JPH02168652A - semiconductor equipment - Google Patents

Abstract

PURPOSE:To improve reliability in humidity resistance by using a graft copolymer as a protective film of a semiconductor, element, the copolymer consisting of a fluororubber unit and a crystalline fluororesin unit. CONSTITUTION:A bonding pad section for leading out an external electrode is formed in a part of an insulating film 2 formed on the surface of a chip 1, and a passivation film 3 is formed on an aluminum interconnection layer thereof. The passivation film 3 is coated with a protective film 6 of a graft copolymer. The graft copolymer consists of a fluororubber unit and a crystalline fluororesin unit and it may be exemplified by a graft copolymer having a copolymerized fluororubber unit containing vinylidene fluoride and a polyvinylidene fluoride resin unit. In order to provide the copolymer as the protective film in a semiconductor element, it is used in the state of varnish by dissolving pellets or powder of the graft copolymer in an organic polar solvent such as dimethyl formamide or the like. In this manner, the protective film is allowed to have high reliability in humidity resistance.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a semiconductor device.

<Prior art> It is generally known that the surface of a semiconductor element is coated with polyimide resin or silicone resin in order to protect the semiconductor device electrically, mechanically, or chemically from the outside. It is being

By forming a protective film in this way, when semiconductor elements are molded with epoxy resin, etc., moisture absorption and impurity ion transfer from the mold resin to the semiconductor element can be prevented, and stress concentration from the mold resin to the semiconductor element surface can be prevented. It can also prevent aluminum wiring sliding and passivation cracks caused by

Furthermore, as electronic devices have become thinner, smaller, and lighter in recent years, semiconductor devices are also required to have lighter, thinner, and shorter packages. In particular, IC cards etc. have a thickness of 0.8 mm.
Thinness has progressed to below TAB (
tape automated bonding), COB
(chip-on-board) and other thin semiconductor devices are on the rise.

Among these, COB, which attaches the chip directly to the circuit board,
G (chip-on-glass) is a promising thinning mounting method because it allows chips to be directly attached to flexible printed circuit boards. A common method for electrical connection between the chip and the board is to bond with gold wire, but since the chip surface is exposed and failures can occur due to humidity, heat, adhesion of foreign matter, etc., it is usually coated with epoxy resin or silicone resin. , methods have been adopted to electrically, mechanically, or chemically protect semiconductor devices from the outside.

However, polyimide resins and epoxy resins usually have a
It has a water absorption rate of about 3% by weight, and silicone resin also has the disadvantage of high moisture permeability, so it cannot be said to be the best material in terms of moisture resistance and reliability when used in semiconductor devices. It's something that doesn't exist.

On the other hand, semiconductor devices in which a protective film of fluororesin is formed on the surface of a semiconductor element in order to improve moisture resistance reliability are disclosed in Japanese Patent Laid-Open No. 54-142067 and Japanese Patent Laid-Open No. 55-166942.
This method has been proposed in Japanese Patent Laid-Open No. 564256.

JP-A-54-142067 discloses a semiconductor device in which a fluororesin layer is formed on the surface of a semiconductor element by heat-pressure bonding, and then the photoresist bonding pad is irradiated with oxygen plasma to perform etching opening treatment. The semiconductor device thus obtained has a corrosion-preventing effect due to the acid resistance, alkalinity, moisture resistance, and water resistance of the fluororesin. However, the fluororesin disclosed in this publication is fluorinated ethylene-
It is a propylene copolymer, and this copolymer has a melting point of 25
Since the temperature is as high as 0 to 270''C, it is difficult to form a protective film in complete contact with the surface of a semiconductor element having surface steps without generating bubbles even if the heat treatment is performed.

Further, Japanese Patent Application Laid-Open No. 55-166942 discloses a semiconductor device in which a part or all of the surface of a semiconductor element having a polyimide resin protective film is coated with a fluororesin. The fluororesins used here are tetrafluoroethylene resin, tetrafluoroethylene-ethylene copolymer,
It is used in the form of an aqueous dispersion of fluorinated ethylene-perfluoroalkyl vinyl ether, etc., and is intended to protect semiconductor elements from damage caused by moisture and stress and improve reliability. However, in the aqueous dispersion of fluororesin, since the specific gravity of the suspended particles is large, a phenomenon of sedimentation of the particles occurs over time, and it is necessary to redisperse the particles before use, resulting in poor workability. In addition, if drying is insufficient because an aqueous dispersion is used, the moisture resistance reliability may be deteriorated.

