JPS63294010A - Surface acoustic wave resonator - Google Patents

Abstract

PURPOSE:To obtain a surface acoustic wave resonator having a good resonance characteristic by forming a piezoelectric thin film on a semiconductor substrate and forming a glass material layer on this thin film and forming surface wave reflecting groove rows on both sides of input/output electrodes provided on the piezoelectric thin film. CONSTITUTION:The surface wave generated by electrodes 4 and 5 is propagated to both sides of electrodes and are efficiently reflected on groove rows 6 whose period is integer-number of times as long as a half wavelength of the surface wave. A standing wave of the surface wave is generated between groove rows 6 and 6 and is detected by electrodes 4 and 6. With respect to the constitution of a two-port resonator, an AlN piezoelectric thin film layer 2 is formed on an Si substrate 1 with 0.5mum thickness, and a phosphor silicate glass layer 3 is formed on this layer 2 with about 2.5mum thickness. IDTs as electrodes 4 and 6 consist of Al, and the wavelength of the surface wave is 32mum and its propagation direction is the Si direction. The depth of reflecting grooves 6 is set to about 5000Angstrom .

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in surface acoustic wave resonators using piezoelectric thin films.

[Summary of the Invention] According to the present invention, a vitreous layer is formed on a piezoelectric thin film, and groove arrays (groups) are formed in the vitreous layer to form a resonator.

[Prior Art] Conventional surface acoustic wave resonators are mainly made of crystal, LiTa
It is composed of a piezoelectric single crystal substrate such as O. On the other hand, a surface acoustic wave resonator with a monolithic structure in which a piezoelectric thin film is formed on a semiconductor substrate has one part including one peripheral circuit.
Chip integration can be realized.

This is expected to be a promising device structure.

[Problems to be solved by the invention] In the conventional piezoelectric thin film resonator, Zn is used as the piezoelectric thin film.
O pressure'? B, thin film, A Q N piezoelectric thin film is often used, but ZnO piezoelectric thin film.

1) Electrical instability occurs due to voltage application.

2) It is difficult to form a high-quality film.

3) A protective film (Sin2) is required on the silicon single crystal substrate.

4) The propagation loss of surface acoustic waves is large in the high frequency region.

5) Does not match normal silicon IC process. .

Because of these drawbacks, it is particularly desirable to use AflN thin pancreas as a piezoelectric thin film for one-chip integration.

As an example of a resonator constructed using the AQN thin film of the silicon single crystal substrate mentioned above, L, G, Pearce
tal (Appl, Phys, Letl Vol 39
(1981) Dec, Vo, 11°NetiYor
K, U, S, A) describe the application of Al2N thin film to a two-port resonator.

The configuration of this resonator is A Q N / SiOz /
In the S l structure, the grating reflector is short-circuited 40
It is formed of 0 Au strips.

The characteristics of the resonator are as follows: resonance frequency 121, . 7
At MHz, insertion loss is 27 dB, Qualit
y Factor) 3370, which cannot be said to be a sufficient characteristic.

With conventional device construction means, it is extremely easy to obtain a resonator that is small and has good characteristics.

An object of the present invention is to provide a piezoelectric thin film type surface acoustic wave resonator suitable for integrating one surface acoustic wave element and peripheral circuits on one chip.

[Means for Solving the Problems] In order to achieve the above object, the present invention forms a piezoelectric thin film on a semi-concentric substrate, further forms a vitreous layer thereon, and forms a piezoelectric thin film on the vitreous layer. , surface wave reflecting groove arrays are formed on both sides of the input/output electrodes provided on the piezoelectric thin film, thereby solving the above-mentioned problems.

As the glassy layer, silicon oxide (SiO2
), phosphosilicate glass (PSG), borosilicate glass (
BSG), phosphorus silicate glass (BPSG), etc.

[Operation] In the above configuration, a standing wave of surface waves is generated between the rows of surface wave reflecting grooves located on both sides of the input/output electrode, and is detected by the electrodes.

