JP7436240B2 - Underfill material and method for manufacturing semiconductor devices using the same - Google Patents

Description

The present technology relates to an underfill material and a method of manufacturing a semiconductor device using the same.

2. Description of the Related Art As a method for manufacturing semiconductor devices, flip-chip mounting is known in which components such as a substrate and a semiconductor chip (die), a semiconductor chip and a semiconductor chip, and the like are bonded together using solder. An underfill film (underfill material) is known as a sealing material that fills gaps between components.

In the flip-chip mounting method using an underfill film, the conventional method is to mount a semiconductor chip provided with an underfill film on another semiconductor chip or substrate under heat, and then flow the underfill film between the semiconductor chips. After filling the voids, the underfill film may be cured by heating in a heating oven. However, the number of stacked semiconductor chips has increased significantly in the field of memory devices such as DRAM (Dynamic Random Access Memory), and if the underfill film is flowed each time a semiconductor chip is stacked, the mounting time of the semiconductor chips will be reduced. There are concerns that the period will become longer. Therefore, in the mounting process, for example, when mounting a semiconductor chip, only solder bonding is performed without allowing the underfill film to flow, and the underfill film is filled between the components and hardened in a heated and pressurized atmosphere. This may be done using an oven that can handle this.

By the way, when filling gaps between constituent elements, a portion called a void where the underfill film is insufficiently filled may occur. Voids may cause a decrease in connection reliability (durability) of a semiconductor device.

Further, the required fluidity of an underfill film used in a mounting process under a heated and pressurized atmosphere is different from that of a conventional underfill film used in a mounting process under a heated atmosphere.

JP 2019-19194 Publication

This technology has been proposed in view of these conventional circumstances, and it is an underfill material that suppresses voids during mounting under a heated and pressurized atmosphere and provides good connection reliability, and this technology. A method for manufacturing a semiconductor using an underfill material is provided.

The underfill material according to the present technology contains a binder resin, a liquid epoxy resin, a curing agent, and a filler, the weight average molecular weight of the binder resin is 200,000 or more, and the glass transition of the binder resin is The temperature is less than 30°C, the melt viscosity at a heating rate of 10°C/min in the range of 150 to 170°C is less than 150 Pa s, the melt viscosity at 250°C is 500,000 Pa s or more, and 250 The reaction rate after heating at ℃ for 60 seconds is less than 30%.

A method for manufacturing a semiconductor device according to the present technology includes a step of mounting a semiconductor chip on which a soldered electrode is formed and an underfill material is bonded to the electrode surface on a substrate on which a counter electrode facing the soldered electrode is formed. , and a step of curing the underfill material, the underfill material being the underfill material described above.

According to the present technology, voids can be suppressed in a heated and pressurized atmosphere, and good connection reliability can be obtained.

FIG. 1 is a cross-sectional view showing an example of a plurality of semiconductor chips and a semiconductor wafer before being mounted. FIG. 2 is a cross-sectional view showing an example of a state in which a plurality of semiconductor chips are stacked on a semiconductor wafer. FIG. 3 is a graph showing an example of the pressure and temperature profile of the curing process. FIG. 4 is an example of an ultrasound image when the area of the void is less than 1% of the chip area. FIG. 5 is an example of an ultrasound image when the area of the void is 5% or more of the chip area.

Embodiments of the present technology will be described below with reference to the drawings. As used herein, "normal temperature" refers to the range of 15 to 25° C. as defined in JIS K 0050:2019 (General Rules for Chemical Analysis Methods).

<Underfill material>
The underfill material according to this embodiment contains a binder resin, a liquid epoxy resin, a curing agent, and a filler. Further, the weight average molecular weight of the binder resin is 200,000 or more, and the glass transition temperature (Tg) of the binder resin is less than 30°C. Furthermore, the underfill material has a melt viscosity of less than 150 Pa·s at a heating rate of 10°C/min in the range of 150 to 170°C, a melt viscosity of 500,000 Pa·s or more at 250°C, and a melt viscosity of 500,000 Pa·s or more at 250°C. The reaction rate after heating for 60 seconds is less than 30%.

