JP3340578B2 - Multilayer wiring of semiconductor device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum (not limited to pure aluminum) in a semiconductor integrated circuit device, including aluminum containing a small amount of Si or Cu, and including aluminum alloy used as wiring for the semiconductor integrated circuit device. The present invention relates to a multilayer wiring of aluminum (Al) and a method of manufacturing the same.

[0002]

2. Description of the Related Art In an aluminum multilayer wiring, when a lower Al wiring and an upper Al wiring are connected through a through hole (also called a via hole), an upper Al film is formed in order to improve filling of the through hole with Al. It is said that an Al heating sputtering method in which a substrate is heated to a high temperature, for example, about 500 ° C., and is performed by a sputtering method at the time of formation.

In order to further improve the embedding, the upper layer Al
In the film sputtering process, in order to improve the wettability of the upper Al film on the lower Al film or on the surface of the interlayer insulating film,
It has been proposed to form a titanium (Ti) film as a wetting layer prior to the formation of the upper Al film (1992 Symposium on VLSI Technology of Technical P
apers, 74-75 (1992 IEEE)). The report states that through-holes having a hole diameter of 0.15 μm and an aspect ratio of 4.5 could be completely filled by the Al heating sputtering method.

FIG. 1 shows an example of a two-layer wiring structure. A first interlayer film 4 is formed on a silicon substrate 2, and a contact hole is formed in the interlayer film 4. The inner surface of the contact hole and the upper surface of the interlayer film 4 are a two-layer film 6 of lower Ti and upper TiN.
Then, the contact holes are buried with the tungsten layer 8. On the interlayer film 4, a first Al wiring 10 formed by an Al non-heated sputtering film formed by a sputtering method without forcibly heating the substrate is formed.
A second interlayer film 12 is formed from above the wiring 10, a through hole is formed in the interlayer film 12, and a Ti sputter film 14 is deposited on the inner surface of the through hole and the upper surface of the interlayer film 12. Is formed. The lower layer of the Al wiring 16 is an Al unheated sputtered film 16a, and the upper layer is an Al heated sputtered film deposited by heating the substrate to about 500 ° C. The substrate is not forcibly heated during the formation of the Al non-heated sputtered film, but the temperature rises spontaneously during sputtering.
It seems that the temperature was about 50 ° C.

[0005]

The lower layer A is formed by a through hole.
Although the l wiring 10 and the upper Al wiring 16 are in contact with each other, the lower Al wiring 10 is a non-heated sputtered film, whereas the upper layer 16b of the upper Al wiring 16 is a heated sputtered film. When the substrate is heated during sputtering, the grain size of the formed Al film grows and increases, and the lower Al wiring 10 and the upper A
In the boundary region with the l wiring 16, A
It has been found that a current flows through the 1 film and electromigration resistance deteriorates. An object of the present invention is to improve electromigration resistance in a multilayer wiring using Al.

[0006]

According to the present invention, a contact hole is formed in a first interlayer film formed on a semiconductor substrate, and a contact hole is formed on the first interlayer film via the contact hole. A first metal wiring is formed, a second interlayer film is formed on the first metal wiring, and the first metal wiring is connected to the first metal wiring via a through hole formed in the second interlayer film. In a multi-layer wiring in which a second metal wiring is formed on the second interlayer film, a refractory metal film and a refractory metal nitride film thereon are formed on the inner surface of the contact hole of the first interlayer film. A refractory metal layer is formed on the refractory metal nitride film, and a contact hole is buried by the refractory metal layer. A refractory metal film is formed on the inner surface of the through hole of the second interlayer film. And the first and second meta Wirings are has a two-layer structure of the Al-free heating sputtered film greater Al heating sputtered film than the grain size of Al without heating sputter film thereon.

The through hole is a portion where a hole is formed in an intermediate interlayer film in the multilayer wiring structure to connect upper and lower wirings. The contact hole is a portion where a hole is formed in an interlayer film formed on a semiconductor substrate or a polysilicon electrode, and a wiring on the interlayer film is connected to the substrate or the polysilicon electrode through the hole.

In the contact hole of the first interlayer film, a refractory metal layer is formed on the refractory metal nitride film, and the contact hole is filled with the refractory metal layer.

