WO2020194592A1 - Bonding structure, semiconductor device using same, and method for producing semiconductor device - Google Patents

Abstract

The present invention is a bonding structure which is used in a semiconductor device, and which is characterized by containing Cu particles, a compound that contains a noble metal, Cu and Su, a compound that contains a noble metal and Sn, and a compound that contains Sn and an organic component. In addition, a semiconductor device which comprises a semiconductor element and a substrate, and which is characterized in that the semiconductor element and the substrate are bonded with each other by means of this bonding structure. The present invention is able to provide: a bonding structure which has improved heat resistance and is not susceptible to decrease in the bonding strength even under heat cycles, thereby having excellent bonding reliability; a semiconductor device which uses this bonding structure; and a method for producing a semiconductor device.

Description

A bonded structure, a semiconductor device using the bonded structure, and a method for manufacturing the semiconductor device.

The present invention relates to a bonded structure used in an electronic device or the like, a semiconductor device using the bonded structure, and a method for manufacturing the semiconductor device.

In recent years, the demand for reliability in a semiconductor device in which a semiconductor element is mounted on a substrate has been increasing, and in particular, reliability of a bonded structure for joining a semiconductor element having a large difference in coefficient of thermal expansion and the substrate (hereinafter referred to as “reliability”). , "Joining reliability") is strongly required to be improved.

Conventionally, silicon (Si) and gallium arsenide (GaAs) having an operating temperature of 100 ° C. to 125 ° C. have been generally used as the semiconductor element. When Si is used as a semiconductor element, the bonding material of the bonding structure for bonding the semiconductor element and the substrate contains lead (Pb) typified by Sn-38Pb (mass%) and Pb-5Sn (mass%). Solder and lead-free (that is, lead-free) tin (Sn) typified by Sn-3Ag-0.5Cu (mass%), Sn-9Zn (mass%), Sn-0.7Cu (mass%) ) System solder etc. have been mainly used. When GaAs is used as a semiconductor element, gold (Au) -containing solder typified by 80Au-20Sn (mass%) and Sn-10Au (mass%) has been mainly used as the bonding material. However, the Pb-containing solder containing harmful Pb has a problem that the environmental load increases, and the Au-containing solder has a problem that the cost increases from the viewpoint of the soaring price of precious metals and the reserves. It was. Therefore, as a conventional bonding material, Pb-free Sn-based solder is advantageous from the viewpoint of environmental load and cost.

In recent years, from the viewpoint of energy saving, semiconductor devices using silicon carbide (SiC) and gallium nitride (GaN) as semiconductor elements have been actively developed as next-generation devices. As a bonding material used in this semiconductor device, Pb-free Sn-based solder can be a candidate from the viewpoint of environmental load and cost.

As a bonded structure using such Pb-free Sn-based solder, for example, in Patent Document 1, a plurality of Sn-based solder balls and a plurality of metal balls covered with a nickel (Ni) / gold (Au) layer are used. A bonding material containing is used.

Further, in the bonding structure of Patent Document 2, a bonding material containing a metal ball such as copper (Cu) and a Sn-based solder ball is used.

Japanese Unexamined Patent Publication No. 2007-273982 Japanese Unexamined Patent Publication No. 2004-247742

In the joint structure of the conventional semiconductor device shown in Patent Documents 1 and 2, an intermetallic compound having a high melting point is formed by a diffusion reaction between a metal typified by Cu or Ni and Sn, but diffusion In the process of the reaction, Sn with a low melting point and weak strength remains, so that sufficient heat resistance cannot be obtained, and cracks occur in the heat cycle test (bonding reliability test at 175 ° C.) to improve the bonding reliability. It is difficult to secure.

The present invention has been made to solve the above-mentioned problems, and is a bonding structure having excellent bonding reliability, which improves heat resistance and does not easily reduce bonding strength even in a heat cycle environment. It is an object of the present invention to provide a semiconductor device using the above and a method for manufacturing the semiconductor device.

The present invention is a bonded structure used in a semiconductor device, and is characterized by including Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn, and a compound having Sn and an organic component. And.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a bonding structure having excellent bonding reliability, which is improved in heat resistance and whose bonding strength is unlikely to decrease even in a heat cycle environment, and a semiconductor device using the bonding structure and a method for manufacturing the semiconductor device. be able to.

