KR100714129B1 - Low temperature co-fired ceramic multilayer type microwave tunable device and method of fabricating the same device - Google Patents

Abstract

Provided are a low temperature co-fired stacked ultra-high frequency variable element having a ferroelectric characteristic and greatly reduced in size, and a method of manufacturing the same. The variable element has a plurality of green sheets each having a conductive pattern formed thereon and each conductive pattern is connected through a connection contact, and at least one of the green sheets is formed of a ferroelectric green sheet. Low temperature co-fired ceramic (LTCC) stacked type ultra-high frequency variable device of the present invention is laminated on the ferroelectric layer showing different capacitance characteristics with respect to the applied DC voltage, the low-temperature co-fired voltage in the direction perpendicular to the substrate By implementing variable capacitors, design diversification can be achieved while simplifying the device fabrication process and significantly reducing device size. As a result, it is possible to easily realize an ultra-high frequency variable element having a frequency / phase variable characteristic as well as cost reduction and miniaturization.

Ultra-high frequency variable element, ferroelectric, low temperature simultaneous firing, frequency / phase variable

Description

Low temperature co-fired multilayer ultra-high frequency variable device and its manufacturing method {Low Temperature Co-fired Ceramic Multilayer Type Microwave Tunable Device and method of fabricating the same device}

FIG. 1A is a circuit diagram illustrating a design circuit in which a band pass filter according to an embodiment of the present invention is implemented as a Lumped Element.

FIG. 1B is a graph showing reflection and transmission loss characteristics according to frequencies obtained through ultra-high frequency simulation of the circuit of FIG. 1A.

2A and 2B are a manufacturing diagram and a cross-sectional view of a multilayer capacitor including a ferroelectric green sheet used in the band pass filter of FIG. 1A.

3A is a perspective view illustrating a three-dimensional implementation of the band pass filter of FIG. 1A by simultaneously stacking ceramic green sheets at low temperature.

FIG. 3B is a view in which the band pass filter of FIG. 3A corresponds to the circuit of FIG. 1A.

FIG. 4 is a graph showing frequency characteristics of the band pass filter of FIG. 3A according to a change in capacitance of a voltage variable capacitor formed using a ferroelectric green sheet.

<Description of main parts in the drawing>

100, 140: Ceramic Green Sheet ... 120: Ferroelectric Green Sheet

220,240: Conducting pattern ......... 310,320: Connection contact

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to ultra-high frequency devices, and more particularly, to a stacked ultra-high frequency variable device formed through a low temperature co-fired ceramic (LTCC) process and a manufacturing method thereof.

Ferroelectrics have various fields of application due to the characteristics of the material itself. Among them, applications to ultra-high frequency variable devices utilize a phenomenon in which the dielectric constant of the ferroelectric material is changed due to the change in the microstructure of the material. .

This characteristic is stable in a very wide frequency band, which can be used to effectively improve the active antenna system which can be electrically controlled without mechanically adjusting the direction of the antenna. For example, it is possible to improve the characteristics by applying ferroelectrics to various parts of the active antenna system, such as phase shifters, frequency variable filters or voltage regulating capacitors, and voltage regulating resonators, oscillators, voltage regulating dividers, or impedance matching blocks. Can be.

In addition, ferroelectrics can reduce device size and light weight due to large dielectric constants, and have low electrical power consumption due to response characteristics and low leakage current, high stability against changes in transmission microwave power, and device manufacturing process. It is simple and can lower the production cost, and thus has many advantages over the conventional ferromagnetic or competitive devices made of semiconductors.

On the other hand, in order to realize such ultra-high frequency variable devices, many researches have been conducted on planar devices having a two-dimensional structure using a thin film on a single crystal substrate due to the development of a ceramic substrate or a thin film deposition technology. In such a structure, a method of implementing a capacitor and an inductor, which are main components of a communication device, implements characteristics by arranging lines having a length of about 1/4 of a wavelength corresponding to an operating frequency on a plane.

However, the planar ultra-high frequency variable device has a relatively simple process, but as the operating frequency decreases, the wavelength increases and the size of the device increases, so that the overall size of the device is increased when integrated on one substrate through an integration process with other devices. It has the disadvantage of becoming larger.

