JP5572196B2 - Glass substrate and glass substrate manufacturing method - Google Patents

Description

  The present invention relates to a glass substrate and a method for producing a glass substrate.

  Conventionally, glass substrates have been used in the manufacture of flat panel displays such as liquid crystal display devices. In the manufacturing process of a flat panel display, in order to form a semiconductor element such as a TFT (Thin Film Transistor) on the surface of the glass substrate, the glass substrate is placed on a susceptor in a reaction vessel of a semiconductor manufacturing apparatus, and a film forming process is performed. Is done. In order to form a plurality of types of thin films on a glass substrate, the film forming process is performed a plurality of times by a plurality of semiconductor manufacturing apparatuses. Each time a film forming process is performed, the glass substrate is removed from the susceptor. At this time, static electricity due to friction, that is, peeling electrification occurs between the metal surface of the susceptor on which the glass substrate is placed and the glass substrate surface, and the static electricity is accumulated on the glass substrate. For this reason, a glass substrate on which a plurality of film formation processes has been performed accumulates a large amount of static electricity. In particular, a glass substrate made of alkali-free glass used for a liquid crystal display device is easily charged on the surface, and static electricity is difficult to remove. And when generation | occurrence | production of peeling electrification is repeated, a glass substrate will adhere easily with the static electricity with respect to the metal surface of a susceptor. Thereby, when removing a glass substrate from a susceptor, a glass substrate may be damaged by giving an excessive force to a glass substrate. In addition, a voltage caused by static electricity accumulated due to peeling charging may destroy a semiconductor element formed on the surface of the glass substrate. Furthermore, particles may be attracted to the surface of the glass substrate due to electrostatic charging of the glass substrate.

  Under such circumstances, it has been proposed to manufacture a glass substrate in which surface charging is unlikely to occur in a flat panel display manufacturing process. For example, a glass substrate disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2005-255478) has a first surface on which electrode wires and various devices are formed, and a second surface opposite to the first surface. The second surface is a physically polished or chemically treated surface and has an arithmetic average roughness Ra of 0.3 nm to 10 nm. The glass substrate is prevented from being charged by the roughening treatment of the second surface.

  The roughened surface of the glass substrate has a minute uneven shape. Further, the smaller the contact area between the glass substrate and the table on which the glass substrate is placed, the less peeling charge is generated. Therefore, the larger the number of convex portions of the roughness curve on the surface of the glass substrate, the smaller the contact area between the glass substrate and the table, so that the charging of the glass substrate is more effectively suppressed. However, Ra, which is a kind of parameter representing the degree of roughening of the glass substrate surface, has no correlation with the number of convex portions of the roughness curve of the glass substrate surface. Therefore, even when the surface of the glass substrate is roughened so that Ra is within a predetermined range, the charging of the glass substrate may not be sufficiently suppressed.

  An object of the present invention is to provide a glass substrate in which surface charging is effectively suppressed, and a method for producing the glass substrate.

  The glass substrate which concerns on this invention is a glass substrate for flat panel displays in which a semiconductor element or a color filter is formed. The glass substrate includes a first surface and a second surface. The first surface is a surface on which a semiconductor element or a color filter is formed. The second surface is a surface opposite to the first surface. The second surface has an Rsk that is less than zero. Rsk is a kind of parameter representing the surface irregularity shape measured by an atomic force microscope, and is the skewness of the surface roughness curve.

  The glass substrate has a second surface that has been subjected to a surface treatment such as polishing and etching. A parameter Rsk representing the skewness of the roughness curve of the second surface is smaller than zero. Therefore, the roughness curve of the second surface has a shape with more peaks than the valleys with respect to the surface roughness center plane of the second surface. That is, the ratio of the convex part formed in the 2nd surface is larger than the ratio of a recessed part. Therefore, when the glass substrate is placed on the table, the area of the second surface that contacts the table surface is reduced by the surface treatment. The smaller the contact area between the glass substrate and the table, the more effectively the charging of the glass substrate is suppressed. Therefore, charging of this glass substrate is effectively suppressed.

  The second surface preferably has an Rsk smaller than −0.3.

  More preferably, the second surface has an Rsk greater than −1.5 and less than −0.5.

