JPH06308039A - Foreign matter analyzer - Google Patents

Abstract

(57) [Summary] [Object] To provide a means for observing the shape and analyzing the composition of a very small foreign substance having a diameter of half micron or less, which is attached to the surface. [Structure] The foreign matter inspection device 3
1 and a scanning electron microscope 41. As a result, the minute foreign matter detected by the foreign matter inspection apparatus can be driven into the ultra-high-magnification visual field of the electron microscope. Therefore, it is possible to easily and quickly observe an extremely small foreign substance, which has been difficult and takes a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for analyzing minute foreign matter adhering to the surface of an object, and more particularly to an apparatus for analyzing foreign matter for analyzing and reducing foreign matter on the surface of a semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, as the degree of integration of semiconductor integrated circuits has increased, there has been a problem that the product yield is reduced due to fine pattern defects. The main cause of the defects is foreign matter that adheres to the wafer surface during the manufacture of the semiconductor integrated circuit. Therefore, in order to find out and reduce the generation source of the surface-attached foreign matter, the foreign matter attached to the wafer surface is detected by a foreign matter inspection apparatus, and then observed by a scanning electron microscope (SE
Shape observation by M) and energy dispersive X-ray analysis (ED
The method of performing composition analysis according to X) is generally performed. In recent years, as the degree of integration of semiconductor integrated circuits has increased, demands for higher accuracy and higher throughput of foreign matter analyzers have increased.

An example of a conventional surface foreign matter analyzer will be described below with reference to the drawings. FIG. 4 shows the overall structure of a conventional surface foreign matter analyzer. In FIG. 4, 11 is a wafer to be inspected, 24 is an XYθ stage, 25 is a stage encoder, 31 is a foreign matter inspection device, 41 is an electron microscope, and 42 is an energy dispersive X-ray analysis device. The operation of the foreign matter analyzing apparatus configured as described above will be described below. First, a foreign matter inspection device detects a foreign matter, displays the position coordinates of each foreign matter from the position of the XY stage and the position of the laser spot, and when the foreign matter to be observed is designated, the XY stage moves the foreign matter into the field of view of the electron microscope, SE in electron microscope
The foreign matter was observed and analyzed by M and EDX42.
(For example, Hitachi review VOL.71 No.5 P.8
3-88).

[0004]

However, the above-mentioned analyzer has the following problems.
In order to analyze extremely minute foreign matter, which is a problem in sub-micron devices or less, it is necessary to capture the foreign matter within the ultra-high magnification field of view of an electron microscope. However, since the conventional foreign matter analyzer uses an encoder to detect the position of the stage, the position detection accuracy of the foreign matter inspection device is ± 10 μm (the accuracy of the stage + the spatial resolution of the inspection device) and the view of the electron microscope field. Position reproducibility during movement ± 5 μm (stage accuracy) coordinate error occurs, and foreign substances may fall out of the field of view when the SEM magnification is 3000 times or more.
When the S / N ratio of the EM image is good, about 0.3 μm or more, SE
There is a problem that only foreign matter of about 0.6 μm or more can be found when the S / N ratio of the M image is poor. Furthermore, in order to perform three-dimensional observation with a scanning electron microscope, it is effective to observe the foreign matter in the oblique visual field, but it is difficult to maintain the center of the visual field for the foreign matter during the tilting operation of the θ stage. After tilting the stage, it was necessary to search again for a foreign object that was out of the field of view.

In view of the above-mentioned problems, the present invention provides a foreign matter analyzing apparatus for easily and quickly analyzing minute foreign matter adhering to the surface, and for observing a three-dimensional shape by a tilted SEM easily and in a short time. To do.

[0006]

In order to solve the above-mentioned problems, the foreign matter analyzer of the present invention has a laser interferometer for measuring and controlling the position within the operating range of an XY stage.
It has a structure in which a foreign matter inspection device, a vertical SEM, and an inclined SEM are arranged.

[0007]

According to the present invention, due to the above-described structure, the accuracy of the stage is improved, the position detection error in the foreign substance inspection device and the position accuracy error when moving to the electron microscope field of view are improved, and the high-magnification electron microscope field of view is improved. It is possible to catch a foreign object. Therefore, it is possible to easily observe and analyze minute foreign matter in a short time.

Further, since the oblique SEM is provided, θ
Since there is no need to operate the stage or to search again for the foreign matter thereafter, it becomes possible to easily and stereoscopically observe a minute foreign matter in a short time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A foreign matter analyzer according to a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the entire structure of a foreign matter analyzer according to the first embodiment of the present invention. In FIG. 1, 11 is a wafer to be inspected, 21 is an XY stage, 22 is a mirror, 23 is a laser interferometer, 31 is a foreign matter inspection device, 41 is an electron microscope mirror, and 42 is an energy dispersive X-ray.
It is a line analyzer.

The operation of the foreign matter analyzing apparatus constructed as above will be described below with reference to FIG.

