JPS63313041A - Inspecting device for foreign matter - Google Patents

Abstract

PURPOSE:To facilitate the evaluation of sticking foreign matter, the specification of a foreign matter source, etc., and to improve the yield of semiconductor manufacture process by providing a foreign matter detecting means, a foreign matter observing means, a foreign matter height detecting means, etc. CONSTITUTION:A wafer 22 supported on a sample table 21 is irradiated with S-polarized light from a light source, and its reflected light from the wafer 22 is photodetected by a photodetection part 28 and converted into an electric signal corresponding to the quantity of the light. Then the electric signal is amplified 29 and compared by a comparison part 30 with a threshold value P0. Then when the signal is larger than the threshold value P0, foreign matter is judged and the comparison part 30 sends out a foreign matter detection signal. Further, the distribution state of the foreign matter on the wafer 222 which is found by a foreign matter detecting means 23 is displayed on a display. Further, a place to be observed visually is selected according to the foreign matter distribution displayed on the display. Namely, a mirror 31 is moved by a driving device to between an objective 25 and a polarizing plate 26. Thus, the evaluation of the foreign matter, the specification of the foreign matter source, etc., are carried out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a visual inspection technique and a technique that is particularly effective when applied to the visual inspection of wafers. related to technology.

[Prior Art] The present inventor has studied wafer visual inspection technology in the manufacture of semiconductor devices. Although the following is not a publicly known technique, it is a technique studied by the present inventor, and its outline is as follows.

FIG. 3 shows an example of a foreign matter inspection device studied by the present inventor.

In the figure, reference numeral 1 represents a sample stage that holds a wafer 2. As shown in FIG. The sample stage 1 can be moved vertically and horizontally within a certain plane or rotated around a certain vertical axis by means of a drive device 18, for example, and can also be moved in the vertical direction. . In this foreign matter inspection device, the foreign matter distribution of the wafer 2 held on the sample stage 1 is detected by the foreign matter detection means 3, and the foreign matter detected by the foreign matter detection means 3 is visually inspected and inspected by the foreign matter FA inspection means. R? ;It is designed to do I8.

Here, the foreign matter detection means 3 includes a light source (not shown) that emits S-polarized light. Note that S-polarized light means secondary polarized light, and refers to plane-polarized light in which the vibration direction of the light propagation vector is perpendicular to the plane of incidence. Further, P-polarized light means primary-polarized light, and refers to plane-polarized light when the vibration direction of the light propagation vector is included in the incident plane.

In this foreign matter detection means 3, when the S-polarized light is irradiated, the light reflected from the wafer 2 is transmitted to an objective lens 5. The light is received by a detection unit 8 through a polarizing plate 6 and a slit 7. That is, in this foreign matter detection means 3, the reflected light from the wafer 2 is converged by the objective lens 5, and only the P-polarized light component in the reflected light is extracted by the polarizing plate 6.

Therefore, the detection unit 8 has the slit 7 of the P polarized light component.
Only those that have passed through will be incident.

Further, in this foreign object detection means 3, an electrical signal corresponding to the amount of received light is outputted from the detection section 8 to the comparison section 10 via the amplification section 9, and the amplified electrical signal is outputted to the comparison section 10. It is designed to be compared with the value P0. Then, from the comparator 10, the electric signal is sent to the threshold value P
, a high level signal (foreign object detection signal) is output. Threshold value P0 in this case
teeth.

It is determined in order to remove noise from the detection section 8 and the amplification section 9 and to select the size of the foreign object to be detected. Then, the distribution of foreign matter on the wafer 2 determined by the foreign matter detection means 3 is displayed on a display (not shown).

On the other hand, the foreign object observing means 4 includes an objective lens 5 which also constitutes a part of the foreign object detecting means 3, and a mirror 11 provided between the objective lens 5 and the polarizing plate 6 so as to be able to appear and retract freely.
A microscope @f having an optical axis orthogonal to the optical axis of the objective lens 5
i12. And this foreign object lol
In t detection means 4.

A mirror 11 is moved between an objective lens 5 and a polarizing plate 6, and foreign matter on the wafer 2 is optically observed vA by a microscope 12. In this case, the selection of the foreign object to be visually observed is performed by selecting the location to be observed on the display based on the foreign object distribution displayed on the display. The direction and lateral size, that is, the two-dimensional size are determined.

Incidentally, in this foreign matter inspection apparatus, a driving device that drives the sample stage 1 in the vertical direction functions as a focusing means for focusing the microscope 12.

Regarding conventional foreign substance inspection equipment, for example,
Electronic Materials Special Edition “Ultra LSI Manufacturing and Testing Equipment Guidebook” No. 213 published by Kogyo Kenkyukai on November 20, 1999
It is described on pages 219 to 219.

[Problems to be Solved by the Invention] However, the technology considered by the present inventor only has the function of detecting the size in the vertical and horizontal directions as described above, There is a problem in that it is not possible to accurately identify the source.

