JPH07111265A - Wiring formation method - Google Patents

Abstract

(57) [Summary] [Object] To provide a wiring forming method capable of forming a wiring having a tapered surface on a shoulder portion by one-step dry etching. [Structure] The Al film formed on the insulating film 11 is a resist 1
Etching is performed using 3 as a mask to form a tapered surface 13A on the shoulder of the resist 13. As the etching progresses and the tapered surface 13A of the resist recedes, the shoulder portion of the Al wiring 12 is also exposed and processed into the tapered surface 12C. Therefore, the step difference of the Al wiring is relaxed, and the coverage of the interlayer insulating film 15 is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring forming method. The present invention can be used in the field of manufacturing semiconductor devices.

[0002]

2. Description of the Related Art In recent years, with the increase in the speed and integration of LSIs, the demand for an increase in the number of wiring layers and miniaturization of wiring patterns has rapidly increased even in a multilayer wiring structure, and the multilayer wiring technology has been developed in a submicron process. It has become an important issue. In this multilayer wiring technique, it is an urgent task to realize the flattening of the wiring pattern step and the flattening of the interlayer insulating film.

Conventionally, as shown in FIG. 3, an Al wiring 2 having a rectangular cross section is patterned on an insulating film 1 formed on the surface of a semiconductor substrate, and a SiO ₂ insulating film 3 and the like are formed on the Al wiring 2 by CVD. It was deposited by the method. However, the SiO ₂ insulating film 3 has an overhang portion 3A above the shoulder portion of the Al wiring 2. For this reason, when forming an upper wiring layer,
There is a problem that Al residue (stringer) is generated under the step portion and causes a short circuit between wirings. Therefore, as a means for avoiding this, as shown in FIG. 4, a flattening process such as an etch-back is introduced to form a structure in which a plurality of insulating films 4, 5 and 6 are laminated. The insulating film 4 serves as a sidewall that alleviates a steep step of the Al wiring 2. However, this method has a problem that the number of steps is increased because deposition of an insulating film and etching back are repeated.

In contrast to the conventional technique in which the Al wiring 2 has a rectangular cross section, the technique disclosed in Japanese Patent Laid-Open No. 2-303033 discloses means for processing the shoulder portion of the Al wiring into a tapered surface. In this method, a tungsten silicide (WSix) film is previously formed on the Al surface, a photoresist is patterned thereon, and the WSix film is isotropically etched to reduce the line width on the Al film. The process is performed by switching to anisotropic etching of the film.

[0005]

However, in such a conventional technique, the W film is etched before the Al film is etched.
Since a step of forming a cap layer such as a Six film and a step of isotropically etching only the cap layer are required, there is a problem in that there are many steps other than the dry etching of the Al film. Furthermore, because the controllability of isotropic etching of the cap layer is not good, the cap layer is lost by isotropic etching in the submicron process.
There was a problem that resist peeling occurred.

The problem to be solved by the present invention is to reliably form a tapered surface on the shoulder portion of the wiring without increasing the number of steps, reduce the wiring step, improve the coverage of the interlayer insulating film, and improve the reliability. What kind of means should be taken to form a high wiring.

[0007]

Therefore, according to the present invention, after a wiring material film is formed on a substrate, a resist is patterned on a portion where a wiring is to be formed, and a reaction sub film is formed on the etching side surface of the wiring material film. A side wall protective film made of a material to be formed is formed, and dry etching for forming a tapered surface on a resist shoulder portion is advanced along with etching to expose the processed shoulder portion of the wiring from the shoulder tapered surface of the resist. The processing means is to process the shoulder portion of the wiring into a tapered surface.

[0008]

The resist patterned on the wiring material film serves as a mask, and the wiring material film in the region not covered with the resist is etched and dug down. At this time, a reaction by-product of the resist and the etchant adheres to the side surface of the wiring processed portion as a sidewall protective film. Since this reaction by-product is mainly generated from a large area of the resist shoulder exposed to the etchant, the resist shoulder is processed into a tapered surface. Further, as etching progresses, the shoulder portion of the wiring starts to be exposed from the tapered surface of the resist, and the shoulder portion of the wiring is also processed into the tapered surface. At this time, the resist film thickness may be set before the etching so that the region of the wiring material film which is not covered with the resist is already removed by etching to be in the over-etched state.

