JP2010262973A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device that prevents breakage of an ultra-low dielectric-constant layer and breakage of a bump made of lead-free solder. <P>SOLUTION: The semiconductor device 1 includes a wiring board 11; a semiconductor chip 12 flip-chip connected to the wiring board 11 via bumps 13 made of lead-free solder; and an underfill resin 14 for filling a gap between the semiconductor chip 12 and the wiring board 11. The underfill resin 14 contains epoxy resin, a curing agent and an inorganic filler. The underfill resin is configured, such that the glass transition temperature is ≥125°C, the thermal expansion coefficient at 25°C is ≤30 ppm/°C; the storage elastic modulus in a temperature region of ≥-55°C and less than the glass transition temperature is ≥4 GPa and ≤9 GPa; and the loss elastic modulus in the temperature region of ≥-55°C and less than the glass transition temperature is ≥100 MPa, while the loss elastic modulus has a plurality of peaks. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor device, and more particularly to a semiconductor device having a structure in which a semiconductor chip is flip-chip bonded onto a wiring board and a gap between the semiconductor chip and the wiring board is filled with an underfill resin. .

  In recent years, electronic devices and communication devices such as portable devices and digital home appliances are flip chip connected via a bump to a semiconductor chip due to demands for lighter, smaller, thinner, higher density, higher speed transmission, etc. Such a semiconductor device is used. In this semiconductor device, an underfill resin is filled in the gap between the semiconductor chip and the wiring board to protect the bumps. In particular, recent semiconductor chips include ultra-low dielectric constant films (Low-k films, UL-k films, ELow-k films) as interlayer insulating films, and bumps are made of lead-free solder from the viewpoint of environmental protection. It has come to be.

Prior to the use of a low-k film for an insulating film of a semiconductor chip, the glass transition temperature (T _g ) of the underfill resin is the upper limit of a general guaranteed operating temperature range (−55 ° C. to + 125 ° C.). A material having a modulus of elasticity higher than 125 ° C., for example, 130 ° C. to 140 ° C. and having a high elastic modulus of 11 GPa at −55 ° C., which is the lower limit of the guaranteed operating temperature range, has been used. Here underfill resin harden according to cool at a temperature range below T _g. For this reason, internal stress concentrates on the corners of the semiconductor chip, and peeling occurs at the interface between the chip surface and the underfill resin, cracks occur in the fillet of the underfill resin, and the semiconductor chip is vulnerable. There is a problem that peeling occurs in the ultra-low dielectric constant film.

On the other hand, if an underfill resin having a low glass transition temperature (T _g ) and a low elastic modulus on the low temperature side is used, it is considered that such a problem does not occur. The present inventors are 80 ° C. lower than 125 ° C. T _g is the upper limit of the guaranteed operation temperature range as such underfill resin, the underfill elastic modulus at low-temperature region and a low characteristic than 4GPa An evaluation test using a resin was performed.

As a result, the following evaluation results were obtained. That is, a thermal stress generated due to a difference in thermal expansion coefficient between the semiconductor chip and the wiring board is generated on the bump connecting the semiconductor chip and the wiring board. Further, the bump made of lead-free solder has a low creep limit and becomes brittle in a low temperature region near the lower limit of the guaranteed operating temperature range. When the semiconductor device was cooled to a low temperature region, the underfill resin could not disperse the thermal stress, causing a problem that the bump made of lead-free solder was destroyed. Further, in such underfill resin, the thermal expansion coefficient of the following The _{T g} is 30~60ppm / ℃, the thermal expansion coefficient exceeds a _{T g} becomes very high and 100 ppm / ° C. or higher. When heated to the reflow temperature at the time of mounting, the underfill resin lifts the semiconductor chip from the wiring board due to the large thermal expansion coefficient of the underfill resin and the volume expansion of the resin. There was a problem of breaking the bump joint beyond the solder creep limit.

Furthermore, in recent years, a low-k film has been used for an insulating film of a semiconductor chip, and it has become necessary to lower the stress of the above-described underfill resin. In contrast, for example, in Patent Document 1, when a glass transition temperature (T _g ) of 100 ° C. to 120 ° C. and a thermal expansion coefficient α _{1 at} 125 ° C. of 30 ppm / ° C. or less is used, a semiconductor element, an interposer, and a print are used. It is described that the breakage and breakage between each of the substrates can be reduced.

