JP6750351B2 - Cluster ion beam generation method and cluster ion beam irradiation method using the same - Google Patents

Description

The present invention relates to a cluster ion beam generation method and a cluster ion beam irradiation method using the same.

The cluster ion beam is a surface processing technology for colliding a solid mass with a plurality of (usually about 2 to 2000, sometimes several hundred to several thousand) atoms or molecules bound to each other and ionized to a solid surface. Used. In recent years, attention has been focused on the application of the cluster ion beam technology in nanofabrication processes for various devices such as semiconductor devices, magnetic/dielectric devices, and optical devices.

The basic principle of the cluster ion beam generation method will be schematically described with reference to FIG. First, the raw material 1 is supplied, and electrons are made to collide with the raw material 1 by an electron impact method to dissociate the bond of the raw material 1 to obtain ionized cluster ions 2. When the cluster ions 2 are generated, monoatomic ions 4 and polyatomic ions 6 are usually formed. Further, the unstable polyatomic ion 6 may be further dissociated. Next, in order to select cluster ions 2 having a desired cluster size, mass separation of generated ions is performed. Then, the selected cluster ions 2 are extracted with a predetermined acceleration voltage to form a cluster ion beam. The surface of the target T can be processed by colliding the thus obtained cluster ion beam with the surface of the target T. The raw material 1 may be any of gas, liquid and solid under a normal temperature and normal pressure environment, and the raw material 1 is gasified immediately before the collision of electrons with the raw material 1 in the apparatus.

In addition, in the present specification, the “cluster ion” means the above-mentioned ionized lump-shaped group, and the “cluster ion beam” means a bundle-like shape obtained by accelerating and focusing the cluster ion in a vacuum. Shall mean a beam that translates to. Further, the “cluster size” means the number of atoms or molecules forming one cluster.

Here, the applicant of the present application discloses, in Patent Document 1, a cluster ion beam irradiation for irradiating a semiconductor wafer with cluster ions to form a modified layer in which the constituent elements of the cluster ions are solid-solved on the surface of the semiconductor wafer. A method for manufacturing a semiconductor epitaxial wafer is proposed, which comprises steps and a step of forming an epitaxial layer on the modified layer of the semiconductor wafer.

In the technique described in Patent Document 1, since the surface of the semiconductor wafer is irradiated with cluster ions, the constituent elements of the cluster ions are locally and highly concentrated as compared with the ion implantation region formed by the monomer ion implantation technique. Regions can be formed. Therefore, according to the technique described in Patent Document 1, it is possible to obtain a semiconductor epitaxial wafer having an extremely excellent gettering ability as compared with the related art, and it is possible to suppress heavy metal contamination.

In addition, the applicant of the present application proposes the following method for manufacturing a semiconductor epitaxial wafer in Patent Document 2 in order to provide a method for manufacturing a semiconductor epitaxial wafer having high gettering ability and suppressing generation of epitaxial defects. doing. That is, in the method for manufacturing a semiconductor epitaxial wafer disclosed in Patent Document 2, the surface of a semiconductor wafer is irradiated with cluster ions, and the surface portion of the semiconductor wafer is modified so that the constituent elements of the cluster ions form a solid solution. A cluster ion beam irradiation step of forming a layer, and a step of forming an epitaxial layer on the modified layer of the semiconductor wafer, wherein the cluster ion beam irradiation step is a part of the modified layer in the thickness direction. Is an amorphous layer, and the average depth of the surface of the amorphous layer on the semiconductor wafer surface side is 20 nm or more from the semiconductor wafer surface.

International Publication No. 2012/157162 JP, 2005-130402, A

Here, in order to perform the cluster ion beam irradiation process disclosed in Patent Documents 1 and 2, although it depends on the dose amount, the beam current value, and the wafer diameter of the semiconductor wafer, the cluster ion beam is applied to one semiconductor wafer. It took a lot of time to perform irradiation. Therefore, in order to mass-produce semiconductor epitaxial wafers by including cluster ion beam irradiation in the process, improvement in throughput is desired.

In the cluster ion beam irradiation step, if the dose amount is the same, the irradiation time can be shortened as the beam current value of the cluster ion beam increases. For example, Patent Document 2 discloses that C ₃ H ₅ clusters are generated from cyclohexane in the example, and the beam current value thereof is 400 μA. In order to improve the throughput, the present inventor has recognized that increasing the beam current value is a new problem.

