JPH0547341A - Ion implanter - Google Patents

Abstract

PURPOSE:To perform an ion implantation action with nearly the preset dose quantity even if there is a difference between the beam current measured by a dose faraday and the beam current of an ion beam actually radiated to a wafer. CONSTITUTION:The beam current of an ion beam 12 is measured by a dose faraday 7 located outside the orbit of the ion beam 12 radiated to a wafer 6 during an implantation action, and the moving speed of the wafer 6 is controlled by an implantation controller 13 based on the measured result. During the control of the moving speed of the wafer 6, i.e., the control of the implantation quantity, the dose correction coefficient is determined from the measured result by a back faraday 14 located on the orbit of the ion beam 12 actually radiated to the wafer 6 and the measured result by the dose faraday 7, and the ion implantation quantity is corrected via the dose correction coefficient.

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 object to be ion-irradiated such as a wafer, and more particularly to ion implantation for measuring an ion beam beam current to control an ion implantation amount. It relates to the device.

[0002]

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

As shown in FIGS. 5 and 6, the ion implanter is designed to handle a large ion irradiation target (for example, an 8-inch wafer), as shown in FIGS.
Ion beam 5 in X direction (for example, horizontal direction) by 51
There is a so-called hybrid scan type that electrically scans 4 and mechanically scans the ion irradiation target 56 in the Y direction (eg, vertical direction) orthogonal to the X direction.

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

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

In the ion implantation apparatus, the beam current of the ion beam 54 is measured, and the ion implantation amount is controlled based on the measurement result. In the above hybrid scan type ion implanter, the dose Farade 5 is usually placed outside the orbit of the ion beam 54 for irradiating the ion irradiation target 56.
7 is provided, and the beam current is measured by this dose Faraday 57.

The beam current of the ion beam 54 incident on the dose Farade 57 is integrated by the current integrator 58, converted into a pulse signal corresponding to the amount of electric charge per unit time (for example, per one beam scanning), and then injected. It is output to the controller 59.

The implantation controller 59 drives the holding member so that ions are implanted at a preset dose amount set by the operation of the input key 60 based on the pulse signal corresponding to the charge amount per unit time. The movement of the holding member 53, that is, the scanning speed of the ion irradiation target 56 in the Y direction is controlled by controlling the operation of the mechanism 52. By controlling the Y-direction scanning speed, the amount of ion implantation into the ion irradiation target 56 is controlled.

[0009]

When the ion implantation operation is performed with the above-described configuration, the beam current measured by the dose Farade 57 is not the ion beam actually irradiated on the ion irradiation target 56. There is a possibility that a difference occurs between the beam current measured by the dose Faraday 57 and the beam current of the ion beam that is actually irradiated on the ion irradiation target 56.

In particular, in today's ion implanters, which are required to improve the uniformity of implantation, the uniformity of implantation may be improved by shaping the waveform of the scanning voltage applied to the scanning electrodes 51, 51. When such a correction operation is performed, conditions such as the influence of fringing (a phenomenon in which an electric field that is substantially parallel in the central portion in the electric field between the scanning electrodes 51, 51 is deflected as it approaches the scanning electrodes 51, 51), etc. Changes, and the path of the ion beam 54 changes accordingly. Therefore, the ratio of the beam current measured by the dose Farade 57 to the beam current of the ion beam actually irradiated on the ion irradiation target 56 is several percent. There may be differences in degree.

Conventionally, the control of the ion implantation amount by the implantation controller 59 is performed based on the beam current measured by the dose Farade 57 as described above. Therefore, due to the error of the beam current measured by the dose Farade 57, There is a problem that the implantation dose is controlled differently from the set dose amount.

The present invention has been made in view of the above, and an object thereof is to provide an ion implantation apparatus which can perform an ion implantation operation with a dose amount which is set substantially.

