High-performance semiconductor-grade dimethylaluminum chloride

Abstract

A novel high-purity dimethylaluminum chloride composition suitable for semiconductor applications such as atomic layer etching and aluminum ion implantation is provided. The reduction or minimization of certain gaseous impurities allows the vapor phase of DMAC to have a purity level of 99.9 mol% or greater to selectively etch various atomic layers with high selectivity and high etching precision at acceptable etch rates, and to have a purity level of 99 mol% or greater to ion-implant aluminum ions without substantial implantation of CH ions into wafer devices, thereby avoiding wafer device degradation or failure. Storage conditions are established that help maintain the high purity levels required for such semiconductor applications.

Description

[Technical Field]

[0001] The present invention relates to a novel high-purity dimethylaluminum chloride material suitable for use in semiconductor-grade applications such as atomic layer etching and ion implantation. More particularly, the present invention relates to high-purity dimethylaluminum chloride at purity levels of 99.9 mole % or greater, with the remainder of a specifically identified combination of gaseous impurities maintained at or below their respective upper concentration limits to ensure excellent etchant performance that is not adversely affected by the presence of any one gaseous impurity. Still further, the present invention relates to high-purity dimethylaluminum chloride at purity levels of 99 mole % or greater for ion implantation of aluminum ions in the substantial absence of CH ions. [Background technology]

[0002] Atomic layer etching (ALE) is utilized as part of a promising new technology for advanced node manufacturing of semiconductor devices. ALE is a process for thin film removal based on sequential self-limiting surface reactions. The thin film is typically a layer of material previously deposited on a substrate by atomic layer deposition (ALD). The thickness of the thin film removed by ALE ranges from a fraction of a nanometer (i.e., a monolayer) to several micrometers. ALE requires thin film removal with atomic layer control and precision. The ALE process is based on two steps. The first step is surface modification of the substrate or wafer by reaction with a first gas, such as HF, to produce a modified surface. The purpose of the modification step is to chemically modify the etched surface layer for reaction with a second gas in the second step. In the case of HF used as the first gas, the modification reaction results in the formation of a fluorinated layer on the surface, producing water that is removed as vapor under the conditions of the first reaction. The unmodified surface does not react with the second gas, or the reaction rate is too slow for practical purposes. The second step is the removal of the modified surface by the use of a second gas. The second gas can be any suitable etchant, including dimethylaluminum chloride (DMAC). In the case of a fluorinated surface and DMAC, the removal reaction involves halogen exchange when chlorine atoms from the DMAC molecule are replaced with fluorine atoms from the modified surface, producing dimethylaluminum fluoride and metal chlorides, both of which are volatile under the conditions of the second reaction. The second reaction self-terminates when the surface-derived fluorine atoms are depleted, leaving a clean surface ready for the next ALE cycle. A general overview of ALE processes using various etchants, including low-grade DMAC, is provided in U.S. Pat. No. 10,381,227 to George et al., the details of which are incorporated herein by reference in their entirety for all purposes.

[0003] Furthermore, there is an increasing need for aluminum (Al) implantation for doping various semiconductor substrates. Aluminum ion (Al) implantation is gaining interest in integrated circuit (IC) manufacturing. DMAC raw materials are typically utilized in the industry to perform Al ion implantation. However, currently, process challenges exist for the effective implantation of Al ions. The inclusion of C2H3 ion fragments in the plasma during Al ion implantation processes has been widely observed in the industry. Due to its atomic mass being virtually identical to that of Al, C2H3 can inadvertently cross-contaminate portions of the Al-based ion beam, potentially resulting in undesired carbon cross-contamination with the ionized DMAC in the plasma. C2H3 has the same atomic mass as Al ions, thereby complicating the removal of C2H3 impurities with mass analysis magnets, which are intended to function by deflecting ions from an Al-based ion beam in trajectories that vary according to their mass (e.g., mass-to-charge ratio). Ions of undesired mass are deflected away from the path of the Al-based ion beam. However, as a result of the identical atomic masses of the C2H3 impurities and the Al ions, the mass analysis magnet cannot deflect or remove the undesired C2H3 impurities from the Al ions. The adverse effect is that the C2H3 impurities are implanted along with the Al ions.

[0004] Numerous solutions have been proposed to minimize C2H3 cross-contamination from aluminum ion implantation. For example, one solution for reducing the presence of such C2H3 is disclosed in U.S. Patent Publication No. 2022 / 0139644, which introduces molecular fluorine into the ion chamber in the form of a co-flowing gas. Many different sources and / or mixtures of fluorine and fluorine-containing compounds are proposed, with the design objective of increasing the mass of C2H3 contaminants to a mass sufficiently greater than 27 masses, thereby enabling their removal from the Al-based ion beam by a mass analysis magnet.

[0005] Another technique for Al ion implantation utilizes solid aluminum salts as the source material, which are heated in a vaporizer to generate sufficient vapor pressure of Al that can then be fed into the ion chamber. However, one drawback of using solid aluminum salts is that the implantation process is unacceptably slow and requires additional equipment, such as a solid-source vaporizer, connected to the ion chamber.

[0006] In yet another process, a pure aluminum metal or aluminum oxide target placed in an ion source is sputtered using a plasma. The plasma produces Al ions. However, this process is prone to contamination of the ion chamber with aluminum deposits, requiring frequent chamber cleaning. Furthermore, this method exhibits short filament life.

[0007] There continues to be a need to identify etchants with improved performance in terms of their ability to selectively etch certain atomic layers of material over others. The need for selective etching and greater atomic precision for ALE is increasing to effectively meet the ever-increasing semiconductor industry demands for wafer device miniaturization. Also, there remains a need to effectively implant aluminum ions without cross-contamination with C2H3 ions. Summary of the Invention

[0008] In a first aspect of the present invention, there is provided a high purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, the composition comprising: the high purity DMAC composition maintained under storage conditions in a liquid phase in substantial equilibrium with a high purity vapor phase; and a high purity vapor phase having a purity level of about 99.9 mole % or greater of DMAC based on the total moles in the vapor phase, the total moles in the vapor phase being exclusive of any optional blanket gas that may occupy the vapor phase, with the remainder of the total moles in the vapor phase being occupied by gaseous impurities, the gaseous impurities being: (i) H, O, N, Ar, CO, C (ii) hydrocarbons of the general formula CxHy, where x and y are greater than 0 and can have any integer value; (iii) gaseous impurities including moisture, HO, (iv) volatile hydrides, (v) chloride derivatives of volatile hydrides, (vi) volatile chlorides, (vii) oxychlorides of volatile hydrides, and (viii) alkyl aluminum compounds and their corresponding chlorine derivatives, each of the gaseous impurities being present in an amount greater than 0 mol % and less than or equal to about 0.1 mol %, with the proviso that the total amount of all of the gaseous impurities is less than or equal to about 0.1 mol %.

[0009] In a second aspect of the present invention, there is provided a high-purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, the composition comprising: the high-purity DMAC composition maintained under storage conditions having a gas phase in substantial equilibrium with a liquid phase; a liquid phase having impurities; and the impurities contained in the liquid phase include: (i) hydrocarbons of the general formula CxHy, where x and y are greater than 0 and can have any integer value; (ii) water, HO; and (iii) greater than 0 mol% and at least about 0.01 mol%. and (iv) hydrides comprising at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and may have any integer value; and impurities comprising (v) chloride derivatives of volatile hydrides; (vi) chlorides; (vii) oxychlorides of chlorides; and (viii) alkylaluminum compounds and their corresponding chlorine derivatives, wherein each of the impurities in the liquid phase is contained in an amount greater than 0 mol % and less than or equal to about 0.1 mol %, with the proviso that the total amount of all liquid phase impurities is less than or equal to about 0.1 mol %.

[0010] In a third aspect, a high-purity semiconductor-grade DMAC composition is maintained under storage conditions in a liquid phase that is in substantial equilibrium with a high-purity vapor phase, whereby the high-purity vapor phase of the high-purity DMAC composition is configured for use as an atomic layer etchant having an etch selectivity of species x to species y of about 10:1 or greater in a semiconductor manufacturing process using HF as a first etchant gas followed by the high-purity vapor phase of the high-purity DMAC composition as a second etchant gas.

