JP2004014323A - Ion beam irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply quickly measure an electron supply amount in the vicinity of a substrate from an electron supply source. <P>SOLUTION: This ion beam irradiation device is equipped with a plasma generation device 14 as an example of an electron supply source for supplying electrons to a substrate 4 held to a holder 6 to restrain charge up of the substrate 4 caused by ion beam irradiation. The device is provided with: a measurement electrode 20 installed in the vicinity of the holder 6 and at a position where electrons in plasma 16 emitted from the generation device 14 reach; a D.C. bias power source 24 for applying a positive bias voltage Vb to the measurement electrode 20; and an ammeter 26 for measuring a current flowing through the measurement electrode 20. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for performing processes such as ion implantation by irradiating a substrate with an ion beam, and relates to an ion beam irradiation apparatus including an electron supply source for suppressing charge-up (charging) of a substrate surface due to ion beam irradiation. .
[0002]
[Prior art]
FIG. 2 shows a conventional example of this type of ion beam irradiation apparatus. This ion beam irradiation device is a device that irradiates a substrate (for example, a semiconductor wafer) 4 held by a holder 6 with an ion beam 2 and performs a process such as ion implantation on the substrate 4.
[0003]
In order to irradiate the entire surface of the substrate 4 with the ion beam 2, in this example, the ion beam 2 is reciprocally scanned in an X direction (for example, a horizontal direction) by an electric field or a magnetic field. Is mechanically reciprocated in the Y direction (for example, the vertical direction) via the shaft 12.
[0004]
In such an ion beam irradiation apparatus, when the substrate 4 is irradiated with the ion beam 2, the surface of the substrate 4 is charged up by the positive charges of the ions in the ion beam 2, and eventually discharge occurs to damage the surface of the substrate 4. receive. For example, a semiconductor device (for example, a MOS-FET) formed on the surface of the substrate 4 is destroyed.
[0005]
In order to suppress (relax) this charge-up, conventionally, simultaneously with the irradiation of the ion beam, electrons or a plasma containing electrons (in other words, electrons in the plasma) are supplied to the substrate from an electron supply source. It has been practiced to neutralize the positive charge of an ion with the negative charge of an electron (see, for example, JP-A-3-93141).
[0006]
The ion beam irradiation apparatus in FIG. 2 also includes a plasma generator 14 provided near the upstream side of the holder 6 as an example of an electron supply source. The plasma generator 14 generates a plasma (including electrons, of course) 16 and supplies it to the path of the ion beam 2, supplies the electrons in the plasma 16 together with the ion beam 2 to the substrate 4, This suppresses charge-up.
[0007]
[Problems to be solved by the invention]
Even if the plasma generator 14 (electron supply source) as described above is provided, the charge-up of the substrate 4 cannot be sufficiently suppressed unless the amount of electrons supplied to the vicinity of the substrate is appropriate. Charges up positively or negatively, causing the aforementioned damage.
[0008]
Therefore, conventionally, measurement using a test wafer has been performed in order to grasp the degree of charge-up suppression by the plasma generator 14 in advance (that is, before the original processing of the substrate 4). That is, a test wafer having a large number of TEGs (Test Element Group) on its surface is mounted instead of the substrate 4 and ion beam irradiation is actually performed on the test wafer. Was checked to determine the charge-up state.
[0009]
However, according to this method, not only is it expensive to manufacture or purchase a test wafer, but it also takes a lot of time to perform measurement, so that the substantial throughput of the ion beam irradiation apparatus is reduced. In addition, since a large time difference occurs between the irradiation of the test wafer with the ion beam and the actual irradiation of the substrate 4 with the ion beam, the measurement result on the test wafer does not reflect the state of the actual processing of the substrate 4. There was fear.
[0010]
In order to prevent a large charge-up from occurring in the substrate 4, it is preferable to measure the amount of electrons supplied from the electron supply source to the vicinity of the substrate. By this measurement, it is possible to predict whether or not there is a possibility that a large charge-up occurs in the substrate without using a test wafer.
[0011]
Accordingly, an object of the present invention is to provide an ion beam irradiation apparatus capable of easily and quickly measuring an electron supply amount from an electron supply source to the vicinity of a substrate.
[0012]
[Means for Solving the Problems]
An ion beam irradiation apparatus according to the present invention includes a measurement electrode provided in the vicinity of the holder and at a position where electrons from the electron supply source reach and electrically insulated from the other. A DC bias power supply to which a bias voltage can be applied and an ammeter for measuring a current flowing through the measurement electrode are provided.
