.0% v / v to 5.0% v / v), preferably less than 2% v / v (i.e., 0.0% v / v to 2.0% v / v), and more preferably less than 1% v / v (i.e., 0.0% v / v to 1.0% v / v). Purity can be determined by distillation and / or by passing the gas-liquid mixture through a suitable adsorbent (e.g., Molecular sieves are used to purify the disclosed co-reactants.

[0208] The disclosed inhibitor deposition method can be used with any deposition method known to those skilled in the art to deposit films and fill gaps on high aspect ratio structures. Examples of suitable vapor phase deposition methods include CVD and ALD. Exemplary CVD methods include thermal CVD, plasma-enhanced CVD (PECVD), pulsed CVD (PCVD), low-pressure CVD (LPCVD), subatmospheric pressure CVD (SACVD), atmospheric pressure CVD (APCVD), hot-wire CVD (HWCVD, also known as cat-CVD, where the hot filament acts as the energy source for the deposition process), radical-bonded CVD, and combinations thereof. Exemplary ALD methods include thermal ALD, plasma-enhanced ALD (PEALD), spatial ALD, hot-wire ALD (HWALD), radical-bonded ALD, and combinations thereof, and supercritical fluid deposition can also be used. The deposition method is preferably ALD, PE-ALD, or spatial ALD to provide suitable step coverage and film thickness control.

[0209] The film deposited on the HAR structure using the disclosed inhibitor deposition method can be a metal film, a metal oxide film, a silicon-containing film, an alloy, etc. Exemplary films deposited on the HAR structure are ZrO2 and HfO2.

[0210] For suitable vapor deposition methods, the disclosed precursors and inhibitors can be supplied in pure form or as blends with suitable solvents such as ethylbenzene, xylene, mesitylene, naphthane, decane, and dodecane. The disclosed precursors and inhibitors can be present in the solvent at different concentrations. The pure or blended precursors and pure or blended inhibitors can be introduced into the reactor separately in vapor form using conventional devices such as pipes and / or flow meters. Vapor form can be generated by vaporizing the pure or blended precursors and inhibitors via conventional vaporization steps (such as direct vaporization, distillation, bubbling, or by using a sublimator). The pure or blended precursors and inhibitors can be fed as liquid into a vaporizer before being introduced into the reactor, where they are vaporized. Alternatively, the pure or blended precursors and inhibitors can be vaporized by bubbling a carrier gas into the composition, which is then passed to a container containing the composition. The carrier gas can include, but is not limited to, Ar, He, N2, and mixtures thereof. Bubbling with a carrier gas can also remove any dissolved oxygen present in the pure or blended precursors and inhibitors. The carrier gas and precursors, as well as the carrier gas and inhibitors, are then introduced into the reactor as vapors, respectively. Similarly, if liquid co-reactants are used, the vapor form of the co-reactants will be generated in the same manner as the precursors and inhibitors.

[0211] If necessary, the container holding the disclosed precursor, inhibitor, and co-reactant may be heated to a temperature that allows the disclosed precursor, inhibitor, and co-reactant to be in their liquid phase and have sufficient vapor pressure. The container may be maintained at a temperature in the range of, for example, about 0°C to about 200°C. Those skilled in the art will recognize that the container temperature can be adjusted in known ways to control the amount of vaporized precursor.

[0212] The reactor or reaction chamber can be any enclosed chamber within an apparatus in which the deposition method is carried out, such as, but not limited to: parallel plate reactors, cold-wall reactors, hot-wall reactors, single-wafer reactors, multi-wafer reactors, and other types of deposition systems under conditions suitable for inducing the reaction of the compounds and the formation of a layer. Those skilled in the art will recognize that any of these reactors can be used for ALD or CVD deposition processes.

