Semiconductor device and method for manufacturing a semiconductor device

Abstract

To provide a semiconductor device capable of realizing a metal electrode with low connection resistance to a nitride semiconductor.SOLUTION: A semiconductor device comprises: a first gallium nitride region that is an n-type semiconductor; and a second gallium nitride region that is in contact with the first gallium nitride region, being made of metal and including a first element that is at least one element selected from a group consisting of Be, Mg, Ca, Sr, Ba, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, V, Nb, Ta, Li, Na, K, Rb, Ce, and Zn.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] Embodiments of the present invention relate to semiconductor devices and methods for manufacturing semiconductor devices. [Background technology]

[0002] Semiconductor elements such as transistors and diodes are used in circuits such as switching power supply circuits and inverter circuits. These semiconductor elements require high voltage resistance and low on-resistance. There is a trade-off relationship between voltage resistance and on-resistance, which is determined by the element material.

[0003] Thanks to advances in technological development, semiconductor devices have achieved extremely low on-resistance, close to the limits of silicon, the primary device material. To further improve voltage resistance or reduce on-resistance, it is necessary to change the device material. By using nitride semiconductors such as gallium nitride and aluminum gallium nitride as the device material for semiconductor devices, the trade-off relationship determined by the device material can be improved. This makes it possible to dramatically increase the voltage resistance and lower the on-resistance of semiconductor devices.

[0004] When forming semiconductor devices using nitride semiconductors, it is desirable to achieve metal electrodes with low connection resistance to the nitride semiconductor. By forming metal electrodes with low connection resistance to the nitride semiconductor, high performance of semiconductor devices can be achieved. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-68722 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The problem that this invention aims to solve is to provide a semiconductor device that can realize metal electrodes with low connection resistance to nitride semiconductors.

Means for Solving the Problem

[0007] The semiconductor device according to the embodiment includes a first gallium nitride region that is an n-type semiconductor, and a first element that is in contact with the first gallium nitride region and is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn), and is a metal target and a second gallium nitride region that is a metal, and includes The sheet resistance of the second gallium nitride region is 0.1 Ω / sq or less. .

Brief Description of the Drawings

[0008] [Figure 1] Schematic cross-sectional view of the semiconductor device according to the first embodiment. [Figure 2] Diagram showing the manufacturing flow of the manufacturing method of the semiconductor device according to the first embodiment. [Figure 3] Explanation diagram of the operation and effect of the semiconductor device according to the first embodiment. [Figure 4] Schematic cross-sectional view of the semiconductor device according to the second embodiment.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same or similar members are denoted by the same reference numerals, and the description of the members once described may be omitted.

[0010] In this specification, in order to indicate the positional relationship of components and the like, the upward direction of the drawing is described as "up" and the downward direction of the drawing is described as "down". In this specification, the concepts of "up" and "down" are not necessarily terms indicating the relationship with the direction of gravity.

[0011] Also, in the following description, n

[0013] , , n, n - and, p + , p, p - If there is notation of, p, p, it represents the relative high and low of the impurity concentration in each conductivity type. That is, n + indicates that the n-type impurity concentration is relatively higher than n, and n - indicates that the n-type impurity concentration is relatively lower than n. Also, p + indicates that the p-type impurity concentration is relatively higher than p, and p - indicates that the p-type impurity concentration is relatively lower than p. Note that the n + type, n - type may simply be described as the n-type, and the p + type, p - type may simply be described as the p-type.

[0012] (First Embodiment) The semiconductor device of the first embodiment includes a first gallium nitride region that is an n-type semiconductor, and a first element that is in contact with the first gallium nitride region and is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn), and a second gallium nitride region that is a metal.

[0013] Figure 1 is a schematic cross-sectional view of a semiconductor device according to the first embodiment. The semiconductor device according to the first embodiment is a contact structure 100 that electrically connects a gallium nitride layer and a metal electrode.

[0014] The contact structure 100 of the first embodiment comprises a gallium nitride layer 10 and a metal electrode 11. The gallium nitride layer 10 includes a first gallium nitride region 10a and a second gallium nitride region 10b.

