JPH03242591A - Measuring device for beam current density distribution - Google Patents

Abstract

PURPOSE:To detect automatically that the beam current density distribution of an ion beam is out of a reference set beforehand, by measuring the beam current density distribution of the ion beam and by determining whether it is within the reference or not. CONSTITUTION:A position signal S1 outputted from a counter 32 in a switching control circuit 30 and related to which switching element 21 of an analog switch 20 is to be turned ON and a measuring signal S3 outputted from the analog switch 20 are amplified by an amplifier 44 and subjected to A/D conversion 48, and a measuring signal S4 thus obtained is taken in a microcomputer 50. A first storage means 55 relates the value of the measuring signal S4 to the content of the position signal S1 and stores it. In a second storage means 56 the upper and lower limit values of the beam current density of an ion beam 2 allowed from each position of a collector electrode 4 are stored beforehand. A determining means 57 outputs an alarm signal S5 when the value of the measuring signals S4 is not within the limits of the upper and lower limit values.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is used in ion processing equipment such as ion implantation equipment and ion beam etching equipment, and is used to measure the beam current density distribution of an ion beam. This invention relates to a distribution measuring device.

[Conventional technology]

For example, in an ion implantation apparatus, in order to reduce charge-up of the wafer, it is important to make the beam current density distribution of the ion beam irradiating the wafer as uniform as possible and to widen the width of the distribution.

To do this, it is first necessary to measure the beam current density distribution of the ion beam, and for this purpose a beam current density distribution measuring device as shown in FIG. 4 has been proposed.

This device includes a plurality of collector electrodes 4, a conversion circuit 10, an analog switch 20, a switching control circuit 30, a D/A converter 42, an amplifier 44, and a display device 46.

In this example, the collector electrodes 4 are arranged in a cross shape in the X direction and the Y direction in front of a catch plate 6 that receives the ion beam 2 traveling from the front side to the back side of the page.

The conversion circuit 10 has a plurality of resistors 11 connected to each collector electrode 4, and a measurement signal ( A voltage signal) S3 is generated respectively.

The analog switch 20 has a plurality of switching elements 21 connected to each resistor 11 of the conversion circuit 10,
Under the control of the switching control circuit 30, each measurement signal S3 from the conversion circuit 10 is selectively switched and output.

The switching control circuit 30 includes a pulse generator 31 that generates pulses of a predetermined frequency. A counter 32 counts this pulse (repeating amplifier counting and down counting), outputs a position signal S1 indicating which switching element 21 of the analog switch 20 is to be turned on, and switches the analog switch 20 based on this position signal S. It has a decoder 33 that selectively sequentially switches on the elements 21 to turn them on.

The position signal St from the switching control circuit 30 is a D/A
The triangular wave signal S is converted into analog by the converter 42.
2, which is the display device (e.g. oscilloscope) 4
It is input to the X-axis terminal of 6.

On the other hand, the measurement signal S3 from the analog switch 20 is amplified by the amplifier 44, and YI[lI
Manual power is applied to the terminal.

Therefore, on the display device 46, for example, as shown by the solid line M in FIG.
The beam current density of the ion beam 2 measured by the collector electrode 4 is displayed, and thereby the beam current density distribution of the ion beam 2 is displayed.

[Problem to be solved by the invention]

However, the beam current density distribution of the ion beam 2 changes depending on how the operator selects the parameters of the ion source that generates the ion beam 2, or due to changes in the parameters over time. If you just display it on the display device 46,
The operator must constantly monitor the display device 46 for abnormalities in the beam current density distribution, which is very time-consuming and goes against the trend of FA (factory automation).

Therefore, the present invention provides a beam current density distribution measuring device that sets a certain standard for the beam current density distribution of an ion beam and can automatically detect when the distribution falls outside of this standard. The main purpose is to

[Means to solve the problem]

In order to achieve the above object, the beam current density distribution measuring device of the present invention includes a plurality of collector electrodes arranged in parallel in an ion beam irradiation area, and generates measurement signals corresponding to the beam current flowing through each of the collector electrodes. a conversion circuit that selectively switches and outputs each measurement signal from the conversion circuit; a switching control circuit that controls switching of the switch and generates a position signal representing the switching position; (2) storage means for storing the value of the measurement signal output from the switch in association with the contents of the device signal output from the switching control circuit; and an upper limit for the beam current density of the ion beam for each position of each collector electrode. a second storage means storing the value and the lower limit value in advance;
Determine whether or not the value of the measurement signal stored in the first storage means is within the range of the upper and lower limit values stored in the second storage means for each collector electrode position. The present invention is characterized in that it includes a determining means for outputting an alarm signal when there is something that is not within the range.

[Operation] According to the above output, when the switch is sequentially switched by the switching control circuit with the ion beam being irradiated onto the portions of a plurality of collector electrodes, the beam current flowing through each collector electrode is stored in the first storage means. The value of the corresponding measurement signal is stored in association with the content of the device signal output from the switching control circuit.