The melt viscosity of the underfill material in the range of 150 to 170° C. affects, for example, the mounting load of semiconductor chips. By setting the melt viscosity of the underfill material at a heating rate of 10° C./min in the range of 150 to 170° C. to be less than 150 Pa·s, it is possible to suppress an increase in mounting load when semiconductor chips are stacked and mounted. In particular, in order to more effectively suppress the increase in mounting load when stacking semiconductor chips, the melt viscosity of the underfill material in the range of 150 to 170°C is preferably 140 Pa・s or less, and 100 Pa・s or less. More preferred. The lower limit of the melt viscosity of the underfill material in the range of 150 to 170° C. is not particularly limited, but can be, for example, 1 Pa·s or more, and can also be 10 Pa·s or more.

The melt viscosity of the underfill material at 250° C. affects the generation of voids when the underfill material is completely cured in a heated and pressurized atmosphere using a pressure oven or the like, for example. Since the melt viscosity of the underfill material at 250°C is 500,000 Pa・s or more, voids are unlikely to reoccur when the underfill material is completely cured in a heated and pressurized atmosphere (the collapsed voids will not reappear). voids can be suppressed. In particular, in order to suppress voids more effectively, the melt viscosity of the underfill material at 250° C. is preferably 600,000 Pa·s or more, more preferably 1,000,000 Pa·s or more. The upper limit of the melt viscosity of the underfill material at 250° C. is not particularly limited, but may be, for example, 5,000,000 Pa·s or less.

The underfill material has a reaction rate of less than 30% after heating at 250° C. for 60 seconds. As a result, when the underfill material is used in a mounting process in a heated and pressurized atmosphere, for example, in a semiconductor device manufacturing method that includes a mounting process and a curing process described below, the underfill material hardens too much in the mounting process. Therefore, recurrence of voids due to insufficient curing of the underfill material in the curing process can be suppressed. Further, it is preferable that the underfill material has a reaction rate of 80% or more after being heated at 200° C. for 2 hours. As a result, when the underfill material is used in a mounting process in a heated and pressurized atmosphere, for example, in a semiconductor device manufacturing method that includes a mounting process and a curing process described below, voids due to insufficient curing of the underfill material in the curing process can be avoided. recurrence can be more effectively suppressed and better connection reliability can be obtained.

[Binder resin]
The underfill material contains a binder resin having a weight average molecular weight of 200,000 or more and a glass transition temperature of less than 30°C. The binder resin functions as a film-forming resin.

When the glass transition temperature of the binder resin is less than 30° C., the reaction characteristics (for example, the above-mentioned melt viscosity) of the underfill material can be improved. The glass transition temperature of the binder resin is preferably 12° C. or lower, more preferably −10° C. or lower, from the viewpoint of improving the reaction characteristics of the underfill material. Further, the lower limit of the glass transition temperature of the binder resin is not particularly limited, but can be set to -30°C or higher, for example. A known method can be used to measure the glass transition temperature of the binder resin, and for example, it can be measured using a thermomechanical analyzer at a heating rate of 10° C./min.

The weight average molecular weight of the binder resin is 200,000 or more, more preferably 300,000 or more, and even more preferably 350,000 or more from the viewpoint of film-forming properties. Further, the upper limit of the weight average molecular weight of the binder resin is preferably 1,000,000 or less, and can also be 900,000 or less, from the viewpoint of the viscosity of the underfill material and voids during mounting.

As the binder resin, for example, acrylic polymer (acrylic rubber) can be used. Specifically, as the binder resin, an acrylic polymer having at least one functional group selected from a carboxyl group, a hydroxyl group, an epoxy group, and an amide group can be used. Specific examples of binder resins include Teisan Resin series manufactured by NagasemteX, SG-280 (Tg; -29°C), SG-P3 (Tg; 12°C), SG-70L (Tg; -13°C), and SG. Examples include -708-6 (Tg; 4°C), WS-023 EK30 (Tg; -10°C), SG-80H (Tg; 12°C), and SG-600TEA (Tg; -37°C).

The binder resin may be used alone or in combination of two or more. The underfill material is a film-forming resin other than a binder resin with a weight average molecular weight of 200,000 or more and a glass transition temperature of less than 30°C, such as a binder resin with a glass transition temperature of 30°C or more, or a Preferably, it does not substantially contain a binder resin having an average molecular weight of less than 200,000.

