Pellicle frame and process for manufacturing same

Abstract

Provided is a pellicle frame that can prevent generation of haze and reduces a surface glittering defect under irradiation with collected light, and a method of manufacturing the same. The pellicle frame is obtained by using an aluminum frame material having a structure satisfying predetermined conditions on the circle-equivalent diameters of a Mg.sub.2Si crystallized product, an AlCuMg crystallized product, an AlFe-based crystallized product (Al.sub.mFe or Al.sub.7Cu.sub.2Fe), and an Al.sub.2CuMg crystallized product and on the area ratios of those crystallized products each having a circle-equivalent diameter of 1 m or more, and in addition, subjecting the aluminum frame material to anodic oxidation processing using an alkaline electrolytic solution containing as an electrolyte a predetermined organic acid salt. In addition, the method of manufacturing a pellicle frame includes: preparing an aluminum frame material having a structure as described above; and subjecting the aluminum frame material to anodic oxidation processing using an alkaline electrolytic solution containing a predetermined organic acid salt, to form an anodic oxide film.

Claims

1. A pellicle frame, comprising: an aluminum frame; an anodic oxide film formed on a surface of the aluminum frame, wherein the aluminum frame comprises an Al-Zn-Mg-based aluminum alloy having a structure, in which a Mg.sub.2Si crystallized product has a maximum circle-equivalent diameter of 7 m or less, an area ratio of a Mg.sub.2Si crystallized product having a circle-equivalent diameter of 1 m or more is less than 0.10%, an AlCuMg crystallized product, an Al-Fe-based crystallized product, and an Al.sub.2CuMg crystallized product each have a maximum circle-equivalent diameter of 9 m or less, and a total area ratio of an AlCuMg crystallized product, an Al-Fe-based crystallized product, and an Al.sub.2CuMg crystallized product each having a circle-equivalent diameter of 1m or more is less than 0.20%; the anodic oxide film is obtained through anodic oxidation processing using an alkaline electrolytic solution containing as an electrolyte any one kind or two or more kinds selected from the group consisting of dicarboxylic acid salts and tricarboxylic acid salts; the pellicle frame having less than 0.005 ppm of a concentration of a sulfate ion (SO.sub.4.sup.2-) in terms of concentration to be eluted in 100 ml of pure water per 100 cm.sup.2 of a surface area of the pellicle frame; the aluminum frame is obtained by subjecting a DC cast billet to homogenization processing comprising heating and retaining the DC cast billet at a temperature of 460 C. or more for 12 hr or more in total; and the DC cast billet satisfies a JIS A7075 standard and comprises 0.30 mass % or less of Mn, 5.1 to 6.1 mass % of Zn, 0.25 mass % or less of total amount of Zr and Ti, 2.1 to 2.6 mass % of Mg, 1.2 to 1.6 mass % of Cu, 0.18 to 0.28 mass % of Cr, 0.07 mass % or less of Fe, 0.04 mass % or less of Si, and the balance of Al.

2. A pellicle frame according to claim 1, wherein the homogenization processing comprises: first homogenization processing comprising heating and retaining the DC cast billet at a temperature of 460 C. or more for 12 hr or more in total; and second homogenization processing comprising retaining the DC cast billet at a temperature higher than the temperature of the first homogenization processing for 1 hr or more in total.

3. A pellicle frame according to claim 1 or 2, wherein the anodic oxide film is dyed with a black dye.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1A and 1B are schematic views for illustrating a hollow extruded profile and an aluminum frame material cut out therefrom produced in Examples.

(2) FIGS. 2A, 2B and 2C are optical micrographs of cut surfaces of aluminum frame materials used in Examples.

DESCRIPTION OF EMBODIMENTS

(3) Preferred embodiments of the present invention are hereinafter described on the basis of Examples and Comparative Examples.

EXAMPLES

Production of Aluminum Frame Material i

(4) A billet was produced by a DC casting method so as to achieve an alloy composition A shown in Table 2. The billet was subjected to homogenization processing including: heating and retaining the billet at 460 C. for 2 hr; increasing the temperature at a rate of 100 C./hr; and heating and retaining the billet at 470 C. for 10 hr, in the atmosphere. Next, the billet after the homogenization processing was cut into a predetermined length, and then extruded to obtain a hollow extruded profile 1 having a rectangle shape illustrated in FIGS. 1A and 1B. Then, the hollow extruded profile 1 was subjected to artificial aging hardening processing under the tempering conditions T651 described in JIS H0001. The hollow extruded profile 1 was cut in a direction perpendicular to an extrusion direction (cut along a cross section) and machined, to produce 50 pieces of aluminum frame materials i in total each having a frame shape and measuring, as external dimensions, 149 mm122 mm5.8 mm in thickness.

Production of Aluminum Frame Material ii

(5) A total of 50 pieces of aluminum frame materials ii were produced in the same manner as in the case of the aluminum frame materials i except that the billet was further subjected to homogenization processing including: increasing the temperature to 480 C. at a rate of 100 C./hr; heating and retaining the billet at 480 C. for 10 hr; then increasing the temperature at a rate of 100 C./hr; and heating and retaining the billet at 500 C. for 10 hr, in addition to the homogenization processing as in the case of the aluminum frame materials i.

Production of Aluminum Frame Material iii

(6) A billet was produced by a DC casting method so as to achieve an alloy composition B shown in Table 2. Then, a total of 50 pieces of aluminum frame materials iii were produced in the same manner as in the case of the aluminum frame materials i.

(7) TABLE-US-00002 TABLE 2 (Unit: mass %) Alloy Al and com- other posi- impu- tion Si Fe Cu Ti Mn Cr Zn Mg rities A 0.019 0.018 1.31 0.041 0.002 0.216 5.29 2.28 Balance B 0.050 0.084 1.63 0.039 0.009 0.228 5.52 2.59 Balance

(8) One aluminum frame material was sampled from each of the obtained aluminum frame materials i to iii, and the cut surfaces (surfaces perpendicular to the extrusion direction of the hollow extruded profile 1) of the aluminum frame materials were each photographed with an optical microscope. Then, an observation field of 9.9610.sup.5 m.sup.2 was arbitrarily selected from the photographed image, and the circle-equivalent diameters of crystallized products and the areas of the crystallized products each having a circle-equivalent diameter of 1 m or more were measured in the observation field with an image analyzer (Luzex).

(9) Herein, FIG. 2A shows a photograph of the cut surface of the aluminum frame material iii. In the photograph, an area coming out relatively dense corresponds to a Mg.sub.2Si crystallized product (an area surrounded by a solid-line circle), and the largest one has a maximum length of about 20 m. In contrast, an area coming out lighter than the Mg.sub.2Si crystallized product corresponds to crystallized products other than the Mg.sub.2Si crystallized product (an area surrounded by a broken-line circle). On the other hand, FIG. 2B shows a photograph of the cut surface of the aluminum frame material i. FIG. 2B shows that all the crystallized products are fine and reduced in number as compared to those in the case of the aluminum frame material iii. In addition, FIG. 2C shows a photograph of the cut surface of the aluminum frame material ii. FIG. 2C shows that all the crystallized products are further fine and reduced in number as compared to those in the case of the aluminum frame materials i and iii. In addition, the crystallized products other than the Mg.sub.2Si crystallized product observed in the cut surfaces of the aluminum frame materials i and iii were identified for their component composition by X-ray analysis. As a result, the crystallized products were found to be an AlCuMg crystallized product, an AlFe-based crystallized product (Al.sub.mFe (3m6) or Al.sub.7Cu.sub.2Fe), and an Al.sub.2CuMg crystallized product as shown in Table 3. It should be noted that the Mg.sub.2Si crystallized product was confirmed to be Mg.sub.2Si by etching using hydrofluoric acid. In addition, in each of FIGS. 2A to 2C, a quadrangular area surrounded by a broken line shown in a photograph on the reader's left represents the largest Mg.sub.2Si crystallized product shown in a photograph on the reader's right.

