JPS63102148A - Electron beam equipment - Google Patents

Abstract

PURPOSE:To enable the detection of only electron beams, which are generated from a sample, with a good S/N and to obtain a good image of the sample by making a value of secondary electrons, which are separately detected from an inner wall of this equipment, subtracted from a detection value of a secon dary electrons. CONSTITUTION:A sample 7 and an electrode 21 are made equipotential to radi ate electron beams 2, and secondary electrons detected by a secondary electron detecting device 23 are memorized in a memory device 26. Next, a negative voltage is applied to the electrode 21 so as to radiate electron beams 2. Only secondary and reflecting electrons generated from an inner wall of this equip ment are detected by the use of a secondary electron detecting device 23 and memorized by the use of a memory device 27. Next, the detection value memo rized in the memory device 27 is subtracted from the detection value memorized in the memory device 26 by the use of an operational device 28 controlled synchronizing with a controlling device 30, and so only a value of secondary electrons generated from the sample 7 is detected as an operational result and a sample image signal with a good S/N ratio can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electron beam device used in an electron microscope or the like, which detects secondary electrons by subtracting two detected values.

[Conventional technology]

2. Description of the Related Art Conventionally, there is an electron beam device such as an electron microscope for detecting secondary electrons generated from a sample, as shown in FIG. 3, for example. The electron beam 2 from the electron gun 1 passes through the inner wall 3 of the device, passes through a focusing lens 4, a deflection coil 5, and an objective lens 6, reaches the sample 7, and is scanned by a scanning power source 8, but the electron beam 2 emitted from the sample 7 The secondary electrons 9 are detected as a voltage by the detector lO, amplified by the amplifier 11, and
It is input to the RT display device 12. CRT display device 21t1
2 was scanned by a power source synchronized with the scanning power source 8 that drove the deflection coil 5, and the sample image was displayed on a CRT display device 2112.

[Problem that the invention seeks to solve]

However, in such a conventional electron beam device for detecting secondary electrons, only the sample 7 is incident on the detector 10.
In addition to the secondary electrons 9 from the
There was a problem in that the secondary electron signal from the sample 7 had a poor S/N ratio because it also contained reflected electrons 13 that were directly incident. In order to prevent reflected electrons from entering, an aperture (not shown) is sometimes inserted between the lower surface of the objective lens 6 and the sample 7, but in this case, the distance between the objective lens 6 and the sample 7 becomes longer. This increases the aberration of the objective lens, making it impossible to perform high-magnification, high-resolution observation.

This IJI was developed by focusing on these conventional problems, and is a method for detecting secondary 'deuterons' that can improve the S/N ratio of the secondary electrons 9 entering the detector 10 from the sample 7. The purpose is to provide an electron beam device for use.

[Means for solving problems]

The present invention provides an apparatus for irradiating a sample with an electron beam and thereby detecting secondary electrons generated from the sample 1, including an electrode for suppressing secondary electrons disposed near the sample; 'Iti: a voltage generator that applies a voltage to the pole, a detector that detects secondary electrons generated from the sample, and a detection value detected by the detector that is applied to the voltage applied from the voltage generator. A plurality of storage devices that store data in a distributed manner, and an arithmetic device that subtracts two stored values from memory A1 stored in the plurality of storage devices, and these devices are synchronized in synchronization with changes in the storage device. and a control device for controlling the system.

[Effect]

First, the same potential is applied between a sample and an electrode disposed near the sample, an electron beam is irradiated, the secondary electrons are detected by a detector, and the secondary electrons are stored in a first storage device. Next, if a negative voltage is applied to the electrode and an electron beam is irradiated,
The secondary electrons generated from the sample cannot pass through the electrode, and the high-energy backscattered electrons pass through the electrode and collide with the inner wall of the device, and only the secondary electrons and backscattered electrons generated from the inner wall of the device are detected. Detected by a detection device. If this is stored in the second storage device and subtracted from the stored value stored in the first storage device, only the value of the secondary electrons generated from the sample remains as the calculation result, and S/ A sample image signal with a good N ratio can be obtained.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing an embodiment of the unreleased Ill. The electron microscope 20 has almost the same structure as shown in FIG.
The same-P materials are indicated by the same reference numerals.

The beam 2 from the electron gun 1 passes through the inner wall 3 of the device, the focusing lens 4, the deflection coil 5, and the objective lens 6 and reaches the sample 7, but between the sample 7 and the objective lens 6, A voltage generator 22 that includes a mesh-like electrode 21 for suppressing secondary electrons and changes the voltage applied to the electrode 21
will be established. - A/D converter 25 that is provided with a detection device 23 that detects secondary electrons 9 generated from the actual sample 7 and an amplification device 24 that amplifies the detected voltage, and converts the amplified voltage into a digital value; A first storage device H26 and a second storage device 27 that store the converted digital values are connected to an @ calculation device 28 that subtracts two stored values stored in the storage devices 2126 and 27. the first from the amplifier 24;
The input to the second memory device 26,27 is such that it is synchronized with the operation of the voltage generator 22 that applies the voltage to the electrode 21.
Controlled by the control device 30, when the electrode 21 is at the same potential as the sample 7, the first memory device 2126 is stored, and when the electrode 21 is at a negative potential, the second memory device 27 is stored, and the amplifier 24, A/
The signal is input through a D converter 2125.

