JPS5851378B2 - Micro Haspattering Ion Gen - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a microwave ion source that generates plasma using microwaves and extracts an ion beam from the plasma, and performs sputtering to obtain an ion beam of a desired type. This is to realize the following.

FIG. 1 is a diagram illustrating a microwave ion source according to the prior art.

In the figure, microwaves emitted from a microwave oscillator 1 pass through a three-dimensional circuit 2 and are supplied to a plasma source chamber 3.

A DC magnetic field is applied to the plasma source chamber by the coil 6, and electron cyclotron resonance occurs between the magnetic field and the microwave supplied through the microwave-plasma coupling element 4, and plasma is generated.

A sample gas is introduced into the ion source chamber 3 through a gas leak valve and piping 7.

An ion beam 10 is extracted from the generated plasma through an extraction electrode system 8.

Note that 5 is a vacuum seal plate made of an insulator.

Conventionally, in order to obtain the desired metal ions with the structure shown in Figure 1, a compound gas containing metal was used as the sample gas, or a mechanism for heating the solid metal sample was built into the plasma source chamber or attached to it. I let them do it.

In this case, the generated metal ions in the plasma collide with the microwave-plasma coupling element 4 and the plasma source chamber wall, sputtering their constituent materials (usually metal), and as a result, a large amount of impurity ions are added to the extracted ions. was mixed in.

The first object of the present invention is to use the desired metal as the constituent material of the microwave-plasma coupling element 4 and the plasma source chamber 3, thereby converting the metal element by sputtering into plasma and producing a high-purity metal ion beam. It's about pulling out.

FIG. 2 is a diagram illustrating the present invention in detail.

In the figure, the microwave-plasma coupling element 4 and the plasma source chamber 3 are electrically insulated by, for example, an insulator 5, and a voltage from a DC power source 11 is applied between them.

With respect to the polarity of the applied voltage shown in FIG. 2, since a negative voltage is applied to the wall of the plasma source chamber, electrons in the plasma cannot reach the wall.

On the other hand, the ions are accelerated by the applied voltage and collide with the wall.

Sputtering starts by increasing the applied voltage to several tens of volts or more.

It is clear that if the polarity of voltage application is reversed to that shown in FIG. 2, sputtering of the microwave-plasma coupling element 4 will occur.

Now, a method for obtaining a high purity metal ion beam will be explained below.

1. First, a plasma is created using a gaseous gas, and the ions in this plasma are used to perform sputtering in the plasma source chamber and the microwave-plasma coupling element.

If the applied voltage and the type of gas are appropriately selected, the sputtering efficiency will be 1 or more.

Here, the sputtering efficiency is the ratio of atoms or ions that are sputtered per one ion collision.

Therefore, after the sputtering efficiency reaches 1 or more, plasma generation can be maintained only with the sputtered metal, and no gas is needed.

As a result, highly pure metal plasma is generated and an ion beam thereof is obtained.

Furthermore, even if the sputtering efficiency is less than 1, if the conventional method is performed using a plasma source chamber made of the target metal material and the present invention is added to this, the amount of metal ion beam extracted can be further increased. is clear.

Next, the second object of the present invention is to use BCA for use in ion implantation! 3. To obtain large current ions such as B++ P by microwave discharge of compound gases such as PCl3, B2H6, and BF3, B+ and P+ ions with larger current are generated by sputtering the B and P elements attached to the inner wall of the plasma source chamber. It's about getting the beam.

Below are the characteristics and effects when the present invention is added to compound gas discharge.
The example will be described in detail.

Conventionally, in order to obtain B (homo) ions as the target ion beam with the structure shown in Figure 1, normally BC
Gases such as l3, BF3, and B2H6 are used.

BCJ! Taking the three gases as an example, these compounds are variously decomposed in the plasma source chamber, and ions and electrons such as B+, Cl+, + + BC72, and BCA are generated to form plasma.

On the other hand, the operating pressure of microwave discharge is 10 Torr.
The generated B+ collides with the inner wall of the plasma source and the microwave-plasma coupling element+ without colliding with other ions or BCl3 molecules.

B that collides with the wall has a high probability of adhering to the surface, so it adheres to the surface.

