JPH0714838A - Formation of al wiring - Google Patents

Abstract

PURPOSE:To make it possible to embed favorably an Al wiring material layer in a connection hole, which has a high aspect ratio and is microscopic, and to form a highly reliable Al wiring. CONSTITUTION:A process for opening a connection hole 3W in an insulating layer 3 on a semiconductor substrate 2, a process for forming a base layer 4, which has a good wettability with Al, on at least the side-wall surface and bottom in the interior of the hole 3W, a process for forming an Al base material layer in the hole 3W, a heat treating process, in which the substrate 2 is heated to form the layer 4 and the Al base material layer into an alloy layer 8, and a process in which an Al wiring material layer 5 is deposited by a high- temperature sputtering method after the heat treating process to fill the hole 3W, are employed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Al wiring suitable for manufacturing semiconductor devices such as large scale integrated circuit devices LSI, VLSI, ULSI (Al wiring in this specification means not only Al alone but also Al wiring. (Including alloy wiring).

[0002]

2. Description of the Related Art Semiconductor devices, especially LSI, VLSI, and U
In an LSI or the like, a lower semiconductor layer, an electrode, a wiring, etc. are formed through a connection hole formed through an insulating layer such as a surface insulating layer or an interlayer insulating layer formed over a semiconductor substrate, for example, an insulating layer such as silicon oxide. A multi-layer wiring structure for connecting (hereinafter referred to as lower layer wiring) and upper layer wiring is adopted. In this structure, the opening diameter of the connection hole is also miniaturized as the design rule is highly sophisticated. Since the aspect ratio has exceeded 1, the technique of embedding a wiring material in this fine connection hole has become important.

As a method of burying an Al-based material of Al or an Al alloy as the wiring material, for example, a connection hole is opened in the above-described insulating layer formed on the lower wiring formed on the substrate so as to cover the lower wiring. First, an underlayer of Ti, TiN or the like, which is so-called wettable with an Al-based material, is formed in the connection hole, and the substrate is heated to a temperature near the melting point of the Al-based wiring material at a high temperature. A high-temperature sputter of a system wiring material is performed while the Al-based material is introduced into the connection hole to form a film, and the Al-based wiring material is used to form a wiring layer with excellent filling of the connection hole and surface flatness. A high-temperature sputtering method is known in which both of the above are simultaneously performed.

This high temperature sputtering method involves forming a wiring layer and
A method of using a plug made of tungsten W by a CVD (chemical vapor deposition) method because it is possible to simultaneously embed a connection hole, that is, so-called plug formation, and to simplify the process and because Al is a low resistance material. Is considered to be advantageous over the.

By the way, it is known that the embedding characteristics of the Al-based wiring material are greatly influenced by the base material of the Al-based wiring material layer.

As a base material for this Al-based wiring material, T
Good wettability with Al such as i and TiN, that is, Al
A material that has good reactivity with the system material and is easy to form an alloy is used.

FIG. 10 shows that Al is formed by this high temperature sputtering.
FIG. 3 is a schematic cross-sectional view of a case where wiring is formed, in which case insulation of SiO ₂ oxide formed on the substrate 2 on which the lower wiring 1 such as Al wiring is formed so as to cover the lower wiring 1. A layer 3 is formed, a connection hole 3W is opened therein, an underlayer 4 made of Ti or TiN is formed in the connection hole 3W, and Al-based wiring made of Al or an Al alloy is formed thereon by the high temperature sputtering. The material layer 5 is formed.

By doing so, at the same time as the high temperature sputtering of the Al-based wiring material layer 5, this material layer 5, Al and the underlying layer 4 are formed.
Al-T alloy of Al and Ti at the interface with
The alloy layer 8 of i is formed, and along with this, Al is drawn into the connection hole, and good burying is achieved.

However, if the aspect ratio of the connection hole is further increased, even if such an underlayer 4 is formed, it becomes difficult to embed it, and as shown in its schematic cross-sectional view in FIG. Cavity 13 with poor embedding occurs in the connection hole 3W, electrical and mechanical connection to the lower layer wiring 1 of the upper layer wiring formed by the Al-based wiring material layer 5 becomes insufficient, and the occurrence rate of defective products is increased. , Come with a decrease in reliability.

