JP3257205B2 - 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 implanter for uniformly implanting impurity ions into an object to be irradiated with ions, such as a semiconductor wafer, and more particularly, to an ion implanter for measuring the beam current of an ion beam to control the amount of ion implantation. It relates to an injection 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 as necessary, 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.

As shown in FIG. 9, a spot-shaped ion beam 50 is applied to a first scanning electrode 51 in the ion implantation apparatus.
A holding member 54 holding a wafer 53 as a beam irradiation target while electrostatically scanning in the X direction (for example, the horizontal direction) by the 51 and the second scanning electrodes 52;
There is a so-called hybrid scan type that mechanically drives in a Y direction (for example, a vertical direction) orthogonal to the X direction.

In the above-described hybrid scan type ion implantation apparatus, the wafer 53 is held at the implantation position by the holding member 5.
In the state where the ion beam 50 is held, the holding member driving mechanism 55 is driven to reciprocate in the Y direction so as to cross the irradiation range of the ion beam 50. As shown in FIG. 10, a mask 56 having a slit-shaped opening 56a is arranged on the upstream side of the holding member 54. The opening 56a of the mask 56 is formed in the beam scanning direction in the beam scanning area, and only the ion beam 50 that has passed through the opening 56a is irradiated on the wafer 53 held by the holding member 54 behind the opening 56a. It has become.

In the ion implantation apparatus, the beam current of the ion beam 50 is measured during the implantation process in order to uniformly implant the ions into the wafer 53 and to control the implantation amount to a specified value, and the ion implantation amount (dose amount) is measured. ) Need to be counted. In the above-described hybrid scan type ion implantation apparatus, the beam current flowing into the wafer 53 held by the holding member 54 cannot be directly measured.
In the vicinity of the holding member 54 in the beam scanning range (on the side of the opening 56a of the mask 56), a Faraday cup (hereinafter, referred to as dose Farade) 57 for measuring a beam current is provided.
The beam current measuring circuit 59 measures the current of the ion beam 50 incident on the dose Faraday 57. In addition, this dose Farade 57
Is used not only for measuring the beam current but also for confirming the overscan of the ion beam 50.

Since the dose Faraday 57 does not measure the ion beam 50 actually implanted in the wafer 53, the current of the ion beam 50 actually implanted in the wafer 53 and the dose Faraday 57 are used. Does not match the measured beam current. For this reason, if the injection amount is controlled using the measured value of the beam current by the dose Faraday 57 as it is, the dose amount will not be as set.

In order to correct the measurement error caused by the dose Faraday 57, as shown in FIG. 11, a back Faraday 58 having a configuration in which a plurality of Faraday cups are densely arranged in parallel in the beam scanning direction is provided behind the injection position. Provided. That is, if the holding member 54 is made to stand by outside the beam irradiation area, the ion beam 50 to be actually implanted into the wafer 53 is incident on the back Faraday 58. Therefore, the beam current is measured by the dose Farade 57 and the back Faraday 58. By comparing the values, Dose Farade 57
Can correct the measurement error.

More specifically, prior to the start of the implantation process, the ion beam 50 is scanned in the same manner as during the implantation process, and the ratio of the inflow beam current densities of the dose Faraday 57 and the back Faraday 58 is measured to correct the dose. A “dose correction coefficient” is obtained, and during the injection process, the above “dose correction coefficient”
Based on the value obtained by multiplying the dose and the set dose, and the measured value of the beam current flowing into the dose Faraday 57 during the injection, the injection controller 60 shown in FIG. 10 controls the injection amount to a specified value. Has become.

[0009]

Conventionally, only the above-described dose amount correcting operation is performed before the start of the implantation process.
Until the implantation conditions are changed, including during the implantation process, no confirmation of the beam state other than the change in the beam amount is performed.
That is, since the beam current is measured by the dose Faraday 57 during the implantation process, if the beam current fluctuates greatly, it is possible to detect the beam current. No change in beam state can be detected.

