JPH0535537B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention generates ions by an electron beam,
The present invention relates to an electron beam excited ion irradiation device that irradiates a sample with generated ions.

(Prior Art) Ion irradiation devices are used for microfabrication of integrated circuits, etc. Ion irradiation devices known today irradiate a sample with ions in the following manner.
Plasma is generated by DC discharge, RF discharge, or ECR (electron cyclotron resonance), and only ions from this plasma are extracted by an electric field.
In this way, the sample is irradiated with ions.

(Problems to be Solved by the Invention) In order to effectively perform ion beam etching, etc. without leaving major damage to the sample, it is necessary to irradiate the sample with a large current ion beam in a low energy region. In conventional devices, it was not possible to increase the ion beam current in the low energy region. Conventionally, the ion beam current was less than 10 mA/cm ² in the low energy region.

An object of the present invention is to provide an apparatus capable of irradiating a large current ion beam in a low energy region.

(Means for Solving the Problems) The above purpose is to provide a plasma region, an accelerating cathode, an electron beam accelerating region, an accelerating anode, an ion generation region, and a target cathode in this order, and to provide a negative electrode to the accelerating anode. means capable of applying a potential to the target cathode and controlling the value of this potential, and an ion irradiation object that attracts positive or negative ions generated in the ion generation region and is irradiated with the ions. This is achieved by an electron beam-excited ion irradiation apparatus that is equipped with an ion irradiation target installation section in which an ion irradiation object installation section is installed.

(Operation) Electrons in the plasma region are extracted by the accelerating anode and rush into the ion generation region. The incoming electrons collide with the inert gas (or metal vapor) in the ion generation region to generate ions, but due to the reverse flow of these ions, a negative potential barrier is formed near the exit of the accelerating cathode. is prevented. Therefore, a high current electron beam proportional to the plasma density in the plasma region can flow into the ion generation region. In the ion generation region, ions are generated in a number proportional to the current value of the incoming electron beam.
As shown in the figure, a potential well is formed by the accelerating cathode, accelerating anode, and target cathode, and electrons reciprocate within this potential well to efficiently generate plasma. Ions in the generated plasma are extracted by the ion irradiation object installation section and irradiate the ion irradiation object. The energy (velocity) of the ions is controlled by the potential of the ion irradiation target installation part. Plasma can be efficiently generated by providing a multipole magnetic field, a mirror magnetic field, or a potential well in the ion generation region to prevent lateral diffusion of charged particles.

Note that etching can be performed by filling the apparatus of the present invention with an inert gas such as argon or a reactive etching gas such as _CF4 , and etching can be performed by filling the apparatus with a film-forming gas such as _SiF4 . membrane can be done.

(Embodiment) FIG. 1 is a schematic diagram of an embodiment of the electron beam excited ion irradiation apparatus of the present invention. A cathode 1, an accelerating cathode 2 which also functions as an anode, an accelerating anode 3, and a sample installation section 4 which is an ion irradiation object installation section which also functions as a target cathode are provided in this order. The space between the cathode 1 and the acceleration cathode 2 becomes a plasma region 5 filled with plasma, and the space between the acceleration cathode 2 and the acceleration anode 3 becomes an electron beam acceleration region 6 that accelerates electrons extracted from the plasma region 5.
An ion generation region 7 is located between the accelerating anode 3 and the sample installation section 4 . A voltage is applied between the cathode 1 and the accelerating cathode 2 by a discharge power source 8, so that a plasma-generating discharge is generated in the plasma region 5. An accelerating power source 9 that generates a potential difference between the accelerating cathode 2 and the accelerating anode 3 extracts electrons from the plasma region 5 and generates an ion generating region 7.
The ions inside are pulled out to the accelerating cathode 2. The acceleration cathode 2 is directly grounded, and the sample installation section 4
is grounded via a voltage-variable ion energy control power source 10, and the sample installation section 4 is configured to be able to control the voltage applied to the accelerating anode 3. Usually inert gas such as argon gas is inlet 1
It flows into the device from 1a and 11b, and the discharge port 1
It is discharged from 2a, 12b, and 12c. Further, in this embodiment, a magnetic field is applied along the traveling direction of electrons and ions, thereby preventing the electron flow and ion flow from spreading in the lateral direction. The partitions 13a and 13b provided in the plasma region 5 are for creating a gas pressure difference.

