JPS62297747A - Method and device for inspection - Google Patents

Abstract

PURPOSE:To improve the sensitivity of inspection by comparing the difference between reflected or scattered light beams generated at a 1st time and a 2nd time with a specific threshold value. CONSTITUTION:A specific area on a body 2 to be inspected is irradiated with inspection light 3 from a light source 4 and then the surface of the body 3 to be inspected is scanned continuously by the inspection light 3. At this time, scattered or reflected light 7 generated in the specific area of the surface of the objective body 2 irradiated with the inspection light 3 is made incident on an photoelectric transducing means 6 through an objective 5. Here, the signal S1 of the quantity of light 7 detected by the means 6 at the 1st time is transmitted to a comparison part 10 through a 1st signal line 8 where a delay part D is interposed. Further, the signal S2 of the quantity of light 7 detected by the means 6 at the 2nd time which is a specific time after the 1st time is transmitted directly to a comparison part 10 through a 2nd signal line 9 and the comparison part 10 inputs the signals S1 and S2 of the quantities of light 7 at the same time and the difference in the quantity of light is compared with the specific threshold value. Thus, the sensitivity of the inspection can be improved.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an inspection technique, and particularly to a technique that is effective when applied to the visual inspection of semiconductor wafers in the manufacture of semiconductor devices.

[Prior art] Regarding the appearance inspection of semiconductor wafers in the manufacture of semiconductor devices, see Kogyo Kenkyukai Co., Ltd., published November 15, 1983, "Electronic Materials J November 1983 issue, P2O4"
~P2O9.

The outline of this method is to irradiate inspection light such as a laser onto the surface of a semiconductor wafer that is being rotated and translated in parallel, and at this time, the amount of scattered light generated from the irradiated area of the inspection light is detected using a photodiode, etc. The presence or absence of foreign matter on the surface of a semiconductor wafer is inspected by comparing it with a threshold value.

[Problems to be Solved by the Invention] However, in the foreign object inspection described above, when the surface of the semiconductor wafer is mirror-like and flat, the scattered light from the foreign object and the scattered light from the underlying portion are relatively small. Although it is clearly distinguished, if a thin film of aluminum or polycrystalline silicon is formed on the surface and there are irregularities due to crystal grains, the scattered light from the foreign object will be buried in the scattered light from the underlying part. The inventors have discovered that this method has the disadvantage that the sensitivity for detecting foreign objects and the like is reduced.

An object of the present invention is to provide an inspection technique that can improve inspection sensitivity.

The above and other objects and novel features of the present invention include:
It will become clear from the description herein and the accompanying drawings.

[Means for Solving the Problems] A brief overview of typical inventions disclosed in this application is as follows.

That is, a predetermined inspection is performed by comparing the difference in the amount of reflected light or scattered light generated at different first and second times from the surface of the inspected object scanned by the inspection light with a predetermined threshold value. It was designed to be carried out.

[Operation] According to the above-described means, the difference in the amount of scattered light or reflected light from different parts of the object to be inspected is compared with a predetermined threshold value, so that, for example, it is possible to detect the presence of irregularities on the surface of the object to be inspected. Even when the object is inspected, the components of scattered light or reflected light as noise due to the unevenness of the surface of the object to be inspected are canceled out, and the scattered light or reflected light from the target foreign object is replaced by the scattered light from the unevenness of the underlying part. Alternatively, it can be clearly detected with a relatively large contrast with the reflected light, and the sensitivity in inspecting the object to be inspected is improved.

[Embodiment 1] FIG. 1 is an explanatory diagram showing the main parts of an inspection device that is an embodiment of the present invention.

An object to be inspected 2, such as a semiconductor wafer, is removably fixed on a sample stage 1 that is rotatable and horizontally movable within a predetermined plane.

In the vicinity of the sample stage l, there is a light source 4 that irradiates inspection light 3 such as a laser of a predetermined wavelength onto a predetermined area of the surface of the object to be inspected 2 placed on the sample stage 1 at a predetermined angle. It is provided.

By rotating the sample stage 1 with respect to the light source 4 and moving it in parallel in a predetermined direction, the entire area of the object to be inspected 2 placed on the sample stage 1 is scanned by the inspection light 3. .

Above the sample stage l, an objective lens 5 consisting of a predetermined lens group, etc. and a light-to-electrical conversion means 6 are provided.
The structure is such that scattered light or reflected light 7 generated from a predetermined area irradiated with the inspection light 3 on the surface of the object 2 to be inspected is incident on the light-to-electrical conversion means 6 via the objective lens 5. There is.

