JP2000311867A - Method and device for beam measuring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a beam measuring method, which can correctly measure the quantity of an ion beam which also includes the quantity of neutral particles, and a beam measuring device. SOLUTION: An electron gun 14 for radiating an electron beam 16 on the path of an ion beam 2 is kept provided in the vicinity of the side of the upstream of a Faraday cup 10 and an ionic current Ii, which is made to flow into the cup 10 in a state where the beam 16 is not emitted from the gun 14 is measured, an ionic current It, which is made to flow to the cup 10 in a state that the beam 16 is emitted from the gun 14, is measured. Moreover, a value IT converted the quantity of all neutral particles existing in the progressing path of the beam 16, which is incided in the cup 10, into a current is found on the basis of the following formula using an electron density (n) of the beam 16 at the time when this ionic current It is measured, a width (w) in the ion beam progressing direction of the beam 16 and the sectional area α of the beam at the time, when electrons in the beam 16 collide with the neutral particles exising in the progressing path of the beam 16 and the electrons are ionized. This processing is performed by an arithmetic control unit 20, for example. Equation is set to IT= It-Ii.exp(-nσw)}/ 1-exp(-nσw)}.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion beam irradiation apparatus such as an ion implantation apparatus, an ion doping apparatus (non-mass separation type ion implantation apparatus), an ion beam sputtering apparatus, and a thin film forming apparatus with ion beam irradiation. More specifically, the present invention relates to a beam amount measuring method and apparatus for measuring the amount of an ion beam, and more specifically, the amount of an ion beam including neutral particles generated as the ion beam passes through a residual gas. And a means for accurately measuring.

[0002]

2. Description of the Related Art FIG. 5 shows a conventional example of this type of beam amount measuring apparatus. The beam amount measuring apparatus includes a Faraday cup 10 for receiving an ion beam 2 to be measured and measuring an ion current of incident ions, a suppressor electrode 6 provided near an entrance thereof, and a mask provided on an upstream side thereof. And a plate 4. In this example, a current measuring device 12 that measures a current flowing through the Faraday cup 10 is connected to the Faraday cup 10. A negative voltage of, for example, about −100 V is applied to the suppressor electrode 6 from the suppressor power supply 8.

The ion beam 2 is applied to an opening 5 in a mask plate 4.
Pass through the opening 7 of the suppressor electrode 6 and enter the Faraday cup 10. As a result, an ion current corresponding to the amount of the incident ion beam 2 flows through the Faraday cup 10, and is measured by, for example, the current measuring device 12. Thus, the amount of the ion beam 2 can be measured as a current (beam current).

In such a case, when the ion beam 2 is incident on the Faraday cup 10, secondary electrons are emitted from the Faraday cup 10, so that the emitted secondary electrons cause a measurement error as it is. Therefore, usually, a suppressor electrode 6 is provided and a negative voltage as described above is applied to the suppressor electrode 6 to suppress the emission of the secondary electrons, or to push the emitted secondary electrons back to the Faraday cup 10 again. , The amount of the ion beam 2 can be accurately measured.

[0005]

The ion beam 2 is generated using, for example, an ion source. For generating plasma in the ion source, a method of introducing a gas into the ion source is often used. In addition, in an ion implantation apparatus or the like, in order to prevent charge-up (charging) accompanying ion implantation of a substrate (for example, a semiconductor wafer; the same applies hereinafter),
In many cases, a plasma flood gun (PFG) for supplying a neutralizing plasma to the ion beam is used.

In any case, gas is often used in the ion beam irradiation apparatus, so that the residual gas pressure in the path of the ion beam 2 inevitably increases to some extent.
When the ion beam 2 passes through the residual gas, charge conversion occurs between gas molecules and a part of the ion beam 2 becomes high-speed neutral particles. This is shown as neutral particles 3 in the figure.

However, since the Faraday cup 10 electrically measures incident particles, that is, measures the ion current of incident ions, even if the neutral particles 3 are incident, they cannot be measured. Therefore, when the neutral particles 3 are incident together with the ion beam 2, more particles are actually incident than the current amount measured by the Faraday cup 10. This phenomenon becomes more remarkable as the degree of vacuum in the path of the ion beam 2 becomes worse.

As a result, for example, when measuring or controlling the implantation amount (dose amount) to the substrate using the above-mentioned beam amount measuring device in the ion implantation apparatus, the measurement and control become inaccurate. More specifically, the injection amount is excessive (overdose) by the amount of the incident neutral particles 3, which hinders substrate processing such as device formation.

On the other hand, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open Publication No. H11-176,086 describes a technique for providing an ionization means for ionizing neutral particles upstream of a Faraday cup. This ionization means comprises a pair of ionization electrodes and a bias power supply for applying a voltage thereto. With this ionization means, neutral particles can be ionized and incident on the Faraday cup.

