JPS60102750A - Conductive adhesive film for fixing semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a conductive adhesive film capable of being applied to a semiconductor element, the back thereof requires metallization, by applying a mixture consisting of a thermoplastic resin and conductive fillers on both surfaces of the conductive film as a fusion agent. CONSTITUTION:A mixture manufactured by compounding conductive fillers such as carbon to a thermoplastic resin is applied on both surfaces of a conductive film through solution coating to form a layer of a fusion agent, thus manufacturing the conductive adhesive film 1. When a semiconductor element 4 is die- bonded on a lead frame 5a as a semiconductor substrate through said film 1, the film 1 cut in predetermined size is placed on the lead frame 5a, the element 4 is placed on the film 1, and the lead frame, the film and the element are heated and contact-bonded at a temperature where the fusion agent for the film 1 is melted and softened. The element 4 and lead frames 5b, 5c are connected by bonding wires 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called die bonding adhesive film for fixing a semiconductor element onto a substrate such as a stem or lead frame.

Die bonding is the process of adhesively fixing a semiconductor element to a semiconductor substrate such as a stem or lead frame. Conventionally, die bonding materials for this adhesive fixation are
Au has the function of electrical connection between the substrate and the element.
-5i eutectic and conductive silver paste compositions are known.

The above-mentioned A, -5i eutectic is one in which a substrate is pre-plated with A, and a silicon chip as a semiconductor element is bonded to this plate under high temperature to form a metal adhesive layer made of an Au-Si eutectic alloy. A conductive silver paste composition is made by kneading silver powder as a conductive material into a solution of a precursor of an epoxy resin or polyimide resin to form a base, which is applied as an intermediary between a substrate and an element, and then heated. It hardens.

However, although adhesion using the AuSi eutectic described above enables highly reliable adhesion in a short time, it requires expensive AIJ, which is economically disadvantageous.

On the other hand, since conductive silver paste compositions use precursors of epoxy resins and polyimide resins as binders for silver powder, it takes a long time to harden, and AuSi
In addition to being inferior in die bonding workability compared to eutectic, epoxy resins in particular lack moisture resistance at high temperatures and have the disadvantage that the wiring patterns of the elements corrode over time. In addition, this type of base composition has the disadvantage that it is difficult to apply it to a uniform thickness on the substrate, which causes the semiconductor device to tilt, hindering wire bonding and causing uneven distortion of the device. .

These drawbacks are all due to the characteristics of the binder resin and the adoption of a liquid (paste) coating method.

From the above point of view, the inventors conducted extensive research to find a material for die bonding suitable for semiconductor devices that do not require metallization on the back side, and as a result, they fused thermoplastic resin on both sides of a heat-resistant film. It has been found that a film-like material coated as an agent is extremely useful as the above-mentioned material, and has already been proposed in Japanese Patent Application No. 111286/1986.

According to this adhesive film, by thermocompression bonding a substrate and a semiconductor element through this film, die bonding can be performed instantly due to the heat fusion properties of the adhesive of the film, which is different from conventional epoxy. The workability of die bonding can be greatly improved compared to those using thermosetting resins such as resins and precursors of polyimide resins. Moreover, since expensive Al is not used, it can contribute to cost reduction of semiconductor devices.

Furthermore, the above film does not have the risk of deterioration in moisture resistance, unlike conventional silver paste compositions using epoxy resins. In particular, when a fluoropolymer is used as a fusion agent, a significant improvement in the above-mentioned moisture resistance properties can be expected.

Furthermore, in die bonding using this type of film, there is a risk that the thickness of the adhesive layer may become uneven, as seen in conventional paste coating methods, which may interfere with subsequent wire bonding or cause damage to semiconductor devices. There is no problem of non-uniform distortion, and from this point of view as well, a highly reliable semiconductor device can be obtained.

As described above, according to the adhesive film, it is possible to obtain a highly reliable semiconductor device with good productivity and economy.

However, the above-mentioned adhesive films that have already been proposed are applicable only to semiconductor elements that do not require metallization on the back side or to semiconductor elements in which sub-electrodes can be drawn out from the bonding pads on the semiconductor element.

