JP3093224B2 - Semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor device, and more particularly, to a passivation film provided on a chip surface for protecting a circuit.

[Prior art] The function required for this kind of passivation film is to prevent moisture and impurities from entering the chip, to prevent the Al wiring of the circuit from corroding, or to change the element characteristics. To prevent the chip from being deformed or damaged by the stress of the resin encapsulating the chip. In addition, it is required that its properties be excellent in adhesion to a base and covering properties.

For this passivation film, silicon oxide, PSG or silicon nitride is used as an inorganic material, and a polyimide film is used as an organic material.

Above all, a silicon nitride film is excellent in moisture resistance and ion permeation resistance, and is therefore frequently used in semiconductor devices requiring reliability. This nitride film is formed mainly by a low-temperature plasma CVD method using a mixed gas of monosilane and ammonia or nitrogen.

Further, the polyimide film is formed by spin-coating a polyimide precursor solution and then performing a heat treatment to volatilize the solvent and close the imide ring of the precursor.

[Problems to be Solved by the Invention] A silicon nitride film has an excellent function as a passivation film, for example, it is dense and hard to be mechanically damaged. Is becoming a problem.

First, a void is generated in the Al wiring under the silicon nitride film, and an accident occurs in which the void becomes almost disconnected. It is considered that the cause is that a large compressive stress inherent in the silicon nitride film acts as a tensile stress on the Al wiring, and Al is deformed to relieve this stress.

Second, when a thermal stress is applied after the chip is sealed with a resin, the Al wiring on the chip surface is deformed as if crushed. It is presumed that the cause is that silica particles contained in the encapsulating resin locally press the chip surface, so that the silicon nitride film at this location bends and crushes the Al wiring.

Polyimide is known as a material that can avoid these problems, but a film of this material has no problem in the above points, but is inferior in moisture resistance, and easily generates a leak current in a circuit due to moisture absorption. Has disadvantages. Therefore, conventionally, when it is necessary to use different materials according to the characteristic requirements of the circuit or to suppress the stress and maintain the moisture resistance, a polyimide film and a silicon nitride film are used in combination to cope with this. . This means that process management is complicated for a production line that needs to manufacture many types of products, and using multiple passivation films on the same chip increases man-hours and complicates the process. Invite.

[Means for Solving the Problems] A semiconductor device according to the present invention includes a semiconductor substrate on which a predetermined circuit is formed, an interlayer insulating film covering the semiconductor substrate, and a bonding pad electrode formed on the interlayer insulating film. And a passivation film having an opening for exposing the bonding pad electrode and covering the interlayer insulating film, and the passivation film is formed only of a polytetrafluoroethylene film formed by an RF sputtering method or a vacuum evaporation method.

Example Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 (e) is a cross-sectional view showing a first embodiment of the present invention, and FIGS. 1 (a) to 1 (d) are cross-sectional views for explaining the manufacturing steps.

FIG. 1 (a) is a view showing a portion of a bonding pad electrode in an integrated circuit formed by a known method, and as shown in FIG. Aluminum film 3 to be an electrode
Are formed via the interlayer insulating film 2. For this semiconductor device, as shown in FIG. 1 (b), a PTFE film 4 was formed to a thickness of about 1 μm on the substrate surface by RF sputtering. The method for forming this film is as follows. The plate-shaped PTFE is attached to the RF electrode in the chamber, and the surface of the silicon substrate is opposed to the PTFE. 10 ^-6 inside this chamber
After reducing the pressure to Torr or less, an argon gas was introduced into the atmosphere at about 10 ^-2 Torr.
The PTFE film was made to collide with the surface of the PTFE plate, and PTFE molecules were scattered.

Next, as shown in FIG. 1C, a photoresist 5 having a thickness of about 5 μm and having an opening on the pad electrode was formed by a usual photolithography technique.

Subsequently, as shown in FIG. 1 (d), the PTFE film exposed on the photoresist and the pad electrode was removed by a plasma etching method. The conditions are as follows: a pressure of a mixed gas of CF ₄ and O ₂ : about 0.5 Torr, a substrate heating temperature: about 100 ° C.,
High-frequency power: 100 W, etching time: 5 minutes. PTFE
The PTFE film on the pad electrode could be selectively removed because the thickness of the photoresist was larger in advance than the film.
Finally, the photoresist was removed using a normal resist removing solution to obtain a semiconductor device shown in FIG. 1 (e).

The semiconductor device manufactured in this manner has a passivation film having excellent moisture resistance and a high stress buffering ability, so that no void or disconnection occurs in the Al wiring, and that the leakage current is suppressed. Become. In addition, since the film formed under the above conditions has good adhesion to the base and excellent coverage, it has been found that this film is extremely effective for the purpose of improving the reliability of the semiconductor device.

Next, as a second embodiment of the present invention, a film forming method by a vacuum evaporation method will be described. Attach a silicon substrate in a vacuum chamber and attach a PTFE plate to its anode, apply a pressure of about 10 ^-5 Torr to the chamber, and then apply a voltage of about 8 kV between the anode and the cathode that generates thermoelectrons. By irradiating the PTFE plate with an electron current of about 0.1 mA, the PTFE was heated and evaporated, and a PTFE film could be formed on the silicon substrate.

[Effects of the Invention] As described above, the present invention forms a passivation film of a semiconductor device using PTFE having high stress buffering properties and excellent water resistance. Can play.

Even with a film of an organic material, the water supply is not as high as that of polyimide, so that sufficient moisture resistance can be secured.

Since the PTFE film itself has low stress, it deforms to the underlying Al wiring,
No damage.

The stress can be absorbed and reduced by the passivation film due to the silica particles in the encapsulating resin generated by the thermal stress.

Since a single material or a single film is sufficient, the trouble associated with changing the film material is eliminated, and the process is not complicated as in the case of using a composite film.

Since a film can be formed by a sputtering method or a vacuum evaporation method which has been widely used in a semiconductor device manufacturing process, it can be easily incorporated into a manufacturing line.

According to the above method, a film having excellent adhesion and covering properties can be formed.

[Brief description of the drawings]

FIG. 1 (e) is a sectional view showing one embodiment of the present invention, and FIG.
FIGS. 7A to 7D are cross-sectional views for explaining the manufacturing process. 1 ... silicon substrate, 2 ... interlayer insulating film, 3 ... aluminum film, 4 ... polytetrafluoroethylene film, 5 ...
... photoresist.

Claims (2)

(57) [Claims] A semiconductor substrate on which a predetermined circuit is formed; an interlayer insulating film covering the semiconductor substrate; a bonding pad electrode formed on the interlayer insulating film; and an opening exposing the bonding pad electrode. A semiconductor device having a passivation film covering the interlayer insulating film, wherein the passivation film comprises only a polytetrafluoroethylene film formed by an RF sputtering method. A semiconductor substrate on which a predetermined circuit is formed; an interlayer insulating film covering the semiconductor substrate; a bonding pad electrode formed on the interlayer insulating film; and an opening exposing the bonding pad electrode. A passivation film that covers the interlayer insulating film, wherein the passivation film is made of only a polytetrafluoroethylene film formed by a vacuum deposition method.