KR20030054245A - Voltage Controlled Oscillator with Film Bulk Acoustic Resonator - Google Patents

Abstract

PURPOSE: A VCO(Voltage Controlled Oscillator) using an FBAR(Film Bulk Acoustic Resonator) is provided to reduce a device size by forming only an inductor part of a resonance portion. CONSTITUTION: A VCO includes a power supply portion for supplying DC power, a variable portion for varying an output frequency, a resonance portion for setting up a desired frequency, an oscillation portion having a negative resistance circuit, and an amplification portion for amplifying an output level of the oscillation frequency. An inductor part of the resonance portion is formed with an FBAR. The FBAR includes a substrate(2), an acoustically reflective layer(4), a lower electrode(6), a lower pad portion, a piezoelectric layer(10), an upper electrode(8), an upper pad portion, a couple of upper and lower lead lines(18,16), and a package member(20). The acoustically reflective layer is formed on the substrate. The lower electrode is formed on the acoustically reflective layer by using a conductive material. The lower pad portion is connected to the lower electrode. The piezoelectric layer is formed on the substrate and the lower electrode by using a piezoelectric material. The upper electrode is formed on the piezoelectric layer by using the conductive material. The upper pad portion is connected to the upper electrode. The upper lead line and the lower lead line are connected to the upper electrode and the lower electrode, respectively. The package member is used for covering the lower electrode, the upper electrode, and the piezoelectric layer.

Description

Voltage Controlled Oscillator with Film Bulk Acoustic Resonator

The present invention relates to a voltage controlled oscillator using a thin-film volume-elastic resonator, and more particularly, the inductor of the resonator unit is formed by using a thin-film volume-elastic resonator packaged in a chip form to be mounted on a small printed circuit board. The present invention relates to a voltage controlled oscillator using a thin-film volume-elastic resonator capable of light weight and excellent quality factor.

In general, a voltage controlled oscillator (VCO) is an oscillator whose oscillation frequency is changed in accordance with the change of the applied voltage. The oscillator is used to stably oscillate the local oscillation frequency of a portable telephone or a cordless telephone by an applied voltage of a control circuit. It is often used as a variable frequency oscillator module. In order to use a voltage controlled oscillator in a portable telephone or a cordless telephone, small weight reduction along with low power consumption and low voltage operation is urgently required.

The conventional voltage controlled oscillator supplies a DC power supply for operation and is free from surge, ripple, and voltage fluctuation, a variable part for adjusting voltage for variable output frequency, a resonator part for setting a desired frequency, and an oscillation. For this purpose, the oscillator comprises a negative resistance circuit and an amplifier for increasing the output level of the oscillation frequency.

In particular, the method of implementing the inductor part of the resonator part is very important. The dielectric resonator used in the prior art has reduced the stability of the characteristics and the manufacturing cost. there is a problem.

Recently, a method of making and using an inductor structure inside a multilayer PCB (printed circuit board) has been proposed for miniaturization, but this method is possible because of the miniaturization and low quality factor of the inductor in the high frequency band. The quality of the manufactured voltage controlled oscillator is further degraded than when using a dielectric resonator. Nevertheless, in order to meet the recent trend of miniaturization and weight, a method of manufacturing a voltage controlled oscillator device using a multilayer PCB substrate has been widely used.

As another method of implementing the inductor portion of the resonator, an inductor structure or a resonator structure is manufactured by using a multilayered ceramic structure such as low temperature co-fired ceramic (LTCC). Since the quality factor is low, it is difficult to obtain a voltage controlled oscillator having excellent characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a voltage controlled oscillator using a thin film volumetric elastic resonator which is easy to manufacture, mass-produced, miniaturized, and has a high quality coefficient even in a high frequency band. It is for.

1 is a block diagram schematically showing an embodiment of a voltage controlled oscillator using a thin film volume-elastic resonator according to the present invention;

Figure 2 is a circuit diagram schematically showing an embodiment of a voltage controlled oscillator using a thin film volume-elastic resonator according to the present invention.