[0015] The gallium nitride layer 10 is, for example, single-crystal gallium nitride.

[0016] The first gallium nitride region 10a is an n-type semiconductor. The first gallium nitride region 10a is gallium nitride, an n-type semiconductor. The first gallium nitride region 10a contains, for example, silicon (Si) as an n-type impurity. The n-type impurity concentration of the first gallium nitride region 10a is, for example, 1 × 10⁻⁶ 18 cm -3 The above 1 x 10 21 cm -3 The following applies:

[0017] The second gallium nitride region 10b is provided on top of the first gallium nitride region 10a. The second gallium nitride region 10b is in contact with the first gallium nitride region 10a. The second gallium nitride region 10b is provided between the first gallium nitride region 10a and the metal electrode 11.

[0018] The second gallium nitride region 10b is metallic. The second gallium nitride region 10b is metallic gallium nitride. The second gallium nitride region 10b is gallium nitride that has been metallicized from semiconductor gallium nitride.

[0019] For example, since the second gallium nitride region 10b is a metal, the electrical resistance of the second gallium nitride region 10b increases with increasing temperature.

[0020] The sheet resistance of the second gallium nitride region 10b is, for example, 0.1 Ω / sq or less.

[0021] The work function of the second gallium nitride region 10b is, for example, 3.7 eV or less. The work function of the second gallium nitride region 10b can be measured, for example, using ultraviolet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), or Auger electron spectroscopy (AES). Alternatively, using a Kelvin probe, it can be measured as the difference in intermetallic work functions between the sample and the probe.

[0022] The second gallium nitride region 10b consists of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), and terbium (Tb). It contains a first element which is at least one element selected from the group consisting of dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn).

[0023] The concentration of the first element in the second gallium nitride region 10b is, for example, 1 × 10 19 cm -3 The above 1 x 10 22 cm -3 The following applies:

[0024] The thickness of the second gallium nitride region 10b is, for example, 0.1 μm or more and 1.0 μm or less.

[0025] In the second gallium nitride region 10b, the amount of the first element that bonds with gallium (Ga) is greater than, for example, the amount of the first element that bonds with nitrogen (N). In other words, in the second gallium nitride region 10b, the amount of the first element located at the nitrogen site of the gallium nitride crystal structure is greater than the amount of the first element located at the gallium site of the gallium nitride crystal structure. In other words, the amount of the first element that substitutes for the nitrogen atom in the gallium nitride crystal structure is greater than the amount of the first element that substitutes for the gallium atom in the gallium nitride crystal structure.

[0026] Among the first elements contained in the second gallium nitride region 10b, the amount of the first element that bonds with gallium (Ga) is, for example, 10 times or more the amount of the first element that bonds with nitrogen (N). Among the first elements contained in the second gallium nitride region 10b, the amount of the first element located at the nitrogen site of the gallium nitride crystal structure is, for example, 10 times or more the amount of the first element located at the gallium site of the gallium nitride crystal structure.

[0027] The relationship between the amount of the first element that bonds with gallium (Ga) and the amount of the first element that bonds with nitrogen (N) can be measured, for example, using X-ray photoelectron spectroscopy (XPS).

[0028] The metal electrode 11 is placed on the second gallium nitride region 10b. The metal electrode 11 is in contact with the second gallium nitride region 10b.

[0029] The metal electrode 11 is a metal or a metal compound. The chemical composition of the metal electrode 11 is different from the chemical composition of the second gallium nitride region 10b.

[0030] The metal electrode 11 includes, for example, titanium, titanium nitride, aluminum, or tungsten. The metal electrode 11 has a laminated structure of, for example, a titanium film and an aluminum film.

[0031] Next, an example of a method for manufacturing the semiconductor device according to the first embodiment will be described.

[0032] The first embodiment of the semiconductor device manufacturing method involves adding beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), and tan to an n-type gallium nitride layer. A first ion implantation is performed to implant a first element, which is at least one element selected from the group consisting of tal (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn). A second ion implantation is performed to implant gallium (Ga) into the gallium nitride layer. A third ion implantation is performed to implant hydrogen (H) into the gallium nitride layer. After the first, second, and third ion implantations, a coating layer is formed on the surface of the gallium nitride layer. A first heat treatment is performed after the formation of the coating layer. After the first heat treatment, the coating layer is peeled off. After the peeling off of the coating layer, a second heat treatment is performed.