Therefore, in view of the above problems, it is an object of the present invention to provide a cluster ion beam generation method capable of increasing the beam current value of the cluster ion beam as compared with the conventional method. A further object of the present invention is to provide a cluster ion beam irradiation method and a semiconductor epitaxial wafer manufacturing method using this cluster ion beam generation method.

The present inventor has diligently studied to solve the above problems. As a result of intensive studies by the present inventors, it was confirmed that the beam current value could be increased to some extent by changing the decomposition condition of the raw material in the ion source, but there was a limit to the increase. Therefore, the present inventor paid attention to the raw material, and particularly to the molecular structure of the hydrocarbon compound raw material. When generating a beam of cluster ions containing carbon and hydrogen as constituent elements, the current value of the cluster ion beam is greatly improved by using a branched chain saturated hydrocarbon of a specified structure as a hydrocarbon compound material. The present inventor has found out that this can be done, and has completed the present invention. That is, the gist of the present invention is as follows.

(1) A cluster ion beam producing method for producing a cluster ion beam having carbon and hydrogen as constituent elements from a hydrocarbon compound raw material, wherein the hydrocarbon compound raw material is a branched chain saturated hydrocarbon having side chains. The method for producing a cluster ion beam according to claim 1, wherein the branched chain saturated hydrocarbon is branched only by a tertiary carbon atom.

(2) The cluster ion beam generation method according to (1), wherein the branched chain saturated hydrocarbon has only one of the tertiary carbon atoms.

(3) The branched chain saturated hydrocarbon has 2 or 3 or more of the tertiary carbon atoms, and the 2 or 3 or more of the tertiary carbon atoms are all 1 or 2 or more of the secondary carbon atoms. The method for producing a cluster ion beam according to the above (1), wherein the cluster ion beam is coupled via

(4) The cluster ion beam generation method according to (3), wherein the branched chain saturated hydrocarbon has two tertiary carbon atoms.

(5) The cluster ion beam generation method according to (4), wherein the two tertiary carbon atoms are bonded via one secondary carbon atom.

(6) A cluster ion beam irradiation method, which comprises irradiating a surface of a semiconductor wafer with a cluster ion beam generated by using the cluster ion beam generation method according to any one of (1) to (5) above.

According to the present invention, it is possible to provide a cluster ion beam generation method capable of increasing the beam current value of a cluster ion beam as compared with the conventional method. Further, the present invention can provide a cluster ion beam irradiation method capable of increasing the beam current value as compared with the conventional method.

FIG. 6 is a schematic diagram for explaining the basic principle of cluster ion beam generation. FIG. 6 is a schematic cross-sectional view illustrating a method for manufacturing a semiconductor epitaxial wafer 100 using a cluster ion beam irradiation method according to an embodiment of the present invention.

(Cluster ion beam generation method)
A cluster ion beam generation method according to one embodiment of the present invention is a cluster ion beam generation method for generating a beam of cluster ions having carbon and hydrogen as constituent elements from a hydrocarbon-based compound raw material. Here, the hydrocarbon compound raw material contains a branched chain saturated hydrocarbon having a side chain, and the branched chain saturated hydrocarbon is branched only by the tertiary carbon atom. Inevitable impurities may be contained in the hydrocarbon compound raw material.

The basic principle of the cluster ion beam generation method is as described above with reference to FIG. That is, first, the raw material 1 is supplied, and electrons are made to collide with the raw material 1 by an electron impact method to dissociate the bond of the raw material 1 to obtain ionized cluster ions 2. Then, mass separation of the generated ions is performed to select the cluster ions 2, and the cluster ions 2 are extracted by a predetermined acceleration voltage to form a cluster ion beam, whereby a cluster ion beam can be generated. The surface of the target T can be irradiated with the cluster ion beam thus obtained. As a cluster ion implanter using such a principle, for example, CLARIS (registered trademark) manufactured by Nissin Ion Equipment Co., Ltd. can be used.

In this embodiment, the above-mentioned hydrocarbon compound raw material gas is used as the raw material 1. The constituent elements of the cluster ions 2 forming the obtained cluster ion beam have carbon and hydrogen, and in particular, the constituent elements of the cluster ions 2 can be composed only of carbon and hydrogen.