Further, as one of the causes of such a filling failure, when the insulating layer 3 is an insulating layer containing oxygen such as SiO ₂ oxide, the oxygen in the insulating layer 3 is reduced during heating during high temperature sputtering. The base layer 4 on the side wall surface of the connection hole 3W is oxidized by being diffused into Ti or TiN of the formation layer 4 and the wettability with the Al-based wiring material layer 5 is deteriorated. From the above, it was found that the wettability and the reactivity with the Al-based wiring material layer 5 are deteriorated.

[0011]

DISCLOSURE OF THE INVENTION The present invention, in the above-described Al wiring forming method by high-temperature sputtering, is suitable for an Al wiring material which is formed in an insulating layer on a semiconductor substrate and has a high aspect ratio. Provided is an Al wiring forming method capable of forming a buried layer and forming a highly reliable Al wiring.

[0012]

According to a first aspect of the present invention, a step of forming a connection hole in an insulating layer on a semiconductor substrate, and an underlayer having a good wettability with Al are formed on at least a side wall surface and a bottom surface inside the connection hole. A step of forming, an step of forming an Al-based underlayer material layer in the connection hole, a heat treatment step of heating the semiconductor substrate to alloy the underlayer and the Al-based underlayer material layer, and then Al by a high temperature sputtering method. A step of depositing a system wiring material layer and filling the connection hole.

In a second aspect of the present invention, in the above-described method of the present invention, a step of forming an antioxidant film of the underlayer on at least the side wall surface of the connection hole is formed prior to the formation of the underlayer.

According to a third aspect of the present invention, the antioxidation film of the underlayer is a semiconductor layer or a metal layer.

According to a fourth aspect of the present invention, the semiconductor layer or metal layer constituting the underlayer anti-oxidation film is made of amorphous Si, polycrystalline Si, Pt, Cu or Pd.

The fifth aspect of the present invention employs a step of selectively forming an antioxidation film of an underlayer made of an insulating layer on the side wall surface of the connection hole before forming the underlayer.

[0017]

According to the present invention described above, an Al-based underlayer is formed on an underlayer having good wettability with Al, and this is alloyed with the underlayer, and then the Al-based wiring material layer is heated to a high temperature. Sputtering is performed. In this case, the Al-based wiring material layer can be satisfactorily introduced into the connection hole, and the Al-based wiring material layer can be satisfactorily introduced into the connection hole having a high aspect ratio. Could be embedded.

Further, when the insulating layer is an insulating layer containing oxygen, an antioxidant film of the underlying layer, that is, oxygen is introduced into the underlying layer, especially on the side wall surface of the insulating layer where the underlying layer is deposited. Since the partition layer for isolation is provided, diffusion of oxygen from the oxide insulating layer containing oxygen to the base layer can be prevented.

Therefore, in the method of the present invention, Al
In spite of the heat treatment for alloying the base underlayer and the high temperature heat treatment for high temperature sputtering of the Al based wiring material layer, oxygen diffuses into the underlayer and oxidizes the underlayer to form Al. It is possible to avoid the inconvenience of deteriorating the wetting with the system wiring material layer.

Therefore, the Al-based wiring material layer, and thus the upper wiring formed by the Al-based wiring material layer, can be satisfactorily filled in the connection hole of the insulating layer, and the lower wiring can be satisfactorily contacted. The wiring can be formed.

[0021]

EXAMPLE As described above, the present invention includes the step of forming a contact hole in an insulating layer on a semiconductor substrate and the step of forming an underlayer having good wettability with Al on at least the side wall surface and the bottom surface inside the contact hole. And a step of forming an Al-based underlayer material layer in the connection hole, a heat treatment step of heating the semiconductor substrate to alloy the underlayer and the Al-based underlayer material layer, and then an Al-based wiring material by high-temperature sputtering. Depositing layers to fill the contact holes.

Further, in this method, a step of forming an antioxidant film of the underlayer on at least the side wall surface of the connection hole is formed prior to the formation of the underlayer.

An embodiment of the present invention will be described in detail with reference to FIGS.

In this example, the lower layer wiring 1, for example, the Al lower layer wiring is formed on the substrate 2 so as to cover the lower layer wiring 1.
This is a case where the insulating layer 3 is formed and the Al-based wiring material layer 5 forming the upper layer wiring is in ohmic contact with the lower layer wiring 1.

