JP6287667B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device used for, for example, control of high power and a semiconductor device manufactured by the method.

  Patent Document 1 discloses a semiconductor device in which silicon rubber is formed on a side surface of a semiconductor substrate.

JP-A-8-222724

  For example, in a high breakdown voltage semiconductor device, an insulating portion may be formed on the side surface of the semiconductor substrate to prevent discharge. This insulating part is formed by placing a semiconductor substrate in a mold. When removing the mold from the semiconductor substrate, there has been a problem that the insulating portion is peeled off from the semiconductor substrate. There is also a problem that bubbles are generated in the insulating portion.

  The present invention has been made to solve the above-described problems, and a semiconductor device that can prevent an insulating portion formed on a side surface of a semiconductor substrate from being peeled off or bubbles from being generated in the insulating portion. An object is to provide a method and a semiconductor device.

  In the method of manufacturing a semiconductor device according to the present invention, the first electrode is formed on the first main surface, the second electrode is formed on the second main surface opposite to the first main surface, and the side surface is resin-coated. Placing the semiconductor substrate in the first mold, forming a first insulating portion in contact with the resin coating, and placing the semiconductor substrate on which the first insulating portion is formed in the second mold. And a step of forming a second insulating portion covering the first insulating portion.

  According to the present invention, since the insulating portion that protects the side surface of the semiconductor substrate is formed by multiple moldings, it is possible to prevent the insulating portion from being peeled off or bubbles from being generated in the insulating portion.

1 is a cross-sectional view of a semiconductor device according to a first embodiment. It is sectional drawing, such as an edge part of a semiconductor substrate. It is a figure which shows the process of forming a 1st insulation part. It is a figure which shows the process of forming a 1st insulation part. It is a figure which shows the process of forming a 2nd insulation part. It is a figure which shows the process of forming a 2nd insulation part. It is sectional drawing of the semiconductor substrate taken out from the 2nd mold metal mold | die. It is sectional drawing, such as a mold die of a comparative example. It is sectional drawing, such as a mold die of a comparative example. It is a figure which shows peeling of an insulation part. It is a figure which shows the bubble of an insulation part. It is a partial sectional view of a semiconductor substrate concerning a modification. FIG. 6 is a partial cross-sectional view of a semiconductor device according to a second embodiment.

  A method for manufacturing a semiconductor device and a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repeated description may be omitted.

Embodiment 1 FIG.
FIG. 1 is a sectional view of a semiconductor device 10 according to the first embodiment of the present invention. The semiconductor device 10 is a pressure contact type semiconductor device including a semiconductor substrate 12. A cathode electrode 14 and a gate electrode 16 are formed on the upper surface side of the semiconductor substrate 12. An anode electrode 18 is formed on the lower surface side of the semiconductor substrate 12.

  The side surface of the semiconductor substrate 12 has a bevel structure (an inclined structure). A resin coating 20 is formed on the side surface, upper surface end portion, and lower surface end portion of the semiconductor substrate 12. The resin coating 20 is formed to stabilize the side surface of the semiconductor substrate 12 and the end portion of the semiconductor substrate and to prevent discharge. The material of the resin coating 20 is, for example, polyimide silicon. The resin coating 20 may be referred to as a junction coating resin.

  A first insulating portion 22 that contacts the resin coating 20 is formed. A second insulating portion 24 that contacts the first insulating portion 22 is formed. The first insulating portion 22 and the second insulating portion 24 are provided to protect the side surface of the semiconductor substrate 12, prevent discharge, and improve the withstand voltage. The material of the first insulating part 22 and the second insulating part 24 is, for example, silicon rubber.

  An anode strain buffer plate 30 is in contact with the anode electrode 18. An anode main electrode 32 is in contact with the anode strain buffer plate 30. By providing a metal positioning pin 34 between the anode strain buffer plate 30 and the anode main electrode 32, the position of the anode main electrode 32 with respect to the anode strain buffer plate 30 is determined.