That is, in the semiconductor manufacturing process, it is not only the two-dimensional size of the foreign object that affects the yield, but also the height of the foreign object. In other words, when forming, for example, a wiring pattern on the wafer 2 where foreign matter is present, the JK
When the height of the object is large, it may cause pattern breakage or disconnection. Therefore, it is essential to measure not only the two-dimensional size of the foreign object but also the three-dimensional size of the foreign object by measuring the height of the foreign object in order to improve the yield of semiconductor processes. Furthermore, it is essential to know the height of the foreign object in order to accurately identify the source of the foreign object.

However, at present, there is no foreign object inspection device that can easily measure the height of foreign objects.

The present invention has been made in view of the above points, and provides a foreign matter inspection device that has a simple structure, can easily evaluate attached foreign matter, identify the source of foreign matter, etc., and can improve the yield in the semiconductor manufacturing process. The purpose is to provide.

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.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

That is, a foreign matter detection means for determining the distribution state of foreign matter adhering to the sample surface, a foreign matter observation means for visually observing the foreign matter optically, a focusing means for focusing the foreign matter observation means, and a focusing means for focusing the foreign matter observation means. a foreign object height detection means for determining the height of the foreign object from the amount of vertical movement of the sample when the foreign object wt detection means is focused on both the top of the foreign object and the surface of the sample; It is designed to find the target size.

[Function] According to the above-mentioned means, the two-dimensional size of the foreign object is determined by visual observation Ffl of the foreign object on the sample using the foreign object observation means, and furthermore, the foreign object detection means is placed on the top of the foreign object or on the surface of the sample. When the focus is adjusted, the position of each sample is determined by the foreign object height detection means, and
This is due to the effect that the height of the foreign object is determined from the difference in the surface positions mentioned above.

The three-dimensional size of the foreign object can be easily determined. Therefore, according to this means, evaluation of attached foreign matter, identification of the foreign matter source, etc. are facilitated, and as a result, the above-mentioned objective of improving the yield in the semiconductor manufacturing process is achieved.

[Example code] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of a foreign matter inspection device according to the present invention.

In the figure, reference numeral 21 represents a sample stage that holds a wafer 22. The sample stage 21 can be moved vertically and horizontally within a certain plane, rotated around a certain vertical axis, and also moved up and down by a drive device 38, for example. In this foreign matter inspection apparatus, the wafer 2 held on the sample stage 21 is
The foreign matter detection means 23 detects the distribution of foreign matter on the foreign matter detection means 23, and the foreign matter detected by the foreign matter detection means 23 can be visually observed by the foreign matter a detection means 24. In addition, in this foreign matter inspection device,
A foreign object height detection means 33 is provided so that the height of the foreign object can be determined from the amount of vertical movement of the sample stage 21 when focusing on the top of the foreign object on the wafer 22 and the surface of the wafer 22. It has become. Note that focusing in this case is performed by a drive device 38 that moves the sample stage 21 in the vertical direction. In other words, in the foreign matter inspection device of this embodiment,
A drive device 38 that moves the sample stage 21 in the vertical direction functions as a focusing means.

Here, the foreign object detection means 23 includes a light source (not shown) that emits S-polarized light. In this foreign matter inspection device, when irradiating S-polarized light, the wafer 22
The light reflected from the sea urchin/) passes through an objective lens 25, a polarizing plate 26, and a slit 27 placed on the sea urchin/) 22, and is received by a detection unit 28. That is, in this foreign object detection means 23, the reflected light from the wafer 22 is converged by the objective lens 25, and only the P-polarized light component in the reflected light is extracted by the polarizing plate 26. Therefore, only the P-polarized light component that has passed through the slit 27 is incident on the detection unit 28 .

Further, in this foreign object detection means 23, an electrical signal corresponding to the amount of received light is outputted from the detection section 28 to the comparison section 30 via the amplification section 29, and the amplified electrical signal is Value P. It has come to be compared with Then, when the electric signal exceeds the threshold value P, the comparator 3o outputs a high level signal (
foreign object detection signal) is output. The threshold value Pl in this case is determined in order to remove noise from the detection section 28 and the amplification section 29 and to select the size of the foreign object to be detected. Then, the distribution of foreign matter on the wafer 22 determined by the foreign matter detection means 23 is displayed on a display (not shown).

On the other hand, the foreign object vA detection means 4 includes an objective lens 25 that also constitutes a part of the foreign object detection means 23, and a mirror 31 provided between the objective lens 25 and the polarizing plate 26 so as to be able to appear and retract. , and a microscope 32 having an optical axis perpendicular to the optical axis of the objective lens 25. In this foreign matter observation means 24, foreign matter on the wafer 22 can be visually observed using a microscope fi 32 when the mirror 31 is present between the objective lens 25 and the polarizing plate 26. In this case, the selection of the foreign object to be visually observed is performed by selecting the location to be observed on the display based on the foreign object distribution displayed on the display,
Through this visual inspection w4, the size of the foreign object in the vertical and horizontal directions, that is, the two-dimensional size, can be detected directly or based on a microscopic photograph.