The lower limit of the binder resin content in the underfill material can be, for example, 3% by mass or more, may be 5% by mass or more, or may be 7% by mass or more. Further, the upper limit of the content of the binder resin in the underfill material can be 14% by mass or less, may be 12% by mass or less, and may be 11% by mass or less. By not increasing the binder resin content in the underfill material too much, voids during mounting can be more effectively suppressed while improving film formability.

[Liquid epoxy resin]
The underfill material contains an epoxy resin that is liquid at room temperature as a thermosetting resin. Since the underfill material contains an epoxy resin that is liquid at room temperature, the fluidity of the underfill material becomes good when the underfill material is completely cured under a heated and pressurized atmosphere, which effectively eliminates voids. It is also possible to suppress an increase in the mounting load of the semiconductor chip.

As the epoxy resin that is liquid at room temperature, it is preferable to use a polyfunctional epoxy resin having three or more epoxy groups from the viewpoint of high adhesiveness and heat resistance. It is more preferable to use epoxy resin). Examples of the polyfunctional epoxy resin include aliphatic epoxy resins (eg, sorbitol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerol polyglycidyl ether), and the like.

Furthermore, as the epoxy resin that is liquid at room temperature, a bifunctional epoxy resin may be used in combination with a polyfunctional epoxy resin. Examples of the bifunctional epoxy resin include those having a flexible skeleton, such as an ethylene oxide (EO) modified skeleton or a propylene oxide (PO) modified skeleton.

The epoxy resin that is liquid at room temperature preferably has an epoxy equivalent of 100 to 400 g/eq, more preferably 100 to 200 g/eq.

Specific examples of epoxy resins that are liquid at room temperature include Denacol EX612, EX614B (sorbitol polyglycidyl ether), EX411 (pentaerythritol polyglycidyl ether) (manufactured by Nagase ChemteX), and JER604 (tetraglycidyldiaminodiphenylmethane type epoxy resin). , manufactured by Mitsubishi Chemical Corporation), a compound obtained by oxidizing the allyl group of allyl bisphenol A type epoxy resin, Epolead GT401 (tetra(3,4-epoxycyclohexylmethyl) butanetetracarboxylate modified ε-caprolactone, manufactured by Daicel Corporation), AER -9000 (manufactured by Asahi Kasei E-Materials).

The lower limit of the content of the epoxy resin, which is liquid at room temperature, in the underfill material can be, for example, 20% by mass or more, and may be 24% by mass or more. Further, the upper limit of the content of the epoxy resin that is liquid at room temperature in the underfill material may be, for example, 40% by mass or less, may be 36% by mass or less, or may be 35% by mass or less. . Epoxy resins that are liquid at room temperature may be used alone or in combination of two or more.

[Curing agent]
The curing agent is a curing agent for epoxy resins, and phenols, imidazoles, acid anhydrides, amines, hydrazides, polymercaptans, Lewis acid-amine complexes, and the like can be used. Examples of the phenols include phenol novolac compounds, cresol novolac compounds, aromatic hydrocarbon formaldehyde resin-modified phenol compounds, dicyclopentadienephenol addition type compounds, and phenol aralkyl compounds. Among these, a phenol novolac resin (for example, PSM-4261 (manufactured by Gunei Chemical Industry Co., Ltd.)) obtained by polycondensing phenol and formaldehyde in the presence of an acid catalyst is preferred.

Further, the curing agent preferably contains a curing agent that satisfies the following conditions. That is, the underfill material is a mixture in which 15 parts by mass of a curing agent is added to 100 parts by mass of bisphenol A type epoxy resin (epoxy equivalent: 190), and the viscosity at 25°C doubles from the initial stage. It is preferred to contain a curing agent that is 50 days or more. Specific examples of such curing agents include FujiCure 7000, FujiCure 7001, FujiCure 7002 (manufactured by T&K TOKA, liquid at 25°C), and 1-cyanoethyl-2-phenyl, which is imidazole with the 1-position protected by a cyanoethyl group. Imidazole, Imidazole curing agent with basicity protected with isocyanuric acid (Product name: 2MA-OK), 2-phenyl-4-methyl-5-hydroxyimidazole (Product name: Curazole 2P4MHZ), 2-phenyl-4,5 -Dihydroxymethylimidazole (trade name: Curazole 2PHZ) (manufactured by Shikoku Kasei Kogyo Co., Ltd.), Amicure PN-H, PN-40, PN-50 (imidazole-based latent curing agent, manufactured by Ajinomoto Fine Techno Co., Ltd.), U-CAT 3513N (manufactured by Sun-Apro), etc.

One type of curing agent may be used alone, or two or more types may be used in combination. In particular, the viscosity at 25°C of a mixture in which 15 parts by mass of a curing agent was added to 100 parts by mass of a phenol novolac resin and a bisphenol A epoxy resin (epoxy equivalent: 190) was doubled from the initial level. It is preferable to use at least one type of curing agent that takes 50 days or more to cure. The total content of the curing agent in the underfill material can be, for example, 16 to 27% by mass.

[Filler]
The filler is used, for example, for the purpose of adjusting the fluidity of the underfill material during pressure bonding (in the mounting process and curing process of the semiconductor device manufacturing method described later). As the filler, for example, inorganic fillers such as silica, talc, titanium oxide, calcium carbonate, and magnesium oxide can be used, and silica is preferable. One type of filler may be used alone, or two or more types may be used in combination. The total content of fillers in the underfill material can be, for example, 26 to 50% by mass, and can also be 26 to 32% by mass.

The underfill material may further contain components other than the above-described binder resin, liquid epoxy resin, curing agent, and filler within a range that does not impair the effects of the present technology.

Examples of the shape of the underfill material include film, paste, and the like. When an underfill material is previously attached to the semiconductor chip side on which soldered electrodes are formed or the substrate side on which a counter electrode facing the soldered electrodes is formed, it is preferable to use a film-like underfill material.

As described above, the underfill material according to the present embodiment contains a binder resin, a liquid epoxy resin, a curing agent, and a filler. Further, the weight average molecular weight of the binder resin in the underfill material is 200,000 or more, and the glass transition temperature (Tg) of the binder resin is less than 30°C. Furthermore, the underfill material has a melt viscosity of less than 150 Pa·s at a heating rate of 10°C/min in the range of 150 to 170°C, a melt viscosity of 500,000 Pa·s or more at 250°C, and a melt viscosity of 500,000 Pa·s or more at 250°C. The reaction rate after heating for 60 seconds is less than 30%. According to such an underfill material, voids can be suppressed under a heated and pressurized atmosphere, and good connection reliability can be obtained.

Next, a method for manufacturing an underfill film in which an underfill material is formed into a membrane will be described. First, an adhesive composition containing the above-described binder resin, liquid epoxy resin, curing agent, and filler is dissolved in a solvent. As the solvent, toluene, ethyl acetate, etc., or a mixed solvent thereof can be used. After adjusting the resin composition, it is coated onto a release base material using a bar coater, a coating device, or the like. The release base material has a laminated structure in which a release agent such as silicone is applied to PET (Poly Ethylene Terephthalate), OPP (Oriented Polypropylene), PMP (Poly-4-methylpentene-1), PTFE (Polytetrafluoroethylene), etc. To prevent the composition from drying out and to maintain the shape of the composition. Then, the resin composition applied onto the release base material is dried using a thermal oven, a heat drying device, or the like. Thereby, an underfill film of a predetermined thickness is obtained.

<Method for manufacturing semiconductor devices>
Next, a method for manufacturing a semiconductor device using the above-mentioned underfill material will be described. For example, in a method for manufacturing a semiconductor device, a semiconductor chip on which soldered electrodes are formed and an underfill film made of an underfill material is bonded to the electrode surface is placed on a substrate on which a counter electrode facing the soldered electrodes is formed. It has a step of mounting (mounting step) and a step of curing the underfill film (curing step).

An example of a method for stacking and mounting semiconductor chips in multiple stages on a semiconductor wafer will be described below with reference to FIGS. 1 and 2. FIG. 1 is a sectional view showing an example of a plurality of semiconductor chips and a semiconductor wafer before being mounted, and FIG. 2 is a sectional view showing an example of a state in which a plurality of semiconductor chips are stacked on a semiconductor wafer.

