JP4872422B2 - Pn junction diode and method of manufacturing pn junction diode - Google Patents

Description

  The present invention relates to a pn junction diode and a method of manufacturing a pn junction diode.

Non-Patent Document 1 describes a nanocolumn made of GaN provided on a sapphire substrate. The nanocolumn described in Non-Patent Document 1 is grown on Al ₂ O ₃ using an RF gun and has an average diameter of 40 to 45 nm. This nanocolumn has a multilayer structure composed of GaN / Al _0.18 Ga _0.82 N. Patent Document 1 discloses a light-emitting diode including an n-type GaN nanorod, an InGaN quantum well provided on the n-type GaN nanorod, and a p-type GaN nanorod provided on the InGaN quantum well. ing.
Masaki Yoshizawa et.al, “Self-organization of GaN / Al0.18Ga0.82Nmulti-layer nano-columns on (0001) Al2O3 by RF molecularbeam epitaxy for featuring GaN quantum disks”, Journal of CrystalGrowth, 1998, 189/190, p138 -p141. JP 2005-228936 A

  Conventionally, Si is used for a power device to which a relatively high voltage is applied. However, when a Si semiconductor is used as a power device, there are limitations in terms of withstand voltage and on-resistance. Therefore, there is GaN which is a wide gap semiconductor as a material replacing Si. However, a conventional bulk type GaN single crystal (hereinafter referred to as a bulk GaN single crystal) has a relatively high dislocation density compared to other semiconductor crystals. A power device using this bulk GaN single crystal is currently in the research stage.

  On the other hand, the present inventors have found that the above-mentioned nanocolumns made of GaN have a lower dislocation density than conventional bulk GaN single crystals. Therefore, the present inventors have studied the device structure that is suitable for a power device, not a light emitting diode as described in Patent Document 1, and can make use of the characteristics of the nanocolumn, and have achieved the present invention. An object of the present invention is to provide a pn junction diode for a power device having a nanocolumn made of GaN.

  The present invention relates to a pn junction diode for a power device, comprising 1) a first electrode, 2) a nanocolumn region having a plurality of nanocolumns provided on the first electrode, and 3) on the nanocolumn region. A semiconductor portion of the second conductivity type provided; and 4) a second electrode provided on the semiconductor portion. Each of the nanocolumns extends in a direction from the first electrode toward the semiconductor portion, and is formed of GaN or AlGaN. A first nanocolumn part of the first conductivity type made of and a second nanocolumn part of the second conductivity type made of GaN or AlGaN, wherein the first nanocolumn and the second nanocolumn are connected by homojunction. Features. Furthermore, the pn junction diode of the present invention may further include an AlN region provided between the first electrode and the nanocolumn region.

  The first nanocolumn part and the second nanocolumn part form a pn junction, and the pn junction is provided for each of the plurality of nanocolumns. For this reason, the location where the pn junction is provided is dispersed in the pn junction diode. Therefore, since this pn junction diode has a large thermal radiation and is difficult to increase in temperature, good characteristics are maintained even for a large current value. Therefore, this pn junction diode is suitable for a power device, for example. Thus, according to the pn junction diode of the present invention, a pn junction diode for a power device having a nanocolumn made of GaN is provided. In addition, in such a nanocolumn made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn, so that the crystal structure has a high quality.

  The pn junction diode of the present invention may further include an insulating portion provided between the plurality of nanocolumns. This insulating portion improves the mechanical strength and withstand voltage of the pn junction diode.

  The present invention also relates to a pn junction diode for a power device, comprising 1) a first electrode, 2) a substrate provided on the first electrode, and 3) a plurality of nanocolumns on the substrate. A nanocolumn region provided; 4) a second conductivity type semiconductor portion provided on the nanocolumn region; and 5) a second electrode provided on the semiconductor portion. The first nanocolumn portion of the first conductivity type made of GaN or AlGaN and the second nanocolumn portion of the second conductivity type made of GaN or AlGaN, the first nanocolumn and the second nanocolumn, Are connected by homojunction. Furthermore, the pn junction diode of the present invention may further include an AlN region provided between the substrate and the nanocolumn, and the substrate is preferably made of GaAs or Si.

  The first nanocolumn part and the second nanocolumn part form a pn junction, and the pn junction is provided for each of the plurality of nanocolumns. For this reason, the location where the pn junction is provided is dispersed in the pn junction diode. Therefore, since this pn junction diode has a large thermal radiation and is difficult to increase in temperature, good characteristics are maintained even for a large current value. Therefore, this pn junction diode is suitable for a power device, for example. Thus, according to the pn junction diode of the present invention, a pn junction diode for a power device having a nanocolumn made of GaN is provided. In addition, in such a nanocolumn made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn, so that the crystal structure has a high quality. Further, since the substrate is made of GaAs or Si, dicing is facilitated.

In the pn junction diode of the present invention, the dislocation density of the nanocolumn is preferably lower than 10 ⁵ cm ⁻² . Thus, the crystal quality of the nanocolumn is improved.