[0213] The reactor contains one or more substrates on which a film will be deposited. A substrate is generally defined as the material on which the process is performed. The substrate can be any suitable substrate used in the manufacture of semiconductor, photovoltaic, flat panel, and LCD-TFT devices. Examples of suitable substrates include wafers, such as silicon, silicon dioxide, glass, and GaAs wafers. The wafer can have one or more layers of different materials deposited thereon from previous manufacturing steps. For example, the wafer may include a dielectric layer. Furthermore, the wafer may include silicon layers (crystalline, amorphous, porous, etc.), silicon oxide layers, silicon nitride layers, silicon oxynitride layers, carbon-doped silicon oxide (SiCOH) layers, metals, metal oxides, metal nitride layers (Ti, Ru, Ta, etc.), and combinations thereof. Additionally, the wafer may include copper layers and noble metal layers (e.g., platinum, palladium, rhodium, gold). The wafer may include barrier layers, such as manganese, manganese oxide, etc. Plastic layers, such as poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) [PEDOT:PSS], may also be used. Layers can be planar or patterned. The patterned layer can be an alternating layer of two specific layers (such as In2O3 and ZrO2 used in 3D NAND). The wafer can have one or more holes formed therein from previous manufacturing steps. Holes can be vias, trenches, gaps, etc., formed in the wafer or substrate. The aspect ratio of the holes can range from about 5:1 to about 200:1. The disclosed method can deposit films directly on the holes of the wafer. Furthermore, those skilled in the art will recognize that the terms "film" and "layer" as used herein refer to a quantity of material placed or spread on a surface of a certain thickness, and that surface can be trenches or lines. Throughout the specification and claims, the wafer and any associated layers thereon are referred to as a substrate.

[0214] The temperature and pressure within the reactor or reaction chamber are maintained under conditions suitable for vapor deposition (such as ALD and CVD). In other words, after the vaporized precursor, inhibitor, and co-reactant are introduced into the reactor, the conditions within the reactor are such that at least a portion of the precursor is deposited onto the substrate to form a layer. For example, the pressure within the reactor or the deposition pressure may be maintained at approximately 10 °C, as required by the deposition parameters. -3 Between 100 and approximately 100, more preferably between 10 -2The reactor temperature is between approximately 100 and 100. The temperature of the reactor can be controlled by controlling the temperature of the substrate holder and the temperature of the reactor walls. Apparatus for heating the substrate is known in the art. The reactor walls are heated to a sufficient temperature to obtain the desired film at a sufficient growth rate and with the desired physical state and composition. Non-limiting exemplary temperature ranges to which the reactor walls can be heated include from room temperature to approximately 650°C. When using a plasma deposition process, the reactor temperature can be in the range of approximately 100°C to approximately 500°C. Alternatively, when performing a thermal process, the reactor temperature can be in the range of approximately 100°C to approximately 650°C.

[0215] Alternatively, the substrate can be heated to a sufficient temperature to obtain a desired film with a sufficient growth rate and a desired physical state and composition. Non-limiting exemplary temperature ranges to which the substrate can be heated include from room temperature to about 650°C. Furthermore, those skilled in the art will recognize that during the deposition process, the reactor temperature and the substrate temperature will reach an equilibrium temperature. Throughout the specification and claims, reactor temperature and substrate temperature refer to the deposition temperature. Therefore, the deposition temperature of the disclosed method is in the range from room temperature to about 650°C. When using a plasma deposition process, the deposition temperature can be in the range from about 100°C to about 500°C. Alternatively, when performing a thermal process, the deposition temperature can be in the range from about 100°C to about 650°C.

[0216] The disclosed precursors, inhibitors, and co-reactants can be introduced into the reactor simultaneously (CVD) or sequentially (ALD) in various supply sequences. The reactor can be purged with an inert gas (e.g., N2, Ar, Kr, Xe) between the introduction of the inhibitors, precursors, and co-reactants. Alternatively, the inhibitors, precursors, and co-reactants can be mixed together to form an inhibitor / precursor / co-reactant mixture, and then introduced into the reactor as a mixture. Alternatively, the inhibitor and precursor can be mixed together to form an inhibitor / precursor mixture, introduced into the reactor as a mixture, and then the co-reactant can be introduced into the reactor.

[0217] In the disclosed process, the substrate exposure time can range from 0.1 seconds to 30 minutes, preferably from 0.5 seconds to 10 minutes; the exposure time of the disclosed precursor can range from 0.1 seconds to 30 minutes, preferably from 0.5 seconds to 10 minutes; the exposure time of the disclosed inhibitor can range from 0.1 seconds to 30 minutes, preferably from 0.5 seconds to 10 minutes; and the exposure time of the co-reactant can range from 0.1 seconds to 30 minutes, preferably from 0.5 seconds to 10 minutes. In the disclosed process, the dose of the inhibitor can be greater than the dose of the precursor, and vice versa; the dose of the inhibitor can be greater than the dose of the co-reactant, and vice versa.

