JP5080177B2 - Resist coating device - Google Patents

Description

  The present invention relates to a resist film coating apparatus, and more particularly to an electrodeposition coating apparatus for forming a resist film on a piezoelectric wafer formed as a piezoelectric vibrator.

The crystal resonator is incorporated in a transmission device as a frequency control element, and is incorporated in various electronic devices including a communication device. As communication devices become smaller and thinner, there is a demand for further reduction in size and thickness of crystal units.

Usually, a quartz vibrator is provided on the entire surface of the piezoelectric wafer, and an electrodeposition resist film is formed by a spray resist method. For example, in Patent Document 1, a plurality of electrode needles provided at the tip of the discharge nozzle in order to form a resist film having a uniform thickness are arranged at equal intervals on the outer periphery of the discharge nozzle. As a result, an electrodeposition resist having a uniform film thickness can be formed.
JP 2006-58628 A

  However, the invention described in Patent Document 1 described above has a structure in which an electrode needle for charging the mist-like resist fine particles at the tip of the discharge nozzle is provided on the outer periphery of the discharge nozzle, so that a fine vortex generated around the electrode needle. As a result, there is a problem that a thin resist film cannot be stably obtained at the corners of the irregularities processed on the surface of the wafer substrate.

Further, the resist fine particles from the discharge nozzle are ionized by a plurality of electrode needles arranged uniformly on the outer periphery of the discharge nozzle and reach the piezoelectric wafer to form an electrodeposition resist film. However, there is a problem in adjustment such as resist fine particles adhering to the electrode needle and wiping with a solvent such as thinner.
In addition, there is a problem that ionization of resist fine particles becomes non-uniform depending on the state of adhesion, and a stable thin resist film cannot be obtained.

  Further, the discharge nozzle includes an electrode needle outside the discharge nozzle. When a single electrode needle is provided outside the discharge nozzle, there is a problem that an ion wind is generated in a direction away from the electrode needle, and a resist film having a uniform thickness cannot be obtained.

  Accordingly, the present invention is to provide a resist film coating apparatus by a spray resist method capable of forming an electrodeposition resist film having a uniform resist film thickness by reducing resist fine particles.

A resist coating apparatus according to a first aspect is a resist coating apparatus for applying a resist to a piezoelectric wafer, the discharge nozzle having a predetermined cross section for applying a mist-like resist, and a central portion of the predetermined cross section of the discharge nozzle, An electrode needle having an axis extending in the ejection direction; and a voltage applying unit that applies a predetermined voltage to the electrode needle.
With this configuration, the distance between the mist-like resist applied from the discharge nozzle and the electrode needle becomes substantially equal, so that the mist-like resist is charged to substantially the same potential. Therefore, the mist resist is applied almost uniformly on the piezoelectric wafer.

In the resist coating apparatus according to the second aspect, the distance between the tip of the electrode needle and the piezoelectric wafer is set to 10 mm to 100 mm, and the voltage application unit applies a voltage of 50 kV to 150 kV to the needle electrode and the piezoelectric body. .
When a mist-like resist used for a piezoelectric wafer is uniformly applied to the piezoelectric wafer, the voltage and distance are set within this range, and the resist layer is also applied to the corners or through holes formed in the piezoelectric wafer. Easy to form.

The electrode needle of the resist coating apparatus according to the third aspect includes a material having a specific resistance of 1 * 10 −5 Ωcm or less.
When the specific resistance, that is, the resistance per unit volume is 1 * 10 −5 Ωcm or less, the mist resist is easily charged uniformly.

The electrode needle of the resist coating apparatus according to the fourth aspect has protrusions extending radially from the shaft.
According to this configuration, since the distance between the mist resist applied from the discharge nozzle and the electrode needle can be made more uniform, the mist resist can be charged to substantially the same potential.

A resist coating apparatus according to a fifth aspect includes a substrate holder that connects the piezoelectric wafer to a reference potential point and supports the piezoelectric wafer so as to intersect the discharge nozzle.
When the mist-like resist is applied to the piezoelectric wafer, it becomes a reference potential, and the mist-like resists that have been repelled with each other by the Coulomb force can stick to each other to form a resist film.

According to the present invention, the resist coating thickness can be uniformly and thinly formed on the wafer substrate even at the corners.
Embodiments of the present invention will be described below with reference to the drawings.

