JPH1027791A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: Provided is a highly reliable semiconductor device which avoids fluctuations in charge density and increases in leakage current. A semiconductor device includes a pn junction on an exposed side surface of a semiconductor substrate in which a pn junction portion of an n base layer, a p base layer, a p emitter layer, and an n emitter layer is exposed on a side surface.
A first insulating protective layer 5 and a second insulating protective layer 8 are formed on the joint portion, and the dielectric constant formed by the filler 9 in the second insulating protective layer 8 is set such that the dielectric constant is from the center line of the semiconductor substrate toward the outer periphery. It has a slope distribution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device to which a high voltage is applied, such as a thyristor or a diode, and to a high breakdown voltage semiconductor device having a stable voltage blocking characteristic even when a high voltage is applied.

[0002]

2. Description of the Related Art In a high breakdown voltage semiconductor device such as a thyristor, a gate turn-on thyristor, or a diode, a side surface of a semiconductor substrate is processed into a bevel shape, and a stabilized protective film is formed on the processed side surface. As a conventional technique relating to high reliability of a high breakdown voltage semiconductor device, a technique disclosed in Japanese Patent Application Laid-Open No. 6-53485 is known. In this technique, the thyristor is machined so as to be inclined so that the central portion of the side surface has a depression. With this inclination, when a reverse bias voltage is applied to one pn junction of the pnp structure on the side surface of the semiconductor substrate, the depletion layer on the surface of the pn junction expands mainly to the n-layer side by the positive bevel structure. Thus, the breakdown voltage of the semiconductor device can be increased.

On the other hand, the depressed portion on the side surface has an advantage in that the depletion layer is unlikely to spread, so that punch-through in the pnp structure portion on the side surface can be prevented. The side surface of the semiconductor device where the pn junction is exposed and the surface where the semiconductor substrate is exposed are formed of an insulating film such as polyimide as a first insulating protective layer and a silicone rubber or the like as a second insulating protective layer disposed thereon. It is said that it is protected by an insulating film and that high reliability can be achieved.

According to the technique disclosed in Japanese Patent Application Laid-Open No. 57-80764, a semiconductor device having good and stable electric characteristics is made of a silicon resin member made of an addition type silicon resin containing no filler and no reinforcing agent. A configuration including a first layer as a first insulating protective layer and a second layer as a second insulating protective layer made of an additional silicon resin containing at least one of a filler and a reinforcing agent is shown. ing.

Further, a technique for weakening the electric field intensity in the insulating protective film is disclosed in Japanese Patent Publication No. 50-10103. This technology forms a low dielectric constant material that does not adversely affect the element characteristics of a semiconductor device on a side surface where the semiconductor device pn junction is exposed, and further forms a high dielectric constant material on the surface of the low dielectric constant material. It is. By using a high dielectric constant material as the insulating protective film, it is possible to reduce the electric field strength in the insulating protective film.

[0006]

However, according to the techniques disclosed in Japanese Patent Application Laid-Open No. 57-80764 and Japanese Patent Application Laid-Open No. 6-53485, the first test is a high temperature bias life test in which the substrate is exposed to a high temperature while a voltage is applied. No consideration is given to the problem that the charge accumulated at the interface between the insulating protective layer and the second insulating protective layer adversely affects the blocking characteristics of the semiconductor device.

That is, when a high withstand voltage of a semiconductor device is required and the electric field intensity applied to the insulating protective layer is increased, the reliability of the insulating protective layer has a great influence on the reliability of the semiconductor device. An important factor that the insulating protective layer affects the blocking characteristics of the semiconductor device is the charge density in the insulating protective layer, and a change in the charge density causes defects such as an increase in leakage current and a decrease in withstand voltage of the semiconductor element. Generally, the charge density depends on the charge near the interface between the semiconductor and the insulating protective layer.

[0008] The charge density is determined by the first insulating protective layer /
The charge is also affected by charges generated by interface polarization at the interface of the second insulating protective layer (positive charges 10 accumulated at the interface of the insulating film and negative charges 11 accumulated at the interface of the insulating film shown in FIG. 12). That is, when a voltage is applied to the insulating protective layer, charges are induced on the semiconductor surface by the interfacial polarization charges, and the charge density changes due to the induced charges, so that the blocking characteristics deteriorate and the long-term reliability of the semiconductor device increases. There is a problem that adversely affects

According to the technique disclosed in Japanese Patent Publication No. 50-10103, although the electric field strength in the insulating protective layer can be reduced, the interface between the high dielectric constant material and the low dielectric constant material (third layer described later). ) Is formed, there is a problem that the interface polarization charge tends to increase.

