JPH06196483A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a semiconductor device of certain structure wherein crystal grains of Al and Al alloy can be effectively controlled in in-plane rotation. CONSTITUTION:An SiO2 film 2 is formed on a silicon substrate 1 as an interlayer insulating film, and a Ti film 3a whose surface is rugged is formed on the SiO2 film 2. An Al film 7 is formed on the Ti film 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly to rotation control of orientation of an aluminum film or an aluminum alloy film in wiring.

[0002]

2. Description of the Related Art LSI (Large Scale Integrated Circu)
Aluminum (Al) wiring used for it) is gradually miniaturized, and at present, semiconductor devices having a submicron line width are manufactured. With the miniaturization of this Al wiring, A
The current density flowing in the 1-wiring increases, the reliability of the Al wiring is impaired, and a failure is likely to occur.

Factors that impair the reliability of Al wiring include electromigration and stress migration. Among them, the stress migration can be solved by a laminated structure of aluminum and a refractory metal. However, there is no complete solution for electromigration. Proposed methods include alloying Al with Cu, a laminated structure with a refractory metal, controlling the orientation of the aluminum film, and single-crystallizing the aluminum film. However, Cu alloying or a laminated structure with a refractory metal is not a perfect countermeasure, while there is a problem that single crystallization of an Al film cannot be formed on SiO ₂ which is an actual device structure.

Attention is paid to the control of the orientation of the Al crystal grains. This is a method of forming an Al film that is polycrystalline but close to a single crystal. Since failure due to electromigration occurs due to grain boundary diffusion of Al, it is possible to improve the reliability of the Al film by forming a film with a grain boundary as small as possible or a film with less crystal disorder at the grain boundary as much as possible.

The Al film is usually formed by a sputtering method, but the Al film formed by this sputtering method is usually (11
1) Shows (Mirror index) orientation. However, as shown in FIG. 4, (200) orientation may be mixed in a part of the Al film.
The disorder of the lattice becomes large at the boundary between the crystals of different orientations, and the disorder of the lattice easily causes electromigration. The (111) orientation can be achieved by increasing the vacuum of the film forming apparatus and selecting the material of the underlying barrier metal. FIG. 5 shows the (111) -oriented Al film. However, as shown in FIG. 5, if the rotation angle of the crystal plane orientation with respect to the <111> axis is random, a boundary with different crystal plane orientations is obtained. Therefore, the disorder of the crystal of the grain boundary becomes large, and a highly reliable film cannot be obtained. On the other hand, as shown in FIG. 6, if the rotation angle of the crystal plane orientation with respect to the <111> axis is controlled, a highly reliable Al film is obtained.

By the way, recently, a method of controlling rotation about the <111> axis has been proposed by the following method.

FIG. 7 is a diagram showing a conventional method for controlling the rotation angle with respect to the <111> axis. As shown in FIG.
First, a SiO ₂ film 20 as an interlayer insulating film is formed on the entire surface of a silicon substrate 1 by a CVD (Chemical Vapor Deposition) method. Next, by photolithography and RIE, the width S of the concave portion S = 0.15 μm, the width L of the convex portion L = 0.15 μm,
Irregularities with a depth d = 10 nm are periodically formed. Next is pure A
The I film 70 is formed under the following conditions.

Ar flow rate 100 SCCM Gas pressure 0.5 Pa Wafer heating temperature 500 ° C. Target power 22.5 kW Al film thickness 0.6 μm Since nucleation at the initial stage of film formation was localized at the linear step,
A certain directionality was generated in the crystal orientation, and the Al film 70 in which the <220> direction was within a range of approximately ± 10 degrees could be formed.
However, 10 to 20% did not fall within this range.

[0009]

When an Al film is directly formed on a silicon substrate in a contact hole, a disorder due to mutual diffusion is likely to occur. As a barrier metal layer for preventing this, Ti or Ti is used as a base of the Al film.
The compound is used. For example, Ti single layer, TiW single layer,
2 layers from top layer with TiN / Ti, 2 layers with TiON / Ti
Layers, 3 layers of Ti / TiN / Ti, Ti / TiON / T
Three layers such as i are used as the base of the Al film. The film thickness of these bases is 0.1 to 0.2 μm, and when the Ti film 130 is formed on the SiO ₂ film 20 as shown in FIG. 8, the step is filled up, and the in-plane rotation control of Al crystal grains is performed. This is a problem because the effect of is reduced.

Therefore, an object of the present invention is to provide a semiconductor device having a structure for effectively controlling the in-plane rotation of crystal grains of Al and Al alloy and a method for manufacturing the same.

[0011]

According to the present invention, there is provided an interlayer insulating film formed on or above a semiconductor substrate,
An intermediate film made of a refractory metal or a compound of the refractory metal having uneven steps formed on the flat surface of the interlayer insulating film; and an aluminum film or an aluminum alloy film formed on the intermediate film. It is solved by a semiconductor device characterized by having.

