JP3141382B2 - Wiring formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method, and more particularly, to a wiring forming method including a step of filling a base opening with a high-melting metal layer. INDUSTRIAL APPLICABILITY The present invention can be used, for example, for forming a wiring structure of a semiconductor device or a wiring of various other electronic materials. However, the present invention can be applied to the case of manufacturing a semiconductor device using this as a wiring.

[Summary of the Invention]

The invention of claim 1 of the present application is to form a high melting point metal layer on a base having an opening, thereby forming an adhesion layer when filling the opening, and after forming the high melting point metal layer,
By performing the etch-back by making the etching rate of the refractory metal layer and the adhesion layer substantially equal to each other, the refractory metal layer and the adhesion layer are etched back to the same extent, so that no step is generated between the two. Thereafter, improvement in reliability in forming an upper layer wiring is achieved.

[Conventional technology]

In the field of electronic materials requiring wiring, for example, in the field of semiconductor devices, there is a remarkable tendency toward miniaturization and integration.
There are techniques described in JP-A-64-23554 and JP-A-64-10629). Along with this, openings (connection holes called contact holes and via holes, etc.) formed in a base on which wirings are to be formed have been further miniaturized. Against this background, the hole was conventionally filled by the Al (aluminum) bias sputtering method, but instead of this, the filling is made with a high melting point metal such as a poly-Si plug W filled with polysilicon. Proposals have been made for both high melting point metal plugs such as W plugs.

However, the above technique has a drawback that the obtained connection has a high resistance value. In addition, of the above techniques, the selective growth of a high melting point metal material such as selection W has a disadvantage that the growth of the metal is not stable and the process is unstable.

For this reason, attention has been paid to a technique of covering the entire area where a film is required to be formed with a high melting point metal and then patterning, which is another technique described above. A typical technique is a blanket W-CVD method when W is used as a wiring material. The blanket W-CVD method is a technique in which W is coated on the entire area where film formation is required, and then patterning is performed, but the process stability is much better than that of W filling by the selective CVD method. It is practical and can form W with a lower resistance than, for example, a sputtering method. This kind of technique is described in, for example, JP-A-62-219945.

[Problems to be solved by the invention]

However, W obtained by the planket W-CVD method (hereinafter sometimes abbreviated as BLK-W) has a problem that its adhesion is poor. Therefore, in order to improve the adhesion of BLK-W, it is necessary to form a thin film such as TiN or sputter W on the base and use this as an adhesion layer.

However, when forming BLK-W, as described above, TiN or the like is used as an adhesion layer, and then the opening is filled with BLK-W to form a W plug.
When etching is performed under conditions where the etching rate is higher, a step is formed between the buried W and TiN as an adhesion layer. (Void) generation may reduce reliability.

More specifically, referring to the drawing, an adhesion layer 3 is formed on a base 1 having an opening 2 by sputtering of TiN or the like as shown in FIG. 5 (a), and then a refractory metal layer 4 as a BLK-W layer is formed by CVD. 5 (b), and then the opening 2 is formed.
Etch back only to leave high melting point metal,
When the etch-back is performed under the above-described conditions, the adhesion layer 3 is etched more, and a stepped gap 3a is generated as shown in FIG. 5 (c). In FIG. 5 (c), a broken line indicates a portion 3 'where the adhesion layer 3 was present.

In addition, in the case of etchback, if the selectivity between the adhesion layer of TiN or the like and the BLK-W layer as the high melting point metal layer is not sufficient, TiN or the like is also etched back as shown in FIG. 5 (c). As a result, when an upper layer wiring is formed thereon, for example, when the upper layer wiring is Al, the TiN formed as the adhesion layer 3 is formed.
Another layer of barrier metal must be formed in addition to the layers. This also results in lower overall throughput.

The present invention solves the above-mentioned problems caused by the step of forming or disappearing by removing the adhesion layer on the base during the etching back of the refractory metal layer, thereby achieving the reliable filling of the opening. It is another object of the present invention to provide a technique capable of forming the same without lowering the throughput.

[Means for solving the problem]

The present invention has the following configuration to achieve the above object.

That is, the invention of claim 1 of the present application is a wiring forming method including a step of forming a high melting point metal layer on a base having an opening and thereby filling the opening, thereby forming an adhesion layer on the base. Then, a high-melting metal layer is formed, and then etch-back is performed using a mixed gas whose mixing ratio is adjusted so that the etching rates of the high-melting metal layer and the adhesion layer are substantially equal to each other, and then upper wiring is formed. This is a method of forming a wiring.

