JP3127502B2 - Ion implanter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus for uniformly implanting impurity ions into an ion irradiation object such as a wafer, and more particularly to an ion implantation apparatus for measuring the beam current of an ion beam to control the amount of ion implantation. It concerns the device.

[0002]

2. Description of the Related Art An ion implantation apparatus ionizes impurities to be diffused, selectively extracts the impurity ions by mass spectrometry using a magnetic field, accelerates the ions by an electric field, and irradiates the ion irradiation target with ions. This is for implanting impurities into the irradiation object. This ion implantation apparatus is an important apparatus for manufacturing integrated circuits at present because it can implant impurities that determine device characteristics in an arbitrary amount and depth with good controllability in a semiconductor process.

[0003] The ion implantation apparatus is designed to be able to cope with a large ion irradiation target (for example, an 8-inch wafer). As shown in FIG. There is a so-called hybrid scan type that electrically scans the ion beam 54 and mechanically scans the ion irradiation target 56 in the Y direction (perpendicular to the paper) perpendicular to the X direction.

In the above-described hybrid scan type ion implantation apparatus, the ion irradiation target 56 is held by the holding member 53 at the implantation position, and is driven by the holding member driving mechanism 52 to reciprocate (scan) in the Y direction. ing.

An irradiation mask 55 having an opening 55a having a predetermined area is disposed upstream of the holding member 53. The opening 55a of the irradiation mask 55 is formed in the beam scanning region, and only the ion beam 54 that has passed through the opening 55a is irradiated on the ion irradiation target 56 held by the holding member 53 behind the opening 55a. It has become.

An opening 5 in the beam scanning area
On the side of 5a, a dose Faraday 57 for measuring the beam current is provided. The beam current of the ion beam 54 incident on the dose Faraday 57 is converted into a signal suitable for signal processing by the implantation controller 59 by a current integrator 58 having an OP amplifier and the like, and is output to the implantation controller 59. The implantation controller 59 controls the operation of the holding member drive mechanism 52 based on the amount of charge per one beam scan of the ion beam 54 incident on the dose Faraday 57, and moves the holding member 53, that is, the ion irradiation target 56. Of the Y-direction scanning speed. By controlling the Y-direction scanning speed, the amount of ion implantation into the ion irradiation target 56 is controlled, and a uniform implantation amount is obtained.

[0007]

In the current integrator 58, noise is generated due to a change in the baseline due to, for example, the temperature characteristics of the OP amplifier, an electromagnetic wave generated in an ion source or the like, a discharge generated in the device, or the like. .

Since the area of the opening 57a of the dose Faraday 57 has a small occupation area ratio (for example, about 1/20) with respect to the entire beam scanning area, the ion beam 54 incident on the dose Faraday 57 is small. For this reason, the beam current value to be measured is very small, about several nA to several mA, so that the S / N ratio with respect to noise or baseline drift generated in the beam current measurement system such as the current integrator 58 is low. Susceptible.

For example, in an ion implantation apparatus in which the beam scanning width is set to 300 mm and the width of the opening 57a of the dose Faraday 57 is set to 15 mm, the peak value of the beam current of the ion beam 54 incident on the dose Faraday 57 is the current integrator 58. Even if the current is 100% of the range, the average current is (15/300) × 100 = 5 (%), that is, only 5% of the range of the current integrator 57.

If the baseline drift is, for example, 0.1% of the above range, the effect on the current measurement is (0.1 / 5) × 100 = 2 (%) That is, It corresponds to 2%. Furthermore, the influence of noise is also taken into account.

In today's ion implanters, measured value fluctuations of as much as 2% can be said to be too large for differences in injection volume between batches (eg, specifications within 1%).

The ion beam 54 collected by the dose Faraday 57 and measured by the current integrator 58
4 is a signal as shown in FIG. 4, for example, in a normal state in which only the beam current of the incident ion beam 54 is measured. However, the base line drifts as shown in FIG. When a noise signal is generated as shown in (1), the apparent beam current increases.

Conventionally, the control of the ion implantation amount by the implantation controller 59 is performed by the charge amount per one beam scanning measured by the beam current measuring system as described above, so that the drift of the baseline and the noise are controlled. Occurs, control is performed such that the injection dose is smaller than in the normal state. That is, in the above-described conventional ion implantation apparatus, there is a problem that an implantation amount control different from a set implantation dose amount is performed due to an error in a measured value of a beam current due to a baseline drift or noise. Have a point.

