JP2006039407A - Method for manufacturing glass plate, and pellicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass plate having high parallelism and high smoothness and to provide a pellicle having a pellicle plate suitable for an F<SB>2</SB>laser exposure mask. <P>SOLUTION: A synthetic quartz glass plate having ≤0.1 μm/50 mm parallelism and ≤0.15 nm surface roughness (rms) is manufactured by polishing a glass plate by using an abrasive having 10 to 200 nm average particle size and a polishing cloth having ≤10% compression rate and ≤90% elastic compression modulus. A pellicle film 2 comprising the above synthetic quartz glass is adhered to one opening of a pellicle frame 1 in a frame form having openings on the upper face and the bottom face. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a glass plate applicable to a method of manufacturing a pellicle plate used in a pellicle mounted on a mask or reticle (hereinafter, both referred to as a mask) used in an integrated circuit manufacturing process. About.

  In pattern formation on a wafer by an exposure apparatus in a photolithography process of a semiconductor process, a pellicle is attached in order to prevent generation of scratches or adhesion of foreign matters on the mask (or reticle) surface on which a circuit pattern is formed. FIG. 1 is a front view of the pellicle and a cross-sectional view taken along line A-A ′. As shown in FIG. 1, the pellicle includes a pellicle frame 1 that is a rectangular frame and a pellicle film 2 that is attached to the pellicle frame 1 with an adhesive 3.

On the other hand, exposure using short-wavelength light such as an F ₂ laser having a wavelength of 157 nm has been performed due to recent pattern miniaturization and higher density. For this reason, the use of synthetic quartz glass having high durability against short-wavelength light such as an F ₂ laser is also being studied for the pellicle film 2. When synthetic quartz glass is used as the pellicle film, the thickness of the synthetic quartz glass is determined in the range of 0.1 to 2.0 mm in order to achieve both transmittance and processing accuracy. For this reason, the thickness of the pellicle film using synthetic quartz glass is thicker than that of a pellicle film made of fluorine resin or the like that has been conventionally used. This is called a “pellicle plate”.

  Since the pellicle plate made of synthetic quartz glass is thicker than the conventional pellicle film as described above, the exposure light is refracted when the parallelism of the pellicle plate is insufficient or the pellicle plate is warped, etc. In some cases, the dimensional accuracy and position accuracy of the wafer pattern deteriorate. For this reason, the warpage of the pellicle plate adhered on the pellicle frame is required to be 2 μm or less in terms of the PV value (Peak Value value) within the effective range and 0.1 μm / 50 mm or less in parallelism. As means for solving this technical problem, a method for processing a pellicle plate has been devised by the present inventors (see Patent Document 1). In addition, a method for bonding the pellicle plate and the pellicle frame has been devised by the present inventors (see Patent Document 2 and Patent Document 3).

On the other hand, in the case of a pellicle for the purpose of preventing scratches on the mask surface and adhesion of foreign matter, the level of scratches and foreign matter on the surface is reduced compared to the required level for scratches and foreign matter on the mask surface. If there is a foreign substance on the surface, it may be an obstacle to exposure. For this reason, it is required that the surface of the pellicle plate should not be scratched with a size of 38 μm or more, and that no foreign matter with a size of 8 μm or more should be attached.
However, there is no means for efficiently discriminating scratches having a size of about 8 μm on the glass surface and adhering foreign substances, and as a result, there is virtually no demand for scratches having a size of 8 μm or more.

  A general method for obtaining a pellicle plate is described below. Since synthetic quartz glass is sliced from a molded block and processed into a plate, it is necessary to polish the plate after slicing and process it to a predetermined thickness in order to use it as a pellicle plate. For polishing, a double-side polishing apparatus is generally used.

  The polishing of the pellicle plate includes a lapping process that is roughing and a polishing process that is mirrored. In either step, a double-side polishing apparatus is used to perform one-step or multi-step processing.

