JPH0384842A - Ion processor - Google Patents

Abstract

PURPOSE:To prevent undesirable conditions such as negative electrification of a wafer, etc., by detecting the position of a disk and emitting primary electrons and secondary electrons only when the wafer located on the disk is within the irradiation area of an ion beam. CONSTITUTION:A disk position detecting means comprises a counter 44 which counts translation control signals SP output from a translation control device 42 and a D/A convertor 46 which converts the output of the counter 44 to analogue to obtain a triangular signal SD indicative of the position of a disk. The triangular signal SD is input to a decision circuit 48 to decide whether or not the signal SD is more than a preset value, thereby deciding whether or not the position of the disk 4 is within a predetermined irradiation area of an ion beam. A switching means 50 is inserted in series into an extension supply 18 and is turned on only when the disk 4 is within the predetermined beam irradiation area; only in this case primary electrons 21 are taken out from a filament 14 to emit secondary electrons 22. Thus the action of preventing a wafer 6 from being electrified is carried out with accuracy to prevent undesirable conditions such as negative electrification of the wafer, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an ion processing apparatus, such as an ion implantation apparatus, which irradiates a wafer with an ion beam in a vacuum and performs a process such as ion implantation on the wafer. In particular, the present invention relates to improvements in means for preventing electrification of wafers.

[Background technology]

The same applicant has separately proposed an ion processing apparatus that can accurately prevent static electricity on a wafer by controlling the disk current to exactly the desired set value.

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

On the path of the ion beam 2, there is a neutral cup 10 and a suppressor electrode that prevent secondary electrons emitted when the ion beam 2 hits the disk 4 etc. from escaping to the ground etc., as components of a Faraday system. A catch plate 8 is provided on the front side of the disk 4, and in this example, a catch plate 12 is provided on the rear side of the disk 4, which receives the ion beam 2 instead when the disk 4 is translated outward.

Then, the disk 4 via the disk current measuring resistor 24
, catch plate 12 and neutral cup 10
are electrically connected in parallel to each other and connected to a current measuring device 26 such as a current integrator, thereby making it possible to accurately measure the beam current Is of the ion beam 2.

In addition, in order to prevent the surface of the wafer 6 from becoming positively charged during irradiation with the ion beam 2, especially when the surface is an insulator, causing problems such as discharge, the sides of the neutral cup 10 are A filament 14 constituting a primary electron emission source is provided in the filament 14, and the primary electrons 21 emitted from the filament are applied to the opposing surface of the neutral cup 10 to emit secondary electrons 22 therefrom. The secondary electrons 22 are supplied to the wafer 6 in the ion beam irradiation area on the disk 4 to neutralize the positive charges caused by the ion beam 2 on the surface thereof.

16 is a filament power supply for heating the filament 14;
Reference numeral 18 denotes an extraction power source for extracting the primary electrons 21.

In that case, the disk current measuring resistor 24 basically contains the beam current I8 and the secondary electrons 2 for neutralization.
Secondary electron current due to 2 ■ Disk current I that is a composite of 2
n (=In + Ig) flows.

A disk current corresponding voltage output amplifier 2 constitutes a disk current measuring circuit together with a disk current measuring resistor 24.
8 is connected to both ends of the disk current measuring resistor 24, and then the disk current ■. , the desired disk current is set in the disk current setting circuit 30 in the form of voltage V3 in this example, and both voltages VD and V
, is input to an arithmetic circuit 32 including a differential amplifier, and the difference between the two voltages (VD Vs) is determined there.

Then, in the control circuit 34, the output (
■. -VS) becomes zero by controlling the filament power supply 16 and adjusting the filament current to control the amount of primary electrons 21 emitted from the filament 14.

