JPH088248A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the reliability in wiring by suppressing the erosion of a lower-layer wiring without reducing the film quality when baking a thick-film inorganic SOG film. CONSTITUTION:A process for forming wirings 2 (2A and 2B) where at least a surface-layer part consists of refractory metal or its alloy are formed on a semiconductor substrate 1 and a process for applying inorganic spin-on-glass (SOG) film 4, where a molecular end is sealed with proton and silazane boning exists in a skeleton by covering wiring, to the semiconductor substrate 1 and for baking the inorganic SOG film 4 are provided. Refractory metal is tungsten or titan and its alloy is titanium nitride.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device manufacturing method, and more particularly to a wiring method for planarizing a substrate surface using a thick inorganic SOG (spin on glass) film.

[0002]

2. Description of the Related Art In the manufacturing process of LSIs, conventionally, inorganic flattening using tetraalkoxysilane as a raw material has been used for flattening to eliminate steps due to wiring layers formed on a substrate.
Organic SO made from G film and methyltrialkoxysilane
The G film has been used, but in recent years, as an SOG film that achieves both crack resistance and oxygen plasma resistance, an inorganic SOG film having a silazane bond in the skeleton with a molecular end represented by the formula shown below is practically used. Has been converted. Moreover, it was difficult to increase the thickness of the conventional inorganic SOG film required for planarization,
Since this inorganic SOG film can be formed into a thick film, it is also called a thick film inorganic SOG film.

[0003]

Embedded image Unlike conventional SOG films, this thick-film inorganic SOG film can be converted into a dense and high-quality oxide film by oxidizing it during firing. It is desirable that this firing be performed in a steam atmosphere or an oxygen atmosphere.

However, when the above-mentioned thick inorganic SOG film is used for planarization, moisture at the time of baking the SOG film causes depression (erosion) in the underlying aluminum (Al) wiring, which lowers the reliability of the wiring. I was letting it.

3A and 3B are explanatory views of a conventional example. In Fig. 3 (A), an Al wiring 5 with a thickness of 1 µm is formed on a semiconductor substrate 1 having an insulating film deposited on the surface, and a thickness of 0.6 µ is formed on the Al wiring 5.
m CVD SiO ₂ film 3 is grown, and then a thick inorganic SOG film 4 having a thickness of 0.5 μm on the step is applied as a flattening film.
Bake.

The firing conditions at this time are as follows:
Heat at 50 ℃ for 30 minutes. By this high temperature firing, SOG
Water is generated from the film, and many erosion points are generated in the Al wiring as shown in the perspective view of FIG. 3 (B).

[0007]

As a measure to prevent erosion of Al wiring, there is a method of suppressing the generation of moisture and stress during baking by lowering the baking temperature or shortening the baking time.

However, according to the present invention, since a good quality film is obtained by promoting the oxidation as described above, the film quality is deteriorated by such a baking method. The present invention is based on SOG
The purpose of the present invention is to suppress the erosion of the lower layer wiring and improve the reliability of the wiring without deteriorating the quality of the film when it is baked.

[0009]

Means for Solving the Problems To solve the above problems, 1) a step of forming wiring 2; 2A, 2B having at least a surface layer made of refractory metal or an alloy thereof on a semiconductor substrate 1, and the semiconductor substrate 1 An inorganic spin-on-glass (SOG) film 4 which covers the wiring and whose molecular ends are sealed with protons and has a silazane bond in the skeleton is applied to the top of the inorganic SOG
A method for manufacturing a semiconductor device having a step of baking the film 4,
Alternatively, 2) it is achieved by the method for manufacturing a semiconductor device according to the above 1, wherein the refractory metal is tungsten or titanium and the alloy thereof is titanium nitride.

[0010]

The present invention prevents the wiring from being corroded by the water generated during the firing of the SOG film by using refractory metal having high corrosion resistance at least in the surface layer of the lower wiring of the SOG film. .

That is, as the refractory metal, tungsten (W), titanium (Ti) or its alloy (TiN:
Corrosion of the wiring is prevented by using (titanium nitride) or the like as the wiring layer or by coating the surface layer of the Al wiring.

In the present invention, the reason why tungsten or titanium is used as the refractory metal is
This is because all of them are excellent in corrosion resistance, but selection of tungsten and blanket vapor phase growth technology have been established, and titanium and titanium nitride can be easily formed by a sputtering method as compared with conventional methods. In particular, titanium nitride is effective as a glue layer and also has a high conductivity. This is because reliability can be guaranteed by using existing technology.

