JP3082230B2 - 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 present invention relates to a method for forming a wiring in which a refractory metal is arranged on a lower wiring, wherein an interlayer insulating film having a contact hole is formed on the lower wiring, and the refractory metal is coated on the entire surface including the contact hole. The step of depositing the high melting point metal and the step of etching back the high melting point metal are continuously performed using the same chamber or a plurality of chambers connected in a vacuum through a gate valve, and the high melting point metal is placed in the contact hole. In this way, it is possible to avoid peeling of the wiring, improve oxidation resistance and surface morphology, and to form a wiring with high reliability.

[Prior art] In next-generation ultra-super LSIs, fine contact holes (0.35 μm □) and via holes are buried, and as a wiring layer forming technology, step coverage (step coverage) is used.
However, blanket tungsten CVD technology, which has a lower contact resistance than conventional polysilicon plugs, is attracting attention. This technology is based on the “Monthly Semiconductor
World, 1989.12, p. 197 to p. 200 ". At present, a thin film as an adhesion layer such as titanium nitride (TiN) or titanium tungsten (TiW) is deposited on the lower layer by a sputtering method due to a problem of adhesion between the lower layer and tungsten.

3A and 3B show a conventional example in which tungsten is buried in a contact hole.

In this conventional example, first, an impurity diffusion region 2 is formed on a silicon substrate 1, an interlayer insulating film 3 made of SiO ₂ is deposited thereon, and a contact hole 4 where the impurity diffusion region 2 is exposed is formed by a known technique. Open using. Next, as shown in FIG. 3A, a tungsten nitride film 5 is deposited on the entire surface of the substrate by using a sputtering method as an adhesion layer.

Next, as shown in FIG. 3B, a tungsten film 6 is formed by performing blanket tungsten CVD.

[Problem to be Solved by the Invention] However, such a conventional method has the following problems.

That is, the titanium nitride film 5 deposited on the inner surface of the interlayer insulating film 3 and the contact hole 4 cannot be deposited on the portion of the clamp (shown by a broken line in FIG. (A part that is not deposited). Thereafter, as shown in FIG.
Is deposited, there is a problem that the clip mark is peeled off (shown by a broken line in the drawing). In addition, it causes the tungsten film on the edge of the wafer to peel off.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the conventional example, and has as its object to obtain a highly reliable wiring forming method without wiring peeling.

Means for Solving the Problems In view of the above, the present invention provides a step of forming an interlayer insulating film having a contact hole on a lower wiring, depositing a refractory metal on the entire surface including the contact hole, The step of performing etch-back is performed continuously using the same chamber or a plurality of chambers connected by a vacuum through a gate valve, and the refractory metal is left in the contact hole. .

[Operation] The refractory metal deposited in the contact hole and on the interlayer insulating film is etched back, so that the metal located on the interlayer insulating film is removed. Therefore, peeling of the refractory metal on the interlayer insulating film is prevented, and the reliability of the wiring is improved.

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

First Embodiment FIGS. 1A and 1B show a first embodiment of the present invention.

In this embodiment, first, an impurity diffusion region 10a as a lower wiring is formed in a silicon substrate 10. Next, after depositing an interlayer insulating film 11 made of SiO ₂ by a CVD method, a contact hole 11a is opened on the impurity diffusion region 10a using a known technique. Then, in the contact hole 11a and on the interlayer insulating film 11, titanium nitride (TiN) as an adhesion layer is formed.
The film 12 is applied by a sputtering method. Further, FIG. 1A
As shown in FIG. 5, a tungsten film 13 is deposited by a blanket tungsten CVD method so as to fill the contact hole 11a, and further deposit it above the interlayer insulating film 11.

Here, the conditions of blanket tungsten CVD were set in two stages as described below.

First stage Temperature 475 ° C Pressure 80 Torr Atmospheric gas and its flow rate Tungsten hexafluoride (WF ₆ ) 25 _SCCM silane (SiH ₄ ) 15 _SCCM Second stage Temperature 475 ° C Pressure 80 Torr Atmospheric gas and its flow rate Tungsten hexafluoride (WF ₆₎ 60 _SCCM hydrogen (H ₂ ) 360 _SCCM Next, a continuous etching back is performed under the following conditions in order to expose the titanium nitride film 12 and to form a contact hole.
Tungsten film (tungsten plug) only in 11a
Was left.

Etching back conditions Etching gas and its flow rate Sulfur hexafluoride (SF ₆ ) 30 _SCCM oxygen (O ₂ ) 28 _SCCM RF output 150 W Pressure 50 mTorr In this embodiment, since the tungsten plug was formed by a continuous process, Since the tungsten film 13 as the cause does not exist on the titanium nitride film 12, a highly reliable wiring can be formed.