  An example of a double-side polishing apparatus is shown in FIGS. The polishing apparatus includes a lower surface plate 6 and an upper surface plate 7. In the lapping process, the glass plate 11 is polished by the surface of the surface plate made of cast iron or the like. In the polishing process, a polishing cloth is applied to a surface plate made of stainless steel or the like, and the glass plate 11 is polished. The carrier 8 which is a glass plate holder has an outer peripheral portion processed into a gear. By setting the carrier 8 between the sun gear 9 and the internal gear 10 in the apparatus main body, both or either of the upper and lower surface plates rotate while the carrier 8 rotates, and both surfaces of the glass plate 11 can be polished simultaneously. It is characterized by. Although not shown, the upper surface plate 7 has an abrasive supply hole so that the abrasive can be supplied to the glass plate 11 during polishing.

  In the lapping process, it is common to use an abrasive having a particle size of about # 400 to 1500 mainly composed of silicon carbide or aluminum oxide. In the polishing step, it is common to use an abrasive mainly composed of cerium oxide having an average particle size of 0.8 to 2.0 μm (hereinafter referred to as cerium oxide abrasive) as the abrasive.

  The polishing process is usually performed in two stages. In the first polishing step, a hard material, for example, hard velor, foamed urethane, foamed urethane impregnated with an abrasive, non-woven fabric, etc., is used as the polishing cloth with emphasis on processing efficiency. In the second polishing step, a soft material such as soft velor or suede is used as the polishing cloth for the purpose of reducing surface roughness and scratches.

  At the time of polishing, in order to achieve the high parallelism of the glass plate described above, it is necessary to use a hard polishing cloth and make the polishing amount on both sides uniform. However, when a hard polishing cloth is used, the roughness of the glass plate surface increases, and at the same time, scratches generated by polishing increase. On the other hand, when a soft abrasive cloth is used for the purpose of reducing the surface roughness by polishing or reducing scratches, the surface flatness of the abrasive cloth being polished is not constant, and the polishing speed depends on the portion. However, the polishing amount becomes non-uniform. As a result, the flatness and parallelism of the glass plate are deteriorated. This also occurs when a soft polishing cloth is used for finishing the glass plate once polished with a hard polishing cloth. That is, it can be said that parallelism (or flatness) and surface roughness (or surface scratches) in polishing are governed by contradictory conditions.

JP 2001-312047 A JP 2002-107915 A Japanese Patent Laid-Open No. 2003-307832

In view of the current situation, an object of the present invention is to provide a method for producing a glass plate that can be applied to a pellicle plate used for a pellicle suitable for an F ₂ laser exposure mask.

  As a result of repeated tests using a double-side polishing apparatus conventionally used in the manufacture of pellicle plates, the inventors have obtained polishing conditions for obtaining high smoothness while maintaining high parallelism.

  In aspect 1 of the present invention, a glass plate is polished using an abrasive having an average particle size in the range of 10 to 200 nm, and a polishing cloth having a compression rate of 10% or less and a compression modulus of 90% or less. There is provided a method for producing a glass plate, characterized in that a glass plate having a degree of 0.1 μm / 50 mm or less and a surface roughness (rms) of 0.15 nm or less is obtained.

  Aspect 2 of the present invention is a pellicle comprising a frame-shaped pellicle frame having openings on the top and bottom surfaces, and a glass plate made of synthetic quartz glass bonded to one opening of the pellicle frame, the glass plate Provides a pellicle manufactured by the glass plate manufacturing method of the invention of aspect 1.

  That is, as usual, in the first stage polishing, polishing is performed using a hard polishing cloth and a cerium oxide abrasive having an average particle size of about 0.8 to 2.0 μm, and the parallelism formed by lapping is maintained and improved. However, the crack layer (generally sand) generated in the lapping process is removed with high processing efficiency.

