JPH11154485A - Mass spectrograph and ion implantation device equipped with it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately conduct ion beam mass spectrometry by suppressing the arrival of secondary ions generated in a mass separator and left the mass separator at an ion detector. SOLUTION: In this mass spectrometer 20a, a reflection electrode 46 equipped with an ion passing through hole 48 and having a positive voltage V3 applied from a DC power source 50 is provided between a mass separator 26 and an ion detector 32. The level of the positive voltage V3 is set to be smaller than a voltage V1 obtained by converting the kinetic energy of an incident ion beam 6 to a mass separator 26 into an acceleration voltage, and is set to be larger than a voltage V2 obtained by converting the kinetic energy of secondary ions 44 generated in the mass separator 26 into an accelerating voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer for performing mass spectrometry of an ion beam to measure the composition and the like of the ion beam, and a non-mass separation type ion implantation apparatus including the same.

[0002]

2. Description of the Related Art FIG. 4 shows an example of an ion implantation apparatus provided with such a mass spectrometer. A similar ion implantation apparatus is disclosed in, for example, JP-A-6-36737.

[0003] This ion implantation apparatus is a so-called non-mass separation type apparatus, and is basically drawn from an ion source 2 mounted on an upper part thereof in a processing chamber 8 which is evacuated by an evacuation apparatus 10. Ion beam 6
Irradiation is performed on an object (for example, a semiconductor wafer or another substrate) 12 without mass separation (that is, selection of only a specific ion species), and ion implantation is performed on the object 12. . Reference numeral 4 denotes an electrode for extracting an ion beam from the ion source 2, which may be a single electrode as shown in the illustrated example or a plurality of electrodes.

In this ion implantation apparatus, the ion beam 6 extracted from the ion source 2 is directly irradiated onto the object 12 without mass separation, so that the desired ion implantation amount (dose amount) into the object 12 is obtained. In order to measure the composition, it is necessary to know the composition of the ion beam 6 extracted from the ion source 2. For this purpose, a portion of the processing chamber 8 facing the ion source 2 is communicated through the opening 14. , A mass spectrometer 20, and a part of the ion beam 6 extracted from the ion source 2 is made incident on the mass spectrometer 20.

[0005] As shown in FIG. 5, the conventional mass spectrometer 20 has a mass separator 26 for receiving the ion beam 6 and separating the mass of the ion beam 6, and a mass separator 26 downstream of the mass separator 26. An ion detector 32 provided to receive the ions extracted from the mass separator 26. Further, the mass spectrometer 20 is provided with the mass separator 2.
The apparatus includes a cylindrical vacuum vessel 24 that accommodates a part or all of 6 and an ion detector 32, and a mask 22 that is provided at an entrance of the vacuum vessel 24 and restricts the incidence of the ion beam 6.

In this example, the mass separator 26 separates the mass of the ion beam 6 by using an orthogonal electromagnetic field (E × B), and an electric field (static) is applied in a direction orthogonal to the incident direction of the ion beam 6. A pair of electrodes 28 for generating an electric field (E) E and a pair of magnets 30 for generating a magnetic field B orthogonal to the electric field E (the magnets on the front side of the paper are not shown in the drawing).
This mass separator 26 is also called an ExB separator or Wien filter. The electrode 28 is provided in the vacuum vessel 24. The magnet 30 may be provided inside or outside the vacuum vessel 24.

In this example, the ion detector 32 includes a Faraday cup 38 for receiving ions derived from the mass separator 26 and measuring them as a current.
Further, in this example, in order to perform ion current measurement more accurately, a secondary electron that is provided immediately upstream of the Faraday cup 38 and generated when ions enter the Faraday cup 38 is transmitted from the Faraday cup 38. A suppressor electrode for suppressing leakage and a suppressor electrode
6 and a mask 34 which is provided immediately upstream of the mask 6 and restricts passing ions. Faraday cup 3
An ammeter 40 is connected to 8 so that an ion current flowing through the Faraday cup 38 can be measured. The suppressor electrode 36 has a suppressor power supply 42
A negative suppression voltage is applied.

