KR20010026587A - micromachined tunable filter and production method - Google Patents

Abstract

PURPOSE: A micro-machined tuneable filter and a manufacturing method thereof are provided to produce high resonant frequencies and high Q values and improve reliability by employing passive elements such as inductors and capacitors. CONSTITUTION: In a micro-machined tuneable filter, a voltage is given between a spiral inductor(3) and an upper electrode(5) and forms an electrostatic force used for moving the upper electrode(5) vertically. The vertical movement of the upper electrode(5) changes the capacitance between the inductor(3) and the upper electrode(5) forming a virtual variable capacitor. As shown in an equivalent circuit, an oscillating circuit is formed with a variable capacitor connected in parallel with the spiral inductor(3). Here, the change of distance between the upper electrode(5) and the bottom electrode(4) changes the capacitance of the variable capacitor and modulates the frequency. Thus, by adjusting the inductance and the capacitance, the frequency width can be controlled.

Description

Micromachined tunable filter and production method

The present invention relates to a micromachined tunable filter used for the purpose of frequency modulation or the like in a signal processing system or a communication system.

Until now, the mechanical tunable filters have high Q through many researches and developments, but since the resonant frequency is low and composed of a mechanically moving structure, many problems in reliability have been raised and are not commercially available yet. .

As described above, the micromachined tunable filter according to the related art has a low resonance frequency and a mechanically moving structure instead of having high characteristic vectors, thereby raising reliability problems.

Therefore, the present invention has been made to solve the above problems, by constructing filters with passive elements (inductors and capacitors) made using conductors deposited by electroplating, high resonance frequency, high Q value, and high The objective is to make a reliable micromachined tunable filter and to use it commercially.

1 is a block diagram of a micromachined tunable filter according to the present invention

2A to 2B are equivalent circuit diagrams of a micromachined tunable filter according to the present invention.

FIG. 3 is a view illustrating a configuration in which the upper electrode moving in FIG. 1 is excluded.

4 is a block diagram of another embodiment of a micromachined tunable filter according to the present invention;

5 is another configuration diagram of the upper electrode according to the present invention;

6 is a block diagram of a micromachined tunable filter composed of two inductors and capacitors shown in FIG.

7A to 7H illustrate a first embodiment showing a manufacturing process according to the configuration of FIG. 1.

8A to 8G illustrate a second embodiment showing a manufacturing process according to the configuration of FIG. 4.

* Explanation of symbols for main parts of the drawings

1 substrate 2 bonding pad

3: inductor 4: lower electrode

5: upper electrode 5 ': sheet metal

6: air bridge 7: hinge

8: via post 9: variable capacitor

10, 11: insulation layer 12, 14: sacrificial layer

A feature of the micromachined tunable filter according to the present invention for achieving the above object is a substrate, an inductor formed in a predetermined pattern on the substrate, and formed in a bridge shape with a predetermined space on the inductor, up and down It includes a moving upper electrode and a lower electrode formed under the upper electrode to form a variable capacitor (upper electrode).

According to another aspect of the present invention, there is provided a process of sequentially forming a first insulating layer and a metal layer on the substrate, and patterning the metal layer to form an inductor having a predetermined pattern, a lower electrode, and a plurality of bonding pads. 2) forming an insulating layer, depositing and patterning a sacrificial layer on the entire surface, etching the second insulating layer to expose only a portion of the metal layer, forming a seed layer on the entire surface, and forming a mold on the entire surface. Forming a sacrificial layer having a, and forming a metal layer using an electroplating in the mold, by removing the sacrificial layer and the seed layer to the upper electrode and the lower electrode electrically connected to the different bonding pads in the form of an air bridge It comprises a step of forming each of the.

The operation according to the characteristics of the present invention is that CMOS tuner filters, which are used for frequency modulation, filtering and other purposes in signal processing or communication systems, use the same process as CMOS processing. Simultaneous integration with the schematics makes it easy to implement small systems of chip size.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

A preferred embodiment of the micromachined tunable filter and manufacturing method according to the present invention will be described with reference to the accompanying drawings.

1 is a configuration diagram of a micromachined tunable filter according to the present invention. Referring to FIG. 1, a substrate 1, a spiral inductor 3 formed in a predetermined pattern on the substrate 1, An upper electrode 5 formed in a bridge shape with a predetermined space on the inductor 3 and moving up and down, and a lower electrode 4 formed under the upper electrode 5 to form a variable capacitor; And an air bridge 6 connecting the bonding pad 2 and the lower electrode 4 to each other.

Referring to the operation of the micromachined tuneable filter configured as described above, a voltage is applied between the spiral inductor 3 and the upper electrode 5, and the upper electrode 5 is formed by electrostatic force formed at this time. This moves up and down.

As described above, a variable capacitor is formed between the inductor 3 and the upper electrode 5 according to the movement of the upper electrode 5.

That is, the tunable filter is composed of a resonant circuit in which the variable capacitor 9 and the spiral inductor 3 are connected in parallel, as shown in the equivalent circuit diagram of FIG. 2A, so that the upper electrode 5 and the lower electrode 4 are connected. The capacitance of the variable capacitor 9 changes due to the distance change therebetween, and thus frequency modulation is performed.

