JP2013195950A - Pellicle and photomask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellicle and a photomask mounting the pellicle which need no adhesive nor new facility introduction, and facilitate cleaning of the photomask after detachment of the pellicle.SOLUTION: Instead of mask adhesive for laminating a pellicle and a photomask, carbon nano-fiber 4 deposited at a formation density of one hundred million carbon nano-fibers or more per square millimeter is used as a mounting layer, and the pellicle is constituted to be mounted on the photomask with the molecular force of the carbon nano-fibers 4.

Description

  In the present invention, for example, foreign matter adheres to a photomask (also called a reticle) used in a lithography process when manufacturing a semiconductor device such as an LSI (Large Scale Integrated Circuit) or a TFT type LCD (Thin Film Transistor Liquid Crystal Display). In order to prevent this, the present invention relates to a pellicle used by being mounted on a photomask and the photomask.

  A semiconductor using a silicon wafer or the like is manufactured by a projection exposure system in which a pattern formed on a photomask is exposed by a projection optical system onto a substrate coated with a photosensitive agent such as a photoresist.

  When foreign matter adheres to the pattern of these photomasks, defects appear in the product because the image of the portion is prevented during exposure. In order to prevent such poor resolution due to foreign matters adhering to the surface of the photomask, the photomask is equipped with a pellicle as a dust-proof cover having translucency on the surface (see Patent Document 1).

  Even in a photomask with a pellicle mounted, defects have recently occurred depending on the usage environment. This is due to the fogging caused by the combination of organic gas, photomask, sulfuric acid and ammonia present in the atmosphere with high exposure light energy, as well as foreign matter floating around. Is due to the effect of gradually depositing on the photomask.

  When foreign matter adheres to the photomask or when cloudiness accumulates over a certain level, it is necessary to clean the photomask in order to remove the foreign matter and cloudiness. However, the pellicle is attached to the photomask via a strong adhesive, and even if the pellicle is peeled off from the photomask, the adhesive remains on the photomask. The adhesive remaining on the photomask cannot be easily removed, and cleaning with sulfuric acid or strong alkali is considered to cause damage to the pattern, and there is a need for technology and members that do not leave the adhesive on the photomask substrate. (See Patent Document 2).

JP 2011-100016 A Japanese Patent No. 4403775

  The method using an adhesive as disclosed in Patent Document 1 has a problem that the adhesive remains on the photomask when the pellicle is peeled off.

  Further, the method of adjusting the pressure inside the space between the pellicle and the photomask as disclosed in Patent Document 2 has a problem that a mechanism such as a gas supply pipe or a gas discharge pipe is required.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a pellicle and a photomask that can be easily washed after being attached or detached without requiring an adhesive or new equipment.

  The invention according to claim 1 is a pellicle used for protecting a photomask, wherein the pellicle film, a pellicle frame that supports the pellicle film, an adhesive layer that bonds the pellicle film to the pellicle frame, and the pellicle film And a peeling jig insertion hole provided in the pellicle frame.

  The invention according to claim 2 is characterized in that, in the pellicle according to claim 1, the mounting layer is made of carbon nanofibers.

  The invention according to claim 3 is characterized in that, in the pellicle according to claim 2, the formation density of carbon nanofibers is at least 100 million per square millimeter.

  According to a fourth aspect of the present invention, a photomask having the pellicle according to any one of the first to fourth aspects is attached.

  According to the present invention, it is possible to easily realize peeling of the pellicle without leaving a mounting mark on the photomask while realizing reliable mounting of the photomask and the pellicle. Therefore, even if the pellicle is peeled off from the photomask during photomask cleaning, no adhesive remains on the photomask, and damage due to cleaning can be reduced.

It is a block diagram which shows the pellicle which concerns on one embodiment of this invention, The figure (a) shows the state seen from the upper surface side typically, The figure (b) shows the figure (a) A- A cross section cut along A ′ is schematically shown. FIGS. 2A and 2B are configuration diagrams illustrating an enlarged main part of FIG. 1, in which FIG. 1A shows a peeled state of the pellicle, and FIG. 1B shows a mounted state of the pellicle. FIGS. 2A and 2B are diagrams for explaining the effect of the pellicle of FIG. 1, in which FIG. 1A shows an observation result of an example of the pellicle according to the present invention, and FIG. 1B shows a measurement result of a comparative example. .