  The manufacturing method of the glass substrate which concerns on this invention is a manufacturing method of the glass substrate for flat panel displays in which a semiconductor element or a color filter is formed. The method for manufacturing a glass substrate includes a surface treatment process. In the surface treatment step, a second surface which is a surface opposite to the first surface which is the surface of the glass substrate on which the semiconductor element or the color filter is formed is surface-treated. The second surface is surface treated in the surface treatment step so that the second surface that has been surface treated in the surface treatment step has an Rsk less than zero. Rsk is a kind of parameter representing the surface irregularity shape measured by an atomic force microscope, and is the skewness of the surface roughness curve.

  In this glass substrate manufacturing method, the second surface of the glass substrate is subjected to surface treatment such as polishing and etching. A parameter Rsk representing the skewness of the roughness curve of the second surface subjected to the surface treatment is smaller than zero. Therefore, the roughness curve of the second surface has a shape with more peaks than the valleys with respect to the surface roughness center plane of the second surface. That is, the ratio of the convex part formed in the 2nd surface is larger than the ratio of a recessed part. Therefore, when the glass substrate is placed on the table, the area of the second surface that contacts the table surface is reduced by the surface treatment. The smaller the contact area between the glass substrate and the table, the more effectively the charging of the glass substrate is suppressed. Therefore, the glass substrate manufactured by this glass substrate manufacturing method is effectively prevented from being charged.

  In addition, the second surface is preferably surface-treated in the surface treatment step so that the second surface subjected to the surface treatment in the surface treatment step has an Rsk smaller than −0.3.

  Further, the second surface is subjected to the surface treatment in the surface treatment step so that the second surface subjected to the surface treatment in the surface treatment step has an Rsk larger than −1.5 and smaller than −0.5. Is more preferable.

  In the surface treatment step, the second surface is preferably etched using an etchant containing hydrogen fluoride.

  Further, in the second surface subjected to the surface treatment in the surface treatment step, convex portions having a height of 1 nm or more from the surface roughness center plane of the second surface are provided in a dispersed manner, and the second surface of the convex portion is provided. The second surface is preferably surface-treated in the surface treatment step so that the area ratio in the area is within a predetermined range. Thereby, when a glass substrate is mounted on a table, the area of the convex part of the 2nd surface which contacts a table surface increases by surface treatment. Therefore, the glass substrate manufactured by this glass substrate manufacturing method is effectively prevented from being charged.

  As for the glass substrate manufactured by the glass substrate which concerns on this invention, and the manufacturing method of a glass substrate, surface charging is suppressed effectively.

It is sectional drawing of the glass substrate which concerns on embodiment. It is a flowchart which shows the manufacturing method of the glass substrate which concerns on embodiment. It is a figure which shows an example of a dry etching apparatus. It is a figure which shows an example of a wet etching apparatus.

(1) Outline of Glass Substrate Manufacturing Method An embodiment of the present invention will be described with reference to the drawings. The glass substrate 10 manufactured by the glass substrate manufacturing method used in the present embodiment is used for manufacturing flat panel displays (FPD) such as liquid crystal displays, plasma displays, and organic EL displays. The glass substrate 10 has a thickness of 0.2 mm to 0.8 mm, for example, and has a size of 680 mm to 2200 mm in length and 880 mm to 2500 mm in width.

  FIG. 1 is a cross-sectional view of the glass substrate 10. The glass substrate 10 has an element forming surface 12a which is one main surface and a roughened surface 12b which is the other main surface. The element forming surface 12a is a surface on which a plurality of thin films including a semiconductor element such as a TFT, a polysilicon thin film, an ITO (Indium Thin Oxide) thin film, and a color filter are formed in the FPD manufacturing process. Therefore, in general, the element formation surface 12a is an extremely smooth surface having an arithmetic average roughness Ra of 0.2 nm or less. On the other hand, the roughened surface 12b is a surface on which minute irregularities are formed by an etching process in the manufacturing process of the glass substrate 10, as will be described later. In the present embodiment, the roughened surface 12b of the glass substrate 10 is surface-treated by dry etching, wet etching, pad polishing, CMP polishing, tape polishing, or the like.

  An example of the glass substrate 10 is glass having the following composition.