[0011] In a fourth aspect, there is provided a semiconductor-grade dimethylaluminum chloride (DMAC) material stored in a substantially hermetically sealed, passivated canister, the DMAC material comprising a liquid phase in substantial equilibrium with a gas phase occupying a predetermined headspace of the canister, the substantially hermetically sealed, passivated canister configured to maintain the gas phase at a semiconductor-grade purity level of 99.9 mole % or greater based on the total number of moles in the predetermined headspace during shipping, storage, and use of the substantially hermetically sealed, passivated canister, the total number of moles in the predetermined headspace excluding any optional blanket gas that may occupy the gas phase.

[0012] In a fifth aspect, a high purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, the composition comprising: a substantially hermetically sealed and passivated canister; the high purity DMAC composition maintained in the substantially hermetically sealed and passivated canister under storage conditions in a liquid phase that is in substantial equilibrium with a high purity vapor phase; and a high purity vapor phase having a purity level of about 99.9 mole % or greater DMAC based on the total number of moles in the vapor phase. a high purity gas phase and gaseous impurities occupying a predetermined volume of headspace within a substantially hermetically sealed and passivated canister, wherein the total number of moles in the gas phase excludes any optional blanket gas that may occupy the gas phase, with the remainder of the total number of moles being occupied by gaseous impurities, the gaseous impurities comprising: (i) atmospheric gases selected from the group consisting of H, O, N, Ar, CO, CO, and any combination thereof; (ii) at least one of SixHy, GexHy, NH, PH, AsH, and SbH; (iii) moisture, H2O; (iv) volatile hydrides comprising at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3; (v) chloride derivatives of volatile hydrides, the chloride derivatives comprising at least one of SixHyClz and GexHyClz, where x, y, and z are greater than 0 and may have any integer value; (vi) volatile chlorides comprising at least one of Cl2, HCl, CCl4, SiCl4, and TiCl4; (vii) COCl2, MoO2C and (viii) alkylaluminum compounds and their corresponding chlorine derivatives, including at least one of Al(CH), CHAlCl, and (C)H)AlCl, where x and y are greater than 0 and may have any integer value, whereby the total amount of gaseous impurities is 0.1 mole % or less based on the total number of moles in the vapor phase.

[0013] In a sixth aspect, a semiconductor-grade dimethylaluminum chloride (DMAC) material has a purity of 99.9 mol% or greater, the semiconductor-grade DMAC material containing impurities, the impurities including at least one of hydrocarbons, moisture, hydrides, chlorides, alkylaluminum compounds and corresponding chlorine derivatives, and atmospheric gases selected from the group consisting of H, O, N, Ar, CO, and CO, whereby the total amount of impurities is greater than 0 mol% and less than or equal to about 0.1 mol%, the balance being the semiconductor-grade DMAC material.

[0014] In a seventh aspect, a method of filling a canister configured to deliver semiconductor-grade DMAC material having a purity of 99.9 mol% or greater includes providing a hermetically sealed or substantially sealed canister; evacuating the interior volume of the canister; passivating the interior walls of the canister to remove residual solvent, moisture, particles, and / or other impurities adsorbed on the interior walls; and subsequently introducing semiconductor-grade DMAC material having a purity of 99.9 mol% or greater into the canister, thereby eliminating air intrusion and maintaining a purity of 99.9 mol% or greater.

[0015] In an eighth aspect, there is provided a semiconductor-grade dimethylaluminum chloride (DMAC) material having a purity of 99.9 mol% or greater, the semiconductor-grade DMAC material comprising impurities comprising at least one of hydrocarbons, moisture, hydrides, chlorides, alkylaluminum compounds and corresponding chlorine derivatives, atmospheric gases selected from the group consisting of H, O, N, Ar, CO, and CO, whereby a total amount of the impurities is greater than 0 mol% and less than or equal to about 0.1 mol%, the balance being the DMAC material, with the proviso that when the impurities comprise hydrocarbons, the hydrocarbons comprise one or more of CH, ... When the impurities include hydrides, the hydrides include one or more of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer values, except that when the impurities include chlorides, the chlorides include one or more of SixHyClz, GexHyClz, COCl2, MoO2Cl2, SOCl2, Cl2, HCl, CCl4, CHCl3, CH2Cl2, CHCl3, SiCl4, and TiCl4, where x, y, and z are greater than 0 and can have any integer values, except that when the impurities include alkyl aluminum compounds and the corresponding chlorine derivatives, the alkyl aluminum compounds and the corresponding chlorine derivatives include one or more of Al(CH3)3, CH3AlCl2, and (C2H5)xAlCly, where x and y are greater than 0 and can have any integer values.

[0016] In a ninth aspect, a method of using semiconductor-grade dimethylaluminum chloride DMAC includes providing a canister at least partially filled with a liquid phase of semiconductor-grade DMAC material; withdrawing the liquid phase of semiconductor-grade DMAC material from the canister at a semiconductor-grade purity of 99.9 mol % or greater; directing the liquid phase of semiconductor-grade DMAC material to an intermediate buffer vessel; accumulating a sufficient amount of DMAC material in the intermediate buffer vessel until a steady flow of DMAC vapor from the intermediate buffer vessel can be produced; and distributing the DMAC vapor from the intermediate vessel to a downstream tool for atomic layer etching associated with a semiconductor manufacturing process, wherein the DMAC vapor is introduced to the downstream tool at a semiconductor-grade purity of 99.9 mol % or greater.

[0017] In a tenth aspect, a semiconductor-grade dimethylaluminum chloride (DMAC) feedstock suitable for use in an improved aluminum ion implantation process has a purity of at least about 99 mole percent or greater, based on the total number of moles in the DMAC feedstock, and has reduced levels of impurities in the material capable of producing C2H3 ions, the impurities being selected from the group consisting of: (i) hydrocarbons represented by the general formula CxHy, where x is equal to 2 and y is selected from saturated, unsaturated, cyclic, aromatic, and other hydrocarbons; (ii) halogen derivatives of hydrocarbons represented by the general formula CxHyHalz, where x is equal to 2 and "Hal" is either Cl, F, Br or I; (iii) alkyl or alkoxy halides or hydrides of aluminum, where x, y, or z = 0 to 3 and x + y + z = 3, such as (C2H5)x(CH3)yAlClz, (C2H5)3Al, (C2H5)2AlCl, (C2H5)AlCl 2, alkyl or alkoxy halides or hydrides of aluminum, including (C2H5)2(CH3)Al, (C2H5)(CH3)2Al, and (C2H5)(CH3)AlCl, and dimers and trimers thereof; (iv) alkyl or alkoxy halides or hydrides of silicon, wherein x, y, or z=0 to 4 and x+y+z=4, such as (C2H5)x(CH3)y4SiClz, (C2H5)4Si, (C2H5)3SiCl, (C2H5)2SiCl2, (C2H5)SiCl3, (C2H5) and (v) alkyl, alkylidene, or alkoxy functional groups, including ethyl (HC—CH—), vinyl (HC═CH—), or ethoxy (HC—CH—O—), whereby the total amount of such impurities in the material capable of generating CH ions is greater than 0 mol % and less than about 1 mol %, with the remainder being the semiconductor-grade DMAC material.

[0018] In an eleventh aspect, there is provided a semiconductor-grade dimethylaluminum chloride (DMAC) raw material suitable for use in an improved aluminum ion implantation process, the DMAC raw material having a purity of at least about 99 mol% or greater, the semiconductor-grade DMAC raw material including reduced levels of one or more impurities capable of producing CH ions in the material, whereby a total amount of the one or more impurities capable of producing CH ions is greater than 0 mol% and less than or equal to about 1 mol%, with the balance being the semiconductor-grade DMAC material.

[0019] In a twelfth aspect, an improved method for performing aluminum ion implantation includes removing high-purity DMAC source material in a vapor phase from a storage and delivery package, wherein the DMAC source material in the vapor phase has a purity of at least about 99 mol % or greater, and the semiconductor-grade DMAC source material includes reduced levels of one or more impurities in the material capable of producing CH ions in an amount greater than 0 mol % and less than or equal to about 1 mol %; flowing the high-purity DMAC source material in the vapor phase without a co-flow gas configured to capture the CH ions; and introducing the high-purity DMAC source material into an ion source chamber.

[0020] The present invention may include any of the aspects in the various combinations and embodiments disclosed herein. DETAILED DESCRIPTION OF THE INVENTION

[0021] The advantages of the present invention will be better understood from the following detailed description of relevant embodiments thereof. The present disclosure is described herein in various embodiments and with reference to various features, aspects, and embodiments of the invention, each of which can be used in various orders and combinations without departing from the scope of the invention. The present disclosure may be further specified as comprising, consisting of, or consisting essentially of any such combinations and permutations of these particular features, aspects, and embodiments, or selected one or more of them.

