JPH05102064A - Method for manufacturing semiconductor device - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] A method for forming a metal plug in a via hole 3 in a semiconductor device, particularly a method for forming a metal plug using a laser melting technique. A method for forming a metal plug by forming a thin metal continuous film on the sidewall of a via hole and laser melting the same is provided. [Structure] Before depositing the metal thin film for plug formation, the thickness
It is configured to have a step of forming a base film 6 made of a material having a good wettability of 50 nm or less and a step 4 of depositing the plug forming metal material 4 at a substrate temperature of 100 ° C. or less.

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 metal plug in a via hole in a semiconductor device, and more particularly to a method for forming a metal plug using a laser melting technique.

Recently, in a semiconductor device which is highly integrated, miniaturization of each element, flattening of wiring layers, and a method of connecting each wiring layer are important keys.

[0003]

2. Description of the Related Art In wiring used in integrated circuits,
Conventionally, a conductor film is deposited by a method such as vapor deposition or sputtering. However, in this case, the step coverage rate of the via hole is generally small, and the step coverage rate becomes smaller and smaller as the diameter of the via hole becomes smaller. This is because the shadow effect reduces the amount of the conductor film on the sidewall of the via hole.

In order to solve this problem, a method of embedding a conductor film in the entire via hole (metal plug forming method)
Is effective. If the metal plug can be easily formed, the wiring layer is flattened, which solves the problem of the depth of field during lithography exposure, and the layout in which one via hole is placed directly above another via hole is also possible. Therefore, the metal plug forming technique is very convenient for the multilayer wiring layer.

In the metal plug forming technique, a conductor film pattern (metal cap) formed by covering and patterning a via hole is irradiated with a pulse laser beam to melt the metal cap and move the metal to move the plug. Form. (Laser Plug Forming Method) FIG. 3 is a schematic diagram for explaining the laser plug method. In Fig. 3 (a), a via hole 53 is formed in an insulator layer 52 on a Si substrate (or Si layer) 51, a metal film is deposited by a physical vapor deposition method such as a sputtering method, and the via hole 53 is covered. After that, a metal cap 54 formed by patterning the metal film is shown. 3B is a metal plug formed by irradiating the metal cap 54 of FIG. 3A with pulsed laser light to melt the metal cap and moving the metal.
55 is shown. The thickness of the metal cap 54 is set to 0 in order to avoid damage to the Si layer 51 due to laser light irradiation.
By reducing the thickness to less than 5 μm, the irradiation pulse energy density required for plug formation is reduced.

In general, the deposition of a metal film starts with island-like growth first, and then it progresses into a network-like growth, and finally it progresses to continuous film growth. Therefore, when the film thickness is thin, there is a high possibility that the deposition will end at the island stage. Especially, on the sidewall of the via hole, the probability of metal atoms coming in is small, so the possibility of deposition ending at the island stage is even greater.

FIG. 4 is a schematic diagram for explaining the laser plug method from the continuous film state. FIG. 4 (a) is a diagram showing a state in which a metal film is formed in a continuous film state on the sidewall of the via hole 53. By laser melting the metal film in this state, a desired plug 55 as shown in FIG. 4 (b) is formed.

FIG. 5 is a schematic diagram for explaining the laser plug method from a discontinuous film state. FIG. 5 (a) is a diagram showing a state in which a discontinuous metal film such as island-shaped growth or mesh-shaped growth is formed on the sidewall of the via hole 53. When the metal film in this state is laser-melted, part or all of the metal film on the side wall is mass-transferred to the top or bottom of the via 53, as shown in FIG. 5 (b).
The void 56 shown in FIG.

Even if the metal film thickness is thin, a thin continuous film can be obtained if the continuous film growth can be started quickly.
Therefore, one way is to weaken the aggregating action of incoming metal atoms. That is, a metal having a small aggregation action may be selected as the metal to be deposited.

[0010]

[Problems to be Solved by the Invention] However, conventional LSI, VLS
Aluminum (Al), which has excellent conductivity, is the most popular material for wiring used in semiconductor devices such as I. On the other hand, this Al exhibits strong cohesive action when deposited on the SiO ₂ interlayer insulating layer. Therefore, there is a demand for a new method in which Al can be used as a metal cap material.

Therefore, the present invention provides a method of forming a continuous film of a thin metal on a sidewall of a via hole by reducing a cohesive action peculiar to a metal, and forming a metal plug by laser melting the continuous film. To aim.

[0012]

[Means for Solving the Problems] The above-mentioned problems are caused by the wettability of 50 nm or less before depositing a metal thin film for forming a plug.
The process of forming a base film made of a good material is 100 °
The metal material for forming the plug (A
l) is solved by a method for forming a metal plug.