[0033] Figure 2 is a diagram showing the manufacturing flow of the first embodiment of the semiconductor device manufacturing method. The first embodiment of the semiconductor device manufacturing method comprises a gallium nitride layer preparation step S101, a magnesium ion implantation step S102 (first ion implantation), a gallium implantation step S103 (second ion implantation), a hydrogen ion implantation step S104 (third ion implantation), a silicon nitride layer formation step S105 (coating layer formation), a first nitrogen annealing step S106 (first heat treatment), a silicon nitride layer peeling step S107 (coating layer peeling), a second nitrogen annealing step S108 (second heat treatment), and a metal film formation step S109.

[0034] The following explanation will refer to Figure 1. Furthermore, the following explanation will use the case where the first element is magnesium (Mg) as an example.

[0035] First, a gallium nitride layer 10 is prepared (S101). The gallium nitride layer 10 is single-crystal gallium nitride (GaN). A first n-type semiconductor gallium nitride region 10a is formed in the gallium nitride layer 10.

[0036] Next, magnesium (Mg) is ion-implanted onto the surface of the gallium nitride layer 10 using a known ion implantation method (S102). The ion implantation of magnesium corresponds to the first ion implantation.

[0037] The region where magnesium is ion-implanted ultimately becomes the second gallium nitride region 10b of the contact structure 100. For example, magnesium may be ion-implanted in multiple steps using different ion implantation energies.

[0038] The magnesium dose is, for example, 1 × 10⁻⁶ 14 cm -2 The above 5 x 10 15 cm -2 The following applies:

[0039] Next, gallium (Ga) is ion-implanted into the surface of the gallium nitride layer 10 using a known ion implantation method (S103). The ion implantation of gallium corresponds to the second ion implantation.

[0040] Gallium is introduced into the region where magnesium has been ion-implanted. For example, gallium may be ion-implanted in multiple stages using different ion-implantation energies.

[0041] The dose of gallium is greater than, for example, the dose of magnesium. 14 cm -2 The above 1 x 10 16 cm -2 The following applies:

[0042] The second ion implantation creates, for example, a large number of nitrogen vacancies within the gallium nitride layer 10.

[0043] Next, hydrogen (H) is ion-implanted into the surface of the gallium nitride layer 10 using a known ion implantation method (S104). The ion implantation of hydrogen corresponds to the third ion implantation.

[0044] Hydrogen is introduced into the region where magnesium and gallium have been ion-implanted. For example, hydrogen may be ion-implanted in multiple stages using different ion-implantation energies.

[0045] The hydrogen dose in the third ion implantation is, for example, greater than the magnesium dose in the first ion implantation. The hydrogen dose in the third ion implantation is, for example, greater than the gallium dose in the second ion implantation. The hydrogen dose is, for example, 1 × 10⁻⁶ 15 cm -2 The above 5 x 10 16 cm -2 The following applies:

[0046] Next, a silicon nitride layer is formed on the surface of the gallium nitride layer 10 using a known film growth method (S105). The silicon nitride layer is an example of a coating layer. The coating layer is not limited to silicon nitride.

[0047] The coating layer is, for example, an insulator. The coating layer is, for example, silicon nitride, silicon oxide, silicon oxynitride, or aluminum nitride.

[0048] The coating layer is, for example, a conductor or a semiconductor. The coating layer is, for example, polycrystalline silicon.

[0049] Next, a first nitrogen annealing is performed (S106). The first nitrogen annealing is performed, for example, in a nitrogen gas atmosphere at a temperature of 950°C to 1250°C. The first nitrogen annealing is an example of a first heat treatment.

[0050] The first heat treatment is carried out in a non-oxidizing atmosphere containing, for example, argon, nitrogen, hydrogen, or helium.