Accordingly, an object of the present invention is to provide a low temperature co-fired stacked ultra-high frequency variable device having a ferroelectric characteristic and greatly reduced in size in terms of device size, and a method of manufacturing the same.

In order to achieve the above technical problem, the present invention provides a plurality of green sheets (green sheet) laminated with a conductive pattern formed on each; And a connection contact connecting the respective conductive patterns, wherein at least one of the green sheets provides a low temperature co-fired ceramic (LTCC) stacked ultra high frequency variable element formed of a ferroelectric green sheet.

According to an embodiment of the present invention, the ferroelectric green sheet serves as a dielectric of a voltage variable capacitor, and the voltage variable capacitor has a characteristic of decreasing capacitance as an applied voltage increases.

In one embodiment of the present invention, the variable element includes a plurality of stacked capacitors and an inductor to function as a band pass filter, and includes a variable capacitor by a dielectric green sheet. The pass frequency band is moved in accordance with the change in the capacitance of the.

In addition, in order to improve the pass frequency band characteristics of the variable element, the capacitor and the inductor are formed in a structure that is repeated periodically, the entire variable element may be formed in a rectangular parallelepiped shape of one side is 2.5 mm or less in length.

In accordance with another aspect of the present invention, there is provided a method of forming a plurality of green sheets, the at least one being a ferroelectric green sheet. Forming a contact hole in the green sheet; Forming a conductive pattern on the green sheet and filling the contact hole with a conductive material; And stacking and sintering the green sheet. Provides a method for manufacturing a low temperature co-fired ceramic (LTCC) stacked type ultra-high frequency variable device.

According to an embodiment of the present invention, the lamination and sintering of the green sheet is preferably performed through a low temperature simultaneous firing process. Meanwhile, conductive patterns and holes of the stacked green sheets form a plurality of stacked capacitors and inductors, and the ferroelectric green sheet serves as a dielectric of a voltage variable capacitor among the stacked capacitors.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention; In the following description, when a component is described as being on top of another component, it may be directly on top of another component, and a third component may be interposed therebetween. In addition, in the drawings, the thickness or size of each component is omitted or exaggerated for convenience and clarity of description, and the same reference numerals in the drawings refer to the same element. On the other hand, the terms used are used only for the purpose of illustrating the present invention and are not used to limit the scope of the invention described in the meaning or claims.

1A is a circuit diagram illustrating a design circuit in which a band pass filter according to an embodiment of the present invention is implemented as a lumped element, and is a circuit for a frequency variable band pass filter using a voltage variable capacitor.

Referring to FIG. 1A, the band pass filter includes a resistor R and a capacitor and inductor that are structurally repeated. Where Vs denotes the signal power supply, and the capacitance of each capacitor is C ₀ : 0.2623pF, C ₁ : 4.5531pF and C ₂ : 3.725pF, and the inductance of each inductor is L ₀ : 5.55248nH, L ₁ : 1nH and L ₂ : 1nH. With these capacitance and inductance values, the band pass filter has a center frequency, band width, insertion loss, ripple, and return loss of 2440 MHz, 45 MHz, and 2.5, respectively. It exhibits the characteristics below dB, below 1.5 dB, and above 20 dB.

In general, the filter consists of a capacitor and an inductor, and in the case of the band pass filter, it has a structure having a periodic repeating arrangement in order to improve the pass characteristics. The pass frequency band has a capacitance between each capacitance, an inductance, and a coupling between blocks Determined by the ring. However, in the frequency variable band pass filter using the voltage variable capacitor according to the present invention, the pass frequency band is shifted as the capacitance value of the capacitor changes according to the applied voltage. A more detailed description thereof will be described later with reference to FIG. 4.

FIG. 1B is a graph showing reflection and transmission loss characteristics according to frequencies obtained through ultra-high frequency simulation of the circuit of FIG. 1A, and is a graph when there is no change in capacitance, that is, when the capacitance is set in FIG. 1A.

Referring to FIG. 1B, the above-described characteristics, that is, the center frequency, the bandwidth, the insertion loss, the ripple, and the reflection loss, may be confirmed in a graph. However, the ripple portion does not appear exactly, but appears in the transmission frequency band portion of the transmission loss graph, that is, less than 1.5 dB in the transmission loss graph portion between the frequency 2.4 ~ 2.5 GHz.