There are various causes for the above-mentioned beam drift. One of the causes is that an extraction electrode for extracting ions as a beam from plasma formed by an ion source thermally expands with time. The extraction electrode has an electrode slit through which the ion beam passes, but the ion beam hits the extraction electrode, the temperature of the electrode rises, thermally expands, and the position of the electrode slit is changed from the start of operation. Also changes slightly. Another cause is that the magnet current slightly changes due to a rise in the temperature of the power supply unit and the magnet coil unit of the electromagnet (analysis magnet) that performs a mass analysis by forming a predetermined deflection magnetic field in the path of the ion beam extracted from the ion source. However, the magnetic flux density of the deflection magnetic field changes.

As described above, when the position of the electrode slit or the magnetic flux density of the deflecting magnetic field changes, the beam trajectory shifts. An analysis slit that allows only desired ions to pass is provided behind the exit of the analysis magnet. However, even if a slight deviation occurs in the beam trajectory, the beam must pass through the analysis slit if it is within the allowable range. Can. When the trajectory of the beam shifts as described above, the entry position of the spot-shaped ion beam 50 into the scanning unit is shifted from the center position between the first scanning electrodes 51, as shown by the two-dot chain line in FIG. Will be. For this reason, the beam scanning width does not change, but the beam scanning area shifts by an amount corresponding to the deviation of the beam trajectory.

As described above, when the beam scanning area changes due to the beam drift during the implantation process, the beam current density flowing into the dose Faraday 57 and the current density of the ion beam 50 actually implanted into the wafer 53 (ie, the back Faraday In general, the ratio of the "dose correction coefficient" to the "dose correction coefficient" also needs to be updated. However, conventionally,
Since it is not possible to detect that beam drift has occurred,
"Dose correction coefficient" obtained for a beam that scans a predetermined scanning area before implantation processing even if beam drift occurs
Is used to control the injection amount. Normally, the "dose correction coefficient" is not recalculated until the injection conditions are changed.

As described above, conventionally, if a beam drift occurs, there is a high possibility that the injection amount is controlled using an erroneous “dose correction coefficient”. However, there is a problem that the injection reproducibility is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to detect the occurrence of a beam drift which has been impossible to detect in the past to prevent the deterioration of injection reproducibility caused by the beam drift. It is an object of the present invention to provide an ion implantation apparatus that can prevent the ion implantation.

[0015]

According to the present invention, there is provided an ion implantation apparatus including beam scanning means for scanning an ion beam.
The ion irradiation is performed by irradiating the beam irradiation object with the beam while scanning the ion beam, and in order to solve the above problem, the following means are taken. is there.

That is, the ion implantation apparatus includes a plurality of beam measuring units (for example, Faraday cups) installed in a beam scanning area, and a beam for individually measuring a beam current flowing into each of the plurality of beam measuring units. Current measuring means and a ratio of each beam current density based on a measured value of a beam current flowing into each of the plurality of beam measuring units is determined, and whether or not a beam drift has occurred is detected from a change in the ratio during the implantation process. Beam drift detecting means.

[0017]

According to the above arrangement, during the injection process, continuously,
Beam currents (beam amounts) flowing into a plurality of beam measuring units provided in the beam scanning area are individually measured by the beam current measuring means, and the ratio of the beam current densities is checked by the beam drift detecting means.

Since the ion beam has a different beam shape and scanning speed depending on the position in the beam scanning region, the beam amount (the amount of beam flowing into the unit area per unit time per unit time) depends on the position in the beam scanning region. Is different. For this reason, when the beam scanning area shifts due to the beam drift, the beam current flowing into each beam measurement unit changes, and as a result, the ratio of the beam current flowing into each beam measurement unit also changes. If the beam drift does not occur, the ratio of the beam current flowing into each beam measuring unit hardly changes due to the fluctuation of the beam amount in a certain range of the ion beam itself.

Therefore, by checking the ratio of the beam current flowing into each beam measuring unit during the implantation process as in the above configuration, it is possible to detect the beam drift which could not be detected conventionally, The deterioration of the injection reproducibility due to the above can be prevented beforehand.