  The present invention relates to a method of manufacturing a pn junction diode for a power device, and 1) a first conductivity type substrate having a first conductivity type, and a plurality of first nanocolumn portions made of GaN formed of GaAs or Si. A first nanocolumn portion forming step to be formed thereon; and 2) a second nanocolumn portion forming a plurality of second nanocolumn portions made of GaN, which are of the second conductivity type, at the ends of the plurality of first nanocolumn portions. And 3) after the formation of the second nanocolumn, by supplying more Ga than the supply amount of Ga in each step of the first nanocolumn portion forming step and the second nanocolumn portion forming step, And a semiconductor part forming step of forming a semiconductor part having a second conductivity type in which ends are coupled to each other. Further, the manufacturing method of the pn junction diode of the present invention includes 1) a first electrode forming step of forming a second electrode on the semiconductor portion after forming the semiconductor portion, and 2) after forming the second electrode. The method may further include a substrate removing step for removing the substrate, and 3) a second electrode forming step for forming the first electrode at the end of the first nanocolumn portion after removing the substrate.

  The present invention also relates to a method of manufacturing a pn junction diode for a power device. 1) A first conductivity type is shown, in which a plurality of first nanocolumn parts made of GaN are replaced with a first conductivity type made of GaAs or Si. A first nanocolumn part forming step formed on the substrate, and 2) a second nanocolumn showing a second conductivity type and forming a plurality of second nanocolumn parts made of GaN at end portions of the plurality of first nanocolumn parts. And 3) after the formation of the second nanocolumn, by supplying more Ga than the supply amount of Ga in each step of the first nanocolumn portion formation step and the second nanocolumn portion formation step, the second nanocolumn And a semiconductor part forming step of forming a semiconductor part having a second conductivity type in which end parts of the parts are coupled to each other. The manufacturing method of the pn junction diode of the present invention includes 1) a first electrode forming step of forming a second electrode on the semiconductor portion after forming the semiconductor portion, and 2) a substrate after forming the second electrode. And a second electrode forming step of forming a first electrode thereon.

  The first nanocolumn part and the second nanocolumn part form a pn junction, and the pn junction is provided for each of the plurality of nanocolumns. For this reason, the location where the pn junction is provided is dispersed in the pn junction diode. Therefore, the manufactured pn junction diode has a large heat radiation and is difficult to increase in temperature, and therefore, good characteristics are maintained even for a large current value. Therefore, this pn junction diode is suitable for a power device, for example. Thus, according to the method for manufacturing a pn junction diode of the present invention, a pn junction diode for a power device having a nanocolumn made of GaN is manufactured. In addition, in such a nanocolumn made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn, so that the crystal structure has a high quality. Therefore, the pn junction diode manufacturing method of the present invention can manufacture a high quality pn junction diode as compared with a conventional pn junction diode made of bulk GaN single crystal.

  According to the present invention, a pn junction diode for a power device having a nanocolumn made of GaN can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the description of the drawings, where possible, the same reference numerals are assigned to the same elements, and duplicate descriptions may be omitted.

<First Embodiment>
FIG. 1 is a cross-sectional view showing a configuration of a pn junction diode 1a according to the first embodiment. The pn junction diode 1a is a power device including a first electrode 4a, a nanocolumn region 5a, an AlN region 7a, a semiconductor portion 12a, and a second electrode 14a. The nanocolumn region 5a is provided on the first electrode 4a via the AlN region 7a, and has a plurality of nanocolumns 10a (nano-colmns). The semiconductor part 12a is provided on the nanocolumn region 5a, and the second electrode 14a is provided on the semiconductor part 12a.

Each of the nanocolumns 10a extends in the direction from the first electrode 4a toward the semiconductor portion 12a, and includes a first nanocolumn portion 6a and a second nanocolumn portion 8a. Each of the nanocolumns 10a is provided apart from each other. The dislocation density of the nanocolumn 10a is lower than 10 ⁵ cm ⁻² . The first nanocolumn portion 6a is provided on the first electrode 4a via the AlN region 7a, and is made of GaN showing the first conductivity type (one of p-type or n-type). The first nanocolumn portion 6a is connected to the first electrode 4a. An AlN region 7a made of AlN is provided between the nanocolumn region 5a and the first electrode 4a, more specifically, between the first nanocolumn portion 6a and the first electrode 4a, and the first nanocolumn portion 6a The AlN region 7a is connected to the first electrode 4a. The second nanocolumn portion 8a is provided at each end portion of the plurality of first nanocolumns and is made of GaN indicating the second conductivity type (the other of the p-type and the n-type). The first nanocolumn part 6a and the second nanocolumn part 8a are connected by homojunction. The first nanocolumn part 6a and the second nanocolumn part 8a form a pn junction. The semiconductor portion 12a is provided at each end of the plurality of second nanocolumn portions 8a and is made of GaN showing the second conductivity type. The semiconductor part 12a has a thickness of 1 μm or more. Currently, the semiconductor portion 12a having a thickness of about 2 μm is supplied. The semiconductor part 12a is connected to the second nanocolumn part 8a. The second electrode 14a is an electrode provided on the semiconductor portion 12a and is connected to the semiconductor portion 12a. For example, Si is preferable as the n-type impurity, and Mg or Be is preferable as the p-type impurity. The concentration of the n-type impurity is, for example, 10 ¹⁷ cm ⁻³ or less. Currently, a concentration of n-type impurities of about 10 ¹⁴ cm ⁻³ is supplied. Further, the concentration of the p-type impurity is 10 ¹⁸ cm ⁻³ or more.