  A cathode strain buffer plate 40 is in contact with the cathode electrode 14. A cathode main electrode 42 is in contact with the cathode strain buffer plate 40. A metal film is preferably formed on the anode main electrode 32 and the cathode main electrode 42 by plating.

  A center gate extraction electrode 50 is in contact with the gate electrode 16. The center gate extraction electrode 50 is provided to electrically connect the gate electrode 16 to the outside. The center gate extraction electrode 50 is in contact with the elastic body 56 through the metal plate 52 and the insulator 54. The elastic body 56 is an annular elastic body such as a disc spring. A portion of the center gate extraction electrode 50 that is in contact with the gate electrode 16 is protected by the insulating cylinder 58, and a portion extending to the outside is protected by the insulating cylinder 60.

  The configuration described above is covered with the ceramic package 70 and the flange 72 so that the anode main electrode 32 and the cathode main electrode 42 are exposed to the outside. When the semiconductor device 10 is energized, a pressure contact type semiconductor device is configured using a pressure contact electrode that presses the cathode main electrode 42 downward and a pressure contact electrode that presses the anode main electrode 32 upward. Further, the center gate extraction electrode 50 is pressed against the gate electrode 16 by the elastic body 56, and the contact between the center gate extraction electrode 50 and the gate electrode 16 is ensured. In this state, the main current between the cathode electrode 14 and the anode electrode 18 is controlled by passing a current between the gate electrode 16 and the cathode electrode 14.

  FIG. 2 is a cross-sectional view of an end portion and the like of the semiconductor substrate 12. A resin coating 20 is formed on the side surface 12 a, the upper surface end portion 12 b, and the lower surface end portion 12 c of the semiconductor substrate 12. In FIG. 2, NE, PB, NB, and PE indicate an n emitter layer, a p base layer, an n base layer, and a p emitter layer, respectively.

  A method for manufacturing the semiconductor device 10 will be described. First, the cathode electrode 14, the gate electrode 16, and the anode electrode 18 are formed on the semiconductor substrate 12. Next, a bevel is formed on the side surface of the semiconductor substrate 12 with a grindstone or sandblast. Then, for example, the resin coating 20 is formed on the side surface, the upper surface end portion, and the lower surface end portion of the semiconductor substrate 12 by spin coating or brush coating.

  Next, the first insulating portion 22 is formed. The step of forming the first insulating portion will be described with reference to FIGS. When forming the first insulating portion 22, the first mold 100 shown in FIG. 3 is used. The first mold 100 includes a lower mold 102 and an upper mold 104. After placing the semiconductor substrate 12 on a predetermined location of the lower mold 102, the upper mold 104 is placed on the lower mold 102. As a result, the semiconductor substrate 12 is put in the first mold 100.

  In the state where the lower mold 102 and the upper mold 104 are overlapped, a cavity C1 surrounding the end portion (resin coating 20) of the semiconductor substrate 12 is formed. In order to reduce the size of the cavity C1, the distance y1 from the upper surface of the semiconductor substrate 12 to the upper mold 104 is set to 2 mm or less, and the distance y2 from the lower surface of the semiconductor substrate 12 to the lower mold 102 is set to 2 mm or less. preferable. The cavity C1 is connected to an inlet 106 for injecting the material of the first insulating portion into the cavity C1 and an outlet 108 for discharging excess material.

  Next, as shown in FIG. 4, the injection nozzle 110 is applied to the injection port 106, and liquid silicon rubber is injected into the cavity C1. Silicon rubber is sufficiently injected to the extent that excess silicon rubber 112 exits from the discharge port 108, and the cavity C1 is filled with silicon rubber. At this time, the temperature of the lower mold 102 and the upper mold 104 is set to about 150 ° C., for example. This state is maintained for about 2 minutes, for example, and the liquid silicone rubber is cured.

