JPH0383353A - Manufacture of electronic device - Google Patents

Abstract

PURPOSE:To enhance a prevention effect to water content and to improve the reliability of an electronic component, which is performed an organic resin- sealing, by a method wherein a base body is arranged in a space filmed with plasma and a protective film is formed at a room temperature or at a temperature in the vicinity of the room temperature. CONSTITUTION:An electronic component chip 28 is coupled with a pad 38' of a stem 35 for coupling a two layer pad 38, which consists of an Al layer and a gold layer, with an electronic component chip of a lead frame through a conductor 39, such as by soldering. Moreover, a protective film for deterioration prevention use, in particular a multilayer film 27 consisting of a silicon nitride film, a silicon oxynitride film, a silicon carbide film or these films and a diamond-like carbon film is applied on the surface of this chip 28, the surface of the pad 38, coupling parts 38, 38' and 39 and the rear and the side surface of the chip 28. The protective film like this silicon nitride film is formed by the so-called plasma vapor phase method, in which silicide gas and nitride gas are introduced in a reaction furnace at a room temperature or at a temperature in the vicinity of the room temperature and an electric energy is fed here.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention aims to further reduce the size of electronic components such as semiconductor devices,
The present invention relates to a method for manufacturing an electronic device that provides a means for achieving higher reliability.

"Conventional Technology" Conventionally, final coating for forming a protective film on electronic component chips was performed at the wafer level. For this reason, the aluminum (
In general, 100 μm x 100 μm) was exposed to the epoxy mold part.

Aluminum pads are prone to corrosion, leading to deterioration of the characteristics and reliability of semiconductor devices.

The present invention relates to a method for forming a protective film to prevent a decrease in reliability that occurs in such conventional electronic components sealed with organic resin.

Previously, Patent H by the present inventor (Semiconductor device manufacturing method, Patent Application No. 106452, June 14, 1982)
(application filed in Japan) is known.

The inventor's proposal is effective in preventing corrosion of the pad, but when the pad is kept in a humid atmosphere for a long period of time and soldered to it, the soldering temperature of 260°C The rapid temperature change caused the moisture in the organic resin to rapidly evaporate, causing the package to crack. In particular, there was a lot of separation from the organic resin at the die part on the back side of the electronic component chip.

This is thought to be due to the generation of strain energy due to the difference in thermal expansion coefficient between the die and the organic resin. There has been a need for a structure for electronic components that can compensate for such a decrease in reliability, and for countermeasures therefor.

"Purpose" This invention relates to plastic mold (organic resin) encapsulation, and the formation of a protective film for final coating on semiconductor chips (hereinafter referred to as electronic component chips or electronic components such as transistors or semiconductor devices in which multiple transistors are integrated) Not only the surface of the chip (simply called a chip), but also the surface of the lead frame (
It covers the entire surface (the assembly that ultimately constitutes the lead of the electronic component) and its connection part (the entire area for connecting the pad of the electronic component chip and the pad of the stem part of the lead frame). By providing a protective film,
The purpose is to form highly reliable electronic devices.

In a plastic mold package, the present invention prevents moisture such as water that reduces reliability not only from the bulk of the plastic package, but also from water that enters through the surface of the lead portion L. It is characterized by the provision of a highly reliable semiconductor device that has a bronking effect.

"Structure of the Invention" FIGS. 1A and 1B show a vertical cross-sectional view of an electronic component sealed with an organic resin having the structure of the present invention.

Figure 1 (A) shows an electronic component chip (28) and a two-layer pad (38) made of metal such as aluminum and gold.
) and the pad (38″) of the stem (35) for connection with the electronic component chip of the lead frame.
) For example, connect by soldering, and then connect this chip (2
8> Surface, pad (38) surface, connecting portion (3B).

