JPS6128227B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel structure of a semiconductor integrated circuit device that integrally includes a surface acoustic wave element.

In conventional semiconductor integrated circuits, resonant circuits including coils and capacitors cannot be integrated into the circuit, and tuning circuits, filter circuits, etc. cannot be connected externally by extending terminals from the semiconductor integrated circuit. It was taken. For this reason, the integration density of high-frequency circuits and the like has not increased, and the number of terminals on the package has increased unnecessarily, making it impossible to satisfactorily meet the demand for miniaturization of equipment.

On the other hand, although an electric vibrating element that replaces the electrical resonance phenomenon with mechanical resonance can obtain excellent characteristics as a single unit, the structure of the electromechanical transducer and the holding mechanism of the vibrating body are complicated, and it is difficult to integrate it into an integrated circuit. has been considered difficult. However, recently, attempts have been made to realize high-performance filters and the like using elements that apply surface acoustic wave vibration. When using surface acoustic waves, the holding mechanism becomes simple, but since surface acoustic waves are traveling waves, electromechanical conversion losses are relatively large, and input and output amplification circuits are usually separate to compensate for the losses. Since integrated circuits or individual components must be added, miniaturization and reduction in the number of integrated circuit package terminals have not been achieved.

The present invention aims to provide a novel structure in which a surface acoustic wave element is integrated into such a semiconductor integrated circuit, and its purpose is to miniaturize the circuit including the resonant circuit, Yet another objective is to reduce assembly costs and increase reliability by reducing the number of terminals on an integrated circuit and eliminating traditional wire connections.

Still another object is to stabilize the characteristics of the surface acoustic wave element by integrating the elements. According to the present invention, a surface acoustic wave element includes a transistor, a diode, a resistor, a capacitor, etc. configured by a combination of PN junctions in a semiconductor substrate, and further includes a piezoelectric thin film on one main surface of the substrate. An integrated semiconductor integrated circuit device is obtained in which each element in the substrate and the surface acoustic wave element on the surface of the substrate are connected by wiring.

Next, in order to better understand the features of the present invention, specific embodiments of the present invention will be explained using figures.

FIG. 1 is a top configuration diagram showing a first embodiment of the present invention, and FIG. 2 is a sectional view taken along the line 1--' in FIG. In the figure, 1 is a P-type silicon substrate with a resistance of 10 to 20 Ω-cm, and after an n ⁺ buried diffusion layer 2 is provided in a predetermined region, an n-type epitaxial layer with a resistivity of 1 Ω-cm and a thickness of 12 microns is formed. A growth layer is formed,
The epitaxial growth layer is separated by an island region 4 by a p ⁺ type isolation diffusion region 3 using a well-known selective diffusion technique.
and 5. In the island region 4, integrated circuit transistors are formed. That is, the p-type base region 6 and
An n ⁺ type emitter region 7 is formed, and a collector contact n ⁺ region 8 is also formed simultaneously with the formation of the emitter region. The protective insulating film 9 on the surface is usually a silicon nitride film, a silicon oxide film, or a metal oxide film.
This insulating film 9 is usually a thick insulating film 9' in a region where a surface acoustic wave element is to be formed in order to reduce capacitance.

Then, electrical wiring 12 made of a thin metal film electrically connects the comb-shaped electrodes 10 and 11 of the surface acoustic wave device to the transistor configured in the island region 4 and various elements in other island regions (not shown), and the comb teeth. The state conversion electrode 10 is constructed simultaneously by vapor deposition of a metal thin film and photolithography. Furthermore, ZnO 13, which is a piezoelectric thin film for surface acoustic wave conversion, is selectively deposited on the top of the comb-wave conversion electrode 10 to a thickness of about 1.2 microns by sputtering, and a metal thin film 14 is further formed as a counter electrode on top of the ZnO film 13, which is a piezoelectric thin film for surface acoustic wave conversion. An integrated semiconductor device according to an embodiment of the invention is obtained.

Now, in this device, the signal input from the input terminal that constitutes the integrated circuit is amplified to an appropriate amplitude by the amplifier in the integrated circuit (in Fig. 1, a part of the signal is used for the integrated circuit in the island area 4). An electrical signal (shown as a transistor) is applied via electrical wiring 12 to the comb-like transducer electrode 10 of a surface acoustic wave transducer. When the ZnO thin film 13, which is a piezoelectric material, is electrically excited and the signal is converted into a surface acoustic wave, the other comb-shaped conversion electrode 11 is excited, and the signal is converted back into an electric signal, taken out, and generated again. Wiring (not shown) leads to the integrated circuit.

The wavelength of the surface acoustic wave is determined from the frequency of the surface acoustic wave and the speed of sound. When this wavelength matches the pitch of the comb-shaped electrode, the electrical signal and the surface acoustic wave are synchronized, and the conversion efficiency between the electrical signal and the surface acoustic wave is the highest. . This frequency corresponds to the center frequency of the filter.