The ion irradiation device configured in this manner operates as follows. Plasma is generated in the plasma region 5 by the discharge between the cathode 1 and the accelerating cathode 2 . The electrons that make up this plasma are at the accelerated anode 3
The particles are attracted by the ions, enter the ion generation region 7, and generate ions. Some of these ions are attracted to the acceleration cathode 2 and pull down a negative potential barrier formed near the opening of the acceleration cathode 2. Therefore, an electron flow with a current value proportional to the plasma density in the plasma region flows into the ion generation region 7. In the ion generation region 7, ions are generated that are proportional to the current value (number) of the electrons that have flowed in. The energy of these ions is controlled by the potential of the sample placement section 4, and the sample 18 on the sample placement section 4 is irradiated with the ions. In this embodiment described above, the gas filled in the apparatus is argon gas, and the accelerating cathode 2 and accelerating anode 3
The voltage between sample installation part 4 and ground is -34V, and the degree of vacuum in plasma region 5 is 110V.
0.7 Torr, vacuum degree of electron beam acceleration region 6 is 1.1×
10 ^-4 Torr, vacuum degree of ion generation region 7 is 2.0×
10 ^-3 Torr, the relationship between the ion current and the initial discharge current (approximately equal to the electron beam current) when the distance between the accelerating anode 3 and the sample installation part 4 is 10 cm is expressed as
As shown in the figure. From this graph, it can be seen that according to the present invention, an ion current that is about two orders of magnitude larger than that of the conventional technique can be obtained. Note that the ionic current is controlled by the resistor 14.
was measured by measuring the voltage across it with a voltmeter 16.

Note that an AC (high frequency) power source can be used as the ion energy control power source 10,
The potential of the sample 18 can be changed by controlling the voltage of this AC power supply.

Further, the voltage between the sample installation section 4, which is the conductive ion irradiation object installation section, and the accelerating anode 3 does not control the voltage of the ion energy control power source 10, but rather the voltage between the accelerating cathode 2 and the accelerating anode 3. It can also be changed by controlling the voltage value of the acceleration power supply 9 between the two. Examples of this case are shown in Figures 3 and 4.
As shown in the figure. In both the examples shown in FIGS. 3 and 4, the ion energy control power source 1
0 is not provided, the sample installation section 4 is directly grounded, and the ion energy is controlled by controlling the voltage of the acceleration power source 9. In the embodiment shown in FIG. 4, the cathode, not the accelerating cathode 2, is grounded, so that even if the voltage of the discharge power source is changed, the voltage between the sample setting part 4 and the accelerating anode 3 will change. be able to.

FIG. 5 shows an example of an ion source that emits ions based on the same principle as the present invention, although this is not the present invention. In this example, the sample installation section 4' does not need to be electrically conductive. A grid electrode 17 is arranged between the accelerating anode 3 and the sample setting section 4'.
This grid electrode 17 is connected to the cathode of the ion energy control power source 10. The rest of the structure is exactly the same as the embodiment shown in FIG. In this embodiment, the ion energy is controlled by changing the potential of the grid electrode 17 to control the number and energy of electrons directed toward the installation part 4', and thereby by changing the potential of the sample 18. be exposed. Furthermore, by controlling the potential of the grid electrode 17 and the potential of the sample installation section 4', low energy ions can be made to enter the sample at a large current density. As an example of this case, it is also possible to maintain the grid electrode 17 at a floating potential (always more negative than the plasma potential of the ion generation region) and control the ion energy by the potential of the sample installation section 4'.

Also in this embodiment, the ion energy control power source 10 may be omitted and the grid electrode 17 may be directly grounded, similar to the embodiment shown in FIG.

It has been confirmed that uniform ion beam irradiation with a diameter of approximately 15 mm can be performed even when a uniform magnetic field is used as the electron beam guide magnetic field, as in the embodiments shown in FIGS. 1 and 5. , Figure 6a,
As shown in FIG. 6b, by arranging permanent magnets 20 around the outer periphery of the ion generation region 7 to form a multipole magnetic field, the ion beam can be further expanded and uniform irradiation of a large area sample becomes possible. .

In the present invention, various modified embodiments can be considered, but the accelerating anode may be divided into two and separated into a first ion generation region and a second ion generation region, or as shown in FIG. As shown, the ion generation region 7 and the sample chamber 23 may be separated by two target cathodes 21 and 22 provided with an insulator 24 in between. In this way, the inside of the sample chamber 23 can be brought into a high vacuum state. From the ion generation region 7 to the sample chamber 23
The inflow of ions into the sample is performed by the sample setting section 4. An ion source plasma region may be provided between the ion generation region and the target cathode, and the sample may be irradiated with ions generated in this ion source plasma region. In this case, as shown in FIGS. 6a and 6b, a multipole magnetic field is applied to the ion generation region, the ion source plasma region, and the sample chamber, and the ion beam acceleration electrode is a mesh electrode or an electrode having a large number of openings. By doing so, the ion beam diameter can be expanded.

FIG. 8 shows an embodiment in which the present invention is used as a sputtering device. The ions generated in the ion generation region 7 collide with the target 25 on the installation part 4'' which also serves as a target cathode.The target material scattered by the ion collision is deposited on the substrate 26. When a potential is applied so as to cause the target atoms to be scattered in a gaseous state by ion collisions and then ionized by electron beam irradiation, the target atoms are transferred to the substrate 26.
It can also be attracted to.

FIG. 9 shows another embodiment in which the present invention is used as a sputtering device. When the target 25 is irradiated with an ion beam, a target material gas is generated, and when this gas is further irradiated with an electron beam, ions are generated. These target material gas ions are transferred to the acceleration cathode 2.
The negative ions are drawn toward the plasma region 5, and a film is formed on the substrate 26 by capturing the negative ions. In this embodiment, it is preferable to set the aperture of the accelerating anode 3 rather large and to set a magnetic field near the target so that the ion beam is concentrated on the target 25. Furthermore, the accelerating cathode 2 itself may be used as the stand on which the substrate 26 is placed.

FIG. 10 is a schematic diagram showing an embodiment capable of irradiating negative ions. The Larmor radius differs greatly between ions and electrons. Therefore, when an external magnetic field is applied, only ions exist in a space that is farther away from the plasma in a direction that crosses the lines of magnetic force by more than the Larmor radius of the electrons. This embodiment is based on this. That is, the sample installation section 4 is provided apart from the electron path section 28. When the sample installation part 4 has a negative potential with respect to the plasma potential (approximately the same potential as the accelerating anode 3), positive ions are extracted. Conversely, when the potential is positive with respect to the plasma potential, negative ions are extracted.

In each of the above-mentioned embodiments, it is also extremely effective to arrange a plasma potential distribution shaping electrode between the cathode and the accelerating cathode in accordance with Japanese Patent Application No. 59-276738.

(Effects of the Invention) The ion irradiation apparatus of the present invention can control the current (number of ions) of ions to be irradiated by controlling the plasma density in the plasma region. In addition, independently of this, the energy of ions can be controlled by controlling the voltage between the sample installation stage or grid electrode and the accelerating anode. Therefore, a large number of low-energy ions can be irradiated onto a sample, and the sample can be efficiently processed without causing crystal defects in the semiconductor substrate or the like.

Further, in the present invention, since plasma is generated by flowing an electron beam into the ion generation region from the outside, the stability of the plasma against changes in the composition of the filling gas and the incorporation of impurities is high.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the present invention,
2 is a graph showing the relationship between the ion current and the initial discharge current in the embodiment of FIG. 1, FIGS. 3 and 4 are schematic diagrams of another embodiment of the present invention, and FIG.
The figure is a schematic diagram of an embodiment using grid electrodes, Figures 6a and 6b are side views and cross-sectional views showing a multi-port magnetic field for electron beam guide, and Figure 7 is a diagram showing the target cathode and ion irradiation target. FIG. 8 is a schematic diagram showing an embodiment in which the body installation part is separated from the body installation part; FIG. 8 is a schematic diagram showing another embodiment in which the present invention is used as a sputtering device; FIG.
It is a schematic diagram showing another example when the present invention is used as a sputtering device. FIG. 10 is a schematic diagram showing an embodiment capable of emitting negative ions;
FIG. 11 is a diagram illustrating the operation of the present invention. DESCRIPTION OF SYMBOLS 1... Cathode, 2... Accelerating cathode, 3... Accelerating anode, 4... Conductive sample setting part, 4'... Sample setting part, 5... Plasma region, 6... Electron beam acceleration region, 7... ...Ion generation region, 8...Discharge power source, 9...Acceleration power source, 10...Ion energy control power source, 17...Grid electrode, 21, 22
...Target cathode.

Claims (1)

[Claims] 1. A plasma region, an acceleration cathode, an electron beam acceleration region, an acceleration anode, an ion generation region, and a target cathode are provided in this order, and a negative potential with respect to the acceleration anode is applied to the target cathode. ion irradiation object installation, in which an ion irradiation object is installed, in which means capable of applying and controlling this potential, and an ion irradiation object that attracts positive ions or negative ions generated in the ion generation region and are irradiated with the ions; An electron beam excited ion irradiation device comprising: 2. The electron beam excited ion irradiation device according to claim 1, wherein the target cathode also serves as the ion irradiation object installation section.