JPH10106472A - Reflected electron detection device for charged corpuscular beam device and charged corpuscular beam device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor reflected electron detection device less influenced by a temperature-dependent noise. SOLUTION: This device has a semiconductor reflected electron detector 4 to detect a reflected electron C2 from a sample 3, an electrothermal element 10 to cool the detector 4, a temperature sensor 11 to detect the temperature of the detector 4, and a temperature controller 12 to control the cooling output of the electrothermal element 10 so as to keep the temperature of the detector 4 constant. As a result, a temperature-dependent noise included in the output signal of the detector 4 becomes almost constant and the noise can be easily suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backscattered electron detector and a charged particle beam device used in a charged particle beam device.

[0002]

2. Description of the Related Art FIG. 5 is a view for explaining a conventional backscattered electron detecting device used in a charged particle beam device, and shows a part of the charged particle beam device. 1 is a charged particle beam device, 2 is an electron lens constituting a part of an optical system of the charged particle beam device, 3 is a sample irradiated with the electron beam C1 passing through the electron lens 2, and 4 is a sample from the sample 3. This is a semiconductor backscattered electron detector that detects backscattered electrons C2. The semiconductor backscattered electron detector 4 includes a semiconductor sensor composed of a pn junction or a pin junction of Si (silicon), and is arranged such that the pn junction or the pin junction of the semiconductor sensor is located at the incident position of the backscattered electrons C2. You. At this time, it is desirable to arrange the detector 4 as close as possible to the sample 3 in order to increase the detection efficiency. However, usually, the detector 4 is arranged near the electron lens 2 so as to see the electron beam irradiation position of the sample 3. The electron lens 2, the sample 3, and the semiconductor backscattered electron detector 4 are housed in a vacuum vessel 5, and the inside of the vacuum vessel 5 is kept in a vacuum during operation of the charged particle beam apparatus.

[0003]

In the charged particle beam apparatus of this type, the beam current and the current of the electron lens tend to increase in recent years, and the irradiation of the electron beam C1 and the electron lens
The temperature of the semiconductor backscattered electron detector 4 rises during the operation of the charged particle beam device 1 due to the influence of heat generation and the like, and the noise of the output signal of the semiconductor backscattered electron detector 4 increases. By the way, noise that increases with an increase in temperature includes thermal noise, shot noise, dark current, and the like. Among them, the dark current greatly depends on temperature. FIG. 6 is a diagram showing an example of the relationship between temperature and dark current, where the horizontal axis is temperature and the vertical axis is dark current. In the example of FIG. 6, the dark current is increased about 5 times for a temperature rise of 10 K, which has a serious influence on the measurement.

An object of the present invention is to provide a backscattered electron detector and a charged particle beam device for a charged particle beam device which are less affected by temperature-dependent noise.

[0005]

