JP2021177509A - Semiconductor device - Google Patents

Abstract

To provide a semiconductor device in which heat radiation is efficiently performed.SOLUTION: A semiconductor device comprises: a semiconductor laminate structure; and a diamond layer that is formed on the semiconductor laminate structure, that has a first surface at a side of the semiconductor laminate structure and a second surface being opposite to the first surface, and that is composed of a plurality of diamond crystal particles. A number density of the plurality of diamond crystal particles on the first surface is higher than a number density on the second surface, and an average particle diameter of the plurality of diamond crystal particles on the first surface is less than or equal to 1 μm.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to semiconductor devices.

Nitride semiconductors have features such as high saturated electron velocity and wide bandgap, and their application to high withstand voltage and high output semiconductor devices is being studied. For example, the bandgap of GaN, which is a nitride semiconductor, is 3.4 eV, which is larger than the bandgap of Si (1.1 eV) and the bandgap of GaAs (1.4 eV), and has a high fracture electric field strength. Therefore, nitride semiconductors such as GaN are extremely promising as materials for semiconductor devices for power sources that obtain high voltage operation and high output. As a semiconductor device using a nitride semiconductor, many reports have been made on field effect transistors, particularly high electron mobility transistors (HEMTs).

In HEMTs using such nitride semiconductors, a high voltage is applied and a large current flows, so that heat generation is large, so that efficient heat dissipation is required. For example, a technique for depositing a diamond layer using a chemical vapor deposition (CVD) method is known. Specifically, diamond synthesized by the CVD method on the back surface of a substrate provided with a semiconductor device having a large calorific value such as a laser diode or a semiconductor device using a nitride semiconductor such as gallium nitride (GaN). There is a known technique for joining a diode (for example, Patent Document 1). Further, there is known a technique of forming an insulating film such as TiC or AlC on the surface of a substrate provided with a similar semiconductor device and then laminating a diamond layer (for example, Patent Document 2).

Special Table 2016-359510 JP-A-2007-157829

Diamond Relat. Mater. 10, 744 (2001) Appl. Phys. Lett. 111, 041901 (2017)

By the way, as described in Patent Document 1, even if diamond is provided on the back surface of the substrate, efficient heat dissipation is not performed, and as described in Patent Document 2, an insulating film is provided on the surface of the substrate. When the diamond layer is formed on the insulating film, heat conduction is hindered in the insulating film and efficient heat dissipation is not performed.

Therefore, there is a demand for a semiconductor device that can efficiently dissipate heat.

According to one aspect of the present embodiment, the semiconductor laminated structure, the first surface formed on the semiconductor laminated structure and on the semiconductor laminated structure side, and the second surface on the side opposite to the first surface are formed. It has a diamond layer composed of a plurality of diamond crystal grains, and the number density of the plurality of diamond crystal grains on the first surface is higher than the number density on the second surface. A semiconductor device is provided in which the average particle size of the plurality of diamond crystal grains on the first surface is 1 μm or less.

According to the present disclosure, efficient heat dissipation can be achieved.

It is a structural drawing of the semiconductor device which concerns on 1st Embodiment. It is a process drawing (1) of the manufacturing method of the semiconductor device which concerns on 1st Embodiment. It is a process drawing (2) of the manufacturing method of the semiconductor device which concerns on 1st Embodiment. It is a process drawing (3) of the manufacturing method of the semiconductor device which concerns on 1st Embodiment. It is a process drawing (4) of the manufacturing method of the semiconductor device which concerns on 1st Embodiment. It is explanatory drawing of sheet resistance in a semiconductor device. It is a structural drawing (1) of the semiconductor device used for measuring the sheet resistance. It is a structural drawing (2) of the semiconductor device used for measuring the sheet resistance. It is an SEM image of the cross section of a diamond layer. It is an SEM image of the upper surface of the diamond layer. It is an SEM image of the upper surface in the early stage of crystal growth. It is a structural drawing of the semiconductor device which concerns on 2nd Embodiment. It is a structural drawing of the semiconductor device which concerns on 3rd Embodiment. It is a figure which shows the discrete package which concerns on 4th Embodiment. It is a wiring diagram which shows the PFC circuit which concerns on 5th Embodiment. It is a wiring diagram which shows the power supply device which concerns on 6th Embodiment. It is a wiring diagram which shows the amplifier which concerns on 7th Embodiment.