[0051] The first heat treatment causes, for example, magnesium to enter the nitrogen sites of gallium nitride. The first heat treatment causes, for example, magnesium to enter the nitrogen vacancies. The magnesium that has entered the nitrogen sites of gallium nitride is bonded with, for example, hydrogen.

[0052] Next, the silicon nitride layer on the surface of the gallium nitride layer 10 is removed using a known wet etching method (S107). The surface of the gallium nitride layer 10 is exposed.

[0053] Next, a second nitrogen annealing is performed (S108). The second nitrogen annealing is performed, for example, in a nitrogen gas atmosphere at a temperature of 950°C to 1250°C. The second nitrogen annealing is an example of a second heat treatment.

[0054] The second heat treatment is carried out in a non-oxidizing atmosphere, for example, containing argon, nitrogen, or helium. The second heat treatment is carried out in a hydrogen-free atmosphere, for example.

[0055] The second heat treatment, for example, removes hydrogen that was bonded to magnesium from the magnesium.

[0056] Next, a laminated film of titanium and aluminum is formed on the gallium nitride layer 10 (S109). The laminated film of titanium and aluminum is an example of a metal film. The laminated film of titanium and aluminum ultimately becomes the metal electrode 11 of the contact structure 100.

[0057] By the above manufacturing method, the contact structure 100 of the first embodiment shown in Figure 1 is formed.

[0058] Next, the operation and effects of the semiconductor device and semiconductor manufacturing apparatus according to the first embodiment will be described.

[0059] When forming semiconductor devices using nitride semiconductors, it is desirable to realize metal electrodes with low connection resistance to the nitride semiconductor. By forming metal electrodes with low connection resistance to the nitride semiconductor, high performance of semiconductor devices can be achieved.

[0060] The contact structure 100 of the first embodiment, by including a second metallic gallium nitride region 10b, has low connection resistance with the n-type gallium nitride region, enabling the realization of a highly reliable metal electrode. This will be described in detail below.

[0061] The junction between the gallium nitride region of an n-type semiconductor and the metal electrode is a semiconductor-metal junction. From the perspective of work function, the number of metal materials that can form an ohmic junction with n-type gallium nitride is extremely limited. Considering the affinity of metal materials to semiconductor processes, it is difficult to form an ohmic junction between the gallium nitride region of an n-type semiconductor and the metal electrode. Therefore, the junction between the gallium nitride region of an n-type semiconductor and the metal electrode is likely to be a Schottky junction. Consequently, it is difficult to lower the connection resistance between the gallium nitride region of an n-type semiconductor and the metal electrode.

[0062] Furthermore, the interface between the gallium nitride region of the n-type semiconductor and the metal electrode is a semiconductor-metal interface. Therefore, the strength of the interface may decrease due to the application of temperature and stress. Consequently, for example, delamination may occur at the interface, potentially reducing the reliability of the metal electrode.

[0063] Figures 3(a) and 3(b) are explanatory diagrams illustrating the operation and effects of the semiconductor device of the first embodiment. Figure 3(a) is the energy band diagram of undoped gallium nitride, in which conductive impurities are not actively introduced. Figure 3(b) is the energy band diagram of metallic gallium nitride corresponding to the second gallium nitride region 10b of the first embodiment.

[0064] Undoped gallium nitride contains a certain amount of nitrogen vacancies. As shown in Figure 3(a), in undoped semiconductor gallium nitride, the energy level of the nitrogen vacancies is located below the lower end of the conduction band. It is located near the lower end of the conduction band. The energy at the lower end of the conduction band in gallium nitride is 3.65 eV.

[0065] As shown in Figure 3(b), in metallic gallium nitride, magnesium (Mg) is present at the nitrogen site of the gallium nitride. The work function of magnesium has an energy near the lower end of the conduction band. In other words, it has an energy near the energy level of the nitrogen vacancy.

[0066] First-principles calculations by the inventor revealed that when a large number of nitrogen vacancies coexist in gallium nitride with magnesium present at the nitrogen sites, electrons are supplied from the magnesium to the nitrogen vacancies. Furthermore, it was revealed that this supply of electrons from magnesium to the nitrogen vacancies broadens the nitrogen vacancy energy band. In addition, it was revealed that the Fermi level of gallium nitride falls within the conduction band.