It is the schematic which shows the semiconductor device which used the junction structure of Embodiment 1. FIG. It is a flowchart which shows the procedure at the time of manufacturing the semiconductor device which used the junction structure of Embodiment 1. It is the schematic which shows the 1st process at the time of manufacturing the semiconductor device which used the junction structure of Embodiment 1. FIG. It is the schematic which shows the 2nd process at the time of manufacturing the semiconductor device which used the junction structure of Embodiment 1. FIG. It is the schematic which shows the 3rd process at the time of manufacturing the semiconductor device which used the junction structure of Embodiment 1. FIG. It is the schematic which shows the 4th process at the time of manufacturing the semiconductor device which used the junction structure of Embodiment 1. FIG. It is the schematic which showed the detail of the state before and after heating of the bonded structure of Embodiment 1. 6 is a cross-sectional SEM photograph of the joint structure of the first embodiment. It is a table which shows the Example and the comparative example of the semiconductor device which used the junction structure of Embodiment 1. It is a graph which shows the relationship between the weight ratio of the compound which has Sn of the junction structure of Embodiment 1 and an organic component, and the change of thermal resistance.

Embodiment 1.
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The elements common to or corresponding to each other in the drawings are designated by the same reference numerals, and duplicate description will be omitted. The present invention is not limited to this embodiment.

FIG. 1 shows a schematic view of a semiconductor device using the bonded structure according to the first embodiment. In the semiconductor manufacturing apparatus 12 of FIG. 1, the substrate 9 and the semiconductor element 10 are joined by a joining structure 11. The bonded structure 11 is characterized by containing Cu particles 2, a compound 5 having a noble metal, Cu and Sn, a compound 6 having a noble metal and Sn, and a compound 7 having Sn and an organic component. The compound 5 having a noble metal, Cu, and Sn exists around the Cu particles 2 and is formed so as to connect the Cu particles 2 existing in the bonding structure 11. Further, inside the compound 5 having a noble metal, Cu and Sn, a compound 6 having a noble metal and Sn and a compound 7 having Sn and an organic component are present.

The substrate 9 is not particularly limited, and may be various members that are required to be bonded to the semiconductor element 1. Examples of the substrate 9 include a circuit board such as a DBC substrate, a metal plate, a ceramic plate, and the like. The material of the semiconductor element 10 is not particularly limited, and materials known in the art can be used. Examples of the material of the semiconductor element 10 include Si (silicon), GaAs (gallium arsenide), SiC (silicon carbide), GaN (gallium nitride), diamond and the like. Among these, wide bandgap semiconductors such as SiC, GaN, and diamond, which are capable of high-temperature operation and are useful for next-generation devices, are preferable, and SiC is particularly preferable.

The weight ratio of the compound 7 having Sn and the organic component is not particularly limited, but from the viewpoint of heat resistance, it preferably occupies a weight of 5% or more and less than 15% with respect to the total weight of the entire bonded structure 11. The balance is Cu particles 2, compound 5 having a noble metal, Cu and Sn, and compound 6 having a noble metal and Sn. If the weight ratio of the compound 7 having Sn and an organic component is less than 5%, the excess Sn deteriorates during the heat cycle test during the heat cycle test, cracks occur, and the thermal resistance decreases in the manufacturing process of the bonded structure, resulting in heat resistance. Is inferior. If the weight ratio of the compound 7 having Sn and the organic component is 15% or more, Sn that connects the Cu particles 2 is missing, so that cracks occur without being connected, the thermal resistance is lowered, and the heat resistance is inferior. is there.

Compound 7 having Sn and an organic component need only be able to play a role in which Sn chemically reacts with the organic component and does not leave excess Sn. R is an alkyl group, and X is an anion such as chloride, fluoride, oxide, or hydroxide.

The noble metal used in the compound 5 having the noble metal, Cu and Sn, and the compound 6 having the noble metal and Sn is not particularly limited, but it is difficult to form an oxide film on the surface, and Sn gets wetter than Cu when heated. From the viewpoint of easy spread, it is preferably at least one of silver (Ag), white silver (Pt), and palladium (Pd).

The ratio of Cu particles and Sn particles used is not particularly limited, but when Sn melts, it wets and spreads on the semiconductor element and the substrate, forms a compound at the temperature at the time of bonding, and does not leave a Sn single phase at the bonding portion. From the viewpoint of such a method, the weight ratio is preferably 40/60 or more and 60/40 or less.