Figure 3 is a cross-sectional view showing an embodiment of a thin film volume-elastic resonator according to the present invention.

4 is a cross-sectional view taken along the line A-A of FIG.

Figure 5 is a process block diagram showing a process for manufacturing an embodiment of a thin film volume-elastic resonator according to the present invention.

Figure 6 is a process diagram showing a process for manufacturing an embodiment of a thin film volume-elastic resonator according to the present invention.

Figure 7 is a cross-sectional view showing another embodiment of a thin film volume-elastic resonator according to the present invention.

Figure 8 is a cross-sectional view showing another embodiment of a thin film volume-elastic resonator according to the present invention.

9 is a cross-sectional view showing yet another embodiment of a thin film volume-elastic resonator according to the present invention;

10 is a cross-sectional view showing another embodiment of a thin film volume-elastic resonator according to the present invention;

The voltage controlled oscillator using the thin-film volume-elastic resonator proposed by the present invention has a power supply unit for supplying DC power, a variable unit for adjusting the voltage for variable output frequency, a resonator unit for setting the desired frequency, and a negative resistance circuit for oscillation. In the voltage controlled oscillator comprising an oscillation unit constituting the amplifier and an amplifier for increasing the output level of the oscillation frequency,

The inductor portion of the resonator portion has a substrate having a predetermined size, an acoustic reflective layer formed on the substrate, a lower electrode formed on the acoustic reflective layer, a piezoelectric layer formed on the substrate and the lower electrode, And a package member having an upper electrode formed on the piezoelectric layer, a pair of upper lead wires and lower lead wires connected to the upper electrode and the lower electrode, respectively, and surrounding the lower electrode, the upper electrode, and the piezoelectric layer. It is made using a thin film volumetric elastic resonator.

The acoustic reflective layer may be formed of an air layer that is an empty space, or may be formed in a multilayer by alternately stacking materials having different acoustic impedances.

Next, a preferred embodiment of the voltage controlled oscillator using the thin film volume-elastic resonator according to the present invention will be described in detail with reference to the accompanying drawings.

First, an embodiment of the voltage controlled oscillator using the thin film volume-elastic resonator according to the present invention, as shown in Figures 1 and 2, the power supply unit 100 for supplying DC power, and the variable to adjust the voltage for the output frequency variable The unit 300, the resonator 200 for setting the frequency to be implemented, the oscillator 400 for configuring the negative resistance circuit for oscillation, and the amplifier 500 for increasing the output level of the oscillation frequency do.

The power supply unit 100 is configured such that there is no surge, ripple, voltage fluctuation, or the like.

In the resonator 200, the inductor portion is formed using a thin film-type bulk elastic resonator 310 provided in a chip form.

In addition to the above-described configuration, the configuration of the power supply unit 100, the variable unit 300, the resonator unit 200, the oscillator 400, and the amplifier 500 can be implemented in the same configuration as that generally implemented. Description is omitted.

In the configuration of the power supply unit 100, the variable unit 300, the resonator unit 200, the oscillator 400, and the amplifier 500, all components such as chip resistors, chip capacitors, and chip inductors are provided in chip form. And mainly use standard products such as 1005, 0806, 0603.

In addition, the transistors used in the oscillator 400 and the amplifier 500 are selected in consideration of operating frequency, operating voltage, power gain, noise characteristics, and the like. The varactor used in the resonator 200 includes reverse voltage magnitude and capacitance change amount. In this case, the capacitance is selected in consideration of the change in capacitance and the quality factor according to the voltage change.

In addition, the thin film volume-elastic resonator 210 constituting the inductor portion of the resonator 200 is selected in consideration of a resonance frequency, a quality factor, an impedance characteristic, and the like.

As shown in FIG. 3 and FIG. 4, the thin film type volume elastic resonator 210 may include a substrate 2 having a predetermined size, an acoustic reflective layer 4 formed on the substrate 2, The lower electrode 6 formed on the acoustic reflective layer 4, the piezoelectric layer 10 formed on the substrate 2 and the lower electrode 2, and the piezoelectric layer 10. An upper electrode 8 formed thereon, and a pair of upper lead wires 18 and lower lead wires 16 connected to the upper electrode 8 and the lower electrode 6, respectively, are provided and the lower electrode 6 is provided. And a package member 20 surrounding the upper electrode 8 and the piezoelectric layer 10.

The substrate 2 is made of silicon (Si), glass, or the like.

The lower electrode 6 and the upper electrode 8 are formed by depositing a conductive material such as NiCr, Au, Ti, Cr, etc. using an evaporator.

The lower pad portion 7 and the upper pad portion 9 connected to the lower lead line 16 and the upper lead line 18 are integrally connected to the lower electrode 6 and the upper electrode 8.

The piezoelectric layer 10 is formed by depositing a piezoelectric material such as ZnO or AlN by sputtering.

As shown in FIGS. 5 and 6, the acoustic reflective layer 4 is coated with a material such as photoresist PR on the substrate 2 in a predetermined pattern to form a sacrificial layer 5. The lower electrode 6, the piezoelectric layer 10, and the upper electrode 8 are sequentially formed on the sacrificial layer 5, and then the air layer is an empty space formed by removing the sacrificial layer 5. Is done.

In the above description, the acoustic reflective layer 4 is formed as an air space, which is an empty space. However, the present invention is not limited thereto, and two or more kinds of materials having different acoustic impedances are alternately plural as shown in FIG. It is also possible to form the acoustic reflective layer 3 by lamination.

The acoustic reflection layer 3 is formed of, for example, a first reflection layer 14 made of a silicon oxide (SiO ₂ ) film having a predetermined acoustic impedance, and silicon oxide, which is a material of the first reflection layer 14. A second reflection layer 15 made of a tungsten (W) film having an acoustic impedance greater than that of the SiO ₂ ) film is alternately stacked.

The package member 20 has the substrate 2, the piezoelectric layer 10, and the lower pad part along the circumference at predetermined intervals from side edges of the lower electrode 6 and the upper electrode 8. 7) and a partition wall 24 formed at a height higher than the surface of the upper electrode 8 above the upper pad part 9, a plate-shaped cover 22 covered and sealed on the partition wall 24, The lower lead wire 16 and the upper lead wire formed by coating a conductive material on the lower pad part 7 and the upper pad part 9 and electrically connected to the lower electrode 6 and the upper electrode 8. 18).

The partition wall 24 is formed by using an insulating material such as photoresist PR, and the height thereof is formed to be about several tens of micrometers or more.

The lower lead wire 16 and the upper lead wire 18 are made of a conductive material, and are connected to a circuit printed on the printed circuit board through wire bonding or the like when mounted on the printed circuit board.

Next, a process of manufacturing the thin film volume-elastic resonator 210 will be described with reference to FIGS. 5 and 6.

First, a sacrificial layer 5 for dividing a substrate 2 having a predetermined size into one or more rows and columns and applying a material such as photoresist in a predetermined pattern to each divided region 1 to form an acoustic reflective layer 4 A sacrificial layer forming step (P12) of forming a lower electrode, and a lower electrode forming step (P20) of forming a lower electrode 6 and a lower pad part 7 by applying a conductive material on each sacrificial layer 5; A piezoelectric layer forming step (P30) of forming a piezoelectric layer (10) by applying a piezoelectric material on the substrate (2) and the lower electrode (6), and applying a conductive material on the piezoelectric layer (10) to the upper electrode (8). And an upper electrode forming step (P40) for integrally forming the upper pad part (9), and a sacrificial layer removing step (P14) for removing the sacrificial layer 5 to form an acoustic reflective layer 4 including empty spaces. Cutting each zone 1 separated into one or more rows and columns to form one or more resonator chips 30 In step P50, the upper lead line 18 and the lower lead line 16 are electrically connected to the upper electrode 8 and the lower electrode 6, respectively, and the lower electrode 6 of each resonator chip 30 It comprises a packaging step (P60) for wrapping and sealing the upper electrode (8) and the piezoelectric layer (10).