  The first electrode 4a is composed of Ti / Au / Ti / Au (each thickness is about 20/100/20/300 nm) when the first conductivity type is n-type and the second conductivity type is p-type. Has been. The first electrode 4a is made of Ni / Au (each thickness is about 50/100 nm) when the first conductivity type is p-type and the second conductivity type is n-type. The second electrode 14a is provided on the semiconductor unit 12a and is connected to the semiconductor unit 12a. The second electrode 14a is made of Ni / Au (each thickness is about 50/100 nm) when the first conductivity type is n-type and the second conductivity type is p-type. The second electrode 14a is composed of Ti / Au / Ti / Au (each thickness is about 20/100/20/300 nm) when the first conductivity type is p-type and the second conductivity type is n-type. Has been.

  When the first conductivity type is n-type and the second conductivity type is p-type, the length L1a of the first nanocolumn portion 6a indicating the n-type is 1 μm or more. Currently, a length L1a of about 3 μm is realized in the first nanocolumn portion 6a showing the n-type. Further, the length L2a of the second nanocolumn portion 8a showing the p-type is 0.1 μm or more. Currently, a length L2a of about 0.5 μm is realized in the second nanocolumn portion 8a showing the p-type. The length L1a of the first nanocolumn part 6a is thicker than the length L2a of the second nanocolumn part 8a (FIG. 1 shows the case where the first conductivity type is n-type and the second conductivity type is p-type). ) On the other hand, when the first conductivity type is p-type and the second conductivity type is n-type, the length L1a of the first nanocolumn part 6a indicating the p-type is 1 μm or more. Currently, a length L1a of about 3 μm is realized in the first nanocolumn portion 6a showing the p-type. The length L2a of the second nanocolumn portion 8a showing the n-type is 0.1 μm or more. Currently, a length L2a of about 0.5 μm is realized in the second nanocolumn portion 8a showing the n-type. The length L1a of the first nanocolumn part 6a is thinner than the length L2a of the second nanocolumn part 8a.

  In the pn junction diode 1a according to the first embodiment described above, the first nanocolumn part 6a and the second nanocolumn part 8a form a pn junction. Accordingly, a pn junction diode for a power device having a nanocolumn 10a made of GaN is provided. Further, in such a nanocolumn 10a made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. Therefore, the crystal structure of the pn junction diode 1a is high quality. The pn junction of the pn junction diode 1a is provided for each nanocolumn 10a. Thus, the locations where the pn junctions are provided are dispersed in the pn junction diode 1a. Therefore, since heat radiation is large and it is difficult to increase the temperature, good characteristics are maintained even for a large current value. For this reason, the pn junction diode 1a is suitable for a power device, for example. Further, the first electrode 4a made of an alloy (Ti / Au / Ti / Au or Ni / Au) has excellent heat conductivity, and therefore has high heat dissipation. In addition, when the first nanocolumn portion 6a is n-type, the first nanocolumn portion 6a has a low contact resistance with respect to the first electrode 4a of the alloy (Ti / Au / Ti / Au), so that heat generation due to current is reduced. The Further, since the substrate 2a is made of GaAs or Si, dicing is facilitated.

Next, a manufacturing method of the pn junction diode 1a according to the first embodiment will be described with reference to FIG. The manufacturing method of the pn junction diode 1a described below includes a substrate preparation step A1 shown in FIG. 2A, a formation step A2 shown in FIG. 2B, and a first electrode formation step A3 shown in FIG. 2D, a substrate removal step A4 shown in FIG. 2D and a second electrode formation step A5 shown in FIG. First, the substrate preparation step A1 will be described with reference to FIG. As shown in FIG. 2A, the following substrate 21a is prepared. The substrate 21a is a Si substrate having a surface orientation (111) and having a diameter of at least 7.6 × 10 ⁻² m (3 inches) and having a first conductivity type. Currently, a Si substrate having a diameter of 3.0 × 10 ⁻¹ m (12 inches) is supplied. Since the pn junction diode 1a can be manufactured using such a large-diameter substrate, the number of pn junction diodes 1a obtained from a single substrate increases. Therefore, manufacturing cost and manufacturing time can be reduced. After this substrate 21a is RCA cleaned, the cleaned substrate 21a is placed in the MBE apparatus. With this MBE apparatus, the substrate 21a is heated in a vacuum at a temperature in the range of 850 degrees Celsius to 950 degrees Celsius for 10 minutes to 40 minutes. Thereby, the natural oxide film formed on the substrate 21a is removed. The substrate 21a may be a GaAs substrate. This GaAs substrate is a substrate having a surface orientation (111) and a diameter of 7.6 × 10 ⁻² m (3 inches) or more indicating the first conductivity type. Currently, a GaAs substrate having a diameter of 1.5 × 10 ⁻¹ m (6 inches) is supplied (the substrate preparation step A1).