The present invention has been made in view of the above, and an object of the present invention is to reduce the influence of baseline drift and noise on the control of the injection amount, thereby achieving an injection dose substantially as set. An ion implantation apparatus capable of performing an ion implantation operation is provided.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an ion implantation apparatus according to the present invention has an ion beam in a first direction.
First direction scanning means for scanning the beam, and irradiation in the second direction
Second direction scanner for scanning an object or an ion beam
A step and an opening are formed, and ions passing through the opening are formed.
An irradiation mask for irradiating only the beam to the irradiation target, a beam current measuring unit for measuring a beam current of the ion beam, and an implantation control unit for controlling an ion implantation amount based on an output from the beam current measuring unit. The following means are taken in the ion implantation apparatus having the above.

That is, the beam current measuring means includes a beam
Provided on the side of the opening in the scanning area
Dose Faraday with a fixed opening and the measurement
A signal indicating the beam current of the ion beam incident on the aperture
And a current integrator that outputs
You. Moreover, the injection control means, i Onbimu is the de
Above definitive at the time of the state that is not incident on the Zufarade
One time based on the output signal of the current integrator
The error value per beam scan is determined. In addition,
During the ion implantation operation.
Then, from the output signal of the current integrator,
The measured value per frame scan is calculated, and the
The amount of ion implantation is controlled based on the correction value obtained by subtracting the error value.

[0017]

According to the above construction, when the ion beam is not incident on the beam collector, for example, before the ion implantation operation, the output signal of the current integrator is output.
The error value per beam scan is calculated based on
It is. That is, the error value, the mosquitoes in the ion implantation operation
Rent integrator output signal
This corresponds to a value obtained by removing the beam current of the ion beam from the measured value per beam scanning, and is a noise level and / or a baseline level caused by noise generated in the beam current measuring means or drift of the baseline.

Here, the above-mentioned dose Faraday is
Is provided on the side of the opening of the
The product occupies a small area with respect to the entire beam scanning area. I
Therefore, small beam measurement range of the beam current measuring means, the ion beam can be measured is slight, the measured beam current value of the beam current measuring means are very not small. Also, do
Of the beam current of the ion beam
The peak value is 10 for the range of the current integrator.
Even at 0%, the average current is, for example,
The area of the measurement aperture is 5% of the entire beam scanning area
And only 5% of the range of the current integrator
Absent. As a result, the measurement beam
The current value is susceptible to noise and baseline drift . However, the control of the injection amount by the injection control unit is performed based on a correction value obtained by subtracting the error value from the measurement value measured by the beam current measurement unit. The effects of noise are reduced.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 3, the ion implantation apparatus of the present embodiment has an ion beam 12 in an X direction (for example, a horizontal direction).
Is electrically scanned by a pair of scanning electrodes 1, and a wafer 6 as an ion irradiation target is mechanically scanned in a Y direction (for example, a vertical direction) orthogonal to the X direction, so-called hybrid scan type. It is.

Although the above-described hybrid scan type ion implantation apparatus is a normal type in which the ion beam 12 is swept in a fan shape, a parallel beam type having a mechanism for parallelizing the ion beam 12 may be used. Good.

As shown in FIG. 2, the ion implantation apparatus ionizes an implantation element and extracts only an ion source section 41 for extracting the ion as an ion beam 12 (see FIGS. 1 and 3), and only predetermined implantation ions. The mass separation unit 42 to be taken out,
A beam line unit 43 including functions of accelerating the ion beam 12 as necessary during transporting the ion beam 12 and shaping, focusing, and scanning the beam shape, and an end station unit 44 for setting the wafer 6 and performing an implantation process. Have been.

The ion source section 41 includes a gas box 45 for supplying an ion source material gas (for example, BF ₃ ), an ion source 40 for ionizing implanted elements, and an extraction power supply 46 for extracting the ion beam 12. Have been. The inside of the ion source 41 is maintained in a vacuum state by an ion source vacuum pump 47. The ion source 40 is, for example, a hot cathode PIG type, has a source magnet, a filament (not shown), an arc electrode, and the like, and generates a plasma by performing an arc discharge triggered by thermionic emission from the filament in the arc chamber. The ion beam 12 is extracted from the ion source 40 to which the extraction voltage is applied from the extraction power supply 46. As the ion source material, not only a gas but also a solid (such as As) can be used. When a solid is used, the solid ion source is evaporated in a solid oven and led to an arc chamber, and the solid ion source is used. Ionize substances.