In this embodiment, an n ⁺ buried diffusion layer 2 is provided in the collector region of the island region 4, but it is well known that this is usually for the purpose of reducing collector resistance and may be omitted in some cases. That's right.

Further, the counter electrode 14 of the surface acoustic wave element may also be omitted depending on the required electrical characteristics. As for the construction method of the transducer, it is also possible to construct the transducer upside down, that is, to first form the counter electrode 14 on the surface of the insulating film 9 at the same time as the metal wiring 12, and then to form a thin film of piezoelectric material on top of the counter electrode 14. It is also possible to form the comb-shaped electrodes 10 and 11 on the top surface after depositing ZnO 13, or to form the metal wiring 12 and the comb-shaped electrodes 10 and 11 at the same time after forming the counter electrode 14 and depositing ZnO 13. In this case, the counter electrode 14 can be omitted by utilizing the conductivity of the semiconductor substrate.

Furthermore, in the explanation of the above embodiment, an example was explained in which the island region 4 of the integrated circuit transistor and the island region 5 of the surface acoustic wave element section were provided in separate regions of the silicon substrate 1, but for the purpose of reducing the silicon substrate area. A structure in which comb-shaped electrodes 10 and 11 and a piezoelectric ZnO thin film 13 are provided on the surface of each element for an integrated circuit configured in a silicon substrate via an insulating film 9, and a surface acoustic wave element is formed on the integrated circuit in the substrate. Needless to say, it is possible.

FIG. 3 is a cross-sectional view showing a second embodiment of the present invention. In order to reduce the capacitance from the surface acoustic wave comb-shaped electrode to the semiconductor substrate, a PN junction is provided at the bottom of the electrode, and the junction capacitance is reduced. This is an attempt to reduce the combined capacitance by connecting them in series and improve the characteristics for high frequency signals. That is, in order to make the understanding clear in the diagram, parts common to those in the first embodiment will be explained using common numbers. First, a p-type silicon crystal of 10 to 20 Ω-cm is prepared as a semiconductor substrate 1. do. In the first embodiment, a description was given of providing a buried diffusion layer on the substrate surface, but since it is not directly related to the main purpose of the present invention, this will be omitted.Next, we will explain the epitaxial growth of n-type 1Ω-cm layer is substrate 1
The epitaxial growth layer becomes island regions 4 and 5 separated by the p ⁺ type isolation diffusion layer 3 . In the island region 4, a p-type base region 6, an n ⁺ -type emitter region 7, and a collector contact n ⁺ region 8 are formed as a transistor for an integrated circuit. P ⁺ diffusion regions 15 and 16 are provided below the comb-shaped electrodes 10 and 11 of the surface acoustic wave element No. 5.
form. Reference numeral 9 denotes an insulating film for surface protection, and on the surface of the insulating film 9, electrical wiring 12 made of a metal thin film and comb-shaped conversion electrodes 10 and 11 are formed. The comb-shaped electrodes 10 and 11 are located above the p ⁺ -type diffusion regions 15 and 16 with an insulating film 9 in between.
It is also possible to arrange that 0 and 11 are electrically connected directly to the surfaces of p ⁺ diffusion regions 15 and 16. Which of these is chosen depends on the required electrical characteristics, but is also constrained by the wiring and bias voltage of the electrical circuits constituting the entire integrated circuit. On top of the comb-shaped electrodes 10 and 11, ZnO 13 as a piezoelectric material is selectively deposited to a thickness of about 1.2 microns by sputtering. Furthermore, a counter electrode 14 is formed on the top of the piezoelectric material to increase the electric field concentration effect within the piezoelectric material, but as described in the first embodiment, this may be omitted, or one transducer electrode 10 and the other transducer electrode 14 may be omitted. It may be placed at a position intermediate to the comb-shaped electrode 11 with a shielding effect, and various methods can be considered for the shape of the counter electrode 14 and the connection with the electrode wiring 12, but as described above, the main purpose of the present invention Since this is not the case, a detailed explanation will be omitted.

Further, a third embodiment of the present invention will be described with reference to FIGS. 4 and 5. Figure 4 shows the third embodiment of the present invention.
FIG. 5 is a sectional view taken along the dashed line -' in FIG. 4. As in the previous example, after growing an n-type 1 Ω-cm epitaxial crystal to a thickness of about 12 microns on a p-type 10 to 20 Ω-cm silicon substrate 1, p ⁺ type was separated and diffused from the surface using selective diffusion technology. Region 3 is formed to form the epitaxial growth layer into independent n-type island regions 4 and 5, respectively. In the island region 4, a p-type base region 6, an n ⁺ -type emitter region 7, and a collector contact n ⁺ region 8 are formed as a transistor for an integrated circuit. P ⁺ diffusion regions 17 and 18, which are to serve as electrical signal-to-surface acoustic wave conversion electrodes, are also formed within 5.