In this way, the base used frequency band is adjusted according to the proper design of the values of inductance and capacitance.

FIG. 3 is a block diagram illustrating a tunable filter excluding the upper electrode in FIG. 1, and shows the connection of the lower electrode 4 and the bonding pad 2 using the air bridge 6.

In this case, when a capacitor having a high capacitance is used as necessary, a high capacitance is formed by depositing an insulator having a high dielectric constant on the lower electrode 4 of the capacitor.

4 is a configuration diagram of another embodiment of the micromachined tunable filter according to the present invention. The micromachined tunable filter shown in FIG. 4 is different from the mitromachine tunable filter shown in FIG. Except that it matches.

The difference is that in FIG. 1, the upper electrode 5 and the via posts 8 are formed through one process so that the thicknesses of the metal layers of the upper electrode 5 and the via column 8 are the same. In FIG. 4, the movable upper electrode 5 and the via pillar 8 are formed through two different processes, respectively, so that the metal thicknesses of the upper electrode 5 and the via pillar 8 are different.

As shown in FIG. 5, the upper electrode 5 is divided into a zigzag hinge 7 and a plate 5 ′, whereby the movement of the upper electrode 5 can be performed at a low voltage. Let's do it.

FIG. 6 is a schematic diagram of a micromachined tuneable filter including two inductors and a capacitor shown in FIG. 2B.

The manufacturing process of the micromachined tunable filter according to the present invention is similar to the CMOS process, and can be manufactured simultaneously with the CMOS circuit, thereby easily implementing a compact system having a chip size.

Next, the manufacturing process of the micromachined tunable filter having the above structure will be described in detail with reference to the accompanying drawings.

First embodiment

7A to 7H illustrate an embodiment of a manufacturing process according to the configuration of FIG. 1. First, as shown in FIG. 7A, first, silicon dioxide and silicon nitride, which is an insulator 10, are formed on a silicon substrate 1. Or either polymer. However, if a polymer is used, it must be cured.

The process of depositing the insulating layer 10 is not necessary using an insulating substrate such as quartz.

Subsequently, a metal film 2 such as Cr / Au, Ti / Au, Ti / Cu, or Cr / Cu is deposited on the insulating layer 10 using a sputter or an evaporator.

As shown in FIG. 7B, the metal film 2 is patterned by a photolithography process and wet etching to form a spiral inductor 2, a lower electrode 4 of a variable capacitor, and a plurality of bondings. Bonding pads 2 are formed.

At this time, the metal film 2 is formed of Au or Cu having a high conductivity that can be deposited by the electroplating method.

Then, an insulator 11 such as silicon dioxide, silicon nitride, or polymer is coated on the front surface as shown in FIG. 7C.

Subsequently, as shown in FIG. 7D, a pattern is formed using a sacrificial layer 12 made of photoresist, polyimide, or pure aluminum to provide a space for the upper electrode 5 of the variable capacitor to move.

The formed photoresist, polyimide, and aluminum layer will be removed after formation of the structure.

As shown in FIG. 7E, only a portion of the insulating layer 11 is exposed by selectively etching using dry etching or wet etching.

Subsequently, a seed layer 13 is deposited on the entire surface as shown in FIG. 7F.

As shown in FIG. 7G, the sacrificial layer 14 is coated with a photoresist and then patterned to form a mold for electroplating.

Subsequently, after depositing a metal layer made of any one of NiFe alloy (permalloy), Ni, Au, or Cu by electroplating, the sacrificial layer 14 may be dried or wet etched. ) And the seed layer 13 are selectively etched.

The metal film is deposited by electroplating to form a metal air bridge 6 electrically connected to the movable upper electrode 5, the lower electrode 4, and the bonding pad 2 of the variable capacitor.

Subsequently, as shown in FIG. 7H, the photoresist, polyimide, or aluminum layer deposited on the sacrificial layer 12 is removed using dry etching or wet etching to form a metal air bridge electrically connected to a bonding pad.

As such, the process of making a micromachined tunable filter is very similar to that of a CMOS process, allowing the CMOS circuit design to be made simultaneously with the tunable filter, and because the substrate is formed of silicon, it is possible to use a batch fabrication process on one substrate. The advantage is that multiple filters can be created at the same time.

Second embodiment

8A to 8G are process diagrams illustrating a manufacturing process according to the configuration of FIG. 4. First, as shown in FIG. 8A, a silicon dioxide, silicon nitride, or polymar, which is an insulator 10, is formed on a silicon substrate 1. Coating. However, if polymer is used, it should be cured.

In this case, a process of depositing the insulating layer 10 is not necessary by using an insulating substrate such as quartz.

Subsequently, the metal film 2, which is one of Cr / Au, Ti / Au, Ti / Cu, or Cr / Cu, is deposited using a sputter or an evaporator.

In addition, as shown in FIG. 8B, the metal layer 2 is helically inductor 3, the lower electrode 4 of the variable capacitor, and a plurality of bonding pads using a photolithography process and wet etching. (bonding pads) 2 are formed.