The Sn particles used are not particularly limited, but are preferably an average particle size of 5 μm or more and less than 50 μm from the viewpoint of manufacturing cost. Further, the shape is not particularly limited, but as described above, it is preferably spherical from the viewpoint of cost.

The Cu particles used are not particularly limited, but from the viewpoint of manufacturing cost, the average particle size is 5 μm or more and less than 50 μm.
Further, the shape is not particularly limited, but as described above, it is preferably spherical from the viewpoint of cost.

Next, a method of manufacturing a semiconductor device using the bonded structure of the first embodiment will be described in order according to the flowchart shown in FIG. The method for manufacturing a semiconductor device using the bonded structure of the first embodiment includes a first step of mixing Sn particles, an organic component (solvent), and Cu particles coated with a noble metal to form a paste. The second step of applying this paste-like paste on the substrate, the third step of placing the semiconductor element on the paste coated on the substrate, and heating the low boiling point solvent of the organic component (solvent) in the paste. It includes a fourth step of drying and a fifth step of heating at a temperature equal to or higher than the melting point of Sn to join the semiconductor element and the substrate. Hereinafter, each step will be described in detail.

First, as the first step, paste 8 is prepared. FIG. 3 is a schematic view showing a first step when manufacturing a semiconductor device 12 using the bonded structure 11 of the first embodiment. Sn particles 3, Cu particles 2 coated with a noble metal 1, and an organic component (solvent) 4 are mixed.

The organic component 4 contains, for example, 2- (2-Phenoxyethoxy) ethanol (Japanese name: diethylene glycol monophenyl ether, also known as phenyldiglycol), and is not limited to this. The organic component 4 may be appropriately selected so as to cause a diffusion reaction with Sn after Sn is melted and wet and spread.

Add a low boiling point solvent to this for viscosity adjustment and stir to prepare paste 8. The method for producing the particles is not particularly limited, and a known method such as an atomizing method can be used in the art. Terpineol was used as the low boiling point solvent this time, but it is not limited to this. The low boiling point solvent is not particularly limited as long as it can reduce and remove the oxide film on the bonding surface. For example, polyhydric alcohols, carboxylic acids, amines and the like can be mentioned. These compounds can be used alone or in combination of two or more. Further, these compounds can be used as they are if they are in a liquid state, but they may be used by dissolving them in a solvent such as water if they are in a solid state.

The polyhydric alcohol is not particularly limited as long as it has two or more hydroxyl groups in the molecule. Further, the polyhydric alcohol may have a functional group other than the hydroxyl group (for example, an aldehyde group, an ester group, a sulfanyl group, a ketone group, etc.). Examples of polyhydric alcohols are ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), 1,2-propanediol, 1,3-propanediol, 1,2- Butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, glycerol, 1,1,1 -Trishydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, tray Thor, erythritol, pentaerythritol, pentitol, 1-propanol, 2-propanol, 2-butanol, 2-methyl-2-propanol, xylitol, ribitol, arabitol, hexitol, mannitol, sorbitol, zulcitol, glycerin aldehyde, dioxyacetone , Treose, Elittlerose, Erythrose, Arabinose, Ribos, Ribulose, Xylose, Xylrose, Lixose, Glucose, Fructose, Mannose, Idos, Sorboth, Growth, Talose, Tagatos, Galactose, Allose, Altrose, Lactose, Isomaltose, Glucoheptose, Heptose , Maltotriose, lactulose, trehalose and the like. These can be used alone or in combination of two or more.

The carboxylic acid is not particularly limited as long as it is a compound having one or more carboxy groups in the molecule, and any of a primary carboxylic acid, a secondary carboxylic acid or a tertiary carboxylic acid can be used. Further, the carboxylic acid may have a functional group other than the carboxy group (for example, an aldehyde group, an ester group, a sulfanyl group, a ketone group, etc.).
Examples of carboxylic acids include butanoic acid, pentadecanoic acid, hexanoic acid, heptanic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid. Examples thereof include alkylcarboxylic acids such as acids, octadecanoic acid, nonadecanic acid and icosanoic acid. These can be used alone or in combination of two or more.

