JPH0289318A - Manufacture of multilayer interconnected semiconductor integrated circuit device - Google Patents

Abstract

PURPOSE:To prevent difference in thickness of an insulating film at the shoulder part of a lower aluminum wiring layer and at the flat part scarcely by depositing and forming the insulating film mainly consisting of polyimide over the whole surface of a semiconductor substrate including the lower wiring having an inorganic or organic insulating film left on the side surface thereof. CONSTITUTION:A silicon nitride film 3 is etched by about 1mum by reactive ion etching utilizing carbon tetrafluoride gas plasm until the surface of a lower aluminum wiring layer 2 is exposed. Because this etching is anisotropic etching, the silicon nitride film 3' is left on the side surface of the lower aluminum wiring layer 2. Lastly, polyamide precursor solution is applied by spin application process so that the film thickness at the part may be about 1mum, and baking up to about 400 deg.C is carried out stepwise to form a polyimide interlayer insulating film 4. In this case, since polyamide precursor solution is applied to the shoulder part of the lower aluminum wiring layer 2 on the basis of the surface of the silicon nitride film 3', the polyimide interlayer insulating film 4 formed on the shoulder part of the lower aluminum wiring layer 2 scarcely differs from that formed on the flat part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a multilayer interconnect semiconductor integrated circuit device, and more particularly to a method for forming multilayer metal interconnects.

[Conventional technology]

Conventionally, polyimide polymer films have been used as interlayer insulating films for forming multilayer wiring structures. The reason for this is that the insulating film is formed by spin-coating a solution onto the substrate and then baking it, which has the effect of smoothing out wiring steps and making it easier to remove upper layer wiring. This is because it can be formed.

[Problem that the invention seeks to solve]

However, in the film formed by the above-described spin coating method, the film thickness 6 at the shoulder portion of the lower aluminum wiring 2 is thinner than the film thickness at other flat portions, as shown in FIG. This is a problem that cannot be avoided in principle because the cross-sectional shape of the film is determined depending on the surface tension of the solution at the time of application. As a countermeasure for this, conventionally the lower layer was made of aluminum! ! In order to ensure the dielectric strength of the interlayer insulating film at the shoulder portion of 2, the flat part is approximately 1. ．． The film thickness is estimated from the beginning so that it will be approximately 5 to 2 times as thick as the coating. As a result, the thickness of the interlayer insulating film at the locations where the wirings are connected vertically increases, resulting in a drawback that connection failures are more likely to occur. The reason for this is that the upper layer aluminum wiring
After making through holes in the glabellar insulating film, physical paper deposition such as sputtering is usually used (
Physical Vapor Deposition
) law, so-called.

Although it is attached using the PVD method, since the PVD method has poor coverage of the stepped portion, as shown in FIG. 2, the deeper the through hole is, the more likely it is that poor coverage 8 will occur in the upper layer aluminum wiring 7. .

In view of the above-mentioned circumstances, an object of the present invention is to avoid forming a film thicker than necessary on the flat part, and to create a film with almost no difference in film thickness between the shoulder part and the flat part of the lower layer aluminum wiring. It is an object of the present invention to provide a method for manufacturing a multilayer wiring semiconductor integrated circuit device, which includes a step of forming a glabellar insulating film.

[Means for solving problems]

