JPH0776753B2 - Foreign matter inspection device - Google Patents

Description

The present invention relates to an apparatus for detecting foreign matter such as minute dust, and particularly to a foreign matter inspection apparatus suitable for detecting foreign matter attached to a reticle having a fine pattern formed thereon. Regarding

[Conventional technology]

Conventionally, there is known a method for detecting foreign matter on a patterned substrate as described in JP-A-59-82727. However, in this method, since the detected foreign matter also becomes finer as the pattern becomes finer, the ability to discriminate between the foreign matter and the pattern decreases, and no consideration has been given to erroneous pattern detection.

[Problems to be solved by the invention]

In the above-mentioned prior art, in order to discriminate a pattern from a foreign substance and obtain a signal of only the foreign substance, a subject is irradiated with a polarized laser, and scattered light scattered from the subject is vertically polarized from the foreign substance through a polarizing filter (hereinafter referred to as S-polarized light). Although only the component is detected, as the pattern becomes finer, the detected foreign matter also becomes smaller, and the signal component of the pattern, which is a noise component, increases, and conversely, because the foreign matter becomes smaller and the signal level decreases, S There is a problem that the / N ratio decreases more and more.

An object of the present invention is to provide a foreign matter inspection apparatus that can reliably detect a foreign matter without being affected by the pattern even if the pattern is miniaturized.

[Means and Actions for Solving Problems]

The above-mentioned object can be solved by utilizing the polarization characteristics of a polarized laser scattered from a foreign substance and a pattern in multiple ways.

Thus, the present invention is a foreign matter inspection apparatus for detecting a foreign matter adhered on a patterned substrate using a polarized laser,
The scattered light emitted from the subject by irradiation of the polarized laser is 0 °.
, And a signal detected through a polarization filter having a polarization angle of 90 ° respectively and detected through a polarization filter having a polarization angle of 0 ° is larger than a signal detected through a polarization filter having a polarization angle of 90 °. Provided is a foreign matter inspection device, which is provided with means for determining to a foreign matter, and only in that case, transmitting a signal detected through a polarization filter having a polarization angle of 0 ° to an arithmetic processing unit.

The present invention irradiates a subject with a polarized laser, changes the polarization angle of the polarization filter to 0 ° and 90 °, and compares the signal level of the pattern with that of the foreign matter.
Then, since the foreign matter is smaller than the pattern, the ability to discriminate the foreign matter from the pattern can be dramatically improved by comparing the signal with the polarization angle of 0 ° and the signal with the polarization angle of 90 °.

In short, due to the polarization characteristics of the foreign matter and the pattern (see FIG. 3 described later), the signal level is 0 °> 90 ° for the foreign matter, and 0 ° <90 ° for the pattern, and the magnitude relationship between the signal levels is opposite. Therefore, the former case can be distinguished from the foreign matter.
Therefore, only when it is determined that the foreign matter is present, the signal detected through the polarization filter having the polarization angle of 0 ° can be transmitted to the arithmetic processing unit, and the foreign matter size can be calculated. In this calculation result, only the information from the foreign matter is output and the information from the pattern is lost.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the points of the detection system, in which a pellicle 2 composed of a plastic film of 0.8 μm thickness and a metal frame is attached to an object, for example, the reticle 1 in order to prevent foreign matter from adhering to the pattern formation. Has been. In order to inspect the foreign matter on the reticle 1, first, a polarized laser is irradiated as in A to scan the reticle 1 in the direction indicated by Y, and the scattered light generated on the Y line is detected without being affected by the frame of the pellicle 2. Therefore, the left and right on the Y line are divided into two, and the scattered light 1a and the scattered light 2a are detected by the detector 3 and the detector 4, respectively.

On the other hand, the reticle 1 completes the inspection of the half surface on the reticle 1 on the front side in the X direction by the movement of the stage (not shown). Next, the laser is irradiated from the opposite direction like B to inspect the front half surface.

FIG. 2 is a diagram showing the principle of the detection system. When the S-polarized laser L ₀ is irradiated from the direction of the arrow, the scattered light L _{1 in} which S-polarized light and vertical-polarized light (hereinafter abbreviated as P-polarized light) are mixed from the foreign matter 7. The P-polarized scattered light L ₂ is mainly generated from the pattern 8. In order to detect the scattered light of both, the light is received by the detector 4 through the polarization filter 9. The polarization characteristic at this time will be described with reference to FIG. At this time, the polarization filter 9 is configured such that scattered light emitted from the subject upon irradiation with the S-polarized laser has polarization angles of 0 ° and 90 °, as in the embodiment described below.

That is, when the polarization angle of the polarization filter 9 is changed, the intensity of scattered light emitted from the foreign matter 7 and the pattern 8 greatly changes between the foreign matter 7 and the pattern 8, as shown in FIG.
It can be seen that the magnitude relationship of the signal levels is opposite between the foreign matter 7 and the pattern 8. Therefore, a detection system is constructed as shown in the embodiment of FIG.

