JPH01310560A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To lessen an inter-wiring capacity and to minimize an inter-wiring crosstalk by a method wherein the film thickness of a first insulating film at a region other than metal wiring regions is made thinner than that of the first insulating film positioned right under the metal wirings. CONSTITUTION:The film thickness of a first insulating film 2 at a region other than metal wiring regions 3-1 and 3-2 is made thinner than that of the first insulating layer 2 positioned right under the wirings 3-1 and 3-2 or the film 2 is left only right under the wirings 3-1 and 3-2 and the film 2 at the region other than the wiring regions 3-1 and 3-2 is removed. Accordingly, part or the whole part of the film 2 positioned between a plurality of the wirings 3-1 and 3-2 parallel to each other can be substituted for the air of permittivity lower than that of the layer 2 or an atmosphere equivalent to that. Thereby, a line-to-line capacity is reduced by the amount of permittivity difference and a line-to-line crosstalk can be inhibited.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a structure and a method for forming the same for reducing crosstalk between a plurality of parallel metal lines in a high-speed integrated circuit.

BACKGROUND OF THE INVENTION The speeding up and miniaturization of integrated circuits has been brought about by reducing the width of interconnects and spacing between interconnects, as well as improving performance by reducing the size of transistors. However, with the reduction in line width and line spacing, new problems have arisen, such as signal propagation delay due to increased resistance and crosstalk due to increased capacitance between lines. Particularly in high-speed digital integrated circuits, multiple metal wires are often routed in parallel to each other, which poses serious problems such as malfunctions and noise caused by crosstalk between the wires. Crosstalk between wires is determined by the capacitance and amount between wires, so how to reduce the capacitance between wires is an important point.

FIG. 5 is a first example showing a conventional semiconductor device. In FIG. 5, a semi-insulating GaAa substrate 1 is used as a semiconductor substrate, and a first metal wiring 3-1 and a second metal wiring 3-2 are directly formed in parallel to each other on this semi-insulating GaAa substrate 1. be.

In the configuration shown in FIG. 5, the capacitance between the first metal wiring 3-1 and the second metal marking line 3-2 that are parallel to each other is 80 f F/ when the wiring spacing and wiring width are each 1 μm.
It showed a very large value of about 100 fF/mm to 100 fF/mm. This large inter-wiring capacitance is due to the large permittivity and electric constant of the semi-insulating GaAa substrate 1 (for example, the semi-insulating GaAa
In the case of the substrate, the dielectric constant is approximately 12.9).

FIG. 6 shows a second example of a conventional semiconductor device. Also in FIG. 6, a semi-insulating GaAa substrate 1 is used as the semiconductor substrate. After depositing a first insulating film 2 on this semi-insulating GaAa substrate 1, first insulating films 2 are deposited parallel to each other as shown in FIG.
A metal wiring 3-1 and a second metal wiring 3-2 are formed. As the first insulating film 2, 5i02 is usually used.

First metal wiring 3-1 and second metal wiring 3- parallel to each other
By using the first insulating film 2, which has a dielectric constant lower than that of the semi-insulating GaAa substrate 1, under the semi-insulating GaAa substrate 1, the capacitance between the first metal wiring 3-1 and the second metal wiring 3-2, which are parallel to each other, is reduced. is 10 f F/mm to 20 when the film thickness of the first insulating M2 is 1 μm and the wiring spacing and wiring width are each 1 μm.
Although it is approximately f F/mm, which is a large decrease compared to the first example of the conventional semiconductor device shown in FIG. 5, it is not sufficient to minimize the crosstalk between wiring lines. 1st
This capacitance increases when the thickness of the insulating film 2 is reduced to 1 μm or less.

Problems to be Solved by the Invention In the conventional semiconductor device shown in FIGS. 5 and 6, the first metal wiring 3-1 and the second metal wiring 3- are parallel to each other.
2, the wiring spacing and wiring width are each 1 μm.
m, from 10 f F/mm to 100 f F/
It is about mm, which is insufficient to minimize crosstalk between wiring lines. If the wiring spacing becomes narrower, the capacitance between the wirings will further increase and crosstalk will also increase.

