JPH0795436B2 - Ion processing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion treatment apparatus, such as an ion implantation apparatus, which irradiates a wafer with an ion beam in a vacuum and performs a treatment such as ion implantation on the wafer. In particular, it relates to improvement of means for preventing electrification of the wafer.

[Background technology]

The same applicant has separately proposed an ion processing apparatus in which the antistatic action of the wafer can be accurately performed by controlling the disk current so that it has a desired set value.

An example of this will be described with reference to FIG. 2. This ion treatment apparatus is of a so-called mechanical scan type, and basically, the peripheral portion of the disk 4 rotated and translated in a vacuum container (not shown). The plurality of wafers 6 mounted on the wafer are irradiated with the ion beam 2 and subjected to a process such as ion implantation.

On the path of the ion beam 2, a neutral cup 10 and a suppressor electrode, which constitute a Faraday system, prevent secondary electrons emitted when the ion beam 2 hits the disk 4 or the like from escaping to the ground. 8 is provided on the front side of the disk 4, and in this example, a catch plate 12 for receiving the ion beam 2 when the disk 4 is translated outward is provided on the rear side of the disk 4.

Then, the disk 4 via the disk current measuring resistor 24,
The catch plate 12 and the neutral cup 10 are electrically connected in parallel to each other and connected to a current measuring device 26 such as a current integrator so that the beam current I _B of the ion beam 2 can be accurately measured. I have to.

Further, in order to prevent the surface of the wafer 6 from being positively charged and causing a problem such as discharge when the surface of the wafer 6 is an insulator due to the irradiation of the ion beam 2, side portions of the neutral cup 10 are prevented. A filament 14 is provided on the filament 14, and the primary electron 21 emitted from this is applied to the facing surface of the neutral cup 10 to emit a secondary electron 22 from it, that is, in this example, the neutral cup 10 serves as a secondary electron emitting member, and The secondary electrons 22 are supplied onto the wafer 6 in the ion beam irradiation region on the disk 4 so that the ion beam 2 on the surface thereof neutralizes the positive charges. 16 is a filament power supply for heating the filament 14, and 18 is a primary electron
It is a drawer power supply for 21 drawers.

In that case, basically, the disk current measuring resistor 24,
A disk current I _D (= I _B +) obtained by combining the beam current I _B and the secondary electron current I ₂ by the secondary electrons 22 for neutralization.
I ₂ ) flows.

Then, take out the voltage V _D corresponding therefrom connected with the disk current measurement resistor 24 and disk current-dependent voltage output amplifier 28 constituting the disk current measuring circuit across the disk current measurement resistor 24 to the disc current I _D, the disk current In the setting circuit 30, the desired disk current is set in the form of a voltage V _S in this example, and both voltages V _D and V _S are input to an arithmetic circuit 32 including a differential amplifier, where the voltage difference (V _D −V _s ).

Then, in the control circuit 34, the output (V _D −
The filament power source 16 described above is controlled so that V _s ) becomes zero, and the amount of primary electrons 21 emitted from the filament 14 is controlled by controlling the filament current.

According to the above configuration, when a desired disk current is set by the disk current setting circuit 30, the disk current measurement resistance
The emission amount of the primary electrons 21 from the filament 14 and thus the emission amount of the secondary electrons 22 from the neutral cup 10 are automatically controlled so that the disc current I _D measured by 24 etc. becomes the same, and as a result, the disc 4 etc. The disk current I _D flowing through the disk reaches the set value. As a result, the amount of secondary electrons 22 supplied to the wafer 6 on the disk 4 can be made exactly the desired amount, whereby the antistatic action of the wafer 6 can be accurately performed.

[Problems to be Solved by the Invention]

However, in the above-mentioned device, the disk 4 is indicated by the arrow A during processing.
Therefore, even if the wafer 6 is not in the irradiation area of the ion beam 2,
When the wafer 6 leaves the beam irradiation region, the disk current _ID flows through the disk current measuring resistor 24 by hitting the disk 4, and the secondary electrons 22 are emitted so that the disk current _ID becomes a predetermined value. There is still room for improvement in that there is a possibility that only the secondary electrons 22 will be supplied to the wafer 6 and the wafer 6 will be negatively charged.

Therefore, the main object of the present invention is to provide an ion processing apparatus in which such a point is further improved.