[0022] All percentages herein, unless otherwise specified, are expressed as mole percentages, specified as mole %, and are specified as volume %, with the understanding that volume percentages and mole % are equivalent for gases and therefore may be used interchangeably to describe the concentration of a gas.

[0023] The terms "sufficiently," "adequately," "substantially," and "about" may be used herein to express the inherent degree of uncertainty that may result from any quantitative comparison, value, measurement, or other representation. These terms are also used herein to express the extent to which a quantitative representation may vary from the stated standard without resulting in a change in the basic functionality of the subject matter in question.

[0024] Various aspects of the present invention may be presented in range format. When a range of values ​​expresses a parameter, all subranges, point values, and endpoints within or defining that range are expressly disclosed therein unless expressly disclosed otherwise. All physical property, dimension, concentration, and ratio ranges and subranges between those physical property, dimension, concentration, and ratio range endpoints are considered to be expressly disclosed herein unless expressly disclosed otherwise. For example, description of a range such as 1 to 10 should be considered to specifically disclose subranges such as 1 to 7, 2 to 9, 7 to 10, etc., as well as individual numbers within that range, such as 1, 5.3, and 9.

[0025] "GC-FID" means gas chromatography with flame ionization detector.

[0026] "CRDS" means cavity ring-down spectroscopy.

[0027] "FTIR" means Fourier transform infrared spectroscopy.

[0028] "GC-MS" means gas chromatography with mass spectrometer detector.

[0029] "Semiconductor grade" and "high purity" are used interchangeably herein and throughout to mean purities of 99.9 mole % or greater for ALE applications and 99 mole % or greater for ion implantation applications.

[0030] "Low grade" means a purity level less than 99.9 mole % and / or a purity level unacceptable for use in semiconductor applications.

[0031] "Semiconductor applications" include, but are not limited to, the fabrication of gate-all-around (GAA) and 3D NAND structures.

[0032] "High-precision atomic layer etchant" or "high-precision etchant" or "etch precision" may be used interchangeably herein to refer to atomic layer removal of material from features, structures, or devices characterized as having a relatively high aspect ratio, the aspect ratio being the ratio of height to depth of the feature, structure, or device.

[0033] "Etch selectivity" means the ratio of the amount of desired material etched to the amount of undesired material etched from any feature, structure, or device.

[0034] A "feature, structure, or device" includes, but is not limited to, any aspect, portion, or component of a 3D NAND structure or other semiconductor component.

[0035] "DMAC material" or "material," which may be used interchangeably herein and throughout, is intended to mean, without further limitation, liquid and / or gas phase dimethylaluminum chloride.

[0036] The present inventors have found that while several etchants are commercially available for use in ALE processes, none have emerged as suitable materials for ALE in the manufacture of various semiconductor applications, such as advanced 3D NAND memory devices. For example, U.S. Patent No. 10,381,227 to George et al. provides a list of representative etchants, including low-grade DMAC, that have been evaluated at a laboratory scale for technical feasibility, but George et al. and others have not been able to identify a specific high-purity, semiconductor-grade etchant with a compositional profile suitable for effective commercial use in semiconductor applications, such as 3D NAND processes. Of particular importance, no one has recognized or determined which combinations of impurities in a particular etchant are harmful and adversely affect etchant performance, nor what upper concentration, if any, each of the impurities can be tolerated in the etchant without adversely affecting its ALE performance in various semiconductor applications, such as 3D NAND manufacturing processes.

[0037] It is from these deficiencies in the current state of the art that the present invention emerged. In one aspect of the present invention, the inventors have determined that high-purity DMAC material having a composition of 99.9 mol% or greater can function as an excellent atomic layer etchant for semiconductor applications, more preferably in processes for fabricating 3D NAND devices. However, high-purity DMAC of at least 99.9 mol% is not sufficient for ALE in semiconductor applications, as the present invention recognizes that certain impurities within the high-purity DMAC material must be controlled so as not to exceed their respective concentration limits. In one embodiment, the remainder of the high-purity DMAC material may contain traceable impurities in the form of gaseous impurities that total 0.1 mol% or less as measured by certain measurement methods disclosed herein.

[0038] High-purity DMAC of 99.9 mol% or greater exhibits favorable etch selectivity of various metal oxides (desired etched materials), such as Al2O3, HfO2, and ZrO2, over Si, SiO2, Si3N4, and TiN materials (undesired etched materials), at etch ratios of 10:1 or greater. Selective etching of such metal oxides can be performed at acceptably high etch rates (typically defined as angstroms of metal oxide material removed per cycle) in a manner that advantageously produces acceptably low film roughness. Furthermore, DMAC compositions possess the ability to selectively etch various 3D NAND structures with high precision, in some cases having aspect ratios exceeding 50:1. Each of these performance characteristics of high-purity DMAC compositions is desirable for use in ALE processes for manufacturing 3D NAND.

[0039] To ensure that all of the above-mentioned etchant performance characteristics of semiconductor-grade DMAC for 3D NAND manufacturing processes can be achieved, the present invention defines an impurity profile. An impurity profile is a specific combination of impurities in semiconductor-grade DMAC material that cannot exceed corresponding upper concentration limits, thereby avoiding the risk of adverse etchant performance during atomic layer removal of specific materials (e.g., metal oxides) for 3D NAND manufacturing processes. Furthermore, by reducing the impurities below their respective upper concentration limits, risks to device yield or throughput of 3D NAND devices are reduced or minimized.

[0040] In accordance with the principles of the present invention, high-purity DMAC compositions are provided that can be used as precision atomic layer etchants with etch selectivity for semiconductor applications by maintaining a combination of specifically identified gaseous impurities below a predetermined upper concentration limit. Storage conditions for the DMAC material can allow the liquid phase to be in substantial equilibrium with the corresponding high-purity vapor phase of DMAC. Certain impurities present in DMAC partition between the vapor and liquid phases based on their respective K values, which indicate the vapor-liquid partition ratio (i.e., the ratio of the amount of a particular impurity occupying the vapor phase to the amount in the liquid phase). High-K impurities, including but not limited to volatile solvents such as methanol, methyl chloride, small ethers, and trimethylaluminum, are volatile gaseous impurities that partition preferentially into the vapor phase over the liquid phase. Low-K impurities, including but not limited to methylaluminum chloride, CCl4, higher chlorine-substituted hydrocarbons, and low-boiling organic solvents, are relatively nonvolatile and partition preferentially to the liquid phase. However, when the DMAC material in the vapor phase is supplied for use in the ALE process, additional low-K impurities in the liquid phase vaporize and replenish the vapor phase, restoring the liquid-vapor equilibrium of the low-K impurities. As a result, the low-K impurities become non-negligible. The present invention aims to control the amount of both high-K and low-K impurities in the DMAC material to ensure a reliable and continuous supply of high-purity vapor-phase DMAC material for use in ALE.

[0041] Therefore, it is necessary to maintain several gaseous impurities below threshold levels in the DMAC vapor phase. Atmospheric gases in the DMAC vapor phase are considered gaseous impurities and are maintained below 0.1 mole percent based on the total moles in the vapor phase. Relevant atmospheric impurities include hydrogen, nitrogen, oxygen, argon, carbon monoxide, and carbon dioxide. Preferably, atmospheric gaseous impurities have an upper concentration in the vapor phase of 0.01 mole percent or less, more preferably 0.001 mole percent or less. Atmospheric impurities can be measured by GC-TCD, GC-DID, GC-PDHID, GC-MS, or other measurement techniques.

[0042] Hydrocarbons are a second type of gaseous impurity that can occupy the vapor phase of DMAC. Hydrocarbons can be represented by the general formula CxHy, where x and y are integers greater than 0. Typical hydrocarbons expected to occupy the vapor phase of DMAC include CH4, CH6, CH4, CH8, CH6, or any combination thereof. Many such hydrocarbons are volatile (i.e., high-K impurities) and tend to reduce the DMAC etch rate and etch selectivity of DMAC. To avoid adverse etch performance, hydrocarbons are maintained at 0.1 mol% or less based on the total moles in the vapor phase. Preferably, hydrocarbon gaseous impurities are maintained at 0.01 mol% or less, more preferably 0.001 mol% or less in the vapor phase to ensure that the presence of hydrocarbons in the vapor phase does not reduce the etch rate or etch selectivity of 99.9 mol% or greater pure DMAC during semiconductor applications. Hydrocarbons can be measured by GC-FID or other gas chromatography measurement methods.