(A) SiO ₂ : 50% by mass to 70% by mass,
(B) Al ₂ O ₃ : 10% by mass to 25% by mass,
(C) B ₂ O ₃ : 5% by mass to 18% by mass,
(D) MgO: 0% by mass to 10% by mass,
(E) CaO: 0% by mass to 20% by mass,
(F) SrO: 0% by mass to 20% by mass,
(G) BaO: 0% by mass to 10% by mass,
(H) RO: 5% by mass to 20% by mass (R is at least one selected from Mg, Ca, Sr and Ba),
(I) R ′ ₂ O: 0% by mass to 2.0% by mass (R ′ is at least one selected from Li, Na and K),
(J) At least one metal oxide selected from SnO ₂ , Fe ₂ O ₃ and CeO ₂ .
The glass having the above composition is allowed to contain other trace components in the range of less than 0.1% by mass.

  The glass substrate 10 is formed by a float method, a down draw method, or the like. In the present embodiment, a manufacturing process of the glass substrate 10 for FPD using the overflow downdraw method will be described. FIG. 2 is an example of a flowchart showing a manufacturing process of the glass substrate 10. The manufacturing process of the glass substrate 10 mainly includes a melting process (step S10), a clarification process (step S20), a stirring process (step S30), a molding process (step S40), and a slow cooling process (step S50). The plate-making process (step S60), the cutting process (step S70), the roughening process (step S80), and the end face machining process (step S90). The melting step S10, the refining step S20, the stirring step S30, the forming step S40, the slow cooling step S50, the plate-drawing step S60, and the cutting step S70 are substrate manufactures in which the glass substrate 10 is manufactured from glass raw materials. It is a process. The roughening step S80 is a surface treatment step in which the roughened surface 12b of the glass substrate 10 is roughened by a dry etching process, a wet etching process, a pad polishing process, a CMP polishing process, a tape polishing process, or the like. Next, an example of the outline of each process will be described.

  In the melting step S10, the glass raw material is melted by a heating means such as a burner in the melting tank, and high-temperature molten glass at 1500 ° C. to 1600 ° C. is generated. The glass raw material is prepared so that a glass having a desired composition can be substantially obtained. Here, “substantially” means that the presence of other trace components is allowed in the range of less than 0.1% by mass. The molten glass is sent to a downstream process from an outlet provided at the bottom of the melting tank.

In the clarification step S20, the molten glass is clarified by further raising the temperature of the molten glass generated in the melting step S10 in the clarification tank. In the clarification tank, the temperature of the molten glass is raised to 1600 ° C to 1800 ° C, preferably 1650 ° C to 1750 ° C. In the clarification tank, fine bubbles of O ₂ , CO ₂ and SO ₂ contained in the molten glass grow by absorbing O ₂ generated by the reduction of the fining agent such as SnO ₂ contained in the glass raw material. Ascend to the liquid level.

  In the stirring step S30, the molten glass clarified in the clarification step S20 is stirred and chemically and thermally homogenized in the stirring tank. In the stirring tank, the molten glass is stirred by a rotating shaft stirrer while flowing in the vertical direction, and sent to a downstream process from an outlet provided at the bottom of the stirring tank. Moreover, in stirring process S30, the glass component which has specific gravity different from the average specific gravity of molten glass, such as a zirconia rich molten glass, is removed from a stirring tank.

  In the forming step S40, a glass ribbon is formed from the molten glass stirred in the stirring step S30 by the overflow downdraw method. Specifically, the molten glass that overflows from the upper part of the forming cell flows downward along the side wall of the forming cell, and joins at the lower end of the forming cell, whereby the glass ribbon is continuously formed. The molten glass is cooled to a temperature suitable for molding by the overflow downdraw method, for example, 1200 ° C. before flowing into the molding step S40.

  In the slow cooling step S50, the glass ribbon continuously produced in the forming step S40 is gradually cooled to the annealing point or lower while the temperature is controlled so as not to cause distortion and warpage.

  In the plate-drawing step S60, the glass ribbon slowly cooled in the slow cooling step S50 is cut for each predetermined length.

  In cutting process S70, the glass ribbon cut | disconnected for every predetermined length by the plate-drawing process S60 is cut | disconnected by the predetermined magnitude | size, and the glass substrate 10 is obtained.

  In the roughening step S80, as will be described later, a surface treatment for increasing the surface roughness of the roughened surface 12b of the glass substrate 10 obtained in the cutting step S70 is performed. The roughening step S80 mainly includes a cleaning step for cleaning the roughened surface 12b of the glass substrate 10 and an etching step for etching the roughened surface 12b cleaned in the cleaning step.

