JP2000077019A - Electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently detect defects on the whole surface of a sample having a through hole by irradiating electron beams to the sample having a through hole, and detecting upward reflecting electrons and downward passing electrons from the sample. SOLUTION: Primary electron beams 5 from an electron gun 4 are focused with a condenser lense 3 and an objective lense 2, irradiated on a sample 1 having a through hole, two step-deflected with beam deflecting system 7, 8, and the sample 1 is surface-scanned with deflected beams in an X direction and in a Y direction. Secondary electrons and reflected electrons emitted upward from the sample 1 are efficiently collected with a secondary electron detector 9, a signal is outputted and amplified with an amplifier 18, and displayed on a display. On the other hand, electrons passing through a pattern hole of the sample 1 and electrons reflected by an inner wall of the pattern hole or dust are detected with a passing through electron detector 11, a signal is outputted, amplified with an amplifier 17, and displayed on a display. Upside information of the sample 1 and inner wall information of the pattern hole can clearly be displayed in the same position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron microscope for displaying the shape of a through hole by scanning a sample having a through hole with an electron beam, and printing an IC or LSI circuit on a wafer by exposure. The present invention relates to an electron microscope that efficiently measures dimensions and defect inspection of a fine pattern such as a stencil mask sometimes serving as a master using an electron beam.

[0002]

2. Description of the Related Art In recent years, the degree of integration of LSIs has been steadily improving. However, in the LSI manufacturing process, the conventional exposure technology using light has reached its limit, and ArF optical excimer lasers and X-ray And electron beam exposure technology are listed as the next candidates. Among them, measurement using light from a stencil mask serving as a master for exposure with an electron beam cannot perform length measurement and defect inspection, and only the surface shape is measured using a scanning electron microscope.

In order to observe the shape near the back surface, the same measurement is performed with the sample turned upside down. A conventional length measuring machine using a scanning electron microscope scans a sample while irradiating it with a narrow beam, and detects secondary electrons and reflected electrons emitted from the sample at that time by a secondary electron detector, and an amplifier. And an image is displayed on a display device.

[0004]

However, the stencil mask has a thickness, and information in the depth direction cannot be obtained with a conventional scanning electron microscope. For this reason,
There has been a problem that there is no other way but to find a defect on the stencil mask from an actually drawn pattern.

Further, it is necessary to detect defects on the entire surface of the stencil mask, and an efficient detection method is required. In order to solve these problems, the present invention includes means for detecting electrons passing through a sample having a through-hole such as a stencil mask, and realizes defect detection not only at the surface but also at the center by a passing electron signal. It is another object of the present invention to efficiently detect defects on the entire surface such as a stencil mask.

[0006]

Means for solving the problem will be described with reference to FIG. In FIG. 1, beam deflectors 7 and 8 deflect an electron beam and scan the sample 1.

The secondary electron detector 9 detects secondary electrons and reflected electrons emitted upward from the sample 1. The passing electron detector 10 detects electrons passing through the through hole of the sample 1, secondary electrons emitted from the inner wall of the through hole, and reflected electrons reflected on the inner wall of the through hole.

Next, the configuration and operation will be described. Sample 1 having a through-hole through which an electron beam is irradiated by beam deflectors 7 and
, The secondary electrons emitted upward and reflected reflected electrons are detected by the secondary electron detector 9, and the electrons passing through the through-hole of the sample 1 and the inner wall of the through-hole are detected. The emitted secondary electrons and the reflected electrons reflected on the inner wall of the through hole are detected by the passing electron detector 10, and an image of one or both of the detected signals is displayed on a display device (not shown). I have.

At this time, a bias voltage is applied between the sample 1 and the passing electron detector 10 as the second detector, and the sample 1
The secondary electrons emitted from the inner wall are extracted and detected efficiently.

An operation (for example, OR operation) is performed on each signal detected by the secondary electron detector 9 as the first detector and the passing electron detector 10 as the second detector.
The calculated (calculated, added, subtracted, etc.) image is displayed.