On the other hand, since the stick-like C1 has a lower adhesion probability than B+, even if it collides with the wall, most of it is returned to the space of the plasma source chamber as a gas.

As a result, the proportion of Cl ions in the plasma source chamber increases, so that out of the ion current 10 drawn out,
The percentage of B+ is small at around 30.

In contrast, if the present invention is used, the B solid attached to the inner wall of the plasma source chamber is returned to the space of the plasma source chamber by sputtering and ionized, thereby increasing the proportion of B+ ion current drawn out. becomes possible.

Examples will be described below.

FIG. 3 is a diagram illustrating an embodiment of the present invention.

In the figure, a coaxial tube is used as the three-dimensional circuit.

An auxiliary coaxial tube 12 having a length of λ/4 and perpendicular to the coaxial tube is provided in the middle of the coaxial tube.

Here, λ is the wavelength of the microwave.

By providing a choke structure shown in FIG. 3 on the end surface of the tube 12, the coaxial outer cylinder and the center conductor are electrically insulated from each other.

On the end face of No. 12, by selecting the centerline length of the groove from A to X to C through λ to be -, point 7A on the end face becomes an apparent short circuit in terms of microwaves.

The center conductor of the coaxial tube is also insulated in a direct current manner using the structure shown in the figure.

In other words, λ, the center line distance of the DE groove is -, and if such a length is taken, it becomes a short circuit in terms of microwaves, and the microwaves are transmitted to the plasma source chamber 3 without loss.

Therefore, by providing these choke structures,
A DC voltage can be applied between the microwave-plasma coupling element 4 and the ion source chamber 3.

FIG. 4 is a diagram showing another embodiment of the present invention.

By providing a choke flange in the middle of the auxiliary coaxial tube, which has a length of - in the figure, the outer and inner cylinders of the coaxial tube are insulated in terms of direct current.

In other words, if the center line distance of only A'X' in the figure is chosen to be - at λ, point K appears to be short-circuited in terms of microwaves.

Also in FIG. 4, it is possible to apply current and voltage between the microwave-plasma coupling element 4 and the ion source chamber 30.

FIG. 5 shows another embodiment of the present invention.

In the figure, a short hand 14 is newly inserted into the plasma source chamber 3, and a DC voltage is applied between this short hand and the plasma source chamber 3.

In this case, the microwave-plasma coupling element 4 and the plasma source chamber 3 are generally short-circuited inside the magnetron 1, so that sputtering occurs simultaneously for 4 and 3.

The above inventions are from BCJ! In addition, the target sample ion beam may be evaporated gas from a solid sample or other compound gases (PCl3.5iC14, AsC).
It is clear that similar effects can be obtained by using microwave discharge (such as #3).

Furthermore, although the present invention has been described here with reference to an ion source, it can also be applied to a plasma source with the extraction electrode removed. In that case, the target sample ions occupy This means that the ratio can be increased.

With the above invention, the sample attached to the surface of the plasma source chamber and the microwave-plasma coupling element is sputtered with ions in the plasma, and the sputtered sample is turned into plasma again, thereby increasing the amount of sample ion beam extracted. However, in practical use, the effect is remarkable.

Further, by making the plasma source chamber and the microwave-plasma coupling element from a sample metal and adding the present invention thereto, a large current, high purity ion beam can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining a microwave ion source according to the prior art, FIG. 2 is a diagram explaining the present invention in detail, FIG. 3 is a diagram explaining an embodiment based on the present invention, and FIG. FIG. 5 is a diagram illustrating another embodiment of the present invention.

Claims (1)

[Claims] 1 A microwave oscillator that generates microwaves, a three-dimensional circuit whose one end is connected to the microwave oscillator for transmitting the microwave, and a three-dimensional circuit installed at the other end of the three-dimensional circuit to convert the introduced gas into plasma. a plasma source chamber having a microwave-plasma coupling element configured to form an electric field by the microwave, an extraction electrode system for extracting an ion beam from the plasma source chamber, the microwave-plasma coupling element and the plasma The plasma source chamber is characterized by comprising an insulating means for DC electrically insulating between the plasma source chamber and a DC voltage source connected between the insulated microwave-plasma coupling element and the plasma source chamber. Microwave sputtering ion source.