JP2001267456A - Semiconductor device and method of assembling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device which can eliminate the need for polishing and can realize electric connection of the semiconductor device with a low cost. SOLUTION: The method for assembling a semiconductor device includes steps of (1) applying substance having a flux action to tip ends of eutectic solder bumps of a multiplicity of semiconductor elements formed on a wafer for electric connection with a substrate, (2) coating thermosetting liquid sealing resin composition thereon, (3) curing the composition to the B-stage, (4) dicing the wafer into individual semiconductor elements, and (5) joining the individual semiconductor elements, fluidically heating the B-staged thermosetting composition and cooling it for compression bonding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of assembling a semiconductor element to be bonded to a substrate by a bump bonding method, and relates to a semiconductor device manufactured by using the method.

[0002]

2. Description of the Related Art A flip-chip mounting method has emerged from the demand for high integration and high density of IC chips and miniaturization of IC packages. This mounting method enables miniaturization and thinning by directly electrically connecting the IC chip surface and the printed circuit board with metal bumps such as eutectic solder instead of the conventional wire bonding. But chips,
Since the printed wiring board and the solder have different coefficients of thermal expansion, thermal stress is generated during the thermal shock test. In particular, thermal stress is locally concentrated on metal bumps near corners far from the center of the chip. For this reason, cracks occur at the joints, and the operation reliability of the circuit is greatly reduced.

Therefore, sealing with a liquid injection sealing underfill material is performed for the purpose of reducing thermal stress. However, this method requires a method of injecting an underfill material into a gap between the chip and the printed wiring board, and curing and encapsulating the underfill material. Further, in the case of such a semiconductor device, a wafer manufacturing process, an electric circuit forming process on a wafer, a singulation process, a bump forming process, a bump bonding process, and an underfill sealing process are required. There was a problem in that the company or factory was often different and the delivery cost was also high.

Therefore, a method has been devised in which an electric circuit is formed on a wafer, bumps are formed without singulation, and then singulation is performed. This method can also produce a semiconductor device with bumps in one line from wafer production, and may greatly reduce the production cost of the device.
However, even with this method, an underfill sealing step is required to increase the reliability, and there remains a problem that this is reflected in the cost.

[0005] Further, when mounting on a substrate in general flip chip mounting, a flux is applied to the substrate or the like in advance in order to join eutectic solder. After mounting, the flux is often washed using an appropriate solvent. In this case, when underfill sealing is performed in a later step with the residual flux remaining, the underfill material is often peeled off at the interface of the remaining flux thin film.
It has been found that the cause is generally that the flux is an acidic component such as an organic carboxylic acid, which is generally poor in wettability with an underfill material using a thermosetting resin.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem of the assembling process of a semiconductor device with bumps, and its object is to greatly reduce the manufacturing process and reduce the cost. It is intended to provide a method for assembling a semiconductor device which is highly reliable and excellent in reliability.

[0007]

According to the present invention, there is provided 1) a step of applying a substance having a flux action to a wafer on which a number of semiconductor elements having eutectic solder bumps for electrical connection with a substrate are formed; 2) a step of applying the thermosetting liquid sealing resin composition; 3) a step of converting the thermosetting liquid sealing resin composition to a B-stage; 4) a step of dicing the wafer to singulate semiconductor elements. 5) A method for assembling a semiconductor element comprising a pressure bonding step of joining a singulated semiconductor element and a substrate, and simultaneously heating and flowing the B-staged thermosetting liquid sealing resin composition, followed by cooling.

As a further preferred embodiment, there is provided a method for assembling a semiconductor device, wherein the substance having a flux action is a substance having poor wettability to the thermosetting resin composition.

[0009]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail.
First, eutectic solder bumps are formed on a large number of semiconductor devices having electric circuits formed on a wafer, and a material having a flux action is applied on the bumps by screen printing or stamping (FIGS. 1 and 2). (Fig. 2). When the substance having the flux action is solid, it can be dissolved in a solvent and diluted. Examples of the substance having a flux action include organic carboxylic acids (including polymers and monomers), substances having a reduction action such as hydroquinone and naphthoquinone, and compounds having the structure. As the above-mentioned compound, a low-molecular compound can be used, but a low-molecular compound is more compatible, and in a method in which a flux action is locally applied only to the metal post as in the present invention, a high-molecular compound is used. Molecules are more preferred.

It is preferable that the substance having the flux action has poor wettability with the liquid sealing resin and does not cause any trouble in manufacturing the device during and after sealing.

Subsequently, a thermosetting liquid sealing resin composition is applied to the entire wafer on the circuit forming surface. It is preferable that the thermosetting liquid sealing resin composition used is liquid at room temperature or has fluidity when heated, and has poor wettability with a substance having a flux action at room temperature or when heated. As examples of the thermosetting liquid sealing resin, known thermosetting resins such as epoxy resin, cyanate resin, urethane resin, polybutadiene resin, silicone resin, phenol resin, acrylic resin, and methacryl resin may be applied. Can be done. More preferred are an epoxy resin and a cyanate resin. Further, for the purpose of sealing the semiconductor element, it is preferable that impurities, especially ionic impurities, be small.

It is preferable to add an inorganic filler to make the water resistance and the coefficient of linear expansion close to the adherend. Examples include silica, calcium carbonate, alumina, aluminum nitride, and the like. The shape is preferably spherical because fluidity is required at the time of joining. Further, its size is such that the average particle size is in the range of 0.5 μm to 12 μm and the maximum particle size is 5 μm.
It is preferably a spherical filler having a diameter of 0 μm or less.

If the average particle diameter is less than 0.5 μm, the fluidity of the B-staged thermosetting liquid sealing resin composition which melts at the time of bump bonding becomes insufficient, and the resin composition is immersed outside the chip. There is a risk that the fillet will be insufficient and the reliability will be reduced due to insufficient adhesion. On the other hand, if the average particle diameter exceeds 12 μm, if a filler remains on the bumps at the time of applying the thermosetting liquid sealing resin composition, contact failure may occur at the time of subsequent bump bonding, which is not preferable. Regarding the maximum particle size, the bump height is generally 100 μm
Therefore, at least the coating thickness of the thermosetting liquid sealing resin composition must be equal to or less than the height of the bump. If the maximum particle size exceeds 50 μm, the coating thickness varies greatly, and there is a possibility that contact failure may occur during bump bonding.

When the device is a memory device, it is more preferable that the device has low radiation. Although the shape may be spherical, crushed, flake, or the like, the spherical shape is necessary because the linear expansion coefficient can be reduced by increasing the amount of filler. The amount of the spherical inorganic filler added is 1 to the total composition.
0 to 90% by weight is desirable. If it is less than 10% by weight,
90% by weight with increased moisture resistance and coefficient of linear expansion of cured product
Exceeding the viscosity is not preferred because the viscosity of the resulting composition becomes too high and the flow characteristics deteriorate.

When the thermosetting resin is solid, it can be dissolved in a solvent before use. The solvent is not particularly limited as long as it dissolves the thermosetting resin contained in the thermosetting liquid sealing resin composition. However, the boiling point is preferably 210 ° C. or lower in order to minimize the residual solvent when the B stage is formed. Further, if necessary, a curing agent, a curing accelerator, an antifoaming agent, a leveling agent, a coloring agent, a low stress agent and the like can be added.

As these sealing methods, conventionally known methods such as dispensing, printing, spin coating, a sealing method using a molding die, and transfer can be used. It is preferable to use a method that can be left on a crystal solder so as to repel. Among them, a spin coating method or a printing method is preferable. This is because it can be performed at relatively low cost, the film thickness can be easily controlled, the resin composition remaining on the bumps can be reduced as much as possible, and no contact failure occurs at the time of joining.

Next, the wafer is diced to singulate the elements. Further, the applied element is bonded to a substrate. The method is performed by passing through a reflow furnace. The surface of the solder is activated by a substance having a flux action, and is joined to the metal terminal of the substrate. At the same time, the thermosetting liquid sealing resin composition is melted and sealed. If the curing is insufficient, post-baking may be performed after joining. Also, because the present invention applies flux only to the tip of the solder,
Flux contamination to other parts can be reduced as much as possible.

The thermosetting liquid sealing resin composition used in the present invention is a resin composition which can be B-staged. In general, the B-stage is formed by applying a resin composition and then proceeding to cure at a low temperature. At room temperature, the reaction can hardly proceed any more, and the state is a tack-free state. Means a state where it is possible to stop. Further, it is preferable that impurities, especially ionic impurities, are small (eg, hydrolyzable chlorine is 1000 ppm or less). The B-stage of the thermosetting liquid encapsulating resin composition is made tack-free to facilitate handling, storage at room temperature, and dicing. However, there is a problem that the liquid resin composition thus obtained does not have a uniform tilted film thickness or is inferior in dicing properties.

Next, a plastic polymer can be added to the thermosetting liquid sealing resin composition used in the present invention in order to prevent peeling and chipping during dicing.

In the method for producing the thermosetting liquid sealing resin composition used in the present invention, first, an epoxy resin or a cyanate resin (in the case of a solid, dissolved in a solvent) and other additives are weighed and roll kneading is performed. And evenly disperse. Further, it is made by defoaming. A semiconductor device manufactured by using the method of assembling a semiconductor device according to the present invention can be manufactured at low cost. As a method of assembling a semiconductor device other than the present invention, a conventionally known method can be used.