[0218] Alternatively, vaporized inhibitors, precursors, and co-reactants can be sprayed simultaneously from different parts of the spray head (without mixing of inhibitors, precursors, and co-reactants) while keeping the substrates of several wafers rotating under the spray head (space ALD).

[0219] Depending on the specific process parameters, deposition may proceed for varying durations. Typically, deposition can be allowed to continue for the desired length necessary to produce a film or interstitial filler with the required properties. Typical film thicknesses can range from a few angstroms to hundreds of micrometers, and typically vary from 2 to 100 nm, depending on the specific deposition process. Typical interstitial depths can range from hundreds of nanometers to hundreds of micrometers, and typically vary from 100 nm to 100 μm, depending on the specific deposition process. If necessary, the deposition process can also be performed multiple times (e.g., ALD cycles) to obtain a desired film with improved or perfect step coverage (e.g., ≥100%) and desired interstitial fill, without the formation of voids and / or weak points in the deposited film and interstitial filler. In some cases, although perfect step coverage (e.g., ≥100%) is not achieved, the disclosed inhibitor deposition method can improve step coverage and interstitial fill by adding inhibitors compared to the case without inhibitor application.

[0220] In a non-limiting exemplary ALD process for forming a metal oxide film, a three-step method can be performed. First, the vapor phase of a disclosed inhibitor (such as dimethoxyethane (DME)) is introduced into a reactor, where it is physically adsorbed onto the surface. Excess inhibitor can then be removed from the reactor by purging and / or venting the reactor, i.e., by purging the reactor with an inert gas (e.g., N2, Ar, Kr, Xe) or by passing the substrate through a section under high vacuum and / or a carrier gas curtain. Second, a precursor (such as ZrCp(NMe2)3 or HfCp(NMe2)3) is introduced into the reactor, where it is adsorbed (both chemisorbed and physisorbed) onto the substrate. Excess precursor can then be removed from the reactor by purging and / or venting the reactor with an inert gas. Third, a co-reactant (e.g., O3) is introduced into the reactor, where it reacts with the adsorbed precursor to deposit a film on the surface in a self-limiting manner and reacts with the physically adsorbed inhibitor to remove it from the surface. Subsequently, any excess co-reactant is removed from the reactor by purging and / or evacuating the reactor. If the desired membrane is an oxide (such as ZrO2), the three-step process—inhibitor-precursor-co-reactant—can be repeated until a membrane with the necessary thickness and desired step coverage is obtained, or the gaps are filled. Alternatively, the order in which the inhibitor, precursor, and co-reactant are introduced into the reactor in this three-step process can vary. For example, the three-step process could be precursor-inhibitor-co-reactant in sequence; inhibitor-precursor-co-reactant in sequence; precursor-co-reactant-inhibitor in sequence; inhibitor-co-reactant-precursor in sequence, with both inhibitor and precursor followed by co-reactant; and so on. This three-step process can provide the desired membrane thickness and conformability, as well as the desired gap filling.

[0221] In some embodiments, the disclosed method relates to a vapor deposition process, such as CVD or ALD, which employs the disclosed inhibitors to improve step coverage of the deposited film in the substrate.

[0222] Figure 1It is a schematic diagram showing the poor step coverage of HAR holes. There is a hole 104 in the substrate 102. A film 106 is deposited on the top and side walls of the hole 104 using a vapor deposition process such as ALD. In this case, the film 106 is mainly deposited on the top of the hole and no film is deposited on the bottom of the hole because the deposition precursor cannot reach the deep part of the hole during the deposition process. The hole 104 can be a hole, through-hole, trench, gap, opening, etc. formed in the substrate 102 from a previous manufacturing process. The aspect ratio of the hole 104 can range from about 5:1 to about 200:1. Without using an inhibitor, the film 106 deposited on the hole is non-conformal. Here, the step coverage is defined as b / a×100% (bottom thickness / top thickness×100%); the aspect ratio is defined as L / d. As shown, in this case without using an inhibitor, b < a, so the step coverage is less than 100%.