Example 1 In this case, as shown in FIG. 1, on the substrate 1 on which the lower layer wiring 1 is formed, the insulating layer 3 containing SiO ₂ or oxygen is CV.
It was formed by the D (chemical vapor deposition) method.

A contact hole 3W is formed through the insulating layer 3 by RIE (reactive ion etching) by photolithography at a connection portion with the upper layer wiring of the lower layer wiring 1. The thickness of the insulating layer 3, that is, the depth of the connection hole 3W was 0.8 μm, and the opening diameter of the connection hole 3W was 0.5 μm.

Next, Ti as the underlayer 4 is continuously formed by the usual magnetron sputtering method, and then A is continuously formed in vacuum.
An Al-Si alloy containing 1% of Si as the 1-based base material layer 7 was sequentially formed to have a film thickness of 100 nm.

Ti underlayer 4 and Al--Si wiring material layer 5
The film forming conditions of were selected as follows. Film formation conditions for Ti underlayer 4: DC power 4 kW Gas system and supply amount Ar 100 sccm Pressure 0.4 Pa Growth temperature 150 ° C.

Film forming conditions for the Al-Si base material layer 7: DC power 20 kW Gas system and its supply amount Ar 100 sccm Pressure 0.4 Pa Growth temperature Room temperature to 150 ° C.

In this case, the step coverage of the Al alloy is Ti
In comparison with the above, Al is deposited almost on the upper surface of the insulating layer 3, the opening peripheral portion of the connection hole 3W, and the bottom surface of the connection hole 3W, and hardly deposited on the side wall surface of the connection hole.

Next, without heating to the atmosphere, the substrate is continuously heated to alloy the Al—Si of the base material layer 7 with the Ti of the base layer 4, and as shown in FIG. To
The alloy layer 8 is formed.

The substrate heating is performed by a gas conduction heating system in which an assist gas of Ar is introduced between the heater block installed on the back surface of the substrate and the back surface of the substrate to heat the substrate.
The substrate heating conditions were selected as follows. Substrate heating conditions: Gas system and its supply amount Ar 100 sccm Substrate back pressure 8 Torr pressure 0.4 Pa Heating temperature 500 ° C. Heating time 40 seconds

Next, as shown in FIG. 5, an Al-based wiring material layer 5 is continuously formed in vacuum to a thickness of 500 nm by high temperature sputtering. The film forming conditions were selected as follows. Film-forming conditions for the Al-Si based wiring material layer 5: DC power 10 kW Gas system and supply amount Ar 100 sccm Pressure 0.4 Pa Growth temperature 500 ° C.

FIGS. 3 and 4 show the process of filling the Al-based wiring material layer 5 into the connection hole 3W shown in FIG. 5 at this time. In this case, the Al-Si of the wiring material layer 5 is formed.
However, due to the wettability of the underlayer 4 with Ti, A of the alloy layer 8
Since the wettability with respect to 1-Si-Ti is better, the Al-Si of the wiring material layer 5 at the initial stage of film formation is easily Al.
Wetting proceeds on the -Si-Ti alloy layer 8 and enters into the connection hole 3W. Then, after that, Al-S of the wiring material layer 5
i further forms the alloy layer 8 at the interface with the Ti of the underlayer 4 existing on the side wall surface of the inner periphery of the connection hole 3W, and further penetrates deeply into the connection hole 3W as the alloy layer 8 is formed. Finally, as shown in FIG. 5, the connection hole 3W is embedded. Moreover, at this time, the surface becomes flat. Here, A shown in FIG.
The shape in which l-Si enters the inside of the connection hole 3W while it is wetted makes it extremely easy for the subsequent Al-Si to be drawn into the connection hole 3W through the process of FIG.

Next, another embodiment (second embodiment) of the present invention will be described with reference to FIGS. 6 and 7.

Also in this example, the lower layer wiring 1 is covered on the substrate 2 on which, for example, the Al lower layer wiring is formed so as to cover the lower layer wiring 1.
The insulating layer 3 is formed. In this case, the insulating layer 3 is formed.
Is a SiO ₂ oxide insulating layer, that is, an insulating layer containing oxygen, and the diffusion of oxygen from this is a problem.

Example 2 In this example, the connection hole 3 of the insulating layer 3 containing oxygen was used.
The underlayer of the antioxidant film 6 is formed in W.
This is the case where the anti-oxidation film 6 uses insulating SiN.