  Next, in the second stage polishing, a hard polishing cloth having a compression rate of 10% or less and a compression modulus of 90% or less is used, and the average particle size is 10 smaller than that of a general polishing abrasive. Use abrasives in the ~ 200 nm range. As a result, it has been found that a surface having a surface roughness or scratch level equal to or higher than that obtained when a conventional soft abrasive and cerium oxide abrasive is used can be obtained without degrading parallelism. It was. Specifically, the manufacturing method of the glass plate whose parallelism is 0.1 micrometer / 50 mm or less and whose surface roughness (rms) is 0.15 nm or less was discovered.

  If processing efficiency is ignored, the initial purpose can be achieved even if the first-stage polishing after the lapping process is omitted and the second-stage polishing is performed directly.

Furthermore, the synthetic quartz glass obtained by the above manufacturing method is used as a pellicle plate, and the pellicle plate is bonded to one opening of a frame-shaped pellicle frame having openings on the top and bottom surfaces, thereby enabling F ₂ laser exposure. A pellicle suitable for a mask can be obtained.

  According to the present invention, a glass plate having a parallelism of 0.1 μm / 50 mm and a surface roughness (rms) of 0.15 nm or less can be obtained.

  The parallelism defined in the present invention refers to two surfaces using a thickness deviation calculated by measuring the thickness of a plurality of points in a glass plate surface using a micrometer or a laser displacement meter, or optical interference. It is calculated | required by measuring the parallelism between.

  The surface roughness can be measured with a contact surface roughness meter, an optical surface roughness meter, or the like, but can be measured with an AFM (atomic force microscope).

  In the present invention, as described above, it is preferable to polish the glass plate to be polished using the double-side polishing apparatus, the polishing cloth, and the abrasive.

  The method for measuring the compressibility and compressive modulus of the polishing cloth in the present invention differs depending on whether the polishing cloth is a suede or a polishing cloth other than the suede. Each measuring method is as follows. In the present invention, the abrasive cloth other than suede means hard velor, soft velor, urethane foam, urethane impregnated with an abrasive, and nonwoven fabric.

First, a measurement method when the polishing pad is sued will be described. A polishing cloth is cut out to about 10 cm × 10 cm and used as a measurement sample. Using a pressure surface having a diameter of 1 cm with a shopper type thickness measuring device, a pressure of 100 g / cm ² is applied to the measurement sample for 30 seconds. Measure the thickness t ₀ of the measurement sample after 30 seconds of application.

Further, a pressure of 1120 g / cm ² is applied to the measurement sample for 300 seconds. 300 seconds test sample after the application measuring a thickness _{t 1.} The measurement sample is left unpressed for 300 seconds, and a pressure of 100 g / cm ² is again applied to the measurement sample for 30 seconds. Measure the thickness t ₀ ′ of the measurement sample after 30 seconds of application. Using the above t ₀ , t ₁ , t ₀ ′, the compressibility and the compressive modulus of the polishing cloth are obtained from the above formulas 1 and 2.

Next, a measurement method when the polishing cloth is other than suede will be described. A polishing cloth is cut out to about 10 cm × 10 cm and used as a measurement sample. Using a pressure surface having a diameter of 1 cm with a shopper type thickness measuring device, a pressure of 300 g / cm ² is applied to the measurement sample for 30 seconds. Measure the thickness t ₀ of the measurement sample after 30 seconds of application.

Further, a pressure of 1800 g / cm ² is applied to the measurement sample for 60 seconds. The thickness t ₁ of the measurement sample after application for 60 seconds is measured. The measurement sample is left unpressed for 60 seconds, and a pressure of 100 g / cm ² of the measurement sample is again applied to the measurement sample for 30 seconds. Measure the thickness t ₀ ′ of the measurement sample after 30 seconds of application. Using the above t ₀ , t ₁ , t ₀ ′, the compressibility and the compressive modulus of the polishing cloth are obtained from the above formulas 1 and 2.

