JPH05217965A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a preprocess method capable of preventing a formation of an insulation layer composed of a layer insulating film on a surface layer of a first wiring layer exposed on a through hole bottom and also effectively removing a fluorocarbon group polymer formed on the surface layer of the first wiring layer in a process for forming the through hole. CONSTITUTION:A substrate 1 is first introduced into a preprocess chamber inside a film-forming device and treated in plasmas generated by using preprocess gas 7 mixed with CF4 and O2, to remove a polymer 6 formed on a first wiring layer 2 in a process for forming a through hole. The preprocess gas 7 produces an active species which is rich in reactivity with silicon and its oxide film, whereby an insulation layer composed of a layer insulating film 3 is formed on a surface layer of the first wiring layer 2 exposed on a through hole bottom, and thereafter through a film-forming process, the first wiring layer 2 can be connected to a second wiring layer 9 without forming the insulation film between them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a pretreatment method for forming a wiring layer.

[0002]

2. Description of the Related Art Conventionally, a pretreatment method for forming a wiring layer of this type has been performed as shown in FIGS. That is, Al already formed on the substrate 1
Of the through hole to the interlayer insulating film (silicon oxide film) 3 by reactive ion etching using a fluorocarbon-based gas alone or a mixed etching gas 5 of O ₂ to establish connection with the first wiring layer 2. Formation process (Fig. 2 (a),
In (b)), Ar or the like is used for the purpose of removing the fluorocarbon-based polymer 6 formed on the surface layer of the first wiring layer 2 exposed at the bottom of the through hole during the over-etching performed near the end thereof. Was performed by the sputter etching by the high frequency discharge using the pretreatment gas 10 having a relatively large sputtering field (see FIG. 2C).

[0003]

According to this method, the fluorocarbon polymer 6 formed on the surface of the first wiring layer 2 exposed at the bottom of the through hole of the interlayer insulating film 3 is removed, and at the same time, the through hole is formed. Even the interlayer insulating film 3 exposed at the shoulder of the hole is sputter-etched, and the insulating layer 8 is formed by reattaching the interlayer insulating film 3 on the surface layer of the first wiring layer 2 exposed at the bottom of the through hole. (FIG. 2D), the performance and reliability of the finally completed semiconductor device were significantly deteriorated.

Therefore, it is an object of the present invention to provide a pretreatment method which does not have such drawbacks.

[0005]

According to a method of manufacturing a semiconductor device of the present invention, an interlayer insulating film layer covering a first wiring layer provided on a semiconductor substrate on which a semiconductor element is formed is provided with a second wiring layer. Through holes for establishing electrical continuity are formed by reactive ion etching using a fluorocarbon-based gas alone or a mixed gas with O ₂ reflecting the mask pattern formed by the photolithography method, and the mask is formed. After the pattern is removed, it is provided in the apparatus for forming the second wiring layer and can be transferred to the processing chamber for forming the wiring layer in a state where it is shielded from the outside air by vacuum or an inert gas. In the pretreatment process for forming the second wiring layer performed in the treatment chamber, the fluorocarbon gas or a part or all of the fluorocarbon gas is contained. Nitrogen of carbon, sulfur, characterized in that for mixing gas plasma processing using a plasma generated by using a single gas which is substituted compound is replaced with either a hydrogen, or a O _2, also It has a feature of using high frequency discharge or microwave discharge to generate plasma.

[0006]

The present invention will be described below with reference to the drawings. 1A to 1D are cross-sectional views showing, in the order of steps, the steps up to forming a second wiring layer using the pretreatment method according to the present invention. Al on the substrate 1 on which elements have already been formed
After forming the first wiring layer 2 having a thickness of 0.5 μm,
A silicon oxide film having a thickness of 0.6 μm is formed as an interlayer insulating film 3 on the first wiring layer 2, and a mask pattern of a through hole is formed on the interlayer insulating film 3 with a photoresist 4 (FIG. 1). (A)).

Next, reactive ion etching is performed using CF ₄ etching gas 5 alone to form a through hole in the interlayer insulating film 3. At this point, a fluorocarbon-based polymer 6 is formed on the Al first wiring layer 2 (see FIG. 1).
(B)). After removing the photoresist 4 by using O ₂ plasma, the substrate 1 is placed in a film forming apparatus equipped with a pretreatment chamber for microwave discharge to form a second wiring layer 9 of Al.
To introduce. In this film forming apparatus, the pretreatment chamber and the film forming chamber are connected by a transfer chamber kept in a high vacuum, and the substrate 1 is not exposed to the outside air.

In the film forming apparatus, the substrate 1 is first transferred to the pretreatment chamber, and the pretreatment gas 7 mixed at a flow rate ratio of CF ₄ 100 sccm and O ₂ 100 sccm is used to generate a microwave output of 1 KW. Then, the fluorocarbon polymer 6 formed on the first wiring layer 2 is removed by processing in the plasma (FIG. 1C). Even with this pretreatment gas, the interlayer insulating film 3 exposed on the shoulder portion of the through hole is etched as in the conventional method, but the pretreatment gas 7 itself produces active species highly reactive with silicon and its oxide film. However, since these are converted into reaction products having a high vapor pressure, a new insulating layer made of a silicon oxide film is not formed on the surface layer of the first wiring layer 2 exposed at the bottom of the through hole.

Immediately after removing the polymer 6, the substrate 1
Is transferred to the film forming chamber without being exposed to the outside air to form a second wiring layer 9 of Al (FIG. 1D), and the second wiring layer 9 is formed between the first wiring layer 2 and the second wiring layer 9. The connection can be made without forming an insulating layer.

In the above embodiment, the plasma treatment was carried out using a mixed gas system of CF ₄ and O _2.
Similar effects can be obtained by replacing the plasma treatment with plasma generated by using a gas such as ₆ , NF ₃ or HF alone or a mixed gas with O ₂ .

In the above embodiments, the microwave discharge is used to generate the plasma, but the same effect can be obtained by replacing the microwave discharge with the high frequency discharge. In this case, there is an advantage that the size of the entire device can be reduced as compared with the case where microwave discharge is used.

[0012]

As described above, in the pretreatment method according to the present invention, the surface layer of the first wiring layer exposed at the bottom of the through hole cannot be escaped by the conventional pretreatment method for forming the wiring layer. To prevent the formation of an insulating layer due to redeposition of an interlayer insulating film, and to use a fluorocarbon gas alone or O
_{In the} process of forming a through hole in an interlayer insulating film using reactive ion etching using a mixed gas system with ₂ , the first wiring layer exposed at the bottom of the through hole during overetching performed near the end of the through hole is formed. There is an effect that the fluorocarbon-based polymer formed on the surface layer can be effectively removed. This makes it possible to form multilayer wiring without deteriorating the performance and reliability of the finally completed semiconductor device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing steps (a) to (d) of one embodiment of the present invention.

2A to 2D are cross-sectional views showing steps (a) to (d) until a second wiring layer is formed by using a conventional pretreatment method in the order of steps.

[Explanation of symbols]

1 substrate 2 first wiring layer (Al) 3 interlayer insulating film (silicon oxide film) 4 photoresist 5 etching gas (CF ₄ ) 6 fluorocarbon-based polymer 7 pretreatment gas (CF ₄ + O ₂ ) 8 insulating film 9 second Wiring layer (Al) 10 Pretreatment gas (Ar)

Claims (2)

[Claims] 1. A through hole is formed by photolithography in an interlayer insulating film, which covers a first wiring layer provided on a semiconductor substrate having a semiconductor element formed thereon, for establishing electrical connection with a second wiring layer. The mask pattern is formed by reactive ion etching using a fluorocarbon-based gas alone or a mixed gas with O _2, and after removing the mask pattern, a second wiring layer is formed. In order to form the second wiring layer, which is provided in the apparatus and can be transferred to the processing chamber for forming the wiring layer, in a state where it is shielded from the outside air by a vacuum or an inert gas In the pretreatment process of step 1, the fluorocarbon-based gas or a substitution product in which a part or all of the carbon contained in the fluorocarbon-based gas is replaced with nitrogen, sulfur, or hydrogen The method of manufacturing a semiconductor device which is characterized in that the sole is gas or a plasma treatment using a plasma generated by using a mixed gas of O _2. 2. The method of manufacturing a semiconductor device according to claim 1, wherein high frequency discharge or microwave discharge is used to generate plasma in the plasma processing.