Hereinafter, embodiments of the present disclosure will be specifically described with reference to the accompanying drawings. In the present specification and the drawings, components having substantially the same functional configuration may be designated by the same reference numerals to omit duplicate explanations.

(First Embodiment)
By the way, diamond is one of the materials having high thermal conductivity. It is considered that the heat generated in the substrate is dissipated through the diamond layer by providing the diamond layer having high thermal conductivity on the substrate including the heating element such as a semiconductor device. However, when a diamond layer is formed on the surface of a substrate provided with a semiconductor device using a nitride semiconductor such as GaN by the CVD method, the hydrogen gas used when forming the diamond layer is used to nitride the GaN or the like. Ga is desorbed from the physical semiconductor, damages the nitride semiconductor, and the characteristics of the semiconductor device change, making it impossible to obtain good characteristics.

Therefore, it is conceivable to form an insulating film as a protective film on the nitride semiconductor and to form a diamond layer on the formed insulating film. In order not to damage the nitride semiconductor, an insulating film having a certain thickness is required. However, since the insulating film has a lower thermal conductivity than diamond, heat dissipation is not efficient. In order to efficiently dissipate heat from the diamond layer, when the insulating film is thinned, the insulating film is also etched by the hydrogen gas used when laminating diamonds, and the nitride semiconductor is damaged, resulting in good characteristics in the semiconductor device. You can't get it.

[Semiconductor device]
Next, the semiconductor device according to the first embodiment will be described with reference to FIG. In the semiconductor device 100 according to the first embodiment, a nitride semiconductor layer such as a nucleation layer 11, a buffer layer 12, an electron traveling layer 21, and an electron supply layer 22 is formed on a substrate 10 by metalorganic vapor phase growth (metal). It is formed by the organic vapor phase epitaxy (MOVPE) method. Nitride semiconductor layers such as the nucleation layer 11, the buffer layer 12, the electron traveling layer 21, and the electron supply layer 22 are included in the nitride semiconductor laminated structure 20. In the present embodiment, the case where the nitride semiconductor layer is formed by the MOCVD method will be described, but the film may be formed by the molecular beam epitaxy (MBE) method.

In the electron traveling layer 21, 2DEG21a is generated in the vicinity of the interface between the electron traveling layer 21 and the electron supply layer 22. Further, a gate electrode 31, a source electrode 32, and a drain electrode 33 are formed on the electron supply layer 22. A cap layer (not shown) may be formed on the electron supply layer 22, and a gate electrode 31, a source electrode 32, and a drain electrode 33 may be formed on the cap layer.

Silicon carbide (SiC), sapphire (Al ₂ O ₃ ), silicon (Si), GaN, zinc oxide (ZnO) and the like are used for the substrate 10. The nucleation layer 11 is formed of, for example, AlN having a film thickness of 160 nm, and the buffer layer is formed of, for example, AlGaN having a film thickness of 500 nm in which the composition ratio of Al is gradually changed with the film formation. There is.

The electron traveling layer 21 is formed of i-GaN having a film thickness of about 1 μm. The electron supply layer 22 is formed of Al _0.2 Ga _0.8 N having a film thickness of about 20 nm. The electron supply layer 22 may be formed of InAlN or InAlGaN.

The diamond layer 50 is formed on the semiconductor laminated structure 20. The diamond layer 50 has a first surface 50A on the semiconductor laminated structure 20 side and a second surface 50B on the side opposite to the first surface 50A, and is composed of a plurality of diamond crystal grains 51. The thickness of the diamond layer 50 is, for example, 1 μm or more.