Next, the formation step A2 will be described with reference to FIG. In the process described below, an RF gun and MBE (Molecular Beam Epitaxy) to which a K cell is attached are used. As materials, Ga (7N) and Al (7N), N ₂ (6N) for RF gun, Si cell for dopant, Mg cell, and K cell are used. The forming step A2 includes a nanocolumn forming step and a semiconductor part forming step. First, the nanocolumn forming process will be described. Al is deposited on the surface of the substrate 21a at 500 degrees Celsius to form a 1-3 monolayer. Thereafter, active nitrogen (N) is supplied from the RF gun. Thereby, an AlN region 71a made of AlN is formed on the surface of the substrate 21a. Thereafter, in the temperature range of 750 degrees Celsius to 850 degrees Celsius, Ga and active nitrogen are supplied to the surface of the substrate 21a provided with the AlN region 71a to form the nanocolumn 10a. At this time, by making the supply amount of active nitrogen larger than the supply amount of Ga, nucleation of Ga and migration of GaN are suppressed. As a result, nanocolumns grow in the (0001) growth direction on the AlN region 71a, and the nanocolumns 10a are formed.

The formation of the first nanocolumn part 6a and the second nanocolumn part 8a in the nanocolumn 10a will be described. First, after forming the first nanocolumn portion 6a showing the n-type, the second nanocolumn portion 8a showing the p-type is formed (when the first conductivity type is n-type and the second conductivity type is p-type). explain. For example, Si is preferable as the n-type impurity, and Mg or Be is preferable as the p-type impurity. The concentration of the n-type impurity is, for example, 10 ¹⁷ cm ⁻³ or less. Currently, a concentration of n-type impurities of about 10 ¹⁴ cm ⁻³ is supplied. Further, the concentration of the p-type impurity is 10 ¹⁸ cm ⁻³ or more.

(First nanocolumn part forming step) The first nanocolumn part 6a showing the n-type is grown on the AlN region 71a to 1 μm or more. At present, it is also possible to grow the first nanocolumn portion 6a showing n-type to about 3 μm. This growth is performed while adding n-type impurities. Thereby, a plurality of first nanocolumn portions 6a exhibiting n-type are formed (the first nanocolumn portion forming step). The conditions for forming the first nanocolumn part are as follows.
Growth temperature: 800 degrees Celsius N ₂ Flow rate: 6 sccm
RF input: 400W
Pressure: 2.7 × 10 ⁻³ Pa (2 × 10 ⁻⁵ Torr)
Ga cell temperature: 1100 degrees Celsius Mg cell temperature: 600 degrees Celsius (shutter closed)
Si cell temperature: 1000 degrees Celsius (shutter open)
In this case, by appropriately setting the thickness and carrier concentration of the first nanocolumn portion 6a showing the n-type, it is possible to realize a suitable breakdown that does not cause punch-through. The n-type first nanocolumn portion 6a is a dislocation-free high-grade drift layer.

(Second Nanocolumn Part Forming Step) Each end of each of the plurality of first nanocolumn parts 6a showing the n-type formed as described above is provided with 0.1 μm or more of each of the plurality of second nanocolumn parts 8a showing the p-type. To grow. At present, it is also possible to grow the second nanocolumn portion 8a showing the p-type to about 0.5 μm. This growth is performed while adding p-type impurities. As a result, a plurality of second nanocolumn portions 8a exhibiting p-type are formed at each end of the plurality of first nanocolumn portions 6a exhibiting n-type (the second nanocolumn portion forming step). The formation conditions of the second nanocolumn part are as follows.
Growth temperature: 800 degrees Celsius N ₂ Flow rate: 6 sccm
RF input: 400W
Pressure: 2.7 × 10 ⁻³ Pa (2 × 10 ⁻⁵ Torr)
Ga cell temperature: 1100 degrees Celsius Mg cell temperature: 600 degrees Celsius (shutter open)
Si cell temperature: 1000 degrees Celsius (shutter closed)

Next, in the case where the first nanocolumn portion 6a indicating p-type is formed and the second nanocolumn portion 8a indicating n-type is formed (when the first conductivity type is p-type and the second conductivity type is n-type). explain. For example, Si is preferable as the n-type impurity, and Mg or Be is preferable as the p-type impurity. The concentration of the n-type impurity is, for example, 10 ¹⁷ cm ⁻³ or less. Currently, a concentration of n-type impurities of about 10 ¹⁴ cm ⁻³ is supplied. Further, the concentration of the p-type impurity is 10 ¹⁸ cm ⁻³ or more.

  (First nanocolumn part forming step) The first nanocolumn part 6a showing the p-type is grown on the AlN region 71a to 1 μm or more. Currently, it is also possible to grow the first nanocolumn portion 6a showing the p-type to about 3 μm. This growth is performed while adding p-type impurities. Thereby, a plurality of first nanocolumn parts 6a exhibiting p-type are formed (the first nanocolumn part forming step).

  (Second Nanocolumn Part Forming Step) Each end of each of the plurality of first nanocolumn parts 6a showing the p-type formed as described above is provided with 0.1 μm or more of each of the plurality of second nanocolumn parts 8a showing the n-type. To grow. At present, it is also possible to grow the second nanocolumn portion 8a showing the n-type to about 0.5 μm. This growth is performed while adding n-type impurities. As a result, a plurality of second nanocolumn portions 8a exhibiting n-type are formed at each end of the plurality of first nanocolumn portions 6a exhibiting p-type (the second nanocolumn portion forming step). In this case, by appropriately setting the thickness and carrier concentration of the first nanocolumn portion 6a showing the n-type, it is possible to realize a suitable breakdown that does not cause punch-through. The n-type second nanocolumn portion 8a becomes a high-quality drift layer without dislocation.

