JPS58196021A - Inspection of reticle for defect - Google Patents

Abstract

PURPOSE:To judge a reticle as having no problem in function as a mask to be satisfactory, even if an foreign matter exists therein by the concurrent use of the detection of diffused light rays of laser beams irradiated on both surfaces of a reticle and that of transmitting light rays of laser beam irradiated on the reticle vertically. CONSTITUTION:As laser beams are irradiated from laser beam irradiating devices 3, 3' on both surface of a reticle 1 composed of an underside B on which chrome patterns 2, 2' are formed and a front surface A, a detector 4 doesn't receive light rays when no foreign matter 5 exists, but the detector 4 receives diffused light rays caused by a foreign matter 5 which exists on the surface. Here, if the foreign matter 5 is such a light transmitting substance that causes no problem in function as a mask, a laser beam from a laser beam irradiating device 6 irradiated on a surface 1 vertically transmits through the surface 1 and enters a detector 7. From this fact, it is known that such a foreign matter that causes no problem in function is no longer required to be subjected for retreatment such as washing, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reticle defect inspection method, and more particularly to a reticle defect inspection method for detecting dust, foreign matter, etc. attached to a reticle and inspecting the reticle for defects.

From hand-drawn drawings to artwork, the actual pattern shape is approximately 1
It is customary to inspect a reticle with a size multiplied by 0 in this state for defects due to dust or foreign matter attached to the surface.

The defect inspection is carried out by various methods, but the method shown in FIG. 1 is generally used.

FIG. 1 is a diagram explaining the principle of a conventional reticle optical defect inspection method. In the figure, l is the reticle, 2 and 2'
is a chrome pattern formed on the surface of the reticle, 3 and 3' are laser beam projection devices provided on the A side and B side, respectively, and 4 and 4' are detectors that receive the lights of 3 and 3', respectively. . Further, 5 and 5I are foreign substances attached to the A side and the B side. Foreign objects 5 and 5
’ was detected as follows. That is, on the A plane, when the light X emitted from the laser beam projection device 3 hits the smooth surface of the reticle, it is reflected in the Y direction at the same reflection angle as the incident angle. Since the detector is not on the reflected beam, it does not receive any light. However, if a foreign object 5 exists on the entrance surface, the incident light X is diffusely reflected on the irregular surface of the foreign object, and the light is dispersed in various directions. When dispersed, the light in the Z direction hits the detector 4 and is received, a signal is obtained and the foreign object can be confirmed. Furthermore, if there is a foreign object on the B plane, the light X' emitted from the laser beam projection device will be diffusely reflected by the foreign object, and the light that is diffusely reflected in the Z' direction without being concentrated in the normal direction Y' will be received by the detector 4' and a signal will be obtained. foreign matter on side B can be confirmed. In other words, conventional methods for detecting dust and foreign matter attached to a reticle scan the front and back surfaces with light, diffuse the reflected light from the foreign matter, and detect the presence of foreign matter by receiving the diffusely reflected light with a detector.A reticle with foreign matter or foreign matter is determined to be defective. It is determined that the product is a product, and a cleaning process is added to remove foreign substances.

However, even if there is dust or foreign matter on the reticle, as long as it is transparent to non-light light, there is no need for it to be functionally problematic; therefore, it is necessary to perform reprocessing such as cleaning, which takes a lot of man-hours. There isn't. However, if the presence of dust or foreign matter is confirmed by the above-mentioned inspection method, it is treated as a defective product, and a troublesome work to remove the dust or foreign matter is carried out. This required a large amount of man-hours and caused problems in production management.

Therefore, the present invention has been made to address the above problems, and is a reticle defect inspection method that allows a reticle that transmits non-light light and functions as a mask to be treated as a non-defective item. is to provide.

That is, the gist of the present invention is to irradiate each side of a reticle with a laser beam and detect the scattered light of the laser beam, and to irradiate the reticle with another laser beam directly and detect the transmitted light from the reticle. The reticle defect inspection method includes the step of IVf6.

