JPS63138808A - Integrated type piezoelectric thin film function element - Google Patents

Abstract

PURPOSE:To easily incorporate a piezoelectric thin film to an adjacent integrated circuit without damaging the piezoelectric thin film by protecting the piezoelectric thin film by a 2nd dielectric film and connecting it to the metallic film wire through a connection hole formed to a part of the dielectric film. CONSTITUTION:A 1st dielectric film 4 is formed on a protective film 3 with the protection film 3 so as to form an air gap layer whose part has openings 5a, 5b. A 1st electrode 6, the piezoelectric thin film 7, a 2nd electrode 8 and the 2nd dielectric film 9 are formed on the dielectric film 4 sequentially. The protection film 3 on the metallic wire pattern 2 is etched at two positions to form a connection hole 12 and a metal such as Al, Au/Ti or the like is formed to form the metallic film wire 13 by etching. Thus, the thin film 7 is incorporated easily to the adjacent integrated circuit without giving damage to the thin film 7.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention provides a structure in which a resonator using a piezoelectric thin film as a vibrating membrane and a semiconductor integrated circuit are integrated on the same substrate. This relates to a relic piezoelectric::fF film capacitor.

(Prior art) V) (Piezoelectric thin film resonators are attracting attention as a resonator that can be used in very high frequency bands such as the F band and UHF band and can be integrated. One vibrating membrane is made of Thin II+4.

JP-A-60-18 already proposed by the inventors of this application
Publication No. 9307 describes a conventional example of such an insulated film resonator, in which a piezoelectric thin film is formed on a substrate, and the piezoelectric thin film is placed at a position corresponding to the vacuole layer. A configuration in which a pair of low poles are provided facing each other is shown.

In this case, by applying the 'IIL'A signal between a pair of electrodes, the composite vibrating membrane of the dielectric film and the piezoelectric thin film in the corresponding part of the gap No. 1 vibrates, forming a resonator and forming a gap layer. Therefore, compared to a method in which recesses as voids are formed on the substrate itself by etching, this method has advantages in that it is superior in mass production and does not impair the mechanical strength of the substrate.

By the way, since these pressure-4 thin film resonators are ultra-small and can be formed by thin film forming processing, they can be integrated into a semiconductor circuit board on which amplifiers etc. are already formed, so that, for example, one chip can be formed. It is possible to realize a type oscillator circuit.

However, piezoelectric thin film resonators and semiconductor integrated circuits (RWQ and counterfeit) must be integrated on the same substrate, but there have been no examples disclosed of technology that integrates these. 7 for Yoyoi Tsuji.

For this reason, the piezoelectric thin film resonator and the semiconductor element are actually constructed as separate components and connected and wired using bonding wires, making it difficult to integrate them into a single chip. In such a conventional configuration, the capacitance of the resonator due to the influence of stray capacitance:
As the ratio increases, when used as a VOO (-It pressure control oscillator), there is a problem that the frequency variable width decreases, and the g! I couldn't achieve my dreams.

(Problems to be Solved by the Invention) In the case where the piezoelectric thin film resonator and the semiconductor element are configured as individual components as described above, it is difficult to integrate them into a single chip.
There were problems in that the frequency variable range available to the voltage control generator was narrow, and it was not possible to achieve ultra-miniaturization and reliability.

This invention was made to solve these problems, and it is possible to easily integrate a piezoelectric thin film resonator and a semi-dedicated circuit on the same substrate, thereby achieving ultra-miniaturization and high reliability. It is an object of the present invention to provide an integrated piezoelectric thin film functional element that can achieve a wide range of frequency variations when configured as a voltage-controlled oscillator.

[Structure of the Invention] (Means for Solving the Problems) The integrated piezoelectric thin functional element of the present invention includes a void layer, a first dielectric film, a first electrode, a piezoelectric A piezoelectric thin film resonator configured by sequentially forming a thin film, a second electrode, and a second dielectric film, and an integrated circuit on the substrate, are connected to a second dielectric film on the first and second poles. It is characterized by being connected and integrated by metal film wiring through a connection hole provided in a part of the body membrane.

(Function) In the collector-type piezoelectric thin-diameter functional element of the present invention, the piezoelectric film is protected by the second dielectric film, and this
A metal pattern is formed through a connecting hole formed in a part of the body membrane.
Since the piezoelectric thin film is connected through this connection, it can be easily integrated with an adjacent integrated circuit without damaging the piezoelectric thin film. Therefore, this makes it possible to achieve ultra-miniaturization and high reliability.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1(a) is a plan view of the same embodiment, Figure 1b) is fa)
It is a longitudinal sectional front view taken along the line BB'1 in the figure and looking straight ahead in the direction of the arrow.