The hydrocarbon compound raw material used in this embodiment will be described in more detail below. The hydrocarbon compound raw material is a branched chain saturated hydrocarbon having a side chain, and it is important that the branched chain saturated hydrocarbon is branched only by a tertiary carbon atom. Such a branched chain saturated hydrocarbon can be represented by the following formula (I).
Here, in the above formula (I), R ₁ , R ₂ and R _{3 which} are bonded to the tertiary carbon atom are all independent linear or branched alkyl groups having 1 or 2 or more carbon atoms. is there. R ₁ , R ₂ and R ₃ may all be the same alkyl group, or any two of them may be the same alkyl group, or they may all be different. The term "straight-chain" as used herein includes a case where the number of carbon atoms is 1 or more and 3 or less and no branching occurs, and is hereinafter referred to as "straight-chain" in the same meaning.

The branched chain saturated hydrocarbon used in the present embodiment may be any of gas, liquid and solid under normal pressure and normal pressure environment, and is a raw material in a chamber under vacuum (for example, 10 ⁻² Pa or less). It suffices that the branched chain saturated hydrocarbon is gasified immediately before the collision with the electron. That is, when the raw material is introduced into the chamber and collided with the electrons, the liquid raw material may be vaporized and supplied into the chamber, or the solid raw material may be heated and vaporized in a vacuum in another apparatus to form the chamber. The gas may be introduced into the chamber, or the raw material gas itself may be supplied into the chamber. The number of carbon atoms of such a branched chain saturated hydrocarbon can be, for example, 4 or more and 16 or less. The branched chain saturated hydrocarbon preferably has 5 or more carbon atoms, more preferably 6 or more carbon atoms. On the other hand, the branched chain saturated hydrocarbon preferably has 10 or less carbon atoms, more preferably 8 or less carbon atoms, and particularly preferably 7 or less carbon atoms. Therefore, the total carbon number of R ₁ , R ₂ and R ₃ can be 3 or more and 15 or less. The total number of carbon atoms of R ₁ , R ₂ and R ₃ is preferably 4 or more, more preferably 5 or more. On the other hand, the total carbon number of R ₁ , R ₂ and R ₃ is preferably 9 or less, more preferably 7 or less, and particularly preferably 6 or less.

The carbon numbers of R ₁ , R ₂ and R ₃ in the above formula (I) are each independently 1 or more, and can be 2 or more, as long as the total number of carbons described above is satisfied. It can be 3 or more. Similarly, while satisfying the above-mentioned total carbon number, the carbon numbers of R ₁ , R ₂ and R ₃ can be independently 4 or less, 3 or less, and 2 or less. Can be The carbon numbers of R ₁ , R ₂ and R ₃ may all be the same, or any two of them may have the same carbon number, or they may all be different.

Here, as a result of diligent studies by the present inventor, when a cluster ion beam is generated from a hydrocarbon-based compound raw material, in order to significantly increase the beam current value as compared with the conventional method, adjustment of the raw material decomposition condition in the ion source is performed. There was a limit alone. Here, in the saturated hydrocarbon (alkane), the bond between the tertiary carbon atom and the alkyl group is a primary carbon atom or a secondary carbon atom because the radical generated at the time of dissociation is stable. And the bond dissociation energy is smaller than the bond between the alkyl group and the alkyl group. Therefore, when an electron collides with a branched chain saturated hydrocarbon represented by the above formula (I) by the electron impact method, the bond between the tertiary carbon atom and the alkyl group to which it bonds is preferentially dissociated. Occurs, and radicals and ions are easily generated. Therefore, the present inventor considered that the generation efficiency of the cluster ion beam can be increased. Therefore, the present inventor pays attention to this point, and uses the branched chain saturated hydrocarbon represented by the above formula (I) as a hydrocarbon compound raw material, so that the beam current value of the generated cluster ion beam is compared with the conventional one. We found that it can be significantly increased, and experimentally clarified its effect.

As described above, by using the branched chain saturated hydrocarbon according to the present embodiment as the hydrocarbon compound raw material, the beam current value of the cluster ion beam can be significantly increased as compared with the conventional one. According to the present embodiment, in the hydrocarbon-based cluster ion beam, the beam current value obtained can be 1000 μA or more, 1200 μA, 1500 μA or more, and 1800 μA or more. Further, it can be 2000 μA or more.

