JPH0816265B2 - Cluster detector - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cluster detection apparatus capable of easily detecting cluster formation in a cluster ion beam deposition method (hereinafter referred to as ICB method).

[Conventional technology]

Various methods have been developed and put into practical use as means for forming metal thin films, semiconductor thin films, magnetic thin films, and dielectric thin films on various substrates.

Among them, Japanese Patent Publication No. 54-9592 discloses a dense and high-quality thin film forming means having good adhesion and few grain boundaries by utilizing the effects of kinetic energy and electric field of ions. There is ICB method. The ICB method, the vacuum chamber was heated putting material to be deposited in the sealed crucible, the crucible vapor pressure of the substance 10 ^-2 to several Torr crucible 10 ^-7 from the nozzle 10 as a ^- Eject into a vacuum region of about ⁴ Torr. At this time, due to the supercooling phenomenon due to adiabatic expansion, a cluster in which 100 to 200 atoms are loosely bonded is formed. Then, an electron shower is bathed in this cluster to ionize one atom of the atomic group forming the cluster to form a cluster ion, and to give an appropriate kinetic energy,
It is vapor-deposited on a substrate together with neutral clusters or atoms that do not form clusters.

FIG. 4 is a diagram showing an outline of an apparatus for performing the ICB method. A vacuum container 2 is placed on the base plate 1, and the inside is evacuated to a vacuum degree of about 10 ⁻⁷ to 10 ⁻⁴ Torr through an exhaust hole 3. The vapor deposition material 4 is loaded into the crucible 5,
The crucible 5 is carried by a support rod 6 on the base plate 1.

Although various heating means for the crucible 5 are conceivable, the heating means 7 composed of filaments surrounding the crucible 5 is used in the illustrated embodiment. And heated crucible 5
When the material 4 inside evaporates and is jetted into the high vacuum atmosphere through the nozzle 8 provided on the upper part of the crucible 5, the material atoms form a cluster of atomic atoms, that is, clusters due to the pressure difference inside and outside the crucible 5. .

The formed clusters or atoms that do not form clusters fly as a cluster beam 12 due to the kinetic energy at the time of ejection from the crucible 5, and a part of them fly to the filament 9 and the grid arranged adjacent to the filament 9. It is ionized when it passes through the ionization section consisting of 10. And an accelerating electrode installed on top of the grid 10.
The ionized clusters are accelerated by 11 and the accelerated cluster ions are deposited on the substrate 13 facing the crucible 5 together with the neutral clusters and the atoms that do not form the clusters.

Since this ICB method can ionize only one atom in the cluster of 100 to 2000 atoms as described above, the specific charge (e / m) is extremely small, and it is equivalent to several ev It can be said to be an industrially excellent vapor deposition method because it can transport a large-volume beam at a low speed of up to several + ev. In addition, the cluster is destroyed at the time of the collision with the substrate to become individual atomic particles, and the effect of rolling in the lateral direction, that is, the migration effect is large, so that the surface diffusion energy of the vapor deposition particles on the substrate is large. Further, by freely changing the accelerating voltage, it is possible to form a film having a feature that the kinetic energy can be freely controlled, a strong adhesive force and a high surface flatness.

By the way, the embodiment shown in FIG. 4 has one crucible 5
Material 4 is vapor-deposited according to Japanese Patent Publication No. Sho 56-
As disclosed in Japanese Patent No. 41165, a plurality of crucibles are individually loaded with materials to form a compound thin film. Alternatively, as described in Japanese Patent Publication No. 56-6333,
This ICB method is also used for forming oxide and nitride thin films by introducing a reactive gas into a vacuum chamber.

[Problems to be solved by the invention]

The ICB method uses the pressure difference between the inside and outside of the crucible 5 to form the cluster beam of the material 4 as described above. And in this case, to form clusters,
The vapor pressure in the crucible is Po and the pressure in the vacuum area around the crucible is P
If, then Po / P ≧ 10 ² or more, when the ejected particles pass through the nozzle area, they repeatedly collide with each other to exchange energy and cause a sufficient adiabatic phenomenon to become a supercooled state. There are many conditions such as that.

Therefore, in order to carry out the ICB method with the device shown in FIG. 4, the temperature of the crucible 5 heated by the heating device 7 is controlled, and the vapor pressure of the material 4 in the crucible 5, the shape of the nozzle, and the like are as described above. It is set to satisfy the conditions.