According to the above configuration, when a desired disk current is set by the disk current setting circuit 30, the amount of primary electrons 21 emitted from the filament 14 is adjusted so that the disk current ID measured by the disk current measuring resistor 24, etc. matches the desired disk current.
In turn, the amount of secondary electrons 22 emitted from the neutral cup 10 is automatically controlled, and as a result, the disk current 1. becomes the set value. Thereby, the amount of secondary electrons 22 supplied to the wafer 6 on the disk 4 can be made exactly as desired, and thereby the antistatic effect on the wafer 6 can be performed accurately.

[Purpose of the invention]

However, in the above apparatus, the disk 4 is translated in the direction of the arrow during processing, so even if the knee halo is not within the irradiation area of the ion beam 2, the ion beam 2
When this hits the disk 4, a disk current ■ appears in the disk current measuring resistor 24. flows, and secondary electrons 22 are emitted so that it becomes a predetermined value, so when the wafer 6 leaves the beam irradiation area, only the secondary electrons 22 are supplied to the wafer 6, and the wafer 6 becomes negatively charged. There is still room for improvement in that there is a possibility that problems such as problems may occur.

Therefore, the main object of the present invention is to provide an ion processing apparatus that is further improved in these respects.

[Summary of the invention]

In order to achieve the above object, the present invention provides, in general terms, in addition to the above-described means for controlling the amount of primary electron emission and ultimately the amount of secondary electron emission so that the disk current reaches a set value. , ■Means for detecting the position of the disk and emitting primary electrons and eventually emitting secondary electrons only when the wafer on the disk is within the ion beam irradiation area; ■Detecting the position of the disk; A means for correcting the set value of the disk current according to the position of the wafer on the disk to control the amount of primary electron emission and, by extension, the amount of secondary electron emission, or both of the above means (1) and (2) is further provided. It is characterized by

〔Example〕

FIG. 1 is a block diagram of the main parts of an ion processing apparatus according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the example of FIG. 4, and the differences from the previous example will be mainly explained below.

In this example, the disk current ■. The amount of emitted primary electrons 21, and eventually the secondary electrons 22, is adjusted so that
In addition to the above-mentioned means for controlling the amount of emitted, the following means are further provided.

Specifically, the disk 4 described above is rotated by a motor 36 and translated by a motor (stepping motor) 38 via a mechanism section 40 . At this time, the translation speed V of the disk 4 is determined by applying a translation control signal SP in the form of a pulse signal from the translation 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 to satisfy the following well-known relationship.

v ccl , / R where R is the distance between the rotation center of the disk 4 and the center of the ion beam 2.

Therefore, in this embodiment, the translation control signal SP output from the translation control device 42 is counted by the counter 44 (counts up when the disk 4 is translating on the outward path, and counts down when the disk 4 is translating on the return path). output D
The /A converter 46 converts the triangular wave signal SI to analog to obtain a triangular wave signal SI representing the disk position, and this configuration constitutes a disk position detecting means.

This triangular wave signal S is then input to a determination circuit 48 including, for example, a window comparator, and it is determined whether the value of the triangular wave signal S is equal to or higher than a predetermined value. It is determined whether the position is within a predetermined beam irradiation area.

On the other hand, switching means (
In the illustrated example, a relay) 50 is inserted, and this is applied to the judgment circuit 4.
When the disk 4 is within the predetermined beam irradiation area, 02 is turned on by a signal from 8, and only at that time, primary electrons 21 are extracted from the filament 14 and secondary electrons 22 are emitted.

Note that in this example, the integration circuit 33 is inserted between the arithmetic circuit 32 and the control circuit 34 described above, because it is convenient for preventing hunting in control, etc., but it is not essential. .

According to the above configuration, when the wafer 6 on the disk 4 is within the irradiation area of the ion beam 2, the slow switch means 5
0 is turned on and 22 secondary electrons are emitted, which are supplied to the wafer 6. The amount of secondary electrons 22 emitted at that time is controlled by 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 example C.

Therefore, the amount of secondary electrons 22 supplied to the wafer 6 can be precisely set to a desired value to accurately prevent static electricity on the wafer 6, and when the wafer 6 is outside the beam irradiation area, It is possible to prevent problems such as being negatively charged due to the supply of electrons 22 from occurring.