  In the end face processing step S90, the end portion of the glass substrate 10 whose surface is roughened in the roughening step S80 is polished and ground.

  In addition, the washing | cleaning process and test | inspection process of the glass substrate 10 are performed after end surface processing process S90. Details of the cleaning process and the inspection process are omitted. Finally, the glass substrate 10 is packed and shipped to the FPD manufacturer. The FPD manufacturer manufactures an FPD by forming a thin film made of TFT or the like on the element forming surface 12a of the glass substrate 10.

(2) Details of Roughening Step Next, the cleaning step and the etching step of the roughened surface 12b performed in the roughening step S80 will be described.

(2-1) Cleaning Step In the cleaning step, the roughened surface 12b is cleaned. The cleaning process is, for example, a plasma cleaning process. In the plasma cleaning process, for example, air, which is a mixed gas of nitrogen and oxygen, and a gas activated in a plasma state generated from argon are used.

  In the plasma cleaning process, the gas activated in the plasma state is sprayed onto the roughened surface 12b of the glass substrate 10, whereby the organic thin film adhering to the roughened surface 12b is removed. The organic thin film functions as a mask in a later etching process. Therefore, before the etching process, a cleaning process for removing the organic thin film from the roughened surface 12b is performed.

  In the cleaning process of the roughened surface 12b, instead of performing the plasma cleaning process, an organic gas thin film can be removed by performing an ozone gas spray process and an ultraviolet irradiation process. In the cleaning step, at least the organic thin film may be removed by oxidizing or modifying the organic matter. Note that the cleaning process performed before the surface treatment in the etching process is not an essential process, and is not necessary if the cleanliness of the roughened surface 12b to be surface-treated is high.

(2-2) Etching Step In the etching step, the roughened surface 12b is etched. The etching process is, for example, a dry etching process or a wet etching process. In the etching process, a fluorine-based etchant is used, and in particular, an etchant containing hydrogen fluoride is preferably used.

  FIG. 3 is a diagram illustrating an example of a dry etching apparatus. The dry etching apparatus 30 mainly includes an etching nozzle 31 and a conveyance roller 32. The glass substrate 10 is conveyed by the conveyance roller 32. The roughened surface 12 b of the glass substrate 10 is a surface that contacts the transport roller 32. The etching nozzle 31 is a slit-like nozzle that extends in the width direction of the glass substrate 10. The etching nozzle 31 sprays an etchant on the roughened surface 12b of the glass substrate 10 to be conveyed. The etchant is, for example, gaseous hydrogen fluoride generated by passing a mixed gas of carbon tetrafluoride and water through a carrier gas in a plasma state. Nitrogen, argon, etc. are used as carrier gas.

  FIG. 4 is a diagram illustrating an example of a wet etching apparatus. The wet etching apparatus 40 mainly includes a conveyance roller 42, a roughening roller 44, a contact roller 46, and an etchant tank 48. The glass substrate 10 is transported by the transport roller 42 and the roughening roller 44. The roughened surface 12 b of the glass substrate 10 is a surface in contact with the conveying roller 42 and the roughened roller 44. The outer peripheral surface of the roughening roller 44 is made of sponge. A part of the outer peripheral surface of the roughening roller 44 is immersed in an etching solution 49 stored in an etchant tank 48. The etchant 49 is, for example, hydrofluoric acid. The surface of the roughening roller 44 absorbs the etching solution 49. Therefore, the etching liquid 49 absorbed by the roughening roller 44 comes into contact with the roughened surface 12b of the glass substrate 10, and thus the etching liquid 49 is applied to the roughened surface 12b. In order to adjust the amount of the etching solution 49 applied to the roughened surface 12 b, a part of the etching solution 49 absorbed by the roughening roller 44 presses the surface of the roughening roller 44. Squeezed by. Further, by blowing air or the like to the element forming surface 12a of the glass substrate 10, the pressure at which the roughened surface 12b of the glass substrate 10 and the roughening roller 44 come into contact can be kept high.

  In the etching step, the time required for the etching process can be adjusted by adjusting the conveyance speed of the glass substrate 10, and the amount of the etchant adhering to the roughened surface 12b can be adjusted. Before the etching process is performed, the roughened surface 12b of the glass substrate 10 is uniformly etched because the organic thin film is removed in the cleaning process.

  Rsk of the roughened surface 12b after the etching process is smaller than zero. Note that Rsk of the roughened surface 12b after the etching step is preferably smaller than −0.3, more preferably larger than −1.5 and smaller than −0.5. Rsk is a kind of parameter representing the surface irregularity shape measured by an atomic force microscope, and is the skewness of the surface roughness curve. Specifically, Rsk is a skewness conforming to JIS B 0601-2001. In order to calculate Rsk, first, the root mean square height Rq of the surface roughness curve is calculated according to the following equation.

Here, L is a reference length, and Z (x) is a roughness curve. Rsk is a value obtained by dividing the cube average of the roughness curve Z (x) at the reference length by the cube of the root mean square height Rq, and is calculated according to the following equation.

  Rsk is a parameter representing the deviation of the roughness curve distribution with respect to the surface roughness center plane of the glass substrate 10. When Rsk is zero, the roughness curve distribution is symmetric with respect to the surface roughness center plane. When Rsk is greater than zero, the roughness curve distribution is biased downward from the surface roughness center plane. When Rsk is smaller than zero, the roughness curve distribution is biased upward from the surface roughness center plane.

  When Rsk of the roughened surface 12b of the glass substrate 10 is smaller than zero, the roughness curve of the roughened surface 12b has a shape in which there are more peaks than valleys with respect to the surface roughness center plane of the roughened surface 12b. have. That is, the ratio of the convex part formed in the roughened surface 12b of the glass substrate 10 becomes larger than the ratio of the concave part.

(3) Features The glass substrate 10 manufactured by the method for manufacturing a glass substrate according to the present embodiment has a roughened surface 12b roughened by an etching process. By the etching process for making Rsk of the roughened surface 12b smaller than zero, the roughened surface 12b has a shape in which the ratio of the convex portions is larger than the ratio of the concave portions. Therefore, when the glass substrate 10 is placed on the table, the area of the roughened surface 12b that contacts the table surface is reduced by the etching process. And charging of the glass substrate 10 is suppressed more effectively, so that the contact area of the glass substrate 10 and a table is small. Therefore, charging of the roughened surface 12b of the glass substrate 10 is effectively suppressed by the roughening treatment that makes Rsk smaller than zero.

Further, as Rsk of the roughened surface 12b is smaller, charging of the roughened surface 12b is more effectively suppressed. Rsk of the roughened surface 12b is preferably smaller than −0.3, more preferably larger than −1.5 and smaller than −0.5. In order to set Rsk of the roughened surface 12b to −1.3 or less, for example, a polishing step of the roughened surface 12b is required in addition to the etching process, and it becomes difficult to control the surface state. Therefore, the surface treatment process of the roughened surface 12b may be long. In addition, the management of the surface treatment process of the roughened surface 12b may be complicated.

  In addition, when Rsk of the roughened surface 12b is −1.5 or less, the contact area between the glass substrate 10 and the table is increased by increasing the number of convex portions formed on the roughened surface 12b. The tendency for the charging property of the glass substrate 10 to become difficult to fall is seen.

  In the flat panel display manufacturing process, a thin film having a plurality of layers made of a semiconductor element such as a TFT, a polysilicon thin film, an ITO thin film, or the like is formed on the element forming surface 12a of the glass substrate 10. Each time a film forming process is performed on the element forming surface 12a, the glass substrate 10 is removed from the susceptor in the reaction container of the semiconductor manufacturing apparatus. At this time, peeling electrification occurs between the metal surface of the susceptor on which the glass substrate 10 is placed and the roughened surface 12b of the glass substrate 10. When static electricity is accumulated on the glass substrate 10 due to peeling charging, the roughened surface 12b of the glass substrate 10 is likely to stick to the metal surface of the susceptor due to static electricity. Thereby, when removing the glass substrate 10 from a susceptor, the glass substrate 10 may be damaged by giving an excessive force to the glass substrate 10. In addition, a voltage caused by static electricity accumulated due to peeling charging may destroy a semiconductor element or the like formed on the element formation surface 12 a of the glass substrate 10.

  In the glass substrate manufacturing method according to the present embodiment, charging of the roughened surface 12b of the glass substrate 10 is effectively suppressed. Therefore, in the manufacturing process of the flat panel display, it is possible to effectively suppress the breakage of the glass substrate 10 and the destruction of the semiconductor elements and the like formed on the surface of the glass substrate 10. Further, it is possible to prevent particles from adhering to the surface of the glass substrate 10 due to electrostatic charging of the glass substrate 10, and to prevent color filter peeling and wiring electrode peeling due to the adhesion of particles.

(4) Modifications Although the method for manufacturing a glass substrate according to the present invention has been described above, the present invention is not limited to the above-described embodiment, and various improvements and modifications can be made without departing from the spirit of the present invention. May be. Of course, the present invention is effective not only on a glass substrate on which a semiconductor element is formed on the surface but also on a glass substrate on which a color filter is formed on the surface.

(4-1) Modification A
In the present embodiment, the surface treatment by etching is performed so that the roughened surface 12b of the glass substrate 10 has Rsk smaller than zero. However, the roughened surface 12b of the glass substrate 10 may be subjected to other surface treatment. For example, the roughened surface 12b is first subjected to a polishing process for polishing the roughened surface 12b using a cerium oxide abrasive, and then attached to the roughened surface 12b using hydrofluoric acid. The removal process which removes the cerium oxide abrasive | polishing agent currently performed may be performed. Since the roughened surface 12b is etched by the surface treatment including the polishing treatment and the removal treatment, the roughened surface 12b subjected to the surface treatment has an Rsk smaller than zero.

(4-2) Modification B
In the present embodiment, only the roughened surface 12b of the glass substrate 10 is subjected to a roughening process by etching. However, the element forming surface 12a and the roughened surface 12b of the glass substrate 10 may be roughened by etching. Thereby, not only charging of the roughened surface 12b but also charging of the element forming surface 12a is effectively suppressed.

  In addition, since a semiconductor element such as a TFT (Thin Film Transistor) is formed on the element forming surface 12a of the glass substrate 10, the element forming surface 12a is roughened to the extent that the formation of the semiconductor element is not hindered. Is preferred. Specifically, the roughened element forming surface 12a preferably has an arithmetic average roughness Ra of less than 2.0 nm.

(4-3) Modification C
In the present embodiment, as an example of the wet etching process for the roughened surface 12b of the glass substrate 10, the roller etching process for applying an etching solution to the roughened surface 12b using the roughening roller 44 has been described. However, the wet etching process of the roughened surface 12b may be, for example, a shower etching process and a dip etching process.

  In the shower etching process, fine droplets of the etching solution are sprayed on the roughened surface 12b of the glass substrate 10. As a result, the etchant uniformly adheres to the roughened surface 12b, and the roughened surface 12b is roughened.

  In the dip etching process, the entire glass substrate 10 is immersed in an etching solution tank in which an etching solution is stored. Thereby, the element formation surface 12a and the roughened surface 12b of the glass substrate 10 are roughened.

(5) Example As an example of the method for producing a glass substrate according to the present invention, surface treatment was performed on a plurality of glass substrates under different conditions, and the surface roughness and chargeability of the surface-treated surface were determined. It was measured. A glass substrate for a liquid crystal display device using boroaluminosilicate glass was used as the glass substrate. Evaluation of the charging property of the glass substrate was a glass substrate having a size of 730 mm × 920 mm and a thickness of 0.5 mm.

  First, one main surface of the glass substrate was cleaned using a plasma cleaning apparatus. In the cleaning step, plasma surface argon gas was sprayed on the surface of the glass substrate at a predetermined amount per minute to clean the surface of the glass substrate.

  Next, the surface of the cleaned glass substrate was roughened by a dry etching process or a wet etching process. In the dry etching process, hydrogen fluoride as an etching gas was generated by passing a mixed gas of carbon tetrafluoride and water through a carrier gas composed of argon in a plasma state. And the produced | generated etching gas was sprayed on the surface of the glass substrate, and the surface of the glass substrate was etched. In the wet etching process, a shower etching process was performed.

  Next, a square sample having a side of 50 mm was cut out from the surface-treated glass substrate, and the etched glass substrate surface was evaluated.