According to the present invention, a method for manufacturing a multilayer wiring semiconductor integrated circuit device includes the steps of selectively forming a lower layer wiring on a semiconductor substrate, and forming an inorganic or organic insulating film on the semiconductor substrate including the lower layer wiring. a step of selectively removing the inorganic or organic insulating film, leaving the inorganic or organic insulating film on the side surfaces of the lower wiring; and a step of selectively removing the inorganic or organic insulating film on the side surfaces of the lower wiring; The method includes a step of forming an insulating film between the eyebrows, and a step of depositing an insulating film mainly made of polyimide.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIGS. 1(a) to 1(d) are process diagrams for forming an interlayer insulating film showing one embodiment of the present invention. According to this embodiment, as shown in FIG.
As shown in a), a lower aluminum wiring 2 is formed on a semiconductor substrate 1.
is formed first. That is, an aluminum film with a thickness of about 1 μm is first deposited on the substrate 1 by sputtering, and then active aluminum film is applied using chlorine plasma gas using a photoresist formed by ordinary photolithography as a mask. Ion etching is performed to form lower layer aluminum wiring 2. Next, approximately 1 μm
A silicon nitride film 3 with a thickness of m is applied [Fig. 1(b)].
Then, this silicon nitride film 3 is etched by about 1 μm by active ion etching using carbon tetrafluoride (CF4) gas plasma until the surface of the lower layer aluminum wiring 2 is exposed. Since this etching is anisotropic etching, silicon nitride pA3' is left on the side surfaces of the lower aluminum wiring 2 [see FIG. 1(c)]. Finally, a polyamide precursor solution is applied using a spin coating method so that the film thickness on the flat part is approximately 1 μm, and baking is performed stepwise to approximately 400°C to form a polyimide interlayer insulating film. 4 is formed [Fig. 1(d)
reference〕. At this time, since the polyamide precursor solution is applied to the shoulder part of the lower aluminum wiring 2 with reference to the surface of the silicon nitride film 3', the polyimide precursor solution is applied to the shoulder part of the lower aluminum wiring 2, which has almost no difference from the flat part. An interlayer insulating film 4 is formed.

FIGS. 2(a) to 2(d) are process diagrams for forming a glabellar insulating film showing another embodiment of the present invention. According to this embodiment, a polyimide film 5' is formed on the side surface of the lower aluminum wiring 2 in place of the silicon nitride film 3' of the previous embodiment. That is, after forming the lower aluminum wiring 2 [see Fig. 2 (a>)], a polyamide precursor solution was spin-coated to a film thickness of about 1 μm on the flat part, and heated to about 400°C. A polyimide film 5 is applied by stepwise baking (see FIG. 2(b)).

Next, this polyimide film 5 is etched by about 1 μm by plasma isotropic etching using oxygen gas plasma until the surface of the lower aluminum wiring 2 is exposed. At this time, since the polyimide film 5 is formed thicker than the flat part on the wiring step part, the thickness of the polyimide film 5 is about 0.5 on the side surface of the wiring after etching.
A polyimide film 5' having a width and height of approximately μm is left behind [see FIG. 2(c)]. Finally, if the polyimide interlayer insulation H4 is formed using the spin coating method, the shoulder part of the lower aluminum wiring 2 will have a polyimide glabella as shown in FIG. Insulating film 4 is formed.

〔Effect of the invention〕

As explained in detail above, according to the present invention, when forming a multilayer wiring structure, even if a polyimide polymer film is used as an interlayer insulating film as in the past, the side surface of the lower layer wiring has a height comparable to that of the wiring. Since an insulating film having a width and a width is formed, the polyimide polymer film is less likely to become thinner at the shoulder portions of the lower wiring than at the flat portions. Therefore,
It is possible to form a relatively thin insulating film between the eyebrows and reduce the depth of the through hole, which solves problems such as poor coverage of the upper layer wiring in the through hole and poor connection. .

FIG. 5 is a diagram showing structural defects in the interlayer insulating film produced by the conventional method.

1... Semiconductor substrate, 2... Lower layer aluminum wiring, 3...
・Silicon nitride film, 3'...Silicon nitride film left on the side surface of the lower layer aluminum wiring, 4...Polyimide interlayer insulating film, 5...Polyimide film, 5'...On the side surface of the lower layer aluminum interconnection The remaining polyimide film.

Claims (1)

[Claims] A step of selectively forming a lower layer wiring on a semiconductor substrate, a step of coating an inorganic or organic insulating film on the semiconductor substrate including the lower layer wiring, and a step of forming an inorganic or organic insulating film on a side surface of the lower layer wiring. It consists of a step of selectively removing the remaining inorganic or organic insulating film, and a step of depositing an insulating film mainly made of polyimide over the entire surface of the semiconductor substrate, including the lower layer wiring, leaving the inorganic or organic insulating film on the side surfaces. A method for manufacturing a multilayer wiring semiconductor integrated circuit device, comprising a step of forming an interlayer insulating film.