JPH03255632A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To restrain the migration or hillock due to the stress on a wiring surface from occurring by a method wherein an element for preventing the diffusion of an Al element is formed at least on the surface of a wiring comprising Al or an alloy mainly containing Al on a substrate. CONSTITUTION:A pure Al film 3 and a Cu film 4 are successively formed on an SiO2 film 2 by the sputtering process. Next, the Al film 3 and the Cu film 4 are selectively and successively etched by dryetching process so as to form an Al wiring 3a with one surface coated with the Cu film 4a. Next, the Al wiring 3 is annealed to mutually diffuse an Al element and a Cu element so as to form a transition layer 4b containing the Cu element in high concentration on the surface of the Al wiring 3a. At this time, a surface layer 5 is formed of a Cu film and the transition layer 4b. Since after the formation of Cu capable of producing an eutectic alloy on the Al wiring 3a, etc., Al and Cu are mutually diffused accordingly to be formed into the transition layer 4b, the diffusion preventive effect can be heightened. Furthermore, Pd and Mg can be used as the element for the surface layer 5.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Field of Application Conventional Technology Problems to be Solved by the Invention Examples of Means and Effects for Solving the Problems ■First. Embodiments of the second and fifth inventions (Fig. 1, 5
(Fig.) ■Example of the first and third inventions (Fig. 2, Fig. 6) ■Example of the fourth invention (Fig. 3, Fig. 4, Fig. 7) Effect of the invention [Summary] Regarding a semiconductor device and its manufacturing method, more specifically, regarding a semiconductor device's wiring structure and its manufacturing method, there is a need for a wiring structure that can suppress the occurrence of migration and hillocks caused by stress on the wiring surface without adversely affecting others. For the purpose of providing a semiconductor device having a structure, a film containing an element that prevents diffusion of Al element is formed on at least the upper surface of a wiring made of Al or an alloy mainly containing Al on a substrate. Contain and compose.

[Industrial application field]

The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a wiring structure of a semiconductor device and a method of manufacturing the same.

[Prior Art] It is known that electromigration of -C to Al wiring or 41 alloy wiring mainly occurs due to grain boundary diffusion of Al atoms. Therefore, in order to suppress the grain boundary diffusion of Al atoms, the metal elements Cu and Ti, which form eutectic alloys with Al, are
, Pd, Mg, etc., or elements such as Cr, C, etc. that form compounds with Al, may be added to the Al wiring or Al alloy wiring in an amount of several percent to ten-odd percent. This reduces the number of vacancies present at the grain boundaries, thereby reducing the diffusion ability at the grain boundaries and improving the electromigration lifetime.

In addition, in order to prevent hillocks from occurring in the Al wiring or 41 alloy wiring due to electromigration, the Al wiring or Al alloy wiring is coated with a high melting point metal film such as hard metal Ti, Mo, or W. , the surface of the wiring is mechanically pressed.

(Problem to be Solved by the Invention) By the way, as a result of suppressing grain boundary diffusion, the influence of surface diffusion of Al atoms constituting wiring has become relatively large. Distortion occurs on the surface of the wiring due to the thermal stress difference between it and the cover insulating film, which causes defects such as vacancies of Al atoms in the surface layer, and as a result, This is caused by the Al atoms becoming more mobile. Therefore, in order to suppress surface diffusion, it is necessary to add a suppressing element at a higher concentration to compensate for defects such as vacancies and make it difficult for the Al atoms to move. .

However, there is a problem in that, for example, when the Cu element is increased, overetching becomes noticeable during selective etching for forming wiring. Furthermore, there is a problem in that increasing the C element increases electrical resistance.

Furthermore, even if coated with a high melting point metal film such as Ti, Mo, or W, these films do not have very good adhesion to the Al wiring.
A! Electromigration of the wiring itself cannot be suppressed, and cracks may be formed in weak areas of the high-melting point metal film, which poses a problem.

The present invention has been made in view of these conventional problems, and provides a wiring structure that can suppress the occurrence of migration and hillocks caused by stress on the wiring surface without adversely affecting others. The object of the present invention is to provide a semiconductor device having the following characteristics.

