JP2003222990A - Loading structure of photomask with pellicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loading device of a photomask with a pellicle which does not degrade the parallelism of a pellicle plate and a photomask surface by adhesion of at lest the photomask surface and a pellicle frame. <P>SOLUTION: In the loading structure of the photomask 5 with the pellicle equipped with the pellicle frame 1 and the pellicle plate 2 glued to one aperture of the pellicle frame 1, at least portions of the surfaces with which the pellicle frame 1 and the photomask 5 are contiguous come into direct contact with each other without the intervention of adhesives. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mounted on a photomask or reticle (hereinafter, both are collectively referred to as a photomask) used in a manufacturing process of an integrated circuit for the purpose of preventing foreign matter from adhering, and in particular, F ₂ Laser (wavelength 157.
The present invention relates to a structure for mounting a pellicle on a photomask, which is suitable for photolithography using light of 6 nm).

[0002]

2. Description of the Related Art In a photolithography process used in a process of manufacturing an integrated circuit, a semiconductor wafer coated with a resist material is exposed to form a pattern.
If the photomask used at this time has scratches or foreign matter, the scratches and foreign matter are transferred to the wafer along with the pattern,
It may cause a short circuit or disconnection of the circuit.

For this reason, a method of mounting a pellicle on one side or both sides of the photomask has been adopted to prevent foreign matter on the surface of the photomask.

Conventionally, the pellicle has an outer shape as shown in the front view and side view of FIG. 5, and has a pellicle frame 1 made of aluminum or the like and a pellicle made of an organic resin such as nitrocellulose or fluororesin and having a thickness of several nm to several μm. The film 2 adhered with the adhesive 3 is used, and the film 2 is fixed and used so as to cover the pattern on the photomask. However, in a pellicle using such an organic resin film, when the wavelength used to improve the exposure accuracy becomes shorter, the optical energy is so strong that the organic components are decomposed and used in the actual exposure. It does not have enough durability for the number of shots with the energy to use, in other words, the usage time.

Therefore, in recent years, it has been considered to use a pellicle plate obtained by processing a synthetic quartz glass into a thin plate in place of the organic resin pellicle film. This synthetic quartz glass is obtained by, for example, reacting a silicon source and an oxygen source in a vapor phase to grow a porous material called soot, which is made of silicon oxide, and is obtained by sintering other porosity to obtain substantially only silicon oxide. It is made of glass. The pellicle plate made of this synthetic quartz glass is often provided with an antireflection film on one side or both sides in order to improve the transmission efficiency.

When a pellicle using synthetic quartz glass as a pellicle plate is actually used in an exposure step, the synthetic quartz glass itself absorbs light energy and has heat.
Expands. Also, the pellicle frame itself takes on heat.
At this time, a metal conventionally used as a pellicle frame material, such as aluminum or titanium, has a coefficient of thermal expansion different from that of synthetic quartz glass, and therefore stress is exerted on the synthetic quartz glass that is the pellicle plate, so that the optical path of birefringence is reduced. There is a problem of causing fluctuations in the optical path due to fluctuations and mechanical bending. Therefore, as the pellicle frame material, a material having a thermal expansion coefficient equal to or closer to that of synthetic quartz glass is desirable.

On the other hand, when synthetic quartz glass is used as a pellicle plate, it is desirable that the thickness of the pellicle plate be 0.01 to 2 mm. When the pellicle plate is used, if the thickness of the pellicle plate varies, the exposure light 4 is refracted and the optical path of the light is changed as shown in FIG. 6, so that the position of the transfer pattern is displaced and good lithography cannot be performed. It has been known. For this reason, the parallelism of the upper and lower surfaces allowed for the pellicle plate is said to be 0.1 μm / 50 mm.

Similarly, even when a pellicle plate satisfying the above parallelism is used, the pellicle plate 2 fixed to the upper and lower surfaces of the pellicle frame 1 as shown in FIG. If the parallelism of the surfaces is poor, the position of the transfer pattern will shift.

Further, since the pellicle plate is bonded to the pellicle frame to form a pellicle, if the flatness of the bonding surface is not accurate, the bonded pellicle plate is corrected to the shape of the upper surface of the pellicle frame. By doing so, an optical defect such as bending or an increase in birefringence due to the correction force occurs. Furthermore, if the flatness of the lower surface of the pellicle frame is poor, the pellicle frame itself may be distorted or warped when it is bonded to the photomask surface, and may even bend to the pellicle plate.