[0020]

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

As shown in FIG. 9, the ion implantation apparatus according to this embodiment applies a spot-shaped ion beam 50 to the X-ray beam by the first scanning electrodes 1a and 1b and the second scanning electrodes 2a and 2b as scanning means. A parallel beam method in which electrostatically parallel scanning (parallel scanning) is performed in a direction (for example, horizontal direction) and a wafer 10 as an ion irradiation target is mechanically driven in a Y direction (for example, vertical direction) orthogonal to the X direction. Is a hybrid scan type.

As shown in FIG. 1, the above-described ion implantation apparatus includes a first scan electrode 1a, 1b and a second scan electrode 2a,
2b is provided with a scanning power supply for applying a substantially triangular scanning voltage. The scanning power supply includes a waveform controller 5 for generating a signal corresponding to a substantially triangular scanning voltage waveform, and high voltage amplifiers 6 and 7 for outputting scanning voltages of opposite polarities in accordance with a signal from the waveform controller 5. Have.

As shown in FIG. 3, the waveform controller 5 includes a CPU (Central Processing Unit) 5a, a memory 5b, and a digital / analog conversion unit (hereinafter, D / A / D converter).
(Referred to as part A) 5c, and scan voltage waveform data is stored in the memory 5b. In the waveform controller 5, the CPU 5a reads out the scanning voltage waveform data from the memory 5b, and the D / A unit converts the scanning voltage waveform data into an analog amount and outputs the analog amount to the high-voltage amplifiers 6 and 7. I have.

The first scanning electrodes 1a and 1b and the second scanning electrodes 2a and 2b are arranged to face each other in parallel, and the gap between the first scanning electrodes 1a and 1b, their electrode length, Of the second scanning electrode 2a
-It is comprised so that the ratio of the gap between 2b and their electrode length may substantially correspond.

A substantially triangular-wave scanning voltage having a phase difference of 180 degrees from the scanning power source is applied to each of the first scanning electrodes 1a and 1b, and each of the second scanning electrodes 2a and 2b is applied to the first scanning electrodes 1a and 1b. Also, a substantially triangular scan voltage having a phase difference of 180 degrees from the scan power supply is applied to the scan voltage. And
The same scan voltage is applied to the first scan electrode 1a and the second scan electrode 2b, and the same scan voltage is applied to the first scan electrode 1b and the second scan electrode 2a. This allows
The spot-shaped ion beam 50 passing substantially at the center between the first scanning electrodes 1a and 1b becomes a fan-shaped scanning beam by an electric field formed between the first scanning electrodes 1a and 1b, and thereafter, the second scanning electrode A parallel beam is formed by the electric field formed between 2a and 2b.

As shown in FIG. 9, the first scanning electrode 1a
Deflection electrodes 3.3 for deflecting the ion beam 50 by a required angle in the Y direction are provided between the installation location of 1b and the installation locations of the second scanning electrodes 2a and 2b.

As shown in FIG. 1, the second scanning electrode 2a
A mask 8 having a slit-shaped opening 8a is arranged behind 2b. The opening 8a of the mask 8
Only the ion beam 50 formed in the beam scanning area and passing through the opening 8a is irradiated on the wafer 10 held by the holding member 9 behind it.

As shown in FIG. 9, the holding member 9 is driven by a holding member drive mechanism 23, and reciprocates in the Y direction so as to cross the irradiation range of the ion beam 50.

As shown in FIG. 1, on both sides of the opening 8a in the mask 8, an ion beam 50 is applied to two Faraday cups of a dose farad (beam measuring unit) 11 and a beam farad (beam measuring unit) 12. Openings 8b and 8c for incidence are formed, respectively, and behind each of the openings 8b and 8c, a dose farad 11 and a beam farad 12 having the same structure are respectively installed.

The above-described dose Faraday 11 is conventionally used for calculating a dose correction coefficient, counting the dose during implantation, and confirming overscan of the ion beam 50. In addition, the Faraday cup is also used for detecting a beam drift as described later.

Although the above-mentioned beam Faraday 12 is conventionally used only for confirming the overscan of the ion beam 50, in the present embodiment, not only this but also a dose correction coefficient is calculated and a beam correction coefficient is calculated. This is a Faraday cup that is also used to detect drift.