In the case of a multi-layer wiring, a third interlayer film is formed on the second metal wiring, a through hole is also formed in the third interlayer film, and a high melting point metal is formed on the inner surface of the through hole. A film is formed, and on the third interlayer film, a third metal wiring connected to the second metal wiring via the through hole is formed of an Al non-heated sputtered film and a grain size of Al It is formed with a two-layer structure of an Al heating sputtered film larger than a non-heated sputtered film.

The method for manufacturing a multilayer wiring according to the present invention includes the following steps (A) to (J). (A) a step of forming a first interlayer film on a semiconductor substrate, and (B) a step of connecting a first metal wiring formed on the first interlayer film to a base of the first interlayer film. Forming a contact hole in the first interlayer film, (C) depositing a high melting point metal film from the first interlayer film, and changing the surface of the high melting point metal film to a nitride film by RTA treatment; (D) exposing the semiconductor substrate to the atmosphere without exposing the semiconductor substrate to the atmosphere; Without forcibly heating the semiconductor substrate, an Al film is deposited on the refractory metal film by sputtering, and then the substrate is heated to a temperature in the range of 400 ° C. to the melting point of Al by sputtering. With the film applied 1 Forming eye metal film, forming a first metal wiring by patterning the (E) 1-layer metal film,
(F) a step of forming a second interlayer film from above the first metal wiring, and (G) a step of connecting a second metal wiring formed on the second interlayer film to the first metal wiring. Forming a through hole in the second interlayer film, (H) forming a refractory metal film on the second interlayer film and attaching the refractory metal film to the inner surface of the through hole, (I) exposing the semiconductor substrate to the atmosphere. Without exposing and without forcibly heating the semiconductor substrate, an Al film is deposited on the high melting point metal film by a sputtering method, and then the substrate is heated to a temperature in a range from 400 ° C. to the melting point of Al. A step of depositing an Al film by a sputtering method to form a second metal film, and (J) forming a second metal wiring by patterning the second metal film.

In the present invention, the lower Al wiring and the upper Al wiring which are in contact with each other through the through hole have a two-layer structure in which a non-heated sputtered film and a heated sputtered film are laminated.
Electromigration (EM) resistance is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a multilayer wiring of a semiconductor device on which the present invention is based will be described with reference to FIG. A first interlayer film 22 is formed on a silicon substrate 20 on which elements such as a MOS transistor, a bipolar transistor, a resistor, and a capacitor are formed. The interlayer film 22 is, for example, a SiO ₂ film or a SiO ₂ film.
A BPSG (SiO ₂ into which boron and phosphorus is introduced) film is laminated on the film. The silicon substrate 2 is used as the interlayer film 22.
A contact hole 24 is formed for connecting 0 to a metal wiring on the interlayer film 22. The lower layer is about 80 nm on the inner surface of the contact hole 24 and the surface of the interlayer film 22.
A two-layer film 26 made of a Ti film having a thickness of about 30 nm and an upper layer made of a TiN film having a thickness of about 30 nm is applied. A first-layer metal wiring 28 is formed on the two-layer film 26, and the metal wiring 28 is connected to the silicon substrate 20 via the contact hole 24.

The metal wiring 28 is composed of two layers of Al films 28a and 28a.
8b, the lower Al film 28a is a non-heated sputtered film formed without forcibly heating the substrate, the thickness thereof is about 200 nm, and the upper Al film 28b is formed by heating the substrate. Grain size lower Al film 28
This is a heated sputtered film larger than the grain size of a, and its thickness is about 400 nm.

A second interlayer film 30 is formed on the metal wiring 28. The second interlayer film 30 is made of TEOS (Tetraethylorthosilil).
icate) a SiO ₂ film formed by a method, a through hole 32 is formed at a position connecting the metal wiring on the metal wiring 28 and the SiO ₂ film 30. The inner surface of the through hole 32 and the surface of the interlayer film 30 have a thickness of about 50 n.
m of Ti film 34 is deposited. 2 on the Ti film 34
A second-layer metal wiring 36 is formed. The second-layer metal wiring 36 is connected to the first-layer metal wiring 2 through the through hole 32.
8 is connected. The metal wiring 36 is also a two-layer Al film 3
6a and 36b, and the lower Al film 36a is a non-heated sputtered film having a thickness of about 200 nm and an upper Al film.
The film 36b is a heat-sputtered film having a thickness of about 400
nm.

