JPH0276249A - Electronic device and manufacture thereof - Google Patents

Abstract

PURPOSE:To prevent the occurrence of re-release from an organic substance into a molding agent by fixing an electronic part and the organic substance on a substrate or a lead frame and by coating these elements including the organic substance with an inorganic protecting film. CONSTITUTION:A chip 28 made to adhere to a die 35' of a lead frame by silver paste 24 containing an organic substance, or the like, is provided, and wire- bonding of a gold wire 39 is made between an aluminum pad 38 of this chip 28 and a stem 35. An unnecessary gaseous component in organic substances 24 and 24' is deaerated from the surface of said chip 28, the surface of the pad 38, the surface of the wire 39 and the back of the die 35', the surface of metal is exposed 30 by a plasma processing of a non-produced substance gas, and coating with a protecting film of an inorganic material for preventing deterioration, silicon nitride films 27, 27', 27'', 27''' and 27'<4> in particular, by a plasma CVD method is conducted. Thereby improvement in the adhesion of molding resin and the metal and prevention of melting of the organic substance outside can be attained.

Description

[Detailed description of the invention] "Industrial application field" This invention can be used as a substrate for electronic components such as semiconductor devices.

The present invention relates to high-performance φ■ of electronic devices which are fixed onto a die of a lead frame or a lead frame using an organic substance, and a method for manufacturing the same.

For this reason, the present invention removes the vaporized components in the organic matter by holding the whole in a vacuum container, and also prevents the vaporized components from adhering to the substrate or die so that it adheres to the substrate or die. This is intended to improve the adhesion with the protective film or organic resin to be coated.

By improving the adhesion between the goo and the protective film that adheres to it, cracks and blisters (the molding agent on the back side of the die swells due to vaporization of water near the die due to temperature rise during soldering) It is intended to prevent cancer from occurring.

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

However, in the past, as shown in Fig. 4, the lead frames (35), (35') and especially the die (35') to which the IC chip is die-attached were made of metal such as copper or 4270I; M side) is printed with gold.

And when die attaching electronic parts (24), 30
The IC chip was fixed on the die (35') by heat treatment at 0 to 400'C and pressure treatment.

Another method for fixing this IC chip onto a die is a method using an organic substance heated to room temperature to 300°C. However, unnecessary organic gas (
24°"), (24'), etc. are degassed and adhere to the substrate or lead frame. Therefore, if the organic resin molding (41) treatment is performed immediately after this, this molding agent and the copper Alternatively, an adsorbent and a lower oxide layer (32), which are extremely easy to peel off, remain between the adsorbent and the 4270i.

``Conventional drawbacks'' For this reason, as shown in Figure 4, plastic mold packages generally have water, etc. that reduce reliability, which collects on the back side of the die of the lead frame. When the molding agent is immersed in molten solder for 10 seconds), the molding agent is rapidly vaporized, resulting in stress that causes the molding agent to expand. Therefore, the die (35') and molding agent (4
1'), cracks (33) occur due to thermal strain at the interface.

(33') and voids (42) are induced.

Up until now, electronic components (
(hereinafter also referred to as a chip) is fixed.

For this fixing material, a fixing material (2
4), (24') was used. When an electronic component is fixed onto a substrate or frame using this fixing material, organic matter that is initially in a molten state is solidified through a chemical reaction or a thermochemical reaction. This is inexpensive and extremely suitable for mass production. However, this organic matter fixing material (24)
, (24”) is the state of room temperature in the atmosphere or heating (
100 to 300°C), the fixed organic material or vaporized component remains. This residue gradually evaporates,
Since it is adsorbed onto the substrate or die, it also impairs the adhesion with the protective film or mold resin that will be formed later.

"Structure of the Invention" The present invention provides a hybrid RC in which a conventional DIP or flat pack molded semiconductor integrated circuit or a plurality of electronic components are fixed on a substrate or lead frame with an adhesive containing an organic substance. The present invention provides an electronic device with high reliability, such as the present invention, and a manufacturing method for preventing a decrease in reliability thereof. In the present invention, electronic components are fixed onto these substrates or metal lead frames using an organic material, and an inorganic protective film is further provided to cover the organic material. At the same time, this protective film is characterized in that a protective film of an inorganic material is formed between the mold resin and the metal for the purpose of improving moisture resistance, improving adhesion, and preventing organic matter from melting to the outside.

For this reason, by holding the electronic device in a vacuum container that is evacuated using a turbo molecular pump, unnecessary gas components in the organic matter are degassed, and oil mist flowing back from the rotary pump during exhaust processing is also prevented. , to achieve high confidence.