  After the silicon rubber is cured, the upper and lower molds 102 and 104 are separated and the semiconductor substrate 12 on which the first insulating portion 22 is formed is taken out. Immediately after the removal, the first insulating portion 22 is in a temporarily cured state, so that the first insulating portion 22 and the resin coating 20 are not sufficiently adhered. Therefore, in order to bring the first insulating portion 22 into close contact with the resin coating 20, the semiconductor substrate 12 is stored for about 5 hours in a high-temperature bath maintained at about 200 ° C., and the first insulating portion 22 is further cured. In this way, the first insulating portion 22 in contact with the resin coating 20 is formed.

  Next, the second insulating portion 24 is formed. The process of forming the second insulating portion will be described with reference to FIGS. When forming the second insulating portion 24, the second mold 120 shown in FIG. 5 is used. The second mold 120 includes a lower mold 122 and an upper mold 124. After placing the semiconductor substrate 12 on a predetermined location of the lower mold 122, the upper mold 124 is placed on the lower mold 122. As a result, the semiconductor substrate 12 is put in the second mold 120.

  In a state where the lower mold 122 and the upper mold 124 are overlapped, a cavity C2 surrounding the end portion (the resin coating 20 and the first insulating portion 22) of the semiconductor substrate 12 is formed. The cavity C2 is connected to an inlet 126 for injecting the material of the second insulating portion into the cavity C2 and an outlet 128 for discharging excess material.

  Next, as shown in FIG. 6, the injection nozzle 130 is applied to the injection port 126, and liquid silicon rubber is injected into the cavity C2. Silicon rubber is sufficiently injected to the extent that excess silicon rubber 132 exits from the discharge port 128, and the cavity C2 is filled with silicon rubber. At this time, the temperature of the lower mold 122 and the upper mold 124 is set to about 150 ° C., for example. This state is maintained for about 2 minutes, for example, and the liquid silicone rubber is cured.

  Thereafter, the upper and lower molds 122 and 124 are separated, and the semiconductor substrate 12 on which the second insulating portion 24 is formed is taken out. And the 2nd insulating part 24 is further hardened by putting the semiconductor substrate 12 in a high temperature tank. In this way, the second insulating portion 24 that covers the first insulating portion 22 is formed.

  FIG. 7 is a cross-sectional view of the semiconductor substrate taken out from the second mold 120. The semiconductor substrate is, for example, circular in plan view. The resin coating 20, the first insulating part 22, and the second insulating part 24 are formed over the entire outer periphery of the semiconductor substrate. In order to easily separate the first insulating part 22 from the first mold and to easily separate the second insulating part 24 from the second mold, the side surfaces of the first insulating part 22 and the second insulating part 24 are Tapered shape. When the side surfaces of the first insulating portion 22 and the second insulating portion 24 are tapered, the releasability is improved. Each component is attached to the semiconductor substrate shown in FIG. 7 to complete the semiconductor device 10 shown in FIG.

  Here, comparative examples will be described in order to facilitate understanding of the features of the present invention. FIG. 8 is a cross-sectional view of a comparative mold or the like. The mold 200 includes a lower mold 202 and an upper mold 204. The mold 200 has the same shape as the second mold 120 described above.

  Silicon rubber is injected while the semiconductor substrate 12 on which the resin coating 20 is formed is placed in the mold 200. This state is maintained for about 2 minutes, for example, and the liquid silicon rubber is cured. Thereby, the insulating part 206 is formed. After the silicon rubber is cured, the upper and lower molds 202 and 204 are separated and the semiconductor substrate 12 is taken out from the mold 200 as shown in FIG. Thereafter, the semiconductor substrate 12 is stored in a high temperature bath, and the insulating portion 206 is further cured.

  FIG. 10 is a cross-sectional view of a semiconductor substrate or the like manufactured by the method for manufacturing a semiconductor device according to the comparative example. The resin coating 20 is covered with one large insulating portion 206. When the semiconductor substrate 12 is taken out from the mold 200, the insulating part 206 is pulled on the mold 200, and the insulating part 206 is peeled off 220.

