Pellicle frame and pellicle

Abstract

The present invention provides a pellicle frame which can effectively inhibit deformation of an exposure master plate (8) caused by affixing the pellicle (1), and which does not have a complex shape, and a pellicle which uses said pellicle frame are provided. The pellicle frame with an anodized film on a surface of an aluminum alloy frame is characterized in that: the aluminum alloy frame comprises an aluminum alloy which contains Ca: 5.0 to 10.0% by weight with the remainder aluminum and unavoidable impurities are contained, and has an area (volume) ratio of an Al.sub.4Ca phase, which is a dispersed phase, is greater than or equal to 25%, and a crystal structure of a part of the Al.sub.4Ca phase is monoclinic; wherein the anodized film contains Al.sub.4Ca particles.

Claims

1. A pellicle frame with an anodized film on a surface of an aluminum alloy frame, characterized in that: the aluminum alloy frame comprises an aluminum alloy which contains Ca: 5.0 to 10.0% by weight with the remainder aluminum and unavoidable impurities are contained, and has an area (volume) ratio of an Al.sub.4Ca phase, which is a dispersed phase, is greater than or equal to 25%, and a crystal structure of a part of the Al.sub.4Ca phase is monoclinic; wherein the anodized film has Al.sub.4Ca particles.

2. The pellicle frame according to claim 1, wherein a V content and a Fe content of the aluminum alloy are 0.0001 to 0.005% by weight and 0.05 to 1.0% by weight, respectively.

3. The pellicle frame according to claim 1, wherein an average crystal grain size of the Al.sub.4Ca phase is 1.5 m or less.

4. A method for manufacturing a pellicle frame, comprising: a first step for obtaining an aluminum alloy plastic worked by subjecting an aluminum alloy ingot which contains 5.0 to 10.0% by weight of Ca with the remainder aluminum and inevitable impurities, and has a volume ratio of an Al.sub.4Ca phase which is a dispersed phase of 25% or more to a plastic working, a second step for subjecting the aluminum alloy plastic worked to a heat treatment in a temperature range of 100 to 300 C., and a third step for subjecting the heat-treated aluminum alloy plastic worked to an anodizing treatment with an alkaline electrolytic solution containing an alkali metal and/or an alkaline earth metal as an electrolyte, or an alkaline electrolytic solution containing at least one organic acid selected from maleic acid, oxalic acid, salicylic acid and citric acid.

5. The method for manufacturing a pellicle frame according to claim 4, wherein a V content and a Fe content of the aluminum alloy are 0.0001 to 0.005% by weight and 0.05 to 1.0% by weight, respectively.

6. The method for manufacturing a pellicle frame according to claim 5, wherein, before the first step, the aluminum alloy ingot is subjected to a heat treatment where the ingot is maintained at a temperature of 400 C. or more.

7. The method for manufacturing a pellicle frame according to claim 4, wherein, after the third step, a secondary electrolytic coloring is further achieved with an electrolytic solution containing a metal salt.

8. A pellicle comprising the pellicle frame according to claim 1 and a pellicle film supported by the pellicle frame.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic cross-sectional view showing one example of the pellicle of the present invention configured using the pellicle frame of the present invention.

(2) FIG. 2 is a schematic plan view showing one example of the pellicle frame of the present invention.

(3) FIG. 3 is an X-ray diffraction pattern of the aluminum alloy plastic worked obtained in Example.

(4) FIG. 4 is an optical microscopic photograph of the cross section of the pellicle frame of Example.

(5) FIG. 5 is a SEM photograph of the cross section relating to the pellicle frame of Example.

(6) FIG. 6 is a SEM photograph of the cross section relating to the pellicle frame of Comparative Example 2.

EMBODIMENTS FOR ACHIEVING THE INVENTION

(7) Hereinafter, representative embodiments of the pellicle frame and the pellicle of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to only these examples. In the following description, the same or equivalent parts are denoted by the same numerals, and there is a case that redundant explanation may be omitted. In addition, since the drawings are for conceptually explaining the present invention, dimensions of the respective constituent elements expressed and ratios thereof may be different from actual ones.

(8) 1. Pellicle Frame and Pellicle

(9) The pellicle frame of the present invention is a pellicle frame characterized by being made of an AlCa alloy, and by stretching and affixing a pellicle film on one end surface of the pellicle frame via an adhesive for pellicle film, it is possible to use as a pellicle frame for lithography.