  Patent Document 2 discloses that in a flip chip package using a build-up type multilayer substrate, the thermal expansion coefficient and glass transition temperature of the underfill resin are appropriately designed in accordance with the thickness of the core material and the thermal expansion coefficient of the substrate. By doing so, it is disclosed that the internal stress of the semiconductor package accompanying the temperature change is relaxed and the damage is suppressed.

JP 2006-24842 A International Publication No. 2008/032620 Pamphlet

  However, in the said patent document 1, the kind of solder used for a bump and the kind of insulating film with which a semiconductor chip is provided are not examined. Further, in Patent Document 2, when the glass transition temperature of the underfill resin is within the guaranteed temperature range of the semiconductor device, when the temperature of the semiconductor device exceeds the glass transition temperature of the underfill resin, the thermal expansion coefficient increases rapidly. The internal stress due to the difference in coefficient of thermal expansion between the semiconductor chip and the multilayer board is not only caused by this, but the problem that the semiconductor chip is lifted away from the multilayer board and destroys the solder bumps is considered. It has not been. Further, the difference in thermal expansion coefficient that causes a problem in the reflow temperature at the time of mounting the semiconductor device and the internal stress due to the difference are not taken into consideration.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a semiconductor device capable of preventing both destruction of an ultra-low dielectric constant film and destruction of bumps made of lead-free solder. That is.

  A semiconductor device according to the present invention includes a wiring board, a semiconductor chip that is flip-chip bonded to the wiring board via bumps made of lead-free solder, and an underfill resin that fills a gap between the semiconductor chip and the wiring board. It has. The underfill resin contains an epoxy resin, a curing agent, and an inorganic filler. The underfill resin has a glass transition temperature of 125 ° C or higher, a thermal expansion coefficient at 25 ° C of 30 ppm / ° C or lower, and a storage elastic modulus of 4 GPa or higher in a temperature range of -55 ° C or higher and lower than the glass transition temperature. The loss elastic modulus is 9 MPa or less and the loss elastic modulus is 100 MPa or more, and the loss elastic modulus has a plurality of peaks.

  In the semiconductor device of the present invention, since the glass transition temperature of the underfill resin is 125 ° C. or more which is the upper limit of the guaranteed operating temperature range of the semiconductor device, the mechanical characteristics do not change significantly within the guaranteed operating temperature range. In other words, since the elastic modulus and the coefficient of thermal expansion do not change greatly, it is possible to suppress the occurrence of a large thermal stress during the operation of the semiconductor device.

  Further, in the semiconductor device of the present invention, the thermal expansion coefficient at 25 ° C. of the underfill resin is a low value of 30 ppm / ° C. or lower, and thus the value is lower in the lower temperature range, while the operation guarantee temperature upper limit of 125 is reached. The coefficient of thermal expansion at 0 ° C does not increase dramatically. Therefore, the difference in thermal expansion coefficient between the semiconductor chip and the wiring board can be effectively reduced. Even if the glass transition temperature is 125 ° C. or more, which is the upper limit of the guaranteed operating temperature range, if the coefficient of thermal expansion is high like the underfill resin used in conventional semiconductor devices, The stress becomes relatively high, and there is a risk of causing problems such as cracks and peeling in the semiconductor device.

  Furthermore, in the semiconductor device of the present invention, the storage elastic modulus of the underfill resin in the temperature range of −55 ° C. or higher and lower than the glass transition temperature is 9 GPa or lower. Therefore, the thermal stress concentrated on the corner portion of the semiconductor chip particularly in the low temperature region is reduced, and the peeling of the ultra-low dielectric constant film and the peeling between the semiconductor chip and the underfill resin can be suppressed. On the other hand, because the storage elastic modulus in the temperature range is 4 GPa or more, the thermal stress applied to the solder due to the difference in thermal expansion coefficient between the semiconductor chip and the wiring board is dispersed and relaxed in the low temperature range. Thus, breakage of the solder bumps can be suppressed.