The sacrificial layer forming step (P12), the lower electrode forming step (P20), the piezoelectric layer forming step (P30), the upper electrode forming step (P40) and the like are all commonly used a photo etching method (photo etching) method It is possible to form in a predetermined pattern so that detailed description is omitted.

The sacrificial layer removing step P14 is performed to remove the sacrificial layer 5 made of the photoresist using an ashing method.

In the above, the sacrificial layer forming step P12 and the sacrificial layer removing step P14 are combined to form a reflective layer forming step.

As described above, the method for forming the acoustic reflective layer 4 by using the sacrificial layer 5 is a conventional method of forming an acoustic reflective layer by removing an opposite side where the lower electrode 6 of the substrate 2 is formed by anisotropic etching. Compared to the method described above, the sacrificial layer 5 is formed of a material such as a photoresist in which the lower electrode 6 and the like are not damaged or damaged and the etching is easier than that of the substrate 2, thereby making it easy to manufacture.

It is also possible to configure such that the cutting step P50 for separating the respective zones 1 to form the resonator chip 30 is performed after the packaging step P60.

The packaging process P60 is performed on the substrate 2 and the piezoelectric layer 10 along the periphery with a predetermined distance from the side edges of the lower electrode 6 and the upper electrode 8. The partition forming step (P62) for forming the partition wall (24) at a height higher than the surface, the sealing step (P64) for covering and sealing the plate-shaped cover (22) on the partition wall (24), and the conductive material of the partition wall (24) A lead line forming process P66 is applied to the outside to form an upper lead line 18 and a lower lead line 16 electrically connected to the upper electrode 8 and the lower electrode 6, respectively.

The barrier rib forming step P62 and the lead wire forming step P66 may be formed in a predetermined pattern using a photo etching method which is generally used, and thus, detailed description thereof will be omitted.

The lead wire forming step P66 may be formed to form the upper lead wire 18 and the lower lead wire 16 using a printing and plating method.

As shown in FIG. 8, the thin film type volume elastic resonator 210 includes an upper lead line 48 and a lower portion of the package member 40 connected to the upper pad portion 9 and the lower pad portion 7, respectively. A lead wire 46 is provided at the side edge portion and a plate-shaped bottom plate 42 made of an insulating material, and the lower electrode 6, the piezoelectric layer 10, and the upper electrode 8 are attached to the bottom plate 42. It is also possible to include the sealing member 44 which wraps and seals the whole surface from the side edge of the board | substrate 2 in the state which positioned the board | substrate 2 in between.

When the upper pad portion 9 and the lower pad portion 7 are formed at a height higher than the surface of the upper electrode 8, respectively, the bottom plate 42 is sealed in close contact with the bottom plate 42. It is preferable because a space can be secured between the upper electrode 8 and the piezoelectric layer 10.

The upper lead wire 48 and the lower lead wire 46 may be plated on both side edges of the bottom plate 42 (the edges of positions corresponding to the upper pad part 9 and the lower pad part 7, respectively). Form by the method.

The upper lead wire 48 and the lower lead wire 46 are formed by printing and / or plating a conductive material so as to surround the side edges of the bottom plate 42 in a substantially "⊂" shape.

In the above description, the upper lead wire 48 and the lower lead wire 46 are described as being formed in a substantially "⊂" shape. However, the present invention is not limited thereto, and may be formed in a step shape, a straight shape, a "H" shape, or the like. Do.

The bottom plate 42 is made of a material having insulation and predetermined strength, such as ceramics.

The sealing member 44 is made of a polymer synthetic resin such as epoxy or silicon, and is sealed by molding treatment and / or can treatment.

In addition, the sealing member 44 may be formed by molding with a polymer synthetic resin and then sealing the can.

The resonator chip 30 and the bottom plate 42 are welded or ultrasonically crimped, for example, by soldering the lower pad portion 7 and the lower lead wire 16 and the upper pad portion 9 and the upper lead wire 18. It is made by fixing by using a method such as a law.