The amine is not particularly limited as long as it is a compound having one or more amino groups in the molecule, and any of primary amine, secondary amine and tertiary amine can be used. Further, the amine may have a functional group other than the amino group (for example, an aldehyde group, an ester group, a sulfanyl group, a ketone group, etc.). Examples of amines are butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine. , Octadecylamine, nonadecilamine, icodecylamine and other alkylamines. These can be used alone or in combination of two or more. Further, an amine having a branched structure such as 2-ethylhexylamine and 1,5-dimethylhexylamine may be used.

Next, as a second step, the paste 8 prepared above is applied onto the substrate 9. FIG. 4 is a schematic view showing a second step when manufacturing the semiconductor device 12 using the bonded structure 11 of the first embodiment. The method for applying the paste 8 onto the substrate 9 is not particularly limited, and a coating method known in the art can be used.

Next, as a third step, the semiconductor element 10 is further placed on the paste 8 coated on the substrate 9. FIG. 5 is a schematic view showing a third step when manufacturing a semiconductor device 12 using the bonded structure 11 of the first embodiment. Further, the mounting method of the semiconductor element 10 is not particularly limited, and a device known in the art can be used. For example, a dedicated machine capable of automatically recognizing the paste-coated surface, for example, a chip mounter machine made by athlete FA can be used. If used, it can be mounted with high accuracy.

Next, as a fourth step, the low boiling point solvent in the paste 8 is dried and removed at a predetermined heating temperature and heating time. FIG. 6 is a schematic view showing a fourth step when manufacturing a semiconductor device 12 using the bonded structure 11 of the first embodiment. The heating method is not particularly limited, and a method known in the art can be used. For example, the heating temperature is set so that the low boiling point solvent can be completely vaporized under predetermined heating conditions and Sn does not melt in the heat treatment carried out in the subsequent fifth step.

The temperature at which the low boiling point solvent can be completely vaporized may be appropriately set according to the type and composition of the solvent formed, but is generally 100 ° C. or higher and lower than 200 ° C., preferably 150 ° C. or higher and lower than 200 ° C. .. The heating time may be appropriately set according to the heating temperature, but is generally 1 minute or more and less than 60 minutes, preferably 3 minutes or more and less than 30 minutes. In this step, by completely vaporizing the low boiling point solvent, only the Sn particles 3, the Cu particles 2 coated with the noble metal 1 on the surface, and the organic component 4 are the bonding structure 11 between the substrate 9 and the semiconductor element 12. Remain in.

Next, as a fifth step, the Sn particles 3 were melted and the substrate 9 and the semiconductor element 10 were joined. The figure which shows this result is FIG. The heating method is not particularly limited, and a method known in the art can be used, but heating is performed under heating conditions in which Sn is melted. The heating temperature at which Sn melts is generally 232 ° C. or higher. The heating time may be appropriately set according to the heating temperature, but is generally 1 minute or more and less than 60 minutes, preferably 3 minutes or more and less than 30 minutes.

After heating, a semiconductor device 12 having the bonding structure 1 according to the first embodiment was produced by natural cooling. The bonded structure 11 obtained by this production method includes Cu particles 2, a compound 5 having a noble metal, Cu and Sn, a compound 6 having a noble metal and Sn, and a compound 7 having Sn and an organic component. Includes. Further, the compound 5 having a noble metal, Cu and Sn is present around the Cu particles 2 and is formed so as to connect the Cu particles 2 existing in the bonding structure 11. Further, inside the compound 5 having a noble metal, Cu and Sn, a compound 6 having a noble metal and Sn and a compound 7 having Sn and an organic component are present.

The phenomenon that occurs in the fifth step of joining the semiconductor element 10 and the substrate 9 by heating at a temperature equal to or higher than the melting point of Sn will be described in more detail with reference to FIG. FIG. 7 is a schematic view showing a state before and after heating in the fifth step. When the melting point temperature of Sn reaches 232 ° C., the Sn particles 3 are melted and spread on the surface of the substrate 9 and at the same time cover the Cu particles 2 and the organic component 4. Since the noble metal is a material in which an oxide film that inhibits wettability is difficult to form, the molten Sn particles 3 wet and spread on the noble metal 1 on the surface of the Cu particles 2. At the same time as this phenomenon, the Sn particles, the Cu particles, and the noble metal form a compound 5 having the noble metal, Cu, and Sn by the diffusion reaction of the metal. This compound formation occurs around each Cu particle 2, and is formed so as to connect the Cu particles 2 to each other. During that time, Sn also chemically reacts with the noble metal to form a compound 6 having the noble metal and Sn. As the heating progresses and the temperature rises further, the fluidity of Sn becomes higher. This also promotes the diffusion reactivity of Sn. Then, Sn chemically reacts with the organic component 4, and a compound 7 having Sn and the organic component is formed.