(10) TABLE-US-00003 TABLE 3 Aluminum AlCuMg Al.sub.2CuMg MgZn.sub.2 AlmFe Mg.sub.2Si frame material 10.5 19.1 22.1 25.7 40.2 iii 1 7.5 1.3 9.6 1.2 2.5 2 7.8 2.0 8.3 1.3 3.0 3 6.3 2.2 9.5 1.4 3.0 ave. 7.2 1.8 9.1 1.3 2.8 std. 0.8 0.5 0.7 0.1 0.3 i 1 9.6 9.5 2 11.1 8.2 3 9.9 8.5 ave. 10.2 8.7 std. 0.8 0.7

(11) As is apparent from the results of the X-ray diffraction shown in Table 3, of the Mg.sub.2Si crystallized product, the AlCuMg crystallized product, the AlFe-based crystallized product (Al.sub.mFe or Al.sub.7Cu.sub.2Fe), and the Al.sub.2CuMg crystallized product, all of those crystallized products were detected in the aluminum frame material iii, but only the AlCuMg crystallized product was detected in the aluminum frame material i. That is, it was confirmed that the Al.sub.mFe crystallized product, the Al.sub.2CuMg crystallized product, and the Mg.sub.2Si crystallized product were reduced in amount and size. It should be noted that Table 3 shows the results of the X-ray diffraction as a diffraction angle of a peak (2) representing respective phases and a value of integral diffraction intensity (unit: kcounts). The aluminum frame materials were each measured three times, and the three measured values, an average (ave.) and standard deviation (std.) thereof were shown as the results.

(12) The measurement using an image analyzer as described above was performed on the respective aluminum frame materials in 58 pieces of cumulative fields. In the measurement, the maximum value and average value of the circle-equivalent diameter of the Mg.sub.2Si crystallized product were determined, and the area ratio of the Mg.sub.2Si crystallized product having a circle-equivalent diameter of 1 m or more with respect to the total area of the cumulative fields was also determined. Table 4 shows the results. Similarly, the maximum value and average value of the circle-equivalent diameter of the AlCuMg crystallized product, AlFe-based crystallized product (Al.sub.mFe or Al.sub.7Cu.sub.2Fe), and Al.sub.2CuMg crystallized product were determined, and the total area ratio of the AlCuMg crystallized product, AlFe-based crystallized product (Al.sub.mFe or Al.sub.7Cu.sub.2Fe), and Al.sub.2CuMg crystallized product each having a circle-equivalent diameter of 1 m or more with respect to the total area of the cumulative fields was also determined. Table 5 shows the results.

(13) TABLE-US-00004 TABLE 4 Circle-equivalent diameter of Mg.sub.2Si Area ratio Relationship between size of circle-equivalent diameter and number crystallized of Mg.sub.2Si Aluminum of grains of Mg.sub.2Si crystallized product product (m) crystallized frame Exceed- Exceed- Exceed- Exceed- Exceed- Exceed- Exceed- Maximum Average product of 1 material ing 10 m ing 9 m ing 8 m ing 7 m ing 6 m ing 5 m ing 4 m value value m or more (%) i 0 0 0 0 3 3 4 6.8 1.2 0.05 ii 0 0 0 0 0 0 0 2.4 1.0 0.02 iii 0 2 3 5 7 10 12 9.5 1.3 0.10

(14) TABLE-US-00005 TABLE 5 Relationship between size of circle-equivalent diameter and number of grains of AlCuMg crystallized product, Al-Fe-based crystallized product (Al.sub.mFe or Circle-equivalent Area ratio of Aluminum Al.sub.7Cu.sub.2Fe), and Al.sub.2CuMg crystallized product diameter (m) crystallized frame Exceed- Exceed- Exceed- Exceed- Exceed- Exceed- Exceed- Maximum Average product of 1 material ing 10 m ing 9 m ing 8 m ing 7 m ing 6 m ing 5 m ing 4 m value value m or more (%) i 0 0 3 6 10 15 26 8.7 0.9 0.12 ii 0 0 3 6 9 13 22 9.5 0.7 0.12 iii 2 3 17 21 53 104 207 10.3 1.6 0.86

Example 1

(15) The obtained aluminum frame material i was subjected to shot blasting processing using stainless steel having an average grain diameter of about 100 m, and then subjected to anodic oxidation processing through electrolysis using as an electrolytic solution an alkaline aqueous solution (pH=13.0) having dissolved therein 53 g/L of sodium tartrate dihydrate (Na.sub.2C.sub.4H.sub.4O.sub.6.2H.sub.2O) and 4 g/L of sodium hydroxide at a bath temperature of 5 C. and a constant electrolysis voltage of 40 V for 15 min. At this time, a dummy material was subjected to anodic oxidation to control the amount of dissolved Al in the electrolytic solution to 0.3 g/L. Then, after being washed with pure water, an anodic oxide film formed on the surface of the aluminum frame material was measured with an eddy current-type film thickness meter (manufactured by Fischer Instruments K.K.) and found to have a thickness of 5 m.

(16) Next, the aluminum frame material subjected to the anodic oxidation processing was put in an aqueous solution containing an organic dye (TAC411 manufactured by Okuno Chemical Industries Co., Ltd.) at a concentration of 10 g/L, and subjected to dyeing processing by being immersed therein at a temperature of 55 C. for 10 min. After the dyeing processing, the aluminum frame material was placed in a steam sealing device and subjected to sealing processing for 30 min while steam having a relative humidity of 100% (R.H.), a pressure of 2.0 kg/cm.sup.2G, and a temperature of 130 C. was generated. Thus, a test pellicle frame according to Example 1 was obtained.

(17) The test pellicle frame according to Example 1 was produced in 50 pieces in the same manner as described above. The 50 pieces of test pellicle frames were each visually observed under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lux (lx), and the number of test pellicle frames in which a white spot involving light reflection was generated was confirmed (even the case where one white spot was present was counted as one). Table 6 shows the results. No white spot was found in the visual observation under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lx.

(18) In addition, one test pellicle frame according to Example 1 was put into a polyethylene bag and the bag was sealed after 100 ml of pure water was added thereto. Then, the test pellicle frame was immersed therein for 4 hr while the temperature was kept at 80 C. After that, extraction water in which eluted components were extracted was analyzed with an ion chromatography analyzer (ICS-2000 manufactured by Dionex Corporation) under the conditions of a cell temperature of 35 C., a column (Ion Pac AS11-HC) temperature of 40 C., and 1.5 ml/min. An acetate ion, a formate ion, a hydrochloride ion, a nitrite ion, a nitrate ion, a sulfate ion, and an oxalate ion were detected from the extraction water, and the concentrations of those ions to be eluted in 100 ml of pure water per 100 cm.sup.2 of the surface area of the pellicle frame were determined. The case where the concentration of a sulfate ion closely associated with haze was less than 0.005 ppm, which was a quantitative limit (lower limit) of the used ion chromatography analyzer, was represented by Symbol 0 in haze evaluation. The case where the concentration of a sulfate ion was 0.005 ppm or more was represented by Symbol x in haze evaluation. Table 4 shows the results. The evaluation revealed that the generation of haze was suppressed in the test pellicle frame according to Example 1.

(19) TABLE-US-00006 TABLE 6 Test pellicle frame Electrolytic Number of pellicle Alu- solution in frames in which a white minum anodic spot is generated Haze frame oxidation Fluorescent Collected evalua- material processing.sup.1) light light tion Example 1 i Na.sub.2C.sub.4H.sub.4O.sub.6 0 0 NaOH Example 2 ii Na.sub.2C.sub.4H.sub.4O.sub.6 0 0 NaOH Example 3 i Na.sub.3C.sub.6H.sub.5O.sub.7 0 0 NaOH Comparative iii Na.sub.2C.sub.4H.sub.4O.sub.6 18 25 Example 1 NaOH Comparative i H.sub.2SO.sub.4 0 0 x Example 2 Comparative ii H.sub.2SO.sub.4 0 0 x Example 3 Comparative iii H.sub.2SO.sub.4 2 3 x Example 4 .sup.1)Na.sub.2C.sub.4H.sub.4O.sub.6 represents sodium tartrate dihydrate, and Na.sub.3C.sub.6H.sub.5O represents sodium citrate dihydrate.