  Next, the semiconductor part forming step will be described. After the formation of the nanocolumn 10a in the nanocolumn formation step described above, by supplying more Ga than the supply amount of Ga in each step of the first nanocolumn portion formation step and the second nanocolumn portion formation step (another expression is used). For example, the ratio of Ga supply amount and active nitrogen supply amount (Ga supply amount) / (Active nitrogen supply amount) is increased as compared with the formation of nanocolumns 10a), Ga nucleation, Increases Ga migration. Thereby, the edge part (edge part of the 2nd nanocolumn part 8a) of the adjacent nanocolumn 10a is couple | bonded. Thereafter, the supply of Ga and active nitrogen is continued at the same supply amount as described above until the thickness of the semiconductor portion 12a from the second nanocolumn portion 8a (the end portion of the second nanocolumn portion 8a) reaches 10 μm or more. At present, it is possible to form the semiconductor portion 12a having a thickness of about 1000 μm. This semiconductor part forming step is performed while supplying the second conductivity type impurity at a concentration similar to that of the second nanocolumn part 8a. As a result, the semiconductor part 121a is formed on the second nanocolumn part 8a (the end part of the second nanocolumn part 8a) (the semiconductor part forming step). Above, formation process A2 is complete | finished.

  Next, the first electrode formation step A3 will be described with reference to FIG. In the first electrode formation step A3, the second electrode 14a is formed on the semiconductor portion 121a. When the semiconductor portion 121a exhibits p-type conductivity (when the first conductivity type is n-type and the second conductivity type is p-type), Ni / Au (each thickness is about 50/100 nm) on the surface of the semiconductor portion 121a. The second electrode 14a as a p-type electrode of about 10 mm square is obtained using a lift-off method. Further, when the semiconductor portion 121a exhibits n-type conductivity (when the first conductivity type is p-type and the second conductivity type is n-type), Ti / Au / Ti / Au (each of which is formed on the surface of the semiconductor portion 121a). After vapor deposition of a thickness of about 20/100/20/300 nm, the second electrode 14a as an n-type electrode of about 10 mm square is obtained using a lift-off method. Note that a guard ring can be provided on the surface of the semiconductor portion 121a. This guard ring can be formed by ion implantation or the like using a metal mask (the first electrode forming step).

Next, the substrate removal step A4 will be described with reference to FIG. In this substrate removal step A4, the substrate 21a is separated from the nanocolumns 10a using a solution showing strong acidity or strong alkalinity. As for this solution, HF + HNO ₃ (further added with CH ₃ COOH) or the like is used for Si, and H ₂ SO ₄ + H ₂ O ₂ + H ₂ O or aqua regia is used for GaAs. Is used. Thereby, an increase in drive voltage is suppressed. Further, the warp of the semiconductor portion 121a is also eliminated (the substrate removing process).

  Next, the second electrode formation step A5 will be described with reference to FIG. In the second electrode formation step A5, after the substrate 21a is separated, the first electrode 41a is formed on the first nanocolumn portion 6a (the end portion of the first nanocolumn portion 6a) instead of the separated substrate 21a. . When the first nanocolumn portion 6a exhibits n-type conductivity (when the first conductivity type is n-type and the second conductivity type is p-type), the end of the first nanocolumn portion 6a is Ti / Au / Ti. The first electrode 41a as the n-type electrode is obtained by evaporating / Au (each thickness is about 20/100/20/300 nm). When the first nanocolumn part 6a exhibits p-type conductivity (when the first conductivity type is p-type and the second conductivity type is n-type), Ni / Au (each of the first nanocolumn part 6a with respect to the end of the first nanocolumn part 6a) The first electrode 41a as a p-type electrode is obtained by vapor-depositing a thickness of about 50/100 nm. Next, dicing is performed along the line indicated by reference numeral D1 in FIG. Thereby, the pn junction diode 1a is obtained (the second electrode forming step). In addition, since the semiconductor part 121a is made of GaN, dicing is easy as compared with a sapphire substrate or the like.

  As described above, the first nanocolumn portion 6a and the second nanocolumn portion 8a form a pn junction. Therefore, according to the manufacturing method of the pn junction diode 1a according to the first embodiment, a pn junction diode for a power device having the nanocolumn 10a made of GaN is manufactured. Further, in such a nanocolumn 10a made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. Therefore, the crystal structure of the pn junction diode 1a is high quality.

<Second Embodiment>
FIG. 3A is a cross-sectional view showing a configuration of a pn junction diode 1b according to the second embodiment. The pn junction diode 1b is a power device including a substrate 2b, a first electrode 4b, a nanocolumn region 5b, a first nanocolumn portion 6b, an AlN region 7b, a second nanocolumn portion 8b, a nanocolumn 10b, a semiconductor portion 12b, and a second electrode 14b. is there. Each of the nanocolumn region 5b, the first nanocolumn portion 6b, the AlN region 7b, the second nanocolumn portion 8b, the nanocolumn 10b, the semiconductor portion 12b, the second electrode 14b, the length L1b, and the length L2b is the same as that in the first embodiment described above. This is the same as each of the nanocolumn region 5a, the first nanocolumn portion 6a, the AlN region 7a, the second nanocolumn portion 8a, the nanocolumn 10a, the semiconductor portion 12a, the second electrode 14a, the length L1a, and the length L2a of the pn junction diode 1a. is there. In the following, among the components of the pn junction diode 1b, detailed description of the same components as the pn junction diode 1a is omitted, and the substrate 2b and the first electrode 4b that are components different from the pn junction diode 1a are omitted. This will be described in detail.