On the other hand, Japanese Unexamined Patent Publication No. 56-4256 discloses a semiconductor device in which a paste-like face obtained by dispersing a fluororesin powder with good moisture resistance in an epoxy resin or a polyimide resin is used as a protective film. There is. However, since epoxy resins and polyimide resins, which have lower moisture resistance than fluorine resins, are used as binder resins, the moisture resistance reliability is insufficient compared to semiconductor devices whose protective films are formed using fluorine resins alone. isn't it.

<Problems to be Solved by the Invention> As mentioned above, the moisture resistance and reliability of semiconductor devices can be improved by using fluororesin, which has low water absorption and moisture permeability, as a protective film for semiconductor elements, but it is still not practical. The reality is that a semiconductor device with sufficient humidity resistance reliability has not yet been obtained.

Therefore, an object of the present invention is to obtain a semiconductor device provided with a protective film that exhibits an excellent effect in terms of moisture resistance and reliability.

Means for Solving the Problems> As a result of intensive studies to achieve the above object, the present inventors have found that by using a face made of a specific fluororesin, a protective film can be formed on a semiconductor element with good workability. The present inventors have discovered that the resulting semiconductor device has excellent moisture resistance and reliability, and has completed the present invention.

That is, the present invention provides a semiconductor device characterized in that a graft copolymer consisting of a fluororubber unit and a crystalline fluororesin unit is used as a protective film for a semiconductor element.

In particular, it is suitable for semiconductor devices in which a protective film is provided on the surface of a semiconductor element and/or the back surface of a die pad, or in the vicinity of the surface of a semiconductor element, including resin-sealed type, tape carrier type, flip chip type, chip-on-board type, and chip type. It can be used as an on-glass semiconductor device.

The graft copolymer used in the present invention consists of a fluororubber unit and a crystalline fluororesin unit, for example, a vinylidene fluoride copolymerized fluororubber unit,
A graft copolymer having a polyvinidene fluoride resin unit or a block copolymer containing the unit portion can be used.

In addition, in order to protect semiconductor elements from damage caused by stress, the tensile modulus must be 50 to 1400 kg r /
It is preferable to use a material with a saturated water absorption rate of about c+fl (25° C.) and, from the viewpoint of water resistance, a material with a saturated water absorption rate of 0.1% by weight or less.

In order to provide the above-mentioned graft copolymer as a protective film on a semiconductor device, a pellet or powder of the above-mentioned graft copolymer is usually mixed with dimethylformamide or N-methyl-2
- It is preferable to dissolve it in an organic polar solvent such as pyrrolidone and use it as a varnish. Furthermore, a low boiling point organic solvent such as methyl ethyl ketone or methanol can be used as a diluting solvent or co-solvent to the extent that the above-mentioned copolymer does not precipitate.

The thus obtained graft copolymer varnish is applied to a semiconductor element and dried to form a protective film, thereby obtaining the product of the present invention. Examples of methods for forming the protective film include the following methods.

The graft copolymer varnish obtained as described above is coated onto a silicon wafer on which a circuit is formed using a spin code method, and the solvent is removed by drying at a temperature of about 100 to 300°C to form a protective film. Form. In this case, it is preferable to dry the graft copolymer at a temperature higher than its melting point (around 165° C.) after removing the solvent, since this further improves the adhesion of the protective film to the wafer. Next, using a photoresist film with openings formed by exposure and development in a conventional manner as a mask material,
The protective film can be etched and opened using an oxygen plasma method, a KrF excimer laser method, or an X-ray laser method.

In addition, a semiconductor element pellet formed by dividing a silicon wafer on which a circuit is formed in advance is bonded to a lead frame using the Au-3T eutectic method, silver paste method, or soldering method.
It is also possible to form a protective film by potting the graft copolymer used in the present invention onto a pellet obtained by electrically bonding with Au wire or 11 wire and drying by heating.

In order to produce a resin-sealed diode, specifically, the graft copolymer varnish used in the present invention is applied with a syringe or the like onto a silicon beret of a diode in which a mesa-shaped semiconductor beret and a silver-plated lead wire are joined by soldering. A protective film can be formed by botting and drying by heating while rotating automatically. In addition, roll coating, dip coating,
Coating methods such as brush coating can also be employed. This protective film-formed diode is molded with epoxy resin to obtain a resin-sealed diode.