Then, the determination means determines whether the value of the measurement signal stored in this way is within the range of the upper limit value and the lower limit value of the beam current density, which are stored in advance in the second storage means. A determination is made for each position of the collector electrode, and if there is a position that is not within the range, an 11 signal is output.

In this way, it is possible to automatically detect that the beam current density distribution of the ion beam deviates from the standard.

〔Example〕

FIG. 1 is a diagram showing a beam current density distribution measuring device according to an embodiment of the present invention. The same reference numerals are given to the same or corresponding parts as in the conventional example shown in FIG. 4, and the differences from the conventional example will be mainly explained below.

In this embodiment, in addition to the output explained in FIG.
It further includes a microcomputer 5o having a CPU 51, a memory 52, and an I10 port 53, and an A/D converter 48.

Then, an output from the counter 32 in the switching control circuit 3o described above determines which switching element 21 of the analog switch 2o is to be turned on (that is, the collector electrode 4 of the analog switch 2o).
The amplifier 44 amplifies the position signal SI and the measurement signal S3 outputted from the analog switch 2o described above, and the measurement signal S4, which is converted into a digital signal by an A/D converter, is sent to the microcomputer 5o. I'm trying to incorporate it into

Functionally, this microcomputer 50 has a first storage means 55, a second storage means 5, as shown in FIG.
6 and determination means 57.

The first storage means 55 stores the value of the captured measurement signal s4 in association with the content of the position signal S1.

The position signal S1 represents the position of the selected collector electrode, and the measurement signal S4 represents the beam current density at the position of the collector electrode. The actually measured beam current density distribution as shown is stored.

The second storage means 56 stores in advance the upper and lower limits of the beam current density of the ion beam 2 that are permissible for each position of the collector electrode 4. That is, for example, the third
In the figure, an upper limit beam current density distribution as shown by a broken line U and a lower limit beam current density distribution as shown by a broken line are stored.

This is the standard beam current density distribution.

Then, the determining means 57 determines whether the value of the measurement signal S4 stored in the storage means 55 is within the range of the upper limit value and the lower limit value stored in the storage means 56 for each collector electrode 4. A judgment is made for each position, and if there is something that is not within the range, an alarm signal S is output. That is, it is determined whether the actually measured beam droplet flow density distribution shown by the solid line M in FIG. In this case, an alarm signal S5 is output.

In this way, it is possible to automatically detect that the beam current density distribution of the ion beam 2 is outside the standard.

There are various ways to use the alarm signal S, for example, it may be used to display an alarm, or it may be further used as an interlock to stop ion implantation or the like.

In the above example, a large number of collector electrodes 4 are arranged in a cross shape so that the beam current density distribution in the X direction and Y direction of the ion beam 2 can be switched and measured. The number of resistors 11 in the conversion circuit 10 and the number of switching elements 21 in the analog switch 20 may be determined depending on the number of resistors 11 and the switching elements 21 in the analog switch 20.

Further, it would be convenient to provide a D/A converter 42 and a display device 46 as in the conventional example, but these are not essential for achieving the purpose of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, the beam current density distribution of the ion beam is measured and the determining means determines whether it is within a predetermined standard. It is possible to automatically detect that the current density distribution deviates from the standard.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a beam current density distribution measuring device according to an embodiment of the present invention. FIG. 2 is a functional block diagram of the microcomputer in FIG. 1. Figure 3 shows
FIG. 3 is a diagram showing an example of beam current density distribution. Figure 4 shows
1 is a diagram showing an example of a conventional beam current density distribution measuring device. 29.・Ion beam, 4...Collector electrode, IO・
...Conversion circuit, 20...Analog switch, 30...
・Switching control circuit, 48.・・A/D converter, 50...
Microcomputer, 55...first storage means, 5
6... second storage means, 57. ...Judgment means.

Claims (1)

[Claims] (1) A plurality of collector electrodes arranged in parallel in the ion beam irradiation area, a conversion circuit that generates measurement signals corresponding to the beam current flowing through each collector electrode, and selection of each measurement signal from the conversion circuit. A switch for uniformly switching and outputting, a switching control circuit that controls switching of this switch and generates a position signal representing the switching position, and a switching control circuit that controls the value of the measurement signal output from the switch. a first storage means that stores the position signal in association with the content of the position signal output from the ion beam, and a second storage means that stores in advance an upper limit value and a lower limit value of the beam current density of the ion beam for each position of the collector electrode. Then, it is determined for each collector electrode position whether or not the value of the measurement signal stored in the first storage means is within the range of the upper limit value and lower limit value stored in the second storage means. 1. A beam current density distribution measuring device characterized by comprising: determining means for determining whether or not the current density is within the range, and outputting an alarm signal if there is something that is not within the range.