In FIGS. 1(a) and 1(b), a semiconductor film 3 of Si, GaAs, etc. is formed at l.

For example 8 i 0. on this hold +1[3. The first consisting of
Parts of the dielectric film 4 and the protective film 3 are 3a and 3b.
The gap layer 5 is formed to have an opening shown in FIG.

Furthermore, a first electrode 6 is placed on this first dielectric 13M4.
, a piezoelectric thin film 7 made of, for example, a ZnO film, a second electrode 8
, and the second dielectric material ag9, the piezoelectric thin film resonator 2 is constructed.

The first electrode 6 and the second electrode 8 are provided across the piezoelectric thin film 7 to face each other at positions corresponding to the cavities 5 and 5. The thickness of the cavity layer 5 is equal to that of the resonator. It is sufficient if the vibration displacement is several times the vibration displacement of the diaphragm at one operating frequency, and from the viewpoint of ease of production, a range of several hundred amperes to several μm is appropriate.

In the piezoelectric thin film resonator 20 having such a configuration, when an electric signal is applied between the first electrode 6 and the second electrode 8, the first dielectric film 4 on the gap layer 5 and the piezoelectric The composite vibrating membrane composed of the thin film 7 and the second dielectric film 9 vibrates, thereby operating as a resonator.

Therefore, in this embodiment, the piezoelectric thin film resonator 20
A configuration is adopted in which the integrated circuit 10 and the integrated circuit 10 are interconnected. Further, to specifically explain the manufacturing process of this element, first, the entire surface of the protective film 3 is coated.

It should be noted that the second electrode 8 forms extended pores 11 in weak spots of ZnO [acid or alkali IJ]. At this time, the connection hole 11 is opened at the inner edge of the second electrode 8 to prevent damage to the ZnOg during etching.

Next, place 14 layers of gold on the metal wiring pattern 2 by placing the protective W1 pattern 3 in two places! 113 is formed. Wiring is made between the connection hole 11 and the connection hole 12 through this one.

With this configuration, wiring at the urgently installed stepped portions of the piezoelectric thin film resonator 2o, which is difficult to form using the lift-off method, can be easily performed. It is formed.

In this way, it is possible to achieve ultra-miniaturization and high reliability of the integrated piezoelectric thin functional element.

Next, a second embodiment of the invention will be described with reference to FIG.

The second factor is the second dielectric film 9 of the first embodiment.
And the upper part of the metal film wiring 13 is 8 i 0. .

This is covered by providing a chemically stable third dielectric film 14 of Si, N, or the like. In the embodiment shown in FIG. 2, parts corresponding to those in FIG. 1 are designated by the same reference numerals.

By brazing with the third dielectric film 14 in this manner, oxidation of the metal film wiring 13 and the influence of outside air such as moisture can be prevented, and reliability can be further improved.

Furthermore, since the piezoelectric thin film resonator 20 can be wired integrally with the integrated circuit 10 and configured as a oscillator, delicate frequency adjustments can be made by forming the dielectric film 14 while monitoring the oscillation frequency. It has the important advantage that it can be done.

Furthermore, by using SiO,g, which has a frequency temperature coefficient of opposite sign to that of the piezoelectric film 7, as the dielectric film 14, the temperature characteristics can be compensated. Even if the second dielectric film 9 is formed thinner than the desired film thickness necessary to achieve zero temperature coefficient, the third dielectric film 14 will eventually achieve zero temperature coefficient. Since the first dielectric film 4 and the second dielectric film 9 can be made thinner, the step coverage of the gold elliptical film wiring 13 at the step portion of these dielectric films 4 and 9 can be improved. This has the valuable effect of facilitating formation and improving reliability.

Next, a third embodiment of the present invention will be described with reference to FIGS. 3(a) and 3(b).

In the embodiment shown in FIG. 1, gold W4 pattern hems 13 for connecting the piezoelectric thin film resonator 20 to the integrated circuit 10 are led out to both sides of the piezoelectric thin film resonator 20, and further integrated via the metal wiring pattern 2 [circuit Since it is connected to IO, the connecting conductor portion has a certain length, but in the embodiment shown in FIG. A pair of gold (gold) l & rims 13 are provided in parallel.

This eliminates the need for the connection hole 12 and the metal wiring pattern 2, making it possible to further shorten the length of the connection conductor portion.

Therefore, not only can the shape of the element be further miniaturized, but also the length of the connecting conductor portion can be shortened, which reduces the stray capacitance and parasitic inductance of this portion, making it possible to further stabilize the characteristics of the element.

Further, oblique vapor deposition for improving the ability to remove the step from the step portion is only required in one direction, which facilitates manufacturing and improves reliability.

In FIG. 3, parts corresponding to those in FIG. 1 are designated by the same reference numerals for convenience of understanding.

In FIG. 3, care has been taken to ensure that a film such as wiring can be accurately formed by slanting the stepped portion and performing diagonal vapor deposition from the direction in which the metal is deposited thickly. This embodiment has the advantage of performing this oblique deposition.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented with various modifications within the scope of the invention without changing the gist.

For example, the material of the dielectric material that serves as the support for the piezoelectric thin film is not limited to 8i02, but also 8i1N4 and 8i0.
．． ζphosphorus-doped PSGl or 8i0. It may be made of glass such as BP80 doped with boron and phosphorus, or it may be a composite material in which approximately several types of dielectric thin films are laminated. In either case, it is desirable that the frequency temperature coefficient has the opposite sign to that of the piezoelectric thin film.

Also, the material of the piezoelectric thin film is limited to ZnO.

Nb, TaIQ, PbTi0. etc. can be used.

The homogeneous film for forming voids is not limited to ZnO, but any material such as metal, oxide, semiconductor, dielectric, polymer material, etc. may be appropriately selected as long as it can be easily resolved from Erachan 11 for forming voids. There is no.

Furthermore, in the present invention, a plurality of upper electrodes (second electrodes) are arranged to face a common lower electrode (first electrode), and a plurality of upper electrodes (second electrodes) are made to face each other to such an extent that elastic coupling can be maintained between the pole facing portions of each ′. It is also possible to configure a multi-element type resonator having a plurality of independent resonators by separating the electrodes or by providing an adjoining sound absorbing material between each electrode facing portion.

Furthermore, a bandpass filter can be configured by making a plurality of upper electrodes face a common lower electrode and utilizing elastic coupling between the electrode facing parts.

FIG. 4 shows an embodiment of the bandpass filter. In the figure, 15 is a common lower electrode (first electrode), and 16 and 17 are upper electrodes (second electrodes) corresponding to the input electrode and output electrode of the bandpass filter. In this example, a common electrode is formed on the bottom and a plurality of electrodes are formed on the top, but it is also possible to create a structure in which a common X electrode is formed on the top and a plurality of electrodes are formed on the bottom. It is.

[Effects of the Invention] According to the present invention, a piezoelectric thin film resonator and a semiconductor circuit can be integrated on the same substrate, and ultra-miniaturization and high reliability can be achieved, and when a voltage controlled oscillator is configured. It is possible to provide an integrated piezoelectric thin functional element with a wide frequency variable width.

[Brief explanation of the drawing]

1(a) and 1(b) show an embodiment of the present invention, where Ta) is a plan view and FIG. 1(b) is a longitudinal section taken along line B-B line 1 in FIG. A front view, FIG. 2 is a longitudinal sectional front view showing a second embodiment of the present invention, and FIGS.
) shows a third embodiment of the present invention, (a) is a perspective view showing the overall configuration of this embodiment, and (b) is (a) Figure B.
- A longitudinal partial view of the line section viewed in the direction of the arrow;
FIG. 4 shows a perspective view of an embodiment of the present invention configured as a bandpass filter. l...Semiconductor substrate 2...Metal wiring pattern 3
...Protective film 4...First dielectric film 5...
-Gap 71 5a, 5b...opening 6...
First 4 poles 7...Piezoelectric thin film 8...Second electrode 9...Second dielectric film 10...Integrated circuit 11.12...Connection hole 13...Gold FX pattern?
fM 14...Third dielectric film 15...Common lower electrode 16.17...Upper electrode 20...Piezoelectric thin film resonator (b) Fig. 3

Claims (3)

[Claims] (1) On the semiconductor circuit board, a void layer, a first dielectric film,
A piezoelectric thin film resonator configured by sequentially forming a first electrode, a piezoelectric thin film, a second electrode, and a second dielectric film, and an integrated circuit on the substrate, 1. An integrated piezoelectric thin model functional element, characterized in that it is connected and integrated by all metal film wiring through a connection hole provided in a part of a second dielectric film on an electrode. (2) The integrated piezoelectric thin film functional element according to claim 1, wherein the second dielectric film and the metal film wiring are covered at their upper portions by a third dielectric film. . (3) The metal film wiring for connecting the piezoelectric thin film resonator and the integration surface is led out on the same side of the piezoelectric thin film resonator so as to be substantially parallel to each other. An integrated piezoelectric thin film functional element according to item 1 or 2.