(10) A schematic sectional view of one example of the pellicle of the present invention constituted by using the pellicle frame of the present invention and a schematic plan view of the pellicle frame of the present invention are shown in FIG. 1 and FIG. 2, respectively. The pellicle 1 is obtained by stretching and affixing a pellicle film 6 on the upper end surface of a pellicle frame 2 via an adhesive layer 4 for affixing the pellicle film. When using the pellicle 1, a pressure sensitive adhesive layer 10 for adhering the pellicle 1 to the exposure master plate (mask or reticle) 8 is formed on the lower end surface of the pellicle frame 2, and a liner (not shown) is peelably adhered to the lower end surface of the pressure sensitive adhesive layer 10.

(11) It is preferable that the pellicle frame 2 is made of an AlCa alloy, and the AlCa alloy is processed as a hot extruded material or a hot rolled material, or manufactured by a die casting method. By using these methods, it is possible to efficiently obtain an AlCa alloy having both the low Young's modulus and the mechanical strength required for the pellicle frame. The process steps of the hot extrusion, hot rolling, and die casting are not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known methods can be used.

(12) The AlCa alloy is not particularly limited as long as the effect of the present invention is not impaired, and various conventionally known AlCa alloys can be used, but it is necessary that the alloy has Ca: 5.0 to 10.0% by weight with the remainder aluminum and unavoidable impurities, the area (volume) ratio of the Al.sub.4Ca phase which is the dispersed phase is greater than or equal to 25%, and the crystal structure of a part of the Al.sub.4Ca phase is monoclinic.

(13) By adding Ca, a compound of Al.sub.4Ca can be prepared, and the effect of lowering the Young's modulus of the aluminum alloy can be achieved. The effect becomes remarkable when the content of Ca is greater than or equal to 5.0%. Conversely, when added in excess of 10.0%, the castability decreases, particularly casting by continuous casting such as DC casting becomes difficult, and thus it is necessary to manufacture by a method with high production cost such as a powder metallurgy method. In the case of manufacturing by a powder metallurgy method, oxides formed on the surface of the alloy powder may get mixed in the product, which may lower the yield strength.

(14) The crystal structure of the Al.sub.4Ca phase used as the disperse phase is basically tetragonal. However, as the present inventors' extensive study, it was found that when the Al.sub.4Ca phase has monoclinic crystal structure, the yield strength is not so decreased but the Young's modulus decreased greatly. Here, by setting the volume ratio of the Al.sub.4Ca phase to greater than or equal to 25%, the Young's modulus can be greatly decreased while maintaining the yield strength as it is.

(15) It is preferable that the AlCa alloy contains a V content and a Fe content of the aluminum alloy are 0.0001 to 0.005% by weight and 0.05 to 1.0% by weight, respectively. When V is present in the AlCa alloy in an amount of around 1%, a compound having a size of 30 m or more is formed with Ca, Ti, Al or the like, and white spot defects sometimes become apparent after the anodizing treatment. On the other hand, by inhibiting the V content within the range of 0.0001 to 0.005% by weight, it is possible to inhibit the white spot defects.

(16) Also, when casting the AlCa alloy, there is a case that a fine eutectic structure may be formed in the vicinity of the a phase (Al phase), and after subjecting the AlCa alloy having the fine eutectic structure to plastic working, when applying the anodizing treatment, the portion corresponding to the fine eutectic texture is emphasized in black due to the difference in the structure, which results in a black defect. On the other hand, the AlCa alloy to which 0.05 to 1.0% by weight of Fe is added is made coarse and has a homogeneous cast structure to make the fine eutectic is blurred, so that it can be prevented from becoming black defects.

(17) Further, the average crystal grain size of the Al.sub.4Ca phase is preferably smaller than or equal to 1.5 m. By dispersing finer Al.sub.4Ca phases, it is possible to promote the blackening after the anodizing treatment.

(18) A powder sintered material may also be used for the above AlCa alloy. In order to improve the flatness of the exposure master plate (mask or reticle) 8 after adhering the pellicle 1, the pellicle frame 2 having a low Young's modulus is required. Comparing with general aluminum alloys, the AlCa alloy has a low Young's modulus, and in addition thereto, a Young's modulus thereof can be set to a lower value by using the powder sintered material having voids.

(19) The AlCa alloy is not particularly limited as long as the effects of the present invention are not impaired, and various conventionally known AlCa alloys can be used, but, according to the crystal structure, shape control, and the like of the Al.sub.4Ca crystal, it is preferable to use an AlCa alloy that achieves both the low Young's modulus and the excellent rolling processability.

