JPH11118677A - Object to be inspected for calibration, manufacture thereof, calibration method of inspection instrument and inspection instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an accurate calibration for a long time without being affected by environmental foreign matters. SOLUTION: In this apparatus, secondary inspection light 3 containing reflected light, scattered light, diffracted light, polarized light and the like as obtained by scanning an object to be inspected carried on a stage 5 using inspection light 2 from a light source 1 is processed by an inspection optical system 6, a detector 7, a signal processing part 8, an inspection data memory 9, a reference data memory 10, a differential circuit 11, a threshold comparison circuit 12 and an output part 13. In the calibration of the apparatus, a defect pattern 52 having a plurality of defects 52a intentionally produced is provided on a main surface of a substrate 51 and a wafer 50 for calibration is used having the defect pattern 52 covered with a transparent film layer 53. The thickness of the transparent film layer 53 is set to a value outside the range of the depth of focus of the inspection optical system 6 and environmental foreign matters 4 adhering to the surface of the transparent film layer 53 will not affect the results of inspection, namely, the results of calibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object to be inspected for calibration and a manufacturing technique therefor, and a calibration technique and an inspection apparatus for an inspection apparatus using the same. The present invention relates to a technique which is effective when applied to calibration of various inspection devices used in an inspection process such as an inspection.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, for example, evaluation of the presence or absence of a foreign substance or a pattern defect on a semiconductor wafer flowing through the process is an important factor which affects the product yield. In such an inspection apparatus, it is indispensable to properly manage and guarantee the inspection sensitivity from the viewpoint of obtaining accurate inspection results.

Conventionally, as a method of calibrating the sensitivity of such an inspection apparatus, for example, a wafer having accurately known information such as the number and position of attached foreign matter and pattern defects (such a wafer is usually used for calibration) A wafer or a standard wafer, hereinafter referred to as a calibration wafer) is mounted on a target inspection apparatus, an inspection is performed, and the inspection result at this time is accurately compared with the known information. ,
Calibration has been performed by evaluating the sensitivity of the inspection device.

[0004]

However, since the above-described calibration wafer is used repeatedly over a long period of time, for example, the surface is deteriorated, the defect signal level is changed, and foreign substances in the environment are removed. There is a technical problem that the number of attached foreign substances and the total number of defects such as defect patterns fluctuate from the values at the time when the calibration wafer is formed, and accurate calibration becomes difficult.

To avoid such technical problems, measures such as storing the calibration wafer in a clean environment can be considered. However, another technical problem that the storage management becomes unnecessarily complicated. Is generated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a calibration test object capable of performing accurate calibration for a long period without being affected by environmental foreign substances and the like, and a technique for manufacturing the same.

Another object of the present invention is to provide an object for calibration which can perform accurate calibration for a long period of time without causing deterioration or the like, and a technique for manufacturing the same.

Another object of the present invention is to provide an object to be calibrated which can be accurately calibrated for a long period of time without requiring special storage management and the like, and a technique for manufacturing the same. It is in.

It is another object of the present invention to provide a method and a device for calibrating an inspection apparatus capable of performing accurate calibration without being affected by environmental foreign substances and the like.

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

[0011]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

The calibration test object of the present invention covers a defect in a calibration test object in which at least one of the number, position, size, shape, and material is known on one principal surface of the substrate. It has a protective film.

[0013] In the method for manufacturing a calibration object according to the present invention, a first step of forming a defect whose at least one of the number, position, size, shape, and material is known on one principal surface of the substrate; Forming a protective film covering the defect.

The calibration method for an inspection apparatus according to the present invention is a method for calibrating an inspection apparatus in which inspection light passing through an inspection object is captured by an inspection optical system to inspect the inspection object. On the surface, at least one of the number, position, size, shape, and material is a known defect, and a calibration test object including a protective film that covers the defect is used.The depth of focus of the inspection optical system is set to be smaller than the thickness of the protective film. The inspection device is calibrated by controlling the inspection object to be calibrated to a small size.

Further, according to the inspection apparatus of the present invention, the inspection optical system captures inspection light passing through the inspection object and inspects the inspection object. A calibration test object consisting of a defect whose size, shape, and material are known and a protective film covering the defect is provided, and the depth of focus of the inspection optical system is controlled to be smaller than the thickness of the protective film for calibration. The inspection device is calibrated by inspecting the inspection object.