  FIG. 11 is a cross-sectional view of a portion different from FIG. 10, such as a semiconductor substrate manufactured by the method for manufacturing a semiconductor device according to the comparative example. Bubbles 222 are generated in the insulating portion 206. When liquid silicon rubber is injected into the mold mold cavity from the mold mold inlet, the air in the cavity is pushed out and the cavity is filled with liquid silicon rubber. Ideally, all the air in the cavity is pushed out of the mold. However, for example, if there is a large cavity on the lower surface side of the end portion of the semiconductor substrate, bubbles tend to remain in this portion. In particular, bubbles are likely to remain near the exit.

  If the peeling 220 or the bubble 222 is present, there is a possibility that internal discharge occurs when a voltage is applied to the semiconductor device, or the withstand voltage deteriorates with time. Since the peeling 220 or the bubbles 222 are more likely to occur as the insulating portion is larger, the peeling 220 or the bubbles 222 can be suppressed by reducing the insulating portion. However, in a high breakdown voltage semiconductor device, it is necessary to secure a large insulation distance with respect to the voltage, and thus it is necessary to increase the insulation portion. Therefore, the method of the comparative example cannot suppress the peeling 220 or the bubbles 222 while ensuring the withstand voltage.

  However, according to the method for manufacturing a semiconductor device according to the embodiment of the present invention, it is possible to prevent the insulating portion from being peeled off or bubbles from being generated in the insulating portion without reducing the insulating portion. In the method of manufacturing the semiconductor device according to the first embodiment, the first insulating portion 22 and the second insulating portion 24 are formed in separate steps. That is, first, the first insulating portion 22 is formed using the first mold 100 having the small cavity C1 surrounding the end portion of the semiconductor substrate 12. Since the cavity C1 is small, the first insulating portion 22 formed therein is also small. The small first insulating portion 22 can be obtained by setting the distances y1 and y2 in FIG. 3 to 2 mm or less, for example. Therefore, it is possible to prevent the first insulating portion 22 from being peeled off from the resin coating 20 when the semiconductor substrate 12 is taken out from the first mold 100. Further, since the cavity C1 is small, it is possible to prevent bubbles from being generated when the cavity C1 is filled with liquid silicon rubber. In addition, peeling and bubbles can be reliably prevented by setting the distances y1 and y2 shown in FIG. 3 to 2 mm or less, respectively, but the distances y1 and y2 may be changed as long as peeling and bubbles can be suppressed.

  The cavity C <b> 2 of the second mold 120 is narrowed by the amount of the first insulating portion 22 as compared with the comparative example without the first insulating portion 22. Therefore, peeling of the second insulating portion 24 and generation of bubbles can be prevented. In this way, the first insulating portion 22 and the second insulating portion 24 are sequentially formed by two mold dies, thereby providing an insulating portion (first insulating portion 22 and second insulating portion 24) that achieves a desired breakdown voltage. Since it forms, the peeling of an insulation part or a bubble can be prevented.

  The semiconductor device manufacturing method and the semiconductor device according to the embodiments of the present invention can be variously modified. For example, although the insulating part is composed of the first insulating part 22 and the second insulating part 24, three or more insulating parts may be formed sequentially. In order to stabilize the pressure resistance characteristics and facilitate material management, it is preferable that the first insulating portion 22 and the second insulating portion 24 be formed of the same material. However, these may be formed of different materials as long as a sufficient breakdown voltage can be obtained. Further, the first insulating portion 22 and the second insulating portion 24 may be formed of a material other than silicon rubber. The material of the resin coating 20 may be any material that has good adhesion to the semiconductor substrate 12 and is not limited to polyimide silicon.

  The shape of the end (side surface) of the semiconductor substrate 12 is not particularly limited. For example, a mesa bevel structure shown in FIG. 12 may be adopted. The semiconductor device 10 employs a center gate structure, but is not necessarily limited thereto, and various types of semiconductor devices may be employed. A pressure-contact type semiconductor device can be configured as long as the semiconductor substrate has the first electrode formed on the first main surface and the second electrode formed on the second main surface opposite to the first main surface. That is, a pressure contact type semiconductor device is formed by sandwiching a semiconductor substrate between the first main electrode electrically connected to the first electrode and the second main electrode electrically connected to the second electrode. For example, the present invention is applied to power semiconductor devices such as BTB (Back to Back) and SVG (Static Var Generator), industrial semiconductor devices such as inverters for driving steel mills, and other high voltage / large capacity switches. The semiconductor substrate can be used.

