Method for generating cluster ion beam and method for implanting cluster ions

Abstract

To provide a cluster ion beam generation method capable of stably and controllably generating ion beams containing light hydrogen and deuterium simultaneously.SOLUTION: The cluster ion beam generation method includes a hydrocarbon compound mixing step in which a first hydrocarbon compound containing deuterium and a second hydrocarbon compound containing at least partly light hydrogen are mixed to obtain a hydrocarbon-based compound mixture source material and a mass number selection step for ionizing the hydrocarbon-based compound mixture material to determine a convergence range of a cluster ion beam by selecting a selection range of mass numbers containing both cluster ions containing light hydrogen and cluster ions containing deuterium. The first hydrocarbon-based compound source material and the second hydrocarbon-based compound source material have the same carbon skeleton.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for generating a cluster ion beam and a method for implanting cluster ions. [Background technology]

[0002] In this specification, when simply referring to hydrogen or hydrogen atom, this refers to hydrogen (or hydrogen atom) in the broad sense, and refers to all hydrogen atoms with one proton. A hydrogen atom with only one proton (i.e., mass number 1) is described as proton-hydrogen and has the chemical symbol H. A hydrogen atom with one proton and one neutron (mass number 2) is described as deuterium and has the chemical symbol D. Tritium (tritium: chemical symbol T), which has two neutrons (mass number 3), is also included in deuterium in the broad sense, but when simply referring to "deuterium" in this specification, it refers to deuterium.

[0003] In recent years, cluster ion beam technology, which bombards solid surfaces with ions, has been attracting attention as a surface processing technology for nanofabrication processes of various devices such as semiconductor devices, magnetic / dielectric devices, and optical devices.

[0004] Patent Document 1 proposes a method for producing an epitaxial silicon wafer, which includes a cluster ion beam irradiation step of irradiating a silicon wafer with cluster ions containing C (carbon) and H (proton) as constituent elements at a predetermined beam current to form a modified layer in the surface layer of the silicon wafer, in which the constituent elements of the cluster ions are solid-dissolved, and a step of forming an epitaxial layer on the modified layer of the silicon wafer. The cluster ions referred to here are ions of various atomic numbers obtained by electron bombardment, which causes electrons to collide with gaseous molecules as a hydrocarbon compound mixed material, thereby dissociating the bonds of the gaseous molecules.

[0005] The technology described in Patent Document 1 is expected to not only provide excellent gettering ability but also provide a passivation effect for point defects in the epitaxial layer due to the protons contained in the cluster ions.

[0006] Furthermore, Patent Document 2 discloses a method of annealing a wafer with deuterium. According to Patent Document 2, deuterium annealing does not sufficiently repair crystal defects in the inner wall layer of the trench, and also tends to form interface (surface) states in the inner wall layer of the trench. However, these problems are resolved by annealing with deuterium. Specifically, deuterium atoms bond to crystal defects generated in the wafer, repairing the crystal defects, and deuterium atoms bond to crystal defects in the inner wall layer, reducing the interface states formed in the inner wall layer of the trench. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-051729 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-150415 Summary of the Invention [Problem to be solved by the invention]

[0008] While hydrogen has the advantage of excellent diffusion and reactivity, deuterium has the advantage of strong bonding strength. The present inventors wanted to clarify the differences between implanting a cluster ion beam containing carbon, hydrogen, and deuterium as constituent elements into a silicon wafer and implanting cluster ions consisting of carbon and hydrogen. However, a method for generating a cluster ion beam containing both hydrogen and deuterium as constituent elements stably enough for industrial use has not yet been established.

[0009] In view of the above problems, the present invention aims to provide a cluster ion beam generation method that can stably control and generate an ion beam that simultaneously contains protons and deuterium. Another aim of the present invention is to provide a cluster ion implantation method that implants the cluster ion beam thus generated into the surface of a silicon wafer. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems. They came up with the idea of ​​using a hydrocarbon compound containing deuterium and a hydrocarbon compound containing at least a portion of protium as raw materials. They then discovered that by selecting an appropriate range of mass numbers during ionization to extract desired cluster ions, it is possible to stably control and generate an ion beam containing both protium and deuterium. The present invention, which was completed based on the above findings, has the following main features.