[Mounting process]
In the mounting process, as shown in FIG. 1, intermediate layer semiconductor chips 2 to 4 and an uppermost layer semiconductor chip 5 are stacked on a semiconductor wafer 1 with underfill films 6 to 9 interposed therebetween. In the mounting process, as shown in FIG. 2, a group of semiconductor chips in which a plurality of underfill films 6 to 9 and semiconductor chips 2 to 5 are stacked is placed, although fluidity occurs in the underfill films 6 to 9. Pressing is performed using a thermocompression bonding tool (for example, a flip chip bonder) at a predetermined temperature, load, and time such that main curing does not occur. As a result, the solders 2c to 5c of the soldered electrodes are melted to obtain a laminate in which metallic bonds are formed.

The conditions of temperature, load, and time when pressing using a thermocompression bonding tool are such that the range in which the solders 2c to 5c are melted to form a metallic bond and the semiconductor wafer 1 and the semiconductor chips 2 to 5 are electrically connected is determined. preferable. For example, it is preferable that the reaction rate of the underfill film after the mounting step is less than 30%. Since the reaction rate of the underfill film after the mounting process is less than 30%, that is, the underfill film after the mounting process is in a substantially uncured state, voids can be easily removed in the subsequent curing process. As a specific example of the conditions of temperature, load, and time when pressing using a thermocompression bonding tool, for example, the temperature can be 200 to 280°C, the load can be 50 to 200 N, and the time can be about 1 to 3 seconds. . In this way, in the mounting process, the time for each mounting process can be reduced to about 1 to 3 seconds, so the takt time can be reduced in response to an increase in the number of semiconductor chips mounted.

For example, the semiconductor wafer 1 is fixed onto a support substrate 10 with a temporary adhesive 11 interposed therebetween. The material of the semiconductor wafer 1 may be silicon or a compound semiconductor (eg, gallium nitride, etc.). Electronic circuits are formed on the semiconductor wafer 1 for each unit that will be diced later.

The semiconductor wafer 1 has, for example, a soldered electrode 1a formed on one surface and an electrode 1b formed on the other surface. The soldered electrode 1a is, for example, the top of a Cu pillar plated with solder. The solder 1c of the soldered electrode 1a is a so-called lead-free solder, and for example, Sn/Ag/Cu solder (melting point: 220°C to 240°C), Sn/Ag solder (melting point: 220°C), etc. can be used. . The electrode 1b is connected to the soldered electrode 2c of the semiconductor chip 2, and can be made of, for example, a Cu pillar.

The support substrate 10 has, for example, the same surface shape as the semiconductor wafer 1, and is used to fix the semiconductor wafer 1. The support substrate 10 is made of, for example, glass, silicon, or the like. The thickness of the support substrate 10 can normally be about 500 to 1000 μm.

The temporary adhesive material 11 is for fixing the semiconductor wafer 1 to the support substrate 10, and is, for example, an adhesive layer made of an adhesive material. Since the temporary adhesive material 11 is peeled off after mounting, it is preferable to have a relatively soft composition. As the temporary adhesive material 11, for example, an acrylic photocurable adhesive (for example, UV-Curable Adhesive LC-3200 (manufactured by 3M)) can be used.

The semiconductor chips 2 to 4 have, for example, silicon through electrodes, soldered electrodes 2a to 4a formed on one surface, and electrodes 2b to 4b formed on the other surface. A silicon through electrode is an electrode that vertically penetrates inside a semiconductor chip, and connects the upper and lower chips to each other. The soldered electrodes 2a to 4a, the electrodes 2b to 4b, and the solders 2c to 4c can be configured in the same manner as the soldered electrodes 1a, electrodes 1b, and solder 1c described above.

The semiconductor chip 5 has a soldered electrode 5a formed on one surface. The soldered electrode 5a, like the semiconductor chips 2 to 4, is made by plating the top of a Cu pillar with solder, for example.

Underfill films 6 to 9 are bonded in advance to one side of each of the semiconductor chips 2 to 5 on which the soldered electrodes 2a to 5a are formed, respectively. As a result, the number of steps for stacking and arranging the semiconductor chips 2 to 5 can be reduced.