Furthermore, if necessary, all these surfaces, including this metal surface, are then protected in the same reactor without external heating at the same time, preferably at room temperature (there is some self-heating due to the plasma) using a plasma vapor phase method. It is characterized by covering it with a film and applying a coating, followed by sealing using a plastic molding process.

FIG. 1 shows a cross-sectional view of a plastic DIP (dual in-line package) or flat pack package constructed according to the present invention.

In the drawing, a chip (28) is closely attached to a die (35') of a lead frame with a paste (24) containing an organic substance. Unwanted organic matter to be fixed during chip attachment protrudes around the side as (24'). A wire bond of gold wire (39) is made between the chip (28) and its aluminum pad (38) and stem (35).

The present invention degass unnecessary gas components in the organic substances (24) and (24') from the surface of the chip (28), the surface of the pad (38), the surface of the wire (39), and the back surface of the guide (35'). and prevent them from being reabsorbed by the surfaces mentioned above. For this purpose, the electronic device containing the adhesive is kept under high vacuum. Under this high vacuum, 5×LO-'
~ I
Use. Since this turbomolecular pump exhausts air continuously, it can prevent backflow of oil mist, which is an organic gas. Furthermore, by plasma treatment of non-product gas, unnecessary organic gas components, lower oxides, and natural oxides generated during die attach are removed, exposing the metal surface (30), and then protecting the inorganic material for preventing deterioration. films, especially silicon nitride films (27), (27'), (2
7"), (27'"), and (27""°) coating by plasma CVD method.

Figure 2 shows a substrate with a structure in which the chip of the present invention is bonded to a frame, and a substrate (2
) (hereinafter abbreviated as "substrate"), and plasma treatment is used to remove unnecessary semi-solid organic substances and lower oxides, and in the same reactor, they are exposed to the atmosphere and water is removed. Plasma CV
An outline of an apparatus for coating a silicon nitride film by method D is shown.

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

The reaction system has a vacuum container (hereinafter also referred to as reaction chamber) (1) and a preliminary chamber (7), and gate valves (8) and (9).
It has The reaction chamber (1) has a supply side hood (
13), and the reactive gas from the inlet side (3) is blown downward from the nozzle (13) of the hood (14) and exhausted.

In FIG. 2, the reactive gas is pumped by a turbo molecular pump (20) using a 5
O-'~IXl0-"torr preferably lXl0-
'~LX10-8 Lorr for 5 to 30 minutes, the unnecessary organic gas in the fixing agent in FIG. 1 was degassed into vacuum and prevented from being adsorbed onto the substrate, frame, etc.

The plasma processing method of the present invention may use an inert gas such as argon, neon, helium, or krypton, or hydrogen, nitrogen, or ammonia. However, argon is preferable because it has a large mass, is relatively inexpensive, and is a gas that easily turns into plasma. Electronic devices are placed in this vacuum to degas unnecessary gas components in organic matter, prevent organic gas components from re-deposition on the surface of electronic devices, and remove unnecessary organic components that have inadvertently re-deposited. The initial plasma treatment and subsequent formation of a protective film of an inorganic material were carried out using a plasma treatment apparatus as shown in FIG. 2 without exposing the electronic device to the outside air. Further, a plastic mold (41) was formed on this upper surface.

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

After forming a protective film for preventing deterioration such as a silicon nitride film to a thickness of 300 to 5,000 layers, generally about 1,000 layers, an organic resin such as epoxy (for example, 410B) is coated by a known injection molding method. It was injected and sealed using a molding method. Furthermore, attach the frame to the lead part (
37) and cut the tie bar. Furthermore, after acid-washing the lead portion, the lead was solder-plated.

Using this reaction vessel, a plasma reaction was carried out to remove unnecessary organic substances, semi-organic substances, and lower oxides and to form a protective film on the substrate or substrate (2). After plasma treatment or reaction, the valve (21) is passed through the exhaust port (4) from the nozzle (13') of the discharge side hood (14').

The turbomolecular pump (20) further leads to a rotary vacuum pump or dry vacuum pump (23).

The electric energy from the high frequency power source (10) passes through the matching transformer (26) and is transmitted to a power of 1 to 500 MH2, for example
．． A frequency of 56 FIHz is applied to a pair of equal-sized mesh molds +m(11), (11') between the upper and lower sides. The middle point (25') of the matching transformer was set at the ground level (25). Further, if the peripheral frame structure holder (40) is a conductor, it is at the ground level (22), or it may be an insulator.

The reactive gas is excited by high frequency energy supplied by a pair of electrons 1 (11) and (12).

