JPH10228879A - Secondary electron observing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily observe a large size wafer by alternately emitting electron beams from a plurality of electron beam radiating devices arranged in the same vacuum case body toward the inside of the same area on a sample at different angles by time sharing, separating the received signals in the secondary electron detector from each other by time sharing, and outputting secondary electron images from a plurality of angles in a real time. SOLUTION: For example, converged electron beams emitted from two electron beam radiating devices 1A, 1B making a predetermined angle between them are radiated alternately to the same area in a sample. The generated secondary electrons are detected by means of a secondary electron detector 3, and the received signals are separated from each other by time sharing synchronizing with the radiation, and two secondary electron images in the same area from the different angles are provided on a CRT in a real time. Therefore, no inclination of a wafer or the electron beam radiating devices 1A, 1B is required. Desirably, a driving mechanism 5, which is moved and tilted in the X direction, Y direction, and z direction on a sample table 7, for a plurality of electron beam radiating devices uses a motor generating no magnetic field as a driving source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary electron observation apparatus for irradiating an electron beam and using a secondary electron image to inspect the appearance of, for example, a wafer.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, as is well known, an optical microscope or a scanning electron microscope is used for inspecting a resist pattern on a wafer, an etching process, a resist peeling process, and the like. When using an optical microscope, the operation is relatively simple, and the apparatus can be downsized, but there is a drawback that high-resolution observation cannot be performed. When a scanning electron microscope is used, high-resolution observation is possible. However, irradiating the electron beam in a vacuum complicates the operation and increases the size of the apparatus.

That is, in the method using a scanning electron microscope, a wafer to be inspected is placed in a sample chamber of the scanning electron microscope, and a vacuum is applied to irradiate an electron beam. While observing each desired part while moving, rotating, or tilting the X, Y, and Z axes, wafers have become increasingly large in recent years, and large wafers of 12 inches or more have been observed. When it is completed, it is inserted into the sample chamber of the scanning electron microscope and moved.
Rotating and tilting are impractical in terms of accuracy and efficiency, and an optical microscope must be used for inspection of a large wafer.

[0004]

As described above, in order to observe a wafer at a high resolution as described above, a secondary electron image using a scanning electron microscope is used. However, there is a problem that the visual inspection cannot be performed at the same time.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a secondary electron observation apparatus capable of easily observing a large wafer with a secondary electron image.

[0006]

A secondary electron observation apparatus according to the present invention has a function of scanning at least a sample stage and a narrowly focused electron beam on the surface of a sample by emitting a narrowly focused electron beam into the same vacuum housing. A plurality of electron beam irradiators, and a secondary electron detector, so that each electron beam emitted from each electron beam irradiator is irradiated from a different angle into the same area on the sample. The electron beam irradiation device is installed at a predetermined angle, and the electron beam irradiation device emits an electron beam alternately in a time-division manner, and separates the signals received by the secondary electron detectors in the time-division manner. It is characterized in that secondary electron images from a plurality of angles of the area are output in real time. Therefore, secondary electron images from different angles can be obtained in real time using multiple beams in the same vacuum housing.

Further, an electromagnetic shield mechanism is provided between each of the plurality of electron beam irradiation devices. Therefore, it is possible to prevent the electromagnetic fields generated by the electron beam irradiation device from interfering with each other.

Further, the plurality of electron beam irradiation devices are
As a set, it is characterized in that it is installed on an irradiation device drive mechanism for freely moving and tilting in the X, Y, and Z axis directions on the sample table. This eliminates the need to move and tilt the sample for observation, and enables observation of a large sample.

The sample stage is provided with a rotating mechanism. Since the electron optical system is configured to move and tilt, the sample stage only needs to have a rotating mechanism, and even if the sample is large, the positioning accuracy can be kept high.

[0010] The invention is characterized in that a motor that does not generate a magnetic field is used as a drive source of the irradiation device drive mechanism and / or the sample stage rotation mechanism. Therefore, it is possible to avoid the adverse effect of the magnetic field generated by the motor on the electron optical system and the image output system.

[0011] Further, the vacuum chamber is evacuated by a single vacuum pump, and a high vacuum is formed in each of the electron beam irradiation devices by an individual ion pump. Therefore, the entire apparatus can be reduced in size, and the evacuation operation can be performed only once.