  First, Rsk of the etched glass substrate surface was calculated. Specifically, using an atomic force microscope, the uneven shape of the sample surface was measured from three-dimensional data obtained by measuring 256 points × 256 points in a 1 μm × 1 μm scan range of a glass substrate sample. And the roughness curve of the surface was calculated | required from the uneven | corrugated shape of the surface, and Rsk was computed using said formula. Further, the arithmetic average roughness Ra of the sample surface was calculated from the surface roughness curve. Ra is the average of the absolute values of the roughness curve Z (x) at the reference length L, and is calculated according to the following equation.

  Second, the chargeability of the glass substrate surface was evaluated. Evaluation of charging property was performed in an environment of a temperature of 25 ° C. and a humidity of 50%. Specifically, first, the glass substrate was placed on the table, and the glass substrate and the table surface were brought into close contact with each other for a predetermined time by vacuum suction. Next, using a pin, the glass substrate was lifted and peeled off from the table surface. Next, the amount of charge on the surface of the glass substrate was measured using a surface potentiometer (manufactured by OMRON Corporation). The above process was repeated four times at predetermined intervals to measure the maximum charge amount on the glass substrate surface. And it was determined that the smaller the absolute value of the maximum charge amount on the glass substrate surface, the lower the chargeability of the glass substrate surface.

  Table 1 below shows the etching method, Rsk, and Ra measurement results for the seven glass substrates of Examples 1 to 5 and Comparative Examples 1 and 2. In Table 1, “treatment method” represents a method for etching the glass substrate surface. Note that the etchant used for the etching treatment is hydrogen fluoride. In Table 1, “Chargeability” is “◎”, “◯”, “Δ”, and “×” in order of increasing absolute value of the maximum charge amount on the glass substrate surface in the evaluation of the charge amount on the glass substrate surface. expressed.

  In Example 1, a dry etching process was performed, and in Examples 2 to 5, a wet etching process was performed. The concentrations of the etching solutions used in Examples 2 to 5 were all the same. In Examples 4 and 5, the surface of the glass substrate was polished with a brush using a cerium oxide abrasive before the etching process. The shower etching process time in Example 5 was longer than the shower etching process time in Example 4. In Comparative Example 1, pad polishing treatment with abrasive grains was performed. In Comparative Example 2, the glass substrate surface was not etched.

    According to Table 1, as shown in Examples 1 to 5, it was confirmed that the chargeability of the glass substrate having a surface with Rsk smaller than zero was suppressed. Further, as shown in Examples 4 and 5, first, the glass substrate is polished, and then the polishing surface is cleaned by hydrofluoric acid to etch the polishing surface. It was confirmed that Rsk becomes a large negative value. On the other hand, it was confirmed that when the shower etching treatment time was made longer than that in Example 5, the Rsk of the polished surface was larger than that in Example 5. This is considered to be because the convex portions were formed on the polished surface of the glass substrate by the polishing treatment and the etching treatment, but the convex portions formed by the excessive etching treatment were reduced.

  It was confirmed that the glass substrates on which the surface treatments of Examples 1 to 5 were performed had no problem of static electricity accumulation. Further, as shown in Table 1, no correlation was confirmed between Rsk and Ra.

  In Comparative Example 1, as in Example 1, it was confirmed that the chargeability of the glass substrate was lowered. However, there is a problem that uneven polishing tends to occur on the polished surface, and uneven charging occurs in the surface of the glass substrate.

  From the above, it has been confirmed that the surface treatment of the glass substrate is effectively suppressed by performing the surface treatment of the glass substrate so that the Rsk of the glass substrate is smaller than zero.

  Moreover, the area ratio of the convex part which occupies for the whole sample surface was computed from the uneven | corrugated shape of the sample surface obtained from the measurement result by an atomic force microscope. Here, the convex portion is a portion having a height of 1 nm or more from the surface roughness center plane of the surface treated sample surface. Hereinafter, a method for calculating the area ratio of the convex portions will be described.

  First, a 50 mm × 50 mm sample was produced from a glass substrate. Next, the uneven | corrugated shape of each produced sample was measured by non-contact mode using atomic force microscope (The ParkSystems company make, model XE-100). Prior to the measurement, the atomic force microscope was adjusted so that surface irregularities having a small surface roughness such as an arithmetic average roughness Ra of less than 1 nm could be measured. During measurement, the scan area was 1 μm × 1 μm (sampling number was 256 points × 256 points), and the scan rate was 0.8 Hz. The servo gain in the non-contact mode of the atomic force microscope was set to 1.5, and the set point was automatically set. By this measurement, a two-dimensional surface profile shape related to the surface irregularities of the sample was obtained. Next, a histogram of surface irregularities is obtained from this surface profile shape, sliced at a height of 1 nm from the surface roughness center plane, and the number of pixels in the image having a height of 1 nm or more is counted. The area of the convex portion was obtained. Next, the area ratio (%) of the protrusions was calculated from the area of the protrusions obtained.