According to the present invention described above, even if environmental foreign matter adheres to the protective film of a calibration inspection object such as a calibration wafer,
By setting the thickness of the protective film outside the depth of focus of the inspection device to be calibrated, environmental foreign substances on the protective film are not detected, and therefore, accurate calibration is always performed without increasing or decreasing the number of detected defects. be able to. In addition, since standard defects such as foreign substances and pattern defects intentionally arranged on the surface of the calibration wafer are covered with the protective film, the quality of the standard defects such as the foreign substances and pattern defects can be prevented from being deteriorated, and the standard defects can be prevented. It is possible to avoid occurrence of erroneous inspections and the like due to deterioration.

Thus, the calibration of the inspection apparatus can be performed stably and accurately even if the same object to be inspected is used for a long period of time without requiring special consideration for the storage method and the like. Will be possible.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a conceptual diagram showing an example of a configuration of an inspection apparatus using a calibration object according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of a method of manufacturing a calibration inspection object according to an embodiment of the present invention in the order of steps. Similarly, FIG. 3 is a schematic cross-sectional view showing an example of a method of manufacturing a calibration inspection object according to an embodiment of the present invention in the order of steps.

FIGS. 4 and 5 are flowcharts showing an example of a method of manufacturing a calibration inspection object according to an embodiment of the present invention. FIG. 6 is a flowchart illustrating an example of a configuration method of an inspection apparatus using a calibration inspection object according to an embodiment of the present invention.

In the present embodiment, as an example of an object to be calibrated, a case where the present invention is applied to a calibration wafer used for a calibration operation such as a sensitivity adjustment of an inspection apparatus used in a semiconductor device manufacturing process or the like. However, it goes without saying that the present invention can be applied to a calibration inspection object of a general inspection apparatus.

First, an example of a method of manufacturing a calibration wafer according to the present embodiment will be described with reference to FIG.

First, for example, a defect 5 such as an attached foreign matter, a pattern defect, or a pattern blister is intentionally formed on one main surface of the substrate 51 as shown in FIG.
A defect pattern 52 composed of a circuit pattern in which 2a is formed is formed (FIG. 2B). At this time, the position, shape, number, material, etc. of the individual defects 52a in the defect pattern 52 are, for example, the defect patterns 52a.
Is exactly known at the level of the design data.

Thereafter, as exemplified in FIG.
In the case of the present embodiment, a transparent film layer 53 is formed so as to cover the defect pattern 52. This transparent film layer 53
Can be obtained by depositing a thin film of, for example, silicon oxide (SiO2) to a desired thickness D by a method such as CVD. As described later, the value of the thickness D of the transparent film layer 53 is set to a value larger than the depth of focus in the inspection apparatus to be calibrated.

In this manner, a defect pattern 52 having a plurality of intentionally created defects 52 a is provided on one main surface of the substrate 51, and the defect pattern 52 is further covered with the transparent film layer 53. Thus, a calibration wafer 50 having the above structure is obtained.

FIG. 3 shows an example of a method of manufacturing another calibration wafer according to the present embodiment. In the case of the calibration wafer 60 illustrated in FIG. 3, for example, a defect such as an adhered foreign substance, a pattern defect, or a pattern blister is intentionally formed on one main surface of the substrate 61 in FIG. A defect pattern 62 composed of a circuit pattern in which 62a is formed is formed (FIG. 3B). At this time, the position, shape,
The number, material, etc. are, for example, the defect pattern 6
It is exactly known at the level of two design data.

Thereafter, a frame member 63 having a desired height H is arranged and formed so as to surround the defect pattern 62.
A transparent film 64 is attached so as to cover the upper end opening of the third. This transparent film 64 is made of, for example, cellulose or the like. The height H of the frame member 63, that is, the interval (stand-off) between the transparent film 64 and the defect pattern 62 is set to a value larger than the depth of focus in the inspection apparatus to be calibrated as described later.

The flow of the manufacturing process of the calibration wafer 50 and the calibration wafer 60 illustrated in FIGS. 2 and 3 as described above is shown in the flowchart of FIG.