[Means for Solving the Problems] First, the above problems are such that a film containing an element that prevents diffusion of Al element is formed on at least the upper surface of a wiring made of Al or an alloy mainly containing Al on a substrate. Second, the element according to the first invention is copper (Cu).

Achieved by a semiconductor device characterized in that the element is palladium (Pd) or magnesium (Mg), and thirdly, the element according to the first invention is carbon (C) or chromium (Cr). This is achieved by a semiconductor device having the following characteristics: Fourthly, firstly. Achieved by a semiconductor device characterized in that a film on a wiring surface made of an alloy mainly containing Al or aluminum according to the second or third invention is coated with a high melting point metal film, and fifth, a substrate. a step of forming a wiring made of Al or an alloy mainly containing Al on a surface; a step of forming a metal film made of a metal capable of forming a eutectic alloy with Al at least on the upper surface of the wiring; and a step of heating the wiring to interdiffuse the metal and the Al to form a transition layer made of the metal and Al.

[For production]

In the semiconductor device of the first invention, AlAl or Al
A film containing an element that prevents diffusion of Al element is formed on the surface of the wiring made of an alloy mainly containing Al. Therefore, defects such as vacancies in the Al element constituting the wiring, which occur on the surface of the Al wiring etc. due to stress strain from the cover insulating film, can be sufficiently compensated for by the diffusion preventing element. As a result, even if a defect such as a vacancy in the wiring element occurs on the surface of the wiring, the wiring element can be made difficult to move, so that surface diffusion of the Al element constituting the wiring can be prevented.

In addition, since the film made of a diffusion prevention element is formed locally only on the surface of the wiring, unlike the conventional method, an Al film or
1 has almost no adverse effect on the electrical and chemical properties of the alloy film itself. That is, when forming wiring, Al1l and Al
It is possible to prevent the alloy film from being overetched and from increasing the electrical resistance of the formed wiring.

Since the surface of the wiring is covered with a cover insulating film or the like via this film, the stress exerted on the wiring from the cover insulating film or the like can be alleviated by this surface layer.

From the above, electromigration caused by stress from the cover insulating film or the like can be suppressed without having almost any adverse effect on the electrical and chemical properties of the Al wiring or Al alloy wiring itself.

In particular, as in the semiconductor device of the second invention, copper (Cu), palladium (Pd), or magnesium (M
g) It is effective to use a film containing the element and carbon (C) or chromium (Cr) element as in the semiconductor device of the third invention.

Further, according to the method for manufacturing a semiconductor device of the fifth invention, A
After forming a metal capable of forming a eutectic alloy with At on the L wiring etc., Al and Cu are interdiffused to form a transition layer, which further increases the diffusion prevention effect.

Furthermore, according to the semiconductor device of the fourth invention, the surface film according to the first, second or third invention is coated with a high melting point metal film having good adhesion to these films or the insulating film. Therefore, for example, when covering this high melting point metal film with a cover insulating film, this high melting pre-metal RIA film improves the adhesion between the cover insulating film and the wiring, and since this high melting point metal film is hard, , to reduce the surface diffusion of wiring elements and the occurrence of hillocks.
N can be actually suppressed.

〔Example〕

Hereinafter, embodiments of the first to fifth inventions will be specifically described with reference to the drawings.

(+1 1st. Embodiment of the 2nd and 5th invention Fig. 1(d)
1 is a cross-sectional view of a semiconductor device having a wiring structure according to an embodiment of the first and second inventions.

In the figure, 1 is a Si substrate, and 2 is a 5i on the Si substrate 1.
02 films, these tit; the substrate. In addition, 3a is an Al wiring with a thickness of about 1 μm on the 5i02 film 2, and 5 is nΔ which forms a eutectic alloy with Al formed on the surface of the Al wiring 3a.
A surface layer (film) consisting of a copper (Cu) film 4a with a thickness of approximately 200 mm and a transition layer containing a high concentration of Cu element on the surface of the Al wiring 3a, 6 serves as a cover insulating film to protect the Al wiring 3a. It is a PSG film.