[0013]

1 (A) and 1 (B) are cross-sectional views of an embodiment of the present invention. Figure 1 (A) shows a semiconductor substrate with an insulating film deposited on the surface 1
A 1 μm-thick W wiring 2 is formed on top of it, and a 0.6 μm-thick silicon oxide film is formed on top of it as an interlayer insulating film.
A (CVD SiO ₂ ) film 3 is grown, and then a thick inorganic SOG film 4 having a thickness of 0.5 μm is formed on the step as a flattening film by spin coating and baking.

The firing conditions are heating in a steam atmosphere or an oxygen atmosphere at a temperature of 430 to 450 ° C. for about 30 minutes. Here, the W wiring 2 is formed by vapor-phase growth of tungsten hexafluoride on the substrate, and then patterning using ordinary photolithography technology.

In FIG. 1B, an Al wiring 2A having a thickness of 1 μm and a W wiring 2B having a thickness of 0.1 μm are formed as wiring of a laminated structure on a semiconductor substrate 1 having an insulating film deposited on the surface thereof. A 0.6 μm-thick CVD SiO ₂ film 3 is spin-grown on top as an interlayer insulating film, and then a 0.5 μm-thick inorganic SOG film 4 with a thickness of 0.5 μm is spin-coated on the step as a flattening film and baked.

The firing conditions are the same as in the embodiment of FIG. 1 (A). Here, for the laminated wiring of the Al wiring 2A and the W wiring 2B, Al is deposited on the entire surface of the substrate by sputtering or vapor deposition,
W is vapor-deposited on the entire surface by using tungsten hexafluoride, and then an Al / W laminated film is formed by patterning using ordinary photolithography technology.

No erosion of the wiring was observed in any of the above examples. In the examples, W was used as the refractory metal, but instead of this, Ti and its alloys were used.
Even if TiN or the like is used, the effect of the present invention does not change.

FIG. 2 is a diagram showing the effect of the present invention. The figure shows the dependence of the number of erosion points on the wiring width. After forming the wiring with the following wiring materials, a silicon oxide film was grown by the vapor phase epitaxy method, an inorganic SOG film was applied on it, and baked in a steam atmosphere. The number of erosion points on the wiring was visually measured.

Al wiring only (thickness 1 μm) (conventional example) W wiring only (thickness 1 μm) (Example 1) W wiring (thickness 0.1 μm) laminated on Al wiring (thickness 1 μm) Wiring structure (Example 1) As shown in the figure, the occurrence of erosion was confirmed only under the condition of, and the tendency becomes larger as the wiring width becomes narrower.

In the laminated wiring structure, the upper layer W film was peeled off and only the lower layer Al film was formed, and the same baking was performed, but no erosion occurred. This is probably because even if the W film is peeled off, the surface of the underlying Al film is alloyed with W by the baking treatment.

From these results, as a flattening film, the SO having a silazane bond in the skeleton whose molecular ends are sealed with protons
When the G film is used, it can be seen that the erosion of the wiring during SOG firing is suppressed by using the lower wiring structure of refractory metal alone or as the uppermost layer of the laminated wiring.

In the present invention, as the refractory metal,
Although general tungsten, titanium, and titanium nitride were used, in addition to them, there are molybdenum, tantalum, nickel, cobalt, neobium, hafnium, etc., and their alloys include titanium tungsten, etc. There is.

[0023]

According to the present invention, the erosion of the lower layer wiring is suppressed without deteriorating the quality of the SOG film during firing.
The reliability of wiring can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a diagram showing the effect of the present invention.

FIG. 3 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1 Semiconductor substrate 2 W wiring 2A Lower layer Al film of laminated wiring 2B Upper layer W film of laminated wiring 3 CVD SiO ₂ film 4 Thick inorganic SOG film 5 Al wiring

Claims (2)

[Claims] 1. Wirings (2), (2) at least a surface layer portion of which is made of refractory metal or an alloy thereof on a semiconductor substrate (1).
A, 2B), and an inorganic spin-on-glass (SOG) film (4) that covers the wiring on the semiconductor substrate (1) and whose molecular ends are sealed with protons and has a silazane bond in the skeleton. A step of applying and firing the inorganic SOG film (4). 2. The method of manufacturing a semiconductor device according to claim 1, wherein the refractory metal is tungsten or titanium, and the alloy thereof is titanium nitride.