The scattered lights L ₁ and L ₂ respectively emitted from the foreign matter 7 and the pattern 8 are guided to the two polarization filters 9a and 9b, and are respectively detected by the detectors 4a and 9b.
Receive light at 4b.

Here, the polarization angle of the polarization filter 9a is set to 0 °, and the polarization angle of the polarization filter 9b is set to 90 °. By doing so, the light transmitted through the polarization filters 9a and 9b is based on the scattered light characteristics of the polarization angles of 0 ° and 90 ° shown in FIG. Therefore, the comparator 10 compares the signals of the detectors 4a and 4b, and when the intensity is 4a> 4b, it is the scattered light L ₁ from the foreign matter 7, and when 4a <4b, the scattered light from the pattern 8 is obtained.
Since it can be recognized as L ₂ , only when 4a> 4b, only the signal from the detector 4a is transmitted to the arithmetic processing unit 11 to calculate the foreign matter size. In this way, the calculation processing unit 11 has the pattern 8
Since the signal from No. 1 is not transmitted, as the calculation result, only the information from the foreign matter 7 is output and the information from the pattern 8 is lost.

FIG. 5 is a view showing another embodiment according to the present invention,
The scattered light emitted from the subject is configured to be guided to one polarization filter 9. This filter 9 has a polarization angle of 0 °.
It is connected to the filter rotation drive unit 12 that can be changed to 90 ° and
12 generates a drive signal, whereby the polarization angle of the filter 9 is changed to 0 ° and 90 °, and the scattered light emitted from the subject is received by the detector 4. Further, the arithmetic processing unit 11 stores the received light signals corresponding to the polarization angles of 0 ° and 90 ° in synchronization with the drive signal of the filter 9, respectively, and performs the comparison and the arithmetic operation in the same manner as in the above-mentioned embodiment, thereby performing the above-mentioned operation The same effect as the embodiment can be obtained.

〔The invention's effect〕

According to the present invention, scattered light emitted from a subject by irradiation of a polarized laser is detected through a polarization filter having a polarization angle of 0 ° and 90 °, respectively, and a signal detected through a polarization filter having a polarization angle of 0 ° is detected. Is larger than the signal detected through a polarization filter having a polarization angle of 90 °, it is judged as a foreign matter, and only in that case, 0
Since a means for transmitting the signal detected through the polarization filter having a polarization angle of ° to the arithmetic processing unit is provided, the foreign matter and the pattern can be reliably discriminated from each other by the polarization characteristics of the foreign matter and the pattern. If the pattern becomes finer, the phenomenon that would have been a false alarm will be completely eliminated, so if a pattern that will be further miniaturized in the future is formed on the object, for example, the reticle, a great effect can be expected in detecting foreign matter adhering to the reticle. .

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of the detection system of the present invention, and FIG.
FIG. 3 shows the principle of detection, FIG. 3 shows polarization characteristics, and FIG.
FIG. 5 is a diagram showing a first configuration example of the detection system, and FIG. 5 is a diagram showing a second configuration example of the detection system. 1 …… Reticle (subject), 2 …… Pellicle, 3,4
…… Detector, 7 …… Foreign matter, 8 …… Pattern, 9a …… 0 °
Polarization filter with polarization angle of 9b ... Polarization filter with polarization angle of 90 °, 10 ... Comparator, 11
...... Arithmetic processing unit, 12 …… Filter rotation drive unit, L ₀ ……
S-polarized laser.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Juichiro Ukon 2 Higashi-cho, Kichijoin-miya, Minami-ku, Kyoto-shi, Kyoto Inside Horiba Seisakusho Co., Ltd. (72) Yutaka Saijo 2 Higashi-cho, Kichijoin-miya, Minami-ku, Kyoto HORIBA, Ltd. (56) Reference JP-A-61-230048 (JP, A)

Claims (3)

[Claims] 1. A foreign matter inspection apparatus for detecting a foreign matter adhered on a patterned substrate using a polarized laser, wherein scattered light emitted from a subject upon irradiation of the polarized laser is 0 ° and 90 °.
If the signal detected through a polarization filter having a polarization angle of 0 ° is larger than the signal detected through a polarization filter having a polarization angle of 0 °, the signal is detected as a foreign substance. A foreign matter inspection apparatus provided with means for making a judgment and only in that case, transmitting a signal detected through a polarization filter having a polarization angle of 0 ° to an arithmetic processing unit. 2. The polarization laser is an S polarization laser, and the scattered light emitted from the subject is guided to a polarization filter having a polarization angle of 0 ° and a polarization filter having a polarization angle of 90 ° and received by a detector respectively. The foreign matter inspection apparatus according to claim 1, wherein the comparator is configured to compare the signals of the respective detectors. 3. The polarization laser is an S polarization laser, is configured to guide scattered light emitted from the subject to one polarization filter, and the polarization filter can be changed to polarization angles of 0 ° and 90 °, respectively. The foreign matter inspection apparatus according to claim 1, further comprising a mechanism.