FIG. 1 is a diagram for explaining the principle of the present invention. As shown in the figure, only the side wall and the bottom of the via hole 3 formed on the Si substrate 1 are coated with the material for the plug metal having good "wettability" as the base film 6. An Al thin film 4 serving as a metal cap is formed thereon as a continuous film. The desired metal plug is obtained by laser melting this metal cap.

[0014]

[Operation] As described above, in the initial stage of metal film deposition,
In order to quickly realize a continuous film state, it is necessary to weaken the agglomeration action when flying metal atoms are deposited. Therefore, in the present invention, titanium (Ti) or titanium nitride (Ti
The material film 6 having good "wettability" of flying metal such as N) is formed as a base. However, if the material film 6 with good "wettability" is also formed on the upper surface of the insulator layer 2, when the metal cap 4 is melted, the molten metal on the upper surface of the insulator layer 2 inhibits mass transfer. As a result, it becomes difficult for molten metal to flow into the via hole 3, and the void 56 in Fig. 5 (b)
Can occur. Therefore, as shown in Fig. 1, the material film 6 having good "wettability" needs to be formed only on the side wall and the bottom of the via hole 3.

When the material film 6 having good “wettability” is Ti, when the metal cap is laser-melted, the Ti film is also melted at the same time, so that it becomes difficult for the cap metal to flow into the via hole 3. There is no such thing.

On the other hand, by maintaining the substrate temperature at 100 ° C. or lower when forming the cap metal, the cohesive force of the metal is reduced.

[0017]

EXAMPLES Examples of the present invention will be described below. Figure
2 is a schematic view for explaining a manufacturing process for forming a metal plug.

As shown in FIG. 2 (a), the surface of the Si substrate 1 is oxidized to form a Si oxide film (SiO ₂ film) 2 and a via hole 3 is formed in the SiO ₂ film 2 by a normal method. To do. As shown in Fig. 2 (b), a TiN film with a thickness of 100 nm is deposited as a base material film 6 having good "wettability" by an ordinary sputtering method.

As the base material film 6 having good “wettability”, Ti
Instead of the N film, a Ti film with a thickness of 20 nm can be used. As shown in Fig. 2 (c), RIE (Reactive Ion Etch
ing) method, the Ti film 6 is removed so that it remains only on the sidewall of the via hole 3.

As shown in FIG. 2 (d), an Al film having a thickness of about 200 nm is deposited by a normal sputtering method. At this time, the substrate temperature is maintained at a constant temperature in the range of room temperature to 100 ° C. Then, this is patterned to form a metal cap 4.

As shown in FIG. 2 (e), pulsed laser irradiation is performed to melt the metal cap 4 by laser and form a metal plug 5 in the via hole 3. A XeCl excimer laser was used as the laser, and the pulse energy density was about 0.6.
It is J / cm ² .

As a base material film 6 having good “wettability”, TiN
If a Ti film is used instead of the film, cap metal 4
Since the Ti film also melts at the same time when laser melting of
The step corresponding to (c) can be omitted.

[0023]

According to the present invention, it is possible to form a thin metal continuous film on the side wall of a via hole and laser-melt it to form a metal plug. As a result, high integration of a semiconductor device, It greatly contributes to the manufacturing technology for higher density.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention.

FIG. 2 is a schematic diagram for explaining a manufacturing process of forming a metal plug.

FIG. 3 is a schematic diagram illustrating a laser plug method.

FIG. 4 is a schematic diagram illustrating a laser plug method from a continuous film state.

FIG. 5 is a schematic diagram illustrating a laser plug method from a discontinuous film state.

[Explanation of symbols]

 1, 51 Si substrate 2, 52 Insulator layer 3, 53 Via hole 4, 54 Metal cap 5, 55 Metal plug 6 Underlayer film with good wettability

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/3205 21/90 A 7353-4M

Claims (3)

[Claims] 1. A semiconductor device in which a via hole formed in an insulating layer on a semiconductor substrate and a metal cap layer arranged only around the via hole are laser-melted to embed the cap layer metal in the via hole to form a metal plug. In the wiring method, before forming the metal cap layer, a base film made of a material having better wettability to the cap layer metal than the insulator layer is formed on the insulator layer by covering the via hole. A method of manufacturing a semiconductor device, comprising: a step; and a step of depositing the metal cap layer. 2. The method according to claim 1, further comprising a step of removing a base film made of a material having a good wettability, which is deposited on a portion other than at least a side wall and a bottom portion of the via hole, before forming the metal cap layer. 1. The method for manufacturing a semiconductor device according to 1. 3. The method of manufacturing a semiconductor device according to claim 1, wherein when the metal of the cap layer is aluminum, the base film is selected from titanium and titanium nitride.