The beam current flowing into the dose Faraday 11 or the beam Faraday 12 is measured by a beam current measuring circuit (beam current measuring means) 13. As shown in FIG. 2, the beam current measurement circuit 13 includes a Faraday selection circuit 14 for selecting the dose Faraday 11 or the beam Faraday 12, an amplification circuit for converting a small beam current flowing into the dose Faraday 11 or the beam Faraday 12 into a voltage and amplifying the voltage. And an analog / digital converter for converting the output of the amplifier circuit 15 into analog / digital at high speed.
A digital conversion circuit 16 is provided.

The waveform controller 5 includes a dose Faraday integration counter 17 for integrating the beam current flowing into the dose Faraday 11 while the ion beam 50 is swept by one, and the waveform controller 5 flows into the beam Faraday 12 while the ion beam 50 is swept by one. Beam Faraday integrating counter 18 for integrating the beam currents to be added, an adding circuit 19 for adding the output of the dose Faraday integrating counter 17 and the output of the beam Faraday integrating counter 18, N sweeps of the ion beam 50 (for the set number of times). N) adder circuit 20 for dose farada that adds the output of the dose counter 17 for dose farada, N-number adder circuit 21 for beam farada that adds the output of the beam farada count counter 18 for N sweeps of the ion beam 50,
And a division circuit 22 for dividing the output of the above-mentioned N-time addition circuit 20 for dose Faraday and the N-time addition circuit 21 for beam Faraday.

The output of the adder circuit 19, that is, the signal corresponding to the beam current flowing into the dose Faraday 11 and the beam Faraday 12, is processed in the waveform controller 5 to obtain a dose correction coefficient, and is used for a dose count. In this case, the injection is performed by an injection controller 24 that controls the injection amount by controlling the holding member driving mechanism 23. The injection controller 24 is configured by a microcomputer or the like. The output of the division circuit 22, that is, the ion beam 50
The signal corresponding to the ratio of the beam currents flowing into the dose Faraday 11 and the beam Faraday 12 while N sweeps N times is processed in the waveform controller 5 to check for beam drift.

The waveform controller 5 switches the Faraday selection circuit 14 of the beam current measurement circuit 13 based on the address data of the scanning voltage waveform data (hereinafter referred to as a waveform address), and performs a dose Faraday integration counter 17. Counter 18 for beam and Faraday
And so on.

The ion beam 50 is transmitted to the waveform controller 5
The scanning is performed by being deflected by the scanning voltage corresponding to the scanning voltage waveform data stored in the memory 5b, and the position of the beam in the scanning area is uniquely determined by the scanning voltage waveform data and its waveform address. . For example, assuming that the scanning voltage waveform is a substantially triangular wave, the waveform address of the scanning voltage waveform data for one sweep is 0 to 3999.
Then, as shown in FIG. 4, the end of the beam scanning area on the beam Faraday 12 side (time t ₀ , waveform address “0”)
The ion beam 50 which starts scanning from is located substantially at the center of the beam scanning area at time t ₁ when the waveform address becomes “1000”, and the other of the beam scanning area at time t ₂ when the waveform address becomes “2000”. It comes to the end (turning point). Thereafter, the ion beam 50, the waveform address is "3000" located in the approximate center of the beam scanning region in becomes the time t _3, the waveform address is "0" again returns to the scan starting point in the composed time t ₄ in.

That is, during one sweep, the ion beam 50 has a waveform address “0” (time t ₀ ) to a waveform address “1000” (time t ₁ ) and a waveform address “3000” (time t ₁ ). _{From 3} ) to the waveform address “0” (time t ₄ ), the light enters the beam Faraday 12,
It is incident on the dose Faraday 11 between the waveform address “1000” (time t ₁ ) and the waveform address “3000” (time t ₃ ). FIG. 5 shows the relationship between the beam current measured by the dose Faraday 11 or the beam Faraday 12 and the time or the waveform address.