[0011] (1) a hydrocarbon compound mixing step of mixing a first hydrocarbon compound containing deuterium with a second hydrocarbon compound containing at least a portion of protons to obtain a hydrocarbon compound mixed raw material; a mass number selection step of ionizing the hydrocarbon compound mixed material and selecting a mass number range that includes both protium-containing cluster ions and deuterium-containing cluster ions, A cluster ion beam generating method, wherein the first hydrocarbon-based compound raw material and the second hydrocarbon-based compound raw material have the same carbon skeleton.

[0012] (2) The method for generating a cluster ion beam according to (1) above, wherein the first hydrocarbon compound and the second hydrocarbon compound are hydrocarbons.

[0013] (3) The first hydrocarbon compound is represented by the general formula C n H x D y (x+y=2n+2, n is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C n H 2n+2 (n is an integer of 5 to 7).

[0014] (4) The first hydrocarbon compound is represented by the general formula C m H z Dw (z+w=2m, m is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C m H 2m (m is an integer of 5 to 7).

[0015] (5) A method for implanting cluster ions, which comprises implanting a cluster ion beam generated by the method for generating a cluster ion beam according to any one of (1) to (4) into a surface of a silicon wafer. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a cluster ion beam generation method that can stably control and generate a cluster ion beam that simultaneously contains protons and deuterium. Furthermore, the present invention can provide a cluster ion implantation method that implants the thus generated cluster ion beam into the surface of a silicon wafer. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic diagram for explaining the basic principle of a cluster ion beam generation method according to the present invention. FIG. [Figure 2] 1 is a graph showing mass spectra of various cluster ions obtained from cyclohexane (C6D12) and cyclohexane (C6H12) as hydrocarbon compound mixture materials, based on an experiment conducted by the inventor. [Figure 3] 1 is a graph showing concentration profiles of carbon, deuterium, and protium in a silicon wafer when the mass number selection value is set to 42 in Example 1. [Figure 4] 10 is a graph showing concentration profiles of carbon, deuterium, and protium in a silicon wafer when the mass number selection value is set to 46 in Example 2. [Figure 5] 10 is a graph showing concentration profiles of carbon, deuterium, and protium in a silicon wafer when the mass number selection value is set to 48 in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Cluster ion beam generation method) A cluster ion beam generation method according to the present invention includes a hydrocarbon compound mixing step of mixing a first hydrocarbon compound containing deuterium with a second hydrocarbon compound containing at least a portion of protium to obtain a hydrocarbon compound mixed material, and a mass number selection step of ionizing the hydrocarbon compound mixed material to select a range of mass numbers that includes both cluster ions containing protium and cluster ions containing deuterium. The first hydrocarbon compound raw material and the second hydrocarbon compound raw material have the same carbon skeleton. Details of each step will be explained below.

[0019] <Hydrocarbon compound mixing process> First, in the hydrocarbon compound mixing step, a first hydrocarbon compound containing deuterium and a second hydrocarbon compound containing protons are mixed to obtain a hydrocarbon compound mixed raw material. In addition to the first and second hydrocarbon compounds, the hydrocarbon compound mixed raw material may contain other compounds and unavoidable impurities, if necessary.

[0020] <<First hydrocarbon compound>> The first hydrocarbon compound is not particularly limited in terms of molecular species or structure, as long as it is a hydrocarbon compound containing deuterium. "Containing deuterium" here refers to a hydrocarbon compound in which a certain amount of protium atoms, among the constituent elements in the carbon skeleton of the hydrocarbon compound, have been artificially substituted with deuterium atoms. The proportion of deuterium among hydrogen atoms present in nature is 0.015%. Therefore, the first hydrocarbon compound in this specification significantly differs from the proportion of deuterium unintentionally contained in natural hydrocarbon compounds.

[0021] The first hydrocarbon compound may be a commercially available product or a synthetic product. Generally, a deuterium-containing hydrocarbon compound can be obtained by adding deuterium using a deuterium reduction addition reaction. The proportion of deuterium contained in the hydrocarbon compound can be confirmed by 1H-NMR or the like, but the measurement method is not limited thereto. Alternatively, a deuterium-containing hydrocarbon compound contained in a natural hydrocarbon compound may be extracted and the extract may be concentrated to obtain the first hydrocarbon compound.

[0022] The first hydrocarbon-based compound contains deuterium, and therefore, during ionization in the mass number selection step described below, various cluster ions obtained from the first hydrocarbon-based compound include cluster ions containing deuterium as at least a part of their constituent elements.

[0023] <<Second hydrocarbon compound>> The second hydrocarbon compound is a hydrocarbon compound that contains protons at least in part. Here, "containing protons at least in part" means that at least a portion of the hydrocarbon compound contains protons, and all of the hydrogen atoms may be protons.

[0024] Here, the first hydrocarbon compound and the second hydrocarbon compound have the same carbon skeleton. In the present invention, "having the same carbon skeleton" refers to a structure in which the two compounds have the same skeletal structure when all hydrogen atoms are substituted with hydrogen atoms.

[0025] The second hydrocarbon compound may be a commercially available product or a synthetic product, except for those having the same number of proton atoms and deuterium atoms as the first hydrocarbon compound. The proportion of deuterium contained in the hydrocarbon compound can be confirmed by 1H-NMR or the like, but the measurement method is not limited thereto.

[0026] The second hydrocarbon compound contains at least a portion of protons, and therefore, during ionization in the mass number selection step described below, various cluster ions obtained from the second hydrocarbon compound include cluster ions containing protons as at least a portion of their constituent elements.

[0027] The first hydrocarbon compound and the second hydrocarbon compound are preferably hydrocarbons, and may be any of chain saturated hydrocarbons, chain unsaturated hydrocarbons, cyclic hydrocarbons, and aromatic hydrocarbons, and may have functional groups, and may have oxygen atoms, phosphorus atoms, arsenic atoms, and antimony atoms in addition to carbon and hydrogen. In particular, the first hydrocarbon compound and the second hydrocarbon compound are preferably compounds that can easily extract desired cluster ions during ionization. For example, the first hydrocarbon compound is represented by the general formula C n H x D y (x+y=2n+2, n is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C n H 2n+2 (n is an integer of 5 to 7). In addition, the first hydrocarbon compound is preferably a compound represented by the general formula C m H z D w (z+w=2m, m is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C m H 2m (m is an integer of 5 to 7). In this case, x, y, z, and w are each an integer. For example, cyclohexane in which all hydrogen atoms are replaced with deuterium atoms (i.e., the general formula: C6D 12 ) is used as the first hydrocarbon compound, in this case cyclohexane CH 12 can be used for the second hydrocarbon.

[0028] <Mass number selection process> In the mass number selection step, the hydrocarbon compound mixture material obtained in the previous step is ionized to select a range of mass numbers that includes both cluster ions containing protium and cluster ions containing deuterium. The mass number selection step will be explained below using a schematic example with reference to FIG.

[0029] First, a hydrocarbon compound mixed material obtained by mixing a first hydrocarbon compound and a second hydrocarbon compound is supplied into an ionization chamber. Next, electrons are bombarded into the hydrocarbon compound mixed material in the ionization chamber by electron bombardment, dissociating the bonds of the first and second hydrocarbon compounds contained in the hydrocarbon compound mixed material and generating various ionized cluster ions. Because the first and second hydrocarbon compounds have the same carbon skeleton, their vaporization conditions and the energy required for ionization are similar, and their respective cluster ions can be generated simultaneously under ionization conditions in the same chamber.

[0030] Among the generated cluster ions, some ions derived from the first hydrocarbon compound contain deuterium, and some ions derived from the second hydrocarbon compound contain at least a portion of protons. At this stage, cluster ions containing deuterium and cluster ions containing protons are respectively obtained in the chamber. Then, a desired range of mass numbers is selected and mass separation is performed to selectively extract the cluster ions so that both cluster ions containing deuterium and cluster ions containing protons are obtained from the generated cluster ions. Next, the cluster ions are extracted using a predetermined acceleration voltage, and the cluster ions are accelerated and focused in a vacuum to form a cluster ion beam. The cluster ion beam thus obtained contains at least carbon, protons, and deuterium.

