JPH07162230A - Oscillation circuit for gate array semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To obtain an oscillation circuit which can oscillate at a high frequency by forming an LC circuit on the gate array semiconductor integrated circuit. CONSTITUTION:A resonance circuit 50 is provided between the output terminal and input terminal of an inverter circuit 40 and a coil 48 is included in this resonance circuit. The coil 48 consists of gate electrodes of plural basic cells of the gate array type semiconductor integrated circuit. Namely, the adjacent gate electrodes which are arrayed in parallel and constituted are connected by slanting wiring. Consequently, the coil can be constituted only in a semiconductor process. Therefore, the LC oscillation circuit can be realized by using only circuits on the gate array semiconductor integrated circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an oscillator circuit in a gate array semiconductor integrated circuit.

[0002]

2. Description of the Related Art Conventionally, in order to construct an oscillation circuit on a semiconductor integrated circuit, a special special circuit has been required.

A gate array semiconductor integrated circuit is widely used in which a basic cell including a predetermined number of transistors is spread and a wiring layer is provided based on design information to form a desired circuit. An oscillation circuit in this gate array semiconductor integrated circuit is disclosed in, for example, Japanese Patent Laid-Open No.
No. 307267.

A circuit diagram of the oscillator circuit described in this publication is shown in FIG. As shown in FIG.
A resistor 12 is provided between the output terminal and the input terminal of the inverter circuit 10. The capacitor 14 is provided between the input terminal of the inverter circuit 10 and the ground, and the capacitor 16 is provided between the output terminal of the inverter circuit 10 and the ground. With such a circuit configuration, oscillation is performed at the oscillation frequency determined by the resistor 12 and the capacitors 14 and 16. A crystal oscillator circuit is constructed by connecting an external crystal oscillator between the output terminal and the input terminal of the inverter circuit 10.

The above publication describes in detail how the oscillation circuit as shown in FIG. 4 is constructed on a gate array semiconductor integrated circuit. A detailed circuit diagram of the inverter circuit 10 is shown in FIG. As shown in FIG. 5, in the inverter circuit, a PMOS type transistor 18 and an NMOS type transistor 20 are connected in series between a power source VCC and a ground, and a so-called CMOS type is provided.
It has a type structure. That is, the gate terminal of the PMOS type transistor 18 and the NMOS type transistor 20
Is connected in common with the gate terminal of and forms an input terminal. Further, the drain terminal of the PMOS type transistor 18 and the source terminal of the NMOS type transistor 20 are commonly connected, and form the output terminal of the inverter circuit 10.

FIG. 6 is an explanatory view for explaining a method of forming the capacitors 14 and 16. As shown in FIG. 6, in the gate array semiconductor integrated circuit, a large number of basic cells 22 are provided, and each basic cell 22 usually includes a plurality of transistors. For example, as shown by 6, the gate electrode 24 has a P well 26
And the N well 28. According to the above publication, it is possible to connect a plurality of the gate electrodes 24 to form one terminal of the capacitors 14 and 16. That is, the capacitance between the gate electrode 24 and the substrate is used. One terminal of this capacitor is taken out from the gate electrode 24 and the other terminal is always grounded. As shown in FIG. 4, both terminals of the capacitors 14 and 16 are grounded,
The capacitors 14 and 16 can be realized with the configuration as shown in FIG.

FIG. 7 is an explanatory diagram showing the structure of the resistor 12. As shown in FIG. 6, the gate array semiconductor integrated circuit is provided with a large number of elongated gate electrodes 24, and the gate electrodes 24 are usually formed of polysilicon in many cases. Therefore, it is possible to form a constant resistance value by connecting a plurality of elongated gate electrodes 24 in a zigzag manner. As described above, by connecting the gate electrodes 24 in a zigzag manner in series, it is possible to obtain a predetermined resistance value without increasing the inductance.

In FIGS. 6 and 7, a cross mark represents a contact hole, and a line extending from the contact hole is a wiring formed by a so-called wiring layer.

Thus, in the past, a so-called RC oscillation circuit was formed by using the inverter circuit 10 and the feedback circuit using RC.

[0010]

However, although the RC oscillator circuit can oscillate a low frequency of 10 Hz to 1 MHz, it cannot oscillate a high frequency of several MHz or more. This is described, for example, in “Analog Electronic Circuit”, Nobuo Fujii, Shokoido, page 183. This page 183 states, "RC oscillators can easily oscillate at low frequencies by using high resistance, and sine waves of about 10 Hz to 1 MHz can be obtained. Therefore, LC is used for the oscillation circuit because a good inductance can be realized. ”

Therefore, it has been difficult to oscillate a high frequency with the oscillation circuit provided on the conventional gate array integrated circuit.

The present invention has been made in view of the above problems, and an object thereof is to provide an LC oscillation circuit by forming an inductor by forming a coil on a gate array semiconductor integrated circuit. is there.

[0013]

In order to solve the above-mentioned problems, the first invention is an inverter circuit and a feedback circuit for feeding back an output signal of the inverter circuit to an input terminal of the inverter circuit. And a resonance circuit including an inductance and a capacitance, the inductance is a gate electrode group of transistors included in a basic cell forming a gate array semiconductor integrated circuit, and strip electrodes are parallel to each other. A plurality of wirings for connecting the gate electrode group arranged in a line and each adjacent gate electrode of the gate electrode group,
An end of each of the strip-shaped gate electrodes on one side in a direction at a right angle to the side where the other adjacent gate electrode exists and an end of the other adjacent gate electrode in the opposite direction to the one direction. And an oblique wiring group for connecting the gate wiring to the gate array semiconductor integrated circuit.