[0010] However, it is impossible to ionize the neutral particles by 100% even if the above ionization means is provided. Therefore, the amount of current measured by the Faraday cup is measured as a value smaller than the actual amount of incident particles, and there is still a problem that the measurement and control of the injection amount described above become inaccurate. ing.

Accordingly, it is a primary object of the present invention to provide a beam amount measuring method and apparatus capable of accurately measuring the amount of an ion beam including neutral particles.

[0012]

According to a beam amount measuring method according to the present invention, an electron gun for irradiating an electron beam to a path of the ion beam near an upstream side of the Faraday cup is provided, and the electron gun transmits the electron beam from the electron gun. Ion current I _i flowing through the Faraday cup without emitting a beam
The measures, said from the electron gun electron beam to measure the ion current I _t flowing through the Faraday cup in the injection state, further the electron density n of the electron beam when measuring the ion current I _t, the electron beam Using the width w in the traveling direction of the ion beam and the cross-sectional area σ when the electrons in the electron beam collide with the neutral particles existing in the traveling path and ionize it. Current conversion value I of the total amount of particles incident on the Faraday cup based on
It is characterized by finding _T.

[0013]

## EQU1 ## I _T = {I _t −I _i · exp (−nσw)} /
{1-exp (-nσw)}

According to another aspect of the present invention, there is provided a beam amount measuring apparatus for irradiating an electron beam on a path of the ion beam near an upstream side of the Faraday cup, and the Faraday cup without emitting the electron beam from the electron gun. the ion current I _i flows, the electron gun ion current flowing through the Faraday cup while emitting the electron beam from the I _t, the electron density n of the electron beam when measuring the ion current I _t, of the electron beam Using the width w in the traveling direction of the ion beam and the cross-sectional area σ when electrons in the electron beam collide with and neutralize neutral particles existing in the traveling path, based on the above equation 1, It is characterized in that it comprises an arithmetic control unit for determining the current conversion value I _T of the total amount of particles incident on the Faraday cup.

According to the above-described measuring method and measuring device, neutral particles traveling with the ion beam can be ionized by the electron beam emitted from the electron gun and can be incident on the Faraday cup. Therefore, the amount of the incident particles can be measured by a Faraday cup as an ion current.

In this case, the ionization rate of the neutral particles by the electron beam does not need to be 100%. Equation 1 above
Includes an element for determining the amount of all neutral particles from the amount of some ionized neutral particles.

Therefore, according to the present invention, the total amount of particles incident on the Faraday cup, that is, the amount of the ion beam including neutral particles, regardless of the degree of ionization of the neutral particles by the electron beam, is determined. , Can be measured accurately.

[0018]

FIG. 1 is a view showing an example of a beam amount measuring apparatus for implementing a beam amount measuring method according to the present invention. Parts that are the same as or correspond to those in the conventional example shown in FIG. 5 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.

This beam amount measuring apparatus is provided near the upstream side of the above-mentioned Faraday cup 10, more specifically, between the mask plate 4 and the suppressor electrode 6.
An electron gun 14 for irradiating an electron beam 16 from a direction intersecting (for example, orthogonally) to the path of the ion beam 2 is provided. The electron gun 14 is an electron gun power supply 18 in this example.
Driven by

Further, while controlling the electron gun 14 (specifically, the electron gun power supply 18), based on the information from the electron gun 14 and the Faraday cup 10, the following arithmetic control is performed. An arithmetic and control unit 20 is provided. Information (signal) from the electron gun 14 and the Faraday cup 10 is taken into the arithmetic and control unit 20 via the electron gun power supply 18 and the current measuring device 12 in this example.

The high-speed neutral particles 3 generated by the charge conversion and traveling together with the ion beam 2
, The electron beam 1 emitted from the electron gun 14
It collides with the electrons in 6 and is partially ionized. The ionized particles have almost the same kinetic energy as the ion beam 2, and thus go straight and enter the Faraday cup 10. As a result, a current corresponding to the amount of incident ions flows through the Faraday cup 10 and the current measuring device 12, so that the amount of incident ions can be measured. Of course, also in this case, although the secondary electrons are generated from the Faraday cup 10, there is no problem because the secondary electrons are suppressed by the suppressor electrode 6 as in the case of the normal ion beam.

However, even when the electron beam 16 is used, it is generally difficult to ionize all the neutral particles 3 (that is, set the ionization rate to 100%). Therefore, it is difficult to accurately measure the total amount of incident particles with the Faraday cup 10 simply by providing the electron gun 14. To solve this, the present invention employs the following means.

That is, first, in this example, the arithmetic and control unit 20
By controlling the electron gun power supply 18 so as not to emit electron beams 16 from the electron gun 14, then the measured ion current I _i flowing through the Faraday cup 10, it takes in the value to the arithmetic and control unit 20. This ion current I _i is
Only the current by the ion beam 2 (ion beam current).

Next, in this example, a predetermined energy E and a predetermined electron beam current I _e are calculated by the arithmetic and control unit 20.
The electron gun power supply 18 is controlled so that an electron beam 16 having Thereby, a part of the neutral particles 3 traveling with the ion beam 2
6 and is incident on the Faraday cup 10. Of course, the ion beam 2 also enters the Faraday cup 10. In this case by measuring the ion current I _t flowing through the Faraday cup 10, it takes in the value to the arithmetic and control unit 20. This ion current It is _equal to the ion current I.
It is the sum of _i and the current due to some neutral particles ionized by the electron beam 16. Accordingly, the current I _n by neutral particles of partially ionized is represented by the following equation.

[0025]

[Number 2] I _n = I _t -I _i

Further, when the current conversion value of total neutral particle amount incident on the Faraday cup 10 and I _N, the following relationship is established. Here, n (see FIG. 2) is the electron density of the electron beam 16 when measuring the ion current I _t, w is the ion beam traveling direction of the electron beam 16 width, sigma is the electron beam 16 that proceeds This is the cross-sectional area (collision cross-section) when neutral particles existing in the path collide and are ionized.

[0027]

Equation 3] _{I n = I t -I i =} I N {1-exp (-nσw)}

The following equation is derived from the equation (3).

[0029]

Equation 4] _{I N = (I t -I i} ) / {1-exp (-nσw)}

[0030] Finally, determine values or current converted value I _T of the total amount of particles entering the Faraday cup 10 is expressed by the following equation.

[0031]

## EQU5 ## I _T = I _i + I _N

[0032] From this number 5 and the number 4 which, current conversion value I _T of the total amount of particles entering the Faraday cup 10 is expressed by the following equation.

[0033]

## EQU6 ## I _T = {I _t −I _i · exp (−nσw)} /
{1-exp (-nσw)}

The equation (6) is the same as the equation (1) described above. Based on this equation, the incident light on the Faraday cup 10 is obtained regardless of the ionization rate of the neutral particles 3 by the electron beam 16. , Ie, the amount of the ion beam 2 including the neutral particles 3 can be accurately measured.

As a result, for example, if the measurement or control of the amount of implantation into the substrate is performed by using the above-described measuring method or measuring device in an ion implantation apparatus, the measurement and control become accurate, and the occurrence of overdose occurs. And substrate processing such as device formation can be performed with high quality.

The processing such as the calculation of the above equation 6 (that is, the equation 1) is as follows.
Although it may be performed by a device other than the arithmetic and control unit 20, the arithmetic and control unit 20 performs the process in this example. Thus, in this example, the arithmetic and control unit 20 can determine the current conversion value I _T of the total particle weight.

The cross-sectional area σ may be measured in advance, for example, or a value described in a literature may be used. The electron density n and the width w may be measured in advance, for example. Alternatively, the electron density n may be obtained as follows.

That is, the sectional area of the electron beam 16 is represented by S (FIG. 2).
Assuming that the speed of the electron beam 16 is v and the elementary charge is e, the electron beam current I _e is expressed by the following equation.

[0039]

[Mathematical formula-see original document] _Ie = envS

Assuming that the energy of the electron beam 16 is E and the mass of the electrons is m, the following relationship is established.

[0041]

[Equation 8] mv ^2/2 = eE

From equation (8) and equation (7), the electron beam 1
The electron density n of 6 can be obtained, and is given by the following equation.

[0043]

N = (I _e / eS) √ (m / 2eE)

The calculation of equation (9) may be performed, for example, by the arithmetic and control unit 20, and may be used for the electron density n in equation (6).

Further, in the present invention, since the electron gun 14 is used for ionizing the neutral particles 3, compared with the case of using the ionization means including the ionization electrode and the bias power source described in the above publication, the following is provided. There are such advantages.

That is, the ionization means comprising the ionization electrode and the bias power source is configured to strip off electrons from the neutral particles by the positively biased ionization electrode and ionize the neutral particles when passing near the ionization electrode. Therefore, it is not easy to ionize neutral particles, and to increase ionization efficiency, it is necessary to apply a fairly large bias voltage. This may cause problems such as dielectric breakdown.

On the other hand, as in the present invention, the electron gun 1
When the electron beam 16 from the electron beam 4 is used, the electron beam 1
The energy of 6 is about several tens of eV, and at most 10
Since about 0 eV is sufficient, the electron gun 14 and the electron gun power supply 1
8 requires only a small capacity. Also, there is no problem of dielectric breakdown. Further, not only can the amount of the electron beam 16 be accurately controlled, but also the ratio of the neutral particles 3 to be ionized can be determined accurately, so that the amount of the neutral particles can be determined accurately.