The plurality of diamond crystal grains 51 include a first diamond crystal grain 61 and a second diamond crystal grain 62. The first diamond crystal grain 61 includes a third surface 61A forming a part of the first surface 50A and a fourth surface 61B forming a part of the second surface 50B. The second diamond crystal grain 62 has a height smaller than that of the first diamond crystal grain 61 and includes a surface 62A forming a part of the first surface 50A, but includes a surface forming a part of the second surface 50B. No. The plurality of diamond crystal grains 51 are located above the second diamond crystal grain 62, are smaller in height than the first diamond crystal grain 61, and the surface forming a part of the first surface 50A is also the second surface 50B. Other diamond grains that also do not have a partially forming surface may be included.

The number density of the plurality of diamond crystal grains 51 on the first surface 50A is higher than the number density on the second surface 50B. For example, the number density of the plurality of diamond crystal grains 51 on the first surface 50A is 1 × 10 ⁸ cm- ² or more, and the number density of the plurality of diamond crystal grains 51 on the second surface 50B is 1 × 10 ⁸ cm-2. Less than ^-2. The number density of the plurality of diamond crystal grains 51 on the first surface 50A may be, for example, 1 × 10 ⁸ cm ^-2 or more and 1 × 10 ¹² cm ^-2 or less.

The average particle size of the plurality of diamond crystal grains 51 on the first surface 50A is 1 μm or less. The average particle size of the plurality of diamond crystal grains 51 on the first surface 50A may be, for example, 5 nm or more and 1 μm or less. The average particle size of the plurality of diamond crystal grains 51 on the first surface 50A is preferably 5 nm or more and 100 nm or less, and more preferably 5 nm or more and 20 nm or less.

The average particle size of the plurality of diamond crystal grains 51 on the second surface 50B is more than 1 μm.

In the semiconductor device 100 according to the first embodiment, since the diamond layer 50 is provided so as to be in direct contact with the semiconductor laminated structure 20, the heat generated in the channel including the 2DEG21a during the operation of the semiconductor device 100 is efficiently dissipated. be able to.

The thermal conductivity of the diamond layer formed of diamond having a small average particle size of about 5 nm is about 10 W / m · K. On the other hand, the thermal conductivity of the diamond layer formed of diamond having a large average particle size of more than 1 μm is about 2000 W / m · K. Therefore, it is preferable that the plurality of second diamond crystal grains 62 are provided in a thin layer. For example, although a description of the manufacturing method will be described later, the plurality of second diamond crystal grains 62 are formed in as thin a layer as possible within a range that does not damage the semiconductor laminated structure 20 when forming the first diamond crystal grains 61. It is preferable that it is.

Diamond crystals having a small average particle size can be formed at a lower temperature than diamond crystals having a large average particle size, and in some cases, they can be formed without being exposed to radical hydrogen or the like. .. Therefore, a plurality of diamond crystal grains having a small average particle size are provided on the semiconductor laminated structure 20, and diamond crystal grains having a large average particle size are grown from some of these diamond crystal grains to form a semiconductor laminated structure. The diamond layer 50 can be formed without damaging 20. As a result, deterioration of the characteristics of the semiconductor device 100 when forming the diamond layer 50 can be suppressed.

[Manufacturing method of semiconductor devices]
Next, a method of manufacturing the semiconductor device 100 according to the first embodiment will be described.

First, as shown in FIG. 2, the nucleation layer 11, the buffer layer 12, and the electron traveling on the substrate 10 by a crystal growth method such as the MOVPE method or the molecular beam epitaxy (MBE) method. The semiconductor laminated structure 20 including the layer 21, the electron supply layer 22, and the like is formed. When the semiconductor laminated structure 20 such as the nucleation layer 11, the buffer layer 12, the electron traveling layer 21, and the electron supply layer 22 is formed by the MOVPE method, trimethylaluminum gas, trimethylgallium gas, and ammonia gas are used as raw material gases. Use a mixed gas of. Depending on the composition of the nitride semiconductor layer to be formed, the presence or absence of supply of trimethylaluminum gas as an Al source and trimethylgallium gas as a Ga source and the flow rate are adjusted to form a film. The flow rate of the supplied ammonia gas is 100 ccm to 10 LM. The pressure in the chamber when forming the semiconductor laminated structure 20 is about 7 kPa (50 Torr) to about 40 kPa (300 Torr), and the film formation temperature is 1000 ° C to 1200 ° C. When the electron supply layer 22 is formed of InAlGaN, the pressure in the chamber is about 7 kPa (50 Torr) to about 27 kPa (200 Torr), and the film formation temperature is 650 ° C to 800 ° C. Trimethylindium gas can be used when growing the semiconductor layer containing In.