Accordingly, it is an object of the present invention to provide a highly reliable semiconductor device in which fluctuations in charge density and increase in leakage current are avoided and characteristics are stable for a long period of time, and a method of manufacturing the same.

[0011]

A feature of a semiconductor device that achieves the above object is that a first insulating protective layer in which an exposed side surface of a semiconductor formed of at least one pn junction is in contact with the exposed side surface and the first insulating protection layer. (1) In a semiconductor device covered and protected with a second insulating protective layer containing a filler abutting on the outer peripheral side of the insulating protective layer, the second insulating protective layer is formed of the filler in the second insulating protective layer. It has a density distribution in which the dispersion density continuously increases from the inner periphery to the outer periphery of the second insulating protective layer.

Another feature of the semiconductor device is that the exposed side surface of the semiconductor formed of at least one pn junction is brought into contact with the exposed side surface and the outer peripheral side of the first insulating protective layer. In a semiconductor device covered and protected by a second insulating protective layer containing a filler abutted on the second insulating protective layer, the filler is made of a filler having a non-uniform particle size. The point is that the filler has a particle size distribution in which the average particle size of the filler in the layer increases from the inner circumference to the outer circumference of the second insulating protective layer.

The features of the method for manufacturing a semiconductor device are as follows.
After processing and exposing a side surface of a semiconductor made of at least one pn junction, and forming a first insulating protective layer on the exposed side surface, a semiconductor base made of the first insulating protective layer and the semiconductor is cast into a casting jig. Embedded in the casting jig so that the insulating material containing a filler is in contact with the outer peripheral side of the first insulating protective layer, after rotating the semiconductor base together with the casting jig, the insulating material The second insulating protective layer is formed by curing the insulating material while rotating the semiconductor base together with the casting jig to form a second insulating protective layer.

According to the present invention, the electric field intensity in the second insulating protective layer is reduced, and the interfacial polarization charge at the interface between the two insulating protective layers is suppressed, so that a change in charge density and an increase in leakage current are avoided. Thus, a highly reliable semiconductor device is provided.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. An example of the embodiment will be described as an example.

(Embodiment 1) FIG. 1 is a sectional view showing a semiconductor device according to an embodiment of the present invention. A thyristor as a press-contact power semiconductor device is shown in cross section. In FIG. 1, 1 is an n base layer, 2 is a p base layer, 3 is a p emitter layer, 4 is an n emitter layer, 5 is a first insulating protective layer as a first insulating protective film, and 6 is a cathode electrode. , 7 are anode electrodes, 8 is a second insulating protective layer as a second insulating protective film, and 9 is a filler.

The feature of the semiconductor device according to the present invention is that the n base layer 1, the p base layer 2, the p emitter layer 3, and the n
An exposed side surface of a semiconductor (semiconductor substrate) formed of a pn junction of the emitter layer 4 is made of an insulating material containing a filler 9 and a first insulating protective layer 5 in contact with the exposed side surface. Is covered and protected by a second insulating protective layer 8 which is in contact with the outer peripheral (surface) side of the second insulating protective layer 8, and the dispersion density of the filler 9 in the second insulating protective layer is the second insulating protective layer. The structure has a density distribution that continuously increases toward the outer periphery of the layer 8.

In other words, since the dispersion density of the filler 9 on the inner peripheral (surface) side of the second insulating protective layer 8 which is in contact with the first insulating protective layer 5 is low, the dielectric constant on the inner peripheral side becomes low, On the other hand, the filler 9 on the outer periphery (surface) side of the second insulating protective layer 8
Since the dispersion density is high, it can be said that the point is that the dielectric constant on the outer peripheral side is increased, that is, the dielectric constant in the second insulating protective layer is made to have a gradient distribution. As a result, the intensity of the electric field generated by applying a voltage to the semiconductor device is increased by the filler 9 on the inner peripheral side (near) where the first insulating protective layer and the second insulating protective layer 8 are in contact with each other.
Can be made lower than in the case where the dispersion density is uniform. Therefore, the fluctuation of the charge density can be suppressed.