  Hereinafter, a pellicle and a photomask according to embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic structure of a pellicle according to an embodiment of the present invention, which is used as a light-proof dust-proof cover that constitutes a photomask, for example, is placed on a quartz substrate 21.

  A pellicle 10 according to the present invention includes a mounting layer 5 formed of a pellicle film 1, a pellicle frame 6, and carbon nanofibers 4. A mounting layer 5 is formed on the lower surface of the pellicle frame 6, and an adhesive layer 2 is formed on the upper surface of the pellicle frame 6. A pellicle film 1 is stretched on the upper surface of the pellicle frame 6 with an adhesive layer 2 interposed therebetween. A jig hole 7 for inserting a peeling jig is formed in the outer frame of the pellicle frame 6.

  The pellicle film 1 has translucency, traps foreign matter, and is formed of a transparent thin film.

  Here, the pellicle frame 6 is provided to hold the pellicle film 1 and is preferably blackened to prevent light scattering during exposure, and the shape affects the exposed portion. Any shape is acceptable as long as it is not. In addition, the pellicle frame 6 may be provided with an adhesive on the inner wall portion for the purpose of preventing dust generation and preventing the dust generated from other sources from being present in the exposed portion.

  The material of the pellicle frame 6 may be any material as long as it is resistant to ultraviolet light and the generation of outgas is small. Usually, metals and metal oxides are used, and examples thereof include oxides such as Cr, Ti, Mo, Si, Al, Zr, and alloys thereof. The pellicle frame 6 is provided with a filter (not shown) for adjusting the pressure difference between the inside and outside of the pellicle frame 6.

  The pellicle film 1 is held by the pellicle frame 6 and is provided so as to cover the exposure area of the photomask 20. For this reason, the pellicle film 1 has translucency so as not to block energy by exposure. Further, the pellicle film 1 is stretched so that a uniform force is applied to the pellicle frame 6 so as not to make a shadow on the surface of the photomask 20 due to wrinkles or the like.

  The pellicle film 1 and the pellicle frame 6 are stretched through an adhesive of the adhesive layer 2. The adhesive for the adhesive layer 2 may be any material as long as the adhesive strength between the pellicle film 1 and the pellicle frame 6 is sufficient. Examples of the material include acrylic resin, epoxy resin, polybutene resin, and silicone resin. Further, as the pellicle film 1, a transparent film such as fluorine-based or cellulose acetate, quartz glass, or the like can be used.

  The jig holes 7 are provided at two locations near the corner of the opposite side of the pellicle frame 6 and a total of four or more locations on both sides, and are used for attaching and peeling the pellicle frame 6.

  The filter (not shown) is provided in order to prevent dust from entering through a hole that exists in the side surface of the pellicle frame 6 to relieve the pressure difference between the inside and outside. As this filter (not shown), polypropylene (PP), pertetrafluorofuran (PTFE), etc. used for HEPA filters and ULPA filters can be used.

  The photomask 20 has a light shielding film 22 covered with a metal such as Cr or MoSi having a single layer or multiple layer structure on a quartz substrate 21, and a pattern is formed by the light shielding film 22.

  In the pellicle 10, the mounting layer 5 is composed of the carbon nanofibers 4 shown in FIG. When the photomask 20 and the pellicle 10 of the present invention are in contact via the mounting layer 5, an intermolecular force is generated between the photomask 20 and the carbon nanofiber 4, and the photomask 20 is attached to the mounting layer 5. Is supported with a certain adsorption force. This adsorption force is generated both in the air and in a vacuum, and the greater the number of carbon nanofibers per unit area, the greater the force.

