JP3158421B2 - Wiring formation method - Google Patents

Description

The present invention relates to a method for forming a wiring of a semiconductor device, and more particularly, to a method for forming a wiring in which a refractory metal wiring is formed on a lower wiring.

[Summary of the Invention] The invention according to claim 1 is a method for forming a wiring for selectively growing a refractory metal on a lower wiring, wherein the lower wiring is formed by forming a silicon thin film on a aluminum wiring via a barrier metal. Form an interlayer insulating film on top,
A contact hole is formed by over-etching the interlayer insulating film, and a refractory metal made of tungsten is selectively grown in the contact hole so that the refractory metal can be stably embedded in the contact hole. It is.

[Prior Art] In the next-generation ultra-ultra LSI, the miniaturization is progressing more and more, and the fine processing of 0.35 μm rule or less is required. With the progress of miniaturization in this way, selective tungsten CVD has
Attention has been paid to a method for forming a wiring in which tungsten (W) is surely buried in a contact hole or a via hole having a diameter of 5 μm or less by vapor phase growth.

Such a wiring forming method, as shown in FIG. 8A,
SiO ₂ interlayer insulating film 2 formed on silicon substrate 1
Then, a contact hole 2a is opened, and vapor phase growth of tungsten is performed. First, nucleated tungsten grains 3a grow on the bottom surface of the contact hole 2a. Next, this tungsten grain
The seed 3a grows as a seed and almost completely fills the bottom of the contact hole 2a as shown in FIG. 8B. Further, the growth of tungsten 3 proceeds, and contact holes are buried as shown in FIG. 8C.

Next, FIG. 9 is a sectional view showing another conventional example. First, an interlayer insulating film 5 is formed on an aluminum (Al-Si 1%) film 4 as a lower wiring layer, a contact hole 5a is opened in the interlayer insulating film 5, and a silane reduction method is formed in the contact hole 5a. To selectively form tungsten 6. As another conventional example, a (polycide gate) selection W is formed on a tungsten silicon (WSi) film.
Are known.

[Problems to be Solved by the Invention] However, in the above-described conventional example, when tungsten is selectively grown on a silicon substrate as a lower wiring, seeding nucleated tungsten grains are formed at the bottom of the contact hole. If not, tungsten will not grow. In particular, on tungsten silicide (WSix), the number of nuclei is small, and 0.35 μm, 0.
As the contact hole diameter decreases to 2 μm, there are contact holes where tungsten grows and contact holes where tungsten does not grow.
There was a problem that could be an unstable factor.

When tungsten is formed on an aluminum film as a lower wiring by the silane reduction method described above, an oxide of aluminum (such as a natural oxide film formed after opening a contact hole) or a fluorine film of aluminum is formed at an interface between the tungsten and the aluminum film. There is such product (produced during the reduction of WF _6), the contact resistance at the impact there is a problem to be very unstable. Further, as a countermeasure for such a problem, etching by Ar sputtering in InSitu or plasma etching by a chlorine-based gas is used.
In the case of using sputtering, there is a problem in selectivity, and in plasma etching or the like using a chlorine-based gas, chlorine (Cl) atoms remain at the interface, and the contact resistance becomes unstable.

Further, in the conventional example in which tungsten is selectively grown on the WSi layer as described above, there is a problem that an oxide film easily grows on WSi, and in addition, there is a problem that a delay time occurs in growth on WSi. is there. In particular, when it must be formed simultaneously on the impurity diffusion layer of the silicon substrate, there is a problem that the influence of the above-mentioned delay time appears as a difference in the buried film thickness and the like, which causes inconvenience.

The present invention has been made in view of such a conventional problem, and is capable of stably embedding a refractory metal in a contact hole, stabilizing a contact resistance and controlling film growth. It is an object of the present invention to obtain a method for forming a wiring to be enhanced.

[Means for Solving the Problems] Accordingly, the present invention provides a method for forming an interlayer insulating film on a lower wiring formed by forming a silicon thin film on an aluminum wiring via a barrier metal, and over-etching the interlayer insulating film. The solution is to form a contact hole and selectively grow a refractory metal in the contact hole.

[Function] In the present invention, the selective growth of the refractory metal from the interface between the interlayer insulating film and the lower wiring is facilitated by forming the contact hole by over-etching the interlayer insulating film. For this reason, stable embedding is enabled.

EXAMPLES Hereinafter, details of a method for forming a wiring according to the present invention will be described based on examples shown in the drawings.

(First Embodiment) FIGS. 1A to 1C and FIG. 2 show a first embodiment according to the present invention.
An example is shown.