[0031] This step will be described in more detail. 12 ) as the second hydrocarbon compound, and cyclohexane (CH 12The mass spectrum (solid line) of the hydrocarbon compound mixture material when using cyclohexane (C6D) is shown in Figure 2. Furthermore, from the mass spectrum of the solid line part in Figure 2, it is clear that cyclohexane (C6D) 12 The mass spectrum of cyclohexane (CH) is shown with a dashed line. 12 The mass spectrum of the mixture ionized as a single element is shown spectrally separated by the dotted line. In the mass spectrum of the mixture shown by the solid line, by focusing a cluster ion beam from the mass range having both the dashed and dotted line peaks, it is possible to extract cluster ions containing both deuterium and protium.

[0032] The mass number selection range may be, for example, a mass number value that includes both of the target peaks derived from deuterium and protium cluster ions. However, focusing the beam within a range with a certain width around the selected value is preferable, as this increases the beam current. For example, to select mass number 41 for the peak derived from protium-containing cluster ions and mass number 43 for the peak derived from deuterium-containing cluster ions, the mass number selection range can be set to 42±1. For example, in Figure 2, the mass number selection range of 42±3 when the mass number selection value is 42 is shown by a dotted line frame.

[0033] In the mass number selection step, it is preferable to focus cluster ions within a range of the mass number selection value ±3 as a beam. This is because by setting the selection range of the mass number for extracting cluster ions to a range larger than the selection value itself, it becomes easier to focus many cluster ions as a beam.

[0034] <<Cluster ion peaks>> The peak of the cluster ions is determined by forming an ion beam under the condition of the highest mass resolution, and then measuring the mass number dependency of the measured beam current value.

[0035] The mass number of the cluster ions can be controlled by adjusting the gas pressure of the gas ejected from the nozzle, the pressure of the vacuum chamber, the voltage applied to the filament during ionization, etc. The mass number of each cluster ion can be determined by determining the number distribution of each cluster by mass analysis using a quadrupole high-frequency electric field or time-of-flight mass analysis, and then averaging the number of each cluster. Specific cluster ions to be focused into a cluster ion beam can be obtained by mass separating ionized cluster ions of various atomic numbers and extracting cluster ions of a specific mass number.

[0036] (Cluster ion implantation method) Furthermore, the method for implanting cluster ions according to the present invention is a method for implanting a cluster ion beam generated using the above-described method for generating a cluster ion beam into the surface of a silicon wafer S (see FIG. 1).

[0037] The cluster ion beam obtained by the above-described method for generating a cluster ion beam can be irradiated onto the surface of any silicon wafer. The silicon wafer can be a silicon wafer obtained by slicing a single crystal silicon ingot grown by the Czochralski method (CZ method) or the floating zone melting method (FZ method) with a wire saw or the like. Carbon and / or nitrogen may be added to the silicon wafer. Any impurity dopant may also be added to make it n-type or p-type. The silicon wafer can also be an epitaxial silicon wafer in which a silicon epitaxial layer is formed on the surface of a bulk silicon wafer.

[0038] The conditions for implanting cluster ions can be adjusted by controlling the size (mass number selection range), dose, acceleration voltage, beam current value, and ion irradiation time of the cluster ions. The dose of cluster ions per carbon atom is, for example, 1.0 × 10 12 ~1.0×10 16 atoms / cm 2As a cluster ion implantation device using this principle, for example, CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd. can be used.

[0039] The silicon wafer thus obtained can contain protium and deuterium in the surface layer. [Example]

[0040] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples in any way.

[0041] Example 1 Using an ion generator (manufactured by Nissin Ion Equipment Co., Ltd., model number: CLARIS (registered trademark)), cyclohexane (CH 12 ; mass number 84.16) 10g and cyclohexane (C6D 12 10 g of hydrogen (mass number 96.23) was introduced into the ionization chamber as a raw material, and a cluster ion beam was generated with a mass number selection value of 42. The implantation conditions for the cluster ions were an acceleration voltage of 80 keV / Cluster (acceleration voltage per hydrogen atom: 1.9 keV / atom, acceleration voltage per carbon atom: 22.8 keV / atom), and a dose of 3.3 × 10 14 ion / cm 2 (The dose per carbon atom is 1.0 × 10 15 ion / cm 2 The beam current value of the obtained cluster ions was 700 μA.

