JP2001357813A - Method of measuring ion component ratio in ion irradiating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply and accurately find in a short time a ratio of an purposive componental ion contained in an ion beam extracted from an ion source. SOLUTION: In this measuring method, a deflector 24 to receive the ion beam 10 extracted from the ion source 2 and bend it by a magnetic field, and a Faraday cup 30 provided at a position where the ion beam 10 making a straight advance in the deflector 24 is injected are used. When magnetic field strength in the deflector 24 is reduced to zero, an ion current I0 passing through the Faraday cup 30 is measured, and when the magnetic field strength in the deflector 24 is gradually increased, ion currents I1 and I2 on two flat parts where the change of the ion current I passing through the Faraday cup 30 becomes almost zero near the magnetic field strength corresponding to the purposive componental ion are individually measured. Thereby, a ratio of |I1-I2|/I0 is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-mass separation type ion irradiation apparatus which irradiates an object to be processed with an ion beam extracted from an ion source without passing through a mass separator, and is included in the ion beam. The present invention relates to a method for determining the ratio of target component ions (for example, B ₂ H _x ions, PH _x ions, etc.).

[0002]

2. Description of the Related Art FIG. 4 is a schematic view showing an example of a conventional ion irradiation apparatus. This ion irradiation apparatus includes an ion source 2
The object 12 is irradiated with the ion beam 10 extracted from the object 12 without passing through a mass separator (for example, a mass separation electromagnet), and the object 12 is subjected to processes such as ion implantation and surface modification. I have. Such a non-mass separation type apparatus that performs ion implantation on the workpiece 12 is also called a non-mass separation type ion implantation apparatus or an ion doping apparatus. What performs the surface modification of the to-be-processed object 12 is also called an ion shower apparatus.

In this example, the ion source 2 comprises a plasma generator 4 for ionizing the introduced source gas 3 to generate a plasma 6, and an extraction accelerating electrode system for extracting an ion beam 10 from the plasma 6 by the action of an electric field. 8 is provided.

The object to be processed 12 is, for example, a semiconductor substrate, a glass substrate for a liquid crystal display, or the like. In this example, as shown by an arrow D, the object to be processed is put into and taken out of the irradiation area of the ion beam 10 and within the irradiation area. It is scanned back and forth. However, it is not limited to this.

The raw material gas 3 contains, for example, boron (B).
When used as a dopant, B _TwoH₆(Diborane)
Is diluted with hydrogen. Dopa for phosphorus (P)
When using as a_ThreeHydrogen (phosphine)
The diluted one is used.

The ion beam 10 extracted from the ion source 2 contains ions of several component systems (in other words, component groups) regardless of the type of the ion source 2. For example, when the raw material gas 3 obtained by diluting B ₂ H ₆ with hydrogen is used, the ion beam 10 is roughly divided into hydrogen-based (that is, H _x -based, x = 1, 2, 3) ions, boron 1
Ions in the atomic system (ie, BH _x system; x = 0, 1, 2, 3, 4), and boron diatomic system (ie, B ₂ H _x system; x =
0, 1, 2, 3, 4, 5, and 6). Similarly, when the raw material gas 3 obtained by diluting PH ₃ with hydrogen is used, the ion beam 10 is roughly divided into hydrogen-based (that is, H _x -based, x = 1, 2, 3) ions and phosphorus 1-atom-based system. (Ie, PH _x system; x = 0, 1, 2, 3, 4) and phosphorus diatomic system (ie, P ₂ H _x system; x = 0,
1, 2, 3, 4).

[0007] Unlike a normal (ie, mass separation type) ion implantation apparatus in which an ion beam is mass-separated by a mass separator to select only one mass of ion species and perform ion implantation. In a non-mass separation type ion irradiation apparatus, target component ions (for example, B ₂ H _x ions or PH ions) contained in the ion beam 10 are usually used.
_Since the amount of ion irradiation (for example, the amount of ion implantation) to be processed 12 is controlled by the amount of ( _x- type ions), it is necessary to find the ratio (ratio) of the component ions in the ion beam 10. By multiplying this ratio by the beam amount (beam current) of the entire ion beam 10, the amount of target component ions can be easily obtained.