Further, the foreign object height detecting means 33 may include, but is not particularly limited to, the sample height position detecting section 34. Storage section 35 and calculation section 3
It consists of 6. Here, the sample height position detection section 3
4, the top of the foreign object on the wafer 22 and the wafer 22
The height position of the wafer is detected when the foreign matter detection means is focused on the surface. In addition, the storage unit 35
In this case, the sample stage height position detected by the sample stage height position detection section 34 is stored. moreover,
In the calculation unit 36, the amount of vertical movement of the sample stage 31 and thus the wafer 22 is determined from the difference in the height of the sample stage when the foreign matter detection means is focused on the top of the foreign matter on the wafer 22 and the surface of the wafer 22. , whereby the height of the foreign substance on the wafer 22 can be determined.

Next, the operation of the foreign object detection device configured as described above will be explained as follows.

First, the wafer 22 supported on the sample stage 21 is irradiated with S-polarized light from a light source. Then, the reflected light from the wafer 22 is received by the detection unit 28, where it is converted into an electrical signal corresponding to the scene. Then, the electrical signal is sent to the amplification section 2.
9, and the comparison section 30 compares the amplified signal with a threshold value P0. And threshold 26
If it is more than that, it is determined that it is a foreign object, and the comparator 30 issues a foreign object detection signal. Such operations are performed on the entire surface of the wafer 22. Then, the distribution state of the foreign matter on the wafer 22 determined by the foreign matter detection means 23 is displayed on a display (not shown).

Next, a location to be visually observed is selected based on the foreign material distribution displayed on the display.

That is, the mirror 31 is moved between the objective lens 25 and the polarizing plate 26 by a drive device (not shown). and,
As shown in FIG. 2, the microscope 12 is focused on the top of the foreign object, and the height direction coordinate Z1 of the sample stage 21 at that position is detected. Next, the focus of the microscope 12 is on the wafer 2.
2 surface, and the height direction coordinate Z2 of the sample stage 21 at that position is detected. Note that the focusing at this time is performed by the drive device 38 of the sample stage 21. Next.

The detected height direction coordinate difference (Z□-22) is calculated by the calculation unit 3.
6, and thereby the height of the foreign object is detected.

According to the foreign object detection device of the embodiment configured in this way, the following effects can be obtained.

That is, according to the foreign matter inspection device of the embodiment, the foreign matter observation means 2
Foreign matter 2 was detected by visual inspection a of foreign matter on wafer 22 according to step 3.
When the dimensional size of the foreign object is determined and the foreign object detection means 23 is focused on the top of the foreign object or the wafer surface, the foreign object height detection means 33 determines the position of each sample stage and the wafer position. By determining the height of the foreign object from the difference in position, the three-dimensional size of the foreign object can be easily determined. Therefore, evaluation of attached foreign matter, identification of the foreign matter source, etc. are facilitated.

As a result, it becomes possible to improve the yield in the semiconductor manufacturing process.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, in the foreign object inspection apparatus of the above embodiment, a driving device that moves the sample stage 21 in the vertical direction is used as a focusing means, but this focusing means is not one that moves the objective lens 25 in the vertical direction. Alternatively, the microscope 32 may be optically brought closer to or separated from the wafer 22.

In the above explanation, the invention made by the present inventor has mainly been described as being applied to an apparatus for inspecting foreign matter on a wafer, which is the background field of application, but the present invention is not limited to such embodiments. It can also be used to inspect masks or reticles for foreign objects.

[Effects of the Invention] The effects obtained by typical inventions disclosed in this application are briefly explained below.

That is, according to the foreign object inspection device of the present invention, the two-dimensional size of the foreign object is determined by visual observation of the foreign object on the sample by the foreign object observation means, and the focus of the foreign object detection means is on the top of the foreign object or the surface of the sample. When the two surfaces are aligned, the foreign object height detection means determines the position of each sample stage and thus the sample position, and the height of the foreign object is determined from the difference in surface position, so the three-dimensional size of the foreign object can be easily determined. Desired. Therefore, evaluation of attached foreign matter, identification of the foreign matter source, etc. are facilitated, and as a result, it is possible to improve the yield in the semiconductor manufacturing process.

[Brief explanation of the drawing]

Fig. 1 is a schematic front view of an embodiment of the foreign object inspection device according to the present invention, Fig. 2 is a diagram of the principle of measuring the height of a foreign object in the foreign object inspection device of Fig. 1, and Fig. 3 is a diagram that was studied by the present inventor. FIG. 2 is a schematic front view of the foreign matter inspection device.

Claims (1)

[Claims] 1. Foreign matter detection means for determining the distribution state of foreign matter adhering to the sample surface using reflected light from the surface of the sample held on the sample stage, and an optical method for detecting foreign matter detected by the foreign matter detection means. a foreign matter observation means for visually observing the foreign matter, and a focusing means for focusing the foreign matter observation means by moving the optical component or the sample constituting the foreign matter observation means;
and foreign object height detection means for determining the height of the foreign object from the amount of movement of the optical component or the sample when the foreign object observation means is focused on both the top of the foreign object and the sample surface by the focusing means. Features of foreign matter inspection equipment. 2. The foreign matter inspection apparatus according to claim 1, wherein the focusing means is a drive device that drives the sample stage in the vertical direction.