It is considered that the organic component 4 does not undergo a diffusion reaction with the Cu particles 2 as follows. Since the noble metal 1 formed on the surface of the Cu particles 2 easily undergoes a diffusion reaction with the Sn particles 3, the noble metal and Cu formed after preferentially diffusing with the Sn particles 3 and disappearing from the surface of the Cu particles 2. It is considered that the organic component 4 does not undergo a diffusion reaction with the Cu particles 2 because the compound 5 having the above and Sn covers the Cu particles 2.

Hereinafter, the details of the joint structure according to the first embodiment will be described with reference to Examples and Comparative Examples, but the joint structure according to the first embodiment is not limited thereto.
(Samples 1-8)
First, a predetermined amount of spherical Sn particles having an average particle diameter of 20 μm, Cu particles coated with Ag as a noble metal, and a solid organic component are prepared. The atomizing method was used to prepare the particles. The weight ratio of Sn particles to Cu particles was 60:40.
Next, terpineol (low boiling point solvent) was added to the Su particles and Cu particles for adjusting the organic component and viscosity, and the mixture was stirred to prepare a paste.
Next, the paste prepared above was applied onto the substrate. SUS with an opening size of 10 mm and a thickness of 150 μm on a 20 mm DBC substrate (Direct Bonded Copper metal / ceramic / metal, thickness 0.4 mm / 0.6 mm / 0.4 mm) on which a Cu layer was formed as a material to be bonded. It was applied with a metal mask made of squeegee.
Next, on the paste applied on the substrate, silicon carbide (SiC) having an opening size of 10 mm and a thickness of 0.3 mm, which is formed by laminating Ti, Ni, and Au in this order on the bonded layer, is further pasted as a semiconductor element. It was placed on the coated surface.
Next, the paste was heated between the semiconductor element and the DBC substrate under the conditions of a heating temperature of 200 ° C. and a heating time of 10 minutes in a vacuum reflow furnace. Then, the temperature was raised to 300 ° C. at a temperature rising rate of 30 ° C./min, held for 10 minutes when the temperature reached 300 ° C., and then naturally cooled to prepare a semiconductor device having a bonded structure.

For each sample obtained above, different weight ratios (%) of compounds having Sn and organic components in the junction structure were used. The weight ratios used are shown in the table of FIG. Here, a method for calculating the weight of a compound having Sn and an organic component will be described. FIG. 8 shows a cross-sectional SEM photograph of the joint. The compounds having Sn and an organic component are Cu particles 2, a compound 5 having a noble metal, Cu and Sn, and a compound 6 having a noble metal and Sn, as shown in the bonding cross section SEM photograph shown in FIG. Compound 7 having Sn and an organic component is interposed therein. Identification of a compound having Sn and an organic component is possible by GC / MS analysis (gas chromatograph mass spectrometer). The weight of the compound having Sn and the organic component calculated from this analysis method is measured, and the weights of the remaining Cu particles, the compound having the noble metal and Cu and Sn, and the weight of the compound having the noble metal and Sn are each at the time of paste preparation. Calculated from the amount of metal powder added, the weight ratio of the compound having Sn and the organic component is (Sn and the compound having the organic component / (Cu particles, the compound having the noble metal and Cu and Sn, and the noble metal and Sn). Calculated as "Compound having + Sn and compound having organic component" x 100%. In the table of FIG. 9, "Cu particles, compound having noble metal and Cu and Sn, compound having noble metal and Sn, Sn and organic "Compounds having components" are defined as "other metals and metal compounds".