In this case, in the ICB method, it is ideal that all the atoms of the material 4 ejected from the nozzle 8 of the crucible 5 form clusters, but it is not always completely clustered depending on the operating conditions and structure. Not exclusively.

On the other hand, the formation of clusters has a great influence on the film quality of the thin film deposited on the substrate 13, and it is important to carry out the ICB method to check whether or not the clusters are formed.

However, heretofore, this was controlled only by ensuring a sufficient pressure difference between the inside and outside of the crucible.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a cluster detection apparatus that can reliably carry out the ICB method by qualitatively capturing the generation of clusters.

In order to achieve the above-mentioned object, the cluster detection device according to the present invention has the following configuration.

That is, a cluster flow ejected from a nozzle of a closed crucible heated in a vacuum chamber, a light source for irradiating excitation light, and a cluster excited by the light source arranged in a direction orthogonal to the irradiation direction of the light source. The detector is configured to detect the spectral intensity of fluorescence emission or excitation emission from the flow.

[Work]

When light is applied to atoms or molecules, light of a specific wavelength is absorbed and excited. The excited atoms lose energy through the process of emission or non-emission, but the light emitted by the emission process becomes fluorescence or excitation light. And the wavelength of this fluorescence is unique to the element,
Moreover, it depends on whether the element is atomic or molecular.

Therefore, if the cluster beam is irradiated with light and the fluorescence is spectrally analyzed and the spectral intensity in the molecular state of the element increases, it is estimated that clusters are formed.

The present invention is intended to detect the formation of clusters by irradiating the cluster beam with light and performing the fluorescence spectroscopic analysis based on the above-described operation principle.

〔Example〕

FIG. 1 is a schematic diagram showing a principle configuration in which a cluster detection device according to the present invention is attached to an ICB device.

Here, 21 is a vacuum chamber for carrying out the ICB method,
A vapor stream of material ejected from a nozzle of a closed crucible (not shown) forms a cluster beam 22. Further, the vacuum layer 21 is provided with a window portion 25 through which the excitation light 26 from the light source 23 enters through the optical system 24 and a window portion 28 for detecting the fluorescence 27 from the cluster beam 22. . And excitation light
26 is adjusted by the optical system 24 so as to focus on the center of the cluster beam 22.

The fluorescence 27 taken out of the vacuum chamber 21 through the window 28 enters the spectroscope 30 through the optical system 29, is spectrally analyzed, and is recorded in the recorder 31.

The excitation light 26 and the detection side of the fluorescence 27 are arranged at right angles, in order to minimize the interference between the excitation light 26 and the spectroscope 30. Further, in practice, means for amplifying the output of the spectroscope 30 with a photomultiplier and amplifying only the signal component by lock-in with the signal from the optical chopper arranged in front of the light source 23 is also adopted. Furthermore, the window
Baffles are placed on 25 and 28 to prevent stray light from the crucible,
Alternatively, the window portion may be prevented from being contaminated by the evaporation material. A high-pressure mercury lamp is used as the light source 23. In addition, it is also possible to use laser light as this light source.

Next, the measurement results by the cluster detecting apparatus according to the present invention based on the principle configuration of FIG. 1 will be described.

First, silver (Ag) was selected as a vapor deposition material, and it was loaded in a crucible and vapor deposition was performed by the ICB method. The nozzle diameter of the crucible at this time is 1 mmφ. And the heating temperature of the crucible,
Therefore, FIGS. 2A to 2C show spectral distributions of fluorescence emission from the cluster beam at various heating temperatures when the vapor pressure of Ag in the crucible was changed.

FIG. 2 (a) shows the case where the crucible temperature is 1305 ° C.,
At this temperature, a sharp spectrum is seen near 328 nm and 338 nm. It is known that this wavelength is the fluorescence spectrum of Ag single atom, and it can be seen that the beam ejected from the nozzle is in the atomic state.

The spectrum distribution when the crucible temperature is raised to 1510 ° C. is the result shown in FIG. 2 (b). In this case, fluorescence from the Ag single atom (spectrum around 328 nm and around 338 nm) is reduced, and fluorescence having a spectral line between 430 and 450 nm is generated. It is known that the fluorescence spectrum of Ag ₂ has a sharp spectral distribution in the wavelength band before and after the peak at around 447 nm, and at this crucible temperature of 1510 ° C, at least many molecular particles are generated in the beam. It is understood that it is done.

