JPS63262856A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To lower contact resistance in wiring connection, and to improve reliability by forming an electrode window, applying an insulating film for preventing the permeation of a gas contained in the insulating film, leaving the insulating film only on the side face of the electrode window and shaping an Al wiring. CONSTITUTION:An Al wiring 3 and an inter-layer insulating film 4 are formed onto a semiconductor substrate 1 in succession. The film 4 is shaped by laminat ing a hillock preventive film 41, an SOG film 42 and a PSG film 43. The film 4 is anisotropic-etched to bore an electrode window 5, and an Si3N4 film 15 is applied onto the whole surface, and used for preventing the permeation of a gas included into the film 4. Only the film 15 vertically applied onto the side face of the electrode window 5 is left. Al is applied onto the film 4 containing the window 5, the side face of which has the film 15, and patterned to shape an Al wiring 16. Accordingly, degassing from the window 5 is inhibited by the film 15, an Al film is attached completely into the window 5, and the wirings 3 and 16 are connected perfectly.

Description

[Detailed Description of the Invention] [Summary] After forming an electrode window on an insulating film on a semiconductor substrate, a second insulating film that prevents permeation of a gas containing the insulating film is deposited on the surface including the electrode window, and then The second insulating film is etched vertically so that it remains only on the side surfaces of the electrode windows. Next, aluminum is deposited to form wiring. Then, the aluminum wiring with low contact resistance is connected to the electrode window.

[Industrial Field of Application] The present invention relates to a method of forming an interlayer insulating film among methods of manufacturing a semiconductor device.

Semiconductor devices such as ICs and LSIs are highly densely integrated, and a large number of semiconductor elements are provided on a semiconductor substrate, and wiring for connecting them is formed in multiple layers, including two layers 13N.

On the other hand, various materials are used for these wirings, such as aluminum, polycrystalline silicon, metal silicide, and high-melting point metals, but aluminum, which has been used since the beginning, has good electrical conductivity and good adhesion with insulating films. It is still widely used because it is good and available at low cost.

However, the reliability of ICJP LSI largely depends on the reliability of the wiring, such as disconnection or short circuit of the wiring, and there is a need for a highly reliable method of forming wiring and interlayer insulating films.

[Prior Art] FIGS. 2(a) to 2(C) show a conventional method in which a first layer of aluminum wiring is formed, an interlayer insulating film is formed on the first layer of aluminum wiring, and then an interlayer insulating film is formed on the first layer of aluminum wiring. FIG. 3 is a step-by-step sectional view of a forming method for forming a second layer of aluminum wiring.

See FIG. 2(a); silicon oxide (S) on the semiconductor substrate 1.
iO2) The first layer of aluminum metallization via the film 2
3 is formed, and an interlayer insulating film is formed thereon, and the interlayer insulating film 4 consists of a hillock prevention film 41 and a spin-on glass.
(SOG) film 42 and phosphorus silicate glass (PSG)
This is an insulating film consisting of three layers in which the film 43 and the film 43 are sequentially laminated.

The first layer of the hillock prevention film 41 is made of protrusions (hillocks) that are formed by heat treatment of aluminum.
This is because the film is used to prevent the formation of k), and if hillocks form, there is a risk of short-circuiting between the upper and lower wiring. This hillock prevention film is a 5i02 film deposited by sputtering (film thickness approximately 1,500 mm).
An insulating film having hardness and hardness is used.

The second layer SOG film 42 is a well-known liquid film made by mixing silicon hydroxide with an organic solvent, and has the advantage of flattening the surface. After coating, it is heated to 450°C in nitrogen to volatilize the solvent. The film is then metamorphosed into a 5i02 film, which has a thickness of about 3,000 layers in the thick part and 600 layers in the thin part.

The third PSG film 43, which is the uppermost layer, is the main interlayer insulating film, and is made to a thickness of about 5,000 to 6,000 by heating the substrate to about 400 to 450°C and using vapor phase growth under reduced pressure or normal pressure. Goya's PSG film is a so-called passivation film that absorbs moisture and prevents aluminum from oxidizing.