  In the semiconductor device of the present invention, the loss elastic modulus of the underfill resin in the temperature range of −55 ° C. or higher and lower than the glass transition temperature is 100 MPa or higher and has a plurality of peaks. Therefore, the thermal stress applied to the underfill resin in the low temperature range is converted to heat by the movement of the molecular chain, and the effect of mitigating is increased. In addition, since there are a plurality of peaks of the loss modulus, the movement of the molecular chain occurs at the temperature at which each peak appears, and the stress can be relaxed a plurality of times, so that the thermal stress relaxation effect is further increased.

  As described above, according to the semiconductor device of the present invention, it is possible to provide a semiconductor device capable of preventing both the destruction of the ultra-low dielectric constant film and the destruction of the bump made of lead-free solder.

It is a schematic sectional drawing which shows the structure of a semiconductor device. It is a flowchart which shows the outline of the manufacturing method of a semiconductor device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

  First, the structure of the semiconductor device in one embodiment of the present invention will be described. Referring to FIG. 1, a semiconductor device 1 according to the present embodiment includes a wiring board 11, a semiconductor chip 12 flip-chip bonded to the wiring board 11 via bumps 13 made of lead-free solder, and the semiconductor chip 12. And an underfill resin 14 that fills a gap between the wiring board 11 and the wiring board 11. The semiconductor chip 12 includes an ultra-low dielectric constant film (Low-k film, UL-k film, or ELow-k film) as an interlayer insulating film. Furthermore, the semiconductor device 1 includes a ring 15 disposed on the wiring substrate 11 so as to surround the semiconductor chip 12, and a heat spreader 18 disposed on the semiconductor chip 12 and the ring 15. The ring 15, the wiring substrate 11, and the heat spreader 18 are joined together by an adhesive 16. Further, the semiconductor chip 12 and the heat spreader 18 are connected via a heat radiation resin 17. With the above configuration, in the semiconductor device 1, the semiconductor chip 12 and the wiring board 11 are electrically connected by the bumps 13, and heat generated by the operation of the semiconductor chip 12 is transferred from the heat radiation resin 17 to the heat spreader. Conducted to 18 and discharged from the heat spreader 18 to the outside.

  Here, the underfill resin 14 contains an epoxy resin, a curing agent, and an inorganic filler. The underfill resin 14 has a glass transition temperature of 125 ° C. or higher, a thermal expansion coefficient at 25 ° C. of 30 ppm / ° C. or lower, and a storage elastic modulus in a temperature range of −55 ° C. or higher and lower than the glass transition temperature. The loss elastic modulus has a plurality of peaks with respect to the change in temperature in the temperature range of −55 ° C. or higher and lower than the glass transition temperature.

  In the semiconductor device 1 in the present embodiment, the glass transition temperature of the underfill resin 14 is 125 ° C. or more, which is the upper limit of the guaranteed operating temperature range of the semiconductor device 1. As a result, since the elastic modulus and thermal expansion coefficient of the underfill resin 14 do not change significantly in the guaranteed operating temperature range, it is possible to suppress a large thermal stress from being generated suddenly during the operation of the semiconductor device 1.

  Moreover, in the semiconductor device 1 in the present embodiment, the thermal expansion coefficient of the underfill resin at 25 ° C. is 30 ppm / ° C. or less. For this reason, it is avoided that the thermal expansion coefficient becomes a remarkably high value in the guaranteed operating temperature range, and the difference in thermal expansion coefficient between the semiconductor chip and the wiring board is effectively reduced.

  Furthermore, in the semiconductor device 1 in the present embodiment, the storage elastic modulus of the underfill resin 14 in the temperature range of −55 ° C. or higher and lower than the glass transition temperature is 9 GPa or lower. Therefore, the thermal stress concentrated on the corner portion of the semiconductor chip 12 particularly in the low temperature region is reduced, and the peeling of the ultra-low dielectric constant film and the peeling between the semiconductor chip 12 and the underfill resin 14 are suppressed. On the other hand, since the storage elastic modulus in the temperature range is 4 GPa or more, the thermal stress applied to the bump 13 due to the difference in thermal expansion coefficient between the semiconductor chip 12 and the wiring substrate 11 is caused by the underfill resin 14 in the low temperature range. It is dispersed and relaxed, and the destruction of the bumps 13 is suppressed.