For this reason, the flatness of each surface of the pellicle frame (the entire difference between the upper and lower surfaces constituting the frame body, the maximum difference between the unevenness and the ideal plane) is set to 1 μm or less, and at the same time, the upper and lower surfaces are parallel to each other. The degree (the maximum difference when an arbitrary point is taken on the entire surface of the frame) is required to be 2 μm or less. On the other hand, also in the bonding of the pellicle plate and the pellicle frame, and the photomask and the pellicle frame, the method of bonding while maintaining the above-mentioned accuracy is necessary.

As a means for solving this, the thickness of the adhesive between the pellicle plate and the pellicle frame, the adhesive of the photomask and the pellicle frame or the adhesive (hereinafter, both are collectively referred to as an adhesive) is reduced. The method is being tried.

However, these adhesives are generally made of an organic material, and as described above, when they are irradiated with light having large optical energy, they are decomposed or deteriorated, and the adhesive parts are peeled off or peeled off. Problems such as dust generation or a decrease in the transmittance of light of the used wavelength due to degassing of organic components occur. On the other hand, as a measure for preventing the deterioration of the adhesive between the pellicle plate and the pellicle frame, the inventors of the present invention have proposed Japanese Patent Laid-Open No. 2002-107915. According to this, even the flatness of the bonding surface of the pellicle frame is satisfied. If you do that, you can see that you can get the initial effect.

[0013]

[Patent Document 1] Japanese Patent Laid-Open No. 2002-107915

[0014]

However, sufficient measures have not been taken in bonding the pellicle frame and the photomask surface. The present invention has been made to solve such a problem.

[0015]

The inventors of the present invention have paid attention to the fact that the surface of the photomask surface of the pellicle frame to be bonded can be made flat with high precision, and arrived at the present invention.

That is, the present invention is a mounting structure for a photomask of a pellicle including a pellicle frame and a pellicle plate adhered to one opening of the pellicle frame, wherein the pellicle frame and the photomask contact each other. At least a part of the contact surface is in direct contact with no adhesive, and the pellicle is attached to the photomask.

That is, it is considered that the parallelism between the pellicle plate and the photomask surface is maintained when at least the entire surfaces to be bonded or a part of the surfaces are in contact with each other without an adhesive. As a structure for that,
(1) Use an auxiliary member that presses the pellicle frame toward the photomask. In particular, an auxiliary member having an L-shaped cross-sectional structure is engaged with at least a part of the pellicle to bond the auxiliary member to the photomask, thereby pressing the pellicle frame toward the photomask. (2) An adhesive is placed on the outer peripheral portion of the pellicle frame to bond the pellicle frame and the photomask together. (3) The surface of the pellicle frame to be bonded is concavely processed, and the concave is filled with the adhesive. For example, the pellicle frame may be adhered to the photomask.

The material of the pellicle plate is not limited as long as it is a material that transmits exposure light, but it is synthetic quartz glass because it has high transparency and high resistance to short wavelength ultraviolet light. preferable.

Further, it is desirable that the material of the pellicle frame has a coefficient of thermal expansion equivalent to that of synthetic quartz glass.
In this respect, synthetic quartz glass is the most desirable, followed by fused quartz glass, other component type glass, ceramics, alloys and the like.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, and is a sectional view of a state in which a pellicle is mounted on a photomask.

On the outer peripheral side surface of the pellicle frame 1, there is a protruding portion 1 having a surface parallel to the surface bonded to the surface of the photomask 5.
a is integrally processed to form a stepped portion. And L
The pellicle frame 1 is pressed to the photomask 5 side by engaging the protruding portion 1a with the L-shaped horizontal portion of the auxiliary member 8 having a V-shaped cross-sectional structure as the engaging surface. Further, the L-shaped top portion of the auxiliary member 8 is bonded to the photomask 5 as a bonding surface. In order to fix the pellicle frame 1 to the surface of the photomask 5, an adhesive is applied to the joining surface 6 where the auxiliary member 8 contacts the surface of the photomask 5 and the engagement surface 7 where the upper surface of the projection 1a of the pellicle frame 1 contacts. By using, it is firmly held between the photomask and the pellicle frame without an adhesive.