Further, the semiconductor device according to the present invention has a semiconductor substrate having one and the other main surfaces and having at least a pn junction exposed on the side, and an insulating protective film on the pn junction exposed on the side. It can also be said that the configuration is characterized by a configuration in which the concentration of the filler in the insulating protective film is inclined so as to increase in the outer peripheral direction from the center line connecting the centers of the one and the other main surfaces. Due to this feature, a portion where the concentration of the filler 9 is high has a higher dielectric constant than a portion where the concentration is low, and the electric field intensity in a portion where the concentration of the filler 9 is low in the insulating protective film can be reduced. That is, a highly reliable semiconductor device can be provided while suppressing a change in charge density.

On the other hand, if the second insulating protective layer is formed by a rotational molding method according to the present invention described later, a portion where an interface is formed between polyimide as the first insulating protective layer and silicone rubber as the second insulating protective layer. While keeping the dielectric constant of
The insulating protective layer / second insulating protective layer interface (polyimide / silicone rubber interface) can be adhered. That is, at the interface between the first insulating protective layer and the second insulating protective layer, room for forming or interposing a third layer such as an air layer or a dust adhesion layer where charges are easily stored is extremely reduced, An increase in interfacial polarization charge is avoided.

In other words, the second insulating protective layer is formed in close contact with the first insulating protective layer so that no charge is added to the polarization interface between the first insulating protective layer and the second insulating protective layer. It can be said that the polarization ability is the same. In other words, the electric field strength applied to both insulating protective layers can be reduced without significantly changing the interfacial polarizability, that is, the interfacial polarization charge is reduced, and the charge density that affects the semiconductor characteristics of the semiconductor device is appropriately adjusted. Can be kept. Therefore, a change in charge density and an increase in leakage current in the semiconductor device are avoided, and a highly reliable semiconductor device is provided.
It is known that the interfacial polarization charge is proportional to the electric field intensity applied to the interface.

Next, a method of manufacturing a semiconductor device according to the present invention will be described with reference to one embodiment of a thyristor manufacturing process shown in FIG. FIG. 2 is a diagram showing a method of manufacturing a semiconductor device according to one embodiment of the present invention. In FIG. 2A, first, an n base layer 1 made of high-resistance n-type silicon is used.
Then, the p base layer 2, the p emitter layer 3, and the n emitter layer 4 are diffused to produce a semiconductor substrate. Then, FIG.
, The n-emitter layer 4 of the main thyristor portion, the n-emitter layer 4 of the auxiliary thyristor layer,
Forming n-emitter layers 4 of light-receiving thyristors,
Next, a cathode electrode 6 and an anode electrode 7 are formed by vapor deposition.

Next, in FIG. 2 (c), the end 13 which is the side surface of the semiconductor substrate is machined into a Σ shape by a grinding machine or sandblasting, and the semiconductor substrate is cleaned to remove chipping and dirt on the end 13. Chemically etching the exposed part,
After washing and drying, the first insulating protective film resin is applied by spin coating, dip coating, brush coating, dispenser, or the like, and then heated and cured in a nitrogen atmosphere to form the first insulating protective film resin.
An insulating protective layer 5 is formed. The first insulating protective film resin as the first insulating protective layer 5 is a polyimide resin, and the curing conditions are 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour. The semi-finished product having the shape shown in FIG. 2C is called a semiconductor base 14.

FIG. 3 is a diagram showing a method of rotationally molding a semiconductor device according to an embodiment of the present invention. In FIG. 3, the semiconductor base 14 is replaced with a casting upper mold 15, as shown in FIG.
Installed in the lower mold 16 for casting, the surface of the first insulating protective film layer 5
(Outer peripheral side) pour the second insulating protective film resin. next,
The semiconductor base 14 is fixed to the turntable 17 while the semiconductor base 14 is incorporated in the molds 15 and 16, and after rotating, the second insulating protective film resin is cured, or the second insulating protective film resin is rotated while rotating. By curing, the second insulating protective layer 8 is formed.
Thus, the semiconductor device shown in FIG. 2D is manufactured.

The second insulating protective film resin as the insulating material formed as the second insulating protective layer 8 is an addition type silicone rubber which is previously mixed and contains barium titanate as a filler. The curing conditions are 100
1 hour at 150 ° C., 1 hour at 150 ° C., and 2 hours at 200 ° C.