An example of the operation of the mass spectrometer 20 will be described. The ions constituting the ion beam 6 incident on the mass separator 26 are directed in a certain direction by a magnetic field B (in this example, rightward in FIG. Direction), and an electric field E causes it to bend in the opposite direction (to the left in the figure). Therefore, by applying an appropriate magnetic field B and electric field E according to the mass of the ions, the magnitude of the force received by the ions from both becomes equal,
Since the ions travel straight through the mass separator 26 and enter the ion detector 32 (more specifically, the Faraday cup 38), the intensity (amount) of the ions can be measured as an ion current.

The condition under which ions travel straight in the mass separator 26 is expressed by the following equation, as is well known. Here, v is the velocity of the ion, m is the mass of the ion, q is the charge of the ion, V ₁
Is the accelerating voltage of the ions in the ion source 2.

[0010]

[Number 1] v = E / B However mv ^2/2 = qV ₁

Further, by changing the E / B, it is possible to change the type of ions (specifically, the difference of q / m) which goes straight through the mass separator 26 and enters the ion detector 32. . Thereby, mass analysis of the ion beam 6 can be performed. For example, it is possible to obtain a mass spectrum that indicates what mass of ions are included in the ion beam 6 and how much, and thereby the composition and the composition ratio of the ion beam 6 can be measured.

[0012]

The inside of the mass spectrometer 20 including the mass separator 26 is generally not very good in vacuum. This is because the inside of the mass spectrometer 20 is evacuated together with the processing chamber 8 by the above-described evacuation unit 10 and through the mask 22 at the entrance, so that the pressure in the mass spectrometer 20 is reduced. This is because the pressure inside the processing chamber 8 becomes higher by at least the conductance of the mask 22 (that is, the degree of vacuum becomes worse). as a result,
In the mass separator 26, the secondary ions 4 having low energy (for example, about 300 eV to 500 eV) are generated by collision between the incident ion beam 6 and the residual gas and charge conversion.
4 occurs.

Alternatively, besides the above cause, the incident ion beam 6 is bent by the magnetic field B or the electric field E in the mass separator 26 and the
To strike out the ions of the elements constituting the electrode 28 or ionize the gas adhering to the surface of the electrode 28, thereby generating low-energy secondary ions 44.

The secondary ions 4 generated in the mass separator 26
4, when the magnetic field B and the electric field E satisfy appropriate conditions with respect to the mass, drift movement is performed toward the downstream side, exits the mass separator 26, reaches the ion detector 32, and is detected. Will be.

Then, in the ion detector 32,
Since an ion species that does not originally exist in the ion beam 6 is erroneously detected, the mass analysis of the ion beam 6 becomes inaccurate, and the composition and composition ratio of the ion beam 6 measured by the mass spectrometer 20 are reduced. It will be different from the original one.

In this case, for example, in the ion implantation apparatus shown in FIG.
Is measured based on the composition ratio of the ion beam 6 measured in the step (a), and the amount of implantation is controlled so that the implantation amount becomes a desired value. (Overdose) occurs. More specifically, for example, an ion beam 6 having a desired ion composition ratio of 1 (100%) is extracted from the ion source 2 and irradiates the workpiece 12, but the mass spectrometer 20 described above. In order to erroneously detect the secondary ions 44, the mass spectrometer 20
The composition ratio of the desired ions in the ion beam 6 measured by the above is, for example, 0.9 (90%). Then, since the difference is excessively injected into the processing object 12, the injection amount is excessive.

[0017] Therefore, the present invention suppresses secondary ions generated in the mass separator and exiting the mass separator from reaching the ion detector, and enables accurate mass analysis of the ion beam. It is a main object to provide a mass spectrometer that can be used.

[0018]

According to the present invention, there is provided a mass spectrometer provided with a reflection electrode having an ion passage hole and applied with a positive voltage between the mass separator and the ion detector.
Moreover, the magnitude of the positive voltage is smaller than the voltage obtained by converting the kinetic energy of the ion beam incident on the mass separator into an acceleration voltage, and the kinetic energy of the secondary ions generated in the mass separator is reduced by the acceleration voltage. It is characterized by being larger than the voltage converted to.

According to the above configuration, the secondary ions generated in the mass separator and exiting the mass separator have the magnitude of the positive voltage applied to the reflection electrode arranged on the downstream side of the secondary ions. Since the kinetic energy of the next ion is larger than the voltage obtained by converting the kinetic energy to the acceleration voltage, the ion is repelled by the reflection electrode and does not reach the ion detector.