The performance 1X device 28 is also connected to an image display storage device 2129, all of which are connected to the control device i! Controlled by t30.

The same potential is applied between the sample 7 and the pole 21 disposed near the objective lens 6 by a voltage generator 21i22, and the sample 7 is scanned with the electron beam 2.

When detected by the detection device 23 that detects secondary electrons, in addition to the secondary electrons 9 from the sample 7, other secondary electrons and the like described in the related art are also detected. This is amplified by the amplifier 24, and the A/D
If a negative voltage is applied to the electrode 21 by the voltage generator 2t22 through the conversion device 2125 and stored in the first storage device 26, and the sample 7 is scanned with the electron beam 2, the second Since the secondary electrons 9 cannot pass through the electrode 21, they do not reach the detection device 23, and the reflected electrons 13 with high energy
passes through the electrode 21 and collides with the inner wall of the device, causing the inner wall 3
Secondary electrons 14 generated from and reflected electrons 13 directly incident
Only the secondary electrons are detected by the detection device 2123 that detects secondary electrons. The value stored in the second storage device 27 is subtracted from the value stored in the first storage device 26 by the arithmetic unit 28. do. As a result, only the values of the secondary electrons 9 generated from the sample 7 remain in the storage device, and a sample image with a good S/N ratio can be obtained. This sample image is sent to the image display storage type fi 29 and can be stored in the image storage device 29a. Note that in the above, storage in the first and second storage devices 26 and 27 may be performed for each pixel or for each scanning line, or may be performed for several scanning lines at once. You can also do this for each screen.

Next, as an application of the present invention, we will describe the case where the line width of a pattern formed on a semiconductor wafer is measured using an electron microscope. is necessary. Furthermore, such line width measurement is automated and incorporated into the line of semiconductor SJ manufacturing equipment, and wafers are automatically fed. After the predetermined length measurement location is calculated by the calculation unit 128 according to the method of the above embodiment, it can be stored in the image storage device 29a, and the image can be displayed and observed later. In addition, the image signal of the arithmetic unit 28 may be recorded on a floppy disk (not shown), or the signal of the edge portion of two points at a predetermined length measurement point may be detected and the scanning line between the two points may be detected. It is also possible to measure and record the dimensions from both J numbers and magnification. In this way, the image signal from the arithmetic unit 2128 is as follows.

Depending on the operator's instructions to the control device and 30, storage, display, recording, and length measurement recording are selected dynamically or automatically.

Further, in this case, after the data is stored in the storage devices 26 and 27, the scanning by the deflection coil 5 and the arithmetic unit 2128 do not necessarily need to be synchronized.

Furthermore, if the image signals of the memory type 2126.27 can be displayed independently and simultaneously on - number of display devices, it will be possible to use the When changing the acceleration voltage, it is also possible to adjust the voltage generator 22 while observing the voltage applied to the electrode 21 on the screen.

In this case, it goes without saying that the images can be viewed simultaneously on the image display storage device 29 as well. Further, the distance between two points on the pattern of the semiconductor wafer can be measured by further calculating the pulses of the sample image signal obtained in this way.

FIG. 2 shows another embodiment of the present invention, in which an objective lens 6 and a sample 7
and the secondary electron detection device 31 between them.
In this case, sample 7 and detection device g13 are installed.
Although a mesh-like electrode 32 is provided between the two electrodes 1 and 1, the operation and effect are the same.

〔Effect of the invention〕

Since the present invention has the configuration and operation as explained above,
Only the secondary electrons generated from the sample can be detected with a good S/N ratio, and when applied to a scanning electron m-microscope, a good sample image can be obtained. Furthermore, the device according to the invention is characterized by being easy to handle and convenient to use.

[Brief explanation of the drawing]

FIG. 3 is a block diagram of a conventional electron microscope. 2... Electron beam 7... Sample 21... Electrode 22... Voltage generator 23... Secondary electron detection device 26... First storage device 27... Second storage device 28. ...Arithmetic unit 30...Control device patent applicant Akashi Seisakusho Co., Ltd. -, r, ,
” ' -,. Agent Patent attorney Sat Tachibana Hao・No. 1 H 2... Electric) Ji° -4 7... Sample 21... Mio day 22... Voltage generation engineer 23... Near 1+ , to the training! 26-・'Name-3 Otsu (tun 4 AI 27... to; Otsu d1! 28-;ll'1 1 30-i!'I 'Ill 11 Fig. 2

Claims (1)

[Claims] In a device that irradiates an electron beam onto a sample and thereby detects secondary electrons generated from the sample, an electrode for suppressing secondary electrons is placed near the sample, and a voltage is applied to the electrode. a voltage generating device for detecting secondary electrons generated from the sample; and a detecting device for detecting secondary electrons generated from the sample, and distributing the detected values detected by the detecting device in synchronization with changes in the voltage applied from the voltage generating device. a plurality of storage devices for storing;
An electron beam device comprising: an arithmetic device that subtracts two stored values among the stored values stored in the plurality of storage devices; and a control device that synchronizes and controls these devices. .