<Outline of resist coating device>
FIG. 1 is a schematic cross-sectional view showing a configuration example of a resist coating apparatus 100 that forms a resist film by applying resist fine particles R <b> 1 to a quartz wafer substrate 10. The resist coating apparatus 100 includes a coating chamber 70, a resist fine particle generation chamber 80, and a resist tank 90.

  The resist tank 90 contains a resist agent R2. For example, the resist agent R2 is a novolac positive resist. The resist agent R2 in the resist tank 90 is sent to the resist fine particle generation chamber 80 by the liquid supply pump 92. The inside of the resist tank 90 is set to about 10 ° C to 30 ° C.

The resist agent R <b> 2 sent by the liquid supply pump 92 is first sent to a spray nozzle 82 attached to the upper part of the resist fine particle generation chamber 80. Further, an inert carrier gas such as nitrogen (N ₂ ) or argon pressurized to spray the resist R ₂ is supplied to the spray nozzle 82. The spray nozzle 82 is a two-fluid nozzle, and the resist agent R2 is jetted from the inner pipe, and the carrier gas is jetted from the outer pipe covering the inner pipe. For this reason, the spray nozzle 82 can spray the resist agent R2 into fine particles (mist form).

  The fine resist particles R1 float in the fine resist particle generation chamber 80. Of the resist fine particles R1, the resist fine particles R1 having a large diameter, that is, the heavy resist fine particles R1 fall below the resist fine particle production chamber 80 due to their own weight. The resist particles that have fallen below the resist particle generation chamber 80 adhere to each other and become the resist agent R2. The resist agent R2 is temporarily stored on the bottom surface of the resist fine particle generation chamber 80, and is returned again to the resist tank 90 by the return pump 94 via the valve 84.

  On the other hand, the resist particles R 1 having a small diameter drift in the resist particle generation chamber 80 without falling below the resist particle generation chamber 80. Then, the resist fine particles R1 are supplied from the discharge port 81 to the discharge nozzle 71 together with the carrier gas. That is, the resist fine particle generation chamber 80 is pressurized with the carrier gas, and the resist fine particles R1 are sent to the discharge nozzle 71 disposed in the coating chamber 70 via the discharge port 81 by the pressure of the carrier gas.

  The resist fine particles R <b> 1 are jetted from the discharge nozzle 71 toward the surface 10 a of the crystal wafer substrate 10 together with the carrier gas in the coating chamber 70. The quartz wafer substrate 10 is held horizontally by a chuck 73 on an orientation flat 10c. The chuck 73 is connected to the Y-direction driving means 75 and is movable in the left-right direction in FIG. Further, the Y-direction driving means 75 is connected to the X-direction driving means 77, and the chuck 73 is movable in the front and back direction (front-rear direction) in FIG. This configuration will be described in detail with reference to FIG.

  The resist fine particles R1 that have not been applied to the quartz wafer substrate 10 in the application chamber 70 are attracted to each other and fall to the bottom surface of the application chamber 70 by their own weight. By collecting these, the resist agent R2 is obtained, and is returned again to the resist tank 90 by the return pump 94 via the valve 85. In the process of changing the resist agent R2 to the resist fine particles R1, the solvent of the resist agent R2, for example, thinner, is vaporized, so that the concentration of the resist agent R2 gradually increases. For this reason, it is preferable to periodically replenish the coating chamber 70 or other piping with a solvent.

<Quartz wafer substrate>
FIG. 2A is a perspective view showing a configuration of a circular crystal wafer substrate 10 used in the present embodiment. The circular quartz wafer substrate 10 is made of, for example, an artificial single crystal quartz having a thickness of 0.8 mm, and the diameter of the circular quartz wafer substrate 10 is 3 inches or 4 inches. Further, an orientation flat 10c for specifying the crystal direction of the crystal is formed on a part of the peripheral portion 10e of the crystal wafer substrate 10 so that the axial direction of the circular crystal wafer substrate 10 can be specified.

  FIG. 2B is a perspective view showing a configuration of a rectangular crystal wafer substrate 15 used in the present embodiment. The rectangular quartz wafer substrate 15 is made of, for example, an artificial quartz having a thickness of about 0.8 mm, and one side of the rectangular quartz wafer substrate 15 is 2 inches. Further, an orientation flat 15c for specifying the crystal direction of the crystal is formed on a part of the peripheral portion 15e of the crystal wafer substrate 15 so that the axial direction of the rectangular crystal wafer substrate 15 can be specified.