  By using the mounting layer 5, the pellicle 10 is mounted on the photomask 20 without using an adhesive in the atmosphere, so that no adhesive remains on the surface of the photomask 20 after the pellicle 10 is peeled off. As a result, the photomask 20 can be easily cleaned.

  Next, a pellicle 10 according to the present invention was manufactured as an example, mounted on the photomask 20 through the mounting layer 5, and a comparative example in which the photomask and the pellicle were bonded together using an adhesive was manufactured. These are observed and compared with an optical microscope.

(Example)
As an example, carbon nanofibers 4 having a diameter of 10 nm and a height of 1 μm are grown by introducing methane, which is a raw material gas, into a reaction tube in which a substrate is installed and decomposing methane on the heated substrate. A pellicle 10 according to the present invention having a mounting layer 5 formed at a density of about 200 million per square millimeter is manufactured, and a pressure of 25 kfg is applied to the pellicle 10 with a mounter for 2 minutes to form a photomask. The light shielding film 22 was attached to the quartz substrate 21 on which no light shielding film 22 was formed by intermolecular force.

  Thereafter, it was removed from the mounter, and it was confirmed that the mounting of the pellicle 10 of the present invention was maintained even when the pellicle 10 was directed to the lower side of the quartz substrate 21.

  After being left for one week with the pellicle 10 of the present invention mounted on the quartz substrate 21, a pin-shaped jig (not shown) is inserted into the jig hole 7 to lift the pellicle 10 of the present invention, and the quartz substrate 21 is lifted. Peeled off.

  The site of the mounting layer 5 in the photomask 20 was observed for the pellicle peeling trace with an optical microscope. As a result of the observation, as shown in FIG. 3A, the pellicle mounting trace was not confirmed from the quartz substrate 21 peeled off after mounting the pellicle 10 according to the present invention.

(Comparative example)
As a comparative example, a photomask and a pellicle were bonded together with a mask adhesive. Then, after the liner on the mask adhesive applied to the pellicle frame of the pellicle is peeled off, the pellicle frame is bonded to the specified position of the photomask, and a pressure of 25 kfg is applied for 2 minutes with a simple mounter to form a light shielding film. It was mounted on a quartz substrate on which no film was formed.

  After being left for 1 week with the pellicle mounted on the quartz substrate, a pin-shaped jig (not shown) was inserted into the jig hole, and the pellicle was lifted and peeled off from the quartz substrate.

  The pellicle peeling trace was observed with an optical microscope for the mask adhesive portion in the photomask. As a result of the observation, as shown in FIG. 3B, it was confirmed that the mask adhesive 3 was attached to the quartz substrate which was peeled off after the pellicle was mounted.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  For example, even if some constituent elements are deleted from all the constituent elements shown in the embodiment, the problems described in the column of problems to be solved by the invention can be solved, and the effects described in the effects of the invention can be obtained. In some cases, a configuration from which this configuration requirement is deleted can be extracted as an invention.

  According to the present invention, there is provided a pellicle that is mounted to prevent foreign matter from directly adhering to the surface of the photomask and that can be easily peeled without leaving a mounting mark, and a pellicle that is easy to peel off. A photomask can be provided.

DESCRIPTION OF SYMBOLS 1 ... Pellicle film 2 ... Adhesion layer 3 ... Mask adhesive 4 ... Carbon nanofiber 5 ... Mounting layer 6 ... Pellicle frame 7 ... Jig hole 10 ... Pellicle 20 ... Photomask 21 ... Quartz substrate 22 ... Light shielding film

Claims (4)

In the pellicle used to protect the photomask,
A pellicle membrane;
A pellicle frame that supports the pellicle membrane;
An adhesive layer for bonding the pellicle film to the pellicle frame;
A mounting layer for mounting the pellicle film to the photomask;
A peeling jig insertion hole provided in the pellicle frame;
A pellicle characterized by comprising:   The pellicle according to claim 1, wherein the mounting layer is formed of carbon nanofibers.   The pellicle according to claim 2, wherein the formation density of the carbon nanofibers is at least 100 million per square millimeter.   A photomask having the pellicle according to claim 1 attached thereto.

Images