The calibration wafer of the present invention is not limited to a wafer in which a defect pattern is formed, and a standard particle such as latex whose particle size or the like is accurately known is used as a foreign substance on a wafer without a pattern. When it is used as a calibration wafer by collecting the information of the adhesion state (number, position, etc.) of these standard particles in advance with an accurate inspection device that guarantees the measurement accuracy. Also applicable to

That is, as exemplified in the flowchart of FIG. 5, first, a suspension in which standard particles are suspended at a desired concentration is prepared, and this suspension is applied to the surface of an unpatterned wafer. ,dry. Then, as shown in FIG.
A transparent film layer and a protective film composed of a frame material and a transparent film are formed on the surface of a non-patterned wafer on which standard particles are adhered as foreign matter by a method as exemplified in (1). As described above, the thickness of the protective film is set to be larger than the depth of focus of the optical system of the inspection apparatus to be calibrated. Thereafter, in a clean environment where there is no adhesion of environmental foreign substances and the like, information such as the number and coordinates of standard particles as foreign substances adhering to the surface of the unpatterned wafer was measured, and measurement accuracy was guaranteed. Collect with an accurate inspection device and record it so that it can be used as a reference value for later calibration.

Next, an example of a method of calibrating an inspection apparatus in which the calibration wafer 50 of the present embodiment as described above is used for calibration of inspection sensitivity will be described. First, the outline of the configuration of the inspection apparatus of the present embodiment will be described with reference to FIG. In the following description, as an example of the calibration wafer,
The calibration wafer 50 illustrated in FIG. 2 described above is used.

In FIG. 1, 1 is a light source, 2 is an inspection light, 3
Is a secondary inspection light, 4 is an environmental foreign substance, 5 is a stage, 6 is an inspection optical system, 7 is a detector, 8 is a signal processing unit, 9 is an inspection data memory, 10 is a reference data memory, 11 is a difference circuit, 1
2 is a threshold value comparison circuit, and 13 is an output unit.

The secondary inspection light 3 includes, for example, light including reflected light, scattered light, diffracted light, polarized light, and the like generated from the scanned portion by reflecting the surface state of the scanned portion of the inspection light 2 on the inspection object. It is.

The stage 5 on which the process wafer to be inspected and the calibration wafer 50 which flow in the normal process are placed
The two-dimensional parallel movement in the horizontal plane, the vertical movement in the optical axis direction of the inspection optical system 6, and the rotational movement are possible, and the scanning of the inspection object relative to the optical axis of the inspection optical system 6 can be performed. A focus adjustment operation (AF) or the like by shifting the inspection object in the optical axis direction of the inspection optical system 6 can be performed.

Hereinafter, an example of the operation of the calibration method of the inspection apparatus using the calibration wafer 50 of the present embodiment will be described with reference to the flowcharts of FIGS.

First, in the inspection of a normal process wafer (steps 101 and 102), when it is determined that calibration of the inspection apparatus is necessary, a calibration wafer 50 is set on the stage 5 instead of the process wafer (step 101). 10
3).

Then, the inspection light 2 such as white light is emitted from the light source 1 to the calibration wafer 50. At this time, the height of the stage 5 is controlled and the calibration wafer 50 of the inspection optical system 6 is controlled so that the object to be measured is a defect 52a such as a pseudo foreign substance in the transparent film layer 53 of the calibration wafer 50. Is adjusted (step 104). That is, a defect 52a such as a pseudo foreign matter in the transparent film layer 53 is detected,
Inspection conditions for the height of the stage 5 (depth of focus Fd) are set such that environmental foreign substances 4 adhering to the transparent film layer 53 are not detected. Therefore, in the case of the calibration wafer 50 of the present embodiment, by appropriately setting the thickness D of the transparent film layer 53, the environmental foreign matter 4 adhering on the transparent film layer 53 has no effect on the inspection result. No longer.

For example, in the existing foreign substance inspection apparatus, as an example, the depth of focus Fd is 500 μm, and the distance G between the lower end of the objective lens of the inspection optical system 6 and the surface of the inspection object is about 10 mm. The thickness D of 53 may be set to at least 500 μm.

In the current visual inspection apparatus, for example, the depth of focus Fd is 30 μm to 1 mm, and the distance G between the lower end of the objective lens 6 a of the inspection optical system 6 and the surface of the inspection object is about 100 μm to 200 μm. Therefore, the transparent film layer 5
The thickness D of 3 may be set to less than about 100 μm.