Therefore, the inventors have conducted intensive studies to impart conductivity to the adhesive film, with the aim of obtaining a conductive adhesive film that can be applied to semiconductor devices that require metallization on the back side while taking advantage of the advantages of the adhesive film. As a result, this invention was made.

That is, the present invention relates to a conductive adhesive film for fixing a semiconductor element, which is formed by coating both sides of a conductive film with a mixture of a thermoplastic resin and a conductive filler as a fusion agent.

The conductive adhesive film for fixing semiconductor elements of the present invention has the advantages of the above-mentioned adhesive films already proposed, namely:
Compared to conventional methods using thermoplastic resins such as epoxy resins and polyimide resin precursors, the workability of die bonding can be greatly improved, and moreover, it is possible to use expensive AU.
Because it does not use silver paste compositions, it can contribute to reducing the cost of semiconductor devices, and there is no risk of deterioration in moisture resistance, which is the case with conventional silver paste compositions using epoxy resins, and there is no risk of deterioration in moisture resistance, which is seen in conventional paste coating methods. This conductive adhesive film has advantages such as having no disadvantages, and also has an electrical connection function comparable to that of Al1-5i eutectic and conductive silver paste compositions. It can be applied to semiconductor devices that require metallization.
A highly reliable semiconductor device can be obtained with good productivity and economy.

Hereinafter, this invention will be explained and explained with reference to the drawings.

FIG. 1 shows a cross-sectional view of a conductive adhesive film for fixing a semiconductor element according to the present invention. Conductive filler such as carbon and silver particles is blended into thermoplastic resin on both sides of the conductive film 2, which is made of a film obtained by blending a conductor such as silver particles into a heat-resistant resin and forming a thin film. and a fusion agent 3, 3' which is obtained by applying a mixture obtained by coating the mixture by solution coating or melt coating.

``The heat-resistant resin in the conductive film 2 is usually ``
It has a heat resistance higher than the fusing temperature of the second fusing agent 3, 3'. On the other hand, as the thermoplastic resin in the fusing agents 3 and 3', A) a resin having the same melting point on both sides of the conductive film 2 may be used, or B) a resin having a different melting point on each side may be used. .

The thermoplastic resin used in the case of A has a melting point of 17
A temperature of 0 to 320°C is preferred. When the conductive adhesive film obtained in this case is used for die bonding, it is cut to match the size of a semiconductor element cut from a silicon wafer.

The thermoplastic resin used in case B has a melting point of 1
in the range of 70 to 820°C, the melting point of one thermoplastic resin is 15°C or more higher than the melting point of the other thermoplastic resin, and the thermal decomposition temperature of both resins is higher than the melting point of the resin on the higher melting point side.
It is preferable that the temperature is higher than soC. According to the conductive adhesive film obtained in this case, this adhesive film is preliminarily fused to the back side of a silicon wafer via a fusing agent containing a thermoplastic resin having a lower melting point, and a wafer with a conductive adhesive film rem is formed. This wafer can be fully cut and scribed into semiconductor elements with a conductive adhesive film, and this semiconductor element can be attached to stems, lead frames, etc. via a fusing agent containing a thermoplastic resin with a higher melting point. Since die bonding can be performed, there is no need to cut the conductive adhesive film to match the size of the semiconductor element, and the workability of die bonding can be further improved.

In either case A or B, if the melting point of the thermoplastic resin is too low, problems tend to occur in the heat resistance of the semiconductor device, and if it is too high, a high temperature is required during die bonding, which is not preferable. In the case of B, if the difference in the melting points of thermoplastic resins with different melting points is too small, when the adhesive film is fused to the back surface of the silicon wafer using a fusing agent containing a thermoplastic resin with a lower melting point, This is undesirable because a fusing agent containing a resin with a high melting point becomes sticky and attracts dust. Furthermore, if the difference between the melting point of the higher melting point resin and the thermal decomposition temperature of one or both resins is too small, the thermoplastic resin will heat up during die bonding with a fusing agent containing the higher melting point resin. Undesirable because it decomposes.