[Curing process]
In the curing process, the underfill films 6 to 9 of the laminate in which the semiconductor wafer 1 and the semiconductor chips 2 to 5 were electrically connected in the mounting process are cured. The curing step is preferably performed in a heated and pressurized atmosphere in order to suppress the generation of voids. The curing step can be performed using, for example, a pressure oven (pressure cure oven, autoclave, etc.). By using a pressure oven, a large number of laminates can be easily and uniformly heated, which improves productivity.

The temperature in the curing step is, for example, raised at a predetermined rate from the first temperature to the second temperature under a predetermined pressure, and the conditions are such that the curing rate of the underfill films 6 to 9 is 90% or more. preferable. The pressure can be in the range of 0.1 to 20 MPa, for example. The first temperature can be in the range of 80 to 150°C, for example. The temperature increase rate can be, for example, in the range of 0.5 to 10° C./min. The holding time at the first temperature can be, for example, in the range of 5 to 60 minutes. The second temperature can be in the range of 180-250°C, for example. The holding time at the second temperature can be, for example, in the range of 5 to 180 minutes. After being held at the second temperature, the cooling rate can be, for example, 5 to 40° C./min.

FIG. 3 is a graph showing an example of the pressure and temperature profile of the curing process. In Figure 3, the horizontal axis represents time (min), the vertical axis on the left represents temperature (°C), the vertical axis on the right represents pressure (MPa), and the solid line (Temp) represents the change in temperature over time. , a broken line (Pressure) represents a change in pressure over time.

As described above, in the method for manufacturing a semiconductor device according to the present embodiment, since an underfill film made of the above-described underfill material is used, voids are suppressed in a heated and pressurized atmosphere in the curing process, and the resulting semiconductor It is possible to improve the connection reliability of the device.

In the specific example described above, a plurality of semiconductor chips 2 to 5 are stacked on the semiconductor wafer 1 with the underfill films 6 to 9 interposed therebetween and are pressed together at once, but the present invention is not limited to this. For example, semiconductor chips may be pressure-bonded and mounted one by one.

Further, in the above-described specific example, a method was described in which semiconductor chips are stacked in four stages on a semiconductor wafer, but the method is not limited to this, and semiconductor chips may be mounted in a stack in five or more stages on a semiconductor wafer. Semiconductor chips may be stacked and mounted in 12 or more stages on a semiconductor wafer.

Further, in the specific example described above, the underfill films 6 to 9 are bonded in advance to the sides of the semiconductor chips 2 to 5 on which the soldered electrodes 2a to 5a are formed, but the present invention is not limited to this. For example, it may be bonded in advance to the electrode 1b side of the semiconductor wafer substrate 1 and the electrodes 2b to 4b sides of the semiconductor chips 2 to 4.

Examples of the present technology will be described below. Note that the present technology is not limited to the following examples.

An underfill film was produced using the following materials.
[Binder resin]
Acrylic rubber: SG-80H (manufactured by NagasemteX), Tg: -12°C, Mw: 350,000
Acrylic rubber: SG-70L (manufactured by NagasemteX), Tg: -13°C, Mw: 900,000
Phenoxy resin: YP-50 (manufactured by Nippon Steel Chemical & Materials), Tg: 84°C, Mw: 70,000
[Epoxy resin]
JER-604: Tetrafunctional epoxy resin (manufactured by Mitsubishi Chemical Corporation), liquid at 25°C, epoxy equivalent: 110 to 130 g/eq
EX-614: Tetrafunctional epoxy resin (manufactured by NagasemteX), liquid at 25°C, epoxy equivalent: 167 g/eq
AER-9000: Bifunctional epoxy resin (PO-modified polyether type epoxy resin) (manufactured by Asahi Kasei Corporation), liquid at 25°C, epoxy equivalent: 380 g/eq
JER-1032H60: Trifunctional epoxy resin (manufactured by Mitsubishi Chemical Corporation), solid at 25°C, epoxy equivalent: 163 to 175 g/eq
JER-1031S: Tetrafunctional epoxy resin (manufactured by Mitsubishi Chemical Corporation), solid at 25°C, epoxy equivalent: 200g/eq
[Curing agent]
Phenol resin: PSM-4261 (manufactured by Gunei Chemical Industry Co., Ltd.)
Modified amine: Fuji Cure 7002 (manufactured by T&K TOKA)
Urea resin: U-CAT 3513N (manufactured by Sun-Apro)
[Filler]
Amorphous silica: SC1050 (manufactured by Admatex), solvent-dispersed amorphous silica: YA050C-MJE (manufactured by Admatex)