The secondary inspection light 3 generated from the scanning portion of the inspection light 2 on the calibration wafer 50 is captured by the inspection optical system 6 and converged by the detector 7 to be converted into an electric signal. Divided into sizes. Each pixel is converted into a 256-level gray level signal and stored in the inspection data memory 9. The stored signal is compared with the image signal of each chip or the adjacent cell previously stored in the reference data memory 10 by the difference circuit 11 and compared with a predetermined density threshold by the threshold comparison circuit 12. Then, the scanning portion whose difference is equal to or more than a predetermined value is determined as a defect. The result is output to the output unit 13. This process is performed on the entire surface of the calibration wafer 50 by moving the stage 5 horizontally or rotationally and scanning the inspection light 2 relative to the calibration wafer 50 (step 105).

At the end of the inspection, the information output to the output unit 13 such as the number and coordinates of the defect 52a is
If the inspection apparatus has a normal inspection sensitivity, it needs to exactly match a known reference value with a predetermined accuracy at the time of producing the calibration wafer 50 (step 106).

That is, if the measurement result of the defect 52a detected this time is equal to or smaller than the reference value, it is considered that the light source 1 is deteriorated, that is, the light amount of the inspection light 2 is reduced. (Steps 107 and 108).

If the measurement result of the defect 52a detected this time is equal to or larger than the reference value, it is considered that the abnormality is caused by, for example, the signal processing unit 8, the difference circuit 11, and the like. Adjust the system (step 109,
Step 110).

If the measurement result of the defect 52a detected this time matches the reference value, it is determined that there is no abnormality (step 111), and the routine returns to the normal inspection.

As described above, in the case of the present embodiment, the transparent film layer 53 is formed on the surface of the calibration wafer 50 on which the defect pattern 52 having a plurality of intentionally created defects 52a is formed. Therefore, even if the environmental foreign matter 4 or the like adheres to the surface of the transparent film layer 53, the environmental foreign matter 4 is set by setting the transparent film layer 53 to a value outside the range of the depth of focus.
Does not affect the inspection result of the calibration wafer 50 at all, and the calibration operation such as sensitivity verification and adjustment of the inspection apparatus using the calibration wafer 50 can be performed accurately.

The defect pattern 5 having a plurality of defects 52a intentionally created in the calibration wafer 50
Since 2 is covered with the transparent film layer 53 and protected from the external environment, the occurrence of deterioration over time of the defect pattern 52 having the defect 52a can be prevented, and the occurrence of erroneous inspection or the like due to the deterioration can be avoided. .

Further, it is not necessary to take special measures such as preventing the environmental foreign matter 4 from adhering to the storage of the calibration wafer 50, and the storage and handling of the calibration wafer 50 can be simplified.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say, there is.

For example, the object to be calibrated is not limited to the wafer for calibration, but can be applied to any object to be calibrated to be calibrated by any inspection apparatus.

In the above description, the invention made mainly by the inventor has been applied to the calibration of the inspection apparatus in the manufacturing process of the semiconductor device, which is the background of the application. However, the invention is not limited to this. It can be widely applied to calibration of

[0051]

Advantageous effects obtained by typical ones of the inventions disclosed in the present application will be briefly described.
It is as follows.

According to the object to be calibrated and the method of manufacturing the same according to the present invention, an effect is obtained that accurate calibration can be performed over a long period of time without being affected by environmental foreign substances.

Further, according to the inspection object for calibration and the method for manufacturing the same of the present invention, an effect is obtained that accurate calibration can be performed for a long period of time without causing deterioration or the like.

Further, according to the inspection object for calibration and the method of manufacturing the same of the present invention, accurate calibration can be performed for a long period of time without requiring special storage management and the like.
The effect is obtained.

According to the method for calibrating an inspection apparatus and the inspection apparatus of the present invention, there is an effect that accurate calibration can be performed without being affected by environmental foreign substances.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an example of a configuration of an inspection apparatus using a calibration inspection object according to an embodiment of the present invention.

FIGS. 2A to 2C are schematic cross-sectional views illustrating an example of a method for manufacturing a calibration inspection object according to an embodiment of the present invention in the order of steps.

FIGS. 3A to 3C are schematic cross-sectional views illustrating an example of a method of manufacturing a calibration inspection object according to an embodiment of the present invention in the order of steps.