The first electrode 4b is made of a conductive metal such as Al. The substrate 2b is a low-resistance substrate having a plane orientation (111) and showing the first conductivity type. The substrate 2b is provided on the first electrode 4b, and the first electrode 4b is connected to the substrate 2b. A plurality of first nanocolumn portions 6b are erected on the substrate 2b, and the substrate 2b is connected to the first nanocolumn portions 6b. More specifically, the substrate 2b is connected to the AlN region 7b. When the substrate 2b is Si, the first electrode 4b is an Al—Si alloy. The substrate 2b may be a GaAs substrate. This GaAs substrate is a substrate having a surface orientation (111) and a diameter of 7.6 × 10 ⁻² m (3 inches) or more indicating the first conductivity type. Currently, a GaAs substrate having a diameter of 1.5 × 10 ⁻¹ m (6 inches) is supplied.

  In the pn junction diode 1b according to the third embodiment described above, the first nanocolumn part 6b and the second nanocolumn part 8b form a pn junction. Accordingly, a pn junction diode for a power device having a nanocolumn 10b made of GaN is provided. Further, in such a nanocolumn 10b made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. For this reason, the crystal structure of the pn junction diode 1b is of high quality. The pn junction included in the pn junction diode 1b is provided for each nanocolumn 10b. Thus, the locations where the pn junctions are provided are dispersed in the pn junction diode 1b. Therefore, since heat radiation is large and it is difficult to increase the temperature, good characteristics are maintained even for a large current value. For this reason, the pn junction diode 1b is suitable for a power device, for example. Moreover, since the substrate 2b made of Si and the first electrode 4b made of an alloy are excellent in thermal conductivity, they have high heat dissipation.

  Next, with reference to FIG. 4, the manufacturing method of the pn junction diode 1b which concerns on 2nd Embodiment is demonstrated. The manufacturing method of the pn junction diode 1b described below includes a substrate preparation step B1 shown in FIG. 4A, a formation step B2 shown in FIG. 4B, and a first electrode formation step B3 shown in FIG. And a second electrode formation step B4 shown in FIG. The substrate preparation step B1, the formation step B2, and the first electrode formation step B3 are respectively the substrate preparation step A1, the formation step A2, and the first step in the method of manufacturing the pn junction diode 1a according to the first embodiment described above. This is performed in the same manner as in each of the electrode forming steps A3. In this case, in the manufacturing method of the pn junction diode 1a described above, instead of the substrate 21a, the first nanocolumn part 6a, the AlN region 71a, the second nanocolumn part 8a, the nanocolumn 10a, the semiconductor part 121a, and the second electrode 14a, The substrate 21b, the first nanocolumn portion 6b, the AlN region 71b, the second nanocolumn portion 8b, the nanocolumn 10b, the semiconductor portion 121b, and the second electrode 14b are used. In the above, the process similar to that of the pn junction diode 1a has been described. Subsequently, the second electrode formation step B4 shown in FIG. 4D, which is different from the method for manufacturing the pn junction diode 1a, will be described in detail. Note that the method of manufacturing the pn junction diode 1b according to the second embodiment does not include the substrate removal step of the method of manufacturing the pn junction diode 1a according to the first embodiment.

  The second electrode formation step B4 will be described with reference to FIG. After the first electrode formation step B3 (the substrate 2b is not removed), Al is evaporated on the surface of the substrate 21b to form the first electrode 41b. In particular, when the substrate 21b is a Si substrate, first, the oxide film on the surface of the substrate 21b is removed using buffered hydrofluoric acid, and then Al—Si (Si is contained at about 1 weight percent) is formed on the surface using a sputtering method. Form. In this case, an ohmic electrode is obtained by annealing at about 450 degrees Celsius for about 30 minutes. Thereby, the first electrode 41b is formed. Next, dicing is performed along the line indicated by reference numeral D2 in FIG. Thereby, the pn junction diode 1b is obtained.

  As described above, the first nanocolumn portion 6b and the second nanocolumn portion 8b form a pn junction. Therefore, according to the method of manufacturing the pn junction diode 1b according to the second embodiment, a pn junction diode for a power device having the nanocolumn 10b made of GaN is manufactured. Further, in such a nanocolumn 10b made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. For this reason, the crystal structure of the pn junction diode 1b is of high quality.

