JPH02121350A - Formation of multilayer interconnection - Google Patents

Abstract

PURPOSE:To prevent foreign substances from generating at the time of dry etching of a metal layer for upper-layer wiring conductor formation use in the forming method of a multilayer interconnection using a polyimide film as an interlayer insulating film by a method wherein a film of a kind different from the kinds of the polyimide film and the metal layer is interposed between the polyimide film and the metal layer. CONSTITUTION:First-layer wiring conductors 25, which are connected to electrode parts of a circuit element 22 through contact holes 24 and consist of Al, are formed on an SiO2 insulating film 23. Then, a polyimide film 26 is formed on the whole surface of the film 23 on a substrate 21 as an interlayer insulating film. After that, an exposure and a developing are performed on said film 26 and a through hole 27 to lead to the conductor 25 is formed in the film 26. After that, after a cure of the film 26 is conducted, a tungsten film 28, for example, is deposited on the whole surface of the film 26 including the whole surface of the hole 27 as a first interposing film. After that, an Al film 29 is formed on the whole surface of the film 28 as a metal layer for second-layer wiring conductor formation use. After that, a patterning is performed on the film 29 by a normal photolitho method and the film 29 is etched by a dry etching method. Thereby, a second-layer wiring conductor 29a is formed on the film 29.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for forming multilayer wiring in a semiconductor integrated circuit, and more particularly to a method for forming multilayer wiring using a polyimide film as an insulating film between the eyebrows.

(Prior art) A conventional method for forming multilayer wiring in a semiconductor integrated circuit using a polyimide film as an insulating film between the eyebrows is disclosed in Japanese Patent Application Laid-Open No. 61-1999.
There is one disclosed in Japanese Patent No. 230337. The method will be explained with reference to FIG. 2. 1 is a semiconductor substrate, a circuit element 2 is formed on the surface of this substrate 1, the surface is covered with an insulating film 3 such as SiJ, and then the circuit element is The wiring conductor 5 of the 2nd layer is formed to be connected to the electrode 4 of the PIQ.
(Hitachi Chemical 1 Co., Ltd.) prepolymer is coated and finally cured by heating in an inert atmosphere at a temperature of 300°C or higher to form the first polymer resin insulating film, PIQ1116. Next, after forming an opening at a predetermined position in the PIQ film 6, a polyimide prepolymer containing a photosensitive agent is applied to form the second layer wiring conductor 7, and prebaking is performed at 85°C for 30 minutes. , 0 to form the photosensitive polymer resin film 8
Next, the polyimide polymer in the unexposed areas (openings) is removed by exposure to normal UV light and a mixed developer of N-methyl-2-pyrrolidone and water to form openings 9, and finally 350° Cured by heating in a nitrogen atmosphere for 130 minutes.

Thereafter, a third layer of wiring conductor 10 is formed. In this way, by repeating the formation of the polyimide film, the opening of through holes, and the formation of wiring conductors, it is possible to form multilayer wiring in any number of layers.

(Problems to be Solved by the Invention) However, with the conventional methods described above, when a semiconductor integrated circuit is designed at a design level of 1.2 pm, it is difficult to achieve satisfactory multilayer interconnection and even semiconductor integrated circuits. I couldn't get it. The reason is 1.2 tr
This is because in order to form an extremely thin wiring conductor of 5° 7.10 mm at the m level, dry etching is required to etch the M film for forming the wiring conductor. Polyimide film (PIQ film 6. Photosensitive polymer resin film 8) by dry etching
When the upper M film is etched, residual foreign matter is deposited on the exposed polyimide film after etching. This accumulated foreign matter causes poor reliability and the like.

The foreign matter is stubborn and cannot be removed by cleaning chemicals. Further, foreign matter generation occurs only when the polyimide film is formed under the A/film. If there is no polyimide film, this phenomenon will not occur. Moreover, no foreign matter is generated when the polyimide film is formed on the M film, as opposed to when the polyimide film is formed on the M film.