[0223] Figure 2 It is a schematic diagram showing the inhibitory effect of an inhibitor on the step coverage of HAR holes according to the disclosed method. The hole 204 can be a hole, through-hole, trench, gap, etc. formed in the substrate 202 from a previous manufacturing process. The aspect ratio of the hole 204 can range from about 5:1 to about 200:1. An inhibitor adsorption layer (not shown) can form a physically adsorbed vertical gradient along the hole, with high adsorption near the top entrance of the hole and low adsorption deep in the bottom. Due to the inhibitor being physically adsorbed on it (not shown), the incoming deposition precursor may be able to reach the deeper part of the hole and adsorb on it. The deposition precursor adsorption includes physical adsorption and chemical adsorption. The inhibitor adsorption layer may compete with the incoming deposition precursor for the active binding sites on the hole surface, causing the deposition precursor to adsorb in the deep part of the hole. The concentration of the precursor in the bottom of the hole 204 is higher than the concentration of the precursor in the top of the hole 204. The incoming co-reactant reacts with the adsorbed precursor to form a film 206 from the deep part of the hole. This cycle is repeated more times, and the film 206 grows from the deep part of the hole 204 towards the top entrance of the hole 204 and gradually reaches the top entrance of the hole. Finally, a film 206 with a desired thickness and perfect step coverage is formed, as Figure 3a (a schematic diagram showing 100% (b = a) step coverage of a HAR hole with a conformal film) and Figure 3b(A schematic diagram showing >100% (b>a) step coverage of a HAR pore with a superconducting film is shown.) As illustrated, pore 304 can be a hole, via, trench, gap, etc., formed in substrate 302 by a previous fabrication process. The incoming co-reactant reacts with the adsorbed precursor, forming film 306 from the depth of the pore. This cycle is repeated many times, and film 306 grows from the depth of pore 304 toward the top of pore 304 and gradually reaches the top entrance of the pore. Here, before exposing the pore to the deposition precursor, a purging step is performed using an inert gas (e.g., N2, Ar, Kr, etc.) to remove excess inhibitor. Before exposing the pore to the co-reactant, a purging step is performed to remove excess deposition precursor. For the next cycle, a purging step is performed before exposing the pore to the inhibitor to remove excess co-reactant. In this way, the disclosed inhibitor deposition method can produce perfect conformal step coverage and super-conformal step coverage, i.e., step coverage with ≥100% film thickness on pores having an aspect ratio ranging from about 5:1 to about 200:1.

[0224] This cycle continues, even more times, with membrane 306 growing from the deep bottom of pore 304 to the top of pore 304, and gradually filling pore 304 from the bottom, as... Figure 3c As shown, pore 304 has been filled to the middle. Continuing to repeat the cycle even more times, membrane 306 continues to grow towards the top of pore 304 and gradually fills pore 304, as... Figure 3d As shown, hole 304 has been filled to the top and is completely filled. The cycle can stop when hole 304 is completely filled.

[0225] Figures 4a to 4d These are different exemplary timelines of the methods and sequences for supplying inhibitors, precursors, and co-reactants according to the disclosed inhibitor deposition method, wherein each feed (i.e., inhibitor, precursor, and co-reactant) can be pulsed. The flow rate and supply time of the respective feeds may be... Figures 4a to 4c The pulse height and width shown are not proportional.

[0226] Figure 4a This refers to a three-step deposition process in the order of inhibitor-precursor-co-reactant. Although the formation of a metal oxide film was described above, this article provides a more detailed explanation. When the inhibitor is introduced into the reactor, it can be physically adsorbed onto the surface of the substrate within the reactor. The reactor can then be purged with a purge gas to remove excess inhibitor, leaving the physically adsorbed inhibitor as a very thin layer (possibly a monolayer or thinner).

[0227] Next, a precursor is added. The precursor can be physically and chemically adsorbed onto the surface of the pores in the substrate, while the chemical adsorption of the precursor on the substrate is controlled by an inhibitor layer for physical adsorption. Since a large portion of the pore surface is covered by inhibitors, the precursor can be physically adsorbed onto the surface by the inhibitors. When the reactor is purged again with a purge gas, excess precursor is removed, and an adsorbed layer can be obtained by adsorbing the precursor onto the surface. The adsorbed layer can be at a very thin level, which can be a monolayer or thinner. More specifically, in this way, over-adsorption of the precursor can be fairly controlled at the inlet and top of the pore. The precursor can reach the depths of the pore.

[0228] Next, a co-reactant is introduced. The co-reactant can react with the adsorbed precursor to form a film, and react with the co-reactant to remove it. Then, excess co-reactant and reaction byproducts can be removed from the reactor by purging.