The waveform controller 5 selects the beam Faraday 12 when the waveform address is 0 to 1000 and 3000 to 3999, and selects the dose Faraday 11 when the waveform address is 1001 to 2999. The Faraday selection circuit 14 of the beam current measurement circuit 13 is switched. The injection controller 24 determines whether the waveform address is between 0 and 1000 and between 3000 and 3999.
At this time, the counting of the beam Faraday integrating counter 18 is performed while the waveform address is 1001 to 2999.
At this time, the counters 17 and 18 are controlled so that the dose Faraday integrating counter 17 is counted.

Behind the injection position (behind the holding member 9), as shown in FIG. 6, a back Faraday 2 having a configuration in which a plurality of Faraday cups are densely arranged in the beam scanning direction.
7 is provided, and as shown in FIG.
The ion beam 50 that has passed through the opening 8a of the mask 8
(A beam that is actually injected into the wafer 10).

The beam current measuring circuit 13 includes an amplifier circuit for measuring a beam current flowing into each Faraday and an analog / digital conversion circuit. And outputs a signal corresponding to the beam current flowing into the device.

Further, as shown in FIG. 1, the ion implantation apparatus has an input operation section 26 for setting implantation conditions including a dose to be implanted into the wafer 10. Is set in the injection controller 24.

The operation of the ion implantation apparatus having the above configuration will be described below.

First, before the start of the implantation process, the beam current is measured using the dose Faraday 11, the beam Faraday 12, and the back Faraday 25 while the ion beam 50 is scanned in the same manner as in the implantation process, and the dose correction coefficient is calculated. I do.

That is, the beam current flowing into the dose Faraday 11 and the beam Faraday 12 is measured by the beam current measuring circuit 13, and the sum of the beam currents flowing into the two Farades 11 and 12 is added to the adding circuit 19 of the waveform controller 5. Required by The beam current flowing into the back Faraday 25 is also measured by the beam current measurement circuit 13, and the measured value is also taken into the waveform controller 5.

The waveform controller 5 corrects the dose based on the beam current (I _DOSE + I _BEAM ) flowing into the Faraday 11 and 12 fetched from the beam current measuring circuit 13 and the beam current I _BACK flowing into the back Faraday 25. The coefficient K is calculated by the following equation (1). This dose correction coefficient is supplied from the waveform controller 5 to the injection controller 2.
4 is output. In the injection controller 24, the dose correction coefficient is multiplied by the set dose and used for controlling the injection amount.

K = [S _BACK / (S _DOSE + S _BEAM )] · [(I _DOSE + I _BEAM ) / I _BACK ] (1) S _BACK : Opening area of back farade 25 S _DOSE : Opening area of dose farad 11 S _BEAM : opening area of beam Faraday 12 I _BACK : beam current flowing into back Faraday 25 I _DOSE : beam current flowing into dose Faraday 11 I _BEAM : beam current flowing into beam Faraday 12 Note that the above-mentioned beam currents I _BACK and (I _DOSE) + I _BEAM )
Is a value measured by multiple sweeps.

When calculating the dose correction coefficient before the start of the injection process, the ratio between the amount of beam flowing into the dose Faraday 11 and the amount of beam flowing into the beam Faraday 12 is obtained.
That is, the beam current flowing into the dose Faraday 11 and the beam Faraday 12 is measured by the beam current measurement circuit 13, and the ratio of the beam current flowing into both the Faraday 11 and 12 while the ion beam 50 sweeps N times is determined by the waveform controller 5. Is stored in the internal memory.

After the above-described preparation operation before the start of the injection process, the actual injection process is performed. During the implantation process, the implantation controller 24 determines, via the beam current measurement circuit 13, the holding member 9 holding the wafer 10 based on the dose Faraday 11 fetched from the addition circuit 19 of the waveform controller 5 and the beam current flowing into the beam Faraday 12.
Is adjusted by the control of the holding member driving mechanism 23. Specifically, when the beam current decreases, the moving speed of the holding member 9 is decreased in proportion thereto, and conversely, when the beam current increases, the moving speed is controlled to increase in proportion thereto. By controlling the moving speed of the holding member 9, uniformity of implantation in the Y direction on the surface of the wafer 10 is ensured.