  These modifications can be appropriately applied to the semiconductor device manufacturing method and the semiconductor device according to the following embodiments. Since the following embodiment has much in common with the first embodiment, the difference from the first embodiment will be mainly described.

Embodiment 2. FIG.
FIG. 13 is a partial cross-sectional view of the semiconductor device according to the second embodiment of the present invention. The second insulating part 300 has a first side surface 300 a facing the outside of the semiconductor substrate 12 and a second side surface 300 b facing the inside of the semiconductor substrate 12. The first side surface 300 a and the second side surface 300 b are orthogonal to the longitudinal direction (x direction) of the semiconductor substrate 12. The second insulating part 300 is made of a material harder than the first insulating part 22.

  When assembling the semiconductor device, it is necessary to position the semiconductor substrate 12 at a correct position. The first side surface 300a or the second side surface 300b is used for this positioning. Specifically, a positioning member can be pressed against the first side surface 300a or the second side surface 300b to position the semiconductor substrate 12 at a predetermined location. Therefore, positioning accuracy can be improved as compared with the case where the side surface of the second insulating portion has a taper and is not orthogonal to the longitudinal direction of the semiconductor substrate.

  If the second insulating portion is formed of a soft material, the second insulating portion may be deformed during positioning, and the positioning accuracy may be reduced. Therefore, in the second embodiment of the present invention, the second insulating part 300 is formed of a material harder than the first insulating part 22, thereby preventing the deformation of the second insulating part 300 during positioning. By using a material suitable for maintaining the withstand voltage for the first insulating portion 22 and using a material harder than the first insulating portion 22 for the second insulating portion 300, positioning accuracy can be increased while maintaining the withstand voltage.

  If at least one of the first side surface 300a and the second side surface 300b is orthogonal to the longitudinal direction of the semiconductor substrate 12, the semiconductor substrate 12 can be aligned. Therefore, only one of the first side surface and the second side surface may be perpendicular to the longitudinal direction of the semiconductor substrate 12.

  DESCRIPTION OF SYMBOLS 10 Semiconductor device, 12 Semiconductor substrate, 12a Side surface, 12b Upper surface edge part, 12c Lower surface edge part, 14 Cathode electrode, 16 Gate electrode, 18 Anode electrode, 20 Resin coating, 22 1st insulation part, 24 2nd insulation part, 30 Anode strain buffer plate, 32 Anode main electrode, 40 Cathode strain buffer plate, 42 Cathode main electrode, 50 Center gate extraction electrode, 100 First mold die, 120 Second mold die, 220 Peel, 222 Bubble, 300 Second Insulating part, 300a first side, 300b second side

Claims (5)

The first electrode is formed on the first main surface, the second electrode is formed on the second main surface opposite to the first main surface, and the semiconductor substrate whose side surface is resin-coated is placed in the first mold. And forming a first insulating portion in contact with the resin coating;
Placing the semiconductor substrate on which the first insulating portion is formed in a second mold and forming a second insulating portion that covers the first insulating portion. Device manufacturing method.   The method of manufacturing a semiconductor device according to claim 1, wherein the first insulating portion and the second insulating portion are formed of the same material. The second insulating portion has a first side surface facing the outside of the semiconductor substrate and a second side surface facing the inside of the semiconductor substrate,
2. The method of manufacturing a semiconductor device according to claim 1, wherein at least one of the first side surface and the second side surface is orthogonal to a longitudinal direction of the semiconductor substrate.   The method of manufacturing a semiconductor device according to claim 3, wherein the second insulating portion is formed of a material harder than the first insulating portion.   The method of manufacturing a semiconductor device according to claim 1, wherein the first insulating portion is formed of silicon rubber.

Images