Further, the present invention is characterized in that a plurality of electron beam irradiation devices are provided as one set on the sample stage. With such a configuration, it is possible to simultaneously observe a plurality of locations with a multi-image.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of the configuration of the secondary electron observation apparatus of the present invention.
A and 1B are electron beam irradiation devices, 2 is an electromagnetic shield plate, 3 is a secondary electron detector, 4A and 4B are ion pumps respectively, 5 is an irradiation device driving mechanism, 6 is a vacuum pump,
Reference numeral 7 denotes a sample stage, and 10 denotes a vacuum housing.

In the secondary electron observation apparatus of the present invention, a plurality of electron beam irradiation apparatuses (in this embodiment, 2A of 1A and 1B in this embodiment) are so arranged that a narrowed electron beam irradiates the same area on the sample to scan. One set of units, but one set of three units
Irradiating device driving mechanism 5 at a predetermined angle.
And an electromagnetic shield plate 2 is provided between the electron beam irradiation devices 1A and 1B. Each electron beam irradiator 1 corresponds to a so-called barrel in a conventional scanning electron microscope, and its electron gun can be a thermal field emission electron gun (TFE) having a low acceleration voltage and a high resolution. In order to reduce the size only, a two-stage eight-electrode electrode is provided.
The polar static electrode has the functions of two-stage electrostatic deflection, two-stage mode alignment, non-movable beam blanker, and stig meter. Thus, one electron beam irradiation device can be configured to have a length of 10 cm, a diameter of 3 cm, and a weight of 1 kg or less.

The electron beams emitted from each of the electron beam irradiation devices 1A and 1B have a predetermined angle so as to scan the same area on the sample table 7 as described above (note that the electron beams are emitted). This angle is configured to be adjustable). The irradiation device is attached to a driving mechanism 5, and each irradiation device is configured to emit an electron beam alternately in a time division manner by beam blanking. An electromagnetic shield plate 2 made of a lead plate or the like is provided between the electron beam irradiation devices 1A and 1B so that an electromagnetic field generated from one electron beam irradiation device does not interfere with the other device. ing.

The same irradiation area of each of the electron beam irradiation devices 1A and 1B can be freely moved in the X, Y and Z-axis directions by using the irradiation device driving mechanism 5, whereby a conventional scanning electron microscope can be used. Instead of tilting and moving the sample as described above, it is possible to make a configuration in which the irradiation device is moved to perform observation, the mechanical movement distance for large samples can be reduced, and even when observing a large wafer of 12 inches or more. It can be performed relatively easily without increasing the size of the device.
Further, the sample stage 7 does not need to be provided with a moving mechanism or a tilting mechanism, and need only be provided with a rotating mechanism.

The irradiation device driving mechanism 5 is composed of a so-called high-precision robot arm or the like, and its driving source is a motor that does not generate a magnetic field such as an ultrasonic motor so as not to adversely affect the electromagnetic field. Care is taken not to adversely affect the electron optical system or the image output system by using it. Further, by providing the electron beam irradiation devices 1A and 1B, the secondary electron detector 3, the irradiation device driving mechanism 5, and the sample stage 7 in the same vacuum housing 10, a vacuum is pulled by one vacuum pump 6. it can. Further, since a higher vacuum is required in the electron beam irradiators 1A and 1B, each electron beam irradiator 1A, 1B
1B has ion pumps 4A and 4B attached thereto, respectively. The configuration and operation of an image output system for outputting a secondary electron image on a CRT with the secondary electrons detected by the secondary electron detector 3 are described on a time-division basis on the CRT by each of the electron beam irradiation devices 1A and 1B. The configuration is the same as that of each conventional scanning electron microscope, except for the configuration for outputting the video of FIG.

FIG. 2 is a view for explaining the case of observing a resist residue on a wafer with the secondary electron observation apparatus of this embodiment. In the figure, reference numeral 20 denotes a wafer, 21 denotes a resist residue, and 30A denotes an electron. An electron beam 30B is emitted from the beam irradiation device 1A, and an electron beam 30B is emitted from the electron beam irradiation device 1B. When such a wafer inspection is performed, in the conventional method using a scanning electron microscope, the wafer is moved by first irradiating the electron beam 30 perpendicularly to the wafer 20 as shown in FIG. The observation position is searched, and thereafter, the state of the residue is observed by, for example, tilting the wafer as shown in FIG. 3B. For this purpose, the observable wafer 20 is inserted into the sample chamber of the scanning electron microscope. X and X,
It is necessary to be able to move in the Y- and Z-axis directions and to be able to incline at about 45 °, which is practically impossible when inspecting a large wafer of 12 inches or more.