[0008] The above ratio was conventionally determined as follows. That is, as shown in FIG. 4, a curved mass analyzer 14 that receives a part of the ion beam 10 extracted from the ion source 2 and bends it by a magnetic field to perform mass analysis of the ion beam 10, A Faraday cup 20 provided at a position where the ion beam 10 bent at a curvature is incident is used. In this example, in front of the Faraday cup 20, a slit 16 for narrowing the width of the incident ion beam and a suppressor electrode 18 for suppressing escape of secondary electrons emitted from the Faraday cup 20 are provided. The ion current I flowing through the Faraday cup 20 with the incidence of the ion beam 10 is, for example,
It is measured by the current measuring device 22.

The intensity of the magnetic field in the mass analyzer 14 is gradually changed (for example, increased), and the ion current I flowing through the Faraday cup 20 at that time is measured.
The data obtained thereby has a spectral waveform composed of a number of peaks, for example, as shown in FIG. 2A or 3A. This is because the mass and amount of ions incident on the Faraday cup 20 change one after another with the change in the magnetic field intensity.

[0010] Conventionally, quantification has been performed from such peak values. That is, the ratio of the sum of the peaks of the target component ions to the sum of the respective peak values has been determined.
For example, in the case of the example of FIG. 2A, assuming that the main peak values of the ion current I are I _{1 to} I ₁₃ , the ratio of B ₂ H _x -based ions is obtained by the following equation.

[0011]

(I ₇ +... + I ₁₃ ) / (I ₁ +... + I ₁₃ )

[0012]

In the conventional measuring method as described above, a large number of peak values of the ion current I (for example, I ₁
ＩI ₁₃ ) has to be measured, which takes a lot of time and effort, and is not easy.

Moreover, since it is practically difficult to measure the peak values of all sizes, the peak values below a certain value must be neglected, and the measurement accuracy is poor.

Accordingly, the present invention provides a measuring method capable of easily and accurately obtaining the ratio of target component ions contained in an ion beam extracted from an ion source. It is the main purpose.

[0015]

The measuring method according to the present invention comprises:
A deflector that receives an ion beam extracted from the ion source and bends it by a deflection field composed of at least one of a magnetic field and an electric field, and a Faraday cup provided at a position where an ion beam that has traveled straight in the deflector is incident. Is used to measure the ion current I ₀ flowing through the Faraday cup when the intensity of the deflection field in the deflector is zero or almost zero, and in a region where the intensity of the deflection field in the deflector is greater than zero. When gradually changed, the ion current I ₁ at the two flat portions at which the change in the ion current flowing through the Faraday cup becomes almost zero before and after the deflection field intensity corresponding to the target component ions.
And I ₂ are measured, and the ratio of the following equation is obtained.

[0016]

| I ₁ −I ₂ | / I ₀

When the intensity of the deflection field in the deflector is set to zero or almost zero, the ion beam travels straight without being bent in the deflector, and the Faraday cup is provided at the straight traveling position. The ions of all components contained in the ion beam enter the Faraday cup. The total amount is measured as the ion current I ₀ .

On the other hand, when the intensity of the deflecting field in the deflector is gradually changed in a region larger than zero, for example, when the intensity is gradually increased from zero, ions having a light mass in the ions contained in the ion beam The ion current flowing through the Faraday cup decreases stepwise while passing through the flat portion, since the Faraday cup is largely bent in order from the Faraday cup. This flat portion is a portion where the change in the ion current becomes almost zero with respect to the change in the deflection field intensity, and this portion represents a portion where the main component ions do not exist, that is, a partition between the component ions. I have.