(38'), (39) On the back and side surfaces of the electronic component chip (28), apply a protective film for preventing deterioration, especially a silicon nitride film, a silicon oxynitride film, a silicon carbide film, or a diamond-like carbon (LC) film together with these. Coating with a multilayer film (27) is performed.

This protective film such as a silicon nitride film was formed by a so-called plasma vapor phase method in which a silicide gas and a nitride gas were introduced into a reactor and electrical energy was supplied thereto at room temperature or a temperature close thereto.

After forming the protective film for preventing deterioration to a thickness of 300 to 5,000 layers, generally about 1,000 layers, the epoxy resin (33
) was injected and sealed. Furthermore, the tie bars (those that temporarily connect the leads of the lead frame to prevent them from dispersing) are cut, the frame is bent at the lead (37) portion, and the lead portion is pickled. Solder plating was performed on (37).

In the structure of the semiconductor device of the present invention, water that reduces reliability impregnates the molding material (33), and the chip (28),
Pad (38), pad (38') of stem (35)
gather on the surface of High reliability is achieved by preventing this water from coming into direct contact with electronic component chips and the like.

Thus, in FIG. 1(A), since the chip is not wire-bonded, there is no die under the electronic component chip, and bonding wires are also omitted, resulting in miniaturization.

In Figure 1 (B), a PCB (printed circuit board)
The electronic component (29) is brought into close contact with the die side. This further prevents the occurrence of cranking of the package due to the expansion of water impregnated in the organic resin in the event of a sudden heat rise of 260 DEG C. for 10 seconds during soldering.

Figure 2 shows a structure in which the electronic component chip of the present invention is bonded or mounted to a lead frame, and one substrate is mounted on a holder, or a plurality of substrates (2) are mounted on a holder and assembled. An outline of a plasma CVD apparatus for coating a protective film such as a silicon nitride film using a plasma vapor phase method is shown below.

In the drawing, it has a reaction system (6) and a doping system (5).

The reaction system (6) has a reaction chamber (1) having a reaction space, a preliminary chamber (7), and gate valves (8) and (9). The reaction chamber (1) has a supply hood (13) inside.
The hood (13) blows reactive gas downward from the nozzle (3) on the inlet side to cause a plasma reaction,
A protective film was formed on the substrate or substrate. After the reaction, the valve (2
1), leading to the vacuum pump (20). High frequency power supply (10)
The electric energy of
A pair of mesh electrodes of the same size between the upper and lower sides (
11).

Add to (II'). Furthermore, the center point (25") of the matching transformer is set to the ground level (25), and a bias supply source (24) is connected between this level and the base (2)
C or AC bias (1~500KIIz e.g. 50
KHz) was added. Additionally, the surrounding reactive gas was prevented from spreading to the inner wall of the reaction chamber. Frame structure holder (40
) is a floating level if it is a conductor, or it may be an insulator. The reactive gas is transported between a pair of electrodes (11) and (1
The electronic component having the surface to be formed is excited by high frequency energy supplied by 1°) and biased by low frequency bias energy to coat the electronic component chip, the stem bonded to the chip, or the lead frame. I made it so that it would be done. plasma cv
In method D, the object (2) on which the film is formed (hereinafter referred to as the substrate (2)
) is parallel to the direction of the electric field between a pair of electrodes within a frame-structured holder (40) disposed on a supporter (40''), and either electrode (11).

(11"). The plurality of substrates are arranged at a constant interval (3 to 13 cm, e.g. 8ca+) or approximately constant interval from each other. This large number of substrates (
2) is placed inside the company with sunlight in the plasma created by glow discharge.

FIG. 3(A) is an enlarged view of the parts of the base body (2). That is, the base body (2) in FIG. 2 shows a substrate (2') on which 5=tO chips of electronic parts are mounted on a lead frame.