[0042] Example 2 A cluster ion beam was generated under the same conditions as in Example 1, except that the mass number selection value was set to 46.

[0043] Example 3 A cluster ion beam was generated under the same conditions as in Example 1, except that the mass number selection value was set to 48.

[0044] The mass spectra obtained during the ionization of cluster ions in Examples 1 to 3 are as shown in FIG. 2 referred to above. Also, FIGS. 3 to 5 show the ion implantation profiles in the depth direction of an epitaxial silicon wafer into which the generated cluster ion beam was implanted, with the profiles of carbon, light hydrogen, and heavy hydrogen shown by solid lines, dashed lines, and dotted lines, respectively.

[0045] <Evaluation of Hydrogen and Deuterium Concentration Profiles by SIMS> For the epitaxial silicon wafer implanted with the cluster ion beam obtained under the above manufacturing conditions, SIMS measurement was used to measure the concentration profiles of carbon, light hydrogen, and heavy hydrogen in the depth direction from the surface of the epitaxial layer. As a result, a peak of hydrogen (light hydrogen) was observed near the surface layer of 50 nm of the silicon wafer, and a peak of heavy hydrogen was observed near 100 nm, and their existences were confirmed in regions with different depths.

[0046] Also, as shown in FIGS. 3 to 5, when the mass number selection value is 42, the concentration of hydrogen is greater than the concentration of heavy hydrogen. As the mass number selection value is increased, the proportion of heavy hydrogen increases, and it can be confirmed that in the result with a mass number selection value of 48, the proportion of heavy hydrogen is greater than the proportion of hydrogen. This is consistent with the fact that in the mass spectrum of the cluster ions confirmed in FIG. 2, in the region with a mass number of 40 or more, the amount of cluster ions containing heavy hydrogen increases as the mass number increases. Therefore, in view of Examples 1 to 3, considering the balance of the implantation amounts of light hydrogen and heavy hydrogen, it is conceivable to select 47 as the optimum value of the mass number selection value.

Industrial Applicability

[0047] According to the present invention, a cluster ion beam generation method capable of stably controlling and generating a cluster ion beam containing light hydrogen and heavy hydrogen simultaneously can be provided. Further, the present invention can provide a cluster ion implantation method for implanting the cluster ion beam generated in this way onto the surface of a silicon wafer. [Explanation of symbols]

[0048] S Silicon wafer

Claims

1. a hydrocarbon compound mixing step of mixing a first hydrocarbon compound containing deuterium with a second hydrocarbon compound containing at least a portion of protons to obtain a hydrocarbon compound mixed raw material; a mass number selection step of ionizing the hydrocarbon compound mixed material and selecting a mass number range that includes both protium-containing cluster ions and deuterium-containing cluster ions, A cluster ion beam generating method, wherein the first hydrocarbon-based compound source and the second hydrocarbon-based compound source have the same carbon skeleton.

2. 2. The method for generating a cluster ion beam according to claim 1, wherein the first hydrocarbon-based compound and the second hydrocarbon-based compound are hydrocarbons.

3. The first hydrocarbon compound is represented by the general formula C ｎ H ｘ D ｙ (x+y=2n+2, n is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C ｎ H ２ｎ＋２ 3. The method for generating a cluster ion beam according to claim 2, wherein n is an integer of 5 to 7.

4. The first hydrocarbon compound is represented by the general formula C ｍ H ｚ D ｗ (z+w=2m, m is an integer of 5 to 7), and the second hydrocarbon compound is represented by the general formula C ｍ H ２ｍ 3. The method for generating a cluster ion beam according to claim 2, wherein m is an integer of 5 to 7.

5. A method for implanting cluster ions, comprising implanting a cluster ion beam generated by the method for generating a cluster ion beam according to any one of claims 1 to 4 into a surface of a silicon wafer.

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