According to the present invention, the above object is to form an intermediate film made of a refractory metal or a compound of the refractory metal on an interlayer insulating film formed on or above a semiconductor substrate; This can be solved by a method for manufacturing a semiconductor device, which includes a step of forming unevenness steps in a flat region of the film and a step of forming an aluminum film or an aluminum alloy film on the intermediate film.

Further, according to the present invention, the above-mentioned problems are preferably solved by a semiconductor device and a method for manufacturing the same, in which the recess of the intermediate film does not reach the interlayer insulating film.

Further, according to the present invention, the above-mentioned problems are preferably solved by a semiconductor device and a manufacturing method thereof, wherein the intermediate film is made of Ti, TiN, TiON or a laminated structure of these.

[0015]

According to the present invention, as shown in FIG. 1 (d), the interlayer insulating film 2 is formed above the semiconductor substrate 1, and the refractory metal 3a having uneven steps is formed on the interlayer insulating film 2. An Al film 7 is formed on the refractory metal 3a. Al film 7
Since the nucleation at the initial stage of film formation is localized at the step on the straight line of the refractory metal 3a, the crystal orientation of the Al film 7 can have a certain directionality.

The crystal orientation of the Al film 7 is Ti, Ti
Since it depends on the film thickness and orientation of the underlayer such as N and TiON, the crystal rotation orientation of the Al film 7 can be improved by controlling the film thickness and orientation of these underlayers. In particular, Ti (200) or TiN (200)
The unit cell size of Al is close to that of Al and has good compatibility.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1D is a sectional view of a first embodiment of a semiconductor device having an aluminum crystal in-plane rotation control structure according to the present invention. Silicon substrate 1 as shown in FIG.
An SiO ₂ film as an interlayer insulating film 2, a Ti film 3a that is periodically patterned on a flat portion of the SiO ₂ film 2,
An Al film 7 is formed on each Ti film 3a. T
Since the i film 3a is patterned and unevenness is present on the surface, the nucleation is localized in the stepped portion (recess) at the initial stage of film formation of the Al film 7, so that the orientation of the crystal plane of the Al film 7 should be provided. In the experiment, the crystal plane orientation of the Al film 7 was within the range of approximately ± 8 degrees in the <220> direction. This is because the Ti film 3a has a better influence on the orientation of the Al film 7 than the SiO ₂ film, so that the Al film 7 having a better rotational orientation was formed.

Next, a method for controlling the above semiconductor device will be described.

FIG. 1 is a sectional view of a manufacturing process of the above-mentioned semiconductor device. First, as shown in FIG. 1A, a SiO ₂ film 2 as an interlayer insulating film is formed on a silicon substrate 1 by a CVD method, and then a Ti film 3 is formed under the following sputtering conditions.

Ar flow rate 100 SCCM Gas pressure 0.5 Pa Wafer heating temperature 150 ° C. RF power 4 KW Ti film thickness 20 nm Next, as shown in FIG. 1B, the resist pattern 10 is widened using a phase shift mask and an excimer laser stepper. It is formed with 0.2 μm and a pitch of 0.4 μm. Next, using the resist pattern 10 as a mask, the Ti film 3 is patterned by reactive ion etching under the following conditions to form a Ti film 3a as shown in FIG.

Gas BCl ₃ / Cl ₂ = 60/90 SCCM Gas pressure 2Pa Microwave power 1000W RF bias power 50W Next, the resist pattern 10 is removed, and then FIG.
As shown in, the Al film 7 is formed under the following conditions.

Ar flow rate 100 SCCM Gas pressure 0.5 Pa Wafer heating temperature 200 ° C. Target power 22.5 KW Al film thickness 0.6 μm FIG. 2D shows a semiconductor device having an aluminum crystal in-plane rotation control structure according to the present invention. It is sectional drawing of 2 Example. In the second embodiment, the base of the Al film 7 is formed on the Ti film 4 and the Ti film.
It has a laminated structure with the N film 5a. Hereinafter, a method of manufacturing this semiconductor device will be described.

First, as shown in FIG.
SiO on the plate 1 as an interlayer insulating film ₂The film 2 is formed.
Next, a Ti film 4 is formed by the sputtering method under the following conditions.
It

Ar flow rate 100 SCCM Gas pressure 0.5 Pa Wafer heating temperature 150 ° C. Target power 4 KW Ti film thickness 5 nm Next, a TiN film 5 is formed by a sputtering method under the following conditions.

Ar / N ₂ flow rate = 40/70 SCCM Gas pressure 0.5 Pa Wafer heating temperature 150 ° C. Target power 5 KW TiN film thickness 10 nm Next, as shown in FIG. 2B, a phase shift mask and an excimer laser stepper were used. Thus, the resist pattern 10 is formed with a width of 0.2 μm and a pitch of 0.4 μm. Next, using the resist pattern 10 as a mask, the TiN film 5 is etched by reactive ion etching under the following conditions to form a TiN film 5a as shown in FIG. 2 (c).