  Moreover, in the semiconductor device 1 in the present embodiment, the loss elastic modulus of the underfill resin 14 in the temperature range of −55 ° C. or higher and lower than the glass transition temperature is 100 MPa or higher and has a plurality of peaks. Therefore, the thermal stress applied to the underfill resin 14 in the low temperature region is converted to heat by the movement of the molecular chain, and the effect of relaxing is increased. In addition, since there are multiple peaks of loss modulus, molecular chain movement occurs at the temperature at which each peak appears, and multiple stress relaxations are possible, further increasing the thermal stress relaxation effect. .

  As described above, the semiconductor device 1 according to the present embodiment is a semiconductor device capable of preventing both the destruction of the ultra-low dielectric constant film and the destruction of the bumps 13 made of lead-free solder.

  Next, details of the underfill resin 14 included in the semiconductor device 1 will be described. As the underfill resin 14 in the present embodiment, for example, an epoxy resin composition mainly containing (a) an epoxy resin, (b) a curing agent, and (c) an inorganic filler, which are main components, can be employed. . Since the underfill resin 14 is also required to have a function as an adhesive, it is optimal to use a thermosetting epoxy resin with good adhesion.

  Any epoxy resin having two or more epoxy groups in one molecule can be used. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, etc. can be used. it can. In addition, the epoxy resin is preferably liquid at room temperature, but even if it is a solid epoxy resin at room temperature, it can be used by heating and liquefying within a range that does not affect the properties of the underfill resin. Is also possible. Further, the underfill resin 14 is often filled between the semiconductor chip 12 and the wiring substrate 11 by utilizing a capillary phenomenon. Therefore, the thing with a viscosity as low as possible is preferable. Moreover, in order to obtain a required characteristic, the epoxy resin contained in the underfill resin 14 does not need to be one type, and a plurality of types may be mixed and used at an appropriate ratio.

  As the curing agent, various curing agents can be adopted as long as they can cure the epoxy resin. For example, known ones such as amine resins, acid anhydride resins, and phenol resins may be used. it can. Among these, amine resins can be preferably used from the viewpoints of low viscosity and high adhesive strength. The addition amount of the curing agent may be an effective amount that cures the epoxy resin, and is approximately equimolar with the epoxy group. If the epoxy group is excessive, homopolymerization between the epoxy groups occurs and the entire resin is cured, but the elastic modulus after curing is increased. On the other hand, when the curing agent is excessive, the curing reaction with only the curing agent does not occur, so that an uncured curing agent remains. As a result, the resin as a whole is not sufficiently cured and the necessary physical properties are not exhibited. If the molar ratio between the epoxy group and the curing agent is approximately equal, curing proceeds sufficiently and desired characteristics can be obtained. It is not necessary for the curing agent contained in the underfill resin 14 to be one type, and a plurality of types may be appropriately mixed and used at a necessary ratio.

  As the inorganic filler (inorganic filler), for example, silica or the like can be used. The addition amount (filling rate) of the filler can be arbitrarily determined within a range that does not impair the effect of the underfill resin 14 in the present embodiment. In particular, the underfill resin 14 has a ratio of 50 to 70% by mass. It is preferable to be added. This filler may have been surface-treated with a silane coupling agent or the like. Moreover, the particle size of the filler needs to be smaller than the gap due to the property that the underfill resin 14 fills the gap (gap) between the semiconductor chip 12 and the wiring substrate 11 by capillary action. Furthermore, since the viscosity of the underfill resin 14 tends to increase as the amount of filler added increases, an appropriate particle size distribution for suppressing the increase in viscosity is required. Further, from the viewpoint of ensuring fluidity and preventing damage to the wiring surface, the particle shape is preferably a spherical shape, not a crushed shape (indefinite shape).