Here, the branched chain saturated hydrocarbon represented by the above formula (I) preferably has only one tertiary carbon atom. That is, R ₁ , R ₂ and R ₃ in the formula (I) are all preferably linear saturated alkyl groups. For example, R ₁ can be a methyl group, an ethyl group, an n-propyl group, or an n-butyl group, and R ₂ and R ₃ can be either a methyl group or an ethyl group.

Examples of such branched chain saturated hydrocarbons include 2-methylpropane, 2-methylbutane, 2-methylpentane, 2-methylhexane, and 2-methylheptane. By using these branched chain saturated hydrocarbons as the hydrocarbon compound raw material, the beam current value of the cluster ion beam can be increased more reliably.

The branched chain saturated hydrocarbon represented by the above formula (I) has 2 or 3 or more tertiary carbon atoms, and these 2 or 3 or more tertiary carbon atoms are all 1 or 2 or more. It is preferable to bond via the secondary carbon atom of. In particular, the branched chain saturated hydrocarbon preferably has two tertiary carbon atoms. The latter branched chain saturated hydrocarbon can be represented by the following formula (II).
Here, in the above formula (II), R ₄ bonded to the tertiary carbon atom is a linear saturated alkylene group, and R ₅ , R ₆ , R ₇ and R ₈ are all linear. It is a saturated alkyl group.

As described above, when there are tertiary carbons, carbon radicals are easily generated. However, according to the study by the present inventor, when the tertiary carbons are bonded to each other, the bond dissociation energy is too small, and ionization explosively occurs due to electron collision, which may make control difficult. It was confirmed that there is. In such a case, the beam current value of the cluster ion beam may be rather reduced. Therefore, in the branched chain saturated hydrocarbon used in the present embodiment, when there are 2 or 3 or more tertiary carbon atoms, these 2 or 3 or more tertiary carbon atoms are all 1 or 2 or more primary carbon atoms. It is preferable to use those bonded via a secondary carbon atom.

Here, the carbon number of the branched chain saturated hydrocarbon represented by the formula (II) is also the same as the carbon number of the branched chain saturated hydrocarbon of the formula (I) except that the lower limit is 7. Therefore, the total carbon number of R ₄ , R ₅ , R ₆ , R _7, and R ₈ can be 5 or more and 14 or less. In addition, the total carbon number of R ₄ , R ₅ , R ₆ , R ₇ and R ₈ is preferably 5 or more, more preferably 6 or more, and even more preferably 7 or more. On the other hand, the total carbon number of R ₄ , R ₅ , R ₆ , R ₇ and R ₈ is preferably 9 or less, more preferably 8 or less, and even more preferably 7 or less.

The carbon number of R ₄ , R ₅ , R ₆ , R ₇ and R _{8 in} the above formula (II) is independently 1 or more and 2 or more while satisfying the above-mentioned total carbon number. It can be set to 3 or more. Similarly, the carbon number of R ₄ , R ₅ , R ₆ , R ₇ and R ₈ can be independently set to 4 or less and 3 or less while satisfying the above-mentioned total carbon number. It can be set to 2 or less. The carbon numbers of R ₄ , R ₅ , R ₆ , R ₇ and R ₈ may all be the same, or any two, three or four carbon numbers may be the same or they may all be different. May be.

Examples of such branched chain saturated hydrocarbons include 2,4-dimethylpentane, 2,4-dimethylhexane, 2,4-dimethylheptane, 2,5-dimethylhexane and 2,5-dimethylheptane. it can. By using these branched chain saturated hydrocarbons as the hydrocarbon compound raw material gas, the beam current value of the cluster ion beam can be increased more reliably.

Further, when the branched chain saturated hydrocarbon of the above formula (II) is used, it is preferable that two tertiary carbon atoms are bonded via one secondary carbon atom. That is, R ₄ in formula (II) is preferably a methylene group. For example, as the branched chain saturated hydrocarbon according to the above formula (II), 2,4-dimethylpentane, 2,4-dimethylhexane and 2,4-dimethylheptane can be used. By using such a branched chain saturated hydrocarbon as the hydrocarbon compound raw material gas, the beam current value of the cluster ion beam can be increased more reliably.

There are various types of cluster ions depending on the binding mode, and they can be generated by a known method as described in the following documents, for example. (1) Charged particle beam engineering: Junzo Ishikawa: ISBN978-4-339-00734-3: Corona, (2) Electron and ion beam engineering: Institute of Electrical Engineers: ISBN4-88686-217-9: Ohm, (3) ) Cluster ion beam basics and applications: ISBN4-526-05765-7: Nikkan Kogyo Shimbun. Generally, a Nielsen type ion source or Kaufman type ion source is used to generate positively charged cluster ions, and a large current negative ion source using a volume generation method is used to generate negatively charged cluster ions. To be

The acceleration voltage per carbon atom of the generated cluster ions is more than 0 keV/atom and 50 keV/atom or less, preferably 40 keV/atom or less. Further, the cluster size may be 2 to 50 or less, though it depends on the branched chain saturated hydrocarbon constituting the hydrocarbon compound raw material.

In addition, two methods of (1) electrostatic acceleration and (2) high frequency acceleration are generally used for adjusting the acceleration voltage. As the former method, there is a method in which a plurality of electrodes are arranged at equal intervals and an equal voltage is applied between them to create a uniform acceleration electric field in the axial direction. As the latter method, there is a linear linac method in which ions are linearly run and accelerated by using a high frequency. Further, the cluster size of the cluster ion beam and the beam current value can be adjusted by adjusting the pressure of the vacuum container (the flow rate of the gas to be introduced) and the voltage applied to the filament at the time of ionization. The cluster size can be determined by a mass separation method using a quadrupole high frequency electric field or a single converging sector magnetic field.

Hereinafter, a cluster ion beam irradiation method according to another embodiment of the present invention will be described with reference to FIG. In principle, the same constituent elements will be given the same reference numerals, and the description thereof will be omitted. Note that in FIG. 2, for convenience of description, the thickness of the epitaxial layer 20 is exaggerated with respect to the semiconductor wafer 10, unlike the actual ratio of the thickness.

(Cluster ion beam irradiation method)
As shown in FIG. 2A, in the cluster ion beam irradiation method according to the embodiment of the present invention, the cluster ion beam C generated by using the embodiment of the cluster ion beam generation method is supplied to the surface 10A of the semiconductor wafer 10. Irradiate. In the present embodiment, it is possible to perform the cluster ion beam irradiation in which the beam current value is higher than in the conventional case. Therefore, if the same dose of cluster ions as the prior art is applied, the irradiation time can be shortened as compared with the prior art.

The semiconductor wafer 10 is, for example, a bulk single crystal wafer made of silicon or compound semiconductor (GaAs, GaN, SiC) and having no epitaxial layer on the surface. As the semiconductor wafer 10, 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 can be used. Further, carbon and/or nitrogen may be added to the silicon wafer. In addition, an n-type or a p-type may be added by adding an arbitrary impurity dopant. Further, as the semiconductor wafer 10, it is also possible to use an epitaxial semiconductor wafer having a semiconductor epitaxial layer formed on the surface of a bulk semiconductor wafer.

The dose amount of cluster ions can be adjusted by controlling the beam current value and the ion irradiation time. The carbon dose of the cluster ions can be set to, for example, 1×10 ¹³ to 1×10 ¹⁶ atoms/cm ² . And, as described above, the beam current value can be 1000 μA or more, 1200 μA or more, 1500 μA or more, 1800 μA or more, and further 2000 μA or more. be able to.

(Reference Embodiment: Method for Manufacturing Semiconductor Epitaxial Wafer)
As shown in FIGS. 2A to 2C, the surface 10 A of the semiconductor wafer 10 is irradiated with the cluster ion beam C generated by using the embodiment of the cluster ion beam generation method described above, and the surface of the semiconductor wafer 10 is irradiated with the cluster ion beam C. Part includes a cluster ion beam irradiation step of forming a modified layer 18 in which constituent elements of cluster ions are solid-solved, and an epitaxial layer forming step of forming an epitaxial layer 20 on the modified layer 18 of the semiconductor wafer 10. As a result, the semiconductor epitaxial wafer 100 can be manufactured.

The modified layer 18 formed by the cluster ion beam irradiation step is a region where carbon is locally present as a solid solution at the interstitial position or substitution position of the crystal on the surface portion of the semiconductor wafer 10, and strong gettering is performed. Can work as a site.