In both cases A and B above, the thermoplastic resin is preferably a fluorine-based polymer, and other thermoplastic resins having the same melting point as above, such as Borienether, nylon 6/6, and polyparaphenylene sulfide, may be used in some cases. You may.

The fluorine content of the above fluorine-based polymer is usually 20
The amount used is at least 50% by weight, preferably from 50 to 76% by weight. Particularly suitable are perfluoroalkene or perfluorovinyl ether remers or copolymers, typical examples of which are tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP),
Structural formula: E CF2-CF2-CF2-CF (O
Tetrafluoroethylene-perfluorovinylether copolymer (hereinafter referred to as PFA) represented by Rf)-F (wherein Rf means a fluorinated alkyl group having 7 or less carbon atoms, preferably 1 to 3) can be mentioned. Commercial products of the above PFA include Neoflon PFA (trade name) manufactured by Daikin Industries, Ltd. and Teflon PFA (trade name) manufactured by DuPont.

Other examples of the above-mentioned fluorine-based polymers include those in which part of the fluorine in PFA represented by the above structural formula is replaced with hydrogen, and polychlorotrifluoroethylene (hereinafter referred to as PCTF).
Ethylene-te-1-lafluoroethylene copolymer (hereinafter referred to as ETFE), ethylene-chlorotrifluoroethylene copolymer, etc. can also be used.

These fluoropolymers are non-adhesive at room temperature, but when heated above their melting point, they easily fuse to metals, etc., and the polymer flows less when melted. ing.

As the conductive filler to be mixed into the above thermoplastic resin, particles of carbon, silver, etc. are preferable, but particles of other metals can also be used. Note that different conductive fillers may be used depending on the surface of the conductive film. The proportion of these conductive fillers in the total amount of these conductive fillers and thermoplastic resin is usually 3 to 5% by weight for carbon, and usually 70 to 85% by weight for silver. It is better to If these proportions are too small, the conductivity of the conductive adhesive film will be insufficient, and if they are too large, it will be difficult to uniformly disperse them or the adhesiveness will deteriorate, which is not preferable.

Note that the combination of the conductive filler and thermoplastic resin is not particularly limited. However, depending on this combination, the conductivity of the resulting conductive adhesive film may decrease slightly, but in that case, sufficient conductivity can be achieved by etching the surface of the adhesive on the adhesive film using a method such as sputter etching. is obtained.

The thickness of the conductive adhesive film 1 having the above structure is generally 7 to 150 μm, preferably 20 to 11 μm.
The thickness of the conductive film 2 is 5 to 0 μm.
90 μm 1 preferably 10 to 70 μm, and the thickness of each of the adhesives made of the thermoplastic resin and conductive filler coated on both sides of the film 2 is 1 to 30 μm 1
It is preferably 5 to 20 μm.

FIGS. 2 and 3 show a semiconductor device obtained by die-bonding a semiconductor element using a conductive adhesive film 1 obtained by using thermoplastic resins having the same melting point as the thermoplastic resins in the fusing agents 3 and 3'. An example is shown in which 4 is a semiconductor element die-bonded or adhesively fixed by the film 1 on a lead frame 5a serving as a semiconductor substrate, and 6 and 6 are electrodes 7 and 7 formed on the element 4. A bonding wire 8 connecting the lead frames 5b and 5c is a stabbing resin that integrally surrounds each of the above components.

Die bonding of the element 4 using the conductive adhesive film 1 is carried out by placing the film 1 cut into a predetermined size on the lead frame 5a, placing the element 4 on the lead frame 5a, and applying the adhesive for the film 1. This is done by heating and pressing at a temperature at which 3°3' melts and softens.

In addition, if the conductive adhesive film is obtained by using thermoplastic resins having different melting points as described above as the thermoplastic resin in the fusion agent, the conductive adhesive film 1 is first adhered to the back surface of a silicon wafer, and then the conductive adhesive film 1 is Leave as a wafer with adhesive film.