  The circular crystal wafer substrate 10 in FIG. 2A and the rectangular crystal wafer substrate 15 in FIG. 2B show a situation in which the tuning fork type crystal vibrating piece 20 has already been formed. The tuning fork type crystal vibrating piece 20 is not completely a single vibrating piece, and a part of the base of the tuning fork type crystal vibrating piece 20 is connected to the circular crystal wafer substrate 10 or the rectangular crystal wafer substrate 15. ing. Therefore, hundreds to thousands of tuning fork type crystal vibrating pieces 20 can be used as one crystal wafer substrate 10 and crystal wafer substrate 15 without processing the tuning fork type crystal vibrating pieces 20 on a pallet or the like. Can be handled.

  In the quartz wafer substrate 10, after the tuning fork type quartz vibrating piece 20 is formed, the electrode film 18 is formed by sputtering or the like. The electrode film 18 has a structure in which a chromium (Cr) layer is formed on the quartz wafer substrate 10 at several hundred angstroms, and a gold (Au) layer is formed on the chromium layer at several hundred angstroms. The electrode film 18 is also formed on the through hole, the orientation flat 10c, and the like due to the tuning fork type crystal vibrating piece 20 being formed. In the following embodiment, description will be made with a circular crystal wafer substrate 10 having an orientation flat 10c shown in FIG.

<Configuration of wafer driving means>
3A is an enlarged view of the inside of the coating chamber 70 of FIG. 1, and FIG. 3B is a plan view of FIG. The resist fine particles R1 discharged from the discharge nozzle 71 can be moved in the directions of the arrows AR1 and AR2 by the Y direction driving means 75 and the X direction driving means 77 in order to uniformly apply the quartz wafer substrate 10 with a uniform thickness. It is. As a result, the quartz wafer substrate 10 moves. The Y direction driving means 75 and the X direction driving means 77 are constituted by linear motors, or are constituted by stepping motors and ball screws. The moving speed of the quartz wafer substrate 10 is appropriately set according to the film thickness of the resist fine particles R1 and the supply amount of the resist fine particles R1 from the discharge nozzle 71.

  The outer surface of the chuck 73, the Z direction driving means 75, or the X direction driving means 77 is covered with a non-conductive material such as plastic. The chuck 73 holds the orientation flat 10 c of the crystal wafer substrate 10. As for the chuck | zipper 73, the electroconductive material has come out on the surface only in the part which touches the electrode film 18 of the orientation flat 10c. This is to make it difficult for the resist fine particles R1 to adhere to the chuck 73 or the driving means.

  The discharge nozzle 71 is provided with an electrode needle 72 in the center, and a high voltage direct current of about 50 kV to 150 kV is applied to the electrode needle 72 from the direct current power supply unit 79. On the other hand, the electrode film 18 of the quartz wafer substrate 10 is configured to be grounded. When the resist fine particle R1 passes near the electrode needle 72, the resist fine particle R1 is charged. Therefore, the resist fine particles R1 discharged from the discharge nozzle 7 are applied to the quartz wafer substrate 10 by the Coulomb force together with the discharge pressure.

  Since the quartz wafer substrate 10 is provided with hundreds to thousands of tuning-fork type crystal vibrating pieces 20, a plurality of through holes or irregularities are formed in the quartz wafer substrate 10. For example, in FIG. 3A, one through hole 10f is exaggerated. The resist fine particles R1 to be applied are uniformly formed in the through holes 10f and in the corners by Coulomb force.

  In the present embodiment, the discharge nozzle 71 is fixed and the crystal wafer substrate 10 moves in the XY plane. However, the discharge nozzle 71 may move in the XY plane and the crystal wafer substrate 10 may be fixed. Further, since the resist fine particles R1 are attracted to the quartz wafer substrate 10 by Coulomb force, the gravitational action is almost negligible. Therefore, the discharge nozzle 71 is fixed horizontally and the quartz wafer substrate 10 is moved to the XZ plane or YZ plane. Good.