In practicing the above invention, various forms can be adopted as a form using a mixed gas whose mixture ratio is adjusted so that the etching rate ratio between the high melting point metal layer and the adhesion layer at the time of etch back is substantially equal. For example, a form in which a chlorine-based gas is added to a fluorine-based gas at an adjusted mixing ratio to form an etching gas, or a form in which an oxygen (O ₂ ) gas or the like is added to a fluorine-based gas at an adjusted mixing ratio is used be able to.

(Operation)

In the invention of claim 1 of the present application, since the etching rates at the time of etching back the refractory metal layer and the adhesion layer are substantially equal, both are etched to the same extent. As a result, there is no step between the two. Therefore, when the upper layer wiring is formed thereafter, inconvenience such as disconnection does not occur, and the reliability can be improved.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Of course, each invention is not limited by the illustrated embodiment.

Example 1 FIG. 1 is a sectional view of this example in the order of steps. This embodiment embodies the invention of claim 1 of the present application, and provides a miniaturized and integrated semiconductor device applicable to a 16 Mbit class SRAM.

In this embodiment, for example, an opening 2 is formed in a base 1 made of a substrate such as a silicon substrate by a photolithography technique using an ordinary resist process, and then an adhesion layer 3 is formed.
To form a TiN layer. The adhesion layer 3 can be formed under any conditions, for example, under the following conditions.
-It can be formed by a CVD method.

Gas used: TiCl ₄ / NH ₃ / (H ₂ ) / Ar = 10/10 / (100) / 40 SCCM (Hydrogen in parentheses does not need to be used) Pressure: 5 × 10 ^-3 Torr Micro Wave: 800 W RF: 300 W The adhesion layer 3 may be formed by various other methods.

 Thus, the structure shown in FIG. 1A is obtained.

Next, a W layer is formed as the high melting point metal layer 4 by a blanket W-CVD method. Planket W- in this case
The CVD method can be performed under various conditions. For example, BLK-W can be formed under the following conditions.

Pressure: 0.1 to 50 Torr Gas used: WF ₆ / SiH ₄ = 20/30 (gas ratio) Temperature: 375 to 500 ° C. The refractory metal layer 4 may be formed under various other conditions.

 Thus, the structure shown in FIG. 1B is obtained.

Next, the BLK forming the high melting point metal layer 4
−W and the selectivity of TiN forming the adhesion layer 3 is set to 1,
Perform etch back.

In the present embodiment, the BLK-
Etchback was performed by making the etching rates of W and TiN approximately equal. The selectivity can be controlled, for example, by the amount of chlorine gas added. Since TiFx is solid at room temperature, TiN is hard to be etched by a fluorine-based gas, but is etched by a chlorine-based gas.

Specifically, a gas system in which Cl ₂ (chlorine gas) was added to SF ₆ which is a fluorine-based gas was used, and the amount of Cl ₂ added was adjusted to obtain a desired etching rate ratio. That is,
As shown in FIG. ₂ , the etching rate II of TiN increases as the addition amount of Cl ₂ increases, but the etching rate I of BLK-W decreases on the contrary, and there is a Cl ₂ addition amount at which both become equal. (Intersection of speeds I and II). Therefore, etchback is performed under the Cl ₂ addition amount condition.

For example, in the setting of this embodiment, the used gas system: SF ₆ / Cl ₂ = 5/5 to 20 SCCM (appropriate flow ratio in this range is adopted) Pressure: 10 mTorr Applied power: 0.23 W / cm ² Performed etch back. As a result, the etching rate of BLK-W, which is the refractory metal layer 4, and the etching rate of TiN, which is the adhesion layer 3, are made equal to each other, thereby performing the etch back, as shown in FIG. 1 (c). , Both
3 and 4 were obtained with the same depth and etched without any step. (Note that, in FIG. 1 (c), in order to clearly show the progress of the etchback, the etching is extremely deeply drawn in the opening 2, but ideally the opening 2 is just buried. Flat embedding can be achieved).

In addition, the etch-back can be performed by adding O ₂ (oxygen gas) to a fluorine-based gas.
In this case, the selectivity can be controlled by, for example, the amount of O ₂ added. For example, if O ₂ gas is added to fluorine-based gas, TiFx
Is but solid at room temperature, since TiOFx volatilizes, the relationship II third diagram of the relationship I, and O ₂ amount and TiN etch rate of the etching rate of the same O ₂ amount and BLK-W and the As shown in the figure, at the intersection of I and II, a point where both etching rates are equal can be found.