FIG. 4 shows an example of a wafer with a conductive adhesive film, where 9 is a silicon wafer, and 10 is a wafer with a conductive adhesive film made by adhering the conductive adhesive film 1 to the wafer 9. Note that the melting point of the thermoplastic resin contained in the fusing agent 3 in the conductive adhesive film 1 is lower than that of the resin contained in the fusing agent 3'.

This conductive adhesive film-coated wafer 9 is fully cut and scribed to produce a conductive adhesive film-coated semiconductor element, and this is placed on a lead frame as a semiconductor substrate using a fusing agent 3' containing a resin on the high melting point side of the film 1. Die bonding is performed by heating and pressing at a temperature at which the material melts and softens.

In the semiconductor device thus obtained using the conductive adhesive film of the present invention as a die bonding material, the substrate and the element are electrically connected by the adhesive film. The resistance between the material and the substrate is usually 10-3 to 2, although it depends on the thickness of the adhesive film.
The conductivity is approximately 102Ω, which is comparable to the conductivity of Au-5i eutectic and conductive silver paste compositions.

Examples of the present invention will be described below to explain it more specifically. In addition, below, % means weight %.

Examples 1 to 5 A fusion agent consisting of a thermoplastic resin and a conductive filler (powder) shown in the table was melt-coated on both sides of a conductive film as shown in Table 1 below to a coating thickness shown in the table. Thus, a conductive adhesive film for fixing a semiconductor element of the present invention was obtained.

In addition, in the same table and Table 3 below, conductive polyimide refers to a paste (trade name ■R1000) made from Nitto Electric Kogyo Co., Ltd. consisting of a polyimide resin precursor and silver powder that is cured into a fi) Vlx shape. This is the obtained conductive polyimide film.

Table 1 Using the conductive adhesive film obtained as described above, silicon chips (3 x 8 m+n) were placed on a 42 alloy plate, which is a lead frame material, at f 350 °C, 5
Heat and pressure bonding was carried out under the conditions of K9/cA and 5 seconds. After adhesion, it was cooled to room temperature and attempts were made to measure the shear adhesion force using a push-pull gauge, but in both cases the adhesion strength was so large that the device was destroyed. Furthermore, when the shear adhesion J was measured at 200° C., the adhesive strength shown in Table 2 below was shown, and all values were greater than the adhesive strength required for wire bonding.

Furthermore, the results of measuring the resistance between the silicon chip and the 42 alloy plate during the bonding process are also listed in Table 2 below.

Table 2 Next, using the above film, a model element for aluminum corrosion measurement was bonded to a 16-pin DIP lead frame in the same manner as above, and the prescribed wire bonding was performed, and then epoxy Molding material M
A semiconductor device was manufactured by molding and sealing with P-10. A pressure puller bias test was performed on this device at 143° C., 4 atmospheres, 95% RH, and 10 volt bias.

The results were as shown in Table 5 below.

Examples 6 to 10 A fusion agent containing a conductive filler (powder) was applied to each surface of both sides of a conductive film as shown in Table 3 below to a thickness of 10 μm (
However, in Example 10, the conductive adhesive film for fixing a semiconductor element of the present invention was obtained by melt coating with a coating thickness of 20 μm.

Table 3: The conductive adhesive film obtained as described above was placed on the back side of a silicon wafer, with the side containing the thermoplastic resin having the lower melting point sealed with a fusing agent, and placed on a hot plate at 290°C. A wafer with an adhesive film was obtained by fusing using a roll.

The obtained adhesive film-coated wafers were scribed to obtain adhesive film-coated semiconductor elements each having a size of 3 mm x 3 mm.

Next, these semiconductor elements with adhesive films are placed on a 42 alloy plate, which is a lead frame material, at 350°C via a fusing agent containing a resin with a higher melting point than the adhesive film.
Heat and pressure bonding was carried out under the conditions of 5 kg/c for 4.5 seconds. After adhesion, the devices were cooled to room temperature and an attempt was made to measure the shear adhesion strength of each using a push-pull gauge, but in both cases the adhesion strength was so large that the device was destroyed. Furthermore, when the shear adhesive strength of each was measured at the measurement temperature shown in Table 4 below, the adhesive strength shown in Table 4 below was obtained, and both values were greater than the adhesive strength required for wire bonding. Ta.