[Means for Solving the Problems]

In order to achieve the above object, the ion processing apparatus of the present invention is a disk current measuring circuit for measuring a disk current flowing through the disk, a disk current setting circuit for setting a desired disk current, and a disk current measuring circuit. And an arithmetic circuit for obtaining the difference between the disk current and the disk current set by the disk current setting circuit,
A control circuit for controlling the filament power supply so as to eliminate this difference and controlling the amount of primary electrons emitted from the filament, and turning on and off the extraction voltage applied between the filament and the secondary electron emission member from the extraction power supply. The disk position detecting means includes switch means and disk position detecting means for detecting the translational position of the disk and turning on the switch means only when the translational position of the disk is within a preset predetermined area. But,
An up / down counter that receives the translation control signal output from the translation control device, counts the number of pulses, and digitally outputs the result, and receives the output from the up / down counter and converts it to analog. A D / A converter that outputs a triangular wave signal that represents the translational position of the disk,
The triangular wave signal output from this D / A converter is received and it is determined whether or not the value is equal to or greater than a predetermined value set in advance, whereby the translational position of the disk is within a predetermined area set in advance. And a determination circuit that determines whether or not the switch means is turned on only when it is within a predetermined area.

〔Example〕

FIG. 1 is a block diagram of the essential parts of an ion processing apparatus according to an embodiment of the present invention. The same or corresponding parts as those in the example of FIG. 2 are designated by the same reference numerals, and the differences from the preceding example will be mainly described below.

In this embodiment, in addition to the above-mentioned means for controlling the emission amount of the primary electrons 21 and thus the emission amount of the secondary electrons 22 so that the disk current _ID becomes a set value, the following means are further provided. Is provided.

Specifically, the disk 4 described above is rotated by a motor 36 and is also a motor (stepping motor).
It is translated by mechanism 38 via mechanism 40. At this time, the translational velocity v of the disk 4 is determined by applying the translational control signal S _P in the form of a pulse signal from the translational control device 42 to the motor 38 in order to uniformly irradiate each wafer 6 on the disk 4 with the ion beam 2. Is controlled so as to satisfy the following well-known relationship.

v∝I _B / R where R is the distance between the center of rotation of the disk 4 and the center of the ion beam 2.

Therefore, in this embodiment, the translation control signal S _P output from the translation control device 42 is counted by the up / down counter 44 (up-counting while the disk 4 is translating in the forward path and down-counting when the disk 4 is translating in the return path). The output of the counter 44 is converted into analog by the D / A converter 46 to obtain the triangular wave signal S _D representing the translational position of the disk. Then, the triangular wave signal S _D is input to the determination circuit 48 including, for example, a window comparator, and it is determined whether or not the value of the triangular wave signal S _D is equal to or more than a predetermined value set in advance. It is determined whether or not the translational position is within a predetermined beam irradiation area. The disk position detecting means is constituted by such a structure.

On the other hand, a switch means (relay in the illustrated example) 50 is inserted in series with the above-mentioned extraction power source 18, and is turned on only when the disc 4 is within the predetermined beam irradiation area by a signal from the determination circuit 48. Only at that time, an extraction voltage is applied between the filament 14 and the neutral cup 10 from the extraction power source 18, and only at that time the primary electron 21 is extracted from the filament 14 and the secondary electron 22 is emitted.

In this example, the integration circuit 33 is inserted between the arithmetic circuit 32 and the control circuit 34, which is preferable for preventing hunting in control, but is not essential.

According to the above configuration, the switch means 50 is provided only when the wafer 6 on the disk 4 is within the irradiation area of the ion beam 2.
Are turned on to emit secondary electrons 22, which are supplied to the wafer 6. Moreover, the amount of secondary electrons 22 emitted at that time is controlled by the operation of the control circuit 34 and the like so that the disk current _ID becomes a desired set value, as in the case of the prior art.

Therefore, the amount of the secondary electrons 22 supplied to the wafer 6 can be made exactly the desired amount, and the antistatic action of the wafer 6 can be accurately performed. It is possible to prevent the occurrence of a problem such as negative charge due to the electrons 22 being supplied.

Moreover, according to the disk position detecting means as described above, the translational position of the disk 4 is detected by electrically processing the same translational control signal S _P used for translational control of the disk 4, so that the translational position of the disk 4 is detected. Can be accurately detected.

Moreover, the translation control device 42 is originally provided for translation control of the disk 4, and the translation control signal S _P output from it is output.
Is processed by the up / down counter 44 and the D / A converter 46 and is judged by the judgment circuit 48, the translation position of the disk 4 can be accurately detected.

In addition, the disk position detecting means is used for the switch means.
Since the extraction voltage is turned on and off by turning 50 on and off, the response speed is faster than when controlling the filament current according to the disk position, and therefore whether the secondary electron 22 is extracted according to the disk position. Can be quickly switched, and thereby the electrostatic charge of the wafer 6 can be accurately prevented.