Gas BCl ₃ / Cl ₂ = 60/90 SCCM Gas pressure 2Pa Microwave power 1000W RF bias power 50W Next, the resist pattern 10 is removed, and then the same sputtering conditions as in the first embodiment are used, as shown in FIG. As shown in
The film 7 is formed.

FIG. 3D is a sectional view of a third embodiment of a semiconductor device having an aluminum crystal in-plane rotation control structure according to the present invention. In the third embodiment, as in the second embodiment,
The underlying layer of the Al film 7 has a laminated structure of the Ti film 4 and the TiN film 50a, and is characterized in that the TiN film 50a remains in the recess. Hereinafter, a method of manufacturing this semiconductor device will be described.

First, as shown in FIG.
SiO on the plate 1 as an interlayer insulating film ₂The film 2 is formed.
Next, the TiN film 4 is sputtered under the same conditions as in the second embodiment.
Formed by. Next, under the same conditions as in the second embodiment, Ti
The N film 50 is formed with a thickness of 15 nm. Next, FIG. 3 (b)
Forming a resist pattern 10 as shown in FIG.
Using the resist pattern 10 as a mask, the TiN film 50 is removed.
Etching with reactive ions to form a TiN film 50a
It

Gas BCl ₃ / Cl ₂ = 60/90 SCCM Pressure 2Pa Microwave power 1000W RF bias power 50W Etch film thickness 10 nm Next, an Al film 7 is formed by the sputtering method as in the first embodiment.

In this embodiment, T is used as a base material for the Al film.
i, TiN / Ti was used, but TiON / Ti, Ti / T
It is of course possible to have a laminated structure of iN / Ti, Ti / TiON / Ti or the like. Also, the Al film is Cu or S
An alloy such as i may be used.

[0032]

As described above, according to the present invention, an Al film having a uniform crystal orientation can be formed, which is a film close to a single crystal even though it is polycrystal, and electromigration can be suppressed. Improves reliability. T
By controlling the orientation of the base such as i, TiN,
The orientation of the Al film can be further improved, and the reliability of the Al film is further improved. A base film for enhancing the orientation of the Al film and the Al alloy film can be selected, and the degree of freedom in base selection is expanded. Since the Al film with uniform orientation has a uniform film thickness,
It is difficult to leave metal residue during processing and the yield can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an Al orientation rotation control process according to a first embodiment.

FIG. 2 is a sectional view of an Al orientation rotation control process according to a second embodiment.

FIG. 3 is a sectional view of an Al orientation rotation control process according to a third embodiment.

FIG. 4 is a diagram showing a (111), (200) orientation mixed film.

FIG. 5 is an Al film without (111) orientation rotation control.

FIG. 6 is an Al film having (111) orientation rotation control.

FIG. 7 is a sectional view (I) of an Al orientation rotation control structure according to a conventional example.

FIG. 8 is a sectional view (II) of an Al orientation rotation control structure according to a conventional example.

[Explanation of symbols]

1 Silicon substrate (semiconductor substrate) 2 SiO ₂ film (interlayer insulating film) 3,3a, 4,130 Ti film 5, 5a, 50, 50a TiN film 7,70 Al film 20 SiO ₂ film

Claims (6)

[Claims] 1. An intermediate layer composed of an interlayer insulating film formed on or above a semiconductor substrate, and a refractory metal or a compound of the refractory metal having uneven steps formed on a flat surface of the interlayer insulating film. A semiconductor device comprising: a film; and an aluminum film or an aluminum alloy film formed on the intermediate film. 2. The semiconductor device according to claim 1, wherein the recess of the intermediate film does not reach the interlayer insulating film. 3. The semiconductor device according to claim 1, wherein the intermediate film is made of Ti, TiN, TiON or a laminated structure of these. 4. A step of forming an intermediate film made of a refractory metal or a compound of the refractory metal on an interlayer insulating film formed on or above a semiconductor substrate; and for a flat region of the intermediate film. A method of manufacturing a semiconductor device, comprising: a step of forming unevenness steps; and a step of forming an aluminum film or an aluminum alloy film on the intermediate film. 5. A step of forming an intermediate film made of a refractory metal or a compound of the refractory metal on an interlayer insulating film formed on or above a semiconductor substrate; and for a flat region of the intermediate film. A method of manufacturing a semiconductor device, comprising: a step of forming a step of unevenness so that a recess does not reach the interlayer insulating film; and a step of forming an aluminum film or an aluminum alloy film on the intermediate film. 6. The method of manufacturing a semiconductor device according to claim 4, wherein the intermediate film is made of Ti, TiN, TiON or a laminated structure of these.