During the injection process, the injection controller 24
Is the dose Faraday 11 fetched from the addition circuit 19 of the waveform controller 5 via the beam current measurement circuit 13.
The dose is counted based on the value of the beam current flowing into the beam Faraday 12. When the dose count reaches a value obtained by multiplying the dose correction coefficient K obtained before the injection process by the set dose, the holding member 9
Is retracted from the beam irradiation area, and the next new wafer 1
For 0, the same injection processing as described above is performed.

That is, the dose D is generally expressed by the following equation (2).

D = I · t / n · e · S (2) I: beam current, t: implantation time, n: valence, e: implantation area, S: implantation area Actual implantation into wafer 10 Since the beam to be emitted corresponds to the beam current flowing into the back Faraday 25, D = I _BACK・ t / ne ・ S _BACK (3)

Since the dose correction coefficient K is defined as in the above equation (1), I _BACK = (1 / K) ・ [S _BACK / (S _DOSE + S _BEAM )] ・ (I _DOSE + I _BEAM ) (1 '). When the above equation (1 ') is substituted into the above equation (3) and transformed, KD = (I _DOSE + I _BEAM ) t / _ne・ (S _DOSE + S _BEAM ) (4)

Therefore, the dose to the wafer 10 is determined by the value obtained by multiplying the dose D set by the input operation unit 26 by the dose correction coefficient K and the measurement count of the beam current flowing into the dose Faraday 11 and the beam Faraday 12. Can be controlled.

During the implantation process, the waveform controller 5 uses the division circuit 22 of the beam current measuring circuit 13 to determine the ratio of the beam current flowing into the dose farad 11 and the beam farad 12 every time the ion beam 50 sweeps N times. Ask. The waveform controller 5 compares the ratio obtained by the division circuit 22 with the ratio of the two Faradays 11 and 12 obtained before the injection processing, and when a change exceeding a predetermined allowable range is detected, a beam drift has occurred. And outputs an interlock signal to the injection controller 24. When the interlock signal is input, the injection controller 24 performs a hold process for temporarily stopping injection. For example, a ratio is determined by taking 500 sweeps as one cycle, and interlock (hold processing) is applied at a change of 2%. The above-mentioned holding process is a process in which the holding member 9 is made to wait outside the beam irradiation area and the injection is temporarily stopped.

Incidentally, the waveform controller 5 constitutes a beam drift detecting means described in claims. In the above description, the division circuit 2 of the waveform controller 5
2, the ratio is obtained, for example, the injection controller 2
4 may be operated internally.

As described above, the main cause of the change in the ratio of the beam current flowing into the dose Faraday 11 and the beam Faraday 12 is the beam drift. That is, the beam amount of the ion beam 50 varies depending on the position in the beam scanning region. When the beam scanning region shifts due to the beam drift, the beam current flowing into the dose farad 11 and the beam current flowing into the beam farada 12 fluctuate. The ratio of the beam current flowing into the two Farades 11 and 12 also changes. If the beam drift does not occur, even if the beam amount of the ion beam 50 itself fluctuates within a certain range, the ratio of the beam current flowing into the two Farades 11 and 12 does not change.

The main reason why the beam amount of the ion beam 50 differs depending on the position in the beam scanning area is as follows.
The beam shape and the scanning speed are different depending on the position in the beam scanning area.

One of the causes of the difference in beam shape depending on the position in the beam scanning area is that a static flat plate scanning electrode such as the first scanning electrode 1a or 1b or the second scanning electrode 2a or 2b is used. Neutral point action in electric scan. This is because, when the ion beam 50 passes through a certain electric field intensity or more, electrons contained to some extent in the beam are absorbed by the electric field, and the neutrality of space charge is broken. This is due to the spread, and in most of the beam scanning area,
Although the beam spreads as described above, at the center of the beam scanning area where the electric field between the scanning electrodes becomes 0 (zero),
Since electrons in the beam are not lost, a phenomenon occurs in which the beam travels while being narrowed. That is, the beam is small and the current density is high at the center of the beam scanning area, and the beam is large and the current density is low in other scanning areas.