Next, as shown in FIG. 3, a gate electrode 31, a source electrode 32, and a drain electrode 33 are formed on the semiconductor laminated structure 20.

Next, as shown in FIG. 4, a diamond layer 70 composed of a plurality of nanodiamond particles 71 is formed on the semiconductor laminated structure 20, the gate electrode 31, the source electrode 32, and the drain electrode 33. The nanodiamond particles 71 are an example of diamond particles. Specifically, the diamond layer 70 is formed by adhering a plurality of nanodiamond particles 71 on the semiconductor laminated structure 20 or the like. For example, the diamond layer 70 is formed by immersing an electron supply layer 22 or the like in an aqueous solution or the like in which a plurality of nanodiamond particles 71 are dispersed so as to adhere to the semiconductor laminated structure 20 or the like. .. For example, the average particle size of the nanodiamond particles 71 is 5 nm or more and 1 μm or less, and the number density of the nanodiamond particles 71 on the surface of the diamond layer 70 on the semiconductor laminated structure 20 side is 1 × 10 ⁸ cm ^-2 to 1 × 10. ^{It is 12} cm- ² . Another method for forming the diamond layer 70 includes a bias enhanced nucleation (BEN) method. However, the method of adhering the nanodiamond particles 71 dispersed in the aqueous solution or the like to the surface of the semiconductor laminated structure 20 or the like as described above is preferable because the damage to the semiconductor laminated structure 20 is small.

Next, as shown in FIG. 5, a diamond layer 50 composed of a plurality of diamond crystal grains 51 is formed by growing diamond crystal grains using the nanodiamond particles 71 as growth nuclei by a CVD method. As the raw material gas, a mixed gas of methane gas and hydrogen gas is used. Depending on the growth conditions and the like, oxygen gas, nitrogen gas or the like may be supplied into the CVD chamber. The ratio of methane gas to hydrogen gas shall be about 0.05% by volume to 10% by volume. The growth pressure is about 0.5 kPa to 100 kPa, and the growth temperature is about 350 ° C. to 1200 ° C. The crystal growth has anisotropy, and during the formation of the diamond layer 50, some of the diamond crystal grains come into contact with each other, and the growth of the diamond crystal grains located between them is hindered. Then, the diamond crystal grains that could grow without being hindered by other diamond crystal grains became the first diamond crystal grain 61, and the diamond crystal grains whose growth was hindered by the first diamond crystal grain 61 became the second diamond crystal grain 62. Become. As described above, the plurality of diamond crystal grains 51 are located above the second diamond crystal grain 62, are smaller in height than the first diamond crystal grain 61, and also form a part of the first surface 50A. Other diamond crystal grains that do not have a surface forming a part of the second surface 50B may be included.

In this way, the semiconductor device 100 according to the first embodiment can be manufactured.