For each of the samples obtained above, the remeltability of the joint structure and the change in thermal resistance before and after the heat cycle (joint reliability) test were measured for each of the heat resistance and joint strength of the joint structure. Regarding remeltability, even if the bonded structure is cut out after bonding the semiconductor element and the substrate and heated to 300 ° C by differential thermal analysis (DSC), melting at a melting point of 210 to 240 ° C derived from the Sn main phase It was confirmed whether a peak occurred, and when a melting peak was detected, it was evaluated as x, and when a melting peak was not detected, it was evaluated as 〇. The specific analysis method is to set the temperature rise rate from room temperature to 300 ° C in the air at 10 ° C / min, and if the dissolution peak amount from 210 ° C to 240 ° C is smaller than 20 mJ / mg, it dissolves. It was judged that it was (melted), and it was marked as x. Here, the state in which the melting peak is detected refers to the state in which Sn remains in the joint structure before remelting. Further, the state in which the melting peak is not detected means a state in which Sn does not remain in the bonded structure before remelting, and all of them chemically react to form a compound with another metal. If Sn remains in the bonded structure, the heat resistance is inferior, and if it has completely reacted with other metals and does not remain, the heat resistance is good.

Next, regarding the change in thermal resistance, the initial thermal resistance was measured by the laser flash method, and after the measurement, it was put into a liquid tank type heat cycle test simulating the high temperature operation of the semiconductor device. The test conditions were + 50 ° C.⇔+ 175 ° C. for 30 seconds per cycle, and the treatment was performed up to 100,000 cycles. Next, the thermal resistance was measured, and if it showed a value larger than 10% with respect to the thermal resistance of the initial bonded structure, it was evaluated as x, otherwise it was evaluated as 〇. If the value is larger than 10% with respect to the thermal resistance of the initial joint structure, cracks have occurred in the heat cycle test, and the joint strength is lowered. If this is not the case, the joint strength is good. As described above, the table of FIG. 9 shows the results of evaluating the two items of remeltability and change in thermal resistance in the heat cycle test simulating high temperature operation as heat resistance and bonding strength, respectively.

As shown in the results of FIG. 9, Comparative Example 1 is a compound having Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn in a weight ratio of 99%, and a compound having Sn and an organic component. The weight ratio is 1%. At this time, as described above, the remeltability by DSC measurement was x. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 50%, which was higher than the target of 10%. It is considered that this is because there are few compounds having Sn and an organic component, so that excess Sn deteriorates during the test and cracks occur.

In Comparative Example 2, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 98%, and a weight ratio of a compound having Sn and an organic component is 2%. At this time, as described above, the remeltability by DSC measurement was x. In the heat cycle (joint reliability test), the change in thermal resistance before and after the test was 33%, which was higher than the target of 10%.

In Comparative Example 3, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 97%, and a weight ratio of a compound having Sn and an organic component is 3%. At this time, as described above, the remeltability by DSC measurement was x. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 20%, which was higher than the target of 10%.

In Comparative Example 4, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 96%, and a weight ratio of a compound having Sn and an organic component is 4%. At this time, as described above, the remeltability by DSC measurement was x. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 18%, which was higher than the target of 10%.

In Example 1, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 95%, and a weight ratio of a compound having Sn and an organic component is 5%. At this time, as described above, the remeltability by DSC measurement was ◯. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 5%, which was lower than the target of 10%, and the target was achieved.

In Example 2, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 92%, and a weight ratio of a compound having Sn and an organic component is 8%. At this time, as described above, the remeltability by DSC measurement was ◯. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 1%, which was lower than the target of 10%, and the target was achieved.

In Example 3, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 86%, and a weight ratio of a compound having Sn and an organic component is 14%. At this time, as described above, the remeltability by DSC measurement was ◯. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 4%, which was lower than the target of 10%, and the target was achieved.

In Comparative Example 5, the weight ratio of Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn is 85%, and a weight ratio of a compound having Sn and an organic component is 15%. At this time, as described above, the remeltability by DSC measurement was ◯. In the heat cycle (joint reliability) test, the change in thermal resistance before and after the test was 32%, which was higher than the target of 10%. It is presumed that if a compound having Sn and an organic component is formed too much, Sn that connects Cu particles will be missing in the future, so that the compounds will not be connected and cracks will occur, resulting in a defect (deterioration of thermal resistance). To.

Here, FIG. 10 shows a graph in which the weight ratio (%) of the compound having Sn and the organic component is on the horizontal axis and the change in thermal resistance (%) is on the vertical axis. It was confirmed that the change in thermal resistance was lower than 10% in the range shown by the dotted line. That is, in this range, it was confirmed that the bonding strength is unlikely to decrease even in a heat cycle environment.

