Metallizing process of semiconductor industry

Details Metallizing process of semiconductor industry Metallizing process of semiconductor industry

2000-11-29

2002-04-30

Niebling, John F. (Department: 2812)

Semiconductor device manufacturing: process

Coating with electrically or thermally conductive material

To form ohmic contact to semiconductive material

Reexamination Certificate

active

06380072

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a metallizing process for a semiconductor device.
BACKGROUND OF THE INVENTION
In an integrated circuit manufacturing process, the stressed point, after main parts of hundreds of thousands of transistors have been completed, is to interconnect them to present an integral electronic device. The process to so interonnect is generally referred to as a metallizing process.
For a semiconductor metallizing process, aluminum is the most popularly used material for the device runner. When the integration of the semiconductor device becomes higher an d higher, it would be difficult to use an aluminum-based runner again in that silicon exists a specific solid solubility with respect to aluminum and that the interface between silicon and aluminum will easily result in a spiking phenomenon through interdiffusion in a relatively high temperature to cause a poor contact between aluminum wire and MOS transistor. In addition, when the breadth of the aluminum becomes narrower as the device becomes smaller, the aluminum atom is caused to move by electromigration to result in an open state of the aluminum wire.
Accordingly, the present semiconductor manufacturing process adopts the aluminum alloy, e.g. AlCu alloy to serve as the conducting material for the semiconductor device. In order to further realize the metallization in the known technique, in FIGS.
1
A~
1
D, we use the AlCu alloy serving as the conducting material to illustrate the metallizing process and shortcomings according to the prior art.
FIG. 1A
schematically shows the following steps of providing a silicon substrate
11
, forming on silicon substrate
11
by DC sputtering an AlCu alloy layer
12
having a thickness of about 5,000 Å~10,000 Å, and forming on AlCu alloy
12
a titanium nitride (TiN) layer
13
having a thickness of about 200 Å~1500 Å by reactive DC sputtering. It is to be noticed that in the general metallizing process for the semiconductor device, the metal layer is provided thereon with an anti-reflection layer of a conducting material in order to avoid a pattern transfer error in the photolithography process. As such, the purpose of forming titanium nitride (TiN) layer
13
is to prevent the surface of AlCu alloy
12
layer from reflection in order to secure the exposure exactitude for the subsequent photolithography process. Thus, the device runner is consisted of AlCu layer
12
and titanium nitride (TiN) layer
13
. Since the material property of titanium nitride (TiN) layer
13
is hard and the curvature of the chip surface in the semiconductor process is not the same, titanium nitride (TiN) layer
13
is extremely prone to crack to form a crack
131
as shown in FIG.
1
A.
After the anti-reflection titanium nitride (TiN) layer
13
is formed on AlCu layer
12
, there are proceeded with photolithography and etching processes. The photoresist developer, e.g. the alkaline solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH), the etching solution, e.g. a solution using the chloride as the primary reacting gas, or the washing agent used in the washing process will leak through crack
131
. Since there exists an oxidizing potential difference between titanium nitride (TiN) layer
13
and AlCu alloy layer
12
, there will be resulted in a local spontaneous electrochemical reaction, just like the function of a galvanic cell, to have an equivalent circuit diagram as shown in
FIG. 1D
where titanium nitride layer
13
serves as an anodic plate
14
and AlCu alloy layer
12
serves as a cathodic plate
15
in the concerned circuit. The spontaneous electrochemical reaction between two electrode plates
14
,
15
converts the chemical energy into the electric energy. In addition to consume the material of AlCu alloy layer
12
, the spontaneous electrochemical reaction will leave an unetchable by-product beneath AlCu alloy layer
12
. The by-product, as shown in
FIG. 1B
, is an aluminum oxide (Al
2
O
3
)
121
having a thickness of about 30 Å~50 Å. This aluminum oxide
121
cannot be removed by the etching chloride plasma etching titanium nitride layer
13
and AlCu alloy layer
12
.
Accordingly, the device runner having been subjected to an etching process will present an etched result as shown in FIG.
1
C. Specifically, the AlCu alloy layer
12
right beneath aluminum oxide
121
will not be etched away and will present an AlCu alloy residue
122
. AlCu alloy residue
122
will primarily explain why the runner of AlCu alloy layer
12
is short-circuited. Furthermore, since AlCu alloy layer
12
will be undesiredly partly etched away, it is impossible to obtain a correct runner-etching result to seriously adversely influence the required short-circuiting condition between device runners which should be overcome as soon as possible.
It is therefore tried by the Applicant to deal with the above situation encountered in the prior art.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a process for metallizing a semiconductor device without an etching residue.
It is further an object of the present invention to provide a process for metallizing a semiconductor device having a desired runner pattern.
It is additional an object of the present invention to provide a process for metallizing a semiconductor device having a relatively high yield rate.
According to the present invention, a process for metallizing a semiconductor device comprising the steps of a) providing a semiconductor substrate, b) forming a conductive layer on the semiconductor substrate, c) forming a dielectric layer on the conductive layer, d) forming a titanium nitride layer directly on the dielectric layer without contacting the conductive layer, and e) patternizing the titanium nitride layer, the dielectric layer and the conductive layer, wherein the dielectric layer is used for avoiding spontaneous electrochemical reaction between the titanium nitride layer and the conductive layer.
Certainly, the step b) can be executed by a reactive DC sputtering. The conductive layer can be a metal layer which can be made of an AlCu alloy. The conductive layer can have a thickness ranged from 5,000 Å~10,000 Å. The step c) can be executed by oxidation.
Further, the dielectric layer can be an oxide layer which can be an aluminum oxide (Al
2
O
3
) layer having a thickness ranged from 10 Å to 20 Å, or a silicon dioxide (SiO
2
) layer having a thickness ranged from 10 Å to 50 Å.
Certainly, the step c) can be executed by nitridation. The dielectric layer can be a nitride layer which can be an aluminum nitride (AlN) having a thickness ranged from 10 Å to 50Å.
Still more, the step d) can be executed by a reactive DC sputtering. The titanium nitride (TiN) layer can have a thickness ranged from 200 Å~1,500 Å.
Preferably the step e) further includes the following sub-steps of e1) executing a photolithography process according to a specific runner pattern to cover a photoresist layer on the titanium nitride layer, e2) executing a first etching process to etch away portions of the titanium nitride layer, the dielectric layer and the conductive layer not covered by the photoresist layer, and e3) executing a second etching process to etch away the photoresist layer, the titanium nitride layer and the dielectric layer.
The present invention may best be understood through the following descriptions with reference to the accompanying drawings, in which:


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