[0013]
According to the above configuration, a positive bias voltage is applied from a bias power supply to a measurement electrode provided in the vicinity of the holder, that is, in the vicinity of the substrate, and the ion beam irradiation is performed by the measurement electrode to which the positive bias voltage is applied. Accordingly, a substrate that has been positively charged can be simulated. At this time, the ion beam is not made incident on the measurement electrode. In this state, when the electron source is operated, the electrons emitted from the electron source reach the vicinity of the measurement electrode and are drawn into the measurement electrode by the positive bias voltage. The amount of electrons drawn into the measurement electrode in this way corresponds to the amount of electrons drawn into the positively charged substrate. The amount of electrons drawn into the measurement electrode can be measured by an ammeter.
[0014]
In this way, the amount of electrons supplied from the electron supply source to the vicinity of the substrate can be easily and quickly measured without using complicated means. In addition, since the measurement electrode to which the positive bias voltage is applied simulates a positively charged substrate as described above, the measurement of the amount of supplied electrons can be performed as compared with a case where a bias power supply is not provided. Can be performed accurately.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a schematic view showing an example of an ion beam irradiation apparatus according to the present invention. Parts that are the same as or correspond to those in the conventional example shown in FIG. 2 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below.
[0016]
The ion beam irradiation apparatus includes a measurement electrode 20 that is electrically insulated from others at a position near the holder 6 where electrons in the plasma 16 emitted from the plasma generator 14 reach. Have. The measurement electrode 20 is made of, for example, carbon. In this example, the measuring electrode 20 is attached to the shaft 12 of the holder driving mechanism 10 via an insulator 22. Since the substrate 4 is held by the holder 6, it can be said that the measurement electrode 20 is provided near the substrate 4.
[0017]
The ion beam irradiation apparatus further comprises a bias power source 24 of direct current that can be applied to at least a positive bias voltage V _B to the measuring electrode 20, and an ammeter 26 for measuring the current flowing through the measuring electrode 20 . The bias power source 24 is connected between the measurement electrode 20 and the ground potential portion, and an ammeter 26 is inserted in series between the electrodes. Therefore, it can be said that the ammeter 26 measures the output current of the bias power supply 24.
[0018]
Bias power source 24 is, for example, a DC power supply to the measuring electrode 20 applies a positive bias voltage V _B. Although the output voltage may be fixed, it is preferable to make the output voltage variable as in this example. By doing so, the positively charged substrate 4 can be simulated more freely and more accurately. The bias power source 24 is not only variable output voltage, and in that the output bias voltage V _B can be varied from a negative of a value to a positive of a certain value (i.e., bipolar DC power supply output voltage variable) May be. The usage in that case will be described later.
[0019]
According to the ion beam irradiation device, the vicinity of the holder 6, i.e. the measuring electrode 20 provided in the vicinity of the substrate 4, by applying a positive bias voltage V _B from the bias power source 24, the positive bias voltage V _B Can be simulated by the measurement electrode 20 to which the substrate is positively charged with the ion beam irradiation. The magnitude of the bias voltage V _B is preferably about charging voltage of the substrate 4 to be expected if no supply electrons for neutralizing the substrate 4 is irradiated with only the ion beam 2. For example, it is set to about + 10V.
[0020]
At this time, the ion beam 2 is not made incident on the measurement electrode 20. In that sense, the ion beam 2 is indicated by a two-dot chain line in FIG. In order to prevent the ion beam 2 from being incident on the measurement electrode 20, for example, the scanning of the ion beam 2 may be stopped at a position other than the measurement electrode 20, or the generation of the ion beam 2 may be stopped. good.
[0021]
At the time of measurement, it is more preferable that the measurement electrode 20 is located at a position where the substrate 4 is irradiated with the ion beam 2 or in the vicinity thereof, as in the example shown in FIG. In this example, the holder drive mechanism 10 raises the holder 6 and the measurement electrode 20 in the Y direction to realize this. With this configuration, the position where the substrate 4 is irradiated with the ion beam 2 and the measurement electrode 20 are substantially at the same position, so that the positively charged substrate 4 can be more accurately simulated by the measurement electrode 20. .
