JPS63777B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention provides a method for covering a transparent substrate such as a photomask or reticle used in semiconductor manufacturing with a pellicle film to prevent foreign matter from adhering to the transparent substrate and the pellicle film. The present invention relates to a method for fixing and rendering harmless minute foreign matter that has been mixed and encapsulated between objects, and an apparatus therefor. Here, the term "fine foreign matter" refers to foreign matter particles that are large enough to float in the air.

[Background of the invention]

In order to prevent foreign matter from adhering to transparent substrates such as photomasks and reticles for semiconductor manufacturing, a pellicle film is used, which has a structure in which a thin film made of nitrocellulose is attached to a metal frame. FIG. 1 is a perspective view thereof.

1 is a transparent substrate, and 2 is its surface. On the other hand, a pellicle film 5 is formed by pasting a thin film made of nitrocellulose on the metal frame 3, and this is attached to the surface of the transparent substrate 1 to prevent attachment of foreign matter. Although only one side is shown in this figure, pellicle films 5 are usually attached to both sides of the transparent substrate 1, respectively. Although this operation is performed in a dust-free chamber, it is unavoidable that a minute amount of floating foreign matter gets mixed in between the pellicle film and the transparent substrate.

FIG. 2a is an explanatory diagram of a state in which minute foreign matter is mixed in, and the minute foreign matter is enlarged to make it easier to read.

Foreign substances can be roughly divided into two types: those that exhibit high stickiness due to moisture or oil, and those that have dried and become electrically charged.
It can be divided into types.

8a and 8d shown in FIG. 2a represent minute foreign matter attached to the inner surface 4 of the metal frame 3. It is particularly difficult to detect foreign matter adhering to the inner surface 4 of the metal frame in this way.

7a and 7b represent minute foreign matter floating in the space 6, and 8b and 8c represent minute foreign matter adhering to the pellicle membrane 5, respectively.

As described above, since it is difficult to detect minute foreign matter adhering to the inner surface 4 of the metal frame, it is easy to overlook it during the semiconductor manufacturing process. If these foreign particles continue to adhere, they will not cause any damage, but as shown in Figure 2b, they can be caused by vibrations during transportation and the loss of charge of microscopic foreign particles due to natural discharge. There is a risk that the foreign matter will move and adhere to the transparent substrate 1, and if exposure is performed in this state, defects will occur on the wafer.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides a method capable of fixing and rendering harmless minute foreign matter that has been mixed and sealed between a pellicle film and a transparent substrate, and is suitable for implementing the above-mentioned method. The purpose is to provide a device that is easy to use.

[Summary of the invention]

To achieve the above object, the present invention provides a method for covering a transparent substrate with a pellicle film supported on a metal frame to prevent the adhesion of foreign matter, in which a thin film of an adhesive substance is previously provided on the inner surface of the metal frame. When a minute foreign object sealed between the pellicle film and the transparent substrate floats, the minute foreign object is fixed by adhering to the adhesive substance, making the minute foreign object harmless, and the pellicle film is The transparent substrate covered with the transparent substrate is placed in an electric field, and the minute foreign matter is attracted to the metal frame by Coulomb force, and is fixed by adhering to the adhesive substance, thereby rendering the minute foreign matter harmless.

[Embodiments of the invention]

FIG. 3 is an explanatory diagram of an example of implementing the foreign matter fixing method of the present invention using a foreign matter fixing device to which the present invention is applied.

Inner surface 4 of metal frame 3 supporting pellicle membrane 5
A thin film 9 of adhesive substance is formed on the surface.

In this embodiment, double-sided adhesive tape is attached to the inside of the metal frame 3 to form an adhesive thin film 9.

Floating minute foreign matter 10a to 10h mixed and sealed in the space 6 between the transparent substrate 1 and the pellicle film 5
move irregularly as shown by the wavy arrows, but as time passes, they come into contact with the adhesive thin film 9 with a certain probability. Once the contacting minute foreign matter touches the adhesive thin film 9, it is captured by the adhesive force,
It is fixed in that position and becomes the state shown in FIG. 3b.

FIGS. 4a to 4d are explanatory diagrams of an embodiment different from the above. The transparent substrate 1, metal frame 3, pellicle film 5, and adhesive thin film 9 are the same constituent members as in the previous embodiment. Then, the electrode 1 is placed on the metal frame 3.
Furthermore, an electrode 1 is connected to the top surface of the pellicle membrane 5 with a size that covers the entire pellicle membrane.
An electrode 12 having a polarity opposite to that of 1 is provided. Note that the electrode 12 is separated from the pellicle film 5 by several mm so as not to damage the pellicle film. 15 is a high voltage power supply for applying a high voltage to the electrodes 11 and 12, and 14 is a polarity switching device for switching the polarity of the high voltage.

