JPH0525614A - Cluster forming device - Google Patents

Abstract

PURPOSE:To allow the use of metals and oxides as well, the formation of high- purity clusters without intrusion of impurities, the control of the sizes of the generated clusters, the continuous formation of the clusters of arbitrary sizes, and the assurance of the sizes. CONSTITUTION:This device is made into a horizontal type gas flow the construction constituted by connecting a sample vapor generating chamber 10 and cluster forming chamber 30 and a mass analysis chamber 50 which are connected to a discharge system via skimmers 40, 60. The sample vapor generated by irradiating a sample rod 14 with a laser beam 16 and the carrier gas and reactive gases introduced into the chambers are ejected to the cluster forming chamber 30 through the skimmers 40, 60. The clusters are formed by utilizing the adiabatic expansion generated at this time. A mass filter 34 is provided in the cluster forming chamber 30 and a mass spectrograph is provided in the mass analysis chamber 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for continuously producing clusters of metal or the like. More specifically, the present invention relates to an apparatus that uses a laser as an evaporation source, supplies a carrier gas and a reaction gas, ejects the evaporated sample together with an evaporated sample from a skimmer, and uses the condensation phenomenon due to adiabatic expansion to generate clusters. This apparatus can be used for forming thin films of various materials.

[0002]

2. Description of the Related Art Agglomeration of atoms or molecules of about several to several thousand is called a cluster. Most of the cluster atoms are surface atoms because the number of atoms forming the cluster is small. Therefore, it has been found that they have excellent physical and chemical properties that cannot be obtained by general bulk materials. Due to such characteristics, the cluster is expected to be applied in many technical fields.

Conventionally, as a typical technique for producing metal clusters, there is a method of obtaining a metal vapor beam by sealing a raw material in a crucible container and heating it. This gives a neutral cluster. For example, when accelerating vapor deposition of this cluster, it is ionized by irradiation with an electron beam or a laser beam.

[0004]

However, in the conventional technique for heating the crucible to generate the metal clusters as described above, it is difficult to use the high melting point material, the maintenance of the apparatus is troublesome, and the crucible inner wall However, there are drawbacks such as the inability to prevent the inclusion of impurities.

Further, as described above, since the generated clusters are neutral, it is necessary to irradiate them with an electron beam or a laser beam for ionization. Furthermore, there is still a problem that the size of the generated cluster cannot be controlled or confirmed at all.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an apparatus which can use any raw material and can produce high-purity clusters without contamination of impurities. Another object of the present invention is to provide a device capable of controlling the size of generated clusters, continuously generating clusters of arbitrary size, and confirming the size.

[0007]

As shown in the principle explanatory view of FIG. 1, the present invention has a structure in which a sample vapor generation chamber 10 and a cluster generation chamber 30 both connected to an exhaust system are connected via a skimmer 40. It is a cluster generator with. The sample vapor generation chamber 10 includes a forward rotation drive mechanism 15 that supports the sample rod 14 to be rotatable forward, a laser irradiation window 17 for evaporating a sample by irradiating the surface of the sample rod 14 with a laser beam 16, and a carrier gas. And a gas supply system 18 through which the reaction gas flows. Then, the sample vapor generated in the sample vapor generation chamber 10, the carrier gas and the reactive gas are ejected to the cluster generation chamber 30 through the skimmer 40, and adiabatic expansion at that time is used to generate the cluster. There is.

Here, the rotation driving mechanism 15 for the sample rod 14 is used.
Has a structure that includes a servo motor that controls the forward movement and a stepping motor that controls the rotation.
For rotation, an O-ring seal is used to ensure vacuum tightness, and the stepping motor is controlled to rotate the sample rod 14 in synchronization with a fixed number of oscillation pulses of a pulse laser for vaporizing the sample. It is preferable that the sample vapor generation conditions during that period are the same. Further, it is optimum that the sample rod 14 is tilted about 45 degrees with respect to the laser beam 16.

The entire apparatus as described above preferably has a horizontal gas flow tube structure. Exhaust gas differentially (while letting gas flow from one side, evacuation from the other side)
This is because it is possible to make the flow direction the lateral direction the simplest structure and it is convenient for the arrangement of various devices. A mass filter 34 is installed in the cluster generation chamber 30.
Further, it is preferable that the mass analysis chamber 50 connected to an exhaust system is connected to the downstream side of the cluster generation chamber 30 via a skimmer 60 in the subsequent stage, and the mass analysis chamber 50 is provided with a mass analyzer.

As a carrier gas, helium gas or argon gas is the best in consideration of cooling by adiabatic expansion. In addition, as a reactive gas for making clusters,
Hydrogen and deuterium are preferred.

