JP6969065B2 - Ion implantation method, ion implantation device - Google Patents

Description

The present invention relates to an ion source, and more particularly to an ion source maintenance technique used in an ion implanter.

In recent years, a method for manufacturing a silicon carbide (SiC) substrate, which is superior in heat resistance and withstand voltage as compared with existing silicon (Si) substrates, has been established and can be obtained at a relatively low cost.
In the process using the SiC substrate, there is a process of implanting aluminum ions as a dopant, and an ion implanter having an ion source for generating an aluminum ion beam is used.

FIG. 2 is a cross-sectional view showing the inside of the conventional ion generation chamber 50.
The ion generation chamber 50 has a vacuum chamber 51, and an ion generation container 52 is arranged inside the vacuum chamber 51.
An opening 51b is provided on the side wall of the vacuum chamber 51, and the opening 51b is sealed by a lid portion 51c. The ion generation container 52 is fixed to the lid portion 51c by the holding mechanism 54.

A gas supply container 59 is arranged outside the vacuum chamber 51. The raw material having an atom to be injected into an object to be injected such as a substrate may be arranged in the gas supply container 59 or inside the ion generation container 52, and is arranged inside the gas supply container 59. In this case, the raw material is vaporized inside the gas supply container 59, and the generated raw material gas is supplied from the gas supply container 59 to the ion generation container 52.

When the raw material is arranged in the ion generation container 52, the reactive gas is arranged in the gas supply container 59, and the reactive gas supplied from the gas supply container 59 and the raw material react inside the ion generation solubilizer 52. Gas is generated.
In either case, the gas inside the ion generation container 52 is ionized to form plasma.

One side wall of the ion generation container 52 is arranged facing the wall surface of the vacuum chamber 51, and the extraction electrode 53 is arranged between the one side wall of the facing ion generation container 52 and the wall surface of the vacuum tank 51. .. The extraction electrode 53 is fixed to the vacuum chamber 51 by an insulator 57.

The ion generation container 52 is connected to the extraction power supply 56 via the lid portion 51c and the holding mechanism 54, and the extraction electrode 53 is connected to the acceleration / deceleration power supply 58.
The vacuum chamber 51 is connected to the ground potential, a positive voltage is applied to the ion generation container 52 by the extraction power supply 56, and a negative voltage is applied to the extraction electrode 53 by the acceleration / deceleration power supply 58.

Here, aluminum nitride is arranged as a raw material inside the ion generation container 52, and PF ₃ gas is supplied as a reactive gas from the gas supply container 59 to the ion generation container 52. The raw material reacts with the reactive gas inside the ion generation container 52 to generate a compound gas containing aluminum, and plasma is generated by electron beam irradiation or the like.

Drawer holes 52a, 51a, 53a are provided in one side wall of the ion generation container 52 facing each other, the wall surface of the vacuum chamber 51, and the drawer electrode 53 arranged between them, respectively, and the ion generation container 52 is provided. The ions generated inside the vacuum chamber 51 are drawn out of the ion generation vessel 52 by the electric field formed by the extraction electrode 53 and the ion generation vessel 52, and are ejected from the extraction hole 51a of the vacuum chamber 51 to the outside of the vacuum chamber 51. NS.

In such an ion generation chamber 50, when aluminum ions are generated, a fluorine-based gas (for example, PF ₃ ) is arranged as a reactive gas in the gas supply container 59, and aluminum nitride is provided inside the ion generation container 52. Alternatively, alumina is arranged as a raw material, a reactive gas is introduced inside the ion generation container 52, and the reaction is carried out to generate Al ions, which are passed through the extraction holes 52a, 53a, 51a and discharged to the outside of the vacuum chamber 51. ..

_{However, in such a method of reacting PF 3} with aluminum nitride or the like, _{insulating aluminum fluoride (AlF x} ) is generated as a by-product, and the generated aluminum fluoride is used as an inner wall surface in the vacuum chamber 51. When the insulating films 60 and 61 are formed by adhering to the aluminum, there is a problem that an abnormal discharge occurs in the vacuum chamber 51.

When such an abnormal discharge occurs, the ion beam current fluctuates and the yield of the object to be implanted decreases, and electromagnetic noise may cause a failure of the power supply of the ion implanter or the vacuum pump.

