JP3317710B2 - Semiconductor device including high-frequency oscillator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device including a high frequency oscillator integrated on a semiconductor substrate.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a frequency conversion circuit composed of individual components, and FIG.
It is a frequency distribution figure in the position shown by-F.

The frequency conversion circuit comprises an oscillator 17 for generating a high-frequency signal, a mixer 13 for mixing the high-frequency signal output from the oscillator 17 with an input signal, filters 14, 16 and amplifiers 12, 15.
It is composed of A conductor shield 19 is provided around the oscillator 17.

The operation of the frequency conversion circuit will be described below.

[0005] For example, the frequency is applied to the signal f _in is the input terminal 11 of the 100 MHz. This signal is transmitted to the mixer 13 via the amplifier 12. On the other hand, oscillator 17
Generates, for example, a signal f _OSC having a frequency of 150 MHz. At this time, from the oscillator 17, as shown in FIG. 4, in addition f _OSC, f 1/2 of the frequency of the signal (1/2 f _OSC) of _OSC, 2 times the frequency of the signal (2f _OSC) and A signal (not shown) having three times the frequency is output at the same time. However, since only the required signal is f _OSC , the band-pass filter 16 removes signals other than f _OSC (150 MHz).

[0006] The mixer 13 mixes the output of the amplifier 12 and the output of the bandpass filter 16. From this mixer _{13, f in (100MHz),} f in -f OSC
(50 MHz) and the frequency signal of f _in + f _OSC (250MHz) is output. Required signal among these, the signal frequency is lower than f _in f _in -f _OSC (i.e., f _IF) is only. Therefore, signals other than _fIF are removed by the bandpass filter 14. The amplifier 15 is a bandpass filter 1
4 and outputs the amplified signal to an output terminal 18.

In the case where such a circuit is constituted by individual components, a conductor shield 19 such as a copper plate, a brass plate, or a tin-plated iron plate is usually provided around the oscillator 17. By shielding the electromagnetic wave by the conductor shield 19, the oscillator 1
7 prevents the high frequency signal generated from leaking to other circuits.

In recent years, with the progress of semiconductor technology, frequency conversion circuits have also become monolithic integrated circuits (hereinafter referred to as I / O).
C) on a single semiconductor substrate.

FIG. 5 shows a monolithic I frequency conversion circuit.
FIG. 4 is a cross-sectional view illustrating a C-shaped semiconductor device.

On a silicon (Si) semiconductor substrate 1, elements such as a mixer 2, an oscillator 3, and an amplifier 4 are formed. The elements are separated from each other by an insulating film 6 such as SiO ₂ or a trench (insulating groove; not shown).

The high frequency signal generated by the oscillator 3 is
The signal is input to the mixer 2 via the wiring 5. Note that a band-pass filter may be interposed between the oscillator 3 and the mixer 2 as in the circuit shown in FIG. Conventionally, when integrated as a semiconductor device, only the periphery of the oscillator 3 is surrounded by the insulating film 6.

[0012]

However, a semiconductor device having a conventional high-frequency oscillator in the form of a monolithic IC has the following problems. For example, in the semiconductor device shown in FIG. 5, only the insulating film 6 is provided around the oscillator 3, and no conductor member for shielding electromagnetic waves is provided. Therefore, when the oscillation frequency of the oscillator is high, the leakage B of the high-frequency signal occurs as shown in FIG. For this reason, as shown in FIG. 7, even if only the signal having the frequency of _fIF is separated by the filter 14, the signal leaked from the oscillator 17 causes oscillation and interference, thereby causing a malfunction and causing frequency conversion. Normal operation of the circuit may not be possible.

The present invention has been made in view of the above problems, and provides a semiconductor device including a high-frequency oscillator capable of preventing signal leakage generated by the high-frequency oscillator and preventing occurrence of malfunction. The purpose is to:

[0014]

Semiconductor device including a high-frequency oscillator according to the present invention, in order to solve the problem] is a semiconductor device including a high-frequency oscillator that is formed integrated on a semiconductor substrate, contact the semiconductor substrate and the bottom all directly, the A first conductor film is provided around the high-frequency oscillator with an insulating film interposed between the high-frequency oscillator and the high-frequency oscillator.
Further, it is preferable that a second conductor film is provided on the high frequency oscillator.