[0043] Water is a third impurity that can occupy the vapor phase of DMAC. Water is maintained at 0.1 mol% or less based on the total number of moles in the vapor phase. Preferably, water has an upper concentration limit of 0.01 mol% or less, more preferably 0.001 mol% or less in the vapor phase. Water can be measured by CRDS or FTIR measurement.

[0044] Volatile hydrides are a fourth impurity that may occupy the vapor phase of DMAC. Volatile hydrides include at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and may have any integer value. Volatile hydrides are maintained at 0.1 mol% or less based on the total number of moles in the vapor phase. Preferably, volatile hydrides have an upper concentration of 0.01 mol% or less, more preferably 0.001 mol% or less in the vapor phase. Volatile hydrides can be measured by GC-MS or FTIR measurement.

[0045] Chloride derivatives of the aforementioned volatile hydrides are a fifth impurity that may occupy the gas phase of DMAC. The chloride derivatives of the volatile hydrides include at least one of SixHyClz and GexHyClz, where x, y, and z are greater than 0 and may have any integer value. The chloride derivatives are maintained at 0.1 mol% or less based on the total number of moles in the gas phase. Preferably, the chloride derivatives have an upper concentration of 0.01 mol% or less, more preferably 0.001 mol% or less in the gas phase. The chloride derivatives can be measured by GC-MS or FTIR measurement.

[0046] Volatile chlorides are a sixth impurity that can occupy the vapor phase of DMAC. Volatile chlorides include at least one of Cl2, HCl, CCl4, SiCl4, and TiCl4. Volatile chlorides are maintained at 0.1 mole percent or less based on the total moles in the vapor phase. Preferably, volatile chlorides have an upper concentration of 0.01 mole percent or less, more preferably 0.001 mole percent or less in the vapor phase. Volatile chlorides can be measured by GC-MS or FTIR measurement.

[0047] Oxychlorides are a seventh impurity that can occupy the vapor phase of DMAC. Oxychlorides include at least one of COCl2, MoO2Cl2, and SOCl2. Oxychlorides are maintained at 0.1 mole percent or less based on the total moles in the vapor phase. Preferably, oxychlorides have an upper concentration of 0.01 mole percent or less, more preferably 0.001 mole percent or less in the vapor phase. Volatile chlorides can be measured by GC-MS or FTIR measurement.

[0048] Alkyl aluminum compounds and their corresponding chlorine derivatives are an eighth impurity that may occupy the gas phase of DMAC. The alkyl aluminum compounds and their corresponding chlorine derivatives include at least one of Al(CH3)3, CH3AlCl2, and (C2H5)xAlCly, where x and y are greater than 0 and may have any integer value. The alkyl aluminum and their corresponding chlorine derivatives are maintained at 0.1 mol% or less based on the total moles in the gas phase. Preferably, the alkyl aluminum and their corresponding chlorine derivatives have an upper concentration of 0.01 mol% or less, more preferably 0.001 mol% or less in the gas phase. The alkyl aluminum and their corresponding chlorine derivatives can be measured by GC-MS or FTIR measurement.

[0049] By maintaining each of the above-mentioned gaseous impurities at or below their respective upper concentration limits, the amount of gaseous impurities co-flowing with and / or entrained in the DMAC vapor phase during the etching process is not substantial and is not expected to dilute the DMAC high-purity vapor phase or degrade its performance characteristics (e.g., etch rate, etch selectivity, and etch precision). To the extent that any of the gaseous impurities is an active impurity, as defined herein as having a tendency to etch any feature, device, or structure of an undesired material, reducing each of the gaseous impurities to an amount at or below its respective upper concentration limit can reduce, minimize, or eliminate the risk of reducing DMAC etchant selectivity and creating irreparable defects that could ruin the structure being fabricated. For example, active impurities such as SOCl exhibit higher etch selectivity for TiN than AlO, and even at relatively low concentrations in DMAC, SOCl may undesirably etch TiN, while DMAC may etch the fluorinated surface of an AlO film to produce AlF, thereby undesirably reducing etch selectivity. The present invention aims to reduce, minimize or eliminate the deleterious effects of such active impurities.

[0050] The present invention further requires maintaining a combination of specifically identified liquid impurities in the liquid phase of DMAC at or below a predetermined upper concentration limit. Specifically, the liquid impurities contained in the liquid phase include: (i) hydrocarbons of the general formula CxHy, where x and y are greater than 0 and can have any integer value; (ii) moisture, HO; (iii) metals in an amount greater than 0 mole % and less than or equal to about 0.01 mole %; (iv) hydrides including at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer value; (v) chloride derivatives of volatile hydrides; (vi) chlorides; (vii) oxychlorides of chlorides; and (viii) alkyl aluminum compounds and their corresponding chlorine derivatives. With the exception of metals, each of the liquid phase impurities is present in the liquid phase in an amount greater than 0 mol% and less than or equal to about 0.1 mol%, provided that the total amount of all gaseous impurities is less than or equal to about 0.1 mol%. In another embodiment, each of the liquid phase impurities is present in the liquid phase in an amount greater than 0 mol% and less than or equal to about 0.01 mol%, provided that the total amount of all liquid phase impurities is less than or equal to about 0.01 mol%. In yet another embodiment, each of the liquid phase impurities is present in the liquid phase in an amount greater than 0 mol% and less than or equal to about 0.001 mol%, provided that the total amount of all liquid phase impurities is less than or equal to about 0.001 mol%.

[0051] Impurities in the liquid phase can be measured by NMR or GC-MS using direct sampling. Metals can be measured by ICP-MS or ICP-OES using indirect sampling involving DMAC hydrolysis.

[0052] Having identified the combination of specific impurities and their respective upper concentration limits that can be tolerated without adversely affecting DMAC etch performance, the present invention further considers that commercially available low-grade DMAC material requires the implementation of one or more specific purification processes to achieve the desired semiconductor-grade purity. Various purification processes are contemplated. The exact purification depends on the types of impurities present in the low-grade DMAC and their respective concentrations. As non-limiting examples, low-grade DMAC can be subjected to rectification, distillation, freeze-degassing, adsorption, or a combination thereof to achieve an impurity profile with the upper concentration limits described above. In this manner, the low-grade DMAC material is converted into a suitable semiconductor-grade DMAC material.

[0053] After purification of the DMAC material, the purified DMAC material is then packaged in a storage source, such as a hermetically sealed or substantially sealed canister, under specific storage conditions that allow the high-purity vapor phase of DMAC to remain highly pure in the headspace, ensuring that atmospheric impurities do not enter the canister. Furthermore, canister passivation is used to avoid another source of contamination of the high-purity DMAC material from various surfaces of the canister. Specifically, canister passivation is required to remove residual solvents, moisture, particles, and other impurities that may desorb from the canister's surfaces when the DMAC is packaged in the canister or that may react with the DMAC material over its storage period. Alternatively, or in addition, active sites on the canister's constituent materials may themselves react with DMAC or catalyze its decomposition. Examples of suitable canister preparations prior to filling with purified DMAC material include (i) degassing at room temperature or elevated temperatures by evacuation, purging, and cycle purging; (ii) pickling with an active solution to render the canister surface inert; and (iii) passivation at room temperature or elevated temperatures with a passivation gas, such as F, Cl, O, other active fluorine-, chlorine-, or oxygen-containing chemicals or mixtures thereof, or DMAC or other alkylaluminum chlorides. The canisters can be leak-proof (e.g., substantially hermetically sealed) and filled with a blanket gas to ensure no air ingress occurs during storage and transportation. In this manner, appropriate storage conditions are created that allow the high-purity DMAC composition to be maintained and remain chemically stable without decomposition. In connection with the purification of DMAC material and canister passivation, suitable measurement methods for analysis of the specific target impurities described above can be modified, customized, and / or developed, including FTIR with direct and indirect sampling, various GC methods, MS, NMR, and CRDS.

[0054] DMAC can be loaded into the canister either as a liquid or a gas. One exemplary method for liquid loading involves connecting the canister to a source vessel using a dip tube that extends into the liquid phase of the DMAC. The source vessel is pressurized with an inert pusher gas, such as nitrogen, argon, helium, or other suitable gas, which forces the liquid DMAC out of the source vessel and into the canister. The canister pressure is maintained low enough to allow for controlled transfer of the liquid DMAC. The inert pusher gas can be maintained as a blanket gas within the canister.

