JPS6179233A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the generation of cracks of an insulating film by providing a cover insulating film composed of a three-layer film in which the first insulating films sandwiches the second insulating film which has the opposite stress. CONSTITUTION:A cover insulating film has the composite film structure composed of three layers in which a PSG film 10, an Si nitride film 11, a PSG film 12 are laminated and the film 11 is sandwiched. Namely, the cover insulating film composed of a three-layer film in which the PSG film 10 and 12 whose film quality is soft, sandwich the Si nitride film 11 having the opposite stress is arranged. Thus the balance of the stress in the cover insulating film is contrived and the surface is formed by the soft PSG films 10 and 12, so that even if the cover insulating film is in contact with a plastic mold package, the stress is small and generation of cracks can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor device, and particularly to a cover insulating film that covers a semiconductor chip thereof.

As is well known, in a semiconductor device such as an IC, a semiconductor chip is manufactured and the chip is housed in a package.

This semiconductor chip is created by a wafer process, and in the final step of the wafer process, the upper surface of the wafer is coated with a cover insulating film to protect the elements provided inside, and then it is divided into dice-shaped chips.

Therefore, the cover insulating film on the surface of the chip sufficiently plays the role of internal protection even after it is housed in the package.
Sufficient consideration must be given to its protection.

[Prior Art] Now, FIG. 2 ta+ illustrates a partial cross-sectional view of a semiconductor chip, in which 1 is a silicon substrate, 2 is a silicon dioxide (S)
i02) film, 3 is MO3+- transistor element, 4 is phosphorus silicate glass (PSG) film, 5 is aluminum wiring,
6 is a cover insulating film.

For the cover insulating film 6, a PSG film or a plasma silicon nitride (plasma SiN) film is often used.
These are usually produced by chemical vapor deposition Ju (CVD) method.
It is deposited to a film thickness of approximately 1 μm.

Among the many deposition methods, the CVD method, especially the low pressure CVD method, is known as a deposition method with extremely good coverage.

Note that the plasma silicon nitride film refers to a silicon nitride film deposited by a plasma CVD method, and when a silicon nitride film is deposited by a normal CVD method, the aluminum wiring 5 melts due to a high-temperature decomposition reaction. be done. In order to avoid this, the film is deposited using a low-temperature decomposable plasma CVD method.

[Problems to be Solved by the Invention] Incidentally, the deposited PSG film itself generates tensile stress, which tends to cause cracks. Also,
Compressive stress occurs in the silicon nitride film, which makes it susceptible to cracking. Therefore, in the case of a ceramic or metal pancage, there are relatively no problems after sealing, but if the package is a plastic mold, for example, moisture can enter the chip and cause a fatal reliability problem. easy.

Therefore, recently, when using a plastic mold package, as shown in the partial cross-sectional view shown in Fig.
A composite film structure consisting of a silicon nitride film 8 of μm thickness is adopted. This is because both the tensile and compressive stresses cancel each other out, reducing the occurrence of cranks and improving reliability.

However, it has become clear that cracks do not necessarily decrease in reality. This is thought to be because when the plastic mold and the cover insulating film come into contact, stress is generated between the hard mold and the silicon nitride film, which causes cracks to occur.

The present invention proposes a cover insulating film to eliminate such problems.

[Means for Solving the Problem 1] The problem is that a composite cover film in which a second insulating film to which stress opposite to that of the first insulating film is applied is sandwiched between the first insulating films is used. This can be solved by a semiconductor device provided on a semiconductor chip.

For example, a composite cover insulating film in which a silicon nitride film, which is subjected to stress opposite to that of the phosphosilicate film, is sandwiched between the phosphosilicate films is solved by a semiconductor device provided on a semiconductor chip.

[Function] That is, a cover insulating film consisting of three layers sandwiching a silicon nitride film having opposite stress is provided using pscl* having a soft film quality. In this way, by balancing the stress within the cover insulating film and using a soft PSG film on the surface, even if the plastic mold package and the cover insulating film are in contact, the stress is small and cracks are suppressed.

[Example〕 Examples will be described in detail below with reference to nine drawings.

FIG. 1 illustrates a partial cross-sectional view of a semiconductor chip covered with a cover insulating film according to the present invention, and the same members as in FIG. 2 described above are given the same symbols. As shown in the figure, the cover insulating film is a PSG film 10 degrees, a silicon nitride film 11 degrees, and a silicon nitride film 11 degrees. P.S.
The G film 12 is laminated to form a composite film structure consisting of three layers sandwiching the silicon nitride film 11.

For example, the thickness of the PSGllilo is 0.5 μm, the thickness of the silicon nitride film 11 is 0.5 μm, and the thickness of the p3Q film 12 is 0.
．． 5 μm, the stress within the cover insulating film made of this composite film is balanced and the internal stress is ideally reduced to zero.

This eliminates the occurrence of cracks in the cover insulating film.

At this time, since the tensile stress of the PSG film can also be adjusted by the phosphorus content, the stress is balanced by taking this into account.

In addition, since the surface is soft due to the presence of the PSG film 12, even if it comes into contact with a hard plastic molding material, such as an epoxy resin, the PSG film 12 acts as a buffer and relieves stress.

Furthermore, there is a PSG film 10 on the inner surface of this cover insulating film, which makes soft contact with the transistor elements provided on the semiconductor chip.The PSG film also has a large bancivation effect that absorbs mobile ions, which has been known for a long time. These advantages are in no way diminished by the present structure.

[Effects of the Invention] Therefore, as is clear from the above explanation, the semiconductor device provided with the composite cover insulating film according to the present invention has improved capacitance and is highly reliable, and is particularly suitable for semiconductor devices having plastic molded packages. Trust IQ-1'n1
It contributes significantly to J=.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a semiconductor chip according to the present invention, and FIGS. 2(a) and 2(b) are partial sectional views of a conventional semiconductor chip. In the figure, 1 is silicon. 2 is a silicon dioxide crotch, 3 is an MO3+- transistor element, 4 is a PSG film, 5 is an aluminum wiring, 6 is a cover insulating film (PSC film or plasma silicon nitride film), 10 and 12 are PSC films (cover insulating film) ), 11 indicates the silicon nitride film (of the cover insulating film).

Claims (2)

[Claims] (1) A composite cover insulating film in which a second insulating film to which stress opposite to that of the first insulating film is applied is sandwiched between the first insulating films is provided on the semiconductor chip. semiconductor device. (2) A composite cover insulating film in which a silicon nitride film to which a stress opposite to that of the phosphorus silicate glass film is applied is sandwiched between the phosphorus silicate films is provided on the semiconductor chip. A semiconductor device according to scope 1.