  A curing accelerator may be added to the underfill resin 14 in the present embodiment as necessary. The addition amount of the curing accelerator may be 0.1 to 10 parts by mass with respect to the epoxy resin, and there is a problem that if it is added excessively, the long-term storage stability is lowered, and the reaction rate increases at the time of thermosetting, and the reaction heat As a result, the problem that the properties of the cured product deteriorate may occur. If the curing accelerator is added in a deficient manner, the reaction rate is lowered, and there is a possibility that the problem that the curing takes time and the workability is lowered and that the entire resin becomes uncured state may occur.

  A stress reducing agent may be added to the underfill resin 14 of the present invention as needed for the purpose of reducing the internal stress of the resin. As the stress reducing agent, silicone rubber, silicone oil, polybutadiene rubber, thermoplastic resin, or the like can be used. These may be chemically reacted with an epoxy resin or a curing agent, or may not be involved in the reaction. When these stress reducing agents are solid, the particle shape and particle size are adjusted so as not to increase the viscosity and thixotropy of the underfill resin 14. In addition, when these stress reducing agents are liquid, they separate from the epoxy resin and the curing agent and float when the underfill resin 14 is thermally cured, thereby reducing the adhesion of the underfill resin, and the cured material properties. It is necessary to make adjustments so that the semiconductor components are not deteriorated or spilled and contaminated.

  The underfill resin 14 of the present invention further includes a filler surface treatment agent such as a silane coupling agent that promotes adhesion and adhesion at the interface between the filler and the matrix resin, a colorant such as carbon black, an ion trap, if necessary. Agents, reactive diluents, leveling agents, and other additives can be blended.

  The molecular structure and molecular weight of the epoxy resin, curing agent, stress reducing agent, etc. constituting the underfill resin 14 in the present embodiment are not particularly limited, but the storage elastic modulus and loss of the underfill resin 14 that is a cured product. Mechanical properties such as elastic modulus, glass transition temperature, thermal expansion coefficient, and strength are defined by the molecular structure, cross-linked structure, and distance between cross-linking points when the epoxy resin and the curing agent are three-dimensionally cross-linked. When the molecular weight of the epoxy resin or the curing agent is low and the distance between the crosslinking points is short, the storage elastic modulus is high, the loss elastic modulus is low, and the strength tends to be low. On the other hand, when the molecular weight of the epoxy resin or the curing agent is high and the distance between the crosslinking points is long, the storage elastic modulus tends to be low and the loss elastic modulus tends to be high. If there are many crosslinking points, the glass transition temperature rises, the thermal expansion coefficient tends to be low, and the strength tends to be high. That is, mechanical properties such as storage elastic modulus, loss elastic modulus, glass transition temperature, thermal expansion coefficient, and strength of the cured product are the molecular weight, molecular structure, epoxy resin, curing agent, and other resins involved in crosslinking. Depends on the number of functional groups.

  The underfill resin 14 in the present embodiment has a glass transition temperature of 125 ° C. or higher and a thermal expansion coefficient at 25 ° C. of 30 ppm / ° C. or lower. For example, a glass transition temperature of 125 ° C. or higher and a thermal expansion coefficient of 30 ppm / ° C. or lower can be realized by increasing the cross-linking density of the epoxy resin and the curing agent using a bifunctional or higher functional resin. . The coefficient of thermal expansion of 30 ppm / ° C. or less can also be realized by increasing the filler filling rate within a range in which the viscosity, storage elastic modulus, and loss elastic modulus of the resin can be maintained within desired ranges.

  The underfill resin 14 in the present embodiment has a storage elastic modulus in a temperature range of −55 ° C. or higher and lower than the glass transition temperature of 4 GPa or more and 9 GPa or less. In addition to blending an epoxy resin, a curing agent and an inorganic filler, a low stress agent such as silicone rubber is added when the storage elastic modulus is too high. A stress-reducing agent such as silicone rubber or silicone oil does not have a glass transition point within the operation guaranteed temperature range of the semiconductor device, and maintains a low elastic modulus in the temperature range. Therefore, the elastic modulus of the underfill resin 14 can be adjusted by adjusting the addition amount within a range that does not impair other characteristics of the underfill resin 14. Also, the storage elastic modulus can be effectively reduced by reducing the amount of the inorganic filler added.