The mass separation section 42 is provided with a mass analysis magnet. The mass analysis magnet selects necessary ions from the ion beam 12 extracted from the ion source unit 41, and narrows the ion beam 12 to the analysis slit 48 by utilizing the magnetic focusing function to the beam line unit 43. It is leading.

The beam line section 43 includes an accelerating tube 49 for accelerating the ion beam emitted from the analysis slit 48 of the mass separation section 42, an electrostatic lens (triple quadrupole lens) 50 for focusing the ion beam 12, A pair of scanning electrodes 1.1 for scanning the beam 12 in the X direction is provided.
The inside of the beam line unit 43 is maintained in a vacuum state by a beam line unit vacuum pump 55.

A scanning power source (not shown) is connected to the scanning electrodes 1. From this scanning power source, scanning electrodes 1
By applying scanning voltages 180 degrees out of phase to each other, scanning of the ion beam 12 in the X direction is performed as shown in FIG.

In the end station section 44, FIG.
As shown in FIG. 2, a wafer holding member (hereinafter, referred to as a platen) 3 for holding a wafer 6 is provided, and the inside of the end station section 44 is maintained in a vacuum state by an end station section vacuum pump 51. A swing arm 4 shown in FIG. 3 is attached to the platen 3. The platen 3 is driven by the platen drive mechanism 2 (see FIG. 1) and reciprocates in the direction of arrow A to perform scanning in the Y direction.

Further, on the upstream side of the platen 3, FIG.
As shown in FIG. 5, an irradiation mask 5 having an opening 5a having a predetermined area is arranged. Opening 5a of this irradiation mask 5
Are formed in the beam scanning area, and only the ion beam 12 that has passed through the opening 5a is irradiated on the wafer 6 held on the platen 3 behind the ion beam.

The opening 5 in the beam scanning area
On the side of “a”, a dose Faraday 7 as a beam collector for measuring a beam current is provided. In the case of this embodiment, the beam scanning width is 300 mm, the width of the opening 7a of the dose farada 7 is 15 mm, and the area of the opening 7a of the dose farada 7 is about 1/20 of the total beam scanning area. It is getting smaller. The beam current of the ion beam 12 incident on the dose Faraday 7 is input to the current integrator 8.

The current integrator 8 is input from a current-voltage conversion circuit (hereinafter referred to as an I / V circuit) 9 for converting the beam current from the dose Faraday 7 into a voltage signal proportional thereto, and is input from the I / V circuit 9. Also, an OP amplifier 10 that amplifies a voltage signal proportional to the beam current to a signal suitable for an input signal of a subsequent circuit, and a voltage-frequency conversion circuit (hereinafter, V / F) that converts a voltage signal from the OP amplifier 10 into a pulse signal. F circuit 11).

That is, the beam current from the dose Faraday 7 is converted by the current integrator 8 into a pulse signal corresponding to the charge amount per one beam scanning, and is output to the injection controller 13. The dose Faraday 7 and the current integrator 8 constitute a beam current measuring means.

The injection controller 13 includes a CPU, measures a pulse signal input from the current integrator 8 for a predetermined time (for example, about 1 second) when the ion injection operation is not performed, and performs one time. It has an average value of the charge amount per beam scanning to determine the error value C _n. Moreover, the injection controller 13 is not shown region for storing the error value C _n are formed RAM
Has a storage device etc., the error value C _n after the calculation is adapted to store in the storage device.

When the ion implantation operation is being performed, the implantation controller 13 controls the current integrator 8.
A pulse signal corresponding to the charge amount per beam scanning one from once charge per beam scanning of the ion beam 12 which is incident on Dozufarade 7 (hereinafter, referred to as the measured value) determine the C _s.

