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 deuterium-containing hydrocarbon compound preparation step for preparing a deuterium-containing hydrocarbon compound having a hydrocarbon group containing light hydrogen and deuterium and a mass number selection step in which the deuterium-containing hydrocarbon compound is ionized to determine the convergence range of a cluster ion beam by selecting a selection range of mass numbers that includes both light hydrogen-containing cluster ions and deuterium-containing cluster ions.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 epitaxial silicon wafers, which includes a cluster ion beam irradiation step in which a silicon wafer is irradiated 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 in which an epitaxial layer is formed on the modified layer of the silicon wafer. The cluster ions referred to here are ions of various atomic numbers obtained by colliding electrons with gaseous molecules, which are a hydrocarbon compound mixed material, by electron impact to dissociate 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 deuterium-containing hydrocarbon compound having a hydrocarbon group containing protium and deuterium atoms as a source of an ion beam. They then discovered that by selecting an appropriate mass number during ionization to extract desired cluster ions, it is possible to stably and controllably 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 deuterium-containing hydrocarbon compound preparation step of preparing a deuterium-containing hydrocarbon compound having a hydrocarbon group containing protons and deuterium; a mass number selection step of ionizing the deuterium-containing hydrocarbon compound and selecting the mass number of cluster ions containing both protium and deuterium.

[0012] (2) The method for generating a cluster ion beam according to (1) above, wherein the deuterium-containing hydrocarbon compound preparation step is performed by adding deuterium to a raw material hydrocarbon compound having an unsaturated hydrocarbon group or an aromatic hydrocarbon group composed of carbon and protons through a deuterium reduction reaction, thereby obtaining the deuterium-containing hydrocarbon compound.

[0013] (3) The deuterium-containing hydrocarbon compound obtained by the deuterium reduction reaction has the general formula C n H x D y (x+y=2n+2, where x and y are natural and even numbers, and n is an integer of 5 to 7).

[0014] (4) The deuterium-containing hydrocarbon compound obtained by the deuterium reduction reaction has the general formula C m H z D w(z+w=2m, where z and w are natural and even numbers, and m is an integer of 5 to 7).

[0015] (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 (1) to (4) above 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. DETAILED DESCRIPTION OF THE INVENTION

[0018] (Cluster ion beam generation method) A cluster ion beam generation method according to the present invention includes a deuterium-containing hydrocarbon compound preparation step of preparing a deuterium-containing hydrocarbon compound having a hydrocarbon group containing protons and deuterium, and a mass number selection step of ionizing the deuterium-containing hydrocarbon compound and selecting the mass number of cluster ions containing both protons and deuterium. Each step will be described in detail below.

[0019] <Preparation of deuterium-containing hydrocarbon compound> In the deuterium-containing hydrocarbon compound preparation process, a deuterium-containing hydrocarbon compound having a hydrocarbon group containing protium and deuterium is prepared. The constituent elements of the deuterium-containing hydrocarbon compound include carbon, protium, and deuterium atoms, and may include other elements if necessary, as well as unavoidable impurities. The term "containing protium and deuterium" as used herein refers to a hydrocarbon compound in which a certain amount of protium atoms among the constituent elements of a hydrocarbon compound have been artificially replaced with deuterium atoms. Note that the proportion of deuterium among hydrogen atoms present in nature is 0.015%. Therefore, the deuterium-containing hydrocarbon compound in this specification differs significantly from the unintentional deuterium content of natural hydrocarbon compounds. The molecular species and structure of the deuterium-containing hydrocarbon compound are not particularly limited, and commercial or synthetic products may be used. The proportion of deuterium contained in the deuterium-containing hydrocarbon compound can be confirmed by 1H-NMR or other methods, but the measurement method is not limited. Alternatively, the deuterium-containing hydrocarbon compound may be obtained by extracting deuterium-containing hydrocarbon compounds contained in natural hydrocarbon compounds and concentrating the extract.

[0020] <<Deuterium reduction reaction>> In preparing the deuterium-containing hydrocarbon compound, it is preferable to add deuterium to a raw material hydrocarbon compound having an unsaturated hydrocarbon group or an aromatic hydrocarbon group by a deuterium reduction reaction.

[0021] In the deuterium reduction reaction, deuterium atoms can be added by using a specific catalyst and deuterium gas (D2, etc.) as a reducing agent. Except for the use of deuterium gas, the deuterium reduction reaction can be carried out by the commonly known hydrogen reduction reaction (also called catalytic hydrogenation), and the reduction conditions, etc. are not particularly limited.

