JP2024094041A - Method for generating cluster ion beam and method for implanting cluster ions - Google Patents

Abstract

[Problem] To provide a cluster ion beam generating method capable of stably controlling and generating an ion beam containing hydrogen and deuterium simultaneously. [Solution] The method includes a hydrocarbon compound mixing step of obtaining a hydrocarbon compound mixed material by mixing a first hydrocarbon compound containing deuterium with a second hydrocarbon compound containing at least a portion of hydrogen, and a mass number selection step of ionizing the hydrocarbon compound mixed material and selecting a selection range of mass numbers that includes both cluster ions containing hydrogen and cluster ions containing deuterium to determine the focusing range of the cluster ion beam, the first hydrocarbon compound raw material and the second hydrocarbon compound raw material having the same carbon skeleton. [Selected Figure] Figure 1

Description

The present invention relates to a method for generating a cluster ion beam and a method for injecting cluster ions.

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

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

Patent Document 1 proposes a method for producing an epitaxial silicon wafer, which includes a cluster ion beam irradiation step in which a silicon wafer is irradiated with cluster ions containing C (carbon) and H (hydrogen) 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 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 as a hydrocarbon compound mixture material by electron impact method to dissociate the bonds of the gaseous molecules.

The technology described in Patent Document 1 is expected to not only provide excellent gettering capabilities, but also provide a passivation effect for point defects in the epitaxial layer due to the hydrogen contained in the cluster ions.

Patent Document 2 also 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 there is a tendency for interface (surface) states to form in the inner wall layer of the trench, but annealing with deuterium solves these problems. Specifically, deuterium atoms bond to crystal defects that occur 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.

JP 2016-051729 A JP 2005-150415 A

While hydrogen has the advantage of excellent diffusion and reactivity, deuterium has the advantage of strong bonding strength. The inventors wanted to elucidate 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, the method itself for stably generating a cluster ion beam containing both hydrogen and deuterium as constituent elements to an extent that it can be used industrially has not yet been established.

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 hydrogen and deuterium. Furthermore, the present invention aims to provide a cluster ion implantation method that implants the cluster ion beam thus generated into the surface of a silicon wafer.

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 have discovered that by selecting an appropriate range of mass numbers during ionization to extract the desired cluster ions, it is possible to stably control and generate an ion beam that simultaneously contains protium and deuterium. The gist of the present invention, which was completed based on the above findings, is as follows.

(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 protium to obtain a hydrocarbon compound mixed raw material;
A mass number selection step of ionizing the hydrocarbon compound mixture material to select a mass number range including both cluster ions including protium and cluster ions including deuterium,
A cluster ion beam generating method, wherein the first hydrocarbon compound source and the second hydrocarbon compound source have the same carbon skeleton.

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

(3) The method for generating a cluster ion beam according to (2) above, wherein the first hydrocarbon compound is of the general formula C _n H _x D _y (x+y=2n+2, n is an integer from 5 to 7), and the second hydrocarbon compound is of the general formula C _n H _2n+2 (n is an integer from 5 to 7).

(4) The method for generating a cluster ion _beam according to (2) above _, wherein the first hydrocarbon compound is of the general formula _CmHzDw (z+w= _2m , m is an integer from 5 to 7), and the second hydrocarbon compound is of the general formula _CmH2m (m is an integer from 5 to 7).

(5) A method for implanting cluster ions, which comprises implanting a cluster ion beam generated using the method for generating a cluster ion beam described in (1) to (4) into a surface of a silicon wafer.

The present invention provides a cluster ion beam generation method that can stably control and generate a cluster ion beam that simultaneously contains hydrogen and deuterium. Furthermore, the present invention provides a cluster ion implantation method that implants the cluster ion beam thus generated into the surface of a silicon wafer.

1 is a schematic diagram for explaining the basic principle of a cluster ion beam generating method in the present invention. FIG. 1 is a graph showing mass spectra of various cluster ions obtained from cyclohexane (C ₆ D ₁₂ ) and cyclohexane (C ₆ H ₁₂ ) as a mixed hydrocarbon compound material, according to an experiment conducted by the present inventor. 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. 13 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. 13 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.

(Method of generating cluster ion beam)
The cluster ion beam generating 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 mass number selection range 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 described below in order.