The present invention has been made in view of the above, and provides an excellent semiconductor device and a device capable of minimizing inter-wiring capacitance and minimizing crosstalk between wirings in a configuration in which a plurality of parallel metal wirings are formed. The purpose of this invention is to provide a manufacturing method for the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method for solving the problems described above.
In a configuration in which a plurality of metal interconnects parallel to each other are formed on an insulating film and the first insulating film, the first insulating film other than the metal interconnect region
Either the thickness of the insulating film is made thinner than the thickness of the first insulating film located directly under the metal wiring, or the first insulating film is left only directly under the metal wiring, and the first insulating film is removed in areas other than the metal wiring area. Remove membrane. The manufacturing method is to form a first insulating film and a plurality of metal wirings parallel to each other on the first insulating film on a semiconductor substrate, and then to etch the first insulating film using the metal wiring as a mask material to remove the area other than the metal wiring area. The thickness of the first insulating film is reduced or completely removed.

Effect of the present invention With the above-described configuration, a portion or the entire portion of the first insulating film located between a plurality of metal wirings parallel to each other is covered with air having a lower dielectric constant than the first insulating film or an atmosphere equivalent thereto. Since it can be replaced by , the inter-line capacitance can be further reduced by the difference in dielectric constant, and crosstalk between the lines can be suppressed. Further, according to the present invention, the first insulating film is etched using the metal wiring formed on the first insulating film as a mask material by the above-described manufacturing method, so that etching is performed in alignment with the metal wiring, and there is no problem such as mask displacement. It is stable and does not require the process of creating a new mask or matching the masks.

Embodiment FIG. 1 is a sectional view of a first embodiment of the semiconductor device of the present invention. In the semiconductor device of the present invention shown in FIG. 1, parts equivalent to those in FIGS. 5 and 6 are designated by the same reference numerals. In FIG. 1, a semi-insulating GaAa substrate 1 is used as a semiconductor substrate, and this semi-insulating G
A first insulating film 2 and a first metal wiring 3-1 and a second metal wiring 3-2 which are parallel to each other are formed on an aAa substrate 1. As the first insulating film 2, SiO2 is used. The first insulating film 2 having a lower dielectric constant than the semi-insulating GaAa substrate 1 is used under the first metal wiring 3-1 and the second metal wiring 3-2 which are parallel to each other, and the first metal wiring which is parallel to each other. 3-
1 and the second metal wiring 3-2.
Since the first insulation is partially etched away, the first insulation 11X2
5 fF/mm to 8 fF/m when the deposited film thickness is 1” μm, and the wiring spacing and wire width are each 1 μm.
The inter-wiring capacitance can be reduced to approximately half of that of the conventional method.

FIG. 2 is a sectional view of a second embodiment of the semiconductor device of the present invention. In FIG. 2, the first insulating film 2 located between the first metal wiring 3-1 and the second metal wiring 3-2, which are parallel to each other, has been completely etched away and is made of semi-insulating Ga.
The As substrate 1 is exposed on the surface. Therefore, when the deposited film thickness of the first insulating film 2 is 1 μm, and the wire spacing and wire width are each 1 μm, the inter-wire capacitance can be further reduced from 3 fF/mm to about 6 fF/mm.

FIG. 3 is a sectional view of a third embodiment of the semiconductor device of the present invention. This is an example in which a second insulating film 4 is deposited over the entire surface of the semi-insulating GaAs substrate 1, the first metal wiring 3-1, and the second metal wiring 3-2 for surface protection. The thickness of the second insulating film 4 is approximately 0.1 μm, which is sufficient. Also in the third embodiment of the present invention shown in FIG. 3, the first insulating film 2 is completely etched away, and the semi-insulating GaAs substrate 1 is left exposed on the surface, and then the second insulating film 4 is removed. Although it is deposited thinly and increases inter-wiring capacitance, it can protect the surface of metal wiring.