In addition, in deaeration by vacuum treatment, plasma treatment, and plasma CVD methods in the same reactor, the object to be formed (2
) (hereinafter referred to as the base (2)) is placed in a frame-structured holder (40) disposed on a supporter (40') parallel to the direction of the electric field between the pair of electrodes, and furthermore, either electrode (11).
, (12). Multiple substrates (2)
are arranged at a constant interval (2 to 13 cm, for example 6 cm) or approximately at a constant interval from each other. This large number of substrates (2) is arranged in a positive column in plasma created by glow discharge.

The main part of this base body is shown in FIG. 3(C).

FIG. 3(A) shows the base body (35) in the base body (2),
(35") on a lead frame that integrates multiple pieces (45")
) with a semiconductor device (28") bonded to a base (45) in which 5 to 25 electronic devices (29) are unitized.
has.

FIG. 3B shows one lead frame (substrate) in one lead frame (45) to which a plurality of semiconductor chips are bonded.

In the drawing, only the left side of the lead is shown for simplicity. This A-A
A vertical cross-sectional view at `` is shown in (29) of FIG. 3(C).

In FIG. 3(C), further 5 to 300 substrates (45) made of lead frames (35), guides (35'), semiconductor chips (28), and metal wires (39) are collected, and jigs (
44) to form a base body (2). This base body (2) corresponds to the base body (2) in FIG. In addition, 5 to 50 of these (7 in the drawing) are installed inside the Yoko company as shown in Figure 2.

The method for degassing organic matter in the method of the present invention as shown in FIG. 2 is as follows:
Followed to hold at orr.

In the present invention, after this high vacuum degassing, the internal pressure of the reaction vessel is reduced to a medium vacuum of 5X10-' to 5X10-' tor.
rFor example, 1xlo-3~IXl0-3~5x10-
When plasma is generated at 1 torr and a silicon nitride film is formed, a sufficiently dense insulating film can be formed without external heating.

An example of this process is shown below.

"Example IJ In the deaeration of unnecessary organic matter by holding under high vacuum in FIG. 2, plasma processing equipment, and plasma CVD equipment, the doping system (5) is disilane (a silicide gas)
SiJJ is supplied from (17), ammonia or nitrogen, which is a nitride gas, is supplied from (16), and argon, which is a non-product gas for plasma processing, is supplied from (15). They are controlled by a flow meter (1B) and a valve (19).

For example, for mass production, the substrate temperature was set to room temperature (including self-heating by plasma) without any active external heating.

First, the reaction space (1) is 1 x 1o bow ~ l x 1O-8tor
The reactor was held at a temperature of R for 5 to 15 minutes to degas the unnecessary gases in the organic matter, and this was promptly exhausted to the outside.

Furthermore, after that, argon was introduced to 5 Xl0-2 torr and at the same time it was evacuated, and electrical energy was applied to generate plasma and perform plasma treatment on the surface of the substrate (2).

That is, for these argon, the output of IKW is applied from a frequency of 13.56 MHz to a pair of electrodes (11), (11"
) for 10 to 30 minutes to generate plasma. This removed the oil mist, unnecessary organic matter, moisture, and lower oxides adhering to the back side of the die, exposing a new metal surface and improving the adhesion of the film being formed. .

Next, a protective film is formed on the plasma-treated surface in the same reactor without exposing it to the atmosphere. That is, when forming a silicon nitride film, the reactive gas is, for example, 5i
J6/Nz = 115. For these argon, IKH output was supplied to a pair of electrodes (11) and (11') at a frequency of 13.56 MHz. In this way, coatings were formed on an average of 1000 people (1000±200 people) for about 10 minutes (average speed 3 A/sec).

The silicon nitride film had a dielectric strength voltage of 8 x 106 V/cm or more, and a specific resistance of 2 x 10'' Ωcm.The infrared absorption spectrum had an absorption peak of 5i-N bond at 864 cm -', and the refractive index was 2. It was .0.

When kept in saline solution (95°C) in which 5χNaCl was dissolved, no deterioration was observed even after 20 hours. Therefore, it was possible to prove that the film can be used as a protective film for preventing deterioration of the present invention.

For electronic devices manufactured by the method of the present invention, 85°C
/85χ (relative temperature) for 1000 hours, and then soldering was performed at 260°C for 5 seconds. However, this mold did not develop any cracks or blisters.

Furthermore, a reliability test was conducted under the conditions that 300 molds were left at 85°C/85χ to absorb water into the plastic mold, and then heated at 260°C for 13 seconds.

Examples are shown in the table below.