[0055] Vapor filling involves the transfer of DMAC from a source container to a canister via the vapor phase. In one exemplary method, the source container can be optionally heated to a predetermined temperature to generate a pressure substantially higher than the canister pressure. The canister can be optionally cooled to reduce the pressure for more efficient DMAC transfer. The canister can be maintained under DMAC vapor pressure, or a blanket gas such as N2, Ar, or He can be added to the canister headspace. In one embodiment, the blanket gas is generally maintained at a pressure of 1 atmosphere and does not substantially disrupt the equilibrium between the liquid phase of DMAC and its corresponding vapor phase occupying the headspace in the canister.

[0056] The high-purity DMAC composition of the present invention enables its use as a suitable material for ALE in semiconductor applications where semiconductor-grade purity levels are required. In a preferred embodiment, selective ALE of HfO2 can be used using a substitution amount of HF with the high-purity DMAC composition. In the first step, surface modification of the HfO2 surface occurs, fluorinating the surface with HF, with the formation of a HfF4 layer and water as a by-product. Subsequently, in the second step, vapor-phase high-purity DMAC can be delivered from a suitable delivery device, such as the passivated canister described above, or an intermediate vessel positioned on the ALE tool that is loaded from the passivated canister. High-purity DMAC is a metal-based precursor that accepts fluorine from the HfF4 layer and donates chlorine ligands to the Hf metal in the metal fluoride, forming HfCl4 as a volatile by-product. This ligand exchange process forms the volatile reaction products (CH3)2AlF and HfCl4, which cause the removal of the HfF4 layer. Due to its semiconductor-grade purity of 99.9 mole % or greater, the DMAC material can be precisely etched with a high etch selectivity of 10:1 or greater that favors the HfO2 material being etched over undesired etch materials (e.g., Si, SiO2, Si3N4, and TiN) being etched from 3D NAND structures, resulting in 3D NAND structures with aspect ratios greater than 50:1. In this manner, one or more cycles of HF followed by delivery of the DMAC high-purity composition material can be used to selectively remove material on an atomic basis with high precision and acceptably high etch rates from all feature walls equally at the top and bottom of trenches in 3D NAND structures, producing features, structures, and / or devices with acceptably low film roughness.

[0057] The operating parameters for using high purity DMAC material in the ALE process, such as temperature, pressure, reaction time, canister volume, and flow rate, can be performed as known in the art, for example, as disclosed in U.S. Pat. No. 10,381,227 to George et al.

[0058] Although selective etching has been described with respect to HfO surfaces, other metal oxide surfaces can also be selectively etched in accordance with the principles of the present invention. For example, other non-limiting examples of suitable metal oxides include AlO, ZrO, ZnO, and TiO.

[0059] The DMAC material can be delivered in several ways. One exemplary delivery method involves removing a portion of the liquid semiconductor-grade DMAC material from a canister and introducing the liquid semiconductor-grade DMAC material into an intermediate buffer container. The intermediate buffer container may be incorporated into the delivery system. The purity of the DMAC material is preferably maintained as it moves from the canister to the intermediate buffer container. The liquid semiconductor-grade DMAC material continues to be loaded into the intermediate buffer container until a sufficient amount of DMAC material has accumulated in the intermediate buffer container so that a steady flow of DMAC vapor from the intermediate container can occur. It should be understood that two or more intermediate buffer containers can be utilized to transfer the high-purity DMAC liquid phase. Once the required amount of liquid material, substantially in equilibrium with the high-purity DMAC vapor phase, has accumulated, the DMAC vapor in the intermediate container can be distributed to downstream tools, such as an ALE tool. The vapor has a semiconductor-grade purity of 99.9 mol% or greater. The vapor can flow to downstream tools under its own vapor pressure. Alternatively, delivery of vapor to the downstream tool can be accomplished by using a carrier gas that can sweep the headspace of an intermediate buffer vessel or be drawn through the liquid phase of the semiconductor-grade DMAC material, either method resulting in a steady, sustained, and sufficient flow of 99.9 mol% or greater DMAC vapor to the downstream tool.

[0060] In another embodiment, a high purity DMAC composition suitable for use as an atomic layer etchant (ALE) in a semiconductor manufacturing process comprises gaseous impurities in a high purity gas phase, the impurity profile being categorized as follows: (i) atmospheric gases having at least one of H, O, N, Ar, CO, CO, and any combination thereof, each of which is greater than 0 and less than or equal to about 10 ppmv based on the total moles in the gas phase as measured by GC-FID; (ii) hydrocarbons having at least one of SixHy, GexHy, NH, PH, AsH, and SbH, where x and y are greater than 0 and can have any integer value, and the total amount of hydrocarbons is greater than 0 and less than or equal to about 50 ppmv based on the total moles in the gas phase as measured by GC-FID; and (iii) hydrocarbons having at least one of SixHy, GexHy, NH, PH, AsH, and SbH, where x and y are greater than 0 and can have any integer value, and the total amount of hydrocarbons is greater than 0 and less than or equal to about 50 ppmv based on the total moles in the gas phase as measured by GC-FID. (iv) volatile chlorides having at least one of Cl, HCl, CCl, SiCl, and TiCl, and oxychlorides of volatile chlorides comprising at least one of COCl, MoOCl, and SOCl, wherein the volatile chlorides and oxychlorides of the volatile chlorides are in a total amount of greater than 0 and less than or equal to about 50 ppmv based on the total moles in the gas phase as measured by FTIR and / or GC-MS; and (v) alkyl aluminum compounds and their corresponding chloride derivatives comprising at least one of Al(CH), CHAlCl, and (CH)AlCl, where x and y are greater than 0 and can have any integer value, and the total amount of alkyl aluminum compounds and their corresponding chloride derivatives is greater than 0 and less than or equal to about 100 ppmv based on the total moles in the gas phase as measured by GC-MS.

[0061] In certain applications, particularly semiconductor applications where miniaturization of features, devices, and structures requires the fabrication of smaller nodes, atomic layer-by-layer etching may require higher purity levels of DMAC etchants to achieve more precise etchant performance and higher etch selectivity. Thus, by way of non-limiting example, higher purity levels of DMAC greater than 99.9 mol%, such as 99.99 mol% or 99.999 mol%, are contemplated. In such cases, when higher purity DMAC is required, the upper concentration limits for each impurity in both the liquid and gas phases described above may need to be further reduced to enable sufficient performance of high-purity gas-phase DMAC as a high-performance etchant.

[0062] It should be understood that the present invention contemplates other semiconductor applications for high-purity DMAC raw materials. As a non-limiting example, according to another embodiment of the present invention, a novel high-purity DMAC raw material having a specific impurity profile is provided for performing an improved Al ion implantation process. The inventors have discovered that the presence of impurities in DMAC raw materials capable of generating C2H3 ions (e.g., C2H5) must be maintained below a specific upper concentration limit to avoid increasing the level of impurities available for ionization by aluminum in the plasma generated in the ion chamber. When C2H5 ionizes, it produces C2H3 ions, which have the same atomic mass as aluminum, 27. Because the atomic masses of C2H3 and aluminum are identical, the mass analysis magnet of the ion implanter cannot selectively deflect or remove C2H3 ion contaminants from the path of the Al ion beam because there is no atomic mass difference between the species. As a result, C2H3 ion contaminants are unintentionally implanted into wafer devices. When implanted, C2H3 contaminants have the adverse effect of reducing wafer device efficiency and / or causing wafer device failure.

[0063] By maintaining the C2H5 in the DMAC source material below a certain upper concentration limit, the Al-based ion beam has significantly reduced C2H3 levels compared to conventional commercial DMAC materials. The advantage is that the amount of C2H5 molecules that are ionized to C2H3 is reduced, thereby reducing the amount of C2H3 contamination in the plasma available to contaminate the Al-based ion beam.

[0064] In a preferred embodiment, a composition for DMAC suitable for use in an Al ion implantation process is provided in which high-purity DMAC is purified to a level of 99 mol% or greater with reduced levels of CH impurities capable of producing CH ions, which have the same atomic mass as aluminum (27). Specifically, the total amount of impurities capable of producing CH ions present in the high-purity DMAC feedstock is reduced to a level of less than about 1 mol%, preferably less than about 0.1 mol%, and more preferably less than about 0.01 mol%, where "about" refers to ±10% of the target value. By maintaining impurities capable of producing CH ions at or below these specified levels, contaminating ions are substantially reduced compared to those observed when utilizing commercially available DMAC feedstock. In one example, the amount of CH groups in the high-purity DMAC feedstock is reduced by about 10-fold or more, preferably about 100-fold or more, and more preferably about 1000-fold or more, compared to commercially available DMAC material.