[0011]

When the laser beam is focused and irradiated on the sample rod, the sample is heated and evaporated to form high temperature plasma.
A carrier gas is flown to cool this plasma, and a reactive gas is flowed to form clusters. The sample vapor,
When jetted from the skimmer utilizing the pressure difference together with the carrier gas and the reactive gas, it jets out as an ultra-high speed jet like a gas spray. At the time of this ejection, adiabatic expansion occurs, the mixed gas is cooled, various clusters are generated by the condensation phenomenon, and these clusters are repeatedly collided with the carrier gas for cooling to be cooled and stabilized. Since plasma is generated in the present invention, both an ion cluster beam and a neutral cluster beam are generated.

The mass filter enables control to take out only clusters of arbitrary size among the clusters generated in the cluster generation chamber. If a mass spectrometer is provided, the cluster size after passing through the mass filter can be confirmed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 shows a plan view of a cluster generating apparatus according to the present invention, and FIG. 3 shows a front view thereof. This cluster generation device has a horizontal flow tube structure and is composed of three chambers with a pressure difference provided by a two-stage skimmer. They are the sample vapor generation chamber 1 in order from the upstream side of the gas flow.
0, the cluster generation chamber 30, and the mass spectrometry chamber 50. Exhaust pumps 12, 3 directly under each chamber through gate valves
Connect 2, 52. 10 per second in the sample vapor generation chamber 10
Using a combination of a rotary pump with a displacement of at least 100 liters and a molecular pump, the cluster generation chamber 30
A diffusion pump or a turbo molecular pump having an exhaust volume of 400 liters per second or more is used for each of the mass spectrometric chamber 50. Here, the horizontal flow tube structure is the easiest way to differentially exhaust gas (flow gas from one side and evacuate from the other side) by making the flow direction horizontal. This is because the horizontal type is excellent in consideration of laser beam irradiation and the like.

Between the sample vapor generation chamber 10 and the exhaust pump 12 immediately below it, an orifice is installed which can control the degree of opening and closing. This is because the pressure in the sample vapor generation chamber 10, which is an important factor for cluster formation, can be arbitrarily changed. The former skimmer diameter is 0.5 mmφ
Hereinafter, the skimmer diameter in the latter stage is set to 1.0 mmφ or less. The skimmer in the former stage is for utilizing adiabatic expansion to cool the mixed gas (sample vapor, reactive gas and carrier gas) and generate clusters by the condensation phenomenon. Also, the pressure in the sample vapor generation chamber 10 and the value of the skimmer diameter in the previous stage are mutually changed to make the flow in the cluster generation chamber 30 a molecular flow. On the other hand, the skimmer in the latter stage holds the pressure in the mass analysis chamber 50 at -10 ^-7 Torr to serve as the operating region of the mass analyzer and also functions as a partition plate of the mass filter. Actually, these skimmers are constructed so that they can be freely moved and positioned in two directions perpendicular to the gas flow direction by an XY drive mechanism.

With this apparatus, the pressure of the sample vapor generating chamber 10 is 0.900 Torr and the pressure of the cluster generating chamber 30 is 4.8 × under the condition that the flow rate is 6000 sccm (valve opening 100%) or more.
10 ^-4 Torr, pressure of mass spectrometric chamber 50 3.4 × 10 ^-7 Torr
Can be obtained. The pressure in the sample vapor generation chamber 10 can be changed from 0 to 3.0 Torr.

Here, the tip (left end in the drawing) of the sample vapor generation chamber 10 is an inlet 19 for the carrier gas and the reactive gas. A forward rotation drive mechanism 15 for the sample rod is mounted diagonally forward of one side surface of the sample vapor generation chamber 10, and a laser beam irradiation window is provided on the opposite side surface of the sample vapor generation chamber 10. 17 are provided. As a result, the inserted sample rod is irradiated with the laser beam at an angle of about 45 degrees. The forward rotation drive mechanism 15 of the sample rod is configured to drive the forward movement by a servo motor and the rotation by a stepping motor. The stepping motor is synchronized with a fixed number of oscillation pulses of a pulse laser to generate sample vapor during that period. The conditions can be made the same. Regarding vacuum tightness, a bellows is used for forward movement and rotation is secured by using an O-ring seal.

Next, a Wien filter is built in the cluster generation chamber 30 as a mass filter. This Wien filter is composed of two electrode plates and a magnet, respectively. It vertically loads an electric field and a magnetic field, and only cluster ions of masses with equal force from both fields go straight and pass through the skimmer at the latter stage. However, the others diverge and are removed by the skimmer in the latter stage. The Wien filter is used because it is particularly small in size and is suitable for linear line systems.