They are also used as a seed layer which is electrically connected to each other so that the via pillars 8 are later electrically connected when the via pillar 8 is deposited by electroplating.

In addition, the spiral type inductor 3, the lower electrode 4 of the variable capacitor, and the bonding pads 2 are formed of Au and Cu of electroplating.

And an insulator 11 such as silicon dioxide, silicon nitride, or polymer is coated on the front surface as shown in FIG. 8C.

Subsequently, as shown in FIG. 8D, a pattern is formed using the sacrificial layer 12 photoresist, polyimide, or pure aluminum to increase the space for the upper electrode of the variable capacitor to move.

That is, the formed photoresist, polyimide, and aluminum layer are removed after forming the structure.

Then, as shown in FIG. 8E, the formed pattern is used as a mask to be selectively etched by dry etching or wet etching to expose a portion of the insulating layer 12, and then via pillar molds are formed by electroplating. Form.

Then, a seed layer 13 is deposited on the entire surface.

Then, as shown in FIG. 8F, a photoresist, which is a sacrificial layer 14, is coated to form a mold for electroplating.

The mold is deposited by using a metal layer (8) made of any one of NiFe alloy (permalloy), Ni, Au, or Cu by electroplating, and then sacrificed using dry etching or wet etching. The layers 14 and seed layer 13 are selectively removed.

The metal layer 8 formed by electroplating forms a moving upper electrode 5 and a metal air bridge 6 for the variable capacitor.

Subsequently, the photoresist, polyimide, or aluminum layer deposited on the sacrificial layer 12 is removed using dry etching or wet etching to form a metal air bridge electrically connected to the bonding pads as shown in FIG. 8G.

As described above, the micromachined tuneable filter according to the present invention has the following effects.

First, as the filter is composed of passive elements made using conductors deposited by electroplating, high resonant frequency, high Q factor (Quality factor), and highly reliable filters can be manufactured and used commercially.

Secondly, the fabrication process is similar to the CMOS process and can be fabricated simultaneously with a CMOS circuit, making it possible to easily implement a small system of chip size.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (12)

Substrate, An inductor formed on the substrate with a predetermined pattern; An upper electrode formed in a bridge shape with a predetermined space on the inductor and moving up and down; And a lower electrode formed under the upper electrode to form an upper electrode and a variable capacitor. The method of claim 1, Bonding pads for applying power to the upper and lower electrodes; And a air bridge formed on the inductor with a predetermined space to electrically connect the lower electrode and the bonding pad. The method of claim 2, The upper electrode is a sheet metal formed in the form of an air bridge corresponding to the lower electrode; A via pillar formed on the bonding pad and supporting the upper electrode; Micromachined tunable filter comprising a hinge for connecting the sheet metal and the via pillar with a predetermined pattern. The method of claim 3, wherein The hinge is a micromachined tuneable filter, characterized in that formed in a zigzag form. The method of claim 1, The inductor is a micromachined tuneable filter, characterized in that formed in a spiral pattern. Sequentially forming a first insulating layer and a metal layer on the substrate; Patterning the metal layer to form an inductor having a predetermined pattern, a lower electrode and a plurality of bonding pads, and forming a second insulating layer on the front surface; Depositing and patterning a sacrificial layer on the entire surface and etching the second insulating layer to expose only a part of the metal layer; Forming a seed layer on the front surface, Forming a sacrificial layer having a mold of a predetermined shape on the entire surface, and forming a metal layer using electroplating in the mold; Removing the sacrificial layer and the seed layer to form an upper electrode and a lower electrode electrically connected to the different bonding pads in the form of an air bridge, respectively. The method of claim 6, The inductor, the lower electrode, and the plurality of bonding pads are micromachined tunable filters, which are deposited by electroplating using Au or Cu having conductivity. The method of claim 6, The metal layer is a method of manufacturing a micromachined tuneable filter, characterized in that made of any one of Cr / Au, Ti / Au, Ti / Cu or Cr / Cu. The method of claim 6, The first and second insulating layer is a method of manufacturing a micromachined tuneable filter, characterized in that made of any one of silicon dioxide, silicon nitride, or a polymer. The method of claim 6, The metal layer is a method of manufacturing a micromachined tunable filter, characterized in that made of any one of NiFe alloy, Ni, Au, or Cu. The method of claim 6, The sacrificial layer is a method of manufacturing a micromachined tunable filter, characterized in that made of any one of a photoresist, polyimide, or pure aluminum. Sequentially forming a first insulating layer and a metal layer on the silicon substrate; Patterning the metal layer to form an inductor having a predetermined pattern, a lower electrode, and a plurality of bonding pads, and forming a second insulating layer on the front surface; Depositing and patterning a sacrificial layer on the entire surface to form a mold of a predetermined shape and etching the second insulating layer to expose only a part of the metal layer; Forming a via pillar using electroplating in the mold, Forming a seed layer on the front surface, Forming a sacrificial layer having a mold of a predetermined shape on the entire surface, and forming a metal layer using electroplating in the mold; Removing the sacrificial layer and the seed layer to form an upper electrode and a lower electrode electrically connected to the different bonding pads in the form of an air bridge, respectively.