JP2729943B2 - Radical beam emitting device and radical beam emitting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for emitting a radical beam to a film forming surface in a thin film forming apparatus such as a molecular beam epitaxy apparatus, and more particularly, to suppressing the emission of ions and emitting only radical atoms. The present invention relates to a radical beam launching device and a launching method.

[0002]

2. Description of the Related Art A typical example of a thin film forming apparatus is a molecular beam epitaxy apparatus (MBE apparatus). This MB
The E apparatus arranges a molecular beam source such as a Knudsen cell (K cell) toward a substrate attached to a substrate holder in a vacuum chamber maintained in a high vacuum, and removes molecules of a thin film raw material from the molecular beam source. The light is emitted toward the film forming surface of the substrate, and a thin film is grown on the film forming surface. In the case of a K cell that generates molecules by electric heating, the heater is surrounded by a shroud cooled by liquid nitrogen or the like.

In such an MBE apparatus, when forming an oxide film such as a high-temperature superconducting thin film or a compound semiconductor film, a beam of electrically neutral and chemically active radical atoms generated in plasma. Is formed while projecting on a film formation surface of a substrate. In this case, in addition to the molecular beam source, a plasma beam source is installed in the vacuum chamber toward the film formation surface of the substrate.

Further, an electron beam accelerated to 10 to 50 keV is made incident on the film formation surface of the substrate at a shallow angle, and the electron beam diffracted on the film formation surface is projected on a fluorescent screen. Reflection high-speed electron diffraction (RHEED) for observing a crystal lattice or the like is used. In this case, an electron gun is installed in the vacuum chamber at a shallow angle toward the film-forming surface of the substrate, and a fluorescent screen is provided on an observation window facing the electron gun.

In the above-described thin film forming apparatus, ions are generated in addition to radical atoms in a cell in which a plasma beam source generates radical atoms because a rare gas is excited into a plasma state. When these ions have a positive charge and are emitted from the plasma beam source onto the film-forming surface of the substrate, they collide with the film-forming surface of the substrate due to the energy of the charge and damage the thin film formed on the film-forming surface. give. Therefore, an electrode applied to a positive potential is arranged near the discharge port of the cell of the plasma beam source, and the emission of ions is suppressed by the electric field.

[0006]

However, it is not easy to know how much voltage should be applied to the electrodes to suppress the emission of ions from the cell. For this reason, conventionally, the electrode potential is determined to some extent by intuition, and therefore the potential is too high or too low, and cannot be optimally controlled. Therefore, it has been difficult to optimally set the film forming conditions. In view of the above-mentioned conventional problems, the present invention provides a radical beam emission method that emits only a radical beam from a radical beam source, completely suppresses the emission of ions, and accurately grasps conditions for preventing the ion emission. The aim is to obtain the device and the launch method.

[0007]

According to the present invention, in order to achieve the above object, a positive voltage is applied to the suppressor electrode 4 provided near the radiation port 26 of the cell 3 so as to suppress the emission of ions, The voltage of the suppressor electrode 4 is adjusted so that current does not flow through the shutter 5 made of a conductor whose radiation port 26 is closed. Then, when the current stops flowing through the shutter 5, the shutter 5 is opened and the radiation port 2 of the cell 3 is opened.
6 emits a radical atom. In this case, whether or not a current is flowing through the shutter 5 is determined by connecting an ammeter 27 between the shutter 5 and the ground and determining whether or not a current is flowing through the ammeter 27.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Radical atoms are generated inside the cell 3 which is placed in the vacuum chamber 2 and is in a plasma state.
A radical beam is emitted from a radiation port 26 of the vacuum chamber 2 toward a predetermined position in the vacuum chamber 2. In the present invention, in such a radical beam emitting device, a shutter 5 composed of a conductor for opening and closing a radiation port 26 of the radical atom of the cell 3, an ammeter 27 connected between the shutter 5 and the ground, A suppressor electrode 4 is disposed between the shutter 5 and the radiation port 26 and suppresses emission of ions from the radiation port 26 of the cell 3. In order to prevent ions from being emitted from the emission port 26, a positive voltage that can be varied is applied to the suppressor electrode 4.

Further, in the radical beam emitting method according to the present invention using such a radical beam emitting device,
A positive voltage is applied to the suppressor electrode 4 and the cell 3
Ammeter 27 through the shutter 5 with the radiation outlet 26 closed
The voltage of the suppressor electrode 4 is adjusted so that no current flows. Then, when the current stops flowing to the ammeter 27, the shutter 5 is opened and the radical atom is emitted from the emission port 26 of the cell 3.

