JP2551405B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a passivation film (insulating protective film) used in a semiconductor integrated circuit.

[Prior Art] FIG. 3 is a diagram showing a schematic sectional structure of a conventional semiconductor device. Referring to FIG. 3, a conventional semiconductor device includes a silicon semiconductor substrate 1 including a semiconductor circuit element, an insulating film 2 formed on the silicon semiconductor substrate 1 by using, for example, a CVD method (chemical vapor deposition method), and an insulating film. The electrode wiring 4 made of, for example, aluminum is selectively formed in a predetermined region on the film 2 by, for example, the sputtering method, and is formed on the insulating film 2 and the electrode wiring 4 by the CVD method or the like. A passivation film (hereinafter referred to as a passivation film) 3 as an insulating protective film serving as a protective film.
This passivation film 3 is usually formed in a single step using a single type of insulating material from the viewpoint of the number of manufacturing steps and the price, so that the semiconductor circuit element formed on the surface of the silicon semiconductor substrate 1 may not absorb moisture. The influence from the outside is eliminated, and each circuit element formed on the surface of the silicon semiconductor substrate 1 is electrically insulated.

FIG. 4 is a diagram schematically showing a cross-sectional structure of the semiconductor device shown in FIG. 3 after resin sealing. In FIG. 4, the semiconductor device is mounted on the lead frame 8 for mounting the semiconductor device via the soft solder 9. The soft solder 9 made of a soft material absorbs stress generated in the semiconductor substrate 1 at the time of resin sealing and fixes the back surface of the semiconductor substrate 1 to the lead frame 8 by soldering. The electrode wiring 4 formed in a predetermined region on the semiconductor substrate 1 through the insulating film 2 has a through hole formed in a predetermined region of the passivation film 3 by using photoengraving and etching. Via the bonding wire 6 via the lead terminal 5 using the wire bonding method. The lead terminal 5 electrically connects the semiconductor device to an external circuit. Lead frame 8, soft solder 9, silicon substrate 1, insulating film 2, and electrode wiring 4
The passivation film 3, the wire bonding wire 6, and part of the lead wire 5 are sealed with a molding material 7 made of plastic resin. The molding material 7 has a function of preventing moisture absorption of the semiconductor device and a function of relieving mechanical damage given from the outside so as not to be transmitted to the semiconductor device.

[Problems to be Solved by the Invention] When the conventional semiconductor device is sealed with the molding material 7, a molding material having a relatively high temperature is used. The semiconductor device is sealed by cooling and solidifying the molding material 7. However, in order to suppress the thermal stress applied to the passivation film 3 and the electrode wiring 4 from the molding material 7 at this time, the passivation film 3 has the film. The thickness is 1.8 μm or more.

FIG. 5 is a cross-sectional view schematically showing the effect of the thickened passivation film on the electrode wiring. As shown in FIG. 5, when the passivation film 3 is thickened, the stress from the molding material 7 can be suppressed, but the passivation film 3 is also formed under a relatively high temperature condition. The stress applied from the thickened passivation film 3 to the electrode wirings 4 increases, voids 10 are generated in the electrode wirings 4, and the wirings are deteriorated or broken due to electromigration. There was a problem that it led to the decrease of.

The problem to be solved by the present invention is to increase the thickness of the passivation film in the method of manufacturing a semiconductor device,
In particular, it is to be able to suppress the stress on the electrode wiring even if the film thickness is increased to 1.8 μm or more.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a step of forming a film made of a single kind of insulating material having a predetermined thin film thickness is performed a plurality of times. The total film thickness is 1.8
The means for forming a thickened passivation film made of a single kind of insulating material having a thickness of μm or more is taken.

The thickness of the passivation film formed in one step is preferably 1.0 μm or less.

[Operation] Since the above measures are taken, the passivation film of a single type of insulating material is formed a plurality of times to form a thickened passivation film made of a single type of insulating material. The film thickness of the passivation film formed in step (5) becomes thin, the amount of heat accumulated in each passivation film is reduced, and after the formation of each thinned passivation film, the electrode wiring from the passivation film is cooled when cooled to room temperature. The stress generated in the is suppressed.

[Embodiment of the Invention] An embodiment of the present invention will be described below.

FIG. 1 is a diagram showing a schematic sectional structure of a semiconductor device according to an embodiment of the present invention. In FIG. 1, as a feature of the present invention, the passivation film 3 has a first passivation film 3a having a predetermined film thickness and a predetermined film thickness formed on the first passivation film 3a. The second passivation film 3b has a multilayer structure. The film thicknesses of the first passivation film 3a and the second passivation film 3b are both 1.0 μm or less, and the total film thickness (film thickness of the passivation film 3)
Is 1.8 μm or more. Next, a method of manufacturing a semiconductor device according to an embodiment of the present invention will be described with reference to FIG. The process of forming the insulating film 2 on the surface of the semiconductor substrate 1 and selectively forming the electrode wiring 4 made of aluminum or aluminum alloy in a predetermined region on the insulating film 2 by using, for example, a sputtering method is the same as the conventional process. Is. Next, a first passivation film 3a made of a silicon nitride film having a predetermined film thickness is formed on the insulating film 2 and the electrode wiring 4 by using the plasma CVD method. In this plasma CVD method, since a thin film is formed under relatively high temperature conditions, the entire semiconductor device is once cooled after forming the first passivation film 3a. Next, a second passivation film 3b made of the same material as the first passivation film 3a is formed again on the first passivation film 3a by the same method as that for forming the first passivation film 3a.
At this time, the film thicknesses of the first passivation film 3a and the second passivation film 3b are both 1.0 μm or less, and the total film thickness of the passivation film 3a and the second passivation film 3b is 1.8 μm or more. To be done.