[0067] In metallic gallium nitride, the interaction between a large number of nitrogen vacancies and magnesium at the nitrogen sites causes the Fermi level to enter the conduction band, resulting in the metallicization of gallium nitride, which is normally a semiconductor.

[0068] The contact structure 100 of the first embodiment includes a second metallic gallium nitride region 10b between a first n-type semiconductor gallium nitride region 10a and a metal electrode 11. The junction between the second metallic gallium nitride region 10b and the metal electrode 11 is an intermetallic junction. Therefore, the junction between the second metallic gallium nitride region 10b and the metal electrode 11 is an ohmic junction, which can reduce the connection resistance.

[0069] Furthermore, since the interface between the second gallium nitride region 10b of the metal and the metal electrode 11 is a metal-to-metal interface, the decrease in strength due to the application of temperature and stress can be suppressed. Therefore, for example, delamination at the interface is suppressed, and the reliability of the metal electrode 11 is increased.

[0070] The junction between the first gallium nitride region 10a of the n-type semiconductor and the second gallium nitride region 10b of the metal is a semiconductor-metal junction. As described above, the Fermi level of the second gallium nitride region 10b is within the conduction band of gallium nitride. In other words, the work function of the second gallium nitride region 10b is smaller than the energy at the lower end of the conduction band of the first gallium nitride region 10a. Therefore, the junction between the first gallium nitride region 10a of the n-type semiconductor and the second gallium nitride region 10b of the metal is an ohmic junction. Thus, the connection resistance between the first gallium nitride region 10a of the n-type semiconductor and the second gallium nitride region 10b of the metal can be reduced.

[0071] The interface between the first gallium nitride region 10a of the n-type semiconductor and the second gallium nitride region 10b of the metal is a continuous interface of gallium nitride crystal structure. Therefore, the interface strength is high. As a result, even if annealing or other processes are performed in later stages, residual oxygen and other substances do not penetrate this continuous interface, making interface delamination unlikely.

[0072] As described above, in the contact structure 100 of the first embodiment, by providing a second metallic gallium nitride region 10b, the junction between the n-type first gallium nitride region 10a and the metal electrode 11 becomes an ohmic junction. Therefore, the connection resistance with the n-type first gallium nitride region 10a is low, and a highly reliable metal electrode 11 can be realized. As a secondary effect, the degree of freedom in selecting the metal electrode 11 is greatly improved. For example, special laminated structures such as a laminated structure of aluminum and titanium are no longer necessary. For example, titanium nitride (TiN), tungsten (W), and polysilicon doped with phosphorus or boron, which have excellent processability, can be used.

[0073] From the viewpoint of reducing the connection resistance of the metal electrode 11, it is preferable that the work function of the second gallium nitride region 10b is 3.7 eV or less.

[0074] From the viewpoint of reducing the connection resistance of the metal electrode 11, the sheet resistance of the second gallium nitride region 10b is preferably 0.1 Ω / sq or less.

[0075] From the viewpoint of reducing the connection resistance of the metal electrode 11, the magnesium concentration in the second gallium nitride region 10b is 1 × 10⁻⁶. 19 cm -3 It is preferable that the amount be greater than or equal to 1 × 10 20 cm -3 More preferably, the above is true, 1 × 10 21 cm -3 It is even more preferable that the above conditions are met.

[0076] From the viewpoint of reducing the connection resistance of the metal electrode 11, it is preferable that the amount of magnesium that bonds with gallium in the second gallium nitride region 10b is greater than the amount of magnesium that bonds with nitrogen, and it is more preferable that the amount of magnesium that bonds with gallium in the second gallium nitride region 10b is 10 times or more the amount of magnesium that bonds with nitrogen.

[0077] In other words, it is preferable that the amount of magnesium located at the nitrogen sites within the second gallium nitride region 10b is greater than the amount of magnesium located at the gallium sites. Furthermore, it is even more preferable that the amount of magnesium located at the nitrogen sites within the second gallium nitride region 10b is 10 times or more the amount of magnesium located at the gallium sites.