First, in this embodiment, as shown in FIG. 1A, for example, a Si film such as a field oxide film on a semiconductor substrate (not shown) is used.
On the O ₂ insulating film 10, for example, a phosphorus-doped polysilicon (hereinafter referred to as DOPOS) film 11 and a tungsten silicide (WSix) film 12 extending along the wafer surface from the gate electrode are formed and patterned. An interlayer insulating film 13 is deposited thereon.

Next, a resist pattern is formed using a lithography technique, and anisotropic etching is performed using the resist as a mask to open a contact hole. At this time, as shown in FIG. 1B, the contact hole 14 is formed by performing over-etching up to the tungsten silicide film 12. Next, tungsten is selectively grown in the contact hole 14 by a CVD method. The conditions for this selective CVD are as follows.

Temperature 260 ° C. Atmospheric pressure 0.2 Torr Atmospheric gas and its flow rate Tungsten hexafluoride (WF ₆ ) 10 _SCCM silane (SiH ₄ ) 7 _SCCM H ₂ … 1000 _SCCM As shown in the figure, first, nucleated tungsten grains 15a begin to grow at the interface between the tungsten silicide (WSix) film 12 and the interlayer insulating film 13. After that, the tungsten grains 15a grow as seeds and fill the contact holes.

In this embodiment, the contact hole 14 is over-etched so as to cut the tungsten silicide film 12,
Since tungsten easily grows from the interface between the interlayer insulating film 13 and the tungsten silicide film 12, a tungsten wiring can be surely formed.

Second Embodiment FIGS. 3A to 3C and 4 show a second embodiment of the present invention.

In this embodiment, as shown in FIG. 3A, a film having a thickness of, for example, 10 μm is formed on the tungsten silicide film 12 in the first embodiment.
A polycrystalline silicon film 16 of about 0 ° is formed.

Next, as in the first embodiment, contact holes 14 are formed.
As shown in FIG. 3B, a tungsten silicide film
Overetch to 12 Next, as shown in FIG. 3C, the contact holes 14 are buried by a selective tungsten CVD method. The conditions for this CVD are the same as in the first embodiment.

In this embodiment, immediately after the start of CVD, as shown in FIG. 4, first, the interface between the tungsten silicide film 12 and the polycrystalline silicon film 16 and the polycrystalline silicon film 16 and the interlayer insulating film are formed.
Nuclear tungsten grains 15b and 15c grow at the interface with 13,
Using this as a seed, the growth of tungsten 15 proceeds. In this embodiment, since the tungsten grains 15b and 15c grow at the two interfaces, the number of seeds is large, and therefore, the tungsten 15 grows stably on the tungsten silicide film 12 and a reliable wiring is formed. it can.

The polycrystalline silicide film 16 may also serve as an anti-reflection film on the tungsten silicide film 12.

The first and second embodiments focus on the drawback that selective tungsten is unlikely to grow on tungsten silicide (WSix) and that tungsten is easily grown from the interface between tungsten silicide and an interlayer insulating film. This is particularly effective when the contact hole diameter is reduced to 0.35 μm or less.

Third Embodiment FIG. 5 shows a cross section of a wiring formed according to a third embodiment of the present invention.

In the present embodiment, as shown in the figure, an aluminum wiring (Al-Si 1%) 4 is formed as a lower layer wiring, and a silicon thin film 17 is continuously formed thereon by a sputtering apparatus.
Patterning is performed to form an interlayer insulating film 18 such as PSG. In the figure, 20 is, for example, And a barrier metal layer.

Next, the interlayer insulating film 18 is etched to open a contact hole 19. At this time, the etching is controlled so that the silicon thin film 17 has a thickness of at least 100 ° at the bottom of the contact hole 19.

Thereafter, selective tungsten CVD is performed to selectively grow tungsten in the contact hole 19. This CVD
The conditions are as follows.

Atmosphere gas and its flow rate Silane (SiH ₄ ) 7 _SCCM Tungsten hexafluoride (WF ₆ ) 10 _SCCM Hydrogen (H ₂ ) 1000 _SCCM Temperature 260 ° C Pressure 0.2Toor When the above method was performed, it was at the bottom of the contact hole 19 Since the silicon thin film 17 is almost eliminated by the Si reduction reaction when the tungsten 15 is formed, the silicon film does not increase the contact resistance with the aluminum wiring 4.

(Fourth Embodiment) FIG. 6 is a sectional view showing a fourth embodiment of the present invention.

This embodiment is different from the structure of the third embodiment in that a barrier metal 21 is interposed between the silicon thin film 17 and the aluminum wiring 4, and the barrier metal 21 is interposed between the silicon thin film 17 and the aluminum wiring 4.
The structure prevents Si and Al from reacting. Then, in order to form a wiring, a selective tungsten CVD may be performed after opening the contact hole 19 as in the third embodiment.