  The underfill resin 14 in the present embodiment has a loss elastic modulus of 100 MPa or more and has a plurality of peaks of loss elastic modulus. The loss elastic modulus of the cured resin shows the relaxation of the molecular chain between the crosslinking points of the resin due to thermal energy, so the functional group that contributes to the crosslinking reaction of the epoxy resin or curing agent However, the above characteristics can be realized by using a flexible structure having a long molecular chain. Furthermore, by using a plurality of types of epoxy resins and curing agents having different molecular weights and molecular structures between functional groups that contribute to the crosslinking reaction, a cured product (underfill resin 14) having a plurality of loss modulus peaks is realized. Can do. In addition, since the inorganic filler hinders the movement of the matrix resin, by reducing the amount of the inorganic filler added, the characteristics of the matrix resin are easily developed, and an increase in loss elastic modulus and a plurality of peaks can be realized.

  Here, in the semiconductor device 1 according to the present embodiment, it is preferable that the storage elastic modulus in the temperature range equal to or higher than the glass transition temperature of the underfill resin 14 is 100 MPa or higher. Thereby, even when the temperature of the semiconductor device 1 exceeds the glass transition temperature of the underfill resin 14, the thermal stress applied to the bump 13 due to the difference in thermal expansion coefficient between the semiconductor chip 12 and the wiring substrate 11 is It is possible to disperse and relax by the underfill resin 14 and suppress the destruction of the bumps 13.

In the semiconductor device 1 according to the present embodiment, the underfill resin 14 has a glass transition temperature of 125 ° C. or higher and a thermal expansion coefficient of 30 ppm at 25 ° C. in the entire range of frequencies from 10 ⁻² Hz to 10 Hz. The storage elastic modulus in the temperature range of −55 ° C. or higher and lower than the glass transition temperature is 4 GPa or higher and 9 GPa or lower, the loss elastic modulus is 100 MPa or higher, and the loss elastic modulus has a plurality of peaks. It is preferable.

  Thus, the reliability of the semiconductor device 1 can be improved by employing the underfill resin 14 having the predetermined characteristics in a wide frequency range.

  Next, a method for manufacturing the semiconductor device 1 will be briefly described. Referring to FIG. 2, in the method of manufacturing a semiconductor device in the present embodiment, first, an underfill resin preparation step and a semiconductor chip bonding step are performed as step (S10) and step (S20), respectively.

  In the step (S10), a predetermined amount of components such as an epoxy resin, a curing agent and an inorganic filler constituting the underfill resin 14 are weighed and mixed while being melted, stirred and dispersed as necessary. . And in order to avoid that a void generate | occur | produces after hardening, after fully deaerating in pressure reduction atmospheres, such as a vacuum, it fills with a syringe.

  On the other hand, in the step (S20), referring to FIG. 1, the semiconductor chip 12 and the wiring board 11 are flip-chip bonded via bumps 13 made of lead-free solder.

  Next, an underfill resin filling step is performed as a step (S30). In this step (S30), the needle having the optimum shape determined by calculation in consideration of the viscosity of the underfill resin, the discharge speed, and the coating amount is applied to the tip of the syringe filled with the underfill resin prepared in step (S10). Is set and the underfill resin is extruded by air pressure or mechanical force. The extruded underfill resin is applied along the periphery of the semiconductor chip 12 and fills the gap between the semiconductor chip 12 and the wiring substrate 11 by capillary action. At that time, the wiring substrate 11 may be heated from the main surface side opposite to the side on which the semiconductor chip 12 is mounted to such an extent that the underfill resin does not chemically react and increase in viscosity. Thereby, the viscosity of the underfill resin is lowered, and filling of the gap between the semiconductor chip 12 and the wiring substrate 11 is promoted. Furthermore, after the gap between the semiconductor chip 12 and the wiring substrate 11 is sufficiently filled, an underfill resin is further applied to the peripheral edge of the semiconductor chip 12 to form a fillet.