By the way, when the density of nanodiamonds on the semiconductor laminated structure 20 is low, the surface of the semiconductor laminated structure 20 is hydrogenated for a long time due to hydrogen gas used for crystal growth of diamonds while the nanodiamonds are used as nuclei for crystal growth. You will be exposed to gas. Therefore, in the present embodiment, a diamond layer 70 composed of nanodiamond particles 71 having a high number density of ^{1 × 10 8} cm- ² to 1 × 10 ¹² cm- ^{2 is formed on the semiconductor laminated structure 20.} The surface of the semiconductor laminated structure 20 is substantially covered. As a result, it is possible to prevent the semiconductor laminated structure 20 from being exposed to hydrogen gas, prevent damage to the semiconductor laminated structure 20, and suppress deterioration of the characteristics of the manufactured semiconductor device 100. In FIG. 4, for convenience of explanation, there are gaps between the nanodiamond particles 71, but the nanodiamond particles 71 having an average particle size of 5 nm or more and 1 μm or less are 1 × 10 ⁸ cm ^-2 to 1 × 10 ¹² cm. ^When provided with a number density of -2, adjacent nanodiamond particles 71 come into contact with each other. Further, there may be nanodiamond particles 71 that overlap in the stacking direction of the semiconductor laminated structure 20.

FIG. 6 shows the sheet resistance of each semiconductor device. As shown in FIG. 7, the semiconductor device 6A is a semiconductor device in which a diamond layer is not formed on the semiconductor laminated structure 20 or the like. As shown in FIG. 1, the semiconductor device 6B is the semiconductor device 100 according to the first embodiment, and is a semiconductor device on which the diamond layer 50 is formed. As shown in FIG. 8, the semiconductor device 6C is a semiconductor device in which a diamond layer 950 composed of a plurality of large diamond crystal grains 81 equivalent to the first diamond crystal grains 61 is formed. In this semiconductor device 6C, diamond crystal grains 81 are grown on the semiconductor laminated structure 20 by a CVD method without providing nanodiamond particles having a small average particle size to form a diamond layer 950.

As shown in FIG. 6, in the semiconductor device 100 according to the first embodiment shown in the semiconductor device 6B, the sheet resistance in the semiconductor laminated structure 20 is about the same as that of the semiconductor device 6A, and the increase in the sheet resistance is suppressed. Has been done. From this, it can be confirmed that in the semiconductor device 100 according to the first embodiment, even if the diamond layer 50 is formed, the semiconductor laminated structure 20 is not damaged due to the formation of the diamond layer 50.

In the semiconductor device 6C, the sheet resistance is remarkably increased. This is because, when the diamond layer 950 is formed, the semiconductor laminated structure 20 is exposed to hydrogen gas for a long time, and the semiconductor laminated structure 20 is damaged such as desorption of Ga. An increase in sheet resistance leads to an increase in on-resistance.

FIG. 9 is a cross-sectional scanning electron microscope (SEM) image of the diamond layer 50 including the first diamond crystal grain 61 and the second diamond crystal grain 62 formed on the nitride semiconductor layer. FIG. 10 is an SEM image of the diamond layer 50 indicated by the arrow in FIG. 9 as viewed from above. In the formation of the diamond layer 50 shown in FIGS. 9 and 10, crystal growth was carried out for about 7 hours after the diamond layer 70 was formed. The thickness of the diamond layer 50 is about 2.5 μm. As shown in FIGS. 9 and 10, it is confirmed that the average particle size of the plurality of diamond crystal grains 51 constituting the diamond layer 50 on the second surface 50B is more than 1 μm.

FIG. 11 is a cross-sectional SEM image of the diamond layer at the time when the diamond is crystal-grown for about 10 minutes after the diamond layer 70 is formed. The nanodiamond particles 71 constituting the diamond layer 70 have an average particle size of about 10 nm and cannot be confirmed by SEM. However, the diamond crystal grains become larger by crystal growth for 10 minutes and are confirmed by SEM. It will be possible. As shown in FIG. 11, the crystal grains of diamond in this state are small, and the average particle size thereof is about 50 nm to 100 nm. However, by growing the crystals for a long time, the average particle size as shown in FIG. 10 can be obtained. Diamond crystal grains over 1 μm can be obtained.

