JPS6196644A - Appearance examination device - Google Patents

Abstract

PURPOSE:To shorten the time for setting the visual field for an examination electron microscope by installing both the electron microscope and an optical microscope with a lower multiplying factor and enabling the same area of the examination subject to be selectively observed by these microscopes. CONSTITUTION:Light from a light source 11 is irradiated upon a wafer 1 through a half mirror 12 and a lens 13 and then reflected light from the wafer 1 is imaged by a lens 13 and picked up by a camera tube 14. The pattern 1a of the wafer 1 is displayed on a CRT16 through a signal converter 15. A control circuit 17 is used to move an XY table 2 by means of a driver 18 thereby locating the pattern 1a in the center of the visual field or on the optical axis. Following that, an electron microscope 3 is driven to scan electron rays discharged from an electron gun 5 over a minute area on the wafer 1 by the effect of lenses 6 and 7. Reflected electrons from the wafer 1 and secondary electrons are then detected by a scintillator 8 before being displayed on a CRT10 through a signal converter 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an appearance inspection apparatus suitable for inspecting element patterns, etc. of semiconductor devices.

[Background technology]

2. Description of the Related Art In semiconductor devices such as ICs and LSIs, it is necessary to inspect the element patterns of the semiconductor devices completed through predetermined steps, and visual inspection equipment is used.

In recent years, with the miniaturization of device patterns, scanning electron microscopes have been used as visual inspection equipment for glazes. Pattern images are recognized by detecting reflected electrons and secondary electrons, and pattern defects and dimension measurements are performed.

By the way, this scanning electron microscope has a high magnification, so it is effective for inspecting minute device patterns, but on the other hand, the observation field of view is narrower, so it is difficult to inspect a predetermined pattern on a wafer within the field of view. Not easy to configure;
It is relatively time consuming. For this reason, electrons are irradiated onto the wafer during this time, resulting in a large total amount of electrons, irradiation to the MOS transistors, which causes damage to the MO3 characteristics, and foreign matter adhering to the wafer, resulting in contamination. In addition, charge-up of electrons causes various problems such as a decrease in the contrast of the shiba-turn image and deformation of the image, making accurate inspection impossible. An example of a detailed description of inspection equipment technology is the electronic material November 1981 special edition published by Kogyo Kenkyukai, published November 15, 1981, P. 243-P. 2.
There are 47.

[Purpose of the invention]

The purpose of the present invention is to enable the required inspection position to be set within the field of view in a short time during observation using a scanning electron microscope, thereby reducing the total amount of electron beam irradiation and preventing element damage and contamination. It is an object of the present invention to provide an appearance inspection device that can prevent the above problems, improve pattern images, and perform highly accurate inspection.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, an electron microscope for inspection and an optical microscope with a lower magnification are installed side by side, and the configuration is such that the same part of the object to be inspected can be observed with both of these microscopes at the same time or by switching at times. By doing so, the field of view for the object to be inspected can be set using an optical microscope, which can shorten the time required to set the field of view using a simulator microscope, reduce the total amount of electron beam irradiation, and prevent element damage, contamination, and This achieves highly accurate inspection.

[Embodiment 1] FIG. 1 shows an embodiment of the appearance inspection apparatus of the present invention, in particular an example in which the object to be inspected is a semiconductor wafer with an element pattern formed on its surface. That is, the wafer 1 is placed on an XY table 2, and above it a scanning electron microscope 3 and an optical microscope 4 are arranged side by side. The electron microscope 3 includes an electron gun 5 that emits an electron beam, a condenser lens 6, and an objective lens 7.
, and irradiates the surface of the wafer 1 with an electron beam. Further, on the negative side thereof, a scintillator 8 for detecting secondary electrons and reflected electrons emitted from the surface of the wafer 1 is provided, and a signal converter 9 is provided.
, CRT (display device) 10 is connected. Note that the optical axis of the electron microscope 3 is set at an angle of .theta..about.90 with respect to the surface of the wafer 1.

On the other hand, the optical microscope 4 includes a light source 11, a half mirror 1
2. A lens 13 is provided to illuminate the surface of the wafer 1, and the reflected light can be imaged by the imaging tube 14. A signal converter 15 and a CRT 16 are connected to the image pickup tube 14. The optical microscope 4 has an optical axis perpendicular to the surface of the wafer 1, and the optical axis intersects with, that is, coincides with, the optical axis of the electron microscope 3 on the surface of the wafer 1. Note that the magnification of the optical microscope 4 is extremely small compared to that of the electron microscope 3, in other words, it is set to have a wide field of view.

Further, each of the signal converters 9.15 is connected to a control circuit 17, and the driving section 18 of the XY table 2 is controlled through this control circuit 17.

According to the above configuration, when inspecting the wafer 1, first the optical microscope 4 is operated. That is, the light from the light source 11 is irradiated onto the wafer 1 through the half mirror 12 and the lens 13, and the reflected light is imaged by the lens 13 and captured by the imaging tube 14. Then, this imaged pattern of the wafer l is passed through the signal converter 15 and displayed on the CRT 16. Since the displayed pattern has a low magnification, it has a wide field of view, and therefore the pattern 1a to be inspected on the wafer can be found easily and in a short time.