[0229] Figure 4b This refers to a three-step deposition method following the sequence of precursor-inhibitor-co-reactant. First, the precursor is introduced into the reactor. The precursor can adsorb onto the surface of the substrate. In this case, a significant amount of the precursor can be directly chemisorbed onto the surface of the pores in the substrate, while additional precursors can be physically adsorbed onto the surface by the chemisorbed precursor. Subsequently, by purging, the physically adsorbed precursors on the substrate can be partially removed, while some of the physically adsorbed precursors remain on the chemisorbed precursors. Since the physically adsorbed precursors are the source material for excess adsorption, it may be necessary to remove them to form a conformal film. Therefore, an inhibitor is added in the next step. Due to van der Waals attraction, the inhibitor can bind to the precursor. More specifically, the inhibitor can bind to the central atom of the precursor. The physically adsorbed precursor can be released by this binding, and a large amount of excess precursor can be removed. Subsequently, by purging, excess inhibitors and reaction byproducts can be removed from the reactor, and a layer of precursors chemisorbed at the level of a very thin layer (a monolayer or thinner) can be obtained. Reaction byproducts may include combinations of inhibitors and precursors.

[0230] Subsequently, a co-reactant is introduced. The co-reactant can react with the chemisorbed, monolayer precursor to form a film, and the inhibitor can react with the co-reactant and be removed. Excess co-reactant and reaction byproducts can be removed from the reactor by purging.

[0231] Figure 4c This refers to a three-step deposition method performed in the order of precursor-co-reactant-inhibitor. In this case, the precursor is first added and then... Figure 4bThe precursor is deposited on the surface of the pores, similar to the previous method. Next, after purging away excess physically adsorbed precursor, a co-reactant is introduced. The co-reactant can react with the chemisorbed precursor to form a film. Then, excess reaction byproducts can be removed from the reactor by purging. Subsequently, an inhibitor is introduced. The inhibitor can adsorb onto the film on the pore surface and onto the chemisorbed precursor. More specifically, the inhibitor can bind to the central atom of the precursor. Because the inhibitor can form a vertical gradient adsorption along the pores, with high adsorption near the top inlet and low adsorption deep at the bottom, the chemisorbed precursor can be released near the top inlet of the pores due to this combination, and excess adsorbed precursor can be largely removed by purging, resulting in a layer of precursor chemisorbed at a monolayer or thinner level. Reaction byproducts may include combinations of inhibitor and precursor.

[0232] Figure 4d This refers to a deposition process that simultaneously introduces inhibitors and precursors, followed by the addition of co-reactants. When initially introduced into the reactor, the precursors can bind together to form dimers or trimers. These dimers or trimers then adsorb onto the pore surface, potentially resulting in the over-adsorption of multiple layers of precursor. When inhibitors and precursors are added simultaneously, the inhibitors reduce the tendency for precursors to form dimers or trimers. Therefore, excessive precursor adsorption can be mitigated, especially near the pore inlet. Excess precursors, inhibitors, and unwanted byproducts can be removed from the reactor by purging. Subsequently, co-reactants are added. The co-reactants react with the adsorbed precursors to form a film, and the inhibitors in the reactor react with the co-reactants and are removed. Excess co-reactants and reaction byproducts can be removed from the reactor by purging.

[0233] Reference Figures 4a to 4d The described process can be executed dynamically to prevent excessive adsorption of precursors. Excess precursors, inhibitors, and co-reactants can be removed from the reactor by purging with a purge gas, and unwanted byproducts can also be removed from the reactor.

[0234] The combination of the order and timing of introducing inhibitors, precursors, and co-reactants into the reactor is not limited to... Figures 4a to 4d Those shown. The disclosed inhibitor deposition methods include all possible combinations of the sequence and timing of introducing inhibitors, precursors, and co-reactants into the reactor.

[0235] In a non-limiting exemplary ALD process, the disclosed ALD process includes i) supplying an inhibitor to a reactor containing a substrate having holes to be deposited, wherein inhibitor molecules are physically adsorbed onto the surface of the holes; ii) purging the inhibitor with a purge gas and removing excess inhibitor; iii) supplying a precursor to the reactor, wherein precursor molecules are adsorbed onto the surface of the holes; iv) purging the precursor with a purge gas and removing excess precursor; v) supplying a co-reactant to the reactor, wherein the co-reactant reacts with the adsorbed precursor to form a film on the surface; vi) purging the co-reactant with a purge gas and removing byproducts and excess co-reactant; vii) repeating steps i) to vi) to achieve a desired thickness of film deposited on the holes or desired gap filling in the substrate. Compared to deposited films and gap fillers without inhibitor generation, the deposited films and bottom-up deposited gap fillers produced by the disclosed inhibitor deposition method have improved step coverage and improved gap filling, and are free of voids, weak points, and / or seams.