For this reason, conventionally, when abnormal discharge occurs frequently, the vacuum chamber 51 of the ion generation chamber 50 is opened to the atmosphere to remove the insulating films 60 and 61, but in the prior art, such maintenance is performed. There was a problem that the production efficiency was deteriorated because it had to be performed frequently.

Therefore, a raw material that does not generate an insulating film is required, and Al (CH ₃ ) ₃ is a source of Al ions. However, when this compound is vaporized and ionized, the value of the charge mass ratio is the same as that of Al ions. "27" hydrogen ion (C ₂ H ₃ ⁺ ) is generated and difficult to separate.

On the other hand, hydrogen, which is injected into a semiconductor single crystal wafer at a high concentration at a depth of several microns, is attracting attention as an ion to be injected. When heat treatment is performed after the injection, the bond of the silicon crystal is broken and the entire surface of the single crystal wafer is exposed. It can be peeled off with a thickness of micron size (smart cut technology). In addition, hydrogen injection has _{come to be used for thin film processing of LiNbO 3} substrates and the like and production of single crystal silicon thin films for next-generation solar cells.

Therefore, ion implantation using hydrogen as a dopant is also attracting attention.
Further, boron is introduced into the surface of a Si substrate as an impurity of a Si power semiconductor, and from these facts, there is a demand for an ion implanter that can easily cope with various types of objects to be implanted to implant different ions.

Japanese Unexamined Patent Publication No. 5-182623

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an ion implantation device that does not generate an abnormal discharge at an ion source.
Another object of the present invention is to provide an ion implantation apparatus capable of selecting and injecting an ion type from aluminum ions, boron ions and hydrogen ions without exchanging raw materials.

In the present invention made to solve the above problems, the boron hydride aluminum is vaporized to generate a boron hydride aluminum gas, the boron hydride aluminum gas is decomposed to form a plasma, and cations are formed from the plasma. Is extracted, one of the desired cations is selected from the three types of ions, hydrogen ion, boron ion, or aluminum ion, based on the charge-mass ratio, and the selected cation is irradiated to the implantation target. This is an ion implantation method for injecting into the object to be implanted.
Further, the present invention is an ion implantation method in which a liquid of the aluminum borohydride is placed in a container and the inside of the container is vacuum exhausted to generate the aluminum borohydride gas.
Further, in the present invention, boron hydride aluminum is arranged as a raw material liquid, and a gas supply device that vaporizes the raw material liquid to generate a raw material gas and the raw material gas vaporized by the gas supply device are supplied to the raw material. From the ion generation container that ionizes gas to form plasma, the extraction electrode that draws cations from the plasma, and the cations extracted by the extraction electrode, three types of ions, hydrogen ion, boron ion, or aluminum ion, It is an ion injection device having a mass analyzer that allows a desired type of cation to pass through, and a substrate placement device on which an injection target to be irradiated with the cation that has passed through the mass analyzer is arranged.

In the present invention, since the insulating film is not deposited in the ion generation chamber, abnormal discharge does not occur at the ion source due to the adhesion of the insulating film.
In the present invention, since a plasma containing aluminum ions, boron ions and hydrogen ions is generated, only by changing the magnetic field strength of the mass spectrometer, any one of aluminum ions, boron ions and hydrogen ions can be generated. It can be injected into the object to be injected by passing ions through it.

In addition, hydrocarbon ions are not generated, and hydrocarbons are not injected into the injection target.
Aluminum borohydride does not require a vaporizer because steam can be obtained by simply placing it in a vacuum atmosphere even at room temperature.

Schematic block diagram showing the whole of the ion implanter using the ion source of the present invention. Partial cross-sectional view showing the internal configuration of an example of a conventional ion source

Reference numeral 2 in FIG. 1 is an ion implanter according to an example of the present invention.
The ion implantation device 2 has an ion generation chamber 12, a main vacuum chamber 11, and an injection chamber 13. The ion generation chamber 12 and the injection chamber 13 are connected by a main vacuum chamber 11.

A vacuum exhaust device 19 is connected to at least the injection chamber 13, and the inside of the ion generation chamber 12, the inside of the main vacuum chamber 11, and the inside of the injection chamber 13 are created in a vacuum atmosphere.
A substrate arranging device 36 is arranged inside the injection chamber 13. In FIG. 1, an injection object 15, which is a substrate for injecting ions, is arranged on the substrate arrangement device 36.