  As the abrasive used in the present invention, an abrasive generally used for glass can be used. Examples thereof include cerium oxide, zirconium oxide, bengara, aluminum oxide, chromium oxide, colloidal silica, and fumed silica. When the relative hardness difference between the abrasive itself and the glass to be polished is large and the abrasive is softer than the glass, the surface roughness of the glass tends to be small. For this reason, it is more preferable to use cerium oxide, colloidal silica, fumed silica or the like among the above abrasives.

  Actually, in order to use these abrasives for polishing, so-called wet polishing in which the abrasive is dispersed in water and used in a slurry state is generally used. In addition to abrasives and water, dispersants for improving polishing efficiency such as anionic, cationic and nonionic surfactants and polyhydric alcohols such as methyl alcohol and IPA (isopropyl alcohol), glass surface It is also possible to add an acid or alkali having a low erosive property, for example, an organic acid such as nitric acid, sulfuric acid or citric acid.

  Further, since the large particles in the abrasive cause scratches, the average particle size of the abrasive is 10 to 200 nm in the particle size D50 in which the integrated particle size distribution is 50% based on the number from the small particle size side. It is preferable that the particle size is within the range, and the particle size D90 that is 90% is more preferably within the same range. Further, it is particularly preferable that the particle size D99 that becomes 99% is in the same range. In the present invention, the average particle diameter of the abrasive refers to the value of D50 of the abrasive.

  The measuring method of the average particle diameter D50 of an abrasive | polishing agent is as follows. Abrasives such as ethanol are diluted and dispersed in an organic solvent. At this time, the concentration of the abrasive is preferably 0.1 to 0.3% by weight. This diluted solution is applied to a sample stage for SEM (scanning electron microscope) observation, and the organic solvent is evaporated and dried. Thereafter, platinum-palladium is deposited on the sample to prepare a measurement sample. This measurement sample is observed using a SEM at a magnification of 50,000 to 100,000, and a photograph is taken. The particle size can be determined from this photograph. The distribution is obtained by moving the field of view of the SEM or observing a plurality of samples, but in order to obtain an accurate distribution, the number of particles to be observed is 500 or more, preferably 1000 or more, more preferably 2000 or more. To be. By integrating the measurement results and adding the frequency (%) from the smaller particle size, the integrated particle size distribution can be obtained. The particle diameter in the present invention can be obtained by setting D50 as the particle diameter at which the integrated frequency is 50%, D90 as the particle diameter at 90%, and D99 as the particle diameter at 99%.

  In particular, in order to reduce the surface roughness due to polishing, D50 is preferably in the range of 10 to 80 nm, D90 is more preferably in the same range, and D99 is particularly preferably in the same range. However, in the case of an abrasive such as cerium oxide in which primary particles are aggregated and secondary particles are present, it is preferable to determine the particle size of the abrasive by the particle size distribution of the secondary particles.

  The concentration at which the abrasive is used is practically about several to 40% by mass. However, if the abrasive is dilute, scratches are likely to occur, and a high concentration is economically disadvantageous. -30 mass% is preferable, and 10-20 mass% is more preferable.

  A polishing cloth that is hard is selected. Specifically, the polishing cloth preferably has a compressibility of 10% or less and a compressive modulus of 90% or less, a compressibility of 3% to 8%, and a compressive modulus of 60. More preferably, it is -90%.

  Hard velours, foamed urethane, foamed urethane impregnated with abrasive, non-woven fabric, etc. can be used in the above-mentioned examples of generally hard abrasive cloth, but impregnated with foamed urethane or abrasive. Urethane foam or the like has insufficient accuracy in the size of the opening of the foam, and the roughness may be uneven. A hard velor or non-woven fabric is preferred.

  When these hard polishing cloths are used, grooves are generally provided on the polishing cloth by means of cutting, thermal deformation, compression or the like in order to improve the flow of the slurry. The grooves at this time are generally processed in a grid shape on the polishing cloth.