(20) As described above, the distortion of the exposure master plate (mask or reticle) 8 by affixing the pellicle 1 to the exposure master plate (mask or reticle) 8 is greatly affected by the distortion of the pellicle frame 2. At the time of the affixing, the pellicle frame 2 is deformed, and the exposure master plate (mask or reticle) 8 is deformed by the deformation stress that tries to back to the original shape. Since the deformation stress depends on the Young's modulus of the material constituting the pellicle frame 2 and the deformation amount thereof, by using an AlCa alloy having a low Young's modulus, it is possible to realize the pellicle frame 2 having a small deformation stress when affixes the pellicle 1 to the exposure master plate (mask or reticle) 8.

(21) As the material of the pellicle frame 2, for example, it is possible to use a material which is obtained by processing the powder sintered body of the AlCa alloy as a hot extruded material. When achieving the hot processing such as hot forging or hot extrusion of the AlCa alloy powder material, though defects such as blister may be generated in some cases, by hot-extruding the AlCa alloy powder sintered body, it is possible to obtain a material in which occurrence of the defect is inhibited.

(22) The method for preparing the hot extruded AlCa alloy powder material used as the material of the pellicle frame 2 is not particularly limited, but it is preferably prepared by molding a raw material powder through a CIP method or the like (for example, AlCa alloy powder prepared by a quenched solidification method such as an atomizing method, a mechanical alloying method, or the like), heating and sintering the AlCa alloy powder molded body in vacuum or in an inert gas atmosphere, cooling the sintered body in vacuum or in an inert gas atmosphere, and hot-extruding the obtained sintered body. Here, the porosity of the hot extruded AlCa alloy powder material can be appropriately controlled depending on the compacting condition, the sintering condition, the extrusion condition, the oxidation state of the surface of the raw powder material, and the like.

(23) Further, in the material of the pellicle frame 2, it is preferable that the Ca content of the AlCa alloy is 0.5 to 15% by mass. When the Ca content is greater than or equal to 0.5% by mass, an Al.sub.4Ca phase is properly formed, and the Young's modulus can be effectively reduced. In addition, when the Ca content is smaller than or equal to 15% by mass, the amount of Al.sub.4Ca phase does not become too large, and it is possible to inhibit that the material becomes brittle, which results in giving the sufficient strength.

(24) In order to form a uniform anodized film, an etching treatment using an acid or an alkali may be achieved as a pretreatment, and in order to facilitate detection when dust or the like adheres to the obtained frame body, a blast treatment or the like may be applied. On the other hand, in order to increase the degree of cleaning, cleaning treatment such as pure water cleaning, hot water cleaning, ultrasonic cleaning or the like may be achieved after the anodizing treatment, the coloring treatment and the sealing treatment.

(25) The shape of the pellicle frame 2 is not particularly limited as long as the effects of the present invention are not impaired and can be various conventionally known shapes according to the shape of the exposure master plate (mask or reticle) 8, but, in general, the plane shape of the pellicle frame 2 is a ring shape, a rectangular shape or a square shape and has a size and shape to cover the circuit pattern portion provided on the exposure master plate (mask or reticle) 8. In addition, the pellicle frame 2 may be provided with an air pressure adjustment vent (not shown), a dust removal filter (not shown) for the vent, jig holes (not shown), and the like.

(26) The height (thickness) of the pellicle frame 2 is preferably 1 to 10 mm, more preferably 2 to 7 mm, and most preferably 3 to 6 mm. By setting the height (thickness) of the pellicle frame 2 to these values, the deformation of the pellicle frame 2 can be inhibited, and good handling property can be ensured.

(27) The cross-sectional shape of the pellicle frame 2 is not particularly limited as long as the effects of the present invention are not impaired and can be various conventionally known shapes, but it is preferable that the cross-sectional shape is a quadrilateral in which the upper side and the lower side are parallel. There are required a width for affixing the pellicle film 6 is required on the upper side of the pellicle frame 2, and a width for adhering to the exposure master plate 8 by providing the adhesive layer 10 for pressure sensitive adhesion on the lower side. For this reason, the width of the upper side and the lower side of the pellicle frame 2 is preferably about 1 to 3 mm.