Example 2

(20) A total of 50 pieces of test pellicle frames according to Example 2 were produced in the same manner as in Example 1 except that the aluminum frame material ii was used. The 50 pieces of test pellicle frames were each visually observed under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lux (lx), and the number of test pellicle frames in which a white spot involving light reflection was generated was confirmed. As a result, no white spot was observed in any of the test pellicle frames. In addition, the concentrations of the ions to be eluted in 100 ml of pure water per 100 cm.sup.2 of the surface area of the pellicle frame were measured in the same manner as in Example 1, and the presence or absence of haze was evaluated. Table 6 summarizes the results.

Example 3

(21) A total of 50 pieces of test pellicle frames according to Example 3 were produced in the same manner as in Example 1 except that an alkaline aqueous solution (pH=13.0) containing 120 g/L of sodium citrate dihydrate (Na.sub.3C.sub.6H.sub.5O.sub.7.2H.sub.2O) and 4 g/L of sodium hydroxide was used as the electrolytic solution. The 50 pieces of test pellicle frames were each visually observed under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lux (lx), and the number of test pellicle frames in which a white spot involving light reflection was generated was confirmed. As a result, no white spot was observed in any of the test pellicle frames. In addition, the concentrations of the ions to be eluted in 100 ml of pure water per 100 cm.sup.2 of the surface area of the pellicle frame were measured in the same manner as in Example 1, and the presence or absence of haze was evaluated. Table 6 summarizes the results.

Comparative Example 1

(22) A total of 50 pieces of test pellicle frames according to Comparative Example 1 were produced in the same manner as in Example 1 except that the aluminum frame material iii was used. The 50 pieces of test pellicle frames were each visually observed under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lux (lx), and the number of test pellicle frames in which a white spot involving light reflection was generated was confirmed. As a result, white spots were observed in 18 pieces of the test pellicle frames under irradiation with fluorescent light and in 25 pieces of the test pellicle frames under irradiation with collected light. In addition, the concentrations of the ions to be eluted in 100 ml of pure water per 100 cm.sup.2 of the surface area of the pellicle frame were measured in the same manner as in Example 1, and the presence or absence of haze was evaluated. The results were found to be the same as those obtained in Example 1.

Comparative Examples 2 to 4

(23) In each of the cases of using the aluminum frame material i (Comparative Example 2), using the aluminum frame material ii (Comparative Example 3), and using the aluminum frame material iii (Comparative Example 4), a total of 50 pieces of test pellicle frames were produced in the same manner as in Example 1 except that 160 g/L of a sulfuric acid aqueous solution was used as the electrolytic solution and the electrolysis was performed at a bath temperature of 20 C. and a constant electrolysis voltage of 17 V for 19 min.

(24) In the same manner as in Example 1, the obtained test pellicle frames according to Comparative Examples 2 to 4 were each visually observed under irradiation with fluorescent light and under irradiation with collected light at an illuminance of 300,000 lux (lx), and the number of test pellicle frames in which a white spot involving light reflection was generated was confirmed. As a result, it was found that no white spot was observed in any of the test pellicle frames of Comparative Examples 2 and 3. In contrast, in the test pellicle frames of Comparative Example 4, white spots were observed in two pieces of the test pellicle frames under irradiation with fluorescent light and in three pieces of the test pellicle frames under irradiation with collected light.

(25) In addition, the concentrations of the ions to be eluted in 100 ml of pure water per 100 cm.sup.2 of the surface area of the pellicle frame were measured in the same manner as in Example 1. As a result, it was confirmed that haze was highly likely to be generated in the pellicle frames of Comparative Examples 2 to 4.

INDUSTRIAL APPLICABILITY

(26) A pellicle device using the pellicle frame of the present invention exhibits particularly excellent effects in an environment of exposure with high-energy light. In addition, the surface glittering defect of the pellicle frame falsely recognized as dust is reduced, and hence the pellicle device can be extremely preferably utilized in the field of manufacturing of a semiconductor device or the like in which thinning increasingly progresses in the future.

REFERENCE SIGNS LIST

(27) 1: hollow extruded profile 2: aluminum frame material 2a: cut surface of aluminum frame material