The reason for the generation of foreign matter is not clear, but it is thought that when the surface of the polyimide film is exposed in the final stage of A/film etching, the polyimide film is sputtered, combines with M atoms, and then re-deposit on the polyimide film. .

As a countermeasure against this, the generation of foreign matter can be prevented by stopping the dry etching of the M film midway and wet-egging the remaining A/film.

However, this method is not preferable because it is contrary to process drying and the steps are complicated.

The present invention eliminates the problem of foreign matter generation during dry etching of a metal layer for forming a wiring conductor in the method using a polyimide film as an interlayer insulating film, and makes it possible to form a good multilayer wiring. The purpose of this invention is to provide a method for forming wiring.

(Means for Solving the Problems) This invention provides a method for forming multilayer wiring using a polyimide film as an insulating film between the eyebrows. A film of a different type from these is interposed between metal layers for forming wiring conductors.

(Function) When the different type of film is interposed, the intervening film serves as an etching stopper during dry etching of the metal layer for forming the upper wiring conductor, and the underlying polyimide film is not exposed. Therefore, no foreign matter is generated during dry etching of the metal layer for forming upper layer wiring conductors.

(Example) An embodiment of the present invention will be described below with reference to FIG.

First, as shown in FIG. 1(a), after forming a circuit element 22 on a semiconductor substrate 21, an insulating film 23 of 5 in 2 is formed on the surface of the substrate 21, and a contact hole 24 is formed in this insulating film 23. A first layer wiring ring body 25 made of M is formed on the insulating film 23 to be connected to the electrode portion of the circuit element 22 through the contact hole 24 .

Next, a polyimide film 26 is formed as an interlayer insulating film on the entire surface of the substrate 21 so as to cover the first layer wiring ring 25, as shown in FIG. 1(b). This polyimide film 26 is formed by spin-coating a photosensitive polyimide prepolymer solution onto the substrate 21 at 300 rpm and performing a post bake at 80° C. for 20 minutes.

Thereafter, the polyimide film 26 is exposed to light and developed to form a through hole 27 communicating with the first layer wiring ring 25 in the polyimide film 26 as shown in FIG. 1(c).

After that, the polyimide film 26 was cured at 100°C, 200°C, and 350'C for 1 hour each, as shown in Fig. 1(c).
As shown in , tungsten (W) is used as the first intervening film.
A film 28 is deposited to a thickness of 1500 nm over the entire surface of the polyimide film 26 including the through holes 27.

Thereafter, as shown in FIG. 1(d), an M film 29 is formed on the entire surface of the tungsten film 28 as a metal layer for forming a second layer wiring ring.
form.

After that, a resist pattern is formed on the M film 29 by normal photolithography, and this resist pattern is used as a mask.
And using BCl3 as an etching gas, the M film 29 is
A second layer wiring ring body 29a is formed by etching using a dry etching method and patterning as shown in FIG. 1(e).

At this time, the tungsten film 28 acts as an etching stone bar and remains, so that the underlying polyimide film 26
is not exposed. Therefore, when the conventional M film was etched and spun, the polyimide film was exposed and sputtered, resulting in an adverse phenomenon in which residual foreign matter was deposited on the exposed polyimide film. This method does not cause such problems and no foreign matter is generated.

Thereafter, by dry etching using CF as an etching gas, the tungsten film 28 is etched into the same pattern as the second layer wiring ring 29a, as shown in FIG. The second layer wiring conductor 29a is connected to the first layer wiring ring body 25 through the through hole 27.

After that, the first layer is applied to the entire surface so as to cover the second layer wiring ring body 29a.
As shown in Figure (g), a polyimide film 30 is formed as a second glabellar insulating film. The method for forming this polyimide film 30 is the same as the method for forming the polyimide film 26 previously.

Thereafter, as shown in the figure, an amorphous silicon film 31 is formed as a second intervening film on the polyimide film 30 to a thickness of 1.
Then, as shown in the figure, a through hole 32 communicating with the second layer wiring ring body 29a is formed in the amorphous silicon film 31 and the polyimide film 30.

Thereafter, by forming an M film on the entire surface and dry etching the M film, the second layer wiring ring 2 is passed through the through hole 32.
A third stone wiring ring body 33 connected to 9a is formed on the polyimide film 3o and the amorphous silicon film 31 as shown in FIG. 1(b).

At this time, the amorphous silicon film 31 acts as an etching stopper for the M film etching and remains, thus preventing the underlying polyimide film 3o from being exposed. No foreign matter is generated.

Thereafter, by dry etching using CZF&+O□ as an etching gas, the amorphous silicon film 31 is etched into the same pattern as the third layer wiring ring 33, as shown in FIG. 1(i). With the above steps, multilayer wiring is completed.

In the above example, a tungsten film and an amorphous silicon film were used as the intervening film, but titanium (T
i), nickel (Ni), copper (cu), chromium (
cr), gold (Au), etc. can also be used as the intervening film. Moreover, a composite film of the above-mentioned materials can also be used as an intervening film. In addition, the thickness of the intervening film is suitably between 100 and 2000. Specifically, in addition to the tungsten film of 1500 and the amorphous silicon film of 1500,
500 people thickness for Ni, 800 people thickness Cr for Cu
In the case of 1000 people thickness and person thickness.

Further, in the above embodiment, the wiring conductor is /u 100! Although it was formed with a film, AZ-1,5χSi, Al-1,0
It may be formed of .chi.Si, AZ-5iCu, or the like, and of course, even in that case, according to the present invention, generation of foreign matter during dry etching can be prevented.

In addition, a photosensitive polyimide film was used as the polyimide film, but
It may also be a non-photosensitive polyimide film.

(Effects of the Invention) As detailed above, according to the method of the present invention, a film of a different type from these is interposed between the polyimide film and the metal layer for forming the upper layer wiring conductor. Since the intervening film prevents the polyimide film from being exposed during dry etching, it is possible to prevent foreign matter from adhering to the polyimide film during the dry etching. Therefore, defective reliability does not occur, and good multilayer wiring and, by extension, semiconductor integrated circuits can be manufactured. Further, according to the present invention, the process can be simplified without compromising the process dryness.

[Brief explanation of the drawing]

FIG. 1 is a process sectional view showing an embodiment of the method for forming a multilayer wiring according to the present invention, and FIG. 2 is a sectional view showing a conventional method for forming a multilayer wiring. 21... Semiconductor substrate, 25... 1st N wiring conductor, 2
6... Polyimide film, 28... Tungsten film, 2
9... M film, 29a... 2nd N wiring conductor, 30...
・Polyimide film, 31... amorphous silicon film,
33... 1st N wiring conductor. Process sectional view of one embodiment of the present invention FIG. 1 21: Semiconductor substrate 25: First layer wiring trench 26: Polyimide film 28 Shio-Tungsten film 29: Af film 29c: Second layer wiring trench 30: Polyimide film 31: Amorphous silicon film 33 = 3rd layer wiring conductor Process cross-sectional diagram of the present invention-embodiment Second cross-sectional diagram showing the conventional method

Claims (1)

[Scope of Claims] (a) A step of forming a polyimide film as an interlayer insulating film on a semiconductor substrate on which a lower layer wiring conductor has been formed; (b) A step of forming a polyimide film and a metal for forming an upper layer wiring conductor on the polyimide film. (c) forming the metal layer for forming the upper layer wiring conductor on the film; (d) forming the upper layer wiring by patterning the metal layer by dry etching. A method for forming a multilayer interconnection comprising the steps of: forming a conductor; and (e) etching the different type of film in the same pattern as the upper layer interconnection conductor.