From this point on, the control circuit 17 moves the XY table 2 using the drive unit 18, and sets this pattern 1a at the center of the field of view, at the position of the optical axis.

Next, the electron microscope 3 is operated, the electron beam emitted from the electron gun 5 is scanned over a minute range on the wafer 1 by the action of the lens 6.7, and the reflected electrons and secondary electrons are detected by the scintillator 8. CRTIO via signal converter 9
Display the pattern.

At this time, since the target pattern 1a of the optical microscope 4 is set on the optical axis position, in other words, on the optical axis position of the electron microscope 3, the electron microscope 3 can immediately find the target pattern 1a, and The inspection of the target pattern 1a can be completed in a short time.

Therefore, the irradiation time of the electron beam on the wafer 1 is shortened to reduce the total amount of electron beam, thereby preventing damage to the characteristics of elements such as 5M0S transistors, preventing contamination, and further reducing contrast due to charge-up. It is possible to realize accurate and high-precision inspection by preventing reduction and image distortion.
As shown in the figure, an XY table 2At with a tilt mechanism may be used. After setting the position using the pick and optical microscope 4, the wafer 1 may be completely tilted using the tilt mechanism to set the wafer 1 perpendicular to the optical axis of the electron microscope 3.

[Embodiment 2] FIG. 3 shows another embodiment of the present invention, in which the same parts as those in FIG.

In this example, the optical axes of the electron microscope 3 and the optical microscope 4 are perpendicular to the wafer 1 and are placed a predetermined distance apart from each other. This predetermined distance information is then transmitted to the control circuit 1.
7 in advance.

Therefore, according to this configuration, the target pattern 1a is first set at the optical axis position of the optical microscope 4 using the optical microscope 4, and then the control circuit 17 and the drive unit 18 are immediately operated to move the XY table 2 to the By moving it a predetermined distance, the target pattern 1a is instantly set at the optical axis position of the electron microscope 3. Thereby, pattern setting and inspection time using the electron microscope 3 can be shortened, and the amount of electron beam irradiation can be reduced, thereby achieving prevention of damage to element characteristics, prevention of contamination, and improvement of inspection accuracy.

In this example, the optical axes of both microscopes 3 and 4 are perpendicular to Waeno 1, and the tilting mechanism and accompanying operation as in the previous example are not required.

〔effect〕

(1) An electron microscope and an optical microscope are installed side by side, and the same part of the object to be inspected can be inspected by both microscopes simultaneously or by switching instantly, so it is possible to position the target pattern of the object to be inspected using the optical microscope. If you do this, you can immediately position the electron microscope. By shortening the inspection time using an electron microscope, it is possible to reduce the total amount of electron beam irradiation on the object to be inspected.

(2) According to (1) above, when semiconductor wafer is applied to the object to be inspected, it is possible to prevent damage to the characteristics of elements such as MOS transistors, and to prevent contamination.
17 and charge-up can be prevented, contrast reduction and image distortion can be eliminated, and high accuracy of inspection can be achieved.

(3) Since the optical axes of the electron microscope and the optical microscope are made to intersect (coincide) on the object to be inspected, it is possible to inspect a target area with the electron microscope and simultaneously observe a wide range with the optical microscope.

(4) The electron microscope and the optical microscope are installed a predetermined distance apart, both optical axes are perpendicular to the object to be inspected, and the object to be inspected is configured to be movable by the predetermined distance. The degree of freedom in arrangement is large, which is particularly advantageous when the object to be inspected is small.

Although the invention made by the present inventor has been specifically explained above based on Examples, it is to be understood that the present invention is not limited to the Examples described above, and that various changes can be made without departing from the gist of the invention. Not even 1. For example, the specific configuration of an electron microscope or an optical microscope can be modified in various ways.

[Application field]

In the above explanation, the invention made by the present inventor has been mainly applied to the field of application which is the background of the invention, which is an inspection device for device patterns on semiconductor wafers. However, the present invention is not limited to this. It can be applied to equipment for inspecting semiconductor devices or other items where it is desired to reduce irradiation as much as possible.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a first embodiment of the present invention, the second diagram is a configuration diagram of a modified example, and FIG. 3 is an overall configuration diagram of a second embodiment. DESCRIPTION OF SYMBOLS 1... Wafer (inspection object), 2... XY table, 3... Electronic P:A microscope, 4... Optical microscope blunt, 8...
...Scintillator, 9...Signal converter, 10...C
RT, 14... Image pickup tube, 15... Signal converter, 16
... CRT, 17... Control m path, 18... Drive section, D... Distance between optical axes.

Claims (1)

[Scope of Claims] 1. An electron microscope that directly inspects the pattern of the object to be inspected and an optical microscope with a lower magnification are installed side by side, and the same part of the object to be inspected is inspected by both microscopes simultaneously or instantaneously. 1. A visual inspection device characterized by being configured so that observation can be performed by switching to . 2. The appearance inspection apparatus according to claim 1, wherein the optical axes of the electron microscope and the optical microscope intersect at the same location on the surface of the object to be inspected. 3. An appearance inspection apparatus according to claim 1, wherein the optical axes of an electron microscope and an optical microscope are set apart by a predetermined distance, and the object to be inspected can be moved between these two optical axes. .