In the radical beam emitting device and the emitting method described above, a positive voltage is applied to the suppressor electrode 4 while the radiation port 26 of the cell 3 is closed by the shutter 5, and a current is supplied to the ammeter 27 through the shutter 5. The voltage of the suppressor electrode 4 is adjusted so as not to flow. Therefore, it can be easily confirmed whether or not ions are emitted from the emission port 26 of the cell 3. That is, the radiation port 2 of the cell 3
When ions, which are charged particles, hit the shutter 5 closing the shutter 6, a current flows through the ammeter 27 when the charge flows to the ground side. On the other hand, when ions as charged particles do not hit the shutter 5, no current flows through the ammeter 27. Therefore, when the current stops flowing through the ammeter 27, the shutter 5 is opened and the radical atoms are emitted from the emission port 26 of the cell 3 to emit only the radical atoms in a state where the emission of ions is completely suppressed. It can be fired from the mouth 26.

In this way, it is possible to prevent ions, which are charged particles, which are to be radiated from the inside of the cell 3, from being emitted from the emission port 26. Only atoms can be fired. Thereby, the problem that the thin film being formed is damaged by the collision of ions with the irradiation destination of the radical beam can be surely solved.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; FIG. 1 shows a radical beam emitting apparatus according to an embodiment of the present invention and a substrate to which a radical beam is irradiated. That is, a substrate holder 19 is arranged in the vacuum chamber 2, a substrate 20 is mounted on the lower surface thereof, and a thin film material is supplied from a molecular beam source not shown in FIG. Are irradiated to form a thin film. The radical beam emitting device is a cell 3 for generating radical atoms.
Is provided at the upper end, and the radiation port 26 of the cell 3 is set to face the film forming surface of the substrate 20.

A frame 9 is hermetically connected to a flange 8 of the vacuum chamber 2 and a guide 1 is provided between the frame 9 and another frame 37 arranged in parallel.
0 and the screw guide 11 are installed in parallel.
Among them, the latter screw guide 11 is rotatably supported by the frames 9 and 37, and the screw guide 11 is rotated by the handle 16.

A movable flange 13 is disposed between the frames 9 and 37, and bushes 17 and 38 fixed to the movable flange 13 are fitted to the outside of the screw guide 11 and the guide 10, respectively. Of these, the bush 38 is slidable in the longitudinal direction with respect to the guide 10, but a thread groove is provided on the inner periphery of the bush 17, which is screwed into the screw guide 11.
Therefore, when the screw guide 11 is rotated by the handle 16, the screw guide 11 and the bush 1 are rotated.
The movable flange 10 moves in the central axis direction of the screw guide 11 and the guide 10 according to the lead of the screw 7.

A cylindrical bellows 12 is airtightly stretched between the frame 9 and the movable flange 13, and a space surrounded by the bellows 12 and the movable flange 13 has the same atmosphere as the inside of the vacuum chamber 2. And is sealed off from the outside. This bellows 12 expands and contracts in the central axis direction of the screw guide 11 and the guide 10,
The movable flange 13 is allowed to move in the same direction.

The radical beam source 1 is erected on the movable flange 13 and is surrounded by a bellows 12. Further, a shutter shaft 6 is rotatably provided near the radical beam source 1, and a disk-shaped shutter 5 made of a conductor is attached to an upper end thereof. The shutter shaft 6 is rotated by a manipulator 39,
Thereby, the upper surface of the radical beam source 1 and the substrate holder 1
The 9 side faces and is shielded.

Further, an optical guide 7 is incorporated in a shutter shaft 6 erected near the radical ion source 1. The optical guide 7 is made of an optical fiber or the like, and has a light receiving end 24 at the upper end thereof.
Is installed toward the cell 3 through a through hole provided in the shield case 21, and the light receiving end 2 of the optical guide 7 is
The light receiving field of view 4 is on the cell 3 side. The viewing end 15 side of the optical guide 7 penetrates the movable flange 13 and is led out of the atmosphere of the vacuum chamber 2. A spectrometer is connected to the viewing light end 15 of the optical guide 7 via, for example, an optical fiber, and the light received by the optical guide 7 is spectrally analyzed. When the above-described spectrometer or the like is not connected to the viewing light end 15 of the optical guide 7, the state of the light incident from the light receiving end 24 side can be directly observed at the viewing light end 15.