[0021]

The present invention will be described with reference to examples and comparative examples. <Examples 1 and 2> 100 parts by weight of a varnish dissolved in 30 parts by weight of methyl isobutyl ketone using 70 parts by weight of a bisphenol A epoxy resin (epoxy equivalent: 250) as a thermosetting resin, and 2-phenyl as a curing accelerator -4
-0.5 parts by weight of ethylimidazole, spherical silica as filler (average particle size 0.8 μm, maximum particle size 20 μm) 80
A weight part was weighed, kneaded and dispersed by three rolls, and then subjected to vacuum defoaming treatment to prepare a thermosetting liquid sealing resin composition.
In Example 1, an active rosin-based flux material A having poor wettability was used on a wafer (350 μm) on which solder bumps having a height of 50 μm had been formed in advance. Manufactured by RMA37
6) In Example 2, an active rosin-based flux material B having poor B wettability (TSF6502, manufactured by KESTER) was applied by screen printing. Thereafter, the thermosetting liquid sealing resin composition was dropped at the center of the wafer and applied using a spin coater. After application, the thermosetting liquid sealing resin composition and the flux at the tip of the metal post were well separated, and an electrical connection could be secured. Thereafter, vacuum drying was performed at 5 torr to make tack-free. The final coating thickness was controlled to be 35 μm. Next, using a dicing saw, the wafer was diced into individual devices (chip size: 6 × 6 mm).

No peeling or cracking was observed in the tack-free thermosetting liquid sealing resin composition layer near the cut surface. Next, the element was temporarily bonded to the organic substrate through an IR reflow furnace at 220 ° C. and a minimum temperature of 183 ° C. for 60 seconds. This could be done simultaneously with the joining of the solder balls to the substrate. Further, it was cured at 150 ° C. for 1 hour as post bake. The resin flowed to the outside of the element to form a fillet. No voids were found during curing. In addition, when a cross section was observed using a metallographic microscope to confirm the adhesion interface of each member after the package was manufactured, no peeling was observed.

<Example 3> A thermosetting liquid sealing resin composition was produced in the same manner as in Example 1. On the wafer shown in Example 1, ascorbic acid which is a low-molecular organic carboxylic acid having a flux action is dissolved in an appropriate amount of a solvent, applied by screen printing, the solvent is dried, and a flux material is placed on a metal post. It was formed as. Subsequently, the thermosetting liquid sealing resin composition was applied, and then the thermosetting liquid sealing resin composition was B-staged to a wafer and evaluated in the same manner as in Example 1.

<Comparative Example 1> A thermosetting liquid sealing resin composition was dropped on the wafer shown in Example 1 without applying any flux treatment to the center of the wafer, and was uniformly applied using a spin coater. It was applied and subsequently evaluated in the same manner as in Example 1.

Table 1 shows the measurement results.

[Table 1]

[0026]

According to the method of manufacturing a semiconductor device of the present invention, the conventional manufacturing process can be greatly shortened without polishing, and the electrical junction can be manufactured at low cost.
Its industrial merit is great.

[Brief description of the drawings]

FIG. 1 shows a schematic diagram of a flux application operation by a printing method.

FIG. 2 shows a schematic view of a flux application operation by a stamping method.

Claims (6)

[Claims] 1. A step of applying a material having a flux action to the tip of a bump on a wafer on which a number of semiconductor elements having eutectic solder bumps for electrical connection with a substrate are formed, 2) thermosetting 3) a step of applying the thermosetting liquid sealing resin composition to the B-stage, 4) a step of dicing the wafer to singulate the semiconductor elements, and 5) a step of applying the thermosetting liquid sealing resin composition to the B-stage. A method of assembling a semiconductor device, comprising: bonding a singulated semiconductor element and a substrate, and simultaneously heating and flowing the B-staged thermosetting liquid sealing resin composition, followed by cooling, and a pressure bonding step. . 2. The method for assembling a semiconductor device according to claim 1, wherein said substance having a flux action is a substance having poor wettability with respect to said thermosetting liquid sealing resin composition. 3. The method for assembling a semiconductor device according to claim 1, wherein said substance having a flux action is applied by screen printing. 4. The method for assembling a semiconductor device according to claim 1, wherein said substance having a flux action is applied by stamping. 5. The method for assembling a semiconductor device according to claim 1, wherein the step of applying the thermosetting liquid sealing resin composition is performed by a spin coating method or a printing method. 6. A semiconductor device manufactured by using the method for assembling a semiconductor device according to claim 1.