In the thin film type volume elastic resonator 210, the package member 50 is connected to the lower pad portion 7 and the upper pad portion 9, respectively, as shown in FIG. 9. And an insulating member 52 made of an insulating material inserted into the upper lead plate 58 and the lower lead plate 56 and the upper lead plate 58 abutted to prevent a short circuit, and the lower part. Sealing member for sealing the entire surface from the side edge of the substrate 2 in a state where the pad portion 7 and the upper pad portion 9 and the lower lead plate 56 and the upper lead plate 58 abut each other ( 54).

In the lower lead plate 56 and the upper lead plate 58, the upper electrode 8 and the piezoelectric layer 10 are attached to the lower lead when the lower pad portion 7 and the upper pad portion 9 are in contact with each other. In order to secure a predetermined space so as not to contact the plate 56 and the upper lead plate 58, it is preferable to form the contact protrusions 57 and 59 at predetermined heights, respectively.

The contact protrusions 57 and 59 and the lower pad portion 7 and the upper pad portion 9 are integrally attached and fixed by a method such as an ultrasonic crimping method in contact with each other.

The lower lead plate 56, the upper lead plate 58, and the contact protrusions 57, 59 are all formed using a conductive material.

The sealing member 54 is configured to protect the resonator chip 30 by molding and / or canning as described above.

The insulating member 52 is made of an insulating material such as glass.

In the thin film-shaped volume elastic resonator 210, the package member 90 is connected to the upper pad portion 9 and the lower pad portion 7 as shown in FIG. 10, and is formed in a substantially stepped shape. Assembled grooves so as to be positioned at a predetermined distance from the upper lead line 98 and the lower lead line 96 and the lower electrode 6 and the upper electrode 8 which are installed in close contact with both side edges of the substrate 2, respectively. 95 is formed in the center portion and formed to surround and seal the lower electrode 6 and the upper electrode 8 on the upper lead line 98 and the lower lead line 96 and the substrate 2 and the piezoelectric layer 10. It is also possible to include the sealing member 94.

The sealing member 94 is made of a polymer synthetic resin such as silicon or epoxy, and is provided with the upper lead wire 98 and the lower lead wire 96 attached thereto.

The upper lead wire 98 and the lower lead wire 96 are formed of a conductive material.

The sealing member 94 provided as described above is positioned on the substrate 2 such that the upper pad portion 9 and the upper lead line 98 and the lower pad portion 7 and the lower lead line 96 abut against each other. Packaging is carried out by fixed attachment and sealing using soldering, ultrasonic pressing, or the like.

In the above description of the preferred embodiment of the voltage controlled oscillator using the thin film volume-elastic resonator according to the present invention, the present invention is not limited thereto, and various modifications are made within the scope of the claims and the detailed description of the invention and the accompanying drawings. It is possible to implement, and this also belongs to the scope of the present invention.

According to the voltage controlled oscillator using the thin-film volume-elastic resonator according to the present invention as described above, since the inductor portion of the resonator is formed by using a chip-shaped resonator, miniaturization and high quality required in products such as portable phones and cordless phones are desperately required. It is possible.

That is, according to the voltage-controlled oscillator using the thin-film volume-elastic resonator according to the present invention, the inductor portion of the resonator part using the thin-film volume-elastic resonator (FBAR), which has a much higher quality coefficient value than the conventional dielectric resonator or surface acoustic wave (SAW) resonator, Because of this configuration, it is possible to provide a high quality miniature voltage controlled oscillator.

In addition, according to the voltage controlled oscillator using the thin-film volume-elastic resonator according to the present invention, the lower electrode, the piezoelectric layer, the upper electrode, and the like are formed by using photoetching and vapor deposition which are mainly used in semiconductor processes. It is possible to form very small, such as 占 퐉, mass production is possible, and the production cost can be greatly reduced.

Also, it is provided in chip form and provides resonators standardized to the same standards as 3216, 2012, 1608, 1005, 0806, 0603, etc., which are standard parts such as power, variable, resonator, oscillator, and amplifier. Since it is possible to automate the assembly process for manufacturing the voltage controlled oscillator, the production process is simplified, the mass production is possible, and the manufacturing cost is greatly reduced.