[0022]
When the plasma generator 14 (electron supply source) is operated in the above state, the electrons in the plasma 16 emitted from the plasma generator 14 reach the vicinity of the measurement electrode 20 and have a positive bias applied to the measurement electrode 20. drawn by the voltage _{V B.} The amount of electrons drawn into the measurement electrode 20 in this way corresponds to the amount of electrons drawn into the positively charged substrate. That is, since the amounts of the two agree with each other or have a fixed relationship, the amount of the latter can be known from the amount of the former. The amount of electrons drawn into the measurement electrode 20 can be measured by the ammeter 26.
[0023]
In this manner, the amount of electrons supplied from the plasma generator 14 to the vicinity of the substrate can be easily and quickly reduced by the simple means of the measuring electrode 20, the bias power supply 24 and the ammeter 26 without using complicated means. Can be measured. Moreover, the positive measurement electrode 20 to which a bias voltage V _B is applied, since simulates a substrate positively charged up as described above, as compared with the case such as provided with no bias power supply 26, the electronic The supply amount can be measured accurately.
[0024]
The electron supply amount measured in this way is fed back to, for example, operating parameters of the ion beam irradiation apparatus (for example, the beam current of the ion beam 2, the density of the plasma 16 generated by the plasma generator 14, and the like), and This can be used for determining whether or not the operating conditions before the ion beam irradiation processing on the substrate 4 are good.
[0025]
In this way, it is possible to predict whether or not there is a possibility that a large charge-up occurs in the substrate 4 without using a test wafer. As a result, the possibility that the substrate 4 is damaged by the charge-up, for example, the possibility that the device formed on the substrate surface will cause the charge-up destruction can be reduced beforehand.
[0026]
Further, according to the above configuration, unlike the case where a test wafer is used, the measurement of the electron supply amount can be performed at a place where the substrate 4 is processed (that is, on the spot), and the measurement result is immediately obtained. Therefore, the measurement of the amount of supplied electrons can be performed immediately before the processing of the substrate 4 (for example, ion implantation), and the ion beam 2 and the plasma generator 14 can be optimized for each processing of the substrate 4.
[0027]
Also, if the electron source is the plasma generating apparatus 14 as in this example, by changing the least magnitude or magnitude and polarity both, the bias voltage V _B to be applied to the measuring electrode 20 from the bias power source 24 ( For example, the current flowing into the measuring electrode 20 is measured by the ammeter 26 at that time by changing the current in the range of −50 V to +50 V). Measuring the electron density and electron temperature in the plasma 16 emitted from the plasma 14, and using the measurement results for feedback of the operating conditions to the plasma generator 14 and for determining the quality of the operating conditions before processing the substrate 4; You can also.
[0028]
However, instead of the plasma generator 14 for generating the plasma 16 containing electrons as described above, only electrons are generated and supplied to the substrate 4 and the ion beam 2 as an electron supply source for suppressing charge-up. An electron generator may be used.
[0029]
【The invention's effect】
As described above, according to the present invention, the measurement electrode to which the positive bias voltage is applied simulates the substrate that has been positively charged up by the ion beam irradiation, and the amount of electron supply from the electron supply source to the vicinity of the substrate. Can be measured. Moreover, this measurement can be performed easily and in a short time without using complicated means. Moreover, since the measurement electrode to which the positive bias voltage is applied simulates a positively charged substrate, the measurement of the electron supply amount can be performed accurately. This makes it possible to predict whether or not the substrate may be significantly charged up without using a test wafer, thereby reducing the possibility that the substrate will be damaged by the charge-up. it can.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of an ion beam irradiation apparatus according to the present invention.
FIG. 2 is a schematic view showing an example of a conventional ion beam irradiation device.
[Explanation of symbols]
2 Ion beam 4 Substrate 6 Holder 14 Plasma generator (Electron supply source)
16 Plasma 20 Measurement electrode 24 Bias power supply 26 Ammeter

Claims (1)

An electron source for irradiating a substrate held by a holder with an ion beam, the electron supply source being provided on an upstream side of the holder and supplying electrons to the substrate to suppress charge-up of the substrate surface due to ion beam irradiation. A measurement electrode provided in the vicinity of the holder and at a position where electrons from the electron supply source reach and electrically insulated from the others, and at least a positive bias applied to the measurement electrode. An ion beam irradiation apparatus comprising: a DC bias power supply capable of applying a voltage; and an ammeter for measuring a current flowing through the measurement electrode.

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