An embodiment of the present invention will be described with reference to FIGS. (1) Explained in association with FIG. 1, the invention of claim 1 is applied to a backscattered electron detection device for a charged particle beam device including a detector 4 for detecting backscattered electrons C2 from a sample 3, and Control means 1 for controlling the temperature of the air to be constant
The above objects are achieved by providing 0, 11, and 12. (2) According to a second aspect of the present invention, in the backscattered electron detector for a charged particle beam device according to the first aspect, the control means detects a cooling means 10 for cooling the detector 4 and a temperature of the detector 4. A temperature sensor 11 and a control device 12 for controlling the cooling output of the cooling means 10 so that the temperature of the child detector 4 becomes constant are provided. (3) Explained in connection with FIG. 4, the invention of claim 3 is the backscattered electron detection device for a charged particle beam device according to claim 1, wherein the control means comprises the detector 4 and the electron of the charged particle beam device. Cooling means 21 for cooling the lens 2;
A temperature sensor 11 for detecting one of the temperatures of the electronic lens 2; and a control device 24 for controlling the cooling output of the cooling means 21 so that the temperature detected by the temperature sensor 11 becomes constant. (4) Explaining in connection with FIG. 3, the invention of claim 4 is applied to a backscattered electron detector for a charged particle beam device, which includes a detector 4 for detecting backscattered electrons C2 from the sample 3, and Means 10 for cooling the cooling means, and cooling means 10 so that the dark current component contained in the output signal of detector 4 is constant.
The above-mentioned object is achieved by providing the control device 12 for controlling the cooling output of the apparatus. (5) Explained in connection with FIG. 2, the invention of claim 5 is a charged particle beam apparatus 1 for irradiating a charged particle beam toward a sample 3 in a vacuum vessel 5 and is made of a good heat conductive insulator. A detector 4 held by the holding member 13 in the vacuum vessel 5 and detecting the reflected electrons C2 from the sample 3; a cooling means 10 attached to the holding member 13 for cooling the detector 4; Temperature sensor 11 to detect, temperature sensor 11
The above-mentioned object is achieved by providing a control means 12 for controlling the cooling means 10 so that the temperature of the detector 4 detected in the step 4 becomes constant. (6) The charged particle beam apparatus 1 for irradiating a charged particle beam toward the sample 3 in the vacuum vessel 5 is held in the vacuum vessel 5 by the holding member 13 made of a good heat conductive insulator. And detector 4 for detecting backscattered electrons C2 from sample 3
A cooling means 10 attached to the holding member 13 for cooling the detector 4; and a control means 12 for controlling the cooling means 10 so that the dark current of the detector 4 is constant. To achieve. (7) According to a seventh aspect of the present invention, in the charged particle beam device according to the fifth or sixth aspect, the holding member 13 is provided to penetrate the vacuum vessel 5 and the cooling means 10 is provided outside the vacuum vessel 5. .

(1) According to the first and second aspects of the present invention, the temperature of the detector 4 is kept substantially constant. (2) According to the third aspect of the invention, the cooling means 21 cools both the detector 4 and the electron lens 2. (3) According to the invention of claim 4, the dark current component contained in the output signal of the detector 4 is kept substantially constant. (4) According to the fifth and sixth aspects of the present invention, the detector 4 is held in the vacuum vessel 5 via the holding member 13 made of a good heat conductive insulator and cooled by the cooling means 10. (5) In the invention of claim 7, since the cooling means 10 is provided outside the vacuum vessel 5 of the charged particle beam device 1, a cooling means having a large cooling capacity can be attached.

[0007] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand. However, the present invention is not limited to the embodiment.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. -First Embodiment- FIG. 1 is a view for explaining a schematic configuration of a backscattered electron detecting apparatus according to the present invention, and shows a part of a charged particle beam apparatus as in FIG. The sign was attached. Reference numeral 10 denotes an electric heating element such as a Peltier element for cooling the semiconductor reflection electron detector 4, and reference numeral 11 denotes a temperature sensor, which are attached to the package of the semiconductor reflection detector 4 in close contact with each other. When the electric heating element 10 and the temperature sensor 11 are attached to the semiconductor reflection detector 4, for example, they are attached via a sheet-like insulator (not shown). The temperature controller 12 controls the cooling output of the electric heating element 10 based on the signal from the temperature sensor 11 so that the temperature of the semiconductor backscattered electron detector 4 is kept constant.

In general, the noise of the semiconductor sensor is reduced by lowering the temperature (see FIG. 6). Therefore, the noise level is reduced by lowering the temperature of the semiconductor backscattered electron detector 4 with the electric heating element 10. Further, as described above, by controlling the temperature to be constant, the level of the noise included in the output signal of the semiconductor backscattered electron detector 4 is substantially constant regardless of whether the electron beam is irradiated or not. Become. As a result, an output signal of the semiconductor backscattered electron detector 4 between shots of the electron beam (ie, a noise signal including a dark current) is measured, and noise is canceled by subtracting the output signal between shots from the output signal at the time of measurement. And measurement accuracy can be improved.