[0013]

In order to solve the above-mentioned problems, the ion implantation apparatus of the present invention is provided with a beam current measuring section outside the trajectory of an ion beam for irradiating an ion irradiation target. The following measures are taken in an ion implantation apparatus in which the amount of ion implantation is controlled so that a preset dose amount is achieved based on the measurement result of the beam current by the measuring unit.

That is, the second beam current measuring unit is provided on the trajectory of the ion beam for irradiating the ion irradiation target, and based on the measurement result of the beam current by the beam current measuring unit and the second beam current measuring unit. The amount of ion implantation is corrected.

[0015]

According to the above structure, the ion implantation amount is controlled based on the measurement result of the beam current measured by the beam current measuring unit provided outside the trajectory of the ion beam for irradiating the ion irradiation target. Be seen.

For this reason, if there is a difference between the beam current measured by the beam current measuring unit and the beam current of the ion beam that is actually irradiated on the ion irradiation target, the setting dose set in advance is left as it is. Although the injection amount is controlled differently from the amount, according to the above configuration,
A second beam current measuring unit is provided on the trajectory of the ion beam that is actually irradiated to the ion irradiation target. The measurement result by the second beam current measuring unit and the measurement result by the beam current measuring unit are Since the comparison is made and the ion implantation amount is corrected on the basis of these measurement results, the ion implantation operation is performed substantially at the set dose amount.

[0017]

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

As shown in FIG. 4, the ion implantation system of this embodiment uses an ion beam 12 with a pair of scanning electrodes 1.1.
Of the so-called hybrid scan type that electrically scans the wafer in the X direction (for example, the horizontal direction) and mechanically scans the wafer 6 as the ion irradiation target in the Y direction (for example, the vertical direction) orthogonal to the X direction. Is.

The hybrid type ion implanter is a normal type which sweeps the ion beam 12 in a fan shape, but it may be a parallel beam type having a mechanism for making the ion beam 12 parallel. ..

As shown in FIG. 3, this ion implanter comprises an ion source 41 for ionizing an implanted element and extracting it as an ion beam 12, a mass separator 42 for extracting only selected implanted ions, and an ion beam. The beam line unit 43 includes a function of accelerating the ion beam 12 during transportation of 12 to shape, focus, and scan the beam shape, and an end station unit 44 that sets the wafer 6 and performs implantation processing. There is.

The ion source section 41 is provided with a gas box 45 for supplying an ion source substance gas (for example, BF ₃ etc.), an ion source 40 for ionizing the implanted elements, and an extraction power source 46 for extracting the ion beam 12. Has been.
Further, the inside of the ion source unit 41 is kept in a vacuum state by an ion source unit 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, etc., and generates plasma by performing arc discharge with thermionic emission from the filament as a trigger in the arc chamber, and the extraction power source 46 The ion beam 12 is extracted from the ion source 40 to which the extraction voltage is applied. As the ion source material, not only gas but also solid (As etc.) can be used. When solid is used,
The solid ion source material is evaporated in a solid oven and introduced into an arc chamber to ionize the solid ion source material.

The mass separation section 42 is equipped with a mass analysis magnet. This mass analysis magnet selects necessary ions from the ion beam 12 extracted from the ion source unit 41, narrows the ion beam 12 to the analysis slit 48 by utilizing the magnetic focusing action, and directs it to the beam line unit 43. It is designed to guide you.

In the beam line section 43, an acceleration 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, and ions. A pair of scan electrodes 1.1 for scanning the beam 12 in the X direction is provided.
The inside of the beam line unit 43 is kept in a vacuum state by the beam line unit vacuum pump 55.

A scanning power source (not shown) is connected to the scanning electrodes 1.1. From this scanning power supply, scan electrode 1
By applying the scan voltages having the phases different from each other by 180 degrees, the ion beam 12 is scanned in the X direction as shown in FIG.