[0065] The impurity profile of the high purity DMAC feedstock can include one or more of the following groups of impurities capable of producing CH ions as discussed herein in a total amount of less than about 1 mol %, preferably less than about 0.1 mol %, and more preferably less than about 0.01 mol %, where "about" means ±10% of the target value:

[0066] A first group of impurities can include hydrocarbons of the general formula CxHy, where x is equal to 2 and y is equal to any integer that satisfies the valence rules of saturated, unsaturated, cyclic, aromatic and other hydrocarbon compounds.

[0067] A second group of impurities in DMAC raw materials can include halogen derivatives of hydrocarbons of the general formula CxHyHalz, where x is equal to 2 and "Hal" is either Cl, F, Br or I.

[0068] A third group of impurities in high purity DMAC feedstock can include alkyl or alkoxy halides or hydrides of aluminum, including (C2H5)x(CH3)yAlClz, (C2H5)3Al, (C2H5)2AlCl, (C2H5)AlCl2, (C2H5)2(CH3)Al, (C2H5)(CH3)2Al, and (C2H5)(CH3)AlCl, where x, y, or z = 0-3 and x + y + z = 3, and dimers and trimers thereof.

[0069] A fourth group of impurities in DMAC raw materials can include alkyl or alkoxy halides or hydrides of silicon, including (C2H5)x(CH3)y4SiClz, (C2H5)4Si, (C2H5)3SiCl, (C2H5)2SiCl2, (C2H5)SiCl3, (C2H5)(CH3)3Si, (C2H5)(CH3)2SiCl, and (C2H5)(CH3)SiCl2, where x, y, or z = 0-4 and x + y + z = 4.

[0070] A fifth group of impurities in DMAC raw materials can include alkyl, alkylidene, and alkoxy functional groups such as ethyl (H3C-CH2-), vinyl (H2C=CH-), and ethoxy (H3C-CH2-0-).

[0071] One or more species from Groups 1, 2, 3, 4, and 5 may be present in the high-purity DMAC feedstock, provided that the total amount of such species is less than about 1 mol %, preferably less than about 0.1 mol %, and more preferably less than about 0.01 mol %. Maintaining an upper concentration limit for one or more species in the high-purity DMAC feedstock reduces the number of C2H3 ions generated in the ion chamber. In contrast to the present invention, due to the abundance of C2H3 ions from commercially available DMAC materials, prior art has attempted to sequester C2H3 ion contaminants by adding a co-flow gas. Specifically, the co-flow gas contains fluorine molecules that bind to the contaminants and significantly change their mass, thereby enabling their removal from the implant beam via a mass analysis magnet. However, in accordance with the principles of the present invention, a DMAC aluminum ion implantation source has a reduced concentration of C2H5 contaminants that ionize to C2H3, having an atomic mass of 27, in the ion chamber, thereby eliminating the need for a co-flow gas to modify these contaminants to a higher atomic mass that can then be removed via a mass analysis magnet. The present invention allows the ion beam to consist primarily of aluminum ions with an atomic mass of 27. In this manner, the Al ion implantation process of the present invention reduces, minimizes, or avoids the implantation of CH ions, providing a substantially simplified and improved process compared to conventional Al ion implantation processes. According to another aspect of the present invention, a method for implanting aluminum ions into a workpiece is provided. The method illustratively includes supplying high-purity DMAC raw material to an ion source. The high-purity DMAC raw material is contained in a suitable storage and delivery package. The storage and delivery package may be a cylinder for maintaining the high-purity DMAC raw material in at least a partial vapor phase under subatmospheric pressure conditions therein. The high-purity DMAC raw material remains chemically stable and does not undergo decomposition within the cylinder. The high-purity DMAC raw material is preferably stored as a liquid at ambient temperature (e.g., 20-25°C) and has sufficient vapor pressure without the use of heat.The high purity DMAC source material in the cylinder is operably connected to an ion implanter where it is ionized in an ion source to produce ions that are primarily aluminum and have an atomic mass of substantially 27. The amount of CH impurity, which may be any one or more species of Groups 1, 2, 3, 4 and / or 5 described above, is negligible in the plasma upon ionization and does not require removal by a co-flowing fluorine-based gas.

[0072] The Al-based ion beam is then transported to the surface of the workpiece. The aluminum ions penetrate into the workpiece to form doped regions with desired electrical and physical properties. The aluminum ions are implanted without substantially implanting C2H3 impurity ion species into the wafer devices, thereby avoiding degradation or failure of the wafer devices.

[0073] The present invention has several advantages. For example, the present invention eliminates the cost, storage, and handling of highly toxic, corrosive, and oxidizing fluorine-based mixtures that must be run in parallel to remove CH contaminants in the plasma. In contrast to current techniques for performing Al ion implantation processes that attempt to remove harmful carbon-hydrogen compounds with an atomic mass of 27, the present invention differs significantly from the prior art in that it reduces or minimizes the number of harmful carbon-hydrogen compounds in the source material, thereby reducing or minimizing the level of contaminants in the plasma to a level that does not adversely affect device performance of the aluminum ions implanted therein. Furthermore, compared to solid aluminum sources, the present invention allows for faster start-up times and results in higher tool utilization.

[0074] While preferred embodiments of the DMAC raw material are designed to improve the aluminum ion implantation process by minimizing CH impurities and reducing, eliminating, or minimizing CH contaminants having an atomic mass of 27, it should be understood that the present invention can be implemented to ensure that the DMAC raw material reduces, eliminates, or minimizes other sources of contaminants that can result in an atomic mass of 27 upon ionization. For example, BH, CBH, HCN, HNC, NBH, BO, and CDH are examples of sources of contaminants that can result in an atomic mass of 27 upon ionization. Therefore, the high-purity DMAC raw material is formulated to reduce, eliminate, or minimize such other impurities other than CH that can produce ions having an atomic mass of 27 upon ionization.

[0075] The above description, along with the accompanying embodiments, represents only one possible configuration for implementing the present invention. It should be understood that the measurement technique disclosed above represents one possible analysis for determining various impurities in DMAC material. It will be understood that a wide variety of other functionally equivalent measurement techniques may be utilized, as needed, to define the impurity fingerprint profile of a high-purity DMAC composition. Furthermore, any suitable purification technique known in the art or modifications to the purification techniques described herein may be used to reduce impurities to below their respective upper concentration limits. Furthermore, any suitable passivation technique may be used to ensure that canister-derived contaminants do not degrade and / or contaminate the high-purity DMAC material stored within the canister.

[0076] While we have shown and described what are considered to be particular embodiments of the present invention, it will of course be understood that various modifications and changes in form or detail can be readily made therein without departing from the spirit and scope of the invention. It is therefore intended that the present invention not be limited to the exact forms and details shown and described herein, nor be limited to anything less than the full scope of the invention disclosed herein and claimed below.

Claims

1. 1. A high purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, said composition comprising: the high purity DMAC composition maintained under storage conditions in a liquid phase that is in substantial equilibrium with a high purity vapor phase; the high purity gas phase having a purity level of the DMAC of greater than or equal to about 99.9 mole percent based on the total moles in the gas phase, the total moles in the gas phase excluding any optional blanket gas that may occupy the gas phase, and further wherein the remainder of the total moles in the gas phase is occupied by gaseous impurities; the gaseous impurities comprising: (i) atmospheric gases selected from the group consisting of H, O, N, Ar, CO, CO, and any combination thereof; (ii) hydrocarbons of the general formula represented by CxHy, where x and y are greater than 0 and may have any integer value; (iii) moisture, HO; (iv) volatile hydrides; (v) chloride derivatives of the volatile hydrides; (vi) volatile chlorides; (vii) oxychlorides of the volatile hydrides; and (viii) alkyl aluminum compounds and their corresponding chlorine derivatives; 1. A high-purity DMAC composition, wherein each of said gaseous impurities is present in an amount greater than 0 mol % and less than or equal to about 0.1 mol %, with the proviso that the total amount of all of said gaseous impurities is less than or equal to about 0.1 mol %.

2. 2. The high purity DMAC composition of claim 1, wherein the hydrocarbon comprises at least one of CH, C2H, C2H, C3H, C3H, C4H, C5H, C6H, C7H, or CxHy, where x is an integer and y=2x-2, 2x, or 2x+2.