In addition, for the production of resin-sealed transistors, specifically,
A semiconductor element pellet made by dividing a silicon wafer on which a circuit has been formed in advance as described above is joined to a lead frame using the Au-3i matching method or soldering method, and the AI! ,
A protective film can be formed by potting the graft copolymer used in the present invention onto a pellet obtained by electrically bonding with a wire and drying by heating.

The protective film formed as described above may be provided on the surface of the semiconductor element and its vicinity, or may be provided on the surface of the semiconductor element and/or in its vicinity.
Alternatively, by providing it on the back surface of the die pad, the moisture resistance reliability of the semiconductor device obtained is improved.

The semiconductor device of the present invention can also be manufactured using a resin-sealed type that is sealed with a package resin, a tape carrier type that uses a plastic film as a carrier, or a flip-chip type that is bonded to a substrate with solder bumps. can.

<Example> Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a sectional view showing an example of a resin-sealed semiconductor device among the semiconductor devices of the present invention.

A silicon chip 1 is bonded to the lead frame 7 with gold foil or the like, and S+O1 is applied to the surface of the chip 1.
The insulating film 2 is formed to have a thickness of approximately 1000 nm. S
A bonding pad made of aluminum for taking out an external electrode is formed in a part of the iO□ insulating film 2, and is connected to a circuit 4'.

This aluminum wiring layer contains PSG, SiN, and Sin.
The passivation film 3 formed from
A protective film 6 made of the graft copolymer used in the present invention is formed to cover this passivation film.

The bonding pad portion is electrically connected to an external lead frame by a connecting wire 5 such as a gold wire or an aluminum wire, and the entire silicon pellet is sealed with a thermosetting epoxy resin 8 to form a semiconductor device. There is.

To obtain a semiconductor device as shown in FIG. 1, first, the graft copolymer is dissolved in a solvent such as dimethylformamide to form a varnish, and the varnish is coated with a spin cord onto a silicon wafer 1 on which a circuit has been formed before dicing. For example 120°C
The protective film 6 is formed by heating and drying at 200° C. for 10 minutes and 200° C. for 30 minutes (see FIG. 2). Next, a photoresist film 9 is formed as an etching mask for opening the bonding pad portion formed on the silicon wafer, and the protective film 6 is dry etched using oxygen plasma or XrF excimer laser. Opening treatment is carried out, and additional metal is vapor deposited to form electrodes 4, thereby obtaining a punctured semiconductor element as shown in FIG.

Next, the photoresist film 9 is rinsed off and scribed to form a semiconductor pellet. A semiconductor device as shown in FIG. 1 is manufactured using the semiconductor pellet thus obtained.

Although the above method is an example in which varnish is used in the first half of the assembly process of a resin-sealed semiconductor device, there is no limitation to this in the present invention. It is also possible to complete electrical bonding with aluminum wire and then apply varnish to the surface of the semiconductor element and its vicinity to form a protective film. Figure 4 shows the case where varnish is used in the latter half of the process. 1 is a cross-sectional view of a semiconductor device of FIG.

FIG. 5 is a sectional view showing an example of a semiconductor device manufactured by the so-called tape carrier method, in which copper wiring 11 is formed on a plastic film 10 such as a polyimide film.

The semiconductor element 12 is electrically connected to the copper wiring via the solder bumps 13, and the surface of the semiconductor element and its vicinity are coated with the fluororesin varnish (graft copolymer) by botting, and then heated and dried. A protective film 6 is formed. Note that the protective film 6 may cover the entire front and back surfaces of the semiconductor element as shown in FIG.

FIG. 7 shows an electrode 1 formed on a substrate 21 made of ceramic or the like.
9 is a sectional view of an example of a fringe chip type semiconductor device in which a semiconductor pellet 15 is bonded to a semiconductor pellet 15 through a solder bump 13 and an electrode is taken out.

The protective film 6 can be obtained by applying a fluororesin varnish (graft copolymer) by botting to cover the semiconductor bead and its vicinity and heating and drying it.

FIG. 8 is a sectional view showing another example of a resin-sealed semiconductor device, in which a protective film 6 is formed over the entire surface of the semiconductor element and the back surface of the semiconductor element.

FIG. 9 is a sectional view showing an example of a resin-sealed diode.

The mesa-shaped silicon pellet 1' is joined to the silver-plated lead cotton 5 through solder 13°, and the silicon pellet 1
The exposed end surface A is mesa-etched using an alkali such as an aqueous sodium hydroxide solution or a mineral acid such as sulfuric acid or fluoric acid. The graft copolymer varnish is applied along this processed/inched end surface A and dried by heating to form a protective film 6, which covers the surface of the silicon pellet 1'' up to the joint end surface of the lead wire. , a resin-sealed diode can be obtained by molding with an epoxy resin sealant 8.