[0078] Magnesium located at the gallium site functions as a p-type impurity. Therefore, the presence of magnesium located at the gallium site is undesirable because it inhibits the metallic properties of the second gallium nitride region 10b.

[0079] In the manufacturing method of the first embodiment, a second gallium nitride region 10b is formed by ion implanting magnesium, gallium, and hydrogen into the same region of the gallium nitride layer 10. By ion implanting gallium, which has a relatively large ionic radius, a large number of nitrogen vacancies are formed within the gallium nitride layer 10. Therefore, a large number of nitrogen vacancies are present in the second gallium nitride region 10b.

[0080] Then, magnesium enters the numerous nitrogen vacancies that are formed. In other words, magnesium enters the nitrogen sites. As mentioned above, when magnesium enters the gallium sites, it functions as a p-type impurity, which is undesirable.

[0081] In the manufacturing method of the first embodiment, ion implantation of gallium causes gallium to preferentially enter the formed gallium vacancies over magnesium. Therefore, the entry of magnesium into the gallium sites is suppressed.

[0082] Furthermore, ion implantation with hydrogen promotes the entry of magnesium into nitrogen vacancies. Magnesium bonded with hydrogen can exist more stably in nitrogen vacancies than magnesium alone.

[0083] On the other hand, magnesium bonded with hydrogen does not serve as an electron source for the nitrogen vacancy energy band. Therefore, a second heat treatment after stripping the coating layer removes hydrogen from the magnesium, allowing the magnesium to function as an electron source.

[0084] The first elements are those other than magnesium, namely beryllium (Be), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), and dysprosium (Dy). Applying at least one element selected from the group consisting of holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn) can yield the same effects and properties as magnesium.

[0085] In particular, among the above elements, elements whose work function is near the lower end of the conduction band of gallium nitride, or whose work function is smaller than the lower end of the conduction band of gallium nitride, are preferred as the first element because they function particularly effectively as sources of electrons for the nitrogen vacancy energy band.

[0086] For example, it is preferable that the first element be cesium (Cs) with a work function of 1.9 eV, potassium (K) with 2.3 eV, niobium (Nb) with 2.3 eV, sodium (Na) with 2.4 eV, strontium (Sr) and barium (Ba) with 2.5 eV, calcium (Ca) with 2.8 eV, lithium (Li) with 2.9 eV, yttrium (Y) with 3.1 eV, scandium (Sc) with 3.5 eV, or zinc (Zn) with 3.6 eV.

[0087] As described above, the semiconductor device and the method for manufacturing the semiconductor device according to the first embodiment can provide a semiconductor device that can realize metal electrodes with low connection resistance to nitride semiconductors.

[0088] (Second embodiment) The semiconductor device of the second embodiment is a vertical High Electron Mobility Transistor (HEMT) including the contact structure of the first embodiment. Hereafter, some descriptions that overlap with the first embodiment may be omitted.

[0089] Figure 4 is a schematic cross-sectional view of the semiconductor device of the second embodiment. The semiconductor device of the second embodiment is a vertical HEMT200.

[0090] The vertical HEMT200 of the second embodiment comprises a gallium nitride layer 10, a source electrode 12 (metal electrode), a drain electrode 13 (metal electrode), a gate electrode 14, an aluminum nitride layer 15, and an interlayer insulating layer 16. The gallium nitride layer 10 is n + Drain region 21 of type (first gallium nitride region), n - Shape drift region 22, p-shaped body region 23, n + Source region 24 of type (first gallium nitride region), p + It includes a contact region 25 of the type, a first metal region 26 (second gallium nitride region), and a second metal region 27 (second gallium nitride region).

[0091] n + The drain region 21 of type n is an example of the first gallium nitride region. + The drain region 21 is an n-type semiconductor. The drain region 21 is gallium nitride, an n-type semiconductor. The drain region 21 contains, for example, silicon (Si) as an n-type impurity. The concentration of n-type impurities in the drain region 21 is, for example, 1 × 10⁻⁶ 18 cm -3 The above 1 x 10 21 cm -3 The following applies:

[0092] The first metallic region 26 is an example of the second gallium nitride region.