The beam scanning speed varies depending on the position in the beam scanning area because the beam incident angle differs between the center and the end of the beam scanning area. That is, although the beam is scanned in parallel by two sets of parallel plate scanning electrodes (first scanning electrode 1a and 1b and second scanning electrode 2a and 2b), it is difficult to obtain a complete parallel beam over the entire scanning area. It is.

Therefore, conventionally, as shown in FIG. 7, a front Faraday 27 having a structure in which a plurality of Faraday cups are densely arranged in the beam scanning direction in front of the injection position is provided. Back Faraday 2
The beam incident angle is obtained by measuring the position of the beam incident on the light emitting element 5, and the scanning voltage waveform is shaped according to the beam incident angle to make the beam scanning speed substantially constant. still,
As shown in FIG. 8, the opening 8a of the mask 8, the back Faraday 25, and the dose Faraday 11 (not shown).
The beam Faraday 12 is provided at a position where the ion beam 50 is deflected by 7 ° in the Y direction by the deflecting electrodes 3.3, while the front Faraday 27 is provided at a position deflected by 3.5 ° in the Y direction. , And the deflection angle is switched by the deflection electrodes 3.

As described above, even if the correction for making the beam scanning speed substantially constant is performed, the scanning speed is not always strictly constant. Even if the beams have the same shape and the same current density distribution, if the scanning speed differs depending on the position, the measured beam current differs depending on the position of the beam. Actually, as described above, the beam shape differs depending on the position. When the beam scanning area shifts due to the beam drift, the ratio of the beam current flowing into the dose Faraday 11 and the beam Farade 12 changes, and the beam drift can be detected. It is.

As described above, the waveform controller 5 detects that the ratio of the beam currents flowing into the two Faradays 11 and 12 before the injection processing has changed more than an allowable range during the injection processing, and sends an interlock signal to the injection controller 24. Is output, and if the implantation process is stopped, the above-described operation is performed again (after the beam readjustment if necessary) to obtain the dose correction coefficient again, and the subsequent processes including the wafer 10 during the implantation process are performed. For the wafer, the injection controller 24 performs injection amount control using the re-determined dose correction coefficient.

As described above, the ion implantation apparatus of the present embodiment uses the first scanning electrodes 1a and 1b as beam scanning means.
A beam is irradiated onto the wafer 10 while scanning the ion beam 50 by the second scanning electrodes 2a and 2b to perform an ion implantation process. The dose Faraday 11 and the beam Faraday serving as a beam measuring unit installed in the beam scanning area. 12, a beam current measuring circuit 13 as a beam current measuring means for individually measuring beam currents flowing into the two Farades 11 and 12, respectively, and a ratio of measured values of the beam currents flowing into the two Farades 11 and 12, respectively. And a waveform controller 5 as beam drift detection means for detecting the presence or absence of a beam drift based on the change in the ratio during the injection processing.

As described above, during the implantation process, the beam amounts flowing into the Faraday cups of the dose Faraday 11 and the beam Faraday 12 are measured independently, and the ratio between them is checked. It is possible to detect a beam drift that has occurred, and it is useful to prevent deterioration of injection reproducibility due to the beam drift.
For example, when detecting a beam drift, as described above, stop injection by interlocking, or
It is possible to perform an alarm operation, such as sounding an alarm or notifying an operator of the occurrence of an abnormality by display. Then, if the beam changed due to the beam drift is readjusted or the dose correction coefficient is obtained again and the injection is restarted, the injection reproducibility can be ensured.

In the above embodiment, the dose farad 1
A dose correction coefficient is determined based on the total amount of beams flowing into the Faraday cups 1 and 12 and the beam amount flowing into the back Faraday 25. During the implantation process, both the Faraday of the dose Faraday 11 and the beam Faraday 12 are determined. The total amount of the beam flowing into the cup is counted to control the injection amount. Conventionally, the injection amount is controlled by counting the beam amount of only the dose Faraday.
Counting the amount of beam flowing into one (three or more) Faraday cups increases the amount of information per time and enables more accurate control of the injection amount.