In this case, the SiN oxidation preventing film 6 was formed on the entire surface to a film thickness of 150 nm by the plasma CVD method.
Subsequently, this antioxidant film 6 is etched back by anisotropic etching perpendicularly to the plate surface of the substrate 2, and as shown in FIG. 6, the substantial film thickness becomes large in this etching direction. The bottom surface of the connection hole 3W and the antioxidant film 6 on the upper surface of the insulating layer 3 are removed by etching, leaving only the portion of the connection hole 3W to be adhered to the inner wall surface as a sidewall.

The conditions for forming the SiN oxidation preventing film 6 and the conditions for etching back were selected as follows. Deposition conditions of the SiN anti-oxidation film 6: Gas system and supply amount SiH ₄ 180 sccm NH ₃ 500 sccm N ₂ 720 sccm Growth temperature 250 ° C. Pressure 40 Pa

Etching conditions of SiN oxidation preventing film 6: Gas system and its flow rate CHF ₃ 75 sccm O ₂ 35 sccm RF power 600 W Pressure 5.3 Pa

After that, the underlayer 4 and the Al-based underlayer 7 are formed in the same manner as in Example 1, that is, the steps similar to those shown in FIGS. 1 to 5 are taken, and the alloy layer 8 is formed by heating the substrate. Then, the Al-based wiring material layer 5 is formed by high temperature sputtering, and the Al-based wiring material layer 5 is embedded in the connection hole 3W as shown in FIG.

The Al-based wiring material layer 5 thus formed
Even if the insulating SiN oxidation preventing film 6 is present, it is selectively formed on the side wall surface, that is, the peripheral side surface of the connection hole 3W. The oxidation prevention film 6 is formed on the bottom surface of the connection hole 3W. Since it is eliminated, the electrical contact with the lower wiring 1 of the Al-based wiring material layer 5 is not hindered.

Next, the case of forming the conductive anti-oxidation film 6 will be described. First, still another embodiment (third embodiment) will be described with reference to FIGS. 8 and 9. Example 3 In this example, amorphous Si was used as the antioxidant film 6. In this case, as shown in FIG. 8, the bottom surface of the connection hole 3W can be formed in the connection hole 3W formed in the SiO ₂ insulating layer 3 by magnetron sputtering, that is, on the lower layer wiring 2. The anti-oxidation film 6 made of amorphous Si was formed to a film thickness of 50 nm. The film forming conditions were selected as follows. Amorphous Si film forming conditions: DC power 10 kW gas system and supply amount Ar 100 sccm pressure 0.4 Pa growth temperature 150 ° C.

After that, the underlayer 4 and the Al-based underlayer 7 are formed in the same manner as in Example 1, that is, the steps similar to those shown in FIGS. 1 to 5 are taken, and the alloy layer 8 is formed by heating the substrate. Then, the Al-based wiring material layer 5 is formed by high temperature sputtering, and the Al-based wiring material layer 5 is embedded in the connection hole 3W as shown in FIG.

In these Examples 2 and 3 as well, as in the case of Example 1, Al- of the wiring material layer 5 at the initial stage of film formation was used.
Si easily wets on the Al-Si-Ti alloy layer 8,
The alloy layer 8 is formed at the interface with Ti of the underlayer 4 existing on the side wall surface of the inner periphery of the connection hole 3W, and the alloy layer 8 is formed along with the formation of the alloy layer 8. Then, the contact hole 3W is finally buried. Moreover, at this time, the surface becomes flat.

In the second and third embodiments, since the base layer 4 and the insulating layer 3 containing oxygen are interposed, the base layer 4 is formed during the alloying process for forming the alloy layer 8. Since the diffusion of oxygen from the insulating layer 3 is prevented even by heating or heating the wiring material layer 5 by high-temperature sputtering,
This oxidation avoids the inconvenience that the wettability with the underlayer 4 is lowered.

The Al-based wiring material layer 5 thus formed by burying the inside of the connection hole 3W is formed into a desired pattern by, for example, selective etching by photolithography to form an Al wiring as an upper wiring. .

In the third embodiment, amorphous Si is used as the anti-oxidation film 6, but instead of this, polycrystalline Si or a metal layer of Pt, Cu, or P is used.
d or the like can be used.

