JPH0589819A - Ion implantation device - Google Patents

Abstract

PURPOSE:To make implantation control of high precision by converting the implantation amount determined by a dosage monitor into the implantation amount to a target on the basis of the proportion of the predicted implantation amounts on the target and dosage monitor, and thereupon performing the control of the implantation amount. CONSTITUTION:A first and a second multi-point monitor 8, 15 emit beam current signals from each channel in response to incidence of an ion beam 1. The locus of the ion beam 1 in scanning is determined to make determination of the beam position on a target 13 and the scanning speed. The implantation amount distribution in the scanning direction on the target 13 and dosage monitor 10 is predicted from a specific formula. This is followed by determination of the ratio of the predicted implantation amount on the target 13 to the predicted implantation amount on the dosage monitor 10 determined through integrative calculations of these predicted implantation amount distributions. The implanting amount into the target 13 is controlled on the basis of this ratio and the beam current value measured by the dosage monitor 10 during implantation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implanter having a target and a dose monitor arranged spatially different from each other. More specifically, the present invention relates to an ion implanter for predicting an implant dose distribution in the target and dose monitor. The present invention relates to an ion implantation apparatus that controls the implantation amount by converting the implantation amount of the above into the implantation amount into a target.

[0002]

2. Description of the Related Art Generally, it is difficult for an ion implanter of a hybrid scan system to use a target portion as a monitor of an implantation beam current as in an electrostatic raster scan system, so that it is dedicated to controlling an implantation dose. I often use a dose monitor.

That is, in the conventional ion implanter, as shown in FIG. 5, a pair of scanning electrodes 52.5 to which a scanning voltage is applied from a scanning waveform oscillator 51 so that their phases are mutually inverted.
2 and a deflection electrode 53 for separating charged particles and neutral particles
53 and the target 54 with respect to the beam scanning direction Z =
A mechanical scanning mechanism 56 that reciprocates in the vertical direction on the Z _T plane, and Z between the target 54 and the deflection electrode 53.
= Z _M plane and the mask slit 57. As shown in FIG. 6, the mask slit 57 is provided with a target opening 57a having an area S ₁ and a dose opening 57b having an area S ₂ , and the mechanical opening is provided in the dose opening 57b. This is a configuration in which a dose monitor 59 to which a CPU 58 for controlling the scanning mechanism 56 is connected is provided.

In the ion implanter having the above structure, the ion beam 55 scanned by the scanning electrode 52 is applied to the target 54 through the target opening 57a of the mask slit 57, and the dose is also applied. The dose monitor 59 is irradiated with the light through the opening 57b, and the injection amount control to the target 54 is executed based on the beam current signal output from the dose monitor 59.

To explain the concept of the above-mentioned implantation dose control, first, the ion beam 55 is scanned at a frequency f in the X direction. At this time, the beam current I _T generated when the beam spot 55a of the scanned ion beam 55 makes one round trip and is irradiated on the target 54 through the mask slit 57 is expressed as follows per unit area. ..

[0006]

[Equation 1]

Here, I _M is the beam current amount measured by the dose monitor 59 when the ion beam 55 makes one round trip.

Impurity ions are implanted by the ion beam 55 into an arbitrary point A on the target 54 when the mask slit 57 is moved to the rear of the target opening 57a as shown in FIG. Only. Therefore, when the scanning cycle is sufficiently short with respect to the time when the point A passes through the target opening 57a, a uniform implantation dose D _{A is} injected on a straight line parallel to the beam scanning direction including the point A. Will be.

[0009]

[Equation 2]

Here, L ₁ is the height of the target opening 57a and the dose opening 57b of the mask slit 57, and v is the mechanical scanning speed.

In this way, in the half cycle of the mechanical scan, the target 54 is uniformly injected with the injection amount D _A represented by the equation (2), and in the actual injection operation, The speed v of the mechanical scan is controlled so that the implantation amount D _A becomes constant in accordance with the beam current amount I _M measured by the dose monitor 59.

[0012]

However, in the above-mentioned conventional ion implantation apparatus, if the implantation uniformity is not constant in the beam scanning direction, the equation (1) will not hold.

[0013]

[Equation 3]

If Z _T = Z _M is not satisfied and the scanned ion beam 55 is not completely parallel, the target surface Z of the ion beam 55 that has passed through the mask slit 57.
The projected area at _T is different from the area S ₁ of the target opening 57a of the mask slit 57. Therefore,
Assuming that this projected area is the area S ₁ ′, the equation (1) is transformed as follows.