In addition, when the voltage controlled oscillator using the thin film volume-elastic resonator according to the present invention is applied, it is also possible to manufacture a PLL (phase locked loop) device by miniaturizing high quality.

Claims (7)

Power supply for supplying DC power, variable for adjusting the voltage for variable output frequency, resonator for setting the desired frequency, and oscillator for configuring negative resistance circuit for oscillation and amplifying part to increase the output level of oscillation frequency. In the voltage controlled oscillator configured, The inductor portion of the resonator portion is made using a thin film volume-elastic resonator, The thin film volume-elastic resonator includes a substrate having a predetermined size, an acoustic reflective layer formed on the substrate, a lower electrode formed of a conductive material on the acoustic reflective layer, and integrally connected to the lower electrode. A lower pad portion, a piezoelectric layer formed of a piezoelectric material on the substrate and the lower electrode, an upper electrode formed of a conductive material on the piezoelectric layer, and an upper portion formed integrally with the upper electrode. A package member having a pad part, a pair of upper lead wires and a lower lead wire electrically connected to the upper electrode and the lower electrode through the upper pad part and the lower pad part, respectively, and surrounding the lower electrode, the upper electrode and the piezoelectric layer. Voltage controlled oscillator using a thin-film volume-elastic resonator comprising. The acoustic reflective layer of the thin film volume-elastic resonator is formed by applying a photoresist in a predetermined pattern on the substrate to form a sacrificial layer, and the lower electrode, the piezoelectric layer, and the upper electrode in order on the sacrificial layer. And a thin film type volume elastic resonator comprising an air layer, which is an empty space formed by removing the sacrificial layer. The voltage controlled oscillator of claim 1, wherein the acoustic reflective layer of the thin film bulk elastic resonator is formed by stacking two or more kinds of materials having different acoustic impedances alternately in a plurality to form a multilayer. The package member of claim 1, wherein the package member of the thin film volume-elastic resonator is disposed on the substrate, the piezoelectric layer, the lower pad portion, and the upper pad portion along a circumference at a predetermined distance from side edges of the lower electrode and the upper electrode. A partition wall formed at a height higher than that of the upper electrode; A plate-shaped cover covered and sealed on the partition wall, A voltage controlled oscillator using a thin film volume-elastic resonator formed by coating a conductive material on the lower pad part and the upper pad part and including a lower lead line and an upper lead line electrically connected to the lower electrode and the upper electrode. The package member of claim 1, wherein the package member of the thin film volume-elastic resonator includes an upper lead wire and a lower lead wire connected to the upper pad portion and the lower pad portion, respectively, at a side edge portion and formed of an insulating material. , A voltage controlled oscillator using a thin-film volume-elastic resonator including a sealing member for encapsulating the entire surface from a side edge of the substrate while the substrate is positioned with the lower electrode, the piezoelectric layer, and the upper electrode disposed on the bottom plate. The method of claim 1, wherein the package member of the thin film volume-elastic resonator includes a lower lead plate and an upper lead plate made of a conductive material, each of which is formed a contact protrusion connected to the lower pad portion and the upper pad portion, respectively; An insulating member made of an insulating material inserted into a portion where the lower lead plate and the upper lead plate are in contact with each other and preventing a short circuit; And a sealing member encapsulating the entire surface from a side edge of the substrate in a state where the lower pad portion and the upper pad portion, and the lower lead plate and the upper lead plate are in contact with each other. The package member of claim 1, wherein the package member of the thin film volume-elastic resonator is connected to the upper pad portion and the lower pad portion, respectively, and is formed in a step shape to be in close contact with both side edges of the substrate. , An assembly groove is formed in the center portion so as to be positioned at a predetermined distance from the lower electrode and the upper electrode, and is formed to enclose and seal the lower electrode and the upper electrode on the substrate and the piezoelectric layer, and the upper lead wire and the lower lead wire are installed. Voltage controlled oscillator using a thin-film volume-elastic resonator including a sealing member.