The end station section 44 is shown in FIG.
As shown in FIG. 3, a wafer holding member (hereinafter referred to as a platen) 3 for holding the wafer 6 is provided, and the inside of the end station section 44 is kept in a vacuum state by the end station section vacuum pump 51. Platen 3 above
1 is driven by the platen drive mechanism 2 to move in the Y direction, as shown in FIG.

In addition, on the upstream side of the platen 3 shown in FIG.
Further, as shown in FIG. 2, an irradiation mask 5 having an opening 5a having a predetermined area is arranged. The opening 5a of the irradiation mask 5 is formed in the beam scanning region, and the opening 5a is formed.
Only the ion beam 12 that has passed through is irradiated onto the wafer 6 held by the platen 3 behind it.

The opening 5 in the beam scanning area
An opening 5b is provided in parallel on the side of a, and the opening 5b
Doose Farade 7 as a beam current measuring unit is behind
Is provided. The beam current of the ion beam 12 incident on the dose Faraday 7 is changed by the connection switching unit 15
Is input to the current integrator 8 via.

The downstream side of the platen 3 (wafer 6
A back Faraday 14 as a second beam current measuring unit is provided on the orbit of the ion beam irradiated to the.

When the platen 3 which moves in the Y direction by the platen drive mechanism 2 is out of the beam orbit, the back farade 14 is of a size that can receive the ion beam 12 that has been irradiated on the platen 3 up to that point. ing. The beam current of the ion beam 12 incident on the back Faraday 14 is input to the current integrator 8 via the connection switcher 15.

The current integrator 8 is a current-voltage conversion circuit (hereinafter referred to as an I / V circuit) 9 for converting the beam current from the dose farade 7 or the back farade 14 into a voltage signal proportional thereto, and an I / V circuit 9 OP amplifier 10 that amplifies a voltage signal, which is input from, and is proportional to the beam current, into a signal suitable for an input signal of a subsequent circuit.
And a voltage-frequency conversion circuit (hereinafter referred to as a V / F circuit) 11 that converts the voltage signal from the OP amplifier 10 into a pulse signal.

That is, the beam current input to the current integrator 8 from the dose farade 7 or the back farade 14 via the connection switch 15 is converted by the current integrator 8 into a pulse signal corresponding to the amount of beam current, and the implantation controller 13 is operated. Is output to.

The connection switching device 15 is composed of the dose Faraday 7 or the back Faraday 14 and the injection controller 13.
It is for switching the connection with the injection controller 13. When one is connected to the injection controller 13, the other is grounded. The operation of the connection switcher 15 is controlled by the injection controller 13.

In this embodiment, the connection switching device 15 is provided in front of the current integrator 8. However, one switch is provided for each of the dose farade 7 and the back farade 14, and the pulse output thereof is switched to switch the injection controller 13. Of course, it may be input to.

The ion implanter is also provided with an input key 16 for setting a dose amount to be implanted in the wafer 6, and the dose amount set by operating the input key 16 is output to the implantation controller 13. To be done.

The implantation controller 13 is provided with a CPU, and based on the beam current amount calculated from the ion beam 12 incident on the dose farade 7 and the back farade 14 before the start of the ion implantation operation, a dose correction coefficient described later is obtained. K and the internally set dose amount C _d ′ are calculated. Further, during the ion implantation operation, the implantation controller 13 is based on the beam current amount calculated from the ion beam 12 incident on the dose Faraday 7 and performs the ion implantation according to the set dose amount set by the operation of the input key 16. The operation of the platen drive mechanism 2 is controlled so that the implantation is performed, and the moving speed of the platen 3, that is, the Y-direction scanning speed of the wafer 6 is controlled.

In the above configuration, the beam current amount calculated from the beam current of the ion beam 12 incident on the dose Faraday 7 is C _d , and the beam current amount calculated from the beam current of the ion beam 12 incident on the back Faraday 14 C _b , the opening area of the dose Farade 7 is S _d ,
When the opening area of the back farade 14 is S _b , the amount of current per unit area of each farade is C _b / S _{d in the} dose farade 7 and C _b / S _{b in the back} farade 14. The above S _d and S _b are structurally determined and are known values.