Moreover, unlike the case where the filament current is controlled according to the disk position, a large load is not applied to the filament 14, so that the life of the filament 14 can be extended.

In each of the above examples, the disk current I _D is measured and controlled in the form of voltage, but it goes without saying that the current may be used as it is.

Whether or not the catch plate 12 is provided on the rear side of the disc 4 does not affect the essence of the present invention.

〔The invention's effect〕

Since the present invention is configured as described above, it has the following effects.

That is, in addition to the means for controlling the amount of primary electron emission, and thus the amount of secondary electron emission, so that the disk current becomes the set value,
Detecting the translation position of the primary electron emission only when the wafer on the disk is within the ion beam irradiation area,
As a result, by further providing the disk position detecting means and the switch means for emitting the secondary electrons as described above, the amount of the secondary electrons supplied to the wafer is exactly desired and the antistatic action of the wafer is accurately achieved. It is possible to prevent the occurrence of such a problem that secondary electrons are supplied to the wafer and the wafer is out of the beam irradiation region to be negatively charged.

Moreover, according to the disc position detecting means as described above, the translation position of the disc is detected by electrically processing the same translation control signal as that used for translation control of the disc, so that the translation position of the disc is accurately detected. be able to.

Moreover, the translation control device is originally provided for the translation control of the disk, and the translation control signal output from the translation control device is processed by the up-down counter and the D / A converter and is determined by the determination circuit. , The translational position of the disk can be accurately detected.

Further, since the disk position detecting means turns on / off the switch means to turn on / off the drawing voltage, the response speed is faster than the case where the filament current is controlled according to the disk position, and accordingly, depending on the disk position. Whether or not to extract the secondary electrons can be quickly switched, and thus the wafer can be accurately prevented from being charged.

Moreover, unlike the case where the filament current is controlled according to the disk position, a large load is not applied to the filament, so that the life of the filament can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram of the essential parts of an ion processing apparatus according to an embodiment of the present invention. FIG. 2 is a main part configuration diagram showing an example of an ion processing apparatus as a background of the present invention. 2 ... Ion beam, 4 ... Disk, 6 ... Wafer, 14 ... Filament, 16 ... Filament power supply, 18
...... Drawer power supply, 24 ...... Disk current measurement resistance, 28 ......
Disk current compatible voltage output amplifier, 30 ... Disk current setting circuit, 32 ... Arithmetic circuit, 34 ... Control circuit, 42 ... Translation control device, 44 ... Up / down counter, 46 ... D / A
Converter, 48 ... Judgment circuit, 50 ... Switch means, 52 ...
Multiplier circuit.

Claims (1)

[Claims] 1. An apparatus for irradiating a wafer mounted on a disk, which is rotated and translated in a vacuum container, with an ion beam to process the wafer, and a motor for translating the disk in response to a pulse signal. A translation control device that applies a translation control signal that is the pulse signal to the motor to control the translation speed of the disk, a filament that emits primary electrons, a filament power source that heats the filament, and a primary electron from the filament. Between the secondary electron emitting member that emits secondary electrons and the filament and the secondary electron emitting member, primary electrons are extracted from the filament and accelerated to collide with the secondary electron emitting member and then An extraction power source for applying an extraction voltage for emitting secondary electrons is provided, and the secondary electrons are stored in the ion beam irradiation region. In an ion processing apparatus adapted to supply to a wafer, a disk current measuring circuit for measuring a disk current flowing in the disk, a disk current setting circuit for setting a desired disk current, and a disk current measured by the disk current measuring circuit. And an operation circuit for obtaining a difference between the disk current set by the disk current setting circuit and a control circuit for controlling the filament power source so as to eliminate the difference and controlling the amount of primary electrons emitted from the filament, Switch means for turning on and off the extraction voltage applied between the filament and the secondary electron emission member from the extraction power source, and detecting the translational position of the disk, and when the translational position of the disk is within a predetermined region set in advance. And a disk position detecting means for turning on this switch means only Moreover, the disk position detecting means receives the translation control signal output from the translation control device, counts the number of pulses thereof, and digitally outputs the result, and receives the output from the up / down counter. D / A converter that outputs a triangular wave signal that represents the translational position of the disk by converting it to analog and a triangular wave signal that is output from this D / A converter, and its value is set to a predetermined value. It is determined whether or not the value is equal to or more than a value, thereby determining whether or not the translational position of the disk is within a predetermined area set in advance, and the switch means is turned on only when it is within the predetermined area. An ion processing apparatus comprising: a determination circuit.