JPH036989B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an improvement in an electron gun evaporation apparatus for depositing a thin film on a semiconductor substrate or the like by evaporating a raw material in a vacuum.

(Prior art and its problems) FIGS. 2 and 3 are schematic sectional views of a conventional electron gun evaporation apparatus. Explanation of each symbol and its parts is in the first page.
It will be described later according to the figure.

Conventionally, this type of device has a function that can be used when the electron beam no longer irradiates a predetermined surface position of the raw material due to a break in the electromagnet for deflecting the electron beam or due to deterioration of the permanent magnet. There is no way to detect it. Since the electron gun uses a very high output power, in the above case, the area directly hit by the electron beam will melt within a short period of time.
If you do too much, there is a risk of a serious accident. If the status of the electron gun was constantly monitored, this accident could be prevented to some extent, but it would be labor-intensive.

Furthermore, although the raw material is gradually reduced by evaporation, the amount of raw material remaining in the crucible can only be estimated from the evaporation rate, evaporation time, etc. other than by visual observation. If the raw materials suddenly run out due to bumping, there is a risk that the electron beam will directly hit the bottom of the crucible, causing a major accident.

(Objective of the Invention) An object of the present invention is to provide an electron gun evaporation apparatus that can detect abnormal irradiation of an electron beam as described above and prevent accidents.

(Structure of the Invention) The present invention accelerates electrons by applying a high voltage in a vacuum, deflects the accelerated electrons by a magnetic field, and irradiates a raw material contained in a crucible. Heating, melting and vaporizing the raw material,
In an electron gun evaporation device that deposits a thin film on a semiconductor substrate, etc., a collector is attached to the rear of the electron gun body to detect electrons reflected from the irradiated raw material, and the amount of electrons incident on the collector is The above object has been achieved by an electron gun evaporation apparatus provided with means for detecting abnormality in the electron gun by detecting a sudden change in the electron gun.

(Function) The backscattered electrons captured by the backscattered electron collector are
This becomes a collector current and is sent to the backscattered electron detector. Then, the current of the electron gun power supply circuit and the collector current are compared, and when the ratio deviates from a predetermined normal state, it is determined that the state is abnormal.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing a schematic configuration of an electron gun according to an embodiment of the present invention.

The electrons emitted from the filament 4 of the electron gun body 1 are deflected by the magnetic field created by the electron beam deflection magnet 7, pass through the electron beam trajectory 2, and irradiate the surface of the raw material 5 housed in the crucible 6 at approximately the center. . Then, some of the electrons are reflected by the raw material 5, deflected by the magnetic field of the deflecting magnet 7, and fly into the reflected electron collector 9 through the reflected electron trajectory 3. 8 is a water cooling pipe for cooling the electron gun body.

In conventional devices, the above-mentioned reflected electrons are either deflected by a magnetic field and taken into the electron gun by widening the rear part of the electron gun as shown in FIG. The backscattered electron collector 9 was installed with an insulating stone to prevent the backscattered electrons from being scattered inside the vacuum chamber. It is attached through.

Now, the backscattered electrons captured by the backscattered electron collector 9 are sent to the backscattered electron detector 11 as a collector current. And here, electron gun power supply circuit 1
2 current (emission current) and collector current are compared, and if this ratio has a value far from a predetermined normal state ratio, it is determined that there is an abnormal state and the output of the electron gun power supply circuit 12 is cut off. to prevent accidents.

FIG. 4 shows a power supply circuit 12 in a certain electron gun.
The relationship between the emission current and the backscattered electron collector current is shown.

Curve 15 is when the electron beam irradiates the back of the crucible near the collector, Curve 16 is when the electron beam irradiates the surface of a normal raw material, and Curve 17 is when the electron beam irradiates the front of the crucible. In this case, curve 18 indicates that the surface of the raw material in the crucible is 20 mm.
When it descends and the electron beam illuminates its surface,
It is.

Each curve can be said to be almost a straight line, and when the electron beam is normal, the emission current is about 9
% flows as collector current.

On the other hand, in cases 15 and 17 where the electron beam irradiates the back and front of the crucible, collector currents of 10% and 8% of the emission current flow, respectively.

In addition, if the surface of the raw material drops by 20 mm, 1
In 8, it is 6%. (Each percentage is also the value when the emission current is approximately 200mA.) In other words, in the case of this device, the emission current is approximately 200mA.
At 200mA, the collector current is 9% of the emission current, and from this ±1
% or more, it is determined that there is an abnormal state and the electron gun power supply circuit can be shut off. This makes it possible to prevent accidents with the electron gun.

(Effects of the Invention) According to the present invention, the electron beam may no longer irradiate a predetermined position due to a break in the electromagnet for deflecting the electron beam or the permanent magnet has deteriorated, or when the raw material is Provided is an electron gun evaporation apparatus that can quickly detect abnormal conditions such as bumping and prevent accidents associated with the abnormal conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an electron gun evaporation apparatus according to an embodiment of the present invention. 2 and 3 are similar conventional views. FIG. 4 is a graph showing the relationship between emission current and backscattered electron collector current. 1...Electron gun body, 2...Electron beam trajectory, 3
...Reflected electron orbit, 4...Filament, 5...
Raw material, 6... Crucible, 7... Magnet for electron beam deflection (electromagnet or permanent magnet), 8... Water cooling pipe, 9... Backscattered electron collector, 10... Insulating stone, 11... Backscattered electron detector, 12... Electron gun power supply, 13... Backscattered electron intake section, 14... Backscattered electron shield.

Claims (1)

[Claims] 1 Accelerate electrons by applying a high voltage in a vacuum, deflect the accelerated electrons using a magnetic field, and irradiate the raw material contained in the crucible to heat and melt the raw material. In an electron gun evaporation device that evaporates and deposits a thin film on a semiconductor substrate, etc., a collector is attached to the rear of the electron gun body to detect electrons reflected from the irradiated raw material, and the electrons are incident on the collector. An electron gun evaporation apparatus comprising means for detecting an abnormality in the electron gun by detecting a sudden change in the amount of electrons.