This embodiment is particularly effective when the temperature rises when forming an interlayer planarizing film (interlayer insulating film) or when forming a contact, and the
This is advantageous when Al may react.

In the third and fourth embodiments described above, since oxides and fluorides of Al are not formed at the interface between the aluminum-based wiring (Al, Al—Si) and tungsten, the selected tungsten having a stable contact resistance can be obtained. Can be formed.

(Fifth Embodiment) FIGS. 7A to 7D show a fifth embodiment of the present invention.

In this embodiment, a silicon-based thin film such as polycrystalline silicon formed as an anti-reflection film on tungsten silicide (WSix) is intentionally left about 100 mm at the time of forming a contact hole when a tungsten polycide gate is formed. Then, selective tungsten is formed. First, in this embodiment, as shown in FIG. 7A, a SiO ₂ insulating film 28 is formed on a silicon substrate (not shown), and a DOPOS film 22 and a tungsten silicide film are formed thereon.
23, a polycrystalline silicon film 24 as an anti-reflection film is sequentially laminated and predetermined patterning is performed to form a gate electrode.

Next, as shown in FIG. 7B, an interlayer insulating film made of SiO ₂
25 are formed, and a contact hole 26 is opened using a known technique (FIG. 7C). At this time, the polycrystalline silicon film 24 is intentionally etched so that about 100 ° remains.

Next, select tungsten in this contact hole 26
The contact wiring is formed by growing tungsten 15 by the CVD method. The above CVD conditions are as follows.

Temperature 260 ° C. Pressure 0.2 Torr Atmospheric gas and its flow rate Silane (SiH ₄ ) 7 _SCCM Tungsten hexafluoride (WF ₆ ) 10 _SCCM Hydrogen (H ₂ ) 1000 _SCCM , 2WF ₆ + 3Si → 2W + 3SiF ₄
As shown in FIG. 7D, tungsten silicide (WSi)
It becomes a film and does not affect the contact hole resistance.

In this embodiment, unlike tungsten silicide (WSi), in which an oxide film is easily formed and which has a long delay time during selective tungsten growth, tungsten is grown on a silicon-based thin film (polycrystalline silicon in this embodiment). Tungsten can be formed stably.

Although the embodiments have been described above, the present invention is not limited to these, and various design changes accompanying the gist of the configuration are possible.

[Effects of the Invention] As is clear from the above description, according to the method for forming a wiring according to the present invention, there is an effect that a refractory metal can be stably embedded in a contact hole.

Further, there is an effect that a refractory metal having a stable contact resistance can be formed with good controllability.

For this reason, the present invention can be applied to those having a contact hole diameter of 0.35 μm or less, which enables finer processing.

[Brief description of the drawings]

1A to 1C are cross-sectional views showing steps of a first embodiment of a method for forming a wiring according to the present invention, FIG. 2 is a cross-sectional perspective view of the first embodiment, and FIGS. FIG. 3C is a sectional view showing a process of the second embodiment, FIG. 4 is a perspective view of a sectional view of the second embodiment, and FIG.
7 is a sectional view of the third embodiment, FIG. 6 is a sectional view of the fourth embodiment, FIGS. 7A to 7D are sectional views showing steps of the fifth embodiment, and FIGS. FIG. C is a cross-sectional view showing steps of a conventional method, and FIG. 9 is a cross-sectional view showing another conventional example. 4 ... aluminum wiring, 12 ... tungsten silicide film, 13 ... interlayer insulating film, 14 ... contact hole, 15
…… Tungsten, 15a, 15b, 15c …… Tungsten particles, 1
6 ... polycrystalline silicon film, 17 ... silicon thin film, 18 ...
Interlayer insulating film, 19 contact hole, 21 barrier metal, 23 WSi film, 24 polycrystalline silicon film, 25 interlayer insulating film, 26 contact hole, 27 WSi film.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-114236 (JP, A) JP-A-64-57664 (JP, A) JP-A-2-132825 (JP, A) JP-A-60-1985 115221 (JP, A) JP-A-63-211650 (JP, A) JP-A-63-240046 (JP, A) JP-A-3-101254 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/3205-21/3213 H01L 21/768

Claims (1)

(57) [Claims] An interlayer insulating film is formed on a lower layer wiring formed by forming a silicon thin film on an aluminum wiring via a barrier metal, and the interlayer insulating film is over-etched to form a contact hole. A method for forming a wiring, comprising selectively growing a refractory metal on a substrate.