[0015]

[Equation 4]

When the above equations (3) and (4) are satisfied, the injection amount D _A 'injected per half cycle of the mechanical scan is

[0017]

[Equation 5]

Thus, the target injection amount D _A cannot be injected by the control using the equation (2).
The above α is a correction coefficient.

Therefore, it is an object of the present invention to provide an ion implantation apparatus capable of performing highly accurate implantation dose control even when the implantation uniformity is not constant in the beam scanning direction.

[0020]

In order to solve the above-mentioned problems, an ion implantation apparatus of the present invention has a target on which a scanned ion beam is incident and a dose monitor which are spatially different from each other. It has the following features.

That is, the ion implanter has multipoint monitors arranged at two positions in front of and behind the axis of the ion beam. Further, the ion implantation apparatus predicts the implantation dose distribution in the scanning direction on the target and the dose monitor by the scanning speed of the ion beam obtained from the multipoint monitor and the current distribution of the beam spot in the scanning direction. , A control for controlling the injection amount to the target based on the ratio between the predicted injection amount on the target and the predicted injection amount on the dose monitor obtained by integrating the distribution of the injection amount and the beam current amount measured by the dose monitor. It is characterized by having a CPU unit which is a means.

[0022]

According to the above structure, the control means obtains the scanning speed of the scanned ion beam by using the front and rear multipoint monitors arranged on the axis of the ion beam, and the beam in the scanning speed and the scanning direction is obtained. Predict the injection dose distribution on the target and in the scanning direction on the dose monitor from the spot current distribution, and obtain the ratio of the predicted injection dose on the target and the predicted injection dose on the dose monitor obtained by integrating these injection dose distributions. It will be. And the control means
The beam current amount measured by the dose monitor is corrected by the above ratio to control the implantation amount to the target.

As a result, the ion implantation apparatus can control the implantation amount by converting the implantation amount in the dose monitor into the implantation amount in the target, so that the implantation uniformity is caused by, for example, the shape of the beam spot or the scanning speed. It is possible to control the injection amount with high accuracy even if the property is poor.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

The ion implantation apparatus according to this embodiment has a beam scanning system for scanning the ion beam 1 in the X direction, as shown in FIG. The beam scanning system includes an arbitrary waveform generator 3 capable of outputting a scanning voltage having an arbitrary waveform in accordance with an instruction from the CPU unit 2 serving as a control unit, and a phase for inverting the scanning voltage output from the arbitrary waveform generator 3. Inverter 6 and
A high-voltage amplifier 4a connected to the phase inverter 6, a high-voltage amplifier 4b connected to the arbitrary waveform generator 3, and a pair of scanning voltages amplified by the high-voltage amplifiers 4a and 4b. It is composed of scanning electrodes 5 and 5.

A pair of deflection electrodes 7 and 7 to which a predetermined voltage is applied are arranged on the side of the scanning electrodes 5 and 5 in the traveling direction of the ion beam 1. These deflection electrodes 7 and 7 are
While the ion beam 1 is traveling, the traveling direction of the charged particles is bent toward the first multi-point monitor 8 and the second multi-point monitor 15 while the neutral particles are moved straight to separate the charged particles from the neutral particles. The Z = Z _F plane in the beam traveling direction, which is the traveling direction of the ion beam 1 composed of separated charged particles, has a plurality of channels for outputting a beam current signal when the ion beam 1 is incident. The 1st multipoint monitor 8 which has is arranged.

On the Z = Z _M plane located in the beam traveling direction from the Z = Z _F plane, a mask slit 9 for blocking the unnecessary ion beam 1 is provided. The mask slits 9, the target opening 9a of the area S _1, the dose opening 9b of the area S _2, and the profile opening 9c is formed, the profile opening 9c, the above CPU A first beam profile monitor 11 connected to the section 2 is provided. Further, the dose opening 9b is provided with a dose monitor 10 connected to a mechanical scan control system (not shown). The dose monitor 10 measures the beam current amount during ion implantation to control the mechanical scan speed. It is designed to let you.

A second beam profile monitor 14 connected to the CPU unit 2 is provided on the Z = Z _T plane located in the beam traveling direction from the Z = Z _M plane.
A target 13, which is an ion irradiation target, is positioned by the mechanical scanning mechanism 12. The mechanical scanning mechanism 12 is configured to reciprocate the target 13 in the direction perpendicular to the beam scanning direction (X direction).

