JPH0831826A - Forming interconnection layer - Google Patents

Abstract

PURPOSE:To form an interconnection layer hardly discontinued without causing any defect due to poor machining and with suppressing the resistance from increasing in thermal steps. CONSTITUTION:In a first step, a layer insulation film 2 and plug 6 are formed on a substrate 1. A first layer 70 of Ti, second layer 71 of Si, third layer 72 of Ti and fourth layer 73 made of a material, at least, contg. Al as a main component except Si are formed on the surface of the substrate 1. In a second step, the layers 72 and 73 are reacted to form an Al-Ti reaction layer 74 but an unreacted layer 75 of the layer 72 is left until the laminate of the layers 70-73 is formed into an interconnection pattern 5. In a third step, the layers 71, 75 and 74 are reacted to form an Al-Si-Ti alloy layer 76 between the layers 70 and 73 in a thermal step thereafter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a wiring layer in a semiconductor device.

[0002]

2. Description of the Related Art As semiconductor devices become more highly integrated, device dimensional rules are becoming finer. And
Disconnection due to electromigration or stress migration of an aluminum (Al) wiring layer caused by miniaturization has become a serious reliability problem.

As one of the measures for preventing the disconnection of the wiring layer, there is a method in which the wiring layer has a so-called barrier metal laminated structure. For example, under the layer made of Al or Al alloy,
This is a method of laying a barrier metal layer made of a conductive refractory metal such as titanium (Ti), titanium nitride (TiN), titanium oxynitride (TiON), or titanium-tungsten (TiW), or an intermetallic compound.

In the wiring layer having such a structure, even if the layer made of Al or Al alloy is broken, the redundant effect of the refractory metal prevents the entire wiring layer from being broken. Especially T
It is known that the i barrier metal layer has good adhesion to silicon oxide (SiO ₂ ). Moreover, it is considered that this barrier metal layer reacts with Al to some extent to suppress migration at the interface with the layer made of Al or Al alloy. Therefore, Ti is a very effective barrier metal material.

On the other hand, in order to prevent Al of the wiring layer from penetrating through the Si substrate at the contact portion with the silicon (Si) substrate, Si of about 1% is conventionally mixed with Al of the wiring material. However, the incorporation of Si is no longer useful with the application of the barrier metal layer described above. On the contrary, Si is deposited during the formation of the wiring pattern, which causes a large defect of processing failure. Therefore, Al that does not contain Si or an Al alloy that does not contain Si, for example, an aluminum-copper (Al-Cu) alloy has begun to be applied to wiring materials.

[0006]

However, in Al or Al alloy containing no Si, the reaction between Al and Ti is likely to proceed. Therefore, in a thermal process such as the formation of an interlayer film or the sintering that is performed after forming the wiring layer, Al and Ti
As the reaction with the Ti (III) -Al alloy (TiAl
_A reaction layer consisting of ₃ ) is formed. The formation of this reaction layer causes a problem that the resistance of the wiring layer increases.

The present invention has been made in order to solve the above-mentioned problems, and it is possible to form a wiring layer that is hard to break without causing a processing defect and suppressing an increase in resistance in a thermal process. It is intended to provide a way.

[0008]

In order to solve the above problems, in the method for forming a wiring layer of the present invention, first, in the first step, a first layer made of Ti and a second layer made of Si are formed on the surface of the substrate. Are sequentially formed. Furthermore, on the second layer, a third layer made of Ti
A layer and a fourth layer made of a material containing at least Al as a main component and not containing Si are sequentially formed. Then, in the second step, the third layer and the fourth layer are reacted with each other to form Al-T until the laminated body including the first layer to the fourth layer is formed into the wiring pattern.
i Form a reaction layer. Along with this, the unreacted layer of the third layer is left. Next, in the third step, the second heating step is performed.
The layer, the unreacted layer, and the Al-Ti reaction layer are reacted. And, Al-Si-Ti is formed between the first layer and the fourth layer.
It is a method of forming an alloy layer consisting of.

