JPS63132143A - Foreign matter inspection instrument - Google Patents

Abstract

PURPOSE:To securely detect foreign matter even when a pattern becomes fine by irradiating a sample with polarized laser and detecting and comparing scattered light beams from the sample through two polarizing filters different in angle of polarization. CONSTITUTION:When S-polarized laser light L0 is projected as shown by an arrow, the foreign matter 7 generates scattered light L1 consisting of S-polarized light and vertical polarized light and the pattern 8 generates scattered light L2 consisting principally of P-polarized light. Those scattered light beams L1 and L2 are guided to the two polarizing filters 9a and 9b and photodetected by detectors 4a and 4b, respectively. Here, the filter 9a is set to for example, a 0 deg. angle of polarization and the filter 9b is set to, for example, 90 deg.. Then, a comparator 10 compares the signals of the detectors 4a and 4b with each other to recognize the scattered light L1 from the foreign matter when 4a>4b in terms of intensity and the scattered light L2 from the pattern 8 when 4a<4b. Therefore, only when 4a>4b, the signal of the detector 4a is sent to an arithmetic processing part 11 to compute the size of the foreign matter. Consequently, the arithmetic result is only output information from the foreign matter 7.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for detecting foreign matter such as minute dust, and in particular, a foreign matter inspection device suitable for detecting foreign matter attached to a reticle formed with a fine pattern. Regarding.

[Conventional technology]

As a conventional device, a method for detecting foreign matter on a patterned substrate is known, as described in Japanese Patent Laid-Open No. 59-82727. However, in this method, as the pattern becomes finer, the detected foreign matter also becomes finer, so that the ability to discriminate between the foreign matter and the pattern deteriorates, and no consideration is given to the possibility of erroneously detecting the pattern.

[Problem that the invention seeks to solve]

In the above conventional technology, in order to distinguish between foreign objects and patterns and obtain a signal of only the foreign objects, the object is irradiated with a polarized laser, and the scattered light from the object is passed through a polarizing filter to form vertically polarized light (hereinafter abbreviated as S-polarized light) from the foreign object. We are trying to detect only the component, but as the pattern becomes finer, the detected foreign matter also becomes finer, and the number of pattern signals that are noise components increases.Conversely, the signal level of foreign matter decreases as the size of the foreign matter becomes finer, so the S A problem arises in which the /N ratio decreases more and more.

An object of the present invention is to provide a foreign matter inspection device that reliably detects foreign matter without being affected by the pattern even if the pattern becomes finer.

[Means for solving problems]

The above object can be achieved by making multifaceted use of the polarization characteristics of the polarized laser that is scattered from the foreign object and the pattern.

In other words, when the S-polarized laser is irradiated onto the subject and the polarization angle of the polarizing filter is changed to 0° and 90° and the signal level of the pattern and the foreign object are compared, Oo is the foreign object> pattern, 9
At 0°, the foreign object changes to the pattern, so by comparing the signals at these two angles, the ability to discriminate between the foreign object and the pattern can be dramatically improved.

〔motion〕

Either Oo and 90' polarizing filters with different angles and a pair of detection elements are arranged in the detection system to detect the scattered light, or one polarizing filter can be used to polarize the same scattered light. Detect at angles of 0° and 90°.

If this is done, as described above, since the signal levels of the foreign object and the pattern are extremely different between 0'' and 90'', the pattern can be discriminated by comparing the signal intensities of the two.

In other words, the foreign object is 90° and the pattern is 0''
Since the angle is 90°, the latter can be recognized as a pattern and can be discriminated.

〔Example〕

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

Figure 1 is a diagram showing the points of the detection system.In order to prevent foreign matter from adhering to the pattern formed on the object to be inspected, for example, the reticle 1, there is a pellicle 2 made of a plastic film with a thickness of 0.8 μm or the like and a metal frame. is pasted. In order to inspect this reticle 1 for foreign matter, first irradiate a polarized laser as shown in A, scan the reticle 1 in the direction shown by Y, and scatter light generated on the Y line without being affected by the frame of the pellicle 2. In order to detect this, the left and right sides on the Y line are divided into two parts, and the scattered light 1a is detected by the detector 3 and the scattered light 2a is detected by the detector 4, respectively.