The wafer 6 is proportional to the amount of current per unit area of the ion beam 12 incident on the back-farade 14.
Since ions are implanted on the upper side, if the set dose amount set by the operation of the input key 16 is D _t and the dose amount actually implanted on the wafer 6 by the implantation operation is D _w , D _w = D _t (C _b / S _b ) / (C _d / S _d ) = D _t (C
_b / C _d ) (S _d / S _b ) ... (1)

In the above equation (1), C _d / S _d = C _b /
If S _b , that is, (C _b / C _d ) (S _d / S _b ) = 1, D _w = D _t , that is, the dose actually implanted on the wafer 6 by the set dose amount and the implantation operation. The amount is the same. However, in reality, (C _b / C _d ) (S _d / S _b ) ≠
In most cases, 1 and D _w ≠ D _t .

In the present invention, C _d and C _b are obtained before the ion implantation operation is performed, and the dose correction coefficient K is obtained by the following equation (2).

K = (C _b / C _d ) (S _d / S _b ) ... (2) Here, the internally set dose amount D _t ′ used when controlling the actual implantation amount is D _t ′ = KD _{Assuming t} ... (3), if the implantation amount is controlled by the internally set dose amount D _t ′, the dose amount D _w implanted into the wafer 6 is D _w = D _t ′ (C _b / S _b ) / (C _d / S _d ) D _t ′ = KD _t , D _w = KD _t (C _b / S _b ) / (C _d / S _d ) = (C _b
/ C _d ) (S _d / S _b ) D _t (C _b / S _b ) / (C _d /
S _d ) = D _t . That is, by performing the implantation amount control using the internally set dose amount D _t ′ obtained by multiplying the set dose amount D _t by the dose correction coefficient K, the dose amount D _w actually implanted on the wafer 6 is determined by the input key. The set dose amount D _t set in 16 is obtained.

Here, the ion implantation operation of the above ion implantation apparatus will be described.

First, before the ion implantation operation is performed, the ion beam 12 is scanned in the X direction while the platen 3 is stopped at a position deviated from the beam trajectory.

At this time, the injection controller 13 controls the operation of the connection switching device 15 to alternately switch the connection between the dose farade 7 or back farade 14 and the current integrator 8.

When the dose dose Faraday 7 and the current integrator 8 are connected, the dose dose Faraday 7
The beam current of the ion beam 12 incident on is converted into a pulse signal corresponding to the beam current amount C _d by the current integrator 8 and output to the implantation controller 13.

When the back Faraday 14 and the current integrator 8 are in a connected state, the beam current of the ion beam 12 incident on the back Faraday 14 is also the beam current amount C _b by the current integrator 8.
Is converted into a pulse signal corresponding to the injection controller 1
3 is output.

The implantation controller 13 calculates the dose correction coefficient K by performing the calculation shown in the above equation (2) from the pulse signals corresponding to the beam current amount C _d and the beam current amount C _b . Further, the implantation controller 13 performs the calculation shown in the above equation (3) from the obtained dose correction coefficient K to determine the internally set dose amount D _t ′. Also, 'After the calculation, the injection controller 13, a storage device such as a RAM (not shown) is built, the internal set dose D _t' internally set dose D _t is adapted to store.

Then, the ion implantation operation is started after the operation of calculating the internally set dose amount D _t ′ is completed.

That is, as shown in FIG.
The ion beam 12 extracted from the ion source 40 of FIG. 1 is selected by the mass separation unit 42 and then accelerated by the acceleration tube 49 of the beam line unit 43 and shaped into a sharp beam by the electrostatic lens 50. , A scanning electrode 1 to which scanning voltages having phases different from each other by 180 degrees are applied from a scanning power source
・ 1 scans in the X direction.

