JPH04133060A - Method for inspecting adhered part or the like of pellicle for photomask - Google Patents

Abstract

PURPOSE:To inspect with hight accuracy the adhesion defect and lack of adhesive of the adhered part of the pellicle for a photomask and a pellicle frame and the coating defect and unequal coating of the tackiness agent on the inside wall surface of the frame by adopting the simple method for selectively observing the distribution of the fluorescent light by irradiating the pellicle with excitation light. CONSTITUTION:The light from a light source L which emits the light of visible rays from UV rays is passed through a excitation filter Fe which allows the selective transmission of only the excitation wavelength lambdaex intrinsic to the adhesive or tackiness agent used for the pellicle film P with the frame. If the pellicle P with the frame which is an object to be inspected is irradiated with this excitation wavelength lambdaex, a part thereof is absorbed by excitation and a fluorescent wavelength lambdaem is emitted. The excitation wavelength lambdaex which is passed straight through the object P to be inspected and is scattered by the same and the fluorescent wavelength lambdaem by the adhesive or tackiness agent are emitted by being mingled with each other. Only the fluorescent wavelength lambdaem is selected by an absorbing filter Fb. the part where the adhesive or tackiness agent exists is selectively viewed in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for inspecting a pellicle attached to a photomask used in a photolithography process in the manufacture of semiconductor integrated circuits such as VLSIs, and particularly relates to a method for inspecting a pellicle frame attached to a photomask used in a photolithography process. This relates to a method for inspecting adhesive parts, etc.

Conventional technology: Traditionally, in the manufacture of semiconductor integrated circuits, when dust adheres to the mask pattern surface of a photomask used in the photolithography process, this dust is projected onto the surface of the semiconductor substrate and is burned, resulting in product defects. To protect the photomask from dust, a pellicle film (transparent thin film) is attached at a distance of r/1 from the mask pattern surface, so that the dust adheres to this pellicle film, and the projection is focused on the mask pattern surface. A photomask with a pellicle has already been proposed (Special Publication No. 54-28716), which prevents dust from forming an image even when the image is blurred, but with the recent increase in the degree of integration of semiconductor integrated circuits, This photomask with a pellicle is used. Figure 3 shows a perspective view (a) and a cross-sectional view of an example of a photomask with a pellicle.
)). In the figure, 1 is a pellicle frame made of metal such as aluminum, and 2 is a pellicle film, which is uniformly stretched over the upper surface of the pellicle frame 1 and bonded at an adhesive portion 3. Reference numeral 4 denotes a photomask substrate, on the surface of which a photomask pattern 5 is provided, and a frame 1 is bonded to the surface of the photomask substrate 4 with an adhesive 6 so that the pellicle film 2 covers the photomask pattern 5.

Problems to be Solved by the Invention] As mentioned above, the pellicle film 2 was originally devised and used as a dust shield for the photomask pattern 5, but the pellicle film 2 was originally designed and used to protect the photomask pattern 5 from dust. There is, and it has been improved. However, even now, it is not possible to eradicate poor adhesion or insufficient adhesion between the bonded portion 3 of the pellicle frame 1 and the pellicle membrane 2, and there is a possibility that dust may be generated from these defective portions.

In addition, in order to prevent dust from adhering to the inner surface of the pellicle frame 1 and adhering to the mask pattern 5,
Poor or uneven application of the adhesive applied to the inner surface of the pellicle frame 1 cannot be eradicated, and there is a possibility that dust may be generated in this area. To explain these points with reference to Figure 2, as shown in Figure (al), the pellicle frame 1
When the pellicle membrane 2 is bonded to the upper end with an adhesive 7, for example, if the adhesive 7 is insufficient at the part indicated by reference numeral 8 and a part of the upper end of the frame 1 is exposed, the frame 1
The minute dust that was attached to the mask pattern 5 pops out.
It may stick to the top. Also, Figure 2(b)
As shown in Figure 2, adhesive 9 is sometimes applied to the inner surface of the pellicle frame 1 to attract dust and prevent it from adhering to the mask pattern surface. , there is a possibility that minute dust adhering to the frame 1 will fly out and adhere to the mask pattern 5.

Therefore, there is a need for an inspection method that accurately eliminates defective products in these bonded parts or adhesive-applied parts, but currently inspections are simply performed visually under an illumination light source.
, Inspection accuracy is poor and failure rate is high.

The present invention has been made in view of the problems of the prior art as described above, and includes problems such as poor adhesion between the pellicle frame and the pellicle membrane, insufficient adhesive, and poor adhesive application on the inner wall surface of the frame. An object of the present invention is to provide a method for inspecting adhesive parts of a photomask pellicle, etc., for easily and accurately inspecting coating unevenness.

[Means to solve the problem]

The method of inspecting adhesive parts of a photomask pellicle according to the present invention which achieves the above object is to irradiate excitation light for fluorescence to the adhesive or pressure-sensitive adhesive used in the framed pellicle film, and to emit the fluorescent light. By selectively observing the distribution,
This method is characterized by inspecting for poor adhesion between the pellicle frame and the pellicle membrane, insufficient adhesive, poor adhesive application on the inner wall surface of the frame, and uneven application.