Therefore, one (for example, I ₁ ) of the ion currents I ₁ and I ₂ at the two flat portions before and after the target component ion is the ion current containing the target component ion, The other (for example, I ₂ ) is an ion current not containing it. Therefore, the difference | I ₁ −
I ₂ | represents the amount of target component ions.
Therefore, the ratio of the above equation (2) represents the ratio of target component ions contained in the ion beam extracted from the ion source.

As described above, according to the measuring method of the present invention,
It is not necessary to measure a large number of peak values of the ion current unlike the conventional measurement method, and the three ion currents I ₀ and I ₁ are not required.
Since I and I ₂ need only be measured, the ratio of target component ions contained in the ion beam can be easily and quickly obtained.

Further, in the measurement method of the present invention, unlike the conventional measurement method, the measurement is not performed while ignoring ions having a small current value, but the ion current I ₀ is determined by the amount of ions of all components. And the difference | I ₁ −I ₂ | of the ion current accurately represents the amount of the target component ions, so that the ratio of the target component ions can be accurately determined. it can.

[0022]

FIG. 1 is a schematic view showing an example of an ion irradiation apparatus used for carrying out a measuring method according to the present invention. Parts that are the same as or correspond to those of the conventional apparatus shown in FIG. 4 are denoted by the same reference numerals, and differences from those will be mainly described below.

In this embodiment, the conventional mass analyzer 14 is used.
As an alternative to the above, there is provided a deflector 24 which receives a part of the ion beam 10 extracted from the ion source 2 and bends it by a magnetic field. When the magnetic field in the deflector 24 is set to zero or almost zero, as shown by a solid line in FIG. 1, the ion beam 10 goes straight in the deflector 24, and when the magnetic field is strengthened, as shown by a dashed line, The ion beam 10 is bent in the deflector 24, and if the magnetic field is further strengthened, the ion beam 10 is bent more in the deflector 24 as shown by a two-dot chain line. Alternatively, if the magnetic field strength is the same, the lighter ions contained in the ion beam 10 are bent more greatly as shown by the two-dot chain line.

Although the deflector 28 uses a magnetic field as a deflection field for bending the ion beam 10 in this example,
An electric field may be used, or a magnetic field and an electric field may be used in combination.

Further, in this embodiment, as an alternative to the conventional Faraday cup 20, a Faraday cup 30 is provided at a position where the ion beam 10 which has traveled straight in the deflector 24 is incident. In front of the Faraday cup 30, as in this example, a mask 26 for shaping the incident ion beam and a negative voltage for suppressing escape of secondary electrons emitted from the Faraday cup 30 are applied. Preferably, a suppressor electrode 28 is provided. The ion current I flowing through the Faraday cup 30 due to the incidence of the ion beam 10 is measured by, for example, a current measuring device 22 as in the conventional example.

Using the deflector 24 and the Faraday cup 30 as described above, the ratio of target component ions contained in the ion beam 10 extracted from the ion source 2 is determined as follows.

That is, the magnetic field intensity in the deflector 24 is set to zero or almost zero, and the ion current I ₀ flowing through the Faraday cup 30 at that time is measured. At this time, since the ion beam 10 travels straight without being bent in the deflector 24, and furthermore, since the Faraday cup 30 is provided at the straight traveling position, the Faraday cup 30 includes all the components included in the ion beam 10. Of the component is incident. For example, when the raw material gas 3 obtained by diluting B ₂ H ₆ with hydrogen is used, ions of all components including the above-described H _x -based ions, BH _x -based ions, and B ₂ H _x -based ions shown in FIG. 2 are incident. . When the source gas 3 obtained by diluting PH ₃ with hydrogen is used, all the ions including the above-described H _x -based ions, PH _x -based ions and P ₂ H _x -based ions shown in FIG. 3 are incident. The total amount is measured as the ion current I ₀ (FIG. 2)
B and FIG. 3B).