In the multi-layer wiring having another structure, the film 26 deposited on the inner surface of the contact hole 24 and the interlayer film 22 shown in FIG. TiN formed by subjecting the Ti film to RTA treatment in nitrogen
Film, a third layer having a thickness of about 50 nm formed thereon.
It is a three-layer film that is an i-film. Other configurations are as described above.

An embodiment of the multilayer wiring of the present invention will be described with reference to FIG. On the inner surface of the contact hole 24 provided in the first interlayer film 22 on the silicon substrate 20, a two-layer film 26a having a lower layer of Ti and an upper layer of TiN is formed. 40 embedded. A three-layer film 26b in which a Ti film is further laminated on a two-layer film 26a of Ti and TiN on the inner surface of the contact hole is deposited on the interlayer film 22, and Ti is deposited on the tungsten layer 40 filling the contact hole.
The film 26c is deposited.

A first-layer metal wiring 28 is formed on the three-layer film 26b and the Ti film 26c, a second interlayer film 30 is formed from above the metal wiring 28, and a through-hole formed in the interlayer film 30 is formed. A second-layer metal wiring 36 connected to the metal wiring 28 via the hole 32 is formed. The materials and wiring structures of the metal wirings 28 and 36 and the interlayer film 30 are the same as those of the multilayer wiring shown in FIG. The multilayer wiring of the embodiment differs from the multilayer wiring of FIG. 2 in that the contact holes 24 are buried with tungsten 40.

In the embodiment, the second-layer metal wiring 36
The same interlayer film as the interlayer film 30 may be further formed thereon, and a third-layer metal wiring connected to the second-layer metal wiring 36 via a through hole may be formed in the interlayer film. The third metal wiring also has a two-layer structure in which the lower layer is an Al non-heated sputtered film and the upper layer is an Al heated sputtered film.

Next, a method of manufacturing the multilayer wiring of FIG. 2 will be described. (A) elements of the first interlayer film 22 and the SiO ₂ film on the wafer of the semiconductor substrate 20 formed is, BPSG on SiO ₂ film
The film is formed as a laminated film. A contact hole 24 is formed in the interlayer film 22 by photolithography and dry etching.

(B) A Ti film is deposited on the interlayer film 22 as a high melting point metal film to a thickness of about 80 nm. A TiN film is continuously formed on the Ti film as a refractory metal nitride film by about 30 nm.
m to form a two-layer film 26. At this point, the two-layer film 26 is also deposited on the inner surface of the contact hole 24.

(C) Next, an Al film is deposited on the interlayer film 22. In this process, after depositing the TiN film of the two-layer film 26, the substrate wafer is evacuated without opening the vacuum device to the atmosphere. And sputtering of the Al film for the Al wiring 28 is performed. In the Al film sputtering, the first Al film 28a was deposited at a deposition rate of about 17 nm without heating the substrate.
Per second to a thickness of about 200 nm. Thereafter, the substrate wafer is further transported in a vacuum, and a second Al film 28b is deposited thereon by a heating sputtering method. In the heating sputtering method, first, a substrate wafer is heated at a temperature of 400 ° C. or higher and lower than the melting point of Al, for example, 530 ° C. for 100 to 120 seconds, and then the Al is deposited at a deposition rate of about 12 nm /
Deposit to a thickness of about 400 nm in seconds. Thus, an Al film having a two-layer structure in which the lower layer is a non-heated sputtered film and the upper layer is an Al heated sputtered film is formed. The Al film is patterned by photolithography and dry etching to form a metal wiring 28.

(D) A second interlayer film 30 is formed on the metal wiring 28. As the interlayer film 30, for example, TE
A SiO ₂ film is formed by the OS method, a SOG (spin-on-glass) film is formed thereon to flatten the surface, and a flattened TEOS-SiO is formed by performing an etch back. _Two films. This TEOS-S
The iO ₂ film is an established technology.

(E) A through-hole 32 is formed in the interlayer film 30 by photolithography and etching at a position where the metal wiring 28 thereunder is connected to the second metal wiring thereon. I do.