FIG. 2 is a diagram showing a first modification of the semiconductor backscattered electron detecting device shown in FIG. Normally, the semiconductor backscattered electron detector 4 is arranged in a very limited space, and it is often difficult to house the electric heating element 10 as a cooling means in a charged particle beam device as shown in FIG. In FIG. 2, a holder 1 to which a semiconductor backscattered electron detector 4 is attached.
Numeral 3 is made of an insulator having good thermal conductivity. As shown in the figure, a semiconductor backscattered electron detector 4 is provided at an end 13a inside the vacuum vessel.
End 13b penetrating through vacuum vessel 5 and exposed to the atmosphere
The electric heating element 10 is attached to each.

Normally, the semiconductor backscattered electron detector 14 is mounted on a mounting portion provided on the vacuum vessel 5 of the charged particle beam device 1 with an insulator interposed therebetween. In the example shown in FIG. 2, the insulator is cooled. Since it is used as a holder, the number of parts can be reduced. Further, since the thermoelectric element 10 is attached to the outside of the vacuum vessel 5, a sufficient space for providing the thermoelectric element 10 is obtained, and the thermoelectric element 10 having a higher cooling capacity can be used. Therefore, the temperature of the semiconductor backscattered electron detector 4 can be further reduced, and the noise signal itself such as dark current can be reduced.

The temperature sensor 11 may be attached to the holder 13 instead of being attached to the semiconductor backscattered electron detector 14. In addition, the thermoelectric element 10 is used for the holder 1.
Instead of cooling 3, a radiation fin may be formed at the end 13 b on the atmosphere side of the holder 13 and cooled by a fan or the like, or a passage may be formed in the holder 13 and a coolant may flow through the passage. The holder 13 may be cooled.

In the above-described first embodiment, the temperature controller 12 controls the electric heating element 10 so that the temperature of the semiconductor reflection detector 4 becomes constant. However, as in the second modification shown in FIG. The electric heating element 10 may be controlled so that the dark current component of the semiconductor backscattered electron detector 4 becomes constant. In this case, there is an advantage that there is no need to provide the temperature sensor 11 and no space is required for it.

Second Embodiment As described above, when the current of the electronic lens is large, a cooling means is further provided on the electronic lens itself to suppress a rise in the temperature of the electronic lens due to the heat generated by the electronic lens, and furthermore, the temperature is reduced. There is a case where a control means for managing the information is provided. FIG. 4 is a view for explaining a second embodiment of the semiconductor backscattered electron detection device according to the present invention. In this embodiment, the cooling means for the electron lens and the temperature control means are replaced by the cooling means for the semiconductor backscattered electron detection device. And also used as temperature control means. Note that the cooling holder 21 is located on the cross section on the left side of the electron lens 2 in the drawing.
Is omitted. The same parts as those in FIG. 5 are denoted by the same reference numerals. Reference numeral 21 denotes a cooling holder for the electron lens 2, in which a coolant passage 211 is formed. In the present embodiment, the semiconductor backscattered electron detector 4 is also attached to the cooling holder 21. 22 is a flow meter for measuring the flow rate of the refrigerant flowing through the cooling holder 21, 23 is a flow rate control valve, and the temperature controller 24 is a temperature sensor 11
The flow control valve 23 is controlled so that the temperature of the electronic lens 2 becomes constant based on the information of the flow meter 22.
Therefore, the temperature of the semiconductor backscattered electron detector 4 attached to the cooling holder 21 is also kept substantially constant.

In the apparatus shown in FIG. 4, the temperature sensor 11 is attached to the electronic lens 2, but may be attached to the cooling holder 21 or the semiconductor backscattered electron detector 4. In particular, when it is attached to the semiconductor backscattered electron detector 4, the temperature of the semiconductor backscattered electron detector 4 can be maintained more accurately and constant. Thus, by keeping the temperature of the semiconductor backscattered electron detector 4 constant, the dark current component included in the signal of the semiconductor backscattered electron detector 4 becomes constant, so that the influence of the dark current can be easily removed.

In the above-described embodiment, the detector 4 is not limited to a semiconductor type detector, and various types can be used.

In the correspondence between the above-described embodiment and the elements described in the claims, the thermoelectric element 10 and the holder 21 are cooling means, the temperature controllers 12 and 24 are control devices, and the holder 13 is a good heat conductive insulator. , Respectively.

[0018]

As described above, according to the first to third aspects of the present invention, since the temperature of the detector is kept almost constant, the noise depending on the temperature of the output signal of the detector is kept almost constant. Noise can be easily removed by using the output signal when the charged particle beam is not irradiated. As a result, measurement by the charged particle beam device can be performed with high accuracy. In particular, claim 3
According to the invention, since both the detector and the electronic lens are cooled by the same cooling means, the space for the cooling means can be reduced and the cost can be reduced. According to the fourth aspect of the present invention, since the dark current component included in the output signal of the detector is kept substantially constant, noise can be easily removed using the output signal when the charged particle beam is not irradiated. ,
Measurement with a charged particle beam device can be performed with high accuracy. Claim 5
According to the inventions of (6) and (6), since the detector is cooled by cooling the insulator member used for mounting the detector, it is possible to save space and cost. According to the invention of claim 7, since the cooling means is provided outside the vacuum vessel of the charged particle device device, a cooling device having a large cooling capacity is used regardless of the space around the detector in the charged particle device device. be able to. As a result, the detector can be cooled to a lower temperature, and the magnitude of the noise itself can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of a backscattered electron detection device according to the present invention.

FIG. 2 is a diagram showing a first modified example of the backscattered electron detection device of FIG. 1;

FIG. 3 is a diagram showing a second modification of the backscattered electron detection device.

FIG. 4 is a diagram illustrating a backscattered electron detection device according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a conventional backscattered electron detection device.

FIG. 6 is a diagram showing an example of the relationship between temperature and dark current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged particle beam apparatus 2 Electron lens 3 Sample 4 Semiconductor backscattered electron detector 5 Vacuum container 10 Electric heating element 11 Temperature sensor 12, 24 Temperature controller 13, 21 Cooling holder 22 Flow meter 23 Flow control valve 211 Passage C1 Electron beam C2 Reflected electron

Claims (7)

[Claims] 1. A backscattered electron detection device for a charged particle beam device comprising a detector for detecting backscattered electrons from a sample, wherein a control means for controlling the temperature of the detector to be constant is provided. Electron detector for charged particle beam equipment. 2. The backscattered electron detection device for a charged particle beam device according to claim 1, wherein said control means is configured to cool said detector, a temperature sensor for detecting a temperature of said detector, A control device for controlling a cooling output of the cooling means so that a temperature of the detector becomes constant. A backscattered electron detecting device for a charged particle beam device. 3. The backscattered electron detection device for a charged particle beam device according to claim 1, wherein the control unit cools the detector and an electron lens of the charged particle beam device, and the detector and the electronic device. A charged particle beam device comprising: a temperature sensor for detecting any temperature of a lens; and a control device for controlling a cooling output of the cooling unit so that the temperature detected by the temperature sensor is constant. Backscattered electron detector. 4. A backscattered electron detector for a charged particle beam device comprising a detector for detecting backscattered electrons from a sample, a cooling means for cooling the detector, and a dark current component included in an output signal of the detector. And a control device for controlling a cooling output of the cooling means so that a constant value is obtained. The backscattered electron detecting device for a charged particle beam device. 5. A charged particle beam apparatus for irradiating a charged particle beam toward a sample in a vacuum vessel, wherein the reflected electron from the sample is held in the vacuum vessel by a holding member made of a good heat conductive insulator. A detector for detecting, a cooling unit attached to the holding member to cool the detector, a temperature sensor for detecting a temperature of the detector, and a temperature of the detector detected by the temperature sensor being constant. And a control means for controlling the cooling means as described above. 6. A charged particle beam apparatus for irradiating a charged particle beam toward a sample in a vacuum container, wherein the reflected electron from the sample is held by the holding member made of a good heat conductive insulator in the vacuum container. A detector for detecting, cooling means attached to the holding member for cooling the detector, and control means for controlling the cooling means so that dark current of the detector is constant. Charged particle beam device. 7. The charged particle beam device according to claim 5, wherein the holding member is provided so as to penetrate the vacuum vessel, and the cooling means is provided outside the vacuum vessel. Charged particle beam device.