JP2755263B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The present invention relates to a method for forming a metal wiring layer of aluminum or the like on a substrate on which a semiconductor device is formed. For the purpose of flattening and forming a metal film having a stable film thickness, a lower insulating film is formed on a substrate, a part of the lower insulating film is opened to form a region to serve as an etching stopper, An upper insulating film is formed on the lower insulating film and the region to be an etching stopper to form a flat insulating film, and then the insulating film is entirely etched until the region to be the etching stopper is exposed. A metal wiring is formed on the insulating film.

The present invention relates to a manufacturing method for forming a metal wiring layer such as aluminum on a substrate on which a semiconductor device is formed.

In a manufacturing process of a semiconductor device, a wiring step of forming a metal wiring layer of aluminum or the like on the elements is performed after a bulk step of forming a number of elements on a substrate. The metal wiring layer is formed on an element formed in a bulk process via an insulating film, and is connected to each element through a through hole formed at a predetermined position in the insulating film. In order to form the metal wiring layer on the insulating film in a stable state, the surface of the insulating film needs to be flattened. The unevenness of the steps is not uniform, and it is increasingly difficult to flatten the surface of the insulating film.

[Prior Art] As shown in FIG. 2, various projections 2 are present at irregular intervals on the substrate 1 after the bulk process is completed, and the projections 2 cause many steps. To form an aluminum wiring layer on such a substrate 1, first, as shown in FIG.
An insulating film 3 such as a PSG film or a BPSG film is formed thereon, and the insulating film 3 is melted at 900 to 1000 ° C., flattened, and a contact hole 4 is formed. Then, an aluminum wiring 5 is patterned on the insulating film 3 as a metal wiring.

However, in such a wiring process, if the thickness of the insulating film 3 is small, the upper surface of the insulating film 3 may not be sufficiently flattened depending on the interval between the protrusions 2. Thin and easy to break.

Then, as shown in FIG. 4, when the thick insulating film 3 is formed and flattened by heating and melting, the upper surface of the insulating film 3 is sufficiently flattened above the protrusion 2 but the contact hole 4 Since the step at the portion becomes large, a sufficient film thickness of the aluminum wiring 5 cannot be secured in the contact hole 4.

In order to solve such a problem, as shown in FIG. 5A, the insulating film 3 is formed thick and flattened, and then the insulating film 3 is entirely etched as shown in FIG. To reduce the film thickness. Then, when the aluminum arrangement 5 is patterned on the insulating film 3, a sufficient film thickness of the aluminum wiring 5 can be obtained even on the protrusion 2 and the contact hole 4 as shown in FIG. 5 (c).

[Problems to be Solved by the Invention] However, in the wiring step shown in FIG. 5, the entire surface of the insulating film 3 is etched with no selectivity to the etching gas, and the etching end point cannot be detected. The thickness of the insulating film 3 after the etching is controlled only by adjusting the etching time.
Therefore, the film thickness of the insulating film 3 after etching becomes unstable, and if the film thickness is thinner than necessary, sufficient insulation cannot be secured, or if the film thickness is too thick, the problem shown in FIG. 4 will occur. There is a point.

An object of the present invention is to provide a manufacturing method capable of forming a metal wiring having a stable film thickness by sufficiently flattening an insulating film formed as a base of a metal wiring while ensuring insulation.

[Means for Solving the Problems] The object is to form a lower insulating film on a substrate, form a region to serve as an etching stopper by opening a part of the lower insulating film, and then form the lower insulating film and the etching An upper insulating film is formed on a region to be a stopper to form a flat insulating film, and then the entire surface of the insulating film is etched until the region to be an etching stopper is exposed. This is achieved by a manufacturing method for forming metal wiring.

[Operation] The insulating film in which the unevenness of the substrate is flattened by the lower insulating film and the upper insulating film is entirely etched until a region to be an etching stopper is exposed, and the insulating film is thinned as far as insulation can be secured. A metal wiring having a stable thickness is patterned on the film.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. The same components as those in the conventional example will be described with the same reference numerals.