In order to solve the above-mentioned problems, a second aspect of the present invention is characterized in that, in the above-mentioned first gate array semiconductor integrated circuit oscillation circuit, a high-permeability material is provided at the core of the inductance. An oscillation circuit for a gate array semiconductor integrated circuit.

[0015]

The inductance according to the first aspect of the present invention is constituted by the gate electrode group and the predetermined diagonal wiring group in the gate array semiconductor integrated circuit. Therefore, the inductance can be easily formed on the gate array semiconductor integrated circuit, and as a result, the LC oscillation circuit is realized.

The inductance in the second invention is
A high-permeability material is provided on the core. Therefore, it is possible to realize a larger value of inductance with the same size coil.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an oscillator circuit which is a preferred embodiment of the present invention. As shown in Figure 1,
Also in this embodiment, the inverter circuit 40 and the predetermined feedback circuit connecting the output terminal and the input terminal of the inverter circuit 40 are included. This feedback circuit includes a resistor 42 connecting the output terminal and the input terminal, as in the conventional case. The feedback circuit also includes a capacitor 44 connecting the input terminal and the ground, and a capacitor 46 connecting the output terminal and the ground.

A characteristic of this embodiment is that a resonance circuit 50 including an inductance 48 is provided between the output terminal and the input terminal. This resonance circuit 5
By providing 0, high frequency oscillation is possible.

The structure of the coil 48 in this embodiment will be described. FIG. 2 is an explanatory diagram illustrating how the coil 48 is configured on the gate array semiconductor integrated circuit. As shown in FIG. 2, the coil 48 is constructed using four cells 52. A feature of this embodiment is that the gate electrodes 54 are connected to adjacent gate electrodes by diagonal wirings 56, as shown in FIG. Since the wiring layer forming the diagonal wiring 56 is provided on the gate electrode 54 via the insulating film, a so-called solenoid coil is formed on the gate array semiconductor integrated circuit.

A cross-sectional view of coil 48 is shown in FIG. As shown in FIG. 3, it is shown that an aluminum first layer (Al1) and a second layer (Al2) are provided on the upper surface of the polysilicon gate electrode 54. Further, FIG. 3 also shows that a high magnetic permeability material core 58 is provided between the gate electrode 54 and the second aluminum layer. As shown in FIG.
An insulating film is first provided on the gate electrode 54 made of polysilicon. The aluminum first layer (Al1) is provided on the insulating film, and the high-permeability material core 5 is provided.
8 is formed. As shown in FIG. 3, the aluminum first layer (Al1) is connected to the above-mentioned gate electrode 54 through a contact hole that is appropriately provided in the insulating film. The high magnetic permeability material core 58 is formed by depositing a material such as ferronickel on the insulating film by a method such as sputtering. Then, finally and again after covering with the insulating film, the aluminum second layer (A
12), the gate electrode 54 and the aluminum first layer (A) are centered around the high-permeability material core 58.
11) and the coil 48 composed of the second layer (Al2) are completed.

A characteristic of this embodiment is that a coil including a magnetic core is formed by the semiconductor process as described above. The resonance circuit 50 of the oscillation circuit of this embodiment is formed using this coil 48. As described above, in this embodiment, since the coil is formed only on the gate array semiconductor integrated circuit by the semiconductor process, it is possible to easily configure the LC type oscillation circuit.

Therefore, according to the present embodiment, an LC oscillating circuit can be obtained by forming the LC oscillating circuit only by the circuit on the gate array semiconductor integrated circuit and oscillating a high frequency of about several tens of MHz. The resistor 42 in this embodiment is
Alternatively, the capacitors 44 and 46 are configured using a conventional method.

[0024]

As described above, according to the first aspect of the present invention, since the coil can be formed by the semiconductor process, the LC oscillator circuit can be realized on the gate array semiconductor integrated circuit. Therefore, according to the first aspect of the present invention, it is possible to oscillate a high frequency without using any external parts.

According to the second invention, the coil having the magnetic core can be provided on the gate array semiconductor integrated circuit by using only the semiconductor process. Therefore, the size of the coil can be reduced, and a smaller oscillation circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an LC oscillator circuit according to a preferred embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a coil 48.

FIG. 3 is a cross-sectional view showing a configuration of a coil 48.

FIG. 4 is a circuit diagram of a conventional oscillator circuit.

FIG. 5 is a circuit diagram of an inverter circuit 10 in a conventional oscillator circuit.

FIG. 6 is an explanatory diagram showing a method of forming capacitors 14 and 16 of a conventional oscillation circuit.

FIG. 7 is an explanatory diagram showing a configuration method of a resistor 12 of a conventional oscillation circuit.

[Explanation of symbols]

 40 Inverter circuit 42 Resistance 44,46 Capacitor 48 Coil 50 Resonance circuit

Claims (2)

[Claims] 1. An oscillator circuit comprising: an inverter circuit; and a feedback circuit that feeds back an output signal of the inverter circuit to an input terminal of the inverter circuit, the resonance circuit including an inductance and a capacitance. The inductance is a gate electrode group of transistors included in a basic cell that constitutes a gate array semiconductor integrated circuit, and includes a gate electrode group in which strip-shaped electrodes are arranged in parallel, and adjacent gates of the gate electrode group. A plurality of wirings connecting the electrodes, one end of the strip-shaped gate electrode on one side in a direction perpendicular to the gate where the adjacent other gate electrode exists and the other adjacent gate electrode And a diagonal wiring group that connects an end in the direction opposite to the one direction in the gate array. Semiconductor integrated circuit for the oscillation circuit. 2. The oscillator circuit for a gate array semiconductor integrated circuit according to claim 1, wherein a high-permeability material is provided in a core portion of the inductance.