(Second Embodiment)
Next, the semiconductor device according to the second embodiment will be described. In the semiconductor device 200 according to the second embodiment, as shown in FIG. 12, the insulating film 140 is formed on the semiconductor laminated structure 20, and the diamond layer 50 is formed on the insulating film 140. The thickness of the insulating film 140 is, for example, 0.5 nm or more and 10 nm or less. From the viewpoint of heat conduction, it is preferable that the insulating film 140 is not provided. On the other hand, in order to further suppress the damage to the semiconductor laminated structure 20 during the crystal growth of diamond, an insulating film 140 is formed on the semiconductor laminated structure 20 and a diamond layer is formed on the insulating film 140. 50 may be formed.

Examples of the material of the insulating film 140 include SiN (silicon nitride), SiO ₂ (silicon oxide), AlN ( _{aluminium nitride), Al 2} O ₃ (aluminum oxide), HfO ₂ (hafnium oxide) and the like.

Other configurations are the same as in the first embodiment.

(Third Embodiment)
Next, the semiconductor device according to the third embodiment will be described. In the semiconductor device 300 according to the third embodiment, as shown in FIG. 13, a diamond layer 50 is formed on the semiconductor laminated structure 20 formed on one surface 10a of the substrate 10, and the back surface 10b is formed on the back surface. The diamond layer 250 is formed. Thereby, a higher heat dissipation effect can be obtained. The back surface diamond layer 250 is an example of the second diamond layer.

The back surface diamond layer 250 formed on the other surface 10b, which is the back surface of the substrate 10, may be polycrystalline or single crystal. The back surface diamond layer 250 may be formed by the formation of growth nuclei and crystal growth, similarly to the diamond layer 50. As the back surface diamond layer 250, a single crystal diamond or a polycrystalline diamond may be bonded to the surface 10b. The thickness of the back surface diamond layer 250 is preferably 1 μm or more, more preferably 2.5 μm.

Other configurations are the same as in the first embodiment.

(Fourth Embodiment)
Next, the fourth embodiment will be described. A fourth embodiment relates to a discrete package of HEMTs. FIG. 14 is a diagram showing a discrete package according to the fourth embodiment.

In the fourth embodiment, as shown in FIG. 14, the back surface of the semiconductor device 1210 having the same structure as that of any one of the first to third embodiments is a land (die pad) 1233 using a die-attaching agent 1234 such as solder. It is fixed to. Further, a wire 1235d such as an Al wire is connected to the drain pad 1226d to which the drain electrode 108 is connected, and the other end of the wire 1235d is connected to the drain lead 1232d integrated with the land 1233. A wire 1235s such as an Al wire is connected to the source pad 1226s connected to the source electrode 107, and the other end of the wire 1235s is connected to a source lead 1232s independent of the land 1233. A wire 1235 g such as an Al wire is connected to a gate pad 1226 g connected to the gate electrode 109, and the other end of the wire 1235 g is connected to a gate lead 1232 g independent of the land 1233. Then, the land 1233, the semiconductor device 1210, and the like are packaged with the mold resin 1231 so that a part of the gate lead 1232g, a part of the drain lead 1232d, and a part of the source lead 1232s project.

Such a discrete package can be manufactured, for example, as follows. First, the semiconductor device 1210 is fixed to the land 1233 of the lead frame using a die attachant 1234 such as solder. Next, the gate pad 1226g is connected to the gate lead 1232g of the lead frame, the drain pad 1226d is connected to the drain lead 1232d of the lead frame, and the source pad 1226s is connected to the source of the lead frame by bonding using the wires 1235g, 1235d and 1235s. Connect to lead 1232s. Then, sealing is performed using the mold resin 1231 by the transfer molding method. Then, the lead frame is separated.

(Fifth Embodiment)
Next, the fifth embodiment will be described. A fifth embodiment relates to a PFC (Power Factor Correction) circuit including HEMT. FIG. 15 is a wiring diagram showing the PFC circuit according to the fifth embodiment.