[0236] In some embodiments, the disclosed method relates to a novel approach for reducing the growth rate or growth per cycle (GPC) or thickness in a vapor deposition process by inserting a so-called “inhibitor” step, while maintaining CVD or ALD behavior without sacrificing any of its benefits. The disclosed method can be adapted to modulate the growth rate or GPC for better control over the thickness of very thin layers and good gap-filling quality.

[0237] In some embodiments, the disclosed method relates to a novel method for gap filling via vapor deposition methods (e.g., ALD and CVD) without plasma by bottom-up superconformal film deposition with additives or inhibitors. (See also...) Figure 3c and Figure 3d As the number of ALD cycles increases, gaps in the substrate can be filled by bottom-up deposition. By adjusting the number of cycles, the disclosed inhibitor deposition method can improve the control of deposited film thickness and step coverage, and enhance gap filling by bottom-up deposition.

[0238] After achieving the desired film thickness, improved step coverage, and desired gap filling, the deposited film and gap filler can be subjected to further processing, such as thermal annealing, furnace annealing, rapid thermal annealing, UV curing, electron beam curing, and / or plasma gas exposure. Those skilled in the art will recognize the systems and methods used to perform these additional processing steps. For example, in an inert atmosphere or an O-containing atmosphere, or a combination thereof, the ZrO2 film can be exposed to temperatures ranging from about 200°C to about 1000°C for durations ranging from about 0.1 seconds to about 7200 seconds. Most preferably, in an inert atmosphere or an O-containing atmosphere, the temperature is 400°C for 3600 seconds. The resulting film may contain fewer impurities and therefore may have improved density, resulting in improved leakage current. The annealing step can be performed in the same reaction chamber in which the deposition process is carried out or in a separate apparatus. Any of the above post-treatment methods, but especially thermal annealing, has been found to effectively reduce carbon and nitrogen contamination of the ZrO2 film. This, in turn, tends to improve the resistivity of the film.

[0239] Example

[0240] The following non-limiting examples are provided to further illustrate embodiments of the invention. However, these examples are not intended to include all examples, nor are they intended to limit the scope of the invention described herein.

[0241] Example 1: In the case of ALD of ZrO2 with ZrCp(NMe2)3 and ozone, there is no inhibitory step coverage.

[0242] The precursor container was heated to 80°C. O3 was used as the co-oxidation reactant and ZrCp(NMe2)3 was used as the precursor. A ZrO2 film was deposited on a patterned wafer with an aspect ratio of approximately 20:1 using an ALD process. The reactor pressure was maintained at approximately 1 Torr. Step coverage was tested under the same deposition conditions without inhibitors on the patterned wafer with an aspect ratio of approximately 20:1 within a temperature window of 200°C–400°C. Figure 5 This is a SEM image showing approximately 60% step coverage of a 20:1 aspect ratio hole without inhibitor.

[0243] Example 2: Step coverage with inhibitor DME in the case of ALD of ZrO2 by ZrCp(NMe2)3 and ozone.

[0244] The precursor container was heated to 80°C. O3 was used as the co-oxidation reactant, DME as the inhibitor, and ZrCp(NMe2)3 as the precursor. A ZrO2 film was deposited on a patterned wafer with an aspect ratio of approximately 25:1 using an ALD process. The reactor pressure was maintained at approximately 1 Torr. Step coverage was tested under the same deposition conditions with the inhibitor on the patterned wafer with an aspect ratio of approximately 25:1 within a temperature window of 200°C–400°C. Figure 6 This is a SEM image showing approximately 100% step coverage of the pores with an aspect ratio of 25:1 containing the inhibitor DME.

[0245] Example 3: Step coverage with inhibitory TEA in the case of ALD of ZrO2 via ZrCp(NMe2)3 and ozone.

[0246] The precursor container was heated to 80°C. O3 was used as the co-oxidation reactant, TEA as the inhibitor, and ZrCp(NMe2)3 as the precursor. A ZrO2 film was deposited on a patterned wafer with an aspect ratio of approximately 25:1 using an ALD process. The reactor pressure was maintained at approximately 1 Torr. Step coverage was tested under the same deposition conditions with the inhibitor on the patterned wafer with an aspect ratio of approximately 25:1 within a temperature window of 200°C–400°C. Figure 7 This is a SEM image showing approximately 100% step coverage of the pores with an aspect ratio of 25:1 containing the inhibitor TEA.

[0247] Example 4: Step coverage with THF inhibitor in the case of ALD of ZrO2 via ZrCp(NMe2)3 and ozone.

[0248] The precursor container was heated to 80°C. O3 was used as a co-reactant, THF as an inhibitor, and ZrCp(NMe2)3 as a precursor. A ZrO2 film was deposited on a patterned wafer with an aspect ratio of approximately 25:1 using an ALD process. A constant reactor pressure was maintained at approximately 1 Torr. Step coverage was tested under the same deposition conditions with the inhibitor on a patterned wafer with an aspect ratio of approximately 20:1 within a temperature window of 200°C–400°C. Figure 8 This is a SEM image showing approximately 100% step coverage of the pores with an aspect ratio of 20:1 containing the inhibitor THF.

[0249] Example 5: ALD with inhibitor administration

[0250] The ALD process was performed at 300 °C. O3 was used as the co-oxidizing reactant and tetrahydrofuran (THF) as the inhibitor. The reactor pressure was maintained at approximately 1 Torr. The partial pressure of THF was 0.3 Torr. The aspect ratio of the SiO2 layer mesopores was 25:1 and the critical size (CD) was 100 nm. The ALD process was repeated as follows: i) 5 s THF flow and 30 s purge; ii) 1 s precursor flow and 30 s purge; and iii) 1 s co-reactant flow and 30 s purge.

[0251] Example 6: Thickness control with the inhibitor tetramethylethylenediamine (TMEDA) in the case of HfO2 ALD

[0252] ALD testing was conducted using tris(dimethylamino)cyclopentadienylhafnium HfCp(NMe2)3, ozone as a co-reactant, and TMEDA as an inhibitor. In ALD suppression, the reactor pressure was kept constant at approximately 0.6 Torr. Figure 9 The growth rate at 300°C decreases continuously with increasing precursor addition time. Here, precursor addition time is shown as source initiation time (sec).

[0253] Example 7: Thickness control with the inhibitor dimethylethylenediamine (DMEDA) in the case of ALD of HfO2

[0254] ALD testing was conducted using tris(dimethylamino)cyclopentadienylhafnium HfCp(NMe2)3, ozone as a co-reactant, and DMEDA as an inhibitor. In ALD suppression, the reactor pressure was kept constant at approximately 0.6 Torr. Figure 10 This is a comparison of GPC with and without an inhibitor (DMEDA) under ALD saturation conditions; it shows a similar decrease in growth rate with precursor addition time at 300°C. Here, precursor addition time is shown as source initiation time (sec).

[0255] Example 8: In the case of ALD of HfO2 with ozone via cyclopentadienyl-tris(dimethylamido)hafnium(IV)HfCp(NMe2)3, bottom-up interstitial filling with the inhibitor tris(2-aminoethyl)amine.

[0256] ALD testing was performed using cyclopentadienyl-tris(dimethylamido)hafnium(IV), in which the container holding the precursor was heated to a maximum of 80°C, O3 was used as the oxidant, and tris(2-aminoethyl)amine was used as the inhibitor. The reactor pressure was maintained at approximately 1 Torr. Figure 11 It grows from the bottom up in an 11:1 aspect ratio structure at 300℃. As the open CD decreases, gap filling occurs. Figure 12It is a complete gap fill in a 25:1 aspect ratio patterned structure, which shows a seamless complete gap fill in a 25:1 aspect ratio structure at 300°C.

[0257] It should be understood that many additional changes in details, materials, steps, and arrangements of parts that have been described and elucidated to explain the essence of the invention can be made by those skilled in the art within the principles and scope of the invention as set forth in the appended claims. Therefore, the invention is not intended to be limited to the specific embodiments given above and / or in the drawings.

[0258] Although embodiments of the invention have been shown and described, those skilled in the art can modify them without departing from the spirit or teachings of the invention. The embodiments described herein are exemplary only and not limiting. Many variations and modifications of the compositions and methods are possible and are within the scope of the invention. Therefore, the scope of protection is not limited to the embodiments described herein, but is defined only by the following claims, the scope of which should include all equivalents of the subject matter of the claims.