  However, the recess formed by the groove of the polishing cloth has little polishing power. In addition, when the carrier 11 and the surface plate 6 shown in FIG. 3 are rotated, a predetermined point on the glass plate 11 and a predetermined point on the surface plate 6 are periodically overlapped. In particular, when the groove pattern of the polishing cloth has a grid shape, the groove portion of the polishing cloth often draws the same locus on the glass plate to be polished at a constant period. For this reason, there exists a possibility that the part with insufficient grinding | polishing may appear in a glass plate surface. Therefore, in order to obtain a highly parallel and highly smooth glass plate as in the present invention, it is preferable to use a polishing cloth without groove processing rather than a grid-like groove pattern. Furthermore, in order to improve the flow of the slurry, it is more preferable to provide radial grooves on the polishing cloth from the center of the surface plate toward the outer periphery.

  Further, the double-side polishing apparatus may use either a 4-way type in which the upper and lower surface plates and the carrier rotate, or a 3-way type in which only the lower surface plate and the carrier rotate, but the straightness of the surface plate before the polishing cloth is attached. Is preferably 2 μm / 100 mm or less. When the diameter of the object to be polished is ½ or more of the effective diameter of the carrier, the center of rotation of the carrier is located in the plane of the glass plate to be polished, so the processing by rotation of the carrier contributes to the surface of the glass plate to be polished. The point that does not occur. In other words, there is a point in the glass plate to be polished that the combined travel distance of the travel distance within the unit time due to the rotation of the surface plate for promoting machining and the travel distance within the unit time due to the rotation of the carrier is only the former. As a result, a difference in polishing rate from the surroundings may occur, resulting in poor flatness. Therefore, it is preferable that the size of the polishing machine can be loaded with a carrier having an effective diameter that is twice or more the diameter of the workpiece.

  The processing method according to this embodiment described above can be used for a synthetic quartz glass pellicle plate. Also, a synthetic quartz glass substrate for high-temperature polysilicon TFT, an ultra-low expansion glass substrate or ultra-low expansion crystal that is a base material for a reflective mask used in lithography processes, particularly used in EUV lithography, in the semiconductor manufacturing process A glass substrate or the like can also be obtained from the production method according to the present invention.

  Next, comparative examples and examples of the present invention will be described. Example 1 below is an example, and Examples 2 and 3 are comparative examples.

  After a synthetic quartz glass material ingot synthesized by a known method is cut into 125 mm × 152 mm × t1.2 mm with a wire saw, the outer dimensions are 122 mm × 149 mm and the end face is R-shaped with a commercially available NC chamfering machine. Forty-five pellicle plate materials that had been chamfered were prepared.

  Next, these materials were immersed in a 5% by mass HF solution to stop the progress of cracks due to cutting and chamfering. Each was lapped to 0.85 mm. At that time, a slurry obtained by suspending 18-20% by mass of FO # 1200 (trade name) manufactured by Fujimi Corporation in filtered water was used as a polishing agent, and a 20B double-sided lapping machine manufactured by Speed Fam was used.

  Further, the same etching treatment as described above was performed on the lapped material. Subsequently, a speed femme 20B double-side polish machine was used, the polishing cloth used was MH-C15A (trade name) manufactured by Rodel Nitta, and Mille 801A (trade name) manufactured by Mitsui Kinzoku Co., Ltd. was used as the abrasive. Polishing was performed to a thickness of 0.805 mm using 45% suspended slurry, and 45 samples after the first stage polishing were collected. At this time, the compressibility of the polishing pad was 3.3%, and the compressive modulus was 89%. These 45 samples were divided into 15 pieces each, and the polishing of the second stage was carried out under different polishing conditions, and the following samples of Examples 1 to 3 were obtained.

<Example 1>
15 pieces of material after the first stage polishing were processed with a Speedfam 20B double-sided polishing machine, the polishing cloth used was SUBA800 (trade name) manufactured by Rodel, and 10 to 10 compol 80 (trade name) manufactured by Fujimi Corporation was used as an abrasive. Polishing was performed at 5 μm on both sides using a slurry in which 12% by mass was suspended. At this time, the compressibility of the polishing pad was 3%, and the compressive elastic modulus was 73%. The average particle diameter D50 of the abrasive was 80 nm.