[0034] In the prior art, the injection controller 13, the control operation of the platen driving mechanism 2 by one beam scanning each of the measured values C _s, the moving speed of the platen 3, i.e. the control of the Y direction scanning speed of the wafer 6 Although so as to perform, in the present embodiment, instead of the measured value C _s, the correction value by subtracting the error value C _n from the measurement values _{C s C s 'C s'} = C s -C n The operation of the platen drive mechanism 2 is controlled using the
Of the Y-direction scanning speed.

Specifically, when the correction value C _s ' decreases, the injection controller 13 slows down the scanning speed in the Y direction by decreasing the swing speed of the swing arm 4 (see FIG. 3) in proportion thereto. if increasing the correction value C _s' Conversely, it controls to a faster swing speed of the swing arm 4 in proportion to speed up the Y-direction scanning speed.

In the above configuration, the ion implantation operation of the ion implantation apparatus will be described below.

[0037] First, before the ion implantation operation is performed by the injection controller 13, a pulse signal inputted from the current integrator 8 is a predetermined measuring time, the error value C _n is determined. At this time, the injection controller 13 stores the error value C _n in the storage device. In this case, the pulse signal input from the current integrator 8 is due to a baseline drift or a noise signal. That is, the error value C _n is the average value of the baseline level and / or noise level per one beam scanning. Usually, baseline levels and noise levels are low, performs a long time (for example, about 1 second) measurement, calculate an average value per one beam scanning as an error value C _n.

It should be noted, may be set to range error value C _n, if the error value C _n exceeds this range, it is also possible that following injection operation over interlock keep the not performed is there.

Then, after the operation for determining the error value C _n is completed, the ion implantation operation is started.

That is, as shown in FIG.
The ion beam 12 is extracted from the ion source 40, and after only predetermined ions are selected by the mass separation unit 42, accelerated by the acceleration tube 49 of the beam line unit 43 and shaped into a sharp beam by the electrostatic lens 50. , As shown in FIG.
Scanning is performed in the X direction by the scanning electrodes 1.1 to which scanning voltages 180 degrees out of phase from each other are applied from a scanning power supply.

Then, the ion beam 12 scanned in the X direction passes through the opening 5a of the irradiation mask 5 and irradiates the wafer 6 held on the platen 3 behind it, and the side of the opening 5a. Is incident on the dose Faraday 7 provided at the first position.

On the other hand, the platen 3 on which the wafer 6 is set
Is driven by the platen driving mechanism 2 and scanned in the Y direction. Thus, the entire surface of the wafer 6 is irradiated with the ion beam 12.

During the ion implantation operation, the beam current of the ion beam 12 incident on the dose Faraday 7 is converted by the current integrator 8 into a pulse signal corresponding to the amount of electric charge for each beam scanning, and the implantation controller 13 Is input to

The injection controller 13, the error value C stored sequentially indexing the measured value C _s of once per beam scanning from the pulse signal output from the current integrator 8, a further beam current value C _s in the storage device by subtracting the _n correction values C _s' an operation for obtaining a (= C _s -C _n) performed for every one beam scanning. Then, the injection controller 13 controls the operation of the platen driving mechanism 2 for each beam scan based on the correction value C _s ' thus obtained, and controls the swing of the swing arm 4 (see FIG. 3). The speed, that is, the scanning speed of the wafer 6 in the Y direction is controlled. By controlling the Y-direction scanning speed, the amount of ions implanted into the wafer 6 can be made uniform.

The area of the opening 7a of the dose Faraday 7 has a small occupied area ratio (for example, about 1/20) with respect to the entire beam scanning area, so that the ion beam 12 incident on the dose Faraday 7 is small. For this reason, the measured beam current value is very small and easily affected by noise and baseline drift. However, in the present embodiment, the control of the injection amount by the injection controller 13 is performed by controlling the error value C before the injection operation. _n , that is, based on the correction value C _s ′ obtained by subtracting the baseline level and / or the noise level from the measured value C _s , the influence of the baseline drift and noise is small, and the injection dose is substantially set. An ion implantation operation can be performed depending on the amount.

[0046] In this embodiment, although measured the error value C _n before injection operation, during the injection operation, timely (a state where the ion beam 12 to Dozufarade 7 does not enter)
Such a configuration may be adopted.