Furthermore, the resistance between the semiconductor element and the 42 alloy plate during the bonding process was measured, and the results are also listed in Table 4 below.

Table 4 Semiconductor devices were fabricated using the above adhesive film in the same manner as in Examples 1 to 5, and a pressure puller bias test was conducted. The results are as shown in Table 5 below.

Comparative Example 1 A 42 alloy plate was plated with gold, and a silicon chip was pressure-bonded thereon at 350° C. and 5 h/ca % for 5 seconds to form an Au-5i eutectic alloy and adhere to it. At this time, the resistance between the silicon chip and the 42 alloy plate is 1×1
It was 0-3Ω. Furthermore, when the shear adhesive strength at 200° C. was measured, the chip was broken.

In addition, we plated the necessary parts of the 16-pin DIP lead frame with gold, and attached a model element for aluminum corrosion measurement to this gold plated part.
-5i Die bonding was performed by forming a eutectic alloy, and a pressure puller bias test was conducted in the same manner as in Example 1. The results should be listed in Table 5 below.

Comparative Example 2 Using a commercially available epoxy silver paste composition, this was
After coating on the alloy plate, a silicon chip was placed thereon and cured at 180°C for 1 hour to adhere the chip to the 42 alloy plate. The resistance between the silicon chip and the 42 alloy plate at this time was 5×10 Ω. In addition, when the shear adhesive strength was measured at 200°C, it was found that 2
It had sufficient adhesive strength of 0 Kg/c4. Next, a model element for aluminum corrosion measurement was subjected to 16-pin DIP using the above silver paste composition under curing conditions of 180°C for 1 hour.
The sample was die-bonded onto a lead frame, and then a pressure test was carried out in the same manner as in Example 1. The results were as shown in Table 5 below.

As is clear from the above results in Table 5, the conductive adhesive film of the present invention employs an adhesion method using Au-5i eutectic alloy, which has excellent workability and is said to be more reliable than conventional ones. It can be seen that a semiconductor device can be obtained which has good moisture resistance reliability and conductivity comparable to those obtained by using this method.

[Brief explanation of the drawing]

FIG. 1 is an adhesive film for fixing semiconductor elements of the present invention, FIG. 2 is a sectional view showing an example of a semiconductor device manufactured using the above film, FIG. 3 is a plan view of the same, and FIG. 4 is a conductive adhesive film. It is a wafer with 2...Heat-resistant film, 3...Fusing agent consisting of thermoplastic resin and conductive filler. Patent applicant: Nichizuka Electric Industry Co., Ltd.

Claims (6)

[Claims] (1) A conductive adhesive film for fixing a semiconductor element, which is formed by coating both sides of a conductive film with a mixture of a thermoplastic resin and a conductive filler as a fusion agent. (2) The conductive adhesive film for fixing a semiconductor element according to claim 11, wherein the thermoplastic resin has a melting point of 170 to 320°C. (3) The conductive adhesive film for fixing a semiconductor element according to claim (1), wherein the thermoplastic resin has a different melting point on both sides of the conductive film. (4) The melting point of the thermoplastic resin is 170 to 820°C,
Claims in which the melting point of one thermoplastic resin is 15°C or more higher than the melting point of the other thermoplastic resin, and the decomposition temperature of both thermoplastic resins is 30°C or more higher than the melting point of the thermoplastic resin with a higher melting point. The conductive adhesive film for fixing a semiconductor element according to item (3). (5) The conductive adhesive film for fixing a semiconductor element according to claims (2) to (4), wherein the thermoplastic resin is a fluorine-based polymer. (6) The conductive adhesive film for fixing a semiconductor element according to claim (5), wherein the fluorine-based polymer is a homopolymer or copolymer of perfluoroalkene or perfluorovinyl ether.