On the image displayed based on the signal of the secondary electron detector 9 as the first detector and / or the passing electron detector 10 as the second detector, a designated area is defined. The beam deflectors 7 and 8 perform scanning control with an electron beam to enlarge and display a designated area.

Also, the signals from the secondary electron detector 9 as the first detector and the passing electron detector 10 as the second detector are displayed by OR operation, addition or subtraction, and displayed. The shape of the entrance of the electron beam and the shape of the inside of the through hole are superimposed and displayed.

Therefore, in a stencil mask or the like having a through hole in the sample 1, it is possible to easily detect not only the surface but also the defects at the center and the exit by the passing electron signal. It is possible to efficiently detect defects on the entire surface of the sample 1 having the through holes.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment and operation of the present invention will be described in detail with reference to FIG. FIG. 1 shows a system configuration diagram of the present invention.

In FIG. 1, a sample 1 detects secondary electrons and reflected electrons emitted by irradiating a narrowly focused primary electron beam to display an image, and displays an image through a stencil mask as the sample 1. The sample is a target for displaying images by detecting electrons passing through the holes and secondary electrons and reflected electrons emitted by irradiating the inner wall of the through holes with a primary electron beam. In particular, it is an object to be subjected to various defect inspections including dust adhering to the wall surface (inner wall) of the pattern hole opened in the sample 1 and to measure the length of the pattern, and is held on the stage 19.

The objective lens 2 irradiates the sample 1 with the primary electron beam being narrowed down. The condenser lens 3 focuses the primary electron beam emitted from the electron gun 4.

The electron gun 4 generates a primary electron beam. The primary electron beam 5 is a primary electron beam generated and emitted by the electron gun 4.

The stop 6 is for giving a predetermined opening angle when the primary electron beam emitted from the electron gun 4 is focused by the condenser lens 3. Beam deflectors 7, 8
Is a deflector (deflection coil or deflection electrode) for deflecting the primary electron beam in two steps and scanning it on the sample 1.

The secondary electron detector 9 detects secondary electrons 14 emitted from the sample 1 when the sample 1 is irradiated with the primary electron beam, and further detects reflected electrons reflected from the sample 1. Or something. The secondary electron detector 9 shown in the drawing has a small opening angle when viewed from the reflected electrons reflected by the sample 1 and has a low sensitivity to the reflected electrons. In the portion facing the sample 1, there is arranged a reflection electron detector having a hole in the center of the semiconductor disk through which primary electrons pass so that the reflected electrons reflected from the sample 1 can be detected with high sensitivity. You may. Further, in order to generate an image of absorbed electrons other than reflected electrons, a signal of the primary electron beam absorbed by the sample 1 is taken out, and the signal is used to display an absorbed electron image instead of a reflected electron image. Good.

The secondary electrode emitted from the sample 1 and accelerated upward while being spirally rotated on the optical axis by the magnetic field of the objective lens 2 at the center of the secondary electron detector 9. This is for applying an electric field so as to reach the secondary electron detector 9 with good light-collecting efficiency while avoiding passing therethrough and going further upward.

The passing electron detector 11 includes passing electrons 15 passing through the pattern holes (through holes) of the sample 1, secondary electrons emitted by irradiating the inner wall of the pattern holes with primary electrons, and reflected electrons reflected. To directly detect these passing electrons, secondary electrons, and reflected electrons, or indirectly detect secondary electrons generated by hitting a specific substance.

The detection electrode 12 efficiently detects the passing electrons passing downward from the pattern hole of the sample 1, the secondary electrons emitted by irradiating the inner wall with the primary electrons, and the reflected reflected electrons. An electric field is applied so as to be detected by the detector 11.

The bias voltage 16 is a bias voltage applied to the sample 1 so that the secondary electrons emitted from the sample 1 are efficiently collected by the secondary electron detector 9 and the passing electron detector 11. To apply an electric field.