(28) The flatness of the pellicle frame 2 is preferably smaller than or equal to 20 m, more preferably smaller than or equal to 10 m. By improving the flatness of the pellicle frame 2, it is possible to reduce the deformation amount of the pellicle frame 2 when the pellicle 1 is attached to the exposure master plate (mask or reticle) 8. The flatness of the pellicle frame 2 is calculated by calculating a virtual plane by measuring the height at a total of 8 points including 4 corners of the pellicle frame 2 and 4 central points of the four sides, and then calculating from the difference obtained by subtracting the lowest point from the highest point among the distances of each point.

(29) 2. Method for Manufacturing Pellicle Frame

(30) The method for manufacturing a pellicle frame of the present invention is a method for manufacturing a pellicle frame, comprising: a first step for obtaining an aluminum alloy plastic worked (aluminum alloy to be plastic-worked) by subjecting an aluminum alloy ingot which contains 5.0 to 10.0% by weight of Ca with the remainder aluminum and inevitable impurities, and has a volume ratio of an Al.sub.4Ca phase which is a dispersed phase of 25% or more to a plastic working, a second step for subjecting the aluminum alloy plastic worked to a heat treatment in a temperature range of 100 to 300 C., and a third step for subjecting the heat-treated aluminum alloy plastic worked to an anodizing treatment with an alkaline electrolytic solution containing an alkali metal and/or an alkaline earth metal as an electrolyte, or an alkaline electrolytic solution containing at least one organic acid selected from maleic acid, oxalic acid, salicylic acid and citric acid.

(31) The Young's modulus of the AlCa alloy varies depending on the amount of the Al.sub.4Ca phase and the crystal structure. Therefore, even if the amount of the Al.sub.4Ca phase is the same, the crystal structure is changed by the plastic working in the first step, and the Young's modulus may be increased in some cases. On the other hand, by achieving a heat treatment (annealing treatment) in the temperature range of 100 to 300 C. after the plastic working, it is possible to return the crystal structure of the Al.sub.4Ca phase to the state before the plastic working and to lower the Young's modulus.

(32) Further, by setting the V content of the aluminum alloy ingot to 0.0001 to 0.005% by weight, it is possible to inhibit the formation of a compound of 30 m or more by reaction with V and Ca, Ti, Al, or the like. As a result, formation of the white spot defects after the anodizing treatment (third step) can be inhibited.

(33) Furthermore, by setting the Fe content to 0.05 to 1.0% by weight, it is possible to make the cast structure of the AlCa alloy coarse and uniform. As a result, the fine eutectic structure emphasized after the anodizing treatment (third step) can be blurred, and the formation of the black defects can be inhibited.

(34) Further, before the first step, it is preferable to subject the aluminum alloy ingot to a heat treatment at a temperature of higher than or equal to 400 C. By holding at a temperature of higher than or equal to 400 C. (homogenizing treatment) prior to plastic working, the eutectic structure can be made coarse and uniform. As a result, as described above, the fine eutectic structure can be blurred, and the formation of the black spot defects can be inhibited.

(35) It is preferable that, after the third step, a secondary electrolytic coloring is further achieved with an electrolytic solution containing a metal salt. For example, the secondary electrolysis with an electrolytic coloring solution containing a Ni salt, a Ni+Sn salt or the like makes it possible to further advance blackening and also to reduce white spot and black spot defects.

(36) The representative embodiments of the present invention have been described above, but the present invention is not limited only to these embodiments, and various design changes are possible, and all such design changes are included in the technical scope of the present invention.

EXAMPLES

Example

(37) An aluminum alloy having the composition (% by weight) shown in Sample 1 of Table 1 was cast into an ingot of 8 inches (billet) by a DC casting method and homogenized at 550 C. for 4 hours, and then, plastic-worked at an extrusion temperature of 500 C. to obtain a plate having a width of 180 mma thickness of 8 mm. Thereafter, after cold rolling to a thickness of 3.5 mm, a heat treatment was carried out to hold at 200 C. for 4 hours to obtain the present aluminum alloy plastic worked.

(38) The thus obtained present aluminum alloy plastic worked was machined to produce an aluminum frame in the shape of frame having an external size of 149 mm122 mma thickness 3 mm. After subjecting the obtained aluminum frame material to a shot blasting treatment by using stainless steel grains having an average grain size of about 100 m, the blast-treated aluminum frame material was subjected to the anodizing treatment by using an alkaline aqueous solution (pH=13.7) as an electrolytic solution in which 8 g/L of sodium hydroxide were dissolved, at a bath temperature of 5 C. under a constant voltage electrolysis of an electrolytic voltage of 40 V for 20 minutes. Then, after washing with pure water, by measuring a thickness if the anodized film formed on the surface of the aluminum frame material with an eddy current type film thickness meter (available from Fischer Instruments Co., Ltd.), the thickness was 6.6 m.