FIG. 2 is a circuit diagram showing the surroundings of a control circuit of an ion processing apparatus according to another embodiment of the present invention. To explain the difference from the embodiment shown in FIG. ■ Multiplying circuit 5 with the settings in the form of
The signal V3·SI obtained thereby is inputted to the arithmetic circuit 32, where the disk current I is multiplied by 2.

The voltage corresponding to■. The filament power supply 16 is controlled by the control circuit 34 so that this difference becomes zero (VD Vs-3D). In this example, there is no need to provide the switch means 50 as described above.

The ion beam 2 usually has a mountain-shaped beam current density distribution, and even within the same beam irradiation area, the beam current density is generally high near the center. Therefore,
The charging status due to ion beam irradiation differs depending on where the wafer 6 is in the ion beam 2.

On the other hand, according to this embodiment, the triangular wave signal S! output from the D/A converter 46! Since l represents the position of the disk 4, the setting value for the arithmetic circuit 32 depends on the position of the disk 4, and therefore the wafer 6 on the disk 4.
It changes depending on the position. As a result, depending on the position of the wafer 6 on the disk 4, that is, depending on the magnitude of the beam current density distribution irradiated onto the wafer 6, the amount of emitted primary electrons 21, and ultimately the amount of secondary electrons 22 supplied to the wafer 6, is determined. The amount of secondary electrons 22 can be controlled as in the previous example.
More fine control is possible than in the case where the emitted amount does not reflect the position of the wafer 6, and thereby the wafer 6 on the disk 4 can be more completely prevented from being charged.

FIG. 3 is a circuit diagram showing the surroundings of a control circuit of an ion processing apparatus according to still another embodiment of the present invention.

This embodiment combines the features of the embodiment shown in FIG. 1 and the features of the embodiment shown in FIG. 2, and has the following circuit configurations:
For example, it can be seen that the determination circuit 48 and switch means 50 described in FIG. 1 are further added to the embodiment of FIG. 2.

Therefore, in this embodiment, until the wafer 6 on the disk 4 enters the irradiation area of the ion beam 2, the secondary electrons are
When the supply of secondary electrons 22 is completely stopped and the wafer 6 begins to enter the beam irradiation area, the supply of secondary electrons 22 is started and the amount is gradually increased until the wafer 6 is completely within the beam irradiation area. When the wafer 6 enters the beam irradiation area, the supply amount of the secondary electrons 22 becomes the maximum set value, and when the wafer 6 starts to come out of the beam irradiation area, the supply amount of the secondary electrons 22 is gradually reduced. The supply of secondary electrons 22 is completely stopped.

Therefore, in this embodiment as well, it is possible to prevent problems such as being negatively charged due to the secondary electrons 22 being supplied to the wafer 6 when it is outside the beam irradiation area. It is possible to more precisely control the amount of secondary electrons emitted when the wafer 6 is within the beam irradiation region, thereby making it possible to more completely prevent the wafer 6 from being charged.

It should be noted that as the disk position detecting means, a device other than the above-described example, such as a potentiometer that responds to the translation of the disk 4, etc. may be used.

Also, on each side above, the disk current ■. Measurement and control are performed in the form of voltage, but it is of course possible to use current as is.

Further, whether or not the catch plate 12 is provided on the rear side of the disk 4 does not affect the essence of the present invention.

〔Effect of the invention〕

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

That is, in addition to a means for controlling the amount of primary electron emission and ultimately the amount of secondary electron emission so that the disk current reaches a set value,
■By further providing the above-mentioned means for detecting the position of the disk and emitting primary electrons and eventually emitting secondary electrons only when the wafer on the disk is within the ion beam irradiation area, the wafer The amount of secondary electrons supplied to the wafer can be adjusted to exactly the desired amount to accurately prevent the wafer from charging, and when the wafer is outside the beam irradiation area, the secondary electrons are supplied to the wafer and the wafer becomes negatively charged. It is possible to prevent problems such as charging.