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

FIG. 2 is a diagram explaining the principle of the reticle defect inspection method according to the present invention. As in the case of Fig. 1, in Fig. 2 as well, chrome patterns 2 and 2' are formed on the back surface (B surface) of the reticle 1, and chrome patterns 2 and 2' are formed on the upper and lower sides of the front surface (A surface) and the back surface of the reticle. is a laser beam projection device 3.3
' is installed, and each surface is scanned by a laser beam emitted from this. As shown in the figure, if there is a foreign object 5 on the A side, the light X emitted from the laser beam projection device would normally be reflected in the Y direction, and the light would not enter the detector 4, which is not on this optical path, but it would be on the foreign object 5. Laser beam▲The light is diffusely reflected by the foreign object L, and a part of the scattering hole is reflected by the detector 4 on the A side.
incident on . In other words, a signal indicating the presence of foreign matter on the A side can be detected. In addition, since there is no foreign matter on the bottom surface (surface B) in this case, the light X' emitted from the laser beam projection device is completely reflected in the normal direction Y' by the smooth surface, and some portion of the light is not received by the detector 4', and the back surface It can be confirmed that no foreign matter is present.

Further, in FIG. 2 of an embodiment of the present invention, a JIE3 laser beam projection device 6 is prepared above the A surface, and the light from this device is prepared so as to strike perpendicularly to the reticle surface.
The light is arranged so as to pass through the reticle and strike the detector 7 provided directly below it. If there is no foreign object or dirt on the plane of the path of the laser beam projection device on the surface of the reticle, the light will be completely received by the detector.

However, when an opaque foreign object is present, it blocks the input and there is no input to the detector 7. However, when the foreign object is semitransparent or smaller than the beam diameter, the light is attenuated and reaches 7. Further, when the foreign object 5 is a light-transmitting object, almost all of the light passes through the foreign object and reaches the detector 7. Therefore, since this foreign material does not have any adverse effect on the i-splash action, there is no need to carry out a time-consuming process for removing the foreign material.

Furthermore, since light received before a foreign object is present will be more or less attenuated, the signal level for determining a defective product can be determined, and if the attenuation exceeds the limit, it can be reprocessed as a defect.

In other words, in the present invention, the presence of foreign matter on the surface of the reticle is confirmed by the conventional method, and the functional surface can be checked by transmitting light from the vertical direction. It is possible to obtain improved testing methods that are only occasionally performed.

FIG. 3 is a signal processing circuit diagram of a detection region in the method of the present invention. In the figure, 11 and 12 are input terminals for foreign matter presence signals on the A side and B side, and 13 is a signal input terminal for image transmission light. Also, 14.15 is NOT circuit, 16 is AN
D circuit, 1 7Fi. An OR circuit, 18 an AND circuit, and 19 an output terminal. In other words, when light is received “
Assuming 1f, if there is dust or foreign matter at the terminals 11° and 12, scattered light enters the detector and a signal of "1m" is sent, and when there is no dust or foreign matter, a signal of 0# is sent.

On the other hand, if there is dust or foreign matter at the terminal 13, the light will be blocked and no transmitted light will be present, so the detector will not receive any light. Therefore, the signal becomes "0", and when there is no gore or foreign object, the detector receives light, so a signal of "1" is sent.

If these signals are processed by the signal processing circuit shown in FIG. 3, dust and foreign matter can be removed by collecting the tickets when the "B" signal is output to the terminal 19.

The relationship between the adhesion conditions of dust and foreign matter and the output of the signal processing circuit will be explained below. FIGS. 4(a) to 4(e) are diagrams showing input/output codes of signals at each stage of the signal processing circuit. Figure 4(a) is an 18 AND circuit, Figure 4(b) is a 15O
The NOT circuit, Figure 4 (C) is the 17 OR circuit, Figure 4 (
d) shows 14 NOT circuits, and Figure 4(e) shows 16 AND circuits.
The status of the circuit is shown.