As a result, after vacuum treatment, plasma treatment, and protective film formation, there were no defective items out of 100 and all were good (No. 1).
~5), and there were no defective products at all during the vacuum treatment and protective film formation steps. (No. 6 to 10) If there is no stain protection film, 4 to 20 out of 20 products are defective (No.
13 to 15), and even with a protective film, if the vacuum treatment was not sufficient, some products were defective. (No
, 11-12) Furthermore, the surface of the aluminum pad generally has poor adhesion to the molding material. However, when a protective film is formed on this aluminum pad (Fig. 1 (3B)) as in the present invention, the adhesion here is improved, and in addition, the silicon nitride film has a blocking effect (mask effect) against water and chlorine. big. Therefore, in electronic devices (for example, semiconductor integrated circuits) having the structure of the present invention, PCT (Pressure Cutcher Test) 2
Atom, even after 20 hours at 120°C, no defects were observed, and conventional IC chips were 50 to 1
The defective rate was 0.00 fits, but now it has become possible to lower the defective rate to 5 to 10 fits.

In addition, in the present invention, it is necessary to maintain under a high vacuum, and in the plasma processing method and PCVD method, not only electric energy but also light energy in which far infrared rays with a wavelength of 10 to 15 μm or ultraviolet light of 300 nm or less are simultaneously added. It is effective to use a photo-cleaning method for removing organic matter.

"Effect J" In the present invention, electronic components and organic substances are fixed on a substrate or lead frame, and these containing organic substances are covered with an inorganic protective film, so that it is possible to prevent the organic substances from being re-released into the molding agent. It was also possible to prevent the migration of the silver added therein. It was also possible to prevent the adhesion between the frame and the molding agent. Also, there was no need for electricity or time for heating. , it has excellent productivity.Since adsorbed organic substances and lower oxides are removed from the back side of the die, the adhesion of the organic resin can be improved.Also, when a protective film is formed, it can be used for a long time. Even after a period of time, there is no disadvantage that lower oxides are formed due to the reaction between the moisture in the organic resin, chlorine, and the metal of the die, reducing reliability.Also, it prevents moisture from entering from the back side. When mounting this electronic device on a PCB using a semiconductor, it was possible to prevent the mold material from swelling due to heating, as shown in the conventional example.

The protective film in the present invention was a silicon nitride film. However, this may be a single layer or multilayer film of a DLC (diamond-like carbon) film, a silicon oxide film, or other insulating film.

Further, in the present invention, the electronic component chip is shown as a semiconductor element, but it may also be a hybrid IC in which a metal conductor is provided on an insulating substrate and a resistor and a capacitor are fixed to these, and bonding can be performed only by wire bonding. Alternatively, flip chip bonding or solder bump bonding may be used.

In the present invention, the size of the chip may be increased and it may be molded without using a die. However, even in that case, it is effective to provide a protective film covering all of the substrate, lead frame, and chip.

Although the above description describes the case where a semiconductor chip is mounted on a lead frame, the present invention is not limited to a dual-in-line type lead frame, but is applicable to a flat pack type lead frame and other lead frames. Even if it has a similar function, similar effects can be expected.

[Brief explanation of the drawing]

FIG. 1 shows a main part of a plastic package semiconductor device in longitudinal section after the moisture resistance test and soldering test of the present 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. FIG. 4 shows a main part of a conventional plastic package in a vertical sectional view after being subjected to a moisture resistance test and a soldering test. 87' Mei IC Nitech ■P 1 (A) ゝ, 0°' E 3 (B Not 41"71

Claims (4)

[Claims] 1. In an electronic device in which an electronic component is fixed to a die of a substrate or a lead frame using a bonding material containing an organic substance, a protective film of an inorganic material is provided, covering the surface of the bonding material and also covering the surface of the substrate or lead frame. An electronic device characterized by being provided with. 2. An electronic device according to claim 1, characterized in that the protective film is covered with an organic resin sealing process. 3. In a method for manufacturing an electronic device in which an electronic component is fixed onto a die of a substrate or a lead frame using a bonding material containing an organic substance, gas components in the organic substance are degassed by holding the electronic device in a high vacuum. process and
The electronic device is 5×10^-^3~5×10^-^1t
The process includes a process of plasma treatment with a non-product gas under a pressure of 1 torr and a process of forming a protective film by a plasma vapor phase reaction method under a pressure of 5 x 10^-^3 to 5 x 10^-^1 torr. The electronic device manufacturing method is characterized in that these steps are performed in the same vacuum container. 4. In claim 3, the electronic device is heated at 5 x 10^-^4 to 1 x 1 in high vacuum without external heating.
A method for manufacturing an electronic device, characterized in that the pressure is maintained at 0^-^8 torr.