<Preparation of underfill film>
Each component was weighed so as to have the compounding ratio (parts by mass) shown in Table 1, and mixed and dispersed in a ball mill at room temperature to obtain a uniformly dissolved and mixed resin composition. The obtained resin composition was applied to release-treated PET using a bar coater and dried in an oven at 80°C for 3 minutes to prepare an underfill film (cover release PET: 25 μm/underfill film: 20 μm). /Base peeled PET: 50 μm)).

[Film properties]
Regarding the produced underfill film, the temperature at which the base film was peeled was evaluated based on the following criteria. The results are shown in Table 1.
A: Base film can be peeled off at room temperature B: Base film can be peeled off at temperatures above 0°C and below room temperature

<Melt viscosity>
The melt viscosity (Pa・s) at 150 to 170°C and the melt viscosity (Pa・s) at 250°C of the underfill film were measured at 10°C using a rheometer (ARES manufactured by TA) for each underfill film. /min, 1Hz. The results are shown in Table 1. "MV" in Table 1 represents melt viscosity.

<Reaction rate>
The reaction rate of the underfill film after heating at 250°C for 60 seconds, assuming the process of mounting a semiconductor chip on a substrate (mounting process), and the reaction rate of the underfill film after heating at 200°C for 2 hours, assuming the process of curing the underfill film (curing process). The reaction rate of the underfill film after heating was measured. The reaction rate of the underfill film is determined by the decrease in epoxy groups in the underfill film before and after it is placed in a pressure-resistant container equipped with a thermometer, pressure gauge, and heater (OM-50, manufactured by O-M Labtech Co., Ltd.). It was calculated from the rate. Specifically, how much the epoxy groups in the underfill film decreased before and after being put into the autoclave was determined by measuring the absorption at 914 cm ^-1 in the infrared absorption spectrum. The results are shown in Table 1.

<Continuity connection>
The following top chip and bottom chip were used as TEG (Test Element Group) for evaluation, and they were pressed with a mounting device (FCB3, manufactured by Panasonic Corporation) under the conditions of a load of 100 N, 240°C, and 3 seconds, and the top chip after pressing was The state of the solder connection (daisy chain connection) between the bottom chip and the bottom chip was confirmed using a probe tester. The case where the connection of all the conductive paths could be confirmed was evaluated as OK, and the case where the connection could not be made at even one place was evaluated as NG. The results are shown in Table 1.
[Top tip]
Size: 6 x 6mm□, thickness: 200μm
Bump specifications: Cu pillar (8μm) + Sn/Ag solder (8μm), φ15μm, number of bumps 5000 pins, pitch 40μm
[Bottom chip]
Size: 8 x 8mm□, thickness: 200μm
Bump specifications: Cu pillar (3μm), φ15μm, number of bumps 5000 pins, pitch 40μm

<Void>
The presence or absence of voids between chips in the TEG package used in the continuity test was non-destructively tested using an ultrasonic imaging device (SAT: Scanning Acoustic Tomograph) (device name: FS300, manufactured by Hitachi High-Technologies). The presence or absence of white spots (voids) in the ultrasound images obtained by observation was evaluated based on the following criteria. The results are shown in Table 1.
A: The void area is less than 1% of the chip area (for example, Figure 4)
B: The void area is 1% or more of the chip area and less than 5% C: The void area is 5% or more of the chip area (for example, Figure 5)

[reliability]
<Moisture absorption reflow>
The TEG package used in the continuity test was allowed to absorb moisture at a temperature of 85°C and a humidity of 85% for 24 hours, and then heated for 3 cycles (moisture absorption reflow) in a reflow oven at a maximum temperature of 260°C. Peeling between chips in the TEG package after moisture absorption reflow was observed using an ultrasound imaging system (SAT). Before and after moisture absorption reflow, the case where there was no change due to peeling was evaluated as OK, and the case where there was a change was evaluated as NG. The results are shown in Table 1.