The PFC circuit 1250 is provided with a switch element (transistor) 1251, a diode 1252, a choke coil 1253, capacitors 1254 and 1255, a diode bridge 1256, and an alternating current power supply (AC) 1257. Then, the drain electrode of the switch element 1251 and the anode terminal of the diode 1252 and one terminal of the choke coil 1253 are connected. The source electrode of the switch element 1251 is connected to one terminal of the capacitor 1254 and one terminal of the capacitor 1255. The other terminal of the capacitor 1254 and the other terminal of the choke coil 1253 are connected. The other terminal of the capacitor 1255 and the cathode terminal of the diode 1252 are connected. A gate driver is connected to the gate electrode of the switch element 1251. AC1257 is connected between both terminals of the capacitor 1254 via a diode bridge 1256. A direct current (DC) is connected between both terminals of the capacitor 1255. Then, in the present embodiment, the switch element 1251 uses a semiconductor device having the same structure as that of any of the first to third embodiments.

In manufacturing the PFC circuit 1250, for example, the switch element 1251 is connected to the diode 1252, the choke coil 1253, etc. by using solder or the like.

(Sixth Embodiment)
Next, the sixth embodiment will be described. A sixth embodiment relates to a power supply device including a HEMT, which is suitable for a server power supply. FIG. 16 is a wiring diagram showing a power supply device according to a sixth embodiment.

The power supply device is provided with a high-voltage primary circuit 1261 and a low-voltage secondary circuit 1262, and a transformer 1263 disposed between the primary circuit 1261 and the secondary circuit 1262.

The primary side circuit 1261 is provided with an inverter circuit connected between both terminals of the PFC circuit 1250 and the capacitor 1255 of the PFC circuit 1250 according to the fifth embodiment, for example, a full bridge inverter circuit 1260. The full-bridge inverter circuit 1260 is provided with a plurality of (four in this case) switch elements 1264a, 1264b, 1264c, and 1264d.

The secondary circuit 1262 is provided with a plurality of (three in this case) switch elements 1265a, 1265b, and 1265c.

In the present embodiment, the switch element 1251 of the PFC circuit 1250 constituting the primary side circuit 1261 and the switch elements 1264a, 1264b, 1264c and 1264d of the full bridge inverter circuit 1260 are the same as those of any of the first to third embodiments. A semiconductor device having a structure is used. On the other hand, ordinary MIS type FETs (field effect transistors) using silicon are used for the switch elements 1265a, 1265b and 1265c of the secondary side circuit 1262.

(7th Embodiment)
Next, the seventh embodiment will be described. A seventh embodiment relates to an amplifier with a HEMT. FIG. 17 is a wiring diagram showing the amplifier according to the seventh embodiment.

The amplifier is provided with a digital predistortion circuit 1271, mixers 1272a and 1272b, and a power amplifier 1273.

The digital predistortion circuit 1271 compensates for the non-linear distortion of the input signal. The mixer 1272a mixes the input signal and the AC signal in which the non-linear distortion is compensated. The power amplifier 1273 includes a semiconductor device having a structure similar to that of any one of the first to third embodiments, and amplifies an AC signal and a mixed input signal. In the present embodiment, for example, the output side signal can be mixed with the AC signal by the mixer 1272b and sent to the digital predistortion circuit 1271 by switching the switch. This amplifier can be used as a high frequency amplifier and a high output amplifier. The high frequency amplifier can be used, for example, in a transmitter / receiver for a mobile phone base station, a radar device, and a microwave generator.

Although the preferred embodiments and the like have been described in detail above, they are not limited to the above-described embodiments and the like, and various modifications and substitutions are made to the above-mentioned embodiments and the like without departing from the scope of claims. Can be added.

Hereinafter, various aspects of the present disclosure will be described together as an appendix.