In the above embodiment, the beam drift is detected based on the ratio of the beam currents flowing into the two Faraday cups (dose Faraday 11 and beam Faraday 12). A Faraday cup (beam current measuring unit) may be provided.
For example, when three Faraday cups A, B, and C are provided, the presence / absence of beam drift can be determined from the inflow beam current ratios of A to B, A to C, and B to C, and the detection accuracy can be improved. .

In the above embodiment, the beam scanning means scans the beam electrostatically. However, the beam scanning means may scan the beam electromagnetically by an electromagnet. The embodiments described above are merely for clarifying the technical contents of the present invention, and should not be construed as being limited to such specific examples in a narrow sense. Various changes can be made within the scope. In particular, this embodiment merely shows a specific example of the functional division of the controller, and various configurations are possible.

[0068]

As described above, the ion implantation apparatus according to the present invention individually measures a plurality of beam measuring units provided in the beam scanning area and beam currents flowing into the plurality of beam measuring units. Beam current measurement means, a beam drift detection means for determining the ratio of the measured value of the beam current flowing into each of the plurality of beam measurement units, from the change of the ratio during the implantation process, to detect the presence or absence of the occurrence of beam drift, It is a configuration provided with.

Therefore, by continuously checking the ratio of the beam current flowing into each of the above-mentioned beam measuring units during the implantation process, it becomes possible to detect the beam drift which could not be detected conventionally, and the beam drift can be detected. There is an effect that deterioration in injection reproducibility due to drift can be prevented beforehand.

[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 block diagram showing a configuration of a main part of a beam current measurement circuit of the ion implantation apparatus.

FIG. 3 is a schematic configuration diagram showing a configuration of a beam scanning system of the ion implantation apparatus.

FIG. 4 is an explanatory diagram showing a relationship between a position of a beam in a beam scanning area and a time or a waveform address in the ion implantation apparatus.

FIG. 5 shows a beam current measured by a dose Faraday or a beam Faraday in the ion implantation apparatus;
FIG. 4 is an explanatory diagram showing a relationship with time or a waveform address.

FIG. 6 shows a dose farad in the ion implantation apparatus.
It is explanatory drawing which shows the positional relationship of a beam Faraday and a back Faraday.

FIG. 7 is a schematic perspective view showing a beam line in the ion implantation apparatus.

FIG. 8 is a schematic side view showing a beam line in the ion implantation apparatus.

FIG. 9 is a schematic perspective view showing a parallel beam type hybrid scan ion implantation apparatus.

FIG. 10 illustrates a conventional example, and is a schematic configuration diagram illustrating a main part of an ion implantation apparatus.

FIG. 11 is an explanatory diagram showing a positional relationship between a dose farad and a back farad of the conventional ion implantation apparatus.

[Explanation of symbols]

1a ・ 1b First scanning electrode (scanning means) 2a ・ 2b Second scanning electrode (scanning means) 5 Waveform controller (beam drift detection means) 8 Mask 8a Opening 9 Holding member 10 Wafer (beam irradiation target) 11 Dose Faraday ( Beam measurement unit) 12 Beam Faraday (beam measurement unit) 13 Beam current measurement circuit (beam current measurement unit) 22 Division circuit (beam drift detection unit) 23 Holding member drive mechanism 24 Injection controller 25 Back Faraday

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 37/317 C23C 14/48 H01J 37/04 H01L 21/265

Claims (1)

(57) [Claims] 1. An ion implantation apparatus comprising a beam scanning means for scanning an ion beam and irradiating a beam irradiation object with a beam while scanning the ion beam to perform an ion implantation process. A plurality of beam measurement units, a beam current measurement unit that individually measures a beam current flowing into each of the plurality of beam measurement units, and a ratio of measurement values of the beam currents respectively flowing into the plurality of beam measurement units, An ion implantation apparatus comprising: a beam drift detection unit configured to detect whether or not a beam drift has occurred based on a change in the ratio during the implantation process.