At this time, the adhesive for the engaging surface 7 is not always necessary, but it is effective for providing a slight cushioning property. Further, the protruding portion 1a formed on the pellicle frame 1 and the auxiliary member 8 do not necessarily have to be on the entire outer peripheral surface of the pellicle frame 1, and may be intermittently arranged on the outer peripheral portion. Furthermore, the protrusion does not have to be parallel to the photomask as long as the auxiliary member can be engaged.

Further, the auxiliary member does not necessarily have to have an L-shaped cross section, and may have at least a joining surface for adhering to the photomask and an engaging surface for engaging with the pellicle.

FIG. 2 is a cross-sectional view of a modified example of the first embodiment of the present invention in which a pellicle is mounted on a photomask.

In the present embodiment, the auxiliary member 8 having an L-shaped sectional structure is engaged with the surface of the pellicle plate 2 on the side not in contact with the pellicle frame 1, and the pellicle frame 1
Is pressed against the photomask 5 side. Also in this case, the adhesive on the joint surface 6 between the photomask 5 surface and the auxiliary member 8 is necessary, but the adhesive is not necessarily used on the engaging surface 7 between the auxiliary member 8 and the pellicle plate 2. Further, the auxiliary member 8 is
It is not always necessary to provide the pellicle frame 1 so as to surround the entire circumference thereof, and the pellicle frame 1 may be arranged at several locations separately.

Further, the auxiliary member does not necessarily have to have an L-shaped cross section, and it suffices if it has at least a joining surface for adhering to the photomask and an engaging surface for engaging with the pellicle. It is similar to the embodiment.

FIG. 3 is another embodiment of the present invention and is a cross-sectional view of a state in which a pellicle is mounted on a photomask.

A notch 10 is formed in a ridge formed by a side surface and a side surface of the pellicle frame 1 which are in contact with the photomask 5 surface, and the notch 10 is filled with an adhesive to form the photomask 5 surface. It is characterized by the fact that it can be adhered. Here, the shape of the notch is shown as a C-chamfered shape for ease of processing, but other structures such as a structure having a rectangular notch may be used. In order to achieve the same purpose, an adhesive may be molded at the boundary between the surface of the photomask 5 and the outer peripheral side surface of the pellicle frame 1.

FIG. 4 is still another embodiment of the present invention and is a cross-sectional view of a state in which a pellicle is mounted on a photomask.

A recess 11 is formed on the surface of the pellicle frame 1 to be adhered to the photomask 5 surface by grinding or the like, and the adhesive filled in the recess 11 enables adhesion to the photomask 5 surface. It is characterized by that. The recess 11 does not necessarily have to be provided on the entire circumference of the pellicle frame 1, and may be intermittently arranged on the surface to be bonded. The shape of the recess is not limited to that shown in the figure, and may be a polygonal pyramid or a hemisphere.

The present invention is not limited to the form used in the above-mentioned embodiments, and any shape may be used as long as it does not impair the gist of the present invention.

In the present invention, the quartz glass which is a preferable material for the pellicle frame may be synthetic quartz glass or fused quartz glass. In this way, the amount of birefringence generated in the pellicle plate due to the temperature change of the pellicle during exposure can be reduced, and the influence on the dimensional accuracy of the exposure pattern can be reduced. Further, distortion of the pellicle due to a difference in thermal expansion between the pellicle frame and the pellicle plate due to a temperature change during exposure and a temperature change during conveyance is eliminated. Particularly, since the thermal strain during frame processing is small, the frame parallelism after processing is good.

The synthetic quartz glass can be easily sliced from a molded block to obtain a plate-shaped blank.
Also, regarding fused silica glass, it is possible to easily obtain a plate-shaped raw plate by melting a glass material and slicing it from a block or forming it into a sheet shape.

In the pellicle frame, it is preferable that at least one surface of the quartz glass plate after polishing has a flatness of 1 μm or less and a parallelism of both surfaces of 2 μm or less in a range of being used as a pellicle frame.

If necessary, the side surface of the pellicle frame may be processed by drilling holes for ventilation or by using an end mill to form dimples for chucking.

Further, as means for improving the strength of the frame and preventing dust generation from the rough surface after processing, the inner side surface and the outer side surface of the frame are polished or the entire frame is H
It is desirable to etch with F or the like.