<Third Embodiment>
FIG. 3B is a cross-sectional view showing a configuration of a pn junction diode 1c according to the third embodiment. The pn junction diode 1c includes a first electrode 4c, a nanocolumn region 5c, a first nanocolumn portion 6c, an AlN region 7c, a second nanocolumn portion 8c, a nanocolumn 10c, a semiconductor portion 12c, a second electrode 14c, and an insulating portion 16c. It is. Each of the first electrode 4c, the nanocolumn region 5c, the first nanocolumn portion 6c, the AlN region 7c, the second nanocolumn portion 8c, the nanocolumn 10c, the semiconductor portion 12c, the second electrode 14c, the length L1c, and the length L2c is as described above. First electrode 4a, nanocolumn region 5a, first nanocolumn portion 6a, AlN region 7a, second nanocolumn portion 8a, nanocolumn 10a, semiconductor portion 12a, second electrode 14a, length of pn junction diode 1a according to the first embodiment It is the same as each of L1a and length L2a. In the following, detailed description of the same components as the pn junction diode 1a is omitted, and the insulating portion 16c that is a different component from the pn junction diode 1a will be described in detail. The insulating portion 16c, which is a component different from the pn junction diode 1a, is provided between the plurality of nanocolumns 10c. The insulating portion 16c is made of an inorganic material such as SOG (Spin On Glass).

  In the pn junction diode 1c according to the third embodiment described above, the first nanocolumn part 6c and the second nanocolumn part 8c form a pn junction. Accordingly, a pn junction diode for a power device having a nanocolumn 10c made of GaN is provided. Further, in such a nanocolumn 10c made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. For this reason, the crystal structure of the pn junction diode 1c is of high quality. The pn junction of the pn junction diode 1c is provided for each nanocolumn 10a. Thus, the locations where the pn junctions are provided are dispersed in the pn junction diode 1c. Therefore, since heat radiation is large and it is difficult to increase the temperature, good characteristics are maintained even for a large current value. For this reason, the pn junction diode 1c is suitable for a power device, for example. In addition, the first electrode 4c made of an alloy (Ti / Au / Ti / Au or Ni / Au) has excellent heat conductivity, and therefore has high heat dissipation. Further, when the first nanocolumn portion 6c is n-type, the first nanocolumn portion 6c has a low contact resistance with respect to the first electrode 4c of the alloy (Ti / Au / Ti / Au), and thus heat generation due to current is reduced. The Further, the mechanical strength and the withstand voltage of the pn junction diode 1c are improved by the insulating portion 16c. -

  Next, with reference to FIG. 5, the manufacturing method of the pn junction diode 1c which concerns on 3rd Embodiment is demonstrated. The manufacturing method of the pn junction diode 1c described below includes a substrate preparation step C1 shown in FIG. 5A, a formation step C2 shown in FIG. 5B, and a first electrode formation step C3 shown in FIG. 5D, a substrate removing step C4 shown in FIG. 5D, an insulating portion forming step C5 shown in FIG. 5E, and a second electrode forming step C6 shown in FIG. The substrate preparation step C1, the formation step C2, the first electrode formation step C3, the substrate removal step C4, and the second electrode formation step C6 are respectively a method of manufacturing the pn junction diode 1a according to the first embodiment described above. The substrate preparation step A1, the formation step A2, the first electrode formation step A3, the substrate removal step A4, and the second electrode formation step A5 are performed in the same manner. In this case, in the above description of the method of manufacturing the pn junction diode 1a, the substrate 21a, the first electrode 41a, the first nanocolumn portion 6a, the AlN region 71a, the second nanocolumn portion 8a, the nanocolumn 10a, the semiconductor portion 121a, and the second electrode Instead of 14a, the substrate 21c, the first electrode 41c, the first nanocolumn portion 6c, the AlN region 71c, the second nanocolumn portion 8c, the nanocolumn 10c, the semiconductor portion 121c, and the second electrode 14c are used, respectively. In the above, the process similar to that of the pn junction diode 1a has been described. Subsequently, the insulating part forming step C5 shown in FIG. 5E, which is different from the method for manufacturing the pn junction diode 1a, will be described in detail.

  With reference to FIG.5 (e), the insulation part formation process C5 is demonstrated. The insulating part forming step C5 is performed after the substrate removing step C4 and before the second electrode forming step C6. In the insulating portion forming step C5, an insulating portion 16c made of an inorganic material such as SOG is formed between the plurality of nanocolumns 10c (the first nanocolumn portion 6c and the second nanocolumn portion 8c). In other words, the insulating portion 16c is formed in a space formed between the plurality of nanocolumns 10c. After this insulating part forming step C5, a second electrode forming step C6 is performed.

  As described above, the first nanocolumn portion 6c and the second nanocolumn portion 8c form a pn junction. Therefore, according to the manufacturing method of the pn junction diode 1c according to the third embodiment, the pn junction diode for the power device having the nanocolumn 10c made of GaN is manufactured. Further, in such a nanocolumn 10c made of GaN, the dislocation density is reduced as compared with a conventional bulk GaN single crystal having no nanocolumn. For this reason, the crystal structure of the pn junction diode 1c is of high quality. In addition, since the insulating portion 16c is provided between the nanocolumns 10c before the first electrode 41c is formed, it is possible to prevent the metal material constituting the first electrode 41c from entering between the nanocolumns 10c when the first electrode 41c is formed.

It is sectional drawing of the pn junction diode which concerns on 1st Embodiment. It is a figure for demonstrating the manufacturing method of the pn junction diode which concerns on 1st Embodiment. It is sectional drawing of the pn junction diode which concerns on 2nd and 3rd embodiment. It is a figure for demonstrating the manufacturing method of the pn junction diode which concerns on 2nd Embodiment. It is a figure for demonstrating the manufacturing method of the pn junction diode which concerns on 3rd Embodiment.