Now, as shown in figure a, when a positive voltage is applied to the electrode 11, that is, the metal frame 3, and a negative voltage is applied to the electrode 12, the lines of electric force generated between the two are from the metal frame 3 as shown in 16. The curve is directed toward the electrode 12.
In this embodiment, an inert material 13 is interposed between the metal frame 3 and the transparent substrate 1 to prevent the electric lines of force 16 from passing through the transparent substrate 1. As a result, as shown in FIG. On the other hand, the negatively charged foreign matter 18 is similarly attracted to the metal frame 3,
It adheres to the surface of the adhesive substance 9 and is fixed semi-permanently.

Next, as shown in figure c, the polarity switching device 14
When the polarities of the metal frame 3 and the electrode 12 are reversed, the lines of electric force generated between them become curves directed from the electrode 12 to the metal frame 3. Therefore, as shown in FIG.
It is attached semi-permanently to the surface of the On the other hand, the negatively charged foreign matter 18 that has already been fixed on the surface of the sticky substance 9 remains sticky because the Coulomb force acting between it and the electrode 12 is smaller than the adhesive force of the sticky substance 9. It is fixed on the surface of substance 9. In this way, when an electric field is applied and the direction of the electric field is switched, all the positively and negatively charged minute foreign objects 17 and 18 existing in the space 6 are fixed to the inner surface of the metal frame 3 and become harmless.

FIGS. 5a and 5b are explanatory diagrams of an embodiment different from the embodiment shown in FIG. 4, and the differences from the previous example are as follows.

In the previous example (Fig. 4), the electrode 11 was configured to apply a potential to the metal frame 3, but in this example (Fig. 5)
The structure is such that the electrode 19 applies a potential to each of the two metal frames 3, and the electrode 20 applies an opposite potential (opposite to the electrode 19) to the transparent substrate 1.

Now, as shown in FIG. The foreign matter 17 adheres to the surface of the pellicle film 5 and the surface 2 of the transparent substrate 1 due to the Coulomb force acting between the electrode 12 and the transparent substrate 1 . On the other hand, the negatively charged foreign matter 18 is similarly attracted to the metal frame 3, adheres to the surface of the adhesive substance 9, and is fixed semi-permanently.

Next, as shown in Figure b, when the polarity of the metal frame 3 and the electrodes 12 and 20 is reversed by the polarity switching device 14, the positive charge attached to the pellicle membrane surface is removed by the same operation as in Figure a. The foreign matter 17 is attracted to the metal frame 3, adheres to the surface of the adhesive substance 9, and is fixed semi-permanently. On the other hand, the negatively charged foreign matter 18 that has already been fixed on the surface of the adhesive substance 9 remains attached to the adhesive substance 9 because the Coulomb force acting between it and the electrode 12 is smaller than the adhesive force of the adhesive substance 9. 9 is fixed on the surface. In this way, the positively charged minute foreign matter 17 and the negatively charged minute foreign matter 18 in the space 6 are all captured by the adhesive thin film 9,
Fixed and harmless.

FIG. 6a shows a further different embodiment. In the embodiment shown in FIG. 4, a plurality of concentric electrodes 21 to 25 are constructed as members corresponding to the electrode 12 constructed in the form of a single plate in the embodiment shown in FIG. 26 to 29 are electrical insulators.

As shown in FIG. 6b, each of the above electrodes 21 to 2
A polarity switching device 30 is provided so that a potential can be individually applied to each of the polarities 5 and 5. FIGS. 7a to 7c are explanatory diagrams of the usage and operation of the above embodiment.

As shown in FIG. 7a, when a positive voltage is applied to the central electrode 21 and a negative voltage is applied to the electrodes 11 and 22 to 25, among the charged minute foreign particles in the space 6,
The positively charged foreign matter 17 is attached to the metal frame 3 and the electrode 22.
Due to the Coulomb force between ~25, some of them are attracted to the metal frame 3, adhere to the surface of the adhesive substance 9, and are fixed semi-permanently, and some of them are attached to the electrodes 22~ on the surface of the pellicle membrane 5. It attaches to the area facing 25. On the other hand, things with a negative charge18
Similarly, on the surface of the pellicle film 5, the electrode 2
It attaches to the area facing 1.