FIG. 4 is a diagram showing the density distribution of the filler in the second insulating protective layer of this embodiment. The density distribution of the filler in the second insulating protective layer 8 of the semiconductor device obtained by the above manufacturing method is as shown in FIG. That is, the dispersion density of the filler 9 depends on the inner circumference of the second insulating protective layer 8 (see FIGS. 3 and 4).
3 shows a density distribution that continuously increases from the part a) to the outer periphery (part b shown in FIGS. 3 and 4). This is because the centrifugal force due to the rotation, which is a feature of the rotational molding method, acts, and the filler is collected by the outer periphery (part b) and cured and molded. That is, it is important to move the filler more densely toward the outer periphery by centrifugal force before the second insulating protective film resin is cured.

Furthermore, since the second insulating protective film resin is cast and cured by heating, the first insulating protective layer / second insulating protective layer interface (polyimide / silicone rubber interface) can be adhered. That is, the first insulating protective layer and the second
It can be said that the formation of a third layer such as an air layer or a dust-adhering layer in which there is almost no gap between the insulating protective layer and the charge is easily stored is extremely reduced. Finally, the semiconductor element was placed in a ceramic package (not shown), the atmosphere inside the package was changed to dry nitrogen, and the package was sealed to complete a semiconductor device. The voltage-current characteristics of this semiconductor device are shown in FIG. 7 described later.

By the way, the second insulating protective layer 8 is formed such that the dispersion density of the filler in the second insulating protective layer is distributed so as to continuously increase from the inner periphery to the outer periphery of the second insulating protective layer. Then, the second insulating protective layer 8 is abutted on the outer peripheral side of the first insulating protective layer 5 and assembled in a later step to manufacture a semiconductor device. However, in the case of the above-mentioned retrofitting method, the third layer is easily formed between the first and second insulating protective layers. The effect of avoiding the increase is diminished. However, it has been confirmed that the reliability is improved as compared with a conventional semiconductor device having a filler uniform dispersion density.

Another feature of the semiconductor device according to the present invention is that a silicone rubber having a high heat-resistant temperature and a small dielectric constant is used as a base material of the insulating material of the second insulating protective layer. (2) The density distribution (gradient distribution of permittivity in the second insulating protection layer) that continuously increases from the inner circumference to the outer circumference in the insulating protection layer is utilized to further enhance the first insulating protection layer / second The point is that interfacial polarization charges at the interface of the insulating protective layer can be reduced.

Another feature of the semiconductor device according to the present invention is that, as a filler material contained in the second insulating protective layer, a solid metal or a material such as lead oxide, alumina, tantalum oxide, titanium oxide, magnesium oxide or the like is used. Metal oxides,
Alternatively, by using a filler having a large dielectric constant such as one or a mixture of two or more of non-metallic substances such as silicon, carbon, and silicon carbide, the dielectric constant in the second insulating protective layer can be appropriately easily adjusted. The point is that the gradient distribution can be made. The filler can be used in a temperature range of −40 to 300 ° C. by insulating the surface of the filler material.

Accordingly, as an insulating material for forming the second insulating protective layer, a filler made of a metal oxide such as lead oxide, alumina, tantalum oxide, titanium oxide, magnesium oxide or the like having a large dielectric constant is added to silicone rubber having a small dielectric constant. Can be said to be desirable.

In the method of manufacturing a semiconductor device according to the present invention, the end face of a semiconductor substrate having a pnpn structure including four semiconductor layers of an n emitter layer, a p base layer, an n base layer, and a p emitter layer is beveled. After etching and drying the area where the surface of the semiconductor substrate is exposed, forming an insulating film such as a polyimide resin on the surface of the etched area, incorporating the semiconductor base into an insulating protective resin casting jig, After the semiconductor base is rotated together with the casting jig, or by curing the insulating protective resin while rotating, the filler in the insulating protective film is formed on one and the other main surface of the semiconductor base. The inclination distribution is made so as to increase in the outer peripheral direction from a center line connecting both centers.

