JPH04199652A - Foreign object check device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for inspecting foreign matter on the surface of a photomask equipped with a pellicle, which is used in the manufacture of semiconductor devices.

[Prior Art] In the photo process of manufacturing semiconductor devices, it is common to use a reduction projection exposure apparatus as a method of forming a desired resist pattern on a semiconductor substrate, but in recent years, with the progress of miniaturization of elements, As the degree of integration increases, transfer of foreign matter onto the photomask has become a problem. A reduction projection exposure apparatus projects a pattern on a photomask after reducing it to one-fifth. However, in recent years, improvements in the resolution of projection lenses and resists have made it possible to sufficiently transfer even micron-sized foreign particles onto a photomask. The transferred foreign matter then becomes a pattern defect, deteriorating the function of the semiconductor element and lowering the yield.

Therefore, recently, pellicles have been used as a method to prevent transfer of foreign substances. As shown in FIG.
is made of a transparent thin film typified by nitrocellulose.
It is fixed at a certain distance from the photomask 21 via a pellicle frame 22 made of metal such as an aluminum alloy, so as to cover and protect the pattern portion on the photomask 21 . Foreign matter in the air adheres to the pellicle 23, but since the focus position during projection exposure is on the surface of the photomask 21, the foreign matter on the pellicle 23 will be out of focus and will have a size of about 50 μm or less. The system is designed to prevent foreign matter from being transferred. As described above, pattern defects caused by foreign matter transfer are significantly reduced by using a pellicle, but foreign matter on the photomask surface after the pellicle is attached must be strictly controlled.

FIG. 2 is a diagram illustrating a conventional foreign matter inspection device for inspecting foreign matter on a photomask equipped with a pellicle.
The foreign object 24 on the photomask 21 is irradiated with a He-Ne laser beam as foreign object detection light 25 through the pellicle 23, and the intensity of the scattered light 26 that has been scattered by the foreign object 24 and passed through the pellicle 23 is measured by the detector 27. It is something to do.

The diameter of the foreign object 24 is determined based on the measured value and the foreign object diameter when using a standard pellicle, which was obtained in advance in an experiment.
This is done by converting using the relationship with the corresponding scattered light intensity, and generally speaking, as the diameter of the foreign object increases, the intensity of the scattered light emitted by the foreign object also increases.

[Problem to be solved by the invention 1 However, the above-mentioned conventional technology has the following problems.

In FIG. 2, the light intensity measured by the detector 27 is lost twice due to absorption by the pellicle 23, upon incidence and upon reflection. In addition, there is no single type of pellicle used in semiconductor device manufacturing depending on the application, and if the type of pellicle changes, its material and film thickness will also change, so naturally the amount of light absorbed will also change. It varies greatly depending on the type of pellicle. Therefore, the scattered light 26 measured by the detector 27
In order to determine the diameter of the foreign object 24 using the intensity of the pellicle, it is also necessary to consider the amount of light absorbed, which varies depending on the type of pellicle 23. However, in conventional foreign object inspection equipment,
Since only the standard pellicle was considered, the diameter of the detected foreign object could not be accurately determined when using other pellicles with different transmittances. The present invention is intended to solve these problems, and its purpose is to accurately determine the diameter of a detected foreign object for any type of pellicle with different transmittance. The company provides a foreign object inspection device.

[Means for Solving the Problems] The foreign matter inspection device of the present invention irradiates foreign matter detection light through the pellicle onto a foreign matter on the surface of a photomask equipped with a pellicle, and scatters the foreign matter by the foreign matter and passes through the pellicle again. In a foreign object inspection device that measures the intensity of the scattered light and determines the foreign object diameter from the relationship between the foreign object diameter when using a standard pellicle obtained in advance in an experiment and the corresponding scattered light intensity, For any pellicle whose transmittance is different from the standard pellicle, the ratio of the transmittance to the standard pellicle is stored and used as a correction value when determining the diameter of a foreign object.

[Example 1 The foreign object detection principle of the foreign object inspection device of this example is the same as that of the conventional device, and although the explanation will be omitted, it is different from the conventional one. The trick is to store the ratio of the transmittance to the standard pellicle for any pellicle whose transmittance to the foreign object detection light is different from that of the standard pellicle, and use it as a correction value when determining the foreign object diameter.