The electronic component chip (28) is abbreviated as a mouth shape in FIG. 3(A). Figure 3 (A) shows the upper and lower auxiliary bars (41) and (41') that temporarily fix the leads of the lead frame.
is shown as a straight line. A vertical cross-sectional view taken along line A'' in FIG. 3(A) is shown in FIG. 3(B). In Figure 3 (B), each electronic component (29-1), (29-2), (29-2)
9-n), that is, corresponding to (29), an auxiliary bar (41),
(41'), lead (37), pad (38),
(38”), an electronic component chip (28) is shown.

An example of forming a protective film for the electronic device shown in FIGS. 1, 2, and 3 is shown.

“Example 1” In FIG. 1, the pad (3) of the electronic component chip (28) is
8) was made into a two-layer film of aluminum and gold. A stem (35) extending from the lead (37) of the lead frame has a nickel-plated pad (38') and solder is locally applied thereto to form a connection. This lead frame is connected to each pad (38), (3
8''') were aligned and irradiated with external heat at 260''C to melt the solder and connect them.

In this way, the structure shown in FIG. 3(B) is created. This is shown in Figure 3 (A
) was attached to one or more holders (2) to form a base, and a protective film was produced using the apparatus shown in FIG.

In the plasma CVD apparatus shown in FIG. 2, the doping system is a silicide gas, disilane (from (17)), a nitride gas, nitrogen (from (14)), and an etching gas in the reaction chamber, such as nitrogen fluoride. From (16),
Ethylene (C2) 14) is also supplied from (15). They are controlled by a flow meter (18) and a valve (19).

For example, when trying to make silicon nitride, the substrate temperature is set at or near room temperature without any active external heating (including self-heating by plasma), and the reactive gas is placed in the reaction chamber at 5id16/Nz = As 1/3, the pressure in the reaction chamber is 0.01 to 0.1 torr, for example 0.05 torr.
was supplied while maintaining the Furthermore, high frequency energy with a frequency of 13.56 MHz is applied to a pair of electrodes (11) using the output of IK-.
.

(11'). Also 5QKI for AC bias
The bias of the frequency of Iz (Step 2) is set to 100 on the substrate (2).
Add at a power of ~500-. Thus, an average of 1000 people (
Film formation was carried out for about 10 minutes (average speed 2 inputs/second) on 1000 people ± 2°0 people).

The silicon nitride film has a dielectric strength of 3 x 10bV/Co! The specific resistance was 2×10′″′Ωcm.The infrared absorption spectrum had an absorption peak of 5i-N bond at 864 cm −′, and the refractive index was 1.7 to 1.8.

When forming DLC, add ethylene from (15) instead of disilane and nitrogen at a similar room temperature to the reaction chamber (1) at a concentration of 100X at a reaction space pressure of 0.01-0.5 torr.
For example, the supply voltage was maintained at 0.05 torr. The high frequency energy bias was the same. Then, at a growth rate of 2λ/sec, 300 to 3000 DLC films, for example 1000
It was possible to form it to a large thickness.

Since DLC does not adhere well to metals and oxides, this film is first formed by depositing a silicon nitride film with a size of 200 to 2000.
Further, DLC was formed thereon to a thickness of 300 to 3000 layers. DLC is resistant to all acids and is excellent for making electronic components at extremely high temperatures.

The holder (40) has an inside size of 60c++ x 6
0c+++, and the distance between the electrodes is 30cm (effective 20
cm).

Further, FIG. 3 shows an enlarged view of the base body (2) in FIG. 2.

In Fig. 3, lead frames (29-1), (29-2), with electronic component chips mounted on the base, are shown.
...(29-n), that is, (29) is arranged. A ^-A° cross-sectional view of this jig is shown in (B). The tip (28) is connected to the stem (35) by a connecting portion including pads (38) and (38'''), which are arranged on a plurality of frames.

In this embodiment, the lead frame section has 80 bins. 4270i or copper frame stem (35)
Bonding is performed directly between the electronic component chip (28) and the bonding pad of the electronic component chip (28).

