JP5308725B2 - Substrate bonding method - Google Patents

Description

  The present invention relates to a method of bonding two substrates together in the manufacturing process of a flat panel display such as a liquid crystal display or a plasma display.

  After holding the upper substrate by electrostatic adsorption using a pressure plate with a built-in electrode plate, release the electrostatic adsorption, drop the upper substrate onto the lower substrate, superimpose both substrates, and lower the pressure plate A substrate bonding method for bonding both substrates to a predetermined gap is known (for example, see Patent Document 1).

  An invention that compensates for the disadvantages of the invention described in Patent Document 1 is also known (see, for example, Patent Document 2).

  In Patent Document 2, (a) an upper substrate is detachably held on an upper holding plate by electrostatic adsorption means, and a lower substrate opposite to the upper substrate is detachably held on a lower holding plate, (B) aligning the upper and lower substrates, and releasing the upper substrate by the electrostatic chucking means when the surroundings are at a desired degree of vacuum; A step of superposing and sealing on the lower substrate, and in step (b), the gas is ejected from the back side of the upper substrate in conjunction with the release of the holding of the upper substrate by the electrostatic chucking means. Describes a substrate bonding method in which the upper substrate is forcibly peeled off from the electrostatic attraction means and pressed onto the lower substrate.

  In the substrate bonding method described in Patent Document 2, the falling speed of the upper substrate increases when the substrate is peeled off, and the substrate may move to cause misalignment. In addition, the degree of vacuum in the vacuum chamber decreases due to the ejection of gas, and the amount of residual air increases due to gas mixing into the display area (in the liquid crystal layer), increasing the factor of bubble generation. For this reason, the reliability of a liquid crystal cell may fall.

Japanese Patent No. 3641709 Japanese Patent No. 3721378

  An object of the present invention is to provide a method for bonding substrates with good quality.

According to one aspect of the present invention, (a) a first sealing agent is applied to one surface of the first and second substrates at a first height, and the first sealing agent is applied. A step of applying a second sealant at a second height higher than the first height so as to surround the above-mentioned portion; and (b) holding the first substrate on the lower side, and By holding the substrate on the upper side by electrostatic adsorption, the first and second substrates are applied to the first substrate and the second substrate by the surfaces applied with the first and second sealing agents. A step of disposing the substrate so as not to be coated with the sealing agent, and (c) a clearance between the first substrate and the second substrate is smaller than the second height. as such, Engineering closer to said first substrate in an atmosphere reducing the pressure around the first and second substrate and the second substrate If, bonding substrate and a step of in (d) of the second to release the electrostatic attraction of the substrate, the first substrate and the second substrate and the substrate gap value set by crimping In the method , the clearance in the step (c) is larger than the set inter-substrate gap value, and the first substrate and the second substrate are sealed with the second sealant. In the step (d), the reduced pressure atmosphere of the step (c) is maintained, and the first substrate and the second are sealed by the second sealant. A step of releasing electrostatic adsorption of the second substrate in a state where an adhesive force between the second substrate and the second substrate is generated; and (d2) the second substrate does not face the first substrate in a reduced pressure atmosphere. A step of blowing a gas onto the surface, and (d3) after blowing the gas, Substrate bonding method comprising the step of returning the periphery of the first and second substrate to the atmospheric pressure is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the method of bonding a board | substrate with favorable quality can be provided.

  At present, non-alkali glass (white plate glass) is used for a glass substrate for large TFTs that is being produced. On the other hand, alkali glass (blue plate glass, soda lime glass) is used for TN and STN type LCDs (passive type LCDs).

  This inventor experimented about the retention strength at the time of hold | maintaining an alkali free glass (white plate glass) board | substrate and an alkali glass (blue plate glass) board | substrate by electrostatic adsorption.

  FIG. 1 shows the experimental results. An alkali-free glass (white plate glass) substrate cannot be held by electrostatic adsorption at a voltage of 0.9 kV or less, and cannot be peeled off from electrostatic adsorption at a voltage of 3.2 kV or more, 1.0 to 3.1 kV Adsorption and peeling were possible at a voltage of Moreover, when it peeled from electrostatic adsorption with the peelable voltage, the time required for peeling was 0 sec.