According to such embodiments of the first and second inventions, Al
Since a surface layer 5 containing a high concentration of Cu element that forms a eutectic alloy with Al is formed on the surface of the wiring 3, stress strain from the PSG film 6 etc. occurs on the surface of the Al wiring 3a.
Defects such as vacancies in the Al element constituting the wiring can be sufficiently compensated for by the Cu element. As a result, the Al wiring 3
Even if there are defects such as vacancies in the Al element on the surface of a, it is possible to make the Al element difficult to move.
Surface diffusion of l elements can be prevented.

Further, since this high concentration layer is formed locally only on the surface of the Al wiring 3a, unlike the conventional method, it does not affect the Al film 3 itself. That is, when forming the Al wiring 3a, Al
113 can be prevented from being overetched.

Furthermore, the surface of the Al wiring 3a is exposed to P through the film 5 on this surface.
Since it is covered with SG film 6 etc., A from PSG film 6 etc.
The stress exerted on the l wiring 3a can be alleviated by the film 5 on this surface.

From the above, it is possible to not only suppress the migration of Al elements caused by stress from the PSG film 6, etc., without having almost any adverse effect on the electrical and chemical properties of the Al wiring 3a itself, but also to suppress the migration of Al elements caused by the stress from the PSG film 6, etc. Electromigration silanes can also be suppressed.

Next, a method for manufacturing a semiconductor device according to an embodiment of the fifth invention having the wiring structure according to the embodiments of the first and second inventions will be described with reference to FIGS. 1(a) to 1(d).

In the same figure (a), Al is deposited on the 5iOz film 2 on the Si substrate l.
FIG. 3 is a cross-sectional view showing a state before forming wiring 3a.

First, as shown in FIG. 2B, a pure Al film 3 containing no additives with a thickness of about 1lII11 and a Cu film 4 with a thickness of about 200% are sequentially deposited on this Sing film 2 by sputtering. Form.

Next, the Al film 3 and the Cu film 4 are selectively etched in sequence by a dry etching method using a resist film (not shown) as a mask to form an Al film 3a whose one surface is covered with the Cu film 4a. Next, annealing is performed at 450'C to mutually diffuse the Al element and the Cu element to form a transition FJ4b containing a high concentration of the Cu element on the surface of the Al wiring 3a. Here, the surface N5 is formed by Cu#4a and the transition layer 4b.
is formed. In this way, the creation of the wiring in the embodiments of the first and second inventions is completed (FIG. 4(c)).

Thereafter, as shown in FIG. 4D, a PSG film 6 as a cover insulating film is formed by CVD, and the semiconductor device is completed.

As described above, according to the method of manufacturing a semiconductor device according to the fifth embodiment of the invention, as shown in FIG.
After Cu, which can form a eutectic alloy with Al, is formed on 8 etc., Al and Cu are interdiffused to form the transition layer 4b, which further increases the diffusion prevention effect. This results in
It is possible to improve the electromigration suppressing effect.

In addition, 1. In the embodiments of the second and fifth inventions, Cu is used as the element of the surface layer 5 that forms a eutectic alloy with Al, but palladium (Pd) or magnesium (M g )
You can also use In addition, pure A is used as a wiring material.
Al alloy containing a small amount of Cu, Si, etc. may also be used.

(2) Embodiments of the first and third inventions FIG. 2(d) is a sectional view of a semiconductor device having the wiring structure of the embodiments of the first and third inventions.

In the same figure, l is a St substrate, 2 is a 5t on a Si substrate 1.
In O1li, these constitute the substrate. Also, 7a is 5
iOzll! Al wiring with a film thickness of about 1 μm on 2, 8 is Al
A surface 71 with a thickness of about 200 people containing a high concentration of carbon (C) element that forms a compound with Al formed on the surface of the wiring 7a!
! (film), 9 is P as a cover insulating film for the Al wiring 7a.
It is an SG film.

Next, a method for manufacturing a semiconductor device having the wiring structure according to the second embodiment of the invention will be described with reference to FIGS. 2(a) to 2(d).