[Example 1] Figures 1 and 2 show an example in which the present invention was implemented in a two-port resonator, in which 1 is a silicon single crystal substrate, and 2 is an AlN piezoelectric thin film layer formed thereon. . 3 is AlN
This is a silicon oxide film layer formed on the piezoelectric thin film layer 2. 4 and 5 are comb-shaped electrodes for generating and detecting surface waves formed between the AlN pressure sensitive R1f film λ layer 2 and the silicon oxide film layer 3.

Reference numeral 6 denotes periodic groove arrays (group play) provided on the surface of the silicon oxide film layer 3 for surface wave reflection, and these are positioned on both sides of the input/output electrodes 4 and 5.

The surface waves generated by the electrodes 4 or 5 propagate to both sides of the electrodes, are efficiently reflected by the groove rows 6 whose period is an integer multiple of half the wavelength of the surface waves, and are reflected between the groove rows 6.6. A standing wave of surface waves is generated, and the standing waves of surface waves are detected by four or five electrodes.

The graph in FIG. 3 shows the pass characteristics of a two-port resonator, and the configuration of the resonator is shown in FIG. 4. That is, an AlN piezoelectric thin film layer 2 is deposited on a 5i (100) substrate 1 at a thickness of 0.5i (100).
It was formed to a thickness of 5 μm, and a phosphosilicate glass layer 3 was further formed thereon to a thickness of about 2.5 μm. The IDT serving as electrode 4.5 is composed of AQ, and the wavelength of the surface wave is 32 μm.
The propagation direction of the surface wave is the Si[100] direction. The depth of the reflective groove 6 is approximately 5,000 people.

Resonator characteristics Resonance frequency 145 MHz Insertion loss 5 dB Load Q 4000 (], oaded Q) The logarithm of the IDT is 16 pairs, the electrode crossing width/nm number of grooves is 230, and the space between the centers of the IDTs is 20λ (λ is the surface wave wavelength) The distance (Lc) between the IDT and the groove edge is approximately 5/8λ.

In the resonator with the above PSG/AQN/SL configuration, Lc5/8λ (usually ~3/8 in the groove)
The condition of λ) is important for efficiently coupling the standing waves of the surface waves.

What is shown in FIGS. 5 and 6 is an embodiment of a one-port resonator, and the present invention can also be applied to this configuration.

[Effects of the Invention] As described above, according to the present invention, a glassy layer is formed on the piezoelectric thin film, and the glassy layer is provided with electrodes located on both sides of the input/output electrodes provided on the piezoelectric thin film. Since the surface wave reflecting groove array is formed, a surface acoustic wave resonator having good resonance characteristics can be obtained.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a surface acoustic wave resonator showing an embodiment of the present invention, Fig. 2 is a plan view, Fig. 3 is a graph showing the passage characteristics of the resonator, and Fig. 4 is the configuration of the resonator. An explanatory diagram, FIG. 5 is a longitudinal sectional view of a surface acoustic wave resonator showing another embodiment, and FIG. 6 is a plan view. 1...Silicon single crystal substrate. 2... AlN piezoelectric thin film layer, 3... Silicon oxide film layer, 4.5... Input/output electrode, 6... Groove array for surface wave reflection. Patent Applicant Clarion Co., Ltd. Agent Patent Attorney Nagai 1) Take Mibe - (1″',... J”:7 Figure 1 Figure 3 Kan Kan Saka (MHz) Figure 4

Claims (4)

[Claims] (1) A piezoelectric thin film is formed on a semiconductor substrate, a glassy layer is formed on top of the piezoelectric thin film, and a surface wave generation and detection electrode formed between the semiconductor substrate and the piezoelectric thin film is formed on this glassy layer. A surface acoustic wave resonator characterized in that a row of surface wave reflecting grooves are formed on both sides. (2) Two ports or one electrode for surface wave generation and detection
Claim 1 configured in any of the ports
The surface acoustic wave resonator described in . (3) The surface acoustic wave according to claim 2, wherein the end-to-end distance (Lc) between the electrode and the surface wave reflecting groove array is Lc≈5/8λ (λ is the wavelength of the surface wave). resonator. (4) The surface acoustic wave resonator according to claim 1, wherein the piezoelectric thin film is made of an AlN thin film.