  Next, a curing step is performed as a step (S40). In this step (S40), a heat treatment for curing the underfill resin applied in step (S30) is performed. Specifically, the said heat processing can be implemented by heating to 90 to 170 degreeC, for example in oven, and hold | maintaining for 0.5 to 3 hours. When the heating temperature is too low or when the heating time is too short, the resin is not sufficiently cured, and the adhesive strength between the semiconductor chip 12 or the wiring substrate 11 and the underfill resin 14 is low, and the strength of the resin itself is low. There is a problem that the reliability is lowered and the reliability of the semiconductor device 1 is lowered. On the other hand, if the heating temperature is too high or the heating time is too long, the temperature rise during curing becomes severe and damages the semiconductor chip 12, or the semiconductor device cracks or peels due to increased thermal stress, Problems such as degradation of resin characteristics occur.

  Next, a ring installation step is performed as a step (S50). In this step (S50), referring to FIG. 1, ring 15 is arranged on wiring substrate 11 so as to surround semiconductor chip 12, and ring 15 and wiring substrate 11 are bonded by adhesive 16.

  Next, a heat spreader installation step is performed as a step (S60). In this step (S60), after the heat radiation resin 17 is applied to the upper surface of the semiconductor chip 12 and the adhesive 16 is applied to the upper surface of the ring 15, the upper surface of the semiconductor chip 12 and the upper portion of the ring 15 are applied. The heat spreader 18 is placed so as to contact the surface. Thereafter, the heat spreader 18 is fixed by curing the heat dissipation resin. With the above process, the semiconductor device 1 in the present embodiment is completed.

  An underfill resin having a different composition was prepared, the characteristics thereof were investigated, a semiconductor device including the underfill resin was manufactured, and an experiment was conducted to investigate the reliability. The experimental procedure is as follows.

  First, a and b as the liquid epoxy resin and c to h as the amine curing agent were adjusted so that the epoxy equivalent and the amino equivalent were almost the same. Then, spherical silica, silane coupling agent, carbon black, a low stress agent such as silicone rubber and the like are blended and mixed uniformly, vacuum degassed, and Example 1 and Comparative Examples 1 to 1 shown in Table 1 are blended. The resin in 5 was adjusted.

  Next, after filling the obtained resin into a silicone tube having an inner diameter of 5 mm clipped on one side, it was cured by heating to 160 ° C. in an oven and holding for 2 hours. The cured resin round bar was cut out to a length of 3 mm, and the bottom surface was polished and parallelized to obtain a sample for measuring the thermal expansion coefficient. Moreover, the glass transition temperature and the thermal expansion coefficient were measured using a thermomechanical property measuring apparatus under conditions of a load of 2 g and a temperature increase rate of 3 ° C./min. Furthermore, by using a silicone tube having a diameter of 3.5 mm as a spacer, a resin is poured between two glass plates stretched with a Teflon sheet so as not to generate voids, heated to 160 ° C. in an oven, and held for 2 hours. The resin was cured. The cured resin plate was cut into a width of 5 mm and a length of 50 mm to prepare a viscoelasticity measurement sample. And the storage elastic modulus and the loss elastic modulus were measured using the viscoelasticity measuring device, changing the frequency at each temperature from 10 to 0.01 Hz every time the temperature was raised from -80 ° C to 210 ° C by 5 ° C.

  On the other hand, the reliability of the semiconductor device was evaluated as follows. A semiconductor chip with a thickness of 600 μm, which includes an ultra-low dielectric constant film as an insulating film, and whose resistance can be measured through a daisy chain through this insulating film, is flip-chipd onto a build-up wiring board with a thickness of 1.0 mm using lead-free solder bumps. After bonding, a package was prepared in which the resistance value of the daisy chain could be measured from the solder ball mounting pad on the back surface of the wiring board. Then, the resin described in Table 1 was filled in the gap between the semiconductor chip and the build-up wiring board, heated to 160 ° C. in an oven, and held for 2 hours to cure the resin. Thereafter, a heat dissipation resin was applied onto the semiconductor chip, a heat spreader was placed, the heat dissipation resin was cured, and the heat spreader and the semiconductor chip were bonded to complete the semiconductor device. The semiconductor device was absorbed by holding it in an environment of a temperature of 30 ° C. and a relative humidity of 70% for 192 hours, and then nitrogen reflow at a maximum temperature of 260 ° C. was passed four times. Further, this semiconductor device was loaded into a thermal cycle test apparatus, held at −55 ° C. for 10 minutes, and then subjected to 2000 thermal cycles of holding at + 125 ° C. for 10 minutes. Then, the semiconductor device was taken out from the thermal cycle test apparatus, a tester was applied to the solder ball mounting pad on the back surface of the wiring board, and the resistance value of the daisy chain was measured to investigate whether or not the circuit was maintained.