FIG. 4 is a process cross-sectional view showing a method of manufacturing a semiconductor device that can specifically realize the semiconductor device of the present invention. Figure 4a
) is a step of depositing a first insulating film 2 on a semi-insulating GaAs substrate 1. FIG. 4b) shows a first metal wiring 3-1 and a second metal wiring 3-2 parallel to each other on the first insulating film 2.
It is a process of forming and forming. In FIG. 4C, the first metal wiring 3-1 and the second metal wiring 3-2 are used as masks to
This is a step of etching 5 the insulating film 2. By the process shown in FIG. 4C), the first metal wirings 3 parallel to each other are
-1 and the first area other than the area covered by the second metal wiring 3-2.
The insulating film 2 is etched and the inter-wiring capacitance is reduced. Etching uses commonly used plasma ions. FIG. 4 d) shows the result of completely removing the first insulating film 2 by the etching process shown in FIG. The first insulating film 2 is left only directly under -2. In the manufacturing method of the present invention shown in FIG. 4, an example is used in which the first insulating film 2 is left only directly under the first metal wiring 3-1 and the second metal wiring 3-2 which are parallel to each other. As shown in FIG. 4C, the line capacitance can be reduced even when about half of the first insulating film 2 located between the lines is removed by etching, which is the same as the detailed explanation of the present invention.

As explained above, by using the semiconductor device and the manufacturing method thereof of the present invention, the thickness of the first insulating film 2 can be reduced to 1 μm, for example.
m, and when the wiring spacing and wiring width are each 1 μm, the inter-wiring capacitance is about 4 fF/mm to 6 fF/mm, which can be reduced to less than half of the conventional value. In addition, since the first insulating film is etched using the metal wiring formed on the first insulating film as a mask material, the etching is performed in alignment with the metal wiring, and there is no problem such as mask displacement (it is stable and requires a new mask). The steps of manufacturing and mask matching are also unnecessary.

Effects of the Invention As described above, the present invention brings about the following effects.

1) The line capacitance between parallel metal wirings ranges from 4 fF/mm to 6 fF/mm, for example, when the thickness of the first insulating film 2 is 1 μm, and the wire spacing and width are each 1 μm.
It becomes a value of about mm, which can be reduced to less than half of the conventional value. Therefore, problems such as crosstalk are reduced, and high-speed signal processing can be performed accurately.

2) Since the first insulating film is etched using the metal wiring formed on the first insulating film as a mask material, the etching is performed in alignment with the metal wiring and is stable without problems such as mask displacement, making it possible to create a new mask. Also, the process of mask alignment is unnecessary.

[Brief explanation of the drawing]

1, 2, and 3 are cross-sectional views of semiconductor devices showing first, second, and third embodiments of the semiconductor device of the present invention, respectively, and FIG. 4 is a method for manufacturing the semiconductor device of the present invention. FIGS. 5 and 6 are cross-sectional views showing conventional semiconductor devices. 1. φ semi-insulating GaAs substrate, 2... first insulating film,
3-1--first metal wiring, 3-2◆-second metal wiring, 4--second insulating film, 5--etching. Name of agent: Patent attorney Toshio Nakao and 1 other person I Senku 9 and Eseha J-Female

Claims (4)

[Claims] (1) In a structure in which a first insulating film and a plurality of metal wirings parallel to each other are formed on the first insulating film on a semiconductor substrate, the film thickness of the first insulating film other than the metal wiring region is A semiconductor device characterized in that the thickness of the first insulating film is thinner than that of a first insulating film located directly below a wiring. (2) The semiconductor device according to claim 1, wherein the first insulating film is left only directly under the metal wiring, and the first insulating film located outside the metal wiring area is removed. (3) The semiconductor device according to claim 1 or 2, further comprising a first insulating film on the semiconductor substrate and a second insulating film all over the metal wiring. (4) After forming a first insulating film and a plurality of metal wirings parallel to each other on the first insulating film on the semiconductor substrate, the first insulating film is etched using the metal wiring as a mask material. A method for manufacturing a semiconductor device.