On the other hand, the fact that the clusters formed are clusters of massive atoms that are loosely bound to each other is described in, for example, “I. Yamada et al.
“The Formation and Kinetics of Ionized Cluster Be
ams "Z.Phys.D Atoms, Molecules and Clusters Vol.3−
It is already understood that the cluster has a spectrum similar to that of the molecular state, as disclosed in a paper such as “2-3, 134-142 (1986)”.

In addition, it is unreasonable from a theoretical analysis that after the nozzle is ejected, it is only molecularly bonded and does not grow into a larger aggregate (eg, “I. Yamada et al“ S ”).
tructure of Vapourized-Metal Clusters "Proceeding
s of the Sixth Symposium on Ion Sources and Ion As
sisted Technology, 47-52 (1982).

Furthermore, from the electron diffraction images of the clusters, it was confirmed that a typical amorphous image with no long-range order but only short-range order was observed. It is considered that binding is dominant.

That is, by increasing the crucible temperature, the fluorescence emission from the molecular state of Ag begins to be observed,
It can be estimated that clusters have been formed, which confirms the generation of clusters.

In this case, the pressure difference between the inside and outside of the crucible Po / P ≧ 10
⁴ , which is a sufficient condition for generating a cluster.

FIG. 2 (c) is a spectrum distribution when the crucible temperature is further raised to 1770 ° C. In this case, it can be seen that the fluorescence emission from the molecular state is dominant as compared with the fluorescence emission from the Ag single atom.

Thus, by spectrally analyzing the fluorescence emission generated by irradiating the cluster beam with the excitation light,
The generation of clusters can be confirmed by detecting the light emission from the molecular state.

The example shown in FIG. 2 is a case where Ag is selected as the vapor deposition material, and the fluorescence spectrum from a single atom and the fluorescence spectrum from the molecular state when the vapor deposition material is gold (Au) are shown in FIG. ), And that for Cu is shown in Fig. 3 (b). In the case of Au, the spectra in the single atom state occur around 242 nm and 267 nm, while the emission in the molecular state is between 500 nm and 535 nm. Similarly, in Cu, while the emission from the single atom state is around 325 nm and 327 nm,
When this becomes a molecular state, it shifts to around 485 nm to around 522 nm.

Thus, for each element, in the atomic state and the molecular state,
Since the fluorescence emission spectra are different, it is possible to detect the fluorescence spectrum in the molecular state and confirm the generation of clusters.

By the way, in the embodiment shown in FIG. 1 described above, the fluorescence emission from the cluster beam is analyzed by using the spectroscope. However, the spectroscope is changed to the atomic state and the molecule depending on the element of the vapor deposition material. A sensor sensitive to the fluorescence emission from the state, for example, a sensor including a combination of a filter that transmits light in a characteristic wavelength range and a photoelectric conversion element may be used.

Other than that, the present invention is not limited to the above-mentioned embodiment, for example, by irradiating a plurality of excitation light having different wavelengths,
Needless to say, various modifications such as changing the wavelength of fluorescence or excitation light to be detected with time and distinguishing from the d / dt signal can be performed.

[Effect]

As described above, the cluster detection device according to the present invention detects the generation of clusters, focusing on the difference in the spectra of the fluorescence from the atomic state and the fluorescence from the molecular state when each element is optically excited. Is.

Therefore, as compared with the conventional method in which the ICB method is performed by simply adjusting the crucible temperature to increase the pressure difference between the inside and outside of the crucible, it becomes possible to confirm the formation of clusters, and it is possible to form a thin film of good quality. .

Further, a detector for detecting the spectral intensity of fluorescence emission or excitation emission from the cluster flow is arranged in a direction orthogonal to the irradiation direction of the light source.

Therefore, the interference between the excitation light emitted from the light source and the detector can be minimized, and the detection accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram showing an embodiment of a cluster detection apparatus according to the present invention, FIG. 2 is a diagram showing a fluorescence spectrum distribution in the embodiment, and FIG. 3 is an example of a fluorescence spectrum distribution of each element. And FIG. 4 are schematic configuration diagrams showing an apparatus for carrying out the ICB method. 21 ... vacuum chamber, 22 ... cluster beam 23 ... light source, 30 ... spectrometer

Claims (1)

[Claims] 1. A light source for irradiating excitation light to a cluster flow ejected from a nozzle of a heated closed crucible disposed in a vacuum chamber and disposed in a direction orthogonal to the irradiation direction of the light source. A cluster detecting device having a detector for detecting the spectral intensity of fluorescence emission or excitation emission from a cluster flow excited by the light source.