When the electrons in the electron beam 16 or the electrons generated by the collision of the electron beam 16 with the neutral particles 3 enter the Faraday cup 10, a measurement error is caused accordingly. However, the energy of the electrons generated by the collision with the electron beam 16 is at most about several eV. Also, the energy of the electron beam 16 may be about the ionization energy of the neutral particles 3. For example, in the case of neon (21.45 eV) having a high ionization energy, the energy may be about 25 eV. Therefore, if a voltage of about −100 V to −50 V is applied to the suppressor electrode 6, the electrons can be prevented from passing through the suppressor electrode 6 and entering the Faraday cup 10.

If the potential in the vicinity of the electron beam 16 does not greatly differ from the potential of the suppressor electrode 6, electrons in the electron beam 16 may pass through the suppressor electrode 6, but in that case, For example, as shown in FIG. 3, the second suppressor electrode 22 is connected to the electron gun 14.
In addition, a negative voltage may be applied from the second suppressor power supply 24 to the gap between the power supply and the suppressor electrode 6. In this case, for example, -100 is applied to the suppressor electrode 6.
V and about −50 V may be applied to the second suppressor electrode 22. In such a case, even if electrons pass through the second suppressor electrode 22, the electrons are blocked by the suppressor electrode 6. Will not be incident.

The Faraday cup 10 described above is
The number may be one, as in the above example, or a plurality may be arranged in a line. FIG. 4 is an example of a case where five Faraday cups 10 are arranged in a vertical example. In this case, one electron gun 14 may be provided for each Faraday cup 10, or one electron gun 14 may be used as in the example shown in FIG.

[0051]

As described above, according to the present invention, neutral particles traveling along with an ion beam can be ionized by the electron beam emitted from the electron gun and incident on the Faraday cup. The amount of all neutral particles can be determined based on the total particle amount incident on the Faraday cup regardless of the magnitude of the ionization rate of the neutral particles by the electron beam, that is, including the neutral particles. The amount of the ion beam can be accurately measured.

Further, since the electron beam from the electron gun is used for ionizing the neutral particles, the power supply and the like need only have a small capacity and use a high voltage as compared with the case where an ionization electrode and a bias power supply therefor are used. Since there is no need to carry out the process, there is no problem such as dielectric breakdown, and the calculation of the amount of neutral particles becomes accurate.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a beam amount measuring device for implementing a beam amount measuring method according to the present invention.

FIG. 2 is a diagram schematically showing a relationship between an ion beam and an electron beam in FIG.

FIG. 3 is a diagram showing another example of the beam amount measuring device for performing the beam amount measuring method according to the present invention.

FIG. 4 is a front view illustrating an example of a beam amount measurement device including a plurality of Faraday cups arranged in a line.

FIG. 5 is a diagram showing an example of a conventional beam amount measuring device.

[Explanation of symbols]

 2 Ion beam 3 Neutral particle 10 Faraday cup 12 Current measuring device 14 Electron gun 16 Electron beam 18 Electron gun power supply 20 Arithmetic controller

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Claims (2)

[Claims] 1. A method of measuring a beam amount of an ion beam by injecting an ion beam into a Faraday cup for measuring an ion current of incident ions, comprising: an electron beam in a path of the ion beam near an upstream side of the Faraday cup; may be provided an electron gun for irradiating, this from the electron gun in a state which does not emit electron beam to measure the ion current I _i flowing through the Faraday cup, flowing through the Faraday cup while emitting the electron beam from the electron gun measuring the ion current I _t, further the electron density n of the electron beam, the ion beam traveling direction of the width w of the electron beam, and electrons its progress in the electronic beam at the time of measuring the ion current I _t Using the cross section σ when colliding with the neutral particles existing in the path and ionizing it, based on the following formula Beam quantity measuring method characterized by determining the total amount of particles current conversion value I _T which enters the serial Faraday cup. I _T = {I _t −I _i · exp (−nσw)} / {1−exp
(-Nσw)｝ 2. An apparatus for measuring a beam amount of an ion beam by injecting an ion beam into a Faraday cup for measuring an ion current of incident ions, comprising: an electron beam in a path of the ion beam near an upstream side of the Faraday cup. An ion current I _i flowing through the Faraday cup without emitting an electron beam from the electron gun, an ion current I _t flowing through the Faraday cup while emitting an electron beam from the electron gun, electron density n of the electron beam when measuring the ion current I _t, collide with neutral particles the ion beam traveling direction of the width w of the electron beam, and electrons in the electron beam is present in the traveling path Then, it is incident on the Faraday cup based on the following equation using the cross-sectional area σ when ionizing it. Beam quantity measuring device, characterized in that it comprises an arithmetic control unit for determining the current conversion value I _T of the total grain volume. I _T = {I _t −I _i · exp (−nσw)} / {1−exp
(-Nσw)｝