On the other hand, when the intensity of the magnetic field in the deflector 24 is gradually changed in a region larger than zero, for example, when it is gradually increased from zero, the mass of the ions contained in the ion beam 10 is reduced. 2B or 3B, the ion current I flowing through the Faraday cup 30 is flattened as shown in FIG. 2B or 3B. It decreases stepwise while passing through F ₁ , F ₂ . The flat portions F ₁ , F _2.
Indicates a portion where the change of the ion current I becomes almost zero with respect to the change of the magnetic field intensity, and this indicates a portion where the main component ions do not exist, that is, a partition between the respective component ions.

FIG. 2B (B_TwoH₆The water
In the case of the example in which the raw material gas 3 diluted with hydrogen is used,
When the intensity is gradually increased from zero, the lightest H
_xSystem ions come off the Faraday cup 30 and
The corresponding ion current I decreases. After that,
BH_xUntil the system ions come off the Faraday cup 30
Because there is room in the magnetic field strength, increase the magnetic field strength
Even if the ion current I hardly changes₁Appears
You. When the magnetic field strength is further increased, BH_xSystem ion
Io deviates from the Faraday cup 30
Current I decreases, and then the next flat portion F_TwoAppears.
When the magnetic field strength is further increased, the heaviest B _TwoH_xSeries Io
Is disengaged from the Faraday cup 30
Ion current I decreases, after which the main component ions
The flat portion F where the ion current I is 0 because it no longer exists_ThreeIs a table
It is.

In the case of using B ₂ H ₆ source gas 3 with hydrogen diluted, usually highest amounts dopant ion B ₂
H _x -based ions are used. For example, this is a target component ion. Therefore, the ion currents I ₁ and I ₂ at the _two flat portions F ₂ and F ₃ before and after the magnetic field intensity corresponding to the B ₂ H _x -based ion are measured, respectively. In this example, I ₂ ≒ 0.

Of the two ion currents I ₁ and I ₂ , one ion current I ₁ is an ion current containing all B ₂ H _x -based ions, and the other ion current I ₂ is a B ₂ H _x -based ion Is an ionic current that does not include any ionic current. Therefore, the difference | I ₁ −I ₂ | between the two ion currents accurately represents the desired amount of B ₂ H _x -based ions.

Further, the ratio shown in the above equation 2, that is, | I ₁ −
Find I ₂ | / I ₀ . This ratio is, as can be seen from the above description, the ion beam 10 extracted from the ion source 2.
It shows the ratio of target B ₂ H _x -based ions contained therein to all ions.

FIG. 3B (PH_ThreeGas 3 diluted with hydrogen
Is the same as above. However
In this case, the dopant ion is usually the most abundant
PH _xSince the system ion is used, the target component system
It is an ion. Therefore, this PH_xCorresponding to system ions
Two flat parts F before and after the magnetic field strength₁And F_TwoIons at
Current I₁And I_TwoRespectively. After that, B_TwoH₆
Is the same as

Contrary to the above example, the magnetic field strength in the deflector 24 may be gradually reduced from the larger one.
Even in such a case, the same data as in FIG. 2B or FIG. 3B can be obtained.

As described above, according to the measuring method of the present invention,
Unlike the conventional measurement method, it is not necessary to measure a large number of peak values of the ion current I (for example, the peak values I _{1 to} I ₁₃ shown in FIG. 2A), and the above three ion currents I ₀ , I ₁ and I ₂ are not required. Is measured, the target component ions contained in the ion beam 10 (for example, B
And the ratio of ₂ H _x based ionic or PH _x based ionic) easily can be obtained in a short time.

[0036] Moreover, in the measuring method of the present invention, the amount of conventional measurement methods and rather than doing measurements, ignoring small ions having a current value different, the ion current I ₀ is the all component ions And the difference | I ₁ −I ₂ | of the ion current accurately represents the amount of the target component ions, so that the ratio of the target component ions can be accurately determined. it can.

