JPS628523A - Ion beam etching device - Google Patents

Abstract

PURPOSE:To correctly measure the exposure of ion beams applied to a material, by arranging magnetic body around projected ion beam fluxes in a space defined between the ion draw-out electrodes and the material, and detecting the magnetic fluxes produced in the magnetic body as a current. CONSTITUTION:Ion beams taken out from an ion source 1 produces a magnetic field around the ion beams and magnetic fluxes thereof are passed through a magnetic circuit formed of a magnetic material 8 and a magnetic detector 9. The magnetic detector 9 serves to convert the magnetic fluxes into an electrical signal. According to this construction, the current value can be contained by measuring the electrical output of the magnetic detector 9, and the etching amount can be estimated correctly therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an ion beam etching apparatus, and in particular,
The present invention relates to an ion beam etching apparatus that can more accurately measure the amount of ion irradiation applied to a sample such as a semiconductor wafer.

[Prior Art] With the ultra-fine processing of semiconductor devices such as LSIs in lithography technology, control of the etching amount (depth) in the dry etching process has become increasingly important. In particular, when etching a polycrystalline silicon layer formed on a silicon single crystal wafer, it is necessary to accurately determine the etching end point in order not to damage the underlying single crystal silicon layer.

FIGS. 2 and 3 show the construction of a conventional ion beam etching apparatus used in this type of etching process.

In the figure, 1 is an ion source, 2 (21, 22) is a group of ion extraction electrodes, 3 is a wafer, 4 is a wafer holder, 5 is an ammeter, and 6 is a Faraday cup. 7 indicates an ion beam.

In these ion beam etching apparatuses, etching is performed by converting etching gas into plasma using an ion source 1 and irradiating the wafer 3 with ions extracted by an extraction electrode group 2.

Since the ion irradiation m is proportional to the ion current integral value,
The amount of radiation can be determined by measuring the current.

By the way, as shown in FIG. 2, when the ion current flowing through the wafer holder current is detected by the ammeter 5, the detected current value also includes ions incident on a portion of the holder 4 other than the wafer 3. Therefore, there is a drawback that only the amount of ions incident on the wafer 3 cannot be accurately determined.

On the other hand, in FIG. 3, the Faraday cup 6 is attached to the final stage extraction electrode 22 as needed, such as before starting etching.
and the wafer 3, and take out a part of the ion beam 7 with the Faraday cup 6. At this time, the Faraday cup 6
The ion current density value during etching is calculated by measuring the current flowing through the etching. In this case, since only a portion of the ion beam is measured to determine the ion flow density, there is a drawback that the amount of ions incident on the sample cannot be accurately measured. Further, since the measurement was not performed while the wafer 3 was actually being irradiated, it was not possible to monitor fluctuations in the ion beam.

Another possible method is to install a Faraday cup 6 around the ion beam and measure the ion irradiation tJ1m during etching, but in this case too, a part of the ion beam is detected and measured, so accurate ion irradiation can be achieved. Quantity cannot be measured.

As described above, the conventional apparatus has the disadvantage that it is not possible to accurately estimate the amount of etching.

[Object of the Invention] In view of the problems of the conventional method described above, an object of the present invention is to provide an ion beam etching apparatus that can accurately measure the amount of ion irradiation to a sample (member to be etched) such as a wafer. shall be.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of an ion beam etching apparatus according to an embodiment of the present invention. Note that parts common or corresponding to those of the conventional type shown in FIGS. 2 and 3 are designated by the same reference numerals. In FIG. 1, 8 is a magnetic material, 9 is a magnetic detector such as a Hall element, 10 is a signal amplifier, and 11 is an etching controller. The magnetic body 8 and the magnetic detector 9 constitute a magnetic circuit surrounding the ion beam 7. In addition, magnetic material 8
Examples include permalloy, silicon steel plate, and ferrite.

In FIG. 1, the ion beam extracted from ion rA1 generates a magnetic field around the ion beam, and passes a magnetic flux through a magnetic circuit composed of a magnetic body 8 and a magnetic detector 9. This magnetic body 8 is for concentrating the magnetic field generated by the ion beam and preventing external influences. A magnetic detector (magnetic sensor) 9 such as a Hall element is provided in a part of the magnetic circuit, and converts magnetic flux into an electric signal.

Here, the magnetic flux penetrating the Hall element and its output current are proportional. Further, the magnitude of the magnetic flux passing through the magnetic circuit is proportional to the amount of current of the ion beam passing inside the ring of the magnetic circuit. Therefore, by measuring the electrical output of the Hall element 9, the current value of the entire ion beam can be obtained, and the total ion irradiation amount can be accurately measured, thereby making it possible to accurately estimate the etching amount.

The output of the Hall element 9 is amplified by a signal amplifier 10 and sent to an etching control section 11. The etching control section determines the etching end point based on this value and controls the etching operation. In addition to the Hall element, the magnetic detector 9 may also include a core (such as a Kramer type DC transformer).
It is possible to use a device that converts the DC magnetic flux in the magnetic body 8) into DC current and outputs the DC current.

According to this embodiment, the sample holder on which the wafer or the like is placed is not used for measuring the ion irradiation amount, so the structure of the sample holder is simplified. Further, since a Faraday cup is not used, there is no need for a Faraday cup moving mechanism in vacuum.

[Effects of the Invention] As explained above, according to the present invention, in the ion beam etching apparatus, since the magnetic material and the magnetic detector are provided around the irradiated ion beam flux, it is possible to It is possible to accurately measure the irradiation tooth of the ion beam.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an ion beam etching apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a conventional etching apparatus for measuring the ion current incident on a wafer holder, and FIG. 3 is a block diagram of a faraday etching apparatus. 1 is a configuration diagram of a conventional etching apparatus that measures ion current using a cup; FIG. 1: ion source, 2 (21, 22): ion extraction electrode, 3: wafer, 4: holder, 7: ion beam, 8: magnetic material, 9:
Magnetic detector, 10: signal amplification section, 11: etching control section.

Claims (1)

[Scope of Claims] 1. In an ion beam etching apparatus that performs etching by irradiating a sample with ions extracted from an ion source by an extraction electrode, the area around the irradiated ion beam bundle within the gap from the ion extraction electrode to the sample. An ion beam etching apparatus characterized in that a magnetic body is disposed in the ion beam etching apparatus, and a means for detecting magnetic flux generated in the magnetic body as an electric current is provided. 2. The ion beam etching apparatus according to claim 1, wherein the magnetic material is permalloy, silicon steel plate, or ferrite. 3. The ion beam etching apparatus according to claim 1 or 2, wherein the detection means includes a Hall element or a Kramer type DC transformer.