In the same figure (a), the upper part of the 5iOz film 2 on the Si substrate 1 is shown.
7 is a cross-sectional view showing a state before forming an I wiring 7a. FIG.

First, as shown in FIG. 4B, a ^1 film 3a having a thickness of about 1 μm is formed on the SiO□ film 2 by sputtering, and then buttered.

Next, the Si substrate 1 is placed on one of the parallel plate electrodes in a reduced pressure chamber whose pressure is adjusted to 10-tTorr. Then approximately 10% CI+4, Czlla or C
Introducing Ar gas containing Jz to reduce the pressure in the room to approximately 5 m.
After holding at Torr, RF power of 100 W is applied between the electrodes to ionize the gas, and the ionized carbon particles are accelerated by the electric field and introduced into the surface and both sides of the old wiring. As a result, carbon is introduced at a high concentration into the surface and both side surfaces of the Al wiring, and a carbonized surface N (film) 8 of approximately 200 layers is formed. In this way, the creation of the wiring in the embodiments of the first and third inventions is completed ((C) in the same figure).
).

After that, PSGWJ, 9 as a cover insulating film was deposited by CVD.
The process takes shape and the semiconductor device is completed ((d) in the same figure).
.

According to such embodiments of the first and third inventions, Al
Since the surface layer 8 containing a high concentration of C element that forms a compound with Al is formed on the surface of the wiring 7a, vacancies in the Al element constituting the wiring occur on the surface of the Al wiring 7a due to stress strain from the PSGWX9. Defects such as these can be sufficiently compensated for by the C element. As a result, even if defects such as Al element vacancies occur on the surface of the Al wiring 7a, the
Since the Al element can be made difficult to move, surface diffusion of the Al element can be prevented.

Moreover, since this high concentration layer is formed locally only on the surface of the Al wiring 7a, unlike the conventional method, it hardly affects the electrical and chemical properties of the Al film itself. That is, when forming the Al wiring 7a, the shaped Al wiring 7a
It is possible to prevent the electrical resistance from increasing.

Furthermore, the surface of the Al wiring 7a is connected to ps via this surface layer 8.
Since it is covered with a c film 9 or the like, the stress exerted on the ^1 arrangement 7a from the PSGIIIJ9 or the like can be alleviated by this surface rfi8.

From the above, electromigration caused by stress from the PSG film 9 and the like can be suppressed without having almost any adverse effect on the electrical and chemical properties of the Al wiring 7a itself.

Note that in the embodiments of the first and third inventions, C is used as the element for the surface layer 8, but chromium (Cr) or the like may also be used. In this case, about 5% Cr as gas
(Co) Using A gas containing b, the substrate was heated to a temperature of 250℃.
While heated to °C, reduce the pressure in the vacuum chamber to 10+Tarr.
The plasma is maintained at a temperature of about 150 H to generate plasma, and the plasma is introduced onto the wiring surface.

In addition, although pure Al is used as the wiring material, Cu and S
An Al alloy containing i or the like may also be used.

(3) Embodiment of the fourth invention ■First embodiment of the fourth invention FIG. 3(d) is a cross-sectional view of a semiconductor device having the wiring structure of the first embodiment of the fourth invention. be.

The difference from the embodiment of the first invention in FIG. 3D is that titanium (T i ) G, which is a high melting point metal, has a film thickness of about 200 Å between the surface layer 5 and the PSG film 6 as a cover insulating film.
10a is interposed therebetween.

In FIG. 1(d), the same reference numerals as in FIG. 1(d) indicate the same components as in FIG. 1(d).

Next, a method for manufacturing a semiconductor device having a wiring structure according to a third embodiment of the invention will be described with reference to FIGS. 3(a) to 3(d).

In the same figure (a), Al is deposited on the 3iOz film 2 on the Si substrate 1.
This is a cross-sectional view showing a state before wiring 3a is formed, and the St substrate 1 and the Stag film 2 constitute a substrate.

First, as shown in the figure (b), on this 5iOz film 2, an Al film 3 with a film thickness of about 1 μ- and a film thickness of about 2
(1(lλ of CuH14 and Pi thickness of about 1000λ T t
M IO are sequentially formed.

Next, using a resist film (not shown) as a mask, the Ti film 10, Cu film 4, and A are selectively etched by dry etching.
Cu114 a /T
iF! Al wiring 3a whose one surface is covered with 10a
to give form to. Next, annealing at a temperature of 450'C
When L and Cu are mutually diffused to form a transition layer 4b containing a high concentration of Cu on the surface of the Al wiring 30, the Cu film 4aai
A surface layer (film) 5 is formed with the lj transfer layer 4b. In this way, the creation of the wiring of the first embodiment of the fourth invention is completed ((C) in the same figure).

Thereafter, as shown in FIG. 4(d), the PSG film 11 as a cover insulating film is formed by the CVD method, and the semiconductor device is charged.

According to the first embodiment of the fourth invention, the surface N5 described in the embodiment of the first invention is
Since it is coated with Ti1llOa which has good adhesion to the sc film 5, the adhesion between PSG #11 and the Al wiring 3a is improved through this Ti film 10a, and this Ti1llOa
Since it is hard, it is possible to more reliably suppress the surface diffusion of the Al element and the formation of hillocks.

In addition, in the above-mentioned first embodiment, the Cu element of the embodiment of the second invention is used as the element contained in the surface layer 5, but even if the C element of the embodiment of the third invention etc. is used. good.

In addition, Ti is used as a material for the high melting point metal film, but
Zirconium (Zr), hafnium (Hf).

Other high melting point metals such as tungsten (W) can be used.

■Second embodiment of the fourth invention Instead of the two-layer film of the surface layer 5 containing the Cu element and Ti#10a as the high melting point metal film of the first embodiment, Cu-Ti was used.
Mixed membranes can also be used.

In this case, an example of how to create the wiring is shown in Figures 4(a) to (d).
) will be explained next.

That is, as shown in Figure (a), 5i0
8Wl! form 2. Note that these commands steal the board.

Next, as shown in the same figure (b), after forming an Al film 3 with a thickness of about 1 μm on the 5iotl 192, a film with a thickness of about 1000 μm was formed on the Al film 3 by sputtering using a Cu-Ti target. A Cu-Ti mixture 11912 is formed.

Next, after patterning the Al film 3 and the Cu-Ti mixed film 12 in the same pattern, heat treatment is performed to
i and Al are mutually diffused to form a transition layer 12b containing Cu and Ti at the interface between the Al wiring 3a and the Cu--Ti mixed film 12a. The Cu--Ti mixed film 12a and the transition layer 12b become the surface layer (film) 13 (FIG. 3(C)).

Thereafter, as shown in FIG. 3(d), a PSGS raw film is formed as a cover insulating film, and the semiconductor device is completed.

As described above, according to the second embodiment of the fourth invention, C
Since the u-Ti mixed film 12a is formed and then heat-treated to cause Cu, Tt, and Al to interdiffuse, the high concentration of Cu and Ti prevents vacancies in the Al element on the surface of the Al wiring 3a. Defects are sufficiently compensated and surface diffusion of Al element can be suppressed. Moreover, the Ti of the Cu-Ti mixed film 12a
Since it is possible to improve the adhesion between the PSGS raw film and the Al wiring 3a, it is possible to suppress the surface diffusion of the Al element and to suppress the occurrence of hillocks.

Next, a test was conducted to confirm the lifetime of the Cu-Ti mixed film itself against migration.

As a test sample, 5iOdt! Width 2 μm on i.

Cu-Ti mixed film/Ti with a length of 2 mm and a total film thickness of 1 μm
A multilayer film of N film/W film was formed and then coated with a PSG film. For comparison, Al alloy wiring (Cu
2% content) was also tested at the same time.

Test conditions were current density 5 x 10'A/cm" and temperature 2.
The temperature was 50°C.

The experimental results are shown in FIG. 5. In the figure, the life span represents the point in time when the wiring becomes electrically open, and is expressed in units of time. The defect rate is expressed as the cumulative number of defects relative to the total number of samples.