<Example 2>
15 pieces of the material after the first stage polishing is made of Rodel's SUBA800 (trade name), which is a hard material made of a speed fam 20B double-side polish machine, and Mille 801A is used as an abrasive in an amount of 10 to 12% by mass. 5 μm was polished on both sides using the suspended slurry. At this time, the compressibility of the polishing pad was 3%, and the compressive elastic modulus was 73%. The average particle diameter D50 of the abrasive was 0.86 μm.

<Example 3>
15 Polished materials in the first stage were polished with BELATRIX N7512 (trade name) manufactured by Kanebo Co., Ltd., which is a soft material using a SpeedBam 20B double-sided polishing machine, and the above-mentioned Mille 801A was used as a polishing agent. Polishing was performed on both sides by 5 μm using a slurry in which the mass% was suspended. The abrasive cloth at this time had large variations in physical properties, the compression rate was 5.3 ± 2.0%, and the compression modulus was 80 ± 20%. The average particle diameter D50 of the abrasive was 0.86 μm as in Example 1.

  The polished pellicle plate obtained by the above means is washed and dried with a multi-stage washing machine using a neutral surfactant as a main cleaning agent, and an atomic force microscope (AFM) is used to evaluate the surface roughness. ) SPI3800N (trade name) manufactured by Seiko Instruments Inc., visual inspection in a clean room darkened as an evaluation of scratches, a thickness measuring instrument using laser light as an evaluation of parallelism (Laser Focus Displacement Meter manufactured by Keyence Corporation) Went. In the visual inspection, it has been confirmed by comparing with the observation result of the microscope that it is possible to detect scratches and foreign matters of approximately 10 μm or more by using a light source of 100,000 Lux or more.

  The results of Examples 1 to 3 are shown in Table 1, Table 2, and Table 3, respectively.

The sample of Example 1 using a hard polishing cloth and an abrasive having a small particle diameter gave good results in all items, and the effectiveness of the present invention was confirmed. In the sample of Example 2 using the agent, the average parallelism is as good as 0.081 (μm / 50 mm), but the average surface roughness is as bad as 0.31 nm, and there are many scratches of 100 or more per sheet. It was the result.

  Next, the sample of Example 3 using a soft abrasive cloth and an abrasive having a large particle diameter has an average surface roughness of 0.13 nm, and 0.3 scratches per sheet are good. Is 0.289 (μm / 50 mm) on average, which is worse than the sample of Example 1.

  In addition, not only the apparatus, abrasive | polishing agent, and polishing cloth used in said Example but a kind will be ask | required if equivalent performance and the objective are fulfilled.

The glass plate of the present invention having a parallelism of 0.1 μm / 50 mm or less and a surface roughness (rms) of 0.15 nm or less can be suitably used as a pellicle plate for an F ₂ laser exposure mask pellicle. .

Front view and sectional view of an example of a pellicle Side view of essential parts showing an example of a double-side polishing machine Perspective view of main part showing an example of a double-side polishing apparatus

Explanation of symbols

1. 1. Pellicle frame 2. Pellicle membrane Adhesive 6. Lower surface plate7. Upper surface plate8. Carrier 9. Sun gear 10. Internal gear 11. Glass plate

Claims (2)

An abrasive having an average particle size in the range of 10 to 200 nm;
A polishing cloth having a compression rate of 10% or less and a compression modulus of 90% or less;
Polish the glass plate using
A method for producing a glass plate, comprising obtaining a glass plate having a parallelism of 0.1 μm / 50 mm or less and a surface roughness (rms) of 0.15 nm or less. A pellicle comprising a frame-shaped pellicle frame having openings on an upper surface and a bottom surface, and a glass plate made of synthetic quartz glass bonded to one opening of the pellicle frame, wherein the glass plate is the glass according to claim 1. A pellicle manufactured by a plate manufacturing method.

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