As shown in FIG. 1 (a), the projection 2
First, a lower insulating film 7a having a thickness necessary for ensuring insulation is formed on the substrate 1 on which BPSG film is formed, for example. Then, as shown in FIG. 1 (b), scribe lines 8 for dicing are opened in the lower insulating film 7a by photoetching.

Next, as shown in FIG. 1C, the lower insulating film 7a is formed.
Similarly, an upper insulating film 7b is formed from a BPSG film to form an insulating film 7, and the insulating films 7a and 7b are simultaneously heated and melted to be flattened as shown in FIG.

Next, the entire surface of the insulating film 7 is etched until the scribe lines 8 are exposed. That is, when the etching is performed with the exposure of the substrate 1 having a certain area corresponding to the scribe line 8 as the end point of the entire surface etching, as shown in FIG. 1E, the insulating film 7 becomes the lower insulating film 7a. , The sufficient insulation is secured, and the upper portion of the protrusion 2 is sufficiently flat.

Next, as shown in FIG. 1 (f), a contact hole 4 is formed in the insulating film 7 by photo-etching and an aluminum wiring 5 is formed, and the aluminum wiring 5 having a uniform thickness is formed on the flat insulating film 7. The contact hole 4 is formed and the step of the contact hole 4 is relatively small.
Aluminum wiring 5 having a sufficient thickness is formed therein. Therefore, according to the method for manufacturing an aluminum wiring as described above, a sufficient insulating property can be ensured and a flat insulating film 7 can be formed, so that the aluminum wiring 5 formed on the insulating film 7 can be formed. It can be formed with a stable film thickness.

Next, the present invention can be carried out in the following modes.

B) In the above embodiment, the scribe line 8 is formed on the lower insulating film 7a.
After opening the upper insulating film 7b, the lower insulating film 7a and the upper insulating film 7b were simultaneously heated and melted to be flattened. When the upper insulating film 7b is formed, the insulating film 7 can be sufficiently flattened even if the thickness of the upper insulating film 7b is reduced. As a result, the etching amount of the entire surface of the insulating film 7 can be reduced, so that the insulating film 7 having a stable film thickness can be formed as a base layer of the aluminum wiring 5.

B) The lower insulating film 7a may be an SiO ₂ film formed by a CVD method. Since the SiO ₂ film does not melt at the above-mentioned heating temperature, the planarization is performed exclusively by the upper insulating film 7b.

(C) By making the upper insulating film thicker, flattening can be achieved without heating and melting. Such a method is particularly effective when forming the upper layer wiring of the two-layer aluminum wiring, and the scribe line opened in the lower insulating film is used as the end point of the whole surface etching as in the above embodiment.

[Effects of the Invention] As described in detail above, according to the manufacturing method of the present invention, the insulating film formed as the base of the metal wiring is sufficiently flattened while securing the insulating property to form the metal wiring having a stable film thickness. Demonstrate excellent effects that can be.

[Brief description of the drawings]

1 (a) to 1 (f) are manufacturing process diagrams embodying the present invention, FIG. 2 is a cross-sectional view showing a substrate on which metal wiring is provided, and FIGS. 3 and 4 are problems with conventional metal wiring. A sectional view showing the
5 (a) to 5 (c) are process diagrams showing an example of a conventional manufacturing method. In the figure, 1 is a substrate, 5 is a metal wiring (aluminum wiring), 7 is an insulating film, 7a is an upper insulating film, 7b is a lower insulating film, and 8 is a region (scribe line) to be an etching stopper.

Claims (1)

(57) [Claims] A lower insulating film is formed on a substrate, a part of the lower insulating film is opened to form a region to be an etching stopper, and then an upper layer is formed on the lower insulating film and a region to be an etching stopper. Forming an insulating film to form a flat insulating film, and then etching the entire insulating film until the region to be the etching stopper is exposed, and forming a metal wiring on the etched insulating film. Manufacturing method of a semiconductor device.