On the other hand, the reticle 1 is moved by the movement of the stage (not shown).
The laser beam is irradiated from the opposite direction as shown in B to inspect the front half of the reticle 1.

Figure 2 is a diagram showing the principle of the detection system. When the S-polarized laser Lo is irradiated from the direction of the arrow, the foreign object 7 generates scattered light LL, which is a mixture of S-polarized light and vertically polarized light (hereinafter abbreviated as P-polarized light). , the pattern 8 mainly generates P-polarized scattered light Lz. In order to detect the scattered light of both, a polarizing filter 9 is used.
The light is received by the detector 4 through the light. The polarization characteristics at this time are
This will be explained using figures.

As shown in the figure, when the polarization angle of the polarizing filter 9 is changed, the intensity of scattered light emitted from the foreign object 7 and the pattern 8 changes significantly. Therefore, a detection system is constructed as shown in one embodiment of FIG.

1' emitted from foreign object 7 and pattern 8! 1 Scattered light I, 1.
r and a are guided to two polarizing filters 9a and 9b, and are received by detectors 4a and 4b, respectively. Here, the polarizing filter 9a has a polarization angle of, for example, Oo, and the polarizing filter 9b
is set to, for example, 90''.

If this is done, the light transmitted through the polarizing filters 9a and 9b will be based on the scattered light characteristics of polarization angles of 0'' and 90@ as shown in FIG. Comparing the signals of 4a and 4b, the nozzle whose intensity is 4a>4b can be recognized as the scattered light L1 from the foreign object 7, and in the case of 4a (4b), it can be recognized as the scattered light L2 from the pattern 8. Therefore, only in the case of 4a) and 4b, only the signal from 4a is sent to the arithmetic processing section 11 to calculate the foreign object size.In this way, the signal from pattern 8 is not sent to the arithmetic processing section 11. Therefore, as a calculation result, only the information from the foreign object 7 is output, and the information from the pattern 8 is not output.

FIG. 5 is a diagram showing another embodiment according to the present invention,
A polarizing filter 9 constitutes one unit, and this filter 9 is connected to a filter rotation drive unit 12 that can change the polarization angle, and generates a drive signal in response to a synchronization signal from an arithmetic processing unit 11. The polarization angle of 0@ and 90
”The scattered light Lx is changed to two predetermined angles such as “.

A detector 4 receives Lz. Furthermore, the arithmetic processing unit 11
, are 0° and 90° in synchronization with the drive signal of filter 9.
It is possible to obtain the same effect as in the above embodiment by storing the received light signals corresponding to the polarization angles respectively in memory, and performing calculations with the comparator 10 and the corresponding subsequent ones in the same manner as in the above embodiment.

〔Effect of the invention〕

According to the present invention, patterns can be reliably distinguished by the polarization characteristics of patterns and foreign objects, and the phenomenon that conventionally caused false alarms when patterns become finer can be completely eliminated. It is expected that a great effect will be achieved by equipping the foreign object inspection device on the reticle.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an outline of the detection system of the present invention, and FIG.
Figure 3 is a diagram showing the detection principle, and Figure 4 is a diagram showing polarization characteristics.
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. DESCRIPTION OF SYMBOLS 1... Reticle, 2... Pellicle, 3... Detector, 4... Detector, 7... Foreign object, 8... Pattern, 9... Polarizing filter, 10... Comparator ,
11...Arithmetic processing unit/
'7-h Agent Patent Attorney Katsuo Ogawa
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Claims (1)

[Claims] 1. In an apparatus for detecting foreign matter attached to a patterned substrate using a polarized laser, scattered light emitted from a subject is
1. A foreign object inspection device characterized by detecting the two signals through polarizing filters having different polarization angles, and discriminating between foreign objects and patterns based on the intensity determination results of the two signals. 2. The foreign matter inspection device according to claim 1, wherein the polarizing filter is composed of two filters having different polarization angles. 3. The foreign matter inspection device according to claim 1, comprising a detection system having one polarizing filter and a mechanism for changing the polarization angle of the filter.