Such a pellicle frame is particularly suitable for waves.
Light with a length of 220 nm or less, especially F _TwoUse laser light
It can be used for a pellicle suitable for exposure.

In the present invention, the pellicle plate has a thickness of 0.01.
It is preferably made of quartz glass of about 2 mm, particularly when used for short wavelength exposure of 220 nm or less,
It is preferable to use synthetic quartz glass.

The thickness of the pellicle plate is preferably 2 mm or less. This is preferable because the birefringence of the pellicle plate itself can be suppressed. Especially 1 mm
In the following cases, the transmittance is good and there is no absorption in the pellicle plate, so the temperature rise of the pellicle plate during exposure can be reduced. Therefore, thermal stress is less likely to occur in the pellicle, which is preferable. The thickness of the pellicle plate is preferably 0.01 mm or more in terms of strength.

As the adhesive used for adhering the pellicle plate and the pellicle frame, for example, polybutene resin, acrylic resin, epoxy resin, silicone adhesive, fluorine adhesive or the like can be used. Fluorine-based adhesives are particularly preferable because they have good resistance to ultraviolet light and do not generate dust.

The thickness of the adhesive member is preferably 1 μm or more. This is because the deformation of the pellicle due to the temperature change can be alleviated by the adhesive member, and good exposure can be performed. Further, when the pellicle plate is bonded to the pellicle frame, if the thickness of the adhesive member is 1 μm or more, the pellicle mounter can apply a uniform force, and the pellicle plate can be fixed in a horizontal state with respect to the frame. There are also advantages.

[0043]

According to the present invention, the parallelism between the pellicle plate and the photomask surface is not deteriorated by at least the adhesion between the photomask surface and the pellicle frame. Further, there is also an advantage that the adhesive is not deteriorated because a part of the adhesive is not directly exposed to at least the space inside the pellicle and the photomask.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of the invention.

FIG. 2 is a sectional view showing a modification of the first embodiment of the invention.

FIG. 3 is a cross-sectional view showing another embodiment of the invention.

FIG. 4 is a cross-sectional view showing yet another embodiment of the invention.

FIG. 5 is a front view and a side view showing the pellicle.

FIG. 6 is a conceptual diagram of an exposure optical path shift due to the parallelism of the pellicle plate.

FIG. 7 is a conceptual diagram of deviation of an exposure optical path due to parallelism between a pellicle plate and a photomask.

[Explanation of symbols]

1: Pellicle frame 2: Pellicle film (pellicle plate) 3: Adhesive 4: Exposure ray 5: Photo mask 6: Joined surface 7: Engaging surface 8: Auxiliary member

Claims (8)

[Claims] 1. A mounting structure for a photomask of a pellicle comprising a pellicle frame and a pellicle plate adhered to one opening of the pellicle frame, wherein the pellicle frame and the photomask are in contact with each other. At least a part of the pellicle is in direct contact with the photomask, not through an adhesive. 2. The structure for mounting a pellicle on a photomask according to claim 1, further comprising an auxiliary member for mounting the pellicle on the photomask. 3. The mounting structure for a pellicle on a photomask according to claim 2, wherein the auxiliary member has at least a joining surface for adhering to the photomask and an engaging surface for engaging with the pellicle. 4. The auxiliary member has an L-shaped cross section, is joined to the photomask by using the L-shaped top portion as a joining surface, and is engaged with the pellicle by using the L-shaped horizontal portion as an engaging surface. Structure for mounting the pellicle on the photomask. 5. A structure for mounting a pellicle on a photomask according to claim 3, wherein the pellicle frame has a step portion on its outer periphery, and the auxiliary member engages with the pellicle at the step portion. 6. The structure for mounting a pellicle on a photomask according to claim 3, wherein the auxiliary member engages with the pellicle on the surface of the pellicle plate. 7. The structure for mounting a pellicle on a photomask according to claim 1, wherein an adhesive is arranged on an outer peripheral portion of the pellicle frame to bond the pellicle frame and the photomask. 8. The structure for mounting a pellicle on a photomask according to claim 1, wherein a recess is provided on a surface of the pellicle frame in contact with the photomask, and the recess is filled with an adhesive to bond the pellicle frame to the photomask.