  As a result, in Examples 1 to 5, it was confirmed that the convex portions having a height of 1 nm or more were formed dispersed over the entire surface, and the area ratio of the convex portions was at least 2%. In addition, the charging of the glass substrate surface is more effectively suppressed as the area ratio of the convex portion is larger. As shown in Examples 1 to 5, by performing the surface treatment of the glass substrate so that the Rsk of the glass substrate is smaller than zero, the convex portions are formed to the extent that the charging of the glass substrate surface is effectively suppressed. It was confirmed that it was formed in a dispersed manner and the area ratio of the convex portion was increased. Further, when the area ratio of the convex portions was further confirmed, when Rsk is smaller than zero and the area ratio is 0.5% to 10%, the charging in the surface of the glass substrate is effectively suppressed. Was confirmed.

10 Glass substrate 12a Element formation surface (first surface)
12b Roughened surface (second surface)

JP 2005-255478 A

Claims (8)

A glass substrate for a flat panel display on which a semiconductor element or a color filter is formed,
A first surface on which a semiconductor element or a color filter is formed;
A second surface that is a surface opposite to the first surface;
With
The second surface is larger than −1.5 and smaller than −0.5 Rsk (a kind of parameter representing the surface irregularity shape measured by an atomic force microscope, and the skewness of the surface roughness curve. in a.) I have a,
A substrate using boroaluminosilicate glass having a composition containing SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ .
Glass substrate. The composition is 50 mass% to 70 mass% SiO. ₂ 10% to 25% by weight of Al ₂ O _Three 5% by mass to 18% by mass of B ₂ O _Three 5 mass% to 20 mass% RO (R is at least one selected from Mg, Ca, Sr and Ba), and 0 mass% to 2.0 mass% R ' ₂ O (R ′ is at least one selected from Li, Na and K),
The glass substrate according to claim 1. A method for producing a glass substrate for a flat panel display in which a semiconductor element or a color filter is formed,
A surface treatment step of surface-treating a second surface which is a surface opposite to the first surface which is a surface of a glass substrate on which a semiconductor element or a color filter is formed
The second surface subjected to the surface treatment in the surface treatment step is larger than −1.5 and smaller than −0.5 Rsk (a kind of parameter representing the surface irregularity shape measured by an atomic force microscope). The second surface is surface treated in the surface treatment step, so that the surface roughness curve has a skewness).
The glass substrate is a substrate using boroaluminosilicate glass having a composition containing SiO ₂ , Al ₂ O ₃ and B ₂ O ₃ .
A method for producing a glass substrate. In the surface treatment step, the second surface is surface-treated by roll etching treatment.
The manufacturing method of the glass substrate of Claim 3 . In the surface treatment step, the second surface is subjected to a surface treatment by a shower etching treatment after being brush-polished.
The manufacturing method of the glass substrate of Claim 3 . In the surface treatment step, the second surface is etched using an etchant containing hydrogen fluoride.
The manufacturing method of the glass substrate of any one of Claims 3-5 . In the second surface that has been surface-treated in the surface treatment step, convex portions having a height of 1 nm or more from the surface roughness center plane of the second surface are provided in a dispersed manner, and the first portion of the convex portion is provided. The second surface is surface-treated in the surface treatment step so that the area ratio in the area of the two surfaces is 0.5% to 10%.
The manufacturing method of the glass substrate of any one of Claims 3-6 . The composition is 50 mass% to 70 mass% SiO. ₂ 10% to 25% by weight of Al ₂ O _Three 5% by mass to 18% by mass of B ₂ O _Three 5 mass% to 20 mass% RO (R is at least one selected from Mg, Ca, Sr and Ba), and 0 mass% to 2.0 mass% R ' ₂ O (R ′ is at least one selected from Li, Na and K),
The manufacturing method of the glass substrate of any one of Claims 3-7.

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