If a He--Ne laser (wavelength 633 nm) is used as the light source of the interferometer 23, the positioning accuracy of the stage 11 is about several tenths of the laser wavelength, and therefore about 0.01 μm. The amount of deviation of the foreign matter from the center of the field of view of the electron microscope 41 is the position detection accuracy in the foreign matter inspection device 31 (the accuracy of the stage + the spatial resolution of the inspection device) and the position reproducibility when moving to the field of view of the electron microscope 41 (of the stage). accuracy)
Therefore, the amount of deviation of the foreign matter from the center of the visual field of the electron microscope 41 according to this embodiment is about ± 5 μm, which is the spatial resolution of the inspection device. Therefore, the foreign matter can be captured within the field of view of 10,000 times the electron microscope, and the S / N of the SEM image can be captured.
It is possible to easily observe a foreign substance having a ratio of about 0.1 μm or more when the ratio is good and about 0.2 μm or more when the S / N ratio of the SEM image is bad, in a short time. Also, once a foreign object is captured within the SEM field of view, it can be observed at a higher magnification, and the ED
Elemental analysis by X42 becomes possible.

In the first embodiment, the foreign matter analyzing means is an energy dispersive X-ray analyzer (EDX), but an auger electron spectroscopic analyzer (AES) has the same effect.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the overall structure of a foreign matter analyzer according to the second embodiment of the present invention.
In FIG. 2, 11 is a wafer to be inspected, and 21 is X.
Y stage, 22 is a mirror, 23 is a laser interferometer, 31 is a foreign matter inspection device, 41a is an electron microscope arranged vertically to the XY stage, and 42 is an energy dispersive X-ray analyzer.
The above is the same as the configuration of FIG.

The difference from FIG. 1 is that the electron microscope mirror 41b tilted on the XY stage is provided within the operation range of the XY stage.

The operation of the foreign matter analyzer having the above-described structure will be described below with reference to FIGS. 2 and 3.

In FIG. 3, (a) is a SEM image of the foreign matter observed by an electron microscope 41a arranged vertically, and (b) is X-ray.
It is the SEM image of the foreign material observed by the electron microscope 41b inclined 45 degrees to the direction. In the SEM image observed by the vertically arranged electron microscope 41a, it is possible to observe the planar size of the foreign matter, but it is difficult to interpret the unevenness.
On the other hand, the electron microscope 41b tilted 45 ° to the right in FIG.
In the SEM image observed in step 1, the irregularities of the foreign matter can be easily confirmed, which is a great clue for knowing the cause of the defect. As described above, in order to perform a three-dimensional observation of a foreign matter, there is no need to operate the θ stage and a subsequent re-search for a foreign matter, which has been conventionally required. Therefore, it is possible to easily and stereoscopically observe a minute foreign matter in a short time. It is possible to do it. When adjusting the focus of the SEM image observation, the foreign substance can be kept at the center of the visual field by correcting the product of the tangent of the movement amount of the focal plane and the tilt angle T of the electron microscope by moving the stage in the tilt direction.

As described above, by arranging the electron microscope at an angle inclined with respect to the plane of the XY stage within the operating range of the stage for measuring and controlling the position by the laser interferometer, the three-dimensional appearance of the minute foreign matter is reduced. The observation can be performed easily and in a short time.

In the second embodiment, the tilt of the electron microscope is tilted to the right in the figure by 45 °, but the tilt angle is 45 ° even if tilted in the front, rear, left, right or in the middle. The same effect can be obtained by inclining at an angle other than. Further, even if they are arranged within the operation range of the plurality of XY stages, the same effect is obtained.

Further, in the second embodiment, by arranging the focused ion beam device (FIB) within the operating range of the XY stage, it is possible to easily and in a short time observe the cross section of a defect caused by a foreign matter such as a semiconductor element. You can also do it.

[0021]

As described above, according to the present invention, the foreign matter inspection device and the electron microscope are provided within the operation range of the XY stage whose position is measured and controlled by the laser interferometer. The foreign matter can be captured within the ultra-high magnification field of view of the electron microscope, and the observation of extremely minute foreign matter, which has been difficult and time-consuming in the past, can be performed easily and in a short time. Further, by arranging the electron microscope with an inclination with respect to the plane of the XY stage, it is possible to easily and stereoscopically observe the foreign matter in a short time.

[Brief description of drawings]

FIG. 1 is a perspective view of a foreign matter analyzer according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a foreign matter analyzer according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a foreign matter analyzer according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a conventional foreign matter analysis and inspection device.

[Explanation of symbols]

11 wafer to be inspected 21 XY stage 22a X-direction mirror 22b Y-direction mirror 23a X-direction laser interferometer 23b Y-direction laser interferometer 24 XYθ stage 25a X-direction encoder 25b Y-direction encoder 31 foreign matter inspection device 41 electron microscope 41a Electron microscope 41b arranged vertically to the XY stage 42b Electron microscope inclined to the XY stage 42 Energy dispersive X-ray analyzer (EDX)

Claims (2)

[Claims] 1. An XY stage for measuring and controlling a position by a laser interferometer, a foreign substance inspection device for detecting a foreign substance and specifying coordinates within an operating range of the stage, and an electron microscope for observing and analyzing the foreign substance. A foreign matter analyzing apparatus, comprising: the foreign matter inspecting apparatus, wherein the foreign matter is moved into the field of view of the electron microscope by the stage based on the foreign matter coordinates detected by the foreign matter inspecting apparatus, and the foreign matter is observed and analyzed. 2. The foreign matter analyzing apparatus according to claim 1, wherein an electron microscope is arranged in an operation range of the XY stage at an angle inclined with respect to a plane of the XY stage.