FIG. 10 is a cross-sectional view of an example of a resin-sealed transistor.

A planar type transistor element having a circuit formed thereon is bonded to the lead frame 7 with solder 13', and electrical connection between the transistor silicon chip 1 and the lead frame 7 is made with an A42 wire 5. The graft copolymer varnish is applied to the surface of the silicon chip 1 and dried by heating to form a protective film 6. The entire surface of the silicon chip 1 is covered and molded with an epoxy resin encapsulant 5 to form a resin-sealed transistor. Obtainable.

FIG. 11 is a sectional view showing an example of a chip-on-board type semiconductor device.

An IC chip 12'' on which a circuit has been formed is adhesively fixed with a cured epoxy silver paste 13'' to a glass epoxy printed board on which a copper wiring 11 with a thickness of 18 to 35 μm is wired on a glass epoxy substrate 21'. The connection between the bonding pad and the glass epoxy printed wiring board is
Electrical connection is made using an Au wire 5 using a wire bonding method.

Note that the copper wiring 11 is provided with a metal plating layer of 1,000 to 5,000 layers. The entire chip mount area was coated with the graft copolymer varnish to a dry film thickness of 1 to 1.
Botting coating to 00μm, 120°C
The protective film 6 is formed by heating and drying at 2 DEG C. for 10 minutes and then at 2 DEG C. for 30 minutes to obtain a chip-on-board semiconductor device.

FIG. 12 is a sectional view showing an example of a chip-on-glass type semiconductor device.

In the same manner as in FIG. 11, a gold wiring pattern 11 with a thickness of 500 to 1000 layers is formed on a glass plate 21'' by vapor deposition,
The rc chips 12' are bonded together using the Au-3i eutectic method, and external connections are made using gold wires. A chip-on-glass type semiconductor device can be obtained by forming a protective film 6 of the graft copolymer on the entire chip mount portion in the same manner as shown in FIG. 11.

Table 1 shows the physical properties of the graft copolymer used in the present invention, as well as PTFE (polytetrafluoroethylene) and PVDF (polyvinylidene fluoride) as comparative measurements.

The product of the present invention in the table is a graft copolymer (manufactured by Central Glass Co., Ltd., Cefral Soft G150) that uses vinylidene fluoride copolymer as the fluororubber unit and polyvinylidene fluoride resin as the crystalline fluororesin unit.
).

(Hereinafter, blank spaces) <Effects of the Invention> As described above, since the semiconductor device and semiconductor element of the present invention use a specific fluorine-based graft copolymer as a protective film for the semiconductor element, the water absorption rate and moisture permeability are improved. This protective film is a buffer film with low moisture resistance and stress reduction.
Since it is effective as an α-ray shielding film for preventing soft errors, it improves the reliability of semiconductor devices and also significantly improves workability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a resin-sealed semiconductor device of the present invention, and FIGS.
4 is a sectional view of another example of a resin-sealed semiconductor device; FIG. 5 is a sectional view of an example of a tape carrier type semiconductor device; FIG. 6 is a cross-sectional view of an example of a method for forming a protective film on a semiconductor element, FIG. 7 is a cross-sectional view of an example of a flip-chip semiconductor device, and FIG. 8 is a resin-sealed semiconductor device. 9 is a sectional view showing an example of a resin-sealed diode, FIG. 10 is a sectional view showing an example of a resin-sealed transistor, and FIG. 11 is a chip-on-board. FIG. 12 is a sectional view showing an example of a chip-on-glass type semiconductor device.

Claims (6)

[Claims] (1) A semiconductor device characterized in that a graft copolymer consisting of a fluororubber unit and a crystalline fluororesin unit is used as a protective film for a semiconductor element. (2) The semiconductor device according to claim (1), wherein the protective film is provided on the surface of the semiconductor element and/or the back surface of the die pad. (3) The semiconductor device according to claim (1), wherein the protective film is provided in the vicinity of the surface of the semiconductor element. (4) Claims (1) to 10 where the semiconductor device is one type selected from a resin-sealed type, a tape carrier type, and a flip-chip type.
(3) Semiconductor device as described. (5) The semiconductor device according to claim (4), wherein the semiconductor device is a resin-sealed diode or a resin-sealed transistor. (6) The semiconductor device according to claim (1) or (2), wherein the semiconductor device is of a chip-on-board type or a chip-on-glass type.