JPH04151663A - Foreign matter inspecting 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 a photomask equipped with a pellicle 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, recently, 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 bump 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 Figure 2, the pellicle (2
3) is made of a transparent thin film represented by nitrocellulose, and the pellicle frame (22) is made of metal such as aluminum alloy.
It is fixed at a certain distance from the photomask (21) via the photomask (21) so as to protect the pattern section 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 photomask (21) surface, the pellicle (23)
The mechanism is such that foreign matter on the top is out of focus, and foreign matter with a size of about 50 μm or less is not transferred. As described above, pattern defects caused by foreign matter transfer are significantly reduced by using a pellicle, but foreign matter on the photomask after the pellicle is attached must be strictly controlled.

FIG. 2 is a diagram illustrating a conventional foreign matter inspection apparatus for inspecting foreign matter on a photomask equipped with a pellicle.
25), the He-Ne laser beam is applied to the pellicle (23).
The detector (27) measures the intensity of the scattered light (26) that is scattered by the foreign object (24) and passes through the pellicle (23). The size of the foreign object (24) is determined by converting the measured value, the intensity of scattered light determined experimentally in advance, and the relationship between the size of the foreign object. Problem 1 to be Solved by the Invention However, the above-mentioned prior art has the following problems.

In Fig. 2, the light intensity measured by the detector (27) is
It suffers two losses at the time of incidence and reflection due to absorption by the pellicle (23). Furthermore, 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 vary. It varies greatly depending on the type of pellicle. Therefore, in order to determine the size of the foreign object (24) using the intensity of the scattered light (26) measured by the detector (27), it is necessary to take into account the amount of light absorption that varies depending on the type of pellicle (C23). No. To do this, it is necessary to experimentally determine the relationship between the intensity of the scattered light (26) and the size of the foreign object for each type of pellicle for each type of pellicle that may be used, which takes a lot of time. Inspection efficiency was reduced. Further, even if the pellicles are of the same type, the amount of light absorption varies slightly due to variations in quality, so the accuracy in determining the size of foreign objects is also insufficient.

SUMMARY OF THE INVENTION The present invention aims to solve these problems, and its purpose is to provide a foreign object inspection device that can efficiently and accurately determine the size of detected foreign objects regardless of the type of pellicle. It is in a place where we provide.

[Means for Solving the Problems 1] The foreign object inspection device of the present invention irradiates a foreign object on a photomask equipped with a pellicle with foreign object detection light through the pellicle, and detects the light scattered by the foreign object and passing through the pellicle. A foreign object inspection device that determines the size of the foreign object by measuring the intensity of light, comprising a mechanism for measuring the amount of loss in light intensity when the foreign object detection light passes through the pellicle, is used as a correction value when determining the size of the foreign object.

[Example] The foreign object detection principle of the foreign object inspection device of the present invention is the same as that of the conventional technology, and the explanation will be omitted. However, the difference from the conventional method is the amount of loss of light intensity when the foreign object detection light passes through the pellicle. It is characterized by having a mechanism for measuring the size of a foreign object and using it as a correction value when determining the size of a foreign object.

FIG. 1 is a diagram illustrating a mechanism for measuring the amount of loss in light intensity when foreign object detection light passes through a pellicle in the foreign object inspection apparatus of the present invention. He, which is the foreign object detection light (17)
Half of the -Ne laser beam is reflected by a half mirror (14), and the incident intensity is measured by a detector (15).

Next, the remaining half of the light that has passed through the half mirror (14) passes through the pellicle [13] and passes through the photomask (11).
reaches the chromium lli (12) surface, which is the light-shielding region of
Half of the light (18) reflected there is reflected again by the half mirror (14), and the intensity of the light after passing through the pellicle is measured by a detector (16). and,
The half mirror (14) and the chromium film (12)
) is considered to be constant even when inspecting a photomask, so the light intensity after passing through the pellicle (13) measured by the detector (]6) is The value divided by the incident intensity measured by the detector (15) was defined as the loss of light intensity due to the pellicle (13).

Next, a Keyaki quasi-pellicle was set up to determine the size of the detected foreign object. We then measured the loss of light intensity for this pellicle using the method described above, and also experimentally determined the relationship between the intensity of light scattered by a foreign object and the size of the foreign object when this pellicle was used. were determined and set as the respective standard values. Therefore, when inspecting a photomask equipped with a pellicle of a different type from the standard pellicle, the loss of light intensity due to this pellicle is measured and compared with the standard value to determine the intensity of light scattered from foreign objects.
It is now possible to compensate for losses caused by pellicles. Specifically, the intensity of the scattered light from the foreign object is corrected by an amount corresponding to the ratio of the measured optical loss value to the standard value, and then The true size of the foreign object is determined by converting it from the relationship between the intensity of light scattered by the foreign object and the size of the foreign object.
This provides the following advantages:

Since the relationship between the light scattered by the foreign object and the size of the foreign object only needs to be determined for the standard pellicle, inspection efficiency is improved.

・Even if a photomask is equipped with a different type of pellicle, the loss of light intensity can be measured and corrected, so the size of a foreign object can be determined easily and accurately.

Since the loss of light intensity can be corrected for each photomask,
Even if there are variations in quality between pellicles of the same type, this can be compensated for, improving accuracy when determining the size of foreign objects.

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 the manufacture of semiconductor devices has been described. It can be easily applied to detect foreign substances present in the
Moreover, similar effects can be obtained.

[Effects of the Invention] As described above, according to the present invention, foreign object detection light is directed through the pellicle onto a foreign object on a photomask equipped with a pellicle, and the light scattered by the foreign object and passed through the pellicle is detected. A foreign object inspection device that determines the size of the foreign object by measuring the intensity of light, the foreign object detection light having an 81M width that measures the amount of loss in light intensity when the foreign object detection light passes through the pellicle, By using the amount as a correction value when determining the size of the foreign object, the size of the detected foreign object can be determined efficiently and with high accuracy regardless of the type of pellicle. be.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a mechanism for measuring the loss of light intensity when foreign object detection light passes through a pellicle in the foreign object inspection apparatus of the present invention. FIG. 2 is a diagram illustrating a conventional foreign matter inspection apparatus for inspecting foreign matter on a photomask equipped with a pellicle. 11.21... Photomask 12... Chrome film 13.23... Pellicle 14... Half mirror 15, I6.2
7...Detector 17.25-=Foreign object detection light () (e-Ne laser beam) 18......Reflected light 22......Pellicle frame 24...Foreign object 26・・・・・・More than scattered light

Claims (1)

[Claims] A foreign object inspection in which a foreign object on a photomask equipped with a pellicle is irradiated with foreign object detection light through the pellicle, and the size of the foreign object is determined by measuring the intensity of the scattered light that is scattered by the foreign object and passes through the pellicle. In the device,
A foreign object inspection characterized by having a mechanism for measuring the amount of loss in light intensity when the foreign object detection light passes through the pellicle, and using the loss amount as a correction value when determining the size of the foreign object. Device.