In FIG. 1, reference numeral 40 denotes a high-frequency power supply connector for supplying a high-frequency current to a high-frequency coil 22 described later, reference numeral 18 denotes a supply port for supplying a rare gas as a raw material of radical atoms into the cell 3, and reference numeral 14 denotes a supply port. , A filament power supply connector for supplying a current to a filament 25 described later. FIG. 2 shows a main part of the radical beam source 1, that is, an upper end thereof and an electrical connection state of each element. The radical beam source 1 is classified into a capacitive type using a magnetic field and an inductive type using a high-frequency power source according to a method of generating an electric field inside the cell 3. Although FIG. 2 particularly shows the latter system, the present invention can be similarly applied to the former system.

The outer shell of the radical beam source 1 is made up of a cylindrical shield case 21, and a cell 3 is housed in the upper end inside the shield case. The cell 3 is made of a transparent cylindrical container-like member that is chemically stable and has heat resistance, such as quartz glass. A gas introduction nozzle 23 for supplying a lean gas into the inside of the cell 3 and a filament 25 for emitting electrons into the inside of the cell 3 are attached to the bottom of the cell 3. Further, a high frequency coil is wound around the outer periphery of the cell 3. The upper end of the cell 3 is open, and this opening serves as a radiation port 26 for a radical beam.

On the radiation port 26 of the cell 3, a suppressor electrode 4 for suppressing the emission of ions is arranged.
A variable voltage power supply 28 whose voltage is variable is connected to the suppressor electrode 4, and a positive voltage is applied. A voltmeter 29 for measuring the voltage is connected to the variable voltage power supply 28. As described above, the shutter 5 is made of a conductor, and the shutter 5 is grounded via an ammeter 27.

In the radical beam emitting apparatus having such a configuration, first, the shutter 5 closes the radiation port 26 of the cell 3 with the shutter 5. Further, a positive voltage is applied to the suppressor electrode 4 by the variable voltage power supply 28. In this state, a gas such as nitrogen gas is introduced from the gas introduction nozzle 23 into the inside of the cell 3 to make the inside of the cell 3 a rare gas atmosphere, and a high-frequency current is passed through the high-frequency coil 22 to form an electric field inside the cell 3. At the same time, electrons are emitted from the filament 25 into the cell 3, and the inside of the cell 3 is brought into a plasma state. As a result, activated radical nitrogen atoms are generated inside the cell 3.

On the other hand, along with such radical nitrogen atoms, ions such as nitrogen ions are generated inside the cell 3.
Since these ions are charged particles having a positive charge, they are suppressed by an electric field generated from the suppressor electrode 4 to which a positive voltage is applied, and are prevented from being emitted from the emission port 26 of the cell 3. However, when some ions are released from the outlet 26 of the cell 3, the shutter 5 closing the outlet 26
, A current flows through the ammeter 27. Therefore, when it is confirmed that a current flows through the ammeter 27, the voltage applied to the suppressor electrode 4 by the variable voltage power supply 28 is increased,
The current is prevented from flowing through the ammeter 27. That is, when ions are emitted from the emission port 26 and it is confirmed by the pointer of the ammeter 27 that the ions are hitting the shutter 5, the voltage applied to the suppressor electrode 4 is adjusted, and the emission of the ions from the emission port 26 is performed. Is completely suppressed, so that ions do not hit the shutter 5.

When the shutter 5 is opened in this state, only electrically neutral radical atoms are emitted from the emission port 26 of the cell 3 by the energy possessed at the time of generation, and are irradiated on the substrate 20. In this way, the film formation surface of the substrate 20 is irradiated with only electrically neutral radical atoms, so that the film formation surface of the substrate 20 is not damaged by collision of charged particles or the like. Further, the plasma emission in the cell 3 when the radical atoms are generated in this manner is received by the light receiving end 24 of the optical guide 7 through the outer wall of the transparent cell 3, and the light is emitted to the visual end outside the vacuum chamber 2. 15 (see FIG. 1)
You can see it in

The irradiation of the radical beam onto the film-forming surface is performed by operating the handle 16 of the moving mechanism of the radical beam source 1 shown in FIG.
The process is performed by bringing the film to a suitable distance close to the film formation surface of No. 0. On the other hand, RHE
When the film is analyzed by a reflection type high-speed electron diffraction image by irradiating electrons at a shallow angle to the film formation surface of the substrate 20 by the ED electron gun, the cell 3 is formed on the substrate 20 by operating the handle 16. Perform the test at a sufficient distance from the surface. As a result, a required reflection-type high-speed electron diffraction image can be obtained without affecting the beam path from the RHEED electron gun to the film formation surface of the substrate 20.

FIG. 4 shows an example in which the above-described radical beam emitting device is incorporated in an MBE device. The inside of the vacuum chamber 2 composed of a pressure-resistant container is reduced to a predetermined vacuum degree by a vacuum pump (not shown). A substrate introduction chamber is provided above the vacuum chamber 2, and the tip of the manipulator 35 is introduced from the substrate introduction chamber, and the substrate holder 19 is attached to the tip of the manipulator 35.
A substrate 20 is attached to the lower surface of the substrate holder 19, and the lower surface of the substrate 20 is a film forming surface.

At the lower part of the vacuum chamber 2, various kinds of effusion cells are placed on a substrate 20 held by a substrate holder 19.
It is installed facing the film formation surface of. That is, a molecular beam source 31 such as a K cell is arranged as an emission source of the thin film raw material, and the molecules of the thin film raw material are irradiated toward the film forming surface of the substrate 20 from here. The above-mentioned plasma beam source 1 is also provided facing the film formation surface of the substrate 2, and only a beam of electrically neutral and chemically active radical atoms generated by the plasma beam source 1 forms the substrate 20. Irradiation to the film surface is as described above.

At the side of the substrate 20, the RHEED electron gun 3
3 is installed, and is directed at a shallow angle to the deposition surface of the substrate 20. From the RHEED electron gun 33, 10
An electron beam accelerated to about 50 keV is incident on the film formation surface of the substrate 20 at a shallow angle. The RH of the vacuum chamber 2
An observation window 36 is provided at a position facing the EED electron gun 33, and the electron beam diffracted on the film formation surface of the substrate 20 is projected on a fluorescent screen stretched over the observation window 36. A so-called reflection-type high-speed electron diffraction (R
HEED).

Further, a rod-shaped image guide 34 made of a fiberscope or the like is inserted into the observation window 36 side, and the image guide 34 is slidably inserted left and right in FIG. Partitioned airtight. The image guide 34 has an observation section at the base end thereof, and a spectrometer,
A detector or a monitor display can also be connected. With this image guide 34, for example, the state of a film being formed on the film formation surface of the substrate 20, the state of the emission port of the irradiation source 31 of the raw material, and the like can be observed.

[0029]

As described above, in the radical beam emitting apparatus according to the present invention, before the shutter 5 is opened and the radical beam is emitted from the emission port 26 of the cell 3, ions are not emitted from the emission port 26. The voltage applied to the suppressor electrode 4 can be adjusted. As a result, only the radical beam can be emitted from the radiation port 26 of the cell 3, and for example, damage to the film surface formed on the substrate can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic partial vertical sectional side view showing a plasma beam emitting device according to an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a main part of the plasma beam emitting device according to the embodiment and an electrical connection state diagram thereof.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a schematic vertical sectional side view showing an example of an MBE device incorporating a plasma beam emitting device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Radical beam source 2 Vacuum chamber 3 Cell 26 Cell emission port 27 Ammeter 28 Variable voltage power supply 29 Voltmeter

Claims (3)

(57) [Claims] 1. A vacuum chamber (2) which is disposed in a vacuum chamber (2) and generates radical atoms inside a cell (3) in a plasma state, and from a radiation port (26) of the cell (3). A radical beam emitting device that emits a radical beam toward a predetermined position in the cell, a shutter (5) comprising a conductor for opening and closing a radiation atom emission port (26) of the cell (3), and the shutter (5).
And an ammeter (27) connected between the shutter (5) and the emission port (26), and ions are emitted from the emission port (26) of the cell (3). A radical beam emitting device, comprising: 2. The radical beam emitting device according to claim 1, wherein a positive voltage that can be varied is applied to the suppressor electrode. 3. A vacuum chamber (2) which is arranged in a vacuum chamber (2) and generates radical atoms inside a cell (3) in a plasma state, and from a radiation port (26) of the cell (3). A method of emitting a radical beam from a radical beam emitting device for emitting a radical beam toward a predetermined position in a cell, wherein a shutter (5) comprising a conductor for opening and closing a radiation atom emission port (26) of the cell (3). A current meter (27) is connected between the shutter (5) and the radiation port (26) of the cell (3) is closed by the shutter (5), and a positive voltage is applied to the suppressor electrode (4). The voltage is adjusted so that the current does not flow through the ammeter (27). When the current disappears, the shutter (5) is opened to emit radical atoms from the emission port (26) of the cell (3). A radical beam emitting method.