JPH05243212A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device having a fine passivation film which has a high moisture resistance, a good coverage and has no cracks even if it is formed thick. CONSTITUTION:A polysilazane film 5 which has a good coverage is supplied to the surface of a semiconductor device. The polysilazane film 5 is cured and oxidized at relatively low temperatures in an oxydizing atmosphere such as a wet oxygen atmosphere. By this method, a passivation film which is a fine silicon oxide film of a small hygroscopic property is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device characterized by a method of forming a passivation film.

[0002]

2. Description of the Related Art The influence of moisture on a semiconductor device, particularly a semiconductor integrated circuit device, has conventionally been regarded as a problem, and it has a relatively hygroscopic property as a passivation film for protecting active regions and wirings of the semiconductor device from moisture. Small plasma SiN
Films and plasma SiON films have been used.

[0003]

However, when the above plasma SiN film or plasma SiON film is used as the passivation film, the characteristics of the semiconductor device are not changed or deteriorated in the process of forming these passivation films. Even if the film is cured at the limit temperature, it is not sufficient as the temperature for densifying the film quality and cannot have the necessary moisture resistance.Thus, by increasing the thickness of these passivation films, it is necessary to provide the necessary moisture resistance. Then, there is a problem that cracks are generated.

Further, since these passivation films have poor coverage, they cannot be deposited thickly on the side walls of the step portion, and the film thickness that can be deposited is 5000 Å, and even if it is thick, the limit is about 1.0 μm. Also, there was a part where the film thickness was thin.

Further, it has been attempted to apply polyimide in order to compensate for the cracks in the passivation film or the deterioration of the moisture resistance in the portion where the film thickness is insufficient, but the polyimide is formed without flattening the steps. Then,
It was impossible to completely block the penetration of the moisture of the highly hygroscopic polyimide into the active region of the semiconductor device because the polyimide was thickly formed in the depression.

In order to solve such a problem, the present invention provides a semiconductor device having a fine passivation film which has good moisture resistance, good coverage, and does not cause cracks even when formed thick. With the goal.

[0007]

In the method for manufacturing a semiconductor device according to the present invention, a step of applying polysilazane to the surface of the semiconductor device and a dense and low hygroscopic property by curing and oxidizing the applied polysilazane. A process of forming a passivation film made of a silicon oxide film is adopted.

[0008]

The inventors of the present invention investigated the applicability of polysilazane to the passivation film of the semiconductor device, and conducted repeated experiments. As a result, polysilazane was actively oxidized at a low temperature of about 450 ° C. and the silazane bond was a Si—O bond. It was found that a silicon oxide film having a high density and a high moisture resistance was formed by being converted into.

According to the present invention, the cover SiN film and the cover SiON film, which have been conventionally used in the final step of film formation of a semiconductor device, are used.
In order to improve the moisture resistance of a passivation film such as a film or a polyimide film, polysilazane having a good covering property is applied in place of these passivation films, or before or after the formation of these passivation films, and relatively. It is characterized in that a passivation film made of a silicon oxide film which is dense and has excellent moisture resistance is formed by performing curing in a wet oxygen atmosphere at a low temperature and replacing nitrogen of polysilazane with oxygen.

When an inorganic SOG conventionally used as a passivation film is used, the following chemical formula 1 is given, and (OH) and (OH) of the left inorganic SOG are (H
₂ O), and after that (O) remains on the right side, it is oxidized in the form of (Si-O-Si), so the atomic weight decreases from 34 to 16 and the volume shrinks accordingly. This will cause cracks.

[0011]

[Chemical 1]

When organic SOG is used,
As shown in Formula 2, the organic group of the organic SOG on the right side
It leaves and is oxidized in the form of (Si-O-Si), but R is
CH ₃, Then the atomic weight increases from 15 to 16
Therefore, the volume expands slightly and the thickness is increased without cracks.
It is possible to form a transparent film.

[0013]

[Chemical 2]

However, since organic SOG has insufficient heat resistance, it cannot be used in a bulk process in which a high temperature treatment of 550 ° C. or higher is performed.