In this way, an interlayer insulating film consisting of three layers is formed, and as a pretreatment for window opening, after the interlayer insulating film is deposited, the film is heated at 450° C. in a neutral or reducing atmosphere.

Degassing is performed by heating for about 30 minutes.

Refer to FIG. 2(b); next, an electrode window 5 is opened in this interlayer insulating film 4. This is a connection hole between the first layer of aluminum wiring 3 and the second layer of aluminum wiring to be formed on the interlayer insulating film 4, and its formation method is to use a photoresist film (not shown). Using a mask, the glabellar insulating film 4 in the electrode window forming area is exposed, and that portion is dry-etched.

The dry etching method is plasma etching using a mixed gas of carbon tetrachloride (CF4) and trifluoromethane (CHFa) as a reactive gas, and is vertical etching or active ion etching (RIE).

Refer to FIG. 2(C); Next, an aluminum film is deposited on the interlayer insulating film 4 including the electrode window 5 by a sputtering method and patterned by a photo process to form a second layer of aluminum wiring 6. . Note that when depositing the aluminum film, the substrate is heated to about 260°C.

The above is a general method for forming a multilayer aluminum wiring including a conventional interlayer insulating film.

[Problems to be Solved by the Invention] However, when the second layer of aluminum wiring 6 is formed by depositing an aluminum film by sputtering as described above, the aluminum film is not completely covered in the electrode window 5. There are areas where the particles are not deposited and do not adhere, and void areas are generated as shown by the arrows in FIG. 2(C). When depositing the second layer of aluminum wiring 6, the substrate is heated to about 260°C and 10-
When an aluminum film is sputtered under a high vacuum of 2 to 10 Torr, the gas contained in the glabella insulating film grown at low temperature escapes into the electrode window due to the high vacuum, and this is thought to be hindering the deposition of the aluminum film. Conceivable.

As mentioned above, after the glabella insulating film is deposited, it is heated and degassed once, but at that time, only the surface is heated and melted, and unreacted and undecomposed substances contained inside still remain. This makes it difficult for this gas to be degassed from the molten surface, and it is thought that this is extracted into the electrode window by high vacuum treatment and is interfering with the adhesion of aluminum.
In particular, the adhesion to the side surfaces of the SOG film 42 is not good.

Recently, as ICs have become more integrated and denser, electrode windows have become smaller, for example, smaller than 2 μm square, resulting in a significant increase in contact resistance. It has been viewed as such.

Moreover, the underlying cause is that the melting point of the aluminum film is low, at 450℃.
Although it is impossible to heat the aluminum wiring to a higher level, it is important to solve these problems in order to use aluminum wiring, which has good electrical conductivity and has many other benefits. The present invention proposes a method for forming an interlayer insulating film in order to reduce the contact resistance of aluminum wiring caused by this interlayer insulating film.

[Means for solving the problem] The purpose is to open a window in the insulating film to form an electrode window, and then
A step of depositing a second insulating film that prevents permeation of the gas contained in the insulating film on the surface including the electrode window, and then etching the second insulating film vertically to form the electrode window. This is achieved by a method for manufacturing a semiconductor device that includes the steps of leaving the second insulating film only on the side surfaces, and then depositing and patterning an aluminum film on the entire surface including the electrode window to form an aluminum wiring. Ru.

[Function] That is, in the present invention, after forming the electrode window, a second insulating film that prevents the permeation of the gas containing the insulating film is deposited on the surface including the electrode window, and the second insulating film is vertically disposed. Etching is performed to leave only the side surfaces of the electrode windows, and aluminum wiring is formed thereon. Then, aluminum wiring with low contact resistance is formed in the electrode window.

[Example] Hereinafter, embodiments will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(e) show step-by-step diagrams of the forming method according to the present invention.

See FIG. 1(a); as in the conventional case, five
A first layer of aluminum wiring 3 is formed via the i02 film 2, and a glabellar insulating film 4 is formed thereon.

This interlayer insulating film 4 also has a hillock prevention film 41 similar to the conventional one.
The insulating film is made up of three layers in which a SOG film 42 and a PSG film 43 are sequentially laminated, and the method of forming it is the same as the conventional one. After applying the glabellar insulating film, the temperature was also 450°C.
Heat for 30 minutes to degas.

