JPS5972745A - Semiconductor device - Google Patents

Abstract

PURPOSE:To form a highly reliable interlayer insulating film having a small diffusing coefficient against movable ions, by forming a first insulating layer comprising an oxide or nitride on a first layer, forming a second insulating layer comprising macromolecular resin thereon, forming a third insulating layer comprising an oxide or nitride thereon, thereby reducing the wiring capacity between the layers. CONSTITUTION:A first layer wiring 2 is formed on a GaAs substrate 1, wherein a specified semiconductor element is formed in advance. Si3N4 as a first insulating layer 3 is formed by a plasma CVD method at a temperature of 300 deg.C. As the insulating film 3, an oxide film can be used. Polyimide PIQ is rotatably applied on the film 3 as a second insulating film 4 comprising a macromolecular resin. The film is heated and hardened at 330 deg.C. Furthermore, an SiO2 film is formed by a plasma CVD method as a third insulating film 5. Then, a second wiring 6 is formed by evaporating Ti/Pt/Au, and thereafter performing lift off.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device using an interlayer insulating film for multilayer wiring.

Conventional Structure and Problems Materials for the glabellar insulating film of multilayer wiring in semiconductor devices include oxides such as S102 or 82203, nitrides such as Si3N4, and polymers.

There are resins, etc. By sandwiching these films between the first layer wiring and the second layer wiring, the wirings are insulated from each other.

Such an interlayer insulating film is required to have a high dielectric strength, be stable for a longer period than the life of the semiconductor device used, have a small diffusion coefficient for mobile ions, and have a material that does not interfere with the high-speed operation of the semiconductor device. The parasitic capacitance between wirings is small enough to avoid the following.

However, insulating films made of oxides and nitrides usually have a CV
, D method, and there is a difference between the coefficient of thermal expansion of these films and that of the substrate, and this causes cracks in the insulating film, so the film thickness cannot be increased. Therefore, the parasitic capacitance between wirings increases. Furthermore, when an interlayer insulating film is formed using a polymer resin, the film thickness can be made thicker than the above-mentioned insulating film made of oxide or nitride, but the stability of the composition is insufficient. Furthermore, the shielding ability against mobile ions such as Na + ions was not sufficient.

3. Purpose of the Invention The present invention improves the above-mentioned drawbacks.The purpose of the present invention is to increase the film thickness to reduce the interlayer wiring capacitance, and to reduce the diffusion coefficient for mobile ions. , to form a highly reliable interlayer insulating film.

Structure of the Invention A first layer of wiring is formed on a semiconductor substrate on which a predetermined semiconductor device is formed, and a first insulating film made of oxide or nitride is formed on the first layer of wiring, and is tightly adhered thereon. Then, a second insulating film made of polymer resin is formed. Furthermore, a third insulating film made of oxide or nitride is formed in close contact thereon. The second layer of wiring is then applied.

In this case, the first insulating film and the third insulating film made of oxide or nitride are respectively applied on top and bottom of the insulating film made of polymer resin, but these two insulating films are made of the same material. It doesn't have to be.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail using embodiments shown in the drawings. In FIG. 1, a first layer of wiring 2 is made of Au on a GaAs substrate 1 on which predetermined semiconductor elements are formed in advance.
It is formed by evaporating Ge/Au to a thickness of 0, e microns and then lift-on.

As the first insulating film 3, Si3N4 is formed to a thickness of 0.4 microns using a plasma CVD method at a formation temperature of 300.degree.

Note that this insulating layer 3 may be an oxide film. On top of that, a second insulating film 4 made of polymeric resin is made of polyimide "IQ (IX)IVimide 1soind".
r.

quinazol 1nedione) was applied by spin coating and cured by heating at 330°C. The thickness of this film 4 is 2.
It is 2 microns.

Further, as the third insulating film 5, S is formed by plasma CVD method.
After forming an iO2 film of 0.4 microns, a second layer wiring 6 is formed by depositing Ti/Pt/Au and then lifting off.

FIG. 2 shows a second embodiment of the invention. Semiconductor substrate 1
Above, between the first layer wiring 2 and the second layer wiring 6, a first insulating film 3 made of oxide or nitride, a third insulating edge 5, and a fifth insulating five-core film are formed. 8, a second insulating film 4 made of polymer resin, and a fourth insulating film 7 are alternately formed in close contact with each other. In this case as well, the first insulating film 3 made of oxide or nitride, the third insulating film 6, and the fifth insulating film 8 do not need to be made of the same material, but are made of polymer resin. The second insulating film 4 and the fourth insulating film 7 do not need to be the same.