The ion generation container 22 is arranged inside the ion generation chamber 12, and the gas supply device 21 is arranged outside the ion generation chamber 12.
The gas supply device 21 has a container shape and is connected to the ion generation container 22, and the ion generation container 22 is connected to the main vacuum chamber 11.

A raw material liquid which is a liquid aluminum borohydride (Al (BH ₄ ) _{3) is arranged in the gas supply device 21.} The compound of this raw material liquid is also called aluminum borohydride.

The boiling point of boron hydride aluminum is 45 ° C., the ion generation chamber 12 and the main vacuum chamber 11 are evacuated, the inside of the ion generation container 22 and the inside of the gas supply device 21 are also evacuated, and the raw material liquid is in a vacuum atmosphere. When placed in, the raw material liquid is vaporized to generate a raw material gas. Even if the raw material liquid is at room temperature, vaporization occurs only when the raw material liquid is placed in a vacuum atmosphere, and the inside of the gas supply device 21 is filled with the raw material gas.

The raw material gas inside the gas supply device 21 moves from the gas supply device 21 to the ion generation container 22, and is irradiated with an electron beam inside the ion generation container 22 to decompose, and Al ⁺ , H ^+, and B ⁺ are generated. The contained plasma is formed.

Al (BH ₄ ) ₃ does not contain carbon atoms, does not generate carbon-containing ions even when decomposed, and does not generate solid insulation, so no film of insulation is deposited, gas pipes, etc. No blockage or abnormal discharge occurs.

The ion generation container 22 is connected to the traveling portion 14 of the main vacuum chamber 11, and a slit 20 and an ion extraction electrode 23 are arranged inside the traveling portion 14.

The main vacuum chamber 11, the injection chamber 13, and the ion generation chamber 12 are connected to a ground potential, a positive voltage is applied to the ion generation container 22, and a negative voltage is applied to the ion extraction electrode 23. Reference numeral 31 is a power source for applying a voltage to the ion generation container 22 and the ion extraction electrode 23.

Due to the electric field formed by the ion extraction electrode 23 and the ion generation container 22, cations from the plasma formed inside the ion generation container 22 pass through the slit 20 and are extracted and extracted into the traveling portion 14. The cations travel inside the traveling unit 14.

A mass spectrometer 24 is provided in the main vacuum chamber 11 in front of the drawn cations in the traveling direction.
The mass spectrometer 24 has electromagnets 25a and 25b.

A control device 18 and an analysis power supply 32 are arranged outside the main vacuum chamber 11, current is supplied from the analysis power supply 32 to the electromagnets 25a and 25b, and a magnetic field is formed inside the mass spectrometer 24. Will be done.

The analysis power supply 32 is connected to the control device 18, and the current supplied by the analysis power supply 32 to the electromagnets 25a and 25b is controlled by the control device 18. Therefore, the strength of the magnetic field formed inside the mass spectrometer 24 is controlled by the control device 18.

When the ions extracted by the ion extraction electrode 23 enter the inside of the mass spectrometer 24, the incident ions receive Lorentz force by the magnetic field formed by the electric magnets 25a and 25b, and are formed with the value of the charge mass ratio of the ions. The flight direction of the ions is curved according to the strength of the magnetic field.

The tank wall of the portion of the main vacuum chamber 11 provided with the mass spectrometer 24 is curved in a predetermined direction, and ions whose flight direction is curved corresponding to the curvature of the tank wall pass through the mass spectrometer 24. do. Among the ions, ions having other curvatures collide with the members provided on the curved tank wall of the main vacuum chamber 11 and cannot pass through the mass spectrometer 24.

The curvature of the ion in the flight direction is a magnitude determined by the strength of the magnetic field formed inside the mass spectrometer 24 and the value of the charge mass ratio of the ion, and the control device 18 controls the amount of energization to the electric magnets 25a and 25b. By doing so, the magnetic field strength is changed, and ions having a desired charge-mass ratio can be passed through. In this case, ions having other charge-mass ratios cannot pass through the mass spectrometer 24.

The ions that have passed through the mass spectrometer 24 are ions having a predetermined charge-mass ratio, and the acceleration unit 28 is arranged in the main vacuum chamber 11 in front of the traveling direction.
The acceleration unit 28 has a first slit 26 and a second slit 27 arranged in front of the first slit 26 in the traveling direction of ions, and is between the first slit 26 and the second slit 27. Is arranged with a plurality of acceleration electrodes 29.