Next, as shown in FIG. b, the polarity continuous switching device 3
When the polarity of the electrode 22 is reversed by 0 and the others are left as is, the electrode 22 on the surface of the pellicle membrane 5
The positively charged foreign matter 17 attached to the region facing the pellicle film 5 may be attached to the surface of the adhesive substance 9 and fixed semi-permanently, or may be attached to the surface of the pellicle membrane 5 facing the electrodes 23 to 25. It sticks to the area.
Similarly, if the polarities of the electrodes 23 to 25 are successively directed toward the outer circumferential direction and then reversed, the final result will be c.
As shown in the figure, all of the positively charged foreign substances 17 adhere to the surface of the adhesive substance 9 and are fixed semi-permanently.

On the other hand, at this point, the negatively charged foreign object 18
is attached to the entire surface of the pellicle film 5, as shown in FIG. Therefore, as shown in FIG. 8a, by reversing the polarity of the electrode 11, that is, the metal frame 3, and the electrode 21, the negative charge attached to the area of the surface of the pellicle membrane 5 facing the electrode 21 is removed. Foreign object 1
8 is attracted to the metal frame 3 and adheres to the surface of the adhesive substance 9 and is fixed semi-permanently, or it adheres to the area of the surface of the pellicle membrane 5 facing the electrodes 22 to 25. Next, as shown in Figure b, if the polarity of the electrode 22 is reversed and the others are left as is, the negative charge attached to the area of the surface of the pellicle membrane 5 facing the electrode 22 will be charged. The foreign matter 18 is semi-permanently fixed on the surface of the adhesive substance 9 or attached to a region of the surface of the pellicle membrane 5 facing the electrodes 23 to 25. In the same way, when the polarities of the electrodes 23 to 25 are successively turned toward the outer circumferential direction and reversed, all the negatively charged foreign matter 18 is finally removed from the adhesive substance 9, as shown in FIG. It is attached to the surface and fixed semi-permanently. By the above operation, all the positively and negatively charged minute foreign objects 17 and 18 existing in the space 6 can be fixed semi-permanently on the surface of the adhesive substance 9.

In the above action, the electrodes 2 configured concentrically
Since the distance between two adjacent electrodes among Nos. 1 to 25 is short, a Coulomb force larger than the applied voltage can be obtained, and the charged minute foreign matter can be reliably fixed.

〔Effect of the invention〕

As described in detail above, according to the method of the present invention, minute foreign matter that has entered and been encapsulated in the space between the pellicle film and the transparent substrate can be fixed and rendered harmless. Further, according to the apparatus of the present invention, the above-described method of the present invention can be easily carried out and its effects can be fully exhibited.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a transparent substrate equipped with a pellicle film, and FIG. 2 is an explanatory diagram showing the behavior of charged minute foreign matter adhering to the pellicle film and the surface of the metal frame.
3 a, b and 4 a, b, c, d are sectional views of one embodiment for explaining the structure of the device of the present invention and the operation and effects of the method of the present invention, and FIG. 5 a,
Similarly, b is a cross-sectional view of an embodiment different from the above, and the sixth
Figure a is a plan view of an embodiment different from the above, and figure b is a sectional view of the same. Figure 7 a-c and Figure 8 a-
FIG. 6c is a sectional view for explaining the operation of the embodiment shown in FIGS. 6a and 6b. 1... Transparent substrate, 3... Metal frame, 5... Pellicle film, 9... Adhesive substance, 11, 12, 19-2
5... Electrode, 13,26-29... Insulating material,
14...Polarity switching device, 30...Polarity continuous switching device, 15...High voltage power supply.

Claims (1)

[Claims] 1. In a method of covering a transparent substrate with a pellicle film supported on a metal frame to prevent the adhesion of foreign matter, a thin film of an adhesive substance is previously provided on the inner surface of the metal frame, and the pellicle film and A method for fixing foreign matter, characterized in that, when a minute foreign matter is floating between the transparent substrate and the transparent substrate, the minute foreign matter is fixed by being attached to the adhesive substance, thereby making the minute foreign matter harmless. 2. Positioning the transparent substrate covered with the pellicle film in an electric field, attracting the minute foreign matter to the metal frame by Coulomb force and fixing it on the sticky substance, rendering the minute foreign matter harmless. A method for fixing foreign matter according to claim 1, characterized in that: 3. In a foreign matter adhesion prevention structure in which a transparent substrate is covered with a pellicle film that is obstructed by a metal frame, a thin film of an adhesive substance is provided on the inner surface of the metal frame to prevent minute particles that have entered between the pellicle film and the transparent substrate. A foreign matter fixing device characterized in that, when a foreign matter floats, the minute foreign matter is attached to a thin film of an adhesive substance, and this is fixed to render the minute foreign matter harmless. 4. The foreign object fixing device according to claim 3, wherein the pellicle membrane supported by the metal frame is provided with means for applying an electric field.