[0022] The starting compound used in the deuterium reduction reaction to obtain a deuterium-containing hydrocarbon compound is not particularly limited as long as it is a starting hydrocarbon compound having an unsaturated hydrocarbon group consisting of carbon and hydrogen or an aromatic hydrocarbon group. Here, specific embodiments in which the starting hydrocarbon compound is a chain unsaturated hydrocarbon having double bonds and triple bonds as the bonding mode of the carbon chain, and an aromatic hydrocarbon group will be described in detail.

[0023] -In the case of double bonds (chain unsaturated hydrocarbons)- First, the deuterium reduction of a chain unsaturated hydrocarbon containing a double bond can be represented by the following formula (I). [ka]

[0024] In the above formula (I), R and R bonded to the carbon atom 2、 R3 and R4 may be independent straight-chain or branched alkyl groups having 1 or more carbon atoms, or may be hydrogen atoms or other atoms. 2、 R3 and R4 may all be the same alkyl group, any two of them may be the same alkyl group or atom, or they may all be different. Note that the term "straight chain" as used herein includes a case where the number of carbon atoms is 1 to 3 and no branching occurs, and hereinafter the term "straight chain" will be used in the same sense.

[0025] As can be seen from formula (I), two deuterium atoms are added to each double bond by reduction. Therefore, if a specific starting hydrocarbon compound is used, the number of deuterium atoms added is uniquely determined by the structure of the compound, making it possible to obtain a deuterium-containing hydrocarbon compound with a desired deuterium ratio with good control. For example, hexene (general formula: CH 12 ) is deuterated to form hexane (general formula: CH 12 D2) can be obtained.

[0026] In the deuteration reduction, a catalyst is used, and examples thereof include Pd / C (palladium on carbon), but any substance can be used as the catalyst.

[0027] -In the case of triple bonds (chain unsaturated hydrocarbons)- Next, the deuterium reduction of a chain unsaturated hydrocarbon containing a triple bond can be represented by the following formula (II). [ka]

[0028] Here, R5 and R6 may be any alkyl group or atom, as in the case of formula (I).

[0029] In this reaction, as can be seen from formula (II), four deuterium atoms are added to each triple bond site by reduction. Therefore, if a specific starting hydrocarbon compound is used, the number of deuterium atoms added is uniquely determined by the structure of the compound, and a deuterium-containing hydrocarbon compound with the desired deuterium ratio can be obtained with good control. As an example, hexyne (general formula: CH 10 ) is deuterated to form hexane (general formula: CH 10 D4) can be obtained.

[0030] -In the case of aromatic hydrocarbons- Furthermore, the deuterium reduction of aromatic hydrocarbons can be represented by formula (III). [ka]

[0031] Here, R7~R 12 As in the case of formulas (I) and (II), may be any alkyl group or atom.

[0032] As can be seen from formula (III), six deuterium atoms are added to the aromatic ring. Therefore, if a specific starting hydrocarbon compound is used, the number of deuterium atoms added is uniquely determined by the structure of the compound, and a deuterium-containing hydrocarbon compound with a desired deuterium ratio can be obtained with good control.

[0033] In particular, in formula (III), R to R 12 When benzene, in which all carbon atoms are hydrogen (H), is used as the starting hydrocarbon compound, the deuterium-containing hydrocarbon compound obtained by reduction is cyclohexane, which has the general formula C6H6D6. In this case, both hydrogen and deuterium are bonded to all carbon atoms, and when ionized, a high proportion of cluster ions containing both hydrogen and deuterium are produced, which is preferable from the perspective of throughput. Examples of catalysts used in the deuteration reduction of benzene include Pt / C (platinum on carbon), but any substance can be used as a catalyst.

[0034] In this way, a deuterium-containing hydrocarbon compound having a desired ratio of deuterium can be obtained by adding deuterium to a raw material hydrocarbon compound having an unsaturated hydrocarbon group or an aromatic hydrocarbon group composed of carbon and hydrogen through a deuterium reduction reaction. Furthermore, as shown in the above reactions, when a hydrocarbon is used as the raw material hydrocarbon compound, the numbers of hydrogen and deuterium are both natural and even numbers.