As described above, the interfacial polarization in the insulating protective film due to the long-term continuous use of the semiconductor element is suppressed, and the fluctuation or increase of the leakage current is prevented even when a high voltage is applied to the semiconductor device for a long time. Since the electric field strength in the inside and the interfacial polarization charge are reduced, the fluctuation of the charge density is suppressed, and the generation of the leakage current during the operation of the semiconductor device is suppressed. In other words, the electric field strength in the insulating protective film is weakened. As a result, the interface polarization that affects the charge density is reduced, and the leakage current fluctuation and increase of the semiconductor device are suppressed.
A semiconductor device having stable semiconductor characteristics over a long period of time and high reliability is provided.

(Embodiment 2) FIG. 5 is a sectional view showing a semiconductor device of another embodiment according to the present invention. 6 shows a cross section of a thyristor which is a press-contact type power semiconductor device according to a second embodiment. In Example 2, a semiconductor substrate was processed, chemically etched, rinsed and dried in the same manner as in Example 1, and then a polyimide varnish as a first insulating protective film resin was applied by spin coating, and heated in a dry nitrogen atmosphere. The first insulating protective layer 5 was formed by curing. The curing conditions were 10
0 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour.

Next, according to the manufacturing method shown in FIG. 3, the semiconductor base 14 is incorporated into the molds 15 and 16, and the second insulating protective film resin is poured into the outer peripheral surface of the first insulating protective layer 5. Then, while the semiconductor base 14 was incorporated in the molds 15 and 16, these were fixed to the turntable 17, and the insulating protective film resin was cured while rotating to form the second insulating protective layer 8, thereby manufacturing a semiconductor device. . The second insulating protective layer 8 is an addition type silicone rubber in which silicon carbide having a particle size distribution in the range of 0.1 to 200 μm is mixed in advance, and the curing conditions are 100 ° C. for 1 hour and 150 ° C. for 1 hour. For 2 hours at 200 ° C.

FIG. 6 is a view showing the particle size distribution (average particle size distribution) of the filler in the second insulating protective layer of Example 2. The distribution of the average particle size of the filler in the second insulating protective layer 8 obtained by the above manufacturing method is as shown in FIG. That is,
The distribution of the average particle size of the filler 9 varies from the inner circumference (a part shown in FIGS. 5 and 6) of the second insulating protective layer 8 to the outer circumference (b part shown in FIGS. 5 and 6).
Shows a distribution that continuously increases toward. This is because a centrifugal force due to rotation, which is a feature of the rotational molding method, acts, and the filler 9 having a larger particle diameter is collected by the outer periphery (part b) and cured and molded. In the case of Example 2, it can be said that a method of curing the second insulating protective film resin while rotating so that the moved filler does not return before being cured. In addition, since the second insulating protective film resin is cast and cured by heating, the interface between the first insulating protective layer and the second insulating protective layer can be adhered. Finally, the semiconductor element was placed in a ceramic package, the atmosphere inside the package was changed to dry nitrogen, and the package was sealed to complete a semiconductor device. FIG. 7 also shows the voltage-current characteristics of this semiconductor device.

As described above, still another feature of the semiconductor device according to the present invention is that the use of the filler having a non-uniform particle diameter in the range of 0.1 to 200 μm makes it relatively easy to use the second filler. The point is that the dielectric constant in the insulating protective layer can be made to have a gradient distribution. That is, another feature of the semiconductor device according to the present invention is that at least pn
The bonding portion has an insulating protective film layer on the semiconductor substrate exposed on the side surface and the pn junction portion exposed on the side surface, and the particle size of the filler in the insulating protective film is in both centers of one and the other main surfaces. It is in a place where the inclination distribution is made so as to increase in the outer peripheral direction from the connecting center line. Due to this feature, the dielectric constant of the outer peripheral portion where the particle diameter of the filler is large is higher than that of the inner peripheral portion where the filler particle size is small, and the electric field intensity in the insulating protective film can be reduced.

Further, since the dielectric constant of the portion where the interface between the polyimide and the silicone rubber is generated can be kept low, the interfacial polarizability at the polyimide / silicone rubber interface remains unchanged. In other words, the electric field intensity applied to the insulating protective film can be reduced without significantly changing the interfacial polarizability, so that the interfacial polarization charge can be reduced and the charge density that affects the element characteristics of the semiconductor device can be appropriately maintained. it can.