<Configuration of discharge nozzle>
4A and 4B are conceptual diagrams showing the relationship among the discharge nozzle 71, the electrode needle 72, and the crystal wafer substrate 10. FIG. As the discharge nozzle 71, a linear discharge nozzle 71a and a discharge nozzle 71b having a wide opening at the end can be applied. Further, as the electrode needle 72, there can be applied one electrode needle 72a extending on the axis and electrode needles 72b or 72c branching radially from the tip of the needle extending on the axis.

  In FIG. 4A (a), the discharge nozzle 71a has a cylindrical shape with a diameter φR or an elliptical cross section, and an electrode needle 72a is attached at substantially the center thereof. A current of 10 mA to 80 mA is applied to the electrode needle 72 a with a positive or negative high voltage of about 50 kV to 150 kV from the DC power supply unit 79. The discharge nozzle 71a has a length of 50 mm to 150 mm and a diameter φR of 10 mm to 20 mm.

  The tip of the electrode needle 72a protrudes from the tip of the discharge nozzle 71a by a length L2. The length L2 can be appropriately changed depending on the voltage applied to the electrode needle 72a or the type of resist, but is about 10 mm to 30 mm. Further, the length L1 from the tip of the discharge nozzle 71a to the quartz wafer substrate 10 is separated. The length L1 can be appropriately changed depending on the voltage applied to the electrode needle 72a or the type of resist, but is about 10 mm to 100 mm, and preferably about 30 mm to 50 mm.

  When the electrode needle 72a is applied to a high voltage, the resist fine particles R1 are positively or negatively charged. On the other hand, the chuck 73, the Z direction driving means 75, or the X direction driving means 77 for holding the crystal wafer substrate 10 are configured to be grounded. That is, the electrode film 18 formed on the quartz wafer substrate 10 is at 0V. For this reason, the resist fine particles R1 sprayed from the discharge nozzle 71a are applied to the electrode film 18 of the quartz wafer substrate 10 by Coulomb force. Further, since the discharged resist fine particles R1 are charged with the same polarity, they repel each other by Coulomb force, and the resist fine particles R1 diffuse and uniformly distribute to reach the surface of the quartz wafer substrate 10. The resist fine particles R 1 that have arrived release electric charges to the electrode film 18 of the quartz wafer substrate 10.

  The diameter of the resist fine particle R1 is several microns or 1 micron or less, but since the surface tension works, a film having a film thickness smaller than the diameter of the resist fine particle R1 is formed in a state where the film is formed after adhering to the electrode film 18. The Moreover, the discharge nozzle 71a can adjust the film thickness of the resist layer formed on the quartz wafer substrate 10 according to the voltage applied to the electrode needle 72a provided. That is, if the potential of the electrode needle 72a is set high, the diffusion diameter decreases, and if the potential of the electrode needle 72a is set low, the diffusion diameter increases. Further, if the distance between the discharge nozzle 71a and the quartz wafer substrate 10 is short, the diffusion diameter is reduced. Further, as the relative movement speed between the discharge nozzle 71a and the quartz wafer substrate 10 increases, the applied resist layer becomes thinner. In consideration of these conditions, the thickness of the resist layer necessary for the quartz wafer substrate 10 or the application to the through holes is optimized.

In the present embodiment, the electrode needle 72a is made of stainless steel (SUS), but any material having a specific resistance of 1 × 10 ⁻⁵ Ωcm or less is basically applicable. For example, materials such as silver, copper, aluminum, chromium, nickel or carbon steel are preferable. Further, by disposing the electrode needle 72a at the center of the discharge nozzle 71a, the resist fine particles R1 discharged from the discharge nozzle 71a can be charged to substantially the same charge.

  FIG. 4A (b) is a modified example of FIG. 4 (a), and the discharge nozzle 71a has electrode needles 72b branched in a plurality radially from the tip of the needle extending on the axis at the center. Since the tip of the electrode needle 72b is radially branched, the distance between the resist fine particles R1 discharged from the discharge nozzle 71a and the electrode needle 72b can be made uniform. When the resist fine particles R1 are charged to the same potential, the resist layer can be more uniformly applied to the quartz wafer substrate 10.

  FIG. 4B (c) is a modified example of FIG. 4 (b), and is an example in which the discharge nozzle 71b whose opening is widened toward the end is arranged in the coating chamber. The discharge nozzle 71b also has an electrode needle 72c that diverges radially from the tip of the needle extending on the axis in the center. The discharge nozzle 71b has a maximum opening diameter φWR. The diameter φWR is, for example, about 30 mm to 60 mm. Since the opening widens toward the end, the electrode needle 72c has a greater number of radial branches than the electrode needle 72b. When the discharge nozzle 71b is used, a wide range of resist fine particles R1 can be applied.