Next, experimental results will be described. Here, in Table 1, T _g is the glass transition temperature, α ₁ is the thermal expansion coefficient at 25 ° C., E ′ (<T _g ) is the storage elastic modulus in the temperature range of −55 ° C. or more and less than the glass transition temperature, E ′ (> T _g ) is the storage elastic modulus in the temperature range above the glass transition temperature, E ″ is the loss elastic modulus in the temperature range above −55 ° C. and below the glass transition temperature, and E ″ peak number is −55 ° C. and below the glass transition temperature. The number of peaks of loss elastic modulus in the temperature range is shown. In Table 1, “the rate of change after 2000 cycles” means the thermal cycle having the characteristics that changed most significantly before and after the thermal cycle among the above T _g , α ₁ , E ′ (<T _g ), and E ″. Further, in Table 1, “Circuit maintenance” is indicated as “open”, that is, when no circuit disconnection occurred, and as “x” when circuit disconnection occurred. is doing.

Referring to Table 1, it can be seen that T _g , α ₁ , E ′ and E ″ can be changed relatively freely by changing the composition of the underfill resin. After 2000 cycles In the semiconductor device adopting the underfill resin of Comparative Examples 1 to 5 in which the change rate of 20 to 60% is, the circuit is disconnected by the thermal cycle, whereas the change rate is 15 %, It was possible to avoid circuit disconnection in the semiconductor device of Example 1. Therefore, according to the semiconductor device of the present invention, destruction of the ultra-low dielectric constant film and lead-free soldering were achieved. It was confirmed that it was possible to provide a semiconductor device with improved reliability by preventing the destruction of bumps made of

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The semiconductor device of the present invention can be particularly advantageously applied to a semiconductor device having a structure in which a semiconductor chip is flip-chip bonded onto a wiring board and a gap between the semiconductor chip and the wiring board is filled with an underfill resin. .

  DESCRIPTION OF SYMBOLS 1 Semiconductor device, 11 Wiring board, 12 Semiconductor chip, 13 Bump, 14 Underfill resin, 15 Ring, 16 Adhesive, 17 Heat radiation resin, 18 Heat spreader.

Claims (4)

A wiring board;
A semiconductor chip flip-chip bonded to the wiring board via bumps made of lead-free solder;
An underfill resin that fills a gap between the semiconductor chip and the wiring board;
The underfill resin is
Contains epoxy resin, curing agent and inorganic filler,
The glass transition temperature is 125 ° C. or higher,
The coefficient of thermal expansion at 25 ° C. is 30 ppm / ° C. or less,
A semiconductor device having a storage elastic modulus of 4 GPa to 9 GPa in a temperature range of −55 ° C. or higher and lower than a glass transition temperature, a loss elastic modulus of 100 MPa or higher, and the loss elastic modulus having a plurality of peaks.   The semiconductor device according to claim 1, wherein a storage elastic modulus in a temperature range equal to or higher than a glass transition temperature of the underfill resin is 100 MPa or more.   3. The semiconductor device according to claim 1, wherein a filling factor of the underfill resin filler is 50 to 70% by mass. The underfill resin has a glass transition temperature of 125 ° C. or higher, a thermal expansion coefficient at 25 ° C. of 30 ppm / ° C. or lower, and a glass transition temperature of −55 ° C. or higher in the entire range of frequencies from 10 ⁻² Hz to 10 Hz. The storage elastic modulus in a temperature range of less than 4 GPa or more and 9 GPa or less, the loss elastic modulus is 100 MPa or more, and the loss elastic modulus has a plurality of peaks. 2. The semiconductor device according to claim 1.

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