Figure 1 shows the relationship between the actual particle diameter and the particle diameter determined by the device when a photomask equipped with a standard pellicle and an arbitrary pellicle 1.2 with different transmittance is inspected for foreign particles using a conventional device. FIG. For the standard pellicle, as mentioned above, the relationship between the foreign object diameter and the corresponding scattered light intensity is obtained through experiments, and the absorption of the foreign object detection light by the pellicle is taken into account, so the actual foreign object diameter and the equipment There is a 1:1 correspondence with the diameter of the foreign object determined by, for example, a foreign object of 3 μm is determined to have a diameter of 3 μm. However, for Velicle 1.2, since the difference in transmittance with respect to the standard pellicle is not taken into account, the particle diameter is determined from the relationship between the particle diameter when using the standard pellicle and the corresponding scattered light intensity. , as shown in FIG. 1, the determination result deviates from the true value. In Fig. 1, pellicle 1 has a higher transmittance than the standard pellicle, so the intensity of scattered light is large, and the diameter of the foreign object is determined to be larger than the actual diameter.
m, which has doubled. On the other hand, Pellicle 2 has a lower transmittance than the standard pellicle, so the intensity of the scattered light is small, and the diameter of the foreign object is determined to be smaller than the actual diameter. There is. Here, since the slopes of the respective graphs are the same, 2@ for pellicle 1 and 2/3 times for pellicle 2 can be used as correction values for the foreign particle diameter with respect to the standard pellicle. Also, the values of 2 times and 2/3 times the above are
vs. standard pellicle. It goes without saying that each is the ratio of the transmittance of a pellicle of 1.2. In this embodiment, these values are stored as correction values for a pellicle of 1.2, and are compared to the foreign object diameter when using the standard pellicle described above. The true determination result was determined by multiplying the foreign object diameter, which was calculated from the relationship between the scattered light intensity and the corresponding scattered light intensity, by the reciprocal of the correction value. In this way, for any pellicle, by using the ratio of the transmittance to the standard pellicle as a correction value, even for a pellicle with a different transmittance from the standard pellicle, the actual foreign particle diameter can be compared with the foreign particle diameter determined by the device. is now compatible with 1.1.

As described above, in the embodiments of the present invention, an apparatus for inspecting foreign matter on the surface of a photomask equipped with a pellicle used in semiconductor device manufacturing has been described. It can be easily applied to detecting foreign substances present in a substance through the substance, and similar effects can be obtained.

[Effect of the Invention 1 As described above, according to the present invention, foreign matter detection light is irradiated through the pellicle to a foreign matter on the surface of a photomask equipped with a pellicle, is scattered by the foreign matter, and passes through the pellicle again. In a foreign object inspection device that measures the intensity of scattered light and determines the foreign object diameter from the relationship between the foreign object diameter when using a standard pellicle obtained in advance in an experiment and the corresponding scattered light intensity, By storing the ratio of the transmittance to the standard pellicle for any helical whose transmittance is different from that of the standard pellicle, and using it as a correction value when determining the diameter of a foreign object, it is possible to This also has the effect of accurately determining the diameter of a detected foreign object for a pellicle.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the actual particle diameter and the particle diameter determined by the device when a photomask equipped with a standard pellicle and arbitrary pellicles 1 and 2 with different transmittances is inspected for foreign particles. It is. FIG. 2 is a diagram illustrating a conventional foreign matter inspection apparatus for inspecting foreign matter on the surface of a photomask equipped with a pellicle. 21... Photomask 22... Pellicle frame 23... Pellicle 24... Foreign object 25... Foreign object detection light (He-Ne laser beam) 26... Scattered light 27... Detector and above Applicant Seiko Epson Corporation

Claims (1)

[Claims] irradiating foreign matter detection light through the pellicle to a foreign matter on a photomask surface equipped with a pellicle, measuring the intensity of the scattered light that is scattered by the foreign matter and passing through the pellicle again;
In a foreign object inspection device that determines the foreign object diameter from the relationship between the foreign object diameter when using a standard pellicle obtained in advance in an experiment and the corresponding scattered light intensity, the transmittance for the foreign object detection light is different from that of the standard pellicle. A foreign object inspection device characterized in that a ratio of transmittance of an arbitrary pellicle to the standard pellicle is stored and used as a correction value when determining a foreign object diameter.