[0015]

In the present invention, the semiconductor substrate and the bottom surface are all
A first conductive film which is directly in contact with is disposed around the high frequency oscillator. Therefore, the signal from the high-frequency oscillator does not pass between the semiconductor substrate and the first conductive film, and the electromagnetic wave from the oscillator is shielded with high efficiency. Accordingly, malfunctions due to signal leakage from the high-frequency oscillator can be avoided by the electromagnetic wave shield of the first conductive film.

[0016]

Next, an embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1A is a sectional view showing a semiconductor device having a high-frequency oscillator according to a first embodiment of the present invention.
(B) is a plan view of the same.

The silicon semiconductor substrate 1 has a mixer 2
Elements such as an oscillator 3 and an amplifier 4 are formed. These elements are separated by an insulating film 6 made of SiO ₂ or a trench.

The oscillator 3 and the mixer 2 are connected to a wiring 5
Are electrically connected to each other. Oscillator 3
A conductor film 7 of aluminum having a thickness of about 5000 ° is formed so as to surround the oscillator 3 on the side of the substrate 1.

In this embodiment, since the conductor film 7 is formed around the oscillator 3, this conductor film 7
Acts as an electromagnetic wave shield, and it is possible to avoid malfunctions such as interference and oscillation due to electromagnetic waves leaked from the oscillator 3.

For example, the semiconductor device according to the present embodiment has an effect that the used frequency band is increased by about 20% at around 100 MHz as compared with the conventional semiconductor device without the conductor film 7. it can.

FIG. 2 is a sectional view showing a semiconductor device having a high-frequency oscillator according to a second embodiment of the present invention.

The present embodiment is different from the first embodiment in that a conductor film is also provided above the oscillator 3, and the other structure is basically the same as that of the first embodiment. Therefore, in FIG. 2, the same components as those in FIG. 1A are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, a conductor film 7a is formed so as to cover the oscillator 3. That is,
On the side and above the oscillator 3, a conductor film 7a made of aluminum having a thickness of about 5000 ° is formed.
Note that the wiring 5 is electrically insulated from the conductor film 7a.

In this embodiment, since the conductor film 7a is formed not only on the side of the oscillator 3 but also above it, the shielding effect of the conductor film is higher than that of the first embodiment. It is certain.

[0026]

As described above in detail, according to the present invention, since the first conductive film whose entire bottom surface is in direct contact with the semiconductor substrate is arranged around the high-frequency oscillator, the signal from the high-frequency oscillator is Electromagnetic waves from the oscillator can be shielded with high efficiency without passing between the semiconductor substrate and the first conductive film. For this reason, malfunctions such as interference and oscillation due to signal leakage from the high-frequency oscillator can be reliably avoided by the electromagnetic wave shield of the first conductive film.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view illustrating a semiconductor device including a high-frequency oscillator according to a first embodiment of the present invention, and FIG. 1B is a plan view of the same.

FIG. 2 is a cross-sectional view illustrating a semiconductor device including a high-frequency oscillator according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram illustrating an example of a frequency conversion circuit configured by individual components.

FIG. 4 is a frequency distribution diagram at each position of the circuit of FIG. 3;

FIG. 5 is a cross-sectional view showing a conventional semiconductor device in which a frequency conversion circuit is integrated.

FIG. 6 is a circuit diagram showing a disadvantage of a semiconductor device having a conventional high-frequency oscillator.

FIG. 7 is a frequency distribution diagram showing inconvenience of a semiconductor device having a conventional high-frequency oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Semiconductor board | substrate 2, 13; Mixer 3, 17; Oscillator 4, 12, 15; Amplifier 5; Wiring 6; Insulating film 7; Conductive film 11; Input terminal 14, 16;

Claims (2)

(57) [Claims] 1. A semiconductor device including a high-frequency oscillator integrated on a semiconductor substrate, wherein all of the bottom surface of the semiconductor device is in direct contact with the semiconductor substrate, and an insulating film is interposed between the high-frequency oscillator and the high-frequency oscillator. A semiconductor device including a high-frequency oscillator having a first conductive film provided in such a manner. 2. The semiconductor device including the high-frequency oscillator according to claim 1, wherein a second conductor film is provided on the high-frequency oscillator.