In the apparatus of the present embodiment, for example, secondary electrons generated by alternately irradiating the same area with an electron beam are respectively emitted from two electron beam irradiation apparatuses 1A and 1B installed at an angle of 45 °. Since the received signal is separated by time division synchronized with the beam irradiation detected by the secondary electron detector 3 and two secondary electron images differing by, for example, 45 ° can be obtained in the same area, it is necessary to tilt the wafer. In addition, there is no need to tilt the electron beam irradiator particularly for the usual inspection of the resist pattern, the etching process, the resist stripping process and the like of the wafer. In addition, the apparatus according to the present embodiment has a configuration in which a signal detected by one secondary electron detector 3 is used for a plurality of images in a time-sharing manner even in a configuration in which a plurality of electron beams are irradiated. Images from a plurality of angles can be obtained in real time while sharing the secondary electron detector 3. Further, in the same vacuum housing 10, electron beam irradiation devices 1A and 1B, an electromagnetic shield plate 2, a secondary electron detector 3, an ion pump 4A,
4B, the irradiation device driving mechanism 5, and the sample stage 7 are accommodated, so that only one vacuum pump 6 is required, so that a device capable of obtaining a multi-image by using a multi-beam can be miniaturized.

In the above embodiment, two electron beam irradiators 1A and 1B are used as one set. However, three electron beams may be used as one set, and not only one set but also a plurality of sets are arranged on the sample table 7. It is good also as a structure performed.

[0021]

As described above, the secondary electron observation apparatus according to the present invention can provide a small-sized apparatus capable of obtaining multiple images having different angles in the same area in real time using multiple beams. Also, without moving and tilting the sample, the electron optical system that emits multiple beams with different angles in advance is moved.
Since the tilting configuration is adopted, it is possible to observe a large sample, and in particular, it is possible to easily inspect a large wafer with a minimum number of steps.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a configuration of a secondary electron observation device of the present invention.

FIG. 2 is a diagram for explaining a wafer observation operation in the apparatus of the present embodiment.

FIG. 3 is a diagram for explaining a wafer observation operation when a conventional scanning electron microscope is used.

[Explanation of symbols]

 Reference Signs List 1A, 1B electron beam irradiation device 2 electromagnetic shield plate 3 secondary electron detector 4A, 4B ion pump 5 irradiation device driving mechanism 6 vacuum pump 7 sample table 10 vacuum housing 20 wafer 21 resist residue 30, 30A, 30B electron beam

Claims (7)

[Claims] 1. A sample stage, a plurality of electron beam irradiators having a function of emitting a narrowly focused electron beam and scanning the surface of the sample, and a secondary electron beam in the same vacuum housing; A detector, so that each electron beam emitted from each electron beam irradiation device is irradiated from different angles into the same area on the sample,
Each electron beam irradiator is installed at a predetermined angle, each electron beam irradiator emits an electron beam alternately in a time-division manner, and the signal received by the secondary electron detector is separated in the time-division manner. A secondary electron observation apparatus characterized in that a secondary electron image from a plurality of angles of the same area is output in real time. 2. The secondary electron observation device according to claim 1, wherein an electromagnetic shield mechanism is provided between each of the plurality of electron beam irradiation devices. 3. A plurality of electron beam irradiators are installed as a set in an irradiator drive mechanism for freely moving and tilting in the X, Y, and Z axis directions on the sample stage. The secondary electron observation device according to claim 1 or 2, wherein: 4. The secondary electron observation apparatus according to claim 1, wherein said sample stage has a rotation mechanism. 5. The irradiation device driving mechanism or (and)
5. The secondary electron observation apparatus according to claim 3, wherein a motor that does not generate a magnetic field is used as a drive source of the sample stage rotation mechanism. 6. The vacuum chamber is evacuated by one vacuum pump, and a high vacuum is formed in each of the electron beam irradiation devices by an individual ion pump. Claims 1, 2, 3, and 4
Item 7. The electron beam irradiation apparatus according to Item 5 or 5. 7. The apparatus according to claim 1, wherein a plurality of sets of said plurality of electron beam irradiation devices are provided on said sample stage. Paragraph, fifth
Item 7. The electron beam irradiation device according to item 6 or 6.