However, it goes without saying that it is also possible to have any number and shape of pins other than this shape.

That is, the present invention not only has the feature of coating a silicon nitride film or a multilayer film of a silicon nitride film and DLC as a protective film after connecting an electronic component chip and a lead frame at a connecting portion, but also coats a silicon nitride film or a multilayer film of a silicon nitride film and DLC as a protective film. The protective film is coated with a uniform thickness even on the exposed surface.

And for this purpose, the conductor of the lead frame is passed through the substrate (
Since the AC bias applied in 2) can be applied equally to all frames during film formation, an extremely dense film thickness can be produced. Furthermore, since high frequency was used to activate the reactive gas, the activation rate could be increased.

Furthermore, in the present invention, as shown in FIGS. 1(A) and 1(B), the epoxy resin was molded (33) by the transfer molding method. Then, the lead and the electronic component chip were integrated.

Additionally, the kuiper and auxiliary bar were removed. Then connect the lead part outside the mold to the lead (37) shown in Figure 1 (A).
Bend the lead into a predetermined shape and pickle the surface of the lead.
Completed soldering.

In the present invention, the PCVO method uses not only electrical energy but also a photoCVD (or FPCVD) method that uses light energy that simultaneously adds far infrared rays with a wavelength of 10 to 15 μ or ultraviolet light of 300 nm or less. That is valid.

``Effect'' Materials different from metal leads, electronic component chips, and connecting parts generally have poor adhesion to organic resins. However, in the present invention, high reliability can be achieved by forming a protective film with good adhesion on these and sealing the surface with good adhesion with the protective film with an organic resin film. In particular, the leads and electronic component chips are mechanically protected with an organic resin, and the defects of this resin are covered with a protective film. Furthermore, by removing the gougs and wires that were conventionally used, it was possible to achieve ultra-miniaturization.

In addition, a protective film such as silicon nitride has a large blocking effect (mask effect) against water and chlorine. For this reason, the semiconductor having the structure of the present invention is subjected to PCT (Pressure Test HOatom) for 100 hours at 150°C.
Even under these conditions, no defects were observed, and conventional IC chips had a defective rate of 50 to 100 feet, but it became possible to lower that defective rate to 5 to 10 feet.

The protective film in the present invention was a silicon nitride film. But DL
It may be a single layer or a multilayer film of a C (diamond-like carbon) film, a silicon oxide film, or another insulating film.

Further, in the present invention, the electronic component chip is shown as a semiconductor integrated circuit, but it may also be a resistor or a capacitor, and the bonding may be not only wire bonding but also flip chip bonding or solder bump bonding.

Although the above description describes the case where semiconductor chips are placed on a lead frame, the present invention is not particularly limited to lead frames, and even if the semiconductor chips have the same function as a lead frame, The effects can be expected.

[Brief explanation of drawings]

FIG. 1 shows a longitudinal sectional view of an electronic device according to the invention. FIG. 2 shows an outline of a plasma gas phase reactor for carrying out the method of the present invention. FIG. 3 shows an enlarged view of the base portion of the device of FIG. ^-1 Condolence/ Diagram

Claims (1)

[Claims] 1. Plasma space is formed on a substrate on which a plurality of electronic components are arranged, or on a substrate on which such substrates are assembled, in which the pad of an electronic component chip and the pad of the stem portion of a lead frame are connected by a conductor. 1. A method of manufacturing an electronic device, comprising: disposing the substrate or base body on the substrate; and forming a protective film at or near room temperature. 2. Place the substrate or substrate in a plasma space on a substrate on which a plurality of electronic components are arranged, in which the pad of the electronic component chip and the pad of the stem portion of the lead frame are connected by a conductor, or on a substrate on which the substrates are assembled. a step of forming a protective film over the electronic component; a step of performing a resin sealing treatment; and a step of removing a peripheral portion that held the lead frame to form an electronic device. A method for manufacturing an electronic device characterized by the following.