As is clear from FIG. 5, the end portion 19 of the p ⁺ diffusion region 17 for the comb-shaped electrode is
The island region 4 is connected to the base region 6 of the integrated circuit transistor by an electrical thin film electrical interconnect 12 on top (not shown in the figure). After the insulating film 9 is formed and the metal thin film electrical wiring 12 is formed, a ZnO thin film 13 of about 1.2 microns, which is a piezoelectric material, is deposited by sputtering on the upper regions of the p ⁺ -type diffusion regions 17 and 18 for the comb-shaped electrodes. An integrated integrated circuit including a surface acoustic wave transducer is obtained.

In this embodiment, unlike the first and second embodiments described above, the conversion electrode for converting surface acoustic waves to electric signals or vice versa is made of an impurity diffusion region itself in the semiconductor substrate, unlike the first and second embodiments, in which the conversion electrode is made of a metal thin film. In the example given here, a p-type impurity diffusion region formed at the same time as the base region 6 is used, but a p-type island region is further formed within the island region 5, and a p-type impurity diffusion region is formed within the island region 5. A comb-shaped conversion electrode can also be constructed by high-concentration n ⁺ diffusion. Also, similarly
Of course, it is also possible to form the p ⁺ -type diffusion regions 17 and 18 by high-concentration p ⁺ -type diffusion separately from the selective diffusion of the base region 6 of the integrated circuit transistor.

By forming the conversion electrode in the diffusion region in the semiconductor substrate in this way, it is possible to eliminate the unevenness caused by the electrode in the ZnO thin film 13 as a piezoelectric material, and to reduce the deterioration of characteristics due to the generation of unnecessary acoustic waves. . Furthermore, by applying an appropriate bias voltage to the diffusion regions 17 and 18, the junction capacitance due to reverse bias of the PN junction can be reduced, and the equivalent capacitance to the substrate can be reduced to improve high frequency characteristics. Furthermore, since the sound velocity and expansion coefficient of the comb-shaped electrode made of the substrate and diffusion are almost the same, there is little reflection of surface acoustic waves at the electrode interface, and it is stable and highly reliable against temperature changes. .

As described above, by the present invention, an integrated semiconductor integrated circuit including a surface acoustic wave element has been achieved for the first time, and the miniaturization of electronic circuits has progressed significantly, the integration density has been improved, and the number of terminals has increased. It has become possible to bring about limitless effects, such as cost reduction and improved reliability due to the reduction in the number of components and assembly man-hours, and the improvement and stabilization of high frequency characteristics that can only be achieved by integrating them.

In the embodiments of the present invention, an example in which a surface acoustic wave element is used as a filter has been explained, but it can also be used as a delay element by appropriately selecting the electrode positions, and it can also be used as a general transducer. It is clear that the gist of the present invention can also be applied to applications as a user.

In the above embodiments, for the sake of simplicity, we have explained the case where an amplifier is used as an integrated circuit, a filter is used as a surface acoustic wave element, and a ZnO thin film is used as a piezoelectric thin film. We use surface acoustic wave devices that perform signal processing by applying optical properties and optical deflection effects, and other methods such as piezoelectric thin films.
ZnS, CdS, etc. can also be used, and it is also possible to construct a semiconductor integrated circuit having other functions by combining these materials, and these are, of course, included in the scope of the present invention.

Further, although the case where a p-type silicon crystal is used as the semiconductor substrate has been described, the present invention also works when the opposite conductivity type is applied to all the structures. Further, as the semiconductor crystal substrate, in addition to silicon, germanium and gallium arsenide compound semiconductor crystals can also be used.

Further, although the embodiment of the present invention has been described in which a separation/diffusion method is used to form an island region of an integrated circuit, the present invention can be applied in exactly the same manner to other isolation methods.

[Brief explanation of the drawing]

FIG. 1 is a top configuration diagram showing a semiconductor integrated circuit device according to a first embodiment of the present invention, and FIG. 2 is a broken line shown in FIG. 1.
3 is a cross-sectional view showing the device of the second embodiment of the present invention, FIG. 4 is a top configuration diagram showing the device of the third embodiment of the present invention, and FIG. is a sectional view taken along the line -' in FIG. 4; DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 3... Separation diffusion layer, 4, 5... Island region, 10, 11... Comb-shaped electrode, 12... Metal wiring,
13... Piezoelectric material thin film, 15, 16, 17, 18...
Diffusion area.

Claims (1)

[Scope of Claims] 1. A semiconductor characterized in that a surface acoustic wave element including at least a piezoelectric thin film is formed on one main surface of a semiconductor substrate having a plurality of island regions including active or passive elements. Integrated circuit device. 2. In a predetermined region on one main surface of the semiconductor substrate,
A semiconductor integrated circuit device according to claim 1, wherein a region having a conductivity type opposite to the predetermined region is formed, and the surface acoustic wave element is disposed on the predetermined region via a metal electrode. . 3. A region having a conductivity type opposite to that of the predetermined region is formed in a predetermined region on one main surface of the semiconductor substrate, and the region having the opposite conductivity type is used as a conversion electrode for surface acoustic waves and electric signals in the surface acoustic wave element. A semiconductor integrated circuit device according to claim 1, characterized in that: