Semiconductor device

Abstract

To provide a semiconductor device that improves reliability when a semiconductor element is operated at high temperature.SOLUTION: A semiconductor device 1, in which a maximum value of operating temperature of a semiconductor element 50 is 150°C or higher, includes: a conductor pattern 20; a semiconductor element 50 disposed on the conductor pattern 20 via a bonding member 40; and a sealing member 30 that is in contact with the conductor pattern 20, the bonding member 40, and the semiconductor element 50 to seal them, and to which an ion scavenger 32 is added to capture metal ions (metal ions 42) contained in the bonding member 40.SELECTED DRAWING: Figure 2C

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] In reliability tests for semiconductor devices, they are required to not fail under specified conditions. For example, Patent Document 1 describes a semiconductor package that improves reliability after long-term storage by keeping the chlorine and sulfur contents in the sealing material below a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-019031 Summary of the Invention [Problem to be solved by the invention]

[0004] The semiconductor package of Patent Document 1 is described as reducing the defect rate in a test in which the package is stored in a high-temperature environment without being operated. However, when the package is operated, the influence of current and voltage inside the semiconductor device causes failures in a different manner than when the package is not operated, and different measures are required compared to when the package is not operated. The inventors confirmed that when the temperature at which the semiconductor element is operated is increased, metal contained in the bonding material, such as solder, migrates into the sealing material, causing failures. The present invention has been made to solve the above problems, and has as its object to provide a semiconductor device that improves the reliability when the semiconductor element is operated at high temperatures. [Means for solving the problem]

[0005] In order to solve this problem, the semiconductor device of the present invention is a semiconductor device in which the maximum operating temperature of a semiconductor element is 150°C or higher, and includes a conductor pattern, the semiconductor element placed on the conductor pattern via a bonding member, and a sealing member that contacts the conductor pattern, the bonding member, and the semiconductor element to seal them, and to which an ion trapping agent that captures metal ions contained in the bonding member has been added. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a semiconductor device that improves the reliability when the semiconductor element is operated at high temperatures. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an enlarged cross-sectional view illustrating a schematic example of a portion of a semiconductor device according to an embodiment. [Figure 2A] 10 is a cross-sectional view illustrating a schematic example of a state in which metal contained in a bonding member is ionized and metal ions move into a sealing member in a semiconductor device according to an embodiment. FIG. [Figure 2B] FIG. 10 is a cross-sectional view illustrating an outline of a state in which metal ions are further moving in the semiconductor device according to the embodiment. [Figure 2C] 1 is a cross-sectional view illustrating a schematic example of a state in which metal ions are captured by an ion capturing agent in a semiconductor device according to an embodiment. [Figure 3] 1 is a cross-sectional view illustrating an outline of a state in which a short circuit occurs due to metal ions in a conventional semiconductor device. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments and examples. The drawings show components necessary for the explanation, and the size and shape of each component may be exaggerated.

[0009] [Semiconductor Devices] A semiconductor device 1 according to an embodiment will be described with reference to Fig. 1. The semiconductor device 1 is a device in which a semiconductor element is sealed together with a substrate or the like, and includes various forms such as a unit in which one or more semiconductor elements are arranged on a single substrate, or a module in which multiple units are combined into one. Meanwhile, the various forms of semiconductor device 1 have a common configuration in the vicinity of the semiconductor element. 1, the semiconductor device 1 is a semiconductor device in which the maximum operating temperature of the semiconductor element 50 is 150°C or higher, and includes a conductor pattern 20, the semiconductor element 50 disposed on the conductor pattern 20 via a bonding member 40, and a sealing member 30 that contacts and seals the conductor pattern 20, the bonding member 40, and the semiconductor element 50 and has an ion trapping agent 32 added thereto that traps metal ions contained in the bonding member 40. Each component of the semiconductor device 1 will now be described.

[0010] (Conductor pattern) The conductor pattern 20 is a conductive member to which the electrodes of the semiconductor element 50 are bonded. Here, the conductor pattern 20 is part of the wiring that connects the semiconductor element 50 to the outside of the semiconductor device 1. The conductor pattern 20 can be formed to a predetermined shape and thickness, and has an area to which the electrodes of the semiconductor element 50 are bonded. The conductive pattern 20 is formed on an insulating substrate 10. The insulating substrate 10 is an insulating plate-like member. The material of the conductive pattern 20 can be a metal such as gold, silver, copper, or an alloy thereof, and copper is used here. The material of the insulating substrate 10 is, for example, a ceramic such as silicon nitride or a highly thermally conductive resin.

[0011] (semiconductor element) The semiconductor element 50 is a semiconductor chip on which transistors, diodes, etc. are formed. The semiconductor element 50 includes an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a diode, etc. The semiconductor element 50 may be a single element such as an IGBT, or may include multiple IGBTs, etc., for example, an IGBT and a diode. The semiconductor in the semiconductor element 50, i.e., the semiconductor that is the material of the wafer or the like on which the semiconductor element 50 is formed, can be silicon (Si) or silicon carbide (SiC). Here, the semiconductor in the semiconductor element 50 is Si and includes an IGBT. The semiconductor in the semiconductor element 50 may also be SiC and include a MOSFET.

[0012] The semiconductor element 50 is disposed on the conductor pattern 20 via the bonding member 40. The semiconductor element 50 has electrodes on the surface facing the conductor pattern 20 and on the opposite surface. In order to match the drawings, the surface facing the conductor pattern 20 may be referred to as the lower surface and the opposite surface as the upper surface. The electrode 51 on the lower surface is joined to the conductive pattern 20 via the joining member 40. In this example, there is one electrode 51 on the lower surface, which is covered by the joining member 40. A bonding wire or the like is connected to the electrode 52 on the top surface. The electrode 52 on the top surface is in contact with the sealing member 30. That is, the semiconductor element 50 has a region where the material of the electrode 52 is the uppermost surface, and the sealing member 30 is in contact with the electrode 52 in that region. Here, the electrode 52 on the top surface is provided in a position close to the periphery of the semiconductor element 50. The semiconductor element 50 may have an electrode on its top surface in addition to the electrode 52. Note that bonding wires, lead frames, etc. are not shown in the figure.

[0013] In the semiconductor device 1, minimum and maximum operating temperatures of the semiconductor element 50 are specified. The operating temperature refers to the temperature range in which the semiconductor element 50 maintains its expected functions and operates normally. Although semiconductor elements 50 are generally sensitive to heat, the maximum operating temperature of the semiconductor element 50 in this specification is 150°C or higher, and can be, for example, 150°C or 175°C. If the maximum operating temperature is 150°C, the semiconductor element 50 can operate normally at temperatures lower than 150°C. The maximum operating temperature may be between 150°C and 175°C, or may be 175°C or higher. The operating temperature refers to the temperature of the semiconductor element 50 itself, such as the temperature of the pn junction surface. The semiconductor device 1 is used so that the operating temperature of the semiconductor element 50 is within a specified range. The operating temperature of the semiconductor element 50 while it is energized can be calculated using the power loss and thermal resistance. It should be noted that the maximum operating temperature can be increased by using a material that can withstand higher temperatures for the semiconductor elements.

[0014] (jointing material) The bonding member 40 is a member that bonds and electrically connects the semiconductor element 50 and the conductor pattern 20. The bonding member 40 can be a solder or conductive paste containing a metal such as gold, silver, or copper, and in this example, is a solder containing tin (Sn). When the bonding member 40 is solder, a solder whose solidus temperature is higher than the maximum operating temperature of the semiconductor element 50 is used. The bonding member 40 is bonded to the conductive pattern 20 on the conductive pattern 20 side, and is bonded to an electrode 51 on the bottom surface of the semiconductor element 50 on the opposite side. The bonding member 40 is in contact with the sealing member 30 between the conductive pattern 20 and the semiconductor element 50.

[0015] (Sealing member) The sealing member 30 is a member that seals the semiconductor element 50 and the like. The sealing member 30 contacts and seals the conductive patterns 20, the bonding member 40, and the semiconductor element 50. The sealing member 30 also contacts the electrodes 52 of the semiconductor element 50. The sealing member 30 can also seal other members such as bonding wires. Here, the sealing member 30 is a potting resin. The potting resin can contact and seal the conductive patterns 20, the bonding members 40, and the semiconductor element 50. The sealing member 30 may also be a molding resin. In the case of a molding resin, the sealing member 30 also contacts and seals the conductive patterns 20, the bonding members 40, and the semiconductor element 50.

[0016] The potting resin and the molding resin are formed using different methods, and the types and ratios of the components they contain are also different. Here, the encapsulated body will be described as a body in which the semiconductor element 50 and the like are encapsulated with potting resin or molding resin. Note that the semiconductor device 1 may have multiple encapsulated bodies. Potting resin is formed by the potting method, while molding resin is formed by the molding method. In the potting method, a case member that will become part of the sealed body after hardening is used as a frame, and unhardened resin is injected and hardened. On the other hand, in the molding method, the resin is molded in a mold and then removed from the mold after molding. Therefore, the appearance of the sealed body differs between potting resin and molding resin in terms of whether or not the sealed body has a case member. In the case of molding resin, the outer surface of the sealed body is formed by the sealing member 30.

[0017] The sealing member 30 can be a resin composition for semiconductor sealing, such as an epoxy resin composition. The sealing member 30 used has a glass transition temperature equal to or higher than the maximum operating temperature of the semiconductor element 50. For example, if the maximum operating temperature is 150°C, the glass transition temperature of the sealing member 30 should be 150°C or higher, and if the maximum operating temperature is 175°C, the glass transition temperature of the sealing member 30 should be 175°C or higher. The sealing member 30 contains an ion trapping agent 32 .

[0018] (ion scavenger) The ion scavenger 32 is a substance added to the sealing member 30 and captures metal ions 42 that are ions of the metal contained in the joining member 40 . Generally, three types of ion trapping agents are known: a cation trapping type that traps cations, an anion trapping type that traps anions, and a dual ion trapping type that traps both cations and anions. As an example, the metal ions contained in the bonding member 40 are tin ions, which are cations. The ion trapping agent 32 can trap metal ions 42 by being either a cation trapping type or a dual ion trapping type. The ion trapping agent 32 may contain both a cation trapping type and a dual ion trapping type.

[0019] A commercially available ion scavenger can be used as the ion scavenger 32. Examples of commercially available ion scavenger include IXEPLAS (registered trademark) from Toagosei Co., Ltd., and the ADK STAB (registered trademark) CDA series and ZS series from ADEKA Corporation. The amount of the ion scavenger 32 can be set to 10 ppm or more and 10% or less, and preferably 100 ppm or more and 1% or less, in terms of mass ratio relative to the sealing member 30. The lower limit of this ratio can be adjusted depending on the amount of metal ions 42 in the sealing member 30. On the other hand, by reducing the upper limit of this ratio, it is possible to suppress the influence on the properties of the sealing member 30 as a resin composition for semiconductor sealing.

[0020] The semiconductor device 1 having the above-described configuration includes a sealing member to which an ion capture agent that captures metal ions contained in the bonding member is added. This makes it possible to suppress the migration of metal into the sealing member, which can cause failure, even when the semiconductor element is operated at high temperatures, thereby improving reliability.

[0021] Conventionally, reliability tests for semiconductor devices have been conducted by operating the semiconductor element under conditions that result in the maximum operating temperature, and maintaining this condition for a long period of time, such as 1,000 hours. Such tests were also conducted on a conventional semiconductor device 100 having a semiconductor element 50, as shown in Figure 3. However, when the maximum operating temperature was set to 175°C, which is higher than conventional values, a short-circuit failure not previously observed occurred. In the conventional semiconductor device 100, the conductive pattern 20 is made of copper, the bonding member 40 is a solder containing tin, and the sealing member 300 is in contact with the electrode 52 of the semiconductor element 50. The semiconductor element 50 uses silicon as a semiconductor and has an IGBT. On the other hand, the sealing member 300 does not contain the ion capturing agent 32.

[0022] When the cause of this short circuit failure was investigated, it was confirmed that metal ions 42 were present in the sealing member 300 from the edge of the top surface of the semiconductor element 50 to the conductive pattern 20, as illustrated in Fig. 3. The metal ions 42 are tin ions, and are ions of a metal contained in the bonding member 40. An electrode 52 is present on the periphery of the top surface of the semiconductor element 50, and the sealing member 300 is in contact with the electrode 52 of the semiconductor element 50. From this, it is thought that the tin ions distributed in the sealing member 300 formed a current path P1, causing the short circuit failure. Therefore, when an ion trapping agent 32 that traps tin ions was added to the sealing member of the semiconductor device 1, no short-circuit failure occurred. This result will be explained with reference to FIGS. 2A to 2C. In this semiconductor device 1, the material of the conductor pattern 20 is copper, the bonding member 40 is solder containing tin, and the sealing member 30 is in contact with the electrode 52 of the semiconductor element 50. The semiconductor element 50 uses silicon as a semiconductor and has an IGBT. The maximum operating temperature of the semiconductor element 50 is set to 175°C, and the ion trapping agent 32 that traps tin ions is added to the sealing member 30.

[0023] 2A, when a reliability test is started in which the conductive pattern 20 is operated at a high temperature, the metal contained in the bonding member 40 near the conductive pattern 20 ionizes, and metal ions 42 migrate into the sealing member 30. In this case, the metal ions 42 are tin ions. One reason for this is thought to be that residues of the etching solution, cleaning agent, etc. used in the formation process of the conductive pattern 20 may adhere to the surface of the conductive pattern 20, and components of such residues promote the ionization of the metal contained in the bonding member 40, which has a higher ionization tendency than the metal of the conductive pattern 20. The generation of tin ions can be explained by the fact that tin has a higher ionization tendency than copper. 2B, the metal ions 42 continue to move in the direction of the electric field in the sealing member 30. The electric field is generated by the application of a current or voltage under the test conditions.

[0024] 2C , however, no current path is formed because the ion trapping agent 32 of the sealing member 30 traps the metal ions 42. By adding an ion trapping agent that traps tin ions to the sealing member 30, the semiconductor device 1 can suppress the occurrence of short-circuit failures and improve reliability. The maximum value of the operating temperature may exceed 175° C. When the maximum value of the operating temperature of the semiconductor element 50 is 175° C. or higher, the semiconductor device 1 can suppress the occurrence of short-circuit failures and improve reliability.

[0025] This short-circuit failure tends to occur more easily when the operating temperature is high, the applied current and voltage are large, and the test time is long. For this reason, it is thought that the short-circuit failure became more likely to occur because the conventional semiconductor device 100 had an IGBT that could apply a large current and voltage and set the maximum operating temperature to 175°C, which was higher than conventional. Furthermore, in the conventional semiconductor device 100, even if the maximum operating temperature is 150°C, similar short-circuit failures are expected to occur due to changes in conditions such as an increase in the applied current or voltage or an increase in the test time. The semiconductor device 1 can also handle these conditions, and the ion trapping agent added to the sealing member traps metal ions, suppressing the occurrence of short-circuit failures and improving reliability.

[0026] When the semiconductor in the semiconductor element 50 is silicon carbide, reliability tests are performed at higher temperatures and under conditions of larger applied currents and voltages, and it is expected that short-circuit failures are more likely to occur. Even when the semiconductor in the semiconductor element 50 is silicon carbide, the ion trapping agent added to the sealing member traps metal ions, suppressing the occurrence of short-circuit failures and improving reliability.

[0027] Regarding the ionization of the metal contained in the joining member 40, when attention is paid to the ionization tendency, it is predicted that a similar phenomenon will occur not only when the metal of the conductor pattern 20 is copper and the metal of the joining member 40 is tin, but also when the ionization tendency of the metal of the joining member 40 is greater than that of the metal of the conductor pattern 20. [Example]

[0028] In order to confirm the effect of the present invention, IGBT modules of the example and comparative example were manufactured and subjected to reliability tests. The example has the structure shown in Figure 1, in which the sealing member is in contact with the electrodes of the IGBT. The semiconductor element is an IGBT, the bonding member is tin-copper-antimony solder, the material of the conductor pattern is copper, and the sealing member is a potting resin to which an ion trapping agent has been added. The ion trapping agent is a dual-ion trapping type that can trap tin ions. The comparative example differs from the example in that no ion scavenger was added to the sealing member.

[0029] For reliability testing, a collector-emitter DC blocking test was conducted under the same conditions for both the example and comparative examples. The collector-emitter DC blocking test is a test in which a specified voltage is applied to the IGBT terminals and the IGBT is operated continuously under conditions that result in the maximum operating temperature. The maximum operating temperature of the IGBT was set to 175°C. As a result of the test, a short circuit failure occurred in the comparative example after 1000 hours. On the other hand, no failure occurred in the example even after 1000 hours. In other words, the example of the present invention solves the problem of short circuit failure in the blocking test by adding an ion scavenger to the sealing resin, and can improve the reliability when the semiconductor element is operated at high temperatures. [Explanation of symbols]

[0030] 1. Semiconductor device 10. Insulating substrate 20 Conductor pattern 30 Sealing member 32 Ion scavenger 40 Joint material 42 Metal ions 50 Semiconductor elements 51 Electrode (bottom surface) 52 electrode (top)

Claims

1. A semiconductor device in which the maximum operating temperature of a semiconductor element is 150°C or higher, A conductor pattern; the semiconductor element disposed on the conductor pattern via a bonding member; a sealing member that contacts the conductive pattern, the bonding member, and the semiconductor element to seal them, and that contains an ion capturing agent that captures metal ions contained in the bonding member.

2. The semiconductor device according to claim 1 , wherein the sealing member contacts an electrode of the semiconductor element.

3. 2. The semiconductor device according to claim 1, wherein the metal ions are tin ions.

4. 2. The semiconductor device according to claim 1, wherein the joining member is a solder containing tin.

5. 2. The semiconductor device according to claim 1, wherein the semiconductor element comprises an insulated gate bipolar transistor.

6. 2. The semiconductor device according to claim 1, wherein the semiconductor in the semiconductor element is silicon carbide.

7. 2. The semiconductor device according to claim 1, wherein the maximum value of the operating temperature is 175[deg.] C. or higher.

8. 2. The semiconductor device according to claim 1, wherein the ion trapping agent is a cation trapping agent that traps cations.

9. 2. The semiconductor device according to claim 1, wherein the ion trapping agent is a dual ion trapping agent that traps both cations and anions.

10. 10. The semiconductor device according to claim 1, wherein the sealing member is a potting resin.

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