(Appendix 1)
Semiconductor laminated structure and
A diamond layer formed on the semiconductor laminated structure, having a first surface on the semiconductor laminated structure side and a second surface on the side opposite to the first surface, and composed of a plurality of diamond crystal grains. ,
Have,
The number density of the plurality of diamond crystal grains on the first surface is higher than the number density on the second surface.
A semiconductor device characterized in that the average particle size of the plurality of diamond crystal grains on the first surface is 1 μm or less.
(Appendix 2)
The semiconductor device according to Appendix 1, wherein the number density of the plurality of diamond crystal grains on the first surface is 1 × 10 ⁸ cm- ^{2 or more.}
(Appendix 3)
The semiconductor device according to Appendix 1 or 2, wherein the average particle size of the plurality of diamond crystal grains on the first surface is 5 nm or more and 100 nm or less.
(Appendix 4)
The semiconductor device according to any one of Supplementary note 1 to 3, wherein the average particle size of the plurality of diamond crystal grains on the first surface is 5 nm or more and 20 nm or less.
(Appendix 5)
The semiconductor device according to any one of Supplementary note 1 to 4, wherein the thickness of the diamond layer is 1 μm or more.
(Appendix 6)
A substrate having the semiconductor laminated structure formed on one surface,
A second diamond layer in contact with the other surface of the substrate,
The semiconductor device according to any one of Supplementary note 1 to 5, wherein the semiconductor device has.
(Appendix 7)
The semiconductor device according to any one of Supplementary note 1 to 6, further comprising an insulating film formed between the semiconductor laminated structure and the diamond layer.
(Appendix 8)
The semiconductor device according to Appendix 7, wherein the thickness of the insulating film is 0.5 nm or more and 10 nm or less.
(Appendix 9)
The semiconductor laminated structure is
An electron traveling layer formed of a nitride semiconductor and
An electron supply layer formed of a nitride semiconductor on the electron traveling layer,
Have,
The semiconductor device according to any one of Supplementary note 1 to 8, further comprising a gate electrode, a source electrode, and a drain electrode formed on the electron supply layer.
(Appendix 10)
A step of forming a diamond layer composed of a plurality of diamond crystal grains having a first surface on the semiconductor laminated structure side and a second surface on the side opposite to the first surface on the semiconductor laminated structure. Have,
The step of forming the diamond layer is
A step of providing a plurality of diamond particles having an average particle size of 1 μm or less on the semiconductor laminated structure, and
A step of crystal growth using a part of the plurality of diamond particles as growth nuclei,
A method for manufacturing a semiconductor device.
(Appendix 11)
An amplifier comprising the semiconductor device according to any one of Supplementary notes 1 to 9.
(Appendix 12)
A power supply device comprising the semiconductor device according to any one of Supplementary notes 1 to 9.

10: Substrate 20: Semiconductor laminated structure 50: Diamond layer 50A: First surface 50B: Second surface 51: Diamond crystal grains 61: First diamond crystal grains 61A: Third surface 61B: Fourth surface 62: Second diamond crystal Grain 62A: Surface 70: Diamond layer 71: Nano diamond particle 81: Diamond crystal grain 100, 200, 300: Semiconductor device 140: Insulation film 250: Back surface diamond layer

Claims (5)

Semiconductor laminated structure and
A diamond layer formed on the semiconductor laminated structure, having a first surface on the semiconductor laminated structure side and a second surface on the side opposite to the first surface, and composed of a plurality of diamond crystal grains. ,
Have,
The number density of the plurality of diamond crystal grains on the first surface is higher than the number density on the second surface.
A semiconductor device characterized in that the average particle size of the plurality of diamond crystal grains on the first surface is 1 μm or less. The semiconductor device according to claim 1, wherein the number density of the plurality of diamond crystal grains on the first surface is 1 × 10 ⁸ cm- ^{2 or more.} A substrate having the semiconductor laminated structure formed on one surface,
A second diamond layer in contact with the other surface of the substrate,
The semiconductor device according to claim 1 or 2, wherein the semiconductor device has. The semiconductor device according to any one of claims 1 to 3, further comprising an insulating film formed between the semiconductor laminated structure and the diamond layer. The semiconductor laminated structure is
An electron traveling layer formed of a nitride semiconductor and
An electron supply layer formed of a nitride semiconductor on the electron traveling layer,
Have,
The semiconductor device according to any one of claims 1 to 4, further comprising a gate electrode, a source electrode, and a drain electrode formed on the electron supply layer.

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