The amplifier 17 amplifies the signal detected by the passing electron detector 11. Amplifier 18
Amplifies the signal detected by the secondary electron detector 9.

The stage 19 fixes the sample 1 and moves it in the X direction, the Y direction and, if necessary, the Z direction. Next, the configuration and operation will be described.

(1) The primary electron beam generated by the electron gun 4 is focused by the condenser lens 3 and further focused by the objective lens 2 to irradiate the sample 1 with a thin primary electron beam. The primary electron beam is surface-scanned in the X direction and the Y direction on the sample 1 by two-stage deflection by the deflectors 7 and 8.

(2) Secondary electrons emitted upward from the sample 1 in the state of (1) are efficiently collected by a secondary electron detector 9 provided on the objective lens 2 to output a signal. At the same time, the reflected electrons are also detected by the secondary electron detector 9 to output a signal, or the reflected electrons are output by a thin donut-shaped reflected electron detector having a hole in the optical axis portion on the lower surface of the objective lens 2 (not shown). And outputs a signal.

(3) The electrons (primary electrons) passing through the pattern hole of the sample 1 in the state of (1), and the inner wall of the pattern hole and dust are emitted when the primary electron beam is irradiated. Secondary electrons and reflected electrons that are reflected are detected by the passing electron detector 11 to output a signal. At this time, a bias voltage 16 is applied to the sample 1 to efficiently pass the secondary electrons generated on the inner wall of the pattern hole of the sample 1 through the passing electron detector 1.
The information is extracted in the direction of No. 1 and detected, and information (image) of a defective portion of the pattern hole is obtained with a good S / N ratio.

(4) The signals output in (2) and (3) are amplified and displayed on a display device, or both signals are operated (OR operation, addition and subtraction) on the display device. The information is displayed on the upper side of the sample 1 and the information on the inner wall of the pattern hole of the sample 1 so as to be easily visible and displayed at the same position.

As described above, the sample 1 is scanned by irradiating the sample 1 with the primary electron beam, and the secondary electrons on the surface when viewed from above the pattern shape of the sample 1 by secondary electrons and reflected electrons emitted upward. Image and reflected electron image, and furthermore, a passing electron image of passing electrons passing through the pattern hole of the sample 1, a secondary electron image of secondary electrons emitted from an inner wall of the pattern hole, and reflection of reflected electrons. An electron image can be displayed. Further, a secondary electron image or a reflected electron image viewed from above the sample 1 and a passed electron image or a secondary electron image or a reflected electron image of the inner wall of the pattern hole are displayed. Overlap and display information such as the upper side of the pattern hole and the inner wall at the same time and inspect (inspection of the diameter of the pattern hole, the adhesion of dust on the inner wall, the shape of the pattern hole wide and narrow, etc.) Can be easily performed. Hereinafter, the defect inspection of the pattern hole will be described in detail.

(1) The primary electron beam is spread over a wide area of the sample 1 (for example, the entire surface or an area obtained by dividing the entire surface by a predetermined number).
And a low magnification passing electron image (a passing electron image generated by primary electrons (passing electrons) passing through the pattern hole of the sample 1) is displayed.

(2) Among the pattern holes on the passing electron image displayed in (1), a pattern hole is extracted in which dust adheres to the pattern hole or the diameter of the pattern hole is smaller than the inspection value. (3) The current supplied to the beam deflectors 7 and 8 is reduced to display a passing electron image obtained by enlarging the pattern hole so that the pattern hole extracted in (2) is displayed on the entire surface.

(4) The diameter of the pattern hole and the adhesion of dust are inspected based on the transmitted electron image enlarged in (3). Further, the secondary electron image and the reflected electron image emitted in the upward direction of the sample 1 and the secondary electron image and the reflected electron image emitted from the inner wall of the pattern hole are displayed in a superimposed manner. Based on the shape of the upper surface, the secondary electron image or the reflected electron image inside the pattern hole, and the passing electron image, it is possible to easily inspect at which position the shape is abnormal (for example, The secondary electron image, reflected electron image, secondary electron image of the inner wall, reflected electron image, and transmitted electron image in the upward direction are each color-coded and superimposed and displayed as a line image, so that it is easy to determine which location has an abnormal shape. Can be inspected).