According to the figure, it was found that the lifespan of the Cu--Ti mixed film itself against migration was improved by about two orders of magnitude compared to the conventional case. As a result, even when applied to the wiring structure of the second embodiment of the fourth invention, the diffusion of Al element in the old surface layer is suppressed by the high concentration of Cu and Ti, so the Cu-Ti mixed film It can be considered to have almost the same lifespan as the case of .

In addition, the above 1. In the embodiments of the second and fourth inventions, heat treatment is performed as shown in FIG. 1(C), FIG. 3(c), and FIG. 4(c), but this heat treatment is omitted. You can also.

〔Effect of the invention〕

As described above, according to the semiconductor device of the first to third inventions, copper (Cu), palladium (P
d) or magnesium (Mg) element, and carbon (C),
The chromium (Cr) element can sufficiently compensate for defects such as vacancies in elements constituting Al wiring, etc.
Surface diffusion of wiring elements caused by vacancies in the wiring elements caused by stress strain from the cover insulating film or the like can be suppressed.

Further, since the film made of the diffusion-preventing element can be formed locally only on the surface of the wiring, it has almost no adverse effect on the electrical and chemical properties of the wiring itself, unlike the conventional method.

Further, since the surface of the wiring is covered with a cover insulating film or the like via this film, the stress exerted on the wiring from the cover insulating film or the like is alleviated by this surface film.

From the above, electromigration caused by stress from the cover insulating film or the like can be suppressed with almost no adverse effect on the electrical and chemical properties of the Al wiring or Al alloy wiring body.

Further, according to the method for manufacturing a semiconductor device of the fifth invention, a metal capable of forming a eutectic alloy with Al is formed on the old wiring, and then Al and Cu are interdiffused to form a transition layer. Therefore, the migration suppression effect can be further increased.

Furthermore, according to the semiconductor device of the fourth invention, the film on the wiring surface according to the first to third inventions is coated with a high melting point metal film that has good adhesion to these films and the insulating film. For example, when this high melting point metal film is covered with a cover insulating film, the adhesion between the cover insulating film and the wiring is improved through the high melting point metal film, and since the high melting point metal film is hard, the surface Diffusion and the occurrence of hillocks can be suppressed more reliably.

[Brief explanation of drawings]

Figure 1 shows 1. A cross-sectional view illustrating a method for manufacturing a semiconductor device having wiring structures according to embodiments of the second and fifth inventions. FIG. 3 is a sectional view illustrating a method for manufacturing a semiconductor device having a wiring structure according to the first embodiment of the fourth invention; FIG. FIG. 5 is a cross-sectional view illustrating a method for manufacturing a semiconductor device having the wiring structure of the fourth embodiment. FIG. 5 is a life comparison diagram of the CuTi mixed film of the second embodiment of the fourth invention with respect to migration. [Explanation of symbols] 1...Si substrate, 2...SiO□ film, 3...Al film, 3a, 7a...Al wiring, 4.48...Cu film, 4b, 12b... - Transition layer, 5.8.13... Surface layer (film), 6.9,11.14... PSG film, 10, 10a''4i19j, 12, 12 a-Cu-Ti mixed film.

Claims (5)

[Claims] (1) A semiconductor device characterized in that a film containing an element that prevents diffusion of Al element is formed on at least the upper surface of a wiring made of Al or an alloy mainly containing Al on a substrate. (2) The element according to claim 1 is copper (Cu), palladium (
A semiconductor device characterized in that the element is Pd) or magnesium (Mg). (3) The element according to claim 1 is carbon (C) or chromium (C).
r) A semiconductor device characterized by being an element. (4) A semiconductor device characterized in that a film on a wiring surface made of Al or an alloy mainly containing Al according to claim 1, claim 2, or claim 3 is coated with a high melting point metal film. (5) forming a wiring made of Al or an alloy mainly containing Al on the substrate surface; and forming a metal film made of a metal that can form a eutectic alloy with Al on at least the upper surface of the wiring; , by heating the metal film and the wiring, the metal and the Al
A method for manufacturing a semiconductor device, comprising the step of interdifusing the metal and Al to form a transition layer made of the metal and Al.