Therefore, by using such a measuring method, for example, it is possible to control the injection amount to the workpiece 12 accurately. Further, the feedback control to the ion source 2 can be promptly performed.

Further, since it is not necessary to accurately measure (quantify) many peak values of the ion current I unlike the conventional measurement method, it is not necessary to use a high-resolution measurement system.
The point is that the separation parts of the component ions, that is, the flat parts F ₁ , F
₂ ... It is only necessary to be able to identify.

The area of the Faraday cup 30 (and the corresponding mask 26 and suppressor electrode 28)
Is preferably larger than the Faraday cup 20 of the conventional example, as in this example. If the area of the Faraday cup 30 is small, the ion current I changes abruptly (rapidly decreases) due to a small change in the magnetic field strength, so that the flat portions F ₁ , F ₂ .
When the area of the Faraday cup 30 is increased, the ion current I is not changed until the magnetic field intensity is changed to some extent.
Changes. That is, the horizontal axes of FIGS. 2B and 3B are enlarged. As a result, the flat portions F ₁ and F ₂
.. Clearly appear, and the flat portions F ₁ , F
₂ becomes easy to identify.

If a small Faraday cup 32 (illustration of a slit and a suppressor electrode thereof is omitted) is provided next to the Faraday cup 30,
Like the conventional example, it is possible to obtain a spectrum view similar to FIG. 2A or FIG. 3A, it, each flat portion F _1,
It may be used as a reference for identifying F ₂ .

In the present invention, the ion source 2 is not limited to the one described above. For example, JP
An ion source provided with a magnet (magnetic filter) for suppressing extraction of light ions may be provided in the ion source as described in 1-329270.

[0042]

As described above, according to the present invention, it is not necessary to measure a large number of peak values of the ion current as in the conventional measuring method, and the three ion currents I ₀ , I ₁ and I ₂ are not required. , The ratio of the target component ions contained in the ion beam can be obtained easily and in a short time.

Further, in the measurement method of the present invention, unlike the conventional measurement method, the measurement is not performed while ignoring ions having a small current value, but the ion current I ₀ is determined by the amount of ions of all components. And the difference | I ₁ −I ₂ | of the ion current accurately represents the amount of the target component ions, so that the ratio of the target component ions can be accurately determined. it can.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an ion irradiation apparatus used for carrying out a measurement method according to the present invention.

FIG. 2 schematically shows a change in ion current with respect to a change in magnetic field intensity when a raw material gas obtained by diluting B ₂ H ₆ with hydrogen is obtained by the conventional measurement method (A) and the measurement method of the embodiment. And FIG.

FIG. 3 schematically shows a change in ion current with respect to a change in magnetic field intensity when a source gas obtained by diluting PH ₃ with hydrogen is measured by a conventional measurement method (A) and a measurement method of an embodiment (B). FIG.

FIG. 4 is a schematic view showing an example of a conventional ion irradiation device.

[Explanation of symbols]

 2 Ion source 10 Ion beam 12 Workpiece 24 Deflector 30 Faraday cup

Claims (1)

[Claims] In a non-mass separation type ion irradiation apparatus for irradiating an object to be processed with an ion beam extracted from an ion source without passing through a mass separator, target component ions contained in the ion beam A deflector that receives the ion beam extracted from the ion source and bends it with a deflection field consisting of at least one of a magnetic field and an electric field; and an ion beam that travels straight in the deflector. The ion current I ₀ flowing through the Faraday cup when the intensity of the deflection field in the deflector is set to zero or almost zero using a Faraday cup provided at a position
And when the intensity of the deflection field in the deflector is gradually changed in a region larger than zero, the ion current flowing through the Faraday cup before and after the deflection field intensity corresponding to the target component ions the change in the two flat portion becomes substantially zero ion current I ₁ and I ₂ were measured respectively, and | I ₁ -I ₂ | Request / I ₀ a ratio, of the ionic component ratio, characterized in that Measurement method.