When the weight ratio of Sn particles 3 and Cu particles 2 is 50:50 and the weight ratio of Sn particles 3 and Cu particles 2 is 40:60, the same test as described above is performed and the same effect is obtained. Obtained. Further, in the above experiment, a heat shock test was carried out using a DBC substrate, and a predetermined addition amount was optimized. However, increasing the Cu thickness of the DBC substrate improves the heat dissipation of the substrate, while the coefficient of thermal expansion Will increase, and the appropriate value will change depending on the design items of the semiconductor device. Therefore, the weight ratio of the compound having Sn and the organic component is a recommended value, but is not limited to this.

The Sn particles and Cu particles were spherical in this evaluation, and the average particle size was set to a typical 20 μm, but the same effect can be obtained if the average particle size is not 20 μm but 5 μm or more and less than 50 μm. In addition, although typical evaluation results were shown at the junction between the semiconductor element and the substrate this time, the evaluation results are not limited to this, and for example, the junction between the semiconductor element and the lead frame and the junction between the substrate and the cooling fins are also shown. Can be used. Further, the present invention is not limited to one semiconductor element on one substrate, and a plurality of semiconductor elements and members may be arranged on the substrate and bonded at the same time.

As can be seen from the above results, according to the bonding structure of the present embodiment and the semiconductor device and the method for manufacturing the semiconductor device using the same, the heat resistance is improved and the bonding strength is lowered even in a heat cycle environment. It is possible to provide a bonding structure that is difficult and has excellent bonding reliability, a semiconductor device using the bonding structure, and a method for manufacturing the semiconductor device.

1 noble metal, 2 Cu particles, 3 Sn particles, 4 organic components, 5 compounds having noble metals, Cu and Sn, 6 compounds having noble metals and Sn, 7 compounds having Sn and organic components, 8 pastes, 9 substrates 10, semiconductor element, 11 junction structure, 12 semiconductor device

Claims (10)

1. A bonded structure comprising Cu particles, a compound having a noble metal and Cu and Sn, a compound having a noble metal and Sn, and a compound having Sn and an organic component.
2. The bonding structure according to claim 1, wherein the compound having the noble metal, Cu, and Sn exists around the Cu particles so as to connect the Cu particles to each other.
3. The compound having Sn and an organic component is 5% or more and less than 15% with respect to the total weight of the whole, and the weight of the balance is the Cu particles, the compound having the noble metal, Cu and Sn, and the noble metal and Sn. The bonded structure according to claim 1 or 2, wherein the compound has.
4. The compound having Sn and an organic component is a compound represented by a chemical formula of R4Sn, R3SnX, R2SnX2, RSnX3, wherein R is represented by an alkyl group and X is represented by an anion. 3. The joint structure according to 3.
5. The bonded structure according to claim 1, wherein the noble metal is at least one of Ag, Pt, and Pd.
6. A semiconductor device having a semiconductor element and a substrate,
   A semiconductor device characterized in that the semiconductor element and the substrate are joined by the joining structure according to any one of claims 1 to 5.
7. A method for manufacturing a semiconductor device having a semiconductor element and a substrate.
   The first step of mixing Sn particles, organic components, and Cu particles coated with a precious metal to form a paste, and
   The second step of applying the paste-like paste onto the substrate, and
   A third step of placing the semiconductor element on the paste coated on the substrate, and
   The fourth step of heating and drying the low boiling point solvent of the organic component in the paste, and
   A method for manufacturing a semiconductor device, which comprises a fifth step of joining a semiconductor element and a substrate by heating at a temperature equal to or higher than the melting point of Sn.
8. The method for manufacturing a semiconductor device according to claim 7, wherein the ratio of the Cu particles coated with the noble metal to the Sn particles is 40/60 or more and 60/40 or less in terms of weight ratio.
9. The method for manufacturing a semiconductor device according to claim 7 or 8, wherein the Cu particles coated with the noble metal have an average particle size of 5 μm or more and less than 50 μm.
10. The method for manufacturing a semiconductor device according to claim 7, wherein the Sn particles have an average particle size of 5 μm or more and less than 50 μm.

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