(39) Subsequently, the aluminum frame material was placed in a steam sealing apparatus and was subjected to a sealing treatment for 30 minutes while generating steam at a relative humidity of 100% (R.H.), 2.0 kg/cm.sup.2G at a temperature of 130 C. to obtain the present pellicle frame.

(40) FIG. 3 shows the X-ray diffraction pattern of the present aluminum alloy plastic worked. In the X-ray diffraction measurement, a specimen of 20 mm20 mm was cut out from the present plate-like aluminum alloy plastic worked, the surface layer portion was scraped by about 500 m, and then a -2 measurement was carried out with respect to the region from a Cu-K beam source. From the peak position of the Al.sub.4Ca phase in FIG. 3, it can be seen that the tetragonal Al.sub.4Ca phase and the monoclinic Al.sub.4Ca phase are mixed in the present aluminum alloy plastic worked.

(41) The result of the structure observation (optical microscopic photograph) on the cross section of the present pellicle frame is shown in FIG. 4. The black region was the Al.sub.4Ca phase, and the area (volume) ratio of the Al.sub.4Ca phase was measured by an image analysis and was 36.8%.

(42) The present pellicle frame was cut into a test piece, and a tensile strength was measured by a tensile test, and a yield strength and a Young's modulus were measured. The obtained results are shown in Table 2. In addition, the present pellicle frame was cut and aligned to form a 3030 mm surface, and the lightness index L* value was measured using a CR-400 available from KONICA MINOLTA CORPORATION using a Hunter's color difference formula of the pellicle frame of the example. The results are shown in Table 2.

Comparative Example 1

(43) A comparative pellicle frame 1 having an anodized film having a film thickness of 7.1 m was prepared in the same manner as in Example 1 except that the composition (% by weight) shown in Sample 2 in Table 1 was used. A tensile strength, a yield strength, a Young's modulus and an L* value of the comparative pellicle frame 1 were measured in the same manner as in the above example. The obtained results are shown in Table 2.

(44) Further, in the same manner as in the above example, the structure observation on the cross section of the comparative pellicle frame 1 was carried out, and an area (volume) rate of the Al.sub.4Ca phase was measured by an image analysis and found to be 15.9%.

Comparative Example 2

(45) A comparative pellicle frame 2 having an anodized film with a film thickness of 6.6 m was prepared by anodizing in the same manner as in the above example except that 53 g/L of sodium tartrate was added as the electrolytic solution for anodizing treatment. A tensile strength, a yield strength, a Young's modulus and an L* value of the comparative pellicle frame 2 were measured in the same manner as in the above example. The obtained results are shown in Table 2.

(46) TABLE-US-00001 TABLE 1 Ca V Fe Al Sample 1 7.44 0.001 0.05 Bal. Sample 2 2.53 0.001 0.06 Bal.

(47) TABLE-US-00002 TABLE 2 Tensile Yield strength strength Young's modulus (MPa) (MPa) (GPa) L* value Example 224 171 50.2 40.6 Com. Example 1 185 161 62.5 54.2 Com. Example 2 224 171 50.2 78.8

(48) The Young's modulus of the pellicle frame produced from the 7.44% by weight Ca alloy in the example is 50.2 GPa, which is much smaller than that of the Comparative example 1 (62.5 GPa). Here, the Young's modulus of Comparative Example 2 also shows a small value of 50.2 GPa, but the L* value is as large as 78.8.

(49) FIG. 5 and FIG. 6 show SEM photographs (apparatus used: ULTRA PLUS available from ZEISS) of the cross section of the present pellicle frame and the Comparative pellicle frame 2, respectively. In the present pellicle frame, the Al.sub.4Ca phase remains in the anodized film, whereas in the Comparative pellicle frame 2, the Al.sub.4Ca phase is removed from the anodized film due to dissolution, which results in a porous state. From the observation result, it is considered that the L* value increased due to removal of the Al.sub.4Ca phase in the Comparative pellicle frame 2.

EXPLANATION OF SYMBOLS

(50) 1: Pellicle 2: Pellicle frame 4: Adhesive layer for affixing the pellicle film 6: Pellicle film 8: Exposure master plate (mask or reticle) 10: Pressure sensitive adhesion layer