Claims

1. A deposition method for improving thickness control of films deposited on high aspect ratio (HAR) holes in a substrate, the method comprising: i) Expose the substrate sequentially or simultaneously to the vapors of the inhibitor, the precursor, and the co-reactant; as well as ii) Deposit a film with desired thickness control on the HAR pores by a vapor deposition process, wherein the precursor is HfCp(NMe2)3, ZrCp(NMe2)3, Nb(=NtBu)Cp(NMe2)2 or TiCp*(OMe)3; The inhibitor is selected from dimethoxyethane (DME), triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA), or tris(2-aminoethyl)amine.

2. The deposition method as described in claim 1, further comprising: The temperature of the substrate is maintained in the range from room temperature to 650°C.

3. The deposition method as described in claim 1, wherein, The inhibitor is a vapor or gaseous free radical form of the inhibitor, produced in the presence or absence of plasma within a temperature range from room temperature to 650°C.

4. The deposition method as described in claim 1, wherein, The membrane has a step coverage of ≥100%.

5. The deposition method as described in claim 4, wherein, The step coverage is greater than that in the absence of the inhibitor.

6. The deposition method as described in claim 1, wherein, The membrane is a seamless gap filler for the HAR pore.

7. The deposition method as described in claim 1, wherein, The gap filler is formed by bottom-up deposition.

8. The deposition method as described in claim 1, wherein, The HAR ratio is in the range of 5:1 to 200:

1.

9. The deposition method as described in claim 1, wherein, The vapor deposition process is ALD, CVD, or a combination thereof.

10. The deposition method as described in claim 1, wherein, The co-reactants are O3, O2, H2O, H2O2, D2O, alcohols, NH3, N2, N2H2, H2, free radicals or mixtures thereof generated by plasma.

11. The deposition method as described in claim 1, wherein, The co-reactant is O3 or an O3 radical generated by plasma.

12. The deposition method as described in claim 1, wherein, The order in which the substrate is exposed to the inhibitor, the precursor, and the co-reactant includes: a) Sequential exposure to the inhibitor, the precursor, and the co-reactant; b) Sequential exposure to the precursor, the inhibitor, and the co-reactant; c) Sequential exposure to the precursor, the co-reactant, and the inhibitor; or d) Simultaneous exposure to the inhibitor and the precursor, followed by exposure to the co-reactant, wherein after each exposure, excess of one or more of the inhibitor, precursor, and co-reactant is purged and removed using a purge gas. The purging gas is an inert gas selected from N2, Ar, Kr, or a combination thereof.

13. The deposition method according to any one of claims 1 to 12, wherein, The growth rate of the membrane decreased compared to the growth rate in the absence of the inhibitor.

14. The deposition method according to any one of claims 1 to 12, wherein, The precursor, the inhibitor, or both may be plasma-activated or not.

15. A deposition method for improving thickness control of a ZrO2, HfO2, Nb2O5, or TiO2 film deposited on a substrate with an aspect ratio of 5:1 to 200:1, the method comprising: i) Expose the substrate to the vapor of an inhibitor selected from the group consisting of: dimethoxyethane (DME) and triethylamine (TEA), tetramethylethylenediamine (TMEDA), dimethylethylenediamine (DMEDA) and tris(2-aminoethyl)amine; ii) Expose the substrate to the vapor of a precursor selected from the group consisting of: ZrCp(NMe2)3, HfCp(NMe2)3, Nb(=NtBu)Cp(NMe2)2 and TiCp*(OMe)3; iii) Expose the substrate to the vapor of the co-reactant O3; as well as iv) Repeat steps i) to iii) until the desired thickness of the ZrO2, HfO2, Nb2O5, or TiO2 film deposited on the pore is achieved by ALD process at temperatures ranging from room temperature to 650°C. The step coverage of the ZrO2, HfO2, Nb2O5 or TiO2 film is ≥100%; The amount of ZrO2, HfO2, Nb2O5 or TiO2 film per cycle of growth decreases relative to the amount of precursor; The ZrO2, HfO2, Nb2O5 or TiO2 membrane is a seamless gap filler, wherein after each exposure, excess inhibitors, excess precursors and excess co-reactants are removed by purging with N2.

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