JPS62139323A - Control of ion beam dosage - Google Patents

Abstract

PURPOSE:To produce the titled ion beam dosage with high precision by a method wherein a probe current is converted into frequency using a part of primary ion beams to correct beam irradiating time at each deflecting point immediately referring to the data on the conversion. CONSTITUTION:Ion beam led out of a fluid metallic ion source 7 by an electrode 8 are limited by a throttle 9 to be focussed by lenses 6a, 6b for deflection by a deflector 5 in a vacuum chamber 101. The ion current Ip to the throttle 9 is linearized to be converted into frequency f while signals to be the clock 1' of pattern producer 1 are transmitted from photocouplers 11. When the beam stop clock number is assumed to be n, the beam dosage D=n/K and f=K.Ip therefore if Ip and f are measured to calculate a constant K and the beam stop clock number n is set up, D value shall be a constant not to be fluctuated even if the Ip is fluctuated during scanning process so that the dosage may be made constant to provided processing and implantation with high precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ion microbeam apparatus, particularly to a control method for obtaining a highly accurate ion beam irradiation amount.

[Conventional technology]

The conventional method is described in Japanese Patent Application Laid-Open No. 60-143630, and its principle diagram is shown in FIG. This device performs maskless ion implantation using a narrowly focused ion beam, and by using a variable frequency oscillator 2 as a clock signal source for the pattern generator 1, it is possible to continuously control the amount of ion implantation. It is something. According to this, the probe current is measured in advance with the Faraday cup 4, and the oscillation frequency of the variable frequency oscillator is set based on the information. Therefore, it is assumed that the measured value of the probe current measured before writing does not change during writing, and the drift of the beam current during writing time has not been taken into consideration.

This becomes a problem especially when drawing for a long time is required.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration the drift of the beam current during writing, and there is a problem in that the drift of the beam current during writing directly causes a fluctuation in the beam irradiation amount.

An object of the present invention is to maintain the beam irradiation amount at a desired value even if there is a drift in the beam current during writing.

The purpose is to perform high-precision drawing.

[Means for solving problems]

The above purpose is to convert the probe current using a part of the primary ion beam, and use that information to correct the beam irradiation time at each deflection point in real time.
achieved.

[Effect]

With the above configuration, even if there is a drift in the beam current, the beam irradiation time at each deflection point can be corrected in real time, so the beam irradiation amount can be maintained at a desired value.

〔Example〕

Before describing embodiments, the principle of the present invention will be explained first.

In Figure 1, a current I reflecting the probe current 1p
When (I=F (Ip)) is linearized and converted to frequency f, the following equation is obtained.

f=K・Ip (Hz) K: Constant (1) Assuming that the pattern generator 1 holds the beam stationary at the deflection point while counting the clock n times, the beam irradiation amount at the deflection point can be expressed by the following formula. .

D=niblob flow x beam rest time”Ip・−=n/K (2) Therefore,
Even if Ip varies, the desired beam irradiation amount set by n can be obtained.

An embodiment of the present invention will be described below with reference to FIG. Second
The figure shows an ion microbeam device, in which an ion beam is extracted from a liquid metal ion source 7 in a vacuum column 10 by an extraction electrode 8, the beam aperture angle is limited by an aperture 9, and an electrostatic lens 6a.

6b focuses the beam, and deflector 5 deflects the beam. At this time, the ion current flowing into the aperture 9 was converted into a frequency by the current-frequency converter 2, and a signal was transmitted by the high-voltage photocoupler 11 and used as a clock for the pattern generator. In the region where the total ion current Itot from the ion source is 5 μA or less, the current flow into the aperture 9 and the probe current I
Since a substantially proportional relationship was established between p, one signal linearization was not performed in this embodiment. faraday cup 4
By means of the probe, the electric current is measured, and in addition, the black.

Measuring the frequency f and finding k from equation (1) = f/Ip = 17x108/100xIO-" = 1
．． 7X1014.If the beam resting clock number n is set to 170, the beam irradiation amount becomes D=n/==170/1.7xlO"=IX10""
(C) Even if Ip varied, the value of D did not vary, and uniform drawing was possible.

A similar beam irradiation amount control function was also confirmed when converting the probe current from the secondary electrons and current generated when the aperture was irradiated with the ion beam.

In the above embodiment, the beam irradiation amount was controlled based on the ion current flowing into the diaphragm, but since Ip is directly set to the hexagonal current-frequency converter 2, the above embodiment also applies when the sample current is monitored. Similarly, the beam irradiation amount could be controlled.

〔Effect of the invention〕

According to the present invention, a constant beam irradiation amount can be obtained even if the beam current fluctuates during scanning with a focused ion beam, so that highly accurate processing, implantation, etc. can be performed.

Furthermore, uniform beam irradiation can be achieved even when using an ion source that is not specially provided with a stabilizing circuit.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of the present invention, and FIG. 2 is a diagram of the present invention. FIG. 3 is a block diagram showing a conventional example of the apparatus. 1... Pattern generator, 2... Variable frequency oscillator,
3...CPU, 4...Faraday cup, 5...
Deflector, 6a, 6b... Electrostatic lens, 7... Ion source, 8... Extraction electrode, 9... Aperture, 10... Vacuum column, 11... High voltage withstand photocoupler.

Claims (1)

[Claims] 1. In an ion beam device having an ion source and an optical system for focusing and deflecting the ion beam emitted from the ion source, a part of the primary ion beam is used to convert the probe current, A method for controlling ion beam irradiation amount, which is characterized in that the beam irradiation time at each deflection point is corrected in real time based on the information. 2. A patent characterized in that a probe current value converted into a frequency from a part of the primary ion beam is input as a clock to a pattern generator that generates a drawing pattern in synchronization with a reference clock and deflects the beam. Claim 1
Method for controlling ion beam irradiation amount described in Section 1. 3. A method for controlling ion beam irradiation amount according to claim 1 or 2, characterized in that a probe current is converted from a primary ion beam flowing into an extraction electrode, an aperture, or the like. 4. The method for controlling the ion beam irradiation amount according to claim 3, characterized in that the probe current is converted from secondary electrons generated by irradiation with the primary ion beam.