JPH04338639A - Ion generator - Google Patents

Abstract

PURPOSE:To provide such an ion generator as the ion amount can be controlled without being attended by contamination, as to an ion generator to be used in a manufacturing process, etc. of a semiconductor device. CONSTITUTION:This device has a plasma generators 3, 8 which generate plasma 4 in a plasma generating chamber 10, a magnetic field generator 1B located outside the plasma generating chamber, a magnetic flux density controller 2B which controls a magnetic flux density of the magnetic field generator, and an ion take-out port 5 installed on the plasma generating chamber at the magnetic field generator side. The device is so constructed as the ion amount to be taken out from the plasma may be controlled by controlling the magnetic flux density of the ion take-out port. The lower limit of the variation range of the magnetic flux density of the ion take-out port is such a value as stipulated by the formula B=q/2pifme (B: magnetic flux density, q: quantum of electrocity, pi: ratio of the circumference of a circle to its diameter, f: frequency of electromagnetic wave for generating plasma, me: weight of electron).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion generating apparatus used in semiconductor device manufacturing processes and the like. In recent years, in the field of etching in semiconductor wafer processes, etc.
With advances in microfabrication technology, it has become necessary to control the amount of ions required for processing.

The present invention can be used as a device that meets this need.

0003

2. Description of the Related Art FIG. 3 is a block diagram of a conventional device. In the figure, 1 is a magnetic field generation means and a coil, 2 is a magnetic flux density control means and is a DC power source, 3 is an energy supply means for plasma generation and is a μ-wave generator, 4 is plasma, and 6 is a sample stage on which the object to be processed is placed. , 7 is an ion amount measuring device (consisting of a probe 7A, an ammeter 7B, and a DC power supply 7C),
8 is a gas supply means for plasma generation, 9 is an exhaust device, 10 is a plasma generation chamber, 11 is a processing chamber for ion irradiation, and 12 is an ion extraction means (from metal mesh electrodes 12A, 12B and a DC power source 12C). ).

FIG. 4 is a diagram showing the relationship between the amount of ions and the voltage applied to the electrode 12B. From the figure, electrode 12B
It can be seen that the amount of ions can be controlled by changing the voltage applied to.

[0005] The conventional ion generator uses a mesh-like high melting point metal for the electrodes 12A and 12B for extracting ions. The amount of ions was controlled by changing the voltage applied to this electrode. However, inserting such foreign matter into the processing chamber 11 has the disadvantage that the object to be processed is contaminated with various elements contained in the foreign matter.

[0006]

[Problems to be Solved by the Invention] Therefore, there has been a strong demand for controlling the amount of ions without inserting foreign matter into the processing chamber and into the ion irradiation path.

It is an object of the present invention to provide an apparatus capable of controlling the amount of ions for treatment without contamination.

[0008]

[Means for solving the problem] The solution to the above problem is 1)
Plasma generation means (3), (8) for generating plasma (4) in the plasma generation chamber (10), and magnetic field generation means (1B) arranged outside the plasma generation chamber (10).
, a magnetic flux density control means (2B) for controlling the magnetic flux density of the magnetic field generation means (1B), and an ion extraction port (5) provided in the plasma generation chamber (10) on the side of the magnetic field generation means (1B). and the ion extraction port (5).
an ion generator capable of controlling the amount of ions extracted from the plasma (4) by controlling the magnetic flux density of the plasma (4), or 2) plasma generation means (3), (8) for generating plasma (4) in the plasma generation chamber (10). ), magnetic field generating means (1A), (1B) arranged above and below the outside of the plasma generation chamber (10) to confine the plasma, and controlling the magnetic flux density of the magnetic field generating means (1A), (1B). and an ion extraction port (5) provided in the plasma generation chamber (10) on the side of one of the magnetic field generation means (1B), The plasma (
4) An ion generator that can control the amount of ions extracted from the ion generator, or 3) The lower limit of the range of change in the magnetic flux density of the ion extraction port (5) is expressed by the following formula B=q/2πfme, where B: magnetic flux density [T ] q: elementary charge (1.6×10-19 [C]) π: pi f: frequency of electromagnetic waves to generate plasma [Hz
]me: Electron mass (9.1×10-31 [kg]
). This is achieved by the ion generating device described in 1) or 2) above, which has a value defined by .

[0009]

[Operation] FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 1A and 1B are magnetic field generating means with coils, 2A and 2B.
3 is a magnetic flux density control means, which is a DC power supply, and 3 is an energy supply means for generating plasma at 2.45 GHz.
4 is a plasma, 5 is an ion extraction port, 5A is the outer periphery of the ion extraction port, 6 is a sample stage on which the object to be processed is placed, and 7 is an ion amount measuring device using the Langmuir probe method. It consists of an ammeter 7B and a DC power supply 7C, 8 is a gas supply means for generating plasma, 9 is an exhaust device, 10 is a plasma generation chamber,
11 is a processing chamber in which ion irradiation is performed.

Gas supply means 8 is provided in the plasma generation chamber 10.
A reactant gas is introduced from the reactor, and a microwave is supplied from a microwave generator to generate a plasma of the reactant gas. Inside the plasma generation chamber 10, a mirror magnetic field is formed by the upper and lower coils 1A and 1B to confine the plasma.

The probe 7A is a metal plate whose back surface is covered with an insulator, and the ammeter 7B measures the amount of current corresponding to the amount of ions reaching the sample stage 6. Further, the DC power supply 7C applies a negative voltage of about -50 V to the probe 7A.

FIG. 2 is an explanatory diagram of the operation of the present invention. The figure is
The relationship between the amount of ions and the magnetic flux density at the outer peripheral portion 5A of the ion extraction port is shown using the apparatus of the present invention.