Then, as shown in FIGS. 1 and 2, the ion beam 12 scanned in the X direction passes through the opening 5a of the irradiation mask 5 and the wafer 6 held on the platen 3 behind it. While being irradiated, it passes through the openings 5b arranged side by side to the openings 5a and is incident on the dose farade 7 behind the openings 5b.

On the other hand, the platen 3 on which the wafer 6 is set
Are driven by the platen drive mechanism 2 and scanned in the Y direction. As a result, the entire surface of the wafer 6 is irradiated with the ion beam 12.

After the operation for calculating the internally set dose amount D _t ′ is completed, the connection switching device 15 is switched to the connection between the dose farade 7 and the current integrator 8 by the injection controller 13. That is, during the ion implantation operation, only the beam current of the ion beam 12 incident on the dose Faraday 7 is applied to the current integrator 8.
Entered in. Then, the beam current from the dose Faraday 7 is converted into a pulse signal corresponding to the beam current amount C _d by the current integrator 8 and output to the implantation controller 13.

The implantation controller 13 calculates the moving speed of the platen 3 by performing a predetermined calculation using the beam current amount C _d obtained from the current integrator 8 per unit time and the above-mentioned internally set dose amount D _t ′. , And controls the operation of the platen drive mechanism 2.

In this embodiment, the set dose amount D _t is corrected by multiplying the obtained dose correction coefficient K by the set dose amount D _t , and as a result, the injection amount is corrected. , The obtained dose correction coefficient K is the beam current amount C _d obtained from the current integrator 8 every unit time.
Even if the beam current amount C _d is corrected by
Similarly, the injection amount can be corrected.

In the present embodiment, the dose correction coefficient K is calculated before the injection operation is started, but the dose correction coefficient K may be calculated during the injection operation. In this case, the connection switching device 15 may perform the connection switching operation when the platen 3 reaches a position deviated from the beam trajectory.

[0055]

As described above, according to the ion implantation apparatus of the present invention, the second beam current measuring unit is provided on the trajectory of the ion beam for irradiating the ion irradiation target, and the ion beam for irradiating the ion irradiation target is provided. The ion implantation dose is corrected based on the measurement result of the beam current by the beam current measuring unit provided outside the orbit and the second beam current measuring unit.

Therefore, even if there is a difference between the beam current measured by the beam current measuring unit and the beam current of the ion beam that is actually irradiated on the ion irradiation target, the dose amount will be approximately set. The effect that the ion implantation operation can be performed is achieved.

[Brief description of drawings]

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

FIG. 2 is a schematic explanatory diagram illustrating the arrangement of the main parts when the ion implantation apparatus is viewed from above.

FIG. 3 is a schematic overall configuration diagram showing an example of a configuration of the ion implantation apparatus.

FIG. 4 is an X of an ion beam in the above-mentioned ion implantation apparatus
FIG. 3 is a schematic explanatory diagram showing scanning in a direction and scanning in a Y direction on a wafer.

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

FIG. 6 is a schematic explanatory diagram illustrating the arrangement of the main parts when the ion implantation apparatus is viewed from above.

[Explanation of Codes] 1 Scanning Electrode 2 Platen Driving Mechanism 3 Platen 6 Wafer 7 Dose Farade (Beam Current Measuring Unit) 8 Current Integrator 12 Ion Beam 13 Implantation Controller 14 Back Farade (Second Beam Current Measuring Unit) 15 Connection Switcher

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/265

Claims (1)

[Claims] 1. A beam current measuring unit is provided outside the trajectory of an ion beam for irradiating an ion irradiation target, and a preset dose amount is set based on a measurement result of the beam current by the beam current measuring unit. In the ion implantation apparatus in which the ion implantation amount is controlled so that the second beam current measuring unit is provided on the trajectory of the ion beam for irradiating the ion irradiation target, the beam current measuring unit and the second beam current measuring unit are provided. An ion implantation apparatus, wherein an ion implantation amount is corrected based on a measurement result of a beam current by the section.