FIG. 2A is a manufacturing diagram of a stacked capacitor including a ferroelectric green sheet used in the band pass filter of FIG. 1A.

Referring to FIG. 2A, a multilayer capacitor is formed by stacking a plurality of green sheets 100, 120, and 140 through low temperature co-fired ceramic (LTCC). The ferroelectric green sheet 120 is inserted into the stacked capacitor of the present embodiment to form a voltage variable capacitor. The top green sheet 100 serves as a cover, and the other green sheets 140 are general ceramic green sheets, but their characteristics may be different. Therefore, the lamination process in the manufacturing process through low temperature simultaneous firing requires techniques such as control of interfacial reactivity and simultaneous sinter shrinkage control by laminating ceramic green sheets of different materials.

Here, the low temperature simultaneous firing and lamination process will be briefly described. First, the materials for forming each green sheet are mixed in a slurry form and drawn out in a sheet or tape shape. Next, holes are formed in required portions of each sheet. This hole is for the contact of the conductive patterns formed later. A conductive pattern is formed in each sheet and the hole is filled with a conductive material. Then, the lamination process of each sheet is performed, and unnecessary portions are cut and removed. Next, heat and pressure are applied to sinter to complete the desired device. The device thus formed is combined via a packaging process into other related electronic components. At this time, the sintering process is performed at a low temperature, that is, about 1000 ° C. or less, thereby minimizing the decrease in the dielectric constant and the quality factor of the green sheet. On the other hand, by performing a process in such a way that the test between each process and feed-back to the entire process, it is possible to manufacture a device of more improved quality.

On the other hand, in the present embodiment, as shown in the green sheet 'l'-shaped conductive patterns 220,240 are alternately formed to the left and right ends alternately, such a conductive pattern serves as an electrode of the capacitor. This conductive pattern of the present embodiment is only one example, of course, can be variously formed.

FIG. 2B is a cross-sectional view of the I-I part after the stacked capacitor of FIG. 2A is completed, and shows a state in which the connection contact is formed at the left and right sides.

Referring to FIG. 2B, a voltage is applied to the conductive pattern formed on the green sheet through the connection contacts 310 and 320 formed to the left and right sides. As a result, charge is charged into the dielectric between each conductive pattern. On the other hand, the portion where the ferroelectric green sheet 120 is formed to form a voltage variable capacitor, and has a characteristic that the capacitance changes according to the magnitude of the voltage applied.

In this embodiment, one sheet of ferroelectric green sheet is used, but may be formed more than necessary, and the position may be formed by selecting a suitable place according to the characteristics of the device. On the other hand, although not shown in the drawings, the inductor is also formed in a stacked type, but the characteristics of the green sheet used for the inductor and the capacitor are different. This is because of the different forms of energy stored in capacitors and inductors. In addition, a plurality of stacked capacitors and inductors may be formed simultaneously through low temperature simultaneous firing and lamination processes.

The stacked capacitor and the stacked inductor including the ferroelectric green sheet as in the present embodiment may be periodically repeated to form a three-dimensional frequency variable band pass filter.

FIG. 3A is a perspective view illustrating a three-dimensional implementation of the band pass filter of FIG. 1A by stacking ceramic green sheets at a low temperature at the same time, and is a band pass filter including a voltage variable capacitor having the ferroelectric green sheet of FIG. 2A.

Referring to FIG. 3A, it can be seen that an inductor L portion in which the conductive pattern is wound upward and a portion in which the capacitor C as shown in FIG. 2A is formed. The size of the device shown here is a cube size of about 2.5 mm in length on one side, which is much smaller than the size of a microwave variable device made of a general thin film or ceramic.

In addition, the device is complex as shown, but basically consists of a stacked capacitor and an inductor, and consists of a repetition of a block of the stacked capacitor and the inductor.

In this embodiment, the ferroelectric green sheet is embedded between the ceramic green sheets which are simultaneously fired at low temperature, thereby implementing a voltage variable capacitor, and using the same, a frequency band according to a change in the voltage applied to the variable capacitor in the ultra high frequency variable element, for example, the ultra high frequency. It is possible to realize a three-dimensional frequency variable band pass filter to be moved. As the ultra-high frequency variable device is formed in three dimensions as described above, the device can have various advantages such as ease of device design, diversity, simplified manufacturing process, and small device size.