[0035] When the deuterium-containing hydrocarbon compound obtained by the above-mentioned deuterium reduction reaction is a chain hydrocarbon, it is represented by the general formula C n H x D y (x+y=2n+2, where x and y are natural and even numbers, and n is an integer of 5 to 7). When the deuterium-containing hydrocarbon compound obtained by the deuterium reduction reaction is a cyclic saturated hydrocarbon, it is preferably a chain hydrocarbon represented by the general formula C m H z D w(z+w=2m, where z and w are natural and even numbers, and m is an integer of 5 to 7). Taking a carbon number of 6 as a specific example, an open-chain saturated hydrocarbon is hexane, in which some of the hydrogen atoms are replaced with deuterium atoms, such as C6H2D 12 ,C6H4D 10 ,C6H6D8,C6H8D6,C6H 10 D4,C6H 12 It is preferable to use D2, and the cyclic saturated hydrocarbon is cyclohexane, in which some of the hydrogen atoms are replaced with deuterium atoms, C6H2D 10 ,C6H4D8,C6H6D6,C6H8D4,C6H 10 It is preferable to use D2. Here, in order to stably ionize the deuterium-containing compound in the mass number selection step described later, it is preferable that the above n and m each be an integer in the range of 5 to 7.

[0036] In the deuterium-containing hydrocarbon compound preparation step, protons can also be added to a raw material hydrocarbon compound having an unsaturated hydrocarbon group or an aromatic hydrocarbon group consisting of carbon and deuterium by a proton reduction reaction, similar to the above-described deuteration reaction. This is a reaction in which protons are used as a reducing gas when all the hydrogen in the raw material saturated hydrocarbon or aromatic hydrocarbon is converted to deuterium in each of the deuteration reactions described in formulas (I) to (III).

[0037] <Mass number selection process> In the mass number selection step, the deuterium-containing hydrocarbon compound prepared in the previous step is ionized, and the mass number of the cluster ions containing both protium and deuterium is selected. The mass number selection step will be explained below using a schematic example with reference to FIG.

[0038] First, the prepared deuterium-containing hydrocarbon compound is supplied into an ionization chamber, and then, by electron impact, electrons are collided with the deuterium-containing hydrocarbon compound in the ionization chamber to dissociate the bonds of the deuterium-containing hydrocarbon compound having hydrocarbon groups containing protium and deuterium contained in the deuterium-containing hydrocarbon compound, thereby generating various ionized cluster ions.

[0039] Since the deuterium-containing hydrocarbon compound has a hydrocarbon group containing protons and deuterium, some of the generated cluster ions can be obtained in the chamber, and cluster ions containing both protons and deuterium can be obtained. Then, a desired range of mass numbers is selected and mass separation is performed to selectively extract the 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.

[0040] The mass number range may be selected from the mass number value of the target peak derived from cluster ions containing both protium and deuterium, but it is preferable to focus the beam within a range with a certain width before and after the selected value, as this allows the beam current to be increased.

[0041] <<Cluster ion peaks>> The peak of each cluster ion is determined by measuring the mass number dependency of the measured beam current value after forming an ion beam under the condition of the highest mass resolution.

[0042] 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.

[0043] (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).

[0044] 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.

[0045] 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 2 As a cluster ion implantation device using this principle, for example, CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd. can be used.

[0046] The silicon wafer thus obtained can contain protium and deuterium in the surface layer. [Industrial Applicability]

[0047] 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 protium 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. [Explanation of symbols]

[0048] S Silicon wafer

Claims

1. a deuterium-containing hydrocarbon compound preparation step of preparing a deuterium-containing hydrocarbon compound having a hydrocarbon group containing protium and deuterium; a mass number selection step of ionizing the deuterium-containing hydrocarbon compound and selecting the mass number of cluster ions containing both protium and deuterium.

2. 2. The method for generating a cluster ion beam according to claim 1, wherein the deuterium-containing hydrocarbon compound preparation step adds deuterium to a raw material hydrocarbon compound having an unsaturated hydrocarbon group or an aromatic hydrocarbon group composed of carbon and protons by a deuterium reduction reaction, thereby obtaining the deuterium-containing hydrocarbon compound.

3. The deuterium-containing hydrocarbon compound obtained by the deuterium reduction reaction has the general formula C ｎ H ｘ D ｙ 3. The method for generating a cluster ion beam according to claim 2, wherein the cations are chain saturated hydrocarbons represented by the formula: (x+y=2n+2, where x and y are natural and even numbers, and n is an integer of 5 to 7).

4. The deuterium-containing hydrocarbon compound obtained by the deuterium reduction reaction has the general formula C ｍ H ｚ D ｗ 3. The method for generating a cluster ion beam according to claim 2, wherein the cyclic saturated hydrocarbon is represented by the formula: (z+w=2m, where z and w are natural and even numbers, and 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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