On the other hand, when polysilazane is used, it is represented by the following chemical formula 3, and (H) of the polysilazane on the left side is replaced by (O) as shown on the right side (Si-O-Si). ), The atomic weight increases from 1 to 16 and the volume expands to generate a compressive force.

[0016]

[Chemical 3]

The compressive force densifies the passivation film to prevent cracks from occurring, and the metal wiring such as Al receives a compressive force to suppress electromigration of the metal, thereby improving reliability of the wiring. improves. Further, this compressive force has an effect of improving not only the above-mentioned wiring but also the reliability of the insulating film and the circuit element therebelow.

Further, since the polysilazane film has excellent coverage, the polysilazane film can be easily formed to a thickness of about 1.5 μm. Therefore, the moisture content of the silicon oxide film itself formed by oxidizing the polysilazane film can be improved. Is about half the plasma CVD-SiN film, and if it can be formed to have a thickness five times that of the plasma CVD-SiN film, the amount of water that permeates the passivation film can be reduced to 10 times the conventional amount. It can be reduced to about 1.

[0019]

EXAMPLE An example of the present invention will be described. FIG. 1 (A)-
(C) is a manufacturing process explanatory diagram of the semiconductor device of one embodiment of the present invention. In this figure, 1 is a semiconductor substrate, 2 is wiring, 3 is a bonding pad, and 4 is plasma CVD-S.
iN film, 5 is a polysilazane film, 6 is a silicon oxide film, 7
Is a polyimide film. A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to the manufacturing process explanatory diagram.

First step (see FIG. 1A) A circuit element or the like is formed on a semiconductor substrate 1 by a conventionally known step, and Al-C having a thickness of 1.0 μm is formed thereon.
The wiring 2 and the bonding pad 3 made of a u-Ti alloy are formed. Then, as a passivation film, a thickness of 50
A plasma CVD-SiN film 4 of 00Å is formed. The plasma CVD-SiN film 4 is formed in steps on the surfaces of the semiconductor substrate 1, the wiring 2 and the bonding pad 3.

Second step (see FIG. 1B) Polysilazane is spin-coated on the stepped plasma CVD-SiN film 4 by about 8000 Å, and baked at 200 ° C. for about 3 minutes to remove the organic solvent and solidify. Then, the polysilazane film 5 is formed.

Third step (see FIG. 1C) In a wet oxygen atmosphere, baking is performed at 450 ° C. for 30 minutes to replace nitrogen in the polysilazane 5 with oxygen to convert it into a silicon oxide film 6. Most of the silicon oxide film 6 is SiO ₂ , but there is a small amount of SiON in which nitrogen (N) of polysilazane remains. Then, the silicon oxide film 6
A polyimide film 7 is formed on the bonding pad 3, and the polyimide film 7, the silicon oxide film 6 and the plasma CVD-SiN film 4 on the bonding pad 3 are removed by photolithography and plasma etching to expose the bonding pad 3. . The polyimide film 7 is formed to protect the silicon oxide film 6 having a slightly weak etching resistance.

[0023]

As described above, according to the present invention,
By coating and oxidizing a polysilazane film to form a passivation film made of a silicon oxide film, the poor coverage and the passivation film itself, which had been the cause of the hygroscopicity which was the problem of the plasma-SiN film of the prior art. Since the hygroscopicity can be eliminated, it is possible to surely prevent the infiltration of moisture, which largely contributes to the improvement of the reliability of the semiconductor device.

[Brief description of drawings]

1A to 1C are explanatory views of a manufacturing process of a semiconductor device according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Wiring 3 Bonding pad 4 Plasma CVD-SiN film 5 Polysilazane film 6 Silicon oxide film 7 Polyimide film

Claims (1)

[Claims] 1. A step of applying polysilazane having excellent coverage to a surface of a semiconductor device, and a step of curing the applied polysilazane to oxidize it to form a passivation film made of a silicon oxide film which is dense and has low hygroscopicity. A method of manufacturing a semiconductor device, comprising: