JPH0642495B2 - Electronic device and manufacturing method thereof - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device having a protective film formed to cover an electronic component such as a semiconductor integrated circuit and a method for manufacturing the electronic device.

“Prior Art and Problems Thereof” FIG. 4 shows a state of an electrode lead-out portion of a conventional electronic component (IC) (28).

In FIG. 4, the lead (35) of the frame and the die (35 ') of the frame molded with the organic resin mold (41) are shown.

In the drawing, this organic resin (41) is an insulating material with a high specific resistance (also called specific resistance) of 1 × 10 ¹⁷ Ωcm or more, so SMT (surface mount technology)
In surface mounting technology), the mold material may be contacted with the jig surface during assembly or during storage.
There was a problem that static electricity was locally accumulated on the surface of (41).

When the thickness of the organic resin is large, this static electricity causes the electric field strength to be relatively small for the electronic component, and it is unlikely to cause electrostatic breakdown of the electronic component, but the thickness of the molding material is small.
When the thickness is 1.5 mm or less, the electric field strength due to static electricity becomes relatively large, which is a problem in ensuring the reliability of electronic parts.

Further, the die (35 ') to which the IC chip (28) which is an electronic component is die-attached is made of metal such as copper or 42 alloy, and the electronic component (28) is die-attached (24 (3) a lower oxide (3
2) exists.

Therefore, immediately after this, the organic resin molding material (41)
Molded with copper or copper or 42
The oxide layer (32), which is very easily peeled off from the alloy, remains, which causes a problem that the adhesiveness of the molding material (41) deteriorates.

Then, if this electronic device is stored for a long period of time, the mold material absorbs moisture from the atmosphere and collects in the vicinity of the oxide layer (32), resulting in 260 ° C in the subsequent process (IC mounting process). During heating during soldering for 3 to 10 seconds, the mold material around the die is cracked by a sudden thermal shock.
(33) and (33 ') are generated, and the moisture accumulated on the back surface of the die is vaporized to form voids (42), which causes blistering (41') on the molding material on the back surface. Will occur.

As a result of the problems described above, deterioration of the characteristics and reliability of the semiconductor device due to the intrusion of water and impurities from the cracked portion have been induced for long-term use in the mounted state.

[Object of the Invention] In order to solve the problems of the conventional electronic device as described above, the present invention solves the problems of thermal shock in mounting the electronic device, the problem of deterioration of the molding material caused by long-term use, and the electronic device of impurities. It is an object of the invention to solve the problem of invasion into the inside and the like.

"Structure of the Invention" (First Invention) The first aspect of the present invention is "an electronic device characterized in that a carbon coating having a diamond structure is formed so as to cover an electronic component covered with an organic resin mold". Is the gist.

The structure in which the electronic component is covered with the organic resin mold is a conventionally known structure.

The present invention is further characterized in that a carbon coating having a diamond structure is formed so as to cover the organic resin mold.

The carbon coating having the diamond structure is carbon having the same SP ³ bond as diamond and is also called DLC (diamond-like carbon). (Hereinafter, abbreviated as DLC in the present specification.) (Second invention) The second aspect of the present invention is "a step of covering an electronic component surface to form an organic resin molding material, and And a step of removing impurities by deaeration in a vacuum, and a step of forming a carbon film having a diamond structure by covering the organic resin molding material ”. It is what

In the above invention, the reason why the impurities in the organic resin molding material are degassed in a vacuum is to remove impurities such as organic gas, chlorine, and water existing in the molding material in advance before forming DLC.

This is to prevent the occurrence of inconvenience due to the expansion and activation of these impurities in the subsequent heating step if the impurities are present in the molding material.

A carbon film having a diamond structure is formed by using a gas phase method using plasma.

"Function" By forming a carbon film having a diamond structure to cover electronic parts, it is possible to prevent water from entering the organic resin molding material, and suppress the occurrence of the above-mentioned problems due to the heating process. can do.

Moreover, the carbon coating having a diamond structure is 1 × 10 ⁶ to
Since it has a specific resistance of 5 × 10 ¹³ Ωcm, it is possible to eliminate the influence of static electricity.

Furthermore, impurities such as water in the organic resin molding material are removed by vacuum deaeration, and then a carbon coating having a diamond structure is formed, so that the influence of impurities such as water existing in advance in the organic resin molding material is eliminated. Can be eliminated.

Hereinafter, examples using the present invention will be shown.

Example 1 In this example, a plasma CVD method using a carbide gas was used, and carbon or a coating film containing carbon as a main component (hereinafter referred to as “carbon” having good thermal conductivity and excellent adhesion to an organic resin molding material) DL
(Also abbreviated as C) is formed by coating on an electronic component covered with an organic resin molding material.

The DLC is formed to have a thickness of 0.05 to 5 μm, preferably 0.1 to 1 μm.

In order to form this film, the molded electronic device is evacuated in advance, and the moisture in the molding material is deaerated in vacuum.

Then, carbon or a carbon-based film (DLC) having a diamond structure, which has a weak insulating property against static electricity and has a function of preventing water from invading from the outside, is formed on the upper surface thereof.
Film) is formed by a plasma CVD method to form a protective film.

The characteristic feature of this film formation is that a plasma gas phase reaction is carried out while forming a film with a sputtering effect.

FIG. 1 shows a vertical cross-sectional view of a plastic DIP (dual in-line package) or flat pack package in this embodiment.

In the drawing, an electronic component chip (28) adhered to the die (35 ') of the lead frame with an organic resin silver paste (24), a glass silver paste, a gold-silicon alloy method or the like, and an aluminum A wire bond of gold wire (39) formed between pad (38) and metal lead (stem) (35) is shown.

In order to obtain the structure shown in FIG. 1, first, the surface of the chip (28),
The surface of the pad (38), the surface of the wire (39) and the back surface of the die (35 ') are plasma-treated with a non-product gas to remove the lower oxides and natural oxides generated during die attach, and the metal surface Is exposed (30), and a protective film for preventing deterioration, particularly silicon nitride films (27) and (27 '), is coated on these by a plasma CVD method.

In this way, a protective film for preventing deterioration such as a silicon nitride film is formed.
After forming to a thickness of 300 to 5000Å, generally about 1000Å,
An organic resin such as epoxy (for example, 410B) (41) is injected and sealed by a known injection molding method, the frame is bent at the lead portion (37), and the tie bar is cut.

Then, after pickling the leads, the leads are solder-plated.

In the molding material (41), impurities such as organic gas, chlorine, and water that reduce reliability are present during molding.

In order to remove these, the impurities are removed by placing an electronic device in a vacuum device that has been evacuated.

Further, in order to activate the surface of the organic resin mold, the surface of the organic resin mold is activated by plasma sputtering with an inert gas such as argon, neon, helium, krypton or nitrogen.

After that, the specific resistance of the insulating organic resin molding material (41) having a specific resistance of 10 ¹⁷ Ωcm or more is 1
DLC (43) having a density of 10 ^{6 to} 5 × 10 ¹³ Ωcm is formed to a thickness of 0.05 to 5 μm.

This protective film such as the DLC film has a carbon fluoride (C ₂ F) content at or near room temperature (a temperature at which self-heating is caused by plasma sputtering without actively performing external heating).
₆ , C ₃ F ₈ , CHF ₃ , CH ₂ F _{2 and the} like, which has a bond of C and F) and hydrogen, or carbon fluorides and ethylene
(C ₂ H ₄ ) was mixed in a ratio of 1/4 to 4/1, for example, 1/1, and this was introduced into a plasma reactor and formed by a so-called plasma vapor phase method in which electric energy was supplied thereto.

In order to control the specific resistance of the DLC film, in addition to carbon hydride such as ethylene, B ₂ H ₆ , B (CH ₃ ) ₃ , BF ₃ , NH ₃ , NF ₃ , N (CH ₃ ) ₃ , N
A method of adding a III-valent or V-valent impurity such as (C ₂ H ₂ ) ₃ , PH ₃ , P (CH ₃ ) ₃ or a method of varying the position of the DC bias is effective.

Further, by using the two methods, it was possible to adjust the thermal expansion with the base molding material.

FIG. 2 shows a flat-pack structure substrate in which the chips are bonded to a frame and a mold material is coated in the present embodiment, and a base body (1) in which a plurality of the flat pack structures are assembled.
A plurality of substrates (both the substrate and the substrate will be abbreviated below) are arranged, the surface of the organic resin mold is activated by the plasma treatment method, and the DLC is performed by the plasma CVD method.
1 shows an outline of an apparatus for performing film coating.

In the drawing, it has a reaction system (50) and a doping system (20).

The reaction system has a reaction chamber (7) and a gate valve (9).

In the reaction chamber (8), the reactive gas blows downward from the nozzle (25) to generate a plasma reaction in the reaction space (8). Then, vacuum drying on the substrate or the substrate (1), activation of the surface of the molding material and formation of a protective film are performed.

The exhaust gas reaches the valve (21), the turbo molecular pump (22), and the vacuum pump (23) through the exhaust port (6).

Energy for generating plasma is generated by a pair of high frequency power supplies (15-1), (15-2) from a matching box (16-1),
(16-2) Further, it passes through the paths (4-1) and (4-2) and is added from a pair of mesh electrodes (3-1) and (3-2) having the same size.

The applied frequency is 1 to 500 MHz, for example 13.56 MHz.

The phase of the high frequency power from each electrode is controlled by the phase adjuster (26) within 0 ° ± 30 ° or within 180 ° ± 30 °.

If the holder (40) of the peripheral frame structure is a conductor, this is the ground level. However, the holder 40 may be an insulator.

In plasma processing and plasma CVD method, the object to be formed
(1-1), (1-2) ... (1-n), that is, (1) (hereinafter referred to as the substrate) is disposed on the supporter (20), and between the pair of electrodes in the frame structure (40). It is arranged parallel to the direction of the electric field. Furthermore, the electrodes (3-1) and (3-2) and the reaction reaction container (7) are separated from each other by a capacitor (19) in terms of direct current.

The plurality of substrates (1) are at regular intervals (2 to 13 cm, for example 6 cm)
Alternatively, they are arranged with a substantially constant interval.

AC bias with a frequency of 50 to 100 KHz is applied to this substrate (1).
DC bias of -50 to -2000V is added from (17-1).
-2) added.

This bias turns the switch (10) to (11-2) when forming the DLC.
Add by connecting to.

The application of this bias is extremely important for making a DLC having a hard specific resistance of 1 × 10 ^{6 to} 5 × 10 ¹³ Ωcm. The other end of the above power source is grounded (5-1), (5-2), (5-3).

The large number of substrates (1) are arranged in a positive column in a plasma created by glow discharge.

FIG. 3 (A) shows the stem (35) and the die (3) in the substrate (1).
The electronic device (29) after the electronic component (29) is bonded to the metal lead frame (45) on which a plurality of 5 ') (see FIG. 1) are integrated and the molding process (41) is performed is performed. 5 to 25 units are shown.

The frame (board) of one electronic device in one frame (45) is shown in Fig. 3 (B), and the vertical sectional view taken along line AA 'is shown in Fig. 3 (C) (29). Show.

In FIG. 3 (C), the lead frame (35) and the die (3
5 '), semiconductor chip (28), metal wire (39), molding material
Further collect 5 to 300 frames (45-1), (45-2), etc. in which 5 to 25 units of the electronic device (29) consisting of (41) are united and integrated by a jig (44) to form a base ( It is configured as 1).

It is effective to cover the external connection part with DLC so that it is not coated with this jig. This substrate (1) corresponds to each of the substrates (1-1), (1-2) ... (1-n) in FIG. In FIG. 2, 5 to 50 sheets (7 sheets in the drawing) are arranged in a positive column.

In FIG. 2, the reactive gas is in a plasma activated state inside the holder (40) having a frame structure and inside the hood (13-2) from the hood (13-1), and the reactive gas is present on the molding material. Plasma treatment is performed to form a dense layer. A dense layer as a protective film is formed on this molding material.

Further, when forming the DLC film, a sufficiently dense layer can be formed without applying external bias to heat the layer.

In this example, prior to the formation of the DLC film by the plasma CVD method, plasma activation of the mold material surface was performed with argon plasma at room temperature.

This activation is performed by holding the substrate in the positive column plasma region of the non-product gas.

Further examples are given below.

[Example 2] In the plasma CVD apparatus of FIG. 2, the doping system (20)
Therefore, carbon fluoride C ₂ F ₆ or C ₃ F ₈ from (20-1),
N (CH ₃ ) ₃ which is a nitride gas is converted from (20-4) to B (CH ₃ ) ₃ (20-
From 3), ethylene is supplied from (20-2), and hydrogen or argon, which is a non-product gas for plasma treatment, is supplied from (20-5).

They are controlled by a flow meter (19) and a valve (18).

The substrate temperature was set to room temperature (including self-heating by plasma) in which external heating was not particularly actively performed.

First, the substrate after the mold treatment shown in FIG. 3 was held in the reaction space (1), and argon was introduced.

Then, the whole of these was evacuated to 1 × 10 ⁻³ torr or less (10 to 30 minutes) to degas the organic gas, chlorine, and water in the molding material.

Next, plasma treatment was performed on the substrate (1), especially on the surface of the molding material (41). Also here B (CH ₃ ) ₃ or N (CH ₃ ) ₃ / (C ₂ H ₄ + C
₂ F ₆ ) = 0.0013 to 0.03 were added simultaneously.

Then, an output of 1 KW was supplied to the pair of electrodes (3-1) and (3-2) for 10 to 30 minutes at a frequency of 13.56 MHz for plasma treatment.

A DLC protective film was further formed on the plasma-treated substrate.

In the case of forming a DLC film on the formation surface subjected to the plasma treatment, the reactive gas is, for example, C ₂ H ₄ / C ₂ F ₆ / H ₂ = 1/1 /
It was set to 5.

And for these gases, the frequency of 13.56MHz
An output of 1 KW was supplied to the pair of electrodes (11) and (11 ') to carry out plasma vapor phase reaction to form a film.

Thus, a film was formed on an average of 5000Å (5000Å ± 200Å) for about 30 minutes (average speed 3 A / sec).

The resistivity of the DLC film can be controlled to 1 × 10 ^{6 to} 5 × 10 ¹³ Ωcm by increasing the AC bias (50 KHz, ± 300 V) and the DC bias voltage (-50 V to -2000 V).

By further addition of _{NH 3, B (CH 3)} 3 or the like here, improving the adhesion between the substrate and the Vickers hardness 500~3000K
It can be greater than g / mm ² and 200-400 Kg / mm ^{2 of the} molding material.

Noise Research Laboratory ESS-62
The electrostatic resistance characteristics were tested using 35 electrostatic breakdown testers. The IC has a 256K DRAM C / MOS memory, and the organic resin mold has a thickness of 1.4 mm. DLC is 0.5 μm thick and specific resistance is 10 ⁹ ~
10 ¹¹ Ωcm.

The test was performed by setting the output voltage to 20 KV and repeatedly applying this to the DLC 900 times.

However, no electrostatic breakdown was observed.

The number of samples was 20.

On the other hand, in the sample which does not form the DLC of the present invention, all of the 20 samples had destroyed the input pins and the like under the same conditions.

1000 ° C at 85 ° C / 85% (relative temperature) for the electronic device of the present invention
After left for a while, soldering was performed at 260 ° C. for 5 seconds. However, in this electronic device, no crack or swelling occurred in any of the 20 samples.

Of course, all those which do not have the DLC coat of the present invention are the fourth
It had the defects shown in the figure.

In this example, the plasma processing method and PCVD
In the method, it is effective to use a photo CVD (or photo FPCVD) method in which not only electric energy but also far infrared rays having a wavelength of 10 to 15 μm or ultraviolet light having a wavelength of 300 nm or less are simultaneously applied.

[Effect] In the present invention, as a dense film on the mold, 1 × 10 ⁶ to
By forming a DLC film having a specific resistance of 5 × 10 ¹³ Ωcm as a blocking film, it was possible to prevent water from entering the organic resin mold.

In addition, when performing the plasma treatment, since there is a vacuum degassing step of the impurity gas in the molding material and moisture, a reaction occurs between the moisture in the organic resin, chlorine and the metal of the die to form a lower oxide, We were able to prevent the drawback of reducing reliability.

Further, when the electronic device was mounted, it was possible to prevent the molding material from swelling due to heating.

Then, it is possible to provide an electronic device having high quality and high reliability.

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

In the present invention, the chip may become larger and may be molded without using a die. However, even in that case, it is effective to provide the DLC protective film of the present invention so as to cover all of the lead frame as the substrate and the chip.

In the above description, the case where the semiconductor chip is embedded in the lead frame has been described, but the present invention is not limited to the metal lead frame, and the hybrid
The same effect can be expected for a substrate or a substrate in which an active element or a passive element such as an IC or a film thickness IC is mounted on a substrate and an organic resin molding process is performed on the entire element.

[Brief description of drawings]

FIG. 1 shows an essential part of a vertical cross section of a plastic package semiconductor device after a moisture resistance test and a soldering test according to this embodiment. FIG. 2 shows an outline of a plasma gas phase reaction apparatus for carrying out the method of the present invention. FIG. 3 shows an enlarged view of the base portion of the apparatus shown in FIG. FIG. 4 shows an essential part of a vertical cross-sectional view after a moisture resistance test and a soldering test are performed on a conventional plastic package.

Front page continued (72) Inventor Mitsunori Tsuchiya 398 Hase, Atsugi, Kanagawa Prefecture, Semiconducting Energy Laboratory Ltd. (72) Inventor Shigenori Hayashi, 398, Hase, Atsugi, Kanagawa Prefecture, Semiconducting Energy Laboratory Ltd. (72) Inventor Naoki Hirose 398 Hase, Atsugi, Kanagawa Prefecture, Semiconducting Energy Laboratory Co., Ltd. (72) Inventor, Mari Sasaki 398, Hase, Atsugi, Kanagawa Prefecture, Semiconducting Energy Laboratory, Ltd. (72) Inventor, Noriya Ishida Atsugi, Kanagawa 398, Hase, Hachinohe Co., Ltd., Semiconductor Energy Laboratory Co., Ltd. (72) Inventor, Kohei Wada, 398, Hase, Atsugi, Kanagawa Pref., Semiconductor Co., Ltd., Semiconductor Energy Laboratory Co., Ltd. Koichi Kato (56) Reference JP 62-2557 (JP) , A) JP-A-57-53968 (JP, A) JP-A-56-49530 (JP, A)

Claims (2)

[Claims] 1. An electronic device, wherein a carbon coating having a diamond structure is formed to cover an electronic component covered with an organic resin mold. 2. A step of forming an organic resin molding material so as to cover a surface of an electronic component, a step of removing impurities in the organic resin molding material by deaeration in a vacuum, and the organic resin molding material. And a step of forming a carbon film having a diamond structure so as to cover it, and a method of manufacturing an electronic device.