Refer to FIG. 1(b); Next, in order to open the electrode window 5, the glabellar insulating film 4 is etched. Similarly to the conventional method, anisotropic etching is performed by RIE using a photoresist film (not shown) as a mask and using the same <CF4:CHF3=1:I mixed gas as a reaction gas.
Now.

Refer to FIG. 1(e); Next, a silicon nitride (Si3 N4) film 15 having a thickness of about 1000 layers (range of 500 to 2000 layers) is deposited over the entire surface by plasma vapor deposition.

543N4 film, for example, monosilane (SiH4) and nitrous acid (N20) are introduced to form a 0.543N4 film.
This is a method of growing by reducing the pressure to about 1 Torr and applying 200 KH2O high frequency to turn the reaction gas into plasma. This Si3N4 film 5 is the hillock prevention film 41.
．． SOG film 42. The insulating film shown in Fig. 2 is impermeable to gases contained in the PSG film 43, such as hydrogen gas, -carbon oxide gas, and water vapor, and has a dense film quality, is difficult to etch, and has a certain degree of hardness. It is.

Refer to FIG. 1(d); Next, in the same way as when the electrode window 5 was opened, the Si3N4 film was anisotropically etched vertically by RIE using CF4:CHF3=1:1 as a reaction gas. In this way, only the Si3N4 film 15 vertically deposited on the side surface of the electrode window 5 can remain, and all the Si3N4 films on other surfaces can be removed.

Refer to FIG. 1(e): After that, a film with a thickness of 0
．． A 7-1 μm aluminum film is deposited by sputtering,
A second layer of aluminum wiring 16 is formed by patterning using a photo process. Then, degassing from the electrode window is suppressed by the Si3N4 film 15, and the aluminum film can be completely adhered within the electrode window 5.

Therefore, the connection between the first-layer aluminum wiring and the second-layer aluminum wiring at the electrode window becomes perfect, and contact resistance can be reduced.

The above is an example, and in this example, Si3N grown by plasma vapor phase growth was used as the second insulating film with low gas permeability.
Although the fourth film 15 has been described, the present invention is not limited to this film, and any other insulating film may be used as long as it can prevent the gas contained in the insulating film from permeating. For example, a 5i02 film deposited by sputtering or a 5i02 film deposited by plasma vapor deposition can also be used. Etching resistance is considered as a guideline for the film quality. For example, when etching with 2.5% hydrofluoric acid, the etching speed is 1000 people/
Anything less than a minute is suitable.

[Effects of the Invention] As is clear from the above description, according to the present invention, the contact resistance in the electrode window for wiring connection is reduced, which greatly contributes to improving the quality and reliability of highly integrated ICs and LSIs. It is.

[Brief explanation of the drawing]

1A to 1141 are step-by-step sectional views of a forming method according to the present invention, and FIGS. 2A to 2C are step-by-step sectional views of a conventional forming method. In the figures, 1 is a semiconductor Substrate, 2 is 5i02 film, 3 is first layer aluminum wiring, 4 is interlayer insulation film (insulating film), 41 is hillock prevention film, 42 is SOG film, 43 is PS
G film, 5 is an electrode window, 6.16 is the second layer aluminum wiring, 15 is Si3N grown in plasma vapor phase.
4 film (second insulating film with low gas permeability). Oki θFir-ti To Kenei iyl * kf My Figure 1 Figure 4 Invention IJ' or 5P=F”k”J Shin/l r#ff#
#61D Fig. 1 Folding vermilion/shape fit rga eruption m Fig. 2

Claims (1)

[Claims] After forming an electrode window by opening an insulating film, a step of depositing a second insulating film on the surface including the electrode window to prevent the gas contained in the insulating film from permeating. Next, etching the second insulating film vertically to leave the second insulating film only on the side surfaces of the electrode window; Next, depositing and patterning an aluminum film on the entire surface including the electrode window. A method for manufacturing a semiconductor device, comprising the step of forming an aluminum wiring.