<Hydrocarbon compound mixing process>
First, in the hydrocarbon compound mixing step, a first hydrocarbon compound containing deuterium and a second hydrocarbon compound containing protium 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.

<<First Hydrocarbon Compound>>
The first hydrocarbon compound is not particularly limited in molecular species or structure as long as it is a hydrocarbon compound containing deuterium. Here, "containing deuterium" refers to a hydrocarbon compound in which a certain amount of light hydrogen atoms among the constituent elements in the carbon skeleton of the hydrocarbon compound are artificially replaced with deuterium atoms. The proportion of deuterium among hydrogen atoms present in nature is 0.015%. Therefore, the first hydrocarbon compound in this specification is significantly different from the content of deuterium unintentionally contained in natural hydrocarbon compounds.

The first hydrocarbon compound may be a commercially available product or a synthetic product. In general, a hydrocarbon compound containing deuterium can be obtained by adding deuterium using an addition reaction by deuterium reduction. 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. 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.

The first hydrocarbon compound contains deuterium. Therefore, during ionization in the mass number selection step described below, the various cluster ions obtained from the first hydrocarbon compound include cluster ions whose constituent elements contain deuterium at least in part.

<<Second Hydrocarbon Compound>>
The second hydrocarbon compound is a hydrocarbon compound that at least partially contains protons. Here, "at least partially containing protons" means that at least a portion of the hydrocarbon compound contains protons, and all of the hydrogen atoms may be protons.

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 skeleton structure is the same when all hydrogen atoms are replaced with hydrogen atoms.

The second hydrocarbon compound may be a commercially available product or a synthetic product, except for those having the same number of hydrogen 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.

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

The first and second hydrocarbon compounds are preferably hydrocarbons, and may be any of chain saturated hydrocarbons, chain unsaturated hydrocarbons, cyclic hydrocarbons, and aromatic hydrocarbons, 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 and second hydrocarbon compounds are preferably compounds that can easily extract desired cluster ions during ionization. For example, the first hydrocarbon compound is preferably a 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 preferably a general formula C _n H _2n+2 (n is an integer of 5 to 7). In addition, it is also preferable that the first hydrocarbon compound is a 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 preferably a 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 (i.e., general formula: C ₆ D ₁₂ ) can be used as the first hydrocarbon compound, and in this case, cyclohexane C ₆ H ₁₂ can be used as the second hydrocarbon.

<Mass Number Selection Step>
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 including both cluster ions containing protium and cluster ions containing deuterium. The mass number selection step will be described below with reference to FIG.

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 with the hydrocarbon compound mixed material in the ionization chamber by electron bombardment to dissociate the bonds of the first and second hydrocarbon compounds contained in the hydrocarbon compound mixed material, generating various ionized cluster ions. Since the first and second hydrocarbon compounds have the same carbon skeleton, the vaporization conditions and the energy required for ionization are similar, and the respective cluster ions can be generated simultaneously under ionization conditions in the same chamber.

Among the cluster ions generated, 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 protium. At this stage, cluster ions containing deuterium and cluster ions containing protium are 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 protium 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, protium, and deuterium.

This step will be described in more detail. Figure 2 shows the mass spectrum (solid line) of a hydrocarbon compound mixture material in which cyclohexane (C ₆ D ₁₂ ) is used as the first hydrocarbon compound and cyclohexane (C ₆ H ₁₂ ) is used as the second hydrocarbon compound. In Figure 2, the mass spectrum of the solid line portion is further separated by a dashed line to show the mass spectrum when cyclohexane (C ₆ D ₁₂ ) is ionized alone, and the mass spectrum of cyclohexane (C ₆ H ₁₂ ) is ionized alone is separated by a dotted line. In the mass spectrum of the solid line portion obtained from the mixture, the cluster ion beam is focused from the mass number range having both the dashed and dotted line peaks, thereby allowing cluster ions containing both deuterium and protium to be extracted.

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

In the mass number selection process, 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 numbers for extracting cluster ions to a range larger than the selection value itself, it becomes easier to focus many cluster ions as a beam.

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

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 vessel, 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 using mass analysis with a quadrupole radio frequency field or time-of-flight mass analysis, and then taking the average number of each cluster. Specific cluster ions to be focused into a cluster ion beam can be obtained by mass separation of ionized cluster ions of various atomic numbers and extracting cluster ions of specific mass numbers.

