JPH0377358A - Semiconductor integrated circuit - Google Patents

Abstract

PURPOSE:To isolate an analog circuit from a digital circuit which can be a noise source by a method wherein the analog circuit is built in a three- dimensional position separated from the digital circuit by using a semiconductor substrate which is connected to a power supply or grounded. CONSTITUTION:Separating insulating films 1 are provided in order to separate analog circuits 5a and 5b from digital circuits 4a and 4b. Semiconductor substrates 2 which are connected to a power supply or grounded are provided for building the analog circuits 5a and 5b in three-dimensional positions. That is, gate electrodes, wirings, insulating films, etc., are built up on the digital circuit 4a formed in a semiconductor substrate 3 to form digital circuit 4b. Further, the insulating films 1 for the separation between the analog and digital circuits are built up and, after the films 1 are etched, the semiconductor substrates 2 for the analog circuits are formed and the analog circuits 5a and 5b are built in and on the semiconductor substrates 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor integrated circuit, and particularly to a large-scale semiconductor integrated circuit in which analog circuits and digital circuits coexist.

[Conventional technology]

FIG. 2 is a sectional view showing a conventional semiconductor integrated circuit including both analog circuits and digital circuits.

In the figure, (3) is a semiconductor substrate, (4a) is a digital circuit formed inside the semiconductor substrate (3), (4b> is a digital circuit laminated on the digital circuit (4a) outside the semiconductor substrate (3), 5a) is an analog circuit formed inside the semiconductor substrate (3) at a location different from the digital circuit (4a); (5b) is an analog circuit layered on the analog circuit (5a) outside the semiconductor substrate +31; (6) are digital circuits (4a), (4b) and analog circuits (
5a), metal wiring for electrical connection with (5b), (
7) Metal wiring (6) means semiconductor substrate (3), digital circuit (4a), (4b), and analog circuit (5a)
, (5b).

Next, the effect will be explained.

A conventional semiconductor integrated circuit in which analog circuits and digital circuits coexist is constructed as described above, and has a semiconductor substrate (3
) A digital circuit (4a) and an analog circuit (5a) are formed inside, and a gate electrode, wiring, an insulating film, etc. are laminated on the digital circuit (4a) to form a digital circuit (4b). On the other hand, the necessary gate electrode wiring or insulating film, etc. are laminated on the analog circuit (5a) to form the analog circuit (5b), and the digital circuit (5b) is formed.
4a), (4b) and analog circuits (5a), (5b)
) was made using metal wiring (6).

[Invention tries to solve! i title]

Conventional semiconductor integrated circuits that include both analog and digital circuits are configured as described above, and because the analog and digital circuits are formed on the same semiconductor substrate, noise from the digital circuits has a negative impact on the analog circuits. However, there are problems such as the difficulty of completely preventing the negative effects from digital circuits. was there.

The present invention has been made to solve the above-mentioned problems, and its purpose is to make an analog circuit separate and independent from a digital circuit which is a source of noise generation.

[Means for Solving the Problems] A semiconductor integrated circuit in which analog circuits and digital circuits are mixed according to the present invention separates the analog circuit from the digital circuit, which is a source of noise, by an insulating film and a semiconductor substrate, and separates the analog circuit from the digital circuit, which is a source of noise, by using an insulating film and a semiconductor substrate, and separates the analog circuit from the digital circuit, which is a source of noise. form and be independent from digital circuits.

[Function] The analog circuit in this invention is formed in a three-dimensional position separated from the digital circuit by a semiconductor substrate supplied with power or grounded.

〔Example〕

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

FIG. 1 is a cross-sectional view showing a semiconductor integrated circuit in which analog circuits and digital circuits coexist.

In the figure, (31, (4a), (4b), (5a
), (5b), (6) and (7) are the same as those shown in the conventional example of FIG. 2, so their explanations will be omitted. (1) is a digital circuit (4a) (4b) and an analog circuit (5a)
, (5b), and (2) is a semiconductor substrate for analog circuits that is supplied with power or grounded for forming analog circuits (5a) and (5b) in three-dimensional positions.

Next, the effect will be explained.

In a semiconductor integrated circuit in which analog circuits and digital circuits configured as described above coexist, a semiconductor substrate (
3) Layer gate electrodes, wiring, insulating films, etc. on the digital circuit (4a) formed inside to form the digital circuit (4a).
4b). Furthermore, an insulating film for analog/digital isolation (1) is laminated, and after etching, a semiconductor substrate for analog circuits (2) is formed, and analog circuits (5a) and (5b) are built inside and on the substrate. I'm taking it.

In the above embodiment, an example was shown in which the digital circuit is formed in a three-dimensional position with the analog circuit, but the digital circuit may be formed in a three-dimensional position and the same effect can be obtained.

Furthermore, in semiconductor integrated circuits consisting only of digital circuits, circuits that affect the entire chip, such as clock generator circuits and other circuits that create the timing of chip operation, may be formed in a three-dimensional position separate from other circuits. This has the advantage of not being adversely affected by other circuits.

〔Effect of the invention〕

As described above, according to the present invention, the analog circuit is separated and independent from the digital circuit, which is a source of noise, by a semiconductor substrate that is powered or grounded, so the analog circuit can be protected from noise from the digital circuit, and the analog circuit Since they are formed in three-dimensional positions, the chip area can be reduced and a large-scale semiconductor integrated circuit can be realized.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a semiconductor integrated circuit in which analog circuits and digital circuits are mixed according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional semiconductor integrated circuit in which analog circuits and digital circuits are mixed. be. In the figure, (1) is an isolation insulating film, (2) is a semiconductor substrate for analog circuits, (3) is a semiconductor substrate, (4a),
(4b) is a digital circuit, (5a) and (5b) are analog circuits, and (6) is metal wiring. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a semiconductor integrated circuit in which analog circuits and digital circuits coexist, the semiconductor integrated circuit is characterized by having at least a structure in which the analog circuit is built in a three-dimensional position separate from the digital circuit in order to separate the analog circuit from the digital circuit. semiconductor integrated circuits.