  On the other hand, an alkali glass (blue plate glass) substrate cannot be held by electrostatic adsorption at a voltage of 0.4 kV or less, cannot be peeled off from electrostatic adsorption at a voltage of 0.8 kV or more, and 0.5 to 0.00. Adsorption and peeling were possible at a voltage of 7 kV. Furthermore, when peeling from electrostatic adsorption with a peelable voltage, it took 10 to 18 seconds for peeling.

  It can be seen that the alkali glass (blue plate glass) substrate can be held at a low electrostatic adsorption setting voltage, but is difficult to peel off. In addition, during an experiment in a voltage setting region where adsorption and separation are possible, the alkali glass (blue plate glass) substrate was unstable in holding, such as a drop phenomenon. For this reason, in order to hold | maintain an alkali glass (blue plate glass) board | substrate, it is thought desirable also to use the voltage of the non-peelable area | region of 0.8 kV or more.

  Next, the inventor of the present application investigated the relationship between the voltage setting value at the time of electrostatic attraction and the glass substrate attraction force.

FIG. 2 shows the experimental results. When the voltage setting value was 0.5 kV, the adsorption force of the alkali-free glass (white plate glass) substrate was 0.2 g / cm ² , and the adsorption force of the alkali glass (blue plate glass) substrate was 1.9 g / cm ² . Moreover, when the voltage setting value was 1.0 kV, the adsorption power of the alkali glass (blue plate glass) substrate was 12.1 g / cm ² . Furthermore, when the voltage setting value was 1.5 kV, the adsorption force of the alkali-free glass (white plate glass) substrate was 1.2 g / cm ² , and the adsorption force of the alkali glass (blue plate glass) substrate was 27 g / cm ² or more. . When the voltage setting value was 2.5 kV, the adsorption force of the alkali-free glass (white plate glass) substrate was 2.9 g / cm ² .

  From the results shown in FIG. 2, it can be seen that the adsorptive power of the alkali glass (blue plate glass) substrate significantly increases with an increase in the voltage setting value. For this reason, it is understood that the voltage installation width capable of stably performing adsorption and peeling of the alkali glass (blue plate glass) substrate is extremely narrow.

  From the results shown in FIG. 1 and FIG. 2, the inventor of the present application has a voltage in a non-peelable region in order to stably hold and peel the alkali glass (blue plate glass) substrate by utilizing the electrostatic adsorption force. It was desirable to use and hold the glass substrate, and thought that it was necessary to perform a peeling operation using a stronger peeling method compared to a non-alkali glass (white plate glass) substrate.

  Hereinafter, the substrate bonding method according to the embodiment will be described with reference to FIGS.

  FIG. 3A is a perspective view showing the lower substrate 50 held by the lower holding plate of the substrate bonding apparatus used in the substrate bonding method according to the embodiment.

  On the lower substrate 50, main sealants 52a to 52d are applied to areas where each liquid crystal display element is manufactured. Further, an outer peripheral seal (double seal) agent 51 is applied to the peripheral portion of the lower substrate 50 so as to surround the region where the main seal agents 52a to 52d are applied.

  FIG. 3B is a cross-sectional view taken along line 3B-3B in FIG. The outer peripheral sealing agent 51 is applied higher than the application height of the main sealing agents 52a to 52d. The application height of the outer peripheral sealant 51 is, for example, 30 to 50 μm, and the application height of the main sealants 52a to 52d is, for example, 20 to 40 μm.

  Reference is made to FIG. The substrate bonding apparatus used in the substrate bonding method according to the embodiment includes an upper chamber unit 10a, a lower chamber unit 10b, an upper holding plate 20 having a plurality of ventilation holes 20x, and a lower holding plate 30 having a plurality of ventilation holes 30x. Consists of including.

  The upper chamber unit 10a and the lower chamber unit 10b constitute a vacuum chamber that achieves a desired degree of vacuum inside. The upper holding plate 20 is formed of an insulating member with a built-in electrode, and has an electrostatic adsorption means for holding the upper substrate 40. The lower holding plate 30 has an electrostatic attraction function and holds the lower substrate 50. Both the upper holding plate 20 and the lower holding plate 30 have a bipolar type electrostatic chuck function capable of alternately applying positive and negative voltages. The parallelism margin between the upper holding plate 20 and the lower holding plate 30 is, for example, ± 5 μm or less.