Explanation of symbols

1a, 1b, 1c ... pn junction diode, 2a, 2b, 2c ... substrate, 4a, 4b, 4c ... first electrode, 5a, 5b, 5c ... nanocolumn region, 6a, 6b, 6c ... first nanocolumn portion, 7a, 7b, 7c ... AlN region, 8a, 8b, 8c ... second nanocolumn part, 10a, 10b, 10c ... nanocolumn, 12a, 12b, 12c ... semiconductor part, 14a, 14b, 14c ... second electrode, 16c ... insulating part.

Claims (11)

A pn junction diode for a power device,
A first electrode;
A nanocolumn region having a plurality of nanocolumns and provided on the first electrode;
A semiconductor portion of a second conductivity type provided on the nanocolumn region;
A second electrode provided on the semiconductor part,
Each of the nanocolumns extends in a direction from the first electrode toward the semiconductor portion, and includes a first conductivity type first nanocolumn portion made of GaN or AlGaN and a second conductivity type second made of GaN or AlGaN. Including the nanocolumn part,
The first nanocolumn and the second nanocolumn are connected by homojunction ,
When the first conductivity type is n-type and the second conductivity type is p-type, the length of the first nanocolumn part is greater than the length of the second nanocolumn part, or the first conductivity type is p-type When the second conductivity type is n-type, the length of the second nanocolumn part is larger than the length of the first nanocolumn part .   The pn junction diode according to claim 1, further comprising an AlN region provided between the first electrode and the nanocolumn region.   The pn junction diode according to claim 1, further comprising an insulating part provided between the plurality of nanocolumns. A pn junction diode for a power device,
A first electrode;
A substrate provided on the first electrode;
A nanocolumn region provided on the substrate having a plurality of nanocolumns;
A semiconductor portion of a second conductivity type provided on the nanocolumn region;
A second electrode provided on the semiconductor part,
Each of the nanocolumns extends in a direction from the substrate toward the semiconductor portion, and includes a first conductivity type first nanocolumn portion made of GaN or AlGaN and a second conductivity type second nanocolumn portion made of GaN or AlGaN. Including
The first nanocolumn and the second nanocolumn are connected by homojunction ,
When the first conductivity type is n-type and the second conductivity type is p-type, the length of the first nanocolumn part is greater than the length of the second nanocolumn part, or the first conductivity type is p-type When the second conductivity type is n-type, the length of the second nanocolumn part is larger than the length of the first nanocolumn part .   The pn junction diode according to claim 4, wherein the substrate is made of GaAs or Si.   The pn junction diode according to claim 4, further comprising an AlN region provided between the substrate and the nanocolumn region. 7. The pn junction diode according to claim 1, wherein a dislocation density of the nanocolumn is lower than 10 ⁵ cm ⁻² . A method of manufacturing a pn junction diode for a power device, comprising:
A first nanocolumn portion forming step of forming a plurality of first nanocolumn portions of the first conductivity type and made of GaN on a substrate of the first conductivity type made of GaAs or Si;
A second nanocolumn portion forming step of forming a plurality of second nanocolumn portions of the second conductivity type and made of GaN at end portions of the plurality of first nanocolumn portions;
After the formation of the second nanocolumn, by supplying more Ga than the supply amount of Ga in each step of the first nanocolumn part forming step and the second nanocolumn part forming step, an end of the second nanocolumn part is formed. have a semiconductor forming step of forming a semiconductor portion of a second conductivity type parts to each other are coupled,
When the first conductivity type is n-type and the second conductivity type is p-type, the length of the first nanocolumn part is greater than the length of the second nanocolumn part, or the first conductivity type is p-type When the second conductivity type is n-type, the length of the second nanocolumn part is larger than the length of the first nanocolumn part . A first electrode forming step of forming a second electrode on the semiconductor portion after forming the semiconductor portion;
A substrate removing step of removing the substrate after forming the second electrode;
The method of manufacturing a pn junction diode according to claim 8, further comprising: a second electrode forming step of forming a first electrode at an end of the first nanocolumn portion after removing the substrate. . A method of manufacturing a pn junction diode for a power device, comprising:
A first nanocolumn portion forming step of forming a plurality of first nanocolumn portions of the first conductivity type and made of GaN on a substrate of the first conductivity type made of GaAs or Si;
A second nanocolumn portion forming step of forming a plurality of second nanocolumn portions of the second conductivity type and made of GaN at end portions of the plurality of first nanocolumn portions;
After the formation of the second nanocolumn, by supplying more Ga than the supply amount of Ga in each step of the first nanocolumn portion formation step and the second nanocolumn portion formation step, an end of the second nanocolumn portion is formed. have a semiconductor forming step of forming a semiconductor portion of a second conductivity type parts to each other are coupled,
When the first conductivity type is n-type and the second conductivity type is p-type, the length of the first nanocolumn part is greater than the length of the second nanocolumn part, or the first conductivity type is p-type When the second conductivity type is n-type, the length of the second nanocolumn part is larger than the length of the first nanocolumn part . A first electrode forming step of forming a second electrode on the semiconductor portion after forming the semiconductor portion;
A second electrode forming step of forming the first electrode on the substrate after forming the second electrode;
The method of manufacturing a pn junction diode according to claim 10, further comprising:

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