JPH04116930A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve step coverage on a contact hole by sputtering the inert gas ions to the wiring material overlaid on a semiconductor substrate so as to flatten the surface of the wiring material. CONSTITUTION:Inert gas ions are sputtered to the wiring material on a semiconductor substrate 1, and under the sputtering condition that the separation and the adhesion are balanced, the atoms or the molecules of the wiring material are shifted to the surface or its vicinity so as to bury the corner at the angle of the irregularity to modify it into smooth wiring, whereby the surface of the material 10 becomes flat, for example, the coverage of the sidewall of a contact hole also is elevated, and minute wiring high in reliability can be made.

Description

[Detailed Description of the Invention] [Summary] Regarding a wiring formation method, the purpose of improving the coverage of uneven parts such as contact holes is to apply an inert gas to the wiring material deposited on the semiconductor substrate. Ions are sputtered, and the atoms or molecules of the wiring material are moved nearby by the inert gas ions, thereby lowering the convex portions of the uneven portions formed in the wiring material, filling the concave portions, and flattening the wiring material. It is characterized by

The wiring material is characterized by being made of an aluminum film, an alloy film thereof, or a barrier metal film, and the uneven portion is a contact hole portion.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming wiring.

In recent years, semiconductor devices such as ICs and LSIs have become highly integrated,
As miniaturization progresses, problems related to the reliability of wiring are increasing, and the present invention relates to a proposal for increasing the reliability of fine wiring.

[Prior art and the problem to be solved by the invention] Even when semiconductor devices are miniaturized and internal wiring patterns are formed finely, the thickness of the glabella insulating film remains unchanged in order to maintain dielectric strength voltage. . Therefore, the current situation is that, for example, when a wiring material is buried in a deep contact hole with a minute cross section, the workability of uneven portions or stepped portions is reduced, and the coverage thereof is deteriorating.

FIG. 5 (al~(C1 is a diagram showing the problems of the conventional method, but the symbols in the figures are common, and l is a semiconductor substrate.

2 is a lower wiring made of a polycrystalline silicon film, 3 is a thin upper wiring made of an aluminum film, 4 is an insulating film, 5 is a thick upper wiring made of an aluminum film, C is a contact hole, and N is a recess. There is.

FIG. 5 (Al is an example in which a thin upper layer wiring 3 is formed, and a break occurs at a contact hole C.

In order to improve this problem, even if it is possible to form a slightly thicker upper layer wiring to eliminate the step break (indicated by the arrow) and connect it, the current density increases at the step part during operation, causing electromigration silane failure. may occur. Therefore, it is important to make the film thickness as thick as possible at the stepped portions.

FIG. 5 (bl) is an example in which a thick upper layer wiring 5 is formed. In order to make the film thickness as thick as possible at the stepped portion, the thick wiring is formed as shown in the figure to improve coverage.

However, in that case, a crack (indicated by an arrow) occurs at the bottom corner of the contact hole C. In order to eliminate these cracks, high-temperature sputtering deteriorates the coating properties, causing a thin layer to be deposited on the stepped portions as in the case of the thin wiring described above, increasing the current density and causing electron migration failure. In addition, thick interconnections have the disadvantage of further promoting step differences, and are therefore not very desirable interconnections.

Furthermore, when thick wiring is formed, not only disconnections but also short circuits occur. FIG. 5 (C1 is a perspective view illustrating this, and a short circuit occurs in a recess N (indicated by an arrow) in a portion sandwiched between two parallel upper layer wirings 5 due to wiring patterning.The reason for this is that the recess N If the wiring material is buried in the recess N, a mixed residue (polymer) of the resist and the wiring material is generated during etching removal for patterning the wiring, which blocks the entrance of the recess N and is buried in the bottom. This is because the wiring material contained in the wafer cannot be removed by etching.

As described above, as the wiring becomes finer, various problems arise that reduce its reliability, and for example, defects such as poor coverage due to high-temperature sputtering occur at stepped portions.

The present invention solves these problems and proposes a method for forming interconnects with the aim of improving coverage of uneven parts such as contact holes.

[Means to solve the problem]

The problem is, as shown in the principle diagram shown in FIG. An uneven portion (for example, a contact hole portion) formed in the wiring material by moving atoms or molecules of the wiring material laterally using active gas ions.
This problem can be solved by a manufacturing method that lowers the convex portion and fills in the concave portion to flatten the surface.

[For production]

That is, in the present invention, the atoms or molecules of the wiring material are moved to the vicinity of the surface by sputtering inert gas ions I and the sputtering conditions are such that desorption and adhesion are in an equilibrium state, thereby rounding the corners of the uneven parts and filling the corners. Correct the wiring so that it is gentle.

In this way, uneven portions can be formed into smooth wiring, and, for example, the coverage of the side walls of contact holes can be improved, resulting in the formation of highly reliable fine wiring.

〔Example〕

Examples will be described in detail below with reference to the drawings.

FIGS. 2(a) and 2(b) show the forming method (1) according to the present invention.
), first, as shown in FIG. 2(a), an insulating film 4 (film Thickness 1μm
), and after forming a contact hole C in the insulating film 4, a thin aluminum film 13 (film thickness 1 μm
(below) is deposited by sputtering. The sputtering method is a method in which target aluminum is bombarded with argon (Ar) ions and deposited on the opposing semiconductor substrate, while the semiconductor substrate 1 is heated to about 400 to 500°C.

Next, as shown in FIG. 2(b), when the aluminum film 13 is irradiated with Ar ions (inert gas ions) from above the semiconductor substrate on which the aluminum film is adhered, the aluminum atoms move nearby and form the convex portion. The aluminum fills the recesses, gradually reducing the unevenness and correcting the wiring shape. Therefore, aluminum is also deposited on the side wall of the contact hole C, and the wiring shape is modified to be smooth by connecting at the side wall portion where the aluminum film was previously broken.

In the sputtering process for moving the atoms, the semiconductor substrate is kept at room temperature, and sputtering is performed at an optimum energy level in order to maintain a balance between detachment and attachment of aluminum atoms. Its optimum value is Suba.

This can be obtained by changing the ion concentration, substrate bias conditions, etc. as the evening conditions.

After sputtering in this manner, the aluminum film is patterned into upper layer wiring 13 by applying lithography technology. In some cases, patterning may be performed before performing the sputtering method described in FIG. 2 (bl).

Next, FIGS. 3(al) and 3(b) show step-by-step cross-sectional views of the forming method (n) according to the present invention. This is an example of forming wiring.

As shown in FIG. 3(a), an insulating film 4 is coated on the lower wiring 2 made of a polycrystalline silicon film on one side of the semiconductor substrate, a contact hole C is formed in the insulating film 4, and a thick layer is formed on the insulating film 4. An aluminum film 15 (film thickness of 1 μm or more) is deposited by sputtering. The sputtering method is carried out in substantially the same manner as in the above example, and the semiconductor substrate is heated at a lower temperature (approximately 300° C.) than in the above example, and the semiconductor substrate is deposited thickly as shown in the figure.

Next, as shown in FIG. 3 (bl), when the aluminum film 15 deposited on the semiconductor substrate is irradiated with Ar ions from above, the aluminum atoms move to the vicinity and the aluminum atoms in the convex parts fill the concave parts, gradually The unevenness is reduced and the wiring shape is corrected.As a result, the aluminum film thickly coats the side wall of contact hole C, and even the bottom of the contact hole, which had a hollow shape, is filled with the aluminum film, making the surface of the contact hole smooth. A connection wiring having a recess is formed.

Note that during sputtering, the semiconductor substrate must be kept at room temperature, and
As in the above example, irradiation is performed using sputtering energy that maintains an equilibrium state between detachment and attachment of aluminum atoms.

After sputtering and ivy in this way, the aluminum film is patterned into the upper layer wiring 15 by applying lithography technology, but such upper layer wiring 15 has fewer disconnections and short circuits, and has a uniform current density. Electron migration defects are also reduced, resulting in higher reliability.

In the above embodiments, an aluminum film is used as an example of the wiring material, and aluminum is the most important wiring material in semiconductor devices. In addition, alloy films thereof are also frequently used, and although aluminum alloy films are wiring materials containing several percent of silicon or copper, such aluminum alloy films can also be processed in the same manner. Furthermore, by changing the sputtering conditions, the present invention can also be applied to polycrystalline silicon films and silicide films.

Next, FIGS. 4(al) and 4(b) show step-by-step cross-sectional views of the forming method (III) according to the present invention, and this example is an example applied to a barrier metal film. Tungsten), TiN (titanium nitride), etc. are interposed between the silicon substrate 7 polycrystalline silicon and aluminum wiring, etc., to suppress the reaction between the two, increase the resistance of the wiring, prevent disconnection, and improve reliability. Although the structure is known, in that case, the coverage at the bottom corner of the contact hole C is not sufficient, and for this reason, a conventional method has been adopted in which the film is deposited thicker than necessary.
This is an example to improve this.

First, Figure 4! 8), an insulating film 4 is coated on the semiconductor substrate 1, a contact hole C is formed in the insulating film 4, and a TiW film 23 (film thickness 1000 to 200 mm) is formed on the insulating film 4.
0 person) by sputtering method. The sputtering method is similar to the above example, and the semiconductor substrate is heated to the same extent, but
The TiW film has a high melting point and is thin, so it does not adhere well to the bottom corners.

Therefore, as shown in FIG. 4(b), the TiW film 23 deposited on the semiconductor substrate is irradiated with Ar ions from above. Then, the TiW molecules move to the vicinity and fill the bottom corner of the contact hole C, so that the TiW molecules can be uniformly deposited on the bottom of the contact hole C. Note that during sputtering, the semiconductor substrate is kept at room temperature, and, as in the above example, irradiation is performed with such energy that an equilibrium state between detachment and attachment of TiW molecules is maintained.

In this way, TiW is uniformly deposited on the bottom of the contact hole.
After depositing the film, if a wiring material such as an aluminum film is deposited, the TiW film (barrier metal film) can sufficiently serve as a barrier even if it is deposited thinner than before. In addition, by reducing the thickness of the barrier metal film in this way and reducing the aspect ratio (ratio of It!J thickness/cross-sectional area), the capacitance of the wiring becomes smaller, which helps speed up the operation.

Note that the inert gas ions used in the wiring repair method according to the present invention are not limited to the above-mentioned Ar ions, but also nitrogen gas (N) ions, etc. can be used, and a normal dry etching device can be used as the processing device. be able to.

〔Effect of the invention〕

As is clear from the above description of the embodiments, the processing method according to the present invention reduces disconnections and short circuits in semiconductor devices, improves manufacturing yield, suppresses electromigration, and improves reliability. Moreover, it has a remarkable effect that contributes to the improvement of its performance.

15 is a thick aluminum film or upper layer wiring, 23 is Ti
W film (barrier metal film); C indicates contact hole;

[Brief explanation of drawings]

FIG. 1 is a principle diagram, and FIGS. 2(a) and (b) are forming methods (1) according to the present invention.
), and FIGS. 3(a) and 3(b) are cross-sectional views of the forming method (I) according to the present invention.
I) step-by-step cross-sectional views of FIG.
), and FIGS. 5(a) to 5(e) are diagrams showing the problems of the conventional method. In the figure, 1 is a silicon substrate (semiconductor substrate), 2 is a lower layer wiring, 4 is an insulating film, 10 is a wiring material, 13 is a thin aluminum film or upper layer wiring, Fig. 1, 4d * Pier C

Claims (4)

[Claims] (1) Inert gas ions are sputtered onto the wiring material deposited on the semiconductor substrate, and the atoms or molecules of the wiring material are moved to the vicinity by the inert gas ions to form on the surface of the wiring material. A method for manufacturing a semiconductor device, characterized in that the convex portions of the uneven portion are lowered and the concave portions are filled and flattened. (2) The method for manufacturing a semiconductor device according to claim (1), wherein the wiring material is made of an aluminum film or an alloy thereof. (3) The method for manufacturing a semiconductor device according to claim (1), wherein the wiring material is made of a barrier metal film. (4) The method for manufacturing a semiconductor device according to claim (1), wherein the uneven portion is a contact hole portion.