In other words, when the magnetic flux density generated by the coil 1A is kept constant at 1.650 kG (1G=10-4T) and the magnetic flux density generated by the coil 1B is varied, the amount of ions reaching the sample stage 6 is shown. Ta. Here, the amount of ions is the amount of current indicated by the ammeter 7B.

From the figure, it can be seen that when the magnetic flux density is greater than 875 G, the amount of ions can be accurately controlled. The reason why the amount of ions is extremely small when the magnetic flux density of the coil 1B is smaller than 875 G is that the plasma generation mechanism is different from that when the magnetic flux density is larger than 875 G.

[0015] This means that the coils 1A and 1B are 875
This is because when the magnetic flux density of the coil 1B is smaller than 875 G, this coil does not provide a magnetic field for plasma generation, although when the magnetic flux density of the coil 1B is smaller than 875 G, both coils provide a magnetic field for plasma generation.

Next, the boundary magnetic flux density is 875 G
Derive. First, in the ECR (electron cyclotron resonance) phenomenon, when plasma exists in a magnetic field, the electromagnetic waves injected to maintain the plasma have a frequency that efficiently generates plasma, and that frequency is a function of the magnetic flux density. It is related by the following formula.

B=q/2πfme where, B: Magnetic flux density [T] q: Elementary charge (1.6×10-19 [C]) π: Pi ratio f: Electromagnetic wave for generating plasma Frequency [Hz
]me: Electron mass (9.1×10-31 [kg]
) Substituting f=2.45 GHz into this formula, B
=875 G is obtained.

From the above, when the magnetic flux density of the coil 1B is greater than 875 G, the amount of ions can be accurately controlled.

[0019]

EXAMPLE Using the apparatus shown in FIG. 1, the ion amount measuring device was removed, and a 4-inch diameter silicon wafer whose surface was oxidized to a thickness of 500 Å was placed on the sample stage 6 and etched.

The results are shown in Table 1.

[0021]

[Table 1]

It can be seen that the etching rate of the silicon oxide film can be controlled by controlling the ions. Next, as a comparative example, the apparatus shown in FIG. 1 was used, the ion amount measuring device was removed, and a 4-inch diameter silicon wafer whose surface was oxidized to a thickness of 500 Å was placed on the sample stage 6 and etched.

The results are shown in Table 2.

[0024]

[Table 2]

Here, the ion extraction electrodes 12A, 1
Molybdenum (Mo) was used for 2B, the mesh size was 1 mm, and the distance between the electrodes was 5 mm. Although the etching rate changes by changing the positive voltage applied to the electrode 12B, it can be seen that the range of the amount of ions that can be controlled is narrower than in Table 1 of the example.

Next, contamination in Examples and Comparative Examples will be investigated. The silicon wafer whose surface was oxidized to a thickness of 500 Å was etched to make the oxide film 100 Å thick, a MOS diode was fabricated, and the flat band voltage shift ΔVFB was measured. Table 3 shows the results.

[0027]

[Table 3]

From Table 3, it can be seen that the example has a Δ
It can be seen that VFB is small and contamination is reduced.

[0029]

[Effects of the Invention] An apparatus capable of controlling the amount of ions for treatment without contamination was obtained. Furthermore, according to the present invention, the control range of the ion amount can be made larger than in the conventional example.

As a result, it was possible to contribute to improvements in device reliability and manufacturing yield.

[Brief explanation of the drawing]

[Figure 1] Diagram explaining the principle of the present invention

[Figure 2] Diagram explaining the action of the present invention

[Figure 3] Configuration diagram of a conventional device

[Figure 4] Diagram showing the relationship between the amount of ions and the voltage applied to the electrode 12B

[Explanation of symbols]

1A, 1B Coils 2A, 2B by magnetic field generating means
DC power supply 3 as magnetic flux density control means 2.45 GHz μ wave generator 4 as energy supply means Plasma 5 Ion extraction port 5A Outer periphery of ion extraction port 6 Sample stage 7 on which the object to be processed is placed Probe in the ion amount measuring device 7A and ammeter 7B
and a DC power supply 7C, 8 gas supply means 9 exhaust device, 10 plasma generation chamber 11 processing chamber for ion irradiation.

Claims (3)

[Claims] [Claim 1] Plasma generation means (3), (8) for generating plasma (4) in a plasma generation chamber (10).
, a magnetic field generating means (1B) arranged outside the plasma generation chamber (10), a magnetic flux density control means (2B) for controlling the magnetic flux density of the magnetic field generating means (1B), and a magnetic field generating means ( 1B) side, and the magnetic flux density of the ion extraction port (5) is controlled to generate the plasma (4).
An ion generator characterized by being able to control the amount of ions extracted. [Claim 2] Plasma generation means (3), (8) for generating plasma (4) in the plasma generation chamber (10).
and magnetic field generating means (1A) arranged above and below the outside of the plasma generation chamber (10) to confine the plasma.
1B) and magnetic flux density control means (2A), (2B) for controlling the magnetic flux density of the magnetic field generation means (1A), (1B).
and an ion extraction port (5) provided in the plasma generation chamber (10) on one of the magnetic field generation means (1B) sides.
An ion generation device characterized in that the amount of ions extracted from the plasma (4) can be controlled by controlling the magnetic flux density of the ion extraction port (5). 3. The lower limit of the variation range of the magnetic flux density of the ion extraction port (5) is expressed by the following formula B=q/2πfme, where B: magnetic flux density [T] q: elementary charge (1.6×10 -19 [C]) π: Pi f: Frequency of electromagnetic waves for generating plasma [Hz
]me: Electron mass (9.1×10-31 [kg]
). 3. The ion generating device according to claim 1, wherein the ion generating device has a value defined by .