The mass spectrometer 50 is provided with a mass analyzer 54 (quadrupole mass analyzer or time-of-flight mass analyzer) so that the cluster size after passing through the mass filter can be confirmed. Further, it is possible to find optimum conditions such as a ratio of carrier gas to reactive gas and pressure for obtaining clusters of a required size.

The operating procedure of this apparatus is as follows. Sample vapor generation chamber 10 evacuated to about 10 ^-2 Torr in advance
Insert the sample rod while rotating it forward from one of the three heads. Next, toward the sample rod, a laser irradiation window 17
A laser beam focused through is irradiated to generate a partial plasma state and generate a sample vapor. At that time, the carrier gas and the reactive gas are allowed to flow into the system,
In a state of being mixed with the sample vapor, the skimmer in the previous stage ejects the skimmer into the cluster generation chamber 30 to generate clusters. As the pulse laser, for example, excimer laser 50 to 100
mJ (100Hz) is used, and carrier gas and its flow rate are H
e to 3000 sccm or Ar to 5000 sccm, the reactive gas is H ₂ , and its flow rate is 10 to 20% of the carrier gas.

The mass spectrometer 54 confirms the formation of clusters. The ratio of the carrier gas to the reactive gas, the flow rate, the pressure, the pressure in the sample vapor generation chamber, and the skimmer in the previous stage are mutually changed so that the amount of clusters of the required size becomes maximum. Determine while looking at the value.
Then, the values of the electric field and the magnetic field of the Wien filter are adjusted by also referring to the values of the mass analyzer 54, and only the clusters of the required size are continuously generated.

The preferred embodiment of the present invention has been described above, but the present invention is not limited to this.
Positional relationship between sample rod and laser beam, relationship between them and gas flow direction, arrangement of each chamber, type of mass filter,
In addition, it can be appropriately changed according to the use and demand.

[0022]

EFFECTS OF THE INVENTION Since the present invention is a method of generating a sample vapor by irradiating the surface of a sample rod with a laser beam in a concentrated manner, regardless of the type of sample, that is, a metal or an oxide can be used, and a high melting point It may be a material, and high-purity sample vapor can be obtained. Further, since plasma is generated by laser beam irradiation, both an ion cluster beam and a neutral cluster beam can be generated at the same time.

By incorporating a mass filter and a mass analyzer in the cluster generation chamber, it is possible to continuously generate clusters of any size. If a mass spectrometer is installed on the downstream side of the gas and a mass analyzer is installed, the cluster size can be confirmed, and by adjusting the gas flow rate, pressure, skimmer diameter, etc., the cluster of any size can be confirmed. It is possible to grasp the optimum conditions for generation and efficiently extract a desired cluster beam.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the principle of a cluster generation device according to the present invention.

FIG. 2 is a plan view showing an embodiment of a cluster generation device according to the present invention.

3 is a front view of the device of FIG.

[Explanation of symbols]

10 Sample vapor generation chamber 14 Sample rod 15 Forward rotation drive device 16 laser beam 18 gas inflow system 30 Cluster generation room 34 Mass Filter 40 Skimmer 50 mass spectrometry room 60 Second Skimmer

Claims (4)

[Claims] 1. A sample vapor generation chamber and a cluster generation chamber, both of which are connected to an exhaust system, are connected via a skimmer, and the sample vapor generation chamber includes a forward rotation drive mechanism for rotatably supporting a sample rod. A sample vapor and carrier gas generated in the sample vapor generation chamber are provided with a laser irradiation window for evaporating a sample by laser beam irradiation on the surface of the sample rod, and a gas supply system for introducing a carrier gas and a reaction gas. And a reactive gas is ejected through the skimmer into the cluster formation chamber, and adiabatic expansion at that time is utilized to generate the cluster. 2. A rotation driving mechanism for a sample rod comprises a servo motor for controlling the forward movement and a stepping motor for controlling the rotation, and the forward movement uses a bellows and the rotation uses an O-ring seal to ensure vacuum airtightness. The apparatus according to claim 1, wherein the stepping motor rotates the sample rod in synchronization with a fixed number of oscillation pulses of a pulse laser for vaporizing the sample. 3. The apparatus according to claim 1, wherein the entire apparatus has a horizontal gas flow tube structure, and a mass filter is incorporated in the cluster generation chamber. 4. A mass spectrometry chamber is connected to a downstream side of the cluster generation chamber via a second skimmer, and the mass spectrometry chamber has a mass analyzer and is connected to an exhaust system. Equipment.