FIG. 4 is a flowchart illustrating an example of a method for manufacturing a calibration inspection object according to an embodiment of the present invention.

FIG. 5 is a flowchart illustrating an example of a method of manufacturing a calibration inspection object according to an embodiment of the present invention.

FIG. 6 is a flowchart illustrating an example of a configuration method of an inspection apparatus using a calibration inspection object according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source 2 inspection light 3 secondary inspection light 4 environmental foreign matter 5 stage 6 inspection optical system 7 detector 8 signal processing unit 9 inspection data memory 10 reference data memory 11 difference circuit 12 threshold comparison circuit 13 output unit 50 calibration wafer 51 substrate 52 Defect Pattern 52a Defect 53 Transparent Film Layer 60 Calibration Wafer 61 Substrate 62 Defect Pattern 62a Defect 63 Frame Material 64 Transparent Film

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masami Ikoda 2326 Imai, Ome-shi, Tokyo Inside the Device Development Center, Hitachi, Ltd. Engineering Co., Ltd.

Claims (10)

[Claims] An object to be calibrated in which at least one of a number, a position, a size, a shape, and a material having a known defect is formed on one principal surface of a substrate, and a protective film that covers the defect is provided. An inspection object for calibration, characterized in that: 2. The inspection object for calibration according to claim 1, wherein the protective film is formed so as to cover the defect existing on the one main surface of the substrate, and an inspection used by an inspection apparatus to be calibrated. An object to be calibrated, wherein the object is a transparent film layer that is transparent to light, and the thickness of the transparent film layer is greater than a depth of focus in an optical system of the inspection device. 3. The inspection object for calibration according to claim 1, wherein the protective film is attached to the frame member protruding around a region where the defect is formed on the substrate, and is attached to the frame member, and the calibration film is calibrated. It is a transparent thin film transparent to the inspection light used by the target inspection device, and the distance from the one main surface to the transparent thin film is larger than the depth of focus in the optical system of the inspection device. Inspection object for calibration. 4. The inspection object for calibration according to claim 1, wherein the defect is a foreign substance intentionally attached to one main surface of the substrate and a defect intentionally attached to one main surface of the substrate. An inspection object for calibration, comprising at least one of the formed defect patterns. 5. The inspection object for calibration according to claim 1, wherein the inspection object for calibration is an inspection apparatus for inspecting a semiconductor wafer for a foreign substance or a defect in a semiconductor device manufacturing process. An inspection object for calibration, which is a calibration wafer used for calibration. 6. A first step of forming, on one main surface of a substrate, a defect whose number, position, size, shape, and material are known, and a second step of forming a protective film covering the defect. And a method of manufacturing a calibration inspection object. 7. The method according to claim 6, wherein, in the first step, an operation of intentionally attaching a foreign substance as the defect to the one main surface, or the one main surface. And performing an operation of intentionally transferring and forming a defect pattern by photolithography as the defect. 8. The method according to claim 6, wherein, in the second step, the protective film covers the defect existing on the one main surface of the substrate. An operation of forming a transparent film layer transparent to the inspection light used by the inspection device to be calibrated, or, as the protective film, projecting a frame material so as to surround the formation region of the defect on the substrate, A method of manufacturing a calibration object to be inspected, comprising: performing an operation of attaching a transparent thin film to a frame material with respect to inspection light used by an inspection device to be calibrated. 9. A method for calibrating an inspection apparatus for inspecting an inspection object by capturing inspection light passing through the inspection object by an inspection optical system, comprising: At least one of the size, shape, and material is a known defect, and a calibration inspection object including a protective film that covers the defect is used.The depth of focus of the inspection optical system is controlled to be smaller than the thickness of the protective film. A calibration method for an inspection apparatus, wherein the inspection apparatus is calibrated by inspecting the calibration object. 10. An inspection apparatus for inspecting an inspection object by capturing inspection light passing through the inspection object by an inspection optical system, wherein the number, position, size, and shape of one main surface of a substrate are provided. And a material to be calibrated comprising at least one of a known defect and a protective film covering the defect, wherein the calibration optical device controls the depth of focus of the inspection optical system to be smaller than the thickness of the protective film. An inspection apparatus, wherein the inspection apparatus is calibrated by inspecting an object to be inspected.