(Embodiment 3) FIG. 8 shows Embodiment 3 of the present invention.
FIG. 3 is a cross-sectional view illustrating the semiconductor device of FIG. In the third embodiment, the manufacturing method of the first embodiment is applied to a gate turn-off thyristor (GTO).
The method for forming the insulating protective layer was the same as that in Example 1. The semiconductor substrate was processed, chemically etched, washed and dried, then the first insulating protective layer 5 was formed, and then the second insulating protective layer 8 was formed. . Finally, the semiconductor element was placed in a ceramic package (not shown), the atmosphere inside the package was changed to dry nitrogen, and the package was sealed to manufacture a semiconductor device.

(Embodiment 4) FIG. 9 shows Embodiment 4 of the present invention.
FIG. 3 is a cross-sectional view illustrating the semiconductor device of FIG. In the fourth embodiment, the manufacturing method of the second embodiment is applied to a gate turn-off thyristor (GTO). The method for forming the insulating protective layer is described in Example 2.
After processing the semiconductor substrate, chemically etching, washing and drying, the first insulating protective layer 5 was formed, and then the second insulating protective layer 8 was formed. Finally, the semiconductor element was placed in a ceramic package (not shown), the atmosphere inside the package was changed to dry nitrogen, and the package was sealed to manufacture a semiconductor device.

(Embodiment 5) FIG. 10 is a sectional view showing a semiconductor device according to Embodiment 5 of the present invention. In the fifth embodiment, the manufacturing method of the first embodiment is applied to a diode. The method for forming the insulating protective layer was the same as that in Example 1. The semiconductor substrate was processed, chemically etched, washed with water and dried, then the first insulating protective layer 5 was formed, and then the second insulating protective layer 8 was formed. Finally, this semiconductor element is
(Not shown), the atmosphere inside the package was changed to dry nitrogen, and the package was sealed and a semiconductor device was manufactured.

(Embodiment 6) FIG. 11 is a sectional view showing a semiconductor device of Embodiment 6 according to the present invention. In the sixth embodiment, the manufacturing method of the second embodiment is applied to a diode. The method for forming the insulating protective layer was the same as in Example 2. The semiconductor substrate was processed, chemically etched, washed with water and dried, then the first insulating protective layer 5 was formed, and then the second insulating protective layer 8 was formed. Finally, this semiconductor element is
(Not shown), the atmosphere inside the package was changed to dry nitrogen, and the package was sealed and a semiconductor device was manufactured.

(Comparative Example 1) A semiconductor substrate was processed and chemically etched, washed with water and dried in the same manner as in Example 1, spin-coated with a first insulating protective film resin, and then heat-cured in a nitrogen atmosphere to form a first substrate. An insulating protective layer 5 is formed. This first insulating protective film resin is a polyimide resin, and the curing condition is 100 ° C. for 1 hour.
Time, 200 ° C. for 1 hour and 300 ° C. for 1 hour. Next, the second insulating protective film resin is poured into the mold on the surface of the first insulating protective layer, and is heated and cured as it is to form the second insulating protective layer 8, thereby manufacturing a semiconductor device.

The second insulating protective layer 8 is an addition type silicone rubber in which barium titanate is previously mixed, and the curing conditions are 100 ° C. for 1 hour, 150 ° C. for 1 hour, and 200 ° C. for 2 hours. Finally, the semiconductor element was placed in a ceramic package, the atmosphere inside the package was changed to dry nitrogen, and the package was sealed to manufacture a semiconductor device. FIG. 7 shows the voltage-current characteristics of the semiconductor device of Comparative Example 1.

Comparative Example 2 A semiconductor substrate was processed, chemically etched, washed with water and dried in the same manner as in Example 1, then spin-coated with a first insulating protective film resin, and then heated and cured in a nitrogen atmosphere to form a first substrate. An insulating protective layer 5 is formed. This first insulating protective film resin is a polyimide resin, and curing conditions are 100 ° C. for 1 hour, 200 ° C. for 1 hour, and 300 ° C. for 1 hour.
Next, a second insulating protective film resin is poured into the surface of the first insulating protective layer 5 in a mold, and heat-cured to form a second insulating protective film layer 8, thereby manufacturing a semiconductor device.

The second insulating protective layer 8 has a particle size of 0.1 to
It is an addition type silicone rubber in which silicon carbide having a particle size distribution of 200 μm is previously mixed, and curing conditions are 100 ° C. for 1 hour, 150 ° C. for 1 hour, and 200 ° C. for 2 hours. Finally, put this semiconductor element in a ceramic package,
After the atmosphere inside the package was changed to dry nitrogen, the package was sealed and a semiconductor device was manufactured. FIG. 7 shows the voltage-current characteristics of the semiconductor device of Comparative Example 2.