Incidentally, in an ion implantation apparatus of a type in which the measured beam current by Faraday is relatively large, such as when the entire platen serves as a beam current measuring section (Faraday), the signal of the measured beam current and the base drift Since the S / N ratio with the level and / or the noise level is large, the effect is smaller than that of the above embodiment. However, even in such an ion implantation apparatus, when the beam current of the ion beam is small and the S / N ratio is relatively small, the effect can be sufficiently expected by applying the present invention.

Further, since the present embodiment describes the hybrid scan type ion implantation apparatus, the implantation controller 13 as the implantation control means controls the swing speed of the swing arm 4 (see FIG. 3). However, for example, in a beam scanning type ion implantation apparatus that electrostatically scans the ion beam 12 in both the X and Y directions with a high frequency voltage, the implantation control means controls the scanning voltage and the implantation time to reduce the implantation amount. Perform control.

Of course, the present invention may be applied to a parallel type ion implantation apparatus in which the ion beam 12 is made parallel and implanted substantially perpendicularly to the wafer 6.

[0050]

As described above, according to the ion implantation apparatus of the present invention, the beam current measuring means is provided beside the opening of the irradiation mask.
Dose fara provided on the side and formed with a measurement opening
And the beam of the ion beam incident on the measurement aperture.
Current integrator that outputs a signal indicating the current
Doo is provided, the injection control means, the ion beam is the de
Above definitive at the time of the state that is not incident on the Zufarade
One time based on the output signal of the current integrator
Calculate the error value per beam scanning and ion injection.
During the input operation, the current
Measured value per beam scan from the output signal of the grater
And based on the correction value obtained by subtracting the error value from the measured value , control the scanning speed of the second direction scanning means.
This is a configuration for controlling the amount of ion implantation.

Therefore, the dose of the beam current measuring means
Arade is provided on the side of the opening of the irradiation mask,
Even if the measured beam current value of the beam current measuring means is easily affected by noise and baseline drift,
Baseline drift and noise effects on injection volume control
And the ion implantation operation can be performed with a substantially set implantation dose.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a schematic configuration diagram illustrating a main part of an ion implantation apparatus.

FIG. 2 is a schematic overall configuration diagram showing an example of the configuration of the ion implantation apparatus.

FIG. 3 shows the X of the ion beam in the ion implantation apparatus.
FIG. 4 is a schematic explanatory view showing scanning in a direction and scanning in the Y direction of a wafer.

FIG. 4 is an explanatory diagram showing a beam current signal of an ion beam measured by a current integrator.

FIG. 5 is an explanatory diagram showing the beam current signal in a state where the baseline has drifted.

FIG. 6 is an explanatory diagram showing the beam current signal accompanied by noise.

FIG. 7 shows a conventional example, and is a schematic configuration diagram showing a main part of an ion implantation apparatus.

[Explanation of symbols]

1 scan electrode (a first direction scan means) 2 platen driving mechanism (the second direction scan means) 3 platen 5 irradiated mask 5a opening 6 wafer (irradiation target) 7 Dozufarade (bi chromatography beam current measuring means) 7a opening ( Measurement opening) 8 Current integrator (beam current measuring means) 12 Ion beam 13 Injection controller (injection control means)

Claims (1)

(57) [Claims] A first direction for scanning an ion beam in a first direction;
Direction scanning means, an irradiation object or ion beam in a second direction.
A second direction scanning means for scanning the beam, and an opening formed therein.
Only the ion beam that has passed through the aperture
An ion implantation apparatus having an irradiation mask for irradiating an object, a beam current measurement unit for measuring a beam current of an ion beam, and an implantation control unit for controlling an ion implantation amount based on an output from the beam current measurement unit. The beam current measuring means is provided in the beam scanning area.
Is provided on the side of the opening, and a measurement opening is formed.
Dose Faraday and incident on the measurement aperture
Karen that outputs a signal indicating the beam current of the ion beam
Doo integrator and is provided, the injection control means, i Onbimu the above Dozufara
Definitive at the time of the state that are not incident to de above Karentoi
One beam scan based on the output signal of the integrator
Calculate the error value per hit, and during the ion implantation operation,
Each time the beam is scanned, the current integrator
Determining the measured value per beam scan from the output signal
Controlling the scanning speed of the second direction scanning means to control the ion implantation amount based on a correction value obtained by subtracting the error value from the measured value. apparatus.