Further, on the Z = Z _B plane located in the beam traveling direction from the Z = Z _T plane, there is provided a second multipoint monitor 15 having a plurality of channels for outputting a beam current signal upon incidence of the ion beam 1. It is arranged. The second multipoint monitor 15 is connected to the data logger 16 together with the first multipoint monitor 8 described above, and the data logger 16 is connected to the CP.
It is connected to the U section 2. Then, when the beam spot of the ion beam 1 is sufficiently small, the CPU unit 2 executes the first
The beam current signals of the respective channels of the multipoint monitor 8 and the second multipoint monitor 15 are subjected to signal processing, and the correction coefficient α of the equation (5) is calculated.
Is calculated, the injection uniformity in the dose monitor 10 is converted into the injection quantity into the target 13, and the arbitrary waveform generator 3 is controlled.

When the beam spot is large,
The first multipoint monitor 8 and / or the second multipoint monitor 15,
Alternatively, the first and second beam profile monitors 11
After confirming the beam profile by 14, the signal processing is performed on this beam profile and the beam current signal of each channel of the first and second multipoint monitors 8 and 15 (5).
The correction coefficient α of the equation is obtained, the injection uniformity is predicted, the injection amount in the dose monitor 10 is converted into the injection amount into the target 13, and the arbitrary waveform generator 3 is controlled.

Next, a signal processing method for obtaining the correction coefficient α will be described.

First sampled by the data logger 16
By knowing the time t when the ion beam 1 passes from the beam current waveform of a certain channel of the second multipoint monitor 8.15, the voltage data value j (t) output by the arbitrary waveform generator 3 at that time can be obtained. Ask. As a result, in all channels of the first and second multi-point monitors 8.15,
By obtaining such voltage data value j (t),
A series of data points 17 as shown in FIG. 2 are obtained together with the monitor position X (i) which is known in advance. Then, by applying appropriate interpolation or extrapolation to this series of data points 17, the function X (j) of the relationship curve 18 between the voltage data value j (t) and the beam position which is the position of the ion beam 1 is obtained. Will be required.

The function X (j) thus obtained is Z
= Z _F plane and Z = Z _B plane, respectively, and set as X _F (j) and X _B (j). The ion beam 1 is applied to the scanning electrode 5
Since the vehicle goes straight except when passing through 5, the function X (j) of the voltage data value j (t) on the arbitrary surface Z and the beam position is obtained.
Is represented as follows:

[0034]

[Equation 6]

From this function X (j), an arbitrary point X on the Z plane
The scanning speed and the time change V _T (t) of the scanning speed at are calculated as follows.

[0036]

[Equation 7]

Letting the inverse function of the waveform data be T (x),
The scanning speed V (x) at an arbitrary point X on the Z plane is expressed as follows.

[0038]

[Equation 8]

In this way, the scanning speed V (x) is obtained for each reciprocating beam scanning, and the scanning speed V _up (x) is obtained.
And the scanning speed V _dn (x). At the point X, the ion beam 1 passes back and forth twice while scanning the ion beam 1 once. Therefore, when the beam spot is sufficiently small with respect to the distance at which the implantation dose distribution largely changes (for example, about 1%), the implantation dose distribution function D (x) in the beam scanning direction is expressed as ..

[0040]

[Equation 9]

FIG. 3 shows an example in which the round-trip and average predicted implantation dose distribution of beam scanning calculated from the above equation (9) is compared with the implantation dose distribution obtained from the sheet resistance value.

Next, the case where the beam spot is large will be described. When the beam spot is sufficiently small, the injection dose distribution can be accurately obtained by the equation (9), but in the case of a large beam spot, It is necessary to use the exact distribution function D (x).

[0043]

[Equation 10]

When the above equation (10) is used, X
It is necessary to know the beam profile in the direction (scanning direction). This beam profile can be known using the first and second beam profile monitors 11 and 14, and one channel of the first multipoint monitor 8 and / or the second multipoint monitor 15 can be used as a beam profile monitor. I can know.

That is, the first and second beam profile monitors 11 and 14 and the first and second multipoint monitors 8 and 15
The beam current waveform obtained from the beam profile monitor of FIG. 4 is as shown in FIG. 4, and if this beam profile is Pm (t), the beam profile function P (x) in the equation (10) is as follows. expressed.

[0046]

[Equation 11]

When collecting the beam profile data, since there should be no difference in the round trip of the beam scanning, the beam profile function P (x) is obtained as the average of the round trip.

At this time, when the beam spot is very large, the divergence angle of the ion beam 1 is also expected to be large. Therefore, the first and second multipoint monitors 8.1
When 5 is used as the beam profile monitor, the beam spot on the target 13 may not match the monitored beam profile. In this case, the beam profile function P (x) is as follows.
Can be asked.

That is, the beam profile functions in the Z = Z _F plane and the Z = Z _B plane are respectively P _F (x) and P _F (x)
Let _B (x) be the half width X _{F1 / 2} and X _{B1 / 2} . Z =
Assuming that the ion beam 1 diverges uniformly between the Z _F plane and the Z = Z _B plane, the beam profile function P
(X) is calculated as follows.

[0050]

[Equation 12]

Or

[0052]

[Equation 13]

By using the beam profile function P (x) obtained by the equation (12) or (13), the implantation dose distribution can be predicted by the equation (10).

In the actual numerical calculation, (10)
The integral range of the equation is calculated as about 1/10 of the beam profile (about 98% of the beam current is set if a normal distribution is assumed).

[0055]

[Equation 14]

From the above equations (9) and (10) or the above equation (10) ', Z = Z _T plane and Z = Z _M
The injection amount distribution D (x) on the plane is determined as D _T (x) and D _M (x), respectively, and the target 1 of the injection amount distribution D _T (x) is obtained.
The average D _T of over 3 injection weight distribution obtaining the average D _M of on dose monitors 10 D _M (x).

[0057]

[Equation 15]

[0058]

[Equation 16]

As a result, the correction coefficient α in the equation (5) is obtained as follows.

[0060]

[Equation 17]

The operation of the ion implanter having the above structure will be described.

First, as shown in FIG. 1, the ion beam 1
After being scanned in the X direction by the scanning electrodes 5 and 5, the traveling direction of the charged particles of the ion beam 1 is bent by the deflection electrode 7, and the charged particles and the neutral particles are separated.
Then, the ion beam 1 composed of the separated charged particles
Is incident on the first multipoint monitor 8 and is incident on the second multipoint monitor 15.

The first multipoint monitor 8 and the second multipoint monitor 15 output beam current signals from the respective channels when the ion beam 1 is incident, and these beam current signals are output by the data logger 16. Will be sampled. Then, the time t at which the ion beam 1 passes is detected from the beam current waveform of a certain channel of the first and second multipoint monitors 8 and 15 sampled by the data logger 16, and the arbitrary waveform is obtained at this time. The voltage data value j (t) output by the generator 3 will be obtained.

The above-mentioned voltage data value j (t) is obtained for all the channels of the first and second multipoint monitors 8.15, so that the monitor position X which is known in advance can be obtained.
Together with (i), a series of data points 17 as shown in FIG. 2 will be obtained. And this series of data points 17
To the voltage data value j (t)
Then, the function X (j) of the relational curve 18 between the beam position, which is the position of the ion beam 1, is obtained. After this,
The above-mentioned function X (j) is obtained on the Z = Z _F plane and the Z = Z _B plane, respectively, and the scanning speed V (x) at the arbitrary point X on the Z plane is calculated from this function X (j). Will be required.

Next, when the beam spot is sufficiently small with respect to the distance where the implantation dose distribution fluctuates greatly,
The distribution function D (x) of the equation (9) is selected.
On the other hand, when the beam spot is large, the distribution function D (x) of the equation (10) is selected, and when the first and second multipoint monitors 8 and 15 are used as beam profile monitors. , The distribution function D (x) of the equation (10) ′ is selected.

Then, from the distribution function D (x) of the equation (9), the equation (10), or the equation (10) ′, the average D _T on the target 13 in the Z = Z _T plane and the Z = Z _M plane is obtained. After the average D _M on the dose monitor 10 is obtained, (1
The correction coefficient α is calculated from the equation (6). Then, the CPU unit 2 substitutes the calculated correction coefficient α into the equation (5), and measures the beam current amount I _M measured by the dose monitor 10.
Therefore, the injection amount on the target 13 is controlled.