FIG. 7 is a diagram showing voltage-current characteristics of the semiconductor devices of the example and the comparative example. As shown in FIG. 7, the semiconductor device of the embodiment manufactured by the rotational molding method according to the present invention has a density distribution in which the dispersion density of the filler continuously increases from the inner circumference to the outer circumference of the second insulating protective layer. Have,
Alternatively, since the filler has a particle size distribution in which the average particle size increases from the inner circumference to the outer circumference of the second insulating protective layer, the leakage current is reduced as compared with the conventional comparative example, and the voltage-current characteristics are excellent. Turned out to be.

[0048]

According to the present invention, there is an effect that a fluctuation in charge density and an increase in leakage current are suppressed, and a semiconductor device having high long-term reliability is provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of manufacturing a semiconductor device according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating a rotational molding method for a semiconductor device according to an embodiment of the present invention.

FIG. 4 is a diagram showing a density distribution of a filler in a second insulating protective layer of Example 1.

FIG. 5 is a sectional view showing a semiconductor device according to another embodiment of the present invention.

FIG. 6 is a diagram showing a particle size distribution of a filler in a second insulating protective layer of Example 2.

FIG. 7 is a diagram showing voltage-current characteristics of semiconductor devices of an example and a comparative example.

FIG. 8 is a sectional view showing a semiconductor device according to a third embodiment of the present invention.

FIG. 9 is a sectional view showing a semiconductor device according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view showing a semiconductor device according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view showing a semiconductor device according to a sixth embodiment of the present invention.

FIG. 12 is a partial cross-sectional view showing a conventional semiconductor device.

[Explanation of symbols]

1 ... n base layer, 2 ... p base layer, 3 ... p emitter layer,
4 ... n emitter layer, 5 ... first insulating protective layer, 6 ... cathode electrode, 7 ... anode electrode, 8 ... second insulating protective layer, 9 ... filler, 10 ... positive charge accumulated at interface of insulating film, 11 ... insulation Negative charges accumulated at the film interface, 12 ... insulating protective film layer, 13
... End of semiconductor base, 14 ... Semiconductor base, 15 ... Top mold for casting, 16 ... Bottom mold for casting, 17 ... Rotating table, 18 ... Gate electrode, 19 ... N + layer, 20 ... P + layer, 21 ... n-layer

Continuing from the front page (72) Inventor Yasuo Onose 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd.

Claims (4)

[Claims] 1. A semiconductor device comprising: a first insulating protective layer in which an exposed side surface of a semiconductor comprising at least one pn junction is in contact with the exposed side surface; and a filler which is in contact with an outer peripheral side of the first insulating protective layer. A second insulating protective layer, wherein the dispersion density of the filler in the second insulating protective layer is from the inner circumference to the outer circumference of the second insulating protective layer. A semiconductor device having a density distribution that continuously increases toward the center. 2. A semiconductor device comprising: a first insulating protective layer having an exposed side surface of a semiconductor comprising at least one pn junction in contact with the exposed side surface; and a filler having an outer peripheral side in contact with the first insulating protective layer. In the semiconductor device covered and protected with a second insulating protective layer, the filler is made of a filler having a non-uniform particle diameter, and the second insulating protective layer is formed of an average particle of the filler in the second insulating protective layer. A semiconductor device having a particle size distribution in which the diameter increases from the inner circumference to the outer circumference of the second insulating protective layer. 3. The semiconductor device according to claim 2, wherein the filler having a non-uniform particle size has a particle size in a range of 0.1 to 200 μm. 4. A semiconductor comprising said first insulating protective layer and said semiconductor, after processing and exposing a side surface of a semiconductor comprising at least one pn junction and coating said exposed side surface with a first insulating protective layer. The base was incorporated into a casting jig, and an insulating material containing a filler was injected into the casting jig so as to be in contact with the outer peripheral side of the first insulating protective layer, and the semiconductor base was rotated together with the casting jig. Afterwards, the insulating material is cured to form a second insulating protective layer, or the insulating material is cured while rotating the semiconductor base together with the casting jig to form a second insulating protective layer. A method for manufacturing a semiconductor device.