The continuous process may be performed using the same chamber, or a plurality of chambers connected by a vacuum through a gate valve.

Second Embodiment FIGS. 2A to 2D show a second embodiment. The same members as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

In this embodiment, after a tungsten film is formed by blanket tungsten CVD, tungsten is ion-implanted into the tungsten film, the surface of the film is made amorphous to planarize the surface, and a high dose of N ₂ is ion-implanted. The tungsten film surface is covered with a highly dense film of silicon nitride (Si ₃ N ₄ etc.), and the surface of the tungsten film is turned into tungsten nitride (WN _x ) to improve the oxidation resistance and surface morphology of the tungsten film. . For this reason,
As in the first embodiment, the reliability of the wiring is improved.

First, in this embodiment, as shown in FIG. 2A,
A tungsten film having a thickness of, for example, about 4000 mm on a titanium nitride film 12 having a thickness of, for example, about 700 mm, which is deposited in the contact hole 11a and the interlayer insulating film 11 by reactive sputtering.
13 is formed in the same manner as in the first embodiment. The tungsten film was formed by two-step blanket tungsten CVD using silane (SiH ₄ ) + hydrogen (H ₂ ) reduction under the following conditions.

First stage Temperature 475 ° C Atmospheric gas and its flow rate Silane (SiH ₄ ) 15 _SCCM Tungsten hexafluoride (WF ₆ ) 25 _SCCM pressure 80 Torr Second stage Temperature 475 ° C Atmospheric gas and its flow rate Tungsten hexafluoride (WF ₆ ) 60 _SCCM hydrogen (H ₂ ) 360 _SCCM pressure 80 Torr Next, as shown in FIG. 5A, tungsten (W) is ion-implanted into the tungsten film 13 under the conditions of 60 to 100 KeV, 10 ¹⁵ to 10 ¹⁶ cm ⁻² , The surface of the film 13 is made amorphous by making the surface amorphous.

Then, as shown in FIG. 2B, nitrogen (N ₂ ) is applied to the surface of the tungsten film 13 by, for example, 50 to 80 KeV, 10 ¹⁷ to 10 10.
A high dose ion implantation of ¹⁸ cm ^-2 is performed to form an amorphous nitrogen ion implantation layer 13a of tungsten and nitrogen (N ₂ ).

Next, as shown in FIG. 2C, the nitrogen ion implanted layer 13a
An Si ₃ N ₄ film 14 is laminated thereon with a thickness of about 300 mm. The Si ₃ N ₄ film 14 is a film having a high density, and prevents the escape of N ₂ by annealing in a later step, for example, silane (SiH ₄ ) / N
Plasma CVD (360 ° C) using a reaction system such as H ₃ / nitrogen (N ₂ )
Is obtained.

Then, for example, rapid thermal annealing (RTA) 900
Annealing is performed in a N ₂ atmosphere at 60 ° C. for 60 seconds to change the nitrogen ion implanted layer 13a into a tungsten nitride (WN _x ) layer. At this time, as described above, the Si ₃ N ₄ film 14 prevents the N ₂ from coming out of the nitrogen ion implanted layer 13a to the surface by the annealing. Also, like this, the tungsten film
By 13 the surface of the ized WN _X, oxidation resistance of the tungsten film 13, thereby improving the surface morphology.

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

For example, in both embodiments, the impurity diffusion region is used as the lower wiring, but the present invention is not limited to this, and various wirings can be applied.

[Effects of the Invention] As is clear from the above description, according to the wiring forming method of the present invention, the effect of preventing peeling of the refractory metal film and dramatically improving the reliability of the wiring is obtained. is there.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views of a first embodiment of a method of forming a wiring according to the present invention, FIGS. 2A to 2D are cross-sectional views of a second embodiment, FIGS. FIG. 3B is a sectional view of a conventional example. 10a: impurity diffusion region, 11: interlayer insulating film, 12: TiN
Film, 13 ... tungsten film, 13a ... nitrogen ion implanted layer, 13b ... WN _x film, 14 ... Si ₃ N ₄ film.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/28-21/288 H01L 21/3205 H01L 21/3213 H01L 21/44-21/445 H01L 21 / 768 H01L 29/40-29/51

Claims (1)

(57) [Claims] A step of forming an interlayer insulating film having a contact hole on a lower wiring and depositing a refractory metal over the entire surface including the contact hole and etching back the refractory metal by the same chamber. Alternatively, the method is carried out continuously by using a plurality of chambers connected in a vacuum via a gate valve, and the refractory metal is left in the contact hole.