Further, the substrate heating is not limited to the above-mentioned gas conduction heating method, and for example, lamp heating, excimer heating,
Various methods such as heating by laser irradiation can be applied.

Further, in the above-mentioned example, T is used as the base layer 4.
When i is used, other than that, TiN, TiO
N, TiW, or a laminated structure of these may be used.

The wiring material layer is made of Al-Si described above.
Not limited to Al alone or Al-Si-Cu, Al-
An Al-based material such as Cu or Al-Ge can be used.

[0052]

According to the present invention described above, an Al-based undercoating material layer is formed on an undercoating layer having good wettability with Al, and this is alloyed with the undercoating layer, and then the Al-based wiring material layer is formed. The high temperature sputtering is performed, but in this case, the Al-based wiring material layer can be satisfactorily introduced into the connection hole, and the Al-based wiring can be satisfactorily injected into the connection hole having a high aspect ratio. The material layer can be embedded.

When the insulating layer is an insulating layer containing oxygen, the antioxidant film of the underlayer, that is, the introduction of oxygen into the underlayer, is particularly formed on the side wall surface of the insulating layer which is covered with the underlayer. Since the partition layer for isolation is provided, diffusion of oxygen from the oxide insulating layer containing oxygen to the base layer can be prevented.

Therefore, in the method of the present invention, Al
In spite of the heat treatment for alloying the base underlayer and the high temperature heat treatment for high temperature sputtering of the Al based wiring material layer, oxygen diffuses into the underlayer and oxidizes the underlayer to form Al. It is possible to avoid the inconvenience of deteriorating the wetting with the system wiring material layer.

Therefore, it is possible to satisfactorily fill the Al-based wiring material layer, and thus the upper wiring formed by the Al wiring material, into the connection hole of the insulating layer, and to make good contact with the lower wiring. The wiring can be formed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a manufacturing process of an example of the method of the present invention.

FIG. 2 is a schematic cross-sectional view of a manufacturing process of an example of the method of the present invention.

FIG. 3 is a schematic cross-sectional view of a manufacturing process of an example of the method of the present invention.

FIG. 4 is a schematic cross-sectional view of an example manufacturing process of the method of the present invention.

FIG. 5 is a schematic cross-sectional view of a manufacturing process of an example of the method of the present invention.

FIG. 6 is a schematic cross-sectional view of a manufacturing process of another example of the method of the present invention.

FIG. 7 is a schematic cross-sectional view of a manufacturing process of another example of the method of the present invention.

FIG. 8 is a schematic cross-sectional view of a manufacturing process of yet another example of the method of the present invention.

FIG. 9 is a schematic cross-sectional view of a manufacturing process of yet another example of the method of the present invention.

FIG. 10 is a sectional view of an Al wiring portion formed by a conventional method.

FIG. 11 is a sectional view of an Al wiring portion formed by a conventional method.

[Explanation of symbols]

 1 Lower Layer Wiring 2 Substrate 3 Insulating Layer Containing Oxygen 3 W Connection Hole 4 Underlayer 5 Al-based Wiring Material Layer 6 Antioxidant Film 7 Al-based Underlayer 8 Alloy Layer

Claims (5)

[Claims] 1. A step of forming a connection hole in an insulating layer on a semiconductor substrate, a step of forming an underlayer having a good wettability with Al on at least a side wall surface and a bottom surface inside the connection hole, and Al in the connection hole. System underlayer material layer, heat treatment step of heating the semiconductor substrate to alloy the underlayer layer with the Al underlayer material layer, and then depositing an Al based wiring material layer by high temperature sputtering. A step of burying the connection hole
l Wiring forming method. 2. The method for forming an Al wiring according to claim 1, further comprising a step of forming an antioxidant film of the underlayer on at least a side wall surface of the connection hole before forming the underlayer. 3. The A according to claim 2, wherein the antioxidant film of the underlayer is a semiconductor layer or a metal layer.
l Wiring forming method. 4. A semiconductor layer or a metal layer forming the anti-oxidation film of the underlayer is formed of amorphous Si, polycrystalline Si,
The Pt, Cu, or Pd is used, and the Al wiring forming method according to claim 2. 5. The method according to claim 1, wherein a step of selectively forming an antioxidant film of the underlayer made of an insulating layer on a side wall surface of the connection hole is formed prior to the formation of the underlayer. Al wiring forming method.