[0093] The first metal region 26 is provided below the drain region 21. The first metal region 26 is in contact with the drain region 21. The first metal region 26 is provided between the drain region 21 and the drain electrode 13.

[0094] The first metallic region 26 is a metal. The first metallic region 26 is metallic gallium nitride. The first metallic region 26 is gallium nitride, which is semiconductor gallium nitride that has been metallized.

[0095] The first metallic region 26 includes a first element which is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn).

[0096] Among the first elements contained in the first metallic region 26, the amount of the first element that bonds with gallium (Ga) is greater than, for example, the amount of the first element that bonds with nitrogen (N).

[0097] The drain electrode 13 is an example of a metal electrode. The drain electrode 13 is located below the first metal region 26. The drain electrode 13 is in contact with the first metal region 26.

[0098] The drain electrode 13 is a metal or a metallic compound. The chemical composition of the drain electrode 13 is different from the chemical composition of the first metallic region 26.

[0099] n +The source region 24 of type n is an example of the first gallium nitride region. Source region 24 is an n-type semiconductor. Source region 24 is gallium nitride, an n-type semiconductor. Source region 24 contains, for example, silicon (Si) as an n-type impurity. The n-type impurity concentration of source region 24 is, for example, 1 × 10⁻⁶ 18 cm -3 The above 1 x 10 21 cm -3 The following applies:

[0100] The second metallic region 27 is an example of the second gallium nitride region.

[0101] The second metal region 27 is provided on the source region 24. The second metal region 27 is in contact with the source region 24. The second metal region 27 is provided between the source region 24 and the source electrode 12.

[0102] The second metallic region 27 is a metal. The second metallic region 27 is metallic gallium nitride. The second metallic region 27 is metallic gallium nitride, which is semiconductor gallium nitride.

[0103] The second metallic region 27 includes a first element which is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn).

[0104] In the second metallic region 27, the amount of the first element that bonds with gallium (Ga) is greater than, for example, the amount of the first element that bonds with nitrogen (N).

[0105] The source electrode 12 is an example of a metal electrode. The source electrode 12 is placed on the second metal region 27. The source electrode 12 is in contact with the second metal region 27.

[0106] The source electrode 12 is a metal or a metallic compound. The chemical composition of the source electrode 12 is different from the chemical composition of the second metallic region 27.

[0107] Source region 24 contains, for example, silicon (Si) as an n-type impurity. For example, silicon, nitrogen, and hydrogen are implanted simultaneously. p-type body region 23, p + The contact region 25 of the type contains, for example, magnesium (Mg) as a p-type impurity. Magnesium, nitrogen, and hydrogen are implanted simultaneously. Then, magnesium, gallium, and hydrogen are implanted to form the second metal region 27. Subsequently, the process proceeds with coating layer formation, first heat treatment, coating layer peeling, and second annealing, resulting in the source region 24, the p-type body region 23, and p + A contact region 25 and a second metal region 27 are formed.

[0108] In the second embodiment of the vertical HEMT200, a contact structure similar to the contact structure 100 of the first embodiment is applied to the contact structure between the drain electrode 13 and the gallium nitride layer 10. Therefore, the connection resistance between the drain electrode 13 and the gallium nitride layer 10 is reduced. In addition, the reliability of the drain electrode 13 is improved.

[0109] Furthermore, the vertical HEMT200 of the second embodiment applies a contact structure similar to the contact structure 100 of the first embodiment to the contact structure between the source electrode 12 and the gallium nitride layer 10. Therefore, the connection resistance between the source electrode 12 and the gallium nitride layer 10 is reduced. In addition, the reliability of the source electrode 12 is improved.

[0110] Therefore, for example, a vertical HEMT200 with reduced on-resistance and improved reliability can be realized.

[0111] Furthermore, in the second embodiment of the vertical HEMT200, the source electrode 12 has p as the electrode material. + Any metal material can be selected to reduce the connection resistance with the contact area 25 of the type.