(5) In addition, the dimensions of the pattern holes of the enlarged secondary electron image and the passing electron image are respectively measured to determine whether or not each of them is within a predetermined inspection allowable range, and the pattern holes have a so-called C-shape. However, the inclination of the hole (for example, the taper angle in a stencil mask) can be obtained (the upper dimension is measured by the secondary electron image in the upward direction, and the dimension of the narrowest portion of the pattern hole is measured by the transmitted electron image). To determine the slope of the hole).

[0035]

As described above, according to the present invention,
A sample 1 having a through-hole is irradiated with a primary electron beam to irradiate a secondary electron image upward, a reflected electron image, an electron image passing through the through-hole, a secondary electron image emitted from the inner wall of the through-hole, The structure that displays the backscattered electron image reflected by the inner wall of the through hole is adopted. (1) The passing electron image of the passing electron that has passed through the hole pattern on the sample 1 can be displayed, and the entire inner surface of the hole can be displayed. Adhering protrusions can be observed.

(2) A bias voltage is applied to the sample 1 to extract secondary electrons emitted from the inner wall of the through hole of the sample 1 to display a secondary electron image, and to change the shape of the protrusion on the inner wall of the through hole. It can be displayed and observed at a high S / N ratio.

(3) The secondary electron image, the reflected electron image, the secondary electron image of the inner wall of the through hole of the sample 1, the reflected electron image, and the electron image passing through the through hole of the sample 1 are displayed together. And
The shape of the upper surface of the through hole and the shape of the inner wall of the through hole are simultaneously displayed, so that the shape can be inspected three-dimensionally.

(4) Accordingly, when the thickness of the through-hole is large, it is difficult to inspect only with the conventional secondary electron image in the conventional upward direction. For example, the shape of the inner wall of the hole of the stencil mask can be improved. Can be easily inspected.

(5) Also, after displaying the entire image of the sample 1, only a part of the image is enlarged and displayed, and the shape of the through-hole and dust adhered to the inside can be easily observed and inspected. .

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of the present invention.

[Explanation of symbols]

 1: Sample 2: Objective lens 3: Condenser lens 4: Electron gun 7, 8: Beam deflector 9: Secondary electron detector 11: Transmission electron detector 16: Bias voltage 19: Stage

Claims (5)

[Claims] 1. An electron microscope for displaying a shape of a through-hole by scanning a sample in which a through-hole is formed with an electron beam, wherein the scanning means scans the sample in which the through-hole is formed with an electron beam; The first is provided on the side irradiated with an electron beam to detect secondary electrons or reflected electrons emitted from the sample.
And a detector provided on the side opposite to the side where the sample is irradiated with the electron beam, electrons passing through the through hole of the sample, secondary electrons emitted from the inner wall of the through hole, or reflection reflected by the inner wall of the through hole. A second detector for detecting electrons; and means for displaying an image of one or both of the signals detected by the first detector and the second detector. electronic microscope. 2. A device for applying a bias voltage between said sample and said second detector for guiding secondary electrons emitted from an inner wall of a through hole to said second detector. The electron microscope according to claim 1, wherein 3. An electron microscope according to claim 1, further comprising means for displaying an image obtained by calculating a signal detected by said first detector and said signal detected by said second detector. . 4. An image displayed on the basis of a signal from the first detector and / or the second detector, wherein the scanning means controls the electron beam to scan a designated area and performs the designated designation. The electron microscope according to any one of claims 1 to 3, further comprising means for enlarging and displaying the selected area. 5. The signal from the first detector and the second detector is displayed by OR operation, addition or subtraction, and the shape of the entrance of the electron beam in the through hole of the sample and the inside of the through hole are displayed. The electron microscope according to any one of claims 1 to 4, further comprising means for displaying a shape.