Further, in the present invention, the heating step is performed at 200 ° C.
It is a method of forming a wiring layer, which is a thermal process involving heating at a predetermined temperature in the range of 550 ° C.

[0010]

In the present invention, Al-
A Ti reaction layer is formed and a third unreacted layer is left. Therefore, in the step of forming the wiring pattern, the S of the second layer is formed.
Since i and Al of the fourth layer are not in direct contact with each other, no Si precipitate is generated. Further, in the subsequent thermal process, the reaction between Al and Ti is suppressed by Si of the second layer, and Al-
The reaction proceeds in the direction of forming an Si-Ti alloy layer.

[0011]

Embodiments of the method for forming a wiring layer according to the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram showing an example of the present invention, showing a case where a substrate provided with a first interlayer film and a plug is used as a base and a wiring layer is formed on the surface thereof.

That is, as shown in FIG. 1A, in this embodiment, the element isolation region 11 is formed in the substrate 1 made of Si so as to surround the region 10 where the element is to be formed. A source / drain diffusion layer 12 is formed in the intended region 10. A first interlayer film 2 is formed on the substrate 1, and a contact hole 3 is formed in the first interlayer film 2. Then, for example, tungsten (W) is buried in the contact hole 3 via the barrier metal layer 4a to form the plug 4.

As described above, in this embodiment, the first
Using the substrate 1 provided with the interlayer film 2 and the plug 4 as a base, the first step shown in FIG. 1B is performed. First, the first layer 70 made of Ti is formed on the surfaces of the first interlayer film 2 and the plug 6. On the first layer 70, a second layer 71 made of Si,
A third layer 72 made of Ti is sequentially formed. Furthermore the third
A fourth layer 73 made of a material containing at least Al as a main component and not containing Si is formed on the layer 72.

Here, the third layer 72 is the next wiring pattern 5
When it reacts with the fourth layer 73 before the formation of, the thickness is formed such that an unreacted layer remains. These first layer 70 to fourth layer 7
For example, a sputtering method is used for the film forming methods up to 3.

In the following, the first layer 70 is formed to a film thickness of about 25 nm, the second layer 71 and the third layer 72 are formed to a film thickness of about 5 nm, respectively, and is further made of Al-0.5% Cu. An example of the sputtering conditions when forming the fourth layer 73 with a film thickness of about 500 nm will be described.

First, in forming the first layer 70, an argon (Ar) gas is used as a sputtering gas. Then, the flow rate of Ar gas into the film forming atmosphere is 100 sccm (standard cubic
cm / min), the heating temperature of the substrate 1 is set to about 150 ° C., the DC power is set to 5 kW, and the pressure of the film forming atmosphere is set to about 0.4 Pa.

In the film formation of the second layer 71, Ar gas is used as the sputtering gas, and the flow rate of Ar gas into the film formation atmosphere is 1
00sccm, the heating temperature of the substrate 1 is about 150 ° C,
The direct current power is set to 10 kW and the pressure of the film forming atmosphere is set to about 0.4 Pa.

In forming the third layer 72, the same setting conditions as in the case of the first layer 70 are used. Further, in forming the fourth layer 73, Ar gas is used as a sputtering gas, the flow rate of Ar gas into the film forming atmosphere is about 100 sccm, the heating temperature of the substrate 1 is about 150 ° C., the DC power is 10 kW, and the film forming atmosphere is The pressure is set to about 0.4 Pa.

Next, in a second step shown in FIG. 1C, a resist film (not shown) is formed on the fourth layer 73. After that, the laminated body including the first layer 70 to the fourth layer 73 is patterned by lithography and etching to form the wiring pattern 5.

By the time the wiring pattern 5 is formed,
The Al—Ti reaction layer 74 is formed by reacting the third layer 72 and the fourth layer 73. The Al-Ti reaction layer 74 is mainly composed of Ti.
It consists of Al ₃ . Further, the Al—Ti reaction layer 74 is formed and the unreacted layer 75 which is a part of the third layer 72 is left. After that, the resist film is removed by, for example, plasma asher processing or wet processing.