[0112] As described above, the semiconductor device of the second embodiment provides a semiconductor device that can realize metal electrodes with low connection resistance to nitride semiconductors.

[0113] In the second embodiment, a vertical HEMT was described as an example of a semiconductor device, but the present invention can also be applied to other semiconductor devices. For example, the present invention can be applied to a horizontal HEMT, a diode, or an optoelectronic device such as an LED (Light Emmitting Diode).

[0114] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. For example, components of one embodiment may be replaced or modified with components of another embodiment. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0115] 10 Gallium nitride layer 10a First gallium nitride region 10b Second gallium nitride region 11 Metal electrode 12. Source electrode (metal electrode) 13. Drain electrode (metal electrode) 21 Drain region (first gallium nitride region) 24. Source region (first gallium nitride region) 26. First metallic region (second gallium nitride region) 27. Second Metal Region (Second Gallium Nitride Region) 100 Contact Structure (Semiconductor Device) 200 Vertical HEMT (Semiconductor Device)

Claims

1. The first gallium nitride region is an n-type semiconductor, Adjacent to the first gallium nitride region is a second gallium nitride region which is metallic and contains a first element which is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn). Equipped with, A semiconductor device having a sheet resistance of 0.1 Ω / sq or less in the second gallium nitride region.

2. The semiconductor device according to claim 1, further comprising a metal electrode in contact with the second gallium nitride region.

3. The first gallium nitride region is an n-type semiconductor, Adjacent to the first gallium nitride region is a second gallium nitride region which is metallic and contains a first element which is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn). Equipped with, The concentration of the first element in the second gallium nitride region is 1 × 10⁻⁶ １９ cm －３ That's all. A semiconductor device having a work function of 3.7 eV or less in the second gallium nitride region.

4. The concentration of the first element in the second gallium nitride region is 1 × 10⁻⁶ ２０ cm －３ The semiconductor device according to claim 3.

5. The concentration of the first element in the second gallium nitride region is 1 × 10⁻⁶ １９ cm －３ The semiconductor device according to claim 1.

6. The first gallium nitride region is an n-type semiconductor, Adjacent to the first gallium nitride region, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium ( A second gallium nitride region comprising a first element which is at least one element selected from the group consisting of Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn), wherein the amount of the first element bonded with gallium (Ga) is greater than the amount of the first element bonded with nitrogen (N), A semiconductor device equipped with a semiconductor device.

7. The semiconductor device according to claim 6, further comprising a metal electrode in contact with the second gallium nitride region.

8. The semiconductor device according to claim 6, wherein the work function of the second gallium nitride region is 3.7 eV or less.

9. The semiconductor device according to claim 6, wherein the sheet resistance of the second gallium nitride region is 0.1 Ω / sq or less.

10. The concentration of the first element in the second gallium nitride region is 1 × 10⁻⁶ １９ cm －３ The semiconductor device according to claim 6.

11. A first ion implantation is performed on an n-type gallium nitride layer, in which a first element is implanted into the n-type gallium nitride layer, which is at least one element selected from the group consisting of beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), vanadium (V), niobium (Nb), tantalum (Ta), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and zinc (Zn). A second ion implantation is performed to implant gallium (Ga) into the gallium nitride layer. A third ion implantation is performed in which hydrogen (H) is implanted into the gallium nitride layer. After the first ion implantation, the second ion implantation, and the third ion implantation, a coating layer is formed on the surface of the gallium nitride layer. After forming the aforementioned coating layer, a first heat treatment is performed. After the first heat treatment, the coating layer is peeled off. A method for manufacturing a semiconductor device, comprising performing a second heat treatment after peeling off the aforementioned coating layer.

12. The method for manufacturing a semiconductor device according to claim 11, further comprising forming a metal film on the gallium nitride layer after the second heat treatment.

13. The method for manufacturing a semiconductor device according to claim 11, wherein the dose of hydrogen in the third ion implantation is greater than the dose of gallium (Ga) in the second ion implantation, and the dose of gallium (Ga) in the second ion implantation is greater than the dose of the first element in the first ion implantation.

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