FIG. 3B is a view in which the band pass filter of FIG. 3A corresponds to the circuit of FIG. 1A, and the inductor L and the capacitor C shown in FIG. 3A are shown in a two-dimensional shape.

FIG. 4 is a graph showing frequency characteristics of the band pass filter of FIG. 3A according to a change in capacitance of a voltage variable capacitor formed using a ferroelectric green sheet.

Referring to FIG. 4, reflection and transmission loss characteristics are shown through ultra-high frequency simulation using a change in capacitance due to voltage as a variable in a voltage variable capacitor, and it is understood that a pass frequency band or a center frequency is shifted according to the change in capacitance. Can be.

In more detail, when there is no change in the capacitance (thin solid line), the center frequency is about 2.45 GHz, and the center frequency is shifted to 2.57 GHz by 10% change in the capacitance (thick solid line). It can be seen that the center frequency moves to 2.72 GHz due to the change in the capacitance (dotted line). That is, it can be seen that the frequency variable characteristic of about 10% or more with respect to the change in the 20% power storage capacity based on the center frequency. Here, the change in power storage capacity represents the amount to be reduced, and such a decrease in power storage capacity is a result of the increase in the voltage applied to the voltage variable capacitor.

The low temperature co-fired stacked ultrahigh frequency variable element using the ferroelectric green sheet according to the present invention can be applied to various ultra high frequency variable elements such as a variable voltage capacitor, a voltage variable resonator, a phase shifter, a divider, an oscillator, an impedance matching block, as well as a band pass filter. Can be.

So far, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. will be. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described in detail above, the multilayered microwave variable device of the present invention secures a variety of designs by realizing a voltage variable capacitor in a direction perpendicular to the substrate by simultaneously firing a voltage variable ferroelectric layer when stacking ceramic green sheets. At the same time, it has the effect of simplifying the device fabrication process and greatly reducing the size of the device.

Accordingly, it is possible to implement a very small low power and low cost communication module by mounting to the relevant device.

Claims (9)

A plurality of green sheets stacked with conductive patterns formed on each of the green sheets; And A connection contact connecting the respective conductive patterns; At least one of the green sheets is a low temperature co-fired ceramic (LTCC) stacked ultra-high frequency variable element formed of a ferroelectric green sheet. The method of claim 1, The ferroelectric green sheet is a low-temperature co-fired stacked ultra-high frequency variable device, characterized in that it serves as a dielectric of a voltage variable capacitor (capacitor). According to claim 1, The variable device includes a plurality of stacked capacitors and inductors to function as a band pass filter, characterized in that the low-temperature simultaneous firing stacked ultra-high frequency variable device. The method of claim 3, wherein The variable element includes a voltage variable capacitor by a ferroelectric green sheet, The variable element is a low-temperature simultaneous firing stacked ultra-high frequency variable element, characterized in that the pass frequency band is moved in accordance with the change in the capacitance of the capacitor. The method of claim 3, wherein In order to improve the pass frequency band characteristics of the variable element, Low-temperature co-fired stacked ultra-high frequency variable element, characterized in that the capacitor and the inductor is formed in a repeating structure periodically. Forming a plurality of green sheets, at least one of which is a ferroelectric green sheet; Forming a contact hole in the green sheet; Forming a conductive pattern on the green sheet and filling the contact hole with a conductive material; And Laminating and sintering the green sheet; Low temperature co-fired ceramic (LTCC) stacked type ultra-high frequency variable device manufacturing method comprising a. The method of claim 6, The stacking and sintering step is a low-temperature co-fired stacked ultra-high frequency variable device manufacturing method characterized in that it is made through a low-temperature co-fired process. The method of claim 6, Low temperature co-fired stacked ultra-high frequency variable device manufacturing method characterized in that the process is carried out by performing a test in each of the steps and feeds the results back to the previous step (feed back). The method of claim 6, The conductive patterns and holes of the stacked green sheets form a plurality of stacked capacitors and inductors, And the ferroelectric green sheet serves as a dielectric of a voltage variable capacitor among the stacked capacitors.

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