  The upper substrate 40 is electrostatically attracted to the upper holding plate 20. Further, the lower substrate 50 coated with a sealing agent as shown in FIGS. 3A and 3B is electrostatically attracted to the lower holding plate 30. For both the upper substrate 40 and the lower substrate 50, the set voltage at the time of suction is, for example, 2 kV. A liquid crystal material is dropped into a region of the lower substrate 50 where the main sealants 52a to 52d are applied. Both the upper and lower substrates 40 and 50 are made of alkali glass (blue plate glass). An ITO electrode is formed on the substrate surface.

  Reference is made to FIG. The upper and lower chamber units 10a and 10b are brought into close contact with each other, and the pressure in the sealed vacuum chamber is reduced to 1 Pa. Further, the upper and lower substrates 40 and 50 are aligned.

  Reference is made to FIG. The upper substrate 40 is lowered to a position where the clearance between the upper substrate 40 and the lower substrate 50 is sealed by the outer peripheral sealant 51.

  Reference is made to FIG. By controlling the voltage applied to the electrodes in the upper holding plate 20, the electrostatic chuck is released (unchucked), and the upper substrate 40 is peeled from the upper holding plate 20. Further, in order to prevent an unchucking error due to a substrate state difference, after the unchucking voltage operation is completed, an inert gas is ejected from the vent hole 20x of the upper holding plate 20, and the upper substrate 40 is not peeled off by voltage control. However, the upper substrate 40 is peeled from the upper holding plate 20. The peeled upper substrate 40 is pressure bonded to the lower substrate 50. Thereafter, the inside of the chamber is returned to atmospheric pressure, and a predetermined gap is formed between the upper and lower substrates 40 and 50.

  FIG. 5 shows an example of voltage control of the electrostatic chuck. The substrate is electrostatically chucked by applying 2 kV, which is the voltage in the non-peelable region shown in FIG. For this reason, when releasing the holding of the substrate, control is performed so as to alternately apply positive and negative voltages so as to prevent unchucking failure.

  For example, as shown in this figure, the electrostatic unchuck operation is performed with a PLS time of 1 sec, a voltage reversal count of 3 times, a reverse voltage applied voltage decay rate of 50%, and a switching off time of 0.2 sec. Here, the PLS time can be referred to as a voltage application holding time when a reverse voltage is applied.

  In the substrate bonding method according to the example, the outer peripheral seal (double seal) was printed higher than the other seals. Further, the upper and lower substrate clearances when the substrate was unchucked were clearances in which the outer peripheral seal (double seal) completely brought the upper and lower substrates into close contact to form a sealed space between the upper and lower substrates.

  For this reason, even when an inert gas is ejected after the electrostatic unchucking operation, no gas is mixed into the cell display portion, and the vacuum degree in the vacuum chamber is reduced from 1 Pa. 1 Pa can be maintained.

  In addition, since an adhesive force is generated between the upper and lower substrates by the outer peripheral seal (double seal), misalignment of the upper and lower substrates hardly occurs when the upper substrate is peeled off.

  By the way, it is extremely difficult to set the parallelism between the substrates when the upper and lower substrates are bonded to zero. For this reason, in the board | substrate bonding technique performed without forming an outer periphery seal | sticker (double seal | sticker), the place which is not made into the place which is in contact with the main sealing agent on the upper board | substrate in the initial stage of bonding arises. The main seal begins to collapse from the place where it is in contact with the upper substrate, and the speed of reaching the set inter-substrate gap value differs within the substrate surface. For this reason, it is easy to form a location where a seal leak occurs after the atmospheric pressure is released. Also, the liquid crystal material dropped on the substrate flows from the dropping position due to a capillary phenomenon that occurs in the gap between the two substrates, and hits the main seal agent, causing a seal breakage.

  In the embodiment, since the outer peripheral seal (double seal) is formed higher than the application height of the main seal, the outer peripheral seal (double seal) contacts the upper substrate before the main seal when the upper and lower substrates are overlapped. To do. Therefore, even when the parallelism of the upper and lower substrates is slightly deviated, it is possible to obtain a state in which the outer peripheral seal (double seal) can reliably contact the entire periphery of the upper substrate. This prevents gas from being mixed into the inner part of the outer peripheral seal (double seal) after the atmospheric pressure is released, and a good cell can be obtained.

  According to the substrate bonding method according to the embodiment, an alkali glass (blue plate glass) substrate can be chucked and unchucked with high reliability. Further, the substrate can be bonded to a uniform thickness with a small misalignment. Further, the substrates can be bonded with a high yield.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto.