In this case, if both the excitation wavelength and the fluorescence wavelength are in the visible range, it is necessary to selectively observe the distribution of the fluorescence light through an absorption filter that transmits only the fluorescence wavelength.

Furthermore, when the excitation wavelength is in the ultraviolet region, an absorption filter is required to protect the eyes.

[Effect]

The present invention uses a simple method of irradiating excitation light and selectively observing the distribution of the fluorescent light. It is possible to easily and accurately inspect adhesive coating defects and coating unevenness on the inner wall surface.

〔Example〕

The inspection method of the present invention utilizes the fact that the adhesive at the adhesive part of the pellicle frame-stopping pellicle film and the adhesive applied to the inner wall surface of the frame usually emit fluorescence.

Fluorescence is a phenomenon in which a substance absorbs ultraviolet light or short wavelength light and re-emits light with a longer wavelength than the absorbed light.
The wavelength of the former light is called the excitation spectrum, and the wavelength of the latter light is called the fluorescence spectrum. This excitation spectrum and fluorescence spectrum are unique to each substance. Moreover, as mentioned above, it is used as an adhesive for the bond between the pellicle frame and the pellicle membrane, and as an adhesive applied to the inner wall of the frame.
The substances used are usually fluorescent. Therefore, for materials used in such adhesives and adhesives, only the light in the wavelength range that most efficiently emits fluorescence is extracted and irradiated to the pellicle as excitation light, and the emitted fluorescence and the scattered light are extracted. By extracting and observing only the fluorescence in the wavelength range necessary for observation from the excitation light, it is possible to capture the fluorescence emitted by the adhesive and the adhesive itself, and selectively identify the adhesive and the area where the adhesive is present. can be detected. Even objects that can only be seen uniformly under illumination sources such as floodlights and fluorescent lights can be made to stand out with high sensitivity due to such fluorescence.

The optical arrangement of the apparatus for such fluorescence inspection is as shown in FIG. That is, light from a light source that emits light ranging from ultraviolet rays to visible light is passed through the excitation filter F, and only the excitation wavelength λ specific to the adhesive or pressure-sensitive adhesive used in the framed pellicle membrane P is selectively transmitted. When the frame-attached pellicle film P, which is an object to be inspected, is irradiated with this excitation wavelength λ, 8, a part of the pellicle film P with a frame is absorbed due to excitation and emits a fluorescence wavelength λ, 8. The excitation wavelength λ□ that passes directly through the object to be inspected or is scattered by it, and the fluorescence wavelength λ caused by the adhesive or adhesive are mixed together, but the absorption filter F, (for example, attached to glasses) ), the fluorescence wavelength λ0. By selecting only the pellicle frame and pellicle membrane, you can selectively see the adhesive or the area where the adhesive is present, and check for poor adhesion between the pellicle frame and the pellicle membrane.
It is possible to accurately inspect for insufficient adhesive, poor adhesive application, and uneven application on the inner wall of the frame. In addition, when multiple different types of adhesives and pressure-sensitive adhesives are used in the frame-attached pellicle membrane P, multiple excitation filters F adapted to the excitation wavelength λ□ and fluorescence wavelength λ, specific to each substance, are used. , absorption filter F are prepared, and inspection is performed while switching between these.

Furthermore, it is desirable that the inspection device be arranged such that, for example, a laminar flow of clean air flows from above the object to prevent dust and foreign matter from adhering to the surface of the object to be inspected.

〔Effect of the invention〕

In the above-described method for inspecting adhesive parts of a pellicle for a photomask of the present invention, a simple method of irradiating excitation light and selectively observing the distribution of the fluorescent light is used to inspect the pellicle for a photomask. It is possible to easily and accurately inspect for poor adhesion of the adhesive part of the pellicle frame, insufficient adhesive, poor adhesive application on the inner wall surface of the frame, and uneven application.

[Brief explanation of drawings]

Fig. 1 is an optical layout diagram of a device for carrying out the method of inspecting bonded parts of a photomask pellicle according to the present invention, and Fig. 2 is a diagram illustrating the reason why dust is generated from a pellicle membrane with a frame. FIG. 3 is a perspective view (a) and a cross-sectional view (a) of an example of a photomask with a beam. 1... Pellicle frame, 2... Pellicle membrane, 3.
... Adhesive part, 4... Funatomask substrate, 5... Photomask pattern, 6... Adhesive, 7... Adhesive,
8... Defective adhesion part, 9... Adhesive, 10... Defective coating part, L... Light source, F... Excitation filter, P
... Pellicle membrane with frame, F, ... Absorption filter Applicant Dai Nippon Printing Co., Ltd. Agent Patent attorney Hiroshi Nirasawa (7 others) ↓

Claims (2)

[Claims] (1) By irradiating the adhesive or pressure-sensitive adhesive used in the frame-attached pellicle membrane with excitation light for fluorescence and selectively observing the distribution of the fluorescent light, the bond between the pellicle frame and the pellicle membrane can be measured. A method for inspecting bonded parts of pellicles for photomasks, etc., characterized by inspecting for poor adhesion, insufficient adhesive, poor adhesive application on the inner wall surface of the frame, and uneven application. (2) The method for inspecting a bonded portion of a photomask pellicle according to claim 1, wherein the selective observation of the distribution of fluorescent light is performed through an absorption filter that transmits only fluorescent wavelengths.