FIG. 2 is a diagram showing the relationship between the energization time and the cumulative failure rate in a semiconductor device using a passivation film which is an embodiment of the present invention and a conventional semiconductor device. In FIG. 2, the horizontal axis represents the energization time in a high temperature holding state at room temperature or higher, and the vertical axis represents the cumulative failure rate. Further, the symbol Δ indicates the experimental result for the conventional semiconductor device, and the symbol ● indicates the experimental result for the semiconductor device according to one embodiment of the present invention. That is, in the conventional semiconductor device, the passivation film having a thickness of 1.8 μm or more is a plasma nitride film formed once by using the plasma CVD method, and the passivation film made of the plasma silicon nitride film of the semiconductor device according to the present invention. Has a total film thickness of 1.8 μm or more,
The thickness of the passivation film made of a plasma silicon nitride film formed in one step is set to 1.0 μm or less, and this step is repeated twice.

As can be seen from FIG. 2, when the semiconductor device is continuously energized while being kept at a high temperature of room temperature or higher, the cumulative failure rate is much lower in the semiconductor device having the passivation film according to the present invention.

In the above embodiments, the case where the passivation film is a nitride film using the plasma CVD method and the passivation film is formed in two steps is described. However, the passivation film is formed in three or more steps. Even if they are separately formed, the same effect as that of the above embodiment can be obtained.

Further, although the plasma CVD silicon nitride film is used as the passivation film in the above-mentioned embodiment, in the case of another passivation film, for example, a PSG (phosphorus glass) film formed by using the plasma CVD method, an oxidization using the plasma CVD method is used. Even when the nitride film is used, the same effect as that of the above-mentioned embodiment can be obtained.

As described above, according to the present invention, since the passivation film is formed by dividing the passivation film into a plurality of times, generation of voids in the electrode wiring and deterioration of the electrode wiring due to electromigration are suppressed. Therefore, a highly reliable semiconductor device can be obtained.

In addition, since the passivation film of the same material is only formed multiple times, it is not necessary to change the source gas and replace the film forming chamber, and it is necessary to drastically change the conventional passivation film manufacturing process. There is no.

[Brief description of drawings]

FIG. 1 is a sectional view showing a schematic structure of a semiconductor device according to an embodiment of the present invention. FIG. 2 is a diagram showing the results of experimentally obtaining the relationship between the energization time during high temperature holding and the cumulative failure rate in the semiconductor device according to one embodiment of the present invention and the conventional semiconductor device. FIG. 3 is a sectional view showing a schematic configuration of a conventional semiconductor device. FIG. 4 is a sectional view showing a state in which the semiconductor device is resin-sealed. FIG. 5 is a diagram schematically showing the effect of the thickened passivation film on the electrode wiring. In the figure, 1 is a silicon semiconductor substrate, 2 is an insulating film, 3
Is a passivation film, 3a and 3b are passivation films according to the present invention, and 7 is a molding material for sealing. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eisuke Tanaka 4-chome, Mizuhara, Itami City, Kita Itami Works, Mitsubishi Electric Corporation (56) Reference JP 57-124444 (JP, A) JP 57- 45931 (JP, A)

Claims (6)

(57) [Claims] 1. A method of manufacturing a semiconductor device, wherein an insulating protective film is formed on the uppermost layer, wherein the step of forming the insulating protective film has a total film thickness of 1.
A method of manufacturing a semiconductor device, comprising: a step of forming a film made of a single kind of insulating material to a predetermined thickness so as to have a thickness of 8 μm or more. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the film made of a single kind of insulating material has a predetermined film thickness of 1.0 μm or less. 3. The film made of a single kind of insulating material,
The method for manufacturing a semiconductor device according to claim 1, which is a silicon nitride film formed by using a plasma chemical vapor deposition method. 4. The film made of a single kind of insulating material,
The method for manufacturing a semiconductor device according to claim 1 or 2, which is a phosphorus glass film formed using a plasma chemical vapor deposition method. 5. The film made of a single kind of insulating material,
The method for manufacturing a semiconductor device according to claim 1 or 2, which is a silicon oxynitride film formed by plasma enhanced chemical vapor deposition. 6. The insulating protective film covers electrode wiring selectively formed on a semiconductor substrate, and the electrode wiring is formed using aluminum or aluminum alloy. A method of manufacturing a semiconductor device according to any one of items 1 to 5.