On the other hand, the original (desired) ions mass-separated from the ion beam incident thereon in the mass separator have the magnitude of the positive voltage applied to the reflecting electrode, That is, since the kinetic energy of the ion beam is smaller than a voltage obtained by converting the kinetic energy into an acceleration voltage, the kinetic energy passes through the ion passage hole of the reflection electrode and reaches the ion detector, where it is detected.

As a result, secondary ions generated in the mass separator and exiting the mass separator are prevented from reaching the ion detector, and the mass analysis of the ion beam can be performed accurately.

[0022]

FIG. 1 is a sectional view showing an example of a mass spectrometer according to the present invention. Parts that are the same as or correspond to those in the conventional example of FIG. 5 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

The mass spectrometer 20a of this embodiment has an ion passage hole 48 in the vacuum vessel 24 between the mass separator 26 and the ion detector 32, and is grounded from a DC power supply 50. and the reflective electrode 46 provided a positive voltage V ₃ is applied to the potential.

The ion passage hole 48 of the reflection electrode 46 is provided coaxially with the mass separator 26 and the ion detector 32, so that desired ions separated by mass at the mass separator 26 can pass straight. I can do it.

The ion passage hole 48 of the reflection electrode 46 is
For example, a single hole as shown in FIG. 2 may be used, or a single hole as shown in FIG. 3 may be used. Alternatively, the reflection electrode 46 may be formed in a mesh shape having many small ion passage holes.

The magnitude of the positive voltage V ₃ applied to the reflection electrode 46 is smaller than the voltage V _{1 obtained} by converting the kinetic energy of the ion beam 6 incident on the mass separator 26 into its acceleration voltage, and It is greater than the voltage V ₂ obtained by converting the low energy of the kinetic energy of the secondary ions 44 described above occurring within 26 to its acceleration voltage. That is, the relation of the equation 2 is satisfied.

[0027]

[Equation 2] V ₂ <V ₃ <V ₁

For example, when the kinetic energy of the ion beam 6 incident on the mass separator 26 is XeV, the voltage V _{1 obtained} by converting the kinetic energy into an acceleration voltage is X. To give a more specific example, the kinetic energy of the ion beam 6 drawn from the ion source 2 described above is, for example, about 5KeV～50keV, voltages V ₁ obtained by converting this 5kV~50
kV. Similarly, if the kinetic energy of the secondary ions 44 generated in the mass separator 26 is YeV, the voltage V ₂ converted to the acceleration voltage is Y. To give a more specific example, the energy of the secondary ions 44 is about 300eV~500eV As described above, the voltage V ₂ obtained by converting this are 300V～500V. Therefore, in the mass spectrometer 20a of this embodiment, the relationship of Expression 3 is satisfied.

[0029]

(3) (300 V to 500 V) <V ₃ <(5 kV to 50 kV)

In this case, it is preferable that the voltage V ₃ is sufficiently smaller than the voltage V ₁ , so that the original ions mass-separated from the ion beam 6 in the mass separator 26 are reflected by the reflection electrode 46. Since the voltage V ₃ has almost no effect on passing through the ion detector 32,
Has almost no adverse effect on the detection of the original ions at For example, under the condition of Equation ₃ , the voltage V3 is 1 kV to ₃ k.
It is preferably about V.

In the mass spectrometer 20a, the secondary ions 44 generated in the mass separator 26 and leaving the mass separator 26 are supplied to a positive electrode 46 applied to a reflection electrode 46 disposed downstream thereof. The magnitude of V ₃ depends on the secondary ion 44
Since the kinetic energy is greater than the voltage V ₂ in terms of the acceleration voltage, reflected by the electrode 46 (the positive voltage V ₃ which is more specifically applied to the reflective electrode 46) bounced by (is reflected), It does not reach the ion detector 32.

On the other hand, the original (desired) ions that have been mass-separated from the ion beam 6 incident thereon in the mass separator 26 are different in the magnitude of the positive voltage V ₃ applied to the reflection electrode 46 from the mass separation. The kinetic energy of the ions, ie, the kinetic energy of the ion beam 6 is smaller than the voltage V _{1 obtained} by converting the kinetic energy into an acceleration voltage.
(More specifically, by the positive voltage V ₃ applied to the reflective electrode 46), and passes through the ion passage hole 48 of the reflective electrode 46 without being repelled.
And is detected normally.

As a result, the secondary ions 44 generated in the mass separator 26 and exiting the mass separator 26 are prevented from reaching the ion detector 32, and the mass analysis of the ion beam 6 can be accurately performed. It can be carried out.

In particular, in the non-mass separation type ion implantation apparatus as shown in FIG. 4, as described above, it is important to accurately measure the composition and the composition ratio of the ion beam 6 applied to the object 12 to be processed. Therefore, if the mass spectrometer 20a is used instead of the conventional mass spectrometer 20 for such an ion implanter (see FIG. 4), accurate measurement of the composition and the composition ratio of the ion beam 6 becomes possible. In other words, the accuracy of controlling the injection amount (dose amount) with respect to the processing target 12 can be improved.

The reflecting electrode 46 has a function of repelling low-energy secondary ions generated between the mass separator 26 and the reflecting electrode 46 in the same manner as the secondary ions 44. When it is also expected that the next ion is repelled, the reflection electrode 46 should be set within a range in which the positive voltage V ₃ does not adversely affect the detection of ions by the ion detector 32 (a mask grounded as in the example of FIG. 1). 34 has no adverse effect even if approached.
It is preferable to dispose them closer to the camera.

Further, the mass separator 26 is provided in the above-described example of the E × B
The type is preferable because it can be a linear type apparatus, but other types may be used. For example, a magnetic field deflection type in which the ion beam 6 is deflected only by the magnetic field to separate the mass may be used.

The ion detector 32 is also the mask 3 of the above example.
4. The one composed of the suppressor electrode 36 and the Faraday cup 38 is preferable because of its high detection accuracy, but may be other than that. For example, it may be composed only of the Faraday cup 38 or may be composed of a simple flat plate.

[0038]

Since the present invention is configured as described above, it has the following effects.

According to the mass spectrometer of the first aspect, secondary ions generated in the mass separator and exiting the mass separator are repelled by the reflection electrode, and the original ions separated by the mass separator in the mass separator are Since the secondary ions can pass through the reflective electrode, the secondary ions can be prevented from reaching the ion detector, and the mass analysis of the ion beam can be performed accurately.

According to the ion implantation apparatus of the second aspect,
Since the mass spectrometer according to claim 1 is provided, it is possible to accurately perform mass analysis of an ion beam that is extracted from an ion source and irradiates an object to be processed. In addition, accurate measurement of the composition ratio can be performed, and the accuracy of controlling the injection amount with respect to the object to be processed can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a mass spectrometer according to the present invention.

FIG. 2 is a front view showing an example of a reflective electrode in FIG.

FIG. 3 is a front view showing another example of the reflective electrode in FIG.

FIG. 4 is a schematic diagram illustrating an example of an ion implantation apparatus including a mass spectrometer.

FIG. 5 is a cross-sectional view illustrating an example of a conventional mass spectrometer.

[Explanation of symbols]

 2 Ion source 6 Ion beam 8 Processing chamber 12 Object to be processed 20a Mass spectrometer 26 Mass separator 32 Ion detector 44 Secondary ion 46 Reflecting electrode 48 Ion passage hole 50 DC power supply

Claims (2)

[Claims] 1. A mass separator for mass-separating an ion beam using at least one of a magnetic field and an electric field, and ions provided downstream of the mass separator for receiving ions derived from the mass separator In a mass spectrometer that includes a detector and performs mass analysis of an ion beam,
A reflection electrode having an ion passage hole and applied with a positive voltage is provided between the mass separator and the ion detector, and the magnitude of the positive voltage is controlled by an ion beam incident on the mass separator. A mass spectrometer characterized in that the kinetic energy of the secondary ions generated in the mass separator is smaller than a voltage obtained by converting the kinetic energy of the secondary ions generated in the mass separator into an acceleration voltage. 2. An apparatus for irradiating an object to be processed with an ion beam extracted from an ion source without mass separation in a processing chamber evacuated to a vacuum and performing ion implantation on the object to be processed. 2. An ion implantation apparatus, wherein the mass spectrometer according to claim 1 is provided in a portion facing the ion source, and a part of the ion beam extracted from the ion source is made to enter the mass spectrometer. .