  FIG. 4B (d) is a modification of (a), and the discharge nozzle 71a has an electrode needle 72a extending on the axis at the center, and the diameter φr of the discharge nozzle 71a is about 5 mm to 10 mm. Yes. Such discharge nozzles 71a are arranged in parallel in a straight line. Although not shown, the number of the discharge ports 81 is one, and the resist fine particles R1 are supplied to the plurality of discharge nozzles 71a from there by being divided by piping. Even if a plurality of discharge nozzles 71a are used, a wide range of resist fine particles R1 can be applied.

The spray nozzle 82 is supplied with a carrier gas of an inert gas such as nitrogen or argon that has been pressurized in order to spray the resist agent R2, but basically any pressurized gas can be applied.
Further, although the object on which the resist film is formed is the crystal wafer substrate 10 having irregularities, it can be applied to a flat plate or other materials. In the above embodiment, the quartz wafer is described. However, other than quartz, piezoelectric materials such as lithium tantalate and lithium niobate can be used.

It is a schematic sectional drawing which shows the structural example of the resist film coating apparatus 100 explaining one Example regarding application | coating of a resist fine particle. FIG. 2A is a perspective view showing a circular crystal wafer substrate 10 used in this embodiment, and FIG. 2B is a perspective view showing a rectangular wafer substrate 15. (A) is an enlarged view in the coating chamber 70 of FIG. 1, (b) is a plan view of (a). (A) is the enlarged view of the discharge nozzle 71a of FIG. 1, and is a schematic sectional drawing which shows the one electrode needle 72a. (B) is a schematic sectional drawing which shows the structure of the electrode needle 72b branched into multiple pieces radially. (C) is a schematic cross-sectional view showing the configuration of a radial electrode needle 72c with a divergent discharge nozzle 71b. (D) is a schematic sectional view showing a configuration in which a plurality of thin discharge nozzles 71a are arranged in parallel.

Explanation of symbols

10 ... quartz wafer substrate (10a ... surface, 10c ... orientation flat)
15: Crystal wafer substrate (15c: Orientation flat, 15e: Peripheral part)
DESCRIPTION OF SYMBOLS 18 ... Electrode film 20 ... Tuning fork type crystal vibrating piece 70 ... Coating chamber 71, 71a, 71b ... Discharge nozzle 72, 72b, 72c ... Electrode needle 73 ... Chuck 75 ... Y direction drive means 77 ... X direction drive means 79 ... DC power supply Part 80 ... Resist fine particle generation chamber 81 ... Discharge port 82 ... Spray nozzle 84, 85 ... Valve 90 ... Resist tank 92 ... Liquid supply pump 94 ... Return pump 100 ... Resist coating apparatus AR1, AR2 ... Arrows L1, L2 ... Length R1 ... Resist fine particle R2 ... Resist agent

Claims (5)

In a resist coating apparatus that coats a resist on a piezoelectric wafer,
A discharge nozzle for applying a mist-like resist having a predetermined cross-section with a constant diameter or widening ;
A needle electrode having a shaft that the centrally disposed portion of a given cross-section, extending in the discharge direction of said discharge nozzle,
A voltage application unit for applying a voltage to the electrode needle ,
The voltage application unit sets the voltage higher to reduce the diffusion diameter than the predetermined section of the discharge nozzle, or sets the voltage lower to increase the diffusion diameter than the predetermined section of the discharge nozzle. A resist coating apparatus. The distance between the tip of the electrode needle and the piezoelectric wafer is set from 10 mm to 100 mm,
The resist coating apparatus according to claim 1, wherein the voltage applying unit applies a voltage of 50 kV to 150 kV to the needle electrode and the piezoelectric body. The resist coating apparatus according to claim 1, wherein the electrode needle includes a material having a specific resistance of 1 * 10 ⁻⁵ Ωcm or less.   The resist coating apparatus according to claim 1, wherein the electrode needle has a protrusion extending radially from the shaft.   5. The substrate holding unit that connects the piezoelectric wafer to a reference potential point and supports the piezoelectric wafer so as to intersect the discharge nozzle. 6. Resist coating equipment.