3. 2. The high-purity DMAC composition of claim 1, wherein the chloride derivatives of the volatile hydrides comprise at least one of SixHyClz and GexHyClz, where x, y, and z are greater than 0 and can have any integer value.

4. 2. The high-purity DMAC composition of claim 1, wherein the alkyl aluminum compounds and their corresponding chlorine derivatives comprise at least one of Al(CH), CHAlCl, and (C)AlCl, where x and y are greater than 0 and can have any integer value.

5. 2. The high purity DMAC composition of claim 1, wherein the volatile hydride comprises at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer value.

6. 2. The high-purity DMAC composition of claim 1, wherein the volatile chloride comprises at least one of Cl, HCl, CCl, CHCl, CHCl, CHCl, SiCl, and TiCl.

7. 2. The high purity DMAC composition of claim 1, wherein the oxychloride comprises at least one of at least one of COCl, MoOCl, and SOCl.

8. 10. The high purity DMAC composition of claim 1, wherein each of said atmospheric gases is contained in an amount of about 10 ppmv or less.

9. 2. The high purity DMAC composition of claim 1, wherein the amount of water is about 10 ppmv or less.

10. 3. The high purity DMAC composition of claim 2, wherein the amount of hydrocarbons is about 50 ppmv or less.

11. 2. The high purity DMAC composition of claim 1, wherein the amount of volatile chlorides and oxychlorides is about 50 ppmv or less.

12. 2. The high purity DMAC composition of claim 1, wherein the amount of said alkyl aluminum compound and said corresponding chlorine derivative is about 100 ppmv or less.

13. 10. The high-purity DMAC composition of claim 1, wherein the storage conditions of the high-purity DMAC composition are adapted to maintain the purity level of about 99.9 mole % or greater and to remain chemically stable at ambient temperatures without undergoing decomposition under the storage conditions.

14. 1. A high purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, said composition comprising: the high-purity DMAC composition maintained under storage conditions having a gas phase in substantial equilibrium with a liquid phase; the liquid phase having impurities; the impurities contained in the liquid phase include: (i) hydrocarbons of the general formula represented by CxHy, where x and y are greater than 0 and can have any integer value; (ii) moisture, HO; (iii) metals in an amount greater than 0 mol % and less than or equal to about 0.01 mol %; (iv) hydrides comprising at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer value; (v) chloride derivatives of the volatile hydrides; (vi) chlorides; (vii) oxychlorides of the chlorides; and (viii) alkyl aluminum compounds and their corresponding chlorine derivatives; 1. A high-purity DMAC composition, wherein each of said impurities in said liquid phase is contained in an amount greater than 0 mol % and less than or equal to about 0.1 mol %, with the proviso that the total amount of all of said liquid phase impurities is less than or equal to about 0.1 mol %.

15. 15. The high purity DMAC composition of claim 14, wherein each of said metals is contained in an amount of about 1 ppmv or less.

16. 15. The high purity DMAC composition of claim 14, wherein the hydrocarbon comprises at least one of CH, C2H6, C2H4, C3H8, or C3H6.

17. 15. The high purity DMAC composition of claim 14, wherein the chloride comprises at least one of Cl2, HCl, CCl4, SiCl4, and TiCl4.

18. 15. The high purity DMAC composition of claim 14, wherein the oxychloride comprises at least one of at least one of COCl, MoOCl, and SOCl.

19. 15. The high purity DMAC composition of claim 14, wherein the chloride derivatives of the volatile hydrides comprise at least one of SixHyClz and GexHyClz, where x, y, and z are greater than 0 and can have any integer value.

20. 15. The high purity DMAC composition of claim 14, wherein the hydride comprises at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer value.

21. 1. A high-purity semiconductor-grade DMAC composition maintained under storage conditions in a liquid phase that is in substantial equilibrium with a high-purity vapor phase, whereby the high-purity vapor phase of the high-purity DMAC composition is configured for use as an atomic layer etchant having an etch selectivity of species x to species y of about 10:1 or greater in a semiconductor manufacturing process using HF as a first etchant gas, followed by the high-purity vapor phase of the high-purity DMAC composition as a second etchant gas.

22. 22. The high purity DMAC composition of claim 21, wherein the species x is selected from the group consisting of Al2O3, HfO2, ZrO2, ZnO, and TiO2, and the species y is selected from the group consisting of Si, SiO2, Si3N4, and TiN, and any combination of the species x and the species y can be selectively etched in the semiconductor manufacturing process with an etch selectivity ratio of 10:1 or greater.

23. 1. A semiconductor-grade dimethylaluminum chloride (DMAC) material stored in a substantially hermetically sealed, passivated canister, the DMAC material comprising a liquid phase in substantial equilibrium with a vapor phase occupying a predetermined headspace of the canister, the substantially hermetically sealed, passivated canister configured to maintain the vapor phase at a semiconductor-grade purity level of 99.9 mole% or greater based on the total number of moles in the predetermined headspace during shipping, storage, and use of the substantially hermetically sealed, passivated canister, the total number of moles in the predetermined headspace excluding any optional blanket gas that may occupy the vapor phase.

24. 1. A high purity dimethylaluminum chloride (DMAC) composition suitable for use as a precision atomic layer etchant (ALE) in a semiconductor manufacturing process, said composition comprising: a substantially hermetically sealed and passivated canister; the high purity DMAC composition maintained in the substantially hermetically sealed and passivated canister under storage conditions in a liquid phase that is in substantial equilibrium with a high purity vapor phase; the high purity gas phase having a purity level of the DMAC of greater than or equal to about 99.9 mole percent based on the total moles in the gas phase, the total moles in the gas phase excluding any optional blanket gas that may occupy the gas phase, and further wherein the remainder of the total moles in the gas phase is occupied by gaseous impurities; the gaseous impurities occupying a predetermined volume of headspace within the substantially hermetically sealed and passivated canister include: (i) atmospheric gases selected from the group consisting of H, O, N, Ar, CO, CO, and any combination thereof; (ii) hydrocarbons including at least one of SixHy, GexHy, NH, PH, AsH, and SbH; (iii) moisture, HO; (iv) volatile hydrides including at least one of SixHy, GexHy, NH, PH, AsH, and SbH; and (v) chloride derivatives of the volatile hydrides, the chloride derivatives including at least one of SixHyClz and GexHyClz, and having the formula wherein x, y, and z are greater than 0 and may have any integer value; (vi) chloride derivatives thereof, wherein x, y, and z are greater than 0 and may have any integer value; (vii) volatile chlorides, wherein the chloride derivatives are Cl2, HCl, CCl4, SiCl4, and TiCl4; (vii) oxychlorides of the volatile chlorides, wherein the chloride derivatives are COCl2, MoO2Cl2, and SOCl2; and (viii) alkylaluminum compounds and their corresponding chlorine derivatives, wherein the alkylaluminum compounds and their corresponding chlorine derivatives are Al(CH3)3, CH3AlCl2, and (C2H5)xAlCly, wherein x and y are greater than 0 and may have any integer value; A high-purity DMAC composition, wherein the total amount of said gaseous impurities is 0.1 mol% or less based on the total number of moles in said vapor phase.

25. A semiconductor-grade dimethylaluminum chloride (DMAC) material having a purity of 99.9 mol% or greater, the semiconductor-grade DMAC material containing impurities, the impurities including at least one of hydrocarbons, moisture, hydrides, chlorides, alkylaluminum compounds and corresponding chlorine derivatives, and atmospheric gases selected from the group consisting of H, O, N, Ar, CO, and CO; a total amount of said impurities is greater than 0 mol % and less than or equal to about 0.1 mol %, the balance being said semiconductor grade DMAC material.

26. 26. The DMAC material of claim 25, wherein the semiconductor grade DMAC material exhibits etch selectivity defined as an etch selectivity ratio of 10:1 or greater.

27. 27. The semiconductor-grade DMAC material of claim 26, wherein the etch selectivity ratio of 10:1 or greater is for selective etching of species x over species y, wherein species x is selected from the group consisting of Al2O3, HfO2, ZrO2, ZnO, and TiO2, and species y is selected from the group consisting of Si, SiO2, Si3N4, and TiN, and any combination of species x and species y can be selectively etched with an etch selectivity ratio of 10:1 or greater in the semiconductor manufacturing process.