In the first step, the first layer 70 is formed to a film thickness of about 25 nm, the second layer 71 and the third layer 72 are formed to a film thickness of about 5 nm, respectively. Cu
An example of etching conditions for the wiring pattern 5 when the fourth layer 73 made of is formed to a film thickness of about 500 nm is shown below.

As the etching gas, for example, boron trichloride (BCl ₃ ) gas and chlorine (Cl ₂ ) gas are used. Then, the flow rate of each gas is set to BCl ₃ / Cl ₂ = 60
/ 90 sccm, the pressure in the reaction chamber is about 2 Pa, the high frequency power is about 50 W, and the microwave current is about 0. Etching is performed by setting it to about 3A.

Next, as shown in FIG. 1D, in the third step, the second layer 71 in the wiring pattern 5 is formed in the subsequent heat step.
And the unreacted layer 75 and the Al—Ti reaction layer 74 are reacted. Then, between the first layer 70 and the fourth layer 73, Al-S
An i-Ti ternary alloy layer 76 is formed.

The above heating step is a step involving heating at a predetermined temperature in the range of about 200 ° C to 550 ° C. For example, a step of forming the second interlayer film 7 on the first interlayer film 2 so as to cover the wiring pattern 5 by a CVD method, 400
Examples include a step of sintering at about ° C. Through the above steps, the wiring layer 6 including the wiring pattern 5 of the first layer 70, the Al—Si—Ti ternary alloy layer 76, and the fourth layer 73 is formed.

In the above embodiment, the first layer 70 made of Ti is used.
After the second layer 71 made of Si is formed between the third layer 72 and the third layer 72, the Al—Ti reaction layer 7 is formed until the wiring pattern 5 is formed.
4 is formed and the unreacted layer 75 of the third layer 72 is left. Therefore, in the process of forming the wiring pattern 5, the second layer 7
Since Si of 1 does not directly contact with Al of the fourth layer 73,
No Si precipitate is generated.

The lower layer of the Al--Ti reaction layer 74 is
Since the second layer 71 of Si is formed via the unreacted layer 75, in the subsequent thermal process, the reaction in the direction of forming the Al-Si-Ti ternary alloy layer 76 is performed rather than the reaction of Al and Ti. Advances. That is, the reaction between Al and Ti is suppressed by Si, and the increase in resistance due to the formation of TiAl ₃ is suppressed.

Therefore, according to the above-mentioned embodiment, the wiring layer 6 which is not easily broken can be formed without causing a processing defect due to the deposition of Si. Further, since the increase in resistance is suppressed in the heating step, the wiring layer 6 having low resistance and high reliability can be formed with high yield.

In the above embodiment, the case where the wiring layer 6 is formed on the plug 4 has been described, but the wiring layer 6 having the above structure can be formed even in the contact hole 3 in which the plug 4 is not embedded. is there.

In the above embodiment, the case where the antireflection film is not formed on the fourth layer 73 has been described.
Even if an antireflection film is formed on 3 and the wiring pattern 5 is formed and the heating step is performed, the same effect as that of the above-described embodiment can be obtained.

FIG. 2 is a sectional view showing an example of the process of forming the antireflection film. As shown, the antireflection film 8 is formed by
It is performed between the first step and the second step. For example, after forming the fourth layer 73, silicon oxynitride (SiO 2) is formed under the following conditions.
The antireflection film 8 made of N) film is formed.

Silane (SiH ₄ ) gas and nitrous oxide (N ₂ O) gas are used as reaction gases. Further, the flow rate of each gas is SiH ₄ / N ₂ O = about 50/25 sccm, the film forming temperature is about 360 ° C., and the film forming atmosphere pressure is 33.
The high frequency power is set to about 0 Pa and the high frequency power is set to about 800 W. As a result, the antireflection film 8 having a film thickness of about 25 nm is formed.

Here, by forming the antireflection film 8 on the fourth layer 73, the heat applied to the laminated body of the first layer 70 to the fourth layer 73 is reflected by the end of the second step described above. The amount of the prevention film 8 formed increases. Therefore, when the antireflection film 8 is formed, the thickness of the third layer 72 made of Ti is set to be thicker than that in the above-described embodiment. Therefore, as compared with the above-mentioned embodiment, S is deeper than the surface of the fourth layer 73.
The second layer 71 made of i will be provided.

For example, the depth can be calculated as follows. That is, in general, the diffusion coefficient D is expressed by the equation (1)
It is known to be represented as.

[0034]

[Equation 1] Here, k = 8.6 × 10 ⁻⁵ eV / K. Further, D ₀ and Ea are values peculiar to the substance, and Ti that reacts with Al
D ₀ and Ea of the above are Do ≈0.15 cm ² / s from the literature values.
ec and Ea≈1.85 eV.

Therefore, at T = 360 ° C., Ti
The diffusion coefficient D can be calculated as in equation (2).

[Equation 2]

On the other hand, it is known that the diffusion distance L is expressed by the equation (3).

(Equation 3) Therefore, for example, the diffusion distance L of Ti that diffuses into Al when the heating step is performed for 30 minutes is calculated as in Expression (4).

[0037]

[Equation 4] From this result, the film thickness of the third layer 72 made of Ti is set to about 10 nm with a margin. That is, the depth from the surface of the third layer 72 to the second layer 71 made of Si is set to about 10 nm, which is deeper than that in the above-described embodiment.

Therefore, when the thicknesses of the first layer 70 to the third layer 72 are the same as those in the above embodiment, if the thickness of the third layer 72 is set to about 10 nm as described above, for example, the second layer 71 is used. Is about 5 nm, and the first layer 70 is about 20 nm thick.

[0039]

As described above, in the wiring layer forming method of the present invention, the Al—Ti reaction layer is formed and the third unreacted layer is left until the wiring pattern is formed. Therefore, in the step of forming the wiring pattern, the second layer Si and the fourth layer Al do not come into direct contact with each other, and no Si precipitate is generated. Therefore, a wiring layer that is difficult to break is formed without causing processing defects. can do.

In the subsequent heating step, the reaction between Al and Ti is suppressed by the Si in the second layer, and Al-Si-T
Since the reaction proceeds in the direction of forming the alloy layer of i, Al and T
The increase in resistance due to the reaction with i is suppressed. Therefore, according to the present invention, a wiring layer having low resistance and high reliability can be formed with high yield.

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of the present invention.

FIG. 2 is a cross-sectional view showing an example of a process of forming an antireflection film.

[Explanation of symbols]

 1 Substrate (Base) 5 Wiring Pattern 6 Wiring Layer 70 First Layer 71 Second Layer 72 Third Layer 73 Fourth Layer 74 Al-Ti Reaction Layer 75 Unreacted Layer 76 Al-Si-Ti Ternary Alloy Layer

Claims (2)

[Claims] 1. A first layer made of titanium on the surface of a substrate,
A second layer made of silicon and a third layer made of titanium,
A first step of sequentially forming a fourth layer made of a material containing at least aluminum as a main component and not containing silicon, and forming a laminate of the first layer to the fourth layer into a wiring pattern, A second step of reacting the third layer with the fourth layer to form an aluminum-titanium reaction layer and leaving an unreacted layer of the third layer, and a subsequent heating step, the second layer and the unreacted layer. A third step of reacting a reaction layer with the aluminum-titanium reaction layer to form an alloy layer of aluminum-silicon-titanium between the first layer and the fourth layer. Method for forming wiring layer. 2. The method for forming a wiring layer according to claim 1, wherein the heating step is a heating step involving heating at a predetermined temperature in a range of 200 ° C. to 550 ° C.