A predetermined voltage is applied to each accelerating electrode 29, and ions incident on the accelerating portion 28 and passing through the first slit 26 are accelerated by the accelerating electrode 29 when passing between the plurality of accelerating electrodes 29. It passes through the second slit 27. Reference numeral 37 indicates a power source that applies a voltage to the acceleration electrode 29.

An electrostatic scan unit 33 is arranged in front of the traveling direction of the ions that have passed through the second slit 27.
A plurality of control electrodes 34 are arranged inside the electrostatic scan unit 33, a voltage is applied to each control electrode 34, and an electric field is formed inside the electrostatic scan unit 33. Reference numeral 38 indicates a power source that applies a voltage to the control electrode 34.

When the ions that have passed through the second slit 27 are incident on the electric field formed inside the electrostatic scanning unit 33, the flight direction is curved by the electric field and passes through the electrostatic scanning unit 33.
The injection chamber 13 is arranged in front of the traveling direction of the ions that have passed through the electrostatic scan unit 33, and the ions that have passed through the electrostatic scan unit 33 are incident inside the injection chamber 13.

A substrate arranging device 36 is provided in front of the traveling direction of the ions incident on the injection chamber 13, and the ions incident on the injection chamber 13 are irradiated to the injection target 15 arranged in the substrate arranging device 36 for injection. It is injected onto the surface of the object 15.

The power supply 38 that applies a voltage to the control electrode 34 is connected to the control device 18, the magnitude of the voltage output to the control electrode 34 is controlled by the control device 18, and the magnitude of the curvature of the ion in the flight direction is the control device. It is changed by 18 so that ions are irradiated to a desired position on the substrate arrangement device 36, the irradiation position of the ion beam is moved by the control device 18, and a predetermined amount is applied to all one side of the injection target 15. Ions are irradiated and injected.

When a predetermined amount of ions are implanted into the surface of the object to be implanted 15, the ion implantation work for the object to be implanted 15 is completed and the ion is carried out from the injection chamber 13.

Here, when the Al ions are made to pass through the mass spectrometer 24 by the magnetic field formed by the electromagnets 25a and 25b, the injection target 15 is irradiated with the Al ions, and Al is the surface of the injection target 15. A predetermined amount is injected into. When the injection target 15 into which Al has been injected is carried out from the injection chamber 13, and then the injection target into which B is injected is carried into the injection chamber 13 and placed in the substrate arranging device 36, the analysis power supply 32 The amount of current supplied to the electromagnets 25a and 25b is changed, and B ions pass through the mass spectrometer 24 to irradiate the object to be injected. Further, when the injection target for injecting H is arranged in the substrate arranging device 36, the amount of current supplied by the analysis power supply 32 to the electromagnets 25a and 25b changes so that the H ions pass through the mass spectrometer 24. Then, the injection target is irradiated with H ions.

As described above, the mass analyzer 24 of the ion injection device 2 of the present invention has three types of ions, hydrogen ion, boron ion or aluminum ion, from the cations drawn from the ion generation container 22 by the ion extraction electrode 23. , It is possible to pass a desired kind of ion.

2 …… Ion implantation device 12 …… Ion generation chamber 15 …… Injection target 21 …… Gas supply device 22 …… Ion generation container 24 …… Mass spectrometer

Claims (3)

Vaporizing aluminum borohydride to produce aluminum borohydride gas,
The boron hydride aluminum gas is decomposed to form a plasma, cations are extracted from the plasma, and one of the three types of ions, hydrogen ion, boron ion, and aluminum ion, is charged with a desired cation. An ion injection method in which selection is performed based on a mass ratio, and the selected cations are irradiated on the injection target to be injected into the injection target. The ion implantation method according to claim 1, wherein the liquid of aluminum borohydride is placed in a container and the inside of the container is vacuum exhausted to generate the aluminum borohydride gas. A gas supply device in which aluminum borohydride is arranged as a raw material liquid and vaporizes the raw material liquid to generate a raw material gas.
An ion generation container to which the raw material gas vaporized by the gas supply device is supplied and ionizes the raw material gas to form plasma.
An extraction electrode that draws cations from the plasma,
A mass analyzer that allows a desired one of the three types of ions, hydrogen ion, boron ion, and aluminum ion, to pass from the cation extracted by the extraction electrode.
A substrate placement device on which an injection target to be irradiated with cations that have passed through the mass spectrometer is placed, and a substrate placement device.
Ion implanter with.

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