(F) A Ti film 34 is deposited on the interlayer film 30 as a refractory metal film to a thickness of about 50 nm. Ti film 3
4 is also attached to the inner surface of the through hole 32. In this state, the substrate wafer is transported in a vacuum without exposing the substrate wafer to the atmosphere to form an Al film 36 for the second-layer Al wiring. A
The lower layer 36a of the l film 36 is deposited by a sputtering method at a deposition rate of about 17 nm / sec to a thickness of about 200 nm without heating the substrate wafer, and is further vacuum-transported to form an upper layer of Al.
This time, the substrate 36 is heated at a temperature of 400 ° C. or more, for example, 5 ° C.
After heating at 30 ° C. for 100 to 120 seconds, the film is deposited to a thickness of about 400 nm at a deposition rate of about 12 nm / sec while the heating is continued. As a result, the second Al film 36 has a two-layer structure of the Al non-heated sputtered film 36a formed on the Ti layer 34 and the Al heated sputtered film 36b thereon. Thereafter, the Al film 36 is patterned by photolithography and dry etching to form a second-layer Al wiring 36.

If necessary, an interlayer film similar to the interlayer film 30 is further formed on the Al wiring 36, a through hole is formed in the interlayer film, and a third Al film is formed on the interlayer film 30. Then, a third-layer metal wiring may be formed by patterning.

In FIG. 2, the film 26 is a Ti film, and the T
In the case of manufacturing a multi-layer wiring having a three-layer film of an iN film and a Ti film thereon, a Ti film is first deposited to a thickness of about 100 nm as a refractory metal film after forming the contact hole 24. After that, the surface is nitrided by RTA treatment in an N ₂ atmosphere to form a Ti layer and a TiN layer on the Ti layer.
It is a layer film. At this point, Ti
A two-layer film of a layer and a TiN layer is deposited. In this case, when depositing the Al film for the Al wiring 28, it is necessary to carry out the transfer in a vacuum without exposing the base to the atmosphere. First, a Ti film is deposited to a thickness of about 50 nm on the layer film, and then conveyed in a vacuum without opening to the atmosphere to deposit an Al unheated sputtered film 28a and an Al heated sputtered film 28b.

A method of manufacturing the embodiment shown in FIG. 3, that is, the embodiment in which the contact holes are filled with the refractory metal layer will be described. Contact hole 2 in interlayer film 22
4 and the inner surface of the contact hole 24 and the interlayer film 22 are formed.
After depositing a two-layer film 26a of a Ti film and a TiN film on the surface,
When the contact hole 24 is buried with tungsten as a high melting point metal, for example, a general blanket CV
A tungsten layer is deposited by the D-W method, etched back, and the tungsten layer 40 is formed only in the contact hole.
Leave. At this time, since the etch back of the tungsten layer is generally performed so as to be over-etched, although the tungsten layer 40 is embedded in the contact hole 24, the surface of the tungsten layer 40 is
It is in a state where it has fallen below the surface.

Next, on the tungsten layer 40 and the interlayer film 2
2, a Ti film is deposited to a thickness of about 50 nm. Thus, the Ti film 26c and the interlayer film 2 are formed on the tungsten layer 40.
2, a three-layer film 26b in which a Ti film 26c is further formed on the previously formed two-layer film 26a of Ti and TiN is formed. Thereafter, the lower Al non-heated sputtered film 28a and the upper Al heated sputtered film 28b are formed by being transported in vacuum without opening to the atmosphere. After that, it is the same as the method of manufacturing the multilayer wiring of FIG.

FIG. 4 shows the result of comparing the electromigration resistance between the conventional two-layer wiring shown in FIG. 1 and the two-layer wiring shown in FIG. 2 which is the basis of the present invention. The horizontal axis represents time relatively indicated on a logarithmic scale, and the vertical axis represents cumulative failure rate (MTTF) (%). In FIG. 4, the straight line indicated by symbol A is the measurement result of the conventional two-layer wiring of FIG. 1, and the straight line indicated by symbol B is the measurement result of the two-layer wiring of FIG. From this comparison result, the two-layer wiring which is the basis of the present invention is the conventional two-layer wiring.
It can be seen that the lifetime is about four times as long as the cumulative failure rate as compared with the layer wiring.

[0030]

According to the present invention, the lower metal wiring and the upper metal wiring connected through the through hole are both A
(1) an unheated sputtered film and an Al heated sputtered film having a larger grain size than the Al unheated sputtered film
Because of the layer structure, electromigration resistance is improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a conventional two-layer wiring.

FIG. 2 is a schematic sectional view showing a two-layer wiring on which the present invention is based.