For example, if the wiring material film is Al (Al-1% S
i) If the film is a novolac-based resist,
Boron trichloride (BCl ₃ ) and chlorine (Cl ₂ ) are used as etching gases, and the etching selection ratio is Al / resist =
The thickness is set to about 1.6, and the film thickness is, for example, 1 for Al.
On the other hand, the resist can be set to about 0.8 to 1.5. Further, when the wiring material film is W, Mo, Cn or the like, the same effect can be obtained by appropriately changing the etching gas and other conditions.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the wiring forming method according to the present invention will be described below with reference to the embodiments shown in FIGS. 1 (A) to 1 (C) and FIGS. The present embodiment is an example in which the present invention is applied when the wiring material film is Al.

First, in this embodiment, as shown in FIG. 1A, an Al film 12 is formed on an insulating film 11 made of SiO _{2 by} , for example, a sputtering method, and a resist 13 is patterned thereon. . Then, the wafer was set in a microwave etcher, and dry etching was performed under the following conditions.

Etching gas and its flow rate BCl ₃ / Cl ₂ = 60/90 sccm pressure 8 mTorr power 80 W μwave current 300 mA etching rate ratio value Al / resist = 1.5 etching proceeds under the above conditions Then, as shown in FIG. 1B, the Al film 12 is etched by using the resist 13 as a mask. At this time, the upper portion of the resist 13 is also etched by the etchant, but since the resist shoulder has a large surface area, it is easily etched and the tapered surface 13 as shown in FIG. Further, due to the etched resist and etchant, for example, a CClx-based reaction by-product adheres to the side surface of the resist and the side wall of the wiring processed portion 12A as the side wall protection film 14. Figure 1
(C) shows a state where the Al film 12 is just etched. In this state, although the Al wiring 12B is formed, the taper processing of the shoulder portion is not completed.

Then, when further over-etching is performed, the shoulder portion of the Al wiring 12 is exposed from the tapered surface 13A of the resist 13 as shown in FIG.
Processed to 2C. Next, the etching is finished in this state, and a wet process for removing the ashing for resist and for removing the side wall protection film 14 is performed.

The Al wiring 12 thus formed
Has a tapered shoulder 12C, so that a steep step is alleviated. As shown in FIG. 2B, even if the interlayer insulating film (SiO ₂ ) 15 is deposited in the subsequent process, it is possible to improve the step coverage without forming an overhang portion in the interlayer insulating film 12. did it.

Although the embodiment has been described above, the present invention is not limited to this, and various materials and various conditions can be changed.

For example, although Al is used as the wiring material in the above embodiment, it can be applied to various wirings such as Cu, W, and Mo. Incidentally, when W is used, a CFx-based sidewall protection film can be formed by using a fluorine-based etching gas.

The underlying insulating film of the wiring may be either a silicon oxide film or an interlayer insulating film.

[0018]

As is apparent from the above description, according to the present invention, the step coverage of the insulating film covering the wiring is improved and the flatness is improved. Further, since the flatness is improved, there is an effect of preventing the occurrence of a trigger or the like and preventing a short circuit between wirings. Further, since the etching process only needs to be performed once, the number of processes can be reduced. Therefore, it is possible to improve the multilayer wiring technology and further increase the device speed and integration.

[Brief description of drawings]

1 (A) to 1 (C) are cross-sectional views of essential parts showing an embodiment of the present invention.

2A and 2B are cross-sectional views of the essential part showing an embodiment of the present invention.

FIG. 3 is a sectional view of a main part of a conventional example.

FIG. 4 is a sectional view of a main part of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Insulating film 12 ... Al film 12A ... Wiring processing part 12B ... Al wiring 12C ... Tapered surface 13 ... Resist 13A ... Tapered surface 14 ... Side wall protective film 15 ... Interlayer insulating film

Claims (1)

[Claims] 1. After forming a wiring material film on a substrate, a resist is patterned on a portion where wiring is formed, and a side wall protective film made of a reaction by-product is formed on an etched side surface of the wiring material film. In addition, dry etching is performed to form a tapered surface on the resist shoulder along with the etching, exposing the processed shoulder of the wiring from the shoulder tapered surface of the resist and processing the shoulder of the wiring to the tapered surface. A wiring forming method characterized by the above.