JPH0338042A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain uniform step-coverage independent of the aspect ratio of a via hole by raising substrate temperature, applying a bias to a substrate, and using a first metal film whose surface energy is larger than that of a second metal film. CONSTITUTION:A first metal film 13 is stuck on an insulating film 12 in which a via hole is formed. The thickness of a first metal film 13 is thinned so as not to cause self-shadowing effect. Thereby the first metal film 13 can be almost uniformly stuck independently of the amount of surface energy of an insulating film 12 turning to a substratum. A second metal film 14 is sequential stuck. In this case, a substrate is heated and a bias is applied to the substrate. In addition, the first metal film 13 whose surface energy is larger than a second metal film 14 is used, thereby improving the wetability of the second metal film 14 on the first metal film 13. Hence the wiring metal layer 14 can be uniformly stuck independently of the aspect ratio of a via hole.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to provide a method for uniformly filling via holes with a wiring metal film, regardless of the aspect ratio, with respect to a method for forming a wiring metal film. A first metal film is sputter-deposited on the substrate on which the film is formed to a thickness that does not cause a self-shadowing effect, and then a second metal film having a surface energy smaller than that of the first metal film is sputter-deposited. In this case, the temperature of the substrate is raised to such an extent that surface diffusion of atoms constituting the second metal film on the surface of the first metal film is promoted, and the second metal deposited on the stepped portion of the via hole is heated. The wiring metal film is formed in the via hole by applying substrate pi and as to such an extent that the film does not cause a self-shadowing effect.

[Industrial application field]

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

In order to improve the reliability of ICs, it is necessary to uniformly fill all via holes with various aspect ratios (the ratio between the depth and the diameter of the via hole) with a wiring metal film to obtain good step coverage. .

[Conventional technology]

FIG. 4 shows a cross-sectional view of a wiring metal film deposited on an insulating film having via holes with different aspect ratios using a conventional sputter deposition method. In the figure, 31 is a substrate;
32 is an insulating film having a via hole, and 33 is a wiring metal film such as an At film. As the thickness of the AI film 33 to be deposited increases, the surface to which the film is deposited changes as shown by a, b, and c in the figure. That is, at the initial stage of deposition, the At film 33 is relatively uniformly deposited on the step part of the via hole, but as the thickness of the At film 33 increases, it is deposited on the upper surface of the via hole in the shape of a canopy, and the AI atoms that fly in after that are deposited on the top surface of the via hole. A self-shadowing effect occurs in which the inner wall of the via hole cannot be reached because it is blocked by the eaves-like Al film, and as a result, the thickness of the Al film 33 becomes non-uniform at the step portion of the via hole.

Therefore, as shown in the figure, voids are generated inside the via hole with a large aspect ratio, and the cross-sectional shape of the At film becomes an inverted trapezoid in the stepped portion of the via hole with a small aspect ratio. Such a phenomenon causes problems such as disconnection of the A1 film or an increase in resistance.

In order to avoid the above-mentioned problems, a so-called high-temperature, high-bias sputter deposition method has been proposed in which sputter deposition is performed while heating the substrate and applying a bias voltage to the substrate. An increase in the substrate temperature promotes the surface diffusion of the incoming AI atoms on the substrate surface, which acts to improve the wettability of the At film to the substrate, thereby promoting uniformity of the thickness of the At film. The substrate temperature T, with respect to the melting point T, of the metal film to be deposited. T, >T,, b >0.6 T
It is known that the surface diffusion of deposited atoms is promoted when the temperature is set so that , . Further, since the eaves-shaped At film at the step portion of the via hole is sputter-etched by applying a bias voltage to the substrate, the above-mentioned self-shadowing effect is prevented.

FIG. 5 shows a cross-sectional view of an At film deposited using the above-described high-temperature, high-bias sputter deposition method, and the same parts as in FIG. 4 are given the same numbers.

As is clear from the figure, the shape of the eaves of the At film at the step portion of the via hole is relaxed, and no voids or inverted trapezoidal shapes are observed.

[Problem to be solved by the invention]

However, even when the above method is used, as shown in Figure 5, the thickness of the At film deposited on the inner wall of the via hole is thinner than that of the At film deposited on other parts. As a result, the present inventors experimentally confirmed that although via holes with a large aspect ratio are filled with AIIQ, the film thickness at the step portion of the via hole with a small aspect ratio, indicated by J in the figure, becomes thinner. In other words, although it is possible to prevent the self-shadowing effect from occurring by applying a substrate bias, heating the substrate alone is not sufficient to eliminate the difference in the thickness of the At film between the inner wall of the via hole and other parts. It was revealed.

Therefore, an object of the present invention is to obtain uniform step coverage regardless of the aspect ratio of the via hole.

[Means to solve the problem]

To solve the above problem, a first metal film is sputter-deposited on a substrate on which an insulating film having via holes is formed to a thickness that does not cause self-shadowing, and then a surface energy When sputter-depositing a second metal film with a small
raising the substrate temperature to an extent that surface diffusion on the surface of the metal film is promoted, and applying a substrate bias to an extent that the second metal film deposited on the step portion of the via hole does not cause a self-shadowing effect; This is achieved by a method for manufacturing a semiconductor device characterized by forming a wiring metal film within the via hole.

[For production]

It is generally known that the uniformity of the film thickness of a substance deposited on a substrate is affected by the wettability of the substance to the substrate, and that this is determined by the relative size relationship of the surface energies of the two. FIG. 1 schematically shows a cross-sectional shape when substances having different surface energies are partially deposited on the same substrate.

In the figure, the surface energy of the first substance 2 is larger than that of the substrate l, and the surface energy of the second substance 3 is greater than that of the substrate l.
It shows the case where it is smaller than that of .

As can be seen in the figure, if the surface energy of the deposited material is lower than that of the substrate, the thickness of the deposited material will be more uniform. Surface energy has a value specific to each substance, as shown in Table 1.

Table 1 The present invention utilizes the above phenomenon, and first, a first metal film is deposited on the insulation crotch in which the via hole is formed. By reducing the thickness of the first metal film to such an extent that no self-shadowing effect occurs, the first metal film can be deposited almost uniformly regardless of the surface energy of the underlying insulating film. I can do it. A second metal film is deposited by applying vt, but at this time, although the self-shadowing effect is suppressed only by heating the substrate and applying a substrate bias, the thickness of the AI film on the inner wall of the via hole becomes thinner, and as a result, the height difference in the via hole As mentioned above in connection with the conventional method, there is a problem with the uniformity of the film thickness in some areas.

Therefore, in the present invention, in addition to the above-described heating of the substrate and application of a substrate bias, a film having a surface energy larger than that of the second metal film is used as the first metal film. This improves the wettability of the second metal film on the first metal film and eliminates the difference in thickness between the inner wall of the via hole and the second metal film deposited on the other parts.

As described above, in the present invention, in order to improve the uniformity of the second metal film, the substrate temperature is increased, a substrate bias is applied, and the first metal film having a higher surface energy than the second metal film is used. This prevents the AI film on the inner wall surface of the via hole from becoming thinner, thereby making it possible to correct the non-uniformity of the film thickness at the stepped portion of the via hole.

〔Example〕

FIG. 2 is a sectional view for explaining the present invention in detail.

As shown in Figure (a), an oxide film 12 with a thickness of 1 #m formed on a substrate 11 by the CVD method has a diameter of 1 μm and a diameter of 3 μm.
Forms Maro's beer hall. Next, this is set in the sputter deposition apparatus shown in FIG.

In FIG. 3, 21 is a substrate, 22 is a heater, 23 is a substrate support stand, 24 is a target, 25 is a target support stand, 26 is a gas inlet, 27 is a gas exhaust port, 28 is a high frequency power supply, and 29 is a DC power supply. It is. A from gas inlet port 26
Flow r gas at 30 SCCM and set the pressure inside the device to 0.03T.
orr, and apply 15KW of DC power from the DC power supply 29 to Ti
The substrate heating and substrate bias application at this stage, which sputter-deposit a Ti film on the substrate 21 by supplying it to the target 24 consisting of Does not occur. As described above, as shown in FIG. 2(b), a Ti film 13 having a thickness of 0.1 pm+ is deposited. According to experiments conducted by the present inventors, the self-shadowing effect does not occur when the Ti film thickness is 0.2 mm or less, and therefore the Ti film thickness is almost uniformly deposited on the inner wall of the via hole. Then, the substrate temperature was increased to 400' using the heater 22.
C and applying a substrate voltage of 500 V using the high frequency power source 28 with a frequency of 13.56 Mllz, and depositing an AI film of 1 μm using the target 24 made of ^l, as shown in FIG. 2 (C). In this case, the small via hole is filled in, and the film thickness at the step of the large via hole becomes uniform.

Note that in the above embodiments, W, W,
TiW, TiN, etc. are used as the second metal film on A1 of each building.
An alloy film can be used.

〔Effect of the invention〕

As described above, according to the present invention, a wiring metal film can be uniformly deposited regardless of the aspect ratio of a via hole, which is useful for improving the reliability of an IC.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a cross-sectional view showing an embodiment of the present invention, Fig. 3 is a cross-sectional view of a sputter deposition apparatus used for carrying out the present invention, Figs. FIG. 3 is a cross-sectional view showing problems in the conventional example. In the figure, 1111.21.31 is the substrate, 2 is the first material, 3 is the second material, 12 is the oxide film, 13 is the Ti film, 14.33 is AIB! A. 22 is a heater 23 is a substrate support base, 24 is a target, 25 is a target support base, 26 is a gas inlet, 27 is a gas exhaust port, 28 is a high frequency power supply, 29 is a DC power supply, 32 is an insulating film, , ffi theory B moon map 13? -eTA/) 'l 'f'-・bu71i'a
$v#, g3 Hotting Fes, Ei4f! +: At+6x,・gu・ntaE,
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Claims (1)

[Claims] A first metal film is sputter-deposited on a substrate on which an insulating film having via holes is formed to a thickness that does not cause a self-shadowing effect, and then a second metal film having a surface energy smaller than that of the first metal film is deposited. When the film is sputter-deposited, the substrate temperature is raised to such an extent that surface diffusion of atoms constituting the second metal film on the surface of the first metal film is promoted, and the second metal film deposited on the stepped portion of the via hole is 2. A method of manufacturing a semiconductor device, characterized in that a wiring metal film is formed in the via hole by applying a substrate bias to such an extent that the metal film does not cause a self-shadowing effect.