In the epitaxial layer forming step, the epitaxial layer 20 formed on the modified layer 18 may be a silicon epitaxial layer, and can be formed under general conditions. For example, hydrogen is used as a carrier gas, a source gas such as dichlorosilane or trichlorosilane is introduced into the chamber, and the growth temperature varies depending on the source gas used, but the semiconductor is formed by the CVD method at a temperature of about 1000 to 1200° C. It can be epitaxially grown on the wafer 10. The thickness of the epitaxial layer 20 is preferably within the range of 1 to 15 μm.

By using the cluster ion beam irradiation method according to the present embodiment, the throughput at the time of manufacturing a semiconductor epitaxial wafer having excellent gettering ability can be improved as compared with the conventional method.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

(Invention Example 1)
A cluster ion generator (manufactured by Nisshin Ion Equipment Co., Ltd., model number: CLARIS) was used to generate cluster ionized C ₃ H ₅ cluster ions using 2-methylpentane (C ₆ H ₁₄ ) as a raw material. The beam current value of the obtained cluster ion beam was 2000 μA.

(Invention Example 2)
Inventive Example 1, cluster ionized C ₃ H ₅ clusters were obtained in the same manner as in Inventive Example 1 except that 2,4-dimethylpentane (C ₇ H ₁₆ ) was used as a raw material instead of 2-methylpentane. Generated ions. The beam current value of the obtained cluster ion beam was 1800 μA.

(Conventional example 1)
Inventive Example 1 was repeated, except that cyclohexane (C ₆ H ₁₂ ) was used as a raw material instead of 2-methylpentane, to produce cluster ionized C ₃ H ₅ cluster ions in the same manner as in Inventive Example 1. The beam current value of the obtained cluster ion beam was 850 μA.

(Comparative example 1)
Inventive Example 1 produced cluster ions of C ₃ H _{5 in} the same manner as in Inventive Example 1 except that hexane (C ₆ H ₁₄ ) was used as a raw material instead of 2-methylpentane. The beam current value of the obtained cluster ion beam was 850 μA.

(Comparative example 2)
Inventive Example 1, except that 2,3-dimethylbutane (C ₆ H ₁₄ ) was used as a raw material instead of 2-methylpentane, in the same manner as in Inventive Example 1, cluster ionized C ₃ H ₅ clusters. Generated ions. The beam current value of the obtained cluster ion beam was 20 μA.

The results of Invention Examples 1 and 2, Conventional Example 1 and Comparative Examples 1 and 2 are shown in Table 1 below.

<Evaluation>
In Invention Examples 1 and 2, it was confirmed that the beam current value obtained was twice or more the beam current value obtained in Conventional Example 1. Inventive Examples 1 and 2 are different from Conventional Example 1 and Comparative Example 1 in that a bond dissociation is likely to occur due to the inclusion of a tertiary carbon atom, and as a result, the C ₃ H ₅ cluster ion is easily extracted. Conceivable. On the other hand, in Comparative Example 2, although the tertiary carbon atoms were contained, the discharge current was large and the formation of the cluster ion beam was difficult, so that the beam current value was smaller than that in Conventional Example 1. This is because the bond between the tertiary carbons in the center of 2,3-dimethylbutane is very weak, and the ion generation explosively progressed to such an extent that it was difficult to control when generating cluster ions. Conceivable.

According to the present invention, it is possible to provide a cluster ion beam generation method capable of increasing the beam current value of a cluster ion beam as compared with the conventional method. Further, the present invention can provide a cluster ion beam irradiation method capable of increasing the beam current value as compared with the conventional method. Therefore, it is particularly useful in the semiconductor industry.

1 Raw Material 2 Cluster Ion 4 Monoatomic Ion 6 Polyatomic Ion 10 Semiconductor Wafer 10A Semiconductor Wafer Surface 18 Modified Layer 20 Epitaxial Layer 100 Semiconductor Epitaxial Wafer C Cluster Ion Beam T Target

Claims (2)

A method for producing a cluster ion beam, which produces a beam of cluster ions having carbon and hydrogen as constituent elements from a hydrocarbon compound raw material,
The hydrocarbon compound raw material is selected from the group consisting of 2-methylpropane, 2-methylbutane, 2-methylpentane, 3-methylpentane, 2-methylhexane, 3-methylhexane and 2,4-dimethylpentane. A method for producing a cluster ion beam , which is one or more compounds . A cluster ion beam irradiation method, which comprises irradiating a surface of a semiconductor wafer with a cluster ion beam generated by using the cluster ion beam generation method according to claim 1 .