(Method of Injecting Cluster Ions)
The method for implanting cluster ions according to the present invention is a method for implanting a cluster ion beam generated by the above-mentioned method for generating a cluster ion beam into the surface of a silicon wafer S (see FIG. 1).

The cluster ion beam obtained by the above-mentioned 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 be added to make the wafer 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.

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

The silicon wafer obtained in this way can contain hydrogen and deuterium in the surface layer.

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

Example 1
Using an ion generator (manufactured by Nissin Ion Equipment Co., Ltd., model number: CLARIS (registered trademark)), 10 g of cyclohexane (C ₆ H ₁₂ ; mass number 84.16) and 10 g of cyclohexane (C ₆ D ₁₂ ; mass number 96.23) were introduced into the ionization chamber as raw materials, and a cluster ion beam was generated with a mass number selection value of 42. The cluster ion injection conditions 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 amount of 3.3×10 ¹⁴ ions/cm ² (dose amount per carbon atom was 1.0×10 ¹⁵ ions/cm ² ). The beam current value of the obtained cluster ions was 700 μA.

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

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

The mass spectra obtained during ionization of cluster ions in Examples 1 to 3 are as shown in Figure 2, which was referenced above. In addition, the ion implantation profiles in the depth direction of the epitaxial silicon wafer implanted with the generated cluster ion beam are shown in Figures 3 to 5, with the carbon, protium, and deuterium profiles shown by the solid line, dashed line, and dotted line, respectively.

<Evaluation of hydrogen and deuterium concentration profiles by SIMS>
For the epitaxial silicon wafer implanted with a cluster ion beam obtained under the above manufacturing conditions, the concentration profiles of carbon, protium, and deuterium in the depth direction from the surface of the epitaxial layer were measured by SIMS. As a result, a hydrogen (protium) peak was observed at about 50 nm in the surface layer of the silicon wafer, and a deuterium peak was observed at about 100 nm, confirming the presence of each at different depth regions.

As shown in Figures 3 to 5, when the mass number selection value is 42, the hydrogen concentration is greater than the deuterium concentration, and as the mass number selection value is increased, the proportion of deuterium increases, and when the mass number selection value is 48, the proportion of deuterium is greater than the proportion of hydrogen. This is consistent with the fact that in the mass spectrum of cluster ions confirmed in Figure 2, in the region of mass numbers of 40 and above, the amount of cluster ions containing deuterium increases as the mass number increases. Therefore, in light of Examples 1 to 3, and taking into account the balance of the implantation amounts of protium and deuterium, it is thought that 47 can be selected as the optimal mass number selection value.

According to the present invention, it is possible to provide a cluster ion beam generation method capable of stably controlling and generating a cluster ion beam that simultaneously contains hydrogen and deuterium. Furthermore, the present invention can provide a cluster ion implantation method in which the cluster ion beam thus generated is implanted into the surface of a silicon wafer.

S Silicon wafer

Claims (5)

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 raw material;
A mass number selection step of ionizing the hydrocarbon compound mixture material to select a mass number range including both cluster ions including protium and cluster ions including deuterium,
A cluster ion beam generating method, wherein the first hydrocarbon compound source and the second hydrocarbon compound source have the same carbon skeleton. The method for generating a cluster ion beam according to claim 1, wherein the first hydrocarbon compound and the second hydrocarbon compound are hydrocarbons. 3. The method for generating a cluster ion beam according to claim 2, wherein the first hydrocarbon compound is of the general formula C _n H _x D _y (x+y=2n+2, n is an integer from 5 to 7), and the second hydrocarbon compound is of the general formula C _n H _2n+2 (n is an integer from 5 to 7). 3. The method for generating a cluster ion beam according to claim 2, wherein the first hydrocarbon compound is of the general formula C _m H _z D _w (z+w=2m, m is an integer from 5 to 7), and the second hydrocarbon compound is of the general formula C _m H _2m (m is an integer from 5 to 7). A method for implanting cluster ions, which comprises implanting a cluster ion beam generated using the method for generating a cluster ion beam according to any one of claims 1 to 4 into the surface of a silicon wafer.

Images