In addition to the means for controlling the amount of primary electron emission and ultimately the amount of secondary electron emission so that the disk current reaches a set value,
■By further providing the above-mentioned means for detecting the position of the disk and correcting the set value of the disk current according to the position of the wafer on the disk, it is possible to Since the amount of secondary electron emission can be controlled by using the method, more fine control is possible, and thereby electrification of the wafer can be more completely prevented.

Furthermore, in addition to means for controlling the amount of primary electron emission and ultimately the amount of secondary electron emission so that the disk current reaches a set value,
By further providing both of the above means and (2), it is possible to prevent problems such as being negatively charged due to secondary electrons being supplied to the wafer when it is outside the beam irradiation area, and More fine control of the amount of secondary electron emission is possible when the wafer is within the beam irradiation area, thereby making it possible to more completely prevent charging of the wafer.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the main parts of an ion processing apparatus according to an embodiment of the present invention. Figures 2 and 3 are, respectively,
FIG. 3 is a circuit diagram showing the surroundings of a control circuit of an ion processing apparatus according to another embodiment of the present invention. FIG. 4 is a diagram illustrating a main part configuration of an example of an ion processing apparatus which is the background of the present invention. 2... Ion beam, 4... Disk, 6... Wafer, 14... Filament, 16... Filament power supply, ■8... Output power supply, 24... Disk current measuring resistor, 2 3...Disk current compatible voltage output amplifier, 30...Disk current setting circuit, 32...Arithmetic circuit, 349. - Control circuit, 42... Translation control device, 44... Counter 1.46... D/A converter, 4
8... Judgment circuit, 500.・Switch means, 52...
・Multiplication circuit.

Claims (3)

[Claims] (1) A device that processes a wafer mounted on a disk that is rotated and translated in a vacuum chamber by irradiating the wafer with an ion beam, and includes a primary electron emission source that emits primary electrons, and A disk current measuring circuit that measures a disk current flowing through the disk, the device comprising a secondary electron emission source that emits secondary electrons when the secondary electrons are received and supplies the secondary electrons to a wafer in an ion beam irradiation area. , a disk current setting circuit that sets a desired disk current, and an arithmetic circuit that calculates the difference between the disk current measured by the disk current measuring circuit and the disk current set by the disk current setting circuit, so that this difference is eliminated. a control circuit that controls the primary electron emission source to control the amount of primary electrons emitted therefrom; a disk position detection means that detects the position of the disk and outputs a signal representing the disk position; a determination circuit that determines whether the disc position is within a predetermined area in response to a signal from the detection means; and a determination circuit that determines whether the disc position is within a predetermined area in response to a signal from the determination circuit and switch means for activating the primary electron emission source and emitting primary electrons from the primary electron emission source only when the primary electron emission source is located within the ion processing apparatus. (2) A device that processes a wafer mounted on a disk that is rotated and translated in a vacuum chamber by irradiating the wafer with an ion beam, and includes a primary electron emission source that emits primary electrons, and A disk current measuring circuit that measures a disk current flowing through the disk, the device comprising a secondary electron emission source that emits secondary electrons when the secondary electrons are received and supplies the secondary electrons to a wafer in an ion beam irradiation area. a disk current setting circuit for setting a desired disk current; a disk position detection means for detecting the position of the disk and outputting a signal representing the disk position; and a signal from the disk position detection means and the disk current setting. a multiplier circuit that multiplies the disk current set by the circuit; an arithmetic circuit that calculates the difference between the signal from the multiplier circuit and the disk current measured by the disk current measurement circuit; An ion processing device comprising: a control device that controls an electron emission source to control the amount of primary electrons emitted from the electron emission source. (3) a determination circuit that determines whether or not the disc position is within a predetermined area in response to a signal from the disc position detection means; 3. The ion processing apparatus according to claim 2, further comprising a switch means for activating the primary electron emission source to cause the primary electron emission source to be emitted from the primary electron emission source only when the disk is within the predetermined area.