From figure (1) of wJ4, the condition for the output of the AND circuit 18 to be 1# is that all the signals input to it must be ``1#'', so both the outputs of 15 and 17 must be ``1#''. This is the case. The first condition for the output of 15 to be “1#” is the 4th
As shown in Figure (b), the output of 13 is "0", that is, the vertically input light is blocked by dust or foreign matter, and no light is transmitted, or only light below the limit is transmitted.

Since the output of 17 is "1", the second condition is that one or both of the outputs of 11 and 16 are "1" from FIG. 4(C).
”.In other words, both outputs are 0.”
If so, it will be excluded.

Here, consider a case where both outputs fall to 0#.

First, when the output of 11 becomes "0", the output of 14 becomes "1" from FIG. 4(d). Then the output of 16 is 10”
This is the case where either or both of the outputs 14 and 12 are "0" from FIG. 4(e), but 1
Since the output of No. 4 is "1", the output of No. 16 becomes "θ' only when the output of No. 12 is "0#". That is, the outputs of 11 and 16 both become "0#" when the outputs of both 11 and 12 become "0".

Here, the second condition for the output of 18 to be "1" is when both the output of 11 and the output of 16 are "O", so either one of 11 and 12 is "1" or both are "1". is "1". That is, when there is dust or a foreign object on at least one of the A side or the B side, the projected light is diffusely reflected by the foreign object, is detected by the detector, and a 1'' signal is sent to the terminal 11 or 12 or both.

Based on the above, the present invention determines it as a defect only when dust or foreign matter is present on either side of the reticle and the dust or foreign matter is non-transparent or only transmits less than a limit of light. Therefore, a reticle that transmits % non-lighting light and has no problems in functioning as a mask can be treated as a good product.

That is, if the signal detected by the detector is processed by the signal processing circuit shown in FIG. 3, the results of the present invention can be quickly and easily determined, and the process can be further streamlined.

In the explanation of the above embodiment, laser beam projection devices were installed on both sides of the reticle, but it is also possible to use a reflector.
It is easy to project light onto both sides with a stand.

Also, if you display the detection results by level, it's garbage.

Not only can the determination of foreign matter become more accurate, but also the removal work can be streamlined.

As explained above, according to the present invention, even if there is dirt or foreign matter on the reticle surface, a reticle that transmits the 11-day light and has no functional problems as a mask will not be treated as a defective product. This eliminates the need for unnecessary reticle replacement and cleaning, resulting in a significant reduction in man-hours.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of a conventional reticle optical defect inspection method, Fig. 2 is an explanatory diagram of the principle of a reticle optical defect inspection method according to an embodiment of the present invention, and Fig. 3 is a diagram illustrating the principle of a reticle optical defect inspection method according to an embodiment of the present invention. The signal processing circuit diagrams of FIGS. 4(a) to 4(e) are diagrams showing the input/output codes of signals at each stage of the signal processing circuit. 1...Reticle, 2.2'...Chrome pattern, 3s3's6...Laser beam projection device, 4,4'. 7...Detector, 5.5'...Dust or foreign matter, 11°12.13...Input terminal, 1
4.15...NOT circuit, 16,18...
...AND circuit, 17...OR circuit, 19...
...Output terminal, x, x'...Laser beam projection light, Y, Y'...Reflected light, A side...
・Side without chrome pattern, B111! 】・・・・・・
Surface with chrome pattern. No. 5 (a) Figure 3 4th section

Claims (1)

[Claims] The method is characterized by including a step of irradiating each side of the reticle with a laser beam and detecting the scattered light of the wrinkled laser beam, and a step of irradiating another laser beam perpendicularly to the reticle and detecting the transmitted light from the reticle. A reticle defect inspection method.