As described above, in the ion implantation apparatus of this embodiment, the trajectory of the scanned ion beam 1 is changed to the ion beam 1
The beam position on the target 13 and the scanning speed are obtained by using the first and second multipoint monitors 8 and 15 arranged at two front and rear positions on the axis of
1 channel of multipoint monitor 8.15, 1st and 2nd beam profile monitors 11 and 14 and 1 channel of 1st and 2nd multipoint monitors 8 and 15 are used for measuring the current distribution of the beam spot in the scanning direction. , (9)
On the target 13 obtained by predicting the injection amount distribution in the scanning direction on the target 13 and the dose monitor 10 from the calculation formulas (10) and (10) ', and integrating these predicted injection amount distributions. Injection dose and dose monitor 1
The ratio of the predicted injection amount on 0 is calculated, and the injection amount to the target 13 is controlled based on this ratio and the beam current amount I _M measured by the dose monitor 10 during the injection.

Therefore, in this ion implantation apparatus, even if the implantation uniformity is poor due to, for example, the shape of the beam spot or the scanning speed, the implantation amount can be predicted, so that the implantation amount can be accurately controlled. As a result, it is possible to eliminate the restriction on the arrangement position of the dose monitor 10. In addition, the injection amount control using this estimated injection amount is less affected by the sensitivity of each monitor than when a monitor dedicated to injection amount correction is used.
Since the first and second multi-point monitors 8 and 15 and the first and second beam profile monitors 11 and 14 are used only for obtaining the beam shape, they are high like the monitors dedicated to the above-mentioned injection amount correction. It does not have to be accurate.

Although the non-parallel scan type is used for the ion implantation apparatus of this embodiment, the present invention is not limited to this, and the parallel scan type may be used.

[0070]

As described above, the ion implantation apparatus of the present invention has the target on which the scanned ion beam is incident and the dose monitor which are spatially different from each other, and is located on the axis of the ion beam. The injection amount in the scanning direction on the target and the dose monitor is determined by the multi-point monitors arranged at the front and rear, the scanning speed of the ion beam obtained from the multi-point monitor, and the current distribution of the beam spot in the scanning direction. A distribution is predicted, and the target injection amount based on the ratio of the predicted injection amount on the target and the predicted injection amount on the dose monitor obtained by integrating this injection amount distribution and the beam current amount measured by the dose monitor. And a control means for controlling.

As a result, based on the ratio of the predicted injection amount on the target and the predicted injection amount on the dose monitor, the injection amount is controlled by converting the injection amount in the dose monitor into the injection amount in the target. Even if the injection uniformity is poor due to the shape, the scanning speed, etc., it is possible to perform the injection amount control with high accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an ion implantation apparatus of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a voltage data value and a beam position.

FIG. 3 is an explanatory diagram showing a relationship between prediction of an injection amount distribution and an actually measured value.

FIG. 4 is an explanatory diagram of a beam current waveform.

FIG. 5 shows a conventional example and is an explanatory diagram showing a schematic configuration of an ion implantation apparatus.

FIG. 6 is an explanatory diagram showing a state where an arbitrary point A on the target is irradiated with an ion beam.

[Explanation of symbols]

 1 Ion Beam 2 CPU Unit (Control Means) 3 Arbitrary Waveform Generator 4a ・ 4b High Voltage Amplifier 5 Scanning Electrode 6 Phase Inverter 7 Deflection Electrode 8 First Multipoint Monitor 9 Mask Slit 9a Target Aperture 9b Dose Aperture 9c Profile opening 10 Dose monitor 11 First beam profile monitor 12 Mechanical scanning mechanism 13 Target 14 Second beam profile monitor 15 Second multi-point monitor 16 Data logger 17 Data point 18 Relation curve

Claims (1)

[Claims] 1. An ion implanter having a spatially different arrangement of a target on which a scanned ion beam is incident and a dose monitor, and a multi-point monitor disposed at two front and rear positions on the axis of the ion beam. , The ion beam scanning speed obtained from the multipoint monitor, and the current distribution of the beam spot in the scanning direction,
Predict the implantation dose distribution on the target and in the scanning direction on the dose monitor, integrate the implantation dose distribution, and calculate the ratio between the predicted implantation dose on the target and the predicted implantation dose on the dose monitor, and the beam measured by the dose monitor. An ion implantation apparatus comprising: a control unit that controls an implantation amount into a target based on an electric current amount.