Specifically, for example, it can be from conditions take a selectivity ratio (e.g. conditions described in JP-A-1-130529), the O ₂ most added to the condition that matches the above.

Using this embodiment, the structure shown in FIG. 1C can be obtained.

As described above, in this embodiment, the refractory metal layer 4 in the opening 2 is formed.
And the adhesion layer 3 are etched to the same extent.
Since there is no step, a good wiring structure is obtained when an upper layer wiring is formed thereon, and the reliability is improved.

Example 2 This is a reference example.

 Please refer to FIG.

As shown in FIG. 4A, an adhesion layer 3 is formed on a base having an opening 2 (such as a contact hole).

In this embodiment, Ti / TiON /
The adhesion layer 3 is formed in a laminated structure of Ti = 300/700/300 °.
This structure may be appropriately changed. However, this adhesion layer 3
Has a configuration that can finally function as a barrier metal.

Next, BLK-W is grown, and this is
And For example, BLK-W can be formed by CVD under the following conditions.

Gas used: WF ₆ / SiH ₄ = 20/30 (gas ratio) Pressure: 0.1 to 50 Torr Temperature: 375 to 500 ° C. Thus, the structure shown in FIG. 4 (b) is obtained.

Next, the BLK-W forming the high melting point metal layer 4 is etched back by RIE. At this time, the etch-back is performed under the condition that the etching rate ratio between the two is large so that the selectivity with the adhesion layer 3 can be obtained. In this example, etching back under this condition was performed by etching with a low ion energy using a fluorine-based gas. Since a fluorine-based gas can be etched under a condition of low ion energy, BLK-W forming the high melting point metal layer 4 and, for example, TiON forming the adhesion layer 3 can be used.
Can be selected.

 Specifically, the following etching conditions were used.

Working gas system: SF ₆ = 30 SCCM Pressure: 50 mTorr Applied power: 0.08 W / cm ² As a result, the structure shown in FIG. 4 (c) in which the adhesion layer 3 remained was obtained.

Next, the upper wiring 5 is formed. For example, in the case of forming an Al wiring, the upper wiring 5 is formed by forming, for example, Al-Si (aluminum alloy containing Si-1%) with a thickness of about 4000 °. At this time, the adhesion layer 3 remains, and this serves as a barrier metal, so that the barrier metal has already been formed, and it is not necessary to form it here.

As described above, in the present embodiment, the adhesion layer 3 functioning as a barrier metal is formed in advance on the base 1 having the opening 2, and then the high melting point metal layer 4 made of BLK-W is formed.
When the high melting point metal layer 4 is selectively left in the opening 2, the high melting point metal layer 4 is etched back at a selectivity with respect to the adhesion layer 3 also serving as the barrier metal.
Can be used as it is as a barrier metal.

As described above, in this reference example, it is possible to adopt a configuration that also serves as the barrier metal of the upper wiring and the adhesion layer of BLK-W that forms the high-melting-point metal layer. Therefore, the adhesive layer can be used as it is as a barrier metal for the upper wiring, and the overall throughput can be improved.

〔The invention's effect〕

As described above, according to the present invention, at the time of etch-back, the etching rates of the high-melting-point metal layer and the adhesion layer during the etch-back are substantially equal, so that both are etched to the same extent, and as a result, a step is formed between the two. When the upper layer wiring is formed afterwards, no inconvenience such as disconnection occurs,
Reliability can be improved.

[Brief description of the drawings]

1 (a) to 1 (c) are cross-sectional views showing the steps of Example 1 in order, and FIGS. 2 and 3 show Example-1.
FIG. 4 is a diagram showing a comparison of etching rates between a high melting point metal and an adhesion layer for explaining the above. 4 (a) to 4 (d) are cross-sectional views showing the steps of Example-2 in order. 5 (a) to 5 (c) show a conventional technique. 1 ... Underlayer, 2 ... Opening, 3 ... Adhesion layer, 4 ... High melting point metal layer (BLK-W).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/3065 H01L 21/3205 H01L 21/3213 H01L 21/768

Claims (1)

(57) [Claims] 1. A method for forming a wiring, comprising the steps of: forming a refractory metal layer on a base having an opening, thereby burying the opening; And thereafter performing etch-back using a mixed gas whose mixing ratio is adjusted so that the etching rates of the refractory metal layer and the adhesion layer are substantially equal to each other, and thereafter forming an upper layer wiring. Forming method.