In this case, the optical-to-electrical converter 6 receives a signal of scattered light or reflected light 7 from a portion of the object to be inspected 2 that is irradiated with the inspection light 3 detected by the optical-to-electrical converter 6 for a predetermined period of time. The comparator 10 is connected via a first signal line 8 which is provided with a delay section that transmits the signal with a delay of 1, and a second signal line 9 that is directly connected to the optical-to-electrical conversion means 6. The difference in the amount of scattered light or reflected light 7 detected by the optical-to-electrical converting means 6 at different first times T1 and second times T2, that is, the difference in the amount of light detected by the optical-to-electrical converting means 6 for the inspected object 2 The structure is such that the difference in the amount of scattered light or reflected light 7 from different parts of the body is calculated.

Furthermore, a determination unit 11 is connected to the comparison unit 10,
In this determination section 11, by comparing the difference in the amount of scattered light or reflected light 7 from different parts of the inspection object 2 calculated in the comparison section 10 with a predetermined threshold value, After canceling out the components of the scattered light or reflected light from the underlying portion of the inspection object 2, by comparing it with a predetermined threshold value, the scattered light from, for example, a foreign object (not shown) existing on the surface of the inspection object 2 is detected. or reflected light 7
However, the scattered light or reflected light 7 from the underlying part of the object to be inspected 2
It can be clearly distinguished and detected.

The operation of this embodiment will be explained below.

First, a sample stage 1 on which an object 2 to be inspected such as a semiconductor wafer is placed is rotated and linearly moved in a predetermined direction, and a light source 4 irradiates inspection light 3 onto a predetermined area of the object 2 to be inspected. By doing so, the surface of the object to be inspected 2 is continuously scanned by the inspection light 3, and at this time, the scattered light or reflected light generated from a predetermined area on the surface of the object to be inspected 2 that is irradiated with the inspection light 3. 7 is incident on the optical-to-electrical conversion means 6 via the objective lens 5.

Here, for example, at the first time T1, the optical-electrical conversion means 6
A signal S representing the amount of scattered light or reflected light 7 detected by the detector is sent to the comparator 1 via a first signal line 8 in which a delay section is interposed.
The signal S2 of the amount of scattered light or reflected light 7 is transmitted to 0 and detected by the optical-to-electrical conversion means 6 at a second time T2, which is a predetermined time elapsed from the first time T1. The signals of the object to be inspected 2 detected by the optical-to-electrical conversion means 6 at different first times T1 and second times T2 are directly transmitted to the comparison unit IO via the signal line 9 of 2. signals S1 and S2 of the amount of scattered light or reflected light 7 from different parts of the object 2 to be inspected that are continuously scanned by the inspection light 3, and S2 is input at the same time.

For example, if there is a foreign object that scatters or reflects the inspection light 3 more easily than the underlying part in the part of the inspection object 2 where the scattered light or reflected light 7 detected at the first time T1 is generated, the scattered light Alternatively, in the optical-to-electrical conversion means 6 into which the reflected light 7 is incident, the scattered light or reflected light 7 from the foreign object and the scattered light or reflected light 7 from the underlying portion are detected as a mixture of the second signal s1. Signal S of scattered light or reflected light 7 detected by optical-to-electrical conversion means 6 at time T2
If 2 is only the signal S of the scattered light or reflected light 7 from the underlying portion, then, for example, Fig. 2+a) and (
b).

Further, in the comparator 10, the signal S1 of the scattered light or reflected light 7 at the first time T1 and the second time T2
When calculating the difference signal S between , the signal component from the foreign object contained in the scattered light or reflected light 7 is detected in good contrast with the signal component from the underlying portion of the object to be inspected 2, and is further compared with a predetermined threshold value T6 in the determination section 11. As a result, only signals from foreign matter adhering to the object to be inspected 2 can be clearly detected without being affected by noise from the underlying portion.

For this reason, for example, even if the inspected object 2 is a semiconductor wafer on which a thin film of aluminum, polycrystalline silicon, etc. is formed and the entire surface has unevenness due to crystal grains, etc., Foreign matter adhering to the surface of the object 2 can be detected accurately and stably without being affected by the unevenness of the underlying surface, and the sensitivity of the inspection for foreign matter on the object 2 to be inspected such as a semiconductor wafer is improved.

In this way, the following effects can be obtained in this embodiment.

(1) Object 2 to be inspected scanned by inspection light 3 from light source 4
The optical-to-electrical conversion means 6 detects scattered light or reflected light 7 generated from a predetermined region of Department lO
and a different first time TI and a second time T!
, signals SI and S2 of the amount of scattered light or reflected light 7 detected by the optical-to-electrical conversion means 6, respectively;
That is, after calculating the difference S between the signals S1 and S2 of the amount of scattered light or reflected light 7 from different parts of the object 2 to be inspected, the judgment section 11 compares it with a predetermined threshold T1, thereby determining the amount of light to be inspected. In order to inspect foreign matter adhering to the surface of the inspection object 2, the inspection object 2 is, for example, a semiconductor wafer on which a thin film of aluminum or polycrystalline silicon is formed, and whose surface has irregularities due to crystal grains. Even if there is, the components of the scattered light or reflected light 7 from the underlying part are canceled out, and the scattered light or reflected light 7 from foreign objects etc. is stabilized in good contrast with the scattered light or reflected light 7 from the unevenness of the underlying part. Moreover, it can be clearly detected, and the sensitivity of inspection of foreign matter adhering to the surface of the object 2 to be inspected such as a semiconductor wafer can be improved.

(2) As a result of +11 above, it is possible to detect finer foreign objects attached to the object 2 to be inspected.

(3) As a result of the above 111, foreign matter inspection can be performed not only on semiconductor wafers with mirror surfaces, but also on semiconductor wafers with thin films such as aluminum and polycrystalline silicon, and with relatively rough surfaces. The performance of the visual inspection equipment is improved.

(4) As a result of +11, the productivity in visual inspection of semiconductor wafers in the manufacture of semiconductor devices is improved.

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 Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, the first signal line provided with the delay section may be configured with a plurality of signal lines each provided with delay sections having different delay times, and furthermore, The object to be inspected may be scanned by the inspection light by parallel movement in a zigzag manner.

The above explanation has mainly been about the application of the invention made by the present inventor to the visual inspection technology of semiconductor wafers, which is the background field of application, but the invention is not limited thereto. It can be widely applied to technologies that require inspection of minute foreign objects attached to the surface of objects.

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

That is, a light source that is moved relative to the object to be inspected and scans the inspection light on the surface of the object to be inspected, and a light-to-electrical conversion means that detects the amount of scattered light or reflected light from the surface of the object to be inspected. , to the optical-to-electrical converting means via a first signal line and a second signal line in which a delay section that delays and transmits the signal detected by the optical-to-electrical converting means by a predetermined time is interposed. connected and said light at different first and second times.
A structure including a comparison section that calculates a difference in the amount of scattered light or reflected light from the surface of the object to be inspected that is detected by the electrical conversion means, and a determination section that compares the difference in the amount of light with a predetermined threshold value. Therefore, the difference in the amount of scattered light or reflected light from different parts of the object to be inspected is compared with a predetermined threshold. The components of scattered light or reflected light as noise caused by unevenness on the surface of the object are canceled out, and the scattered light or reflected light from the target foreign object is compared with the scattered light or reflected light from the unevenness of the underlying part. It can be clearly detected with a large contrast, and the sensitivity in inspecting the object to be inspected is improved.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the main parts of an inspection device that is an embodiment of the present invention, and Fig. 2 (al~+11.) shows the amount of scattered light or reflected light detected by a plurality of optical-to-electrical conversion means. FIG. 2 is a diagram showing an example of a signal waveform of FIG. 1... Sample stage, 2... Workpiece, 3... Inspection light,
4... Light source, 5... Objective lens, 6... Light-electric conversion means, 7... Scattered light or reflected light, 8... First
9... second signal line, 10... comparison section,
11... Determination unit, D... Delay unit, S,... Signal of scattered light or reflected light at the first time (first signal line), S2... Signal of the scattered light or reflected light at the first time (second signal line),... Signal of scattered light or reflected light on the signal line), Sn...difference signal between Sl and S2, Tゎ...threshold value. \ゝge

Claims (1)

[Claims] 1. Detecting scattered light or reflected light generated from the surface of the object to be inspected scanned by the inspection light at different first and second times; An inspection method characterized in that a predetermined inspection is performed on the surface of the object to be inspected by comparing the difference in the amount of light of the scattered light or reflected light detected with a predetermined threshold value. 2. The inspection method according to claim 1, wherein the inspection light is a laser that irradiates the surface of the object to be inspected at a predetermined angle. 3. The inspection method according to claim 1, wherein the object to be inspected is a semiconductor wafer, and the inspection is an appearance inspection. 4. A light source that is moved relative to the object to be inspected and scans the inspection light on the surface of the object to be inspected, and a light-to-electrical conversion means that detects the amount of scattered light or reflected light from the surface of the object to be inspected. , to the optical-to-electrical converting means via a first signal line and a second signal line in which a delay section that delays and transmits the signal detected by the optical-to-electrical converting means by a predetermined time is interposed. a comparison unit that is connected and calculates a difference in the amount of scattered light or reflected light from the surface of the object to be inspected that is detected by the optical-to-electrical conversion means at different first and second times, and a difference in the amount of light; 1. An inspection device comprising: a determination unit that compares the value of the value with a predetermined threshold value. 5. The inspection according to claim 4, wherein scanning of the surface of the object to be inspected with the inspection light is performed by rotating and moving the object to be inspected parallel to the light source. Device. 6. The inspection device according to claim 1, wherein the object to be inspected is a semiconductor wafer, and the inspection device is an appearance inspection device.