28. 26. The semiconductor-grade DMAC material of claim 25, wherein the DMAC material is maintained under storage conditions that promote the semiconductor-grade DMAC material to remain chemically stable without undergoing decomposition.

29. 26. The semiconductor-grade DMAC material of claim 25, wherein the impurities comprise the hydrocarbon further defined as at least one of CH4, C2H6, C2H4, C3H8, C3H6, C4H10, C5H12, C6H14, C7H16, or CxHy, where x is an integer and y = 2x - 2, 2x, or 2x + 2.

30. 26. The semiconductor-grade DMAC material of claim 25, wherein the impurities comprise alkyl aluminum compounds and corresponding chlorine derivatives, the alkyl aluminum compounds and corresponding chlorine derivatives being further defined as at least one of Al(CH), CHAlCl, and (C H )AlCl, where x and y are greater than 0 and can have any integer value.

31. 26. The semiconductor-grade DMAC material of claim 25, wherein the impurities comprise chloride, the chloride being further defined as at least one of SixHyClz, GexHyClz, COCl2, MoO2Cl2, SOCl2, Cl2, HCl, CCl4, CHCl3, CH2Cl2, CHCl3, SiCl4, and TiCl4, where x, y, and z are greater than 0 and can have any integer value.

32. 26. The semiconductor-grade DMAC material of claim 25, wherein the impurities comprise hydrides, the hydrides being further defined as at least one of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and can have any integer value.

33. 26. The semiconductor-grade DMAC material of claim 25, wherein the semiconductor-grade DMAC material is maintained in a substantially hermetically sealed and passivated canister.

34. 1. A method of filling a canister configured to deliver semiconductor grade DMAC material having a purity of 99.9 mole % or greater, comprising: providing said canister hermetically sealed or substantially sealed; evacuating the interior volume of the canister; passivating the interior walls of the canister to remove residual solvent, moisture, particles and / or other impurities adsorbed on the interior walls; and introducing semiconductor grade DMAC material having a purity of 99.9 mol% or greater into said canister, thereby excluding air ingress to maintain said purity of 99.9 mol% or greater.

35. 35. The method of claim 34, further comprising forcing a liquid phase of the semiconductor-grade DMAC material from a source vessel into the canister using a pusher gas.

36. 35. The method of claim 34, further comprising establishing a sufficient pressure differential between the semiconductor-grade DMAC material source container and the canister to allow transfer of the vapor phase of the semiconductor-grade DMAC material into the canister.

37. A semiconductor-grade dimethylaluminum chloride (DMAC) material having a purity of 99.9 mol% or greater, the semiconductor-grade DMAC material containing impurities, the impurities including at least one of hydrocarbons, moisture, hydrides, chlorides, alkylaluminum compounds and corresponding chlorine derivatives, and atmospheric gases selected from the group consisting of H, O, N, Ar, CO, and CO; the total amount of said impurities is greater than 0 mol % and less than or equal to about 0.1 mol %, the balance being said DMAC material; with the proviso that if the impurities include hydrocarbons, the hydrocarbons include one or more of CH4, C2H6, C2H4, C3H8, C3H6, C4H10, C5H12, C6H14, C7H16, or CxHy, where x is an integer and y=2x-2, 2x, or 2x+2; with the proviso that when the impurity comprises a hydride, the hydride comprises one or more of SixHy, GexHy, NH3, PH3, AsH3, and SbH3, where x and y are greater than 0 and may have any integer value; with the caveat that if the impurities include chloride, the chloride comprises one or more of SixHyClz, GexHyClz, COCl2, MoO2Cl2, SOCl2, Cl2, HCl, CCl4, CHCl3, CH2Cl2, CHCl3, SiCl4, and TiCl4, where x, y, and z are greater than 0 and may have any integer value; provided that, when the impurities include alkyl aluminum compounds and corresponding chlorine derivatives, the alkyl aluminum compounds and corresponding chlorine derivatives include one or more of Al(CH3)3, CH3AlCl2, and (C2H5)xAlCly, where x and y are greater than 0 and may have any integer value.

38. A method using semiconductor grade dimethylaluminum chloride DMAC, providing a canister at least partially filled with a liquid phase of said semiconductor grade DMAC material; removing the liquid phase of the semiconductor grade DMAC material from the canister at a purity of 99.9 mole percent or greater semiconductor grade; directing the liquid phase of the semiconductor grade DMAC material to an intermediate buffer vessel; accumulating a sufficient amount of the DMAC material in the intermediate buffer vessel until a steady flow of DMAC vapor from the intermediate buffer vessel can occur; and distributing the DMAC vapor from the intermediate vessel to a downstream tool for atomic layer etching associated with a semiconductor manufacturing process, wherein the DMAC vapor is introduced to the downstream tool at a semiconductor grade purity of 99.9 mol % or greater.

39. A semiconductor-grade dimethylaluminum chloride (DMAC) raw material suitable for use in an improved aluminum ion implantation process, the DMAC raw material having a purity of at least about 99 mole percent or greater based on the total number of moles in the DMAC raw material, and having reduced levels of impurities in materials capable of generating CH ions; The impurities in the material capable of producing the C2H3 ions are (i) hydrocarbons represented by the general formula CxHy, where x is equal to 2 and y is equal to any integer satisfying the valence rules of saturated, unsaturated, cyclic, aromatic, and other hydrocarbon compounds; (ii) halogen derivatives of hydrocarbons represented by the general formula CxHyHalz, where x is equal to 2 and "Hal" is either Cl, F, Br, or I; (iii) alkyl or alkoxy halides or hydrides of aluminum, where x, y, or z=0-3 and x+y+z=3, such as (C2H5)x(CH3)yAlClz, (C2H5)3Al, (C2H5)2AlCl, (C2H5)AlCl2, (C2H5)2(CH3)Al, (C2H5)(CH3)2Al, and (C2H5 (iv) alkyl or alkoxy halides or hydrides of aluminum, including (CH)AlCl, and dimers and trimers thereof; (iv) alkyl or alkoxy halides or hydrides of silicon, wherein x, y, or z=0 to 4 and x+y+z=4, such as (C2H5)x(CH3)y4SiClz, (C2H5)4Si, (C2H5)3SiCl, (C2H5)2SiCl; (v) alkyl, alkylidene, alkoxy functional groups, including ethyl (HC—CH—), vinyl (HC═CH—), ethoxy (HC—CH—O—), and the like; a total amount of said impurities in said material capable of generating C2H3 ions is greater than 0 mol % and less than about 1 mol %, the balance being said semiconductor-grade DMAC material.

40. 40. The semiconductor-grade dimethylaluminum chloride (DMAC) feedstock of claim 39, wherein a total amount of the impurities in the material capable of producing CH ions is greater than 0 mol% and less than about 0.1 mol%, the balance being the semiconductor-grade DMAC feedstock.

41. 40. The semiconductor-grade dimethylaluminum chloride (DMAC) raw material of claim 39, wherein a total amount of the impurities in the material capable of producing CH ions is greater than 0 mol % and less than about 0.01 mol %, the balance being the semiconductor-grade DMAC material.

42. A semiconductor-grade dimethylaluminum chloride (DMAC) raw material suitable for use in an improved aluminum ion implantation process, said DMAC raw material having a purity of at least about 99 mole percent or greater, said semiconductor-grade DMAC raw material containing reduced levels of one or more impurities therein capable of producing C2H3 ions; a semiconductor-grade dimethylaluminum chloride (DMAC) raw material, wherein a total amount of the one or more impurities in the material capable of generating C2H3 ions is greater than 0 mol % and less than or equal to about 1 mol %, with the remainder being the semiconductor-grade DMAC material.

43. 1. An improved method for performing aluminum ion implantation, comprising: removing from a storage and delivery package a high purity DMAC raw material in a vapor phase, wherein the DMAC raw material in the vapor phase has a purity of at least about 99 mol% or greater, and wherein the semiconductor grade DMAC raw material includes reduced levels of one or more impurities therein capable of producing CH ions in an amount greater than 0 mol% and less than or equal to about 1 mol%; flowing the high purity DMAC source material in the gas phase without a co-flow gas configured to trap the C2H3 ions; introducing the high purity DMAC source material into an ion source chamber.

44. ionizing the high-purity DMAC raw material without substantially generating C2H3 ions from the one or more impurities contained in the high-purity DMAC raw material; generating aluminum ions; 44. The improved method of claim 43, further comprising the step of: implanting said aluminum ions into wafer devices, wherein said implanted aluminum ions are not contaminated with said C2H3 ions.

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