<Temperature cycle (TCT) test>
A temperature cycle test of -55°C (30 min)⇔125°C (30 min) was conducted for 200 cycles of the TEG package used in the continuity connection test. Continuity resistance was measured for each mounted body after the temperature cycle test using a digital multimeter, and evaluation was made based on the following criteria. The results are shown in Table 1.
A: Resistance increase is within 5% B: Resistance increase is over 5% and within 10% C: Resistance increase is over 10%

In Comparative Examples 1, 2, and 5, an underfill material with a melt viscosity of 150 Pa·s or more at a heating rate of 10°C/min in the range of 150 to 170°C was used, so the results of void and reliability tests were good. However, it turned out that the connectivity was not good either.

In Comparative Example 3, an underfill material with a melt viscosity of 150 Pa·s or more at a heating rate of 10°C/min in the range of 150 to 170°C was used, so the results of the void and reliability tests were not good. Do you get it.

In Comparative Example 4, it was found that the results of the reliability test were not good because an underfill material containing no filler was used.

In Comparative Example 6, since an underfill material having a reaction rate of 30% or more after heating at 250° C. for 60 seconds was used, the results of the void and reliability tests were not good.

In Comparative Example 7, since an underfill material having a melt viscosity at 250° C. of less than 500,000 Pa·s was used, it was found that the results of the void and reliability tests were not good.

Comparative Example 8 is an underfill that does not contain a binder resin with a glass transition temperature of less than 30°C and has a melt viscosity of 150 Pa·s or more at a heating rate of 10°C/min in the range of 150 to 170°C. It was found that the results of void and reliability tests were not good, and the connectivity was also not good because of the material used.

In Comparative Example 9, an underfill material with a melt viscosity of 150 Pa·s or more at a heating rate of 10°C/min in the range of 150 to 170°C was used, so it was found that the results of the void and reliability tests were not good. Ta.

1 substrate (semiconductor wafer), 2, 3, 4, 5 semiconductor chip, 1a, 2a, 3a, 4a, 5a soldered electrode, 1b, 2b, 3b, 4b electrode, 1c, 2c, 3c, 4c, 5c solder, 6, 7, 8, 9 underfill film, 10 support board, 11 temporary pasting material

Claims (10)

binder resin,
liquid epoxy resin,
a hardening agent;
Contains a filler,
The binder resin is an acrylic polymer having at least one functional group selected from a carboxyl group, a hydroxyl group, an epoxy group, and an amide group,
The weight average molecular weight of the binder resin is 200,000 or more, and the glass transition temperature of the binder resin is less than 30°C,
The melt viscosity at a heating rate of 10 °C/min in the range of 150 to 170 °C is less than 150 Pa s,
The melt viscosity at 250°C is 500,000 Pa·s or more,
An underfill material having a reaction rate of less than 30% after heating at 250°C for 60 seconds. The underfill material according to claim 1, having a reaction rate of 80% or more after heating at 200°C for 2 hours. The underfill material according to claim 1 or 2, wherein the liquid epoxy resin contains a tetrafunctional epoxy resin. The underfill material according to any one of claims 1 to 3, wherein the content of the liquid epoxy resin is 24 to 36 wt%. The underfill material according to any one of claims 1 to 4, wherein the curing agent contains a phenolic novolac resin. The underfill material according to any one of claims 1 to 5, wherein the curing agent contains a curing agent that satisfies the following conditions;
It takes 50 days or more for the viscosity at 25°C of a mixture in which 15 parts by mass of a curing agent is added to 100 parts by mass of bisphenol A type epoxy resin (epoxy equivalent: 190) to double from the initial state. The underfill material according to any one of claims 1 to 6, which is used in a heated and pressurized atmosphere. The underfill material according to any one of claims 1 to 7, which is in the form of a film. a step of mounting a semiconductor chip on which a soldered electrode is formed and an underfill material is bonded to the electrode surface on a substrate on which a counter electrode facing the soldered electrode is formed;
curing the underfill material,
A method for manufacturing a semiconductor device, wherein the underfill material is the underfill material according to any one of claims 1 to 7. 10. The method of manufacturing a semiconductor device according to claim 9, wherein in the step of curing the underfill material, the underfill material is cured in a heated and pressurized atmosphere.