  For example, in the embodiment, for the electrostatic chuck operation, the upper substrate 40 suction voltage setting value is 2 kV, the lower substrate 50 suction voltage setting value is 2 kV, and for the electrostatic unchuck operation, the PLS time is 1 sec. The number of voltage reversals was 3 times, the voltage decay rate when applying a reverse voltage was 50%, and the switching off time was 0.2 sec.

  For electrostatic chuck operation, the upper substrate 40 suction voltage setting value is 0.5 kV or more, the lower substrate 50 suction voltage setting value is 0.5 kV or more, and for electrostatic unchuck operation, the PLS time is 0.5 to 10 sec. The substrate can be satisfactorily bonded by setting the number of voltage reversals to 1 to 10 times, the voltage decay rate during reverse voltage application to 20 to 80%, and the switching off time to 0.05 to 5 sec. .

  In the embodiment, the sealant is applied to the lower substrate 50, but may be applied to the upper substrate 40.

  It will be apparent to those skilled in the art that other various modifications, improvements, combinations, and the like can be made.

  It can be suitably used for the manufacture of LCD products in general, particularly simple matrix LCDs.

It is a table | surface which shows the experimental result performed about the retention strength at the time of hold | maintaining an alkali free glass (white plate glass) board | substrate and an alkali glass (blue plate glass) board | substrate by electrostatic adsorption. It is a table | surface which shows the result of having investigated the relationship between the voltage setting value at the time of electrostatic attraction, and a glass substrate adsorption force. (A) is a perspective view which shows the lower substrate hold | maintained at the lower holding plate of the board | substrate bonding apparatus used for the board | substrate bonding method by an Example, (B) is the 3B-3B line | wire of (A). FIG. (A)-(D) are sectional drawings for demonstrating the board | substrate bonding method by an Example. It is a figure which shows an example of the voltage control of an electrostatic chuck.

Explanation of symbols

10a Upper chamber unit 10b Lower chamber unit 20 Upper holding plate 20x Vent hole 30 Lower holding plate 30x Vent hole 40 Upper substrate 50 Lower substrate 51 Peripheral sealant 52a to 52d Main sealant

Claims (5)

(A) The first sealing agent is applied to one surface of the first and second substrates at a first height, and the first sealing agent is applied so as to surround a portion where the first sealing agent is applied. Applying a second sealant to a second height higher than the height of 1;
(B) holding the first substrate on the lower side and holding the second substrate on the upper side by electrostatic attraction, so that the first substrate and the second substrate are Arranging the second sealant so that a surface to which the first and second sealants are not applied faces the substrate.
(C) In an atmosphere in which the periphery of the first and second substrates is depressurized so that a clearance between the first substrate and the second substrate is smaller than the second height. Bringing the first substrate and the second substrate closer;
(D) in the second to release the electrostatic attraction of the substrate, the substrate bonding method and a step of the first substrate and the second substrate and the substrate gap value set by crimping There,
The clearance in the step (c) is larger than the set inter-substrate gap value, and the first substrate and the second substrate are sealed with the second sealant to form a sealed space. Is the size to be
The step (d)
(D1) In the state where the reduced pressure atmosphere of the step (c) is maintained and the adhesive force between the first substrate and the second substrate is generated by the second sealing agent, A step of releasing the electrostatic adsorption of the substrate,
(D2) blowing a gas onto a surface of the second substrate that does not face the first substrate under a reduced pressure atmosphere;
(D3) returning the surroundings of the first and second substrates to atmospheric pressure after spraying the gas;
A substrate bonding method including: The second substrate is formed of alkali glass;
In the step (b), the second substrate is electrostatically adsorbed at a voltage of 0.5 kV or more,
In the step (d), the electrostatic adsorption of the second substrate is canceled with a PLS time of 0.5 to 10 sec, a voltage reversal count of 1 to 10 times, and a voltage decay rate when reverse voltage is applied of 20 to 80%. The substrate bonding method according to claim 1. The substrate bonding according to claim 1, wherein the step (c) is performed in a vacuum chamber, and the pressure in the vacuum chamber is reduced to 1 Pa to bring the first substrate and the second substrate closer to each other. Method.   4. The method according to claim 1, wherein the step (b) includes a step of reducing the pressure around the first and second substrates after the first substrate and the second substrate are arranged to face each other. The substrate bonding method according to item. The first substrate is formed of alkali glass;
The substrate bonding method according to claim 1, wherein, in the step (b), the first substrate is held by electrostatic adsorption with a voltage of 0.5 kV or more.

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