In the embodiment of FIG. 1, the openings for connections between layers are as follows:
Form as follows. S 1 which is the third insulating film 5
02 is CHF after forming a photoresist mask.
Etching can be performed by performing reactive ion etching using three gases. PI which is the second insulating film 4
Q can be subjected to reactive ion etching with 02 gas using the third insulating film 5 as a mask. At this time, the photoresist is also removed. Thereafter, the Si3N4 film 3, which is the first insulating film underneath, can be etched by reactive ion etching using a mixed gas of CF4 and 20 inches of N2 gas, using the third insulating film 6 as a mask.

By using such a laminated insulating film structure, as in the case of this embodiment, an 813N4 film 3 suitable for preventing diffusion of A8 from the GaAs substrate 1 due to heat treatment is provided on the surface in contact with the GaAs substrate 1. By forming the polymer resin PIQ film 4, the film thickness can be increased without causing cracks. Furthermore, the upper surface contains N, which has an adverse effect on semiconductor devices.
513N4 membrane 5 with a small diffusion coefficient for a″-ions
By forming this, the reliability of the entire semiconductor device can be increased.

FIG. 3 shows the total thickness of the insulating film on the GaAs substrate and the number of cracks that occur. The curve 1 shows the number of cracks in the 513N4 film by plasma CVD, and the curve 2 shows the number of cracks in the insulating film according to the present invention. This shows that by adopting the structure of the present invention, the film thickness can be increased while keeping the number of cracks the same. In the case of the example shown above, the total thickness of the insulating film is 3 microns, so if 3 microns is formed of an insulating film made of Si3N4 film with a relative permittivity of 7.0, the relative permittivity is 3. .6 PIQ membrane to 2.2
The capacitance per unit area of the insulating film of the present invention using 7 μm is about 6% smaller than that of the insulating film of the present invention.

Furthermore, since the insulating film made of polymeric resin is sandwiched between insulating films that have a barrier against mobile ions, the influence of impurities in the polymeric resin on other layers or the semiconductor device can be reduced.

Further, by using the structure of the present invention, the first layer wiring and unevenness and steps on the semiconductor substrate can be flattened by spin coating of a polymer resin. As a result, the reliability of the second and subsequent layers is improved, and fine processing of the structure formed on the second and subsequent layers is possible. By changing the etching gas, the openings between the layers can be formed in the same process. Furthermore, the openings can be formed in a self-aligned structure using the upper insulating film as an etching mask, and the openings can be formed with high precision. I can do it.

In the configuration shown in FIG. 1, the fourth insulating film 7 and the fifth insulating film 7
By adding the insulating film 8, the structure shown in FIG. 2 is obtained. As a result, the shielding effect against Na+ ions is even greater than that of the insulating film having the structure shown in FIG. 1, and the dielectric strength voltage is also much higher.

Industrial implementation of the present invention can be carried out using a normal insulating film manufacturing process and a process that is almost the same as photoresist spin coating.

Effects of the Invention According to the present invention, an insulating film structure with low interlayer capacitance, less likely to cause diffusion of mobile ions, and high reliability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor device according to a first embodiment of the present invention, FIG. 2 is a cross-sectional view of a semiconductor device according to a second embodiment of the present invention, and FIG. 3 is a cross-sectional view of a semiconductor device according to a second embodiment of the present invention. FIG. 3 is an explanatory diagram showing the relationship with the number of cracks. 1... Semiconductor substrate including a semiconductor device, 2...
...First layer wiring, 3...First insulating film made of oxide or nitride, 4... Second insulating film made of polymer resin, 5 ...Third insulating film made of oxide or nitride, 6...Second layer wiring, 7...Made of resin with a high molecular weight of 9% Fourth insulating film, 8...Fifth insulating film made of oxide or nitride. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
figure

Claims (2)

[Claims] (1) A first insulating film made of an oxide or nitride on a semiconductor substrate, a second insulating film made of a polymer resin on it, and a second insulating film made of an oxide or nitride on it. A semiconductor device characterized in that an insulating film of No. 3 is present. (2) The semiconductor device according to claim 1, wherein the first insulating film and the second insulating film are alternately stacked in close contact with each other.