FIG. 3 is a schematic cross-sectional view showing a two-layer wiring according to one embodiment.

4 is a diagram comparing electromigration resistance between the conventional example of FIG. 1 and the two-layer wiring of FIG. 2;

[Explanation of symbols]

 Reference Signs List 20 silicon substrate 22 first interlayer film 24 contact hole 26 two-layer film of Ti and TiN 28 first-layer Al wiring 28a, 36a unheated sputtered film 28b, 36b Al-heated sputtered film 30 second interlayer film 32 through hole 34 Ti film 36 Second layer Al wiring

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/768 H01L 21/285 301

Claims (4)

(57) [Claims] 1. A is a contact hole in the first interlayer film formed on the semiconductor substrate is formed, first the on the first interlayer film that is connected to the base via the contact hole
Metal wiring is formed, and the second metal wiring is formed on the first metal wiring.
Is formed, and the second metal film is connected to the first metal wiring via a through hole formed in the second metal film.
In the multilayer metal wiring is formed on the second interlayer film wiring, the contact hole inner surface of the first interlayer film refractory metal film and the refractory metal nitride film thereon are formed, further the
A refractory metal layer is formed on the refractory metal nitride film,
The tact hole is filled with the refractory metal layer.
Thus, a refractory metal film is formed on the inner surface of the through hole of the second interlayer film. The first and second metal wirings have an Al non-heated sputtered film and a grain size thereon are larger than the Al non-heated sputtered film. A multilayer wiring of a semiconductor device having a two-layer structure with an Al heating sputtered film. 2. A third interlayer film is formed on the second metal wiring, a through hole is also formed in the third interlayer film, and a refractory metal film is formed on the inner surface of the through hole. On the third interlayer film, a third metal wiring connected to the second metal wiring via the through hole is provided.
(1) an unheated sputtered film and an Al heated sputtered film having a larger grain size than the Al unheated sputtered film
2. The multilayer wiring according to claim 1 , wherein the multilayer wiring has a layer structure. 3. A method for manufacturing a multilayer wiring including the following steps (A) to (J). (A) a step of forming a first interlayer film on a semiconductor substrate; (B) a step of connecting a first metal wiring formed on the first interlayer film to a base of the first interlayer film; For one interlayer film
Forming a contact hole, (C) depositing a refractory metal film from the first interlayer film, and
After the surface of the refractory metal film is changed to a nitride film by A treatment,
A step of burying a high-melting-point metal layer in the contact hole and further depositing a high-melting-point metal film on the nitride film and on the high-melting-point metal layer buried in the contact hole; (D) exposing the semiconductor substrate to the atmosphere And, without forcibly heating the semiconductor substrate, an Al film is deposited on the high melting point metal film by a sputtering method, and then the sputtering method is performed while heating the substrate to a temperature in a range from 400 ° C. to the melting point of Al. (E) forming a first metal wiring by patterning the first metal film, and (F) forming a first metal wiring. A step of forming a second interlayer film from above; (G) a through hole in the second interlayer film at a position connecting the second metal wiring and the first metal wiring formed on the second interlayer film; Work to form (H) a step of forming a high melting point metal film from above the second interlayer film and attaching it to the inner surface of the through hole; (I) forcing the semiconductor substrate without exposing the semiconductor substrate to the atmosphere. Without heating, an Al film is deposited on the high melting point metal film by a sputtering method, and then an Al film is deposited by a sputtering method while heating the substrate to a temperature in a range from 400 ° C. to the melting point of Al. Forming a second metal film; and (J) forming a second metal wiring by patterning the second metal film. 4. A method of manufacturing a multilayer wiring according to claim 3 comprising between step further following steps subsequent to (J) (K) to (O). (K) a step of forming a third interlayer film from above the second metal wiring, and (L) a step of connecting the third metal wiring formed on the third interlayer film to the second metal wiring. Forming a through hole in the third interlayer film; (M) forming a refractory metal film from above the third interlayer film to form a third hole;
(N) forming an Al film by sputtering on the high melting point metal film without exposing the semiconductor substrate to the atmosphere and without forcibly heating the semiconductor substrate. Depositing an Al film by sputtering while heating the substrate to a temperature in the range of 400 ° C. to the melting point of Al to form a third metal film; (O) third layer Forming a third metal wiring by patterning the metal film of FIG.